JPS6181536A - Method of controlling feed of fuel during idle running of internal-combustion engine - Google Patents

Abstract

PURPOSE:To stabilize idle running, by a method wherein, when the temperature value of an engine and the number value of revolutions of an engine are below a given value, a fuel amount is controlled so that the air-fuel ratio of fuel-air mixture is adjusted to a low value on the fuel excess rich side. CONSTITUTION:When, in a step 505, a water temperature value TW of an engine is below a given discriminating water temperature value TWIDL, progress is made to a step 507. When, in the step 507, the number value Ne of revolutions of an engine is below the given discriminating number value NIDL of revolutions, a correction factor KIDL is set to a given value XIDLO in a step 508. It is decided that an engine is in a running region in that stable operation is difficult to make, and fuel-air mixture is forced into a rich condition. This enables stabilization of idle running of an engine.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an idling fuel supply control method for stabilizing idling operation when a release condition for air-fuel ratio feedback control is satisfied when an internal combustion engine is idling.

(Technical background of the invention and its problems) In an internal combustion engine, an oxygen concentration detector (hereinafter referred to as "02 sensor") detects the concentration of exhaust gas components, such as oxygen, in exhaust gas.
), and this 02 sensor outputs ○,
Feedback control of the air-fuel ratio of the air-fuel mixture supplied to the engine to the stoichiometric air-fuel ratio value based on the Xl1 degree signal (
The engine is equipped with an exhaust gas purification device installed in the engine's exhaust system to improve the exhaust gas characteristics of the internal combustion engine. to reduce the amount of harmful substances emitted from the

For example, a three-way catalyst device is used as an exhaust gas purification device.

A device that simultaneously purifies the three components of Co, HC, and NOx in exhaust gas is known.

By the way, if the temperature of the 02 sensor itself is low, it will not be activated and will not be able to output the correct value of the 02'a degree signal. In particular, when the exhaust gas temperature is low, such as during idling when the engine speed is low, the temperature of the 02 sensor itself tends to become low. Therefore, in such a case, the above 02
Feedback control is not possible, and it becomes difficult to accurately set the air-fuel ratio at idle to a required value, resulting in deterioration of exhaust gas characteristics and, in particular, increased emissions of Co and HC.

Further, when the engine is idling at a low speed, the engine temperature also decreases, and the amount of CO and HC emissions increases. Moreover,
If the exhaust gas temperature is low, not only will the catalyst bed temperature of the three-way catalyst device decrease and the purification ability of the three-way catalyst will decrease, but also the air-fuel mixture supplied to the engine will have a stoichiometric air-fuel ratio (A/F = 14.7).
When it is on the richer side, the CO and HC purification efficiency of the three-way catalyst further decreases. On the other hand, when the air-fuel mixture is on the lean side, the amount of CO and HC itself discharged from the engine decreases, and the purification rate of CO and HC in the three-way catalyst increases. Therefore, in view of the above-mentioned engine exhaust gas characteristics and three-way catalyst characteristics, when the cancellation condition for 02 feedback control is satisfied, such as when the Q2 sensor is in an inactive state while the engine is idling, the air-fuel mixture is made lean. CO and HC
A fuel supply control method for reducing the amount of emissions has been proposed (for example, Japanese Patent Application Laid-open No. 35136/1983).

By the way, the engine temperature when starting the engine cold is
For example, when the temperature is 55° C. or lower, drivability during idling tends to deteriorate. In particular, the lower the idle speed, the more significant the deterioration in drivability becomes.6 However, with the above-mentioned conventional method, regardless of engine temperature and engine speed,
If the condition for canceling the feedback control is satisfied and the air-fuel mixture is made lean, engine stability may be impaired and engine stall may occur.

(Object of the Invention) The present invention has been made in order to solve the above problems, and is an idling engine that stabilizes idling operation when the release condition for air-fuel ratio feedback control is satisfied when the internal combustion engine is idling. The purpose of the present invention is to provide a fuel supply control method.

