JPH0710061Y2 - Cylinder pressure signal abnormality determination device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a device for determining an abnormality in a cylinder pressure signal, and in particular, a device for determining whether an engine misfire or partial combustion has occurred based on the cylinder pressure signal. Regarding

( _Prior Art) Recently, in an area where engine knocking does not occur, ignition is performed so that the crank angle position (Θ _ptax ) where the cylinder pressure becomes maximum comes to a constant position (Θ ₀ ) where the engine generated torque becomes maximum. The timing is controlled (so-called MBT control) (see JP-A-59-39974).

This will be explained with reference to FIG. 9. Reference numeral 1 is an in-cylinder pressure sensor formed in the shape of a washer of an ignition plug, and the in-cylinder pressure sensor 1 converts the in-cylinder pressure into an electric charge by a piezoelectric element, and outputs the sensor output S ₁ from the charge amplifier 2 Output to. The charge amplifier 2 comprises a so-called charge-voltage conversion amplifier, which converts the sensor output S ₁ into a voltage signal S ₂ and outputs it to the sampling circuit 3.

The sampling circuit 3 to which the signals Ref and Pos from the crank angle sensor 4 are also input, has a predetermined crank angle (for example, 2 °).
At each predetermined crank angle section (ATDC 50 ° from compression top dead center)
The voltage signal S ₂ representing the in-cylinder pressure is sampled for up to a certain degree), and the sampling signal S ₃ is output to the in-cylinder pressure maximum crank angle detection circuit 5.

In the detection circuit 5, the sampling signal S ₃ and the crank angle signal
The crank angle position (Θ _pmax ) that maximizes the cylinder pressure is detected based on Ref and Pos.

The theta in an apparatus for performing the MBT ignition timing control as detection information _pmax, theta _pmax so coincides with ₀ fixed position theta after compression top dead center _(e.g. ATDC10 ° ~20 °), both of the deviation (theta _pmax A correction amount (M) is calculated based on −θ ₀ ) and the basic ignition timing is corrected and controlled by the correction amount M.

It should be noted that the crank angle sensor 4 outputs a pulse signal (Re signal that becomes a high level at a predetermined position of each cylinder at every explosion interval (crank angle is 120 ° in a 6-cylinder engine, 180 ° in a 4-cylinder engine).
f) is output, and a pulse signal (Pos) that becomes high level for each unit angle of crank angle (for example, every 1 °)
Is output.

(Problems to be solved by the invention) By the way, in such a device, the sampling interval is from the compression top dead center to a predetermined crank angle position (ATDC about 50 °). The reason for limiting to this section is that if combustion is normally performed, Θ _pmax always exists in this section and should not exist outside this section.

Therefore, if combustion is not performed normally, Θ _pmax may not be accurately detected. For example, if the ignition timing is advanced (or retarded) too much, or if misfire or partial combustion occurs in an operating range where combustion is not normally performed due to a low load, etc., the peak position of the mere compression pressure is Detected as Θ _pmax .

In particular, if the ignition timing is retarded too much and misfire occurs, and if the ignition timing is advanced too far and Θ _pmax is near the compression top dead center, it is assumed that Θ _pmax is near the compression top dead center. Although it is detected, in the former case, although the ignition timing should originally be corrected in advance, the ignition timing is erroneously corrected in the latter case. That is, Θ
It can be said that _pmax is an erroneous detection, but if the combustion of the engine is controlled based on the erroneously detected information, drivability and fuel consumption will be deteriorated.

On the other hand, as an apparatus for determining misfire, there is one described in Japanese Utility Model Application No. 60-181263. However, since this device is configured to determine whether a misfire has occurred based on the magnitude comparison between the peak value of the in-cylinder pressure and the in-cylinder pressure at the compression top dead center position, there is an error in the peak value of the in-cylinder pressure due to noise. If it occurs, it may be erroneously determined, and it is hard to say that the misfire is properly determined.

Further, according to the combustion state detecting device of Japanese Patent Laid-Open No. 61-128133, the period from the ignition timing to Θ _pmax is measured, and when this value is too small compared to the average value up to the previous time, for example, , it is determined to be occurring clogging misfire not due combustion pressure, holds the theta _pmax up to the previous time stored in the memory in place of the currently detected theta _pmax is is configured, theta _pmax compression If it occurs near the top dead center,
It is not determined whether the cause is that the ignition timing is advanced too much or that the ignition timing is retarded too much to cause misfire.

