JPS626276Y2 - - Google Patents

Description

[Detailed explanation of the idea] This invention relates to an improvement in a carburetor for an internal combustion engine.

There is an air passage from the bench lily to the intake pipe via the throttle valve downstream of it, a main fuel passage (main passage) from the float chamber to the main jet to the nozzle opening into the bench lily, and a throttle valve from the float chamber via the slow jet. Conventional carburetors have a low-speed fuel passage (slow passage) leading to a slow port that opens on the downstream side of the throttle valve at a predetermined opening, but when the intake air amount is large and the intake pipe negative pressure is small, The air-fuel ratio tends to be lean (too lean), and when the intake pipe negative pressure is large, the air-fuel ratio tends to become rich even at low loads when the amount of intake air is small, which affects drivability during acceleration and at low loads. This was a less favorable characteristic than in terms of fuel efficiency.

In view of the above, the purpose of this invention is to propose a carburetor that improves both fuel efficiency and drivability by keeping the air-fuel ratio lean during low loads and rich during acceleration.

In conventional carburetors, the opening of the low-speed fuel passage, that is, the slow port, which is the fuel outlet, is generally located downstream of the throttle valve. Therefore, the diagram of the air-fuel ratio (A/F) with respect to the intake air amount is not horizontal. The reason for this is that even when the amount of intake air is constant, when the intake pipe negative pressure applied to the low-speed fuel passage (slow passage) is large, the slow passage fuel (slow flow rate) increases and the air-fuel ratio becomes rich; This is because when the pressure is low, the slow flow rate decreases and the air-fuel ratio becomes lean.

In a normal carburetor, when the throttle valve is at a low opening, that is, when the amount of intake air is small, the slow port is located astride the downstream and upstream sides of the throttle valve, and the throttle valve opens more than a predetermined amount. The slow port is always located on the downstream side of the throttle valve, and as shown in Figure 1, the characteristics of the slow passage negative pressure with respect to the intake air amount are such that when the amount of air exceeds a predetermined amount, the intake pipe negative pressure The slow passage negative pressure is different.

The fuel flow rate in the main passage flows out according to the amount of intake air, so when the amount of intake air exceeds a certain value, it increases proportionally. Since it flows out in accordance with the negative pressure, as is clear from Figure 2, more air flows out when the intake pipe negative pressure is 360 mmHg than when it is -120 mmHg.

When the fuel flow rates in both the slow passage and the main passage are combined, the characteristics shown in FIG. 3 are obtained. Intake pipe negative pressure is -360mm
If the characteristics of the total fuel flow rate in Figure 3 are designed so that the air-fuel ratio is constant when Hg is applied, the total fuel flow rate at -120mmHg will be the fuel flow rate when the air-fuel ratio is constant at a predetermined amount of air or more, as shown in Figure 3. less.

Therefore, as shown in FIG. 4, when the amount of air exceeds a predetermined amount, the air-fuel ratio (A/F) becomes leaner as the intake pipe negative pressure becomes smaller. Also, in areas where the intake pipe negative pressure is large, there is a tendency for the intake pipe to become rich. This causes problems such as deterioration of drivability and fuel efficiency. In particular, when the intake air amount is B' in Figures 1 to 4 and the intake pipe negative pressure is -360 mmHg at point C', the throttle is opened to accelerate, and the intake air amount A',
When the intake pipe negative pressure becomes -120 mmHg, some of the fuel supplied from the carburetor adheres to the intake pipe and becomes lean, and the air-fuel ratio becomes lean because the operating conditions shift from point C' to point D'. At the same time as this, the air-fuel ratio supplied to the engine becomes leaner, deteriorating vehicle drivability and emitting more NOx components in the exhaust gas.

Conversely, in order to decelerate, the operating conditions change from point D′.
As we move to point C', the air-fuel ratio supplied by the carburetor becomes rich, the negative pressure in the intake pipe rises, the fuel in the intake pipe evaporates, and the amount of fuel supplied increases. The problem is that the fuel ratio becomes rich and more HC is emitted.

