JP2008291711A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further accurately estimate the flow rate of exhaust gas passing through a catalyst when the catalyst is arranged so that a part of the exhaust gas instead of the total thereof passes through an exhaust passage of an internal combustion engine. <P>SOLUTION: This exhaust emission control device of an internal combustion engine is provided with: a catalyst passage rate calculation means S103 of calculating a catalyst passage rate being a ration of the flow rate of the exhaust gas passing through the catalyst to the total flow rate of the exhaust gas based on a ratio of HC concentration of the exhaust gas flowing in the catalyst to HC concentration of the exhaust gas obtained by mixing the exhaust gas having passed through the catalyst with the exhaust gas without passing through the catalyst on the downstream side of the catalyst; and a catalyst passage exhaust gas flow rate calculation means S104 of calculating the flow rate of the exhaust gas passing through the catalyst based on the catalyst passage rate calculated by the catalyst passage rate calculation means and the total flow rate of the exhaust gas. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine provided with a catalyst having an oxidation function provided in an exhaust passage of the internal combustion engine.

  When a catalyst having an oxidation function is provided in the exhaust passage of an internal combustion engine, for example, a catalyst is installed so that exhaust flows between the outer peripheral surface of the catalyst and the inner peripheral surface of the exhaust passage, or a plurality of exhaust passages are provided in the middle. In some cases, the catalyst is installed such that a part of the exhaust gas passes through the catalyst instead of the total amount of exhaust gas by branching to the branch passage and arranging the catalyst only in a part of the branch passages.

Patent Document 1 discloses a configuration in which two NOx catalysts for reducing NOx in exhaust gas are arranged in series in an exhaust passage of an internal combustion engine. In this Patent Document 1, the active state and the HC reaction amount of the downstream NOx catalyst are estimated from the difference between the inflow gas temperature and the outflow gas temperature of the downstream NOx catalyst, and the post injection timing in the internal combustion engine is retarded accordingly. Alternatively, the reforming degree of the fuel injected by the post injection is advanced by adjusting the advance angle. Thus, the amount of HC supplied to the downstream NOx catalyst is adjusted by adjusting the amount of HC reaction in the upstream NOx catalyst.
JP 11-350939 A JP 2006-90147 A

  The present invention can estimate the flow rate of exhaust gas passing through the catalyst with higher accuracy when the catalyst is installed in the exhaust passage of the internal combustion engine so that a part of the exhaust gas passes through the catalyst instead of the total amount of exhaust gas. The purpose is to provide technology.

An internal combustion engine exhaust gas purification apparatus according to a first invention is
A catalyst having an oxidation function installed so that a part of the exhaust gas passes through the exhaust passage of the internal combustion engine instead of the total amount;
Based on the ratio of the HC concentration of the exhaust flowing into the catalyst and the HC concentration of the exhaust mixed with the exhaust that has passed through the catalyst and the exhaust that has not passed through the catalyst on the downstream side of the catalyst, A catalyst passage rate calculating means for calculating a catalyst passage rate that is a ratio of a flow rate of the exhaust gas passing through the catalyst with respect to a total flow rate;
And a catalyst passing exhaust flow rate calculating means for calculating a flow rate of exhaust gas passing through the catalyst based on the catalyst passing rate calculated by the catalyst passing rate calculating means and the total exhaust flow rate.

  Here, the HC concentration of the exhaust gas flowing into the catalyst is referred to as the upstream HC concentration, and the HC concentration of the exhaust gas in which the exhaust gas that has passed through the catalyst downstream and the exhaust gas that has not passed through the catalyst is mixed is defined as the downstream HC concentration. This is called concentration.

  When only a part of the exhaust gas passes through the catalyst, the downstream HC concentration is reduced relative to the upstream HC concentration by the amount of HC in the exhaust gas that has flowed into the catalyst being oxidized in the catalyst. At this time, it can be determined that the lower the HC concentration on the downstream side, the more HC oxidized in the catalyst, that is, the greater the flow rate of the exhaust gas that has passed through the catalyst. Therefore, the catalyst passage rate can be calculated based on the ratio between the upstream HC concentration and the downstream HC concentration.

  According to the present invention, when only part of the exhaust gas passes through the catalyst, the flow rate of the exhaust gas passing through the catalyst can be estimated with higher accuracy.

  In the present invention, the catalyst passage rate calculation means passes through the upstream side HC concentration detection means for detecting the HC concentration of the exhaust gas flowing into the catalyst, and the exhaust gas that has passed through the catalyst downstream of the catalyst in the exhaust passage. And an HC sensor that detects the HC concentration of the exhaust provided after the position where the exhaust that has not been mixed is mixed. In this case, the catalyst passage rate can be calculated based on the HC concentration detected by the upstream HC concentration detecting means and the HC concentration detected by the HC sensor.

In the present invention, the catalyst passage rate calculating means includes upstream O ₂ concentration detecting means for detecting the O ₂ concentration of the exhaust gas flowing into the catalyst, and exhaust gas that has passed through the catalyst on the downstream side of the catalyst in the exhaust passage. And an O ₂ sensor that detects the O ₂ concentration of the exhaust gas that is provided after the position where the exhaust gas that has not passed through the catalyst is mixed.

Here, referred to O ₂ concentration detected by the upstream O ₂ concentration detector and the upstream O ₂ concentration, referred to as O ₂ concentration detected by the O ₂ sensor and the downstream O ₂ concentration.

When a part of the exhaust gas flows into the catalyst and HC in the exhaust gas flowing in is oxidized in the catalyst, O ₂ in the exhaust gas flowing in is consumed. For this reason, exhaust gas having a reduced O ₂ concentration flows out from the catalyst. As a result, the downstream O ₂ concentration decreases with respect to the upstream O ₂ concentration by the amount of O ₂ consumed for the oxidation of HC in the catalyst. Accordingly, the ratio between the upstream O ₂ concentration and the downstream O ₂ concentration is equal to the ratio between the upstream HC concentration and the downstream HC concentration.

Therefore, in the case of the above configuration, the ratio between the upstream HC concentration and the downstream HC concentration is calculated based on the upstream O ₂ concentration and the downstream O ₂ concentration.

  In the present invention, the catalyst passage rate calculating means detects the temperature of the exhaust gas flowing into the catalyst, the upstream temperature detecting means, and the exhaust gas passing through the catalyst downstream of the catalyst in the exhaust passage and passing through the catalyst. And a temperature sensor that is provided after the position where the exhaust gas that has not been mixed is detected and that detects the temperature of the exhaust gas.

  Here, the temperature detected by the upstream temperature detection means is referred to as upstream temperature, and the temperature detected by the temperature sensor is referred to as downstream temperature.

  When a part of the exhaust gas flows into the catalyst and HC in the exhaust gas flowing in is oxidized in the catalyst, the temperature of the exhaust gas flowing out from the catalyst rises. As a result, the downstream temperature rises with respect to the upstream temperature by the amount of heat generated by the oxidation of HC in the catalyst. Therefore, the ratio between the upstream HC concentration and the downstream HC concentration can be calculated from the ratio between the upstream temperature and the downstream temperature.

  Therefore, in the case of the above configuration, the ratio between the upstream HC concentration and the downstream HC concentration is calculated based on the upstream temperature and the downstream temperature.

An exhaust emission control device for an internal combustion engine according to a second invention
A catalyst having an oxidation function installed so that a part of the exhaust gas passes through the exhaust passage of the internal combustion engine instead of the total amount;
Upstream temperature detection means for detecting the temperature of the exhaust gas flowing into the catalyst;
A first temperature sensor that is provided so as to face the downstream end of the catalyst in the exhaust passage downstream of the catalyst and detects the temperature of the exhaust gas flowing out of the catalyst;
A second temperature sensor that is provided downstream of the first temperature sensor and detects the temperature of the exhaust gas provided after the position where the exhaust gas that has passed through the catalyst and the exhaust gas that has not passed through the catalyst are mixed;
Let Gcat be the flow rate of the exhaust gas that passes through the catalyst,
The exhaust gas temperature detected by the upstream temperature detection means is Tgin,
The temperature of the exhaust detected by the first temperature sensor is Tgd1,
When the temperature of the exhaust detected by the second temperature sensor is Tgd2,
Gcat = (Tgd2-Tgin) / (Tgd1-Tgin) (1)
And a catalyst passing exhaust gas flow rate calculating means for calculating the flow rate of the exhaust gas passing through the catalyst from the equation represented by

  Here, the temperature of the exhaust detected by the upstream temperature detection means is referred to as upstream temperature Tgin, the temperature of the exhaust detected by the first temperature sensor is referred to as first downstream temperature Tgd1, and is detected by the second temperature sensor. The temperature of the exhausted gas is referred to as a second downstream temperature Tgd2.

