Exhaust emission control device of internal combustion engine

Abstract

To efficiently consume electric power for heating a dispersion plate.SOLUTION: A dispersion plate 200 for dispersing urea water injected from an urea addition valve is fixed to an exhaust passage 52. Blade portions 201 to 204 of the dispersion plate 200 are provided with electric heaters H1 to H4 connected in series by a power line PL and further provided with dispersion plate temperature sensors 115a to 115d. Bypass power lines BL1 to BL4 respectively bypassing the electric heaters H1 to H4 are provided with switches SW1 to SW4. When a temperature detected by the dispersion plate temperature sensors 115a to 115d is a prescribed value or more, the corresponding switches SW1 to SW4 is switched ON (closing), and energization of the corresponding electric heaters H1 to H4 is stopped.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an exhaust gas purification device for an internal combustion engine. [Background technology]

[0002] Japanese Patent Publication No. 2020-172912 (Patent Document 1) describes a method in which urea water is supplied from a urea addition valve to an exhaust passage of an internal combustion engine, and ammonia (NH3) generated by decomposition of the urea water is used as a reducing agent to reduce and purify NOx in the exhaust gas using a selective reduction catalyst. In this Patent Document 1, a dispersion plate that can be heated by an electric heater is provided between the urea addition valve and the selective reduction catalyst, and the amount of electricity supplied to the electric heater is controlled so that the temperature of the dispersion plate is higher than a predetermined lower limit temperature. This ensures that the urea water supplied from the urea addition valve is decomposed (converted) into ammonia and supplied to the selective reduction catalyst. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-172912 A Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the entire dispersion plate is heated by an electric heater (electrical heating element). When the urea water added from the urea addition valve is dispersed by the dispersion plate, the temperature of the portion of the dispersion plate where the urea water collides drops and may fall below a lower limit temperature. If the temperature of the dispersion plate drops, the decomposition reaction of the urea water to ammonia is suppressed, so it is desirable to raise the temperature of the portion where the urea water collides to above the lower limit temperature as soon as possible.

[0005] When the amount of electricity supplied to the electric heating element is increased in order to raise the temperature of the portion where the urea water impinges, the temperature of the entire dispersion plate rises, and therefore there is a concern that the temperature of the portion where the urea water does not impinge will rise excessively, and the power supplied to the electric heating element will not be consumed effectively.

[0006] An object of the present disclosure is to efficiently consume the power for heating the dispersion plate. [Means for solving the problem]

[0007] The exhaust purification device for an internal combustion engine of the present disclosure includes a selective reduction catalyst provided in an exhaust passage, a urea supply means provided upstream of the selective reduction catalyst and supplying urea water to the exhaust passage, a dispersion plate provided in the exhaust passage between the urea supply means and the selective reduction catalyst and dispersing the urea water, a plurality of electric heating units provided in the dispersion plate, a plurality of temperature detection units provided on the dispersion plate corresponding to the plurality of electric heating units and detecting temperatures of portions heated by the plurality of electric heating units, and a control unit that controls the supply of electricity to the corresponding electric heating unit based on the temperatures detected by the temperature detection units.

[0008] According to this configuration, the urea water is dispersed by a dispersion plate provided in the exhaust passage between the urea supply means and the selective reduction catalyst and flows into the selective reduction catalyst. The dispersion plate is provided with a plurality of electric heating units. The electric heating units heat the dispersion plate, and the temperature of the dispersion plate increases. The heat of the dispersion plate promotes atomization and decomposition of the urea water. The temperature of the dispersion plate at the points where the urea water collides decreases.

[0009] The temperature detection unit detects the temperatures of the areas heated by the multiple electric heating units. The control unit controls the energization of the corresponding electric heating unit based on the temperatures detected by the temperature detection unit. This makes it possible to control the energization of the electric heating unit corresponding to the area where the urea water impinges and the temperature is reduced, making it possible to efficiently consume the power for heating the dispersion plate.

[0010] Preferably, the electric heating units are resistive heaters, and a switch is provided on a bypass power line that bypasses each of the electric heating units, and when the temperature detected by the temperature detection unit reaches or exceeds a predetermined value, the control unit may close the switch that bypasses the corresponding electric heating unit, thereby stopping the flow of electricity to the electric heating unit.

