JPS5859327A - Air-fuel ratio control method for internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve operating characteristics, by controlling the air-fuel ratio at a specified value or more in the region where an engine speed is a specified rotational speed or more, changing the air-fuel ratio in response to the change in the rotational speed below the specified rotational speed, and controlling torque fluctuation at the operating region at the low engine speed. CONSTITUTION:A control circuit 18 computes and controls a valve opening time of a fuel injection valve 28 based on the detected value of a crank angle sensor 22 provided in a distributor 20 and the detected value of a pressure sensor 14 provided in an air intake path 12, and controls the air-fuel ratio of air-fuel mixture. The control device 18 controls the air-fuel ratio in such a way that the air-fuel ratio is 20 in the region where the engine speen N is 1,200rpm or more, and the air-fuel ratio is changed at a changing rate of 1.25-2.75 every time the engine speed changes by 100rpm in the region less than 1,200rpm. Thus the torque fluctuation due to the misfiring at the low engine speed region and the low torque at the high engine speed region are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control method for an ultra-lean burn internal combustion engine.

Theory ** Ratio> If you control the air-fuel ratio, for example, m/r≧20 K engine O air-fuel ratio, the 0NOx component in the exhaust gas will be eliminated and the fuel consumption will be reduced. rate will improve. However, if the 1 mO ultra-lean air-fuel ratio control is performed entirely in the 011 range, the following problem arises. That is, in a low-speed operation region or a low-load operation region, if the air-fuel ratio is too lean, turbulence etc. will occur and silk fluctuation will occur. i
9. Sufficient engine silk cannot be obtained in the high-load operation region, which is one expansion and height change operation region, and the operation characteristics deteriorate.

The present invention solves the above-mentioned problems when performing ultra-lean combustion. That is, an object of the present invention is to improve operating costs in a low-speed operating range or a high-load operating range in an internal combustion engine that operates at a super-lean air-fuel ratio.

The feature of the present invention that achieves the above-mentioned objectives is that the air-fuel ratio is controlled to 20 or more in the region where the engine rotational speed is 1200fl1 or more, and the rotation WI1! is controlled in the region where the engine rotational speed is 1200fl1 or less. The air-fuel ratio may be controlled so that when I changes by 100, the air-fuel ratio changes by t25 to 175.

Furthermore, in the operating range where the intake pipe internal pressure is 640wHp or less, the control air-fuel ratio is controlled to 20 or more, and in the operating range where the intake pipe internal pressure is 640wHp or higher, when the intake pipe internal pressure changes by 1011111f. Air fuel ratio is 0
．． Kl to change from 5 to! It is desirable to control the working ratio.

The following is a detailed explanation of the present invention with reference to the drawings. Part 2 and Figure 1 show an embodiment of the present invention in which the i-microcomputer controls the fuel injection amount and thereby performs air-fuel ratio distribution. Internal combustion 4j@' (D- example is schematically shown. In the figure, 10 is a throttle valve provided in the middle of the intake passage 12 of the engine. A pressure output port 14a of a pressure sensor 14 that detects the pressure inside the intake pipe and generates a voltage corresponding to the detected value is open in the intake passage 12. It is sent to the control circuit 18.

The distributing shaft 20 of the engine is provided with a crank angle sensor 22 that generates an angular position signal every time the distributing shaft 20 m rotates by a predetermined angle, for example, 30 degrees in terms of crank angle. There is. crank angle senna 2
Angular position signal from 2, control circuit 1B via line 24
sent to.

From the control rigid path 18, through the wire 26, the singular or -
An injection signal is sent to the fuel injection valve 28, and the injection valve 28 intermittently injects pressurized fuel from a fuel supply system (not shown) into the intake port.

FIG. 2 is a four-wheel diagram showing an example of the control road 18. FIG.

Since the output voltage from the pressure sensor 14 is not directly related to the present invention, the output voltage from the pressure sensor 14 is 1 along with voltages from other sensors not shown.
analog! The signal is sent to an A/D converter 50 including a luteplexer. In the A/D switch 3, O, the input voltage is
It is sequentially converted into a binary sign at a predetermined conversion cycle.