  As described above, when part of the exhaust gas flows into the catalyst and HC in the exhaust gas that has flowed in is oxidized in the catalyst, the temperature of the exhaust gas flowing out from the catalyst increases. At this time, both the first downstream temperature Tgd1 and the second downstream temperature Tgd2 rise. However, since the temperature of the exhaust gas that has flowed downstream from the catalyst without passing through the catalyst does not rise, the second downstream temperature, which is the temperature of the exhaust gas mixed with the exhaust gas that has passed through the catalyst and the exhaust gas that has not passed through the catalyst. The side temperature Tgd2 is lower than the first downstream side temperature Tgd1, which is the temperature of the exhaust gas flowing out from the catalyst.

At this time, assuming that the total exhaust flow rate is Ga, the relationship between the upstream temperature Tgin, the first downstream temperature Tgd1, the second downstream temperature Tgd2, the exhaust flow rate Gcat passing through the catalyst, and the exhaust total flow rate Ga is as follows. Equation (2) is obtained.
(Tgd1−Tgin) × Gcat / Ga = (Tgd2−Tgin) × Ga (2)

  The above equation (1) can be derived from the equation (2), and the flow rate of the exhaust gas passing through the catalyst can be calculated from the above equation (1).

  In the first or second invention, the flow rate of the exhaust gas passing through the catalyst calculated by the catalyst passing exhaust gas flow rate calculating means may be corrected based on the temperature of the catalyst.

  Even when the flow rate of exhaust gas actually passing through the catalyst is the same and the amount of HC flowing into the catalyst is the same, the oxidation amount of HC in the catalyst may vary depending on the temperature of the catalyst. Therefore, the flow rate of exhaust gas passing through the catalyst can be calculated with higher accuracy by correcting the flow rate of exhaust gas passing through the catalyst calculated by the catalyst passing exhaust gas flow rate calculating means based on the temperature of the catalyst.

  In the first or second invention, when the temperature of the catalyst is equal to or higher than the most active temperature, the flow rate of exhaust gas passing through the catalyst may be calculated by the catalyst passing exhaust gas flow rate calculating means. At this time, the most active temperature is a threshold value at which the degree of activity of the catalyst is near the upper limit.

  When the temperature of the catalyst becomes equal to or higher than the most active temperature, the oxidation amount of HC in the catalyst hardly changes depending on the temperature of the catalyst. Therefore, when the catalyst temperature is equal to or higher than the most active temperature, the flow rate of the exhaust gas passing through the catalyst is calculated by the catalyst passing exhaust gas flow rate calculation means, thereby estimating the flow rate of the exhaust gas passing through the catalyst with higher accuracy. I can do it.

In the first or second invention, the catalyst passage exhaust gas flow rate calculating means may calculate the reference value of the flow rate of the exhaust gas passing through the catalyst by the above-described methods when the temperature of the catalyst is a predetermined temperature. . In this case, when the catalyst temperature is other than the predetermined temperature, the catalyst passing exhaust gas flow rate calculating means may calculate the flow rate of the exhaust gas passing through the catalyst by correcting the reference value based on the catalyst temperature.

  The higher the temperature of the catalyst, the higher the temperature of the exhaust flowing through the catalyst, and the viscosity coefficient of the exhaust flowing through the catalyst increases accordingly. Therefore, even if the flow rate of exhaust flowing through the exhaust passage upstream of the catalyst is the same, the flow rate of exhaust passing through the catalyst decreases as the temperature of the catalyst increases.

  Therefore, as described above, the reference value of the flow rate of the exhaust gas passing through the catalyst when the temperature of the catalyst is a predetermined temperature is calculated, and the reference value is corrected according to the temperature of the catalyst, so that the temperature of the catalyst is reduced. The flow rate of the exhaust gas passing through the catalyst at a temperature other than the predetermined temperature can be calculated.

An internal combustion engine exhaust gas purification apparatus according to a third aspect of the invention includes:
A catalyst having an oxidation function installed so that a part of the exhaust gas passes through the exhaust passage of the internal combustion engine instead of the total amount;
Upstream temperature detection means for detecting the temperature of the exhaust gas flowing into the catalyst;
A first temperature sensor that is provided so as to face the downstream end of the catalyst in the exhaust passage downstream of the catalyst and detects the temperature of the exhaust gas flowing out of the catalyst;
A second temperature sensor that is provided downstream of the first temperature sensor and detects the temperature of the exhaust gas provided after the position where the exhaust gas that has passed through the catalyst and the exhaust gas that has not passed through the catalyst are mixed;
The timing at which the exhaust temperature detected by the first temperature sensor starts to decrease and the exhaust temperature detected by the second temperature sensor when the exhaust temperature detected by the upstream temperature detection means decreases. And a catalyst passing exhaust gas flow rate calculating means for calculating the flow rate of the exhaust gas passing through the catalyst based on a time difference from the timing of starting to decrease.

  Here, similarly to the above, the temperature of the exhaust detected by the upstream temperature detecting means is referred to as the upstream temperature, the temperature of the exhaust detected by the first temperature sensor is referred to as the first downstream temperature, and the second temperature sensor. The temperature of the exhaust detected by the above is referred to as the second downstream temperature.

  As the upstream temperature decreases, the temperature of the exhaust gas that has passed through the catalyst in the exhaust passage downstream of the catalyst and the temperature of the exhaust gas that has not passed through the catalyst both decrease. However, the temperature of the exhaust gas that has passed through the catalyst is less likely to be lower than the temperature of the exhaust gas that has not passed through the catalyst. Therefore, the timing at which the first downstream temperature starts to fall below the second downstream temperature is delayed. At this time, the time difference between the timing at which the first downstream temperature starts to decrease and the timing at which the second downstream temperature begins to decrease increases as the flow rate of the exhaust gas passing through the catalyst increases.

  Therefore, the flow rate of the exhaust gas passing through the catalyst can be calculated based on the time difference between the timing at which the first downstream temperature starts to decrease and the timing at which the second downstream temperature starts to decrease when the upstream temperature decreases. .

  In the first to third aspects of the invention, when the flow rate of the exhaust gas passing through the catalyst calculated by the catalyst passing exhaust gas flow rate calculating means is not more than a predetermined flow rate, the upstream end face of the catalyst is clogged by raising the temperature of the catalyst. You may perform clogging elimination control to eliminate.

  When the upstream end face of the catalyst becomes clogged, the flow rate of the exhaust gas passing through the catalyst is greatly reduced. Here, the predetermined flow rate is a threshold value at which it can be determined that the upstream end face of the catalyst is clogged.

According to the above, clogging of the upstream end face of the catalyst can be resolved at a suitable timing.

  In the first to third inventions, the catalyst may be installed in the exhaust passage so that the exhaust gas flows between the outer peripheral surface of the catalyst and the inner peripheral surface of the exhaust passage. In this case, the catalyst is formed such that the cross-sectional area of the catalyst in the direction perpendicular to the direction in which the exhaust gas flows is smaller than the cross-sectional area in the direction perpendicular to the direction in which the exhaust gas flows in the exhaust passage. According to such a configuration, a part of the exhaust gas passes through the catalyst instead of the total amount.

  In the first to third aspects of the invention, the exhaust passage is formed so as to branch into a plurality of branch passages on the way and the plurality of branch passages gather on the downstream side, and the catalyst has a plurality of branches. It may be installed only in one of the passages. Even with such a configuration, a portion of the exhaust gas passes through the catalyst instead of the total amount.

