JPS63183234A - Control device for air-fuel ratio of internal combustion engine - Google Patents

Abstract

PURPOSE:To perform accurate air-fuel ratio control irrespective of changes in suction air temperature by detecting the suction air temperature on the downstream side of a supercharger, calculating a correction factor for compensating the escape of fresh intake according to the detected value, and correcting a fuel supply rate. CONSTITUTION:A 2-cycle internal combustion engine 1 or the like having a large escape ratio of fresh intake is provided with a means 2 for supplying a required rate of fuel to the engine 1 and a means 3 for calculating the fuel supply rate determined by operating conditions such as load and rpm of the engine 1. A means 4 is also provided for detecting a temperature of suction air on the downstream side of a supercharger 2' and a means 5 is further provided for calculating a correction factor value for compensating the escape of the fresh intake according to the detected temperature of the suction air and for correcting the fuel supply rate calculated with the means 3. A means 6 is further provided for forming a fuel supply signal to be sent to the means 2 so that a corrected rate of fuel is supplied to the internal combustion engine 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a fuel supply control system suitable for a two-stroke internal combustion engine.
n device. Further, the present invention can be applied to a four-stroke internal combustion engine, such as a four-valve engine, which has a long valve overlap period and has a large amount of fresh air blown through.

[Conventional technology]

In a two-stroke internal combustion engine, the period during which the intake port and exhaust port are in communication for scavenging is extremely long. When fuel is normally supplied to the cylinder in the form of a mixture using a carburetor, it is often discharged directly into the exhaust system through blow-through. Therefore, a system has been proposed in which a fuel injector is installed and fuel is injected only during a predetermined period in the intake cycle of the engine. However, even if such a fuel injection system is adopted, the problem of intake air blow-by itself cannot be eliminated. In other words, in a two-stroke internal combustion engine, the fresh air taken in is blown directly into the exhaust pipe without participating in total heat combustion within the cylinder bore, and the amount of fresh air that is actually involved in combustion is smaller than the amount of air that passes through the engine intake system. The amount of air in the cylinder bore decreases, and the proportion of air that blows through changes depending on engine operating conditions such as load and rotation speed. On the other hand, the amount of fuel supplied to the engine is calculated from the amount of air passing through the intake system based on the set air-fuel ratio. Therefore, in a two-stroke internal combustion engine, the amount of injected fuel no longer corresponds to the amount of air actually involved in combustion within the cylinder bore, making it impossible to maintain the air-fuel ratio at the set value.

Therefore, JP-A No. 53-27731 proposes a method in which a correction is made according to the blow-through ratio to the basic injection amount determined by the engine load and rotation speed, and the corrected amount of fuel is injected. are doing. Here, the correction amount is changed according to an algebraic function such as an exponential function depending on the intake air amount and the engine speed. That is, the manner in which the correction amount changes with respect to the intake air amount and engine speed is approximated to an exponential function, and the basic injection amount is corrected to obtain the final amount of fuel injected.

[Problem that the invention seeks to solve]

The conventional technique is based on the idea that a change in the blow-through ratio is corrected by assuming that the change depends only on the load and the rotational speed. However, the change in the blow-through ratio depending on the operating conditions changes not only depending on the load and rotation speed but also on the temperature conditions of the engine.

In particular, when the internal combustion engine is equipped with a supercharger, the temperature of the intake air changes significantly, and the scavenging characteristics change in accordance with this change, which affects the amount of air blow-through. In the prior art, since the correction was made only based on the load and rotational speed, it was not possible to completely compensate for blow-by, and it was not possible to accurately control the air-fuel ratio to the set air-fuel ratio.

It is an object of the present invention to accurately compensate for blow-by and to obtain a set air-fuel ratio despite changes in temperature conditions.

