JPS6321026B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio correction device for a carburetor, and in particular to a correction air passage that supplies correction air according to the operating state of an engine to air metered by slow air bleed. The present invention relates to an air-fuel ratio correcting device for a carburetor, in which the amount of air passing through the correcting air passage is adjusted by a solenoid valve.

FIG. 1 is a sectional view of a carburetor equipped with a conventional air-fuel ratio correction device known from Japanese Patent Application Laid-Open No. 53-117133. A main nozzle 2 opens at a bench lily portion of the carburetor 1, and a throttle valve 3 is installed downstream of the bench lily portion. An air passage 4 opened upstream of the bench lily portion communicates with an idle port and a bypass port opened near the throttle valve 3 via a slow air bleed 5 and a slow passage 6. Further, the upper end of the slow passage 6 communicates with a solenoid valve via a correction air passage 7, and the middle stage of the slow passage 6 is connected to a slow jet 8.
It communicates with

The upper end of the slow jet 8 is sealed with a blind lid 9, and the lower end thereof communicates with the float chamber via a slow fuel passage 10. Also, slow jet 8
An air passage from the economizer bleed 11 is in communication with the lower end of the economizer bleed 11 .

An outline of the operation of such an air-fuel ratio correction device will be described next. When the engine is operating at low speed, negative pressure is generated in the slow passage 6, so the air taken in from the air passage 4 is metered by the slow air bleed 5, mixed with the fuel taken in from the slow jet 8, and then flows from the idle port and bypass port into the intake passage. The air is then ejected into the engine, mixed with air taken in from the intake passage, and then supplied to the engine. At this time, a solenoid valve (not shown) operates to introduce air for correcting the air-fuel ratio through the correction air passage 7. Note that the air sucked through the economizer bleed 11 rises in the fuel in the slow jet 8 as a large number of small bubbles, and has the effect of atomizing the fuel introduced from the slow jet 8 into the slow passage 6.

The conventional air-fuel ratio correction device configured as described above has the following problems.

(1) The solenoid valve that supplies correction air is connected via the correction air passage 7 and is separate from the carburetor 1, so the total amount of air supplied by the slow air bleed 5 and the solenoid valve is When making test measurements, the solenoid valve must be connected. This consumes a lot of time in the process of testing the performance of the vaporizer, causing a decrease in efficiency.

(2) The total air amount in (1) above determines the amount of slow fuel supplied, so it must be adjusted in relation to the engine speed, but it is also necessary to adjust the amount of air in each of the slow passage 6 and slow air bleed 5. Since the characteristics are usually different, the solenoid valve is adjusted. As mentioned above, since the carburetor and solenoid valve are separated, it is inconvenient to adjust them.

The present invention aims to eliminate the above-mentioned drawbacks of the prior art, and in order to achieve this purpose, a seat part facing a valve attached to the tip of a plunger of a solenoid valve for supplying correction air, and a seat part facing the valve attached to the tip of a plunger of a solenoid valve for supplying correction air, and a correction air The passage and another air passage that short-circuits this correction air passage before and after the seat part are placed together in the solenoid block of the solenoid valve, and a slow air bleed is provided in the other air passage, and a slow air bleed is provided at the tip of the air passage. The solenoid block is characterized in that an adjusting screw is attached to the solenoid block so as to abut on the seat portion of the solenoid valve and adjust the stroke of the plunger by adjusting the screwing amount.

FIG. 2 is a cross-sectional view of a carburetor equipped with an air-fuel ratio correction device according to an embodiment of the present invention, in which the same parts as in FIG. 1 are given the same reference numerals. The difference from the device shown in FIG. 1 is that a solenoid valve 15, which is an actuator, is attached to a solenoid block 17 so that it is integrated with the carburetor 1. Further, a seat portion 12 is attached to the tip of the plunger 14 of the solenoid valve 15, and the correction air passage 7 is opened and closed by the seat 12.
That is, the air passage 4b communicates the upstream side of the slow air bleed 5 in the air passage 4a with the space below the seat part 12 of the solenoid valve 15, and the space above the seat part 12 and the space downstream of the slow air bleed 5. The slow passage 6 is communicated with the correction air passage 7. The seat portion 12 faces the lower end of an adjustment screw 16 having a space communicating with the correction air passage 7, and the adjustment screw 16 is screwed into a solenoid block 17.

