JP2019210891A - Exhaust gas temperature control method and exhaust gas purification device - Google Patents

Abstract

To provide a method capable of performing exhaust gas temperature control with satisfactory and accurate responsiveness to sudden fluctuation of a control state.SOLUTION: In exhaust gas temperature control, a catalyst non-arrival rate funr to be used for calculating a post injection fuel quantity Qpost that is the quantity of a non-combusted fuel injected by post injection is calculated as funr=(Qpost-Qhbur)/Qpost by using the post injection fuel quantity Qpost and a combusted hydrocarbon quantity Qhbur that is a hydrocarbon quantity combusted by an oxidation catalyst or nitrogen oxide storage/reduction catalyst. The combusted hydrocarbon quantity Qhbur is calculated as a differential between an oxygen concentration at an upstream side of the oxidation catalyst or the nitrogen oxide storage/reduction catalyst and an oxygen concentration at a downstream side of the oxidation catalyst or the nitrogen oxide storage/reduction catalyst, thereby securing satisfactory responsiveness to sudden fluctuation of a control state.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for controlling exhaust gas temperature in an exhaust gas purification apparatus, and more particularly, to an apparatus for improving responsiveness, reducing apparatus cost, and the like.

  In vehicles using diesel engines, in order to perform exhaust that complies with exhaust gas regulations, nitrogen oxide storage and reduction catalyst (NSC) that stores nitrogen oxides (NOx) and exhaust particulates in exhaust gas are collected. It is well known that an exhaust gas purifying device configured using a diesel particulate filter (DPF) or the like is mounted.

In such an exhaust gas purification device, exhaust gas temperature control is required for desulfurization of the nitrogen oxide storage reduction catalyst and regeneration of the diesel particulate filter.
Various methods and devices have been proposed and put into practical use for the method of temperature control for desulfurization of the nitrogen oxide storage reduction catalyst and regeneration of the diesel particulate collection filter. By supplying unburned hydrocarbons (HC) to the catalyst by post-injection, and raising the temperature of the exhaust gas by oxidation reaction heat, or injecting unburned fuel directly into the exhaust pipe and burning the fuel in the exhaust pipe As a typical method, a method of raising the exhaust temperature by the above is known (for example, see Patent Document 1).

In the method of controlling the temperature of exhaust gas by post injection as described above, the amount of fuel required for post injection and the amount of fuel directly injected into the exhaust pipe are based on the temperature of the catalyst itself and the temperature information around it. It is often calculated.
In recent years, a method using a temperature model has been put to practical use in the temperature control of exhaust gas as described above.

For example, based on the test results and simulation results, a catalyst temperature model that models the temperature change of the oxidation catalyst or nitrogen oxide storage reduction catalyst is set, and the temperature of the catalyst itself can be calculated and other temperatures required. A temperature control system used for calculating an estimated value or the like has been constructed and used as an exhaust gas temperature control system.
In such a temperature control system, the fuel amount required for post injection (hereinafter referred to as “post-injection fuel amount”) is obtained based on Equation 1 below.

  dmPoI1 = (dmFuOpnLop-dmFuPoI2) / (1-facPoI1 cmb) Equation 1

  Here, “dmPoI1” is the indicated post-injection fuel amount, “dmFuOpnLop” is the amount of fuel to be supplied to the oxidation catalyst or nitrogen oxide storage reduction catalyst, and “facPoI1cmb” is the amount of fuel injected against the amount of fuel injected. The ratio of the amount of fuel that does not reach the catalyst or the nitrogen oxide storage reduction catalyst (hereinafter referred to as “catalyst unreachable rate” for convenience of explanation), “dmFuPoI2” is performed to increase the exhaust temperature after the main injection. It is the amount of fuel that reaches the oxidation catalyst or the nitrogen oxide storage reduction catalyst without burning during after injection.

