JPS6038039Y2 - Engine air-fuel ratio control device - 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 operation for an engine supplied with air-fuel mixture by a carburetor.

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

As one type of air-fuel ratio control device, the air-fuel ratio is feedback-controlled by controlling the amount of air bleed from the carburetor while detecting the concentration of exhaust components in the exhaust gas discharged from the engine using an exhaust sensor such as the 02 sensor. What it does is known.

Generally, when an engine decelerates, especially when the engine is cold, a large amount of fuel adhering to the wall of the intake passage evaporates rapidly, causing the air-fuel ratio of the mixture supplied to the engine to become extreme. becomes smaller.

At this time as well, if the air bleed amount is feedback-controlled based on the signal from the oxygen sensor, the control valve that controls the air bleed amount is opened wide to increase the air-fuel ratio.

Therefore, if acceleration is performed immediately after deceleration, new fuel will adhere to the wall of the intake passage, and there will be a delay in the start of fuel at the beginning of acceleration, which will increase the air-fuel ratio. Due to the delay in the response of the control system and the delay in the operation of the control valve, the air-fuel ratio becomes even larger because the control valve is still wide open, and as a result, a very lean mixture is supplied to the engine.
As a result, the engine misfires, resulting in deterioration of drivability and an increase in the concentration of HCJ in the exhaust gas.

On the other hand, if the air-fuel ratio control by air bleed control is stopped when the engine is cold, the above problem will not occur, but since the air-fuel ratio control will not be performed even during steady operation, the engine The three-way catalytic converter will no longer operate effectively as the fuel-air mixture will no longer be supplied.

In view of the above-mentioned problems with conventional air bleed control type air-fuel ratio control devices, the present invention has been developed to develop an improved engine that performs appropriate air-fuel ratio control under various operating conditions even when the engine is cold. The purpose of the present invention is to provide an air-fuel ratio control device.

This purpose includes an air bleed passage provided in the carburetor, an additional air supply port for supplying additional air to the engine intake system, an inlet open to the atmosphere and an outlet via first and second passage means, respectively. a control valve connected to the air bleed passage and the additional air supply port; an exhaust sensor that detects the concentration of exhaust components in exhaust gas discharged from the engine;
a control device for opening and closing the control valve based on a signal generated by the exhaust sensor; an air-fuel ratio control for an engine, comprising a switching valve that opens a second passage means, opens the first passage means and closes the second passage means when the degree of warm-up is higher than a predetermined value; distantly related to the device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an engine equipped with a fuel supply device according to the present invention, and its intake system and exhaust system.

In the figure, 1 indicates the engine.

The engine 1 inhales a mixture of fuel and air through an air cleaner 2, a carburetor 3, and an intake manifold 4, and exhaust gas generated by combustion in a combustion chamber (not shown) is passed through an exhaust manifold 5, an exhaust pipe 6, three-way catalytic converter 7,
It is designed to be released into the atmosphere through an exhaust pipe 8.

FIG. 2 is a configuration diagram showing the main parts of the fuel supply device according to the present invention.

The carburetor 3 is configured as a twin-barrel carburetor and has a primary intake passage 10 and a secondary intake passage 30.

A large venturi 11.31 is provided in the middle of the primary intake passage 10 and the secondary intake passage 30, and a small venturi 12.3 is provided at the throat thereof.
2 is provided.

Primary intake passage 10 downstream from the large venturi
A primary throttle valve 13 and a secondary throttle valve 33 are provided in the secondary intake passage 30, and a choke valve 14 is provided in the primary fuel passage 10 upstream of the small venturi 15.

The primary throttle valve 13 is opened according to the amount of depression of the accelerator pedal, and the secondary throttle valve 33 is opened according to the amount of depression of the accelerator pedal.
is opened when the primary throttle valve 13 is opened by a predetermined amount and the amount of intake air exceeds the predetermined amount.

Main fuel nozzles 15.35 are opened in the throats of the small venturis 12 and 32, respectively, and fuel (gasoline) stored in a common float chamber 16 is fed to the main fuel nozzles 15.35 into the main fuel jet. 17.37
The two fuels are individually supplied to each other through the main fuel passages 18 and 38, with the flow rates being adjusted by the main fuel passages 18 and 38.

