WO2013171139A2 - Method for operating an ignition device of a motor vehicle - Google Patents

Description

description

Method for operating an ignition device of a motor vehicle

The invention relates to a method for operating an ignition device for a spark plug of a motor vehicle, in which an adjustable Energieguelle the series circuit of the primary winding of an ignition transformer and a controllable switching element is connected in parallel, in which for storing energy in the magnetic field of the ignition transformer both the energy source and the Switching element can be controlled.

Such a method is known from DE 10 2009 057 925 AI. To charge the local - also known as ignition - ignition transformer designed as IGBT (Insulated Gate Bipolar Transistor) switching element is turned on and applied a supply voltage to the series circuit of the primary winding of the ignition transformer and the IGBT, during which charging the supply voltage are changed in time must ensure that the voltage induced on the secondary side remains safely below the current breakdown voltage, since no secondary-side blocking diode is used, which could prevent a secondary-side overvoltage, which could lead to unwanted ignition.

Such a switch-on high voltage leading to an unwanted ignition arises essentially from two effects: the secondary voltage of a transformer results from the voltage transformation ratio of the transformer of the product of the primary voltage with this transmission ratio. This behavior is inherent to a transformer and can not be prevented. To prevent a critical secondary high voltage, the maximum amplitude of the primary voltage must be so small that the secondary voltage does not reach the critical amplitude that could lead to turn-on sparking. On the other hand, a rapid increase in the effective voltage across the primary winding of the ignition coil causes kundärseitig due to the inductance of the primary winding and parasitic capacitances and the capacity of the spark plug electrodes is excited a vibration which leads to a secondary voltage pulse, which can lead to an unwanted ignition.

From DE 102004013561 AI it is known to form the drive voltage for the switching element ramped to avoid this problem. However, a complex control circuit is used for this.

It is the object of the invention to avoid this problem.

The object is achieved by a method according to claim 1. Advantageous further developments are specified in the subclaims.

In accordance with the invention, the source of energy supplies a voltage which increases continuously from zero volts to a maximum value or a current with a slew rate limited to a maximum value. In addition, the switching element can be driven with a drive voltage continuously increasing from 0 volts. The limitation of the voltage of the energy source to a maximum value, if this is a source of voltage in an embodiment of the invention, prevents an excessively high secondary voltage being able to occur due to the transmission ratio. In addition, the voltage of the energy source, if this is realized in an embodiment of the invention as a voltage source, not jumped, but increases continuously from 0 volts or, if the power source is designed as a power source, the rate of increase of the supplied current to a Maximum value limited. In addition, the switching element can be driven with a drive voltage continuously increasing from 0 volts. This can prevent the secondary-side voltage from starting to oscillate and reaches an amplitude that would result in an unwanted spark.

In one embodiment of the invention, the voltage of the energy source and / or the drive voltage for the switching element increase in a ramp.

In order to shorten the charging process of the ignition coil, in an alternative embodiment of the invention, when approaching the ignition point or at the top dead center of the piston, the gradient of the voltage of the energy source can also be increased - e.g. non-linear but quadratic or exponential - as the breakdown voltage at the spark plug increases as the pressure in the cylinder increases as the piston approaches top dead center.

The invention will be explained in more detail using an exemplary embodiment with the aid of figures. Showing:

1 shows a schematic circuit diagram of an ignition device for a motor vehicle,

 Figure 2 shows the voltage profile when driven with a

 changeable supply voltage and

 Figure 3 shows the voltage curve with variable drive voltage of the switching element.

An ignition device for a motor vehicle usually has an ignition transformer ZSP, often referred to as an ignition coil, with a primary winding PW and a secondary winding SW. A spark plug ZK is connected in parallel to the secondary winding SW of the ignition transformer ZSP.

In series with the primary winding PW of the ignition transformer ZSP, a switching element embodied as an IGBT is connected, which is controlled by a control circuit STS with a drive voltage VI _G BT. The series connection of the primary winding PW and the switching element IGBT is connected in parallel in the illustrated example of FIG. can be supplied voltage V _Supp i _y to supply the ignition transformer ZSP when switching element IGBT. Alternatively, the energy source EQ can also be designed as an electricity source.

FIG. 2 shows a first variant of the control of the ignition device shown in FIG. The drive voltage V _{IGBT of} the switching element IGBT should increase abruptly according to this embodiment, so that the switching element IGBT completely turns on. However, the voltage Vs _Upp i _y of Energieguelle EQ increases, controlled by a control circuit, not shown, linearly in the form of a ramp to a maximum value. Basically, other rise curves would be possible, it is essential that no jumps occur that can cause overshoot of the secondary voltage. As a result of the ramp-up of the voltage V _Supp i _{y of} the energy source EQ, the voltage V _Prim at the primary winding PW of the ignition transformer ZSP will also rise in a ramp.

Alternatively or additionally, as shown in FIG. 3, the drive voltage VIGBT of the switching element IGBT can rise from 0 V in a ramp-like manner. This prevents that, even in the event of an abruptly rising voltage V _Supp i _{y of} the energy source EQ, the primary voltage V _Prim at the primary winding PW of the ignition transformer ZSP can suddenly rise, since the collector emitter voltage V _{CE of} the load path of the primary voltage V _Prim formed in series with the primary voltage V _Prim Switching element IGBT can also change only ramped.

By the method according to the invention can be prevented even in the absence of Sekundärärseifiger diode swing over the secondary side of the ignition transformer and thus an unwanted ignition of the spark plug.

Claims

claims 1. A method for operating an ignition device for a spark plug (ZK) of a motor vehicle, in which an adjustable power source (EQ), the series connection of the primary winding (PW) of an ignition transformer (ZSP) and a controllable switching element (IGBT) is connected in parallel, in which both the energy source (EQ) and the switching element (IGBT) are driven to store energy in the magnetic field of the ignition transformer (ZSP), characterized, in that the energy source (EQ) supplies a voltage which increases continuously from 0V to a maximum value limited to a maximum value (V _Supp i _y ) or a current with a slew rate limited to a maximum value. 2. The method according to claim 1, characterized in that the switching element (IGBT) is driven by a continuously increasing from 0V to drive voltage (V _IGBT ). 3. The method according to claim 1 or 2, characterized in that the voltage (ν _3υρρ ι _γ ) of the energy source (EQ) and / or the driving voltage (V _IGBT ) rise ramped. 4. The method according to any one of claims 1 to 3, characterized in that the energy source (EQ) is a voltage source. 5. The method according to any one of claims 1 to 3, character- ized in that the energy source (EQ) is a power source.