JP4123324B2 - Device for determining gap quality of spark plug of internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gap quality determination device for an ignition plug of an internal combustion engine for determining whether or not a spark gap in the ignition plug of the internal combustion engine is appropriate.
[0002]
[Prior art]
As this type of spark plug gap quality determining device, for example, a spark plug inspection method described in JP-A-10-170407 can be cited. In this known inspection method, a discharge voltage is applied to a spark plug assembled in an engine, and a value related to the applied voltage is detected to inspect the state of the spark plug. Specifically, a discharge voltage application device is connected to a spark plug to apply a discharge voltage, and the spark gap collapse or insulator is based on the result of measuring the primary voltage generated by the application device and the induction discharge time. Checking for cracks.
[0003]
[Problems to be solved by the invention]
The above-described known inspection method is effective when the ignition plug assembled in the engine is inspected alone, but it is used to inspect the entire ignition system including the ignition coil connected to the ignition plug. Is not suitable. That is, when the discharge voltage application device is used for inspection as described above, the inspection can be performed only before the ignition coil is connected to the spark plug. Therefore, in the known inspection method, the ignition including the ignition coil is actually performed. System discharges are not the subject of inspection. In addition, since the secondary voltage in an actual ignition system is extremely high compared to the primary voltage, the detection of the secondary voltage may be avoided in the known inspection method because of the limit of the withstand voltage performance of the measuring instrument. In many cases, the inspection is performed by measuring only the primary voltage. In this case, for example, in a plug top type ignition coil with a built-in power transistor, the coil electrode is structurally not exposed to the outside, so that the primary voltage cannot be taken out and measured as it is.
[0004]
As described above, regarding the spark plug gap inspection, further technical improvement has been desired. Therefore, the present invention has an object to provide a more preferable improved technique for the gap inspection of the spark plug.
[0005]
[Means for Solving the Problems]
An internal combustion engine spark plug gap quality determining apparatus according to the present invention (Claim 1) detects a secondary voltage induced in an ignition coil at a position near the coil in a state where an ignition system is assembled to the internal combustion engine. The counter electromotive force generated at the end of the secondary discharge is read while monitoring the output waveform of the secondary voltage signal, and the quality of the spark gap of the spark plug is determined based on the amount of change in the counter electromotive force. .
[0006]
The detection of the secondary voltage in the present invention can be performed by detecting the change in the magnetic field induced by the discharge on the secondary side of the ignition coil. Therefore, the discharge of the ignition system used in an actual internal combustion engine is inspected. It becomes the object of. At this time, if the primary current is made constant, the secondary current also becomes constant, so that the discharge time is proportional to the dielectric breakdown voltage proportional to the spark gap of the spark plug. In addition, since the back electromotive force generated at the end of the secondary current discharge is proportional to the amount of change in the magnetic field, the amount of change increases as the spark gap increases, and the amount of change in the back electromotive force is read from the change in the magnetic field at this time. Thus, it is possible to specifically determine whether the spark gap is good or bad.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIG. 1, the present invention can be implemented as a gap quality determining device for inspecting the spark gap of the spark plug 2 in a state where the ignition system 1 is assembled to the internal combustion engine. When the internal combustion engine is a multi-cylinder type, the spark plug 2 can be inspected for each cylinder.
[0008]
The ignition system 1 shown in FIG. 1 is called a so-called direct ignition system, and each ignition plug 2 is equipped with a plug top type ignition coil 4. The ignition coil 4 includes a primary coil 8 and a secondary coil 10 that are arranged around a ferrite core 6, and a predetermined turn ratio is set between the primary and secondary coils 8 and 10. A power supply cord 12 is connected to the primary coil 8 via a primary terminal (not shown), and the switching operation can be controlled using a power transistor (not shown). The power transistor is built in the mold 14 of the ignition coil 4 and receives an ignition signal from, for example, an electronic control unit (not shown) of the internal combustion engine to energize the primary current. The secondary coil 10 is connected to a terminal nut (none of which is shown) of the spark plug 2 via a secondary terminal.
[0009]
The gap quality determination device of the present invention has a detection coil 18 arranged, for example, immediately above the ignition coil 4, and this detection coil 18 converts a change in magnetic field due to the discharge of the secondary coil 10 into a change in voltage. And a function of outputting as a secondary voltage signal (detection means).
Further, the gap quality determination device includes an inspection unit 20, and the output of the above-described detection coil 18 is taken into the inspection unit 20. The inspection unit 20 incorporates an oscilloscope, for example, and has a function of displaying the secondary voltage signal from the detection coil 18 as a voltage waveform or displaying numerically. A display device other than the oscilloscope may be used for the inspection unit 20. The inspection unit 20 also has a function of monitoring the output waveform of the secondary voltage signal together with these display functions (monitoring means).
[0010]
【Example】
Hereinafter, an embodiment of the spark gap quality determination method according to the present invention will be described. Further, through the description of the following embodiments, other configurations (determination means) in the gap quality determination device will be clarified.
As shown in FIG. 1, the ignition system 1 is actually operated in a state where the inspection coil 18 is disposed immediately above the ignition coil 4 to cause the spark plug 2 to spark. At this time, the internal combustion engine may stop its operation, or may perform either a motoring operation or a firing operation.
[0011]
