WO2017047349A1

WO2017047349A1 - Exhaust gas purification device

Info

Publication number: WO2017047349A1
Application number: PCT/JP2016/074773
Authority: WO
Inventors: 青木　秀樹
Original assignee: 株式会社豊田自動織機
Priority date: 2015-09-15
Filing date: 2016-08-25
Publication date: 2017-03-23
Also published as: DE112016004177T5; JP2017057766A; JP6146447B2

Abstract

This exhaust gas purification device (1) is provided with: a DPF (6) for capturing PM included in exhaust gas; a fuel addition valve (7) for supplying fuel to the DPF; a differential pressure sensor (8) for detecting the pressure differential (DPF pressure differential) between pressure on the upstream side of the DPF and pressure on the downstream side of the DPF; a reproduction control unit (15) for controlling the fuel addition valve so as to burn the PM deposited on the DPF with fuel when the DPF differential pressure is equal to or greater than a differential pressure determination threshold value; a differential pressure change rate calculation unit (12) for calculating the change rate of the DPF differential pressure; an ash deposit amount estimation unit (13) for estimating the amount of ash deposited on the DPF on the basis of the rate of change of the DPF differential pressure; and a differential pressure determination threshold value setting unit (14) for setting a differential pressure determination threshold value according to the amount of ash deposited. The greater the amount of ash deposited, the greater the differential pressure determination threshold value setting unit makes the differential pressure determination threshold value.

Description

Exhaust purification device

One aspect of the present invention relates to an exhaust purification device.

For example, a device described in Patent Document 1 is known as a conventional exhaust gas purification device. An exhaust purification device described in Patent Document 1 includes a filter for collecting particulates (particulate matter), two pressure sensors for detecting pressures on the input side and output side of the filter, and two pressure sensors. A first process of calculating a differential pressure across the filter in response to the pressure signal, estimating a particulate accumulation amount on the filter based on the differential pressure across the filter, and determining whether to regenerate the filter according to the estimation result And a second processing unit that estimates the residual amount of ash in the filter from the differential pressure across the filter when the regeneration of the filter is completed.

JP 2004-76605 A

Conventionally, when the differential pressure between the pressure on the upstream side of the filter and the pressure on the downstream side of the filter (the differential pressure of the filter) exceeds the differential pressure determination threshold, the amount of particulate matter deposited on the filter is the deposition limit. Estimating that the value has been reached, starting filter regeneration. However, when ash accumulates on the filter, the filter differential pressure changes in accordance with the amount of ash accumulated, so that regeneration of the filter may not be started at an appropriate timing. Specifically, as the amount of ash deposited on the filter increases, the differential pressure of the filter increases. Therefore, before the amount of particulate matter deposited reaches the deposition limit, the differential pressure of the filter reaches the differential pressure determination threshold. The filter regeneration may be started.

An object of one aspect of the present invention is to provide an exhaust purification device capable of starting regeneration of a filter at an appropriate timing.

An exhaust emission control device according to one aspect of the present invention is an exhaust emission control device that purifies exhaust gas discharged from an internal combustion engine, a filter that collects particulate matter contained in the exhaust gas, and fuel that supplies fuel to the filter When the differential pressure detected by the supply unit, the differential pressure between the upstream pressure of the filter and the downstream pressure of the filter, and the differential pressure detected by the differential pressure detector exceeds a differential pressure determination threshold A regeneration control unit that controls the fuel supply unit so that the particulate matter deposited on the filter is burned by the fuel, and a differential pressure change rate calculation unit that calculates a change rate of the differential pressure detected by the differential pressure detection unit; Based on the differential pressure change rate calculated by the differential pressure change rate calculation unit, the ash deposition amount estimation unit for estimating the ash deposition amount in the filter, and the ash deposition amount estimated by the ash deposition amount estimation unit Meet And a differential pressure determination threshold setting unit for setting a differential pressure judgment threshold Te, the differential pressure judgment threshold value setting section increases the higher the differential pressure judgment threshold amount of deposited ash increases.