The angular position signal for every 60 degrees of crank angle from the crank angle sensor 22 is sent to the speed signal generator (b) l#152, and further sent to the central processing unit l1ll (CPU) 34 as a crank angle synchronization interrupt signal. It will be done.

This speed signal forming circuit 52Fi is equipped with a gate that is controlled to open and close by the above-mentioned signal every 30'' of crank angle, and a counter that counts the number of clock pulses that pass through this gate and are output from the q-tock generating circuit 56. Shi, the rotation of the engine!
Two moderate signals with profits corresponding to If are formed. Note that the speed signal forming circuit 52 may not be provided, and the speed signal may be formed by software within the CPU 34.

When an injection signal having an injection time of 6 hours and an hour equal to the injection time τ is seen at a predetermined position of the output boat 400 from within the CPU 34 via the bus '5B, the signal is sent to the fuel injection valve 28 via the drive circuit 42. When the power is connected, the injection valve 28 is energized for a time TK, and a large amount of fuel is injected into the combustion chamber of the engine according to the time TK.

The A/D converter 50, the speed signal forming circuit 32, and the output port 40 are the components of the micropunbi 34 and the lead-on 9fimo V (ROM).
) 44, random access memory (RAM) t6, and clock generation circuit 36 via path 38! I/O data is transferred via this path 3B. Although the second FMIK is not shown, the microcombiner island is further provided with an input/output control circuit, a memory control circuit, etc. by a known method.

In the ROM 44, programs such as a main processing routine logsum, which will be described later, as well as tables, number of runs, etc. necessary for the arithmetic processing thereof are stored in advance.

Next, the fuel injection process a(
Air-fuel ratio control) processing details for $115! This will be briefly explained using H. As shown in the figure, when the power is turned on, the CPU 54 executes an initialization routine 50 and performs an RA
Performs processing to reset the contents of M46 and sets initial values for each constant. Next, the program proceeds to the main routine 51, where fuel injection calculations and the like, which will be described later, are repeatedly executed. Also, the crank angle from the crank angle sensor 22! Each time the interrupt routine 52 based on the crank angle synchronization interrupt signal for each So' is executed, for example, an injection signal is generated at every crank angle of 12o0 or 180°, and this is sent to the skewer boat 40.
Execute fuel injection processing to transfer to. What is this fuel injection process? The interrupt routine 53 may be executed using a timer interrupt signal every 9r period.

On the other hand, the CPU 54 receives data representing the engine speed N from the speed signal forming circuit 32 during the main processing routine or other interrupt routine, and stores it in a predetermined area in the RAM J6. Further, when the A/D conversion interrupt routine, which is executed at predetermined time intervals or at a determined crank angle position, is completed, data representing the intake pipe absolute pressure P is fetched from the M/D converter 30 and stored in a predetermined area in the RAM 46. Store in.

FIG. 4 is a flowchart showing the fuel injection amount calculation processing routine. The CPU 34ti performs the arithmetic processing shown in FIG. 4 in the middle of the main routine.

First, in step 60, the detection data representing the rotational speed Nt is loaded from the RAM 44, and in the next step, 61
, the intake pipe internal pressure pVts is set to RA
Take in from Mt6. Next, in step 62, the basic injection pulse width τ1 is calculated from the rotational speed N and the intake pipe internal pressure P using a map. In the 80M44, the characteristics of the basic injection pulse width with respect to the rotational speed N and the absolute pressure PK in the intake pipe are stored in advance in the form of a map as shown in Fig. 5 or 86m1IC. Using this map, t is calculated from the imported N and P. In this case, interpolation calculations may be used as necessary. Next, in step 63, the final fuel injection pulse is determined according to the basic injection pulse value, the ineffective injection time τ7 determined according to the battery voltage, etc., the suction temperature, and the addition time! ! 4Pi is calculated from the following equation from the correction coefficient α determined according to the degree of warming up, etc.

τ=τ鳳・α10嘗V The nine fuel injection pulses calculated in this way are stored in a predetermined wheel area of RAMA6 in the next Stella Pro 4. This stored 9τ is read out by the fuel injection processing interrupt routine 52 or 53 shown in FIG. 1C, converted into an injection signal, and sent to the output port 40.
Thus, the fuel injection pulse, and therefore the air/fuel north side, is performed.

