Patent Application
20140360476
The present disclosure relates to a dual coil ignition system for controlling spark energy provided to a spark plug of an engine.
Engine systems may be configured with boosting devices, such as turbochargers or superchargers, for providing a boosted aircharge and improving peak power outputs. Responsive to the boosted output provided by such engine systems, efficient operation of a spark plug and stable combustion may be achieved by providing high peak secondary currents at high speed and high load conditions, while providing long spark durations at low speeds and loads under lean and/or dilute conditions. However, high peak secondary currents and long spark durations are competing characteristics for ignition coil configuration, resulting in systems that devalue operation under one or more of the above-identified conditions in favor of another condition.
The inventors have recognized the issues with the above approach and offer a system to at least partly address them. In one embodiment, a system comprises a first inductive ignition coil including a first primary winding and a first secondary winding and a second inductive ignition coil including a second primary winding and a second secondary winding. The second secondary winding is connected in series to the first secondary winding. The system further comprises a diode network including a first diode and a second diode connected between the first secondary winding and the second secondary winding.
In this way, each the two coils may be configured for a different one of the competing characteristics (e.g., high peak secondary currents or long spark duration), and steering diodes combine the output of each coil such that additional spark energy is only provided when operating conditions warrant.
The present disclosure may offer several advantages. For example, by only providing long spark duration when operating conditions call for additional spark energy, overall electrical energy consumption may be decreased in comparison to systems that always provide long spark duration. Further, the configuration decreases component stress, thereby extending component life span, by exposing the current steering diodes to a much lower maximum voltage in comparison to diodes utilized in parallel connected dual coil ignition systems. Furthermore, the lower maximum voltage enables compact coil packaging of a plug top coil positioned on top of a pencil or stick coil, thereby decreasing packaging real estate requirements on the engine in comparison to dual coil systems that are constructed with two side by side plug top coils in one housing or two separate coil packages.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
A dual coil ignition system having secondary windings connected in series via a current steering diode network is disclosed herein. The series-connection of the two ignition coils enables efficient control by allowing independent control of start of dwell times, while ending dwell for each ignition coil simultaneously with a single command. By connecting a relatively low inductance ignition coil to a relatively high inductance ignition coil, the resulting configuration provides high peak secondary currents and long spark duration based on combustion conditions.
Fuel injector 66 is shown positioned to inject fuel directly into cylinder 30, which is known to those skilled in the art as direct injection. Alternatively, fuel may be injected to an intake port, which is known to those skilled in the art as port injection. Fuel injector 66 delivers liquid fuel in proportion to the pulse width of signal FPW from controller 12. Fuel is delivered to fuel injector 66 by a fuel system (not shown) including a fuel tank, fuel pump, and fuel rail. Fuel injector 66 is supplied operating current from driver 68 which responds to controller 12. In addition, intake manifold 144 is shown communicating with optional electronic throttle 62 which adjusts a position of throttle plate 64 to control airflow to engine cylinder 30. This may include controlling airflow of boosted air from intake boost chamber 146. In some embodiments, throttle 62 may be omitted and airflow to the engine may be controlled via a single air intake system throttle (AIS throttle) 82 coupled to air intake passage 42 and located upstream of the boost chamber 146.
In some embodiments, engine 10 is configured to provide exhaust gas recirculation, or EGR. When included, EGR is provided via EGR passage 135 and EGR valve 138 to the engine air intake system at a position downstream of air intake system (AIS) throttle 82 from a location in the exhaust system downstream of turbine 164. EGR may be drawn from the exhaust system to the intake air system when there is a pressure differential to drive the flow. A pressure differential can be created by partially closing AIS throttle 82. Throttle plate 84 controls pressure at the inlet to compressor 162. The AIS may be electrically controlled and its position may be adjusted based on optional position sensor 88.
