JP2688672B2 - Misfire detection device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art An ignition plug is provided for each cylinder for igniting a fuel-air mixture taken into a cylinder of an internal combustion engine. Normally, a high voltage generated in an ignition coil of an internal combustion engine is sequentially distributed to a spark plug of each cylinder via a power distribution device to ignite the fuel mixture. In this case, if ignition by the ignition plug is not performed normally, that is, if misfire occurs, various adverse effects occur. For example, the driving performance is deteriorated, the fuel efficiency is deteriorated, and furthermore, the unburned gas is post-burned in the exhaust system, resulting in an increase in the catalyst temperature in the exhaust gas purification device. Therefore, misfires that cause such adverse effects must be absolutely prevented. The causes of this misfire can be roughly classified into those related to the fuel system and those related to the ignition system. The former related to the fuel system is caused by lean or rich fuel mixture, and the latter related to the ignition system is caused by so-called miss spark. Miss spark means that a normal spark discharge does not occur in the spark plug.

As a conventional misfire detecting device, there is one disclosed in Japanese Patent Publication No. 51-22568. This makes use of the fact that the frequency of the damped oscillating voltage generated in the primary circuit of the ignition circuit every time the switch contacts are opened is higher in the case of ignition than in the case of misfire.

[0004]

However, the conventional misfire detection device detects only the frequency of the damped oscillation voltage generated in the ignition circuit, that is, only the presence or absence of discharge between both electrodes of the ignition plug. However, it was not possible to judge whether or not the cause was due to the fuel system in which the mixture was not ignited due to lean or rich air-fuel mixture, and it was not always satisfactory in terms of quick troubleshooting.

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

[0006]

Means for Solving the Problems The present invention to achieve the above object, the engine operating condition detecting means for detecting the value of the engine OPERATION parameter, to determine the ignition timing based on the value of the engine operating parameters Signal generating means for generating an ignition command signal, an ignition means for generating a high voltage for discharging an ignition plug provided in the engine based on the ignition command signal, and a high voltage for the ignition means. In a misfire detection device for an internal combustion engine having current detection means for detecting a discharge current value at the time, whether a misfire has occurred by comparing the discharge current value of the ignition means after the ignition command signal is generated with a predetermined value There is provided misfire determination means for determining whether or not the value of the discharge current is after a first predetermined time has elapsed and a second predetermined period has elapsed since the ignition command signal was generated. Is obtained so as to determine that the misfire when it becomes smaller than a predetermined value.

[0007]

In the misfire determination means of the misfire detection device for the internal combustion engine according to the present invention, the value of the discharge current is greater than the predetermined current value in the period after the first predetermined time and before the second predetermined time after the ignition command signal is generated. When it becomes smaller, it is determined that there is a misfire related to the fuel system. This allows you to accurately understand the misfire condition,
It is possible to determine whether or not there is a misfire related to the fuel system.

[0008]

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

FIG. 1 is a circuit diagram showing one embodiment of a device for detecting misfire of an internal combustion engine according to the present invention. In this embodiment, when a misfire related to the fuel system (hereinafter, abbreviated as “FI misfire”) occurs, the value of the discharge current of the spark plug is a negative value that does not occur in the case of normal combustion. This is what 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 comprising a primary coil 2 and a secondary coil 3, and the primary coil 2 and the secondary coil 3 are connected to each other. The coil 3 is connected to one end of the coil 3,
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 is grounded. The other end of the secondary coil 3 is connected to the center electrode 5a of the ignition plug 5 via the current detecting means 6,
The ground electrode 5b of the spark plug 5 is grounded. A current flows through the coil 61 of the current detecting means 6 according to the current flowing through the coil 3. The coil 61 is connected to a voltage generating resistor 62, which generates a voltage according to the current flowing through the coil 61. The output side of the current detecting means 6 is an ECU 7
Through the filter means 71 and the A / D converter 72
73. Further, the CPU 73 is connected via an input circuit 74 to an engine operation parameter sensor (engine operation state detecting means) 8 for detecting values of various engine operation parameters (parameters such as an engine speed and an engine load). It is connected to the base of the transistor 4 via a drive circuit 75 for amplifying the ignition command signal A. The above C
The PU 73 has signal generation means for determining an ignition timing based on the engine operation state and generating an ignition command signal A, and misfire determination means for determining whether or not a misfire has occurred.

