JPS5941628A - Mixture controller for internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent the stall of an engine, by applying a test signal at the time of idling to detect the behavior of the rotational frequency of an engine at that time and by judging the present mixture ratio set region in terms of the best torque to control the fed quantity of fuel to stabilize the combustion of the engine. CONSTITUTION:The quantity Q of sucked air and the rotational frequency N of an engine are detected by an air flow meter 15 and a crank angle sensor 22, respectively, for a calculation circuit 27 to determine a basic fed quantity Tp of fuel. A calculation circuit 29 determines another basic fed quantity Tp' of fuel from the sucked air quantity Q and another engine rotational frequency N' obtained by applying a time lag factor to the engine rotational frequency N. A basic fed quantity alphaTp for testing, which is a product of the basic fed quantity Tp and a coefficient alpha, is determined by a calculation circuit 30. When a judgment circuit 31 has found out the time of idling from the output of a throttle sensor 18, the fuel is fed by the basic quantity alphaTp for testing. The engine rotational frequency changed by the feed of the fuel is detected to judge a mixture ratio set region. The basic fed quantity Tp or Tp' is applied to a calculation circuit 36 depending on the result of the judgment to determine a final fed quantity T.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel mixture control device for properly controlling the air-fuel ratio when a throttle valve is fully closed, stabilizing combustion, and preventing the occurrence of engine stall.

As a conventional air-fuel mixture control device for an internal combustion engine, for example, the first
A combination of the fuel system shown in Fig. 2, the air system shown in Fig. 2, and the electronic control system is known.

In the fuel system shown in Figure 1, the fuel is in the Tsuyuel tank 1.
It is sucked in by the Tsuyuel pump 2, pressurized, and pumped out. Next, the fuel pulsation generated by the fuel pump 2 is damped by the fuel damper 3, and the fuel filter 4
After dust and moisture are removed by the pressure regulator 5, the fuel is regulated to a constant fuel pressure and is injected into the injector (fuel injection valve) attached to the intake manifold 9 near the intake valve 8 of each cylinder 7 of the engine 6. ]
From 0, fuel is injected at a predetermined time by a predetermined injection amount T (injection time) calculated by the control unit 11 as described later.

Incidentally, surplus fuel is returned to the tsuyuel tank 1 from the pressure regulator 5. 12 is a water temperature sensor that detects the temperature of the cooling water; 13 is a cold start valve that is opened to increase the amount of fuel supplied when starting the engine when the temperature of the cooling water is low.

The air system is as shown in Figure 2, air is supplied to air cleaner 1.
The intake air amount Q is adjusted by the air flow meter 5, the intake air amount Q is adjusted by the throttle valve 17 in the throttle chamber 16, and the intake air amount Q is adjusted by the intake manifold 9.
The air-fuel mixture is supplied to each cylinder 7 after being mixed with the fuel injected from the injector 10 described above. A throttle switch 18 is attached to the throttle chamber 16 and outputs an off (low) signal when the throttle valve 17 is open, and an on (high) signal when the throttle valve 17 is closed. 19 is a bypass passage for intake air when the throttle valve 17 is closed (i.e., idling); 20 is the bypass passage 19;
Idle adjustment screw, which adjusts the air flow rate of
An air regulator 21 serves as an auxiliary air valve to increase the amount of air during startup and subsequent warm-up operation.

Next, the electronic control system uses the intake air amount Q signal from the air flow meter 15 and the crank angle sensor 22 attached to the crankshaft of the engine 6 in the control unit 11.
Basic injection amount Tp Tp=K (Q/N) (K is a constant)
...Calculate (1).Furthermore, various information detected on the state of the engine and each part of the vehicle is input, and correction of the injection amount is calculated to determine the actual fuel injection amount T. Based on this T, the injector 10 is driven simultaneously in each cylinder once per engine revolution.

To explain the various corrections in detail, the battery voltage correction Ts as a correction due to fluctuations in the drive voltage of the injector IO is the third
As shown in the figure, depending on the battery voltage VB, Ts=a+b(14VB) (where a and b are constants)...(2) is given.

