IGNITION COIL AND METHOD FOR OPERATING

Abstract

A method for operating an ignition coil is described, wherein a secondary voltage pulse is generated by feeding a primary voltage pulse into a transformer of the ignition coil, and a primary current, a primary voltage, a secondary current and/or a secondary voltage are measured, wherein the course of the primary current, the primary voltage, the secondary voltage and/or the secondary current are monitored and, when a malfunction is determined during subsequent primary voltage pulse, an error signal is generated which indicates that a malfunction has occurred during the previous primary voltage pulse and classifies the malfunction. In addition, a corresponding ignition coil is described.

Claims

1. A method for operating an ignition coil, comprising: feeding a primary voltage pulse into a transformer of the ignition coil and thereby generating a secondary voltage pulse; measuring a primary current, a primary voltage, a secondary current and/or a secondary voltage; monitoring the course of the primary current, the primary voltage, the secondary voltage and/or the secondary current; and when a malfunction is determined from the monitoring, generating an error signal during a subsequent primary voltage pulse, wherein the error signal indicates that a malfunction occurred during the previous primary voltage pulse and the error signal classifies the malfunction.

2. The method according to claim 1, wherein the classification of the malfunction is a function of the duration of the error signal.

3. The method according to claim 1, wherein the error signal is generated at a signal output at which a monitoring signal pulse is generated at least during some primary voltage pulses, the monitoring signal pulse being started as soon as the primary current reaches a first predetermined threshold value, and the monitoring signal pulse being terminated as soon as the primary current reaches a second predetermined threshold value that is greater than the first predetermined threshold value.

4. The method according to claim 3, wherein the error signal is started and terminated before the primary current reaches the first threshold value.

5. The method according to claim 1, wherein the beginning of the error signal is triggered by an increase of the primary voltage to a predetermined value.

6. The method according to claim 1, wherein the error signal is a pulse.

7. An ignition coil, comprising: a transformer having a primary side and a secondary side; a signal output; and a control and monitoring unit having sensors, the control and monitoring unit configured to: control the transformer and feed a primary voltage pulse into the primary side of the transformer to generate a secondary voltage pulse for a spark plug; monitor the course of primary current, primary voltage, secondary voltage and/or secondary current to detect a malfunction; in response to the detection of a malfunction, generate during a subsequent primary voltage pulse, an error signal on the signal output, the error signal indicating that a malfunction has occurred during the previous primary voltage pulse; and classify the malfunction.

8. The ignition coil according to claim 7, wherein the classification of the malfunction is a function of the duration of the error signal.

9. The ignition coil according to claim 7, wherein the control and monitoring unit is configured to generate a monitoring signal pulse on the signal output at least during some primary voltage pulses, which is started as soon as the primary current reaches a first predetermined threshold value, and the monitoring signal pulse is terminated as soon as the primary current reaches a second predetermined threshold value, which is greater than the first predetermined threshold value.

10. The ignition coil according to claim 7, wherein the control and monitoring unit only generates the monitoring signal pulse if no malfunction has been determined during the preceding primary voltage pulse.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0014] FIG. 1 is a schematic view of an ignition coil with opened housing;

[0015] FIG. 2 schematically shows the course of primary and secondary current as well as the potential on the signal output with error-free operation of the ignition coil;

[0016] FIG. 3 schematically shows the course of the primary current and the potential on the signal output for a faulty and a subsequent operating cycle of the ignition coil;

[0017] FIG. 4 schematically shows the course of the primary current and the potential on the signal output for a further example of a faulty and a subsequent operating cycle of the ignition coil; and

[0018] FIG. 5 schematically shows the course of the primary current and the potential on the signal output for a further example of a faulty and a subsequent operating cycle of the ignition coil.

DESCRIPTION

[0019] The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.

