JPH0454282A - Internal combustion engine misfire judging method - Google Patents

Abstract

PURPOSE:To obtain an internal combustion engine misfire judging method which can ignore any accidental misfire and does not mar reliability, by comparing a misfire information with a threshold, and judging a cylinder digestive condition when a misfire counter reaches a predetermined number of times. CONSTITUTION:An ECU 10 makes a power transistor 11 ON/OFF, and generates a spark at an ignition plug 13 by driving the primary coil and the secondary coil of an ignition coil 12. At this time, a large quantity of positive ion is gener ated at the gap space of the plug 13, and the ion electric current I is converted to an ion electric current value V by means of partial pressure resistors 24 & 25, and inputted into the comparison input terminal- of a comparator 27. Meanwhile, a threshold TH set by means of partial pressure resistors 28 & 29 is inputted into the reference input terminal+ of the comparator 27. In this instance, a misfire information (V) is compared with the threshold TH in the ECR 10, and as a result, a misfire counter is incremented, while the misfire counter is reset at the time of a non-misfire judgment. A misfire is judged when the misfire counter reaches a predetermined number of times.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for determining the misfire state of an internal combustion engine based on cylinder misfire information after the ignition stroke, and in particular to a method for improving reliability through statistical processing. The present invention relates to a method for determining misfire in an internal combustion engine.

[Prior Art] In general, an internal combustion engine used for an automobile gasoline engine, etc. has a plurality of cylinders (for example, four cylinders) to provide intake air,
It is driven by four cycles: compression, explosion, and exhaust. In such an internal combustion engine, calculations are performed electronically by a microcomputer in order to optimally control the ignition timing, fuel injection order, etc. for each cylinder. For this reason,
In addition to various operating conditions, the microcomputer takes in a reference position signal for each cylinder synchronized with the rotation of the internal combustion engine, a cylinder identification signal corresponding to a specific cylinder, etc., identifies the operating position of each cylinder, and determines the optimal timing. It is controlled by.

Further, as a means for generating the reference position signal and the cylinder identification signal, a rotation signal generator is used which detects the rotation of the camshaft or crankshaft of the internal combustion engine and generates a synchronization signal.

For example, when controlling the ignition of each cylinder, it is necessary to combust the air-fuel mixture compressed by the piston using the spark from the ignition plug, but depending on the condition of the fuel and the ignition plug, combustion may not be possible in the ignition-controlled cylinder. . If such a situation occurs, an abnormal load will be applied to other cylinders, damaging the engine, and there is a risk that gas will leak out, causing various problems.

Therefore, in order to ensure the safety of the engine, it is necessary to detect whether combustion has occurred reliably in each cylinder at each ignition stroke cycle. For this reason, devices have been proposed that detect ion current generated between the gaps of spark plugs as misfire information to determine combustion or misfire conditions.

FIG. 5 is a block diagram showing a general internal combustion engine misfire determination device that uses ionic current as misfire information.

In the figure, (1) is a crankshaft serving as a drive shaft of an internal combustion engine, and is connected to pistons of a plurality of cylinders (not shown) to be rotationally driven.

(2) is a camshaft that rotates in synchronization with the crankshaft (1);
(3) is a timing belt that connects the crankshaft (1) and the camshaft (2).

For a typical 4-stroke engine, the crankshaft (1)
Suction, compression, explosion and exhaust are performed for two rotations of
The camshaft (2) rotates once for every two rotations of the crankshaft (1), and the camshaft (2) rotates once in synchronization with one period of the four-cycle operation of each cylinder. Therefore, 4
In the case of a cylinder engine, the operating position of each cylinder is out of phase with respect to the crankshaft (1) by 180° (1/2 period of one rotation), and with respect to the camshaft (2). 174
The phase is shifted by a period.

(4) is a rotating shaft of a rotational signal generator connected to the camshaft (2), and (5) is a rotating disk for detecting a reference position provided at one end of the rotating shaft (4). (6) is a slit-shaped window formed in the rotating disk (5), and is provided so as to correspond to a reference position (predetermined rotation angle) for each cylinder. Further, the rotary disk (5) is provided with a cylinder identification window (not shown) corresponding to a specific cylinder, if necessary.

(8) is a fixed plate placed opposite to a part of the rotating disk (5). This fixed plate (8) is provided with a photocoupler sensor (not shown) facing the window (6), and is configured to generate a reference position signal for each cylinder. Here, one end of the window (6) on the front side in the rotation direction corresponds to the first reference position of each cylinder, and one end of the window (6) on the rear side in the rotation direction corresponds to the second reference position of each cylinder. The signal is
The pulse waveform rises at the first reference position and falls at the second reference position.