In the middle of the main fuel passage 18, there are wells 19 and 38, respectively.
39 is formed, and these wells 19, 39 are provided with air bleed tubes 20, 40.

Air bleed tubes 20.40 each have small holes 20', 4
0' and is connected at the end to a fixed air bleed jet 21.41.

The fuel flowing from the float chamber 16 through the main fuel passage 18.38 to the main fuel nozzle 15.35 flows through the well 19,
At 39, the air sucked into the wells 19, 39 from the main air bleed jet 21.41 through the small holes 20', 40' is mixed in, and the air is mixed in with the air from the tip of the main fuel nozzle into the small venturi 12.32. is discharged.

The flow rate of fuel discharged from the main fuel nozzle is well 1.
In 9.39, the larger the amount of air mixed in, that is, the amount of air bleed, the smaller the amount, and the larger the air-fuel ratio of the mixture of fuel and air becomes.

Also, in the carburetor 3, when the throttle valves 13, 33 (7) are located upstream of the throttle valves 13 and 33 (7) in the idle link position as shown in the figure, and the throttle valves are slightly opened, A slow fuel port 22.42 is provided that opens into the primary intake passage 10 and the secondary intake passage 30.

Furthermore, an idle port 23 is provided on the primary side, which always opens into the primary intake passage 10 at a location located downstream of the throttle valve 13.

slow port 22. A part of the fuel flowing through the main fuel passage 18.38 is provided in the idle port 23 and the slow port 42 through a slow fuel passage 24.44 formed by branching from the middle of these fuel passages. The flow rate is metered and supplied by a slow fuel jet 25.45.

Further, the slow fuel passage 24.44 is connected to a fixed air bleed jet 27.47 in the middle, and the fuel sucked into the slow fuel passage mixes with the air sucked from the air bleed jets 27, 47. slow port 2
2. The signal is sent to the idle port 23 and slow port 42.

The flow rate of fuel discharged from the idle port 23 is set by an idle adjustment screw 26.

The main fuel nozzle 15 is also connected at its root to one end of the air bleed passage 28.48.

This air bleed passage 28.48 is connected to the conduit 2 at the other end.
It is connected to one end of 9°49.

The conduits 29,49 each project out of the carburetor at the other end.

Conduit 29 is connected by conduit 50 to one connection port of three-pronged tube 51, and tube 49 is connected to conduit 52 and check valve 5.
3. It is connected to another connection port of the trifurcated tube 51 via a conduit 54.

Another connection port of the trifurcated pipe 51 is connected to the outlet 57 of the control valve 56 via the conduit 55b1, the switching valve 66, and the conduit 55a.

An additional air supply port 68 is formed in the intake manifold 4, and this additional air supply port 68 is connected to the conduit 55c.
1 switching valve 66, the outlet 57 of the control valve 56 via the conduit 55a
It is connected to the.

Control valve 56 is open to the atmosphere at its inlet port 58;
The effective opening area of a valve port provided in the interior of the valve port in the middle of a passage connecting the inlet 58 and the outlet 57 is quantitatively controlled by the valve element.

The control valve 56 may be constituted by a so-called electric air control valve (EACV), which is well known in itself and drives a valve element according to an amount of electricity, such as a linear motor type, a linear solenoid type, or a step motor type.

The switching valve 66 is sensitive to the engine cooling water temperature detected by the engine cooling water temperature sensor 67, and is set to a predetermined value, for example, 5.
When the temperature is below 0℃, connect ports a and C and
When the temperature is above °C, port a is connected to port b instead of port C.

The check valve 53 only allows fluid to flow from the conduit 54 toward the conduit 52, and the opening pressure of this check valve is set to a very small value substantially close to zero.

The carburetor 3 is also provided with an air bleed tube 59 that opens toward the slow port 22 at one end, and this air bleed tube 59 is connected to the outlet 62 of the control valve 61 through a conduit 60 at the other end. There is.

The control valve 61 is opened to the atmosphere at its end 63 and is constituted by an electric air control valve similar to the control valve 56 described above.