  According to the present invention, when the catalyst is installed in the exhaust passage of the internal combustion engine such that a part of the exhaust gas passes through the catalyst instead of the total amount, the flow rate of the exhaust gas passing through the catalyst can be estimated with higher accuracy. I can do it.

  Hereinafter, specific embodiments of an exhaust emission control device for an internal combustion engine according to the present invention will be described with reference to the drawings.

<Example 1>
<Schematic configuration of intake and exhaust system of internal combustion engine>
Here, a case where the present invention is applied to a diesel engine for driving a vehicle will be described as an example. FIG. 1 is a diagram showing a schematic configuration of an intake / exhaust system of an internal combustion engine according to the present embodiment.

  The internal combustion engine 1 is a diesel engine for driving a vehicle. An intake passage 3 and an exhaust passage 2 are connected to the internal combustion engine 1. A throttle valve 7 and an air flow meter 8 are provided in the intake passage 3.

  The exhaust passage 2 is provided with a particulate filter (hereinafter referred to as a filter) 5 that collects particulate matter (hereinafter referred to as PM) in the exhaust. The filter 5 carries an NOx storage reduction catalyst (hereinafter referred to as NOx catalyst).

  An oxidation catalyst 4 is provided upstream of the filter 5 in the exhaust passage 2. The oxidation catalyst 4 has a cylindrical shape, and the outer diameter thereof is smaller than the inner diameter of the exhaust passage 2. That is, the cross-sectional area perpendicular to the direction in which the exhaust gas of the oxidation catalyst 4 flows is smaller than the cross-sectional area in the direction perpendicular to the direction in which the exhaust gas flows through the exhaust passage 2. With such a configuration, exhaust gas flows between the outer peripheral surface of the oxidation catalyst 4 and the inner peripheral surface of the exhaust passage 2. In this embodiment, the oxidation catalyst 4 corresponds to the catalyst having an oxidation function according to the present invention. The oxidation catalyst 4 may be a catalyst having an oxidation function, and may be, for example, a three-way catalyst or a NOx catalyst.

  A fuel addition valve 6 for adding fuel is provided in the exhaust passage 2 upstream of the oxidation catalyst 4. The fuel addition valve 6 is disposed close to the oxidation catalyst 4 so that the fuel injection hole into which the fuel is injected faces the upstream end face of the oxidation catalyst 4. From the fuel injection hole of the fuel addition valve 6, fuel is injected in a conical shape (in FIG. 1, the hatched portion represents fuel spray). When the fuel is injected from the fuel injection hole of the fuel addition valve 6, the upstream end face of the oxidation catalyst 4 is positioned during the spraying of the fuel formed in a conical shape.

  Further, an HC sensor 9 for detecting the HC concentration of the exhaust is provided between the oxidation catalyst 4 and the filter 5 in the exhaust passage 2. The HC sensor 9 passes between the exhaust gas that has passed through the oxidation catalyst 4 in the exhaust passage 2 and the exhaust gas that has not passed through the oxidation catalyst 4 (that is, between the outer peripheral surface of the oxidation catalyst 4 and the inner peripheral surface of the exhaust passage 2). It is provided after the position where the (exhaust) is mixed.

  The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 10 for controlling the internal combustion engine 1. An air flow meter 8, an HC sensor 9, a crank position sensor 11, and an accelerator opening sensor 12 are electrically connected to the ECU 10. These output signals are input to the ECU 10.

  The crank position sensor 11 is a sensor that detects the crank angle of the internal combustion engine 1. The accelerator opening sensor 12 is a sensor that detects the accelerator opening of a vehicle on which the internal combustion engine 1 is mounted. The ECU 10 calculates the engine speed of the internal combustion engine 1 based on the output value of the crank position sensor 11, and calculates the engine load of the internal combustion engine 1 based on the output value of the accelerator opening sensor 12.

  The ECU 10 is electrically connected to the throttle valve 7, the fuel addition valve 6, and the fuel injection valve of the internal combustion engine 1. These are controlled by the ECU 10.

<Temperature control>
In the present embodiment, the temperature of the filter 5 is raised when the PM collected by the filter 5 is oxidized and removed, or when the SOx stored in the NOx catalyst carried by the filter 5 is released and reduced. When it is necessary to cause the temperature to rise, the temperature rise control for raising the temperature of the exhaust gas flowing into the filter 5 is executed.

  The temperature increase control according to the present embodiment is realized by adding fuel from the fuel addition valve 6 and supplying the fuel to the oxidation catalyst 4. The fuel supplied to the oxidation catalyst 4 is oxidized in the oxidation catalyst 4. The exhaust gas flowing into the filter 5 is heated by the oxidation heat generated at this time.

  As described above, in this embodiment, the outer diameter of the oxidation catalyst 4 is smaller than the inner diameter of the exhaust passage 2. In this case, the passage resistance of the exhaust gas when the exhaust gas passes through the oxidation catalyst 4 is larger than the case where the outer diameter of the oxidation catalyst 4 is equal to or larger than the inner diameter of the exhaust passage 2. The flow rate of the exhaust flowing inside is reduced. For this reason, when fuel is supplied from the fuel addition valve 6, it takes a longer time for the fuel to pass through the oxidation catalyst 4, and the oxidation reaction of the fuel in the oxidation catalyst 4 is more easily promoted. As a result, the temperature rise of the exhaust is accelerated.

<Calculation method of exhaust gas flow rate through catalyst>
In the case of the configuration as in the present embodiment, a part of the exhaust gas passes through the oxidation catalyst 4 instead of the total amount of exhaust gas. When the temperature increase control as described above is performed, it is necessary to control the amount of fuel added from the fuel addition valve 6 according to the flow rate of the exhaust gas passing through the oxidation catalyst 4. Therefore, in order to control the temperature of the oxidation catalyst 4 to the target temperature, it is important to accurately estimate the flow rate of the exhaust gas passing through the oxidation catalyst 4.

  Here, a method of calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to the present embodiment will be described based on the flowchart shown in FIG. FIG. 2 is a flowchart showing a routine for calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to the present embodiment. This routine is stored in the ECU 10 in advance. This routine may be repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1, or may be executed when a predetermined condition is satisfied during the operation of the internal combustion engine 1.

  In this routine, the ECU 10 first in S101, based on the operating state of the internal combustion engine 1, etc., the HC concentration of exhaust flowing through the exhaust passage 2 upstream of the oxidation catalyst 4, that is, the HC of exhaust flowing into the oxidation catalyst 4 The concentration (hereinafter referred to as upstream HC concentration) Chcin is calculated. In the present embodiment, the ECU 10 that executes S101 corresponds to the upstream HC concentration detecting means according to the present invention.

  Next, the ECU 10 proceeds to S102, in which the HC concentration (hereinafter referred to as downstream HC) of the exhaust gas mixed with the exhaust gas that has passed through the oxidation catalyst 4 and the exhaust gas that has not passed through the oxidation catalyst 4 detected by the HC sensor 9 is detected. Read Chcd (referred to as density).

  Next, the ECU 10 proceeds to S103, and calculates a catalyst passage rate Rcg, which is a ratio of the flow rate of the exhaust gas passing through the oxidation catalyst 4 with respect to the total flow rate of the exhaust gas, from the ratio between the upstream HC concentration Chcin and the downstream HC concentration Chcd. To do.

  The downstream HC concentration Chcd is lower than the upstream HC concentration Chcin by the amount of HC in the exhaust gas flowing into the oxidation catalyst 4 being oxidized in the oxidation catalyst 4. That is, it can be determined that the flow rate of the exhaust gas passing through the oxidation catalyst 4 increases as the decrease in the downstream HC concentration Chcd with respect to the upstream HC concentration Chcin increases. Therefore, the catalyst passage rate Rcg can be calculated based on the ratio between the upstream HC concentration Chcin and the downstream HC concentration Chcd. In this embodiment, the catalyst passage rate calculating means according to the present invention is configured including the ECU 10 that executes S103.

