JP2021095879A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

To provide an exhaust emission control device for an internal combustion engine, which can appropriately output microwaves with microwave absorption efficiency in PMs taken into consideration.SOLUTION: An exhaust emission control device for an internal combustion engine comprises: a filter collecting particulate matters included in exhaust gas exhausted from the internal combustion engine; an electromagnetic wave output device outputting electromagnetic waves enabling the temperature of the particulate matters to be raised when predetermined conditions are satisfied; and an absorption efficiency detection device capable of detecting electromagnetic wave absorption efficiency in the particulate matters. The electromagnetic wave output device is controlled in such a manner that the output of the electromagnetic waves is smaller when the electromagnetic wave absorption efficiency detected by the absorption efficiency detection device is high than when it is low.SELECTED DRAWING: Figure 1

Description

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

For example, the exhaust gas of an internal combustion engine contains particulate matter (hereinafter referred to as "PM"), and a filter is used in the exhaust passage to collect PM. Generally, a GPF (gasoline particulate filter) is used in the case of gasoline, and a DPF (diesel particulate filter) is used in the case of diesel.

If the amount of PM collected by the filter exceeds the permissible value, the pressure of the exhaust gas may increase due to clogging, which may deteriorate the fuel consumption of the internal combustion engine. Therefore, it is necessary to remove the PM from the filter. Therefore, there is known an exhaust gas purification device capable of heating PM and removing it by combustion by outputting microwaves to PM collected by a filter (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-200063

The PM collected by the filter contains various components, for example, soot. Furthermore, there are several types of soot, such as coal and activated carbon, depending on the composition, and the relative permittivity differs depending on the type. If the relative permittivity is different, the microwave absorption efficiency will be different even if the same microwave output is applied.

For example, when the microwave absorption efficiency is high (the relative permittivity is large), it is heated faster by absorbing more energy than when the microwave absorption efficiency is low (the relative permittivity is small). Therefore, the temperature of the filter may rise sharply and the filter may be melted. On the contrary, when the microwave absorption efficiency is low, the heating of PM becomes slow. For this reason, the microwave output time is lengthened in order to burn and remove PM, which may worsen the electricity cost.

The present invention has been made in view of the above, and an object of the present invention is to provide an exhaust gas purification device for an internal combustion engine capable of appropriately outputting microwaves in consideration of microwave absorption efficiency in PM. ..

The exhaust gas purification device for an internal combustion engine according to the present invention has a filter that collects particulate matter contained in exhaust gas discharged from the internal combustion engine, and can raise the temperature of the particulate matter when a predetermined condition is satisfied. In an exhaust gas purification device of an internal combustion engine including an electromagnetic wave output device that outputs an electromagnetic wave and an absorption efficiency detection device that can detect the absorption efficiency of the electromagnetic wave in the particulate matter, the electromagnetic wave output device detects the absorption efficiency. When the absorption efficiency of the electromagnetic wave detected by the apparatus is high, the output of the electromagnetic wave is controlled to be smaller than when the absorption efficiency of the electromagnetic wave is low.

Further, the electromagnetic wave output device may be controlled so that the output of the electromagnetic wave becomes small when the absorption efficiency of the electromagnetic wave is equal to or higher than the first predetermined value.

Further, the electromagnetic wave output device may be controlled so that the output of the electromagnetic wave becomes small when the absorption efficiency of the electromagnetic wave is equal to or higher than the first predetermined value and the amount of electromagnetic wave absorption of PM is larger than the predetermined value. ..

Further, the electromagnetic wave output device may be controlled so that the output of the electromagnetic wave is increased when the absorption efficiency of the electromagnetic wave is equal to or less than the second predetermined value smaller than the first predetermined value.

