CN109026411B

CN109026411B - Internal combustion engine diagnostic method and engine controller

Info

Publication number: CN109026411B
Application number: CN201810728990.9A
Authority: CN
Inventors: 马修·A·杨金斯; 路易斯·J·塞拉诺
Original assignee: Tula Technology Inc
Current assignee: Tula Technology Inc
Priority date: 2014-11-10
Filing date: 2015-11-09
Publication date: 2020-12-25
Anticipated expiration: 2035-11-09
Also published as: CN109139278B; CN107076041A; JP2019206969A; CN109113878B; CN109026407B; JP7030341B2; DE112015005091T5; WO2016077246A1; CN107076041B; CN109026493B; CN109113878A; JP6568214B2; JP2017533382A; CN109026407A; JP2019206968A; DE112015005091B4; CN109026411A; CN109139278A; JP6850032B2; CN109026493A

Abstract

The invention relates to a method and an engine controller for diagnosing an internal combustion engine having an intake manifold, a plurality of working chambers, and an exhaust passage. Wherein a method for diagnosing an internal combustion engine having an intake manifold, a plurality of working chambers, and an exhaust passage, wherein each working chamber has at least one intake valve actuated by a cam and has at least one exhaust valve, is provided, comprising: operating the internal combustion engine in a multi-stage skip fire firing sequence, wherein the at least one cam-actuated intake valve can be adjusted for low or high torque output; assigning a target window to the ignition opportunity; providing a model or threshold of an engine parameter during the target window; measuring an engine parameter during the target window; and determining whether an engine problem exists based on a comparison of the measured engine parameter to a model or threshold of the engine parameter.

Description

Internal combustion engine diagnostic method and engine controller

Cross Reference to Related Applications

The application is a divisional application of a Chinese patent application with international application date of 2015, 11 and 09, date of entering Chinese country stage of 2017, 05 and 03, application number of '201580059861. X', and the title of 'multi-stage skip fire'.

This application claims priority from U.S. provisional patent application No. 62/077,439 entitled "Multi-Level Dynamic Skip Fire" filed 11/10 2014, U.S. provisional patent application No. 62/117,426 entitled "Multi-Level Dynamic Skip Fire" filed 2/17 2015, U.S. provisional patent application No. 62/121,374 entitled "Using Multi-Level Skip Fire" filed 26/2 2015, U.S. patent application No. 14/919,011 entitled "Multi-Level Skip Fire" filed 21/10 2015, and U.S. patent application No. 14/919,018 entitled "Multi-Level Skip Fire" filed 21/10/2015, each of these applications is incorporated herein in its entirety for all purposes.

Technical Field

The invention relates to a method and an engine controller for diagnosing an internal combustion engine having an intake manifold, a plurality of working chambers, and an exhaust passage, and a method and a system for operating the engine in a skip fire manner. In various embodiments, skip fire engine control systems are described that can selectively deactivate a working chamber and fire it at various output levels.

Background

Most vehicles in use today (and many other devices) are powered by Internal Combustion (IC) engines. Internal combustion engines typically have multiple cylinders or other working chambers in which combustion occurs. Under normal driving conditions, the torque generated by the internal combustion engine needs to be varied over a wide range in order to meet the driver's operational needs. Over the years, various methods for controlling the torque of internal combustion engines have been proposed and utilized. Some such approaches allow for varying the effective displacement of the engine. Engine controls that vary the effective displacement of the engine can be categorized into two types of controls, multiple fixed displacement and skip fire. In fixed multi-displacement control, some fixed groups of cylinders are deactivated under low load conditions; for example, an 8-cylinder engine can be operated with the same 4 cylinders under certain conditions. In contrast, skip fire engine control contemplates selectively skipping firing of certain cylinders during selected firing opportunities. Thus, a particular cylinder may be fired during one engine cycle and then may be skipped during the next engine cycle, and then selectively skipped or fired during the next engine cycle. For example, firing every second cylinder in a 4-cylinder engine will provide an effective displacement of l/3 of the maximum engine displacement, which is a component displacement that cannot be obtained by simply deactivating a group of cylinders. Similarly, firing every other cylinder in a 3-cylinder engine will provide 1/2's effective displacement, which is a component of displacement that cannot be obtained by simply deactivating a group of cylinders. U.S. patent No. 8,131,445 (filed by the assignee of the present application and incorporated herein by reference in its entirety for all purposes) teaches a variety of skip fire engine control implementations. In general, skip fire engine control is believed to offer a number of potential advantages, including the potential to significantly improve fuel economy in many applications. Although the concept of skip fire engine control has existed for many years and its benefits are apparent, skip fire engine control has not achieved significant commercial success.

It is well known that running engines tend to be a significant source of noise and vibration, often referred to collectively in the art as NVH (noise, vibration and harshness). Generally, the insight associated with skip fire engine control is that engine skip fire operation will cause the engine to run significantly rougher, i.e., increase NVH relative to a conventionally operated engine. In many applications, such as automotive applications, one of the most significant challenges presented by skip fire engine control is vibration control. In fact, the inability to satisfactorily address NVH concerns is considered a major obstacle that has prevented the widespread adoption of skip fire type engine controls.

U.S. patent nos. 7,954,474; 7,886,715, respectively; 7,849,835, respectively; 7,577,511, respectively; 8,099,224, respectively; 8,131,445 and 8,131,447 and U.S. patent application No. 13/004,839; 13/004,844, respectively; and others describe a wide variety of engine controllers that make it feasible to operate a wide variety of internal combustion engines in skip fire operating modes. Each of these patents and patent applications is incorporated herein by reference. While the illustrated controller works well, efforts continue to further improve the performance of these and other skip fire engine controllers to further mitigate the NVH problem of operating the engine under skip fire control. The present application sets forth additional skip fire control features and improvements that can improve engine performance in a wide variety of applications.

Disclosure of Invention

The invention relates to skip fire engine control. In one aspect, a method for controlling an engine is described. Skipping selected skipped duty cycles and firing selected active duty cycles to deliver the desired transmitter output. One or more working chambers can generate multiple possible levels of torque output, for example, for the same cam phaser setting and/or MAP (intake manifold absolute pressure) setting. A particular level of torque output (e.g., high or low torque output) is selected for each of the fired working chambers (i.e., the working chambers to be fired). This is referred to herein as multi-stage skip fire engine control. In many different designs, the air intake of the fired working chambers is adjusted based on whether a high or low torque output is selected on the fired working chambers. Various embodiments relate to engine controllers, software, and systems that facilitate implementing the above-described methods.

In another aspect, an engine controller is described. The engine controller includes a plurality of working chambers. Each working chamber includes at least one cam-actuated intake valve. The engine controller includes a firing fraction calculator, a firing timing determination module, and a firing control unit. The firing fraction calculator is arranged to determine a firing fraction suitable for delivering the desired torque. The spark timing determination module is arranged to generate a skip fire firing sequence based on the firing fraction. The skip fire firing sequence indicating whether the selected working chamber is deactivated or fired during the selected firing opportunity; and further indicates whether the spark produced a low or high torque output for each spark. The firing control unit is arranged to operate the working chambers in a skip fire manner based on the firing sequence. In various embodiments, the firing control unit is further arranged to adjust the air intake of the fired working chamber based on whether the firing sequence indicates a low or high torque output for each fired working chamber (i.e. each working chamber to be fired).

Multi-stage skip fire engine control may be performed in a variety of ways. In some embodiments, a determination is made as to whether each duty cycle is firing or skipping, for example, on a firing opportunity by firing opportunity basis, and/or a determination is made as to whether a particular level of torque output is selected for the fired working chamber. Such a decision may be made by using one or more look-up tables, circuits, sigma delta converters, or other techniques.

A variety of different systems may be used to control the torque output of the fired working chambers. For example, in some approaches, one or more of the working chambers (each including one or more intake valves) are independently controlled. The intake valves may be opened or closed at different times and/or according to different cycles (e.g., Atkinson and Otto cycles), which may help vary the torque output of the working chamber. The intake valves of the working chambers may be independently actuated or deactivated on a duty cycle by duty cycle basis. In various embodiments, a valve control system for a working chamber enables the working chamber to provide two, three, or more levels of torque output under the same engine conditions (e.g., the same cam phaser setting, throttle position setting, and/or engine speed setting). It should be appreciated that the method for implementing multi-stage skip fire engine control described herein may be used with any suitable working chamber design or valve control system.

In another aspect, an engine system is described. The engine system includes an intake manifold, one or more working chambers, and two or more intake passages. In various embodiments, two intake passages are associated with the working chamber. The two intake passages are arranged relative to the working chamber such that a central axis of each of the intake passages substantially intersects a central axis of the working chamber.

In yet another aspect, a method for diagnosing an internal combustion engine having an intake manifold, a plurality of working chambers, and an exhaust passage, wherein each working chamber has at least one intake valve actuated by a cam and has at least one exhaust valve, is described, comprising: operating the internal combustion engine in a multi-stage skip fire firing sequence, wherein the at least one cam-actuated intake valve can be adjusted for low or high torque output; assigning a target window to the ignition opportunity; providing a model or threshold of an engine parameter during the target window; measuring an engine parameter during the target window; and determining whether an engine problem exists based on a comparison of the measured engine parameter to a model or threshold of the engine parameter.

In yet another aspect, an engine controller is described for an internal combustion engine including a plurality of working chambers, wherein each working chamber has at least one intake valve actuated by a cam and has at least one exhaust valve, the engine controller comprising: a firing fraction calculator arranged to determine a firing fraction suitable for delivering the requested engine torque; a spark timing determination module arranged to determine a skip fire firing sequence based on the firing fraction, wherein the skip fire firing sequence indicates whether the selected working chamber was skipped or fired during the selected firing opportunity and further indicates whether the firing produced a low or high torque output level for each firing; a firing control unit arranged to operate the plurality of working chambers of the engine in a multi-stage skip fire manner based on the skip fire firing sequence to deliver the requested torque; and an engine diagnostic module to determine an engine parameter measured during a target window and a model or threshold of the engine parameter, wherein the engine diagnostic module determines whether an engine problem exists based on a comparison of the engine parameter measured during the target window and the model or threshold of the engine parameter during the target window.

Drawings

The invention, together with its advantages, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

fig. 1A and 1B are cross-sectional views of a working chamber and associated valve control system according to certain embodiments of the present invention.

Fig. 2-7 are block diagrams illustrating valve control systems according to various embodiments of the present invention.

FIG. 8 is a graph showing valve lift adjustment for a working chamber according to a particular embodiment of the present invention.

FIG. 9 is a valve control system according to a particular embodiment of the present invention.

FIG. 10 is a diagram illustrating an exemplary intake air passage.

FIG. 11 is a block diagram illustrating an intake passage according to certain embodiments of the invention.

Figures 12A-12F are diagrammatic views showing operating stages of a working chamber and an intake valve according to various embodiments of the present invention.

13A-13B are graphs showing how valves may be operated to produce torque outputs of working chambers at different levels, according to different embodiments of the present invention.

Fig. 14A-14H are diagrams illustrating different arrangements and features of working chambers according to various embodiments of the present invention.

FIG. 15 is a block diagram of a bank of cylinders in accordance with a particular embodiment of the invention.

FIG. 16 is a block diagram of an engine controller according to certain embodiments of the present disclosure.

Fig. 17 is a flow chart of a method for implementing multi-stage skip fire engine control in accordance with certain embodiments of the present invention.

FIG. 18 is an exemplary lookup table indicating maximum allowable working chamber output as a function of engine speed and effective firing fraction.

Fig. 19 is an exemplary lookup table showing firing fractions and level fractions as a function of effective firing fraction.

Fig. 20 is a diagram of an exemplary circuit that generates a multi-stage skip fire firing sequence in accordance with certain embodiments of the present invention.

Fig. 21 is a diagram of an exemplary circuit that generates a multi-stage skip fire firing sequence in accordance with another embodiment of the present invention.

Fig. 22 is an exemplary look-up table that provides a multi-stage skip fire firing sequence as a function of effective firing fraction.

FIG. 23 is a flowchart illustrating an exemplary method of using multi-stage skip fire engine control during transitions between firing fractions.

FIG. 24 is a flowchart illustrating an exemplary method for detecting and managing knock in an engine in accordance with certain embodiments of the invention.

FIG. 25 is a flowchart illustrating an exemplary method of using multi-stage skip fire engine control in response to a particular engine operation.

FIG. 26 is a flowchart illustrating an exemplary method for diagnosing and managing engine problems according to certain embodiments of the present invention.

In the drawings, the same reference numerals are sometimes used to designate the same structural elements. It should also be appreciated that the depictions in the figures are diagrammatic and not to scale.

Detailed Description

The present invention relates to a system for operating an engine in a skip fire mode. More specifically, various implementations of the present invention relate to a skip fire engine control system capable of selectively firing working chambers at a plurality of different torque output levels.

In general, skip fire engine control contemplates selectively skipping firing of certain cylinders during selected firing opportunities. Thus, for example, a particular cylinder may be fired during one firing opportunity and then may be skipped during the next firing opportunity, and then selectively skipped or fired during the next firing opportunity. This is in contrast to conventional variable displacement engine operation, where a fixed group of cylinders is deactivated during certain low load operating conditions.

One challenge with skip fire engine control is reducing undesirable noise, vibration and harshness (NVH) to acceptable levels. Noise and vibration generated by the engine can be transmitted to occupants in the vehicle compartment through a variety of ways. Some of these approaches, such as powertrains, can vary the amplification of a variety of different frequency components present in the engine noise and vibration characteristics. In particular, lower transmission gear ratios tend to amplify vibration because the transmission is increasing torque and torque variation at the wheels. Noise and vibration can also excite a variety of different vehicle resonances, which can be funneled into the vehicle cabin.

Some noise and vibration frequencies can be especially frustrating to vehicle occupants. In particular, low frequency, repeating patterns (e.g., frequency components in the range of 0.2 to 8 Hz) tend to produce undesirable vibrations that are perceived by vehicle occupants. Higher order harmonics of these patterns can cause noise in the passenger compartment. In particular, frequencies of about 40Hz may resonate within the vehicle cabin, so-called "rumble" frequencies. Commercially viable skip fire engine controls require operation at acceptable NVH levels while providing an engine torque output desired or required by the driver and achieving significant fuel efficiency gains.

The NVH characteristics vary with engine speed, firing frequency, and transmission gear. For example, consider an engine controller that selects a particular firing frequency that indicates the percentage of firing necessary to provide a desired torque at a particular engine speed and gear. Based on the firing frequency, the engine controller generates a repeating firing pattern to operate the working chambers of the engine in a skip fire manner. As is well known to those skilled in the art, an engine that runs smoothly with some ignition patterns at a given engine speed may produce undesirable acoustic or vibratory effects with other ignition patterns. Similarly, a given firing pattern may provide acceptable NVH at one engine speed, while the same pattern may produce unacceptable NVH at other engine speeds. The noise and vibration introduced by the engine is also affected by the cylinder load or working chamber output. If less air and fuel is provided to the cylinder, the ignition of the cylinder will produce less output, and less noise and vibration. As a result, if cylinder output decreases, some firing frequencies and sequences that were once unusable due to their poor NVH characteristics may become usable.

As described in U.S. patent application No. 14/638,908 (which is incorporated herein in its entirety for all purposes), the following skip fire engine controller design is generally desirable: delivering the required engine output while minimizing fuel consumption and providing acceptable NVH performance. This is a challenging problem due to the wide range of operating conditions encountered during vehicle operation. The requested engine output may be expressed as a torque request at the engine operating speed. It should be appreciated that the amount of engine torque provided may be represented by the product of the firing frequency and the cylinder load. Thus, if the Firing Frequency (FF) increases, the Cylinder Torque Fraction (CTF) may be decreased to produce the same engine torque, and vice versa. In other words,

engine Torque Fraction (ETF) ═ CTF × FF (equation 1)

Where ETF is a value representing normalized net or indicated engine torque. All values in this equation are dimensionless, which allows it to be used with all types of engines and for all types of vehicles. That is, a wide variety of different firing frequency and CTF combinations may be used to provide the same engine torque. Equation 1 does not include the effect of engine friction. Friction may be included to accomplish a similar analysis. The parameter calculated in this case should be the brake torque fraction. The net engine torque fraction, the engine braking torque fraction, the fraction of torque indicated by the engine, or some similar metric may be used as the basis for the control algorithm. For clarity, the term engine torque fraction may refer to any of these measures of engine output and will be used in the subsequent discussion of engine controllers and engine control methods.

Various embodiments of the present invention relate to a skip fire engine control system capable of firing selected working chambers at a plurality of different output levels. This is referred to herein as a multi-stage skip fire operation. In some embodiments, multi-level skip fire operation may be modeled by modifying equation 1 above to include multiple firing level possibilities as follows:

engine Torque Fraction (ETF) ═ CTF₁*FF₁+CTF₂*FF₂+..+CTF_n*FF_n(equation 2)

Wherein the CTF₁Is the cylinder torque fraction at the first level and FF₁Is the fraction of ignition, CTF₂Is the cylinder torque fraction at the second level and FF₂Is the fraction of ignition, and CTF_nIs the cylinder torque fraction at the nth level and FF_nIs the firing fraction. The plurality of differencesIs equal to the total firing fraction, i.e.

FF＝FF₁+FF₂+FF_n(equation 3)

In some embodiments described below, n is equal to two, but this is not limiting.

