JPS60142045A - Carburetor for engine associated with supercharger - Google Patents

Abstract

PURPOSE:To eliminate delivery through fuel nozzle by communicating between the float chamber and the downstream of throttle valve through a check valve thereby reducing the high pressure to be produced in the float chamber under deceleration of engine associated with supercharger by means of negative pressure. CONSTITUTION:The float chamber 4 of carburetor 1 having a supercharger in the upstream is communicated through a conduit with the upstream of carburetor to apply supercharged pressure against the liquid face in the float chamber. While the downstream of throttle valve 2 and the float chamber 4 are communicated through a check valve 13 and conduit 7. Upon closing of throttle valve 2 under deceleration of engine, the negative pressure in the downstream of throttle valve 2 will function in the direction to open the check valve 13 where supercharge pressure has been applied onto the check valve 13 thereby the check valve 13 is opened by the combined force to lower the pressure in the float chamber thus to prevent delivery of nozzle through main nozzle 9 and acceleration nozzle 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an improvement in a carburetor for a supercharged engine.

[Background of the invention]

Conventionally, a system in which a carburetor is disposed downstream of a supercharger is disclosed in Japanese Patent Application Laid-Open No. 55-164741. However, with this type of carburetor, during deceleration after high supercharging operation, water is emitted from the carburetor's main nozzle and accelerator pump nozzle.
There was a phenomenon in which unnecessary fuel was discharged, impeding driving performance.

This phenomenon occurs when the high supercharging pressure immediately before deceleration of the vehicle acts on the carburetor intake cylinder due to the inertia of the supercharger, and the pressure inside the float chamber becomes abnormal due to the partial pressure of the venturi of the carburetor. This is because fuel in the float chamber is discharged from the main nozzle or the acceleration pump nozzle due to the pressure difference between the float chamber and a portion of the venturi. The cause of this pressure difference is that the pressure in the venturi part approaches atmospheric pressure in a short time due to the suction negative pressure acting due to the existence of a gap around the throttle valve.
The pressure inside the float chamber is throttled at the outlet by the main jet or accelerator pump nozzle, so it maintains a value close to high pressure (supercharging pressure at the beginning of deceleration) for a relatively long time. This will cause a large pressure difference between the part and the float chamber.

[Purpose of the invention]

The present invention was made in view of the above-mentioned situation, and an object of the present invention is to provide a carburetor for a supercharged engine that can prevent unnecessary fuel from being discharged into an intake cylinder during deceleration operation. It is.

[Summary of the invention]

The carburetor for a supercharged engine of the present invention includes a carburetor disposed downstream of the supercharger, and the carburetor includes an intake cylinder to which a throttle valve is attached, a float chamber, and a main jet in the float chamber. and a main nozzle that communicates with the float chamber via a main fuel passage and opens into a part of the venturi provided in the intake cylinder, and an acceleration pump chamber that communicates with the float chamber through an acceleration fuel passage and opens into a part of the venturi. a pump nozzle, a pressure conduit communicating the downstream side of the throttle valve and the space above the oil surface of the float chamber, and a valve attached to the pressure conduit so as to be biased and closed by the tension of a spring. The valve member is installed to open when a pressure difference between the float chamber side and the throttle valve side of the valve member reaches a predetermined value or more.

That is, as shown in the drawing, a pressure conduit passage connecting the downstream side of the carburetor throttle valve and the float chamber is provided, and a valve member of a one-way switching valve is provided in this passage. The structure is such that the valve seat on the float chamber side is closed by the tension of the spring even during deceleration with high pressure. From this state, high supercharging pressure is applied as shown by the arrow to enter the operating state, and when the next deceleration operation is performed, the pressure difference across the valve member is due to the inertia of the supercharger acting on the float chamber. The floater chamber pressure (PF) in the supercharging pressure (PT) and the high negative pressure (PIM) downstream of the throttle valve act, and this large pressure difference causes the valve member to open, and other than this large pressure difference, the valve member opens. The pushing load (tension) of the spring is selected so as not to open the valve seat, and therefore, at the beginning of deceleration, the venturi partial pressure (Pm) and the float chamber pressure (py
) to prevent a large pressure difference from occurring between the two.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The carburetor for a supercharged engine according to the present invention will be explained below using embodiments and drawings. The figure shows a cross-sectional view, 1 is a vaporizer,
2 is a throttle valve, 3 is a venturi part, 4 is a float chamber, 5 is a main jet, 6 is an accelerator pump nozzle, 7 is a carburetor throttle valve 2
A pressure conduit that communicates the downstream and the space above the oil surface of the float chamber 4, 8
1 is a main fuel passage communicating the main jet 5 and the main nozzle 9, and 10 is an intake cylinder. 11 is an acceleration pump chamber, and 12 is an acceleration fuel passage that communicates the acceleration pump chamber 11 and the acceleration pump nozzle 6. Reference numeral 13 denotes a valve member attached to the pressure conduit 7, which is attached so as to close the valve seat 15 via a spring 14 which is biased so as to press from the downstream side of the throttle valve 2 toward the float chamber 4 side. It is configured to close even during deceleration when the suction pipe negative pressure is large and no supply pressure is applied.

