JP2830413B2 - Air-fuel ratio control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for an internal combustion engine, and more particularly to an air-fuel ratio control device that controls an air-fuel ratio during acceleration.

[Conventional technology]

Conventionally, the rotational behavior after an acceleration instruction is detected, and when the rotational acceleration is equal to or less than a negative predetermined value, the time from the acceleration instruction time to the time when the internal combustion engine rotational acceleration is equal to or more than a positive predetermined value is detected. . If this time is shorter than the predetermined time, the air-fuel ratio is determined to be excessively rich, and the fuel supply amount is reduced and corrected.
If the time is longer than a predetermined time, the air-fuel ratio is determined to be lean, and the fuel supply amount is corrected to be increased (for example, JP-A-1-170737).

[Problems to be solved by the invention]

However, some engine models do not respond sensitively to the air-fuel ratio. Therefore, in such an engine, the difference between the time when the acceleration is instructed and the time when the rotational acceleration of the internal combustion engine becomes equal to or more than the positive predetermined value does not appear much when the air-fuel ratio is lean and when it is rich. Therefore, there is a problem that the air-fuel ratio at the time of acceleration cannot be correctly detected and the air-fuel ratio at the time of acceleration cannot be properly controlled.

An object of the present invention is to improve the acceleration performance by controlling the air-fuel ratio at the time of acceleration even in an engine that does not react sensitively to the air-fuel ratio.

[Means for solving the problem]

As means for solving the above-mentioned problems, the present invention provides, as shown in FIG. 1, an acceleration instructing means for instructing acceleration to an internal combustion engine, and a fuel when the acceleration instructing means detects that acceleration of the internal combustion engine is instructed. An acceleration increasing means for performing a predetermined acceleration increase, a rotation speed decrease detecting means for detecting whether or not the rotation speed of the internal combustion engine has decreased even though the acceleration increasing has been performed by the acceleration increasing means; When a decrease in the rotation speed of the internal combustion engine is detected by the speed decrease detecting means, the acceleration increase is temporarily corrected to the increasing side and the decreasing side sequentially after it is determined by the acceleration instruction means that a steady state has been attained. A temporary acceleration increase correction means to perform, and a decrease in the rotation speed at the initial stage of acceleration becomes empty according to the increase in the rotation speed when the acceleration increase is corrected to the increase side and the decrease side by the temporary acceleration increase correction means. A determination means for determining that the fuel ratio is lean or rich; and an acceleration increase correction means for correcting the acceleration increase to either increase or decrease based on the determination result of the determination means, for an internal combustion engine. An air-fuel ratio control device is proposed.

[Action]

Thereby, if the rotation speed decreases after the acceleration instruction is detected and the fuel injection amount is increased, the acceleration instruction means determines that the steady state has been reached, and then temporarily increases the acceleration increase amount. It is determined in order that the decrease in the rotational speed at the initial stage of acceleration was lean or rich in the air-fuel ratio according to the increase in the rotational speed at that time, and the increase in the acceleration was determined based on the determination result. Correct to either increase or decrease.

〔The invention's effect〕

As described above, in the present invention, the acceleration increase is temporarily corrected to the increase side and the decrease side in order, and the decrease in the rotational speed at the initial stage of the acceleration corresponds to the lean or excessive air-fuel ratio according to the increase in the rotational speed at that time. It is determined that the fuel density is rich, and the increase in acceleration is corrected to either increase or decrease based on the determination result, so that the increase in acceleration is corrected so that the air-fuel ratio becomes appropriate. Therefore, even in an engine that does not respond sensitively to the air-fuel ratio, if the rotation drops during acceleration or the backlash occurs, it is possible to determine whether the air-fuel ratio is too lean and control the air-fuel ratio to optimize the air-fuel ratio during acceleration. There is an excellent effect that the property is improved.

〔Example〕

FIG. 2 shows a first embodiment in which the fuel supply control device for an internal combustion engine according to the present invention is applied to a gasoline-type automobile internal combustion engine.

In the figure, an internal combustion engine 1 includes a cylinder 2, a piston 3,
It has a combustion chamber 6 formed by a cylinder block 4 and a cylinder head 5. An ignition plug 7 is provided in the combustion chamber 6. The rotational driving force from the piston 3 is
It is transmitted to driving wheels (not shown) via various devices such as a transmission (not shown). Further, the rotation driving force rotates a generator (not shown) to supply power to each device, and stores the power in a power supply battery (not shown).

