KR100231335B1 - Misfire detection method for gasoline engine vehicle - Google Patents

Abstract

The present invention relates to a misfire detection method of a vehicle gasoline engine. Conventionally, in the explosion of a mixer, the ECU detects an ignition failure due to damage of a crank angle sensor or the like by using a signal of the crank angle sensor itself. The misfire caused by the deterioration of the capability is not easy to detect and requires a separate means, so there is a problem that it is difficult to warn the user of the deterioration of the engine due to the deterioration of the ignition capability or to inform the mechanic promptly.

Accordingly, in the present invention, as shown in FIG. 3, the output torque of the engine is related to the angular velocity of the crankshaft, and the angular velocity is related to the ignition cycle, so that the combustion stability ER is determined from the ignition cycle. ER is calculated for each group, and it is determined that it is a misfire from the difference between the average value and the maximum value and the minimum value, and based on this, the cylinder that caused the misfire is identified and the fuel injection of the cylinder is stopped and the warning device is activated.

Therefore, the engine misfire can be detected and control of the engine based on the existing means only without a separate sensor or device.

Description

Misfire detection method of vehicle gasoline engine

The present invention relates to a misfire detection method for a vehicle gasoline engine, and more particularly, to a method for detecting a vehicle gasoline engine for determining a cylinder in which misfire has occurred from an ignition cycle.

Gasoline engines, commonly referred to as spark ignition engines, are used as spark ignition engines, as opposed to diesel engines, which are compression and ignition engines.The spark plugs used in the combustion chamber are compressed and the pistons are located at the top dead center. The resulting explosion of the mixer is the power source.

Therefore, it is important that the spark plug is discharged at an appropriate position of the piston, and in a vehicle equipped with an electronically controlled fuel injection device, the discharge of the spark plug is controlled by an ECU (Electronic Control Unit) from the crank angle sensor and the advance device. Doing.

1 is a schematic diagram showing the principle of the crank angle sensor, Figure 1 (a) is a schematic diagram showing the crank angle expression principle of the target wheel, (b) is a block diagram of the crank angle sensor, Figure 1 (c) ) Shows the signal from the crank angle sensor to the ECU.

Permanent magnets are built into the crank angle sensor 10, whereby magnetic force lines are formed. In addition, a crank pulley or a fly wheel is provided with a target wheel 12, and the target wheel 12 is provided with teeth 14 of a gear at regular intervals.

Therefore, when the crank shaft of the engine is rotated, the target wheel 12 is rotated to interrupt the magnetic force line of the crank angle sensor 10, and the waveform of (C) is generated according to the angle θ where each tooth 14 is moved. Will be.

At this time, the generated AC waveform, that is, the signal generated twice the cycle signal of the target wheel teeth when the crank shaft rotates once. Therefore, the ECU divides the number of signals input for one minute by twice the number of teeth 14 of the target wheel 12, which is the engine speed.

The ECU adjusts the fuel injection amount and the like according to the engine revolutions, and a portion of the gear wheel is omitted in a portion of the target wheel 12, where the generation of the waveform is different and the spark plug is generated by this signal. Will be energized.

In general, the maximum explosive force in the engine occurs when the crank angle is about 10 degrees from the top dead center, and the omission point of the teeth described above is determined by the angle.

The point of occurrence of the maximum explosion force is the point of maximum explosion pressure of the mixer, which does not coincide with the point of ignition. That is, considering that the number of revolutions per minute of the target wheel 12 according to the engine speed is high, and the period of the waveform according to the angle θ of the tooth 14 is extremely minute time, the ignition time and the maximum explosion pressure generation time are the minute time. There is a difference between.

Exemplary drawing Figure 2 is a schematic diagram illustrating this, the normal combustion process can be divided into the ignition time 16, the combustion time 18, the maximum explosion pressure 20, the end of combustion 22, the maximum explosion pressure When the time point 20 is about 10 ° from the top dead center 24, the maximum explosive power time point at which the maximum output of the engine is generated is shown, and the dotted line shown from the combustion time point 18 represents the change of the diesel misfire.

In addition, since the viewpoints vary according to the engine speed, it is an advance device to adjust the ignition point 16 so that the viewpoint of the maximum explosion pressure 20 is about 10 °, and such an advance device is a crank angle sensor. In conjunction with (10), the ECU controls the ignition point.

Therefore, when an error signal is input to the ECU due to a breakage of the crank angle sensor 10, a failure in assembling the target wheel 12, or a broken tooth, the ECU malfunctions or does not operate the spark plug.

In this case, the ECU sends a signal to the warning lamp of the engine failure located in the instrument panel of the vehicle and sends a signal to the self-diagnosis device, and the maintenance worker is damaged from the signal of the ECU such as a crank angle sensor and the like and the spark plug Malfunctions or misfires can be determined.

Here, the meaning of the misfire is a small meaning of the operation stop of the spark plug, as well as the case that the explosion stroke does not occur due to the deterioration of the ignition ability also belongs to the category of misfire, in this case is not a phenomenon associated with damage to the crank angle sensor, etc. to be.