  Here, the amount “dmFuOpnLop” of the fuel to be supplied to the oxidation catalyst or the nitrogen oxide storage reduction catalyst is calculated by the following equation 2.

  dmFuOpnLop = dmFuSum / (1-rSlip) Equation 2

In Equation 2, “dmFuSum” is the amount of fuel that needs to be burned in the oxidation catalyst or nitrogen oxide storage reduction catalyst to achieve the target temperature of the oxidation catalyst or nitrogen oxide storage reduction catalyst, and “dmFuOpnLop” On the other hand, the amount corresponding to the unfueled amount that flows downstream from the catalyst without being completely treated with the catalyst is subtracted.
This “dmFuSum” is a test result in advance using a target temperature downstream of the oxidation catalyst or nitrogen oxide storage reduction catalyst, an actual measurement temperature upstream of the oxidation catalyst or nitrogen oxide storage reduction catalyst, an actual measurement value of the exhaust gas flow rate, and the like. Or an arithmetic expression determined on the basis of a simulation result or the like.

“RSlip” is supplied when the amount of fuel “dmFuOpnLop” to be supplied to the oxidation catalyst or nitrogen oxide storage reduction catalyst described above is supplied to the oxidation catalyst or nitrogen oxide storage reduction catalyst. It is a slip ratio which shows the ratio of the quantity of the fuel which remains without being burned with respect to the quantity of the made fuel.
This slip ratio is determined based on an arithmetic expression determined based on a test result or a simulation result, and is further corrected using a catalyst temperature or an exhaust gas flow rate.

  Further, the catalyst unreachable rate facPoI1cmb is determined by, for example, a map created based on a test result or a simulation result. The catalyst non-reaching rate facPoI1 cmb determined by such a map is determined according to the operating condition of the engine, for example. Specifically, the engine operating status is, for example, engine speed, engine torque, and the like, and the map is configured so that the catalyst non-reaching rate facPoI 1 cmb corresponding to the input can be read out using these as inputs. .

By the way, in the temperature control system using the temperature model as described above, a plurality of sensors are used. However, some errors and fluctuations are inevitable in these output values, and further, deterioration of the catalyst is also avoided. I want to.
For this reason, in the temperature control system as described above, in order to improve the accuracy and reliability of the temperature control, the sensor output value and temperature model are considered in consideration of sensor errors and fluctuations, as well as catalyst deterioration. In general, various compensations are performed based on various temperature information. Specifically, the exhaust gas temperature model value equivalent to the temperature sensor downstream of the catalyst derived from the temperature model is compared with the exhaust gas temperature model value measured by the actual exhaust gas temperature sensor, and the difference is used as a model error. A method for correcting the catalyst inlet temperature as an input is known.

JP, 2006-20737, A

In general, compensation based on temperature has relatively good adaptability as a whole control, but on the other hand, depending on the usage situation, it becomes a slow change until it reaches the desired control state, and there is a problem that it is inferior in terms of responsiveness and responsiveness. is there.
For example, the above-mentioned catalyst unreachable rate facPoI1 cmb is determined according to the operating condition of the engine. However, if there is a sudden change in the operating condition of the engine for some reason, the compensation based on the temperature information cannot ensure accurate exhaust gas temperature control with good responsiveness, and deviates from the desired exhaust gas temperature control state. There is a problem of falling into.

  The present invention has been made in view of the above circumstances, and provides an exhaust gas temperature control method and an exhaust gas purification device that are capable of accurate exhaust gas temperature control with good responsiveness to rapid fluctuations in the control state. is there.

