Method for regenerating a particulate filter for a turbocharged direct injection engine

Abstract

Method for regenerating a particulate filter (80) of a gasoline engine (10) with direct injection, comprising: Increasing the overlap between an inlet valve (26) and an exhaust valve (28) of a cylinder in response to an operating condition of the particulate filter (80), and Increasing the boost pressure of the gasoline engine (10) in response to the operating condition of the particulate filter (80), wherein The operating condition is a pressure drop across the particle filter (80).

Description

Technical field

[0001] The present invention relates to the field of motor vehicle pollutant limitation systems and methods, namely a method for regenerating a particulate filter of a gasoline engine with direct injection. Background and Summary

[0002] It has recently been shown that direct-injection gasoline engines improve engine performance and reduce transient air / fuel disturbances that can be caused by fuel adhering to the intake manifold and engine ports. However, at higher engine speeds and loads, particulate matter can form in the exhaust gas. Under certain conditions, particulate formation may be related to the short time between fuel injection into the cylinder and combustion being initiated by a spark plug. Specifically, there may be only a brief opportunity for the injected fuel to completely vaporize and form a homogeneous mixture before combustion is initiated.If a homogeneous air / fuel mixture is not formed in the cylinder before combustion is initiated, stratification pockets can form, and soot can be produced by burning richer areas in the cylinder's air / fuel mixture. Particulate filters have been proposed as one way to reduce soot emissions.

[0003] For example, German patent application DE 10 2009 012 336 B3 discloses a method for regenerating a particulate filter of a gasoline direct-injection engine, in which, after the need for particulate filter regeneration has been detected, the timing of the intake and exhaust valves is changed during subsequent gas exchanges so that an overlap of their opening times is ensured. Furthermore, German patent application JP 2007-291995 A discloses an internal combustion engine with an exhaust gas purification system, in which fuel is injected during an overlap period with the intake and exhaust valves open simultaneously. German patent application DE 10 2007 056 216 A1 further discloses a method for heating a catalyst in the exhaust system of a turbocharged internal combustion engine with direct fuel injection and variable valve timing, in which the valve overlap is increased during idle after a cold start.The overlap cross-section is increased compared to normal operation with an already heated catalyst. Further methods for regenerating a particulate filter are known from US 7,275,516 B1 and WO 2008 / 127755 A2.

[0004] The present inventors have developed a method for regenerating a particulate filter that does not require an external air supply. To solve the aforementioned problem, the invention proposes methods according to claims 1, 5, and 10, with preferred embodiments of the invention being the subject of the dependent claims. In particular, the inventors have developed a method for regenerating a particulate filter of a direct-injection gasoline engine, which comprises: increasing the overlap between an intake valve and an exhaust valve of a cylinder in response to an operating condition of the particulate filter.

[0005] By increasing the overlap between an intake and exhaust valve of a cylinder, air can flow from the intake system to the exhaust system, providing excess oxygen for regenerating a particulate filter. Since air flowing through the cylinder does not affect the cylinder's air / fuel mixture, the cylinder can operate at stoichiometric or rich conditions, resulting in less NOₓ being emitted from the cylinder during particulate filter regeneration. xis generated. In one embodiment, the boost pressure and fuel quantity of the cylinder can be adjusted in response to a condition of the particulate filter, so that the amount of excess oxygen in the exhaust gases can be adjusted to the amount of soot held by the particulate filter. In another embodiment, the boost pressure and fuel quantity of the cylinder can be adjusted in response to an oxidation rate of soot held by the particulate filter.

[0006] The described procedure offers several advantages. Specifically, it can improve engine emissions by allowing one cylinder to operate at stoichiometric conditions while a particulate filter regenerates. Furthermore, the amount of excess oxygen supplied to oxidize the soot held by the particulate filter can be adjusted, resulting in efficient soot combustion. Additionally, oxygen can be supplied to a particulate filter in the exhaust system without the need for an auxiliary air pump.

[0007] The aforementioned advantages, as well as other advantages and features of the present invention, will become readily apparent from the following detailed description, either alone or in conjunction with the accompanying drawings.

[0008] It is understood that the foregoing summary is intended to present, in simplified form, a selection of concepts that are further described in the detailed description. It is not intended to identify any essential or key features of the claimed subject matter, the scope of which is defined solely by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address the disadvantages mentioned above or in any part of this disclosure. Brief description of the drawing Fig. Figure 1 shows a schematic view of an exemplary embodiment of a gasoline engine with direct injection; Fig. Figure 2 shows a flowchart of a particle filter regeneration routine; Fig. Figure 3 shows a flow diagram of a flow control routine for adjusting the flow from the intake system to the inlet of a particulate filter; and Fig. Figure 4 shows a fuel control routine for controlling engine fuel during the regeneration of a particulate filter; and Fig. Figure 5 shows a flowchart for an alternative method for regenerating a particle filter. Detailed description of the depicted embodiments

[0009] Fig. Figure 1 shows an exemplary embodiment of a gasoline engine system with direct injection, generally at 10. In detail, the internal combustion engine 10 comprises several cylinders, one of which is in Fig. Figure 1 shows the engine 10 being controlled by an electronic engine control unit 12. The engine 10 comprises a combustion chamber 14 and cylinder walls 16 with a piston 18 positioned therein and connected to a crankshaft 20. The combustion chamber 14 is connected to an intake manifold 22 and an exhaust manifold 24 by means of an intake valve 26 and an exhaust valve 28, respectively.

[0010] The intake manifold 22 is connected to a throttle valve port 30 via a throttle valve 32. In one embodiment, an electronically controlled throttle can be used. In this embodiment, the throttle is electronically controlled to maintain a defined vacuum value in the intake manifold 22 regularly or continuously. It should be noted that in some applications, the port 30 and the throttle plate 32 can be located downstream of a compression device 90. In a configuration where the throttle is located downstream of the compression device, the tap for allowing intake system gases to flow to the exhaust system can be located downstream of the compression device and upstream of the throttle. Alternatively, a throttle port 30 and a throttle plate 32 can be omitted.

[0011] The combustion chamber 14 is also shown with an associated fuel injection device 37 for supplying fuel proportional to the pulse width (fpw) of the signal from the control unit 12. Fuel is supplied to a fuel injection device 37 by a conventional fuel system (not shown) comprising a fuel tank, a fuel pump, and a fuel distribution pipe (not shown). In the case of direct injection engines, as in Fig. Figure 1 shows a high-pressure fuel system, for example a common rail system.

[0012] In gasoline engine applications, the spark plug 34 provides an ignition source for the contents of the combustion chamber 14. Energy for generating a spark is provided by the ignition system 35. The control unit 12 adjusts the charging of the ignition coil, which supplies electrical voltage to the spark plug 34. In diesel applications, the spark plug 34 and the ignition system 35 are not required.

[0013] In the embodiment shown, the control unit 12 is a conventional microcomputer and comprises a microprocessor 40, input / output ports 42, an electronic memory 44, which in this particular example may be an electronically programmable memory, a working memory 46 and a conventional data bus.

[0014] The control unit 12 receives various signals from sensors connected to the engine 10, including but not limited to: measurements of the intake air mass flow (MAF) from an air flow meter 50 connected to the air filter [A in Fig. 1] is coupled; engine coolant temperature (ECT) from a temperature sensor 52 connected to a cooling jacket 54; a manifold pressure (MAP) measurement from a manifold pressure sensor 56 coupled to the intake manifold 22; a throttle position (TP) measurement from a throttle position sensor 58 coupled to the throttle valve 32; and an ignition profile sensor signal (PIP) from a Hall sensor 60 (or variable magnetic resistance sensor) connected to the crankshaft 20, indicating engine speed.

