JPH0693846A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the purifying performance for HC by estimating a total amount of HC to be adsorbed on an adsorbent based on the amount of exhausted HC in exhaust, flow velocity of exhaust, and temperature of the adsorbent with high precision and controlling the degree of opening of a bypass passage provided with the adsorbent in accordance with residual amount based on the total amount. CONSTITUTION:A catalyst for purifying emission 3 is provided in an exhaust passage 2 of an internal combustion engine 1. The exhaust passage 2 in the upstream of the catalyst for purifying emission 3 is branched into a main passage 4 and a bypass passage 6 provided with an adsorbent 5. Further, each control valve 7, 8 which controls dividing flow ratio of exhaust is provided at each of upper and lower branch points of each passage 4, 6. In this case, each electromagnetic valve 7, 8 is controlled by a control unit 12 based on each detected signal from an exhaust temperature sensor 9, a water temperature sensor 10, and an air temperature and revolving speed sensor 11. That is, the total amount of HC to be adsorbed on the adsorbent 5 is estimated in accordance with the amount of exhausted HC, flow velocity of exhaust, and temperature of the adsorbent based on each detected signal.

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 improvement of an apparatus having a function of temporarily adsorbing HC in exhaust gas.

[0002]

2. Description of the Related Art In an internal combustion engine for a vehicle, in order to purify exhaust gas, HC (unburned gas) and CO in the exhaust gas are oxidized into H ₂ O and CO ₂ in the exhaust passage, while NO _X is converted into N ₂ . An exhaust gas purification catalyst called a three-way purification catalyst that reduces and purifies is installed. By the way, of the harmful components in the exhaust gas, H
The discharge amount of C is particularly susceptible to the exhaust temperature. In other words, even if a noble metal catalyst is used, it is generally 3
A catalyst temperature of 00 ° C or higher is required. Therefore, in the exhaust gas purification device only including the three-way catalyst, it is difficult to purify the HC by the catalyst when the exhaust gas temperature is low, such as immediately after the engine is started cold.

Therefore, as an exhaust emission control device for vehicles,
As disclosed in Japanese Patent Application Laid-Open No. 63-68713, there has been proposed one in which an adsorbent for adsorbing HC is interposed in the exhaust passage on the upstream side of the exhaust purification catalyst. This one utilizes the fact that the adsorbent adsorbs HC at low temperatures and desorbs the adsorbed HC at high temperatures, so that the adsorbent is provided in a part of the exhaust passage upstream of the exhaust purification catalyst. The inserted bypass passages are connected in parallel to selectively open and close the main passage and the bypass passage, and the bypass passage is opened at a low temperature before activation of the exhaust gas purification catalyst to cause HC to be adsorbent. After adsorbing, and once closing the bypass passage, the temperature becomes high and the exhaust purification catalyst is activated, and then the bypass passage is opened again to desorb the adsorbed HC and the exhaust purification catalyst purifies it. It has become. As the adsorbent, for example, a monolith carrier coated with zeolite has been proposed because zeolite has excellent adsorbability.

[0004]

By the way, in an exhaust gas purification apparatus provided with such an adsorbent, the amount of HC adsorbed by the adsorbent during adsorption or the amount of HC remaining in the adsorbent during desorption is conventionally determined. The desorption operation is performed without knowing it. For this reason, it is necessary to complete desorption in order to maximize the adsorption capacity during the next adsorption, so the desorption time is set longer than necessary, and adsorption is restarted after desorption. There are problems such as the timing being delayed, the time exposed to high temperature exhaust gas is increased to accelerate the temperature deterioration of the adsorbent, and the exhaust resistance due to passage of the adsorbent is increased to deteriorate fuel efficiency. It was

The present invention has been made in view of such conventional problems, and estimates the amount of HC adsorbed to the adsorbent during the adsorption operation, the remaining amount of HC of the adsorbent during desorption, and the like. Further, it is an object of the present invention to provide an exhaust gas purification apparatus for an internal combustion engine in which the HC purification performance can be enhanced as much as possible by controlling the desorption operation based on such estimation.

