JP2023079029A - Exhaust emission control device - Google Patents

Abstract

To cause sufficient chemical reaction of a target component in exhaust gas while suppressing electric power consumption in an electrochemical reactor.SOLUTION: An exhaust emission control device includes: an electrochemical reactor 45 disposed in an exhaust passage of an internal combustion engine; and a power source device 81 supplying an electric current to the electrochemical reactor. The electrochemical reactor includes a cell 78 having an ion conductive solid electrolyte layer 75 and an anode layer 76 and a cathode layer 77 that are disposed on the surface of the solid electrolyte layer, and causes chemical reaction of a target component in exhaust gas flowing in the exhaust passage when an electric current flows in the anode layer and the cathode layer. The power source device supplies an electric current to be caused to flow in the anode layer and the cathode layer. The cell and the power source device are configured so that in a region of the cell where a concentration of the target component in surrounding exhaust gas is relatively large, an electric current flowing between the anode layer and the cathode layer becomes large, compared to in a region of the cell where the concentration of the target component in the surrounding exhaust gas is relatively small.SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD The present disclosure relates to an exhaust purification system having an electrochemical reactor.

Conventionally, there has been known an exhaust purification device having an electrochemical reactor comprising a plurality of cells each having an ion-conducting solid electrolyte layer and an anode layer and a cathode layer arranged on the surface of the solid electrolyte layer (for example, patent Reference 1). In such an electrochemical reactor, when an electric current is supplied to the electrochemical reactor so as to flow from the anode layer through the solid electrolyte layer to the cathode layer, NOx is reduced to _N2 and purified on the cathode layer.

In particular, in the electrochemical reactor described in Patent Document 1, when the amount of exhaust gas increases, the amount of current supplied to the electrochemical reactor is increased, and when the amount of exhaust gas decreases, the amount of current supplied to the electrochemical reactor is increased. The amount of current flowing through is reduced.

JP 2009-138522 A

By the way, in the electrochemical reactor described in Patent Literature 1, a current flows uniformly over the entire surfaces of the anode layer and the cathode layer. Therefore, oxygen ions move uniformly within the solid electrolyte layer from the cathode layer to the anode layer.

On the other hand, since the target component (for example, NOx) purified by the electrochemical reactor is purified by the electrochemical reactor, around the region downstream of the electrochemical reactor, around the region upstream of the electrochemical reactor Its concentration is relatively low. Therefore, setting the current flowing between the anode and cathode layers to match the concentration of the component of interest around the region upstream of the electrochemical reactor results in excessive production of oxygen ions in the region downstream of the electrochemical reactor. and the power consumption becomes excessively large. On the other hand, if the current flowing between the anode layer and the cathode layer is set to match the concentration of the component to be purified around the region downstream of the electrochemical reactor, it will be sufficiently targeted around the region upstream of the electrochemical reactor. Ingredients cannot be cleaned.

In view of the above problems, an object of the present disclosure is to provide an electrochemical reactor capable of sufficiently chemically reacting target components in exhaust gas while suppressing power consumption in the electrochemical reactor.

The gist of the present disclosure is as follows.

(1) An exhaust purification system having an electrochemical reactor arranged in an exhaust passage of an internal combustion engine and a power supply device for supplying current to the electrochemical reactor,
The electrochemical reactor comprises a cell having an ionically conductive solid electrolyte layer and anode and cathode layers disposed on the surface of the solid electrolyte layer, and an electric current is passed through the anode and cathode layers. and the target component in the exhaust gas flowing through the exhaust passage chemically reacts,
The power supply supplies a current to flow through the anode layer and the cathode layer,
In the cell or the power supply, a region of the cell where the concentration of the target component in the surrounding exhaust gas is relatively high is higher than a region of the cell where the concentration of the target component in the surrounding exhaust gas is relatively low. , an exhaust purification device configured to increase the current flowing between the anode layer and the cathode layer.
(2) In the electrochemical reactor and the power supply, in the cell region relatively upstream in the exhaust gas flow direction, compared to the cell region relatively downstream in the exhaust gas flow direction, The exhaust purification device according to (1) above, which is configured to increase the current flowing between the anode layer and the cathode layer.
(3) the solid electrolyte layer is arranged between the anode layer and the cathode layer and is arranged to extend along the flow of the exhaust gas;
The solid electrolyte layer is formed such that the thickness on the relatively upstream side in the flow direction of the exhaust gas is smaller than the thickness on the relatively downstream side in the flow direction of the exhaust gas. ).
(4) The exhaust purification device according to (3) above, wherein the solid electrolyte layer is formed so as to continuously increase in thickness from the upstream side toward the downstream side in the flow direction of the exhaust gas.
(5) The exhaust purification device according to (3) above, wherein the solid electrolyte layer is formed so as to become thicker in stages from the upstream side toward the downstream side in the flow direction of the exhaust gas.
(6) the cell has an upstream cell and a downstream cell that are electrically divided in the flow direction of the exhaust gas;
In the power supply device, the voltage applied between the anode layer and the cathode layer of the upstream cell is higher than the voltage applied between the anode layer and the cathode layer of the downstream cell, The exhaust purification device according to any one of (2) to (5) above, which supplies the electric current.

