JPS61169670A - Device for detecting weak ignition of spark plug - Google Patents

Abstract

PURPOSE:To make it possible to precisely detect weak ignition of a spark plug, by noticing that the amplitude of oscillation which is determined in accordance with the secondary impedance and floating capacity of an ignition coil, decreases when smolder and dirt exist on the spark plug, and by utilizing this fact to detect weak ignition. CONSTITUTION:With respect to a discharge voltage waveform detected by a voltage detecting section 15, a band filter circuit 16 extracts the oscillating component corresponding to the oscillating frequency upon normal operation. Further, the thus extracted oscillating component is subjected to a half-wave rectification and is smoothed, and is then led to a comparator circuit 18. Further, a reference signal SR from a reference signal generating circuit 17 is compared with a signal SA from the band pass filter circuit 16, and when the ignition is normal, a detection signal SD may be obtained. At this stage, if the detection signal may not be obtained in a predetermined time from the ignition timing, it is determined that any smoke or dirt is generated on a spark plug 9. With this arrangement, it is possible to precisely determine the presence of inferior ignition irrespective of the values of pressure in a combustion chamber and vortex flow in the spark gap.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a device for detecting ignition failure in one spark plug, and more specifically, in an internal combustion engine or the like that uses a spark plug for ignition, the present invention relates to a device for detecting ignition failure caused by fouling due to smoldering of one spark plug. This invention relates to a device for detecting ignition failure.

[Prior Art] Conventionally, as a method for detecting ignition failure in a spark plug, ignition failure caused by smoldering contamination is detected by measuring discharge resistance from the discharge voltage at the time of ignition in the ignition plug and the flowing current. This method is based on the principle that when smoldering occurs, the discharge resistance of the spark plug increases. As a conventional ignition failure detection device applying such a method, for example, JP-A-58
There is one disclosed in No.-8111182.

Figure ts4 shows an example of such a conventional device, where:
1 is a power source, 2 is an ignition switch, 3 is an ignition coil, and 4 is an ignition signal generation circuit that generates a signal in synchronization with the rotation of the internal combustion a5ff. Reference numeral 5 denotes an ignition timing control circuit that controls a power transistor circuit 6 that conducts/cuts off the primary current of the ignition coil 3 based on the ignition signal. 9 is a spark plug connected to one of the secondary terminals of the ignition coil 3; 7 is connected to the other secondary terminal of the ignition coil 3 for detecting a current value 12 during spark discharge in the ignition plug 9; It is a resistor.

11 is a division circuit that divides the collector voltage υ1 of the power transistor circuit 6 by a current value 12; 12 is a division circuit that compares the result of the division with a reference signal supplied by the reference signal generation circuit 13; is a comparator circuit that generates a contamination detection signal when is greater than a reference signal.

Note that 8 is a capacitor for absorbing a transient state during current detection, and IO shown by a broken line isometrically represents the discharge resistance of the ignition plug 9.

[Problems to be solved by the invention] That is, in such a conventional ignition failure detection device,
The collector voltage υl and discharge current 12 of the power transistor circuit 6 are detected, and the discharge resistance value in the ignition plug 9 is determined by dividing the collector voltage υ1 by the discharge current 12.
The configuration is such that the presence or absence of ignition failure is detected by comparing this value with a reference value. However, the discharge resistance value of the spark discharge path becomes large even when the pressure in the fuel chamber is high or when there is a strong air-fuel mixture vortex in the spark gap of the spark plug 8, so that a normal spark discharge may not occur. Nevertheless, there are cases where a ignition failure detection signal is generated, and therefore, the conventional device has a problem in that it lacks reliability.

[Object of the Invention] The present invention has been made in view of the above-mentioned problems, and the present invention is based on the discharge voltage waveform during spark discharge from the ignition plug. Focusing on the fact that the amplitude of vibration determined by stray capacitance becomes small, ignition failure is detected from the amplitude, thereby providing a highly reliable ignition plug failure detection device that can accurately detect ignition failure. The purpose is to

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a voltage generating means for generating a spark discharge in the ignition plug, and a discharge voltage detection device for detecting the voltage waveform at the time of spark discharge in the ignition plug. means, extraction means for extracting a signal of a frequency component determined by the characteristics of the voltage generation means from the detected discharge voltage waveform, and ignition failure detection means for detecting ignition failure of the spark plug from the magnitude of the amplitude of the extracted signal. It is characterized by having the following.

[Function] According to the present invention, whether ignition is good or bad is determined based on the amplitude of the electric signal of a predetermined frequency component extracted by the extraction means, so that the pressure in the combustion chamber and the magnitude of the vortex in the spark gap can be determined. Regardless of the situation, the presence or absence of ignition failure can always be accurately determined.

[Example] The present invention will be described in detail below with reference to one drawing.

Figures 3 (A) and (B) are respectively This figure shows the spark discharge voltage waveform of an ignition plug that has been damaged or contaminated.