The water temperature increase correction Ft when the engine is not sufficiently warmed up is:
It is determined from the characteristic diagram shown in FIG. 4 according to the water temperature.

In order to obtain smooth starting performance and to smoothly transition from starting to idling, the post-start increase correction KAs is the initial value KAs when the starter motor is turned on.
is determined from the characteristic diagram shown in FIG. 5 according to the water temperature at that time, and thereafter decreases to O as time passes.

The post-idle increase correction KAi, which is used to smooth the start when the warm-up has not been performed sufficiently, is performed by adjusting the throttle switch 1.
The initial value KAio when 8 is turned off is determined from the characteristic diagram shown in FIG. 6 according to the water temperature at that time, and thereafter decreases to 0 with the passage of time.

In addition, correction using an exhaust sensor may also be performed.

Furthermore, the following control is performed when starting the engine.

T I=TpX (14KAs) X 1.3 +
Ts − f31T 2 = TST X KNSTX
KTST --- (4) Calculate the two values and use the larger one as the fuel injection amount at startup.

However, TST, KNST, and KTST in equation (4) are 1 water temperature.

Fig. 7, respectively, depending on the engine speed and the elapsed time after starting.

It is obtained from the characteristic diagrams shown in FIGS. 8 and 9.

However, in such a conventional mixture control device, the basic injection amount Tp is determined by the intake air amount Q and the engine speed N.
(from formula 11, it is configured to inject fuel corresponding to Tp-K (Q/N), but when the throttle valve 17 is fully closed (at this time, the airflow flowing through the throttle is equal to the speed of sound) It becomes a flow of speed, and the amount of intake air Q
becomes constant. ), while the rotational speed changes suddenly, the amount of air q taken into the cylinder per rotation changes relatively slowly, causing a phase difference between the fuel and air and making the mixture ratio unstable. Become. In particular, when the clutch is engaged in an idling state, as shown in Fig. 10, the engine speed N drops by about 20 Orpm at the same time as the clutch is engaged, while the intake air amount Q is constant and the basic injection amount Tp is jp, = KQ/N
However, the amount of air q taken into the cylinder increases gradually due to the compressibility of the air, so the mixture ratio becomes richer.

Here, during idling, the engine speed N changes as shown in FIG. 11 in response to changes in the mixture ratio. For this reason, if the set mixture ratio is high when the clutch is engaged, the mixture ratio becomes even richer as described above, which tends to lower the engine speed, resulting in a problem that engine stall is more likely to occur.

On the other hand, when the set mixture ratio is low, even if the mixture ratio becomes rich, the engine speed N increases, resulting in a stable system.

The present invention has been made with attention to the above points, and when the throttle valve is fully closed, a test amount different from the set value of the fuel supply amount based on the current detection information is supplied to examine the behavior of the engine speed. By this, it is detected whether the mixture ratio setting range is on the rich side or lean side, and the fuel supply amount is newly controlled according to this detection result to stabilize the mixture ratio and prevent occurrences such as engine stalls. An object of the present invention is to provide a mixture control device for an internal combustion engine that can effectively prevent such problems.

The present invention will be explained below based on illustrated embodiments.

However, since the fuel system and air system of the engine are the same as those of the conventional example shown in FIGS. 1 and 2, the same reference numerals will be used to describe them.

FIG. 12 is a block diagram showing an embodiment of the air-fuel mixture control device according to the present invention.

In the figure, the control unit 23 includes a crank angle sensor 22 that detects the t14 rotation speed, an air flow meter 15 that detects the amount of intake air, a reference pulse generator 24 that generates a reference pulse every engine rotation, and a throttle valve 17.
Each signal is input from the throttle switch 18, which is turned on when the throttle switch is fully closed, and turned off at other times. The control unit Edict is composed of each unit described below. That is, the pulse counter 25 counts the pulse signal from the crank angle sensor 22 every 1 degree of engine rotation, and calculates the engine rotation speed N.
Output a signal. The A/D converter 26 converts the intake air amount signal from the air flow meter 15 from analog to digital, and outputs a digital intake air amount Q signal. Tpii
The M calculation circuit 27 calculates the engine rotation speed N from the pulse counter 25.
By inputting the signal and the intake air amount Q signal from the A/D converter 26, the basic injection amount Tp=K according to the equation 11 described above.
(Q/N) is calculated. The N' calculation circuit 28 calculates N1 with a time delay element relative to the current engine rotational speed N detected by the pulse counter U.

