JPH0565868A - Misfire detection device for internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] Accurately detect misfiring (FI misfiring) related to fuel system. [Configuration] Ignition voltage value (B,
B ') exceeds the comparison level (C, C') (t7-
t8, t7 to t9) is measured, and when the voltage (F, F ') according to the length of this period exceeds the predetermined voltage VTREF, F
I Determined that a misfire has occurred. The comparison level (C, C ') is the peak hold value of the ignition voltage value (B, B') by a predetermined number (<
1.0) times and is reset to the value 0 between times t5 and t6.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A spark plug is provided for each cylinder for igniting a fuel-air mixture drawn into a cylinder of an internal combustion engine. Usually, the high voltage generated in the ignition coil of the internal combustion engine is sequentially distributed to the ignition plugs of the respective cylinders via a distributor to ignite the fuel mixture. In this case, if the ignition by the spark plug is not normally performed, that is, if misfire occurs, various harmful effects occur. For example, there are adverse effects such as deterioration of driving performance, deterioration of fuel consumption, and further increase of catalyst temperature in the exhaust gas purification device due to post-combustion of unburned gas in the exhaust system passage. Therefore, it is absolutely necessary to prevent misfires that cause such harmful effects. The causes of this misfire are roughly classified into those related to the fuel system and those related to the ignition system. 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.

As a conventional misfire detecting device, for example, there is one disclosed in Japanese Patent Publication No. 51-22568. This utilizes the fact that the frequency of the damping oscillation voltage generated in each opening of the distributor contacts in the primary circuit of the ignition circuit is higher in the case of ignition than in the case of misfire.

[0004]

However, since the conventional misfire detection device detects only the frequency of the damping oscillation voltage generated in the ignition circuit, that is, the presence or absence of discharge between both electrodes of the spark plug, the misfire is detected. It was not possible to judge whether or not the cause was discharge, but the mixture was related to the fuel system such that the mixture did not ignite due to lean or rich, and it was not always satisfactory in terms of quick failure countermeasures.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a misfire detecting device for an internal combustion engine, which can detect whether or not the cause of the misfire is related to the fuel system. To do.

[0006]

In order to achieve the above object, the present invention provides an engine operating condition detecting means for detecting a value of an engine operating parameter, and an ignition timing is determined based on the value of the engine operating parameter. Signal generating means for generating an ignition command signal, ignition means for generating a high voltage for discharging an ignition plug provided in the engine based on the ignition command signal, and high voltage for the ignition means In a misfire detection device for an internal combustion engine having a voltage value detection means for detecting a voltage value at the time, whether or not a misfire has occurred by comparing an ignition voltage value after the ignition command signal is generated with a predetermined voltage value. A misfire determining means for determining is provided, and the misfire determining means has a period limiting means for limiting a comparison period in which the ignition voltage value and the predetermined voltage value are to be compared, and the ignition voltage is set in the comparison period. Value is what the ignition voltage value is so as to determine a misfire condition based on at least one of the area of the portion exceeding the predetermined voltage value in the length and the comparison period of time exceeding the predetermined voltage value.

The comparison period is a period near the end of the discharge period of the spark plug, a period after a predetermined period has elapsed since the ignition command signal was generated, or a predetermined period near the end of the discharge period of the spark plug or ignition. It is desirable to set the second predetermined period after the first predetermined period has elapsed since the command signal was generated.

Further, it is desirable that the predetermined voltage value is set according to the engine operating condition or 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 is provided with a current suppressing means for suppressing a current in a direction opposite to a current at the time of spark plug discharge. Is desirable.

[0010]

The comparison period in which the ignition voltage value and the predetermined voltage value are to be compared is limited, and the length of the period during which the ignition voltage value exceeds the predetermined voltage value and / or the ignition voltage value exceeds the predetermined voltage value in the comparison period. The misfire state is determined based on the area of the crossing portion.

The predetermined voltage value is set according to the operating state of the engine or the ignition voltage value.

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

[0013]

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

FIG. 1 is a circuit diagram showing an embodiment of a misfire detecting device for an internal combustion engine according to the present invention. In the present embodiment, when a misfire related to the fuel system (hereinafter, abbreviated as "FI misfire") occurs, the value of the capacity discharge voltage in the latter stage of discharge is larger than that in the case of normal combustion, and therefore the capacity discharge is shown. The fact that the value of the area of the portion of the characteristic curve that is equal to or greater than the predetermined voltage value is also large is used.