[Means for solving problems]

According to the present invention, in FIG. 1, in an internal combustion engine equipped with a supercharger such as a two-stroke internal combustion engine, which has a large amount of fresh air blowing through, the air-fuel ratio control device supplies a desired amount of fuel to the internal combustion engine 1. A fuel supply means 2, a fuel supply amount calculation means 3 that calculates a fuel supply amount determined by operating conditions such as the load and rotational speed of the internal combustion engine, and a temperature of intake air downstream of the supercharging a2' are detected. The intake air temperature detection means 4 calculates a correction factor value for compensating for blow-through according to the intake air temperature detected by the intake air temperature detection means 4, and calculates the fuel supply amount calculated by the fuel supply amount calculation means 3. The fuel supply amount correcting means 5 comprises means for correcting the amount of fuel supplied, and means for controlling the fuel supply signal to the fuel supply means so that the corrected amount of fuel is supplied to the engine.

[For production]

The fuel supply amount calculation means 3 calculates the fuel supply amount according to the load and rotation speed, and the fuel supply amount correction means 5 calculates the amount of fuel supplied according to the intake air temperature detected by the intake air temperature detection means 4 in the intake pipe downstream of the supercharger 2'. Depending on the air temperature, calculate the fuel supply correction factor,
The fuel supply amount calculating means 3 corrects the fuel supply amount calculated according to the fresh air blow-through amount, and the fuel supply signal forming means 6 forms a signal to the fuel supply means 2 so that the corrected fuel supply amount is obtained. do.

〔Example〕

FIG. 2 schematically shows the overall configuration of a six-cylinder two-stroke internal combustion engine having an intake valve and an exhaust valve to which the present invention is applied, and FIG. 3 shows one cylinder.

As will be explained later, this type of two-stroke internal combustion engine generates an exhaust swirl during the backflow of exhaust gas after blowdown, creating a stratification effect in which fresh air is concentrated near the spark plug at the top of the combustion chamber. This was devised to improve ignitability during operation. However, the present invention is not limited to this type of two-stroke internal combustion engine, but can also be applied to ordinary piston-valve type two-stroke internal combustion engines. Further, even in a 4-cycle internal combustion engine, the idea of the present invention can be applied to a 4-valve type engine in which the valve overlap period is long and there is a lot of blow-by of intake air. In Fig. 2.3, 10 is the main body of the internal combustion engine, which includes a cylinder block 12, a cylinder bore 14, a crankshaft 15, a piston 16, and a combustion chamber 1.
7, a cylinder head 18, and a spark plug 19.

The cylinder head 18 has two intake boats 2oa and 20b.
.

It has two exhaust bows) 22a, 22b, and an intake valve 24a, 24b for opening and closing the respective intake boats and exhaust ports.
It is a so-called four-valve type equipped with exhaust valves 26a and 26b. The intake valve and the exhaust valve are driven to open and close by dedicated cams 27 and 28, respectively. 30.31 is a pulp spring. The exhaust ports 22a, 22b are shaped to provide a swirl of the exhaust gas in the cylinder bore about its vertical axis when the exhaust gas flows back into the cylinder bore due to its negative pressure after blowdown. .

In FIG. 2, numeral 32 indicates a surge tank, which is connected to intake pipes 33 corresponding to the number of cylinders.

The intake pipe 33 has an internal partition wall 33-1, and two intake passages 34a and 34b are formed, each of which is connected to the intake boat 20a.
, 20b. The second intake passage 34b has a larger effective dimension than the first intake passage 34a (and is provided with an intake control valve 36).

The intake control valve 36 of each cylinder is connected to an actuator 37 by link means 36'. The actuator 37 is, for example, a diaphragm mechanism that operates under negative pressure, and is switched between negative pressure and atmospheric pressure by a switching valve (not shown), and the intake control valve 36 has a position where the intake passage 34b is opened and a position where it is closed. can be taken selectively. As will be described later, the intake control valve 36 is closed when the load is light and opened when the load is high. Fuel injectors 38a, 38b are arranged in intake passages 34a, 34b. 40a.

40b is a reed valve, which is installed as necessary to control backflow.

