JPS59196932A - Air-fuel ratio controlling apparatus for internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve the performance of an engine, by preventing deterioration of the engine performance at the time when the engine is not warmed up sufficiently and operated continuously at a low speed after starting of the engine by controlling the air- fuel ratio by use of the vehicle speed in addition to the temperature of engine cooling water. CONSTITUTION:A basic injection quantity of fuel is obtained from the output signals of an air-flow meter 10 and an engine-speed detector 11, and the basic injection quantity of fuel is corrected according to the output signal of an O2-sensor 12. In case that the vehicle speed detected by a vehicle-speed detector 19 is higher than a prescribed value and the temperature of cooling water is also higher than a prescribed value, feedback control of O2 is executed. By employing such a method, it is enabled to prevent deterioration of the engine performance at the time when the engine is not warmed up sufficiently and operated continuously at a low speed after starting of the engine. Further, in case of operating the engine in an intermediate-speed, intermediate-load region where combustion is relatively complete and the engine operation is excellent after starting of the engine, it is enabled to reduce the amount of noxious components contained in the exhaust gas.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to an air-fuel ratio control (referred to as λ-control) device for an internal combustion engine, and more particularly, to an air-fuel ratio control device during the warm-up process after starting the engine. The present invention relates to an air-fuel ratio control device having characteristics.

(Background Art) As a conventional air-fuel ratio control device, there is one shown in FIG. 1, for example. 10 is an air flow meter that detects the amount of air taken into the engine (intake air amount); 11 is a rotation speed detector that detects the engine rotation speed; and 12 is an air flow meter that is attached to the exhaust pipe and detects the amount of oxygen in the exhaust gas. 02 sensor whose output voltage changes and obtains a signal according to the air-fuel ratio; 13 C water temperature sensor which detects the cooling water temperature of the engine; 14 is a control unit which detects the intake air amount Q detected by the air flow meter 10 and the rotation speed. The engine rotational speed N detected by the control unit 11 is input, QlN is calculated as the basic fuel injection amount 'rp=, and in order to further control the air-fuel ratio, λ, - λ, supplied from the control unit 15. -Control signal-02 se7
The controller inputs all the information on the correction amount α according to the detection signal from the engine 12, calculates the actual fuel injection amount Ti=Tpxα, and supplies this q+1 to the fuel injection device]7. The control unit 15 and 7 calculates the correction amount α by inputting the detection signal from the 02 setter 12, and the result is λ.
- Output to the control unit 14 as a control signal. Note that correcting the basic fuel injection amount by determining the correction amount α based on the information from the 02 sensor in this manner is called no-control. 16) The 2λ-control on/off unit compares the water temperature Tw detected from the water temperature sensor 13 with a predetermined value Twc. Determine the conditions for controlling the λ-control off and on, and 7
, - Output to the control unit 15. When the λ,-control control signal is off, the λ-control is off, and the λ,-control signal is used as a crank knob to control the air-fuel ratio to enrich. On the other hand, when it is off, the λ-control is on, and the human control unit 15 activates the λ-conotrol signal and controls the air-fuel ratio to be stoichiometric (stoichiometric air-fuel ratio).

17) The fuel injection system supplies Ti calculated by the control unit 4 to the engine.

Next, the operation will be explained using flowchart 1 in FIG. This routine is executed at fixed time intervals or at fixed rotation intervals. Instead, in step 20, it is determined whether the input control is on or off. If it is off, proceed to step B 1
．． Turn on λ-Co/Troll as is. When it is off, the process proceeds to step 22, where the 7λ-control on/off unit sets the detected engine cooling water temperature Tw to a predetermined value TWC.
Compare with.

When Tw)Twc, the process proceeds to step Z3, where the engine is assumed to have been sufficiently warmed up and the λ-conotrol control signal is turned on, and the λ,-control is turned off to control the air-fuel ratio to be stoichiometric. Tw) When Twc, the process proceeds to step 22, where the engine control signal is turned off because the engine has not been warmed up sufficiently, and the air-fuel ratio is controlled to be rich.

