FR2498257A1 - IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES - Google Patents

Abstract

An ignition system for internal combustion engines with a sensor (10) for detecting the knocking signals in combustion processes is proposed, the knocking signals being divided by an engine speed-dependent factor n. As a function of the resulting values, a retarding element (14) can be controlled, by means of which the ignition signals are retarded so that retarding of the ignition is achieved should knocking signals occur.

Description

 The subject of the invention is an ignition installation for internal combustion engines, comprising a detector for producing possible rattling signals during the combustion processes, and means for moving the ignition point in the direction of the delay in function of these knock signals.

 Knocking adjustment devices of this type are already known, for example from DE-OS documents 27 31 841, 28 32 594 and 29 21 125. Known adjustment devices process an adjustment algorithm with increments of crankshaft angle. This method is too complicated and too expensive, especially for simple ignition systems.

 The object of the invention is to avoid this drawback and for this purpose relates to an ignition installation of the above type, characterized in that the knock signals are divided by a factor "n" as a function of the speed of rotation and a delay device is controlled according to the resulting values, the spark plug ignition signals being delayed by this device.

 Compared with known embodiments, the ignition installation according to the invention has the advantage that the costly formation of the crankshaft angle increments is eliminated and that the adjustment algorithm is simplified.

It is therefore particularly suitable in the case of simple ignition installations.

 Provisions indicated in the following allow advantageous embodiments and improvements to be made to the ignition installation according to the invention.

 The invention will be better understood with reference to the description below and the appended drawing representing an exemplary embodiment of the invention. In this drawing, the single figure is a block diagram of an ignition installation according to the invention.

 A "knock" detector 10 is connected to a signal preparation circuit 11. In this circuit, the signal produced in the knock detector 10 is separated from the parasitic signals and it is converted into a knock signal by combustion process. This is known from the state of the art mentioned in the preamble.

The prepared knock signal A is sent to a divider stage 12 to which is further sent a signal n as a function of the speed of rotation. The output of this stage is connected, via a digital-analog converter 13 and an intermediate memory 17, to the delay control input of a delay member 14. The output signal
Z (t) of an ignition point caculator stage 15, of any known type, is sent, by means of delay device 14, to an ignition terminal stage 16 in which the control signals are used to produce ignition sparks on the spark plugs.

 The operating mode of the embodiment shown in the figure consists in that the prepared knock signal A is weighted in the divider stage 12 with the speed of rotation, by division of this knock signal by the value n depending on the speed of rotation.

The knock signal is thus lengthened or shortened depending on the speed of rotation. The series of weighted knock signals is converted into a control voltage in the digital-to-analog converter 13. This can take place, for example, by forming an average value. This control voltage determines the delay time of the delay member 14. The ignition signal Z (t) delayed by a value dt is sent in the form of a delayed control signal Z (t + djt) to the ignition terminal stage 16.

 It is obvious that a delay only occurs when there are knock signals. Otherwise, the delay time tt can take the value 0. This shift of the ignition point takes place in the direction of the delay, so that the operating range of the internal combustion motear is moved out of the knock range.

 So that this does not happen suddenly with the disappearance of the knock signals, the control voltage of the delay member 14 is gradually canceled in an intermediate memory 17 according to a determined time function. The intermediate memory 17 can, for example, be arranged in the form of a capacitor with a discharge member. The entire assembly thus constitutes an adjustment assembly. By weighting the knock signal A with the factor 1 / n; the same ignition point offset is caused for the same knock frequency. regardless of the speed of rotation.

 it is clear that instead of an analog delay member, one can provide a digital construction element whose delay time is adjustable by means of a digital quantity, a frequency or a number. Instead of the digital-analog converter 13, an appropriate converter must then be provided. In the case of a digital representation of the delay time, the delay member 14 can, for example, be arranged in the form of an adder stage.

Claims (3)

 1.- Ignition installation for internal c-combustion engines, comprising a detector to produce possible knock signals during the combustion processes, and means for moving the ignition point in the direction of the delay as a function of these knock signals, characterized in that the knock signals are divided by a factor p as a function of the speed of rotation and a delay member (14) is controlled according to the resulting values, the spark ignition signals being delayed by this organ.  2.- Ignition installation according to claim 1, characterized in that the knock signals weighted with the factor (1 / n) are converted into an analog voltage which is sent to the delay member (14) as order quantity.  3.- ignition installation according to one of claims 1 and 2, characterized in that the weighted knock signals are then processed according to a function of time.