JPS5854256B2 - Air-fuel ratio control device for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for purifying the exhaust gas of an internal combustion engine having a carburetor by setting the air-fuel ratio set in the carburetor to a desired lean value depending on the operating conditions of the engine. It is.

Traditionally, the main air bleed method (a method in which atmospheric air is introduced into the main nozzle of the carburetor via the atmospheric air intake valve) and air There was a bypass method (a method in which atmospheric air is introduced into a bypass air inlet provided on the throttle bore wall of the carburetor through an air intake valve), a multi-stage power one-way type, and a parallel power one-way type.

However, these methods have problems with the degree of freedom in setting the air-fuel ratio, the characteristics and reliability of the air-fuel ratios that can be set, and in particular, the main air bleed method is not effective in making the air-fuel ratio lean when the intake pipe negative pressure is large. On the other hand, the air bypass method has little effect on making the air-fuel ratio lean when the intake pipe negative pressure is small, so both of these methods have the disadvantage of not being able to properly compensate for the entire negative pressure range in which they are used. Ta.

The main purpose of this invention is to utilize the conflicting characteristics of the main air bleed system and the air bypass system mentioned above, and to balance the effects of both systems to lean the air-fuel ratio. An object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that can supply an air-fuel mixture having an air-fuel ratio leaner than the air-fuel ratio based on the settings of a carburetor, regardless of the negative pressure in an air pipe.

Next, the present invention will be explained with reference to drawings showing embodiments.

In FIG. 1 showing the first embodiment, 1 is a carburetor, 2 is a throttle valve, 3 is a venturi, 4 is a main nozzle,
5 indicates a main jet, and 6 indicates a float chamber.

Reference numeral 1 designates an atmospheric air introduction valve 7, which is connected to an atmospheric pressure chamber 7d in the center and negative pressure chambers 7e, ? f
It is divided into.

Negative pressure chambers 7e and 7f have springs 7g and 7h, respectively.
is built-in.

An air exhaust pipe 71 having an opening facing the diaphragms 7b and 7c is provided in the atmospheric pressure chamber 7d (ζ), and two air exhaust lowers j and 7k are provided facing each other on the pipe wall.

A partition wall 71 is provided inside the air exhaust pipe 71 and faces the air exhaust lowers j and 7k.

There are gaps S1. between each end of the air exhaust pipe 71 and the diaphragms 7b, 7c. S2 is provided, and this gap S1
°S2 is opened and closed in an on/off manner by diaphragms 7b and 7c.

The negative pressure chamber 7e is connected to the venturi 3 of the carburetor 1 by the negative pressure passage 8.
The negative pressure chamber 7f communicates with an intake pipe negative pressure port 11 downstream of the throttle valve 2 through a negative pressure passage 10.

The lower air discharge pipe 71 communicates with the main nozzle 4 of the carburetor 1 through an air bleed passage 12, and the air bleed passage 12 is provided with a metering orifice 12a.

The air exhaust lower j is communicated with a bypass air inlet 14 provided in the throttle bore wall upstream of the throttle valve 2 through an air bypass passage 13, and a metering orifice 15 is provided in the bypass air inlet 14.

The atmospheric pressure chamber 7d also communicates with an atmospheric air inlet 17 provided in the wall of the air horn section upstream of the venturi 3 through an atmospheric passage 16.

In the above configuration, when the engine speed is constant and the opening degree of the throttle valve 2 is small, that is, when the negative pressure at the intake pipe negative pressure port 11 is larger than the value set by the diaphragm 7c and the spring 7h of the atmosphere introduction valve 7, The diaphragm γC of the air introduction valve 7 is pulled down against the spring force of the spring 7h, and since the negative pressure in the negative pressure passage 8 is in a low state, the diaphragm γb is pushed down by the spring force of the spring 7g.

As a result, a gap S2 is formed between the lower end of the air exhaust pipe 71 (in FIG. 1) and the diaphragm 7c, and the upper end of the air exhaust pipe 71 is closed by the diaphragm 7b.

Also, by sequentially opening the throttle valve 2 while keeping the engine speed constant, the airflow flowing through the venturi section 3 causes the negative pressure port 9 to be higher than the value set by the diaphragm 7b and spring 7g of the air inlet valve 7. When negative pressure is generated, the diaphragm 7b of the air inlet valve 7 is pulled upward, creating a gap S between the diaphragm 7b and the upper end of the air exhaust pipe 71.

is formed.

When the opening degree of the throttle valve 2 further increases and the negative pressure at the intake pipe negative pressure port 11 becomes smaller than the value set by the diaphragm 7c and the spring 7h, the atmosphere inlet valve 7
The diaphragm 7c is pushed up by the spring 7h, and the gap S2 between the diaphragm 7c and the air exhaust pipe 71 is closed.

