JP7122873B2 - Exhaust gas temperature control method and exhaust gas purification device - Google Patents

Description

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

Vehicles with diesel engines use a nitrogen oxide storage reduction catalyst (NSC) that absorbs nitrogen oxides (NOx) and collects exhaust particulates in the exhaust gas in order to emit exhaust gas that complies with exhaust gas regulations. As is well known, an exhaust gas purifying device configured using a diesel particulate filter (DPF) or the like is installed.

In such an exhaust gas purifier, 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 as temperature control methods for desulfurization of the nitrogen oxide storage reduction catalyst and regeneration of the diesel particulate filter. A method of supplying unburned hydrocarbons (HC) to the catalyst by post-injection and raising the exhaust gas temperature with the heat of oxidation reaction, or injecting unburned fuel directly into the exhaust pipe to burn fuel in the exhaust pipe A typical method is known as a method of increasing the temperature of the exhaust gas by increasing the temperature of the exhaust gas (see, for example, Patent Document 1).

In the method of controlling exhaust gas temperature 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 determined based on the temperature of the catalyst itself and temperature information around it. It is often computed.
In recent years, in the above-described exhaust gas temperature control, a method using a temperature model has been put to practical use.

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

dmPoI1=(dmFuOpnLop-dmFuPoI2)/(1-facPoI1cmb) Equation 1

Here, "dmPoI1" is the instructed post-injection fuel amount, "dmFuOpnLop" is the amount of fuel to be supplied to the oxidation catalyst or the nitrogen oxide storage reduction catalyst, and "facPoI1cmb" is the amount of fuel to be oxidized relative to 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 the "catalyst non-arrival rate" for convenience of explanation), "dmFuPoI2", is performed after the main injection to increase the exhaust temperature. It is the amount of fuel that reaches the oxidation catalyst or the nitrogen oxide storage reduction catalyst without being burned during after-injection.

Here, the amount of fuel "dmFuOpnLop" to be supplied to the oxidation catalyst or nitrogen oxide storage reduction catalyst is calculated by Equation 2 below.

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". , the amount corresponding to the amount of unfueled fuel flowing downstream of the catalyst without being completely processed by the catalyst is subtracted.
This "dmFuSum" is calculated in advance using the target temperature on the downstream side of the oxidation catalyst or nitrogen oxide storage reduction catalyst, the measured temperature on the upstream side of the oxidation catalyst or nitrogen oxide storage reduction catalyst, the measured value of the exhaust gas flow rate, etc. is obtained from an arithmetic expression determined based on simulation results and the like.

In addition, "rSlip" is the amount of fuel to be supplied to the oxidation catalyst or nitrogen oxide storage reduction catalyst "dmFuOpnLop" described above when the amount "dmFuOpnLop" is supplied to the oxidation catalyst or nitrogen oxide storage reduction catalyst. It is a slip ratio that indicates the ratio of the amount of fuel that remains unburned to the amount of fuel that has been burned.
This slip ratio is determined based on an arithmetic expression determined based on test results and simulation results, and is further corrected using the catalyst temperature and exhaust gas flow rate.

Further, the catalyst non-arrival rate facPoI1cmb is determined, for example, by a map created based on test results and simulation results. The catalyst non-arrival rate facPoI1cmb determined by such a map is determined, for example, according to the operating conditions of the engine. Specifically, the operating conditions of the engine are, for example, engine speed, engine torque, etc., and the map is configured so that the catalyst non-arrival rate facPoI1cmb corresponding to the input can be read using these as inputs. .

By the way, in a temperature control system using a temperature model as described above, a plurality of sensors are used, and some errors and fluctuations in the output values of these sensors are unavoidable, and deterioration of the catalyst is inevitable. I want to.
For this reason, in the temperature control system described above, in order to improve the accuracy and reliability of temperature control, the output value of the sensor and the temperature model are adjusted in consideration of the error and fluctuation of the sensor and the deterioration of the catalyst. Therefore, various types of compensation are normally performed based on various types of temperature information. Specifically, the exhaust temperature model value corresponding to the temperature sensor downstream of the catalyst derived from the temperature model is compared with the exhaust temperature model value actually measured by the exhaust temperature sensor, and the difference is taken as the model error and applied to the model. Methods are known for correcting the input catalyst inlet temperature.

