JPH0544547B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an air-fuel ratio control device for an internal combustion engine that prevents the air-fuel ratio of the engine from overshooting due to air flow meter overshoot during a shift change in a manual transmission vehicle.

BACKGROUND OF THE INVENTION In manual transmission vehicles, during a shift change, especially during an upshift, the pressure inside the intake pipe changes suddenly, causing the output signal of the air flow meter to overshoot. In other words, although air is actually passing through the air flow meter, this air is used to increase the pressure in the surge tank and is not sucked into the engine body. As a result, the air-fuel ratio of the engine becomes overbalanced after acceleration after a shift-up, resulting in deterioration of emission (CO, HC) characteristics.

In order to prevent the above-mentioned emission deterioration, when the rate of change in the amount of intake air per revolution of the engine is less than a predetermined value and the clutch is off, it is determined that the shift is up and the fuel is cut. It is known (Japanese Unexamined Patent Publication No. 195030/1983).

Problems to be Solved by the Invention However, the above-mentioned conventional type requires a clutch switch as a means for determining whether the clutch is on or off, which increases manufacturing costs, and also requires time and effort to shift up. If the clutch is left off for a long period of time, the fuel will continue to be cut off, causing the engine to stall.Furthermore, clutch activation other than during a shift-up, such as when the clutch is turned off immediately after starting at an intersection and then stopped, will also cause the engine to stall. There was the problem of inviting

Means for Solving the Problems In view of the above-mentioned problems, it is an object of the present invention to eliminate the need for a clutch switch, reduce manufacturing costs, and prevent engine stall due to time-consuming shift-up or clutch-off operations other than shift-up. In particular, the means for doing so is shown in FIG.

In Fig. 1, the means for determining the amount of intake air per revolution is Q/the amount of intake air per revolution of the internal combustion engine.
It is determined whether Ne is less than or equal to a predetermined value. Further, the rotational speed determination means determines whether or not the engine rotational speed Ne is equal to or higher than a predetermined value B. Further, the intake air amount change rate per revolution determining means determines whether the change rate ΔQ/Ne of the intake air amount per revolution of the engine is less than or equal to a predetermined value C. As a result, the fuel cut means
The amount of intake air per revolution is below the specified value (Q/Ne
≦A), the rotation speed is above a predetermined value (Ne≧B), and 1
Fuel supply to the engine is stopped when the rate of change in intake air amount per revolution is below a predetermined value (ΔQ/Ne≦C). Further, the fuel cut operation period limiting means limits the maximum period of operation of the fuel cut means by the engine rotational speed or time.

Function According to the above-mentioned configuration, clutch off at the time of a shift change is determined based on the condition of the intake air amount per revolution Q/Ne without providing a clutch switch, and the change rate ΔQ of the intake air amount per revolution is determined. With the condition of /Ne, fuel cut is not performed during slow deceleration; due to the condition of rotation speed Ne, fuel cut is not performed in the low rotation speed range, and furthermore, with the operation period restriction condition, the fuel cut period is limited by the rotation speed or time. The Rukoto.

Strictly speaking, these conditions in the present invention are for detecting states in which fuel can be cut, including not only when the shift is up but also in other working states. Normally, a discriminating means for this purpose is provided, and since the conditions of the present invention are restrictive, there is no particular inconvenience, and the present invention is particularly effective when shifting up.

Embodiment FIG. 2 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. 2, an air flow meter 3 is provided in an intake passage 2 of an engine body 1. As shown in FIG. air flow meter 3
The device directly measures the amount of intake air, and includes a built-in potentiometer to generate an analog voltage output signal proportional to the amount of intake air. This output signal is supplied to an A/D converter 101 with a built-in multiplexer of the control circuit 10. Distributor 4 has an axis whose axis is converted into a crank angle, for example.
A crank angle sensor 45 generates a reference position detection pulse signal every 720° and converts it into a crank angle.
A crank angle sensor 6 is provided that generates a pulse signal for detecting angular position every 30 degrees. The pulse signals of these crank angle sensors 5 and 6 are transmitted to the control circuit 10.
The output of the crank angle sensor 6 is supplied to the input/output interface 102 of the CPU 10.
3 interrupt terminal.

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 port for each cylinder.

The control circuit 10 is configured as a microcomputer, for example, and includes an A/D converter 101, an input/output interface 102, a CPU 103, and
A ROM 104, a RAM 105, etc. are provided.