(10) is a microcomputer (hereinafter referred to as ECU) constituting the electronic control unit, and includes a reference position signal and
Fuel control and ignition control for each cylinder are performed based on operating status signals from various sensors (not shown). The ECU (10) includes a distribution unit that controls ignition of each cylinder according to the determined cylinder order.

(11) is a common emitter power transistor driven by the ignition signal from ECU (10);
) is an ignition coil whose secondary coil side is connected to the power transistor (11), (13) is a spark plug connected to the secondary coil side of the ignition coil (12), and (14) is an ignition coil (12) and an ignition coil. This is a backflow prevention diode inserted between the plug (13) and the plug (13). Although the ignition section for one cylinder is representatively shown here, such an ignition section is provided for each cylinder.

(20) is one end of the spark plug (13) and the ECU (10)
This is an ion current detector inserted between a backflow prevention diode (21) connected to one end of the spark plug (13) and a load resistor (22) connected to the cathode of the diode (21). ), an anode-grounded DC power supply (23) connected in series to the load resistor (22), and the load resistor (22).
The voltage dividing resistors (24) and (25) are connected in parallel to the series circuit consisting of the load resistor (22) and the DC power supply (23), and the voltage dividing resistor (22) and the voltage dividing resistor (24) are inserted at the connection point. capacitor (26), voltage dividing resistor (24) and (2
A comparator (27) whose connection point of 5) is connected to the comparison input terminal (-) and whose output terminal is connected to ECU (10).
and voltage dividing resistors (28) and (29) connected in series between the power supply and the ground and inputting the threshold TH from the intermediate connection point to the reference input terminal (+) of the comparator (27).

The voltage dividing resistors (24) and (25) constitute voltage generating means that generates a voltage (ion current value) corresponding to the ion current I, and the voltage dividing resistors (28) and (29) constitute a It constitutes a threshold generation means that generates a threshold T r (which becomes a judgment standard. Also, the ion current value V
is input to the comparator (27) as misfire information.

The ion current detector (20) having the above configuration is provided only on the spark plug (13) of a specific cylinder or on the spark plug (13) of each cylinder, as necessary.

Next, a conventional internal combustion engine misfire determination method using the internal combustion engine misfire determination device shown in FIG. 5 will be described.

When the rotary disk (5) rotates together with the camshaft (2) that interlocks with the crankshaft (1), the photocoupler sensor on the fixed plate (8) outputs a reference position signal corresponding to the window (6). be done. For example, this reference position signal rises at the first reference position B of each cylinder at 75 degrees, and rises at the second reference position B of each cylinder.
The waveform will fall at 5°.

The first reference position B75° is 75° from TDC (top dead center).
° This is the front crank angle position and corresponds to the control reference and initial energization angle. Also, the second reference position B5° is
This is the crank angle position 5 degrees before TDC, and corresponds to the initial ignition position during cranking. Further, another cylinder identification signal (which may be included in the reference position signal) is output when a reference position signal corresponding to a specific cylinder (fs, for example, #1 cylinder) is generated.

The reference position signal thus obtained is input to the ECU (10) together with the operating state signal. Also, as the operating status signal, for example, engine (crank) rotation speed and load status! ! ! (accelerator opening degree) is input.

The E CU (10) distributes the ignition signal to each cylinder identified by the reference position signal, and
The power transistors (11) are turned on in the order of cylinder, #4 cylinder, and #2 cylinder. After passing the secondary coil current of the ignition coil (12) for the required time, the power transistor (11) is cut off, and the secondary coil side of the ignition coil (12) is driven to generate a spark in the spark plug (13). to occur. At this time, the power supply voltage applied to the ignition coil (12) is a negative high voltage, but is cut off after discharge occurs at the ignition plug (13).

When an explosion (combustion) occurs around the spark plug (13) due to this discharge, a large amount of cations are generated immediately between the gaps of the spark plug (13). These positive ions become ion current I, which flows from between the gap of the spark plug (13) through the diode (21) and the load resistor (22), being drawn by the negative voltage of the DC power supply (23).

After this ionic current I is converted into a voltage across the load resistor (22), the DC component is cut off by the capacitor (26), and further, the voltage dividing resistor (24) and (25)
is converted into an ion current value V and inputted to the comparison input terminal (-) of the comparator (27). The ion current value ■ is
Usually, if an explosion occurs, the value will be high, and if no explosion occurs, the value will be low. On the other hand, the reference input terminal (+) of the comparator (27) receives a threshold TH that is appropriately set in advance by voltage dividing resistors (28) and (29).

