JPS5996422A - Exhaust gas purifying device of internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent after-burning by opening and closing a solenoid valve for supplying secondary air to the upper stream of a ternary catalyst at the frequency of 1-2Hz, periodically varying an air-fuel ratio within the range of + or -0.2- + or -1.0, and fully opening the solenoid valve after temporarily fully closing said valve at engine deceleration. CONSTITUTION:A secondary air supplying hole 60 is provided on an exhaust manifold 3, and secondary air is supplied to the upper stream of a ternary catalyst 5 via a control valve 50 and a check valve 59. Negative pressure is introduced into the negative pressure chamber 53 of the control valve 50 via a solenoid valve 51, and this solenoid valve 51 is opened and closed at the frequency of 1-2Hz by means of a solenoid driving circuit 70, and an air-fuel ratio is periodically varied within the range of + or -0.2-+ or -0.1 via the control valve 50 taking a theoretical air-fuel ratio as a center. An idle switch 71 and a number-of- revolutions switch 72 are connected to the driving circuit 70, and the solenoid valve 51 is fully opened after temporarily fully closing said valve at deceleration, so as to allow after-buring to be prevented as well as an exhaust gas purifying characteristic to be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas purification device for an internal combustion engine, and relates to an exhaust gas purification system for an internal combustion engine. A three-way catalyst is known as a catalyst that can simultaneously reduce NOx and NOx.The purification efficiency R of this three-way catalyst shows that the air-fuel ratio A/F is almost stoichiometric as shown in Figure 1(a). The purification efficiency R is highest when the fuel ratio is, for example, 80% or more.
't-The air-fuel ratio range that can be obtained is when the air-fuel ratio is 0.06.
It is a fairly narrow width.

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 systems, acid concentration detectors are installed in all engine exhaust passages that can determine whether the air-fuel ratio is greater or less than the stoichiometric air-fuel ratio, and the output signal of this acid concentration detector is Based on this, the air-fuel ratio is controlled to be the air-fuel ratio of the window W circle. 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, 5AEpaper No.

As described in No. 760201 and 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. When the fuel ratio is on the lean side compared to the stoichiometric air-fuel ratio, the three-way catalyst takes away oxygen and gold from NOx, increasing NOx.
x k while reducing and retaining this stolen oxygen,
When the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio, all of the retained oxygen is released to oxidize Co and HC.O Therefore, the air-fuel ratio is alternately varied to the lean side and rich side with respect to the standard air-fuel ratio, which is the full stoichiometric air-fuel ratio. Even if the reference air-fuel ratio deviates from the stoichiometric air-fuel ratio, the above-mentioned oxygen retention function promotes the reduction of NOx and the oxidation of Co and HC (3), resulting in high purification efficiency. Figure 1(b)
is the air-fuel ratio at a frequency of I Hz with respect to the reference air-fuel ratio by ±1.
The window Wok of the reference air-fuel ratio A/F' when the fluctuation is increased by 0 is shown. Figures 1(a) and 1('b)
) It can be seen from the figure that when the air-fuel ratio is varied at a constant frequency, the window Wo becomes wider. This term means that if the predetermined air-fuel ratio is varied in full cycles, high purification efficiency can be obtained even if the reference air-fuel ratio deviates somewhat from the stoichiometric air-fuel ratio. -If the air-fuel ratio fluctuation frequency is lowered, that is, if the air-fuel ratio fluctuation period is lengthened, the oxygen retention function of the three-way catalyst will become saturated, and the oxidation-reduction ability based on the oxygen retention function will decrease, resulting in purification of the three-way catalyst. Efficiency decreases. 1st
Figure (C) clearly shows this. 1st (e)
In the figure, the vertical axis R shows the purification efficiency, and the horizontal @F shows the fluctuation frequency of the air-fuel ratio? When the air-fuel ratio fluctuation range is reduced to 0, the air-fuel ratio cannot be varied alternately between the rich side and the lean side, so the width of the window becomes narrower. Therefore, it can be seen that there is an optimal air-fuel ratio fluctuation cycle and fluctuation period in order to widen the window width (4).

