JPH0689687B2 - Fuel control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel control for an internal combustion engine, which detects an intake air amount of the internal combustion engine by an intake air amount sensor and controls the fuel supply amount of the internal combustion engine by the detection output. It relates to the device.

[Conventional technology]

When performing fuel control of an internal combustion engine, an intake air amount sensor (hereinafter abbreviated as AFS) is arranged upstream of the throttle valve, and the intake air amount per intake air is obtained from this information and the engine speed to determine the supply fuel amount. Control is taking place.

By the way, when an AFS is arranged upstream of the throttle valve in the air intake passage to detect the intake air amount of the internal combustion engine, when the throttle opens suddenly, the intake passage between the throttle valve and the engine is opened. Since the amount of air to be filled is also measured, the amount of air that is actually sucked into the internal combustion engine is more than the amount actually measured, and if the fuel amount is controlled as it is, there is a problem that it becomes overrich. For this reason,
Conventionally, the output of AFS, that is, the detected intake air amount at a predetermined crank angle is AN ₍ t ₎ , n-1 times of the predetermined crank angle and n
The amount of air taken in by the internal combustion engine at the second time is calculated as AN ₍ n _-1 ) and
If AN ₍ n ₎ is K and the filter constant is K, then AN ₍ n ₎ is calculated by the formula: AN ₍ n ₎ = K ₁ × AN ₍ n _-1) + K ₂ × AN ₍ t ₎ and this AN ₍ n ₎ There is a method of performing fuel control by using a fuel injection method, which smoothes the intake air amount for each predetermined crank angle (annealing process) and performs appropriate fuel control.

[Problems to be solved by the invention]

Conventionally, as described above, the intake air amount AN during a predetermined crank angle obtained from the output of the intake air amount sensor during acceleration of the internal combustion engine.
If fuel control is performed using (t) as it is, it becomes overrich, and conversely, it becomes lean when decelerating. Therefore, it is possible to perform fuel control using AN (n) obtained by smoothing (filtering) this intake air amount. Was being considered. However, although this smoothing process can prevent overrich during acceleration and over lean during deceleration, it causes a delay in detection and calculation of the intake air amount due to the smoothing process. Sometimes, there was a problem that it became overrich.

The present invention has been made to solve the above problems, and it is possible to prevent over lean at the time of deceleration by the smoothing process and also to prevent the overrich due to the smoothing process. The purpose is to obtain a control device.

[Means for solving problems]

The fuel control device for an internal combustion engine according to the present invention includes an intake air amount sensor provided upstream of a throttle valve of the internal combustion engine, a crank angle sensor for detecting a predetermined crank angle of the internal combustion engine, and an output of the intake air amount sensor. From the output of the crank angle sensor and the output of the crank angle sensor, an AN detection means for detecting the intake air amount AN (t) between predetermined crank angles of the internal combustion engine in synchronization with the output of the crank angle sensor, and the AN (t) for each predetermined crank angle. In the fuel control device for an internal combustion engine, which performs the smoothing process and generates a smoothed intake air amount AN (n), and the fuel control device for the internal combustion engine which controls the fuel supply amount of the internal combustion engine based on the AN (n).
Intake air amount decrease detection means for detecting that (n) has decreased, and the supply fuel according to the decrease amount ΔAN of AN (n) when the decrease amount of AN (n) is larger than a predetermined value. It is designed to reduce the amount.

[Action]

When controlling the amount of fuel supplied to the internal combustion engine based on the intake air amount at each predetermined crank angle, the detected intake air amount is used in order to suppress undershoot during transition. When the smoothed intake air amount is decreasing and the decreasing amount is equal to or larger than the predetermined value, the supplied fuel amount is decreased according to the decreasing amount.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows a model of an intake system of an internal combustion engine, where 1 is an internal combustion engine, having a volume of V _C per stroke, and having a Karman vortex flowmeter AFS13, a throttle valve 12, a surge tank 11 and an intake pipe 15. Intake air through the fuel through the injector
Supplied by 14. Also, here the throttle valve 12
The volume from to the internal combustion engine 1 is V _S. 16 is an exhaust pipe.