In the intake system upstream of the surge tank 32, an ink cooler 42, a mechanical supercharger 44, a throttle/nottle valve 46, an air flow meter 48, and an air cleaner 50 are arranged in this order. The mechanical supercharger 44 is configured by, for example, a roots pump or a vane pump, and a pulley 52 is provided on the drive shaft 44-1, and a belt 54 connects the crankshaft 15.
It is connected to the upper pulley 56. A bypass control valve 45 is installed in a bypass passage 44' that bypasses the mechanical supercharger 44, and adjusts the pressure between the supercharger 44 and the throttle valve 46. In this embodiment, the intercooler 42 is configured as an air-cooled type, and has an inlet container 42-1 and an outlet container 42-1.
2, a heat exchange tube 42-3 communicating therebetween, and fins 42-4 attached on the heat exchange tube 42-3.

In this embodiment, two exhaust manifolds 54 are separately installed for cylinder groups #1 to #3 and cylinder groups #4 to #6, respectively.

This grouping is such that ignition alternates between these two groups. That is, in this example, the firing order is #1. #6. #2. #4゜#3. Assume that #5Φ order. By grouping the cylinders with alternating ignition, it is possible to prevent the exhaust pressure of one cylinder from being affected by the exhaust pressure of other cylinders during the scavenging stroke, as will be described later. Cylinder groups #1 to #3, #4 to
The exhaust manifolds 54 of the #6 cylinder group are each connected to a dedicated catalytic converter 56 (which may also be used as a muffler or a dedicated muffler may be installed separately).

A distributor 58 is, as is well known, connected to the spark plug 19 of each cylinder and controlled by an igniter and an ignition coil (not shown) so that ignition is performed at a desired crank angle.

The control circuit 60 controls the operation of the injectors 38a and 38b so as to obtain a desired air-fuel ratio according to the present invention, and is configured as a microcomputer system. The control circuit 60 includes a microprocessing unit (MPU) 60-1, a memory 60-2, input ports 0-3, output ports 0-4, and a path 60-5 connecting these. Input Portro 0-
Each sensor is connected to 3, and an operating condition signal is inputted thereto. The air flow meter 48 may be of a volumetric flow rate type, and measures the flow rate Q of intake air passing through the intake pipe. The present invention can also be applied to a fuel injection system in which a pressure sensor for detecting intake pipe pressure is installed instead of an air flow meter. In this case, a semiconductor-type intake pipe pressure sensor 60 is installed downstream of the throttle valve 46 and upstream of the supercharger 44, and generates a signal corresponding to the intake pipe pressure PM. The pressure sensor is installed in the bypass passage 44.
In this embodiment, it is preferable to install the bypass passage 44' upstream of the connection point of the bypass passage 44' so that the pressure is not affected by the bypass air flow rate. If the supercharging system does not include a bypass, it is also possible to install a pressure sensor downstream of the supercharger. A crank angle sensor 62.degree. 64 is installed on the distributor 58. The first crank angle sensor 62 is connected to the distributor shaft 5
It is installed facing the magnet piece 58-2 fixed on the magnet 8-1, and generates a pulse signal every 360'' of the crank angle (corresponding to one cycle of the a-circle), and serves as a reference signal.

On the other hand, the second crank angle sensor 64 is installed facing the magnet piece 58-3 on the distributor shaft 58-1, and generates a pulse signal every 30 degrees of the crank angle, for example, so that the engine speed can be determined. , which is the start signal for the fuel injection routine. An intake air temperature sensor 68 is installed in the intake pipe downstream of the supercharger 44, preferably downstream of the ink cooler 42, and measures the temperature T of the intake air introduced into the engine.
A signal corresponding to '+H is obtained.

The MPU 60-1 executes arithmetic processing according to the program and data stored in the memory 60-2, and controls the intake control valve actuator 37 and injectors 38a and 38b.
The drive signal forming process is executed. Output port 0-4
is the actuator 37 and the fuel injector 3 of each cylinder.
8a and 38b, and a drive signal is applied thereto.

FIG. 4 shows an intake valve 24a in one cylinder determined by the profile and orientation of cams 27 and 28.

24b and the operation timings of the exhaust valves 26a and 26b. First, the intake valves 24a, 24b and the exhaust valves 26a, 26b begin to open at 80 degrees before the bottom dead center (B D C) and finish closing at 40 degrees after the bottom dead center (B D C).

