JP2015229942A - Internal combustion engine exhaust emission control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine exhaust emission control system capable of suppressing an increase in a difference between a pressure in front of a particulate filter and a pressure in rear of the particulate filter.SOLUTION: An exhaust emission control system comprises: a particulate filter collecting particulate matter; and accumulation amount estimation means estimating an accumulation amount of ashes of the particulate matter. The particulate filter contains platinum catalyst particles and rhodium catalyst particles carried on carriers. The platinum catalyst particles are carried on the carriers at a concentration of 1.0 g/L, and the rhodium catalyst particles are carried on the carriers at a concentration of 1.2 g/L. If the accumulation amount of the ashes of the particulate filter exceeds a preset accumulation amount determination value, the exhaust emission control system exerts a control to heat the particulate filter up to a temperature in a range from 750°C to 900°C.

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine.

In an internal combustion engine, fuel is burned in the engine body and exhaust gas is discharged. Exhaust gas discharged from the engine body is purified by an exhaust purification device. The exhaust gas contains particulate matter (PM) in addition to carbon monoxide (CO), unburned hydrocarbon (HC) and nitrogen oxide (NO _x ). Carbon monoxide, unburned hydrocarbons and nitrogen oxides are purified by being oxidized or reduced by a catalyst.

  In order to remove particulate matter from the exhaust gas, a collection filter called a particulate filter is disposed in the engine exhaust passage. Particulate matter is collected and deposited on the particulate filter. When the amount of accumulated particulate matter increases, the particulate matter can be burned by regeneration control in which the temperature of the particulate filter is raised in an atmosphere with excess air.

  Japanese Patent Application Laid-Open No. 2012-012941 discloses an internal combustion engine including a catalyst that purifies exhaust gas and an exhaust gas recirculation device that recirculates part of the exhaust gas and mixes it with intake air. A catalyst deterioration suppression control method for an internal combustion engine is disclosed in which a catalyst temperature is estimated from an air amount, and fuel cut is prohibited when the estimated catalyst bed temperature exceeds a determination value.

JP 2012-012941 A

  Particulate matter contained in the exhaust gas includes particulate matter called ash in addition to soot (soot) contained in the exhaust gas discharged from the engine body. Ash is generated, for example, when lubricating oil in the engine body flows into the combustion chamber from the sliding portion between the cylinder bore and the piston. It is known that ash is a sulfuric acid compound produced mainly from sulfur components contained in engine oil. For example, in a compression self-ignition internal combustion engine, ash is mainly composed of calcium sulfate. In a spark ignition type internal combustion engine, ash contains calcium phosphate in addition to calcium sulfate.

  Soot contained in the exhaust gas can be burned and removed by regeneration control of the particulate filter. However, the ash remains without burning even when the regeneration control is performed. Ash remaining in the particulate filter closes the opening of the base material of the particulate filter. For this reason, there is a problem that the differential pressure before and after the particulate filter gradually increases.

  Ash has the property of shrinking in a high temperature atmosphere. When the ash contracts, the closed portion of the particulate filter is reduced, and an increase in the differential pressure before and after the particulate filter can be suppressed. However, the temperature at which the ash shrinks is very high, and if the catalyst particles are supported on the filter, the purification ability of the catalyst may be reduced. For example, when the particulate filter becomes very hot, there is a possibility that a sintering phenomenon occurs in which the catalyst particles aggregate and the purification rate decreases.

  For this reason, the conventional technique has a problem that it is not possible to carry out control for shrinking the ash. For example, when the temperature of the collection filter exceeds a predetermined determination value, control for suppressing an increase in the temperature of the collection filter has been performed in order to suppress deterioration of the catalyst carried on the collection filter. As a result, there is a problem that the differential pressure of the collection filter increases due to the accumulation of ash.

  An object of the present invention is to provide an exhaust emission control device for an internal combustion engine that suppresses an increase in differential pressure before and after a collection filter.

  An exhaust gas purification apparatus for an internal combustion engine according to the present invention includes a collection filter that collects particulate matter including a combustion component that burns when the temperature rises in an excess air atmosphere and a remaining non-combustion component, and particles of the collection filter And a deposit amount estimating means for estimating the deposit amount of the non-combustion component of the particulate matter. The collection filter includes a support containing at least one of ceria, zirconia, alumina, and barium, and platinum and rhodium catalyst particles supported on the support. The platinum catalyst particles are supported on the carrier at a concentration of 1.0 g / L, and the rhodium catalyst particles are supported on the carrier at a concentration of 1.2 g / L. The exhaust purification device performs control to raise the collection filter to a temperature within a range of 750 ° C. or more and 900 ° C. or less when the accumulation amount of the non-combustion component of the collection filter exceeds a predetermined accumulation amount determination value. carry out.