In order to achieve the above object of the present invention, an exhaust gas temperature control method according to the present invention comprises:
An exhaust gas temperature control method for controlling the exhaust purification device to a desired temperature by injecting unburned fuel by post injection,
The post-injection fuel amount Qpost, which is the amount of unburned fuel injected by the post-injection, is used to set the oxidation catalyst or nitrogen oxide storage reduction catalyst as the exhaust purification device to a desired temperature. The amount of fuel Qnsc to be supplied to the physical storage reduction catalyst, the catalyst unreachable rate funr, which is the ratio of the amount of fuel that does not reach the nitrogen oxide storage reduction catalyst among the post injection fuel amount to the post injection fuel amount, And, using the amount Qafr of the fuel that reaches the oxidation catalyst or the nitrogen oxide storage reduction catalyst without burning during the after injection, it is obtained as Qpost = (Qnsc−Qafr) / (1-funr) In the exhaust gas temperature control method used for post injection,
The catalyst unreachable rate funr is calculated by using the post-injected fuel amount Qpost and the combustion hydrocarbon amount Qhbur which is the amount of hydrocarbon burned by the oxidation catalyst or the nitrogen oxide storage reduction catalyst, and funr = (Qpost−Qhbur) / Qpost is required,
The combustion hydrocarbon amount is configured to be obtained as a difference between an oxygen concentration upstream of the oxidation catalyst or the nitrogen oxide storage reduction catalyst and an oxygen concentration downstream of the oxidation catalyst or the nitrogen oxide storage reduction catalyst. It will be.
In order to achieve the above object of the present invention, an exhaust gas purifying apparatus according to the present invention comprises:
While having an oxidation catalyst or nitrogen oxide storage reduction catalyst and a diesel particulate filter in an exhaust pipe connected to the internal combustion engine of the vehicle,
The electronic control unit performs unburned fuel injection by post-injection of the fuel injection valve in order to regenerate the catalyst and diesel particulate collection filter or to activate the nitrogen oxide selective reduction catalyst installed downstream. In the exhaust gas purification apparatus configured to be able to control the temperature in the exhaust gas purification device to a desired temperature,
The electronic control unit is
In order to set the post-injected fuel amount Qpost, which is the amount of unburned fuel injected by the post injection, to the desired temperature for the oxidation catalyst or the nitrogen oxide storage reduction catalyst as the exhaust purification device, the oxidation catalyst or The amount of fuel Qnsc to be supplied to the nitrogen oxide storage reduction catalyst, and the catalyst unreachable which is the ratio of the amount of fuel not reaching the nitrogen oxide storage reduction catalyst to the post injection fuel amount in the post injection fuel amount Calculated as Qpost = (Qnsc−Qafr) / (1−funr), using the rate funr and the amount Qafr of the fuel that reaches the oxidation catalyst or the NOx storage reduction catalyst without burning during after-injection And
Using the post-injected fuel amount Qpost and the combustion hydrocarbon amount Qhbur which is the amount of hydrocarbon burned by the oxidation catalyst or the nitrogen oxide storage reduction catalyst, the catalyst unreachable rate funr is expressed as funr = (Qpost−Qhbur) / While calculating Qpost,
The combustion hydrocarbon amount is calculated as a difference between the oxygen concentration upstream of the oxidation catalyst or the nitrogen oxide storage reduction catalyst and the oxygen concentration downstream of the oxidation catalyst or the nitrogen oxide storage reduction catalyst. It will be.

  According to the present invention, instead of using the catalyst unreachable rate set in advance from the experimental results based on temperature or the like, the catalyst unreachable rate is always calculated, so even if a sudden change in the control state occurs In addition, the post-injection fuel amount calculated using the catalyst unreachable rate can be set to an accurate value with good responsiveness, and accurate exhaust gas temperature control can be realized with good responsiveness to sudden fluctuations in the control state. This is an effect.

