JPH01195940A - Air-fuel ratio feed back controller of internal combustion engine - Google Patents

Abstract

PURPOSE:To avoid reduction in fuel consumption ratio and improve the stability of idling operation by setting the cramping point of an compensatory air-fuel ratio feedback value at the time of the idling time according to the temperature of an engine. CONSTITUTION:When a control unit 14 decides that the condition where the air-fuel ratio feedback compensatory coefficient is to be cramped is satisfied, said unit 14 retrieves and finds the cramping value corresponding to the temperature of cooling water detected by a water temperature sensor 18 on the basis of a map in advance stored according to the temperature of cooling water. The cramping value is stored that it is increased over the reference value when the temperature of cooling water is lower. Thus the temperature of cooling water is able to be controlled suitably according to each temperature of cooling water so that the reduction in fuel consumption ratio may be avoided and the idling operation at each temperature of cooling water be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an air-fuel ratio feedback control device for an internal combustion engine, and more particularly to a technique for improving air-fuel ratio feedback control in an engine idling operating state.

<Prior art> As an electronically controlled fuel injection type internal combustion engine having an air-fuel ratio feedback control function, conventional
There is one as shown in Publication No. 1.

That is, an oxygen sensor is installed in the exhaust system to detect the oxygen concentration in the exhaust gas, which is closely related to the air-fuel ratio of the engine intake air-fuel mixture, and the output signal of this oxygen sensor and the slice level corresponding to the target air-fuel ratio (theoretical air-fuel ratio) are By comparing with This is to set an air-fuel ratio feedback correction coefficient LAMBDA for correcting the amount.

Here, the value of the air-fuel ratio feedback correction coefficient LAMBDA is changed by proportional-integral (PI) control to ensure stable control. This compares the output signal of the oxygen sensor with the slice level, and if there is a difference between the slice level and the slice level, the air-fuel ratio is increased without making the air-fuel ratio suddenly richer or leaner. In the case of rich (lean), first lower (raise) the air-fuel ratio feedback correction coefficient LAMBDA by a predetermined proportional bone (P minute), then gradually lower (raise) it by a predetermined integral minute (1 minute). ), and controls the air-fuel ratio to become leaner (richer).

However, under certain conditions in which air-fuel ratio feedback control is not performed, such as during startup, high-load operation, or idling operation where the engine is to be operated at a richer side than the target air-fuel ratio in normal operating conditions, the above-mentioned air-fuel ratio feedback correction The coefficient LAMBDA is clamped to a constant value.

In particular, the air-fuel ratio feedback correction coefficient LAMBD^ is clamped in the idling state by the correction coefficient LAMB.
This is to avoid deterioration of the stability of idling operation due to surges caused by air-fuel ratio fluctuations due to changes in DA.

<Problem to be solved by the invention> By the way, it is difficult to determine the stability in the idling state when the machine is cold (
Of course, stability is better during warm-up (in the middle of warm-up) and when fully warmed up, but at present, the air-fuel ratio feedback correction coefficient LAMBD is
The clamp value of A is set. This was done in consideration of the idling stability and fuel efficiency when the engine is completely warmed up, and there was a problem in that it was disadvantageous in terms of the stability of idling operation when the engine was cold.

In other words, as shown in Fig. 5, in the case of a constant air-fuel ratio, the stability of idling becomes worse when the engine is cold (the lower the cooling water temperature Tw, which represents the engine temperature), but the stability of idling when the engine is cold deteriorates. If the air-fuel ratio is rich-corrected at idle by setting the clamp value of the air-fuel ratio feedback correction coefficient LAMBDA to a large value in order to ensure performance, then when the engine is completely warmed up, unnecessary rich correction may result in deterioration of idle stability and fuel efficiency. Therefore, the clamp value of the air-fuel ratio feedback correction coefficient LAMBD^ was set so that the air-fuel ratio is controlled to an air-fuel ratio that provides stability and good fuel efficiency during idling operation when fully warmed up.

