JPH0539746A - Misfire judging device for spark-ignition engine - Google Patents

Abstract

PURPOSE:To adequately judge misfire in a spark-ignition engine. CONSTITUTION:The exhaust gas temperatures of each cylinder depending upon operating state are stored in a storage means B and for each cylinder, the stored exhaust gas temperature is compared by a judging means C1 with the exhaust gas temperature detected by an exhaust gas temperature detection means A1. A misfire from the cylinder is confirmed if the difference between the two values is above a certain criteria. Therefore, a misfire is adequately judged even if there is scatter in the measured exhaust gas temperatures of each cylinder and the difference between those values is large and this constitution allows the reliability of judgement to be substantially improved compared with measurement using common thresholds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire determination device for determining a misfire in a spark ignition type internal combustion engine for each cylinder.

[0002]

2. Description of the Related Art In this type of misfire determination device, it is most common to set a certain threshold value for the exhaust gas temperature and determine a misfire when the exhaust gas temperature of each cylinder falls below the threshold value. However, in such a system, if the difference between the exhaust temperatures of the cylinders such as a relatively small engine is large, it may be difficult to appropriately determine the misfire. Further, in a lean burn gas engine, since the air-fuel mixture is thin, the exhaust gas temperature is low, and it is difficult to detect misfire by the above-mentioned determination method. Furthermore, it is often difficult to detect a decrease in exhaust temperature unless misfires continue for several times, and it is difficult to accurately detect even a single misfire. Can't figure out.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of these points, and an object thereof is to accurately determine misfire in a spark ignition type internal combustion engine.

[0004]

In order to achieve the above object, in the first aspect of the invention, an exhaust gas temperature detecting means for detecting the exhaust gas temperature for each cylinder and a load and an engine speed during normal operation are provided. The storage means for storing the exhaust temperature of each cylinder and the detected exhaust temperature are compared with the exhaust temperature stored in the storage means, and if there is a difference equal to or more than a certain determination value, it is determined that the cylinder is misfiring. And a determining means for performing. FIG. 1 is a diagram showing a configuration of the present invention, in which A ₁ is an exhaust gas temperature detecting means, B is a storing means, C ₁ is a determining means, D is a load detecting means, and E ₁ is a rotational speed detecting means.

A second aspect of the present invention relates to a lean burn gas engine, which includes exhaust temperature detecting means for repeatedly detecting the exhaust temperature of each cylinder when operating at a constant speed, and exhaust temperature of all cylinders. It corresponds to the case where the average value and the calculating means for sequentially calculating the deviation value of the exhaust temperature of each cylinder with respect to this average value and the calculated deviation value are compared with a certain judgment value, and the deviation value exceeds the judgment value. And a determination means for determining a cylinder misfire. FIG. 2 is a diagram showing a configuration of the present invention, in which A ₂ is an exhaust gas temperature detecting means, F is a calculating means,
C ₂ is a determination means.

Further, in the third aspect of the invention, a rotation speed detecting means for constantly detecting the engine rotation speed and an average value of the rotation speeds are calculated, and the average value and the detected rotation speeds are sequentially compared to obtain a constant judgment value. When there is the above difference, the determining means determines the cylinder causing the decrease in the rotation speed from the relationship with the ignition timing and determines that cylinder as a misfire. FIG. 3 is a diagram showing the configuration of the present invention, in which E ₂ is the rotation speed detecting means,
G is an igniter, and C ₃ is a determination means.

[0007]

In the first aspect of the present invention, the exhaust gas temperature of each cylinder corresponding to the operating state is stored, and the detected exhaust gas temperature is compared for each cylinder. Also, the misfire of each cylinder is accurately determined. Further, in the second aspect of the invention, since the deviation value of the exhaust gas temperature of each cylinder with respect to the average value of the exhaust gas temperature of all the cylinders is sequentially calculated in the operating state at a constant speed and is compared with the determination value, the exhaust gas temperature is low. Even in a lean burn gas engine, the misfire of each cylinder is accurately determined. Furthermore, a third aspect of the present invention sequentially compares the average value of the number of revolutions with the detected number of revolutions, and when the number of revolutions decreases, the cylinder causing the decrease is discriminated from the relationship with the ignition timing to determine the cylinder. Is determined to be a misfire, so even a single misfire can be reliably detected.

[0008]

[First Embodiment of the Invention] The illustrated embodiment will be described below. First, an embodiment of the first invention will be described with reference to FIGS. In FIG. 4, 1 is a spark ignition type internal combustion engine, 2 is a control unit using a microcomputer, 3 is a load sensor for detecting a load by the intake negative pressure of the engine 1, and 4 is an exhaust pipe for each cylinder of the engine 1. A temperature sensor 5 is provided to detect the exhaust gas temperature, and 5 are rotational speed sensors that detect the rotational speed of the engine 1. The detection signals of the respective sensors are input to the control unit 2, and the control unit 2 performs the misfire determination in the procedure as shown in FIG. 5 and outputs the determination output signal 6, for example, issues an alarm or stops the engine. It is configured to do.

