JPH09291852A - Starting fuel supplying device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply a sufficient amount of fuel to an engine while acting a choke, and execute early first explosion at an extremely low temperature, by arranging an excess fuel passage opened from the constant fuel chamber of a carburetor to the downstream side of the choke valve of an intake pass, and arranging an opening/closing valve in a part where the excess fuel passage of a valve shaft is crossed. SOLUTION: In a diaphragm carburetor, an excess fuel passage 27 which is extended from a constant fuel chamber 14 and opened in the skirt of a venturi 3, is so formed that it crosses at right angles the part of the valve shaft 33 of a choke valve 2. A fuel chamber side part 28 and an intake passage side part 29 are also formed in this part, and a part where the excess fuel passage 27 of the valve shaft 33 is opened is acted upon as an opening/closing valve 35, thereby two parts 28, 29 communicate with each other when the choke valve 2 is closed. Hereby, fuel is supplied to an engine from both sides of the excess fuel passage 27 in which a main nozzle 21 and a check valve 30 are opened by intake negative pressure generated at the same time when the cranking of the engine is started, and first explosion can be executed at few cranking numbers even at an extremely low temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a device for supplying extra fuel to an intake system in order to improve a low temperature startability of a general-purpose two-cycle engine.

[0002]

2. Description of the Related Art Most of general-purpose two-cycle engines used as drive sources for agricultural machinery, forestry work machines, small vehicles, etc., have a constant fuel chamber which is separated from the atmosphere by a diaphragm and regulates fuel to a constant pressure. Fuel is supplied by the equipped membrane vaporizer.

The membrane type carburetor is equipped with a diaphragm type fuel pump driven by the pulse pressure generated in the crankcase of the engine, and the fuel in the fuel tank is introduced into the constant fuel chamber by this fuel pump. It has a structure that sucks it into the intake passage and supplies it to the engine.In addition to this, in order to improve the startability at low temperature, extra fuel is sent to the intake passage before starting the engine, or more than specified in the constant fuel chamber. It usually comprises a means for introducing the fuel, generally a manual starting pump.

In the case where the starting pump is provided, the fuel is a fuel tank → fuel pump → constant fuel chamber (→ intake passage) →
Those that flow in the order of the starting pump (JP-A-55-69748)
Fuel tank → starting pump → fuel pump →
There are those that flow in the order of a constant fuel chamber (→ external overflow) (see Japanese Utility Model Laid-Open No. 47-38218). However, since the starting fuel is sent to the intake passage roughly, the amount cannot be normally confirmed. Since it is introduced into the fuel chamber and caused to overflow, the amount can be divided into those that can always be confirmed.

[0005]

When the engine is cranked while the starting fuel is stored in the intake passage or the constant fuel chamber as described above, the starting fuel flows toward the engine due to the intake negative pressure. At low temperatures, this flow is a liquid flow that travels along the walls of the intake passage and intake pipe. Therefore, at an extremely low temperature where the fuel is hardly vaporized, the fuel is not supplied to the engine unless the cranking is repeated many times.

On the other hand, in the case where the carburetor has a choke valve at the inlet of the intake passage, the choke valve is closed to perform cranking so that the fuel in the constant fuel chamber is discharged from the main nozzle in addition to the idle port. Although the amount of the starting fuel is sucked out and increased, the main nozzle diameter is limited, so that it is not possible to expect a sufficient increase in the amount of cranking, and it is not possible to greatly reduce the number of crankings at extremely low temperatures.

In order to deal with this, in the method of flowing the starting fuel into the intake passage, it is possible to change the number of times of operation of the starting pump according to the temperature. It is not common because it requires skill. Further, in the system in which the starting fuel is introduced into the constant fuel chamber, a certain amount or more cannot be secured, and therefore the number of cranking times cannot be reduced.

