JP7238818B2 - Exhaust purification device control device, exhaust purification device, and vehicle - Google Patents

Description

The present disclosure relates to a control device for an exhaust purification device, an exhaust purification device, and a vehicle.

Conventionally, as an exhaust purification device for an internal combustion engine (hereinafter referred to as "engine"), there is known one in which an oxidation catalyst and a PM (Particulate Matter) filter are provided in order from the upstream side to the downstream side in the exhaust pipe. there is

This type of PM filter has an upper limit to the amount of PM that can be collected. (also referred to as "playback") is performed (see, for example, Patent Document 1).

When regenerating the PM filter, in general, the post injection is performed by the fuel injection device in the engine, or the fuel injection is performed by the fuel injection device provided in the exhaust pipe, so that the oxidation catalyst is freed from the unburned fuel. Control is performed to supply hydrocarbons (hereinafter referred to as HC), cause an oxidation reaction of HC with an oxidation catalyst, and raise the temperature of the exhaust gas. In such control, the outlet temperature of the oxidation catalyst (representing the temperature of the exhaust gas discharged from the oxidation catalyst; the same shall apply hereinafter) is usually detected by a temperature sensor, and the temperature at the outlet of the oxidation catalyst is adjusted so as to approach the target value. It regulates the amount of fuel supplied from the fuel injection device.

JP 2010-169052 A

By the way, it is known that the oxidation catalyst used in this type of exhaust purification device deteriorates with the lapse of the period of use, and the function of oxidizing HC (that is, purification rate) decreases. When the purification rate of the oxidation catalyst decreases, the amount of HC that slips downstream from the oxidation catalyst increases. The HC slipped in this way adheres to the PM filter, burns in the PM filter (or undergoes an oxidation reaction with an oxidation catalyst carried on the PM filter), and raises the temperature of the PM filter.

When such a situation occurs, the method of controlling the fuel injection amount based on the outlet temperature of the oxidation catalyst, as in the conventional technology, injects excessive fuel even though the PM filter is in an overheated state. will continue to do so. As a result, not only is fuel consumption worsened, but high-temperature exhaust gas is caused to flow downstream of the PM filter, causing heat damage to the SCR (Selective Catalytic Reduction) catalyst, etc., installed downstream of the PM filter. leads to

The present disclosure has been made in view of the above problems, and aims to optimize the amount of unburned fuel supplied to the oxidation catalyst for regeneration of the PM filter even when the oxidation catalyst has deteriorated. It is an object of the present invention to provide a control device for an exhaust gas purification device, an exhaust gas purification device, and a vehicle that make it possible.

The main disclosure that solves the above-mentioned problems is
A control device for an exhaust purification device having an oxidation catalyst and a PM filter arranged in order from upstream to downstream in an exhaust pipe of an internal combustion engine,
an HC slip amount estimator for estimating an HC slip amount of the unburned fuel supplied to the oxidation catalyst and arriving at the PM filter after slipping from the oxidation catalyst;
The PM filter is virtually divided into a plurality of cells along the exhaust gas flow direction, and each of the plurality of cells is determined based on the temperature and flow rate of the exhaust gas flowing into the PM filter and the HC slip amount. a temperature distribution estimation unit that estimates temperature;
a target fuel supply amount calculation unit that calculates a target supply amount of unburned fuel to be supplied to the oxidation catalyst for regeneration of the PM filter based on the deviation of the estimated temperature of each of the plurality of cells from the target temperature;
It is a control device comprising

Also, in other aspects,
It is an exhaust emission control device including the above control device.

Also, in other aspects,
A vehicle including the above exhaust purification device.

According to the control device for an exhaust purification device according to the present disclosure, even when the oxidation catalyst is deteriorated, it is possible to optimize the amount of unburned fuel supplied to the oxidation catalyst for regeneration of the PM filter. is.

A diagram showing an example of the configuration of an exhaust purification device according to the first embodiment. FIG. 2 is a diagram showing an example of the configuration of a PM filter according to the first embodiment; FIG. A diagram showing an example of a calculation map referred to when an HC slip amount estimator according to the first embodiment estimates an HC slip amount. A diagram showing an example of a mode in which the temperature distribution estimator according to the first embodiment virtually divides the PM filter into a plurality of cells along the flow direction of the exhaust gas. FIG. 4 is a diagram schematically showing arithmetic processing in the temperature distribution estimator according to the first embodiment; A diagram showing an example of the temperature distribution of a PM filter during filter regeneration. A diagram showing an example of the temperature distribution of the PM filter during filter regeneration. A diagram showing an example of an HC adhesion amount distribution model that the temperature distribution estimator according to the first embodiment refers to when calculating the HC amount that adheres to each cell. FIG. 4 is a diagram showing an example of a PM deposition amount distribution model referred to when the temperature distribution estimator according to the first embodiment calculates the PM deposition amount deposited in each cell; The figure which shows an example of a structure of the target fuel supply amount calculation part which concerns on 1st Embodiment. Flowchart showing the operation of the ECU according to the first embodiment The figure which shows an example of a structure of the exhaust gas purification apparatus which concerns on 2nd Embodiment. The figure which shows an example of a structure of the 2nd target fuel supply amount calculation part which concerns on 2nd Embodiment.

Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same functions are denoted by the same reference numerals, thereby omitting redundant description.

(First embodiment)
[Configuration of exhaust gas purification device]
Hereinafter, the configuration of the exhaust purification system according to the first embodiment will be described with reference to FIGS. 1 and 2. FIG. In this embodiment, as an example, a mode in which the exhaust purification device of the present invention is applied to a diesel engine will be described.

FIG. 1 is a diagram showing an example of the configuration of an exhaust purification device U according to this embodiment. FIG. 2 is a diagram showing an example of the configuration of the PM filter 42 according to this embodiment.

An exhaust purification device U according to the present embodiment is mounted on, for example, a diesel engine vehicle, and purifies exhaust gas from an engine 10 of the vehicle.

The engine 10 includes, for example, a combustion chamber and a fuel injection device (not shown) that injects fuel into the combustion chamber. Engine 10 combusts and expands a mixture of fuel and air in a combustion chamber to generate power. The engine 10 is connected to an intake pipe 20 that introduces air into the combustion chamber and an exhaust pipe 30 that discharges post-combustion exhaust gas from the combustion chamber to the outside of the vehicle.

When the engine 10 receives from the ECU 100 of the exhaust purification device U a control command signal related to the amount of fuel supply required to regenerate the PM filter 42, for example, the fuel injection device is caused to perform post-injection, and the fuel is supplied. Unburned fuel corresponding to the amount is discharged to the exhaust pipe 30 .

The exhaust purification device U includes an oxidation catalyst 41, a PM filter 42, an SCR catalyst 43, an aqueous urea injection device 43a, various sensors 51-53, and an ECU (Electronic Control Unit) 100.

The oxidation catalyst 41 oxidizes and removes unburned fuel hydrocarbons and carbon monoxide contained in the exhaust gas. The oxidation catalyst 41 is configured by, for example, carrying an oxidation catalyst such as platinum or cerium oxide on a carrier such as cordierite or silicon carbide.

The oxidation catalyst 41 is arranged adjacent to the upstream side of the PM filter 42 in the exhaust pipe 30 . When the PM filter 42 is regenerated, the oxidation catalyst 41 also functions to oxidize hydrocarbons (HC) in the unburned fuel discharged from the engine 10 side and increase the temperature of the exhaust gas by the heat of oxidation. . Note that the oxidation catalyst 41 may be arranged upstream of the PM filter 42 and spaced apart from the PM filter 42 .

The PM filter 42 is arranged in the exhaust pipe 30 and captures PM contained in the exhaust gas. The PM filter 42 is made of, for example, cordierite or silicon carbide porous ceramics, and has a honeycomb structure in which inlets and outlets are alternately plugged so that the exhaust gas passes through collection walls made of the porous ceramics. presenting. Exhaust gas discharged from the engine 10 flows downstream while passing through the porous collection wall of the PM filter 42, during which PM is collected by the collection wall.

The PM filter 42 may carry an oxidation catalyst so that the HC that has passed through the oxidation catalyst 41 can be removed by oxidation.

The SCR catalyst 43 adsorbs ammonia hydrolyzed by the urea water injected from the urea water injection device 43a arranged upstream of the SCR catalyst 43, and selectively reduces and purifies NOx from the exhaust gas by the adsorbed ammonia. .

Various sensors 51 to 53 are provided to detect the state of the exhaust gas flowing through the exhaust pipe 30, the state of the PM filter 42, and the like. The various sensors 51-53 include, for example, a differential pressure sensor 51, a temperature sensor 52, and a flow velocity sensor 53.

The differential pressure sensor 51 has, for example, one end arranged in the exhaust pipe 30 on the upstream side of the PM filter 42 and the other end arranged in the exhaust pipe 30 on the downstream side of the PM filter 42 . The differential pressure between the side exhaust pressure and the downstream side exhaust pressure (hereinafter referred to as "the differential pressure across the PM filter 42") is detected. In this embodiment, the flow resistance when the exhaust gas passes through the oxidation catalyst 41 is extremely small, so the differential pressure across the differential pressure sensor 51 is substantially the same as the differential pressure across the PM filter 42 . be.

The temperature sensor 52 is arranged, for example, between the oxidation catalyst 41 and the PM filter 42 in the exhaust pipe 30 and detects the temperature of the exhaust gas flowing into the PM filter 42 .

The flow velocity sensor 53 is arranged downstream of an air cleaner (not shown) in the intake pipe 20, for example, and detects the flow velocity of air flowing into the engine 10 (hereinafter simply referred to as flow velocity). The flow rate sensor 53 indirectly detects the flow rate of the exhaust gas flowing into the PM filter 42 . The exhaust gas flow rate is generally obtained by summing the intake air amount indicated by the flow sensor 53 and the fuel injection amount in the engine 10 .

These various sensors 51 to 53 sequentially transmit sensor information obtained by detection to the ECU 100 (dotted line arrows in FIG. 1). Incidentally, these various sensors 51 to 53 can be realized by known sensors.