According to the present disclosure, there is provided an electrochemical reactor capable of sufficiently chemically reacting target components in exhaust gas while suppressing power consumption in the electrochemical reactor.

FIG. 1 is a schematic configuration diagram of an internal combustion engine. FIG. 2 is a cross-sectional side view of the reactor. FIG. 3 is a schematic diagram of an exhaust purification device showing an enlarged partition wall of a reactor. FIG. 4 is an enlarged sectional view of each cell. FIG. 5 is a schematic view, similar to FIG. 3, of the exhaust purification system showing an enlarged view of the partition wall of the reactor. FIG. 6 is a schematic view, similar to FIG. 3, of the exhaust purification system showing an enlarged view of the partition wall of the reactor.

Hereinafter, embodiments will be described in detail with reference to the drawings. In the following description, the same reference numerals are given to the same constituent elements.

・First embodiment <Description of the entire internal combustion engine>
A configuration of an internal combustion engine 1 equipped with an electrochemical reactor according to the first embodiment will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of an internal combustion engine 1. As shown in FIG. As shown in FIG. 1, the internal combustion engine 1 includes an engine body 10, a fuel supply device 20, an intake system 30, an exhaust system 40, and a control device 50.

The engine body 10 includes a cylinder block in which a plurality of cylinders 11 are formed, a cylinder head in which intake ports and exhaust ports are formed, and a crankcase. A piston is arranged in each cylinder 11, and each cylinder 11 communicates with an intake port and an exhaust port.

The fuel supply device 20 includes a fuel injection valve 21 , a delivery pipe 22 , a fuel supply pipe 23 , a fuel pump 24 and a fuel tank 25 . A fuel injection valve 21 is arranged in the cylinder head so as to inject fuel directly into each cylinder 11 . The fuel pressure-fed by the fuel pump 24 is supplied to the delivery pipe 22 through the fuel supply pipe 23 and injected into each cylinder 11 from the fuel injection valve 21 .

The intake system 30 includes an intake manifold 31 , an intake pipe 32 , an air cleaner 33 , a compressor 34 of the supercharger 5 , an intercooler 35 and a throttle valve 36 . An intake port of each cylinder 11 communicates with an air cleaner 33 via an intake manifold 31 and an intake pipe 32 . In the intake pipe 32, a compressor 34 of the supercharger 5 that compresses and discharges intake air, and an intercooler 35 that cools the air compressed by the compressor 34 are provided. The throttle valve 36 is driven to open and close by a throttle valve drive actuator 37 .

The exhaust system 40 includes an exhaust manifold 41 , an exhaust pipe 42 , a turbine 43 of the supercharger 5 , an exhaust purification catalyst 44 and an electrochemical reactor (hereinafter simply referred to as “reactor”) 45 . An exhaust port of each cylinder 11 communicates with an exhaust purification catalyst 44 via an exhaust manifold 41 and an exhaust pipe 42 , and the exhaust purification catalyst 44 communicates with a reactor 45 via an exhaust pipe 42 . The exhaust purification catalyst 44 is, for example, a three-way catalyst or a NOx storage reduction catalyst, and purifies components in the exhaust gas such as NOx and unburned HC when the temperature reaches a certain activation temperature or higher. A turbine 43 of the supercharger 5 that is rotationally driven by the energy of the exhaust gas is provided in the exhaust pipe 42 . The exhaust port, exhaust manifold 41, exhaust pipe 42, exhaust purification catalyst 44 and reactor 45 form an exhaust passage. Therefore, the reactor 45 is arranged in the exhaust passage. The exhaust purification catalyst 44 may be provided downstream of the reactor 45 in the flow direction of the exhaust gas (hereinafter referred to as "exhaust flow direction").