In FIG. 1, a power supply terminal T1 to which a power supply voltage VB is supplied is connected to an ignition coil (ignition means) 1 composed of a primary side coil 2 and a secondary side coil 3, and a primary side coil 2 and a secondary side. The coil 3 is 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 via a node N1 at which an ignition voltage (primary voltage) is generated, and the base of the transistor 4 is connected to an input terminal T2 to which the ignition command signal A is input. , Its emitter is grounded. The other end of the secondary coil 3 is connected to the center electrode 5a of the spark plug 5 via a node N2 where an ignition voltage (secondary voltage) is generated, and the ground electrode 5b of the spark plug 5 is grounded. .. Further, the node N1 is connected to the input side of the attenuator (voltage value detecting means) 6, and the node N2
Is connected to the input side of an attenuator (voltage value detecting means) 7, and the output sides of the attenuator 6 and the attenuator 7 are filter means 8 of an electronic control unit (hereinafter abbreviated as "ECU").
1, A / D converter 82 and filter means 83, A / D
It is connected to the CPU 85 via the converter 84. The attenuators 6 and 7 are voltage dividing means and divide the voltage with a predetermined voltage dividing ratio (for example, 1/1000 and 1/100). As a result, hundreds of volts on the primary side of the ignition coil,
On the secondary side, the voltage of tens of KV is lowered to about tens of V. Further, the CPU 85 is connected to the base of the transistor 4 via the drive circuit 86 to which the ignition command signal A is supplied, and detects various engine operating parameter values such as engine speed and engine load via the input circuit 87. It is connected to an operating parameter sensor (engine operating state detecting means) 9. The CPU 85 has a signal generating means for determining an ignition timing based on the engine operating state and generating an ignition command signal A,
And a misfire determination means for determining whether or not there is a misfire.

A distributor is provided between the node N2 and the center electrode 5a, but it is not shown in FIG.

FIG. 2 is a flow chart showing a program for executing the misfire detection operation of the circuit of FIG. 1, and this program is repeatedly executed at a predetermined cycle. 3 and 5 are ignition voltages of an ignition voltage (primary voltage) V generated in the primary coil 2 of the ignition coil 1 and an ignition voltage (secondary voltage) V generated in the secondary coil 3 due to generation of the ignition command signal A. It is a time chart which shows a characteristic curve, and in Drawing 3 and Drawing 5, a solid line shows an ignition voltage characteristic curve at the time of normal combustion of a fuel mixture, and a dotted line shows an ignition voltage characteristic curve at the time of FI misfire.

Next, each ignition voltage characteristic will be described with reference to FIG.

First, the ignition voltage characteristic during normal combustion (characteristic indicated by the solid line) will be described. Immediately after the ignition command signal A generation time t0, the ignition voltage rises to a value that destroys the insulation of the fuel mixture (between the discharge gaps of the spark plugs) (curve a). For example, as shown in FIG. 3, when the value of the ignition voltage V exceeds the value of the reference voltage for normal ignition determination Vfire ₀ (V
> Vfire ₀ ) The insulation of the fuel mixture is destroyed, and the discharge voltage is almost constant from the capacity discharge state (discharge state for a very short time due to current of several hundred amperes) before the breakdown. (Curve b) (discharge period of about several milliseconds with current of about several tens of milliamperes). The induced discharge voltage rises as the pressure in the cylinder rises with the compression stroke after time t0. this is,
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 it destroys the insulation of the fuel mixture again, but
The remaining energy of the ignition coil 1 is small and the voltage rise is slight (curve c). 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.

