Exhaust gas purification device and method for controlling the exhaust gas purification device

Abstract

Including an exhaust gas purification device: a filter device (18), wherein the filter device (18) comprises: a particulate filter (19) arranged in an exhaust pipe (16) of an internal combustion engine (10), wherein the filter (19) is made of an electrically conductive material; and two electrodes (21, 24) which are fixed to an outer surface of the filter (19); a resistance value reference unit (25, 27) which is configured to obtain an electrical resistance value of the filter (19) between the two electrodes (21, 24) on the outer surface of the filter (19) as an electrical filter resistance value (Rf); an energy supply unit (12, 14, 17, 23) configured to supply energy which is converted into heat which is absorbed by the filter (19); and a controller (27) configured to perform a filter regeneration process and a soot combustion process, wherein the filter regeneration process eliminates soot that has accumulated in the filter (19) using the energy supplied by the energy supply unit (12, 14, 17, 23), wherein the soot combustion process eliminates soot that has accumulated in a gap section between the filter (19) and the exhaust pipe (16) using the energy supplied by the energy supply unit (12, 14, 17, 23), wherein a total amount of energy supplied by the energy supply unit (12, 14, 17, 23) during the filter regeneration process is greater than a total amount of energy supplied by the energy supply unit (12, 14, 17, 23) during the soot combustion process, the controller (27) is configured to execute the filter regeneration process when the electrical filter resistance value (Rf) obtained from the resistance value reference unit (25, 27) is less than a predetermined first setpoint (R2), and to execute the soot combustion process when the electrical filter resistance value (Rf) is greater than or equal to the first setpoint (R2) and less than a second setpoint (R3) that is preset to be greater than the first setpoint (R2), and the controller (27) is further configured to calculate an electrical resistance value between the filter (19) and the exhaust pipe (16) as an insulation resistance value (Ri) and to carry out the soot combustion process even if the insulation resistance value (Ri) is smaller than a predetermined third value (R1).

Description

Background 1. Area

[0001] The present application relates to an exhaust gas purification device comprising a filter device that traps particles in the exhaust gas of an internal combustion engine, and to a method for controlling an exhaust gas purification device. 2. Description of the state of the art

[0002] Japanese patent application JP 2018-053782A discloses a known exhaust gas purification device for an internal combustion engine. The exhaust gas purification device disclosed in this document comprises an electrically heated catalyst device. The electrically heated catalyst device includes a catalytic support and two electrodes. The catalytic support is formed in an exhaust pipe and consists of an electrically conductive material. The two electrodes are fixed to the outer surface of the catalytic support. Based on the electrical resistance value between the electrodes, the exhaust gas purification device of this document determines the amount of soot that has accumulated in a gap section between the catalytic support and the exhaust pipe. If the determined amount of accumulated soot exceeds a certain threshold, the exhaust gas purification device performs a soot combustion process.The soot combustion process heats the catalytic support to the temperature required to burn soot and eliminates the soot that has accumulated in the gap between the catalytic support and the exhaust pipe.

[0003] Some exhaust gas purification systems include a filter device that traps particles in the exhaust gas. This filter device comprises a particulate filter located in the exhaust pipe. The size of the particles in the soot contained in the exhaust gas is in the micrometer range. The filter traps soot, which is larger than particles.

[0004] When a large amount of soot accumulates in the filter, its particle capture efficiency decreases. Therefore, before this reduction in particle capture efficiency occurs, the exhaust aftertreatment system, which includes the filter, performs a filter regeneration process to eliminate the accumulated soot. This system also performs a soot combustion process to eliminate the soot that adheres to the gap between the filter and the exhaust pipe.

[0005] Furthermore, according to JP 2002-021537A, the electrical properties (electrical resistance or electrostatic capacitance between filter ends) of a conductive filter inserted into the exhaust port of a machine are measured, and a capture quantity closely related to the electrical properties is calculated with reference to a characteristic curve. Based on the calculated captured quantity, it is determined whether a filter regeneration process is required; and if so, the particles collected on the filter are burned off by an electric heater or burner to regenerate the filter.

[0006] DE 11 2012 007 041 T5 discloses a vehicle and a vehicle control method, wherein an ECU executes a program with the following steps: Determining whether an insulation resistance is less than a threshold value; if the insulation resistance is less than the threshold value, Determining whether there is an electrical leakage current between the vehicle body and an electrical heat catalyst, and whether there is a possibility that there is an electrical leakage current at a location other than a location between the vehicle body and the electrical heat catalyst; and if there is an electrical leakage current between the vehicle body and the electrical heat catalyst, Performing a heating control.

[0007] DE 10 2004 007 039 A1 discloses a device and a method for determining the soot load of a particle filter designed as a molded body for cleaning combustion engine exhaust gas, comprising a measuring arrangement with a pair of electrodes, one with a first electrode and one with a second electrode. A partial volume region is arranged between the first and second electrodes, and the electrical impedance acting between the first and second electrodes, or a related characteristic parameter, can be detected by the measuring arrangement. The method provides that the electrical impedance acting between the first and second electrodes, or a related characteristic parameter, is detected, and the soot load of the particle filter is determined from the impedance or the characteristic parameter.

[0008] Further relevant state of the art is disclosed in WO 93 / 13 303 A1. Summary

[0009] The present invention provides an exhaust gas purification device capable of efficiently performing a filter regeneration process for a filter device and a soot combustion process.

