JPS58174127A - Air fuel ratio control system of internal-combustion engine - Google Patents

Abstract

PURPOSE:An operating system of an engine with desired logical air fuel ratio by feedback control, in which a quantity of fuel injected from a fuel injection valve provided to an intake side of the engine is controlled in accordance with an output signal from an oxygen sensor provided to an exhaust side of the engine. CONSTITUTION:A controller, which calculates a basic injection amount of fuel from a speed of an internal-combustion engine and its intake air amount, compares a speed N with a relatively lower reference value N0 in a step F20, to branch to a step 21 for the lower while to a step F21' for the higher. Then in steps F21, F26, F29 or F21', F26', F29', whether cooling water temperature T is not higher than T0, larger than T0 and not larger than T1, or not less than T1 or not is decided to determine an upper limit value of a basic injection amount tp, calculated in accordance with each tmeperature, to values t0, t1, t2 (t0>t1> t2) in steps F22, F27, F29 or to values t'0, t'1, t'2 (t'0>t'1>t'2) in steps F22', F27', F29'.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control method for an internal combustion engine, particularly an internal combustion engine in which the air-fuel ratio is controlled by feedback control under predetermined conditions. This is related to the method.

-1- In recent years, as exhaust gas regulations have been tightened and the energy situation has worsened, there has been a demand for an internal combustion engine that burns fuel more efficiently and exhaust gas more cleanly.

In response to these demands, the amount of fuel injected from the fuel injection valve installed on the intake side of the engine is controlled according to the output signal from the oxygen sensor installed on the exhaust side of the engine. A system has been provided that operates at a desired stoichiometric air-fuel ratio using feedback control.

Note that in this method, feedback control is performed only under certain conditions. That is, depending on the load condition, if the air-fuel ratio is maintained at the stoichiometric air-fuel ratio by feedback control, there may be problems such as insufficient engine output. Feedback control of the air-fuel ratio is performed only when the conditions are satisfied, and when the conditions are not satisfied, processing is performed according to the flowchart shown in FIG. 1, for example.

-2= The flowchart in FIG. 1 will be explained below. First, when it is determined that the engine is in a high load state, execution of the program shown below is started, and in step F1, it is determined whether the engine is in the low rotation range, that is, the rotation speed N is smaller than NO. If the determination is "NO", the process moves to step F2. In step F2, the magnitude of the basic injection 1tp of the fuel extracted from the engine speed N and the intake air IQ is compared with the preset upper limit value to of the basic injection amount, and it is determined that "tp≧[0"]. After setting the upper limit 1ito as the value of the injection 111 in step F3, the process proceeds to step F5.On the other hand, when it is determined that l tp<tOJ in step F2, the process proceeds to step F3.
4, the basic injection 1tp is determined as the injection 11t in step F.
Proceed to step 5.

In step F5, since the engine is currently in a high-input state, the injection amount 1 is increased by a predetermined ratio and stored as a value "αXtJ" in the register t. The processing of this routine is completed, and the fuel stored in the register 3-out is outputted to the fuel injection valve at a predetermined timing according to a program (not shown).

Further, when it is determined in step F1 that the engine is at high rotation speed based on the engine rotation speed N, the same processing as that shown in steps F2 to F5 is performed in steps F2= to F5=.

However, with the control method shown in the conventional example explained above, if the engine is not warmed up sufficiently, the fuel is not sufficiently vaporized, so the air-fuel ratio that produces the desired output is reduced, that is, the output air-fuel ratio. The fuel ratio cannot be obtained and the output air-fuel ratio becomes leaner than the output air-fuel ratio.

This caused misfires to occur during acceleration, resulting in uneven rotation and a lack of acceleration response, some said.

An object of the present invention is to provide an air-fuel ratio control method that solves the above-mentioned problems. This purpose is to perform feedback control in an air-fuel ratio control method that performs feedback control of a fuel injector on the intake side based on the output signal of an oxygen sensor provided on the exhaust side under engine conditions that allow feedback control. Based on the engine speed and intake air amount under conditions where
An internal combustion engine characterized in that a basic injection amount of fuel is calculated, an upper limit value is set for the basic injection amount in accordance with engine load, and the upper limit value is changed depending on the temperature of engine cooling water. The sky is burning.