FIG. 4 shows the relationship of the intake air amount with respect to a predetermined crank angle in the internal combustion engine 1, and (a) shows the predetermined crank angle (hereinafter referred to as SGT) of the internal combustion engine 1. (B) is AFS
The amount Qa of air passing through 13 and (c) show the amount Qe of air sucked by the internal combustion engine 1, and (d) shows the output pulse f of the AFS 13. Also, S
The period of n-2 to n-1 rising of GT is tn _-1 , n-1
~ The rising period of the nth time is set to tn, and the periods tn _-1 and tn
The intake air amount that passes through the AFS13 is Qa ₍ n _-1) and Qa, respectively.
₍ n ₎ , Qe ₍ n _-1) and Qe ₍ n ₎ are the air amounts taken in by the internal combustion engine 1 during the periods tn _-1 and tn, respectively. Further, the average pressure and the average intake air temperature in the surge tank 11 during the periods tn _-1 and tn are Ps ₍ n _-1) and Ps ₍ n ₎ and Ts ₍ n _-1) and Ts ₍ n ₎ , respectively. Here, for example, Qa ₍ n _-1) corresponds to the number of output pulses of the AFS 13 during tn _-1 . Also, since the rate of change of intake air temperature is small,
Assuming that Ts ₍ n _-1) ≈ Ts ₍ n ₎ and the charging efficiency of the internal combustion engine 1 is constant, Ps ₍ n _-1) · Vc = Qe ₍ n _-1) · R · Ts ₍ n ₎ …… (1 ) Ps ₍ n ₎・ Vc ＝ Qe ₍ n ₎・ R ・ Ts ₍ n ₎・ ・ ・ (2). However, R is a constant. Then, the amount of air accumulated in the surge tank 11 and the intake pipe 15 during the period tn is ΔQa ₍ n ₎
Then, And, from equations (1) to (3), Is obtained. Therefore, the air amount Qe ₍ n _{) taken in} by the internal combustion engine 1 in the period tn can be calculated by the equation (4) based on the air amount Qa ₍ n ₎ passing through the AFS 13. Here, Vc = 0.
5 and Vs = 2.5, Qe ₍ n ₎ = 0.83 x Qe ₍ n _-1) + 0.17 x Qa ₍ n ₎ ... (5). FIG. 5 shows a state in which the throttle valve 12 is closed. In FIG. 5, (a) is the opening of the throttle valve 12, and (b) is the intake air amount Qa passing through the AFS 13.
And overshoot. (C) is the amount Qe of air taken in by the internal combustion engine 1 corrected by equation (4), and (d) is the pressure P of the surge tank 11. (E) is the amount of change in Qe ΔQe
And (f) shows the fuel supply amount f. Where f ₁ is Qe
And f ₂ is corrected based on ΔQe.

FIG. 1 shows the structure of a fuel control device for an internal combustion engine according to the present invention. 10 is an air cleaner arranged upstream of the AFS 13, and AFS 13 is shown in FIG. 4 according to the amount of air taken into the internal combustion engine 1. The crank angle sensor 17 outputs a pulse as shown in FIG. 4 (d), and the crank angle sensor 17 outputs a pulse as shown in FIG. 4 (a) according to the rotation of the internal combustion engine 1 (for example, a crank angle of 180 ° from one pulse rising to the next rising). Is output). Reference numeral 20 denotes AN detection means, which is within the predetermined crank angle of the internal combustion engine 1 by the output of the AFS13 and the output of the crank angle sensor 17.
Calculate the number of output pulses of. Reference numeral 21 is an AN calculation means, which performs the same calculation as the equation (5) from the output of the AN detection means 20 and calculates the number of pulses corresponding to the output of the AFS13 corresponding to the air amount considered to be taken in by the internal combustion engine 1. To do. Further, the control means 22 drives the injector 14 according to the amount of air taken in by the internal combustion engine 1 based on the output of the AN calculation means 21 and the output of a water temperature sensor 18 (for example, a thermistor) that detects the cooling water temperature of the internal combustion engine 1. The time is controlled to control the amount of fuel supplied to the internal combustion engine 1.