Next, the ignition voltage characteristic (characteristic indicated by the dotted line) when the FI misfire occurs (when combustion does not occur) when the fuel mixture becomes lean or cut due to an abnormality in the fuel supply system, etc. will be explained. To do. Immediately after the time t0 at which the ignition command signal A is generated, the ignition voltage V rises to a value at which the insulation of the fuel mixture between the spark plug electrodes is destroyed, but the value of the insulation breakdown voltage at this time is the air occupying the fuel mixture. Is included more than in the normal state, the dielectric strength of the fuel mixture becomes large, and since combustion does not occur, the fuel mixture is not ionized and the electrical resistance between the plug gaps is Since it becomes higher, it becomes higher than the voltage value during normal combustion (curve a ′). After that, the state shifts to the induction discharge state as in the normal combustion, but since the discharge resistance is larger than that in the normal combustion, the state shifts to the upper capacity discharge state earlier than the normal combustion (curve b ′). The value of the capacity discharge (the latter capacity discharge) generated at the final stage of the induction discharge is higher than that during normal combustion as shown in FIG. 3 because the breakdown voltage of the fuel mixture is larger than that during normal combustion. (Curve c '). Therefore, immediately after this capacitive discharge, the remaining energy of the ignition coil sharply decreases, so that the ignition voltage rapidly drops to substantially zero (curve c ').

FIG. 5 shows the ignition voltage characteristic on the secondary side of the ignition coil. Since the characteristic is similar to the ignition voltage characteristic on the primary side shown in FIG. 3, its explanation is omitted.

Next, the operation of the circuit shown in FIG. 1 will be described with reference to FIGS.

First, it is determined whether or not "1" is set in the IG flag (FlagIG) indicating whether or not the ignition command signal A is generated (step S1). "1" indicates that the ignition command signal A is generated. The process of setting the IG flag to "1" is performed by a routine different from the routine of FIG. 2, for example, an ignition magnetic calculation processing routine. Since "1" has not risen before the ignition command signal A is generated, the determination in step S1 is negative, and steps S2, S3, S4, S
5, the ECU 8 timer (timer for measuring the elapsed time after the ignition command signal A is generated) has a predetermined time Tmis ₀ , Tmis.
₁ is set, the area S is initialized to zero and stored in the memory,
This program is terminated by setting "0" in the fire flag and the IG flag. The predetermined time Tmis ₀ (first predetermined period) is set to be equal to or longer than the time from the generation of the ignition command signal A to the end of the capacity discharge immediately thereafter, and is the time from time t0 to t1 in FIG.
Further, the predetermined time Tmis ₁ is slightly longer than the time from the generation of the ignition command signal A to the generation of the capacity discharge at the final stage of the induction discharge during normal combustion (time t0 in FIG. 3).
From the map or the table according to the engine operating state (engine operating parameter value).

The values of the predetermined times Tmis ₀ and Tmis ₁ are read from a map or a table according to the engine operating condition (engine operating parameter value), for example, engine speed, engine load, battery voltage, engine temperature and the like. It is a value. The same applies to Vmis ₁ and Smis described later.

Next, when the ignition command signal A is generated and the IG flag is set to "1", the process proceeds from step S1 to S6, and it is determined whether or not the value of the ignition voltage V exceeds the value of the reference voltage Vfire ₀ . Is determined (see FIG. 3). If V> Vfire ₀ , it is judged that normal ignition or FI misfire has occurred, and fire
"1" is set in the flag (step S7), and step S9
Move to. If V ≦ Vfire _0, the process proceeds to step S8, and it is determined whether or not “1” is set in the fire flag. When the fire flag is set to "1", V> Vfire ₀ is satisfied once, so the process proceeds to step S9, and it is determined in the subsequent processing whether normal ignition or FI misfiring. If "1" is not set in the fire flag, V> Vfire ₀ is not satisfied even once, so it is neither normal ignition nor FI misfire, or it must be in a state where it can be determined whether normal ignition or FI misfire. Judge and terminate this program.

Next, in step S6, V> Vfire ₀
Or V ≦ Vfire in steps S6 and S8
_{If the} flag is ₀ and "1" is set in the fire flag, it is determined in steps S9 and S10 whether the current time is between t1 and t2 (second predetermined period). ,
If between times t1 and t2, since it is time to be the normal ignition or FI misfire determination of whether to compare the value of the ignition voltage V and the predetermined voltage VMIS ₁ (step S11), V> in VMIS ₁ If so, it is determined that the capacity discharge in the latter stage of the FI misfire is occurring, and the value (V−) of the stored area S is set to (V−
The value of Vmis ₁ ) is added (step S12), and V ≦ Vmis ₁
If so, it is determined that the capacity discharge in the latter period at the time of FI misfire has not occurred, and this program ends. Such an operation is performed at regular intervals during a predetermined period from time t1 to time t2. In step S9, the current time is before time t1 (Tmi
If it is before s ₀ ), the latter capacity discharge at the time of FI misfire has not occurred at that time, so this program ends. If the current time is after the time t2 in step S10, the latter capacity discharge at the time of FI misfire no longer occurs, so the fire flag and the IG
The flag is set to "0" (steps S4 and S5), and this program ends.