[0010] This summary serves to introduce a selection of concepts in simplified form, which are described in more detail below. This summary is not intended to identify the key or essential features of the subject matter of the application, nor should it be used as an aid in determining the scope of protection of the subject matter of the application.

[0011] The aforementioned problems and the resulting task are solved by the subject matter of claims 1 and 5. Advantageous embodiments of the invention are the subject matter of the dependent claims that follow.

[0012] A first explanatory aspect of the present disclosure establishes an exhaust gas purification device comprising a filter device. The filter device comprises: a particulate filter arranged in an exhaust pipe of an internal combustion engine, the filter being made of an electrically conductive material; and two electrodes fixed to an outer surface of the filter. The exhaust gas purification device also comprises a resistance reference unit configured to obtain an electrical resistance value between the two electrodes.to obtain; an energy supply unit configured to supply energy that is converted into heat absorbed by the filter; and a controller configured to perform a filter regeneration process and a soot combustion process, wherein the filter regeneration process eliminates soot that has accumulated in the filter using the energy supplied by the energy supply unit, and wherein the soot combustion process eliminates soot that has accumulated in a gap section between the filter and the exhaust pipe using the energy supplied by the energy supply unit. The total amount of energy supplied by the energy supply unit during the filter regeneration process is greater than the total amount of energy supplied by the energy supply unit during the soot combustion process.The controller is configured to execute the filter regeneration process when the electrical resistance value, referenced by the resistance value reference unit, is less than a predetermined first setpoint, and executes the soot combustion process when the electrical resistance value is greater than or equal to the first setpoint and less than a second setpoint, which is preset to be greater than the first setpoint.

[0013] A second explanatory aspect of the present disclosure provides a method for controlling an exhaust gas purification device comprising a filter device. The filter device comprises: a particulate filter arranged in an exhaust pipe of an internal combustion engine, the filter being made of an electrically conductive material; and two electrodes fixed to an outer surface of the filter. The exhaust gas purification device also comprises: a resistance reference unit configured to obtain an electrical resistance value between the two electrodes.to obtain; an energy supply unit configured to supply energy that is converted into heat absorbed by the filter; and a controller configured to perform a filter regeneration process and a soot combustion process, wherein the filter regeneration process eliminates soot that has accumulated in the filter using the energy supplied by the energy supply unit, and wherein the soot combustion process eliminates soot that has accumulated in a gap section between the filter and the exhaust pipe using the energy supplied by the energy supply unit. The total amount of energy supplied by the energy supply unit during the filter regeneration process is greater than the total amount of energy supplied by the energy supply unit during the soot combustion process.The procedure includes executing the filter regeneration process by the controller when the electrical resistance value, referenced by the resistance value reference unit, is less than a predetermined first setpoint, and executing the soot combustion process when the electrical resistance value is greater than or equal to the first setpoint and less than a second setpoint, which is preset to be greater than the first setpoint.

[0014] Other features and aspects will become apparent from the following detailed description, the drawing, and the claims. Brief description of the drawing Fig. Figure 1 is a schematic representation showing the configuration of an exhaust gas purification device according to one embodiment. Fig. Figure 2 is a flowchart that represents a filter maintenance control sequence performed by the exhaust gas purification device controller. Fig. Figure 3 is a time-lapse diagram showing the relationship between the soot combustion process and the filter regeneration process, which are carried out by the exhaust gas cleaning device, and the times at which the soot combustion process and the filter regeneration process are carried out, in which area (a) shows changes in a gap deposit amount, area (b) shows changes in an internal deposit amount, and area (c) shows changes with respect to the filter resistance value.

[0015] In the drawing and the detailed description, the same reference symbols refer to the same elements. The drawing may not be to scale, and the relative size, proportions, and representation of elements in the drawing may be enlarged for clarity, illustration, and simplicity. Detailed description

[0016] This description provides a comprehensive understanding of the described methods, devices, and / or systems. Variations and equivalents of the described methods, devices, and / or systems are apparent to a person skilled in the art. Sequences of processes are exemplary and may be modified in a manner apparent to a person skilled in the art, with the exception of processes that must necessarily occur in a specific order. Descriptions of functions and designs that are generally known to a person skilled in the art may have been omitted.

[0017] Exemplary embodiments can be of various kinds and are not limited to the examples described. However, the examples described are detailed and complete and represent the full scope of the invention to an average person skilled in the art.

[0018] An exhaust gas purification device according to one embodiment will now be described in detail with reference to the Fig. 1, Fig. 2 to Fig. 3 described. The exhaust gas purification device of the present embodiment is used in an internal combustion engine 10 which is mounted in a vehicle.

[0019] As in Fig. As shown in Figure 1, the internal combustion engine 10 comprises an intake port 11. The intake port 11 is equipped with an injector 12 that injects fuel into the intake air flowing through the intake port 11. The internal combustion engine 10 comprises a combustion chamber 13. The combustion chamber 13 is equipped with an ignition device 14 that ignites a fuel-air mixture drawn in through the intake port 11 by means of a spark discharge. The internal combustion engine 10 comprises an exhaust port 15, which includes an exhaust pipe 16. The exhaust pipe 16 is made of an electrically conductive material, such as stainless steel. The exhaust pipe 16 is electrically grounded to the vehicle body.