(Structure of the Invention) For this purpose, according to the present invention, the amount of fuel supplied to the internal combustion engine is determined by an output signal from an exhaust gas component concentration detection means disposed in the exhaust passage of the internal combustion engine. On the other hand, when the internal combustion engine is in a predetermined operating state at idle, the feedback control of the fuel supply amount is stopped so that the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is lower than the stoichiometric air-fuel ratio. In the idle fuel supply control method of controlling the fuel supply amount to a large value on the fuel lean side, the engine temperature of the internal combustion engine is detected, the engine rotation speed is detected, and the internal combustion engine is brought into the predetermined operating state. Yes, and when the detected engine temperature is below a predetermined temperature value and the detected engine rotation speed is below a predetermined rotation value, the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is a smaller value on the fuel rich side than the stoichiometric air-fuel ratio value. A method for controlling fuel supply at idle time for an internal combustion engine 6 is provided, which controls the fuel supply amount so that the amount of fuel supplied is as follows.

(Example of the invention) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of the apparatus of the present invention.

Reference numeral 1 indicates, for example, a four-cylinder internal combustion engine, and an intake pipe 2 is connected to the engine 1. A throttle body 3 is provided in the middle of the intake pipe 2, and a throttle valve 3' is provided inside. A throttle valve opening (θH) sensor 4 is connected to the throttle valve 3'.
The valve opening is converted into an electrical signal and sent to an electronic control unit (hereinafter referred to as rECUJ) 5.

A fuel injection valve 6 is provided in the intake pipe 2 between the engine 1 and the throttle hob 43. The fuel injection valve 6 is provided for each cylinder in the intake pipe 2 slightly upstream of an intake valve (not shown). The fuel injection valve 6 is connected to a fuel pump (not shown). The fuel injection valve 6 is electrically connected to the ECU 3, and the opening time of fuel injection is controlled by signals from the EC and U5.

On the other hand, an absolute pressure (PBA) sensor 8 is provided downstream of the throttle valve 3' of the throttle body 3 via a pipe 7. The pressure signal is sent to the ECU 3.

The engine 1 main body is provided with an engine water temperature (Tw) sensor 9. This sensor 9 consists of a thermistor, etc., and is inserted into the circumferential wall of the engine cylinder filled with cooling water, and the detected water temperature signal is sent to E C, U 5. supply to.

Engine speed sensor (hereinafter referred to as rNe sensor) 1
0 and a cylinder discrimination sensor 11 are attached around the camshaft or crankshaft (not shown) of the engine, the former 10 detects a predetermined crank angle position every 18° rotation of the engine crankshaft, and the latter 11 detects a specific cylinder. A pulse signal is output at each predetermined crank angle position, and these pulse signals are sent to the ECU 3.

A three-way catalyst 13 is disposed in the exhaust pipe 12 of the engine 1 to purify HC, CO, and NOx components in the exhaust gas. An 02 sensor 14 is inserted into the exhaust pipe 12 upstream of the three-way catalyst 13, and this sensor 14 detects the oxygen concentration in the exhaust gas and supplies an 02 concentration signal to the ECU 3.

Further, other parameter sensors 15 such as an atmospheric pressure sensor are connected to the ECU 5, and the other parameter sensors 15 supply their detection signals to the ECU 3.

The ECU 3 adjusts the TDC based on the various parameter signals mentioned above.
The fuel injection time ToutT given by the following equation during which the injection valve is opened in synchronization with the signal is calculated.

Tou Ding = T i XKID and XKo, XKLs XK
, +2...(1) Here, Ti indicates the basic fuel injection time of the fuel injection valve 6, and this basic injection time is stored in the memory in the ECUS based on, for example, the intake pipe absolute pressure PaA and the engine speed Ne. Read from the device. KIDL is an idle correction coefficient according to the present invention, and its value is set by a KID system subroutine to be described later.