The exhaust manifold 5 is provided with an 02 sensor 64 (see FIG. 1).

The 02 sensor 64, as is well known in itself, detects excess oxygen in the exhaust gas and generates an electrical signal in accordance with the detection result.

This electrical signal is input to the control device 65.

The control device 65 outputs an electrical drive signal to the control valves 56 and 61 based on the electrical signal generated by the 02 sensor 64.

That is, the control device 65 generates a signal to increase the opening amount of each control valve when the 02 sensor 64 does not detect excess oxygen in the exhaust gas, and when the 0□ sensor 64 detects excess oxygen in the exhaust gas. When the control valve is open, a signal is generated to reduce the opening amount of each control valve.

In the carburetor 3, when the control valves 56 and 61 are closed and no additional air bleed is performed, the fuel flow rate in each fuel passage is predetermined so as to create an air-fuel mixture with an air-fuel ratio smaller than the stoichiometric air-fuel ratio. There is.

When the 02 sensor 64 is not detecting excess oxygen in the exhaust gas, the engine 1 is being supplied with an air-fuel mixture having an air-fuel ratio smaller than the stoichiometric air-fuel ratio, that is, a rich air-fuel mixture. 65 outputs an electric signal to the control valves 56 and 63 to increase the amount of valve opening, so the amount of opening of each control valve increases.

When the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is higher than the stoichiometric air-fuel ratio, there is no surplus oxygen in the exhaust gas, so at this time the 02 sensor 64 no longer detects the surplus oxygen in the exhaust gas. .

At this time, the control device 65 outputs an electric signal to the control valves 56, 63 to reduce the opening amount, so that the opening amount of each control valve decreases.

When the engine coolant temperature is below 50°C and the engine 1 has not been sufficiently warmed up, the switching valve 66 disconnects port a from port b in response to a signal generated by the engine coolant temperature sensor 67. is connected to.

Therefore, at this time, air is sucked into the intake manifold 4 from the additional air supply port 68 via the control valve 56, the conduit 55a1 switching valve 66, and the conduit 55 due to the intake pipe negative pressure within the intake manifold 4.

The flow rate of this air is determined by the differential pressure between the intake pipe negative pressure and atmospheric pressure and the effective opening area (diaphragm) of the control valve 56.

Air at a flow rate determined by the differential pressure and the degree of restriction of the control valve 56 is supplied to the intake manifold 4 from the additional air supply port 68.
During steady operation, the air-fuel ratio of the air-fuel mixture supplied to the engine 1 becomes approximately the stoichiometric air-fuel ratio.

The amount of additional air required to compensate for the air-fuel ratio is also larger than the amount of air bleed that compensates for the air-fuel ratio, but when the engine 1 is not sufficiently warmed up, so-called cold, fuel vaporization is poor and this Therefore, the base air-fuel ratio of the carburetor 3 becomes larger than after completion of warm-up, that is, the air-fuel ratio is close to the stoichiometric air-fuel ratio, and therefore the amount of additional air required for air-fuel ratio compensation is not very large. The control valve 56 may have a flow control width equivalent to that of a control valve used in conventional air bleed control.

When the throttle valve of the carburetor 3 is closed to decelerate the engine 1, the intake pipe negative pressure within the intake manifold 4 increases rapidly.

Therefore, a large amount of droplet fuel adhering to the wall surface of the intake passage such as the wall surface of the intake manifold 4 rapidly evaporates, and the air-fuel ratio of the air-fuel mixture supplied to the engine 1 tends to decrease.

However, at this time, the intake pipe negative pressure has become very large, so even if the effective opening area of the control valve 56 is not increased much, a relatively large amount of additional air is supplied due to the differential pressure between the intake pipe negative pressure and atmospheric pressure. The air is drawn into the intake manifold 4 through the port 68, and the air-fuel mixture to be supplied to the engine 1 is diluted.As a result, the engine 1 is supplied with a rich air-fuel mixture that exceeds the heatable range. This is avoided.

When the throttle valve of the carburetor 3 is opened to accelerate immediately after deceleration as described above, the negative pressure in the intake pipe decreases.