[0006]

Therefore, the present invention is based on FIG.
As shown in FIG. 3, an exhaust gas purification catalyst is provided in the exhaust gas passage of the engine, and a part of the exhaust gas passage upstream of the exhaust gas purification catalyst is connected in parallel to the main passage and the main passage to adsorb HC in the exhaust gas at low temperature. And a low temperature state before activation of the exhaust gas purification catalyst while controlling the exhaust gas flow dividing ratio between the main passage and the bypass passage, and a bypass passage having an adsorbent having a function of desorbing at a high temperature. The HC in the exhaust gas is adsorbed by the adsorbent, and the H adsorbed by the adsorbent in the high temperature state after activation of the exhaust gas purification catalyst
An exhaust gas purification apparatus for an internal combustion engine, wherein C is desorbed and purified by an exhaust gas purification catalyst, means for detecting the amount of HC emission in exhaust gas, means for detecting the flow velocity of exhaust gas passing through an adsorbent, and adsorption Means for detecting the temperature of the agent, and means for estimating the total amount of HC adsorbed by the adsorbent during the HC adsorbing operation based on the HC discharge amount, the exhaust flow velocity and the adsorbent temperature detected by these respective means, It was composed including.

Further, based on the flow rate of the exhaust gas passing through the adsorbent and the adsorbent temperature detected by the respective means, the H
A means for estimating the total amount of HC desorbed from the adsorbent during the desorption operation of HC from the adsorbent of C is included, and the total amount of HC estimated to be adsorbed by the adsorbent is desorbed from the adsorbent. Means for estimating the remaining amount of HC adsorbed on the adsorbent by subtracting the estimated total amount of HC.

Further, it may be configured to include means for controlling the flow division ratio of the exhaust gas in the main passage and the bypass passage based on the remaining amount of HC estimated to be adsorbed by the adsorbent. Further, when it is determined that the desorption is completed based on the remaining amount of HC estimated to be adsorbed by the adsorbent, the diversion ratio control means fully closes the bypass passage to end the desorption operation. May be included.

[0009]

[Advantageous Effects] During the adsorption operation of HC, the HC emission characteristic of the HC emission amount for each operating condition such as the engine operating condition, for example, engine speed, load, water temperature, etc. is previously obtained by an experiment or the like, and the operating conditions are successively calculated. It is detected by searching each value, the flow velocity of the exhaust gas passing through the adsorbent is detected by using the exhaust gas flow rate or the intake air flow rate, and the adsorbent temperature is detected directly by a temperature sensor or the like, or the exhaust gas temperature or engine operating conditions, It is detected from the elapsed time after starting.

Here, the amount of HC discharged is the amount of HC supplied to the adsorbent, and the HC adsorption performance of the adsorbent is determined by the flow rate of exhaust gas and the temperature of the adsorbent. Specifically, the higher the exhaust flow rate and the higher the adsorbent temperature, the more difficult it is to adsorb. Therefore, these tendencies are determined in advance, and the HC adsorbing performance of the adsorbent according to the detected value is calculated and supplied. The total amount of HC adsorbed during the adsorption operation can be obtained by integrating the amount of HC adsorbed by the adsorbent per unit time based on the relationship between the amount of HC adsorbed and the adsorption performance.

In addition, during desorption operation, the flow velocity of the exhaust gas passing through the adsorbent increases the flow velocity of the exhaust gas, which increases the thermal energy of the exhaust gas flowing into the reference crank angle within a unit time, as opposed to the adsorption flow velocity. Are easily desorbed, and a rise in the adsorbent temperature also increases the kinetic energy of HC molecules, so that HC is easily desorbed. Therefore, by predetermining these tendencies, the HC desorption performance from the adsorbent according to the detected value is calculated, and the HC desorbing from the adsorbent at every unit time is calculated.
If the amounts are integrated, the total amount of HC desorbed during the desorption operation can be obtained. Then, by subtracting the total amount of HC estimated to be desorbed from the adsorbent during the desorption operation from the total amount of HC estimated to be adsorbed to the adsorbent during the adsorption operation, The amount of HC remaining can be estimated.

Further, if the residual amount of HC adsorbed on the adsorbent is known as described above, in consideration of the HC purification performance of the exhaust purification catalyst during desorption, the exhaust gas of the main passage and the bypass passage will be considered. By controlling the split ratio, the exhaust flow rate to the bypass passage, that is, the adsorbent can be controlled so that the HC that can be processed by the exhaust purification catalyst is desorbed without excess or deficiency, and the HC purification performance can be improved. It is possible to shorten the desorption operation time while ensuring the speed, and accelerate the regeneration of the adsorbent.