  Next, the ECU 10 proceeds to S104, and the exhaust gas passing through the oxidation catalyst 4 is multiplied by multiplying the total exhaust gas flow rate Ga calculated based on the detected value of the air flow meter 8 by the catalyst passage rate Rcg calculated in S103. The flow rate Gcat is calculated. In this embodiment, the ECU 10 that executes S104 corresponds to the catalyst passage exhaust gas flow rate calculating means according to the present invention.

  According to the routine described above, the flow rate of the exhaust gas passing through the oxidation catalyst 4 can be calculated with higher accuracy. As a result, the temperature of the oxidation catalyst 4 can be controlled to the target temperature with higher accuracy when the temperature increase control is executed.

  In the present embodiment, the upstream HC concentration Chcin is calculated based on the operating state of the internal combustion engine 1, but the upstream HC concentration Chcin may be detected by the HC sensor as with the downstream HC concentration Chcd. . In this case, the HC sensor provided in the exhaust passage 2 upstream of the oxidation catalyst 4 corresponds to the upstream HC concentration detecting means according to the present invention.

<Modification 1>
Next, a first modification of the present embodiment will be described. In this modification, an O ₂ sensor that detects the O ₂ concentration of the exhaust gas is provided instead of the HC sensor 9. The other configuration is the same as the configuration shown in FIG.

  Here, a method for calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to this modification will be described based on the flowchart shown in FIG. FIG. 3 is a flowchart showing a routine for calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to this modification. S104 in this routine is the same as S104 in the flowchart shown in FIG. This routine is stored in the ECU 10 in advance. This routine may be repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1, or may be executed when a predetermined condition is satisfied during the operation of the internal combustion engine 1.

In this routine, the ECU 10 first in S301, based on the operating state of the internal combustion engine 1, etc., the O ₂ concentration of exhaust flowing through the exhaust passage 2 upstream of the oxidation catalyst 4, that is, the exhaust flowing into the oxidation catalyst 4 is determined. An O ₂ concentration (hereinafter referred to as upstream O ₂ concentration) Coin is calculated. In this modification, the ECU 10 that executes S301 corresponds to the upstream O ₂ concentration detection means according to the present invention.

Next, the ECU 10 proceeds to S302, and the O ₂ concentration (hereinafter referred to as the downstream side) of the exhaust gas mixed with the exhaust gas that has passed through the oxidation catalyst 4 and the exhaust gas that has not passed through the oxidation catalyst 4 detected by the O ₂ sensor. Read Cod) (referred to as O ₂ concentration).

Next, the ECU 10 proceeds to S303, calculates the ratio between the upstream HC concentration Chcin and the downstream HC concentration Chcd from the ratio between the upstream O ₂ concentration Coin and the downstream O ₂ concentration Cod, and this upstream HC concentration. The catalyst passage rate Rcg is calculated based on the ratio between Chcin and the downstream HC concentration Chcd.

The downstream O ₂ concentration Cod is lower than the upstream O ₂ concentration Cou by the amount of O ₂ consumed for the oxidation of HC in the exhaust gas flowing into the oxidation catalyst 4. Therefore, the ratio between the upstream O ₂ concentration Coin and the downstream O ₂ concentration Cod is equal to the ratio between the upstream HC concentration Chcin and the downstream HC concentration Chcd. In this modification, the catalyst passage rate calculating means according to the present invention is configured including the ECU 10 that executes S203. The ECU 10 having calculated the catalyst passage rate Rcg proceeds to S104.

  Also according to this modification, the flow rate of the exhaust gas passing through the oxidation catalyst 4 can be calculated with higher accuracy.

In this modification, the upstream O ₂ concentration Coin is calculated based on the operating state of the internal combustion engine 1 and the like, but the upstream O ₂ concentration Coin is detected by the O ₂ sensor in the same manner as the downstream O ₂ concentration Cod. May be. In this case, the O ₂ sensor provided in the exhaust passage 2 upstream of the oxidation catalyst 4 corresponds to the upstream O ₂ concentration detecting means according to the present invention.

<Modification 2>
Next, a second modification of the present embodiment will be described. In this modification, a temperature sensor that detects the temperature of the exhaust gas is provided in place of the HC sensor 9. The other configuration is the same as the configuration shown in FIG.

  Here, a method of calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to the present modification will be described based on the flowchart shown in FIG. FIG. 4 is a flowchart showing a routine for calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to this modification. S104 in this routine is the same as S104 in the flowchart shown in FIG. This routine is stored in the ECU 10 in advance. This routine may be repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1, or may be executed when a predetermined condition is satisfied during the operation of the internal combustion engine 1.

  In this routine, first in step S401, the ECU 10 determines the temperature of the exhaust gas flowing through the exhaust passage 2 upstream of the oxidation catalyst 4, that is, the temperature of the exhaust gas flowing into the oxidation catalyst 4 based on the operating state of the internal combustion engine 1 ( Hereinafter, Tgin is calculated. In this modification, the ECU 10 that executes S401 corresponds to the upstream temperature detection means according to the present invention.

Next, the ECU 10 proceeds to S402, and the temperature of the exhaust gas detected by the temperature sensor and mixed with the exhaust gas that has passed through the oxidation catalyst 4 and the exhaust gas that has not passed through the oxidation catalyst 4 (hereinafter referred to as downstream temperature). ) Read Tgd.

  Next, the ECU 10 proceeds to S403, calculates the ratio of the upstream HC concentration Chcin and the downstream HC concentration Chcd from the ratio of the upstream temperature Tgin and the downstream temperature Tgd, and the upstream HC concentration Chcin and the downstream The catalyst passage rate Rcg is calculated based on the ratio with the side HC concentration Chcd. The downstream temperature Tgd rises higher than the upstream temperature Tgin by the amount of heat generated by oxidizing the HC in the exhaust gas flowing into the oxidation catalyst 4. Therefore, the ratio between the upstream HC concentration Chcin and the downstream HC concentration Chcd can be calculated based on the ratio between the upstream temperature Tgin and the downstream temperature Tgd. In this modification, the catalyst passage rate calculating means according to the present invention is configured including the ECU 10 that executes S403. The ECU 10 having calculated the catalyst passage rate Rcg proceeds to S104.

  Also according to this modification, the flow rate of the exhaust gas passing through the oxidation catalyst 4 can be calculated with higher accuracy.

  In the present modification, the upstream temperature Tgin is calculated based on the operating state of the internal combustion engine 1, but the upstream temperature Tgin may be detected by a temperature sensor as with the downstream temperature Tgd. In this case, the temperature sensor provided in the exhaust passage 2 upstream of the oxidation catalyst 4 corresponds to the upstream temperature detection means according to the present invention.

<Modification 3>
Next, a third modification of the present embodiment will be described. FIG. 5 is a diagram showing a schematic configuration of an exhaust passage according to this modification. In FIG. 5, the arrow indicates the direction in which the exhaust flows, and the upstream end of the exhaust passage 2 is connected to the internal combustion engine 1 as in the case of the configuration shown in FIG. 1.

  The exhaust passage 2 in the present embodiment is branched into a first branch passage 2a and a second branch passage 2b on the way, and the first branch passage 2a and the second branch passage 2b are gathered downstream. . The oxidation catalyst 4 is provided in the first branch passage 2a, and no catalyst is provided in the second branch passage 2b.

  The outer diameter of the oxidation catalyst 4 is larger than the inner diameter of the first branch passage 2a. A fuel addition valve 6 is provided upstream of the oxidation catalyst 4 in the first branch passage 2a. An HC sensor 9 is provided in the exhaust passage 2 on the downstream side of the downstream gathering portion of the first branch passage 2a and the second branch passage 2b. A filter 5 is provided in the exhaust passage 2 downstream of the HC sensor 9.

  Since the configuration other than the above is the same as the configuration shown in FIG. 1, their illustration and description are omitted.

