JPH0536999Y2 - - Google Patents

Description

[Detailed explanation of the idea]

(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 detects combustion pressure and controls a combustion state. (Prior Art) In recent years, control of internal combustion engines and their peripheral devices has also been computerized, allowing more precise control.
In such control, the combustion state of the internal combustion engine is detected, and operating parameters such as ignition timing and air-fuel ratio (hereinafter referred to as combustion operation parameters) that can control the combustion state are manipulated based on the detection results. Generally, when considering engine efficiency and fuel consumption, the minimum advance angle at maximum torque, so-called MBT (Minimum advance for
It is known that it is best to ignite near the best torque, and so-called MBT control is used to change the MBT ignition timing depending on the engine condition.
For example, Japanese Patent Application Laid-Open No. 61-16269
There is a device described in the publication. This device detects the pressure inside the combustion chamber (hereinafter referred to as cylinder pressure),
The ignition timing is controlled by MBT so that the crank angle at which the pressure is maximum (hereinafter referred to as maximum cylinder pressure timing) θpmax comes to the target position θpmaxo that maximizes the torque generated by the engine, and the target position θpmaxo is set according to the combustion speed. By setting this, the ignition timing is always controlled to the best fuel efficiency point to improve fuel efficiency even if there is a deviation in combustion speed due to engine operating conditions, individual variations, or usage environment. On the other hand, one of the important parameters for determining the amount of fuel required by the engine in a certain operating state is the intake air amount of the engine detected by an air flow meter. A conventional fuel supply control device for an internal combustion engine that determines the amount of fuel required by the engine from the amount of intake air is disclosed in, for example, Japanese Patent Laid-Open No. 61-229959. With this device, the amount of intake air detected by the air flow meter temporarily becomes extremely larger than the amount of intake air actually requested by the engine due to the effect of the collector volume between the throttle valve and the intake valve during a transient state. In order to prevent the air-fuel ratio from fluctuating due to the overshoot phenomenon, if there is a load fluctuation that exceeds a predetermined value, the system switches from ignition timing control to air-fuel ratio control to control fluctuations in the air-fuel ratio during operation. We are trying to improve sexual performance. (Problem to be solved by the invention) However, in the case of such conventional combustion control devices for internal combustion engines, it is difficult to control the ignition timing.
Because the configuration was designed to achieve MBT, even if the ignition timing is set to MBT, the air-fuel ratio may change due to environmental changes, individual variations, changes over time, etc. to the maximum torque producing air-fuel ratio, the so-called LBT (Leanst
There was a problem that the maximum torque generated and drivability deteriorated because the engine sometimes deviated from the maximum torque (Maxture for Best Torque). (Purpose of the invention) Therefore, the present invention focuses on the fact that there is a certain correlation between the combustion speed and the air-fuel ratio, and uses the maximum timing of the basic in-cylinder pressure set according to the operating condition of the engine as the reference in-cylinder pressure. The reference ignition timing is set as the maximum timing, and the reference ignition timing is corrected so that the maximum cylinder pressure timing matches the reference maximum cylinder pressure timing, and when knocking is detected, the reference maximum cylinder pressure timing and reference ignition timing are retarded. By correcting the basic fuel supply amount by comparing the corrected ignition timing with the reference ignition timing, the air-fuel ratio can be set to a predetermined value to achieve a predetermined combustion speed, and the occurrence of knocking can be prevented. The purpose is to improve drivability and fuel efficiency by controlling not only the ignition timing but also the air-fuel ratio to the optimum value even if there are influences such as environmental changes. (Means for Solving 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, a knock detection means b for detecting knocking occurring in the engine, an operating state detection means c for detecting the operating state of the engine based on the engine load and rotational speed, and a knock detection means b for detecting knocking occurring in the engine; a cylinder pressure maximum timing detection means d for detecting the crank angle at which the pressure is maximum as the cylinder pressure maximum timing, and when knocking is less than a predetermined level;
