JPH01121546A - Combustion control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To enhance the rate of fuel consumption and the output torque at the time of knockings being suppressed, by correcting the fundamental air-fuel ratio so that the intra-cylinder pressure max. timing is in a position a little delayed from the target position when knocking is suppressed. CONSTITUTION:In a control unit 4 knockings are sensed by an intra-cylinder sensor 1 through a knocking processing circuit 2, and the fundamental ignition timing is corrected so as to suppress eventually generated knocking. The intra- cylinder pressure max. timing is sensed by the sensor 1 through an intra-cylinder pressure sensing circuit 3, and while knocking are suppressed, the fundamental air-fuel ratio is corrected so that the intra-cylinder pressure max. timing will be in a position a little delayed from the specified target position where the torque generated by the engine maximizes. Thus optimum air-fuel ratio is obtained while knockings are suppressed.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a combustion control device for an internal combustion engine such as an automobile, and more particularly to a device that appropriately corrects the air-fuel ratio during knocking suppression to increase fuel efficiency and output torque. (Prior art) Generally, it is desirable to determine the ignition timing of an internal combustion engine so as to maximize efficiency according to the engine operating condition.
B T (Minimum advance for
Be5tT. It is well known to set the advance angle close to rque). However, depending on the operating condition of the engine, knocking may occur and the output of the engine may decrease, and in some cases, damage to the engine may occur. Therefore, so-called knocking control, which suppresses knocking while emphasizing engine efficiency, is carried out.As a conventional knocking control device for an internal combustion engine, for example, the one described in Japanese Patent Application Laid-Open No. 138435/1983 is a conventional knocking control device for internal combustion engines. There is. With this device, no. If the operating condition is in the high-load, high-speed range when knocking occurs, the air-fuel ratio is corrected to the rich side, and in other operating conditions, the ignition timing is corrected to the retarded side to suppress knocking. are doing. (Problems to be Solved by the Invention) However, in such a conventional combustion control device for an internal combustion engine, when the operating state of the engine falls within a predetermined range (for example, a partial load range or a low-to-medium speed range), At certain times, knock suppression control is performed using the ignition timing and the air-fuel ratio is fixed at a predetermined value, and when the operating condition is in a predetermined range (for example, high speed and high load range), the ignition timing is set to a predetermined value and knock control is performed. Since the configuration was such that the air-fuel ratio was controlled for suppression, there were the following problems. (1) Since air-fuel ratio control is not performed in a region where knock suppression is performed only by ignition timing, fuel efficiency cannot be improved. (II) In a region where knock suppression is performed using the air-fuel ratio, the air-fuel ratio is lynched to suppress knock, resulting in poor fuel efficiency. (Purpose of the Invention) Therefore, the present invention suppresses knocking by adjusting the ignition timing, and when suppressing knocking, the cylinder pressure maximum timing is set at a predetermined position slightly later than a predetermined target position at which the engine generates maximum torque. By correcting the basic air-fuel ratio so as to achieve the desired position, the air-fuel ratio at the time of knocking suppression is set to an appropriate value, and the purpose is to improve fuel efficiency and output torque at the time of knocking suppression. (Means for Explaining the Problems) In order to achieve the above object, the combustion control device for an internal combustion engine according to the present invention has a pressure detection means for detecting the cylinder pressure of the engine, as shown in FIG. a, knock detection means b for detecting knocking occurring in the engine, operating state detection means C for detecting the operating state of the engine, and pressure detection means when the cylinder pressure reaches its maximum based on the output of the pressure detection means a. Maximum timing detection means d detects the crank angle as the timing of maximum cylinder pressure, and sets basic ignition timing based on the operating state of the engine, and corrects the basic ignition timing so as to suppress knocking when it occurs. ignition timing control means e; ignition means f for igniting the air-fuel mixture based on the output of the ignition timing control means e; a correction amount calculation means g that calculates an air-fuel ratio correction amount to correct the basic air-fuel ratio so that the basic air-fuel ratio is adjusted to the correct position; an air-fuel ratio control means that corrects the air-fuel ratio according to the air-fuel ratio correction amount and calculates a control value that achieves the air-fuel ratio determined in this way;
an operating means i for manipulating the air-fuel ratio by changing the amount of intake air or the amount of fuel supplied based on the output of the air-fuel ratio control means;
It is equipped with (Function) In the present invention, the basic ignition timing is corrected to suppress knocking when it occurs, and when knocking is suppressed, the maximum cylinder pressure timing is adjusted to a predetermined value that maximizes engine generation and torque. The basic air-fuel ratio is corrected so that it reaches a predetermined position that is slightly behind the target position. Therefore, the air-fuel ratio at the time of suppressing knocking becomes appropriate, and fuel efficiency and output torque at the time of suppressing knocking improve. (Example) Hereinafter, the present invention will be explained based on the drawings. 2 to 7 are diagrams showing a first embodiment of the present invention. First, the configuration will be explained. In Fig. 2, numeral 1 denotes a cylinder pressure sensor (pressure detection means), which converts the combustion pressure in the cylinder box into an electric charge using a piezoelectric element, and outputs an electric charge S.