  In the above invention, the fuel cut control for stopping the supply of fuel to the combustion chamber when the required load becomes zero is formed so that the temperature of the collection filter is increased when the fuel cut control is performed. It is configured to prohibit fuel cut control when it exceeds a predetermined thermal deterioration judgment value, and when the accumulation amount of the non-combustion component of the collection filter exceeds a predetermined deposition amount judgment value When the temperature of the collection filter is estimated to be within the range of 750 ° C. or more and 900 ° C. or less by performing the fuel cut control, the prohibition of the fuel cut control can be canceled.

  In the above invention, when the accumulation amount of the non-combustion component of the collection filter exceeds a predetermined accumulation amount determination value, the control is performed to raise the collection filter to a temperature in the range of 800 ° C. or more and 900 ° C. or less. It is preferable to implement.

  ADVANTAGE OF THE INVENTION According to this invention, the exhaust gas purification apparatus of the internal combustion engine which suppresses the raise of the differential pressure before and behind a collection filter can be provided.

1 is a schematic view of an internal combustion engine in an embodiment. It is a schematic front view of the particulate filter in an embodiment. It is the schematic sectional drawing which cut the particulate filter in an embodiment along the flow direction of exhaust gas. It is a graph of the change width of the gap between the ash and the substrate after the temperature of the particulate filter is raised. It is a graph of the compression ratio of the ash after raising the temperature of a particulate filter. It is a graph of the purification performance of the catalyst after raising the temperature of the particulate filter. It is a flowchart of control which estimates the accumulation amount of the ash in embodiment. It is a map for estimating the deposition amount of the particulate matter deposited on the particulate filter in the embodiment. It is a flowchart of operation control in an embodiment.

  With reference to FIGS. 1 to 9, an exhaust emission control device for an internal combustion engine in the embodiment will be described. In the present embodiment, a spark ignition type internal combustion engine will be described as an example.

  FIG. 1 schematically shows an internal combustion engine in the present embodiment. The internal combustion engine includes an engine body 1. The engine body 1 includes a cylinder block 2 and a cylinder head 4 fixed to the cylinder block 2. A hole (cylinder bore) is formed in the cylinder block 2, and a piston 3 that reciprocates inside the hole is disposed. The combustion chamber 5 is configured by a space surrounded by the hole of the cylinder block 2, the piston 3, and the cylinder head 4. An intake port 7 and an exhaust port 9 are formed in the cylinder head 4. The intake valve 6 opens and closes the intake port 7, and the exhaust valve 8 is formed to open and close the exhaust port 9.

  On the inner wall surface of the cylinder head 4, a spark plug 10 is disposed at the center of the combustion chamber 5, and a fuel injection valve 11 is disposed at the periphery of the inner wall surface of the cylinder head 4. The spark plug 10 is configured to generate a spark in response to the ignition signal. The fuel injection valve 11 injects a predetermined amount of fuel into the combustion chamber 5 according to the injection signal. The fuel injection valve 11 may be disposed so as to inject fuel into the intake port 7.

  The intake port 7 of each cylinder is connected to a surge tank 14 via a corresponding intake branch pipe 13. The surge tank 14 is connected to an air cleaner 16 via an intake pipe 15. The intake port 7, the intake branch pipe 13, the surge tank 14, and the intake pipe 15 constitute an engine intake passage. A throttle valve 18 driven by an actuator 17 is disposed inside the intake pipe 15. The throttle valve 18 can be changed by the actuator 17 to change the opening area of the engine intake passage.

  The internal combustion engine includes an exhaust purification device. The exhaust purification device of the present embodiment includes an exhaust purification catalyst 20 and a particulate filter 23 as a collection filter disposed downstream of the exhaust purification catalyst 20. The exhaust purification catalyst 20 of the present embodiment is disposed in the vicinity of the engine body 1. Further, the particulate filter 23 is arranged under the floor.

