JPH0262826B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spark plug inspection device for a multi-cylinder engine.

Conventionally, when inspecting spark plugs,
The spark plugs were removed from the engine and measured visually or with a thickness gauge, or an inspection probe was attached to the spark plugs and a high voltage was applied from the outside to determine whether the spark plugs were good or not based on the discharge voltage. There were problems such as lack of reliability. In order to solve this problem, from the required voltage of the spark plug when the engine suddenly accelerates, that is, the maximum value of the ignition voltage,
A method of determining whether a spark plug is good or bad has been proposed. The method that utilizes the magnitude of this required voltage is that when the engine suddenly accelerates, the air-fuel mixture in the cylinder becomes lean instantly, so the required voltage of the spark plug required to ignite and burn this air-fuel mixture is lower than that during normal operation ( This method takes advantage of the fact that the engine rises more during idling or constant speed driving. In other words, if a defective spark plug occurs, the required voltage of the spark plug will show an abnormal value when the engine suddenly accelerates (for example, if the gap between the center electrode and the ground electrode becomes large, it may be excessive, or it may be due to smoldering contamination). If this occurs, it is too low), and the quality of the spark plug is determined from the required voltage of the spark plug when the engine suddenly accelerates. This method can determine whether a spark plug is good or bad simply by measuring the required voltage of the spark plug and determining the magnitude of the required voltage, and is an effective method with excellent workability, especially in multi-cylinder engines. However, the required voltage of the spark plug during sudden engine acceleration varies greatly depending on the gap length and shape of the spark plug, the air-fuel ratio of the air-fuel mixture in the cylinder, etc. If the quality of a spark plug is determined only from the value of the required voltage of the spark plug, there is a problem in that subtle spark plug defects cannot be determined.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a spark plug inspection device for a multi-cylinder engine that can inspect even subtle defects in spark plugs with extremely high accuracy.

In order to achieve the above object, the present invention includes an ignition voltage detection circuit that detects a secondary voltage from an ignition device that generates a spark discharge in a spark plug provided in each cylinder and outputs an ignition voltage signal; a signal processing circuit that detects the maximum value of the ignition voltage of each spark plug from the ignition voltage signal and outputs the maximum ignition voltage signal; an operating state detection circuit that detects the engine operating state and outputs an operating state detection signal; a discrimination circuit that detects the occurrence of the spark discharge in the spark plug and outputs a reference signal; and a discrimination circuit that detects the occurrence of the spark discharge in the spark plug and outputs a reference signal; determining the average value of the maximum values, and determining the maximum value of the ignition voltage corresponding to each spark plug based on the maximum ignition voltage signal and the reference signal when a sudden acceleration of the engine is detected by the operating state detection signal; The apparatus further includes an arithmetic circuit that compares this average value with the maximum value of the ignition voltage corresponding to each of the spark plugs and outputs a comparison signal.

In determining the maximum value of the ignition voltage, an average value may be determined for each spark plug, or an average value for all spark plugs may be determined. As a result of the above configuration, the maximum value of the ignition voltage of each spark plug when the engine is rapidly accelerating is compared with the average value of the maximum value of the ignition voltage when the engine is idling, and a comparison signal output from the arithmetic circuit is used. The quality of the spark plug is determined.

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a basic circuit of a first embodiment of the present invention. As shown in the figure, an ignition voltage detection circuit 1 that detects a secondary voltage from an ignition device that generates a spark discharge in a spark plug and outputs an ignition voltage signal is connected to an arithmetic unit 4 via a signal processing circuit 2. and the signal processing circuit 2 via the timing circuit 3.
It is connected to the. Further, a discrimination circuit 5 that detects the occurrence of spark discharge in a specific spark plug and outputs a reference signal is connected to the arithmetic circuit 4 via a cylinder discrimination circuit 6. A timing circuit 3 is connected to this cylinder discrimination circuit 6. Furthermore,
The arithmetic circuit 4 is connected to a display device 7 and an operating state detection circuit 8 that detects the operating state of the engine and outputs an operating state detection signal.