In such an exhaust purification device, when the differential pressure between the pressure upstream of the filter and the pressure downstream of the filter (hereinafter referred to as the differential pressure of the filter) becomes equal to or greater than the differential pressure determination threshold, it accumulates on the filter. The filter is regenerated by controlling the fuel supply unit so that the particulate matter is burned by the fuel. Here, the rate of change of the differential pressure of the filter is calculated, the amount of ash accumulated in the filter is estimated based on the rate of change of the differential pressure, and a differential pressure determination threshold is set according to the amount of accumulated ash. . At this time, the differential pressure determination threshold increases as the amount of ash accumulated in the filter increases. For this reason, when the differential pressure of the filter reaches the differential pressure determination threshold, a desired amount of particulate matter is deposited on the filter even if ash is accumulated on the filter. Thus, the regeneration of the filter is prevented from starting before the desired amount of particulate matter is deposited on the filter. Thereby, the regeneration of the filter can be started at an appropriate timing.

In one embodiment, the differential pressure change rate calculation unit calculates an average value of the differential pressure change rate, and the ash deposition amount estimation unit calculates the average value of the differential pressure change rate calculated by the differential pressure change rate calculation unit. The amount of ash deposited may be estimated based on the above. In this case, the estimation accuracy of the ash accumulation amount in the filter can be improved.

In one embodiment, the differential pressure determination threshold setting unit increases the differential pressure determination threshold as the ash accumulation amount increases until the ash accumulation amount reaches a specified value, and the ash accumulation amount reaches the specified value. In some cases, the differential pressure determination threshold may be maximized. In this case, since the regeneration of the filter is started before the differential pressure of the filter becomes sufficiently high, the internal combustion engine can be protected.

According to one aspect of the present invention, filter regeneration can be started at an appropriate timing.

FIG. 1 is a schematic configuration diagram illustrating an exhaust emission control device according to an embodiment. FIG. 2 is a graph showing a DPF differential pressure map representing the relationship among the PM accumulation amount, the ash accumulation amount, and the DPF differential pressure. FIG. 3A is a graph showing the relationship between the travel distance and the slope of the DPF differential pressure, and FIG. 3B is the ash deposition amount showing the relation between the slope of the DPF differential pressure and the ash deposition amount. FIG. 3C is a graph showing a differential pressure determination threshold map representing the relationship between the ash deposition amount and the differential pressure determination threshold. FIG. 4 is a graph showing the relationship between travel time, DPF differential pressure, and differential pressure determination threshold when the differential pressure determination threshold map shown in FIG. 3C is used. FIG. 5 is a graph showing a modification of the differential pressure determination threshold map representing the relationship between the ash deposition amount and the differential pressure determination threshold. FIG. 6 is a graph showing the relationship between travel time, DPF differential pressure, and differential pressure determination threshold when the differential pressure determination threshold map shown in FIG. 5 is used.

Hereinafter, an embodiment will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an exhaust purification device according to an embodiment. In FIG. 1, an exhaust emission control device 1 of this embodiment is mounted on a vehicle. The exhaust purification device 1 purifies exhaust gas discharged from a diesel engine (hereinafter simply referred to as an engine) 2 that is an internal combustion engine. The engine 2 has a plurality of injectors 3 that inject fuel into a plurality of cylinders (not shown).

The exhaust purification apparatus 1 includes a diesel oxidation catalyst (DOC) 5 and a diesel exhaust particulate removal filter (DPF: Diesel) disposed in order from an upstream side to a downstream side in an exhaust passage 4 connected to an engine 2. Particulate Filter) 6. The DOC 5 oxidizes and removes particulate matter (PM) contained in the exhaust gas. The DPF 6 collects PM contained in the exhaust gas.

Further, the exhaust purification device 1 includes a fuel addition valve 7 that is disposed on the upstream side of the DOC 5 in the exhaust passage 4 and that adds fuel to the exhaust passage 4. The fuel added from the fuel addition valve 7 is mainly used as a reducing agent when the DPF 6 is regenerated. The regeneration of the DPF 6 is to burn the PM deposited on the DPF 6 with a high-temperature fuel. The fuel addition valve 7 constitutes a fuel supply unit that supplies fuel to the DPF 6.

