Voltage transformer circuit and method for ionic current measurement of a spark plug

Patent metadata

Field	Value
Publication number	US-9985419-B2
Application number	US-201615234522-A
Country	US
Kind code	B2
Filing date	Aug 11, 2016
Priority date	Aug 14, 2015
Publication date	May 29, 2018
Grant date	May 29, 2018

Abstract

A voltage transformer circuit is described for supplying a spark plug with ignition energy and for ionic current measurement. A transformer of the circuit generates a secondary voltage from a primary voltage and applies the secondary voltage to the spark plug to ignite an electric arc. Using a current effected by the secondary voltage, a capacitor is charged to a breakdown voltage of a Zener diode bridging the same, via a first branch, which leads from the transformer to a first of two sides of the capacitor. The primary voltage is disconnected from the transformer in order to extinguish the electric arc. The capacitor delivers charges for an ionic current via a second branch, which connects the second side of the capacitor to the transformer. A measuring signal of the ionic current is obtained by measuring a voltage drop at a measuring resistor.

First claim

What is claimed is:

1. A voltage transformer circuit for supplying a spark plug with ignition energy and for ionic current measurement, comprising:
a transformer having a primary side and a secondary side, the secondary side configured to generate a secondary voltage from a primary voltage applied on the primary side;
a primary circuit comprising the primary side of the transformer, a connector for a primary voltage source and a switch for closing the primary circuit; and
a secondary circuit comprising in a series connection a capacitor, the secondary side of the transformer, a switch-on spark suppression diode and a connector for the spark plug;
wherein in the secondary circuit, the secondary side of the transformer is arranged between the capacitor and the connector for the spark plug and both the capacitor and the connector for the spark plug are each arranged between ground and the secondary side of the transformer;
wherein the capacitor is bridged by a Zener diode and is arranged in a loop which connects both sides of the capacitor to the same end of the secondary side of the transformer;
wherein a first circuit element is arranged in the loop on a first side of the capacitor between the capacitor and the secondary side of the transformer, said first circuit element being configured to only allow a charging current of the capacitor to pass, and a second circuit element is contained on a second side of the capacitor between the capacitor and the secondary side of the transformer, said second circuit element being configured to only allow a discharging current of the capacitor to pass.

2. The voltage transformer circuit according to claim 1 , wherein the first circuit element is a first diode and the second circuit element is a second diode, which is orientated oppositely to the first diode.

3. The voltage transformer circuit according to claim 1 , wherein a circuit branch branches from the loop between the capacitor and the second circuit element, which leads to ground and contains a third circuit element, which is configured to only allow a charging current of the capacitor through.

4. The voltage transformer circuit according to claim 3 , wherein the third circuit element is a diode.

5. The voltage transformer circuit according to claim 1 , wherein the loop is connected to a voltage source between the first circuit element and the capacitor via a transistor switch, wherein the transistor switch is actuated by a control signal, the value of which indicates whether the primary voltage is applied on the primary side of the transformer.

6. The voltage transformer circuit according to claim 1 , wherein a further circuit branch branches from the loop on the side of the second circuit element facing away from the capacitor, which leads to ground and contains a second capacitor.

7. The voltage transformer circuit according to claim 6 , wherein the second capacitor is bridged by a second Zener diode.

8. The voltage transformer circuit according to claim 6 , wherein the second capacitor in the further circuit branch is connected in series to a measuring resistor for ionic current measurement.

9. The voltage transformer circuit according to claim 8 , wherein the measuring resistor is bridged by a further Zener diode.

10. The voltage transformer circuit according to claim 1 , wherein a resistor is arranged in the loop on the side of the second circuit element facing away from the capacitor.

11. A method for measuring an ionic current of a spark plug, comprising:
using a transformer to generate a secondary voltage from a primary voltage and applying the secondary voltage to the spark plug to ignite an electric arc;
using a current effected by the secondary voltage to charge a capacitor to a breakdown voltage of a Zener diode bridging the same, via a first branch, which leads from the transformer to a first of two sides of the capacitor, the first branch including a first circuit element configured to only allow a charging current of the capacitor to pass;
disconnecting the primary voltage from the transformer in order to extinguish the electric arc;
using the capacitor to deliver charges for an ionic current via a second branch, which connects the second side of the capacitor to the transformer, the second branch including a second circuit element configured to only allow a discharging current of the capacitor to pass, and
obtaining a measuring signal of the ionic current by measuring a voltage drop at a measuring resistor.

12. The method according to claim 11 , wherein at least a portion of the charges delivered from the capacitor for an ionic current measurement is temporarily stored in a second capacitor which is arranged in a third branch, which branches from the second branch.

13. The method according to claim 12 , wherein the second capacitor is connected to earth via the measuring resistor.

Assignees

• Borgwarner Ludwigsburg Gmbh

Inventors

• Wüstenhagen Dirk

Classifications

• F02P2017/125

  Measuring ionisation of combustion gas, e.g. by using ignition circuits · CPC title

• H01T13/50

  having means for ionisation of gap (H01T13/52 takes precedence) · CPC title

• F02P17/12

  Testing characteristics of the spark, ignition voltage or current (testing of sparking plugs H01T13/60) · CPC title

• H01T15/00 Primary

  Circuits specially adapted for spark gaps, e.g. ignition circuits (ignition circuits for internal-combustion engines F02P; electric spark ignition for combustion apparatus F23Q; protection circuits using spark gaps H02H9/06) · CPC title

• H01T13/40

  structurally combined with other devices (combined or associated with fuel injectors F02M57/06; structurally combined with other parts of internal-combustion engines F02P13/00) · CPC title