JPS6045751A - Fuel-cut controller of internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent an engine stall and improve fuel consumption by providing a higher set level of a revolutional speed at which fuel is cut off and using the level only when a revolutional speed or a car speed drops quickly or the car is put into the state of an abnormally low speed. CONSTITUTION:A control circuit 10 processes the detected signals from an air flow meter 3, revolutional angle sensors 7 and 8, a throttle sensor 5 and a car speed sensor 11 to control a fuel injection valve 9. In fact, the latest data of the air flow meter 3 is stored in the specified range of RAM110. Various fixed data, constants and so on needed for the programming and the processing of a main routine, fuel injection quantity computing control routine, ignition timing computing control routine, etc. are stored in ROM111. CPU108 sends the fuel injection quantity data computed through the fuel injection computing control routine, to the specified position of an output interface 102 to make a driving circuit 115 energize or interrupt the operation of the fuel injection valve 9. The quantity of fuel according to the fuel injection period may be therefore sent into a combustion chamber so that fuel is cut off properly.

Description

[Detailed description of the invention] Technical field The present invention relates to a fuel cut control device for an internal combustion engine.

PRIOR ART In general, fuel cut is a measure to improve fuel efficiency by stopping fuel injection during deceleration, and fuel cut is controlled by the opening degree of the throttle valve, the rotational speed of the engine, etc. For example, when the throttle valve is Fuel cut is performed when the engine is fully closed and the engine rotation speed is above the fuel cut rotation speed, and the throttle valve is not fully open, or when the throttle valve is fully closed and the engine rotation speed is less than the fuel cut return rotation speed. The fuel cut is canceled. In this case, the fuel cut rotation speed is set higher than the fuel cut return rotation speed. In other words, a hysteresis characteristic is provided.

Conventionally, the above-mentioned fuel cut rotational speed and fuel cut return rotational speed have been set constant regardless of the rate of change in the rotational speed of the engine, the rate of change in the speed of the vehicle (hereinafter referred to as vehicle speed), or the vehicle speed. Therefore, in order to prevent engine stall from occurring even in abnormal conditions such as a sudden drop in engine rotational speed after racing or sudden braking, a sudden drop in vehicle speed, or a drop in vehicle speed itself, the fuel power and throat rotational speed are Also, the fuel cut return rotational speed is set high, resulting in a problem of low fuel consumption.

OBJECTS OF THE INVENTION In view of the problems of the conventional type described above, an object of the present invention is to increase the fuel cut rotation speed and fuel power/throat return rotation speed in abnormal conditions, while setting them low in normal conditions. The purpose is to prevent engine stall and improve fuel efficiency.

Structure of the Invention The structure of the present invention for achieving the above object is shown in FIG. In FIG. 1, the sudden braking state detection means detects the sudden braking state of the internal combustion engine. As a result, the fuel cut rotational speed setting means sets the first fuel cut rotational speed when no sudden braking condition is detected, and on the other hand, sets the first fuel cut rotational speed higher than the first fuel cut rotational speed when the sudden braking condition is detected. Set the fuel cut rotation speed of 2. Further, the throttle valve fully open determining means determines whether the throttle valve of the engine is fully closed or not, and the rotational speed determining means determines whether the rotational speed of the engine is equal to or higher than the set fuel cut rotational speed. and,
The fuel cut execution means executes the fuel cut when the throttle valve is fully closed and the rotational speed of the engine is equal to or higher than the set fuel cut rotational speed.

Further, according to another aspect of the present invention, instead of the above-mentioned sudden braking state determining means, a heavy braking determining means for detecting that the vehicle speed of the vehicle in which the engine is mounted is low is provided, and the fuel is cut in accordance with this. Calculating rotation speed.

Example The present invention will be described in detail with reference to the drawings from FIG. 2 onwards.

FIG. 2 is an overall schematic diagram showing an embodiment of a fuel cut control device for an internal combustion engine according to the present invention. In FIG. 2, an air flow make 3 is provided in the intake passage 2 of the engine body 1. As shown in FIG. The air flow meter 3 directly measures the amount of intake air, has a built-in potentiometer, and generates an analog voltage electrical signal proportional to the amount of intake air. Further, a throttle sensor (also referred to as an idle switch) 5 is provided on the shaft of the throttle valve 4 provided in the intake passage 2 of the engine body 1 to detect whether or not the throttle valve 4 is fully closed. .