The control device 50 includes an electronic control unit (ECU) 51 and various sensors. Various sensors include, for example, a flow rate sensor 52 that detects the flow rate of intake gas flowing through the intake pipe 32, an air-fuel ratio sensor 53 that detects the air-fuel ratio of the exhaust gas, and a NOx concentration of the exhaust gas that flows into the reactor 45. A NOx sensor 54 and the like are included, and these sensors are connected to the ECU 51 . The various sensors also include a load sensor 55 for detecting the load of the internal combustion engine 1 and a crank angle sensor 56 for detecting the engine speed. These sensors are also connected to the ECU 51 . The ECU 51 is also connected to actuators that control the operation of the internal combustion engine 1 . In the example shown in FIG. 1, the ECU 51 is connected to the fuel injection valve 21, the fuel pump 24 and the throttle valve driving actuator 37 and controls these actuators.

<Configuration of exhaust purification device>
Next, the configuration of the exhaust purification system including the reactor 45 according to the present embodiment will be described with reference to FIGS. 2 to 4. FIG. FIG. 2 is a cross-sectional side view of reactor 45 . As shown in Figure 2, the reactor 45 comprises a septum 71 and a passageway 72 defined by the septum. The partition walls 71 are composed of a plurality of first partition walls extending parallel to each other in the exhaust flow direction (that is, the axial direction of the reactor 45), and a plurality of second partition walls extending perpendicular to and parallel to the first partition walls in the exhaust flow direction. and a partition. The passage 72 is defined by the first partition wall and the second partition wall and extends parallel to each other in the exhaust flow direction. Therefore, the reactor 45 according to this embodiment has a honeycomb structure. Exhaust gas entering the reactor 45 flows through a plurality of passages 72 . In addition, the partition 71 may be formed by only a plurality of partitions extending parallel to each other, and may be formed so as not to include partitions perpendicular to the plurality of partitions.

FIG. 3 is a schematic diagram of the exhaust purification system showing an enlarged partition wall 71 of the reactor 45. As shown in FIG. The arrows in the figure indicate the direction of exhaust gas flow through the reactor 45 . As shown in FIG. 3, the partition wall 71 of the reactor 45 comprises a solid electrolyte layer 75, an anode layer 76 disposed on one surface of the solid electrolyte layer 75, and a surface opposite to the surface on which the anode layer 76 is disposed. and a cathode layer 77 disposed on the surface of the solid electrolyte layer 75 on the side. The solid electrolyte layer 75 is thus arranged between the anode layer 76 and the cathode layer 77 . These solid electrolyte layer 75, anode layer 76 and cathode layer 77 form a cell 78 and each extend along the exhaust flow.

Solid electrolyte layer 75 includes a porous solid electrolyte having proton conductivity. Solid electrolytes include, for example, perovskite-type metal oxides MM′ _1-x R _x O _3-α (M=Ba, Sr, Ca, M′=Ce, Zr, R=Y, Yb, for example, SrZr _x Yb _1-x O _3-α , SrCeO ₃ , BaCeO ₃ , CaZrO ₃ , SrZrO ₃ etc.), phosphates (eg SiO ₂ —P ₂ O ₅ based glasses etc.), metal-doped Sn _x In _1-x P ₂ O ₇ (eg SnP ₂ O ₇ etc.) or zeolites (eg ZSM-5) are used. In this embodiment, the solid electrolyte layer 75 contains a solid electrolyte having proton conductivity, but may contain a solid electrolyte having other ion conductivity such as oxygen ion conductivity.

Anode layer 76 and cathode layer 77 both comprise a noble metal such as Pt, Pd or Rh. Also, the anode layer 76 includes a material capable of retaining (ie, capable of adsorbing and/or absorbing) water molecules. Specific examples of substances capable of holding water molecules include zeolite, silica gel, and activated alumina. Cathode layer 77, on the other hand, includes a material capable of retaining (that is, capable of adsorbing and/or absorbing) NOx. Specific examples of substances capable of retaining NOx include alkali metals such as K and Na, alkaline earth metals such as Ba, and rare earth metals such as La.