FIG. 2 shows a system of an embodiment of an internal combustion engine to which the present invention is applied. In the figure, 1 is the engine body from the engine body, 2
is the piston, 3 is the spark plug, 4 is the exhaust manifold,
5 is an oxygen sensor provided in the exhaust manifold 4 and detects the residual oxygen concentration in the exhaust gas; 6 is a fuel injection valve that injects fuel into the intake air of the engine body 1; 7 is an intake manifold; 8 is provided in the intake manifold 7. 1 an intake air temperature sensor that detects the temperature of intake air sent to the engine body 1; 9 a water temperature sensor that detects the temperature of engine cooling water; 10 a throttle valve; 11 a throttle valve 10; A throttle position sensor outputs a signal according to the opening degree of the throttle valve 10, a bypass passage 12 is an air passage that bypasses the throttle valve 10, and an idle speed 13 controls the opening area of the bypass passage 12. control valve (
(hereinafter simply referred to as rSC pulp), 14 represents an air flow meter for measuring the amount of intake air, and 15 represents an air cleaner for purifying the intake air. Note that the throttle valve 10 is driven by an accelerator pedal (not shown).

Also, 16 is an igniter that outputs the high voltage necessary for ignition,
17 is a distributor which is connected to a crankshaft (not shown) and distributes the high voltage generated by the igniter 16 to the spark plugs 3 of each cylinder; 18 is installed inside the distributor 17;
A rotation angle sensor that outputs 24 pulse signals per rotation, that is, two rotations of the crankshaft, 19 is a distributor 17Q
) Cylinder discrimination function that outputs a pulse signal once per rotation.
6 - sensor, 20 is an electronic control circuit, 21 is a key switch, 22
each represents a starter motor.

Further, 23 indicates a passage for air to flow bypassing the throttle valve when the resin is cold, that is, a fast idle bypass passage, and 24 indicates an air valve that controls the amount of air passing through the fast idle bypass passage 23. There is.

Note that the air valve 24 operates to open the fast idle bypass passage 23 in order to secure the engine rotational speed necessary for warm-up operation when the engine is cooled down.

FIG. 3 represents a block diagram of the electronic control circuit 20.

In the figure, numeral 30 inputs and calculates the data output from each sensor as described above, that is, the detection means for the III-related state, according to a control program, and also performs processing for controlling the operation of various devices such as the ISO valve 13. A central processor unit (hereinafter simply referred to as CPU), 31 is a read-only memory (hereinafter simply referred to as ROM) in which a control program and initial data are respectively stored;
32 is an electric terminal 7 = random access memory (hereinafter simply referred to as RAM) in which necessary data is read and written; 33 is a key switch 21
Backup RA/Random Access Memory (hereinafter referred to simply as Backup RA) is backed up by a battery so that data necessary for engine operation is retained even when the RA is turned off.
Call it M. ) respectively.

Reference numeral 34 denotes an input port (not shown), a waveform shaping circuit provided as necessary, a multiplexer that selectively outputs output signals from each sensor to the CPU 30, an A/D converter that converts analog signals into digital signals, etc. The provided input section 35 is provided with an output port in addition to an input port (not shown), and a fuel injection valve 6 etc. can be connected to the CP as necessary.
A letter input/output section 36 includes a drive circuit etc. driven based on a control signal from the CPU 30. It represents a path line connecting each element such as the ROM 31, the input section 34, and the input/output section 35, and through which various data are sent.

-8- FIG. 4 is a 70-chart of the control program showing the "basic injection amount first" routine of this embodiment.

This routine starts execution at a predetermined timing, for example, based on a signal from the rotation angle sensor 1g, and first
At step F20, it is determined whether the engine speed N is in a relatively low speed range, that is, a speed range lower than the reference value NO. If it is determined that rN<NoJ, the next step F21
It is determined whether the engine cooling water humidity T determined from the output of the water temperature sensor 9 is lower than TO (for example, 10° C.).

If it is determined that the water GT is less than or equal to To, the process moves to the next step F22, and the basic injection l1ltp is calculated based on the engine speed N and the intake air IQ obtained from the output signal of the air flow meter 14. It is determined whether it is larger than the upper limit value to, and if it is determined that p≧toJ, the process moves to step F23, where the upper limit value to is determined as the chain of injection 11 and the process proceeds to the next step F24. If it is determined in step F22 that the basic injection amount tp is smaller than the upper limit to, that is, tp<toj, then in step F25-9- the tp is determined as the value of the injection amount t, and the process proceeds to the next step F.
24.

