JPS6148626B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device for an engine, and more particularly to an air-fuel ratio control device for an engine to which an air-fuel mixture is supplied by a carburetor.

In carburetor type engines, in order to effectively operate the three-way catalytic converter and improve fuel efficiency, the air-fuel ratio of the mixture supplied to the engine is kept within a fairly narrow range around the stoichiometric air-fuel ratio. Air-fuel ratio control devices have been proposed in the past.

As one type of air-fuel ratio control device, the air _- fuel ratio is controlled by feedback controlling the amount of air bleed from the carburetor while detecting the concentration of exhaust components in the exhaust gas emitted from the engine using an exhaust sensor such as an O 2 sensor. What controls is known.

By the way, when the engine is operated at low load, the concentration of NOx in the exhaust gas is low, and the amount of NOx in the exhaust gas is reduced by correcting the air-heat ratio of the mixture supplied to the engine to an air-fuel ratio that deviates from the stoichiometric air-fuel ratio.
NOx concentration can be maintained at a sufficiently low value.

The present invention focuses on the above-mentioned fact, and when the engine is operating at low load, the feedback control is stopped so that a lean air-fuel mixture with an air-fuel ratio higher than the stoichiometric air-fuel ratio is supplied to the engine, and furthermore, when the engine is idling, the feedback control is stopped. A rich air-fuel mixture with an air-fuel ratio lower than the stoichiometric air-fuel ratio is supplied to the engine so that stable idling operation can be achieved and high-output operation can be achieved during high-load operation, improving fuel efficiency and purifying exhaust gas. The object of the present invention is to provide an improved feedback control type air-fuel ratio control device that achieves both of the following and improves drivability.

According to the present invention, this purpose includes an exhaust sensor that detects the concentration of exhaust components of exhaust gas discharged from the engine, and a signal that indicates the air-fuel ratio of the air-fuel mixture supplied to the engine based on a signal generated by the exhaust sensor. an arithmetic device that generates a signal; an air bleed control device that is driven based on the signal generated by the arithmetic device and performs feedback control of the air bleed amount of the carburetor so that the air-fuel ratio becomes an air-fuel ratio near the stoichiometric air-fuel ratio; and an idling operation. an air bleed increase correction device for increasing the amount of air bleed by the air bleed control device so that the air-fuel ratio becomes substantially larger than the stoichiometric air-fuel ratio by prohibiting the feedback control during low-load operation other than during idling; an air bleed reduction correction device that inhibits the feedback control during operation or high-load operation to reduce the amount of air bleed by the air bleed control device so that the air-fuel ratio becomes an air-fuel ratio substantially smaller than the stoichiometric air-fuel ratio; This is achieved by an engine air-fuel ratio control device characterized in that it has a delay device that provides a time delay to the operation of the air bleed increase correction device.

According to the configuration described above, the air-fuel ratio of the air-fuel mixture supplied to the engine is selectively switched between the stoichiometric air-fuel ratio and the lean air-fuel ratio according to the engine operating state by controlling the air bleed amount by the air bleed control device. Moreover, by controlling the amount of air bleed by the air bleed control device, a rich air-fuel mixture can be supplied to the engine during idling or high-load operation without the need for a special enrichment device or power device, resulting in stable idling. An operating state or a high output operating state can be obtained. Furthermore, since the switching of the air-fuel ratio to the lean air-fuel ratio as described above is carried out with a time delay given by the delay device, even if the operating state of the engine changes frequently and repeatedly under the switching conditions, the switching of the air-fuel ratio to the lean air-fuel ratio is performed immediately. Frequent and repeated switching of the air-fuel ratio is avoided, and the hunting phenomenon is avoided.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. The attached FIG. 1 is a schematic configuration diagram showing one embodiment of an air-fuel ratio control device according to the present invention. In the figure, 1 indicates the engine,
The engine 1 sucks a mixture of fuel and air through the carburetor 2 through the manifold 3 and discharges exhaust gas to the exhaust manifold 4.