Therefore, the comparator (27) turns off the output signal when the ion current value V is smaller than the threshold TH, turns on the output signal when it is higher than the threshold 78, and goes to the H level only when the ion current value V is detected at the H level. The detected ion current value C is input to the ECU (10).

The ECU (10) confirms that combustion has occurred normally in the ignition-controlled cylinder based on the cylinder identified from the reference position signal and the detected ion current value C. if,
If the ignition-controlled cylinder is normal, the spark plug (13
), an explosion occurs and many positive ions are generated between the spark plugs (13), but unless there is some obstacle and an explosion does not occur, very few positive ions will be generated.This will cause the cylinder to misfire. The state can be determined.

However, during many ignition strokes, accidental misfires may occur even if there is no particular abnormality, and it is not practical to determine a misfire based on only one misfire detection.

[Problems to be Solved by the Invention] As described above, the conventional internal combustion engine misfire determination method simply determines the misfire state when the ion current value (misfire information) becomes below the threshold TH. There is a problem in that a misfire determination is made even in the case of a targeted misfire, making it impossible to make a highly reliable misfire determination.

This invention was made to solve the above-mentioned problems, and its purpose is to obtain a highly reliable internal combustion engine misfire determination method by ignoring accidental misfires using statistical processing. do.

[Means for Solving the Problems] An internal combustion engine misfire determination method according to the present invention includes the steps of: taking in misfire information of a cylinder after the ignition stroke; comparing the misfire information with a threshold; and when the misfire information is below the threshold. incrementing the misfire counter in the following cases; resetting the misfire counter when the misfire information is greater than a threshold; and determining the misfire state of the cylinder when the misfire counter reaches a predetermined number of times. It is something.

Further, an internal combustion engine misfire determination method according to another aspect of the present invention includes a step of taking in misfire information of a cylinder after an ignition stroke;
incrementing a ignition counter; comparing the misfire information with a threshold; incrementing the misfire counter if the misfire information is less than or equal to the threshold; and based on the value of the misfire counter when the ignition counter reaches a predetermined number of times. The method includes a step of calculating the misfire rate of the cylinder based on the engine speed, and a step of determining whether the misfire is in a similar state when the misfire rate is equal to or higher than a reference value.

[Operation] In the present invention, a misfire is determined when it is continuously detected that misfire information is below a threshold a predetermined number of times.

In another aspect of the present invention, the number of misfires detected within a predetermined number of ignitions is calculated as a misfire rate, and a misfire is determined when the misfire rate is equal to or higher than a reference value.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a flowchart diagram showing one embodiment of this invention.
The figure is an explanatory diagram showing the counter operation according to the present invention.

The device to which this invention is applied may be, for example, the one shown in FIG. good.

Further, the functions of the threshold generation means (28) and (29>) and the comparator (27) may be included in E CU <10), and if necessary, the ion current value V may be peak-held or AD converted after integration. Alternatively, the threshold TH may be corrected according to the operating condition.

In this way, by using peak-held or integrated misfire information, false detection can be prevented even if a noise pulse is superimposed on the misfire information. Also, in this case, E C
U (10) includes an AD converter that converts misfire information corresponding to the level of the ion current value V into a digital signal, and a threshold T based on the reference position signal and the operating status signal.
It includes a threshold calculation section that calculates H, and a comparison section that compares the AD-converted misfire information with the threshold TH and outputs a misfire detection signal.

Further, the misfire information is not limited to the ion current I in the cylinder after the ignition stroke, but may also be the cylinder pressure, etc. In this case, a misfire is detected when the cylinder pressure after the ignition stroke is below a reference value. will be done.

Here, a case will be described in which the ion current value ■ is used as the misfire information, as described above.

First, a misfire counter CNT for counting the number of consecutive misfire detections is reset (cleared to 0), a misfire determination flag is reset, and a predetermined number N for misfire determination is set in advance.

The ECU (10) discharges the spark plug (13) at a predetermined timing based on a reference position signal corresponding to the crank angle of each cylinder. At this time, the spark plug (1
The ion current I generated between the gaps 3) is converted into an ion current value V by an ion current detector (20), and is then subjected to, for example, peak hold or integration.

The ECU (10) performs AD conversion on the peak-held or integrated ion current value V at a predetermined timing based on the reference position signal, and takes it in as misfire information (step S1).

Next, the misfire information V is compared with a predetermined threshold TH (step S2), and if it is less than the threshold TH,
Increment the misfire counter CNT in step S3.
), it is determined whether the misfire counter CNT has reached a predetermined number of times N (step S4).

If the predetermined number N has not been reached, the misfire determination flag is reset (step S5), and if the predetermined number N has been reached, the misfire determination flag is set and a misfire determination is performed (step S6), and the process returns.

