JPS5915620A - Exhaust gas purifier of internal-combustion engine - Google Patents

Abstract

PURPOSE:To ensure good accelerating operation and good high loaded operation, by providing a bypass passage connecting a fuel passage in the upstream of a metering jet and a fuel passage in the downstream of the metering jet. CONSTITUTION:A bypass passage 30 of squared shape with one end open detouring a metering jet 26 is formed in a carburetor housing 2. A fuel flow inlet 31 of this bypass passage 30 is opened to the inside of a fuel passage 25 in the upstream of the metering jet 26 while a fuel flow outlet 32 of said passage 30 is opened to the inside of the fuel passage 25 in the downstream of the metering jet 26. A metering jet 33 for metering fuel flowing in the bypass passage 30 is inserted into the bypass passage 30 in the vicinity of the fuel flow inlet 31. One side of the bypass passage 30 is connected through the first air bleed passage 35 to the inside of an intake passage 7, and the other is connected through the second air bleed passage 36 to a solenoid valve 50.

Description

[Detailed description of the invention] The present invention relates to an exhaust gas purification device for an internal combustion engine.

A three-way catalyst is known as a catalyst that can simultaneously reduce three harmful components HC, CO, and NOx in exhaust gas. The purification efficiency R of this three-way catalyst is highest when the air-fuel ratio A/F is approximately the stoichiometric air-fuel ratio, as shown in FIG. The possible air-fuel ratio range is 1J, which is a narrow air-fuel ratio of about 06. Usually, this air-fuel ratio range in which a purification efficiency of 80 or more cents or more can be obtained is called a window W. Therefore, in order to simultaneously reduce the three harmful components in the exhaust gas using a three-way catalyst, the air-fuel ratio must be maintained within this narrow window W at all times.

To this end, in conventional exhaust gas purification systems, an oxygen concentration detector that can determine whether the air-fuel ratio is greater or less than the stoichiometric air-fuel ratio is installed in the engine exhaust passage, and the output signal of the oxygen concentration detector is used to detect the air-fuel ratio. The fuel ratio is controlled to be within the air-fuel ratio within the window W. However, an exhaust gas purification device using such an oxygen concentration detector uses expensive oxygen l! I
There is a problem in that the manufacturing cost of the exhaust gas purification device increases because it requires a U detector and an expensive electronic control unit for air-fuel ratio control.

However, recently, S A E paper H
As described in Japanese Patent Publication No. 760201 and Japanese Patent Publication No. 56-4741, the function of the three-way catalyst was gradually elucidated, and it was discovered that the three-way catalyst had an oxygen retention function. In other words, when the air-fuel ratio is on the lean side compared to the stoichiometric air-fuel ratio, the three-way catalyst removes oxygen from NOx, reduces NOx, and retains this removed oxygen, so that the air-fuel ratio is on the richer side than the stoichiometric air-fuel ratio. When this happens, the retained oxygen is released to oxidize CO4IC.1 Therefore, when the air-fuel ratio is alternately varied to the lean side and rich side with respect to the standard air-fuel ratio, the standard air-fuel ratio deviates from the stoichiometric air-fuel ratio. However, due to the oxygen retention function mentioned above, pNOx
The reduction action of CO and the oxidation action of HC are promoted, and high purification efficiency can be obtained. FIG. 1(b) shows the window WO of the standard air-fuel ratio A/F when the air-fuel ratio is varied by ±1.0 with respect to the standard air-fuel ratio at a frequency of IHz. It can be seen from FIGS. 1(a) and 1(b) that the window W0 becomes wider when the air-fuel ratio is varied at a constant frequency. This means that if the air-fuel ratio is varied at regular intervals, high purification efficiency can be obtained even if the reference air-fuel ratio deviates somewhat from the stoichiometric air-fuel ratio. On the other hand, when the air-fuel ratio fluctuation frequency is shortened, that is, when the air-fuel ratio fluctuation period is lengthened, the oxygen retention capacity of the three-way catalyst becomes saturated, and the oxidation-reduction ability based on the oxygen retention function decreases, resulting in purification of the three-way catalyst. 3. Figure 1(c) clearly shows this. In FIG. 1(c), the vertical axis R represents the purification efficiency, and the horizontal MF represents the fluctuation frequency of the air-fuel ratio. Furthermore, if the air-fuel ratio fluctuation fi] is made smaller, the air-fuel ratio cannot be varied alternately between the rich side and the rich side, so the width of the window becomes narrower. Therefore +4 of window
It can be seen that there is an optimal air-fuel ratio fluctuation cycle and fluctuation period in order to widen J.

