JP2016136011A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate an ash accumulation amount on a filter for collecting PM with high accuracy.SOLUTION: A particulate matter (PM) accumulation amount is calculated on the basis of an output of a differential sensor 33 during stop of execution of regeneration control, a filter inflow ash amount (amount of ash flowing into a gasoline particulate filter (GPF) 25) is estimated on the basis of an operating condition of an engine 11, and an integrated value by this time, of the filter inflow ash amount is determined by integrating the present filter inflow ash amount to the last integrated value of the filter inflow ash amount. When the regeneration control is started, an ash collection rate of the GPF 25 is determined according to the PM accumulation amount in starting the regeneration (PM accumulation amount of GPF 25 in starting regeneration control), and the ash collection rate is increased in accordance with increase of the PM accumulation amount in starting the regeneration. Then the integrated value of the filter inflow ash amount is multiplied by the ash collection rate to determine an ash collection amount (increase of ash accumulation amount), and the present ash accumulation amount is determined by integrating the present ash collection amount to the last ash accumulation amount.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an internal combustion engine control device including a filter that collects particulate matter in exhaust gas from an internal combustion engine.

  In internal combustion engines mounted on vehicles, demand for in-cylinder gasoline engines is expected to increase as fuel efficiency regulations are tightened. However, the in-cylinder injection type gasoline engine has a problem that the amount of PM (Particulate Matter) emission increases as compared with the intake port injection type gasoline engine. As a countermeasure, there is one in which a filter for collecting PM discharged from the engine is disposed in the exhaust passage of the engine.

  In a system equipped with such a filter for collecting PM, the amount of PM deposited on the filter is estimated in order to perform filter regeneration control (control for burning and removing PM deposited on the filter), abnormality diagnosis, and the like. There is something like that. Also, the PM collection filter collects and deposits ash, which is a non-combustible substance in the exhaust gas (for example, ash due to engine oil), but the ash deposited on the filter reduces the amount of PM deposited. Since this is an error factor in estimation, it may be necessary to estimate the amount of ash deposition.

  As a technique for estimating the ash accumulation amount of a filter for collecting PM, for example, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2002-242660), a filter is used based on engine torque and rotational speed. There is a method in which an accumulated ash amount is calculated and the ash amount is cumulatively calculated to obtain an ash accumulation amount (ash cumulative amount).

JP 2002-242660 A

  According to the applicant's research, the ash collection rate of a filter for collecting PM is not necessarily constant, and the amount of ash discharged downstream of the filter during regeneration control depending on the amount of PM deposited at the start of filter regeneration control. It has been found that the ash collection rate (ash remaining rate) changes. In particular, in gasoline engine vehicles, PM accumulated in the filter is burned and reduced by fuel cut control executed at the time of deceleration or the like (that is, fuel cut control also serves as regeneration control). The PM accumulation amount at the start is not always constant, and the ash collection rate is likely to change.

  However, in the technique of the above-mentioned Patent Document 1, such a situation is not taken into consideration at all, and the ash amount calculated based on the engine torque and the rotational speed is simply calculated to obtain the ash accumulation amount. It is difficult to accurately estimate the amount of ash deposition.

  Therefore, the problem to be solved by the present invention is to provide a control device for an internal combustion engine that can accurately estimate the ash accumulation amount of a filter for collecting PM.

  In order to solve the above-mentioned problems, the present invention provides a control device for an internal combustion engine comprising a filter (25) for collecting particulate matter (hereinafter referred to as “PM”) in exhaust gas of the internal combustion engine (11). Inflow ash amount estimating means (30) for estimating the ash amount flowing into the filter (25) based on the operating conditions of the internal combustion engine (11) (hereinafter referred to as “filter inflow ash amount”), and the filter (25) Ash trap that sets the ash collection rate of the filter (25) according to the PM deposition amount of the filter (25) at the start of regeneration control for removing the accumulated PM (hereinafter referred to as "PM deposition amount at the start of regeneration") A collection rate setting means (30), and an ash accumulation amount estimation means (30) for estimating the ash accumulation amount of the filter (25) based on the filter inflow ash amount and the ash collection rate. It is obtained by the configuration.

  In this configuration, taking into account that the ash collection rate (ash remaining rate) varies depending on the PM accumulation amount at the start of regeneration (PM accumulation amount at the start of regeneration control), the PM accumulation amount at the start of regeneration is determined. By setting the ash collection rate, the ash collection rate can be set with high accuracy. By estimating the ash accumulation amount of the filter based on the ash collection rate and the filter inflow ash amount, the ash accumulation amount can be accurately estimated.

