JPS6032029B2 - variable venturi type vaporizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable venturi carburetor for use in an internal combustion engine.

As is well known, a variable venturi type carburetor is equipped with a spring-loaded movable suction piston that forms a variable venturi section in the carburetor intake air passage, and the negative pressure chamber of the movable suction piston is connected downstream of the venturi section. It connects to the negative pressure generation area and also connects the atmospheric pressure chamber of the movable suction piston to the atmospheric pressure area upstream of the venturi part, and balances the negative pressure acting in the negative pressure chamber of the movable suction piston with the suction piston bias. , the suction piston is moved up and down so that an approximately constant pressure is generated downstream of the venturi, that is, the flow velocity of the intake air passing through the venturi is approximately constant, thereby changing the cross-sectional area of the venturi. I try to let them do it.

In this type of variable venturi type carburetor, when the amount of intake air is relatively small, the flow rate of the intake air is controlled to be constant as described above, but when the amount of intake air exceeds a certain limit, the suction piston moves to the venturi section. When the intake air is fully opened and the amount of intake air increases thereafter, the flow velocity of the intake air also increases accordingly. In such a variable venturi type carburetor, in order to promote atomization of the fuel ejected into the venturi area, it is only necessary to increase the flow velocity of the air passing through the venturi part, and therefore, for this purpose, the opening area of the venturi part should be made small. do it. However, if the open area of the venturi portion is reduced in this manner, flow resistance increases during high-speed, high-load operation, resulting in a problem that the filling efficiency decreases. To ensure high filling efficiency during high-speed, high-load operation, the air flow rate through the venturi section should be increased to 100%.
If the inlet area of the venturi section is made smaller in order to make the upstream distance farther than this, the filling efficiency will decrease as mentioned above.Therefore, with conventional variable venturi type vaporizers, Air flow rate is 10 during load operation
The maximum Sekiguchi area of the venturi section is set so that the speed is 0 m/s or less. In the conventional variable pentu IJ type carburetor set in this way, the amount of intake air is small, so when a constant negative pressure is generated downstream of the venturi part, even if the cross-sectional area of the venturi part is narrowed by the suction piston, the venturi part The flow velocity of the intake air passing through the tube is only about 30 m/s at most. Therefore, in this type of conventional variable venturi type carburetor, fuel atomization is not sufficient when the amount of intake air is relatively small, and most of the fuel ejected into the venturi becomes liquid fuel and enters the intake air passage of the carburetor. It will flow along the wall. On the other hand, in this type of variable venturi type carburetor, in order to increase the flow velocity of the intake air flowing through the venturi section when the amount of intake air is relatively small, the biasing spring force of the suction piston is strengthened to reduce the closed area of the venturi section. However, in this case, there is a problem that a sufficiently large opening area of the venturi portion cannot be obtained during high-speed, high-load operation, and thus the filling efficiency decreases. The present invention provides a variable speed control system that increases the flow rate of intake air passing through the venturi section when the amount of intake air is relatively small while ensuring high charging efficiency during high-speed, high-load operation, thereby promoting atomization of fuel. The purpose of the present invention is to provide a venturi type vaporizer.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Referring to FIG. 1, 1 is a variable venturi type carburetor housing; 2 is an intake passage; 3 is a suction piston that can move up and down; 4 is a carburetor throttle valve; 5 is a choke valve;
7 is a diaphragm fixed to the upper end of the suction piston 3; 7 is a pressure chamber formed above the diaphragm 6;
8 is an atmospheric pressure chamber formed below the diaphragm 6, 9 is a compression spring that constantly presses the suction piston 3 downward, 10 is a movable needle fixed to the lower wall surface 33 of the suction piston 3, and 11 is a carburetor. Float chambers 12 each indicate a fuel metering jet cooperating with a movable needle 10.

Note that in FIG. 1, intake air flows in the intake passage 2 in the direction indicated by arrow A. The negative pressure chamber 7 is connected to the intake passage 2 downstream of the suction piston 3 via a negative pressure boat 13 formed on the lower wall surface 3a of the suction piston 3, while the atmospheric pressure chamber 8 is connected through an atmospheric vent hole 14. It is connected to the intake passage 2 upstream of the suction piston 3 through the suction piston 3 . As is well known, the spring force of the compression spring 9 is set to be relatively weak.

