JP2001115828A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely treat regeneration of a HC adsorbing material for burning and eliminating coking material such as soot stuck on the HC adsorbing material disposed in a bypass exhaust passage, in an exhaust emission control device for an internal combustion engine. SOLUTION: After a desorption treatment of HC component adsorbed is completed (S100), when NE rotating speed and intake pipe internal absolute pressure PBA exceed each prescribed value (S106, S108), and when a temperature (a temperature at a front of an adsorbing material tmp.fr.trs) of exhaust gas to be supplied to a HC adsorbing material is a prescribed temperature TMP.COKE or more (S110), a bypass exhaust passage is opened, exhaust gas is led, and then, the coking material is burnt and eliminated (S112).

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, and more particularly, to an exhaust system (pipe) of an internal combustion engine.
Adsorbent (adsorption means) in the bypass exhaust passage branched from
In the one that adsorbs unburned components by providing a, coking substance such as soot attached to the adsorbent is removed by burning,
Therefore, the present invention relates to a device for preventing deterioration of the adsorbent.

[0002]

2. Description of the Related Art In an internal combustion engine, a catalyst is provided in an exhaust system to remove HC, NOx, and CO components in exhaust gas to purify the exhaust gas. However, when the catalyst is not activated, such as at the time of a cold start of the engine. The unburned components, in particular, the unburned HC components are directly discharged out of the engine.

[0003] Therefore, the exhaust pipe of the internal combustion engine is branched downstream of the catalyst, and a bypass exhaust passage opened and closed via a switching valve is provided to accommodate adsorption means such as a zeolite-based adsorbent, and the catalyst is activated. When the engine is not in operation, the bypass exhaust passage is opened to introduce exhaust gas when the engine is started to adsorb unburned components, and after the catalyst is activated, the adsorbed unburned components are desorbed and purified by the catalyst, or There has been proposed an exhaust gas purifying apparatus that recirculates the system, reburns, purifies with a catalyst, and discharges the outside of the engine.

[0004] As such exhaust gas purifiers are used more and more, substances such as soot, so-called caulking substances, adhere to the adsorbent and cause clogging, thereby deteriorating or deteriorating the performance of the adsorbent.

Therefore, as proposed in Japanese Patent Application Laid-Open No. 9-324621, after the desorption process of the adsorbed unburned components is completed, an operation state in which the oxygen concentration in the exhaust gas is high such as during fuel cut or lean operation. There has been proposed a technique for detecting the pressure, and opening the bypass exhaust passage to introduce the exhaust gas in such an operating state to burn and remove the adhering caulking substance, thereby regenerating the adsorbent.

That is, in the above-mentioned prior art, the temperature of the adsorbent is increased by being heated by the introduced exhaust gas, and the reaction between the adhered substance and the unreacted oxygen in the exhaust gas is promoted by the increased temperature. Thus, the adhered substances are removed by the resulting combustion.

[0007]

As described above, in the above-mentioned prior art, the temperature of the exhaust gas rises without directly determining the temperature of the exhaust gas to be supplied to the adsorbent. Since an adsorbent is regenerated by an indirect method of detecting a possible operating state, a sufficient adsorbent regeneration effect cannot always be obtained.

Accordingly, the present invention solves the above-mentioned disadvantages of the prior art, and in an exhaust gas purifying apparatus for an internal combustion engine in which an unburned component in exhaust gas is adsorbed by an adsorbing means provided in a bypass exhaust passage, The temperature of the exhaust gas to be supplied is directly obtained, and when the obtained temperature of the exhaust gas is equal to or higher than the predetermined temperature, the exhaust gas is introduced by opening the bypass exhaust passage according to the operation state and the like, and thus the coking It is an object of the present invention to provide an exhaust gas purifying apparatus for an internal combustion engine in which combustion is removed to surely regenerate the adsorption means.

[0009]

In order to achieve the above object, according to the present invention, the present invention is characterized in that the present invention is arranged in a bypass exhaust passage branched from an exhaust system of an internal combustion engine and opened and closed via a switching valve. An exhaust gas purification device for an internal combustion engine, wherein the exhaust gas is introduced at the time of starting the internal combustion engine by opening and closing the bypass exhaust passage, and an unburned component in the exhaust gas is adsorbed by the adsorption device. A desorption completion determining means for determining whether or not the desorption processing of the unburned components has been completed; an operating state for detecting an operating state of the internal combustion engine and determining whether the detected operating state is a predetermined operating state Determining means, determining the temperature of the exhaust gas to be supplied to the adsorption means, determining whether the determined temperature of the exhaust gas is higher than a predetermined temperature, and completing the desorption process. When it is determined that the detected operating state is in the predetermined operating state and the determined temperature of the exhaust gas is equal to or higher than the predetermined temperature, the bypass exhaust passage is opened to release the exhaust gas. It is configured to include a bypass exhaust passage opening means for introducing the gas.

As described above, when it is determined that the desorption process has been completed, it is determined that the detected operating state is in the predetermined operating state and the determined temperature of the exhaust gas is higher than the predetermined temperature. In addition, since it is configured to include a bypass exhaust passage opening means for opening the bypass exhaust passage and introducing the exhaust gas, in other words, the temperature of the exhaust gas to be supplied to the adsorption means is directly obtained, and the obtained exhaust gas is obtained. When the temperature is equal to or higher than a predetermined temperature, the bypass exhaust passage is opened and the exhaust gas is introduced according to the operation state, etc., so that the caulking substance is burned and removed in the operation region where the regeneration is truly possible. Therefore, the adsorption means can be reliably regenerated. In the above description, "determining the temperature of the exhaust gas to be supplied to the adsorption means" is used to include both a case where the temperature is detected using a temperature sensor and a case where a calculation (estimation) is performed by logic.