Next, a second embodiment of the present invention will be described with reference to FIG.
Will be described with reference to FIG. 4 and 5, in FIG.
The difference from FIG. 3 is that the predetermined time Tmis ₀ ′, Tmis ₁ ′,
Reference voltages Vfire ₀ ′, Vmis ₁ ′ and times t ₀ ′, t ₁ ′, t
₂ ', and Tmis ₀ , Tmis ₁ , Vfire ₀ , and V in FIGS.
It corresponds to mis ₁ and t ₀ , t ₁ and t ₂ , respectively. Since the operation shown in FIG. 4 is the same as the operation shown in FIG. 2, its description is omitted. Further, in FIGS. 3 and 5, Tmis ₀ , Tmi
_{s 1, Tmis 0 ', Tmis} 1' but are using a symbol that,
Tmis ₀ and Tmis ₁ may be different from Tmis ₀ ′ and Tmis ₁ ′. The reference voltages Vfire ₀ and Vmis ₁ are usually set to values smaller than Vfire ₀ ′ and Vmis ₁ ′, respectively.

As can be seen from the above description, in FIGS. 2 and 4, the value of the ignition voltage V within the second predetermined period from time t1 to t2 is V> Vmis ₁ (V> Vmis ₁ '). When the ignition voltage characteristic curve reaches a predetermined voltage Vmis ₁ (Vm
is ₁ '), the value of the area of a portion of the ignition voltage characteristic curve equal to or higher than the predetermined voltage Vmis ₁ (Vmis ₁ ') is calculated, and the calculated area value is cumulatively added, and the cumulatively added area is calculated. When the value of S is equal to or larger than the value of the predetermined area Smis (Smis'), the FI misfire is determined. In this way, it is possible to accurately determine the type of misfire, that is, whether or not there is FI misfire, so that it is possible to detect a failure location early and take appropriate measures against the failure.

FIG. 6 is a diagram showing the construction of the misfire detection device according to the third embodiment of the present invention. The primary coil 2 and the transistor 4 of the ignition coil 1 are the same as those in the first embodiment of FIG. It is connected. The secondary coil 3 is connected to the anode of the diode 11, and the cathode of the diode 11 is connected via the distributor 12 to the center electrode 5 of the spark plug 5.
It is connected to a. A voltage sensor 13 that is electrostatically coupled to the connection line 14 (which forms a capacitor of several PF) is provided in the middle of the connection line 14 that connects the distributor 12 and the center electrode 5a. The output of the voltage sensor 13 is connected to the peak hold circuit 22 and the non-inverting input of the first comparator 25 via the input circuit 21. 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. Further, the peak hold circuit 22 is connected to a reset circuit 23 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 the input signal as it is, and the output of the first comparator 25 is at a high level during the gate period. 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 VTREF is
It is set according to the engine operating state.

In this embodiment as well, the ECU 8 (FIG. 1) for controlling the ignition timing of the engine and the like is similarly provided. The circuit block 8a in FIG. 6 may be configured as a part of the ECU 8, but the circuit block 8b is preferably provided near the engine body.

FIG. 7 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 also 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. For 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 a reset signal that is high level at reset is input to the base from the reset circuit 23.

