JPH01247752A - Air fuel ratio correction device for carburetter - Google Patents

Abstract

PURPOSE:To constitute the air fuel ratio correction device of a carburetter simply and also inexpensively, by forming an air pump chamber at the diaphragm chamber of a diaphragm type fuel pump, and connecting this air pump chamber to the down stream side of the throttle valve of the carburetter. CONSTITUTION:The inside of a diaphragm type fuel pump 3 supplying fuel to the float chamber 2 of a carburetter 1, is separated by means of a diaphragm 4 into a fuel pump chamber 5 and an air pump chamber 6. In this case, a valve mechanism 9 which intakes the outer air and an air exit 10 which sends out the air intaken, are provided at the air pump chamber 6. And the air exit 10 communicates with the down stream side of a throttle valve 11 at the inside of the carburetter 1 through a correction air flow passage 12. As a result, the correction of an air fuel ratio is conducted by supplying the outer air intaken and pressurized in the air pump chamber 6 to an overly mixed gas generated at the time of the carburetter 1 being at a high temperature. Accordingly, an air fuel ratio correction device is constituted simply and also inexpensively.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an air-fuel ratio correction device for a carburetor in which fuel is supplied to a float chamber by a diaphragm fuel pump.

Conventional technology When a vehicle equipped with a gasoline engine continues to drive at low speeds in the summer, the temperature rise in the engine compartment warms the fuel in the carburetor, which may eventually overflow into the venturi and enrich the mixture. .

The resulting overly rich mixture can cause problems such as the engine stalling, poor idling, and difficulty in starting, so a bimetallic air-fuel ratio correction device that detects the rise in carburetor temperature and operates is installed. It is being This air-fuel ratio correction device will be explained based on FIG. 5 and FIG. 6.
The valve 25 opens and closes by the action of the bimetal 24.
It communicates with the correction air flow path 12' via. This correction air flow path 12' forms an air bypass flow path leading from the upstream side of the venturi section 22 to the downstream side of the throttle valve 11, and when the pulp 25 is opened when the temperature of the vaporizer 1' has increased, a part of the air 20 is directly supplied. It is configured to flow downstream of the throttle valve 1.1 to dilute the overly rich air-fuel mixture 21 and always correct the air-fuel ratio to an appropriate level.

By the way, a diaphragm fuel pump is used as one of the means for supplying fuel to the float chamber 2 of the carburetor 1'.This will be explained based on FIG. The fuel 19 is transferred to the inlet dome 1 by the vertical reciprocating movement of the diaphragm 4 driven by the engine.
7 and pressurized in the fuel pump chamber 5 to the outlet dome 1.
8 to the float chamber 2.

Problems to be Solved by the Invention According to the bimetal type air-fuel ratio correction device described above, the time when the bimetal reaches the set temperature (normally 50) The relationship between the carburetor temperature and the correction air flow rate is as shown in FIG. As the carburetor temperature rises, the correction air flow rate is increased from the beginning of the valve opening until it is fully opened, and after it is fully opened, it remains almost constant. This was inconvenient because it may not be possible to obtain enough correction air to dilute the air-fuel ratio.Moreover, it is expensive to incorporate a bimetallic air correction device into a carburetor that is small but has a complex and precise internal structure. It was also disadvantageous.

Therefore, the present invention focuses on a diaphragm fuel pump that is installed near the carburetor of the engine body and supplies fuel to the float chamber, and provides a carburetor air-fuel ratio correction device that effectively utilizes the diaphragm fuel pump. It is.

Means for Solving the Problems The present invention solves the above-mentioned problems, and provides a carburetor in which fuel is supplied to a float chamber using a diaphragm fuel pump, in which outside air is supplied to the diaphragm chamber of the diaphragm fuel pump. The air pump chamber is provided with an air outlet and a valve mechanism for sucking in air, and a correction air flow path that communicates the air outlet with the downstream side of the throttle valve of the carburetor. An air-fuel ratio correcting device for a carburetor, characterized in that the air-fuel ratio is corrected by supplying pressurized outside air sucked in the air pump chamber to the rich mixture.