This invention was made by paying attention to such a conventional _problem.The cause of Θ _{pmax in the} vicinity of the compression top dead center is whether the ignition timing is advanced too much, or it is too retarded to cause misfire. It is an object of the present invention to provide a device for determining whether it has occurred by comparing Θ _pmax with the ignition timing set at that time.

(Means for Solving the Problem) This invention, as shown in FIG. 1, is a means 11 for setting an ignition timing, a means 12 for performing ignition in accordance with the set ignition timing (D), and an engine Sensor that detects the crank angle
13, a sensor 14 for detecting the in-cylinder pressure of the engine, a means 15 for sampling the detected value of the in-cylinder pressure sensor 14 at every predetermined crank angle (for example, every 2 °), and data obtained by the sampling means 15. a means 16-cylinder pressure to detect the crank angle position (theta _pmax) having a maximum, the spark-cylinder pressure maximum crank angle position theta _pmax when the cylinder pressure up to a crank angle position theta _pmax is near compression top dead center By comparing the ignition timing D set by the timing setting means 11 with the ignition timing D, there is provided means 17 for determining whether the ignition timing is advanced too much or retarded too much to cause misfire. It was

( _Operation ) Θ _pmax appears near the compression top dead center not only when the ignition timing is advanced too much, but also when the ignition timing is retarded too much and misfire occurs. However, in the former case and the latter case,
The relative positions of _pmax and ignition timing are close to each other in the former case and farther from that in the latter case.

Therefore, when Θ _pmax and the ignition timing are compared in the present invention, the two are clearly distinguished. In other words, even when the combustion pressure is not used, it is possible to avoid making an erroneous determination as if the combustion pressure was generated.

(Embodiment) FIG. 2 is a block diagram of an embodiment in which the present invention is applied to an apparatus which performs so-called MBT control using Θ _pmax as detection information.
The same parts as those in FIG. 9 are designated by the same reference numerals, and the description thereof will be omitted. The sampling section by the sampling circuit 3 is from the compression top dead center to about ATDC 30 °.

In FIG. 2, reference numeral 22 is an ignition timing setting circuit, and this circuit 22
Then, the basic ignition timing (N) is obtained by table lookup or calculation according to the operating state (for example, the engine speed and the intake air flow rate as the engine load), and this N is corrected by the correction amount (M) described later. Then, the final ignition timing D (= N + M) is set. This D is output to the ignition timing storage circuit 23 and saved in the memory.

Further, the ignition signal Sp is output to the ignition means 24 at the timing corresponding to this D. The ignition means 24 is composed of an ignition coil 24A, an ignition plug 24B, etc., and generates a high voltage based on the ignition signal Sp to ignite an air-fuel mixture.

In the determination circuit 25 which inputs Θ _pmax from the detection circuit 5 and the memory value (that is, ignition timing) D ′ of the storage circuit 23, Θ _pmax
Is near the compression top dead center, it is judged whether it is due to the ignition timing being advanced too much or the ignition timing being retarded too much, resulting in misfire. Output to the correction amount calculation circuit 26.

The correction amount calculation circuit 26 detects Θ _pmax and the signal detected this time.
Based on Sh, a correction amount M is calculated so that the next Θ _pmax will come to a constant position (Θ ₀ ) that maximizes the torque generated by the engine, and this is output to the ignition timing setting circuit 22.

Sampling circuit 3 and ignition timing setting circuit 2 shown in FIG.
2, ignition timing storage circuit 23, determination circuit 25, correction amount calculation circuit 26
Can be configured by hardware, but if the control unit 21 including a microcomputer is used, each circuit can realize its function by the program shown below.

Next, the operation of this embodiment will be described with reference to FIGS.

FIG. 3 is a program for sampling the in-cylinder pressure.
It corresponds to the function of the means 15 in the figure. First, the voltage signal (corresponding to the in-cylinder pressure waveform) S ₂ that represents the in-cylinder pressure at P ₁ is A / D converted to
The converted value (represented simply as “A / D value” in the figure, the same in FIG. 4) is saved in the memory. In this case, the sampling section starts from the compression top dead center, and the A / D conversion value of the first in-cylinder pressure is at the compression top dead center position. At P ₂ , A / D every 2 ° in crank angle after compression top dead center
The conversion process is started, and the A / D converted value is saved in the memory in a pair corresponding to the crank angle at that time. Then, this processing is executed every time this routine is executed by a predetermined angle Θ _END.
Repeat until (ATDC30 °). That is, Θ _END defines the end of the sampling interval. As a result, the in-cylinder pressure waveform that changes according to the combustion state is 2 ° in the sampling section.
A / D conversion is performed every time.

