JP2000087733A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recognize the deterioration of the absorber that absorbs the unburned hydrocarbon constituent when the catalyst is not activated, and prevent the release of desorbed hydrocarbons once the absorption limit has been reached. SOLUTION: Based on the knowledge that the absorber temperature and the exhaust gas temperature of downstream of the absorber are maintained during the absorption operation, an elapsed time tm.dtrs after the engine started is compared with a threshold value dtrs.lmt, and if it is lower than the threshold value, it is recognized that the absorber has deteriorated (S32). In addition, when the temperature tmp.trs exceeds the threshold value X.TRS.TLMT, the branch path (the by-pass exhaust path) in which the absorber is disposed is closed off (S34).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine.

[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. , Unburned components, particularly unburned HC components, are released as they are from the engine.

Therefore, in the technique described in Japanese Patent Application Laid-Open No. 9-324621, an exhaust passage is branched downstream of a catalyst device, and an adsorbing means made of a zeolite-based adsorbent is arranged on one of the branched passages to activate the catalyst. When it is not, the unburned components are adsorbed by the adsorption means, and after the catalyst is activated, the adsorbed unburned components are desorbed and returned to the intake system, reburned, purified by the catalyst, and released outside the engine. It has been proposed to.

The present applicant has also proposed a similar technique in Japanese Patent Application Laid-Open No. Hei 10-153112.

[0005]

Since the adsorption means for adsorbing unburned components when the catalyst is inactive is deteriorated, the amount of adsorption decreases and the intended adsorption performance cannot be realized. It is desirable to determine the deterioration.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an exhaust gas purifying apparatus for an internal combustion engine in which the deterioration of the adsorbing means for adsorbing unburned components when the catalyst is inactive is determined.

Further, irrespective of whether or not the adsorption means has deteriorated, no further adsorption can be expected after the adsorption amount is saturated. Therefore, it is necessary to stop the supply of the exhaust gas to the adsorption means as soon as possible.

Therefore, a second object of the present invention is to stop the supply of exhaust gas to the adsorbing means as soon as possible when the adsorbed amount of the adsorbing means is estimated to be saturated. An object of the present invention is to provide an exhaust gas purification device for an internal combustion engine.

[0009]

According to a first aspect of the present invention, there is provided an adsorbing means disposed in an exhaust system of an internal combustion engine for adsorbing unburned components of exhaust gas after the engine is started. In an exhaust purification device for an internal combustion engine equipped with
Temperature detecting means for detecting at least one of the temperature of the adsorption means and the temperature at a downstream position thereof, an elapsed time measuring means for measuring an elapsed time until the detected temperature reaches a predetermined value, and the measured elapsed time It is configured to include a suction means deterioration determination means for determining whether the suction means has deteriorated based on time (more specifically, by comparing the measured elapsed time with a threshold value).

[0010] Thus, while having a simple configuration,
It is possible to accurately determine the deterioration of the adsorption means for adsorbing unburned components when the catalyst is inactive. In the above, it is desirable that the suction means deterioration determining means operate the warning means when determining that the suction means has deteriorated.

According to a second aspect of the present invention, the apparatus further comprises second temperature detecting means for detecting a temperature at an upstream position of the adsorbing means, and the elapsed time measuring means detects the temperature by the second temperature detecting means. Measuring the elapsed time based on the detected temperature (more specifically, comparing the temperature detected by the second temperature detecting means with a threshold, and determining that the elapsed time is equal to or greater than the threshold, Was measured). Accordingly, in addition to the above-described effects, the point in time when the inflow of the exhaust gas starts can be detected more directly, and the deterioration of the adsorption means can be determined with higher accuracy.

According to a third aspect of the present invention, the suction means deterioration determining means is configured to determine whether the suction means has deteriorated by comparing the measured elapsed time with a threshold value. . Thus, it is possible to accurately determine the deterioration of the suction means while having a simple configuration.

According to a fourth aspect of the present invention, there is further provided an adsorbed amount estimated value calculating means for calculating an adsorbed amount of the unburned component adsorbed by the adsorbing means, and the threshold value is set to the calculated unburned component value. The apparatus is configured so as to include a threshold value setting means for setting according to the estimated amount of adsorption. Since the suction capacity of the suction means differs depending on the amount of suction, the threshold value can be set accurately, and the deterioration of the suction means can be determined with higher accuracy.

According to a fifth aspect of the present invention, the threshold value setting means sets the threshold value in accordance with the temperature detected by the temperature detection means. Since the adsorption capacity of the adsorption means differs depending on the adsorption amount and the temperature, the threshold value can be set more accurately by this, so that the deterioration of the adsorption means can be more accurately determined.

According to a sixth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine having an adsorbing means disposed in an exhaust pipe of the internal combustion engine to adsorb unburned components of exhaust gas. A branch path for branching and storing the suction means, a temperature detection means for detecting at least one of a temperature of the suction means and a temperature at a downstream position thereof, and a temperature based on the detected temperature. The detected temperature is compared with a threshold value, and when the detected temperature is equal to or higher than the threshold value, switching control means for switching between opening and closing of the exhaust pipe and the branch path to close the branch path is provided. . Regardless of whether or not the adsorption means has deteriorated, no further adsorption can be expected after the adsorption amount is saturated, and if the exhaust gas is further supplied, the desorbed HC component is released to the atmosphere. Thus, such inconvenience can be effectively avoided.

[0016]

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

FIG. 1 is a schematic diagram showing an exhaust gas purifying apparatus for an internal combustion engine according to the present invention.

