Determination of the particle quantity of a particulate filter for an internal combustion engine

Abstract

Exhaust gas purification system of an internal combustion engine, comprising: a filter (23) which is arranged in an exhaust duct of the internal combustion engine and captures particles in the exhaust gas, a differential pressure sensor (40) that detects a differential pressure before and after the filter (23) or a differential pressure between a pressure in the exhaust gas duct on an upstream side of the filter (23) and an atmospheric pressure, a temperature sensor (41) which is arranged in the exhaust duct on a downstream side of the filter (23) and detects the temperature of the exhaust gas flowing out of the filter (23), and a deposit calculation part (51) configured to calculate a particle quantity that is deposited on the filter (23), wherein the deposit calculation part (51) is configured to calculate a first estimate of the particle quantity based on the differential pressure, a second estimate of the particle quantity based on a temperature increase of the exhaust gas due to the supply of oxygen to the filter (23), and calculates the particle quantity based on the first estimate and the second estimate, characterized by the fact that the deposit calculation part (51) is configured to calculate a particle quantity value in a range where a range of the first estimate and a range of the second estimate overlap.

Description

AREA

[0001] The present invention relates to an exhaust gas purification system of an internal combustion engine and in particular to the determination of a particle quantity of a particle filter for an internal combustion engine. BACKGROUND

[0002] In the past, it was known to place a filter to capture particulate matter (PM) in the exhaust gas in an exhaust duct of an internal combustion engine in order to improve exhaust emissions.

[0003] However, as the amount of particulate matter (PM) deposited on the filter increases, the filter becomes clogged and backpressure increases. Therefore, when a large amount of PM deposits accumulates, the engine's power output must be limited to prevent engine damage. Furthermore, if the PM is burned on the filter when the amount of PM deposited is large, the filter temperature will rise excessively, and the filter may deteriorate.

[0004] For this reason, it is desirable to be able to accurately calculate the PM deposit amount for suitable control of an internal combustion engine depending on the PM deposit amount. In this context, JP 2005 - 226 547 A describes the provision of a temperature sensor at the exhaust duct on the downstream side of the filter and the calculation of the PM deposit amount based on the exhaust temperature detected by the temperature sensor during PM combustion. An exhaust gas purification system for an internal combustion engine according to the preamble of claim 1 is known from DE 10 2008 016 858 A1. Regarding the prior art, reference is also made to DE 10 2014 113 474 A1. SUMMARYTECHNICAL PROBLEM

[0005] However, the temperature of the exhaust gas on the downstream side of the filter detected by the temperature sensor fluctuates due to individual differences of the temperature sensors, the outside air temperature, etc. For this reason, it is difficult to accurately calculate the PM deposition amount with the prior art disclosed in JP 2005 - 226 547 A.

[0006] In view of this problem, an object of the present invention is to increase the accuracy of calculating the amount of PM deposited on a filter arranged in an exhaust passage of an internal combustion engine. SOLUTION TO THE PROBLEM

[0007] The summary of the present invention is as follows. (1) An exhaust gas purification system of an internal combustion engine, comprising: a filter arranged in an exhaust passage of the internal combustion engine and trapping particulates in the exhaust gas; a differential pressure sensor that detects a differential pressure before and after the filter or a differential pressure between a pressure in the exhaust passage on an upstream side of the filter and an atmospheric pressure; a temperature sensor arranged in the exhaust passage on a downstream side of the filter and detecting a temperature of the exhaust gas flowing out of the filter; and a deposition calculation part configured to calculate an amount of particulates deposited on the filter, wherein the deposition calculation part is configured to calculate a first estimated value of a particulate amount based on the differential pressure; and a second estimated value of a particulate amount based on a temperature increase of the exhaust gas due to the supply of oxygen to the filter.and calculates a particulate matter quantity based on the first estimated value and the second estimated value. The deposition calculation part is configured to calculate, as the particulate matter quantity, a value within a range where a range of the first estimated value and a range of the second estimated value overlap. (2) The exhaust gas purification system of an internal combustion engine as described in (1) above, wherein the deposition calculation part is configured to calculate, as the particulate amount, a maximum value in the range where the range of the first estimated value and the range of the second estimated value overlap. (3) The exhaust gas purification system of an internal combustion engine as described in (1) or (2) above, wherein the deposition calculation part is configured not to calculate the particulate amount based on the first estimated value and the second estimated value when a width of the range in which the range of the first estimated value and the range of the second estimated value overlap is equal to or larger than a predetermined value. (4) The exhaust gas purification system of an internal combustion engine as described in any of (1) to (3) above, wherein the deposit calculation part is configured to calculate the first estimated value based on the differential pressure detected by the differential pressure sensor when a flow amount of the exhaust gas flowing into the filter is equal to or greater than a predetermined flow amount. (5) The exhaust gas purification system of an internal combustion engine as described in (4) above, wherein the deposit calculation part is configured to calculate the first estimated value based on the differential pressure detected by the differential pressure sensor when the flow amount of the exhaust gas is equal to or greater than the predetermined flow amount and a fluctuation amount of the flow amount is equal to or less than a predetermined value. (6) The exhaust gas purification system of an internal combustion engine as described in any of (1) to (5) above, wherein the deposit calculation part is configured to calculate the second estimated value based on a temperature rise of the exhaust gas when a fuel cut control that stops the supply of fuel to combustion chambers of the internal combustion engine is executed. (7) The exhaust gas purification system of an internal combustion engine as described in any of (1) to (6) above, wherein the deposit calculation part is configured to calculate the second estimated value only when a temperature of the filter at the start of supply of oxygen to the filter is equal to or higher than a predetermined temperature. (8) The exhaust gas purification system of an internal combustion engine as described in any of (1) to (7) above, wherein the deposition calculation part is configured not to calculate the particulate matter amount based on the first estimated value and the second estimated value when a difference between a time point of calculating the first estimated value and a time point of calculating the second estimated value is equal to or greater than a predetermined time, when a total amount of intake air supplied to the combustion chambers of the internal combustion engine between the time point of calculating the first estimated value and the time point of calculating the second estimated value is equal to or greater than a predetermined amount, or when a total amount of fuel supplied to the combustion chambers of the internal combustion engine between the time point of calculating the first estimated value and the time point of calculating the second estimated value is equal to or greater than a predetermined amount. (9) The exhaust gas purification system of an internal combustion engine as described in any of (1) to (8) above, wherein the deposition calculation part is configured to calculate the particulate matter amount based on an operating state of the internal combustion engine when it does not calculate the particulate matter amount based on the first estimated value and the second estimated value. (10) The exhaust gas purification system of an internal combustion engine as described in any of (1) to (9) above, further comprising a catalyst disposed in the exhaust passage on an upstream side of the filter, wherein the deposit calculation part is configured to calculate the second estimated value in consideration of an oxygen concentration in the exhaust gas flowing into the filter when the catalyst is supplied with fuel when the filter is supplied with oxygen. Advantageous effects of the invention