It should be appreciated that there are many equivalent ways of expressing the concepts described above. For example, instead of modeling based on Engine Torque Fraction (ETF), modeling may be based on net Engine Torque (ET) because these quantities are simply proportional. The Cylinder Torque Fraction (CTF) may be proportional to a Net Mean Effective Pressure (NMEP) and the nth level Firing Fraction (FF)_n) May be at the nth level (FED)_n) The fractional engine displacement of the operating cylinders is proportional. Equation 2 can therefore be expressed equivalently as

ET＝NMEP₁*FED₁+NMEP₂*FED₂+...+NMEP_n*FED_n(equation 4)

Equation 4 above is merely an exemplary improvement and many equivalent improvements are contemplated. They all have in common a quantity related to the engine output torque, expressed as the sum of a plurality of quantities, where each quantity is related to the output of a cylinder bank, and there are at least two cylinder banks with different non-zero outputs.

An example of a multi-stage skip fire operation may be described as follows. The working chamber may be deactivated during one selected duty cycle, fired at a high level output during the next duty cycle, and then fired at a lower level output (e.g., 0-80% of the high level output) during the next duty cycle. In a number of different implementations, this low level output may correspond substantially to the working chamber load that provides the best fuel efficiency, i.e., the lowest BSFC (brake specific fuel consumption) operating point. As is well known, BSFC working chamber load varies with RPM. Thus, in various embodiments of the present invention, the ratio between the high and low ignition levels may vary as engine RPM and possibly other variables vary. These firings and deactivations are coordinated to produce the desired engine torque. The availability of multiple skip fire operation allows the engine control system to have more options to find a balance between engine output, fuel efficiency, noise, and vibration.

It should be appreciated that any suitable technique may be used to implement multi-stage skip fire operation. For example, in some embodiments, throttle control, spark timing, valve timing, MAP adjustment, and/or exhaust gas recirculation are used to control the working chamber torque output. In this application, various studio control systems and arrangements are described. Such systems are arranged to enable the working chamber to produce multiple horizontal torque outputs. The present application also describes a number of different multi-stage skip fire engine control methods that may be implemented using the above-described system (e.g., as described in connection with fig. 16-26). However, the methods are not limited to the systems described herein and may be used with any suitable studio design, system or facility.

Control system for working chamber valve

Various embodiments of the present invention relate to a working chamber valve control system. Referring initially to fig. 1A and 1B, two cross-sectional views of an exemplary working chamber valve control system 100 will be described. The working chamber valve control system 100 includes a working chamber 102 with a piston 104, two intake valves 120a/120b and two exhaust valves 122a/122 b. Actuators 116a/116b control the opening and closing of the intake valves. Intake passages 110a/110b couple intake valves 120a/120b, respectively, with an intake manifold (not shown).

When the intake valve is open, air is delivered from the intake manifold into the working chamber 102 through the corresponding intake passage 110a/110 b. As is well known to those of ordinary skill in the art, if a working chamber 102 is to be ignited, air is mixed with fuel in the working chamber 102 and the fuel-air mixture is ignited. The resulting combustion drives the piston 104 to the bottom of the working chamber 102. The exhaust valves 122a/122b are opened and exhaust gas is pushed out of the working chamber 102 into the exhaust passage 112a/l12b as the piston 104 is raised.

In many conventional designs, the intake valves 120a/120b of the working chamber 102 are opened and closed simultaneously. I.e. they are controlled by the same actuator and/or are opened and closed according to the same lifting curve. The timing of the lift profile may be adjusted using a cam phaser that varies the time that the valve opens and closes relative to crankshaft motion. However, in a number of different conventional designs, the mechanical means of the cam phaser in general allow only small changes in the valve timing on a cycle-by-cycle basis and operate all cylinders in a similar manner. In the illustrated embodiment, however, the intake valves 120a/120b are independently actuated and operated. The timing of the opening and closing of one intake valve may be different or the same as the other intake valve from one working cycle to the next. For example, during a selected working cycle, the intake valve 120a may remain deactivated or closed while the intake valve 120b is opened to allow air into the working chamber. Alternatively, during the selected working cycle, the intake valve 120a may be opened and closed based on an otto cycle, while the other intake valve 120b may be opened and closed based on an atkinson or other cycle. One or both of the intake valves may be deactivated or closed during any selected operating cycle. In various embodiments, each intake valve of the working chamber 102 may be independently actuated or deactivated on a firing opportunity by firing opportunity basis.

The ability to independently control the intake valves of the same working chamber provides a variety of advantages. For example, the torque output of the working chamber may be dynamically adjusted. For example, in various designs, if two intake valves are open during an intake stroke and then closed during a subsequent compression stroke, deactivation of one of the intake valves during the selected working cycle will result in less air being delivered to the working chamber. This in turn reduces the torque produced by the firing of the working chamber relative to the situation where the two intake valves are open. Also, closing one or both of the intake valves before the end of the intake stroke will result in less air induction and lower duty cycle torque output. Similarly, keeping one or both of the intake valves open during both the intake stroke and a portion of the compression stroke will result in a lower duty cycle output. In which case the air introduced into the cylinder is exhausted from the cylinder before the power stroke begins. By using independent control of each intake valve and using different types of opening/closing timing of each intake valve, two, three, or more levels of working chamber output are possible, as discussed later in this application. As previously discussed, this ability to rapidly modulate the working chamber torque output, for example, on a firing opportunity by firing opportunity basis, may allow for better control of vibration, noise, and fuel consumption.

The actuators 116a/116b may use a variety of mechanisms to control the opening and closing of the intake valves 120a/120b of the working chamber 102. For example, in various embodiments, each intake valve is cam actuated and/or mechanically controlled. For example, in the illustrated embodiment, the

actuators

116a and 116b are separate cams that independently operate the

intake valves

120a and 120b, respectively. In some designs, a stall motion, a collapsible valve lifter, a collapsible lash adjuster, a collapsible roller finger follower, or a collapsible concentric barrel may be provided in the valve train to allow deactivation of the valve. These devices may allow the intake valves to be activated or deactivated during any given operating cycle. In some embodiments, an axially moving camshaft may also be used to control valve movement, where different cam lobes may be offset to engage the intake valve stem. In this case, one of the cam lobes may be a zero lift lobe, effectively deactivating the cylinder. In some embodiments, only a single intake valve may be used, and the opening of the valve may track and be based on two or more different lift profiles. Different cams may be used or different curves may be generated by using a more complex valve train. However, it should be appreciated that various other designs are also possible, as discussed later in this application. Actuation of the intake valve may be performed mechanically, electromechanically, electro-hydraulically, or using any other suitable mechanism.

A wide variety of systems may be used to actuate and control the intake and exhaust valves of the working chamber 102. Some exemplary designs are illustrated in fig. 2-7. Fig. 2-7 are diagrammatic top views of an example working chamber valve control system (e.g., working chamber control system 100 illustrated in fig. 1A and 1B). Fig. 2-7 each illustrate the working chamber 102, the actuator 116a/116b, the intake valve 120a/120b, the exhaust valve 122a, and possibly an additional exhaust valve 122 b. The line drawn between the actuator and the particular valve represents: the actuator controls the opening and closing of the valve. In general, when a line is drawn between an actuator and two or more valves, this means that when the actuator is activated, the valves must all be actuated during a selected duty cycle; alternatively, if the actuator is not activated during a work cycle, the valves must all be deactivated during the work cycle. If no line is drawn between the actuator and a particular valve, this means that the actuator does not control that particular valve. The above-described actuation may be performed using any suitable technique or mechanism, such as by using a camshaft assembly that includes one or more cams and/or camshafts.

A variety of different valve control arrangements are possible. For example, in fig. 2, intake valve 120a and exhaust valve 122a are located on one side of working chamber 102 (i.e., on one side of line of symmetry 105). An intake valve 120b and an exhaust valve 122b are located on the other side of the working chamber 102 (i.e., on the other side of line 105). An actuator 116a controls the valves on one side of the working chamber 102 (i.e., intake valve 120a and exhaust valve 122a), and another actuator (actuator 116b) controls the valves on the other side of the working chamber (i.e., intake valve 120b and exhaust valve 122 b).

Figure 3 shows a slightly different arrangement. In this example, each actuator 116a/116b controls an intake valve on one side of the working chamber and an exhaust valve on the other side of the working chamber. That is, actuator 116a controls intake valve 120a and exhaust valve 122b, while actuator 116b controls intake valve 120b and exhaust valve 122 a.

The above arrangement can create different flows in the interior of the working chamber 102. For example, if an actuator controls both an intake valve and an exhaust valve on the same side of the working chamber (e.g., as shown in fig. 2), air flowing from the intake valve to the exhaust valve tends not to flow through the middle or central axis 106 of the working chamber. If the actuator controls both intake and exhaust valves on different sides of the working chamber (e.g., as shown in fig. 3), the air flowing between the intake and exhaust valves tends to pass through the middle or central axis of the working chamber. This may have different effects on the swirling or tumbling of the air and gases in the chamber. Different control schemes and arrangements for the actuators and valves can help achieve a desired amount of swirl within the chamber. In general, moderate amounts of swirl are desirable. If there is too much swirl, too much thermal convection can be caused to the walls of the working chamber. If there is less swirl, the combustion rate in the working chamber may be low.

Other valve control arrangements are possible. For example, in fig. 4, the actuator 116a controls an intake valve 120a on one side of the working chamber 102 and two exhaust valves 122a/122b on the other side of the working chamber. The other actuator 116b controls the remaining intake valve (intake valve 120 b). Therefore, actuator 116a must also be activated whenever actuator 116b is activated to open intake valve 120b during a selected duty cycle and an exhaust event is desired to occur. In other words, actuator 116a must be activated whenever an exhaust event is desired to occur within a selected duty cycle and intake valve 120a and the two

exhausts

122a and 122b will be opened during the duty cycle. Opening both exhaust valves may help improve exhaust, i.e., exhaust gas from the working chamber just before the piston reaches top dead center (i.e., before the intake stroke begins).

Fig. 5 illustrates another valve control system. In this example, the actuator 116a controls an intake valve 120a and the two

exhaust valves

122a and 122b on one side of the working chamber 102. The further actuator 116b has a similar function in that it controls the inlet valve 120b on the other side of the working chamber as well as the two

outlet valves

122a and 122 b. This arrangement also causes the two exhaust valves 122a/122b to be actuated during a selected duty cycle during which an exhaust event is desired to occur and/or whenever one of the intake valves 120a/120b is actuated during the selected duty cycle. If the

actuator

116a or 116b is activated, the

exhaust valves

122a and 122b will be activated. However, in contrast to FIG. 4, when a combustion event is desired, the intake valve 120b may be opened during the selected duty cycle without opening the intake valve 120 a.

Although the above example refers to a working chamber with two intake valves and two exhaust valves, this is not a requirement and the working chamber may include any suitable number of intake and exhaust valves. For example, FIG. 6 illustrates the working chamber 102 with two intake valves 120a/120b and a single exhaust valve 122 a. Actuator 116a controls an intake valve 120a on one side of the working chamber and an exhaust valve 122 a. The actuator 116b controls an intake valve 120b on the other side of the working chamber 102 and controls an exhaust valve 116 b. Thus, during the selected operating cycle, the exhaust valve 122a is opened regardless of which intake valve is opened, if an exhaust event is desired.

Fig. 7 depicts a different control scheme that also involves the working chamber 102 with two intake valves 120a/120b and a single exhaust valve 122 a. In this exemplary scheme, the actuator 116a controls an intake valve 120a on one side of the working chamber 102 and controls the exhaust valve 122 a. The actuator 116b controls an inlet valve 120b on the other side of the working chamber. In contrast to the control system shown in FIG. 6, actuator 116b also does not control exhaust valve 122 b. Thus, if an exhaust event is desired to occur during the selected duty cycle, actuator 116a must be activated and intake valve 120a must be opened. That is, during a selected working cycle in which combustion and exhaust events will occur in that working chamber 102, the intake valve 120b will not be the only intake valve actuated, but will always be actuated along with the intake valve 120 a. However, intake valve 120a and exhaust valve 122a may be opened during the selected operating cycle while intake valve 120b remains deactivated.

Fig. 8 and 9 depict another type of control scheme involving actuators that can vary the duration and timing of intake valve opening. In other words, in some of the above examples, the actuator can only achieve two states — either deactivating or activating the corresponding intake valve. If the intake valve is actuated, the timing and duration of the opening of the intake valve is fixed during the selected work cycle. However, in other embodiments, the actuator has additional functionality. That is, the actuator is capable of achieving a plurality of cam profiles or valve lift settings, each of which has different valve timing characteristics.

An example of this approach is shown in fig. 8 and 9. Fig. 8 and 9 relate to a working chamber 102 (fig. 9) with a single intake valve 120a, exhaust valve 122a, and actuator 116 a. As seen in fig. 9, the actuator 116a controls all valves in the working chamber 102. To vary the output of the working chamber, the actuator 116a is arranged to selectively adjust the valve lift of the intake valve 120a based on a valve lift adjustment setting or cam profile.

FIG. 8 is a graph 800 indicating valve lift over time.

Curves

802 and 804 represent two valve lift adjustment settings. The actuator 116a is arranged to operate the intake valve 120a based on any of the valve lift adjustment settings. In a number of different embodiments, the actuator 116a can be shifted between the settings on a duty cycle by duty cycle basis. The curve 800 indicates how the duration and degree of opening of the intake valve 120a varies from one setting to the next. That is, for the setting represented by curve 804, the maximum valve lift and amount of time that the intake valve 120a is opened during the selected duty cycle is greater than the setting represented by curve 802. Thus, different settings cause different amounts of air to be delivered to the working chamber 102, which results in different levels of torque output by the working chamber 102. Implementation of the different valve lift adjustment settings may be performed using any suitable technique or valve adjustment mechanism.

As noted above, some of the above valve control systems may be used to help control the tumbling and/or swirling of the gas within the working chamber. The control of the gas flow in the working chamber can be further improved by a specific inlet passage design. A number of different examples of such designs are shown in fig. 10 and 11.

For comparison purposes, FIG. 10 is a top view of the working chamber 1002 and its associated intake passages 1006a/1006b of conventional design. The two intake passages 1006a/1006b connect the two intake valves of the working chamber 102 with the intake manifold 1014, respectively. In this example, the divided intake passages 1006a/1006b are formed by dividing the single intake passage 1004 with the common passage wall 1112. It should be noted that the central axis of each intake passage (

axes

1008a and 1008b) does not intersect the central axis 1010 of the working chamber. (the central axis 1010 may be understood as the line rising from the page)

FIG. 11 illustrates another intake passage design according to certain embodiments of the present invention. In fig. 11, two intake passages 1106a/1106b communicate an intake manifold 1114 with the working chamber 1102 and each with a separate intake valve on the working chamber 1102. The inlet passages 1106a/1106b are splayed, i.e. they do not extend parallel to each other and are connected at an angle to the working chamber 1102. In the illustrated embodiment, the intake passage 1106b for one working chamber 1102 shares an air flow path with the intake passage 1122 for an adjacent working chamber 1120, but in other embodiments the intake passages for adjacent working chambers are completely separate.

The angle at which each intake passage 1106a/1106b communicates with the working chamber 1102 is such that the central axis 1108a/1108b of each intake passage 1106a/1106b intersects (substantially) the central axis 1110 of the working chamber 1102. Due to this design, air delivered using the intake passages 1106a/1106b is delivered directly to the center of the working chamber, thereby potentially reducing the amount of swirl or mixing relative to the arrangement of fig. 10. Such an arrangement, optionally in combination with the valve system illustrated in fig. 1A, 1B, and 2-7, can help improve control of gas movement in the working chamber 1102.

Additional adjustments may be made to the design of the working chamber to further control the delivery of air into the working chamber and/or the flow of gas in the working chamber. In some embodiments, for example, the intake valves of the working chambers (e.g., intake valves 120a/120B of fig. 1A and 1B) have different sizes and/or diameters. That is, their shape, size or design renders the air flow rate through the valves different. The asymmetric delivery of air into the working chamber may help induce swirl in the working chamber, which may be desirable in some situations.

When the intake valves of the working chambers are controlled independently (e.g., as described in fig. 1A, 1B, and 2-7), they may also follow different valve lift curves and/or have different open/close times. These curves and valve open/close times can be mixed and matched as desired to fit available valve control mechanisms. For example, an intake valve may be actuated to achieve a lift profile that causes the valve to open throughout the intake stroke and close shortly after BDC. This lift curve allows for the introduction of the maximum air intake and may be referred to as the normal timing and lift curve. The other intake valve is actuated to achieve either an Early Intake Valve Closing (EIVC) or a Late Intake Valve Closing (LIVC) profile. Both the EIVC and LIVC curves and timings result in reduced air induction compared to the normal lift curve. Using a normal timing versus lift curve will result in the engine operating in an otto cycle, i.e. where the valve timing produces substantially the maximum air intake. Using either the EIVC or LIVC valve timing will produce a smaller air intake and therefore a lower effective compression ratio. This is commonly referred to as operating the engine using the atkinson or Miller (Miller) cycle. The use of different lift curves and timings may help provide additional control over working chamber output, vibration, noise, and fuel efficiency.

