JPH084595A - Acceleration device for carburetor - Google Patents

Abstract

PURPOSE:To prevent the occurrence of defective acceleration during rapid opening of a throttle, which is easy to occur to a fixed venturi type carburetor, through a simple mechanism to pressurize an air passage for an air bleed formed in the carburetor. CONSTITUTION:In a fixed venturi type carburetor having an air passage 18 through which air is fed to an air bleed part 17 communicated with a main nozzle 16, an acceleration device for the carburetor comprises an air chamber in a casing 25 communicated with the air passage 18; a moving member 23, such as a diaphragm, to increase and decrease the volume of the air chamber ; and an interlocking mechanism 23a to operate the moving member 23 in a direction in which the volume of an air chamber is decreased in linkage with opening operation of the throttle valve of the carburetor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accelerator for a fixed venturi type carburetor mainly used in engines for outboard motors.

[0002]

2. Description of the Related Art A fixed venturi type carburetor has a problem in that when the throttle valve is rapidly opened, the flow velocity in the venturi portion is reduced, fuel is not sucked out, and acceleration failure occurs. A vaporizer with a variable venturi type or an acceleration pump is known as a vaporizer for solving such a problem.
When used in an outboard motor, the variable venturi type carburetor has the problem that salt damage may cause sticking of the venturi piston, and in the outboard motor, the engine is arranged so that the cylinder column direction is vertical, so that It is necessary to provide a carburetor for each cylinder so that the concentration of the air-fuel mixture does not change in the cylinder on the side, and it is difficult in terms of cost and space to use this carburetor with an acceleration pump. .

[0003]

By the way, the carburetor is provided with an air passage for supplying air to the air bleed portion connected to the main nozzle. The fuel discharge can be promoted by increasing the air pressure in the air passage. . It is an object of the present invention to provide a device which can prevent acceleration failure at the time of sudden opening of a throttle in a fixed venturi-type carburetor by utilizing the air passage by paying attention to such a point.

[0004]

In order to achieve the above object,
In the present invention, in a fixed venturi type carburetor having an air passage for supplying air to the air bleed portion connected to the main nozzle, an air chamber communicating with the air passage, and a movable member for increasing or decreasing the volume of the air chamber, An interlocking mechanism is provided for operating the movable member in the direction of decreasing the volume of the air chamber by interlocking with the opening operation of the throttle valve of the carburetor. By the way, when the throttle valve is closed rapidly, the air-fuel mixture may become overrich and stalled due to the influence of the wall film flow of the fuel in the intake pipe due to the rapid increase in the intake negative pressure. In order to eliminate such a problem, the interlocking mechanism should be provided with a driven plate that is coaxially supported by a drive cam that opens and closes the throttle valve, and the rotational direction in which the throttle valve of the drive cam is opened should be positive. As a rolling direction, the driven plate is configured to be forwardly rotated by the forward rotation of the drive cam in association with the forward spring against the return spring, and the movable member is fixed to the driven plate by the forward rotation of the driven plate. The movable member is operatively connected to reduce the volume of the air chamber and prevents the closing of the throttle valve when the drive cam reverses over the driven plate to the driven plate. A one-way valve that forms a working cam portion and further allows a flow of air from the air chamber to the air passage in a pipe line that connects the air chamber and the air passage, and a jet that is parallel to the one-way valve. To It can be set.

[0005]

The operation when the interlocking mechanism is provided with the driven plate as described above will be described. When the throttle valve is suddenly opened, that is, when the drive cam is rapidly rotated in the forward direction, the driven plate is also rapidly rotated in the forward direction to rapidly contract the air chamber through the movable member, and the air in the air chamber is unidirectionally moved. It is pushed out to the air passage through the valve, the air pressure in the air passage, that is, the air bleed portion rises, and the fuel is pushed out from the main nozzle, thus preventing acceleration failure at the time of sudden opening of the throttle.