[0015] Engine 10 may include an exhaust gas recirculation (EGR) system to reduce NOₓ. xand contribute to other emissions. The engine 10 can, for example, include a high-pressure EGR system in which exhaust gas is supplied to the intake manifold 22 through a high-pressure EGR pipe 70, which is connected to the exhaust manifold 24 at a point upstream of an exhaust turbine 90a of a compression device 90 and to the intake manifold 22 at a point downstream of an inlet compressor 90b of the compression device 90. The high-pressure EGR system shown includes a high-pressure EGR valve assembly 72 located in the high-pressure EGR pipe 70. Exhaust gas flows from the exhaust manifold 24 first through the high-pressure EGR valve assembly 72 and then to the intake manifold 22. An EGR cooler [in Fig. [1 shown at Y] can be arranged in the high-pressure EGR pipe 70 to cool recirculated exhaust gases before they enter the intake manifold. Cooling is typically achieved using engine water, but an air-to-air heat exchanger can also be used.

[0016] The engine 10 can also include a low-pressure EGR system. The illustrated low-pressure EGR system comprises a low-pressure EGR pipe 170, which connects to the exhaust manifold 24 at a point downstream of the exhaust turbine 90a and to the intake manifold 22 at a point upstream of the intake compressor 90b. A low-pressure valve assembly 172 is arranged in the low-pressure EGR pipe 170. Exhaust gas in the low-pressure EGR circuit flows from the turbine 90a through a catalytic device 82 (for example, a three-way catalyst, which may have a washcoat comprising platinum, palladium, and rhodium) and a particulate filter 80 before entering the low-pressure EGR pipe 170. The catalytic device 82 conditions engine exhaust gases, for example, to oxidize exhaust gas components. A low-pressure EGR cooler Ya can be positioned along the low-pressure EGR pipe 170.

[0017] The high-pressure EGR valve assembly 72 and the low-pressure EGR valve assembly 172 each have a (not shown) valve for controlling a variable area restriction in the high-pressure EGR pipe 70 and low-pressure EGR pipe 170, which thereby controls the flow of high-pressure or low-pressure EGR.

[0018] Compressed air from compressor 90b is supplied to the particulate filter regeneration circuit 179. The compressed air flows to a point in the exhaust system between the catalyst 82 and the particulate filter 80. Depending on the system configuration, gases from the intake system can be routed upstream of a throttle port or downstream of a throttle port. For example, if a compressor is located upstream of a throttle port, intake system gases can be driven to the exhaust system from both downstream of the compressor and upstream of the throttle port. Conversely, if the throttle port is located upstream of the compressor, intake system gases can be driven to the exhaust system from both downstream of the throttle port and upstream of the compressor. In an alternative embodiment, an additional three-way catalyst can be positioned downstream of the particulate filter 80.If necessary, exhaust gases can be drawn through the particulate filter regeneration circuit to the intake manifold during conditions in which the engine is operating and the intake manifold has a lower pressure than the exhaust system pressure between the particulate filter 80 and the catalyst 82.

[0019] Vacuum regulators 74, 174, and 177 are connected to the high-pressure EGR valve assembly 72, the low-pressure EGR valve assembly 172, and the particulate filter air supply valve assembly 77, respectively. The vacuum regulators 74, 174, and 177 receive actuation signals from the control unit 12 to control the valve positions of the high-pressure EGR valve assembly 72, the low-pressure EGR valve assembly 172, and the particulate filter supply valve assembly 77. In a preferred embodiment, the high-pressure EGR valve assembly 72 and the low-pressure EGR valve assembly 172 are vacuum-actuated valves. However, any type of flow control valve or flow control valves can be used, for example, an electric solenoid-operated valve or a valve operated by a stepper motor.An outlet and a pressure sensor arrangement 79 provide data which can be processed by the control unit 12 using the Bernoulli equation to determine current between the intake system and the exhaust system when the particulate filter air supply valve arrangement 77 is in an open position.

[0020] The compression device 90 can be a turbocharger or any other such device. The illustrated compression device 90 has a turbine 90a installed in the exhaust manifold 24 and a compressor 90b, which is located in the intake manifold 22 by means of an intercooler [in Fig. [1 shown at X] is connected, which is typically an air-to-air heat exchanger, but could be water-cooled. The turbine 90a is typically connected to the compressor 90b by means of a drive shaft 92. (This could also be a sequential turbocharger arrangement, a single VGT, twin VGTs, or any other arrangement of turbochargers that could be used).

[0021] The oxygen concentration present in the exhaust system can be assessed by oxygen sensors 178 and 176. Furthermore, an additional oxygen sensor (not shown) can be installed between the catalytic converter 82 and the particulate filter 80. Oxygen sensor 178 detects the engine exhaust oxygen concentration, while oxygen sensor 176 detects exhaust oxygen after the catalytic converter and after the particulate filter. Oxygen sensors can be wide-range sensors with a linearized output, or they can be sensors that indicate a high-gain signal under near-stoichiometric conditions.

[0022] Furthermore, an accelerator pedal 94 is shown along a driver's foot 95. A pedal position sensor (pps) 96 measures the angular position of the pedal actuated by the driver.

[0023] It is understood that the illustrated motor 10 is shown only as an example and that the systems and procedures described herein can be implemented or applied in any other suitable motor which has suitable components and / or a suitable arrangement of components.

[0024] With reference to now Fig. Figure 2 shows a flowchart of a particulate filter regeneration routine 200. In Figure 202, engine operating conditions are determined by sensors and actuators. In one example, the routine 200 determines the engine temperature, ambient temperature, pressure drop across a particulate filter, time since engine start, engine load, engine torque demand, engine speed, and the amount of air supplied to the engine. In other exemplary embodiments, additional or fewer operating conditions can be determined based on specific tasks.

[0025] At 204, the EGR target quantity can be determined in response to engine operating conditions. Specifically, engine speed and requested torque are used to index a table or function of empirically determined EGR quantities. The values ​​contained in the table cells or in the function are interpolated, and a specific EGR quantity corresponding to the prevailing operating conditions is determined. It should be noted that in one embodiment, regardless of whether a particulate filter is regenerating, the outlet pressure of a supercharger or turbocharger is adjusted in response to a torque demanded by the driver, which is determined at 204. After determining the EGR target quantity, routine 200 advances to 206.

[0026] At step 206, routine 200 determines which EGR circuit the EGR should be drawn from. Specifically, routine 200 selects the EGR circuit (high-pressure or low-pressure) in response to intake manifold pressure, engine speed, and driver-demanded torque. If EGR via the low-pressure circuit is desired, routine 200 advances to step 208. Otherwise, routine 200 advances to step 210. In an alternative embodiment, a combination of high-pressure and low-pressure EGR can be used in response to operating conditions.

[0027] At 210, the control unit 12 issues commands to the vacuum control valve 74 to adjust the position of an EGR valve in the EGR valve assembly 72. Specifically, the control unit 12 adjusts the position of the EGR valve in response to the pressure differential between the exhaust system pressure and the intake system pressure at a point downstream of the compressor 90b, in order to provide a target EGR quantity that is empirically determined and stored in a table or function that can be indexed according to engine speed and a torque demand requested by the driver. In one embodiment, the routine adjusts the position of the EGR valve in response to the pressure differential detected across an orifice to achieve the target EGR flow rate. The position of the EGR valve can be controlled in an unregulated or regulated manner. For example, the position of the EGR valve can be adjusted by a PID controller located in the control unit 12.Thus, the position of the EGR valve can be adjusted to direct exhaust gases from a point upstream of a particulate filter to the intake system. In this configuration, EGR can be drawn in from a point in the exhaust system located upstream of the particulate filter and directed to the intake system at a point downstream of a compressor. After adjusting the high-pressure EGR, the routine proceeds to 212.