  The engine exhaust passage is constituted by an exhaust port 9 of each cylinder, an exhaust manifold 19, an exhaust pipe 22, and the like. The exhaust port 9 is connected to an exhaust manifold 19. The exhaust manifold 19 has a plurality of branches connected to the plurality of exhaust ports 9 and a collective part in which these branches are assembled. A collecting portion of the exhaust manifold 19 is connected to the exhaust purification catalyst 20. The exhaust purification catalyst 20 is connected to the particulate filter 23 via the exhaust pipe 22.

  An exhaust emission control device for an internal combustion engine includes a control device. The control device of the present embodiment is composed of an electronic control unit (ECU) 31. The electronic control unit 31 is composed of a digital computer and includes a RAM (random access memory) 33, a ROM (read only memory) 34, a CPU (microprocessor) 35, an input port 36 and An output port 37 is included.

  A load sensor 43 that generates an output voltage proportional to the amount of depression of the accelerator pedal 42 is connected to the accelerator pedal 42. The output voltage of the load sensor 43 is input to the input port 36 via the corresponding AD converter 38. The crank angle sensor 44 generates an output pulse every time the crankshaft rotates 15 degrees, for example, and this output pulse is input to the input port 36. The CPU 35 detects the engine speed and the crank angle based on the output pulse of the crank angle sensor 44. On the other hand, the output port 37 is connected to the actuator 17 that drives the spark plug 10, the fuel injection valve 11, and the throttle valve via a corresponding drive circuit 45.

  An air flow meter 39 for detecting the flow rate of air flowing through the intake pipe 15 is disposed inside the intake pipe 15. The output of the air flow meter 39 is input to the input port 36 via the corresponding AD converter 38.

  When the ratio of the exhaust gas air and fuel (hydrocarbon) supplied to the engine intake passage, combustion chamber, or engine exhaust passage is referred to as the air-fuel ratio (A / F) of the exhaust gas, An air-fuel ratio sensor 40 for detecting the air-fuel ratio of the exhaust gas flowing out from the engine body 1 is disposed. The air-fuel ratio sensor 40 can detect the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 20. The particulate filter 23 is provided with a differential pressure sensor 24 that detects a differential pressure across the particulate filter 23. A temperature sensor 25 is disposed upstream of the particulate filter 23 as a temperature detector that detects the temperature of the upstream end of the particulate filter 23. A temperature sensor 26 is arranged downstream of the particulate filter 23 as a temperature detector for detecting the temperature of the downstream end of the particulate filter 23. The output signals of the temperature sensors 25 and 26, the air-fuel ratio sensor 40, and the differential pressure sensor 24 are input to the input port 36 via the corresponding AD converter 38.

  The exhaust purification catalyst 20 of the present embodiment is a three-way catalyst that functions as a so-called startup catalyst. The exhaust purification catalyst 20 can oxidize unburned hydrocarbons and carbon monoxide from a low temperature range after the internal combustion engine is started. The exhaust purification catalyst 20 is not limited to a three-way catalyst, and a catalyst that purifies any exhaust gas can be disposed. Alternatively, the exhaust purification catalyst 20 may not be arranged.

  FIG. 2 shows a schematic front view of the particulate filter of the present embodiment. FIG. 3 is a schematic cross-sectional view when the particulate filter is cut along the axial direction. The particulate filter 23 is a filter for removing particulate matter (PM) contained in the exhaust gas. The particulate filter 23 in the present embodiment is formed in a cylindrical shape.

  The particulate filter 23 has a honeycomb structure. The particulate filter 23 has a plurality of passages 60 and 61 extending along the flow direction of the exhaust gas. The downstream end of the passage 60 is closed by a plug 62. The passage 61 is closed at the upstream end by a plug 63. In FIG. 2, the plug 63 is hatched. The passages 60 and the passages 61 are alternately formed with thin partition walls 64.

  The base material of the particulate filter 23 is formed of a porous material. The base material of this embodiment is formed of cordierite containing alumina, silica, and magnesium oxide. The passage 60 through which the exhaust gas flows is surrounded by a passage 61 through which the exhaust gas flows out. The exhaust gas flowing into the passage 60 flows out to the adjacent passage 61 through the surrounding partition wall 64 as indicated by an arrow 200. Particulate matter is collected when the exhaust gas passes through the partition wall 64. The exhaust gas from which the particulate matter has been removed flows out of the particulate filter 23 through the passage 61. In this way, the particulate matter is collected by the particulate filter.