When the drive cam is rotated in the reverse direction to close the throttle valve, the driven plate is rotated in the reverse direction while expanding the air chamber by the urging force of the return spring. At this time, the one-way valve is closed and only the jet is passed. Since air is sucked into the air chamber, negative pressure acts on the air chamber, and the negative pressure causes the driven plate to reversely rotate slowly. Therefore, when the drive cam is rapidly rotated in the reverse direction, the drive cam is rotated in the reverse direction over the driven plate, and the cam portion formed on the driven plate prevents the closing of the throttle valve. The throttle valve is closed along with the gradual reverse rotation. As a result, the engine stall due to the sudden closing of the throttle valve is prevented.

Considering the deceleration performance of the drive cam during the rapid reverse rotation, the throttle valve is rapidly closed halfway,
It is desirable to close the throttle valve in the low opening range where the intake negative pressure sharply increases.To do this, the forward rotation of the driven plate is regulated during the forward rotation of the drive cam, and the drive cam rotates forward of the driven plate. It is necessary to prevent the cam portion from working until it is reversed to the regular position. In this case, an intermediate plate connected to the drive cam via a torque spring is coaxially supported, and the drive cam is When the driven plate is pushed forward by the forward rotation of the driven plate and the driven plate is rotated normally, the torque spring functions as a lost motion spring that allows the drive cam to rotate forward beyond the normal rotation regular position of the driven plate. It works and can meet the above requirements.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawings show an embodiment in which the device of the present invention is applied to a carburetor for a three-cylinder engine for outboard motors. As shown in FIG. 1, upper and lower three intake pipes having a common fixing flange (1) for the engine. Each of (2) was connected to an air cleaner (4) via a separate vaporizer (3).

Each of the carburetors (3) is composed of a fixed venturi type carburetor equipped with a throttle valve (5) and a choke valve (6). Each of the throttles of these three carburetors (3) Throttle arms (7) connected to valves (5) and choke arms (8) connected to each choke valve (6)
Connect them to each other via links (9) (10), and connect the throttle arm (7) of the lower carburetor (3) to the throttle lever (11).
The drive cam (12), which is connected to the shaft through the rod (11a), is engaged with the cam hole (12a) formed through the pin (7a), and the throttle lever (11) is operated to operate the three carburetors. The throttle valve (5) of (3) can be opened and closed synchronously, and the choke arm (8) of the lower carburetor (3) is connected to the starting solenoid (1
3) is connected to the choke lever (14) via the rod (8a), and when the engine is started, the starting solenoid (13) is energized to rotate the choke lever (14) clockwise in the drawing,
The choke valves (6) of the three vaporizers (3) were closed.

In each of the vaporizers (3), as shown in FIG. 2, an air passage (18) communicating with an air bleed portion (17) below the main nozzle (16) facing the venturi portion (15) is formed. Has been done,
The air passage (18) is communicated with an air cleaner (4) through a main air jet (not shown), and air is supplied to the fuel flowing from the float chamber (19) through the main jet (20) at the air bleed portion (17). The mixed and emulsified fuel was sucked out from the main nozzle (16) by the Venturi negative pressure. In the figure (21) is the slow jet (22) at the lower end
The fuel pipe of the slow system which attached is shown.

Although the above construction is not particularly different from the conventional one, in the present embodiment, a diaphragm case (25) having an air chamber (24) defined by the diaphragm (23) is provided inside, and Install the stay (25a) vertically attached to the case (25) as shown in FIG.
2, the boss (2a) formed in the lower intake pipe (2) is fastened by a bolt that constitutes the support shaft (26) of the drive cam (12), and the air chamber (24) is connected to the boss (2a) of FIG. As shown in Fig. 7, when the throttle valve (5) is communicated with the air passage (18) of each carburetor (3) and the throttle valve (5) is opened by the normal rotation (clockwise rotation) of the drive cam (12) as described above, The diaphragm (23) is moved upward via the interlocking mechanism (27) interlocking with 12) to contract the air chamber (24).

