JPH0515911B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a carburetor that adjusts and controls the concentration and amount of air-fuel mixture supplied to an engine, and particularly relates to a carburetor that is connected to an intake passage that passes through the carburetor body. This invention relates to a constant vacuum carburetor in which a negative pressure responsive valve is disposed within a negative pressure responsive valve guide cylinder to variably control the intake passage area in accordance with the negative pressure generated in the intake passage.

[Prior Art] As is well known, according to the negative pressure responsive valve of such a constant vacuum type carburetor, the negative pressure in the ventilate section formed in the intake passage is a high negative pressure that is almost constant under any operating condition of the engine. Since the fuel is maintained in this state, the fuel sucked out from the needle jet that opens into the ventilate becomes finely atomized.
The combustion state of the engine is improved, and the engine has excellent performance in terms of engine performance, fuel economy, and exhaust gas characteristics.

A specific example will be explained with reference to Fig. 3.
1 is a carburetor body through which an intake passage 31 passes, and a throttle valve 33 is attached to the intake passage 31 to a throttle valve shaft 32 rotatably supported by the carburetor body 30.

A float chamber 35 is formed by the lower recess of the carburetor main body 30 and the float chamber main body 34, and a float 36 is disposed within the float chamber 35. Due to this action, a constant liquid level is formed within the float chamber 35.

On the other hand, a negative pressure responsive valve guide cylinder 37 that opens upward is connected to the middle part of the intake passage 31, and within this negative pressure responsive valve guide cylinder 37, a negative pressure responsive valve 38 that moves within the guide cylinder is installed. The lower part of the negative pressure responsive valve 38 and the intake passage 31 form a ventilate section V.

The effective diameter of the intake passage 31A on the upstream side A (on the right side in the figure) of the negative pressure responsive valve 38 gradually expands and opens to the upstream end 30A of the carburetor main body 30. The side end portion 30A is formed into a planar shape, and a base 39 of an air cleaner for filtering intake air or an air funnel made of wire mesh or the like is disposed thereon.

The negative pressure responsive valve 38 has a lower plate 40, a partition body 41 made of a diaphragm, etc., and an upper plate 42 arranged in this order in a small diameter part provided at the upper part thereof.
By caulking the upper part, they are integrally formed into the negative pressure responsive valve 38.

The partition body 41 is arranged on the carburetor main body concave portion on the outer periphery of the negative pressure responsive valve guide cylinder 37 of the carburetor main body 30, and its upper part is covered with a negative pressure responsive valve cover 43. A pressure receiving chamber P is formed by the negative pressure responsive valve cover 43, and an atmospheric chamber R is formed by the other side of the partition body 41 and the recessed portion of the carburetor body.

Note that 44 is the intake passage 31 at the bottom of the negative pressure responsive valve 38.
This is a negative pressure introduction hole drilled to communicate with the inside of the 45
is a negative pressure responsive valve spring which is compressed in the pressure receiving chamber P and has one end locked to the negative pressure responsive valve cover 43 and the other end to the negative pressure responsive valve 38;
The jet needle is inserted into a needle jet 49 that is connected to the main jet 47 and the mixing tube 48 below a constant liquid level. Reference numeral 50 denotes an atmospheric air introduction passage for introducing atmospheric pressure into the atmospheric chamber R, and opens into the expanding diameter portion of the intake passage 31A upstream of the negative pressure responsive valve 38.

[Problems to be Solved by the Invention] According to the conventional constant vacuum carburetor, when negative pressure is generated in the intake passage 31 as the engine is operated,
The negative pressure is introduced into the pressure receiving chamber P through the negative pressure introduction hole 44, and the pressure within the pressure receiving chamber P exerts an upward suction force on the partition 41, causing a downward pressing force by the negative pressure responsive valve spring 45. The opening degree of the negative pressure responsive valve 38 is regulated by the balance.

In a constant vacuum carburetor that functions as described above, when the throttle valve 32 is opened to a high opening and the engine is operating at high speed, a large negative pressure is generated in the intake passage 31, and this negative pressure is Therefore, the negative pressure responsive valve 38 is pulled up to its maximum open position.