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. In addition, if a narrow fuel supply system is used during fluctuations in the reference air-fuel ratio, the oxygen concentration lf,
O thermal theory means that high purification efficiency can be obtained without using feedback control based on the output signal of the detector, and if a fuel injection valve is used as the fuel supply system, it is possible to narrow the fluctuation period of the reference air-fuel ratio. However, since the fuel injection position is expensive, there is a problem in that the manufacturing cost of the engine increases.Furthermore, if the air-fuel ratio supplied to the engine cylinder is varied in this way, even if the air-fuel ratio is varied,
%, combustion fluctuates periodically, resulting in a problem that vehicle drivability deteriorates.

An object of the present invention is to provide a complete exhaust gas purification device that can ensure high exhaust gas purification efficiency without using an oxygen concentration detector or without changing the air-fuel ratio supplied to an engine cylinder. Hereinafter, the present invention will be described in detail with reference to all the attached drawings. Referring to FIG. 2, 1 is an intake manifold, 2 is a variable venteri type carburetor installed on the intake manifold 1,
3 shows the exhaust manifold, 4 shows the catalytic converter,
A three-way monolith catalyst 5 is arranged inside the catalytic converter 4 . The variable venturi carburetor 2 includes a carburetor housing 6, an intake passage 7 extending vertically within the housing 6, a suction piston 8 that moves horizontally within the intake passage 7, and is 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; a throttle valve 11 provided in the intake passage 7 downstream of the suction piston 8; A venturi portion 13 is formed between the tip end surface of the suction piston 8 and the spacer 10. A hollow cylindrical casing 14 is fixed to the carburetor housing 6, and this casing 14
A guide sleeve 15 is mounted inside the casing 14 and extends in the axial direction of the casing 14 . A bearing 17 with a plurality of poles 16 is pushed into the guide sleeve 15, and the outer end of the guide sleeve 15 is closed by a blind cover 18. - A guide rod 19 is fixedly attached to the suction piston 8, and the guide rod 19 is inserted into a bearing 17 so as to be movable in the direction of the line of the guide port 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 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 pentier section 13. Ru. The negative pressure chamber 20 is connected to the venturi section 13 through a suction hole 23 formed in the suction piston 81C, and the atmospheric pressure chamber 21 is connected to the suction piston 8 upstream through the air (7) hole 24 formed in the carburetor housing 6. intake passage 7
connected within.

10,000, the fuel passage 2 extends in the @ line direction of the needle 9 so that the needle 9 can be inserted later into the carburetor housing 6FKJ.
A metering jet 2 is formed in this fuel passage 25.
6 is provided. Metering jet 26 Earth flow fuel passage 25
is connected to the float chamber 12 via a fuel vibrator 27 extending downward.
Ki! The fuel in the float chamber 12 is sent into the fuel passage 25 via this fuel bypass 127. Further, the spacer IOK includes one nozzle 28 in the shape of a hollow cylinder arranged coaxially with the fuel passage 25. This nozzle 2
8 protrudes into the venturi portion 13 from the inner wall surface of the spacer 10, and the lower half of the tip of the nozzle 28 protrudes toward the suction piston 8 from the lower half. The needle extends completely through the nine-point 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 supplied from the nozzle 28 into the intake passage 7.

(8) As shown in FIG. 2, the upper end of the spacer 10 Vcrc
A raised wall 29 projecting horizontally into the intake passage 7 is formed between the raised wall 29 and the tip of the suction piston 8 to control the flow rate. When engine operation is started, air flows downward in the intake passage 7. At this time, since the viewing flow is constricted between the suction piston 8 and the raised wall 29, a negative pressure is generated in the venturi portion 131C, and this negative pressure is passed through the suction hole 23 to the negative pressure chamber 20.
0 suction piston 8 guided inside U negative pressure chamber 20
In other words, the bench area 1 is adjusted such that the pressure difference between the
Move so that the negative pressure inside 3 remains almost constant.

