JP6772958B2 - Exhaust treatment device - Google Patents

Description

The present invention relates to temperature rise control of a filter that collects particulate matter contained in exhaust gas discharged from an engine.

An exhaust treatment device is provided in the exhaust pipe in order to purify particulate matter (PM: Particulate Matter) in the exhaust of a diesel engine or the like. This exhaust treatment device includes, for example, a PM removal filter that collects particulate matter and an oxidation catalyst (DOC: Diesel Oxidation Catalyst) that is arranged upstream of the exhaust flow from the PM removal filter. When the amount of particulate matter accumulated in the PM removal filter increases, the filter becomes clogged and the exhaust gas purification function deteriorates. Therefore, by raising the temperature of the PM removal filter, the collected particulate matter is burned and the filter is filtered. The so-called PM removal filter is regenerated.

In the regeneration of the PM removal filter, fuel is added to the exhaust gas, the added fuel is reacted with an oxidation catalyst, and the heat of the reaction raises the exhaust gas to a temperature range in which the PM removal filter can be regenerated. Then, the high-temperature exhaust gas circulates through the PM removal filter, so that the PM in the PM removal filter burns.

The amount of fuel added to the exhaust gas is adjusted so that the temperature of the exhaust gas flowing into the PM removal filter can be raised to a temperature range in which the PM removal filter can be regenerated.

For example, Japanese Patent Application Laid-Open No. 2008-202529 (Patent Document 1) describes the temperature of the PM removal filter and the target temperature rise each time when the temperature of the PM removal filter is controlled to the target temperature by adding fuel to the exhaust gas. A technique for controlling the temperature rise of the PM removal filter while learning the amount of fuel added that can correct the deviation of the fuel and reflecting the learned value in the amount of fuel added is disclosed.

Japanese Unexamined Patent Publication No. 2008-20259

In the exhaust treatment device having the above-described configuration, in the middle of the fuel flow path in the fuel system from the fuel tank to the fuel addition device, for example, a component such as a fuel filter for removing foreign matter from the flowing fuel. Is provided. Parts such as fuel filters are consumables, and their function deteriorates after long-term use, so they are replaced with new parts on a regular basis. When parts such as fuel filters are replaced with new ones, the resistance in the fuel flow path from the fuel tank to the fuel addition device decreases, so fuel is added after parts replacement based on the learning values learned before parts replacement. If the device is controlled, the amount of fuel added after the replacement of parts may be larger than desired. Therefore, in general, when a part is replaced with a new one at a predetermined maintenance timing, the learning value learned before the replacement of the part is reset to the initial value in accordance with the replacement. However, for example, when the user replaces the parts independently other than the predetermined maintenance timing, it is conceivable that the learning value of the addition amount is not reset to the initial value after the parts are replaced. In this case, even after the parts are replaced, the fuel addition control for regenerating the PM removal filter is controlled based on the learning value before the parts replacement, so that the learning value before the parts replacement is large. If there is, the amount of fuel added to the exhaust gas from the fuel addition device becomes larger than necessary, and the temperature of the exhaust gas flowing through the PM removal filter rises above the target temperature. Then, if the temperature of the exhaust gas flowing through the PM removal filter becomes too high, the PM removal filter may break down, so that fuel addition is immediately stopped. In this way, if the learning value learned before the replacement is not reset after the replacement of the consumable parts, the temperature of the exhaust gas flowing into the PM removal filter is highly accurate when the regeneration control of the PM removal filter is executed. Problems such as being out of control occur.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to perform after parts replacement even when the learning value is not reset to the initial value when the parts of the fuel system are replaced. It is an object of the present invention to provide an exhaust treatment device capable of accurately controlling the temperature of the exhaust gas flowing into the PM removal filter when the regeneration control of the PM removal filter is executed.

The exhaust treatment device according to a certain aspect of the present invention includes an oxidation catalyst provided in the exhaust passage of the engine, a fuel addition device provided at a position upstream of the oxidation catalyst in the exhaust passage, and adding fuel into the exhaust passage. A filter that is installed downstream of the oxidation catalyst in the exhaust passage and collects particulate matter contained in the exhaust that flows through the exhaust passage, and the amount of particulate matter that is collected in the filter is the deposition amount judgment value. If it is larger than, it includes a control device that controls the fuel addition device based on the command addition amount for setting the exhaust temperature, which is the temperature of the exhaust gas flowing into the filter, to the target temperature. The control device calculates a learning value for correcting the command addition amount so that the exhaust temperature approaches the target temperature when a predetermined learning condition is satisfied. When the exhaust temperature exceeds the temperature determination value higher than the target temperature, the control device reduces the learning value regardless of whether or not the learning condition is satisfied.

In this way, for example, whether or not the learning condition is satisfied when the exhaust temperature exceeds the temperature determination value by increasing the actual fuel addition amount with respect to the command addition amount due to the replacement of fuel system parts or the like. Regardless, the amount of fuel added into the exhaust passage can be reduced by reducing the learning value. As a result, the exhaust temperature can be lowered. After that, when the learning conditions are satisfied, an appropriate learning value can be calculated. Therefore, the fuel addition device can be controlled so that the exhaust temperature reaches the target temperature.