According to a second aspect of the present invention, the predetermined operating condition is that the load of the internal combustion engine exceeds a predetermined load,
The engine is configured to be in an operating state in which the rotation speed of the internal combustion engine exceeds a predetermined rotation speed.

[0012] Thereby, the adsorption means can be regenerated more reliably.

According to a third aspect of the present invention, the apparatus further comprises a temperature raising means for raising the temperature of the exhaust gas when it is determined that the obtained temperature of the exhaust gas is not higher than a predetermined temperature. .

Thus, after the desorption process is completed, the regeneration process can always be performed when the operation state shifts to a predetermined operation state, and even if the caulking substance adheres, the regeneration process can be performed at an early stage.

According to a fourth aspect of the present invention, there is further provided combustion promoting means for increasing the oxygen concentration in the bypass exhaust passage to promote combustion, and wherein the bypass exhaust passage opening means opens the bypass exhaust passage. In such a case, the combustion promoting means is configured to operate.

As a result, the unreacted oxygen is additionally supplied to the adsorbing means together with the high-temperature exhaust gas, so that the combustion of the adhered coking substance is promoted. As a result, the adsorbing means can be regenerated more effectively. .

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic view showing an entire exhaust gas purifying apparatus for an internal combustion engine according to one embodiment of the present invention.

In the drawing, reference numeral 10 denotes an OHC in-line four-cylinder internal combustion engine (hereinafter referred to as "engine") (only one cylinder is shown), and an air cleaner (not shown) disposed at the tip of an intake pipe (intake passage) 12 ) Is sent to each cylinder via two intake valves 20 (only one is shown) through a surge tank 16 and an intake manifold 18 while the flow rate is adjusted by a throttle valve 14.

The intake pipe 12 has a bypass passage 2 near the position where the throttle valve 14 is disposed.
2 is provided, and a valve (EACV) 24 composed of an electromagnetic solenoid valve for opening and closing is inserted therein.

An injector (fuel injection valve) 26 is provided near the intake valve 20 of each cylinder to inject fuel. The air-fuel mixture that has been injected and integrated with the intake air is sucked into the combustion chamber 28 of the cylinder in the intake stroke, compressed in the compression stroke, ignited via a spark plug (not shown), burned, and the piston 30 Is driven downward in the figure.

The exhaust gas after combustion is supplied to two exhaust valves (1
The exhaust gas is discharged to an exhaust pipe (exhaust passage) 38 through an exhaust manifold 36 and an exhaust pipe 38. The first catalyst device (3) is provided in the exhaust pipe 38 below the floor of a vehicle (not shown) downstream of the exhaust manifold 36. Source catalyst) 40, and second and third catalyst devices (both three-way catalysts) 4 provided downstream thereof
2 and 44, and is discharged to the atmosphere via a rear end 46 including a muffler and a tail pipe (both not shown) further downstream.

The engine 10 has a so-called variable valve timing mechanism 50 (shown as V / T in FIG. 1). The variable valve timing mechanism 50 is disclosed in, for example, Japanese Patent Laid-Open No. 2-275.
The intake and exhaust valve timing is switched between high and low timing characteristics in accordance with operating conditions such as the engine speed NE and the intake pipe absolute pressure PBA. The valve timing characteristic includes an operation of stopping one of the two intake valves.

The exhaust pipe 38 is branched downstream of the position where the third catalyst device 44 is disposed, and the branch pipe 52 is connected to a cylindrical case 54 that is hermetically mounted around the exhaust pipe 38 so as to surround the exhaust pipe 38. Is done. Thereby, the main exhaust passage 38a passing through the inside of the exhaust pipe 38 serves as an exhaust gas passage.
Then, a bypass exhaust passage 56 passing through the internal space of the branch pipe 52 and the cylindrical case 54 is formed. The exhaust gas discharged from the combustion chamber 28 flows through one of the exhaust passages.

A switching valve 60 is provided at a branch point of the exhaust pipe 38. FIG. 2 is an enlarged explanatory sectional view of the switching valve 60, and FIG. 3 is an enlarged explanatory sectional view taken along line III-III of FIG.

Referring to FIGS. 2 and 3, the switching valve 60 includes a valve disc 60a having a plane circular shape larger in diameter than an exhaust pipe circular inner wall surface 38b defining a main exhaust passage 38a, and an inverted C-shaped cross section. And a valve disc 60c, which is fixed via the arm 60b and has a larger diameter than the circular inner wall surface 52a of the branch pipe 52 that defines a part of the bypass exhaust passage 56. Valve disk 6
0c is fixed to the shaft 60e via the stem 60d.

As shown in FIG. 1, the shaft 60e is connected to a valve operating mechanism 64. The valve operating mechanism 64 is connected to a position downstream of the throttle valve 14 via a negative pressure introducing passage 66. An electromagnetic solenoid valve (TRPV) 68 is provided in the negative pressure introducing path 66. When the TRPV 68 is turned on (excited), the negative pressure introducing path is opened to introduce a negative pressure.

When a negative pressure is introduced, the valve operating mechanism 64 rotates the shaft 60e to a position shown by a solid line in FIG. As a result, the valve disc 60a contacts the valve seat 60f provided in the exhaust pipe 38, and closes the main exhaust passage 38a.

When the TRPV 68 is turned off (de-energized),
The negative pressure introducing passage 66 is opened to the atmosphere, and the shaft 60e is rotated to the position shown by the imaginary line in FIG. 2 by the action of a return spring (not shown). As a result, the valve disc 60c contacts the valve seat 60g, and closes the bypass exhaust passage 56.

By properly driving the TRPV 68 to adjust the amount of negative pressure to be introduced, the valve disk 60c
It is also possible to drive (and the valve disc 60a) an intermediate position between the positions indicated by the imaginary and solid lines in FIG. 2, for example, a position that opens the bypass exhaust passage 56 by a small amount.

