Firing fraction management in skip fire engine control
First Claim
1. A skip fire engine controller for a spark ignition engine having a throttle and a camshaft having a plurality of cams, the skip fire controller comprising:
- a lookup table embodied in a computer readable media, wherein each entry in the lookup table includes a firing fraction field that stores a firing fraction indicator indicative of a desired firing fraction associated with such entry, wherein the firing fraction indicator does not identify any specific cylinders to fire;
a firing fraction determining unit arranged to determine a firing fraction suitable for delivering a requested engine output, wherein the firing fraction determining unit utilizes the lookup table to determine a desired firing fraction, wherein the firing fraction determining unit utilizes at least (i) the requested engine output, and (ii) a current engine speed as indices to select a desired firing fraction;
a firing controller arranged to direct firings in a skip fire manner that delivers the desired firing fraction; and
a powertrain parameter adjusting module arranged to adjust at least one engine actuator that affects mass air charge (MAC) such that the engine delivers the requested engine output at the desired firing fraction, wherein the at least one engine actuator affects at least one of cam phase, cam lift and throttle position.
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Accused Products
Abstract
The described embodiments relate generally to skip fire control of internal combustion engines and particularly to mechanisms for determining a desired operational firing fraction. In some embodiments, a firing fraction determining unit is arranged to determine a firing fraction suitable for delivering a requested engine output. The firing fraction determining unit may utilize data structures such as lookup tables in the determination of the desired firing fraction. In one aspect the desired engine output and one or more operational power train parameters such as current engine speed, are used as indices to a lookup table used to select a desired firing fraction. In other embodiments, additional indices to the data structure may include any one of: transmission gear; manifold absolute pressure (MAP); manifold air temperature; a parameter indicative of mass air charge (MAC); cam position; cylinder torque output; maximum permissible manifold pressure; vehicle speed; and barometric pressure.
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Citations
26 Claims
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1. A skip fire engine controller for a spark ignition engine having a throttle and a camshaft having a plurality of cams, the skip fire controller comprising:
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a lookup table embodied in a computer readable media, wherein each entry in the lookup table includes a firing fraction field that stores a firing fraction indicator indicative of a desired firing fraction associated with such entry, wherein the firing fraction indicator does not identify any specific cylinders to fire; a firing fraction determining unit arranged to determine a firing fraction suitable for delivering a requested engine output, wherein the firing fraction determining unit utilizes the lookup table to determine a desired firing fraction, wherein the firing fraction determining unit utilizes at least (i) the requested engine output, and (ii) a current engine speed as indices to select a desired firing fraction; a firing controller arranged to direct firings in a skip fire manner that delivers the desired firing fraction; and a powertrain parameter adjusting module arranged to adjust at least one engine actuator that affects mass air charge (MAC) such that the engine delivers the requested engine output at the desired firing fraction, wherein the at least one engine actuator affects at least one of cam phase, cam lift and throttle position. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 19)
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11. A skip fire controller for a spark ignition engine having a, the skip fire controller comprising:
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a lookup table embodied in a computer readable media, the lookup table having a multiplicity of entries, each entry including a firing fraction field arranged to store an associated firing fraction indicator indicative of a desired firing fraction, wherein the firing fraction indicator does not identify any specific cylinders to fire, and wherein indices for the lookup table include, (i) a desired engine output, and (ii) a first operational power train parameter; a firing controller arranged to direct firings in a skip fire manner that delivers a desired firing fraction selected using the lookup table; and a powertrain parameter adjusting module arranged to adjust at least one engine setting that affects at least one of mass air charge (MAC) and spark timing, such that the engine delivers a requested engine output at the desired firing fraction. - View Dependent Claims (12, 13, 23)
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14. A method of operating a spark ignition engine, the method comprising:
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determining a desired engine output in terms of a desired torque fraction, wherein the desired torque fraction is indicative of the desired engine output relative to a reference maximum available engine output; determining a desired operational firing fraction based on a lookup table that utilizes desired torque fraction as a first index and current engine speed as a second index wherein the lookup table has a multiplicity of entries, each entry including a firing fraction field arranged to store an associated firing fraction indicator indicative of a desired firing fraction, and wherein the firing fraction indicator does not identify any specific cylinders to fire; and determining a desired cylinder mass air charge (MAC) based at least in part on the determined desired operational firing fraction; directing one or more engine actuators to operate in a manner that delivers the desired mass air charge; and directing skip fire operation of the engine at the desired operational firing fraction in a manner that delivers the desired engine output; and wherein operation at the desired cylinder mass air charge and the desired operational firing fraction causes the engine to deliver the desired engine output. - View Dependent Claims (25, 26)
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15. A skip fire engine controller arranged to determine which cylinder working cycles of a spark ignition engine to fuel and fire, and which cylinder working cycles to skip, the skip fire engine controller comprising:
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a firing fraction determining unit arranged to dynamically determine a desired firing fraction based on a multi-dimensional lookup table, wherein indices for the multi-dimensional lookup table include i) a desired engine output; ii) a current engine speed; and iii) a current transmission gear; and a firing controller arranged to direct firings in a skip fire manner that delivers the desired firing fraction. - View Dependent Claims (16, 17, 18, 22, 24)
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20. A method of controlling skip fire operation of an engine comprising:
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determining a desired operational firing fraction by accessing a multi-dimensional lookup table having a multiplicity of entries, each entry including a firing fraction field arranged to store an associated firing fraction indicator indicative of a desired firing fraction, the multi-dimensional lookup table having a plurality of indices, each of which is used in the determination of desired operational firing fraction, wherein the indices for the multi-dimensional lookup table include; (i) a desired engine output; (ii) engine speed; and (ii) a first operational power train parameter that is different than the engine speed; and determining a desired cylinder mass air charge (MAC) based at least in part on the determined desired operational firing fraction; directing one or more engine actuators to operate in a manner that delivers the desired mass air charge; and directing skip fire operation of the engine at the desired operational firing fraction in a manner that delivers the desired engine output; and wherein operation at the desired mass air charge and the desired operational firing fraction causes the engine to deliver the desired engine output. - View Dependent Claims (21)
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Specification