Patent Application
20140034032
The invention is related to a method and device for controlling an ignition coil and, more particularly, to a smart ignition coil including such a device.
Ignition systems in engines are usually controlled via mechanical or electronic elements. In both cases, ignition is achieved by a sudden break of the current flow in the first transformer winding of an ignition coil, which in turn leads to a rapidly collapsing magnetic field. The change in the magnetic field induces a high voltage in the secondary windings of the ignition coil. For mechanical solutions, current breakers are used for breaking the circuit, while in electronic solutions e.g. a transistor or thyristor is used for switching the transformer coil current. The high voltage at the second coil may also be distributed via a distributor to several spark plugs of an engine.
Ignition timing is crucial for the performance of an engine. Bad timing of the ignition sparks may impair engine performance or even damage parts of the engine. Angular sensors such as hall triggers are usually used for electronically synchronizing valve cycles and ignition timing Additional circuit elements may be implemented in an electronic ignition system for achieving a specific ignition timing behaviour, for example, advancing or retarding the timing as desired.
As an example, ramp generators may be used to provide a voltage signal of desired magnitude and pulse length in relation to engine speed.
However, all these features of an ignition system require a separate circuit element that is only adapted to a specific task. Optimizing the ignition system for an engine then requires providing engine specific, application specific hardware components. Changes to a set system are complex and elaborate.
There is thus a need for a flexible, low cost ignition coil control which allows using a single hardware solution in a wide variety of different setups and requirements. Such a solution is given by the device and the method recited in the claims.
Disclosed is a device comprising an ignition coil, a power stage and a controller connected to said ignition coil via said power stage. The controller is adapted to receive commands and/or parameters related to engine operation and to process said commands and/or parameters, and the controller is further adapted to output a voltage signal to said ignition coil via said power stage, said signal being based at least in part on said processed commands and/or parameters.
In the following, exemplary embodiments will be described in more detail, wherein
The controller 3 shown in
With a programmable microcontroller or microprocessor 3, an ignition system may be flexibly adjusted to different operating conditions, different engine hardware, errors and any other desired parameter relevant for ignition. The microcontroller 3 may run application software that allows command line inputs and/or engine parameters before and during operation. When characteristics of the ignition system require a change, no hardware changes need to be made to the ignition circuit design or any other hardware; rather, the microcontroller firmware may be updated as needed or parameters fed to the microcontroller may be changed externally. By providing a dedicated coil controller 3 with each ignition coil 2 in an engine, a fine ignition management for each cylinder separately is achieved with a minimum number of discrete components. As there is no need for any additional circuit components for the ignition coil, a coil system with integrated controller logic requires less space and effort for installation, and the coils may easily be adapted to different conditions and engines.
Parameters that may be taken account by the application software of the microcontroller may be input directly via commands, may be transmitted from another controller such as an engine control unit (ECU) which is responsible for controlling the complete engine behaviour, or may be received from suitable sensors connected to the microcontroller.
The controller 3 may be provided with inputs for one or more of these data signals, and the inputs may optionally include an analog/digital converter for sampling analog data. As an example, engine temperature and battery voltage parameters may be received directly at the microcontroller 3. These values may be obtained from single or combined sensors 7 which are adapted for measuring and transmitting the parameters periodically or continually. The parameters may either be transmitted from the sensors to one or more controllers, e.g. to both engine control unit (not shown) and coil microcontroller 3, or may be transmitted to a single central controller which may relay the parameter values to other devices as necessary. An input filter may be optionally applied at any of the microcontroller inputs.
It will be understood that the parameters influencing the microcontroller output are not limited to temperature and battery voltage. Any parameter that is relevant for ignition control at all may be used in the corresponding application software of the microcontroller.
Further examples are combustion parameters, spark duration, spark frequency, misfiring detection, octane rating, knock behaviour, and others.
Between the coil and the microcontroller a power stage 4 is connected. The power stage may work like a primary circuit breaker. This power stage may be designed as generally known in the art and as such may include e.g. a power transistor. The power stage may be driven by an output driver stage 5 implementing a digital/analog converter (DAC) which receives the digital signal from the microcontroller 3 output. The output driver stage 5 may include an RC filter element which is fed by the pulse width modulated (PWM) signal from the microcontroller output. The RC element may low pass filter the PWM signal to extract the average voltage for driving the primary circuit breaker. In this way, the pulse width modulation output and the RC filter together form a D/A converter to generate a voltage ramp for the power stage 4, which may e.g. be implemented as an insulated gate bipolar transistor IBGT. In that case, the ramp voltage is supplied to the IGBT gate terminal in order to modulate the collector current. The microcontroller 3 may use a specific designed value resistor to achieve fast discharge of the capacitor and generate the spark. Alternatively, it would be possible to use a pair of bipolar junction transistors to fast charge/discharge the capacitor. Also, the microcontroller may include a full digital/analog converter itself instead of the pulse width modulated output together with the RC filter element. In both cases, the primary circuit breaker or power stage is fed with an analog signal voltage which is calculated by the microcontroller.