Preferably, when the exhaust temperature exceeds the temperature determination value, the control device sets a value obtained by subtracting a predetermined value from the immediately preceding learning value as the learning value.

By doing so, it is possible to suppress an unnecessarily decrease in the amount of increase in the exhaust temperature due to the addition of fuel by subtracting the learning value by a predetermined value.

More preferably, when the exhaust temperature exceeds the temperature determination value, the control device reduces the immediately preceding learning value to the initial value.

In this way, the exhaust temperature can be quickly lowered by reducing the learning value to the initial value.

More preferably, the control device reduces the learning value when the exhaust temperature exceeds the temperature determination value a plurality of times.

By doing so, it is possible to prevent the learning value from being unnecessarily reduced by reducing the learning value when the exhaust temperature exceeds the temperature determination value a plurality of times.

More preferably, the learning condition includes at least a condition that the state in which the exhaust temperature is constant continues for a predetermined time.

In this way, an appropriate learning value is set to make the exhaust temperature reach the target temperature by calculating the learning value when the condition that the state where the exhaust temperature is constant continues for a predetermined time is satisfied. can do. Therefore, the temperature rise control of the filter can be executed with high accuracy.

According to the present invention, even if the learning value is not reset when the fuel system parts are replaced, the temperature of the exhaust gas flowing into the PM removal filter is determined when the regeneration control of the PM removal filter is executed after the parts replacement. It is possible to provide an exhaust gas treatment device that can be controlled with high accuracy.

It is a figure which shows the schematic structure of the engine in this embodiment. It is a figure for demonstrating the correction method of the command addition amount. It is a timing chart which shows the change of the exhaust temperature when the learning value is not updated. It is a flowchart which shows the control process executed by a control device. It is a timing chart for explaining the operation of a control device. It is a flowchart which shows the control process executed by the control device in the modification.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are designated by the same reference numerals. Their names and functions are the same. Therefore, detailed explanations about them will not be repeated.

FIG. 1 is a diagram showing a schematic configuration of an engine 1 according to the present embodiment. In the present embodiment, the engine 1 will be described, for example, as an example of a common rail type diesel engine. However, the engine 1 may be another type of engine (for example, a gasoline engine or the like).

The engine 1 includes an engine body 10, an air cleaner 20, an intercooler 26, an intake manifold 28, a supercharger 30, an exhaust manifold 50, an exhaust treatment device 56, and a first exhaust gas recirculation device (hereinafter, first). 1 EGR (Exhaust Gas Recirculation) device 60, a second exhaust gas recirculation device (hereinafter referred to as a second EGR device) 70, a control device 200, an engine rotation speed sensor 202, an air flow meter 208, and the like. It includes a fuel pump 210, a fuel filter 212, and a fuel tank 214.

The engine body 10 includes a plurality of cylinders 12, a common rail 14, and a plurality of injectors 16. In the present embodiment, the engine 1 will be described by taking an in-line 4-cylinder engine as an example, but may be an engine having another cylinder layout (for example, V type or horizontal type).

The plurality of injectors 16 are fuel injection devices provided in each of the plurality of cylinders 12 and each of which is connected to the common rail 14. The fuel stored in the fuel tank 214 is pressurized to a predetermined pressure by the fuel pump 210 via the fuel filter 212 and supplied to the common rail 14. The fuel supplied to the common rail 14 is injected from each of the plurality of injectors 16 at a predetermined timing. The plurality of injectors 16 operate based on the control signals IJ1 to IJ4 from the control device 200.

The air cleaner 20 removes foreign matter from the air sucked from the outside of the engine 1. One end of the first intake pipe 22 is connected to the air cleaner 20.

The other end of the first intake pipe 22 is connected to the inlet of the compressor 32 of the turbocharger 30. One end of the second intake pipe 24 is connected to the outlet of the compressor 32. The compressor 32 supercharges the air flowing from the first intake pipe 22 and supplies it to the second intake pipe 24. The detailed operation of the compressor 32 will be described later.

One end of the intercooler 26 is connected to the other end of the second intake pipe 24. The intercooler 26 is an air-cooled or water-cooled heat exchanger that cools the air flowing through the second intake pipe 24.

One end of the third intake pipe 27 is connected to the other end of the intercooler 26. An intake manifold 28 is connected to the other end of the third intake pipe 27. The intake manifold 28 is connected to each intake port of the plurality of cylinders 12 of the engine body 10. In the upstream of the intake manifold 28, for example, exhaust gas recirculated from the exhaust manifold 50 via the first EGR device 60 (hereinafter, the exhaust gas recirculated to the intake passage is also referred to as EGR gas) is circulated to the intake manifold. An intake throttle valve for this purpose may be provided.

The exhaust manifold 50 is connected to each exhaust port of the plurality of cylinders 12 of the engine body 10. One end of the first exhaust pipe 52 is connected to the exhaust manifold 50. The other end of the first exhaust pipe 52 is connected to the turbine 36 of the turbocharger 30. Therefore, the exhaust gas discharged from the exhaust port of each cylinder is collected in the exhaust manifold 50 and then supplied to the turbine 36 via the first exhaust pipe 52.