The carburetor 2 has a large bench lily 6 in its intake bore 5 . A throttle valve 7 is provided in the intake bore 5 on the downstream side of the large bench lily 6, and a choke valve 8 is provided in the intake bore 5 on the upstream side of the large bench lily 6. A small bench lily 9 is provided at the throat of the large bench lily 6, and a main fuel nozzle 10 opens at the throat of this small bench lily. The main fuel nozzle 10 has a float chamber 1
A liquid fuel such as gasoline stored in the fuel tank 1 is supplied through a main fuel passage 13 while its flow rate is adjusted by a main fuel jet 12. A well 14 is formed in the middle of the main fuel passage 13, and within this well 14 is provided an air bleed tube 15 having a plurality of small holes. Air bleed tube 15 is connected to a fixed air bleed jet 38. An air bleed conduit 16 is connected to the base of the main fuel nozzle 10, and a proportional actuator 17 is connected to this conduit for controlling the flow rate of air flowing through the conduit. The proportional actuator 17 is a flow control valve, and this device includes a cylindrical guide tube 19 with a valve port 18, and a cylindrical guide tube 19 that moves in the axial direction of the guide tube 19 and controls the effective opening of the valve port 18. A slide sleeve 20 for controlling the area is included. An electromagnetic coil 21 is attached to the slide sleeve 20, and as the current supplied to the electromagnetic coil increases, the slide sleeve 20 cooperates with a permanent magnet 22 to resist the action of a compression coil spring 23. Move to the right in the diagram and select valve port 18.
The effective aperture area of the Power supply control to the electromagnetic coil 21 is performed by a computer 24, which will be described later.

Further, the carburetor 2 is provided with a slow port 25, and a part of the fuel flowing through the main fuel passage 13 is transferred to the slow port 25 into a slow fuel passage 26 which is branched from the middle of the passage. A slow jet 27a provided along the way
The gas is supplied while its flow rate is adjusted by the economizer jet 27b. Further, an idle adjustment screw 28 is provided in the slow port 25 portion. In addition, a fixed air bleed jet 2 is installed in the middle of the slow fuel passage 26.
9 is provided.

An air bleed conduit 30 is connected to the slow port 25, and a proportional actuator 31 is connected to this conduit. The proportional actuator 31, like the proportional actuator 17, has a guide tube 33 with a valve port 32.
, a slide sleeve 34 to which an electromagnetic coil 35 is attached, a permanent magnet 36, and a compression coil spring 3.
7, which operates in the same manner as the proportional actuator, and whose operation is controlled by the computer 24. Proportional actuator 3
1 is designed so that when the valve port 32 of this valve is fully opened, air bleed is performed with a relatively large amount of air to the extent that it substantially prevents fuel from being discharged from the slow port 25 to the intake bore 5. The size of the valve port is set.

An O ₂ sensor 40 is attached to the exhaust manifold 4. The O ₂ sensor 40 detects excess oxygen in the exhaust gas flowing inside the exhaust manifold 4,
It is designed to generate an electrical signal in response to that. This O ₂ sensor 40 outputs a voltage signal of about 1.0V when the air-fuel ratio is smaller than the stoichiometric air-fuel ratio, whereas it outputs a voltage signal of about 0.1V when the air-fuel ratio is larger than the stoichiometric air-fuel ratio, that is, when lean. death,
These voltage signals are input to the computer 24.