Using suitable control algorithms with the microcontroller 3, it may be possible to generate any voltage level and slope that is required to manage the coil primary current and secondary high voltage generation. In
These and other electrical or electronic elements may be provided in the form of through-hole technology elements on printed circuit boards, of surface-mounted device (SMD) elements, or any desirable combination of these. SMD elements would allow an even smaller package design of the control elements on the coil.
Although coil 2, spark plug 1, microcontroller 3 and other elements are shown in the figure as separate elements, this is only to be understood as a schematic view of circuit connections. In practical implementations, the microcontroller and the further electronic components such as power stage and filter may be assembled on the coil directly and may optionally be combined with the spark plug in a single device. Such an embodiment would provide a single hardware solution which is capable of fitting many different requirements, such as different engines and different operating conditions. The embodiments described herein allow transferring the ignition related control tasks from the engine control unit or from static electronic designs to the dedicated ignition controller, thus presenting a “smart ignition coil” for various engine setups.
The software-based control of ignition features may also provide direct error control for the ignition process, either based on a feedback control loop which may use measurement values of the running engine for feedback, or via external commands and parameter inputs when errors are detected e.g. by another controller device. No hardware changes are necessary for optimal tuning of an engine or for special requirements, which may also be only temporary settings and may be reversed when conditions change.
All elements of the controller and connected devices may be suitably grounded and provided with power supplies, filters and connections where required. These elements are well known in the art and will not be described in detail, although examples may be shown in the figures. For example, an electromagnetic interference filter (EMI) may be used in between a power supply and the coil, and an input filter may be inserted at the command line input of the microcontroller. A regulator may be employed for providing the required voltage to the microcontroller, e.g. 5 V. Further common elements of an engine ignition system such as spark plug, cylinder and valve elements, or power supplies for sensors and controllers are well known in the art and will also not be discussed here in detail, but may of course be combined in any suitable way with the teachings provided herein.
The application software within the controller of
The application software may be split into several modules in the case of at least partially software based functions. Again, these modules may be exchangeable and may be customized via parameters, firmware updates and/or commands both before and during operation. They may also be combined with some hardware based functional modules. In some embodiments, a part of the software modules related to ignition control may be located at the local dedicated coil controller 3, while the remaining algorithms are executed at separate control entities such as the engine control unit ECU. Results and values obtained from the ECU may then be further processed at the coil controller, and data may also be transmitted back to the ECU. In other embodiments, any ignition related software application modules may be implemented within the coil controller 3. Alternatively, the application software of the microcontroller may be present in a single application.
The modules may include various elements that are usually implemented via hardware circuit solutions in prior art. For example, obtained sensor values may be compared with stored values for determining whether predefined threshold values are maintained during operation. Spark-free operation may be desired at certain times, for example in hybrid vehicles which rely on other sources of energy besides the combustion engine or which apply start-stop systems, and deactivating and activating the ignition system correctly may need to be controlled. Further elements that might be implemented via software modules in the microcontroller directly on the coil are ramp generators for generating a pulse width modulated signal with increasing or decreasing duty cycle in order to control the primary current slope and limit the secondary voltage; dwell measure related to the duration of the activation signal provided by the main engine control unit; or multi-spark generators for deciding on the number of sparks fired during a cycle and their timing. Any of these modules may use input signals received from other modules, signals produced by circuit blocks or sensors, and/or they may drive other modules and parts of the control system, such as a primary circuit breaker transistor. All these modules are only examples of common modules for ignition control, and they may be complemented or replaced by additional modules not mentioned here.
It will be understood that the described details of embodiments are only given by way of example. Elements may be exchanged and combined between the exemplary embodiments without departing from the general solution described herein, which is based on local ignition coil control via a dedicated controller preferably mounted on the coil. Especially, the skilled person will be aware that elements described in detail with a specific embodiment may in the same way be applied to another embodiment where these details have not been mentioned explicitly, as long as the technical features are compatible with each other.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2011/052056 | 2/11/2011 | WO | 00 | 10/22/2013 |
