Patent Grant
8528532
The present invention relates generally to the plasma-generation systems between two electrodes of a spark plug, used notably for the controlled radiofrequency ignition of a gas mixture in combustion chambers of an internal combustion engine.
For such a motor vehicle ignition application, with plasma generation, plasma-generating circuits incorporating plug coils are used to generate multi-filament discharges between their electrodes, to initiate the combustion of the mixture in the combustion chambers of the engine. The multi-spark plug referred to here is described in detail in the following patent applications filed in the name of the applicant: FR 03-10766, FR 03-10767 and FR 03-10768.
Referring to
When the resonator is powered by a high voltage at its resonance frequency Fc≈(½π√{square root over ((L×C))}), the amplitude at the terminals of the capacitor C is amplified, making it possible to develop multi-filament discharges between the electrodes of the plug, over distances of the order of a centimeter, at high pressure and for peak voltages less than 20 kV.
The sparks produced are then called “branched sparks”, inasmuch as they involve the simultaneous generation of at least several ionization lines or paths in a given volume, their branchings also being omnidirectional.
This application to radiofrequency ignition entails the use of a power supply, capable of generating voltage pulses, typically of the order of 100 ns, that can reach amplitudes of the order of 1 kV, at a frequency very close to the resonance frequency of the radiofrequency resonator of the plug coil. The greater the difference between the resonance frequency of the resonator and the operating frequency of the power supply is reduced, the higher the overvoltage coefficient of the resonator (ratio between the amplitude of its output voltage and its input voltage) becomes.
a schematically illustrate such power supplies.
According to the embodiment of
A control device 5 of the power supply circuit generates a control logic signal V1 and applies this signal to the gate of the power MOSFET transistor M, at a frequency which should be substantially aligned on the resonance frequency of the resonator 1.
The radiofrequency ignition system made up of the power supply circuit 2 and the resonator 1 is powered by a power supply voltage Vinter, designed to be applied by the switch M to an output of the power supply circuit, at the frequency defined by the control signal V1.
The power supply voltage Vinter is more specifically supplied via a parallel resonant circuit 4, comprising an inductor Lp in parallel with a capacitor Cp, and connected between a capacitor Cb of the power supply circuit, charged at the power supply voltage Vinter, and the drain of the switch M. The capacitor Cb, charged at the power supply voltage Vinter, is used notably to stabilize the current on an ignition command.
a details a variant of the power supply of
Close to its resonance frequency, the parallel resonator 4 transforms the power supply voltage Vinter into an amplified voltage Va, corresponding to the power supply voltage multiplied by the Q-factor of the parallel resonator. It is therefore the amplified power supply voltage Va which is applied to the output of the power supply circuit at the level of the drain of the switch transistor M.
The switch M then applies the amplified power supply voltage Va to the output of the power supply, at the frequency defined by the control signal V1, that should be made as close as possible to the resonance frequency of the plug coil. In practice, on an ignition command, in order to be able to set the radiofrequency ignition system to resonance mode and so maximize the transfer of energy to the resonator forming the plug coil, said plug coil must be controlled substantially at its resonance frequency.
The aim of the present invention is to determine this optimum resonance frequency of the radiofrequency plugcoil, in order to achieve optimum control at this resonance frequency of the plug coil.
The invention thus proposes a power supply device for a radiofrequency ignition system, comprising a power supply circuit configured to apply, to an output intended to be connected to a plasma-generating resonator, a power supply voltage at a frequency defined by a control signal supplied by a power supply circuit control device, characterized in that the control device comprises:
Preferably, the module for determining the optimum control frequency is configured to determine an optimum control frequency that is substantially equal to the resonance frequency of the plasma-generating resonator.
According to one embodiment, the power supply circuit comprises a switch controlled by the control signal and connected to the output.
Preferably, the capacitor of the power supply circuit is charged at the power supply voltage at the beginning of each ignition command.
