JPS6114349B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for adjusting the fuel flow rate of a carburetor for an internal combustion engine, which is advantageous in improving fuel efficiency and at the same time taking measures against exhaust gases, and an apparatus directly used for carrying out the method. In general, the fuel consumption rate g (gr/PS·Hr) of an internal combustion engine is at its minimum near the rotational speed at which the engine produces maximum output. If you set the carburetor etc. to reduce this fuel consumption rate g, the air-fuel mixture will be leaner and fuel efficiency will improve. It starts to occur. Therefore, in order to continue operating the engine, it is necessary to keep the fuel consumption rate g always larger than a certain minimum value. (This minimum value will be referred to as the engine's movable lean limit). The fuel consumption rate g gradually increases as the engine speed moves away from its minimum value, and the air-fuel mixture becomes rich, which not only reduces fuel efficiency but is also disadvantageous in terms of exhaust gas control. Ta. This invention was made in view of the above-mentioned problems, and the amount of bleed air in the carburetor is set in advance so that the fuel consumption rate is below the movable lean limit near the engine speed that produces maximum output. , by detecting the rotational speed of the engine during operation, detects the engine rotational speed below the movable lean limit, and within this detected rotational speed range, the fuel consumption rate is adjusted to the movable leanness by adjusting the preset bleed air amount. It is an object of the present invention to provide a method for adjusting the fuel flow rate of a carburetor, which can improve fuel efficiency and take advantage of measures against exhaust gas by reducing the fuel flow rate to more than the limit, and an apparatus that can be used directly to implement this method. This is the purpose. The present invention will be explained in detail below based on the drawings. Figure 1 shows the fuel consumption rate g (g
This is a graph showing the characteristics of r/PS・Hr), in which curve a shows the characteristics when the carburetor is set so that the engine rotational speed N is smaller than the movable lean limit b in a certain range A. , curve c shows the characteristics when the air-fuel mixture is enriched by limiting the amount of bleed air in the carburetor, and its minimum value is set to overlap the movable lean limit at rotational speed r. Note that this characteristic remains almost constant with respect to changes in throttle valve opening. The present invention can be configured, for example, to detect the certain range A and to supply fuel according to curve c within this range and according to curve a outside this range. (See the solid line in FIG. 1) That is, as shown in the block diagram of FIG. Based on the result, the battery 3 connected via the main switch 2 is connected to and connected to the solenoid valve 4. 3 and 4 are system diagrams showing an embodiment in which the present invention is applied to a slow system of a piston valve type carburetor. In this figure, reference numeral 5 denotes a carburetor, and intake air flows in the direction of arrow 7 in an air flow path 6 and is guided to an internal combustion engine (not shown). A bench lily 8 is formed in the air flow path 6, and a piston-type throttle valve 9 can be seen from above and can be moved up and down by operating an accelerator wire 10.
11 is a float chamber, in which float 1 is
Fuel (gasoline) whose liquid level is kept constant by 2.
is stored. 13 is a main bleed pipe, a main nozzle 14 provided at its upper end opens so as to face approximately the center of the throttle valve 9, and a main jet 15 provided at its lower end is connected to a float chamber. 11 is immersed in fuel. 16 is the main body boss portion 5a of the carburetor 5
A main air passage that is bored in the main bleed pipe 13 and supplies bleed air to the main bleed pipe 13,
A main air jet 17 is provided therein. 18 is a jet needle suspended from the throttle valve 9, and as the throttle valve 9 moves up and down, the main nozzle 18
and move up and down inside the main bleed pipe 13. This increases or decreases the amount of fuel drawn up from the main nozzle 18. The main system is configured as described above. Next, the slow system will be explained. A slow bleed pipe 19 has a slow nozzle 20 at its upper end that opens near the lower end of the throttle valve 9 on the engine side, and a slow jet 21 at its lower end that is immersed in the fuel in the float chamber 11. . Reference numeral 22 denotes a slow air passage, one end of which opens to the atmosphere through a solenoid valve 23 inserted and fixed into the main body boss portion 5a of the carburetor 5. FIG. 4 is an enlarged cross-sectional view taken along the line 23 showing the vicinity of the tip valve portion 23a of this electromagnetic valve 23. Contact and separation from. The solenoid valve 23 is of a normally closed type, and the valve stem 24 closes the valve seat 25 in a non-energized state.