  The particulate filter 23 of the present embodiment has a function as a three-way catalyst. The particulate filter 23 has a coat layer formed on the surface of the substrate. The coating layer includes a carrier that supports catalyst particles of metal having a catalytic action. The carrier is made of at least one material selected from ceria, zirconia, alumina, barium and the like. The coat layer of the present embodiment carries platinum (Pt) catalyst particles and rhodium (Rh) as noble metals. Purifying unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) simultaneously by setting the air-fuel ratio of the exhaust gas flowing into the particulate filter 23 to be close to the theoretical air-fuel ratio. Can do. In the particulate filter 23 of the present embodiment, a coat layer having a total coat amount of 100 g / L is formed on the surface of a cordierite base material. The concentration of platinum catalyst particles is 1.0 g / L, and the concentration of rhodium catalyst particles is 0.2 g / L.

  When the amount of particulate matter deposited on the particulate filter reaches the regeneration determination value, regeneration control of the particulate filter is performed. In the regeneration control of the particulate filter, the air-fuel ratio of the exhaust gas flowing into the particulate filter is maintained at a lean air-fuel ratio (greater than the theoretical air-fuel ratio). Then, the temperature of the particulate filter 23 is raised to a temperature at which regeneration is possible. For example, since the particulate matter can be combusted at about 500 ° C. or higher, the temperature of the particulate filter is raised to about 650 ° C. At least a part of the deposited particulate matter burns. And it maintains at predetermined temperature until the combustible particulate matter burns.

  The particulate matter contained in the exhaust gas discharged from the engine body 1 includes a combustion component that burns by regeneration control and a non-combustion component that remains without being burned by regeneration control. Combustion components include carbon particles called soot (soot), high-boiling organic compounds called sof (SOF), and sulfur component particles called sulfate. On the other hand, the non-combustion component is called ash, and calcium sulfate is the main component. The amount of ash deposited is proportional to the sulfated ash content of the lubricating oil that lubricates each part of the engine body 1. That is, it is proportional to the amount of sulfur component contained in the engine oil.

  Ash is deposited in layers on the surface of the passage of the particulate filter 23. The ash layer shrinks when the temperature is very high. When the ash layer contracts, a crack is generated, and exhaust gas flows through the crack. Further, when the ash layer contracts, the gap between the base material and the ash layer increases, and the exhaust gas flows through the gap. As a result, an increase in the differential pressure before and after the particulate filter 23 can be suppressed.

  In the internal combustion engine of the present embodiment, a test was performed in which a lubricant is mixed with fuel and an ash layer is intentionally generated in the particulate filter 23. As the oil mixed with the test fuel, an engine oil for an API (American Petroleum Institute) standard CF-4 grade diesel engine was used. This engine oil was mixed with 2% gasoline, the engine body was driven, and an ash layer was formed on the surface of the base material of the particulate filter 23. And the behavior of the ash layer when the temperature of the particulate filter was raised was tested.

  FIG. 4 shows the result of measuring the change width of the gap that occurs when the temperature of the particulate filter is raised. In the test, one cycle of several minutes is set, and the cycle for depositing the particulate matter and the cycle for raising the particulate filter to a predetermined temperature to burn the particulate matter and shrink the ash are set as one cycle. It is repeating. These cycles are repeated for 20 hours.

  Thereafter, one passage of the particulate filter 23 is selected, and five gaps between the base material and the ash layer are measured on the wall surface of the selected passage. The horizontal axis is the maximum temperature when the temperature of the particulate filter 23 is raised. In this test, the test is performed a plurality of times while changing the temperature from 650 ° C. to 900 ° C. The change width on the vertical axis indicates the change width from the width of the gap when the maximum temperature of the particulate filter 23 is 650 ° C.

  It can be seen that the width of the gap increases as the temperature of the particulate filter increases at all measurement points. When the width of the gap is increased, the flow path of the exhaust gas is increased and the exhaust gas is easily circulated. It can be seen that the temperature of the particulate filter 23 is preferably higher in order to shrink the ash. Further, at all the measurement points, when the maximum temperature is approximately 800 ° C. or higher, the increase in the change width becomes gradual and the width of the gap is almost constant.

