JPS60198350A - Air-fuel ratio control device for internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent an NOX emission from worsening, by controlling an air- fuel ratio in making it come into being more than the theoretical one at the lean side only in time of acceleration of that immediately after deceleration, in case of a device bearing the above caption which adopts a lean-burn system. CONSTITUTION:In time of engine running, a lean air-fuel ratio compensation value is calculated by an operational device according to a specified running state parameter of an engine, while engine acceleration is calculated by an acceleration operational device. A variation in this acceleration are compared with a negative specified value -L1 and a positive specified value L2 by each of first and second acceleration variation comparing devices. And, when this acceleration variation comes down more than the value -L1, first specified time T1 is measured by a first timer device, and when the acceleration variation goes beyond the value L2, second specified time T2 is measured by a second timer device. Next, in operation of the second timer device, a fuel injection quantity is calculated with a setting compensation value more than being equivalent to a theoretical air-fuel ratio, while at time other than its operation, the fuel injection quantity is calculated with a lean air-fuel ratio compensation value.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an air-fuel ratio control device for an internal combustion engine employing a lean burn system.

BACKGROUND ART Recently, in order to prevent exhaust pollution and improve fuel efficiency, a lean burn system has been adopted in which an internal combustion engine is operated at a lean air-fuel ratio. For example, the air-fuel ratio can be controlled to the lean side by providing a lean sensor in the exhaust passage and using the output sensor of the lean sensor to feedbank the air-fuel ratio of the engine to an arbitrary value on the lean side. For this reason, the lean burn system
x concentration characteristics are used. In Figure 1, X and Y are N before and after the three-way catalytic converter installed in the exhaust passage.
Ox ff indicates 3 degrees. Therefore, the excess air ratio λ, that is, the air-fuel ratio is controlled to be lean so that the difference between the dashed line and the allowable value is within the range C, thereby improving NOx emissions.

However, in the lean burn system, when acceleration is increased and the air-fuel ratio becomes rich, control is performed within range B in FIG. 1, resulting in a problem in that NOx emissions deteriorate.

Purpose of the Invention The purpose of the present invention is to solve the problems of the conventional type described above.
The purpose is to prevent deterioration of NOx emissions by controlling the air-fuel ratio to be richer than the stoichiometric air-fuel ratio in range A in FIG. 1 only during acceleration or during acceleration immediately after deceleration.

Note that if control in range A in Figure 1 continues for a long time, CO
, ) It is preferable to set the control time in the above range A to be short because it causes deterioration of Ic emission.

Structure of the Invention The structure of the present invention for achieving the above-mentioned objects is shown in FIG. The lean air-fuel ratio correction amount calculating means calculates a lean air-fuel ratio correction amount in accordance with predetermined operating state parameters of the engine. On the other hand, the acceleration calculation means calculates the acceleration of the engine and calculates the acceleration of the engine.
The acceleration change comparing means compares the acceleration change with a negative predetermined value -Ll.
The second acceleration change comparing means compares the acceleration change with a positive predetermined value L2. The first timer means starts measuring a first predetermined time T when the change in acceleration falls below a negative predetermined value -L. The second timer means starts measuring the second predetermined time when the first timer means is measuring and the acceleration change exceeds a positive predetermined value L2. The fuel injection amount calculating means calculates the fuel injection amount using a predetermined correction amount equal to or more than the stoichiometric air-fuel ratio while the second timer means is measuring the second predetermined time;
When the second timer means is not measuring, the lean air-fuel ratio correction amount is used to calculate the fuel injection amount. In this way, a predetermined time 'I' after acceleration (deceleration) below a predetermined value -LI
When an acceleration exceeding a predetermined value L2 is detected within 1, the fuel injection control is carried out for a predetermined time T2.

Example The present invention will be described in detail with reference to the drawings from FIG. 3 onwards.

FIG. 3 is an overall schematic diagram showing an embodiment of an air-fuel ratio control device for an internal combustion engine according to the present invention. In FIG. 1, an intake pressure sensor 3 for detecting negative pressure PM is provided in an intake passage 2 of the engine body.

The distributor 4 is provided with two rotation angle sensors 5 and 6 which generate angular position signals each time the shaft rotates, for example, 360' and 30' in terms of crank angle. The angular position signals of the rotation angle sensors 5 and 6 function as an interrupt request signal for the fuel injection time calculation routine, a reference timing signal for ignition timing, an interrupt request signal for the ignition timing calculation routine, and the like.

Further, the intake passage 2 is provided with a fuel injection valve 7 for supplying pressurized fuel from a fuel supply system to the intake boat for each cylinder.

The control circuit 10 digitally processes signals from the intake pressure sensor 3 and the rotation angle sensor 5.6 to control the fuel injection valve 7, and is configured as, for example, a microcomputer.