The suction piston 3 moves up and down due to the pressure difference between the negative pressure chamber 7 and the atmospheric pressure chamber 8, and thus a constant negative pressure generation region B is formed between the suction piston 3 and the throttle valve 4. The suction piston 3 rises as the amount of intake air increases, thereby changing the open square area of the bench lily portion C formed between the suction piston lower wall surface 3a and the bottom wall surface of the intake passage 2. When the intake air flows in the direction of arrow A, the movable needle 1
Fuel is ejected into the venturi section C from the annular gap between the fuel metering jet 12 and the fuel metering jet 12. When the throttle valve 4 opens wide and the amount of intake air exceeds a predetermined amount, the suction piston 3 rises to the maximum raised position and fully opens the venturi portion C. Even if the amount of intake air increases further, the suction piston 3 remains in the maximum raised position. 1st
In the embodiment shown in the figure, the cross-sectional area of the venturi portion C when the suction piston 3 is at the maximum raised position is set so that the flow velocity of the intake air flowing through the venturi portion C when the maximum amount of intake air flows in is 100 m/s or less. ing. 1st
Referring to the drawings and FIG.
are formed, and these pressure passages 15, 16, 17, 18,
The atmospheric pressure chamber 8 is connected to the constant negative pressure generating area B via the constant negative pressure generating area B.

A throttle 20 and an adjusting screw 22 formed with a tapered portion 21 for controlling the closing area of the throttle valve are provided in the negative pressure passage 16. Further, as shown in FIG. 2, a negative pressure responsive valve 23 for controlling the communication between the negative pressure passage 17 and the negative pressure passage 18 is attached to the carburetor housing 1. This negative pressure responsive valve 23 has a negative pressure chamber 25 and an atmospheric pressure chamber 26 formed by a membrane diaphragm 24, and a compression spring 27 for pressing the diaphragm is inserted into the negative pressure chamber 25. Further, a valve body 29 is connected to the diaphragm 24 and is arranged to face the closing boat 28 of the negative pressure passage 17, and the negative pressure chamber 25 is connected to the negative pressure pipe 30.
It is connected to a negative pressure boat 31 (FIG. 1) which opens into the intake passage 2 downstream of the throttle valve 4 through the throttle valve 4. On the other hand, as shown in FIG. 1, a fixed throttle 32 is provided in the atmospheric air vent 14, and furthermore, a bypass passage that bypasses the fixed throttle 32 and connects the atmosphere and the atmospheric pressure chamber 8 without being throttled is controlled to open and close. A negative pressure responsive valve 33 is provided.

The negative pressure responsive valve 33 has a negative pressure chamber 35 and an atmospheric pressure chamber 36 separated by a membrane diaphragm 34, and the atmospheric pressure chamber 36 is connected to the atmospheric vent 14 via a bypass passage 37 on the one hand. On the other hand, it is connected to the atmospheric pressure chamber 8 via a bypass passage 38 . Note that the diaphragm 34 has a valve body 39 disposed on the opposite side of the valve boat 4 of the bypass passage 38.
are concatenated. A compression spring 41 for pressing the diaphragm is inserted into the negative pressure chamber 35, and this negative pressure chamber 41 is connected via a negative pressure conduit 42 to a negative pressure boat 31 that closes in the intake passage 2 downstream of the throttle valve 4. be done. The spring force of the compression spring 41 of the negative pressure responsive valve 33 shown in FIG. 1 and the spring force of the compression spring 27 of the negative pressure responsive valve 23 shown in FIG. When the negative pressure is greater than a predetermined negative pressure, the diaphragms 34 and 24 are at the positions shown in FIGS. 1 and 2, respectively, and when the negative pressure in the intake passage 2 becomes less than the predetermined negative pressure, the diaphragms 34 and 24 are set to simultaneously move to the left. be done.

That is, as shown in FIG. 1, the valve body 39 of the negative pressure responsive valve 33 closes the valve boat 40 when the negative pressure in the intake passage 2 downstream of the throttle valve 4 is greater than a predetermined negative pressure, and When the negative pressure in the air intake channel 2 becomes 4° lower than a predetermined negative pressure, the valve port 40 is opened. On the other hand, as shown in FIG. 2, the valve element 29 of the negative pressure responsive valve 23 opens the closing boat 28 when the negative pressure in the intake passage 2 downstream of the throttle valve 4 is greater than a predetermined negative pressure. When the negative pressure in the intake passage 2 downstream of the valve 4 becomes smaller than a predetermined negative pressure, the closing boat 28 is closed. The throttle valve 4 has a coefficient of 4.