Referring to FIGS. 3 and 4, the entire tip surface of the suction piston located on the upstream side of the needle 9 is bulged 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 piston. The upstream $1!1 end 31a of this groove 31 has a U-shaped cross section and is located closer to the tip of the needle 9 than the needle mounting end face 30, and the remaining groove portion 31b is on the upstream side. From the end 31a to the needle mounting end face 30
The reeds grow almost straight. Furthermore, the needle 9 also has a V which expands from the concave $31 toward the bench area 13 in the cross-sectional shape of the suction piston tip surface located on the upstream side.
Therefore, a pair of inclinations f7 + wall surface portions 32a are formed in the shape of a letter and are inclined toward the concave groove 31 at the tip end surface portion of the suction piston.

32b.

As can be seen from FIG. 3, when the amount of intake air is small, the raised wall 29 and the inclined wall portions 32a and 32b.

and concave groove upstream fliJl? The i portion 31a forms an intake air control throttle K having a substantially isosceles triangular shape.

In this way, the suction piston 8 is lifted 1] by forming the intake air control throttle part to be the intake air control throttle! It becomes proportional to the opening area of IIK, and therefore, the lift amount of the suction piston 8 clearly increases as the amount of intake air increases. Furthermore, since the suction piston 8 is supported by the shaft 9L7, it moves with good response to changes in the amount of intake air, and thus, when the amount of intake air to the suction piston 8 increases, it responds to the increase in the amount of intake air. Moves smoothly and smoothly. As a result, even when the intake air volume 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 that the amount of fuel supplied from the nozzle 28 increases. The amount of air intake will always be proportional to the amount of air inhaled. 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 entire center of the intake passage 7. 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 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 intake air is supplied to the engine cylinders at the same time, the air-fuel ratio of the air-fuel mixture supplied to the engine cylinders remains almost constant even if the intake air amount 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.
In this way, the suction piston 8 can move with good responsiveness to changes in the amount of intake air, regardless of the engine temperature.
In this way, when the variable venturi type carburetor 2 shown in FIG. 2 is fully used, the fuel ratio of the air-fuel mixture supplied into the engine cylinder can be adjusted regardless of the engine temperature and engine operating condition. It is possible to maintain it at about 14.0, for example.

Therefore, a rich air-fuel mixture with an air-fuel ratio of about 14.0 is constantly supplied into the engine cylinders.

Referring to FIG. 2, a mound-shaped 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 in the inner peripheral wall of the metering jet 26. The air chamber 33 is connected to the intake passage 7 upstream of the raised wall 29 via air bleed passages 35, 36 and air bleed jets 37, and wax 9P38 is applied to the joint between these air bleed passages 35 and 36. A valve body 39 that is driven by is arranged. wax valve 3
A cooling water circulation chamber 39 is formed around the temperature sensor @ 38a of No. 8, and cooling water is introduced into this cooling water circulation chamber 39 from a cooling water inlet 40, and is discharged from a cooling water outlet 41 to this cooling water. . When the engine cooling water temperature rises, the valve body 39 moves to the left, which increases the flow area of the air bleed passage, thereby increasing the amount of air bleed. When the machine operation is completed, the valve body 39 fully opens the air bleed passage. At this time, the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder is 14.
．． The mixture becomes a rich mixture of about 0.

- A secondary air supply control valve 50 for controlling the supply of secondary air is attached to the engine exhaust manifold 3, and a solenoid valve 51 for controlling the operation of the secondary air supply control valve 50 is attached to the intake manifold 1. The attached secondary air supply control valve 50 has a negative pressure chamber 53 and an atmospheric pressure chamber 54 separated by a diaphragm 52, and a compression spring 55 for pressing the diaphragm is inserted into the negative chamber 53. A hollow nitrogen pipe 56 protruding toward the diaphragm 52 is firmly disposed in the atmospheric pressure chamber 54,
Inside this, a valve port 57 is formed at the end of the pipe 56, which is controlled to open and close by a valve body 58 fixed to the diaphragm 52. This valve boat 57 is connected to the inside of the exhaust manifold 3 via a check valve 59 and a secondary air supply hole 60 that allow flow only from the valve boat 57 into the exhaust manifold 3 .