The particular scheme involving the use of particular lift profiles and/or valve timings with respect to one or more intake valves in order to produce particular torque levels is referred to herein as a valve control scheme. Thus, there may be a number of different valve control schemes for generating corresponding different levels (e.g., low, moderate, and/or high) of torque from the ignited working chamber. Each valve control scheme involves independently controlling each intake valve in the working chamber such that each intake valve operates using a particular lift profile and/or timing cycle (e.g., otto, evison, etc.). A particular valve control scheme may cause multiple intake valves of a working chamber to be operated using the same or different lift curves and/or timing cycles.

Referring now to fig. 12A-12E, some differences between such a valve control system and a conventional valve control system are described. For comparison purposes, FIG. 12A illustrates a number of different operating phases of the working chamber during the intake and compression strokes of an exemplary Otto (Otto) cycle, which is currently used in many automotive engines. The working chamber includes two intake valves (

intake valves

1202a and 1202b) that are both operated in the same manner based on the normal timing and lift curves, resulting in the engine operating in an otto cycle.

During the intake stroke, the two valves 1202a/1202b are opened. Piston 1206 moves from Top Dead Center (TDC) to Bottom Dead Center (BDC). The valve lifts to its maximum point approximately 40 before the piston 1206 reaches BDC. Once the piston 1206 reaches BDC, the compression stroke begins. The piston then moves back toward Top Dead Center (TDC). Approximately 40 deg. after BDC, these intake valves are closed.

During the atkinson cycle, the intake valves may be closed early or late. The former is known as Early Intake Valve Closing (EIVC). An example of the operation of an EIVC valve is shown in FIG. 12B. In fig. 12B, the two intake valves 1202a/1202B are operated according to an EIVC atkinson cycle. The intake valves 1202a/1202b are closed at the end of the intake stroke by the time the piston 1206 reaches BDC. This is much earlier than the otto cycle shown in fig. 12A, in which the intake valves close 40 ° later. Thus, the intake valves are closed early and remain open for a shorter period of time than in the otto cycle, resulting in less air in the working chamber and lower torque output.

Fig. 12C illustrates an alternative atkinson cycle in which both intake valves are closed late with respect to the standard otto cycle. This approach is known as Late Intake Valve Closing (LIVC). An exemplary LIVC valve control system is illustrated in fig. 12C. As shown, in the middle of the compression stroke, the intake valves 1202a/1202b are closed approximately 90 ° after BDC. In contrast, in the exemplary otto cycle, the intake valves close 40 ° after BDC. This results in a relatively small amount of air being delivered to the working chamber because more air delivered to the working chamber during the intake phase is pushed out of the working chamber during the compression stroke.

Because the air delivered to the working chamber from the intake manifold in the atkinson cycle is reduced relative to the otto cycle, less torque output is produced by firing the working chamber. However, the atkinson cycle is generally more fuel efficient than the otto cycle, as a larger portion of the combustion energy may be converted into useful torque. A working chamber operating in an atkinson cycle may have the working chamber operating at or near its minimum BSFC operating point.

In the example shown in fig. 12A-12C above, two intake valves are simultaneously enabled based on the same cycle. 12D-12E contemplate implementations in which multiple independently controlled intake valves are opened and closed based on different cycles. The intake valves described in the embodiments may be controlled or actuated using any of the techniques described above (e.g., as described in connection with fig. 1A, 1B, and 2-11).

In fig. 12D, the inlet valve 1202b is operated using the EIVC atkinson cycle. The otto cycle is used to operate the intake valve 1202 a. Thus, as shown, intake valve 1202a closes approximately 40 ° after BDC when piston 1206 is early in the compression stroke. However, when the piston is at BDC, the intake valve 1202b closes earlier, i.e., approximately at the end of the intake stroke.

Fig. 12E shows a system in which the intake valve 1202a is operated using the otto cycle and the intake valve 1202b is operated using the LIVC atkinson cycle. Thus, during the compression stroke, intake valve 1202b closes later than intake valve 1202a, i.e., approximately 90 ° after BDC, rather than about 40 ° after BDC.

Using different cycles to operate the intake valve provides a variety of potential advantages. For example, it provides another means of controlling flow within the working chamber. For example, in fig. 12D, air enters the working chamber 1206 asymmetrically. That is, during the intake phase, air passing through one intake valve (intake valve 1202a) is longer than the other intake valve. This may have a desirable effect on the gas operation in the working chamber, for example may cause increased swirl. In fig. 12E, during the compression stroke, air is pushed out of one intake valve (e.g., intake valve 1202b) for a longer period of time than the other intake valve. Such asymmetric air flow may advantageously increase combustion intake motion (i.e., swirl and tumble), thereby improving combustion characteristics.

In some approaches, the intake valves are offset, i.e., they are staged relative to each other. An example of this approach is shown in fig. 12F. The

intake valves

1202a and 1202b operate based on the same otto cycle, but with offset opening and closing times. That is, the intake valve 1202a opens earlier and closes earlier than the intake valve 1202 b. This system functions substantially similar to the system shown in fig. 12E. Air leaves the working chamber in an asymmetric manner, which may affect the swirl in the working chamber. The amount of deviation can vary widely as desired for a particular application.

An additional advantage of using different cycles to independently operate the inlet valves of a working chamber is that a high degree of control over the torque output of that working chamber can be provided depending on how the valves are operated. Referring next to fig. 13A and 13B, a number of different exemplary valve control schemes are described. That is, the graphs illustrated in fig. 13A and 13B indicate how the intake valve is operated in different ways to produce different levels of torque. In some embodiments, the valve control schemes illustrated in fig. 13A and 13B use the systems illustrated in fig. 12D and 12E, respectively.

Fig. 13A depicts a working chamber valve control system in which there are two intake valves that are independently controlled, for example, by different actuators or cams. The valve control system may have any of the features of the systems described in connection with fig. 2-7 and/or fig. 12D. During a selected operating cycle, the intake valve 1202a can be deactivated or actuated using the otto cycle (hereinafter referred to as a "normal valve"). During this selected duty cycle, the intake valve 1202b can also be deactivated or actuated using an Electrohessian (EIVC) cycle (hereinafter referred to as an "EIVC valve"). Thus, four different valve control schemes are possible for the conventional valve and the EIVC valve, which will produce four different results 1302/1304/1306/1308, which are shown in the graph 1300 of FIG. 13A.

In results 1302, 1304, and 1306, the working chamber is fired during the selected working cycle and the level of torque output produced by the firing is dependent upon the valve control scheme. The result 1302 in the graph indicates that the highest working chamber torque output can be achieved if both intake valves are actuated. This also produced a moderate amount of swirl. If the EIVC valve is deactivated and the normal valve is actuated, a next higher level of working chamber output may be generated (result 1306). When the EIVC valve is enabled and the normal valve is disabled, the next highest level working chamber output (i.e., lower output than results 1302 and 1306) is generated (result 1304). This is because the EIVC operation limits the amount of air delivered to the working chamber. In results 1304 and 1306, a higher amount of swirl may be generated (i.e., higher than in result 1302) because activating only one valve promotes flow and mixing of gas in the working chamber. Additionally, both intake valves may be deactivated, meaning that no combustion occurs and no torque output is produced during the selected duty cycle, as indicated by the result 1308 in the graph of FIG. 13A.

Fig. 13B includes a graph 1350 of similar construction, but in this figure the intake valve 1202B can be deactivated or operated by using an atkinson (LIVC) cycle (hereinafter referred to as a LIVC valve). The valve 1202a can be deactivated or operated based on the otto cycle (hereinafter referred to as a normal valve). Thus, for a selected working cycle, four different valve control schemes are possible as well: 1) the LIVC valve is actuated, the normal valve is actuated, a combustion event occurs; 2) the LIVC valve is deactivated, the normal valve is actuated, a combustion event occurs; 3) the LIVC valve is actuated, the normal valve is deactivated, and a combustion event occurs; 4) the LIVC valve is deactivated, the normal valve is deactivated, and no combustion event occurs. The results for each valve control scheme are shown in fig. 13B. The valve control system used to implement any of the valve control schemes of fig. 13B may have any of the features of the systems described in connection with fig. 2-7 and/or fig. 12E.

The results shown in graph 1350 are very different from those in graph 1300 of fig. 13A. Specifically, when the normal valve is actuated and the LIVC valve is deactivated, the highest working chamber torque output is achieved (result 1356). If both valves are actuated, a lower, moderate level of working chamber output is achieved (result 1352). This is because when both valves are actuated, some of the air delivered through both valves is pushed out of the working chamber due to the delayed closing of the LIVC valve during the compression stroke. If the normal valve is disabled and the LIVC valve is enabled, then a low level studio output is also achieved (i.e., less than the output in result 1352) (result 1354). In result 1358, both intake valves are deactivated and no torque output is generated.

As discussed previously, results 1354 and 1356 involved a higher amount of swirl than result 1352 because the air was delivered asymmetrically to the working chamber. Additionally, both the LIVC valve and the normal valve may also be deactivated (result 1358), i.e., skipping over the working chamber.

The graphs illustrated in fig. 13A and 13B indicate that the use of independently controlled intake valves and different cycles for different valves allows for increased flexibility in the operation of the working chamber. That is, the working chamber is capable of achieving three or four different levels of torque output. Additionally, the working chamber can selectively use the atkinson cycle on a single valve to produce a lower level of torque output in a more fuel efficient manner than some other techniques (e.g., reducing torque output by adjusting spark timing, throttle, etc.).

It should be appreciated that it is not necessary that all working chambers in an engine have the same valve control system. Rather, the working chambers may be divided into two or more different groups, each having a different capacity. For example, one or more working chambers may be capable of only two modes (i.e., deactivated or firing upon actuation of all intake valves) or only one mode (i.e., firing without skipping during each engine cycle). However, other working chambers may have a plurality of independently controlled intake valves as described above in connection with FIGS. 1A, 1B, 2-11, 12A-12F and 13A-13B. Such a hybrid group of working chambers still allows for greater flexibility and control over conventional engines and helps to reduce hardware costs and complexity over engines in which each working chamber is capable of multiple torque outputs.

Fig. 14A-14H depict various exemplary studio arrangements. Each of these maps includes a chart having a plurality of cells, and an index relating to power level and cylinder number. Each chart indicates the different levels of power (i.e., torque output levels) that can be achieved by each cylinder (identified by the numbers 1-4) in the exemplary four-cylinder engine. That is, if a cylinder has a cell associated with filling power level 1, this means that the cylinder can be fired to produce a high torque output (e.g., CTF 1.0 or 100% maximum allowable output). If a cylinder has a cell associated with filling power level 2, this means that the cylinder can be fired to produce a low or partial torque output (e.g., CTF 0.7 or 70% maximum allowable output). If a cylinder has a cell associated with filling out power level 3, this means that the cylinder can be deactivated (and therefore not produce torque output during the selected work cycle).

In the illustrated embodiment, only three power levels are available, however in other embodiments at least some of the cylinders may be capable of producing more than three power levels, such as shown in fig. 13A-13B. Each of the graphs in fig. 14A-14H indicates different arrangements and combinations of working chamber/valve systems having different capabilities. The cylinders described in the graphs are arranged to generate different levels of power using any of the valve control systems, operations, and features described herein (e.g., discussed in connection with fig. 1A, 1B, 2-11, 12A-12F, and 13A-13B).

Each graph is also associated with a fuel efficiency value. Each fuel efficiency value is based on simulations performed by the inventors. This value indicates the estimated fuel efficiency gain with this configuration relative to a conventional four cylinder engine (e.g., without any ability to deactivate cylinders). It should be appreciated that the fuel efficiency values associated with each of the graphs in fig. 14A-14H are preliminary, based on experimental simulations, and may vary for different engine designs and applications.

For comparison purposes, FIG. 14A is a chart indicating a cylinder configuration in which all cylinders are only capable of two power levels, i.e., each cylinder can be skipped or fired to produce a single level of torque output. Such a configuration may be used in a skip fire engine control system. In this design, both intake valves are actuated during any firing event. The amount of air intake associated with ignition may be adjusted by a cam phaser that controls the opening and closing time of the valve and a throttle that controls MAP for all cylinders. These control systems do not allow for large, rapid adjustments to the output of the isolated working chambers. While the output of the working chamber can be reduced by retarding the spark timing, it is generally desirable to avoid this control method because it is less fuel efficient. The cylinder configuration shown in FIG. 14A has moderate fuel efficiency because ignition under such conditions helps reduce pumping losses in the working chamber and in some cases can ignite the cylinder near optimum fuel efficiency.

FIG. 14B illustrates a configuration of a conventional engine with cylinder deactivation. Both cylinders are fired, i.e., cannot be deactivated, during each engine cycle. During the selected operating cycle, two other cylinders may be fired to produce a single level of torque output, or deactivated. Since such engines cannot skip every cylinder, their fuel efficiency may be slightly less than the configuration shown in fig. 14A. However, less hardware may be required to support such a system relative to a single-stage skip fire engine design for all cylinders (e.g., as shown in fig. 14A).

FIG. 14C depicts a configuration in which three output levels per cylinder can be achieved: deactivated (no torque output) and fired at two other different power levels. Such a configuration may be achieved by using any of the valve control systems described in the present application (e.g., independently controlling the intake valves for each cylinder, operating the intake valves based on otto and atkinson cycles, etc.). Such an approach may provide significant gains in fuel efficiency. However, additional hardware and valve control related features may also be required for each cylinder.

FIG. 14D represents a simpler approach in which two cylinders are able to achieve the three power levels labeled in FIG. 14C. However, the remaining two cylinders are non-deactivatable and fire at a single power level during each engine cycle. Accordingly,

cylinders

2 and 3 may require little or no additional hardware relative to cylinders in a conventional non-skip fire engine.

In some embodiments, the cylinders 1-4 labeled in FIG. 14D are arranged to utilize space in the engine most efficiently. An example of such an arrangement is shown in fig. 15. FIG. 15 is a top view of a bank or row of cylinders 1-4 in an engine 1500.

Cylinders

1 and 4 are positioned at both ends of the bank and

cylinders

2 and 3 are located in the middle of the bank.

Fig. 15 illustrates an example in which cylinders capable of more output levels/capable of deactivation are positioned at both ends of a group of cylinders, and cylinders with fewer output levels and/or that cannot be deactivated are positioned in the middle. This allows additional hardware to be more easily attached to the cylinders at both ends of the bank; the cylinders with less hardware requirements are positioned in the middle of the bank where there is less space and each cylinder is bounded on either side by another cylinder. The illustrated embodiment includes four cylinders, but it should be understood that a similar arrangement may be used for groups/banks having more or fewer cylinders (e.g., banks having three, five, or more cylinders). In other words, in a number of different implementations, the outermost cylinders (e.g., one or more cylinders at or near both ends of the bank) are capable of achieving a greater number of output levels, and the inner cylinders (e.g., one or more cylinders closer to the middle of the bank and/or surrounded on both sides by other cylinders) have a lesser number of output levels. In engines having two or more banks, each bank may have the same arrangement as shown in fig. 15.

Fig. 14E represents a configuration that is a modification of the configuration shown in fig. 14D and/or fig. 15. In fig. 14E, just as in fig. 14D,

cylinders

1 and 4 are able to achieve three output levels. However,

cylinders

2 and 3 are capable of achieving two output levels (i.e., they may be skipped or fired at a single torque output level). The configuration illustrated in FIG. 14E may also be arranged as shown in FIG. 15, as the innermost cylinders (cylinders 2 and 3) may require less hardware and have fewer associated output levels than the outermost cylinders (cylinders 1 and 4).

In fig. 14F, each cylinder has two output levels, but the types of output levels can be different. In this example configuration,

cylinders

1 and 4 have two output levels — they can be fired to produce a single torque output level and can also be deactivated during selected operating cycles.

Cylinders

2 and 3 cannot be deactivated, but can fire at two different output levels. The configuration illustrated in fig. 14F may require less hardware relative to a configuration in which each cylinder is capable of producing three or more output levels. Preliminary tests also indicate that such a configuration may be quite fuel efficient even compared to a single-stage skip fire engine system (as illustrated in fig. 14A).

FIG. 14G illustrates a configuration in which two of the cylinders (cylinders 1 and 4) have three output levels (i.e., deactivated and firing at two different torque output levels). The other two cylinders (cylinders 2 and 3) cannot be deactivated but can be fired to produce two different torque output levels. The configuration depicted in fig. 14G may also be arranged as shown in fig. 15. That is,

cylinders

1 and 4 with a greater number of output levels are placed at both ends of the bank/group, while cylinders with a lesser number of output levels (cylinders 2 and 3) are positioned in the middle or inner portion of the bank/group. As previously discussed, in various embodiments,

cylinders

1 and 4 require more hardware to support additional output levels, and the outer end of the bank/group provides more space for such hardware to install.

FIG. 14H represents a variation in which all cylinders cannot be deactivated or skipped. However, each cylinder can be fired to produce two different levels of torque output. In various implementations, this configuration may have less NVH relative to conventional skip fire engine control systems and may require less hardware relative to systems in which cylinders are capable of more output levels.