In FIG. 1, 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 path) 12 The air sucked from the first cylinder passes through a surge tank 16 and an intake manifold 18 while being controlled in its flow rate by a throttle valve 14, passes through two intake valves 20 (only one is shown) from the first cylinder to a fourth cylinder. Sent to the cylinder.

The intake pipe 12 has a bypass passage 2 near the position where the throttle valve 14 is disposed.
2 are provided. A valve (EACV) 24 composed of an electromagnetic solenoid valve for opening and closing the bypass passage 22 is provided in the bypass passage 22.
Is inserted.

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
Through an exhaust manifold 36 and an exhaust pipe 38 (more specifically, a main exhaust passage 38 described later).
a) and the exhaust manifold 3 in the exhaust pipe 38
First catalyst device (three-way catalyst) 4 provided immediately below 6
0, a rear end portion 46 which is passed through second and third catalytic devices (both three-way catalysts) 42 and 44 provided downstream thereof and further includes a muffler and a tail pipe (not shown) further downstream.
It is released to the atmosphere via.

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,
No. 5,043, the engine speed N
The intake / exhaust valve timing is switched between high and low timing characteristics in accordance with operating conditions such as E and the intake pipe absolute pressure PBA. The valve timing characteristic is 2
The operation includes stopping one of the intake valves.

Here, the exhaust pipe 38 is provided with a cylindrical case-shaped chamber 52 downstream of the position where the third catalyst device 44 is disposed. That is, the exhaust pipe 38 is branched downstream of the position where the third catalyst device 44 is disposed, and the branch pipe 5
4 is connected to a chamber 52 which is hermetically mounted around the exhaust pipe 38 so as to surround it. As a result, a main exhaust passage 38a passing through the exhaust pipe 38 and a branch passage (bypass exhaust passage) 56 passing through the branch pipe 54 and the internal space of the chamber 52 are formed as exhaust gas passages.

An exhaust pipe opening / closing valve 58 for opening / closing the main exhaust passage 38a and a branch passage opening / closing valve 60 for opening / closing a branch passage (bypass exhaust passage) 56 are provided integrally near the branch point. That is, the exhaust pipe opening / closing valve 58 and the branch passage opening / closing valve 60 are composed of a combination of two butterfly valves similar to the throttle valve 14.
It has a plurality of circular plate surfaces 58a, 60a and a single shaft 58b fixed coaxially thereto.

The two circular plates 58a and 60a are attached to the shaft 58b so that the circular surfaces are substantially 90 degrees different from each other. When the main exhaust passage 38a is closed, the branch passage (bypass exhaust passage) 56 is opened. When the main exhaust passage 38a is opened, the branch passage (bypass exhaust passage)
56 operates to be closed.

The shaft 58b is connected to a valve operating mechanism 64, and the valve operating mechanism 64
4 When a negative pressure is introduced from the downstream position via the negative pressure introduction passage 66, the exhaust pipe opening and closing valve 58 and the branch passage opening and closing valve 60 are driven to close the main exhaust passage 38a,
The branch passage (bypass exhaust passage) 56 is opened. In other words, unless a negative pressure is introduced, the exhaust pipe opening / closing valve 58 is in the open position and the branch passage opening / closing valve 60 is in the closed position (FIG. 1).
).

An electromagnetic solenoid valve TRPV68 is provided in the negative pressure introduction path 66, and a control unit (EC
U) Operate according to the command of 86 to open and close the negative pressure introduction path,
In response, the valve operating mechanism 64 opens and closes the exhaust pipe opening and closing valve 58 and the branch passage opening and closing valve 60. When the negative pressure introduction path is closed, it is opened to the atmosphere.

The chamber 52 is configured to completely surround the exhaust pipe 38, and a space 72 is formed between the chamber 52 and the exhaust pipe 38. In the latter half of the space 72, two adsorbents (beds) (corresponding to the above-mentioned "adsorbing means") supported by a carrier (honeycomb body), more specifically, an upstream first adsorbent (bed) 74a and a second adsorbent (bed) 74b on the downstream side are disposed.

As the adsorbent, the applicant of the present invention disclosed in
A crystalline aluminosilicate proposed in JP-A-71427, specifically, a mixture of a ZSM-5 zeolite and a catalyst element, which is supported on a honeycomb body, is used.

The 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 adsorbent adsorbs unburned HC components when the exhaust system temperature is lower than 100 ° C.
Unburned HC components adsorbed at a temperature of from 250C to 250C are desorbed.

The exhaust pipe 38 is formed with four holes 76 at 90 ° intervals near the end in the chamber 52. That is, as described above, in the chamber 52, the branch pipe 54 and the space 7 in the chamber 52 are arranged in parallel with the main exhaust passage 38a.
A bypass exhaust passage 56 is formed which passes through the positions of the second and adsorbents 74 and merges again at the hole 76.

The exhaust pipe portion extending from the branch pipe 54 to the junction (the position where the hole 76 is formed) 78 is provided in the space 7 in the chamber 52.
2 and the adsorbent 74 are disposed so as to be in contact with or close to each other at a predetermined distance. More specifically, as shown in FIG. 2, the chamber 52 is formed to have a circular cross section completely surrounding the exhaust pipe 38, and the exhaust pipe 38 is disposed close to the adsorbent 74 to promote the temperature rise of the adsorbent. As a result, the unburned components are desorbed at an early stage, and thus can be quickly returned to the intake system.