This idea eliminates these problems, and includes an air passage from the bench lily to the intake pipe via the downstream throttle valve, a main passage from the float chamber to the nozzle opening into the bench lily via the main jet, and a main passage from the float chamber to the nozzle opening into the bench lily. In a carburetor having a slow passage from the slow jet to the slow port that opens on the downstream side of the throttle valve when the throttle valve is at a predetermined opening degree, there is a slow passage facing the first diaphragm 9 having a small area. A pressure chamber 19, a negative pressure chamber 20 sandwiched between the first diaphragm 9 and a second diaphragm 10 having a larger area, and the second diaphragm 10.
A regulator 8 is provided in which atmospheric chambers 21 facing the air are arranged adjacent to each other in order, and the center portions of the first diaphragm 9 and the second diaphragm 10 are connected to a valve 16, and the valve 16 and a seat cooperating therewith are connected to each other. 1
Atmospheric chamber 2 via pressure control valve 18 consisting of
1 to the slow passage 3, and the atmospheric chamber 2
1 is communicated with the opening 25 upstream of the throttle valve via the communication passage 24, furthermore, the pressure regulating chamber 19 is communicated with the slow passage 3, the negative pressure chamber 20 is communicated with the opening 27 of the intake pipe 7, and the valve 16 is kept open at all times. A double diaphragm leg is provided with a spring 22 that biases it toward the closing side, and the valve 16 is set to move away from the seat 17 when the negative pressure in the pressure regulating chamber 19 or the negative pressure chamber 20 increases. It is a vaporizer with a urator.

The following description will be made based on the embodiments shown in the drawings.

In FIG. 5, the carburetor 1 includes a slow passage 3 communicating with a slow port 2. As shown in FIG. 4 is an idle port, 5 is a throttle valve, 7 is an intake pipe, and the slow passage 3 communicates with the float chamber via a slow jet (not shown). Further, the slow port 2 is located near the tip of the throttle valve 5 when the opening degree of the throttle valve 5 is small, and
When the throttle valve 5 reaches a predetermined opening degree or more, it is always located on the downstream side of the throttle valve. Further, a main passage (not shown) opens into the float chamber at one end, communicates with a main nozzle which opens into the bench lily portion of the carburetor at the other end, and is provided with a main jet in a portion close to the float chamber. A regulator 8 has an upper cover 11, a center cover 12, and a lower cover 13 that airtightly sandwich the peripheries of a small-diameter diaphragm 9 with a small area and a large-diameter diaphragm 10 with a large area, and both diaphragms 9 and 10 are located at the center. portion is held between members 14, 15 and valve 16. In other words, member 14,1
5 and the valve 16 are integrally fixed across both diaphragms. The lower surface of the valve 16 cooperates with a seat 17 formed on the lower cover 13 to form a pressure control valve 18 . The atsupah cover 11 and the diaphragm 9 control the pressure regulation chamber 19, and the center cover 1
2 and both diaphragms 9 and 10 form a negative pressure chamber 20, and the lower cover 13 and diaphragm 10 form an atmospheric chamber 21.
form each. Spring 22 biases valve 16 downwardly. The slow passage 3 is connected to the pressure regulating chamber 19 via the communication passage 23, and to the pressure control valve 1 through the communication passage 23'.
It communicates with the atmospheric chamber 21 via 8. Atmospheric chamber 2
1 is connected to the throttle valve 5 via another communication path 24.
It communicates with the upstream opening 25 of. The negative pressure chamber 20 communicates with an opening 27 of the intake pipe 7 via a communication passage 26 . Therefore, the slow passage negative pressure is in the pressure regulating chamber 19, the intake pipe negative pressure is in the negative pressure chamber 20, and the pressure in the upstream opening 25 of the throttle valve 5 and the pressure in the upstream opening 25 of the throttle valve 5 is in the atmospheric chamber 21 via the pressure control valve 18. A slow passage negative pressure is applied respectively.

With this configuration, when the negative pressure in the intake pipe 7 is at the normal intermediate pressure, if the negative pressure in the slow passage 3 is large, the negative pressure in the pressure adjusting chamber 19 moves the valve 16 upward against the spring 21, and the pressure control valve 18
The pressure from the opening 25 is increased to the atmospheric chamber 21.
The negative pressure in the slow passage 3 decreases as the negative pressure in the pressure adjusting chamber 19 decreases, and the valve 16 moves downward by the force of the spring 21.
The opening of the pressure control valve 18 is reduced to open the slow passage 3.
In this way, the pressure adjusting chamber 19 sets the pressure in the slow passage 3 to a predetermined pressure. To make it easier to understand the function of this pressure adjusting chamber 19, let us assume that the pressure in the negative pressure chamber 20 is fixed at a constant value. When the intake pipe negative pressure exceeds a certain value, the pressure adjusting chamber adjusts the negative pressure applied to the slow passage to the predetermined pressure, and works to maintain the air-fuel ratio at a constant value regardless of the intake pipe negative pressure. In reality, the intake pipe negative pressure is applied to the negative pressure chamber 20, so the fifth
The carburetor in the figure further works as follows: When the intake air amount is A in Fig. 6 to Fig. 9, if the negative pressure in the intake pipe 7 transmitted to the negative pressure chamber 20 is small, at -120mmHg, the force acting on the valve 16 is greater than the upward force caused by the pressure difference between the top and bottom of the second diaphragm with a larger diameter, by the downward force caused by the pressure difference between the top and bottom of the first diaphragm with a smaller diameter and the downward force caused by the spring 22, so that the valve 16 is pressed against the seat 17, the opening of the pressure control valve 18 becomes smaller, and it becomes difficult for the bleed to enter the slow passage 3 via the regulator 8, the negative pressure in the slow passage 3 becomes larger, the slow fuel flow rate increases, and the air-fuel ratio becomes rich.