Advantageously, the module for determining the optimum control frequency is configured to compare two successive deviation values between a value of the voltage at the terminals of the capacitor of the power supply at the start of an ignition command and a value of the voltage at the terminals of the capacitor of the power supply at the end of an ignition command, to modify the control frequency in a first direction if the difference between the successive deviation values has a first sign and to determine that the preceding control frequency is the optimum control frequency if the difference between the successive values has a second sign.
The invention also relates to a radiofrequency ignition device comprising a power supply device as claimed in any one of the preceding claims, and a plasma-generating resonator connected to the output of the power supply device.
Advantageously, the plasma-generating resonator is suitable for ignition in one of the following implementations: controlled combustion engine ignition, ignition in a particulate filter, decontamination ignition in an air conditioning system.
Other features and benefits of the present invention will become more clearly apparent from reading the following description, given by way of illustrative and nonlimiting example, and with reference to the appended figures in which:
a is a variant of the power supply of
As has been seen, for the ignition to be able to take place, it is necessary to determine an optimum control frequency for the control signal V1, controlling the switch M for the application of the high power supply voltage to the output of the power supply circuit to which the resonator 1 is connected. The optimum control frequency for the application of the power supply voltage to the plasma-generating resonator is a control frequency as close as possible to the resonance frequency of the resonator.
To achieve this, the control device 5 of the power supply comprises a module 53 for determining the optimum control frequency that is used, on reception of a request to determine an optimum control frequency on an interface 52 provided for this purpose, to determine and supply this optimum control frequency to a module 54, delivering the control signal V1 at the frequency determined on an output interface 55 of the control device to which the gate of the switch M is connected. The switch M then applies the high voltage, at the duly-defined frequency, to the output of the power supply circuit to which the plasma-generating resonator is connected.
There now follows a more detailed description of the process for determining the optimum control frequency applied by the control device, upon reception of a request to determine an optimum control frequency.
Tcb(t) is taken to be the voltage at the terminals of the capacitor Cb as a function of time.
At the instant t=0, the control signal V1 is applied to the control gate of the switch M, thus making it possible to apply the high voltage to the terminals of the resonator of the plug coil, at the frequency defined by the control signal V1.
At the instant t=D, following the application of the high voltage to the terminals of the resonator of the plug coil for a duration D, the spark is produced between the electrodes of the plug coil.
Upon such an ignition command, the radiofrequency resonator of the plug coil is driven at its resonance frequency if, and only if, the deviation, denoted ΔTcb, between the value of the voltage at the terminals of the capacitor Cb of the power supply circuit at the start of ignition, denoted Tcb(0) (i.e. at the instant t=0, when the control signal V1 is applied to the control gate of the switch M) and at the end of ignition, denoted Tcb(D) (i.e. after a duration D of application of the control signal V1 at the end of which the spark is produced between the electrodes of the plug) is maximum. Preferably, the above-mentioned voltage values used for calculating ΔTcb are squared.
In other words, the radiofrequency plasma-generating resonator 1 is driven at its resonance frequency if and only if:
ΔTcb=([Tcb(0)]2−[Tcb(D)]2) is a maximum.
Therefore, the module 53 for determining the optimum control frequency, upon successive ignitions, takes an electrical measurement of the voltage at the terminals of the capacitor Cb of the power supply at the start of ignition and at the end of ignition, via an interface 51 for receiving such measurement signals.
These electrical measurements of the value of the voltage at the terminals of the capacitor Cb at the start and at the end of ignition upon successive ignitions will then be used, on the basis of the principles explained above and as will be seen in more detail below, to determine an optimum control frequency for driving the plasma-generating resonator, corresponding substantially to the resonance frequency of the resonator. The optimum control frequency is then stored, then used as the control frequency for the switch M, in a normal operating phase of the radiofrequency ignition device, during which a plasma must be generated between the electrodes of the plug coil.
The plasma-generating device can include a plasma-generating resonator suitable for performing a controlled ignition of the combustion engine, suitable for performing an ignition in a particulate filter or suitable for performing a decontamination ignition in an air conditioning system.
In a step 101, a check is carried out to ensure that a request to determine the resonance frequency Fc of the resonator has been received.