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to improve the idling stability when the engine is cold while ensuring stability during idling operation and good fuel efficiency when the engine is fully warmed up. .

<Means for Solving the Problems> In order to achieve the above object, the present invention configures an air-fuel ratio feedback control device for an internal combustion engine, including the following means A to ■, as shown in FIG. .

(A) Engine operating state detection means for detecting the engine operating state (B) Basic fuel injection amount setting means for setting the basic fuel injection amount based on the engine operating state detected by the engine operating state detection means (C) Engine exhaust An air-fuel ratio detecting means (D) for detecting the air-fuel ratio of the engine intake air-fuel mixture by detecting the air-fuel ratio by comparing the air-fuel ratio detected by the air-fuel ratio detecting means with a target air-fuel ratio to determine the actual air-fuel ratio. Feedback correction value setting means (E) for setting a feedback correction value for correcting the basic fuel injection amount so as to approximate the fuel ratio; (F) engine temperature detection means for detecting engine temperature; (F) engine temperature detection means for detecting the engine temperature detected by the engine temperature detection means; Clamp value setting means (G) for variably setting a clamp value of the feedback correction value in a predetermined idle operating state in accordance with engine temperature; Feedback correction value clamping means (El) clamps the feedback correction value to the clamp value set by the basic fuel injection amount set by the basic fuel injection amount setting means, and the feedback correction value set by the feedback correction value setting means or Fuel injection amount setting means (I) for setting the fuel injection amount based on the feed balance 2 correction value clamped by the feedback correction value clamping means; a drive pulse signal corresponding to the fuel injection amount set by the fuel injection amount setting means; The basic fuel injection amount setting means B is the engine operating state detection means A.
The basic fuel injection amount is set based on the engine operating state detected by the feedback correction value setting means, and the basic fuel injection amount is set so that the actual air-fuel ratio detected by the air-fuel ratio detection means C approaches the target air-fuel ratio. Set the feedback correction value to correct the amount.

Further, the clamp value setting means F sets the clamp value of the feedback correction value according to the engine temperature detected by the engine temperature detection means E. The feedback correction value clamping means G clamps the feedback correction value to the clamp value set by the clamp value setting means F in a predetermined idle operating state.

The fuel injection amount setting means H uses the basic fuel injection amount set by the basic fuel injection amount setting means B and the feedback correction value set by the feedback correction value setting means, or clamps it by the feedback correction value clamping means G in a predetermined idling operating state. A fuel injection amount is set based on the feedback correction value, and fuel corresponding to this fuel injection amount is injected and supplied to the engine by the fuel injection means I on and off.

<Example> An embodiment of the present invention will be described below based on the drawings.

In FIG. 2, air is taken into the engine 1 through an air cleaner 2, a throttle body 3, and an intake manifold 4. As shown in FIG.

A throttle valve 5 that operates in conjunction with an accelerator pedal (not shown) is provided within the throttle body 3, and a fuel injection valve 6 serving as fuel injection means is provided upstream thereof. The fuel injection valve 6 is an electromagnetic fuel injection valve that opens when the solenoid is energized and closes when the energization is stopped.
The valve is energized by a drive pulse signal from a control unit 14, which will be described later, to open the valve, and fuel is injected and supplied under pressure from a fuel pump (not shown) and adjusted to a predetermined pressure by a pressure regulator. Although this example is a single-point injection system, it may be a multi-point injection system in which a fuel injection valve is provided for each cylinder in a branch of the intake manifold 4 or in an intake boat of the engine.

An ignition plug 7 is provided in the combustion chamber of the engine 1.

A high voltage generated by an ignition coil 8 is applied to the ignition plug 7 via a distributor 9 based on an ignition signal from a control unit 14, thereby igniting a spark to ignite and burn the air-fuel mixture.

From engine 1, exhaust manifold 10. Exhaust duct 11
．． Exhaust gas is discharged via the three-way catalyst 12 and the muffler 13.

The control unit 14 includes a CPU and a ROM.