Further, as can be seen from FIG. 3, in the present embodiment, the solid electrolyte layer 75 of each cell 78 is formed so as to continuously thicken from the upstream side toward the downstream side in the direction of flow of the exhaust gas. Therefore, in the present embodiment, the solid electrolyte layer 75 is formed such that the thickness on the upstream side in the exhaust flow direction is smaller than the thickness on the relatively downstream side in the exhaust flow direction. Therefore, the solid electrolyte layer 75 is thinnest at the upstream end in the exhaust flow direction and thickest at the downstream end in the exhaust flow direction.

On the other hand, as can be seen in FIG. 3, in this embodiment the anode layer 76 and cathode layer 77 of each cell 78 have a uniform thickness. Therefore, each cell 78 is formed such that its thickness continuously increases from the upstream side toward the downstream side in the exhaust flow direction.

In this embodiment, among the plurality of cells 78 defining one passageway 72 , some cells 78 have anode layers 76 exposed to this passageway 72 and other cells 78 have cathode layers 77 exposed to this passageway 72 . is exposed. Reactor 45 is thus configured such that each passageway 72 exposes both the anode layer 76 and the cathode layer 77 .

In addition, the exhaust purification device includes a power supply device 81 and an ammeter 82 .

The power supply device 81 is connected to the reactor 45 and supplies current to the reactor 45 . That is, the power supply supplies current to flow through the anode layer 76 and the cathode layer 77 . The positive electrode of power supply 81 is connected to anode layer 76 and the negative electrode of power supply 81 is connected to cathode layer 77 . The power supply device 81 may be connected in parallel or in series with the plurality of cells 78 . The power supply 81 is configured so that the voltage applied between the anode layer 76 and the cathode layer 77 can be varied. The power supply device 81 is also configured to change the magnitude of the current supplied to the reactor 45 so as to flow from the anode layer 76 through the solid electrolyte layer 75 to the cathode layer 77 .

Ammeter 82 detects the current supplied from power supply 81 to cell 78 of reactor 45 . The ammeter 82 is connected in series with the power supply device 81 .

The power supply device 81 is connected to the ECU 51 and controlled by the ECU 51 . In this embodiment, the power supply device 81 controls the voltage so that the current value detected by the ammeter 82 becomes the target value, for example. Also, the ammeter 82 is connected to the ECU 51 and transmits the detected current value to the ECU 51 .

<Purification by reactor>
The reactions that occur in the reactor 45 configured as described above will be described with reference to FIG. FIG. 4 is an enlarged cross-sectional view of each cell 78. As shown in FIG. In the reactor 45, when a current is supplied from the power supply device 81 to the anode layer 76 and the cathode layer 77, the reactions represented by the following formulas occur in the anode layer 76 and the cathode layer 77, respectively.
Anode side 2H ₂ O→4H ⁺ +O ₂ +4e ⁻
Cathode side 2NO+4H ⁺ +4e ^- →N ₂ +2H ₂ O

That is, in the anode layer 76, water molecules retained in the anode layer 76 are electrolyzed to generate oxygen and protons. The produced oxygen is released into the exhaust gas, and the produced protons move through the solid electrolyte layer 75 from the anode layer 76 to the cathode layer 77 . In the cathode layer 77, NO retained in the cathode layer 77 reacts with protons and electrons to produce nitrogen and water molecules.

Therefore, according to this embodiment, NO in the exhaust gas can be reduced to N ₂ and purified by applying current from the power supply device 81 of the reactor 45 to the anode layer 76 and the cathode layer 77 .

In the anode layer 76, when unburned HC, CO, etc. are contained in the exhaust gas, oxygen ions react with these HC, CO, etc. according to the following formula to produce carbon dioxide and water. be done. Since unburned HC contains various components, it is expressed as C _m H _n in the following reaction formula. Therefore, according to this embodiment, HC and CO in the exhaust gas can be oxidized and purified by applying current from the power supply device 81 of the reactor 45 to the anode layer 76 and the cathode layer 77 .
_CmHn +(2m+0.5n) ^O2- → _mCO2 + _0.5nH2O + ₍ 4m+n) ^e-
CO+ ^O2- → _CO2 + ^2e-

In this way, when current flows through the anode layer 76 and the cathode layer 77, the reactor 45 chemically reacts and purifies components to be purified (unburned HC, CO, NOx, etc.) in the exhaust gas flowing through the exhaust passage. . Also, as noted above, in this embodiment the reactor 45 is positioned such that each passageway 72 exposes both the anode layer 76 and the cathode layer 77 . Therefore, most of the passages 72 defined by the cells 78 are cleaned of NOx and HC and CO in the exhaust gas by applying current from the power supply 81 .

