JP2019152138A - Exhaust emission control device of internal combustion engine and vehicle - Google Patents

Abstract

To provide an exhaust emission control device of an internal combustion engine which can reduce an unburned portion of particulate matters (PM) in a PM filter during forcible regeneration of the PM filter.SOLUTION: An exhaust emission control device 40 of an internal combustion engine includes: an oxidation catalyst 41 and a PM filter 42 which are disposed from the upstream side to the downstream side in a written order at an exhaust passage 30 of an internal combustion engine; an electric heater 43 which is disposed adjacent to the oxidation catalyst 41; and a control device 47 which controls the electric heater 43 so that an outer periphery part of the oxidation catalyst 41 is heated during forcible regeneration of the PM filter 42.SELECTED DRAWING: Figure 4

Description

  The present disclosure relates to an exhaust emission control device for an internal combustion engine and a vehicle.

  In general, an exhaust purification device such as a PM filter that collects particulate matter (hereinafter referred to as “PM”) contained in exhaust gas is provided in an exhaust passage of an internal combustion engine.

  Since this type of PM filter has an upper limit in the amount of PM that can be collected, filter regeneration for burning and removing PM in the PM filter is performed.

  Conventionally, as an exhaust gas purification device for efficiently performing filter regeneration in this type of PM filter, an exhaust gas purification device in which an oxidation catalyst and a PM filter are provided side by side from the upstream side is known (for example, Patent Documents). 1).

In such an exhaust emission control device, during normal operation (representing a time other than during forced regeneration), the PM filter uses NO ₂ generated by oxidation of NO contained in the exhaust gas. Regeneration is performed continuously (hereinafter referred to as “continuous regeneration”), and when PM cannot be completely removed by the continuous regeneration, the PM filter is forcibly heated to perform regeneration of the PM filter (hereinafter, “ This is referred to as “forced regeneration”.

Continuous regeneration generally occurs even when the temperature of the exhaust gas is low (for example, 300 to 400 ° C.), and is performed without particularly controlling the engine or the like. At the time of continuous regeneration, the oxidation catalyst oxidizes NO contained in the exhaust gas to NO ₂ , and oxidizes and removes PM (for example, soot) deposited on the PM filter using the NO ₂ oxidizing power.

On the other hand, the forced regeneration is generally performed by intentionally increasing the injection amount of fuel (HC) injected from an injector such as an engine when the PM accumulation amount in the PM filter increases. In forced regeneration, the HC is oxidized by an oxidation catalyst (hereinafter also referred to as “HC oxidation”), and the exhaust gas is heated to a high temperature using the heat of HC oxidation in the oxidation catalyst (for example, about 600). ° C). As a result, the PM filter is heated, and PM in the PM filter is burned and removed using O ₂ in the exhaust gas.

Japanese Patent Laying-Open No. 2015-172341

  By the way, when the PM filter is forcibly regenerated, it is required to increase the temperature of the PM filter evenly in order to surely burn and remove the PM deposited on the PM filter.

  However, in the forced regeneration according to the prior art, in practice, a temperature distribution in the radial direction (representing the radial direction of the exhaust pipe; hereinafter the same) may occur in the PM filter. This is because the temperature distribution in the radial direction is generated in the oxidation catalyst that sends the exhaust gas heated to the PM filter. Specifically, the temperature of the oxidation catalyst is high because the flow rate of the exhaust gas is fast at the center, while the temperature is low at the outer periphery due to heat radiation. For this reason, in the outer peripheral portion of the oxidation catalyst, there may occur a state where a part of the HC additionally injected from the injector of the engine remains unreacted and slips.

  As described above, when a slip state of HC occurs in the outer peripheral portion of the oxidation catalyst, the temperature of the outer peripheral portion of the PM filter is not sufficiently raised to a temperature for burning and removing PM (for example, about 600 ° C.). Become. As a result, PM remains unburned in the PM filter, leading to a situation where the regeneration interval of the PM filter is shortened.

  The present disclosure has been made in view of the above problems, and provides an exhaust purification device for an internal combustion engine and a vehicle that can suppress unburned PM in the PM filter when the PM filter is forcibly regenerated. Objective.