In addition, the exhaust purification device 1 includes a differential pressure sensor 8 (differential pressure detection unit) that detects a differential pressure between the pressure upstream of the DPF 6 and the pressure downstream of the DPF 6 (hereinafter referred to as DPF differential pressure), and fuel addition A controller 10 connected to the valve 7 and the differential pressure sensor 8 is provided. The controller 10 inputs a detection signal of the differential pressure sensor 8, performs a predetermined process, and controls the fuel addition valve 7 so as to perform a regeneration process of the DPF 6.

The controller 10 includes a PM accumulation amount estimation unit 11, a differential pressure change rate calculation unit 12, an ash accumulation amount estimation unit 13, a differential pressure determination threshold setting unit 14, and a regeneration control unit 15.

The PM deposition amount estimation unit 11 estimates the amount of PM deposited on the DPF 6, that is, the amount of PM deposition on the DPF 6 (hereinafter simply referred to as PM deposition amount). The PM accumulation amount estimation unit 11 estimates the PM accumulation amount using a known estimation formula based on, for example, the engine speed, the fuel injection amount from the injector 3, and the travel distance or travel time.

The differential pressure change rate calculation unit 12 calculates the change rate of the DPF differential pressure based on the DPF differential pressure detected by the differential pressure sensor 8 and the PM deposition amount estimated by the PM deposition amount estimation unit 11. The change rate of the DPF differential pressure is also referred to as the slope of the DPF differential pressure. The change rate of the DPF differential pressure is, for example, the change amount of the DPF differential pressure per unit increase amount of the PM deposition amount.

The differential pressure change rate calculation unit 12 calculates the change rate (slope) of the DPF differential pressure using, for example, the DPF differential pressure map shown in FIG. The DPF differential pressure map is a map representing the relationship between the PM deposition amount, the ash deposition amount, and the DPF differential pressure, and is obtained in advance through experiments or the like. The amount of ash deposited is the amount of ash deposited on the DPF 6, that is, the amount of ash deposited on the DPF 6. Note that ash is an incombustible material discharged from the engine, and mainly includes Ca compounds contained in engine oil.

In FIG. 2, the solid line P is data when the ash deposition amount is zero. The solid line Q is data when the ash deposition amount is 200 g. The solid line R is data when the ash deposition amount is 300 g. The solid line S is data when the ash deposition amount is 400 g. The greater the amount of PM deposited, the greater the DPF differential pressure. As the ash deposition amount increases, the DPF differential pressure increases.

The differential pressure change rate calculation unit 12 calculates the change rate of the DPF differential pressure from the two DPF differential pressures. At this time, the differential pressure change rate calculation unit 12 calculates the change rate of the DPF differential pressure a plurality of times (for example, 10 times), calculates the average value of these DPF differential pressure change rates, and finally calculates the average value. It is determined as the change rate of the DPF differential pressure.

The change rate (slope) of the DPF differential pressure increases as the travel distance becomes longer, as shown in FIG. The reason for this is that the amount of ash deposition increases as the travel distance increases.

The ash accumulation amount estimation unit 13 estimates the ash accumulation amount based on the final change rate of the DPF differential pressure calculated by the differential pressure change rate calculation unit 12 (an average value of the change rate of the DPF differential pressure). The ash accumulation amount estimation unit 13 estimates the ash accumulation amount using, for example, an ash accumulation amount map shown in FIG. The ash deposition amount map is a map that represents the relationship between the change rate (slope) of the DPF differential pressure and the ash deposition amount, and is obtained in advance through experiments or the like. The ash accumulation amount map is set so that the ash accumulation amount increases as the change rate (slope) of the DPF differential pressure increases.

The differential pressure determination threshold setting unit 14 sets a differential pressure determination threshold according to the ash accumulation amount estimated by the ash accumulation amount estimation unit 13. The differential pressure determination threshold is used when determining whether or not to regenerate the DPF 6 in the regeneration control unit 15 described later.