Ko2 is a 02 feedback correction coefficient, and its value is set by the Ko subroutine described later. KLS
is a lean correction coefficient, and the engine
When the load on the engine is in the lean operating range shown in the figure below.

This is a correction coefficient set to lean the air-fuel ratio of the air-fuel mixture. K4 and K2 are respectively a correction coefficient and a correction variable calculated according to various engine parameter signals,
It is set to a predetermined value that allows optimization of fuel consumption characteristics, engine acceleration characteristics, and other fuel characteristics depending on the engine operating state.

ECU3 calculates the fuel injection time Tou as described above.
Based on T, a drive signal for opening the fuel injection valve 6 is output.

FIG. 3 is a block diagram showing the circuit configuration inside the ECU 3 in FIG. 1, in which the pulse signal from the Ne sensor 10 in FIG. Processing unit (hereinafter referred to as rCPUJ)
The signal is supplied to the Me counter 503 as an interrupt signal to start a program to be described later, and is also supplied to the Me counter 502 . The Me counter 502 counts the time interval from the input of the previous predetermined position signal from the Ne sensor 11 to the input of the current predetermined position signal, and the counted value Me is proportional to the reciprocal of the engine rotation speed Ne. Me counter 502 supplies this counted value Me to CPU 503 via data bus 510.

Absolute pressure sensor 8, engine water temperature sensor 9, o2 in Fig. 1
After each output signal from various sensors such as sensor 14 is corrected to a predetermined voltage level by a level correction circuit 504, it is sequentially sent to an A/D converter 506 by a multiplexer 505.
supplied to The A/D converter 506 sequentially converts the output signals from the aforementioned sensors into digital signals and supplies the digital signals to the CPU 503 via the data bus 510.

The CPU 503 further connects a read-only memory (hereinafter referred to as rROMJ) 507 and a random access memory (hereinafter referred to as rRAMJ) 508 via a data bus 510.
The RAM 508 temporarily stores the calculation results of the CPU 503t-, and is connected to the RO drive circuit 509.
The M507 stores control programs and the like executed by the CPU 303.

The CPU 503 stores the fuel injection times To+, rr of the fuel injection valve 6 according to the various engine parameter signals described above according to the ROM 507 L knee storage sales control program.
These calculated values are supplied to the drive circuit 509 via the data bus 510. The drive circuit 509 supplies the fuel injection valve 6 with a drive signal for opening the fuel injection valve 6 according to the calculated value.

FIG. 4 shows a flowchart of the KO2 subroutine for setting the 02 feedback correction coefficient value KO□, which is executed within the CPU 503 of FIG.

First, in step 401, it is determined whether activation of the 02 sensor 14 in FIG. 1 has been completed. As a method for determining activation of the 02 sensor, for example, an internal resistance detection method is known in which a required current is passed through the 02 sensor and activation is diagnosed as completed when the output voltage of the 02 sensor crosses a reference voltage and falls. ing. If the activation has been completed (the determination result in step 401 is affirmative (Yes)), the process proceeds to step 402.

In step 402, it is determined whether the engine water temperature value Tw is greater than a predetermined determination water temperature value T w o (for example, 70° C.). When the engine temperature becomes lower than the predetermined water temperature value Two Driving tends to become unstable. For this reason, the amount of fuel supplied is increased to enrich the air-fuel mixture. In order to stop the 02 feedback control when the amount of fuel is increased, that is, when the air-fuel mixture is enriched, it is determined based on the engine water temperature whether or not the engine is in an operating state where the amount of fuel should be increased. If the engine water temperature value Tν is larger than the predetermined determination water temperature value Two□, it is determined that there is no need to increase the amount of fuel, and the process proceeds to step 406.