Therefore, unless the intake pipe negative pressure is smaller than the set value and the negative pressure of the venturi section 3 is also smaller than the set value, at least one of the gaps S1 and S2 of the atmosphere introduction valve 7 is formed. The atmospheric air introduced into the atmospheric pressure chamber 7d is discharged from the main nozzle 4 through the air bleed passage 12 to make the air-fuel ratio lean.

Further, at a throttle opening such that the bypass air inlet 14 is located downstream of the edge of the throttle valve 2, the atmosphere is drawn in from the bypass air inlet 14 through the air bypass passage 13 and has an air-fuel ratio. do.

Next, FIGS. 2 to 4 will be explained based on actual driving.

Figure 2 shows the relationship between the intake pipe negative pressure and the air-fuel ratio when the vehicle is running at high speed, that is, when the throttle valve opening is relatively large and the vehicle is moving slowly downhill. Line A shows the relationship between the air-fuel ratio due to air bypass. The effect of making the air-fuel ratio leaner increases as the throttle valve opening gradually decreases.

The M line shows the characteristics of the air-fuel ratio due to air bleed, and as the throttle valve opening gradually becomes smaller, the effect of making the air-fuel ratio leaner becomes smaller.

The B line shows the carburetor setting base air-fuel ratio, and the R line shows the A line and M line.
Shows the sum of the lines.

In FIG. 2, the R line is parallel to the B line, but the R line can be inclined at a desired angle with respect to the B line by setting the metering orifice 12a or 15.

That is, the composite air-fuel ratio characteristic of the air-fuel ratio characteristic due to air bleed and the air-fuel ratio characteristic due to air bypass can be set to a desired value with respect to fluctuations in the intake pipe negative pressure.

In addition, in the case of uphill driving, the effect of making the air-fuel ratio leaner due to the air bypass and the effect of making the air-fuel ratio leaner due to the air bleed are opposite to the above, but the characteristic of the arrowed R line is obtained.

Next, Figure 3 shows the relationship between engine speed and air-fuel ratio when slow acceleration is being performed under a light load condition. As the amount of cover on the valve 2 increases, the effect of making the air-fuel ratio leaner due to the air bypass gradually increases.At engine speeds or higher, the proportion of the intake air-fuel mixture increases compared to the amount of air bypass introduced, so the effect of making the air-fuel ratio leaner. becomes smaller.

(Line A in Figure 3) On the other hand, the air-fuel ratio lean effect due to air bleed is small while the engine speed is low and the main system fuel discharge amount is small, and increases as the engine speed increases and the main system fuel discharge amount increases. .

(Line M in Figure 3) The sum of the air-fuel ratio characteristics in air bleed and air bypass is always leaner at an almost constant rate than the carburetor setting air-fuel ratio (line B), as shown in line R in Figure 3. be able to.

Next, Figure 4 shows the relationship between the engine speed and the air-fuel ratio when the vehicle is slowly accelerating from a high load state. On the other hand, the air-fuel ratio lean effect of air bleed increases linearly as the engine speed increases, as shown by the M line.

The sum of both air-fuel ratio lean effects is substantially parallel to the carburetor set air-fuel ratio (line B), as shown by line R, and results in a leaner state.

In this case, as in the case of Fig. 2, by appropriately setting the size of the metering orifice 12a or 15, the synthetic air-fuel ratio %tt (shape and slope of the R line) due to air bleed and air bypass can be adjusted to the desired value. can be set in the state.

In the above embodiment, if the horizontal axis is the engine speed and the vertical axis is the engine shaft torque, the air-fuel ratio range to be set is as shown in FIG.

In the figure, the A curve is at maximum load, and the mouth curve is at load load.
The C curve shows the engine +11E when the intake pipe negative pressure is set, and the second curve shows the engine +11E when the venturi negative pressure is set.

Also, the area surrounded by the two curved lines in the figure is the atmosphere inlet valve 7.
Both diaphragms 7b and 7c are connected to the air exhaust pipe 11.
This applies when the pipe end is open.

FIG. 6 shows a second embodiment of the present invention, in which the diaphragm-type atmosphere introduction valve 7 operated by intake pipe negative pressure and venturi negative pressure in FIG. 1 is replaced with vehicle speed, engine speed, engine load, transmission switch, water temperature, , shows an electromagnetic atmosphere introduction valve 30 that is activated by switching a switch depending on the oil temperature or the like.

The counter valve 30 has a cylindrical plunger chamber 30a and a cylindrical atmospheric pressure chamber 30b located below the plunger chamber 30a, aligned with and connected thereto, and wider than the plunger chamber 30a.

