JPH05550B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an ignition timing control method for an internal combustion engine.
More specifically, it is an ignition timing control for an internal combustion engine that corrects ignition timing by detecting fluctuations in internal combustion engine cylinder pressure and detects transient conditions of engine operation to improve transient response. Regarding the method.
Note that in this specification, the term "transient state" is used to mean acceleration or deceleration of engine operation.

(Prior art) In conventional transient control of an internal combustion engine, the ignition timing main control value is determined based on the engine speed and load condition, and is also determined based on engine cooling water temperature, throttle valve opening, manifold negative pressure, etc. The main control value was corrected by detecting the transient state of engine operation. One example is the technique described in Japanese Patent Publication No. 58-40027.

Furthermore, an example has recently been proposed in which the cylinder pressure of an internal combustion engine is detected and the ignition timing is controlled so that the maximum pressure angle is located at the target angle, and the transient state is detected from the engine cooling water temperature, etc., as in the past. One example of this is the technique described in Japanese Patent Publication No. 56-21913.

(Problems to be Solved by the Invention) However, in the first conventional example, a large number of detection means and their processing circuits are required in order to detect a transient state, which has the disadvantage of complicating the device configuration. Ta. Furthermore, when detecting a transient state, the detection accuracy is not sufficient because it is detected indirectly through changes in engine cooling water temperature, etc., and since it is not feedback control, we cannot expect much of a correction effect. It was hot. Therefore, the main control values had to be precisely determined, and corrections were only used as a side effect, which inevitably led to an increase in the main control value map and the need for large-capacity memory to store it. The disadvantage was that it was necessary to prepare for Furthermore, since the detection of transient states was indirect, it was difficult to say that the transient response was sufficient, and it was difficult to say that sufficient consideration was given to drivability.

Further, the second prior art example does not suffer from the same disadvantage in that a large number of detection means and their processing circuits are required to detect a transient state. In addition, feedback control is used, which directly detects the combustion state of the engine, determines the deviation between the target angle and the actual maximum pressure angle, and determines control values to eliminate the deviation.
There was no suggestion as to how to eliminate the deviation, especially in a transient state, without impairing drivability.
Furthermore, no countermeasures were provided for knocking, which tends to occur frequently during transient conditions. In addition, as described in JP-A No. 57-28842, a technology has been proposed that detects the combustion state from changes in light intensity and determines the maximum pressure angle and transient state. A fatal drawback was that the changes were similar to, but not equivalent to, changes in combustion pressure.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks of the conventional example, to directly detect the combustion state of the engine by detecting the internal cylinder pressure of the engine, and to feedback control the ignition timing, and in particular to control the pressure fluctuation. By measuring and detecting the transient state of engine operation only, the maximum pressure angle target value is retarded in stages, improving transient response and drivability, and
Ignition timing control for an internal combustion engine that prevents knocking, allows more accurate detection of transient states by detecting from the combustion state, and reduces the number of detection means and processing circuits. The purpose is to provide a method.

Furthermore, by directly detecting the combustion state and converging the maximum pressure angle θpmax to the target value, it is possible to achieve ignition closer to the so-called MBT, thereby improving output.
It is an object of the present invention to provide an ignition timing control method for an internal combustion engine that enables control to avoid knocking that often occurs when ignition near BT occurs.

(Means and operations for solving the problems) In order to achieve the above object, the present invention detects the pressure inside the cylinders of a multi-cylinder internal combustion engine and positions the maximum pressure angle at the target value, as shown in FIG. In the ignition timing control method for an internal combustion engine, which controls the ignition timing so as to
Calculate the rate of pressure increase before and after ignition in one cylinder and find the ratio between the two (step 10), then find a similar ratio for the same or another cylinder (step 10).
12) Next, find the fluctuation rate of those ratios, and if the fluctuation rate exceeds a predetermined range, it is determined that the engine operation is in a transient state, and the maximum pressure angle target value is retarded by a predetermined amount from the steady operating state. At the same time, the ignition timing of the cylinder to be ignited next time is retarded by an amount smaller than the predetermined amount (steps 14 and 16).

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. For convenience, an apparatus for implementing the method according to the present invention will be explained with reference to the block diagram of FIG. 2 and the waveform diagram of FIG. 3.

