JPS5928013A - Purifier for exhaust gas of internal combustion engine - Google Patents

Abstract

PURPOSE:To obtain high purification efficiency for exhaust gas with a simple structure, by providing a solenoid valve opening and closing at given frequency in an auxiliary fuel duct connected with a bypass duct connecting parts of a fuel duct upstream and downstream a metering jet of a variable venturi type carburetor. CONSTITUTION:A needle 9 is pulled out of a metering jet 26 as a suction piston 8 is moved to the left in proportion to an increase of a suction air quantity, and with this construction, increased fuel is spouted into a suction duct 7 from a nozzle 28. A bypass duct 30 detouring around the metering jet 26 is provided and is connected with the suction duct 7 through an air bleed duct 35, in a carburetor like this. An auxiliary fuel duct 34 is made to diverge from the bypass duct 30 and connected with an inflow opening 38 of fuel opening within a fuel duct 25. A solenoid valve 40 which is opened and closed at given frequency of about 1-2Hz is provided in the duct 34, and an opening area of the valve 40 is fixed so that an air-fuel ratio is varied through the opening and closing of the valve 40 periodically within a range of about + or -0.2-+ or -1.0 to a mean value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an IJl' gas purification device for an internal combustion engine.

As a catalyst that can simultaneously reduce the three harmful components J-IC, CO and NOx in exhaust gas, the purification efficiency R is highest at a five-dimensional stoichiometric air-fuel ratio, for example, 80% or more. The air-fuel ratio range in which this is possible is narrow, with an air-fuel ratio of about 0.06. Usually 80 like this
The air-fuel ratio range in which the purification efficiency can be increased by more than 1% is called window W7. Therefore, the three-way catalyst is
In order to simultaneously reduce the three harmful components in exhaust gas, the air-fuel ratio must be maintained within this narrow window W at all times. But, L! 11116 Check whether the air-fuel ratio is higher or lower than the air-fuel ratio ↑ (A separate oxygen concentration detector is installed in the engine air passage, and based on the output signal of this oxygen concentration detector, the air-fuel ratio is within the window W. However, such an exhaust gas purification device using an oxygen detector requires an expensive oxygen concentration detector and an expensive electronic control unit to control the air-fuel ratio. Another problem is that the manufacturing cost of exhaust gas purification devices is rising.

However, recently, SAE paper Nn7
As described in No. 60201 or Japanese Patent Publication No. 56-4741, the function of the three-way catalyst was gradually elucidated.
It was discovered that the three-way catalyst has an oxygen retention function. In other words, when the air-fuel ratio is on the lean side with respect to the stoichiometric air-fuel ratio, the three-way catalyst takes oxygen from NOx and
At the same time, this stolen oxygen is retained, and when the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio, the retained oxygen is released to oxidize CO and HC. Therefore, if the air-fuel ratio is alternately varied between the lean side and the rich side with respect to the standard air-fuel ratio, even if the standard air-fuel ratio deviates from the stoichiometric air-fuel ratio, the oxygen retention function described above will reduce NOx and Co, HC. The oxidation effect of the gas is promoted and high purification efficiency can be obtained. Figure 1(b) shows the air-fuel ratio at frequency I
Window W of the standard air-fuel ratio A/F when the standard air-fuel ratio is varied by ±1.0 in Hz.

It shows. 1(a) and 1(b), when the air-fuel ratio is varied at a constant frequency, the window Wo
It can be seen that the area becomes wider. 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. Efficiency decreases. Figure 1(c) clearly shows this. In the IN 1 (C) diagram, the vertical axis R shows the purification efficiency, and the horizontal axis F shows the fluctuation frequency of the air-fuel ratio. Furthermore, if the air-fuel ratio is changed to a smaller value, the air-fuel ratio alternately changes from the rich side to the rich side and becomes less than 4, so that the window iJ becomes narrower. Therefore, it can be seen that there are optimal air-fuel ratio fluctuation periods and fluctuation periods in order to widen the window width.

As mentioned above, if the air-fuel ratio is fluctuating relative to the standard air-fuel ratio and the fluctuation frequency is appropriately selected, the window will become wider.
Therefore, high purification efficiency can be obtained even if the reference air-fuel ratio varies somewhat with respect to the stoichiometric air-fuel ratio. This means that by using a narrow fuel supply system during fluctuations in the reference air-fuel ratio, high purification efficiency can be obtained without using feedback control based on the output signal of the oxygen concentration detector.
Of course, 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 base air-fuel ratio fluctuates widely, and in conventional variable venturi type carburetors, the reference air-fuel ratio fluctuates greatly during acceleration or depending on engine temperature, so these fixed It is a national problem to obtain high purification efficiency even if a Be/Teuri type vaporizer or a variable venturi type vaporizer is used.