On the other hand, if at least one of the steps 401 and 402 is negative (NO), it is determined that the engine is in an operating state in which the 02 feedback control should be stopped, and the process proceeds to step 403, where the engine is in the idle operating region. Determine whether it exists or not. In the idle operating region, for example, the engine speed Ne is lower than a predetermined discrimination rotation value N+ot,a (for example, 1200 rpm), and the absolute pressure in the intake pipe is also lower than a predetermined discrimination absolute pressure value PBAIDL (for example, 360 m m
Hg ) is the lower operating region and is shown in FIG. 2 as region ■. If the determination result in step 403 is negative (NO), it is assumed that the engine is in a region other than the idle operating region, and the correction coefficient value Ko is set to 1.0 (step 404), and the program is terminated. On the other hand, if the determination result in step 403 is affirmative (Yes), that is, if the engine is in the idle operating region, the correction coefficient value K o is set to the KO2 value applied when the engine is in the 02 feedback operating region, which will be described later. average value K
REP is set (Step 405), and this program is ended.

Here, the reason why the correction coefficient value KO□ is set to be different from the average value will be described below. Specific operating conditions of the engine (e.g. lean operating conditions, high load operating conditions).

Open-loop control applies preset coefficients corresponding to these specific operating conditions to obtain the predetermined air-fuel ratio that best suits each specific operating condition. The aim is to improve engine fuel efficiency and driving performance.

In this way, during open-loop control, it is desirable to obtain a preset predetermined air-fuel ratio using the setting coefficients, but manufacturing variations in various detectors for engine operating conditions, fuel injection device drive control system, etc. There is a high possibility that the actual air-fuel ratio will deviate from the predetermined air-fuel ratio due to changes over time, and in such a case, the required stability of engine operation and driving performance will not be obtained. Therefore, EP is calculated and stored based on the average value of the correction coefficient values KO2 applied during 02 feedback control, and the correction coefficient KO□ is applied during open loop control.
By setting KREP to the average value, the air-fuel ratio during such open-loop control can be controlled to a value closer to the predetermined air-fuel ratio corresponding to each specific operating state.

Note that when the engine is in the operating range where step 405 is executed, the idle correction coefficient KIDL according to the present invention is set to the value XIDL by a program to be described later.

Both steps 401 and 402 are affirmative (Ye
In the case of s), the process proceeds to step 406, where it is determined whether the engine is in the 02 feedback operating region. 02 feedback operation area is the shaded area in Figure 2 (
If the 6 engines shown as (■ and ■) are in the 02 feedback operation region, a correction coefficient value KO□ is calculated according to the 02a degree signal value from the 02 sensor, and feedback control is performed according to the calculated KO□ value. At the same time, 0
The average value of the two values! Calculate EP (step 407)
.

The average value and the error are calculated using one of the following methods.

KHp=””' ・K o , p + ・K
22p'-C A A ... (2) However, Ko and p are 0 □ K immediately before or after the operation in which the sensor inverts its output level (hereinafter referred to as "P-term operation")
O□ value, A is a constant (for example, 256), CIIEP is a variable, set to an appropriate value between 1 and A, KR
l:,' is the average value of KO□ obtained up to the previous time. In this case, the values are stored in the storage device without being erased even if the engine is stopped and then restarted.

Since the ratio of the Ko2ρ value to the value during each P term operation changes depending on the value of the variable Crr, this CREP value can be adjusted according to the specifications of the target 02 feedback control device, engine, etc. By setting an appropriate value within the range, the optimum value of E can be obtained.

As mentioned above, the KEEP value is calculated based on the KO□P value immediately before or after the P term operation, but the reason for this is that the KEEP value is calculated based on the KO The air-fuel ratio of the engine mixture is the stoichiometric air-fuel ratio (
= 14.7), and as a result, it is possible to obtain the average value of the correction coefficient fiK O, when the air-fuel ratio of the air-fuel mixture is close to the stoichiometric air-fuel ratio. It is possible to calculate the KeEP value that is most suitable for the operating conditions.