  In this modification, the exhaust gas flowing through the exhaust passage 2 is divided into a first branch passage 2a and a second branch passage 2b. For this reason, in the case of the configuration as in the present modified example, as in the case of the configuration shown in FIG. Then, the HC sensor 9 detects exhaust gas that has passed through the oxidation catalyst 4 (that is, exhaust gas that has flowed through the first branch passage 2a) and exhaust gas that has not passed through the oxidation catalyst 4 (that is, exhaust gas that has flowed through the second branch passage 2b). The HC concentration of the exhaust gas mixed with is detected.

  Therefore, even in the case of the configuration as in this modification, the method for calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 as described above can be applied.

<Example 2>
FIG. 6 is a diagram showing a schematic configuration of the intake and exhaust system of the internal combustion engine according to the present embodiment. In this embodiment, instead of the HC sensor 9 in the first embodiment, first and second temperature sensors 13 and 14 for detecting the temperature of the exhaust are provided. The first temperature sensor 13 is provided in the exhaust passage 2 on the downstream side of the oxidation catalyst 4 so as to face the downstream end of the oxidation catalyst 4, and detects the temperature of the exhaust gas flowing out from the oxidation catalyst 4. The second temperature sensor 14 is provided downstream of the first temperature sensor 13 in the exhaust passage 2 and after a position where the exhaust gas that has passed through the oxidation catalyst 4 and the exhaust gas that has not passed through the oxidation catalyst 4 are mixed. Yes. The first and second temperature sensors 13 and 14 are electrically connected to the ECU 10. These output signals are input to the ECU 10.

  Since the configuration other than the above is the same as the configuration shown in FIG. 1, the same reference numerals are given to the same components and the description thereof is omitted. Also in this embodiment, the filter 5 is oxidized when the PM collected by the filter 5 is oxidized and removed, or when the SOx occluded in the NOx catalyst supported by the filter 5 is released and reduced. When it is necessary to raise the temperature, the temperature raising control similar to that in the first embodiment is performed.

<Calculation of exhaust gas flow rate through catalyst>
Here, a method for calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to the present embodiment will be described. In this embodiment, the exhaust temperature detected by the first temperature sensor 13 is a first downstream temperature Tgd1, and the exhaust temperature detected by the second temperature sensor 14 is a second downstream temperature Tgd2.

  As the HC in the exhaust gas flowing into the oxidation catalyst 4 is oxidized in the oxidation catalyst 4, the first and second downstream temperatures Tgd1, Tgd2 compared to the upstream temperature Tgin which is the temperature of the exhaust gas flowing into the oxidation catalyst 4 Becomes higher. At this time, since the temperature of the exhaust gas that has flowed downstream from the oxidation catalyst 4 without passing through the oxidation catalyst 4 does not increase, the exhaust gas that has passed through the oxidation catalyst 4 and the exhaust gas that has not passed through the catalyst are mixed. Is lower than the first downstream temperature Tgd1, which is the temperature of the exhaust gas flowing out from the oxidation catalyst 4.

And in a present Example, following formula (1) is materialized.
Gcat = (Tgd2-Tgin) / (Tgd1-Tgin) (1)
Gcat: the flow rate of exhaust gas passing through the oxidation catalyst 4

  Therefore, in this embodiment, the flow rate of the exhaust gas passing through the catalyst is calculated based on the above formula (1).

  Here, a routine for calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to the present embodiment will be described based on the flowchart shown in FIG. This routine is stored in the ECU 10 in advance. This routine may be repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1, or may be executed when a predetermined condition is satisfied during the operation of the internal combustion engine 1.

  In this routine, first, in S501, the ECU 10 calculates the upstream temperature Tgin based on the operating state of the internal combustion engine 1 and the like. In this embodiment, the ECU 10 that executes S501 corresponds to the upstream temperature detecting means according to the present invention.

  Next, the ECU 10 proceeds to S502, and reads the first downstream temperature Tgd1 detected by the first temperature sensor 13.

Next, the ECU 10 proceeds to S503, and reads the second downstream temperature Tgd2 detected by the second temperature sensor 14.

  Next, the ECU 10 proceeds to S504, and calculates the flow rate Gcat of the exhaust gas passing through the oxidation catalyst 4 based on the above equation (1). In the present embodiment, the ECU 10 that executes S504 corresponds to the catalyst passage exhaust gas flow rate calculating means according to the present invention.

  According to this embodiment, the flow rate of the exhaust gas passing through the oxidation catalyst 4 can be calculated with higher accuracy.

  In the present embodiment, the upstream temperature Tgin is calculated based on the operating state of the internal combustion engine 1, but the upstream temperature Tgin is detected by the temperature sensor as with the first and second downstream temperatures Tgd1 and Tgd2. May be. In this case, the temperature sensor provided in the exhaust passage 2 upstream of the oxidation catalyst 4 corresponds to the upstream temperature detection means according to the present invention.

<Modification 1>
Next, a first modification of the present embodiment will be described. FIG. 8 is a diagram showing a schematic configuration of an exhaust passage according to this modification. The shape of the exhaust passage 2 according to this modification is the same as the shape of the exhaust passage 2 according to Modification 3 of the first embodiment. Further, the oxidation catalyst 4, the filter 5, and the fuel addition valve 6 are provided at the same positions as in the third modification of the first embodiment. Further, the first temperature sensor 13 is provided downstream of the oxidation catalyst 4 in the first branch passage 2a, and the second temperature sensor 14 is provided at the position where the HC sensor 9 is provided in the third modification of the first embodiment. Is provided.

  Also in the configuration of this modification, the first temperature sensor 13 detects the temperature of the exhaust gas flowing out from the oxidation catalyst 4, and the second temperature sensor 14 is the exhaust gas that has passed through the oxidation catalyst 4 and the exhaust gas that has not passed through the oxidation catalyst 4. The temperature of the exhaust gas mixed with is detected. Therefore, even in the case of the configuration as in this modification, the method for calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to this embodiment can be applied.

<Example 3>
The schematic configuration of the intake and exhaust system of the internal combustion engine according to the present embodiment is the same as that of the first embodiment. Also in this embodiment, the filter 5 is oxidized when the PM collected by the filter 5 is oxidized and removed, or when the SOx occluded in the NOx catalyst supported by the filter 5 is released and reduced. When it is necessary to raise the temperature, the temperature raising control similar to that in the first embodiment is performed.

<Calculation method of exhaust gas flow rate through catalyst>
Even if the actual flow rate of exhaust gas passing through the oxidation catalyst 4 is the same and the amount of HC flowing into the oxidation catalyst 4 is the same, the higher the temperature Tc of the oxidation catalyst 4, the more HC is oxidized in the oxidation catalyst 4. Become more. Therefore, the higher the temperature Tc of the oxidation catalyst 4, the lower the downstream HC concentration Chcd, and as a result, the value of the flow rate Gcat of the exhaust gas passing through the oxidation catalyst 4 calculated by the method according to the first embodiment may increase. There is. Therefore, in this embodiment, the flow rate Gcat of the exhaust gas passing through the oxidation catalyst 4 calculated by the same method as in the first embodiment is corrected based on the temperature of the oxidation catalyst 4.

  Hereinafter, a routine for calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to the present embodiment will be described based on the flowchart shown in FIG. This routine is stored in the ECU 10 in advance. This routine may be repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1, or may be executed when a predetermined condition is satisfied during the operation of the internal combustion engine 1. Since S101 to S104 in this routine are the same as the flowchart shown in FIG. 2, only S605 to S607 will be described.

In this routine, the ECU 10 proceeds to S605 after S104. In S605
The ECU 10 calculates the temperature Tc of the oxidation catalyst 4 based on the operating state of the internal combustion engine 1 and the like.

  Next, the ECU 10 proceeds to S606, and calculates a correction coefficient α for correcting the flow rate Gcat of the exhaust gas passing through the oxidation catalyst 4 in S607 described later based on the temperature Tc of the oxidation catalyst 4. In the present embodiment, the relationship between the temperature Tc of the oxidation catalyst 4 and the correction coefficient α is stored in advance in the ECU 10 as a map. In the map, the correction coefficient α is set to a smaller value as the temperature Tc of the oxidation catalyst 4 is higher.