According to the present invention, microwaves can be appropriately output in consideration of the microwave absorption efficiency of PM. For example, when the microwave absorption efficiency is high, the microwave output is controlled to be smaller than when the microwave absorption efficiency is low. As a result, the energy of the microwave absorbed by the PM is reduced, and the heating of the PM is slowed down, so that the temperature of the filter rises sharply and the filter is prevented from being melted. On the other hand, when the microwave absorption efficiency is low, the microwave output is controlled to be larger than when the microwave absorption efficiency is high. As a result, it is possible to prevent the power consumption from deteriorating due to the lengthening of the microwave output time for burning and removing the PM by accelerating the heating of the PM.

FIG. 1 is a block diagram showing a configuration of an exhaust gas purification device for an internal combustion engine according to the first embodiment. FIG. 2 is a front view of the filter according to the first embodiment. FIG. 3 is a side sectional view of the filter according to the first embodiment. FIG. 4 is a diagram showing the amount of PM deposited from the internal combustion engine according to the first embodiment. FIG. 5 is a diagram showing the types of soot contained in PM and the relative permittivity. FIG. 6 is a diagram showing the relationship between the amount of PM deposited and the amount of PM oxidation in PMs having different relative permittivity. FIG. 7 is a diagram showing the relationship between the microwave absorption efficiency and the amount of PM oxidation in the first embodiment. FIG. 8 is a flowchart of the control contents executed by the exhaust gas purification device of the internal combustion engine according to the first embodiment. FIG. 9 is a diagram showing the relationship between the amount of microwave absorption and the amount of PM oxidation in the second embodiment. FIG. 10 is a flowchart of the control contents executed by the exhaust gas purification device of the internal combustion engine according to the second embodiment. FIG. 11 is a timing chart of the control executed by the exhaust gas purification device of the internal combustion engine according to the second embodiment. FIG. 12 is a diagram showing the relationship between the microwave absorption rate and the amount of PM oxidation in the third embodiment. FIG. 13 is a flowchart of the control contents executed by the exhaust gas purification device of the internal combustion engine according to the third embodiment.

Hereinafter, embodiments for carrying out the present invention (hereinafter, referred to as “embodiments”) will be described with reference to the accompanying drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of an exhaust gas purification device for an internal combustion engine according to the first embodiment. This system can also be suitably used as an internal combustion engine in a gasoline engine or a diesel engine.

The internal combustion engine 10 is provided with an exhaust passage 11, and the exhaust passage 11 is provided with a particulate filter (hereinafter referred to as “filter”) 12, an exhaust purification catalyst 13, and a muffler 14 in this order from the upstream.

The filter 12 is a filter capable of collecting PM, and the filter 12 is provided with a temperature sensor 121 capable of detecting the temperature inside the filter 12. As the filter 12, a GPF (gasoline particulate filter) can be used when the internal combustion engine 10 has a gasoline engine, and a DPF (diesel particulate filter) can be used when the filter 12 has a diesel engine.

2 and 3 are block diagrams of the filter according to the first embodiment. FIG. 2 is a front view of the filter according to the first embodiment, and FIG. 3 is a side sectional view of the filter according to the first embodiment.

As shown in FIGS. 2 and 3, the filter 12 has a honeycomb structure and includes a plurality of exhaust flow passages 122 and 123 extending parallel to each other and a partition wall 124 separating the exhaust flow passages 122 and 123 from each other. ..

The exhaust flow passages 122 and 123 are provided by an exhaust inflow passage 122 whose upstream end is open and whose downstream end is closed by a downstream plug 126, and an exhaust outflow passage 123 which is closed by an upstream plug 125 and whose downstream end is open. It is composed. In FIG. 2, the hatched portion indicates the upstream plug 125. Therefore, the exhaust inflow passage 122 and the exhaust outflow passage 123 are alternately arranged via the thin partition wall 124. In other words, the exhaust inflow passage 122 and the exhaust outflow passage 123 are arranged so that each exhaust inflow passage 122 is surrounded by four exhaust inflow passages 123 and each exhaust outflow passage 123 is surrounded by four exhaust inflow passages 122. ..