JP 2016-20637 A

In general, compensation based on temperature has relatively good adaptability as a whole control, but depending on the conditions of use, changes may be slow until the desired control state is reached, resulting in poor responsiveness and immediate response. be.
For example, the above-mentioned catalyst non-arrival rate facPoI1cmb is set to a value according to the operating conditions of the engine. However, when a sudden change occurs in the operating conditions of the engine for some reason, the compensation based on the temperature information cannot ensure accurate exhaust gas temperature control with good responsiveness, and the state deviates from the desired exhaust gas temperature control state. There is a problem of falling into

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned actual situation, and provides an exhaust gas temperature control method and an exhaust gas purifying apparatus which are capable of performing accurate exhaust gas temperature control with good responsiveness to rapid fluctuations in the control state. be.

In order to achieve the object of the present invention, the exhaust gas temperature control method according to the present invention comprises:
An exhaust gas temperature control method for controlling an 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 set to a desired temperature of the oxidation catalyst or the nitrogen oxide storage reduction catalyst as the exhaust purification device. a fuel amount Qnsc to be supplied to the mass storage reduction catalyst; a catalyst non-arrival rate funr, which is the ratio of the amount of fuel that does not reach the nitrogen oxide storage reduction catalyst in 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 being burned during the after-injection, Qpost=(Qnsc-Qafr)/(1-funr). In the exhaust gas temperature control method for post injection,
The catalyst non-arrival rate funr is obtained by using the post-injection fuel amount Qpost and the combustion hydrocarbon amount Qhbur, which is the amount of hydrocarbons burned by the oxidation catalyst or nitrogen oxide storage reduction catalyst, funr=(Qpost−Qhbur)/ Qpost is required,
The combustion hydrocarbon amount is determined as the difference between the oxygen concentration on the upstream side of the oxidation catalyst or nitrogen oxide storage reduction catalyst and the oxygen concentration on the downstream side of the oxidation catalyst or nitrogen oxide storage reduction catalyst. It is a thing.
In order to achieve the object of the present invention, the exhaust gas purifying device according to the present invention includes:
While having an oxidation catalyst or a nitrogen oxide storage reduction catalyst and a diesel particulate filter in an exhaust pipe connected to an internal combustion engine of a vehicle,
The electronic control unit executes injection of unburned fuel by post-injection of the fuel injection valve in order to regenerate the catalyst and diesel particulate filter, or to activate the nitrogen oxide selective reduction catalyst installed downstream. In an exhaust gas purifying device configured to be able to control the temperature of the exhaust gas purifying device to a desired temperature,
The electronic control unit is
In order to set the post-injection fuel amount Qpost, which is the amount of unburned fuel injected by the post-injection, to a desired temperature of the oxidation catalyst or the nitrogen oxide storage reduction catalyst as the exhaust purification device, the oxidation catalyst or A fuel amount Qnsc to be supplied to the nitrogen oxide storage reduction catalyst, and a catalyst non-reaching ratio, which is the ratio of the amount of fuel that does not reach the nitrogen oxide storage reduction catalyst to the post-injection fuel amount, out of the post-injection fuel amount. Using the rate funr and the quantity Qafr of fuel reaching the oxidation catalyst or nitrogen oxide storage reduction catalyst without burning during after injection, it is calculated as Qpost = (Qnsc - Qafr) / (1 - funr) death,
The catalyst non-arrival rate funr is calculated by using the post-injection fuel amount Qpost and the combustion hydrocarbon amount Qhbur, which is the amount of hydrocarbons burned by the oxidation catalyst or nitrogen oxide storage reduction catalyst, funr=(Qpost−Qhbur)/ While calculating Qpost,
The combustion hydrocarbon amount is calculated as the difference between the oxygen concentration on the upstream side of the oxidation catalyst or nitrogen oxide storage reduction catalyst and the oxygen concentration on the downstream side of the oxidation catalyst or nitrogen oxide storage reduction catalyst. It is a thing.

According to the present invention, instead of using a catalyst non-arrival rate preset from experimental results based on temperature or the like, the catalyst non-arrival rate is constantly calculated. , the post-injection fuel amount calculated using the catalyst non-arrival rate can be set to an accurate value with good responsiveness, and accurate exhaust gas temperature control with good responsiveness to rapid fluctuations in the control state can be realized. It has the effect of

1 is a configuration diagram showing a configuration example of an exhaust gas purifier to which an exhaust gas temperature control method according to an embodiment of the present invention is applied; FIG. 4 is a subroutine flowchart showing the procedure of exhaust gas temperature control processing in the embodiment of the present invention; FIG. 3 is a functional block diagram showing functions required for an electronic control unit for execution of exhaust gas temperature control processing in the embodiment of the present invention. FIG. 4 is a functional block diagram showing functions performed in the electronic control unit when propagation time compensation in exhaust gas temperature control processing in the embodiment of the present invention is executed in the electronic control unit. FIG. 4 is a functional block diagram showing functions performed in the electronic control unit when learning processing in exhaust gas temperature control processing in the embodiment of the present invention is executed in the electronic control unit.

