JPH0636266Y2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to an exhaust emission control device for an internal combustion engine having a mechanism for supplying secondary air to an exhaust system.

[Conventional technology]

2. Description of the Related Art There is known an internal combustion engine provided with a so-called fuel cut mechanism that cuts off fuel supply to improve fuel efficiency when the engine speed is higher than a predetermined value during deceleration operation. In such an internal combustion engine, combustion may become unstable when the vehicle speed becomes low during deceleration operation.
The internal combustion engine is operated with a rich air-fuel ratio. However, when the air-fuel ratio is rich, there is a problem that so-called catalytic odor occurs in an exhaust system having a three-way catalyst because the sulfur component increases in the exhaust gas, and HC and CO in the exhaust gas increase. Therefore, conventionally, in a rotational range lower than the above-mentioned predetermined value, secondary air is supplied to the exhaust system to remove catalytic odor and purify HC and the like. The supply of the secondary air is cut off, as disclosed in Japanese Utility Model Laid-Open No. 61-126024, because harmful components in the exhaust gas are reduced as the engine speed further decreases.

[Problems to be solved by the invention]

However, especially in AT (automatic) vehicles, when the engine speed suddenly drops despite the high vehicle speed, such as when the vehicle changes from an accelerated state to a decelerated state, the secondary air supply is cut off according to the conventional device. As a result, there arises a problem that unburned harmful components increase in the exhaust gas.

[Means for solving problems]

As shown in the block diagram of the invention of FIG. 1, an exhaust gas purification apparatus for an internal combustion engine according to the present invention includes a means A for detecting an operating state of the internal combustion engine, and a secondary air for an exhaust system according to the operating state. And a means B for supplying the secondary air.
Is for supplying secondary air to the exhaust system during deceleration and when the engine speed is lower than the first value, and during deceleration while the engine speed is lower than the second value which is lower than the first value. Is also low and the vehicle speed is lower than a predetermined value, the supply of secondary air is cut off.

〔Example〕

 The present invention will be described below with reference to illustrated embodiments.

FIG. 2 shows an internal combustion engine to which an embodiment of the present invention is applied.
A cylinder head 12 is placed on the cylinder block 11, and an intake manifold 21 and an exhaust manifold 31 are attached to the cylinder head 12. The fuel injection valve 22 is provided on the downstream side of the intake manifold 21, and the throttle body 24 having the throttle valve 23 is connected to the upstream opening of the intake manifold 21. The air flow meter 25 is connected to the throttle body 24 via an intake pipe 26, and an air filter 27 is provided on the upstream side of the air flow meter 25. On the other hand, the exhaust pipe 32 is connected to the downstream opening of the exhaust manifold 31, and the three-way catalyst device 33 is connected to the downstream opening of the exhaust pipe 32.

In order to supply the secondary air to the exhaust system, the secondary air supply pipe 41 is installed in the exhaust port (not shown) formed in the cylinder head.
Are connected. The inlet portion of the supply pipe 41 is connected to the air filter 27, and an air pump 42, a control valve 43, and a check valve 44 are provided in the middle of the supply pipe 41. The air pump 42 sucks in air through the air filter 27, pressurizes it, and supplies it to the exhaust port through the control valve 43 and the check valve 44. Control valve 43
Is a conventionally known daiyaflam type valve, which is a negative pressure switching valve.
Switching control is performed by 45 to open and close the supply pipe 41. The negative pressure switching valve 45 is controlled by a solenoid 46, and when the solenoid 46 is excited, it supplies a negative pressure to the control valve 43 to open it.
When the solenoid 46 is demagnetized, atmospheric pressure is guided to the control valve 43 to close it. Therefore, the negative pressure port of the negative pressure switching valve 45 is the intake manifold 21 and immediately downstream of the throttle valve 23, and the atmospheric pressure port of the negative pressure switching valve 45 is the air filter 27.
The output port of the negative pressure switching valve 45 is connected to the control valve 43.

An electronic control unit (ECU) 51 supplies secondary air to the exhaust system of the engine during deceleration of the engine, controls fuel cut, and performs feedback control of air-fuel ratio. Therefore, signals indicating the operating state of the engine are input to the ECU 51 from various sensors. The throttle sensor 61 is connected to the throttle valve 23 and detects the opening degree of the throttle valve 23. The rotation speed sensor is provided in the distributor 62 and detects the engine rotation speed. The water temperature sensor 63 is attached to the water jacket 13 formed in the cylinder block 11 and forms the engine cooling water temperature as the engine temperature.
The O ₂ sensor 64 is attached downstream of the exhaust pipe 32 and detects the oxygen concentration in the exhaust gas.