One end of the second exhaust pipe 54 is connected to the turbine 36. The other end of the second exhaust pipe 54 is connected to the inlet portion of the exhaust treatment device 56. The exhaust treatment device 56 includes an oxidation catalyst (DOC: Diesel Oxidation Catalyst) 56a, a PM removal filter 56b, a fuel addition device 56c, and an exhaust temperature sensor 56d.

The PM removal filter 56b is provided on the downstream side of the exhaust flow path (exhaust passage) with respect to the oxidation catalyst 56a. The fuel addition device 56c is provided on the upstream side in the exhaust flow path with respect to the oxidation catalyst 56a. The exhaust temperature sensor 56d is provided in the exhaust flow path between the oxidation catalyst 56a and the PM removal filter 56b.

The PM removal filter 56b collects particulate matter (hereinafter, referred to as PM (Particulate Matter)) contained in the circulating exhaust gas. The PM removal filter 56b is made of, for example, ceramic or stainless steel. The collected PM is deposited in the PM removal filter 56b.

The oxidation catalyst 56a and the fuel addition device 56c function as a regeneration mechanism that burns and removes (regenerates) PM deposited on the PM removal filter 56b. When the exhaust gas is circulated, the oxidation catalyst 56a oxidizes nitrogen oxides (NOx), carbon oxides (COx), etc. in the circulated exhaust gas, and also contains fuel added from the fuel addition device 56c into the exhaust gas. If so, oxidize the fuel. The heat of reaction generated by the oxidation of the fuel raises the temperature of the exhaust gas passing through the oxidation catalyst 56a. When the high-temperature exhaust gas passes through the PM removal filter 56b, the temperature of the PM removal filter 56b rises, and the PM deposited in the PM removal filter 56b is oxidized and removed (combusted). As a result, the PM removal filter 56b is regenerated.

One end of the third exhaust pipe 58 is connected to the outlet portion of the exhaust treatment device 56. An additional exhaust treatment device, a muffler, or the like that removes a specific component from the exhaust such as a catalyst is connected to the other end of the third exhaust pipe 58. Therefore, the exhaust gas discharged from the turbine 36 is discharged to the outside of the vehicle via the second exhaust pipe 54, the exhaust treatment device 56, the third exhaust pipe 58, various catalysts, a muffler, and the like.

The third intake pipe 27 and the exhaust manifold 50 are connected by the first EGR device 60 without passing through the engine body 10. The first EGR device 60 includes a first EGR valve 62, a first EGR cooler 64, and a first EGR passage 66. The first EGR passage 66 connects the third intake pipe 27 and the exhaust manifold 50. The first EGR valve 62 and the first EGR cooler 64 are provided in the middle of the first EGR passage 66.

The first EGR valve 62 adjusts the flow rate of the EGR gas flowing through the first EGR passage 66 in response to the control signal from the control device 200. The first EGR cooler 64 is, for example, a water-cooled or air-cooled heat exchanger that cools the EGR gas flowing through the first EGR passage 66. The exhaust gas in the exhaust manifold 50 is returned to the intake side as EGR gas via the first EGR device 60, so that the combustion temperature in the cylinder is lowered and the amount of NOx produced is reduced.

The first intake pipe 22 and the third exhaust pipe 58 are connected by the second EGR device 70 without passing through the engine body 10. The second EGR device 70 includes a second EGR valve 72, a second EGR cooler 74, and a second EGR passage 76. The second EGR passage 76 connects the first intake pipe 22 and the third exhaust pipe 58. The second EGR valve 72 and the second EGR cooler 74 are provided in the middle of the second EGR passage 76.

The second EGR valve 72 adjusts the flow rate of the EGR gas flowing through the second EGR passage 76 in response to the control signal from the control device 200. The second EGR cooler 74 is, for example, a water-cooled or air-cooled heat exchanger that cools the EGR gas flowing through the second EGR passage 76. The exhaust gas in the third exhaust pipe 58 is returned to the intake side as EGR gas via the second EGR device 70, so that the combustion temperature in the cylinder is lowered and the amount of NOx produced is reduced.

The supercharger 30 includes a compressor 32 and a turbine 36. The compressor wheel 34 is housed in the housing of the compressor 32, and the turbine wheel 38 is housed in the housing of the turbine 36. The compressor wheel 34 and the turbine wheel 38 are connected by a connecting shaft 42 and rotate integrally. Therefore, the compressor wheel 34 is rotationally driven by the exhaust energy of the exhaust gas supplied to the turbine wheel 38.

The operation of the engine 1 is controlled by the control device 200. The control device 200 includes a CPU (Central Processing Unit) that performs various processes, a memory that includes a ROM (Read Only Memory) that stores programs and data, a RAM (Random Access Memory) that stores the processing results of the CPU, and the like. Includes input / output ports (neither shown) for exchanging information with the outside. The above-mentioned sensors (for example, exhaust temperature sensor 56d, engine speed sensor 202, air flow meter 208, etc.) are connected to the input port. Devices to be controlled (for example, a plurality of injectors 16, a fuel addition device 56c, a fuel pump 210, etc.) are connected to the output port.

