Internal combustion engine and control method for internal combustion engine

Abstract

Provided are an internal combustion engine and a control method for the internal combustion engine. A deposit amount calculation section (111) calculates an accumulation amount ΣDp of deposits with fuel injection amount fq and engine speed NE as parameters, and switches between an inlet and an outlet of an EGR cooler if the accumulation amount ΣDp exceeds a first threshold value. A condensed water calculation section (121) calculates an accumulation amount ΣCw of condensed water with fuel injection amount fq and engine speed NE as parameters, and switches between the inlet and the outlet of the EGR cooler if the accumulation amount ΣCw exceeds a second threshold value.

Description

Technical Field

[0001] This disclosure relates to internal combustion engines and control methods for internal combustion engines, and more particularly to internal combustion engines and control methods for internal combustion engines having exhaust gas recirculation devices. Background Technology

[0002] An internal combustion engine is known to include an exhaust gas recirculation (EGR) device that returns a portion of the exhaust gas to the intake system in order to reduce nitrogen oxides (NOx) contained in the exhaust gas and improve fuel economy. The lower the temperature of the portion of exhaust gas returning to the intake system (hereinafter also referred to as EGR gas), the higher the density of the EGR gas, and the better the NOx reduction and fuel economy effects. Therefore, an EGR cooler that cools the EGR gas in the EGR device is also known.

[0003] If the EGR gas is cooled by an EGR cooler, it loses thermal energy, thus reducing its kinetic energy. Furthermore, during the cooling process, condensate and lubricating oil mist contained in the EGR gas (exhaust) combine with particulate matter in the EGR gas to form foreign matter (deposits). Therefore, deposits accumulate at the EGR cooler outlet side where the EGR gas flow rate decreases. Additionally, the temperature at the EGR cooler outlet side is low, so the condensate remaining there does not evaporate but remains.

[0004] If deposits accumulate in the EGR cooler, it will cause blockage of the EGR cooler and a reduction in cooling efficiency. In order to eliminate the accumulation of deposits in the EGR cooler, Japanese Patent Application Publication No. 2011-38440 (Patent Document 1) discloses an EGR device in which a first EGR branch pipe and a second EGR branch pipe are provided in the EGR piping, and the midpoint between the first EGR branch pipe and the second EGR branch pipe is connected to the EGR cooler.

[0005] In the EGR device disclosed in Patent Document 1, the cooling efficiency is calculated based on the inlet and outlet temperatures of the EGR cooler. If the cooling efficiency is below the allowable value, it is determined that soot (deposits) has accumulated in the EGR cooler, and the inlet and outlet of the EGR cooler are switched to remove the deposits. Alternatively, the accumulation of deposits can also be identified based on the pressure drop of the EGR cooler.

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-38440

[0007] In the EGR device disclosed in Patent Document 1, the cooling efficiency of the EGR cooler is used to estimate the accumulation of deposits. However, the cooling efficiency is also affected by the flow rate of the refrigerant, such as cooling water. Therefore, there are cases where the refrigerant flow rate decreases for some reason, resulting in the cooling efficiency falling below the permissible value. Furthermore, when identifying deposit accumulation based on the pressure drop of the EGR cooler, the pressure drop is calculated based on the differential pressure between the inlet and outlet of the EGR cooler. However, when the EGR gas flow rate changes due to the opening and closing of the EGR valve, the differential pressure may change drastically, leading to incorrect identification of deposit accumulation. Additionally, it is difficult to estimate the amount of condensate remaining (retained) in the EGR cooler based on the cooling efficiency and pressure drop. Summary of the Invention

[0008] The purpose of this disclosure is to accurately remove deposits or condensate by estimating the amount of deposits accumulated in the EGR cooler or the amount of condensate remaining in the EGR cooler with relatively high accuracy.

[0009] The internal combustion engine disclosed herein is an internal combustion engine having an exhaust gas recirculation device that recirculates a portion of the exhaust gas, namely EGR gas, back to the intake passage. The internal combustion engine includes: an EGR cooler disposed in the EGR passage for supplying EGR gas flow, for cooling the EGR gas; a switching unit that switches the direction of EGR gas flow to a first mode in which EGR gas flows in a predetermined direction within the EGR cooler and a second mode in which EGR gas flows in the opposite direction to the predetermined direction within the EGR cooler; and a control device. The control device includes at least one of a deposit control unit or a condensate control unit. The deposit control unit includes: a deposit amount calculation unit that calculates the amount of deposits accumulated in the EGR cooler using the fuel injection quantity and engine speed of the internal combustion engine as parameters; and a first switching command unit that commands a switch between the first mode and the second mode when the amount of deposits exceeds a first threshold. The condensate control unit includes: a condensate volume calculation unit that calculates the amount of condensate remaining in the EGR cooler using the fuel injection quantity and speed of the internal combustion engine as parameters; and a second switching command unit that commands a switch between the first mode and the second mode when the amount of condensate exceeds a second threshold.

[0010] According to this structure, the switching unit can switch between a first mode in which EGR gas flows in a predetermined direction in the EGR cooler and a second mode in which EGR gas flows in the opposite direction to the predetermined direction in the EGR cooler, thereby enabling switching between the inlet and outlet of the EGR cooler.

[0011] The control device includes at least one of a deposit control unit or a condensate control unit. The deposit control unit calculates the amount of deposits accumulated in the EGR cooler using the fuel injection quantity and engine speed of the internal combustion engine as parameters. When the amount of deposits exceeds a first threshold, a first switching command unit instructs a switch between a first mode and a second mode. Since the amount of deposits accumulated in the EGR cooler exceeds the first threshold, the system switches between the inlet and outlet of the EGR cooler, thus removing the accumulated deposits. The amount of deposits accumulated in the EGR cooler varies depending on the operating state of the internal combustion engine, particularly the fuel injection quantity and engine speed. The deposit quantity calculation unit calculates the amount of deposits accumulated in the EGR cooler using the fuel injection quantity and engine speed as parameters, thus enabling a relatively high-precision estimation of the amount of deposits accumulated in the EGR cooler and accurate removal of the deposits.

[0012] The condensate control unit calculates the amount of condensate remaining in the EGR cooler using the internal combustion engine's fuel injection quantity and speed as parameters. When the condensate accumulation exceeds a second threshold, the second switching command unit instructs a switch between the first and second modes. Since the amount of condensate remaining in the EGR cooler exceeds the second threshold, the system switches between the EGR cooler's inlet and outlet, thus removing the accumulated condensate. The amount of condensate remaining in the EGR cooler varies depending on the internal combustion engine's operating conditions, particularly the fuel injection quantity and speed. The condensate calculation unit calculates the amount of condensate remaining in the EGR cooler using the engine's fuel injection quantity and speed as parameters, allowing for a relatively high-precision estimation of the amount of condensate remaining in the EGR cooler and accurate removal of the condensate.

[0013] Alternatively, preferably, the control device is configured to control the switching unit to switch between the first mode and the second mode when the first switching command unit instructs the switching unit to switch between the first mode and the second mode, or when the second switching command unit instructs the switching unit to switch between the first mode and the second mode.

[0014] According to this structure, when the amount of deposits exceeds the first threshold or when the amount of condensate exceeds the second threshold, the switching unit is controlled by the control device to switch between the first mode and the second mode. Therefore, when the internal combustion engine is working, the deposits or condensate can be removed at the appropriate time.

[0015] Alternatively, preferably, the sediment quantity calculation unit is configured to calculate the sediment accumulation amount in the EGR cooler in the first mode, and the sediment control unit further includes a sediment reset value calculation unit, which performs a subtraction calculation on the sediment accumulation amount in the second mode. The control device is configured to control the switching unit to switch from the first mode to the second mode when instructed by the first switching command unit to switch between the first mode and the second mode, and to control the switching unit to switch from the second mode to the first mode when the sediment accumulation amount calculated by the sediment reset value calculation unit becomes less than or equal to the first reset value.

[0016] Alternatively, the condensate volume calculation unit may be configured to calculate the amount of condensate remaining in the EGR cooler in the first mode. The condensate control unit may also include a condensate reset value calculation unit, which performs a subtraction calculation on the amount of condensate in the second mode. The control device may be configured to control the switching unit to switch from the first mode to the second mode when instructed by the second switching command unit to switch between the first mode and the second mode, and to control the switching unit to switch from the second mode to the first mode when the amount of condensate calculated by the condensate reset value calculation unit becomes less than or equal to the second reset value.

[0017] In Mode 1 and Mode 2, the direction of EGR gas flow differs, thus the cooling efficiency of the EGR cooler may vary. According to this structure, the internal combustion engine operates in Mode 1 until the amount of deposits accumulated in the EGR cooler exceeds a first threshold, or until the amount of condensate retained in the EGR cooler exceeds a second threshold. Furthermore, if the amount of deposits accumulated in the EGR cooler exceeds the first threshold, or if the amount of condensate retained in the EGR cooler exceeds the second threshold, it switches to Mode 2 to remove the deposits or condensate. Compared to the accumulation of deposits or the retention of condensate, the removal of deposits or condensate occurs in a very short time. Therefore, in Mode 2, the amount of deposits calculated by the deposit reset calculation unit quickly falls below the first reset value, and the system switches from Mode 2 to Mode 1. Similarly, in Mode 2, the amount of condensate calculated by the condensate reset value calculation unit quickly falls below the second reset value, and the system switches from Mode 2 to Mode 1. Therefore, even if the cooling efficiency changes when switching from mode 1 to mode 2, the internal combustion engine operates for a shorter time in mode 2, thus minimizing its impact.

[0018] Alternatively, preferably, the control device is configured to communicate with the diagnostic tool, and the control device is configured to control the switching unit to switch between the first mode and the second mode when the diagnostic tool detects that the first switching command unit has instructed to switch between the first mode and the second mode, or when the second switching command unit has instructed to switch between the first mode and the second mode.

[0019] When an internal combustion engine is operating, switching between the inlet and outlet of the EGR cooler can cause significant fluctuations in the EGR rate. This design allows switching between modes 1 and 2 to be controlled by connecting a diagnostic tool that can communicate with the control unit. Since switching between the EGR cooler's inlet and outlet is possible when diagnosing the internal combustion engine using the diagnostic tool, significant fluctuations in the EGR rate can be suppressed during engine operation.