According to a test conducted by the applicant of the suction efficiency of air supplied to the engine when the negative pressure responsive valve 38 is fully open, the upstream side of the carburetor main body 30 in the intake passage 31A upstream of the negative pressure responsive valve 38 Side end 3
It has been found that the suction efficiency is influenced by the distance L to 0A, and that the air suction efficiency is improved by shortening this distance L.

Generally speaking, the intake path 31A upstream of the negative pressure responsive valve 38 is connected to the upstream end 31A of the carburetor main body 30.
It expands continuously and gradually toward A,
When a large amount of air flows through the slope of the upstream intake passage 31A, as when the engine is operating at high speed, a vortex is generated on the slope of the intake passage 31A, and this vortex obstructs the flow of air toward the downstream. It is from.

Now, if we look at the conventional constant vacuum vaporizer,
Negative pressure responsive valve 38 and upstream end 3 of carburetor main body 30
It is possible to reduce the distance L to 0A from the viewpoint of the design of the vaporizer. However, if this distance L is simply shortened, the upstream end 30E for attaching the float chamber body 34 formed in the carburetor body 30
The upstream end 30F for attaching the negative pressure responsive valve cover 43 protrudes from the upstream end 30A where the intake passage 31A of the carburetor main body 30 opens.

This is because the dimensions of the float chamber main body 34 are determined by the size of the float 36, and the negative pressure responsive valve cover 43 is determined by the size of the partition body 41.

According to the above, the upstream end 3 of the carburetor main body 30
It is difficult to make 0A a flat surface, and it forms a concave surface. In particular, when attaching the base 39, these protrusions (upstream ends 30E, 30
F) It is necessary to escape, and the air cleaner base mounting surface has an extremely complicated shape, making installation work difficult, and also causing problems such as loss of compatibility with conventional air cleaners and bases. In view of this problem, it is not possible to easily shorten the distance L between the intake passage 31A upstream of the negative pressure responsive valve 38 and the upstream end 30A of the carburetor body 30, and therefore the intake efficiency is reduced. There was no hope for improvement.

[Means for Solving the Problems] The constant vacuum type vaporizer according to the present invention has been developed in view of these drawbacks, and its main purpose is to provide the vaporizer with high suction efficiency. In order to achieve the above purpose, the following structure is adopted.

That is, a bottomed first intake passage having a bottom is provided downstream from the first upstream end of the carburetor body, and a second upstream side thereof is provided upstream from the bottom of the first intake passage. An intake passage boss whose end does not reach the first upstream end of the carburetor body is provided protrudingly, and an annular passage is formed by the outer periphery of the intake passage boss and the inner periphery of the first intake passage; , the intake passage boss is provided with a second intake passage whose one end opens to the second upstream end and the other end opens to the downstream end of the carburetor body, and a negative A pressure-responsive valve is disposed, and a throttle valve is disposed in the second intake passage downstream of the negative pressure-operated valve.

[Function] According to the above, the distance of the second intake passage upstream of the negative pressure responsive valve, which is located upstream of the negative pressure responsive valve and opens at the second upstream end of the intake passage boss, is The distance of the first intake path, which is located upstream of the responsive valve and reaches the first upstream end of the carburetor main body, can be made smaller than that of the first intake path, thereby achieving improvement in suction efficiency.

[Example] Hereinafter, an example of the constant vacuum type vaporizer according to the present invention will be described with reference to FIGS. 1 and 2. (The same reference numerals are used for the same structure as that of the conventional example, and the explanation is omitted.) 1 is the first upstream end which is the upstream end A of the carburetor main body 2 (the right side in FIG. 1). This is a first intake passage with a bottom formed from the side end portion 2A toward the downstream side B (left side in FIG. 1).
The downstream side (left side) reaches the bottom 1A, and the upstream side (right side) opens to the first upstream end 2A.

A base 3 is placed on this first upstream end 2A.
9 is attached. A bottom portion 1A of the first intake passage 1 reaches near a negative pressure operating valve guide cylinder, which will be described later. 1st
An intake passage boss 3 is erected from the bottom 1A of the intake passage 1 toward the upstream side A.

The second upstream end 3A formed on the upstream side A of the intake passage boss 3 is connected to the first upstream end 3A of the carburetor main body 2.
It does not reach the upstream end 2A, but is located downstream B (on the left side in FIG. 1) from the first upstream end 2A.