It is a block diagram which shows the structural example of the exhaust gas purification apparatus with which the exhaust gas temperature control method in embodiment of this invention is applied. It is a subroutine flowchart which shows the procedure of the exhaust gas temperature control process in embodiment of this invention. It is a functional block diagram showing the function required for an electronic control unit for execution of exhaust gas temperature control processing in an embodiment of the invention with a functional block. It is a functional block diagram showing the function performed in an electronic control unit by a functional block when propagation time compensation in exhaust gas temperature control processing in an embodiment of the invention is performed in an electronic control unit. It is the functional block diagram which represented the function performed in an electronic control unit by the functional block when the learning process in the exhaust gas temperature control process in embodiment of this invention is performed in an electronic control unit.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.
The members and arrangements described below do not limit the present invention and can be variously modified within the scope of the gist of the present invention.
First, a configuration example of an exhaust gas purification apparatus to which an exhaust gas temperature control method according to an embodiment of the present invention is applied will be described with reference to FIG.
The exhaust gas purifying apparatus according to the embodiment of the present invention includes a nitrogen oxide storage and reduction catalyst (NOx Storage Catalyst) 23 and a diesel particulate filter (Diesel Particulate Filter) as exhaust purification devices provided at appropriate positions of the exhaust pipe 22. ) 24 and an electronic control unit 30 for controlling the temperature of the exhaust gas.

More specifically, first, an intake pipe 21 for taking in air necessary for fuel combustion is provided in an intake manifold 20a of a diesel engine (hereinafter referred to as "engine") 20, and an exhaust manifold 20b is provided in an exhaust manifold 20b. Are connected to exhaust pipes 22 for exhaust.
An airflow sensor 1 for measuring the intake air intake amount is provided at an appropriate position of the intake pipe 21.
On the other hand, a nitrogen oxide storage / reduction catalyst (hereinafter referred to as “NSC”) 23 and a diesel particulate filter (hereinafter referred to as “DPF”) 24 are arranged in order from the upstream side at appropriate positions of the exhaust pipe 22. Has been.

  Here, the NSC 23 occludes nitrogen oxide (NOx) when the vehicle is in a normal driving state. When the fuel combustion state in the engine 1 is an excessive fuel combustion state that reduces the oxygen concentration in the exhaust gas, the stored nitrogen oxides can be reduced to harmless nitrogen and oxygen. Such a configuration is basically the same as the conventional one.

  Further, the DPF 24 is the same as the conventional one configured by using, for example, a honeycomb structure filter formed of a ceramic material.

A first lambda sensor 2 and a first temperature sensor 4 are respectively provided at appropriate positions of the exhaust pipe 22 on the upstream side of the NSC 23, while at an appropriate position of the exhaust pipe 22 between the NSC 23 and the DPF 24. A second lambda sensor 3 and a second temperature sensor 5 are provided.
Detection signals of these sensors 1 to 5 are input to the electronic control unit 30.

  The electronic control unit 30 includes, for example, a microcomputer having a known and well-known configuration, a storage element (not shown) such as a RAM and a ROM, and an input / output interface circuit (not shown). It is configured as a main component.

The electronic control unit 30 includes various detection signals of the sensors 1 to 5 as well as various signals necessary for operation control of the vehicle detected by a sensor (not shown), such as atmospheric pressure, engine speed, accelerator opening, The engine coolant temperature and the like are input.
As described above, the various detection signals input to the electronic control unit 30 are used for the fuel injection control process of the fuel injection valve 25, the exhaust gas temperature control process in the embodiment of the present invention to be described later, and the like. ing.

Next, the exhaust gas temperature control process in the embodiment of the present invention executed by the electronic control unit 30 will be described with reference to FIGS.
First, as a premise, in the exhaust gas purification apparatus according to the embodiment of the present invention, the exhaust gas temperature is controlled for activation of the exhaust gas purification device, that is, for desulfurization of the NSC 23 and regeneration of the DPF 24. It shall be. In this exhaust gas temperature control, unburned fuel is injected into a cylinder (not shown) of the engine 20 by the fuel injection valve 25 to generate oxidation reaction heat and raise the exhaust gas temperature, as in the prior art.