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

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. are connected to an exhaust pipe 22 for exhaust.
An airflow sensor 1 for measuring the amount of intake air is provided at an appropriate position on 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 this order from the upstream side at appropriate positions in the exhaust pipe 22. It is

Here, the NSC 23 stores nitrogen oxides (NOx) when the vehicle is in normal driving conditions. Further, when the state of fuel combustion in the engine 1 is a state of excessive fuel combustion that reduces the oxygen concentration in the exhaust gas, the occluded nitrogen oxides can be reduced to harmless nitrogen and oxygen. , such a configuration is basically the same as the conventional one.

Also, the DPF 24 is similar to the conventional one, which is configured using, for example, a filter with a honeycomb structure made of a ceramic material.

A first lambda sensor 2 and a first temperature sensor 4 are provided at appropriate positions in the exhaust pipe 22 on the upstream side of the NSC 23, respectively. , a second lambda sensor 3 and a second temperature sensor 5 are provided, respectively.
Detection signals from 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 well-known configuration, storage elements (not shown) such as RAM and ROM, and an input/output interface circuit (not shown). It is configured as a main component.

The electronic control unit 30 includes various signals detected by sensors (not shown) necessary for controlling the operation of the vehicle, such as atmospheric pressure, engine speed, accelerator opening, Engine cooling water temperature and the like are input.
Various detection signals input to the electronic control unit 30 as described above are used for fuel injection control processing of the fuel injection valve 25, exhaust gas temperature control processing in an embodiment of the present invention, etc., which will be described later. ing.

Next, exhaust gas temperature control processing according to the embodiment of the present invention executed by the electronic control unit 30 will be described with reference to FIGS. 2 to 5. FIG.
First, as a premise, in the exhaust gas purifying device according to the embodiment of the present invention, the exhaust gas temperature is controlled for activation of the exhaust gas purifying device, that is, desulfurization of the NSC 23 and regeneration of the DPF 24. It is assumed that there is In this exhaust gas temperature control, the fuel injection valve 25 injects unburned fuel into a cylinder (not shown) of the engine 20 to generate heat of oxidation reaction to raise the exhaust gas temperature.

The amount of fuel required for injecting unburned fuel is determined based on the formula 1 shown in the description of the prior art, as in the conventional art, as will be described below.

dmPoI1=(dmFuOpnLop-dmFuPoI2)/(1-facPoI1cmb) Equation 1

Here, "dmPoI1" (hereinafter referred to as "Qpost" for convenience of explanation) is the post-injection fuel amount, and "dmFuOpnLop" (hereinafter referred to as "Qnsc" for convenience of explanation) is supplied to the nitrogen oxide storage reduction catalyst. The amount of fuel to be delivered, "facPoI1cmb" (hereinafter referred to as "funr" for convenience of explanation), is the catalyst non-arrival rate.
The fuel injection according to the embodiment of the present invention is premised on a mode in which after-injection for burning unburned fuel is performed after main injection, and then post-injection is performed.
"dmFuPoI2" is the amount of fuel that reaches the oxidation catalyst or nitrogen oxide storage reduction catalyst without being burned during the above-mentioned after-injection.

The amount of fuel Qnsc to be supplied to the nitrogen oxide storage reduction catalyst is determined based on Equation 2 shown in the description of the prior art, as in the conventional art, as shown below. .

Qnsc=dmFuSum/(1-rSlip) Equation 2

Under this premise, in the exhaust gas temperature control process according to the embodiment of the present invention, the non-arrival rate funr of the catalyst, which is used in the above-mentioned formula 1, is obtained by the calculation process specific to the present invention described below, unlike the conventional one. It is something that can be done.

The processing for calculating the catalyst non-arrival rate funr will be described below with appropriate reference to the flowchart shown in FIG. 2 and the functional block diagrams shown in FIGS.
When control by the electronic control unit 30 is started, first, the 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 as the catalyst upstream oxygen concentration, and the detected value of the second lambda sensor 3 is used as the catalyst downstream oxygen concentration.
Since the lambda sensor outputs a signal with an output level corresponding to the oxygen concentration, the output signal can be used as the oxygen concentration at a desired location.

A propagation delay occurs before 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. Therefore, in order to use the detection values of the first and second lambda sensors 2 and 3 for arithmetic processing, it is necessary to compensate for the difference in propagation time.