FIG. 2 is an electrical circuit diagram illustrating one embodiment of computer 24. A voltage signal generated by the O ₂ sensor 40 is input to a non-inverting terminal of a comparator 44 via a voltage follower 41 , an variable gain amplifier (AGC) 42 , and a resistive element 43 . A comparator 44 outputs the output voltage Vx of the variable gain amplifier 42 and the set voltage Vr of the constant voltage generation circuit 45 input to its inverting terminal.
When Vx≧Vr, in other words, when the air-fuel ratio is smaller than the predetermined air-fuel ratio (theoretical air-fuel ratio), a high-level voltage signal “1” is output, and when Vx<Vr
When this happens, a low level voltage signal “0” is output. That is, the comparator 44 outputs a pulse signal according to the fluctuation of the air-fuel ratio. This pulse signal is input to the inverting terminals of an integrator 46 and an inverting amplifier 47, which are connected in parallel. The integrator 46 is an operational amplifier 46
A, a resistance element 46b, and a capacitor 46c, the input voltage is integrated according to an integral constant determined by the resistance element 46b and the capacitor 46c, and a voltage signal proportional to the integrated value is output. A non-inverting terminal of the integrator 46 is connected to a constant voltage generating circuit 46d. The inverting amplifier 47 is the operational amplifier 4
7a and resistance elements 47b and 47c,
Invert and amplify the input signal. A non-inverting terminal of the inverting amplifier 47 is connected to a constant voltage generating circuit 47d. The output signals of the integrator 46 and the inverting amplifier 47 are each input to the inverting terminal of the adder 48. The adder 48 includes an operational amplifier 48a and resistance elements 48b, 48.
c and 48d, and performs non-in-phase addition of both signals and outputs an integral signal with a skip. A non-inverting terminal of the adder 48 is connected to a constant voltage generating circuit 48e. This output signal is selectively inputted to a non-inverting terminal of a comparator 51 via an analog switch 49 and a resistive element 50. The comparator 51 receives the triangular wave generated by the triangular wave generating circuit 52 via a resistor 53 to its inverting terminal, compares this triangular wave with the signal from the adder 48, and generates a pulse signal with a duty ratio based on the comparison result. occurs. The triangular wave generated by the triangular wave generation circuit 52 is 200
It may have a frequency of about Hz.

When the comparator 51 receives a signal from the adder 48, it generates a pulse signal with a larger duty ratio as the air-fuel ratio is smaller, that is, as the air-fuel mixture is richer.

The pulse signal generated by the comparator 51 is transmitted to the resistive element 5.
4 and 55, and are input to the base terminals of transistors 56 and 57, respectively. The transistor 56 has its collector terminal connected to the electromagnetic coil 21 of the proportional actuator 17, and its emitter terminal grounded. The transistor 57 has its collector terminal connected to the electromagnetic coil 35 of the proportional actuator 31, and its emitter terminal grounded. Further, the base terminal and collector terminal of each of the transistors 56 and 57 are connected to a capacitor 58,
59.

The pulse signal generated by the comparator 51 is input to the electromagnetic coil of the proportional actuator via a transistor. The pulse signal given to the electromagnetic coil is
Since it is a pulse signal with a frequency of about 200Hz, this pulse signal acts on the electromagnetic coil as an averaged DC current signal, and the larger the duty ratio, the more the slide sleeve is driven to the right as seen in Figure 1, and the valve is activated. This increases the effective opening area of the port.

Further, a constant voltage generated by a constant voltage generating circuit 60 is selectively inputted to the non-inverting terminal of the comparator 51 via an analog switch 61. When the constant voltage generated by the constant voltage generating circuit 60 is input to the comparator 51 via the analog switch 61, the comparator 51 generates a pulse signal with a relatively large predetermined duty ratio. When this pulse signal is applied to the electromagnetic coils 21 and 35, the proportional actuators 17 and 31 operate the valve port 18 so that the air-fuel ratio of the mixture supplied to the engine 1 is larger than the stoichiometric air-fuel ratio, for example, about 18. , 32 are adjusted.

Analog switches 49 and 61 are respectively conductive when a "1" signal is applied to their gate terminals, and are non-conductive when a "0" signal is applied to their gate terminals.

