JPS6146658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a carburetor equipped with a fuel passage that supplies fuel stored in a float chamber to an intake passage.
In particular, the present invention relates to a carburetor which is suitable for use in an exhaust gas purifying automobile engine using a three-way catalyst and which exhibits less transient air-fuel ratio fluctuations during acceleration and deceleration.

An example of a carburetor commonly used in conventional automobile engines is shown in FIG. In the figure, 1
0 is a float chamber in which the float 12 is floated;
14 is an intake passage in which a small bench lily 16, a large bench lily 18 and a throttle valve 20 are arranged; 22 is a main nozzle 24 in the small bench lily 16 that connects the float chamber 1
The main system 25 for supplying fuel within the range 0 is a low speed port 26 formed immediately above the throttle valve 20.
and an idle port 30 having an idle adjustment screw 28 also formed immediately below the throttle valve 20.
This is a low-speed system for supplying fuel in the float chamber 10.

The main system 22 includes a main jet 32 attached to the side wall of the float chamber 10 for regulating the fuel flow rate, and a main fuel passage for supplying the fuel metered by the main jet 32 to the main nozzle 24. 34
and an air jet 36 for bleeding air into the main fuel passage 34.

Further, the low speed system 25 is connected to the main fuel passage 34.
A low-speed jet 38 that regulates the flow rate of fuel flowing into the low-speed system and a low-speed air jet 42 that regulates air bled into the low-speed fuel passage 40 are arranged in the middle of the low-speed fuel passage 40 branched from the low-speed fuel passage 40. have

Although sufficient performance can be obtained under steady operating conditions in such conventional vaporizers,
The following problem occurred during acceleration/deceleration. That is, during acceleration, if the throttle valve opening is suddenly increased as shown by the solid line A in Figure 2, the fuel discharge amount cannot follow the instantaneous increase in the amount of intake air, especially from the low-speed system. During light load acceleration where fuel discharge is switched to the main system, due to the pressure balance between the low speed system and the main system, as shown by solid line B in Fig. The air-fuel ratio becomes lean temporarily, causing stiffness, sluggishness, etc. in a car. Furthermore, even if the fuel discharge amount increases during acceleration, the amount of liquid fuel retained in the intake pipe increases due to a temporary decrease in intake flow velocity, a decrease in intake negative pressure, etc. The dilution phenomenon is promoted.

On the other hand, during deceleration, as shown by solid line C in Figure 3, if the throttle valve opening is suddenly reduced, the intake negative pressure increases, causing the liquid fuel that had been flowing and adhering to the inner wall of the intake pipe to It vaporizes temporarily, and the intake air-fuel ratio temporarily becomes excessively rich for several seconds to ten-odd seconds after the throttle valve is suddenly closed, as shown by the solid line D in FIG.
This phenomenon is especially noticeable when decelerating after acceleration.
May cause misfire or afterburn.

The above-mentioned dilution and overconcentration phenomena during acceleration and deceleration are unfavorable in terms of exhaust gas countermeasures, and in particular,
In exhaust gas purification engines using three-way catalysts that require the air-fuel ratio in the exhaust system to be kept within a narrow fixed range, there has been a problem in that the exhaust gas purification rate is significantly reduced.

As a way to solve these problems, the air-fuel ratio compensation control is performed by increasing or decreasing the fuel discharge amount according to the intake negative pressure during acceleration and deceleration, that is, when the throttle valve suddenly opens and closes.The air-fuel ratio compensation is also controlled according to the engine characteristics. In order to adjust the intake pressure, it has been proposed that a constriction means is provided in the intake negative pressure detection line (Japanese Utility Model Publication No. 156318/1983).

However, according to what is disclosed in the above publication, by appropriately selecting the throttle area of the throttle means provided in the intake negative pressure detection system, the air-fuel ratio can be appropriately compensated in the normal state of the engine (after warm-up). However, if the orifice area is selected to be small according to the conditions after warm-up, there is a problem that the response of the fuel discharge amount adjustment is delayed when the engine is unstable during warm-up.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks.The present invention prevents air-fuel ratio fluctuations during acceleration and deceleration, which vary depending on engine characteristics, by adjusting the fuel discharge amount, and also allows the adjustment to be applied to warm-up conditions. The purpose of the present invention is to provide a vaporizer that can be used accordingly. The carburetor of the present invention is connected midway through a main fuel passage connecting the float chamber and the main nozzle, and discharges a certain amount of fuel during acceleration, and sucks it during deceleration to adjust the amount of fuel discharged from the main nozzle. A pumping means that partitions a pump chamber that is operated by a movable member into a negative pressure chamber that communicates with an intake passage downstream of a throttle valve, and performs a pumping action by introducing negative intake pressure into the negative pressure chamber and displacing the movable member. A conduit for introducing negative pressure into the negative pressure chamber is provided with a throttle means that is controlled to have a large throttle area when the temperature is low and a small throttle area when the temperature is high, depending on the engine temperature.