[0020] FIG. 1 schematically shows an ignition coil when the housing 1 is open. A transformer 2 is arranged in the housing, the transformer being controlled by a control and monitoring unit 3. In the embodiment shown, the control and monitoring unit 3 is configured as a circuit board with a circuit arranged thereon, which sits in the housing. The housing 1 carries a connector 4, via which the ignition coil can be electrically connected to a primary voltage source, for example the electrical system of a vehicle. The connector 4 may additionally form a signal input with one of its contacts and a signal output with another contact. Signal input and signal output can also be provided at another location on the housing in order to be connected with a separate connector to an engine control unit.

[0021] A secondary voltage pulse for an ignition coil is generated by feeding a primary voltage pulse into the transformer 2 of the ignition coil. The control and monitoring unit 3 of the ignition coil monitors the course of primary current and secondary current or primary voltage and secondary voltage with suitable sensors.

[0022] In FIG. 2, the course of the primary current I.sub.1 and of the secondary current I.sub.2 are shown schematically for an error-free operation of the ignition coil. In addition, the potential on the potential output S of the ignition coil is shown. In FIG. 2, the respective signal curve is plotted for two operating cycles of the ignition coil. At the beginning of a working pulse, a primary voltage pulse is fed into the transformer of the ignition coil. This primary voltage pulse causes a corresponding primary current pulse, as shown in FIG. 2. The primary current pulse is followed immediately by a secondary current pulse I.sub.2, which is delivered to a spark plug which is connected to the ignition coil. The increase of the primary current I.sub.1 is important for a precise control of the ignition timing. Therefore, a diagnostic signal pulse D is generated on the signal output S, which begins as soon as the primary current I.sub.1 has reached a first predetermined threshold value, for example 3 A, and is terminated as soon as the primary current I.sub.1 has reached a second threshold value, for example 6 A.

[0023] The width of such a diagnostic signal pulse D on the signal output of the ignition coil thus indicates to an engine control unit the rate of increase of the primary current I.sub.1.

[0024] FIG. 3 shows in FIG. 2 corresponding representations the course of primary current I.sub.1 and secondary current I.sub.2 over two operating cycles of the ignition coil, wherein a malfunction occurs in the first operating cycle. The malfunction appears in the course of the secondary current I.sub.2 in that it decays too slowly, so even after a predetermined period of time, it is still located above a predetermined threshold. This indicates that no spark has formed. In the subsequent operating cycle of the ignition coil, therefore, an error signal F is generated on the signal output S, for example, in the form of a voltage pulse or current pulse. The diagnostic signal pulse generated in the previous faulty operating cycle is omitted.

[0025] The error signal F is substantially shorter than a diagnostic signal pulse D and can already be reliably distinguished from a diagnostic signal pulse D. In addition, the error signal F is already generated at an earlier time in the operating cycle of the ignition coil, in particular, the error signal F is already terminated when the primary current I.sub.1 reaches the first threshold value.

[0026] FIG. 4 shows, by way of example, the signal courses in the event of a further error. In the case of an error of FIG. 4, the secondary current I.sub.2 decays much too quickly after the first primary voltage pulse, for example, because no spark has formed as a result of a sliding discharge. In the subsequent primary voltage pulse I.sub.1, an error signal F is therefore generated and the diagnostic signal pulse D is omitted.

[0027] Another example of an error is shown schematically in FIG. 5. In this error, the primary voltage pulse is much too long and the primary current I.sub.1 therefore remains very high for too long, which can happen, for example, by too long an activation of the transformer of the ignition coil. In this case, the diagnostic signal pulse D is omitted in the subsequent primary voltage pulse and instead an error signal F is generated.

[0028] The error cases explained in the preceding figures can be indicated by different length error signals to the engine control unit, for example, different length pulses or pulse sequences. Differences in the pulse length of 20 s can be detected reliably, so that even relatively small differences in the pulse length are sufficient to provide error signal pulses with a different length depending on the error. For example, a minimum pulse length of the error signal pulse in the range of 200 s to 300 s can be selected and the cause of error can be coded by pulse length differences of 20 s or more.

[0029] While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.