[0008] With the present invention, it is possible to increase the accuracy of calculating an amount of PM deposited on a filter arranged in the exhaust passage of an internal combustion engine. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of an internal combustion engine to which an exhaust gas purification system of an internal combustion engine according to a first embodiment of the present invention is applied. Fig. Figure 2 is a functional block diagram of an ECU. Fig. 3 is a view showing a relationship between a differential pressure before and after a filter and a PM deposition amount. Fig. 4 is a view showing the relationship between the temperature rise of the exhaust gas when oxygen is supplied to a high-temperature filter and the PM deposition amount. Fig. 5 is a flowchart showing a control routine of the deposition amount calculation processing in the first embodiment of the present invention. Fig. 6 is a view showing a map for calculating a first estimated value based on a differential pressure before and after a filter and a flow amount of the incoming exhaust gas. Fig. 7 is a view showing a relationship between the temperature rise of the outflowing exhaust gas when the PM deposition amount is a predetermined amount and a temperature of a filter at the start of fuel cut control. Fig. 8 is a view showing a map for calculating a second estimated value based on the temperature rise of the exhaust gas flowing out and the temperature of a filter when oxygen is started to be supplied to the filter. Fig. 9 is a view showing a map for calculating a second estimated value based on a temperature rise of the outflowing exhaust gas and an oxygen concentration in the inflowing exhaust gas. Fig. 10 is a view showing a map for calculating a second estimated value based on a temperature rise of the outflowing exhaust gas, a temperature of a filter at the start of supply of oxygen to the filter, and an oxygen concentration in the inflowing exhaust gas. Fig. 11A is a flowchart showing a control routine of deposition amount calculation processing in a second embodiment of the present invention. Fig. 11B is a flowchart showing a control routine of the deposition amount calculation processing in a second embodiment of the present invention. Fig. 12 is a flowchart showing a control routine of deposition amount calculation processing in a third embodiment of the present invention. Fig. 13 is a view showing an example of the overlap of a range of the first estimated value and a range of the second estimated value. DESCRIPTION OF EMBODIMENTS

[0009] Embodiments of the present invention will be explained in detail below with reference to the drawings. It should be noted that similar component elements are designated by the same reference numerals in the following explanation. <Erste Ausführungsform>

[0010] In the following, a first embodiment of the present invention will be described with reference to Fig. 1 to Fig. 10 explained. <Konfiguration des Verbrennungsmotors>

[0011] Fig. Figure 1 is a schematic diagram of an internal combustion engine to which an exhaust gas purification system of an internal combustion engine according to a first embodiment of the present invention is applied. The internal combustion engine is a spark-ignition internal combustion engine (Spark ignition engine), more specifically, a gasoline-powered engine. The internal combustion engine is installed in a vehicle.

[0012] The internal combustion engine is formed with an engine body 1 including a cylinder block 2 and a cylinder head 4. Several cylinders are formed in the cylinder block 2. Pistons 3 are arranged in the cylinders, reciprocating in the axial direction of the cylinders. Combustion chambers 5 are formed between the pistons 3 and the cylinder head 4.

[0013] The cylinder head 4 is formed with intake ports 7 and exhaust ports 9. The intake ports 7 and exhaust ports 9 are connected to the combustion chambers 5. The internal combustion engine is further provided with intake valves 6 and exhaust valves 8 arranged in the cylinder head 4. The intake valves 6 open and close the intake ports 7, while the exhaust valves 8 open and close the exhaust ports 9.

[0014] The internal combustion engine is further equipped with spark plugs 10 and fuel injection nozzles 11. The spark plugs 10 are arranged at the central portions of the inner wall surfaces of the cylinder head 4 and generate sparks in response to ignition signals. The fuel injection nozzles 11 are arranged at the peripheral portions of the inner wall surfaces of the cylinder head 4 and inject fuel into the combustion chambers 5 in response to injection signals. In the present embodiment, gasoline with a stoichiometric air-fuel ratio of 14.6 is used as the fuel.

[0015] The internal combustion engine is further equipped with intake ports 13, a surge tank 14, an intake pipe 15, an air cleaner 16, and a throttle valve 18. The intake ports 7 of the cylinders are each connected to the surge tank 14 via corresponding intake ports 13. The surge tank 14 is connected to the air cleaner 16 via the intake pipe 15. The intake ports 7, the intake ports 13, the surge tank 14, the intake pipe 15, etc., form a fuel cut-off control system that supplies air to the combustion chambers 5. The throttle valve 18 is arranged within the intake pipe 15 between the surge tank 14 and the air cleaner 16 and is driven by a throttle drive actuator 17 (e.g., a DC motor). The throttle valve 18 is rotated by the throttle valve drive actuator 17, making it possible to change the open area of ​​the intake port according to the degree of opening.

[0016] The internal combustion engine is also equipped with an exhaust manifold 19, an exhaust pipe 22, a catalytic converter 20, and a filter 23. The exhaust ports 9 of the cylinders are connected to the exhaust manifold 19. The exhaust manifold 19 has a plurality of branch portions connected to the exhaust ports 9 and a manifold duct in which these branch portions are collected. The manifold duct of the exhaust manifold 19 is connected to an upstream housing 21 in which the catalytic converter 20 is installed. The upstream housing 21 is connected through the exhaust pipe 22 to a downstream housing 24 in which the filter 23 is installed. The exhaust ports 9, the exhaust manifold 19, the upstream housing 21, the exhaust pipe 22, the downstream housing 24, etc. form an exhaust passage which discharges the exhaust gas generated by the combustion of the air-fuel mixture in the combustion chambers 5.

[0017] The various control operations of the internal combustion engine are performed by an electronic control unit (ECU) 31 based on the outputs of various types of sensors provided on the internal combustion engine, etc. The ECU 31 consists of a digital computer equipped with components interconnected via bidirectional buses 32, such as 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.

[0018] The ECU 31 receives the outputs of various types of sensors as input. In the present embodiment, the outputs of an air flow sensor 39, a differential pressure sensor 40, a temperature sensor 41, a load sensor 43, and a crank angle sensor 44 are input to the ECU 31.