In FIG. 5, in step S1, the outputs of the load sensor 3 and the rotation speed sensor 5 are read to detect the load and the rotation speed at that time, and the normal exhaust temperature T ₁ to each cylinder in this operating state. Tn is read in step S2. The exhaust temperature of the engine increases as the load and the rotational speed increase, but there is considerable variation between the exhaust temperatures of the cylinders.
Moreover, the tendency of the height changes depending on the operating state at that time, that is, the load and the rotational speed. FIG. 6 shows an example of this.
Indicates a low load, b indicates a medium load, and c indicates a high load. As described above, the exhaust temperatures T _{1 to} Tn are different for each operating state, so this data is stored in the form of a map in the memory of the control unit 2 in advance, for example, at the time of shipping operation, or actually. The output of each sensor that is sequentially input at the time of driving is stored and used, and if there is no corresponding data, it can be obtained by the interpolation method using similar data.

Next, in step S3, the current exhaust gas temperatures t _{1 to} tn of the respective cylinders are input, and in step S4, a difference ΔTi = Ti-ti from the normal exhaust temperature is calculated for each cylinder. Then, in step S5, a comparison is made with the misfire determination value H _1, and if the difference is small and H ₁ > ΔTi, it is determined to be normal, and if the difference is large and H ₁ > ΔTi, the i-th cylinder is misfiring. The judgment is made and the judgment output signal 6 is outputted.
(Step S6). As the misfire determination value H _{1, an} appropriate value is selected in advance by test operation or the like.

As described above, in this embodiment, the normal exhaust temperature and the detected exhaust temperature in the operating state at that time are compared for each cylinder, so that there is a difference in the exhaust temperature between the cylinders and the operating state is different. Even if it changes, the misfire of each cylinder can be accurately determined. Further, if the learning function of sequentially inputting and storing the exhaust gas temperature during normal operation as described above is used, it is possible to judge the state of deterioration from the change.

[0012]

[Embodiment of the Second Invention] FIGS. 7 to 9 show an embodiment of the second invention. In FIG. 7, 11 is a lean burn gas engine operated at a constant speed, and 12 is a control unit using a microcomputer. , 13 is a temperature sensor for detecting the exhaust gas temperature provided for each cylinder of the engine 11, 14 is a supercharger, 15 is an intercooler, 16 is a governor, 17 is a gas regulator, 1
8 is a gas cutoff valve, and 19 is an air intake pipe.

In this embodiment, as shown in FIG. 8, the exhaust gas temperature of each cylinder is first read in step S11, and the average value M _{1 and} the deviation value Si of the exhaust gas temperature of each cylinder from this average value are read in step S12. Is calculated. Then, in step S13, the deviation value Si is sequentially compared with the preselected misfire determination value H _2, and if Si> H ₂ , it is determined that the i-th cylinder is misfiring and the gas cutoff valve 18 is closed.
(Step S14). If Si> H _{2 is} not reached, the process proceeds to the next step S15 and the threshold value K set to a value lower than the misfire determination value H ₂ is compared. The shutoff valve 18 is closed. In addition,
The above misfire determination is not performed at the start and end of operation,
It is performed only during a period of operation at a predetermined rotation speed.

That is, in this embodiment, since the average value of the exhaust temperature of all the cylinders is compared with the exhaust temperature of each cylinder, even in a lean burn gas engine having a low exhaust temperature, the misfire of each cylinder can be accurately determined. can do. Also, with this judgment function alone, the average value of the exhaust temperature of all cylinders decreases in the case of complete misfire, and the difference with the exhaust temperature of each cylinder becomes small, so misfire judgment cannot be performed. By using the judgment together, it is possible to judge the complete misfire without any trouble. Therefore, the threshold value K in this embodiment is considerably lower than the conventional threshold value, for example, 250 to 300 ° C.
It is set to a degree. FIG. 9 exemplifies the relationship between the exhaust temperature of each cylinder and the average value M ₁ , the threshold value K, and the like.

[0015]

[Third Embodiment of the Invention] FIGS. 10 to 12 show an embodiment of the third invention. In FIG. 10, 21 is an engine, 22 is a control section using a microcomputer, 23 is an igniter, and 24 is an ignition coil. , 25 is an ignition pulser, 26 is a rotation speed sensor,
Reference numeral 27 is an input conversion unit including an F / V converter and a bandpass filter. An ignition signal from the ignition pulser 25 and a voltage signal V obtained by converting the engine speed into a voltage from the input conversion unit 27 are input to the control unit 22, and the control unit 2 determines misfire by the procedure of FIG. 11. Is configured.

First, in step S21, the voltage signal V is input and the average value M ₂ is calculated. Since the engine is accelerated in each combustion stroke of each cylinder, the voltage signal V fluctuates finely and periodically as shown in FIG. 12 (b). The numbers in the waveform are the cylinder numbers. For example, if the No. 2 cylinder misfires, acceleration in the No. 2 cylinder's combustion stroke is not performed. Therefore, as indicated by the broken line in (b), The voltage signal V drops. Step S22 In this voltage signal V as compared with only low average M ₂ misfire judgment value H ₃ pre set from misfire if V <M ₂ -H ₃ is determined to have occurred.