In more detail, as described above, in general, the spark of the spark ignition engine is caused by electric discharge, and when the spark is blown into the mixer by the electric discharge, a hot gas nucleus called a flame nucleus is formed.

It is the process of spark ignition until the gas nucleus grows and a flame plane capable of self-propagating is established, and when the flame energy is insufficient, the flame nucleus dies and dies.

These phenomena affect the lowering of the ignition ability, such as discharge type, discharge time, electrode shape, flame interval length, mixing ratio of the mixer, temperature, laminar flow, turbulent flow, and the like. It is irrelevant to the damage of the or the like and the defect of the target wheel 12.

Therefore, the misfire due to the deterioration of the ignition ability does not have a separate detection means directly in the vehicle body, and the measurement of the flame energy is performed by measuring voltage and current using a voltage divider and a current sensor having excellent frequency characteristics and calculating the time integration of the product. A separate detection means is required, such as obtaining or using a calorimetry method.

As described above, the spark plug is discharged from the crank angle sensor at the optimum piston position to explode the mixer.

However, in the explosion of the mixer, the ECU detects misfire due to damage of the crank angle sensor, etc., but the signal of the crank angle sensor itself is easy to detect, but the misfire due to the deterioration of ignition is not easy to detect. Because of this need, there is a problem that it is difficult to warn the user of the deterioration of the engine due to the deterioration of the ignition ability, or to inform the mechanic promptly.

Therefore, the present invention has been devised to solve the above problems, the user or the mechanic to tell the state of misfire due to the deterioration of the ignition capability from the ignition cycle input from the signal of the crank angle sensor, which is an existing device, without a separate device. It is an object of the present invention to provide a misfire detection method for a vehicle engine that can be easily informed.

According to the present invention, the output torque of the engine is related to the angular velocity of the crankshaft, and the angular velocity is related to the ignition cycle, so that the combustion stability ER is determined from the ignition cycle. It is judged that it is a misfire from the difference between the average value and the maximum value and the minimum value of the mean value, and based on this, the cylinder in which the misfire has occurred is found to stop fuel injection and operate a warning device.

Therefore, the engine misfire can be detected and control of the engine based on the existing means only without a separate sensor or device.

1 (a) is a schematic diagram showing the principle of the crank angle representation of the target wheel,

(B) is a schematic diagram showing the configuration of the crank angle sensor,

(C) Schematic diagram showing the signal input to the ECU from the crank angle sensor,

Figure 2 is a schematic diagram showing the pressure change of the combustion chamber from the ignition in the micro-section,

3 is a flowchart of a misfire detection method according to the present invention.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

The present invention comprises a first step of detecting each cylinder ignition period (T) of the three crank shaft rotations from the crank angle sensor;

Calculating a combustion stability coefficient ER (k) from the ignition period T measured for each of the two cylinders in one group;

When the average value ER _m (k) is calculated from the measured ER (k) and the difference between the maximum value and the minimum value of the average value ER _m (k) ΔER _m (k) is compared with the normal zone set in the ECU, the engine is out of the normal zone. Detecting the fact that it is true;

In the case of detecting the misfire in step 3, the misfire of the gasoline engine in four stages which compares with the ER (k) of the abnormal region, estimates the cylinder in which misfire has occurred, and confirms that the misfire occurrence cylinder is from the estimated ignition period T of the cylinder. Detection method.

3 is a flowchart illustrating the present invention, and the present invention is to detect misfire of an engine based on combustion stability (ER).

Here, the combustion stability (ER) is derived from the ignition cycles of three crankshaft rotations, and thus, the ECU detects the ignition cycles of three revolutions of the crankshaft rotation.

That is, the equation for torque balance in the crankshaft

M: engine torque,

W: load,

J: moment inertia,

ω: engine angular speed

Misfires cause very large combustion fluctuations, and thus the engine torque fluctuations cause the angular acceleration fluctuations.

Where the engine angular velocity at the ignition period T _i , the time from one ignition to the next

4π: Rotation angle of 2 strokes of 4 stroke engine

c: number of cylinders

to be.

Therefore, the angular velocity ω _i and the ignition period T _i are inversely related, and when the change in the angular velocity is regarded as an evaluation criterion for combustion stability (ER), the following equation is derived.

From the combustion stability evaluation criteria of the engine can be defined as follows.

Therefore, in order to find the combustion stability ER, T _i-1 , which is the previous stage, and T _{i-2, which} is the previous stage, are required, including the current combustion cycle T _i , and the ignition cycle T of three revolutions of the crankshaft is detected in the first stage. .

In step 2, ER is calculated from two cylinders in one group. This is because the ER equation is applied without any influence during the constant speed or acceleration, but the ER may be changed by the disturbance of the drive system or the change of the road condition, not the combustion fluctuation.

Therefore, to exclude the effects of disturbances other than combustion fluctuations, two cylinders are calculated as one group.

Taking a four-cylinder engine as an example, assuming that the cycle for three revolutions of the crankshaft is measured in the first step, the time required for the combustion stroke is one section. do.

