JPH048838A - Air fuel ratio control device for engine - Google Patents

Abstract

PURPOSE:To design improvement in the running performance in the state of non-idle driving and stabilization of rotational speed of an engine in the state of its idle driving by setting a smaller compensation in the state of non-idle driving than in the state of idle driving when the air fuel ratio is turned to be richer in response to an increase in a load of the engine. CONSTITUTION:A compensation amount for turning an air fuel ratio to be richer in the state of non-idle driving is set by an air-fuel ratio decreasing compensation quantity setting means M1 to be smaller than a compensation amount for turning the air fuel ratio to be richer in the state of idle driving the air fuel ratio decreasing compensation quantity setting means M1. Then the air fuel ratio is turned to be richer than a compensation amount set by an air fuel ratio decreasing compensation quantity setting means M1 by an air fuel ratio decreasing means 2 in response to an increase in a load of the engine. Namely, when the air fuel ratio is turned to be richer in response to an increase in a load of the engine by the air fuel ratio decreasing means M2, a compensation in the state of non-idle driving is made to be smaller than that in the state of idle driving. Thus, stabilization of rotational speed of the engine at the time of idle driving and the running performance at the time of non-idle driving can be secured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air-fuel ratio control device for an engine that enriches the air-fuel ratio in order to prevent a decrease in engine speed due to an increase in load.

[Conventional technology] Conventionally, in engine air-fuel ratio control systems, when the engine load does not suddenly increase due to the operation of an air conditioner switch (air conditioner), etc., the air-fuel ratio is enriched to prevent a drop in engine speed. For example, Japanese Patent Application Laid-Open No. 60-69246 discloses that the closing of the air conditioner switch during idling is corrected by increasing the basic fuel injection time by a predetermined time at least in response to the operation of the air conditioner during idling. A technique has been disclosed for preventing lean fluctuations in the air-fuel ratio during idle up due to engine speed.

[Problem to be solved by the invention] However, conventionally, when the load of an air conditioner or the like increases, the air-fuel ratio is made uniformly rich regardless of whether the engine is running at high speed, driving at high speed, or idling. If you set a correction amount to enrich the air-fuel ratio to prevent engine deterioration, the air-fuel ratio will become over-rich when the engine rotates at high speeds or when driving at high speeds, making the engine speed unstable and driving performance worse. There is a problem with doing so.

[Purpose of the Invention] The present invention has been made in view of the above-mentioned circumstances, and is intended to stabilize the engine speed during idling operation and to stabilize the engine speed during non-idling operation when enriching the air-fuel ratio to cope with an increase in engine load. It is an object of the present invention to provide an air-fuel ratio control device for an engine that can ensure running performance during operation.

[! [Means for Solving the Problem] In order to achieve the above object, the engine air-fuel ratio control device according to the present invention adjusts the correction amount for enriching the air-fuel ratio in a non-idling operating state to The air-fuel ratio enrichment correction amount setting means M1 is set to be smaller than the correction amount for enriching the air-fuel ratio in the idling operating state, and the air-fuel ratio enrichment correction amount setting means M1 is set in response to an increase in engine load. The air-fuel ratio enriching means M2 enriches the air-fuel ratio by the corrected amount.

[Function] In the engine air-fuel ratio control device having the above configuration, the air-fuel ratio enrichment correction amount setting means M1 sets the correction amount for air-fuel ratio enrichment in the non-idling operating state to be the same as that of the air-fuel ratio enriching in the idling operating state. When the air-fuel ratio enrichment means M2 enriches the air-fuel ratio in response to an increase in engine load, the correction amount is set smaller in the non-idling operating state than in the idling operating state.

[Embodiments of the invention] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 and subsequent figures show an embodiment of the present invention, FIG. 2 is a schematic diagram of an engine control system, FIG. 3 is a flowchart showing a fuel injection control procedure, FIG. 4 is a flowchart showing an air conditioner increase coefficient setting procedure, Figure 5 shows when the air conditioner switch is turned on.
5 is a time chart showing an off state and a setting state of an air conditioner increase coefficient.

(Configuration of engine control system) Reference numeral 1 in the figure is an engine body, and the figure shows a horizontally opposed four-cylinder engine. An intake manifold 3 is communicated with an intake port 2a formed in a cylinder head 2 of this engine body 1. A throttle chamber is connected to the upstream side of the intake manifold 3 via an air chamber 4, and an air cleaner 7 is attached to the upstream side of the throttle chamber 5 via an intake pipe 6.

