JPS6147299B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a starting device that enriches the air-fuel ratio of the air-fuel mixture during a cold start of an engine.It has a simple structure and can be used over a wide temperature range from room temperature to extremely low temperatures below freezing. The purpose of this is to improve engine startability over time.

BACKGROUND ART Conventionally, a so-called bi-starter system has been known as a low-temperature starting device for a carburetor, in which a starting air passage bypassing a throttle valve is provided, and a starting valve that opens at low temperatures and a starting fuel injection port are attached to the starting air passage.

This invention increases the amount of low-speed fuel supplied from the low-speed fuel nozzle with air bleed provided in a conventional carburetor during cold starting, enriches the air-fuel ratio of the air-fuel mixture taken in, and improves the starting temperature. A special fuel nozzle was installed to further increase the amount of fuel from cranking to complete explosion, improving low-temperature startability.

The present invention will be explained below with reference to illustrated embodiments. The carburetor includes an intake passage 2 formed in an intake body 1,
It has a piston-shaped throttle valve 3 that moves forward and backward into the intake passage 2 by manual operation. 4 is a needle valve supported by a throttle valve; 5 is a main nozzle port that cooperates with the needle valve 4 to change the opening area; and 6 is a low-speed fuel nozzle port. Reference numeral 7 denotes a float chamber provided on the lower surface of the intake shell 1, and fuel therein is supplied to the main nozzle 5 through a main fuel passage 8 and to the low-speed fuel nozzle 6 through a low-speed fuel passage 10 having an emulsion tube 9. 11 is a slow air passage, one end of which communicates with the low speed fuel passage 10, and the other end of which communicates with the atmosphere via an air jet 12. 13 is a pilot air screw that changes the amount of air bleed flowing through the slow air passage to adjust the air-fuel ratio to lean or rich. A starting air passage 14 is provided between the slow air passage 11 and the intake passage 2 downstream of the throttle valve 3. 15
is a starting valve installed in the middle. Starting valve 1
5 is provided in the air passage 14 and consists of an orifice-shaped valve seat 16 and a corresponding conical valve body 17. The valve body 17 is supported slidably within the valve box 19 by a guide cylinder 18 on the back side, and a bimetal 22 is provided in an outer circumferential groove 21 at the rear end.
is engaged to pull the valve body 17 away from the valve seat 16 when the engine temperature is low. Bimetal 2
The base end of 2 is fixed to the valve box with bolt 23,
The free end can move within the outer circumferential groove 21 within an axial clearance a. A spring 24 presses the bimetal 22 toward the lower end of the outer circumferential groove. A leak passage 25 communicates the starting air passage 14 on the upstream side of the valve seat 16 with the valve chamber on the back side of the valve body 17, so that the negative pressure inside the air passage 14 acting on the front side of the valve body 17 increases (pressure The starting valve 15 is configured as a pressure sensitive valve so that when the starting valve 15 decreases, the ventilation area formed between the starting valve 15 and the valve seat 16 decreases.

A starting fuel nozzle 26 is provided to increase the amount of fuel during the period from engine cranking to complete explosion, and is provided anywhere from the starting air passage 14 downstream of the starting valve 15 to the intake passage 2. . The nozzle 26 communicates with the inside of the float chamber 7 via a passage 27, and the passage 27 is provided with a negative pressure operated fuel valve 28 for communicating and cutting off communication therebetween. The passage 27 is connected to the emulsion pipe 29 and the metering pipe 3 in the float chamber 7.
The upper end of the metering tube 31 opens above the float chamber through a jet 32. The fuel in the float chamber 7 enters the passage 27 through a small hole 33 opened on the side of the metering tube 31, and is maintained at the same level as the float chamber 7 when the engine is stopped. 34 is a starting fuel jet.

The negative pressure operated fuel valve 28 is a normally closed type that presses a valve body 35 with a spring 36 on the back side and acts to close the passage 27 at all times.
7 are connected. An atmospheric chamber 38 connected to the upper surface of the float chamber is formed on one side of the elastic membrane 37, and a negative pressure chamber 39 connected to the slow air passage 11 upstream of the starter valve 15 is formed on the other side.