The ECU 100 (corresponding to the “control device” of the present invention) estimates the PM deposition amount in the PM filter 42 . The ECU 100 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input port, and an output port. The functions of the ECU 100 are implemented, for example, by the CPU referring to control programs and various data stored in the ROM and RAM.

The ECU 100 is connected for communication with the engine 10 and configured to be able to control the engine 10 . Further, the ECU 100 acquires sensor information from various sensors 51 to 53, and detects the state of the exhaust gas flowing through the exhaust pipe 30, the state of the PM filter 42, etc. based on the sensor information. .

In this embodiment, the fuel injection device provided in the engine 10 is used as means for supplying fuel to the oxidation catalyst 41 when the PM filter 42 is regenerated. As means for performing this, a fuel injection device (not shown) provided in the exhaust pipe 30 may be used.

[Configuration of ECU]
The configuration of the ECU 100 according to the present embodiment will be described below with reference to FIGS. 3 to 9. FIG.

The ECU 100 includes a PM deposition amount estimator 101 , an HC slip amount estimator 102 , a temperature distribution estimator 103 , and a target fuel supply amount calculator 104 .

<Regarding PM deposition amount estimation unit 101>
The PM deposition amount estimation unit 101 estimates the PM deposition amount deposited on the PM filter 42 . The PM deposition amount estimator 101 estimates the PM deposition amount in the PM filter 42 based on the sensor value of the differential pressure sensor 51 that detects the differential pressure across the PM filter 42, for example. At this time, the PM accumulation amount estimating unit 101 uses, for example, a calculation map showing the relationship between the differential pressure across the PM filter 42 and the PM accumulation amount in the PM filter 42, which is stored in advance in the ROM or the like of the ECU 100. to estimate the amount of PM accumulated in the PM filter 42 .

The PM deposition amount estimator 101 estimates the PM deposition amount in the PM filter 42 periodically (for example, at intervals of 100 msec), for example, while the engine 10 is in operation. Then, when the PM deposition amount in the PM filter 42 increases to a threshold value or more, the PM deposition amount estimation unit 101 sets the regeneration request flag, and the HC slip amount estimation unit 102, the temperature distribution estimation unit 103, and the The target fuel supply amount calculation unit 104 is activated to regenerate the PM filter 42 .

Any method may be used by the PM deposition amount estimator 101 to estimate the PM deposition amount in the PM filter 42 . The PM deposition amount estimating unit 101 calculates the amount of PM discharged from the engine 10 per unit time based on, for example, the operating state of the engine 10 (for example, fuel injection amount, engine rotation speed, engine load, EGR rate, etc.). The PM deposition amount in the PM filter 42 may be estimated by calculating the amount and accumulating the PM amount.

<Regarding HC Slip Amount Estimating Unit 102>
The HC slip amount estimating unit 102 calculates the amount of HC supplied from the oxidation catalyst 41 from the oxidation catalyst 41 from the fuel injection device (here, the fuel injection device of the engine 10) while the PM filter 42 is being regenerated. The amount of HC that slips and reaches the PM filter 42 (hereinafter also referred to as "HC slip amount") is estimated.

FIG. 3 is a diagram showing an example of a calculation map that the HC slip amount estimator 102 refers to when estimating the HC slip amount.

The HC slip amount estimator 102 uses, for example, a calculation map as shown in FIG. The current purification rate of the oxidation catalyst 41 is specified. Then, the HC slip amount estimator 102 calculates the HC slip amount from the current purification rate of the oxidation catalyst 41 and the amount of HC reaching the oxidation catalyst 41 (for example, the amount of unburned fuel discharged by post-injection of the engine 10). calculate.

However, the method by which the HC slip amount estimation unit 102 estimates the HC slip amount is arbitrary. The HC slip amount estimator 102 estimates the purification rate of the oxidation catalyst 41 based on, for example, the temporal change in the outlet temperature of the oxidation catalyst 41 during filter regeneration (that is, the rate-determining value of the outlet temperature of the oxidation catalyst 41). good too.

<Regarding temperature distribution estimation unit 103>
The temperature distribution estimator 103 virtually divides the PM filter 42 into a plurality of cells along the flow direction of the exhaust gas. Based on the calculated HC slip amount and the PM deposition amount in the PM filter 42 estimated by the PM deposition amount estimation unit 101, the temperature of each of the plurality of cells is estimated. That is, the temperature distribution estimator 103 accurately calculates the fuel supply amount (here, the post-injection amount in the fuel injection device) to be supplied to the oxidation catalyst 41 in order to regenerate the PM filter 42 near the target temperature. A temperature distribution within the PM filter 42 is estimated.

FIG. 4 is a diagram showing an example of a mode in which the temperature distribution estimator 103 virtually divides the PM filter 42 into a plurality of cells along the flow direction of the exhaust gas.

FIG. 5 is a diagram schematically showing calculation processing in the temperature distribution estimation unit 103. As shown in FIG.