On the other hand, the intake valves 24a and 24b begin to open at 60 degrees before the bottom dead center (BDC) and finish closing at 60 degrees after the bottom dead center (BDC). Note that ■ indicates the fuel injection period. FIG. 5 is a timing diagram showing the operating period of the exhaust valve in each cylinder with respect to the crank angle. Since it is a two-stroke engine, the -cycle is completed at 360@CA, and the exhaust valve is opened for the period EX shown in FIG. 3 at every 60 degrees of crank angle according to the ignition order. One group (#1 to #3 or #4 to #
Regarding 6), the exhaust valve is opened every 120°,
In each group, the open periods of the exhaust valves do not overlap between cylinders that are adjacent in the firing order. This prevents the exhaust pressure of one cylinder from affecting the exhaust pressure of the next cylinder in the group to be fired. In other words, the exhaust pressure pulsates due to the effect of blowdown, but when this pulsation is transmitted to other cylinders, the pressure changes in an unpredictable manner, resulting in a loss of predictability in the amount of fresh air blown through. This is intended to prevent this from occurring, since it is conceivable that this would have an adverse effect on the operation, which will be described later, of accurately compensating the air-fuel ratio according to the amount of blow-through. on the other hand,
Including the two groups, the opening period of the exhaust valve overlaps between cylinders with adjacent ignition orders, but since the exhaust manifold 54 is separate between these cylinders, the exhaust valve opening period of one cylinder The pressure does not affect the exhaust pressure of other cylinders.

First, the combustion operation of a two-stroke internal combustion engine equipped with an intake valve and an exhaust valve to which the present invention is applied will be explained. When the engine is under light load, the intake control valve 36 is closed and intake air is introduced into the engine only through the first intake passage 34a. In the process of the downward movement of the piston 16, the exhaust valves 26a and 26b first begin to open around 80'' before bottom dead center (BDC).

Therefore, the exhaust gas from the combustion chamber moves to arrow P in Figure 6 (a).
The air flows out to the exhaust ports 22a and 22b, causing so-called blowdown, but this blowdown is weak and ends quickly.

Since the cylinder to be ignited next belongs to a group other than another exhaust manifold 54, the pressure of the cylinder 22b is not affected by the exhaust pressure of that cylinder. When the piston 16 further descends, the inside of the cylinder bore 14 becomes a weak but negative pressure, and the pressure difference between the exhaust boats 22a and 22b causes the exhaust gas to flow back toward the cylinder bore as shown by arrow Q (see Figure 6). )), and exhaust bow)26
a.

Because of the shape of 26b, a swirl of exhaust gas as shown by arrow R is formed in the cylinder bore. These days,
The intake valve 24a (also 24b) begins to open, but its lift is still small, the throttle valve 46 is throttled, the intake; ttlf control valve 36 is closed, and the intake passage 34b, which has a large effective dimension, is closed. Since air can only flow through the intake channel 34a, which has a small effective dimension, virtually no fresh air is introduced. As the piston 16 moves further down, the exhaust gas swirl is mVE while the intake valve 24a.

As the lift of 24b increases, fresh air is introduced into the cylinder bore as shown by arrow S, and at this time, the exhaust gas rides on the swirl and moves to the lower part of the cylinder bore 14, while the fresh air mixed with the injected fuel flows into the swirled exhaust gas. Stratification is achieved by gathering near the spark plug electrode above the gas section (FIG. 6(c)). This stratified state of the exhaust gas R and fresh air S is maintained even when the piston reaches the bottom dead center (BDC) (FIG. 6(d)). (E) Intake valve 24a
, 24b are closed to prevent fresh air from blowing back. The piston then moves upward, but this stratified state is maintained until compression is completed, making it easy to ignite the fresh air near the spark plug.

In high engine load conditions, the intake control valve 36 is opened.