Therefore, the valve boat 57 and the secondary air supply hole 60 form a secondary air supply passage. a negative pressure boat 64 that opens into the intake manifold 1, an atmospheric boat 65 that opens into the valve chamber 62 and communicates with the atmosphere, and a movable plunger connected to the valve body 63.
66 and a solenoid 67 for suctioning the movable plunger 66, and a negative pressure boat 642 and an atmospheric boat 6.
5 is connected to a negative pressure chamber 53 of an air supply control valve 50 through a conduit 68 to a valve chamber 62 whose opening and closing are controlled by a valve body 63, and a solenoid 67 is connected to an electronic control unit 70. - 10,000, an idle switch 71 is connected to the throttle valve 11, and an output terminal of the idle switch 71 is connected to an electronic 71i111Ml unit 70. This idle switch 71 is turned on when the throttle valve 11 is in the idle link position. Furthermore, the electronic control unit 70K includes a rotation speed switch 7 that responds to the engine 11 rotation speed.
2 is connected, and this rotation speed switch 72 sets the engine rotation speed to a predetermined rotation speed, for example, 1600 r, p,
The idle switch 71 and the rotation speed switch 72, which are turned on when the engine speed exceeds m, constitute the entire deceleration operation detector that detects the deceleration operation state of the engine.

FIG. 6 shows a circuit diagram of the multiplex control unit 70.

Referring to FIG. 6, the output sound of the idle switch 71 is inputted to the electronic control unit 70.
5(a) IH as shown in
A pulse generator 76 that generates a rectangular pulse with a frequency of 2 Hz to 2 Hz, an AND gate 77 that takes the output of the inverter 74 as an input of 10,000, and the output of the pulse generator 76 as the other input, and a monoanzi multivibrator 75 The output sound of -10,000 is the output of the AND gate 77.The other input is the Nants gate 78, and the power amplifier 79 is connected to the output terminal of the Nands gate 78. The output terminal of the power amplifier 79 is connected to the solenoid 67.

FIG. 7 shows the signals in each part of the control unit 70?
It shows. FIG. 7 (a) shows the output pulse signal of the pulse generator 76, and (e) shows the solenoid control signal applied to the solenoid 67. l
In addition, in Fig. 7, there is a section 'r+i idle switch 71.
is off, and when the rotation speed switch 72 is off,
In other words, this indicates a time when the vehicle is not in deceleration operation. At this time, as shown in FIG. 7(b), the output voltage of the inverter 74 becomes a high level 29, and therefore, as shown in FIG. A pulse corresponding to the output pulse is generated. Furthermore, at this time, the output voltage of the monostable multivibrator 75 is at a low level as shown in FIG. A control pulse as shown in FIG. 7(e) is applied to the solenoid 67. Ten thousand,
FIG. 7 shows when both the idle switch 712 and the rotation speed switch 72 are turned on at time ta, that is, when deceleration operation starts, and in FIG.
! When zero deceleration operation is started, which indicates the continuation period of deceleration operation at At the same time, the output voltage of the inverter 74 becomes low level, and the output voltage of the AND gate 77 becomes low level as shown in FIG. 7(C). Ten thousand,
At this time, the inverter 7 is connected to the monostable multivibrator 75.
The output voltage of the monostable multivibrator 75 is triggered by the fall of the output voltage of the monostable multivibrator 75, and as shown in FIG. As shown in FIG. 7(e), while the output voltage of the monostable multivibrator 75 is at a high level, the output voltage of the Nandt gate 78 is at a low level. Solenoid 67 is deenergized. When a certain period of time Tz has elapsed after the start of deceleration operation, the output voltage of the monostable multivibrator 75 becomes a low level, so the output voltage of the Nant gate 78 becomes a high level, and the output voltage of the Nant gate 78 continues deceleration operation. It is maintained at a high level during period T3. Therefore, a certain period of time T after the start of deceleration operation.