FIG. 2 shows a concrete circuit of the basic circuit. The ignition voltage detection circuit 1 is composed of a partial voltage probe 10 using a resistor, a capacitor, an induction coil, etc.
It is attached directly or by clamp connection to the secondary voltage output terminal or the high voltage cord that electrically connects the ignition coil and the distributor, and divides the secondary voltage during engine operation to generate the ignition voltage signal a. Output. That is, since the secondary voltage of a normal ignition/discharge type ignition device is a high voltage of several tens of kilovolts, this voltage dividing probe 10 converts it into an ignition voltage signal of several volts and outputs it.

The signal processing circuit 2 includes a peak hold circuit 20 and a sample hold circuit 21 connected in series to the peak hold circuit 20.
The timing circuit 3 also includes a waveform shaping circuit 30 having a filter function for shaping the ignition voltage signal output from the partial voltage probe 10, and a signal processing circuit 2 based on the signal output from the waveform shaping circuit 30. It is composed of a pulse generation circuit 31 that outputs a timing signal. This timing signal is transmitted to the peak hold circuit 20 of the signal processing circuit 2.
It includes a reset signal b output to the sample hold circuit 21, and a sampling signal c output to the sample hold circuit 21.

The discrimination circuit 5 is composed of a trigger probe 50 using a capacitor or an induction coil, and is attached directly or by clamp connection to a high voltage cord connected to a spark plug provided in a specific cylinder (for example, the first cylinder). be done. Therefore, the reference signal f is output when the ignition voltage is applied to the ignition plug provided in the specific cylinder.

The cylinder discrimination circuit 6 includes a shaping circuit 60 that converts a reference signal (trigger signal) f output from the trigger probe 50 into a pulse and outputs a pulse signal g;
The pulse signal h for each spark plug, that is, for each cylinder, output from the waveform shaping circuit 30 of the timing circuit 3 is discriminated and separated for each cylinder based on the reference signal g.
It is composed of a selector circuit 61 that converts the cylinder signal in.

The arithmetic circuit 4 includes an A/D converter 40 that performs analog-to-digital (A/D) conversion of the signal output from the signal processing circuit 2, inputs various signals to a microcomputer 42, and outputs comparison signals to a display device 7. I/O interface 41 for outputting to
and a microcomputer 42, a calculation program for averaging the maximum value of the ignition voltage signal and performing comparison calculations for each cylinder, a reference value for determining the value of the comparison result, a maximum value of the ignition voltage, etc. It is configured to include a storage section 43 using a read-on memory, a random access memory, etc., and an input section 44 for inputting engine constants such as the number of cylinders of the engine to be inspected.

The operating state detection circuit 8 is composed of a throttle positioner that detects the opening degree of the throttle valve, an engine rotation speed sensor that detects the engine rotation speed, and the like. A sudden acceleration signal is output when the engine suddenly accelerates, that is, when the engine suddenly accelerates. Note that when using an engine speed sensor, engine idling and sudden engine acceleration are detected from changes in engine speed.

The operation of the first embodiment will be described below with reference to FIGS. 2 and 3. When the engine is rotated, each spark plug is ignited in sequence, and the ignition voltage signal a shown in FIG.

The waveform shaping circuit 30 of the timing circuit 3 outputs a pulse signal h having a pulse width corresponding to the time during which the level of the ignition voltage signal exceeds a predetermined level. Therefore, this pulse signal h becomes high level each time each cylinder, that is, each spark plug is fired. This pulse signal h is generated by the pulse generation circuit 31
and is input to the selector circuit 61.

