JPH0123662B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel mixture control device for an internal combustion engine, which appropriately controls the air-fuel ratio when a throttle valve is fully closed, stabilizes combustion, and prevents engine stall.

As a conventional air-fuel mixture control system for an internal combustion engine, one that combines, for example, a fuel system shown in FIG. 1, an air system shown in FIG. 2, and an electronic control system is known.

In the fuel system shown in FIG. 1, fuel is sucked from a fuel tank 1 by a fuel pump 2, pressurized, and pumped. Next, the fuel damper 3 dampens the pulsation of the fuel generated by the fuel pump 2, and the fuel filter 4 removes dust and moisture, and the pressure regulator 5 adjusts the fuel pressure to a constant level. From an injector (fuel injection valve) 10 attached to an intake manifold 9 near the intake valve 8 of each cylinder 7 of the engine 6, a predetermined injection amount T( injection time).

Incidentally, surplus fuel is returned to the fuel 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 opens to increase the amount of fuel supplied when starting the engine when the temperature of the cooling water is low.

As shown in FIG. 2, in the air system, air is sucked in from an air cleaner 14 to remove dust, an air flow meter 15 measures the amount of intake air Q, and a throttle valve 17 in a throttle chamber 16 measures the amount of intake air. Q is adjusted and mixed with the fuel injected from the above-mentioned injector 10 in the intake manifold 9, and then the air-fuel mixture is supplied to each cylinder 7. A throttle switch 18 is attached to the throttle chamber 16 and provides 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 (that is, idling); 20 is an idle adjustment screw that adjusts the air flow rate in the bypass passage 19; and 21 is an air regulator for starting and subsequent warm-up. This serves as an auxiliary air valve to increase the amount of air during operation.

Next, the electronic control system is controlled by control unit 11.
, the basic injection amount Tp Tp=K(Q/N)( However, K is a constant) ...(1) is calculated. Furthermore, by inputting various information detected on the state of the engine and each part of the vehicle, correction of the injection amount is calculated to obtain the actual fuel injection amount T. Based on this T, the injector 10 is simultaneously applied to each cylinder at a rate of Drive times.

To explain each correction in detail, battery voltage correction as a correction due to fluctuations in the drive voltage of the injector 10
As shown in Figure 3, Ts is determined according to the battery voltage VB by Ts=a+b(14-VB) (where a and b are constants)
……(2) is given by.

Water temperature increase correction when the engine is not sufficiently warmed up
Ft is determined from the characteristic diagram shown in Figure 4 depending on the water temperature.

In order to obtain smooth starting performance and to smoothly transition from starting to idling, the after-start increase correction KAs changes from the initial value KAs ₀ when the starter motor is turned on to the fifth value according to the water temperature at that time. It is determined from the characteristic diagram shown in the figure, and thereafter decreases to 0 as time passes.

The post-idle increase correction Kai, which is used to smooth the start when warm-up has not been performed sufficiently, is the initial value Kai ₀ when the throttle switch 18 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 ₁ = Tp × (1 + KAs) × 1.3 + Ts ... (3) T ₂ = TST × KNST × KTST ... (4) Calculate the two values, and use the larger one as the fuel injection amount at startup.

However, TST, KNST, and KTST in formula (4) are each
It is determined from the characteristic diagrams shown in FIGS. 7, 8, and 9 depending on the water temperature, engine speed, and elapsed time after starting, respectively.

However, in such a conventional air-fuel mixture control device, the basic injection amount Tp is equal to the intake air amount Q.
From equation (1), Tp=K(Q/
N), but when the throttle valve 17 is fully closed (at this time,
The airflow flowing through the throttle becomes a sonic flow with a speed equal to the speed of sound, 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 while idling, as shown in Figure 10,
At the same time as the clutch is engaged, the engine speed N drops by about 200 rpm, while the intake air amount Q is constant and the basic injection amount Tp increases rapidly as Tp = K Q/N, but the air amount q taken into the cylinder is Due to the compressibility of , the mixture ratio increases gradually and the mixture ratio becomes thicker.