  FIG. 5 shows the relationship between the maximum temperature of the particulate filter and the compression ratio of the ash layer. The vertical axis represents the rate of change in the cross-sectional area of the ash layer as a result of shrinking the particulate filter at a high temperature. The vertical axis represents the ratio with the cross-sectional area of the ash layer when the test is conducted at a maximum temperature of 650 ° C. as 1.

  As the maximum temperature of the particulate filter increases, the compression ratio decreases. A compression ratio of about 10% is obtained at 750 ° C. and about 20% at 800 ° C. or higher. As with the change width of the gap, the compression ratio is almost constant at 800 ° C. or higher. Thus, the same tendency is obtained that the change width and the compression ratio of the gap portion are substantially constant when the maximum temperature of the particulate filter is 800 ° C. or higher.

  On the other hand, the exhaust purification catalyst undergoes thermal deterioration in which the catalyst performance deteriorates as the temperature rises. Thermal degradation includes, for example, a sintering phenomenon. The sintering phenomenon is a phenomenon in which catalyst particles such as platinum are joined together to increase the particle size, and as a result, the total surface area of the catalyst particles is reduced to reduce the purification ability. When the temperature of the exhaust purification catalyst is high and the atmosphere around the exhaust purification catalyst is excessive in air, a sintering phenomenon may occur. In the test of the present embodiment, a test for confirming the catalyst performance was performed.

  FIG. 6 shows a graph of the 50% purification rate temperature of the catalyst against the maximum temperature of the particulate filter. The vertical axis is the temperature that achieves a purification rate of 50% for carbon monoxide. That is, the temperature of the particulate filter when 50% of carbon monoxide contained in the exhaust gas is purified.

  It can be seen that when the maximum temperature of the particulate filter exceeds 900 ° C., the 50% purification rate temperature rapidly increases. That is, when the maximum temperature of the particulate filter 23 exceeds 900 ° C., it can be seen that the purification performance deteriorates. On the other hand, until the temperature of the particulate filter 23 reaches 900 ° C., the 50% purification rate temperature is substantially constant. That is, it can be seen that when the temperature of the particulate filter 23 is up to 900 ° C., the reduction in purification performance as an exhaust purification catalyst is small.

  From these test results, the inventors set the temperature of the particulate filter 23 to a temperature within the temperature range of 750 ° C. or more and 900 ° C. or less, thereby suppressing deterioration in the purification performance of the particulate filter 23 and ashing. Has been found to effectively shrink. It has also been found that the ash can be more effectively contracted by setting the temperature of the particulate filter 23 within the temperature range of 800 ° C. or higher and 900 ° C. or lower. These temperature ranges include a temperature that is higher than the temperature for regeneration control of the particulate filter, and further includes a temperature that is higher than a thermal deterioration determination value for catalyst deterioration suppression control described later.

  Thus, by maintaining the particulate filter 23 within a predetermined temperature range, the ash layer can be contracted while suppressing thermal deterioration such as sintering. As a result, an increase in the differential pressure before and after the particulate filter can be suppressed. In addition, although the said test was implemented by changing the volume of a particulate filter in the range from 0.9L to 1.3L, the same result was obtained. For this reason, it is considered that suppression of the differential pressure before and after and reduction of the purification rate do not depend on the size of the particulate filter.

  The internal combustion engine of the present embodiment includes a deposition amount estimation unit that estimates the amount of ash deposition. In the present embodiment, the control device for the exhaust gas purification device functions as the accumulation amount estimating means. The control device estimates the amount of ash deposited on the particulate filter 23, and when the amount of ash deposited exceeds a predetermined deposition amount determination value, the particulate filter 23 is set to 750 ° C. or higher and 900 ° C. or lower. Implement control to increase temperature.

  By the way, in the exhaust purification apparatus of the present embodiment, the catalyst deterioration suppression control is performed so that the temperature of the particulate filter 23 does not become higher than the heat deterioration determination value for suppressing the heat deterioration. The exhaust emission control device according to the present embodiment includes temperature estimation means for estimating the temperature of the particulate filter. As the thermal deterioration determination value, for example, a temperature within a range of 700 ° C. or higher and 800 ° C. or lower can be employed. In the present embodiment, the temperature of the particulate filter 23 is estimated when the ash accumulation amount exceeds a predetermined accumulation amount determination value, and the temperature of the particulate filter is 750 ° C. or more and 900 ° C. or less. Performs control for prohibiting catalyst deterioration suppression control.

