JP3346138B2 - Misfire detection device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a technique for detecting the presence or absence of a misfire in an internal combustion engine by using a misfire parameter calculated based on the operating state of the engine.

[0002]

2. Description of the Related Art As a conventional misfire diagnosis device for an internal combustion engine,
Reference signals generated at every crank angle [720 ° / n (n is the number of cylinders) in a four-cycle engine] corresponding to the stroke phase difference of each cylinder are continuously measured, and the cycle (rotational speed) for each generation of the reference signal is measured. (Reciprocal number), a misfire parameter corresponding to the fluctuation state of the cycle, that is, the fluctuation rate of the engine rotation is calculated, and the presence or absence is determined based on the misfire parameter.
(See Japanese Utility Model Laid-Open No. 5-17172).

[0003]

By the way, when a misfire occurs, the larger the torque of the engine (in a non-misfire state) as a base at that time, the larger the torque drop due to the misfire occurs. As shown, the rotational fluctuation rate increases in proportion to the base torque, and the value of the misfire parameter increases accordingly.

Here, the misfire is determined by comparing the calculated misfire parameter with a reference value set for each of a plurality of areas divided by the engine speed and the engine torque. Since it is determined that there is a misfire when the center deviates from within a predetermined range, the reference value is set in proportion to the engine torque. For this reason, if there is a request to perform misfire detection over a wide operating range as in recent years, the number of bits representing misfire parameters and reference values is insufficient, and it is necessary to set reference values in detail according to torque changes. It has occurred that the number of areas for storing the reference value increases and the storage area of the memory increases.

The present invention has been made in view of such a conventional problem. By setting the misfire parameter in consideration of the engine torque, it is possible to greatly reduce the change width of the reference value for determination. Accordingly, it is possible to provide a misfire detection device for an internal combustion engine that can reduce the number of bits representing a misfire parameter and a reference value, and can greatly save a storage area of a memory that stores a reference value. Aim.

It is another object of the present invention to improve the accuracy of the misfire determination.

[0007]

Therefore, according to the present invention, as shown in FIG. 1, a misfire of an internal combustion engine for detecting the presence or absence of a misfire based on a misfire parameter calculated based on an operation state of the engine is provided. in the detection device, a basic value that is calculated based on the engine rotational variation, a torque equivalent value of the engine Rights
A misfire parameter calculating means for calculating a misfire parameter by dividing by a smoothed value; and a misfire determination means for comparing the calculated misfire parameter with a reference value for judgment to determine the presence or absence of a misfire. It is characterized by comprising.

For example, a reference signal generated every crank angle 720 ° / n (n is the number of cylinders) corresponding to a stroke phase difference of a cylinder is continuously measured, and a cycle (reciprocal of the rotational speed) for each generation of the reference signal is measured.
The basic value of the misfire parameter is calculated on the basis of the above, and the basic value is divided by the value obtained by smoothing the value corresponding to the engine torque to set the misfire parameter. On the other hand, a reference value is set for each area divided by the engine speed and the engine torque, a reference value corresponding to the current area is selected, and the calculated misfire parameter is compared with the reference value. To determine if there is a misfire.

Further, the invention according to claim 2 is characterized in that a basic fuel injection amount of the engine is used as the engine torque equivalent value .

The invention according to claim 3 is characterized in that the engine torque equivalent value is smoothed by a weighted averaging process between a latest value and a past value, so that the weighted average processing is performed during a transient operation of the engine as compared with a steady operation. It is characterized in that the weight of the latest value in the averaging process is set large.

Since the amount of change in the engine torque is large during the transient operation of the engine, the weight of the latest value of the weighted averaging process is increased and the smoothed engine torque value is used.
Misfire determination can be made well even during transition.

[0012]

According Effects of the Invention to the invention according to claim 1, the basic value based misfire parameter on the engine speed change rate, the engine torque
By correcting the equivalent value by dividing it by the smoothed value ,
As a result, the range of change of the misfire parameter and the reference value for determination in the entire operation region is greatly reduced, so that the number of bits representing these can be reduced, and the number of set reference values for each operation region can be significantly reduced, and the memory Storage area can be saved.

According to the second aspect of the present invention, the basic fuel injection amount is set to a value faithfully reflecting the engine torque. Therefore, by using the basic fuel injection amount as the engine torque equivalent value, Normalization of the misfire parameter by the engine torque is performed well .

According to the third aspect of the present invention, by using the engine torque equivalent value smoothed by increasing the weight of the latest value of the weighted averaging process, misfire determination can be performed well even during a transition.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. 2 and subsequent figures showing one embodiment, the internal combustion engine 1 is a four-cylinder engine, and the ignition order is {1 → ♯}.
3 → ３4 → ♯2. The control unit 10 incorporates a microcomputer, performs arithmetic processing based on signals from various sensors, and operates the fuel injection valve 2 and the ignition coil 3 provided for each cylinder (# 1 to # 4) of the engine. Control.