As shown in FIG. 2, two valve discs 6
0a and 60c are the shafts 60 so that they form a predetermined angle θ.
e, when the valve disc 60a closes the main exhaust passage 38a, the valve disc 60c separates from the valve seat 60g and does not prevent the exhaust gas from flowing into the bypass exhaust passage 56.
When c closes the bypass exhaust passage 56, the valve disc 60a is configured to separate from the valve seat 60f so as not to prevent the exhaust gas from flowing into the main exhaust passage 38a.

Returning to FIG. 1, an HC adsorbent (HC adsorbing means or HC adsorbing catalyst) 74 supported by a carrier (honeycomb body) is disposed in the bypass exhaust passage 56 in the cylindrical case 54. The HC adsorbent 74 has two beds: a first adsorbent (bed) 74a on the upstream side (the side near the branch pipe 52) and a second adsorbent (the side near the rear end 46) on the downstream side (the side near the rear end 46). Bed) 74b.

More specifically, as shown in FIG. 4, the cylindrical case 54 surrounds the exhaust pipe 38 and has a circular cross section.
That is, the exhaust pipe 38 is arranged close to the HC adsorbent 74, and is configured to promote the temperature rise of the HC adsorbent 74 to quickly remove unburned components and quickly return to the intake system. .

The HC adsorbent is a crystalline aluminosilicate previously proposed by the present applicant in Japanese Patent Application Laid-Open No. Hei 8-71427, more specifically, a thin metal plate made of a mixture of ZSM-5 zeolite and a catalyst element. What is supported on a honeycomb core body wound and laminated in a spiral shape is used.

This crystalline aluminosilicate has a heat-resistant temperature of 900 ° C. to 1000 ° C. and exhibits excellent high-temperature durability as compared with activated carbon and the like. This HC adsorbent adsorbs unburned HC components when the exhaust system temperature is lower than 100 ° C.
Unburned HC components adsorbed between 00 ° C and 250 ° C are desorbed.

In the exhaust pipe 38, four holes 76 are formed at 90 ° intervals downstream of the cylindrical case 54 (closer to the rear end 46), and the main exhaust passage 38a and the bypass exhaust passage 5 are formed.
6 is communicated through a hole 76. Therefore, the bypass exhaust passage 56 joins the main exhaust passage 38a at this position.

On the other hand, an EGR (exhaust gas recirculation) passage 82 is connected to the cylindrical case 54 on the upstream side (closer to the branch pipe 52), and the EGR (exhaust gas recirculation) passage 82 is provided between the bypass exhaust passage 56 and the intake pipe 12 at a position downstream of the throttle valve 14. Communication is established between them. E
An EGR control valve 84 composed of an electromagnetic solenoid valve is inserted at an appropriate position in the GR passage 82. When the EGR control valve 84 is turned on (excited), the EGR passage 82 is closed.

A crank angle sensor 90 is provided in a distributor (not shown) of the engine 10 and outputs a signal corresponding to a TDC position of the piston 30 and a crank angle obtained by subdividing the TDC position. The throttle valve 14 is provided with a throttle opening sensor 92, and outputs a signal corresponding to the throttle opening (position) θTH.

The intake pipe 12 is provided with an absolute pressure sensor 94 at a position downstream of the throttle valve 14, and outputs a signal corresponding to the intake pipe absolute pressure PBA indicating the engine load. A water temperature sensor 96 is provided near a cooling water passage (not shown) of the engine, and outputs a signal corresponding to the cooling water temperature TW.

In the exhaust system, a wide area air-fuel ratio sensor 98 (“LAF sensor”) is provided at an exhaust pipe 38 downstream of the exhaust manifold 36 (exhaust system collecting portion) and upstream of the first catalyst device 40.
And outputs a signal proportional to the oxygen concentration in the exhaust gas in a wide range from lean to rich.

An O ₂ sensor 100 is provided downstream of the first catalyst device 40 in the exhaust pipe 38, and is an on / off signal that is inverted each time the oxygen concentration in the exhaust gas changes from lean to rich or from rich to lean. Is output.

An exhaust temperature sensor 102 for detecting the temperature of the third catalyst device or the temperature TCAT of the exhaust system is provided near the third catalyst device 44, and outputs a signal corresponding to the detected value.

Further, a second temperature sensor 104 is provided in the exhaust pipe 38 downstream of the third catalyst device 44 and upstream of the cylindrical case 54, and is supplied to the HC adsorbent 74 via the bypass exhaust passage 56. Output tmp. Depending on the temperature of the exhaust gas to be exhausted (hereinafter referred to as "temperature before adsorbent"). fr.
Output trs.

Further, an HC adsorbent 74 is provided in the bypass exhaust passage 56 in the cylindrical case 54, and more specifically, a third temperature sensor 106 is provided downstream (on the side closer to the rear end 46) of the second adsorbent 74b. The output tmp. Corresponding to the temperature of the exhaust gas near the junction of the bypass exhaust passage 56 and the main exhaust passage 38a (or a temperature sufficient to estimate the temperature of the HC adsorbent 74). Output out.

Further, as shown in FIG. 2, two limit switches 108 and 110 are provided near the valve seats 60f and 60g of the switching valve 60 so as to open or close the main exhaust passage 38a. When the valve disc 60c that opens and closes the exhaust passage 56 is driven to the seating position of the valve seat 60f or 60g (or in the vicinity thereof), an ON signal is output.

Further, a valve timing (V / T) sensor (not shown) is provided in a hydraulic circuit (not shown) of the variable valve timing mechanism 50 via a hydraulic pressure to detect a selected valve timing characteristic. A lift sensor (not shown) is provided in the vicinity of the EGR control valve 84, and outputs a signal corresponding to the displacement amount (lift amount).

The output of the above-mentioned sensor is sent to an electronic control unit (ECU) 114 composed of a microcomputer.