An intake system of the internal combustion engine 1 communicates with an upstream intake pipe 9 via an intake valve 8 of a combustion chamber 6, and a surge tank 10 for absorbing pulsation of intake air is provided upstream of the intake pipe 9. A throttle valve 11 is provided upstream of the surge tank 10. The opening of the throttle valve 11 is adjusted by a driver's instruction of acceleration / deceleration of an accelerator pedal 12.

On the other hand, the exhaust system of the internal combustion engine 1 passes through an exhaust pipe 17 and a catalytic converter 17a for exhaust gas purification via an exhaust valve 16 of the combustion chamber 6.

The fuel system includes a fuel supply source including a fuel tank and a fuel pump (not shown), and a fuel injection valve 18 disposed in a fuel supply pipe and an intake pipe 9.

The ignition system includes an igniter 19 for outputting a high voltage necessary for ignition and a distributor 20 for distributing and supplying the high voltage generated by the igniter 19 to the ignition plug 7 in conjunction with a crankshaft (not shown). Have been.

Further, the internal combustion engine 1 serves as a detector, which is provided in front of the intake pipe 9 to measure an intake air flow rate.
1, an intake air temperature sensor 32 provided in the intake pipe 9 for measuring the intake air temperature, a throttle position sensor 33 for detecting the opening of the throttle valve in conjunction with the throttle valve 11, and a cooling system for the cylinder block 4. A water temperature sensor 34 is provided to detect a cooling water temperature, and an oxygen sensor 35 is provided in the exhaust pipe 17 and detects residual oxygen in exhaust gas. The throttle position sensor 33 also includes an idle switch 33a that outputs an ON signal when the throttle valve 11 is fully closed.

The rotation angle signal N and the camshaft of the distributor 20 are provided in the distributor 20 every 1/24 rotation of the camshaft of the distributor 20, that is, every integer multiple of the crank angle from 0 ° to 30 °. A rotation sensor 38 is provided for outputting two crank angle position signals G1 and G2 once for each rotation, that is, for every two rotations of a crankshaft (not shown).

The signals from the sensors are input to an electronic control unit (hereinafter, simply referred to as an ECU) 40, and the ECU 40 controls the internal combustion engine 1 based on the signals and other information.

Next, the configuration of the ECU 40 will be described with reference to FIG.

The ECU 40 has a CPU 40a, a ROM 40b, a RAM 40c, and a backup RAM 40d.
And a logical operation circuit mainly composed of the clock 40z and the like. The ECU 40 performs input / output with the outside via a common bus 40e, an input / output port 40f, an input port 40g, and an output port 40h. The power supply circuit 41 is connected to a power supply line 42, and the power supply line 42 is connected to a power supply / power storage battery 44 via a key switch 43.

The backup RAM 40d is configured to be supplied with power from another power supply circuit 46 and retain the stored contents even when the key switch 43 is turned off and the power supply to the ECU 40 is stopped.

The ECU 40 includes a buffer 40 for the detection signal of each sensor described above.
e, 40j, 40k, 40w, a multiplexer 40n, and an A / D converter 40p, and these detection signals are supplied to the CPU 40 via an input / output port 40f.
Entered in a.

Also, the ECU 40 is provided with a signal of the oxygen detection signal buffer 40q, the comparator 40r, and the idle switch 33a and the rotation sensor.
A waveform shaping circuit 40s with 38 signals is provided, and these signals are input to the CPU 40a via the input port 40g.

Further, the ECU 40 includes the driving circuit 40u for the fuel injection valve 18 described above.
And a drive circuit 40y for the igniter 19. The CPU 40a outputs a control signal to the drive circuits 40u and 40y via the output port 40h.

Next, a first embodiment executed by the ECU 40 will be described. FIG. 4 is a flowchart showing the contents of arithmetic processing which is stored in the ROM 40b and executed by the CPU 40a of the ECU 40 and detects lean and rich air-fuel ratios during acceleration. This routine is executed at a predetermined time (for example, every 8 ms).

7 and 8 are time charts showing the relationship between the engine speed NE, the acceleration increase FAEW, the correction coefficients KKAEW, KAEW, and the like in the air-fuel ratio rich during acceleration and the air-fuel ratio lean during acceleration, respectively.

The operation in the flowchart shown in FIG. 4 will be described with reference to this time chart.