  The amount of fuel required for the injection of unburned fuel is obtained on the basis of Equation 1 shown in the description of the prior art as described above, as will be described later.

  dmPoI1 = (dmFuOpnLop-dmFuPoI2) / (1-facPoI1 cmb) Equation 1

Here, “dmPoI1” (hereinafter referred to as “Qpost” for convenience of description) is supplied to the post-injection fuel amount, and “dmFuOpnLop” (hereinafter referred to as “Qnsc” for convenience of description) is supplied to the nitrogen oxide storage reduction catalyst. The amount of fuel to be used, “facPoI 1 cmb” (hereinafter referred to as “funr” for convenience of explanation) is the catalyst unreachable rate.
The fuel injection in the embodiment of the present invention is based on the premise that after the main injection, after injection for burning unburned fuel is performed, and then post injection is performed.
“DmFuPoI2” is the amount of fuel that reaches the oxidation catalyst or the nitrogen oxide storage reduction catalyst without burning during the above-described after injection.

  The amount of fuel Qnsc to be supplied to the nitrogen oxide storage reduction catalyst is obtained based on the equation 2 shown in the description of the prior art as described above, as will be described later. .

  Qnsc = dmFuSum / (1-rSlip) Equation 2

  Under such a premise, in the exhaust gas temperature control process in the embodiment of the present invention, the catalyst unreachable rate funr used in the above-described equation 1 is obtained by a calculation process unique to the present invention described below, unlike the conventional case. It is supposed to be

Hereinafter, the calculation process of the catalyst unreachable rate funr will be described with appropriate reference to the flowchart shown in FIG. 2 and the functional block diagrams shown in FIGS.
When the control by the electronic control unit 30 is started, first, measured values of the catalyst upstream oxygen concentration and the catalyst downstream oxygen concentration are input (see step S100 in FIG. 2).
The detected value of the first lambda sensor 2 is used for the catalyst upstream oxygen concentration, and the detected value of the second lambda sensor 3 is used for the catalyst downstream oxygen concentration.
Since the lambda sensor outputs a signal having an output level corresponding to the oxygen concentration, the output signal can be used as the oxygen concentration at a desired location.

  There is a propagation delay until the exhaust gas whose oxygen concentration has been detected by the first lambda sensor 2 reaches the position of the second lambda sensor 3 on the downstream side. For this reason, in order to use the detection values of the first and second lambda sensors 2 and 3 for the arithmetic processing as described later, it is necessary to compensate for the difference in propagation time.

Therefore, in the next step S110, propagation time compensation is performed on the detection value of the first lambda sensor 2 (see reference numeral BL3-1 in FIG. 3).
FIG. 4 is a functional block diagram illustrating specific processing contents of propagation time compensation. Hereinafter, propagation time compensation in the embodiment of the present invention will be described with reference to FIG.

First, the propagation delay time is calculated with respect to the exhaust gas flow rate obtained based on the intake air amount detected by the airflow sensor 1 (see reference numeral BL4-1 in FIG. 4).
This propagation delay time is calculated on the basis of appropriately selected actual measurement data.
Specifically, for example, when the exhaust gas flow rate per hour is 50 kg / h, the propagation delay time until the exhaust gas reaches the second lambda sensor 3 from the first lambda sensor 2 is A second. To do.
If the exhaust gas flow rate at the time of obtaining the propagation delay time is Q kg / h, the propagation delay time at this exhaust gas flow rate is calculated as propagation delay time = A × (50 ÷ Q).

Here, “A” described above is a fixed value obtained in advance by a test, and is stored in an appropriate storage area in the electronic control unit 30 and used when calculating the propagation delay time.
Next, the catalyst upstream oxygen concentration obtained by the first lambda sensor 2 is subjected to the delay of the propagation delay time obtained as described above to obtain the catalyst upstream oxygen concentration that has been compensated for the delay time. (See symbol BL4-2 in FIG. 4).