, outputs. Specifically, the cylinder pressure sensor 1 is formed as a washer for a spark plug that is screwed onto the cylinder head of an engine, and the spark plug is fixed by being pressed by the parts. Alternatively, a flush mount type cylinder pressure sensor that directly detects combustion pressure may be used. The output of the cylinder pressure sensor 1 is input to a knocking processing circuit (knock detection means) 2 and a cylinder pressure detection circuit 3, and the knocking processing circuit 2 detects the pressure signal SI from the cylinder pressure sensor 1, which is particularly high when knocking occurs. A waveform that includes a bandpass filter that passes only high-frequency components, half-wave rectification of the high-frequency components, and an envelope signal formed from the half-wave rectified signal (envelope detection) to be output as a knocking signal S2 according to the knocking level. It is composed of a shaping circuit. In addition, the cylinder pressure detection circuit 3 is composed of a charge amplifier and a low-pass filter, and includes an output S1 of the cylinder pressure sensor.
is converted into an electric signal by a charge-voltage conversion amplifier using a charge amplifier, and from this voltage signal, only signals below a predetermined offset frequency (for example, about IKIIZ) are extracted and high frequency components are removed and controlled as signal S. Output to unit 4. The intake air flow 11Qa is detected by the air flow meter 5, and the temperature Tw of the cooling water flowing through the water jacket is detected by the water temperature sensor 6. Further, the crank angle of the engine is detected by a crank angle sensor 7, and the crank angle sensor 7 detects the explosion interval (120" for a 6-cylinder engine,
In a 4-cylinder engine, each cylinder is set at a predetermined position before compression top dead center (TDC) every 180°, for example, at 70° BTDC (H
) level pulse, and outputs the reference signal REF as a pulse at the level [H
] Outputs a unit signal PoS as a level pulse. Note that the engine rotation speed Ng can be determined by counting the pulses of the signal REF. The air flow meter 5, water temperature sensor 6, and crank angle sensor 7 constitute an operating state detecting means 8, and outputs from the operating state detecting means 8, knocking processing circuit 2, and cylinder pressure detecting circuit 3 are input to the control unit 4. be done. The control unit 4 performs combustion control based on this information. The control unit 4 has functions as maximum timing detection means, ignition timing control means, correction amount calculation means, and air-fuel ratio control means, and includes CP Ull, ROM
12, a RAM 13, and an I10 interface 14, which are connected to each other by a common bus 15. The CPU II takes in necessary external data according to the program written in the ROM 12, and while exchanging data with the RAM 13, calculates processing values necessary for knock suppression control and air-fuel ratio control. The processed data is output to the I10 interface 14 as necessary. ROM12 is CP Ull
The ROM 12 stores data used in calculations in the form of a map or the like. I
Signals from the respective sensors are input to the I10 interface 14, and the injection signal Si and ignition signal Sp are output from the I10 interface 14 to the injector (operating means) 15 or the ignition means 16, respectively. Then, fuel is injected at a predetermined timing and for a predetermined injection time according to this injection signal Si. On the other hand, the ignition signal Sp is input to the ignition means 16, and the ignition signal Sp is input to the ignition means 16.