The main present disclosure for solving the above-described problems is as follows.
An exhaust purification device for an internal combustion engine,
An oxidation catalyst and a PM filter disposed in order from the upstream side to the downstream side in the exhaust passage of the internal combustion engine;
An electric heater disposed adjacent to the oxidation catalyst;
A controller for controlling the electric heater so that the outer peripheral portion of the oxidation catalyst is heated during forced regeneration of the PM filter;
It is an exhaust emission control device provided with.

In other aspects,
A vehicle including the exhaust gas purification apparatus for an internal combustion engine.

  According to the exhaust gas purification apparatus for an internal combustion engine according to the present disclosure, it is possible to suppress unburned PM in the PM filter during forced regeneration of the PM filter.

The figure which shows an example of a structure of the vehicle containing the exhaust gas purification apparatus which concerns on one Embodiment. The figure which shows an example of a structure of the oxidation catalyst of the exhaust gas purification apparatus which concerns on one Embodiment The flowchart which shows an example of operation | movement of the exhaust gas purification apparatus which concerns on one Embodiment. The figure which shows typically operation | movement of the heater control part which concerns on one Embodiment.

  Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the appended drawings. In the present specification and drawings, components having substantially the same function are denoted by the same reference numerals, and redundant description is omitted.

[Configuration of exhaust purification system]
Hereinafter, with reference to FIG. 1 and FIG. 2, a configuration of an exhaust emission control device according to an embodiment will be described.

  In the present embodiment, a mode applied to a diesel engine will be described as an example of an exhaust purification device of an internal combustion engine (hereinafter also referred to as “engine”). However, it is needless to say that the exhaust emission control device according to the present embodiment can be applied not only to a diesel engine but also to a gasoline engine.

  FIG. 1 is a diagram illustrating an example of a configuration of a vehicle 1 including an exhaust purification device 40 according to the present embodiment. FIG. 2 is a diagram illustrating an example of the configuration of the oxidation catalyst 41 of the exhaust purification device 40 according to the present embodiment.

  The vehicle 1 according to the present embodiment includes an engine body 10, an intake passage 20, an exhaust passage 30, an air cleaner 21, a turbo charger 22, an intake throttle valve 23, an EGR device 31, an exhaust purification device 40, and the like.

  The engine body 10 includes a combustion chamber, an injector (not shown), and the like. The engine body 10 generates power for the vehicle 1 by repeatedly performing an air intake stroke, an air compression stroke, a combustion gas expansion stroke, and a combustion gas exhaust stroke in the combustion chamber.

  The engine body 10 includes an engine ECU (not shown) that controls the injector and the EGR device 31. Then, in response to a filter regeneration request from the ECU 47 (details will be described later) of the exhaust purification device 40, the engine ECU causes the injector of the engine body 10 to operate in a low fuel consumption operation mode (hereinafter referred to as “normal operation”) giving priority to fuel efficiency. Or a forced regeneration operation mode in which the PM filter 42 is forcibly regenerated.

  The engine body 10 according to the present embodiment is a four-cylinder engine, and branches from the intake passage 20 to four combustion chambers via the intake manifold, and from the four combustion chambers to the exhaust passage 30 via the exhaust manifold. It is configured to merge.

  The intake passage 20 is an intake pipe that draws fresh air (air) from the upstream intake port 20 a and supplies the fresh air to the engine body 10. In the intake passage 20, an air cleaner 21, a compressor of a turbocharger 22, an intake throttle valve 23, and the like are provided in order from the upstream intake port 20 a to the combustion chamber.

  The exhaust passage 30 is an exhaust pipe that exhausts the exhaust gas after combustion discharged from the engine body 10 to the outside of the vehicle 1. The exhaust passage 30 is provided with an EGR device 31, a turbine of the turbocharger 22, an exhaust purification device 40, and the like in order from the engine body 10 toward the downstream side.

