JP5724942B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust emission control device that is applied to an internal combustion engine in which a filter that collects particulate matter in exhaust gas is provided in an exhaust passage and estimates the amount of particulate matter that has accumulated in the filter.

  2. Description of the Related Art Conventionally, an exhaust gas purification apparatus in which a filter is provided in an exhaust passage of a diesel engine and particulate matter (PM) in exhaust gas is collected by this filter is well known (see, for example, Patent Document 1). As the accumulated amount of PM collected by the filter increases, the pressure loss at the filter increases, and as a result, the exhaust back pressure of the engine increases and the engine output decreases, and the fuel consumption deteriorates. Arise.

  Therefore, the PM accumulation amount (hereinafter referred to as PM accumulation amount) collected in the filter is estimated, and when this estimated value reaches a predetermined value or more, the temperature of the exhaust gas flowing into the filter through the execution of post injection or the like is set. The temperature of the filter is raised to raise the temperature, whereby the PM accumulated on the filter is oxidized (burned) and removed to regenerate the filter.

  Here, as a method for estimating the PM accumulation amount, there is a method for detecting the differential pressure across the filter with a differential pressure sensor and estimating the PM accumulation amount based on the detected value. This focuses on the tendency that the differential pressure across the filter increases as the PM deposition amount increases.

JP 2009-228487 A

  By the way, in the configuration in which the PM accumulation amount is estimated based on the differential pressure across the filter, the estimation accuracy of the PM accumulation amount deteriorates as the differential pressure across the filter increases. Therefore, the PM accumulation amount on the filter is accurately estimated. It has become difficult to do.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an exhaust emission control device for an internal combustion engine that can accurately estimate the amount of particulate matter deposited on a filter.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
(1) The invention according to claim 1 is applied to an internal combustion engine in which a filter for collecting particulate matter in exhaust gas is provided in an exhaust passage, and estimates the amount of particulate matter deposited on the filter. In the exhaust gas purification apparatus, the estimated amount of particulate matter accumulated in the filter is calculated by multiplying a value obtained by dividing the differential pressure across the filter by the exhaust gas flow rate by a correction coefficient, and the correction coefficient is Prior to calculating the estimated amount of accumulated particulate matter, the estimated amount of particulate matter accumulated in the filter calculated so far, and the estimated amount of accumulated ash in the filter calculated so far It is the gist that it is set based on the exhaust flow rate.

  Even if the amount of particulate matter deposited on the filter is the same, the greater the exhaust flow rate, the greater the differential pressure across the filter. According to the above configuration, the estimated accumulation amount of the particulate matter is calculated based on the value obtained by dividing the differential pressure across the filter by the exhaust flow rate. For this reason, it becomes possible to reduce the influence of the exhaust gas flow rate on the estimated amount of accumulated particulate matter.

  Here, it has been found by the inventors that the value obtained by dividing the differential pressure across the filter by the exhaust flow rate is not always a constant value even if the amount of particulate matter deposited is the same. In other words, the exhaust gas that actually passes through the filter is compressed as the differential pressure across the filter increases, and the exhaust pressure compresses as the differential pressure across the filter increases. Therefore, the value obtained by dividing the differential pressure across the filter by the exhaust flow rate tends to be calculated small. Further, even if the amount of particulate matter deposited is the same, the greater the amount of ash deposited, the more likely the filter will become clogged, and the differential pressure across the filter will tend to increase. According to the above configuration, the correction coefficient is set based on the estimated accumulation amount of particulate matter calculated so far, the estimated accumulation amount of ash calculated so far, and the exhaust gas flow rate. The For this reason, the correction coefficient includes the estimated accumulation amount of particulate matter, the estimated accumulation amount of ash, and the exhaust gas flow rate, and the correction coefficient is set to an appropriate value. Therefore, the amount of particulate matter deposited on the filter can be accurately estimated.

Incidentally, when the estimated accumulation amount of particulate matter and the exhaust gas flow rate are constant, the correction coefficient is set to a larger value as the estimated amount of accumulated ash is larger.
(2) The invention according to claim 2 is the exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the particulate matter accumulation amount estimated value in the filter, the ash accumulation amount estimated value in the filter, and the exhaust gas A gist is provided that defines a relationship between a flow rate and the correction coefficient, and the correction coefficient is set with reference to the map.