[0028] At 208, the control unit 12 issues commands to the vacuum control valve 172 to adjust the position of an EGR valve in the EGR valve assembly 174. Specifically, the control unit 12 adjusts the position of the EGR valve in response to the pressure differential between the exhaust system pressure and the intake system pressure at a point upstream of the compressor 90b to provide a target EGR quantity, which is empirically determined and stored in a table or function indexed according to engine speed and a torque demand requested by the driver. In one embodiment, the routine adjusts the position of the EGR valve in response to the pressure differential detected across an orifice to achieve the target EGR flow rate. The position of the EGR valve can be controlled in an unregulated or regulated manner. For example, the position of the EGR valve can be adjusted by a PID controller located in the control unit 12.Thus, EGR is drawn in from a point in the exhaust system located upstream of the particulate filter and directed to the intake system at a point upstream of the compressor. After adjusting the high-pressure EGR, the routine progresses from 200 to 212.

[0029] At 212, the routine decides whether or not the particulate filter needs to be regenerated. In one embodiment, routine 200 makes a decision based on the pressure drop across a particulate filter. In another embodiment, routine 200 can decide to regenerate the particulate filter in response to a model. For example, a soot accumulation model that estimates the amount of soot produced by an engine can be the basis for regenerating a particulate filter. If the estimated amount of soot exceeds a threshold, particulate filter regeneration is triggered. Conversely, if a pressure across the particulate filter is detected by a sensor or an estimating model, particulate filter regeneration can be triggered after the detected or estimated pressure exceeds a threshold.

[0030] Furthermore, other conditions can be included to determine when the particulate filter needs to regenerate. For example, filter regeneration must not occur if the engine temperature is above or below a threshold temperature. In another example, filter regeneration must not occur if the filter temperature is below a threshold value. However, if soot has accumulated on the filter, the control unit 12 can raise the filter temperature by retarding the ignition timing and increasing the engine airflow until a filter threshold temperature is reached. In this example, particulate filter regeneration can then occur after the threshold temperature is reached. In yet another example, particulate filter regeneration must not occur for a period of time after the engine is started.For example, particulate filter regeneration must not be triggered until sufficient time has elapsed for the engine speed to stabilize after the engine has started. In another embodiment, particulate filter regeneration can be triggered during overrun fuel cut-off. In yet another embodiment, particulate filter regeneration must not be triggered unless the engine load is greater than a threshold value (for example, the engine load could be the engine's rated torque divided by the total torque available from the engine; in other applications, the load could be the cylinder air charge divided by the total theoretical cylinder air charge), for example, a load of 0.3. If particulate filter regeneration is desired and the conditions are met, routine 200 advances to 214. Otherwise, routine 200 advances to 226.

[0031] At step 214, routine 200 determines whether there is sufficient pressure in the intake system to allow gases to flow from the intake system to the exhaust system. In one example, a table or function, which may be indexed by engine speed, turbocharger boost control valve position, or vane position and target torque, can be used to determine whether there is a pressure differential between the intake and exhaust systems sufficient to drive gas flow from the intake to the exhaust system. In another embodiment, the pressure in the intake and exhaust systems can be determined by pressure sensors. The pressure in the intake system can be generated by a turbocharger compressor or by a supercharger. If the boost pressure in the intake system exceeds the exhaust pressure, routine 200 advances to step 216. Otherwise, routine 200 advances to step 218.

[0032] In the 218, adjustments are made to the engine actuators so that the boost pressure can be adjusted while maintaining the target engine torque or following the driver's demand. In one embodiment, if the boost pressure (e.g., pressure in the intake system downstream of a compressor) is lower than the exhaust system pressure at a point upstream of the particulate filter, the cam timing is adjusted to produce the target engine torque while increasing the boost pressure. This method allows gases to flow from the intake system to the exhaust system while the engine torque follows the driver's demand. Depending on the engine configuration, cam timing with respect to valve opening operations relative to the crankshaft position can be advanced or retarded when boost pressure is increased.The cam timing adjustments can be determined from tables or functions containing empirically derived cam timing adjustments to provide an engine air volume equivalent to the air volume before the particulate filter regeneration is triggered. It should be noted, however, that the engine air volume before and after the charge increase is equivalent if the torque demanded by the driver remains constant; but if the torque demanded by the driver increases during filter regeneration, the cam timing and throttle position can be adjusted to provide the target air volume corresponding to the increased torque demanded by the driver.

[0033] In another embodiment, if the torque demanded by the driver is essentially zero (e.g., less than 2% of the full-load engine torque), the compressor boost pressure can be adjusted so that the boost pressure is below a threshold when the torque demanded by the driver is essentially zero and when the particulate filter is not regenerating. Thus, the boost pressure can be reduced below a threshold when the particulate filter is not regenerating, resulting in less work for the engine and thus fuel savings.

[0034] In another embodiment, the ignition timing can be retarded so that the engine's target torque is achieved when the boost pressure is increased. The ignition timing can be retarded as a function of the boost pressure increase. For example, if the boost pressure is increased by 40 mmH2O, the ignition timing can be retarded by 5 degrees of crankshaft angle.

[0035] In another embodiment, if a throttle is located downstream of a compression device, the throttle position can be moved towards a closed position when the boost pressure is increased. Particularly if a throttle is located downstream of a compressor, the amount of the throttle opening can be reduced so that gases upstream of the throttle port can be directed to a point in the exhaust system upstream of the particulate filter.

[0036] In another embodiment, ignition timing, throttle position, and cam timing can be adjusted when the boost pressure is adjusted to compensate for the increased boost pressure that forces gas from the intake system to the exhaust system. In still other embodiments, combinations and sub-combinations of ignition, throttle, and cam settings can be made to accommodate boost pressure adjustments. After adjusting the actuators, routine 200 advances to 220.

[0037] At 220, the boost pressure is increased so that gases can flow from the intake system to the exhaust system. In one example, the variable geometry vanes of the turbocharger can be adjusted to increase boost pressure. In another example, the position of the turbocharger boost pressure control valve can be adjusted to increase boost pressure. The boost pressure can be increased subject to shock and compressor limitations. For example, if increasing the boost pressure would result in a shock condition, the boost pressure can be increased to a pressure lower than the shock threshold pressure. In one example, the boost pressure is increased by a constant amount above the boost pressure that induces flow from the intake system to the exhaust system. The boost pressure can, for example, be increased by 60 mm H2O above a value that produces flow from the intake system to the exhaust system.The actuator adjustments that increase the charge can be based on empirical data stored in the memory of a control unit. After adjusting the boost pressure, the routine progresses from 200 to 222.

[0038] At 222, routine 200 adjusts the position of the low-pressure and / or high-pressure EGR valve depending on which pressure circuit is activated. Since EGR can flow into the intake system at the same time as intake system gases flow to the exhaust system, the position of the EGR valve can change when the boost pressure is increased. For example, the opening of the low-pressure EGR valve can decrease when the boost pressure is increased. Furthermore, increasing the flow into the intake system can tend to increase the EGR flow to the compressor if the position of the EGR valve remains constant, because the pressure at the compressor inlet may be reduced, which can increase the pressure differential between the intake system and the exhaust system. Therefore, the low-pressure EGR valve is moved towards a closed position.In another example, the flow in the high-pressure EGR circuit can decrease if the position of the high-pressure EGR valve remains constant, because the pressure increase in the intake system can reduce the flow from the exhaust system to the intake system. Therefore, the high-pressure EGR control valve can be moved to a more open position so that the target EGR flow rate can be achieved when the boost pressure increases. After adjusting one or more EGR valves, the routine progresses from 200 to 224.