  Next, the ECU 20 proceeds to S607, and calculates a correction value Gcat ′ for the flow rate of the exhaust gas passing through the oxidation catalyst 4 by multiplying the correction rate α to the flow rate Gcat of the exhaust gas passing through the oxidation catalyst 4 calculated in S104. To do. Thereafter, the ECU 10 once terminates execution of this routine.

  According to the routine described above, the flow rate of the exhaust gas passing through the oxidation catalyst 4 is calculated in consideration of the temperature Tc of the oxidation catalyst 4. Therefore, the flow rate of the exhaust gas passing through the oxidation catalyst 4 can be calculated with higher accuracy.

  It should be noted that the correction method for the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to the present embodiment may also be applied to the above-described modification of the first embodiment and the second embodiment.

<Example 4>
The schematic configuration of the intake and exhaust system of the internal combustion engine according to the present embodiment is the same as that of the first embodiment. Also in this embodiment, the filter 5 is oxidized when the PM collected by the filter 5 is oxidized and removed, or when the SOx occluded in the NOx catalyst supported by the filter 5 is released and reduced. When it is necessary to raise the temperature, the temperature raising control similar to that in the first embodiment is performed.

<Calculation method of exhaust gas flow rate through catalyst>
As described above, the amount of HC oxidized in the oxidation catalyst 4 changes according to the temperature Tc of the oxidation catalyst 4. However, when the temperature of the oxidation catalyst 4 is equal to or higher than the maximum activation temperature, which is a threshold at which the degree of activity is near the upper limit, the amount of HC oxidized in the oxidation catalyst 4 is difficult to change according to the temperature of the oxidation catalyst 4. For this reason, when the temperature of the oxidation catalyst 4 becomes equal to or higher than the most active temperature, the influence of the temperature of the oxidation catalyst 4 on the ratio of the upstream HC concentration and the downstream HC concentration becomes small. Therefore, in this embodiment, the flow rate of the exhaust gas passing through the oxidation catalyst 4 is calculated when the temperature of the oxidation catalyst 4 is equal to or higher than the most active temperature.

  Hereinafter, a routine for calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to the present embodiment will be described based on the flowchart shown in FIG. This routine is stored in the ECU 10 in advance. This routine may be repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1, or may be executed when a predetermined condition is satisfied during the operation of the internal combustion engine 1. Since S101 to S104 in this routine are the same as the flowchart shown in FIG. 2, only S701 and S702 will be described.

  In this routine, the ECU 10 first calculates the temperature Tc of the oxidation catalyst 4 based on the operating state of the internal combustion engine 1 in S701.

  Next, the ECU 10 proceeds to S702 and determines whether or not the temperature Tc of the oxidation catalyst 4 is equal to or higher than the most active temperature Tcm. The most active temperature Tcm is predetermined based on experiments and the like. If an affirmative determination is made in S702, the ECU 10 proceeds to S101, and if a negative determination is made, the ECU 10 once ends the execution of this routine.

  According to the routine described above, the flow rate of the exhaust gas passing through the oxidation catalyst 4 is calculated when the ratio between the upstream HC concentration and the downstream HC concentration is stable. Therefore, the flow rate of the exhaust gas passing through the oxidation catalyst 4 can be calculated with higher accuracy.

  In the modified example of Example 1 and Example 2 as well, the flow rate of the exhaust gas passing through the oxidation catalyst 4 can be calculated when the temperature of the oxidation catalyst 4 is equal to or higher than the most active temperature. Good.

<Example 5>
The schematic configuration of the intake and exhaust system of the internal combustion engine according to the present embodiment is the same as that of the first embodiment. Also in this embodiment, the filter 5 is oxidized when the PM collected by the filter 5 is oxidized and removed, or when the SOx occluded in the NOx catalyst supported by the filter 5 is released and reduced. When it is necessary to raise the temperature, the temperature raising control similar to that in the first embodiment is performed.

<Calculation method of exhaust gas flow rate through catalyst>
The higher the temperature of the oxidation catalyst 4, the higher the temperature of the exhaust gas flowing through the oxidation catalyst 4, and the viscosity coefficient of the exhaust gas flowing through the oxidation catalyst 4 increases accordingly. Therefore, even if the flow rate of the exhaust gas flowing through the exhaust passage 2 upstream of the oxidation catalyst 4 is the same, the flow rate of the exhaust gas passing through the oxidation catalyst 4 decreases as the temperature of the oxidation catalyst 4 increases.

  Therefore, in this embodiment, when the temperature of the oxidation catalyst 4 is a predetermined temperature, the reference value of the flow rate of the exhaust gas passing through the oxidation catalyst 4 is calculated by the same method as in the first embodiment. When the temperature of the oxidation catalyst 4 is other than the predetermined temperature, the flow rate of the exhaust gas passing through the oxidation catalyst 4 is calculated by correcting the reference value according to the temperature of the oxidation catalyst 4.

  Hereinafter, a routine for calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to the present embodiment will be described based on the flowchart shown in FIG. This routine is stored in the ECU 10 in advance. This routine may be repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1, or may be executed when a predetermined condition is satisfied during the operation of the internal combustion engine 1. Since S101 to S103 in this routine are the same as those in the flowchart shown in FIG. 2, only the other steps will be described.

  In this routine, first, in S801, the ECU 10 calculates the temperature Tc of the oxidation catalyst 4 based on the operating state of the internal combustion engine 1 and the like.

  Next, the ECU 10 proceeds to S802, and determines whether or not the temperature Tc of the oxidation catalyst 4 is a predetermined temperature Tc0. The predetermined temperature Tc0 is a predetermined temperature. If an affirmative determination is made in S802, the ECU 10 proceeds to S101, and if a negative determination is made, the ECU 10 proceeds to S805.

  In this routine, the ECU 10 proceeds to S804 after S103. In step S804, the ECU 10 multiplies the total exhaust gas flow rate Ga calculated based on the detected value of the air flow meter 8 by the catalyst passage rate Rcg calculated in step S103, thereby determining the reference flow rate of the exhaust gas passing through the oxidation catalyst 4. The value Gcatbase is calculated. This reference value Gcatbase is stored in the ECU 10. Thereafter, the ECU 10 once ends this routine.

On the other hand, the ECU 10 having advanced to S805 calculates a correction coefficient β for correcting the reference value Gcatbase of the flow rate of the exhaust gas passing through the oxidation catalyst 4 in S806 described later, based on the temperature Tc of the oxidation catalyst 4. The relationship between the temperature Tc of the oxidation catalyst 4 and the correction coefficient β is stored in advance in the ECU 10 as a map. As described above, even if the flow rate of the exhaust gas flowing through the exhaust passage 2 upstream of the oxidation catalyst 4 is the same, the oxidation catalyst 4 increases as the temperature Tc of the oxidation catalyst 4 increases.
The flow rate of the exhaust gas passing through is reduced. Therefore, in the map, the correction coefficient β is larger than 1 in the region where the temperature Tc of the oxidation catalyst 4 is lower than the predetermined temperature Tc0, and the correction coefficient β in the region where the temperature Tc of the oxidation catalyst 4 is higher than the predetermined temperature Tc0. Is smaller than 1. Further, the correction coefficient β is smaller as the temperature Tc of the oxidation catalyst 4 is higher.

  Next, the ECU 10 proceeds to S806, and calculates the flow rate Gcat of the exhaust gas passing through the oxidation catalyst 4 by multiplying the reference value Gcatbase stored in the ECU 10 by the correction coefficient β calculated in S805. Thereafter, the ECU 10 once ends this routine.

  According to the routine described above, the flow rate of the exhaust gas passing through the oxidation catalyst 4 is calculated in consideration of the temperature Tc of the oxidation catalyst 4. Therefore, the flow rate of the exhaust gas passing through the oxidation catalyst 4 can be calculated with higher accuracy.