The pulse generating circuit 31 outputs a sampling signal c that becomes high level every time the pulse signal h rises, and also outputs a reset signal b that becomes high level every time the pulse signal h falls. This reset signal b is input to the peak hold circuit 20, and the peak hold value is reset every time the reset signal b becomes high level. Here, the ignition voltage signal a has a DC component and a number
The signal includes a frequency component of 10 KHz, and the signal component indicating the value of the required voltage of the spark plug is included in the frequency component. Therefore, peak hold circuit 2
0, the required voltage value of the spark plug, that is, the maximum value of the ignition voltage signal a, is detected by holding the peak value within the period in which the level of the ignition voltage signal exceeds a predetermined level.

The peak hold signal d output from the peak hold circuit 20 is input to the sample hold circuit 21, and the peak hold value of the peak hold signal d is input every time the sampling signal c output from the pulse generation circuit 31 becomes high level. The DC signal e for each spark plug shown in FIG. 3 is output.

As described above, due to the effects of the signal processing circuit 2 and the timing circuit 3, the maximum value of the ignition voltage signal output from the secondary voltage detection circuit 1, that is, the required voltage value of the ignition plug, is determined for each spark plug, that is, for each cylinder. A/D converter 4
0, converted into a digital signal by the A/D converter 40, and then input to the microcomputer 42 via the input/output interface 41.

On the other hand, the reference signal (trigger signal) f detected by the trigger probe 50 is converted into a pulse signal g by the shaping circuit 60 and input to the selector circuit 61 . Furthermore, the pulse signal h output from the waveform shaping circuit 30 is input to the selector circuit 61 . This selector circuit 61 selects the pulse corresponding to the pulse of the pulse signal g of the pulse signal h, the first pulse corresponding to the pulse of the pulse signal g, and the second pulse corresponding to the pulse of the pulse signal g.
The th...th pulse is selected and the cylinder discrimination signal in
Output as . Figure 3 shows the cylinder discrimination signal of a 4-cylinder engine, where i ₁ is the first cylinder,
i ₂ is a cylinder discrimination signal corresponding to the second cylinder, i ₃ is the third cylinder, and i ₄ is the cylinder discrimination signal corresponding to the fourth cylinder. This cylinder discrimination signal in is input to the microcomputer 42 via the input/output interface.

Further, an engine idling signal and an engine sudden acceleration signal outputted from the driving state determination circuit 8 are input to the microcomputer 42 via the input/output interface 41.

The microcomputer 42 uses the engine constants such as the number of cylinders inputted through the input section 44, the cylinder discrimination signal inputted via the input/output interface 41, the operating state detection signal, and the maximum value of the ignition voltage signal, and stores them in advance. The following processing is performed according to the calculation program stored in the read-only memory of the unit 43.

First, when the engine idling signal is input, the cylinder discrimination signal in and the DC signal e indicating the maximum value of the ignition voltage signal are used to calculate the average value of the maximum value of the ignition voltage signal within a predetermined time for each cylinder. It is calculated and stored in the random access memory of the storage unit 43.
For example, in the case of a 4-cylinder engine, the cylinder discrimination signal i ₁
The maximum value of the ignition voltage signal input when the pulse is input is that of the first cylinder, so
By adding this maximum value within a predetermined period of time and dividing by the number of additions, the average value V ₁ ave of the maximum value of the ignition voltage signal of the No. 1 cylinder is obtained. The value V ₂ ave, the average value V ₃ ave of the third cylinder, and the average value V ₄ ave of the fourth cylinder are determined.

On the other hand, when a sudden engine acceleration signal is input, the maximum value of the ignition voltage (in the case of a 4-cylinder engine, V _1max ,
V ₂ max, V ₃ max, V ₄ max) are stored in random access memory.

Next, calculate the difference between the above average value and the maximum value for each cylinder (in the case of 4 cylinders, V ₁ max - V ₁ ave,
V ₂ max−V ₂ ave, V ₃ max−V ₃ ave, V ₄ max−V ₄
-ave), input this difference as a comparison signal to the display device 7 via the input/output interface and display it,
The quality of the spark plug for each cylinder is determined from the displayed results.