[0020] Alternatively, preferably, the sediment amount calculation unit is configured to calculate the amount of sediment accumulated in the EGR cooler in the first mode. The sediment control unit also includes a sediment reset value calculation unit, which performs a subtraction calculation on the amount of sediment in the second mode. For the control device, it is configured to control the switching unit to switch from the first mode to the second mode when the diagnostic tool detects that the first switching command unit has instructed to switch between the first mode and the second mode. Furthermore, it is configured to control the switching unit to switch from the second mode to the first mode when the amount of sediment calculated by the sediment reset value calculation unit becomes less than or equal to the first reset value.

[0021] Alternatively, the condensate volume calculation unit may be configured to calculate the amount of condensate remaining in the EGR cooler in the first mode. The condensate control unit may also include a condensate reset value calculation unit, which performs a subtraction calculation on the amount of condensate in the second mode. For the control device, it may be configured to control the switching unit to switch from the first mode to the second mode when the diagnostic tool detects that the second switching command unit has instructed a switch between the first mode and the second mode. Furthermore, it may be configured to control the switching unit to switch from the second mode to the first mode when the amount of condensate calculated by the condensate reset value calculation unit is below the second reset value.

[0022] According to this structure, even if the cooling efficiency of the EGR cooler changes when switching from mode 1 to mode 2, the operating time of the internal combustion engine in mode 2 can be shortened, thus reducing its impact.

[0023] The control method for an internal combustion engine disclosed herein includes an exhaust gas recirculation (EGR) device that recirculates a portion of the exhaust gas, i.e., EGR gas, back to the intake passage. The internal combustion engine comprises: an EGR cooler disposed in an EGR passage supplying EGR gas for cooling the EGR gas; and a switching unit that switches the direction of EGR gas flow between a first mode in which the EGR gas flows in a predetermined direction within the EGR cooler and a second mode in which the EGR gas flows in the opposite direction to the predetermined direction within the EGR cooler. The control method includes the following steps: calculating the amount of deposits accumulated in the EGR cooler using the fuel injection quantity and engine speed of the internal combustion engine as parameters; and switching between the first mode and the second mode when the amount of deposits exceeds a first threshold.

[0024] According to this control method, when the amount of deposits exceeds a first threshold, the system switches between a first mode and a second mode. Therefore, switching between the inlet and outlet of the EGR cooler removes the accumulated deposits. The amount of deposits accumulated in the EGR cooler is calculated using the fuel injection quantity and speed of the internal combustion engine as parameters. Therefore, the amount of deposits accumulated in the EGR cooler can be estimated with relatively high accuracy, enabling precise removal of the deposits.

[0025] The control method for an internal combustion engine disclosed herein includes an exhaust gas recirculation (EGR) device that recirculates a portion of the exhaust gas, i.e., EGR gas, back to the intake passage. The internal combustion engine comprises: an EGR cooler disposed in an EGR passage supplying EGR gas for cooling the EGR gas; and a switching unit that switches the direction of EGR gas flow between a first mode in which the EGR gas flows in a predetermined direction within the EGR cooler and a second mode in which the EGR gas flows in the opposite direction to the predetermined direction within the EGR cooler. The control method includes the following steps: calculating the amount of condensate retained in the EGR cooler using the fuel injection quantity and engine speed of the internal combustion engine as parameters; and switching between the first mode and the second mode when the amount of condensate retained exceeds a second threshold.

[0026] According to this control method, when the accumulated condensate exceeds a second threshold, the system switches between mode 1 and mode 2. Therefore, switching between the inlet and outlet of the EGR cooler removes the condensate. The amount of condensate remaining in the EGR cooler is calculated using the engine's fuel injection quantity and speed as parameters. Therefore, the amount of condensate remaining in the EGR cooler can be estimated with relatively high accuracy, enabling precise removal of the condensate.

[0027] According to this disclosure, the amount of deposits accumulated in the EGR cooler or the amount of condensate remaining in the EGR cooler can be estimated with relatively high accuracy, and the deposits or condensate can be removed accurately. Attached Figure Description

[0028] Figure 1 This is an overall structural diagram of the internal combustion engine involved in this embodiment.

[0029] Figure 2 This is a diagram showing the structure of the EGR device 60.

[0030] Figure 3 This diagram illustrates the first mode of the EGR device 60.

[0031] Figure 4 This diagram illustrates the second mode of the EGR device 60.

[0032] Figure 5 This diagram illustrates the bypass mode in which the EGR cooler 61 is bypassed when the EGR unit 60 is operating in the first mode.

[0033] Figure 6 This diagram illustrates the bypass mode in which the EGR cooler 61 is bypassed when the EGR unit 60 is operating in the second mode.

[0034] Figure 7 This is a diagram showing the functional modules constituted by the E / G-ECU100.

[0035] Figure 8 This is a flowchart illustrating the sediment / condensate control process performed by the E / G-ECU100.

[0036] Figure 9 It is a graph representing the mapping of the amount of sediment Dp stored in memory 102 to the mapping of the amount of condensate Cw.

[0037] Figure 10 This is a flowchart illustrating the mode switching control process executed by the E / G-ECU100.

[0038] Figure 11 This is a diagram showing the functional modules constituted by E / G-ECU100 in Embodiment 2.

[0039] Figure 12 This is a flowchart illustrating the OBD control process executed by the E / G-ECU100.

[0040] Figure 13 This is a flowchart representing the diagnostic / switching process performed by diagnostic tool 400.

[0041] Figure 14 This is a diagram showing the functional modules constituted by E / G-ECU100 in Embodiment 3.

[0042] Figure 15This is a flowchart illustrating the sediment / condensate control process performed by the E / G-ECU100 in Embodiment 3.

[0043] Figure 16 This is a graph showing the time shifts (time shifts of sediment accumulation ΣDp and condensate accumulation ΣCw) in the first and second modes of implementation method 3.

[0044] Figure 17 This is a diagram showing the functional modules constituted by E / G-ECU100 in Embodiment 4.

[0045] Figure 18 This is a flowchart illustrating the sediment / condensate control process performed by the E / G-ECU100 in Embodiment 4.

[0046] Figure 19 This is a flowchart illustrating the diagnostic / switching process performed by the E / G-ECU100 in Implementation 4.

[0047] Figure 20 This is a diagram showing the schematic structure of the EGR device 60A in the modified example.

[0048] Figure 21 This diagram illustrates the first and second modes of the EGR device 60A.

[0049] Figure 22 This diagram illustrates the bypass mode that allows the EGR cooler 61c to bypass. Detailed Implementation

[0050] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, the same or equivalent parts in the drawings will be labeled with the same reference numerals, and their descriptions will not be repeated.

[0051] (Implementation Method 1)

[0052] Figure 1 This is an overall structural diagram of the internal combustion engine involved in this embodiment. The internal combustion engine 1 is a compression ignition internal combustion engine (diesel engine), which injects fuel from the fuel injection valve (injector) 14 into the combustion chamber formed by the cylinder 12 of the internal combustion engine body 10 and performs compression ignition. An air filter 22, an intercooler 24 and an intake throttle valve (electronic throttle valve) 26 are provided in the intake passage 20 of the internal combustion engine 1. Fresh air (air) that has been cleaned of impurities by the air filter 22 is pressurized (compressed) by the compressor 32 of the turbocharger 30, cooled by the intercooler 24, and then supplied to the intake manifold 28, and supplied to each combustion chamber from the intake port.

[0053] Exhaust gas exiting the combustion chamber is collected in the exhaust manifold 40 and released to the outside atmosphere via the exhaust passage 42. Additionally, a portion of the exhaust gas flows back to the intake manifold (intake passage) 28 via the exhaust gas recirculation (EGR) device 60. Details regarding the EGR device 60 will be described later.

[0054] In the exhaust passage 42, starting from the upstream side, there is a turbocharger 30 turbine 34, an oxidation catalyst 70, a DPF (Diesel Particulate Filter) 72, a selective reduction catalyst 74, and an oxidation catalyst 76. The oxidation catalyst 70 oxidizes carbon monoxide (CO) in the exhaust to carbon dioxide (CO2) and hydrocarbons (HC) in the exhaust to water (H2O) and CO2. Furthermore, it oxidizes nitric oxide (NO) in the exhaust to nitrogen dioxide (NO2). This is because the reduction reaction of nitrogen oxides (NOx) is fast when the NO to NO2 ratio is 1:1. Therefore, since the exhaust of a diesel internal combustion engine contains a relatively large amount of NO, the NO in the exhaust is oxidized to NO2, making the NO to NO2 ratio close to 1:1.

[0055] DPF72 purifies the exhaust by capturing particulate matter and removing it through proper combustion. A selective reduction catalyst (hereinafter also referred to as an SCR catalyst) 74 reduces and purifies the NOx in the exhaust. Details of the SCR catalyst 74 will be described later. An oxidation catalyst 76 purifies the exhaust by oxidizing the ammonia gas emitted (escaped) from the SCR catalyst 74.

[0056] The SCR catalyst 74 is constructed, for example, by supporting copper (Cu) ion-exchange zeolite on a ceramic support as a catalyst, and exhibits a high purification rate by using ammonia (NH3) as a reducing agent. Ammonia, which is used as a reducing agent, is generated by hydrolyzing urea water supplied to the exhaust passage 42 upstream of the SCR catalyst 74. A urea injection valve (urea water injector) 80 is provided in the exhaust passage upstream of the SCR catalyst 74, and urea water pumped from the urea water tank 82 by a pump (not shown) is injected from the urea injection valve 80 into the exhaust passage 42 upstream of the SCR catalyst 74.

[0057] Figure 2This diagram illustrates the structure of the EGR device 60. The EGR device 60 is located in the EGR passage 50, which connects the exhaust manifold 40 to the intake manifold 28. A portion of the exhaust gas, i.e., EGR gas, flows in the EGR passage 50. A switching valve 62 is located upstream of the EGR passage 50, which is connected to the exhaust manifold 40. The EGR passage 50 branches into a first branch passage 63a and a second branch passage 63b, with the switching valve 62 as a branch. The switching valve 62 can be, for example, a three-way valve. The downstream of the first branch passage 63a is connected to the manifold passage 65 via an on / off valve 64a. The downstream of the second branch passage 63b is connected to the manifold passage 65 via an on / off valve 64b. The downstream of the manifold passage 65 is connected to the EGR passage 50 via an EGR valve 67, and the EGR gas flows back to the intake manifold 28. By adjusting the opening of the EGR valve 67, the EGR rate (EGR quantity) can be controlled.