First, in step 101, it is determined whether or not there is an acceleration instruction based on the rate of change of the throttle opening (TA). If there is an acceleration instruction, that is, if there is a throttle opening change rate equal to or more than a predetermined value, the process proceeds to step 102, where a counter described later is used.
Clear C _RICH and C _LEAN . Further counter C ₁ is also clear that to calculate the increase time by the correction coefficient KKAEW temporarily corrected acceleration increase at step 103. Next, at step 104, it is determined from the change rate .DELTA.NE of the engine rotational speed whether there is any slack in the initial stage of acceleration, a decrease in rotation, or the like. If ΔNE is smaller than 0, that is, if there is a drop in rotation or the like, the routine proceeds to step 105, where it is determined from the throttle opening change rate ΔTA whether or not the throttle is in a steady state. When it is determined that the vehicle is in the steady state, the process proceeds to step 106, where the temporary acceleration increase correction coefficient KKAEW is set to a predetermined value (1.5 in this embodiment) that increases the acceleration increase AEW.
To load. In step 107, it is determined from ΔNE whether or not fuel injection based on the increase by KKAEW is performed to improve the acceleration (slack, rotation drop). When ΔNE is larger than 0, that is, when the acceleration is improved, the routine proceeds to step 109, where the counter C _RICH is incremented.

If the acceleration is temporarily increased in step 106 and the fuel injection is performed based on the increased acceleration, and as a result the acceleration is improved in step 107, the air-fuel ratio was in a lean state before the acceleration was temporarily increased. Become. The operation of ΔNE, KKAEW in the air-fuel ratio lean state is shown in FIG. Counter C _RICH
Increases or decreases according to the engine change rate ΔNE when the acceleration is temporarily increased, and when ΔNE is greater than 0, C is determined in step 109.
_{The RICH} is incremented. If ΔNE is smaller than 0, the C _RICH is decremented in step 108. Below counter C
Counter C ₁ at step 110 the increment or decrement the _RICH is determined whether or not reached a predetermined time B, step 105 until the counter C ₁ reaches the predetermined time B
Steps 110 to 110 are repeated. At this time, in the air-fuel ratio lean state, the counter C _RICH increases as shown in FIG. When the counter C ₁ reaches the predetermined time B proceeds to step 111.
Incidentally, the predetermined time B is set so that fuel is injected at least once during this time. In step 111 clears the counter C _2. The counter C ₂ is to calculate the loss time due to temporary acceleration increase correction coefficient KKAEW temporarily corrected acceleration increase AEW.

Continue the counter C ₂ meet and step 112 compares the throttle opening change rate ΔTA and a predetermined value A, and determines whether the throttle steady state. Steady state or ΔTA
If it is determined that .ltoreq.A, the routine proceeds to step 113, where a predetermined value (0.5 in this embodiment) for decreasing the acceleration increase AEW is loaded to the temporary acceleration increase correction coefficient KKAEW. In step 114 KK
It is determined from ΔNE whether or not the fuel injection based on the weight reduction by AEW is performed and the acceleration performance (slack, rotation drop, etc.) is improved. When acceleration is improved, that is, ΔNE ≧ 0
If determined to be, the process proceeds to step 116.

In step 113, the fuel is temporarily reduced, and the fuel injection based on the reduced fuel is performed. As a result, when it is determined in step 114 that the acceleration is improved, the air-fuel ratio was in an excessively rich state before the temporary reduction. Will be. The operation of ΔNE, KKAEW in the air-fuel ratio rich state is shown in FIG.

The counter C _LEAN is increased or decreased in accordance with the engine change rate ΔNE when the acceleration increase is temporarily reduced. When ΔNE is larger than 0, C _LEAN is incremented in step 116, and when smaller than 0, the processing proceeds to step 115. Decrement the counter C _LEAN by. Or more, the counter C _LEAN the ink or decremented, the counter C ₂ is determined whether or not reached a predetermined time D proceeds to step 117, the counter C ₂
Are repeated until the predetermined time D is reached. At this time, if the air-fuel ratio is
_LEAN increases as shown in FIG. The predetermined time D is set so that fuel is injected at least once during this time.

Counter C ₂ loads the 1 per hour increase correction coefficient KKAEW at step 118 reaches a predetermined time D, and terminates the routine. Also, when there is no acceleration instruction in step 101, when there is no rotation drop in response to the acceleration instruction in step 104, and when it is determined that the throttle is not in a steady state in steps 105 and 112, the temporary increase correction coefficient KKAEW is also added in step 118. 1 is loaded, and this routine ends.

FIG. 5 shows a calculation flow of the acceleration increase correction coefficient KAEW.
This calculation flow is executed at a sufficiently short time interval, for example, every 4 ms.