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

First, the propagation delay time for the exhaust gas flow rate is calculated based on the intake air amount detected by the airflow sensor 1 (see symbol BL4-1 in FIG. 4).
Calculation of this propagation delay time is performed based on appropriately selected actual measurement data.
Specifically, for example, when the exhaust gas flow rate per hour is 50 kg/h, the propagation delay time from the first lambda sensor 2 to the second lambda sensor 3 is A seconds. do.
Assuming that the exhaust gas flow rate is Qkg/h when the propagation delay time is obtained, the propagation delay time at this exhaust gas flow rate is calculated as propagation delay time=A×(50÷Q).

Here, the above-mentioned "A" is a fixed value obtained in advance through tests, stored in an appropriate storage area in the electronic control unit 30, and used when calculating the propagation delay time.
Next, the oxygen concentration on the upstream side of the catalyst obtained by the first lambda sensor 2 is delayed by the propagation delay time obtained as described above to obtain the oxygen concentration on the upstream side of the catalyst after delay time compensation. (See symbol BL4-2 in FIG. 4).

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

After this filtering process, the difference between the catalyst upstream oxygen concentration and the catalyst downstream oxygen concentration after propagation time compensation is calculated (see symbols BL3-4 in FIG. 3). (see reference numeral BL3-5 in FIG. 3). Here, the difference between the oxygen concentration upstream of the catalyst and the oxygen concentration downstream of the catalyst after propagation time compensation is proportional to the amount of hydrocarbons (HC) burned in the NSC 23 (hereinafter referred to as "combusted hydrocarbon amount" for convenience of explanation) Qhbur. .

If the exhaust gas contains a large amount of hydrocarbons due to post-injection, etc., the oxygen concentration detected by the lambda sensor tends to be lower than the true oxygen concentration due to the internal structure of the lambda sensor. It is known.
Therefore, when calculating the above-described difference between the oxygen concentration upstream of the catalyst and the oxygen concentration downstream of the catalyst, the difference between the detected value and the true value is compensated to obtain the difference between the true upstream oxygen concentration and the true 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 catalyst upstream oxygen concentration detection value and is denoted as "ro2Us-m", and the detection value of the second lambda sensor 3 is defined as the catalyst downstream oxygen concentration detection value. , "rO2Ds-m".

Also, the true upstream oxygen concentration of the catalyst is denoted as "rO2Us" and the true downstream oxygen concentration of the catalyst is denoted as "rO2Ds".
Further, the hydrocarbon concentration on the upstream side of the catalyst is denoted as "rHCUs", and the hydrocarbon concentration on the downstream side of the catalyst is denoted by "rHCDs".

Under this 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 hydrocarbon concentration on the upstream side of the catalyst, and the carbonization value on the downstream side of the catalyst. Between the hydrogen concentrations, the relationships represented by the following formulas 3a and 3b are established.

rO2Us-m=rO2Us-f×rHCUs Equation 3a

ro2Ds-m=rO2Ds-f×rHCDs Equation 3b

where f is the compensation factor. Since this compensation coefficient varies depending on the specific specifications of the lambda sensor, it is preferable to set an appropriate value based on test results and simulation results, taking into consideration 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 upstream oxygen concentration and the true downstream oxygen concentration of the catalyst is represented 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 device is started to be used.

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

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

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

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

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

Here, the above-described predetermined conditions, that is, whether or not the driving state of the vehicle is suitable for storing and holding the acquired catalyst non-arrival rate funr as a learning value, depends on specific conditions. It is not limited. In practice, the appropriate predetermined conditions differ depending on the specifications of the vehicle and the exhaust gas purifier, so it is preferable to consider these specific specifications and determine them appropriately based on test results and simulation results. is.

Thus, if it is determined that the learning conditions determined as described above are satisfied (in the case of YES), the catalyst non-arrival rate funr obtained in the previous step S130 is used as a learning value by electron It is stored and held in the learning map secured in the learning value storage area secured in an appropriate storage area of the control unit 30 (step S150 in FIG. 2, reference symbol BL3-5 in FIG. 3, and FIG. 5 (see code BL5-1).
After the learned value is stored, the process returns to the previous step S110 to acquire a new catalyst non-arrival rate funr.

On the other hand, if it is determined in step S140 that the conditions for starting the learning process are not satisfied (if NO), the catalyst non-arrival rate funr acquired in step S130 is not stored or retained as a learned value. , and the process returns to step S110 to acquire a new catalyst non-arrival rate funr.

In the embodiment of the present invention described above, the post-injection by the fuel injection valve 25 is used to inject the unburned fuel, but 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 to inject unburned fuel directly into 21 on the upstream side of NSC 23 (see FIG. 1).