Therefore, the intake passage 34b, which has been closed until now, is opened. In FIG. 7, when the exhaust valves 26a and 26b open during the downward movement of the piston 16, the exhaust gas in the cylinder bore 14 is blown down to the exhaust port 22a,
22b, but the blowdown is stronger and lasts longer than when the load is light (Figure 7 (a)).
A large amount of exhaust gas is discharged into the exhaust port. The intake valves 24a and 24b begin to open at the time shown in FIG. Since it is operating, fresh air is introduced as shown by arrow T. At this time, fresh air is introduced from both the intake ports 20a and 20b, and this fresh air flows from top to bottom along the cylinder bore wall as shown by arrow T, and the exhaust gas flows as shown by arrow U. 22a and 22b, so-called cross scavenging is realized. At the point in FIG. 7(c), a negative pressure component in the pressure wave pulse due to strong blowdown appears, and the exhaust bows 22a and 22b temporarily become negative pressure, resulting in the introduction of fresh air T into the cylinder bore further. Some of the fresh air flows out to the exhaust boats 22a and 22b and is stored as shown in (2). This stored fresh air is transferred to the exhaust port 22a
.

When the pressure in 22b returns to positive pressure, it flows back into the cylinder bore as shown by arrow W, producing fresh air swirl X (FIG. 7 (d)). This causes turbulence and improves flame propagation after ignition. At the time of FIG. 7(E), the intake valve 24a
, 24b completes the closure and fresh air is prevented from blowing back.

Next, the operation of the control circuit 60 that operates the intake control valve 36 in the combustion operation described above will be explained with reference to the flowchart of FIG. This routine can be executed at regular intervals.

In step 100, it is determined whether the flag FTVTS=1. When FTVIS = 0, step 102
Then, the intake air amount to revolution speed ratio Q/NE is set to a predetermined value (Q/NE).
NIE).

It is determined whether the rotation speed NE is larger than the predetermined value (NU) in step 104. It is determined whether or not the value is larger than that.

Intake air amount to rotation speed ratio Q/NE > Predetermined value (Q/NE)
.

Or rotation speed NE>predetermined value (N[). Step 1
06, a signal is outputted from the output capo 60-4 to the actuator 37 to open the intake control valve 36. In step 10B, the flag FTVIS=1 is set. When FTVIS = 1, the process advances to step 110, and the intake air amount to revolution speed ratio Q/NE is set to a predetermined value (Q/N
E) It is determined whether or not the rotation speed NE is smaller than a predetermined value (NU)l. Intake air amount to rotation speed ratio Q/NE <predetermined value (
Q/NE), rotation speed NE<predetermined value (NE) +
In this case, the process proceeds to step 114, where a signal for causing the actuator 37 to close the intake control valve 36 is outputted from the output ports 0-4. In step 116, the flag FTVI
S=O is set.

Next, fuel injection control according to the present invention will be explained.

Similar to a normal fuel injection control device for a four-stroke engine, this embodiment also measures the amount of intake air in principle and injects the amount of fuel according to the measured value to obtain the desired air-fuel ratio. This is what we are trying to do. However, similar problems occur in ordinary piston-valve two-stroke internal combustion engines, but because the tJl' air valve and the intake valve are held open at the same time for a long period of time, fresh air often blows through.

The proportion of fresh air that blows through depends on the load, rotation speed,
It changes in a complicated manner depending on other operating conditions. Therefore, in this embodiment, data on fresh air capture coefficients corresponding to a plurality of operating conditions are stored in the memory 60-2, and the fresh air capture coefficients are calculated by interpolation during actual driving. By correcting the fuel injection amount, it is intended that the desired air-fuel ratio can be obtained even if the blow-through ratio changes depending on the operating conditions.

However, the blow-through ratio is affected by the intake air temperature in addition to the load and rotation speed. That is, the pressure of fresh air changes depending on the intake air temperature, which affects the scavenging characteristics.