In step 201, by comparing the counter C _RICH with a predetermined value E, it is determined whether or not the required increase value of the engine is on the increase side with respect to the already set acceleration increase AEW. When the requested increase value is determined to be on the increase side, that is, the counter C
_{If RICH} exceeds the predetermined value E, KAEW at step 202
Add 0.05 to. The updated KAEW obtained by the addition is stored in the backup RAM 40d. Next, in step 205, the counter C _RICH is cleared, and this routine ends.

If it is determined in step 201 that the requested increase value is not on the increase side, the process proceeds to step 203. In step 203, by comparing the counter C _LEAN with a predetermined value F, it is determined whether or not the required increase amount of the engine is on the decrease side with respect to the already set acceleration increase amount AEW. If the requested increase value is determined to be on the decrease side, that is, if the counter C _LEAN exceeds the predetermined value F, in step 204 the acceleration increase correction coefficient KAEW is used.
Subtract 0.05. The updated KAEW obtained by the subtraction is stored in the backup RAM 40d. Next, in step 206, the counter C _LEAN is cleared, and this routine ends. When the determination in step 203 is NO, that is, when the counter C _LEAN has not reached the predetermined value F and the counter C _RICH has not reached the predetermined value E, KAEW is not updated and this routine ends. When the processing according to this routine is executed, the processing shown in FIG. 4 is interrupted and waits.

FIG. 6 shows a calculation flow of the acceleration increase. This processing is executed at a sufficiently short time interval, for example, every 4 ms.

First, in step 301, the acceleration increase AEW is calculated from the following equation.

AEW = AEWB × DLQN / K AEWB is a correction coefficient determined by the water temperature, DLQN is a change rate of the intake air amount, and K is a constant determined by the engine.

Next, in step 302, the acceleration increase AEW is corrected by the following formula, and the corrected acceleration increase FAEW is calculated.

FAEW = AEW x KAEW x KKAEW KAEW is the acceleration increase correction coefficient that corrects the acceleration increase AEW according to the lean / rich air-fuel ratio, and KKAEW is the forced increase AEW to detect the lean / rich air-fuel ratio. Is a temporary acceleration increase correction coefficient for increasing / decreasing.

The CPU 40a calculates the injection pulse width TAU of the fuel valve 18 based on the FAEW obtained as described above. When the processing according to this routine is executed, the processing shown in FIG. 4 is interrupted and waits. In the first embodiment, steps 101 and 10
Steps 5 and 112 correspond to the acceleration instruction means of the present invention.
Corresponds to the acceleration increasing means of the present invention, step 104 corresponds to the rotational speed decrease detecting means, steps 106 and 113 correspond to the temporary acceleration increasing correction means, and steps 107 and 114 correspond to the determining means of the present invention. Steps 102, 103, 108-110, 11
5 to 117 and 201 to 206 correspond to the acceleration increase correction means of the present invention.

The second embodiment will be described with reference to the flowchart shown in FIG.

First, it is determined in step 801 whether or not there is an acceleration instruction based on the throttle opening change rate, and if there is an acceleration instruction, it is determined in step 802 whether or not there is a rotation drop from the rotational speed change rate ΔNE. If it is determined that there is a rotation drop, step 803
Is used to determine whether or not the throttle is in a steady state from the throttle opening degree change rate ΔTA. When the steady state is determined, the temporary acceleration increase correction coefficient KKAEW is incremented in step 804. This incremented KKA in step 805
It is determined whether the fuel injection based on the EW has been performed and the acceleration has been improved. When the acceleration is improved, that is, when ΔNE> 0, the process proceeds to step 813 to store the KKAEW at this time. If it is determined that the acceleration is not improving, step 80
Proceeding to 6, it is determined whether or not KKAEW has reached a predetermined value (1.5 in this embodiment). Step 80 until KKAEW reaches 1.5
Steps 3 to 806 are repeated. In step 805, it is not determined that ΔNE is larger than 0, and when KKAEW reaches 1.5, the routine proceeds to step 807, where KKAEW is once returned to 1. Next, at step 808, it is determined whether or not the throttle is in a steady state. If the throttle is in a steady state, KKAEW is decremented. In step 810, the fuel injection based on the decremented KKAEW is performed, and it is determined from the rotation speed change rate whether or not the acceleration is improved. When the acceleration is improved, the process proceeds to step 813 to store the KKAEW at this time.