FIG. 5 is a block diagram showing details of the ECU 114. The output of the LAF sensor 98 is the first detection circuit 1
The detection signal is input to the detection signal 16 and is subjected to appropriate linearization processing to output a detection signal having a linear characteristic proportional to the oxygen concentration in the exhaust gas in a wide range from lean to rich.

The output of the O ₂ sensor 100 is input to a second detection circuit 118 and outputs a detection signal indicating whether the air-fuel ratio of the mixture supplied to the engine 10 is rich or lean with respect to the stoichiometric air-fuel ratio.

The output of the first detection circuit 116 is supplied to a CP 120 via a multiplexer 120 and an A / D conversion circuit 122.
U and are sequentially stored in the RAM 124. Similarly, the output of the second detection circuit 118 and the output of an analog sensor such as the throttle opening sensor 92 are also transmitted to the CP via the multiplexer 120 and the A / D conversion circuit 122.
U and is stored in the RAM 124.

After the output of the crank angle sensor 90 is shaped by a waveform shaping circuit 126, the output value is counted by a counter 128, and the count value is input to the CPU. Calculate NE. The CPU core 130 calculates a control value (operating amount) in accordance with a command stored in the ROM 132, and drives the injector 26 of each cylinder via the drive circuit 134.

Further, the CPU core 130 includes the driving circuit 1
The switching valve 60 is operated (driven) via an electromagnetic solenoid valve (TRPV) 68 and a valve operating mechanism 64 (not shown in FIG. 5) via 36 to perform an exhaust purification operation by HC adsorption at the time of engine start. The regeneration process of the HC adsorbent 74 is also performed.

Further, the CPU core 130 includes the driving circuit 13
8 to control the driving of the EACV 24 and the EGR via the drive circuit 140 in accordance with the detected lift amount.
The driving of the control valve 84 is controlled. Further, the CPU core 130 turns on a warning lamp 144 (not shown in FIG. 1) via the drive circuit 142 as necessary.

Next, the operation of the exhaust gas purifying apparatus for an internal combustion engine according to one embodiment of the present invention will be described.

FIG. 6 is a flow chart showing the operation. Before starting the description of FIG. 6, the exhaust gas purifying process will be outlined with reference to FIG.

In the illustrated exhaust gas purification apparatus, when the engine 10 is cold started, the switching valve 60 is driven to a position shown by a solid line in FIG. 2 for a predetermined time (for example, 40 seconds) from the start, and FIG. ), The main exhaust passage 38a is closed and the bypass exhaust passage 56 is opened.

In the case of a cold start, the first to third catalytic devices 40, 40 on the upstream side until the predetermined time elapses.
Since the exhaust gases 42 and 44 are not normally activated, the exhaust gas flows through the bypass exhaust passage 56 as shown by the arrow without being purified there, and the unburned HC components in the exhaust gas are transferred to the HC adsorbent 74. Adsorbed.

After the predetermined time has elapsed, the upstream catalytic devices 40, 42 and 44 are heated and activated, so that the switching valve 60 is driven to the position shown by the imaginary line in FIG. As shown in FIG. 7B, the main exhaust passage 38a is opened and the bypass exhaust passage 56 is closed.

Accordingly, the upstream catalytic converters 40, 42, 4
The exhaust gas purified in step 4 flows through the main exhaust passage 38a, and the heat of the exhaust heats the HC adsorbent 74, so that the adsorbed unburned HC component starts to be desorbed. At this time, since the pressure of the exhaust gas flowing through the main exhaust passage 38a is higher than that of the bypass exhaust passage 56, a part of the exhaust gas flows back to the bypass exhaust passage 56 through the hole 76.

As shown in FIG. 7C, the unburned H
When the EGR operation is started, the C component is changed to the EGR passage 82.
Is returned to the intake side via. At this time, a part of the exhaust gas flowing through the main exhaust passage 38a is sucked by the negative pressure on the intake side, flows into the bypass exhaust passage 56 through the hole 76, and
While promoting the heating of the C adsorbent 74, the bypass exhaust passage 5
6 flows back into the intake system through the EGR passage 82 and is recombusted.

The exhaust gas thus generated is purified by the upstream catalyst devices 40, 42 and 44 and discharged to the outside of the engine through the main exhaust passage 38a.

As described above, as this type of exhaust gas purifier is used, caulking substances such as soot adhere to the HC adsorbent 74 and cause clogging, and the performance of the HC adsorbent 74 decreases or deteriorates with time. Let it.

Therefore, according to the present invention, after the desorption treatment is completed, the pre-adsorbent temperature tmp. fr. When trs is equal to or higher than a predetermined temperature and in a predetermined operation state, as shown in FIG. 7D, the bypass exhaust passage 56 is opened again to introduce the exhaust gas, and the adhered coking substance is burned and removed. Then, the HC adsorbent 74 was regenerated.
Hereinafter, this adsorbent regeneration processing is referred to as “coking prevention processing”.

The operation of this apparatus will be described with reference to the flow chart of FIG. The illustrated program is started when an ignition switch (not shown) is turned on, and is executed every 100 msec thereafter.

First, in S10, it is determined whether or not the engine 10 has started. Note that the engine 10 is started by determining whether or not fuel injection has been started since the cranking was started.

In the first program loop, the judgment in S10 is normally negated, and the program proceeds to S12, in which the detected water temperature TW is set to the predetermined value X. TRS. It is determined whether it is less than TW, that is, whether it is a cold start. The value indicated by the prefix X in this specification and the drawings indicates a predetermined (fixed) value.

When the result in S12 is affirmative, the program proceeds to S14,
Flag f. hctrs. The on bit is set to 1, and if not, the process proceeds to S16, and the flag bit is reset to 0.

Flag f. hctrs. Set on bit to 1
Setting to open the bypass exhaust passage 56, 0
Resetting means to issue an operation (drive) command for the switching valve 60 so as to close the bypass exhaust passage 56 for the subsequent processing. In S14, an operation command is issued to open the bypass exhaust passage 56 for the HC adsorption operation described above.