The distributor 6 is provided with two rotation angle sensors 7 and 8 which generate angular position signals every time the shaft rotates, for example, 360 degrees and 30 degrees in terms of crank angle. The angular position signal of the rotation angle sensor 7.8 acts as an interrupt request signal for the fuel injection time calculation control routine, a reference timing signal for the ignition timing, and the like.

Further, the intake passage 2 is provided with a fuel injection valve 9 for supplying pressurized fuel from a fuel supply system to the intake boat for each cylinder.

11 is a vehicle speed sensor, for example, a reed switch l.
1a and a permanent magnet 11b. That is, when the permanent magnet 11b is rotated by the speedometer cable, the reed switch lla turns on and off, and as a result, a pulse signal with a frequency proportional to the vehicle speed is generated.

The control circuit 10 includes an air flow meter 3 and a rotation angle sensor 7.
．． 8. It processes each signal of the throttle sensor 5 and the vehicle speed sensor 11 to control the fuel injection valve 9, and is constituted by, for example, a microcomputer.

FIG. 3 is a detailed block circuit diagram of the control circuit 10 of FIG. In FIG. 3, the analog signal of the air flow meter 3 is sent to the A/D converter 1 via the multiplexer
02. That is, the A/D converter 102
uses the clock signal CLK of the clock generation circuit 109 to A/D convert the analog output signal of the air flow meter 3 sent through the multiplexer 101 selectively controlled by the CPU 108, and generates an interrupt signal after the A/D conversion is completed. is sent to the CPU 108. As a result, in the interrupt routine, the latest data of the air flow meter 3 is fetched and stored in a predetermined area of the RAM 110.

Each pulse signal of the rotation angle sensor 7.8 is supplied to a timing generation circuit 103 for generating an interrupt request signal and a reference timing signal. Timing generation circuit 103
has a timing counter, which is incremented by the pulse signal of the rotation angle sensor 8 every 30'' and reset by the pulse signal of the rotation angle sensor 7 every 360''. Furthermore, the pulse signal of the rotation angle sensor 8 is supplied to a predetermined position of the input interface 105 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° CA, and a clock generation circuit 109 that passes through this gate.
A binary signal is formed that is inversely proportional to the rotational speed of the engine.

The digital output signal of the throttle sensor 5 is directly supplied to a predetermined position of the input interface 105.

The digital output signal of the vehicle speed sensor 11 is sent to the waveform shaping circuit 1.
06 and a vehicle speed forming circuit 107 to a predetermined position of the input interface 105.

The waveform shaping circuit 106 converts the output signal of the vehicle speed sensor 11 into a rectangular wave signal and supplies it to the vehicle speed forming circuit 107 . The vehicle speed forming circuit 107 is composed of, for example, a flip-flop, a gate, and a counter. That is,
The square wave signal of the waveform shaping circuit 106 causes the flip-flop to be alternately centered and reset, so that the gate is opened only while the flip-flop is being centered or reset. The counter counts the number of pulses of the clock signal CLK of the clock generation circuit 109 via the open gate. Therefore, the value of the counter is inversely proportional to the frequency of the rectangular wave signal, that is, inversely proportional to the vehicle speed.

The ROM 111 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 CPo 10B sends fuel injection amount data (time) calculated in the fuel injection amount calculation control routine to a predetermined position of the output interface 112 together with a strobe signal. As a result, the fuel injection amount data is reduced to the down counter 11.
The flip-flop 114 is preset to 3 and the flip-flop 114
is also set. As a result, the drive circuit 115 starts energizing the fuel injection valve 9.

On the other hand, the down counter 113 is connected to the clock generation circuit 109.
Finally, the carrier terminal becomes ul'' level, and as a result, the flip-flop 114 is reset and the drive circuit 115 stops energizing the fuel injection valve 9.In other words, the above-mentioned fuel The fuel injection valve 9 is energized for the 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.

FIG. 4 is a flowchart for explaining the operation of the control circuit shown in FIG. 2, and shows a fuel injection time calculation control routine. Step 401 is placed in the middle of the main routine,
Each time the main routine is viewed, it is configured to start from here. In Step 7 402, the counter value incremented by a timer routine (not shown) is read and the counter value is incremented by 50n.
It is determined whether or not isec has elapsed. That is, steps 404 to 412 for setting the fuel cut rotation speed NC and the fuel cut return rotation speed N are executed every 50 m5ec. The engine rotational speed N determined in step 403 by another angle interrupt routine (not shown)
Incorporate.