Inside the plunger chamber 30a, a plunger 30c that is slidable on the wall of the plunger chamber and a push spring 30d that pushes the plunger downward are housed.

A valve 30e is attached to the lower end of the plunger 30G and moves up and down within the atmospheric pressure chamber 30b.

An air exhaust pipe 30f having an opening facing the valve 30e is provided on the bottom surface 301 of the atmospheric pressure chamber 30b, and a partition wall 30g is provided at the center of the air exhaust pipe 30f. air outlet 30h, 30i
is formed.

There is a gap S between the upper end of the air exhaust pipe 30f and the valve 30e.

This gap S is opened and closed in an on/off manner by a valve 30e.

The air outlet 30i communicates with the bypass air inlet 14 through a bypass air passage 31, and the air outlet 30h communicates with the main nozzle 4 of the carburetor 1 through an air bleed passage 32.

32a is a metering orifice provided in the air bleed passage.

The atmospheric pressure chamber 30b is communicated with the atmospheric air inlet 17 through an atmospheric passage 33.

34 is an excitation coil, and 35 is a changeover switch.

As described above, this air intake valve 30 is switched by the changeover switch 35 when the vehicle speed, engine speed, etc. reach a predetermined value.

For example, in the case of switching based on vehicle speed, when the vehicle speed is below a predetermined value, the excitation coil is not excited, so the plunger 30C is pushed down by the push spring 30d, closing the gap S, so that the air from the atmospheric air intake port 17 is used as bypass air. It does not flow into the passage 31 and the air bleed passage 32.

When the vehicle speed reaches a predetermined value, the changeover switch 35 is switched automatically or manually, so the plunger 30c moves upward due to excitation, and a part of the air sucked into the carburetor 1 is transferred from the bypass air passage 31 and the bleed air passage. It enters the carburetor 1 and the air-fuel ratio becomes lean.

As described above, the present invention has an atmospheric pressure chamber for sucking in atmospheric air and two air exhaust ports for discharging the atmospheric air sucked into the atmospheric pressure chamber, and these air exhaust ports are connected to an internal combustion engine with a vaporizer. An atmospheric air intake valve that has the function of opening and closing simultaneously depending on engine operating conditions is attached to the internal combustion engine, and the atmospheric pressure chamber is communicated with the atmosphere through an atmospheric air intake port provided, for example, on the air horn wall of the carburetor or on the clean side of the air cleaner. , one air outlet is connected to the main nozzle of the carburetor, and the other air outlet is connected to a bypass port provided in the throttle bore wall directly above the throttle valve in the idle position of the carburetor. By combining the different air-fuel ratio lean effects of bleed and air bypass, the desired operating range (here, the desired operating range that is leaner than the carburetor setting base air-fuel ratio regardless of engine speed and intake pipe negative pressure) is achieved. This has the effect of obtaining a mixture having specific characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of an embodiment of the present invention. Figure 2 is a diagram showing the relationship between the intake pipe negative pressure and the air-fuel ratio when the vehicle is running at high speed, that is, when the throttle valve opening is relatively large and the vehicle is slowly descending. FIG. 4 is a diagram showing the relationship between engine speed and air-fuel ratio obtained by the device of the present invention when slow acceleration is performed under a light load condition.
The figure shows the relationship between the engine speed and the air-fuel ratio when the vehicle accelerates slowly from a high load state, and the figure shows the relationship between the engine speed, the shaft torque, and the air-fuel ratio when using the device according to the invention. It is a figure showing a relationship. FIG. 6 is an explanatory diagram of another embodiment of the present invention. 1... Carburizer, 4... Main nozzle,
7, 30...Atmospheric introduction valve, 7d, 30b...
...Atmospheric pressure chamber, 7j, 7, 30b, 30i...
...Air discharge port, 12.32...Air bleed passage, 13,31...Air bypass passage, 14...Bypass air introduction hole, 17...・・・
・Atmospheric intake port.

Claims (1)

[Claims] 1. An internal combustion engine with a carburetor has an atmospheric pressure chamber for sucking in atmospheric air and two air outlets for discharging the air sucked into this atmospheric pressure chamber, and these air outlets are used for internal combustion. An air inlet valve having a function of opening and closing simultaneously depending on the operating conditions of the engine is installed, one of the air outlet ports of this air inlet valve is communicated with the main nozzle of the carburetor, and the other air outlet port is placed in the idle position of the carburetor. An air-fuel ratio control device for an internal combustion engine, characterized in that the air-fuel ratio control device communicates with a bypass air inlet provided in a throttle bore wall directly above a certain throttle valve.