JPH07103037A - Air fuel ratio controller of engine - Google Patents

Abstract

PURPOSE:To reduce the capacity of a catalyst when the fuel consumption is reduced compared with a conventional case and when a catalyst for purification of exhaust is to be provided at the time of making the air fuel ratio of a mixture generated by fuel supply from a carburetor constantly smaller than a theoretical air fuel ratio so as to improve the driving performance of a vehicle. CONSTITUTION:The air fuel ratio of a mixture 24 generated by fuel 12 supply of a carburetor 3 in relation to intake air 23 is made to be constantly smaller than a theoretical air fuel ratio. An exhaust detection sensor 33 for detecting the condition of exhaust 25 is provided. The carburetor 3 is controlled by the detection signal from the exhaust detection sensor 33 to adjust the amount of the fuel 12 supply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control system for an engine which adjusts the amount of fuel supplied by a carburetor so that the air-fuel ratio falls within a predetermined range.

[0002]

2. Description of the Related Art In a motorcycle, in order to particularly enhance acceleration in driving performance, the fuel concentration in the air-fuel mixture is made sufficiently high under normal operating conditions, that is, the air-fuel ratio of the air-fuel mixture is equal to
A (air weight) / F (fuel weight) is the theoretical air-fuel ratio (= 1
It is common practice to drive the engine with a value smaller than 4.7).

For example, a fuel injection valve may be used to supply the above-mentioned fuel, but a carburetor which is cheaper than this is often used.

By the way, due to the structure of the carburetor, the fuel supply amount by the carburetor tends to vary even if the amount of intake air and the negative pressure are constant, so that the fluctuation range of the air-fuel ratio tends to become large. .

Therefore, in the fluctuation range of the air-fuel ratio, even if the air-fuel ratio becomes large, in order to ensure the above-mentioned predetermined operating performance, the fuel concentration as a whole remains unchanged in the fluctuation range. The carburetor is set in advance so that it becomes higher, that is, the air-fuel ratio becomes smaller as a whole while the fluctuation range remains the same.

[0006]

However, if the air-fuel ratio is reduced as a whole as described above, there arises a problem that the fuel consumption becomes excessive.

Further, as described above, if the air-fuel ratio is made small as a whole, the oxygen deficiency becomes large, and the CO in the exhaust gas is reduced.
The amount increases. For this reason, when an exhaust gas purification catalyst is provided, the burden on this catalyst increases, and the capacity of this catalyst must be increased.

[0008]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the above circumstances and is intended to improve the driving performance of a vehicle.
When the air-fuel ratio of the air-fuel mixture generated by the fuel supply by the carburetor is always made smaller than the stoichiometric air-fuel ratio, it is possible to reduce the fuel consumption amount compared with the conventional one, and the exhaust purification catalyst is used. The purpose of the present invention is to make the capacity of this catalyst small when it is provided.

[0009]

In order to achieve the above object, the present invention is directed to a fuel 1 of a carburetor 3 for intake air 23.
In an air-fuel ratio control device for an engine in which the air-fuel ratio of the air-fuel mixture 24 generated by two supply is always smaller than the stoichiometric air-fuel ratio, an exhaust gas detection sensor 33 for detecting the property of the exhaust gas 25 is provided. Is used to control the vaporizer 3 to adjust the amount of fuel 12 supplied.

[0010]

[Operation] The operation of the above configuration is as follows.

Due to the structure of the carburetor 3, even if the amount of the intake air 23 and the negative pressure are constant, the supply amount of the fuel 12 is likely to vary, and if it is left as it is, the fluctuation range of the air-fuel ratio becomes large.
However, according to the present invention, the supply amount of the fuel 12 is adjusted to an appropriate amount every moment by the control of the carburetor 3 by the detection signal of the exhaust gas detection sensor 33, so that the fluctuation range of the air-fuel ratio is narrowed.

[0012] Therefore, even if the air-fuel ratio is widened, the predetermined operating performance is ensured even if the air-fuel ratio is narrowed. Therefore, as described above, the air-fuel ratio is increased. As a result, the amount of fuel 12 supplied by the vaporizer 3 is reduced overall.

Further, as described above, as the air-fuel ratio can be increased, the deficiency of oxygen in the air-fuel mixture 24 decreases and the exhaust gas 2
The amount of CO in 5 is also reduced, and therefore, when the catalyst 5 for purifying the exhaust 25 is provided, the load on the catalyst 5 is reduced.

