JPH0670410B2 - Sliding throttle valve type carburetor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sliding throttle valve type carburetor, and in particular to a vacuum piston which constitutes a variable venturi in response to negative pressure of a venturi, and an operation of an accelerator lever or the like. The present invention relates to an improvement of a sliding throttle valve type carburetor that is provided with a throttle valve that controls an intake flow rate.

<Prior Art> A variable Venturi type carburetor with a sliding throttle valve is commonly used as a carburetor for motorcycles because it can exhibit good engine performance over a wide operating range and can be made smaller and lighter. As such a vaporizer, there are a vaporizer called an Amal type and a vaporizer called a CV type.

The former is to change the venturi diameter of a sliding piston valve that is installed across the intake passage by directly operating it with an accelerator lever, but the throttle valve and the venturi piston are common. From
There is an advantage that the structure is simple and there is no remaining intake resistance in the intake passage when the throttle valve is fully opened, and the intake efficiency is extremely high. Also, since the driver controls the venturi diameter by itself, the reaction of the engine to the accelerator operation is sensitive, but when the throttle valve is suddenly opened, the balance between the engine speed and the intake air amount is momentarily balanced. Breathing may occur due to collapse, and the driver is required to perform delicate accelerator control.

In the latter, the throttle valve and the Venturi piston are separate units, and the Venturi piston automatically operates according to the intake air flow velocity of the Venturi part, so the intake air amount that is always adapted to the rotation speed is controlled, and it is easy to use. However, if a time lag occurs between the operation of the throttle valve and the venturi piston, sharp sensitivity of the accelerator response may be hindered. Further, since a butterfly valve is generally used as the throttle valve, the valve shaft becomes an intake resistance when the throttle valve is fully opened, and the structure tends to be relatively complicated. (See Japanese Patent Laid-Open No. 59-32660) <Problems to be Solved by the Invention> In view of the advantages and disadvantages of the sliding throttle valve type carburetor according to the conventional art, the main object of the present invention is to It is an object of the present invention to provide a sliding throttle valve type carburetor capable of smoothing the intake stroke, reducing the suction resistance, and improving the response of the engine.

<Means for Solving Problems> According to the present invention, such a purpose is to provide a vacuum piston connected to a passive body that responds to a negative pressure of a venturi, and a throttle valve that opens and closes an intake passage by a driver's operation. A throttle valve type carburetor having a flat plate shape in which the throttle valve slides along a guide groove formed in the carburetor main body across the intake passage, and is the same as the throttle valve. It is achieved by providing a sliding throttle valve type carburetor characterized in that it has a receiving portion that slidably receives the vacuum piston, and an engagement means that defines a stroke of the vacuum piston. .

<Operation> As described above, by making the throttle valve an opening / closing valve that slides in the groove provided in the carburetor main body, the inner surface of the intake passage can be smoothed and the intake resistance can be reduced.

In addition, the vacuum piston is placed along the throttle valve, and the stroke is regulated by engaging with the throttle valve to prevent overshoot of the vacuum piston, improve the interlocking with the throttle valve, and improve the transient performance. Is possible.

<Embodiment> Hereinafter, the present invention will be described in detail with reference to a specific embodiment with reference to the accompanying drawings.

FIG. 1 shows the entire variable venturi type carburetor according to the present invention. Inside the carburetor main body 1, a main intake passage 2 extending in the left-right direction in FIG. 1 is provided. . The main intake passage 2 has an air horn 2a that is smoothly curved and expanded toward the upstream side at the upstream end along the intake direction A,
It is connected to an air cleaner (not shown) so that clean air can be introduced.

A guide groove 3 is provided in a substantially central portion of the main intake passage 2 in a direction substantially orthogonal to the intake streamline, and in the guide groove 3,
A throttle valve 4 is provided slidably so that the main intake passage 2 can be opened and closed by a pair of partition plates 4a and 4b. The throttle valve 4 is adapted to be remotely operable via a throttle lever (not shown) by engaging with a connecting mechanism 6 provided on a throttle shaft 5 pivotally supported by the carburetor body 1. .

