JPS6338640A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent a temporary excessive richness in air-fuel ratio at the time of sudden deceleration by determining the combination of opening areas of bypass control valves in response to the state of deceleration, when the state of deceleration is discriminated from the variation of throttle valve opening. CONSTITUTION:The detected values of a throttle sensor 30, a water temperature sensor 31, a crank angle sensor 32, an O2 sensor 33, a speed-change-gear position sensor 36, a car-speed sensor 37, an air-conditioner switch 38, a power steering detecting switch 39, or the like are input into a control unit 50, so that an injector 7 is controlled by the timing of each cylinder, and further the combination of idle-up solenoid valves SV1 and SV2 is determined. The control unit 50 calculates the opening variation of the throttle sensor 30, and at the time of deceleration, on the basis of the opening variation in the closing direction, reads out the combination of opening and closing of the idle-up solenoid valves SV1 and SV2, and outputs a control signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an air-fuel ratio control device for an internal combustion engine such as an automobile.
The present invention relates to an air-fuel ratio control device for an internal combustion engine that improves the air-fuel ratio during sudden deceleration.

(Prior art) In general, within! 1! It is necessary to control the amount of fuel with good responsiveness to engine load fluctuations, and a fuel injection device (injector) is optimal in terms of this responsiveness. Incidentally, since the injector generates mechanical noise as it operates, there is a problem in that the quietness deteriorates as the number of installed injectors increases.

For this reason, in recent years, so-called single point injection (SPi) using a single injector has been introduced.
) method has been adopted.

As a conventional air-fuel ratio control device for an internal combustion engine to which this type of SPi method is applied, for example, "Internal Combustion Engine" VOL25 N
o320 Published by Sankaido in July 1986, there is something described on pages 65-69. In this device, a throttle valve is provided in a throttle chamber connected to a gathering part of an intake manifold, and a single injector is provided upstream of the throttle valve.

Fuel is injected from an injector in response to an injection signal corresponding to the ignition timing of each cylinder, and is mixed with an amount of intake air corresponding to the opening degree of the throttle valve to form an air-fuel mixture. This air-fuel mixture is supplied to each cylinder via each branch of the intake manifold, and is ignited and combusted by a spark plug.

(Problems to be Solved by the Invention) However, in such a conventional air-fuel ratio control device for an internal combustion engine, fuel is injected from the upstream side of the throttle valve, and this fuel passes through the opening of the throttle valve. The structure was such that the particles were atomized by the negative pressure difference before and after the throttle valve caused by the air flow, so when the throttle valve opening was large, the negative pressure difference mentioned above decreased, and as a result,
Fuel that is not atomized, so-called liquid fuel, is generated and remains in the intake manifold as fuel that adheres to the wall surface.

By the way, when the accelerator pedal is suddenly released (sudden deceleration occurs) while the vehicle is running, the negative pressure within the intake manifold rises rapidly, and this high negative pressure promotes the vaporization of the fuel adhering to the walls. Therefore, the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber becomes temporarily too rich, resulting in worsening of exhaust emissions (that is, an increase in CO1HC) or, in the worst case, (in an overrich state exceeding the flammability limit). (case) had the problem of misfires and backfires.

(Purpose of the Invention) Therefore, the present invention determines the state of deceleration from the amount of change in the opening of the throttle valve, and increases the amount of intake air according to the state, thereby improving the temporary air-fuel ratio during sudden deceleration. The purpose is to prevent overconcentration and stabilize engine drivability.

(Means for Solving the Problems) In order to achieve the above object, the air-fuel ratio control device for an internal combustion engine according to the present invention detects the operating state of the engine, as shown in the basic conceptual diagram in the first @. Means a, an opening detection means for detecting the opening of the throttle valve, and deceleration determining means C for determining the deceleration state of the engine from the amount of change in the opening of the throttle valve.
and a combination determining means d which determines a combination of the opening areas of the bypass control valves based on the output of the opening detecting means 1 when the engine shifts to a predetermined operating state; Supply amount determining means e which calculates the amount of fuel supplied to the engine in a cycle and outputs a supply signal at timing for each cylinder; and fuel supply means f which supplies fuel to the engine based on the output of the supply amount determining means e. and,
A plurality of bypass control valves having different areas are disposed in a passage that bypasses a throttle valve in an intake passage, and a predetermined number of bypass control valves are selected based on a predetermined combination determined by a combination determining means d. Air amount variable means g that is operated to change the amount of intake air supplied to the engine.

