JPH0693849A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide an exhaust emission control device for internal combustion engine which can purify HC to be exhausted from an engine completely when the engine is started. CONSTITUTION:An emission control device 15 which incorporates an adsorbent 16 in the upstream of an exhaust pipe 14 of an engine and a catalyst device with heater 18 in the downstream is provided, and an engine control device 24 controls it in such a way that adsorbed HC adsorbed in the adsorbent 16 until the engine warms is purified by heating the catalyst device with heater 18 after the engine warms.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine.

[0002]

2. Description of the Related Art For example, a monolith type catalyst is provided in an exhaust pipe in order to purify exhaust gas discharged from an internal combustion engine of an automobile or the like and release it into the atmosphere. This catalyst oxidizes HC and CO in exhaust gas or NO _x
The exhaust gas is purified by reducing the exhaust gas.

By the way, when the exhaust gas is purified only by the above-mentioned catalyst, the catalyst is not activated in a state where the exhaust gas temperature is low, for example, at the time of low temperature starting, so that unburned hydrocarbon (HC) is generated. There is a problem that is passed through the catalyst and released into the atmosphere.

Therefore, an exhaust gas is arranged upstream of the catalyst arranged in the exhaust pipe of the engine so that an HC adsorbent for trapping unburned hydrocarbons (HC) discharged from the engine at low temperature start is arranged. Purification devices are known from JP-A-4-17710 and JP-A-3-141816.

[0005]

However, in the exhaust gas purifying apparatus described in the above-mentioned publication, the HC adsorbed on the adsorbent cannot be completely desorbed, so that the HC is completely purified. There was a problem if I could not do it.

The present invention has been made in view of the above points, and an object thereof is to provide an exhaust gas purifying apparatus for an internal combustion engine, which can completely purify HC discharged from the engine when the engine is started.

[0007]

According to a first aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine, wherein an adsorbent is incorporated in an exhaust pipe of an engine on an upstream side and a catalyst device with a heater is incorporated on a downstream side. A device is provided to heat the HC adsorbed by the adsorbent until the engine reaches a warm-up state by heating the catalyst device with a heater after the engine warms up.
And a control means for purifying the gas with a heater-equipped catalyst device.

According to a second aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine, wherein the exhaust pipe of the engine is equipped with a heater adsorbent on the upstream side and a heater catalytic converter on the downstream side. After the engine warms up the HC adsorbed on the heater-attached adsorbent until the engine reaches a warm-up state, the heater-attached catalyst device is heated and then the heater-attached adsorbent is heated. Control means for desorbing the adsorbed HC and purifying the adsorbed HC by the catalyst device with a heater.

[0009]

According to the first aspect of the present invention, the HC adsorbed by the adsorbent incorporated in the upstream side of the purifying device before the engine is warmed up is incorporated in the downstream side of the purifying device after the engine warms up. The adsorbed HC is controlled to be purified by heating the heater-equipped catalyst device.

According to the second aspect of the present invention, the heat exchanger incorporated in the upstream side of the purifying device before the engine reaches the warm-up state.
After the engine has warmed up the HC adsorbed by the adsorbent with a heater, the catalyst device with a heater incorporated in the downstream side of the purification device is heated, and then the adsorbent with a heater is heated to desorb the adsorbed HC. It is controlled so as to be separated and purified by a catalyst device with a heater.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of an exhaust gas purifying apparatus for an internal combustion engine according to the first embodiment, and FIG. 2 is a flow chart for explaining the operation of the first embodiment.

In FIG. 1, 11 is an engine. An exhaust port (not shown) of the engine 11 is connected to one end of a catalyst device 13 via an exhaust manifold 12. The catalyst device 13 purifies the exhaust gas by oxidizing HC and CO in the exhaust gas or reducing NO _x . The exhaust gas temperature is 400 ° C. or higher to activate the catalyst device 13 (in the case of a deteriorated catalyst).

The other end of the catalyst device 13 is connected to the exhaust pipe 14
It is connected to one end of the purification device 15 via. In the purification device 7, an adsorption cylinder 17 filled with an adsorbent 16 for adsorbing HC is incorporated on the upstream side, and a catalyst device with a heater 18 is incorporated on the downstream side. This adsorbent 1
6 includes activated carbon (for example, coconut shell activated carbon, coal-based activated carbon) and zeolite (for example, activated carbon) capable of efficiently adsorbing unburned hydrocarbons (HC) contained in low-temperature exhaust gas.
Hydrophobic zeolite, Y-zeolite) and the like are suitable.

The heater-equipped catalyst device 18 is heated by the heater-equipped catalyst control device 19, and the catalyst of the heater-equipped catalyst device 18 is activated by the heater-equipped catalyst control device 19. It is controlled to rise to the temperature.