As mentioned above, if the air-fuel ratio is fluctuating and the frequency of the air-fuel ratio is appropriately selected, the window can be widened, and therefore high purification efficiency can be achieved even if the reference air-fuel ratio slightly fluctuates relative to the stoichiometric air-fuel ratio. Obtainable. This means that if a narrow fuel supply system is used during fluctuations in the reference air-fuel ratio, feedback control based on the output signal of the oxygen concentration detector is not used.
1 also means that high purification efficiency can be obtained.

In theory, if a fuel injection valve is used as a fuel supply system, it is possible to narrow the fluctuation period of the reference air-fuel ratio, but since the fuel injection device is expensive, the manufacturing cost of the engine increases.

Therefore, in order to keep the manufacturing cost of the engine low, it is necessary to use a carburetor. However, in conventional fixed venturi type carburetors, the reference air-fuel ratio fluctuates widely, and in conventional variable venturi type carburetors, the reference air-fuel ratio varies greatly during acceleration or depending on engine temperature. Alternatively, it is difficult to obtain high purification efficiency even if a variable Penchili type vaporizer is used.

An object of the present invention is to provide an exhaust gas purification device that can ensure high exhaust gas purification efficiency using an inexpensive carburetor without using an oxygen a degree detector.

The present invention will be described in detail below with reference to the accompanying drawings.

Referring to FIG. 2, 7, 1 is an intake manifold, 2 is a variable venturi type carburetor installed on the intake manifold 1,
3 indicates an exhaust manifold, 4 indicates a catalytic converter,
A three-way monolith catalyst 5 is arranged inside the catalytic converter 4 . The variable venturi type carburetor 2 includes a carburetor housing 6, an intake passage 7 extending vertically within the housing 6, a suction piston 8 that moves laterally within the intake passage 7, and a suction piston 8 that is attached to the distal end surface of the suction piston 8. a spacer 10 fixed on the inner wall surface of the intake passage 7 facing the tip surface of the suction piston 3, a throttle valve J1 provided in the intake passage 7 downstream of the suction piston 8, and a throttle valve J1 provided in the intake passage 7 downstream of the suction piston 8; -) A venturi portion J3 is formed between the distal end surface of the suction piston 8 and the spacer 10. A hollow cylindrical casing 14 is fixed to the carburetor housing 6, and the casing 1
A guide sleeve 15 extending in the axial direction of the casing 14 inside the casing 14 is attached to the guide sleeve 4 . A bearing J7 with a large number of balls 16 is inserted into the guide sleeve 15, and the outer end of the guide sleeve 15 is closed by a blind cover 18, while a guide rod 19 is fixed to the suction piston 8. This guide rod 19 is connected to the bearing 1
7 so as to be movable in the axial direction of the guide rod 19.

Since the suction piston 8 is thus supported by the casing 14 through the support 7, the suction piston 8 can move smoothly in its axial direction. The interior of the casing 14 is divided into a negative pressure chamber 20 and an atmospheric pressure chamber 21 by the suction piston 8.
A compression spring 22 that constantly presses the suction piston 8 toward the penetrating portion 13 is inserted therein. Negative pressure chamber 2o
is the suction hole 23 formed in the suction piston 8
The atmospheric pressure chamber 21 is connected to the venturi section 13 through an air hole 24 formed in the carburetor housing 6 into the intake passage 7 upstream of the suction piston 8 .