[0014]

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

In FIG. 1, reference numeral 1 is an engine mounted on a motorcycle. An intake pipe 2 is connected to an intake port of the engine 1, and a carburetor 3 is provided in the middle of the intake pipe 2. An exhaust pipe 4 is connected to the exhaust port of the engine 1, and a catalyst 5 is provided in the middle of the exhaust pipe 4.

The carburetor 3 is of the air bleed type and has an intake passage 7 therein. A piston 8 is provided which extends and retracts toward the intake passage 7, and a venturi portion 9 is formed between the protruding portion of the piston 8 and the inner peripheral surface of the intake passage 7. A main nozzle 11 that opens toward the venturi portion 9 is provided. The main nozzle 11 communicates with the float chamber 13 storing the fuel 12, and also communicates with the intake pipe 2 on the upstream side of the carburetor 3 via the main air pipe 14. A taper needle 15 is provided on the piston 8 so as to project from the piston 8. The taper needle 15 is inserted into the main nozzle 11.

A butterfly type throttle valve 17 for adjusting the opening of the intake passage 7 on the downstream side of the venturi portion 9.
Is provided. A slow port 18 that opens toward the intake passage 7 is provided at a position corresponding to the throttle valve 17. The slow port 18 communicates with the float chamber 13 and also communicates with the inside of the intake pipe 2 upstream of the carburetor 3 via a slow air pipe 19.

Reference numeral 21 is an engine control device for electronically controlling the engine 1.

When the engine 1 is driven by the control of the engine control device 21, the intake air 23 outside the machine is drawn into the engine 1 through the intake pipe 2. At this time, when the opening degree of the intake passage 7 is increased by operating the throttle valve 17, the venturi portion 9 and the intake passage 7 on the downstream side of the venturi portion 9 respond to the opening operation of the throttle valve 17. The negative pressure becomes high, and the negative pressure causes the fuel 12 to be sucked into the intake passage 7 through the main nozzle 11 and the slow port 18. And the fuel 12
Is mixed with the intake air 23, and the air-fuel mixture 24 generated thereby is sucked into the engine 1 and used for combustion.

Exhaust gas 25 produced by the combustion is discharged through the exhaust pipe 4 and the catalyst 5. At this time, the catalyst 5
Burns the unburned matter in the exhaust gas 25,
To purify.

In FIG. 2, in the constant use region of the engine 1, the air-fuel ratio of the air-fuel mixture 24 is the theoretical air-fuel ratio (14.
Each part of the carburetor 3 is set so as to be always smaller than 7). That is, the operating performance is improved by sufficiently increasing the concentration of the fuel 12 in the air-fuel mixture 24.

In FIGS. 1 and 3, an air-fuel ratio control device 27 for controlling the air-fuel ratio of the air-fuel mixture 24 is provided.
The air-fuel ratio control device 27 will be described.

A main system air valve 28 for adjusting the opening degree of the main system air pipe 14 in the middle of the main system air pipe 14.
Is provided. Further, a main actuator 29 for opening and closing the main air valve 28 is provided. On the other hand, a slow air valve 30 for adjusting the opening degree of the slow air pipe 19 is provided. Further, a slow system actuator 31 for opening and closing the slow system air valve 30 is provided. Each actuator 2
Both 9 and 31 are servomotors or solenoids.

An exhaust gas detection sensor 33, which is a CO sensor for detecting the CO concentration in the properties of the exhaust gas 25, is attached to the exhaust pipe 4. This exhaust gas detection sensor 33
Is, for example, a semiconductor made of a metal oxide made of SnO ₂ as a sensitizer, and as shown in FIG. To detect the CO concentration.

1 and 3, the engine speed detection sensor 34 for detecting the speed of the engine 1 and the throttle opening detection sensor 3 for detecting the opening of the throttle valve 17.
5. A water temperature detection sensor 36 for detecting the temperature of the cooling water of the engine 1, that is, for indirectly detecting the temperature of the engine 1 is provided.

The engine control device 21 includes an operating condition determining means 38, a target air-fuel ratio determining means 39, a comparing means 40,
Actuator control means 41 and air-fuel ratio calculation means 4
Equipped with 2. Then, the CO concentration detection signal (output voltage) from the exhaust gas detection sensor 33 is used as the air-fuel ratio calculation means 4
2, and the air-fuel ratio calculation means 42 calculates the air-fuel ratio (A / F) of the air-fuel mixture 24.