One end of an EGR (exhaust gas recirculation) passage 82 is connected to the chamber 52 at or near the branch point and opens into the chamber 52, and the other end is connected to the intake passage 12 at a position downstream of the throttle valve 14. Being open. An EGR control valve 84 composed of an electromagnetic solenoid valve is inserted at an appropriate position in the EGR passage 82. The ECU 86 determines the EG via the displacement amount of the EGR control valve 84 (the lift amount detected by the lift sensor 88).
The R amount is controlled.

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

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

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

Further, the first catalyst device 40 of the exhaust pipe 38
Downstream of the O ₂ sensor 100 is provided to output an ON-OFF signal of oxygen concentration in the exhaust gas is inverted each time the change from rich to lean or from lean to rich.

Further, in the vicinity of the third catalyst device 44, the temperature of the third catalyst device, more generally, the exhaust system temperature TC
An exhaust temperature sensor 102 for detecting an AT is provided, and outputs a signal corresponding to the detected value.

Further, at the rear end side of the second adsorbent 74b,
A temperature sensor 104 is provided at a position at a certain distance from the rear end, and an output tmp. t
Output rs.

Further, a valve timing (V / T) sensor 106 (not shown in FIG. 1) for detecting a selected valve timing characteristic of the variable valve timing mechanism 50 through a hydraulic pressure is provided.

The output of the above-mentioned sensor is sent to the control unit (ECU) 86 described above.

FIG. 3 is a block diagram showing details of the control unit 86. The output of the LAF sensor 98 is input to a first detection circuit 116, where appropriate linearization processing is performed to generate a detection signal having a linear characteristic proportional to the oxygen concentration in the exhaust gas in a wide range from lean to rich. Output.

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.

The output of the crank angle sensor 90 is shaped by a waveform shaping circuit 126, and the output value is counted by a counter 128. The count value is input to the CPU. Calculate NE. The CPU core 130 is provided in the ROM 13
The control value is calculated in accordance with the command stored in 2 and the injector 26 of each cylinder is driven via the drive circuit 134.

Further, the CPU core 130 includes the driving circuit 1
An electromagnetic solenoid valve (TRPV) 68 is driven via the valve 36, the exhaust pipe opening / closing valve 58 (and the branch passage opening / closing valve 60) is opened / closed via the valve operating mechanism 64, and the EACV 24 via the drive circuits 138 and 140. And the EGR control valve 84 is driven. Furthermore, CPU
The core 130 determines the deterioration of the adsorbent 74 as described later.

FIG. 4 is a flow chart showing the operation of the exhaust gas purifying apparatus for an internal combustion engine according to the present invention. Before starting the description of FIG. 4, the operation of the exhaust gas purifying apparatus according to the present invention will be described.
More specifically, a method of determining the deterioration of the suction means will be outlined.

FIG. 5 is a schematic explanatory view of the vicinity of the chamber 52 of FIG. 1. The inventors have shown that the temperature sensors are A, B, C,
D is placed at four points and the temperature of that part is measured.
When the amount of HC emission (desorbed from the adsorbent) at points α, β, and γ was measured, the results as shown in FIG. 6 were obtained.

Here, point A is a position outside the adsorbent upstream of the first adsorbent 74a, point B is a position inside the first adsorbent 74a, and point C is a position inside the second adsorbent 74b. The point D is a position outside the adsorbent downstream of the second adsorbent 74b. Further, the point α is the same adsorbent upstream position as the above point A, the point β is the position between the first adsorbent 74a and the second adsorbent 74b, and the point γ is the same as the above point D. This is the downstream position of the adsorbent.

As shown in FIG. 6, the temperature of the adsorbent hardly rises during the adsorption, and rises rapidly after the adsorption amount reaches the saturation point of the adsorption capacity (capacity). That is, the HC discharge after each bed due to the desorption reaction of the adsorbent, that is, the HC at β point and γ point
It can be seen that the discharge occurs after the adsorbent temperature (points B and C) before each measurement point and the exhaust gas temperature at the downstream point (point D) reach the rising point.

As described above, since the temperature rise of the adsorbent has a certain dead time, as shown in FIG. 7, if the temperature of the second adsorbent 74b or the temperature of the exhaust gas downstream thereof is detected. In addition, it is possible to detect HC emission due to the desorption reaction of the adsorbent 74.

For example, as shown in FIG. TRS. When the TLMT is set and the second adsorbent temperature exceeds the threshold value, it can be determined that HC discharge by the desorption reaction of the first adsorbent 74a and the second adsorbent 74b has started.

The above is a fact already generally known.

The present inventors have paid attention not to such a known fact but to the fact that the temperature of the adsorbent or the temperature of the exhaust gas downstream thereof is maintained during the HC adsorption reaction. Made.

In other words, the inventors have found that the temperature of the second adsorbent 74b or the temperature of the exhaust gas downstream of the second adsorbent 74b is reduced by the HC adsorption reaction when the engine starts (or the temperature of the exhaust gas upstream of the first adsorbent 74). On the other hand, the dead time (d.TRS,
d. TRS ′), the deterioration of the adsorbent is determined by focusing on having TRS ′).

That is, the dead time (d.TRS, d.T
RS ′) is due to the HC adsorption reaction of the adsorbent 74, and therefore decreases as the adsorption capacity (capacity) of the adsorbent 74 decreases, as shown in FIG. This is shown in FIG.
C at which the adsorbent capacity is larger than the rise time of the point B temperature
This is supported by the slow rise time of the point temperature.