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 shown in FIG. 7, 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 changed from the value 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. 8 is a circuit diagram showing a specific configuration of the gate circuit 26 and the pulse measuring period measuring circuit 27. The transistors 31 to 33 and the resistors 34 to 41 form a three-stage inverting circuit. Further, a transistor 51 is interposed between the collector of the transistor 32 and the ground, and the base of the transistor 51 has a CPU 85.
Supplies the gate signal. Therefore, during the gate period when the gate signal becomes low level, the transistor 3
The collector of 3 becomes low level / high level corresponding to the high / low voltage of the terminal T4, and when the gate signal is high level, the collector of the transistor 33 becomes high level regardless of the voltage of the terminal T4. The collector of the transistor 33 is connected to the base of the transistor 44 via the resistor 42, and the base of the transistor 44 is connected to the power supply line VBS via the resistor 43. The emitter of the transistor 44 is connected to the power supply line VBS, and the collector is connected to the ground via the resistor 45 and the capacitor 47. The connection point between the resistor 45 and the capacitor 47 is connected to the terminal T5 via the operational amplifier 49 and the resistor 50. The operational amplifier 49 is a buffer amplifier. Resistance 45
The connection point of the capacitor 47 and the capacitor 47 is connected to the collector of the transistor 48 via the resistor 46, and the emitter of the transistor 48 is grounded. A reset signal is input from the CPU 85 to the base of the transistor 48.

According to the circuit of FIG. 8, when the gate signal is low level and the terminal T4 is high level, the transistor 33 is turned on.
Becomes low level, the transistor 44 is turned on and the capacitor 47 is charged, while the transistor 4 is turned on when the gate signal is high level or the terminal T4 is low level.
4 is turned off, and the charging of the capacitor 47 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 the time chart shown in FIG. 9 (a), (b), (d), and (e), the solid line shows the operation during combustion, and the broken line shows the operation during FI misfire.

FIG. 7A shows the detected ignition voltage V (B,
B ') and the comparison level VCOMP (C, C') are shown, and the curve B at the time of combustion changes similarly to FIG. 3 described above. On the other hand, the curve B ′ at the time of occurrence of misfire differs from the case of FIG. 3 in the characteristics after the capacity discharge voltage peaks immediately before the end of discharge. This is because the diode 11 is provided between the secondary coil 3 and the distributor 12 as shown in FIG. Hereinafter, this point will be described in detail.

The electric energy generated in the ignition coil 1 is
It is supplied to the spark plug 5 via the diode 11 and the distributor 12, and is discharged between the electrodes of the spark plug 5. The electric charge that could not be discharged at this time is stored in the stray capacitance between the diode 11 and the spark plug 5,
At the time of combustion, this charge is neutralized by the ions existing in the vicinity of the electrode of the spark plug 5, so that the ignition voltage V (B in FIG. 9A) at the end of the capacitive discharge is the same as in the case without the diode 11. Decrease rapidly. On the other hand, at the time of misfire, almost no ions exist near the electrode of the spark plug 5, so the charge accumulated between the diode 11 and the spark plug 5 is not neutralized by the ions, and the diode 1
Since it cannot flow back to the ignition coil 1 by 1, it is held as it is, and when the pressure in the cylinder decreases and the discharge required voltage becomes equal to the voltage applied by this charge, the spark plug 5 is discharged. (Fig. 9
(A), time t9). Therefore, even after the end of the capacity discharge, the ignition voltage V is maintained for a relatively long time (compared to the normal combustion).
The high voltage state continues.

Curves C and C'in FIG. 9A indicate the ignition voltage V
Comparison level VCOMP obtained from the peak hold value of
, And is reset between times t5 and t6. Further, FIG. 9B shows the output of the first comparator 25. As is clear from FIGS. 9A and 9B, V> VCOM during the time t0 to t8 during combustion.
P, during which the output of the first comparator 25 goes high.

On the other hand, at the time of misfire, V> VCOMP between time t4 and t9, but between time t3 and t4, the ignition voltage V (B ') rises and falls near the comparison level VCOMP (C') ( When multiple discharges occur, such fluctuations occur), and the output of the first comparator 25 changes to high / low.

Therefore, when the gate signal input of the gate circuit 26 shown in FIG. 8 is constantly at a low level (that is, the gate is always open), the output voltage VT of the pulse generation period measuring circuit 27 is: It changes as shown in FIG. 9 (e), reaching the level indicated by VB during combustion, and VMI during misfire.
Reach the level indicated by S. On the other hand, in this embodiment,
A gate signal as shown in FIG. 9C is supplied to the gate signal input of the gate circuit 26, and the first gate signal is supplied only between time t7 and time t10.
Since the output of the comparator 25 is input to the pulse generation period measuring circuit 27, the output voltage VT of the measuring circuit 27 changes as shown in FIG.
The level indicated by is reached, and at the time of misfire, the level indicated by VGMIS is reached.