Further, an intake air amount sensor (a hot wire air flow meter in the figure) 8 is interposed immediately downstream of the air cleaner 7 in the intake pipe 6, and a throttle valve 5a provided in the throttle chamber 5 is connected to a throttle valve 5a provided in the throttle chamber 5. A bypass passage 5b is provided with an opening sensor 9a and an idle switch 9b for detecting fully closed throttle valve, and communicates the upstream side and the downstream side of the throttle valve 5a.
Idle speed control valve (ISCV) 5
c is interposed.

Further, an injector 10 is disposed immediately upstream of each intake port 2a of each cylinder of the intake manifold 3, and a spark plug 11 whose tip is exposed to the combustion chamber is provided for each cylinder of the cylinder head 2. installed.

The injector 10 is communicated with a fuel tank 13 via a fuel supply path 12, and a fuel pump 14 and a fuel filter 1 are connected to the fuel supply path 12 from the fuel tank 13 side.
5 is interposed.

Further, the injector 10 communicates with a pressure regulator 17 via a return passage 16, and the downstream side of the pressure regulator 17 is connected to the fuel tank 1.
It is connected to 3.

Further, a crank rotor 18 is pivotally attached to the crankshaft 1b of the engine main body 1, and this crank rotor 1
A crank angle sensor 19 consisting of an electromagnetic pickup or the like for detecting the crank angle is provided on the outer periphery of the crank angle 8 . Further, 1/2 of the crankshaft 1b is
A cam rotor 20 is pivotally attached to a rotating camshaft IC, and a cam angle sensor 21 for cylinder discrimination is provided on the outer periphery of the cam rotor 20.

In addition, a cooling water temperature sensor 22 is installed in a cooling water passage (not shown) forming a riser formed in the intake manifold 3.
An air-fuel ratio sensor such as an 02 sensor 24 is connected to an exhaust pipe 23 that communicates with the exhaust boat 2b of the cylinder 2. Note that the reference numeral 25 is a catalytic converter.

(Circuit configuration of control device) On the other hand, reference numeral 30 is a control device (ECU) consisting of a microcomputer, and the CPU 31 . R
OM32. RAM33, backup RAM34,
and the I10 interface 35 is connected to the pass line 36
are connected to each other via a constant voltage circuit 37, and a predetermined stabilized voltage is supplied from the constant voltage circuit 37.

The ECU 3O provides an air-fuel ratio enrichment correction amount setting means for setting a correction amount for enriching the air-fuel ratio in a non-idling operating state to be smaller than a correction amount for enriching the air-fuel ratio in an idling operating state, and In response to the increase, an air-fuel ratio control function such as an air-fuel ratio enrichment means that enriches the air-fuel ratio by the correction amount set by the air-fuel ratio enrichment correction amount setting means, and other functions such as ignition timing control. is realized.

The constant voltage circuit 37 is connected to three batteries via a control relay 38, and supplies control power to each part when the key switch 40 is turned on and the relay contact of the control relay 38 is closed. It is directly connected to the battery 39, and when the key switch 40 is turned off and the relay contact of the control relay 38 is opened, backup power is supplied to the backup RAM 34 to hold data.

In addition, the input port of the I10 interface 35 includes the respective sensors 8, 9a, 19, 21°22.24,
The idle switch 9b is connected, the positive terminal of the battery 39 is connected, and its terminal voltage VB is monitored, and the vehicle speed sensor 27 and air conditioner switch 28 are also connected.

On the other hand, the spark plug 11 is connected to the output port of the I10 interface 35 via an igniter 26, and the I5C is connected via a drive circuit 41.
V5c, injector 10, and fuel pump 14 are connected.

The ROM 32 stores the Wi control program and fixed data for control, and the RAM 33 stores the output values from each sensor after data processing and the C
Data processed by the PU 31 is stored. Further, the backup RAM 34 stores learning value data and the like, and the stored data is retained even when the key switch 40 is in the OFF state.

The CPU 31 calculates the intake air amount from the output signal of the intake air amount sensor 8 according to the control program stored in the ROM 32, and calculates the intake air amount based on various data stored in the RAM 33 and the backup RAM 34. In addition to calculating the fuel injection amount commensurate with the engine speed, the ignition timing is calculated, and the duty ratio of the signal is also calculated.

Then, a drive pulse width signal corresponding to the fuel injection amount is outputted via the drive circuit 41 to the injector 10 of the corresponding cylinder at a predetermined timing to inject fuel, and via the igniter 26 at a predetermined timing. An ignition signal is output to the spark plug 11 of the cylinder. In addition, when the air conditioner switch 28 is turned on during idling, the l
5CV5c is driven to control the amount of air in the bypass passage 5b and idle up.

