JPH0454255A - Avoidance of misfire for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve misfire avoidance controllability by comparing a misfire judgement information with a first standard value and a second standard value, avoiding misfire by way of cutting off fuel in the case of a misfire state at a high level in accordance with its comparison result and by avoiding misfire by way of control correction processing in the case of the misfire state at a low level. CONSTITUTION:A standard position signal L is output by way of arranging a fixing plate 8 on a part of a rotational disc 5 detect standard position facing against the rotational disc 5 and by a photo coupler sensor (not described in the drawing) provided on the fixing plate 8. Fuel control, ignition control and others of each cylinder are carried out by an ECU 10 on the basis of this standard position signal L and a drive state signal from each of various kinds of sensors. At the time of computing processing by this ECU 10, a misfire judgement information is calculated by way of statistically processing a misfire information of the cylinder after an ignition process and this misfire judgement information is compared with a first standard value and simultaneously, when the misfire judgement information is higher than the aforementioned first standard value, it is compared with a second standard value. In the case when the misfire judgement information is higher than the second standard value, supply of fuel is cut off, and in the case when the misfire judgement information is between the first standard value and the second standard value, control correction processing is carried out against the cylinder.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for avoiding a misfire state in an internal combustion engine based on cylinder misfire information after an ignition stroke, and in particular, a method for determining a misfire state in stages. The present invention relates to an internal combustion engine misfire avoidance method that improves misfire avoidance controllability.

[Prior Art] In general, internal combustion engines used in automobile gasoline engines etc. have a plurality of cylinders (for example, 4 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., and identifies the operating position of each cylinder to determine the optimal timing. It is controlled by. Further, as 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. 3 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 degrees corresponding to 172 cycles of one revolution, and with respect to the camshaft (2), the operating position of each cylinder is out of phase by 180 degrees corresponding to 172 cycles of one rotation. 4
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, ignition control, etc. of each cylinder are performed based on operating state 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 connected to one end of the spark plug (13) and ECU (1
0), a backflow prevention diode (21) connected to one end of the spark plug (13), and a load resistor connected to the cathode of the diode (21). (22), an anode-grounded DC power supply (23) connected in series to the load resistor (22), and a voltage dividing resistor connected in parallel to the series circuit consisting of the load resistor (22) and the DC power supply (23). Connection of the capacitor (26) inserted at the connection point of the load resistor (22) and the voltage dividing resistor (24), and the voltage dividing resistor (24) and (5). Comparator (2) whose point is connected to the comparison input terminal (-) and whose output terminal is connected to ECU (10)
), and voltage dividing resistors (28) and (29) that are connected in series between the power supply and the ground and input 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 for generating a voltage (ion current value) corresponding to the ion current, and the voltage dividing resistors (28) and (29) It constitutes a threshold generation means that generates a threshold TH that serves as a criterion. In addition, the ion current value V is
This 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 and misfire avoidance method using the internal combustion engine misfire determination device shown in FIG. 3 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 (for example, cylinder #1) is generated.

The reference position signal thus obtained is input to the ECU (10) together with the operating state signal. Further, as the operating state signal, for example, the engine (crank) rotation speed and the load state fi (accelerator opening) are 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 ■ is converted into a voltage across the load resistor (22), the DC component is cut off by the capacitor (26), and then 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 above the threshold TH, and goes to the H level only when the ion current value I at the H level is detected. The detected ion current value C is input to E CU (10).

The ECU (10) confirms that combustion has occurred normally in the ignition-controlled cylinder based on the cylinder that is not identified from the reference position signal and the detected ion current value C. If the ignition-controlled cylinder is normal, the spark plug (1
3) An explosion occurs due to the discharge, and many positive ions are generated between the spark plugs (13), but unless there is some kind of hindrance and an explosion does not occur, very few positive ions will be generated. It is possible to determine the misfire condition.

When a misfire condition is determined, the supply of fuel to that cylinder is cut, thereby preventing gas from leaking out due to a misfire.

However, during many ignition processes, accidental misfires may occur even if there is no particular abnormality, and it is not practical to make a misfire judgment based on only one misfire detection. In some cases, a misfire may be avoided by control optimization processing such as increasing the ignition energy, and always performing a fuel cut processing when a misfire is determined cannot be said to be an efficient misfire avoidance processing.

[Problems to be Solved by the Invention] As described above, the conventional internal combustion engine misfire avoidance method simply determines the misfire state when the ion current value (misfire information) becomes less than 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.

Furthermore, when a misfire condition is determined, fuel cut processing is performed regardless of the degree of misfire, so there is a problem that misfire avoidance control is not efficient.

This invention was made in order to solve the above-mentioned problems, and it performs highly reliable misfire determination using misfire determination information through statistical processing, and processes the misfire determination information in stages to detect misfires. The purpose of the present invention is to obtain a method for avoiding misfire in an internal combustion engine with improved avoidance controllability.