[0019] The air mass sensor 39 is located in the intake duct, specifically in the intake pipe 15 on the upstream side of the throttle valve 18. The air mass sensor 39 detects the flow rate of air flowing through the intake duct. The air mass sensor 39 is electrically connected to the ECU 31. The output of the air mass sensor 39 is input to the input port 36 via a corresponding AD converter 38.

[0020] The differential pressure sensor 40 is arranged in the exhaust passage and detects a differential pressure between a pressure in the exhaust passage on the upstream side of the filter 23 and a pressure in the exhaust passage on the downstream side of the filter 23, that is, the differential pressure before and after the filter 23. The differential pressure sensor 40 is electrically connected to the ECU 31. The output of the differential pressure sensor 40 is input to the input port 36 via a corresponding AD converter 38.

[0021] The temperature sensor 41 is arranged in the exhaust passage downstream of the filter 23 (more precisely, the exhaust pipe 22) and detects the temperature of the exhaust gas flowing out of the filter 23. The temperature sensor 41 is electrically connected to the ECU 31. The output of the temperature sensor 41 is input to the input port 36 via a corresponding AD converter 38.

[0022] The load sensor 43 is connected to an accelerator pedal 42 mounted on the vehicle on which the internal combustion engine is mounted and detects the degree of depression of the accelerator pedal 42. The load sensor 43 is electrically connected to the ECU 31. The output of the load sensor 43 is input to the input port 36 via a corresponding AD converter 38. The CPU 35 calculates the engine load based on the output of the load sensor 43.

[0023] The crank angle sensor 44 generates an output pulse each time a crankshaft of the internal combustion engine rotates by a predetermined angle (e.g., 15 degrees). The crank angle sensor 44 is electrically connected to the ECU 31. The output of the crank angle sensor 44 is input to the input port 36. The CPU 35 calculates the engine speed based on the output of the crank angle sensor 44.

[0024] On the other hand, the output port 37 is connected to the spark plugs 10, the fuel injectors 11, and the throttle valve actuator 17 via corresponding drive circuits 45. These are controlled by the CPU 35. Specifically, the CPU 35 controls the ignition timing of the spark plugs 10, the injection timing and injection quantities of the fuel injected by the fuel injectors 11, and the opening degree of the throttle valve 18. <Abgasreinigungssystem eines Verbrennungsmotors>

[0025] An exhaust gas purification system of an internal combustion engine according to the first embodiment of the present invention (hereinafter referred to simply as “exhaust gas purification system”) will be explained below.

[0026] The exhaust gas purification system is provided with a catalyst 20 and a filter 23, which are arranged in an exhaust duct of the internal combustion engine. As shown in Fig. As shown in Figure 1, the catalyst 20 is arranged in the exhaust passage on the upstream side of the filter 23. The catalyst 20 removes harmful substances in the exhaust gas. The catalyst 20 is, for example, a three-way catalyst that can simultaneously remove hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) in the exhaust gas.

[0027] The filter 23 captures particulate matter (PM) in the exhaust gas. In the present embodiment, the filter 23 is a gasoline particulate filter (GPF).

[0028] When PM-containing exhaust gas flows into filter 23, the PM deposits on filter 23. If the amount of PM deposited on filter 23 increases, filter 23 becomes blocked (clogged). This impedes the exhaust gas from escaping through filter 23, and the backpressure increases.

[0029] On the other hand, if oxygen is supplied to the filter 23 at a high temperature of the filter 23, the amount of PM deposited on the filter 23 is oxidized and burned. This phenomenon is called "regeneration" of the filter 23. By regenerating the filter 23, the amount of PM deposited on the filter 23 can be reduced.

[0030] The exhaust gas purification system is further equipped with a deposit calculation part 51 and an engine control part 52. Fig. 2 is a functional block diagram of the ECU 31. In the present embodiment, the ECU 31 has the deposit calculation part 51 and the engine control part 52. The deposit calculation part 51 and the engine control part 52 are functional blocks realized by a program stored in the ROM 34 of the ECU 31 and executed by the CPU 35 of the ECU 31.

[0031] The deposition calculation part 51 calculates the amount of PM deposited on the filter 23 (hereinafter referred to as the "PM deposition amount"). When PM deposits on the filter 23, the filter 23 becomes clogged, and the pressure in the exhaust passage on the upstream side of the filter 23 becomes higher than the pressure in the exhaust passage on the downstream side of the filter 23. In addition, the larger the PM deposition amount, the larger the differential pressure before and after the filter 23 becomes. For this reason, the method of calculating the PM deposition amount based on the differential pressure before and after the filter 23 (hereinafter referred to as the "differential pressure method") may be considered.

[0032] However, the relationship between the differential pressure before and after the filter 23 and the PM deposition amount changes depending on the PM deposition state. Fig. Figure 3 is a view showing the relationship between the differential pressure before and after filter 23 and the PM deposition amount. The solid line in the figure shows the relationship between the differential pressure and the PM deposition amount when filter 23 is not regenerated. On the other hand, the dot-dash line in the figure shows the relationship between the differential pressure and the PM deposition amount when filter 23 is regenerated.

[0033] When the filter 23 captures PM, the PM initially deposits on the inside of the walls of the filter 23. In the example of Fig. 3, when the PM deposition amount increases from zero to D1, the PM deposits on the inner sides of the walls of the filter 23. At this time, the amount of increase or the increase in the differential pressure before and after the filter 23 (slope in the figure) becomes larger.

[0034] When the inside of the walls of the filter 23 are filled with PM, the PM then deposit on the surfaces of the walls of the filter 23. In the example of Fig. 3, PM deposits on the surfaces of the walls of the filter 23, with the amount of PM deposited gradually increasing from D2 onward. At this time, the increase in differential pressure before and after the filter 23 becomes smaller compared to the time when PM deposits on the inner surfaces of the walls of the filter 23.

[0035] When the filter 23 is regenerated when the PM deposition amount is D3, the PM deposition amount decreases from D3 to D2. Furthermore, as the PM deposition amount decreases, the differential pressure before and after the filter 23 also decreases. At this time, the PM deposited on the inner surfaces of the walls of the filter 23 are first burned off. For this reason, the decrease in the differential pressure before and after the filter 23 becomes greater. Afterward, when PM-containing exhaust gas flows into the filter 23 again, the PM deposition amount gradually increases from D2, as shown by the dot-dash line.