The present invention utilizes the fact that the engine is started by closing the choke valve when the temperature is low, and in addition to the pre-stored starting fuel and the fuel in the constant fuel chamber sucked from the main nozzle and the idle port, another route is provided. Therefore, by sucking the fuel in the constant fuel chamber into the intake passage, it is intended to solve the above-mentioned problem that the cranking is often performed at an extremely low temperature and it takes time to start the engine.

[0009]

That is, according to the present invention, there is provided a passage through which the fuel in the constant fuel chamber is sucked out into the intake passage at the time of choke action through the on-off valve formed on the valve shaft of the choke valve, and the choke valve is opened. When the choke valve is closed, fuel is supplied only from the main nozzles and idle ports, which are the normal fuel passages, but from another passage when the choke valve is closed. A sufficient amount of fuel was supplied to the engine, which made it possible to measure the initial detonation at extremely low temperatures.

Further, in order to prevent the fuel from being sucked out through the gap around the valve shaft when the choke valve is opened, a means is added so that the fuel is supplied only from the regular fuel path after the completion of warming up. I have something to do.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A carburetor to which a starting fuel supply device of the present invention is applied has a fuel pump and a constant fuel chamber arranged with an intake passage having a choke valve, a venturi, and a throttle valve in that order. Is a diaphragm type that is driven by the pulse pressure generated in the crankcase of the engine and sends the fuel in the fuel tank to the constant fuel chamber. The constant fuel chamber is separated from the atmosphere by the diaphragm, and the main nozzle, idle port, It is usually a membrane vaporizer configured to hold the fuel sent to the slow port at a constant pressure.

Since the fuel in the constant fuel chamber is sucked into the intake passage during choking, the path according to the present invention provided separately from the regular fuel path from the constant fuel chamber to the main nozzle, the idle port and the slow port is a choke. The valve is formed by an increased fuel passage formed in the carburetor body across the valve shaft and an on-off valve formed in the valve shaft.The increased fuel passage is provided at any position downstream of the choke valve, preferably a venturi. To be opened. The on-off valve uses the valve shaft itself as a valve body, and the valve shaft which is the valve body is provided with a valve passage that shuts off the constant fuel chamber side portion and the intake passage side portion of the increased fuel passage when the choke valve is opened but communicates when closed. Such a configuration is advantageous in terms of simplification of configuration and accuracy of operation.

The on-off valve is formed in the valve shaft portion fitted in the shaft hole of the carburetor main body, and if there is no gap around the valve shaft, the increased fuel passage can be completely closed when the choke valve is opened.

However, in reality, in most cases, there is a gap around the valve shaft, so that when the choke valve is opened, the fuel in the constant fuel chamber is gradually sucked into the intake passage through the increased fuel passage due to the negative suction pressure of the engine. , The air-fuel mixture during normal operation after warming up may be thickened. Further, in the system in which the starting fuel flows in the order of fuel tank → fuel pump → constant fuel chamber (→ intake passage) → starting pump, the negative pressure generated in the constant fuel chamber when operating the starting pump is intake air. Due to the air sucked from the passage through the increased fuel passage, the air is lowered and the introduction of the starting fuel deteriorates.

As measures against these, in the present invention, an air passage for introducing the atmosphere is provided in the constant fuel chamber side portion of the increasing fuel passage through the valve passage when the choke valve is opened, and the constant fuel chamber side portion is directed toward the constant fuel chamber. It was decided to install a close check valve. The air passage is shut off from the valve passage when the choke valve is closed to allow fuel supply through the increased fuel passage without hindrance, but when the choke valve is opened it communicates with the valve passage and the check valve is exposed to the atmosphere to maintain the closed state. As described above, the opening is made at an appropriate position around the valve shaft in relation to the shape of the valve passage and the rotation range of the valve shaft.

Although the present invention can be applied to a system in which the starting fuel is stored in either the intake passage or the constant fuel chamber, the starting pump tends to be operated excessively because the amount of the starting fuel cannot be confirmed. Therefore, as compared with the intake passage delivery system in which more than the required amount of starting fuel is often supplied, the constant fuel chamber introduction system in which a constant amount of starting fuel is always secured is applied to compensate for the shortage. It is effective to supply increased fuel.