[0058] The downstream of the first branch passage 63a is connected to one side of the first EGR cooler 61a. The downstream of the second branch passage 63b is connected to one side of the second EGR cooler 61b. The other side of the first EGR cooler 61a and the other side of the second EGR cooler 61b are connected by a connecting passage 66. The first EGR cooler 61a and the second EGR cooler 61b are substantially the same structure. For example, EGR gas flows between cooling fins in a honeycomb structure that forms flat cooling water pipes for cooling water flow, thereby exchanging heat between the EGR gas and the cooling water and cooling the EGR gas. In this embodiment, the other side of the first EGR cooler 61a and the other side of the second EGR cooler 61b are connected by a connecting passage 66, thereby forming the EGR cooler 61.

[0059] A cooling water passage 90 is connected to the EGR cooler 61. For example... Figure 2 As shown by the arrow, cooling water flows in from one side of the second EGR cooler 61b and flows out from one side of the first EGR cooler 61a. Cooling water connection passages 91 are provided on the other side of the first EGR cooler 61a and the other side of the second EGR cooler 61b, configured such that cooling water flows from the second EGR cooler 61b to the first EGR cooler 61a.

[0060] Figure 3 This diagram illustrates the first mode of the EGR device 60. In the first mode, switching valve 62 connects the EGR passage 50 to the first branch passage 63a, while disconnecting the connection between the EGR passage 50 and the second branch passage 63b. Furthermore, on / off valve 64a is closed, and on / off valve 64b is opened. Thus, as... Figure 3As indicated by the dashed arrow, EGR gas flows in the first branch passage 63a, entering from one side of the first EGR cooler 61a and exiting from one side of the second EGR cooler 61b, before flowing into the intake manifold 28 via the EGR valve 67. In the first mode, one side of the first EGR cooler 61a corresponds to the inlet of the EGR cooler 61, and one side of the second EGR cooler 61b corresponds to the outlet of the EGR cooler 61.

[0061] Figure 4 This diagram illustrates the second mode of the EGR device 60. In the second mode, switching valve 62 connects the EGR passage 50 to the second branch passage 63b, while disconnecting the connection between the EGR passage 50 and the first branch passage 63a. Furthermore, opening / closing valve 64b is closed, and opening / closing valve 64a is opened. Thus, as... Figure 4 As indicated by the dashed arrow, EGR gas flows in the second branch passage 63b, entering from one side of the second EGR cooler 61b and exiting from one side of the first EGR cooler 61a, before flowing into the intake manifold 28 via the EGR valve 67. In the second mode, one side of the second EGR cooler 61b corresponds to the inlet of the EGR cooler 61, and one side of the first EGR cooler 61a corresponds to the outlet of the EGR cooler 61.

[0062] Figure 5 This diagram illustrates the bypass mode in which the EGR cooler 61 is bypassed when the EGR unit 60 operates in mode 1. Figure 3 In the first mode of operation shown, the on / off valve 64b is closed, and the on / off valve 64a is opened. Thus, as... Figure 5 As indicated by the dashed arrow, the EGR gas does not flow into the EGR cooler 61, but bypasses it and flows into the intake manifold 28 via the EGR valve 67. Additionally, the on / off valve 64b can also be opened.

[0063] Figure 6 This diagram illustrates the bypass mode in which the EGR cooler 61 is bypassed when the EGR unit 60 operates in mode 2. Figure 4 In the second mode of operation shown, the on / off valve 64a is closed, and the on / off valve 64b is opened. Thus, as... Figure 6 As indicated by the dashed arrow, the EGR gas does not flow into the EGR cooler 61, but bypasses it and flows into the intake manifold 28 via the EGR valve 67. Additionally, the on / off valve 64a can also be opened.

[0064] The internal combustion engine 1 is equipped with an E / G-ECU (Electronic Control Unit) 100 as a control device. The E / G-ECU 100 includes a CPU (Central Processing Unit) 101, a memory 102 consisting of a ROM (Read Only Memory) for storing processing programs and a RAM (Random Access Memory) for temporarily storing data, and input / output ports (not shown) for inputting and outputting various signals. Based on the information stored in the memory 102 and information from various sensors, it performs predetermined calculations. Furthermore, the E / G-ECU 100 controls the internal combustion engine 1 based on the results of the calculations. For example, when the internal combustion engine 1 is used as the power source of a vehicle, the required torque is calculated based on the throttle opening AP detected by the throttle opening sensor 151 and the vehicle speed SPD detected by the vehicle speed sensor 152. The fuel injection quantity Fq and fuel injection timing that output torque from the internal combustion engine 1 in proportion to the required torque are then determined, and the fuel injection quantity and fuel injection timing are controlled.

[0065] Furthermore, the E / G-ECU 100 controls the EGR device 60 of the internal combustion engine 1. For example, it calculates a target EGR rate based on the fuel injection quantity Fq and the engine speed NE detected by the engine speed sensor 153, and controls the opening of the EGR valve 67 in a manner that achieves the target EGR rate. Additionally, it determines whether to cool the EGR gas through the EGR cooler 61 based on the coolant temperature THW detected by the engine coolant temperature sensor 154. For example, if the coolant temperature THW is lower than a preset temperature, it does not perform the process of cooling the EGR gas through the EGR cooler 61, and the EGR gas flows back to the intake manifold 28. In this case, by... Figure 5 or Figure 6 In the bypass mode shown, EGR gas enters the intake manifold 28. When the coolant temperature (THW) is higher than a preset temperature, the EGR gas is cooled by the EGR cooler 61. Furthermore, the state in which the EGR gas cooled by the EGR cooler 61 is returned is called cold EGR.

[0066] In cold EGR, the EGR gas... Figure 3 The first mode shown or Figure 4In the second mode shown, the gas flows into the intake manifold 28. If the EGR gas is cooled by the EGR cooler 61, it loses heat energy, thus reducing its kinetic energy. Furthermore, during the cooling of the EGR gas, condensate and lubricating oil mist contained in the EGR gas (exhaust) combine with soot in the EGR gas to form foreign matter (deposits). Therefore, deposits accumulate near the outlet of the EGR cooler 61, where the ER gas flow rate is lowest. In the first mode, deposits accumulate on one side of the second EGR cooler 61b, and in the second mode, deposits accumulate on one side of the first EGR cooler 61a. If a large amount of deposits accumulates in the EGR cooler 61, the desired NOx reduction and fuel economy effects may not be achieved due to blockage of the EGR cooler 61 and reduced cooling efficiency.

[0067] In a cold EGR, the temperature at the outlet side of the EGR cooler 61 is low. Therefore, the condensate remaining at the outlet side of the EGR cooler does not evaporate but remains. The condensate exhibits strong acidity, and therefore, corrosion of the EGR cooler 61 may occur due to the retained condensate.

[0068] In this embodiment, accumulated deposits and retained condensate are removed by switching between the inlet and outlet of the EGR cooler 61. The switching between the inlet and outlet of the EGR cooler 61 can be achieved by switching from mode 1 to mode 2 or from mode 2 to mode 1. Switching between the inlet and outlet of the EGR cooler 61 makes the outlet side where deposits accumulate and the outlet side where condensate is retained the inlet of the EGR cooler 61. Because of the high flow rate of EGR gas at the inlet side of the EGR cooler 61, accumulated deposits are removed by peeling off from the cooling fins or the like. At the inlet side of the EGR cooler 61, the temperature of the EGR gas is high (high temperature), therefore, the viscosity of the accumulated deposits decreases, and the deposits are easily peeled off. Furthermore, because of the high temperature of the EGR gas at the inlet side of the EGR cooler 61, the temperature at the inlet side of the EGR cooler 61 increases, and retained condensate is heated and evaporated.

[0069] In this embodiment, the amount of deposits ΣDp accumulated in the EGR cooler 61 is calculated using the fuel injection quantity Fq of the internal combustion engine 1 and the engine speed NE as parameters. When the amount of deposits ΣDp reaches a first threshold α or higher, the inlet and outlet of the EGR cooler 61 are switched. Furthermore, the amount of condensate ΣCw stored in the EGR cooler 61 is calculated using the fuel injection quantity Fq of the internal combustion engine 1 and the engine speed NE as parameters. When the amount of condensate ΣCw reaches a second threshold β or higher, the inlet and outlet of the EGR cooler 61 are switched.

[0070] The amount of deposits ΣDp accumulated in the EGR cooler 61 and the amount of condensate ΣCw retained in the EGR cooler 61 vary depending on the operating conditions of the internal combustion engine 1, particularly the fuel injection quantity Fq and engine speed NE. The amount of deposits ΣDp and the amount of condensate ΣCw are calculated using the fuel injection quantity Fq and engine speed NE as parameters. Therefore, the amount of deposits ΣDp accumulated in the EGR cooler 61 and the amount of condensate ΣCw retained in the EGR cooler 61 can be estimated with relatively high accuracy, and the deposits and condensate can be removed accurately.

[0071] Figure 7 This diagram illustrates the functional modules comprised of the E / G-ECU100. The deposit control unit 110 includes a deposit amount calculation unit 111 and a first switching command unit 112. The deposit amount calculation unit 111 calculates the deposit accumulation amount ΣDp based on the fuel injection quantity Fq and the engine speed NE, and outputs the calculated deposit accumulation amount ΣDp to the first switching command unit 112. The method for calculating the deposit accumulation amount ΣDp will be described below. The first switching command unit 112 compares the deposit accumulation amount ΣDp with a first threshold α. If the deposit accumulation amount ΣDp is greater than or equal to the first threshold α, it outputs a switching command to the switching control unit 130, switching between the first mode and the second mode, and switching between the inlet and outlet of the EGR cooler 61.