When it is determined that the desorbed HC is sufficiently low and the desorption is completed,
By closing the bypass passage and fully opening the main passage,
The exhaust gas flow to the adsorbent can be stopped to reduce the exhaust resistance to improve the fuel economy and suppress the thermal deterioration of the adsorbent.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 2 showing the configuration of an embodiment of the present invention, an exhaust gas purification catalyst (three-way catalyst) is provided in an exhaust passage 2 of an internal combustion engine 1.
3, a part of the exhaust passage 2 upstream of the exhaust purification catalyst 3 is composed of a main passage 4 and a bypass passage 6 connected in parallel with the main passage 4 and having an adsorbent 5 interposed therein. Has been done. Means for continuously controlling the opening ratio between the main passage 4 and the bypass passage 6 at the branch points of the main passage 4 and the bypass passage 6 on the upstream side and the downstream side to control the exhaust flow dividing ratio. For example, electromagnetic control valves 7 and 8 are interposed. Note that, for simplicity, the control valve may be provided only at one of the branch points on the upstream side or the downstream side.

A bypass passage 6 downstream of the adsorbent 5 is also provided.
A temperature sensor 9 serving as a means for detecting the temperature of the adsorbent by detecting the exhaust temperature T _E is attached to the. In addition to the temperature sensor 9, a water temperature sensor 10 for detecting the engine cooling water temperature (water temperature) T _W, and a rotation speed sensor 11 for detecting the engine rotation speed N are provided. Each detection signal from these sensors and separately calculated. The basic fuel injection amount T _P is output to the control unit 12 as an engine load detection signal. Based on these signals, the control unit 12 discharges HC in the exhaust gas.
Adsorption and desorption control of

The control of adsorption and desorption of HC in exhaust gas by the control unit 10 will be described with reference to the flow chart shown in FIG. In step (denoted as S in the drawing. The same applies hereinafter) 1, the water temperature T _W detected by the sensors, the engine speed N, and the basic fuel injection amount T _P calculated in another routine are read.

In step 2, it is judged whether or not the operating conditions are such that the adsorbent 5 adsorbs HC. Specifically, when the water temperature T _W is equal to or lower than a predetermined value, the exhaust gas purification catalyst 3 is in an inactive state, the HC purification performance is low, and the HC adsorbent capacity of the adsorbent 5 is sufficiently high. Use adsorption conditions. When it is determined in step 2 that the HC adsorption condition is satisfied, step 3
Then, the control valve 7, 8 is set to fully open the bypass passage 6 side (at this time, the main passage 4 side is fully closed, and hereinafter, the bypass passage 6 side is used as a reference) to start the adsorption operation.

Next, in step 4, the HC
Calculate the emissions (per unit). Specifically, the fuel injection amount
 (Final fuel injection amount T_IOr basic fuel injection amount T_P)
Is calculated by multiplying by the correction coefficient set according to the operating conditions.
It Here, the correction coefficient is the water read in step 1 above.
Temperature T_W, Basic fuel injection amount T_P (Load), engine speed N
Set based on These water temperature T_W, Basic fuel injection amount T
_P, Explain the relationship between engine speed N and HC emissions
Then, the water temperature T_WThe lower the value, the poorer the fuel vaporization
The amount of generated HC is large, and the basic fuel injection amount T_P (Load)
Is larger, the fuel supplied to the engine increases, etc.
For this reason, the amount of generated HC is large and the engine speed N is large.
As the exhaust flow rate increases, it tends to increase proportionally.
It So, for example, using each of these conditions as parameters
A four-dimensional map table of correction factors preset by experiments
Table or search data or stored data amount
Correction coefficient K as shown in FIG.₁，
K₂, K₃As a separate map table
Then, the correction coefficient K retrieved based on each detected value₁, K₂，
K ₃It may be obtained by multiplying by. Also this
In addition, HC emissions are also affected by the air-fuel ratio and ignition timing.
Therefore, it is necessary to take these values into consideration to obtain a more accurate
I can do it.