  According to this configuration, the correction coefficient is set with reference to the map in which the relationship between the estimated accumulation amount of particulate matter, the estimated amount of ash accumulation, and the exhaust gas flow rate and the correction coefficient is defined. Therefore, the correction coefficient can be set easily and accurately.

  (3) The invention according to claim 1 or claim 2 is calculated by multiplying a value obtained by dividing the differential pressure across the filter by the exhaust gas flow rate by a correction coefficient, as in the invention according to claim 3. The embodiment can be embodied in such a manner that the correction coefficient is set based on the estimated amount of accumulated particulate matter.

  In this case, since it is possible to calculate the estimated amount of particulate matter accumulation only by the calculation mode based on the differential pressure across the filter, the calculation mode of the estimated amount of particulate matter deposition should be simplified. Will be able to.

  (4) Further, according to the first or second aspect of the present invention, as in the fourth aspect of the present invention, the estimated amount of particulate matter accumulated in the filter is separately calculated based on the engine operating state. The embodiment can be embodied in such a manner that the correction coefficient is set on the basis of the calculated accumulated amount of the particulate matter.

  In this case, for example, the amount of particulate matter newly deposited on the filter is calculated based on the engine speed and the fuel injection amount at that time, and this is integrated to calculate the estimated amount of particulate matter deposited on the filter. It is preferable to do.

  (5) Further, in the invention according to any one of claims 1 to 4, the internal combustion engine is an in-vehicle internal combustion engine as in the invention according to claim 5, and the consumption amount of engine lubricating oil and The embodiment can be embodied in such a manner that an estimated amount of ash accumulation in the filter is calculated based on at least one of the travel distance of the vehicle, and the correction coefficient is set based on the estimated amount of accumulated ash accumulation. .

  The amount of ash accumulated in the filter has a correlation with the consumption amount of engine lubricating oil and the travel distance of the vehicle. For this reason, according to the above aspect, the estimated amount of accumulated ash can be calculated accurately.

1 is a schematic diagram showing a configuration of an exhaust gas purification apparatus centering on a filter in an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention. The graph which shows the relationship between the ash accumulation amount in case PM accumulation amount is 0g, and the value which remove | divided the pressure difference before and behind a filter by the exhaust flow rate for every different exhaust flow rate. The graph which shows the relationship between the ash accumulation amount in case PM accumulation amount is 15g, and the value which remove | divided the pressure difference before and behind a filter by the exhaust flow rate for every different exhaust flow rate. (A)-(c) is a map which shows the relationship between an ash deposition amount and a correction coefficient for every different exhaust gas flow rate. The flowchart which shows the execution procedure of the calculation process of PM deposition amount estimated value in the embodiment.

Hereinafter, an embodiment in which the present invention is embodied as an exhaust purification device for an on-board diesel engine (hereinafter, engine) will be described with reference to FIGS.
As shown in FIG. 1, the exhaust passage 2 of the engine is provided with an oxidation catalyst 4 and a filter 6 for collecting particulate matter (hereinafter referred to as PM) in the exhaust in order from the upstream side.

  Various controls of the engine including processing for calculating the PM accumulation amount estimated value (hereinafter referred to as PM accumulation amount estimation value) in the filter 6 are executed by the electronic control unit 20. The electronic control unit 20 temporarily stores a central processing unit (CPU) that performs arithmetic processing related to various controls, a read-only memory (ROM) that stores various control programs and data, and results of the arithmetic processing. It comprises a random access memory (RAM) for storing. Then, the electronic control unit 20 reads detection signals from various sensors, executes various arithmetic processes, and comprehensively controls the engine based on the results.

  The various sensors include an engine rotation speed sensor 21 that detects the engine rotation speed NE, an accelerator operation amount sensor 22 that detects the accelerator operation amount ACCP, an intake air amount sensor 23 that detects the intake air amount GA, and the front-back difference of the filter 6. A differential pressure sensor 24 for detecting the pressure ΔP is provided. In addition, various sensors for grasping the engine operating state and the vehicle traveling state are provided. The exhaust flow rate F is obtained from the intake air amount GA and the fuel injection amount Q.

  Now, even if the PM accumulation amount in the filter 6 is the same, the greater the exhaust flow rate F, the greater the differential pressure ΔP across the filter 6. Therefore, in this embodiment, the estimated PM accumulation amount is calculated based on the value ΔP / F obtained by dividing the differential pressure ΔP across the filter 6 by the exhaust flow rate F. As a result, the influence of the exhaust flow rate F on the estimated PM accumulation amount is reduced.

