JPH05263744A - Misfire detecting device for internal combustion engine - Google Patents

Abstract

PURPOSE:To make the specified comparative voltage value appropriate so as to make a correct misfire judgment by generating a recharging command signal after the generation of an ignition command signal, and initializing the specified comparative voltage value for misfire judgment simultaneously with the generation of the recharging command signal. CONSTITUTION:In an ignition coil 1, a primary side coil 2 is connected to a transistor 4, and a secondary side coil 3 is connected to a spark plug 5. The misfire judging circuit 12 of an ECU 8 judges misfire when the period of the detection value of an ignition voltage sensor 10 connected to a connecting line 15 being over the specified comparative voltage value exceeds the reference value. According to the misfire judging result, a CPU 11 controls current application to the transistor 4 through a driving circuit. At this time, the CPU 11 generates a recharging command signal for generating high voltage again to the ignition coil 1 after the generation of an ignition command signal to the ignition coil 1, and initializes the specified comparative voltage value for misfire judgment simultaneously with the generation of the recharging command signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire detecting device for an internal combustion engine, and more particularly to a misfire detecting device for a cause of a fuel system.

[0002]

2. Description of the Related Art Ignition at an ignition plug of an internal combustion engine is not normally performed, that is, misfire may occur. The causes of this misfire are roughly classified into those related to a fuel system and those related to an ignition system. There is. The former is related to the fuel system due to the lean or rich of the fuel mixture, and the latter is related to the so-called miss spark. Miss spark means that normal spark discharge does not occur in the spark plug. For example, there is a case where normal spark discharge is not performed due to smoldering or fogging of the spark plug due to adhesion of unburned fuel, or due to abnormality of the ignition circuit.

The applicant of the present application detects an ignition voltage (inter-electrode voltage of a spark plug) as a misfire detecting device for detecting one of the above-mentioned misfires related to the cause of the fuel system, and the value of this ignition voltage is a predetermined voltage value. It has already been proposed that a misfire be judged when the period of time exceeds a predetermined period of time or more (Japanese Patent Application No. 3-326507).

[0004]

In the above-mentioned proposed device, the period when the ignition voltage value exceeds the predetermined voltage value corresponds to the period in which the stray capacitance in the vicinity of the spark plug stores a predetermined amount of electric charge or more, so that the discharge is performed. Depending on the state, even if a misfire occurs, the electric charge may be discharged within a relatively short period of time. For example, when the voltage at the end of inductive discharge becomes relatively high due to misfire, in such a case, there is a problem that re-discharge is performed between the plug electrodes within a short period of time and it is not possible to determine misfire. is there.

Further, when carbon or the like is attached around the plug electrode to cause a so-called smoldering state in which the insulation resistance is lowered, or when the smoldered substance is about to be recovered by self-cleaning, dielectric breakdown is likely to occur and ignition is ignited. During the period when the voltage value exceeds the predetermined voltage value, there is not much difference between the time of combustion and the time of misfire, and accurate misfire determination cannot be performed.

The present invention has been made to solve this problem, and enables accurate misfire determination even when the ignition voltage becomes a high voltage or when the ignition plug is about to smolder. An object of the present invention is to provide a misfire detection device that can be used.

[0007]

To achieve the above object, the present invention provides an engine operating state detecting means for detecting the value of an engine operating parameter, and an ignition timing determining ignition timing based on the value of the engine operating parameter. Ignition means having an ignition command signal generating means for generating a command signal, an ignition coil, and generating a high voltage for discharging an ignition plug provided in the engine based on the ignition command signal; and the ignition means. A voltage value detecting means for detecting a voltage value on the secondary side of the ignition coil when a high voltage is generated, and a period during which the ignition voltage value after the ignition command signal exceeds a predetermined comparison voltage value is a reference value. In a misfire detecting device for an internal combustion engine having a misfire judging means for judging that the engine is in a misfire state when exceeding, a recharge for again generating a high voltage in the ignition means after the ignition command signal is generated. A recharge command signal generating means for generating a decree signal, the one in which almost simultaneously said predetermined comparison voltage value and recharging command signal generation was provided with an initialization means for initializing.