FIG. 4 is a program for detecting Θ _pmax, which is the means of FIG.
Equivalent to 16 functions. First, read the A / D conversion value of the in-cylinder pressure at P _11, performs a determination of whether (the same. FIG. 5 represented by "TDC" in the figure) crank angle compression top dead center at the time at P ₁₂ At the compression top dead center, a process of setting the value of the memory (P _max memory) for substituting the maximum value (P _max ) of the in-cylinder pressure at P ₁₃ to zero is performed. It is initialized and passes the compression top dead center process P ₁₃ is not performed. The crank angle is detected, for example, by counting the pulses of the signal Pos after the compression top dead center.

In P ₁₄ the A / D converted value of the current cylinder pressure as compared to the value assigned to P _max memory up to the previous time, when A / D conversion value of the in-cylinder pressure is equal to or greater than the memory value this time at P ₁₅ A / D conversion value of P _max
At the same time as substituting into the memory, the crank angle corresponding to the A / D converted value is substituted into the Θ _pmax memory in P ₁₆ . That is, P
_{In the max} memory, the value is sequentially updated with a larger value, so that P _max is obtained and Θ corresponding to P _max.
The value assigned to the _pmax memory gives Θ _pmax .

On the other hand, it is determined that the in-cylinder pressure past the peak of the combustion is lowered when the A / D conversion value of the cylinder pressure is less than the value of P _max memory in step P _14, to jump P _15, P ₁₆ proceed to the P _17.

Count value of the signal in the P ₁₇ P _os the (CP) compared with a numerical value corresponding to a predetermined angle (ATDC 30 °) mentioned above (e.g. 30),
CP is the case that number is 30 or less and ends the current routine and instructs the continuation of the loading process of the A / D conversion value of the cylinder pressure at P _18. And when CP exceeds that number 30, ATD is given on page ₁₉ .
The end of this program (that is, masking) is instructed by interrupting the crank angle of C30 °, and the program shifts to a program for comparing the next ignition timing with Θ _pmax .

Figure 5 shows a program that compares the ignition timing with Θ _pmax .
It corresponds to the function of the means 17 in FIG. At P ₃₁ , it is determined whether Θ _pmax is near the compression top dead center. This is because the _{pmax Θ} too advancing the ignition timing comes to the outside, the compression on the near dead center is also Θ _pmax in the case that caused the misfire too retarded if you came to the vicinity of compression top dead center . In the latter case, Θ _pmax should not be near the compression top dead center unless there is a misfire.
In other words, since it is not based on the combustion pressure, it is an erroneous determination in the latter case that the advance angle is too large. Therefore, when Θ _pmax exists near the compression top dead center, it is necessary to proceed to P ₃₄ to discriminate the two and prevent an erroneous judgment.

Incidentally, whether the determination flag performs exception handling P ₃₂ (IF
Setting 0) (setting IFO = 1) is necessary for ignition timing control, which will be described later, and therefore IF0 = 1 is instructed to perform exceptional processing. On the contrary, IF0 = 0 is a normal MBT
It is telling the control, so that when _pmax theta at P ₃₁ is not in the vicinity of compression top dead center is (a IF0 = 0) Reset the determination flag IF0 at P _33.

Here, paying attention to the combustion waveform of the in-cylinder pressure (that is, the output waveform of the in-cylinder pressure sensor), when the ignition timing is retarded too much and a misfire occurs, the peak of the in-cylinder pressure is overcompressed as shown in FIG. It appears in the vicinity of the dead center, so that Θ _pmax and the ignition timing D set at that time (or the ignition timing D ′ stored in the memory) are close to each other. On the other hand, if the ignition timing is advanced too much, as shown in FIG. 7, the peak of the in-cylinder pressure appears near the compression top dead center. In this case, Θ _pmax and the ignition timing D are misfired. Farther than if you did.

Therefore, prepare a margin amount (A) determined in advance from the combustion speed of the engine, etc., and compare Θ _pmax with D ′ + A at P ₃₄ , and if Θ _pmax does not exceed D ′ + A, retard too much. it is determined that a misfire has occurred Te, determination flag P ₃₆ (IF
1) is reset and the routine ends. Vice versa
_pmax is the case is D '+ A above, it determined to be too in advance sets a determination flag IF1 at P _35. here,
IF1 = 0 means that the ignition is retarded too much and misfire has occurred, and IF1 = 1 means that the ignition is advanced too much, and the value of IF1 distinguishes the two. That is, even when the combustion pressure is not used, it is not necessary to make an erroneous determination as if the combustion pressure was generated. In other words, the information when Θ _pmax is the detection information is accurate, and the Θ _pmax detection accuracy is improved.