[0011] According to this configuration, resistance heating that generates heat by Joule heat is used as the electric heating unit. A switch is provided on the bypass power line for each electric heating unit. When the switch is closed, the current supplied to the electric heating unit flows to the bypass power line, and the power supply to the electric heating unit is stopped. Therefore, when the temperature detected by the temperature detection unit reaches or exceeds a predetermined value, the power supply to the electric heating unit is stopped by closing the switch that bypasses the corresponding electric heating unit.

[0012] Preferably, the plurality of electric heating sections may be electrically connected in series. According to this configuration, the electric heating parts are electrically connected in series, so the combined resistance of the electric heating parts is the sum of the resistances of the individual electric heating parts. When the switch bypassing the electric heating parts is closed, the combined resistance is reduced by the resistance of the electric heating parts. This increases the current flowing through the electric heating parts whose switches are not closed, and increases the amount of heat generated (Joule heat), accelerating the temperature rise of the parts of the dispersion plate whose temperature is below a predetermined value.

[0013] Preferably, a heating unit group in which a plurality of electric heating units are electrically connected in series may be electrically connected in parallel.

[0014] When the number of electric heating parts connected in series increases, the combined resistance increases and the current flowing through the electric heating parts decreases, so that the Joule heat generated in each electric heating part decreases. With this configuration, even when the number of electric heating parts provided on the dispersion plate is large, the Joule heat generated in each electric heating part can be prevented from decreasing by appropriately setting the number of electric heating parts included in the heating part group.

[0015] Preferably, the temperature detection section may be constituted by a thermistor. The temperature range in which the resistance value of the thermistor changes significantly can be set by adjusting the composition (material components). With this configuration, since the temperature detection unit is composed of a thermistor, the temperature range in which the resistance value of the thermistor changes significantly can be set to a temperature (for example, a predetermined value) at which the current supply to the electric heating unit is controlled, making it possible to control the current supply to the electric heating unit with high precision. Effect of the Invention

[0016] According to the present disclosure, the power for heating the dispersion plate can be consumed efficiently. [Brief description of the drawings]

[0017] [Figure 1] 1 is a diagram showing a schematic overall configuration of an exhaust gas purification device for an internal combustion engine according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a schematic configuration diagram of a dispersion plate according to the present embodiment. [Diagram 3] 4 is a flowchart showing an example of a process of electric heater control executed by an ECU in the present embodiment. [Figure 4] FIG. 1 is a diagram showing the relationship between temperature and resistance in a dispersion plate temperature sensor made of a thermistor. [Diagram 5] FIG. 4 is a schematic configuration diagram of a dispersion plate according to Modification 1. [Figure 6] 13 is a diagram showing an example of connection of an electric heater in Modification 2. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference characters, and the description thereof will not be repeated.

[0019] FIG. 1 is a diagram showing a schematic overall configuration of an exhaust purification device for an internal combustion engine according to the present embodiment. Referring to FIG. 1, an engine (internal combustion engine) 1 is a compression ignition type internal combustion engine (diesel engine) equipped with an exhaust purification device 70. The engine 1 is used, for example, as a driving source for a vehicle. The engine 1 is an internal combustion engine that performs compression auto-ignition by injecting fuel from a fuel injection valve (injector) 14 into a combustion chamber formed in a cylinder (cylinder) 12 of an engine body 10. In the present embodiment, the engine 1 has four cylinders. An air cleaner 22, an intercooler 24, and a throttle valve (diesel throttle valve) 26 are provided in an intake passage 20 of the engine 1. Fresh air from which foreign matter has been removed by the air cleaner 22 is supercharged (compressed) by a compressor 32 of a turbocharger 30, cooled by the intercooler 24, supplied to an intake manifold 28, and supplied to each combustion chamber from an intake port.

[0020] Fuel is stored in a fuel tank 40. The fuel in the fuel tank 40 is supplied to a high-pressure fuel pump 42 by a feed pump 41, and the high-pressure fuel discharged from the high-pressure fuel pump 42 is pumped to a common rail 44 via a fuel passage 43. The high-pressure fuel stored in the common rail 44 is injected from the injector 14 into the combustion chamber (inside the cylinder).