In FIG. 2, reference numeral 20 indicates an internal combustion engine;
In the case of the embodiment, four cylinders are provided. A piezoelectric sensor 22 for detecting the cylinder pressure is disposed in each cylinder at a position facing the combustion chamber. The sensor output is input to a low pass filter 24 via a charge-to-voltage converter or high impedance circuit (both not shown). The cutoff frequency of the filter is set higher than the knocking frequency component, so that high frequencies during knocking can also be detected. A multiplexer 26 is connected to the next stage of the low-pass filter 24, and the multiplexer is connected to a control unit 42, which will be described later.
The command causes the filter output to be selectively input to the next stage in the order of cylinder explosion. A peak hold circuit 28 is connected to the next stage of the multiplexer to peak hold the output and output it as shown in FIG. The next stage of the peak hold circuit 28 is an A/D
A conversion circuit 30 is connected. The conversion circuit inputs the output from the peak hold circuit, converts it into digital data every predetermined unit time or angle, and the maximum value of the data indicates the maximum pressure value Pmax. Alternatively, at a predetermined crank angle before peak hold reset, convert the digital value to the maximum pressure value.
It may also be set as Pmax (Figure 3).

Further, the next stage of the peak hold circuit 28 includes an A/
A comparison circuit 32 is connected in parallel with the D conversion circuit 30, and a pulse down edge detection circuit 34 is further connected at the subsequent stage. The comparator circuit 32 has an inverting input terminal to which the peak hold circuit output is input, and a non-inverting input terminal to which the multiplexer output is directly input, giving a slight difference between the input values of the two. The configuration is such that a pulse signal is output at the position where the maximum pressure value occurs from
figure). As shown in Figure 3, the pulse is, in principle, one pulse at the maximum value generation position when knocking does not occur (a in the same figure), and when knocking occurs and high frequency components are superimposed, is configured to output a pulse not only at this position but also every time the sensor (multiplexer) output exceeds the peak hold output, and as a result, a plurality of pulses are output (see figure b). Further, the pulse down edge detection circuit 34 detects the falling edge timing of the output pulse of the comparator circuit and outputs a pulse of a predetermined time width so that it can be easily processed by a circuit to be described later. Therefore, by measuring the time from the reference position, for example, the TDC position, to the pulse generation position and converting the measured value Tpmax into an angle, the maximum pressure angle θpmax can be calculated, and by counting the number of generated pulses, the knocking can be calculated. The presence or absence of occurrence can be detected. Note that, as shown in c in the figure, if the sensor fails, no pulse is generated even after the time measurement is completed.

A crank angle sensor 36 is provided near the rotating part of the internal combustion engine 20, and detects a predetermined crank angle, for example, every 720 degrees when the explosion of four cylinders goes around in the order of the first, third, fourth, and second cylinders. Cylinder discrimination signal, also 180
The TDC signal at the TDC position of each cylinder every time,
Furthermore, an angle measurement signal is output for each predetermined angle obtained by subdividing the TDC signal. Therefore, by counting the TDC signal after the cylinder discrimination signal is generated, the cylinder can be discriminated. Incidentally, the engine rotation speed can also be calculated from the angle measurement signal.

Note that the cylinder discrimination signal may be configured to obtain a required detection signal based on a predetermined amplitude value obtained from a pressure sensor.

Further, the internal combustion engine 20 is provided with a load sensor 38 at an appropriate position between the throttle valve 40 of the internal combustion engine and an intake manifold (not shown) as a sensor for detecting the load state of the engine. This sensor can be used together with the crank angle sensor to detect the operating state of the engine and serve as a backup when the pressure sensor is abnormal, and can also be used for basic ignition timing calculation as described later if desired.

The sensor groups 36 and 38, the A/D conversion circuit 30
A control unit 42 is connected to the next stage of the pulse down edge detection circuit 34, and its outputs are inputted thereto. In an embodiment, the control unit comprises:
It consists of a microcomputer consisting of an input/output interface 42a, a CPU 42b, a memory 42c and a clock 42d. In addition, the CPU has
The pulse counter includes a timer counter that counts the pulses of the clock 42d to measure time, a cycle counter that counts ignition cycles for knocking control, and an advance angle counter that counts the number of ignitions after the knocking ends (Fig. (not shown). The next stage of the control unit is an ignition device 44.
is connected, and in response to its output, the air-fuel mixture in the engine combustion chamber is ignited via a spark plug (not shown). Further, in response to the reset operation of the peak hold circuit 28 and the input of the crank angle sensor 36, the cylinder state is identified and the multiplexer 26 is instructed to select a gate.

Next, an embodiment of the control method according to the present invention will be described with reference to the waveform diagram in FIG. 3 and the flow charts in FIGS. 4 and 5.

First, in step 50, the pressure sensor output is
Start capturing from a predetermined BTDC angle, for example 150 degrees.