In particular, in an internal combustion engine equipped with a supercharger 44, the intake air temperature changes greatly depending on the operation of the engine, so the influence thereof is significant. Therefore, in the present invention, by adding correction based on the intake air temperature downstream of the supercharger 44, it is possible to control the air-fuel ratio accurately to the target air-fuel ratio. FIG. 9 shows a fuel injection routine, and this routine is a crank angle interrupt routine that is executed every time the 30° CA signal from the second crank angle sensor 64 arrives. Step 13
At 0, it is determined whether or not it is fuel injection calculation timing. As shown in FIG. 3, fuel injection is carried out at intake valves 24a and 24b.
Since this calculation is performed within a predetermined angle range after the opening of the crankshaft starts, this calculation is performed at a predetermined crank angle slightly prior to this. This timing is based on the signal from the first crank angle sensor 62.
This can be determined by the value of a counter that is cleared by the 0° CA signal and incremented by the 306 CA signal from the second crank angle sensor 64. If it is determined that it is the fuel injection calculation timing, the process proceeds to step 132, where the basic fuel injection amount 'rp is calculated as follows: Tp=k (Q'/NE). Here, Q' is the intake air iQ converted into mass, which is the value obtained after correcting the measured value of the air flow meter 48 by the intake air temperature and the like. (Intake pipe pressure P
In a system in which the fuel injection amount is determined by M, PM can be used instead of Q'/NE. ) step 134
Then, a map calculation of the fresh air supplement coefficient riR is executed. Here, the fresh air capture coefficient (TR is the amount of fresh air actually involved in combustion within the cylinder bore, which is the amount of intake air measured by the airflow meter 48 minus the amount of fresh air that has flowed out into the exhaust system through the blow-through). This is a correction factor for the fuel injection amount related to the air ratio.Figure 10 conceptually shows how the fresh air capture coefficient fTll changes with respect to the intake air amount/rotation speed ratio and the rotation speed. It can be seen that the intake air amount-to-rotation speed ratio and the rotation speed change in a complicated manner due to the influence of pressure pulsations in the exhaust pipe due to blowdown (the case where there is no influence from blowdown is shown by a broken line). It can also be seen that when the intake control valve 36 is switched between open and closed, the fresh air capture coefficient rTR changes discontinuously at the boundary (
(See double-dashed line). The memory 60-2 stores data of the fresh air capture coefficient rt+t for the combination of intake air amount/rotation speed ratio and rotation speed according to FIG. 1θ. Then, an interpolation calculation is performed based on the actually measured intake air amount-to-rotation speed ratio and the rotation speed, and a fresh air capture coefficient fall that is suitable for the current operating conditions is calculated. In addition, intake pipe pressure PM
In a system that determines the fuel injection amount, a map of the fresh air capture coefficient fT is constructed based on the combination of PM and rotational speed, and interpolation calculation is performed based on the intake pipe pressure actually measured by the pressure sensor 60. In addition, in the embodiment, the basic fuel injection is first calculated and corrected by multiplying it by the fresh air capture coefficient fTR, but the correction by the fresh air capture coefficient fTR is first added to the intake air amount, The basic fuel injection amount may be calculated from the air amount.

In step 136, the intake air temperature T downstream of the supercharger 44 is
The fresh air capture coefficient rT* by IN is calculated as a water temperature correction coefficient. That is, as the intake air temperature downstream of the supercharger 44 increases, the pressure of fresh air entering the cylinder bore increases, and the blow-by tendency is promoted accordingly. Therefore, the fresh air capture coefficient fTR is multiplied by the correction coefficient K, which decreases as the intake air temperature TIN increases, to achieve accurate compensation of the air-fuel ratio in relation to the temperature of the intake air. The memory 60-2 has a map of the intake air temperature correction coefficient according to the intake air temperature TIN, and the intake air temperature correction coefficient for the current intake air temperature downstream of the supercharger actually measured by the intake air temperature sensor 68. Interpolation calculations are performed. In step 13B, the final fuel injection amount T A LJ is calculated by TAU=r, , xKx'rp Xα + β. Here, α and β represent representative correction coefficients and correction amounts whose explanations are omitted because they are not directly related to the present invention.