Equipped with a microcomputer that includes a RAM, an A/D converter, and an input/output ink face, the computer receives occupancy signals from various sensors, performs arithmetic processing as described below, and outputs signals from the fuel injection valve 6 and ignition coil 8. control the operation of

As the various sensors, a potentiometer type throttle sensor 15 is provided on the throttle valve 5,
A voltage signal corresponding to the opening degree α of the throttle valve 5 is output.

Also included in the throttle sensor 15 is an idle switch 1 that is turned on when the throttle valve 5 is in the fully closed position (idle position).
6 is provided.

Further, a crank angle sensor 17 is built into the distributor 9 and outputs a position signal for every 2'' crank angle and a reference signal for every 180'' crank angle (in the case of 4 cylinders).

Here, the engine rotation speed N can be calculated by measuring the number of pulses of the position signal or the period of the reference signal per unit time.

In addition, a water temperature sensor 18 as an engine temperature detection means for detecting an engine cooling water temperature Tw representing the engine temperature, a vehicle speed vs.
A vehicle speed sensor 19 and the like for detecting p is provided.

These throttle sensors 15. The crank angle sensor 17 and the like are means for detecting the engine operating state.

Further, the exhaust manifold 10 is provided with a 0□ sensor 20. The 02 sensor 20 is a known sensor whose electromotive force suddenly changes when the air-fuel mixture is combusted near the stoichiometric air-fuel ratio, which is the target air-fuel ratio.

Therefore, the 0□ sensor 20 is an air-fuel ratio (rich/lean) detection means.

Further, a battery 21 is connected to the control unit 14 via an ignition key switch 22 as its operating power source and for detecting power supply voltage. In addition, as an operating power source for the RAM in the control unit 14, in order to retain the memory contents even after the ignition key switch 22 is turned off, the battery 21 is connected not through the ignition key switch 22 (but through an appropriate stabilized power source). be.

Here, the CPU of the microcomputer built in the control unit 14 performs calculation processing according to the programs (fuel injection amount calculation routine, proportional/integral control routine) on the ROM shown as flowcharts in FIGS. Controls fuel injection.

The functions of the basic fuel injection amount setting means, the feedback correction value setting means, the clamp value setting means, the feedback correction value clamping means, and the fuel injection amount setting means are achieved by the program.

In the fuel injection amount calculation routine shown in FIG.
(Denoted as Sl in the figure. The same applies hereinafter), the throttle valve opening α detected based on the signal from the throttle sensor 15 and the engine rotation speed N calculated based on the signal from the crank angle sensor 17. Load.

In step 2, the intake air flow rate Q corresponding to the throttle valve opening α and the engine speed N is determined in advance through experiments, etc., and Q corresponding to the actual α and N is determined by referring to a map on the ROM. Search and load.

In step 3, a basic fuel injection amount TI)=KXQ/N (K is a constant) corresponding to the intake air flow rate per unit rotation is calculated from the intake air flow rate Q and the engine speed N.

In step 4, the rate of change in the throttle valve opening α detected based on the signal from the throttle sensor 15 or the acceleration correction due to switching from ON to OFF of the idle switch 16 is detected based on the signal from the water temperature sensor 18. Various correction coefficients C0EF including a water temperature correction amount corresponding to the engine cooling water temperature Tw are set.

In step 5, the learning correction coefficient for each area is stored in correspondence with the engine speed N representing the engine operating state and the basic fuel injection amount Tp, and a map on the RAM is referred to, and the actual engine speed N is determined. , search and read the area-specific learning correction coefficient KMAP corresponding to the basic fuel injection amount Tp. This area-specific learning correction coefficient K MAP is set by learning the deviation of the air-fuel ratio feedback correction coefficient LAMBDA from the reference value (1) for each predetermined area. The basic fuel injection amount Tp is corrected by this area-specific learning correction coefficient K MAP so that the base air-fuel ratio obtained by the fuel injection amount Ti calculated without the air-fuel ratio feedback correction coefficient LAMBDA is made to match the target air-fuel ratio, During the air-fuel ratio feedback control, the fuel injection amount Ti is further corrected using the air-fuel ratio feedback correction coefficient LAMBD^.