Compressor 162 draws air from air intake passage 42 to supply boost chamber 146. In some examples, air intake passage 42 may include an air box (not shown) with a filter. Exhaust gases spin turbine 164 which is coupled to compressor 162 via shaft 161. A vacuum operated wastegate actuator 72 allows exhaust gases to bypass turbine 164 so that boost pressure can be controlled under varying operating conditions. In alternate embodiments, the wastegate actuator may be pressure or electrically actuated. Wastegate 72 may be closed (or an opening of the wastegate may be decreased) in response to increased boost demand, such as during an operator pedal tip-in. By closing the wastegate, exhaust pressures upstream of the turbine can be increased, raising turbine speed and peak power output. This allows boost pressure to be raised. Additionally, the wastegate can be moved toward the closed position to maintain desired boost pressure when the compressor recirculation valve is partially open. In another example, wastegate 72 may be opened (or an opening of the wastegate may be increased) in response to decreased boost demand, such as during an operator pedal tip-out. By opening the wastegate, exhaust pressures can be reduced, reducing turbine speed and turbine power. This allows boost pressure to be lowered.
Compressor recirculation valve 158 (CRV) may be provided in a compressor recirculation path 159 around compressor 162 so that air may move from the compressor outlet to the compressor inlet so as to reduce a pressure that may develop across compressor 162. A charge air cooler 157 may be positioned in passage 146, downstream of compressor 162, for cooling the boosted aircharge delivered to the engine intake. In the depicted example, compressor recirculation path 159 is configured to recirculate cooled compressed air from downstream of charge air cooler 157 to the compressor inlet. In alternate examples, compressor recirculation path 159 may be configured to recirculate compressed air from downstream of the compressor and upstream of charge air cooler 157 to the compressor inlet. CRV 158 may be opened and closed via an electric signal from controller 12. CRV 158 may be configured as a three-state valve having a default semi-open position from which it can be moved to a fully-open position or a fully-closed position.
Distributorless ignition system 90 provides an ignition spark to combustion chamber 30 via spark plug 92 in response to controller 12. The ignition system 90 may include a dual induction coil ignition system, in which two ignition coil transformers are connected to each spark plug of the engine. Turning briefly to
The current steering diodes 216 and 218 may be configured to ensure that the energy stored in the second ignition coil 208 is maintained until the contribution of the stored energy to the spark plug 204 is most effective for aiding combustion. For example, the diode network may be configured such that the second ignition coil 208 contributes stored energy to the spark plug 204 when the current through the first ignition coil 202 decays to a level corresponding and/or equivalent to the peak secondary current in the second ignition coil 208 as determined by its state of charge at the end of dwell. The second ignition coil 208 may be configured for a peak current through the secondary windings 214 that is a fraction of the peak current through the secondary windings 212 of the first ignition coil 202. Accordingly, as the current through the secondary windings 212 decays to the peak current of the secondary windings 214, the junction at the anodes of diodes 216 and 218, identified as point B in
As referenced in
Returning to
Controller 12 is shown in
In some embodiments, the engine may be coupled to an electric motor/battery system in a hybrid vehicle. The hybrid vehicle may have a parallel configuration, series configuration, or variation or combinations thereof.
During operation, each cylinder within engine 10 typically undergoes a four stroke cycle: the cycle includes the intake stroke, compression stroke, expansion stroke, and exhaust stroke. During the intake stroke, generally, the exhaust valve 154 closes and intake valve 152 opens. Air is introduced into combustion chamber 30 via intake manifold 144, and piston 36 moves to the bottom of the cylinder so as to increase the volume within combustion chamber 30. The position at which piston 36 is near the bottom of the cylinder and at the end of its stroke (e.g. when combustion chamber 30 is at its largest volume) is typically referred to by those of skill in the art as bottom dead center (BDC). During the compression stroke, intake valve 152 and exhaust valve 154 are closed. Piston 36 moves toward the cylinder head so as to compress the air within combustion chamber 30. The point at which piston 36 is at the end of its stroke and closest to the cylinder head (e.g. when combustion chamber 30 is at its smallest volume) is typically referred to by those of skill in the art as top dead center (TDC). In a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. In a process hereinafter referred to as ignition, the injected fuel is ignited by known ignition means such as spark plug 92, resulting in combustion. During the expansion stroke, the expanding gases push piston 36 back to BDC. Crankshaft 40 converts piston movement into a rotational torque of the rotary shaft. Finally, during the exhaust stroke, the exhaust valve 154 opens to release the combusted air-fuel mixture to exhaust manifold 148 and the piston returns to TDC. Note that the above is described merely as an example, and that intake and exhaust valve opening and/or closing timings may vary, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples.