[0039] At 224, routine 200 activates the particulate filter regeneration and sets the flow rate between the intake system and the exhaust system. The flow rate from the intake system to the exhaust system can be determined in response to the torque demanded by the driver, the EGR quantity, the amount of stored particles, and the particulate filter temperature.

[0040] In one embodiment, the flow from the intake system to the exhaust system can be determined based on a mass flow rate of oxygen. The amount of oxygen entering the engine can be measured by a mass flow sensor. However, since EGR can also flow into the intake system, the gases flowing from the intake system to the exhaust system can contain both oxygen and EGR. Therefore, the total mass of gases flowing from the intake system to the exhaust system via the particulate filter regeneration circuit can be increased to compensate for the proportion of EGR in the intake system compared to a situation where no EGR is present in the intake system. The position of the EGR valve can be determined from the pressure drop occurring across an orifice located in the particulate filter regeneration circuit and the target flow rate.By knowing the mass of EGR entering the intake system and the mass of oxygen entering the intake system, the oxygen concentration in the intake system can be determined. Multiplying the oxygen concentration by the flow rate from the intake system to the exhaust system determines the amount of oxygen supplied to the particulate filter. The air supply valve of the particulate filter can be opened further to increase the amount of oxygen flowing to the particulate filter when EGR flows from the exhaust system to the intake system.

[0041] In another example, the flow rate between the intake system and the exhaust system can be based on empirically determined flow rates that can be adjusted in response to a temperature sensor located downstream of the particulate filter. For instance, the position of the particulate filter's air supply valve assembly can be commanded to a predetermined position when particulate filter regeneration is triggered. If the temperature in the exhaust system rises due to particle oxidation, the valve position can be opened further to supply additional oxygen to the oxidation process once oxidation has begun. However, if the temperature of the particulate filter or downstream of the particulate filter rises above a threshold, the flow of oxygen from the intake system to the exhaust system can be reduced to control the particulate filter temperature.

[0042] In another example, the flow rate between the intake system and the exhaust system can be based on empirically determined flow rates and adjusted in response to an oxygen sensor located upstream or downstream of the particulate filter. For instance, if a particulate filter reaches a temperature at which regeneration can occur, oxygen can be introduced upstream of the filter. If the amount of oxygen detected downstream of the filter exceeds a threshold, the particulate filter's air supply valve can be moved towards a closed position (the valve opening can be reduced). Conversely, if a downstream oxygen sensor indicates a decrease in oxygen compared to the amount of oxygen present upstream of the particulate filter, the flow from the intake system to the exhaust system can be increased.It should be noted, however, that the increase in flow from the intake system to the exhaust system in response to the time since regeneration was initiated and the particulate filter temperature may be limited. For example, if the particulate filter temperature rises above or falls below a threshold temperature, the flow from the intake system to the exhaust system may be reduced. Conversely, the particulate filter's air supply valve may move from an initial open position to a second, more closed position than the initial open position, if the oxygen concentration in the exhaust system between the catalytic converter and the particulate filter exceeds a threshold value.Similarly, the air supply valve of the particulate filter can be moved from a first open position to a second open position, which is more open than the first, if the oxygen concentration in the exhaust system between the catalytic converter and the particulate filter is below a threshold value. Furthermore, if the amount of oxygen in the exhaust system exceeds a threshold value at any point downstream of a particulate filter, the flow of gases from the intake system to the exhaust system can be prevented.

[0043] In yet another example, the position of the particulate filter's air supply valve assembly can follow a predetermined trajectory stored in a control unit. Different air supply valve trajectories for the particulate filter can be configured for various operating conditions. For instance, the position of the particulate filter's air supply valve can be adjusted to follow a first trajectory in response to the amount of soot held in the particulate filter. In another example, the air supply position of the particulate filter can be adjusted to follow a second trajectory in response to a presumed or detected particulate filter temperature. Thus, the amount of oxygen supplied to the particulate filter can vary depending on the operating conditions.

[0044] Furthermore, when intake gases begin to flow from the intake system to the exhaust system, the position of the turbocharger boost pressure control valve or variable geometry vanes can be adjusted to maintain a target boost pressure. For example, a boost pressure control valve can be moved to a more closed position, allowing a greater volume of exhaust gas to impact the turbocharger turbine. In turbochargers with variable geometry vane control, the vanes can be moved so that the exhaust gases perform more work on the turbocharger turbine. This can increase turbine efficiency, causing the turbocharger compressor to pump additional air to the intake system as gases flow from the intake system to the exhaust system. Additionally, the volume of air supplied from the intake system to the exhaust system can be subtracted from the volume of air entering the engine's air intake system.By subtracting the portion of air that goes to the exhaust system, the engine can be operated with an essentially stoichiometric air / fuel mixture when the particulate filter is regenerating.

[0045] At 216, the amount of oxygen supplied to a particle filter can be determined similarly.

[0046] At position 226, the particulate filter regeneration air supply can be reduced. When particulate filter regeneration is complete, or when operating conditions make particulate filter regeneration difficult or impractical, the particulate filter air supply valve can be closed. The particulate filter air supply valve can be closed according to a predetermined trajectory stored in a control unit.

[0047] In another example, the particulate filter's air supply valve can be controlled in response to an oxygen sensor located in the exhaust system downstream of the particulate filter. In some embodiments, it may be advantageous to have a catalyst positioned downstream of the particulate filter. In such configurations, the state of the downstream catalyst can be controlled in response to an oxygen sensor positioned between the particulate filter and the catalyst. For example, fuel can be enriched while the particulate filter's air supply valve is moved to a closed position, thus removing excess oxygen from the downstream catalyst. If the oxygen sensor detects that the post-particulate mixture is leaner than desired, the particulate filter's air supply valve can be closed at an increased rate.If, on the other hand, the oxygen sensor detects that the post-particle mixture is richer than desired, the air supply valve of the particulate filter can be closed at a reduced rate.

[0048] With reference to now Fig. Figure 3 shows a flowchart of a current control routine for adjusting current from the intake system to the inlet of a particulate filter. At step 302, routine 300 determines whether conditions are met to regenerate a particulate filter. These conditions can include, but are not limited to, the pressure drop across the particulate filter, engine temperature, the time since the engine started, and the particulate filter temperature. In one example, regeneration is initiated when the particulate filter temperature exceeds a threshold and when the pressure drop across the particulate filter exceeds a threshold. If particulate filter regeneration is desired, the routine advances to step 304; otherwise, routine 300 terminates.

[0049] At step 304, the routine determines whether more than four attempts have been made to regenerate a particulate filter without success. Alternatively, the number of regeneration attempts can be increased or decreased as needed. For example, if air is introduced into a particulate filter operating at a threshold temperature and there is no increase in the filter temperature, no decrease in the oxygen concentration of gases flowing through the filter, or no reduction in the pressure drop across the filter, then the filter can be considered unregenerated.If routine 300 detects that more than four particulate filter regeneration attempts have been made, it advances to routine 322, where a degradation flag is set. This prevents any further particulate filter regeneration attempts until the system has been checked or a parameter changes that allows for additional regeneration attempts. Of course, fewer or more regeneration attempts may be made.

[0050] In section 306, a mass flow rate can be arranged from the intake system to the exhaust system. In one example, the mass flow rate can be established by setting a position of the particulate filter's air supply valve in response to a table or function indexed by engine speed, EGR quantity, and intake system pressure. The position of the particulate filter's air supply valve can change with operating conditions, thus establishing a target flow rate between the intake system and the exhaust system. The routine then proceeds to section 308.