Next, in step 5, the flow velocity of the exhaust gas passing through the adsorbent 5 is calculated. Basically, since the control valves 7 and 8 are fully opened and almost the entire amount of exhaust gas flows into the bypass passage 6, it is obtained as a value proportional to the flow rate of exhaust gas per unit time. If equal to the flow rate, the intake air flow rate Q obtained as a value proportional to the product of the basic fuel injection amount T _P and the engine speed N or the intake air flow rate Q detected by an air flow meter (not shown)
Can be calculated by multiplying by a coefficient for flow velocity conversion. here,
If the coefficient is set in consideration of the mounting position and capacity of the adsorbent 5, the accuracy is further improved.

In step 6, the adsorbent 5 is detected based on the exhaust gas temperature downstream of the adsorbent 5 detected by the temperature sensor 9.
Detects the temperature of. The sensor may be inserted into the adsorbent to directly detect the temperature of the adsorbent, and the temperature may be detected. Alternatively, the temperature may be estimated from the engine operating conditions, the elapsed time after starting, or the like. In step 7, the amount of HC adsorbed to the adsorbent 5 per unit time (for example, the execution cycle of this routine) is calculated on the basis of the amount of discharged HC, the exhaust flow velocity, and the adsorbent temperature thus obtained. Here, explaining the relationship between each of the above conditions and the amount of adsorbed HC, it is clear that the amount of adsorbed HC increases in proportion to the amount of discharged HC,
Further, the higher the exhaust flow velocity, the shorter the time for which the HC passes through the adsorbent 5, so that it becomes difficult to adsorb, and the higher the adsorbent temperature, the greater the internal energy of the HC molecules, so that it becomes difficult to adsorb. Therefore, the HC adsorption amount is experimentally set by using each of the above conditions as a parameter, and is obtained by a search from a four-dimensional map table, or the correction coefficients K ₄ , K ₅ , and K ₆ shown in FIG. It is only necessary to set it as the map table of No. ₁ and multiply it by the correction coefficients K ₄ , K ₅ and K ₆ retrieved based on each detected value.

In step 8, the amount of HC adsorbed per unit time obtained as described above is integrated to obtain the present adsorbent 5
The amount of HC adsorbed on is determined. In step 9, the purge flag F, which is set to 1 at the end of desorption, is reset to 0. In this way, the adsorption to the adsorbent 5 is performed, and when it is determined that the adsorbent 5 temperature rises as the water temperature rises and the adsorption condition in step 2 is no longer satisfied,
In step 10, it is determined whether or not the condition for desorbing the adsorbed HC from the adsorbent 5 is satisfied.
Specifically, the exhaust purification catalyst 3 has reached a temperature at which it is activated, for example, by detecting that the water temperature T _W or the exhaust temperature T _E is equal to or higher than a predetermined temperature, or a predetermined time has elapsed after the start. It is detected that the air-fuel ratio is not too rich from the air-fuel ratio sensor and the detected value of the operating condition, and that the temperature of the exhaust gas flowing into the adsorbent 5 is equal to or higher than a predetermined value. Also, the desorption condition is set when it is detected that the exhaust gas flow rate detected by the engine speed, the load, etc. is equal to or more than a predetermined value.

There is a normal time from when the adsorption condition for the adsorbent 5 in step 2 is not satisfied until the desorption condition is satisfied, during which time the process proceeds to step 11.
The control valves 7 and 8 are switched to the fully open side of the main passage 4 and the bypass passage 6 is closed. As a result, since the exhaust gas does not flow to the adsorbent 5, the temperature rise of the adsorbent 5 is suppressed and the temperature for desorbing HC is not reached.
Holds C.

After that, the exhaust purification catalyst 3 is activated by an increase in the water temperature T _W , the exhaust temperature, etc.
When the desorption conditions of 10 are satisfied, the process proceeds to step 12 and subsequent steps to start the desorption operation. First, in step 12, the value of the purge flag F is checked to determine whether desorption has been completed.