[0036] As from Fig. As can be seen from Figure 3, when the filter 23 is regenerated, the PM deposition state changes, and the relationship between the differential pressure before and after the filter 23 and the PM deposition amount changes. Therefore, an error occurs in the PM deposition amount calculated using the differential pressure method.

[0037] In addition, the reaction heat during the combustion of PM by supplying oxygen to the filter 23 leads to an increase in the temperature of the filter 23. This also increases the temperature of the exhaust gas flowing out of the filter 23 (hereinafter referred to as “outflowing exhaust gas”).

[0038] Fig. Fig. 4 is a view showing the relationship between the temperature rise of the exhaust gas when oxygen is supplied to a high-temperature filter 23 and the amount of PM deposition. As shown in Fig. As shown in Figure 4, the temperature rise of the exhaust gas becomes larger in proportion to the PM deposition amount. Therefore, the method of calculating the PM deposition amount based on the temperature rise of the exhaust gas due to the supply of oxygen to the filter 23 (hereinafter referred to as the "temperature method") may be considered.

[0039] However, the temperature of the exhaust gas outlet detected by the temperature sensor 41 fluctuates due to individual differences in the temperature sensor 41, the outside air temperature, etc. Furthermore, when the filter 23 is supplied with oxygen at a low temperature of the filter 23, the combustion of PM is inhibited, and the fluctuation of the rise in the temperature of the exhaust gas outlet becomes larger. Therefore, an error occurs in the PM deposition amount calculated by the temperature method.

[0040] Therefore, the method for calculating the PM deposition amount requires improvement. Therefore, in the present embodiment, the final PM deposition amount is calculated based on the PM deposition amount calculated using the differential pressure method and the PM deposition amount calculated using the temperature method. This makes it possible to improve the accuracy of calculating the PM deposition amount. The specific method for calculating the PM deposition amount used by the deposition calculation part 51 will be explained below.

[0041] The deposition calculation part 51 calculates the first estimated value of the PM deposition amount based on the differential pressure before and after the filter 23. The first estimated value corresponds to the PM deposition amount calculated using the differential pressure method. Furthermore, the deposition calculation part 51 calculates the second estimated value based on the amount of temperature rise of the outflowing exhaust gas due to the supply of oxygen to the filter 23. That is, the deposition calculation part 51 calculates the second estimated value based on the increase in temperature of the outflowing exhaust gas when the filter 23 is supplied with oxygen. The second estimated value corresponds to the PM deposition amount calculated using the temperature method.

[0042] In the internal combustion engine, when a predetermined power condition is met, fuel cut control is executed to stop the fuel supply to the combustion chambers 5. The predetermined power condition is met when, for example, the amount of operation of the accelerator pedal 42 is zero or substantially zero (ie, the engine load is zero or substantially zero) and the engine speed is equal to or higher than a predetermined speed, which is higher than the speed at the time of idling.

[0043] When the fuel cut control is performed, air is supplied from the intake passage to the exhaust passage, and oxygen is supplied to the filter 23. At this time, the oxygen concentration in the exhaust gas becomes maximum. For this reason, in the present embodiment, the deposition calculation part 51 calculates the second estimated value of the PM deposition amount based on the increase in the temperature of the outflowing exhaust gas when the fuel cut control is performed. In this way, the second estimated value is calculated when the oxygen concentration in the exhaust gas supplied to the filter 23 is substantially constant, so that the reliability of the second estimated value can be increased.

[0044] The deposition calculation part 51 calculates the PM deposition amount based on the first estimated value and the second estimated value. This can increase the accuracy of the PM deposition amount calculation compared to the PM deposition amount calculation using the differential pressure or temperature method.

[0045] The engine control part 52 controls the internal combustion engine based on the PM deposition amount calculated by the deposition calculation part 51. If the filter 23 is regenerated when the PM deposition amount is large, the temperature of the filter 23 rises excessively, and the filter 23 may deteriorate. For this reason, the engine control part 52, for example, restricts the output of the internal combustion engine to suppress the increase in exhaust gas temperature when the PM deposition amount is equal to or greater than a predetermined amount. Note that the engine control part 52 may prohibit the fuel cut control or limit the time for continuously performing the fuel cut control when the PM deposition amount is equal to or greater than a predetermined amount.

[0046] As the PM deposit amount increases, the filter 23 becomes clogged and the back pressure increases. For this reason, the engine control part 52 can regenerate the filter 23 to quickly reduce the PM deposit amount when the PM deposit amount is equal to or greater than a predetermined amount. Specifically, the engine control part 52 can perform lean control in which the target air-fuel ratio of the air-fuel mixture supplied to the combustion chambers 5 is set to a lean air-fuel ratio leaner than the stoichiometric air-fuel ratio when the PM deposit amount is equal to or greater than a predetermined amount. When lean control is performed, oxygen is supplied to the filter 23 and the combustion of PM is promoted. <Verarbeitung zur Berechnung der Ablagerungsmenge>

[0047] In the following, with reference to the flow chart of Fig. 5 the control for calculating the PM deposition amount is explained in detail. Fig. 5 is a flowchart showing a control routine of the deposition amount calculation processing in the first embodiment of the present invention. The current control routine is repeatedly executed by the ECU 31 at predetermined time intervals.

[0048] In step S101, the deposit calculation part 51 first uses a map or a calculation formula to calculate a first estimated value of the PM deposit amount based on the differential pressure detected by the differential pressure sensor 40. The larger the differential pressure, the larger the first estimated value becomes.

[0049] In the next step S102, the deposit calculation part 51 judges whether the fuel cut control has been executed. If it is judged that the fuel cut control has not been executed, the control routine is terminated. On the other hand, if it is determined that the fuel cut control has been executed, the control routine proceeds to step S103.

[0050] In step S103, the deposition calculation part 51 calculates the second estimated value of the PM deposition amount based on the amount of temperature rise of the outflowing exhaust gas due to the supply of oxygen to the filter 23. The larger the amount of temperature rise of the outflowing exhaust gas, the larger the second estimated value becomes.

[0051] For example, the deposit calculation part 51 subtracts the temperature detected by the temperature sensor 41 at the start of the fuel-cut control from the maximum value of the temperature detected by the temperature sensor 41 when the fuel-cut control is executed to calculate the amount of temperature rise of the outgoing exhaust gas. Note that the deposit calculation part 51 may subtract the temperature detected by the temperature sensor 41 at the start of the fuel-cut control from the temperature detected by the temperature sensor 41 when a predetermined time has elapsed since the start of the fuel-cut control to calculate the temperature rise of the outgoing exhaust gas.