[0051] At 308, routine 300 determines whether a particulate filter regeneration has started. As explained above, particulate filter regeneration can be detected from the particulate filter temperature, a change in oxygen in engine exhaust gases, or a change in the pressure drop across the particulate filter. For example, particulate filter regeneration can be detected as having started if the temperature of a particulate filter increases by more than 10°C without any change in engine operating conditions. In another example, particulate filter regeneration can be detected as having started if the oxygen concentration in gas flowing through a particulate filter decreases by more than 5%, or if there is a decrease in pressure drop of, for example, 2 kPa.Furthermore, if particulate filter regeneration has started and the particulate filter temperature drops below a threshold temperature, routine 300 can advance to 310 and 314 to allow the particulate filter to regenerate further after regeneration has begun. This feature enables particulate filter regeneration even when an engine transitions from partial or full throttle conditions to idle. If the routine detects that particulate filter regeneration has started, it advances from 300 to 316. Otherwise, it advances from 300 to 310.

[0052] At step 310, a second particulate filter regeneration can be attempted by increasing the flow rate between the intake system and the exhaust system. In one example, the flow rate between the intake and exhaust systems is increased by 10%. After increasing the flow from the intake to the exhaust system, routine 300 advances to 312.

[0053] At step 312, it is determined whether the particulate filter regeneration has started, as described in step 308. If regeneration has not started, routine 300 advances to step 314. Otherwise, routine 300 advances to step 316.

[0054] At step 314, the filter temperature is increased. In one embodiment, the filter temperature can be increased by retarding the ignition timing and increasing the air mass flow through the engine. By retarding the ignition timing, the torque demanded by the driver is maintained while the airflow through the engine increases. Therefore, the engine control unit can meet the driver's demand while increasing the amount of heat supplied to the particulate filter. Then, routine 300 advances to 304 and attempts to regenerate the particulate filter again. In one example, the particulate filter temperature is increased by a predetermined amount, for example, 20°C.

[0055] At step 316, routine 300 determines whether the particulate filter has a catalytic coating. If not, routine 300 advances to step 320. If so, the routine advances to step 318. In some engine configurations, a catalytic coating can be advantageous for a particulate filter. The coating can improve particle oxidation and help reduce the amount of hydrocarbons emitted from the vehicle's tailpipe. However, in other applications, a catalytic coating may be less desirable because it can complicate air / fuel control, as the coating can alter exhaust gas constituents in an undesirable way. Therefore, the engine control unit can be programmed to store information about whether or not a particular particulate filter has a washcoat for exhaust gas conditioning.

[0056] At 320, the routine adjusts the flow from the intake system to the exhaust system, doing the same at 226. Fig. The two described procedures are executed. After adjusting the throughput, routine 320 ends.

[0057] At 318, the routine adjusts the flow from the intake system to the exhaust system through the one at 216 of Fig. The procedure described in section 2 is used, but routine 300 also adjusts the flow in response to the oxygen state of the particulate filter. For example, the position of the particulate filter's air supply valve can be changed according to a predefined trajectory or function related to the value of oxygen storage available in the particulate filter's washcoat. In particular, the position of the particulate filter's air supply valve can be modulated at a frequency, e.g., 1 Hz. In another example, the position of the particulate filter's air supply valve and the amount of engine fuel can be modulated in response to the output of an oxygen sensor located downstream of the particulate filter.And in yet another example, the position of the particulate filter's supply valve can be changed in response to an oxygen sensor positioned upstream of the particulate filter and an oxygen sensor positioned downstream of the particulate filter. In particular, the position of the particulate filter's supply valve can be adjusted in response to the oxygen concentration and flow rate of exhaust gases entering the particulate filter, as well as the oxygen concentration of gases exiting the particulate filter. In one embodiment, the position of the particulate filter's air supply valve can be adjusted in response to the amount of oxygen stored in the particulate filter, together with the amount of soot held by the filter and the rate or oxidation of soot.For example, the flow rate of intake gases from the intake system to the exhaust system can be increased if the amount of oxygen used or stored in the particulate filter increases. Similarly, the flow rate from the intake system to the exhaust system can be decreased if the amount of oxygen used or stored in the particulate filter decreases.

[0058] With reference to now Fig. Figure 4 shows a flowchart of a fuel control routine for controlling engine fuel during the regeneration of a particulate filter. At routine 402, engine operating conditions are determined by sensors and actuators. In one example, routine 400 determines the engine temperature, ambient temperature, time since engine start, engine load, engine torque demand, and engine speed. In other exemplary embodiments, additional or fewer operating conditions can be determined based on specific tasks. After determining the operating conditions, routine 402 proceeds to routine 404.

[0059] At 404, routine 400 determines the engine's base fuel quantity. In one example, the base fuel quantity can be determined in response to the driver's requested target torque and engine speed. Specifically, the driver's requested torque is converted into a quantity of fuel and air that may be required at the given engine speed to produce the engine's target torque. The engine's target torque and engine speed can be used to index a table containing an empirically determined fuel quantity corresponding to a fuel quantity in a substantially stoichiometric air / fuel mixture (e.g., ± 0.06 lambda, where lambda is the air / fuel ratio divided by the stoichiometric air / fuel ratio) that will produce the engine's target torque. After determining the engine's base fuel quantity, routine 400 advances to 406.

[0060] At 406, routine 400 determines whether a particulate filter regeneration has started or not. If so, routine 400 advances to 408. If not, routine 400 advances to the end. As with 308 of Fig. As described in section 3, particulate filter regeneration can be initiated if the temperature of a particulate filter rises by more than a threshold amount, e.g., 10°C, without any change in engine operating conditions. Furthermore, particulate filter regeneration can be considered to have started if the oxygen concentration in a gas passing through a particulate filter decreases by more than a threshold amount, for example, 5%. If it is determined that particulate regeneration has started, routine 400 advances to 408. Otherwise, routine 400 advances to the end.

[0061] At step 408, the routine determines whether a particulate filter has a catalytic washcoat or not. In one embodiment, the engine control unit can be programmed to store information about whether the specific particulate filter has a washcoat for exhaust gas treatment. If so, routine 400 advances to 410. If not, routine 400 advances to 418.

[0062] At 418, routine 400 prevents adjustments to the engine base fuel quantity, which is determined at 404. Because oxygen is introduced from the intake system to the exhaust system upstream of the particulate filter and downstream of the catalyst, an oxygen sensor located downstream of the particulate filter may have an output that is influenced by the introduced oxygen. Consequently, if the base fuel is adjusted in response to oxygen introduced from the intake system, the engine fuel supply may deviate from a desired fuel quantity. For example, if an oxygen sensor located downstream of a particulate filter detects excess oxygen, fuel may be increased to the engine, resulting in a rich mixture of gases entering an upstream three-way catalyst, rather than the desired stoichiometric mixture.Consequently, the conversion efficiency of the three-way catalytic converter may deteriorate, at least for some exhaust gas components. In particular, additional hydrocarbons and CO may be present in the tailpipe exhaust. Therefore, the output of an oxygen sensor located downstream of the point where intake gases are introduced into the exhaust system can be ignored by the fuel control routine, so that the base fuel quantity is not affected by the downstream oxygen sensor. After suppressing base fuel adjustments in response to the downstream sensor, the routine advances from 400 to 420.