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 system works to increase the engine speed N, resulting in a stable system.

The present invention has been made focusing on the above points,
When the throttle valve is fully closed, a test amount different from the fuel supply amount set value based on the current detection information is supplied and the behavior of the engine speed is investigated to see if the mixture ratio setting range is on the rich side or lean. A mixture control system for internal combustion engines that detects whether the fuel is on the side and controls the fuel supply amount based on this detection result to stabilize the mixture ratio and effectively prevent engine stalls. The purpose is to provide equipment.

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 engine speed, an air flow meter 15 that detects the amount of intake air, and a reference pulse generator 2 that generates a reference pulse every time the engine rotates.
4. Signals from the throttle switch 18 are input, which are ON when the throttle valve 17 is fully closed, and OFF otherwise. Control unit 2
3 is composed of each unit which will be described later. That is, the pulse counter 25 is connected to the crank angle sensor 22.
The engine rotation speed N signal is output by counting the pulse signal every 1 degree of engine rotation. 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. The Tp calculation circuit 27 uses the engine rotation speed N signal from the pulse counter 25 and the A/D
Input the intake air amount Q signal from the converter 26,
According to equation (1) above, basic injection amount Tp=K(Q/
N) is calculated. That is, _the T _P calculation circuit 27
Corresponds to calculation means. The N' calculation circuit 28 calculates N' with a time delay element for the current engine rotational speed N detected by the pulse counter 25.
That is, the N' calculation circuit 28 corresponds to N' calculation means. For example, this is N' = βN ₁ + (1-β)N ₂ (weighted average of current value N ₁ and past value N ₂ ; 0 < β < 1)
Find it as.

Tp' calculation circuit 29 calculates the value of N' and the intake air amount Q.
The basic injection amount Tp' is calculated by correcting the phase difference obtained from the signal as Tp'=K(Q/N'). That is, the T _P ' calculation circuit 29 corresponds to the T _P ' calculation circuit.

The αTp calculation circuit 30 calculates a basic injection amount α·Tp signal (hereinafter referred to as a test signal) for testing, which is obtained by multiplying the Tp obtained by the Tp calculation circuit 29 by a constant increase coefficient α (>1). That is, the αT _P calculation circuit 30 corresponds to αT _P calculation means.

On the other hand, the idling determination circuit 31 determines whether the engine is idling or not in response to a signal from the throttle switch 18, and transmits the determination signal to a test signal generation determination circuit 32 (described later) and a Tp/Tp signal.
Tp' switching determination circuit 33. 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 consideration. It's okay to be hot. The N change determining circuit 34 determines whether the change N'-N in the engine speed N when the test signal is generated is larger than a predetermined value _N0 from the test signal generation determining circuit 32, and signal
It is output to the Tp/Tp' switching judgment circuit 33.

The Tp/Tp' switching circuit 33 is determined by the idling determination circuit 31 when idling, and the determination by the N change determination circuit 34 is N'-N.
>N ₀ , Tp' calculated by the Tp' calculation circuit 29 is selected; otherwise, Tp calculated by the Tp calculation circuit 27 is selected, and Tp.
It is output to the Tp'/αTp switching circuit 35. That is, the N change determination circuit 34 corresponds to the mixing ratio setting region determination means, and the T _P and T _P ' switching determination circuit corresponds to the basic supply amount switching means.

The Tp/Tp'/αTp switching circuit 35 selects the test signal αTp from the αTp calculation circuit 30 up to a predetermined number of times according to the number of inputs of the judgment signal indicating that a test signal should be generated from the test signal generation judgment circuit 32. When the specified number of times is exceeded, Tp・
The signal Tp or Tp' from the Tp' switching circuit 33 is selected and output to the T calculation circuit 36.

Based on Tp, Tp' or αTp outputted from the Tp/Tp'/αTp switching circuit 35, the T calculation circuit 36 uses this as the basic injection amount and corrects it according to the various characteristics shown in FIGS. 3 to 9. The final fuel injection amount T obtained by That is, T calculation circuit 3
6 corresponds to the T calculation means.