  Returning to the description of the flowchart of FIG. 2 again, after the propagation time compensation for the catalyst upstream oxygen concentration (see step S110 in FIG. 2) is performed as described above, the catalyst upstream oxygen concentration and the catalyst downstream oxygen after the propagation time compensation are performed. A filtering process is performed on the density (see step S120 in FIG. 2 and reference symbols BL3-2 and BL3-3 in FIG. 3). Such filtering processing is generally performed in measurement data processing or the like, and removes abnormal data or noise data.

  After the filtering process, the difference between the catalyst upstream oxygen concentration and the catalyst downstream oxygen concentration after the propagation time compensation is calculated (see reference numeral BL3-4 in FIG. 3), and the difference is used for the catalyst unreachable rate calculation process described below. (See reference numeral BL3-5 in FIG. 3). Here, the difference between the catalyst upstream oxygen concentration and the catalyst downstream oxygen concentration after propagation time compensation is proportional to the amount of hydrocarbon (HC) burned in the NSC 23 (hereinafter referred to as “burned hydrocarbon amount” for convenience of explanation) Qhbur. .

When exhaust gas contains a large amount of hydrocarbons due to post injection or the like, the oxygen concentration detected by the lambda sensor tends to be lower than the true oxygen concentration due to the structure inside the lambda sensor. It is known.
Therefore, when calculating the difference between the catalyst upstream oxygen concentration and the catalyst downstream oxygen concentration, the difference between the detected value and the true value is compensated to obtain the difference between the true catalyst upstream oxygen concentration and the true catalyst downstream oxygen concentration. There is a need.

Specifically, the difference between the true catalyst upstream oxygen concentration and the true catalyst downstream oxygen concentration is obtained as described below.
First, the detection value of the first lambda sensor 2 is defined as the detection value of the upstream oxygen concentration of the catalyst, expressed as “ro2Us-m”, and the detection value of the second lambda sensor 3 is defined as the detection value of the downstream oxygen concentration of the catalyst. , “RO2Ds-m”.

The true catalyst upstream oxygen concentration is expressed as “rO2Us”, and the true catalyst downstream oxygen concentration is expressed as “rO2Ds”.
Further, the hydrocarbon concentration on the upstream side of the catalyst is expressed as “rHCUs”, and the hydrocarbon concentration on the downstream side of the catalyst is expressed as “rHCDs”.

  Under such a premise, first, the catalyst upstream oxygen concentration detection value and the catalyst downstream oxygen concentration detection value, the true catalyst upstream oxygen concentration and the true catalyst downstream oxygen concentration, the catalyst upstream side hydrocarbon concentration and the catalyst downstream side carbonization are detected. The relationship expressed by the following formulas 3a and 3b is established between the hydrogen concentrations.

  rO2Us-m = rO2Us-f * rHCUs Equation 3a

  ro2Ds-m = rO2Ds-f * rHCDs Equation 3b

Here, f is a compensation coefficient. Since this compensation coefficient varies depending on the specific specifications of the lambda sensor, it is preferable to set an appropriate value based on the test results and simulation results in consideration of the specific specifications. .
Further, the difference between the hydrocarbon concentration on the upstream side of the catalyst and the hydrocarbon concentration on the downstream side of the catalyst and the difference between the true catalyst upstream oxygen concentration and the true catalyst downstream oxygen concentration are expressed by the following equation 3c. A relationship is established.

  rHCUs−rHCDs = {4 / (4 + y)} × (rO2Us−rO2Ds) Equation 3c

Here, y is the ratio (H / C) of the amount of hydrogen to the amount of carbon in the fuel used.
The value of y varies depending on the fuel to be used, and is stored and held in advance in an appropriate storage area of the electronic control unit 30 when the apparatus is used.