6 is composed of a spark plug 17, an ignition coil 18, a power source 19, a distributor 20, and a power transistor Q. The ignition means 16 controls the power transistor Q in a 0N10FF manner based on the ignition signal Sp to generate a high voltage Pi on the secondary side of the ignition coil 18, and distributes this high voltage Pi by the distributor 20 to the spark plugs of each cylinder. 17 to ignite the mixture. This ignition timing control (power transistor Q, 0N10FF system?1) is controlled by the I10 interface 14.
Set a value (advance value) corresponding to the determined ignition timing in an advance angle value (ADV) register (not shown) provided inside the
The values of these registers are compared with the count value of the position signal PO8, and when they match, the power transistor Q is activated. Turn ON or OFF. Next, the operation will be explained, but first the basic idea of the present invention will be described. Generally, the cylinder pressure maximum timing θpm at which the ignition timing becomes MBT
ax is determined by the mechanical dimensions of the engine (connecting rod length, piston stroke), and the MBT point is achieved at a constant θpmax (for example, θpmax = 15° ATDC) even if conditions such as intake air temperature, air-fuel ratio, and engine temperature change. I know I will. Therefore, in order to suppress the occurrence of knocking near the fully open state of the engine, θpmax
By controlling the air-fuel ratio so that θpmax is slightly retarded than MBT, the air-fuel ratio during knock suppression control by ignition timing can be adjusted as shown in Fig. 3, which shows the correlation between θpmax and shaft torque (or fuel efficiency). The deterioration of can be appropriately prevented. At this time, the range of retardation of θpmax is, for example, the upper limit is the value of θpmax (named θ1) that is 0.5% lower than the best torque point (same as the best fuel efficiency point), and the upper limit is 2
By controlling the air-fuel ratio so that θpmax falls within this range, with the lower limit of θpmax (named θ2), deterioration in fuel efficiency can be prevented while reliably suppressing knocking. FIG. 4 is a flowchart showing a program for ignition timing control (knocking control) based on the above basic principle, and this program is executed once every predetermined period. First, P.
The basic ignition timing ADV o (ADV
o =func (Qa, Ne, Tw)), and at P2, the slice level S/L for knocking determination is calculated based on the intake air amount Qa and the engine speed Ne.
(S/L=func(Qa, Ne)) is calculated. Next, at P, a knock level S is calculated based on the output signal S2 from the knocking processing circuit 2, and at P4, the knock level S and the slice level S/L are compared. S-5
When in SL, it is determined that knocking is not occurring and P is pressed.
At step s, the feedback correction amount FB is advanced according to the following equation (2) and the process proceeds to P7. FB=FB '+β ・・・・・・■However, FB'
: Previous feedback correction amount β : Predetermined amount Also, when S>SL, it is determined that knocking has occurred, and the feedback correction amount FB is retarded at Ph according to the following formula (2), and the process proceeds to P. FB=FB'-α...■However, α: Predetermined amount In this way, FB is appropriately corrected depending on the presence or absence of knocking. In steps P and ~pH+, a predetermined limit is set for the feedback correction amount FB calculated in the above P or P. That is, P compares FB with the lead angle limit (upper limit) ALl, and when FB:5AL1, it is determined that FB is within the predetermined lead angle limit, and P
, and when FB>ALL, the upper limit cent is set as FB=AL1 at P, and the process proceeds to P. P, compares FB with the retard limit (lower limit) Al1, and finds that FB≧A
When L2, it is determined that FB is within the predetermined retard limit and proceeds to pH, and when FB<Al1, FB is set at Pl+1.