[0021] Exhaust gas discharged from the combustion chamber is collected in an exhaust manifold 50 and released to the outside air via an exhaust passage 52. A portion of the exhaust gas is recirculated to the intake manifold 28 via an EGR (Exhaust Gas Recirculation) passage 60. An EGR cooler 62 and an EGR valve 64 are provided in the EGR passage 60.

[0022] The exhaust passage 52 is provided with a turbine 34 of the turbocharger 30, and downstream of the turbine 34, an exhaust purification device 70 is provided with an oxidation catalyst 71, a DPF (Diesel Particulate Filter) 72, a selective reduction catalyst (hereinafter also referred to as an SCR (Selective Catalytic Reduction) catalyst) 73, and an oxidation catalyst 74. The oxidation catalyst 71 oxidizes and purifies CO (carbon monoxide), HC (hydrocarbon), and SOF (soluble organic fraction) contained in the exhaust gas. In addition, when burning and removing particulate matter (PM) trapped in the DPF 72, the oxidation catalyst 71 burns (oxidizes) the supplied HC to increase the exhaust gas temperature.

[0023] An SCR catalyst 73 is disposed in the exhaust passage 52 downstream of the DPF 72. The SCR catalyst 73 is, for example, a ceramic carrier carrying copper (Cu) ion-exchanged zeolite as a catalyst, and exhibits a high NOx purification rate by using ammonia (NH3) as a reducing agent. The ammonia used as a reducing agent is generated by hydrolysis and thermal decomposition of urea water supplied to the exhaust passage 52 upstream of the SCR catalyst 73. A urea addition valve (urea water injection injector) 80 is provided in the exhaust passage upstream of the SCR catalyst 73, and urea water pumped from a urea water tank 81 by a pump 82 is injected from the urea addition valve 80 into the exhaust passage 52 upstream of the SCR catalyst 73. The urea addition valve 80 corresponds to an example of a "urea supply means" in the present disclosure.

[0024] An oxidation catalyst 74 is provided in the exhaust passage 52 downstream of the SCR catalyst 73, and oxidizes and purifies the ammonia discharged (slip) from the SCR catalyst 73.

[0025] A dispersion plate 200 is disposed in the exhaust passage 52 between the urea addition valve 80 and the SCR catalyst 73. The dispersion plate 200 is provided with an electric heater that generates heat when energized. Power is supplied to the electric heater of the dispersion plate 200 from a battery (DC power source) 90 via a switch SW0. The battery 90 may be an auxiliary battery of the vehicle, and the voltage may be 12 volts, 24 volts, or 48 volts. Details of the dispersion plate 200 will be described later.

[0026] The ECU (Electronic Control Unit) 100 includes a CPU (Central Processing Unit) 101, a memory 102 consisting of a ROM (Read Only Memory) and a RAM (Random Access Memory), an input / output port (not shown) for inputting and outputting various signals, and executes predetermined arithmetic processing based on information stored in the memory 102 and information from various sensors, and controls the injector 14, the throttle valve 26, the urea addition valve 80, the switch SW0, etc. The ECU 100 corresponds to an example of the "control device" of the present disclosure.

[0027] The various sensors input to the ECU 100 include, for example, an engine rotation speed sensor 111, an accelerator pedal sensor 112, an air flow meter 113, an SCR temperature sensor 114, and distributor plate temperature sensors 115a-115d. The engine rotation speed sensor 111 detects the rotation speed NE of the engine 1. The accelerator pedal sensor 112 detects the amount of accelerator pedal operation by the user (hereinafter also referred to as "accelerator opening") AP. The air flow meter 113 is provided in the intake passage 20, and detects the intake amount (intake air amount) Ga of the engine 1. The SCR temperature sensor 114 detects the temperature (for example, catalyst bed temperature) Tc of the SCR catalyst 73. The distributor plate temperature sensors 115a-115d will be described later.

[0028] For example, the ECU 100 calculates the fuel injection amount Fp from the accelerator opening AP and the engine speed NE, and controls the injector 14 so that fuel of the fuel injection amount Fp is injected into the combustion chamber. The ECU 100 estimates the amount of NOx discharged from the engine 1 from the fuel injection amount Fp (or the accelerator opening AP) and the engine speed NE, calculates the addition amount Fu according to the amount of NOx, and controls the urea addition valve 80 so that the urea water of the addition amount Fu is supplied to the exhaust passage 52. Note that the concentration of NOx discharged from the engine 1 may be detected, and the addition amount Fu may be calculated based on the NOx concentration.