[0072] The condensate control unit 120 includes a condensate volume calculation unit 121 and a second switching command unit 122. The condensate volume calculation unit 121 calculates the condensate accumulation ΣCw based on the fuel injection quantity Fq and engine speed NE, and outputs the calculated condensate accumulation ΣCw to the second switching command unit 122. The method for calculating the condensate accumulation ΣCw will be described below. The second switching command unit 122 compares the condensate accumulation ΣCw with a second threshold β. If the condensate accumulation ΣCw is greater than or equal to the second threshold β, it outputs a switching command to the switching control unit 130, switching between the first mode and the second mode, and switching between the inlet and outlet of the EGR cooler 61.

[0073] If the switching control unit 130 receives a switching command, it controls the switching valve 62, the on / off valve 64a and the on / off valve 64b to switch between the first mode and the second mode.

[0074] Figure 8This is a flowchart illustrating the deposit / condensate control process performed by the E / G-ECU100. This flowchart is repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1. In step (hereinafter, step S) 10, it is determined whether the EGR is cold. The EGR gas cooled by the EGR cooler 61 is returned to the intake manifold 28. If it is cold EGR, a positive determination is made, and the process proceeds to S11. If the EGR gas is returned to the intake manifold 28 without cooling via bypass mode, or if the return of the EGR gas is stopped, a negative determination is made, and the current routine ends.

[0075] In S11, it is determined whether the flag Fs has changed. The flag Fs is set by the mode switching control described below. In mode 1, the flag Fs is set to 0, and in mode 2, the flag Fs is set to 1. If no switch between mode 1 and mode 2 is performed between processing the previous routine and processing the current routine, the flag Fs does not change, therefore, a negative determination is made and proceeds to S13. If a switch between mode 1 and mode 2 is performed between processing the previous routine and processing the current routine, the flag Fs changes, therefore, a positive determination is made and proceeds to S12.

[0076] In S12, after setting (rewriting) the previous value ΣDp(n) of the sediment accumulation to the reset value Dps and setting (rewriting) the previous value ΣCw(n) of the condensate accumulation to the reset value Cws, proceed to S13.

[0077] In S13, the amount of deposits Dp accumulated in the EGR cooler 61 and the amount of condensate Cw retained in the EGR cooler 61 are calculated based on the fuel injection quantity Fq and the engine speed NE. Figure 9 It is a graph representing the mapping of the amount of sediment Dp stored in memory 102 to the mapping of the amount of condensate Cw. Figure 9 (A) is the sediment amount Dp mapping, Figure 9 (B) is the mapping of condensate volume Cw.

[0078] Figure 9 In the diagram, the horizontal axis represents the engine speed NE of internal combustion engine 1, and the vertical axis represents the fuel injection quantity Fq of internal combustion engine 1. This is reflected in the deposition quantity Dp mapping (…). Figure 9 In (A), "*" indicates the amount of deposits accumulated per unit time, and each "*" represents a different value. Furthermore, "-*" indicates the amount of accumulated deposits removed. There is also an operating region where, when the internal combustion engine 1 operates at high load and high speed, the amount of EGR gas flowing in the EGR cooler 61 increases, removing the accumulated deposits. (In the condensate flow rate Cw mapping...) Figure 9In (B), "*" indicates the amount of condensate retained per unit time, and each "*" represents a different value. Furthermore, "-*" indicates the amount of condensate removed. There is also an operating region where, when the internal combustion engine 1 is running at high load and high speed, the temperature of the EGR gas flowing in the EGR cooler 61 rises, causing the retained condensate to be removed.

[0079] The amount of sediment accumulated per unit time and the amount of condensate retained per unit time are determined in advance through experiments, etc., and sediment quantity Dp mapping and condensate quantity Cw mapping are created. Moreover, the created sediment quantity Dp mapping and condensate quantity Cw mapping are stored in memory 102 in advance.

[0080] In S13, using the fuel injection quantity Fq and engine speed NE as parameters, the amount of sediment accumulated per unit time (*, -*) is calculated by mapping from the sediment quantity Dp, and the value corresponding to the calculation cycle (predetermined period) of this routine is calculated as the sediment quantity Dp. Furthermore, using the fuel injection quantity Fq and engine speed NE as parameters, the amount of condensate retained per unit time (*, -*) is calculated by mapping from the condensate quantity Cw, and the value corresponding to the calculation cycle of this routine is calculated as the condensate quantity Cw.

[0081] Next, in S14, the previous value ΣDP(n) of the sediment accumulation is read from memory 102, and the sediment amount Dp is added to the previous value ΣDp(n) to calculate the sediment accumulation ΣDp (ΣDp=ΣDp(n)+Dp). Then, the calculated sediment accumulation ΣDp is stored (rewritten) in memory 102 as the previous value ΣDp(n).

[0082] Furthermore, in S14, the previous value ΣDP(n) of the condensate accumulation is read from memory 102, and the condensate volume Cw is added to the previous value ΣCw(n) to calculate the condensate accumulation ΣCw (ΣCw=ΣCw(n)+Cw). Then, after storing (rewriting) the calculated condensate accumulation ΣCw as the previous value ΣCw(n) in memory 102, the process proceeds to S15.

[0083] In S15, it is determined whether the sediment accumulation amount ΣDp is greater than or equal to the first threshold α. If the sediment accumulation amount ΣDp is less than the first threshold α (ΣDp < α), a negative determination is made and proceeds to S16. If the sediment accumulation amount ΣDp is greater than or equal to the first threshold α (ΣDp ≥ α), a positive determination is made and proceeds to S17. The first threshold α is, for example, a value that, if sediment accumulates in the EGR cooler 61 at a value greater than or equal to this, results in the cooling efficiency of the EGR cooler 61 becoming less than the allowable value, and is determined in advance through experiments, etc.

[0084] In S16, it is determined whether the accumulated amount of condensate ΣCw is greater than or equal to the second threshold β. If the accumulated amount of condensate ΣCw is less than the second threshold β (ΣCw < β), a negative determination is made, and the current routine ends. If the accumulated amount of condensate ΣCw is greater than or equal to the second threshold β (ΣCw ≥ β), a positive determination is made, and the process proceeds to S17. The second threshold β is, for example, a value that indicates a faster rate of corrosion in the EGR cooler 61 if condensate remains at a level greater than or equal to this threshold, and is determined in advance through experiments, etc.

[0085] In S17, the current routine ends after setting the flag Fc to 1. The flag Fc is a flag that switches between instruction mode 1 and mode 2. When the flag Fc is set to 1 (Fc = 1), it becomes the switching instruction.

[0086] Figure 10 This is a flowchart illustrating the mode switching control process executed by the E / G-ECU100. This flowchart is interrupted when the flag Fc is set to 1. If in Figure 8 If flag Fc is set to 1 in S17 and the mode switching control is interrupted, then in S20, it is determined whether flag Fs is 1. If the current state of EGR device 60 is mode 1, flag Fs is 0. Therefore, a negative determination is made in S20, and the process proceeds to S21.

[0087] In S21, switching valve 62 is switched to connect EGR passage 50 with the second branch passage 63b, while disconnecting the connection between EGR passage 50 and the first branch passage 63a. Furthermore, by closing the on / off valve 64b and opening the on / off valve 64a, the EGR device 60 is switched to the second mode (see reference). Figure 4 After that, proceed to S22.

[0088] In S22, after setting the flag Fs to 1, proceed to S23, set the flag Fc to 0, and end the current routine.

[0089] In S20, if the current state of the EGR device 60 is in mode 2, the flag Fs is 1, therefore, a positive determination is made, and the process proceeds to S24.

[0090] In S24, switching valve 62 is switched to connect EGR passage 50 with the first branch passage 63a, while disconnecting the connection between EGR passage 50 and the second branch passage 63b. Furthermore, by closing the on / off valve 64a and opening the on / off valve 64b, the EGR device 60 is switched to the first mode (see reference). Figure 3 After that, proceed to S25.

[0091] In S25, after setting the flag Fs to 0, proceed to S23, set the flag Fc to 0, and end the current routine.

[0092] In this embodiment, Figure 8 The processing of S13 and S14 corresponds to the sediment control unit 110, the processing of S15 and S17 corresponds to the sediment quantity calculation unit 111, and the processing of S15 and S17 corresponds to the first switching instruction unit 112. Figure 8 The processing of S13 and S14 corresponds to the condensate flow calculation unit 121, and the processing of S15 and S17 corresponds to the second switching command unit 122. Furthermore, Figure 10 The processing is equivalent to switching control unit 130.

[0093] According to this embodiment, the deposit control unit 110 calculates the deposit accumulation amount ΣDp in the EGR cooler using the internal combustion engine's fuel injection amount Fq and engine speed NE as parameters by the deposit amount calculation unit 111. When the deposit accumulation amount ΣDp exceeds a first threshold α, the first switching command unit 112 commands a switch between a first mode and a second mode. Furthermore, the switching control unit 130 controls the switching unit (switching valve 62, on / off valve 64a, and on / off valve 64b) to switch between a first mode in which EGR gas flows in the EGR cooler 61 in a predetermined direction and a second mode in which EGR gas flows in the EGR cooler 61 in the opposite direction to the predetermined direction, thereby switching between the inlet and outlet of the EGR cooler 61.

[0094] By switching between the inlet and outlet of the EGR cooler 61, the outlet side where deposits accumulate becomes the inlet of the EGR cooler 61. At the inlet side of the EGR cooler 61, due to the high flow rate of the EGR gas, the accumulated deposits are stripped off from the cooling fins and removed. Furthermore, the amount of deposits ΣDp is calculated using the fuel injection quantity Fq and engine speed NE as parameters; therefore, the amount of deposits ΣDp accumulated in the EGR cooler 61 can be estimated with relatively high accuracy, enabling precise removal of the deposits.

[0095] According to this embodiment, the condensate control unit 120 calculates the amount of condensate ΣCw stored in the EGR cooler 61 using the fuel injection quantity Fq of the internal combustion engine and the engine speed NE as parameters by the condensate quantity calculation unit 121. When the amount of condensate ΣCw exceeds the second threshold β, the second switching command unit 122 commands a switch between the first mode and the second mode. Furthermore, the switching control unit 130 controls the switching unit (switching valve 62, on / off valve 64a, and on / off valve 64b) to switch between the first mode in which EGR gas flows in the EGR cooler 61 in a predetermined direction and the second mode in which EGR gas flows in the EGR cooler 61 in the opposite direction to the predetermined direction, thereby switching between the inlet and outlet of the EGR cooler 61.

