1. Field of the Invention
This invention relates generally to a corona discharge ignition system, and more particularly to a system and method for supplying energy to a plurality of corona igniters of the corona discharge ignition system.
2. Related Art
Corona discharge ignition systems provide an alternating voltage and current, reversing high and low potential electrodes in rapid succession which enhances the formation of corona discharge and minimizes the opportunity for arc formation. The system typically includes a transformer receiving energy from a power supply in the form of a direct current, amplifying the voltage, and reducing the current prior to directing the energy in the form of an alternating current toward a central electrode of the corona igniter. The central electrode is charged to a high radio frequency voltage potential and creates a strong radio frequency electric field in a combustion chamber. The electric field causes a portion of a mixture of fuel and air in the combustion chamber to ionize and begin dielectric breakdown, facilitating combustion of the fuel-air mixture, which is referred to as an ignition event. The electric field is preferably controlled so that the fuel-air mixture maintains dielectric properties and corona discharge occurs, also referred to as non-thermal plasma. The ionized portion of the fuel-air mixture forms a flame front which then becomes self-sustaining and combusts the remaining portion of the fuel-air mixture. Preferably, the electric field is controlled so that the fuel-air mixture does not lose all dielectric properties, which would create thermal plasma and an electric arc between the electrode and grounded cylinder walls, piston, metal shell, or other portion of the igniter. An example of a corona discharge ignition system is disclosed in U.S. Pat. No. 6,883,507 to Freen.
Oftentimes, the corona discharge ignition system includes a plurality of corona igniters, such as one in each cylinder of the engine. Thus, the system also includes a plurality of energy transformers each ultimately connected to one of the corona igniters. However, use of this design is limited as each transformer is expensive and increases the size and complexity of the corona discharge ignition system.
One aspect of the invention provides a corona discharge ignition system comprising a plurality of corona igniters for receiving energy and emitting an alternating electrical field to provide a corona discharge. The system also includes a control and drive electronics unit, a single transformer, a control and drive electronics unit for directing the energy from a power supply toward the corona igniters, a plurality of isolated switch controls, and a plurality of igniter switching units. The transformer is disposed between the control and drive electronics unit and the plurality of corona igniters for receiving the energy from the control and drive electronics unit and increasing the voltage of the energy before directing the energy from the control and drive electronics unit toward the corona igniters. Each isolated switch control is connected to the control and drive electronics unit and is also connected to a separate one of the corona igniters for receiving a control signal from the control and drive electronics unit and allowing the energy from the transformer to travel to the one connected corona igniter in response to the control signal. Each igniter switching unit is connected to the transformer and each is disposed between and connected to one of the isolated switch controls and the one connected corona igniter. Each igniter switching unit is activated and deactivated by the connected isolated switch control in response to the control signal to allow current to travel from the transformer to the one connected corona igniter when the igniter switching unit is activated and to prevent current from traveling from the transformer to the one connected corona igniter and from the one connected corona igniter toward the transformer when the igniter switching unit is deactivated. In addition, only one of the igniter switching units is activated at any given time during operation of the system.
According to another embodiment, the system includes a plurality of electromechanical relays each connected to the control and drive electronics unit, the transformer, and to a separate one of the corona igniters for receiving the control signal from the control and drive electronics unit and for allowing the energy from the transformer to travel to the one connected corona igniter in response to the control signal. Each of the electromechanical relays includes the igniter switching unit, which is activated and deactivated in response to the control signal to allow the energy to travel from the transformer to the one connected corona igniter when the igniter switching unit is activated and to prevent the energy from traveling from the transformer to the one connected corona igniter and from the one connected corona igniter toward the transformer when the igniter switching unit is deactivated.
Another aspect of the invention provides a method for operating a corona discharge ignition system. The method includes providing energy from a power supply to a control and drive electronics unit; and transferring the energy from the control and drive electronics unit toward a plurality of corona igniters. Before transferring the energy from the control and drive electronics unit toward the corona igniters, the method includes increasing the voltage. A plurality of igniter switching units each connected to a transformer and to a separate one of the corona igniters is provided, and the method further includes activating the igniter switching units to convey the energy from the transformer through the igniter switching units to the plurality of corona igniters and deactivating the igniter switching units to prevent the energy from traveling to and from the connected corona igniters. The step of activating the igniter switching units includes activating only one of the igniter switching units and conveying current to only one of the corona igniters at any given time during operation of the system.
Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
One aspect of the invention provides a corona discharge ignition system 20 comprising a plurality of corona igniters 22 with reduced costs and complexity.
The system 20 includes a control and drive electronics unit 32 for receiving the energy from the power supply 24 and directing the energy toward the corona igniters 22. A single transformer 34 is disposed between the control and drive electronics unit 32 and the corona igniters 22 for receiving the energy from the control and drive electronics unit 32 and directing the energy from the control and drive electronics unit 32 toward the corona igniters 22. The transformer 34 receives the energy in the form of a switched direct current, amplifies the voltage typically up to 2.5 kilovolts (peak to peak), and reduces the current of the energy prior to directing the energy in the form of an alternating current toward the corona igniters 22. The control and drive electronics unit 32 includes all equipment required to provide the single transformer 34 with a sufficient power supply 24 at the correct frequency. This single transformer 34 is the only transformer 34 in the system 20, unlike comparative systems which include a transformer for each corona igniter, which significantly increases the cost and complexity of the system. In the system 20 of the present invention, the high speed components used to provide power to the transformer 34 are not duplicated, as in comparative systems 20.