[Means for Solving the Problems] A method for avoiding a misfire in an internal combustion engine according to the present invention includes the following steps: (1) calculating misfire determination information by statistically processing cylinder misfire information after the ignition stroke; a step of comparing the misfire determination information with a second reference value that is larger than the first reference value when the misfire determination information is equal to or greater than the first reference value; and a step of comparing the misfire determination information with a second reference value that is greater than the first reference value; The method includes the steps of: cutting the fuel supply to the cylinder; and performing control optimization processing for the cylinder when the misfire determination information is between the first reference value and the second reference value.

[Operation] In this invention, if the misfire condition based on statistically processed misfire determination information is at a high level, misfire is avoided by cutting fuel, and if it is mild, misfire is avoided by control optimization processing.

[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.
2 is a flowchart showing an example of the misfire determination information calculation routine in FIG. 1. FIG.

The device to which the present invention is applied may be, for example, the one shown in FIG. It suffices if the control optimization means includes control optimization means for avoiding such problems.

Furthermore, the functions of the threshold generation means (28) and (29) and the comparator (27) may be included in the ECU (10), and if necessary, the ion current value (2) may be peak held or integrated and then AD converted. Alternatively, the threshold TH may be corrected according to the operating condition.

In this way, by using peak hold or integrated misfire information, false detection can be prevented even if a noise pulse is superimposed on the misfire information. In this case, E CU (
10) includes an AD converter that converts misfire information corresponding to the level of the ion current value ■ into a digital signal, a threshold calculation unit that calculates the threshold TH based on the reference position signal and the operating status signal, and the AD converter. This includes a comparison section for comparing the misfire information obtained with the threshold TH and outputting a misfire detection signal.

Furthermore, the misfire information is not limited to the ion current flow 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 V is used as misfire information in the same way as described above.

First, the misfire rate (misfire determination information) Q is calculated by statistically processing the ions and current values (misfire information) (step 530).
.

Next, in step 5, the misfire rate Q is compared with the first reference value α.
31), if it is greater than or equal to the first reference value α1, it is further compared with a second reference value α2 which is larger than the first reference value α1 (step 532).

If the misfire rate Q is greater than or equal to the second reference value α2, it is regarded as a high level misfire condition, the fuel supply to that cylinder is cut off, and the process returns.

On the other hand, if the misfire rate Q is greater than or equal to the first reference value α1 and smaller than the second reference value, that is, if it is between the first reference value α1 and the second reference value α2, the control for that cylinder is optimized. Set the flag (step 534), and check that the control optimization flag is set (step 535)
After j, control optimization processing (step S36.537)
to avoid misfire and return.

In this case, as control optimization processing, at least one of ignition energy up processing (step 536) and air-fuel ratio (A/F) optimization (step 537) is executed. Although it varies depending on the condition etc.
The weight ratio is about 14.7.

In step S36, the voltage applied to the spark plug (13) is increased or continuous ignition processing is performed, etc.
In step S37, the air-fuel ratio is set to the optimum value. As a result, mild misfire conditions are avoided and normal combustion conditions are obtained.

On the other hand, if it is determined in step S31 that the misfire rate Q is smaller than the first reference value α1, it is not an abnormal misfire but a misfire within the allowable range, so it is considered to be a normal combustion state, and the control optimization flag is (step 538)
After L, the process advances to step S35. And step S
If it is determined in step 35 that the control optimization flag is not set, the process returns directly.

Incidentally, in step S31, the misfire rate Q is set to the first reference value α1.
If it is determined that the misfire determination flag (not shown) for that cylinder is smaller, the process proceeds to step S3.
If the misfire rate Q is determined to be equal to or higher than the second reference value α2 in step 2, a misfire determination flag may be set.

As a result, when the misfire determination flag is set, an alarm or warning display indicating an abnormal misfire can be activated as appropriate, for example.

Next, an example of the misfire determination information calculation routine in step S30 will be described with reference to FIG.

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 the timing of calculating the misfire rate Q 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 generated between the gaps 3) is converted into an ion current value V by the ion current detector (20), and then peak-held or integrated, for example.

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 ignition counter CNTl is incremented (step 511), the misfire information ■ is compared with the threshold TH (step S2), and if the misfire information V is less than the threshold TH, the count start flag XFC is set to indicate that counting has started ( XFC=1).
Step 512).

If the counter has been started (if XFC=1>, the misfire counter CNT is incremented in step S3), and the number of misfire detections is counted. Also, before the count starts (X
If F C = O), the count start flag XFC is set to 1, the values of the ignition counter CNT1 and the misfire counter CNT are set to 1, and the increment of each counter CNTl 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 reached the predetermined number of times N1, the count start flag XF
Determine whether 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 518), and reset the count start flag XFC and the misfire counter CNT. (
Step 517) and return.