[0063] In an alternative embodiment, Routine 400 can adjust the amount of fuel delivered to a cylinder in response to an oxygen sensor located downstream of a particulate filter and upstream of a second three-way catalyst. For example, the amount of fuel delivered to a cylinder can be enriched if the exhaust oxygen concentration downstream of a particulate filter is leaner than stoichiometric exhaust. In another example, the amount of fuel delivered to a cylinder can be leaned out if the exhaust oxygen concentration downstream of a particulate filter is richer than stoichiometric exhaust. Alternatively, the amount of intake gases flowing to the exhaust system can be reduced if the oxygen concentration in the exhaust system at any point downstream of a particulate filter is leaner (i.e., a higher oxygen concentration in the exhaust gases) than that of stoichiometric exhaust gases.The amount of intake gases flowing to the exhaust system can be increased if the oxygen concentration in the exhaust system at a point downstream of the particulate filter is richer (e.g., a lower oxygen concentration in the exhaust gas) than that of stoichiometric exhaust gases.

[0064] In yet another embodiment, routine 400 can adjust the amount of fuel delivered in response to an oxygen sensor located downstream of a particulate filter and in response to the flow of gases from the intake system to the exhaust system. For example, if the oxygen concentration in the exhaust system minus the oxygen concentration supplied to the exhaust system via the intake system is higher than desired, the engine fuel supply can be increased to compensate for the additional oxygen in the exhaust gases. Conversely, if the oxygen concentration in the exhaust system minus the oxygen concentration supplied to the exhaust system via the intake system is lower than desired, the amount of engine fuel can be decreased to compensate for less oxygen in the exhaust gases.

[0065] At 420, the flow from the intake system to the exhaust system can be controlled. In particular, the flow from the intake system to the exhaust system is controlled as in 216 by Fig. The process is controlled as described in section 2. For the sake of brevity, a repetition of the procedure is omitted here.

[0066] At step 422, routine 400 decides whether filter regeneration can be completed or not, or whether the conditions for regeneration no longer exist. In one embodiment, regeneration can be determined to be complete if the pressure difference across the particulate filter is less than a predetermined amount. In another example, regeneration can be determined to be complete if the exhaust gas downstream of the particulate filter shows an increase in the oxygen concentration in the exhaust gases passing through the particulate filter. The increased oxygen concentration can be an indicator that soot in the filter has been oxidized and that the amount of soot has been reduced, so that less oxygen is consumed to oxidize the soot remaining in the filter. If routine 400 decides that regeneration is complete, routine 400 advances to step 424. Otherwise, routine 400 advances to step 420.

[0067] In 424, a control of the engine base fuel determined in 404 is reactivated. Furthermore, the gas flow from the intake system to the exhaust system can be stopped. In one embodiment, the flow from the intake system to the exhaust system can be stopped as in 226. Fig. 2 described to be stopped.

[0068] At 410, routine 400 adjusts the base fuel quantity determined at 404. In one embodiment, the frequency, preload, or degree of leanness or richness of a modulated fuel quantity supplied to the engine cylinders can be adjusted in response to an oxygen sensor located downstream of a particulate filter having a catalytic coating. Note that fuel control terms such as preload, degree of leanness or richness, and frequency can also be adjusted in response to an oxygen sensor located upstream of a catalyst. Furthermore, the fuel control terms preload, degree of leanness or richness, and frequency can be adjusted by one or more oxygen sensors (e.g.,a sensor located upstream of a first catalyst, a sensor located downstream of a particulate filter and a third sensor located downstream of the particulate filter; a sensor located upstream of a first catalyst, a sensor located downstream of a particulate filter and a third sensor located downstream of a second catalyst).When the engine is running and the particulate filter is not regenerating, the engine base fuel can be adjusted in response to the downstream oxygen sensor by a first set of control parameters or variables. This first set of control parameters may include, but is not limited to, a preload term (for example, a rich or lean shift in the average air / fuel mixture of the cylinder), the extent of the lean or rich term, and a first modulation frequency term related to the engine's air / fuel mixture ratio. Furthermore, the first set of control parameters may include cam angle or cam timing, as well as ignition timing and throttle position.The base fuel determined at 404, together with the initial preload, the initial lean or richness level, and the initial modulation frequency, is used to operate the engine at a substantially stoichiometric air / fuel mixture. After the start of particulate regeneration (e.g., after establishing flow from the intake system to the exhaust system), the base fuel can be adjusted in response to the oxygen sensor located downstream of the particulate filter by operating the engine with a second set of control parameters or variables, which differ from the first set of control parameters or variables. This second set of control parameters may include, but is not limited to, a preload term, a second lean or richness level term, and a second modulation frequency term related to the engine's air / fuel mixture ratio.Additionally, the second group of control parameters can include cam angle or cam timing, as well as ignition timing and throttle position. The base fuel determined at 404, together with the second preload, the second degree of leanness or richness, and the second modulation frequency, are used to operate the engine at a substantially stoichiometric air / fuel mixture; however, the mixture may be slightly rich preloaded to compensate for the introduction of air into the exhaust system. By operating the engine at substantially stoichiometric conditions, a three-way catalytic converter positioned upstream of the particulate filter operates at high efficiency, regardless of whether the particulate filter is regenerating or not. Furthermore, the preload, the degree of leanness or richness, and the modulation frequency can be adjusted in response to the amount of soot stored or oxidized during the regeneration process.For example, a rich pre-charge can enrich the engine's air / fuel ratio to such an extent that less NOx is produced by the engine when the particulate filter regenerates, and that the conversion efficiency of NOx by the catalyst during particulate filter regeneration increases. Furthermore, the intake gases introduced into the exhaust system contribute to reducing HC emissions through increased oxidation provided by the excess oxygen downstream of the catalyst.

[0069] At 412, routine 400 controls the flow from the intake system to the exhaust system. Specifically, at 318, this controls... Fig. The procedures described in 318 control the flow between the intake system and the exhaust system. For the sake of brevity, a repetition of the procedure described in 318 is omitted here. In 414, the routine determines whether particulate filter regeneration can be completed. The same procedure used in 422 is employed to determine whether regeneration can be completed. If particulate filter regeneration is not complete, routine 400 advances to 410. Otherwise, routine 400 advances to 416. In 416, the initial preload, the initial lean and rich parameters, and the initial modulation frequency of the engine's air / fuel mixture ratio are reactivated, allowing control of the oxygen storage capacity of the upstream catalyst, the particulate filter, and a catalyst positioned downstream of the particulate filter.In one embodiment, the first preload, the degree of leanness or richness, and the first frequency are adjusted such that between 20% and 80%, and preferably between 40% and 60%, of the available oxygen storage capacity in the aftertreatment system is used to store oxygen when the engine is running. Routine 400 ends after the first set of fuel control parameters is reactivated.

[0070] Thus, the routine of Fig. 4. A method is described in which a control unit supplies fuel to a direct-injection gasoline engine in response to a first set of conditions. Furthermore, the control unit supplies fuel to the direct-injection engine in response to a second set of conditions, the second set of conditions being different from the first set. Thus, the control unit can operate the direct-injection gasoline engine in such a way that the engine fuel is adjusted to facilitate the regeneration of a particulate filter using gases supplied by the intake system.

[0071] Particulate filter regeneration can be further assisted by a turbocharger or supercharger. Specifically, intake manifold gases can be forced through an engine cylinder during intake and exhaust valve overlap to supply oxygen to the particulate filter without creating a lean air / fuel mixture. US Patent 7,275,516 describes a method for directing gases from an intake manifold to an exhaust manifold and is thereby fully incorporated by reference in every respect. When particulate filter regeneration is desired, gases from the intake system can be routed through engine cylinders to the exhaust system by adjusting boost pressure and valve timing. Furthermore, NOx formation can be reduced by enriching the cylinder's air / fuel mixture through fuel injection into the cylinder after the exhaust valve has closed.In this way, lean gases can be routed from the intake system to the exhaust system without leaning out the air / fuel mixture of the cylinder.