In addition, in the embodiment of the present invention described above, the NSC 23 and the DPF 24 are used to purify the exhaust gas. It is also suitable as a configuration in which they are arranged.

In this case, for example, a configuration in which a lambda sensor is arranged upstream of the NSC 23 and a Knox sensor is arranged downstream of the NSC 23 may be employed. 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, respectively.
Further, in the above configuration, a configuration using a diesel oxidation catalyst (DOC: Diesel Oxidation Catalyst) instead of the NSC 23 may be employed.

The present invention can be applied to exhaust gas purifiers that require accurate exhaust gas temperature control with good responsiveness to rapid fluctuations in the control state.

Reference Signs List 1 Air flow sensor 2 First lambda sensor 3 Second lambda sensor 23 Nitrogen oxide storage reduction catalyst 24 Diesel particulate filter 30 Electronic control unit

Claims (4)

An exhaust gas temperature control method for controlling an 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 set to a desired temperature of the oxidation catalyst or the nitrogen oxide storage reduction catalyst as the exhaust purification device. a fuel amount Qnsc to be supplied to the mass storage reduction catalyst; a catalyst non-arrival rate funr, which is the ratio of the amount of fuel that does not reach the nitrogen oxide storage reduction catalyst in 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 being burned during the after-injection, Qpost=(Qnsc-Qafr)/(1-funr). In the exhaust gas temperature control method for post injection,
The catalyst non-arrival rate funr is obtained by using the post-injection fuel amount Qpost and the combustion hydrocarbon amount Qhbur, which is the amount of hydrocarbons burned by the oxidation catalyst or nitrogen oxide storage reduction catalyst, funr=(Qpost−Qhbur)/ Qpost is required,
The combustion hydrocarbon amount is determined as the difference between the oxygen concentration on the upstream side of the oxidation catalyst or nitrogen oxide storage reduction catalyst and the oxygen concentration on the downstream side of the oxidation catalyst or nitrogen oxide storage reduction catalyst. and exhaust gas temperature control method. 2. The exhaust gas temperature control method according to claim 1, wherein values detected by a lambda sensor or a NOx sensor are used for the oxygen concentrations upstream and downstream of said oxidation catalyst or nitrogen oxide storage reduction catalyst. While having an oxidation catalyst or a nitrogen oxide storage reduction catalyst and a diesel particulate filter in an exhaust pipe connected to an internal combustion engine of a vehicle,
The electronic control unit executes injection of unburned fuel by post-injection of the fuel injection valve in order to regenerate the catalyst and diesel particulate filter, or to activate the nitrogen oxide selective reduction catalyst installed downstream. In an exhaust gas purifying device configured to be able to control the temperature of the exhaust gas purifying device to a desired temperature,
The electronic control unit is
In order to set the post-injection fuel amount Qpost, which is the amount of unburned fuel injected by the post-injection, to a desired temperature of the oxidation catalyst or the nitrogen oxide storage reduction catalyst as the exhaust purification device, the oxidation catalyst or the nitrogen oxidation catalyst is A fuel amount Qnsc to be supplied to the mass storage reduction catalyst, and a catalyst non-arrival rate funr, which is the ratio of the amount of fuel that does not reach the nitrogen oxide storage reduction catalyst in the post-injection fuel amount to the post-injection fuel amount. and Qpost = (Qnsc - Qafr) / (1 - funr) using the amount Qafr of fuel that reaches the oxidation catalyst or nitrogen oxide storage reduction catalyst without being burned during after injection,
The catalyst non-arrival rate funr is calculated by using the post-injection fuel amount Qpost and the combustion hydrocarbon amount Qhbur, which is the amount of hydrocarbons burned by the oxidation catalyst or nitrogen oxide storage reduction catalyst, funr=(Qpost−Qhbur)/ While calculating Qpost,
The combustion hydrocarbon amount is calculated as the difference between the oxygen concentration on the upstream side of the oxidation catalyst or nitrogen oxide storage reduction catalyst and the oxygen concentration on the downstream side of the oxidation catalyst or nitrogen oxide storage reduction catalyst. An exhaust gas purifying device characterized by: The electronic control unit converts the detection values of the lambda sensor or the NOx sensor provided upstream and downstream of the oxidation catalyst or nitrogen oxide storage reduction catalyst to the upstream side of the oxidation catalyst or nitrogen oxide storage reduction catalyst. 4. The exhaust gas purifying apparatus according to claim 3, wherein the exhaust gas purifying apparatus is constructed so as to be used for calculating the difference between the oxygen concentration on the downstream side and the oxygen concentration on the downstream side.

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