(Function) In the present invention, the deceleration state is determined from the amount of change in the opening degree of the throttle valve, and the intake air amount is corrected to increase in accordance with the state. Therefore, a temporary rise in negative pressure within the intake manifold during sudden deceleration is avoided, and excessive enrichment of the air-fuel ratio is prevented.

(Example) Hereinafter, the present invention will be explained based on the drawings.

FIGS. 2 to 11 are diagrams showing one embodiment of the present invention, and the present invention is described as SP i (Single Point In
This is an example in which the present invention is applied to a 4-cylinder engine of the 4-cylinder engine.

First, the configuration will be explained. In Fig. 2, reference numeral 1 is an engine, and intake air is passed from an air cleaner 2 to a throttle chamber 3, and is changed to 0N10FF by a heater control signal Si.
After being heated by a PTC heater 4, the fuel is supplied to each cylinder from each branch of an intake manifold 5, and the fuel is supplied to a single injector provided upstream of a throttle valve 6 based on an injection signal STi. (Fuel supply means) 7 injects the fuel. An ignition plug 10 is installed in each cylinder, and the ignition plug 10 receives high-voltage pulses from an ignition coil 12 via a distributor 11.
E is supplied. The air-fuel mixture in the cylinder is high pressure pulse PULS
It ignites and explodes due to the discharge of the spark plug 10 by E.
Harmful components (Co, HC) in the exhaust gas are converted into exhaust gas and passed through the exhaust pipe 14 to the catalytic converter 15.

NOx) is purified by a three-way catalyst and discharged from the muffler 16.

Here, the flow of intake air is controlled by a throttle valve 6 in the throttle chamber 3 that is linked to the accelerator pedal, and when idling, the throttle valve 6 only releases a small amount of air necessary to ensure the minimum amount of air at idling. It is. Therefore, the air flow during idling passes through the bypass passage 18, and the idle up solenoid valve (hereinafter referred to as SV) operates based on the opening signal 5tsc+.
) and an idle up solenoid valve (hereinafter referred to as S V z
) to ensure the appropriate amount of air. SV,
and SVt have valve bodies with different areas, and the area ratio is, for example, 2 for SV and r for Svz.
It is set to lJ. Incidentally, SV, SV collectively constitute the air amount variable means 21.

In addition, a swirl control valve 22 is arranged near the intake boat of each cylinder.
2 is connected to a servo diaphragm 24 via a rod 23. A predetermined control negative pressure is guided to the servo diaphragm 24 from a solenoid valve 25, and the solenoid valve 25 converts the negative pressure supplied from the intake manifold 5 into the atmosphere based on a swirl control signal Sscv having a duty value Dscv. The controlled negative pressure introduced into the servo diaphragm 24 is continuously changed by leaking to the servo diaphragm 24. The servo diaphragm 24 responds to this control negative pressure and adjusts the opening degree of the swirl control valve 22 via the rod 23.

The opening degree α of the throttle valve 6 is detected by a throttle sensor 30, and the temperature Tw of the cooling water is detected by a water temperature sensor 31. Further, the crank angle Ca of the engine is detected by a crank angle sensor 32 built into the distributor 11, and the engine speed N can be determined by counting pulses representing the crank angle Ca. the above,
The throttle sensor 30 and the crank angle sensor 32 together constitute a driving state detecting means, and the throttle sensor 30 also has the function of an angle detecting means. An oxygen sensor 33 is attached to the exhaust pipe 14, and the oxygen sensor 33 is connected to an air-fuel ratio detection circuit 34. The air-fuel ratio detection circuit 34 supplies the pump current 1p to the oxygen sensor 33, detects the oxygen concentration in the exhaust gas from the value of the pump current Ip, and outputs it as an air-fuel ratio signal Vip. The operating position of the transmission is detected by a position sensor 36, and the speed S vsr of the vehicle is detected by a vehicle speed sensor 37. Further, the operation of the air conditioner is detected by the air conditioner switch 38, and the operation of the power steering is detected by the power steering detection switch 39.