  Based on these relational expressions, the difference between the true catalyst upstream oxygen concentration and the true catalyst downstream oxygen concentration is calculated by the following relational expression 3.

  rO2Us-rO2Ds = {(4 + y) / (4 + y-4f)} * (rO2Us-m-rO2Ds-m) Equation 3

Next, the catalyst unreachable rate funr with respect to the amount of fuel injected Qpost is calculated (see symbol BL3-5 in FIG. 3).
The catalyst unreachable rate funr is obtained as funr = (Qpost−Qhbur) / Qpost.

Qpost is calculated and calculated based on the conventional exhaust gas temperature control process described above as the precondition of the exhaust gas purifying apparatus in the embodiment of the present invention.
Qhbur is the difference between the catalyst upstream oxygen concentration and the catalyst downstream oxygen concentration after propagation time compensation as described above.

Next, it is determined whether or not a condition for starting the learning process is satisfied (see step S140 in FIG. 2).
In the embodiment of the present invention, the catalyst non-reaching rate funr acquired as described above is stored and held as a learning value. In order to improve accuracy, reliability, etc. as a learning value, it is determined whether or not a predetermined condition for starting a learning process for storing and holding the acquired catalyst unreached rate funr as a learning value is satisfied.

  Here, whether or not the above-mentioned predetermined condition, that is, the driving state of the vehicle is a state suitable for storing and holding the acquired catalyst unreached rate funr as a learning value, is determined by a specific condition. It is not limited. Actually, the appropriate predetermined conditions vary depending on the specifications of the vehicle and the exhaust gas purification device, and therefore, it is preferable to appropriately determine them based on the test results and simulation results in consideration of these specific specifications. It is.

Therefore, when it is determined that the learning conditions determined as described above are satisfied (in the case of YES), the catalyst unreached rate funr obtained in the previous step S130 is an electronic value as a learning value. It is stored and held in the learning map secured in the learning value storage area secured in the appropriate storage area of the control unit 30 (step S150 in FIG. 2, reference sign BL3-5 in FIG. 3, and FIG. 5). (See BL5-1).
After the learned value is stored, the process returns to the previous step S110 to acquire a new catalyst unreached rate funr.

  On the other hand, if it is determined in step S140 that the conditions for starting the learning process are not satisfied (in the case of NO), the catalyst unreached rate funr acquired in step S130 is not stored or held as a learned value. And the process returns to the previous step S110 to acquire a new catalyst unreachable rate funr.

In the embodiment of the present invention described above, the unburned fuel is injected by the post injection by the fuel injection valve 25. However, the application of the present invention is not necessarily limited to such a configuration.
For example, a dedicated fuel injection valve 25A for exhaust pipe injection may be provided so that unburned fuel is directly injected into the upstream 21 of the NSC 23 (see FIG. 1).

  In the embodiment of the present invention described above, the exhaust gas purification is performed using the NSC 23 and the DPF 24. However, the NSC 23, the DPF 24, and the selective reduction catalyst (SCR: Selective Catalytic Reduction) are sequentially arranged from the upstream side of the 21. The arrangement is also suitable.

In this case, for example, a configuration may be adopted in which a lambda sensor is disposed upstream of the NSC 23 and a knock sensor is disposed downstream. In such a configuration, the upstream lambda sensor corresponds to the first lambda sensor 2, and the downstream knox sensor corresponds to the second lambda sensor 3.
In the above-described configuration, a diesel oxidation catalyst (DOC) may be used instead of the NSC 23.

  The present invention can be applied to an exhaust gas purifying apparatus in which accurate exhaust gas temperature control with good response to a sudden change in the control state is desired.