The other end of the purifying device 15 is connected to one end of the silencer 20 via the exhaust pipe 14a. A tail pipe 21 is connected to the other end of the silencer 20. The purification device 15 is arranged immediately upstream of the muffler 20.

An exhaust gas temperature sensor 22 for detecting the exhaust gas temperature Te is provided immediately upstream of the purifying device 15 in the exhaust pipe 14. A water temperature sensor 23 detects the cooling water temperature Tw of the engine 11. Exhaust temperature sensor 2
The exhaust gas temperature Te detected in 2 and the cooling water temperature Tw detected by the water temperature sensor 23 are input to the engine control device 24. The engine control device 24 outputs a control signal a to the above-mentioned heater-equipped catalyst control device 19. Hi
The catalyst controller with catalyst 19 responds to this control signal a by sending a
The power of the catalyst device with catalyst 18 is controlled to be turned on and off.

The engine control unit 24 is composed of, for example, a microcomputer and its peripheral circuits, and outputs to the engine 11 a signal instructing an optimum fuel injection amount according to the load condition of the engine. Further, the engine control device 24 obtains the intake air amount from the map from the engine speed and the throttle opening after starting the engine 11, obtains the fuel injection amount corresponding to the intake air amount, and burns the fuel. Sometimes it has a function of calculating the amount of HC existing in the exhaust gas, and when the engine 11 is in a warm-up state, it takes in the output voltage of an O ₂ sensor (not shown) mounted upstream of the catalyst device 13. It has a function of performing feedback control (F / B) of the air-fuel ratio. Further, the engine control device 24 also includes a ROM (read only memory) for storing a control program for performing the control shown in FIG.

Next, the operation of the first embodiment of the present invention constructed as described above will be described with reference to the flow chart of FIG. First, it is determined whether the engine cooling water temperature Tw is 40 ° C. or lower (step S1). This step S
If the engine cooling water temperature Tw is higher than 40 ° C. in the judgment of 1, the process is terminated, but in the case of starting the engine, since the engine cooling water temperature Tw is low, step S1
Is determined to be "YES", and the determination in step S2 is performed.

In the determination in step S2, it is determined whether the exhaust gas temperature Te ≧ 50 ° C. detected by the exhaust temperature sensor 22 or the feedback control (F / B) of the air-fuel ratio is being performed. The exhaust gas temperature Te is lower than 50 ° C. and the feedback control is not started until a certain period of time elapses immediately after the engine is started. Therefore, the certain period of time is continuously determined as “NO” in step S2. During this fixed time, unburned HC discharged from the engine 11 passes through the catalyst device 13 and is adsorbed by the adsorbent 16 in the purification device 15.

When the temperature of the exhaust gas increases with the lapse of time after the engine 11 is started, and the exhaust gas temperature Te becomes higher than 50 ° C., step S
It is judged as “YES” in 2 and the adsorbent 1 is calculated from the total exhaust gas amount.
The amount of HC adsorbed on 6 is calculated (step S
3). That is, the intake air amount is obtained from the map from the engine speed and the throttle opening after the engine 11 is started, the fuel injection amount corresponding to the intake air amount is obtained, and when the fuel burns, the amount of intake air is changed into the exhaust gas. The amount of existing HC is calculated.

Then, a control signal a is output to the heater-equipped catalyst control device 19 to heat and activate the heater-equipped catalyst device 18. For example, activation temperature (350-400 ° C)
(Step S4). The HC adsorbed on the adsorbent 16 is desorbed by the exhaust gas, purified by the activated catalyst device with a heater 18, and then released to the atmosphere through the silencer 20.

Then, the time required for desorption from the adsorbed HC amount calculated in step S3 described above is calculated, and the elapsed time after turning on the heater power source of the heater-equipped catalyst device 18 is deducted. It is determined whether or not the time required for separation has been reached (step S5).

The heater-equipped catalyst device 18 continues to be heated until the time elapsed after the heater power supply of the heater-equipped catalyst device 18 is turned on reaches the time required for desorption. The HC desorbed from the adsorbent 16 is completely purified by the catalyst device with a heater 18.

When the time elapsed after the heater power of the heater-equipped catalyst device 18 is turned on reaches the time required for desorption, it is determined to be "YES" in step S5, and the control signal a Output from the catalyst controller with heater 19 to the catalyst device with heater 18, the power of the catalyst device with heater 18 is turned off, that is, the heating of the catalyst device with heater 18 is stopped.
As described above, in the first embodiment, the adsorbent 16 is attached in the middle of the exhaust pipe 14, the HC adsorbed by the adsorbent 16 is desorbed by the exhaust gas, and the heater incorporated downstream of the adsorbent 16 is removed. By activating the catalyst device with a heater 18 for a time required for desorption, the HC desorbed from the adsorbent 16 can be completely purified by the catalyst device with a heater 18.