An encoded dwell command 312 may be utilized to control the flow of current through each of the first and second ignition coils 302 and 304, thereby controlling the associated dwell and fire of the coils. The encoded dwell command 312 may allow a single conductor and/or signal source to supply multiple commands that are differentiated based on pulse widths and/or other encoded features. For example, a first pulse width may indicate a command for a start of dwell for a first ignition coil, and a second pulse width may indicate a command for a start of dwell for a second ignition coil. As illustrated, the encoded dwell command 312 and VIGN may be communicatively connected to a decoder 314. The decoder 314 may also be communicatively connected to a solid-state device, such as transistors 316a and 316b, for establishing and disrupting the current flow to the primary windings of the first and second ignition coils 302 and 304 based on the encoded dwell command 312. The decoder 314 and transistors 316a and 316b may form an intelligent driver for dwell control of the ignition coils, including interpretive logic to decode the dwell commands provided for control of the ignition coils.
The decoder 314 may include a processor communicatively connected to a memory device. The processor may be configured to execute computer- and/or machine-readable instructions stored on the memory device to perform operations such as the decoding and dwell control described herein. The decoder 314 may include instructions executable to evaluate an encoded dwell command in order to determine whether the current flow to the first ignition coil and/or the second ignition coil should change state. For example, the decoder 314 may determine a rising edge of an encoded dwell command generated in response to a desired start of dwell based on engine speed, load, and/or other parameters. Responsive to detecting the rising edge, the decoder 314 may wait for a predetermined amount of time after the rising edge is detected.
Upon expiration of the predetermined amount of time or after a falling edge is detected, the decoder 314 may determine whether a short pulse or a long pulse is detected. For example, if a falling edge was detected prior to the expiration of the predetermined amount of time, the decoder 314 may determine that the encoded dwell command comprised a short pulse, whereas an expiration of the predetermined amount of time without detection of a falling edge may indicate a long pulse. Responsive to a short pulse, the decoder 314 may initiate and/or increase current flow to the second ignition coil 304 by connecting transistor 316b to the voltage source +VIGN. For example, the decoder 314 may include a switching element that controls a connection between the gate of the transistors and the voltage source. Responsive to a long pulse, the decoder 314 may initiate and/or increase current flow to the first ignition coil 302 by connecting transistor 316a to the voltage source. Upon detecting a falling edge of a long pulse, the decoder 314 may stop and/or decrease current flow to the first and second ignition coils by disconnecting transistors 316a and 316b from the voltage source VIGN. In some embodiments, transistors 316a and 316b may be insulated-gate bipolar transistors (IGBTs), which exhibit increased efficiency and switching times in comparison to other transistor configurations. The decoder may comprise a logic unit with instructions and operators formed therein for decoding encoded signals, as described herein.
The second ignition coil may only be dwelled during operating conditions that benefit from the extended spark duration provided by the second, higher inductance ignition coil. For example, during high RPM and/or high load conditions, the output of a first, lower inductance ignition coil may be sufficient to provide reliable combustion, and the method 400 may proceed directly to 406 without outputting an encoded dwell command to start the dwell of the second ignition coil.