The register 37 temporarily stores T transferred from the T calculation circuit 36. 38 is a clock pulse generator, 39 is a counter, which is the clock pulse generator 3.
8, and the count value is reset (becomes "0") by the reference pulse from the reference pulse generator 24. When the reference pulse from the reference pulse generator 24 is input, the comparator 40 turns off the transistor 41.
The injector 10 is energized to open and start fuel injection, and the value of the register 37 (that is, the fuel injection amount T) is compared with the value of the counter 39 (at the beginning of the comparison, the value of the register 37 > the value of the counter 39). ), when the value of the counter 39 increases and the value of the register 37 equals the value of the counter 39, the transistor 41 is turned on and the injector 1 is turned on.
0 to end fuel injection.

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 a time corresponding to the fuel injection amount T.
Fuel is injected by the fuel injection amount T every rotation. That is, in addition to the reference pulse generator 24, each of the electric circuit sections 37 to 41 and the injector 10 correspond to the fuel supply means.

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

From the crank angle sensor 22 to the pulse counter 25
The Tp calculation circuit 27 calculates Tp=K(Q/N ) is calculated.
(Step 50, only numbers shown below).

On the other hand, the N' calculation circuit 28 calculates N'=βN+(1-β)N' based on the engine rotational speed N signal.

Next, the idling judgment circuit 30 makes a judgment based on the signal from the throttle switch 18 (52), and if it is judged that the engine is not idling, the T calculation circuit 36 makes a judgment based on the Tp obtained in step 50. The fuel injection amount T is calculated and stored in register 3.
It will be transferred as 7. If it is determined that the engine is idling, the test signal generation determination circuit 32 determines whether or not the test signal αTp is outputting a signal that should be generated (53), and if the signal is being output, Then, it is determined whether or not the test signal flag was set in the previous flow (54), and if it is not set, the test signal generation determination circuit 32
The count value of counter A built in is cleared (55), and N' is cleared (55).
Store in N ₀ ′ of RAM (i.e., set N ′ → N ₀ ,
56). Further, if the test signal flag is set, counter A is incremented (62). Next, it is determined whether the value of counter A has reached a predetermined value _C0 (57), and if it has not reached _C0 , a test signal flag is set (63), and a test signal should be generated. The signals are Tp・Tp′・
The αTp calculation circuit 30 calculates αTp based on this signal.
is selected and output to the T calculation circuit 36 (64). As a result, T is calculated using αTp as the basic injection amount (67), and this T is transferred to the register 37. or,
When the value of counter A reaches _C0 , the flag of the test signal is cleared (58), and the signal is inputted to the N change determination circuit 34 to determine the change in N'_N0'-
N is calculated and compared to see if this value is greater than a predetermined value _N0 (59). If it is large, it indicates that the mixture ratio is set on the richer side than the best torque point in FIG.
After setting the Tp' flag to use Tp' through the Tp/Tp' switching circuit 33 and the Tp/Tp'/αTp switching circuit 35 (61), input it to the T calculation circuit 36 and set Tp' as the basic injection amount. The calculated T is transferred to the register 37. Also, if N ₀ '-N≦N ₀ , it indicates that the torque is on the lean side from the above-mentioned best torque point, so the Tp' flag is cleared (65) and Tp without phase difference correction is loaded. T output to the calculation circuit 36 and calculated based on Tp
is transferred to 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, the reference pulse of the reference pulse generator 24 (FIG. 14a)
The counter 39 is reset by (14th
At the same time as Fig. 14 (c), a reference pulse is also input to the comparator 40, turning off the transistor 41, opening the injector 10 (Fig. 14 d), and starting fuel injection. Next, as time passes, the value of the counter 39 increases (FIG. 14c), and when the value of the register 37 becomes the same as the value of the counter 39 in the comparator 40, the transistor 41 turns on and the injector 10 closes. (Fig. 14c) 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, while the mixture ratio setting region is on the lean side, which is a stable system. Sometimes as usual,
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 mixing ratio thicker is given as a test signal to determine the mixing ratio region, but even if a test signal that makes the mixing ratio thinner is given, the mixing ratio is not determined. Able to determine ratio areas. That is, in this case, in the flowchart of FIG. 13, the value of the test signal coefficient α calculated in step 64 is set to 0<α<1, and in step 59, when N−N ₀ ′>N ₀ At this time, T is calculated based on Tp' and the injection amount control is performed in the same manner as in the first embodiment.