Set the lower limit as =AL2 and proceed to P. Pl+
Then, the final ignition timing ADV is calculated according to the following formula (0), and the current process ends. ADV = ADV o + F B
・－・・・・■This allows the next ignition timing to be the final ignition time! t, the ignition signal S at the timing corresponding to 1IADV.
p is output and the air-fuel mixture is ignited. Figure 5 shows the maximum cylinder pressure timing θρmax detected and θpmax
This is a flowchart showing a program for comparing x with a reference value, and this program is executed once every predetermined crank angle. First, in P21, the cylinder pressure maximum timing θpmax is calculated, and in P2□, θpn+ax is averaged in order to increase the calculation accuracy of this θpmax. Here, θpmax is calculated using an A/D conversion routine (not shown) to convert an analog signal representing the cylinder pressure S to a timing (
For example, 1” BTDC,?” ATDC, 15°AT
DC, 23° ATDC, 31° ATDC (see Figure 6), and the cylinder pressure P+, P after these A/D conversions.
This is done by applying approximation functions to g, P3, P4, and P. Further, there is a method for averaging θpmax, for example, by using a moving average. Next, P2! , PX3, the reference value θ1 (θ, = fun
c (Qa, Ne)), θ2 (θz = func
(Qa, Ne) or θ2=θr +func (
It is determined whether θpmax after averaging with pzs is within the range of θ1≦θpmax≦θ2. When θ1≦θpmax≦θ2, set the 2-bit flag Flag in pzb.

[00] and Flag = OO), when θplaX > θ2, it is determined that θpmax is too late and Flag = is set at pzh.
Set it to 01. On the other hand, when θpmax <θ1, θpm
Judging that ax is too advanced, Pg? Set Flag=10. FIG. 7 is a flowchart showing a fuel supply control program, and this program is executed once every predetermined period. First, in P31, the basic pulse width To that gives the basic injection amount
(To=func (Qa, Ne. Tw, V, , SW, ΔQa), where SW: idle switch correction, ΔQa: rate of change of Qa during acceleration) is calculated, and in P3□, the learning amount TL (by θpmax) is calculated. TL=fu
nc (Qa, Ne)) is table-look-amplified. Next, at P[, the operating state of the engine meets the predetermined learning condition (
For example, it is determined whether the operating conditions are substantially steady in a high load range), and if the operating conditions are under predetermined learning conditions, the bit configuration of the flag Flag determined in FIG. 5 is determined in P34. When Flag=01, it is determined that θpmax is too delayed, and the air-fuel ratio is enriched at step p2s""pat. That is, the value TLL (TLL=TL+γ) is calculated by adding a predetermined amount γ to TL in pls, and P3b
This TLL is set to a predetermined value TLL 1 (TLL 1 =
func (Qa, Ne) ). TLL≦
When TLLI, the TL learning table is learned by +1 minute at p3t and the process proceeds to Pd2, and when TLL>TLLI, the process directly proceeds to Pd2. On the other hand, when F1ag=IQ, it is determined that θpmax has advanced too much, and the air-fuel ratio is adjusted to a normal value at steps P to P4°. That is, in P311, a value TLL (TLL=TL-δ) is calculated by subtracting a predetermined amount δ from TL, and P
39, this TLL is set to a predetermined value TLL2 (TLL2=fu
Compare with nc (Qa, Ne) ). TLL5T
When LL2, the TL learning table is learned by 1 δ at P4° and the process proceeds to P□, and when TLL>TLL2, the process directly proceeds to Pd2. On the other hand, if the learning condition is not met in P33 or if F1ag=OO in P34, the learning table is not changed and the process directly proceeds to Pd2. In Pd2, the fuel injection amount (final injection amount) that should be output according to the following formula ■
The current process ends after calculating the pulse width Ti. Ti=To+TL ・・・・・・■ Therefore,
As shown in each program above, while knocking is appropriately avoided by ignition timing control, during knock suppression control, θ
A predetermined range where pmax is slightly behind MBT (θ1...
The air-fuel ratio is appropriately learned and controlled so that θpmax≦θ2). Therefore, fuel efficiency can be improved, especially in a high load range, without impairing engine output. Although the first embodiment described above shows fuel supply control using a learning method, feedback control may be used instead of the learning method, and this aspect will be described in the following second embodiment. FIG. 8 is a diagram showing a second embodiment of the present invention, in which steps that perform the same processing as in the first embodiment are given the same numbers and their explanations are omitted, and steps that are different are marked with an O. Number them and explain their contents. FIG. 8 is a flowchart showing a fuel supply control program, and corresponds to FIG. 7 of the first embodiment. In the same figure, flag F is set at P34.