Also, the average value KREP of the correction coefficient value KO□ is calculated using the above formula (2).
It can also be calculated using a linear equation instead of .

However, KO2PJ is the P value j times before the current P term operation.
The Ko2p value generated during the term operation, B is a constant, and is the number of P term operations (02 sensor inversion cycles). The larger the value of the constant B, the greater the Ko2p value during each P-term operation. Since the ratio to the p value changes, similarly to equation (2), the B value is set to an appropriate value depending on the specifications of the target 02 feedback control device, engine, etc.

As shown in equation (3), the average value KREP may be obtained by integrating the KO□pj values during each P-term operation from the current P-term operation to B times before each occurrence.

Furthermore, according to the above equations (2) and (3), the K7ε2 value is updated each time the Ko2p occurs during each 02 feedback control by introducing that value into the equation each time, so the engine's Is the average value sufficiently reflecting the operating condition? can always be obtained.

If the determination result in step 406 is negative (NO), that is, if the engine is in the open loop control operating region, the 02 feedback control is canceled and the correction coefficient value KO□
is set to the average value (step 408), and the program is terminated. The open-loop control operation region is, for example, region I (lean operation region) and region ■ (
The lean operation region I includes the absolute pressure P in the intake pipe when the engine is decelerating. The discrimination value PBA is set to a larger value as the engine speed Ne increases.
The region below LS, low rotation operating region ■ is the engine rotation speed N
e is less than or equal to the above-mentioned discrimination value N and Op, and the intake pipe absolute pressure PE
A region where IA is between the discrimination value P8AIDL (for example, 360 mmHg) and the high load region discrimination value PBAIIOT set according to the engine speed Ne, the high load operation region V
When the intake pipe absolute pressure PBA is the above-mentioned discrimination value PBA at high load,
The region above WOT, the high-speed operation region (2), is a region where the engine speed Ne is above the discrimination value NHOP (for example, 4000 rpm).

FIG. 5 shows a flowchart of a DL subroutine executed in the CPU 503 of FIG. 3 for setting the idle correction coefficient value KIDL.

First, it is determined whether or not the engine is in the aforementioned lean operating region (region I in Fig. 2) (step 501). If the engine is in the lean operating region, the idle correction coefficient KIDL is set to a value of 1.
．． OL: ;1 (step 5o2), this program ends.

If the determination result in step 501 is negative (NO), that is, if the engine is not in the lean operating region, the valve opening value oTH of the throttle valve 3' in FIG. 1 is the predetermined determination opening value θID.
It is determined whether or not it is smaller than L (for example, a value 1° larger than the throttle valve full opening degree) (step 503).

If the oTH value is greater than the oIDL value (step 503
If the determination result in step 502 is negative (No)
Proceed to set the correction coefficient KIDL to a value of 1.0 and eT
If the H value is smaller than the oIDL value (the determination result in step 503 is affirmative (Yes)), it is determined that the engine is in idle operation, and the process proceeds to step 504.

In step 504, it is determined whether the engine is under the aforementioned 0 feedback control or not. If the engine is under the 02 feedback control (if the determination result is affirmative (Yes)), the process proceeds to the aforementioned step 502, and the correction coefficients are set. Set to the value 1.0. If the engine is not under 02 feedback control, the process advances to step 505.

In step 505, it is determined whether the engine water temperature value Tw is larger than a predetermined discrimination water temperature value TIJ+ot (for example, 55°C), which is set to a lower value than the predetermined discrimination value Two (70°C) shown in FIG. If the Tw value is larger than the Tw+oL value (the determination result is positive), stable operation of the engine can be maintained, so correction is performed to make the mixture lean and reduce the amount of CO and HC emissions in the exhaust gas components. Set the coefficient KIDL to a predetermined value X+tn, x (for example, 0.97)
Set to . On the other hand, if the Tw value is smaller than the TWIDL value (determination result is negative (NO)), the process proceeds to step 507.