[0072] With reference to now Fig. Figure 5 shows a flowchart for an alternative method for generating a particulate filter. In step 502, sensors and actuators determine engine operating conditions. In one example, routine 500 determines engine temperature, ambient temperature, the pressure drop across a particulate filter, time since engine start, engine load, engine torque demand, engine speed, and the amount of air supplied to the engine. In other exemplary embodiments, additional or fewer operating conditions can be determined based on specific tasks.

[0073] At 504, the routine decides whether the particulate filter needs to be regenerated or not. In one embodiment, routine 500 makes the decision based on the pressure drop across a particulate filter. In another embodiment, routine 500 can decide to regenerate the particulate filter in response to a model that, at 212, Fig. 2 is described, to regenerate.

[0074] Furthermore, other conditions can be included to determine when the particulate filter needs to regenerate. For example, filter regeneration must not occur if the engine temperature is above or below a threshold temperature. In another example, filter regeneration must not occur if the filter temperature is below a threshold value. However, if soot has accumulated on the filter, the control unit 12 can raise the filter temperature by retarding the ignition timing and increasing the engine airflow until a filter threshold temperature is reached. In this example, particulate filter regeneration can then occur after the threshold temperature is reached. In yet another example, particulate filter regeneration must not occur for a period of time after the engine is started.For example, particulate filter regeneration must not be triggered until sufficient time has elapsed for the engine speed to stabilize after the engine has started. In yet another embodiment, particulate filter regeneration must not be triggered unless the engine load exceeds a certain threshold. If particulate filter regeneration is desired and the conditions are met, routine 500 advances to 506. Otherwise, routine 500 advances to the end.

[0075] In the 506, adjustments are made to the engine actuators so that boost pressure can be increased while intake gases flow to the exhaust system and while maintaining the engine's target torque or following the driver's torque demand. Depending on the engine configuration, cam timing can be advanced or retarded relative to the crankshaft position when boost pressure is increased. These cam timing adjustments can be determined from tables or functions containing empirically derived cam timing adjustments to provide an engine air volume equivalent to the air volume before the particulate filter regeneration is triggered.It should be noted, however, that the engine air volume before and after increasing the charge can be equivalent if the torque demanded by the driver remains constant; however, if the torque demanded by the driver increases during filter regeneration, cam timing can be adjusted to provide the target air volume corresponding to the increased torque demanded by the driver. Furthermore, the exhaust valve opening time and the intake valve closing time are adjusted to allow intake gases to flow from the intake system to the exhaust system. In one example, the valve overlap is described in a table or function that is indexed according to a target flow rate from the intake system to the exhaust system, the target boost pressure, and the engine speed.

[0076] When particulate filter regeneration is required, the time that the intake and exhaust valves are open simultaneously is extended by advancing or retarding the intake or exhaust camshaft, allowing additional intake gases to flow into the exhaust system. In some applications, the throttle position can also be adjusted. Thus, the camshaft timing can be adapted in response to, for example, a particulate filter operating condition, a pressure drop across the particulate filter, or a particulate filter temperature. Furthermore, the boost pressure can be adjusted in response to an oxygen concentration detected by a sensor located upstream or downstream of a particulate filter. In one embodiment, the compressor boost pressure can be reduced if an oxygen concentration detected in the exhaust system exceeds a threshold value.Conversely, if the oxygen concentration detected in the exhaust system is less than a threshold value, the compressor boost pressure can be increased.

[0077] The ignition timing can also be adjusted during particulate filter regeneration. For example, the ignition timing can be retarded to increase the particulate filter temperature. In another example, the ignition timing can be adjusted in response to a particulate filter operating condition. For instance, if the particulate filter retains more than a threshold amount of soot, the ignition timing can be retarded to a first value. When the particulate filter regenerates, the ignition timing can be retarded to a second value, with the second value being less than the first. After adjusting the actuators, routine 500 advances to 508.

[0078] At 508, the boost pressure can be increased so that gases can flow from the intake system to the exhaust system. In one example, the variable geometry vanes of the turbocharger can be adjusted to increase boost pressure. In another example, the position of the turbocharger's boost pressure control valve can be adjusted to increase boost pressure. The boost pressure can be increased subject to shock and compressor limitations. For example, if increasing the boost pressure would result in a shock condition, the boost pressure can be increased to a pressure lower than the shock threshold pressure. In one example, the boost pressure is increased by a constant amount above the boost pressure that induces flow from the intake system to the exhaust system. The boost pressure can, for example, be increased by 60 mm H2O above a value that produces flow from the intake system to the exhaust system.The actuator adjustments that increase the charge can be based on empirical data stored in the memory of an engine control unit. Thus, the compressor boost pressure can be adjusted, for example, in response to a particulate filter condition, a pressure drop across the particulate filter, a soot oxidation rate, or the particulate filter temperature. In one example, the charge can be increased if the soot oxidation rate rises. After adjusting the boost pressure, the routine advances from 500 to 510.

[0079] At 510, the fuel injected into the cylinder during particulate filter regeneration can be enriched. For example, fuel can be injected into the cylinder after the exhaust valve closes, so that no fuel is carried to the exhaust system. Enriching the cylinder mixture can reduce the NOx produced in the engine cylinder, while intake system gases flowing through the cylinder to the exhaust system can be used to oxidize soot on the particulate filter. In another example, the additional fuel injected to enrich the cylinder mixture can be based on the amount of intake gases flowing through the exhaust system that were not involved in combustion in the cylinder. Once the cylinder mixture is enriched, it is subsequently burned and then mixed with the exhaust gases flowing from the intake system to the exhaust system.This allows the gas mixture in the exhaust system to be brought closer to a target oxygen concentration. Thus, the performance of a three-way catalytic converter located upstream or downstream of the particulate filter can be improved compared to supplying a lean exhaust mixture to the catalyst. In another embodiment, the amount of fuel supplied to a cylinder of the engine can be adjusted in response to a rate of soot oxidation. For example, if the temperature of a particulate filter increases or if the pressure drop across a particulate filter decreases, the rate of soot oxidation can be determined to increase. Conversely, if the temperature of a particulate filter decreases or if the pressure drop across a particulate filter remains essentially constant for a given exhaust flow rate, the rate of soot oxidation can be determined to decrease.If the soot oxidation rate increases, the amount of fuel delivered to a cylinder can be increased. If the soot oxidation rate decreases, the amount of fuel delivered to the cylinder can be decreased.

[0080] Furthermore, the amount of fuel enrichment can be adjusted in response to a particulate filter operating condition. For example, when a particulate filter begins to regenerate, it consumes oxygen in the exhaust stream. As regeneration progresses, less oxygen can be consumed from the exhaust stream because less particulate material is being oxidized. Accordingly, the amount of excess oxygen in the exhaust can be adjusted by enriching or leaning the cylinder's air / fuel mixture. For instance, if an oxygen sensor located downstream of a particulate filter indicates an excessive oxygen concentration in the exhaust gases while the particulate filter is regenerating, the cylinder's air / fuel mixture can be enriched to reduce the excess oxygen.If an oxygen sensor located downstream of a particulate filter indicates a low oxygen concentration in the exhaust gases while a particulate filter is being regenerated, the cylinder's air / fuel mixture can be leaned out to increase the excess oxygen.