The basic cylinder pressure maximum timing set according to the engine operating condition is set as the standard cylinder pressure maximum timing, and when knocking is above a predetermined level, the cylinder pressure is corrected to the retarded side. A reference cylinder pressure setting means e sets the maximum timing as the reference cylinder pressure maximum timing, and when knocking is less than a predetermined level, a basic ignition timing set corresponding to the engine operating condition is set as the reference ignition timing, and knocking is set as the reference cylinder pressure maximum timing. is equal to or higher than a predetermined level, the reference ignition timing setting means f sets the ignition timing obtained by retarding the basic ignition timing as the reference ignition timing, and compares the reference cylinder pressure maximum timing with the cylinder pressure maximum timing. ignition timing calculation means g that corrects the reference ignition timing based on; basic fuel supply amount setting means h that sets the basic fuel supply amount based on the operating state of the engine;
corrected fuel supply amount calculation means i for calculating a corrected fuel supply amount based on a comparison between the reference ignition timing and the corrected ignition timing; a fuel injection amount calculation means j for calculating; an ignition means k for igniting the air-fuel mixture based on the output of the ignition timing calculation means g;
and a supply means l for supplying fuel based on the output of the fuel injection amount calculation means i. (Operation) In the present invention, a reference cylinder pressure maximum timing is set based on the operating state of the engine, and the reference ignition timing is corrected so that the cylinder pressure maximum timing coincides with the reference cylinder pressure maximum timing. When knocking is detected, the reference cylinder pressure maximum timing and reference ignition timing are corrected to the retarded side, and the corrected ignition timing and reference ignition timing are compared to correct the basic fuel supply amount. Therefore, the air-fuel ratio is set to a predetermined value to achieve a predetermined combustion speed, preventing the occurrence of knocking, and even under the influence of environmental changes, not only the ignition timing but also the air-fuel ratio is maintained at the optimum value. This control improves generated torque, drivability, and fuel efficiency. (Example) Hereinafter, the present invention will be explained based on the drawings. 2 to 5 are diagrams showing an embodiment of the present invention. First, the configuration will be explained. In FIG. 2, reference numeral 1 denotes a cylinder pressure sensor (pressure detection means), and the cylinder pressure sensor 1 is formed as a washer for a spark plug 2 screwed onto the cylinder head of the engine and is fastened together. The cylinder pressure sensor 1 converts the combustion pressure in the cylinder into an electric charge using a piezoelectric element, and outputs an electric charge output _S1 to a charge amplifier 3. The charge amplifier 3 is composed of a so-called charge-voltage conversion amplifier, converts the sensor output _S1 into a voltage signal S2, and outputs the voltage signal _S2 to the A/D converter 4 and the knocking detection circuit (knocking detection means) 5. The A/D converter 4 converts the signal S ₂ inputted as an analog signal into a digital signal in synchronization with the crank angle, and outputs the digital signal to the control unit 6 . The knocking detection circuit 5 includes a bandpass filter that passes only the high frequency components that are included in a particularly large amount when knocking occurs from the signal _S2 , half-wave rectification of the high frequency components, and formation of an envelope signal from the half-wave rectified signal (envelope detection). )do,
It is composed of a waveform shaping circuit that outputs a knocking signal S _N according to the knocking level. The intake air flow rate Q _a is detected by an air flow meter 7 , and the engine crank angle C _a is detected by a crank angle sensor 8 . The crank angle sensor 8 is set at a predetermined position before compression top dead center (TDC) of each cylinder at every explosion interval (120° of crank angle for a 6-cylinder engine, 180° for a 4-cylinder engine), for example.
A reference signal C _a that becomes a [H] level pulse at 70° BTDC is output, and a unit signal C ₁ that becomes an [H] level pulse for every unit angle of the crank angle (for example, 2°) is output. Incidentally, by counting the pulses of the signal C _a , the engine rotation speed N can be determined, and this processing is performed by the control unit 6, which will be described later. Furthermore, the cylinder discrimination sensor 9 discriminates a specific cylinder (for example, the first cylinder), and determines a predetermined crank angle position before the compression top dead center of the specific cylinder (for example, BTDC80° of the first cylinder).