The partition 124 is formed from a porous material such as ceramics such as cordierite, silicon carbide, silicon nitride, zirconia, titania, alumina, silica, mullite, lithium aluminum silicate, zirconium phosphate. Therefore, as shown by the arrows in FIG. 3, the exhaust first flows into the exhaust inflow passage 122, and then flows out into the adjacent exhaust outflow passage 123 through the pores inside the surrounding partition wall 124. In this way, the partition wall 124 constitutes the inner peripheral surface of the exhaust inflow passage 122.

Returning to FIG. 1, an exhaust purification catalyst 13 for purifying the exhaust gas discharged from the internal combustion engine 10 is provided on the downstream side of the filter 12. As the exhaust gas purification catalyst 13, for example, an oxidation catalyst, a three-way catalyst, a NOx catalyst, or the like can be adopted.

The exhaust gas purification device 20 includes a storage unit 200, an electromagnetic wave output device 201, an absorption efficiency detection device 202, and a control unit 203.

The storage unit 200 includes a ROM (not shown) for storing a processing program and a RAM (not shown) for temporarily storing data, and the storage unit 200 includes a control unit 203 and electrical wiring. It is connected. The storage unit 200 stores a map (FIG. 4) for specifying the PM collection amount previously obtained in an experiment or the like based on the rotation speed Ne of the internal combustion engine and the fuel injection amount Q. Further, in the storage unit 200, α1 is set as a threshold value of the PM accumulation amount that causes a pressure loss due to excessive PM accumulation, and α2 is set as the threshold value of the PM accumulation amount for terminating the control of burning and removing PM. Further, T0 is stored as a threshold value of the filter temperature at which the filter 12 is more likely to be melted.

FIG. 4 is a diagram showing the amount of PM deposited from the internal combustion engine according to the first embodiment. The larger the rotation speed Ne of the internal combustion engine 10 or the larger the fuel injection amount Q, the larger the PM discharged from the internal combustion engine 10, and therefore the larger the PM accumulated amount Mpm. This map is stored in advance in the storage unit 200.

Returning to FIG. 1, the electromagnetic wave output device 201 is connected to the control unit 203 via electrical wiring, and outputs an electromagnetic wave (hereinafter, referred to as “microwave” as an example) to PM deposited on the filter 12. When the electromagnetic wave output device 201 outputs microwaves, the PM is heated, combined with oxygen in the exhaust gas, and burned and removed. The electromagnetic wave output from the electromagnetic wave output device 201 is not limited to microwaves and may be an electromagnetic wave of another wavelength as long as it can heat PM and remove it by combustion.

The absorption efficiency detection device 202 is connected to the control unit 203 via electrical wiring, and is, for example, a power monitor. The absorption efficiency detection device 202 detects the incident microwave intensity output from the electromagnetic wave output device 201 to the PM and the reflected microwave intensity that is reflected and returned without being absorbed by the PM. The difference between the incident microwave intensity and the reflected microwave intensity detected by the absorption efficiency detection device 202 is calculated, and the microwave absorption efficiency η is calculated from the difference value. The calculated microwave absorption efficiency η is transmitted to the control unit 203.

The control unit 203 is connected to the storage unit 200, the electromagnetic wave output device 201, the absorption efficiency detection device 202, and the internal combustion engine control unit 30 via electrical wiring. The control unit 203 acquires the rotation speed Ne and the fuel injection amount Q of the internal combustion engine 10 from the internal combustion engine control unit 30, and refers to the map of the PM accumulation amount Mpm stored in the storage unit 200 to obtain the PM accumulation amount Mpm. To get. Further, the electromagnetic wave output device 201 controls the start and end of the microwave output and the change of the output based on the acquired PM accumulation amount Mpm. The output P is controlled so as not to exceed the output that does not melt due to the excessive temperature rise of the filter 12. The specific control method of the microwave output will be described later.