After , the solenoid 67 is continuously energized until the deceleration operation is completed. Next, at time tb, when the idle switch 71 is turned off and the rotation speed switch 72 is turned off, that is, when the deceleration operation is completed, the output voltage of the inverter 74 becomes low level p1.
As shown in section T4 in e), the output terminal of the Nantes gate 78 has a section T.

A continuous pulse similar to that occurs.

As shown in Figure 7, when not in deceleration operation, rl:
A rectangular pulse with a frequency of IHz to 2Hz is generated by solenoid 6.
7, the opening force I] is applied. Valve body 63 is normal negative pressure valve
4'! When the pulse generator 71 generates a pulse, the solenoid 6 is closed.
7 is energized and the valve body 64 moves to the right, thereby causing the valve body 63 to open the negative pressure boat 64 and close the atmospheric boat 65. Therefore, the negative pressure boat 64 and the atmospheric boat 65 are repeatedly opened and closed at a frequency of IH7 to 2H2, and thus a negative pressure is supplied to the negative pressure chamber 53 of the secondary air supply control valve 50 at a frequency of III Hz to 2Hz. When negative pressure is applied to the zero negative pressure chamber 53 to which pressure or atmospheric pressure is alternately introduced, the valve body 58 opens the valve boat 57, and at this time, due to exhaust pulsation! Air is sucked into the exhaust manifold 3 from the secondary air supply hole 60 by the negative pressure generated in the exhaust manifold 3. Therefore, as mentioned above, when the negative pressure chamber 53 becomes atmospheric pressure and negative pressure alternately at a frequency of IHz to 2Hz, the valve body 58 changes the valve boat 57 from IHz to 2Hz.
Hz, and thus secondary air is intermittently supplied into the exhaust manifold 3 with a frequency of I Hz to 2 Hz. When supplied, the air pressure manifold 3
The degree of oxygen in the exhaust gas changes periodically, and thus the air-fuel ratio changes. Note that the term air-fuel ratio is used here in a slightly different meaning from the usual meaning, and this air-fuel ratio is equivalent to the total amount of air (intake It is the ratio between the sum of air and secondary air) and the total fuel sound. If the three-way catalyst 5 has an oxygen retention function as described above against the excess oxygen present in the exhaust gas, this excess oxygen may be due to intake air supplied to the intake system, or It does not matter whether it is caused by secondary air supplied to the insulation system. Therefore, is the 2nd 9 qi supplied in the 1st qi manifold 3? When the air-fuel ratio is periodically varied by varying the air-fuel ratio, high purification efficiency can be obtained if the average value of the air-fuel ratio is maintained within the window Wo in FIG. 1(b). In the English foil example shown in FIG. 2, when the valve body 58 of the diaphragm 52 has the dimensions of the valve boat 57 and the secondary air supply hole 60, the average value of the air-fuel ratio A/F when the valve boat 57 is repeatedly opened and closed. is the fifth
0) As shown in the figure, K is approximately equal to the stoichiometric air-fuel ratio, and during fluctuations in the total fuel ratio, it is approximately ±0.2 to ±1.
In this way, by repeating the simple opening and closing operation of the valve body 58, the average value kl of the air-fuel ratio A/F is determined to be 0.
This is because the air-fuel ratio of the air-fuel mixture formed in the carburetor 2 is maintained constant even though the fuel ratio can be maintained at the theoretical 9 fuel ratio. Therefore, regardless of the engine operating condition M4K, the air-fuel ratio is approximately I.
l (with a frequency of 2 Hz from Z, it is made to vary within the range of ±0.2 to ±1.0 with respect to the stoichiometric air-fuel ratio,
Moreover, since the average value of this air-fuel ratio is maintained within the window Wo in FIG. 1(b), high purification efficiency can be obtained by utilizing the oxygen retention function of the three-way monolith catalyst 5.