The cylinder discrimination signal REF-i is output. Therefore, this cylinder discrimination signal REF-i is output once every two revolutions of the crankshaft. The air flow meter 7 and the crank angle sensor 8 constitute an operating state detecting means 10, and signals from the operating state detecting means 10 and the cylinder discrimination sensor 9 are input to the control unit 6.
The control unit 6 performs ignition timing control and fuel supply control based on these sensor information. The control unit 6 functions as maximum cylinder pressure timing detection means, reference cylinder pressure setting means, reference ignition timing setting means, ignition timing calculation means, basic fuel supply amount setting means, corrected fuel supply amount calculation means, and fuel injection amount calculation means. CPU11, ROM12,
It is composed of a RAM 13 and an I/O port 14, and is connected to each other by a common bus 15. The CPU 11 takes in necessary external data from the I/O port 14 according to the program written in the ROM 12, and processes necessary processing values while exchanging data with the RAM 13. Then, the processed data is output to the I/O port 14 as necessary. Signals from the sensor groups 7, 8, and 9 are input to the I/O port 14, and injection signals are input from the I/O port 14.
S _i or the ignition signal S _p is output to the injector (supply means) 16 or the ignition device 17 . The ignition device (ignition means) 17 includes an ignition coil 2, a spark plug, etc., and generates a high voltage based on the ignition output _Sp to ignite the air-fuel mixture. Also, ROM12 is
It stores calculation programs for the CPU 11, and the RAM 13 stores data used in calculations in the form of a map or the like. In addition, a part of RAM13 is
For example, it is constituted by a nonvolatile memory, and its stored contents (learning values, etc.) are retained even after the engine is stopped. Next, the operation will be explained, but first the basic principle of the present invention will be explained. The ignition timing and fuel injection amount are calculated based on the intake air amount and engine speed, and when driving an internal combustion engine, the ignition timing or fuel injection amount is not always optimal due to the influence of external environmental changes and changes over time. Sometimes it loses its value. Therefore, if the cylinder pressure maximum timing θpmax is detected and the ignition timing is set so that this θpmax matches a predetermined target value (corresponding to the reference cylinder pressure maximum timing in the claims).
MBT can be achieved. however,
This means that no improvement has been made to air-fuel ratio fluctuations. By the way, the relationship between the combustion speed and the air-fuel ratio is shown in Figure 3, and in the range used for actual combustion (combustion range), the combustion speed decreases as the air-fuel ratio becomes leaner. There is a downward trend to the right. Therefore, by controlling the combustion speed to a predetermined value and setting the air-fuel ratio, it is possible to improve the air-fuel ratio change. From the above, in this embodiment, while setting the ignition timing to a specific θpmax value (target value), the basic fuel supply amount is corrected by comparing the corrected ignition timing with the reference ignition timing. The air-fuel ratio is set to a predetermined value by controlling to obtain a predetermined combustion speed. In addition, in order to prevent the occurrence of knocking, when the knocking is below a predetermined level, the basic cylinder pressure maximum timing set according to the engine operating condition is set as the reference cylinder pressure maximum timing θpmax, and the knocking is prevented. When it is above a predetermined level, the maximum cylinder pressure timing obtained by retarding the basic maximum cylinder pressure timing is set as θpmax, and when knocking is below a predetermined level, the maximum cylinder pressure timing is set according to the engine operating state. The basic ignition timing is set as the reference ignition timing, and when the knocking is above a predetermined level, the ignition timing corrected to the retarded side of the basic ignition timing is set as the reference ignition timing. FIG. 4 is a flowchart showing a combustion control program based on the above basic principle, and this program is based on the cylinder discrimination signal REF from the cylinder discrimination sensor 8.