The differential pressure determination threshold value setting unit 14 sets the differential pressure determination threshold value using, for example, a differential pressure determination threshold value map shown in FIG. The differential pressure determination threshold map is a map representing the relationship between the ash deposition amount and the differential pressure determination threshold, and is obtained in advance through experiments or the like. The differential pressure determination threshold map is set so that the differential pressure determination threshold increases as the ash deposition amount increases from a certain initial value. Therefore, the differential pressure determination threshold value setting unit 14 increases the differential pressure determination threshold value as the ash accumulation amount increases.

As described above, the ash accumulation amount increases as the traveling time becomes longer. For this reason, as shown in FIG. 4, the differential pressure determination threshold A increases as the traveling time increases.

The regeneration control unit 15 determines whether to regenerate the DPF 6 based on the DPF differential pressure detected by the differential pressure sensor 8 and the differential pressure determination threshold set by the differential pressure determination threshold setting unit 14. At this time, the regeneration control unit 15 determines to regenerate the DPF 6 when the DPF differential pressure is equal to or greater than the differential pressure determination threshold. Then, the regeneration control unit 15 controls the fuel addition valve 7 so that fuel is added from the fuel addition valve 7 when the DPF 6 is regenerated.

In the exhaust emission control device 1 configured as described above, as shown in FIG. 4, the amount of accumulated PM increases as the running time elapses, so the DPF differential pressure increases. When the DPF differential pressure reaches the differential pressure determination threshold A, it is determined that the PM deposition amount has reached the deposition limit value, and regeneration of the DPF 6 is started. Then, since fuel is added from the fuel addition valve 7, fuel is supplied to the DPF 6, so that PM deposited on the DPF 6 is burned by the fuel. For this reason, the DPF differential pressure rapidly decreases. When regeneration of the DPF 6 is completed, PM accumulates again on the DPF 6.

Here, as the running time becomes longer, the amount of accumulated ash increases. As the ash deposition amount increases, the DPF differential pressure increases as described above. For this reason, when the differential pressure determination threshold value used when determining whether to regenerate the DPF 6 is a constant value, the DPF differential pressure is determined before the desired amount of PM is deposited on the DPF 6. The threshold may be reached and regeneration of the DPF 6 may be started.

On the other hand, in the present embodiment, the rate of change of the DPF differential pressure is calculated based on the DPF differential pressure and the PM deposition amount, the ash deposition amount is estimated based on the rate of change of the DPF differential pressure, and the ash deposition amount. The differential pressure determination threshold is set according to the above. At this time, the differential pressure determination threshold increases as the ash deposition amount increases. Therefore, as shown in FIG. 4, when the ash accumulation amount increases as the travel time elapses, the differential pressure determination threshold A increases as the ash accumulation amount increases. Therefore, when the DPF differential pressure reaches the differential pressure determination threshold A, a desired amount of PM is deposited on the DPF 6 even if ash is accumulated on the DPF 6. Therefore, the regeneration of the DPF 6 is prevented from starting before the desired amount of PM is deposited on the DPF 6. Thereby, the regeneration of the DPF 6 can be started at an appropriate timing.

Also, since the average value of the change rate of the DPF differential pressure is calculated and the ash deposition amount is estimated based on the average value, the estimation accuracy of the ash deposition amount can be improved.

It should be noted that one aspect of the present invention is not limited to the above embodiment. For example, in the above embodiment, the differential pressure determination threshold value setting unit 14 sets the differential pressure determination threshold value using the differential pressure determination threshold value map shown in FIG. I can't.

The differential pressure determination threshold setting unit 14 may set the differential pressure determination threshold using the differential pressure determination threshold map shown in FIG. The differential pressure determination threshold map shown in FIG. 5 shows that when the ash accumulation amount is equal to or less than the specified value K, the differential pressure determination threshold value increases as the ash accumulation amount increases, and when the ash accumulation amount is equal to or greater than the specified value K, The differential pressure determination threshold is set to be constant at the maximum value M. The maximum value M is determined in consideration of, for example, the rigidity and durability of the exhaust manifold of the engine 2. Therefore, the differential pressure determination threshold value setting unit 14 increases the differential pressure determination threshold value as the ash deposition amount increases until the ash deposition amount reaches the specified value K, and when the ash deposition amount reaches the specified value K, The differential pressure determination threshold is set to the maximum value M.

