JPH0778365B2 - Air-fuel ratio controller for internal combustion engine - Google Patents

Description

The present invention relates to an air-fuel ratio control system for an internal combustion engine equipped with a catalytic converter.

[Conventional technology]

In an internal combustion engine equipped with a catalytic converter, an air-fuel ratio control device is provided, and closed-loop control is performed so that the air-fuel ratio of the air-fuel mixture becomes the stoichiometric air-fuel ratio. In order to activate the catalyst when the engine temperature is low, a system that introduces secondary air upstream of the catalytic converter at low temperature is installed. When the secondary air is introduced, the air-fuel ratio is open loop controlled.

[Problems to be solved by the invention]

In a vehicle equipped with a catalytic converter, there is a problem that a catalytic odor is generated after a lapse of a short time when the vehicle is continuously operated by repeatedly depressing and releasing the low speed alcel pedal, such as when entering a garage or in a traffic jam. This is for the following reason. That is, when the accelerator pedal is released, the amount of fuel is increased in order to prevent the occurrence of lean spike due to overshoot of the air flow meter. Then, when the accelerator pedal is depressed, the acceleration amount is increased. Immediately after returning the accelerator pedal, the air-fuel ratio is kept in a good state by the O ₂ retained in the catalyst, but when the accelerator pedal is repeatedly turned on and off, O ₂ is lost, so a catalyst odor is emitted. .

To solve this problem, turn the accelerator pedal at low speed.
It has been proposed to detect when the vehicle is in the on-vehicle operation such that N and OFF are repeated, introduce secondary air, and stop the air-fuel ratio feedback control. See Japanese Patent Application No. 61-178918.

In this prior application, the introduction of the secondary air is continued even when the garage is put in and the shift lever is returned to the neutral position. This state corresponds to an operation in which engine adjustment such as air-fuel ratio adjustment is performed, but there is a problem that engine adjustment becomes impossible if secondary air is introduced as described above. An object of the present invention is to enable air-fuel ratio control after the completion of garage parking.

[Means for solving problems]

According to the present invention, in the vehicle internal combustion engine in which the catalytic converter 1a is arranged in the exhaust pipe 1, the secondary air introduction means 2 for controlling the introduction of the secondary air upstream of the catalytic converter 1a,
The means 3 for controlling the air-fuel ratio of the air-fuel mixture introduced into the internal combustion engine to a predetermined value, the means 4 for detecting an operating condition for generating an offensive odor, such as garage parking, which produces an offensive odor from the catalytic converter, and the operating condition for generating an offensive odor An air-fuel ratio control device for an internal combustion engine comprising: means 5 for activating the secondary air introduction means; and means 6 for prohibiting the operation of the secondary air introduction means 2 at the time of transition from an offensive odor generating operating condition to an operation in which the air-fuel ratio is adjusted. Will be provided.

〔Example〕

In FIG. 2, 12 is a piston, 14 is a connecting rod, 16 is a combustion chamber, 18 is a spark plug, 20 is an intake valve, 21 is an intake port, 22 is an exhaust valve, and 23 is an exhaust port. The intake port 21 is connected to an air flow meter 30 via an intake pipe 24, a surge tank 26, and a throttle valve 28. Exhaust port 23
Through exhaust manifold 32, exhaust pipe 34 to catalytic converter
Connected to 36.

The fuel injector 38 is attached to the intake pipe 24 near the intake port 21 for each cylinder.

40 is a distributor, the common electrode of which is connected to the ignition coil of the ignition device 42. The distribution electrode is the spark plug of each cylinder.
Connected to 18.

The secondary air introduction system is a so-called air suction system including the reed valve 44. The reed valve 44 has its upstream side connected to the air filter 46, and its downstream side connected to the exhaust manifold 32 via the secondary air control valve 48 and the air suction passage 50. The secondary air control valve 48 is normally closed, and is opened during cold conditions to introduce secondary air to promote the activity of the catalyst in the catalytic converter. Since the reed valve 44 is installed upstream of the secondary air control valve 48, carbon in the exhaust gas or condensed water is prevented from adhering to the valve body portion and the valve seat portion of the reed valve 44. Adhesion of carbon or condensed water may cause heat damage due to backflow of exhaust gas, but this can be prevented.

The secondary air control valve 48, which is driven by negative pressure in this embodiment, includes a diaphragm 54,
Is connected to an electromagnetic switching valve 58 via a negative pressure passage 56. The switching valve 58 switches the diaphragm 54 between a position communicating with the air filter 60 and a position communicating with the surge tank 26. In the normal state, the switching valve 58 connects the diaphragm 54 to the atmospheric pressure side, and at this time, the secondary air control valve 48 is closed, so that the secondary air is not introduced. By exciting the switching valve 58, the diaphragm 54 is communicated with the negative pressure, the secondary air control valve 48 is opened, and the secondary air is introduced.

The control circuit 64 is for performing the air-fuel ratio control according to the present invention, and is configured as a microcomputer system. The control circuit 64 is composed of a micro processing unit (MPU) 66, a memory 68, an input port 69, an output port 70, and a bus 71 connecting these elements. The input port 69 is connected to each sensor and receives an engine operating condition signal. A signal corresponding to the intake air amount Q is input from the air prometer 30. Crank angle sensors 72 and 74 are attached to the distributor 40, and a pulse signal corresponding to the rotation of the distribution shaft, that is, the rotation of the crank shaft is obtained. That is, the first crank angle sensor 72 generates a pulse signal G for each revolution of the engine, that is, for every 720 ° CA.
The crank angle sensor 74 of generates a pulse signal every 30 ° CA, and can know the engine speed NE.

The air-fuel ratio sensor (for example, O ₂ sensor or lean sensor) 75 is installed in the exhaust pipe 34 downstream of the secondary air introduction passage 50 and upstream of the catalytic converter 36. The air-fuel ratio sensor 75 is installed as far from the exhaust manifold 32 as possible, and can be shielded from the thermal influence of the exhaust gas.

The water temperature sensor 76 is installed in the water jacket of the engine and generates a signal THW according to the temperature of the engine cooling water. The LL switch 78 is connected to the throttle valve 28, and is ON when the throttle valve 28 is in the idle position, and is OFF otherwise.
To be done.

The vehicle speed sensor 84 generates a signal according to the vehicle speed V, and can be installed, for example, on the output shaft of the transmission.

The switch 85 is a switch for detecting a shift to operation during engine adjustment and restarting the air-fuel ratio control, and is a switch that is turned on when the operation lever of the transmission is moved to the neutral position. If the vehicle has a manual transmission, the switch may be turned on when the clutch is disengaged.

The memory 68 stores a program for performing air-fuel ratio control and air suction control according to the present invention. The output port 70 is connected to the fuel injector 38, the electromagnetic switching valve 58, and the igniter of the ignition device 42.

The operation of the control circuit 64 will be described below with reference to a flowchart. FIG. 3 shows a calculation routine of the fuel injection amount (TAU). This routine is started by detecting the crank angle at the beginning of the intake stroke, for example, by the signal from the crank angle sensors 72, 74, at which fuel injection should be started. In step 100, the basic injection amount Tp is calculated by Tp = k × Q / NE. k is a constant.

In step 102, the fuel injection amount TAU is calculated by TAU = FAF × Tp (1 + α) β + γ. FAF is a correction coefficient by air-fuel ratio feedback. Here, α, β, and γ represent deceleration increase to prevent lean spike due to overshoot of the air flow meter 30 during deceleration, acceleration increase to increase output during acceleration, and other correction factors. .

In step 104, the calculated fuel injection amount signal TAU is output from the output port 72. Therefore, the calculated amount of fuel is injected from the injector 38.

FIG. 4 is a routine for calculating the air-fuel ratio feedback correction coefficient FAF, and this routine is executed at regular time intervals.
In step 105, it is judged whether or not the condition is the feedback condition. For example, when the load is high or when the temperature is low, it is not a feedback condition. At step 106, it is judged if the flag FX = 1. This flag FX is reset to "0" by the air suction control routine, which will be described later, when the air suction is executed, and is set to "1" at the normal time when the air suction is not performed.

When the air suction is executed under the non-feedback condition or under the feedback condition, the routine proceeds to step 108, where the feedback correction coefficient FAF = 1. Therefore, the air-fuel ratio is open loop control (non-feedback control).

When air suction is not executed under feedback conditions, the process proceeds from step 106 to step 110, and the signal from the air-fuel ratio sensor 75
It is determined whether or not O _X = 1. When the air-fuel ratio is richer than the stoichiometric air-fuel ratio or the set air-fuel ratio, the routine proceeds to step 112 for moving the air-fuel ratio to the lean side, and FAF is decremented by δ ₁ . When the air-fuel ratio is leaner than the theoretical air-fuel ratio, the air-fuel ratio is moved to the rich side.
F is incremented by δ ₂ . The air-fuel ratio is controlled to a predetermined value by the closed loop control (feedback control) in steps 112 and 114.

FIG. 5 shows an air suction control routine, which is also a routine that is processed at regular intervals. At step 120, it is judged if the engine water THW is larger than a predetermined value T ₁ (for example, 10 ° C.). When THW ≦ T _1, the routine proceeds to step 122, where the flag f is reset. The meaning of this counter will be described later. Step 123
Then the flag FX is set. Solenoid valve 5 in step 124
8 is turned off, the secondary air control valve 48 is closed, and the secondary air introduction is stopped. Stopping the introduction of secondary air at THW <10 ℃ is a measure for catalyst heating at low temperatures.

If THW> 10 ℃, proceed to step 126, where THW is the specified value T ₂
(For example, 40 ° C) or more is determined. 10 ℃ <THW <40 ℃
If so, proceed from step 126 to step 128, and flag FX
Is reset, so feedback is also prohibited under feedback conditions. In step 130, the solenoid valve 58
As a result, the intake pipe negative pressure is applied to the diaphragm 54 and the secondary air control valve 48 is opened.
Therefore, the secondary air from the air filter 46 is fed to the reed valve 44.
As a result, the air is introduced into the exhaust manifold 32 via the secondary air introduction passage 50. This promotes warm-up.

Since THW> T ₂ when the engine is warming up, the routine proceeds from step 126 to step 132, and it is judged if the vehicle speed V is smaller than a predetermined value, for example, 4 km. When V ≦ 4km, step 134
And the counter C is incremented. Step 13
At 6, it is determined whether the LL switch 78 is OFF, that is, whether the accelerator pedal is depressed from the idle position. In step 138, it is determined whether or not the LL switch is switched from ON to OFF, that is, the time point is the start time point of depression of the idle pedal. At step 140, it is judged if the flag f = 0. This flag f is 4 km / h during warm-up.
When the following first accelerator pedal is depressed, that is, when entering the garage or driving like traffic, the vehicle is set and the vehicle speed is 4k.
Reset when m / h is exceeded.

At the start of driving like garage parking, f = 0 and step
The program proceeds to 142, the counter C = 0 and the flag f = 1 are set, and the program proceeds to 123 and 124. That is, even if V <4 km / h, the catalyst odor is not generated immediately after the accelerator pedal is depressed, so that the secondary air is not introduced yet.

If the operation of V <4km / h is continued, steps 136, 138, or
From 140, enter step 146. In step 146, it is determined whether or not the counter c ≧ Co. This counter c is V <4km /
At h, the time is measured after the LL switch is first switched from ON to OFF, that is, after the operation state such as entering the garage is entered. In step 146, when the value of the count c <the predetermined value c ₁ , that is, when the time until the generation of the catalytic odor has not started, the process proceeds to steps 123 and 124,
The secondary air control valve 48 is closed and air suction is not performed. Further, the flag FX = 1 is set. When c ≧ Co, that is, when the time when the catalytic odor begins to be generated, the routine proceeds from step 146 to step 148, where the counter c = Co is fixed, then the routine proceeds to step 150, where the neutral switch 85 is OF
If F, that is, if the lever of the transmission is at a position other than the neutral position, the routine proceeds to step 128, where the secondary air control valve 48 is opened and air suction is executed. The introduction of secondary air eliminates the air shortage condition in the catalytic converter 36 and eliminates the catalytic odor.

When the neutral switch 85 is ON, from step 150 to step 123, A / F feedback is permitted,
Secondary air introduction is prohibited. This state matches the conditions for engine adjustment such as air-fuel ratio adjustment, but engine adjustment becomes possible by stopping the secondary air introduction.

FIG. 6 is a timing diagram illustrating the operation of the present invention.
When the deceleration operation is started at time t ₁ , the LL switch is turned on (C).
Vehicle speed becomes less 4km / h at time t _2, the stops at t _3, enters the idle operation. and starting at t _4, as shown in curve A, during normal operation the vehicle speed exceeds immediately 4km / h is, VSV is maintained to OFF, are not secondary air induction (d). When driving at a speed of 4 km / h and turning on and off the accelerator pedal repeatedly (dashed line B), the LL switch 78 is turned ON-OF first.
After switching to F, that is, after T seconds corresponding to c = Co (time t
₅ ) The solenoid valve 58 is operated (d), the air suction is started, the flag FX is reset, and the air-fuel ratio becomes open loop control. And at time t ₆ the neutral switch
When 85 is turned on, the secondary air introduction is stopped and closed loop control becomes possible.

〔The invention's effect〕

In a system where secondary air is introduced by detecting the garage running condition to prevent catalyst odor generation, secondary air introduction is stopped by detecting neutral, etc., so that engine adjustment can be performed without problems. become.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of the present invention. FIG. 2 is a diagram showing the configuration of an embodiment of the present invention. 3 to 5 are flowcharts for explaining the operation of the control circuit shown in FIG. FIG. 6 is a timing chart for explaining the operation of the present invention. 24 …… intake pipe, 28 …… throttle valve, 30 …… air flow meter, 34 …… exhaust pipe, 36 …… catalytic converter, 38 …… fuel injector, 44 …… reed valve, 48 …… secondary air control valve , 64 ... Control circuit, 58 ... Electromagnetic switching valve, 72, 74 ... Crank angle sensor, 76 ... Water temperature sensor, 78 ... LL switch, 85 ... Neutral switch.

Claims (1)

[Claims] 1. In a vehicle internal combustion engine having a catalytic converter arranged in an exhaust pipe, secondary air introducing means for controlling introduction of secondary air upstream of the catalytic converter, and air-fuel ratio of air-fuel mixture introduced into the internal combustion engine. To a predetermined value, a means to detect a strange odor generating operating condition such as a garage where a strange odor is generated from the catalytic converter, a means to operate the secondary air introducing means under a strange odor generating operating condition, an engine from the strange odor generating operating condition An air-fuel ratio control device for an internal combustion engine, which comprises means for prohibiting the operation of the secondary air introduction means at the time of shifting to the operation in which adjustment is performed.