  The exhaust purification device 40 includes an oxidation catalyst 41, a PM filter 42, an electric heater 43, a differential pressure sensor 44, oxygen concentration sensors 45a and 45b, NOx concentration sensors 46a and 46b, and an ECU (Electronic Control Unit) 47. Is done.

  The oxidation catalyst 41 oxidizes and removes unburned fuel hydrocarbons and carbon monoxide contained in the exhaust gas. The oxidation catalyst 41 may be any known oxidation catalyst such as platinum or cerium oxide. For example, a porous ceramic such as cordierite or silicon carbide is used, and the catalyst component is supported thereon. .

Further, the oxidation catalyst 41 is disposed adjacent to the upstream side of the PM filter 42 in the exhaust passage 30. Then, the oxidation catalyst 41 converts NO in the exhaust gas into NO ₂ or the like, and raises the exhaust gas temperature to a level (for example, about 300 ° C.) desirable for oxidizing and removing the PM in the PM filter 42. Also works. Thereby, the continuous regeneration of the PM filter 42 is performed.

  The PM filter 42 captures PM contained in the exhaust gas. As the PM filter 42, typically, a cordierite or silicon carbide porous ceramic is used as a material. The PM filter 42 has, for example, a honeycomb structure in which the inlet and the outlet are alternately sealed so that the exhaust gas passes through the collection wall formed of the porous ceramic.

  The electric heater 43 is typically adjacent to the oxidation catalyst 41 to heat the outer peripheral portion of the oxidation catalyst 41 (representing the outer peripheral portion in the radial direction of the oxidation catalyst 41. The same applies hereinafter). It is arrange | positioned at the wall surface of the part. The electric heater 43 includes, for example, a pair of electrode portions disposed on the wall surface of the outer peripheral portion of the oxidation catalyst 41 and a power source portion (not shown) connected to the pair of electrode portions. The electric heater 43 heats the oxidation catalyst 41 by causing a current supplied from the power supply unit to flow between the pair of electrode portions on the wall surface of the oxidation catalyst 41. The electric heater 43 performs a heating operation of the oxidation catalyst 41 in accordance with a control signal from the ECU 47.

  The heating method of the electric heater 43 may be a heating method using a heating wire or the like instead of resistance heating using the electric resistance of the oxidation catalyst 41 itself.

  The differential pressure sensor 44 detects the differential pressure across the PM filter 42. The oxygen concentration sensor 45 a detects the oxygen concentration on the inlet side of the oxidation catalyst 41. The oxygen concentration sensor 45 b detects the oxygen concentration on the outlet side of the oxidation catalyst 41. The NOx concentration sensor 46 a detects the NOx concentration on the inlet side of the oxidation catalyst 41. The NOx concentration sensor 46 b detects the NOx concentration on the outlet side of the oxidation catalyst 41. These sensors can be realized by any known sensor. The oxygen concentration sensor 45a (45b) and the NOx concentration sensor 46a (46b) may be integrally configured as a sensor for detecting the gas concentration contained in the exhaust gas.

  The differential pressure sensor 44, the oxygen concentration sensors 45a and 45b, and the NOx concentration sensors 46a and 46b each transmit sensor information (hereinafter abbreviated as “sensor information”) related to the sensor value detected by itself to the ECU 47. .

[Configuration of ECU]
Here, an example of the configuration of the ECU 47 (corresponding to the “control device” of the present invention) of the exhaust emission control device 40 according to the present embodiment will be described with reference to FIG.

  The ECU 47 is an electronic control unit that performs regeneration control of the PM filter 42, control of the electric heater 43, and the like.

  The ECU 47 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input port, an output port, and the like. The ECU 47 communicates with each part of the vehicle 1 such as the engine ECU, thereby controlling them and receiving data from them. Further, the ECU 47 acquires sensor information from various sensors (in this embodiment, the differential pressure sensor 44, the oxygen concentration sensors 45a and 45b, and the NOx concentration sensors 46a and 46b) provided in the vehicle 1, and purifies the exhaust gas. The state of each part of the apparatus 40 and the vehicle 1 is detected.

  The ECU 47 includes a PM amount estimation unit 47a, a filter regeneration control unit 47b, and a heater control unit 47c.