Interrupt processing is performed every -i. First, _P1 detects knocking (when knocking occurs, knocking correction amount K=
ΔK), and detect the cylinder pressure maximum timing θpmax at _P2 . The detection of θpmax will be explained in detail in the program described later. Next, in P ₃ , find the difference between θpmax and a predetermined target value after compression top dead center, and the difference is
When it is [+], it is determined that θpmax is on the lagging side,
In P ₄ , advance the correction value ΔS by a specific value A (for example, 0.2°) according to the following formula, and when it is [-], it is determined that θpmax is on the advance side, and in P ₅ , according to the following formula: The correction value ΔS is retarded by a specific value A. Also, the difference

When set to [0], lead/retard angle correction is not performed.
Proceed directly to P ₆ . ΔS=ΔS′+A …… ΔS=ΔS′−A …… However, ΔS′: Previous value Here, set the target value of θpmax to, for example, 15°ATDC.
If fixed as
This will be the setting. However, in reality, there are operating regions where MBT control is not possible due to the occurrence of knocks, combustion noise, etc. Therefore, the target value of θpmax is looked up from a table map with intake air amount Q _a and engine speed N as parameters, and when knocking is detected at P ₁ , this target value is corrected to the retard side by ΔK to prevent knocking. prevent the occurrence of In this way, by changing the target value of θpmax based on the operating conditions and appropriately retarding this target value when knocking occurs, it is possible to change the combustion speed calculated from the ignition timing and the θpmax detection position. This makes it possible to change the air-fuel ratio while preventing knocking. In P ₆ , the basic ignition timing is determined based on the engine speed N and intake air amount Q _a (equivalent to engine load).
Calculate ADVφ and set the standard ignition timing ADVφ,
At _P7 , the basic ignition timing is corrected to suppress knocking according to the following formula to set the reference ignition timing ADVφ, and at _P8 , the corrected ignition timing ADV is calculated according to the following formula. ADVφ=ADVφ−K... However, K: Retard angle correction amount for knock control (K = 0 when knock does not occur) ADV=ADVφ+ΔS...Next, in _P9 , corrected ignition timing ADV and basic ignition Compare the timing ADVφ, and if it is [+], increase the correction amount ΔT _p of the basic fuel correction amount T _p by a specific value B (for example, 0.01 ms) at P ₁₀ according to the following formula, and [-]
In this case, at _P11 , the fuel injection correction amount ΔT _p is reduced by a specific value B according to the following equation. Also, the correction amount ΔT _p is

When it is [0], no increase/decrease correction is performed and the process directly proceeds to _P12 . ΔT=ΔT'+B... ΔT=ΔT'-B... However, ΔT': Previous value P In ₁₂ , the basic fuel injection amount T _p is calculated based on the engine speed N and the intake air amount Q _a , At _P13 , the basic fuel injection amount T _p is corrected according to the following formula. T _p = T _p ′ + ΔT ... However, T _p ′: Previous value Furthermore, at P ₁₄ , the ignition signal S _p is output to the ignition means 17 at the ignition timing corresponding to this ignition timing ADV, and at P ₁₅ , T _p is stored in the output register of the I/O port 14, and an injection signal S _i having a fuel injection pulse width corresponding to this T _p is output to the injector 16 at a predetermined crank angle, and the current process ends. FIG. 5 is a flowchart showing a program for detecting the maximum cylinder pressure timing θpmax, and this process corresponds to step _P2 described in FIG. 4 above.
This program is executed once every 2 degrees of crank angle, and θ=0 when the cylinder discrimination signal is output. First, at P ₂₁ , the analog signal representing the cylinder pressure S ₂ is sent to the A/D
The cylinder pressure after this A/D conversion ( _hereinafter referred to as
(simply referred to as cylinder pressure) P is the maximum cylinder pressure up to the previous time
Compare with Pmax′. When Pmax'≦P, it is determined that the combustion pressure has not reached the maximum yet, and at _P23 , P at this time is set as a new Pmax', and the crank angle θ at that time is set as θpmax'. This process is performed from a predetermined crank angle to a predetermined crank angle (for example,
Repeat from 50°BTDC to 50°ATDC).