This is obtained, for example, as N'=βN++(1-β)N2 (weighted average of current value N+ and past value N2; 0<β<1).

The Tp° calculating circuit 29 calculates a basic injection amount Tp'' with a corrected phase difference obtained as Tp''=K (Q/N') from the value of N'' and the intake air amount Q signal.

The αTp calculation circuit 30 calculates the T calculated by the Tp calculation circuit 29.
The basic injection amount for testing obtained by multiplying p by a certain additional coefficient α (>1) is referred to as a test signal)
Calculate.

On the other hand, the idling determination circuit 31 determines whether the idling is idling or not according to the signal from the throttle switch I8, and transmits the determination signal to a test signal generation determining circuit 32 and a Tp-Tp' switching determining circuit 33, which will be described later. Output. The test signal generation determination circuit 32 determines whether or not the test signal αTp should be output when the idling state is detected by the idling determination circuit 31. For example, as described below, a method is adopted in which the test signal is determined to continue to be generated for a predetermined number of times from the time idling is first detected, and then stopped, but other driving conditions are also taken into account. There may be. The N change amount determination circuit 34 receives from the test signal generation determination circuit 32,
Change N' in engine speed N when the test signal is generated
It is determined whether or not -N is greater than a predetermined value No, and the signal is output to the Tp-Tp' switching determination circuit 33.

T, -Tp' switching time 1? &33 is Tp" which is calculated by the Tpl calculation circuit 29 when the idling determination circuit 31 determines that it is idling, and the determination by the N change determination circuit 34 is N"-N > No.
At other times, Tp calculated by the Tp calculation circuit 27 is selected and output to the Tp-Tp'/αTp switching circuit 35. The test signal αTp from the αTp arithmetic circuit 30 is selected and outputted up to a predetermined number of times according to the number of inputs of the judgment signal to generate a test signal from the circuit 32, and when the predetermined number of times is exceeded, Tp- The signal Tp or T, l from the Tp" switching circuit 33 is selected and output to the T calculation circuit 36.

Based on Tp, Tpl, or αTp output from the Tp-rp'/αTp switching circuit 35, the T calculation circuit 36 corrects the basic injection amount according to the various characteristics shown in FIGS. 3 to 9. The final fuel injection amount 'F is calculated.

The register 37 temporarily stores T transferred from the T calculation circuit 36. 38 is a clock pulse generator, 39 is a counter that counts clock pulses from the clock pulse generator 3B, and the count value becomes 1-0" by the reference pulse from the reference pulse generator 24)
be done. When the reference pulse from the reference pulse generator 24 is input, the comparator 4o turns off the 1-transistor 41, energizes the injector 10 to open and start fuel injection, and also changes the value of the register 37 (i.e., fuel injection Quantity T
) and the value of the counter 39. The initial value of the comparison is the value of the register 37>the value of the counter 39. ), counter 3
The value of 9 becomes larger, and the value of register 37 = counter 3.
When the value reaches 9, the 1-transistor 41 is turned on, the injector 10 is closed, and fuel injection is completed.

Therefore, the injector 10 opens only for a time corresponding to the fuel injection amount T after the reference pulse is emitted from the reference pulse generator 24, that is, the injector 10 opens only for the time corresponding to the fuel injection amount T, that is, for each engine revolution, the fuel injection amount T
only fuel is injected.

Next, the operation will be explained with reference to the block diagram of FIG. 12, the flow chart of FIG. 13, and the waveform diagram of FIG. 14.

The engine speed N signal output from the crank angle sensor 22 via the pulse counter 25 and the air flow meter 15
Based on the intake air amount Q signal output from the A/D converter 26, the Tp calculation circuit 27 calculates Tp=K.
(Q/N) is calculated. (Step 50, only numbers are shown below).