In addition, when processing with a microcomputer, a reference value is set in advance as the limit for whether the spark plug is good or bad, and when the difference between the above average value and the maximum value exceeds the reference value, the digital The determination result may be displayed on a display device. Further, the display method of the display device may be a digital display using the comparison signal, or the comparison signal may be converted into an analog signal and displayed on an analog meter or the like.

Next, a second embodiment of the present invention will be described. In this embodiment, when calculating the average value of the maximum value of the ignition voltage signal, the average value is not calculated for each cylinder but for all cylinders.

First, when the engine idling signal is input, the DC signal e indicating the maximum value of the ignition voltage signal is
The average value Vave of the maximum values of the ignition voltage signals of all the cylinders is determined using , and is stored in the storage section 43. continue,
Similarly to the first embodiment, the maximum value of the ignition voltage signal is determined for each cylinder during sudden engine acceleration, and the difference Vref between this average value and the maximum value is calculated (in the case of a 4-cylinder engine, V ₁ max - Vave, _V2max −Vave,
V ₃ max−Vave, V ₄ max−Vave), a comparison signal is output and displayed on the display device.

A specific example of determining the quality of a spark plug using the difference Vref between the average value and the maximum value of this embodiment will be described with reference to FIG. FIG. 4 is a graph showing the relationship between a comparison signal indicating the difference Vref between the average value and the maximum value and the gap length of the spark plug. The practical gap length of general spark plugs is approximately 0.7 to 1.1 mm, so if this range is set as the normal value, the difference will be
They can be classified as follows based on the Vref value.

Vref≒1.4~4KV...normal Vref≧6KV...abnormal due to large gear length Vref≦0KV...abnormal due to short gear length or smoldering contamination Vref≒4~6KV...not abnormal but requires inspection Vref≒1.4~ 0KV...No abnormality, but inspection is required. In Figure 4, each measurement point is a value that includes the spark plug type, electrode structure, and changes in the air-fuel ratio of the air-fuel mixture in the cylinder. Even if the value of changes, it is possible to accurately determine whether the spark plug is good or bad.

Next, a third embodiment of the present invention will be described in FIGS. 5 and 6.
This will be explained using figures. This embodiment uses a rotation speed discrimination circuit as the operating state detection circuit of the above embodiment,
The object of the present invention is to output a sudden engine acceleration signal at the most suitable time for determining the maximum value of an ignition voltage signal during sudden engine acceleration. Note that parts in FIG. 5 that are the same as or correspond to those in FIG. 1, and parts in FIG. 6 that are the same or correspond to those in FIG.

The difference between this embodiment and the above embodiments is that a rotation speed determination circuit 8 is used as the operating state detection circuit. The rotation speed determining circuit 8 is connected between the timing circuit 3 and the arithmetic circuit 4, as shown in FIG. Specifically, as shown in Figure 6,
This rotation speed determination circuit 8 is a counter that counts the pulse signal h output from the waveform shaping circuit 30 of the timing circuit 3 within a certain period of time, and calculates the rate of increase in the number of pulses of the pulse signal h within this certain period of time. It is composed of a circuit 80. Therefore, this counter circuit 80 outputs an engine idling signal when the count value corresponding to the engine speed is below a predetermined value, and when this count value is above the predetermined value and the rate of increase of the count value is above the predetermined value. When this occurs, a sudden engine acceleration signal is output. In addition, the count value when the engine sudden acceleration signal is output is an increase period of 1000 to 3000 rpm in terms of engine speed,
It is preferable that the rate of increase in the count value is 600 rpm/0.1 seconds or more when converted into the rate of increase in the number of engine rotations. Further, the counter circuit 80 may be incorporated into a microcomputer to calculate the counted value and its rate of increase.