Also, in step F21, the water IT is T.

When it is higher, that is, when it is determined that IT>'rOJ, the process moves to step F26, and in step F26, it is further determined whether water 1jMT is lower than T1 (for example, 70°C), and [T≦T1J] If it is determined that there is, the process advances to step F27.

In step F27, the current water IT is
21. The upper limit value t1 of the injection amount when the water temperature is in the range determined by F26 is compared with the basic injection 1tp [tp
If it is determined that t11, the upper limit value t1 is determined as the value of the injection amount in step F28, and then the process moves to step F24, and in step F27, the rt
l) If it is determined that <tlJ, the above step F
In step 25, the basic injection amount tp is determined as the value of the injection amount t■,
The process moves to step F24.

Further, in step F26, if it is determined that the water IT is higher than T1, that is, rT>TI > The upper limit 1t2 of the basic jet tJA1 in the water temperature range of TI
If it is determined that t2J, the process moves to step F30, and after setting the upper limit value t2 as the value of the injection amount t, the process of step F24 is executed, and in step F29, it is determined that tp<t2. If it is determined that the injection amount t is 1, the basic injection amount 1p is determined as the value of the injection amount t in step F25, and then the process proceeds to step F24.

In step F24, since the engine is currently in a high load state, the air-fuel ratio is maintained at the output air-fuel ratio. Increase fuel m″Ij
The process of setting the control value register, t-out\1, which actually drives the fuel injector 6 by multiplying by

On the other hand, if it is determined in step F20 that [N≧NOJ, the same process as in the case where it is determined in step [21-NO-11-] is performed. However, the upper limit value t O=, t 1-1t 2- and the constant α- are the above-mentioned upper limit value t Olt 1, t in consideration of the engine rotation speed N.
It may be a value different from 2 and α.

In the process of this routine described above, the value calculated and set in the register t·out is output to the fuel injection valve 6 at a predetermined timing according to a program (not shown). The upper limit of the value set in the register tout is set to a different value depending on the water temperature range of engine cooling water as described above, and the value is set in the low temperature range (T≦
To), the air-fuel ratio is made richer than in the conventional system, and the output air-fuel ratio is maintained.

The air-fuel ratio of the internal combustion engine of the present invention described above is 1iIII
] The method uses oxygen provided on the exhaust side under engine conditions that allow feedback control. In an air-fuel ratio control method that feedback-controls the intake-side fuel injection valve based on the output signal of a sensor, under conditions where feedback control is not performed, the fuel The present invention is characterized in that the basic injection amount is limited, an upper limit value is set for the basic injection amount in accordance with the engine load, and the upper limit value is changed depending on the temperature of the engine cooling water.

Therefore, according to the present invention, the air-fuel ratio when air-fuel ratio feedback control is not performed in the high negative direction is maintained at the output air-fuel ratio with a large output, and even in the low temperature range of engine cooling water,
It has an effective rack that can maintain the air-fuel ratio at the output air-fuel ratio and improve the responsiveness of the engine during acceleration in a low temperature range.

[Brief explanation of drawings]

Fig. 1 is a flowchart showing a conventional control program, Fig. 2 is a system explanatory diagram of an embodiment to which the method of the present invention is applied, Fig. 3 is a block diagram showing the electronic control circuit, and Fig. 4 is the same. 1 shows a flowchart of the control program. 1... Engine (internal combustion engine) body 6... Fuel injection valve 9... Water temperature sensor 10... Throttle valve -13- 14... Air 70 meter 18... Rotation angle sensor 20... Electronic control circuit agent Patent attorney Tsutomu Setatsu-14-

Claims (1)

[Claims] Prepared on the exhaust side under engine conditions that allow feedback control! In an air-fuel ratio control method that feedback-controls the intake-side fuel injector based on the output signal of the element sensor, when the feedback control is not performed, the fuel Basic jet 1)! An air-fuel ratio control method for an internal combustion engine, characterized in that the basic injection amount is set with an upper limit value corresponding to the engine load, and the upper limit value is changed depending on the temperature of engine cooling water.