-10,000, When the throttle valve 11 is closed and deceleration operation is started when the engine speed is high, the negative pressure in the intake manifold 1 suddenly stops, so there is a layer on the inner wall surface of the intake manifold 1. The fuel evaporates all at once, and as a result, a considerably rich air-fuel mixture is temporarily supplied into the engine cylinders, so that raw gas is discharged into the exhaust manifold 3. In such a case, if all the secondary air is supplied to the exhaust manifold 3173, the afterburn will take place. Therefore, in the present invention, the valve boat 5 of the secondary air supply control valve 50 is fully deenergized for a certain period of time T after the start of deceleration operation.
It is closed by a 7t valve body 58, thereby completely stopping the supply of secondary air, thereby preventing the occurrence of afterburn. After a certain period of time T has elapsed after the start of deceleration operation, a slightly richer air-fuel mixture is supplied into the engine cylinders. At this time, K generates a small amount of NOx, and it is necessary to purify unburned HC and CO sparingly. Therefore, in the present invention, when a certain period of time T2 has elapsed after the start of deceleration operation, the solenoid 67 is kept fully energized to control the secondary air supply, and the valve boat 57 of the #cell 50 is kept fully open to drain the secondary air into the exhaust manifold 3. and thereby continue to supply unburned fIC.

By promoting the oxidation reaction of CO, the purification effect of unburned HC and CO is completely improved. In this way, according to the present invention, the expensive M element detection detector 2 and the expensive 9 fuel ratio control Since all of the lid gas can be effectively purified using a low-cost carburetor without using an electronic control unit, the manufacturing cost of the exhaust gas purification device can be greatly reduced. Since the total fuel ratio of the air-fuel mixture is maintained at a constant level, combustion fluctuations do not occur.
In this way, smooth engine operation can be ensured.

During deceleration operation, it is possible to completely prevent the occurrence of afterburn after the start of deceleration operation, and it is also possible to greatly reduce the M harmful components in the exhaust gas released into the atmosphere during deceleration operation.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the efficiency of gas purification through gas purification, Fig. 2 is a side sectional view of the engine intake and exhaust system, Fig. 3 is a plan view taken along arrow 1 in Fig. 2, and Fig. 4 is a diagram showing the efficiency of gas purification. A side sectional view of the suction piston, Fig. 5 is a line diagram showing the fluctuations in the combustion rate, Fig. 6 is a circuit diagram of the electronic control unit, and Fig. 7 Ia shows all output signals of each element of the child control unit. This is a time chart. 2... Carburetor, 8... Suction piston, 9... Needle, 25... Fuel passage, 28...
...Nozzle, 50...Secondary air supply control valve, 51...
- Solenoid valve, 60... Secondary observation supply hole, 7o... Electronic control unit, 71... Idle switch, 72...
・Rotation speed switch. Patent applicant Toyota Motor Corporation Patent agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Kyosuke Nakayama Akira Yamaguchi No. 137-L
”＼
F<-1

Claims (1)

[Claims] An internal combustion engine is equipped with a fuel supply device 1 for supplying a rich mixture into the engine cylinders, and a three-way catalytic converter is installed in the engine exhaust passage. Secondary air supply passages are connected, and a solenoid valve that opens and closes at a frequency of about I Hz to 2Hz is disposed in the secondary air supply passage, so that when the secondary air supply passage is opened and closed, the air-fuel ratio is the average value. The entire flow area of the secondary air supply passage is determined so that the air-fuel ratio periodically fluctuates between approximately ±0.2 and ±1.0, and the average value of the air-fuel ratio becomes approximately the ideal fuel-fuel ratio. The apparatus further includes an electronic control unit that generates a solenoid valve control signal for fully closing or fully opening the secondary air supply passage in response to an output signal from a deceleration detector capable of detecting the deceleration operation state of the engine. An exhaust gas purification device for an internal combustion engine, which temporarily fully closes the secondary air supply passage when the deceleration operation is started, and then fully opens the secondary air supply passage when the deceleration operation is completed.