The coil 13 of this solenoid valve 15 is connected to a control circuit (not shown), and the control circuit inputs signals from various detectors that detect the operating state of the engine, calculates a suitable amount of auxiliary air, and determines a suitable amount of auxiliary air.
It is output to 3. Signals input to the control circuit include engine speed, intake pressure, oxygen concentration in exhaust gas, etc., and are closely related to the air-fuel ratio of the air-fuel mixture supplied to the engine. The operation of this solenoid valve 15 is to change the valve opening time ratio by moving the seat part 12 at regular intervals; when the valve opening time ratio is large, the apparent degree of opening is large; As the valve time ratio increases, the apparent degree of valve opening decreases. As a result, when it is desired to enrich the currently supplied air-fuel mixture, the valve-opening time ratio is decreased, and when it is desired to dilute the air-fuel mixture, the valve-opening time ratio is increased to control the air-fuel ratio.

The operation of the air-fuel ratio correction device configured in this manner at low speeds will be described next. Slot valve 3 at low speed
Since the opening degree of is small, negative pressure is generated in the slow passage 6,
Fuel, which is a mixture of air taken in through the air passage 4 and the slow air bleed 5 and air bubbles introduced through the economizer bleed 11, travels through the slow passage 6 and is ejected downstream of the throttle valve 3. As described above, since the coil 13 of the solenoid valve 15 is intermittently supplied with current from the control circuit, the plunger 14 is moved in and out to open and close the correction air passage 7 with the seat portion 12 at regular intervals.
When this seat portion 12 is opened, the air passage 4
The air that has passed through b enters the slow passage 6 through the correction air passage 7 and replenishes air.

Based on 50% duty, when the opening time and closing time of the solenoid valve 15 are equal, when the valve opening time ratio becomes larger than this, the amount of replenishment air increases and the mixture supplied to the engine becomes lean. Therefore, if the valve opening time ratio is reduced from this, the air-fuel mixture will become richer. In this way, the air-fuel ratio of the air-fuel mixture supplied to the engine during low-speed operation is precisely adjusted to achieve a suitable operating condition, and the composition of the exhaust gas is also purified to reduce fuel consumption.

The adjustment screw 16 can be rotated with a screwdriver or the like, and the duty ratio can be adjusted using this. Therefore, even if there are differences in the characteristics of the slow air bleed 5 or the slow passage 6, the amount of replenishment air can be adjusted accordingly. The vaporizer 1 can be arranged. That is, it becomes easy to align the air-fuel ratio correction characteristics at the end of the mass production process of the carburetor.

FIG. 3 is a diagram comparing and showing the control characteristics of solenoid valves, where the horizontal axis shows the valve opening time ratio of the seat portion 12, that is, the on-duty %, and the vertical axis shows the air supplied from the air-fuel ratio correction device. The absolute amount (hereinafter referred to as AB amount)/min is shown. If the on-duty value becomes large and the valve opening time ratio becomes large, the amount of make-up air increases, but depending on the carburetor, it has a width of D and is distributed between _P1 and _P2 . In addition,
The value E in the AB amount is the slow air amount measured by the slow air bleed 5, and this amount is constant regardless of the on-duty.

In the device of this embodiment, it is easy to adjust the position of the adjusting screw 16. Therefore, even if there is a variation of C when the on-duty value is 0%, it is easily possible to match the Q point at the on-duty value of 100%. This makes it easy to reduce the variation within the range surrounded by the broken line in the figure, and it becomes easy to reduce the variation of each vaporizer to half that of the conventional one at the on-duty value of 50%, which is the most used value. In addition, the line _P1 and the broken line,
The shaded area between line P ₃ and the broken line is a range that can be easily removed, and it is possible to greatly improve the adjustment work efficiency of this type of carburetor and improve the air-fuel ratio controllability. can.

Figure 4 shows on-duty value 100% during no-load operation.
This is a diagram that compares and shows the change characteristics of _the air-fuel mixture when in this exhaust
The amount of CO + CO ₂ is when a mixture with a lean air-fuel ratio is supplied. Examining the trends of P ₁ , P _{2 ,} and P ₃ in Figure 3 shows that at N ₁ near idling operation, P ₁ , P ₂ , and P ₃ can all be set to the same CO + CO ₂ by the slow adjust screw. However, if the opening degree of the throttle valve 8 is increased to N ₁ or more, a lower speed air-fuel mixture will be supplied than the bypass port. At this time AB
In the case of a carburetor with a large amount of AB, P ₁ shifts to the lean side of the air-fuel mixture, and in the case of a carburetor with characteristics of a small amount of AB, P ₃ shifts to the side that enriches the air-fuel mixture. When the rotational speed is further increased to _N2 or higher, _P1 , which has a large amount of AB, falls below the stable rotational range shown by the broken line, and the air-fuel ratio deteriorates, resulting in a state in which the engine does not operate smoothly. If this happens, the control circuit that drives the solenoid valve 15 will no longer operate, and the solenoid valve 15 will not close, making duty ratio control impossible.

However, the device of this embodiment can be easily adjusted as shown in _FIG .
It can be set outside the unstable region as shown in FIG. Therefore, it is possible to drive the engine smoothly. Note that the unstable region is the shaded area.