The operation (drive) of the switching valve 60 is performed by the ECU 114 operating the valve operating mechanism 64 in another routine (not shown).

Then, the program proceeds to S18, in which a valve control timer (up counter) tm. Reset trs (n) to zero. In this specification and drawings, (n) means the sampling time of the discrete system, more specifically, the execution time of the flow chart of FIG.

On the other hand, if the result in S10 is affirmative and it is determined that the engine 10 has been started, the routine proceeds to S20, in which the valve operation command flag f. hctrs. ON bit is set to 1, in other words, cold start and H
It is determined whether or not the C suction operation is being performed.

When the result in S20 is affirmative, it is determined that the bypass exhaust passage 56 has been opened and the HC adsorbing operation is being performed, so that the routine proceeds to S22, in which the valve control timer tm. The value of trs (n) is changed to the previous value (n-1) by a predetermined value X. DTM. It is assumed to be a value obtained by adding TRS. That is, the elapsed time from when the bypass exhaust passage opening command is issued is measured.

Next, the routine proceeds to S24, where the timer tm. t
rs is a predetermined value X. TM. TRS. OFF (for example, 4
0 sec), and if affirmative, S
26, the valve operation command flag f. hctrs. o
Reset the n bit to zero.

As a result, the switching valve 60 is operated (driven) in another routine, and the bypass exhaust passage 56
Is closed, and the HC desorption process is started according to the temperature rise of the adsorbent. If the result in S20 is NO, S22 to S2
Skip step 6.

Then, the program proceeds to S28, in which it is determined whether the above-mentioned adsorption or desorption processing has been completed. Regarding the adsorption process, the flag f. hctrs. When the on bit has been reset to 0, it is determined that the suction process has been completed.

The desorption process is performed by referring to a flag bit set in another routine (not shown). That is, in another routine (not shown), the exhaust gas volume is obtained from the engine speed NE and the like every time the program loop is performed, and the exhaust gas volume is multiplied by the HC concentration estimated value to calculate the HC adsorption amount.

Subsequently, when it is determined that the desorption reaction has started, an estimated EGR flow rate is obtained and multiplied by the desorption estimation parameter at each program loop, and the product thus obtained is subtracted from the HC adsorption amount. When it is determined that the HC adsorption amount has reached zero, a flag f. trs. The bit of cp is reset to zero. In S28, it is determined with reference to the bit of the desorption completion flag that the desorption processing has been completed.

Incidentally, since this is described in detail in the application proposed by the applicant of the present invention (Japanese Patent Application No. Hei 11-220225), further description is omitted.

As described above, in S28, f. hc
trs. on flag and desorption completion flag f. trs.
It is determined from the cp bit whether the adsorption process and the desorption process have been completed.

Then, the program proceeds to S30, where a caulking prevention valve switching determination is performed. This is a work of determining whether or not to open the bypass exhaust passage 56 for the coking prevention process.

FIG. 8 is a subroutine flowchart showing the processing.

In the following, in S100, the flag f. trs. It is determined whether or not the cp bit is reset to zero. If not, it is determined that the adsorption process or the desorption process has not been completed.
2 and the flag f. Reset the value of the valve to 0.

As described above, the operation of the switching valve 60 is performed by another routine (not shown).
Resetting does not perform the opening operation of the switching valve 60 in the routine, and the bypass exhaust passage 56
To close.

On the other hand, when the result in S100 is affirmative and it is determined that the adsorption process or the desorption process is completed, the process proceeds to S104, and the flag f. It is determined whether or not the bit of “coke” is set to “1”.

As will be described later, this flag is set to 1 when coking prevention processing is completed, specifically, when the combustion of the coking substance is completed.
Is normally denied, and the routine proceeds to S106, where the detected engine speed NE is equal to the predetermined engine speed NE. COKE
Is determined.

The predetermined engine speed NE. COKE is experimentally determined and set to a relatively high engine speed (for example, 2000 rpm) capable of supplying a high-temperature exhaust gas sufficient to promote the combustion of the caulking substance.

When the result in S106 is negative, the process proceeds to S102, and when the result is affirmative, the process proceeds to S108, and the detected intake pipe absolute pressure (engine load) PBA is reduced to a predetermined load P
B. It is determined whether or not COKE is exceeded.

The predetermined load PB. COKE has a relatively high engine load (e.g., -300 m) that can provide a hot exhaust gas sufficient to promote combustion of the caulking material.
A value (expressed by a negative pressure) equal to or greater than mHg is determined by experiment and set.

When the result in S108 is negative, the process proceeds to S102, and when the result is affirmative, the process proceeds to S110, in which the detected pre-adsorbent temperature tmp. fr. trs is a predetermined temperature T
MP. It is determined whether or not COKE or more.

In order to burn and remove coking substances such as soot, it is necessary to raise the temperature of the HC adsorbent 74 to a temperature higher than the desorption temperature. COK
E is set to a value of, for example, about 600 ° C.

When the result in S110 is affirmative, the conditions necessary for the combustion and removal of the coking substance have been satisfied, so that in S112
To the flag f. Set the value bit of value to 1.

As a result, the switching valve 60 is operated in another routine (not shown), and the bypass exhaust passage 5
6 is driven by a predetermined amount from the position shown by the imaginary line in FIG. 2 to the position shown by the solid line, and the bypass exhaust passage 56 is opened by an opening corresponding to the predetermined amount. As described above, it is not always necessary to drive the switching valve 60 to the maximum mechanically or physically open position indicated by the solid line.

Next, the routine proceeds to S114, where the timer tm. co
The value of X. ke (n) (initial value of zero) is set to a predetermined value X. DTM. TR
S is added to start the time measurement, and the process proceeds to S116, where the value of the timer reaches the predetermined time X. DTM. COKE. It is determined whether it is OFF or more.