<Effect/Modification>
When the exhaust gas flows into the reactor 45, purification target components (unburned HC, CO, NOx, etc.) in the exhaust gas are purified. Therefore, in the vicinity of the region downstream of each cell 78 of the reactor 45 , the concentration of the purification target component in the exhaust gas is lower than in the vicinity of the region near the upstream side of each cell of the reactor 45 . In particular, the concentration of the purification target component in the exhaust gas flowing through the reactor 45 basically gradually decreases from the upstream side to the downstream side of the reactor 45 .

On the other hand, in the present embodiment, the solid electrolyte layer 75 of each cell 78 is formed so as to continuously thicken from the upstream side toward the downstream side in the exhaust flow direction. Therefore, when a current is supplied to the anode layer 76 and the cathode layer 77 on both sides of the solid electrolyte layer 75, protons in the upstream region of the solid electrolyte layer 75 easily move from the anode layer 76 to the cathode layer 77, and the solid electrolyte layer 75 It is difficult for protons to move from the anode layer 76 to the cathode layer 77 in the region downstream of the . Therefore, when a current is supplied from the power supply device 81 to the anode layer 76 and the cathode layer 77 of each cell 78, a relatively large number of protons move in the region on the upstream side of the solid electrolyte layer 75, causing a large current to flow. Relatively few protons move in the region downstream of the electrolyte layer 75 and a small current flows. In particular, in this embodiment, when current is supplied from the power supply device 81 to the anode layer 76 and the cathode layer 77 of each cell 78, the movement of protons is small continuously from the upstream side to the downstream side of the solid electrolyte layer 75, Therefore, the current that flows becomes smaller.

Therefore, in the present embodiment, the reactor 45 is arranged such that, in the region of the cells 78 relatively upstream in the exhaust flow direction, the anode layer 76 and the region of the cells 78 relatively downstream in the exhaust flow direction are closer to each other. It is configured such that the current (ion current) flowing between it and the cathode layer 77 is increased. In particular, in this embodiment, the reactor 45 is configured such that the current (ion current) flowing between the anode layer 76 and the cathode layer 77 decreases from the upstream side to the downstream side in the flow direction of the exhaust gas. .

Then, as described above, the concentration of the component to be purified in the exhaust gas flowing through the reactor 45 gradually decreases from the upstream side to the downstream side of the reactor 45 . Therefore, in the present embodiment, the reactor 45 is configured such that in the region of the cell 78 where the concentration of the purification target component in the surrounding exhaust gas is relatively high, the concentration of the purification target component in the surrounding exhaust gas is relatively low. It can be said that the current flowing between the anode layer 76 and the cathode layer 77 is larger than that in the region 78 . In particular, in the present embodiment, the reactor 45 can be said to be configured such that the current flowing between the anode layer 76 and the cathode layer 77 increases as the concentration of the component to be purified in the surrounding exhaust gas increases. .

As a result, many oxygen ions are generated in the anode layer 76 and many protons are released in the cathode layer 77 in regions where there are many components to be purified in the exhaust gas. As a result, it is possible to sufficiently purify the purification target components in a region where there are many purification target components in the exhaust gas. On the other hand, in a region where the amount of purification target components in the exhaust gas is small, the amount of generated oxygen ions and released protons is small, but the purification target components can be sufficiently purified. In addition, in a region where there are few components to be purified in the exhaust gas, the amount of generated oxygen ions and released protons is small, so the power used to release oxygen ions and protons is suppressed. Therefore, according to the present embodiment, the target components in the exhaust gas can be sufficiently chemically reacted and purified while suppressing power consumption in the reactor 45 .

In the above-described embodiment, in all the cells 78 of the reactor 45, the thickness of the solid electrolyte layer 75 differs between the upstream side and the downstream side in the flow direction of the exhaust gas. However, only some cells 78 of the reactor 45 are formed so that the thickness of the solid electrolyte layer 75 varies between the upstream side and the downstream side in the exhaust gas flow direction, and the remaining cells 78 are formed so that the thickness of the solid electrolyte layer 75 varies. may be formed so as to be uniform.