On the other hand, there are two air channels in the slow air passage 22.
Jets 26 and 27 are provided, one end of a sub air passage 28 joins between the air jets 26 and 27, and the other end of this sub air passage 28 is connected to the valve seat 25,
It opens to the atmosphere via the valve stem 24. Therefore, when the solenoid valve 23 is closed, that is, when the valve stem 24 is blocking the valve seat 25, slow bleed occurs.
Since air is supplied only from the air jet 26, the amount of bleed air is small, but when the solenoid valve 23 is open, the slow bleed air flows through the auxiliary air passage 2.
Since it is also supplied from air 8, the amount of bleed air increases. As a result, as the solenoid valve 23 opens and closes, the flow rate of fuel flowing from the slow system to the intake passage decreases or increases. FIG. 5 is a circuit diagram showing the configuration of the rotational speed detection switching unit 1. As shown in FIG. In this figure, reference numeral 29 is a simplified representation of the rotational speed signal generator, and the output end of the flywheel magneto 30 is connected in parallel to a series circuit of a rectifier 31 and a battery 32, and to an AC regulator 33. . That is, the voltage of the AC output generated by the flywheel magneto 30 is controlled by the AC regulator 33, and further rectified by the rectifier 31 to be connected to the battery 32.
is charged to. Note that 34 is a headlamp that is turned on and off by a switch (not shown). Here, the output of the flywheel magneto 30 is alternating current, and since its frequency is directly proportional to the engine speed (not shown), this is used as the rotational speed signal. Since this signal is in the form of a pulse, it is waveform-shaped into a rectangular wave in the waveform shaping circuit 35 and then guided to the frequency/voltage conversion circuit 36. Here, the frequency of the square wave is
It is converted into a voltage corresponding to this frequency. That is, the rotational speed signal is converted into a voltage corresponding to the rotational speed. Next, this voltage is determined by a comparator 37 within a preset constant voltage range, that is, a voltage range corresponding to the rotational speed range A in FIG. In other words, on the low rotational speed side of this range A, for example
The integrated circuit 37a that detects 4000R.PM is 4000R.P.
Below M, the output is set to high level (H), and
The integrated circuit 37b that detects high rotation speeds in range A, for example, 6000 R.PM, sets its output to low level (L) at 4000 R.PM or higher, and sets its output to low level (L) at 6000 R.PM or lower. P.
M. or above is considered high level (H). That is, the output of the comparator 37 is as shown in the following table.

[Table] The output of such a comparator 37 is led to a drive circuit 39 via an OR circuit 38. In other words, OR
The circuit 38 includes comparators 37a and 3 as shown in the table above.
When any output of the transistor 7b is at a high level (H), the base voltage of the NPN transistor 39a forming the drive circuit 39 is set at a high level (H). As a result, the NPN type transistor 39a becomes non-conductive when the engine speed is within 4000 to 6000 R.PM, and becomes conductive in other ranges. The collector of this NPN type transistor 39a is a PNP power transistor constituting the switching circuit 40.