[0029] The urea water supplied from the urea addition valve 80 is dispersed and atomized by the dispersion plate 200. The urea water is also heated by the dispersion plate 200 (and exhaust heat). As a result, a portion of the urea water supplied from the urea addition valve 80 is thermally decomposed and hydrolyzed to generate ammonia (NH3). The generated ammonia then flows into the SCR catalyst 73. The urea water that is not decomposed also flows into the SCR catalyst 73, where it is thermally decomposed and hydrolyzed to generate ammonia.

[0030] FIG. 2 is a schematic diagram of the dispersion plate 200 in this embodiment. FIG. 2 is a view seen from the upstream side of the exhaust passage 52. In this embodiment, the dispersion plate 200 has a screw shape (propeller shape) and is fixed to the exhaust passage 52. The dispersion plate 200 has four blades 201, 202, 203, and 204. The blade 201 is provided with an electric heater H1. When the blade 201 is a member having electrical conductivity, the electric heater H1 is fixed to the blade 201 via an insulating member. The electric heater H1 is a resistance heater that generates heat by Joule heat. The electric heater H1 may be a metallic heating element made of nickel-chromium or the like, or a non-metallic heating element made of silicon carbide or the like. Similarly, the blades 202, 203, and 204 are provided with electric heaters H2, H3, and H4. The electric heaters H1, H2, H3, and H4 correspond to an example of the "electric heating section" of the present disclosure.

[0031] The electric heaters H1, H2, H3, and H4 are electrically connected in series by a power line PL. The power line PL is connected to a battery 90 via a switch SW0. As shown in FIG. 2, a bypass power line BL1 that bypasses the electric heater H1 is provided, and a switch SW1 is provided on the bypass power line BL1. Similarly, switches SW2, SW3, and SW4 are provided on the bypass power lines BL2, BL3, and BL4 that bypass the electric heaters H2, H3, and H4. The switches SW0 to SW4 have the same configuration, and when closed (ON), they pass current, and when opened (OFF), they cut off the current.

[0032] The blade portion 201 is provided with a dispersion plate temperature sensor 115a. In this embodiment, the dispersion plate temperature sensor 115a is provided on the surface (rear surface) opposite to the surface (front surface) on which the electric heater H1 is provided. The dispersion plate temperature sensor 115a detects the temperature Tpa of the blade portion 201 heated by the electric heater H1. Similarly, the blade portions 202, 203, and 204 are provided with dispersion plate temperature sensors 115b, 115c, and 115d, which detect the temperatures Tpb, Tpc, and Tpd of the blade portions 202, 203, and 204. In this embodiment, the dispersion plate temperature sensors 115a to 115d are thermistors.

[0033] 3 is a flowchart showing an example of the process of electric heater control executed by the ECU 100 in this embodiment. This flowchart is started when the ignition switch is turned ON and the engine 1 is started, the warm-up of the SCR catalyst 73 is completed, and the catalyst bed temperature Tc of the SCR catalyst 73 reaches the activation temperature. When the catalyst bed temperature Tc reaches the activation temperature, the injection of urea water is started from the urea addition valve 80. In step (hereinafter, step is abbreviated as "S") 10, the switch SW0 is turned ON (closed) and the switches SW1 to SW4 are turned OFF (opened). As a result, a current is supplied from the battery 90 to the electric heaters H1 to H4, and the blade portions 201 to 204 of the dispersion plate 200 are heated by the heat generated by the electric heaters H1 to H4, and the temperature of the dispersion plate 200 (the blade portions 201 to 204) increases.

[0034] In the next S11, it is determined whether the temperature Tpa of the blade portion 201 detected by the dispersion plate temperature sensor 115a is equal to or higher than the predetermined value α. FIG. 4 is a diagram showing the relationship between the resistance value and temperature in the dispersion plate temperature sensors 115a to 115d made of thermistors. In FIG. 4, the solid line indicates the characteristic of a CTR (Critical Temperature Resistor) thermistor, and the broken line indicates the characteristic of a PTC (Positive Temperature Coefficient) thermistor. The dispersion plate temperature sensors 115a to 115d may be either a CTR thermistor or a PTC thermistor. In this embodiment, the composition (material components) of the dispersion plate temperature sensors 115a to 115d is adjusted so that the resistance value changes significantly in the temperature range of the predetermined value α as shown in FIG. 4. This allows relatively accurate detection of the temperature detected by the dispersion plate temperature sensors 115a to 115d becoming equal to or higher than the predetermined value α. In the case of an NCT thermistor, when the resistance value is below threshold value A, the temperature is determined to be above a predetermined value α, and in the case of a PTC thermistor, when the resistance value is above threshold value B, the temperature is determined to be above the predetermined value α.