The internal combustion engine control unit 30 is configured as a microprocessor centered on a CPU (not shown), and has a ROM (not shown) that stores a processing program in addition to the CPU and a RAM (not shown) that temporarily stores data. Not) and. The internal combustion engine control unit 30 is connected to the internal combustion engine 10, the temperature sensor 121, and the control unit 203 via electrical wiring, and acquires the filter temperature from the temperature sensor 121. Further, the internal combustion engine control unit 30 receives signals from various sensors for detecting the state of the internal combustion engine 10, for example, a crank position from a crank position sensor (not shown) and a water temperature sensor for cooling water of the engine 10 (not shown). The operation of the internal combustion engine 10 is controlled based on the cooling water temperature and the like.

FIG. 5 is a diagram showing the types of soot contained in PM and the relative permittivity. PM contains several components. For example, there are types of soot such as Coal (coal) and Activated Carbon (activated carbon) depending on the structure and the like, and the relative permittivity εr differs depending on these types. The energy of the microwave absorbed by a dielectric such as soot is proportional to the relative permittivity εr, that is, when the relative permittivity εr is small, the energy absorbed by soot is small, and when the relative permittivity εr is large, it is absorbed. More energy to do.

FIG. 6 is a diagram showing the relationship between the amount of PM deposited and the amount of PM oxidation in PMs having different relative permittivity. In FIG. 6, the horizontal axis shows the amount of PM deposited Mpm, and the vertical axis shows the amount of PM oxidation (the amount reduced by burning PM). The solid line and the broken line are the results when PMs having different relative permittivity εr are output as microwaves at the same output P for a predetermined time. The solid line shows the PM having a large relative permittivity εr (for example, Carbon nanotube in FIG. 5).
The case where the microwave is output to PM containing a large amount of Coal is shown, and the broken line shows the case where the microwave is output to PM having a small relative permittivity εr (for example, PM containing a large amount of Coal in FIG. 5).

According to FIG. 6, PM having a large relative permittivity εr has a larger amount of PM oxidation than PM having a small relative permittivity εr. This indicates that the larger the relative permittivity εr, the more microwave energy is absorbed. That is, when the relative permittivity εr is large, the microwave absorption efficiency η is high. Further, it is shown that the larger the PM deposition amount Mpm, the larger the PM oxidation amount.

FIG. 7 is a diagram showing the relationship between the microwave absorption efficiency and the amount of PM oxidation in the first embodiment. The vertical axis of the figure shows the PM oxidation rate, and the horizontal axis shows the microwave absorption efficiency η. FIG. 7 shows the amount of PM oxidation when the microwave is output for a predetermined time with the reference output Pbase (dashed line) and the output Plow (solid line) smaller than the reference output for each value of the microwave absorption efficiency η. ..

The reference output Pbase is an output P set in consideration of the amount of PM oxidation with respect to the power consumption when the microwave is output for a predetermined time when the PM deposited on the filter 12 has the reference absorption efficiency ηbase. Further, the reference absorption efficiency ηbase is an absorption efficiency η when the PM having a high microwave absorption efficiency η and the PM having a low microwave absorption efficiency η have a predetermined ratio among the PMs deposited on the filter 12.

According to FIG. 7, the higher the microwave absorption efficiency η, the higher the PM oxidation rate. Further, as shown by the solid line, when the microwave output is small, the amount of microwave absorption of PM is small, so that PM is hard to burn, and the PM oxidation rate is slower than the reference output Pbase.

However, as shown by the alternate long and short dash line, when the same microwave absorption efficiency η is output at the reference output Pbase, the PM oxidation rate is faster than when it is output at the output Plow. As the PM oxidation rate increases, the temperature of the filter 12 also tends to increase. If the temperature of the filter 12 rises too much, there is a high possibility that the filter 12 will be melted.

Therefore, β is set as a threshold value of the PM oxidation rate at which the possibility that the filter 12 is likely to be melted when the microwave is output at the reference output Pbase for a predetermined time is increased. When the PM oxidation rate becomes β or more, the PM oxidation rate becomes slow by outputting microwaves at the output Plow. Further, η1 in FIG. 7 is a threshold value (first predetermined value) set in advance as the microwave absorption efficiency η when the PM oxidation amount becomes β, and is a value higher than the reference microwave absorption efficiency ηbase. η1 is stored in the storage unit 200 in advance.