The purpose of the present invention is to provide an exhaust gas purification device that can ensure high exhaust gas purification efficiency using a low-grade carburetor without detecting acidity.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 2, 1 is an intake manifold, 2 is a variable venturi carburetor installed on the intake manifold 1,
3 indicates the exhaust manifold, 4 indicates the catalyst converter,
A three-way monolith catalyst 5 is arranged inside the catalytic converter 4 . The variable penetrating type carburetor 2 includes a carburetor no. a needle 9 attached to the tip 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; and a spacer 10 provided in the intake passage 7 downstream of the suction piston 8 It includes a throttle valve 11 and a foot chamber 12, and a venturi portion 13 is formed between the tip surface of the piston 8 and the spacer 10. A hollow cylindrical casing 14 is fixed to the carburetor housing 6 , and a guide sleeve 15 extending in the axial direction of the casing 14 inside the casing 14 is attached to the casing 14 . A bearing 17 with a 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 . On the other hand, a guide rod 19 is fixed to the suction piston 8, and this guide rod 19 is attached 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 via the bearing 17, the suction piston 8 can move smoothly in its axial direction. The interior of the casing 14 is divided by the suction piston 8 into a negative pressure chamber 20 and an atmospheric pressure chamber 21, and a compression spring 22 is inserted into the negative pressure chamber 20 to constantly press the suction piston 8 toward the venturi section 13. The negative pressure chamber 20 is connected to the pentane part 13 through a chixene hole 23 formed in the suction piston 8, and the atmospheric pressure chamber 21 is connected to the suction piston 8 upstream through an air hole 24 formed in the carburetor housing 6. It is connected to the intake passage 7 of the.

On the other hand, a fuel passage 25 is formed in the carburetor housing 6 and extends in the axial direction of the needle 9 so that the needle 9 can enter therein.
6 is provided. Fuel passage 25 upstream of speed meter jet 26
is connected to the float chamber 12 via a fuel pipe 27 extending downward.
The fuel in the seventh engine chamber 12 is sent into the fuel passage 25 through this fuel pipe 27'jk. Further, a hollow cylindrical nozzle 28 coaxially arranged with the fuel passage 25 is fixed to the spacer lO. This nozzle 28
protrudes into the venturi portion 13 from the inner wall surface of the spacer lO, and the upper half of the tip 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 metering jet 26 , and the fuel is metered by the annular gap formed between the needle 9 and the metering jet 26 from the nozzle 28 into the intake passage 7 .

As shown in FIG. 2, a raised wall 29 is formed at the upper end of the spacer lO and projects horizontally (C) toward the intake passage 7. 1 control is performed. When engine operation is started, air flows downward in the intake passage 7. At this time, the air flow is narrowed between the suction piston 8 and the raised wall 29, so there is a negative impact on the pentier section 13. Pressure is generated, and this negative pressure is guided into the negative pressure chamber 20 through the suction hole 23. In other words, the negative pressure inside the venturi portion 13 is moved to become approximately constant.

Referring to FIGS. 3 and 4, the entire tip surface of the piston located on the upstream side of the needle 9 is raised from the mounting end surface 30 of the needle 9 toward the tip of the needle 9. A groove 31 extending in the axial direction of the intake passage 7 is formed on the tip end surface of the suction piston. The downstream end 31a of this groove 31 has a J-shaped cross section and is located closer to the tip of the needle 9 than the needle mounting end surface 30, and the remaining groove part 31b is From the upstream end 31a to the needle attachment end surface 30
It extends almost in a straight line. Furthermore, the cross-sectional shape of the outside of the tip surface of the piston located upstream of the needle 9 is V-shaped, expanding from the concave groove 31 toward the venturi portion 13. Therefore, the tip surface of the piston The portions are a pair of inclined wall surface portions 32a that are inclined toward the groove 31.

32b.

As shown in Fig. 3, when the intake air q is small, the raised wall 29. Slanted wall portions 32a, 32b.

The upstream end portion 31a of the concave groove forms an intake air control constriction portion K having a substantially isosceles triangular shape.