When Pmax′>P, crank angle θpmax is 0 at P ₂₄
(θ=0) or not, and when θ=0, it is judged that the detection of the maximum cylinder pressure timing in the current combustion process has been completed, and Pmax' and θpmax' are set as Pmax and θpmax, respectively, at _P25 . The cylinder pressure maximum timing θpmax is obtained as follows, and the current process is completed in preparation for the next process by setting Pmax'=0. On the other hand, θ≠0
When , the above steps are repeated until θ=0. In this way, the target value of the cylinder pressure maximum timing θpmax is set to achieve MBT in all operating ranges based on the intake air amount Q _a and the engine speed N, and the basic value is set so that θpmax matches this target value. Ignition timing ADVφ is corrected. When the occurrence of a knock is detected, this target value and ignition timing are set to the retarded side, and the basic fuel supply amount T _p is corrected by comparing the corrected ignition timing ADV and the reference ignition timing ADVφ. Ru. Therefore, it becomes possible to operate at a specified air-fuel ratio while appropriately avoiding knocks, and both output and drivability are improved. (Effects) According to the present invention, the reference cylinder pressure maximum timing is set based on the operating condition of the engine, and the reference ignition timing is set so that the cylinder pressure maximum timing coincides with the reference cylinder pressure maximum timing. At the same time, when knocking is detected, the reference maximum cylinder pressure timing and the reference ignition timing are corrected to the retarded side, and the corrected ignition timing is compared with the reference ignition timing to correct the basic fuel supply amount. As a result, the air-fuel ratio can be set to a predetermined value to achieve a predetermined combustion speed, and while preventing knocking, it is possible to maintain not only the ignition timing but also the air-fuel ratio at the optimum value even under the influence of environmental changes. control to improve generated torque, drivability, and fuel efficiency.

[Brief explanation of the drawing]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 5 are diagrams showing one embodiment of the invention, Fig. 2 is its overall configuration diagram, and Fig. 3 is a diagram showing its combustion speed and air-fuel ratio. FIG. 4 is a flowchart showing the combustion control program, and FIG. 5 is a flowchart showing the program for detecting the maximum cylinder pressure timing. 1... Cylinder pressure sensor (pressure detection means), 5...
Knocking detection circuit (knocking detection means), 6...
Control unit (maximum cylinder pressure timing detection means, reference cylinder pressure setting means, reference ignition timing setting means, ignition timing calculation means, basic fuel supply amount setting means, corrected fuel supply amount calculation means, fuel injection amount calculation means), 10... ...Operating state detection means, 16... Injector (supply means), 17... Ignition device (ignition means).

Claims (1)

[Scope of Claim for Utility Model Registration] a. Pressure detection means for detecting the cylinder pressure of the engine; b. Knock detection means for detecting knocking occurring in the engine; c. (d) maximum cylinder pressure 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 cylinder pressure maximum timing; (e) when the knocking is at a predetermined level. When the maximum cylinder pressure is below, the basic maximum cylinder pressure timing set according to the engine operating condition is set as the standard maximum cylinder pressure timing, and when the knocking is above a predetermined level, the basic maximum cylinder pressure timing is retarded. a reference cylinder pressure setting means for setting the corrected cylinder pressure maximum timing as a reference cylinder pressure maximum timing; a reference ignition timing setting means for setting, as a reference ignition timing, an ignition timing obtained by retarding the basic ignition timing when the knocking is at a predetermined level or higher; g. ignition timing calculation means for correcting the reference ignition timing based on a comparison with the reference ignition timing; (h) basic fuel supply amount setting means for setting the basic fuel supply amount based on the operating state of the engine; i. (a) a corrected fuel supply amount calculation means for calculating a corrected fuel supply amount based on a comparison with the ignition timing; and (j) a fuel injection amount calculation means for calculating a fuel injection amount based on the basic fuel supply amount and the corrected fuel supply amount. k. ignition means for igniting the air-fuel mixture based on the output of the ignition timing calculation means; l. supply means for supplying fuel based on the output of the fuel injection amount calculation means. Combustion control device for internal combustion engines.