When the negative pressure in the intake passage 2 downstream of the tutle valve 4 is large, the valve body 39 of the negative pressure responsive valve 33 closes the valve boat 40, as shown in FIGS. 1 and 2, and the valve of the negative pressure responsive valve 23 closes. body 29
closes the open boat 28. Therefore, the atmospheric pressure chamber 8 is then connected on the one hand to the atmosphere via the throttle 32 and on the other hand to the constant negative pressure region B via the annular spacing between the throttle 20 and the adjusting screw 7 part 21. In the atmospheric pressure chamber 8, a negative pressure intermediate between the negative pressure generated in the constant pressure region B and the atmospheric pressure is generated. When negative pressure is generated in the atmospheric pressure chamber 8 in this way, the pressure difference between the negative pressure chamber 7 and the atmospheric pressure chamber 8 becomes smaller than when atmospheric pressure is applied to the atmospheric pressure chamber 8, resulting in suction. Piston 3 descends and venturi part C
The pressure difference between the negative pressure chamber 7 and the atmospheric pressure chamber 8 is made equal to the pressure difference between the negative pressure chamber 7 and the atmospheric pressure chamber 8 when atmospheric pressure is applied to the atmospheric pressure chamber 8. As a result, constant pressure generation area B
The negative pressure generated inside increases, and at the same time the venturi part C
The flow rate of intake air passing through increases. If the area of the annular opening □ formed between the tapered part 21 of the adjusting screw 22 and the throttle 20 is increased, the negative pressure in the atmospheric pressure chamber 8 will increase, so the pressure difference between the negative pressure chamber 7 and the atmospheric pressure chamber 8 will increase. becomes smaller, and thus the cross-sectional area of the venturi portion C becomes smaller by 4 mm, so that the flow velocity of the intake air flowing through the venturi portion C is increased. On the other hand, if the area of the annular closure between the tapered portion 21 and the orifice 20 is made smaller, the negative pressure in the atmospheric pressure chamber 8 will become smaller, and the pressure difference between the negative pressure chamber 7 and the atmospheric pressure chamber 8 will increase. Since the cross-sectional area of the venturi portion C becomes larger, the venturi portion C
The flow rate of the intake air flowing through becomes slower. By adjusting the adjustment screw 22 in this manner, the flow velocity of the intake air flowing through the venturi portion C can be set arbitrarily. The flow velocity of the intake air flowing through the venturi section C is preferably about 150 m/s to 250 m/s, and therefore the flow velocity of the intake air inside the venturi section C is adjusted to be from 150 m/s to 250 m/s. The negative pressure applied within the atmospheric pressure chamber 8 is adjusted by the screw 22 . As described above, according to the present invention, when the amount of intake air is relatively small, the flow velocity of the intake air flowing inside the venturi portion C can be significantly increased compared to the conventional method.
In this way, atomization of the fuel can be promoted. on the other hand,
When the throttle valve 4 becomes large and the negative pressure generated downstream of the throttle valve 4 becomes small, the valve element 29 of the negative pressure responsive valve 23 closes the Sekiguchi port 28 as described above, so that the pressure inside the atmospheric pressure chamber 8 decreases. The supply of negative pressure to the negative pressure valve 33 is stopped.
The valve element 39 opens the atmospheric pressure chamber 8 to open the valve boat 40.
is connected to the atmosphere without throttling and thus operates similarly to a conventional variable venturi carburetor.

Therefore, high filling efficiency can be ensured during high-speed, high-load operation. In this way, when the opening degree of the throttle valve 4 is small, the atmospheric pressure chamber 8 is connected to the atmospheric pressure region via the fixed throttle 32, and when the opening degree of the throttle valve 4 is large, the atmospheric pressure chamber 8 is not subjected to the throttling action. Since it is connected to the atmospheric pressure region, the fixed throttle 32 and the negative pressure responsive valve 33 throttle the atmospheric pressure communication hole that connects the atmospheric pressure chamber 8 and the atmospheric pressure region according to the engine load, or release the throttling action. It can be seen that a section control device is constructed. FIG. 3 shows another embodiment.

In this embodiment, a negative pressure responsive valve 45 is provided, which is a combination of the negative pressure responsive valve 33 of FIG. 1 and the negative pressure responsive valve 23 of FIG. 2.
This negative pressure responsive valve 45 has a first negative pressure chamber 47 and a second negative pressure chamber 48 formed by a membrane diaphragm 46, and a pair of valve bodies 49 integrally formed with the diaphragm 46,
50 are connected. Atmospheric pressure chamber 51 with valve body 49 inserted
is connected to the atmospheric vent 14 via a bypass passage 52 on the one hand, and an annular groove 5 disposed facing the valve body 49 on the other hand.
3. Connected to the atmospheric pressure chamber 8 via passages 54 and 55. The second negative pressure chamber 48 is connected on the one hand to the constant negative pressure generation area B via a negative pressure conduit 56, and on the other hand to the constriction section formed by the valve boat 57, the passage 58, the flow rate adjusting screw 59, and the passage 55.
It is connected to the atmospheric pressure chamber 8 via. On the other hand, the first negative pressure chamber 4
A compression spring 60 for pressing the diaphragm is inserted into 7,
This first negative pressure chamber 47 is connected via a negative pressure conduit 61 to a negative pressure boat 31 that opens into the intake passage 2 downstream of the throttle valve 4 . When the throttle valve 4 has a small pressure and a large negative pressure is generated in the intake passage 2 downstream of the throttle valve 4, the diaphragm 46 is at the right end position as shown in FIG. At the same time as closing the annular register 53, the valve body 50 closes the valve boat 57.

