JPS5911739B2 - internal combustion engine carburetor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a carburetor for an internal combustion engine, and includes a fuel main jet that opens into an intake passage of the carburetor upstream of a main throttle valve operated by an operator, and a main throttle valve that is operated by an operator. an auxiliary starting device having an auxiliary pipe opening into the region of the intake passage downstream of the engine and supplied with air and fuel, said auxiliary pipe being progressively closed as the temperature of the engine increases; and a first flow restriction valve actuated by a temperature responsive device.

This relates to a carburetor for an internal combustion engine.

This type of carburetor is well known, but in this type of carburetor, when the engine load increases, the concentration of the air/fuel mixture supplied to the engine by the carburetor decreases. As a result, when the engine is at full load at very low temperatures, it is not possible to provide the engine with a sufficiently rich mixture compared to normal operation.

Furthermore, if the engine is configured to provide a sufficiently rich air-fuel mixture, exhaust gases that pollute the environment will be emitted if the engine is not at a low temperature.

In a conventional carburetor, when the main throttle valve of the carburetor is opened after starting the engine at an extremely low temperature, the negative pressure acting on the auxiliary pipe is reduced, and the rich air/fuel mixture supplied by the auxiliary pipe is rapidly released. was reduced.

Therefore, there was a risk that the air/fuel mixture supplied to the engine would become too lean and the engine would stall.

According to this invention, the auxiliary starting device includes a second flow restriction valve located upstream of the first flow restriction valve in the auxiliary pipe, and the second flow restriction valve is configured to pass through the auxiliary pipe. automatically and progressively opens when the flow rate of air increases and is drawn into the auxiliary pipe from the fuel source as a result of the vacuum in the chamber defined by the first and second flow restriction valves in the auxiliary pipe. The fuel metering device is adapted to meter the flow rate of fuel.

The first flow restriction valve, in a preferred embodiment, is a pneumatic control device that is sensitive to negative pressure at a location in the intake passage that passes from downstream to upstream of the main throttle valve when the main throttle valve is opened from an idle operating position. (e.g. a pneumatic capsule), the movement of said first flow restriction valve towards its closed position under the action of said pneumatic control device is limited by abutment means sensitive to the temperature of the engine; The minimum opening position that can be provided by the device to the first flow restriction valve is such that it corresponds to a flow cross-section that decreases as the temperature of the engine approaches normal operating temperature.

The abutment means is configured to adjust the maximum opening position (
The range of movement between the position occupied when the engine is at rest) and the minimum opening position decreases as the engine temperature increases and increases substantially when the engine temperature reaches normal operating temperature. It can be designed to be constructed and arranged to be zero.

In other words, the abutment means are adapted to securely hold the first flow restriction valve in position once the engine has reached normal operating temperature.

Note that this predetermined position will generally be a completely closed position.

The invention will be better understood from the following description of a downward suction vaporizer with auxiliary starting device, which is an embodiment of the invention, without being limited to the practical case thereof.

The description is made with reference to the drawings.

The carburetor has an intake passage 1 in which a main jet 3 opens into a venturi arranged upstream of a main throttle valve 2, exemplified as a butterfly valve operated by the driver.

Main jet 3 has a float chamber (i.e. fuel source)
5 fuels are supplied.

The carburetor has an auxiliary starting device with an auxiliary pipe 6 that communicates with the air intake lower of the carburetor and also with the section of the intake passage 10 located downstream of the small throttle valve 2. .

The auxiliary pipe 6 contains a first flow restriction valve 30 that is indirectly controlled by the engine temperature.

The auxiliary pipe 6 has a built-in second flow rate restriction valve 10 upstream of the first flow rate restriction valve 30, and these first and second flow rate restriction valves 30, 1
0 to define a chamber 29.

The second flow restriction valve 10 is connected to the diaphragm 1 of the pneumatic element 17.
It is moved by a rotating shaft 11 fixed to a lever 12 with a catch ear or similar part 13 that engages in a groove 14 formed in a rod 15 directly connected to the rod 15 .

The diaphragm 16 divides the pneumatic element 17 into two chambers 18.1
It is divided into 9 parts.

Chamber 18 communicates with the upstream portion of auxiliary pipe 6 and is at approximately atmospheric pressure.

The chamber 19 is arranged in a direction that closes the second flow restriction valve 10 (i.e., the first
It has a built-in spring 20 that biases the diaphragm 16 (leftward in the figure), and is communicated with a chamber 29 through a pipe 28.

The rod 15 has a diameter-reduced portion 21 that cooperates with the orifice 22 to form a fuel metering device. It is located in the middle of the flow path leading to the top of the fuel duct 230 which communicates with the float chamber 5 through the fuel duct 230.

The duct 23 also communicates with a chamber 29 by a nozzle 25 located slightly above the steady level of fuel in the float chamber 5.

The rod 15 closes the orifice 22 when the second flow restriction valve 10 is in a position to close the auxiliary pipe 6, and when the second flow restriction valve 10 is opened to a preset angle.
It is designed to increase the flow cross section of the fuel metering device.