By forming the intake air control throttle part K in this way, the rift (t) of the suction piston 8 becomes proportional to the opening area of the intake air control throttle part, and therefore the rift (l) of the suction piston 8 becomes proportional to the intake air amount. It will increase smoothly as it increases. In addition, Sakushi 3 piston 8
Since it is supported by the bearing 17, it moves with good response to changes in the amount of intake air, and thus, when the amount of intake air increases, the piston 8 moves smoothly and responsively to the increase in the amount of intake air. Move to. As a result, even when the amount of intake air changes rapidly, such as during acceleration, the lift of the piston 8 increases in proportion to the increase in the amount of intake air, so that the amount of fuel supplied from the nozzle 28 increases. The amount will always be proportional to the intake air amount. Furthermore, as can be seen from FIG. 3, when the amount of intake air is small, the intake air is forced to flow through the center of the intake passage 7, and as a result, the fuel supplied from the nozzle 28 immediately flows into the engine cylinder together with the intake air flow. Therefore, even when the amount of intake air is small, the fuel supplied from the nozzle 28 is immediately supplied into the engine cylinder. Therefore, even if the amount of intake air increases rapidly as during acceleration, the vertical direction of the fuel supplied from the nozzle 28 is proportional to the amount of intake air as described above.
Moreover, since the fuel supplied from the nozzle 28 is immediately supplied into the engine cylinder, the air-fuel ratio of the mixture supplied into the engine cylinder is maintained almost constant even if the intake air amount changes rapidly. Since the suction piston 8 is supported by a 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. Thus, the second
By using the variable Bay Turri type carburetor 2 shown in the figure, the air-fuel ratio of the air-fuel mixture supplied into the engine cylinders can be maintained at a substantially constant value, for example, at approximately the stoichiometric air-fuel ratio, regardless of engine temperature and engine operating conditions. be able to.

Referring to FIG. 2, a U-shaped bypass passage 30 that bypasses the metering jet 26 is formed in the carburetor nozzle 2. The fuel outlet 32 of the bypass passage 30 opens into the passage 25 and the fuel outlet 32 of the bypass passage 30 is connected to the metering jet 2.
6 opens into the fuel passage 25 . There is a bypass passage 3 in the bypass passage 30 near the fuel inflow 1'' 31.
A metering jet 33 is inserted for metering the fuel flowing through the tank. This bypass passage 30 is connected to the raised wall 2 via an air bleed passage 35 and an air bleed jet 37.
9 - connected into the upstream intake passage 7; Further, an auxiliary fuel passage 34 is branched from the bypass passage 30, and this auxiliary fuel passage 34 has a fuel inlet 3 that opens into the fuel passage 25.
8.

This fuel inlet 38 opens into the fuel passage 25 upstream of the fuel inlet 31 . An auxiliary fuel IT class register 9 for metering auxiliary fuel is inserted into the auxiliary fuel passage 34 near the fuel inlet 38, and a valve whose opening area is controlled by a beam near solenoid valve 40 is inserted in the middle of the auxiliary fuel passage 34. A boat 36 is formed. During engine idling, most of the fuel is supplied to the nozzle 28 via the bypass passage 30. At this time, since the fuel is metered by the metering jet 33 with a constant cross section, the flow of fuel supplied from the nozzle 28 into the intake passage 7 is stable, thus ensuring stable engine idle operation 1. be able to. As the intake air 1 increases, the needle 9 moves to the left, so that the area of the annular gap formed between the jet 26 and the needle 9 increases. At this time, the wrinkles of the fuel flowing in the bypass passage 30 hardly change, and the total amount increases by +1.
The flow of fuel within the annular gap formed between jet 26 and needle 9 increases, increasing the total amount of fuel delivered from nozzle 28.

The linear solenoid valve 40 includes a valve body 41 for controlling the opening surface a of the valve boat 36, a movable plunger 42 connected to the valve body 41, and a solenoid 43 for suctioning the movable plunger 42. 43 is connected to the solenoid drive circuit 50. In this linear solenoid valve 40, the movable plunger 42 moves by a distance proportional to the current flowing through the solenoid 43, and as the current flowing through the solenoid 43 increases, the valve body 41 moves to the right.

Therefore, the opening area of the valve boat 36 changes in proportion to the current flowing through the solenoid 43.

The solenoid drive circuit 50 is a solenoid drive circuit 50 as shown in FIG. 5(a).
It consists of a sawtooth generator 51 that generates a sawtooth voltage with a frequency of Hz to 2Hz, and a voltage-current converter 52 connected to the output terminal of the sawtooth generator 51. The output terminal of the voltage Km converter 52 is connected to the solenoid 43. connected to. As mentioned above, the opening area of the valve boat 36 allows the flow through the solenoid 43 [
It can be seen that the opening area of the valve boat 36 changes in a sawtooth pattern because the current is supplied to the solenoid 43 as shown in FIG. 5(a). When the opening area of the valve boat 36 changes in a serrated manner in this way, the fuel 1 supplied from the auxiliary fuel passage 34 into the bypass passage 30 also changes to #
! The amount of fuel flowing out from the fuel outlet 32 also changes in a sawtooth manner at this time. As a result, the air-fuel ratio supplied into the engine cylinders will vary.

During the fluctuation of the air-fuel ratio, the average value of the fluctuating air-fuel ratio is determined by the jets 33, 37° 39 and the opening area of the valve boat 36. The dimensions of these jets 33, 37.
(b) As shown in the figure, the air-fuel ratio is almost stoichiometric, and the operating range of the air-fuel ratio is approximately 100, 2 to ±1 relative to the stoichiometric air-fuel ratio.
．． It is set to be 0. Therefore, when the amount of intake air is small, the air-fuel ratio of the mixture supplied into the engine cylinders is approximately ±0.2 to ±1.0 with respect to the stoichiometric air-fuel ratio at a frequency of IHz to 2Hz, regardless of the engine temperature. The air-fuel ratio is varied within a range, and the average value of this air-fuel ratio is
(b) Since it is maintained within the window Wo in the figure, high purification efficiency can be obtained by utilizing the oxygen retention function of the three-redundant monolith catalyst 5. On the other hand, as described above, even if the amount of intake air increases, the amount of fuel flowing through the bypass passage 30 hardly changes. Since the amount of fuel supplied to the engine decreases as the amount of intake air increases, the average value of the air-fuel ratio gradually increases as the amount of intake air increases. In this way, when the amount of intake air is large, that is, during medium-load operation where the vehicle is frequently used, the average value of the air-fuel ratio becomes large, so that the fuel consumption rate can be improved. Thermal Theory As mentioned above, even if the average value of the air-fuel ratio becomes large, the average value of the air-fuel ratio is maintained within the window Wo in FIG. 1(b), so it is still possible to obtain a high purification efficiency. More #! As shown in Figure 5 (b), the air-fuel ratio fluctuates smoothly, so the combustion state does not change suddenly, and stable combustion can be ensured at all times regardless of the engine operating state. .

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. (manufacturing cost) f can be greatly reduced. Furthermore, since only a solenoid valve is provided in the air bleed passage, the structure is extremely simple, and therefore the reliability of the exhaust gas purification device can be improved. Also,
Since the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder is smoothly varied, stable combustion can be ensured. Furthermore, since the air-fuel ratio is increased in the operating range where H4 is frequently used, the fuel consumption rate can be improved.

[Brief explanation of drawings]

Figure 1 is a diagram showing exhaust gas purification efficiency, Figure 2 is a side sectional view of the engine intake and exhaust system, Figure 3 is a plan view taken along the arrow mark in Figure 2, and Figure 4 is a diagram of the suction piston. The side sectional view, FIG. 5, is a diagram showing variations in the air-fuel ratio. 2... Carburizer, 8... Sucsidine piston, 30... Bypass passage, 34...
・Auxiliary fuel passage, 40...Linear solenoid valve. Patent Applicant Toyota Motor Corporation Number Patent Application Agent Akira Aoki Patent Attorney Kazuyuki Nishidate Patent Attorney Kyo Nakayama Patent Attorney Akira Yamaguchi

Claims (1)

[Claims] A variable Pentieri type carburetor is installed in the engine intake passage, and a three-way catalytic converter is installed in the engine exhaust passage. An internal combustion engine having a metering jet provided and cooperating with a needle, wherein a bypass passage is provided connecting a fuel passage upstream of the metering jet and a fuel passage downstream of the metering jet, and the bypass passage is connected via an auxiliary fuel passage. The auxiliary fuel passage is connected to the metering jet-E fuel passage, and the auxiliary fuel passage is provided with a solenoid valve that opens and closes at a constant frequency of approximately 11 (Z to 2 Hz), and when the solenoid valve is opened and closed, the air-fuel ratio changes. The opening area of the solenoid valve is determined so that the air-fuel ratio periodically fluctuates between approximately ±0.2 and ±1.0 with respect to the average value, and the average value of the air-fuel ratio is approximately the stoichiometric air-fuel ratio. Gas purification device L