  The PM amount estimation unit 47 a estimates the amount of PM deposited on the PM filter 42 based on the sensor information of the differential pressure sensor 44.

  For example, the PM amount estimation unit 47a calculates a pressure loss caused by PM accumulated in the PM filter 42 from the differential pressure before and after the PM filter 42 indicated by the differential pressure sensor 44, and thereby accumulates in the PM filter 42. Estimate the amount of PM.

  The correspondence relationship between the differential pressure across the PM filter 42 and the amount of PM deposited on the PM filter 42 is obtained in advance through experiments or the like and stored in a storage unit (eg, ROM) such as the ECU 47, for example.

  The filter regeneration control unit 47b acquires the estimated value of the PM accumulation amount in the PM filter 42 calculated by the PM amount estimation unit 47a, and when the estimated value of the PM accumulation amount exceeds a predetermined threshold, the engine body For example, the PM filter 42 is forcibly regenerated by increasing the fuel injection amount 10.

  When the filter regeneration control unit 47b forcibly regenerates the PM filter 42, for example, by outputting a control signal to the engine ECU of the engine body 10 and operating the engine body 10 in the forced regeneration operation mode, The PM filter 42 is forcibly regenerated.

In the forced regeneration operation mode, for example, the engine body 10 increases the amount of HC (hydrocarbon) in the exhaust gas by increasing the fuel injection amount injected from the injector or performing post injection. As a result, the HC is oxidized by the oxidation catalyst 41, and the exhaust gas is heated to about 600 ° C. using the HC oxidation heat in the oxidation catalyst 41. As a result, the PM filter 42 is heated, and the PM in the PM filter 42 is burned and removed using O ₂ in the exhaust gas.

  However, as a forced regeneration method, various conventionally known methods can be applied. For example, when the vehicle 1 is equipped with an exhaust pipe injector, the filter regeneration control unit 47b uses the exhaust pipe injector instead of or in addition to injecting additional fuel with the engine body 10. May be injected.

  The heater control unit 47 c controls the electric heater 43 so that the temperature of the outer peripheral portion of the oxidation catalyst 41 is increased when the PM filter 42 is forcibly regenerated. As a result, the heater control unit 47c slips in the outer peripheral portion of the oxidation catalyst 41 while the additionally injected HC slips unreacted without being oxidized (hereinafter referred to as “slip state of unreacted HC”). Suppress. That is, this uniformly increases the temperature of the exhaust gas that reaches the PM filter 42.

  At this time, the temperature of the outer peripheral portion of the oxidation catalyst 41 is higher than the temperature at which the catalyst of the oxidation catalyst 41 is activated and promotes HC oxidation, at least 250 ° C., more preferably 300 ° C. or more. As described above, the oxidation catalyst 41 is heated by the electric heater 43.

  The heater control unit 47c ends the heating by the electric heater 43 when the temperature of the outer peripheral portion of the oxidation catalyst 41 rises to a temperature that activates the catalyst of the oxidation catalyst 41 and promotes HC oxidation. May be.

  In addition, the heater control unit 47c according to the present embodiment obtains information on the fuel injection amount from the engine ECU of the engine body 10, and the oxidation catalyst 41 from the oxygen concentration sensors 45a and 45b and the NOx concentration sensors 46a and 46b. Information on the oxygen concentration and the NOx concentration on each of the inlet side and the outlet side is acquired. Thus, the heater control unit 47c calculates an actual value and a predicted value of the amount of oxygen used in the oxidation catalyst 41, and detects whether or not an unreacted HC slip state has occurred. Then, the heater controller 47c performs heating of the oxidation catalyst 41 by the electric heater 43 only when the occurrence of a slip state of unreacted HC is detected during forced regeneration (details will be described later).

  However, as a method of detecting the occurrence of the slip state of the unreacted HC by the heater control unit 47c, as described above, instead of the method of calculating the actual value and the predicted value of the amount of oxygen used in the oxidation catalyst 41, the oxidation control A method of detecting indirectly from the temperature drop of the catalyst 41 may be used.

