JPS6139499B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a carburetor equipped with a starter for supplying a rich air-fuel mixture during cold starting of an internal combustion engine.

In an internal combustion engine that has a carburetor with a starter, if the throttle valve is suddenly opened, especially during warm-up, the negative pressure in the intake pipe decreases (approaches atmospheric pressure), and the starting system fuel and fuel are sucked into the intake pipe. While the amount of fuel in the slow fuel system is reduced, the fuel supply to the main fuel system is also delayed, resulting in the mixture becoming too lean and causing the engine to stall. Therefore, not only can the engine not be revved up during warm-up immediately after starting, but it is also almost impossible for a vehicle equipped with this engine to run during warm-up.

This invention was made in view of the above circumstances, and provides a carburetor with a starter that does not stop the engine even if the throttle valve is opened during warm-up operation, allowing the engine to run and the vehicle to run. The purpose is to In order to achieve this objective, the present invention provides a carburetor with a starter that can communicate and shut off a communication passage that leads fuel in a float chamber downstream of a butterfly-shaped throttle valve in an intake passage, and a mixing chamber is formed in the communication passage. In addition, a negative pressure detection port that opens in the vicinity of the rotating end of the butterfly throttle valve on the upstream side of the butterfly throttle valve is communicated with this mixing chamber, so that the opening degree of the butterfly throttle valve is controlled. The structure is such that the mixture concentration is changed accordingly. The present invention will be explained in detail below based on the drawings.

FIG. 1 is a partially sectional side view of a carburetor according to an embodiment of the present invention, FIG. 2 is a partially sectional front view thereof, and FIG. 3 is a system diagram thereof. In these figures, reference numeral 1 denotes a so-called SU type carburetor with a variable bench lily, 2 an intake passage, 3 a piston valve that moves forward and backward so as to face the intake passage 2 from above, and 4 a piston valve that hangs down from the piston valve 3. It's Etsu Needle. Reference numeral 5 denotes a float chamber, in which a main fuel system is formed in which the jet needle 4 moves forward and backward, and the flow rate of fuel sucked into the intake passage 2 is controlled. Reference numeral 6 denotes a diaphragm fixed to the upper end of the piston valve 3. The periphery of the diaphragm 6 is held between the mating surfaces of the main body of the carburetor 1 and the cover 7, and the diaphragm 6 is connected to the negative pressure chambers 8 above and below. It serves as a partition wall of the atmospheric pressure chamber 9. A pressure expanding coil spring 10 is installed between the piston valve 3 and the cover 7 to urge the piston valve 3 downward. The negative pressure chamber 8 communicates with a negative pressure outlet 11 opened at the lower end surface of the piston valve 3. Therefore, the internal pressure of the negative pressure chamber 8 becomes a negative pressure corresponding to the flow rate of the intake air passing through the bench lily formed by the lower end surface of the piston valve 3 and the inner surface of the intake passage 2. On the other hand, atmospheric pressure chamber 9
communicates with an atmospheric pressure outlet 12 that opens into the intake passage 2 on the upstream side of the piston valve 3. Therefore, the piston valve 3 moves up and down in response to the intake flow rate due to the pressure difference between the negative pressure chamber 8 and the atmospheric pressure chamber 9. That is, the opening area of the bench lily changes. Intake passage 2
Inside, a butterfly-shaped throttle valve 13 is provided downstream of the piston valve 3. A fuel supply port (not shown) of a known slow fuel system is opened near the throttle valve 13 .

Next, the starter will be explained. A cylindrical mixing chamber 20 is formed in the main body of the carburetor 1 so that one end thereof is open, and a starter plunger 21 is inserted into the mixing chamber 20 so as to be movable forward and backward. The plunger 21 is integrally formed with an operating rod 22 that projects outward and a protrusion 23 that projects inward. A cap 24 through which the operating rod 22 passes is screwed into an opening at one end of the mixing chamber 20;
Furthermore, a seal 25 is attached. Mixing chamber 20
An engagement hole 26 into which the protrusion 23 enters is formed at the bottom of the float chamber 5, and this engagement hole 26 communicates with the inside of the float chamber 5 through a communication passage 27. That is, an emulsion pipe 28 is connected to the lower part of the communication passage 27, and this emulsion pipe 28 extends into an emulsion chamber 29 formed in the float chamber 5, and is immersed in the fuel in this emulsion chamber 29. An inner jet 30 is provided at the lower end opening of the emulsion pipe 28, and an outer jet 31 is provided at the fuel inflow path at the lower end of the emulsion chamber 29. The emulsion chamber 29 and the inside of the float chamber 5 communicate with each other through a vent hole 32 provided above the fuel liquid level, and bleed air flows into the emulsion chamber 29 through the vent hole 32 .