The area-specific learning correction coefficient K MAP map is based on 8
Areas of the engine operating state are divided into grids of approximately 8x, and area-specific learning correction coefficients KMAP are stored for each area, and when learning has not started, all initial values are 0.
Let me remember this.

In step 6, it is determined whether the vehicle is in a predetermined idling state. Here, the predetermined idling state is, for example, when the idle switch 16 is ON and the transmission is in a neutral state, or when the idle switch 16 is ON and the vehicle speed vSP detected by the vehicle speed sensor 19 is below a predetermined value. It is.
r When it is determined in step 6 that the current operating state is the predetermined idle switch, the process proceeds to step 7 where the air-fuel ratio feedback correction coefficient LAMBDA is set in a proportional/integral control routine (feedback correction coefficient setting routine) to be described later. Load.

On the other hand, if it is determined in step 6 that the current operating state is not the predetermined idling operating state, the process proceeds to step 8 where it is determined whether a condition for clamping the air-fuel ratio feedback correction coefficient LAMBDA is satisfied. here,
The clamp condition is, for example, when the air-fuel ratio feedback correction coefficient LAMBDA is within a predetermined range (±12% of the reference value) including the reference value (1).

In step 8, the air-fuel ratio feedback correction coefficient LAMBD is
When it is determined that the conditions for clamping A are satisfied, the process proceeds to step 9 to set the clamp buoy direct, and when it is determined that the clamp conditions are not satisfied, the process proceeds to step 7 to perform air-fuel ratio feedback control. Read the air-fuel ratio feedback correction coefficient LAMBDA.

In step 9, a corresponding clamp value is searched based on the cooling water temperature Tw detected by the water temperature sensor 18 from a map of clamp values of the air-fuel ratio feedback correction coefficient LAMBDA stored in advance according to the cooling water temperature Tw. and ask.

The clamp value is set to be a larger value than the reference value (1) as the cooling water temperature Tw is lower, so that when the cooling water temperature Tw is low and the engine is cold, the air-fuel ratio feedback correction coefficient LAMBDA is This is so that the rich correction ratio is increased. That is, during idling operation in which the air-fuel ratio feedback correction coefficient LAMBDA is clamped to suppress air-fuel ratio fluctuations and achieve stable operation, by setting the clamp value according to the cooling water temperature Tw, the optimum airflow for each cooling water temperature Tw can be set. It becomes possible to control the fuel ratio, and it is possible to stabilize idling operation at each cooling water temperature Tw while avoiding deterioration of fuel efficiency.

In step 10, a voltage correction numerator s is set based on the voltage value of the battery 21. This is to correct changes in the injection amount (effective valve opening time) of the fuel injection valve 6 due to fluctuations in battery voltage.

In step 11, the fuel injection amount Ti is calculated according to the following equation.

T i = T p XC0EFX (LAM
BDA+KMAF)+TsIn step 12, the calculated fuel injection amount Ti is set in the output register. As a result, at a predetermined fuel injection timing synchronized with the engine rotation (for example, every rotation A), a drive pulse signal having a pulse width of Ti is applied to the fuel injection valve 6, and fuel injection is performed.

FIG. 4 shows a proportional/integral control routine, which is executed every predetermined time (for example, 10 m5), whereby the air-fuel ratio feedback correction coefficient LAMBDA is set under proportional/integral control, and this air-fuel ratio feedback correction coefficient LAMBDA
A controls the actual air-fuel ratio to the target air-fuel ratio (theoretical air-fuel ratio).

In step 21, it is determined whether the current operating state is in a region where air-fuel ratio feedback control (λ control) is performed, and if the current operating state is an operating state where air-fuel ratio feedback control is not performed, this routine is terminated.

When the operating state is one in which feedback control of the air-fuel ratio is performed, the process advances to step 22 and the output voltage of the sensor 20 is set to 0□■. 2 is read, and in the next step 23, rich/lean of the actual air-fuel ratio with respect to the stoichiometric air-fuel ratio is determined by comparing it with the slice level voltage v1° corresponding to the stoichiometric air-fuel ratio which is the target air-fuel ratio.