Each of the above sensors 30.31.32.34.36.37.3
The signals from 8 and 39 are input to the control unit 50, and the control unit 50 performs engine combustion control (ignition timing control: fuel injection control, etc.) based on these sensor information. That is, the control unit 50 has functions as a deceleration determining means, a combination determining means, and a supply amount determining means, and has the functions of a CPU 51, RO
It is composed of an M52, a RAM 53, and a 10 port 54. The CPU 51 takes in necessary external data from the ■/○ boat 54 according to the program written in the ROM 52, and while exchanging data with the RAM 53, processes values necessary for engine combustion control. I1 calculates and processes the data as necessary.
0 port 54. The signals from the sensors 30, 31, 32, 34, 36, 37, 38 and 39 are input to the I10 port 54, and the signals STi, S IGN % S +
sc+-, S+scz, Sscv and SH are output. The ROM 52 stores an arithmetic program for the CPU 51, and the RAM 53 is partially composed of a non-volatile memory, and its stored contents are retained even after the engine 1 is stopped.

Next, the operation will be explained, but first the air flow rate calculation system will be explained.

In this embodiment, when detecting the air flow rate, a conventional air flow meter is not provided, and the injector 7 is measured using the throttle opening α and the engine speed N as parameters.
A method (hereinafter simply referred to as the α-N system) is adopted in which the air 1QAinj (hereinafter referred to as the injector air amount) passing through the part is calculated.

The reason why the injector air amount Q Ain j is calculated using such an α-N system is as follows.

In other words, according to the conventional sensor described above, (a) there is a large fluctuation in the sensor output due to intake pulsation, which causes fluctuations in the fuel injection amount, which causes torque fluctuations, and (b) there is no transient response in terms of sensor responsiveness. (c) The above-mentioned sensor has a relatively high cost. From this point of view, in this example, we will use the α-N system, which is low cost and has excellent responsiveness and detection accuracy. We are hiring
Also, especially in SPi type engines, this α-
By adopting the N system, the accuracy of air-fuel ratio control can be greatly improved.

Below is the injector air amount Q A according to this system.
The calculation of i n j will be explained.

FIG. 3 is a flowchart showing a program for calculating the cylinder air amount QAcyL. First, P, the previous QAc
yL is stored in memory as an old value QAcVL'. Here, Q A c y L is the amount of intake air passing through the cylinder section, and corresponds to the intake air iQa in a conventional device (for example, an EGi engine), as shown in Fig. 8 described later. The air amount QAi in the injector section is determined by the program. This is the basic data when calculating.

Next, the data necessary for Pt, ie, the throttle opening α, the opening signal S+sc to the ISC valve 21, and the engine speed N are read.

In P3, a flow passage area (hereinafter referred to as throttle valve flow passage area) Aα in a portion where the throttle valve 6 is mounted is calculated based on the throttle opening degree α. This is determined, for example, by looking up the corresponding value of Aα from the table map shown in FIG. Similarly, in P4, the opening signal 5IS
Bypass area A preset based on e,
is calculated, and the flow path area A is determined in accordance with the following equation (2) in P45.

A=Aα+A, ・・・・・・■ Next, calculate the steady air IQi using P. To calculate this, first divide the total flow path area A by the engine speed N, and then calculate A/N.
is determined, and the corresponding steady air amount QHO value is looked up from a table map as shown in FIG. 5 using this A/N and engine speed N as parameters.

Next, in P7, with 8 and N as parameters, 2 is looked up as a delay coefficient that takes into account the volume of the intake manifold 5 from the table map shown in FIG. 6, and in P, cylinder air IQAcyl is calculated according to the following equation end.