In FIG. 3 and FIG. 5, the detection signals of the engine speed detection sensor 34, the throttle opening detection sensor 35, and the water temperature detection sensor 36 are the operation state determination means 3.
8 is input, and the operating state determination means 38 determines the operating state. In other words, at start-up, transient, steady state,
It is determined whether the vehicle is idling or idling.
It should be noted that all of these operating states are included in the always-used region of the engine 1 shown in FIG.

In FIG. 5, the operating condition determining means 38 is used.
A desired target air-fuel ratio is preset as a map for the operating state determined by. Then, based on this map, the target air-fuel ratio corresponding to the operating condition determined by the operating condition determining means 38 is determined by the target air-fuel ratio determining means 39.

1 and 3, the comparison means 40 compares the target air-fuel ratio determined by the target air-fuel ratio determination means 39 with the air-fuel ratio calculated by the air-fuel ratio calculation means 42. Based on the comparison result, the main system actuator 29 and the slow system actuator 31 are driven via the actuator control means 41, and the main system air valve 28 and the slow system air valve 30 are opened / closed. By this opening / closing valve operation, the amount of the fuel 12 that is sucked toward the intake passage 7 side through the main nozzle 11 and the slow port 18 is adjusted, and the air-fuel ratio of the air-fuel mixture 24 is adjusted.

More specifically, when the concentration of the fuel 12 in the air-fuel mixture 24 is high (or low), C
The O concentration becomes high (or becomes low), and the air-fuel ratio calculated by the air-fuel ratio calculating means 42 based on the detection signal of the exhaust gas detection sensor 33 that detects this becomes a small value (or
Larger value). When the calculated air-fuel ratio is smaller (or larger) than the target air-fuel ratio determined by the target air-fuel ratio determining means 39, the main system air valve 28 and the slow system air valve 30 are opened ( Or
Valve closing operation), and the intake air 23 is sent (or suppressed to be sent) to the main nozzle 11 and the slow port 18 via the main system air pipe 14 and the slow system air pipe 19. The amount of the fuel 12 sucked into the intake passage 7 is reduced (or increased), whereby the air-fuel ratio is increased (or decreased), and the air-fuel ratio is brought close to the desired value.

For this reason, the vaporizer 3 has the following structure.
Even if the amount and the negative pressure of the intake air 23 are constant, the fuel 12
The supply amount is likely to vary, and the fluctuation range of the air-fuel ratio becomes large if it is left as it is. However, according to the above-described embodiment, the supply amount of the fuel 12 is adjusted to an appropriate amount every moment, so that the fluctuation range of the air-fuel ratio is narrowed. .

Therefore, as the fluctuation range of the air-fuel ratio is narrowed, the air-fuel ratio is increased as a whole,
In this state, predetermined driving performance is secured.

In FIG. 1, the catalyst 5 is an oxidation catalyst,
CO and HC in the exhaust gas 25 react with the catalyst 5 to be burned, whereby the exhaust gas 25 is purified and discharged.

In this case, when the amounts of CO and HC are large, the heat of combustion due to the reaction with the catalyst 5 accelerates the deterioration of the catalyst 5 and the load on the catalyst 5 becomes large, which causes a problem in the life. However, since the air-fuel ratio of the air-fuel mixture 24 is increased as a whole as described above, the amount of oxygen deficiency in the air-fuel mixture 24 decreases and the amount of CO in the exhaust gas 25 also decreases accordingly. The burden on the catalyst 5 for purifying the exhaust gas 25 is reduced.

In FIGS. 1 and 3, an exhaust gas purification device 43 for further purifying the exhaust gas 25 is provided.

The exhaust gas purification device 43 is provided with a secondary air pipe 44 which connects the inside of the intake pipe 2 upstream of the carburetor 3 to the inside of the exhaust pipe 4. A secondary air valve 45 for adjusting the opening degree of the secondary air pipe 44 in the middle of the secondary air pipe 44.
Is installed. Further, a secondary air actuator 46 for opening and closing the secondary air valve 45 is provided. This secondary air actuator 46 is a servo motor,
Alternatively, it is a solenoid or the like.