The various sensors include a crank angle sensor 11, an air flow meter 12, a throttle sensor 13, and the like. The crank angle sensor 11 detects the crank angle.
A reference signal at every 180 ° and a unit signal at every unit crank angle (1 to 2 °) are output, whereby the crank angle can be detected and the engine speed N can be detected. The reference signal includes a cylinder discrimination signal. For example, the pulse width of the reference signal corresponding to the # 1 cylinder is increased to make it possible to discriminate the cylinder.

The air flow meter 12 is, for example, a hot wire type,
The intake air flow rate Q can be detected. Throttle sensor 13
Detects the opening of the throttle valve. Here, the control unit 10 determines the basic fuel injection amount _TP = k · Q / N (k) based on the intake air flow rate Q and the engine speed N.
It calculates a constant), which in the final fuel injection quantity is subjected to various corrections _{T I = T P · COEF (} COEF defines a various correction coefficients), a drive pulse signal having a pulse width corresponding to this T _I The fuel is output to the fuel injection valves 2 of the respective cylinders at a predetermined timing synchronized with the engine rotation to perform the fuel injection.

Further, the control unit 10 has established an ignition timing based on the engine rotational speed N and the basic fuel injection quantity T _P, to perform ignition by controlling the operation of the ignition coil 3 at that timing. Also, separately from the crank angle sensor 11, a ring gear 14 connected to a crankshaft end of the engine 1 is provided.
A pickup 15 for generating a signal each time a tooth of the ring gear 14 passes near the outer periphery of the pickup;
The signal from 15 is input to the control unit 10.

A routine for detecting and diagnosing misfire by the control unit 10 will be described below with reference to flowcharts shown in FIGS. In step 1, it is determined whether or not a signal generated every time the pickup 15 passes through the teeth of the ring gear 14 is generated. When the signal is generated, the process proceeds to step 2 to count up by a counter for measuring the number of teeth. I do.

In step 3, a timer measures the time required each time the number of passing teeth reaches a value corresponding to a predetermined crank angle, which will be described later. In step 4, it is determined whether or not the count value of the counter has reached the crank angle [720 ° / 4 = 180 °] corresponding to the stroke phase difference between the cylinders. The time taken for the rotation of 180 ° crank angle by reading the measured value of
INT1 is stored, and TINT1 to TINT7 for the past seven times including the latest value are left.

In step 6, the engine 1 resets the values of the tooth count counter and the timer, and counts a value corresponding to the total number of misfire determinations in which a misfire determination is performed as described later. Each time the engine rotates, the cumulative number of revolutions n is counted by an engine revolution counter. In step 7, the basic fuel injection amount T _PAV smoothed by performing the weighted averaging process is read as an engine torque equivalent value by another routine.

In step 8, a misfire parameter MISA is calculated by the following equation. MISA = [3 × (TINT6-TINT7) + (TI
In NT6-TINT3)] / [TINT7 3 × T PAV] Step 9, the reference value for misfire determination corresponding to operation region that is determined by the current engine speed Ne and load, read from the map.

In step 10, it is determined whether or not the value of the misfire parameter MISA calculated in step 8 belongs to a predetermined range centered on the reference value set by the following equation. Reference value × 0.75 ≦ MISA ≦ reference value × 1.25 If it is determined that the value of MISA falls within the predetermined range, the process proceeds to step 11, where it is determined that there is a misfire, and the corresponding cylinder for which misfire is to be determined. Count up the value of the misfire counter. The determination of the cylinder to be subjected to the misfire determination is performed based on the cylinder determination signal from the crank angle sensor 11.

In step 12 and subsequent steps, misfire detection of a plurality of cylinders is performed. First, in step 12, it is the same as step 10, except that the misfire parameter MISA belongs to a predetermined judgment level range that is set to be wider than the range of the single cylinder misfire judgment and set by the following equation. Is determined. Reference value × 0.60 ≦ MISA ≦ Reference value × 1.40 When it is determined that the value of the MISA falls within the range of the determination level, it is determined that the cylinder has misfired, and the routine proceeds to step 13 and proceeds to step 13 above. The misfire determination histories for the past one or more times for all cylinders determined in this way are stored in the memory.

Then, the routine proceeds to step 14, in which the number of times of misfire determination in the misfire determination history is equal to or more than a predetermined value (for example, two or more out of four times each for all four cylinders or eight times in total). It is determined whether or not there is any. If it is determined that there is, the process proceeds to step 15, and a multi-cylinder misfire counter for counting the number of misfires of a plurality of cylinders is counted up.

[0026] In step 16, it is determined whether the accumulated number of rotations n of the engine 1 is the total misfire determination count equivalent value measured in the step 2 reaches or exceeds a predetermined value n _0. If it is determined in step 16 that the cumulative number of revolutions n of the engine 1 has reached the predetermined value n ₀ , the process proceeds to step 17, and the total number of misfires m determined to have a misfire during the total number of misfires is determined by: The count value of the cylinder-by-cylinder misfire counter of each cylinder and the count value of the multiple cylinder misfire counter are summed and determined.