If the second flow restriction valve 10 is further opened, the rod 1
5 gradually reduces the flow cross-sectional area of the fuel metering device.

The first flow restriction valve 30 is moved by a rotating shaft 31 fixed to a lever 32 (the first flow restriction valve 30 is also shown far away in FIGS. 1 and 2 for clarity).

The lever 32 is pivotally connected to the end 33 of a rod 34 which is fixed to a movable element 35 (for example a diaphragm) of a pneumatic control device 36 or a pneumatic motor.

A diaphragm 35 divides the housing of the pneumatic control device 36 into two chambers 37,38.

The chamber 37 is maintained at atmospheric pressure by the gap between the rod M and the casing.

The chamber 38 communicates with a duct 39 which communicates with the intake passage 1 through orifices such as those shown at 40 and 41 (FIG. 1).

The orifices 40, 41 are sequentially initially located downstream of the edge of the main throttle valve 2 when the main throttle valve 2 is opened to some extent from its idle operating position.

It is arranged so that it will be located next upstream.

The chamber 38 contains a spring 42 biasing the diaphragm 35 in the direction of opening the first flow rate limiting valve 30, that is, to the left in FIGS. 1 and 2.

The lever 32 also has two protrusions 43, 44 arranged in contact with the cam 45 for respectively limiting the opening and closing movements of the first flow restriction valve.

A cam (ie, abutment means) 45 is rotatably mounted on a shaft 46 attached to the main body of the carburetor.

The cam 45 also connects to the stud 47 and the stud 4.
7 as a thermostatic element (i.e. temperature responsive device) 5
The cam 45 has a spring 48 that applies a spring load to the cam 45 so as to keep it in contact with the movable end of the rod 49 of the cam 45.

Thermostatic element 50 contains a wax-like substance within a sealed chamber that expands when temperature increases.

As the temperature increases, its volume changes and the extent to which the rod 49 also protrudes from the thermostatic element 50 increases.

Thermostatic element 50 is secured within a casing 51 attached to the carburetor body, around which fluid flows at a temperature representative of the operating temperature of the engine.

The fluid may be, for example, engine cooling water or lubricating oil.

The operation is as follows.

When the engine is cold and not running, the spring 42
The first flow rate limiting valve 30 is opened until the second protrusion 44 is in contact with the cam 45 (the position shown in FIG. 1).

The second flow restriction valve 10 remains closed by the spring 20.

During cranking, the negative pressure in the intake passage 1 downstream of the main throttle valve 2 acts without substantial attenuation on the float chamber 5, directing the fuel through the orifice 24 to the duct 23 and nozzle 25.
and suction through.

Therefore, the high concentration air-fuel mixture necessary for starting the engine is supplied to the engine.

As soon as the engine is started, the negative pressure downstream of the main throttle valve 2 increases considerably.

The negative pressure is transmitted through the orifice 40° 41 and the duct 39 to the pneumatic control device 360 chamber 38, rotating the lever 32 clockwise until the protrusion 43 contacts the cam 45 (shown in phantom in FIG. 1). ).

The contour of the cam 45 is such that the first flow restriction valve 30 opens to an extent determined by the engine temperature, which is smaller than before starting (as shown by the dashed line in FIG. 1).

The negative pressure transmitted to the chamber 29 moves the pneumatic element 17, which partially opens the second flow restriction valve 10 to provide a passage for determining the flow rate of air through the auxiliary pipe 6, and By increasing the effective flow cross section between the outer wall of the orifice 22 and the reduced diameter portion 21 of the rod 15, air is injected into the duct 23 and the float chamber 5 also reduces the negative pressure acting to draw in fuel. let

As a result, the amount of fuel supplied through the nozzle 25 decreases, and the concentration of the air-fuel mixture supplied to the engine becomes smaller.
This prevents the engine from stalling due to the high concentration of air-fuel mixture after the engine has started.

As a result, the first flow restriction valve 30 and the second flow restriction valve 10
provides the amount of fuel and air required for normal operation of the cold engine.

If the main throttle valve is next opened by the engine operator, the orifice 40,41 moves upstream of the main throttle valve 2;
Thus, the negative pressure transmitted to the air pressure control device 360 chamber 38 via the duct 39 is reduced.

If the elasticity of spring 42 is appropriately selected, spring 42 will move diaphragm 35 (toward the left in FIG. 1) to open first flow restriction valve 30 an additional amount.

As a result, the air flow rate increases and the pneumatic element 17 and the second flow rate limiting valve 10 are operated.

The second flow restriction valve 10 then regulates the pressure within the chamber 29.

The second flow restriction valve 10 is further opened so that the pressure within the chamber 29 remains substantially constant or increases slightly as the flow rate increases.

Referring to FIG. 1, when the second flow restriction valve 10 is moved beyond a preset degree (i.e. when the flow rate of air in the auxiliary duct 6 increases beyond a preset value), the rod The diameter of the reduced diameter portion 21 of 15 is increased to reduce the flow rate of air entering the duct 23 through the cross-sectional area of free flow created by the rod 15, increasing the negative pressure in the duct 23 and causing air to flow out from the nozzle 25. The flow rate of fuel into the auxiliary pipe 6 is increased, thus increasing the concentration of the mixture supplied through the auxiliary pipe 6.