FIG. 4 is a detailed block circuit diagram of the control circuit IO of FIG. 3. In FIG. 4, the analog signal of the intake pressure sensor 3 is passed through a multiplexer 101 to a Δ/D converter 102.
is supplied to. That is, the A/D converter 102
Multiplexer 1 selectively controlled by PU 106
The analog output signal of the intake pressure sensor 3 sent through the A/D converter 101 is subjected to ^/D conversion using the clock signal CLK of the clock generation circuit 107, and an interrupt signal is sent to the CPU 106 after the A/D conversion is completed. As a result, in the interrupt routine, the latest data of the intake pressure sensor 3 is imported and R
It will be stored in a predetermined area of AM 108.

Each pulse signal from the rotation angle sensors 5 and 6 is supplied to a timing generation circuit 103 for generating an interrupt request signal and a reference timing signal. Timing generation circuit 1
03 has a timing counter, which is incremented by a pulse signal of the rotation angle sensor 6 every 30°C and reset by a pulse signal of the rotation angle sensor 5 every 360°A. Further, the pulse signal of the rotation angle sensor 6 is supplied to a predetermined position of the input interface 1050 via the rotation speed forming circuit 104. The rotation speed forming circuit 104 includes a gate that is controlled to open and close every 30°C, and a clock generation circuit 107 that passes through this gate.
A binary signal is formed that is inversely proportional to the rotational speed of the engine.

The ROM 109 stores in advance programs such as a main routine, a fuel injection amount calculation control routine, an ignition timing calculation control routine, and various fixed data and constants necessary for these processes.

The CPU 106 sends the fuel injection amount data (time) calculated in the fuel injection amount data routine 1 to a predetermined position of the output interface 110 together with the strobe signal S. As a result, the fuel injection amount data is presented to the down counter 111 and the flip-flop 11
2 cents will also be given. As a result, the drive circuit 113 starts energizing the fuel injection valve 7.

On the other hand, the down counter 111 is connected to the clock generation circuit 107.
After counting the clock signal CLK, the carrier terminal A becomes the "L" level, and as a result, the flip-flop 112 is reset and the drive circuit 113 stops energizing the fuel injection valve 7. In other words, the fuel injection valve 7 is energized for the above-mentioned fuel injection time, so that an amount of fuel corresponding to the fuel injection time is sent into the combustion chamber of the engine body 1.

The operation of the control circuit shown in FIG. 3 will be explained with reference to the flowchart 1- in FIGS. 5 and 6 and the timing diagram in FIG. 7.

Step 501 in FIG. 5 starts at predetermined time intervals.

It is assumed that the counter value CINJ is decremented every predetermined time period, for example, 4 ms, or in synchronization with the rotation of the crankshaft, and is initially cleared.

Since CINJ=O in step 502, the flow advances to step 503. In step 503, an intake pressure change ΔPM as a change in acceleration is calculated. In other words, the intake pressure data PMi is taken in and the previous intake pressure data PMi-,
The difference ΔPM=PMi−PMi−+ is calculated and set as PMi, +−PMi in preparation for the next calculation. Next, in step 504, it is determined whether ΔPM>L2. As shown in FIG. 7(A), before time t2, ΔPM<L2, so the flow proceeds directly from step 504 to step 50G, and this routine ends.

Next, as shown in FIG. 7(A), at time t2, Δ
When PM exceeds L2, the flow in step 504 of FIG. 5 proceeds to step 505, where the counter value CINJ is set to T2 and step 50 is performed, as shown in FIG. 7(B).
Proceed to step 6. Therefore, when the next interrupt occurs and the routine of FIG. 5 is executed, flow at step 502 proceeds directly to step 506.

In other words, the counter value CINJ satisfies CINJ>0 for a predetermined time 'pgx4ms, as shown in FIG. 7(B).

FIG. 6 shows a fuel injection control routine in step 60.
1 starts at every predetermined crank angle, for example, 360° CΔ. In step 602, it is determined whether the counter value CINJ set in the routine of FIG. 5 is 0 or not. CINJ
= 0, in step 603 the intake pressure data P
Based on M and rotational speed data Ne, ROM 10!
Lean air-fuel ratio correction 1tpt and pAN are calculated by performing interpolation calculation using the two-dimensional map stored in 11. On the other hand, if CINJ≠0, Fl and EAN are set to 1 in step 604. As a result, the counter value CI
When NJ changes as shown in Figure 7 (B), the correction amount F
LEAN is as shown in FIG. 7(C).

In addition, in a lean burn system, normally, for example, FL
EAN is about 0.65. Then step 605
Then, the fuel injection time τ is τ←τB HFLIiAN −K + r vHowever,
τB is the basic time K. τV is another correction coefficient. τV is the invalid time. In step 606, τ is calculated by a down counter 1.
11 and the routine ends at step 607.

In this way, during acceleration, the predetermined time T2 (more precisely, Tz
A rich fuel injection control of X4ms) is performed.

The flowchart in FIG. 8 and the timing diagram in FIG. 9 are for explaining the operation of another embodiment of the present invention, and are similar to the above-described rich fuel injection side only during acceleration immediately after deceleration, which is difficult to control. 011.

Step 801 in FIG. 8 starts at predetermined time intervals.