The interlocking mechanism (27) includes a driven plate (28) pivotally supported by the support shaft (26) and an intermediate plate (29). As shown in FIG. The diaphragm
Hole for inserting and locking the lower end of the rod (23a) connected to (23)
(28a) and a cam portion (28b) protruding outward at the peripheral edge of the driven plate (28), and an arcuate claw piece (29a) protrudingly provided at the peripheral edge of the intermediate plate (29). A bent portion (29b) abutting the counterclockwise edge of the cam portion (28b) on the clockwise edge of the claw piece (29a), and a drive cam (12) on the counterclockwise edge. A bent portion (29c) that engages with the counterclockwise side edge of the driven plate (28) and the stay (25a). A return spring (30) engaged with the formed engagement portion (28c) and the engagement portion (25b) formed at the lower end of the stay (25a) at the other end is provided, and a drive cam (12)
Between the intermediate plate (29) and the intermediate plate (29), one end is formed on the boss portion of the drive cam (12), and the other end is formed on the intermediate plate (29).
A torque spring (31) engaged with an engaging portion (29d) formed on the peripheral edge of the is interposed.

According to the above construction, when the drive cam (12) is normally rotated from the state shown in FIG. 1, the intermediate plate (29) is normally rotated via the torque spring (31), and the intermediate plate (29) is rotated. 2
The driven plate (28) is pushed back by the pawl (29a) of
It rotates normally against (30), and the diaphragm (23) moves upward via the rod (23a). Then, in the state shown in FIG. 8 (a), the diaphragm (23) moves upward to the stroke end and further normal rotation of the driven plate (28) is restricted, and thereafter the drive cam is wound while the torque spring (31) is being tightened. (12) further forward,
In the state shown in FIG. 8 (b), the throttle valve (5) is fully opened.

A valve casing (33) is provided in a pipe line (32) connecting the air chamber (24) and the air passage (18) of each carburetor (3). 33) is the air passageway (18) as shown in FIG.
Side port (33a), air chamber (24) side port (33b), and the latter port (33b) as shown in FIG. 6 petal-shaped guide hole (33c)
With a valve hole (33d) communicating with each other through a valve hole (33d), which is biased by a spring (34a) so as to close the valve hole (33d) in the valve casing (33). While accommodating the one-way valve (34),
Valve rod (34b) of the one-way valve (34) inserted into the guide hole (33c)
A through hole (34c) is formed in the through hole (34c) to form a side passage in parallel with the one-way valve (34) that always communicates the ports (33a) and (33b) with each other. Jet (35) in the center of 34c)
Was formed.

According to this, when the driven plate (28) is normally rotated by the normal rotation of the drive cam (12) and the diaphragm (23) is moved upward to contract the air chamber (24), The one-way valve (34) is pushed by the air from the air chamber (24) to open the valve, and the air passage (18)
Air flows into the. Here, when the drive cam (12) is slowly rotated in the normal direction, the one-way valve (34) is not opened so much, and the air leak from the main air jet described above occurs, and the air pressure in the air passage (18) is reduced. Drive shaft (1
When 2) is rapidly rotated in the normal direction, the air pressure in the air passage (18) temporarily rises due to the rapid inflow of air from the air chamber (24), and this air pressure is increased by the air bleed portion (17). And the fuel is pushed out from the main nozzle (16) to prevent acceleration failure when the throttle is suddenly opened.

On the other hand, when the drive cam (12) is reversely rotated, the driven plate (28) is reversely rotated by the urging force of the return spring (30).
At this time, the diaphragm (23) moves downward and the air chamber (24) expands. In this case, the one-way valve (34) is closed, so the air chamber (2
Air flows into 4) only via the jet (35), and as a result, negative pressure acts on the air chamber (24) and the driven plate (28) is gently reversed.

Therefore, when the drive cam (12) is rapidly reversed from the state shown in FIG. 8 (b), the drive cam (12) reverses over the driven plate (28) as shown in FIG. 8 (c). , That is, while the driven plate (28) remains in the predetermined forward rotation position, the drive cam
(12) reverses to the stroke end.