Here, the effects of the ash deposition amount, the exhaust flow rate F, and the PM deposition amount on the value ΔP / F obtained by dividing the front-rear differential pressure ΔP by the exhaust flow rate F will be described.
Ash is ash that is not oxidized and removed when the filter 6 is regenerated by post-injection or the like among the deposits deposited on the filter 6. Therefore, even if the PM accumulation amount is the same, the differential pressure ΔP across the filter 6 increases as the ash accumulation amount increases.

  FIG. 2 shows an ash accumulation amount (g) when the PM accumulation amount is 0 g, that is, when PM is not accumulated on the filter 6, and a value ΔP / F obtained by dividing the front-rear differential pressure ΔP by the exhaust flow rate F. The relationship is shown for each different exhaust flow rate F.

  As shown in FIG. 2, when the PM accumulation amount is 0 g, the value ΔP / F obtained by dividing the front-rear differential pressure ΔP by the exhaust flow rate F increases as the ash accumulation amount increases. At this time, when the ash accumulation amount is about 140 g or more, the value ΔP / F obtained by dividing the front-rear differential pressure ΔP by the exhaust flow rate F decreases as the exhaust flow rate F increases.

FIG. 3 shows the relationship between the ash accumulation amount (g) when the PM accumulation amount is 15 g and the value ΔP / F obtained by dividing the front-rear differential pressure ΔP by the exhaust flow rate F for each different exhaust flow rate F.
As shown in FIG. 3, even when the PM accumulation amount is 15 g, the value ΔP / F obtained by dividing the front-rear differential pressure ΔP by the exhaust flow rate F increases as the ash accumulation amount increases. This value ΔP / F becomes larger at the same ash accumulation amount and the same exhaust flow rate F than when the PM accumulation amount is 0 g. At this time, the value ΔP / F obtained by dividing the front-rear differential pressure ΔP by the exhaust flow rate F decreases as the exhaust flow rate F increases in the entire ash accumulation amount.

  Therefore, even if the PM accumulation amount is the same, if other conditions are different, the value ΔP / F obtained by dividing the front-rear differential pressure ΔP by the exhaust flow rate F does not become a constant value. More specifically, since the exhaust gas passing through the filter 6 is actually compressed as the exhaust pressure F increases, as the exhaust flow rate F increases, the front-rear differential pressure ΔP increases. Under such circumstances, the value ΔP / F obtained by dividing the front-rear differential pressure ΔP by the exhaust flow rate F tends to be smaller due to the compressibility of the exhaust. Further, even if the PM accumulation amount is the same, the greater the ash accumulation amount, the more likely the filter 6 becomes clogged, and the differential pressure ΔP across the filter 6 tends to increase.

  Therefore, in this embodiment, the PM accumulation amount estimated value Dp is calculated by multiplying the value ΔP / F obtained by dividing the front-rear differential pressure ΔP by the exhaust flow rate F by the compressibility correction coefficient K through the electronic control unit 20. I have to. Here, the compressibility correction coefficient K includes the PM accumulation amount estimation value Dp calculated in the previous control period and the ash accumulation amount estimation value Da calculated immediately before the PM accumulation amount estimation value. , And the exhaust flow rate F. Specifically, as shown in FIGS. 4A to 4C, the electronic control unit 20 performs the PM accumulation amount estimated value Dp, the ash accumulation amount estimated value Da, the exhaust flow rate F, and the compressibility correction. A map defining the relationship with the coefficient K is provided, and the compressibility correction coefficient K is set with reference to this map.

FIG. 4A shows the relationship between the ash accumulation amount estimated value Da (g) and the compressibility correction coefficient K when the PM accumulation amount estimated value Dp is 0 g for each different exhaust flow rate F.
FIG. 4B shows the relationship between the ash accumulation amount estimated value Da (g) and the compressibility correction coefficient K when the PM accumulation amount estimated value Dp is 10 g for each different exhaust flow rate F.

FIG. 4C shows the relationship between the ash accumulation amount estimated value Da (g) and the compressibility correction coefficient K when the PM accumulation amount estimated value Dp is 20 g for each different exhaust flow rate F.
In these figures, the solid line indicates the exhaust flow rate F is 10 (g / s), the broken line indicates the exhaust flow rate F is 50 (g / s), and the alternate long and short dash line indicates the exhaust flow rate F is 100 (g / s). The above relationships are shown respectively.