[0052] In the next step S104, the deposition calculation part 51 calculates the PM deposition amount based on the first and second estimated values. For example, the deposition calculation part 51 calculates the PM deposition amount as the average of the first estimated value and the second estimated value. After step S104, the current control routine is terminated.

[0053] Note that in step S103, the deposition calculation part 51 may judge whether the fuel cut control has been performed for a predetermined time or longer. Furthermore, in step S103, the deposition calculation part 51 may judge whether the lean control, in which the target air-fuel ratio of the air-fuel mixture supplied to the combustion chambers 5 is set to a lean air-fuel ratio leaner than the stoichiometric air-fuel ratio, has been performed. That is, the deposition calculation part 51 may calculate the second estimated value of the PM deposition amount based on the rise in the exhaust gas temperature when the lean control was performed.

[0054] In addition, even if the PM deposition amount is constant, the differential pressure before and after the filter 23 is influenced by the flow amount of the exhaust gas flowing into the filter 23 (hereinafter referred to as "incoming exhaust gas"). For this reason, the deposit calculation part 51 in step S101 uses, for example, the Fig. 6 to calculate the first estimated value E1 based on the differential pressure DP before and after the filter 23 and the flow rate FA of the incoming exhaust gas. This makes it possible to increase the reliability of the first estimated value. In this case, the flow rate FA of the incoming exhaust gas is substantially proportional to the flow rate of the intake air, so, for example, the deposit calculation part 51 calculates the flow rate FA of the incoming exhaust gas based on the flow rate of the intake air detected by the air mass sensor 39.

[0055] In addition, even if the PM deposition amount is constant, the temperature rise of the outflowing exhaust gas is affected by the temperature of the filter 23 when the supply of oxygen to the filter 23 is started. Fig. Figure 7 shows the relationship between the temperature rise rate of the exhaust gas when the PM deposition amount is a predetermined amount and the temperature of the filter 23 at the start of the fuel cut control. The figure shows the relationship when the PM deposition amount is 5 g with a solid line, the relationship when the PM deposition amount is 3 g with a dashed line, and the relationship when the PM deposition amount is 1 g with a dot-dash line.

[0056] As in Fig. As shown in Figure 7, when the temperature of the filter 23 is low at the time the fuel cut control starts, the temperature of the outgoing exhaust gas does not rise much at all. On the other hand, the higher the temperature of the filter 23 at the time the fuel cut control starts, the greater the temperature rise of the outgoing exhaust gas becomes.

[0057] For this reason, in step S103, the deposit calculation part 51 may, for example, generate a map such as that shown in Fig. 8 to calculate the second estimated value E2 based on the rise IA of the outflowing exhaust gas temperature and the temperature FT of the filter 23 at the start of the supply of oxygen to the filter 23, for example, the temperature of the filter 23 at the time of performing the fuel cut control. In this way, the reliability of the second estimated value can be increased. In this case, the deposit calculation part 51 calculates the temperature of the filter 23 at the start of the supply of oxygen to the filter 23 based on the temperature detected by the temperature sensor 41 at the start of the supply of oxygen to the filter 23. Note that the temperature detected by the temperature sensor 41 can be regarded as the temperature of the filter 23.

[0058] To increase the temperature of the incoming exhaust gas when the filter 23 is supplied with oxygen, the catalyst 20 is sometimes supplied with fuel. For example, by post-injecting fuel from the injectors 11 during the expansion strokes of the cylinders, the catalyst 20 can be supplied with fuel (unburned fuel). Furthermore, by providing a fuel injector in the exhaust passage on the upstream side of the catalyst 20 and supplying fuel from this fuel injector into the exhaust passage, fuel can also be supplied to the catalyst 20.

[0059] When the catalyst 20 is supplied with fuel, the oxygen reacts with the fuel, and the oxygen is consumed at the catalyst 20. This changes the oxygen concentration in the incoming exhaust gas. The magnitude of the temperature increase of the outgoing exhaust gas varies depending on the oxygen concentration in the incoming exhaust gas. Specifically, this means that the higher the oxygen concentration in the incoming exhaust gas, the greater the temperature increase of the outgoing exhaust gas.

[0060] For this reason, when fuel is supplied to the catalyst 20 while oxygen is supplied to the filter 23, the deposit calculation part 51 can consider the oxygen concentration in the incoming exhaust gas to calculate the second estimated value. In this way, it is possible to prevent a decrease in the reliability of the second estimated value when fuel is supplied to the catalyst 20.

[0061] In this case, for example, the deposit calculation part 51 corrects the amount of increase in the temperature of the outflowing exhaust gas based on the oxygen concentration in the inflowing exhaust gas and calculates the second estimated value based on the increase after the correction. The oxygen concentration in the inflowing exhaust gas is calculated based on the amount of fuel supplied to the catalyst 20.

[0062] It should be noted that the deposit calculation part 51 has a map as shown in Fig. 9 to calculate the second estimated value E2 based on the rise IA of the temperature of the outflowing exhaust gas and the oxygen concentration OC in the inflowing exhaust gas. Furthermore, the deposit calculation part 51 may use the three-dimensional map as shown in Fig. 10 to calculate the second estimated value E2 based on the rise IA of the temperature of the outflowing exhaust gas, the temperature FT of the filter 23 at the start of the supply of oxygen to the filter 23 and the concentration of oxygen OC in the inflowing exhaust gas.

[0063] It should be noted that the configuration of the internal combustion engine is not limited to the configuration mentioned above. Therefore, the specific configuration of the internal combustion engine, such as the cylinder arrangement, the fuel injection mode, the intake / exhaust system configuration, the valve operating mechanism configuration, and the presence of a supercharger, may differ from the configuration described in Fig. 1. For example, the fuel injectors 11 may be configured to inject fuel into the intake ports 7.

[0064] When the filter 23 becomes clogged due to PM, the pressure in the exhaust passage upstream of the filter 23 becomes higher. Consequently, the greater the PM deposition amount, the greater the pressure difference between the pressure in the exhaust passage upstream of the filter 23 and atmospheric pressure. Therefore, the differential pressure sensor 40 can detect the pressure difference between the pressure in the exhaust passage upstream of the filter 23 and atmospheric pressure, rather than the pressure difference before and after the filter 23. <Zweite Ausführungsform>

[0065] The exhaust gas purification system according to a second embodiment is substantially the same in configuration and control as the exhaust gas purification system of the first embodiment except for the points explained below. Therefore, the second embodiment of the present invention will be explained below based on the parts that differ from the first embodiment.