(Operation) Next, the operation of the embodiment having the above configuration will be explained according to the flowcharts shown in FIG. 3 and subsequent figures.

(Fuel Injection Control Procedure) FIG. 3 is a flowchart showing the fuel injection control procedure, which is repeated at predetermined intervals synchronized with engine rotation.

First, in step 5101, output signals from the crank angle sensor 19 and intake air amount sensor 8 are read, and engine rotational speed N and intake air amount Q are calculated.

Next, the process proceeds to step 5102, and the step 510 described above is performed.
Calculate the basic fuel injection pulse width Tp from the engine speed N and intake air amount Q calculated in step 1.
/N:K...constant), proceed to step 5103.

In step 5103, the cooling water temperature TW, throttle opening θ, throttle opening θ are detected from the cooling water temperature sensor 22, throttle opening sensor 9a, idle switch 9b, and air conditioner switch 28.
, idle switch output signal ID, and air conditioner switch signal AC, and proceed to step 5104, where various coefficients such as air conditioner increase coefficient KACON, cooling water temperature increase coefficient KTW, post-idle increase coefficient KAI, fuel cut coefficient KFC, etc. and in step 5105, various increase correction coefficients C0FF are set from these coefficients (C
0EF 4-K FC (1+ K ACON+ KTi
KAI+...) Next, in step 8106, the air-fuel ratio feedback correction coefficient α is set based on the output voltage VAF of the 02 sensor 24, and in step 5107, the acceleration increase coefficient KACC is set.
Step 3108: Set a voltage correction pulse width TS for interpolating the invalid injection time of the injector 10 based on the 1 deceleration increase coefficient KDC1 and the terminal voltage 8 of the battery 39.
Proceed to.

In step 8108, the basic fuel injection pulse width TI) calculated in step 5102 is applied to step 8106.
The air-fuel ratio is corrected by the air-fuel ratio feedback correction coefficient α set in step 5105, the acceleration increase coefficient KACC1 deceleration increase coefficient KDC set in step 5107, and the voltage correction pulse The final fuel injection pulse width Ti is set by adding the width Ts (Ti 4 - Tp
αx (COEF+KACC-KDC) 10TS)
.

Then, in step 5109, the drive signal having the fuel injection pulse width Ti set in step 5108 is output to the injector 10 of the corresponding cylinder at a predetermined timing to execute fuel injection, and the routine ends.

(Air conditioner increase coefficient setting procedure) Air conditioner increase coefficient K AC in the above fuel injection procedure
ON is set according to the flowchart shown in FIG.
When the air conditioner switch '28 is turned on, the fuel injection amount is increased and the air-fuel ratio is enriched. Then, as time passes, the air conditioner increase coefficient K ACON is reduced, and the air-fuel ratio is returned to the base air-fuel ratio.

Next, a program for setting the air conditioner increase coefficient 1 will be explained. This program is an interrupt routine that is activated at predetermined intervals. First, in step 5201, it is determined whether or not the air conditioner switch 28 is ON. When the air conditioner switch 28 is OFF, the air conditioner increase coefficient K ACON is set in step 5202. “O” Nishiku KACO
N-0), in step 5203 the air conditioner switch 28
Clear the air conditioner switch switching determination flag F[8G2 (FLAG2←O) to exit the routine.

On the other hand, when the air conditioner switch 28 is ON in step 5201, steps 5201 to 5
Proceed to 204 and check the air conditioner switch switching determination flag FL.
From the value of AG2, the air conditioner switch 28 changes from OFF to O.
It is determined whether the air conditioner switch 28 has been switched to the N state or whether the air conditioner switch 28 is already in the ON state.

In step 5204, if FLAG2 = 1, that is, the air conditioner switch 28 is already in the ON state, steps 5204 to 5205 are executed.
Proceed to the air conditioner increase coefficient K set in the previous routine.
Subtract the setting value K ACONSET from ACON to reduce the air conditioner increase coefficient K ACON.
ON-K ACONKACONSET ), the process proceeds to step 5206 .

The above set value K ACONSET is the calculation cycle time (execution cycle) of this air conditioner power increase coefficient setting routine.
This is the subtraction value of the air conditioner increase coefficient K ACON determined from the air conditioner.In order to avoid sudden fluctuations when returning from a rich air-fuel ratio to the base air-fuel ratio, it is set to a relatively small value to reduce the slope of the air-fuel ratio. That's what I do.

