JPS6128033Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an exhaust gas purification device that comprehensively reduces harmful components carbon monoxide CO, hydrocarbons HC, and nitrogen oxides NOx contained in the exhaust gas of an internal combustion engine. This invention relates to an exhaust system equipped with a three-way catalytic converter to control the air-fuel ratio of air-fuel mixture.

When the internal combustion engine is idling, the combustion temperature is low and little NOx is generated, so in this case it is sufficient to mainly reduce CO and HC. Conventionally, there is a system that significantly dilutes the air-fuel mixture generated in the fuel supply system during idling to reduce the amount of CO and HC generated, but this method narrows the adjustment range during idling. However, it is difficult to stabilize idling operation, and it is also difficult to stabilize the combustion and exhaust system emissions.

In view of these circumstances, the present invention eliminates the above-mentioned instability by making the air-fuel mixture slightly leaner than the stoichiometric air-fuel ratio during idling, and also uses a three-way catalytic converter to purify exhaust gas during idling and above a specified load. An object of the present invention is to provide an exhaust gas purification device for an internal combustion engine that has been improved to be able to perform the exhaust gas purification sufficiently in the following manner.

For this purpose, the present invention makes the air-fuel mixture slightly leaner than the stoichiometric air-fuel ratio during idling, and
Secondary air is introduced into the exhaust system and a three-way catalytic converter is used to reduce CO and HC, and when the load exceeds a specified level, a control valve operated by suction pipe negative pressure is opened and closed to stop the introduction of secondary air and reduce CO and HC. It is characterized by creating a reducing atmosphere in the primary catalytic converter, and synchronously supplying auxiliary fuel to bring the air-fuel mixture to an almost stoichiometric air-fuel ratio, thereby simultaneously reducing CO, HC, and NOx in the three-way catalytic converter. do.

Incidentally, as an example of prior art for removing harmful components, especially unburned components, from exhaust gas, there is a technique described in Japanese Utility Model Application Publication No. 16122/1983, which describes the use of an auxiliary fuel supply device in the fuel supply system. In an internal combustion engine equipped with a secondary air introduction device in the exhaust system, at high speeds and high loads, the operation of the check valve in the exhaust supply passage cannot follow the pulsation of exhaust gas pressure, and the exhaust pressure increases. In connection with the situation in which the amount of secondary air supplied to the exhaust pipe is reduced due to reasons such as this, the starting point of the auxiliary fuel supply device should be shifted to the high load side, or a means should be provided to reduce the amount of additional fuel supplied by the device. This reduces the overenrichment rate of the air-fuel mixture and suppresses the increase in unnatural components contained in the exhaust gas.

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings.

In FIG. 1, numeral 1 is the engine body,
A three-way catalytic converter 4 is provided in an exhaust pipe 3 connected to an exhaust port 2 of the engine body 1, and a secondary air introduction device 5 is provided in front of the three-way catalytic converter 4, for example, in the exhaust port 2. This secondary air introduction device 5 is designed to introduce secondary air only during idling, as will be described later.
It is not necessary to install it in the exhaust system of all cylinders, and it is sufficient to install it in the exhaust system of only one cylinder.
Next air passage 7 passes through control valve 8 to air filter 9
is connected to. The control valve 8 has an operating negative pressure chamber 10 that communicates with the intake pipe 12 of the engine body 1 through a passage 11, and only when the intake negative pressure is large such as during idling, the negative pressure is used to flow through the diaphragm 13. By retracting the valve body 14, the valve port 1
5 is opened, and at this time, secondary air is introduced into the exhaust port 2 from the air filter 9 due to pressure fluctuations in the exhaust port 2 and the exhaust pipe 3 due to exhaust pulsation.

Further, reference numeral 16 is a carburetor, in which a throttle valve 17, an auxiliary fuel supply device 18, etc. are provided. As detailed in FIG. 2, this device 18 pulls the piston 20 upward when the negative pressure in the piston chamber 19 exceeds a predetermined value, thereby causing the valve 21 to
moves upward and closes the fuel passage 22 to stop the supply of auxiliary fuel, and when the negative pressure falls below a predetermined level, the spring 52 moves the valve 21 downward and opens the passage 22 to stop the supply of auxiliary fuel. We are starting to provide additional supplies.