Next, a second embodiment of the present invention will be described with reference to FIGS. In the first embodiment described above, the HC adsorbed by the adsorbent 16 incorporated in the purifying device 15 is desorbed by the exhaust gas, but in the second embodiment, the adsorption cylinder 17 has a heater built therein. In addition, the adsorbed HC adsorbed by the adsorbent 16 is desorbed by heating this heater.

FIG. 3 is an overall configuration diagram of an exhaust gas purifying apparatus for an internal combustion engine according to the second embodiment, and FIG. 4 is a flow chart for explaining the operation of the second embodiment. 3, the same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

That is, the suction cylinder 17 has a heater 17h built therein. Both ends of the heater 17h are connected to the heater control device 31. A control signal b is input from the engine control device 24 to the heater control device 31. When the control signal b from the engine control device 24 is input, the heater control device 24 heats the heater 17h and maintains the temperature of the adsorbent 16 at a constant temperature (200 to 250 ° C.), thereby adsorbing HC. It is designed to promote the detachment of.

Next, the operation of the second embodiment of the present invention constructed as described above will be described with reference to the flowchart of FIG. First, it is determined whether the engine cooling water temperature Tw is 40 ° C. or lower (step S11). If the engine cooling water temperature Tw is higher than 40 ° C. in the determination of step S11, the process is ended, but in the case of starting the engine, since the engine cooling water temperature Tw is low, it is determined “YES” in step S11. Then, the determination of step S12 is performed.

In this step S12, it is determined whether the exhaust gas temperature Te ≧ 50 ° C. detected by the exhaust temperature sensor 22 or the feedback control (F / B) of the air-fuel ratio is being performed. The exhaust gas temperature Te is lower than 50 ° C. and the feedback control is not started until a certain period of time elapses immediately after the engine is started. Therefore, the certain period of time is continuously determined as “NO” in step S12. During this fixed time, the unburned HC discharged from the engine 11 passes through the catalyst device 13, and then the adsorbent 1 in the purification device 15
Adsorbed on 6.

Then, when the temperature of the exhaust gas increases as time elapses after the engine 11 is started, and the exhaust gas temperature Te becomes higher than 50 ° C., step S
It is determined to be "YES" in 12 and the amount of HC adsorbed by the adsorbent 16 is calculated from the total amount of exhaust gas (step S1).
3). That is, the intake air amount is obtained from the map from the engine speed and the throttle opening after the engine 11 is started, the fuel injection amount corresponding to the intake air amount is obtained, and when the fuel burns, the amount of intake air is changed into the exhaust gas. The amount of existing HC is calculated.

Then, a control signal a is output to the heater-equipped catalyst control device 19 to heat and activate the heater-equipped catalyst device 18. For example, activation temperature (350-400 ° C)
(Step S14).

Then, it is determined whether the exhaust gas temperature Te detected by the exhaust temperature sensor 22 is 200 ° C. or lower (step S15). If the determination in step S15 is "Y
If it is determined to be “ES”, it is necessary to heat the adsorbent 16 to accelerate desorption of the adsorbed HC, and therefore, the control signal b is output to the heater control device 31 and the heater control device is output. Three
Under the control of 1, the adsorbent 16 has a constant temperature (200 to 25
The heater 17h is heated so that the temperature becomes 0 ° C.

On the other hand, when the exhaust gas temperature rises with the lapse of time and the exhaust gas temperature Te detected by the exhaust temperature sensor 22 exceeds 200 ° C., the heater 17h is powered off. That is, when the exhaust gas temperature is higher than 200 ° C., the HC adsorbed on the adsorbent 16 is desorbed by the heat of the exhaust gas.

As described above, the HC adsorbed on the adsorbent 16 by the heat of the heater 17h or the heat of the exhaust gas is desorbed and purified by the activated catalyst device 18 with a heater. , Is emitted to the atmosphere through the silencer 20.

Then, the time required for desorption from the adsorbed HC amount calculated in step S13 is calculated,
It is determined whether the elapsed time after the heater power of the heater-equipped catalyst device 18 is turned on is equal to or longer than the time required for desorption (step S18).

The heater-equipped catalyst device 18 continues to be heated until the time elapsed after the heater power source of the heater-equipped catalyst device 18 is turned on reaches the time required for desorption. The HC desorbed from the adsorbent 16 is purified by the catalyst device with a heater 18.