FIG. 1 is a diagram showing a schematic configuration of an engine control system in one embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the PM deposition amount and the PM collection rate. FIG. 3 is a diagram showing the relationship between the PM deposition amount and the ash collection rate. FIG. 4 is a diagram showing the deposition in the pores. FIG. 5 is a diagram showing surface layer deposition. FIG. 6 is a time chart for explaining an estimation method of the ash accumulation amount. FIG. 7 is a flowchart showing the flow of the ash accumulation amount estimation routine. FIG. 8 is a diagram conceptually illustrating an example (part 1) of the ash collection rate map. FIG. 9 is a diagram conceptually illustrating an example (part 2) of the ash collection rate map.

Hereinafter, an embodiment embodying a mode for carrying out the present invention will be described.
First, a schematic configuration of the engine control system will be described with reference to FIG.

  An engine 11 that is an in-cylinder internal combustion engine is an in-cylinder injection gasoline engine that directly injects gasoline as fuel into a cylinder. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11, and an air flow meter 14 for detecting the intake air amount is provided downstream of the air cleaner 13. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

  Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. The surge tank 18 is provided with an intake manifold 20 that introduces air into each cylinder of the engine 11. Each cylinder of the engine 11 has a fuel injection valve 21 that directly injects fuel (gasoline) into the cylinder. It is attached. An ignition plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in each cylinder is ignited by spark discharge of the ignition plug 22 of each cylinder.

On the other hand, the exhaust pipe 23 of the engine 11 is provided with a catalyst 24 such as a three-way catalyst for purifying CO, HC, NO _{x and the} like in the exhaust gas, and the exhaust gas is respectively disposed upstream and downstream of the catalyst 24. Exhaust gas sensors 31, 32 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting the air-fuel ratio or rich / lean of the engine are provided.

  Further, on the downstream side of the catalyst 24 in the exhaust pipe 23 of the engine 11 (downstream side of the exhaust gas sensor 32), GPF is used as a filter for collecting PM (Particulate Matter) in the exhaust gas of the engine 11. (Gasoline Particulate Filter) 25 is provided. In the GPF 25, a plurality of cells are defined by porous partition walls 34 (partition walls), and PM in the exhaust gas adheres to the pores 35 (inner wall surfaces of the pores 35) and the surface wall surfaces 36 of the partition walls 34. (See FIGS. 4 and 5). In addition, ash, which is a non-combustible substance in the exhaust gas (for example, ash due to the oil of the engine 11), is also attached to the pores 35 of the partition wall 34 and collected on the surface wall surface 36 (see FIGS. 4 and 5). .

  Further, a differential pressure sensor 33 is provided for detecting a difference (front-rear differential pressure) between the upstream side exhaust pressure and the downstream side exhaust pressure of the GPF 25. Pressure sensors that detect the exhaust pressure are provided on the upstream side and downstream side of the GPF 25, respectively, and the difference between the upstream exhaust pressure detected by the upstream pressure sensor and the downstream exhaust pressure detected by the downstream pressure sensor. (Differential pressure difference) may be calculated. In this case, the upstream and downstream pressure sensors serve as differential pressure sensors.

  A cooling water temperature sensor 26 that detects the cooling water temperature and a knock sensor 27 that detects knocking are attached to the cylinder block of the engine 11. A crank angle sensor 29 that outputs a pulse signal every time the crankshaft 28 rotates by a predetermined crank angle is attached to the outer peripheral side of the crankshaft 28, and the crank angle and the engine are determined based on the output signal of the crank angle sensor 29. The rotation speed is detected.

  Outputs of these various sensors are input to an electronic control unit (hereinafter referred to as “ECU”) 30. The ECU 30 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount and the ignition timing are determined according to the engine operating state. The throttle opening (intake air amount) and the like are controlled.

  By the way, in the system provided with the GPF 25 for collecting PM, when the PM deposition amount of the GPF 25 (PM amount deposited on the GPF 25) becomes too large, the pressure loss of the exhaust gas becomes large. For this reason, the ECU 30 performs regeneration control for burning and removing the PM deposited on the GPF 25 to regenerate the GPF 25 (reducing the amount of PM deposited on the GPF 25). The regeneration control includes, for example, fuel cut control that is executed when a predetermined fuel cut execution condition is satisfied (for example, during deceleration). Further, when the PM accumulation amount of the GPF 25 exceeds a predetermined upper limit value, for example, control for making the air-fuel ratio lean, control for increasing the exhaust temperature, or the like is executed as regeneration control.