On the other hand, a fuel passage 25 extending in the axial direction of the needle 9 is formed in the carburetor housing 6 so that the needle 9 can enter therein, and a metering jet 26 is provided in the fuel passage 25. ,! The fuel passage 25 upstream of the L jet 26 connects to the float chamber 12 via a fuel flat tube 27 extending downward.
The fuel in the float chamber 12 is connected to this fuel pipe f
27 into the fuel passage 25. Furthermore, a hollow cylindrical nozzle 28 is fixed to the spacer 10 and is arranged cooperatingly with the fuel passage 25 . This nozzle 28 protrudes into the venturi portion 13 from the inner wall surface of the spacer lO,
Moreover, the upper half of the inner end frt portion of the nozzle 28 further protrudes from the lower half toward the suction piston 8. The needle 9 extends through the nozzle 28 and the n1 child jet 26, and the fuel is metered into the annular gap formed between the needle 9 and the metering jet 26 before being fed from the nozzle 2)3 into the intake passage 7. be done. .

As shown in FIG. 2, a raised wall 29 that projects horizontally into the intake passage 7 is formed at the upper end of the spacer 1o, and the flow rate is controlled between this raised wall 29 and the tip of the suction piston 8. 1. When the @Seki operation is started, air flows downward in the intake passage 7. At this time, the air flow is constricted between the suction piston 8 and the raised wall 29, so that negative pressure is generated in the venturi portion 13, and this negative pressure is guided into the negative pressure chamber 2° through the suction hole 23. The pressure difference between the suction piston 8 negative pressure chamber 20 and the atmospheric pressure chamber 21 is determined by the spring force of the compression spring 22, so that the negative pressure in the pentagonal part 13 is constant. move so that

Referring to FIGS. 3 and 4, the entire tip surface of the Zakujon piston located on the upstream side of the needle 9 is raised from the mounting end surface 3o of the needle 9 toward the tip of the needle 9. A groove 31 extending in the direction of line 111 of the intake passage 7 is formed on the tip end surface of the suction piston. The upstream part 31a of this groove 31 has a U-shaped cross section, and the needle mounting end face 3o is also located on the side closer to the tip of the needle 9, and the remaining groove part 31b is on the upstream side. Needle removal from end 31a+
j The end face 301 extends almost straight 1. Historically, the cross-sectional shape of the suction piston tip face located upstream of the needle 9 is V-shaped, expanding from the groove 31 toward the venturi portion 13. Therefore, the tip end surface of the suction piston has a pair of inclined wall portions 32a that are inclined toward the groove 31.

32b.

As can be seen from FIG. 3, when the amount of intake air is small, the raised wall 29, the inclined wall portions 32a, 32b, and the groove upstream end 3ia form the t-hill into an isosceles triangular intake air control constriction part K. It is formed.

By forming the intake air control constriction part K in this way, the lift amount of the suction piston 8 is made to be proportional to the opening area of the intake air control constriction part, and therefore the lift amount of the suction piston 8 is The suction piston 8 is supported by a bearing 17, so it moves with good responsiveness to changes in the intake air amount. When the amount of intake air increases, the piston 8 moves smoothly and responsively to the increase in the amount of intake air. As a result, even when the amount of intake air changes rapidly, such as during acceleration, the lift of the suction piston 8 increases in proportion to the increase in the amount of intake air, so the amount of fuel supplied from the nozzle 28 increases. is always proportional to the amount of intake air 1.Furthermore, as shown in FIG. Since the fuel supplied from the nozzle 28 is immediately supplied into the engine cylinder together with the intake air flow, the furnace material supplied from the nozzle 28 is immediately supplied into the engine cylinder even when the amount of intake air is small. Even if the amount of intake air increases rapidly as during operation, the amount of fuel supplied from the nozzle 28 is proportional to the amount of intake air as described above, and moreover, the amount of fuel supplied from the nozzle 28 is immediately Since the air-fuel mixture is supplied into the engine cylinder, the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder is maintained almost constant even if the amount of intake air changes rapidly. Furthermore, since the suction piston 8 is supported by the bearing 17, the engine temperature does not affect the movement of the suction piston 8, and thus the suction piston 8 responds to changes in the amount of intake air regardless of the engine temperature. Able to move responsively. Thus, when the variable venturi carburetor 2 shown in FIG. 2 is used, the air-fuel ratio of the air-fuel mixture supplied into the engine cylinders is a constant value, e.g., regardless of the engine temperature and engine operating condition. The air-fuel ratio can be maintained at approximately the stoichiometric air-fuel ratio.