A vacuum piston 7 having a rectangular cross section is provided between the pair of partition plates 4a and 4b of the throttle valve 4 so as to slide along the same sliding shaft as the throttle valve 4.
A hollow connecting rod 8 having one end fixed to the vacuum piston 7 extends upward from the vacuum piston 7 along the sliding axis of the vacuum piston 7.

The upper opening of the carburetor main body 1 is closed by a cover member 9. Between the opening and the cover member 9, an outer peripheral portion of a circular diaphragm 10 made of a rubber material or the like is sandwiched. A negative pressure chamber 11 is formed inside the cover member 9, and an atmosphere chamber 1a is formed inside the carburetor body 1.

At the center of the diaphragm 10, the diaphragm retainer 12
Is fixed, and the other end of the above-mentioned connecting rod 8 is fixed to the center thereof. As described above, the connecting rod 8 is hollow, and the main intake passage 2 is introduced into the negative pressure chamber 11 through the negative pressure introducing hole (not shown) formed in the lower portion of the vacuum piston 7.
The internal pressure can be introduced. Further, a compression coil spring 13 is contracted between the cover member 9 and the diaphragm retainer 12, and always urges the vacuum piston 7 downward via the connecting rod 8.

A variable venturi portion 14 is formed between the lower end of the vacuum piston 7 and the inner wall of the main intake passage 2 facing the vacuum piston 7, and by introducing the venturi negative pressure into the negative pressure chamber 11 as described above. The vacuum piston 7 can be raised in accordance with the increase in the Venturi negative pressure.

A main fuel nozzle 15 is provided inside the main intake passage 2 facing the variable venturi portion 14, and inside the nozzle 15,
A jet needle 16 having a tapered shape is inserted. The jet needle 16 is connected to the vacuum piston 7 described above, and is adapted to be capable of appearing and retracting with respect to the main fuel nozzle 15 according to the movement of the vacuum piston 7.
Thus, the jet diameter of the main fuel nozzle 15 is changed in accordance with the increase or decrease in the diameter of the variable venturi portion 14, and the discharge amount of fuel can be automatically adjusted.

An air bleed pipe 17 is connected to an intermediate portion of the main fuel nozzle 15 from diagonally below. The end of the air bleed pipe 17 projects below the fuel level of a float chamber 18 formed in the lower part of the carburetor main body 1, and a main fuel jet 19 for measuring the fuel flow rate is formed at the open end thereof. There is. A large number of small holes are formed in the air bleed tube 17, and the vaporizer body 1
The air introduced from the main air introduction passage formed inside is mixed with the fuel, and the emulsified air-fuel mixture is delivered to the main fuel nozzle 15.

Inside the float chamber 18, a slow jet 20 and a byaster jet 21 are arranged side by side substantially parallel to the main fuel jet 19. Both of these jets 20 and 21 have an air bleed tube like the main fuel jet 19,
Mix air with fuel oil. The slow jet 20 communicates with a low speed fuel discharge port including a bypass port 23a provided immediately in front of the downstream partition plate 4b, and the visor jet 21 is an upper side of the intake passage 2 of the carburetor body 1. Is communicated with the bistor valve 25 provided in the sub-intake passage 24 together with the atmosphere introduced from the bistor air introduction passage 35. Further, a float 22 is suspended in the float chamber 18 so as to be swingable, and the fuel level is always kept constant in cooperation with a float valve (not shown).

As also shown in FIG. 2, the auxiliary intake passage 24 is provided diagonally below the main intake passage 2 in parallel with the main intake passage 2. The auxiliary intake passage 24 is branched from the main intake passage 2 at the variable venturi portion 14, and the partition plate 4b on the downstream side of the throttle valve 4 can open and close the opening together with the main intake passage 2. . Further, as shown in FIG. 2, the positional relationship between the intake passages 2 and 24 and the downstream partition plate 4b is such that the auxiliary intake passage 24 starts to open first as shown by the imaginary line a, and As shown, the openings of both intake passages 2 and 24 are defined so as to be partially overlapped and opened. A primary venturi having a predetermined opening area is formed in the variable venturi portion 14 when the vacuum piston 7 is at the lowest position.