The mixing chamber 20 communicates with the atmospheric pressure chamber 9 through a vent hole 33, and also communicates with the atmospheric pressure chamber 9 through a passage 34, which is connected to a negative pressure opening upstream of the throttle valve 13 and near the rotation end of the throttle valve. It communicates with the detection port 35. Further, a communication passage 36 opens in this mixing chamber 20, and the other end of this communication passage 36 opens downstream of the butterfly-shaped throttle valve 13 in the intake passage 2. In other words, this opening is the starter fuel supply port 37.
It is becoming.

Next, the operation of this vaporizer will be explained.

FIG. 3A shows the throttle valve 13 in the idling position. During a cold start, the starter plunger 21 is pulled out to the position shown in the figure via the operating rod 22 by a manual mechanism (not shown). At the time of A in the figure, the negative pressure detection port 35 is on the atmospheric pressure side, while the starter fuel supply port 37 is on the intake negative pressure side. Therefore, the mixing chamber 20 is drawn to the intake negative pressure, while the atmosphere enters from the negative pressure detection port 35 and the vent hole 33, and the inside of the mixing chamber 20 is the sum of the atmospheric pressure from the negative pressure detection port 35 and the vent hole 33 and the starter. The pressure difference between the negative pressure of the fuel supply port 37 acts and the communication passage 27
The amount of fuel siphoned through is the same as in the preset conventional idling state. Throttle valve 13
When opened and moved to position B in the figure, negative pressure detection port 35
The detected pressure decreases and becomes lower than atmospheric pressure. Therefore, the flow rate of air flowing into the mixing chamber 20 through the communication path 34 decreases, and the negative pressure within the mixing chamber 20 increases (away from atmospheric pressure). As a result, the amount of fuel sucked up from the communication passage 27 increases. Furthermore, as shown in Figure B, when the throttle valve 13 is opened, the negative pressure detection port 3
5 is on the downstream side of the throttle valve 13, so this port 35 is drawn to the intake negative pressure. Therefore, mixing chamber 2
The negative pressure at 0 becomes even greater, and the amount of fuel sucked up also increases.

On the other hand, during idling, fuel is supplied from a slow fuel system (not shown), and when the throttle valve 13 opens, fuel is supplied from the main fuel system. Although the air-fuel mixture tends to become lean temporarily, in this embodiment, as the throttle valve 13 opens, the negative pressure in the mixing chamber 20 of the starter increases, and the amount of fuel sucked up increases. The temporary dilution of the air-fuel mixture due to the delay in the main system accompanying the opening movement is compensated by the rich air-fuel mixture supplied from the starter fuel supply port 37. Therefore, the rotation of the engine increases without stopping.

In this embodiment, an atmospheric pressure chamber 9 is provided in the mixing chamber 20.
A communication hole 33 is provided that communicates with the
By changing the area of 3, it is possible to change the amount of fuel supplied to the starter, and in some cases, it is not necessary to provide this communication hole 33.

As described above, this invention controls the concentration of the air-fuel mixture supplied from the starter by changing the pressure in the mixing chamber provided in the communication path of the starter in accordance with the opening degree of the butterfly throttle valve. Therefore, it is possible to compensate for the temporary lean state of the mixture due to the delay in the operation of the main fuel system when opening the butterfly throttle valve, and it is possible to smoothly increase the speed of the engine and make it possible to start the engine. Furthermore, when a vehicle is equipped with an engine to which the present invention is applied, the vehicle can run even while the engine is being warmed up. Furthermore, a mixing chamber is formed in the middle of the communication passage for the starter, and all the passages for the starter are communicated with and shut off by a plunger provided in the mixing chamber so as to be able to move forward and backward, so that the mixture of fuel and air for the starter is prevented. Not only is the performance improved, but the structure is also simple.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional side view of an embodiment of the present invention, FIG. 2 is a partially sectional front view thereof, and FIG.
The figure also shows the system diagram. 1... Carburizer, 2... Intake passage, 13... Butterfly throttle valve, 20... Mixing chamber, 27, 37... Communication passage, 35... Negative pressure detection port.

Claims (1)

[Claims] 1. In a carburetor with a starter, in which the communication passages 27, 36 that lead the fuel in the float chamber 5 to the downstream side of the butterfly-shaped throttle valve 13 in the intake passage 2 can be communicated and shut off, the communication passages 27, 36 are Mixing chamber 20
A negative pressure detection port 35 is formed in the mixing chamber 20 near the rotating end of the throttle valve 13.
The negative pressure detection port 35 is provided at a position that opens upstream of the throttle valve 13 at an idling opening and opens downstream of the throttle valve 13 at a predetermined opening 20 is a carburetor with a starter, in which a starter plunger 21 that communicates and blocks the communication paths 27 and 36 is provided so as to be movable forward and backward.