  As shown in FIG. 2, the GPF 25 first deposits PM in the pores 35 of the partition wall 34 after PM is removed by regeneration control or the like (after the PM deposition amount becomes almost zero) (FIG. 2). 4), and thereafter, PM is deposited on the surface wall surface 36 of the partition wall 34 (see FIG. 5). In the pore deposition region where PM accumulates in the pores 35 (region where the PM deposition amount is relatively small), the PM collection rate increases as the PM deposition amount increases. Thereafter, in the surface layer deposition region where PM is deposited on the surface wall surface 36 (a region where the PM deposition amount is relatively large), the PM collection rate is substantially constant (approximately 100%).

  In addition, as shown in FIG. 3, ash accumulates in the pores 35 together with PM in the pore deposition region where the PM deposition amount is relatively small (see FIG. 4). When regeneration control is executed in this region, the PM accumulated in the pores 35 is burned and reduced, and the ash accumulated in the pores 35 is discharged downstream of the GPF 25. On the other hand, in the surface layer deposition region where the PM deposition amount is relatively large, the ash is deposited on the surface wall surface 36 together with PM (see FIG. 5). When regeneration control is executed in this region, PM deposited on the surface wall surface 36 and the pores 35 is burned and reduced, but the ash deposited on the surface wall surface 36 is hardly discharged downstream of the GPF 25. For this reason, the GPF 25 has a characteristic that, as the PM accumulation amount at the start of the regeneration control is larger, the proportion of ash remaining in the GPF 25 is higher and the ash collection rate (ash remaining rate) is higher.

  In consideration of such characteristics, in this embodiment, the ECU 30 executes an ash accumulation amount estimation routine shown in FIG. 7 to be described later, whereby the ash accumulation amount of the GPF 25 (the ash amount accumulated on the GPF 25) is set as follows. To estimate.

  Based on the operating conditions of the engine 11, the filter inflow ash amount (the ash amount flowing into the GPF 25) is estimated, and the ash of the GPF 25 according to the PM accumulation amount at the start of regeneration (PM accumulation amount of the GPF 25 at the start of regeneration control). The collection rate is set, and the ash deposition amount of the GPF 25 is estimated based on the filter inflow ash amount and the ash collection rate.

  Specifically, as shown in FIG. 6, the PM accumulation amount is calculated based on the output of the differential pressure sensor 33 by using a map or a mathematical formula while the regeneration control is stopped (before execution). Note that the PM accumulation amount may be calculated by a map or a mathematical expression based on the operating condition of the engine 11 or the like.

  Further, the engine discharge ash amount (the ash amount discharged from the engine 11) based on the operating conditions of the engine 11 (for example, engine rotation speed, load, content of ash contained in oil, travel distance, etc.) is a map or formula The engine exhaust ash amount is calculated as the filter inflow ash amount. Further, the current filter inflow ash amount is integrated to the previous integrated value of the filter inflow ash amount to obtain the integrated value of the filter inflow ash amount up to this time.

In this way, while the regeneration control is stopped, the process of calculating the PM accumulation amount and the process of calculating the integrated value of the filter inflow ash amount are repeatedly executed at a predetermined calculation cycle.
Then, at the time t1 when the regeneration control is started, the ash collection rate is set by a map or a mathematical formula or the like according to the PM accumulation amount at the start of regeneration. At this time, the ash collection rate is increased as the PM accumulation amount at the start of regeneration increases. As a result, the larger the amount of PM deposited at the start of regeneration, the higher the proportion of ash remaining in the GPF 25 and the higher the ash collection rate (ash remaining rate). Increase the collection rate.

After setting the ash collection rate, the integrated value of the filter inflow ash amount is multiplied by the ash collection rate to obtain an ash collection amount (an increase in the ash accumulation amount).
Ash collection amount = integrated value of filter inflow ash amount × ash collection rate

Thereafter, the current ash accumulation amount (the increase in the ash accumulation amount) is added to the previous ash accumulation amount to obtain the current ash accumulation amount.
Current ash accumulation amount = previous ash accumulation amount + current ash collection amount In this manner, the process of calculating the ash accumulation amount is repeatedly executed at every regeneration control execution timing (every start timing).

Hereinafter, the processing content of the ash accumulation amount estimation routine of FIG. 7 executed by the ECU 30 in this embodiment will be described.
The ash accumulation amount estimation routine shown in FIG. 7 is repeatedly executed at a predetermined cycle during the power-on period of the ECU 30, and serves as ash accumulation amount estimation means in the claims. When this routine is started, first, at step 101, it is determined whether or not reproduction control is being executed.