On the other hand, the N' calculation circuit 28 calculates N''-βN+(1-β)No based on the engine rotational speed N signal.

Next, the idling determination circuit 30 makes a determination based on the signal from the throttle switch 1B (52). If it is determined that the vehicle is not idling, the T calculation circuit 36 performs fuel injection based on the Tp determined in step 50. Quantity T
is calculated and transferred to the register 37. If it is determined that the idling is occurring, the test signal generation determination circuit 32 determines whether or not the test signal αTp is outputting a signal that should be generated (53). determines whether the test signal flag was set in the previous flow (54), and if it is not set, clears the count value of counter A built in the test signal generation determination circuit 32 (55), N ' is also the No. of IIIM built in the judgment circuit 32.
' (that is, N"-No. 56). Also, if the test signal flag is set, counter A is incremented (62). Next, counter A is incremented (62).
It is determined whether the value of Co has reached a predetermined value Cn57).
If the test signal has not been reached, after setting the test signal flag (63), a signal indicating that a test signal should be generated is sent to Tp.
-Tp' ·αTρ It is output to the Tp circuit 35, and the switching circuit 35 selects αTp calculated by the αTp calculation circuit 30 based on this signal and outputs it to the T calculation circuit 36 (64).

As a result, T is calculated using αTp as the basic injection amount (6
7), this T is transferred to the register 37. Further, when the value of the counter A reaches Co, the flag of the test signal is cleared (58) and the signal is sent to the N change determination circuit 34.
is input, the change NO'N of N' is calculated, and it is compared whether this value is larger than a predetermined value No (59). If it is large, this indicates that the mixture ratio is set to the Lynch side of the Hoest torque point in FIG.
"Tp-Tp" switching circuit 33, Tp-Tp"・αTp
After setting the Tp1 flag 7 to use Tp" via the switching circuit 35 (61), it is input to the T calculation circuit 36, and T calculated using Tp+ as the basic injection amount is transferred to the register 37. , No' If N≦No, it indicates that the point is leaner than the best 1-lux point (7), so the Tp flag is cleared (65), and Tp without phase difference correction is loaded and T calculation is performed. T, which is output to the circuit 36 and calculated based on Tp, is transferred to the register 37.

In this way, the fuel injection amount T transferred to the register 37 is input to the comparator 40. On the other hand, at the same time that the counter 39 is reset by the reference pulse of the reference pulse generator 24 (FIG. 14(a)) (FIG. 14(C)), the reference pulse is also input to the comparator 40, turning the transistor 41 on.
Fig. 14 (d) when turning on FF and opening injector 10)
, start fuel injection. Next, as time passes, the value of the counter 39 increases (FIG. 14(C)), and when the value of the register 37 becomes the same as the value of the counter 39 in the comparator 40, the transformer 41 is turned on and the injector 1 is turned on.
0 closes (FIG. 14(C)) and fuel injection ends.

With this configuration, by applying a test signal during idling and observing the behavior of the engine speed, it is possible to determine the setting range of the mixture ratio. By controlling the fuel injection amount based on Tp+, which corrects the phase difference, the mixture ratio can be quickly stabilized and engine stall can be prevented. As usual when in
By controlling the fuel injection amount based on Tp, a stable mixture ratio state can be maintained.

As described above, in this embodiment, a signal that makes the mixture ratio thicker is given as a test signal to determine the mixing ratio region, but a test signal that makes the mixture ratio thinner is given. It is also possible to determine the mixing ratio range. That is, in this case, the value of the test signal coefficient α calculated in step 64 in the flowchart of FIG. 13 is set to 0 and α<1,
Also, when N-No'> No in the steering knob 59, it is set to the rich side, so at this time, T is calculated using T and I to control the injection amount in the same way as in the first embodiment. It is done.

In addition, by setting the predetermined value NO to an appropriate value other than 0 in determining the change in N, when the mixture ratio is set near the best torque point, control based on Tp is directly performed to maintain the mixture ratio in a stable state. be able to.