[0035] In S11, if the temperature Tpa is equal to or greater than the predetermined value α, a positive determination is made and the process proceeds to S12, whereas if the temperature TPa is less than the predetermined value α, a negative determination is made and the process proceeds to S13. In S12, the switch SW1 is turned ON and the flag F1 is set to 1, and the process proceeds to S14. As a result, a current flows through the bypass power line BL1, the power supply to the electric heater H1 is stopped, and the heat generation of the electric heater H1 is stopped. In S13, the switch SW1 is turned OFF (if it was OFF, it remains OFF), and the flag F1 is set to 0, and the process proceeds to S14.

[0036] In S14, it is determined whether or not the temperature Tpb of the blade portion 202 detected by the dispersion plate temperature sensor 115b is equal to or higher than a predetermined value α. If the temperature Tpb is equal to or higher than the predetermined value α, a positive determination is made and the process proceeds to S15, whereas if the temperature TPb is less than the predetermined value α, a negative determination is made and the process proceeds to S16. In S15, the switch SW2 is turned ON and the flag F2 is set to 1, and the process proceeds to S17. As a result, a current flows through the bypass power line BL2, the power supply to the electric heater H2 is stopped, and the heat generation by the electric heater H2 is stopped. In S16, the switch SW2 is turned OFF (if it was OFF, it is kept OFF), and the flag F2 is set to 0, and the process proceeds to S17.

[0037] In S17, it is determined whether or not the temperature Tpc of the blade portion 203 detected by the dispersion plate temperature sensor 115c is equal to or higher than a predetermined value α. If the temperature Tpc is equal to or higher than the predetermined value α, a positive determination is made and the process proceeds to S18, whereas if the temperature Tpc is less than the predetermined value α, a negative determination is made and the process proceeds to S19. In S18, the switch SW3 is turned ON and the flag F3 is set to 1, and the process proceeds to S20. As a result, a current flows through the bypass power line BL3, the power supply to the electric heater H3 is stopped, and the heat generation by the electric heater H3 is stopped. In S19, the switch SW3 is turned OFF (if it was OFF, it is kept OFF), and the flag F3 is set to 0, and the process proceeds to S20.

[0038] In S20, it is determined whether or not the temperature Tpd of the blade portion 204 detected by the dispersion plate temperature sensor 115d is equal to or higher than a predetermined value α. If the temperature Tpd is equal to or higher than the predetermined value α, a positive determination is made and the process proceeds to S21, whereas if the temperature Tpd is less than the predetermined value α, a negative determination is made and the process proceeds to S22. In S21, the switch SW4 is turned ON and the flag F4 is set to 1, and the process proceeds to S23. As a result, a current flows through the bypass power line BL4, the power supply to the electric heater H4 is stopped, and the heat generation by the electric heater H4 is stopped. In S22, the switch SW4 is turned OFF (if it was OFF, it is kept OFF), and the flag F4 is set to 0, and the process proceeds to S23.

[0039] In S23, it is determined whether or not all of the flags F1 to F4 are 1. When all of the flags F1 to F4 are 1, an affirmative decision is made and the process proceeds to S24. When at least one of the flags F1 to F4 is 0, a negative decision is made and the process proceeds to S25.

[0040] In S24, switch SW0 is turned OFF (open), and then the process proceeds to S26. When all of flags F1 to F4 are 1 and switches SW1, SW2, SW3, and SW4 are all ON, switch SW0 is turned OFF to prevent a short circuit in battery 90. In S25, switch SW0 is turned ON (if it is ON, it is kept ON), and the process proceeds to S26.

[0041] In S26, it is determined whether the ignition switch is OFF. If the ignition switch is ON, a negative determination is made and the process returns to S11. If the ignition switch is OFF and the engine 1 is stopped, a positive determination is made and the current routine is terminated.