The predetermined time X. DTM. COKE. OFF
The operating conditions of the engine 10 (more specifically, the exhaust gas temperature, the engine speed NE, the absolute pressure PBA in the intake pipe, the fuel injection amount, etc.) or the environmental conditions (more specifically, the outside temperature, the atmospheric pressure, etc.) Is variable depending on the degree of deterioration of the HC adsorbent 74, for example, about 60 seconds.

When the result in S116 is negative, the subsequent processing is skipped. When the result is affirmative, the flow proceeds to S118, and since the coking prevention processing is completed, the flag f. coke is set to 1, the process proceeds to S120, and the flag f. Reset the value of the valve to 0. As a result, the switching valve 60 is closed, and the bypass exhaust passage 56 is closed.

Incidentally, the result in S110 is negative, and the temperature t before the adsorbent is
mp. trs is a predetermined value TMP. When it is determined that it is less than COKE, the process proceeds to S122, and the flag f. trs. Set the bit of rtd to 1. Thereby, as described later,
The temperature rise control of the HC adsorbent 74 is performed.

Returning to the description of the flow chart of FIG. 6, the program proceeds to S32, in which the above-mentioned temperature rise control of the HC adsorbent 74 is performed.

FIG. 9 is a subroutine flowchart showing the operation.

[0099] In the following, in S200, the flag f. trs. It is determined whether or not the rtd bit is set to 1. If not, it is determined that the adsorbent temperature rise control is unnecessary, and the subsequent processing is skipped. f. co
It is determined whether or not the bit of ke is set to 1.

If the result in S202 is negative, it can be determined that the coking prevention processing has not been completed, so the routine proceeds to S204, in which the pre-adsorbent temperature tmp. fr. trs is the second predetermined temperature TMP. COKE. It is determined whether it is equal to or greater than LMT.

The second predetermined temperature TMP. COKE. LMT
Indicates an upper limit value of the temperature raising control, and the predetermined temperature TMP.
A value larger than COKE, for example, 650 ° C. is set. This is to prevent control hunting from occurring with the process of S110.

When the result in S204 is NO and it is determined that the detected temperature is lower than the upper limit value, the process proceeds to S206, in which the ignition timing retard correction amount IG. COKE is set to a predetermined value (fixed value). That is, this temperature raising control is performed through the ignition timing retarding process. The ignition timing IGLOG is determined as follows. IGLOG = IGMAP + IGCR + IG. COKE

In the above, IGLOG: output ignition timing, IG
MAP (basic ignition timing obtained by searching a map from the engine speed NE and the intake pipe absolute pressure PBA), IGCR
(Including the correction amount set from the cooling water temperature TW and the like), IG. COKE: Temperature rise control retard correction amount (positive value)
It is. In the above equation, + indicates an increase in the retard direction.

On the other hand, when the result in S202 is affirmative, it can be determined that the coking prevention processing has been completed, so that the routine proceeds to S208, in which the ignition timing retard correction amount IG. COKE is set to zero, the process proceeds to S210, and the flag f. trs. Reset the bit of rtd to 0. Thereby, the temperature rise control is stopped.

This is also true when the result in S204 is affirmative and the detected temperature is judged to be higher than the upper limit value. That is, it is not preferable for the catalyst device 40 or the like to raise the exhaust gas temperature more than necessary.

As described above, S1 in the flow chart of FIG.
10 and the ignition timing IGLOG is set to IG. Every time the program of the flow chart of FIG. 6 is executed, as long as the result in S204 of the flow chart of FIG. The COKE value is gradually retarded (unless otherwise changed), thereby delaying combustion and continuing to raise the exhaust gas temperature.

Accordingly, S110 in the flow chart of FIG.
Also, when it is determined that the temperature on the upstream side of the HC adsorbent 74 is lower than the predetermined temperature, the determination in S110 of the flow chart of FIG. Is released and the timer value tm. c
oke is a predetermined time X. DTM. COKE. The caulking prevention process is performed until it becomes OFF or more.

The timer value tm. Since the coke is not reset, once the coking prevention process is started, the coke prevention process is temporarily stopped, and is stopped when the condition is satisfied. When the condition is satisfied again, the time measurement is restarted from the held timer value. The coking prevention process is not continued for a long time.

In this embodiment, as described above, the temperature of the exhaust gas to be supplied to the adsorbent (the temperature before the adsorbent t
mp. fr. The high-rotation high-load region where the value of (trs) rises is scheduled as the adsorbent regeneration operation region, and before the process proceeds to the regeneration process (coking prevention process), the temperature before the adsorbent is directly detected to confirm the suitability of exhaust gas introduction. With such a configuration, the HC adsorbent 74 can be regenerated (caulking prevention processing) in an operation region in which the regeneration is truly possible, and thus the desired adsorbent regeneration effect can be sufficiently achieved.

Furthermore, the pre-adsorbent temperature tmp. fr. tr
When s is less than the predetermined temperature, the ignition timing is retarded to increase the temperature. Therefore, after the desorption process is completed, when the operation shifts to the scheduled high-rotation high-load adsorbent regeneration operation region, The reproduction process can always be executed. That is, regardless of the operation state, the regeneration process can be reliably performed, and even if the caulking substance adheres, the regeneration can be performed early.

Further, the time X. DTM.
COKE. Since OFF is also set variably according to the operation state, unnecessary OFF is not performed for a long time.

FIG. 10 is a flowchart similar to FIG. 8, showing the operation of the exhaust gas purifying apparatus for an internal combustion engine according to the second embodiment of the present invention.

The description will be made focusing on the difference from the first embodiment. S109 is provided after S108, and the pre-adsorbent temperature tmp. fr. trs was estimated. That is, in the second embodiment, the temperature sensor 104 is removed and the pre-adsorbent temperature tmp. fr. trs is calculated (estimated) by logic.