The control device 200 controls various devices so that the engine 1 is in a desired operating state based on signals from each sensor and device, as well as maps and programs stored in memory. Note that various controls are not limited to software processing, but can also be processed by dedicated hardware (electronic circuits). Further, the control device 200 has a built-in timer circuit (not shown) for measuring the time.

The exhaust temperature sensor 56d detects the temperature of the exhaust gas flowing out of the oxidation catalyst 56a, that is, the temperature of the exhaust gas flowing into the PM removal filter 56b (hereinafter referred to as the exhaust gas temperature) Tex. The exhaust temperature sensor 56d transmits a signal indicating the detected exhaust temperature Tex to the control device 200. The exhaust temperature Tex may be obtained by estimation from the operating state of the engine 1 or a temperature sensor provided at another location, in addition to being directly detected by the temperature sensor installed near the PM removal filter 56b.

The engine speed sensor 202 detects the speed of the crankshaft of the engine 1 as the engine speed NE. The engine speed sensor 202 transmits a signal indicating the detected engine speed NE to the control device 200.

The air flow meter 208 detects the flow rate (intake air amount) Qin of fresh air introduced into the first intake pipe 22. The air flow meter 208 transmits a signal indicating the detected intake air amount Qin to the control device 200.

The fuel tank 214 stores fuel for supplying the plurality of injectors 16 and the fuel addition device 56c. The fuel pump 210 operates in response to a control signal from the control device 200 to pump the fuel stored in the fuel tank 214 to the common rail 14 or supply the fuel to the fuel addition device 56c. A fuel filter 212 is provided in the passage through which fuel flows between the fuel pump 210 and the fuel tank 214. The fuel filter 212 collects foreign substances contained in the circulating fuel.

In the engine 1 having the above configuration, if the amount of accumulated PM in the PM removal filter 56b is large, the filter portion of the PM removal filter 56b may be clogged and the function may be deteriorated. Therefore, the control device 200 executes regeneration control for reproducing the PM removal filter 56b.

More specifically, the control device 200 acquires the accumulated amount of PM in the PM removal filter 56b. The control device 200 calculates, for example, an estimated value of PM emissions from the plurality of cylinders 12 from the operating conditions of the engine 1 (for example, engine speed NE, fuel injection amount command value, intake air amount Qin, etc.). .. The control device 200 may acquire the accumulated amount by integrating the calculated estimated values. As for the specific calculation method of the amount of PM emission, a well-known technique may be used, and the detailed description thereof will not be given. The control device 200 executes regeneration control when the accumulated amount of PM that has been acquired exceeds the regeneration determination value.

When the regeneration control is executed, the control device 200 starts fuel addition from the fuel addition device 56c. The control device 200 sets, for example, a command addition amount for raising the exhaust temperature Tex to the target temperature, and controls the fuel addition device 56c according to the set command addition amount. Here, the target temperature of the exhaust gas is set as an exhaust gas temperature capable of raising the temperature of the PM removal filter 56b to a temperature at which the PM removal filter 56b can be regenerated.

With the regeneration control as described above, in the exhaust treatment device 56, fuel is added to the exhaust from the fuel addition device 56c, the added fuel reacts with the oxidation catalyst 56a, and the temperature of the exhaust rises due to the reaction heat. Then, the high temperature exhaust gas flows through the PM removal filter 56b, so that the temperature of the PM removal filter 56b rises to a temperature within the reproducible temperature range of the PM removal filter 56b, and the temperature inside the PM removal filter 56 rises. PM is burned. The control device 200 counts the elapsed time in a state where the temperature of the PM removal filter 56b is within the reproducible temperature range of the PM removal filter 56b, and the total of the counted elapsed times sets the predetermined playback end time. If it exceeds, it is determined that the regeneration of the PM removal filter 56b is completed.

By the way, when the operating time of the engine 1 becomes long, any of the components provided between the fuel tank 214 and the control valve of the fuel addition device 56c deteriorates over time, or a filter due to foreign matter collected by the fuel filter 212. When the regeneration control of the PM removal filter 56b is executed due to clogging, the command addition amount of the fuel to be added to the exhaust and the actual addition amount of the fuel actually added to the exhaust from the fuel addition device 56c There may be a gap between the two.

Therefore, the control device 200 calculates a learning value (for example, a correction coefficient) for correcting the command addition amount so that the actual addition amount approaches the command addition amount when a predetermined learning condition is satisfied. .. The control device 200 calculates the learning value based on, for example, the ratio of the exhaust temperature Tex after fuel addition to the target temperature.