Any of the valve control systems described in this application may be used to implement the embodiments shown in fig. 14A-14H. That is, the various embodiments illustrated in fig. 14A-14H involve one or more cylinders that may be deactivated and/or fired to produce levels of torque output. Such multi-level torque output may be achieved in a variety of ways. For example, in some embodiments, each cylinder includes two intake valves, where each intake valve is controlled by a different actuator (e.g., as described in fig. 2-7). To produce a high torque output, air is passed through both intake valves during a selected duty cycle. To produce a low torque output, air is pushed out of the cylinder through only one intake valve or through the LIVC valve during a selected duty cycle. As illustrated in fig. 2-7, control of one or more exhaust valves may be accomplished by one or more actuators. In some approaches, the cylinder is configured with a single intake valve in which valve lift is adjustable such that the cylinder can be fired to produce multiple different torque output levels (e.g., as discussed in connection with fig. 8 and 9). The configuration illustrated in fig. 14A-14H may also be used in an engine system having any of the above-described valve passage arrangements (e.g., as described in connection with fig. 10 and 11). In some designs, each cylinder capable of multi-level torque output uses a different cycle to operate a different intake valve (e.g., as discussed in connection with FIGS. 12A-12E and 13A-13B). That is, the different levels of torque output described in the graphs of FIGS. 14A-14H may be generated using the techniques described in the graphs of FIGS. 13A and 13B (e.g., actuating the EIVC/LIVC valve and the normal valve to generate a particular torque output, and deactivating one of the valves to generate a different second torque output, etc.).

Multi-stage skip fire engine control system

Various embodiments of the present invention relate to a multi-stage skip fire engine control system. One or more working chambers of the engine can be fired to produce at least two different levels of non-zero torque output. The working chamber output torque may be controlled on a firing opportunity by firing opportunity basis. The total engine torque output may be controlled by firing or skipping cylinders on a firing opportunity by firing opportunity basis. Based on the desired engine torque, the engine control system determines a firing sequence for operating the engine in a skip fire manner. The sequence indicates a series of skips and firings. For each firing, the sequence indicates an associated level of torque output. The working chamber of the engine operates to deliver a desired torque based on the firing sequence. Such a skip fire firing sequence is referred to herein as a multi-stage skip fire firing sequence.

The embodiments of the multi-stage skip fire engine control system described may be used with any of the engines, working chambers, intake passages, and valve control systems described in this application. For example, in various embodiments, the system generates a firing sequence that involves firing one or more working chambers at a plurality of torque output levels. Each of these working chambers may produce such high or low torque outputs by using independently controlled intake and/or exhaust valves, by operating the intake valves of the same working chamber according to different cycles (e.g., otto and atkinson), and/or any of the other features or techniques described in connection with the figures. However, it should be appreciated that the described multi-stage skip fire engine control systems are not limited to such systems and operations, and they may be applied to any engine or working chamber design capable of producing multiple levels of working chamber output. It is particularly applicable to control systems that make firing decisions on a firing opportunity by firing opportunity basis, but is not limited to this type of control system.

Referring next to fig. 16, a multi-stage skip fire engine controller 1630 will be described in accordance with a specific embodiment of the present invention. The engine controller 1630 includes a firing fraction calculator 1602, a spark timing determination module 1606, a firing control unit 1610, a powertrain parameter adjustment module 1608, and an engine diagnostic module 1650. The engine controller 1630 is arranged to operate the engine in a skip fire manner.

An engine controller 1630 receives an input signal 1614 representing a desired engine output, as well as a variety of different vehicle operating parameters, such as engine speed 1632 and transmission gear 1634. Input signal 1614 may be processed as a request for a desired engine output or torque. Signal 1614 may be received from or derived from an accelerator pedal position sensor (APP) or other suitable source, such as a cruise control, a torque computer, etc. An optional preprocessor may alter the accelerator pedal signal prior to providing it to the engine controller 1630. However, it should be understood that in other embodiments, the accelerator pedal position sensor may be in direct communication with the engine controller 1630.

Firing fraction calculator 1602 receives input signal 1614 (and when other suitable sources are present) and engine speed 1632 and is arranged to determine a firing fraction that will be suitable for delivering the desired output. In various embodiments, the firing fraction is any data indicative of or representative of the ratio of the number of firings to the number of firing opportunities (i.e., number of firings plus number of hops).

In some implementations, the firing fraction calculator 1602 initially generates an effective firing fraction. In various embodiments, the Effective Firing Fraction (EFF) is the product of the firing fraction and a weighted average normalized reference cylinder air charge for the firing event. (accordingly, in such embodiments, the effective firing fraction (as opposed to firing fraction) may not clearly indicate the ratio of the number of firings to the number of firing opportunities). In various embodiments, the normalized reference cylinder intake air quantity or cylinder torque fraction has at least two potentially distinct non-zero values, each associated with a cylinder bank. Mathematically, the Engine Torque Fraction (ETF) may be expressed in relation to the Effective Firing Fraction (EFF) as

ETF＝EFF*CTF^act _H(equation 5a)

Wherein the CTF^act _HIs the actual intake air amount in the cylinder bank at the highest intake air amount level. For a system with two intake air amount levels, the high level torque intake air amount may be referred to as the full intake air amount, and the low level torque intake air amount may be referred to as the partial intake air amount. In the various examples described above in this application, the amount of torque produced by firing the working chambers is characterized by a Cylinder Torque Fraction (CTF) that gives an indication of the working chamber output relative to a reference value. For example, these CTF values may be relative to the maximum possible output torque produced by the working chamber at the reference atmospheric pressure and temperature, i.e., 100kPa and 0 ℃, and appropriate valve and spark timing to open the throttle. Of course, other ranges and reference values may be used. In this application, CTF is generally a value between 0 and 1.0, although it may be greater than 1.0 in some cases, such as at low atmospheric temperatures and/or operating below sea level or in a supercharged engine. For some embodiments described in this application, the full intake air amount relates to a CTF value of 1.0, and the partial intake air amount relates to a CTF value of 0.7. For clarity, these values will be used in the following description of the invention, but it should be understood that these values will vary depending on the exact engine design and engine operating conditions. It will be appreciated that the actual CTF delivered by the studio may be adjusted according to these parameter values.

In some embodiments, the firing fraction calculator 1602 is arranged to determine one or more combinations of horizontal firing fractions and cylinder torque levels (e.g., as seen in equation 2) that will be suitable for delivering a desired output. These combinations may also be expressed as Effective Firing Fractions (EFF) 1611. In some designs, the Engine Torque Fraction (ETF) may be expressed as the product of EFF and the adjustment factor α:

ETF＝EFF*CTF^act _H＝EFF*CTF^R _Hα (equation 5b)

Wherein C isTF^R _HIs the reference cylinder torque fraction associated with the cylinder bank having the highest cylinder intake air amount. As described above, CTF in the description provided herein^R _HIs assumed to be 1, but this is not required. The adjustment factor a varies depending on engine parameter settings such as spark timing and throttle and cam phaser positions.

The firing fraction calculator 1602 can generate firing fractions in a variety of ways depending on the needs of a particular application. For example, in some implementations, the effective firing fraction is selected from a predefined library and/or look-up table of effective firing fractions. A number of different implementations involve determining effective firing fractions using a lookup table, based on one or more engine parameters (e.g., gear, engine speed, etc.), fuel consumption, maximum allowable CTF, and/or NVH associated with each effective firing fraction. These and other approaches are described in more detail below.

Once the calculator 1602 determines the effective firing fraction, the fraction is communicated to a firing timing determination module 1606. Based on the received effective firing fraction, the spark timing determination module 1606 is arranged to issue a series of spark commands that cause the engine to deliver the percentage number of firings and deliver the requisite level of spark output torque to produce the desired engine output. This sequence can be generated in a variety of ways, for example using a sigma delta converter or by using one or more look-up tables or using a state machine. The series of firing commands (sometimes referred to as the drive pulse signal 1616) output by the spark timing determination module 1606 are delivered to the firing control unit 1610, which directs the actual firing through the firing signal 1619 directed to the engine working chambers 1612.

The series of firing commands issued by the spark timing determination module 1606 indicate a combination of skip and fire and a torque level associated with the fire. In various embodiments, the sequence indicates a particular torque output level for each firing, the torque output level being selected from two or more possible torque output levels. The sequence may take any suitable form. For example, in some embodiments, the sequence is made up of a plurality of values, e.g., 0,0.7, 1. This example indicates that during the next four firing occasions, the associated working chamber should be skipped, fired (at a lower level of working chamber output, e.g., 70% of reference cylinder torque output, etc.) and fired (at a higher level of working chamber output, e.g., 100% of reference cylinder torque output, etc.). The firing sequence that indicates skip and fire with multiple levels of working chamber output is referred to herein as a multi-stage skip fire firing sequence.

The spark timing determination module 1606 can determine the spark decision or spark sequence in a variety of ways. For example, in various implementations, the spark timing determination module 1606 searches one or more lookup tables to determine a plurality of horizontal spark sequences. Suitable multiple horizontal firing sequences may be arranged to maximize fuel economy while achieving acceptable NVH characteristics. Factors that affect NVH may include transmission gear, engine speed, cylinder intake air amount, and/or other engine parameters. Based on the effective firing fraction, fuel economy, NVH considerations, and/or one or more of the above, module 1606 selects a multi-level firing sequence from a plurality of firing sequence options. In other implementations, module 1606 uses a sigma delta converter or algorithm to determine the appropriate firing sequence. Any suitable algorithm or method may be used to generate a firing sequence that will deliver the desired engine torque. Various techniques for determining the firing sequence are described below in connection with fig. 17-22.

In the illustrated embodiment shown in fig. 16, a powertrain parameter adjustment module 1608 is provided in cooperation with the spark timing determination module 1606. The powertrain parameter adjustment module 1608 directs the engine working chambers 1612 to appropriately set selected powertrain parameters to ensure that the actual engine output is substantially equal to the requested engine output. For example, under some conditions, the output produced by each firing of the working chamber must be adjusted in order to deliver the desired engine torque. The powertrain parameter adjustment module 1608 is responsible for setting any suitable engine setting (e.g., charge, spark timing, cam timing, valve control, exhaust gas recirculation, throttle, etc.) to help ensure that the actual engine output matches the requested engine output. The engine output is therefore not limited to operating at discrete levels only, but can be adjusted in a continuous, analog manner by adjusting engine settings in a number of different implementations. Mathematically, in some approaches, this may be expressed as including a multiplicative factor in the output of each cylinder bank. Equation 2 can thus be modified and combined with equation 5 such that

ETF＝α*CTF^R _H*EFF＝α₁*CTF^R ₁*FF₁+α₂*CTF^R ₂*FF₂+...+α_n*CTF^R _n*FF_n(equation 6)

Wherein alpha is₁、α₂And alpha_nRepresents an adjustment factor in cylinder load associated with each cylinder group, and CTF^R ₁、CTF^R ₂And CTF^R _nRepresenting a reference cylinder torque fraction for each cylinder group. It should be appreciated that some engine settings (e.g., throttle position) affect adjustments to all cylinder banks, while some settings (e.g., spark timing and/or injected fuel mass) may be adjusted on a bank-by-bank or even cylinder-by-cylinder basis. In a number of different implementations, each different cylinder bank will have a different spark timing and injected fuel mass. The spark timing for each group may be adjusted to provide the best fuel efficiency for that group, and the injected fuel mass may be adjusted to achieve substantially stoichiometric air-fuel ratio for all groups. In this case, the amount of fuel injected will be approximately proportional to the cylinder torque produced.

The engine controller 1630 also includes an engine diagnostic module 1650. The engine diagnostic module 1630 is arranged to detect any engine problem (e.g., knock, misfire, etc.) in the engine. Any known technique, sensor or detection process may be used to detect these problems. In various embodiments, if a problem is detected, the engine diagnostic module 1650 commands the ignition control unit 1610 to perform operations to reduce the likelihood that the problem will occur in the future. In various embodiments, a multi-stage skip fire firing sequence is generated to address this potential problem. A number of exemplary operations that may be performed by the engine diagnostic unit 1650 are described later in this application, for example, in connection with fig. 24 and 26.

It should be appreciated that the engine controller 1630 is not limited to the particular arrangement shown in FIG. 16. One or more of the illustrated modules may be integrated together. Alternatively, the features of a particular module may instead be distributed across multiple modules. One or more features from one module/component may (alternatively) be performed by another module/component. The engine controller may also include a number of additional features, modules or operations based on the following patent applications: including U.S. patent nos. 7,954,474, 7,886,715, 7,849,835, 7,577,511, 8,099,224, 8,131,445, 8,131,447, and 8,616,181; U.S. patent application nos. 13/774,134, 13/963,686, 13/953,615, 13/953,615, 13/886,107, 13/963,759, 13/963,819, 13/961,701, 13/963,744, 13/843,567, 13/794,157, 13/842,234, 13/654,244, 13/654,248, 14/638,908, 14/799,389, 14/207,109, and 14/206,918; and U.S. provisional patent application nos. 61/080,192, 61/104,222, and 61/640,646, each of which is incorporated herein by reference for all purposes. Any of the features, modules, and operations described in the above patent documents may be added to the illustrated engine controller 1630. In various alternative implementations, the functional blocks may be algorithmically implemented using a microprocessor, ECU or other computing device, using analog or digital components, using programmable logic, using combinations of the foregoing, and/or in any other suitable manner.

Referring next to fig. 17, a method for determining a multiple stage skip fire firing sequence in accordance with a specific embodiment of the present invention will be explained. The method may be performed by the engine controller 1630 illustrated in fig. 16.

Initially, at step 1705, the engine controller 1630 determines a desired engine torque based on the input signal 1614 (fig. 16), current engine operating speed, transmission gear, and/or other engine parameters. Input signal 1614 is derived from any suitable sensor or sensors or operating parameters, including, for example, an accelerator pedal position sensor.

At step 1710, the firing fraction calculator 1602 determines an effective firing fraction suitable for delivering the desired torque. In various embodiments, as previously discussed, the effective firing fraction includes both the firing fraction of each cylinder group and the associated torque level of the cylinder group. The determination of the effective firing fraction may be based on any suitable engine parameter, such as gear, engine speed, etc., as well as other engine characteristics such as NVH and fuel efficiency. In some embodiments, the effective firing fraction is selected from a set of predetermined effective firing fractions that are determined to be fuel efficient and/or have acceptable NVH characteristics for a given engine parameter. The effective firing fraction may be generated or selected using any suitable mechanism, such as one or more lookup tables as described in connection with fig. 18 of the present application. One approach for determining a suitable effective firing fraction is illustrated in fig. 18. Fig. 18 illustrates an exemplary lookup table 1800 that includes an index of engine speed and firing fraction (EFF). This table is associated with a particular gear, i.e. there may be other tables for other gears. Alternatively, in another version of the illustrated table, the gear is an additional index to the table. For each effective firing fraction and engine speed, the table indicates the maximum allowable high level of working chamber torque output that still provides acceptable NVH performance. Each effective firing fraction is based on a combination of the firing fraction associated with each firing level and the output at each level. For the case of a multi-stage skip fire engine with two cylinder banks having different torque levels, the Effective Firing Fraction (EFF) may be expressed as the Firing Fraction (FF), and the ratio of the high level number of firings to the total number of firings is expressed as HLF (high). The FF and HLF values associated with these different effective firing fractions are shown in fig. 19.

This maximum allowable working chamber output value reflects the fact that NVH generally tends to increase at higher levels of working chamber output. Thus, for any given engine speed and effective firing fraction, it is desirable to ensure that the working chamber output does not exceed a certain level, thereby keeping NVH at an acceptable level. In various embodiments, the firing fraction calculator 1602 searches through the table to find one or more effective firing fractions that are suitable for delivering the desired torque and that also meet the working chamber output requirements in the table.

To help clarify how the table may be used, an example will be described. In this example, the desired engine torque fraction is 0.2 and the engine speed is 1300 RPM. If the reference torque value associated with the high level firing cylinder bank is a maximum torque value, the effective firing fraction must equal or exceed the engine torque fraction in order to produce the desired torque. Thus, in this example, only an EFF value of 0.2 or greater can produce the requested torque output. Table 1800 in FIG. 18 lists an array of possible EFF values greater than 0.2 in column 1802.

The firing fraction calculator may search through the rows of column 1802 for engine speed for 1300RPM to find an appropriate effective firing fraction that provides the best fuel efficiency and acceptable NVH while delivering the requested engine torque.

For example, consider an effective firing fraction of 0.57 when the engine load (engine torque fraction) is 0.2. Examination of the table 1800 reveals that the torque levels associated with high torque firings (CTF of equations 5a and 5b)^act _H) A CTF (entry 1804) of less than 0.14 is necessary to obtain acceptable NVH performance. However, it will only produce an ETF of 0.57 x 0.14 to 0.08, which is well below the required torque level. Thus, in this case, the use of an EFF of 0.57 would not be precluded because it would not be able to meet both the NVH and torque requirements. In various embodiments, the firing fraction calculator 1602 searches through the rows of the table 1800 until a suitable effective firing fraction is found. E.g. required to deliver the desired torque at an effective firing fraction of 0.70The studio output (CTF) is 0.2/0.70 is 0.29. Examination of the table shown in fig. 19 indicates that an EFF of 0.7 corresponds to FF ═ 1 and HLF ═ 0. Thus, all of these firings are low level firings corresponding to a low level reference CTF of 0.7, and all of these firing occasions will involve firings and there will be no skip in this case.

