JPH0614045Y2 - Slow fuel supply device for carburetor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a slow fuel supply device for a carburetor provided in an internal combustion engine.

2. Description of the Related Art A conventional slow fuel supply device of this type will be described with reference to FIG. 1 showing an embodiment of the present invention.

The slow system of the illustrated carburetor is called a single bleed type slow system, and the air bleeding is performed to the slow jet 43 only from the right side of the drawing. A branch passage 31 communicates with a portion of the lateral passage 47 on the right side of the slow jet 43, and a tip of the branch passage 31 opens into the large venturi 12 to form a slow air bleed port 33. With this configuration, during low speed operation such as idle operation, the air flowing in from the slow air bleed port 33 is guided from the right side to the slow jet 43 and mixed with the fuel, and the air-fuel mixture is discharged from the slow port 30. It On the other hand, during high speed operation, the negative pressure introduced from the slow air bleed port 33 causes the fuel to constantly flow in the slow fuel passage, so that the throttle valve 16 can be smoothly idled even if the throttle valve 16 is suddenly idled. The fuel is not discharged to the so-called back bleed phenomenon.

It should be noted that Japanese Utility Model Laid-Open No. 52-129830 and Japanese Patent Laid-Open No. 57-186047 are publicly known prior to the filing of the present application as showing a configuration similar to the present invention described later.

Problems to be Solved by the Invention In the above conventional device, when the engine is stopped at high temperature, the fuel temperature of the carburetor rises, which causes percolation and siphon phenomenon in the passage of the slow system to cause slow air bleed. Port 33, slow port 3
0 or the idle port 32 may flow out. In other words, the air-fuel mixture may become too rich and the engine restartability or evaporative emission may deteriorate. As another conventional technique, Japanese Patent Laid-Open No. 50-11
In the 6829 publication, an on-off valve that operates by negative pressure in the intake pipe is provided, and when the engine is stopped, the atmosphere is introduced into the slow passage fuel passage above the oil level in the float chamber to prevent the siphon phenomenon. Although described, in this system, the introduction of the atmosphere by the on-off valve is stopped at the time of low load when the intake pipe negative pressure becomes high, so the air-fuel mixture becomes rich and problems occur in startability and idle stability, On the contrary, since the air introduction by the on-off valve is restarted at the time of high load when the intake pipe negative pressure becomes low, back bleeding may occur and the transition from high load operation to low load operation may not be performed smoothly.

The present invention aims to solve various problems of these conventional techniques.

Means for Solving the Problems In order to solve the above problems, the present invention relates to a vertical passage having a slow fuel passage communicating with a float chamber and extending in the vertical direction and intersecting the upper end of the vertical passage. Connected to the horizontal passage at a position higher than the oil level of the float chamber and extending in the horizontal direction, and a slow port communicating with the horizontal passage and opening in the vicinity of the throttle valve. Inside the large venturi formed on the downstream side of the small venturi inside and communicating with the slow air bleed port that opens at a position below the oil level in the float chamber, and intersects the vertical passage and the horizontal passage. A slow jet is provided in the portion, and the slow jet connects the vertical passage to the slow port and the slow air bleed port through a small hole provided in the slow jet. The air introduced from the slow air bleed port is guided to the slow jet and mixed with the fuel from the vertical passage, and the mixture is discharged from the slow port into the intake passage. In order to allow the atmosphere to be introduced into a portion of the slow fuel passage above the oil level in the float chamber, an atmosphere passage opened near the small venturi of the intake passage or at a position upstream of the small venturi is connected to the engine. Slow system fuel supply for a carburetor, characterized in that it is connected between the slow air bleed port and the slow jet through a valve device that opens when the engine is stopped and started and when the intake pipe negative pressure is high. Provide a device.

In the slow fuel supply device for the carburetor according to the present invention, the atmosphere passage is connected to the slow air bleed port and the slow jet via the valve device that opens when the engine is stopped and when the intake pipe negative pressure is high. First, when the engine is stopped, the atmosphere is introduced between the slow air bleed port and the slow jet, and the portion of the slow fuel passage above the oil level in the float chamber is at atmospheric pressure. To the gas phase. Therefore, the fuel is blocked at this portion, and the fuel is prevented from flowing out into the intake passage due to the percolation and the siphon phenomenon.
As described above, the fuel does not overflow into the intake passage while the engine is stopped, so that the engine is restarted smoothly and the idle stability is not deteriorated.