  In the modification of Example 1 and Example 2 as well, when the temperature of the oxidation catalyst 4 is a predetermined temperature, the reference value of the flow rate of the exhaust gas passing through the oxidation catalyst 4 is calculated by each method, and the oxidation catalyst 4 When the temperature is other than the predetermined temperature, the reference value may be corrected by the same method as in this embodiment.

<Example 6>
The schematic configuration of the intake and exhaust system of the internal combustion engine according to the present embodiment is the same as that of the second embodiment. Also in this embodiment, the filter 5 is oxidized when the PM collected by the filter 5 is oxidized and removed, or when the SOx occluded in the NOx catalyst supported by the filter 5 is released and reduced. When it is necessary to raise the temperature, the temperature raising control similar to that in the first embodiment is performed.

<Calculation of exhaust gas flow rate through catalyst>
Here, a method for calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to the present embodiment will be described. Also in this embodiment, as in the second embodiment, the temperature of the exhaust gas flowing into the oxidation catalyst 4 is set as the upstream temperature Tgin, the temperature of the exhaust gas detected by the first temperature sensor 13 is set as the first downstream temperature Tgd1, The temperature of the exhaust gas detected by the two temperature sensor 14 is set as a second downstream temperature Tgd2.

  In the case of the configuration of the present embodiment, when the upstream temperature Tgin decreases, the first and second downstream temperatures Tgd1 and Tgd2 also decrease accordingly, but the first downstream temperature Tgd1 is the second downstream temperature. The timing at which it begins to decrease is slower than Tgd2. As the flow rate of the exhaust gas passing through the oxidation catalyst 4 increases, the time difference between the timing at which the first downstream temperature Tgd1 begins to decrease and the timing at which the second downstream temperature Tgd2 begins to decrease increases.

  Therefore, in this modified example, the oxidation catalyst 4 is passed based on the time difference between the timing when the first downstream temperature Tgd1 starts decreasing when the upstream temperature Tgin decreases and the timing when the second downstream temperature Tgd2 starts decreasing. Calculate the flow rate of exhaust gas.

  Here, a routine for calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to this modification will be described based on the flowchart shown in FIG. This routine is stored in the ECU 10 in advance. This routine may be repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1, or may be executed when a predetermined condition is satisfied during the operation of the internal combustion engine 1.

  In this routine, the ECU 10 first calculates the upstream temperature Tgin based on the operating state of the internal combustion engine 1 in S901. In the present embodiment, the ECU 10 that executes S901 corresponds to the upstream temperature detecting means according to the present invention.

  Next, the ECU 10 proceeds to S902 and determines whether or not the upstream temperature Tgin has started to decrease. If an affirmative determination is made in S902, the ECU 10 proceeds to S903, and if a negative determination is made, the ECU 10 once ends the execution of this routine.

  In S903, the ECU 10 detects the decrease start timings tdown1, tdown2 of the first and second downstream temperatures Tgd1, Tgd2 based on the output values of the first and second temperature sensors 13, 14, respectively.

  Next, the ECU 10 proceeds to S904, and calculates a time difference Δtdown between the decrease start timing tdown1 of the first downstream temperature Tgd1 and the decrease start timing tdown2 of the second downstream temperature Tgd2.

  Next, the ECU 10 proceeds to S905, and the flow rate Gcat of the exhaust gas passing through the oxidation catalyst 4 based on the time difference Δtdown between the decrease start timing tdown1 of the first downstream temperature Tgd1 and the decrease start timing tdown2 of the second downstream temperature Tgd2. Is calculated. At this time, the ECU 10 determines that the flow rate Gcat of the exhaust gas passing through the oxidation catalyst 4 increases as the time difference Δtdown increases. In this embodiment, the ECU 10 that executes S905 corresponds to the catalyst passage exhaust gas flow rate calculating means according to the present invention.

  According to this embodiment, the flow rate of the exhaust gas passing through the oxidation catalyst 4 can be calculated with higher accuracy.

  Also in this embodiment, the upstream temperature Tgin may be detected by a temperature sensor. In this case, the temperature sensor provided in the exhaust passage 2 upstream of the oxidation catalyst 4 corresponds to the upstream temperature detection means according to the present invention.

  Also in the case of the configuration as shown in FIG. 8, the method for calculating the flow rate of the exhaust gas passing through the oxidation catalyst 4 according to the present embodiment can be applied.

<Example 7>
The schematic configuration of the intake and exhaust system of the internal combustion engine according to the present embodiment is the same as that of the first embodiment. Also in this embodiment, the filter 5 is oxidized when the PM collected by the filter 5 is oxidized and removed, or when the SOx occluded in the NOx catalyst supported by the filter 5 is released and reduced. When it is necessary to raise the temperature, the temperature raising control similar to that in the first embodiment is performed. Further, the flow rate of the exhaust gas passing through the oxidation catalyst 4 is calculated in the same manner as in the first embodiment.

<Clogging elimination control>
The upstream end face of the oxidation catalyst 4 may be clogged with fuel or the like added from the fuel addition valve 6. When such clogging of the upstream end face occurs, the flow rate of the exhaust gas passing through the oxidation catalyst 4 is greatly reduced as compared with the normal case (that is, when the clogging of the upstream end face has not occurred). Therefore, in this embodiment, when the flow rate of the exhaust gas passing through the oxidation catalyst 4 calculated by the above method is equal to or less than a predetermined flow rate, it is determined that the upstream end face of the oxidation catalyst 4 is clogged, and this is determined. Execute clogging elimination control to eliminate.

  Here, the clogging elimination control routine according to the present embodiment will be described based on the flowchart shown in FIG. This routine is stored in advance in the ECU 10 and is repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1.

In this routine, the ECU 10 first reads the flow rate Gcat of the exhaust gas passing through the oxidation catalyst 4 calculated by the method as described above and stored in the ECU 10 in S1001.

  Next, the ECU 10 proceeds to S1002 and determines whether or not the flow rate Gcat of the exhaust gas passing through the oxidation catalyst 4 is equal to or less than a predetermined flow rate Gcat0. Here, the predetermined flow rate Gcat0 is a threshold at which it can be determined that the upstream end face of the oxidation catalyst 4 is clogged. The predetermined flow rate Gcat0 is determined in advance based on experiments or the like. If an affirmative determination is made in S1002, the ECU 10 proceeds to S1003, and if a negative determination is made, the ECU 10 once ends the execution of this routine.

  In step S1003, the ECU 10 executes clogging elimination control by raising the temperature of the oxidation catalyst 4. As a method of raising the temperature of the oxidation catalyst 4, a method of reducing the flow rate of exhaust gas by controlling the throttle valve 7 in the valve closing direction and adding a small amount of fuel from the fuel addition valve 6 in a plurality of times is added. It can be illustrated. By raising the temperature of the oxidation catalyst 4, SOF and the like adhering to the upstream end face is oxidized and removed. As a result, clogging of the upstream end face of the oxidation catalyst 4 is eliminated. Thereafter, the ECU 10 once ends this routine.

  According to the clog elimination control described above, clogging of the upstream end face of the oxidation catalyst 4 can be eliminated at a suitable timing.

  Note that the clogging elimination control according to the present embodiment may also be applied to the modification of the first embodiment and the second to sixth embodiments.

  The above embodiments can be combined as much as possible.