Next, in step 52, the cylinder is determined,
A cylinder is specified by adding a cylinder address C/A=n. This is performed by the arrival of the cylinder discrimination signal and TDC signal of the above-mentioned crank angle sensor signal. This is because this control is characterized by being performed for each cylinder.

Simultaneously with the arrival of the TDC signal, the timer counter (TC) and pulse counter (PC) are started in step 54, and time measurement and pulse counting shown in FIG. 3 are started.

Next, in step 56, the ATDC predetermined angle,
For example, after 30 degrees have elapsed, refer to the counts of both counters. As shown in Figure 3, even though the timer counter has completed time measurement well beyond the maximum pressure value generation position, if the pulse counter value is "0" and no pulse is generated, the pressure It can be determined that the sensor is abnormal (Fig. 3c).

If not, it is determined in step 58 whether or not the pulse counter value exceeds a predetermined value, and whether or not knocking has occurred. The predetermined value is normally set to "1", but may be set to a value of "2" or more in consideration of the possibility that a plurality of pulses may be generated even during normal combustion due to noise or the like.

If the pulse count value is smaller than a predetermined value, it is determined that knocking does not occur, and the maximum pressure angle θpmax is determined in step 60. This can be done by multiplying the elapsed time Tpmax to the position where the maximum pressure value occurs by the converted value. The conversion value is ((rotation speed rpm x 360
degree)/60 seconds).

Subsequently, in step 62, the explosion compression ratio ΔP _EXP / _COM is calculated, which is shown in FIG. 5 as a subroutine. This subroutine will be explained below with reference to FIG. First, to briefly explain, as shown in Fig. 6, the pressure value p1 at an arbitrary point before ignition, the pressure value p2 at a point a minute angle section θ1 away from there, and the pressure value at an arbitrary point after ignition. The pressure value p3 and the pressure value p4 at a point distant from it in a small angle section θ2 are measured, and the pressure increase rate is determined respectively, and then the ratio between the two is calculated. Subsequently, a similar ratio is calculated for another (or the same) ignition cylinder, and the fluctuation rate of the two ratios is calculated. When the rate of variation is not within the "1±predetermined dead band region", it is determined that a transient state exists, and the angle is retarded. That is, the inventor discovered a causal relationship between the above fluctuation rate and the transient state of engine operation, and accomplished the present invention. To explain below, first, in step 62, odor pressure values p1-p4 are read out and measured.

Next, in step 62b, the compression pressure change rate ΔP _COMP , which is the pressure increase rate before ignition, that is, in the compressed state, is determined.
The explosion pressure change rate ΔPEXP, which is the pressure increase rate in the explosive state after ignition, and the ratio of the two, P _EXP / _COMP , are calculated as follows.

∆P _COMP = d (P2 - P1) / dθ1 ∆P _EXP = d (P4 - P3) / dθ2 ∆P _EXP / _COMP = ∆PEXP / ∆PCOMP Note that the point before the formation is the same as the piston rises after the suction bubble is fully closed. Any point during compression may be selected. Further, even after ignition, it may be anywhere within the range between the TDC position and the maximum pressure angle θpmax.
However, the TDC position and maximum angle θpmax are respectively TDC
It is convenient to select these points because the signal and the pressure maximum occurrence position signal (pulse) are obtained. It goes without saying that once the point before ignition is selected, the point is searched for using the crank angle sensor output. This control is performed for each cylinder, so
The calculated value is specified as P _EXP / _COMP n and stored. This operation is performed one after another for each ignition cylinder, and the same type of ratio is calculated and stored.

Subsequently, in step 62c, the calculated values of another explosion cylinder before one ignition and the same cylinder before four ignitions, that is, in the previous cycle, are read out. Note that initial settings are made as appropriate for the first time.

Subsequently, in step 62d, the rate of variation with respect to the ratio of the current cylinder is determined. Note that the rate of change with respect to the ratio before one ignition is P _EXP / _COMP A, and the rate of change with the ratio before four ignitions is P _EXP / _COMP B.