Further, according to the present invention, in the above misfire detection device, the initialization means initializes the predetermined comparison voltage value not after the recharge command signal is generated but after a predetermined period has elapsed since the command signal was generated. It was done.

Further, it is preferable that the initialization means sets the predetermined period according to an engine operating state.

Further, it is preferable that the misfire determination means has a reference level setting means for setting the predetermined comparison voltage value according to the ignition voltage value.

Further, the ignition means has a primary side system path and a secondary side system path, and the secondary side system path suppresses a current in a direction opposite to the current at the time of spark plug discharge. Is desirable.

[0012]

The recharge command signal is generated after the ignition command signal is generated, and the predetermined comparison voltage value is initialized when the recharge command signal is generated or after a predetermined period has elapsed since the recharge command signal was generated.

The predetermined period is set according to the engine operating condition.

The predetermined comparison voltage value is set according to the ignition voltage value.

Further, the current in the direction opposite to the current at the time of spark plug discharge in the secondary system path of the ignition means is suppressed.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the construction of an embodiment of the misfire detection device for an internal combustion engine according to the present invention.

In the figure, the power supply voltage (battery voltage)
A power supply terminal T1 to which VB is supplied is connected to an ignition coil (ignition means) 1 including a primary coil 2 and a secondary coil 3, and the primary coil 2 and the secondary coil 3 are connected to each other at one end thereof. The other end of the primary coil 2 is connected to the collector of the transistor 4, the base of the transistor 4 is connected to the input terminal T2 to which the ignition command signal A is input, and the emitter thereof is grounded. The other end of the secondary coil 3 is connected to the anode of the diode 7, the cathode of the diode 7 is connected to the center electrode 5a of the spark plug 5 via the distributor 6, and the ground electrode 5b of the spark plug 5 is grounded. ing.

An ignition voltage sensor 10 which is electrostatically coupled to the connecting line 15 (forming a connecting line 15 and a capacitor of several PF) in the middle of the connecting line 15 connecting the distributor 6 and the center electrode 5a. Is provided, and the output of the ignition voltage sensor 10 is an electronic control unit (hereinafter referred to as “E”).
(Referred to as “CU”) 8 is connected to the misfire determination circuit 12. The misfire determination circuit 12 includes a CPU (central processing unit) 11
And the determination result is input to the CPU 11. The CPU 11 performs timing control related to misfire determination.

To the CPU 11, via the input circuit 13,
Various engine operating parameter sensors (engine operating state detecting means) 9 for detecting the values of engine operating parameters are connected, and the detected values of the engine operating parameters are input. Further, the CPU 11 is connected to the base of the transistor 4 via the drive circuit 14, and supplies the energization control signal A to the transistor 4.

In the present embodiment, the ECU 8 constitutes an ignition command signal generating means, a misfire determining means and a recharge command signal generating means.

FIG. 2 is a block diagram showing a specific configuration of the misfire determination circuit 12, where the input terminal T3 is the input circuit 21.
Is connected to the non-inverting input of the first comparator 25 via. The output of the peak hold circuit 22 is connected to the inverting input of the first comparator 25 via the comparison level setting circuit 24. In addition, the peak hold circuit 22 is supplied from the CPU 11 with a reset signal R1 that resets the peak hold value at an appropriate timing.

The output of the first comparator 25 is the gate circuit 26.
Is input to the pulse generation period measurement circuit 27 via the pulse generation period, and the measurement circuit 27 outputs a high-level output signal from the first comparator 25 during the gate period in which the gate circuit 26 outputs the input signal as it is. Is measured, and the voltage VT corresponding to the length of the measured period is supplied to the non-inverting input of the second comparator 29. The reference value setting circuit 28 is connected to the inverting input of the second comparator 29, and the reference voltage VTREF for misfire determination is supplied. When VT> VTREF is established, the output of the second comparator 29 becomes high level and FI
It is determined that a misfire has occurred. The reference voltage VTR
The EF is set according to the engine operating state. Further, a gate signal G for determining the gate period of the gate circuit 26 and a reset signal R2 for determining the reset timing of the period measuring circuit 27 are supplied from the CPU 11.

FIG. 3 is a circuit diagram showing a specific configuration of the input circuit 21, the peak hold circuit 22 and the comparison level setting circuit 24 shown in FIG.