Further, in the control circuit 10, a down counter 106, a flip-flop 107, and a drive circuit 108 are for controlling the fuel injection valve 7. That is, in the routine described later, when the fuel injection amount τ is calculated, the fuel injection amount τ is preset in the down counter 106 and the flip-flop 107 is also set. As a result, the drive circuit 108 starts energizing the fuel injection valve 7.
On the other hand, when the down counter 106 counts the clock signal (not shown) and finally its carry out terminal reaches the "1" level, the flip-flop 107 is reset and the drive circuit 108 activates the fuel injector 7. stop. That is, the fuel injection valve 7 is energized by the above-mentioned fuel injection amount τ, and therefore,
An amount of fuel corresponding to the fuel injection amount τ is sent into the combustion chamber of the engine body 1.

Incidentally, an interrupt of the CPU 103 occurs when the input/output interface 102 receives a pulse signal from the crank angle sensor 6 after the A/D converter 101 completes A/D conversion.

The intake air amount data Q of the air flow meter 3 is taken in by an A/D conversion routine executed at predetermined time intervals and stored in a predetermined area of the RAM 105. In other words, data Q in the RAM 105 is updated at predetermined intervals. Further, the rotational speed data Ne is calculated by an interrupt of the crank angle sensor 6 every 30°C and stored in a predetermined area of the RAM 105.

The operation of the control circuit shown in FIG. 2 will be explained below.

FIG. 3 shows a fuel injection amount calculation routine, which is executed, for example, every 360°C. In step 301, it is determined whether the fuel cut flag Fcut calculated in the routine of FIG. 4 or FIG. 6 is "1". If Fcut="1", the process directly advances to step 305, where no injection amount calculation is performed, and therefore no fuel injection is performed. If Fcut="0", step
Proceed to 302.

In step 302, the intake air amount data Q and rotational speed data Ne are read from the RAM 105, and the basic injection amount τ ₀ is calculated by τ ₀ ←kQ/Ne. In step 303, the basic injection amount τ _{0 is} calculated based on other operating state parameters. is corrected to determine the final injection amount τ, and in step 304, as described above,
The CPU 103 down-counts the injection amount τ to the counter 106.
At the same time, the flip-flop 107 is set. The routine then ends at step 305.

FIG. 4 shows a fuel cut routine for determining clutch off at the time of a shift change based on the intake air amount Q/Ne per rotation, which is a premise of the present invention, and cutting fuel. Similarly, the routine is executed every 360°C prior to the routine shown in FIG. 3, but it may also be executed at predetermined intervals. In step 401, the fuel cut counter Ccut is +1.
It is advanced and guarded at the maximum value of 101 in steps 402 and 403. In other words, in the routine shown in FIG. 4, even if the fuel cut condition is satisfied, fuel is cut only for a predetermined period every 100 times the counter Ccut is set as shown in step 406, which will be described later. Ccut does not need to increment to a value of 101 or more, and therefore, the counter value Ccut is guarded at the maximum value of 101 to prevent overflow.

In step 404, as the first fuel cut condition, intake air amount data Q and rotational speed data Ne are read out from the RAM 105, and Q/Ne is calculated.
It is determined whether Q/Ne is less than a predetermined value, for example 0.1/rev. In other words, we focused on the fact that when the clutch is turned off for a shift change, the load on the engine is reduced, and therefore, Q/Ne≦0.1
/rev is considered clutch-off.

If Q/Ne≦0.1/rev, proceed to step 405, and set RAM105 as the second fuel cut condition.
Read the rotational speed data Ne from Ne≧1000rpm.
Determine whether or not. As a result, when Ne≧1000 rpm, the process proceeds to step 406. This prevents engine stall by not executing fuel cut when stopping immediately after starting. In other words, if you start at an intersection and then stop immediately, the clutch will reduce the rotation speed to about 500 rpm when you start, and when you step on the accelerator, the Q/Ne will decrease.
increases, but if the vehicle is stopped immediately after that, Q/Ne decreases due to the accelerator being released and the first fuel cut condition is satisfied, but the second fuel cut condition is still not satisfied. Therefore, if the vehicle stops immediately after starting, fuel cut is not performed.

Only when the first fuel cut condition Q/Ne≦0.1/rev and the second fuel cut condition Ne≧1000 rpm are both satisfied, proceed to step 406, otherwise proceed to step 410, and set the fuel cut flag.
Set Fcut to “0”.

In step 406, it is determined whether the counter Ccut is 100 or more. If Ccut≧100, Ccut is set to 1 and the process proceeds to step 408, and if Ccut<100, the process directly proceeds to step 408. In step 408, Ccut
Determine whether or not ≦10. If Ccut≦10, proceed to step 409 and set the fuel cut flag Fcut to “1”.
If Ccut > 11, proceed to step 410,
Set the fuel cut flag Fcut to “0” and step
At 411, this routine ends.