A transformer switching unit 36 is disposed between and connected to the control and drive electronics unit 32 and the transformer 34. The transformer switching unit 36 allows the energy to travel from the control and drive electronics unit 32 to the transformer 34 when the transformer switching unit 36 is activated by the control and drive electronics unit 32. The transformer switching unit 36 also prevents the energy from traveling from the control and drive electronics unit 32 to the transformer 34 when the transformer switching unit 36 is deactivated by the control and drive electronics unit 32. In the exemplary embodiment of
The system 20 also includes plurality of isolated switch controls 40 each connected to the control and drive electronics unit 32. Each of the isolated switch controls 40 is also connected to a separate one of the corona igniters 22. Thus, the number of isolated switch controls 40 equals the number of corona igniters 22. The isolated switch control 40 receives a control signal 42 from the control and drive electronics unit 32 and allows the energy from the transformer 34 to travel to the one connected corona igniter 22 in response to the control signal 42. The control and drive electronics unit 32 transmits the control signal 42 to only one of the isolated switch controls 40 at any given time during operation of the system 20.
A plurality of igniter switching units 38 each disposed between and connected to one of the isolated switch controls 40 and the one connected corona igniter 22 is also provided in the system 20. Thus, the number of the igniter switching units 38 is proportional to the number of the corona igniters 22. Each of the igniter switching units 38 is connected to the single transformer 34 for allowing current to travel from the single transformer 34 to the one connected corona igniter 22 when the associated igniter switching unit 38 is activated. The igniter switching unit 38 is activated and deactivated by the connected isolated switch control 40 in response to the control signal 42. The igniter switching unit 38 is also capable of preventing current from traveling from the transformer 34 to the connected corona igniter 22 and from the one connected corona igniter 22 toward the transformer 34 when the igniter switching unit 38 is deactivated. This feature is referred to as bidirectional blocking. The igniter switching unit 38 is activated a plurality of times per second, but fewer times per second than the transistors of the transformer switching unit 36 and is deactivated the remainder of each second during operation of the system 20.
Only one of the igniter switching units 38 is activated at any given time during operation of the system 20 in order to selectively enable only one corona igniter 22 at any given time during operation of the system 20. The igniter switching unit 38 needs to only operate at the speed of engine rotation (typically tens of Hz) and only needs to switch once during each period of many milliseconds. This allows for a slower, cheaper, and less complicated circuit in the isolated switch control 40, along with slower and cheaper igniter switching unit 38.
The system 20 of the present invention is preferably designed to avoid parasitic losses caused by connecting multiple igniter switching units 38 to the output of the single transformer 34. For example, parasitic losses can be reduced by careful design of the PCB and the isolated switch controls 40, such as locating the isolated switch controls 40 close to the transformer 34.
At least one of the igniter switching units 38 includes a pair of transistors. In this case, the isolated switch control 40 isolates the transistors from the control signal 42. One of the transistors prevents current from traveling from the transformer 34 to the one connected corona igniter 22 and the other one of the transistors prevents current from traveling from the one connected corona igniter 22 toward the transformer 34 when the igniter switching unit 38 is deactivated. Alternatively, at least one of the igniter switching units 38 includes a triode for alternating current (TRIAC). The TRIAC also prevents the current from traveling from the transformer 34 to the one connected corona igniter 22 and prevents the current from traveling from the one connected corona igniter 22 toward the transformer 34 when the igniter switching unit 38 is deactivated. Another alternative is to use a gallium nitride (GaN) transistor for at least one of the igniter switching units 38.
Another exemplary embodiment of the corona discharge ignition system 20 is shown in
As shown in
One advantage of the system 20 of
Another aspect of the invention provides a method for operating a corona discharge ignition system 20. The method includes providing energy from the power supply 24 to the control and drive electronics unit 32, and transferring the energy from the control and drive electronics unit 32 toward the plurality of corona igniters 22. The method further includes increasing the voltage of the energy before transferring the energy from the control and drive electronics unit 32 toward the plurality of corona igniters 22.
The method then includes activating the igniter switching units 38 to convey the current from the transformer 34 through the igniter switching units 38 to the plurality of corona igniters 22 and deactivating the igniter switching units 38 to prevent the current from traveling to and from the connected corona igniters 22. The step of activating the igniter switching units 38 includes activating only one of the igniter switching units 38 and conveying current to only one of the corona igniters 22 at any given time during operation of the system 20.
The step of activating only one of the igniter switching units 38 is in response to a control signal 42 from the control and drive electronics unit 32. In addition, the step of activating the igniter switching units 38 includes activating each of the igniter switching units 38 a plurality of times per second, and the step of deactivating the igniter switching units 38 includes deactivating each igniter switching units 38 for the remainder of each second during operation of the system 20.
The method typically includes providing the energy from the control and drive electronics unit 32 to the transformer 34 for increasing the voltage of the energy before transferring the energy from the control drive and electronics unit toward the plurality of corona igniters 22. The transformer switching unit 36 allows current to travel from the control and drive electronics unit 32 to the transformer 34 when one of the transistors of the transformer switching unit 36 is activated by the control and drive electronics unit 32 and prevents the current from traveling from the control and drive electronics unit 32 to the transformer 34 when the transistors of the transformer switching unit 36 are deactivated by the control and drive electronics unit 32. The method also includes activating each of the transistors of the transformer switching unit 36 a plurality of times per second, and more times per second than the igniter switching units 38. The method also includes deactivating the transistors of the transformer switching unit 36 the remainder of each second during operation of the system 20.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the appended claims.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/985,709 filed Apr. 29, 2014, which is hereby incorporated by reference in its entirety.
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