[0066] When the incoming exhaust gas flow rate is small, the change in the differential pressure before and after the filter 23 becomes smaller when the PM deposition amount changes. Therefore, when the incoming exhaust gas flow rate is large, it is preferable to calculate the first estimated value based on the differential pressure detected by the differential pressure sensor 40. Furthermore, the error of the first estimated value is likely to be larger when the fluctuation range of the incoming exhaust gas flow rate is large.

[0067] For this reason, in the second embodiment, in the deposit calculation part 51, the first estimated value is calculated based on the differential pressure detected by the differential pressure sensor 40 when the flow rate of the incoming exhaust gas is equal to or greater than a predetermined flow rate and the fluctuation amount of the flow rate of the incoming exhaust gas is equal to or less than a predetermined value. In this way, the reliability of the first estimated value can be increased.

[0068] As in Fig. 7, when the temperature of the filter 23 is low at the start of the supply of oxygen to the filter 23, the supply of oxygen to the filter 23 does not cause the temperature of the outflowing exhaust gas to rise much at all. For this reason, in the second embodiment, the deposit calculation part 51 calculates the second estimated value based on the temperature rise of the outflowing exhaust gas only when the temperature of the filter 23 at the start of the supply of oxygen to the filter 23 is equal to or higher than a predetermined temperature. In other words, the deposit calculation part 51 does not calculate the second estimated value when the temperature of the filter 23 at the start of the supply of oxygen to the filter 23 is lower than a predetermined temperature. In this way, the reliability of the second estimated value can be increased.

[0069] When the time of calculating the first estimated value and the time of calculating the second estimated value are separated from each other, the actual PM deposition amount sometimes fluctuates between the previous and subsequent calculation times. For this reason, in the second embodiment, the deposition calculation part 51 does not calculate the PM deposition amount based on the first and second estimated values ​​when the difference between the time of calculating the first estimated value and the time of calculating the second estimated value is equal to or greater than a predetermined time. In this way, the accuracy of calculating the PM deposition amount can be further improved.

[0070] However, if the PM deposition amount is not calculated, it is not possible to perform appropriate control according to the PM deposition amount in the internal combustion engine. For this reason, it is desirable to always be able to calculate the PM deposition amount even if the calculation accuracy decreases. Therefore, in the second embodiment, the deposition calculation part 51 calculates the PM deposition amount based on the operating state of the internal combustion engine when the PM deposition amount is not calculated based on the first and second estimated values. In this way, the frequency of calculating the PM deposition amount can be prevented from decreasing. <Verarbeitung zur Berechnung der Ablagerungsmenge>

[0071] Fig. 11A and Fig. 11B are flowcharts showing the control routine of the deposition amount calculation processing in the second embodiment of the present invention. The present control routine is repeatedly executed by the ECU 31 at predetermined time intervals.

[0072] In step S201, the deposition calculation part 51 first calculates the PM deposition amount based on the operating state of the internal combustion engine. Specifically, the deposition calculation part 51 calculates the amount of change in the PM deposition amount based on the engine load and the engine speed, and cumulatively adds this change amount to calculate the PM deposition amount. The engine load is calculated based on the output of the load sensor 43, and the engine speed is calculated based on the output of the crank angle sensor 44.

[0073] In the next step S202, the deposit calculation part 51 judges whether the flow rate of the incoming exhaust gas is equal to or greater than a predetermined flow rate. The predetermined flow rate is determined in advance. The flow rate of the incoming exhaust gas is calculated based on the intake air quantity detected by the air mass sensor 39. If it is judged in step S202 that the flow rate of the incoming exhaust gas is equal to or greater than the predetermined flow rate, the present control routine proceeds to step S203.

[0074] In step S203, the deposit calculation part 51 judges whether the fluctuation width of the flow rate of the incoming exhaust gas is equal to or less than a predetermined value. The predetermined value is determined in advance. The fluctuation amount of the flow rate is calculated, for example, as the difference between the maximum value and the minimum value of the flow rate calculated during a predetermined time. If it is judged in step S203 that the fluctuation amount of the flow rate of the incoming exhaust gas is equal to or less than a predetermined value, the control routine proceeds to step S204.

[0075] In step S204, the deposition calculation part 51 calculates in the same manner as step S101 of Fig. 5, the first estimated value of the PM deposition amount. Next, in step S205, the deposition calculation part 51 sets a first flag F1 to "1." The first flag F1 is a flag that is set to "1" when the first estimated value is calculated. The initial value of the first flag F1 is zero.

[0076] After step S205, the control routine proceeds to step S206. On the other hand, if it is judged in step S202 that the flow rate of the incoming exhaust gas is less than a predetermined flow rate, or if it is judged in step S203 that the fluctuation rate of the flow rate of the incoming exhaust gas is greater than a predetermined value, the present control routine skips steps S204 and S205 and proceeds to step S206. In this case, the first estimated value is not calculated.

[0077] In step S206, the deposition calculation part 51 judges in the same manner as in step S103 of Fig. 5, whether the fuel cutoff control has been performed. If it is judged that the fuel cutoff control has been performed, the control routine proceeds to step S207.

[0078] In step S207, the deposit calculation part 51 judges whether the temperature of the filter 23 at the start of the fuel-cut control is equal to or higher than a predetermined temperature. The predetermined temperature is determined in advance. The temperature of the filter 23 at the start of the fuel-cut control is calculated based on the temperature of the exhaust gas flow detected by the temperature sensor 41 at the start of the fuel-cut control. If it is judged in step S207 that the temperature of the filter 23 at the start of the fuel-cut control is equal to or higher than the predetermined temperature, the control routine proceeds to step S208.

[0079] In step S208, the deposit calculation part 51 calculates in the same manner as step S103 of Fig. 5, the second estimated value of the PM deposition amount. Next, in step S209, the deposition calculation part 51 sets a second flag F2 to "1." The second flag F2 is a flag that is set to "1" when calculating the second estimated value. The initial value of the second flag F1 is zero.

[0080] After step S209, the present control routine proceeds to step S210. On the other hand, if it was determined in step S206 that the fuel cut-off control was not being performed, or if it was determined in step S207 that the temperature of the filter 23 was lower than the predetermined temperature at the start of the fuel cut-off control, the present control routine skips steps S208 and S209 and proceeds to step S210. In this case, the second estimated value is not calculated.

[0081] In step S210, the deposition calculation part 51 judges whether the first flag F1 and the second flag F2 are "1." If it is judged that the first flag F1 and the second flag F2 are "1," the control routine proceeds to step S211.