FIG. 8 is a flowchart of the control contents executed by the exhaust gas purification device of the internal combustion engine according to the first embodiment.

First, in step S101, the control unit 203 acquires the rotation speed Ne and the fuel injection amount Q of the internal combustion engine 10 from the internal combustion engine control unit 30, obtains the PM accumulation amount Mpm using the map of the storage unit 200, and further. The temperature T of the filter 12 is acquired via the internal combustion engine control unit 30, and the process proceeds to step S102.

In step S102, the control unit 203 determines whether or not the acquired PM deposit amount Mpm is larger than α1. When the control unit 203 determines that "PM deposition amount Mpm is α1 or less" (step S102: No), it is determined that it is not necessary to burn and remove PM, and the control unit 203 ends the control flow. When the control unit 203 determines that "the PM deposition amount Mpm is larger than α1" (step S102: Yes), the process proceeds to step S103.

In step S103, the control unit 203 determines whether or not the acquired temperature T of the filter 12 is lower than T0. When the control unit 203 determines that "the temperature T of the filter 12 is T0 or higher" (step 103: No), it is determined that the filter 12 is likely to be melted, and the control unit 203 ends the control flow. When the control unit 203 determines that "the temperature T of the filter 12 is lower than T0" (step 103: Yes), the control unit 203 shifts to step S104.

In step S104, after the control unit 203 acquires the absorption efficiency η from the absorption efficiency detection device 202, the control unit 203 determines whether or not the absorption efficiency η is equal to or higher than the first predetermined value (η1) (step S105). ..

In step 105, when the control unit 203 determines that the absorption efficiency η is less than the first predetermined value (η1) (step 105: No), the control unit 203 outputs microwaves from the electromagnetic wave output device 201 at the reference output Pbase. (Step S107), the control unit 203 shifts to step S108. When the control unit 203 determines that “the absorption efficiency η is equal to or higher than the first predetermined value (η1)” (step 105: Yes), the control unit 203 proceeds to step S106.

In step S106, the control unit 203 outputs microwaves from the electromagnetic wave output device 201 with an output plow smaller than the reference output Pbase, and the control unit 203 shifts to step S108.

In step S108, the control unit 203 calculates the PM oxidation amount (the amount by which the PM accumulation amount Mpm is reduced) based on the pressure difference between the exhaust gas on the inflow side and the outflow side of the filter 12. By subtracting the calculated PM oxidation amount from the PM accumulation amount Mpm acquired in step S101 described above, the PM accumulation amount Mpm at the time of step S108 is calculated, and the control unit 203 shifts to step S109.

In step S109, the control unit 203 determines whether or not the calculated PM accumulation amount Mpm is smaller than α2. When the control unit 203 determines that "PM deposition amount Mpm is α2 or more" (step 109: No), the control unit 203 returns to step S106. When the control unit 203 determines that "PM deposition amount Mpm is less than α2" (step 109: Yes), the control unit 203 ends the microwave output control (step S110), and the control unit 203 controls the control flow. To finish.

As described above, according to the first embodiment, when the microwave absorption efficiency η in PM is higher than the first predetermined value (η1), the PM oxidation rate becomes slow by reducing the microwave output P. , It is possible to suppress the melting damage of the filter 12 due to the rapid temperature rise due to the combustion of PM.

(Embodiment 2)
FIG. 9 is a diagram showing the relationship between the amount of microwave absorption and the PM oxidation rate in the second embodiment. The microwave absorption amount S is a value obtained by integrating the microwave absorption amount S per unit time calculated in consideration of the absorption efficiency η. FIG. 8 shows a case where the reference output Pbase (dashed line) and the output Plow (solid line) smaller than the reference output Pbase are output for a predetermined time with respect to the PM of the reference absorption efficiency ηbase.