  In addition to the forced regeneration, the heater control unit 47c is when the PM filter 42 is continuously regenerated, and when detecting a decrease in the oxidation reaction of NO at the outer peripheral portion of the oxidation catalyst 41, The electric heater 43 may be controlled to heat the outer peripheral portion of the oxidation catalyst 41. As a result, the oxidation of NO in the exhaust gas to NOx at the outer periphery of the oxidation catalyst 41 can be promoted, and the continuous regeneration of the PM filter 42 can be promoted.

  The above-described functions of the ECU 47 are realized, for example, when the CPU refers to control programs and various data stored in the ROM, RAM, and the like. However, the function is not limited to processing by software, and can of course be realized by a dedicated hardware circuit.

[Operation of exhaust purification system]
Next, the operation of the exhaust emission control device 40 according to the present embodiment will be described with reference to FIGS. Here, only the operation of the exhaust purification device 40 for forcibly regenerating the PM filter 42 will be described.

  FIG. 3 is a flowchart showing an example of the operation of the exhaust purification device 40. The flowchart shown in FIG. 3 is executed, for example, by the ECU 47 at a predetermined interval (for example, every second) in accordance with a computer program.

  FIG. 4 is a diagram schematically showing the operation of the heater control unit 47c in the flowchart of FIG.

  The heater control unit 47c according to the present embodiment performs the forced regeneration from the viewpoint of suppressing deterioration in energy efficiency and avoiding an excessive decrease in the oxygen remaining amount in the exhaust gas reaching the PM filter 42. When the occurrence of a slip state of unreacted HC is detected, the temperature of the oxidation catalyst 41 is increased by the electric heater 43.

  The presence or absence of occurrence of a slip state of unreacted HC is, for example, the amount of oxygen actually used by HC oxidation in the oxidation catalyst 41 (hereinafter referred to as “the actual value of the amount of oxygen used for HC oxidation”). The amount of oxygen used by HC oxidation predicted from the fuel injection amount (that is, the amount of HC) of the injector of engine body 10 (hereinafter referred to as “predicted value of oxygen amount used for HC oxidation”). This can be determined by comparison. That is, when a slip state of unreacted HC occurs, the actual value of the amount of oxygen used for HC oxidation is less than the predicted value of the amount of oxygen used for HC oxidation. The heater control unit 47c according to this detects the state.

In general, it is considered that HC, O ₂ , NO, and the like in the exhaust gas cause chemical reactions such as the following formulas (1) to (3) in the oxidation catalyst 41.
4HC + 5O ₂ → 2H ₂ O + 4CO ₂ Formula (1)
2NO + O ₂ → 2NO ₂ Formula (2)
8HC + 20NO ₂ → 4H ₂ O + 8CO ₂ + 20NO Formula (3)

However, HC, O ₂ and NO in the formulas (1) to (3) are components in the exhaust gas, and NO ₂ in the formula (3) is a component generated in the formula (2).

  The heater control unit 47c according to the present embodiment uses the chemical reaction of the above formulas (1) to (3) as a reference to determine the actual value of the amount of oxygen used for HC oxidation and the HC oxidation in the oxidation catalyst 41. Calculate the predicted value of the amount of oxygen used. However, since the chemical reaction of the formula (1) occurs preferentially compared to the chemical reaction of the formula (2) and the formula (3) due to the formula (2), the heater control unit 47c The actual value of the amount of oxygen used for HC oxidation and the predicted value of the amount of oxygen used for HC oxidation may be calculated based only on the chemical reaction of formula (1).

  The heater control unit 47c according to the present embodiment uses the oxygen used by the HC oxidation of the above formulas (1) and (3) from the difference between the sensor value of the oxygen concentration sensor 45a and the sensor value of the oxygen concentration sensor 45b. The amount of oxygen used is calculated from the difference between the sensor value of the NOx concentration sensor 46a and the sensor value of the NOx concentration sensor 46b.