When the engine is initially bombed by cranking, then completely blown up, and when the engine shifts to warm-up operation, the fuel pump operates to introduce the fuel in the fuel tank into the constant fuel chamber so as to hold a prescribed amount. The increased fuel passage constantly sucks fuel into the intake passage while the choke valve is closed. For this reason,
It is also possible to expect stable completion of the explosion and early completion of warm-up.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fuel pump 7 and a constant fuel chamber 14 are provided on the outer surface of a carburetor body 1 with an intake passage 5 having a choke valve 2, a venturi 3 and a throttle valve 4 in this order. A description will be given based on an example applied to a membrane vaporizer.

The fuel pump 7 is a well-known diaphragm type, in which the pulse pressure generated in the crankcase of the engine is introduced by the pulse pressure introducing pipe 8 to pulsate the diaphragm, and the fuel in the fuel tank 10 is introduced into the fuel introducing pipe. It is sucked through 11 and pressurized to be sent to the constant fuel chamber 14 through the fuel passage 12.

The constant fuel chamber 14 is separated from the atmosphere chamber 17 in the diaphragm cover 16 by the diaphragm 15, and the fuel valve 20 engaged with the lever 19 brought into contact with the center of the diaphragm 15 by the force of the spring 18 is provided. By opening and closing the fuel passage 12 according to the displacement of the diaphragm 15, a predetermined amount of fuel is held at a constant pressure. The fuel in the constant fuel chamber 14 is supplied from the main nozzle 21 opened in the narrowest part of the venturi 3 and an idle port (not shown) and a slow port opened laterally of the throttle valve 4 to the intake passage 5
It is sucked out into the air, and these are the same as the conventional ones.

A well-known finger pushing dome-shaped starting pump 2 is arranged on the outer surface of the carburetor main body 1 along with the fuel pump 7.
3, the suction passage 24 extending from the constant fuel chamber 14 is connected to the suction port of the starting pump 23, and the discharge passage 25 reaching the fuel tank 10 is connected to the discharge port.

When the engine is stopped by emptying the fuel in the constant fuel chamber 14 or when the engine is stopped due to running out of fuel, the starting pump 23 is manually operated before the next engine operation and the fuel in the fuel tank 10 is stopped. Is sucked into the constant fuel chamber 14 through the fuel introduction pipe 11, the fuel pump 7, and the fuel passage 12 to be replenished. When the engine is started at a low temperature, the starter pump 23 is further operated to fill the constant fuel chamber 14 with fuel. When the starter pump 23 continues to be operated, the fuel is sucked from the suction passage 24 to at least the discharge passage 25 at least. Two
By making the portion close to 3 transparent, it is possible to appropriately know that a sufficient amount of starting fuel has been secured.

Next, the increased fuel passage 27 extending from the constant fuel chamber 14 and opening to the skirt portion of the venturi 3 is connected to the carburetor main body 1.
It is provided inside. Constant fuel chamber 14 of this passage 27
A check valve 30 having a flat valve plate and a valve closing spring is provided at the opening end to the direction toward the constant fuel chamber 14. Further, the passage 27 is formed in the shaft hole 4 of the carburetor main body 1.
3 is formed so as to cross the valve shaft 33 portion of the choke valve 2 which is fitted in the valve 3 at a right angle, and in this portion, the constant fuel chamber side portion 28 and the intake passage side portion 29 are directed at a substantially right angle to each other. Changing.

The portion of the valve shaft 33 where the increased fuel passage 27 is open functions as an on-off valve 35, and an L-shaped valve passage 36 closes the two portions 28 and 29 of the choke valve 2 in this portion. It is formed so as to communicate with each other at some times but to shut off when opened.