In the above structure, when the acceleration pump is not used, the fuel in the float chamber 4 is transferred to the main nozzle 9 in conjunction with the opening of the throttle valve 2.
During acceleration, fuel is injected from the acceleration pump nozzle 6 via the acceleration pump chamber 11 during acceleration. Then, when the intake pressure PT of the carburetor 1 is high just before deceleration of the vehicle to which supercharging pressure is applied as shown by the arrow,
Next, when the throttle valve 2 is suddenly closed and the intake pipe negative pressure PXM increases, the pressure PA in the venturi part 3 suddenly decreases. 5 and the acceleration pump nozzle 6, a rapid pressure drop cannot be expected, and therefore a large kina pressure will be maintained for a while.

In this case, in a structure where the pressure conduit 7 does not exist,
As mentioned above, the pressure P^ of the venturi part 3 and the float chamber 4
Due to the pressure difference between the internal pressure PF, the fuel in the float chamber 4 passes through the main jet 5, passes through the main fuel passage 8, is discharged from the main nozzle 9 into the intake cylinder IO, and is also discharged from the acceleration pump chamber 11 into the acceleration pump chamber 11. The fuel is discharged from the acceleration pump nozzle 9 into the intake cylinder 10 via the fuel passage 12 .

However, in the structure including the pressure conduit 7 of this embodiment, the high intake pipe negative pressure downstream of the throttle valve 2 at the beginning of deceleration weakens the restraining load (tension) of the spring 14 restraining the valve member 13. Acts on the direction. At the same time, high supercharging pressure (positive pressure) in the float chamber 4 acts in a direction to open the valve member 13 from the valve seat 15,
The resultant force of the intake pipe negative pressure downstream of the throttle valve 2 and the supercharging pressure in the float chamber becomes greater than the restraining load (tension) of the spring 14, the valve member 13 is separated from the valve seat 15, and the intake pipe negative pressure is reduced to the float chamber. 4. Therefore, the pressure PF in the float chamber 4 rapidly decreases and is adjusted to be approximately equal to the pressure PA in the venturi portion 3.

In this way, the carburetor for a supercharged engine of this embodiment is provided with a pressure conduit that communicates between the downstream side of the throttle valve and the float chamber, and the pressure in the float chamber is transmitted through this pressure conduit to the downstream side of the throttle valve. A valve member is provided that opens when the pressure is higher than a predetermined value, so a pressure difference will not occur between the float chamber and a portion of the venturi inside the intake cylinder during deceleration after high supercharging operation. This prevents unnecessary fuel discharge and improves running performance and drivability.

〔Effect of the invention〕

As described above, in the carburetor for a supercharged engine of the present invention, unnecessary fuel is removed from the intake cylinder during deceleration operation. This has the effect of preventing discharge and improving drivability.

[Brief explanation of drawings]

The figure is a longitudinal cross-sectional view of an embodiment of a carburetor for a supercharged engine according to the present invention. 1... Carburetor, 2... Throttle valve, 3... Venturi part, 4... Float chamber, 5... Main jet, 6...
- Acceleration pump nozzle, 7... Pressure conduit, 8... Main fuel passage, 9... Main nozzle, 10... Intake cylinder, 11... Acceleration pump chamber, 12... Acceleration fuel passage,
13... Valve member, 14... Spring.

Claims (1)

[Claims] 1. A carburetor is disposed downstream of the supercharger, and the carburetor communicates with an intake cylinder to which a throttle valve is attached, a float chamber, and the float chamber via a main jet and a main fuel passage. A main nozzle that is open to a part of a venturi provided in the main nozzle, and an acceleration pump nozzle that is communicated with the float chamber through an acceleration pump chamber and an acceleration fuel passage and that is opened to a part of the venturi, A pressure conduit communicating the downstream side of the throttle valve and the space above the oil level of the float chamber, and a valve member attached to the pressure conduit so as to be biased and closed by the tension of a spring are provided. A carburetor for a supercharged engine, characterized in that the valve member is installed to open when a pressure difference between the float chamber side and the throttle valve side exceeds a predetermined value.