According to the means described above, a valve mechanism for atmospheric suction and an air outlet are additionally provided in the diaphragm chamber of a diaphragm fuel pump conventionally used to supply fuel to the float chamber of a carburetor. The air-fuel ratio correction air is supplied by providing an air pump chamber and a correction air flow path that communicates this air pump chamber with the downstream side of the throttle valve of the carburetor, so it can be incorporated into the carburetor, which has a small but complex and precise internal structure. The bimetallic air-fuel ratio correction device that was previously used is no longer necessary. Moreover, diaphragm fuel pumps adjust the stroke of the diaphragm (amplitude of reciprocating motion) according to the load as a fuel pump.
The stroke is small when the engine is idling, and the stroke is large when the engine is running or when the fuel becomes hot and vaporizes in the fuel pump chamber. For this reason, when the carburetor becomes hot and the amount of fuel overflowing into the venturi increases, the temperature of the diaphragm fuel pump, which is installed near the carburetor in the engine body and is in almost the same environment, also rises, causing the diaphragm stroke to increase. becomes larger, the supply amount of air-fuel ratio correction air increases, it dilutes the rich mixer flowing from the venturi section, and the air-fuel mixture corrected to an appropriate air-fuel ratio can be sent to the engine combustion chamber.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 to 4. A diaphragm fuel pump 3 that supplies fuel to a float chamber 2 of a carburetor 1 has a pump body connected to a fuel pump chamber by a diaphragm 4. 5 and an air pump chamber 6. This diaphragm 4 is linked to an engine (not shown) via a rocker arm 7 and a diaphragm shaft 8, and performs vertical reciprocating motion like a piston to suck and discharge fuel from the fuel pump chamber 5. .

And the air pump chamber 6 of the diaphragm fuel pump 3
is provided with a valve mechanism 9 for sucking in outside air and an air outlet 10 for sending out the sucked air.
A correction air flow path 12 communicates with the downstream side of the throttle valve 11 inside. Furthermore, to describe the structure of the valve mechanism 9 in detail, as shown in FIGS. 2 and 3, the air element 1 is inserted into the opening provided in the casing 13 of the air pump chamber 6 from the outside.
4 is inserted, and a valve rubber sheet 16 with one end fixed with a clamp pin 15 is swingably attached to the inside of the casing 13. In addition, 17 is an inlet dome of the fuel pump chamber, 18 is an outlet dome, 19 is an arrow indicating the flow of fuel, and 2
0 is an arrow indicating the flow of air, 20a is an arrow indicating the flow of correction air, 21 is an arrow indicating the flow of air-fuel mixture, and 22 is a venturi section.

According to the above-described air-fuel ratio correction device for a carburetor, the fuel 19 is sucked into the fuel pump chamber 5 from the inlet dome 17 by the reciprocating movement of the diaphragm 4 in the vertical direction, and the fuel 19 is sucked into the fuel pump chamber 5 from the inlet dome 17 and transferred to the outlet dome 18.
At the same time, the diaphragm 4, which moves downward when discharging fuel, flows into the air pump chamber 6.
Negative pressure is generated in the valve, and the valve rubber seat 16 opens to suck in atmospheric air. The air sucked into the air pump chamber 6 is compressed by the diaphragm 4 that moves upward and sucks in fuel, and when the valve rubber sheet 16 closes, it is discharged from the air outlet 10 as correction air 20a, and the correction air flow path 12 is discharged as correction air 20a. It flows out downstream of the venturi section 22 through the venturi section 22. Then, from the air cleaner (not shown) to the throttle valve 1
The air 20 sucked in according to the opening degree of the venturi part 11
is mixed with the fuel 19 at the throttle valve 11.
On the downstream side, the correction air 20a joins and is mixed, and the air-fuel mixture 21 whose air-fuel ratio is corrected by the correction air 20a is sent to the engine combustion chamber.

By the way, the diaphragm fuel pump 3 has a characteristic of changing the stroke (amplitude of reciprocating motion) of the diaphragm 4 depending on the load as a fuel pump, and the stroke is small when idling, and large when the pump is running. Further, even when the fuel reaches a high temperature and vaporizes in the fuel pump chamber 5, the stroke of the diaphragm 4 increases.