In addition, in FIG. 3(A), the broken line is the waveform when the mixture vortex in the spark gap is large.According to the applicant's experiments, when contamination occurs, it adheres to the insulator leg of the spark plug. It was confirmed that spark discharge occurs on combustion products such as carbon, but no spark discharge occurs in the air gap, and as a result, the performance of igniting the air-fuel mixture deteriorates. Furthermore, when a normal spark discharge occurs, an oscillating component appears in the discharge voltage as shown in the circle in Figure 3 (A), and when it is contaminated, an oscillating component appears in the discharge voltage as shown in the circle in Figure 3 (B). It was confirmed that no vibration component appeared.

Therefore, in this example, this vibration component is extracted and it is determined whether the ignition is good or bad based on the magnitude of its amplitude.

FIG. 1 and FIG. 2 respectively show an example of the configuration of the ignition failure detection device for a spark plug of the present invention and an example of the configuration of its main parts. are given the same reference numerals and their explanations will be omitted.

15 is a voltage detection unit that detects the discharge voltage υ2, and includes a voltage dividing resistor R1 for adapting the discharge voltage to the circuits of the next stage and subsequent stages.
, R2. 16 is a bandpass filter circuit, and the coil L
4. L3 and capacitors Gl and C2. Here, the frequency f of the oscillating component of the discharge voltage waveform during normal spark discharge is expressed as f-1/2π(L2: inductance of the secondary coil, C: stray capacitance). In a normal ignition system, f = about 3 KHz, so constants of each part are selected so that that frequency band can be extracted.In addition, in the band filter circuit 1B, D performs half-wave rectification of the obtained signal waveform. Diode for C4
is a capacitor for smoothing the half-wave rectified waveform.

17 is a resistor R3 and a capacitor 05. This is a reference signal generation circuit having a Zener diode ZD, which leads the generated reference signal (reference value) SR to a child terminal of a comparator I8, and one terminal of the comparator 18 receives the output signal of the bandpass filter circuit 16. By supplying SA, a comparison with a reference value SR is made and a detection signal is generated when the signal SA is greater than the reference value SR.

With this configuration, the vibration component corresponding to the normal vibration frequency is extracted from the discharge voltage waveform detected by the voltage detection unit 15 by the bandpass filter circuit 1B, and the extracted vibration component is further subjected to half-wave rectification and smoothing. and is led to the comparator circuit 18. By comparing the reference value SR and the signal SA, a detection signal SD is obtained at the time of normal ignition.

That is, when this detection signal SO is not obtained within a predetermined time from the ignition timing, it can be determined that an ignition failure has occurred due to smoldering contamination.

In addition, in the embodiment, ignition failure was detected from the voltage waveform on the secondary side of the ignition coil, but since the primary voltage υ1 and the secondary voltage υ2 have a relationship of υl-E box I-v2, 2
Of course, the primary voltage vl may be used instead of the secondary voltage v2.

[Effects] As explained above, according to the present invention, it is noted that the discharge voltage waveforms are different during normal ignition and during ignition failure due to contamination, and a predetermined frequency component is extracted from the vibration amplitude. Since the system determines whether ignition is good or bad, it is possible to use a highly reliable spark plug that can always accurately detect ignition failure, regardless of the pressure inside the combustion chamber of an internal combustion engine or the size of the vortex in the spark discharge gap. It is possible to realize an ignition failure detection device.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the configuration of a faulty ignition detection device for a spark plug according to the present invention; FIG. 2 is a block diagram showing an example of the configuration of the main parts of the device shown in FIG. 1; FIG. 3(A) and (B) is a waveform diagram showing spark discharge voltage waveforms in normal conditions and in times of ignition failure, respectively. FIG. 4 is a block diagram showing an example of a conventional ignition plug failure detection device. 1...Power supply, 2...Ignition switch. 3... Ignition coil, 4... Ignition signal generation circuit, 5... Ignition timing control circuit, 6... Power transistor circuit, 7... Resistor. 8... Capacitor, 9... Spark plug, 10... Discharge resistor, 11... Division circuit, 12... Comparison circuit, 15... Voltage detection section, 1B... Bandpass filter circuit , 17... Reference signal generation circuit, 18... Comparator. Patent applicant: Nissan Motor Co., Ltd. Representative Patent attorney: Yoshi Tani - Figure 1 Figure 2 Figure 4

Claims (1)

[Scope of Claims] Voltage generating means for causing spark discharge in the ignition plug; Discharge voltage detecting means for detecting a voltage waveform during spark discharge at the ignition plug; and Voltage generating means for detecting the voltage waveform from the detected discharge voltage waveform. An ignition plug characterized by comprising an extraction means for extracting a signal of a frequency component determined by the characteristics of the ignition plug, and an ignition failure detection means for detecting an ignition failure of the ignition plug from the magnitude of the amplitude of the extracted signal. ignition failure detection device.