More specifically, an experiment is performed based on the operating state of the engine 10 (for example, the exhaust gas temperature, the engine speed NE, the absolute pressure PBA in the intake pipe, the fuel injection amount, etc.) or the environmental conditions (for example, the outside temperature, the atmospheric pressure). Appropriate characteristics are obtained, mapped, and configured to be freely searchable from the above parameters. This is because the pre-adsorbent temperature tmp. fr. tr
This is because s does not necessarily have to be strict, and it suffices if the temperature is high enough to promote the combustion of the caulking substance.
As the calculation method, for example, a catalyst temperature calculation method previously proposed by the present applicant in Japanese Patent Application Laid-Open No. H11-62656 can be used.

Therefore, in the second embodiment, S110 in the flow chart of FIG. 10 and FIG.
In the step corresponding to S204 of the flow chart, the estimated value is equal to the predetermined temperature TMP. It will be compared with COKE.

In the second embodiment, the configuration as described above allows the configuration to be simplified as compared with the first embodiment. The remaining configuration and effect including the other steps in FIG. 10 are not different from those of the first embodiment.

FIG. 11 is a flowchart similar to FIG. 8, showing the operation of the exhaust gas purifying apparatus for an internal combustion engine according to the third embodiment of the present invention.

Before describing the figure, the structure of the device according to the third embodiment will be described. In the device according to the third embodiment, as shown by an imaginary line in FIG. 12 and the exhaust pipe 38 on the upstream side of the arrangement position of the throttle valve 14.
The upstream side of the position where the switching valve 60 is disposed is connected by a pipe 200, and an air pump 202 is inserted on the way.

The air pump 202 has a motor 204,
The motor 204 is connected to the ECU 1 via a drive circuit (not shown).
When the motor 204 is driven, the air pump 202 is turned on to supply intake air to the exhaust pipe 38, and when the driving of the motor 204 is stopped, the air pump 2 is turned on.
02 is also turned off, and supply of intake air to the exhaust pipe 38 is stopped. A check valve 206 is inserted into the pipe 200 to prevent exhaust gas from flowing from the exhaust system back to the intake system.

The operation of the apparatus according to the third embodiment will be described with reference to the flow chart of FIG. 11. S113 is provided after S112, in which the air pump 202 is turned on (driven), and S121 is performed after S120. Provided,
Therefore, the air pump 202 is turned off (stopped).

That is, after instructing the switching valve 60 to open in S112, the motor 204 is driven in S113 to turn on (drive) the air pump 202 to supply intake air.
The oxygen concentration in the bypass exhaust passage 56 is increased. As a result, the unreacted oxygen is additionally supplied to the HC adsorbent 74 together with the high-temperature exhaust gas, and the combustion of the adhered coking substance is promoted. As a result, the caulking substance can be effectively removed.

After the command to close the switching valve 60 is issued in S120, the air pump 202 is turned off (stopped) in S113 because it becomes unnecessary.

In the third embodiment, the configuration as described above allows the HC adsorbent 7 to be used in comparison with the first embodiment.
4 can be performed more effectively. The remaining configuration and effect including the other steps in FIG. 10 are not different from those of the first embodiment.

As described above, this embodiment is arranged in the bypass exhaust passage (56) branched from the exhaust system (exhaust pipe 38) of the internal combustion engine (engine 10) and opened / closed via the switching valve (60). An internal combustion engine that opens and closes the bypass exhaust passage to introduce exhaust gas at the time of starting the internal combustion engine, and adsorbs unburned (HC) components in exhaust gas to the adsorption device. In the exhaust gas purification device of the engine, a desorption completion determining means (ECU) for determining whether or not the desorption processing of the adsorbed unburned components is completed.
114, S28, S100), operating state determining means (an operating state determining means (engine speed NE, intake pipe absolute pressure PBA)) for detecting the operating state of the internal combustion engine and determining whether the detected operating state is a predetermined operating state. ECU 114, S30, S1
06, S108), the temperature of the exhaust gas to be supplied to the adsorption means (temperature before the adsorbent tmp.fr.trs) is obtained, and the obtained temperature of the exhaust gas is determined to be a predetermined temperature (TMP.COK).
E) Exhaust gas temperature determining means (ECUs 114, S30, S110) for determining whether or not the temperature is equal to or higher than the above, and when it is determined that the desorption processing is completed, the detected operating state is a predetermined operating state. In addition, when it is determined that the obtained temperature of the exhaust gas is equal to or higher than a predetermined temperature, bypass exhaust passage opening means (ECU 114, S30, S11) for opening the bypass exhaust passage and introducing the exhaust gas.
2, S114, S116). still,
"Determining the temperature of the exhaust gas to be supplied to the adsorbing means" is used to include both the case of detecting using a temperature sensor and the case of calculating (estimating) by logic.

The predetermined operating condition is that the load (intake pipe absolute pressure PBA) of the internal combustion engine is equal to the predetermined load (PB.
COKE) and the operating speed of the internal combustion engine (engine speed NE) exceeds a predetermined speed (NE.COKE).

Further, when it is determined that the obtained temperature of the exhaust gas is not higher than the predetermined temperature, temperature raising means (ECUs 114, S30, S11) for raising the temperature of the exhaust gas.
0, S122, S32, S200 to S210).

Further, a combustion promoting means (air pump 202, motor 204) for increasing the oxygen concentration in the bypass exhaust passage to promote combustion is provided, and the bypass exhaust passage opening means is used for opening the bypass exhaust passage. Operate the combustion promoting means (ECU 114,
(S30, S112, S113).

In the above description, the temperature rise control is performed through the ignition timing retarding process. However, the invention is not limited to this. The temperature rise control may be performed with a slightly lean air-fuel ratio.

In the third embodiment, the combustion is promoted via the air pump.
The air-fuel ratio may be made lean to promote combustion.

In the above description, the reproduction process is performed for a time X.
DTM. COKE. Although determined as OFF, a sensor for detecting the coking state of the HC adsorbent may be provided, and the regeneration process may be performed based on the sensor output.