At 406, the method 400 includes outputting an encoded dwell command to start the dwell of a first, lower inductance ignition coil. For example, the first ignition coil may correspond to first ignition coil 202 of
During the commanded dwell, current is passed through the primary windings of the first and/or second ignition coils to generate a magnetic field. At 410, the method 400 further includes outputting an encoded end of dwell command to fire the first and the second ignition coils. The end of dwell command may include a termination of the long pulse, as indicated at 412. For example, the current flow through the primary windings of the first and/or second ignition coil may be interrupted and/or stopped responsive to detecting the falling edge of the long pulse. The interruption of the current flow through the primary windings causes a high voltage pulse across the respective secondary windings of the ignition coils. In configurations such as the ignition systems 200 and/or 300, illustrated in
Waveform 502 corresponds to an encoded dwell command, which may be provided from a controller, such as controller 12 of
At time T1, the encoded dwell command is at low or ground, resulting in the absence of current through each of the windings of the two ignition coils. Accordingly, the combined output to the spark plug 512 may also be equal to zero. At time T2, however, the encoded dwell command has been issued for a period of time, as indicated by the rising edge and associated duration at a high value illustrated on waveform 502. For example, time T2 may correspond to a threshold period of time after the rising edge of a long pulse encoded dwell command. The threshold period of time may be associated with a confirmation time, utilized to ensure that a “start of dwell” command for the first ignition coil is intended, as opposed to a short pulse, noise, and/or other signal. In some examples, time T2 may correspond to a moment in time 150 μs after the leading edge of the encoded dwell command. Accordingly, as shown on waveform 504, the current through the primary windings of the first ignition coil increases responsive to a threshold period of time elapsing after the rising edge of the encoded dwell command is detected. As described above, the second ignition coil is commanded to dwell responsive to a short pulse, rather than a long pulse, therefore waveforms 508 and 510 do not change at time T2. Likewise, the increase in current at the primary windings of the first ignition coil generates a magnetic field, but does not affect a current through the secondary windings of the first ignition coil, such current flow being blocked by diodes 216 and 218 in
At time T3, however, the falling edge of the encoded dwell command occurs, as illustrated in waveform 502. As this signals the firing of the first ignition coil, the current in the primary windings is interrupted, falling to zero as shown on 504. In response, the magnetic field generated due to the prior current flow in the primary windings of the first ignition coil collapses, inducing a voltage pulse across the secondary windings of the first ignition coil and the peak current output illustrated on waveform 506 at time T3. As no magnetic field was generated in the second ignition coil, waveforms 508 and 510 remain unchanged, and the combined output to the spark plug is equivalent to the secondary current of the first ignition coil. At time T4, the current continues to be discharged from the secondary windings, providing a corresponding output to the spark plug. As the second ignition coil does not contribute to the combined output, the spark plug experiences the high peak current and short spark duration characterized by the configuration of the first ignition coil.
Time T2 of
At time T3, the falling edge of the long pulse is detected. As illustrated in waveforms 604 and 608, the current flow in the primary windings of both the first ignition coil and the second ignition coil is interrupted as the associated coils are fired simultaneously. In response, the secondary currents of the first and second ignition coils are raised to a respective peak value. For example, as the first ignition coil is configured for high peak currents, the secondary current 606 at coil 1 at time T3 may be higher than the secondary current 610 at coil 2 at time T3. Due to the diode network and series-connected secondary windings illustrated in
At time T4, the secondary current of the first ignition coil decays to the level of the peak secondary current of the second ignition coil, as shown by the equivalent levels of waveforms 606 and 610 at time T4. Accordingly, the junction of the anodes of diodes 306 and 308 of
Accordingly, a series-connected configuration, such as the configurations illustrated in
A high inductance ignition coil 712 may be configured as a plug top configuration and positioned above and/or on top of the pencil coil configuration of the low inductance ignition coil 702. The low inductance ignition coil 702 may be communicatively connected to the high inductance ignition coil 712 via a diode network 714. For example, the diode network 714 may include the diode configuration provided by diodes 306 and 308 of
The above-described packaging thereby provides the high peak secondary current and efficient usage of spark plug well space, associated with the pencil coil, and the long spark duration, achieved with a plug top configuration, within a single package. Accordingly, the series-connected dual coil ignition system not only provides an efficient control scheme and lower component stress, but also enables the use of a more compact packaging configuration than parallel-connected dual coil ignition systems.
Note that the example control and estimation routines included herein can be used with various engine and/or vehicle system configurations. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various actions, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations and/or functions may be repeatedly performed depending on the particular strategy being used. Further, the described actions, operations and/or functions may graphically represent code to be programmed into non-transitory memory of the computer readable storage medium in the engine control system.
It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.
The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.