Before completion of desorption, the routine proceeds to step 13, where the flow velocity of exhaust gas passing through the adsorbent 5 is calculated. As for the flow velocity of the exhaust gas, a value obtained by multiplying the intake air flow rate Q by a coefficient is multiplied by a coefficient obtained from the opening ratio between the main passage 4 and the bypass passage 6 by the control valves 7 and 8 as in the case of adsorption. Required. The coefficient corresponding to the opening ratio is set to be larger when the opening on the side of the bypass passage 6 is larger, and is set to 1 at the time of full opening. Multiplying this coefficient is proportional to the flow rate of exhaust gas flowing into the bypass passage 6. The exhaust flow velocity can be obtained as a value.
Since the control valves 7 and 8 fully close the bypass passage 6 at the start of desorption, the coefficient according to the opening ratio becomes zero.

In step 14, the temperature of the adsorbent 5 is detected from the exhaust temperature T _E downstream of the adsorbent 5. In step 15,
Based on the flow rate of the exhaust gas passing through the adsorbent 5, the temperature of the adsorbent 5, and the remaining amount of HC currently adsorbed to the adsorbent 5, the HC per unit time (for example, the execution cycle of this routine) Calculate the desorption amount of. The remaining amount of HC decreases as desorption progresses, as determined by the calculation described later. Here, the amount of desorbed HC tends to increase as the flow velocity of exhaust gas increases, the adsorbent temperature increases, and the HC remaining amount increases. The calculated HC desorption amount can be obtained by searching the four-dimensional map table by
The correction factors K ₇ , K ₈ and K ₉ as shown in (4) are set as individual map tables, and the correction factors K ₇ , K ₈ and K ₉ retrieved based on the respective detected values are multiplied to obtain. do it.

In step 16, the total amount of HC desorbed from the adsorbent 5 after the start of desorption is calculated by integrating the amount of desorbed HC per unit time obtained as described above. Step 17
Then, by subtracting the total amount ΣHC _p of HC desorbed after the start of desorption obtained in step 16 from the total amount ΣHC _{a of} HC adsorbed on the adsorbent 5 during the adsorption operation, Find the remaining amount of HC present.

In step 18, it is determined whether or not the desorption of HC from the adsorbent 5 is completed depending on whether the remaining amount of HC obtained in step 17 is 0 or not. Before completion of desorption, the routine proceeds to step 19, where the opening ratio of the control valves 7 and 8 is controlled based on the remaining amount of HC to control the diversion ratio between the main passage 4 and the bypass passage 6. Here, in order to control the exhaust gas flow rate to the bypass passage 6 so that the amount of HC commensurate with the HC purification capacity in the activated state of the exhaust purification catalyst 3 is desorbed without excess or deficiency, the control valves 7, 8 The split ratio is controlled by controlling the opening ratio. Specifically, as the amount of HC remaining in the adsorbent 5 increases, the desorption amount increases. Therefore, the desorption amount is set as shown in FIG. 7 in order to maintain the desorption amount at a predetermined value commensurate with the purification capacity. Further, the split flow ratio is controlled so that the bypass passage 6 is fully opened 1 and fully closed 0.

When it is determined in step 18 that the desorption is completed by continuing the desorption, step 20
Then, the control valves 7 and 8 are controlled to fully close the bypass passage 6 and fully open the main passage 4. As a result, substantially the entire amount of exhaust gas flows into the main passage 4 and exhaust gas does not flow into the bypass passage 6, so that high-temperature exhaust gas is prevented from flowing unnecessarily to the adsorbent 5 and thermal deterioration of the adsorbent 5 is suppressed. In addition, it is possible to suppress deterioration of fuel consumption due to an increase in exhaust resistance when passing through the adsorbent 5.

Next, in step 21, the purge flag F is set to 1. As a result, when it is determined in step 12 that the purge flag F is 1, the process proceeds to step 11 without performing the HC remaining amount estimation calculation, and the main passage 4 is held fully open (the bypass passage is fully closed). Although the above description does not include the above description in which a catalyst (a so-called pulley catalyst) is arranged upstream of the adsorbent 5, this pulley catalyst may be provided in order to further enhance the exhaust gas purification performance.

[0030]

As described above, according to the present invention, the total amount of HC adsorbed by the adsorbent during the adsorption operation is determined by the amount of HC discharged in the exhaust gas, the flow rate of the exhaust gas passing through the adsorbent, and the adsorbent temperature. Since the configuration is based on the estimation, the total amount of the adsorbed HC can be estimated with high accuracy.