On the other hand, in step S15, the count start flag
If it is determined that the FC is not set, after resetting the ignition counter CNT1 (step S),
Return.

As a result, the number of misfire detections CNT within the predetermined number of ignitions Nl
The ratio, that is, the misfire rate Q, is calculated as misfire determination information.

In this case, when a misfire is detected for the first time, the count start flag XFC is set, and each counter CN
Start counting Tl and CNT (step 51
3) Since this is done, the misfire rate Q is not needlessly calculated when no misfire occurs at all, and since the counters CNTl and CNT are incremented from the time a misfire occurs, the misfire rate Q increases. This means that the calculation is on the safe side.

Note that although the predetermined number of times N1 for misfire determination, the first reference value α1, and the second reference value α2 are set to predetermined values here, they may be corrected depending on the driving state.

Further, 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, because, 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 the number is too large, the level of the misfire information (2) increases, so the threshold TH is corrected to increase.

Furthermore, 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 is calculated from TH=V-J. be able to.

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

Furthermore, the threshold TH is averaged and TH,=k
The current threshold TH, , can be found from l-THe, , l+ and 2·Vl, +K. However, TH,
, is the previous threshold, V is the current misfire information, K
is a correction term depending on the operating condition. Further, kl and ni are averaging processing coefficients, and take values in the range of 1 > k + > k 2 > 0.

In the above embodiment, the misfire determination information obtained by statistically processing the misfire information (2) was used as the misfire rate Q, but the number of consecutive misfire detections may be used as the misfire determination information.

In this case, the misfire counter CNT is used to count the number of consecutive misfire detections, and an abnormal misfire is determined when the number of consecutive misfire detections reaches a reference value (predetermined number of times).

That is, N1kuN.

A first reference value N and a second reference value N2 that satisfy the relationship are set, and when the number of consecutive misfire detections reaches the second reference value N2, fuel cut processing is performed and the first reference value N, and second
Control optimization processing is performed when the value is between the reference value N2.

Further, each of the reference values a1 and α2 for determining the misfire state may be corrected according to the operating state of the internal combustion engine, that is, the rotation speed, load, fuel injection amount, water temperature, intake temperature, etc. Enables highly reliable misfire adjustment 0 For example, if you release the accelerator pedal while driving at high speed, the fuel injection amount will be suppressed and a continuous misfire will occur. Depending on the signal, each reference value α1 and α
If 2 is set to a large value, 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, the following steps are performed: calculating misfire determination information by statistically processing cylinder misfire information after the ignition stroke; and comparing the misfire determination information with a first reference value. ,
a step of comparing the misfire determination information with a second reference value larger than the first reference value when the misfire determination information is equal to or greater than the first reference value; and a step of controlling the supply of fuel to the cylinder when the misfire determination information is equal to or greater than the second reference value. and a step of performing control optimization processing on the cylinder when the misfire determination information is between a first reference value and a second reference value, and when the misfire condition based on the misfire determination information is at a high level. In the event of a misfire, the misfire is avoided by cutting fuel, and in the case of a minor misfire, misfire is avoided by control optimization processing.In addition to making a highly reliable misfire determination, the misfire determination information is processed step by step to prevent a misfire. This has the effect of providing an internal combustion engine misfire determination method with improved avoidance controllability.

[Brief explanation of drawings]

FIG. 1 is a flow chart diagram showing an embodiment of the present invention;
FIG. 2 is a flowchart showing an example of the misfire determination information calculation routine in FIG. 1, and FIG. 3 is a block diagram showing a general internal combustion engine misfire determination device. (10)...ECU ■...Ion current value (misfire information) Q...misfire rate (misfire determination information) α,...first reference value α2...second reference value S3
0...Step S31 for calculating misfire determination information...
Step S32 of comparing the misfire determination information with the first reference value...Step S33 of comparing the misfire determination information with the second reference value...Step S36 of cutting the fuel supply.
S37...Step for performing control optimization processing In addition, in the figure,
The same reference numerals indicate the same or equivalent parts. Figure 1

Claims (1)

[Scope of Claims] A step of calculating misfire determination information by statistically processing the misfire information of the cylinder after the ignition stroke; a step of comparing the misfire determination information with a first reference value; and a step of comparing the misfire determination information with a first reference value. comparing the misfire determination information with a second reference value larger than the first reference value when the misfire determination information is equal to or greater than the second reference value; and stopping the supply of fuel to the cylinder when the misfire determination information is equal to or greater than the second reference value. A method for avoiding a misfire in an internal combustion engine, comprising: cutting the misfire determination information; and performing control optimization processing on the cylinder when the misfire determination information is between the first reference value and the second reference value.