According to FIG. 9, the PM oxidation rate increases as the microwave absorption amount S increases. Further, when the microwave output P is small, the microwave absorption amount S of PM is small, so that the PM oxidation rate is slower than that of the reference output Pbase. Further, S1 (predetermined value) is preset as a threshold value of the microwave absorption amount S when the threshold value β of the PM oxidation rate is reached.

FIG. 10 is a flowchart of the control contents executed by the exhaust gas purification device of the internal combustion engine according to the second embodiment. Since steps S201 to S205 are the same as steps S101 to S105 in FIG. 8, description thereof will be omitted.

In step 205, the control unit 203 determines whether or not the absorption efficiency η is equal to or higher than the first predetermined value (η1). When the control unit 203 determines that the absorption efficiency η is less than the first predetermined value (η1) (step 205: No), the control unit 203 outputs the microwave from the electromagnetic wave output device 201 at the reference output Pbase (step S209). ), The control unit 203 shifts to step S210. When the control unit 203 determines that the absorption efficiency η is equal to or higher than the first predetermined value (η1) (step 205: Yes), the control unit 203 proceeds to step S206.

In step S206, the control unit 203 calculates the microwave absorption amount S absorbed by the PM from the acquired PM accumulation amount Mpm, the absorption efficiency η, and the microwave output P, and then the control unit 203 calculates the calculated microwave absorption amount. It is determined whether or not S is equal to or greater than the predetermined value (S1) (step S207).

When the control unit 203 determines in step S207 that "S is less than a predetermined value (S1)" (step 207: No), the control unit 203 outputs microwaves from the electromagnetic wave output device 201 at the reference output Pbase (step S209). ), The control unit 203 shifts to step S210. When the control unit 203 determines that "S is equal to or greater than a predetermined value (S1)" (step 207: Yes), the control unit 203 shifts to step S208.

In step S208, the control unit 203 outputs microwaves from the electromagnetic wave output device 201 with an output plow smaller than the reference output Pbase, and the control unit 203 shifts to step S210.

In step S210, the control unit 203 calculates the PM oxidation amount (the amount by which the PM accumulation amount Mpm is reduced) based on the pressure difference between the exhaust gas on the inflow side and the outflow side of the filter 12. By subtracting the calculated PM oxidation amount from the PM accumulation amount Mpm acquired in step S201 described above, the PM accumulation amount Mpm at the time of step S210 is calculated, and the control unit 203 shifts to step S211.

In step S211 the control unit 203 determines whether or not the calculated PM accumulation amount Mpm is smaller than α2. When the control unit 203 determines that "PM deposition amount Mpm is α2 or more" (step 211: No), the control unit 203 returns to step S206. When the control unit 203 determines that "PM deposition amount Mpm is less than α2" (step 211: Yes), the control unit 203 ends the microwave output control (step S212), and the control unit 203 controls the control flow. To finish.

FIG. 11 is a timing chart of the control executed by the exhaust gas purification device of the internal combustion engine according to the second embodiment. FIG. 10 shows a case where the microwave absorption efficiency η in the deposited PM is equal to or higher than the reference absorption efficiency ηbase. A timing chart showing how the microwave absorption efficiency η, the microwave output P, the PM deposition amount Mpm, and the microwave absorption amount S of PM change with the passage of time is shown.

First, at time T0, the PM deposition amount Mpm became larger than α1, so the microwave was output at the reference output Pbase. Then, as the microwave starts to be output, the microwave absorption amount S of PM starts to increase from the time T0, and the PM accumulation amount starts to decrease.

Then, at time T1, since the microwave absorption amount S of PM becomes S1 or more, the microwave output P is changed to an output Plow smaller than the reference output Pbase. Since the output is changed to Plow, the increase in the microwave absorption amount S of PM is suppressed, and the slope is smaller than that when the output is performed at the reference output Pbase (the period from time T0 to time T1).

Then, at time T2, the PM deposition amount Mpm became smaller than α2, so that the microwave output control was completed.