Also, in the above embodiments, the anode layer 76 and the cathode layer 77 have a uniform thickness. However, the anode layer 76 and cathode layer 77 do not necessarily have a uniform thickness and may have different thicknesses in different regions. For example, the anode layer 76 and the cathode layer 77 may be formed so as to become thinner continuously from the upstream side to the downstream side in the exhaust gas flow direction. In this case, the anode layer 76 and the cathode layer 77 may be formed so that the thickness of each cell 78 is uniform throughout.

Further, in the above-described embodiment, the solid electrolyte layer 75 is formed so as to continuously increase in thickness from the upstream side toward the downstream side in the exhaust gas flow direction. However, the solid electrolyte layer 75 may be formed to have a different shape, for example as shown in FIG.

FIG. 5 is a schematic view, similar to FIG. 3, of the exhaust purification system showing an enlarged partition wall 71 of the reactor 45. As shown in FIG. In the example shown in FIG. 5, the solid electrolyte layer 75 is formed so as to become thicker in stages from the upstream side toward the downstream side in the exhaust gas flow direction. In particular, in the example shown in FIG. 5, the solid electrolyte layer 75 is formed such that both the surface on the anode layer 76 side and the surface on the cathode layer 77 side swell in stages from the upstream side toward the downstream side in the exhaust flow direction. It is Further, in the example shown in FIG. 5, the solid electrolyte layer 75 is formed so as to increase in thickness in three stages from the upstream side toward the downstream side in the exhaust gas flow direction. Further, in the example shown in FIG. 5, the anode layer 76 and the cathode layer 77 are formed so as to become thinner in steps from the upstream side to the downstream side in the exhaust gas flow direction. are formed to be uniform.

Note that the solid electrolyte layer 75 may be formed so as to be thickened in a plurality of steps other than three steps. Further, the solid electrolyte layer 75 may be formed so that only one surface of the anode layer 76 side and the cathode layer 77 side swells stepwise. Also, the anode layer 76 and the cathode layer 77 may have a uniform thickness.

- Second embodiment Next, with reference to Fig. 6, an exhaust gas purification device according to a second embodiment will be described. Since the configuration of the exhaust purification system according to the second embodiment is basically the same as the configuration of the exhaust purification system according to the first embodiment, the points different from the configuration of the exhaust purification system according to the first embodiment will be described below. Mainly explained.

FIG. 6 is a schematic view, similar to FIG. 3, of the exhaust purification system showing an enlarged partition wall 71 of the reactor 45. As shown in FIG. The arrows in the figure indicate the exhaust flow direction through the reactor 45 .

As shown in FIG. 6, the cell 78 forming each partition 71 has two partial cells, an upstream cell 78a and a downstream cell 78b, which are divided in the exhaust flow direction. The upstream cell 78a has an upstream solid electrolyte layer 75a, an upstream anode layer 76a, and an upstream cathode layer 77a. The upstream anode layer 76a and the upstream cathode layer 77a are formed on both surfaces of the upstream solid electrolyte layer 75a. placed in Similarly, the downstream cell 78b has a downstream solid electrolyte layer 75b, a downstream anode layer 76b, and a downstream cathode layer 77b. Placed on both surfaces. An insulator 79 is arranged between the upstream cell 78a and the downstream cell 78b. In this embodiment, the solid electrolyte layers 75a and 75b are formed with a uniform thickness.

The exhaust emission control device also has an upstream power supply device 81a, a downstream power supply device 81b, an upstream ammeter 82a, and a downstream ammeter 82b. The upstream power supply device 81a and the upstream ammeter 82a are connected to the upstream cell 78a to supply current to the upstream cell 78a. On the other hand, the downstream power source device 81b and the downstream ammeter 82b are connected to the downstream cell 78b to supply current to the downstream cell 78b. Note that the upstream power supply device 81a and the downstream power supply device 81b can be integrally configured as one power supply device if they can supply currents at different voltages to the upstream cell 78a and the downstream cell 78b. may

In this embodiment, the voltage applied to the upstream cell 78a by the upstream power supply device 81a is higher than the voltage applied to the downstream cell 78b by the downstream power supply device 81b. Therefore, the applied voltage between the upstream anode layer 76a and the upstream cathode layer 77a of the upstream cell 78a is higher than the applied voltage between the downstream anode layer 76b and the downstream cathode layer 77b of the downstream cell 78b. big.