[0096] By switching between the inlet and outlet of the EGR cooler 61, the outlet side where condensate is retained becomes the inlet of the EGR cooler 61. At the inlet side of the EGR cooler 61, due to the high temperature of the EGR gas, the retained condensate evaporates (evaporates) and is removed. Furthermore, the condensate accumulation ΣCw is calculated using fuel injection quantity Fq and engine speed NE as parameters; therefore, the condensate accumulation ΣCw in the EGR cooler 61 can be estimated with relatively high accuracy, enabling precise removal of the condensate.

[0097] In this embodiment, the E / G-ECU100 is configured as a deposit control unit 110 and a condensate control unit 120, but it is also possible that the E / G-ECU100 is configured as at least one of the deposit control unit 110 or the condensate control unit 120.

[0098] (Implementation Method 2)

[0099] In the above-described embodiment (Embodiment 1), the switching control unit 130 switches between the first mode and the second mode. However, a diagnostic tool can also be used to switch between the first mode and the second mode.

[0100] Figure 1 In this configuration, the E / G-ECU100 is configured to communicate with the diagnostic tool 400. The diagnostic tool 400 diagnoses abnormalities and faults of the internal combustion engine 1 in a repair shop. For example, when the internal combustion engine 1 is installed in a vehicle as a power source, the diagnostic tool 400 can also be a scanning tool for an on-board diagnostic (OBD) device.

[0101] Figure 11This diagram illustrates the functional modules comprised of the E / G-ECU100 in Embodiment 2. The sediment control unit 110, including a sediment quantity calculation unit 111 and a first switching command unit 112, and the condensate control unit 120, including a condensate quantity calculation unit 121 and a second switching command unit 122, are the same as those in Embodiment 1 (see reference). Figure 7 The sediment control unit 110 and the condensate control unit 120 have the same structure. Therefore, similar to Embodiment 1, Embodiment 2 also implements the same structure. Figure 8 The treatment shown is for controlling sediment / condensate.

[0102] Figure 11 If the OBD control unit 140 receives a switching command from the first switching command unit 112 or the second switching command unit 122, it writes the detection code to the memory 102 and illuminates a warning light (MIL: MalfunctionIndication Lamp) not shown in the figure.

[0103] Figure 12 This is a flowchart representing the OBD control process executed by the E / G-ECU100. This flowchart is interrupted when the flag Fc is set to 1. If in Figure 8 In S17, the flag Fc is set to 1, and the OBD control is interrupted. Then, in S30, a detection code is written to memory 102. This detection code indicates that the amount of sediment accumulation ΣDp is above the first threshold α or the amount of condensate accumulation ΣCw is above the second threshold β. For example, a code like "P1001" can also be used. The detection code written in S30 is also called the EGR code. Next, in S31, after the MIL is illuminated, the current routine ends.

[0104] By illuminating the MIL (Missing Information), for example, if a vehicle equipped with an internal combustion engine 1 is brought to a repair shop, the diagnostic tool 400 connects to the E / G-ECU 100 to perform abnormal diagnosis of the internal combustion engine 1. Figure 13 This is a flowchart illustrating the diagnostic / switching process performed by the diagnostic tool 400. This process is executed when the diagnostic tool 400 is connected to the E / G-ECU 100. First, in S40, the detection codes stored in the memory 102 are read, and it is determined whether the read detection codes contain an EGR code. For example, if the code "P1001" exists in the detection codes read from the memory 102, it is determined that an EGR code exists (EGR code detected). If the code "P1001" does not exist in the detection codes read from the memory 102, a negative determination is made, and the current process ends. If the code "P1001" exists in the detection codes read from the memory 102, a positive determination is made, and the process proceeds to S41.

[0105] In S41, the flag Fs is read from memory 102, and the process proceeds to S20. S20–S25 are related to… Figure 10 The mode switching control S20 to S25 shown are essentially the same process, so detailed explanations are omitted. In addition, the switching to mode 1 in S21 and the switching to mode 2 in S24 are performed by controlling the switching valve 62, the on / off valve 64a, and the on / off valve 64b via the E / G-ECU100.

[0106] In S42, which follows S23, the EGR code stored in memory 102 is cleared (reset), and flags Fs and Fc are written to memory 102. As a result, flag Fc stored in memory 102 is set to 0. Flag Fs stored in memory 102 was set to 0 after processing S25 and to 1 after processing S21. If S42 is processed, the current processing ends.

[0107] In this second embodiment, the switching unit (switching valve 62, on / off valve 64a, and on / off valve 64b) is controlled by a diagnostic tool 400 capable of communicating with the E / G-ECU 100 to switch between the first and second modes. In the first embodiment described above, when the internal combustion engine 1 is running (operating), the switching control unit 130 switches between the inlet and outlet of the EGR cooler 61. Therefore, the EGR rate may fluctuate significantly when the internal combustion engine 1 is operating, causing incongruity for the user. In this second embodiment, when the amount of deposits ΣDp exceeds the first threshold α, a switching command is output from the first switching command unit 112 and an EGR code is written; or when the amount of condensate ΣCw exceeds the second threshold β, a switching command is output from the second switching command unit 122 and an EGR code is written. In a repair shop, when the diagnostic tool 400 is used to diagnose abnormalities in the internal combustion engine 1, the inlet and outlet of the EGR cooler 61 are switched. The abnormal diagnosis of the internal combustion engine 1 is performed using EGR codes. Therefore, it is possible to perform the diagnosis when the internal combustion engine 1 is not running (not working), and it can suppress the situation where the EGR rate fluctuates greatly when the internal combustion engine 1 is running, which may cause the user to feel uncomfortable.

[0108] In this embodiment 2, the E / G-ECU100 may constitute at least one of the deposit control unit 110 or the condensate control unit 120.

[0109] Additionally, in embodiment 2, the diagnostic tool 400 is transmitted via S21 or S24 (see reference). Figure 13The process involves switching between mode 1 and mode 2. Alternatively, the diagnostic tool 400 may display switching instructions for mode 1 and mode 2, and the repair technician may switch between mode 1 and mode 2 by operating the diagnostic tool 400 according to these instructions.

[0110] (Implementation Method 3)

[0111] In Mode 1 and Mode 2, the direction of EGR gas flow is different; therefore, the cooling efficiency of EGR cooler 61 may vary. (Refer to...) Figure 2 Cooling water, such as Figure 2 As indicated by the arrow, the EGR gas flows in from one side of the second EGR cooler 61b and flows out from the other side of the first EGR cooler 61a. Therefore, in the first mode, the EGR gas and cooling water flow in opposite directions, while in the second mode, they flow in parallel. Consequently, in the second mode, the cooling efficiency of the EGR cooler 61 may be reduced compared to the first mode.

[0112] In Embodiments 1 and 2, the control alternates between the first and second modes of the EGR device 60, thus the first and second modes last for almost the same duration. In Embodiment 3, by shortening the period during which the internal combustion engine 1 operates in the second mode, the impact of the change in cooling efficiency when switching from the first to the second mode is reduced.

[0113] Figure 14 This is a diagram showing the functional modules constituted by E / G-ECU100 in Embodiment 3. Figure 14 The function block diagram in the figure refers to the function block diagram of implementation method 1 (see Figure 1). Figure 7 A sediment reset value calculation unit 113 is added to the sediment control unit 110, and a condensate reset value calculation unit 123 is added to the condensate control unit 120.

[0114] In Mode 2, the sediment reset value calculation unit 113 performs a subtraction calculation on the sediment accumulation amount ΣDp. Simultaneously, the sediment quantity calculation unit 111 is configured to calculate the sediment accumulation amount ΣDp in Mode 1. The first switching command unit 112 compares the sediment accumulation amount ΣDp with a first threshold α. If the sediment accumulation amount ΣDp is greater than or equal to the first threshold α, a switching command is output to the switching control unit 130, switching from Mode 1 to Mode 2. Furthermore, when the sediment accumulation amount ΣDp calculated by the sediment reset value calculation unit 113 becomes less than or equal to the first reset value Dps, the first switching command unit 112 outputs a switching command to the switching control unit 130, switching from Mode 2 to Mode 1.

[0115] In the second mode, the condensate reset value calculation unit 123 performs a subtraction calculation on the condensate accumulation ΣCw. Simultaneously, the condensate volume calculation unit 121 is configured to calculate the condensate accumulation ΣCw in the first mode. The second switching command unit 122 compares the condensate accumulation ΣCw with a second threshold β. If the condensate accumulation ΣCw is above the second threshold β, a switching command is output to the switching control unit 130, switching from the first mode to the second mode. Furthermore, when the condensate accumulation ΣCw calculated by the condensate reset value calculation unit 123 becomes below the second reset value Cws, the second switching command unit 122 outputs a switching command to the switching control unit 130, switching from the second mode to the first mode.

[0116] Figure 15 This is a flowchart illustrating the sediment / condensate control process performed by the E / G-ECU100 in Embodiment 3. The flowchart is derived from... Figure 8 The flowchart of Embodiment 1 shown omits S12 and adds SS50-S56, S10, S11, and S13-S17. Figure 8 The process is the same, therefore its description is omitted. In S11, if the flag Fs is 0, a positive determination is made, and steps S13 and thereafter are processed to calculate the amount of sediment ΣDp and the amount of condensate ΣCw using the fuel injection quantity Fq and engine speed NE as parameters. In S15, if the amount of sediment ΣDp is greater than or equal to the first threshold α (ΣDp≥α), a positive determination is made, and when proceeding to S17, the flag Fg is set to 0 in the additional S50 before proceeding to S17. Furthermore, in S16, if the amount of condensate ΣCw is greater than or equal to the second threshold β (ΣCw≥β), a positive determination is made, and when proceeding to S17, the flag Fg is set to 1 in the additional S51 before proceeding to S17.