As described above, according to the second embodiment, when the microwave absorption efficiency η in PM is higher than η1 and the microwave absorption amount S is S1 or more, the microwave output P is reduced. As a result, the rapid temperature rise due to the combustion of PM can be captured more accurately than in the first embodiment, and the output can be changed, so that the filter 12 can be suppressed from being melted. Further, since the reference output Pbase is output until the microwave absorption amount S becomes S1 or more, it is possible to suppress the deterioration of the electricity cost due to the prolongation of the output time due to the reduction of the output.

(Embodiment 3)
FIG. 12 is a diagram showing the relationship between the microwave absorption rate and the PM oxidation rate in the third embodiment. The vertical axis of the figure shows the PM oxidation rate, and the horizontal axis shows the microwave absorption efficiency η. A case where microwaves are output for a predetermined time with a reference output Pbase (dashed line) and an output High (solid line) larger than the reference output Pbase for each value of the microwave absorption efficiency η is shown.

FIG. 12 shows that the lower the microwave absorption efficiency η, the slower the PM oxidation rate. Further, when the microwave output is large, the microwave absorption amount S of PM increases, which indicates that the PM oxidation rate is high.

However, as shown in FIG. 12, when the same microwave absorption efficiency η is output at the reference output Pbase, the PM oxidation rate is slower than when it is output at the output High. In particular, the lower the absorption efficiency, the slower the PM oxidation rate. If the PM oxidation rate is slow, the time to output microwaves is prolonged in order to reduce PM, and the power consumption is deteriorated.

Therefore, γ is set as the threshold value of the PM oxidation rate at which the power consumption due to the output of microwaves begins to deteriorate. When the PM oxidation rate becomes γ or more, the PM oxidation rate increases by outputting at the output High. Further, η2 in FIG. 12 is a threshold value (second predetermined value) preset as the microwave absorption efficiency η when the PM oxidation rate becomes γ, and is a value lower than the reference absorption efficiency ηbase. η2 is stored in the storage unit 200 in advance.

FIG. 13 is a flowchart of the control contents executed by the exhaust gas purification device of the internal combustion engine according to the third embodiment. Since steps S301 to S305 have the same flow as steps S101 to S105 described in FIG. 8, description thereof will be omitted.

In step 305, the control unit 203 determines whether or not the absorption efficiency η is equal to or less than the second predetermined value (η2). When the control unit 203 determines that "the absorption efficiency η is higher than the second predetermined value (η2)" (step 305: No), the control unit 203 outputs the microwave from the electromagnetic wave output device 201 with the reference output Pbase (step 305: No). Step S307), the control unit 203 shifts to step S308. When the control unit 203 determines that “the absorption efficiency η is equal to or less than the second predetermined value (η2)” (step 305: Yes), the control unit 203 proceeds to step S306.

In step S306, the control unit 203 outputs microwaves from the electromagnetic wave output device 201 with an output High larger than the reference output Pbase, and the control unit 203 shifts to step S308.

In step S308, the control unit 203 calculates the PM oxidation amount based on the change in the pressure difference of the exhaust gas between the inflow and outflow of the filter 12, and the calculated PM oxidation amount is calculated from the PM accumulation amount Mpm acquired in step S301. The PM accumulation amount Mpm is calculated by subtraction, and the control unit 203 shifts to step S309.

In step S309, the control unit 203 determines whether or not the PM deposition amount Mpm is smaller than α2. When the control unit 203 determines that "PM deposition amount Mpm is α2 or more" (step 309: No), the control unit 203 returns to step S308. When the control unit 203 determines that "PM deposition amount Mpm is less than α2" (step 309: Yes), the control unit 203 ends the microwave output control by ending the microwave output (step 309: Yes). S310), the control unit 203 ends the control flow.

As described above, according to the third embodiment, when the microwave absorption efficiency η in PM is equal to or less than the second predetermined value (η2), the microwave output is increased. As a result, by increasing the oxidation rate of PM and promoting the combustion of PM, it is possible to suppress the deterioration of power consumption due to the prolongation of the microwave output time.