FIG. 2 is a flowchart showing a program for executing the misfire detecting operation of the circuit of FIG.
Is a time chart showing a discharge current generated in the secondary coil 3 due to the generation of the ignition command signal A, that is, a discharge current flowing between the two electrodes 5a and 5b of the ignition plug 5 (hereinafter, simply referred to as "discharge current"); In FIG. 3, the solid line shows the discharge current at the time of normal ignition of the fuel mixture, and the dotted line shows the discharge current at the time of FI misfire. Next, each discharge current characteristic will be described with reference to FIG.

First, the discharge current characteristic during normal ignition (the characteristic indicated by the solid line) will be described. Immediately after the ignition command signal A generation time t0, the ignition voltage increases to a value that breaks the insulation of the fuel mixture between the spark plug electrodes. Thereafter, a current flows with the dielectric breakdown (curve a). This current is an inrush current at the beginning of dielectric breakdown, and a large current flows. Such as the discharge current when the value of I exceeds the value of the normal ignition determination reference current Ifire ₀ (when becomes I> Ifire ₀₎ of the fuel-air mixture insulation 3 is destroyed, before breakdown The state shifts from the capacity discharge state to the induction discharge, and the induction energy stored in the coil through which the discharge current I flows is released (curve b). Accordingly, the discharge current I decreases toward zero.

Next, a description will be given of the discharge current characteristic (characteristic indicated by a dotted line) when the fuel mixture becomes lean or cut due to an abnormality in the fuel supply system or the like and FI misfire occurs. Immediately after the ignition command signal A generation time t0, the ignition voltage increases to a value that breaks the insulation of the fuel mixture between the spark plug electrodes, as in the normal ignition. After that, current flows with dielectric breakdown. This current is an inrush current at the beginning of dielectric breakdown, and a large current flows. At this time, the peak value of the discharge current (capacity discharge current) is such that the proportion of air in the fuel mixture is larger than that during normal ignition, The dielectric strength of the air-fuel mixture increases and becomes lower than the current value during normal ignition (curve a ′). Thereafter, the state shifts to the inductive discharge state as in the case of normal ignition.However, more energy is consumed than in the case of normal ignition at the time of capacitive discharge, and the voltage at the time of induction discharge is higher than that of normal ignition. The induction discharge time becomes shorter (curve b '). As a result, a transition is made to capacity discharge again due to residual energy in the coil. This discharge current flows in the opposite direction and eventually becomes zero (curve c ′). This is because, after the induction discharge, electric charges are accumulated in the stray capacitance or the like of the high-voltage electric wire, so that the electric charge is released by the residual energy of the coil and becomes a current in the opposite direction. This energy is then attenuated to zero.

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

First, it is determined whether or not "1" is set in an IG flag (Flag IG) indicating whether or not the ignition command signal A has been generated (step S1). “1” indicates that the ignition command signal A has been 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 timing calculation processing routine. Before the ignition command signal A is generated, “1” does not rise, so the determination in step S1 is negative, and the process proceeds to steps S2 and S3.
The first and second predetermined times Tmis ₀ and Tmis ₁ are set in the timer of the ECU 8 (the timer that measures the elapsed time after the ignition command signal A is generated), and the IG flag is set to "0", as shown in FIG.
The operation of the flow is ended. Predetermined time Tmis ₀ and Tmi
s ₁ is the time from the time t0 when the ignition command signal A is generated to the times t1 and t2. Time t1 is a time after the capacitive discharge state ends between the spark plug electrodes and transition to the inductive discharge state, and time t2 is a time when the voltage between the spark plug electrodes becomes substantially zero (see FIG. 3). Note that the above T
The values of mis ₀ and T mis ₁ are values read from a map or table according to the engine operating state (engine operating parameter value), for example, engine speed, engine load, battery voltage, engine temperature, and the like. FI misfire determination reference current Ifire ₁ described later
The same applies to the value of (predetermined current value).