As described above, the deterioration of the adsorbent (adsorbing means) according to the present invention is determined by the dead time (d.TRS, d.TR).
It is based on the finding that S ′) is shortened by a decrease in the adsorption capacity of the adsorbent 74.

More specifically, as shown in FIG. 9, a temperature sensor 104 is disposed at the above-mentioned point C, and the detected temperature is equal to the threshold value X. TRS. The elapsed time since the time became TLMT or more is represented by a timer value tm. dtrs, and the timer value (corresponding to the dead time d.TRS, d.TRS ′) is a threshold value dtrs. When it is less than 1 mt, it is determined that the adsorbing capacity (capacity) of the adsorbent 74 has decreased, in other words, it has deteriorated.

Based on the above, the operation of the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, more specifically, a method of determining the deterioration of the adsorbent by the ECU 86 will be described with reference to the flowchart of FIG.

The ECU 86 starts operation when the ignition switch is turned on, and the program shown in FIG.
This is executed by a timer interrupt for each c.

First, in step S10, the output tmp. Of the temperature sensor 104 disposed at the point C described above. The process samples trs and proceeds to S12 to determine whether the engine 10 has been started.

This determination is made by determining whether the engine 10 has started cranking and fuel injection has been started. Even if cranking has started, the engine 10 has been started unless fuel injection has started. It is determined that the engine 10 has not been started (the detected engine speed NE is compared with the complete explosion speed (for example, 400 rpm), and as long as the detected rotational speed is less than the complete explosion speed, it is determined that the engine 10 has not been started. May be).

When the result in S12 is negative and it is determined that the engine 10 has not been started, the routine proceeds to S14, where the dead time threshold dtrs. lmt is searched in a table. FIG. 10 shows the table characteristics. As shown, the dead time threshold dtrs. lmt is the estimated HC adsorption amount hcm. hat [g] and the detected temperature tmp. Search and find from trs.

The adsorbing capacity of the adsorbent 74 is the HC adsorbed amount estimated value hcm. hat and the detected temperature tmp. trs, the dead time threshold dtrs. l
mt can be set accurately, and as a result, the adsorbent 7
4 can be accurately determined.

Here, the HC adsorption amount estimated value hcm. hat
Is the HC amount estimated that the adsorbent 74 is adsorbed (calculation will be described later). In FIG. 10, for simplification of the drawing, the detected temperature tmp. Although only three types of trs characteristics are shown, four or more types of temperature characteristics may be set.
Characteristics such as species may be interpolated.

Next, the program proceeds to S16, in which the value tm. Reset dtrs (n) to zero. As described above, this timer detects the detected temperature tmp. trs is the temperature rise determination threshold value X. TRS. The elapsed time until TLMT or more is measured.

In the specification and the drawings, n indicates a sampling time of a discrete system, specifically, a start time in the flow chart of FIG. That is, (n) represents the current value, (n-
1) indicates the previous value. Note that, for simplicity of illustration, the addition of (n) to the current value has been minimized.

Next, the process proceeds to S18, where the valve operating mechanism 64
The exhaust gas is introduced into the bypass exhaust passage 56 by opening the branch passage opening / closing valve 60 via, and the exhaust pipe opening / closing valve 58 is closed to block the flow of the exhaust gas into the main exhaust passage 38a. At the same time, the flag f. hctrs. The on bit is set to 1 and the branch path (bypass exhaust path) 56
Is released.

In the next and subsequent program loops, S1
If affirmative in step 2 and it is determined that the engine 10 has been started, the routine proceeds to S20, where the flag f. hctrs. on
Is determined whether or not the bit is set to 1.

Since the flag of this flag is set to 1 in S18, the judgment in S20 is normally affirmed and the process proceeds to S22, where the HC adsorption amount estimation value hcm.
hat [g] is calculated.

FIG. 11 is a subroutine flowchart showing the operation.

To explain below, in S100, the exhaust gas volume, more specifically, the space velocity sp
Estimated value tr of ace velocity (ratio of raw material supply volume rate F to reactor volume V. Unit 1 / hour)
s. sv is calculated.

As shown, the estimated exhaust gas volume t
rs. sv is the detected engine speed NE, the detected intake pipe absolute pressure PBA, and the coefficient X. Calculated from SVPRA. The equation shown is a simple equation for calculating the exhaust gas volume (spatial velocity sv). For example, when the displacement of the engine 10 is 2.2 liters, X. SVPRA is 65.74.

Then, the program proceeds to S102, in which the previous value hcm. hat (n-1). The product of HCMPRA and the currently obtained exhaust gas volume estimation value is added, and the current value hcm. compute hat (n).

In the formulas shown, X. HCMPRA is
This is an HC concentration estimation parameter. It should be noted that this parameter corresponds to the catalyst device 40, 42, 44 such as the catalyst temperature TCAT.
Degree of activity, intake air temperature TA, atmospheric pressure PA, water temperature TW,
The correction may be made based on the engine operating state such as the ATF temperature or the environmental condition.

In addition, the estimated HC adsorption amount hcm. ha
Since t is updated using the previous value, the calculated value is stored in the backup unit of the RAM 124 and is stored after the engine is stopped.

Returning to the flow chart of FIG.
24, and proceeds to the detection temperature tmp. trs is the above-mentioned temperature rise determination threshold value X. TRS. It is determined whether the temperature is equal to or higher than TLMT (for example, 60 ° C.), that is, whether the detected temperature has risen.

If the result in S24 is negative, it is determined that HC is still being inhaled, and the routine proceeds to S26, where the previous value tm. Of the above-described post-engine start timer (adsorbent deterioration determination post-start timer) is set. d
A predetermined value X.trs (n-1) TM. The timer value is incremented by adding TRSJUD.