The piston chamber 19 of the auxiliary fuel supply device 18 is communicated with the passage 11 from which the suction negative pressure is taken out via a passage 23, an electromagnetic on-off valve 24, and a passage 25. One side of the electromagnetic on-off valve 24 has a coil 26 connected to a battery 27, and the other side connected to a boost switch 28 provided in the passage 11. When idling, the boost switch 28 is turned on due to large suction negative pressure. , the electromagnetic on-off valve 24 is energized and the large negative pressure in the passage 11 is transferred to the passage 2.
5. The electromagnetic on-off valve 24 leads to the piston chamber 19 through the passage 23, and when the load exceeds a predetermined load, the boost switch 28 turns off due to a decrease in suction negative pressure. and is guided to the piston chamber 19. Therefore, during idling, secondary air is introduced by the secondary air introduction device 5, but refueling by the auxiliary fuel supply device 18 is no longer performed, and when the load exceeds a predetermined load, the secondary air is introduced by the secondary air introduction device 5. The introduction of air is stopped, and fuel is added by the auxiliary fuel supply device 18, and these are switched and controlled in synchronization using a common suction negative pressure.

The suction negative pressure in the passage 11 is transferred to the passage 2 branched from there.
9 is further supplied to the advance side operation negative pressure chamber 32 side of the vacuum advance device 31 of the distributor 30, whereby the ignition timing is automatically advanced in accordance with the operating state.

Furthermore, the EGR device 33 is connected to the exhaust system, for example, from the exhaust port 2 to the passage 34 and the two EGR valves 35, 3.
6. A part of the exhaust gas is sent to the intake pipe 1 through the passage 37.
2. one side
In the EGR valve 35, an operating negative pressure chamber 38 communicates through a passage 39 with a negative pressure port 40 located immediately upstream of the idling position of the throttle valve 17 of the carburetor 16, and downstream at a predetermined opening degree or more. This EGR in operating conditions other than full throttle
EGR is applied by valve 35. Also the other
The EGR valve 36 has an operating negative pressure chamber 41 and a passage 42,
It communicates with a negative pressure port 45 on the upstream side of the negative pressure port 40 of the carburetor 16 via an electromagnetic on-off valve 43 and a passage 44 . One side of the coil 46 of the electromagnetic on-off valve 43 is connected to the battery 27, and the other side is connected to the temperature and vehicle speed switch side, and is energized when the engine water temperature is below a predetermined value and the vehicle speed is above a predetermined value. Then, the atmosphere is passed through the passage 42 to the EGR valve 3.
6 to the operating negative pressure chamber 41, so in this case,
The EGR valve 36 closes and EGR stops working.
On the other hand, in the most frequently used operating state where the water temperature is above a predetermined value and the vehicle speed is below a predetermined value, the electromagnetic on-off valve 43 is de-energized and the passages 42 and 44 are communicated with each other, thereby controlling the opening of the throttle valve 17. The corresponding negative pressure is led to the operating negative pressure chamber 41 of the EGR valve 36, and acts on the EGR together with the EGR valve 35.

Thus, since the present invention is configured as described above, the auxiliary fuel supply device 18 is not activated during idling.
A large negative suction pressure is introduced into the piston chamber 19 of the engine, and auxiliary fuel is not supplied. At this time, however, the idling fuel supply system of the carburetor 16 causes the air-fuel mixture to be slightly leaner than the stoichiometric air-fuel ratio, for example, around 16 to 17. be made into Further, during such idling, a large suction negative pressure acts on the operating negative pressure chamber 10 of the control valve 8 of the secondary air introduction device 5 and introduces secondary air into the exhaust system, so that the three-way catalytic converter 4 becomes an oxidizing atmosphere, whereby CO and HC, which are relatively abundant in the exhaust gas, are sufficiently oxidized by the three-way catalytic converter 4 and reduced. Furthermore, the ignition timing operates on the advanced side, improving starting performance, and the negative pressure ports 40, 45 of the carburetor 16 are located upstream of the throttle valve 17, and atmospheric pressure is supplied to both EGR valves 35, 45. 3
6 is closed and EGR does not work. Therefore, during idling, the air-fuel mixture is slightly leaner than the stoichiometric air-fuel ratio as described above, so the ignition timing is advanced.
Due to interactions such as no EGR action, drivability becomes very stable and good.

Next, when the load exceeds a predetermined value, the secondary air introduction device 5
The negative pressure in the operating negative pressure chamber 10 of the control valve 8 is reduced, and secondary air is no longer introduced, so that the three-way catalytic converter 4 becomes a reducing atmosphere. Meanwhile, at this time, atmospheric pressure is supplied to the piston chamber 19 of the auxiliary fuel supply device 18 by the electromagnetic on-off valve 24, and auxiliary fuel is supplied. The air-fuel mixture is supplied to approximately the stoichiometric air-fuel ratio, and thus CO, HC, and NOx in the exhaust gas are simultaneously processed and reduced by the three-way catalytic converter 4.