  If it is determined in step 101 that the regeneration control is not being executed, the process proceeds to step 102, and the PM accumulation amount is calculated by a map or a mathematical formula based on the output of the differential pressure sensor 33. Note that the PM accumulation amount may be calculated by a map or a mathematical expression based on the operating condition of the engine 11 or the like. The map or mathematical expression of the PM accumulation amount is created in advance based on test data, design data, and the like, and is stored in the ROM of the ECU 30.

  Thereafter, the process proceeds to step 103, and the engine exhaust ash amount is calculated by a map or a mathematical formula based on the operating conditions of the engine 11 (for example, engine speed, load, ash content contained in oil, travel distance, etc.). This engine exhaust ash amount is defined as a filter inflow ash amount. A map or mathematical expression of the engine exhaust ash amount (filter inflow ash amount) is created in advance based on test data, design data, etc., and is stored in the ROM of the ECU 30. The processing in step 103 serves as inflow ash amount estimation means in the claims.

  Thereafter, the routine proceeds to step 104, where the current filter inflow ash amount is integrated with the previous integrated value of the filter inflow ash amount to obtain the integrated value of the filter inflow ash amount up to this time, and then this routine is terminated. .

  Thereafter, when it is determined in step 101 that the regeneration control is being executed, the process proceeds to step 105, where it is determined whether or not the regeneration control is started (first calculation timing immediately after the start). .

  If it is determined in step 105 that the regeneration control is started, the process proceeds to step 106, and the ash collection rate is set by a map or a mathematical formula according to the PM accumulation amount at the start of regeneration. As the amount of PM deposited at the start of regeneration increases, the ash collection rate is increased.

  In this case, for example, the ash collection rate corresponding to the PM accumulation amount at the start of regeneration is calculated with reference to the ash collection rate map shown in FIG. The map of the ash collection rate in FIG. 8 shows that when the PM accumulation amount at the start of regeneration is smaller than the predetermined value A, the ash collection rate is set to the first predetermined value, and the PM accumulation amount at the start of regeneration. Is equal to or greater than a predetermined value A, the ash collection rate is set to a second predetermined value higher than the first predetermined value. Here, the predetermined value A (see FIGS. 2 and 3) is set to, for example, the PM deposition amount when shifting from the pore deposition region to the surface layer deposition region. The first predetermined value is set to the ash collection rate when the PM deposition amount is in the pore deposition region, and the second predetermined value is the ash collection rate when the PM deposition amount is the surface deposition region. Is set. As a result, when the PM deposition amount at the start of regeneration is in the pore accumulation region (when it is smaller than the predetermined value A), the ash collection rate is set to the first predetermined value, and the PM deposition amount at the start of regeneration Is the surface layer deposition region (when it is greater than or equal to the predetermined value A), the ash collection rate is set to the second predetermined value. The ash collection rate map of FIG. 8 is created in advance based on test data, design data, and the like, and is stored in the ROM of the ECU 30.

  In the case of the GPF 25 having a characteristic that the ash collection rate gradually changes in accordance with the PM accumulation amount at the start of regeneration, referring to the map of the ash collection rate shown in FIG. 9, the PM deposition at the start of regeneration. You may make it calculate the ash collection rate according to quantity. The ash collection rate map in FIG. 9 is set so that the ash collection rate gradually increases as the amount of PM deposition at the start of regeneration increases. The ash collection rate map in FIG. 9 is created in advance based on test data, design data, and the like, and is stored in the ROM of the ECU 30.

  Thereafter, the process proceeds to step 107, where the ash ratio (the ratio of ash to PM in the exhaust gas) is calculated based on the operating conditions of the engine 11 using a map or a mathematical formula, and the ash collection rate is corrected according to this ash ratio. Thus, the higher the ash ratio, the higher the ash collection rate. The ash ratio map or mathematical expression is created in advance based on test data, design data, and the like, and is stored in the ROM of the ECU 30. The processing of these steps 106 and 107 serves as an ash collection rate setting means in the claims.

Thereafter, the process proceeds to step 108, where the integrated value of the filter inflow ash amount is multiplied by the ash collection rate to obtain an ash collection amount (an increase in the ash accumulation amount).
Ash collection amount = integrated value of filter inflow ash amount × ash collection rate

Thereafter, the routine proceeds to step 109, where the current ash collection amount (an increase in the ash accumulation amount) is added to the previous ash accumulation amount to obtain the current ash accumulation amount, and then this routine is terminated.
Current ash accumulation amount = previous ash accumulation amount + current ash collection amount On the other hand, if it is determined in step 105 that the regeneration control is not started, the processing after step 106 is not executed. This routine is terminated.