On the other hand, if it is determined in step S2 that the misfire information V is greater than the threshold TH, the misfire counter CNT is reset (step S7), the misfire determination flag is reset (step S5), and the process returns.

The above steps 81 to S5 are repeated for each ignition stroke based on the timing of the reference position signal.

As a result, the misfire counter CNT indicates the number of consecutive misfire detections as shown in FIG. 2, and a misfire determination flag is set when the number of consecutive misfires reaches a predetermined number N. When the misfire determination flag is set, for example, an alarm or warning display indicating an abnormal misfire is activated as appropriate.

Note that it is desirable that the threshold TH used in the misfire detection step S2 be corrected according to the misfire information or the operating state.For example, when the rotation speed or load of the internal combustion engine is large, the level of the misfire information increases. So,
This is because it is necessary to set a high threshold TH.

In general, the operating status signal is the rotational speed of the internal combustion engine,
There are load, water temperature, intake temperature, fuel injection amount, etc., and ECU
The threshold calculation unit in (10) may, for example, search the threshold map based on the rotation speed, load, etc., and then correct the threshold TH based on the fuel injection amount, etc. In this case, if the fuel injection amount is If it is too large, the level of the misfire information V increases, so the threshold TH is corrected to increase.

Further, the threshold TH may be calculated based on the operating state and misfire information without using a threshold map or the like. In this case, for example, based on the misfire information V, the threshold TH can be calculated from TH=V,J.

However, J is a correction coefficient depending on the driving state.

Furthermore, the threshold TH is averaged and T H-=
k + ・T H11-+ + k 2 ・V,
The current threshold TH, , can be obtained from +K. However, T Hn-1 is the previous threshold, V is the current misfire information, and K is a correction term depending on the operating state. Further, k and 2 are averaging processing coefficients, and take values in the range of 1 > k l > k 2 > 0.

In the above embodiment, as a statistical processing of the misfire detection results, misfire determination is performed when the number of consecutive misfire detections reaches a predetermined number N. However, if the misfire rate within the predetermined number of ignitions exceeds the reference value, A misfire determination may be made in some cases.

Hereinafter, another embodiment of the present invention will be described with reference to the flowchart shown in FIG. In FIG. 3, S1 to S3 and S5 to s7 are the same steps as described above.

First, the ignition counter CN for counting the number of ignitions.
Tl, misfire counter CNT that counts the number of misfire detections
, the misfire determination flag and the count start flag XFC are reset, and a predetermined number of times N1 for determining when to calculate the misfire rate is set in advance.

After detecting the misfire information V (step s1) in the same way as described above, the ignition counter CNTl is incremented (step 5ll), and the misfire information V is compared with the threshold TH (step S2).

If the misfire information V is less than the threshold TH,
Referring to the count start flag XFC, it is determined whether the count has started (XFC=1) (step 51
2).

If the counter has already started, the misfire counter CNT is incremented in step S3), and if the count has not yet started (XFC=O), the count start flag XFC is set to 1 and the ignition counter CNT is incremented.
and misfire counter CNT is set to 1, and each counter CN
Increment of Tl and CNT is started (step 513).

Then, it is determined whether the ignition counter CNTl has reached a predetermined number of times N1 (step 514). On the other hand, if it is determined in step S2 that the misfire information V is greater than the threshold TH, the process immediately proceeds to step S14. .

In step S14, if it is determined that the ignition counter CNTl has not reached the predetermined number of times Nl, the process immediately returns to step S1, and if the ignition counter CNTl has not reached the predetermined number of times N1, the count start flag XF
Determine whether or not C is set (step 51
5).

If the count start flag XFC is set, calculate the misfire rate Q from Q=CNT/Nl using the misfire counter CNT and the predetermined number of times N1 (step 516), and reset the count start flag XFC and the misfire counter CNT. (step 517).

Next, step 518 compares the misfire rate Q with the reference value α.
), if the misfire rate Q is smaller than the reference value α, reset the misfire determination flag (step S5), and if the misfire rate Q is smaller than the reference value α
If it is above, set the misfire determination flag (step S6
), then return.

On the other hand, in step S15, the count start flag
If it is determined that FC is not set, the ignition counter CNTl is reset (step S7) and then the process returns.

As a result, the number of misfire detections CNT within the predetermined number of ignitions Nl
A misfire is determined when the ratio of , that is, the misfire rate Q is greater than or equal to the reference value α.