FIG. 2 shows a more specific structure of this embodiment, 30 is AFS1
3, a control device that receives the output signals of the water temperature sensor 18 and the crank angle sensor 17, and controls the four injectors 14 provided for each cylinder of the internal combustion engine 1.
Reference numeral 30 corresponds to the AN detection means 20 to control means 22 in FIG.
This is realized by a microcomputer (hereinafter abbreviated as CPU) 40 having a RAM 42. Further, 31 is a frequency divider connected to the output of the AFS13, 32 is an exclusive OR gate in which the output of the frequency divider 31 is one input and the other input terminal is connected to the input P1 of the CPU 40. Output terminal is counter 33 and CP
Connected to input P3 of U40. 34 is an interface connected between the water temperature sensor 18 and the A / D converter 35, 36 is a waveform shaping circuit to which the output of the crank angle sensor 17 is input, and the output is input to the interrupt input P4 and the counter 37 of the CPU 40. To be done. Further, 38 is a timer connected to the interrupt input P5, 39 is A / D converting the voltage of the battery (not shown) to A / D and outputting it to the CPU 40.
The D converter, 43 is a timer provided between the CPU 40 and the driver 44, and the output of the driver 44 is connected to each injector 14.

Next, the operation of the above configuration will be described. The output of the AFS 13 is frequency-divided by the frequency divider 31 and input to the counter 33 via the exclusive OR gate 32 controlled by the CPU 40. Counter 33 measures the period between rising edges of the output of gate 32. The CPU 40 inputs the falling edge of the gate 32 to the interrupt input P3, performs an interrupt process every output pulse cycle of the AFS13 or every frequency divided by two, and measures the cycle of the counter 33. The output of the water temperature sensor 18 is converted into a voltage by the interface 34a, converted into a digital value by the A / D converter 35 every predetermined time, and taken into the CPU 40. Crank angle sensor 1
The output of 7 is input to the interrupt input P4 of the CPU 40 and the counter 37 via the waveform shaping circuit 36. The CPU 40 performs an interrupt process every time the crank angle sensor 17 rises, and the crank angle sensor 17
The period between the rising edges of is detected from the output of the counter 37. The timer 38 generates an interrupt signal to the interrupt input P5 of the CPU 40 every predetermined time. The A / D converter 39 performs A / D conversion on a battery voltage (not shown), and the CPU 40 takes in data of this battery voltage at predetermined time intervals. Timer 43 is preset in CPU 40, C
It is triggered by the output port P2 of the PU40 and outputs a predetermined pulse width, which is output via the driver 44 to the injector 14
To drive.

Next, the operation of the CPU 40 will be described with reference to the flowcharts of FIGS. 6 and 8-9. First, FIG. 6 shows the main program of the CPU 40. When a reset signal is input to the CPU 40, the RAM 42, the input / output port, etc. are initialized in step 100, and the output of the water temperature sensor 18 is A / D converted in step 101. , WT is stored in the RAM 42. In step 102, the battery voltage is A / D converted and stored in the RAM 42 as VB. Step
In 103, 30 / T _R is calculated from the cycle T _R of the crank angle sensor 17, and the rotation speed Ne is calculated. In step 104, AN · Ne / 30 is calculated from load data AN and rotation speed Ne, which will be described later, and AFS
Calculate the output frequency Fa of 13. In step 105, the output frequency Fa is set to f ₁ as shown in FIG.
The basic drive time conversion coefficient Kp is calculated from the above. Step 106a
Then, the conversion coefficient Kp is corrected by the water temperature data WT and stored in the RAM 42 as the drive time conversion coefficient K _I. In step 106b deceleration reduction during basic driving time of the conversion coefficient K _PA water temperature data WT
Is corrected by and is stored in the RAM 42 as the drive time conversion coefficient K _IA . That is, when the water temperature is low, there is more fuel and the intake pipe 15
Adheres inside and requires more fuel for that amount,
When the water temperature is high, the adhered fuel amount is small and the supplied fuel amount may be small. In step 107, the data table f ₃ stored in advance in the RAM 41 is mapped from the battery voltage data VB, the dead time T _D is calculated and stored in the RAM 42. step 1
After the processing of 07, the processing of step 101 is repeated again.