P _EXP / _COMP A=P _EXP / _COMP n/ _EXP / _COMP n-1 P _EXP / _COMP B=P _EXP / _COMP n/P _EXP / _COMP n-4 Next, in step 62e, the fluctuation rate P _EXP / _C
It is determined whether _OMP A is larger than "1 + predetermined dead band area", and if it is larger, other fluctuation rates P _EXP / _COMPB are also set to "1 + predetermined dead band area" in step 62f.
Determine whether it is larger. The dead zone is
Set as appropriate, such as “0.1”. If it is determined to be large in step 62f, it can be determined that the fluctuation rate between the cylinders is relatively large and that the engine operation is in a transient state.In order to avoid knocking and deterioration of the exhaust gas composition, the engine should be retarded. to correct. In this way, when looking at fluctuations between cylinders, we compare not only the cylinder before the first ignition, but also the cylinder before the fourth ignition, and only when they are in the same phase do we judge it to be a transient state, so we cannot detect transient fluctuations. There will be no false positives.
Furthermore, by considering the rate of change before and after ignition, errors in judgment are less likely to occur even if the engine speed changes suddenly.

If it is determined that the condition is transient, continue with the step
At 62g, the maximum pressure angle target value θpo is set to the first predetermined angle retard side to prepare for knocking etc. as described above. Therefore, the first predetermined angle is appropriately determined to an extent that prevents knocking and the like.

Subsequently, in step 62h, the correction amount θt for the cylinder to be ignited next time is set to the retard side by a second predetermined angle. This second predetermined angle is also set as appropriate, but as a feature of the present invention, the second predetermined angle is
The value is less than the first predetermined angle. Therefore, if the ignition correction angle θt is larger than the first predetermined angle in step 62l, it is set to the first predetermined angle (step 62m). That is, as will be described later, in the present invention, when a transient state is detected, it is necessary to perform correction to eliminate the deviation that occurs as a result of changing the target angle to the retarded side. If the ignition timing is corrected at once, drivability will deteriorate due to sudden changes in ignition timing, so to prevent this, partial correction is made in the next ignition cylinder, and the transient state is detected in the next ignition cylinder as well. Therefore, partial correction is applied to the next ignition cylinder in the same way, and partial correction is applied one after another in this way, so that the same cylinder after 4 ignitions can finally almost match the target angle. It is. Therefore, the second predetermined angle is appropriately set to a value such that the target angle is reached after four ignitions. Note that in the flow chart, "-" means a retarded angle, and "+" means an advanced angle.

If the answer in step 62e is negative,
In step 62i, it is determined whether _PEXP / _COMP A is smaller than "1-predetermined dead zone area", and if it is smaller, in step 62j, another fluctuation rate P _EXP / _COMB is determined.
Determine whether or not is smaller than “1-dead zone area”,
If it is small, it means that the fluctuation rate is relatively large, so the retarding angle is corrected in the same way.

If the results of steps 62f, 62i, and 62j are negative, the maximum pressure angle target value θpo is set to the initial setting value (62p) assuming that the fluctuation rate is small, and there is no retardation correction value for the ignition correction angle θt. If there is a predetermined retard correction value, the ignition angle is gradually advanced by a second predetermined angle for each ignition cylinder to avoid deterioration of drivability due to sudden changes in ignition timing (step 62p, 62n, 62o, 62k).

Returning to FIG. 4 again, after the subroutine of step 62, in step 64, the maximum pressure angle target value θpo and the actual maximum pressure angle θpmax calculated in step 60 are compared to determine the deviation Δθpmax. Note that if the target value is corrected in the subroutine, the corrected target value is set to θpo.

Next, in step 66, it is determined whether the knocking correction amount _KNR is not "0", that is, the remaining amount of knocking correction is determined by referring to the memory 42c, and if the remaining amount is "0", the next knocking correction amount is determined. In step 68, it is determined whether the deviation Δθpmax is behind or ahead of the target value θpo.

If it is a delay, the deviation correction θpc is set to a value that advances the previous θpc (initial setting "0") by a third predetermined angle set appropriately (step 70), and if it is a advance, the third predetermined angle is subtracted. and set it to a retarded value (step 72), and if there is no deviation, it remains at the previous value (step 74). Incidentally, if this third predetermined angle is set relatively small, the deviation will be gradually eliminated, which has the advantage of improving drivability as in the subroutine. As mentioned above, subtraction means retard angle correction, and addition means advance angle correction.

If knocking is detected in step 58, the knocking correction angle KNR (initial setting "0") is immediately retarded by a fourth predetermined angle set appropriately (step 76), and the amount of retardation is set. The ignition angle is retarded until it reaches a fifth predetermined angle which is set as appropriate to be larger than the fourth predetermined angle (steps 78 and 80), and the deviation correction amount θpc is set to the value at the time of the current ignition (step 82). or,
If there is a knocking correction remaining in step 66, wait for a predetermined period of time or the number of ignitions after the knocking ends, and return to the advance side by the fourth predetermined angle (step 66).
84, 86), when Δθpmax is ahead of the target value, there is no need to return it to the advanced side, so θpc is retarded by the third predetermined angle (steps 88, 72), and when it is delayed, the correction amount θpc is Make it unchanged (step 82). The predetermined time (number of ignitions) after the knocking ends is measured using the cycle counter and advance angle counter of the CPU in the control unit.