Referring to FIG. 2, a U-shaped bypass passage 30 is formed in the carburetor housing 2 to bypass the metering socket 26. As shown in FIG. The fuel inlet 3] of this 24747 passage 30 opens into the fuel passage 25 upstream of the metering jet 26, and the fuel outlet 32 of the bypass passage 30 opens into the fuel passage 25 upstream of the metering jet 26.
6 opens into the fuel passage 25 [1]. In the bypass passage 30 in the vicinity of the coal supply inlet 31, an IT amount fugitate 33 for metering the fuel flowing in the bypass passage 30 is inserted4.
The first air bleed passage 35 is connected to the intake passage 7 upstream of the raised wall 29 , and the second air bleed passage 36 is connected to the solenoid valve 50 . A first air bleed jet 37 is inserted into the first air bleed passage 35, and a second air bleed socket 38 is inserted into the second air bleed passage 36. During idling operation of the 11 engine, most of the fuel is removed. It is supplied to the nozzle 28 via a bypass passage 30. At this time, since the fuel is metered by the metering socket 33 with a constant cross section, the amount of fuel supplied from the nozzle 28 into the intake passage 7 is stable, thus ensuring stable engine idling operation. . As the amount of intake air increases, the needle 9 moves to the left, so that the area of the annular gap formed between the metering socket 26 and the needle 9 increases. At this time, the bypass passage 30
The amount of fuel flowing therein remains largely unchanged, and the amount of fuel flowing in the annular gap formed between the metering jet 26 and the needle 9 increases, increasing the total amount of fuel delivered from the nozzle 28.

The solenoid valve 50 has a valve chamber 52 communicating with the atmosphere via an air filter 51, a valve boat 53 connected to the second air grease passage 36, and a valve port 53 located in the valve chamber 52. It is equipped with a valve body 54 that performs opening/closing control 1, a movable plunger 55 connected to the valve body 54, and a solenoid 56 that sucks the movable gland 55.
is connected to the solenoid drive circuit 60. The solenoid drive circuit 60 includes a pulse generator 61 that generates a rectangular pulse with a frequency of IHz to 2Ity as shown in 5th VI (a), and a η1° force amplification device connected to the output terminal of the nosolus generator 61. The output terminal of the power amplifier 62 is connected to the solenoid 56. When the valve body 54 (normal valve &-) 53 is closed, the 1,000 lux generator 61 generates 9 lus, the solenoid 56 is energized and the valve body 54 opens the valve port 53. Therefore, the valve body 541t
Valve 5r-) 53 with a frequency of 1Hz to 2Hz
will be opened. When the valve element 54 opens the valve 53, air flows through the air filter 51, the valve chamber 52, and the valve.
Since air is supplied into the second air bleed passage 36 via the first air bleed passage 53, air is supplied into the pie gas passage 30 from both the first air bleed passage 35 and the second air bleed passage 36. As a result, the density of the fuel flowing through the bypass passage 3o decreases, so the amount of fuel supplied from the nozzle 28 decreases, and thus the air-fuel mixture supplied into the engine cylinder becomes lean. On the other hand, when the valve body 54 closes the valve boat 53, air is supplied only from the first air bleed passage 35 into the bypass passage 30.
The density of the fuel flowing through the nozzle 2 is high.
The fuel supplied from 8 increases to 1J.In this way, a lean mixture and a rich mixture are alternately supplied into the engine cylinder. , during the air-fuel ratio fluctuation, the second air lead socket 3
The average value of the air-fuel ratio is determined by the dimensions of the components of the carburetor that affect the amount of fuel supplied, such as the first air lead socket 37 and the single-volume jet 26.33. It's enough. Air Predige l-37,
The average value of the air-fuel ratio A/F of the air-fuel mixture supplied into the engine cylinder when the amount of intake air is small is shown in FIG. 5(b). The ratio is set to be the stoichiometric air-fuel ratio, and is determined so that the air-fuel ratio during fluctuation is approximately ±0.2 to ±0.1 with respect to the stoichiometric air-fuel ratio. Therefore, when the amount of intake air is small, the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder regardless of the engine temperature will vary from 1) ±0.2 to ±1. 0, and the original average value of the air-fuel ratio is maintained within the window WO shown in FIG. On the other hand, as described above, even if the amount of intake air increases, the amount of fuel flowing through the pinos passage 30 hardly changes tl, so that the total amount of fuel supplied from the nozzle 28 On the other hand, since the amount of air supplied from the second air bleed passage 36 into the binosu J passage 30 decreases as the amount of intake air increases, the average value of the air-fuel ratio gradually decreases as the amount of intake air increases. In this way, as the amount of intake air increases, the average value of the air-fuel ratio decreases, making it possible to obtain high output during engine acceleration and high-load operation, thus ensuring good acceleration and high engine speed. Load operation can be ensured 1. Thermal Theory As mentioned above, even if the average value of the air-fuel ratio becomes small, the average value of the air-fuel ratio is maintained within the window We shown in Fig. 1(b), so high purification efficiency can be achieved. There is nothing wrong with what you get.