The ECU 51 includes a microcomputer and has a micro processing unit (MPU) 52, a memory 53, an input port 54, and an output port 55, which are bus lines 56.
To connect. The signals of the sensors 61, 62, 63, 64 are input to the input port 54 and processed according to a program described later. That is, the ECU 51 uses O ₂ to control the air-fuel ratio.
In addition to controlling the opening and closing of the fuel injection valve 22 based on the signal of the sensor 64, it controls the fuel cut during deceleration, and also controls the switching of the negative pressure switching valve 45 to supply or cut off the secondary air. . Therefore, the output signal from the output port 55 is sent to the fuel injection valve 22 and the solenoid 46.

FIG. 3 shows a fuel cut control routine, which is interrupted at predetermined time intervals.

At step 101, it is judged if the engine is decelerating. Here, when the throttle valve 23 is almost fully closed, it is determined that deceleration is being performed, but when the intake air amount (Q / N) per engine revolution is less than or equal to a predetermined value, it is determined that deceleration is being performed. You may If not, step 10
4 is executed and fuel is supplied, but if deceleration is being performed, the routine proceeds to step 102, where the engine speed is the first value N ₁
It is determined whether or not the above. When the engine speed is equal to or higher than the _first value N ₁ , the process proceeds to step 103, the fuel supply is cut off,
On the contrary, when the engine speed is lower than the first value N ₁ , the routine proceeds to step 104, where fuel is supplied.

FIG. 4 shows a control routine for supplying secondary air to the exhaust system, which is interrupted every predetermined time.

In step 201, it is determined whether the engine is decelerating,
If the vehicle is not decelerating, steps 202 to 206 below are skipped, and if the vehicle is decelerating, the process proceeds to step 202. Whether or not the vehicle is decelerating is determined by the throttle opening and the like as in step 101 of FIG. Next, when it is determined in step 202 that the engine speed is higher than the first value N ₁ ,
In step 206, the control valve 43 is closed and the supply of secondary air is shut off. That is, in this case, since the fuel cut is being executed, the exhaust system is in excess of oxygen, and it is not necessary to supply secondary air. On the other hand, the engine speed is the first
If the value is less than N ₁ , the step 203 and subsequent steps are executed.
The first value N ₁ is the same as the first value N ₁ in the fuel cut control routine and is, for example, 1500 rpm.

At step 203, it is judged if the engine speed is lower than the second value N ₂ , and if it is low, the routine proceeds to step 204, and if it is not low, step 204 is skipped and the routine proceeds to step 205.
The second value N ₂ is lower than the first value N ₁ , and is the idle speed (for example, 800 rpm) in this embodiment. Step 204
Then, it is determined whether or not the vehicle speed is lower than a predetermined value C (for example, 4 km / h). If the vehicle speed is low, the supply of secondary air is shut off in step 206.
3 is opened and secondary air is supplied.

Then, when the engine decelerates and enters the idle operation, steps 203, 204 and 206 are executed in this order, and the supply of the secondary air is cut off. Further, at this time, in an air-fuel ratio feedback control routine (not shown), feedback control is performed based on the output signal of the O ₂ sensor 64 so that the exhaust gas becomes the stoichiometric air-fuel ratio, and the harmful component in the exhaust gas is a three-way catalyst. Is completely purified by. On the other hand, when the engine speed is lower than the second value N ₂ and the vehicle speed is equal to or higher than the predetermined value C, steps 203, 204 and 205 are executed in this order to supply the secondary air. That is, when the engine speed suddenly drops during deceleration, HC and CO are present in the exhaust gas, but these are oxidized and purified by the supply of secondary air.

[Effect of device]

As described above, according to the present invention, when the vehicle speed is high to some extent even if the engine speed is low, the secondary air is supplied to the exhaust system to effectively purify the exhaust gas.

[Brief description of drawings]

FIG. 1 is a configuration diagram of the device, FIG. 2 is a side view of a portion of an internal combustion engine to which an embodiment of the present invention is applied, FIG. 3 is a flow chart of a fuel cut control routine, and FIG. It is a flow chart of an air control routine. 41 ... Secondary air supply pipe, 43 ... Control valve.

Claims (1)

[Scope of utility model registration request] 1. During deceleration, fuel supply is stopped when the engine speed is equal to or higher than a first value, and the engine speed is equal to the first value.
In the internal combustion engine that resumes fuel supply when the value falls below the value of, the means for detecting the operating state of the internal combustion engine, and means for supplying secondary air to the exhaust system according to the operating state, the secondary The air supply means supplies secondary air to the exhaust system during deceleration and when the engine speed is lower than the first value, and during the deceleration, the engine speed is lower than the first value. When the vehicle speed is lower than the above value and the vehicle speed is less than a predetermined value, the exhaust gas purification device for an internal combustion engine is cut off.