JPH0350278Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention is a low-speed fuel system of a carburetor that is equipped with a low-speed system bench lily and is capable of controlling the air-fuel ratio of the air-fuel mixture particularly in the low-speed range. It is related to.

[Problems to be solved by conventional techniques and ideas]

Generally, as a low speed system of a carburetor, as shown in FIG.
8 and a slow air jet 39 are known. In this case, the amount of fuel flowing out from the slow port 33 is
The fuel flow rate is adjusted by changing the opening area of the slow port 37, which opens downstream of the valve 40, in accordance with the opening degree of the valve 40, thereby measuring the fuel flow rate. By the way, selecting the hole diameter and position of the slow port 37 requires an extremely large number of man-hours, and in principle, the opening degree of the throttle valve 35 cannot accurately control the air flow rate compared to the negative pressure of the bench lily 41. Therefore, controlling the fuel flow rate via the throttle valve 40 is difficult. Conventionally, as described in Japanese Patent Publication No. 61-19822, a pressure sensor is disposed between the main jet and the bench lily to detect the difference in fuel flow rate based on the pressure difference. A method has been proposed for obtaining a proper air-fuel mixture by feedback. However, this method has disadvantages in that it is difficult to detect an extremely low bench lily negative pressure, especially in a low speed range, and there may also be problems with the accuracy of the pressure sensor itself. On the other hand, in Japanese Patent Application No. 60-146627 filed by the present applicant, a fuel system that can be applied extremely effectively to such a low speed range is proposed, but in this case, a low speed system bench lily is not used. A configuration different from that originally proposed has been adopted.

In view of these circumstances, it is an object of the present invention to provide a low-speed fuel supply system for a carburetor that simplifies the setting of bypass selection such as a slow port and has excellent durability.

[Means and effects for solving the problems] The low-speed fuel supply system according to the present invention is provided with a low-speed system bench lily capable of generating negative pressure according to the air flow rate, and the bench lily portion is communicated with the slow jet. A sensor for detecting the level of liquid in the communication passage is disposed at a suitable location between the two, and a fuel flow rate control means provided between the slow jet and the slow port is operated based on a signal from the sensor. Here, the fuel flow rate control means adjusts the fuel flow rate so as to accurately follow the negative pressure of the low-speed system bench lily, which accurately represents the air flow rate, based on the signal from the liquid level sensor that detects whether the liquid level is higher or lower than a set liquid level. Therefore, even if the air flow rate changes, a mixture with an appropriate air-fuel ratio is always supplied in the low speed range.

〔Example〕

1 to 8 show a first embodiment of a low-speed fuel supply system according to the present invention, in which 1 is an intake passage of a carburetor, 2 is an air valve that can open and close the intake passage 1, and 3 is an air valve that can open and close the intake passage 1. Actuation control means for the air valve 2, comprising a diaphragm 3a and a spring 3b connected to the air valve 2, and a negative pressure chamber 3c communicated with the downstream side of the air valve 2; 4 is a fixed bench lily; 5 is a throttle valve; 6 is a main nozzle that opens into the fixed bench lily 4, 7 is a main air jet, 8 is a main jet, 9 is a low-speed system bench lily that bypasses the upstream and downstream sides of the air valve 2 on the downstream side of the fixed bench lily 4, and 10 is a low-speed system. A passage 12 communicates the system bench 9 with the downstream side of the main jet 8 via the slow jet 11, and 12 is a detection means disposed in the passage 10 and consisting of a light emitting element 12a and a light receiving element 12b having a circuit configuration as shown in FIG. 2, for example. , 13 is a slow port that opens into a negative pressure generating portion formed by the outer peripheral edge of the throttle valve 5 and the inner peripheral surface of the intake passage 1;
Reference numeral 14 designates a solenoid valve that is disposed at a suitable location in the fuel passage 15 and can open and close the passage 15 according to changes in input voltage, 16 a control circuit that controls the input voltage to the solenoid valve 14, and 17 a float chamber. . In the above case, the operation control means 3 holds the air valve 2 in the closed position via the diaphragm 3a compressed by the spring 3b when the engine is stopped, and after the engine is started, the operation control means 3 holds the air valve 2 in the closed position at least after the low speed range. The air valve 2 is configured to be able to open the air valve 2 by displacing the diaphragm 3a against the elasticity of the spring 3b by the generated negative pressure. Further, the detection means 12 detects whether the liquid level height of the fuel column 10a in the passage 10 is higher or lower than a set value, and outputs corresponding outputs O _h and O _L (see Figs. 2 and 3). It is configured so that it can output. Furthermore, the control circuit 16
For example, as shown in FIG. 4, the reference voltage V _R is connected to the (-) terminal and the output side of the comparator C to which the output from the detection means 12 can be inputted to the (+) terminal. It includes a transistor T,
Corresponding to the output O _h and O _L from the detection means 12, the solenoid valve 14 is operated in two stages (hereinafter referred to as A stage).
It is constructed so that it can be opened and closed during the B stage.