Therefore, by setting the reference voltage VTREF between the VGB value and the VGMIS value, the FI misfire can be detected, but it is clear by comparing FIGS. 9 (d) and 9 (e). In addition, the level ratio VGMIS / V at the time of combustion and at the time of misfire when the output of the comparator 25 is gated
GB is considerably larger than the level ratio VMIS / VB when gate is not used. That is, the output of the comparator 25 is gated only during the period indicated by TG in FIG. 9C (supplied to the pulse generation period measurement circuit 27), whereby the FI misfire can be detected more accurately and stably.

Although the gate period TG is a predetermined period near the end of the discharge period in this embodiment, the gate period TG is
End time t10 may be any time before the rotor head (not shown) of the distributor 12 reaches the next segment (within a range of about 120 degrees in crank angle from ignition).

The pulse generation period measuring circuit 27 may be composed of a digital counter.

Further, the gate means 2 corresponds to the gate circuit 26 of FIG. 6 and passes the input signal only during the gate period TG.
6'may be provided immediately after the input circuit 21 (FIG. 10A) or immediately before the non-inverting input of the first comparator 25 (FIG. 9B) as shown in FIG.

Considering the characteristics of the diode 11 used in the embodiment of FIG. 6 described above, when the reverse breakdown voltage of the diode 11 is high, and when the stray capacitance between the diode and the plug is large, the piston moves upward. When the cylinder pressure decreases after the dead point, a breakdown (dielectric breakdown) may occur between the electrodes of the spark plug 5 early, and the detected ignition voltage V may decrease without being maintained at a high voltage (Fig. 1
1 (a)). When such a breakdown between the plug electrodes occurs, it cannot be distinguished from the decrease in the detected ignition voltage V due to the ion current during normal combustion, so the misfire determination may not be possible with the above method.

Therefore, as the diode 11, there is no breakdown (5 to 10 KV) between the plug electrodes.
By using the Zener diode having the Zener voltage VZ of, the detected ignition voltage V can be maintained near the Zener voltage VZ for a long time at the time of misfire as shown in FIG. 11B, and misfire determination can be performed.

By using a diode having a low reverse breakdown voltage, the same action and effect as in the case of using a Zener diode can be obtained, but the applied voltage is within the normal operating range (exceeds the reverse breakdown voltage). The condition is that the performance is guaranteed when returning to the range (no range).

Further, as shown in FIG. 12, the breakdown voltage is 5 to 10 KV in parallel with the diode 11 having a high reverse breakdown voltage.
You may make it provide the gap element 11 'which is stable to some extent. With such a configuration as well, the detected ignition voltage at the time of misfire as shown in FIG. 11B can be obtained.

Further, the first or second embodiment and the third embodiment may be combined with each other to determine that misfire has occurred only when the detection results of both are misfire.

The peak hold circuit 22 shown in FIG.
An averaging circuit (integrating circuit) may be used instead.

[0056]

As described above in detail, according to the misfire detecting device of the first aspect, the comparison period for comparing the ignition voltage value and the predetermined voltage value is limited, and the ignition voltage value is predetermined in the comparison period. Since the misfire state is determined based on the length of the period over which the voltage value is exceeded and / or the area of the portion where the ignition voltage value exceeds the predetermined voltage value, the misfire state can be grasped accurately and stably, and the failure location can be detected early. It enables discovery and appropriate troubleshooting.

Further, according to the misfire detecting device of the second to fifth aspects, since the comparison period is set to the latter stage of discharge, the misfire can be detected more reliably.

Further, according to the misfire detection device of the sixth or seventh aspect, since the predetermined voltage value is set according to the engine operating state or the ignition voltage value, even if the engine operating state changes. Accurately detect misfire.

According to the misfire detection device of claim 9,
In the secondary system path of the ignition means, the current in the opposite direction to that at the time of spark plug discharge is suppressed, so when a misfire occurs, the voltage of the secondary system path can be maintained at a high voltage state for a long time, and the misfire state can be maintained. It can be determined more accurately.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a program for executing a misfire detection operation based on a primary side voltage.

FIG. 3 is a time chart showing an ignition voltage (primary side voltage).

FIG. 4 is a flowchart showing a program for executing a misfire detection operation based on a secondary side voltage.

FIG. 5 is a time chart showing an ignition voltage (secondary side voltage).