Furthermore, if a configuration is adopted in which stages are set in comparing the magnitude of the change in N, the deviation from the best torque can be known, and by changing the phase difference correction amount (Tp'') accordingly, A more preferable silk pattern from 1 to 1 can be obtained.Also, N' may be set to a predetermined time, the engine rotational speed before the engine rotation, etc. other than the one shown in this embodiment.

As explained above, according to the present invention, when it is determined that the engine is idling, a test signal is applied, and the behavior of the engine speed N at that time is checked to determine whether the current mixture ratio setting in the V4 region is the best.
The system learns to determine whether the fuel injection amount and intake air amount are on the lean side or on the lean side, and then determines whether or not to correct the phase of the fuel injection amount and intake air amount. Regardless of the range, it can be controlled to form the optimum torque generation pattern according to that range, effectively preventing the occurrence of engine stalls even if the engine speed N changes due to clutch engagement, etc. can be prevented.

In addition, in particular, since the configuration determines the discrimination of the mixture ratio setting range by giving a test signal each time and learning, it is less susceptible to changes over time and variations in engine characteristics compared to methods that make discrimination by comparing with a fixed value. It is also possible to sufficiently respond to various situations, and maintain highly accurate control stably.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a fuel system of a conventional air-fuel mixture control device, Fig. 2 is a configuration diagram of an air system of a conventional device, Fig. 3 is a characteristic diagram showing the relationship between battery voltage and battery voltage correction value, and Fig. 4 The figure is a characteristic diagram showing the relationship between water temperature and the water temperature increase correction value, Figure 5 is a characteristic diagram showing the relationship between water temperature and the initial value of the after-start increase correction, and Figure 6 is the relationship between the water temperature and the initial value of the after-idling increase correction. Figure 7 is a characteristic diagram showing the relationship between water temperature and correction value TST, Figure 8 is a characteristic diagram showing the relationship between engine speed and correction value XNS↑, and Figure 9 is a characteristic diagram showing the relationship between engine speed and correction value value KTST
Figure 10 is a characteristic diagram showing the relationship between
12 is a block diagram of an embodiment of the device according to the present invention. FIG. 13 is a flowchart explaining the operation of the device shown in FIG. 12.
FIG. 4 is an output waveform diagram of the main parts of the device shown in FIG. 11. 6... Engine 10... Injector 15... Air flow meter 18... Throttle switch
22... Crank angle sensor 23... Control l-roll unit 24... Reference pulse generator 25...
・Pulse counter 26...A/D converter 27...
・Tp calculation circuit 2B...N” calculation circuit 29・
・・Tp" operation circuit 30...αTp operation circuit
31... Idling judgment circuit 32... Test signal generation judgment circuit 33... Tp-Tp' switching circuit 34... N change judgment circuit 35... Tp-Tp
'αTp switching circuit 36...T calculation circuit 37.
...Register 38...Clock pulse generator
39...Counter 40...Comparator 4]...
Fujio Sasashima, Patent Attorney, Patent Attorney, Nissan Motor Co., Ltd.

Claims (1)

[Claims] In addition to providing means for detecting the engine speed N, intake air amount Q, and idling state, the basic supply amount Tp of fuel corresponding to Q/N is provided based on the current detection signals of the engine speed N and intake air amount Q. and a new engine speed N' that has a time delay element added to the engine speed N.
N° calculation means for calculating the basic supply amount Tpl of fuel corresponding to Q/N'' based on the engine speed N'' and the intake air amount Q; and the basic supply amount Tp αTp calculating means for calculating the basic supply amount αtp for the fuel test by multiplying the coefficient α (#1) by the coefficient α (#1);
a mixture ratio setting region determining means for supplying a fuel amount based on p and detecting the changing engine speed thereby determining a setting region of the mixture ratio; Basic supply amount switching means that selects the basic supply amount 'rp at times and the basic supply amount TpI at other times, and calculates the final fuel supply amount T based on these basic supply amounts Tp, Tp'', αTp. 1. An air-fuel mixture control device for an internal combustion engine, comprising: l calculation means; and fuel supply means for supplying fuel based on a signal from the l calculation means.