Then, the process proceeds to S28, where the timer value tm. dt
rs is a predetermined value X. TRS. It is determined whether it is less than MODE. The predetermined value X. TRS. MODE is the adsorption operation time limit,
More specifically, the adsorbent 7 while the catalyst is inactive after the engine is started.
4 means the scheduled operation time (for example, 20 sec).

The predetermined value X. TRS. MODE may be changed according to engine operating conditions such as water temperature TW, intake air temperature TA, atmospheric pressure PA, catalyst temperature TCAT, or environmental conditions.

When the result in S28 is affirmative, the flow proceeds to S18 because the operation is within the suction operation limit time.

On the other hand, when the result in S24 is affirmative and the start of desorption is determined, the flow proceeds to S30, in which the post-start timer value tm. hold dtrs,
Proceeding to S32, the deterioration of the adsorbent 74 is determined.

FIG. 12 is a subroutine flowchart showing the processing.

In the following, at S200, the post-start timer value tm. dtrs is
The temperature rise dead time threshold dtrs. l
It is determined whether it is less than mt.

When the result in S200 is affirmative, the program proceeds to S202, in which it is determined that the amount of adsorption has decreased due to the rapid rise in temperature, that is, it is determined that the adsorbent 74 has deteriorated, and the flag f.
trs. Set the bit of agd (initial value 0) to 1. Next, the process proceeds to S204, in which a warning lamp (not shown in FIG. 1 or the like) is turned on.

On the other hand, if the result in S200 is NO, S20
Then, it is determined that the adsorption amount has not decreased since the temperature rise is slow, that is, the adsorbent 74 has not deteriorated, and the flag f. trs. Reset the agd bit to 0.

Returning to the flow chart of FIG.
Then, the process proceeds to step S4, and the branch passage opening / closing valve 60 is closed via the valve operating mechanism 64 to branch the exhaust gas (bypass exhaust passage).
56, the exhaust pipe opening / closing valve 58 is stopped.
And exhaust gas is introduced into the main exhaust passage 38a.
At the same time, the flag f. hctrs. The on bit is reset to 0, indicating that the branch path (bypass exhaust path) 56 has been closed.

That is, irrespective of whether or not the adsorption means has deteriorated,
After the amount of adsorption is saturated, further adsorption cannot be expected,
If the exhaust gas is further supplied, the desorbed HC component is released into the atmosphere. Therefore, it is necessary to stop the supply of the exhaust gas to the adsorption means as soon as possible. Thereby, it is possible to effectively prevent the desorbed HC component from being released into the atmosphere.

When the result of the determination in S28 is negative, the adsorption operation time limit has been exceeded, so the process proceeds to S34 for the same reason, and the branch passage opening / closing valve 60 is closed to close the branch passage (bypass exhaust passage) 56.

Accordingly, in the next and subsequent program loops, the determination in S20 is denied, and the routine proceeds to S36, in which the desorbed HC
Is determined (to the intake system).

FIG. 13 is a subroutine flowchart showing the processing.

The following is an explanation. t
rs. It is determined whether the purge bit is set to 1. This flag is set to 1 when it is determined that the purge is completed, as described later.

If the result in S300 is negative, it is determined that the purge has not been completed.
4, the detected temperature tmp. trs is the temperature rise determination threshold value X. TRS. It is determined whether or not TLMT or more, in other words, whether or not the elimination reaction has started.

When the result in S302 is negative and it is determined that the desorption reaction has not started, the routine proceeds to S304, in which the estimated HC adsorption amount hcm. hat is held (S306).
And the HC adsorption amount estimated value hcm. It is determined whether or not hat is less than or equal to zero. In this case, the determination in S306 is normally denied, and the process proceeds to S308, where the flag f. trs. pur
The bit of ge is reset to 0.

In the next and subsequent program loops, S
When it is affirmed in 302 and it is estimated that the desorption reaction has started, S
Proceeding to 310, it is determined whether or not EGR (exhaust gas recirculation control) is being performed. In this device, EGR (exhaust gas recirculation control) is performed in an appropriate operation state, and HC desorbed at that time is purged to the intake system. Note that the EGR (exhaust gas recirculation control) itself does not directly relate to the gist of the present invention, and thus the description is omitted.

When the result in S310 is negative, the process proceeds to S304 since the desorbed HC cannot be purged into the intake system. When the result is affirmative, the process proceeds to S312, where the EGR flow rate (reflux amount) q. Egr [g] is obtained by searching a table.

FIG. 14 is an explanatory diagram showing the table characteristics. EGR flow rate (reflux amount) estimated value q. egr is EG
It is calculated from the lift amount of the R control valve 84 (more specifically, the lift amount command value) and the detected intake pipe absolute pressure PBA in accordance with the table characteristics shown.

As in the case of FIG. 10, in FIG. 14, only three types of intake pipe absolute pressure PBA characteristics are shown for simplification of illustration, but actually four or more types are set. . In addition, the estimated EGR flow rate (reflux amount) q. eg
r may be corrected based on the atmospheric pressure and / or the exhaust gas temperature, which are parameters indicating the exhaust pressure.

Then, the program proceeds to S314, in which the previous value hcm. from X.hat (n-1). HC. PUR
GE and the EGR flow rate (reflux amount) estimated value q. egr
Is subtracted, and the current value hcm. ha
Calculate t (n). That is, the desorbed HC through the EGR control
Is purged to the intake system, the estimated value of the HC adsorption amount is corrected to be reduced based on the EGR flow rate.