Also, when a misfire is detected for the first time, the count start flag XFC is set, and each counter CNTl and C
Since the count of NT is started (step 513), the misfire rate Q is not needlessly calculated when no misfire occurs at all. Furthermore, since the counters CNTl and CNT are incremented from the time when a misfire occurs, the misfire rate Q is calculated to be large and on the safe side.

In each of the embodiments shown in FIGS. 1 and 3, the predetermined number of times N, Nl and reference value α for misfire determination are set to predetermined values, but they may be corrected depending on the operating state.

FIG. 4 is a flowchart showing a calculation routine for a misfire determination value, which can be executed in advance before the execution of FIG. 1 or FIG. 3.

First, detect the operating state of the internal combustion engine, that is, the rotation speed, load, fuel injection amount, etc. Stella 7821-523), and set the predetermined number of times N, Nl, and reference value α according to the operating state, respectively, N4-N- Then, it is corrected by I N1←N1·K− α←α·N4 (step 524). However, K,,K.

and 4 are correction coefficients depending on the operating state. In addition to the above, water temperature, intake air temperature, etc. may be detected as the operating state.

In this way, by correcting the determination values N, Nl, and α, more reliable misfire determination becomes possible. For example,
If the accelerator pedal is released while driving at high speed, the fuel injection amount is suppressed and a continuous misfire condition occurs, but the predetermined number of times N or the reference value α is set to a large value based on the driving status signals from various sensors indicating the accelerator opening degree. Therefore, an abnormal misfire condition will not be erroneously detected.

Furthermore, although the case has been described in which ion current is used as misfire information, it goes without saying that the same effect can be achieved using other misfire information such as cylinder pressure.

[Effects of the Invention] As described above, according to the present invention, there are a step of taking in misfire information of a cylinder after the ignition stroke, a step of comparing the misfire information with a threshold, and a step of incrementing a misfire counter when the misfire information is less than the threshold. a step of resetting a misfire counter when the misfire information is greater than a threshold; and a step of determining the misfire state of the cylinder when the misfire counter reaches a predetermined number of times, and continuously detecting the misfire a predetermined number of times. Since a misfire is determined when a misfire occurs, an accidental misfire can be ignored, and an internal combustion engine misfire determination method that does not impair reliability can be obtained.

According to another invention of the present invention, the steps include: incrementing the ignition counter each time misfire information is taken in; incrementing the misfire counter when the misfire information is less than a threshold; and when the ignition counter reaches a predetermined number of times. the step of calculating the misfire rate of the cylinder based on the misfire counter value at the time; and the step of determining the misfire state of the cylinder when the misfire rate is greater than or equal to a reference value, and the misfire rate within a predetermined number of ignitions is the reference value. Since the misfire is determined in the above cases, there is an effect that a more reliable internal combustion engine misfire determination method can be obtained.

[Brief explanation of drawings]

FIG. 1 is a flow chart diagram showing an embodiment of the present invention;
FIG. 2 is an explanatory diagram showing the operation of the misfire counter in FIG. 1, FIG. 3 is a flow chart diagram showing an embodiment of another invention of the present invention, and FIG. A flowchart diagram for explaining another embodiment, and FIG. 5 is a configuration diagram showing a general internal combustion engine misfire determination device. (10) -E CU (13), -・Spark plug (20)...Ion current detector■...Ion current value (misfire information) T)I...Threshold CNT...Misfire counter N.・・Predetermined number of times CNTl
...Ignition counter N1...Predetermined number of times Q...Misfire rate α...Reference value

Claims (4)

[Claims] (1) capturing misfire information of the cylinder after the ignition stroke; comparing the misfire information with a threshold; incrementing a misfire counter when the misfire information is less than or equal to the threshold; A method for determining a misfire in an internal combustion engine, comprising: resetting the misfire counter when the misfire counter is larger than the predetermined number; and determining a misfire state of the cylinder when the misfire counter reaches a predetermined number of times. (2) capturing misfire information of the cylinder after the ignition stroke; incrementing an ignition counter; comparing the misfire information with a threshold; and incrementing the misfire counter when the misfire information is less than the threshold. and calculating a misfire rate of the cylinder based on the value of the misfire counter when the ignition counter reaches a predetermined number of times; and determining a misfire state of the cylinder when the misfire rate is equal to or higher than a reference value. A method for determining a misfire in an internal combustion engine, comprising steps. (3) The method for determining a misfire in an internal combustion engine according to claim 2, wherein incrementing of the ignition counter and the misfire counter is started from the time when the misfire information is first determined to be below a threshold. (4) A step of detecting the operating state of the internal combustion engine; and a step of correcting a predetermined number of times and a reference value for misfire determination according to the operating state. The internal combustion engine misfire determination method according to any one of items 3 to 3.