In this case, the atmospheric pressure chamber 8 is thus connected to the atmosphere on the one hand via the throttle 32 and on the other hand is connected to the atmosphere through the passage 55, the throttle section 58 by means of the adjusting screw 59, the second negative pressure chamber 48 and the negative pressure conduit 56.
Since the atmospheric pressure chamber 8 is connected to the constant pressure generating region B through the It will be done. On the other hand, when the throttle valve 4 opens wide and the negative pressure in the intake air passage 2 downstream of the throttle valve 4 decreases, the diaphragm 46 moves to the left by the spring force of the compression spring 60, and as a result, the valve body 49 While closing the annular groove 53, the valve body 50
closes valve boat 57. Therefore, at this time atmospheric pressure chamber 8
It operates similarly to a conventional variable venturi type carburetor because it is exposed to the atmosphere through non-restrictive passages 55, 54, annular groove 53, atmospheric pressure chamber 61, and bypass passage 52. As mentioned above, in order to promote atomization of the fuel when the amount of intake air is small, it is preferable to increase the flow rate of the intake air from 150 degrees/second to a constant flow rate of 250 degrees/second.

In the present invention, as described above, when the amount of intake air is small, the atmospheric pressure chamber is connected to the constant negative pressure generation area via the throttle on the one hand, and to the atmospheric pressure area via the throttle on the other hand, so that the atmospheric pressure chamber is Maintained at constant negative pressure. In this way, when the amount of intake air is small, the atmospheric pressure chamber becomes negative pressure, so the flow rate of the intake air increases.Moreover, at this time, the negative pressure in the atmospheric pressure chamber remains constant, so the flow rate of the intake air changes to the position of the suction piston. Optimal regardless of 150/s to 250
A constant flow rate of /s can be maintained. In this way, good fuel atomization can be ensured when the amount of intake air is small.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a variable venturi type carburetor according to the present invention, FIG. 2 is a sectional view taken along the Rolo line in FIG. 1,
FIG. 3 is a side sectional view of another embodiment. 2... Intake passage, 3... Suction piston, 4... Throttle valve, 6... Diaphragm, 7
…．・．． Negative pressure chamber, 8...Atmospheric pressure chamber, 10...
... Needle, 12 ... Metering jet, 13
... Negative pressure boat, 14 ... Atmospheric vent, 15, 16, 17, 18, 19 ... Personnel pressure passage, 22, 59 ... Adjustment Screw, 23, 33, 45
...Negative pressure responsive valve, 24, 34, 46... Membrane diaphragm, 30, 42, 56, 61...
Negative pressure conduit, 32... throttle. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1 Equipped with a movable suction piston forming a variable bench lily portion in the intake air passage of the carburetor, the upper end of the movable suction piston is connected to a diaphragm, and negative pressure isolated by the diaphragm is created at both ends of the diaphragm. The negative pressure chamber is connected to a constant negative pressure generation area downstream of the bench lily part, and the atmospheric pressure chamber is connected to an atmospheric pressure area upstream of the bench lily part, and the negative pressure chamber is connected to a constant negative pressure generation area downstream of the bench lily part. In a variable bench lily type carburetor in which a movable suction piston reciprocates to change the cross-sectional area of the bench lily so that the pressure is approximately constant, the constant negative pressure generation area downstream of the variable bench lily and the atmospheric pressure chamber are are connected via an atmospheric pressure passage, and a restriction is provided in the negative pressure passage, and a restriction is provided in an atmospheric pressure communication hole that connects the atmospheric pressure region and the atmospheric pressure chamber, and the atmospheric pressure region is bypassed by the restriction. A bypass passage is provided that connects the air pressure chamber and the atmospheric pressure chamber without throttling, and in response to the engine load, the load passage is fully opened when the engine load is smaller than a predetermined load, and the bypass passage is fully opened and the engine load is reduced. A variable bench lily type carburetor is provided with a response valve in the negative pressure passage and the bypass passage, which fully closes the negative pressure passage and fully opens the bypass passage when the load is greater than a predetermined load.