In the above description, an example in which the switching valve and the EGR passage are provided on the upstream side (the side close to the branch pipe 52) as the configuration of the bypass exhaust passage has been described. However, the present invention is not limited to this. -159544
Switching valve and EGR as described in
This is also applicable to an example in which the passage is provided on the downstream side (the side near the rear end 46).

In the above description, the HC adsorbent is not limited to the illustrated one.

In the above description, the switching valve is operated at a negative pressure, but may be electrically operated.

[0134]

According to the present invention, when it is determined that the desorption process has been completed, the detected operating state is in the predetermined operating state, and the obtained temperature of the exhaust gas is equal to or higher than the predetermined temperature. When it is determined that the temperature of the exhaust gas to be supplied to the adsorbing means is directly controlled, the bypass exhaust path is opened to open the bypass exhaust passage and introduce the exhaust gas. When the temperature of the obtained exhaust gas is equal to or higher than a predetermined temperature, the bypass exhaust passage is opened and the exhaust gas is introduced according to the operation state and the like. The caulking substance can be burned off, and the adsorption means can be reliably regenerated.

According to the second aspect, the adsorption means can be regenerated more reliably.

According to the third aspect of the present invention, after the desorption process is completed, the regeneration process can be always performed when the operation state is shifted to a predetermined operation state, and the regeneration can be performed early even if the coking substance adheres. Can be.

According to the present invention, the unreacted oxygen is additionally supplied to the adsorbing means together with the high-temperature exhaust gas, so that the combustion of the adhering coking substance is promoted. Can be done

[Brief description of the drawings]

FIG. 1 is a schematic view showing an entire exhaust gas purifying apparatus for an internal combustion engine according to one embodiment of the present invention.

FIG. 2 is a partial explanatory sectional view showing a structure of a switching valve of the apparatus in FIG. 1;

FIG. 3 is an enlarged explanatory sectional view taken along the line III-III of FIG. 2;

FIG. 4 is an enlarged sectional view taken along line IV-IV of FIG. 1;

FIG. 5 is a block diagram showing details of an electronic control unit (ECU) in the apparatus shown in FIG. 1;

FIG. 6 is a flowchart showing the operation of the apparatus in FIG. 1;

FIG. 7 is an explanatory diagram illustrating an exhaust gas purification operation of the apparatus in FIG. 1;

FIG. 8 is a subroutine flowchart showing a coking prevention valve switching determination operation in the flowchart of FIG. 6;

FIG. 9 is a subroutine flowchart showing the adsorbent temperature raising control in the flowchart of FIG. 6;

FIG. 10 is a flowchart similar to FIG. 8, showing the operation of the exhaust gas purification device for an internal combustion engine according to the second embodiment of the present invention.

FIG. 11 is a flowchart similar to FIG. 8, showing the operation of the exhaust gas purification device for an internal combustion engine according to the third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 internal combustion engine (engine) 12 intake pipe 38 exhaust pipe 38a main exhaust passage 40, 42, 44 catalyst device 54 cylindrical case 56 bypass exhaust passage 60 switching valve 74 HC adsorbent (adsorption means) 76 hole 82 EGR passage 84 EGR control valve 104 second temperature sensor 106 third temperature sensor 108 limit switch 110 limit switch 114 electronic control unit (ECU) 202 air pump (combustion promoting means) 204 motor (combustion promoting means)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01N 3/24 F01N 3/24 R (72) Inventor Tadashi Sato 1-4-1 Chuo, Wako-shi, Saitama Inside Honda R & D Co., Ltd. (72) Inventor Masahiro Sato 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. 3G091 AA11 AA17 AA23 AA28 AB03 AB10 BA11 CA12 CA13 CA23 CA26 CB05 CB07 EA00 EA01 EA06 EA16 EA17 EA18 EA20 EA30 EA33 EA34 FA01 FC01 FC04 FC07 GA08 GB09Y HA12 HA19 HA36 HA37 HA38 HB03 HB05 HB07

Claims (4)

[Claims] 1. Branching from an exhaust system of an internal combustion engine,
Adsorbing means disposed in a bypass exhaust passage opened and closed via a switching valve, opening and closing the bypass exhaust passage to introduce exhaust gas at the time of starting the internal combustion engine, and removing unburned components in the exhaust gas by the adsorbing means; An exhaust gas purifying apparatus for an internal combustion engine to be adsorbed on a: Desorption completion determining means for determining whether or not the desorption processing of the adsorbed unburned components has been completed; b. Operating state determining means for detecting an operating state of the internal combustion engine and determining whether the detected operating state is a predetermined operating state; c. Exhaust gas temperature determining means for determining the temperature of the exhaust gas to be supplied to the adsorption means and determining whether or not the determined temperature of the exhaust gas is equal to or higher than a predetermined temperature; and d. When it is determined that the desorption process is completed, the detected operating state is in a predetermined operating state, and when it is determined that the obtained temperature of the exhaust gas is higher than or equal to a predetermined temperature, the bypass exhaust is performed. An exhaust purification device for an internal combustion engine, comprising: a bypass exhaust passage opening means for opening a passage and introducing exhaust gas. 2. The predetermined operating state is an operating state in which a load of the internal combustion engine exceeds a predetermined load and a rotation speed of the internal combustion engine exceeds a predetermined rotation speed. Exhaust purification device for internal combustion engine. 3. Further, e. 3. The internal combustion engine according to claim 1, further comprising a temperature raising unit configured to raise the temperature of the exhaust gas when it is determined that the temperature of the obtained exhaust gas is not higher than the predetermined temperature. Engine exhaust purification device. 4. Further, f. A combustion promoting unit that increases the oxygen concentration in the bypass exhaust passage to promote combustion, and the bypass exhaust passage opening unit operates the combustion promoting unit when opening the bypass exhaust passage. The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 3, wherein