[0042] According to this embodiment, the urea water is dispersed by the dispersion plate 200 provided in the exhaust passage 52 between the urea addition valve 80 and the SCR catalyst 73 and flows into the SCR catalyst 73. The dispersion plate 200 is provided with a plurality of electric heaters H1-H4. The electric heaters H1-H4 heat the dispersion plate 200, and the temperature of the dispersion plate 200 increases. The heat of the dispersion plate 200 promotes atomization and decomposition of the urea water.

[0043] In the dispersion plate 200, the temperature of the portion where the urea water collides drops. The dispersion plate temperature sensors 115a-115d are provided corresponding to the blade portions 201-204 provided with the electric heaters H1-H4, and detect the temperatures Tpa-Tpd of the blade portions 201-204 heated by the electric heaters H1-H4. The ECU 100 controls the energization of the corresponding electric heaters H1-H4 based on the temperatures Tpa-Tpd detected by the dispersion plate temperature sensors 115a-115d. This makes it possible to control the energization of the electric heaters H1-H4 corresponding to the blade portions 201-204 whose temperature has been reduced by the impingement of the urea water, and therefore makes it possible to efficiently consume the power for heating the dispersion plate 200.

[0044] In this embodiment, switches SW1 to SW4 are provided on bypass power lines BL1 to PL4 bypassing the electric heaters H1 to H4, and when any of the temperatures Tpa to Tpd reaches or exceeds a predetermined value, the switch SW1 to SW4 bypassing the corresponding electric heater H1 to H4 is closed, so that the current flowing through the electric heater flows to the bypass power line, and the power supply to the electric heater is stopped. In addition, since the electric heaters H1 to H4 are electrically connected in series by the power line PL, the combined resistance of the electric heaters is a value obtained by adding up the resistances of the electric heaters H1 to H4. When the switches SW1 to SW4 bypassing the electric heaters H1 to H4 are closed, the combined resistance is reduced by the resistance of the electric heater. This increases the current flowing through the electric heaters whose switches are not closed, and increases the Joule heat. Therefore, the temperature rise of the blades 201 to 204 whose temperatures are below the predetermined value α is promoted in the dispersion plate 200.

[0045] <Variation 1> FIG. 5 is a schematic diagram of a dispersion plate 200a according to the first modification. In the first modification, the dispersion plate 200a has four blades 201a, 202a, 203a, and 204a. The blades 201a to 204a are fixed to an insulating shaft member 220, and fixed to the exhaust passage 52 via an insulating member (not shown). The blades 201a to 204a are formed of, for example, a ceramic heating element, and generate heat when electricity is applied. The blades 201a to 204a are electrically connected in series by the power line PL, as in the above embodiment. Also, as in the above embodiment, bypass power lines BL1 to BL4 are provided to bypass the blades 201a to 204a, and the bypass power lines BL1 to BL4 are provided with switches SW1 to SW4.

[0046] The blade portions 201a to 204a are provided with the dispersion plate temperature sensors 115a to 115d, similar to those in the above embodiment, which detect the temperatures Tpa to Tpd of the blade portions 201a to 201d. In this modification 1 as well, the electric heater control described in the flowchart of FIG. 3 is executed.

[0047] According to this first modification, the entire blade portions 201a to 204a of the dispersion plate 200 can be heated by Joule heat, so that the decomposition of the urea water can be further promoted.

[0048] <Variation 2> In the above embodiment, the dispersion plate 200 has four blades, and four electric heaters H1 to H4 are provided in series. If the number of blades is increased, for example, if a dispersion plate having eight blades is provided with eight electric heaters connected in series, the combined resistance of the electric heaters will be the sum of the resistances of the eight electric heaters. If the combined resistance of the electric heaters is large, the current flowing therethrough will be small, which will reduce the Joule heat of the electric heaters and may slow down the temperature rise of the dispersion plate (blade).

[0049] FIG. 6 is a diagram showing an example of electric heater connection in Modification 2. Modification 2 includes eight electric heaters. For example, an electric heater is provided on each blade of a dispersion plate having eight blades. As shown in FIG. 6, the electric heaters are connected by paths A and B, which are connected in parallel to a battery 90. Path A includes electric heaters H1a, H2a, H3a, and H4a, which are a heating group connected in series to the battery 90 via a switch SW0a. Path B includes electric heaters H1b, H2b, H3b, and H4b, which are a heating group connected in series via a switch SW0b. Switches SW1a to SW4b are provided on bypass power lines that bypass the electric heaters H1a to H4b of the heating groups of paths A and B.