In this way, in the conventional example, switching the air-fuel ratio from rich to stoic depended only on the cooling water temperature of the entire engine, so the combustion state of the engine may vary, especially when starting or at low speeds.
Under unfavorable driving conditions, there are problems such as poor drivability such as engine stalling and heavy breathing, and poor exhaust performance such as high emissions of CO, HC, etc.The air-fuel ratio changes from rich to stoic. The requirements for switching vary depending on the engine speed and load.For example, in low speed ranges such as idling, there is a lot of residual gas in the engine cylinder, so the air-fuel ratio needs to be rich, but in the medium speed range above a certain level When a suitable load is applied, combustion is stable, and it is not necessary to make the air-fuel ratio rich.

(Purpose of the Invention) This invention was made by focusing on such conventional problems, and uses vehicle speed in addition to water temperature as a parameter to control turning off/off of the λ-co/trol. The purpose is to solve the above problems by switching the fuel ratio from rich to stoichiometric.

(Structure and operation of the invention) The present invention will be explained below based on the drawings.

FIG. 3 is a diagram showing an embodiment of the invention.

First, the configuration will be explained. Reference numeral 10 denotes an air flow meter that detects the intake air amount of the engine, and basically consists of a flap that moves to an angle corresponding to the intake air amount and a potentiometer that converts the angle into a voltage signal. Reference numeral 11 denotes a rotation speed detector for detecting the rotation speed of the engine, which is composed of a crank angle sensor and the like. 12 is an 02 sensor whose output voltage changes according to the oxygen concentration in the exhaust gas, and which can obtain a signal according to the air-fuel ratio. Reference numeral 13 denotes a water temperature sensor for detecting the engine cooling water temperature, which is composed of a thermistor or the like whose resistance value changes depending on the temperature of the cooling water. 14 is control
Knit, intake air amount Q,! : In order to calculate -Q/N to the basic fuel injection amount Tp= from the engine rotational speed N and further control the air-fuel ratio, λ, - is supplied from the control unit]5. Inputs λ5 - control signal - which has information on the correction amount α according to the detection signal from the 02 processor, calculates the actual fuel injection amount Ti == Tp × α, and supplies this result to the fuel injection device 17 do.

J5 is a λ-control unit with constant values α1 and 02
All the detection signals from the sensor 12 are input to calculate the correction amount αt, and the result is output to the control unit 14 as a λ-control signal. 18 is a control off/off unit that compares the water temperature and vehicle speed detected from the water temperature sensor 13 and the vehicle speed detector 18 with predetermined values set for each, and turns the λ5 control from off to on. 7λ-control control signal is output to the input control unit 15. As mentioned above, the factors for controlling the air-fuel ratio from rich to stoic vary depending on the engine speed and load. Therefore, the conventional problems can be solved by detecting the engine speed and load in addition to the cooling water temperature and performing the 2λ-control off/off control. Specifically, the rotational speed and load are detected when the engine is warmed up to a certain extent during warm-up, and when an appropriate load is applied at medium speed rotation, the λ-control is turned off and the air-fuel ratio is set to stoichiometric. That is, λ−
- The control unit 14 adjusts the correction amount αt to the stoichiometric air-fuel ratio based on the signal from 02 ce/
to control.

This makes it possible to reduce emissions of C (J, HC, etc.) during warm-up.When running at idle speed or at low speed, the engine speed is low and stable combustion cannot be expected. - The control is turned off and the air-fuel ratio is kept rich, that is, λ - The control unit 14 outputs a fixed correction amount α1 that makes the air-fuel ratio rich.

This prevents the engine from stalling or suffocating. Here, it is possible to detect the engine speed and the load independently, but even if the engine is idle while the vehicle is stopped, the engine speed and load will momentarily become medium speed and medium load. Therefore, in this invention, vehicle speed is used in place of these. This means that when the vehicle speed VSP reaches a predetermined value VSPc corresponding to medium rotation and medium load,
In steady state, the combustion chamber is running under high speed and high load, so the wall temperature of the combustion chamber is higher than the value indicated by the cooling water temperature, so stable combustion can be expected, and generally the engine goes to idle immediately. This is because there is a low possibility that it will return to . Reference numeral 17 denotes a fuel injection device which includes a register, a comparator, a counter, a transistor, an injector, etc. and supplies a fuel injection amount Ti to the engine. A vehicle speed detector 19 detects the vehicle speed by measuring the frequency of a signal having a pulse density proportional to the vehicle speed by turning on/off a reed relay synchronized with the rotation of a magnet fixed to the rotating shaft of the speedometer cable. .