  As shown in FIGS. 4A to 4C, if the PM accumulation amount estimated value Dp is constant, the compressibility correction coefficient K is increased as the ash accumulation amount estimated value Da increases. More specifically, the amount of change in the compressibility correction coefficient K with respect to the ash accumulation amount estimated value Da, that is, the slope, is increased as the ash accumulation amount estimated value Da increases.

At this time, if the ash accumulation amount estimated value Da is constant, the compressibility correction coefficient K is increased as the exhaust flow rate F increases.
Furthermore, the compressibility correction coefficient K is increased as the PM accumulation amount estimated value Dp increases at the same ash accumulation amount estimated value Da and the same exhaust flow rate F.

  Next, with reference to the flowchart of FIG. 5, the execution procedure of the calculation process of the PM accumulation amount estimated value in the present embodiment will be described. This series of processes is repeatedly executed at predetermined intervals by the electronic control unit 20 during engine operation.

As shown in FIG. 5, in this series of processes, first, the differential pressure ΔP across the filter 6 detected by the differential pressure sensor 24 is read (step S1).
Next, the process proceeds to step S2, and the exhaust flow rate F is calculated from the intake air amount GA detected by the intake air amount sensor 23 and the fuel injection amount Q calculated based on the engine operating state.

  Next, the process proceeds to step S3, with reference to the three-dimensional map shown in FIG. 4, the PM accumulation amount estimated value Dp1 calculated in the previous control cycle, the ash accumulation amount estimated value Da calculated immediately before, and the exhaust gas flow rate. A compressibility correction coefficient K is set based on F. Incidentally, in this embodiment, the ash accumulation amount estimated value Da is calculated for each predetermined period through a known calculation process different from the calculation process of the PM accumulation amount estimated value. Specifically, the ash accumulation amount estimated value Da is calculated based on both the consumption amount of engine lubricating oil and the travel distance of the vehicle.

When the compressibility correction coefficient K is set in this way, the process proceeds to step S4, and the value ΔP / F obtained by dividing the front-rear differential pressure ΔP by the exhaust flow rate F is multiplied by the compressibility correction coefficient K (formula (1)). Reference), the PM accumulation amount estimated value Dp2 is calculated, and this series of processes is temporarily terminated.

Dp2 = (ΔP / F) · K (Expression 1)

Next, the operation of this embodiment will be described.

  As described above, the differential pressure ΔP across the filter 6 increases as the exhaust flow rate F increases even if the PM accumulation amount in the filter 6 is the same. According to the present embodiment, the PM accumulation amount estimated value Dp is calculated based on the value ΔP / F obtained by dividing the differential pressure ΔP across the filter 6 by the exhaust flow rate F. For this reason, the influence of the exhaust flow rate F on the PM accumulation amount estimated value Dp can be reduced.

  Further, according to the present embodiment, the compressibility correction coefficient K includes the PM accumulation amount estimated value Dp1 calculated in the previous control cycle, the ash accumulation amount estimated value Da calculated so far, and the exhaust gas flow rate. And F. Therefore, the PM accumulation amount estimated value Dp1, the ash accumulation amount estimated value Da, and the exhaust flow rate F are added to the compressibility correction coefficient K. As a result, the compressibility correction coefficient K is set to an appropriate value. Therefore, the PM accumulation amount in the filter 6 can be estimated with high accuracy.

According to the exhaust gas purification apparatus for an internal combustion engine according to the present embodiment described above, the following effects (1) to (3) can be obtained.
(1) The electronic control unit 20 calculates the PM accumulation amount estimated value Dp2 by multiplying the value ΔP / F obtained by dividing the front-rear differential pressure ΔP by the exhaust flow rate F by the compressibility correction coefficient K. This compressibility correction coefficient K is obtained by calculating the PM accumulation amount estimated value Dp1 calculated in the previous control cycle, the ash accumulation amount estimated value Da calculated immediately before, and the PM accumulation amount estimated value Dp2. It is set based on the exhaust flow rate F. According to such a configuration, the PM accumulation amount can be estimated with high accuracy.

  (2) A three-dimensional map that defines the relationship between the PM accumulation amount estimated value Dp1, the ash accumulation amount estimated value Da, the exhaust flow rate F, and the compressibility correction coefficient K is provided. The compressibility correction coefficient K is set with reference to this three-dimensional map. According to such a configuration, the compressibility correction coefficient K is set with reference to the three-dimensional map, so that the compressibility correction coefficient K can be set easily and accurately. Further, since the PM accumulation amount estimated value can be calculated only by the calculation mode based on the front-rear differential pressure ΔP, the calculation mode of the PM deposition amount estimated value can be simplified.