The negative pressure switch 62 is sensitive to the intake pipe negative pressure of the engine 1, and when it is larger than a predetermined value, for example -
When it is greater than 300 mmHg, a “1” signal is generated and the signal is output to the AND gate 63. The idling switch 64 is, for example, a throttle valve 7.
When the throttle valve is at or near the idling position, a "1" signal is generated, and this signal is output to the AND gate 63 via the NOT gate 65. Therefore, the AND gate 63 generates a "1" signal only during low load operation, excluding idling operation.

Another negative pressure switch 66 is sensitive to the intake pipe negative pressure of the engine 1, and when it is smaller than a predetermined value,
For example, when it is less than -100mmHg, it generates a "1" signal and sends it to the delay circuit 67 and NOT gate 68.
The signal is then output to another AND gate 69.

The output signal of the AND gate 63 is input to the gate terminal of the analog switch 61 via a delay circuit 70, and is input to the gate terminal of the analog switch 61 via a NOT gate 71.
is input. The output signal of NOT gate 65 is
It is input to AND gate 69. AND gate 69
The output signal is input to the gate terminal of analog switch 49.

The air-fuel ratio control device constructed as described above operates as follows. When the engine 1 is operated under medium load, each of the negative pressure switch 62, idling switch 64, and negative pressure switch 66 outputs a "0" signal, so the gate terminal of the analog switch 61 receives a "0" signal. But analog switch 4
A "1" signal is input to the gate terminal of 9. At this time, the analog switch 49 becomes conductive, and the voltage signal generated by the adder 48 is inputted to the comparator 51 via the analog switch 49. Therefore, at this time, the electromagnetic coils 21 and 35 are driven by a pulse signal with a duty ratio determined based on the signal generated by the O ₂ sensor 40, thereby controlling the effective opening areas of the valve ports 18 and 32. The amount of air bleed is feedback controlled. With this air bleed control, engine 1
An air-fuel mixture with an air-fuel ratio near the stoichiometric air-fuel ratio is supplied to the engine. During this operation, the three-way catalytic converter installed in the exhaust system will emit HC, CO, and NOx.
It acts as a three-way catalytic converter that simultaneously purifies three components.

When the engine 1 is operated at low load, the negative pressure switch 62 generates a "1" signal, and the idling switch 64 and negative pressure switch 66 each output a "0" signal.
Since a signal is generated, a “0” signal is sent to the gate terminal of analog switch 49, and
A “1” signal is now input to the gate terminal of “1”. Therefore, at this time, the voltage generated by the constant voltage generating circuit 60 is input to the comparator 51, and the comparator 51 generates a pulse signal with a relatively large predetermined duty ratio based on the voltage. As a result, the electromagnetic coils 21 of the proportional actuators 17 and 31
and 35 is substantially increased, and the effective open area of valve ports 18 and 32 is increased accordingly. As a result, the amount of air bleed increases, and the engine 1 is supplied with a lean air-fuel mixture having an air-fuel ratio, for example, about 18, which is higher than the stoichiometric air-fuel ratio. In addition, during this operation, the three-way catalytic converter installed in the exhaust system is
It acts as an oxidation catalytic converter that purifies unburned components such as.

The delay circuit 70 delays the transmission of the output signal of the AND gate 63 to the gate terminal of the analog switch 61, and only when the engine 1 is continuously operated at a low load for a predetermined period of time or more, the analog switch 61 is activated.
acts so that it becomes conductive.

When the engine 1 is idling, the negative pressure switch 62 generates a “1” signal;
Since the idling switch 64 also generates a "1" signal, AND gates 63 and 69 both output "0" signals. At this time, analog switches 49 and 61 are both non-conductive, and no current is applied to electromagnetic coils 21 and 35.
Valve ports 18 and 32 are fully closed, and carburetor 2 supplies engine 1 with a relatively rich air-fuel mixture necessary for idling operation.