FIG. 8 shows the interrupt processing for the interrupt input P3, that is, the output signal of the AFS13. In step 201, the output T _F of the counter 33 is detected and the counter 33 is cleared. This T _F is the period between the rising edges of the gate 32. If the frequency division fractal in RAM 42 is set in step 202, _TF is _divided into 2 in step 203 and A
It is stored in the RAM 42 as the output pulse cycle T _A of FS13. Then the remaining pulse data P to the integrated pulse data P _R at step 204
Add 2 times _D and add new integrated pulse data P _R
And This integrated pulse data P _R is used by the crank angle sensor 17
The number of AFS13 pulses that are output during the rising edge of is integrated, and is treated as 156 times as much as one pulse of AFS13 for processing reasons. If division flag in step 202 if it is reset, the output pulse period T _A period T _F in step 205
Stored in RAM42 as
The remaining pulse data P _D is added to P _R. In step 207, 156 is set in the remaining pulse data P _D. Step 208
If the division flag is reset by, T _F > 2msec,
If T _F > 4msec if set, step 210
Otherwise, go to step 209. Step 209
Then, the frequency division flag is set, the frequency division flag is cleared in step 210, and P1 is inverted in step 211. Therefore, in the case of the process of step 209, a signal is input to the interrupt input P3 at the timing when the output pulse of the AFS13 is divided by two, and when the process of step 210 is performed, the interrupt input P3 is output for each output pulse of the AFS13. A signal comes in. After processing steps 209 and 211,
Complete the interrupt process.

FIG. 9 shows the interrupt processing when an interrupt signal is generated at the interrupt input P4 of the CPU 40 by the output of the crank angle sensor 17. In step 301, the cycle between the rising edges of the crank angle sensor 17 is read from the counter 37 and stored in the RAM 42 as the cycle T _R ,
Clear counter 37. AFS in step T _R in step 302
If there are 13 output pulses, in step 303, the time t ₀₁ of the output pulse of the AFS 313 immediately before that and the crank angle sensor 17
Calculate the current interrupt time t ₀₂ time difference Δt = t ₀₂ −t ₀₁ ,
This was the period T _S, when the output pulse of AFS13 is not within the period T _R is the period T _R a period T _S. 156 in step 305
The time difference Δt is converted into the output pulse data ΔP of the AFS13 by the calculation of × T _S / T _A. That is, the pulse data ΔP is calculated assuming that the output pulse cycle of the previous AFS13 and the output pulse cycle of the current AFS13 are the same. In step 306, if the pulse data ΔP is smaller than 156, it is clipped to step 308, and if it is large, ΔP is clipped to 156 in step 307. Step
At 308, the pulse data ΔP is subtracted from the remaining pulse data P _D to obtain new remaining pulse data ΔP. Step 30
In 9 if the remaining pulse data P _D is positive, step 313a
In other cases, the calculated value of the pulse data ΔP is too large than the output pulse of the AFS 13, so the pulse data ΔP is made equal to P _{D in} step 310, and the remaining pulse data P _{D is set} to zero in step 312. In step 313, it adds the pulse data ΔP to the integrated pulse data P _R, and the new integrated pulse data P _R. This data P _R corresponds to the number of pulses considered to be output by the AFS 13 during the rising of the crank angle sensor 17 this time. In step 314, the calculation corresponding to the equation (5) is performed. That is, the load data AN and the integrated pulse data P _R calculated up to the previous rise of the crank angle sensor 17
More performs computation of _{K 1 AN + (K 2)} P R, the result of the intake air amount detected by the current new load data AN Namasu. In step 315, this load data AN is the predetermined value α
If it is larger, the value is clipped to α in step 316 so that the load data AN does not become larger than the actual value even when the internal combustion engine 1 is fully opened. In step 317, the integrated pulse data P _R is cleared. Load data in step 318a
The drive time data T _I = AN ・ K _I + T _D is calculated from AN, the drive time conversion coefficient K _I , and the dead time T _D. In step 318b, the difference ΔA between the new load data AN and the previous load data AN _OLD
N is determined, and in step 318c, it is determined whether or not ΔAN is smaller than −β ₁ , and if larger, the process proceeds to step 318g.
If ΔAN <−β ₁ , ΔAN is −β in step 318d.
_It is judged whether it is smaller than ₂ , and if it is larger, the step
318f, and if smaller, proceed to step 318e and ΔAN
Is clipped to -β ₂ and the process proceeds to step 318f. Step
In 318f, drive time data T _I is calculated from T _I , ΔAN and K _IA , and in step 318g the data is updated as AN _OLD = AN and RAM is updated.
Store in 42. Next, in step 319, the drive time data T _I
Is set in the timer 43 and the timer 43 is triggered in step 320, so that four injectors 14 are simultaneously driven according to T _I , and the interrupt processing is completed.

