JP7211192B2 - Exhaust purification device - Google Patents

Description

The present invention relates to an exhaust purification device for purifying exhaust gas discharged from an internal combustion engine.

Exhaust gas from an internal combustion engine, such as a gasoline engine mounted on a vehicle, contains particulate matter (PM) that causes air pollution. Fine particles are a general term for particulate matter such as carbon (soot) and ash derived from engine oil. For this reason, a vehicle equipped with a gasoline engine is equipped with an exhaust purification device for purifying exhaust gas (see Patent Document 1). An exhaust purification device removes particulates from the exhaust gas of a gasoline engine and releases clean gas from which the particulates have been removed into the atmosphere.

An exhaust purification device is configured with a filter (for example, a gasoline particulate filter) for purifying the exhaust, and the filter collects and removes particulates from the exhaust.

If the filter continues to collect particulates, the accumulated particulates may cause clogging of the filter. For this reason, the filter is appropriately regenerated to a state in which fine particles can be appropriately collected. During regeneration, for example, trapped particulates are burned and removed from the filter. By repeating such regeneration, the filter can be used continuously.

Therefore, in order to properly regenerate the filter in order to maintain its performance, it is necessary to accurately estimate the amount of fine particles accumulated in the filter. For example, if the filter is clogged by the accumulation of particulates, a difference in pressure will occur between the inlet and outlet of the exhaust gas to the filter. Specifically, the pressure on the inlet side is high, the pressure on the outlet side is low, and the differential pressure between the two increases as the amount of deposited fine particles increases. Therefore, it is possible to estimate the amount of deposited fine particles according to such a correspondence relationship with the differential pressure.

Japanese Unexamined Patent Application Publication No. 2012-2213

However, at the stage when the deposition amount of fine particles is small (initial stage of deposition), the differential pressure of the exhaust gas is small, and it is difficult to estimate the deposition amount based on the differential pressure. In addition, an estimation error in the deposition amount is likely to occur due to the manner in which the fine particles are deposited, such as unevenness. Therefore, it is required to estimate the deposition amount of fine particles in place of or in addition to the estimation based on the differential pressure.

An exhaust emission control device of the present invention includes an acceleration detection section, a driving condition detection section, a filter section, a temperature difference measurement section, a map storage section, and an accumulation amount estimation section. The acceleration detector detects acceleration of the vehicle. The driving condition detector detects the driving condition of the vehicle including the temperature of the internal combustion engine of the vehicle. The filter section is arranged in an exhaust passage through which exhaust gas from the internal combustion engine flows, and collects particulates contained in the exhaust gas. The temperature difference measuring section measures the temperature difference between the exhaust gas upstream and downstream of the filter section in the exhaust passage. The map storage unit stores a map showing the correspondence relationship between the amount of accumulated particulate matter collected by the filter unit and the difference in exhaust gas temperature between upstream and downstream of the filter unit according to acceleration of the vehicle. The accumulation amount estimating unit determines that the temperature of the internal combustion engine is equal to or higher than a predetermined temperature and that the acceleration of the vehicle is equal to or lower than a predetermined acceleration and that the vehicle is in a steady operating state that continues for a predetermined time or longer. A map is queried according to the acceleration, and the particulate deposition amount is estimated based on the exhaust temperature difference.

The deposition amount estimator estimates the deposition amount of particulates based on a comparison between the temperature difference of the exhaust gas and the temperature difference of the exhaust gas when particulates are not deposited on the filter portion in a steady operation state.

Steady driving conditions further require that the vehicle be stationary.

It further includes a regeneration control unit that removes particulates from the filter unit and regenerates the filter unit based on a comparison between the particulate deposit amount estimated by the deposit amount estimation unit and a predetermined threshold value.

According to the exhaust emission control device of the present invention, it is possible to estimate the deposition amount of fine particles instead of or in addition to the estimation based on the differential pressure.

1 is a block diagram schematically showing the schematic configuration of an exhaust purification device according to one embodiment of the present invention; FIG. FIG. 4 is a diagram showing an example of a map showing the relationship between the amount of fine particles deposited and the temperature difference of the exhaust gas (difference between the inlet temperature and the outlet temperature) during running at a constant speed in the exhaust purification system according to the embodiment of the present invention. FIG. 4 is a diagram showing an example of temporal changes in vehicle speed, exhaust inlet and outlet temperatures, and exhaust temperature difference, which are prerequisites for filter regeneration control in the exhaust purification system according to the embodiment of the present invention. FIG. 2 is a flow chart showing the flow of filter regeneration control in the exhaust purification system according to the embodiment of the present invention. FIG. 2 is a flowchart showing the flow of filter regeneration processing in the exhaust purification system according to one embodiment of the present invention.

1 to 5, an exhaust purification device according to an embodiment of the present invention will be described below. The exhaust purification device of this embodiment is a device for purifying exhaust gas from an internal combustion engine. The internal combustion engine is, for example, various engines mounted on a vehicle, and a gasoline engine is applied in this embodiment. However, it may be a diesel engine or an engine mounted on a hybrid vehicle. The vehicle may be a passenger car for private use or a commercial vehicle such as a truck or a bus, and the use and type of vehicle are not particularly limited. Moreover, it may be either a right-hand drive vehicle or a left-hand drive vehicle.

FIG. 1 is a block diagram showing a schematic configuration of an exhaust purification system 1 of this embodiment. As shown in FIG. 1 , the exhaust purification device 1 is configured to purify the exhaust discharged from the combustion chamber 21 of the engine 2 .

Intake air is taken into the combustion chamber 21 of the engine 2 from the intake passage 3 by opening the intake valve 22 . The amount of intake air to the combustion chamber 21 is adjusted by opening and closing an intake throttle valve 23 . Next, fuel (gasoline) is injected from the injector 24 toward the combustion chamber 21 into the heated and compressed intake air. The spark plug 25 is then ignited and the mixture containing air and fuel is combusted in the combustion chamber 21 . Combustion of the air-fuel mixture causes the piston 26 to reciprocate within the combustion chamber 21, and this energy is converted into rotational motion of a crankshaft 27 connected to the piston 26 and output. The air-fuel mixture (exhaust gas) after combustion is discharged from the combustion chamber 21 through the exhaust passage 4 by opening the exhaust valve 28, purified by the exhaust purification device 1, and then released into the atmosphere. In this embodiment, the engine 2 is a gasoline direct injection type, but it may be a port injection type or a diesel engine.

The engine 2 has an exhaust circulation passage 5 that branches from the exhaust passage 4 and circulates the exhaust to the combustion chamber 21 . The circulating air passes through a circulating air cooler and a turbocharger (both of which are not shown) provided in the exhaust circulation path 5 and is introduced to the most downstream side of the intake passage 3 by opening and closing the circulating air valve 6 .

The exhaust purification device 1 includes a catalyst section 11 , a filter section 12 , a temperature difference measurement section 13 and a pressure measurement section 14 . The catalyst portion 11 and the filter portion 12 are substantially cylindrical structures having therein ventilation passages 11 a and 12 a through which exhaust gas flows. constitute a part. In this embodiment, the catalyst part 11 and the filter part 12 are separated, but they may be integrated. In either case, the catalyst section 11 may be arranged on the upstream side of the flow of the exhaust gas, and the filter section 12 may be arranged on the downstream side, but the arrangement may be reversed.

The catalyst unit 11 is arranged in the exhaust passage 4, and oxidizes and removes hydrocarbons and carbon monoxide contained in the exhaust gas by the catalyst 11c, and reduces nitrogen monoxide to generate nitrogen. In addition, the catalyst unit 11 oxidizes and removes fuel (gasoline) that has not been burned in the combustion chamber 21, unburned engine oil, and the like.

The filter unit 12 is arranged in the exhaust passage 4, and collects and removes particulates contained in the exhaust discharged from the combustion chamber 21 with a filter (for example, a gasoline particulate filter) 12f to purify the exhaust. Particulate Matter (PM) is a general term for particulate matter, but in the present embodiment, it includes carbon (soot), ash derived from engine oil, etc., and is a substance that is collected and deposited on the filter 12f. and Soot is combustible particles and ash is non-combustible particles. Although the configuration of the filter 12f is not particularly limited, it can be configured as a wall-flow filter made of porous ceramic made of silicon carbide, cordierite, or the like, for example. Exhaust gas that has passed through the filter 12f is freed of particulates and flows out of the exhaust purification device 1 in a purified state. However, since the collected fine particles accumulate on the filter 12f, the filter 12f is gradually clogged. For this reason, the accumulated particulates, specifically soot, must be appropriately burned to remove them from the filter 12f, and the filter 12f must be regenerated to a state in which particulates can be appropriately collected.

The temperature difference measurement unit 13 measures the temperature difference between the exhaust gas upstream and downstream of the filter unit 12 in the exhaust passage 4 . In this embodiment, the temperature difference measuring section 13 has two temperature sensors 13a and 13b. The first temperature sensor 13 a measures the temperature of the exhaust gas upstream of the filter portion 12 in the exhaust passage 4 . As an example, the first temperature sensor 13 a is arranged near the inlet 12 i of the filter portion 12 in the exhaust passage 4 . On the other hand, the second temperature sensor 13b measures the temperature of the exhaust downstream of the filter section 12 in the exhaust passage 4. As shown in FIG. As an example, the second temperature sensor 13b is arranged near the outlet 12o of the filter portion 12 in the exhaust passage 4 . The inlet 12 i is an inlet for exhaust gas from the exhaust passage 4 to the filter portion 12 , and the outlet 12 o is an outlet for exhaust gas from the filter portion 12 to the exhaust passage 4 . The exhaust that has flowed into the filter portion 12 from the inlet 12i passes through the filter 12f and flows out to the exhaust passage 4 from the outlet 12o. Hereinafter, the exhaust temperature measured by the first temperature sensor 13a is referred to as the inlet temperature, and the exhaust temperature measured by the second temperature sensor 13b is referred to as the outlet temperature. The temperature difference measuring unit 13 measures the difference between the inlet temperature and the outlet temperature, that is, the difference between the upstream exhaust temperature and the downstream exhaust temperature of the filter unit 12, based on the respective exhaust temperatures measured by the two temperature sensors 13a and 13b. to detect The inlet temperature, the outlet temperature, and the temperature difference data detected by the temperature difference measurement unit 13 are sent to the control unit 7 to be described later via wire or radio.

The pressure measuring unit 14 measures the pressure of exhaust gas flowing through the exhaust passage 4 . In this embodiment, the pressure measuring section 14 has two pressure sensors 14a and 14b. The first pressure sensor 14 a measures the pressure of the exhaust gas upstream of the filter portion 12 in the exhaust passage 4 . As an example, the first pressure sensor 14 a is arranged near the inlet 12 i of the filter portion 12 in the exhaust passage 4 . On the other hand, the second pressure sensor 14b measures the exhaust pressure downstream of the filter portion 12 in the exhaust passage 4. As shown in FIG. As an example, the second pressure sensor 14b is arranged near the outlet 12o of the filter portion 12 in the exhaust passage 4 . The second pressure sensor 14 b is arranged near the outlet 12 o of the filter portion 12 in the exhaust passage 4 . The pressure measurement unit 14 detects the difference between the upstream exhaust pressure and the downstream exhaust pressure of the filter unit 12 based on the respective exhaust pressures measured by the two pressure sensors 14a and 14b. Data on the respective exhaust pressures measured by the pressure sensors 14a and 14b and the pressure difference between them (differential pressure) are sent to the control unit 7, which will be described later, via wire or radio.

The exhaust gas purification device 1 includes a control unit 7 that controls purification of exhaust gas. The control unit 7 includes a CPU, a memory, a storage device, an input/output circuit, a timer, and the like. For example, the control unit 7 reads various data related to control through an input/output circuit, and uses a program read from a storage device to a memory to perform arithmetic processing with a CPU. Based on the processing result, the control unit 7 performs regeneration control of the filter 12f. The control unit 7 may be configured as a vehicle ECU (Electronic Control Unit), or may be configured independently of the vehicle ECU.

As shown in FIG. 1, the control unit 7 includes a detection unit 71 (an acceleration detection unit 71a and a running condition detection unit 71b), a map storage unit 72, an accumulation amount estimation unit 73, a regeneration control unit, and a regeneration control unit 71 (an acceleration detection unit 71a and a driving condition detection unit 71b). A portion 74 is provided.

The detection unit 71 detects the running state of the vehicle that contributes to the regeneration of the filter 12f in purifying exhaust gas, and acquires various kinds of information (detection data). The vehicle is the own vehicle on which the exhaust emission control device 1 is mounted. The detection unit 71 appropriately provides detection data to the accumulation amount estimation unit 73 and the regeneration control unit 74 . The detected data includes vehicle acceleration and engine 2 temperature. Therefore, the detection unit 71 includes an acceleration detection unit 71a and a running condition detection unit 71b. The acceleration detector 71a has, for example, an acceleration sensor and detects the acceleration of the vehicle. The running condition detection unit 71b has various sensors for detecting, for example, the temperature of the cooling water of the engine 2 and the temperature of the engine oil, and detects the running condition of the vehicle including the temperature of the engine 2 .

The map storage unit 72 stores and manages a map 72m used when estimating the deposition amount of fine particles deposited on the filter unit 12 . The map 72m shows the relationship between the amount of particulate matter deposited and the temperature difference of the exhaust gas (the difference between the inlet temperature and the outlet temperature) in accordance with the acceleration of the vehicle. The record indicating the relationship between the deposition amount of fine particles and the exhaust temperature difference is appropriately updated (added, changed, or deleted), and the map 72m is always maintained with the latest information.

FIG. 2 shows an example of the map 72m. In FIG. 2, L21, L22, and L23 respectively indicate the corresponding relationship between the deposition amount of fine particles and the temperature difference of the exhaust gas. L21 is the correspondence relationship when the vehicle is in the idling state, L22 is the correspondence relationship when the vehicle is running at a low speed with a predetermined acceleration or less, and L23 is a correspondence relationship when the vehicle is running at a high speed with the predetermined acceleration or less. The idle state is a state in which the warm-up operation is completed and the temperature of the engine 2 is equal to or higher than a predetermined temperature and the vehicle is stopped. The predetermined temperature (hereinafter referred to as the reference temperature) is a temperature at which the engine 2 can be considered to have warmed up, and is set as the temperature of the cooling water of the engine 2, for example. If it is the value of the cooling water temperature of the engine 2, the reference temperature is about 60.degree. Alternatively, the temperature of the engine 2 may be measured by the temperature of the engine oil, in which case the reference temperature is set as the value of the engine oil temperature. The predetermined acceleration (hereinafter referred to as reference acceleration) is, for example, within a range of approximately 0.02 m/s ² to 0.07 m/s ² , and an example is 0.05 m/s ² . As shown in FIG. 2, the exhaust temperature difference increases as the amount of deposited fine particles decreases, decreases as the amount increases, and becomes zero when a predetermined amount is reached.

The deposition amount estimator 73 estimates the deposition amount of fine particles on the filter 12f based on the detection result of the detection unit 71, the measurement result of the temperature difference measurement unit 13, and the map 72m. The deposition amount estimation unit 73 is stored in the memory as a program, for example. It should be noted that such a program may be stored on the cloud, and the control unit 7 may be appropriately communicated with the cloud so that a desired program can be used. In this case, the control unit 7 is configured to include a communication module with the cloud and the like.

The deposition amount estimator 73 refers to the map 72m corresponding to the acceleration of the vehicle under predetermined conditions, and estimates the particulate deposition amount based on the exhaust temperature difference. The predetermined condition is that the temperature of the engine 2 is equal to or higher than the reference temperature and the acceleration of the vehicle is equal to or lower than the reference acceleration for a predetermined time or longer. In the present embodiment, a vehicle operating state that satisfies a predetermined condition is defined as a steady operating state. The reference temperature and reference acceleration are as described above. The predetermined time (hereinafter referred to as the reference time) is, for example, in the range of about 10 seconds to 60 seconds, and is 30 seconds as an example. The exhaust temperature difference is the difference in exhaust temperature between upstream and downstream of the filter section 12, and in this embodiment, it is the difference between the inlet temperature and the outlet temperature. The particulate deposition amount is the collection amount (accumulation amount) of particulates collected and deposited by the filter section 12 . The deposition amount estimator 73 gives the estimated particulate deposition amount to the regeneration control unit 74 .

The reason why the deposition amount estimator 73 can estimate the deposition amount of fine particles based on the exhaust temperature difference is as follows. FIG. 3 shows an example of changes over time in the vehicle speed, the inlet and outlet temperatures of the exhaust, and the difference in the exhaust temperature. In FIG. 3, L31 is the time change of the vehicle speed. L32 and L33 are the changes over time of the inlet and outlet temperatures of the exhaust in the undeposited state. The non-deposited state includes a new state in which fine particles are not deposited on the filter 12f, and a state immediately after the filter 12f has been regenerated. L34 and L35 are the time variations of the inlet and outlet temperatures of the exhaust in the deposition state. The accumulation state is a state in which fine particles have accumulated on the filter 12f to the extent that regeneration of the filter 12f is required, in other words, a state after a certain period of time has passed since the regeneration or after traveling a certain distance. L36 is the change over time of the exhaust temperature difference in the non-deposited state. L37 is the change over time of the exhaust temperature difference in the deposition state.

As shown in FIG. 3, there is a correlation between the change in vehicle speed over time (acceleration), the amount of particulate matter deposited, and the exhaust temperature difference. For example, in the undeposited state, the inlet temperature is higher than the outlet temperature, creating an exhaust temperature difference. It is considered that this is because the filter 12f itself has a heat capacity and exhaust heat is absorbed by the filter 12f. On the other hand, in the accumulation state, a difference in exhaust gas temperature is generated according to the magnitude of the change in vehicle speed over time. Specifically, in the idle state described above, almost no exhaust temperature difference occurs. After that, when the vehicle speed changes greatly over time, an exhaust gas temperature difference occurs, and when the vehicle speed changes little over time, the exhaust gas temperature difference hardly occurs again.

It is considered that this is due to the following phenomenon. For example, when soot accumulates, exhaust heat is absorbed by the accumulated soot. In addition, the soot itself also has heat, and heat radiation from the soot also raises the temperature of the exhaust gas. For this reason, in an idling state or when the vehicle speed changes little over time, it becomes difficult for exhaust heat to be absorbed by the soot, and the temperature of the exhaust gas rises due to heat dissipation from the soot. On the other hand, when the vehicle speed changes greatly over time, it is considered that the influence of the decrease in heat absorption and heat release due to soot becomes less likely to cause a difference in the exhaust temperature.

Therefore, in the accumulation state, the idle state, for example, from 0 seconds to 40 seconds indicated by L34 and L35 in FIG. does not occur. Next, during acceleration from the idle state, for example, between 40 seconds and 100 seconds indicated by L34 and L35, the change in vehicle speed over time (L31) is large and a difference in exhaust gas temperature occurs. After that, when the steady operation state continues, for example, between 100 seconds and 250 seconds indicated by L34 and L35, the change in vehicle speed over time (L31) is small, and the difference in exhaust gas temperature does not occur again.

The idle state is an example of a steady operating state. A state in which the vehicle speed changes greatly over time is a state in which the vehicle speed changes abruptly. For example, the vehicle speed increases by 15 km/h in 60 seconds from 40 seconds to 100 seconds, as indicated by L31 in FIG. This state has an acceleration of about 0.07 m/s ² and does not correspond to a steady operating state. A state in which the vehicle speed changes little over time is a state in which the vehicle speed changes slowly, for example, the vehicle speed increases by 15 km/h in 150 seconds from 100 seconds to 250 seconds as indicated by L31 in FIG. In this state, the acceleration is approximately 0.02 m/s ² and is an example of a steady operating state.

In this way, in the steady state of operation, a difference in exhaust gas temperature occurs according to the amount of fine particles accumulated. In particular, in an idling state, which is a steady operating state in which the vehicle speed changes less over time than in a steady operating state while the vehicle is running, a significant difference in exhaust gas temperature occurs according to the amount of accumulated fine particles. As shown in the map 72m (FIG. 2), such an exhaust temperature difference increases as the amount of deposited fine particles decreases, and decreases as the amount increases.

Therefore, in the present embodiment, the amount of accumulated fine particles is estimated in a steady operating state including an idle state. On the other hand, in a state other than a steady driving state, for example, in a state where the vehicle speed changes relatively large over time, such as during acceleration from an idling state, an exhaust temperature difference occurs even if fine particles are deposited. Therefore, it is possible to perform more accurate estimation by avoiding the estimation in a state other than the steady operation state and performing the estimation in the steady operation state.

The regeneration control unit 74 determines regeneration conditions for the filter 12f, and performs regeneration processing for the filter 12f when the amount of fine particle deposition reaches a predetermined amount (regeneration start threshold, which will be described later). As the regeneration process, the regeneration control unit 74 performs a particulate combustion process or a temperature raising process for the catalyst 11c.

In the particulate combustion process (hereinafter referred to as particulate combustion process), the regeneration control unit 74 adjusts the temperature of the exhaust gas passing through the filter unit 12 . Specifically, the exhaust temperature is raised to a temperature at which soot, which is combustible particles, can burn and is maintained. In order to increase the temperature of the exhaust gas, the regeneration control unit 74 performs, for example, post-injection of fuel and throttling of intake air. In this case, the regeneration control unit 74 controls the operation of the injector 24, the intake throttle valve 23, and the like to appropriately adjust the amount of fuel sent to the air passage 12a, the amount of intake air to the combustion chamber 21, and the like. Further, for example, the regeneration control unit 74 controls the operation of the circulating air valve 6, etc., and appropriately introduces circulating air to adjust the oxygen concentration. Combustible particles such as soot contained in the particulates deposited on the filter 12f are burned and removed due to the increase in exhaust temperature. As a result, the filter 12f is regenerated to a state in which it can properly collect fine particles.

In the temperature raising process of the catalyst 11c (hereinafter referred to as catalyst temperature raising process), the regeneration control section 74 adjusts the temperature of the exhaust gas passing through the catalyst section 11 or the temperature of the catalyst 11c. Specifically, the exhaust temperature is raised to a temperature at which the catalyst 11c can be activated and maintained. The means for increasing the exhaust temperature is the same as in the particulate combustion process. The temperature of the catalyst 11c is raised by, for example, a heater. As a result, combustible particles such as soot deposited on the filter 12f are combusted and removed from the filter 12f by the oxidation reaction of nitrogen dioxide generated by the oxidation reaction in the catalyst 11c.

FIG. 4 shows a flow of regeneration control of the filter 12f in the exhaust purification device 1. As shown in FIG. A specific example of the regeneration control of the filter 12f and its action will be described below according to the flow shown in FIG.

As shown in FIG. 4, in regeneration control of the filter 12f, first, the running condition of the vehicle is detected, and information (data) of the detected running condition is acquired (S101). Specifically, the acceleration detector 71a detects the acceleration of the vehicle, and the driving condition detector 71b detects the temperature (cooling water temperature) of the engine 2, and acquires these data respectively. The acquired data is given to the deposit amount estimation unit 73 and the regeneration control unit 74 .

Next, the regeneration control unit 74 confirms whether or not it is necessary to start regeneration of the filter 12f. Therefore, the regeneration control unit 74 determines steady operation conditions (S102). The steady operating condition is a condition for determining whether or not the vehicle is in a steady operating state. In this embodiment, the steady operation condition is satisfied when all of the following three requirements are satisfied. The first requirement is that the temperature of the engine 2 (cooling water temperature) is equal to or higher than the reference temperature. A second requirement is that the acceleration of the vehicle is equal to or less than the reference acceleration. A third requirement is that the state in which the acceleration of the vehicle is equal to or less than the reference acceleration continues for a reference time or longer. Therefore, when the temperature of the engine 2 is equal to or higher than the reference temperature and the acceleration is equal to or lower than the reference acceleration continuously for the reference time or longer, the regeneration control unit 74 determines that the steady operation condition is satisfied. On the other hand, if even one of the three requirements is not satisfied, the regeneration control unit 74 determines that the steady operation condition is not satisfied.

In this embodiment, as an example, the steady-state operation condition is established when the above three requirements are satisfied, but the establishment requirement is not limited to this. For example, in addition to the above three requirements, the vehicle speed may be zero, that is, the vehicle should be stopped. Therefore, when the temperature of the engine 2 is equal to or higher than the reference temperature and the vehicle speed is zero, that is, when the vehicle has been stopped for the reference time or longer, the steady operation condition is established. As a result, the accumulated ash amount can be estimated only when the warm-up operation is completed, the temperature of the engine 2 is equal to or higher than the reference temperature, and the vehicle has been stopped for the reference time or longer, that is, the idle state. In the idling state, a significant difference in exhaust temperature occurs according to the amount of deposited ash, so the accuracy of estimating the amount of deposited fine particles can be improved thereafter.

When the steady-state operation condition is satisfied, the deposition amount estimator 73 determines whether or not the filter 12f is in a deposition state (a state in which fine particles are deposited until regeneration is required).

Therefore, the temperature difference measurement unit 13 measures the inlet temperature and the outlet temperature of the exhaust gas, respectively, and acquires data on the temperature difference (S103). The acquired data is given to the deposition amount estimating section 73 .

Subsequently, the accumulation amount estimation unit 73 determines the estimation start condition. The estimation start condition is a condition for determining whether or not to start estimating the particulate deposit amount. In determining the estimation start condition, the deposition amount estimation unit 73 determines whether or not the exhaust gas temperature difference given by the temperature difference measurement unit 13 is less than the estimation start threshold (S104). The estimation start threshold is the value of the exhaust gas temperature difference when the vehicle is in a steady driving state and the filter 12f is in a non-accumulated state. Therefore, if the exhaust gas temperature difference is less than the estimation start threshold, it can be assumed that the filter 12f is in a state where fine particles have accumulated from the non-accumulated state. The estimation start threshold is stored in a memory, for example, and is read out as an argument (program parameter) of the accumulation amount estimation unit 73 when determining the estimation start condition.

When the exhaust temperature difference is less than the estimation start threshold, the deposition amount estimator 73 estimates the particulate deposition amount (S105). In estimating, the deposit amount estimator 73 refers to the map 72m corresponding to the acceleration of the vehicle, and estimates the particulate deposit amount based on the exhaust temperature difference. The estimated particle deposition amount is provided to the regeneration control section 74 .

Subsequently, the regeneration control unit 74 determines regeneration conditions for the filter 12f (S106). The regeneration condition is a condition for determining whether regeneration of the filter 12f is necessary. In determining the regeneration condition, the regeneration control unit 74 compares the particulate deposit amount with the regeneration start threshold. The regeneration start threshold is a value of the amount of deposited particulates that requires regeneration of the filter 12f. The reproduction start threshold value is stored in a memory, for example, and is read out as an argument (program parameter) of the reproduction control unit 74 when judging the reproduction condition. As an example, the regeneration control unit 74 determines that the regeneration condition is satisfied if the particulate deposit amount is equal to or greater than the regeneration start threshold, and determines that the regeneration condition is not satisfied if the particulate deposit amount is less than the regeneration start threshold.

If the regeneration condition is not satisfied, the regeneration control unit 74 terminates regeneration control of the filter 12f without performing regeneration processing of the filter 12f.
If the steady-state operation condition is not satisfied in S102, and if the exhaust gas temperature difference is equal to or greater than the estimation start threshold value in S104, the regeneration control of the filter 12f is similarly terminated.

On the other hand, if the regeneration condition is satisfied, the regeneration control unit 74 performs regeneration processing of the filter 12f (S107).
FIG. 5 is a flowchart showing an example of regeneration processing of the filter 12f in the exhaust gas purification device 1. As shown in FIG.

As shown in FIG. 5, in the regeneration process of the filter 12f, the regeneration control unit 74 confirms whether the inlet temperature of the exhaust gas is within a predetermined range. Therefore, the regeneration control unit 74 determines whether or not the inlet temperature is greater than or equal to the first threshold and less than the second threshold (S701). The first threshold value and the second threshold value are threshold values for determining which of the fine particle combustion process and the catalyst temperature raising process should be performed as the regeneration process for the filter 12f. The first threshold value and the second threshold value are stored, for example, in a memory, and are read out as arguments (program parameters) of the reproduction control unit 74 when determining the content of reproduction processing. The first threshold (T1) is, for example, in the range of about 450°C to 550°C, and is 500°C as an example. The second threshold (T2) is, for example, in the range of about 600°C to 700°C, and is 650°C as an example. 650° C. corresponds to a temperature at which soot, which is combustible particles, can burn.

If the inlet temperature is greater than or equal to the first threshold and less than the second threshold, the regeneration control section 74 determines the temperature increase condition (S702). The temperature increase condition is a condition for determining whether or not the exhaust temperature can be increased to a temperature at which the catalyst 11c can be activated.

If the temperature increase condition is satisfied, the regeneration control unit 74 performs catalyst temperature increase processing (S703). In the catalyst temperature raising process, the regeneration control unit 74 performs post-injection of fuel, intake air throttling, and the like to raise the temperature of the exhaust gas passing through the catalyst unit 11 . Alternatively, the regeneration control unit 74 raises the temperature of the catalyst 11c by operating temperature control means such as a heater. After continuing the catalyst temperature raising process for a predetermined period of time, the regeneration control unit 74 terminates the regeneration process of the filter 12f. As a result, combustible particles such as soot deposited on the filter 12f are burned and removed by the oxidation reaction of the catalyst 11c.
On the other hand, if the temperature increase condition is not satisfied, the regeneration control unit 74 terminates the regeneration process of the filter 12f without performing the catalyst temperature increase process.

On the other hand, if the inlet temperature is equal to or higher than the first threshold and lower than the second threshold in S701, the regeneration control unit 74 determines whether or not the inlet temperature is equal to or higher than the second threshold (S704).

If the inlet temperature is equal to or higher than the second threshold, the regeneration control unit 74 performs particulate combustion processing (S705). In the particulate combustion process, the regeneration control unit 74 performs post-injection of fuel, intake air throttling, and the like, and maintains the temperature of the exhaust gas passing through the filter unit 12 at a temperature at which soot can be combusted. After continuing the particulate combustion process for a predetermined period of time, the regeneration control unit 74 terminates the regeneration process of the filter 12f. As a result, combustible particles such as soot contained in the particulates deposited on the filter 12f are burned and removed.
On the other hand, if the inlet temperature is less than the second threshold, the regeneration control unit 74 terminates the regeneration process of the filter 12f without performing the particulate combustion process.

Then, as shown in FIG. 4, after completing the regeneration process of the filter 12f, the regeneration control section 74 terminates the regeneration control of the filter 12f.

Thus, according to the present embodiment, it is possible to estimate the particulate deposit amount based on the exhaust temperature difference, that is, the exhaust temperature difference between upstream and downstream of the filter section 12 . In this embodiment, the pressure sensors 14a and 14b of the pressure measuring unit 14 measure the exhaust pressure upstream and downstream of the filter unit 12, and based on the differential pressure between them, it is possible to estimate the particulate deposit amount. Therefore, such differential pressure-based estimation can be complemented by temperature differential-based estimation. In particular, in the estimation based on the differential pressure, the differential pressure is small at the stage when the amount of fine particle deposition is small (initial stage of deposition), making it difficult to estimate the deposition amount. Cheap. By complementing the estimation based on the differential pressure with the estimation based on the temperature difference, it is possible to accurately estimate the particulate deposition amount regardless of the initial stage of deposition and the deposition mode. In addition, even if the pressure sensors 14a and 14b have some problem, the temperature sensors 13a and 13b can continue to measure the inlet temperature and the outlet temperature. Therefore, by estimating based on the temperature difference, the particle deposition amount can be continuously estimated.

As a result, it is possible to improve the accuracy of estimating the particulate deposit amount, appropriately regenerate the filter 12f, and maintain the performance of the filter 12f more appropriately. As a result, it becomes possible to improve the fuel efficiency of the engine 2 and improve the fuel efficiency. For example, in the case of a direct gasoline injection type engine such as the engine 2 of the present embodiment, the amount of fine particles contained in the exhaust gas is larger than that of a port injection engine. Therefore, in a gasoline direct injection engine, it is more effective to estimate the amount of particulate deposits based on the difference in exhaust gas temperature to maintain the performance of the filter 12f.

Although the embodiment of the present invention has been described above, the above-described embodiment is presented as an example and is not intended to limit the scope of the invention. Such novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1... Exhaust gas purification apparatus 2... Engine 3... Intake passage 4... Exhaust passage 5... Exhaust circulation path 6... Circulation air valve 7... Control part 11... Catalyst part 11a... Ventilation path 11c... Catalyst , 12 Filter section 12a Air passage 12f Filter 12i Inlet 12o Outlet 13 Temperature difference measuring section 13a First temperature sensor 13b Second temperature sensor 14 Pressure measurement Parts 14a... First pressure sensor 14b... Second pressure sensor 21... Combustion chamber 22... Intake valve 23... Intake throttle valve 24... Injector 25... Spark plug 26... Piston 27... Crank Shaft 28 Exhaust valve 71 Detection unit 71a Acceleration detection unit 71b Driving condition detection unit 72 Map storage unit 72m Map 73 Accumulation amount estimation unit 74 Regeneration control unit.

Claims (4)

an acceleration detection unit that detects the acceleration of the vehicle;
a driving condition detection unit that detects the driving condition of the vehicle including the temperature of the internal combustion engine of the vehicle;
a filter unit disposed in an exhaust passage through which exhaust gas from the internal combustion engine flows and configured to collect particulates contained in the exhaust gas;
a temperature difference measuring unit that measures a temperature difference between the exhaust gas upstream and downstream of the filter unit in the exhaust passage;
a map storage unit for storing a map showing a correspondence relationship between the accumulation amount of the fine particles collected by the filter unit and the difference in temperature of the exhaust gas between upstream and downstream of the filter unit according to acceleration of the vehicle; ,
When the temperature of the internal combustion engine is equal to or higher than a predetermined temperature, and the acceleration of the vehicle is determined to be equal to or lower than a predetermined acceleration, and the state continues for a predetermined time or longer, and the steady operation state continues, and a deposition amount estimating unit that inquires the map using the map and estimates the deposition amount of the fine particles based on the temperature difference of the exhaust gas. The deposition amount estimating unit estimates the deposition amount of the fine particles based on a comparison between the temperature difference of the exhaust gas and the temperature difference of the exhaust gas when the fine particles are not deposited on the filter unit in the steady operation state. The exhaust emission control system according to claim 1, characterized by estimating. The exhaust emission control system according to claim 1, wherein the steady operating state further requires that the vehicle is stopped. 3. The apparatus according to claim 1, further comprising a regeneration control unit that removes the particulates from the filter unit and regenerates them based on a comparison between the deposit amount of particulates estimated by the deposit amount estimation unit and a predetermined threshold value. 4. The exhaust purification device according to any one of 1 to 3.

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