Furthermore, at this time, if the water temperature is below a predetermined value and the vehicle is running without being sufficiently warmed up, or if the vehicle speed is accelerated to a predetermined value or higher, the electromagnetic on-off valve 43 is activated.
EGR valve 36 is closed and one EGR valve 35
This allows a small amount of EGR to be performed, reducing NOx emissions without impairing drivability. However, if the water temperature is above a predetermined value and the vehicle is sufficiently warmed up, and the vehicle speed is below a predetermined value and the vehicle is in normal driving condition,
The carburetor 1 is also installed in the negative pressure chamber 41 of the EGR valve 36.
Negative pressure is supplied from the negative pressure port 45 of No. 6, and a large amount of EGR is performed together with the EGR valve 35, thereby promoting reduction in NOx emissions.

The control valve of the secondary air introduction device 5 is constructed of an electromagnetic type as shown by the reference numeral 47 in FIG. It is also possible to configure the valve body 50 to open and close the valve port 51 on the air filter side by energizing and de-energizing the coil 49.

Note that the negative pressure pipe for operating the control valve of the secondary air introduction device may be separated and connected to the suction pipe at a point located downstream of the idling position of the throttle valve and upstream at a predetermined opening degree.

As described above, according to the present invention, the air-fuel mixture is made slightly leaner than the stoichiometric air-fuel ratio during idling, so idling operation and emission are stabilized, and adjustment is facilitated. This is especially effective when a wide range of idling stability is required, such as sports specifications and AT specifications.
Further, the exhaust gas at this time can be sufficiently purified of CO and HC by the three-way catalytic converter 4 into which secondary air is introduced. Furthermore, since the introduction of secondary air and the supply of auxiliary fuel are performed in synchronization, there are inconveniences such as secondary air being introduced when auxiliary fuel is supplied, or vice versa. does not occur.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of an exhaust gas purification device for an internal combustion engine according to the present invention, and Fig. 2 is a block diagram showing an embodiment of an exhaust gas purification device for an internal combustion engine according to the present invention.
FIG. 3 is a block diagram showing another embodiment of the control valve of the secondary air introduction device. 1...Engine body, 2...Exhaust port, 3...
...Exhaust pipe, 4...Three-way catalytic converter, 5...2
Secondary air introduction device, 6... Check valve, 7... Secondary air passage, 8... Control valve, 9... Air filter, 10
... Operating negative pressure chamber, 11 ... Passage, 12 ... Intake pipe, 13 ... Diaphragm, 14 ... Valve body, 15
... Valve port, 16 ... Carburizer, 17 ... Throttle valve, 18 ... Auxiliary fuel supply device, 19 ... Piston chamber, 20 ... Piston, 21 ... Valve,
22...fuel passage, 23...passage, 24...electromagnetic on-off valve, 25...passage, 26...coil, 27...
...Battery, 28...Boost switch, 29
...Aisle, 30...Day streamer, 31...
...Vacuum advance angle device, 32...Advance side operation negative pressure chamber, 3
3... EGR device, 34... Passage, 35, 36...
...EGR valve, 37...passage, 38, 41...
Working negative pressure chamber, 39, 42, 44... passage, 40,
45... Negative pressure port, 43... Solenoid on-off valve, 46...
Coil, 47... Control valve, 48... Boost switch, 49... Coil, 50... Valve body, 51...
valve port.

Claims (1)

[Scope of utility model registration request] The fuel supply system of the internal combustion engine is provided with an auxiliary fuel supply device, and the exhaust system is provided with a secondary air introduction device and a three-way catalytic converter equipped with a control valve operated by intake pipe negative pressure. The air-fuel mixture is made slightly leaner than the stoichiometric air-fuel ratio, and secondary air is introduced into the exhaust system so that the three-way catalytic converter can be particularly oxidized. When the load exceeds a predetermined load, the control valve is closed and secondary air is introduced into the exhaust system. The three-way catalytic converter is placed in a reducing atmosphere by stopping the introduction of the three-way catalytic converter, and in synchronization with this, auxiliary fuel is supplied to the fuel supply system to bring the air-fuel mixture to approximately the stoichiometric air-fuel ratio. Exhaust gas purification device for internal combustion engines.