On the other hand, when the intake air amount remains at A and the negative pressure inside the intake pipe 7 becomes -360 mmHg, the force applied to the valve 16 is pushed upward by the pressure difference between the upper and lower sides of the second diaphragm, which has a larger diameter. However, the force pushing downward due to the pressure difference between the upper and lower sides of the first diaphragm with a small diameter and the spring 2
2, the force pushing downward becomes stronger, and the valve 16
is separated from the seat 17, the opening degree of the pressure control valve 18 increases, and bleed easily enters the slow passage 3 through the regulator 8, the negative pressure in the slow passage becomes smaller, the slow fuel flow rate decreases, and the air-fuel ratio increases. Become Lean.

As it works as described above, the effect is that when the intake air amount is B in Figures 6 to 9, the throttle valve is opened to accelerate from point C where the intake pipe negative pressure is -360 mmHg, and the intake air amount is is A, and the intake pipe negative pressure is -
Some of the fuel that is set at the D point of 120mmHg will adhere to the intake pipe, but the air-fuel ratio supplied by the carburetor will be richer, so the engine's air-fuel ratio will be less lean, improving drivability. of exhaust gas
The amount of NOX generated can also be reduced. Conversely, when moving from point D to point C to decelerate, the fuel adhering to the intake pipe evaporates and enters the engine, but the air-fuel ratio supplied by the carburetor becomes lean, so the
It has the effect of reducing the occurrence of HC. Furthermore, when the negative pressure in the intake pipe of the vehicle is -360 mmHg in a steady running state, the air-fuel ratio becomes leaner than when it is -120 mmHg in an accelerating state, so it is possible to improve fuel efficiency.

[Brief explanation of the drawing]

Figures 1 to 4 are characteristic diagrams of a conventional carburetor, Figure 5 is a sectional view of an embodiment of this invention, and Figures 6 to 9 are characteristic diagrams of a carburetor of this invention. . DESCRIPTION OF SYMBOLS 1... Carburetor, 2... Slow port, 3... Slow passage, 4... Idle port, 5... Throttle valve, 7... Intake pipe, 8... Regulator, 9... First diaphragm, DESCRIPTION OF SYMBOLS 10... Second diaphragm, 16... Valve, 17... Seat part, 18... Pressure control valve, 19... Pressure regulation chamber, 20
... Negative pressure chamber, 21 ... Atmospheric chamber, 22 ... Spring, 2
3, 23'... Communication path, 24, 26... Communication path,
25, 27...opening.

Claims (1)

[Scope of utility model registration request] The air passage from the bench lily to the intake pipe via the throttle valve downstream of it, the main passage from the float chamber to the nozzle opening into the bench lily via the main jet, and the air passage from the float chamber via the slow jet to the intake pipe when the throttle valve is at a predetermined opening. In a carburetor that has a slow passage leading to a slow port that opens on the downstream side of the throttle valve, there is a pressure regulating chamber 19 facing the first diaphragm 9 having a small area, and a pressure regulating chamber 19 facing the first diaphragm 9 which has a small area. A regulator 8 is provided in which a negative pressure chamber 20 sandwiched between a second diaphragm 10 having a large area and an atmospheric chamber 21 facing the second diaphragm 10 are arranged adjacent to each other in order, and the first diaphragm 9 and Second
A central portion of the diaphragm 10 is connected to a valve 16, and a seat 17 cooperating with the valve 16 is connected to the valve 16.
Atmospheric chamber 21 via pressure control valve 18 consisting of
is connected to the slow passage 3, and the atmospheric chamber 21
communicates with the opening 25 upstream of the throttle valve via the communication passage 24, further communicates the pressure regulating chamber 19 with the slow passage 3, the negative pressure chamber 20 with the opening 27 of the intake pipe 7, and closes the valve 16 at all times. Spring 2 that biases toward the side
2, the valve 16 is connected to the pressure regulating chamber 19 or the negative pressure chamber 2.
A carburetor with a double diaphragm regulator, characterized in that it moves in a direction away from a seat 17 as the negative pressure at zero increases.