FIG. 6 is a diagram showing a configuration of a misfire detection device according to another embodiment of the present invention.

FIG. 7 is a circuit diagram showing a specific configuration of part of the device shown in FIG.

FIG. 8 is a circuit diagram showing a specific configuration of part of the device shown in FIG.

9 is a time chart for explaining the operation of the apparatus of FIG.

10 is a diagram showing a configuration of a modified example of the apparatus of FIG.

FIG. 11 is a time chart showing an ignition voltage.

FIG. 12 is a diagram showing a configuration of a modified example of the apparatus of FIG.

[Explanation of symbols]

1 Ignition coil 2 Primary side coil 3 Secondary side coil 5 Spark plug 6,7 Attenuator (voltage value detection means) 8 ECU 9 Various engine operation parameter sensors (engine operation state detection means) 11 Diode 12 Distributor 13 Voltage sensor 22 Peak Hold circuit 26 Pulse generation period measurement circuit 85 CPU (signal generation means, misfire determination means) 86 Drive circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eitaka Kuroda 1-4-1, Chuo, Wako-shi, Saitama Inside Honda R & D Co., Ltd. (72) Hideaki Arai 1-4-1, Chuo, Wako-shi, Saitama Incorporated company Honda R & D Co., Ltd. (72) Inventor Masatake Kanehiro 1-4-1 Chuo, Wako-shi, Saitama Prefecture Incorporated Honda R & D Co., Ltd. (72) Inventor Takashi Hisaki 1-1-4 Chuo, Wako-shi, Saitama No. Incorporated in Honda R & D Co., Ltd. (72) Inventor Shigeru Maruyama 1-4-1 Chuo, Wako-shi, Saitama Incorporated in Honda R & D Co., Ltd. (72) Inventor Shigeki Baba 1-4-1 Wako-Chu, Saitama No. Stock Company Honda Technical Research Institute

Claims (11)

[Claims] 1. An engine operating state detecting means for detecting a value of an engine operating parameter, a signal generating means for determining an ignition timing based on the value of the engine operating parameter to generate an ignition command signal, and the ignition command signal. An internal combustion engine having an ignition means for generating a high voltage for discharging an ignition plug provided in the engine, and a voltage value detection means for detecting a voltage value when the high voltage is generated in the ignition means. In an engine misfire detection device, a misfire determination means for determining whether or not a misfire has occurred by comparing the ignition voltage value after the ignition command signal is generated with a predetermined voltage value is provided, and the misfire determination means is the It has a period limiting means for limiting a comparison period in which the ignition voltage value and the predetermined voltage value are to be compared, and the length of the period during which the ignition voltage value exceeds the predetermined voltage value in the comparison period and the comparison period. The misfire detection device for an internal combustion engine, wherein the misfire state is determined based on at least one of the areas of the portion where the ignition voltage value exceeds a predetermined voltage value. 2. The comparison period is a period near the end of the discharge period of the spark plug.
A misfire detection device for an internal combustion engine as described above. 3. The misfire detection device for an internal combustion engine according to claim 1, wherein the comparison period is a period after a predetermined period has elapsed since the ignition command signal was generated. 4. The misfire detection device for an internal combustion engine according to claim 1, wherein the comparison period is a predetermined period near the end of the discharge period of the spark plug. 5. The misfire detection device for an internal combustion engine according to claim 1, wherein the comparison period is a second predetermined period after the first predetermined period has elapsed since the ignition command signal was generated. 6. The misfire detection device for an internal combustion engine according to claim 1, wherein the predetermined voltage value is set according to an operating state of the engine. 7. 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 voltage value according to the ignition voltage value. 8. The reference level setting means comprises a smoothing means for smoothing the ignition voltage, and an amplifying means for amplifying an output of the smoothing means at a predetermined amplification factor. Internal combustion engine misfire detection device. 9. The ignition means has a primary side system path and a secondary side system path, and the secondary side system path is provided with a current suppressing means for suppressing 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 any one of claims 1 to 5, wherein: 10. The misfire detecting device for an internal combustion engine according to claim 1, wherein the ignition voltage is a primary side voltage of an ignition coil. 11. The misfire detection device for an internal combustion engine according to claim 1, wherein the ignition voltage is a secondary side voltage of an ignition coil.