A catalyst temperature detecting sensor 47 is attached to the catalyst 5. The catalyst temperature detection sensor 47 directly detects the temperature of the catalyst 5, or indirectly detects the temperature of the catalyst 5 by the temperature of the exhaust gas 25 passing through the catalyst 5. Further, the engine control device 21 is provided with a secondary air supply amount determination means 49 and an actuator control means 50.

The air-fuel ratio calculated by the air-fuel ratio calculating means 42 and the detection signal of the catalyst temperature detecting sensor 47 are input to the secondary air supply amount determining means 49, and based on this, the secondary air supply is determined. The amount determining means 49 determines the amount of the secondary air 23a to be supplied from the inside of the intake pipe 2 through the secondary air pipe 44 into the exhaust pipe 4. Then, the actuator control means 50 operates the secondary air actuator 46 to open and close the valve so that the supply amount of the secondary air 23a thus determined is obtained.

The secondary air 23a is the exhaust gas 2 in the exhaust pipe 4.
CO, H contained in the exhaust gas 25 when supplied to
C is combusted by oxygen in the secondary air 23a and is sufficiently purified.

The catalyst 5 and the exhaust gas purification device 43 are not essential to the present invention. When the engine 1 has multiple cylinders, the air-fuel ratio control device 27 described above is provided for each cylinder.
May be provided. By doing so, it is possible to prevent variations in the output between the cylinders.

[0041]

According to the present invention, in the air-fuel ratio control device for an engine in which the air-fuel ratio of the air-fuel mixture generated by the fuel supply of the carburetor to the intake air is constantly made smaller than the stoichiometric air-fuel ratio, the characteristics of the exhaust gas are controlled. An exhaust detection sensor that detects the
The vaporizer is controlled to adjust the fuel supply amount.

By the way, in the carburetor, even if the amount of intake air and the negative pressure are constant, the fuel supply amount tends to vary due to the structure of the carburetor, and if it is left as it is, the fluctuation range of the air-fuel ratio becomes large.
However, as described above, since the fuel supply amount is adjusted to an appropriate amount momentarily by the control of the carburetor by the detection signal of the exhaust gas detection sensor, the fluctuation range of the air-fuel ratio is narrowed.

Accordingly, even if the air-fuel ratio is increased overall as the fluctuation range of the air-fuel ratio is narrowed, a predetermined driving performance is ensured in the vehicle. As the fuel ratio is increased, the fuel supply amount by the carburetor is reduced as a whole. That is, when the air-fuel ratio of the air-fuel mixture generated by the fuel supply to the carburetor is constantly made smaller than the stoichiometric air-fuel ratio in order to improve the operation performance, the fuel consumption amount can be reduced as compared with the conventional case. .

Further, as described above, the amount of oxygen in the air-fuel mixture is reduced by the amount by which the air-fuel ratio can be increased, so that C in the exhaust gas is reduced.
Since the amount of O also decreases, when the catalyst for purifying the exhaust gas is provided, the burden on the catalyst is reduced.

Therefore, a small capacity of the above catalyst is sufficient.

[Brief description of drawings]

FIG. 1 is an overall diagram.

FIG. 2 is a graph showing the relationship between engine output and air-fuel ratio.

FIG. 3 is an electrical block diagram mainly showing an air-fuel ratio control device.

FIG. 4 is a diagram showing output characteristics of an exhaust gas detection sensor.

FIG. 5 is a map diagram showing a relationship between a target air-fuel ratio and an engine operating state in the air-fuel ratio control device.

[Explanation of symbols]

 1 Engine 2 Intake Pipe 3 Vaporizer 4 Exhaust Pipe 5 Catalyst 12 Fuel 21 Engine Control Device 23 Intake Air 24 Mixture 25 Exhaust 27 Air-Fuel Ratio Control Device 33 Exhaust Detection Sensor 43 Exhaust Purification Device

Claims (1)

[Claims] 1. An exhaust gas detection sensor for detecting a property of exhaust gas in an air-fuel ratio control device for an engine, wherein an air-fuel ratio of an air-fuel mixture produced by supplying fuel to an intake air of a carburetor is always smaller than a stoichiometric air-fuel ratio. And an air-fuel ratio control device for the engine, which controls the carburetor by the detection signal of the exhaust gas detection sensor to adjust the fuel supply amount.