In the slow fuel supply device of the carburetor according to the present invention, the atmosphere is introduced between the slow air bleed port and the slow jet even when the intake pipe negative pressure is high such as at the time of starting and idling or low load. Therefore, the slow air bleed is performed by both this air and the air introduced from the slow air bleed port, and it becomes possible to mix a large amount of air with the slow fuel. Moreover,
Since all of these air is guided to the slow port via the slow jet, neither of the air is directly sucked into the intake pipe due to the negative pressure of the intake pipe, and the fuel corresponding to the air is sucked out in the slow jet. Therefore, the air is not excessive with respect to the fuel. For this reason, appropriately metered air is sufficiently supplied to the fuel passage of the slow system, and it is prevented that the air-fuel ratio becomes excessively rich, which also contributes to improvement of startability and idle stability.

At high load, when the opening of the throttle valve increases, the intake negative pressure acting on the slow jet from the slow port decreases. If the atmospheric passage is left open at this time, the force in the vertical passage that causes the fuel to return to the float chamber due to its own weight and the force that pulls the fuel toward the slow port due to the negative intake pressure are balanced, There is a possibility that a portion of the fuel passage above the oil level in the float chamber is filled with air, and further, there is no fuel in the passage from this portion to the slow port. If the operation shifts to the low load operation in this state, the fuel is not immediately supplied from the slow port, which should originally be supplied with the fuel when the load is low, and the operating condition becomes unsmooth. In the slow fuel supply device of the carburetor of the present invention, since the atmospheric passage is closed at such a high load, the intake negative pressure from the slow air bleed port which increases at the time of the high load causes the suction oil to suck up the fuel oil in the vertical passage. The reduction of the surface is prevented, and the transition from the high load state to the low load state is smoothly performed.

Embodiments The present invention will be described below with reference to illustrated embodiments.

In FIG. 1, reference numeral 10 is a main body of a carburetor, in which a small venturi 14 is located above and inside a large venturi 12, and a throttle valve 16 is located downstream of the small venturi 14.
A main nozzle 18 is provided in the small venturi 14 and communicates with a float chamber 22 via a main fuel passage 20.

A slow port 30 is provided near the throttle valve 16 in the idle position, an idle port 32 is located downstream thereof, and the idle port 32 communicates with the slow port 30 via an idle adjusting screw 34.

The slow fuel passage communicates with the float chamber 22 and extends vertically upward, a horizontal passage 47 connected to the upper end of the first vertical passage 39 and extending in the horizontal direction, and the horizontal passage 47. The second vertical passage 38 is connected to the left end portion and extends vertically downward. The slow port 30 is provided at the lower end of the second vertical passage 38. The slow jet 43 is provided in the first vertical passage 39, and its throttle portion is provided in the first vertical passage 3
9 and the lateral passage 47 are connected to each other.

The air bleeding means is provided on the right side of the slow jet 43 in the middle of the lateral passage 47 and includes a slow air bleed jet 42 and an idle air bleed jet 44. The slow air bleed jet 42 has a lateral passage 47.
Is formed in the branch passage 31 communicating with the right side portion of the slow jet 43 of the large venturi 1
It has a slow air bleed port 33 opening to 2.
The idle air bleed jet 44 is formed on the right side of the drawing with respect to the connection portion of the lateral passage 47 with the branch passage 31, and is connected to the atmosphere via a three-way switching valve 70 and an opening / closing valve 48 provided at the right end of the lateral passage 47. Can be introduced.

The on-off valve 48 is a negative pressure actuated diaphragm 481 that opens and closes depending on whether the engine is idle or not, and the diaphragm 481 is connected to the valve body 482. Disc 482
Is a chamber 48 that can communicate with the passage 47 through the three-way switching valve 70.
3 and the chamber 484 communicating with the atmosphere passage 50 connected to the vicinity of the small venturi 14 of the intake passage or upstream thereof are controlled according to the pressure of the chamber 485 below the diaphragm 481. The spring 486 applies a force to the diaphragm 481 such that the valve body 482 blocks the chamber 483 and the chamber 484, that is, a force to raise the valve body 482. Room 4
Reference numeral 85 communicates with the idle sensing port 64 slightly downstream of the idle position of the throttle valve 16 via the passage 62.

The three-way switching valve 70 connects the lateral passage 47 to the chamber 483 of the opening / closing valve 48.
Alternatively, the solenoid 7 is selectively communicated with the atmosphere passage 50.
Switching control is performed by 2. The solenoid 72 is the control unit 7.
4 is de-excited by outputting a signal indicating whether or not the engine has completed a complete explosion, and is excited by the complete explosion signal to switch the three-way valve 70 to the side for connecting the passage 47 and the chamber 483. The control unit 74 determines whether or not a complete explosion has occurred based on the intake pipe negative pressure or the engine speed, and outputs a complete explosion signal.
As shown in the figure, the three-way switching valve 70 connects a part of the slow system fuel passage, which is higher than the oil level of the float chamber, to a part near the small venturi 14 or an upstream part thereof, or shuts off from this part. ..