The cam portion (2) formed on the driven plate (28)
8b) has a shape such that the pin (7a) of the throttle arm (7) rides on the cam portion (28b) in such a state, and thus when the drive cam (12) is rapidly reversed, the driven plate (8b) 28)
Until the throttle valve (5) exceeds the drive cam (12)
However, when the drive cam (12) exceeds the driven plate (28), the cam portion (28b) prevents the throttle valve (5) from closing further, and thereafter the driven plate (28) is closed. (28) slowly reverses and the throttle valve
The (5) is closed to prevent the engine from stall due to the rapid closing of the throttle valve (5).

Although the embodiment using the diaphragm (23) as the movable member for increasing or decreasing the volume of the air chamber (24) has been described above, the invention is not limited to this, and for example, a bellows may be used as the movable member. .

[0020]

As is apparent from the above description, according to the first aspect of the present invention, the fixed venturi type carburetor is used for the air bleeding which is formed in the carburetor due to the acceleration failure during the rapid opening of the throttle. It can be prevented by a simple mechanism that pressurizes the air passage, and it is possible to solve problems such as stick due to salt damage such as a variable Venturi type carburetor, and large size and high cost such as a carburetor with an acceleration pump, which is good for outboard motors. Has an applicable effect. According to the invention of claim 2,
The same mechanism can prevent the engine stalling when the throttle is rapidly closed as well as the acceleration failure when the throttle is suddenly opened. Further, according to the invention of claim 3, the engine is stalled without impairing the intended deceleration performance when the throttle is rapidly closed. Has the effect of preventing

[Brief description of drawings]

FIG. 1 is a side view of an example of a device of the present invention.

FIG. 2 is a cross-sectional view of the vaporizer.

FIG. 3 is a cross-sectional view of the interlocking mechanism portion cut along the line III-III in FIG.

FIG. 4 is an exploded view showing each component of the interlocking mechanism.

FIG. 5 is a vertical cross-sectional view of a valve housing containing a one-way valve and a jet.

6 is a sectional view taken along line VI-VI of FIG. 5;

7 is a sectional view taken along the line VII-VII in FIG.

8 (a), (b) and (c) are explanatory views of the action of the interlocking mechanism.

[Explanation of symbols]

(3) ... Vaporizer (5) ... Throttle valve (12) ... Drive cam (16) ... Main nozzle (17) ... Air bleed part (18) ... Air passage (23) ... Diaphragm (movable member) (24) ... Air chamber (27)… Interlocking mechanism (28)… Drive plate (28b)… Cam part (29)… Intermediate plate (30)… Return spring (31)… Torque spring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunji Akamatsu 1-4-1, Chuo, Wako-shi, Saitama, Ltd. Honda R & D Co., Ltd.

Claims (3)

[Claims] 1. A fixed venturi type carburetor having an air passage for supplying air to an air bleed portion connected to a main nozzle, comprising: an air chamber communicating with the air passage; and a movable member for increasing or decreasing the volume of the air chamber. And an interlocking mechanism for operating the movable member in a direction to reduce the volume of the air chamber by interlocking with the opening operation of the throttle valve of the carburetor. 2. The interlocking mechanism includes a driven plate coaxially supported by a drive cam that opens and closes a throttle valve, and the rotational direction of opening the throttle valve of the drive cam is defined as a forward rotation direction. When the drive cam is rotated in the normal direction, the movable member is rotated in the normal direction against the return spring in association with the rotation of the drive cam. Is connected to be driven in a decreasing direction, and the driven plate is formed with a cam portion which functions to prevent the closing of the throttle valve when the drive cam is reversed beyond the driven plate, and A one-way valve that allows the flow of air from the air chamber to the air passage and a jet that is parallel to the one-way valve are provided in a pipeline that connects the air chamber and the air passage. Claim 1 Accelerator in the carburetor. 3. An intermediate plate, which is coaxially connected to the drive cam and connected to the drive cam via a torque spring, is axially supported, and the normal rotation of the drive cam pushes the intermediate plate so that the driven plate is positive. 3. The accelerating device for a carburetor according to claim 2, wherein the driven plate is rotated and the forward rotation of the driven plate is restricted during the forward rotation of the drive cam.