Next, we will explain how the air-fuel ratio is controlled by someone who calculates the base injection pulse rate using the map shown in FIG. 5 or 116. In Figures 15 and 116, fBua air-fuel ratio (A/F) is 14, τJuku 14
Fim/F=16, τ, 1. is A/)' = 18, τ is A/F = 20, τ, 3. Each represents an injection pulse width of 20 μm controlled by H/F=22. Therefore, depending on the engine rotational speed N and the intake pipe pressure P, the air-fuel ratio is
The control shown in FIG. 5 and in accordance with the control section shown in FIG. 6 is performed as described above.

That is, according to the present invention, when the rotational speed is 12001% or more, the air-fuel ratio is controlled to about 20 to 24 in the range of 1200 to 2400, and the air-fuel ratio is controlled to about 20 to 24 when the rotational speed is around 80of1m and 2800ral. is controlled to 13 to 151i degrees. Then, when the rotational speed changes by 1001'Pl in the 800-12QOrgIAO region or the 2400-2800% region, the air-fuel ratio changes from 125 to 2.
The rate of change 125 of the air-fuel ratio described above is also calculated by
It is calculated from the rate of change of 2.75ti.

As shown in No. 7111, if the air-fuel ratio is controlled to 20 or more, NOx emissions will be significantly reduced (1-1).Furthermore, the fuel consumption rate will also be extremely small.However, if the air-fuel ratio is controlled to 1- In this case, when the engine speed is low and the rotation rate is low, as shown in Fig. 8, the torque fluctuation becomes large due to misfire etc. Therefore, below 1200, the air-fuel ratio is changed to rich direction, and the idle 1 of 800 rfl. If you change
By controlling the air-fuel ratio to be between 1'5 and 1511 degrees at f, it is possible to improve the driving characteristics in the low rotational noise region even in the S interval of the ultra-lean air-fuel ratio control type.

In addition, in the rotational speed region of 2400f or more, NO
Since increasing engine output is a priority rather than suppressing x emissions, the air-fuel ratio is changed to richer A.
The air-fuel ratio is controlled to be approximately 13 to 15 at 28001% or more.

Further, according to the present invention, the pressure inside the intake pipe is 6401+11
H) In the following range, the air-fuel ratio is 20 to 24, to II
J11 is controlled, and the pressure inside the intake pipe is 760igaHp.
In lr, the air-fuel ratio is controlled to 12-141!11. And in the region of 640 to 7 dOiuHp', the pressure inside the intake pipe is 10 TsuruH? When the air-fuel ratio changes, the air-fuel ratio is controlled to change by cL5 to 1.0. Note that the above-mentioned rate of change of the air-fuel ratio α5ti is set, and the rate of change to is also set. In the intake pipe internal pressure region (high load region) of 640tlH9 or higher, priority is given to increasing the output of one engine, even though suppressing the Noxmffi amount, so the air-fuel ratio is changed to the rich direction, and the 760tlH9
1, that is, the air-fuel ratio is 12 to 1 at atmospheric pressure (fully open throttle).
The above-mentioned change in the rotational speed and the change in the air-fuel ratio to reduce the intake pipe pressure to 0 may be changed in 111 steps, or may be changed continuously. 4.
good.

Instead of detecting the intake pipe internal pressure with a pressure sensor, it is also possible to detect the throttle valve opening, the ratio between the intake air flow rate and the rotational speed, etc., and use it as a substitute for the intake pipe internal pressure.

In the above embodiment, the air-fuel ratio control is performed by controlling the injection plate from the fuel injection valve, but the air-fuel ratio can also be controlled by controlling the fuel supply wrinkle or air bleed amount using an electronically controlled carburetor. Fuel ratio control is possible. Furthermore, secondary sky t! Even if c flow rate, EGR amount, etc. are controlled, the air-fuel ratio remains at control -jh bi.

As explained above, according to the present invention, the air-fuel ratio is controlled to 20 or more in the region where the rotational speed is 1200118 or more, and the air-fuel ratio is controlled to 20 or more in the region where @II degree is 1200≠ or less.
Since the air-fuel ratio is controlled so that when the air-fuel ratio changes by 100T%, the air-fuel ratio changes from 125 to 2.75. It is possible to suppress torque fluctuations in the slow rotation range and improve driving characteristics.