QAcyt=QAcyt” (I K2) +QHX
K2・・・・・・■ However, the value stored in QAeyL':p, the cylinder air amount QAcy [calculated in this way] is
The present invention can be directly applied to an EGi-type engine that injects fuel near the intake port, instead of the Pi-type engine. However, since this embodiment uses the SPi method, the air in the injector section! it Q A i. It is necessary to calculate j, and this calculation is performed using the program shown in FIG. In this program, first, the intake pipe air change amount ΔCM is determined using Pl+ according to the following equation (2). This ΔCM means the amount of air for changing the pressure of the air in the throttle chamber 3 during a transient period with respect to the cylinder air ht Q a Cy t.

ΔCM= KM X (QAcyt QA,,,'
) / N...■ ■ In 2, K and 4 are constants determined according to the volume of the intake manifold 5, and the optimum values are selected according to the model of the engine 1, etc. Next, with P and t, the following formula ■
The injector air amount Q Ar n j is calculated according to the following.

Q A1n1 = QAeyL+ΔCM ・・・・・・
■The Q A i n j obtained in this way has extremely high responsiveness because it uses the throttle valve opening degree α as one of the information parameters, and it is calculated using a table map based on experimental data, so it can be compared with the actual Accurately correlates with the value and has high detection accuracy (high resolution). Furthermore, since existing sensor information is used and only software support by a microcomputer is required, the cost is low. especially,
It is extremely convenient to apply this method to a type in which fuel is injected upstream of the throttle chamber 3, such as the SPi method.

Next, we will discuss the main issue, which is the effect of problem solving.

-i, single point injection (SPi)
In the case of a type that supplies fuel from one place and distributes it to each cylinder, such as the one typified by this type, the vaporization rate of the fuel is influenced by the opening degree of the throttle valve. In other words, in the range where the throttle valve opening is small, the pressure inside the intake pipe is lower than the atmospheric pressure (high negative pressure), so the evaporation rate increases, whereas in the range where the throttle valve opening is large, the evaporation rate increases. decreases.

Therefore, in a driving state where the throttle valve opening is large, such as during acceleration, a portion of the fuel is not vaporized, but flows into the intake pipe as liquid fuel, and becomes densely attached to the pipe wall.

By the way, if you suddenly decelerate (suddenly close the throttle valve) under these conditions, the internal pressure in the intake pipe will suddenly decrease and the negative pressure will rise), and as a result, the liquid fuel that has accumulated on the pipe wall will is suddenly vaporized and the air-fuel ratio of the mixture becomes temporarily excessive?
It becomes a (overrich). Excessive enrichment of the air-fuel ratio reduces the oxidation effect of the three-way catalyst and worsens exhaust emissions (decreases the conversion rate of Co and HC). Furthermore, when the overconcentration exceeds the flammability limit, there is a problem in that misfires and packfires occur.

Therefore, in this embodiment, we focused on the fact that the cause of the above-mentioned problem is a sudden decrease in intake pipe internal pressure (increase in negative pressure) during sudden deceleration, and determined sudden deceleration from the amount of change in throttle valve opening. By increasing the amount of intake air accordingly, the sudden decrease in intake pipe internal pressure is alleviated and the air-fuel ratio is prevented from becoming excessively enriched.

FIG. 8 is a flowchart showing an air-fuel ratio control program based on the above basic principle, and this program is executed once every predetermined time. In the figure, first, the throttle valve opening α is read from the throttle sensor 30 at pzt, and the opening change amount Δα is calculated according to the following equation.

ΔαFullα is also −α1−+ ...■ However, t: Current data sign The amount of change in opening degree Δα represents the amount of change in throttle valve opening degree in a predetermined time, and the predetermined time is determined by the startup interval of this program. Ru. Next, the polarity of the opening change amount Δα is determined at P2□. That is, when the polarity is negative (Δα<0), it is determined that the motor is in a deceleration state, and a table lookup (TLU) of a predetermined combination is performed from the 37 combination data table shown in FIG. 10 using pzt. This table is RAM53
The corresponding optimum data is read out by addressing using the initial value (αL-1) of the throttle valve opening α and the amount of change in opening Δα.

This data is used for idle up solenoid valve (SVI)
), (SVZ), and as the amount of deceleration increases, (SV2) - (SV, ) →
C8V, +S Vz) and their combinations change.