In the absence of such a request, the algorithm goes on to the step 109 and a plasma is generated by the resonator 1 by using the optimum control frequency to apply the high voltage to the resonator 1 via the switch M. The switch M is then controlled to apply to the resonator 1 an adequate voltage to generate a plasma, in a manner that is known per se.
In the presence of a request to find the resonance frequency, the capacitor Cb of the power supply is charged at the voltage Tcb(0) designed to be applied via the switch M to the resonator 1 in the step 102 to command an ignition. This voltage is applied at a predetermined control frequency Ftemp, for example chosen to be equal to Fmin, corresponding to the minimum control frequency of the radiofrequency plasma-generating resonator.
In the step 103, a measurement Tcb(D) is taken of the voltage at the terminals of the capacitor Cb of the power supply after a duration D of application of the control signal V1 to the control gate of the switch M at the frequency Ftemp.
In the step 104, from the measurement signals Tcb(0) and Tcb(D) received over the reception interface, the deviation ΔTcb between the square of the voltage at the terminals of the capacitor Cb at the start of ignition Tcb(0) and the square of the voltage at the terminals of the capacitor Cb at the end of ignition Tcb(D), is calculated and compared to a reference ΔTref, the initial value of which is chosen, for example, to be equal to 0 in an initialization phase for this reference executed in the step 102.
If the calculated deviation ΔTcb exceeds the reference ΔTref, the reference ΔTref is first updated with the value ΔTcb previously calculated in the step 105.
A check is also carried out in the step 106 to ensure that the current value of the control frequency Ftemp is less than Fmax, corresponding to the maximum control frequency of the radiofrequency plasma-generating resonator. If the value Ftemp does not exceed Fmax, the value of the control frequency Ftemp is increased by a certain frequency step ΔF in the step 107.
For more details concerning the calculation of the frequency step used to increase the current value of the control frequency, the reader is urged to refer to the content of the French patent application 05 12769, filed in the name of the applicant.
The steps 102 to 104 are then repeated with the new values of Ftemp and ΔTref.
When, in the step 104, it has been determined that the deviation ΔTcb is less than the reference ΔTref, it is determined that the optimum control frequency of the resonator was the preceding control frequency. In the step 108, the control frequency is updated with its preceding value and the optimum control frequency of the resonator is set at this value, then substantially corresponding to the value of the resonance frequency F, of the plasma-generating resonator.
The optimum control frequency Fc determined in this way can then be used for the plasma generation in the step 109.
The algorithm that has just been described, applied by the module 53 of the control device 5, can then be used to obtain an optimum control at resonance frequency of the plasma-generating resonator.
| Number | Date | Country | Kind |
|---|---|---|---|
| 07 02275 | Mar 2007 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR2008/050216 | 2/12/2008 | WO | 00 | 1/15/2010 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2008/116991 | 10/2/2008 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4369758 | Endo | Jan 1983 | A |
| 5179928 | Cour et al. | Jan 1993 | A |
| 5361737 | Smith et al. | Nov 1994 | A |
| 5587630 | Dooley | Dec 1996 | A |
| 5949193 | Roine et al. | Sep 1999 | A |
| 6913006 | Schleupen et al. | Jul 2005 | B2 |
| 20020043255 | Kameda et al. | Apr 2002 | A1 |
| 20090165764 | Agneray et al. | Jul 2009 | A1 |
| 20090309499 | Agneray et al. | Dec 2009 | A1 |
| Number | Date | Country |
|---|---|---|
| 2 649 759 | Jan 1991 | FR |
| 2 859 831 | Mar 2005 | FR |
| 2007 017481 | Feb 2007 | WO |
| 2007 071865 | Jun 2007 | WO |
| Entry |
|---|
| U.S. Appl. No. 12/096,382, filed Oct. 16, 2008, Agneray et al. |
| U.S. Appl. No. 13/057,349, filed Feb. 3, 2011, Agneray et al. |
| Number | Date | Country | |
|---|---|---|---|
| 20100116257 A1 | May 2010 | US |