In the figure, the input terminal T3 is connected to a resistor 215.
Operational amplifier (hereinafter referred to as “op amp”) 21
6 connected to the non-inverting input. Also, input terminal T1
Is a capacitor 211, a resistor 212 and a diode 214.
Is connected to ground through a circuit in which and are connected in parallel, and is connected to the power supply line VBS via a diode 213. The capacitor 211 is, for example, 10 ⁴ p
The voltage detected by the voltage sensor 13 is used to divide the voltage detected by the voltage sensor 13 into several thousandths. As the resistor 212, a resistor having a resistance of about 500 KΩ is used.
The diodes 213 and 214 are provided so that the input voltage of the operational amplifier 216 falls within the range of approximately 0 to VBS. The inverting input of the operational amplifier 216 is connected to its output, and the operational amplifier 216 operates as a buffer amplifier (impedance conversion circuit). The output of the operational amplifier 216 is connected to the non-inverting input of the first comparator 25 and the non-inverting input of the operational amplifier 221.

The output of the operational amplifier 221 is the diode 22.
Connected to the non-inverting input of operational amplifier 227 via 2,
The inverting inputs of the operational amplifiers 221 and 227 are both connected to the output of the operational amplifier 227. Therefore, these operational amplifiers also operate as buffer amplifiers.

The non-inverting input of the operational amplifier 227 is the resistor 22.
3 and the capacitor 226 are grounded, and the resistor 223
The connection point between the capacitor 226 and the capacitor 226 is connected to the collector of the transistor 225 via the resistor 224. The emitter of the transistor 225 is grounded, and the reset signal R1 that is at high level at reset is input to the base from the CPU 11.

The output of the operational amplifier 227 is grounded via the resistors 241 and 242 which constitute the comparison level setting circuit 24, and the connection point of the resistors 241 and 242 is the first comparator 2.
5 connected to the inverting input.

According to the circuit of FIG. 3, the peak value of the detected ignition voltage V (the output of the operational amplifier 216) is held by the peak hold circuit 22, and the peak hold value is set to 1 by the comparison level setting circuit 24. The first comparator 2 is multiplied by a predetermined small number and used as a comparison level VCOMP.
5 is supplied. Therefore, V> VCOMP is applied to the terminal T4.
When is satisfied, a high-level pulse signal is output.

FIG. 4 is a circuit diagram showing a specific configuration of the gate circuit 26 and the pulse measuring period measuring circuit 27. The transistors 41 to 43 and the resistors 44 to 51 form a three-stage inverting circuit. A transistor 61 is interposed between the collector of the transistor 42 and the ground, and the base of the transistor 61 has the CPU 11
From which a gate signal G is supplied. Therefore, the gate signal G
During the gate period when is low level, the collector of the transistor 43 becomes low level / high level corresponding to the high / low voltage of the terminal T4, and when the gate signal G is high level, the collector of the transistor 43 is at the terminal. It goes high regardless of the voltage of T4. The collector of the transistor 43 is connected to the base of the transistor 54 via the resistor 52, and the base of the transistor 54 is connected to the power supply line VBS via the resistor 53. The emitter of the transistor 54 is connected to the power supply line VBS, and the collector is connected to the ground via the resistor 55 and the capacitor 57. The connection point between the resistor 55 and the capacitor 57 is connected to the terminal T5 via the operational amplifier 59 and the resistor 60. The operational amplifier 59 is a buffer amplifier. The connection point of the resistor 55 and the capacitor 57 is connected to the collector of the transistor 58 via the resistor 56, and
The eight emitters are grounded. The reset signal R2 is input from the CPU 11 to the base of the transistor 58.

According to the circuit of FIG. 4, when the gate signal G is at low level and the terminal T4 is at high level, the transistor 4 is
The collector of 3 becomes low level, the transistor 54 is turned on, the capacitor 57 is charged, and the gate signal G
Is high level or the terminal T4 is low level, the transistor 54 is turned off and the charging of the capacitor 57 is stopped.
Therefore, the voltage VT proportional to the period in which the pulse signal input to the terminal T4 is at the high level in the gate period is obtained at the terminal T5.