The fuel metering system including pneumatic element 17 and rod 15 operates quite differently from the fuel metering system in conventional carburetors of the "constant negative pressure" or needle type.

If the reduced diameter section 21 has a suitable shape, the operator can accelerate by opening the main throttle valve 2.

In addition to the flow of air and fuel from the main jet into the intake passage 1, a rich mixture supply through the auxiliary pipe 6 can be provided.

As the engine heats up, rod 49 of thermostatic element 50 stretches, overcoming the action of spring 48 and causing cam 45 to rotate counterclockwise about its axis 460.

When the cam 45 is rotated in this manner, the range of movement of the lever 32 becomes progressively smaller.

The protrusion 43 is in contact with the cam 45 and is moved in a direction to close the first flow restriction valve 30, thus opening the auxiliary pipe 6.
The amount of fuel and air fed through is gradually reduced.

Finally, when the engine has reached its normal operating temperature, the several members are placed in relative positions as shown in FIG.

Both projections 43,44 contact the cam 45 and prevent the lever 32 from rotating about its axis of rotation 31.

The first flow restriction valve 30 is thus kept closed and the auxiliary pipe 6 has no effect since it is closed.

The auxiliary starting device of the present invention described above uses the cooperation of the first and second flow rate limiting valves placed in series in the auxiliary pipe 6 to generate a high-concentration air-fuel mixture only when necessary for normal operation of the engine. The first flow limiting valve is vacuum controlled and in conjunction with a temperature responsive device which overcomes the vacuum action when the engine reaches its normal temperature, the first flow limiting valve is then The valve is adapted to be closed, and the other additional component of the vaporizer is a second flow restriction, which is another valve located in the auxiliary pipe and whose position is automatically controlled by the air flow rate. It is operated by a valve.

It would not be possible to obtain the same effect as that of the present invention described above by simply placing a single valve in the auxiliary pipe as in the prior art.

[Brief explanation of drawings]

Figure 1 is a partial cutaway diagram of the carburetor when the engine is stopped and cold, as seen from the front, to explain the positions occupied by each member of the carburetor, and Figure 2 is a diagram of the carburetor when the engine is at normal operating temperature. FIG. 3 is a partially cutaway diagram, seen from the front, illustrating the positions occupied by each member. 1... Intake passage, 2... Main throttle valve, 3... Main jet, 4... Venturi, 5... Float chamber,
6... Auxiliary pipe, 7... Air intake port, 10... Second flow rate limiting valve, 12... Lever, 15... Rod, 1
7... Pneumatic element, 19... Chamber, 21... Diameter reduction part, 22... Orifice, 23... Duct, 24...
- Orifice, 25... Nozzle, 30... First flow rate limiting valve, 32... Lever, 35... Diaphragm, 3
6... Air pressure control device, 39... Duct, 40.4
1... Orifice, 43.44... Protrusion, 45...
・Cam, 49...Rod, 50...Thermostat element.

Claims (1)

[Scope of Claims] 1. A fuel main jet that opens into the intake passage of the carburetor upstream of a main throttle valve actuated by the operator, and a main jet that opens into the area of the intake passage downstream of the main throttle valve. and an auxiliary starting device having an auxiliary pipe which is supplied with air and fuel, said auxiliary pipe being actuated by a temperature responsive device to progressively close as the temperature of the engine increases. In the carburetor of an internal combustion engine, the auxiliary starting device includes a second flow meter restriction valve located upstream of the first flow restriction valve in the auxiliary pipe; A flow restriction valve opens automatically and progressively when the flow rate of air through the auxiliary pipe increases, and as a result of a vacuum in the chamber defined by the first and second flow restriction valves within the auxiliary pipe. A carburetor for an internal combustion engine, characterized in that the vaporizer is adapted to actuate a fuel metering device adapted to meter the flow rate of fuel drawn into the auxiliary pipe from the fuel source. 2. In the carburetor as set forth in claim 1, the first flow rate valve is located within the intake passage from downstream to upstream of the main throttle valve when the main throttle valve is opened from an idle operating position. a pneumatic control device receiving a negative pressure at a location, the movement of the first flow restriction valve toward its closed position under the action of the pneumatic control device being restricted by a temperature-sensitive abutment means; Internal combustion engine, characterized in that the minimum opening position that can be given to the first flow restriction valve by the pneumatic control device corresponds to a flow cross section that decreases as the temperature of the engine approaches normal operating temperature. vaporizer. 3. In the carburetor according to claim 2, the movable range of the first flow rate limiting valve between the maximum opening position and the minimum opening position decreases as the temperature of the engine increases, and A carburetor for an internal combustion engine, characterized in that the abutting means is constructed and arranged such that the temperature of the carburetor becomes substantially zero when the temperature reaches a normal operating temperature.