[0020] The exhaust gas purification device comprises a fuel injection valve 17. The fuel injection valve 17 is arranged in the exhaust pipe 16 to inject fuel into the exhaust gas flowing through the exhaust pipe 16. The exhaust gas purification device further comprises a filter device 18. The filter device 18 is arranged in the exhaust pipe 16 on the downstream side of the fuel injection valve 17.

[0021] The filter device 18 comprises a particulate filter 19, which is arranged in the exhaust pipe 16. The filter 19 is made of an electrically conductive, porous material, such as silicon carbide. The filter 19 carries a catalyst used for exhaust gas purification. The catalyst carried by the filter 19 is a three-way catalyst, made, for example, of platinum or palladium. The three-way catalyst oxidizes carbon monoxide and unburned hydrocarbons, which are unburned fuel components in the exhaust gas, and simultaneously reduces nitrogen oxides in the exhaust gas. The three-way catalyst also functions as an oxidation catalyst, accelerating the oxidation of unburned fuel in the exhaust gas.

[0022] The filter device 18 includes an insulating spacer 20, which is arranged between the filter 19 and the exhaust pipe 16. The filter 19 is insulated from the exhaust pipe 16 by the spacer 20. The filter device 18 includes two electrodes, namely a high-voltage side electrode 21 and a grounding side electrode 24. The electrodes 21 and 24 are fixed to the outer surface of the filter 19. The high-voltage side electrode 21 is connected to a high-voltage side terminal of a power supply 23 via a switch 22. The grounding side electrode 24 is electrically grounded to the vehicle body. The filter device 18 includes an electrical circuit through which a current flows between the electrodes 21 and 24. This electrical circuit includes an ammeter 25 and a voltmeter 26. The ammeter 25 detects a filter current value If, ​​which is the value of a current flowing through the filter 19 and then between the electrodes 21, 24.The voltage meter 26 detects an insulation potential difference Ei, which is the potential difference between the high-voltage side area of ​​the electrical circuit and the exhaust pipe 16.

[0023] The exhaust gas purification device further comprises a controller 27, which controls the exhaust gas purification device. The controller 27 includes a computational processing circuit that performs a calculation process to control the exhaust gas purification device, and a memory circuit that stores programs and data for control. The controller 27 receives the filter current value If, ​​which is measured by the ammeter 25, and the insulation potential difference Ei, which is measured by the voltmeter 26. The controller 27 also receives information regarding a load KL of the internal combustion engine 10 from an engine control unit 28, which is an electronic control unit that controls the internal combustion engine 10.During the control of the exhaust gas purification device by the controller 27, the received information is used by the computation processing circuit to execute the programs read from the memory circuit, and then the execution result is used to actuate the fuel addition valve 17 and the switch 22.

[0024] Filter 19 uses the integrated catalyst to clean unburned fuel components and nitrogen oxides in the exhaust gas. Immediately after the internal combustion engine 10 is started, the filter device 18 is unable to adequately clean the exhaust gas because the temperature of filter 19 is low and the catalyst is deactivated. When the internal combustion engine 10 operates at low load or without load, the exhaust gas temperature decreases. This can lower the temperature of filter 19, potentially preventing the catalyst from remaining active. To address this issue, the controller 27, immediately after the internal combustion engine 10 is started and during low-load or no-load operation, activates switch 22 to allow current to flow to filter 19.Responding to the current, filter 19 generates heat, which increases the temperature of filter 19 and activates the catalyst.

[0025] Filter 19 also captures soot containing particles in the exhaust gas. Filter 19 is capable of capturing a limited amount of soot. When the amount of soot deposited in filter 19 reaches a limit, the particle capture efficiency of filter 19 decreases. Additionally, the soot in the exhaust gas enters a gap between filter 19 and exhaust pipe 16 and is deposited there. If a large amount of soot has accumulated in the gap, current flows through the deposited soot from filter 19 to exhaust pipe 16. This can reduce the insulation resistance between filter 19 and exhaust pipe 16. To address this issue, controller 27 performs a filter regeneration process and a soot combustion process, if necessary. The filter regeneration process eliminates the soot deposited in filter 19.The soot combustion process eliminates the soot that has accumulated in the gap section between the filter 19 and the exhaust pipe 16.

[0026] Fig. Figure 2 shows a flowchart representing a filter maintenance control sequence executed by the controller 27 for the filter regeneration process and the soot combustion process. The controller 27 starts this process at the same time it supplies power to the filter 19, immediately after the internal combustion engine 10 is started, and during low-load and no-load operation of the internal combustion engine 10.

[0027] When this process is started, a filter resistance value Rf and an insulation resistance value Ri are first obtained in step S100. The filter resistance value Rf is the electrical resistance of the filter 19. The insulation resistance value Ri is the electrical resistance between the exhaust pipe 16 and the high-voltage side of the electrical circuit in the filter device 18. The filter resistance value Rf obtained in this step is calculated by the controller 27 based on the current value measured by the ammeter 25 and the output voltage of the power supply 23. The insulation resistance value Ri obtained in this step is calculated by the controller 27 based on the insulation potential difference Ei, measured by the voltmeter 26.In the present embodiment, the ammeter 25, which measures the filter current value If, ​​and the controller 27, which calculates the filter resistance value Rf based on the filter current value If, ​​correspond to a resistance value reference unit. The resistance value reference unit refers to the electrical resistance value between the two electrodes 21, 24 of the filter device 18.