6A and 6B are diagrams showing an example of the temperature distribution of the PM filter 42 during filter regeneration. FIG. 6A is a diagram showing an example of the temperature distribution of the PM filter 42 when filter regeneration is started and the temperature of the PM filter 42 is increased. FIG. 6B is a diagram showing an example of the temperature distribution of the PM filter 42 when the PM filter 42 is overheated due to a large amount of HC slip from the oxidation catalyst 41. FIG. 6A and 6B show both the actual temperature of the PM filter 42 (solid line) and the target temperature of the PM filter 42 during filter regeneration (dotted line).

In general, during filter regeneration, the temperature in the PM filter 42 is not uniform, and has a height difference along the exhaust gas flow direction. This is mainly due to heat exchange between the PM filter 42 and the exhaust gas flowing into the PM filter 42, and heat generation accompanying combustion (or oxidation reaction) of HC (that is, HC slipped on the oxidation catalyst 41) in the PM filter 42. , and heat generation due to combustion of PM deposited in the PM filter 42 .

During filter regeneration, HC is supplied to the oxidation catalyst 41, and due to the oxidation reaction of HC in the oxidation catalyst 41, the temperature of the exhaust gas reaching the PM filter 42 is increased (for example, the temperature is increased to about 600° C.). ). Immediately after the filter regeneration is started, the temperature of the upstream end of the PM filter 42 first rises due to the high-temperature exhaust gas. At this time, since the exhaust gas after heat exchange at the upstream end of the PM filter 42 flows through the downstream end of the PM filter 42, the downstream end of the PM filter 42 rises later than the upstream end of the PM filter 42. Warm (see Figure 6A).

Thereafter, the temperature difference between the upstream end of the PM filter 42 and the downstream end of the PM filter 42 becomes smaller as the filter regeneration execution time elapses. However, when the HC slip amount from the oxidation catalyst 41 is large and the amount of heat generated due to the combustion (or oxidation reaction) of HC in the PM filter 42 (hereinafter referred to as "HC calorific value") is large, the PM filter 42 Exhaust gas flowing through the downstream end has a higher temperature than the upstream end of the PM filter 42 by the amount of heat generated. Therefore, when the amount of heat generated by HC is large, the downstream end of the PM filter 42 is considerably hotter than the upstream end of the PM filter 42 (see FIG. 6B).

Although the effect is small compared to the HC calorific value, when the calorific value associated with the combustion of PM deposited in the PM filter 42 (hereinafter referred to as "PM calorific value") is large, the same temperature rise can occur. behavior can be seen.

From this point of view, the temperature distribution estimator 103 virtually divides the PM filter 42 into a plurality of cells along the flow direction of the exhaust gas, and estimates the temperature of each of the plurality of cells. As a result, the target fuel supply amount calculation unit 104, which will be described later, accurately calculates the fuel supply amount required to regenerate the PM filter 42 near the target temperature from the difference between the estimated temperature of each of the plurality of cells and the target temperature. It is possible to calculate

It should be noted that regeneration of the PM filter 42 in an overheated state prevents damage to the PM filter 42 and heat damage to the SCR catalyst 43 and the like disposed downstream of the PM filter 42 (for example, deterioration of catalytic function due to heat). will cause. In addition, the overheated state of the PM filter 42 promotes combustion of PM deposited in the PM filter 42, and causes further overheating due to an increase in PM heat value.

In this embodiment, the temperature distribution estimation unit 103 virtually divides the PM filter 42 into four cells 42a to 42d along the flow direction of the exhaust gas. The temperature of the cell is estimated using a heat balance model 103M that expresses the heat exchange between and by a heat transfer equation. At this time, the temperature distribution estimating unit 103 estimates the temperature of the cell after considering the calorific value of HC that adheres to and burns in the cell and the PM calorific value generated by the combustion of PM that accumulates in the cell. . Note that FIG. 5 schematically shows arithmetic processing for estimating the temperature of one cell by the temperature distribution estimating unit 103 .

The heat balance model 103M is derived in advance based on, for example, the heat transfer coefficient between the exhaust gas and the cells, the heat capacity of the cells, the heat capacity of the exhaust gas, and the like. The heat balance model 103M includes, for example, the temperature of the cell to be calculated one time before, the temperature of the exhaust gas flowing into the cell, the flow rate of the exhaust gas flowing into the cell, the HC calorific value in the cell, and the A PM calorific value is entered. Here, the cell temperature estimated one time ago means, for example, one time ago in the estimation cycle for estimating the temperature of each of the cells 42a to 42d.

Here, the temperature distribution estimation unit 103 performs arithmetic processing using the heat balance model 103M for each cell because the temperature of the exhaust gas flowing into the cell differs for each cell. Then, the temperature distribution estimator 103 calculates, for each cell, the temperature of the cell and the temperature of the exhaust gas flowing out of the cell.