FIG. 2 is a diagram for explaining a method of correcting the command addition amount. When the exhaust temperature before fuel addition is 300 ° C. and the target temperature is 650 ° C., it is necessary to raise the exhaust temperature by 350 ° C. by adding fuel. The control device 200 calculates the command addition amount, which is the amount of fuel added to raise the exhaust temperature by 350 ° C., using the conversion coefficient stored in the memory, the exhaust flow rate, and the like by a preliminary experiment. Then, the control device 200 controls the fuel addition device 56c based on the calculated command addition amount (initial value). As shown in the bar graph on the left side of FIG. 2, for example, the fuel addition device 56c is controlled based on the command addition amount (initial value), and the exhaust temperature Tex increased by the addition of fuel is 50 higher than the target temperature of 650 ° C. When the temperature is 600 ° C., which is lower than the temperature, the control device 200 determines that the actual addition amount of the fuel actually added from the fuel addition device 56c is smaller than the command addition amount (initial value), and determines the actual addition amount as the command addition amount. Calculate the learning value so that it approaches (initial value). In this case, for example, the control device 200 calculates 650/600 = 1.08 as a learning value. The control device 200 stores the calculated learning value in the memory. The initial value of the learning value is, for example, 1.0. After the first learning value is calculated, the control device 200 increases the exhaust temperature Tex by the final command addition amount corrected by using the immediately preceding learning value every time a predetermined learning condition is satisfied. A new learning value is calculated from the ratio between the temperature and the target temperature.

When the learned value is stored in the memory, the control device 200 stores the learned value in the memory with respect to the command addition amount (initial value) calculated from the exhaust temperature, the target temperature, the exhaust flow rate, and the like in the subsequent reproduction control. The final command addition amount (correction value) is calculated by executing the addition amount correction by multiplying the learned learning value. Then, the control device 200 controls the fuel addition device 56c based on the corrected command addition amount (correction value). As a result, the actual amount of fuel added to the exhaust gas from the fuel addition device 56c increases and approaches the command addition amount (initial value), and the heat of reaction when the fuel is oxidized in the oxidation catalyst 56a increases. .. As a result, the exhaust temperature Tex rises. Therefore, as shown in the bar graph on the right side of FIG. 2, the exhaust temperature Tex can be raised to the target temperature of 650 ° C. by correction.

The above-mentioned predetermined learning condition includes, for example, a condition that the time during which the exhaust temperature Tex is in a constant state is equal to or longer than the predetermined time. In addition to the above-mentioned conditions, the predetermined learning conditions include a condition that the time for the temperature of the PM removal filter 56b to be in a constant state is equal to or longer than the predetermined time, and the exhaust gas from the turbine 36. The energy of the exhaust gas flowing through the PM removal filter 56b under the condition that the fluctuation of the energy (for example, the outlet temperature of the turbine 36 × the gas flow rate) is less than the threshold temperature and that the exhaust temperature has reached the target temperature. It may include at least one of a condition that the fluctuation of is less than the threshold value and a condition that the exhaust temperature Tex is equal to or more than the threshold value.

In the control device 200, if the exhaust temperature Tex exceeds the stop determination value Ta while the regeneration control is being executed, the PM removal filter 56b may break down, so that the fuel addition is stopped. The addition device 56c is controlled. Further, in the control device 200, when the exhaust temperature Tex is lower than the restart determination value after the fuel addition is stopped due to the exhaust temperature Tex exceeding the stop determination value Ta during the execution of the regeneration control. , The fuel addition is permitted so that the PM removal filter 56b is regenerated, and the fuel addition device 56c is controlled based on the final command addition amount calculated by the addition amount correction based on the learning value.

In the engine 1 having such a configuration, any part provided in the fuel system between the fuel tank 214 such as the fuel filter 212 and the control valve of the fuel addition device 56c and the control valve of the fuel addition device 56c is replaced. In this case, the degree of restriction on fuel flow due to deterioration or accumulation of foreign matter may change before and after replacement of parts. As a result, even if the command addition amount is corrected using the learning value before parts replacement, it is possible that the actual addition amount actually added from the fuel addition device 56c cannot be brought close to the desired value. Therefore, when the parts are replaced at a predetermined maintenance timing, the learning value stored in the memory of the control device 200 is reset to the initial value.

However, when the user replaces the parts independently at a timing other than the predetermined maintenance timing, the learning value may not be reset (updated) to the initial value after the parts are replaced. In this case, when the regeneration control is executed, the command addition amount is corrected based on the learning value before the parts are replaced. Therefore, if the learning value before parts replacement is large, there arises a problem that the actual addition amount becomes too large and the exhaust temperature Tex rises to a temperature higher than the target temperature.

FIG. 3 is a timing chart showing a change in the exhaust temperature in regeneration control when the learning value learned before parts replacement is large and the learning value is not reset to the initial value after parts replacement. The vertical axis of the upper graph of FIG. 3 indicates the exhaust temperature, and the horizontal axis of the upper graph of FIG. 3 indicates time. The solid line in the upper graph of FIG. 3 shows the change in the exhaust temperature Tex, which is the temperature of the exhaust gas flowing into the PM removal filter 56b. The broken line in the upper graph of FIG. 3 shows the change in the temperature of the exhaust gas flowing out from the PM removal filter 56b. The alternate long and short dash line in the upper graph of FIG. 3 indicates the temperature of the exhaust gas flowing into the oxidation catalyst 56a. Further, the vertical axis of the lower graph of FIG. 3 indicates the learning value, and the horizontal axis of the lower graph of FIG. 3 indicates time.