As best shown in FIGS. 3 and 4, the connecting rod 8 extending upward from the vacuum piston 7 has a hole formed in the center of the connecting portion 4c formed on the upper side of the throttle valve 4. It is inserted relatively loosely in 4d. A space 7 a is formed in the upper part of the vacuum piston 7 between the outer surface of the connecting rod 8 and the outer surface. A cylindrical leak valve 50 having a different diameter that can slide on the outer peripheral surface of the connecting rod 8 is slidably fitted in the space 7a with the inner peripheral surface of the small diameter portion 50a, and the large diameter portion 50b.
A gap is formed between the inner peripheral surface of the and the outer peripheral surface of the connecting rod 8.

The leak valve 50 is constantly urged upward by a coil spring 51 which is contracted to surround the connecting rod 8 and inside the large diameter portion 50b when no external force acts, as shown in FIG. The step portion 50c is adapted to abut on the O-ring 52 fitted to the connecting rod 8. Further, the connecting rod 8 is provided with a leak passage 53, and when the inner step portion 50c of the leak valve 50 comes into contact with the O-ring 52 as described above, the leak passage 53 is closed and the venturi load is reduced. When the pressure is introduced into the negative pressure chamber 11 and the upper end of the leak valve 50 and the upper end of the vacuum piston 7 both come into contact with the lower surface of the connecting portion 4c of the throttle valve 4 as shown in FIG. The leak passage 53 is opened so that the negative pressure chamber 11 and the atmosphere chamber 1a can communicate with each other.

Next, the supply path of the air-fuel mixture will be described mainly with reference to FIG.

In the vicinity of the connection portion with the air horn 2a at the upstream end of the main intake passage 2, an atmosphere passage 30 for introducing the atmosphere into the atmosphere chamber 1a inside the carburetor body 1 via the jet 30a, and the main fuel jet 19
Port 31 of the first main air introduction passage 31 communicating with the bleeder passage 39 for introducing bleed air into the air bleed pipe 17 of
a and are open.

On the side surface of the carburetor body 1, a bistor valve 25 that forms a supply passage for the starting fuel is provided. This bistor valve 25 is connected to a separate driving device (not shown) and slides on the plunger 32. Depending on the position, the atmosphere introduction passage 33 communicating with the atmosphere chamber 1a and the first air passage from the air horn 2a described above
A position where the second main air introduction passage 34 that joins the main air introduction passage 31 communicates with the position (FIG. 5), and a visor air introduction passage 35 that communicates with the atmosphere chamber 1a when the throttle valve 4 is fully closed.
And the Vista fuel passage 36 communicating with the Vista Jet 21.
And a position (FIG. 6) in which each of the vice-mixture passages 37 communicating with the most downstream side of the auxiliary intake passage 24 communicates with each other.

Incidentally, the above-mentioned first and second main air introduction passages 31, 34 are both provided.
The jet 31 to properly balance the air flow rate.
b and 34a are provided.

The low-speed fuel passage 20a through which the emulsified fuel flows from the slow jet 20 is branched in the middle, and one of them is a bypass port provided immediately before the partition plate 4b on the downstream side facing both the main and auxiliary intake passages 2 and 24. The other end communicates with a pilot outlet 38 that is provided in the sub intake passage 24 together with the opening of the bistor mixture passage 37. A pilot screw 39 is screwed into the pilot outlet 38,
The idling mixing ratio can be adjusted from the outside of the vaporizer main body 1.

Next, the operation procedure of the above embodiment will be described with reference to FIGS. 7 to 9.

As shown in FIG. 1, when the engine is started, the throttle valve 4 is fully closed, and by the action of the bistor valve 25, a rich starting air-fuel mixture from the auxiliary intake passage 24 via the ista-air mixture passage 37 is generated. It is delivered to the intake port of.

When the throttle valve 4 is opened during operation of the visor valve 25 (position shown in FIG. 6), the visor air introducing passage 35 is closed by the throttle valve 4 as shown in FIG. Since 34 is blocked, the main bleed air is restricted,
Both the VISTA air-fuel mixture and the main air-fuel mixture become richer, supplementing the richness during cold weather and preventing the engine from breathing. When the visor valve 25 is pushed in (position shown in FIG. 5), the visor system passages 35, 21 and 37 are closed and the main air passages 33 and 34 are communicated. In this state, the main bleed air is the first main air introduction passage 31 and the second main air introduction passage 34.
And is introduced into the air bleed pipe 17. Atmosphere chamber 1a
At the time of low throttle opening where there is almost no pressure difference between the internal pressure of the air horn and the air horn 2a, both the first and second main air introduction passages 3
An appropriate amount of bleed air is supplied from 1, 34.