  First, in step S1, the ECU 47 estimates the PM accumulation amount of the PM filter 42 based on the sensor value of the differential pressure sensor 44, and the PM accumulation amount of the PM filter 42 is a threshold for determining the forced regeneration start (for example, Then, it is determined whether or not the PM accumulation amount of the PM filter 42 is 50% or more. If the PM accumulation amount of the PM filter 42 is equal to or greater than the threshold (S1: YES), the ECU 47 advances the process to step S2. On the other hand, when the PM accumulation amount of the PM filter 42 is less than the threshold value (S1: NO), the ECU 47 ends the series of flows without executing any particular processing.

  In step S2, the ECU 47 starts forced regeneration of the PM filter 42. At this time, for example, the ECU 47 transmits an execution command for the forced regeneration operation mode to the engine ECU of the engine body 10. Thereby, the engine body 10 starts the operation in the forced regeneration operation mode in which the fuel injection amount is increased as compared with the normal operation.

  In step S <b> 3, the ECU 47 acquires information related to the fuel injection amount (HC amount) from the engine ECU of the engine body 10. Then, the ECU 47 calculates a predicted value of the amount of oxygen used for HC oxidation in the oxidation catalyst 41 from the fuel injection amount (HC amount).

  In this step S3, the ECU 47 assumes that the chemical reaction of the formula (3) occurs at a predetermined rate in addition to the chemical reaction of the formula (1) from the current operating state of the engine body 10, for example. A predicted value of the amount of oxygen used for HC oxidation is calculated from the fuel injection amount (HC amount).

  In step S4, the ECU 47 acquires sensor information from the oxygen concentration sensor 45a and the NOx concentration sensor 46a, and detects the oxygen concentration and the NOx concentration on the inlet side of the oxidation catalyst 41.

  In step S5, the ECU 47 acquires sensor information from the oxygen concentration sensor 45b and the NOx concentration sensor 46b, and detects the oxygen concentration and the NOx concentration on the outlet side of the oxidation catalyst 41.

  In step S6, the ECU 47 performs HC oxidation based on the oxygen concentration and NOx concentration on the inlet side of the oxidation catalyst 41 detected in steps S4 and S5 and the oxygen concentration and NOx concentration on the outlet side of the oxidation catalyst 41. Calculate the actual amount of oxygen used.

  In this step S6, for example, the ECU 47 calculates the amount of oxygen used by the HC oxidation of the above formulas (1) and (3) from the difference between the sensor value of the oxygen concentration sensor 45a and the sensor value of the oxygen concentration sensor 45b. The oxygen amount used by the HC oxidation of the above equation (3) is calculated from the difference between the sensor value of the NOx concentration sensor 46a and the sensor value of the NOx concentration sensor 46b.

  The ECU 47 calculates, for example, the ratio of the amount of oxygen used by the HC oxidation of equation (1) and the amount of oxygen used by the HC oxidation of equation (3) based on the calculation result of step S6, If necessary, the predicted value of the amount of oxygen used for HC oxidation may be corrected by correcting the predetermined ratio used in step S3.

  In step S7, the ECU 47 compares the actual value of the oxygen amount used in the HC oxidation calculated in step S6 with the predicted value of the oxygen amount used in the HC oxidation calculated in step S3, and compares the HC oxidation. It is determined whether or not the actual value of the oxygen amount used in the step is smaller than the predicted value of the oxygen amount used for HC oxidation. If the actual value of the amount of oxygen used for HC oxidation is smaller than the predicted value of the amount of oxygen used for HC oxidation (S7: YES), the process proceeds to step S8. On the other hand, when the actual value of the amount of oxygen used for HC oxidation is larger than the predicted value of the amount of oxygen used for HC oxidation (S7: NO), the process proceeds to step S9. In step S7, a margin for preventing a hunting operation is provided, and the ECU 47 determines that the actual value of the oxygen amount used for HC oxidation is greater than the predicted value of the oxygen amount used for HC oxidation. It is determined whether or not the margin is small.

  As in step S7, the ECU 47 according to the present embodiment predicts the oxygen amount actually used in the oxidation catalyst 41 (the actual value of the oxygen amount used for HC oxidation) from the fuel injection amount (HC amount). The occurrence of a slip state of unreacted HC is detected by determining whether or not it is less than the amount of oxygen to be performed (predicted value of the amount of oxygen used for HC oxidation).