FIG. 8 is a program for calculating the ignition timing correction amount using the determination flags (IF0 and IF1) introduced in FIG. First, when in the P ₄₁ IF0 = 0 performs normal MBT control in P _42.
That, theta to come as a constant position detecting next theta _pmax based on information to maximize the torque generated by the engine of _{pmax (Θ 0),} to calculate the feedback amount using the deviation and the feedback constants, it Substitute in M memory and end the routine. That is, the value of the M memory gives the MBT correction amount (M). In a program (not shown), the final ignition timing D (= N + M) is set by correcting the basic ignition timing N with this M.

On the other hand, proceeding as in the case with P ₄₁ of IF0 = 1 is the case of performing exception processing. Since when in P ₄₃ of IF1 = 1 is too in advance, retard amount determined in advance in the M memory P ₄₄ (KRTD)
Is substituted. As a result, combustion is delayed in the cylinder that has advanced too much, and the peak of the combustion pressure shifts beyond the compression top dead center. Since when in P ₄₃ of IF1 = 0 with each other to misfire too retarded contrast substituted advance amount determined in advance in the M memory P ₄₅ a (KADV). As a result, combustion starts earlier in the misfiring cylinder, and quick recovery from misfiring is achieved.

That is, according to the conventional example, even if the ignition timing is retarded too much and the engine misfires, the ignition timing is advanced too much and Θ _pmax is treated in the same way as when it reaches compression top dead center, so MBT control is performed. Then, it was further retarded, and the combustion state was sometimes made worse, but according to this example,
Depending on the value of the judgment flag, the case where the _engine misfires due to excessive retardation is clearly distinguished from the case where Θ _pmax reaches the compression top dead center due to excessive advancement, so appropriate processing for misfire is possible,
The drivability and fuel efficiency are improved.

(Effect of the Invention) This invention compares the maximum crank angle position in the cylinder pressure with the ignition timing set by the ignition timing setting means when the maximum crank angle position in the cylinder pressure is near the compression top dead center.
Or too the advance of the ignition timing, or is provided with the means for determining whether the occurring misfire Plenty of retarded until when misfire too retarded, too advanced theta _pmax Is not confused with the case where the compression top dead center is reached, and not only can the detection accuracy of the cylinder pressure maximum crank angle position be improved, but if this is used as the detection information and MBT control is performed, the Appropriate processing is performed to improve drivability and fuel efficiency

[Brief description of drawings]

1 is a block diagram of the present invention, FIG. 2 is a block diagram of an embodiment in which the present invention is applied to MBT control of ignition timing, and FIGS. 3 to 5 and 8 are FIG. 6 and 7 are flow charts for explaining a control operation when a device similar to that of the above embodiment is realized by a microcomputer, respectively. _In- cylinder pressure waveform diagram when _pmax is near the compression top dead center,
FIG. 9 is a block diagram of a conventional example. DESCRIPTION OF SYMBOLS 1 ... In-cylinder pressure sensor, 2 ... Charge amplifier, 3 ... Sampling circuit, 4 ... Crank angle sensor, 5 ... In-cylinder pressure maximum crank angle detection circuit, 11 ... Ignition timing setting means, 12 ... Ignition means, 13 ... Crank angle sensor, 14 ... In-cylinder pressure sensor, 15 ... Sampling means, 16 ... In-cylinder pressure maximum crank angle detection means,
17 ... Judgment means, 21 ... Control unit, 22 ... Ignition timing setting circuit, 23 ... Ignition timing storage circuit, 24 ... Ignition device, 25
... Judgment circuit, 26 ... Correction amount calculation circuit.

Claims (1)

[Scope of utility model registration request] 1. A means for setting an ignition timing, a means for performing ignition in accordance with the set ignition timing, a sensor for detecting a crank angle of an engine, a sensor for detecting an in-cylinder pressure of an engine, and an in-cylinder pressure of the in-cylinder pressure. A means for sampling the detection value of the sensor for each predetermined crank angle, a means for detecting a crank angle position where the cylinder pressure is maximum from the data obtained by the sampling means, and a cylinder pressure maximum crank angle position for the compression top dead center. When the maximum crank angle position in the cylinder pressure is compared with the ignition timing set by the ignition timing setting means in the vicinity of the point, the ignition timing is advanced too much or is retarded too much, resulting in misfire. An in-cylinder pressure signal abnormality determination device is provided with a means for determining whether or not