In other words, in a four-cylinder engine, there are two ignitions per revolution of the crankshaft, and the 1,4 and 2,3 cylinders have the same ignition cycle.

Therefore, the ignition period T at three revolutions of the crankshaft in a four-cylinder engine is T (n + 1), T (n + 2), T (n + 3), T (n + 4), T (n + 5), T (n + 6), divided into six sections.

Here, T (n + 1, 3, 5) is an ignition period of 1,4 cylinders, and T (n + 2, 4, 6) is an ignition period of 2,3 cylinders.

From these, the ER 1 which is the first and fourth cylinder group is

Then, the ER 2 having 2, 3 cylinders as the second group

to be.

However, it is not possible to estimate in which cylinder misfire has occurred in step 3, which will be described later, using only the ER of two groups in which the two cylinders are one group.

That is, if misfire in the ER 1 occurs, it is impossible to estimate which misfire has occurred in one or four cylinders or whether misfire has occurred in both 1 and 4 cylinders.

Therefore, an additional group is needed to solve this problem, and the ER is calculated as the third and third cylinders as the first and second cylinders as the third group, and weighted to be different from the first and second groups.

In the divided four groups ER (1), ER (2), ER (3), and ER (4), when combustion fluctuations due to misfire occur, the ER values in each group are different from each other. In the case of disturbance, the ER value is almost unchanged due to the absolute value calculation.

Therefore, when the ER values fall outside the range of the value set in the ECU, it is determined as a misfire and this process constitutes the third step of the present invention.

That is, in step 3, the average value ER _m (k) is obtained for each ER (k), and the displacement amount ΔER _m (k) of the average value is obtained and compared with the set value.

here,

ER _m (k) = ZER _m ^old (k) + (1-z)

ER _m ^old (k): ER mean value at all stages

ER (k): Calculated Average

z: filter coefficient

From this, the difference between the maximum and minimum of the mean value of each group

ΔER _m (k) = ER _m (k) _max -ER _m (k) _min

If the operation, and the normal state to the ECU to compare the ΔER _m is set to the calculated ΔER _m and ECU sets a range of ΔER _m.

If it is out of the set range from this, the ECU judges this as a misfire and identifies the cylinder in which the misfire occurred in step 4.

In step 4, the misfired cylinder is estimated from the detected ER (k) value, the misfired cylinder is identified from the ignition period T, and control is performed accordingly.

That is, the misfired cylinders are estimated from the ER (k) of each group in four cylinders as described above.

For example, if misfire occurs in the first cylinder, it is estimated that misfire has occurred in the first cylinder from these two groups because the value of ER 1 and the value of ER 3 are different from the ECU set values.

The ignition cycle T is subsequently monitored by the ECU, confirming that it is a misfire cylinder from the ignition cycle T of the first cylinder.

That is, when misfire occurs, the engine rotation speed becomes unstable due to combustion instability, and the signal waveform of the crank angle sensor of FIG. 1 operated according to the engine speed also changes. At this time, since the ignition period T is inversely related to the engine rotation speed, the ignition period T is increased according to combustion instability.

Therefore, the ECU estimates the misfired cylinder from the comparison of the ER values, confirms the ignition period T of the estimated misfired cylinder, and correctly establishes the misfired cylinder.

If a cylinder with a misfire is found, the ECU performs control to prevent engine deterioration. There are three main types of such control, and the first is to stop feedback control according to the theoretical performance ratio.

That is, an oxygen sensor is installed in the exhaust system of the conventional electronically controlled fuel injection device, and from this, the fuel injection amount according to the theoretical performance ratio is adjusted.

Therefore, when misfire occurs, the unburned oxygen is sensed in the exhaust system so that the feedback control for enriching the mixer is performed so that the exhaust gas is further increased.

Therefore, when a misfire is detected in the ECU, the feedback control is stopped to prevent the emission of exhaust gas.

The second is to prevent the injection of fuel to the cylinder by prohibiting the energization of the cylinder shaft injector.

Third, the engine failure signal is sent to the diagnosing terminal and the warning light in the vehicle compartment to facilitate rapid repair.

As described above, according to the present invention, the ECU calculates ER (k) from the period T of each cylinder input from the crank angle sensor, and detects misfire of any cylinder by comparing ΔER _m (k) with a set range. The engine misfire due to the lowering of the ignition capacity is detected by the existing device alone without the device.

Claims (1)

Detecting a cylinder ignition period T of three revolutions of the crankshaft from the crank angle sensor; Calculating a combustion stability coefficient ER (k) from the ignition period T measured for each of the two cylinders in one group; When the average value ER _m (k) is calculated from the measured ER (k) and the difference between the maximum value and the minimum value of the average value ER _m (k) ΔER _m (k) is compared with the normal zone set in the ECU, the engine is out of the normal zone. Detecting the fact that it is true; In the case of detecting the misfire in step 3, the misfire of the gasoline engine in four stages which compares with the ER (k) of the abnormal region, estimates the cylinder in which misfire has occurred, and confirms that the misfire occurrence cylinder is from the estimated ignition period T of the cylinder. Detection method.