[0081] It should be noted that the intake and exhaust valve timings, along with the intake and exhaust manifold pressures, can be used to infer the amount of air passing through a cylinder without participating in combustion. For example, a table or function of empirically determined air volumes may be indexed by intake and exhaust valve timings and by intake and exhaust manifold pressures. The amount of air flowing from the intake system to the exhaust system during a cylinder cycle can be subtracted from the amount of air flowing into the cylinder during that cycle, thus determining the amount of air held in the cylinder for combustion during a cylinder cycle. Then, routine 500 advances to 512.

[0082] At 512, routine 500 determines whether the exhaust oxygen concentration can be at a target value. If so, routine 500 advances to 514. If not, the routine advances to 506. In one embodiment, the exhaust gas can be controlled to a target oxygen concentration. For example, the valve timing for valve overlap or the amount of fuel injected into a cylinder can be adjusted based on an oxygen concentration detected by an oxygen sensor. If the exhaust oxygen concentration is higher or lower than desired, the boost pressure and cam timing can be adjusted at 506. For example, if the oxygen concentration detected in the exhaust system is higher than desired, the amount of valve overlap and the boost pressure can be reduced.If the oxygen concentration detected in the exhaust system is lower than desired, the amount of valve overlap and the boost pressure can be increased. In one embodiment, if the exhaust oxygen concentration for particulate filter regeneration is lower than desired, the amount of charge can be increased. In another embodiment, if the exhaust oxygen concentration for particulate filter regeneration is lower than desired, the amount of intake and exhaust valve overlap can be increased. In another embodiment, if the exhaust oxygen concentration for particulate filter regeneration is higher than desired, the amount of charge can be decreased. In yet another embodiment, if the exhaust oxygen concentration for particulate filter regeneration is higher than desired, the amount of intake and exhaust valve overlap can be decreased.

[0083] At routine 514, the process determines whether the regeneration of the particulate filter is complete or whether the conditions for regeneration no longer exist. In one embodiment, regeneration can be determined to be complete when the pressure differential across the particulate filter is less than a predetermined amount. In another example, regeneration can be determined to be complete when the exhaust gas flow downstream of the particulate filter indicates an increase in the oxygen concentration in the exhaust gases passing through the particulate filter. The increased oxygen concentration can be an indicator that soot in the filter has been oxidized and that the amount of soot has been reduced, so that less oxygen is consumed to oxidize the soot remaining in the filter. When routine 500 determines that regeneration is complete, routine 500 advances to 516.Otherwise, the routine remains at 514 until regeneration is complete.

[0084] At step 516, actuators that adjust boost pressure, cam timing, and throttle are reset to their baseline values ​​based on engine operating conditions. For example, exhaust valve overlap can be reduced once particulate filter regeneration is complete. Additionally, a rich fuel mixture for the cylinder is removed, allowing the engine cylinders to operate at a near-stoichiometric air / fuel mixture. Then, routine 500 proceeds to its conclusion.

[0085] In this way, the procedure of Fig. 5. First engine valve timings in response to a first condition of a particulate filter and second engine valve timings in response to a second condition of a particulate filter, wherein the second valve timings allow more gases to flow through the intake system to the exhaust system without involving the gases in a combustion process before they flow from the intake system to the exhaust system. Furthermore, the method can be Fig.5. Control the amount of valve overlap in response to one or more oxygen sensors located in the exhaust system. For example, if the oxygen level downstream of a particulate filter exceeds a setpoint, the amount of valve overlap can be decreased. Conversely, if the oxygen level downstream of a particulate filter falls below a setpoint, the amount of valve overlap can be increased. As explained above, the valve overlap can be increased or decreased by adjusting the timing of the intake and exhaust camshafts relative to the crankshaft. In one embodiment, the oxygen sensor can be located upstream of a particulate filter in the exhaust system. In another embodiment, the oxygen sensor is located downstream of the particulate filter.If a configuration is chosen that includes an oxygen sensor located downstream of the particulate filter, the oxygen sensor can detect soot oxidation by detecting reduced oxygen levels in the exhaust gases. Alternatively, a different model can be used instead of an oxygen sensor if required.

[0086] It is understood that the configurations and routines disclosed herein are exemplary and that these specific designs should not be considered restrictive, as numerous modifications are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed-piston, and other engine designs.

[0087] The subject matter of the present disclosure thus includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, as well as other features, functions and / or properties disclosed herein.

[0088] The following claims specifically identify certain combinations and subcombinations which are considered novel and not obvious. These claims may refer to "one" element, "a first" element, or an equivalent thereof. These claims are to be understood as encompassing the integration of one or more such elements, without requiring or excluding two or more of these elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new claims in this or a related application. Such claims, whether broader, narrower, the same, or different from the scope of protection of the original claims, are also considered to be included in the subject matter of the present disclosure.

Claims

[1] Method for regenerating a particulate filter (80) of a gasoline direct injection engine (10), comprising: Increasing the overlap between an inlet valve (26) and an exhaust valve (28) of a cylinder in response to an operating condition of the particulate filter (80), and Increasing the boost pressure of the gasoline engine (10) in response to the operating condition of the particulate filter (80), wherein The operating condition is a pressure drop across the particle filter (80). [2] Method according to claim 1, characterized by , that the boost pressure is increased by adjusting the position of a boost pressure control valve or a vane. [3] Method according to claim 1, characterized by , that the overlap is increased by adjusting a camshaft in relation to a crankshaft. [4] Method according to claim 1, which further comprises subtracting an amount of air flowing from an intake system to an exhaust system during a cylinder cycle from an amount of air entering the cylinder during the cylinder cycle, wherein the amount of air flowing from the intake system to the exhaust system is not involved in the combustion of fuel in a cylinder of the direct-injection gasoline engine (10). [5] Method for regenerating a particulate filter (80) of a gasoline direct injection engine (10), comprising: Increasing the overlap between an inlet valve (26) and an exhaust valve (28) of a cylinder in response to an oxygen concentration in an exhaust system, wherein the oxygen concentration is located downstream of the particulate filter (80); Enrichment of a cylinder air / fuel mixture in response to the operating condition of the particulate filter (80), and Increasing the boost pressure of the gasoline engine (10) in response to an oxygen concentration in the exhaust system, and Adjusting the fuel supply to a cylinder in response to an oxygen concentration in the exhaust system downstream of the particulate filter (80). [6] Method according to claim 5, which further comprises adjusting the cam timing of the gasoline engine (10) with direct injection in response to an oxygen concentration in the exhaust system. [7] Method according to claim 5, which further comprises adjusting ignition timing in response to the operating conditions of the particulate filter (80). [8] Method according to claim 6, characterized by , that adjusting the cam timing includes adjusting the timing of an intake camshaft. [9] Method according to claim 6, characterized by , that adjusting the cam timing includes adjusting the timing of an exhaust camshaft. [10] Method for the regeneration of a particulate filter (80) of a gasoline direct injection engine (10), comprising: Increasing the overlap between an inlet valve (26) and an exhaust valve (28) of a cylinder in response to an operating condition of the particulate filter (80); Enrichment of a cylinder air / fuel mixture in response to the operating condition of the particulate filter (80); Adjusting at least one actuator in response to an oxygen concentration in an exhaust system, Adjusting fuel to a cylinder in response to the operating condition of the particulate filter (80), and Increasing the boost pressure of the direct-injection gasoline engine (10) in response to the operating condition of the particulate filter (80). [11] Method according to claim 10, which further comprises adjusting the cam timing of the gasoline engine (10) with direct injection. [12] Method according to claim 10, which further comprises adjusting ignition timing in response to the operating conditions of the particulate filter (80). [13] Method according to claim 11, characterized by , that adjusting the cam timing includes adjusting the timing of an intake camshaft. [14] Method according to claim 11, characterized by , that adjusting the cam timing includes adjusting the timing of an exhaust camshaft.

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