According to the above configuration, the air-fuel ratio during a transient period can be adjusted according to the engine characteristics by changing the aperture diameter of the throttle means. That is, by changing the aperture diameter of the throttle means, the pump characteristics of the pump means change in accordance with the intake negative pressure, and the amount of fuel discharged can be increased or decreased, so that air-fuel ratio fluctuations during transient times can be suppressed.

First, during deceleration, high intake negative pressure on the downstream side of the throttle valve is gradually transmitted to the negative pressure chamber of the pump means via the throttle means, displacing the movable member. Then, a certain amount of fuel in the main fuel passage is sucked into the pump chamber, so the fuel pressure in the main fuel passage temporarily decreases.
Fuel discharge amount decreases. As a result, the air-fuel ratio temporarily becomes lean, and the temporary richness phenomenon during deceleration is compensated for.

On the other hand, during acceleration, the low intake negative pressure on the downstream side of the throttle valve is gradually transmitted to the negative pressure chamber via the throttle means, displacing the movable member in the opposite direction to that during deceleration. Then, since a certain amount of fuel is supplied from the pump chamber into the main fuel passage, the fuel pressure in the main fuel passage temporarily increases, and the amount of fuel discharged increases. As a result, the air-fuel ratio temporarily becomes too rich, and the temporary lean phenomenon during acceleration is compensated for.

In addition, since the throttle area of the throttle means is variable and controlled according to the engine temperature so that the throttle area is large at low temperatures and small at high temperatures, the above effect will occur after warm-up. Since the throttle area becomes large during engine operation, the fuel discharge amount is adjusted quickly in response to changes in the intake negative pressure, and the stability of the engine is maintained.

Embodiments of the present invention will be described in detail below with reference to the drawings. As shown in FIG. 4, the embodiment of the present invention is provided with a diaphragm pump 50 that temporarily pressurizes the fuel in the main fuel passage 34 when the engine is accelerating and temporarily reduces the pressure when the engine is decelerating. This diaphragm pump 50 has a diaphragm 52
The pump chamber 54 is connected to the main fuel passage 34 by a fuel passage 58, and the negative pressure chamber 56 has a throttle means 100 in the middle thereof. The intake passage 14 is connected to the downstream side of the throttle valve 20 by a negative pressure passage 62 provided therein. The throttle means 100 is formed to have a large throttle area when the temperature is low and a small throttle area when the temperature is high, depending on the engine temperature. For example, as shown in FIG. 5, a throttle 46 is connected in series with a shutoff valve 72 that is opened when the engine temperature is below a predetermined temperature.
can be connected in parallel to the diaphragm 60. The diaphragm 52 is urged toward the pump chamber 54 by a compression spring 64 inserted into the negative pressure chamber 56 . 66 is a pressure adjustment screw for adjusting the pressure of the compression spring 64.

The operation will be explained below. First, during deceleration,
When the throttle valve 20 is closed, the intake negative pressure downstream of the throttle valve 20 in the intake passage 14 increases, so that the high negative pressure gradually enters the negative pressure chamber 56 of the diaphragm pump 50 via the throttle means 100. The pressure inside the negative pressure chamber 56 gradually decreases. Then, the diaphragm 52 is sucked to the right in the figure against the compression spring 64, and the fuel in the main fuel passage 34 is sucked into the pump chamber 54 of the diaphragm pump 50 for a certain period of time. Then, the fuel pressure in the main fuel passage 34 temporarily decreases and the amount of fuel discharged decreases, so the amount of fuel discharged from the main nozzle 24 into the intake passage 14 decreases, and the air-fuel ratio temporarily becomes lower than before. becomes diluted. Therefore, the temporary overconcentration phenomenon that occurs in the prior art is compensated for.

On the other hand, during acceleration, since the throttle valve 20 is opened, the intake negative pressure on the downstream side of the throttle valve 20 in the intake passage 14 decreases, and this is transmitted to the negative pressure chamber 56 of the diaphragm pump 50 via the throttle means 100. As a result, the pressure inside the negative pressure chamber 56 gradually increases.
Then, due to the action of the compression spring 64, the diaphragm 5
2 is pushed out to the left in the figure, and the fuel in the pump chamber 54 is discharged into the main fuel passage 34. Then, the pressure inside the main fuel passage 34 increases, and the amount of fuel discharged from the main nozzle 24 into the intake passage 14 increases, so that the air-fuel ratio becomes richer than before for a certain period of time.
Therefore, the conventional air-fuel ratio lean phenomenon during acceleration is compensated for.