The operation of the misfire detection device configured as described above will be described with reference to FIG. (A) and (b) of the figure show the energization control signal A and the gate signal G, respectively. Further, (c) to (e) of the figure show the characteristics of the fuel mixture at the time of normal combustion, and (f) to (i) of the figure show a misfire related to the cause of the fuel system (hereinafter referred to as "FI misfire"). Shows the characteristics of.

In this embodiment, as shown in FIG.
After the ignition command signal is generated at time t0 (after the primary coil 2 is energized for a period required for ignition and the current is cut off at time t0), the energization is performed again from time t1 to t2 (hereinafter, "re-energization"). ")). At the time of re-energization, at time t2, a voltage of a value (predetermined applied voltage value) that does not cause discharge between the electrodes of the spark plug 5 is applied, and electric charges are stored (charged) in the stray capacitance of the spark plug 5 and its peripheral circuits. This is done in order to do so. Hereinafter, the voltage applied to the spark plug 5 at time t2 is referred to as a recharge voltage (recharge command signal).

FIGS. 9B and 9F show the transitions of the detected ignition voltage (output voltage of the input circuit 21) V (B, B ') and the comparison level VCOMP (C, C'). First, the ignition voltage characteristic at the time of normal combustion will be described with reference to FIG.

In FIG. 3B, immediately after time t0 when the ignition command signal is generated, the ignition voltage V rises to a value that destroys the insulation of the fuel mixture (between the discharge gaps of the spark plugs), and after the insulation breakdown. Changes from a capacitive discharge state (a discharge state for a very short time by a current of several hundred amperes) before dielectric breakdown to an inductive discharge state in which the discharge voltage is approximately constant (a few milliamperes due to a current of several tens of milliamperes). Discharge period of about a second). The induced discharge voltage rises as the pressure in the cylinder rises with the compression stroke after time t0.
This is because the higher the pressure, the higher the voltage required for induction discharge. At the final stage of the induction discharge, the voltage between the spark plug electrodes becomes lower than the voltage for maintaining the induction discharge due to the reduction of the induction energy of the ignition coil, the induction discharge disappears and the capacity discharge state (the latter capacity discharge State). In the capacity discharge state, the voltage between the spark plug electrodes rises because the insulation of the fuel mixture is destroyed again, but the residual energy of the ignition coil 1 is small and the voltage rise is small. This is because the electric resistance between the plug gaps is low when combustion occurs, and is due to ionization of the fuel mixture during combustion.

The charge stored in the stray capacitance between the diode 7 and the spark plug 5 (the charge remaining without being discharged between the electrodes) is not discharged to the ignition coil 1 side because of the diode 7. However, since it is neutralized by the ions existing in the vicinity of the electrode of the spark plug 5, the ignition voltage V at the end of the capacity discharge is rapidly reduced.

After that, when the recharge voltage is applied at the time t2, the ignition voltage V rises, but the electric charge charged at this time is in the vicinity of the electrode of the ignition plug 5 just after the end of the latter capacity discharge described above. Since it is neutralized by the ions present in, it decreases rapidly.

On the other hand, in the illustrated example, the comparison level VCOMP has a value corresponding to the peak value of the ignition voltage V after the previous reset until the time t5, and is predetermined at the times t5 to t2 by the reset signal R1. The low-level fixed state is set, and the state is released at time t2 (hereinafter, the time when the predetermined low-level fixed state is released is referred to as “reset (initialization) timing”). Therefore, after time t2, a value corresponding to the ignition voltage V that has become the peak value due to the recharge voltage (in the present embodiment, 2/3 of the peak value).
The value is about). As a result, the first comparator 25 that compares the ignition voltage V with the comparison level VCOMP
As shown in (d) of the same figure, the output of the gate circuit 26 becomes high level near the time t0, the time t6 to t7, and the time t2 to t8, but the output of the gate circuit 26 is the time t3 when the gate signal G is low level. It becomes a high level only at t7 and times t2 to t8. Therefore, the output VT of the pulse generation period measuring circuit 27 changes as shown in (e) of the figure, does not exceed the reference voltage VTREF, and is determined to be normal combustion.