[0117] If the flag Fs is 1 in S11, a negative determination is performed, and then proceed to S52. Similar to Implementation 1, this Implementation 3 also executes... Figure 10 The mode switching control is shown. When the flag Fs is set to 0, it is mode 1; when the flag Fs is set to 1, it is mode 2. Therefore, by processing S11, in mode 1, processing S13 and subsequent steps calculates the amount of deposit ΣDp and the amount of condensate ΣCw using the fuel injection quantity Fq and engine speed NE as parameters. In mode 2, it proceeds to S50.

[0118] In S52, the amount of sediment removed, Dpd, is calculated based on the engine speed NE. In addition, the amount of condensate removed, Cwd, is calculated based on the engine speed and then proceeds to S51.

[0119] In S53, the previous value ΣDP(n) of the sediment accumulation amount is read from memory 102, and the sediment accumulation amount ΣDp is calculated by subtracting the sediment removal amount Dpd from the previous value ΣDp(n) (ΣDp=ΣDp(n)-Dps). Then, the calculated sediment accumulation amount ΣDp is stored (rewritten) in memory 102 as the previous value ΣDp(n). Furthermore, the previous value ΣDP(n) of the condensate accumulation amount is read from memory 102, and the condensate accumulation amount ΣCw is calculated by subtracting the condensate removal amount Cwd from the previous value ΣCw(n) (ΣCw=ΣCw(n)-Cwd). After storing the calculated condensate accumulation amount ΣCw in memory 102 as the previous value ΣCw(n), the process proceeds to S54.

[0120] In S54, it is determined whether the flag Fg is 0. If the sediment accumulation ΣDp is above the first threshold α and belongs to the second mode, the flag Fg is 0, a positive determination is made, and proceed to S55. If the condensate accumulation ΣCw is above the second threshold β and belongs to the second mode, the flag Fg is 1, therefore, a negative determination is made, and proceed to S56.

[0121] In S55, it is determined whether the sediment accumulation amount ΣDp is below the first reset value Dps. If the sediment accumulation amount ΣDp is below the first reset value Dps (ΣDp≤Dps), a positive determination is made, and the process proceeds to S17. In S17, the flag Fc is set to 1, and the current routine ends. If the sediment accumulation amount ΣDp is greater than the first reset value Dps (ΣDp>Dps), a negative determination is made, and the current routine ends. Furthermore, the first reset value Dps is... Figure 7 The reset value Dps set in S12 is the same as the value.

[0122] In S56, it is determined whether the condensate accumulation ΣCw is below the second reset value Cws. If the condensate accumulation ΣCw is below the second reset value Cws (ΣCw≤Cws), a positive determination is made, and the process proceeds to S17. In S17, the flag Fc is set to 1, and the current routine ends. If the condensate accumulation ΣCw is greater than the second reset value Cws (ΣCw>Cws), a negative determination is made, and the current routine ends. Furthermore, the second reset value Cws is... Figure 7 The reset value Cws set in S12 is the same as the value.

[0123] The processing in S52 and S53 corresponds to the sediment reset value calculation unit 113 and the condensate reset value calculation unit 123. The operating time of the internal combustion engine 1 during which the sediment accumulated after switching from mode 1 to mode 2 peels off from the cooling fins, etc., and the sediment accumulation amount ΣDp decreases from the first threshold α to the first reset value Dps is determined in advance through experiments, etc. Based on this, the sediment removal amount Dpd calculated in S52 is set. For example, when the internal combustion engine 1 is installed in a vehicle, after switching from mode 1 to mode 2, while driving in WLCT (Worldwide-harmonized Light vehicles Test Cycle) urban mode, a mapping of the sediment removal amount Dpd with engine speed NE as a parameter is created based on the operating time of the internal combustion engine 1 during which the sediment accumulation amount ΣDp decreases from the first threshold α to the first reset value Dps, and the sediment removal amount Dpd is calculated based on this mapping. The sediment removal amount Dpd mapping can also be a mapping with fuel injection amount Fq and engine speed NE as parameters. In addition, the amount of sediment removed, Dpd, can also be determined based on the operating time (working time) of the internal combustion engine 1.

[0124] If the EGR device 60 switches from mode 1 to mode 2, the accumulated deposits are stripped off from the cooling fins and other surfaces due to the high-speed EGR gas. As a result, the amount of deposits ΣDp decreases to the first reset value Dps within a relatively short time. For example, after switching from mode 1 to mode 2, the amount of deposits ΣDp decreases to the first reset value Dps within 10 minutes.

[0125] The condensate removal amount Cwd calculated in S52 is set by pre-determining the operating time of the internal combustion engine 1 from the second threshold β to the second reset value Cws after switching from mode 1 to mode 2 through experiments, etc. For example, when the internal combustion engine 1 is installed in a vehicle, a mapping of the condensate removal amount Cwd with engine speed NE as a parameter is created based on the operating time of the internal combustion engine 1 from the second threshold β to the second reset value Cws when driving in WLCT urban mode after switching from mode 1 to mode 2. The condensate removal amount Cwd is calculated based on this mapping. The mapping of the condensate removal amount Cwd can also be a mapping with fuel injection quantity Fq and engine speed NE as parameters. Alternatively, the condensate removal amount Cwd can be determined based on the operating time (working time) of the internal combustion engine 1.

[0126] If the EGR device 60 switches from mode 1 to mode 2, the condensate remaining in the EGR cooler 61 is heated and evaporated by the high-temperature EGR gas and removed. Therefore, the amount of condensate removed, Cwd, decreases to the second reset value, Cws, within a relatively short time. For example, after switching from mode 1 to mode 2, the amount of condensate removed, Cwd, decreases to the second reset value, Cws, within 10 minutes.

[0127] In implementation method 3, it is also executed Figure 10 The mode switching control is shown. That is, if flag Fc is set to 1 in S17, then... Figure 10 The mode switching control is interrupted. Therefore, if in mode 1 (flag Fs = 0), the sediment accumulation ΣDp exceeds the first threshold α (definitely determined in S15), or the condensate accumulation ΣCw exceeds the second threshold β (definitely determined in S16), and flag Fc is set to 1, then in S21 (refer to...) Figure 10 The system switches from mode 1 to mode 2. Furthermore, if in mode 2 (flag Fs = 1), the sediment accumulation ΣDp falls below the first reset value Dps (definitely determined in S55), or the condensate accumulation ΣCw falls below the second reset value Cws (definitely determined in S56), and flag Fc is set to 1, then in S24 (refer to...) Figure 10 Switch from mode 2 to mode 1.

[0128] Figure 16 This is a graph showing the time progression (time progression of sediment accumulation ΣDp and condensate accumulation ΣCw) between the first and second modes in Embodiment 3. According to Embodiment 3, the EGR device 60 operates in the first mode, where the EGR gas and cooling water flow in opposite directions, until the sediment accumulation ΣDp reaches or exceeds the first threshold α, or until the condensate accumulation ΣCw reaches or exceeds the second threshold β. Furthermore, if the sediment accumulation ΣDp reaches or exceeds the first threshold α, or if the condensate accumulation ΣCw reaches or exceeds the second threshold β, the system switches from the first mode to the second mode. Since sediment accumulation in the EGR cooler 61 and condensate accumulation in the EGR cooler 61 occur gradually, the operating time (working time) in the first mode is as follows: Figure 16 The duration shown is over a long period of time.

[0129] If switching to mode 2, the accumulated sediment and retained condensate are removed. Since the sediment and condensate are removed in a relatively short time as described above, the sediment accumulation amount ΣDp calculated by the sediment reset value calculation unit 113 quickly becomes below the first reset value Dps, and the condensate accumulation amount ΣCw calculated by the condensate reset value calculation unit 123 quickly becomes below the second reset value Cws. Therefore, switching from mode 2 to mode 1 in a short time results in... Figure 16 As shown, the internal combustion engine 1 (EGR device 60) can shorten the period of operation in the second mode.

[0130] In this embodiment, the cooling water is configured such that... Figure 2 As indicated by the arrow, the EGR gas flows in from one side of the second EGR cooler 61b and flows out from the other side of the first EGR cooler 61a. In the first mode, the EGR gas and cooling water flow in opposite directions, while in the second mode, they flow in parallel. Therefore, the first mode, which uses a relatively efficient opposite flow for cooling, can be executed continuously for a long time. Furthermore, the second mode, which uses a relatively inefficient parallel flow for cooling, can be completed in a shorter time. Thus, the EGR gas can be cooled with high overall cooling efficiency.

[0131] In this embodiment 3, at least one of the deposit control unit 110 or the condensate control unit 120 can be configured in the E / G-ECU100.

[0132] (Implementation Method 4)

[0133] Alternatively, as in Embodiment 2, in the example where the diagnostic tool 400 is used to switch between the first mode and the second mode, by shortening the period during which the internal combustion engine 1 operates in the second mode, the impact of the change in cooling efficiency when switching from the first mode to the second mode is reduced.

[0134] Figure 17 This is a diagram illustrating the functional modules comprised of the E / G-ECU100 in Embodiment 4. Compared to the functional block diagram of Embodiment 3 (see...). Figure 14 ), Figure 16 The functional block diagram in the previous embodiment replaces the switching control unit 130 with the OBD control unit 140. The functional block diagram of the OBD control unit 140 and Embodiment 2 (see reference) Figure 11 The OBD control unit 140 is essentially the same as the OBD control unit 140. If a switching instruction (flag Fc = 1) is received from the first switching instruction unit 112 or the second switching instruction unit 122, the detection code is written to the memory 102 and the MIL (not shown) is lit.

[0135] Figure 17In the middle, the sediment reset value calculation unit 113 and the condensate reset value calculation unit 123 are the same as in Embodiment 3 (see also Embodiment 3). Figure 14 Since the values ​​are the same, their description is omitted. Furthermore, in Embodiment 4, when the sediment accumulation ΣDp, calculated by the sediment reset value calculation unit 113, becomes below the first reset value Dps, the sediment control unit 110 controls the switching unit (switching valve 62, on / off valve 64a, and on / off valve 64b) to switch from the second mode to the first mode. Additionally, when the condensate accumulation ΣCw, calculated by the condensate reset value calculation unit 123, becomes below the second reset value Cws, the condensate control unit 120 controls the switching unit to switch from the second mode to the first mode.

[0136] Figure 18 This is a flowchart illustrating the sediment / condensate control process performed by the E / G-ECU100 in Embodiment 4. This flowchart is... Figure 15 The flowchart of Embodiment 3 shown is obtained by adding S57 and S58 to it, which is aimed at... Figure 15 The same process applies to the flowchart, so its description is omitted.