[0027] In step 18, the total misfire count m is equal to or a predetermined value m ₀ or more. When it is determined that m ≧ m _0, it is diagnosed that a misfire has occurred in a single cylinder or a plurality of cylinders, and the routine proceeds to step 19. In step 19, among the count values of the respective cylinder counter, only the count value for each one cylinder counter is equal to or a predetermined value m ₁ or more.

If the condition of step 19 is satisfied, the diagnosis is made that a single predetermined cylinder is misfired, and the routine proceeds to step 20, where the predetermined single cylinder is misfired. Otherwise, it is diagnosed that a plurality of cylinders have misfired, and the routine proceeds to step 21, where the NG code of the plurality of cylinders misfires is stored. The diagnostic result corresponding to the NG code finally left in this way is M
The service engineer repairs the misfiring cylinder by referring to the display.

Here, the misfire parameter MISA is:
Basic value based on rotation fluctuation rate (value before dividing by T _PAV )
_Is divided by T _PAV which is an engine torque equivalent value. As described above, since the rotational fluctuation rate increases in proportion to the engine torque, the misfire parameter obtained by dividing the basic value based on the rotational fluctuation rate by the engine torque equivalent value is the engine torque equivalent value. When compared with a basic value that is not divided by, the range of change over the entire operating range of the engine can be greatly reduced.

As a result, the number of bits representing the misfire parameter and the reference value for misfire determination can be reduced, and the number of reference values set in the entire operation area can be greatly reduced, so that the storage area of the memory can be saved. . Next, a routine for smoothing the basic fuel injection quantity T _P, will be described with reference to the flowchart of FIG. This routine is executed every predetermined time (for example, every 10 ms).

In step 31, the intake air flow rate Q detected by the air flow meter is input. In step 32, the engine speed Ne is calculated based on the value detected by the crank angle sensor 11. In step 33, the basic fuel injection amount _TP is calculated in proportion to the cylinder intake air amount by the following equation.

T _P = K · Q / Ne (K is a constant) In step 34, the engine is in a transient operation state depending on whether the change rate ΔTVO of the throttle valve opening detected by the throttle sensor 13 is equal to or greater than a predetermined value. It is determined whether or not there is. Then, when it is determined that the transient operation state, the weighting X to be used in the weighted average processing to be described later proceed to step 35, and X = X _1, if it is determined not to be a transient operating state, to a step 26 Go ahead and set X = X ₂ (X _1,
X ₂ both small positive number from 1). Here, X ₁ > X ₂ is set so that the weight of the latest value becomes larger during the transient operation.

[0033] At step 35, it calculates the weighted average value T _PAV basic fuel injection quantity T _P by the following equation. _{T PAV = X · T P +} (1-X) T PAV (old) [T PAV (old)
The previous value of T _PAV] Thus, using the basic fuel injection quantity T _P representing the engine torque accurately as engine torque corresponding value used to calculate the misfire parameters and the basic fuel injection quantity T _P misfire The misfire determination accuracy can be improved by using a smoothed value that sometimes fluctuates with the fluctuation of the engine speed. Further, in the transient operation, by setting the weight of the latest value of the weighted average to be larger than that in the steady operation with emphasis on responsiveness, the misfire determination accuracy in the transient operation is also guaranteed.

In the present embodiment, TINT is measured by counting the number of teeth of the ring gear. However, the period of the reference signal from the crank angle sensor may be measured as TINT.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a diagram showing a system configuration according to an embodiment of the present invention.

FIG. 3 is a flowchart showing a first stage of a misfire detection and diagnosis routine according to the embodiment;

FIG. 4 is a flowchart showing a middle stage of the routine.

FIG. 5 is a flowchart showing a latter part of the routine.

FIG. 6 is a flowchart of a routine for calculating an engine torque equivalent value used for misfire detection.

FIG. 7 is a diagram showing a relationship between an engine torque and an engine rotation fluctuation rate.

[Explanation of symbols]

 1 Internal combustion engine 10 Control unit 14 Ring gear 15 Pickup

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-228128 (JP, A) JP-A-6-42398 (JP, A) JP-A-4-1322862 (JP, A) JP-A-5-228 17172 (JP, A) JP-A-8-109848 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/00-45/00 G01M 15/00

Claims (3)

(57) [Claims] A misfire detection device for an internal combustion engine that detects the presence or absence of a misfire based on a misfire parameter calculated based on an operation state of the engine, wherein a basic value calculated based on an engine rotation fluctuation rate is equivalent to an engine torque. A misfire parameter calculation unit that calculates a misfire parameter by dividing the value by a value obtained by smoothing the value , and a misfire determination unit that compares the calculated misfire parameter with a reference value for determination to determine whether there is a misfire. A misfire detection device for an internal combustion engine, comprising: 2. The misfire detection device for an internal combustion engine according to claim 1, wherein a basic fuel injection amount of the engine is used as the engine torque equivalent value. 3. The engine torque equivalent value is smoothed by a weighted averaging process between the latest value and a past value, and the weight of the latest value in the weighted averaging process is determined during transient operation of the engine as compared with during steady operation. Characteristically set to be large
The misfire detection device for an internal combustion engine according to claim 1 or 2 .