1 is a diagram showing a schematic configuration of an intake / exhaust system of an internal combustion engine according to Embodiment 1. FIG. 3 is a flowchart showing a routine for calculating a flow rate of exhaust gas passing through an oxidation catalyst according to the first embodiment. 7 is a flowchart showing a routine for calculating a flow rate of exhaust gas that passes through an oxidation catalyst according to a first modification of the first embodiment. 9 is a flowchart showing a routine for calculating a flow rate of exhaust gas that passes through an oxidation catalyst according to a second modification of the first embodiment. FIG. 6 is a diagram illustrating a schematic configuration of an exhaust passage according to a third modification of the first embodiment. FIG. 4 is a diagram illustrating a schematic configuration of an intake / exhaust system of an internal combustion engine according to a second embodiment. 7 is a flowchart showing a routine for calculating a flow rate of exhaust gas passing through an oxidation catalyst according to a second embodiment. FIG. 6 is a diagram illustrating a schematic configuration of an exhaust passage according to a first modification of the second embodiment. 9 is a flowchart showing a routine for calculating a flow rate of exhaust gas that passes through an oxidation catalyst according to a third embodiment. 10 is a flowchart showing a routine for calculating a flow rate of exhaust gas passing through an oxidation catalyst according to a fourth embodiment. 10 is a flowchart showing a routine for calculating a flow rate of exhaust gas that passes through an oxidation catalyst according to a fifth embodiment. 10 is a flowchart showing a routine for calculating a flow rate of exhaust gas passing through an oxidation catalyst according to a sixth embodiment. 10 is a flowchart illustrating a clogging elimination control routine according to a seventh embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Exhaust passage 3 ... Intake passage 4 ... Oxidation catalyst 5 ... Particulate filter 6 ... Fuel addition valve 7 ... Throttle valve 8 ... Air flow meter・ ・ ・ HC sensor 10 ・ ・ ECU
13. First temperature sensor 14. Second temperature sensor

Claims (12)

A catalyst having an oxidation function installed so that a part of the exhaust gas passes through the exhaust passage of the internal combustion engine instead of the total amount;
Based on the ratio of the HC concentration of the exhaust flowing into the catalyst and the HC concentration of the exhaust mixed with the exhaust that has passed through the catalyst and the exhaust that has not passed through the catalyst on the downstream side of the catalyst, A catalyst passage rate calculating means for calculating a catalyst passage rate that is a ratio of a flow rate of the exhaust gas passing through the catalyst with respect to a total flow rate;
An internal combustion engine comprising: a catalyst passing exhaust gas flow rate calculating unit that calculates a flow rate of exhaust gas passing through the catalyst based on the catalyst passing rate calculated by the catalyst passing rate calculating unit and a total exhaust gas flow rate. Exhaust purification equipment. The catalyst passage rate calculating means is
Upstream HC concentration detection means for detecting the HC concentration of the exhaust gas flowing into the catalyst;
An HC sensor that is provided downstream of the catalyst in the exhaust passage and after the position where the exhaust gas that has passed through the catalyst and the exhaust gas that has not passed through the catalyst are mixed, and that detects the HC concentration of the exhaust gas. ,
2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the catalyst passage rate is calculated based on the HC concentration detected by the upstream HC concentration detection means and the HC concentration detected by the HC sensor. The catalyst passage rate calculating means is
Upstream O ₂ concentration detection means for detecting the O ₂ concentration of the exhaust gas flowing into the catalyst;
An O ₂ sensor that is provided downstream of the catalyst in the exhaust passage and after the position where the exhaust gas that has passed through the catalyst and the exhaust gas that has not passed through the catalyst are mixed, and detects the O ₂ concentration of the exhaust gas; Have
Based on said upstream O ₂ wherein the detected O ₂ concentration by the concentration detecting means O ₂ O ₂ concentration detected by the sensor, the HC concentration of the exhaust gas flowing into the catalyst, the downstream side of the catalyst The exhaust emission control device for an internal combustion engine according to claim 1, wherein the ratio of the HC concentration of the exhaust gas in which the exhaust gas that has passed through the catalyst and the exhaust gas that has not passed through the catalyst is mixed is calculated. The catalyst passage rate calculating means is
Upstream temperature detection means for detecting the temperature of the exhaust gas flowing into the catalyst;
A temperature sensor that is provided downstream of the catalyst in the exhaust passage and after the position where the exhaust gas that has passed through the catalyst and the exhaust gas that has not passed through the catalyst are mixed, and detects the temperature of the exhaust gas; ,
Based on the temperature detected by the upstream temperature detection means and the temperature detected by the temperature sensor, the HC concentration of the exhaust gas flowing into the catalyst, the exhaust gas that has passed through the catalyst downstream from the catalyst, and the 2. An exhaust emission control device for an internal combustion engine according to claim 1, wherein the ratio of the HC concentration of the exhaust gas mixed with the exhaust gas not passing through the catalyst is calculated. A catalyst having an oxidation function installed so that a part of the exhaust gas passes through the exhaust passage of the internal combustion engine instead of the total amount;
Upstream temperature detection means for detecting the temperature of the exhaust gas flowing into the catalyst;
A first temperature sensor that is provided so as to face the downstream end of the catalyst in the exhaust passage downstream of the catalyst and detects the temperature of the exhaust gas flowing out of the catalyst;
A second temperature sensor that is provided downstream of the first temperature sensor and detects the temperature of the exhaust gas provided after the position where the exhaust gas that has passed through the catalyst and the exhaust gas that has not passed through the catalyst are mixed;
Let Gcat be the flow rate of the exhaust gas that passes through the catalyst,
The exhaust gas temperature detected by the upstream temperature detection means is Tgin,
The temperature of the exhaust detected by the first temperature sensor is Tgd1,
When the temperature of the exhaust detected by the second temperature sensor is Tgd2,
Gcat = (Tgd2-Tgin) / (Tgd1-Tgin)
An exhaust gas purification apparatus for an internal combustion engine, comprising: a catalyst passing exhaust gas flow rate calculating means for calculating a flow rate of exhaust gas passing through the catalyst from an expression represented by:   6. The exhaust gas purification of an internal combustion engine according to claim 1, wherein the flow rate of exhaust gas passing through the catalyst calculated by the catalyst passing exhaust gas flow rate calculating means is corrected based on the temperature of the catalyst. apparatus.   When the temperature of the catalyst is equal to or higher than a maximum active temperature that is a threshold value at which the degree of activity of the catalyst is near the upper limit, the flow rate of exhaust gas passing through the catalyst is calculated by the catalyst passing exhaust gas flow rate calculating means. An exhaust emission control device for an internal combustion engine according to any one of claims 1 to 5. The catalyst passage exhaust gas flow rate calculating means is
When the temperature of the catalyst is a predetermined temperature, a reference value of the flow rate of the exhaust gas passing through the catalyst is calculated,
6. The flow rate of exhaust gas passing through the catalyst is calculated by correcting the reference value based on the temperature of the catalyst when the temperature of the catalyst is other than the predetermined temperature. The exhaust gas purification apparatus for an internal combustion engine according to any one of the above. A catalyst having an oxidation function installed so that a part of the exhaust gas passes through the exhaust passage of the internal combustion engine instead of the total amount;
Upstream temperature detection means for detecting the temperature of the exhaust gas flowing into the catalyst;
A first temperature sensor that is provided so as to face the downstream end of the catalyst in the exhaust passage downstream of the catalyst and detects the temperature of the exhaust gas flowing out of the catalyst;
A second temperature sensor that is provided downstream of the first temperature sensor and detects the temperature of the exhaust gas provided after the position where the exhaust gas that has passed through the catalyst and the exhaust gas that has not passed through the catalyst are mixed;
The timing at which the exhaust temperature detected by the first temperature sensor starts to decrease and the exhaust temperature detected by the second temperature sensor when the exhaust temperature detected by the upstream temperature detection means decreases. An exhaust gas purification apparatus for an internal combustion engine, comprising: a catalyst passage exhaust gas flow rate calculating means for calculating a flow rate of exhaust gas that passes through the catalyst based on a time difference from a timing of starting to decrease.   When the flow rate of the exhaust gas passing through the catalyst calculated by the catalyst passing exhaust gas flow rate calculating means is equal to or lower than a predetermined flow rate, the clogging elimination control is performed to eliminate the clogging of the upstream end face of the catalyst by raising the temperature of the catalyst. The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 9, wherein the exhaust gas purification device is executed.   The said catalyst is installed in the said exhaust passage so that exhaust_gas | exhaustion may flow between the outer peripheral surface of the said catalyst, and the internal peripheral surface of the said exhaust passage. An exhaust purification device for an internal combustion engine. The exhaust passage is formed so as to branch into a plurality of branch passages on the way, and the plurality of branch passages gather on the downstream side;
The exhaust purification device of an internal combustion engine according to any one of claims 1 to 10, wherein the catalyst is installed only in any one of the plurality of branch passages.

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