Here, idle up solenoid valve S■,,SV
, have bypass control valves with different areas, for example, the area ratio is SV2 to 1 and SV
+ is set to "2". Therefore, by changing the combination of the idle up solenoid valves S2 and SVI, the area of the bypass passage is changed, and the intake air amount is appropriately increased.

Next, the control region is determined based on the combination of the idle up solenoid valves S VZ and S V + described above in pz4. In other words, times of deceleration that require correction to increase the amount of intake air are times of deceleration that promote vaporization of liquid fuel, such as deceleration while driving at low speeds (liquid fuel is difficult to generate) and times when driving at high speeds. This control is not necessary when there is a small deceleration (vaporization is not promoted). When PX3 determines that it is in the control region, P2 outputs opening signals S1, cl and 5ISC2 to idle up solenoid valves S2 and SVI based on lookup data. The idle up solenoid valves sv2, sv operate based on the above signal and drive the bypass control valve. therefore,
The area of the bypass passage is varied stepwise to control the amount of intake air.

In this embodiment, as shown in FIG. 11, immediately after the start of rapid deceleration, the air amount increases instantaneously, and thereafter,
A correction curve that gradually decreases can be obtained.

In addition, as another embodiment, an ISO valve (Idle
It is also possible to linearly vary the area of the bypass passage using a 5-speed control valve, but this method has the drawback of increasing costs, although it is possible to obtain an ideal correction curve (see Figure 10). There is.

In this embodiment, the sudden deceleration state is determined from the amount of change in the opening degree of the throttle valve, but the present invention is not limited to this. In short, anything that represents a change in intake air amount based on driving demands can be applied. For example, the amount of change in the flow path area Aα of the portion where the throttle valve 6 is installed in the α-N system described above can be used, or the operation amount of the accelerator pedal can be directly extracted and used.

(Effects) According to the present invention, the amount of intake air is corrected to increase according to the amount of change in the throttle valve opening during sudden deceleration, thereby preventing temporary over-enrichment of the air-fuel ratio during the deceleration. This makes it possible to stabilize engine drivability.

[Brief explanation of drawings]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 11 are diagrams showing an embodiment of the present invention, Fig. 2 is an overall configuration diagram thereof, and Fig. 3 is a calculation program for the cylinder air i1 QAcyt. 4 is a table map of the throttle valve flow path area Aα, and FIG. 5 is the total flow path area A
A/N divided by engine speed N and engine speed N
FIG. 6 is a table map of the steady air amount QH with parameter , FIG. 6 is a table map of the delay coefficient of 2, FIG. 7 is a flow chart showing the calculation program for the injector air amount Q a = n =, and FIG. A flowchart showing the air-fuel ratio control program, FIG.
A table map of vH adjustment data, FIG. 10 is a timing chart showing the effect of another method for explaining the effect, and FIG. 11 is a timing chart for explaining the effect. 7... Injector (fuel supply means), 21.
... Air amount variable means, 30 ... Throttle sensor (operating state detection means, opening degree detection means), 32 ... Crank angle sensor (operating state detection means), 50. ... Control unit (deceleration determining means, combination determining means, supply amount determining means), SVl.
・・・・・・Idle up solenoid valve, S■2・
...Idle up solenoid valve.

Claims (1)

[Claims] a) operating state detection means for detecting the operating state of the engine; b) opening detection means for detecting the opening of the throttle valve; and c) detecting the engine from the amount of change in the opening of the throttle valve. a deceleration determination means for determining a deceleration state; d) a combination determination means for determining a combination of opening areas of the bypass control valves based on the output of the opening detection means when the engine shifts to a predetermined operating state; ) a supply amount determining means that calculates the amount of fuel supplied to the engine in one combustion cycle based on the operating state of the engine and outputs a supply signal at a timing for each cylinder; f) based on the output of the supply amount determining means; a fuel supply means for supplying fuel to the engine; g) disposed in a passage bypassing a throttle valve in an intake passage;
A variable air amount variable device having a plurality of the bypass control valves having different areas, and varying the amount of intake air supplied to the engine by operating a predetermined number of the bypass control valves based on a predetermined combination determined by a combination determining means. An air-fuel ratio control device for an internal combustion engine, comprising: means.