FIG. 2 shows an output waveform of the secondary voltage signal displayed in the inspection unit 20 described above. For example, when current flows through the primary and secondary coils 8 and 10 in the ignition coil 4, magnetic fields corresponding to the primary and secondary currents are generated. At this time, if the primary current is constant, the secondary current is also constant. Therefore, the discharge time T depends on the magnitude of the breakdown voltage proportional to the magnitude of the spark gap in the spark plug 2. Become. In addition, the magnitude of the back electromotive force generated at the end of the secondary current discharge depends on the amount of change in the magnetic field, and is therefore proportional to the magnitude of the spark gap. Accordingly, at this time, the amount of change in the back electromotive force can be observed as the amplitude H of the secondary voltage signal, and the magnitude of the amplitude H is proportional to the size of the spark gap in the spark plug 2.
[0012]
FIG. 3 shows an example of a preferred chart that can be used to determine the quality of the spark gap in the present invention. The chart of FIG. 3 defines the quality criteria based on the relationship between the discharge time T obtained from the output waveform of the secondary voltage signal in the inspection unit 20 and the amplitude H at the end of discharge and the spark gap in the spark plug 2. It is.
Specifically, as the spark gap in the spark plug 2 is smaller, the discharge time T is longer and the amplitude H of the output waveform accompanying the change in the counter electromotive force tends to be reduced. Conversely, as the spark gap is larger, the discharge time is longer. T is short and the amplitude H tends to be increased. Therefore, for example, if the normal discharge time T ₀ and the normal amplitude H ₀ in the normal spark gap of the spark plug 2 are measured in advance, the normal discharge time T ₀ and the normal amplitude H ₀ in FIG. A regular point P ₀ can be defined on the chart.
[0013]
For example, when the discharge time T obtained during the inspection of the ignition system 1 is shorter than the normal discharge time T ₀ and the amplitude H is larger than the normal amplitude H ₀ , the spark gap of the spark plug 2 to be inspected is It is considered larger than the normal value. On the other hand, when the obtained discharge time T is longer than the normal discharge time T ₀ and the amplitude H is smaller than the normal amplitude H ₀ , the spark gap is considered to be smaller than the normal value.
[0014]
The above-described inspection unit 20 can include, for example, a comparison circuit. In the comparison circuit, the values of the discharge time T and the amplitude H obtained at the time of inspection are respectively set to the normal discharge time T ₀ and the normal amplitude H _0. Compare. As a result, if there is no particular magnitude compared to the normal value, the inspection unit 20 can determine that the spark gap of the spark plug 2 is appropriate (non-defective). On the other hand, when it is recognized that the magnitude is extremely small compared to the normal value, the inspection unit 20 can determine that the spark gap of the spark plug 2 is defective (determination means).
[0015]
More preferably, constant allowable ranges t ₀ and h ₀ can be given to the values of the normal discharge time T ₀ and the normal amplitude H ₀ in the chart of FIG. 3, respectively, and the discharge time T and the amplitude H obtained during the inspection can be given. If the values are included in the allowable ranges t ₀ and h ₀ (hatched portions in the figure), the inspection unit 20 can determine that the spark gap is appropriate (determination means).
[0016]
In this embodiment, the ignition gap 2 is not electrically contacted, and the spark gap is judged to be good or bad based on the discharge by the actual ignition system 1 in a state where all the components of the ignition system 1 are incorporated in the internal combustion engine. It becomes possible. Therefore, the determination result can be applied as it is to the product inspection in the manufacturing process of the internal combustion engine. On the other hand, when the ignition plug is inspected independently using a voltage application device as in the prior art, it is not possible to perform an inspection including the ignition coil that is actually used, so a separate inspection step for the ignition coil is required. And
[0017]
In the above-described embodiment, the determination is made by measuring the discharge time T and the amplitude H on the secondary side as a more preferable mode. However, in the present invention, the determination is made by measuring only the amplitude H in principle. Is possible. That is, according to the inventor of the present invention, it is experimentally confirmed that the difference in length due to the quality of the spark gap hardly appears in the value of the discharge time T, and that a substantial error is included in the actual inspection. On the other hand, the change in the magnetic field due to the back electromotive force at the end of the discharge on the secondary side is likely to cause a difference in size due to the quality of the spark gap. Therefore, it is better to perform the pass / fail judgment based on the magnitude comparison of the amplitude H. More accurate determination can be performed.
[0018]
The specific pass / fail determination by the gap pass / fail determination apparatus of the present invention is not limited to the determination method of the above-described embodiment, and can be implemented in various modes.
Further, the ignition system 1 shown in FIG. 1 is an example, and it goes without saying that various other configurations are planned for the specific configuration of the ignition system 1 to be inspected in the present invention.
[0019]
【The invention's effect】
As described above, the gap determination device for a spark plug of an internal combustion engine according to the present invention (Claim 1) can accurately determine whether a spark plug is good or defective based on a highly accurate determination technique.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a gap quality determining device according to an embodiment.
FIG. 2 is a graph showing an output waveform of a secondary voltage signal.
FIG. 3 is a chart for determining whether a spark gap is good or bad.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ignition system 2 Spark plug 4 Ignition coil 10 Secondary coil 18 Inspection coil (detection means)
20 Inspection unit (monitoring means, judging means)

Claims (1)

A detector that is disposed in the vicinity of an ignition coil of an ignition system assembled in an internal combustion engine, detects a secondary voltage induced by the ignition coil, and outputs a secondary voltage signal;
Monitoring means for monitoring the output waveform of the secondary voltage signal output from the detection means;
A determination means for reading back electromotive force generated at the end of secondary-side discharge in the ignition coil from the output waveform of the secondary voltage signal and determining the quality of the spark gap of the spark plug based on the amount of change; An apparatus for determining whether a gap of a spark plug of an internal combustion engine is good.

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