For example, when the accumulated amount of PM is smaller than the regeneration determination value (that is, when the regeneration control is not executed) and the learning value is Ca (> 1.0), the fuel filter 212 is used by the user. It is assumed that the learning value is not reset to the initial value.

If the amount of PM deposited is smaller than the regeneration determination value, the regeneration control is not executed, so that the temperature of the exhaust gas flowing into the oxidation catalyst 56a, the temperature Tex of the exhaust gas flowing into the PM removal filter 56b, and the PM removal filter 56b The temperature of the outflowing exhaust gas will change at substantially the same temperature (around 300 ° C.). At this time, the learning value is maintained in Ca.

When the amount of accumulated PM in the PM removal filter 56b becomes larger than the regeneration determination value at the time t (0), the regeneration control is executed. In the regeneration control, fuel is added to the exhaust gas from the fuel addition device 56c.

In this case, as shown by the one-point chain line in FIG. 3, the temperature of the exhaust gas flowing into the oxidation catalyst 56a continues to change at around 300 ° C., whereas the fuel is oxidized in the oxidation catalyst 56a and the reaction heat is generated. As shown by the solid line in FIG. 3, the exhaust temperature Tex rises to about 650 ° C., which is the target temperature. Since heat is transferred from the exhaust gas flowing into the PM removal filter 56b to the constituent members of the PM removal filter 56b, the temperature of the exhaust gas flowing out from the PM removal filter 56b follows the exhaust temperature Tex as shown by the broken line in FIG. Ascend like.

When the fuel filter 212 is replaced with a new one, the filter clogging that occurred before the replacement is eliminated. If the learning value before parts replacement is large, the fuel added to the exhaust gas is actually added when the command addition amount is corrected by the learning value before parts replacement and the fuel addition device 56c is controlled after parts replacement. The amount added will be too much more than the amount required to raise the exhaust temperature Tex to the target temperature. As a result, the exhaust temperature Tex rises beyond the target temperature.

At time t (1), when the exhaust temperature Tex exceeds the stop determination value Ta as shown by the solid line in FIG. 3, the addition of fuel from the fuel addition device 56c is stopped. Therefore, the generation of reaction heat is suppressed in the oxidation catalyst 56a, so that the exhaust temperature Tex decreases. After that, at time t (2), when the exhaust temperature Tex becomes lower than the restart determination value and other restart conditions are satisfied, fuel addition is restarted from the fuel addition device 56c. When the addition of fuel is resumed, as described above, the actual addition amount is too much more than the amount required to raise the exhaust temperature Tex to the target temperature, so that the exhaust temperature Tex exceeds the target temperature. Will rise. Then, when the exhaust temperature Tex exceeds the stop determination value Ta, the addition of fuel from the fuel addition device 56c is stopped. In this way, resumption and stop of fuel addition are repeated until the regeneration control is completed.

When resumption and stop of fuel addition are repeated, the exhaust temperature Tex does not become a constant state as shown in FIG. 3, so that the learning condition is not satisfied and the learning value is not updated. As a result, the change in the temperature of the exhaust gas such as the time t (1) to t (2) is repeated. As a result, when the regeneration control of the PM removal filter 56b is executed, there arises a problem that the temperature of the exhaust gas flowing into the PM removal filter 56b cannot be controlled with high accuracy. Further, when the high temperature exhaust gas is repeatedly distributed to the PM removal filter 56b, the deterioration of the PM removal filter 56b is promoted.

Therefore, in the present embodiment, the control device 200 calculates a learning value for correcting the command addition amount so that the exhaust temperature Tex approaches the target temperature when a predetermined learning condition is satisfied. When the exhaust temperature Tex exceeds the temperature determination value higher than the target temperature, the control device shall reduce the learning value regardless of whether or not the learning condition is satisfied.

In this way, if the parts provided in the fuel system are replaced with new ones, but the learning value is not reset to the initial value, and the exhaust temperature Tex exceeds the temperature judgment value, learning is performed. Since the learning value is reduced regardless of whether or not the condition is satisfied, the final command addition amount to the fuel addition device can be reduced. As a result, the exhaust temperature Tex can be controlled to a desired value in the regeneration control. The temperature determination value is a value for determining that the temperature is higher than the target temperature and the exhaust gas flowing into the PM removal filter 56b is in an overheated state. In the present embodiment, the temperature determination value is assumed to be, for example, the same value as the stop determination value described above.

Hereinafter, the control process executed by the control device 200 in the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing a control process executed by the control device 200. The process shown in this flowchart is called and executed from the main routine (not shown) at predetermined control cycles.

At step 100 (hereinafter, step is referred to as S) 100, the control device 200 determines whether or not the learning condition is satisfied. Since the learning conditions are as described above, the detailed explanation thereof will not be repeated. When it is determined that the learning condition is satisfied (YES in S100), the process is transferred to S102.

In S102, the control device 200 executes the learning process. The control device 200 calculates the learning value by the learning process. Since the method of calculating the learning value is as described above, the detailed description thereof will not be repeated.

In S104, the control device 200 determines whether or not the exhaust temperature Tex is larger than the temperature determination value. When it is determined that the exhaust temperature Tex is larger than the temperature determination value (YES in S104), the process is transferred to S106.

In S106, the control device 200 executes the learning value reduction process. Specifically, the control device 200 sets a value obtained by subtracting a predetermined value from the immediately preceding learning value as a new learning value.

If it is determined that the learning condition is not satisfied (NO in S100), the process is transferred to S104. When it is determined that the exhaust temperature Tex is equal to or lower than the temperature determination value (NO in S104), this process is terminated.

The operation of the control device 200 based on the above structure and the flowchart will be described with reference to FIG. FIG. 5 is a diagram for explaining the operation of the control device 200. The upper graph of FIG. 5 is a timing chart showing changes in the temperature of the exhaust gas.

The vertical axis of the upper graph of FIG. 5 indicates the exhaust temperature, and the horizontal axis of the upper graph of FIG. 5 indicates time. The solid line in the upper graph of FIG. 5 shows the change in the exhaust temperature Tex, which is the temperature of the exhaust gas flowing into the PM removal filter 56b. The broken line in the upper graph of FIG. 5 shows the change in the temperature of the exhaust gas flowing out from the PM removal filter 56b. The alternate long and short dash line in the upper graph of FIG. 5 indicates the temperature of the exhaust gas flowing into the oxidation catalyst 56a. Further, the lower graph of FIG. 5 is a timing chart showing changes in the learning value. The vertical axis of the lower graph of FIG. 5 indicates the learning value, and the horizontal axis of the lower graph of FIG. 5 indicates time.

For example, when the accumulated amount of PM is smaller than the regeneration determination value (that is, when the regeneration control is not executed) and the learning value is Ca (> 1.0), the fuel filter 212 is used by the user. It is assumed that it is replaced by.

In this case, the change in the exhaust gas temperature up to the time t (4) is the same as the change in the exhaust gas temperature up to the time t (1) in FIG. Therefore, the detailed description will not be repeated.

At time t (4), when the exhaust temperature Tex exceeds the stop determination value Ta as shown by the solid line in FIG. 5, the addition of fuel from the fuel addition device 56c is stopped. Therefore, the generation of reaction heat is suppressed in the oxidation catalyst 56a, so that the exhaust temperature Tex decreases. After that, at time t (5), when the exhaust temperature Tex is lower than the restart determination value and other restart conditions are satisfied, fuel addition is restarted from the fuel addition device 56c. When the addition of the fuel is restarted, the actual addition amount becomes too much more than the amount required to raise the exhaust temperature Tex to the target temperature, and the exhaust temperature Tex rises beyond the target temperature. When the exhaust temperature Tex exceeds the stop determination value Ta, the addition of fuel from the fuel addition device 56c is stopped. In this way, the resumption and stop of fuel addition are repeated several times.

In a state where resumption and stop of fuel addition are repeated, the exhaust temperature Tex does not become a constant state as shown in FIG. 5, so that the learning condition is not satisfied (NO in S100). However, when the exhaust temperature Tex exceeds the temperature determination value (= stop determination value Ta) at the time t (4) (YES in S104), the learning value reduction process is executed (S106). As shown by the solid line in the lower graph, a value whose learning value is lower than the immediately preceding learning value Ca by a predetermined value is set as a new learning value. After that, every time it is determined that the exhaust temperature Tex exceeds the temperature determination value, the learning value reduction process is executed, so that the learning value is gradually decreased.

At time t (6), when the learning value is reduced to Cb, the exhaust temperature Tex changes at a temperature lower than the temperature determination value. If the learning condition is satisfied at time t (7) by continuing the constant state of the exhaust temperature Tex (YES in S100), the learning process is executed (S102).

The learning value Cc calculated by the learning process is set as a new learning value, and the command addition amount is corrected according to the set learning value. As a result, the exhaust temperature reaches the target temperature.

As described above, according to the exhaust treatment device according to the present embodiment, the exhaust temperature Tex is caused by the fact that the parts provided in the fuel system are replaced with new ones, but the learning value is not reset to the initial value. When the temperature exceeds the temperature determination value, the learning value is reduced regardless of whether or not the learning condition is satisfied, so that the final command addition amount to the fuel addition device 56c can be reduced. As a result, the exhaust temperature Tex can be controlled to a desired value in the regeneration control. After lowering the exhaust temperature Tex, at least the state in which the exhaust temperature Tex is constant continues for a predetermined time, and as a result, the learning value is calculated when the learning condition is satisfied. Therefore, an appropriate learning value for bringing the exhaust temperature Tex to the target temperature can be calculated. Therefore, even if the learning value is not reset when the fuel system parts are replaced, the temperature of the exhaust gas flowing into the PM removal filter is controlled with high accuracy when the regeneration control of the PM removal filter is executed after the parts replacement. It is possible to provide an exhaust treatment device that can be used.

Further, by the learning value reduction process, the command addition amount can be gradually reduced by setting a value obtained by subtracting a predetermined value from the immediately preceding learning value as a new learning value. Therefore, it is possible to suppress an unnecessarily decrease in the amount of increase in the exhaust temperature due to the addition of fuel.

Hereinafter, a modified example will be described.
In the above-described embodiment, in the learning value reduction process, a value obtained by subtracting a predetermined value from the immediately preceding learning value is set as a new learning value. For example, the initial value of the learning value (=) 1.0) may be set as a new learning value.

Further, in the above-described embodiment, the learning value reduction process is executed when the exhaust temperature Tex exceeds the temperature determination value. However, for example, the learning value is executed when the exhaust temperature Tex exceeds the temperature determination value a plurality of times. The reduction process may be performed.

Hereinafter, the control process to which these modified examples are applied will be described with reference to FIG. FIG. 6 is a flowchart showing a control process executed by the control device 200 in the modified example. The processing of S100 and S102 in the flowchart of FIG. 6 is the same as the processing of S100 and S102 of the flowchart of FIG. Therefore, the detailed explanation will not be repeated.

In S200, the control device 200 determines whether or not temperature hunting has occurred. That is, for example, the control device 200 increases the count value of the counter by one each time the exhaust temperature Tex exceeds the temperature determination value, and from the time when the temperature determination value is first exceeded until a predetermined time elapses. When the count value (the number of times the temperature judgment value is exceeded) exceeds the threshold value, it is determined that temperature hunting has occurred. The control device 200 resets the count value to the initial value (= 0) after the elapse of a predetermined time. If it is determined that temperature hunting has occurred (YES in S200), the process is transferred to S202.

In S202, the control device 200 resets the learning value (correction coefficient) to the initial value (= 1.0).

In this way, the exhaust temperature Tex can be quickly lowered by resetting the learning value to the initial value. Further, since the learning value is reset to the initial value when the temperature hunting occurs, it is possible to prevent the learning value from being unnecessarily reduced when the exhaust temperature Tex suddenly changes.

Further, in the above-described embodiment, the command addition amount is corrected by multiplying the command addition amount by the learning value as the correction coefficient. However, for example, the command addition is performed by adding the learning value to the command addition amount. The amount may be corrected.

Further, in the above-described embodiment, the stop determination value and the temperature determination value have been described as having the same value, but different values may be used. For example, the temperature determination value may be lower than the stop determination value. By doing so, the learning value can be reduced before the exhaust temperature Tex reaches the stop determination value, so that the exhaust temperature Tex can be lowered at an early stage.

Further, in the above-described embodiment, the learning value is reduced when the exhaust temperature Tex exceeds the temperature determination value, but when the temperature of the PM removal filter 56b exceeds the temperature determination value instead of the exhaust temperature Tex, The learning value may be reduced. The temperature of the PM removal filter 56b may be estimated based on, for example, the exhaust temperature Tex and the temperature detected by the temperature sensor provided downstream of the PM removal filter 56b, or around the PM removal filter 56b. It may be estimated based on temperature or detected directly using a temperature sensor.

The above-mentioned modification may be carried out in whole or in combination.
It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 engine, 10 engine body, 12 cylinders, 14 common rails, 16 injectors, 20 air cleaners, 22, 24, 27 intake pipes, 26 intercoolers, 28 intake manifolds, 30 superchargers, 32 compressors, 34 compressor wheels, 36 turbines, 38 turbine wheel, 42 connecting shaft, 50 exhaust manifold, 52, 54, 58 exhaust pipe, 56 exhaust treatment device, 56a oxidation catalyst, 56b PM removal filter, 56c fuel addition device, 56d exhaust temperature sensor, 60,70 EGR device, 62,72 EGR valve, 64,74 EGR cooler, 66,76 EGR passage, 200 controller, 202 engine speed sensor, 208 airflow meter, 210 fuel pump, 212 fuel filter, 214 fuel tank.

Claims (3)

The oxidation catalyst provided in the exhaust passage of the engine and
A fuel addition device provided in the exhaust passage at a position upstream of the oxidation catalyst and adding fuel into the exhaust passage.
A filter provided in the exhaust passage at a position downstream of the oxidation catalyst and collecting particulate matter contained in the exhaust gas flowing through the exhaust passage.
When the accumulated amount of the particulate matter collected in the filter is larger than the accumulated amount determination value, the said is based on the command addition amount for setting the exhaust temperature, which is the temperature of the exhaust flowing into the filter, to the target temperature. Equipped with a control device to control the fuel addition device
The control device is
When a predetermined learning condition is satisfied, a learning value for correcting the command addition amount so that the exhaust temperature approaches the target temperature is calculated.
When the exhaust temperature exceeds the temperature determination value higher than the target temperature, the learning value is reduced regardless of whether or not the learning condition is satisfied .
The control device is an exhaust treatment device that reduces the immediately preceding learning value to an initial value when the exhaust temperature exceeds the temperature determination value . The exhaust treatment device according to claim 1, wherein the control device reduces the learning value when the exhaust temperature exceeds the temperature determination value a plurality of times. The exhaust treatment device according to claim 1 or 2, wherein the learning condition includes at least a condition that the state in which the exhaust temperature is constant continues for a predetermined time.

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