The power transistor 40a is connected to the base of a transistor 40a, and is driven to be conductive only when the NPN type transistor 39a is conductive. That is, as shown in the table above, it becomes conductive except in the range of 4000 to 6000 R.PM. This power transistor 4
A surge absorbing diode 40b is connected to the solenoid coil 23a connected to the collector 0a via a lead wire 41. The solenoid coil 23a drives the electromagnetic valve 23. Since this solenoid valve 23 is a normally closed type as described above,
Eventually, at 4,000 to 6,000 R.PM, the solenoid coil 23a becomes de-energized, the auxiliary air passage 28 is closed, and the fuel flow rate from the slow system shown in FIG. 3 increases and reaches the curve c shown in FIG. 1. The engine will be operated. On the other hand, outside the above range, the solenoid coil 23a is energized, so the auxiliary air passage 28 is opened, and the slow system fuel flow rate decreases and is operated on the curve a in FIG. In FIG. 5, 42 is a diode for absorbing reverse surges caused by disconnection and connection of the switch, 43 is a Zener diode for constant voltage, and 44 is a smoothing diode for absorbing ripples in the output of the flywheel magneto 30. It is a capacitor. In the embodiment described above, only the amount of bleed air in the slow system is controlled, but it can be applied not only to the main system but also to the main system and the slow system. FIG. 6 shows an embodiment in which the amount of bleed air in the main system and slow system is controlled by one solenoid valve 23. That is,
A slow air passage 22 and a sub air passage 28 open between the two air jets 45, 46 of the main air passage 16 in FIG. Therefore, outside the rotational speed range A shown in FIG. 1, the amount of bleed air increases in both the slow system and the main system. It becomes possible to drive so as to follow the road more faithfully. In the above embodiment, the bleed air amount is configured to be switched in two stages, but it is also possible to switch it in three or more stages. As explained above, in this invention, the amount of bleed air in the carburetor is set in advance so that the fuel consumption rate is below the movable lean limit near the engine rotation speed at which the maximum output is achieved, and by detecting the engine rotation speed that is below the movable lean limit, and within this detected rotation speed range, reduce the preset bleed air amount so that the fuel consumption rate is above the movable lean limit. Because of this, the air-fuel mixture does not become too rich over a wide range of rotational speeds, improving fuel efficiency. Therefore, since the air-fuel mixture is sufficiently combusted, the amount of unused gas in the exhaust gas is reduced, which is advantageous in terms of exhaust gas countermeasures.
In addition, the solenoid valve that controls the amount of bleed air is installed so that its tip valve opens and closes the auxiliary air passage provided in the boss of the carburetor body, making the entire device extremely compact and improving operational reliability. improves. Furthermore, since this invention controls the amount of bleed air only by the rotational speed of the engine and does not depend on the intake pipe negative pressure, good results can be obtained even when applied to a two-stroke engine with small intake pipe negative pressure. Since a pressure sensor with poor reliability and large product variations is not used, the reliability is further improved and the productivity of the device is improved.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the characteristics of fuel consumption rate versus engine speed, Fig. 2 is a block diagram of the present invention, and Figs. 3 and 4 are system diagrams and - lines showing embodiments in which the invention is applied to a slow system. 5 is a circuit configuration diagram of a rotational speed detection switching unit, and FIG. 6 is a sectional view corresponding to the - line showing another embodiment in which the present invention is applied to a main system and a slow system. 1...Rotation speed detection switching unit,
4, 23...Solenoid valve, 5...Carburizer, 5a...Main body boss section, 16...Main air passage, 22...
Slow air passage, 23a... Tip valve section, 28...
...Secondary air passage.

Claims (1)

[Claims] 1. The amount of bleed air in the carburetor is set in advance so that the fuel consumption rate is below the movable lean limit near the engine rotation speed at which the maximum output is achieved, and the rotation speed of the engine during operation is detected. By doing so, it is possible to detect an engine rotation speed that is below the movable lean limit, and to reduce the preset bleed air amount within the detected rotation speed range so that the fuel consumption rate is equal to or higher than the movable lean limit. Features a fuel flow rate adjustment method for a carburetor. 2. A carburetor whose bleed air amount is set in advance so that the fuel consumption rate is below the movable lean limit near the engine rotational speed that produces maximum output, and an auxiliary air passage that merges with the air passage in the main body boss of this carburetor. The engine is equipped with a solenoid valve that opens and closes, and a rotation speed detection switching unit that detects the rotation speed of the engine and controls the electromagnetic valve, and the rotation speed detection switching unit detects the rotation speed of the engine during operation. detects an engine rotation speed that is below the movable lean limit, and controls a solenoid valve that closes the auxiliary air passage and reduces the preset bleed air amount within the detected rotation speed range. A fuel flow rate adjustment device for a carburetor featuring: