JPS5912113A - Exhaust gas purifying device of internal combustion engine - Google Patents

Abstract

PURPOSE:To obtain high exhaust purifying effect without employing O2 sensor by a structure wherein a negative pressure operated automatic valve to open and close the passage at a predetemined frequency is provided in the air bleed passage of a carburetor and at the same time the flow resistance in the air bleed passage is specified. CONSTITUTION:The titled device is applied to an internal combustion engine, in which a variable Venturi type carburetor 2 is installed in a suction manifold 1 and a catalytic converter 4 is installed in an exhaust manifold 3. An annular air chamber 33 formed around a metering jet 26, into and out of which a needle 9 is inserted and drawn, is communicated through a first air bleed passage 35 to a suction passage 7 and simultaneously through a second air bleed passage 36 to the automatic valve 50, which is equipped with negative pressure diaphragm devices A and B in order to enable to open and close the passage 36 at the fixed frequency of about 1-2Hz. In addition, the sizes of the respective air bleed jets 37 and 38 are determined so that the air-fuel ratio during the opening and closing of the passage 36 changes periodically between nearly + or -0.2-+ or -1.0 in respect of the average value.

Description

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

Three harmful components HC, Co and NOx in exhaust gas
- A three-way catalyst is known as a catalyst that can reduce the amount of water at the same time. The purification efficiency R of this three-way catalyst is the first (a)
As shown in the figure, the air-fuel ratio 5 is highest when it is almost the stoichiometric air-fuel ratio, and for example, the air-fuel ratio range where a purification efficiency of 80 percent or more can be obtained is when the air-fuel ratio is 0.0.
It has a narrow width of about 6 mm.

Usually, the air-fuel ratio region in which a purification efficiency of 80 percent or more can be obtained is called a window W. Therefore, in order to simultaneously reduce the three harmful components in exhaust gas using a three-way catalyst, the air-fuel ratio must be maintained within this narrow window W at all times. For this reason, in conventional exhaust gas purification devices, an oxygen concentration detector that can determine whether the air-fuel ratio is larger or smaller than the stoichiometric air-fuel ratio is installed in the engine exhaust passage, and based on the output signal of this oxygen concentration detector, The air-fuel ratio is controlled to be within the window W. However, an exhaust gas purification device using such an oxygen concentration detector requires an expensive oxygen concentration detector and an expensive electronic control unit for air-fuel ratio control, which increases the manufacturing cost of the exhaust gas purification device. There is a problem.

However, recently, 5Ali) paperNa
As described in No. 760201 or Japanese Patent Publication No. 56-4741, the function of the three-way catalyst was gradually elucidated, and it was found that the three-way catalyst had 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 converts it into NOx.
While reducing x, 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 iic. 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 oxidize CO and HC. The action is promoted and high purification efficiency can be obtained. FIG. 1(b) shows the window W 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 shows. 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 an entirely 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, so the oxidation-reduction ability based on the oxygen retention function decreases, and the purification efficiency of the three-way catalyst decreases. descend. Figure 1(c) clearly shows this. In FIG. 1(c), the vertical axis R represents the purification efficiency, and the horizontal axis F represents the fluctuation frequency of the air-fuel ratio. Further, if the air-fuel ratio is changed within a small range, the air-fuel ratio cannot be varied alternately between the rich side and the lean side, so the window 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 fluctuation range and fluctuation frequency of the air-fuel ratio relative to the reference air-fuel ratio are 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.

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 over a wide range, and in conventional variable bench carburetors, the reference air-fuel ratio fluctuates sharply during acceleration or due to engine temperature V. It is difficult to obtain high purification efficiency using a fixed venturi type vaporizer or a variable venturi type vaporizer.

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 concentration detector.

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 bet/turi 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 zigzag piston 8 that moves laterally within the intake passage 7, and the tip of a suction screw y8. Attached to the surface, the letter 21 dollar 9 and the sakushi 1 piston y 8 + 7) tip i
4) A spacer 10 fixed on the inner wall surface of the intake passage 7 facing the plane, a throttle valve 11 provided in the intake passage 7 downstream of the piston 8, and a float chamber 12.
A venturi portion 13 is formed between the front end surface of the piston 8 and the spacer 10. A hollow cylindrical gun 14 is fixed to the carburetor housing 6,
A guide sleeve 15 is attached to the cushioning 14 and extends inside the cushioning 14 in the axial direction of the cushioning 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 the guide rod 19 is inserted into the bearing 17 so as to be movable along the axis 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 the is 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, and a compression spring 22 is inserted into the negative pressure chamber 20 to constantly press the suction piston 8 toward the venturi portion 13. Ru. The negative pressure chamber 20 is connected to the venturi part 13 through a suction hole 23 formed in the suction piston 8, and is connected to the upstream side of the suction piston 8 through an atmospheric pressure chamber 21 and 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 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 metering jet 26 is connected to the float chamber 12 via a fuel vibrator 27 extending downward, and the fuel in the float chamber 12 is transferred to the fuel vibrator 27.
The fuel is fed into the fuel passage 25 through the fuel. Further, a hollow cylindrical nozzle 28 disposed coaxially with the fuel passage 25 is fixed to the spacer IOK. This nozzle 28 protrudes into the vent IJl 1513 from the inner wall surface of the spacer 10, and the upper half of the tip of the nozzle 28 further protrudes from the lower half toward the succilon 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 before being fed from the nozzle 28 into the intake passage 7.

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 lO, and a space between this raised wall 29 and the tip of the suction piston 8 is formed. Flow rate control is performed by When engine operation is started, air flows downward in the intake passage 7. At this time, since the airflow is restricted between the suction piston 8 and the raised wall 29, negative pressure is generated in the venturi section 13.
This negative pressure is led into the negative chamber 20 through the suction hole 23. The sacsidine piston 8 is arranged so that the pressure difference between the negative pressure chamber 20 and the atmospheric pressure chamber 21 becomes a substantially constant pressure determined by the spring force of the compression spring 22, that is, the negative pressure in the bench portion 13 is maintained substantially constant. move so that

3 and 4, the entire tip surface of the suction 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 upstream end 31& of the concave groove 31 has a U-shaped cross section, and the needle mounting end surface 30 and V are also located on the side closer to the tip of the needle 9, and the concave groove portion 31b of the remaining 9 is on the upstream side From the end 31g to the needle mounting end face 30
It extends straight up to t naho. Furthermore, needle 9jp4
The cross-sectional shape of the suction piston tip end face located on the upstream side is in the shape of a 7 that expands from the groove 31 toward the venturi portion 13. Therefore, the suction piston tip face portion is inclined toward the groove 31. A pair of inclined wall portions 32&.

32b.

As shown in Figure 3, when the amount of intake air is small, Fs
, raised wall 29, and inclined wall portions 32a, 32b.

A substantially isosceles triangular intake air control throttle sK is formed by the upstream end 31a of the concave groove.

By forming the intake air control throttle part K in this way, the lift amount of the saxilon piston 8 becomes proportional to the opening area of the intake air control throttle part 1. Therefore, the lift amount of the saxilon piston 8 is the intake air amount. It increases smoothly as the value increases. Furthermore, since the suction piston 8 is supported by the bearing 17, it moves with good response to changes in the amount of intake air, and thus the suction piston 8 responds to an increase in the intake air I when the amount of intake air increases. Moves smoothly and responsively. 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. is always proportional to the amount of intake air. Furthermore,
As can be seen from Fig. 3, when the intake air k is small, the VC allows the intake air 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 airflow. 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 accelerated driving, 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 increased. Since the air-fuel mixture is supplied into the engine cylinder, the 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, the engine temperature does not affect the movement of the suction piston 8 during engine operation, and thus the suction piston 8 can move with good responsiveness to changes in the amount of intake air regardless of the engine temperature. Thus, when the variable venturi type carburetor 2f shown in FIG. fuel ratio can be maintained.

Referring to FIG. 2, an annular air chamber 33 is formed around the metering jet 26, and a plurality of air bleed holes 34 communicating with the annular air chamber 33 are formed on the inner peripheral wall surface of the metering jet 26. On the one hand, the monkey-shaped nitrogen chamber 33 connects to the intake passage 7 upstream of the raised wall 29 via the first air bleed passage 35.
The second air bleed passage 36 is connected to the automatic on-off valve 50 via the second air bleed passage 36 . A first air bleed jet 37 is inserted into the first air bleed passage 35, and a second air bleed jet 38 is inserted into the second air bleed passage 36. Further, an auxiliary air bleed passage 39 is branched from the common air bleed passage portion of the first air bleed passage 35 and the second air bleed passage 36vC, and this auxiliary air bleed passage 39 is connected to the metering jet 26
It opens into the downstream fuel passage 25.

The automatic opening/closing valve 50 has a first negative pressure diaphragm device A and a second negative pressure diaphragm device A.
It consists of a negative pressure diaphragm device tB.

The first negative pressure diaphragm device A includes a negative pressure chamber 53 and an atmospheric pressure chamber 54 separated by a diaphragm 52 in its housing 51 . The atmospheric pressure chamber 54 has an air filter 5
A compression spring 56 is inserted into the negative royal chamber 53 and presses the diaphragm 52 upward. A valve boat 57 that is always open into the atmospheric pressure chamber 54 is formed on the earth wall surface of the housing 51, and this valve boat 57 is connected to the second air bleed passage 36 via a conduit 58. A valve body 59 for controlling the opening and closing of the valve boat 57 is provided inside the housing 51, and this valve body 59 is supported by a compression spring 60.
It can be constantly suppressed downward by the spring force. A control rod 61 is fixed to the diaphragm 52, and the upper end of the control rod 61 is arranged so as to be engageable with the valve body 59. On the other hand, the second
The negative pressure diaphragm device B includes a negative pressure chamber 63 and an atmospheric pressure chamber 64 separated by a diaphragm 62.

The atmospheric pressure chamber 64 communicates with the atmosphere through an opening 65, and a compression spring 66 is inserted into the negative pressure chamber 63 to press the diaphragm 62 upward. A stopper 67 is fixed to the center of the diaphragm 62, and a valve boat 68 connecting the negative pressure chamber 63 and the atmospheric pressure chamber 64 is formed in the stopper 67. A valve body 69 that controls opening and closing of the valve boat 68 is disposed within the negative pressure chamber 63, and this valve body 69 is connected to the valve port 68.
The valve door 0 is provided with a valve door 0 that penetrates through and projects into the atmospheric pressure chamber 64. A compression spring 71 is inserted between the upper end of the valve rod 70 and the diaphragm 62, and the valve body 69 is inserted into the compression spring 7.
A spring force of 1 normally keeps the valve boat 6B closed.

The control rod 61 of the first negative pressure diaphragm device A passes through the housing 51 and protrudes 1.7 into the atmospheric pressure chamber 64 of the second negative pressure diaphragm device B, and the protruding lower end of the control rod 61 is located at the top of the valve door 0. and the engagement 0T function. Second
The negative pressure group 63 of the negative pressure diaphragm device B is connected to the negative pressure chamber 53 of the first negative pressure diaphragm device fA via a negative pressure conduit 72 on the one hand, and is connected to the negative pressure tank 74 via the negative pressure conduit 73 on the other hand. connected to. Genomes 75 and 76 are inserted into these negative pressure conduits 72 and 73, respectively. The negative pressure tank 74 is connected to the intake manifold 1 via a negative pressure conduit 77, and a check valve 78 is inserted into the negative pressure conduit 77, which allows flow only from the negative pressure tank 74 to one direction of the intake manifold. be done. This check valve 78 opens when the negative pressure in the intake manifold 1 becomes greater than the negative pressure in the negative pressure tank 74, and the negative pressure of 1 yen in the intake manifold becomes larger than the negative pressure in the negative pressure tank 74. The valve closes when it becomes small. Therefore, the inside of the negative pressure tank 74 is maintained at the maximum negative pressure generated in one circle of the intake manifold.

FIG. 2 shows when atmospheric pressure is acting on the negative royal chamber 53.63. At this time, the control rod 61 is connected to the valve body 59.
is pushed up, so the valve boat 57 is open. On the other hand, since the lower end of the control rod 61 is separated from the top of the valve rod 70, the valve body 69 closes the valve boat 68. When the engine starts operating and negative pressure is applied in the negative pressure tank 74, the negative pressure tank 74 flows through the jet 76 into the negative pressure chamber 6.
3, the negative pressure in the negative pressure chamber 63 gradually increases, and the diaphragm 62 descends at the groove where the stopper 67 comes into contact with the inner wall surface of the housing 79. On the other hand, when the negative pressure inside the negative pressure chamber 63 increases, the jet 7
The negative pressure chamber 53 is connected to the negative pressure chamber 53 through the negative pressure chamber 53.
The negative pressure within 3 gradually increases, resulting in diaphragm 52 lowering. When the diaphragm A52 is lowered, the engagement between the valve body 59 and the control rod 61 is released, so that the valve body 59 closes the valve boat 57. Then, when the diaphragm 52 further descends, the lower end of the control rod 61 comes into contact with the valve rod 70 and pushes the valve rod 70 down. As a result, since the valve body 69 opens the valve port 68, the atmosphere is introduced into the negative royal ring 63, and as a result, the diaphragm 62 is raised by the spring force of the compression spring 66. Kotobuki, at this time valve body 6
9 remains stopped. When the pressure inside the negative chamber 63 reaches atmospheric pressure, the negative pressure inside the negative pressure chamber 53 gradually becomes smaller, so that the diaphragm 52 rises 1-2 due to the spring force of the compression spring 56.
As a result, the upper end of the control rod 61 comes into contact with the valve body 59 and pushes the valve body 59 upward. As a result, the valve body 59 is
7 is opened again. When the diaphragm 52 further rises, the valve body 69 reduces the opening area of the valve boat 68, so the negative pressure in the negative pressure chamber 63 increases, causing the diaphragm 62 to descend, and as a result, the valve body 69 closes the valve boat 68. do.

When the valve body 69 closes the valve boat 68, the diaphragm 62
is further lowered, and then the diaphragm 52 is lowered so that the valve body 59 closes the valve port 57 again. Therefore, the valve element 59 of the automatic opening/closing valve 50 repeats the opening/closing operation of the valve boat 57. The frequency at which the valve element 59 opens and closes the valve boat 57 is determined by the dimensions of the diaphragm 52, 62 and the diaphragm 75, 76, and in the embodiment shown in FIG. The dimensions of the diaphragm 52.62 and the jet 75.76 are determined to be 2 m from Z. When the valve body 59 opens the valve boat I57, air flows through the air filter 55, atmospheric pressure chamber 54, valve boat 57, and conduit. 58 to the second air bleed passage 3
6, the amount of air supplied from the air bleed hole 33 and the auxiliary air 7 lead passage 39 into the fuel passage 25 increases, and as a result, the amount of fuel supplied from the nozzle 28 decreases and flows into the engine cylinder. The mixture supplied to becomes leaner.

The dimensions of the first air bleed jet 37 and the second air bleed jet 38 are such that the valve body 59 of the automatic on-off valve 50 is the fifth
(&) When the valve boat 57 is repeatedly opened and closed as shown in FIG. The stoichiometric air-fuel ratio is reached, and the air-fuel ratio is 1 to stoichiometric during fluctuations.
- is determined to be approximately ±0.2 to ±1.0. In addition, in FIG. 5(a), the vertical axis st- is the valve boat 5.
In FIG. 5(b), the vertical axis vF indicates the air-fuel ratio.

Therefore, regardless of engine temperature and engine operating conditions, the air-fuel ratio of the air-fuel mixture supplied into the engine cylinders will be approximately ±0.0.
2 to ±1. Moreover, the average value of this air-fuel ratio is window W in FIG. 1(b). Therefore, high purification efficiency can be obtained by utilizing the oxygen retention function of the three-way monolith catalyst 5.

As described above, according to the present invention, the 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. 3. Furthermore, since only an automatic on-off valve is provided in the air bleed passage, the structure is extremely simple, and therefore the reliability of the exhaust gas purification lid can be improved.

[Brief explanation of drawings]

Fig. 1 is a diagram showing exhaust gas purification efficiency, Fig. 2 is a side sectional view of the engine intake and exhaust system, Fig. 3 is a plan view taken along the arrow ■ in Fig. 2, and Fig. 4 is a suction piston/exhaust gas purification efficiency diagram. FIG. 5 is a diagram illustrating the fluctuation of the air-fuel ratio. 2... Carburetor, 8... Suction piston, 9...
・Neator, 25... Fuel passage, 28... Nozzle, 35° 36... Air bleed passage, 50... Automatic opening/closing valve. Patent Applicant: Toyota Motor Vehicles Co., Ltd. Patent Attorney: Akira Aoki, Patent Attorney: Kazuyuki Nishidate, Patent Attorney: Kyosuke Shinyama, Patent Attorney: Akira Yamaguchi -5 γ γ72! Shiku! Seven days

Claims (1)

[Claims] A carburetor is installed in the engine intake passage, a three-way catalytic converter is installed in the engine exhaust passage, and an air bleed passage is connected to the fuel passage of the carburetor, so that air is supplied from the air bleed passage into the fuel passage. In internal combustion engines,
Insert the air bleed passage into the above air bleed passage #Y
A negative pressure-driven automatic on-off valve that opens and closes at a constant frequency of I Hz to 2 Hz is installed, and when the air bleed passage is opened and closed, the air-fuel ratio tl is ±0.2 to ±1.
An exhaust gas purification device for an internal combustion engine, in which the flow resistance of an air bleed passage is determined to periodically vary between 0 and a carburetor is set so that the average value of the air-fuel ratio is approximately the stoichiometric air-fuel ratio.