[0028] In step S110, it is then determined whether the insulation resistance value Ri is less than a predetermined short-circuit test value R1. If the insulation resistance value Ri is less than the short-circuit test value R1 (step S110: YES), the process proceeds to step S300. If the insulation resistance value Ri is greater than or equal to the short-circuit test value R1 (step S110: NO), the process proceeds to step S120. The short-circuit test value R1 is set such that it is less than the lower limit of a tolerance range for the insulation resistance value Ri in a state of the filter device 18 immediately after its manufacture. The determination in step S110 is made to verify whether the insulation resistance between the filter 19 and the exhaust pipe 16 has decreased.

[0029] If no decrease in insulation resistance between filter 19 and exhaust pipe 16 is detected, the process proceeds to step S120. In step S120, it is determined whether the filter resistance value Rf is less than a predetermined regeneration setpoint R2. If the filter resistance value Rf is less than the regeneration setpoint R2 (step S120: YES), the process proceeds to step S200. If the filter resistance value Rf is greater than or equal to the regeneration setpoint R2 (step S120: NO), the process proceeds to step S130. The regeneration setpoint R2 is set to the filter resistance value Rf that will be used when the amount of soot deposited in filter 19 has increased to such a level that the filter regeneration process must be performed.

[0030] As the process progresses to step S130, it is determined in step S130 whether the filter resistance value Rf is less than a predetermined soot combustion target value R3. If the filter resistance value Rf is less than the soot combustion target value R3 (step S130: YES), the process proceeds to step S140. If the filter resistance value Rf is greater than or equal to the soot combustion target value R3 (step S130: NO), the current process is terminated. The soot combustion target value R3 is set to the filter resistance value Rf that is used when the amount of soot deposited in the gap between the filter 19 and the exhaust pipe 16 has increased to such a level that the soot combustion process must be carried out. As described below, the soot combustion target value R3 is greater than the regeneration target value R2.

[0031] If the filter resistance value Rf is less than the soot combustion determination value R3, the process proceeds to step S140. In step S140, it is determined whether the vehicle's driving distance since the previous soot combustion process is greater than a predetermined soot combustion suspension distance D1. The soot combustion suspension distance D1 is set to the minimum value of a hypothetical range of vehicle driving distances required for a state in which no soot has accumulated in the gap between the filter 19 and the exhaust pipe 16 to one in which soot has accumulated in the gap in an amount that necessitates the execution of the soot combustion process. If the driving distance is less than or equal to the soot combustion suspension distance D1 (step S140: NO), the current process is terminated.If the driving distance is greater than the soot combustion suspension distance D1 (step S140: YES), the process proceeds to step S300. In step S300, the soot combustion process is started.

[0032] If, in step S120, it is determined that the filter resistance value Rf is less than the regeneration target value R2, the process proceeds to step S200. In step S200, the progression to the next process is delayed until the load KL of the internal combustion engine 10 becomes greater than or equal to a predetermined regeneration execution target value KL1. When the load KL of the internal combustion engine 10 becomes greater than or equal to the regeneration execution target value KL1, the process proceeds to step S210. In step S210, the filter regeneration process is started.

[0033] When the filter regeneration process is initiated, the fuel injection valve 17 first begins adding fuel to the exhaust gas in step S210. The addition of fuel to the exhaust gas during the filter regeneration process is carried out by the fuel injection valve 17 intermittently re-injecting fuel. The fuel injected by the fuel injection valve 17 flows into the filter 19 along with the exhaust gas. The fuel is then oxidized by the action of the catalyst integrated into the filter 19. This oxidation generates heat, which increases the temperature of the filter 19.The fuel injection cycles through the fuel injection valve 17 in the filter regeneration process, and the amount of fuel injected through the fuel injection valve 17 in each cycle, are adjusted to maintain the temperature of the filter 19 at a level required for the combustion and cleaning of the soot deposited in the filter 19. Fuel injection continues until time T1, the time required for the complete elimination of soot deposited in the filter 19, has elapsed. When time T1 has expired from the start of fuel injection (step S220: YES), fuel injection is stopped in step S230 to complete the filter regeneration process. The current process then terminates.

[0034] If the process progresses to step S300 as a result of the determination in step S110 or step S140, the soot combustion process is initiated. When the soot combustion process is started, the fuel injection valve 17 begins adding fuel to the exhaust gas in step S300. In the same way as in the filter regeneration process, the addition of fuel to the exhaust gas in the soot combustion process is carried out by the fuel injection valve 17 intermittently repeating the fuel injection.The fuel injection cycles through the fuel injection valve 17 in the soot combustion process, and the amount of fuel injected through the fuel injection valve 17 in each cycle, are set such that the temperature of the filter 19 is maintained at a temperature required for the combustion and cleaning of the soot deposited in the gap between the filter 19 and the exhaust pipe 16. Fuel injection continues until time T2 elapses, the time required for the complete elimination of the soot deposited in the gap between the filter 19 and the exhaust pipe 16. When time T2 has elapsed since the start of fuel injection (step S310: YES), fuel injection is stopped in step S320 to terminate the soot combustion process. The current process then ends.As described below, the time T2 during which fuel is added in the soot combustion process is shorter than the time T1 during which fuel is added in the filter regeneration process. In other words, the execution time of the filter regeneration process is longer than the execution time of the soot combustion process.

[0035] The operation and advantages of the present embodiment will now be described.

[0036] When electrically conductive soot is deposited in the filter 19 and in the gap between the filter 19 and the exhaust pipe 16, the filter resistance Rf, which is the electrical resistance between the electrodes 21, 24 of the filter device 18, decreases. The filter 19 is designed to maintain its particle capture performance even if a relatively large amount of soot is deposited in the filter 19. However, the insulation resistance between the filter 19 and the exhaust pipe 16 decreases if only an electrically conductive path is formed by soot between the filter 19 and the exhaust pipe 16. Therefore, it is likely that the insulation resistance between the filter 19 and the exhaust pipe 16 will decrease even if a smaller amount of soot than the amount deposited in the filter 19, which would reduce the particle capture performance, is deposited in the gap between the filter 19 and the exhaust pipe 16.Accordingly, the filter resistance value Rf, which is measured when soot accumulates to such an extent in the gap between the filter 19 and the exhaust pipe 16 that the insulation resistance would decrease, is greater than the filter resistance value Rf measured when soot accumulates in the filter 19 to such an extent that the particle capture performance decreases. To resolve this issue, the controller 27 executes the filter regeneration process, which eliminates the soot accumulated in the filter 19, when the filter resistance value Rf is less than the regeneration setpoint R2. The controller 27 then executes the soot combustion process when the filter resistance value Rf is less than the soot combustion setpoint R3 and greater than or equal to the regeneration setpoint R2.

[0037] Even if a small amount of soot is deposited in the gap between the filter 19 and the exhaust pipe 16, the insulation resistance between the filter 19 and the exhaust gas 16 can decrease depending on where the deposit occurs. In the present embodiment, the insulation resistance value Ri between the filter 19 and the exhaust pipe 16 is determined based on the measured insulation potential difference Ei between the high-voltage side of the electrical circuit in the filter device 18 and the exhaust pipe 16. If a decrease in the insulation resistance value Ri is observed, the soot combustion process is carried out even if the filter resistance value Rf is greater than or equal to the soot combustion determination value R3.

[0038] In the exhaust gas purification device of the present embodiment, both the filter regeneration process and the soot combustion process are carried out by the fuel injection valve 17 intermittently injecting fuel into an exhaust gas. The fuel injected by the fuel injection valve 17 in these processes is converted into heat, which is absorbed by the filter 19 through oxidation within the filter 19. That is, the fuel injected into an exhaust gas by the fuel injection valve 17 in these processes corresponds to the energy that is converted into heat, which is absorbed by the filter 19. In the present embodiment, the fuel injection valve 17, which injects fuel into an exhaust gas, corresponds to an energy supply unit that provides energy.

[0039] The soot eliminated in the soot combustion process is deposited on the outer surface of the filter 19 and the inner wall surface of the exhaust pipe 16. In contrast, the soot eliminated in the filter regeneration process is deposited in complex pores within the filter 19, which is made of a porous material, and is more difficult to eliminate than the soot burned in the soot combustion process. Therefore, the filter regeneration process must maintain the filter 19 at a high temperature for a longer period than the soot combustion process. Consequently, the filter regeneration process consumes a larger quantity of fuel than the soot combustion process.In other words, the total amount of fuel (energy) supplied through the fuel supply valve 17 (energy supply unit) during the filter regeneration process is greater than the total amount of fuel (energy) supplied through the fuel supply valve 17 (energy supply unit) during the soot combustion process. In the present embodiment, the filter regeneration process, which consumes a larger amount of fuel than the soot combustion process, is carried out under the condition that the load KL of the internal combustion engine 10 is greater than or equal to the regeneration execution value KL1. As the load KL of the internal combustion engine 10 increases, the exhaust gas temperature and the temperature of the filter 19 increase accordingly.Therefore, a smaller amount of fuel is required to maintain the filter 19 at the temperature necessary for soot elimination when the filter regeneration process is carried out under a high load KL of the internal combustion engine 10. This reduces fuel consumption in the filter regeneration process in the present embodiment. Essentially, the soot combustion process consumes a small amount of fuel. Even if the soot combustion process is carried out under a high load KL, the fuel consumption is therefore only marginally reduced. To overcome this issue, in the present embodiment, the soot combustion process is carried out regardless of the load KL of the internal combustion engine 10. This makes it easy to perform the soot combustion process.

[0040] The manner in which the soot combustion process and the filter regeneration process are carried out in the exhaust gas purification device of the present embodiment is now described with reference to Fig. 3 described. Area (a) from Fig. Figure 3 shows changes in the amount of soot deposited in the gap between the filter 19 and the exhaust pipe 16. Area (b) from Fig. Figure 3 shows changes in the internal deposit amount, which is the amount of soot that has accumulated in filter 19. Area (c) from Fig. Figure 3 shows changes in the filter resistance value Rf. The horizontal axis is made up of Fig. Figure 3 represents the operating time of the internal combustion engine 10 at the start of operation. The amount of deposits in the crevices and the amount of deposits in the internal filter device 18 are 0 at the start of operation. Fig. Figure 3 also shows the changes in the amount of soot deposited in the gap and the amount of soot deposited in the internal combustion engine during the operating time of the internal combustion engine 10, while soot is deposited in the gap section between the filter 19 and the exhaust pipe 16 and in the filter 19 at constant speeds.

[0041] After the operation of the internal combustion engine 10 has started, the amount of crevice deposits and the amount of internal deposits increase, while the filter resistance value Rf gradually decreases. At this time t1 in Fig. 3. The soot combustion process is carried out, so that the amount of soot deposited becomes 0 when the filter resistance value Rf decreases to less than the soot combustion determination value R3. In the soot combustion process, the soot that has deposited in the filter 19 is eliminated to a certain extent. Therefore, the amount of internal deposited soot after the soot combustion process is less than before. Due to the elimination of soot, the filter resistance value Rf is also higher after the soot combustion process than before. However, the soot combustion process does not completely eliminate the soot deposited in the filter 19. Therefore, the amount of internal deposited soot does not become 0 after the soot combustion process, and the filter resistance value Rf becomes lower than the value obtained when the operation of the internal combustion engine 10 is started.

[0042] After the soot combustion process has been completed at time t1, the amount of crevice deposits and the amount of internal deposits begin to increase again. As these amounts increase, the filter resistance value Rf decreases. However, after the soot combustion process has been completed at time t1, the filter resistance value Rf is lower than the value obtained when the internal combustion engine 10 is started. At this time, the filter resistance value Rf becomes less than the soot combustion determination value R3 before the amount of crevice deposits changes to such an extent that the soot combustion process must be carried out. To overcome this problem, in the present embodiment, the execution of the next soot combustion process is suspended until the vehicle's driving distance since the execution of the previous soot combustion process exceeds the soot combustion suspension distance D1.This prevents the soot combustion process from being carried out unnecessarily frequently. In areas (a) to (c) from . Fig. 3. At time t2 and time t3, the soot combustion process is carried out in a state in which the filter resistance value Rf is less than the soot combustion determination value R3 and the vehicle's driving distance since the execution of the previous soot combustion process is greater than the soot combustion suspension distance D1. In the exhaust gas purification device of the present embodiment, the soot combustion process is carried out immediately at this time, regardless of the driving distance since the execution of the previous soot combustion process, when the current between the filter 19 and the exhaust pipe 16 is detected.

[0043] The amount of internal deposits obtained after the second soot combustion process at time t2 is greater than the amount obtained after the first soot combustion process at time t1. Similarly, the amount of internal deposits obtained after the third soot combustion process at time t3 is greater than the amount obtained after the second soot combustion process. Therefore, although the amount of internal deposits temporarily decreases with each soot combustion process, it changes in such a way that it exhibits a long-term increasing trend. Furthermore, although the filter resistance value Rf temporarily increases with each soot combustion process, it changes in such a way that it exhibits a long-term decreasing trend.At time t4, when the filter resistance value Rf decreases to less than the regeneration setpoint R2, the filter regeneration process is executed. After the filter regeneration process is complete, the internal deposit amount becomes 0. Furthermore, the filter regeneration process maintains the filter 19 at a higher temperature for a longer period than the soot combustion process. Accordingly, the gap deposit amount also becomes 0 after the filter regeneration process is complete.

[0044] The exhaust gas purification device of the present embodiment has the following advantages.

[0045] (1) The energy supplied by the fuel injection valve 17 is converted into heat absorbed by the filter 19. Thus, the energy supplied by the fuel injection valve 17 heats the filter 19. Furthermore, the heating of the filter 19 eliminates the soot deposited in the filter 19 and in the gap between the filter 19 and the exhaust pipe 16. With the energy supplied by the fuel injection valve 17, the exhaust aftertreatment device thus carries out both the filter regeneration process, which eliminates the soot deposited in the filter 19, and the soot combustion process, which eliminates the soot deposited in the gap between the filter 19 and the exhaust pipe 16. The soot deposited in the filter 19 is more difficult to remove than the soot deposited in the gap between the filter 19 and the exhaust pipe 16. Therefore, the filter regeneration process requires a greater amount of energy than the soot combustion process.

[0046] The filter regeneration process must be carried out before the amount of soot deposited in the filter 19 changes to such an extent that its particle capture performance decreases. The soot combustion process must be carried out before the amount of soot deposited in the gap between the filter 19 and the exhaust pipe 16 changes to such an extent that the insulation resistance between the filter 19 and the exhaust pipe 16 decreases. Since both the filter regeneration process and the soot combustion process consume energy, it is desirable to delay these processes until they are necessary.

[0047] When electrically conductive soot is deposited in the filter 19 and in the gap between the filter 19 and the exhaust pipe 16, the filter resistance between electrodes 21, 24 of the filter device 18 decreases. The insulation resistance between the filter 19 and the exhaust pipe 16 decreases if the soot deposited between the filter 19 and the exhaust pipe 16 merely forms an electrically conductive path. However, the particle capture performance of the filter 19 does not decrease until soot has been deposited over a large area within the filter 19. Accordingly, the electrical resistance between electrodes 21, 24 is lower when soot is deposited in the filter 19 in an amount that necessitates the filter regeneration process than when soot is deposited in the gap between the filter 19 and the exhaust pipe 16 in an amount that necessitates the soot combustion process.

[0048] In the exhaust gas purification device of the present embodiment, the controller 27 executes the filter regeneration process when the electrical resistance value is lower than the electrical resistance in the case where the soot combustion process is carried out. This allows the soot combustion process and the filter regeneration process to be carried out efficiently. In particular, when the filter resistance value Rf is less than the regeneration setpoint R2, the controller 27 executes the filter regeneration process, which eliminates the soot deposited in the filter 19.If the filter resistance value Rf is less than the soot combustion setpoint R3, which has been preset to be greater than and equal to the regeneration setpoint R2, the controller 27 executes the soot combustion process, which eliminates the soot that has accumulated in the gap between the filter 19 and the exhaust pipe 16. The soot combustion process and the filter regeneration process are executed at appropriate times using the filter resistance value Rf, which correlates with the amount of soot accumulated in the filter 19 and in the gap between the filter 19 and the exhaust pipe 16.

[0049] (2) The filter regeneration process adds fuel to the exhaust gas over a longer period of time than the soot combustion process. This prevents the soot combustion process from consuming fuel unnecessarily while the filter regeneration process is being carried out, so that the soot in the filter 19, which is more difficult to eliminate than the soot that has accumulated in the gap between the filter 19 and the exhaust pipe 16, is completely eliminated.

[0050] (3) The filter regeneration process is carried out under the condition that the load KL of the internal combustion engine 10 is greater than or equal to the regeneration execution determination value KL1. This reduces the fuel consumption in the filter regeneration process, which requires fuel injection over a longer period than the soot combustion process.

[0051] (4) The soot combustion process is carried out under the condition that the vehicle's driving distance since the execution of the previous soot combustion process is greater than the soot combustion suspension distance D1. That is, the minimum execution interval of the soot combustion process is set based on the vehicle's driving distance. This prevents the soot combustion process from being carried out unnecessarily due to a decrease in the filter resistance value Rf resulting from the progressive deposition of soot in the filter 19.

[0052] (5) If a decrease in the insulation resistance between the filter 19 and the exhaust pipe 16 is detected, the soot combustion process is carried out immediately at that time. In this way, the decrease in insulation resistance between the filter 19 and the exhaust pipe 16 is quickly eliminated after the decrease is detected.

[0053] The present embodiment can be modified as described below. The present embodiment and the following modifications can be combined as long as they remain technically compatible.

[0054] In the embodiment described above, the minimum execution interval of the soot combustion process is set based on the vehicle's driving distance. The minimum execution interval of the soot combustion process can be set based on another parameter that correlates with the amount of soot deposits, such as the running time of the internal combustion engine 10, an air intake quantity, or a fuel injection quantity. Alternatively, the soot combustion process can be carried out continuously without setting the minimum execution interval if the filter resistance value Rf is less than the soot combustion determination value R3.

[0055] In the embodiment described above, the soot combustion process is carried out when the filter resistance value Rf is less than the soot combustion determination value R3 and also when a decrease in the insulation resistance between the filter 19 and the exhaust pipe 16 is detected. If the exhaust gas cleaning device does not include a device for detecting the insulation resistance, the soot combustion process can be omitted in response to the detection of a decrease in insulation resistance.

[0056] In the embodiment described above, the filter regeneration process can be carried out under the condition that the load KL of the internal combustion engine 10 is greater than or equal to the regeneration execution determination value KL1. The soot combustion process can also be carried out under the condition that the load KL is greater than or equal to a fixed value.

[0057] The condition that the load KL of the internal combustion engine 10 is greater than or equal to the regeneration execution value KL1 can be excluded from the conditions for executing the filter regeneration process. That is, if the filter resistance value Rf is less than the regeneration execution value R2, the filter regeneration process can be executed regardless of the load KL of the internal combustion engine 10.

[0058] In the embodiment described above, the filter regeneration process and the soot combustion process can be carried out by injecting fuel into an exhaust gas through the fuel injection valve 17. Other methods can be used to carry out the filter regeneration process and the soot combustion process by heating the filter 19. For example, the filter 19 can be heated by continuing the fuel injection performed by the injector 12 with the spark discharge of the ignition device 14 stopped, while the vehicle is idling at a reduced speed, and by drawing the fuel injected by the injector 12 into the filter 19 in an unburned state. In this case, the fuel injected by the injector 12 serves as energy that is converted into heat, which is absorbed by the filter 19, and the injector 12 corresponds to the energy supply unit.Alternatively, the filter 19 can be heated by supplying it with current. In this case, the power supplied to the filter 19 serves as energy, which is converted into heat absorbed by the filter 19, and the electrical circuit of the filter device 18, which includes the power supply 23, corresponds to the energy supply unit. As another option, the filter 19 can be heated by delaying the time at which the ignition device 14 ignites a fuel-air mixture, thus reducing the efficiency of combustion of the fuel-air mixture in the combustion chamber 13 and increasing the exhaust gas temperature. In this case, due to the decrease in combustion efficiency, a required output power of the internal combustion engine 10 is achieved, and therefore the amount of fuel burned in the combustion chamber 13 must be increased.The increased fuel volume corresponds to the energy that is converted into heat absorbed by the filter 19. In this case, the internal combustion engine 10, which includes the ignition device 14 and the injector 12, corresponds to the energy supply unit. Furthermore, the filter regeneration process and the soot combustion process can be carried out by combining two or more of these methods for heating the filter 19.

[0059] In the embodiment described above, the filter device 18 is configured to clean unburned fuel components and nitrogen oxides, and to capture particles with the filter 19, which carries the three-way catalyst. If nitrogen oxides are not cleaned in the filter device 18, the catalyst carried by the filter 19 can be an oxidation catalyst that does not serve to reduce nitrogen oxides but only to accelerate the oxidation of unburned fuel. If the filter device 18 only captures particles and the heat generated by the oxidation of unburned fuel in the filter 19 is not used to heat the filter 19 in the filter regeneration process and the soot combustion process, a structure can be used in which the filter 19 does not carry a catalyst.

[0060] Various modifications regarding form and details can be made to the above examples without departing from the spirit and scope of the claims and their equivalents. The examples serve only for descriptive purposes and not for limitation. Descriptions of features in each example should be considered applicable to similar features or aspects in other examples. Suitable results can be obtained if sequences are carried out in a different order and / or if components in a described system, architecture, device, or circuit are combined differently and / or replaced or supplemented by other components or their equivalents. The scope of protection of the invention is not defined by the detailed description but by the claims and their equivalents.All modifications within the scope of protection of the invention and its equivalents are included in the application.

Claims

Exhaust gas purification device comprising: a filter device (18), wherein the filter device (18) comprises: a particulate filter (19) arranged in an exhaust pipe (16) of an internal combustion engine (10), the filter (19) being made of an electrically conductive material; and two electrodes (21, 24) fixed to an outer surface of the filter (19); a resistance value reference unit (25, 27) configured to obtain an electrical resistance value of the filter (19) between the two electrodes (21, 24) on the outer surface of the filter (19) as an electrical filter resistance value (Rf); an energy supply unit (12, 14, 17, 23) configured to supply energy which is converted into heat which is absorbed by the filter (19); and a controller (27) configured to perform a filter regeneration process and a soot combustion process, wherein the filter regeneration process removes soot,the soot deposited in the filter (19) is eliminated with the energy supplied by the energy supply unit (12, 14, 17, 23), wherein the soot combustion process eliminates soot that has deposited in a gap section between the filter (19) and the exhaust pipe (16) with the energy supplied by the energy supply unit (12, 14, 17, 23), wherein a total amount of energy supplied by the energy supply unit (12, 14, 17, 23) during the filter regeneration process is greater than a total amount of energy supplied by the energy supply unit (12, 14, 17, 23) during the soot combustion process, the controller (27) is configured to execute the filter regeneration process when the electrical filter resistance value (Rf) obtained from the resistance value reference unit (25, 27) is less than a predefined first determination value (R2), and to carry out the soot combustion process,if the electrical filter resistance value (Rf) is greater than or equal to the first setpoint (R2) and less than a second setpoint (R3) which is preset to be greater than the first setpoint (R2), and the controller (27) is further configured to calculate an electrical resistance value between the filter (19) and the exhaust pipe (16) as an insulation resistance value (Ri) and to carry out the soot combustion process even if the insulation resistance value (Ri) is less than a preset third setpoint (R1). Exhaust gas purification device according to claim 1, wherein the execution time of the filter regeneration process is longer than the execution time of the soot combustion process. Exhaust gas purification device according to claim 1 or 2, wherein the filter regeneration process is carried out under a condition that a load of the internal combustion engine (10) is greater than or equal to a predetermined value. Exhaust gas purification device according to one of claims 1 to 3, wherein the filter (19) carries an oxidation catalyst which accelerates the oxidation of unburned fuel in an exhaust gas, and the energy supply unit (12, 17) is configured to supply unburned fuel as energy, which is added to the exhaust gas before it flows into the filter (19). Method for controlling an exhaust gas purification device comprising a filter device (18), wherein the filter device (18) comprises: a particulate filter (19) arranged in an exhaust pipe (16) of an internal combustion engine (10), the filter being made of an electrically conductive material; and two electrodes (21, 24) fixed to an outer surface of the filter (19); the exhaust gas purification device comprises: a resistance value reference unit (25, 27) configured to obtain an electrical resistance value of the filter (19) between the two electrodes (21, 24) on the outer surface of the filter (19) as an electrical filter resistance value (Rf); an energy supply unit (12, 14, 17, 23) configured to supply energy which is converted into heat which is absorbed by the filter (19); and a controller (27) configured to perform a filter regeneration process and a soot combustion process.wherein the filter regeneration process eliminates soot deposited in the filter (19) using the energy supplied by the energy supply unit (12, 14, 17, 23), wherein the soot combustion process eliminates soot deposited in a gap section between the filter (19) and the exhaust pipe (16) using the energy supplied by the energy supply unit (12, 14, 17, 23), a total amount of energy supplied by the energy supply unit (12, 14, 17, 23) during the filter regeneration process is greater than a total amount of energy supplied by the energy supply unit (12, 14, 17, 23) during the soot combustion process, the method includes an execution of the filter regeneration process by the controller (27) when the electrical filter resistance value (Rf) provided by the resistance value reference unit (25, 27) is referred to, is smaller than a given first determination value (R2),and an execution of the soot combustion process when the electrical filter resistance value (Rf) is greater than or equal to the first setpoint (R2) and less than a second setpoint (R3) which is preset to be greater than the first setpoint (R2), and the controller (27) is further configured to calculate an electrical resistance value between the filter (19) and the exhaust pipe (16) as an insulation resistance value (Ri), and the method includes an execution of the soot combustion process by the controller (27) even when the insulation resistance value (Ri) is less than a preset third setpoint (R1).

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