At the time of high-speed rotation in which the air horn 2a portion tends to have a negative pressure, the first main air introducing passage 31 and the second main air introducing passage 34 receive a first
Bleed air leaks into the main air introduction passage 31, and as a result, the mixture ratio of the air-fuel mixture discharged from the main nozzle 15 is corrected to the rich side. The balance of the amount of air from both main air introduction passages 31 and 34 is determined by the jet 31 provided in both passages.
It may be set appropriately according to the diameters of b and 34a.

During idling, fuel measured by the slow jet 20 is supplied from the pilot outlet 38 provided in the auxiliary intake passage 24, and the idling is performed according to the throttle opening on the auxiliary intake passage 24 side and the pushing amount of the pilot screw 39. Driving is performed.

When the throttle valve 4 is slightly opened, the opening degree on the side of the auxiliary intake passage 24 increases, and the negative pressure at the edge of the downstream partition plate 4b causes the auxiliary intake passage 24 to open.
The fuel is also sucked out from the bypass port 23b on the side, and the fuel supply amount from the auxiliary intake passage 24 increases. When the throttle valve 4 is further opened, the main intake passage 2 communicates with the auxiliary intake passage 24 and the bypass port 23a provided immediately downstream of the main fuel nozzle 15.
Fuel is also sucked out of the tank (Fig. 7).

As shown in FIG. 7, when the throttle valve 4 and the vacuum piston 7 are continuously operating together, a so-called cutter is provided between the upstream partition plate 4 a and the lower surface of the vacuum piston 7. A way is formed, and the negative pressure acting on the main nozzle 15 and the bypass port 23a can be adjusted to suitably control the mixture concentration at a low opening.

When the throttle valve 4 is opened beyond the diameter of the primary venturi formed at the lowest position of the vacuum piston 7, fuel is sucked from the main fuel nozzle 15.

Further, as the throttle valve 4 is opened, the intake flow rate increases, but as a result, the negative pressure on the downstream side of the intake passage decreases, and the fuel from both bypass ports 23a, 23b and pilot outlet 38 is no longer sucked out, and the main flow gradually increases. Fuel nozzle
It will be operated only with fuel from 15.

On the other hand, as the throttle valve 4 is opened, the leak valve 50 is closed (FIG. 4), and the Venturi negative pressure acts on the negative pressure chamber 11 via the negative pressure passage inside the connecting rod 8. As a result, the vacuum piston 7 rises to a position where the weight related to the vacuum piston, the downward force of the coil spring 13, the atmospheric pressure and the venturi negative pressure are balanced, and the diameter of the variable venturi portion 14 is determined.

When the vacuum piston 7 rises and the leak valve 50 comes into contact with the throttle valve 4 (Fig. 3), the leak passage 53 opens and the vacuum piston 7 descends. In this way
The vacuum piston 7 corresponding to the opening of the throttle valve 4
Operates to maintain proper venturi flow rate. Moreover,
Due to the leak passage 53, the vacuum piston 7 does not generate an ascending force more than necessary, and the vacuum piston 7 does not overshoot due to a sudden negative pressure change, so that an accurate fuel supply amount can always be maintained. You can
It can also improve the stability of the transient state. Further, as shown in FIG. 8, even if the throttle valve 4 is suddenly opened, the vacuum piston 7 does not rise unless the intake passage negative pressure is sufficiently increased, so that the air-fuel mixture is temporarily thinned. It can be prevented and smooth acceleration can be obtained without causing breathing. Further, when the engine load suddenly increases and the rotation speed decreases, the vacuum piston 7 descends to prevent the mixture from becoming too thin.

When the throttle valve 4 is fully opened, as shown in FIG. 9, the vacuum piston 7 is also fully opened according to the rotation speed, and in this state, there is no residual intake resistance on the inner surface of the main intake passage 2. Therefore, extremely high inhalation efficiency can be obtained.