In step 140, it is determined whether the flag FTVIS = 1 or not.
That is, it is determined whether the intake control valve 36 is in an open state or a closed state. When the intake control valve 36 is open, the process proceeds to step 142, where TAU is entered in the address TAUa that stores the fuel injection time of the first fuel injector 38a, and TAU is entered in the address that stores the fuel injection time of the second fuel injector 38b. Zero is placed in TAUb. That is, only the first injector 38a is activated, and the second injector 38b is not activated. In step 140, the intake control valve 3
6 is closed, the process proceeds to step 144, where 1/3 of TAU is entered into the address TAUa where the fuel injection time of the first fuel injector 38a is stored, and the fuel injection time of the second fuel injector 38b is stored. Address T
The remaining 273 of TALJ is placed in AUb. Here, 1/3 and 2/3 have no specific meaning and are adaptation constants.
Effective dimensions of second intake passage 34b>First intake passage 34
Since this is the effective dimension of a, it simply indicates that the amount of fuel injected from the second injector 38b is greater than the amount of fuel injected from the first injector 38a, since the air-fuel ratio is constant in either case.

In step 146, TAUa is calculated from the expected injection start time.

Injector 38a only for a period corresponding to TAUb.

Fuel injection signal formation processing is performed so that 38b is activated. Since this process itself is well known, detailed explanation will be omitted. Step 148 generally shows other processing that is started to be executed every time the 30''CA signal arrives.

〔Effect of the invention〕

In a supercharged internal combustion engine such as a two-stroke internal combustion engine where fresh air often blows through, this invention compensates for the blow-through according to the intake air temperature at the intake pipe downstream of the supercharger. By adopting this system, accurate control of the air-fuel ratio is achieved even when the intake air temperature changes significantly, improving output, preventing overheating of the exhaust system catalyst, and improving fuel consumption.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the present invention. FIG. 2 is a schematic diagram of the entire system according to the embodiment of the present invention. FIG. 3 is a diagram showing a cross section of one cylinder (a diagram taken along line 11 in FIG. 2). FIG. 4 is an angle diagram of the operation timing of the intake valve and exhaust valve of one cylinder in one cycle of the engine. FIG. 5 is a diagram showing the operating timing of the exhaust valves of each cylinder in one cycle of the engine. FIG. 6 is a diagram illustrating combustion operation in one cycle of a two-stroke internal combustion engine with an intake valve and an exhaust valve according to an embodiment of the present invention under light load. FIG. 7 is a diagram illustrating combustion operation in one cycle of a two-stroke internal combustion engine with an intake valve and an exhaust valve according to an embodiment of the present invention at a time of high load. FIGS. 8 and 9 are flowcharts illustrating the operation of the control circuit. FIG. 10 is a conceptual diagram of changes in the fresh air capture coefficient fTII with respect to the intake air amount-rotational speed ratio and the rotational speed. 10... Engine body 17... Combustion chambers 24a, 24b... Intake valves 26a, 26b - Exhaust valves 34a, 34b... Intake passage 36... Intake control valves 38a, 38b... Fuel injector 42 ... Intercooler 44 ... Mechanical supercharger 48 ... Air flow meter 54 ... Exhaust manifold 60 ... Control wholesale circuit 62.64 ... Crank angle sensor 68 ... Intake air temperature sensor No. Figure 1 TDC Exhaust valve closed Figure 4 TDCCBDCTDC 廿Figure 6 Exhaust Figure 7

Claims (1)

[Claims] In a supercharged internal combustion engine such as a two-stroke internal combustion engine that has a large amount of fresh air blowing through, an air-fuel ratio control device comprising the following components, which supplies a desired amount of fuel to the internal combustion engine. a fuel supply means, a fuel supply amount calculation means for calculating the fuel supply amount determined by the load of the internal combustion engine and operating conditions such as the rotation speed, an intake air temperature detection means for detecting the temperature of the intake air downstream of the supercharger; Fuel supply amount correction means for calculating a correction factor value for compensating for blow-through according to the intake air temperature detected by the air temperature detection means, and correcting the fuel supply amount calculated by the fuel supply amount calculation means; Means for shaping the fuel supply signal to the fuel supply means so that a later amount of fuel is supplied to the engine.