Further, when the engine 1 is operated under high load, the negative pressure switch 62 and the idling switch 64 generate a "0" signal, and the negative pressure switch 66 generates a "1" signal.
Since a signal is generated, AND gates 63 and 69 both generate a "0" signal at this time as well. Therefore, at this time, analog switches 49 and 61 are both in a non-conducting state, and no current is applied to electromagnetic coils 21 and 35, so valve ports 18 and 32 are fully closed, and carburetor 2 is closed, which is necessary for high-load operation. A relatively rich air-fuel mixture is supplied to the engine 1. Note that due to the action of the delay circuit 67, the relatively rich air-fuel mixture as described above is supplied during high-load operation only after a predetermined period of time has elapsed since the transition from medium-load operation to high-load operation.

In the above, the present invention has been described in detail with respect to specific embodiments, but it will be understood by those skilled in the art that the present invention is not limited thereto and that various embodiments can be made within the scope of the present invention. It should be obvious.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of an air-fuel ratio control device for an engine according to the present invention, and FIG. 2 is an electrical circuit diagram of the air-fuel ratio control device according to the present invention. 1 - engine, 2 - carburetor, 3 - intake manifold, 4 - exhaust manifold, 5 - intake bore, 6
~ Large bench lily, 7 ~ Throttle valve, 8
~ Chiyoke Valve, 9 ~ Small Bench Lily, 1
0 ~ Main fuel nozzle, 11 ~ Float chamber, 12
~Main fuel jet, 13~Main fuel passage,
14~well, 15~air bleed tube, 1
6 - Air bleed conduit, 17 - Proportional actuator, 18 - Valve port, 19 - Guide tube, 2
0 ~ Slide sleeve, 21 ~ Electromagnetic coil, 22
~Permanent magnet, 23~Compression coil spring, 24~Computer, 25~Slow port, 26~Slow fuel passage, 27a~Slow jet, 27b~Economizer jet, 28~Idle adjuster screw, 29~Air bleed jet, 30~Air bleed conduit, 31~Proportional actuator, 3
2 - Valve port, 33 - Guide tube, 34 - Slide sleeve, 35 - Electromagnetic coil, 36 - Permanent magnet, 37 - Compression coil spring, 40 - O ₂ sensor, 41 - Voltage follower, 42 - Variable gain amplifier, 43 ~Resistance element, 44~Comparator, 45~
Constant voltage generation circuit, 46 - integrator, 47 - inverting amplifier, 48 - adder, 49 - analog switch, 5
0 - resistance element, 51 - comparator, 52 - triangular wave generation circuit, 53 - resistance element, 54, 55 - resistance element,
56, 57 ~ transistor, 58, 59 ~ capacitor, 60 ~ constant voltage generation circuit, 61 ~ analog switch, 62 ~ negative pressure switch, 63 ~ AND gate, 64 ~ idling switch, 65 ~ NOT
Gate, 66~Negative pressure switch, 67~Delay circuit,
68~NOT gate, 69~AND gate, 70~
Delay circuit, 71~NOT gate.

Claims (1)

[Claims] 1: an exhaust sensor that detects the concentration of exhaust components in exhaust gas discharged from the engine; an arithmetic device that generates a signal representing the air-fuel ratio of the air-fuel mixture supplied to the engine based on the signal generated by the exhaust sensor;
an air bleed control device that is driven based on a signal generated by the arithmetic unit and feedback-controls the air bleed amount of the carburetor so that the air-fuel ratio becomes an air-fuel ratio near the stoichiometric air-fuel ratio; an air bleed increase correction device that inhibits feedback control and increases the amount of air bleed by the air bleed control device so that the air-fuel ratio becomes substantially larger than the stoichiometric air-fuel ratio; an air bleed reduction correction device that inhibits feedback control to reduce the amount of air bleed by the air bleed control device so that the air-fuel ratio becomes an air-fuel ratio substantially smaller than the stoichiometric air-fuel ratio; and an air bleed increase correction device that operates. 1. An air-fuel ratio control device for an engine, comprising a delay device that provides a time delay.