Now, when the temperature of the engine or the outside air falls below a predetermined temperature, the bimetal 22 bends upward in the figure, pulls up the valve body 17, and completely passes through the starting air passage 14. When cranking in this condition, air passage 1
Intake negative pressure downstream of the throttle valve 3 acts on the slow air passage 11 through the pilot air screw 13.
The airflow flowing into the low speed fuel passage 10 through the lower speed fuel passage 10 is reduced. Therefore, air bleed, that is, air mixed into the fuel from the low-velocity fuel nozzle 6 is reduced, so that the amount of fuel injected into the intake passage 2 is increased. Therefore, even if the atmosphere is introduced through the air passage 14, the air-fuel ratio of the supplied air-fuel mixture will be rich, and the air-fuel ratio will be enriched automatically as the amount of intake air increases. Furthermore, when starting at a cryogenic temperature where the opening degree of the starting valve 15 is large, for example when starting at sub-zero temperatures, the negative pressure that spreads within the starting air passage 14 is large, so the fuel valve 28 is also opened under the influence of the negative pressure. Therefore, the fuel accumulated in the emulsion pipe 29 and the metering pipe 31 is injected into the intake passage 2 through the jet nozzle 26 in a short time due to the atmospheric pressure acting through the jet 32, and the air-fuel mixture taken in at the time of startup is Enriches to further improve engine startability.

At this point, the engine starts, and when it reaches so-called complete combustion, where the engine can continue to operate on its own from cranking, the engine speed increases rapidly and the intake negative pressure downstream of the throttle valve increases rapidly.

Since the valve element 17 of the starter valve 15 moves downward against the spring 24 and reduces its opening degree (the figure shows this state), the negative pressure in the air passage 14 on the upstream side decreases. As a result, the negative pressure operated fuel valve 28 closes, and the amount of fuel supplied from the low speed fuel nozzle 6 decreases. Note that when the outside temperature is so low that the negative pressure inside the air passage 14 is not sufficiently reduced (approaching atmospheric pressure), the negative pressure responsive valve 28 is kept open, but the negative pressure inside the air passage 27 remains open. After a short time after the fuel has been consumed, an emulsion of air flowing through the jet 32 and a small amount of fuel flowing into the passage 27 through the small hole 33 is metered by the jet 32 into the intake passage 2.

When the engine is warmed up and the temperature rises, the opening degree of the starter valve 15 automatically decreases and finally closes, but during this time the fuel supplied from the low-speed fuel injection port 6 gradually decreases. This reduces the flow rate to the required low flow rate for low speed operation of the engine.

As described above, this invention provides an air passage that communicates the slow air passage with the intake passage downstream of the throttle valve, and a pressure-sensitive valve that reduces the ventilation area when the intake negative pressure acting thereon rises in the middle. A passage is provided to supply fuel to the intake passage downstream of the valve,
There is provided a negative pressure operated fuel valve that closes when the negative pressure in the air passage increases. Therefore, while the two work together to crank the engine, fuel is supplied from the low-speed fuel nozzle and the starting fuel nozzle into the intake passage, making the air-fuel ratio of the intake mixture even richer, which increases the Makes starting easier. When the engine produces an output that allows it to run on its own, the pressure-sensitive valve reduces the amount of fuel supplied from the low-speed fuel nozzle, and the fuel valve stops the supply of starting fuel. Therefore, the air-fuel ratio is diluted at the same time as the engine starts, which has the effect of preventing unstable operation and waste of fuel due to an excessively rich air-fuel ratio during subsequent operation.

Note that the starting fuel nozzle is not limited to one that opens directly into the intake passage, but may be provided within the air passage.

[Brief explanation of the drawing]

The drawing is a configuration diagram of a vaporizer showing an example of carrying out the present invention. 2...Intake passage, 3...Throttle valve, 6...Low speed fuel nozzle, 14...Starting air passage, 15...Starting valve, 26...Starting fuel injection port, 28...Negative pressure operating valve.

Claims (1)

[Claims] 1. In a carburetor in which a low-speed fuel passage is opened in the intake passage downstream of the throttle valve and atmospheric air is introduced into the low-speed fuel passage through the slow air passage, the slow air passage and the intake passage downstream of the throttle valve are used for starting. Connected with an air passage, and connected to this starting air passage,
Providing a starter valve equipped with a temperature-sensitive member that reduces the ventilation area when the intake negative pressure acting on this passage increases and biases the ventilation area in the direction of opening it at low temperatures,
A fuel nozzle is opened in the air passage downstream of the starting valve or the intake passage downstream of the throttle valve, and a negative pressure-operated type that responds to the negative pressure between the starting valve and the slow air passage is connected to the fuel passage connected to the fuel nozzle. A carburetor starting device equipped with a fuel valve.