  Referring to FIG. 1, the internal combustion engine of the present embodiment stops the supply of fuel from fuel injection valve 11 when the required load becomes zero. That is, fuel cut control is performed. When the fuel cut control is performed, the exhaust gas flowing out from the combustion chamber 5 is in an excess air state. When this exhaust gas flows into the exhaust purification catalyst 20 or the particulate filter 23, an oxidation reaction may occur and the temperature may increase. As a result, there is a possibility that the temperature of the particulate filter 23 rises and thermal degradation occurs.

  For this reason, in normal operation control, when it is determined that the temperature of the particulate filter 23 exceeds the thermal deterioration determination value when the fuel cut control is performed, a control for prohibiting the fuel cut control is performed. For example, the current temperature of the particulate filter 23 is estimated, and when this temperature is higher than the thermal deterioration determination value, the fuel cut control can be prohibited. By this control, it is possible to suppress the thermal deterioration of the particulate filter 23. Thus, the control which prohibits fuel cut control is implemented as catalyst deterioration suppression control.

  In the internal combustion engine of the present embodiment, when the fuel cut control is performed, the catalyst deterioration suppression control is prohibited when the temperature of the particulate filter 23 is estimated to be 750 ° C. or more and 900 ° C. or less. That is, by canceling prohibition of fuel cut control, control is performed to raise the temperature of the particulate filter 23 and contract the ash.

  FIG. 7 shows a flowchart of control for estimating the amount of ash deposited on the particulate filter. As described above, ash corresponds to a non-combustion component that remains without being burned even by regeneration control of the particulate filter 23. In the present embodiment, the ash accumulation amount is estimated immediately after the regeneration control of the particulate filter 23 is completed. First, the regeneration control of the particulate filter 23 will be described.

  FIG. 8 shows a map for calculating the amount of particulate matter deposited on the particulate filter. The internal combustion engine of the present embodiment is formed so that the amount of particulate matter deposited on the particulate filter 23 can be estimated. The amount PMA of particulate matter deposited on the particulate filter 23 per unit time can be obtained from the engine speed N and the fuel injection amount Q in the combustion chamber. By accumulating the amount PMA of particulate matter deposited per unit time obtained from this map, the amount of particulate matter deposited at an arbitrary time can be estimated. With reference to FIG. 1, such a map and the calculated amount of accumulated particulate matter can be stored in the electronic control unit 31.

  In this embodiment, the amount of particulate matter deposited per unit time is calculated using a map of the amount of particulate matter deposited per unit time. However, the present invention is not limited to this embodiment, and any method can be used. The amount of particulate matter deposited can be calculated.

  When the amount of particulate matter accumulated exceeds a predetermined regeneration determination value, regeneration control of the particulate filter 23 is performed. For example, unburned fuel is supplied to the exhaust purification catalyst 20 in a state where the air-fuel ratio of the exhaust gas is lean. The temperature of the exhaust gas rises due to the heat of oxidation reaction. The temperature of the particulate filter 23 can be raised by the high-temperature exhaust gas. And regeneration control is continued by the time length when all the combustion components burn out among particulate matter. When the regeneration control is completed, the engine body 1 is returned to the original operating state.

  Referring to FIG. 7, in step 81, it is determined whether or not the regeneration control of the particulate filter 23 has been completed. In step 81, when the regeneration control of the particulate filter 23 is being performed or during the period before the regeneration control is performed, this control is terminated. If the regeneration control of the particulate filter 23 is completed in step 81, the process proceeds to step 82.

  In step 82, the differential pressure across the particulate filter 23 is detected. In the present embodiment, referring to FIG. 1, the differential pressure sensor 24 detects the differential pressure before and after the particulate filter 23.

  Next, in step 83, the amount of ash deposited is estimated. In the present embodiment, when regeneration control of the particulate filter 23 is performed, combustion components are completely removed. Immediately after the regeneration control is finished, it is considered that the non-combustion component remains in the particulate filter 23. For this reason, the amount of ash deposited can be estimated by detecting the differential pressure before and after the regeneration control of the particulate filter 23. For example, the value of the ash accumulation amount as a function of the differential pressure before and after the particulate filter, the intake air amount, and the exhaust gas temperature can be stored in the electronic control unit 31 in advance. Immediately after the regeneration control, the differential pressure before and after, the intake air amount, and the temperature of the exhaust gas flowing into the particulate filter can be detected, and the ash accumulation amount can be estimated based on these values. Thus, the amount of ash deposited can be estimated based on the differential pressure before and after the particulate filter 23.