In step 507, it is determined whether the engine rotation value Ne is smaller than a predetermined discrimination rotation value NIDL (for example, looorpm). If the Ne value is greater than the NIDL value (
If the determination result is negative (No), the process proceeds to step 502 described above, and IDL is set to a value of 1.0 as a correction coefficient. On the other hand, Ne
If the value is smaller than the value N (the determination result is positive)
s)) It is determined that the engine is in an operating range where stable operation is difficult, and the correction coefficient KIDL is set to a predetermined value NIDL in order to enrich the air-fuel mixture and ensure stable engine operation. (
For example, set the value to 1.05), step 508), and end this program.

The 02 feedback correction coefficient value Ko2 shown in FIG. 4 and the idle correction coefficient value K shown in FIG. 5 are set as described above.
IDL is applied to the above equation (1), and the fuel injection time T o u T of the fuel injection valve 6 is set.

Furthermore, the discriminant value T w o 2 in Fig. 4 and the discriminant value θ in Fig. 5
A so-called hysteresis characteristic is provided for each of IDL, TWIDL, and NIDL, so that even if the engine water temperature Tw, throttle valve opening θTH, and engine speed Ne change minutely, the changes are absorbed to ensure stable engine operation. It's okay.

(Effects of the Invention) As detailed above, according to the idle fuel supply control method for an internal combustion engine of the present invention, when the engine is idle,
□When the internal combustion engine is in a predetermined operating state in which feedback control should be canceled, and the engine temperature of the internal combustion engine is below the predetermined temperature value, and the engine rotational speed is below the predetermined rotational speed, the air-fuel ratio is on the fuel-rich side than the stoichiometric air-fuel ratio value. Since the amount of fuel supplied to the internal combustion engine is controlled to a small value, idling operation can be stabilized in an operating state where both engine temperature and engine speed are lower than respective predetermined values.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of a fuel supply control device to which the method of the present invention is applied, Fig. 2 is an engine operating range diagram, and Fig. 3 is a diagram of the
FIG. 4 is a flowchart of the KO□ subroutine, and FIG. 5 is a flowchart of the KIDLID subroutine. 1. Internal combustion engine, 4. Throttle valve opening sensor, 5.-Electronic control unit (ECU), 6.
...Fuel injection valve, 9...Engine water temperature sensor, 10.
° Engine rotation speed sensor (Ne sensor), 13... Three-way catalyst, 14... Exhaust gas concentration detection means (07 sensor), 503... Central processing unit (CPU). 507...Read only memory (ROM), 508
...Random access memory (RAM).

Claims (1)

[Scope of Claims] 1. The amount of fuel supplied to the internal combustion engine is feedback-controlled based on an output signal from an exhaust gas component concentration detection means disposed in the exhaust passage of the internal combustion engine; When in a predetermined operating state during idling, feedback control of the fuel supply amount is stopped, and fuel is supplied so that the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine becomes a larger value on the fuel lean side than the stoichiometric air-fuel ratio. In an idle fuel supply control method for controlling the amount of fuel,
detecting the engine temperature of the internal combustion engine and detecting the engine rotation speed; the internal combustion engine is in the predetermined operating state, the detected engine temperature value is below the predetermined temperature value, and the detected engine rotation value is below the predetermined rotation value. A fuel supply control method for an internal combustion engine during idling, wherein the fuel supply amount is controlled so that the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine becomes a smaller value on the fuel rich side than the stoichiometric air-fuel ratio value. 2. The method for controlling fuel supply at idle for an internal combustion engine according to claim 1, wherein the predetermined operating state is a state in which the exhaust gas component concentration detection means is in an inactive state. 3. The internal combustion engine according to claim 1, wherein the predetermined operating state is a state in which the detected engine temperature value is equal to or lower than a second predetermined temperature value that is larger than the first predetermined temperature value. A method for controlling fuel supply during engine idling.