Further, an annular passage G is formed by the outer circumference 3B of the intake passage boss 3 and the inner circumference 1B of the first intake passage 1.

A second intake passage 4 is bored in the intake passage boss 3, and the upstream side A of the second intake passage 4 opens to the second upstream end 3A of the intake passage boss 3, and the downstream side B opens to the second upstream end 3A of the intake passage boss 3. It passes through the carburetor body 2 and opens at the downstream end 2B of the carburetor body 2.

A negative pressure responsive valve guide cylinder 5 is provided in the second intake passage 4.
are connected upwardly, and a negative pressure operated valve 38 is disposed within the negative pressure operated valve guide cylinder 5 . Further, a throttle valve 33 that is attached to a throttle valve shaft 32 and opens and closes the second intake passage 4 is disposed in the second intake passage 4 on the downstream side B of the negative pressure operated valve guide cylinder 5.

According to the constant vacuum type carburetor of the present invention having such a structure, the air that has passed through the base 39 such as an air cleaner or air funnel flows into the first intake path 1; The air flows down the second intake passage 4 toward the downstream side B by the intake action of the engine.

In such a state, the upstream facing portion 38A of the negative pressure responsive valve 38 and the second upstream end portion 3 of the second intake path 4
Since the distance L1 from A can be made smaller than the distance L2 between the upstream facing portion 38 of the negative pressure operated valve 38 and the first upstream end 2A of the first intake path 1,
The generation of eddies in the second intake path 4 is suppressed,
This makes it possible to improve the suction efficiency of the air flowing through the second intake passage 4.

Furthermore, as the air flows toward the downstream side B in the first intake passage 1, a vortex is generated on the wall surface of the first intake passage 1, and this vortex flows into the annular passage G.
The vortex flow is prevented from directly entering into the second intake passage 4, and the energy of this vortex flow is weakened within the annular passage G, thereby contributing to improving the suction efficiency.

[Effects of the Invention] As described above, the constant vacuum type vaporizer according to the present invention provides the following effects.

Can increase the amount of air flowing through the intake passage,
It is possible to improve the suction efficiency, and it is particularly effective in improving the output of motorcycle carburetors or competitive car carburetors that require high output.

Base installation of air funnels, air cleaners, etc. can be done using the same dimensions or shapes as before, so they are compatible and can be installed without changing the model. It is something.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the constant vacuum type vaporizer according to the present invention, FIG. 2 is a right side view of FIG. 1,
FIG. 3 is a longitudinal sectional view showing a conventional constant vacuum type vaporizer. 1...First intake path, 1A...Bottom, 1B...Inner periphery, 2...Carburetor body, 2A...First upstream end, 2B...Downstream end, 3...Intake path boss ,3
A... Second upstream end, 3B... Outer periphery, 4... Second intake path, 33... Throttle valve, 38... Negative pressure responsive valve, A... Upstream side, B... Downstream side, G ...A circular passage.

Claims (1)

[Claims] 1. A negative pressure responsive valve is movably arranged in a negative pressure responsive valve guide cylinder connected to an intake passage passing through the carburetor body, and the intake passage is mechanically connected to the intake passage downstream of the negative pressure responsive valve. In a constant vacuum vaporizer equipped with a throttle valve that opens and closes, the first upstream end 2A of the vaporizer main body 2
A bottomed first intake passage 1 having a bottom 1A is provided toward the downstream side B, and a second upstream end 3A thereof is provided toward the upstream side A from the bottom 1A of the first intake passage 1.
The intake passage boss 3 is provided so as to protrude so that it does not reach the first upstream end 2A of the carburetor main body 2, and the outer circumference 3B of the intake passage boss 3 and the inner circumference 1 of the first intake passage 1 are
B forms an annular passage G, and the intake passage boss 3 has one end open to the second upstream end 3A;
A second intake passage 4 whose other end opens at the downstream end 2B of the carburetor main body 2 is provided, a negative pressure operated valve 38 is disposed upstream of the second intake passage, and a negative pressure operated valve 38 is disposed downstream of the negative pressure responsive valve 38. A constant vacuum type carburetor characterized in that a throttle valve 33 is disposed in the second intake path 4.