[0082] In step S211, the deposition calculation part 51 judges whether the difference between the time of calculating the first estimated value and the time of calculating the second estimated value is equal to or greater than a predetermined time. The predetermined time is determined in advance. Note that the most recently calculated values ​​are used for the time of calculating the first estimated value and the time of calculating the second estimated value, respectively. If it is judged in step S211 that the difference between the time of calculating the first estimated value and the time of calculating the second estimated value is less than the predetermined time, the present control routine proceeds to step S212.

[0083] In step S212, the deposition calculation part 51 calculates in the same manner as in step S104 of Fig. 5, the PM deposition amount is calculated based on the first and second estimated values. As a result, the PM deposition amount is rewritten from the value calculated in step S201 to the value calculated in step S212. In this case, the engine control part 52 controls the internal combustion engine based on the PM deposition amount calculated based on the first estimated value and the second estimated value.

[0084] Next, in step S213, the deposition calculation part 51 resets the first flag F1 and the second flag F2 to zero. After step S213, the current control routine ends.

[0085] On the other hand, if it is judged in step S210 that at least one of the first flag F1 and the second flag F2 is zero, or if it is judged in step S211 that the difference between the time of calculating the first estimated value and the time of calculating the second estimated value is equal to or greater than a predetermined time, the current control routine is terminated. In this case, the engine control part 52 controls the internal combustion engine based on the PM deposition amount calculated based on the operating state of the internal combustion engine.

[0086] Note that in step S211, the deposition calculation part 51 may judge whether the total amount of intake air supplied to the combustion chambers 5 between the time of calculating the first estimated value and the time of calculating the second estimated value is equal to or greater than a predetermined amount. That is, the deposition calculation part 51 may not calculate the PM deposition amount based on the first estimated value and the second estimated value if the total amount of intake air supplied to the combustion chambers 5 between the time of calculating the first estimated value and the time of calculating the second estimated value is equal to or greater than a predetermined amount. The total amount of intake air is calculated based on the output of the air flow sensor 39.

[0087] Furthermore, in step S211, the deposition calculation part 51 may judge whether the total amount of fuel supplied to the combustion chambers 5 between the time of calculating the first estimated value and the time of calculating the second estimated value is equal to or greater than a predetermined amount. That is, the deposition calculation part 51 may not calculate the PM deposition amount based on the first estimated value and the second estimated value if the total amount of fuel supplied to the combustion chambers 5 between the time of calculating the first estimated value and the time of calculating the second estimated value is equal to or greater than a predetermined amount. The total amount of fuel is calculated based on the target values ​​output from the ECU 31 to the fuel injectors 11.

[0088] In addition, from step S201 to step S203, step S207, and step S211, all four or fewer steps may be omitted. Furthermore, the current control routine may be executed in the same manner as the control routine of Fig. 5 be changed. <Dritte Ausführungsform>

[0089] The exhaust gas purification system according to a third embodiment is substantially the same in configuration and control as the exhaust gas purification system according to the first embodiment except for the points explained below. Therefore, the third embodiment of the present invention will be explained below based on the parts that differ from the first embodiment.

[0090] As explained above, an error arises between the first estimate, corresponding to the PM deposition amount calculated by the differential pressure method, and the second estimate, corresponding to the PM deposition amount calculated by the temperature method. Furthermore, the width of the error varies depending on the value of the parameter used to calculate the PM deposition amount.

[0091] For this reason, in the third embodiment, the deposition calculation part 51 calculates the first estimated value and the second estimated value as values ​​with widths. Furthermore, the deposition calculation part 51 calculates a value in the range where the range of the first estimated value and the range of the second estimated value overlap as the PM deposition amount. That is, the deposition calculation part 51 does not calculate the PM deposition amount based on the first estimated value and the second estimated value when the range of the first estimated value and the range of the second estimated value do not overlap. By calculating the PM deposition amount in the above manner, it is possible to increase the accuracy of calculating the PM deposition amount.

[0092] In addition, when the error of the first estimated value and the second estimated value is large, the width of the range where the range of the first estimated value and the range of the second estimated value overlap (hereinafter referred to as the "overlap range") becomes larger. Therefore, when the width of the overlap range is equal to or larger than a predetermined value, the deposition calculation part 51 does not calculate the PM deposition amount based on the first and second estimated values. In this way, the accuracy of calculating the PM deposition amount can be further increased.

[0093] Furthermore, in the third embodiment, in the same manner as in the second embodiment, the deposition calculation part 51 calculates the PM deposition amount based on the operating state of the internal combustion engine when the PM deposition amount is not calculated based on the first and second estimated values. Thus, the frequency of calculating the PM deposition amount can be prevented from decreasing. <Verarbeitung zur Berechnung der Ablagerungsmenge>

[0094] Fig. 12 is a flowchart showing a control routine of the deposition amount calculation processing in the third embodiment of the present invention. The current control routine is repeatedly executed by the ECU 31 at predetermined time intervals.

[0095] First, the deposit calculation part 51 calculates in step S301, the same manner as in step S201 of Fig. 11A, the PM deposition amount based on the operating condition of the internal combustion engine.

[0096] Next, in step S302, the deposit calculation part 51 calculates in the same manner as in step S101 of Fig. 5, the first estimated value of the PM deposition amount. At this time, the deposition calculation part 51 calculates the first estimated value as a value with a range (e.g., 3 to 5 g). When the first estimated value is calculated based on the flow rate of the incoming exhaust gas, the smaller the flow rate of the incoming exhaust gas, the wider the range of the first estimated value.

[0097] Next, the deposition calculation part 51 judges in step S303, in the same manner as in S103 of Fig. 5, whether the fuel cut control has been performed. If it is judged that the fuel cut control has been performed, the present control routine proceeds to step S304.

[0098] In step S304, the deposition calculation part 51 calculates in the same manner as in step S103 of Fig. 5, the second estimated value of the PM deposition amount. At this time, the deposition calculation part 51 calculates the second estimated value as a value with a width. The smaller the temperature rise of the outflowing exhaust gas due to the supply of oxygen to the filter 23, the wider the range of the second estimated value. Further, when the second estimated value is calculated based on the temperature of the filter 23 at the start of the supply of oxygen to the filter 23, the lower the temperature of the filter 23 at the start of the supply of oxygen to the filter 23, the wider the range of the second estimated value.

[0099] Next, in step S305, the deposition calculation part 51 judges whether the range of the first estimated value and the range of the second estimated value overlap. If it is judged that the range of the first estimated value and the range of the second estimated value overlap, the present control routine proceeds to step S306.