In the equations shown, X. HC. PURGE
Is a parameter for estimating the amount of HC desorption during the EGR flow. Note that this parameter also applies to the detected temperature tmp. trs
(The estimated value may be used.), The exhaust gas temperature or the amount of heat (the estimated value may be used), and the air-fuel ratio feedback correction coefficient may be corrected based on the engine operating state.

Then, the program proceeds to S306, in which the reduced HC is corrected.
It is determined whether or not the adsorption amount estimated value has become equal to or less than zero. trs. pu
rge is set to 0, and when affirmative, the routine proceeds to S316, where the flag f. trs. purg
e is set to 1, and the current value hcm. Set hat to 0.

As a result, the determination in S300 is affirmed in the next and subsequent program loops, and the subsequent processing is skipped.

Since this embodiment is configured as described above, it is possible to accurately determine the deterioration of the adsorbent 74. Furthermore, irrespective of the deterioration of the adsorption means, no further adsorption can be expected after the adsorption amount is saturated, and if the exhaust gas is further supplied, the desorbed HC component is released to the atmosphere. However, this can effectively avoid such inconvenience.

FIG. 15 is a flow chart similar to FIG. 4, showing an exhaust gas purifying apparatus for an internal combustion engine according to the second embodiment of the present invention.

In the second embodiment, as shown by an imaginary line in FIG. 1, a second adsorbent bed 74a is provided upstream of the first adsorbent bed 74a.
Temperature sensor 108 was added. That is, in FIG.
The temperature at point A was detected in addition to the temperature at point.

Focusing on the differences from the first embodiment, the second embodiment will be described with reference to the flowchart of FIG. 15. In S 10 a, the second temperature sensor 10
8 (inlet temperature) tmp. in and the output of the first temperature sensor 104 (detection temperature) tmp. Sample trs.

Then, the program proceeds to S12a, in which the detected output (inlet temperature) of the second temperature sensor tmp. in is the inlet temperature rise determination threshold value X. TRS. TLMTIN
(For example, 60 ° C.) or more.

If the result in S12a is negative, the program proceeds to S14, in which a dead time threshold value is searched in a table, and the program proceeds to S16a, where the timer (in the second embodiment, referred to as "timer after rising of inlet temperature") is reset. Then, the process proceeds to S18.

If the result in S12a is affirmative, the program proceeds to S20 in the same manner as in the first embodiment, and the flag f. hctr
s. An on bit is determined, and S22 is performed according to the determination result.
Alternatively, the process proceeds to S36.

That is, in the present invention, since the deterioration is determined from the rising characteristics of the adsorbent temperature, it is necessary to detect the point in time when the flow of the exhaust gas starts. In the first embodiment, the presence or absence of the start of the engine is detected. However, in the second embodiment, the second temperature sensor 108 is provided to more directly detect the start point of the exhaust gas inflow. I made it.

That is, S12a in the flow chart of FIG.
In the above, the point in time at which the inflow of exhaust gas is started is detected by determining whether or not the inlet temperature has become equal to or higher than the threshold value.

In the second embodiment, the configuration as described above is complicated in that the temperature sensor 108 is added as compared with the first embodiment. By measuring the adsorbent bed inlet temperature using the sensor 108, it is possible to more directly detect the point at which the inflow of exhaust gas starts, and it is possible to more accurately detect the point at which the variation in engine start time is not affected. The deterioration of the adsorbent 74 can be determined well. The remaining configuration and effects are not different from those of the first embodiment.

Here, the position of the first temperature sensor 104 on the downstream side will be additionally described.
It is desirable that the temperature sensor 104 is disposed in a downstream range a as shown in FIG. That is, it is desirable to dispose the second adsorbent at a certain distance b from the rear end.

The first reason is that the method of determining the deterioration of the adsorbent according to the present invention is based on the temperature rise dead time, so that the absolute value of the dead time is large, in other words, the adsorption before the temperature sensor is located. This is because the larger the capacity, the more accurately the deterioration can be determined.

Secondly, when the temperature sensor 104 is disposed at the last end (the end of the distance b) of the second adsorbent 74b, in other words, at a position downstream of the second adsorbent 74b where there is no adsorption capacity, a switching valve (shown in FIG. In the case of a mechanism including the on-off valves 58 and 60) on the front side (upstream side), since the branch passage on-off valve 60 does not close until the sensor output temperature reaches the rising point, the entire adsorbent reaches the desorption temperature and desorbs. This is because the exhausted HC is directly discharged into the atmosphere.

For this purpose, in the first and second embodiments, the temperature sensor 104 is located at the rear end of the second adsorbent 74a and at a certain distance from the rear end (a value corresponding to b in FIG. 16). And placed.

By leaving a predetermined amount of adsorbent behind the temperature sensor 104 in this way, even if the sensor output temperature reaches the rising point, the adsorbent portion at the distance b does not reach the desorption temperature. On the other hand, the HC desorbed in front of the sensor arrangement position is adsorbed at the distance b and is not directly discharged to the atmosphere.

At that point, as shown in FIG. 17, when the switching valves (opening / closing valves 58, 60) are provided downstream of the adsorbent, the temperature sensor 104 is connected to the end of the second adsorbent 74b as shown by a range c. It is possible to minimize the discharge of desorbed HC by closing the branch passage opening / closing valve 60 immediately after the sensor output temperature reaches the rising point, even if it is located at the position or downstream as shown by the imaginary line. It is.