The high level of working chamber output required to deliver the desired torque is 0.29, which is below the high level working chamber output threshold depicted in table 1800 (0.58, entry 1806), and therefore the effective firing fraction can be considered for operating the engine. The firing fraction calculator 1602 continues to search through the rows and may determine that valid firing fractions meet the maximum working chamber output requirement of the table. Each such effective firing fraction is referred to herein as a candidate effective firing fraction.

The firing fraction calculator 1602 then selects one of the candidate effective firing fractions. This selection may be made in any suitable manner. For example, in some implementations, the firing fraction calculator 1602 searches another table or module that indicates the relative fuel consumption or efficiency for each of a plurality of effective firing fractions. Based on this fuel consumption information, the calculator selects one of the candidate valid ignition scores. That is, the calculator 1602 selects the candidate valid ignition score that has the highest or highest fuel efficiency. The selected effective firing fraction exhibits a torque output according to the high and low levels of firing necessary to deliver the desired engine output by adjusting engine parameters to achieve the desired adjustment factor (as described with respect to equation 5). In various implementations, the selected effective firing fraction is generally selected based on having maximized fuel economy while operating with acceptable NVH performance. Once the effective firing fraction has been selected or generated, it is communicated to the spark timing determination module 1606.

Thereafter, at step 1715 of FIG. 17, the spark timing determination module 1606 determines a multi-stage skip fire firing sequence. The multi-stage skip fire firing sequence indicates a series of firing decisions (i.e., firing and skipping). For each firing in the sequence, a working chamber torque output level is selected. In various embodiments, this selection is indicated in the sequence.

The multi-stage skip fire firing sequence may be generated in a variety of ways depending on the needs of a particular application. For example, in some implementations, the spark timing determination module 1606 searches one or more lookup tables that indicate a suitable firing sequence based on one or more selected engine parameters, including the preferred firing fraction. Additionally or alternatively, the spark timing determination module 1606 may include a sigma delta converter or circuit that outputs the firing decisions and/or firing sequences. A variety of different example implementations are described below in fig. 19-22.

One specific implementation is shown in fig. 19-20. In this implementation, the spark timing determination module 1606 uses one or more lookup tables to determine features of a multi-stage skip fire firing sequence. An exemplary lookup table is shown in fig. 19. FIG. 19 is a table indicating a Firing Fraction (FF) and a High Level Fraction (HLF) for each of a set of Effective Firing Fractions (EFFs). The Firing Fraction (FF) indicates a ratio of a number of firings to a number of firing opportunities (e.g., firings and skipped) over an interval of a plurality of firing opportunities. The firing fraction does not necessarily exhibit a fixed level of torque output for each firing. The Level Fraction (LF) is any value that helps indicate the ratio of the number of firings to the total number of firings that each produce a particular (e.g., high or low) level torque output. In the illustrated embodiment, a High Level Fraction (HLF) is used that indicates a ratio of a high level of torque output firings to a total number of firings.

In this particular example, firing the working chamber can produce two different levels of working chamber output: a high level of torque output (e.g., 100% of the reference cylinder torque output) and a low level of torque data (e.g., 70% of the reference cylinder torque output). Since two levels of torque output can be produced per firing, if HLF is 1/3, 1/3 of the number of firings produces a high level of torque output and 2/3 of the number of firings produces a low level of torque output over a certain interval. The system and indicators described above may be modified as appropriate to suit different implementations, such as for working chamber torque outputs of more than two levels.

Using the lookup table illustrated in fig. 19, the spark timing determination module 1606 determines characteristics of a multi-stage skip fire firing sequence (e.g., high level fraction and firing fraction) based on the Effective Firing Fraction (EFF) determined in step 1710. Thus, in the example illustrated in fig. 19, if the EFF is 0.57, the firing fraction is 2/3, and the high level fraction is 1/2.

In various embodiments, the spark timing determination module 1606 then generates a multi-stage skip fire firing sequence that meets the determined firing characteristics. That is, to use the example above, if the firing fraction is 2/3 and the high level fraction is 1/2, the spark timing determination module 1606 generates a blended firing sequence that includes a plurality of firing opportunity outcomes over the selected interval. In this interval, 2/3 for the firing decision is firing and 1/3 is skipping. In firing, 1/2 is associated with a high torque output and the remainder is associated with a low torque output. In some embodiments, the firing sequence takes the form of a series of CTF values, e.g., a sequence of 0,1, 0.7,0 may indicate skip, high torque output fire, low torque output fire, and another skip. The firing sequence may be generated using any suitable algorithm, circuit, or mechanism.

One such circuit is shown in fig. 20. Fig. 20 illustrates a sigma delta circuit 2000 that is part of the spark timing determination module 1606. In the illustrated example, the spark timing determination module 1606 inputs the Firing Fraction (FF) and High Level Fraction (HLF) obtained from the table of fig. 19 into the sigma delta circuit 2000 to generate the appropriate multi-stage skip fire firing sequence. The circuit 2000 may be implemented in hardware or software (e.g., as part of a software module or in executable computer code). In the figure, the symbol 1/z indicates delay.

The top portion of circuit 2000 effectively implements a first order sigma delta algorithm. In this circuit 2000, an ignition fraction (FF) is provided at input 2002. At subtractor 2004, firing fraction 2002 and feedback 2006 are added. The sum 2008 is communicated to the accumulator 2010. The accumulator 2010 adds the sum 2008 to the feedback 2014 to produce a sum 2012. The sum 2012 is fed back to the accumulator 2010 as feedback 2014. The sum 2012 is passed to a quantizer 2018 and converted to a binary stream. That is, quantizer 2018 produces firing values 2020, which form a sequence of 0 s and 1 s. Each 0 indicates that the associated working chamber should be skipped. Each 1 indicates that the associated working chamber should be fired. The firing value is converted to a floating point number at converter 2019 to produce a value 2022, which is input as feedback 2006 to subtractor 2004.

The bottom portion of the circuit indicates, for each firing indicated by the value 2020, what level of torque output the firing should produce in order to deliver the desired torque. The value 2022 is passed to a multiplier 2023, which also receives HLF 2001. The multiplier 2023 multiplies the two input values. Thus, if skip is indicated at the value 2022, this causes the output of the multiplier 2023 to be 0. The above multiplication results in a value 2026, which is passed to subtractor 2035. The subtractor 2035 subtracts the feedback 2027 from the value 2026. The resulting value 2037 is transmitted to the accumulator 2028. The accumulator 2028 adds the value 2037 to the feedback 2030. The resulting value 2032 is fed back to the accumulator 2028 as feedback 2030 and is also passed to the quantizer 2040. The quantizer 2040 converts the input to a binary value, i.e., 0 or 1. (for example, if the input value 2032> -1, the output value of the quantizer is 1, otherwise the output value is 0). The resulting high level flag 2042 indicates whether the associated spark (as indicated by spark value 2020) is a spark that should produce a high level torque output. That is, in this example, if the high level flag 2042 is 0, the associated ignition should produce a low level output. If the high level flag 2042 is 1, the associated ignition should produce a high level output. (if firing value 2020 indicates skip, high level flag 2042 will be 0 and not relevant). The high-level tag 2042 is passed to a converter 2044, which converts the value to a floating-point number. The resulting number 2046 is sent as feedback 2027 to subtractor 2035.

The circuit thus provides a multi-stage skip fire firing sequence that can be used to operate the engine. In this example, a firing value 2020 is generated based on a Firing Fraction (FF) (e.g., determined in step 1710 of fig. 17 and/or in the lookup table of fig. 19). If the firing value 2020 is 1, the associated working chamber is fired. For each such firing, the high level flag 2042 may be either 0 or 1, depending on the (high) level score 2001 (e.g., as determined using the lookup table of fig. 19). If the high level flag is 1, the ignition should be one that produces a high level of output. If 0, the ignition should be one that produces a low level output. If firing value 2020 is 0, the associated working chamber should be skipped. Passing this zero value to multiplier 2023 will cause the associated high level flag to also be 0. Over time, the circuit may generate two binary stream values that indicate ignition decision and studio output levels, such as 1-0 (i.e., ignition value 2020 is 0 or 1, high level flag 2042 is 0 or 1), 0-0, 1-0, 0-1, 1-1.

Fig. 21 illustrates another circuit 2100 arranged to generate a multi-stage skip fire firing sequence using, for example, the Effective Firing Fraction (EFF) determined in step 1710 of fig. 17. Such circuits are sometimes referred to as multi-bit or multi-stage sigma-delta. Beginning with input 2102 representing the effective firing fraction, the circuit is arranged to generate output 2130 indicating skip, fire at a high level torque output, or fire at a low level torque output.

In this circuit, input 2102 (which is the EFF determined in step 1710) is passed to subtractor 2104. Feedback 2132 is subtracted from the input 2102. The resulting value 2106 is passed to an accumulator 2107. The accumulator 2107 adds the feedback 2108 to the value 2106. The resulting sum 2110 is fed back to the accumulator 2107 as feedback 2108. The sum 2110 is also delivered to a subtractor 2126 and a subtractor 2112. A value 2124 is defined as 1, which indicates a high level of studio output. The value 2124 is passed to a switch 2122 and a subtractor 2126. Subtractor 2126 subtracts value 2124 from sum 2110 to produce value 2128, which is passed to switch 2122.

The value 2114 is defined in this example as 0.7 and is intended to indicate a low level working chamber output. The value 2114 is delivered to a subtractor 2112 and a switch 2118. Subtractor 2112 subtracts value 2114 from sum 2110 to produce value 2140, which is communicated to switch 2118.

Switch 2118 receives three input values: value 2114, value 2140, and value 2116. Value 2116 indicates the lowest level working chamber output (e.g., no torque-producing skip). Switch 2118 passes either value 2114 or value 2116 as its output value according to value 2140. If value 2140 is less than 0, the output value of switch 2118 is equal to value 2116. If the value 2140 is greater than or equal to 0, the output value of the switch 2118 is the value 2114. The output value 2120 of the switch is passed to switch 2122.

Switch 2122 receives three input values: value 2120, value 2128, and value 2124. The switch passes either value 2120 or value 2124 as an output value depending on value 2128. If sum 2128 is less than 0, the output value of switch 2130 is value 2120. If value 2128 is greater than or equal to 0, the output value of switch 2130 is value 2124. The output value of switch 2122 is passed as feedback 2132 to subtractor 2104.

The output value 2130 of switch 2122 indicates the firing decision, and if the firing decision relates to firing, what the torque output level of the firing is. In the illustrated embodiment, the output value 2130 is 0,1, or 0.7. Thus, based on the input values 2102, the output value 2130 indicates whether the associated working chamber was skipped, fired at a high level of output, or fired at a low level of output during a particular duty cycle. Over time, the circuit 2100 is arranged to generate a series of values (e.g., 0,1, 0.7,0, 1, etc.) that form a multi-stage skip fire firing sequence (e.g., indicating skip, firing at a high level of torque, firing at a low level of torque, skip, firing at a high level of torque, etc.).

It should be noted that in the above example, the multi-stage skip fire firing sequence has a mixture of at least three different levels 0,0.7, and 1. By using these three different levels, many different sequences may produce the same or similar effective firing fractions. The firing fraction calculator 1602 or the firing timing determination module 1606 (fig. 16) can be used to determine which of the multi-stage skip fire sequences produces the best fuel economy while delivering the requested output torque level and acceptable NVH characteristics. Somewhat counterintuitively, it may sometimes be desirable to insert a high torque output spark even when the total engine torque output can be provided by using all of the low output torque pulses, as the use of high output torque pulses may shift the noise and vibration produced by the engine away from resonance or other undesirable frequencies.

Fig. 22 illustrates another approach for determining a multi-stage skip fire firing sequence based on the Effective Firing Fraction (EFF) determined in step 1710 of fig. 17. In this approach, the spark timing determination module 1606 uses one or more lookup tables to select a multi-stage skip fire firing sequence based on the Effective Firing Fraction (EFF) determined in step 1710.

Fig. 22 includes an exemplary lookup table 2200. The lookup table 2200 indicates a plurality of different multi-stage skip fire firing sequences. Each sequence (e.g., each row in the table) involves multiple firing opportunity outcomes and is associated with a different effective firing fraction. In this table, each firing opportunity result is defined as 0 (designated skip), 1 (designated firing at a high torque output level), or 0.7 (designated firing at a low torque output level). Each firing opportunity is associated with a particular cylinder, as indicated by the columns associated with cylinders 1-4 of a 4-cylinder engine.

In this example, the spark timing determination module 1606 uses the table 2200 to determine a multi-stage skip fire firing sequence that will deliver substantially the same amount of engine torque as the effective firing fraction determined in step 1710. For example, if the effective firing fraction is 0.47, then the associated firing sequence is 0.7,0,0.7, 0.47. This means that in consecutive working cycles, a working chamber is fired, skipped, fired, and skipped. Using 0.7 for each firing and the absence of a 1 indicates that all of the fired working chambers are fired to produce a low torque output and not a high torque output.

It should be appreciated that fig. 18-22 illustrate only some ways for determining a multi-stage skip fire firing sequence, and that the above-described techniques may be modified as appropriate to meet the needs of different applications. For example, in some implementations, the effective firing fraction need not be calculated, and/or a sigma delta converter is not required. Various embodiments involve determining a requested torque (e.g., as described in connection with step 1705 of fig. 17) and querying one or more lookup tables to determine the skip fire firing sequence based on the requested torque. In some approaches, the functions of these tables are instead provided by software modules, software code, algorithms, or circuits.

Referring back to fig. 17, at step 1720, the spark timing determination module 1606 passes the skip fire sequence to the firing control unit 1610. The ignition control unit 1610 then assigns ignition decisions to the associated working chambers and operates the working chambers accordingly. That is, as discussed in connection with step 1715, in various embodiments, each firing in the sequence is associated with a range of torque output levels (e.g., high torque output, low torque output). The firing control unit 1610 assigns each firing in the sequence and its associated torque output level to a particular working chamber. The working chambers are fired and operated to produce their associated torque output levels.

For example, if the firing sequence indicates that multiple working chambers are successively skipped, fired at a high torque output, and then fired at a low torque output, the firing control unit 1610 commands the associated working chamber to operate in this manner. In various embodiments, this may involve independently controlling the intake valves of the associated working chambers to produce the various torque output levels indicated in the skip fire firing sequence. The working chambers may be operated to produce different levels of torque output using any of the valve control techniques described herein (e.g., as discussed in connection with fig. 1A, 1B, 2-11, 12A-12F, 13A-13B, 14A-14H, and 15). The working chambers may also have any of the designs or arrangements discussed in this or the above figures. It should be appreciated that in a number of different embodiments where not all working chambers can be fired/skipped or controlled at different torque levels, the control method described in fig. 17-22 may include identifying engine hardware limitations and commanding a working chamber for high/low firing, proper firing/skip.

In various embodiments, determining an effective firing fraction (step 1710), determining a firing sequence, and/or selecting a high or low level torque output for a selected working cycle and working chamber (step 1715) is performed on a firing opportunity by firing opportunity basis. Accordingly, the various operations described above may be performed quickly in response to changes in requested torque or other conditions. In other embodiments, the above operations are performed at a slightly less frequent rate (e.g., every other firing opportunity or every engine cycle).

The operations of method 1700 of FIG. 17 may be performed using any of the systems described in FIGS. 1A, 1B, 2-11, 12A-12F, 13A-13B, 14A-14H, and 15. For example, method 1700 involves generating a firing sequence, each firing in the firing sequence being associated with a particular torque output level. In various embodiments, these torque output levels are the various power levels or torque output levels discussed in conjunction with fig. 13A-13B and 14A-14H. That is, when the firing sequence is implemented at the engine (step 1720 of fig. 17) and the selected working chamber is fired to produce different levels of torque output, any of the valve control mechanisms and/or other systems described in the figures are used to produce these different levels of torque output.

Transitioning between engine torque fraction and effective firing fraction

One challenge in skip fire engine control is managing transitions between different engine output torque levels. Consider the example where the accelerator pedal is depressed slightly to indicate that more torque is desired. This torque increase request can only be achieved by increasing the cylinder load to a level that exceeds that which provides an acceptable level of NVH. Therefore, a different firing fraction and level fraction are selected. However, if the new mode is suddenly used, the resulting change in delivered torque may be too sudden to create a separate NVH problem. Thus, it may be desirable to have a more gradual transition between two effective firing fractions.

Such transitions may be managed using a variety of techniques. For example, spark timing may be adjusted to reduce torque output during the transition. However, using spark timing in this manner is generally not fuel efficient. Another option is to manage the transition using multi-stage skip fire engine control.

One exemplary technique is depicted in fig. 23. Fig. 23 illustrates a method 2300 of managing a transition between first and second effective firing fractions using multi-stage skip fire engine control. Initially, at step 2305, the engine is operated using a particular effective firing fraction. Thereafter, the engine is operated using a second, different preferred firing fraction (step 2310). These different effective firing fractions are generally associated with different engine output torque levels, but in some cases the engine torque may remain unchanged during the effective firing fraction transitions.

Each of these effective firing fractions may involve operating the engine in a skip fire manner. In some cases, there may be a wide variety of firing patterns, while in other cases, there may be a limited number of firing patterns, such as rolling cylinder deactivation (where the cylinders are thus fired and skipped on alternating firing occasions). In some cases, the effective firing fraction may correspond to variable displacement operation, such as where a fixed group of cylinders are deactivated or operated using all of the cylinders. Even if the variable displacement operation by the fixed bank of cylinders is not a skip fire operation (if supported by engine hardware), the skip fire control may be used to transition between fixed displacement levels. In some cases, the effective firing fraction may be zero, such as when coasting. During each operating state in which the engine is operated using a particular firing fraction, the engine may be operated using any of the techniques described in connection with fig. 16-22.