(Other embodiments)
The present invention should not be limited solely to the embodiments described above. For example, in the first embodiment, the exhaust purification catalyst 13 and the filter 12 are provided separately on the exhaust passage, but the exhaust purification catalyst 13 and the filter 12 may be integrally configured. Further, the exhaust gas purification catalyst 13 may be provided on the upstream side of the filter 12 on the exhaust passage 11.

In the first embodiment, the control unit 203 acquires the rotation speed Ne and the fuel injection amount Q of the internal combustion engine 10 from the internal combustion engine control unit 30, and obtains the PM accumulation amount Mpm from the map of the storage unit 200. The PM accumulation amount Mpm may be estimated from the difference between the air pressures of the intake and the exhaust without using the map of Ne and the fuel injection amount Q, and the above is not limited as long as the PM accumulation amount Mpm can be obtained.

In the first embodiment, when calculating the microwave absorption amount S, the value of the PM accumulation amount Mpm deposited on the filter 12 is used, but the PM accumulation amount with high absorption efficiency may be calculated and used. Further, the output may be reduced when the absorption efficiency η of PM is η1 or more, or when the amount of PM deposited when the absorption efficiency η is η1 or more is a predetermined amount or more. The method of calculating the PM deposition amount having an absorption efficiency η of η1 or more is the ratio of the PM accumulation amount having an absorption efficiency η of η1 or more to the PM accumulation amount Mpm and the microwave absorption efficiency of the entire accumulated PM at that ratio. It is also possible to have a map showing the relationship with η in advance and calculate using the map.

In the first embodiment, the reference absorption efficiency ηbase is set as the electromagnetic wave absorption efficiency when the ratio of the PM having a high electromagnetic wave absorption efficiency and the PM having a low electromagnetic wave absorption efficiency becomes a predetermined ratio among the PMs deposited on the filter 12. The average value of the absorption efficiency of the PM obtained may be set.

10 Internal combustion engine 11 Exhaust passage 12 Filter 121 Temperature sensor 122 Exhaust inflow passage 123 Exhaust outflow passage 124 Partition wall 125 Upstream plug 126 Downstream plug 13 Exhaust purification catalyst 14 Muffler 20 Exhaust purification device 200 Storage unit 201 Electromagnetic wave output device 202 Absorption efficiency detection device 203 Control unit 30 Internal combustion engine control unit

Claims (4)

A filter that collects particulate matter contained in the exhaust gas discharged from the internal combustion engine,
An electromagnetic wave output device that outputs an electromagnetic wave capable of raising the temperature of the particulate matter when a predetermined condition is satisfied, and an electromagnetic wave output device.
An absorption efficiency detector capable of detecting the absorption efficiency of the electromagnetic wave in the particulate matter,
In the exhaust purification device of an internal combustion engine equipped with
The electromagnetic wave output device is characterized in that when the absorption efficiency of the electromagnetic wave detected by the absorption efficiency detection device is high, the output of the electromagnetic wave is controlled to be smaller than when the absorption efficiency of the electromagnetic wave is low. Exhaust purification device. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the electromagnetic wave output device is controlled so that the output of the electromagnetic wave is reduced when the absorption efficiency of the electromagnetic wave is equal to or higher than the first predetermined value. The electromagnetic wave output device is characterized in that when the absorption efficiency of the electromagnetic wave is equal to or higher than the first predetermined value and the amount of electromagnetic wave absorption of PM is larger than the predetermined value, the output of the electromagnetic wave is controlled to be small. The exhaust gas purification device for an internal combustion engine according to claim 2. The electromagnetic wave output device is characterized in that, when the absorption efficiency of the electromagnetic wave is equal to or less than a second predetermined value smaller than the first predetermined value, the output of the electromagnetic wave is controlled to be large. The exhaust gas purification device for an internal combustion engine according to any one.

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