The temperature of the exhaust gas flowing into each of the cells 42a to 42d input to the heat balance model 103M is, for example, the temperature of the exhaust gas flowing out from the downstream end of the cell adjacent to its upstream side (that is, the temperature of the exhaust gas flowing from the cell adjacent to its upstream side). temperature of exhaust gas after heat exchange) is used. That is, in the model of FIG. 4, the exhaust gas temperature indicated by the temperature sensor 52 is used as the temperature of the exhaust gas flowing into the cell 42a located at the upstream end of the PM filter 42, and the temperature of the exhaust gas flowing into the cell 42b is The temperature of the exhaust gas flowing out of the downstream end of the cell 42a is used, the temperature of the exhaust gas flowing into the cell 42c is the temperature of the exhaust gas flowing out of the downstream end of the cell 42b, and the temperature of the exhaust gas flowing into the cell 42d is: The temperature of the exhaust gas exiting the downstream end of cell 42c is used.

Further, the flow rate of the exhaust gas flowing into each of the cells 42a to 42d to be input to the heat balance model 103M is set based on the sensor value of the flow velocity sensor 53, for example. A common value is used for the flow rate in the calculations of the cells 42a to 42d.

The HC calorific value and PM calorific value in each of the cells 42a to 42d are calculated based on, for example, the amount of HC adhering to the cell and the amount of PM deposited on the cell.

FIG. 7 is a diagram showing an example of an HC adhesion amount distribution model that the temperature distribution estimating unit 103 refers to when calculating the HC amount that adheres to each cell. FIG. 8 is a diagram showing an example of a PM deposition amount distribution model that the temperature distribution estimation unit 103 refers to when calculating the PM deposition amount deposited in each cell.

HC that slips from the oxidation catalyst 41 and reaches the PM filter 42 typically adheres to the upstream end side of the PM filter 42 . From this point of view, the present embodiment uses an HC adhesion amount distribution model in which more HC adheres to cells closer to the upstream side of the PM filter 42 . For example, the temperature distribution estimating unit 103 distributes the HC slip amount estimated by the HC slip amount estimating unit 102 in accordance with the HC adhesion amount distribution model, from the upstream end cell 42a toward the downstream end cell 42d. %, 30%, 20%, and 10% in order, the amount of HC adhering to each of the cells 42a to 42d and the amount of heat generated by HC in the cell are calculated (see FIG. 7). In addition, it is preferable to use a distribution model determined in advance by experiments.

Also, the PM deposited in the PM filter 42 typically deposits substantially uniformly along the flow direction of the exhaust gas. This is because if the PM deposition amount increases in a portion of the flow path, only the flow resistance in that portion increases. From this point of view, the present embodiment uses a PM deposition amount distribution model in which the PM deposition amount deposited on each of the cells 42a to 42d of the PM filter 42 is the same. For example, the temperature distribution estimation unit 103 uniformly distributes the PM deposition amount estimated by the PM deposition amount estimation unit 101 to each cell according to the PM deposition amount distribution model (here, 25% each), so that each cell The amount of PM accumulated in the cell and the amount of heat generated by PM in the cell are calculated (see FIG. 8).

The data of the HC adhesion amount distribution model are pre-stored in the ROM or the like of the ECU 100 together with the data showing the relationship between the HC adhesion amount and the HC heat generation amount. Similarly, the data of the PM deposition amount distribution model are stored in advance in the ROM or the like of the ECU 100 together with the data indicating the relationship between the PM deposition amount and the PM heat generation amount.

The temperature distribution estimator 103 calculates, for each cell, the temperature of the cell and the temperature of the exhaust gas when flowing out from the cell by such arithmetic processing.

<Target fuel supply amount calculation unit 104>
The target fuel supply amount calculation unit 104 acquires information related to the estimated temperature of each of the plurality of cells 42a to 42d of the PM filter 42 from the temperature distribution estimation unit 103, and estimates each of the plurality of cells 42a to 42d of the PM filter 42. A target supply amount of unburned fuel to be supplied to the oxidation catalyst 41 for regeneration of the PM filter 42 based on the deviation of the temperature from the target temperature (hereinafter simply referred to as "target fuel supply amount to the oxidation catalyst 41") Calculate Specifically, the target fuel supply amount calculation unit 104 calculates the deviation of the estimated temperature of each of the plurality of cells 42a to 42d of the PM filter 42 from the target temperature. The target fuel supply amount to the oxidation catalyst 41 is calculated by accumulating the gain values set by , and adding them.

Then, the target fuel supply amount calculator 104 controls the fuel injection device of the engine 10 so that the calculated target fuel supply amount is supplied to the oxidation catalyst 41 . When the engine 10 receives a control command related to the target fuel supply amount from the target fuel supply amount calculation unit 104, the engine 10 injects the target fuel supply amount in post-injection, for example.

FIG. 9 is a diagram showing an example of the configuration of the target fuel supply amount calculation unit 104. As shown in FIG.