However, for the above-mentioned reason, it is desirable to arrange the temperature sensor with a distance of about b even in a rear valve type mechanism. This is the same even when the switching valves (opening / closing valves 58 and 60) are modified to be provided upstream and downstream of the adsorbent, respectively.

As described above, in the first and second embodiments, the exhaust gas is disposed in the exhaust system (exhaust pipe 38) of the internal combustion engine (engine 10) and the unburned exhaust gas In an exhaust gas purification apparatus for an internal combustion engine provided with adsorbing means (first adsorbent (bed) 74a, second adsorbent (bed) 74b) for adsorbing HC) components, the temperature of the adsorbing means (points B and C) ) Or at least one of the temperatures at the downstream position (point D) (temperature tmp.trs) (temperature sensor 104, ECU 86, S1)
0, S10a), the detected temperature tmp. trs is a predetermined value (temperature rise determination threshold value X.TRS.TL
MT), the elapsed time measuring means (ECU 86, S24, S26) for measuring the elapsed time (timer after engine start or timer after inlet temperature rise (timer after start for adsorbent deterioration determination) tm.dtrs) to reach MT). The measured elapsed time tm. dtrs (more specifically, by comparing the measured elapsed time tm.dtrs with a threshold value dtrs.lmt), the adsorbing means (the first adsorbent 74a, the second adsorbent 74b). ) For determining whether the adsorption means has deteriorated or not.
86, S32, S200 to S206).

When the suction means deterioration determining means determines that the suction means is deteriorated, the warning means (warning lamp) is operated (turned on) (ECU 86, S
204).

Further, there is provided second temperature detecting means (temperature sensor 108, ECU 86, S10a) for detecting the temperature (entrance temperature tmp.in) at the upstream position of the adsorbing means, and the elapsed time measuring means comprises: 2 detected by the temperature detecting means tmp. in based on the elapsed time tm. dtrs (more specifically, the second
Temperature detected by the temperature detecting means (inlet temperature tm)
p. in) to the threshold X. TRS. Compared to TLMTIN, the elapsed time is measured when it is determined to be equal to or greater than the threshold value (ECU 86, S12a, S26).

The adsorption means deterioration judging means calculates the measured elapsed time tm. dtrs to the threshold X. TR
S. It is configured such that it is determined whether or not the suction means has deteriorated by comparing with the TLMT (ECU 86, S32, S200 to S206).

Further, the estimated value of the unburned component adsorption amount hcm. means for calculating an adsorption amount estimated value (ECU 86, S22, S100 to S10)
2), and the threshold dtrs. Threshold value setting means (ECU 86, S14) for setting lmt in accordance with the calculated unburned component adsorption amount estimated value is provided.

Further, the threshold value setting means sets the temperature tmp. Detected by the temperature detection means. trs, more specifically, the temperature tm detected by the temperature detecting means.
p. trs and the calculated threshold value dtrs. Set lmt (ECU
86, S14).

An internal combustion engine provided with adsorbing means (first adsorbent 74a, second adsorbent 74b) disposed in an exhaust pipe 38 of the internal combustion engine (engine 10) to adsorb unburned components of exhaust gas. In the exhaust gas purifying apparatus, at least one of a branch path (bypass exhaust path 56) branched from an exhaust pipe 38 of the internal combustion engine (engine 10) and containing the adsorbing means, a temperature of the adsorbing means or a temperature at a downstream position thereof Temperature detection means (temperature sensor 104, ECU 86, S10, S10
a) and based on the detected temperature (more specifically, comparing the detected temperature tmp.trs with a threshold X.TRS.LMT, and when the detected temperature is equal to or higher than the threshold, The exhaust pipe 38 (more specifically, the main exhaust passage 38a) and the branch passage (the bypass exhaust passage 5)
6) Switching control means (ECU 86, valve operating mechanism 64, exhaust pipe opening / closing valve 58, branch passage opening / closing valve 60, S24, S28, S34) for switching the opening and closing of 6) to close the branch passage (bypass exhaust passage 56). It was configured as follows.

In the first and second embodiments, the deterioration of the adsorbent 74 is determined by detecting the temperature at the point C (or the points A and C) in FIG. 5, but the deterioration is simply determined. If so, any of the temperatures at points A, B, C, and D may be used.

In the first and second embodiments, the estimation of the start of the elimination reaction in S302 in the flow chart of FIG. 13 is performed from the detected temperature. In the second embodiment, however, the first adsorbent is used. 74a inlet temperature tmp. ad (the first and second adsorbents 74a and 74b)
May be estimated by estimating the temperature.

In the above description, the exhaust pipe opening / closing valve 58
The branch passage opening / closing valve 60 may be of an electric type.

In the above description, the adsorbent 74 is not limited to the disclosed one, but may be various adsorbents having heat resistance.

[0131]

According to the first aspect of the present invention, it is possible to accurately determine the deterioration of the adsorbing means for adsorbing unburned components when the catalyst is inactive while having a simple structure. In the above, it is desirable that the suction means deterioration determining means operate the warning means when determining that the suction means has deteriorated.

According to the present invention, in addition to the above-described effects, the point at which the inflow of exhaust gas starts can be detected more directly, and the deterioration of the adsorption means can be determined with higher accuracy. .

According to the third aspect, it is possible to accurately determine the deterioration of the suction means while having a simple configuration.

According to the fourth aspect, the threshold value can be set accurately, and the deterioration of the suction means can be determined with higher accuracy.