Next, the operation will be explained.

In step 3o, it is determined whether the Noni control is already off using a flag. λ, -kono)0
If the λ-control is on, proceed to step 35, keep the λ-control fully on, and set the air-fuel ratio to stoichiometric. When it is off, the process proceeds to step 31, where the detected cooling water temperature Tw is compared with a predetermined value Tw (preferably 70 to 80°C).

Tw) When Tw, it is assumed that the engine has been sufficiently warmed up, and the process proceeds to step 35.

TV) If 'J'w2, it is assumed that the engine has not warmed up sufficiently, and the process proceeds to step 32. In step 32, Tw is set to another predetermined value '-[' W2 (TW+ >'I'
Compare with W2 temperature (40 to 60°C is preferable).

Tw) At Tw2, the engine is still in a cooled state and ignition and combustion are unstable, so it is necessary to keep the air-fuel ratio rich, and the process proceeds to step 34, where the 2λ--control is turned off. Tw) If Tw2, proceed to step 33. In step 33, the detected vehicle speed vspl predetermined value V S Pc
(Compare with 4,0 to 601 (m/h) and judge whether an appropriate load is being applied at medium speed rotation during warm-up.VSP) When VSPcO, it is necessary to keep the air-fuel ratio rich. Assuming that there is no air-fuel ratio, switch the human control from off to on to keep the air-fuel ratio stoichiometric. VSP)VSP
Since stable combustion cannot be expected at cO, step 3
Proceed to step 4, 7λ, - turn off the control and keep the air-fuel ratio rich. Although not shown in the flowchart of FIG. 4, the above-mentioned Tp is calculated in advance.

The fuel injection amount TI thus obtained is supplied to the engine by the fuel injection device 17 to control the air-fuel ratio.

(Effects of the Invention) As explained above, according to the present invention, the vehicle speed is used in addition to the engine cooling water temperature as a parameter for controlling the λ-control. In addition, when the engine is operated in a medium rotation/medium load range where combustion is relatively smooth after startup and there are no problems with drivability, the exhaust performance can be further improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional air-fuel ratio control device for an internal combustion engine, FIG. 2 is a flowchart showing the operation of the device, and FIG. 3 is a block diagram and a flowchart showing an air-fuel ratio control device for an internal combustion engine according to the present invention. FIG. 4 is a block diagram showing the operation of the device. 10. Air flow meter 11.. Rotation speed detector 12.0
2 sensors 13... Water temperature control/sato control 22 j5... λ-control unit 16, 18 ・λ-control on/off unit 17... Fuel injection device 19... Vehicle speed detector Patent applicant Nissan Motor Co., Ltd. company

Claims (1)

[Claims] The basic fuel injection amount T is determined from the engine intake air amount Q and rotational speed N.
A control unit that calculates p = K, QlN, uses the correction amount α output from the λ-control/control unit for Tp to calculate the actual fuel injection amount Ti = l1lp×α, and outputs it to the fuel injection device. , a correction amount α that is a constant value so that the air-fuel ratio becomes a daughter, and a correction amount αt that changes so that the air-fuel ratio becomes the stoichiometric air-fuel ratio based on the signal from the 02 setsa are calculated and output to the control unit. Ko/
The troll unit switches the two correction amounts α1 and αt by setting the engine cooling water temperature Tw and vehicle speed VSP to predetermined values.
, 'll''w2 (Tw, ) Tw2) and VSPc, and after the engine starts, W>Tw and (6Tw (Tw2 and VSP)VSPc). 1. An air-fuel ratio control device for an internal combustion engine, characterized in that α=α until then, and α−αt thereafter.