  Next, in step 84, the estimated accumulation amount of ash is stored in the electronic control unit 31. In this manner, the amount of accumulated ash can be estimated every time regeneration control of the particulate filter 23 is performed.

  FIG. 9 shows a flowchart of operation control in the present embodiment. In step 91, it is determined whether or not the required load is zero. With reference to FIG. 1, in this Embodiment, it is discriminate | determined whether the required load output from the load sensor 43 is zero. In step 91, when the required load is not zero, this control is terminated. In step 91, when the required load is zero, the routine proceeds to step 92.

  In step 92, the amount of accumulated ash is acquired. That is, the ash accumulation amount is read as estimated by the control for estimating the ash accumulation amount in FIG.

  Next, in step 93, it is determined whether or not the ash accumulation amount is larger than a predetermined accumulation amount determination value. In step 93, when the ash accumulation amount is equal to or less than a predetermined accumulation amount determination value, this control is terminated. When the ash accumulation amount exceeds the predetermined accumulation amount determination value at step 93, the routine proceeds to step 94.

  In step 94, the current temperature Tcc of the particulate filter 23 is acquired. The exhaust emission control device according to the present embodiment includes a temperature detection device that detects the temperature of the particulate filter 23. As the temperature of the particulate filter 23, the temperature of the central portion of the base material of the particulate filter 23 can be adopted. Referring to FIG. 1, in the present embodiment, the temperature of temperature sensor 25 arranged upstream of particulate filter 23 is detected as the temperature of the end portion on the upstream side of particulate filter 23. Then, the temperature of the temperature sensor 26 disposed downstream of the particulate filter 23 is detected as the temperature of the downstream end of the particulate filter 23. The average value of the temperature at the upstream end and the temperature at the downstream end is used as the temperature at the center of the particulate filter 23.

  The temperature of the particulate filter 23 is not limited to this form. For example, the temperature of the exhaust gas flowing out from the particulate filter 23 may be adopted. Alternatively, any device that detects the temperature of the particulate filter 23 can be adopted as the temperature detection device. For example, you may include the temperature sensor which contacts the center part of a base material.

  Referring to FIG. 9, next, in step 95, it is determined whether or not temperature Tcp is within a predetermined temperature increase permission range. As the temperature increase permission range, a temperature at which the temperature of the particulate filter is predicted to be within a range of 750 ° C. or higher and 900 ° C. or lower when fuel cut control is performed can be set. For example, a range obtained by subtracting a predetermined temperature from a range from 750 ° C. to 900 ° C. can be employed.

  In step 95, if the temperature Tcc is not within the allowable temperature rise range, the process proceeds to step 96. In step 96, catalyst deterioration suppression control is permitted. For example, if the temperature of the particulate filter is equal to or lower than a predetermined thermal deterioration determination value when the required load becomes zero, fuel cut control is performed. On the other hand, if the temperature of the particulate filter is higher than the thermal deterioration determination value, fuel cut control is prohibited.

  In step 95, when the temperature Tcc is within the temperature increase permission range, the routine proceeds to step 97. In step 97, catalyst deterioration suppression control is prohibited. That is, when the required load becomes zero, the fuel cut is performed even if the temperature of the particulate filter is higher than the thermal deterioration determination value. By performing the fuel cut, the temperature of the particulate filter 23 falls within the range of 750 ° C. to 900 ° C., and the ash can be contracted while suppressing the deterioration of the catalyst. And after implementing fuel cut control, it can return to the state which permits catalyst deterioration suppression control.

  Thus, in the operation control of the present embodiment, it is possible to effectively suppress an increase in the differential pressure before and after the filter while suppressing catalyst deterioration. This operation control can be performed at predetermined time intervals, for example. A plurality of values can be set in advance for the ash accumulation amount determination value in step 93. By providing such a plurality of determination values, the ash can be contracted every time one determination value is exceeded. Since the ash is shrunk for each predetermined amount of ash deposited, the shrinkage rate of one ash is reduced, and the ash can be shrunk effectively.