In particular, in this embodiment, the ECU 51 of the control device 50 uses the power supply devices 81a and 81b based on the flow rate of the exhaust gas calculated based on the output of the flow rate sensor 52 and the outputs of the air-fuel ratio sensor 53 and the NOx sensor 54. It controls the voltage applied and the amount of current drawn from these power supplies. In this embodiment, when controlling these voltages and currents, the ECU 51 always causes the upstream power supply device 81a to apply the voltage to the upstream cell 78a and the downstream power supply device 81b to apply the voltage to the downstream cell 78b. higher than the voltage to be applied.

As a result, relatively many protons move between the upstream anode layer 76a and the upstream cathode layer 77a of the upstream cell 78a, and a large current flows. Relatively few protons move between the side cathode layer 77b and a small current flows. Therefore, in the present embodiment, the reactor 45 has more anode layer 76 and cathode layer in the region of the cells 78 relatively upstream in the exhaust flow direction than in the region of the cells 78 relatively downstream in the exhaust flow direction. 77 so that the current (ion current) flowing between them is large. As a result, in the present embodiment, as in the first embodiment, the target components in the exhaust gas can be sufficiently chemically reacted and purified while suppressing power consumption in the reactor 45 .

In the above embodiment, each cell 78 is divided into two partial cells, an upstream cell 78a and a downstream cell 78b. However, each cell 78 may be divided into a plurality of sub-cells of three or more in the exhaust flow direction. In this case, a higher voltage is supplied to the upstream partial cell.

Further, in the above embodiment, the insulator 79 is provided between the upstream cell 78a and the downstream cell 78b. However, other configurations may be used as long as the upstream cell 78a and the downstream cell 78b are electrically insulated. Therefore, for example, the upstream cell 78a and the downstream cell 78b may be spaced apart.

Furthermore, the exhaust purification device according to the second embodiment may be combined with the exhaust purification device according to the first embodiment. Therefore, each cell may be divided into a plurality of partial cells in the exhaust flow direction while varying the thickness of each cell in the exhaust flow direction, and a different voltage may be applied to each partial cell.

Although preferred embodiments according to the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims.

Reference Signs List 1 internal combustion engine 10 engine body 20 fuel supply device 30 intake system 40 exhaust system 50 control device 44 exhaust purification catalyst 45 electrochemical reactor 71 partition wall 72 passage 75 solid electrolyte layer 76 anode layer 77 cathode layer 78 cell 81 power supply device

Claims (6)

An exhaust gas purification device comprising an electrochemical reactor arranged in an exhaust passage of an internal combustion engine and a power supply device for supplying current to the electrochemical reactor,
The electrochemical reactor comprises a cell having an ionically conductive solid electrolyte layer and anode and cathode layers disposed on the surface of the solid electrolyte layer, and an electric current is passed through the anode and cathode layers. and the target component in the exhaust gas flowing through the exhaust passage chemically reacts,
The power supply supplies a current to flow through the anode layer and the cathode layer,
In the cell or the power supply, a region of the cell where the concentration of the target component in the surrounding exhaust gas is relatively high is higher than a region of the cell where the concentration of the target component in the surrounding exhaust gas is relatively low. , an exhaust purification device configured to increase the current flowing between the anode layer and the cathode layer. In the electrochemical reactor and the power supply, in the region of the cell on the relatively upstream side in the flow direction of the exhaust gas, the anode layer is higher than in the region of the cell on the relatively downstream side in the flow direction of the exhaust gas. 2. The exhaust gas purification device according to claim 1, configured to increase the current flowing between the cathode layer and the cathode layer. The solid electrolyte layer is arranged between the anode layer and the cathode layer and is arranged to extend along the flow of the exhaust gas,
3. The solid electrolyte layer is formed such that the thickness on the upstream side in the flow direction of the exhaust gas is smaller than the thickness on the relatively downstream side in the flow direction of the exhaust gas. The exhaust purification device according to . 4. The exhaust purification device according to claim 3, wherein said solid electrolyte layer is formed so as to be continuously thickened from upstream to downstream in the flow direction of exhaust gas. 4. The exhaust purification device according to claim 3, wherein said solid electrolyte layer is formed so as to become thicker stepwise from the upstream side toward the downstream side in the flow direction of the exhaust gas. The cell has an upstream cell and a downstream cell that are electrically divided in the flow direction of the exhaust gas,
In the power supply device, the voltage applied between the anode layer and the cathode layer of the upstream cell is higher than the voltage applied between the anode layer and the cathode layer of the downstream cell, The exhaust emission control system according to any one of claims 2 to 5, wherein said electric current is supplied.

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