Further, the intake passage side portion 2 with the valve shaft 33 interposed therebetween.
An air passage 38 opened toward the opening / closing valve 35 at a position facing 9 is provided in the carburetor body 1.
The inlet of the air passage 38 is arranged side by side with the inlet of the intake passage 5 and opens into the air cleaner.

FIGS. 1 and 2 show a state in which the choke valve 2 is open. The air passage 38 communicates with the valve passage 36, and the atmosphere is applied to the back surface of the check valve 30. Further, the on-off valve 35 blocks the constant fuel chamber side portion 28 and the intake passage side portion 29 to prevent the fuel from being sucked out by the suction negative pressure generated by the engine operation. At this time, even if the suction negative pressure acts on the back surface of the check valve 30 through the gap between the valve shaft 31 and the shaft hole 32, the atmosphere is introduced from the air passage 38 through the valve passage 36, so that the negative pressure is negative. The pressure is released, and the check valve 30 can be maintained in the closed state to reliably prevent the fuel from being sucked out.

Therefore, an appropriate amount of fuel is supplied to the engine after completion of warm-up only from the main nozzle 21, the idle port, and the slow port, which are regular fuel paths.

Further, in the type in which the constant fuel chamber 14 has a negative pressure when the starting pump 23 is operated as in this embodiment, the check valve 30 prevents air from being sucked into the low fuel chamber 14. However, this brings about an effect of smoothly introducing the starting fuel.

FIG. 3 shows the state when the choke valve 2 is closed. The on-off valve 35 blocks the air passage 38 from the increased fuel passage 27, but the valve passage 36 has the constant fuel chamber side portion 28. Communicates with the intake passage side portion 29. For this reason, fuel is supplied to the engine from both the main nozzle 21 and the increased fuel passage 27 in which the check valve 30 is opened by the suction negative pressure generated on the downstream side of the choke valve 2 at the same time when the engine cranking is started. Even if the temperature is low, the initial explosion can be performed with a small number of crankings.

Further, while the choke valve 2 is closed, the fuel is continuously supplied from the increased fuel passage 27, so that the fuel increase necessary for warm-up is continuously performed after the complete explosion to stabilize the engine operation. It was possible to expect early completion of warm-up at the same time.

[0031]

As described above, according to the present invention in which the fuel in the constant fuel chamber is sucked out into the intake passage in response to the opening / closing of the choke valve, the excess fuel is properly removed at the low temperature start of closing the choke valve. It is possible to supply the fuel and to make the initial explosion with a small number of cranking times even at an extremely low temperature, and to reliably start the engine in a short time.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing an embodiment of the present invention with a choke valve open.

FIG. 2 is an enlarged partial view of FIG. 1;

FIG. 3 is a partial sectional view of the embodiment of FIG. 1 in a closed state of a choke valve.

[Explanation of symbols]

2 choke valves, 3 venturis, 4 throttle valves,
5 intake passage, 7 fuel pump, 14 constant fuel chamber,
21 main nozzle, 23 starting pump, 27 increasing fuel passage, 28 constant fuel chamber side part, 29 intake passage side part, 30 check valve, 33 valve shaft, 35 on-off valve,
38 Air passage

Claims (2)

[Claims] 1. A device for supplying starting fuel to an intake system in which a carburetor with a choke valve is installed; the choke in an intake passage extending from a constant fuel chamber of the carburetor across a valve shaft of the choke valve. The increasing fuel passage opened to the downstream side of the valve and the portion of the valve shaft across which the increasing fuel passage intersects the constant fuel chamber side portion and the intake passage side portion of the increasing fuel passage when the choke valve is opened. A starting fuel supply device for an engine, comprising: an opening / closing valve that communicates when closed. 2. The starting fuel supply device according to claim 1, wherein an air passage for introducing the atmosphere into the constant fuel chamber side portion through the opening / closing valve when the choke valve is opened, and the constant fuel chamber side portion. An engine starting fuel supply device, comprising: a check valve which is provided and closes toward the constant fuel chamber.