FIG. 10 shows the timing when the frequency dividing flag is cleared in the processing of FIGS. 6 and 8 to 9, (a) shows the output of the frequency divider 31, and (b) shows the crank angle sensor. Shows 17 outputs. (C) shows the remaining pulse data P _D , frequency divider
It is set to 156 for each rising and falling of 31 (rising of the output pulse of AFS13), and is changed to the calculation result of, for example, P _D i = P _D −156 × T _S / T _A for each rising of the crank angle sensor 17. (This corresponds to the processing of steps 305-312.).
(D) shows a change in the integrated pulse data P _R , and shows how the remaining pulse data P _D is integrated every time the output of the frequency divider 31 rises or falls.

In the above embodiment, the crank angle sensor 17 rises between
Although the output pulse of the AFS13 is counted, it may be counted during the falling edge, or the number of AFS13 output pulse during several cycles of the crank angle sensor 17 may be counted. Although the output pulses of the AFS13 are counted, the number of output pulses may be multiplied by a constant corresponding to the output frequency of the AFS13. Furthermore, instead of the crank angle sensor 17 to detect the crank angle,
The same effect can be obtained by using the ignition signal of the internal combustion engine 1.

As described above, according to the present invention, in the one in which the supply fuel amount is controlled based on the smoothed intake air amount, the supply fuel amount is decreased according to the decrease amount of the smoothed intake air amount. It is possible to correct an excessive amount of fuel due to a delay in calculation of the amount, a delay in control, and the like, and prevent unnecessary correction due to output ripple of the intake air amount sensor, noise of the output signal, and the like, and perform appropriate air-fuel ratio control.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a fuel control device according to the present invention, FIG. 2 is a configuration diagram showing an embodiment as a specific example of the fuel control device for the internal combustion engine, and FIG. FIG. 4 is a configuration diagram showing a model of an intake system of an internal combustion engine according to the present invention, FIG. 4 is a diagram showing a relationship of an intake air amount with respect to a crank angle thereof, and FIG. 5 is a change of the intake air amount during a transition of the internal combustion engine. Waveform diagrams, FIGS. 6, 8 and 9 are flowcharts showing the operation of the fuel control device for an internal combustion engine according to an embodiment of the present invention, and FIG. 7 is a graph for the AFS output frequency of the fuel control device for the internal combustion engine. FIG. 10 is a diagram showing the relationship between basic drive time conversion coefficients, and FIG. 10 is a timing chart showing the timing of the flow in FIGS. 8 and 9. 1 ... Internal combustion engine, 12 ... Throttle valve, 13 ... Air flow sensor (Karman vortex flowmeter), 14 ... Injector, 15 ... Intake pipe, 17 ... Crank angle sensor, 18 ... Water temperature sensor, 20 ... ... AN detection means, 21 ... AN calculation means, 22 ...
… Control means. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A crank based on an intake air amount sensor provided upstream of a throttle valve of an internal combustion engine, a crank angle sensor for detecting a predetermined crank angle of the internal combustion engine, an output of the intake air amount sensor and an output of the crank angle sensor. The intake air amount AN during a predetermined crank angle of the internal combustion engine in synchronization with the output of the angle sensor AN
AN detecting means for detecting (t), smoothing means for smoothing the AN (t) for each predetermined crank angle to generate a smoothed intake air amount AN (n), based on the AN (n) In a fuel control system for an internal combustion engine that controls the amount of fuel supplied to the internal combustion engine, an intake air amount decrease detection means that detects that AN (n) has decreased, and a decrease amount ΔAN when AN (n) has decreased. A fuel control device for an internal combustion engine, comprising means for reducing the supplied fuel amount according to the reduction amount ΔAN of AN (n) when it is larger than a predetermined value.