At step 2315, the engine is operated using a multi-stage skip fire firing sequence during the transition between the two effective firing fractions. The multi-stage skip fire firing sequence may be generated in a variety of ways depending on the needs of a particular application. For example, in some implementations, the effective firing fraction is gradually increased to one or more intermediate firing fractions during the transition. A multi-stage skip fire firing sequence is generated based on the one or more intermediate firing fractions and is used to operate the engine during the transition. The rate of change of the effective firing fraction during the transition may be based on any suitable engine parameter, such as absolute manifold pressure. The multi-stage skip fire firing sequence may be generated using any of the techniques described in connection with the figures (e.g., one or more look-up tables, sigma delta converters, etc.). Additionally, various techniques for using skip fire operation during transitions between modes are described in commonly assigned U.S. patent application No. 13/799,389, which is incorporated herein in its entirety for all purposes. Any of the techniques described therein may also be used.

One approach involves storing predetermined multi-stage skip fire firing sequences in a library (e.g., in one or more look-up tables). In various embodiments, each skip fire firing sequence is associated with a particular effective firing fraction. To determine the appropriate multi-level firing sequence to use for the transition, the firing timing determination module 1606 queries the library and selects a sequence from the predetermined sequences. The selected sequence is then used to run the engine during the transition.

Consider the example in which a four-cylinder engine is operated using the following firing sequence, where four working chambers are fired or skipped based on patterns 0.7,0,0.7, 0. That is, these working chambers 1-4 are repeatedly fired, skipped, fired, and skipped, with each firing being a low level output firing (e.g., involving CTF ═ 0.7). Thus the equivalent effective firing fraction is 0.35 for this type of engine operation. The engine then transitions to another type of engine operation where the firing pattern would be 0.7, 0.7. That is, these working chambers will be fired repeatedly and no working chamber will be skipped. Each firing will produce the same low level output (e.g., CTF ═ 0.7). Thus, for this type of engine operation, the effective firing fraction is 0.7. That is, assuming that other engine parameters (such as MAP and spark timing) remain fixed, the engine output torque will double during the transition from the first effective firing fraction (0.35) to the second effective firing fraction (0.7).

In this example, the spark timing determination module 1606 queries one or more lookup tables. Based on the associated effective firing fractions, the one or more lookup tables provide the following transitional multi-stage skip fire firing sequences (underlined below):

0,0.7,0,0.7 (first effective firing fraction)

0，1,0.7,0

0.7,0.7,0,0.7

0.7,0.7,0.7,0.7 (second effective firing fraction)

Next, working chambers 1-4 are operated based on the transition pattern described above as the engine transitions between the two effective firing fractions. Thereby, the engine torque has increased more gradually, thus helping to smooth the transition and improve passenger comfort.

It should be appreciated that the conventional multi-stage skip fire firing sequence used above may be used in a wide variety of engine types. Accordingly, it is not necessary that each working chamber in the engine be capable of being deactivated and/or fired at multiple torque output levels. It is possible that only one or some of these working chambers will have the above-described functions, such as discussed previously in connection with fig. 14A-14H. In the above example, for example, only the first and third cylinders can be deactivated. The second and fourth cylinders are fired during each engine cycle and are capable of regulating working chamber output between a high level and a low level.

In some cases, it may be desirable to change the level fraction during the transition between two effective firing fractions. That is, in an engine control system that allows multiple levels of working chamber torque output to be achieved, it may be useful to vary the frequency at which a particular working chamber output level is used during transitions between effective firing fractions.

Consider the example where the engine is transitioning between two firing fractions. When the engine is operated using the first effective firing fraction, the effective firing fraction is 1/2, and working chambers 1-4 of the engine are operated using a sequence of 1-0-1-0 (e.g., firing at a high level of working chamber torque output, skip). When the engine is operated using the second effective firing fraction, the effective firing fraction is 1, and the engine is operated using a sequence of 1-1-1-1 (i.e., each working chamber is fired at a high level of output). Thus, assuming the other engine parameters remain fixed, the engine torque output doubles during the transition between the two effective firing fractions.

Since the above ignitions all involve producing maximum working chamber output, the ignition fraction for each of the above operating states is equal to the effective ignition fraction (assuming that each ignition involves a CTF of 1.0) and the High Level Fraction (HLF) for both states is 1 (i.e., 100% of the ignitions involve a high level of output). In this example, each of the working chambers is also capable of firing at a low level working chamber torque output (e.g., CTF ═ 0.7). Each effective firing fraction may be characterized by the following values: (X, Y), where X is the firing fraction and Y is HLF, as shown in fig. 19. These two states are therefore characterized as (1/2, 1) and (1, 1).

During the transition between these two different effective firing fractions, it is sometimes desirable to run the engine in a skip fire manner using a different horizontal fraction than that used when the engine is running in one or both of these states. In the context of the above example, during the transition there is a change from (1/2, 1) to (1, 0), i.e. a firing sequence of 0.7-0.7-0.7-0.7. That is, in the firing subset during the transition between these two states, the working chambers fire at a low level output (e.g., CTF ═ 0.7). The effective firing fraction thus transitions from 1/2 to 0.7 to 1. The advantage of using low level ignition during this transition is that the NVH produced by such ignition is low. This is because the firings involve lower cylinder loads and also because there is no skip in the firing pattern.

In the above example, the engine is operated using 1 when operating at a fixed effective firing fraction and a high level fraction of 0 during the transition between these fixed firing fractions. And vice versa. In other words, consider the example where each working chamber can also fire at one of two output levels: a high output level (e.g., CTF ═ 1.0) or a low output level (e.g., CTF ═ 0.7). During the initial effective firing fraction, the engine is operated using (1/2, 0). In the target effective firing fraction, the engine is operated using (1, 0). That is, when operating at a fixed effective firing fraction, the engine operates using a high level fraction of 0 (i.e., the firings each produce a lower level of torque output). However, the transition involves a different high level score. In this example, the engine was run in skip fire fashion using a horizontal fraction of 1(1/2, 1). Thus, the effective firing fraction changes from 0.35 to 0.5 to 0.7.

In other embodiments, the effective firing fraction may be filtered to slow the transition between the initial and final firing fractions. This may be accomplished by filtering the firing fraction, filtering the horizontal fraction, or filtering both quantities. The filtering techniques and time constants for the firing fraction and level fraction may be the same or different depending on the nature of the transition. Methods for filtering and managing transitions are described in U.S. patent application nos. 13/654,244 and 14/857,371, which are incorporated herein by reference in their entirety for all purposes. Any of these methods may be used during this transition. For example, in some embodiments, the EFF is transitioned at a constant rate by transitioning FF monotonically at a constant rate and LF monotonically at an appropriate computational rate. Alternatively, the transition may be first to an intermediate point and then to a final score (e.g., 1/2 to 0.7 to 1), so that LF or FF does not change monotonically. The intermediate value may be determined from a look-up table; for example, a 2D table works well, where one dimension is the start score and the second dimension is the target score. A third dimension may be added, such as the rate of change of engine parameters or accelerator pedal position. Also, in some cases, it may be desirable to maintain a constant effective firing fraction, but vary the firing fraction and level fraction. In this case, FF and LF may transition at constant opposite rates so that their product EFF remains constant.

Knock detection and management

Multiple stage skip fire engine control may be used to help manage knock. Knocking tends to occur more frequently at higher pressures or temperatures, such as when the working chamber is fired with the greatest amount of air and fuel to produce the highest possible torque output. Therefore, under selected conditions, it is desirable to ignite the working chamber at a lower torque output level when knock has been detected.

Referring now to FIG. 24, an example method 2400 for reducing the likelihood of knock in a multi-stage skip fire engine control system is described. Initially, at step 2405, the engine is operated using a multi-stage skip fire firing sequence. That is, the multi-stage skip fire engine controller 1630 receives the torque request and generates a multi-stage skip fire firing sequence to deliver the desired torque. The engine is operated based on the firing sequence. In various embodiments, the engine is operated using any of the multi-stage skip fire operations, mechanisms, and/or systems described herein (e.g., as described in fig. 16 or 17).

In step 2410, the engine diagnostic module 1650 (FIG. 16) detects knock in one or more working chambers of the engine 1612. Any suitable technique or sensor may be used to detect possible knock in the engine. For example, in some implementations, the engine diagnostic module 1650 receives sensor data from one or more knock sensors that detect patterns of vibration generated by the working chambers of the engine 1612. The engine diagnostic module 1650 analyzes the vibration patterns to determine whether knock may have occurred.

In response to detecting (potential) knock in the working chambers of the engine 1612, the engine diagnostic module 1650 requests that the one or more selected working chambers be fired only at one or more lower output levels during the one or more selected working cycles (step 2415). An exemplary multi-stage skip fire engine control system is contemplated in which a particular working chamber may fire at low (e.g., CTF 0.5), medium (CTF 0.7), and high (CTF 1.0) levels. In response to detecting (potential) knock in a particular working chamber, the engine diagnostic module 1650 prevents the working chambers from firing at one or more selected levels (e.g., medium and/or high). In other words, the (high) level fraction may be decreased/changed (from 1 to 0). This limitation may apply to a single working chamber, a subset of working chambers, or all working chambers. But may also be applied to a selected number of duty cycles or to all duty cycles for a predetermined period of time.

In various embodiments, the engine diagnostic module 1650 communicates the above requirements to the spark timing determination module 1606 such that future skip fire sequences take such limitations into account when determining a sequence to deliver requested torque. At step 2420, the engine is operated in a skip fire manner based on the request. That is, the engine is operated as described in step 2405, but only the allowed working chamber output level is used to deliver the requested torque.

Knock tends to occur more frequently when the working chamber is ignited to produce a high torque output (i.e., at higher CTF). This is because the pressure and temperature within the working chamber tend to be significantly higher under such conditions. There are means to reduce the pressure and temperature in the working chamber, for example by adjusting the spark timing. However, such techniques generally tend to be less fuel efficient. By reducing the amount of air intake to limit ignition and thereby reduce the level of torque output, the likelihood of knock may be reduced in a more fuel efficient manner.

Optionally, the engine diagnostic module 1650 includes features for achieving high torque output firing again in response to a high torque request. At step 2425, the engine controller 1630 receives a high torque request, for example, based on data received from the accelerator pedal position sensor. In various embodiments, the high torque request must exceed a predetermined threshold in order for the method to proceed to step 2430.

In step 2430, the engine diagnostic module 1650 causes the engine control system to continue using high output ignition in response to the high torque request. That is, some or all of these limits on high output ignition are eliminated (implemented at step 2415). At step 2435, the engine diagnostic module 1650, the ignition control unit 1610, and/or the powertrain parameter adjustment module 1608 perform one or more suitable operations to reduce the risk of further knock. Any known technique (e.g., spark timing adjustment) may be used to reduce the risk of knock.

Deceleration cylinder interrupt service and start/stop feature

Multi-stage skip fire engine control may also be used in some situations where no working chamber is fired and manifold absolute pressure is raised to atmospheric levels. For example, the driver may remove his or her foot from the accelerator pedal when the vehicle is rolling and/or is about to stop. In such a situation, a number of different engine systems may transition to a mode known as deceleration cylinder interrupt service (DCCO). To conserve fuel in this mode, the cylinders of the engine are deactivated when engine torque is not required. During this period, the intake and exhaust valves are closed and no air is delivered from the intake manifold into the working chambers of the engine.

Another situation is when the start/stop feature is implemented. That is, in some engine systems, when the vehicle has stopped, the engine is not idling but is turned off to conserve fuel. In both of the above situations, since no air is delivered from the intake manifold into the working chamber, the Manifold Absolute Pressure (MAP) is equal to atmospheric pressure. One problem with this is that when the accelerator pedal is depressed again or some other engine controls demand torque, a high MAP may cause the engine to deliver more torque than is required. If no action is taken to mitigate such torque surge, the vehicle and/or engine may suddenly accelerate.

Multi-stage skip fire engine control may be used to solve the above problem. An exemplary method 2500 is illustrated in fig. 25. Initially, at step 2505, the engine is operated using a multi-stage skip fire firing sequence. That is, the multiple stage skip fire engine controller 1630 receives the multiple torque requests and generates multiple stage skip fire firing sequences to deliver the desired torque. The engine is operated based on the firing sequences. In various embodiments, the engine is operated using any of the multi-stage skip fire operations, mechanisms, or systems described herein (e.g., as described in fig. 16 or 17).

In step 2510, the engine controller 1630 (or any suitable module within the controller) detects the presence of one or more conditions. For example, in some embodiments, the controller 1630 detects that the engine has coasting/decelerating, has entered DCCO, and/or has requested torque. In other embodiments, the controller 1630 detects that the engine has stopped using the start/stop feature and/or is requesting torque again.

In response to detecting the one or more conditions, the controller 1630 calls for firing the one or more selected working chambers only at the one or more lower torque output levels during the one or more selected working cycles (step 2515). This requirement can take a wide variety of forms. For example, in some embodiments, controller 1630 prevents any use of one or more higher studio output levels (e.g., CTF ═ 1.0). In other words, the high level score is reduced or maintained at a lower level (e.g., set to 0, 1/2, etc.). The requirements may include any of the operations and features described above in connection with step 2415 of fig. 24, e.g., any number of working chambers or working cycles, etc., may be limited in this manner.

At step 2515, the engine is operated in a multi-stage skip fire manner based on the demand. That is, the engine is operated as described in step 2505, but only the allowed working chamber output level is used to deliver the requested torque. In some embodiments, the request is valid before certain conditions are met or within a predetermined period of time, after which normal multi-stage skip fire engine operation is resumed. Alternatively or additionally, the high level score may be gradually increased over time until normal multi-stage skip fire engine operation is resumed. This gradual increase may be dynamically adjusted based on one or more engine parameters (e.g., manifold absolute pressure). Using a lower high level fraction and/or a lower working chamber torque output level helps mitigate the effects of high MAP.

Alternatively, the engine controller 1630 may have features for achieving high output ignition again in response to a high torque request. At step 2525, engine controller 1630 receives a high torque request, e.g., based on data received from an accelerator pedal position sensor. In various embodiments, the high torque request must exceed a predetermined threshold in order for the method to proceed to step 2530.

At step 2530, in response to the high torque request, the engine controller 1630 causes the ignition control unit 1610 to continue to use high output ignition. That is, some or all of these limitations on high torque output firing are eliminated (implemented at step 2515).

Any of the steps in the method 2500 may be modified as appropriate for different applications. For example, U.S. patent application No. 14/743,581 (hereinafter referred to as the' 581 application and incorporated herein by reference in its entirety for all purposes) describes various techniques for implementing a start-stop feature through skip fire engine control. Any of the features or operations described in the' 581 application may also be included in the method 2500.

Engine diagnostic applications

The use of multi-stage skip fire engine control may also impact the design of the engine diagnostic system. In a variety of different engine diagnostic systems, engine problems are detected based on measured specific engine parameters (e.g., crankshaft acceleration). In various embodiments, such systems take into account the effects of firing that produces different levels of torque output.

Referring to FIG. 26, an exemplary method 2600 for diagnosing an engine problem is described. Initially, at step 2605, the engine diagnostic module 1650 obtains spark information, for example, from the spark timing determination module 1606 and/or the spark control unit 1610. The firing information includes, but is not limited to, a firing decision (e.g., skip or fire), a firing sequence, and an identification of the associated working chamber. The firing information also includes information indicative of the working chamber output level associated with each decision to fire the working chamber.

At step 2610, the engine diagnostic module 1650 assigns a window for each ignition opportunity. The window may be any suitable period or interval corresponding to a target firing opportunity for a target working chamber. A particular engine parameter will later be measured across the window to help determine if an engine problem has occurred within the target operating chamber during the window. The characteristics of the window may vary depending on the type of engine parameter measurement.

Consider an example involving a four-stroke eight-cylinder engine. In this example, the assigned window is an angular window section corresponding to a 90 ° rotation of the crankshaft. Beyond this window, the target working chamber fires. That is, in this example, the window covers the first half of the power stroke of the target working chamber. It will be appreciated that the window may have any suitable length, depending on the needs of a particular application.

At step 2615, the engine diagnostic module 1650 determines a working chamber torque output associated with one or more of the working chambers during the assigned window. In other words, in various embodiments, the spark timing determination module 1606 and/or the spark control unit 1610 have assigned a spark decision to each working chamber. During the particular window assigned in step 2610, the target working chamber fires. During the same window, the other working chambers are in different phases of the operating cycle. To use the above example, some working chambers have completed a power stroke; the other working chambers are still completing or will enter the power stroke later. Each working chamber is arranged to be skipped or fired for its associated power stroke. For each firing, a specific working chamber output level has been assigned, e.g., firing at a low torque output, firing at a high torque output, etc. The engine diagnostic module 1650 determines the working chamber torque output associated with one, some, or all of the working chambers during the assigned window.