In this way, even if the first and second fuel cut conditions (Q/Ne≦0.1/rev, Ne≧1000 rpm) are satisfied, fuel cut is executed only when the value of the counter Ccut is 1 to 10. In other words, when the clutch is held off for a long period of time while shifting up, even if the first and second fuel cut conditions are met, the fuel cut conditions are only performed as necessary.

In the routine of FIG. 4, since it is not possible to distinguish between gradual deceleration and upshifting, the rotational speed for the first fuel cut condition in step 405 is set to a relatively high value of 1000 rpm.

FIG. 5 is a timing diagram supplementary to the flowchart of FIG. 4. In Fig. 5, time t ₀
When the clutch is turned on (off) for upshifting, the rotational speed Ne increases,
The amount of intake air Q/Ne per revolution corresponding to the engine load decreases accordingly. Next, at time t ₁ , when the throttle valve changes from open to closed, the intake air amount Q/Ne per rotation rapidly decreases, and as a result, at time t ₂ , Q/Ne becomes 0.1/rev or less. , the fuel cut flag Fcut is set to "1".
Note that at this time, Ne>1000 rpm. Therefore,
A fuel cut is executed and the air-fuel ratio A/F of the engine is rapidly made lean. Next, when the shift change is completed and the clutch changes from the half-clutch state to the sustained state at time _t3 , the rotational speed Ne decreases, and the amount of intake air per rotation Q/Ne decreases accordingly.
increases, and as a result, at time t ₄ , Q/Ne > 0.1
/rev, and the fuel cut flag Fcut is “0”
and the fuel cut ends. In this way, the air-fuel ratio A/F after the shift change becomes appropriate. Note that the air-fuel ratio A/F indicated by a dotted line indicates a case where fuel cut is not performed, and in this case, the air-fuel ratio is on the rich side. Although not explained in the timing diagram of FIG. 5, the steps in FIG.
It is assumed that fuel cut execution control based on 406, 407, and 408 is executed.

FIG. 6 shows a fuel cut routine for realizing the air-fuel ratio control device for an internal combustion engine according to the present invention, in which a step 601 for determining a third fuel cut condition is added to the routine of FIG. . In this step 601, the value calculated in step 404 is
Read the ratio Q/Ne between intake air amount data Q and rotational speed data Ne stored in RAM105, and calculate ΔQ/N←Q/Ne-Q/N _i-1 , where Q/N _i-1 was executed last time. The Q/Ne value at the time is calculated and it is determined whether ΔQ/Ne≦−0.1/rev or not. In other words, it is determined whether the sudden decrease in load is the other time of decrease or increase. As a result, ΔQ/Ne＞
0.1/rev, that is, when there is a small decrease or increase in the load, the fuel is not cut off.This makes it possible to distinguish between gradual deceleration and upshifting, so step 405
The rotation speed under the first fuel cut condition can be set to a relatively low value of 800 rpm.

Effects of the Invention As explained above, according to the present invention, clutch off in a shift change is determined based on the amount of intake air per rotation without providing a clutch switch, so manufacturing costs can be reduced. Since fuel is cut when the rotation speed is above a predetermined speed, it is possible to prevent the engine from stalling when the clutch is off (disengaged) other than during shift-up, such as when the clutch is off immediately after starting.Furthermore, since the number of times fuel cut is executed is limited, it is possible to This prevents the engine from stalling even when it takes time to change it.

[Brief explanation of drawings]

FIG. 1 is an overall block diagram for explaining the configuration of the present invention, FIG. 2 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, and FIG.
4 is a flowchart for explaining the operation of the control circuit in FIG. 2, FIG. 5 is a graph supplementary explanation of the routine in FIG. 4, and FIG. 6 is an air-fuel ratio of the internal combustion engine according to the present invention. 2 is a flowchart showing a fuel cut routine for implementing one embodiment of the control device. 1... Engine body, 3... Air flow meter, 4
... Distributor, 7 ... Fuel injection valve, 1
0...Control circuit.

Claims (1)

[Claims] 1. Intake air amount determination means per rotation for determining whether the intake air amount per rotation of the internal combustion engine is less than or equal to a predetermined value; and rotation speed determination means for determining whether the rotation speed of the engine is equal to or higher than the predetermined value. means and one of said institutions;
an intake air amount change rate per revolution determining means for determining whether a change rate of an intake air amount per revolution is less than or equal to a predetermined value; fuel cut means for stopping the fuel supply to the engine when the rate of change in intake air amount per revolution is equal to or greater than a predetermined value and equal to or less than a predetermined value;
An air-fuel ratio control device for an internal combustion engine, comprising fuel cut operation period limiting means for limiting the maximum period of operation of the fuel cut means depending on the rotational speed or time of the engine.