In this case, as shown in FIG. 6, until the travel time reaches the specified time, the differential pressure determination threshold A increases as the travel time increases. When the travel time reaches the specified time, the differential pressure determination threshold A A is constant. Thereby, since regeneration of DPF6 is started before DPF differential pressure becomes high enough, engine 2 can be protected.

In the above embodiment, the change rate of the DPF differential pressure is calculated a plurality of times, the average value of the change rate of these DPF differential pressures is calculated, and the ash deposition amount is estimated based on the average value. In particular, the form is not limited, and the rate of change of the DPF differential pressure may be calculated only once, and the ash deposition amount may be estimated based on the rate of change of the DPF differential pressure. In this case, the arithmetic processing by the controller 10 can be simplified.

In the above embodiment, the DPF 6 is regenerated by adding fuel from the fuel addition valve 7. However, the present invention is not particularly limited to this, and a cylinder (not shown) is disposed from the injector 3 disposed in the engine 2. The DPF 6 may be regenerated by injecting the fuel into (). In this case, the injector 3 constitutes a fuel supply unit that supplies fuel to the DPF 6.

Further, in the above-described embodiment, in order to consider an element that changes atmospheric pressure such as altitude, an atmospheric pressure sensor that detects atmospheric pressure may be further provided, and the differential pressure determination threshold value may be corrected each time based on the detected value. . In this case, correction is performed to lower the differential pressure determination threshold as the atmospheric pressure is lower.

At least a part of the embodiments and modifications described above may be arbitrarily combined.

DESCRIPTION OF SYMBOLS 1 ... Exhaust gas purification device, 2 ... Diesel engine (internal combustion engine), 6 ... Diesel exhaust particulate removal filter (filter), 7 ... Fuel addition valve (fuel supply part), 8 ... Differential pressure sensor (differential pressure detection part), 10 ... Controller, 12 ... Differential pressure change rate calculation unit, 13 ... Ash accumulation amount estimation unit, 14 ... Differential pressure determination threshold setting unit, 15 ... Regeneration control unit.

Claims

In an exhaust purification device that purifies exhaust gas discharged from an internal combustion engine,
A filter for collecting particulate matter contained in the exhaust gas;
A fuel supply section for supplying fuel to the filter;
A differential pressure detector that detects a differential pressure between the pressure upstream of the filter and the pressure downstream of the filter;
A regeneration control unit that controls the fuel supply unit so that particulate matter deposited on the filter is burned by fuel when the differential pressure detected by the differential pressure detection unit is equal to or greater than a differential pressure determination threshold;
A differential pressure change rate calculating unit that calculates a change rate of the differential pressure detected by the differential pressure detecting unit;
An ash accumulation amount estimation unit for estimating an ash accumulation amount in the filter based on the differential pressure change rate calculated by the differential pressure change rate calculation unit;
A differential pressure determination threshold value setting unit that sets the differential pressure determination threshold value according to the ash accumulation amount estimated by the ash accumulation amount estimation unit;
The exhaust gas purification apparatus, wherein the differential pressure determination threshold setting unit increases the differential pressure determination threshold as the amount of accumulated ash increases.
The differential pressure change rate calculator calculates an average value of the differential pressure change rate,
The exhaust purification apparatus according to claim 1, wherein the ash accumulation amount estimation unit estimates the accumulation amount of the ash based on an average value of the differential pressure change rate calculated by the differential pressure change rate calculation unit.
The differential pressure determination threshold setting unit increases the differential pressure determination threshold as the ash accumulation amount increases until the ash accumulation amount reaches a specified value, and the ash accumulation amount reaches the specified value. 3. The exhaust emission control device according to claim 1, wherein when the engine pressure is detected, the differential pressure determination threshold value is maximized.