Next, when the ignition command signal A is generated and the IG flag is set to "1", the process proceeds from step S1 to S4, and it is determined whether or not the first predetermined time Tmis ₀ has elapsed in the timer of the ECU 8. To judge. If the predetermined time Tmis ₀ has not elapsed, the operation of FIG. 2 ends. Predetermined time Tmi
When s ₀ has elapsed, it is next determined whether or not the second predetermined time Tmis ₁ has elapsed (step S5). When the predetermined time Tmis ₁ has elapsed, there is no possibility of being determined to be a FI misfire, so the flag IG is set to "0" (step S3), and the operation of FIG. 2 ends. When the predetermined time Tmis ₁ has not elapsed, the value of the discharge current I is the reference current Ifi.
It is judged whether or not it is smaller than the value of re ₁ (negative value in FIG. 3) (step S6), and if I <Ifire ₁ , it is judged to be FI misfire and the operation of FIG. 2 is ended (step S7, If I ≧ Ifire _{1 (} see the characteristic curve shown by the dotted line in FIG. 3), it is determined that FI misfire has not occurred, and the operation in FIG. 2 ends. Step S1, and repeats until the predetermined time TMIS ₁ has elapsed the S4 to S7.

Although the value of Ifire ₁ is set to a negative value in FIG. 3, it is set to zero or a positive value slightly larger than zero so that the predetermined time Tmis ₁ is shortened so as to prevent erroneous determination of FI misfire during normal ignition. It may be set.

[0018]

The present invention as described in detail above, according to the present invention includes the engine operating condition detecting means for detecting a value of the engine OPERATION <br/> parameter, to determine the ignition timing based on the value of the engine operating parameters 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 when a high voltage is generated for the ignition means In a misfire detection device for an internal combustion engine having a current detection means for detecting a discharge current value of, whether or not a misfire has occurred by comparing a discharge current value of the ignition means after the ignition command signal is generated with a predetermined value. A misfire determining means for determining whether or not the second misfire determining means is the second predetermined time after the ignition command signal is generated and the second misfire determining means.
By determining that there is a misfire when the value of the discharge current becomes smaller than the predetermined value before the lapse of the predetermined period of time, it is possible to accurately determine whether or not there is a misfire related to the fuel system, and early detection of a failure location It is possible to take appropriate troubleshooting measures.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing a program for executing a misfire detection operation of the circuit of FIG. 1;

FIG. 3 is a time chart showing a discharge current.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Ignition coil 2 Primary coil 3 Secondary coil 5 Spark plug 6 Current detection means 7 ECU 8 Engine operation parameter sensor (engine operation state detection means) 73 CPU

Front Page Continuation (72) Inventor Eitaka Kuroda 1-4-1 Chuo, Wako-shi, Saitama, Ltd. Inside Honda R & D Co., Ltd. (72) Inventor Hideaki Arai 1-14-1 Chuo, Wako-shi, Saitama Honda R & D Co., Ltd. In the laboratory

Claims (1)

(57) [Claims] And 1. A engine OPERATION parameter engine operating condition detecting means for detecting a value of a signal generating means for generating an ignition command signal to determine the ignition timing based on the value of the engine operating parameter, wherein the ignition command Internal combustion having ignition means for generating a high voltage for discharging an ignition plug provided in the engine based on a signal, and current detection means for detecting a discharge current value when a high voltage is generated in the ignition means In the engine misfire detection device, there is provided misfire determination means for determining whether or not misfire has occurred by comparing a discharge current value of the ignition means after the ignition command signal is generated with a predetermined value. Is a misfire when the value of the discharge current becomes smaller than a predetermined value after a first predetermined time has elapsed and a second predetermined period has elapsed since the ignition command signal was generated. And a misfire detection device for an internal combustion engine.