In addition, the air-fuel ratio is controlled to 20 or more in the operating range where the intake pipe internal pressure is 6゛40■aH9 or less, and the intake pipe internal pressure is 640㎜H? In the operating range where the above conflicts occur, if the air-fuel ratio is controlled so that the air-fuel ratio changes from 0.5 to Sufficient torque is obtained and driving characteristics are greatly improved◎

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an embodiment of the present invention, Fig. 2 is a block diagram of the control circuit of Fig. 1, and Fig. 3 is! A schematic explanatory diagram of the contents of the Iku A combination crystal O process, and Figure 4 is a micro combination crystal.
Flowchart of part of the evening control program, FIG.
Figure 6 is a characteristic diagram of basic injection pulse width with respect to rotational speed and intake pipe internal pressure, Figure 7 is a characteristic diagram of NOx emission amount and fuel consumption rate with respect to air-fuel ratio, and Figure 8 is a characteristic diagram of torque fluctuation as a function of rotational speed. It is a diagram. 14...Pressure sensor, 18...Control circuit, 22...
・Crank angle senna, 28...Fuel injection valve, 30...
・Mu/D encyclopedia, 32...Speed signal formation circuit, 54.
...CPU. 40...Output boat, 44...ROM, 46...
R.A.M. Patent applicant: Toyota Motor Corporation Patent agent: Patent attorney: Akira Aomizu, patent attorney: Kazuyuki Nishidate, patent attorney: Akiyuki Yamaguchi

Claims (1)

[Claims] t. Engine rotational speed and intake pipe internal pressure or intake air flow rate are detected as engine operating condition parameters, and air-fuel mixture is supplied to the engine according to the operating condition parameters. In the air-fuel ratio control method for controlling the fuel ratio, the air-fuel ratio is controlled to 20 or more in the region where the engine rotational speed is 1200Ip1 or more, and the air-fuel ratio is controlled to be 20 or more in the region where the engine rotational speed is 1200Ip1 or less, and when the engine speed changes by 100 in the region where the engine rotational speed is 1200Ip1 or less. An air-fuel ratio control method for an internal combustion engine, characterized in that the air-fuel ratio is controlled so that the fuel ratio changes from t2g to 2.75. 2.11 A unique air-fuel ratio control method in which the air-fuel ratio changes stepwise in response to changes in the rotational speed in a range of 1200 or less. & The air-fuel ratio control method described in paragraph 1, in which the rotational speed is in the O region KTh of 1200° or less, and the air-fuel ratio continuously becomes brutal with respect to a rotational change of 11 degrees. 4 @ In the operating region where the tracheal pressure is 640 mHf or less, the air-fuel ratio is controlled to 20 or more, and the intake pipe pressure is 640 mHf or less.
In the operating range corresponding to 40 mHf or more, the air-fuel ratio is controlled so that the air-fuel ratio changes by 0.5 to 10 when the intake pipe internal pressure changes by 10 tlHp.
Air-fuel ratio control method in section. 5. The air-fuel ratio control method according to claim 4, wherein the air-fuel ratio changes stepwise with respect to changes in the intake pipe pressure in an operating region where the tracheal pressure is equal to or higher than 640 tlHp. '4 II O air-fuel ratio control method according to claim S, in which the air-fuel ratio changes continuously in response to changes in the intake pipe pressure in an operating region where the tracheal pressure is equal to or higher than 640-Hf. 7 The air-fuel ratio is controlled to 20 or more in the area where the WA rotational speed is 1200- or more and 2400- or less, and in the area where the rotational speed is 2400- or more, when the rotational speed increases to 100r%, the air-fuel ratio is 125 to 2. The air-fuel ratio control method according to the first or fourth paragraph of the patent claim, which controls the air-fuel ratio so that the air-fuel ratio changes by .75. 8, 11 In the region where the degree of conversion is 2400 or more, the air-fuel ratio changes stepwise with a change of 11 degrees per rotation. air-fuel ratio control method. ? 8. The air-fuel ratio control method according to claim 7, wherein the air-fuel ratio changes continuously by 9 degrees with changes in rotational speed in a region where the plate speed is 2400 or more.