[0050] A dispersion plate temperature sensor is provided on the blade portion corresponding to the electric heater H1a to H4b. Based on the temperature detected by the dispersion plate temperature sensor, the opening and closing of the switches SW1a to SW4b and the switches SW0a and SW0b are controlled in the same manner as in the above embodiment.

[0051] According to this modification 2, the heating section group (path A, path B) in which the electric heaters are connected in series is connected in parallel, so even if there are a large number of electric heaters, the number of electric heaters connected in series can be reduced. This reduces the combined resistance, prevents the Joule heat generated by the electric heaters from decreasing, and enables the temperature of the dispersion plate (blade portion) to be raised quickly.

[0052] In the above embodiment, a screw-shaped (propeller-shaped) dispersion plate having a plurality of blades is used, but the shape and form of the dispersion plate are not limited to these. For example, a punched plate having a plurality of holes formed in a plate-shaped member may be used as the dispersion plate. In this case, the surface of the punched plate may be divided into a plurality of sections, and an electric heater may be provided in each section, and a dispersion plate temperature sensor may be provided on the back side of each section.

[0053] In the above embodiment, a thermistor is used as the dispersion plate temperature sensor, but other types of temperature sensors, such as a thermocouple, may also be used.

[0054] In the above embodiment, the power supply to the electric heater is controlled by opening and closing a switch provided on a bypass power line that bypasses the electric heater. However, the electric heaters may be connected in parallel to the battery 90 via a switch, and the power supply to each electric heater may be controlled by opening and closing the switch.

[0055] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0056] 1 engine, 10 engine body, 12 cylinder, 14 injector, 20 intake passage, 22 air cleaner, 24 intercooler, 26 throttle valve, 28 intake manifold, 30 turbocharger, 32 compressor, 34 turbine, 40 fuel tank, 41 feed pump, 42 high-pressure fuel pump, 43 fuel passage, 44 common rail, 45 fuel passage, 50 exhaust manifold, 52 exhaust passage, 60 EGR passage, 62 EGR cooler, 64 EGR valve, 70 exhaust purification device, 71 oxidation catalyst, 72 DPF, 73 selective reduction catalyst (SCR catalyst), 74 oxidation catalyst, 80 urea addition valve, 81 urea tank, 82 pump, 90 battery, 91 battery, 100 ECU, 101 CPU, 102 memory, 111 engine speed sensor, 112 Accelerator pedal sensor, 113 air flow meter, 114 SCR temperature sensor, 115a to 115d distribution plate temperature sensors, 200 distribution plate, 201 to 204 blade portion, BL1 to BL4 bypass power lines, H1 to H4 electric heaters, PL power line, SW0 to SW4 switches.

Claims

1. A selective reduction catalyst provided in an exhaust passage; a urea supply means provided upstream of the selective reduction catalyst and supplying urea water to the exhaust passage; a dispersion plate provided in the exhaust passage between the urea supply means and the selective reduction catalyst, the dispersion plate dispersing the urea water; A plurality of electric heating units provided on the dispersion plate; A plurality of temperature detection units are provided on the dispersion plate corresponding to the plurality of electric heating units, and detect the temperatures of the portions heated by the plurality of electric heating units; and a control unit that controls energization of the corresponding electric heating unit based on the temperature detected by the temperature detection unit.

2. The electric heating section is a resistance heating section, A switch is provided on a bypass power line that bypasses each of the electric heating sections, 2. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein when the temperature detected by the temperature detection unit becomes equal to or higher than a predetermined value, the control unit stops the supply of electricity to the electric heating unit by closing the switch that bypasses the corresponding electric heating unit.

3. 3. The exhaust gas purification device for an internal combustion engine according to claim 2, wherein a plurality of said electric heating sections are electrically connected in series.

4. 3. The exhaust gas purification device for an internal combustion engine according to claim 2, wherein a heating unit group, in which a plurality of the electric heating units are electrically connected in series, is electrically connected in parallel.

5. 5. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the temperature detection section is constituted by a thermistor.

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