Next, the operation of the apparatus of this embodiment having the above configuration will be described.

When the engine is stopped, the three-way switching valve 70 connects the lateral passage 47 to the atmosphere passage 50, and the open / close valve 48 is closed. When cranking is performed here and the engine is completely detonated, the solenoid 72 is excited via the control unit 74, and the three-way switching valve 7
0 connects the lateral passage 47 to the chamber 483 of the on-off valve 48.
Then, during idle operation, idle sensing port 6
4 is a downstream side of the throttle valve 16 and the negative pressure generated in the vicinity thereof is guided to the chamber 485, whereby the valve body 482 is sucked downward and opens the passage. Therefore, the atmosphere in the vicinity of the small venturi 14 or at the upstream side of the small venturi 14 is not affected by the atmosphere passage 5
0, the on-off valve 48, the three-way switching valve 70 and the lateral passage 47, and is guided to the idle air bleed jet 44, and the atmosphere flowing from the slow air bleed port 33 is guided to the slow air bleed jet 42 of the branch passage 31. Thus, air bleeding takes place via both these jets 42,44. The opening degree of the throttle valve 16 becomes large, and the end portion of the throttle valve 16 has an idle sensing port 64.
When it comes to the downstream side, the inside of the chamber 485 becomes atmospheric pressure, so the valve body 4
82 rises to block the passage. Therefore, the air bleed through the idle air bleed jet 44 is stopped.

When the engine is stopped, the three-way switching valve 70 turns the lateral passage 47
Is communicated with the atmosphere passage 50, and the atmosphere in the vicinity of the small venturi 14 of the intake passage or upstream thereof is introduced into the slow fuel passage. Therefore, even if the fuel in the carburetor is partially vaporized and percolation occurs at high temperature,
Since the atmosphere is filled in the lateral passage 47, the fuel does not flow out of the slow air bleed port 33, the slow port 30, the idle port 32 and the like into the intake passage due to the siphon phenomenon.

Next, when cranking is performed to restart the engine, the three-way switching valve 70 keeps the lateral passage 4 during the cranking.
7 communicates with the atmosphere passage 50. Therefore, air bleeding is performed through both the slow air bleed jet 42 and the idle air bleed jet 44, the air-fuel ratio of the air-fuel mixture is prevented from becoming rich, and the restart is smoothly performed.

As described above, according to the present invention, even if the engine is stopped at a high temperature, there is no risk of fuel flowing out from the slow air bleed port, the slow port, the idle port, etc., and the mixture becomes rich. Is prevented, the restartability of the engine is improved, and the evaporative emission is improved.

Further, even at the time of starting or low load, the atmosphere is introduced between the slow air bleed port and the slow jet, and the air bleeding of the slow system is performed by both this air and the air introduced from the slow air bleed port. Therefore, the air-fuel ratio is prevented from becoming excessively high, and the startability and idle stability are improved.

Moreover, when the load is high, the atmosphere passage is closed to return to the original slow air bleed state, so there is no risk of fuel interruption in the slow system, and the transition from the high load state to the low load state is performed smoothly. Slow fuel control suitable for all engine conditions is performed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention. 12 ... Large venturi, 14 ... Small venturi, 16 ...
… Throttle valve, 22 …… Float chamber, 30 …… Slow port, 33 …… Slow air bleed port, 39 ……
Vertical passage, 43 ... Slow jet, 47 ... Horizontal passage, 4
8 ... Open / close valve, 50 ... Atmosphere passage, 70 ... Switching valve.

Claims (1)

[Scope of utility model registration request] Claim: What is claimed is: 1. A slow fuel passage communicates with a float chamber and extends in the vertical direction, and a horizontal passage at a position higher than the oil level of the float chamber by intersecting with and connecting to an upper end of the vertical passage. And a slow port communicating with the lateral passage and opening near the throttle valve.The lateral passage is in a large venturi formed on the downstream side of the small venturi in the intake passage. The slow jet is provided at the intersection of the vertical passage and the horizontal passage, which communicates with the slow air bleed port that opens below the oil level in the float chamber. The vertical passage is communicated with the slow port and the slow air bleed port through a small hole, and the air introduced from the slow air bleed port receives the sludge. The fuel is introduced into the jet and mixed with the fuel from the vertical passage, and the mixture is discharged from the slow port into the intake passage. The atmosphere passage that opens near the small venturi of the above-mentioned intake passage or at a position upstream of it so that the atmosphere can be introduced into the portion above the surface A slow-system fuel supply device for a carburetor, which is connected between the slow air bleed port and the slow jet via a valve device that opens when the temperature is high.