JPH0733812B2 - Vaporizer - Google Patents

Description

Description: TECHNICAL FIELD The present invention mainly relates to a carburetor for supplying a fuel / air mixture to an automobile engine.

(Prior art and its problems) As is well known, a carburetor has a main system, a low speed system, an acceleration system, etc. as a fuel system to be supplied to an intake system, but an engine mainly supplied with fuel from the main system. During steady operation, the fuel flow rate tolerance has been limited to an extremely narrow range from the viewpoint of exhaust gas regulation.

As a countermeasure against this, there is a system in which the main jet in the main system is made variable by an adjusting needle so that the combustion flow rate can be adjusted, but the adjustment sensitivity is excessively sensitive, which makes adjustment rather difficult. Alternatively, there is a system in which the main air bleed in the main system is made variable by an adjusting needle so that the bleed air flow rate can be adjusted, but no effect can be expected in the region where the engine intake air amount is small.

Further, it has been proposed to introduce air from the upstream side into a large venturi in a multiple venturi carburetor and adjust the amount of the air by the engine suction negative pressure to control the negative pressure of the main nozzle to increase or decrease the fuel flow rate. (JP-A-55-51932), the fuel flow rate control is uniform because it depends only on the suction negative pressure. On the other hand, it is a well-known fact that the air-fuel ratio temporarily becomes considerably thin when the fuel supply is switched from the low-speed system to the main system, and it is necessary to eliminate such temporary fluctuations in the air-fuel ratio. In addition, in the case of a carburetor that has characteristics such that the air-fuel ratio becomes thin on the low speed side and rich on the high speed side in response to engine requirements, the air-fuel ratio changes from the viewpoints of engine stability, fuel economy, and exhaust gas regulation. Is preferably as small as possible.

Heretofore, there has been no vaporizer having a function that satisfies all of the above requirements.

(Object of the Invention) In addition to adjusting the flow rate of the main fuel, an object of the present invention is to improve the connection between the low-speed fuel and the main fuel and to improve the air-fuel ratio change characteristic according to the engine operating state with a single mechanism. It is to provide a vaporizer capable of performing.

(Constitution of the Invention) In order to achieve the above object, the present invention is a carburetor having a multi-venturi in an intake passage and a main fuel nozzle opening to a small venturi. Two air passages are provided, and the respective outlets of the air passages are opened in the narrowest part of the large venturi in a centrally symmetric position, and one of the air passages is provided with an adjusting mechanism for controlling the effective passage area. This adjusting mechanism is composed of a valve body that opens and closes the air passage and an actuator that drives the valve body at a duty ratio according to the operating state of the engine.

(Embodiment) An embodiment of the present invention will be described with reference to the drawings. A double venturi consisting of a small venturi 3 and a large venturi 4 and a throttle valve 5 are installed in an intake passage 2 of a carburetor main body 1, and the main fuel The nozzle 6 opens into the small venturi 3. In the carburetor main body 1, two air passages 8 and 11 are formed in the carburetor main body 1 in which the outlets 7 and 10 of small diameter are opened at the center symmetrical position in the narrowest portion 4a of the large venturi 4, and the inlets 9 and 12 of these are formed in the intake passage 2. The venturi is opened upstream of the venturi where it is not affected by the negative pressure of the small venturi 3 and the large venturi 4.

An adjusting mechanism 16 operated by an electric signal is provided in one air passage 11.
An electric signal sent from, for example, an electronic control unit, which is composed of a valve body 17 for opening and closing the valve, and an actuator 18 composed of an electromagnet having a movable core having the valve body 17 at its tip and an electromagnetic coil and attached to the carburetor main body 1. The valve body 17 reciprocates with the valve body 17, and the valve body 17 opens and closes the air passage 11 at a duty ratio according to the operating state of the engine to control the amount of air from the outlet 10.

Here, it is known that the air flowing through the large venturi 4 causes a separation phenomenon from the wall surface at the portion where the downstream cross section gradually expands when passing through the narrowest portion 4a.

According to the present embodiment, the negative pressure generated when the air taken into the engine passes through the large venturi 4 causes the two outlets 7 and 10 to be discharged.
The air is sucked out of the narrowest part 4a.
Flows along the downstream side wall surface of the, and acts to eliminate the separation phenomenon by thinning the boundary layer generated in this part. Therefore, it is clear that the negative pressure acting on the main nozzle 6 of the small venturi 3 is different when air is sucked out from both the two outlets 7 and 10 and when neither is sucked out.

In this embodiment, when the outlet 10 on the right side in the drawing is closed and air is sucked out only from the outlet 7 on the left side, the boundary layer formed on the downstream side of the narrowest portion 4a by the intake air flow of the intake passage 2 is thin on the left side. The right side is thick, and the negative pressure acting on the main nozzle 6 is different even when air is sucked out from both of the two outlets 7 and 10 and when air is not sucked out from either of them. From this state, open the air passage 11 on the right side and exit 10
When air is sucked out of the nozzle, the boundary layer on the right side becomes thin according to the sucked amount, and the negative pressure acting on the main nozzle 6 changes.

That is, air corresponding to the Venturi negative pressure is constantly sucked out from the left outlet 7 to thin the boundary layer on the left side, and even if the air passage 11 on the right side is closed, fuel is discharged from the main nozzle 6 in the low engine speed region. It creates a state where it is easily sucked out. By controlling the amount of air sucked from the outlet 10 on the right side according to the engine operating state and controlling the boundary layer on the right side, the negative pressure acting on the main nozzle 6 is increased to increase the fuel flow rate, or It is possible to control so that the pressure is lowered to reduce the fuel flow rate, so that the low speed fuel and the main fuel can be smoothly connected, and the air-fuel ratio control according to the engine operating condition can be appropriately performed. Both will be possible.

It is needless to say that the present invention is also applied to a triple venturi vaporizer.

(Effects of the Invention) According to the present invention, air is sucked out from the respective outlets of the two air passages opened at the central symmetrical position of the narrowest part of the large venturi, and the boundary layer generated on the downstream side of the narrowest part is controlled. By eliminating the separation phenomenon, the negative pressure acting on the main nozzle is increased and the flow rate of the main fuel is adjusted.Therefore, the diameter can be adjusted by appropriately selecting the diameters of the two outlets and the opening / closing duty ratio of the valve body. Sensitivity can be arbitrarily selected, main fuel flow rate tolerance can be limited to an extremely narrow range, connection between low-speed fuel and main fuel can be improved, and air-fuel ratio characteristics can be improved according to engine operating conditions with a single mechanism. It is done in.

[Brief description of drawings]

The drawings are vertical sectional views of an embodiment of the present invention. 2 ... Intake passage, 3 ... Small venturi, 4 ... Large venturi, 6
...... Main nozzle, 7,10 …… Outlet, 8,11 …… Air passage, 9,12…
… Inlet, 16 …… Adjustment mechanism, 17 …… Valve disc, 18 …… Actuator,

Claims (1)

[Claims] 1. A carburetor having a multi-venturi in an intake passage and a main fuel nozzle opening to a small venturi, and two air passages having an inlet on the upstream side of a large venturi are provided. Each of the outlets is opened in the narrowest part of the large venturi at a centrally symmetrical position, and an adjusting mechanism for controlling the effective passage area is provided in one of the air passages, and the adjusting mechanism controls the air passage. A carburetor comprising a valve body that opens and closes and an actuator that drives the valve body at a duty ratio according to an operating state of an engine.