Since the low speed system fuel supply system according to this embodiment is configured as described above, the air valve 2 closes the intake passage 1 in the low speed range of the engine, and the intake air is supplied from the downstream side of the fixed bench lily 4 to the low speed system bench lily. 9 to the manifold. In this low speed range, the negative pressure in the fixed bench lily 4 has not risen enough to cause fuel to be ejected from the main nozzle 6, while the negative pressure in the low speed system bench lily 9 is proportional to the square of the air flow rate. Furthermore, the fuel pressure generated downstream of the slow jet 11 is
Since the fuel pressure is proportional to the square of the fuel flow rate at 5, if this fuel pressure and the negative pressure of the low-speed system bench lily 9 are matched, a predetermined amount of fuel can always be supplied according to the air flow rate of the bench lily 9. Now, the throttle valve 5 is at the low opening position, and therefore the opening area of the slow port 13 on the negative pressure side by the valve 5 is small, and the solenoid valve 14 opens the passage 15 at stage A to open the inside of the passage 15. When fuel is flowing, if the liquid level height of the fuel column 10a in the passage 10 is below the set value, that is, the fuel flow rate is lower than the air flow rate corresponding to the negative pressure generated in the low-speed system bench lily 9. However, since the light emitted from the light emitting element 12a is scattered while passing through the passage 10, the amount of light received by the light receiving element 12b is small. The output will be on the low output side O _L (see Figure 2). This output O _L is sent to the control circuit 16, but in this case, since it is smaller than the reference voltage V _R , the drive signal from the control circuit 16 to the solenoid valve 14 is stopped, and the opening of the solenoid valve 14 is thereby stopped. reaches the B stage, and the fuel pressure on the downstream side of the slow jet 11 is increased. Thus, the liquid level in the fuel column 10a rises based on the pressure difference between this fuel pressure and the negative pressure of the low-speed system bench lily 9. If the liquid level height of the fuel column 10a of the passage 10 is above the set value, that is, the fuel flow rate is too small compared to the air flow rate of the low-speed system bench lily 9, resulting in an overly lean mixture. In this case, the light receiving element 1 from the light emitting element 12a is caused by the fuel in the fuel column 10a.
2b decreases, and as a result, the detection means 12
The output of is O _h on the high output side (see Figure 2). This output _Oh is sent as a drive signal to the solenoid valve 14 via the control circuit 16, thereby switching the opening degree of the valve 14 to the A stage. As a result, the fuel flow rate increases, the fuel pressure on the downstream side of the slow jet 11 decreases, and the liquid level in the fuel column 10a decreases. By repeating this rising and falling of the liquid level alternately, the height of the fuel column 10a is maintained at the set value, and thus the negative pressure in the low-speed system bench 9 and the slow jet 11 are
corresponds to the downstream fuel pressure. That is, since the amount of fuel flowing out from the slow port 13 accurately follows the negative pressure of the low-speed system vent 9, which accurately represents the intake air flow rate, a mixture with an appropriate air-fuel ratio is always supplied throughout the low-speed range. Ru.

As mentioned above, since the relationship between the air flow rate and the fuel flow rate is directly controlled and the air-fuel ratio is determined thereby, there is no need to make delicate settings such as the hole diameter and position of the slow port 13. The air flow rate and fuel flow rate are automatically adjusted, and as a result, such setting man-hours can be significantly reduced.

Incidentally, the light emitting element 12a and the light receiving element 12b of the detection means 12 in the above embodiment may be arranged in the passage 10 as shown in FIG. 5, or may be arranged as shown in FIG. The liquid level height may be detected by floating a float 10b made of an opaque material on the fuel column 10a. In these cases, the output from the detection means 12 sends signals to the control circuit 16 as shown in FIGS. 6 and 8, respectively, depending on the liquid level height, and the same effects as in the above embodiments can be obtained.