If it is determined in step 810 that the acceleration has not improved, the process proceeds to step 811 to determine whether or not KKAEW has reached 0.5. Steps 808-811 until KKAEW reaches 0.5
Is repeated. During this time, it is not determined in step 810 that the acceleration has improved, and when KKAEW reaches 0.5, step 812 is performed.
And set KKAEW to 1.

The difference from the first embodiment is that the temporary acceleration increase correction coefficient KK
AEW operation. In the second embodiment, KKAEW is integrated (increased / decreased) in steps 804 and 809, and the KKAEW where ΔNE becomes larger than 0 is stored and stored in the backup RAM 40d. Then, as shown in the flow of Fig. 10, the acceleration increase AEW
Is corrected by the above stored KKAEW to calculate FAEW.

This eliminates the need for a counter operation and allows the optimum value of FAEW to be obtained at an earlier timing.

 The above operation will be described with reference to FIGS. 11 and 12.

FIG. 11 shows a case where the air-fuel ratio is lean, where there is an acceleration instruction and Δ
When NE becomes smaller than 0, the temporary acceleration increase correction coefficient KKAE
W increases with the passage of time. At this time, the corrected acceleration increase FAEW increases with respect to the acceleration increase AEW. When ΔNE turns positive, KKAEW retains the value at that time. KKA at this time
EW is stored and reflected in the acceleration increase at the next acceleration.

Fig. 12 shows the case when the air-fuel ratio is too rich.
Becomes smaller than 0, KKAEW increases over time. If ΔNE does not become positive in the meantime, KKAEW returns to 1 when it reaches 1.5, and then decreases over time. When ΔNE turns positive, KKAEW retains the value at that time.

The KKAEW at this time is stored and reflected in the acceleration increase at the next acceleration. Note that, in the second embodiment, the step
Steps 801, 803, and 808 correspond to the acceleration instructing means of the present invention, step 802 corresponds to the rotational speed decrease detecting means of the present invention, and steps 804, 806, 809, and 811 correspond to the temporary acceleration increasing correction means of the present invention. Steps 805 and 810 correspond to the determination means of the present invention, and step 813 corresponds to the acceleration increase correction means of the present invention.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a block diagram of the electronic control unit, and FIG. 4 is a processing example of the first embodiment. FIG. 5 is a flowchart showing a process for detecting lean and rich air-fuel ratios performed in accordance with the first embodiment, FIG. 5 is a flowchart showing a process for correcting the acceleration increase correction coefficient in the first embodiment, and FIG. 7 is a time chart showing the operation of various coefficients at the time of lean air-fuel ratio acceleration in the first embodiment, and FIG. 8 is a flowchart showing various coefficients at the time of air-fuel ratio rich acceleration in the first embodiment. FIG. 9 is a flowchart showing the air-fuel ratio lean / rich detection process in the second embodiment, FIG. 10 is a flowchart showing the process for calculating the acceleration increase in the second embodiment, FIG. Figure 11 shows FIG. 12 is a time chart showing the operation of various coefficients during the air-fuel ratio rich acceleration in the second embodiment, and FIG. 12 is a time chart showing the operation of various coefficients during the air-fuel ratio lean acceleration in the second embodiment. 1 Internal combustion engine 33 Throttle position sensor 38
… Rotation sensor, 40 …… Electronic control device.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-195432 (JP, A) JP-A-62-91640 (JP, A) JP-A-1-170737 (JP, A) 56741 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F02D 41/00-41/40

Claims (1)

(57) [Claims] 1. Acceleration instructing means for instructing the internal combustion engine to accelerate, and accelerating increasing means for increasing the fuel by a predetermined amount when the acceleration instructing means detects that acceleration of the internal combustion engine has been instructed. Rotation speed decrease detection means for detecting whether or not the rotation speed of the internal combustion engine has decreased even though acceleration acceleration has been performed by the acceleration increase means; and decrease in the rotation speed of the internal combustion engine by the rotation speed decrease detection means. Is detected, the acceleration instructing means determines that the vehicle is in a steady state, and then temporarily increases the acceleration in order to sequentially increase and decrease the acceleration. A determination is made to determine that the decrease in the rotation speed at the initial stage of acceleration was lean or rich in the air-fuel ratio in accordance with the increase in the rotation speed when the acceleration increase was corrected to the increase side and the decrease side of the acceleration increase. Means for correcting the increase in acceleration to either increase or decrease based on the result of the determination by the determination means, and an air-fuel ratio control device for an internal combustion engine.