[0137] In implementation method 4, the same procedure as in implementation method 2 is followed. Figure 12 The ODB control process is shown. That is, if Figure 15 If flag Fc is set to 1 in S17, then Figure 12 The ODB control shown is interrupted, the detection code (EGR code) is written to memory 102, and the MIL light is illuminated.

[0138] Figure 19 This is a flowchart illustrating the diagnostic / switching process performed by the E / G-ECU 100 in Embodiment 4. This process is performed when the diagnostic tool 400 is connected to the E / G-ECU 100. (The last part, "from...", appears to be a fragment and doesn't translate directly. It likely refers to a flowchart or flowchart, but without further context, it's impossible to translate accurately.) Figure 13 The flowchart of the diagnosis / switching process in Embodiment 2 shown is obtained by omitting S41, S20, S24, and S25. In S40, the detection code stored in memory 102 is read, and it is determined whether the read detection code contains an EGR code. If it does not contain an EGR code, a negative determination is made, and the current process ends. If the detection code contains an EGR code, a positive determination is made, and the process from S21 onwards is executed. The processing of S21 and its subsequent steps is the same as in Embodiment 2 (…). Figure 13 Since they are the same, the explanation is omitted.

[0139] Therefore, after writing the detection code (EGR code) into the memory 102, connect the diagnostic tool 400 to the E / G-ECU 100 and execute... Figure 19 The diagnostic / switching process shown here causes the EGR device 60 to switch from mode 1 to mode 2.

[0140] If the EGR device 60 switches from mode 1 to mode 2 by performing a diagnostic / switching process, then the flag Fs is set to 1. Figure 19 (S22), therefore, refer to Figure 18 In S11, a negative determination is made, and S52 and subsequent steps are executed. If the sediment accumulation ΣDp exceeds the first threshold α and the process switches to mode 2 through diagnostic / switching, the flag Fg is set to 0, a positive determination is made in S54, and the process proceeds to S55. If the sediment accumulation ΣDp calculated in S53 (after subtraction) is below the first reset value Dps, the process proceeds to S57. Furthermore, if the condensate accumulation ΣCw exceeds the second threshold β and the process switches to mode 2 through diagnostic / switching, the flag Fg is set to 1, a negative determination is made in S54, and the process proceeds to S56. If the condensate accumulation ΣCw calculated in S53 (after subtraction) is below the second reset value Cws, the process proceeds to S57.

[0141] In S57, the EGR device is switched to mode 1 in the control switching unit (switching valve 62, on / off valve 64a, and on / off valve 64b) (see reference). Figure 3 After that, enter S58, set the flag Fs to 0, and end this routine.

[0142] Similar to Embodiment 3, in Embodiment 4, the internal combustion engine 1 (EGR device 60) can operate in the second mode for a shorter period. Therefore, the first mode, which uses a relatively efficient counterflow cooling system, can be continuously executed over a longer period of time. Furthermore, the second mode, which uses a relatively inefficient parallel flow cooling system, can be completed in a shorter time. Thus, the EGR gas can be cooled with higher overall cooling efficiency.

[0143] In this embodiment 4, the E / G-ECU100 may be configured as either a sediment control unit 110 or a condensate control unit 120.

[0144] (Modified Example)

[0145] In the above embodiment, the EGR cooler 61 is composed of the first EGR cooler 61a and the second EGR cooler 61b. However, the structure of the EGR cooler is not limited to this. Figure 20 This is a diagram showing the schematic structure of the EGR device 60A in the modified example. (Refer to...) Figure 20The EGR passage 50 branches into a first branch passage 63c and a second branch passage 63d via a switching valve 62. The switching valve 62 can be, for example, a three-way valve. The downstream of the first branch passage 63c is connected to the EGR valve 67 via a switching valve 64. The downstream of the second branch passage 63d is connected to the EGR valve 67 via a switching valve 64. The switching valve 64 can also be, for example, a three-way valve.

[0146] The middle part (midpoint) of the first branch passage 63c is connected to one side of the EGR cooler 61c, and the middle part (midpoint) of the second branch passage 63d is connected to the other side of the EGR cooler 61c. Thus, the middle parts of the first branch passage 63c and the middle parts of the second branch passage 63d are connected via the EGR cooler 61c.

[0147] A cooling water passage 90 is connected to the EGR cooler 61. For example... Figure 20 As shown by the arrow, cooling water flows in from the other side of the EGR cooler 61c and flows out from one side of the EGR cooler 61c.

[0148] Figure 21 This diagram illustrates the first and second modes of the EGR device 60A. Figure 21 (A) is the first mode. Figure 21 (B) is the second mode. For example... Figure 21 As shown in (A), in the first mode, switching valve 62 is switched to connect EGR passage 50 to the first branch passage 63c, and disconnect the connection between EGR passage 50 and the second branch passage 63d. Furthermore, switching valve 64 is switched to connect EGR valve 67 to the second branch passage 63d, and disconnect the connection between EGR valve 67 and the first branch passage 63c. Thus, as... Figure 21 As indicated by the dashed arrow in (A), the EGR gas flows in the first branch passage 63c, entering from one side of the EGR cooler 61c and exiting from the other side, flowing into the intake manifold 28 via the EGR valve 67. In the first mode, one side of the EGR cooler 61c corresponds to the inlet, and the other side of the EGR cooler 61c corresponds to the outlet.

[0149] like Figure 21 As shown in (B), in the second mode, switching valve 62 is switched to connect EGR passage 50 to the second branch passage 63d, and disconnect the connection between EGR passage 50 and the first branch passage 63c. Furthermore, switching valve 64 is switched to connect EGR valve 67 to the first branch passage 63c, and disconnect the connection between EGR valve 67 and the second branch passage 63d. Thus, as... Figure 21As indicated by the dashed arrow in (B), the EGR gas flows in the second branch passage 63d, entering from the other side of the EGR cooler 61c and exiting from one side of the EGR cooler 61c, flowing into the intake manifold 28 via the EGR valve 67. In the second mode, the other side of the EGR cooler 61c corresponds to the inlet, and one side of the EGR cooler 61c corresponds to the outlet.

[0150] Figure 22 This is a diagram illustrating the bypass mode for bypassing the EGR cooler 61c. Figure 22 (A) is a diagram illustrating the bypass mode when the ERG device 60A is operating in mode 1. Figure 22 (B) is a diagram illustrating the bypass mode of the EGR device 60A when it is operating in mode 2.

[0151] exist Figure 21 In the operation of the first mode described in (A), the switching valve 64 is switched to connect the EGR valve 67 to the first branch passage 63c, and disconnect the connection between the EGR valve 67 and the second branch passage 63d. Thus, as... Figure 22 As indicated by the dashed arrow in (A), the GR gas does not flow into the EGR cooler 61c but bypasses the EGR cooler 61c and flows into the intake manifold 28 via the EGR valve 67.

[0152] exist Figure 21 In the second mode of operation described in (B), the switching valve 64 is switched so that the EGR valve 67 is connected to the second branch passage 63d, and the connection between the EGR valve 67 and the first branch passage 63c is cut off. Thus, as... Figure 22 As indicated by the dashed arrow in (B), the GR gas does not flow into the EGR cooler 61c, but bypasses the EGR cooler 61c and flows into the intake manifold 28 via the EGR valve 67.

[0153] Alternatively, as in this variant, if the EGR device 60 is equipped with an EGR cooler capable of switching between the inlet and outlet, it may also have an EGR cooler.

[0154] In this embodiment, a diesel engine is described as internal combustion engine 1, but internal combustion engine 1 may also be a gasoline internal combustion engine (spark-ignition internal combustion engine).

[0155] If the embodiments of this disclosure are illustrated, the following manner can be illustrated.

[0156] 1) An internal combustion engine (1) having an exhaust gas recirculation device (60) that recirculates a portion of the exhaust gas, i.e., EGR gas, back to the intake passage (20, 28), comprising: an EGR cooler (61) disposed in an EGR passage (50) for supplying EGR gas flow, for cooling the EGR gas; a switching unit (62, 64, 64a, 64b) that switches the direction of EGR gas flow to a first mode in which EGR gas flows in a predetermined direction in the EGR cooler (61) and a second mode in which EGR gas flows in the EGR cooler (61) in the opposite direction to the predetermined direction; and a control device (100) comprising a deposit control unit (110) or a condensate control unit (120). At least one of the following, the sediment control unit (110) includes: a sediment amount calculation unit (111) which calculates the amount of sediment accumulated in the EGR cooler (61) using the fuel injection amount and speed of the internal combustion engine as parameters; and a first switching command unit (112) which commands to switch between a first mode and a second mode when the amount of sediment accumulation exceeds a first threshold. The condensate control unit (121) includes: a condensate amount calculation unit (121) which calculates the amount of condensate stored in the EGR cooler (61) using the fuel injection amount and speed as parameters; and a second switching command unit (122) which commands to switch between a first mode and a second mode when the amount of condensate stored exceeds a second threshold.

[0157] 2) Based on 1, the sediment control unit (110) is configured to write a detection code indicating that the sediment accumulation exceeds the first threshold into the memory (120) when the sediment accumulation exceeds the first threshold, and the condensate control unit (120) writes a detection code indicating that the condensate accumulation exceeds the second threshold into the memory (120) when the condensate accumulation exceeds the second threshold.

[0158] 3) Based on 2, the control device (100) is configured to communicate with the diagnostic tool (400). When the diagnostic tool (400) detects a detection code indicating that the amount of sediment accumulation exceeds the first threshold, or when the diagnostic tool (400) detects a detection code indicating that the amount of condensate accumulation exceeds the second threshold, the diagnostic tool (400) controls the switching unit via the control device (100) to switch between the first mode and the second mode.

[0159] 4) Based on 1, the first mode is that EGR gas flows in from one side of the EGR cooler (61) and flows out from the other side of the EGR cooler (61). The second mode is that EGR gas flows in from the other side of the EGR cooler (61) and flows out from one side of the EGR cooler (61). A cooling water passage is provided in the EGR cooler (61) for cooling water to flow in from the other side of the EGR cooler (61) and for cooling water to flow out from one side of the EGR cooler (61). In the first mode, the flow of EGR gas and cooling water is opposite to each other. In the second mode, the flow of EGR gas and cooling water is parallel.