Next, the ignition voltage characteristics (characteristics indicated by broken lines) when the fuel mixture becomes lean or cut due to an abnormality in the fuel supply system or the like and FI misfire occurs (when combustion does not occur) will be described. To do. In FIG. 6 (f), the ignition voltage V (B ') rises to a value at which the insulation of the fuel mixture between the spark plug electrodes is destroyed immediately after the ignition command signal generation time t0. The voltage value contains a larger proportion of air in the fuel mixture than in the normal state, which increases the dielectric strength of the fuel mixture and does not cause combustion, so the fuel mixture is ionized. However, since the electric resistance between the plug gaps tends to increase, the voltage value becomes higher than the voltage value during normal combustion. After this, the state of induction discharge shifts as in normal combustion, but since the discharge resistance is also higher than in normal combustion, it tends to shift to the capacity discharge state earlier than in normal combustion. The value of the capacity discharge (the latter capacity discharge) that occurs in the final stage of the induction discharge is much larger than that during normal combustion because the dielectric breakdown voltage of the fuel mixture is larger than that during normal combustion.

At this time, since almost no ions exist near the electrode of the ignition plug 5, the electric charge accumulated between the diode 7 and the ignition plug 5 is not neutralized by the ions, and the diode 7 causes the ignition coil 1 to operate. However, when the pressure in the cylinder drops and the discharge required voltage becomes equal to the voltage applied by this charge, the discharge is carried out at the electrode of the spark plug 5, but the ignition voltage V When is high, it is discharged relatively early.

After that, when the recharge voltage is applied at the time t2, the ignition voltage V rises again, there is no neutralization by the ions between the plug electrodes as described above, and the action of the diode 7 causes a high voltage state. Continues. And
The cylinder pressure is further reduced and the required discharge voltage is the ignition voltage V.
When they become equal to each other, discharge is generated between the plug electrodes (time t11).

On the other hand, the comparison level VCOMP (C ') is
In the illustrated example, until the time t9, the value corresponds to the peak value of the ignition voltage V after the previous reset, and after the time t9, the value increases with the increase of the ignition voltage V, and the level corresponding to the peak value is changed to the time t5. Hold up to. Time t5
The ignition voltage V is fixed at a predetermined low level at t2 and reaches a peak value due to the recharge voltage after time t2.
Holds the value corresponding to.

As a result, the output of the first comparator 25 becomes high level near time t0, shortly before time t9, at times t9 to t10 and times t2 to t11, as shown in FIG. The output of the gate circuit 26 is at the high level only during the period when it is at the high level during the gate period TG.
Therefore, the output VT of the pulse generation period measuring circuit 27
Changes as shown in (h) of the figure, exceeds the reference voltage VTREF at time t12, and the output of the second comparator 29 becomes high level at times of t2 to t4 as shown in (i) of the figure. , FI misfire is detected.

As shown in FIG. 5 (f), when the ignition voltage V becomes a relatively high voltage during the latter capacity discharge, the ignition voltage V drops early (time t1.
0), at this time, the output VT of the period measuring circuit 27 does not exceed the reference voltage VTREF, so that the FI misfire cannot be detected. Therefore, in the present embodiment, at time t2, the recharge voltage of a value that does not cause discharge between the plug electrodes is applied, so that FI misfire can be reliably performed even when the ignition voltage V becomes a high voltage. Can be detected.

In this embodiment, the gate period TG (time t3 to t4) in which the gate circuit 26 is open is set to a predetermined period from the end point of the latter capacity discharge, but the end time t4 of the gate period TG is It may be any time before the rotor head of the distributor 6 reaches the next segment (within a range of about 120 degrees in crank angle from ignition).

Further, the pulse generation period measuring circuit 27 is reset at time t4.

Further, in the above-mentioned example, the reset timing of the peak hold circuit 22 is set at the same time when the recharge voltage is applied. This is because the level of the ignition voltage V is unstable during the late capacity discharge and immediately after that, so that if the voltage is reset during this period, the comparison level VC
This is because the OMP value becomes unstable, and accurate misfire detection cannot be performed, and there is no point in performing recharging if the recharging voltage is delayed too much. Therefore, the reset timing does not necessarily have to be the same as when the recharge voltage is generated, but it needs to be near the time when the recharge voltage is generated.

Next, the time when the recharge voltage is applied (hereinafter referred to as "recharge timing") will be examined.