FIG. 9 shows a second embodiment, in which the present low-speed fuel supply device is applied to the primary side P of a compound type carburetor. In the figure, 21 is a bench lily, 2
2 is the throttle valve, 23 is the slow jet 2
4 and the bench lily 21 are connected to each other, 25
26 is a slow port that communicates with the slow jet through the passage 27 and opens into the intake passage on the primary side P; 28 is a detection means disposed in the passage 23 and configured similarly to the first embodiment; This is a solenoid valve arranged and configured similarly to the first embodiment, and the secondary side S includes a bench lily 29, a throttle valve 30, a main nozzle 31, a main air jet 32, a main jet 33, and a slow jet 3.
4 and a slow air jet 35, the throttle valve 30 is configured to close the intake passage on the secondary side S in a low speed range by a control means 36 operated by the negative pressure of the bench lily 21 and the vent lily 29. It is set.

In the case of this embodiment, intake air is supplied from the primary side P in the low speed range of the engine, but the detection means 25, solenoid valve 28, etc. operate in the same manner as in the first embodiment. That is, the slow port 26 is adjusted so that the ratio of the fuel pressure on the downstream side of the slow jet 24 to the negative pressure of the bench lily 21, which accurately represents the air flow rate flowing through the vent lily 21, is always a constant value.
Since the flow rate of fuel discharged from the manifold is controlled, a mixture with a constant air-fuel ratio is always supplied to the manifold even if the air flow rate changes. In this case as well, similar effects as in the first embodiment can be obtained, such as reducing the number of man-hours required for setting the slow port 26.
An extremely appropriate air-fuel mixture can be obtained on the primary side P in a low speed range. Further, as the engine speed increases beyond the low speed range, the supply of the air-fuel mixture is gradually shifted to the secondary side S, which is basically the same as in a normal compound type carburetor.

In addition, the solenoid valve 1 in each of the above embodiments
The fuel passages 4 and 28 may be duty-controlled by input pulses, or may be made to conduct or cut off the fuel passages 15 and 27 based on changes in input voltage. Furthermore, floats equipped with electrical contacts may be employed as the detection means 12, 25, and in either case, the same effects as in the above embodiments can be obtained.

[Effect of idea]

As mentioned above, the low-speed fuel supply system according to the present invention has the following advantages:
It has extremely excellent practical advantages, can supply an appropriate air-fuel mixture in a low speed range, and can be extremely effective as a low speed fuel supply device for a carburetor.

[Brief explanation of the drawing]

1 to 8 show a first embodiment of the low-speed fuel supply system according to the present invention, FIG. 1 is a schematic sectional view showing the overall configuration, and FIG. 2 is a detection means for detecting the fuel column height. 3 is a graph showing the relationship between the output of the detection means and the height of the fuel column, FIG. 4 is a control circuit diagram of the solenoid valve, and FIGS. 5 and 7 each show examples of the arrangement of the detection means. 6 and 8 are graphs showing the relationship between the output of the detection means and the height of the fuel column shown in FIGS. 5 and 7, respectively, and FIG. 9 shows the second embodiment. FIG. 10 is a cross-sectional view of a low-speed fuel supply system according to the present invention applied to a compound type carburetor, and FIG. 10 is a cross-sectional view of a low-speed fuel system of a conventional carburetor. 1... Intake passage, 2... Air valve, 3, 36
...Control means, 4...Fixed bench lily, 5,2
2,30...Throttle valve, 6,31...Main jet, 9...Low speed system bench lily, 10,
23...Aisle, 11,24...Slow jet,
12, 25...Detection means, 13, 26...Slow port, 14, 28...Solenoid valve.

Claims (1)

[Scope of utility model registration request] A low-speed fuel passage that communicates with a low-speed bench lily that can generate negative pressure according to the air flow rate, a slow jet and a slow port, a communication passage that communicates the low-speed bench lily and the low-speed fuel passage, and a communication passage that is disposed in the communication passage. a detection means for detecting the liquid level height of the fuel column; and a fuel disposed downstream of a connection portion between the low-speed fuel passage and the communication passage, and whose operation is controlled based on an output signal from the detection means. a flow rate control means, and the fuel flow rate is controlled by the fuel flow rate control means so as to control the liquid level of the fuel column to be constant with respect to the air flow rate. Low speed fuel supply system.