The target fuel supply amount calculator 104 has, for example, a first calculator 104a, a second calculator 104b, a third calculator 104c, and a fourth calculator 104d. Here, the first calculation unit 104a integrates the deviation of the estimated temperature from the target temperature of the cell 42a (ΔT1 in FIGS. 6A and 6B) and the gain value γ1. Calculate the appropriate fuel supply amount. Further, the second calculation unit 104b multiplies the deviation of the estimated temperature from the target temperature of the cell 42b (ΔT2 in FIGS. 6A and 6B) and the gain value γ2, and calculates the temperature required to raise the temperature of the cell 42b to the target temperature. Calculate the fuel supply amount. Further, the third calculation unit 104c multiplies the deviation of the estimated temperature from the target temperature of the cell 42c (ΔT3 in FIGS. 6A and 6B) and the gain value γ3 to calculate the temperature required to raise the temperature of the cell 42c to the target temperature. Calculate the fuel supply amount. Further, the fourth calculation unit 104d multiplies the deviation of the estimated temperature from the target temperature of the cell 42d (ΔT4 in FIGS. 6A and 6B) and the gain value γ4, and calculates the temperature required to raise the temperature of the cell 42d to the target temperature. Calculate the fuel supply amount.

Then, the target fuel supply amount calculation unit 104 calculates the fuel supply amount calculated by the first calculation unit 104a, the fuel supply amount calculated by the second calculation unit 104b, and the fuel amount calculated by the third calculation unit 104c. A target fuel supply amount to the oxidation catalyst 41 is calculated by adding the supply amount and the fuel supply amount calculated by the fourth calculation unit 104d. That is, here, the target fuel supply amount A=ΔT1×γ1+ΔT2×γ2+ΔT3×γ3+ΔT4×γ4.

Note that the first calculation unit 104a calculates the fuel supply amount as a positive value when the estimated temperature of the cell 42a is lower than the target temperature, but when the estimated temperature of the cell 42a is higher than the target temperature , the fuel supply amount is calculated as a negative value. This point is the same for the second calculation unit 104b, the third calculation unit 104c, and the fourth calculation unit 104d. Therefore, for example, when the temperature of the cell 42d at the downstream end is higher than the target value, the value of ΔT4×γ4 becomes a negative value. , will approach zero.

Further, the fuel supply amount calculated by the first calculation unit 104a, the fuel supply amount calculated by the second calculation unit 104b, the fuel supply amount calculated by the third calculation unit 104c, and the fourth calculation unit When the value obtained by adding the fuel supply amount calculated in 104d is smaller than zero, the target fuel supply amount calculation unit 104 calculates the target fuel supply amount to the oxidation catalyst 41 as zero.

When the temperature of a part of the PM filter 42 (typically, the temperature of the cell 42 d at the downstream end) abnormally rises, the target fuel supply amount calculation unit 104 determines that the fuel supply to the oxidation catalyst 41 The target fuel supply amount is set to zero to suppress the occurrence of overheating of the PM filter 42 .

Among the gain values γ1 to γ4 set for each of the plurality of cells of the PM filter 42, the gain value set for the downstream cell is the gain value set for the upstream cell. preferably larger than As a result, the temperature of the cell on the downstream side can have a greater degree of influence when the target fuel supply amount calculation unit 104 determines the target fuel supply amount than the temperature of the cell on the upstream side. As a result, the function of suppressing abnormalities in the temperature of the cell 42d at the downstream end of the PM filter 42 can be further enhanced.

The target temperature of each cell is set to, for example, 500° C. or higher and 650° C. or lower. In this embodiment, the target temperature of each cell is set to the same temperature (see FIGS. 6A and 6B). However, the target temperature may be different for each cell. For example, it is set for the downstream cell considering that the temperature of the downstream cell becomes higher than that of the upstream cell due to the HC heat value and the PM heat value in the PM filter 42 . The target temperature may be higher than the target temperature set for the upstream cell. Also, the target temperature may be changed over time. The amount of heat generated by PM varies depending on the amount of PM deposited in the PM filter 42 . In this regard, the target temperature may be decreased as the regeneration of the PM filter 42 progresses, considering that the amount of heat generated by PM becomes smaller as the regeneration of the PM filter 42 progresses.

[Operation of ECU]
Next, an example of the operation of the ECU 100 is described.

FIG. 10 is a flow chart showing the operation of the ECU 100 according to this embodiment. The flowchart shown in FIG. 10 is repeatedly executed by the ECU 100 at predetermined intervals (for example, every 100 msec) according to the computer program, for example, when the regeneration request flag is set.

The ECU 100 first acquires sensor signals from various sensors (here, the differential pressure sensor 51, the temperature sensor 52, and the flow velocity sensor 53) (step S1). Next, the ECU 100 (PM deposition amount estimator 101) estimates the PM deposition amount in the PM filter 42 (step S2). Next, the ECU 100 (HC slip amount estimator 102) estimates the HC slip amount from the oxidation catalyst 41 (step S3). Next, the ECU 100 (temperature distribution estimator 103) determines the temperature and flow rate of the exhaust gas flowing into the PM filter 42, the PM deposition amount in the PM filter 42 calculated in step S2, and the oxidation catalyst calculated in step S3. The temperature of each cell 42a-42d of the PM filter 42 is estimated based on the HC slip from 41 (step S4). Next, the ECU 100 (target fuel supply amount calculation unit 104) calculates the target fuel supply amount to be supplied to the oxidation catalyst 41 based on the deviation of the estimated temperature from the target temperature of each of the cells 42a to 42d of the PM filter 42. (step S5). Next, the ECU 100 transmits a fuel injection command to the engine 10 so as to inject the target fuel supply amount calculated in step S5 by post injection (step S6).