At step 2620, the engine diagnostic module 1650 provides engine parameter thresholds or models. For example, in some embodiments, the engine diagnostic module 1650 determines an engine parameter threshold (e.g., a crankshaft acceleration threshold) that will be used later to help determine whether an engine problem exists. That is, given the ignition information (step 2605) and the torque output level determination (step 2615), the threshold helps indicate a desired value for subsequent engine parameter measurements. In other embodiments, the engine diagnostic module 1650 determines a model (e.g., a torque model) that may also be used to help identify engine problems. For example, a torque model may be used to help indicate the desired torque that should be produced by the working chamber during the window. The model takes into account firing decisions made for one or more working chambers during the window (e.g., as indicated by the firing information obtained in step 2605) and the associated torque output level for each firing (e.g., as indicated by the determination made in step 2615).

At step 2625, the engine diagnostic module 1650 measures engine parameters during the window. A wide variety of engine parameters may be used depending on the needs of a particular application and the engine problem being diagnosed. For example, some designs involve measuring crankshaft acceleration, MAP, and/or oxygen sensor output during a window, although any suitable parameter may be measured. It should be appreciated that different windows may be used for different measurements.

Based on the measurements (step 2625) and the thresholds/models (step 2620), the engine diagnostic module 1650 next determines whether there is an engine problem. This determination may be performed in a variety of ways. For example, in some embodiments, crankshaft acceleration is measured (step 2625). The measurement can be used to estimate the actual torque produced during the window. This actual torque is compared to the desired torque calculated using the torque model (e.g., step 2620). If the actual torque is less than the desired torque, the engine diagnostic module 1650 determines that an engine problem (e.g., misfire) may exist. In other implementations, the crankshaft acceleration measurement is compared to a threshold (e.g., step 2620) and no torque estimation is needed. If the actual measurement exceeds the threshold, then an engine problem is assumed to exist or likely to exist.

To help demonstrate how some embodiments of the method can be performed, the following examples are provided. In this example, the engine is a four-stroke eight-cylinder engine in which the cylinders are fired in the order of 1-8-7-2-6-5-4-3. Each cylinder has an independently controlled intake valve and/or the valves can be operated using different cycles as described in connection with fig. 1A, 1B, 2-11, 12A-12F, 13A-13B, 14A-14H, and 15. Each cylinder, when fired, is therefore capable of firing at one of two torque output levels: such as a low torque output (e.g., CTF ═ 0.7) or a high output (CTF ═ 1.0).

The engine diagnostic module 1650 is arranged to determine whether the working chamber 8 has failed to fire. The module obtains firing information (step 2605) indicating that working

chambers

1, 8, 7, 2, 6, 5, 4, and 3 are skipped, fired, and fired, respectively, during successive firing opportunities. The module assigns a window to the above firing opportunity for the working chamber 8 (step 2610). The assigned window occurs when the cylinder 8 is in the first half of its power stroke and covers 90 ° of rotation of the crankshaft.

In this example, the engine diagnostic module 1650 also determines that each of the above firings is output at a low torque (step 2615), including the firing of the working chamber 8. In this example, the module 1650 determines a crankshaft acceleration threshold that takes into account the cylinder torque output level. That is, if the engine diagnostic module 1650 instead determines that one, some, or all of the above firings are instead at high torque output, the threshold will be different.

In various embodiments, the crankshaft acceleration threshold is particularly heavily influenced by the operation of the working chamber 8 (i.e., whether the cylinder 8 is firing at a low or high torque output). However, the torque output levels associated with the other cylinders may also have an effect. For example, during the assigned window, when cylinder 8 is in the first half of the power stroke, cylinder 1 is in the second half of its power stroke. Whether cylinder 1 fires with a low torque output rather than a high torque output may also significantly affect the threshold.

The engine diagnostic module 1650 then measures actual crankshaft acceleration during the window (step 2625). Module 1650 compares the measurement to a threshold. If the measured value is (substantially) below the threshold value, it is determined that the working chamber 8 failed to fire (or there is a possibility that it failed to fire).

The above example and method 2600 may be modified in a variety of ways for different applications. For example, commonly assigned U.S. patent application nos. 14/207,109, 14/582,008, 14/700,494, and 14/206,918 (which are incorporated herein by reference in their entirety for all purposes) describe a variety of different engine diagnostic systems and operations. Any of the features or operations described in these applications may be incorporated into method 2600.

Any and all of the described components may be arranged to update their determinations/calculations very quickly. In some preferred embodiments, these determinations/calculations are updated on a firing opportunity by firing opportunity basis (although this is not a requirement). For example, in some embodiments, determining the (effective) firing fraction (step 1710 of fig. 17), determining the multi-stage skip fire firing sequence (step 1715), and/or operating the engine based on the sequence (step 1720) are performed on a firing opportunity by firing opportunity basis. An advantage of controlling the various components on a firing opportunity by firing opportunity basis is that the engine is made very responsive to changing inputs and/or conditions. While firing opportunity-by-firing opportunity operation is very efficient, it should be appreciated that these various components may be more slowly updated while still providing good control (e.g., firing fraction/sequence determinations may be performed every revolution of the crankshaft, every two or more firing opportunities, etc.).

The present invention has been described primarily in the context of operating a naturally aspirated, 4-stroke, internal combustion piston engine suitable for use in a motor vehicle. However, it should be understood that the described application is well suited for use in a wide variety of internal combustion engines. These internal combustion engines include engines for almost any type of vehicle, including automobiles, trucks, boats, airplanes, motorcycles, mopeds, and the like; and is suitable for engines involving ignition of working chambers and virtually any other application utilizing internal combustion engines. These different approaches described work with engines operating under a wide variety of different thermodynamic cycles, including almost any type of two-stroke piston engine, diesel engine, otto cycle engine, two-cycle engine, miller cycle engine, akkerson cycle engine, rotary (Wankel) engine, as well as other types of rotary engines, hybrid cycle engines (e.g., otto and diesel two-cycle engines), hybrid engines, radial engines, and the like. It is also believed that the described methods will work well with newly developed internal combustion engines, whether they are operated with currently known or later developed thermodynamic cycles. Supercharged engines, such as those using over-pressure superchargers or turbochargers, may also be used. The maximum cylinder load in this case may correspond to the maximum cylinder charge obtained by pressurizing the air intake.

It should also be appreciated that any of the methods or operations described herein may be stored in a suitable computer readable medium in the form of executable computer code. These operations are performed when the computer code is executed by a processor. Such operations include, but are not limited to, any and all operations performed by the firing fraction calculator 1602, the spark timing determination module 1606, the firing control unit 1610, the powertrain parameter adjustment module 1608, the engine controller 1630, the engine diagnostic module 1650, or any other module, component, or controller described herein.

Some of the above embodiments relate to deactivating a working chamber. In various implementations, deactivating a working chamber involves preventing air from being pumped through the skipped working chamber during one or more selected skipped working cycles. The working chambers can be skipped or deactivated in a variety of ways. In a number of different approaches, a low pressure spring is formed in the working chamber, i.e. after the exhaust gas is released from the working chamber in a previous working cycle, neither the inlet valve nor the exhaust valve is opened during a subsequent working cycle, thereby forming a low pressure vacuum in the working chamber. In yet still further embodiments, a high pressure spring is formed in the skipped working chamber, i.e. air and/or exhaust gas is prevented from escaping the working chamber. The working chamber may be deactivated in any suitable manner such that the working chamber contributes little or no power during its power stroke.

The present application also relates to the concept of working chambers for generating different levels of torque or having different air intake or cylinder load levels. For example, the torque output levels may be specified in a multi-stage skip fire firing sequence and/or stored in a look-up table or library. As previously discussed, in some embodiments, each such torque output level is implemented using a different set of operations described herein (e.g., opening one intake valve and the other not, opening both intake valves, using different cycles for different intake valves, etc.). In some approaches, the torque level produced by the working chambers may vary on a firing opportunity by firing opportunity basis, e.g., a cylinder may be skipped during a working cycle, fired at a high torque output during the next working cycle, fired at a low torque output during the next working cycle, and then skipped or fired at either torque output level.

Embodiments of the present invention have been described primarily in the context of a skip fire control arrangement in which the cylinders are deactivated during skipped working cycles by deactivating both the intake and exhaust valves to prevent air from being pumped through the cylinders during the skipped working cycles. However, it should be appreciated that some skip fire valve actuation schemes contemplate deactivating only the exhaust valves or only the intake valves to effectively deactivate the cylinders and prevent air from being pumped through the cylinders. Several of the described approaches are equally applicable to such applications. Further, while it is generally preferred to deactivate cylinders, and thus prevent air from passing through the deactivated cylinders during skipped working cycles, there are certain times when it may be desirable to pass air through a cylinder during a selected skipped working cycle. By way of example, this may be desirable when engine braking is desired, and/or diagnostic or operational requirements associated with a particular emissions device. It may also be useful when transitioning out of the DCCO (deceleration cylinder interrupt service) state. The valve control approach described is equally applicable to such applications.

The present application relates to a number of different systems and techniques for selectively producing a number of different (e.g., high or low) torque output levels from an ignited working chamber. In various embodiments, it will be appreciated that a plurality of engine conditions may remain substantially the same during a selected operating cycle (during which the working chamber is fired), although this is not required. Such engine conditions include, but are not limited to, manifold absolute pressure, cam phaser settings, engine speed, and/or throttle position. In other words, the present application describes various exemplary valve control systems and techniques (e.g., as discussed in connection with FIGS. 1A, 1B, 2-11, 12A-12F, 13A, 13B, 14A-14H, and 15) that are arranged to cause a fired working chamber to produce different torque output levels without requiring, for example, changes in throttle position, MAP, engine speed, and/or cam phaser settings to produce those different torque output levels.

Implementations of the present invention are well suited for incorporating dynamic skip fire operations in which an accumulator or other mechanism tracks portions of firings that have been requested but not delivered, or that have been delivered but not requested, so that firing decisions can be made on a firing opportunity by firing opportunity basis. However, the described techniques are equally well suited for almost any skip fire application that includes skip fire operation using a fixed firing pattern or firing sequence as may occur with rolling cylinder deactivation and/or a variety of different other skip fire techniques (in operating modes where individual cylinders are sometimes fired and sometimes skipped during operation in a particular operating mode). Similar techniques may also be used in the control of variable stroke engines in which the number of strokes in each working chamber is varied in order to effectively vary the displacement of the engine.

At least some embodiments of the invention include at least the following.

A method for controlling operation of an internal combustion engine having a plurality of working chambers to deliver a desired output, wherein each working chamber has at least one intake valve actuated by a cam and has at least one exhaust valve, the method comprising:

operating the engine in a skip fire manner that skips selected skipped working cycles and causes selected active working cycles to fire to deliver a desired transmitter output, wherein each working cycle is dynamically determined to be a fire or a skip on a firing opportunity by firing opportunity basis during operation of the engine; and is

Selecting a high torque output or a low torque output on the fired working chamber, wherein whether to use the high torque output or the low torque output is dynamically determined on a firing opportunity by firing opportunity basis during operation of the engine; and is

Adjusting an air intake of the fired working chamber based on whether a high torque output or a low torque output is selected on the fired working chamber.

Scheme 2. the method of scheme 1, wherein the air intake is adjusted to produce either a high torque output or a low torque output by independently controlling at least two intake valves in each of said fired working chambers.

Scheme 3. the method of scheme 1, further comprising:

deactivating the skipped working chamber during a selected skipped working cycle to thereby prevent pumping air through the skipped working chamber during the selected skipped working cycle.

Scheme 4. the method of scheme 1, wherein all of the intake and exhaust valves are actuated by one or more cam lobes coupled with one or more camshafts.

Scheme 5. the method of scheme 1, further comprising:

generating a skip fire firing sequence that indicates for each firing whether the firing involves using a high torque output or a low torque output; and is

The engine is operated based on the skip fire firing sequence.

Scheme 6. the method of scheme 1, further comprising:

determining a horizontal fraction and a firing fraction, wherein the horizontal fraction helps indicate a ratio of a high torque output or low torque output number of firings relative to a total number of firings including the high torque output and low torque output number of firings; and is

The engine is operated in a skip fire manner based on the level fraction and the firing fraction.

Scheme 7. the method of scheme 1, wherein the selection of high or low torque output on the fired working chamber is determined at least in part using a sigma delta converter.

Scheme 8. the method of scheme 1, wherein the selection of the high or low torque output is based on one or more of a look-up table and a state machine.

Scheme 9 the method of scheme 1, wherein the plurality of working chambers each include a first intake valve and a second intake valve, the method further comprising:

the first and second intake valves are opened and closed based on different timing cycles while the engine is operating in a skip fire manner and during selected active duty cycles.

Scheme 10. the method of scheme 9, wherein the first intake valve is operated based on an atkinson cycle and the second intake valve is operated based on an otto cycle.

Scheme 11. the method of scheme 1, wherein:

firing of the selected active duty cycle involves causing the firing of the working chamber at the high torque output or the low torque output based on whether the high torque output or the low torque output is selected on the fired working chamber;

each fired working chamber including a first intake valve and a second intake valve;

independently controlling a first intake valve and a second intake valve of the fired working chamber based on a high torque valve control scheme when the fired working chamber is firing at a high torque output; and is

When the fired working chamber is fired at a low torque output, the first and second intake valves of the fired working chamber are independently controlled based on a low torque valve control scheme different from the high torque valve control scheme.

Scheme 12. the method of scheme 11, wherein:

the high torque valve control scheme involves delivering air through the first and second intake valves during a duty cycle of the selected activity; and is

The low torque valve control scheme involves disallowing air through the first intake valve during a selected active duty cycle.

Scheme 13. the method of scheme 11, wherein:

the high torque valve control scheme involves delivering air through the first intake valve and not through the second intake valve during a duty cycle of the selected activity;

the high torque valve control scheme further involves operating the first intake valve based on an otto cycle during the selected active duty cycle;

the low torque valve control scheme involves delivering air through the first and second intake valves during a selected active duty cycle; and is

The low torque valve control scheme further involves operating the first intake valve based on an otto cycle during the selected active working cycle and operating the second intake valve based on a Late Intake Valve Closing (LIVC) atkinson cycle during the selected active working cycle.

Scheme 14. the method of scheme 1, further comprising:

detecting knock in a working chamber of the engine; and is

In response to the detection, requesting that one or more working chambers fire at the low torque output and not at the high torque output; and is

The engine is operated in a skip fire manner based on the request.

Scheme 15. the method of scheme 1, further comprising:

detecting a condition of one of: 1) vehicle deceleration and coasting; and 2) stopping the engine using a start/stop feature;

detecting an engine torque that has been requested;

in response to said detecting operation, requesting one or more selected working chambers not to fire at the high torque output; and is

The engine is operated in a skip fire manner based on the request.

Scheme 16. the method of scheme 1, further comprising:

assigning a window to a target firing opportunity of a target working chamber;

determining whether a high torque output or a low torque output is selected on one or more working chambers of the plurality of working chambers;

firing the target working chamber during the window;

measuring an engine parameter during the window; and is

Determining whether an engine problem exists based at least in part on the torque output determination and the engine parameter measurement.

Scheme 17. the method of scheme 1, wherein:

the engine includes a first subset of one or more working chambers and a second subset of one or more working chambers;

each working chamber in the first subset is arranged to be selectively fired or deactivated; and is

Each working chamber in the second subset is arranged to be ignited during each engine cycle and cannot be deactivated during operation of the engine.

Scheme 18. the method of scheme 1, wherein:

the engine includes a first subset of one or more working chambers each capable of producing a selected high torque output and low torque output;

the engine further includes a second subset of one or more working chambers each capable of producing a selected high torque output and low torque output; and is

The high or low torque output is selected from the fired working chambers in the first subset but not the second subset.

Scheme 19. the method of scheme 1, wherein:

operating one of the ignited working chambers at substantially minimum brake specific fuel consumption conditions to produce the low torque output.

Scheme 20. the method of scheme 1, wherein:

selecting a high torque output or a low torque output on the fired working chamber based at least in part on noise, vibration, and harshness (NVH) considerations.

Scheme 21. the method of scheme 1, further comprising:

a higher air intake for the fired working chamber for which the high torque output is selected than for the fired working chamber for which the low torque output is selected.

Scheme 22. the method of scheme 1, further comprising:

causing the selected working chamber to be fired at the high torque output based on the selection; and is

Causing the selected working chamber to fire at the low torque output based on the selection, wherein the low torque output firing is more fuel efficient than the high torque output firing.

Scheme 23. the method of scheme 1, further comprising:

determining a plurality of candidate effective firing fractions for delivering the desired engine torque, wherein each candidate effective firing fraction is based on one or more values of the cylinder torque level and a ratio of the number of firings to the number of firing opportunities;

comparing the fuel efficiencies of the candidate effective firing fractions;

selecting one of the candidate effective firing fractions based on the comparison; and is

The engine is operated based on the selected one of the candidate effective firing fractions.

Scheme 24. the method of scheme 1, further comprising:

each fired working chamber including a first intake valve and a first exhaust valve; and is

Actuating the first intake valve to deliver air to the fired working chamber, wherein the first intake valve and the first exhaust valve of the fired working chamber are arranged such that whenever the first intake valve is actuated during a working cycle of a selected activity, the first exhaust valve is also actuated during the working cycle of the same selected activity.

Scheme 25 the method of scheme 1, wherein the intake and exhaust valves are both cam actuated.

Scheme 26. the method of scheme 1, wherein the engine is a four cylinder engine.