  In the present embodiment described above, the filter inflow ash amount is estimated based on the operating condition of the engine 11, the ash collection rate of the GPF 25 is set according to the PM accumulation amount at the start of regeneration, and the filter inflow ash amount and the ash are set. The ash deposition amount of the GPF 25 is estimated based on the collection rate. In this case, considering that the ash collection rate (ash remaining rate) varies depending on the PM accumulation amount at the start of regeneration, the ash collection rate is set according to the PM accumulation amount at the start of regeneration. The collection rate can be set with high accuracy. By estimating the ash accumulation amount of the GPF 25 based on the ash collection rate and the filter inflow ash amount, the ash accumulation amount can be accurately estimated.

  In this embodiment, the ash collection rate is increased as the amount of PM deposited at the start of regeneration increases. As a result, the larger the amount of PM deposited at the start of regeneration, the higher the proportion of ash remaining in the GPF 25 and the higher the ash collection rate (ash remaining rate). The collection rate can be increased, and the estimation accuracy of the ash deposition amount can be improved.

  Further, in this embodiment, when the PM accumulation amount at the start of regeneration is smaller than the predetermined value A, the ash collection rate is set to the first predetermined value, and the PM accumulation amount at the start of regeneration is not less than the predetermined value A. In this case, the ash collection rate is set to a second predetermined value higher than the first predetermined value. As a result, the PM deposition amount at the start of regeneration is the surface layer deposition region (when it is greater than or equal to the predetermined value A), compared with the case where the PM deposition amount at the start of regeneration is less than the predetermined value A. As the ash collection rate increases, the ash collection rate used for estimating the ash deposition amount can be switched in two stages.

  In this embodiment, the higher the ash ratio (the ratio of ash to PM in the exhaust gas), the higher the ash collection rate. As a result, the higher the ash ratio, the higher the ash collection rate, and the higher the ash collection rate, the higher the ash collection rate used for estimating the ash accumulation amount, thereby improving the estimation accuracy of the ash accumulation amount. it can.

  In the above embodiment, the present invention is applied to a system equipped with an in-cylinder gasoline engine. However, the present invention is not limited to this, and a diesel engine or an intake port can be used as long as the system includes a filter for collecting PM. Even a system equipped with an injection gasoline engine can be implemented by applying the present invention.

  The PM collecting filter may be a double-ended filter or a single-ended filter. The double-ended filter has a structure in which the inlet side of some of the plurality of cells is closed and the outlet side of the remaining cells (cells whose inlet side is open) is closed.

  The single-ended filter may have a structure in which the inlet side of some cells is closed and the outlet side of all cells is open, or the inlet side of some cells is closed and the remaining cells (the inlet side is The structure may be such that the outlet side of some of the opened cells) is closed. Alternatively, the structure may be such that the exit sides of some cells are closed and the entrance sides of all cells are open, or the exit sides of some cells are closed and the remaining cells (cells with the exit side opened). ) May have a structure in which the inlet side of some of the cells is closed.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 25 ... GPF (filter), 30 ... ECU (inflow ash amount estimation means, ash collection rate setting means, ash accumulation amount estimation means)

Claims (4)

In a control device for an internal combustion engine, comprising a filter (25) for collecting particulate matter (hereinafter referred to as "PM") in exhaust gas of the internal combustion engine (11),
Inflow ash amount estimation means (30) for estimating an ash amount flowing into the filter (25) (hereinafter referred to as “filter inflow ash amount”) based on operating conditions of the internal combustion engine (11);
The ash of the filter (25) according to the PM accumulation amount of the filter (25) at the start of regeneration control for removing PM accumulated on the filter (25) (hereinafter referred to as "PM accumulation amount at the start of regeneration"). Ash collection rate setting means (30) for setting the collection rate;
An ash accumulation amount estimating means (30) for estimating an ash accumulation amount of the filter (25) based on the filter inflow ash amount and the ash collection rate. .   The control device for an internal combustion engine according to claim 1, wherein the ash collection rate setting means (30) increases the ash collection rate as the PM accumulation amount at the start of the regeneration increases.   The ash collection rate setting means (30) sets the ash collection rate to a first predetermined value when the amount of PM deposition at the start of regeneration is less than a predetermined value, and the PM deposition at the start of regeneration. 3. The control device for an internal combustion engine according to claim 2, wherein when the amount is equal to or greater than the predetermined value, the ash collection rate is set to a second predetermined value higher than the first predetermined value.   The internal combustion engine according to any one of claims 1 to 3, wherein the ash collection rate setting means (30) increases the ash collection rate as the ratio of ash to PM in the exhaust gas increases. Engine control device.

Images