Therefore, the differential pressure between the atmospheric pressure and the intake pipe negative pressure becomes smaller than the deceleration, and as a result, even if the effective opening area of the control valve 56 increases, the additional air supply port 68
The flow rate of air sucked into the intake pipe negative pressure 4 decreases, and at this time, the flow rate of the air-fuel mixture from the carburetor 3 increases, so the ratio of the flow rate of the additional air to the flow rate of the air-fuel mixture becomes and the degree of dilution of the mixture by the additional air becomes smaller.

As a result, even if acceleration is performed immediately after deceleration, the engine 1
This prevents the air-fuel mixture supplied to the engine from becoming diluted, thereby preventing the engine from misfiring, and preventing deterioration of drivability and increase in the HCC bone concentration in the exhaust gas.

When the engine coolant temperature rises above 50°C and the engine 1 warms up, the control valve 66 is switched by the signal generated by the engine coolant temperature sensor 67.
will connect port a to port b instead of port C.

Therefore, at this time, the supply of additional air to the intake manifold 4 is stopped, and the air bleed system is started.

When the opening amount of the control valve 56 increases, the amount of air bleed increases accordingly, the air-fuel ratio of the mixture created by the carburetor 3 increases, and the air-fuel ratio of the mixture supplied to the engine 1 also increases. On the other hand, when the opening amount of the control valve 56 decreases, the amount of air bleed decreases accordingly, and the air-fuel ratio of the mixture created by the carburetor 3 decreases.
The air-fuel ratio of the air-fuel mixture supplied to the engine 1 also becomes smaller.

When the opening degree of the primary throttle valve 13 is relatively small and the secondary throttle valve 33 is closed, no air flows into the secondary intake passage 30.
An air-fuel mixture is not created in this intake passage, and air flows only through the primary intake passage 10, and the air-fuel mixture is supplied to the engine 1 only from this intake passage.

At this time, the inlet 5
From 8, outlet 57, conduit 55, trifurcated tube 51, conduit 50.2
9. By controlling the amount of air bleed through the air bleed passage 28 as described above, an air-fuel mixture having a substantially stoichiometric air-fuel ratio is created in the primary intake passage 10.

At this time, the negative pressure acting on the main fuel nozzle 15 is transmitted to the conduit 54 via the air bleed passage 28, the conduits 29, 50, and the trifurcated pipe 51, but due to the action of the check valve 53, air is transferred from the main fuel nozzle 35 to the main fuel nozzle 35. Air is not sucked toward the nozzle 15, and air bleed control is not disturbed.

When the primary throttle valve 13 is opened relatively wide and the secondary throttle valve 33 is opened in response, air flows into the secondary intake passage 30 in addition to the primary intake passage 10, and air is mixed from this intake passage as well. air is now supplied to engine 1.

At this time, the inlet 5
From 8, outlet 57, conduit 55, trifurcated tube 51, conduit 50, 2
9. The amount of air bleed of the primary fuel system through the air bleed passage 28 is controlled as described above, and at the same time, the flow is controlled from the inlet 58 to the outlet 57, the conduit 55, and the trifurcated pipe 51 according to changes in the opening amount of the control valve 56. , conduit 54, check valve 53,
The air bleed amount of the primary fuel system is controlled through the conduits 52, 49 and the air bleed passage 48, and the air-fuel ratio of the air-fuel mixture created in the secondary intake passage 30 also becomes approximately the stoichiometric air-fuel ratio.

At this time as well, the air-fuel ratio of the air-fuel mixture created in the primary intake passage 10 is approximately the stoichiometric air-fuel ratio, so the engine 1 is supplied with an air-fuel mixture having approximately the stoichiometric air-fuel ratio.

When the opening degree of the primary throttle valve 13 is reduced from the state in which the secondary throttle valve 33 is opened and the secondary throttle valve 33 is closed accordingly, air no longer flows into the secondary intake passage 30, and the air stops flowing into this intake passage. In this case, an air-fuel mixture is no longer produced, and the air-fuel mixture is supplied to the engine 1 only from the primary intake passage 10.