Scheme 27. the method of scheme 1, wherein:

the plurality of working chambers utilize a plurality of different valve actuation systems; and is

Each valve actuation system can be a different set of one or more features, each feature being one of: (1) deactivating the working chamber; 2) firing the working chamber at the low torque output; and 3) firing the working chamber at the high torque output.

An engine controller for an engine including one or more working chambers, each working chamber including one or more cam-actuated intake valves, the engine controller comprising:

a firing fraction calculator arranged to determine a firing fraction suitable for delivering a desired engine torque;

a spark timing determination module arranged to determine a skip fire firing sequence based on the firing fraction, wherein the skip fire firing sequence indicates whether the selected working chamber is deactivated or fired during the selected firing opportunity and further indicates whether the firing produces a low torque output or a high torque output for each firing; and

a firing control unit arranged to operate the one or more working chambers of the engine in a skip fire manner based on the firing sequence, and wherein the firing control unit is further arranged to adjust an air intake of the fired working chamber based on whether the firing sequence indicates a low torque output or a high torque output for each fired working chamber.

Scheme 29 the engine controller of scheme 28, wherein the spark timing determination module is arranged to select the skip fire firing sequence from a library of predefined skip fire firing sequences.

Scheme 30. the engine controller of scheme 28, wherein the spark timing determination module is arranged to generate the skip fire firing sequence by using a sigma delta converter.

An engine controller as recited in claim 28 wherein the firing control unit is arranged to independently control intake valves of the selected working chamber to fire the selected working chamber at either a high torque level or a low torque level based on the skip fire firing sequence.

An engine controller as set forth in claim 28 wherein:

the working chambers of the engine each include a first intake valve and a second intake valve;

the ignition control unit is further arranged to selectively open the first intake valve and not open the second intake valve during a first selected active duty cycle; and is

The ignition control unit is further arranged to selectively open the first and second intake valves during a second selected active duty cycle such that the timing of closing and opening of the first and second intake valves during the second selected active duty cycle is different.

An engine controller as set forth in claim 28 wherein:

the ignition timing determination module is arranged to make ignition decisions on a firing opportunity by firing opportunity basis, each ignition decision indicating whether a selected working chamber is deactivated or fired during a selected firing opportunity; and further indicates whether the spark produces a low torque output or a high torque output for each spark.

Scheme 34 the engine controller of scheme 28, wherein the engine is a four cylinder engine.

An engine controller as set forth in claim 28 wherein:

the one or more working chambers use a plurality of different valve actuation systems; and is

Each valve actuation system can be a different set of one or more features, each feature being one of: 1) deactivating the working chamber; 2) firing the working chamber at the low torque output; and 3) firing the working chamber at the high torque output.

An engine system, comprising:

an intake manifold;

a first group of one or more working chambers, each working chamber in the first group comprising a first intake valve and a second intake valve;

at least two intake passages connecting the intake manifold with one of the working chambers of the first set, wherein the at least two intake passages are arranged relative to the one of the working chambers such that a central axis of each of the intake passages substantially intersects a central axis of the one of the working chambers.

The engine system of claim 36, further comprising:

first and second cams arranged to actuate the first and second intake valves independently, respectively, wherein the engine system is arranged to actuate or deactivate the first and second intake valves independently on a duty cycle by duty cycle basis, and wherein the independent actuation and deactivation of each of the first and second intake valves helps enable the working chamber to produce either a high torque output or a low torque output.

The engine system of claim 37, further comprising:

a second group of one or more working chambers, wherein each working chamber in the second group is incapable of producing a plurality of different levels of torque output.

The engine system of claim 37, further comprising:

a second group of one or more working chambers, wherein each working chamber in the second group cannot be deactivated during operation of the engine system.

The engine system of claim 36, further comprising:

an engine comprising the first set of one or more working chambers, wherein the engine is a four cylinder engine.

The engine system of scheme 36, wherein:

the set of one or more working chambers uses a plurality of different valve actuation systems; and is

A method for controlling operation of an internal combustion engine having a plurality of working chambers, wherein each working chamber has at least one intake valve actuated by a cam and has at least one exhaust valve, comprising:

operating the engine using the first ignition fraction;

operating the engine using a second firing fraction different from the first firing fraction; and is

Operating the engine based on a multi-stage skip fire firing sequence during a transition between the first firing fraction and the second firing fraction, wherein the multi-stage skip fire firing sequence indicates whether the selected working chamber is deactivated or fired during the selected firing opportunity; and further indicates whether the spark produced a low or high torque output for each spark.

Scheme 43 the method of scheme 42, wherein the skip fire firing sequence indicates firing decisions, wherein the firing decisions are each made on a firing opportunity by firing opportunity basis.

Scheme 44. the method of scheme 42, further comprising:

firing the selected working chamber at the high torque output and the low torque output based on the multi-stage skip fire firing sequence;

the air intake amount is adjusted to produce the high and low torque outputs at the fired working chambers by independently controlling at least two intake valves of each of the fired working chambers.

Scheme 45. the method of scheme 42, further comprising:

while operating the engine using the first firing fraction, operating the engine based on a first level fraction, wherein a level fraction helps indicate a ratio of a number of high torque output or low torque output firings relative to a total number of firings including the number of high torque output and low torque output firings;

operating the engine based on a second level fraction while operating the engine using the second firing fraction; and is

Operating the engine during a transition between the first and second firing fractions while operating the engine based on a level fraction that is different from at least one of: 1) the first level score; and 2) the second level score.

Scheme 46. the method of scheme 42, wherein operating the engine based on one of the first firing fraction and the second firing fraction involves variable displacement operation.

Scheme 47. the method of scheme 42, further comprising:

detecting a request for a desired torque while operating the engine based on the first firing fraction;

determining, in response to the request, that the second firing fraction is suitable for delivering the desired torque;

based on the determination of the second firing fraction, automatically selecting one or more intermediate firing fractions during a transition between the first firing fraction and the second firing fraction, wherein the multi-stage skip fire firing sequence is based on the one or more intermediate firing fractions; and is

During the transition, the engine is operated based on the one or more intermediate firing fractions.

Scheme 48. the method of scheme 47, further comprising:

gradually changing a transitional firing fraction for operating the engine during the transition, wherein the multi-stage skip fire firing sequence is based on the transitional firing fraction, and a rate of change of the transitional firing fraction is based on one or more engine parameters.

Scheme 49 the method of scheme 48, wherein one of the engine parameters is absolute manifold pressure.

Scheme 50. a method as set forth in any of schemes 1-27, wherein the air intake is adjusted to produce high or low torque output by independently controlling at least two intake valves in each of the fired working chambers.

Scheme 51. the method of scheme 1 or 50, further comprising:

the skipped working chambers are deactivated during selected skipped working cycles to thereby prevent pumping air through the skipped working chambers during the selected skipped working cycles.

Scheme 52. the method of any of schemes 1, 50, and 51, wherein all of the intake and exhaust valves are actuated by one or more cam lobes coupled with one or more camshafts.

Scheme 53. the method of any of schemes 1 and 50-52, further comprising:

The engine is operated based on the skip fire firing sequence.

Scheme 54. the method of any of schemes 1 and 50-53, further comprising:

Scheme 55. the method of any of schemes 1 and 50-54, wherein the selection of whether to output high or low torque on the fired working chambers is determined at least in part using a sigma delta converter.

Scheme 56. the method of any of schemes 1 and 50-55, wherein the selection of the high or low torque output is based on one or more of a look-up table and a state machine.

Scheme 57 the method of any of schemes 1 and 50-56, wherein the working chambers each include a first intake valve and a second intake valve, the method further comprising:

the first and second intake valves are opened and closed based on different timing cycles while the engine is operated in a skip fire manner and during a selected working cycle.

The method of scheme 57, wherein the first intake valve is operated based on an atkinson cycle and the second intake valve is operated based on an otto cycle.

Scheme 59. the method of any one of schemes 1 and 50-58, wherein:

firing of the selected active working cycle involves causing the working chambers to fire at the high torque output or low torque output based on whether the high torque output or low torque output is selected on the fired working chambers;

Scheme 60. the method of scheme 59, wherein:

the high torque valve control scheme involves delivering air through the first and second intake valves during a selected work cycle; and is

The low torque valve control scheme involves not allowing air to pass through the first intake valve during the selected duty cycle.

Scheme 61. the method of scheme 59, wherein:

the high torque valve control scheme involves delivering air through the first intake valve and not through the second intake valve during the selected work cycle;

the high torque valve control scheme further involves operating the first intake valve based on an otto cycle during the selected work cycle;

the low torque valve control scheme involves delivering air through the first and second intake valves during a selected work cycle; and is

The low torque valve control scheme further involves operating the first intake valve based on an otto cycle during the selected working cycle and operating the second intake valve based on a delayed intake valve closing (LIVC) atkinson cycle during the selected working cycle.

Scheme 62. the method of any of schemes 1 and 50-61, further comprising:

detecting knock in a working chamber of the engine; and is

The engine is operated in a skip fire manner based on the request.

Scheme 63. the method of any of schemes 1 and 50-62, further comprising:

detecting an engine torque that has been requested;

in response to the detecting operations, requesting that one or more selected working chambers not fire at the high torque output; and is

The engine is operated in a skip fire manner based on the request.

Scheme 64. the method of any one of schemes 1 and 50-63, further comprising:

assigning a window to a target firing opportunity of a target working chamber;

determining whether a high or low torque output is selected on one or more of the working chambers;

firing the target working chamber during the window;

measuring an engine parameter during the window; and is

Scheme 65. the method of any one of schemes 1 and 50-64, wherein:

Scheme 66. the method of any one of schemes 1 and 50-65, wherein:

Scheme 67. the method of any one of schemes 1 and 50-66, wherein:

Scheme 68. the method of any one of schemes 1 and 50-67, wherein:

selecting a high torque output or a low torque output on the fired working chambers based at least in part on noise, vibration, and harshness (NVH) considerations.

Scheme 69. the method of any of schemes 1 and 50-68, further comprising:

a higher air intake for the fired working chambers selecting the high torque output than for the fired working chambers selecting the low torque output.

Scheme 70. the method of any of schemes 1 and 50-69, further comprising:

Scheme 71. the method of any one of schemes 1 and 50-70, further comprising:

comparing the fuel efficiencies of the candidate effective firing fractions;

Scheme 72. the method of any of schemes 1 and 50-71, further comprising:

Actuating the first intake valve to deliver air to the fired working chamber, wherein the first intake valve and the first exhaust valve of the fired working chamber are arranged such that whenever the first intake valve is actuated during a selected working cycle, the first exhaust valve is also actuated during the same selected working cycle.

Scheme 73. the method of any of schemes 1 and 50-72, wherein the intake and exhaust valves are cam actuated.

Scheme 74. the method of any of schemes 1 and 50-73, wherein the engine is a four cylinder engine.

Scheme 75. the method of any one of schemes 1 and 50-74, wherein:

An engine controller as recited in any of claims 28-35 wherein the spark timing determination module is arranged to select the skip fire firing sequence from a library of predefined skip fire firing sequences.

Scheme 77 the engine controller of scheme 28 or 76, wherein the spark timing determination module is arranged to generate the skip fire firing sequence using a sigma delta converter.

An engine controller as recited in any of schemes 28 and 76-77 wherein the firing control unit is arranged to independently control intake valves of the selected working chamber to fire the selected working chamber at a high torque level or a low torque level based on the skip fire firing sequence.

An engine controller as set forth in any of schemes 28 and 76-78 wherein:

the ignition control unit is further arranged to selectively open the first intake valve and not open the second intake valve during a first selected working cycle; and is

The ignition control unit is further arranged to selectively open the first and second intake valves during a second selected working cycle such that the timing of closing and opening of the first and second intake valves during the second selected working cycle is different.

The engine controller of any of schemes 28 and 76-79, wherein:

Scheme 81. an engine controller as claimed in any one of schemes 28 and 76 to 80, wherein the engine is a four cylinder engine.

An engine controller as set forth in any of schemes 28 and 76-81 wherein:

The engine system of any of schemes 36-41, further comprising:

The engine system of claim 83, further comprising:

The engine system of any of schemes 36 and 83-85, further comprising:

The engine system of any of aspects 36 and 83-86, wherein:

the first group of one or more working chambers uses a plurality of different valve actuation systems; and is

Scheme 88 the method of any of schemes 42-49, wherein the skip fire firing sequence indicates firing decisions, wherein the firing decisions are each made on a firing opportunity by firing opportunity basis.

Scheme 89 the method of scheme 42 or 88, further comprising:

Scheme 90. the method of any of schemes 42 and 88-89, further comprising:

while operating the engine using the first firing fraction, operating the engine based on a first level fraction, wherein a level fraction helps indicate a ratio of a number of high or low torque output firings relative to a total number of firings including the number of high torque output and low torque output firings;

Scheme 91. the method of any of schemes 42 and 88-90, wherein operating the engine based on one of the first firing fraction and the second firing fraction involves variable displacement operation.

Scheme 92. the method of any of schemes 42 and 88-91, further comprising:

Scheme 93. the method of scheme 92, further comprising:

gradually changing a transitional firing fraction for operating the engine during the transition, wherein the multi-stage skip fire firing sequence is based on the transitional firing fraction and a rate of change of the skip fire fraction is based on one or more engine parameters.

Scheme 94. the method of scheme 93, wherein one of the engine parameters is absolute manifold pressure.

Although several embodiments of the present invention have been described in detail, it should be understood that the invention may be embodied in many other forms without departing from the spirit or scope of the present invention. The term firing fraction is referred to several times. It should be appreciated that the firing fraction may be expressed or represented in a variety of ways. For example, the firing fraction may take the form of a firing pattern, sequence, or any other firing characteristic related to or inherently expressing the firing percentages described above. The term "cylinder" is also referred to several times. It should be understood that in various embodiments, the term cylinder should be understood to broadly encompass any suitable type of working chamber. The engine may also use skip fire type techniques where instead of the cylinder being skipped and fired, it is run with low torque or high torque output firing. In this control scheme, denoted as dynamic firing level modulation, cylinders are not skipped. In dynamic firing level modulation, the output of the fired cylinder is dynamically varied in a skip/fire pattern. For example, a particular cylinder may sometimes fire at a "high" or "higher" torque output level and may sometimes fire at a "low" or "lower" torque output level, where a "low" output level corresponds to "skip" and a "high" output level corresponds to firing in a skip fire pattern. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein.

Claims

1. A method for diagnosing an internal combustion engine having an intake manifold, a plurality of working chambers, and an exhaust passage, wherein each working chamber has at least one intake valve actuated by a cam and has at least one exhaust valve, the method comprising:

operating the internal combustion engine in a multi-stage skip fire firing sequence, wherein the at least one cam-actuated intake valve can be adjusted for low or high torque output;

assigning a target window to the ignition opportunity;

providing a model or threshold of an engine parameter during the target window;

measuring an engine parameter during the target window; and

determining whether an engine problem exists based on a comparison of the measured engine parameter to a model or threshold of the engine parameter,

wherein the engine parameter measured during the target window is selected from: crankshaft acceleration, intake manifold absolute pressure, and exhaust gas oxygen content level.

2. The method of claim 1, wherein at least two of the group consisting of the crankshaft acceleration, intake manifold absolute pressure, and exhaust gas oxygen content level are used to determine if an engine problem exists.

3. The method of claim 1, wherein the target window is different for different measurements.

4. A method as claimed in any one of claims 1 to 3 wherein the modelled engine parameter is engine torque output during the target window.

5. The method of claim 4, wherein the modeled engine torque is based on modeled torque for each working chamber in the engine.

6. A method as claimed in any one of claims 1 to 3, wherein the target window covers the first half of the power stroke of the working chamber.

7. A method as claimed in any one of claims 1 to 3 wherein the engine problem is misfire.

8. A method as claimed in any one of claims 1 to 3 wherein the engine problem is knock.

9. A method as claimed in any one of claims 1 to 3, wherein the diagnosis is made on a firing opportunity by firing opportunity basis.

10. An engine controller for an internal combustion engine including a plurality of working chambers, wherein each working chamber has at least one intake valve actuated by a cam and has at least one exhaust valve, the engine controller comprising:

a firing fraction calculator arranged to determine a firing fraction suitable for delivering the requested engine torque;

a spark timing determination module arranged to determine a skip fire firing sequence based on the firing fraction, wherein the skip fire firing sequence indicates whether the selected working chamber was skipped or fired during the selected firing opportunity and further indicates whether the firing produced a low or high torque output level for each firing;

a firing control unit arranged to operate the plurality of working chambers of the engine in a multi-stage skip fire manner based on the skip fire firing sequence to deliver the requested torque; and

an engine diagnostic module to determine an engine parameter measured during a target window and a model or threshold of the engine parameter, wherein the engine diagnostic module determines whether an engine problem exists based on a comparison of the engine parameter measured during the target window and the model or threshold of the engine parameter during the target window,

11. An engine controller as recited in claim 10 wherein the model or threshold is influenced by the selected firing opportunity and another firing opportunity.

12. An engine controller as recited in claim 10 or 11 wherein the engine problem is misfire.

13. An engine controller as recited in claim 10 or 11 wherein the engine problem is knock.

14. An engine controller as recited in claim 10 or 11 wherein said engine diagnostic module diagnoses on a firing opportunity by firing opportunity basis.

15. An engine controller as recited in claim 10 or 11 wherein said target window covers the first half of the power stroke of the working chamber.