[0100] In step S306, the deposition calculation part 51 judges whether the width of the overlapping area is equal to or greater than a predetermined value. The predetermined value is determined in advance. If the width of the overlapping area is smaller than the predetermined value in step S306, the present control routine proceeds to step S307.

[0101] In step S307, the deposition calculation part 51 calculates the PM deposition amount based on the first and second estimated values. Specifically, the deposition calculation part 51 calculates a value in a range where a range of the first estimated value and a range of the second estimated value overlap as the PM deposition amount.

[0102] For example, the deposition calculation part 51 calculates a maximum value of a range in which a range of the first estimated value and a range of the second estimated value overlap (value X in the example of Fig. 13) than the PM deposition amount. This prevents the PM deposition amount from being estimated as smaller than the actual value. This makes it possible to perform the necessary control in the internal combustion engine before the actual PM deposition amount becomes excessively large. After step S307, the current control routine is terminated.

[0103] It should be noted that at least one of steps S301 and S306 may be omitted. Furthermore, the present control routine may be executed in the same manner as the control routine of Fig. 5 be changed. <Andere Ausführungsformen>

[0104] Preferred embodiments of the present invention have been explained above, but the present invention is not limited to these embodiments and can be modified and modified in various ways within the scope of the claims. For example, the catalyst 20 may be omitted from the exhaust gas purification system.

[0105] Furthermore, the internal combustion engine may be a diesel engine powered by diesel fuel. In this case, an oxidation catalyst as catalyst 20 and a diesel particulate filter (DPF) as filter 23 are arranged in the exhaust duct of the internal combustion engine.

[0106] Furthermore, an upstream temperature sensor that detects the temperature of the incoming exhaust gas may be disposed in the exhaust passage on the upstream side of the filter 23. In this case, the deposit calculation part 51 may subtract the temperature detected by the upstream temperature sensor from the temperature detected by the temperature sensor 41 to calculate the amount of temperature rise of the outgoing exhaust gas.

[0107] Furthermore, the above-mentioned embodiments can be freely combined. For example, when the second and third embodiments are combined, as the values ​​with the width in step S204 and step S208 of Fig. 11A, the first and second estimated values ​​are calculated, and step S305 and step S306 of Fig. 12 are between step S211 and step S212 of Fig. 11B.

Claims

[1] Exhaust gas purification system of an internal combustion engine, comprising: a filter (23) arranged in an exhaust duct of the internal combustion engine and trapping particles in the exhaust gas, a differential pressure sensor (40) which detects a differential pressure before and after the filter (23) or a differential pressure between a pressure in the exhaust gas duct on an upstream side of the filter (23) and an atmospheric pressure, a temperature sensor (41) arranged in the exhaust duct on a downstream side of the filter (23) and detecting a temperature of the exhaust gas flowing out of the filter (23), and a deposition calculation part (51) configured to calculate an amount of particles deposited on the filter (23), wherein the deposit calculation part (51) is configured to calculate a first estimated value of the particulate amount based on the differential pressure, calculate a second estimated value of the particulate amount based on a temperature increase of the exhaust gas due to the supply of oxygen to the filter (23), and calculate the particulate amount based on the first estimated value and the second estimated value, characterized by , that the deposition calculation part (51) is configured to calculate, as the amount of particulate matter, a value in a range in which a range of the first estimated value and a range of the second estimated value overlap. [2] An exhaust gas purification system of an internal combustion engine according to claim 1, wherein the deposition calculation part (51) is configured to calculate, as the particulate amount, a maximum value in the range in which the range of the first estimated value and the range of the second estimated value overlap. [3] An exhaust gas purification system of an internal combustion engine according to claim 1 or 2, wherein the deposition calculation part (51) is configured not to calculate the particulate amount based on the first estimated value and the second estimated value when a width of the range in which the range of the first estimated value and the range of the second estimated value overlap is equal to or larger than a predetermined value. [4] An exhaust gas purification system of an internal combustion engine according to any one of claims 1 to 3, wherein the deposit calculation part (51) is configured to calculate the first estimated value based on the differential pressure detected by the differential pressure sensor (40) when a flow amount (FA) of the exhaust gas flowing into the filter (23) is equal to or greater than a predetermined flow amount (FA). [5] An exhaust gas purification system of an internal combustion engine according to claim 4, wherein the deposit calculation part (51) is configured to calculate the first estimated value based on the differential pressure detected by the differential pressure sensor (40) when the flow amount (FA) of the exhaust gas is equal to or greater than the predetermined flow amount (FA) and a fluctuation amount of the flow amount (FA) is equal to or less than a predetermined value. [6] An exhaust gas purification system of an internal combustion engine according to any one of claims 1 to 5, wherein the deposit calculation part (51) is configured to calculate the second estimated value based on a temperature rise of the exhaust gas when a fuel cut control that stops the supply of fuel to combustion chambers (5) of the internal combustion engine is executed. [7] An exhaust gas purification system of an internal combustion engine according to any one of claims 1 to 6, wherein the deposit calculation part (51) is configured to calculate the second estimated value only when a temperature of the filter (23) at the start of supply of oxygen to the filter (23) is equal to or higher than a predetermined temperature. [8] An exhaust gas purification system of an internal combustion engine according to any one of claims 1 to 7, wherein the deposit calculation part (51) is configured not to calculate the particulate matter amount based on the first estimated value and the second estimated value when a difference between a time of calculating the first estimated value and a time of calculating the second estimated value is equal to or greater than a predetermined time, when a total amount of intake air supplied to the combustion chambers (5) of the internal combustion engine between the time of calculating the first estimated value and the time of calculating the second estimated value is equal to or greater than a predetermined amount, or when a total amount of fuel supplied to the combustion chambers (5) of the internal combustion engine between the time of calculating the first estimated value and the time of calculating the second estimated value is equal to or greater than a predetermined amount. [9] An exhaust gas purification system of an internal combustion engine according to any one of claims 1 to 8, wherein the deposit calculation part (51) is configured to calculate the particulate matter amount based on an operating state of the internal combustion engine when it does not calculate the particulate matter amount based on the first estimated value and the second estimated value. [10] An exhaust gas purification system of an internal combustion engine according to any one of claims 1 to 9, further comprising a catalyst (20) disposed in the exhaust passage on the upstream side of the filter (23), wherein the deposit calculation part (51) is configured to calculate the second estimated value taking into account an oxygen concentration in the exhaust gas flowing into the filter (23) when the catalyst (20) is supplied with fuel when the filter (23) is supplied with oxygen.

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