When the recharge timing is before the end of the discharge generated by the ignition command signal, the ignition voltage V exceeds the comparison level VCOMP for a long period even during combustion, and the ignition voltage V is almost the comparison level V even during misfire.
In some cases, it may not exceed COMP, and accurate misfire determination cannot be performed.

On the other hand, if the recharge timing is delayed too much, the ions generated between the plug electrodes are reduced only during combustion, which makes it indistinguishable from that during misfire.

Therefore, it is optimal that the recharge timing is about 10 degrees after the top dead center in the crank angle.
It must be done at the latest before 40 degrees after top dead center.

In the present embodiment, attention is paid to the fact that the duration of discharge according to the ignition command signal changes depending on the operating state of the engine (particularly engine rotation speed and engine load). I try to determine the charge timing.

Next, the recharge voltage is set to a predetermined voltage value at which discharge does not occur between the plug electrodes as described above. This recharge voltage is controlled by the reenergization time T2.
(See FIG. 5A). This is because the energy stored in the ignition coil 1 changes depending on the reenergization time T2, and the generated voltage at the time of current interruption (time t2) changes.

The re-energization time T2 is CP depending on the engine load and the voltage VB of the battery supplying the spark plug 5 with electric power.
Calculated by U11.

Next, a case where carbon or the like is attached around the spark plug electrode and the insulation property is deteriorated will be described with reference to FIG. In (c) to (e) of the same figure, the solid line shows the characteristic at the time of combustion, and the broken line shows the characteristic at the time of FI misfire. As can be seen from this figure, during combustion, as shown in FIG.
The characteristics are almost the same as those in (e), but at the time of FI misfire, when the ignition voltage V rises during the latter-stage capacity discharge, discharge occurs through the attached carbon and the ignition voltage V immediately decreases (time t9). After that, even when the recharge voltage is generated (time t2), since the same change occurs, the comparison level V
COMP (c ') becomes a value according to the peak value at time t9 or t2, and the ignition voltage V becomes the comparison level VCOMP.
Almost no period exceeds. as a result,
As shown in (d) of the figure, the period during which the output of the first comparator 25 is at a high level in the gate period is almost the same as that during combustion, and the misfire state cannot be detected.

Therefore, in another embodiment of the present invention, as shown in FIG. 7, the reset timing of the peak hold circuit 22 is set to the time t13 after the elapse of a predetermined period TD from the recharge voltage generation time (time t2). As a result, the comparison level VCOMP becomes as shown by the curve c'in the same figure (c), and the ignition voltage V exceeds the comparison level VCOMP from the time t5 to t11 (the same figure (d)). As a result, the output VT of the pulse generation period measuring circuit 27 exceeds the reference voltage VTREF from time t12 to t4 as shown in FIG.

Here, considering that it is necessary to prevent the predetermined period TD from being reset at the protruding portion of the ignition voltage generated by recharging (the portion indicated by P in FIG. 7C), the engine operating state (for example, It is set according to the engine load). This is because the time width of the protruding portion changes depending on the engine operating state.

According to this embodiment, FI misfire can be accurately detected even when the spark plug is about to become smoldered or is about to recover from the smoldered state.

When the FI misfire is detected by utilizing the fact that the electric charges charged in the spark plug and its peripheral circuits differ between FI misfire and combustion as in the above-described embodiment, the ignition is performed. The polarity of the voltage applied to the plug 5 is preferably positive on the side of the center electrode 5a. By setting a positive potential, the charge charged in the peripheral circuit of the plug electrode becomes a positive charge, and it becomes a negative charge, that is, an electron, which neutralizes this at the time of combustion, and the moving speed is faster than that of a positively charged ion .. As a result, the difference between the time of combustion and the time of misfire during the period when the ignition voltage V exceeds the comparison level VCOMP becomes remarkable.

[0060]

As described in detail above, according to the misfire detection device of the first aspect, the recharge command signal is generated after the ignition command signal is generated, and the predetermined comparison voltage value is initialized almost simultaneously with the recharge command signal. Therefore, the predetermined comparison voltage value becomes appropriate, and the misfire determination based on the period in which the ignition voltage value exceeds the predetermined comparison voltage value can be performed more accurately.