  (3) The ash accumulation amount estimated value Da in the filter 6 is calculated based on both the consumption amount of the engine lubricating oil and the travel distance of the vehicle, and the compressibility correction coefficient K is calculated based on the calculated ash accumulation amount estimated value Da. Set. Since the amount of ash accumulated in the filter 6 has a correlation with the consumption amount of engine lubricating oil and the travel distance of the vehicle, according to such a configuration, the estimated amount of ash accumulation Da can be accurately calculated. It becomes like this.

  The exhaust gas purification apparatus for an internal combustion engine according to the present invention is not limited to the configuration exemplified in the above embodiment, and can be implemented as, for example, the following form appropriately modified.

  In the above embodiment, the ash accumulation amount estimated value Da is calculated based on both the consumption amount of engine lubricating oil and the travel distance of the vehicle, but the calculation method of the ash accumulation amount estimated value is not limited to this. Instead, the ash accumulation amount estimated value Da may be calculated based on either the consumption amount of the engine lubricating oil or the travel distance of the vehicle. Further, the ash accumulation amount estimated value may be calculated by another calculation method.

  In the above embodiment, the compressibility correction coefficient K is set based on the PM accumulation amount estimated value Dp1 calculated in the previous control cycle. However, the calculation of the PM accumulation amount estimated value used for setting such a correction coefficient is performed. The method is not limited to this. In addition, for example, the amount of PM newly accumulated on the filter 6 is calculated based on the engine speed NE and the fuel injection amount Q at that time, and the PM accumulation amount estimated value is calculated by integrating this amount. It may be. In this case, when the filter is completely regenerated, the estimated PM accumulation amount may be set to “0”, for example.

  In the above embodiment, the compressibility correction coefficient K is set by referring to the three-dimensional map, but instead, the PM accumulation amount estimated value Dp, the ash accumulation amount estimated value Da, and the exhaust flow rate F It is also possible to prepare a function with the correction coefficient and calculate the correction coefficient with this function.

  The present invention can be embodied as an exhaust gas purification device for a gasoline engine.

  DESCRIPTION OF SYMBOLS 2 ... Exhaust passage, 4 ... Oxidation catalyst, 6 ... Filter, 20 ... Electronic control unit, 21 ... Engine rotational speed sensor, 22 ... Accelerator operation amount sensor, 23 ... Intake air amount sensor, 24 ... Differential pressure sensor

Claims (5)

In an exhaust emission control device for estimating the amount of particulate matter accumulated in the filter, which is applied to an internal combustion engine provided with an exhaust passage in which a filter for collecting particulate matter in exhaust gas is provided.
By multiplying a value obtained by dividing the differential pressure across the filter by the exhaust gas flow rate by a correction coefficient, an estimated amount of particulate matter accumulated in the filter is calculated.
Prior to calculating the estimated deposition amount of the particulate matter, the correction factor is the estimated particulate matter deposition amount in the filter calculated so far, and the ash in the filter calculated so far. An exhaust gas purification apparatus for an internal combustion engine, which is set based on an estimated amount of accumulated gas and an exhaust gas flow rate. The exhaust gas purification apparatus for an internal combustion engine according to claim 1,
An estimated amount of particulate matter accumulated in the filter, an estimated amount of ash accumulated in the filter, and a map defining the relationship between the exhaust flow rate and the correction coefficient;
The exhaust gas purification apparatus for an internal combustion engine, wherein the correction coefficient is set with reference to the map. The exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 2,
An exhaust gas for an internal combustion engine, wherein the correction coefficient is set based on an estimated amount of particulate matter accumulation calculated by multiplying a value obtained by dividing the differential pressure across the filter by an exhaust flow rate by a correction coefficient Purification equipment. The exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 2,
An internal combustion engine characterized by separately calculating an estimated amount of particulate matter accumulated in the filter based on an engine operating state, and setting the correction coefficient based on the calculated estimated amount of particulate matter accumulated Exhaust purification device. The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 4,
The internal combustion engine is an in-vehicle internal combustion engine,
Calculating the estimated amount of ash accumulation in the filter based on at least one of the consumption amount of engine lubricating oil and the travel distance of the vehicle, and setting the correction coefficient based on the calculated estimated amount of ash accumulation. An exhaust gas purification apparatus for an internal combustion engine characterized by the above.