[0160] 5) Based on 4, the sediment quantity calculation unit (110) is configured such that, in the first mode, it calculates the sediment accumulation amount. The sediment control unit (110) also includes a sediment reset value calculation unit (113). In the second mode, the sediment reset value calculation unit (113) performs a subtraction calculation on the sediment accumulation amount. When the sediment accumulation amount calculated by the sediment quantity calculation unit (110) exceeds a first threshold, it switches between the first mode and the second mode. When the sediment accumulation amount calculated by the sediment reset value calculation unit (113) becomes below the first reset value, it switches from the second mode to the upper mode. In the first mode, the condensate volume calculation unit (121) is configured to calculate the condensate volume in the first mode. The condensate control unit (120) also includes a condensate reset value calculation unit (123). In the second mode, the condensate reset value calculation unit (123) performs a subtraction calculation on the condensate volume. When the condensate volume calculated by the condensate volume calculation unit (121) exceeds a second threshold, the system switches from the first mode to the second mode. When the condensate volume calculated by the condensate reset value calculation unit (123) is below the second reset value, the system switches from the second mode to the first mode.

[0161] It should be considered that all aspects of the embodiments disclosed herein are illustrative rather than restrictive. The scope of the invention is shown not by the description of the above embodiments but by the claims, and is intended to include all modifications of the same meaning and scope as the claims.

[0162] Explanation of reference numerals in the attached figures

[0163] 1...Internal combustion engine; 10...Internal combustion engine block; 12...Cylinder; 14...Fuel injection valve; 20...Intake passage; 22...Air filter; 24...Intercooler; 26...Intake throttle valve; 28...Intake manifold; 30...Turbocharger; 32...Compressor; 34...Turbine; 40...Exhaust manifold; 42...Exhaust passage; 50...EGR passage; 60, 60A...EGR unit; 61, 61c...EGR cooler; 61a...First EGR cooler; 61b...Second EGR cooler; 62...Switching valve; 63a, 63c...First branch passage; 63b, 63d...Second branch passage; 64...Switching valve; 64a...On / off valve; 64b...On / off valve; 65...Manifold passage; 66...Connecting passage; 67...EGR valve; 70...Oxidation catalyst Agent; 72...DPF; 74...Selective Reduction Catalyst (SCR Catalyst); 76...Oxidation Catalyst; 80...Urea Addition Valve; 82...Urea Water Tank; 90...Cooling Water Passage; 91...Cooling Water Connection Passage; 100...E / G-ECU; 101...CPU; 102...Memory; 110...Deposit Control Unit; 111...Deposit Amount Calculation Unit; 112...First Switching Command Unit; 113...Deposit Reset Value Calculation Unit; 120...Condensate Control Unit; 121...Condensate Amount Calculation Unit; 122...Second Switching Command Unit; 123...Condensate Reset Value Calculation Unit; 130...Switching Control Unit; 140...OBD Control Unit; 151...Accelerator Opening Sensor; 152...Vehicle Speed ​​Sensor; 153...Engine Speed ​​Sensor; 154...Engine Coolant Temperature Sensor; 400...Diagnostic Tools.

Claims

1. An internal combustion engine having an exhaust gas recirculation device that recirculates a portion of the exhaust gas, i.e., EGR gas, back to the intake passage, characterized in that, have: An EGR cooler is installed in the EGR passage for which the EGR gas flows to cool the EGR gas. The switching unit switches the direction of the EGR gas flow to a first mode in which the EGR gas flows in a predetermined direction in the EGR cooler and a second mode in which the EGR gas flows in the EGR cooler in the opposite direction to the predetermined direction. as well as Control device, The control device includes at least one of a sediment control unit or a condensate control unit. The sediment control unit includes: The sediment accumulation calculation unit calculates the amount of sediment deposited in the EGR cooler using the fuel injection quantity and speed of the internal combustion engine as parameters; and The first switching instruction unit instructs to switch between the first mode and the second mode when the amount of sediment accumulation exceeds a first threshold. The amount of sediment is calculated based on the amount of sediment accumulated per unit time. This is achieved by determining the amount of sediment accumulated per unit time from a pre-created sediment accumulation map using the fuel injection rate and the internal combustion engine speed as parameters. The sediment accumulation Dp is then added to the previous value ΣDp(n), and the total sediment accumulation is calculated using ΣDp = ΣDp(n) + Dp. The condensate control unit includes: A condensate volume calculation unit calculates the amount of condensate remaining in the EGR cooler using the fuel injection rate and the rotational speed as parameters; and The second switching instruction unit instructs the user to switch between the first mode and the second mode when the accumulated condensate exceeds a second threshold value. The condensate volume is calculated based on the amount of condensate retained per unit time. Using the fuel injection rate and the internal combustion engine speed as parameters, the condensate volume retained per unit time is determined from a pre-created condensate volume mapping map. This condensate volume Cw is then added to the previous value ΣCw(n), and the accumulated condensate volume is calculated using ΣCw = ΣCw(n) + Cw. The deposits are formed at least by the combination of soot contained in the EGR gas and the condensate.

2. The internal combustion engine according to claim 1, characterized in that, The control device is configured to control the switching unit to switch between the first mode and the second mode when instructed by the first switching instruction unit to switch between the first mode and the second mode, or when instructed by the second switching instruction unit to switch between the first mode and the second mode.

3. The internal combustion engine according to claim 2, characterized in that, The sediment quantity calculation unit is configured to calculate the sediment accumulation amount in the first mode. The sediment control unit further includes a sediment reset value calculation unit, which calculates the sediment accumulation amount by subtracting the amount of sediment removal from the previous value during the second mode. The control device is configured such that when the first switching command unit instructs the switching unit to switch between the first mode and the second mode, it controls the switching unit to switch from the first mode to the second mode; and when the amount of sediment accumulation calculated by the sediment reset value calculation unit falls below the first reset value, it controls the switching unit to switch from the second mode back to the first mode. The condensate volume calculation unit is configured to calculate the accumulated amount of condensate in the first mode. The condensate control unit also includes a condensate reset value calculation unit, which calculates the accumulated amount of condensate by subtracting the amount of condensate removed from the previous value in the second mode. The control device is configured such that when the second switching command unit instructs the switching unit to switch between the first mode and the second mode, the switching unit switches from the first mode to the second mode; and when the amount of condensate calculated by the condensate reset value calculation unit becomes less than or equal to the second reset value, the switching unit switches from the second mode to the first mode.

4. The internal combustion engine according to claim 1, characterized in that, The control device is configured to communicate with diagnostic tools. The control device is configured to control the switching unit to switch between the first mode and the second mode when the diagnostic tool detects that the first switching instruction unit instructs the switching between the first mode and the second mode, or when the second switching instruction unit instructs the switching between the first mode and the second mode.

5. The internal combustion engine according to claim 4, characterized in that, The sediment quantity calculation unit is configured to calculate the sediment accumulation amount in the first mode. The sediment control unit further includes a sediment reset value calculation unit, which calculates the sediment accumulation amount by subtracting the amount of sediment removed from the previous value during the second mode. For the control device mentioned above The configuration is such that when the diagnostic tool detects a situation where the first switching command unit instructs a switch between the first mode and the second mode, it controls the switching unit to switch from the first mode to the second mode. The configuration is such that when the amount of sediment accumulation calculated by the sediment reset value calculation unit falls below a first reset value, the switching unit is controlled to switch from the second mode to the first mode. The condensate volume calculation unit is configured to calculate the accumulated amount of condensate in the first mode. The condensate control unit also includes a condensate reset value calculation unit, which calculates the accumulated amount of condensate by subtracting the amount of condensate removed from the previous value in the second mode. For the control device mentioned above The configuration is such that when the diagnostic tool detects a situation where the second switching command unit instructs a switch between the first mode and the second mode, it controls the switching unit to switch from the first mode to the second mode. The configuration is such that when the amount of condensate calculated by the condensate reset value calculation unit becomes less than or equal to a second reset value, the switching unit is controlled to switch from the second mode to the first mode.

6. A control method for an internal combustion engine, comprising an exhaust gas recirculation device that recirculates a portion of the exhaust gas, i.e., EGR gas, back to the intake passage, characterized in that, The internal combustion engine has the following features: An EGR cooler, disposed in the EGR passage for the flow of EGR gas, cools the EGR gas; and The switching unit switches the direction of EGR gas flow between a first mode in which the EGR gas flows in a predetermined direction in the EGR cooler and a second mode in which the EGR gas flows in the EGR cooler in the opposite direction to the predetermined direction. The control method includes the following steps: The amount of deposits accumulated in the EGR cooler is calculated using the fuel injection quantity and speed of the internal combustion engine as parameters; and When the amount of sediment accumulation exceeds a first threshold, the system switches between the first mode and the second mode. The amount of sediment is calculated by the amount of sediment accumulated per unit time. This is achieved by determining the amount of sediment accumulated per unit time from a pre-created sediment accumulation map using the fuel injection rate and the internal combustion engine speed as parameters. The sediment amount Dp is then added to the previous value ΣDp(n), and the total sediment accumulation is calculated using ΣDp = ΣDp(n) + Dp. The deposits are formed, at least by the combination of particulate matter contained in the EGR gas and condensate accumulated in the EGR cooler. The control method includes the following steps: The amount of condensate remaining in the EGR cooler is calculated using the fuel injection quantity and speed of the internal combustion engine as parameters; and When the accumulated condensate exceeds a second threshold value, the system switches between the first mode and the second mode. The condensate volume is calculated by the amount of condensate retained per unit time. The amount of condensate retained per unit time is determined from a condensate volume mapping map created in advance through experiments, using the fuel injection amount and the speed of the internal combustion engine as parameters. The condensate volume Cw is added to the previous value ΣCw(n), and the accumulated amount of condensate is calculated by ΣCw=ΣCw(n)+Cw.

7. The control method for an internal combustion engine according to claim 6, characterized in that, The step of switching between the first mode and the second mode is performed by a diagnostic tool that diagnoses the state of the internal combustion engine.

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