# US 5,347,855 A · Misfire detector device for use in an internal combustion engine

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- Number: US 5,347,855 A
- Document ID: US5347855A
- Status: Granted
- Kind: A
- Application number: 08/029,235
- Filed: 1993-03-10
- Granted: 1994-09-20
- Earliest claimed: 1992-03-11
- Assignees: Ngk Spark Plug Co., Ltd.
- Inventors: Shigeru Miyata; Yoshihiro Matsubara; Junichi Kagawa
- Web page: https://patentgrep.com/patent/US5347855A

## CPC

- H01T 13/467: {in parallel connection}
- F02P 17/12: Testing characteristics of the spark, ignition voltage or current (testing of sparking plugs H01T13/60)
- F02P 2017/121: {by measuring spark voltage}
- F02P 2017/123: {Generating additional sparks for diagnostics}
- F02P 2017/125: {Measuring ionisation of combustion gas, e.g. by using ignition circuits}
- H01T: SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES (overvoltage protection circuits H02H)
- F02P: IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES ({anti-pollution means for internal-combustion engines F02B17/00}; specially adapted for rotary-piston or oscillating-piston engines F02B53/12; {ignition of gas turbine plants F02C7/26; ignition of jet propulsion plants F02K9/95; starting of combustion engines F02N9/00}; ignition of combustion apparatus in general, glowing plugs F23Q; measuring of physical variables in general G01; controlling in general G05; data processing in general G06; electrical components in general see Section H; {ignition coils H01F38/12}; sparking plugs H01T13/00)

## Abstract

In a misfire detector device for use in internal combustion engine, an electrical interrupter circuit on-off actuates a primary current flowing through a primary circuit of an ignition coil to induce a sparkplug voltage which is applied to a multi-electrode type spark plug. A check diode or a series gap is provided in a secondary circuit of the ignition coil so as to prevent a current flowing back to the ignition coil. A sparkplug voltage detector circuit detects an attenuation time length of a sparkplug voltage waveform presented subsequent to a predetermined time period after an end of a spark action of the spark plug. On the basis of the attenuation time length, a distinction circuit determines whether a misfire occurs in a cylinder of an internal combustion engine.

## Claims

### Claim 1

A misfire detector device for use in an internal combustion engine comprising:
an ignition coil including a primary coil and a secondary coil;
an electrical interrupter circuit which on-off actuates a primary current flowing through a primary circuit of the ignition coil to induce a sparkplug voltage;
means provided in a secondary circuit of the ignition coil for preventing a current flowing back to the ignition coil;
a multi-electrode type spark plug which is to be energized from the ignition coil;
a voltage charging circuit which re-energizes the primary coil to induce an electromotive voltage in the secondary coil so as to electrically charge a stray capacity inherent in the spark plug at a time predetermined after the end of the spark action of the spark plug;
a voltage divider circuit which detects a divided voltage of the sparkplug voltage applied across electrodes of the spark plug;
a sparkplug voltage detector circuit which detects an attenuation time period length of an attenuation characteristic of a sparkplug voltage waveform presented subsequent to a time period predetermined after an end of a spark action of the spark plug; and
a distinction circuit which determines on the basis of the attenuation time period length of the attenuation characteristic whether or not the spark ignites an air-fuel mixture injected in a cylinder of an internal combustion engine.

### Claim 2

A misfire detector device for use in an internal combustion engine comprising:
an ignition coil including a primary coil and a second coil;
an electrical interrupter circuit which on-off actuates a primary current flowing through a primary circuit of the ignition coil to induce a sparkplug voltage;
means provided in a secondary circuit of the ignition coil for preventing a current flowing back to the ignition coil;
a multi-electrode type spark plug which is to be energized from the ignition coil;
a voltage divider circuit which detects a divided voltage of the sparkplug voltage applied across electrode of the spark plug;
a sparkplug voltage detector circuit which detects an attenuation time period length of an attenuation characteristic of a sparkplug voltage waveform presented subsequent to a time period predetermined after an end of a spark action of the spark plug; and
a distinction circuit which determines on the basis of the attenuation time period length of the attenuation characteristic whether or not the spark ignites an air-fuel mixture injected in a cylinder of an internal combustion engine.

### Claim 3

A misfire detector device for use in an internal combustion engine comprising:
an ignition coil including a primary coil and a secondary coil;
an interrupter circuit which on-off actuates a primary current flowing through a primary circuit of the ignition coil to induce a sparkplug voltage;
means provided in a secondary circuit of the ignition coil for preventing a current flowing back to the ignition coil;
a multi-electrode type spark plug which is to be energized from the ignition coil;
a voltage charging circuit which induces a sparkplug voltage in the secondary circuit of the ignition coil so as to electrically charge a stray capacity inherent in the spark plug at a time predetermined after an end of a spark action of the spark plug when the engine runs at a low revolution with a low load;
a voltage divider circuit which detects a divided voltage of the sparkplug voltage applied across electrodes of the spark plug;
a sparkplug voltage detector circuit which detects an attenuation characteristic of a divided sparkplug voltage waveform presented subsequent to a time period predetermined after an end of the spark action when the engine runs at a high revolution, and detecting an attenuation characteristic of a divided sparkplug voltage waveform derived from the voltage charging circuit when the engine runs at a low revolution with a low load; and
a distinction circuit which determines on the basis of the attenuation characteristic whether or not the spark ignites an air-fuel mixture injected in a cylinder of an internal combustion engine.

### Claim 4 (depends on 1, 2, 3)

A misfire detector device for use in an internal combustion engine as recited in any one of claims 1, 2 or 3, wherein a peak hold circuit is provided to hold a peak voltage of the sparkplug voltage waveform presented after the end of the spark action of the spark plug, so that the distinction circuit detects a misfire on the basis of a peak voltage level or the attenuation characteristic of the sparkplug voltage waveform.

### Claim 5 (depends on 1, 2, 3)

A misfire detector device for use in an internal combustion engine as recited in in any one of claims 1, 2 or 3, wherein the multi-electrode type spark plug has a center electrode, a front end of which is circumferentially coated by a precious metal-based layer, and a front end and its end surface of an outer electrode is also coated by the precious metal-based layer.

### Claim 6 (depends on 1, 2, 3)

A misfire detector device for use in an internal combustion engine as recited in any one of claims 1, 2, 3, wherein said means for preventing a current flowing back to said ignition coil comprises a series gap.

### Claim 7 (depends on 1, 2, 3)

A misfire detector device for use in an internal combustion engine as recited in any one of claims 1, 2, 3, wherein said means for preventing a current flowing back to said ignition coil comprises a check diode.