Then, when the time elapsed after the heater power supply of the heater-equipped catalyst device 18 is turned on reaches the time required for desorption, it is determined to be "YES" in step S18, and the control signal a is Output from the catalyst controller with heater 19 to the catalyst device with heater 18 to turn off the power of the catalyst device with heater 18, that is, the heating of the catalyst device with heater 18 is stopped. The control signal b is output to the controller 31
The power of the heater 17h is controlled to be turned off.

As described above, in the second embodiment, the adsorbent 16 is attached in the middle of the exhaust pipe 14, and the HC adsorbed by the adsorbent 16 is desorbed by the heat of the heater 17h to remove the adsorbent 16. By activating the catalyst device with a heater 18 incorporated in the downstream for a time required for desorption,
The HC desorbed from the adsorbent 16 can be completely purified by the catalyst device with a heater 18.

In the second embodiment, the heater 17h for heating the adsorbent 16 is built in the adsorption cylinder 17, but the exhaust gas flowing into the adsorbent 16 is heated as shown in FIG. It may be configured as follows. FIG. 5 is a cross-sectional view as seen from the side, and the purifying device 15 has a path 15a directed vertically upward with respect to the exhaust pipe 14, and an adsorption cylinder 17 is installed in this path 15a. Heater 17h on the side
I am trying to attach. The path 15a extends in the horizontal direction and is connected to the catalyst device 18.

With this configuration, the heater 1
The exhaust gas is heated by 7h, and the heated exhaust gas rises by convection to heat the adsorbent 16 installed above. By heating the adsorbent 16, adsorbed HC is desorbed. Although the engine control unit 24 is not shown in FIG. 5, the control content is the same as that of the second embodiment.

Further, the adsorbent 16 may be heated by utilizing the radiant heat or heat transfer of the heater-equipped catalyst device 18 without providing a special heater for heating the adsorbent 16. . In this case, the arrangement relationship shown in FIG. 6 may be taken in consideration of heat convection. FIG. 6 is a cross-sectional view seen from the side,
The purifying device 15 has a path 15a vertically upward with respect to the exhaust pipe 14, an adsorption cylinder 17 is mounted in the path 15a, and a heater-equipped catalyst device 18 is mounted in the vicinity of the adsorption cylinder 17 and close thereto. I am trying.

With this structure, when the heater-equipped catalyst device 18 is heated, the adsorbent 16 is also heated by radiant heat or heat transfer, and the adsorbed HC is desorbed. In Figure 6,
Although the engine control device 24 is not shown, the control content is the same as that of the first embodiment.

Further, in the above-mentioned first and second embodiments, the purifying device 15 is arranged immediately upstream of the muffler 20 apart from the engine 11. By arranging in this way,
When the engine is started, the temperature of the adsorbent 16 can be kept low and the adsorption of HC by the adsorbent 16 can be promoted.

[0044]

As described in detail above, according to the present invention, it is possible to provide an exhaust gas purifying apparatus for an internal combustion engine, which can completely purify HC discharged from the engine at the time of engine start.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an exhaust gas purifying apparatus for an internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the first embodiment.

FIG. 3 is an overall configuration diagram of an exhaust gas purifying apparatus for an internal combustion engine according to a second embodiment of the present invention.

FIG. 4 is a flowchart for explaining the operation of the second embodiment.

FIG. 5 is a view showing a modified example of the purifying device.

FIG. 6 is a view showing a modified example of the purification device.

[Explanation of symbols]

11 ... Engine, 12 ... Exhaust manifold, 13 ... Catalyst device, 14 ... Exhaust pipe, 15 ... Purification device, 16 ... Adsorbent,
17 ... Adsorption cylinder, 18 ... Heater-equipped catalyst device, 19 ... Heater-equipped catalyst control device, 20 ... Silencer, 21 ... Tail pipe.

Claims (2)

[Claims] 1. A purifying device having an adsorbent incorporated in the exhaust pipe of the engine on the upstream side and a catalyst device with a heater incorporated on the downstream side, the adsorbent being adsorbed by the adsorbent until the engine reaches a warm-up state. And a control means for purifying the adsorbed HC by the catalyst device with the heater by heating the catalyst device with the heater after the engine is warmed up. apparatus. 2. A purification device having a heater-equipped adsorbent incorporated on the upstream side and a heater-equipped catalyst device incorporated on the downstream side is provided in the exhaust pipe of the engine, and the above-mentioned heat treatment is performed before the engine reaches a warm-up state. After the engine has warmed up the HC adsorbed by the adsorbent with a heater, the catalyst device with a heater is heated, and then the adsorbent with a heater is heated to desorb the adsorbed HC to attach the heater. An exhaust gas purifying apparatus for an internal combustion engine, comprising: a control means for purifying with a catalyst device.