Determine the bit configuration of lag, and if Flag = 01, determine that θpmax is too late, and increase the feedback correction amount TFB using PSI according to the following formula,
When F1ag=10, it is judged that θpn+ax has advanced too much and P,! Then, TFB is corrected by decreasing it according to the following formula (2). TFB=TFB'+γ・・・・・・■However, T
FB': Previous feedback correction amount T: Increased correction amount TFB=TFB'-δ ・・・・・・■However, δ
: Reduction correction amount On the other hand, when Flag=OO, the previous feed bank correction ITFB' is set as the current feedback correction amount TFB in PS3, TFB=TFB'), and the process proceeds to Psa. In Psi, TFB is compared with the predetermined increase limit L2 and decrease limit 1, and when TFB>L2, TFB is determined in pss.
Set FB=L2 and proceed to PS'l, and when TFB<Ll, set TFB=L1 at Psi and proceed to P,7. Also, L
When 1≦TFB≦L2, keep it as PS? Proceed to P.S.
? Then, the pulse width Ti of the final injection amount is calculated according to the following equation (2), and the current process is completed. By executing 0 or more programs, the present embodiment can obtain the same effects as the first embodiment. (Effects of the Invention) According to the present invention, the ignition Knocking is suppressed depending on the timing, and when knocking is being suppressed, the basic air-fuel ratio is corrected so that the timing of maximum cylinder pressure is a predetermined position slightly later than the predetermined target position where the engine generates maximum torque. Therefore, the air-fuel ratio when suppressing knocking can be set to an appropriate value, and fuel efficiency and output torque when suppressing knocking can be improved.

[Brief explanation of the drawing]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 7 are diagrams showing a first embodiment of the present invention, Fig. 2 is an overall configuration diagram thereof, and Fig. 3 is a diagram showing the timing of maximum cylinder pressure and fuel efficiency. 4 is a flowchart showing the ignition timing control program, FIG. 5 is a flowchart showing the program for detecting the maximum cylinder pressure timing and comparing it with a reference value. Fig. 6 is a characteristic diagram showing the relationship between cylinder pressure and crank angle, Fig. 7 is a flow chart showing the fuel supply control program, and Fig. 8 is the fuel supply control program showing the second embodiment of the present invention. It is a flowchart which shows. 1... Cylinder pressure sensor (pressure detection means), 2...
...Knocking processing circuit (knock detection means), 4.
...Control unit (maximum timing detection means,
ignition timing control means, correction amount calculation means, air-fuel ratio control means), 8... operating state detection means, 15... injector (operation means), 16...
...Ignition means.

Claims (1)

[Scope of Claims] a) Pressure detection means for detecting the cylinder pressure of the engine; b) Knock detection means for detecting knocking occurring in the engine; c) Operating state detection means for detecting the operating state of the engine. d) Maximum timing detection means for detecting the crank angle at which the cylinder pressure reaches its maximum based on the output of the pressure detection means as the maximum cylinder pressure timing; and e) Setting the basic ignition timing based on the operating state of the engine. and an ignition timing control means for correcting the basic ignition timing so as to suppress knocking when it occurs; f) an ignition means for igniting the air-fuel mixture based on the output of the ignition timing control means; and g) a cylinder. h) correction amount calculation means for calculating an air-fuel ratio correction amount for correcting the basic air-fuel ratio so that the internal pressure maximum timing is a predetermined position slightly delayed from a predetermined target position at which the engine generates the maximum torque; Control that sets a basic air-fuel ratio based on the operating state, and corrects the basic air-fuel ratio according to the air-fuel ratio correction amount when knocking is suppressed, so that the air-fuel ratio determined in this way is achieved. An internal combustion engine characterized by comprising: an air-fuel ratio control means for calculating a value; and i) an operation means for manipulating the air-fuel ratio by changing the amount of intake air or the amount of fuel supplied based on the output of the air-fuel ratio control means. Engine combustion control device.