Steps 404 to 412 will be explained. Step 4
In step 04, it is determined whether N≧0.95Ni-1, and in step 405, it is determined whether N≦0.9Ni-1.

However, N i -H indicates the rotation speed 50 m5ec ago. As a result, referring to FIG. 5(A), if N≧0.95Ni-1, a flag Fl is set in step 406, and Nc is set to 120 Orp in step 407.
Let it be m. 0.9 Ni-1<N<0.95Ni-
If it is 1, it is determined in step 408 whether the flag F1 is “0”, that is, if the NO 50m5Bc ago is 120Or
pm or 1800 rpm, and N at step 407 or 410. to keep the same value. N≦0.9
If Ni-1, the flag F1 is lowered in step 409, and No is set to 180 Orpm in step 410.

That is, when the rotational speed N suddenly decreases by 90% by 150 m5ec or more, the fuel cut rotational speed Nc is set high. In step 411, the fuel cut return rotational speed N8
is set by N, -N C-300, and step 412
Now, Ni-1-N is set for the calculation cycle after the next 50 m5 ec.

Next, steps 413 to 423 will be explained.

In step 413, the output signal LL of the throttle sensor 5 is
It is determined whether LL="1", that is, whether the throttle valve 4 is fully closed. If the throttle valve 4 is not fully closed, step 415. 416. Each time the routine advances to 417, normal fuel injection is executed.

That is, step 415. At 416, the flag Fl
, F2 are both lowered, and in step 417, the fuel injection time τ, for example, τ;τ6·FAF·(1+K)+τVFAF, the air-fuel ratio correction amount K, and the transient correction factor τ7 are calculated based on the invalid time.

When it is determined in step 413 that the throttle valve 3 is fully closed, it is determined in step 414 whether N≦N, and in step 418 it is determined whether N≧Nc.

That is, referring to FIG. 5(B), if N≦NR, the flags Pi and F2 are lowered in steps 415 and 416, and then the fuel injection time τ is calculated in step 417. If N≧No, flag F is set in step 419.
2 and set to τ-0 in step 420. In other words, it means executing a fuel cut. NR<N<N. If so, it is determined in step 421 whether flag F2="1", that is, whether fuel injection was in progress or fuel cut was in progress in the previous calculation cycle. As a result, step 417 or 42
0 to maintain the previous state. In step 422, the fuel injection time τ calculated in step 417 or 420 is entered in the down counter 113, and step 42
This routine ends at step 3.

In the routine shown in FIG. 6, as a means of setting the fuel cut rotation speed, the vehicle speed SPD is used instead of the rate of change of the rotation speed N.
The rate of change is used. In other words, step 40 in FIG.
Steps 604 to 613 are provided instead of steps 4 to 412.

Steps 604 to 613 will be explained. Step 6
In step 04, the vehicle speed data 5PDi is taken in, and step 505
Determine whether 5PDi≧0.955PDi-1 or not,
In step 606, it is determined whether 5PDi≦0.95PDi-1. However, 5PDi-+ indicates the vehicle speed 50m5ec ago.

As a result, if 5PDi≧0.955PDi-17: If so, flag Fl is set in step 607, and step 60B
At N.

is set to 120 rpm. 0.93PDi-1<5PD
If i<0.95SPDi-1, it is determined in step 609 whether flag F1="0", that is, 50m5e
N before c. It is determined whether 120 Orpm is 180 Orpm, and N is determined in step 608 or 611. to keep the same value. If 5PDi≦0.9SPDi-1, the flag F1 is lowered in step 610, and step 611
At N. is set to 180 rpm. In other words, the vehicle speed is 90
If the speed suddenly decreases by %150m5ec or more, the fuel cut rotational speed N. is set high. In step 612,
The fuel cut return rotational speed NR is set by NR-No-300, and in step 613, 5PDi-1←5PDi is set for the calculation cycle after the next 50m5ec.
shall be.

In the routine shown in FIG. 7, the vehicle speed SPD itself is used as a means for setting the fuel cut rotation speed.