In accordance with such stroke changes of the diaphragm 4, the amount of correction air 20a discharged from the air pump chamber 6 also increases or decreases, and this amount of correction air is shown in FIG. 4 as a relationship with the diaphragm fuel pump temperature. As shown, the temperature increases as the temperature of the diaphragm fuel pump 3 increases and the stroke of the diaphragm 4 increases. Moreover, the diaphragm fuel pump 3 uses the engine's suction and
Since it uses a camshaft for the exhaust valve, its mounting position is limited, and it is mounted on the engine close to the carburetor l. For this reason, the diaphragm fuel pump 3
and the carburetor L are in almost the same temperature environment, and when the fuel inside the carburetor is warmed by the temperature rise of the carburetor L, expands in volume, and overflows into the venturi section 22, the temperature of the diaphragm fuel pump 3 also rises. As a result, the amount of correction air discharged downstream of the throttle valve 11 increases, and the mixture that has become overly rich due to overflowing fuel is diluted and corrected to a mixture with a suitable air-fuel ratio. In this way, the amount of fuel overflowing into the venturi section 22 increases as the temperature of the carburetor 1 increases, so the air pump characteristic of the diaphragm fuel pump 3, in which the amount of correction air increases when the temperature is high, is advantageous for the air-fuel ratio correction device. be. Further, depending on the characteristics of the air pump, it goes without saying that correction air flow rate control means such as an orifice may be provided in the correction air flow path 12.

Effects of the Invention According to the present invention described above, the diaphragm chamber of a conventionally used diaphragm fuel pump is used to form an air pump for supplying air-fuel ratio correction air, and a correction air flow path is formed from the air pump. This is a carburetor air-fuel ratio correction device configured to supply correction air through the carburetor air-fuel ratio correction device, which has a simple structure and is advantageous in terms of cost. Moreover, diaphragm fuel pumps have the characteristic of increasing the stroke of the diaphragm at high temperatures, and this characteristic increases the correction air supply amount at high temperatures and corrects the air-fuel ratio of rich mixtures. Its use in air-fuel ratio correction devices is optimal.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing one embodiment of the present invention, and Fig. 2 is a system diagram showing an embodiment of the present invention.
Fig. 3 is a detailed view showing the part ■ in the figure, Fig. 3 is a view taken along the I-[ [ line of Fig. 2, Fig. 4 shows the characteristics of the air pump in the present invention, and shows the temperature and Figure 5 is a system diagram showing the conventional bimetal type air-fuel ratio correction device, and Figure 6 shows the relationship between the carburetor temperature and the correction air flow rate in the bimetal type air-fuel ratio correction device shown in Figure 5. FIG. 7 is a partial sectional view showing a conventional diaphragm fuel pump. 1. Carburetor, 2. Float chamber, 3. Diaphragm fuel pump, 4. Diaphragm, 5. Fuel pump chamber, 6. Air pump chamber, 7. Rocker arm, 8.
・Diaphragm shaft, 9. Valve mechanism, 10. Air outlet, 11. Throttle valve, 12. Correction air flow path, 13. Casing, 14. Air element, 1
5... Crank pin, 16... Valve rubber seat, 17
・・Entrance dome, 18・・Exit dome, 19・・Fuel,
20... Air, 20a... Correction air, 21... Air mixture,
22...Venturi section. Figure 2 Figure 3 Figure 4 Figure 5 Figure 5

Claims (1)

[Claims] In a carburetor in which fuel is supplied to a float chamber using a diaphragm fuel pump, an air pump chamber is formed by providing an air outlet and a valve mechanism for sucking outside air into the diaphragm chamber of the diaphragm fuel pump; It is equipped with a correction air flow path that communicates the air outlet with the downstream side of the throttle valve of the carburetor, and supplies pressurized outside air by sucking in the air pump chamber to the superrich mixture generated when the carburetor is at high temperature. An air-fuel ratio correction device for a carburetor, characterized in that it is configured to correct an air-fuel ratio.