During filter regeneration, the ECU 100 repeatedly executes such processing to supply the necessary amount of HC to the oxidation catalyst 41 so as to correspond to the internal temperature of the PM filter 42 that changes successively.

[effect]
As described above, the exhaust gas purification apparatus U according to the present embodiment virtually divides the PM filter 42 into a plurality of cells 42a to 42d along the exhaust gas flow direction, and the HC from the oxidation catalyst 41 to the PM filter 42. The temperature of each cell 42a-42d is estimated in consideration of the amount of slip. Then, the exhaust gas purification device U according to the present embodiment provides a target supply of unburned fuel to the oxidation catalyst 41 for regeneration of the PM filter 42 based on the deviation of the estimated temperature of each of the cells 42a to 42d from the target temperature. Calculate quantity.

Therefore, according to the exhaust purification device U according to the present embodiment, even in a situation where HC slip occurs from the oxidation catalyst 41 to the PM filter 42 due to deterioration of the oxidation catalyst 41, the overheated state of the PM filter 42 It is possible to optimize the amount of fuel supplied to the oxidation catalyst 41 (for example, the amount of post-injection in the fuel injection device) so as to suppress the occurrence of .

As a result, an unnecessary increase in the amount of fuel injected from the fuel injection device (the fuel injection device of the engine 10 in this embodiment) can be suppressed, and deterioration of fuel efficiency can be suppressed. In addition, this makes it possible to prevent excessively heated exhaust gas from flowing downstream of the PM filter 42 and causing heat damage to the SCR catalyst 43 and the like on the downstream side of the PM filter 42 .

(Second embodiment)
Next, with reference to FIGS. 11 and 12, the configuration of the exhaust purification device U according to the second embodiment will be described.

The exhaust gas purification device U according to this embodiment differs from the exhaust gas purification device U according to the first embodiment in that the ECU 100 further includes a second target fuel supply amount calculator 105 . In addition, below, the target fuel supply amount calculation part 104 demonstrated in 1st Embodiment is called "the 1st target fuel supply amount calculation part 104" for convenience of explanation.

FIG. 11 is a diagram showing an example of the configuration of an exhaust purification device U according to the second embodiment. FIG. 12 is a diagram showing an example of the configuration of the second target fuel supply amount calculator 105. As shown in FIG.

For example, when the PM filter 42 is regenerated, the second target fuel supply amount calculator 105 calculates the amount of unburned fuel supplied to the oxidation catalyst 41 so that the sensor value of the outlet temperature of the oxidation catalyst 41 approaches the target value. the feedback control.

The second target fuel supply amount calculation unit 105 has a target temperature setting unit 105a and a fifth calculation unit 105b. Here, the target temperature setting unit 105a sets the outlet temperature of the oxidation catalyst 41 based on the output torque of the engine 10 calculated by the ECU 100 based on the fuel injection amount and the like and the rotation speed of the engine 10 detected by the rotation speed sensor 54. Set the temperature target. The target value of the outlet temperature of the oxidation catalyst 41 is set to a temperature of 500° C. or higher and 650° C. or lower, for example.

The fifth calculation unit 105b performs oxidation based on the deviation between the sensor value of the outlet temperature of the oxidation catalyst 41 detected by the temperature sensor 52 and the target value of the outlet temperature of the oxidation catalyst 41 set in the target temperature setting unit 105a. A fuel supply amount for the catalyst 41 is determined. The second target fuel supply amount calculator 105 controls the engine 10 so that the target fuel supply amount determined by the fifth calculator 105b is supplied to the oxidation catalyst 41 . The control of the fuel supply amount by the fifth calculation unit 105b is typically based on PID control.

Here, the ECU 100 detects the outlet temperature of the oxidation catalyst 41 using the temperature sensor 52 arranged between the oxidation catalyst 41 and the PM filter 42 . However, when the distance between the oxidation catalyst 41 and the PM filter 42 is long, the temperature sensor for detecting the inlet temperature of the PM filter 42 and the temperature sensor for detecting the outlet temperature of the oxidation catalyst 41 are separate. may be provided in

Normally, when the temperature of the PM filter 42 is raised immediately after starting regeneration of the PM filter 42, it is better to control the fuel supply amount to the oxidation catalyst 41 based on the outlet temperature of the oxidation catalyst 41. It is preferable from the viewpoint of the stability of supply amount control. This is because the temporal change in the internal temperature of the PM filter 42 is large immediately after regeneration of the PM filter 42 is started.

From this point of view, the ECU 100 according to the present embodiment controls the fuel supply amount to the oxidation catalyst 41 when the internal temperature of the PM filter 42 is equal to or higher than the threshold temperature (for example, 500 degrees). When the amount calculation unit 104 is applied and the internal temperature of the PM filter 42 is less than the threshold temperature, the second target fuel supply amount calculation unit 105 is applied.