DESCRIPTION OF SYMBOLS 1 ... Airflow sensor 2 ... 1st lambda sensor 3 ... 2nd lambda sensor 23 ... Nitrogen oxide storage reduction catalyst 24 ... Diesel particulate collection filter 30 ... Electronic control unit

Claims (4)

An exhaust gas temperature control method for controlling the exhaust purification device to a desired temperature by injecting unburned fuel by post injection,
The post-injection fuel amount Qpost, which is the amount of unburned fuel injected by the post-injection, is used to set the oxidation catalyst or nitrogen oxide storage reduction catalyst as the exhaust purification device to a desired temperature. The amount of fuel Qnsc to be supplied to the physical storage reduction catalyst, the catalyst unreachable rate funr, which is the ratio of the amount of fuel that does not reach the nitrogen oxide storage reduction catalyst among the post injection fuel amount to the post injection fuel amount, And, using the amount Qafr of the fuel that reaches the oxidation catalyst or the nitrogen oxide storage reduction catalyst without burning during the after injection, it is obtained as Qpost = (Qnsc−Qafr) / (1-funr) In the exhaust gas temperature control method used for post injection,
The catalyst unreachable rate funr is calculated by using the post-injected fuel amount Qpost and the combustion hydrocarbon amount Qhbur which is the amount of hydrocarbon burned by the oxidation catalyst or the nitrogen oxide storage reduction catalyst, and funr = (Qpost−Qhbur) / Qpost is required,
The combustion hydrocarbon amount is obtained as a difference between the upstream oxygen concentration in the oxidation catalyst or the nitrogen oxide storage reduction catalyst and the downstream oxygen concentration of the oxidation catalyst or the nitrogen oxide storage reduction catalyst. Exhaust gas temperature control method.   2. The exhaust gas temperature control method according to claim 1, wherein a detected value of a lambda sensor or a Knox sensor is used as the upstream and downstream oxygen concentrations of the oxidation catalyst or the nitrogen oxide storage reduction catalyst. While having an oxidation catalyst or nitrogen oxide storage reduction catalyst and a diesel particulate filter in an exhaust pipe connected to the internal combustion engine of the vehicle,
The electronic control unit performs unburned fuel injection by post-injection of the fuel injection valve in order to regenerate the catalyst and diesel particulate collection filter or to activate the nitrogen oxide selective reduction catalyst installed downstream. In the exhaust gas purification apparatus configured to be able to control the temperature in the exhaust gas purification device to a desired temperature,
The electronic control unit is
In order to set the post-injected fuel amount Qpost, which is the amount of unburned fuel injected by the post injection, to the desired temperature for the oxidation catalyst or nitrogen oxide storage reduction catalyst as the exhaust purification device, the oxidation catalyst or nitrogen oxidation The amount of fuel Qnsc to be supplied to the object storage reduction catalyst, the catalyst unreachable rate funr that is the ratio of the amount of fuel that does not reach the nitrogen oxide storage reduction catalyst among the amount of post injection fuel to the amount of post injection fuel And, using the amount Qafr of the fuel that reaches the oxidation catalyst or the nitrogen oxide storage reduction catalyst without burning during the after injection, it is calculated as Qpost = (Qnsc−Qafr) / (1-funr),
Using the post-injected fuel amount Qpost and the combustion hydrocarbon amount Qhbur which is the amount of hydrocarbon burned by the oxidation catalyst or the nitrogen oxide storage reduction catalyst, the catalyst unreachable rate funr is expressed as funr = (Qpost−Qhbur) / While calculating Qpost,
The combustion hydrocarbon amount is calculated as a difference between the upstream oxygen concentration in the oxidation catalyst or the nitrogen oxide storage reduction catalyst and the downstream oxygen concentration of the oxidation catalyst or the nitrogen oxide storage reduction catalyst. An exhaust gas purification device characterized by comprising:   The electronic control unit is configured to detect the detected values of the lambda sensor or the knock sensor provided on the upstream side and the downstream side of the oxidation catalyst or the nitrogen oxide storage reduction catalyst, respectively, on the upstream side of the oxidation catalyst or the nitrogen oxide storage reduction catalyst. The exhaust gas purification device according to claim 3, wherein the exhaust gas purification device is configured to be used for calculating a difference between the oxygen concentration of the gas and the downstream oxygen concentration.

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