Next, the operation of this embodiment will be explained with reference to FIG. First, in step 71, the engine is placed in an idling state, and in step 72, the average value of the maximum value of the ignition voltage signal is calculated for all cylinders. Then, this average value is stored in the memory A of the storage unit 43.
to be memorized. Next, in step 74, the engine is rapidly accelerated, and in step 75, it is determined whether the rapid acceleration condition satisfies the above-mentioned conditions.
If the acceleration state of the engine does not satisfy the above-mentioned conditions, the process returns to step 74 and the engine is rapidly accelerated again. If the engine is in the predetermined acceleration state, the maximum value of the ignition voltage signal is determined in step 76. is calculated for each cylinder. The maximum value found in step 76 is stored in memory B of the storage section 43 in step 77, and then compared with the average value stored in memory A in step 78, as in the previous embodiment. And step 7
In step 79, the comparison result obtained in step 8 is compared with a reference value, which is a limit on the quality of the spark plug. The comparison result is temporarily stored in the memory C of the storage section 43 in step 80, and then displayed on the display device 7 in step 81.

Note that the average value of the maximum values of the ignition voltage signals may be determined for each cylinder in the same manner as in the first embodiment.

As described above, according to this embodiment, the engine sudden acceleration signal is input at the most appropriate time, so if the engine acceleration is slow or a long time (1 second or more) has elapsed since the engine was suddenly accelerated. etc., it is possible to detect the maximum value of the ignition voltage signal immediately after sudden acceleration of the engine without detecting the maximum value of the ignition voltage signal when the air-fuel mixture in the cylinder does not suddenly become lean. can get.

In each of the above embodiments, an example has been described in which the average value of the maximum value of the ignition voltage signal is subtracted from the maximum value of the ignition voltage signal, but the reverse subtraction may be performed. In addition, the pulse signal g corresponding to the reference signal and the pulse signal h corresponding to each cylinder are input directly to the microcomputer via the input/output interface, and the microcomputer is used in place of the rotation speed discrimination circuit and the cylinder discrimination circuit. You may also do so. Further, although the ignition voltage signal is used as an input signal to the timing circuit, any signal generated from the ignition device and synchronized with the ignition voltage signal may be used, such as the primary voltage of the ignition device.

As explained above, according to the present invention, it is possible to obtain the unique effect that it is possible not only to determine the magnitude of the gap length of the spark plug, but also to determine the delicate quality of the spark plug, such as the state of smoldering and contamination.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a basic circuit of a first embodiment of the present invention, FIG. 2 is a block diagram showing a specific circuit of the embodiment, and FIG. 3 is a signal waveform of each part in FIG. FIG. 4 is a diagram showing the relationship between the comparison signal and the gap length of the spark plug.
FIG. 5 is a block diagram showing a basic circuit of the third embodiment of the present invention, FIG. 6 is a block diagram showing a specific circuit of the third embodiment, and FIG. 7 is a block diagram of the third embodiment. It is a flowchart showing the operation. 1... Ignition voltage detection circuit, 2... Signal processing circuit, 3
...Timing circuit, 4...Arithmetic device, 5...Discrimination circuit, 6...Cylinder discrimination circuit, 7...Display device.

Claims (1)

[Claims] 1. An ignition voltage detection circuit that detects a secondary voltage from an ignition device that generates a spark discharge in the ignition plug installed in each cylinder and outputs an ignition voltage signal, and detects the maximum ignition voltage of each spark plug from the ignition voltage signal. a signal processing circuit that detects the value and outputs a maximum ignition voltage signal; an operating state detection circuit that detects the operating state of the engine and outputs an operating state detection signal; and a signal processing circuit that detects the operating state of the engine and outputs an operating state detection signal; a discrimination circuit that detects the engine idling state and outputs a reference signal; When sudden acceleration of the engine is detected by the state detection signal, the maximum value of the ignition voltage corresponding to each spark plug is determined based on the maximum ignition voltage signal and the reference signal, and the average value and each spark plug are calculated. A spark plug inspection device for a multi-cylinder engine, comprising: an arithmetic circuit that compares a maximum value of a corresponding ignition voltage and outputs a comparison signal;