In addition, even during light load acceleration, such as when crossing the transition area from the low-speed system to the main system, pressurizing the fuel passage allows the fuel flow to be smoothly switched to the main fuel passage, which is different from conventional systems. Temporary dilution of the air-fuel ratio due to fuel tension can be prevented.

In this embodiment, a pressure adjustment screw is provided on the compression spring of the diaphragm pump, and the pressurizing force of the compression spring can be adjusted by the pressure adjustment screw, so that production is easy.

Note that in the embodiment described above, only the fuel pressure within the main fuel passage 34 was adjusted; however,
As shown by the two-dot chain line in FIG. 4, the pump chamber 54 of the diaphragm pump 50 and the low-speed fuel passage 40 are connected through the fuel passage 70, and the air-fuel ratio during acceleration and deceleration is determined when operating in the low-speed system. It is also possible to reduce the fluctuations.

Also, as shown by the broken line in FIG. 4, the fuel passage 58
Of course, it is also possible to provide a throttle 72 in the middle of the pump chamber 54 and the main fuel passage 34 to balance the pressure between the pump chamber 54 and the main fuel passage 34.

Further, in the embodiments described above, a diaphragm pump was used as the pump means, but other types of pumps such as a piston type may also be used.

Next, the operation of the aperture means 100 will be explained.

First, during warm-up, the engine temperature is low, so the shutoff valve 74 is "open" and the intake negative pressure is transmitted through both the throttles 60 and 76, and the throttle area becomes large. As a result, fluctuations in the intake negative pressure are quickly transmitted to the negative pressure chamber of the pump means.

On the other hand, after warming up, the engine temperature is high;
The shutoff valve 74 is "closed" and the intake negative pressure is reduced to the throttle 60.
Since the throttle area is small, fluctuations in the intake negative pressure are gradually transmitted to the negative pressure chamber of the pump means.

As explained above, according to the present invention, a pump means is provided which temporarily pressurizes the fuel in the fuel passage when the engine accelerates and temporarily reduces the pressure when the engine decelerates, so that the air-fuel ratio is temporarily depleted after acceleration. Temporary overconcentration after deceleration or deceleration can be compensated for with a single simple device, and breathing, sluggishness and afterburn can be prevented. The exhaust purification rate can be significantly improved. In addition, since a throttle means is provided in the conduit that introduces the intake negative pressure into the negative pressure chamber, it is possible to obtain air-fuel ratio compensation according to engine characteristics by simply changing the diameter of this throttle, making it suitable for various engines. Easy to use and has excellent versatility. Furthermore, since the throttle area of the throttle means is made variable in accordance with the engine temperature, the fuel discharge amount can be adjusted in accordance with warm-up conditions, and the stability of the engine during warm-up can be maintained.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a conventional carburetor, Fig. 2 is a diagram showing air-fuel ratio fluctuations during acceleration in a conventional carburetor, and Fig. 3 is a diagram showing air-fuel ratio fluctuations during deceleration. FIG. 4 is a sectional view including a partial duct diagram showing an embodiment of the vaporizer according to the present invention, and FIG. 5 is a partial duct diagram showing an embodiment of the throttle means. 10...Float chamber, 12...Float, 14
... Intake passage, 20 ... Throttle valve, 22 ... Main system, 24 ... Main nozzle, 25 ... Low speed system, 34
...Main fuel passage, 40...Low speed fuel passage, 50...
...Diaphragm pump, 52...Diaphragm,
54... pump chamber, 56... negative pressure chamber, 58... fuel passage, 62... negative pressure passage, 64... compression spring,
66...Pressure adjustment screw, 70...Fuel passage, 6
0,72,76... Throttle, 74... Shutoff valve, 10
0... Squeezing means.

Claims (1)

[Claims] 1 A pump chamber and a throttle valve that are communicated in the middle of the main fuel passage connecting the float chamber and the main nozzle, and discharge a certain amount of fuel during acceleration, and suck it during deceleration to adjust the amount of fuel discharged from the main nozzle. A movable member partitions a negative pressure chamber communicating with a downstream intake passage, and a pump means is provided for introducing an intake negative pressure into the negative pressure chamber and displacing the movable member to perform a pumping action. A carburetor characterized in that a conduit for introducing negative pressure into a chamber is provided with a throttle means that is controlled to have a large throttle area at low temperatures and a small throttle area at high temperatures depending on the engine temperature.