Note that the counter value CPLHIN is set for a predetermined period of time, for example, 4 m.
It is assumed that it is incremented every s and is initially set to the maximum value TH.

Since CINJ=O in step 802, the process advances to step 803. In step 803, TI=TM<
T+), the process advances to step 804. Step 8
In step 04, similarly to step 503 in FIG. 5, the intake pressure change Δth as an acceleration change is calculated. Then step 8
At step 05, it is determined whether 62M<-Ll. Figure 9 (A
), before time t1, 62M>-ri, so the flow changes from step 805 to step 809.
Proceeding directly to , the routine ends.

Next, as shown in FIG. 9(A), at time t1, 62M
When the value falls below -L1, the flow at step 805 in FIG. 8 proceeds to step 80G, where the counter value CPLEAN is cleared, as shown in FIG. 9(B).

Therefore, when the next interrupt occurs and the routine of FIG. 8 is executed, the flow at step 803 is changed to step 807.
Proceed to. In step 807, it is determined whether 62M>L2. As shown in FIG. 9(A), before time t2, 6
Since 2M<L2, flow proceeds directly from step 807 to step 809 and the routine ends.

Next, as shown in FIG. 9(A), at time t2, Δ
] When the boar exceeds L2, the flow in step 807 in FIG. 8 proceeds to step 808, where the counter value CINJ is set to 1.
2 and proceed to step 809.

Therefore, when the next interrupt occurs and the routine of FIG. 8 is executed, the flow at step 802 is changed to step 809.
Proceed directly to. In other words, the counter value CINJ is
), CINJ>Q for a predetermined time TzX4ms.
will be satisfied.

The counter value CINJ shown in FIG. 9(C) obtained in the routine of FIG. 8 is used in the fuel injection control routine of FIG. 6, and as a result, the lean air-fuel ratio correction IFLEAN
is as shown in FIG. 9(D).

In this way, rich fuel injection control is performed only during acceleration immediately after deceleration, which is difficult to control.

In the above-described embodiment, the lean air-fuel ratio correction amount FLEAN was set to 1 when performing rich fuel injection control, but as is clear from FIG. 1, it can be set to 1 or more.

In this case, the predetermined time T2 (or T
zX4ms).

Prevents deterioration of 11c emission. Furthermore, although intake pressure data is used to detect acceleration, rotational speed data or intake air amount data may also be used.

As described in detail, according to the present invention, deterioration of NOx emissions can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram for explaining the present invention in detail, FIG. 2 is a block diagram showing the configuration of the present invention, and FIG. 3 is an embodiment of an air-fuel ratio control device for an internal combustion engine according to the present invention. 4 is a detailed block circuit diagram of the control circuit in FIG. 3; FIGS. 5, 6, and 8 are flowcharts for explaining the operation of the control circuit in FIG. 3; Figure 9 is the fifth
FIG. 8 is a timing diagram for supplementary explanation of the flowcharts in FIGS. 6 and 8; FIG. 1... Engine body, 3... Intake pressure sensor, 4...
Distributor, 5.6... Rotation angle sensor, 7... Fuel injection valve, 1
0...Control circuit. Patent Applicant Toyota Motor Corporation Patent Application Agent Akira Aoki Patent Attorney Kazuyuki Nishidate Patent Attorney Akira Yamaguchi Patent Attorney Masaya Nishiyama Figure 1 Rich-E = 1 - Lean excess air ratio No. Figure 6 Figure 7 Figure 2 Figure 8

Claims (1)

[Scope of Claims] 1. Lean air-fuel ratio correction amount calculation means for calculating a lean air-fuel ratio correction amount according to predetermined operating state parameters of the internal combustion engine, acceleration calculation means for calculating acceleration of the engine, and said acceleration change. a first acceleration change comparison means for comparing the acceleration change with a predetermined negative value; a second acceleration change comparison means for comparing the change in acceleration with a predetermined positive value; and when the change in acceleration falls below the predetermined negative value. a first timer means that starts measuring a first predetermined time period when the acceleration change exceeds a predetermined value of the pressure while the first timer means is measuring; second timer means for starting the measurement;
While the second timer means is measuring the second predetermined time, the fuel injection amount is calculated using a predetermined correction amount equal to or more than the stoichiometric air-fuel ratio, while the second timer means an air-fuel ratio control device for an internal combustion engine, comprising a fuel injection amount calculating means for calculating a fuel injection amount using the lean air-fuel ratio correction amount when the lean air-fuel ratio correction amount is not being measured. 2. The air-fuel ratio control device according to claim 1, wherein the acceleration calculation means is an intake pressure change calculation means that detects the intake pressure of the engine and calculates a change in the intake pressure. 3. The air-fuel ratio control device according to claim 1, wherein the acceleration calculation means is a rotation speed change calculation means that detects the rotation speed of the engine and calculates a change in the rotation speed. 4. The air-fuel ratio control device according to claim 1, wherein the acceleration calculation means is an intake air amount change calculation means that detects the intake air amount of the engine and calculates a change in the intake air amount.