That is, only steps 704-712 differ from FIGS. 4 and 6.

Steps 704 to 712 will be explained. Step 7
In step 04, the vehicle speed SPD is taken in, and in step 705, the SP
It is determined whether D≧15 km/h, and in step 706 it is determined whether SPD≧1Q km/h. As a result, S
If PD≧15km/h, flag F1 is set at step 707, and steps 7o8 and N are set at 120Orpm.
shall be. If 10km/h <SPD <15kn+/h, it is determined in step 709 whether flag F1="0", that is, Nc before 50m5'ec is 120Orp.
m or 1800 rpm, and N at step 708 or 711. to keep the same value. SPD≦lQ
km/h, the flag F1 is lowered in step 710, and N is determined in step 711. is set to 180 rpm.

That is, when the vehicle speed SPD is 1Q km/h or less, the fuel cut rotation speed Nc is set high. Step 71
2, the return rotation speed NR of the fuel cup Ml is N, -N. −
It is set by 300.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, as described in detail, the rotational speed suddenly decreases;
Since the fuel cut rotation speed is set high only in abnormal conditions such as a sudden drop in vehicle speed or low vehicle speed, and is normally set low, engine stall can be prevented and fuel efficiency can be improved.

[Brief explanation of drawings]

FIG. 1 is an overall block diagram for explaining the present invention in detail, FIG. 2 is an overall schematic diagram showing an embodiment of the fuel cant control device for an internal combustion engine according to the present invention, and FIG. Detailed block circuit diagrams of the control circuit 10, FIGS. 4, 6, and 7
The figure is a flowchart for explaining the operation of the control circuit 10 of FIG. 2, and FIGS. 5A and 5B are diagrams supplementary to the flowchart of FIG. 4. engine body, 3: air flow meter, 5: throttle sensor, 7, 8: rotation angle sensor, 9: fuel injection valve, 10:
control circuit. Patent Applicant Toyota Motor Corporation Patent Application Agent Patent Attorney Akira Aoki Patent Attorney Kazuyuki Nishidate Patent Attorney Akira Yamaguchi Patent Attorney Masayatei Nishiyama 4th Visit No. 60

Claims (1)

[Claims] 1. Sudden braking state detection means for detecting a sudden braking state of the internal combustion engine, which sets a first fuel cut rotational speed when the sudden braking state is not detected = the sudden braking state is detected. fuel cut rotation speed setting means for setting a second fuel cut rotation speed higher than the first fuel cut rotation speed when the engine is fully open; a rotation speed determining means for determining whether or not the rotation speed of the engine is equal to or higher than the set fuel cut rotation speed; A fuel cut control device for an internal combustion engine, comprising a fuel cut execution means that executes a fuel cut when the engine speed is exceeded. 2. The fuel cut control device for an internal combustion engine according to claim 1, wherein the sudden braking state detection means detects a sudden decrease in the rotational speed of the engine as the sudden braking state. 3. The fuel cut control device for an internal combustion engine according to claim 1, wherein the sudden braking state detection means detects a sudden decrease in speed of a vehicle in which the engine is mounted as the sudden braking state. 4. The fuel cut control device according to claim 1, wherein the fuel cut rotation speed setting means has a hysteresis characteristic. 5. Multiplex determination means for determining that the speed of a vehicle equipped with an internal combustion engine is low; when it is not determined that the speed of the vehicle is low, a first fuel cut rotational speed is set to determine that the speed of the vehicle is low; fuel cut rotation speed setting means for setting a second fuel cut rotation speed higher than the first fuel cut rotation speed when it is determined that the engine is fully closed; and determination means for determining whether or not the throttle valve of the engine is fully closed. , a rotational speed determination means for determining whether the rotational speed of the engine is equal to or higher than the set fuel cant rotational speed, and a rotational speed determination means that determines whether the rotational speed of the engine is equal to or higher than the set fuel cant rotational speed, and when the throttle valve is fully closed and the rotational speed of the engine is lower than the set fuel cant rotational speed. A fuel cut control device for an internal combustion engine, comprising fuel cut execution means for executing a fuel cut when the rotation speed is higher than or equal to the rotation speed. 6. The fuel cut control device according to claim 5, wherein the fuel cut rotation speed setting means has a hysteresis characteristic.