When the air-fuel ratio is lean (■.2ku■,,,f), the process proceeds from step 23 to step 24 and changes from rich to lean.
It is determined whether or not it is the time of reversal (immediately after reversal), and when it is reversed, the process proceeds to step 25 and the feedback correction coefficient LA is
MBDA is increased by a predetermined proportionality constant of 2 minutes relative to the previous value. Otherwise, the process proceeds to step 26, where the feedback correction coefficient LAMBDA is increased by a predetermined integral constant of 1 minute relative to the previous value, and thus the feedback correction coefficient LAMBDA is
Increase DA at a constant slope.

Note that P>>1.

When the air-fuel ratio is rich (■.2>■, .f), the process proceeds from step 23 to step 27, where it is determined whether it is the time of determination from lean to rich (immediately after reversal), and when the air-fuel ratio is reversed, step 28 is performed. Then, the feedback correction coefficient is decreased by a predetermined proportionality constant of 2 from the previous value. Otherwise, proceed to step 29 and set the feedback correction coefficient LAMBD.
A is decreased by a predetermined integral constant of 1 with respect to the previous value, and thus the feedback correction coefficient LAMBDA is decreased at a constant slope.

In this embodiment, a different clamp value is set for each cooling water temperature Tw, but it is possible to allocate each of a plurality of clamp values to a predetermined range of cooling water temperature Tw and set the clamp value in stages. It may be changed.

(Effects of the Invention) As described above, according to the present invention, in a device that prevents surge generation during idling by clamping the air-fuel ratio feedback correction value during idling, the clamp value is adjusted according to the engine temperature. is set, the clamp value at each engine temperature is optimized, and there is an effect that the stability of idling operation can be improved while avoiding deterioration of fuel efficiency.

[Brief explanation of the drawing]

Fig. 1 is a functional block diagram showing the configuration of the present invention, Fig. 2 is a system diagram showing an embodiment of the invention, Figs. 3 to 4 are flow charts showing control contents in the above embodiment, and Fig. 5 is a graph showing the relationship between cooling water temperature and stability of idling operation to explain the conventional problems. 1... Engine 6... Fuel injection valve 14... Control unit 15... Throttle sensor 1
6... Idle switch 17... Crank angle sensor 18... Water temperature sensor 20... 02 sensor Patent applicant Japan Electronics Co., Ltd. Representative Patent attorney Fujio Sasashima Figure 5

Claims (1)

[Scope of Claims] An engine operating state detection means for detecting an engine operating state; a basic fuel injection amount setting means for setting a basic fuel injection amount based on the engine operating state detected by the engine operating state detection means; an air-fuel ratio detection means for detecting exhaust components and thereby detecting an air-fuel ratio of an engine intake air-fuel mixture; and an air-fuel ratio detected by the air-fuel ratio detection means for comparing the air-fuel ratio detected by the air-fuel ratio with a target air-fuel ratio to determine the actual air-fuel ratio. Feedback correction value setting means for setting a feedback correction value for correcting the basic fuel injection amount so as to approximate the fuel ratio; Engine temperature detection means for detecting engine temperature; and Engine temperature detected by the engine temperature detection means. clamp value setting means for variably setting a clamp value of the feedback correction value in a predetermined idling operating state according to the feedback correction value setting means; feedback correction value clamping means for clamping to a clamp value set by the basic fuel injection amount setting means, and a feedback correction value set by the feedback correction value setting means or clamping by the feedback correction value clamping means. a fuel injection amount setting means for setting the fuel injection amount based on the feedback correction value, and a fuel injection amount setting means for supplying fuel to the engine on and off in response to a drive pulse signal corresponding to the fuel injection amount set by the fuel injection amount setting means. An air-fuel ratio feedback control device for an internal combustion engine, comprising: a fuel injection means for supplying fuel by injection;