The air-fuel ratio correction device of this embodiment has the following effects.

(1) Since the solenoid valve that controls the amount of correction air is installed integrally with the carburetor, there is no need for piping to serve as the correction air passage 7 as in the prior art, resulting in a small and simple configuration. This is achieved by communicating the upstream side of the slow air bleed 5 with the space below the seat part 12 of the solenoid valve 15, and the downstream side of the slow air bleed 5 with the space above the seat part 12.

(2) The adjustment screw 16 facing the seat portion 12 of the solenoid valve 15 can adjust the correction air amount so as to significantly reduce the variation in characteristics of the slow fuel system of the mass-produced carburetor 1. The air-fuel ratio control characteristics of the air-fuel mixture during low-speed operation of a carburetor equipped with a correction device can be improved. After the manufacturer has set a suitable position for the adjusting screw 16, the head of the adjusting screw 16 is sealed and tamper-proofed, as shown in FIG. 2, before being shipped.

As explained above, according to the present invention, the adjustment screws for adjusting the slow air bleed, correction air passage, and plunger stroke are installed together in the solenoid block of the solenoid valve for controlling the correction air passage. Measuring, adjusting, and testing the amount of air can now be done with a single solenoid valve that includes a solenoid block, making it possible to perform carburetor performance tests and adjustments more efficiently.

In addition, in the past, the air intakes for the correction air passage and another air passage were separate, so even if the air volume in the slow passage and the air volume in the correction passage were adjusted before installing the carburetor, each air intake Since the pressure changes are different, the amount of air in both passages after installation in the carburetor does not match the amount at the time of adjustment, and there is a problem that readjustment must be made after installation. It may be possible to make adjustments in advance by taking into account the difference in pressure fluctuations, but since the pressure changes in a complex manner depending on the operating condition of the engine, it is necessary to assume this before installing the carburetor and adjust the amount of air in both passages. That's difficult. In the present invention, by installing an air bleed in another air passage that short-circuits the correction air passage, both passages are connected to the same air intake, so that the influence of pressure fluctuations in the intake pipe is avoided on both passages. As a result, the above-mentioned problem before and after installing the carburetor was eliminated, making it possible to make adjustments before installing the carburetor.

In addition, the holes made in the inner wall of the vaporizer can be made into one,
Workability and fear of clogging were reduced by half.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a carburetor equipped with a conventional air-fuel ratio correction device, Fig. 2 is a sectional view of a carburetor equipped with an air-fuel ratio correction device which is an embodiment of the present invention, and Fig. 3 is a solenoid valve. A diagram comparing and showing the control characteristics of
FIG. 4 is a diagram comparing and showing the change characteristics of the air-fuel mixture when the on-duty value is 100% in no-load operation. 1... Carburetor, 2... Main nozzle, 3... Throttle valve, 4... Air passage, 5... Slow air bleed, 6... Slow passage, 7... Correction air passage, 8... Slow jet, 10...Slow fuel passage, 11...Economizer bleed, 12
... Seat portion, 13 ... Coil, 14 ... Plunger, 15 ... Solenoid valve, 16 ... Adjustment screw, 17 ... Solenoid block.

Claims (1)

[Scope of Claims] 1. A slow air bleed, and a correction air passage that supplies correction air according to the operating state of the engine to the air measured by the slow air bleed, and the correction air passage In the air-fuel ratio correction device for a carburetor, which uses a solenoid valve to adjust the amount of air passing through the carburetor, an electromagnetic solenoid section consisting of a coil and a plunger installed in the main body of the carburetor faces a valve attached to the tip of the plunger. The electromagnetic valve is constituted by a solenoid block that is fixed to the carburetor main body and includes a seat portion and the correction air passage extending in front and rearward of the seat portion, and
An air passage is formed in the solenoid block to short-circuit the front and back of the seat portion of the solenoid valve, and the slow air bleed is installed within the air passage, and its tip abuts the seat portion of the solenoid valve. An air-fuel ratio correcting device for a carburetor, characterized in that an adjusting screw is attached to the solenoid block to adjust the stroke of the plunger by adjusting the screwing amount. 2. The device described in claim 1, characterized in that a passage in which an economizer bleed is installed is opened in the air intake passage of the carburetor body to which the correction air passage and the other air passage are connected. Air-fuel ratio correction device for carburetor. 3. In the device described in claim 1, the adjustment screw is formed in a bottomed cylindrical shape having an opening at its tip that is opened and closed by the seat portion, and the correction air passage is formed in the shape of a bottomed cylinder. An air-fuel ratio correction device for a carburetor, characterized in that the device includes a cylindrical portion of an adjustment screw.