Then, when the process proceeds from step 5205 to step 8206, it is determined whether or not the air conditioner increase coefficient K ACON has reached "0", and if K ACON > O, the process jumps to step 5213 to determine whether the air conditioner switch is switched. Set the flag FLAG2 (FL^G2←
1) When the routine is exited and K ACON≦0, the process advances to step 5207 and the air conditioner increase coefficient K AC
Turn ON realistically K ACON←0), similarly, in step 8213, set the air conditioner switch switching determination flag FLA.
Set G2 (FLAG2←1) and exit the routine.

On the other hand, when FLAG2 = Ol in step 5204, that is, the air conditioner switch 28 is not switched from OFF to ON, the process proceeds from step 5204 to step 8208 and thereafter, and the air conditioner volume increase coefficient K is determined.
Determine the conditions for setting the initial value of ACON.

That is, in step 3208, it is determined whether the engine speed N is less than or equal to the set speed NS (for example, 1500 rpm), and in step 5209, it is determined whether the vehicle speed V is equal to or lower than the set vehicle speed VS.
(for example, 2 Km+/h) or less, and in step 5210 it is determined whether the throttle valve is fully closed. And the above steps 5208 and 5209S2
When all 10 conditions are satisfied (N≦NS and V≦■
S and throttle valve fully closed), it is determined that the operating state is idling, and the process proceeds to step 5211, where the air conditioner volume increase coefficient K is determined.
Initial set the first initial value KACONIN11 to ACON.K ACON 4-K ACONINl
l), above step 3208.5209.5210
If even one of the conditions is not satisfied, it is determined that the state is in a non-idling state, and the process proceeds to step 521.
2 is the air conditioner increase coefficient K. ACON is set to the second initial value K.
Initialize ACONINI2 (K A
CON-K ACONINI2).

At this time, the above 1. Second initial value K ACONINll
K ACONINI2 is, for example, KACONIN+1
= 0.2, KACONINI2 = 0.1, and the air conditioner increase coefficient KACON is set to the initial value KACON during idling operation, as shown in Fig. 5.
Elapsed time to enrich NINII and air-fuel ratio
1, during non-idling operation, the initial value K ACON
INI2 is set small and the elapsed time TIME2 for enriching the air-fuel ratio is also set short.

Then, when the air conditioner increase coefficient K ACON is initialized in step 5211 or step 5212, the process proceeds to step 5213, and as described above, the air conditioner switch switching determination flag F is set to AC3.
Set (FLAG2←1) and exit the routine.

As a result, during idling operation, when the air conditioner is activated, the air-fuel ratio is appropriately enriched by the air conditioner increase coefficient K ACON, and a drop in engine speed is prevented.
On the other hand, during non-idling operation, the air conditioner increase coefficient K ACON is set small to prevent the air-fuel ratio from becoming overrich, thereby preventing deterioration of driving performance.

[Effects of the Invention] As explained above, according to the present invention, the air-fuel ratio enrichment correction amount setting means allows the correction amount for enriching the air-fuel ratio in the non-idling operating state to be equal to that for enriching the air-fuel ratio in the idling operating state. is set smaller than the correction amount for
When the air-fuel ratio is enriched by the air-fuel ratio enrichment means in response to an increase in engine load, the correction is made smaller in non-idling operating states than in idling operating states. Not only can driving performance be improved by preventing this, but also excellent effects can be achieved, such as being able to stabilize the engine rotational speed during idling operation.

[Brief explanation of drawings]

Fig. 1 is a block diagram corresponding to claims showing the basic configuration of the present invention, Fig. 2 and the following show an embodiment of the present invention, Fig. 2 is a schematic diagram of the engine control system, and Fig. 3 is a fuel injection control procedure. FIG. 4 is a flowchart showing the air conditioner increase coefficient setting procedure, and FIG. 5 is a time chart showing the on/off state of the air conditioner switch and the setting state of the air conditioner increase coefficient. Ml...Air-fuel ratio enrichment correction amount setting means M2...Air-fuel ratio enrichment means FIG.

Claims (1)

[Scope of Claims] Air-fuel ratio enrichment correction amount setting means for setting a correction amount for enriching the air-fuel ratio in a non-idling operating state to be smaller than a correction amount for enriching the air-fuel ratio in an idling operating state; An air-fuel ratio control device for an engine, comprising an air-fuel ratio enriching means for enriching the air-fuel ratio by a correction amount set by the air-fuel ratio enrichment correction amount setting means in response to an increase in engine load. .