<Effects of the Invention> As described above, according to the present invention, even when the throttle valve is fully opened, it is possible to eliminate obstacles that generate intake resistance and improve intake efficiency. Further, since the interlocking property between the throttle valve and the vacuum piston can be improved,
It is possible to meter fuel and precisely control the air flow rate, and it is possible to exert an extremely great effect in optimizing engine characteristics over a wider rotation range and improving fuel consumption rate.

Furthermore, since the negative pressure can be released when the throttle valve is returned by the leak passage provided in the vacuum piston part, the throttle valve can be returned without making the biasing force of the throttle valve forced return spring too large. It is also effective in reducing the operating force.

[Brief description of drawings]

FIG. 1 is an overall side sectional view of a vaporizer according to the present invention. FIG. 2 is a schematic arrow view taken along the line II-II in FIG. 3 and 4 are enlarged sectional views showing details of the sliding throttle valve portion. FIG. 5 is a schematic development view showing the air-fuel mixture supply path. FIG. 6 is an explanatory diagram of the operation of the bistable valve. 7 to 9 are operation explanatory views of the throttle valve and the vacuum piston. 1 ... Vaporizer body, 1a ... Atmosphere chamber 2 ... Main intake passage, 2a ... Air horn 3 ... Guide groove, 4 ... Throttle valve 4a ... Upstream partition plate, 4b ... Downstream partition plate 4c ...... Connecting part, 5 ...... Throttle shaft 6 ...... Connecting mechanism, 7 ...... Vacuum piston 7a ...... Gap, 8 ...... Connecting rod 9 ...... Cover member, 10 ...... Diaphragm 11 ...... Negative pressure chamber 12 ...... Diaphragm retainer 13 …… Compression coil spring, 14 …… Variable venturi part 15 …… Main fuel nozzle 16 …… Jet needle 17 …… Air bleed tube, 18 …… Float chamber 19 …… Main fuel jet 20 …… Slow jet, 20a ...... Low speed fuel passage 21 ...... Bysta jet 22 ...... Float 23a, 23b ...... Bypass port 24 ...... Auxiliary intake passage, 25 ...... Vista valve 30 ...... Atmosphere passage, 30a ...... Jet 31 ...... First main air Introductory passage 31a …… Port, 31b… Jet 32 …… Plunger, 33 …… Atmosphere introduction passage 34 …… Second Mayair introduction passage 34a …… Jet 35 …… Vista air introduction passage 36 …… Vista fuel passage 37 …… Vista mixture passage 38 …… Pilot outlet 39… … Bleeder passage 50 …… Leak valve, 50a …… Small diameter portion 50b …… Large diameter portion, 50c …… Step portion 51 …… Coil spring, 52 …… O ring 53 …… Leak passage

Claims (4)

[Claims] 1. A sliding throttle valve type carburetor having a vacuum piston connected to a passive body that responds to a Venturi negative pressure, and a throttle valve that opens and closes an intake passage by an operation of a driver, the throttle valve Has a flat plate shape that slides along a guide groove that is recessed in the carburetor body across the intake passage, and a receiving portion that receives the vacuum piston slidably in the same direction as the throttle valve. And a engaging means that defines a stroke of the vacuum piston, and a sliding throttle valve type carburetor. 2. The flat plate has two flat plate-shaped portions in which the throttle valves are substantially parallel to each other, and the upstream side portion of the intake valve starts to open earlier than the downstream side of the intake air. 2. The sliding throttle valve type carburetor according to claim 1, wherein the vacuum piston is slidably held between the inner surfaces of the cylindrical portion facing each other. 3. The passive body comprises a diaphragm device,
The vacuum piston is connected to the diaphragm device via a hollow tubular member, and a leak passage communicating with the atmosphere when the throttle valve and the vacuum piston are engaged is formed in the tubular member. The sliding throttle valve type carburetor according to claim 1 or 2, characterized in that. 4. The leak passage can be closed by a cylindrical member that is slidably attached to the outer peripheral surface of the tubular member and is spring-biased in the closing direction at all times and then fitted. The sliding throttle valve type carburetor according to claim 3, characterized in that