Subsequently, in step 90, the sum of the correction amount θpc and the knocking correction amount KNR is set as the feedback correction amount θf. If it is determined that the sensor is abnormal (step 56), the value obtained by retarding the sixth predetermined angle, which is set as appropriate, is set as the feedback correction amount. (Step 92).

Next, in step 94, the feedback correction amount θf determined in this way is applied to the same cylinder (cylinder address =
Store it once (or rewrite it if it is already stored) so that it will be used as the correction value for the next cycle of n).
Therefore, all the correction amounts including the knocking correction amount obtained in the above-described procedure are reflected only in the relevant cylinder, so that control can be performed according to the particular combustion state of each cylinder.

Subsequently, in step 96, the stored feedback correction amount θf of the cylinder to be ignited next (cylinder address=n+1) is read out (initial setting is "0"), and the ignition of the cylinder is commanded. At this time, the ignition timing is commanded as basic ignition timing + θf + θt (step 98). Note that this "θt" and "KNR" in step 90 themselves mean negative values, so
As a result, it means subtraction, that is, retardation.
This θf is the feedback correction amount for the relevant cylinder read in the previous step, and θt is the transient state correction amount obtained in the subroutine of FIG. Therefore, only the correction amount θt is used as a correction amount across cylinders, and by reflecting a correction amount smaller than the pressure target value correction amount to the next cylinder in this way, even during a transient period. Drivability is improved by retarding the angle in stages. Even with such a stepwise retardation, there is no problem because the transient state is detected relatively quickly by detecting the cylinder pressure and directly monitoring the combustion state. Moreover, since knocking control is also possible, sufficient countermeasures against knocking, which tends to occur during transient periods, have been taken.

Note that this basic ignition timing calculation may be performed only from the cylinder pressure to calculate the maximum pressure angle target angle θpo, or may be performed by detecting the operating state of the engine from the crank angle sensor and the negative pressure sensor. Also good. Even when calculating the basic ignition timing from the engine speed and load, the deviation between the actual maximum pressure angle and the target angle is detected after ignition, and the speed-to-load map value is changed using the corrected angle. Since this is repeated sequentially in preparation for the next ignition and feedback control is performed to the target angle, the number of rotation speed-load map values may be small, and therefore the device implementing this method can use a small memory capacity. Have sufficient advantages.

(Effects of the Invention) The present invention is configured to detect the internal cylinder pressure and detect the transient state of engine operation from the pressure change, and also to retard the maximum pressure angle target value in stages. In addition to improving performance and drivability, it is possible to prevent knocking. Further, by detecting the combustion state, it is possible to grasp the transient state more accurately, and even when this method is implemented, there is an advantage that the number of sensors and processing circuits for detecting the transient state can be reduced. In addition, the basic ignition timing can be calculated from only the cylinder pressure or from the engine speed and load as before, and even if it is detected from the engine speed - load, the cylinder combustion state can also be detected. As a result of feedback control to focus on the target angle, the main control value map only needs to be extremely rough.
When implementing this method, it has the advantage that the device can be configured with a small capacity memory.

[Brief explanation of the drawing]

Fig. 1 is a diagram corresponding to the claims of the present invention, Fig. 2 is a block diagram of a device used to realize the present invention, Fig. 3 is an output waveform diagram thereof, and Figs. 4 and 5 show examples of the present invention. The flow chart shown in FIG. 6 is an explanatory diagram illustrating the contents of the flow chart shown in FIG. 5.

Claims (1)

[Scope of Claims] 1. An ignition timing control method for an internal combustion engine, which detects the pressure in the cylinders of a multi-cylinder internal combustion engine and controls the ignition timing so that the maximum pressure angle is located at a target value, comprising: (a) ignition of one cylinder; (b) Next, find similar ratios for the same or different cylinders. (c) Next, find the fluctuation rate of those ratios, and if the fluctuation rate exceeds a predetermined range, the engine Determining that the operation is in a transient state, the maximum pressure angle target value is retarded by a predetermined amount from that in the steady operating state, and the ignition timing of the cylinder to be ignited next time is retarded by an amount smaller than the predetermined amount. , A method for controlling ignition timing of an internal combustion engine, comprising the following steps.