The ECU 100 according to the present embodiment performs such switching control based on, for example, the temperature of the cell 42d on the downstream end side of the PM filter 42 estimated by the temperature distribution estimator 103 as a reference. However, the method of determining whether the internal temperature of the PM filter 42 has risen to the threshold temperature or more by the ECU 100 may be another method. It may be determined whether or not the internal temperature of the PM filter 42 is equal to or higher than the threshold temperature based on the length of time.

As described above, according to the exhaust purification device U according to the present embodiment, it is possible to stably control the amount of fuel supplied to the oxidation catalyst 41 immediately after regeneration of the PM filter 42 is started.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and various modifications are conceivable.

For example, in the above-described embodiment, as an example of the configuration of the ECU 100, the mode of controlling the fuel supply amount to the oxidation catalyst 41 by controlling the injection amount in the post-injection of the engine 10 is shown. However, when the exhaust emission control device U has a fuel injection device (not shown) provided in the exhaust pipe 30, the ECU 100 may set part or all of the target fuel supply amount in the exhaust pipe 30. It may be supplied to the fuel injection device.

Further, in the above embodiment, the differential pressure sensor 51, the temperature sensor 52, and the flow velocity sensor 53 are shown as examples of various sensors that the ECU 100 refers to. However, the method by which the ECU 100 detects the state of the exhaust gas flowing through the exhaust pipe 30 and the state of the PM filter 42 can be changed in various ways. Alternatively, it may be obtained by arithmetic processing from the operating state of the engine 10 or the like.

In addition, in the above-described embodiment, a diesel engine vehicle is shown as an example of an application target of the exhaust purification device U, but the application target of the exhaust purification device U of the present invention is not limited to this. For example, the exhaust purification device U of the present invention can also be applied to gasoline engine vehicles. In addition, the exhaust purification device U of the present invention may be applied to generators, construction machinery, ships, and the like.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

According to the control device for an exhaust purification device according to the present disclosure, even when the oxidation catalyst is deteriorated, it is possible to optimize the amount of unburned fuel supplied to the oxidation catalyst for regeneration of the PM filter. is.

U exhaust purification device 10 engine 20 intake pipe 30 exhaust pipe 41 oxidation catalyst 42 PM filter 43 SCR catalyst 43a urea water injection device 51 differential pressure sensor 52 temperature sensor 53 flow sensor 54 rotation speed sensor 100 ECU (control device)
101 PM deposit amount estimator 102 HC slip amount estimator 103 Temperature distribution estimator 104 Target fuel supply amount calculator (first target fuel supply amount calculator)
105 second target fuel supply amount calculator

Claims (7)

A control device for an exhaust purification device having an oxidation catalyst and a PM filter arranged in order from upstream to downstream in an exhaust pipe of an internal combustion engine,
an HC slip amount estimator for estimating an HC slip amount of the unburned fuel supplied to the oxidation catalyst and arriving at the PM filter after slipping from the oxidation catalyst;
The PM filter is virtually divided into a plurality of cells along the exhaust gas flow direction, and each of the plurality of cells is determined based on the temperature and flow rate of the exhaust gas flowing into the PM filter and the HC slip amount. a temperature distribution estimation unit that estimates temperature;
a target fuel supply amount calculation unit that calculates a target supply amount of unburned fuel to be supplied to the oxidation catalyst for regeneration of the PM filter based on the deviation of the estimated temperature of each of the plurality of cells from the target temperature;
A control device comprising: The temperature distribution estimator estimates the temperature of each of the plurality of cells based on the temperature and flow rate of the exhaust gas flowing into the PM filter, the HC slip amount, and the PM deposition amount in the PM filter. ,
A control device according to claim 1 . The target fuel supply amount calculation unit integrates a gain value set for each of the plurality of cells with respect to the deviation of the estimated temperature of each of the plurality of cells from the target temperature, and adds the gain values, Calculate the target supply amount,
Among the gain values set for each of the plurality of cells, the gain value set for the downstream cell is greater than the gain value set for the upstream cell,
3. A control device according to claim 1 or 2. a first target fuel supply amount calculator corresponding to the target fuel supply amount calculator;
A second target supply amount of unburned fuel to be supplied to the oxidation catalyst for regeneration of the PM filter is calculated based on the deviation of the outlet temperature of the oxidation catalyst detected by the temperature sensor from the second target temperature. 2 a target fuel supply amount calculation unit,
When controlling the injection amount of a fuel injection device provided in the internal combustion engine or in the exhaust pipe, the first target fuel supply amount calculator and the second target fuel selectively applying a supply amount calculation unit;
4. A control device according to any one of claims 1 to 3. When the temperature of the PM filter is equal to or higher than the threshold temperature, the first target fuel supply amount calculator is applied, and when the temperature of the PM filter is less than the threshold temperature, the second target fuel supply amount calculator is applied. ,
5. A control device according to claim 4. An exhaust purification system comprising the control device according to any one of claims 1 to 5. A vehicle comprising the exhaust emission control device according to claim 6 .

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