According to the fifth aspect, the threshold value can be set more accurately, and the deterioration of the suction means can be determined more accurately.

According to the present invention, no further adsorption can be expected after the amount of adsorption is saturated, regardless of the presence or absence of deterioration of the adsorption means. The disadvantage that the separated HC component is released to the atmosphere can be effectively avoided.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an exhaust gas purifying apparatus for an internal combustion engine according to the present invention as a whole.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a block diagram showing details of a control unit (ECU) in the apparatus shown in FIG. 1;

FIG. 4 is a flowchart showing the operation of the apparatus in FIG. 1, more specifically, the operation of determining the deterioration of the HC adsorbent.

FIG. 5 is a schematic explanatory diagram showing temperature measurement points of the adsorbent disposed in the exhaust system of the apparatus in FIG. 1 for explaining the operation of determining the deterioration of the adsorbent according to the present invention.

FIG. 6 is data of a temperature measurement result of FIG. 5;

FIG. 7 is an explanatory diagram of the temperature characteristics of FIG. 6;

8 is an explanatory diagram of the temperature characteristics of FIG. 6 in the same manner.

9 is an explanatory diagram of the temperature characteristics of FIG. 6 in the same manner.

FIG. 10 is a graph showing characteristics of thresholds used in the flow chart of FIG. 4;

FIG. 11 is a subroutine flowchart showing the operation of calculating the HC adsorption amount estimated value in the flowchart of FIG. 4;

FIG. 12 is a subroutine flowchart showing the HC adsorbent deterioration determination operation in the flowchart of FIG. 4;

FIG. 13 is a subroutine flowchart showing the operation of determining the purge of desorbed HC in the flowchart of FIG. 4;

FIG. 14 is a graph showing characteristics of an EGR flow rate estimated value used in the flow chart of FIG. 13;

FIG. 15 is a flowchart similar to FIG. 4, showing the operation of the device according to the second embodiment of the present invention.

FIG. 16 is an explanatory diagram similar to FIG. 5, showing the temperature measurement points of the adsorbent in the first embodiment and the second embodiment of the present invention.

FIG. 17 is an explanatory view similar to FIG. 5, showing the temperature measurement points of the adsorbent according to the first embodiment and the second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 internal combustion engine (engine) 12 intake pipe 38 exhaust pipe (exhaust path) 38a main exhaust path 40, 42, 44 catalyst device 52 chamber 54 branch pipe 56 branch path (bypass exhaust path) 58 exhaust pipe opening / closing valve 60 branch path opening / closing valve 64 valve operating mechanism 74 adsorbent (adsorbing means) 76 hole 82 EGR passage 84 EGR control valve 86 control unit (ECU) 104 temperature sensor (temperature detecting means) 108 temperature sensor (temperature detecting means)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) F02D 45/00 314 F02D 45/00 314Z (72) Inventor Tadashi Sato 1-4-1 Chuo, Wako-shi, Saitama No. Within Honda R & D Co., Ltd. (72) Inventor Yoshihisa Iwaki 1-4-1 Chuo, Wako-shi, Saitama Pref. Inside the Honda R & D Co., Ltd. No. 1 Inside Honda R & D Co., Ltd. (72) Inventor Takeshi Haga 1-4-1 Chuo, Wako-shi, Saitama Pref. Inside Honda R & D Co., Ltd. (72) Tetsuo Endo 1-4-4 Chuo, Wako-shi, Saitama No. 1 Inside Honda R & D Co., Ltd.

Claims (6)

[Claims] 1. An exhaust gas purifying apparatus for an internal combustion engine, comprising: an adsorbing means disposed in an exhaust system of the internal combustion engine for adsorbing unburned components of exhaust gas after the engine is started. Temperature detection means for detecting at least one of the temperature of the adsorption means and the temperature at a downstream position thereof, b. Elapsed time measuring means for measuring an elapsed time until the detected temperature reaches a predetermined value; c. An exhaust gas purification device for an internal combustion engine, comprising: an adsorption means deterioration determining means for determining whether or not the adsorption means has deteriorated based on the measured elapsed time. 2. The method of claim 2, further comprising: d. A second temperature detecting means for detecting a temperature at an upstream position of the adsorbing means, wherein the elapsed time measuring means measures the elapsed time based on the temperature detected by the second temperature detecting means. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein: 3. The suction means deterioration determining means determines whether the suction means has deteriorated by comparing the measured elapsed time with a threshold value. 3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 2. 4. The method of claim 1, further comprising: e. Adsorbed amount estimation value calculating means for calculating an adsorbed amount of unburned components adsorbed by the adsorbing means; and f. 4. The exhaust gas purifying apparatus for an internal combustion engine according to claim 3, further comprising threshold value setting means for setting the threshold value in accordance with the calculated unburned component adsorption amount estimated value. 5. The exhaust gas purifying apparatus for an internal combustion engine according to claim 4, wherein said threshold value setting means sets said threshold value in accordance with a temperature detected by said temperature detecting means. 6. An exhaust gas purifying apparatus for an internal combustion engine, comprising an adsorbing means disposed in an exhaust pipe of the internal combustion engine for adsorbing unburned components of exhaust gas, comprising: a. A branch for branching from the exhaust pipe of the internal combustion engine and containing the adsorption means; b. Temperature detection means for detecting at least one of the temperature of the adsorption means and the temperature at a downstream position thereof; and c. An exhaust gas purification device for an internal combustion engine, comprising: switching control means for switching between opening and closing of the exhaust pipe and the branch path to close the branch path based on the detected temperature.