  In step 95 of the above operation control, based on the current temperature Tcc of the particulate filter, it is estimated whether or not the temperature of the particulate filter falls within a predetermined temperature range when the fuel cut control is performed. However, the present invention is not limited to this mode, and the temperature Tcp of the particulate filter when the fuel cut control is performed may be estimated. For example, the temperature Tcp of the particulate filter 23 when the fuel cut control is performed can be estimated based on the current temperature Tcc of the particulate filter, the engine speed, the intake air amount, and the like. Further, correction may be made based on the air-fuel ratio of the exhaust gas or the like, or when the combustion component is accumulated on the particulate filter, the temperature rise when the combustion component is combusted. In step 95, it can be determined whether or not the calculated temperature Tcp is within a range of 750 ° C. or higher and 900 ° C. or lower.

  In the above operation control, the temperature of the particulate filter is estimated, and when the temperature of the particulate filter is 750 ° C. or higher and 900 ° C. or lower, control for prohibiting catalyst deterioration suppression control is performed. Control that prohibits catalyst deterioration suppression control when the temperature of the filter is 800 ° C. or higher and 900 ° C. or lower is more preferable. By this control, the ash can be contracted more effectively.

  In the present embodiment, the ash accumulation amount is estimated based on the differential pressure before and after the particulate. However, the present invention is not limited to this mode, and any control capable of estimating the ash accumulation amount is performed. Can do. For example, even if the ash accumulation amount is estimated based on the secular change of the consumption amount of the lubricating oil of the engine body, the sulfated ash content contained in the lubricating oil of the engine body, the operation history of the internal combustion engine, the travel distance, etc. I do not care.

  In the present embodiment, the temperature of the particulate filter is set to 750 ° C. or more and 900 ° C. or less by performing fuel cut control when the amount of accumulated ash exceeds a predetermined determination value. The present invention is not limited, and control for raising the temperature of the particulate filter to a predetermined temperature can be performed at any time and at any time. For example, when the ash accumulation amount exceeds the accumulation amount determination value, the temperature of the particulate filter regeneration control may be temporarily set to 750 ° C. or more and 900 ° C. or less.

  In the present embodiment, the exhaust purification device attached to the spark ignition type internal combustion engine has been described. However, the present invention is not limited to this configuration, and the exhaust purification device of the present invention can also be applied to a compression self-ignition internal combustion engine. .

  The above embodiments can be combined as appropriate. In each of the above-described controls, the order of the steps can be appropriately changed within a range where the function and the action are not changed. Moreover, in each said figure, the same code | symbol is attached | subjected to the part which is the same or equivalent. In addition, said embodiment is an illustration and does not limit invention. Further, in the embodiment, changes of the embodiment shown in the claims are included.

1 Engine Body 23 Particulate Filter 24 Differential Pressure Sensor 25, 26 Temperature Sensor 31 Electronic Control Unit 43 Load Sensor 64 Bulkhead

Claims (3)

A collection filter that collects particulate matter containing combustion components that burn when the temperature rises in an atmosphere of excess air and remaining non-combustion components;
A deposit amount estimating means for estimating a deposit amount of a non-combustible component of the particulate matter of the collection filter;
The collection filter includes a support containing at least one of ceria, zirconia, alumina, and barium, and platinum and rhodium catalyst particles supported on the support,
Platinum catalyst particles are supported on the carrier at a concentration of 1.0 g / L, and rhodium catalyst particles are supported on the carrier at a concentration of 1.2 g / L.
When the accumulation amount of the non-combustion component of the collection filter exceeds a predetermined accumulation amount judgment value, control is performed to raise the collection filter to a temperature in the range of 750 ° C. to 900 ° C. An exhaust purification device for an internal combustion engine. It is configured to enable fuel cut control to stop the supply of fuel to the combustion chamber when the required load becomes zero,
When the temperature of the collection filter exceeds a predetermined thermal deterioration judgment value when the fuel cut control is performed, the fuel cut control is configured to be prohibited.
When the accumulation amount of the non-combustion component of the collection filter exceeds a predetermined accumulation amount judgment value, it is estimated that the temperature of the collection filter falls within the range of 750 ° C. or more and 900 ° C. or less by performing the fuel cut control. The exhaust purification device for an internal combustion engine according to claim 1, wherein the prohibition of fuel cut control is canceled when   The control is performed to raise the collection filter to a temperature in the range of 800 ° C or higher and 900 ° C or lower when the accumulation amount of the non-combustion component of the collection filter exceeds a predetermined accumulation amount determination value. 3. An exhaust emission control device for an internal combustion engine according to 1 or 2.

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