On the other hand, since the ignition signal from the ignition pulsar 25 is input to the control unit 22 as shown in FIG. 12 (a), the control unit 22 determines that the input time of this signal and misfire have occurred. It is determined from the elapsed time L until the determination is made that the misfire is in the second cylinder. It should be noted that the above misfire determination is not performed at the start and end of the operation, but is performed only during the period of operation at a predetermined rotation speed. When the misfire is determined by such a procedure, the number of times n is added in the next step S23, and the preset reference value J is set.
When it exceeds the threshold, an alarm is issued and the operation of the engine is stopped (step S24).

That is, in this embodiment, the average value of the number of revolutions and the detected number of revolutions are sequentially compared, and the cylinder that has misfired is judged from the decrease in the number of revolutions. Therefore, even one misfire is surely detected, and Since this determination is performed in real time without a delay as in the case of the exhaust temperature, it is possible to take prompt action. In addition, since the number of misfires can be counted, it is possible to judge the state of deterioration in advance and prepare for inspection and the like with a margin. Further, it is not necessary to dispose an exhaust temperature sensor for each cylinder, which simplifies the structure and reduces the cost.

[0019]

As is apparent from the above description, the first invention of this application stores the exhaust gas temperature of each cylinder according to the change in the operating state, and the stored exhaust gas temperature and the detected exhaust gas temperature. The temperature is compared for each cylinder. Therefore, even if there is a variation in the exhaust temperature of each cylinder, and even if the difference is large, it is possible to accurately determine the misfire of each cylinder, and it is possible to make a determination as compared with the conventional example that is compared with a common threshold value. The reliability is greatly improved.

A second aspect of the present invention is a lean burn gas engine operated at a constant speed, wherein the deviation value of the exhaust temperature of each cylinder with respect to the average value of the exhaust temperature of all cylinders is compared with a determination value. Is. Therefore, even with a lean burn gas engine having a low exhaust temperature, it is easy to accurately determine misfire of each cylinder, and the reliability of the determination is significantly improved. Further, a third aspect of the present invention is to compare the average value of the number of revolutions with the detected number of revolutions, to discriminate the cylinder causing the lowering of the number of revolutions, and to determine the misfire. Therefore, unlike the case where the misfire is determined based on the exhaust gas temperature, the determination is not delayed or the misfire is not detected, and even a single misfire is reliably detected. In addition, since the state of deterioration can be grasped in advance from the number of misfires, it is possible to make appropriate preparations such as inspections.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first invention.

FIG. 2 is a diagram showing a configuration of a second invention.

FIG. 3 is a diagram showing a configuration of a third invention.

FIG. 4 is a schematic configuration diagram of an embodiment of the first invention.

FIG. 5 is a flowchart showing a control procedure of the embodiment.

FIG. 6 is a graph exemplifying variations in exhaust temperature of cylinders in the same example.

FIG. 7 is a schematic configuration diagram of an embodiment of the second invention.

FIG. 8 is a flowchart showing a control procedure of the embodiment.

FIG. 9 is a graph illustrating an exhaust temperature of a cylinder in the same example.

FIG. 10 is a schematic configuration diagram of an embodiment of the third invention.

FIG. 11 is a flowchart showing a control procedure of the embodiment.

FIG. 12 is a graph exemplifying a variation in engine speed in the example.

[Explanation of symbols]

 1,11,21 Engine 2,12,22 Control Unit 3 Load Sensor 4,13 Temperature Sensor 5,26 Rotation Speed Sensor 14 Supercharger 18 Gas Cutoff Valve 25 Ignition Pulser 27 Input Converter

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hironori Nishizawa 1-32 Chayamachi, Kita-ku, Osaka Yanmar Daisel Co., Ltd.

Claims (3)

[Claims] 1. An exhaust temperature detection means for detecting the exhaust temperature for each cylinder, a storage means for storing the exhaust temperature of each cylinder according to the load and the engine speed during normal operation, and the detected exhaust temperature. Of the spark ignition internal combustion engine, characterized in that the exhaust temperature stored in the storage means is compared with the determination means for determining the misfire of the corresponding cylinder when there is a difference equal to or greater than a certain determination value. Misfire determination device. 2. In a lean burn gas engine, an exhaust gas temperature detecting means for repeatedly detecting an exhaust gas temperature for each cylinder when operating at a constant speed, an average value of the exhaust gas temperature of all cylinders, and each cylinder for this average value. A calculating means for sequentially calculating the deviation value of the exhaust temperature for each, comparing the calculated deviation value with a constant judgment value, and judging means for judging the misfire of the corresponding cylinder when the deviation value exceeds the judgment value, A misfire determination device for a spark ignition type internal combustion engine, comprising: 3. A rotational speed detecting means for constantly detecting the engine rotational speed and an average value of the rotational speeds are calculated, and the average value and the detected rotational speeds are sequentially compared with each other, and there is a difference of a certain judgment value or more. In this case, a misfire determination device for a spark ignition type internal combustion engine, comprising: a determination unit that determines the cylinder that has caused a decrease in the number of revolutions from the relationship with the ignition timing and determines that cylinder as a misfire. ..