Further, H desorbed from the adsorbent during the desorption operation
The total amount of C is also estimated with high accuracy based on the flow rate of the exhaust gas passing through the adsorbent and the adsorbent temperature, and the total amount of desorbed HC is subtracted from the total amount of adsorbed HC, thereby The remaining amount of HC in the adsorbent can also be estimated with high accuracy.
Then, the opening ratio between the main passage and the bypass passage is controlled based on the estimated remaining amount of HC, and the bypass passage is fully closed when the remaining amount becomes sufficiently small and the completion of desorption is detected. As a result, an amount of HC commensurate with the HC purification capacity of the exhaust purification catalyst can be desorbed without excess or deficiency.
While maintaining good purification performance, the desorption time can be shortened as much as possible, and the regeneration of the adsorbent can be accelerated.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration and function of the present invention.

FIG. 2 is a diagram showing a system configuration of an embodiment of the present invention.

FIG. 3 is a flowchart showing an HC adsorption / desorption control routine of the above embodiment.

FIG. 4 is a diagram showing a relationship between each operating condition for calculating an amount of discharged HC in exhaust gas and an amount of discharged HC in the adsorption control routine.

FIG. 5 is a diagram showing the relationship between each state quantity and the HC adsorption amount for estimating the HC adsorption amount per unit time.

FIG. 6 is a diagram showing the relationship between each state quantity and the amount of desorbed HC for estimating the amount of desorbed HC per unit time.

FIG. 7 is a diagram similarly setting the split flow ratio of the main passage and the bypass passage with respect to the estimated HC remaining amount.

[Explanation of symbols]

 1 Internal Combustion Engine 2 Exhaust Passage 3 Exhaust Purification Catalyst 4 Main Passage 5 Adsorbent 6 Bypass Passage 7, 8 Control Valve 9 Temperature Sensor 10 Water Temperature Sensor 11 Rotation Speed Sensor 12 Control Unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location F02D 45/00 358 Z 7536-3G

Claims (4)

[Claims] 1. An exhaust gas purification catalyst is provided in an exhaust gas passage of an engine, and a part of an exhaust gas passage upstream of the exhaust gas purification catalyst is connected in parallel to a main passage and the main passage to keep HC in the exhaust gas at a low temperature. A low temperature before activation of the exhaust gas purification catalyst, which is composed of a bypass passage through which an adsorbent having a function of adsorbing and desorbing at a high temperature is interposed and which controls an exhaust flow dividing ratio between the main passage and the bypass passage. In the state, the adsorbent adsorbs HC in the exhaust gas, and after the exhaust purification catalyst is activated, the adsorbent adsorbs H in the high temperature state.
An exhaust gas purification apparatus for an internal combustion engine, wherein C is desorbed and purified by an exhaust gas purification catalyst, means for detecting the amount of HC emission in exhaust gas, means for detecting the flow velocity of exhaust gas passing through an adsorbent, and adsorption Means for detecting the temperature of the agent, and means for estimating the total amount of HC adsorbed by the adsorbent during the HC adsorbing operation based on the HC discharge amount, the exhaust flow velocity and the adsorbent temperature detected by these respective means, An exhaust gas purification apparatus for an internal combustion engine, characterized in that 2. The HC desorbed from the adsorbent during the desorption operation of the HC from the adsorbent of the HC based on the flow rate of the exhaust gas passing through the adsorbent and the adsorbent temperature detected by the respective means.
And subtracting the total amount of HC estimated to be desorbed from the adsorbent from the total amount of HC estimated to be adsorbed to the adsorbent by subtracting the total amount of HC adsorbed to the adsorbent. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, further comprising: a means for estimating the amount. 3. HC presumed to be adsorbed by an adsorbent
3. The exhaust gas purification device for an internal combustion engine according to claim 2, further comprising means for controlling an exhaust flow dividing ratio of the main passage and the bypass passage based on the remaining amount of the exhaust gas. 4. HC presumed to be adsorbed by an adsorbent
4. When the desorption is judged to be completed based on the remaining amount, the diversion ratio control means is configured to fully close the bypass passage to complete the desorption operation. An exhaust gas purification device for an internal combustion engine as described.