Since the air-fuel ratio of the air-fuel mixture in the primary intake passage 10 is always controlled to approximately the stoichiometric air-fuel ratio, including when the secondary throttle valve 33 is open, the air-fuel ratio of the air-fuel mixture in the primary intake passage 10 is always controlled to approximately the stoichiometric air-fuel ratio. The air-fuel mixture at the stoichiometric air-fuel ratio is now supplied.

Even if the throttle valve of the carburetor 3 is closed to decelerate the engine 1 and the intake pipe negative pressure increases rapidly, by this time the engine 1 has already warmed up, so some particles may adhere to the wall of the intake passage. Since the amount of droplet fuel is small, a rich air-fuel mixture that exceeds the flammable range is not supplied to the engine 1, and the opening degree of the control valve 56 does not increase significantly.

Therefore, at this time, even if acceleration is performed immediately after deceleration, the opening degree of the control valve 56 is not so large that a lean air-fuel mixture exceeding the flammable range is not supplied to the engine 1.

In the above embodiment, the air for air bleed for air-fuel ratio control was supplied to the base of the main fuel nozzle, but the present invention is not limited to this, and the air bleed jet 27 Similarly, the air for air bleed for air-fuel ratio control may be configured to be supplied to the inside of the air bleed tube 20.40. Effects equivalent to those obtained by using this method can be obtained.

Although the present invention has been described in detail with respect to specific embodiments above, it will be appreciated by those skilled in the art that the present invention is not limited to this and that various embodiments are possible within the scope of the present invention. It should be obvious.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an engine equipped with an air-fuel ratio control device according to the present invention and its intake system and exhaust system, and Fig. 2 shows an embodiment of the air-fuel ratio control device according to the present invention and its main parts. The constituent countries shown are: 1... Engine, 2... Air cleaner, 3... Carburetor, 4... Intake manifold, 5... Exhaust manifold, 6...・・・・・・
・Exhaust pipe, 7...Three-way catalytic converter, tail...
...Exhaust pipe, 10...Primary fuel passage,
11...Large venturi, 12...
Small venturi, 13...Primary throttle valve, 14...Choke valve, 15
...Main fuel nozzle, 16...Float chamber, 17...Main fuel jet, 18.
...Main fuel passage, 19...well,
20... Air bleed tube, 21...
... Air bleed jet, 22 ... Slow fuel port, 23 ... Idle port, 24 ...
... Slow fuel passage, 25 ... Slow jet, 26 ... Idle adjustment screw,
27... Air bleed jet, 28...
... Air bleed passage, 29 ... Conduit, 30.
...Secondary intake passage, 31◆...Large venturi, 32...Small venturi,
33...Secondary throttle valve, 35.
...Main fuel nozzle, 37...Main fuel nozzle, 38...Main fuel passage, 39.
...Well, 40...Air bleed tube, 41...Air bleed jet, 42.
... Slow fuel port, 44 ... Slow fuel passage, 45 ... Slow fuel jet, 47
...Air Bleed Jet, 48...
Air bleed passage, 49.50... Conduit, 51
... Trigeminal tube, 52 ... Conduit, 53 ...
...Check valve, 54, 55a, 55b, 55c = Conduit, 56... Control valve, 57... Outlet, 5
8... Inlet, 59... Air bleed tube, 60... Conduit, 1... Control valve, 62... Outlet, 63... ...Inlet, 4 ...02 sensor, 65 ... Control device, 66 ... Switching valve, 67 ... Engine coolant temperature sensor, 8...
...Additional air supply port.

Claims (1)

[Scope of utility model registration request] an air bleed passage provided in the carburetor, an additional air supply port for supplying additional air to the engine intake system, and an inlet opened to the atmosphere and an outlet connected to the air bleed passage through first and second passage means, respectively. a control valve connected to the additional air supply port; an exhaust sensor that detects the concentration of exhaust components in exhaust gas discharged from the engine; and a control device that opens and closes the control valve based on a signal generated by the exhaust sensor. , operates according to the warm-up dust of the engine, and when the warm-up dust is below a predetermined value, the first passage means is closed and the second passage means is opened when the warm-up dust is above a predetermined value, the first passage means is opened. An air-fuel ratio control device for an engine, comprising a switching valve that opens a passage means and closes the second passage means.