Also, in determining the change in N, the predetermined value N ₀ is set to 0.
If the mixture ratio is set near the best torque point by setting it to an appropriate value that is not
Control based on Tp can be performed to maintain the mixing ratio in a stable state.

Furthermore, if a configuration is adopted in which stages are set when 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 torque generation pattern can be obtained. or,
In addition to the value shown in this embodiment, N' may be set to a predetermined time, the engine rotation speed before the engine rotation, or the like.

As explained above, according to the present invention, when it is determined that the engine is idling, a test signal is given and the behavior of the engine speed N at that time is checked to see if the current mixture ratio setting range is on the rich side of the best torque point. The configuration learns to determine whether the fuel injection amount and intake air amount are on the side, and then determines whether or not to correct the phase of the fuel injection amount and intake air amount. The torque generation pattern can be controlled to form an optimal torque generation pattern, and even if the engine speed N changes due to clutch engagement, etc., engine stalling can be effectively 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 the fuel system of a conventional mixture control device, Fig. 2 is a configuration diagram of the air system of the 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 amount TST, Figure 8 is a characteristic diagram showing the relationship between engine speed and correction value KNST, and Figure 9 is a characteristic diagram showing the relationship between engine speed and correction value KNST. A characteristic diagram showing the relationship between KTST, Figure 10 is a diagram showing the change in engine speed and intake air amount when the clutch is engaged in the conventional device, and Figure 11 is a diagram showing the relationship between the mixture ratio and engine speed. FIG. 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, and FIG.
The figure is an output waveform diagram of the main parts of the apparatus shown in FIG. 11. 6... Engine, 10... Injector, 15...
Air flow meter, 18... Throttle switch, 22... Crank angle sensor, 23... Control unit, 24... Reference pulse generator, 2
5...Pulse counter, 26...A/D converter,
27...Tp arithmetic circuit, 28...N' arithmetic circuit, 2
9...Tp' calculation circuit, 30...αTp calculation circuit, 3
1... Idling judgment circuit, 32... Test signal generation judgment circuit, 33... Tp/Tp' switching circuit,
34...N change determination circuit, 35...Tp・
Tp'/αTp switching circuit, 36...T calculation circuit, 37
...Register, 38...Clock pulse generator,
39...Counter, 40...Comparator, 41...Transistor.

Claims (1)

[Claims] 1.In addition to providing means for detecting the engine speed N, intake air amount Q, and idling state, the basic supply amount of fuel corresponding to Q/N is determined based on the current detection signals of the engine speed N and intake air amount Q. A T _P calculating means for calculating T _P and a new engine speed N' which is the engine speed N with a time delay element.
N' calculation means, T _P ' calculation means for calculating the basic supply amount T _P ' of fuel corresponding to Q/N' based on the engine speed N' and the intake air amount Q, and the basic supply amount T P ' αT _P calculation means for calculating a basic supply amount αT _P for testing of fuel by multiplying _P by a coefficient α greater than 1 or less than ₁ ; When a coefficient α larger than 1 is used, the engine speed N decreases, and when a coefficient α smaller than 1 is used, the engine speed N increases. a mixture ratio setting region discriminating means for determining that the mixture ratio is in the over-rich setting region when the mixing ratio is set in the over-rich region _; ′, and a basic supply amount switching means that selects the basic supply amount T _P at other times, and T that calculates the final fuel supply amount T based on these basic supply amounts T _P , T _P ′, αT _P A mixture control device for an internal combustion engine, comprising a calculation means and a fuel supply means for supplying fuel based on a signal from the T calculation means.