As described above, according to the present invention, exhaust gas can be effectively purified using an inexpensive carburetor without using an expensive oxygen concentration detector or an expensive electronic control unit for air-fuel ratio control. The manufacturing cost can be reduced by a large iJ. Furthermore, the structure is extremely simple since only a solenoid valve is provided in the air bleed passage, and the reliability of exhaust gas purification can therefore be improved. Also,
As the amount of intake air increases, the average value of the air-fuel ratio decreases, resulting in better acceleration operation and higher engine output during high-load operation1.

[Brief explanation of drawings]

Figure 1 is line 1 showing the exhaust gas purification efficiency, No. 21 is a side sectional view of the engine intake and exhaust system, Figure 3 is a plan view of the arrow ■ in Figure 2, and No. 4 is line 1. FIG. 5, a side sectional view of the suction piston, is a diagram showing fluctuations in the air-fuel ratio. 2... Carburetor, 8... Suction piston, 9...
・Needle, 25...Fuel channel, 28...Nozzle,
30...Bypass passage, 35.36...Air bleed passage, 50...Solenoid valve. Patent Applicant: Toyota Motor Corporation Patent Attorney: Akira Aoki, Patent Attorney, Kazuyuki Nishidate, Patent Attorney, Takashi Nakayama, Patent Attorney: Akira Yamaguchi

Claims (1)

[Scope of Claims] A variable venturi type carburetor is installed in the engine intake passage, and a three-way catalytic converter is installed in the engine exhaust passage, and the carburetor has a needle fixed to a suction piston, and a fuel passage into which the needle enters. , an internal combustion engine having a metering jet disposed in the fuel passage and cooperating with a needle, comprising: a bypass passage connecting the fuel passage upstream of the metering jet and the fuel passage downstream of the metering soet; The air and air passages are connected to the atmosphere via a solenoid valve that opens and closes at a constant frequency of IHz to 2Hz, and when the solenoid valve is opened and closed, the air-fuel ratio is 1? The opening area of the solenoid valve is determined so that E changes periodically between 10.2 and ±1.0.
Furthermore, an exhaust gas purification device for an internal combustion engine, wherein the carburetor is set so that the average value of the air-fuel ratio is approximately the stoichiometric air-fuel ratio.