According to the misfire detecting device of the second aspect, since the predetermined comparison voltage value is initialized after a predetermined period has elapsed since the recharge command signal was generated, the predetermined comparison voltage value becomes more appropriate and the spark plug is Accurate misfire determination can be performed even when a smoldering state is approaching or when a smoldering state is about to be recovered.

According to the misfire detection device of the third aspect, since the predetermined period is set according to the engine operating condition, it is possible to accurately determine the misfire over a wide range of the engine operating condition.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a misfire detection device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a specific configuration of a misfire determination circuit.

FIG. 3 is a circuit diagram showing a specific configuration of part of a misfire determination circuit.

FIG. 4 is a circuit diagram showing a specific configuration of part of a misfire determination circuit.

FIG. 5 is a time chart for explaining the operation of the misfire determination circuit.

FIG. 6 is a time chart for explaining the operation of the misfire determination circuit.

FIG. 7 is a time chart for explaining the operation of the misfire determination circuit.

[Explanation of symbols]

 1 Ignition coil 2 Primary coil 3 Secondary coil 5 Spark plug 8 Electronic control unit (ECU) 9 Various engine operation parameter sensor 10 Ignition voltage sensor 11 CPU 22 Peak hold circuit 26 Pulse generation period measurement circuit

Front page continued (72) Inventor Takashi Hisaki, 1-4-1, Chuo, Wako-shi, Saitama Stock Research Institute, Honda R & D Co., Ltd. (72) Inventor, Kazuto Sawamura, 1-4-1, Chuo, Wako-shi, Saitama Stock Association Incorporated in Honda R & D Laboratories (72) Inventor Shigeru Maruyama 1-4-1 Chuo Wako, Saitama Stock Company Incorporated in Honda R & D Laboratories (72) Inventor Takuji Ishioka 1-4-1 Chuo Wako, Saitama Inside Honda Research Laboratory

Claims (5)

[Claims] 1. An engine operating state detecting means for detecting a value of an engine operating parameter, an ignition command signal generating means for determining an ignition timing based on the value of the engine operating parameter and generating an ignition command signal, and an ignition coil. And an ignition means for generating a high voltage for discharging an ignition plug provided in the engine based on the ignition command signal, and an ignition coil for generating a high voltage in the ignition means. A voltage value detecting means for detecting a voltage value on the secondary side, and a misfire determining means for determining an engine misfire state when a period during which the ignition voltage value after the ignition command signal exceeds a predetermined comparison voltage value exceeds a reference value. In a misfire detection device for an internal combustion engine having, after the ignition command signal is generated, recharge command signal generating means for generating a recharge command signal for causing the ignition means to generate a high voltage again, A misfire detection device for an internal combustion engine, comprising: an initialization unit that initializes the predetermined comparison voltage value substantially at the same time when the recharge command signal is generated. 2. An engine operating state detecting means for detecting a value of an engine operating parameter, an ignition command signal generating means for determining an ignition timing based on the value of the engine operating parameter and generating an ignition command signal, and an ignition coil. And an ignition means for generating a high voltage for discharging an ignition plug provided in the engine based on the ignition command signal, and an ignition coil for generating a high voltage in the ignition means. A voltage value detecting means for detecting a voltage value on the secondary side, and a misfire determining means for determining an engine misfire state when a period during which the ignition voltage value after the ignition command signal exceeds a predetermined comparison voltage value exceeds a reference value. In a misfire detection device for an internal combustion engine having, after the ignition command signal is generated, recharge command signal generating means for generating a recharge command signal for causing the ignition means to generate a high voltage again, A misfire detection device for an internal combustion engine, comprising: an initialization unit that initializes the predetermined comparison voltage value after a predetermined period has elapsed since the recharge command signal was generated. 3. The misfire detection device for an internal combustion engine according to claim 2, wherein the initialization means sets the predetermined period in accordance with an engine operating state. 4. The misfire detection device for an internal combustion engine according to claim 1, wherein the misfire determination means has a reference level setting means for setting the predetermined comparison voltage value according to the ignition voltage value. .. 5. The ignition means has a primary side system path and a secondary side system path, and the secondary side system path suppresses a current in a direction opposite to a current at the time of spark plug discharge. The misfire detection device for an internal combustion engine according to claim 1, further comprising: