JP4306338B2 - Method for regenerating particulate filter of internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for regenerating a particulate filter discharged from an internal combustion engine.
[0002]
[Prior art]
As a method for regenerating a particulate filter for an internal combustion engine carrying an oxidation catalyst, fuel is injected into the combustion chamber (post-injection) at the end of the expansion stroke of the internal combustion engine to cause combustion in the exhaust passage. A method of self-igniting particulates (particulate matter) is known (see Patent Document 1). Other prior art documents related to the present invention include Patent Documents 2 to 4.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 04-47115
[Patent Document 2]
JP-A-11-262631
[Patent Document 3]
JP 11-262632 A
[Patent Document 4]
JP 2001-336414 A
[0004]
[Problems to be solved by the invention]
In the above-described technique, the temperature of the particulate filter is increased by post injection from the start to the end of regeneration, so that the amount of fuel consumed during regeneration is large.
[0005]
Therefore, an object of the present invention is to provide a filter regeneration method that can reduce the amount of fuel consumed during regeneration of a particulate filter.
[0006]
[Means for Solving the Problems]
In the first particulate filter regeneration method of the present invention, CO in a predetermined absorption temperature region in or near the particulate filter provided in the exhaust passage of the internal combustion engine. ₂ CO that absorbs ₂ When it is necessary to remove the particulates collected in the particulate filter by placing an absorbent material, the CO ₂ The temperature of the absorbent is raised to the absorption temperature range, and the CO in the absorption temperature range is ₂ Absorbent CO ₂ The above-mentioned problem is solved by utilizing the heat generated with the absorption of the water for the oxidation of the particulates collected by the particulate filter (claim 1).
[0007]
According to the present invention, CO generated by oxidation of particulates. ₂ CO ₂ The absorbent absorbs CO ₂ The absorbent material generates heat, and the heat promotes oxidation of the particulates, resulting in CO ₂ Occurs and this is CO ₂ A cycle of absorption by the absorbent material is realized. As a result, at least part of the amount of heat required for particulate oxidation is reduced to CO. ₂ It can be covered by the heat of the absorbent material, and the amount of fuel consumed during regeneration of the particulate filter can be reduced.
[0008]
CO ₂ The position of the absorbent is CO ₂ There is no particular limitation as long as the heat generated by the absorption of can be utilized for oxidation of the particulates. For example, it may be carried on a particulate filter, or may be arranged on the upstream side or downstream side of the particulate filter.
[0009]
In the first particulate filter regeneration method of the present invention, the CO ₂ As an absorbent, CO is absorbed in the absorption temperature range. ₂ And absorbs the absorbed CO ₂ That releases CO in a given release temperature range ₂ An absorption / release material is disposed, and the CO ₂ After utilizing the heat generated by the absorption of the particulates to oxidize the particulates collected in the particulate filter, the CO ₂ The temperature of the absorption / release material may be adjusted to the emission temperature range (claim 2). In this case, CO ₂ By holding the absorbent in the discharge temperature range, the CO stored during regeneration of the particulate filter ₂ In the next regeneration ₂ Can be prepared for absorption.
[0010]
In the second particulate filter regeneration method of the present invention, CO in a predetermined absorption temperature range is provided in or near the particulate filter provided in the exhaust passage of the internal combustion engine. ₂ CO that absorbs ₂ When it is necessary to remove the particulates collected in the particulate filter by placing an absorbent material, the CO ₂ While raising the temperature of the absorbent to the absorption temperature range, the CO ₂ CO of exhaust gas flowing into the absorber ₂ Of the exhaust gas flowing into the particulate filter, and ₂ The above-mentioned problem is solved by lowering the concentration of (Claim 3).
[0011]
According to the present invention, as in the first regeneration method of the present invention, CO generated by the oxidation of the particulates. ₂ CO ₂ The absorbent absorbs CO ₂ The absorbent material generates heat, and the heat promotes oxidation of the particulates, resulting in CO ₂ Occurs and this is CO ₂ Since a cycle of absorption by the absorbent material is realized, it is possible to reduce fuel consumption during regeneration of the particulate filter. Moreover, when the temperature rises, CO ₂ Increase the concentration of CO ₂ Absorption of CO ₂ Since the absorbent material has an atmosphere that easily generates heat, the above-described cycle is easily started early. In addition, after the temperature rises, the exhaust gas CO flowing into the particulate filter ₂ The oxidation of the particulates is promoted by lowering the concentration of CO. ₂ Therefore, the above-described cycle is efficiently repeated.
[0012]
In the second particulate filter regeneration method of the present invention, the particulate filter and the CO ₂ By burning fuel in the exhaust passage upstream of the absorbent, the CO ₂ While raising the temperature of the absorbent to the absorption temperature range, the CO ₂ CO of exhaust gas flowing into the absorber ₂ May be increased (Claim 4). In this case, CO such as an operation of injecting fuel into the combustion chamber at the end of the expansion stroke of the internal combustion engine (so-called post-injection) or an operation of adding a reducing agent to the exhaust passage. ₂ Just by burning the fuel in the exhaust passage upstream of the absorbent, ₂ Absorbent temperature rise and exhaust gas CO ₂ Increase in concentration can be realized.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 shows an embodiment in which the present invention is applied to a diesel engine 1 as an internal combustion engine. An intake passage 3 and an exhaust passage 4 are connected to the cylinder 2 of the engine 1. The intake passage 3 is connected to an air filter 5 for filtering the intake air, a compressor 6 a of a supercharger 6 that uses the exhaust energy to increase the intake pressure, A throttle valve 7 for adjusting the amount is provided, and a turbine 6 b of the supercharger 6 is provided in the exhaust passage 4. The exhaust purification device 19 of the engine 1 is provided with a casing 9 having a particulate filter 8 built therein and a temperature sensor 10 for detecting the temperature of the filter 8 disposed downstream of the turbine 6 b in the exhaust passage 4. . Each cylinder 2 is provided with an injector 11 for injecting fuel into the cylinder 2, and each injector 11 is connected to a common rail 12 for storing pressurized fuel.
[0014]
The operating state of the engine 1 is controlled by an engine control unit (ECU) 13. The ECU 13 is configured as a computer that combines a microprocessor and peripheral devices such as ROM and RAM that function as a main storage device. The ECU 13 controls the operating state of the engine 1 by adjusting the fuel injection amount from the injector 11 with reference to output signals from various sensors. The other engine 1 is provided with an EGR cooler 14 and an EGR valve 15.
[0015]
As shown in FIG. 2A and FIG. 2B, the filter 8 is formed in a honeycomb shape having a large number of cells (through holes) 21. Each of the cells 21 ... 21 is plugged with a plug 22 at one of the ends. The plug 22 is provided so that the cells 21 plugged at the inlet end 21a and the cells 21 plugged at the outlet end 21b are alternately arranged. In the partition wall 23 between the cells 21 adjacent to each other, many fine holes (not shown) are formed so that the exhaust gas can pass but the particulates (PM) cannot pass. The partition wall 23 carries platinum (Pt) as an oxidation catalyst.
[0016]
An appropriate material can be used for the outer wall 20 and the partition wall 23 of the filter 8. For example, ceramic may be used. In addition, alumina, silica-alumina, zeolite, cordierite, or layered oxide may be used.
[0017]
The filter 8 is further CO in the absorption temperature range. ₂ In the release temperature range higher than the absorption temperature range. ₂ CO that emits ₂ The absorbing / releasing material is carried on the partition wall 23. CO ₂ As an absorption / release material, a lithium composite oxide such as lithium silicate (Li ₄ SiO ₄ ) May be used. The absorption temperature range of lithium silicate is 450 to 550 ° C., and this temperature range includes the temperature at which PM collected by the filter 8 is oxidized.
[0018]
CO ₂ As shown in FIG. ₂ An exothermic reaction occurs with the absorption reaction. As shown in FIGS. 3B and 3C, CO ₂ Absorption and release material CO ₂ The absorption rate and heat release rate of CO ₂ The absorption and release material changes as the temperature changes from a ° C. to b ° C. to c ° C., and the absorption rate and heat release rate become the highest at the temperature a ° C. to b ° C. Temperatures a and b are CO ₂ For example, in lithium silicate, a = 500 ° C. and b = 550 ° C., depending on the material of the absorption / release material.
[0019]
The operation of the engine 1 having the above configuration will be described. FIG. 4 is a flowchart showing a procedure of a regeneration control routine executed by the ECU 13. This process is repeatedly executed at a predetermined cycle after the operation of the engine 1 is started.
[0020]
First, the ECU 13 determines whether or not it is necessary to regenerate the filter 8 (step S1). For this determination, various known determination methods may be used. For example, the PM accumulation amount is estimated from the integrated value of the fuel injection amount, and the determination is made based on whether or not the estimated accumulation amount has reached a predetermined level. In the present embodiment, in order to accurately perform deterioration determination (step S7) based on time ΔT, which will be described later, the regeneration start condition is such that the PM accumulation amount of the filter 8 at the start of regeneration of the filter 8 is always a constant value. Set. Similarly, in order to accurately determine the deterioration based on ΔT, CO ₂ Absorption and release material CO ₂ The amount of absorption is always a constant value (see step S11). If the ECU 13 determines that it is not necessary to regenerate the filter 8 in step S1, the ECU 13 ends the routine.
[0021]
If it is determined that the filter 8 needs to be regenerated, an operation of raising the temperature of the filter 8 is executed (step S2). Various methods may be used for raising the temperature of the filter 8. For example, the fuel injection amount from the injector 11 is controlled so that fuel is injected (post-injection) from the injector 11 at the end of the expansion stroke of the engine 1. Execute. The unburned fuel is combusted in the exhaust passage 4 by the post injection, and the temperature of the filter 8 rises as indicated by the solid line L3 in the phase 1 in FIG. The temperature of the filter 8 is CO ₂ When reaching the absorption temperature range of the absorbing and releasing material, CO ₂ The temperature of the filter 8 further rises due to the heat generated as a result of absorption. Further, as the unburned fuel burns, the exhaust gas flowing into the filter 8 is more CO 2 than when no post-injection is performed. ₂ As the concentration increases, O ₂ The concentration is lowered.
[0022]
In step S3, it is determined whether or not the temperature of the filter 8 has been raised until the filter can be regenerated. For example, it is determined whether or not the temperature of the filter 8 has increased to the target temperature d ° C shown in FIG. The target temperature d ° C is the CO supported on the filter 8. ₂ You may set suitably in the temperature range which can oxidize PM collected by the filter 8 within the absorption temperature range of the absorption / release material. For example, CO ₂ May be set within a ° C. to b ° C. (see FIG. 3B and FIG. 3C) in which the absorption reaction (exothermic reaction) becomes the most intense. Further, the temperature of the filter 8 may be directly detected by the temperature sensor 10 as in the present embodiment, or may be estimated from a parameter correlated with the temperature of the filter 8 such as the frequency of execution of post injection. If it is determined that the temperature of the filter 8 has not reached the target temperature d ° C, the process returns to step S2 and the temperature raising operation is continued.
[0023]
If it is determined that the target temperature d ° C has been reached, the temperature raising operation is stopped and the process proceeds to the subsequent steps. This time corresponds to the time t1 when the phase 1 in FIGS. 5A and 5B ends and the phase 2 starts. As shown in FIG. 5A, in phase 2, the post-injection is stopped, so that the exhaust gas CO flowing into the filter 8 is stopped. ₂ As the concentration decreases, the oxidation reaction of PM is activated, and CO generated by the oxidation ₂ CO ₂ Since it is absorbed by the absorption / release material, the oxidizing atmosphere is maintained and PM is continuously oxidized. Further, as shown in FIG. 5 (b), heat generation due to oxidation of PM and CO ₂ Absorption and release material CO ₂ Due to the heat generated by the absorption, the temperature of the filter 8 is maintained at the temperature at which PM is oxidized even in phase 2 where the temperature raising operation is stopped, and the oxidation of PM proceeds. In phase 2, the oxidation of PM proceeds, and the residual amount of PM becomes very small. ₂ Absorption and release material CO ₂ When the oxidation of PM is terminated, for example, because the amount of absorption reaches the limit value, the temperature of the filter 8 decreases.
[0024]
The ECU 13 starts measuring the elapsed time ΔT from time t1 in step S4. In step S5, it is determined whether or not the measurement end condition for ΔT is satisfied. If it is determined that the measurement end condition is satisfied, the measurement of ΔT is ended (step S6). The measurement end condition of ΔT may be set as appropriate, but in the present embodiment, the determination is made based on whether or not the temperature of the filter 8 has decreased to the criteria bed temperature shown in FIG. For example, the lower limit of the temperature at which PM can be oxidized may be set as the criteria floor temperature.
[0025]
CO ₂ When the absorbing / releasing material deteriorates, ΔT becomes shorter as compared with the case where it does not deteriorate (solid line L3), as indicated by a dotted line L4 in FIG. The ECU 13 determines whether or not ΔT is smaller than a predetermined threshold (step S7). If it is determined that ΔT is smaller, the ECU 13 sets a deterioration flag indicating that the filter 8 has deteriorated (step S8). If it is determined that ΔT is not smaller than the predetermined threshold, step S8 is skipped.
[0026]
After that, the ECU 13 ₂ Absorbed and released material absorbs CO ₂ It is determined whether or not the condition for starting the release of the above is satisfied (step S9) and waits until it is determined that the condition is satisfied. This condition may be set as appropriate. For example, the condition may be that a certain time has passed since step S6. When it is determined that the release start condition is satisfied, an operation (step S10) for raising and maintaining the temperature of the filter 8 to the release temperature range is performed in step S11. ₂ Absorption and release material CO ₂ The process is repeated until it is determined that the release completion condition is satisfied, and the routine ends. As the discharge completion condition, for example, it may be set whether or not a predetermined time has elapsed since the start of discharge. The CO at the start of regeneration of the filter 8 ₂ Absorption and release material CO ₂ In step S11, in order to make the deterioration determination based on ΔT accurate, the amount of absorption of CO is always constant. ₂ It is desirable to set conditions so that is sufficiently released.
[0027]
When the ECU 13 executes the regeneration control routine again or executes various routines such as a routine for warning the user that the filter 8 has deteriorated, the ECU 13 uses the deterioration flag set in step S8 as appropriate. To do. For example, when the deterioration flag is set in step S1 of the regeneration control routine, the regeneration start condition may be changed so that the time interval for repeating the regeneration of the filter 8 is shortened. If the deterioration flag is set in step S3, the target temperature is set high, or the temperature raising operation is stopped after a predetermined time has elapsed after the temperature of the filter 8 reaches the target temperature. The amount of heat applied by the injection may be increased. Further, the degree of deterioration may be specified from the length of ΔT, and the time interval at which regeneration is repeated or the target temperature may be changed according to the degree of deterioration. In the present embodiment, a temperature sensor that detects the exhaust gas temperature downstream of the filter 8 may be provided in place of the temperature sensor 10.
[0028]
(Second Embodiment)
FIG. 6A shows a second embodiment of the present invention. However, in this embodiment, the same reference numerals are used for common parts with the first embodiment, and detailed description thereof is omitted. Also in this embodiment, a filter 8 is provided in the exhaust passage 4 of the engine 1 as in FIG. In this embodiment, the exhaust gas CO is disposed downstream of the filter 8. ₂ CO to detect concentration ₂ While the sensor 30 is provided, the temperature sensor 10 is omitted.
[0029]
In the present embodiment, the ECU 13 executes a routine similar to the regeneration control routine of FIG. ₂ CO detected by the sensor 30 ₂ The deterioration of the filter 8 is determined based on the density. As shown by the solid line L10 in FIG. 6B, in the vicinity of time t1 when the phase 1 is shifted to the phase 2, the CO ₂ CO by absorbing and releasing material ₂ Absorption and post-injection stop, so that CO on the downstream side of the filter 8 ₂ The concentration once decreases. After that, CO is oxidized by PM oxidation. ₂ Concentration increases and CO is oxidized while PM oxidation proceeds ₂ The concentration is kept high. After that, when the oxidation of PM ends, CO ₂ The concentration is lowered. CO ₂ When absorption and release material deteriorates, CO ₂ Absorption and release material CO ₂ As shown by the dotted line L11, the absorption reaction and exothermic reaction of ₂ The time during which the concentration is kept high is shortened.
[0030]
The ECU 13 performs CO in phase 2 ₂ A period from time t3 when the concentration is lower than the criterion concentration to time t4 when the concentration is lower than the criterion concentration is again measured as ΔT, and when ΔT is shorter than a predetermined threshold, the filter 8 Is determined to have deteriorated. In order to realize such deterioration determination, the ECU 13 determines the CO between steps S3 and S4 of the regeneration control routine of FIG. ₂ CO detected by the sensor 30 ₂ What is necessary is just to perform the step which progresses to step S4, when it determines whether the density | concentration once became lower than the criterion density | concentration, and became higher than the criterion density | concentration again, and determination is affirmed. In step S5, CO ₂ CO detected by the sensor 30 ₂ When the concentration becomes lower than the criterion concentration, it may be determined that the ΔT measurement end condition is satisfied. In the present embodiment, the measurement of ΔT may be started from time t1 as in the first embodiment.
[0031]
(Third embodiment)
FIG. 7A shows a third embodiment of the present invention. However, in this embodiment, the same reference numerals are used for common parts with the first embodiment, and detailed description thereof is omitted. Also in this embodiment, a filter 8 is provided in the exhaust passage 4 of the engine 1 as in FIG. In the present embodiment, a pressure detection sensor 35 that detects a differential pressure between the upstream side and the downstream side of the filter 8 is provided, while the temperature sensor 10 is omitted.
[0032]
In this embodiment, the ECU 13 executes a routine similar to the regeneration control routine of FIG. 4, but in this embodiment, the deterioration of the filter 8 is determined based on the differential pressure detected by the pressure detection sensor 35. FIG. 7B shows a change in the differential pressure when not deteriorated by a solid line L15 and a change in the differential pressure when deteriorated by a solid line L16. As shown in FIG. 7B, when post-injection is stopped at time t1 and PM oxidation starts, the differential pressure between the upstream side and the downstream side of the filter 8 decreases with PM oxidation. When the filter 8 deteriorates, CO ₂ Absorption and release material CO ₂ The time taken for the absorption reaction and exothermic reaction to weaken and the differential pressure to become the criteria differential pressure becomes longer than when it has not deteriorated.
[0033]
In this embodiment, the time from the time t1 until the differential pressure detected by the pressure detection sensor 35 becomes the criteria differential pressure is measured as ΔT, and it is determined that the filter 8 has deteriorated when ΔT is longer than a predetermined threshold. . In order to realize such deterioration determination, the ECU 13 determines whether or not regeneration is performed in a predetermined manner depending on whether or not the differential pressure detected by the pressure detection sensor 35 has become the criteria differential pressure in step S5 of the regeneration control routine of FIG. Whether or not it has progressed to the state is determined, and in step S6, it may be determined whether or not ΔT is larger than a threshold value.
[0034]
(Fourth embodiment)
FIG. 8 shows a fourth embodiment of the present invention. However, in this embodiment, the same reference numerals are used for common parts with the first embodiment, and detailed description thereof is omitted. Also in this embodiment, a filter 8 is provided in the exhaust passage 4 of the engine 1 as in FIG. As shown in FIG. 8, in this embodiment, a gas concentration sensor 40 for detecting the concentration of a specific substance in the exhaust gas downstream of the filter 8 is provided, and the differential pressure between the upstream side and the downstream side of the filter 8. There is provided a pressure detection sensor 35 for detecting. The gas concentration sensor 40 may be one that detects the concentration of various substances, but is an air-fuel ratio sensor, for example.
[0035]
Also in the present embodiment, the regeneration control routine of FIG. However, in the present embodiment, steps S4 to S8 executed for determining the deterioration of the filter 8 are omitted. Further, the ECU 13 executes a deterioration determination routine shown in FIG. This routine is repeatedly executed at a predetermined cycle in parallel with the regeneration control routine after the operation of the engine 1 is started.
[0036]
In step S20, the ECU 13 performs the CO ₂ CO by absorption and release material ₂ It is determined whether or not the engine 1 is in the operating region where the absorption or release of the gas is performed. This determination may be made based on, for example, whether the temperature detected by the temperature sensor 10 is in the absorption temperature range or the discharge temperature range. In step S21, the PM accumulation amount of the filter 8 is estimated based on the differential pressure detected by the pressure detection sensor 35, and the PM combustion amount is estimated from the difference from the previous estimation amount. In step S22, a heat quantity Q1 of heat generated by the PM combustion is calculated based on the estimated PM combustion quantity. In step S23, the amount of heat received Q2 of the filter 8 is calculated based on the amount of change detected by the temperature sensor 10 from the previous time. In step S24, the CO ₂ Absorption and release material CO ₂ The amount of heat Q4 generated with the absorption of is calculated by the following equation.
[Expression 1]
Q4 = Q2-Q1 + Q3
[0037]
In the above equation, Q3 is the amount of heat released from the filter 8 to the exhaust gas or the outside of the casing 9, and is appropriately determined based on various parameters such as a parameter correlated with the exhaust gas temperature and a temperature detected by the temperature sensor 10. May be estimated. In the above equation, the amount of heat Q4 is expressed as CO ₂ Absorbing and releasing material is CO ₂ If it generates heat by absorbing ₂ It becomes negative when it absorbs heat.
[0038]
In step S25, the CO in one cycle of the deterioration determination routine. ₂ It is determined whether or not the CO heat amount Q4 is smaller than a threshold value set as the heat amount to be generated by the absorption / release material. If it is determined that the value is smaller than the threshold value, a deterioration flag is set (step S26). If it is determined that it is not small, step S26 is skipped.
[0039]
In step S27, based on the heat quantity Q4, the CO ₂ Absorption and release material CO ₂ The amount of absorbed or released is estimated. In step S28, the CO accompanying the combustion of PM calculated from the PM combustion amount estimated in step S21. ₂ Generation amount and CO estimated in step S27 ₂ Of the exhaust gas from the upstream side to the downstream side of the filter 8 based on the amount of absorption or release of ₂ Estimate the amount of concentration change. In step S29, the estimated CO ₂ Based on the amount of change in concentration, the concentration of the specific substance detected by the gas concentration detection sensor 40 is corrected so as to remove the influence of the filter 8.
[0040]
A temperature sensor that detects the exhaust gas temperature downstream of the filter 8 may be provided instead of the temperature sensor 10. In this case, the amount of heat received by the exhaust gas is estimated from the temperature rise of the exhaust gas, and the amount of heat received by the exhaust gas due to the combustion of PM is subtracted from the amount of heat. ₂ Calculate the amount of heat received by the exhaust gas due to the heat generated by the absorbing and releasing material, ₂ Calorific value of absorbed and released material, CO ₂ What is necessary is just to estimate the amount of absorption. Further, the temperature of the filter 8 is estimated from the temperature of the exhaust gas, and as described above, the CO ₂ Calorific value of absorbed and released material, CO ₂ The amount of absorption may be estimated.
[0041]
The present invention is not limited to the above embodiments, and may be implemented in various forms within the scope of the technical idea of the present invention. For example, the engine 1 is not limited to a diesel engine, and may be a gasoline engine. The filter 8 may carry a catalyst for storing and reducing NOx.
[0042]
The temperature raising means is CO ₂ Any form is possible as long as the temperature of the absorbent can be raised. For example, an addition device for adding a reducing agent (fuel) may be provided in the exhaust passage 4 on the upstream side of the filter 8, and the temperature of the filter 8 may be raised using the combustion heat of the added reducing agent. A heating device such as an electric heater may be provided adjacent to the filter 8 to raise the temperature of the filter 8.
[0043]
The deterioration of the filter 8 may be determined by various methods based on various parameters having a correlation with the state of PM oxidation reaction. For example, as shown in FIG. 10, temperature sensors 40 and 40 that detect the temperature of the exhaust gas may be provided on the upstream side and the downstream side of the filter 8, respectively. In this case, the more the PM oxidation reaction, the higher the downstream temperature becomes higher than the upstream temperature. For example, the upstream and downstream temperatures when a predetermined time elapses after the regeneration of the filter 8 is started. The deterioration of the filter 8 may be determined based on the magnitude of the difference, or the deterioration of the filter 8 based on the time from when the regeneration of the filter 8 is started until the temperature difference between the upstream side and the downstream side becomes a predetermined value or less. May be determined.
[0044]
Further, as shown in FIG. 11, the deterioration of the filter 8 may be determined based on the frequency with which the filter 8 is regenerated in a predetermined period T2.
[0045]
Temperature detected by various sensors, CO ₂ Although the example in which the deterioration of the filter 8 is determined based on the time until the concentration and the differential pressure reach the predetermined reference value has been shown, the deterioration is determined by various methods based on the relationship between the detected physical quantity and the elapsed time. Good. For example, in the second embodiment, the CO within a predetermined period from time t1. ₂ It may be determined that the filter 8 has deteriorated when the maximum concentration value is equal to or less than a predetermined reference value. In the third embodiment, the change rate of the decrease in the pressure difference of phase 2 is equal to or less than the predetermined reference value. It may be determined that the filter 8 has deteriorated at a certain time.
[0046]
Determination of deterioration of the filter 8 (steps S4 to S8) and CO ₂ Absorption and release material CO ₂ (Steps S9 to S11) may be executed at a rate of once for a plurality of filter regenerations. In this case, CO ₂ For example, whether or not it is necessary to release ₂ Amount (CO ₂ Determination may be made by estimating the total absorption). CO ₂ The total absorption amount may be estimated as in the modification shown in FIG.
[0047]
In the modification of FIG. 12, a filter 8 is provided in the exhaust passage 4 of the engine 1 as in FIG. As shown in FIG. 12, in this modification, the CO upstream of the filter 8 is ₂ CO to detect concentration ₂ A sensor 30 is provided, and a pressure detection sensor 45 that detects upstream and downstream pressures of the filter 8 is provided.
[0048]
FIG. 13 shows the CO executed by the ECU 13. ₂ It is a flowchart which shows the procedure of an absorption total amount estimation routine. This routine is repeatedly executed at a predetermined cycle after the operation of the engine 1 is started.
[0049]
First, the ECU 13 ₂ CO by absorption and release material ₂ It is determined whether or not the engine 1 is in the operating region where the absorption or release of the gas is performed (step S40). This determination may be made based on, for example, whether the temperature detected by the temperature sensor 10 is in the absorption temperature range or the discharge temperature range. In step S41, based on the output signal of the temperature sensor 10, the CO ₂ Specify the temperature of the absorbent material. In step S42, the pressure detected by the pressure detection sensor 35 and the CO ₂ CO detected by the sensor 30 ₂ Based on concentration and CO ₂ CO in the atmosphere of absorption / release material ₂ Calculate the partial pressure of. In the calculation of partial pressure, CO by oxidation of PM ₂ You may consider suitably the influence of the raise of a density | concentration, and the influence of the pressure difference of the pressure of the upstream of the filter 8, and the pressure of a downstream. In step S43, the previous CO ₂ CO obtained by execution of total absorption amount estimation routine ₂ The total absorption amount is read from the storage area of the ECU 13 and acquired.
[0050]
In step S44, the CO acquired in steps S41 to S43. ₂ Absorption material temperature, atmosphere CO ₂ Partial pressure of the previous CO ₂ Based on the total absorption, CO ₂ Absorption and release material CO ₂ Identify the rate of absorption or release of For example, temperature, partial pressure, absorbed CO ₂ CO with quantity as parameter ₂ In accordance with maps and estimation formulas for determining the absorption rate or release rate of CO ₂ Identify the rate of absorption or release of In step S45, the previous CO ₂ Based on the total absorption and the specified absorption or release rate, the current CO ₂ Estimate the total absorption.
[0051]
As shown in FIGS. 14 (a) to 14 (c), CO ₂ The absorption rate of CO is ₂ Absorption material temperature, atmosphere CO ₂ Partial pressure of absorbed CO ₂ Varies with quantity. The same applies to the release rate. Therefore, in step S44, the CO ₂ Absorption material temperature, atmosphere CO ₂ Partial pressure of absorbed CO ₂ CO based on quantity ₂ By specifying the rate of absorption or release of CO ₂ The total absorption is estimated accurately.
[0052]
CO ₂ The absorption / release material can also be used for temperature adjustment such as prevention of overheating of the exhaust emission control device. For example, CO upstream of the exhaust purification catalyst ₂ When absorption / release material is provided and the temperature of the exhaust purification catalyst becomes high, CO ₂ If CO is released, CO ₂ Thus, the combustion reaction in the catalyst is suppressed, and the temperature rise is suppressed. In this case, CO is estimated by the above estimation method. ₂ Once the total amount of absorption is known, CO necessary and sufficient to prevent overheating ₂ It can be determined whether or not is absorbed. Thus, for example, CO ₂ CO for absorbing and releasing materials ₂ The situation where the temperature raising operation for absorbing the fuel is performed more than necessary is prevented, and the fuel efficiency is improved.
[0053]
CO ₂ Absorption material temperature, CO ₂ The concentration and the pressure of the atmosphere are not limited to those obtained by detection by various sensors, and may be estimated from parameters correlated with these. For example, you may estimate from the parameter correlated with the driving | running state of the engine 1. FIG.
[0054]
【The invention's effect】
As described above, according to the present invention, CO generated by the oxidation of particulates. ₂ CO ₂ The absorbent absorbs CO ₂ The absorbent material generates heat, and the heat promotes oxidation of the particulates, resulting in CO ₂ Occurs and this is CO ₂ A cycle of absorption by the absorbent material is realized. As a result, at least part of the amount of heat required for particulate oxidation is reduced to CO. ₂ It can be covered by the heat of the absorbent material, and the amount of fuel consumed during regeneration of the particulate filter can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an engine according to a first embodiment of the present invention.
FIG. 2 is a view showing a filter provided in an exhaust passage of the engine of FIG.
3 shows CO carried on the filter of FIG. ₂ Absorption and release material CO ₂ FIG.
4 is a flowchart showing a procedure of a regeneration control routine executed by an ECU of the engine shown in FIG.
FIG. 5 is a diagram showing a state of a filter while the regeneration control routine of FIG. 4 is being executed.
FIG. 6 is a diagram showing a second embodiment of the present invention.
FIG. 7 is a diagram showing a third embodiment of the present invention.
FIG. 8 is a diagram showing a fourth embodiment of the present invention.
FIG. 9 is a flowchart showing a procedure of a deterioration determination routine executed by the ECU in the fourth embodiment.
FIG. 10 is a view showing a modification of the present invention.
FIG. 11 is a view showing a modification of the present invention.
FIG. 12 is a view showing a modification of the present invention.
13 shows CO executed by the ECU in the modification of FIG. ₂ The flowchart which shows the procedure of absorption total amount estimation routine.
FIG. 14 CO ₂ Absorption and release material CO ₂ The figure which shows the change of an absorption speed.
[Explanation of symbols]
1 engine (internal combustion engine)
4 Exhaust passage
8 Filter

Claims (4)

A CO ₂ absorbent that absorbs CO ₂ in a predetermined absorption temperature range is disposed in or near the particulate filter provided in the exhaust passage of the internal combustion engine, and it is necessary to remove the particulate collected by the particulate filter. When this occurs, the temperature of the CO ₂ absorbent is raised to the absorption temperature range, and the heat generated by the absorption of CO _{2 by} the CO ₂ absorbent in the absorption temperature range is captured by the particulate filter. A method for regenerating a particulate filter, which is used for oxidizing collected particulates. As the CO ₂ absorbent material, as well as absorbed CO ₂ in the absorption temperature range, place the CO ₂ absorption and release material to release the absorbed CO ₂ at a predetermined release temperature range, with the absorption of the CO ₂ 2. The particulate according to claim 1, wherein the generated heat is used for oxidizing the particulate matter collected by the particulate filter, and then the temperature of the CO ₂ absorbing and releasing material is adjusted to the emission temperature range. How to play the filter. A CO ₂ absorbent that absorbs CO ₂ in a predetermined absorption temperature range is disposed in or near the particulate filter provided in the exhaust passage of the internal combustion engine, and it is necessary to remove the particulate collected by the particulate filter. When the temperature of the CO ₂ absorbent is increased, the temperature of the CO ₂ absorbent is increased to the absorption temperature range, the concentration of CO _{2 in} the exhaust gas flowing into the CO ₂ absorbent is increased, and then flows into the particulate filter. A method for regenerating a particulate filter, characterized in that the concentration of CO _{2 in} the exhaust gas is reduced. By burning fuel in the exhaust passage on the upstream side of the particulate filter and the CO ₂ absorbent, the temperature of the CO ₂ absorbent is raised to the absorption temperature range and flows into the CO ₂ absorbent. The method for regenerating a particulate filter according to claim 3, wherein the concentration of CO ₂ in the exhaust gas is increased.

Images