  In step S <b> 8, the ECU 47 performs heating of the oxidation catalyst 41 by the electric heater 43. At this time, the ECU 47 controls the electric heater 43 so that, for example, the outer peripheral portion of the oxidation catalyst 41 is 300 ° C. or higher.

  In step S8, when the heating of the oxidation catalyst 41 by the electric heater 43 is being executed, the ECU 47 continues the heating of the oxidation catalyst 41 without executing any particular processing. On the other hand, when the determination result of (S7: NO) continues in step S7, heating of the oxidation catalyst 41 by the electric heater 43 is terminated.

  In step S9, the ECU 47 estimates the PM accumulation amount of the PM filter 42 based on the sensor information of the differential pressure sensor 44, and the PM accumulation amount of the PM filter 42 is a threshold value for determining the end of forced regeneration (for example, PM It is determined whether or not the filter 42 has decreased to 0.1%) or less with respect to the upper limit amount of PM deposition amount. Then, when the PM accumulation amount of the PM filter 42 has decreased below the threshold (S9: YES), the ECU 47 advances the process to step S10, and issues an instruction to end the forced regeneration operation mode to the engine ECU of the engine body 10. Transmit, and a series of processing flow ends. On the other hand, when the PM accumulation amount of the PM filter 42 has not decreased below the threshold value (S9: NO), the ECU 47 returns to step S3 and repeats the processes of steps S3 to S8 again.

[effect]
As described above, the exhaust purification device 40 of the internal combustion engine (engine body 10) according to the present embodiment includes the oxidation catalyst 41 and the PM filter that are sequentially disposed in the exhaust passage 30 of the internal combustion engine from the upstream side toward the downstream side. 42, the electric heater 43 disposed adjacent to the oxidation catalyst 41, and the control device 47 that controls the electric heater 43 so that the temperature of the outer periphery of the oxidation catalyst 41 rises during forced regeneration of the PM filter 42. (ECU).

  Therefore, according to the exhaust purification device 40 according to the present embodiment, the outer peripheral portion of the oxidation catalyst 41 can be heated when the PM filter 42 is forcibly regenerated. Further, it is possible to promote the oxidation of the additionally injected fuel) and suppress the occurrence of a slip state of unreacted HC. As a result, the temperature of the exhaust gas that reaches the outer peripheral portion of the PM filter 42 can also be raised. Therefore, when the PM filter is forcibly regenerated, unburned PM (for example, soot) in the PM filter 42 is reduced. Can be suppressed. In other words, this makes it possible to lengthen the interval for forced regeneration of the PM filter 42.

  In particular, the control device 47 of the exhaust purification device 40 according to the present embodiment determines whether or not an unreacted HC slip state has occurred in the oxidation catalyst 41 when the PM filter 42 is forcibly regenerated, and slips the unreacted HC. When the occurrence of the state is detected, the temperature of the oxidation catalyst 41 is increased by the electric heater 43. When the slip state of the unreacted HC is not detected, the temperature of the oxidation catalyst 41 is increased by the electric heater 43. Is configured not to execute. Accordingly, the electric heater 43 can be used by limiting the conditions for raising the temperature, so that the deterioration of energy efficiency associated with the use of the electric heater 43 can be avoided. This also makes it possible to avoid a decrease in the amount of oxygen remaining in the exhaust gas used for PM combustion in the PM filter 42.

  In particular, the control device 47 of the exhaust purification device 40 according to the present embodiment predicts the amount of oxygen used for HC oxidation predicted from the fuel injection amount (HC amount) injected on the upstream side of the oxidation catalyst 41. In addition to calculating the value, the oxygen concentration at the inlet side and the outlet side of the oxidation catalyst is detected to calculate the actual value of the amount of oxygen used for HC oxidation, and by comparing these values, unreacted in the oxidation catalyst 41 It is determined whether or not an HC slip state has occurred. This makes it possible to determine whether or not the unreacted HC slip state has occurred in the oxidation catalyst 41 with high accuracy.

  In particular, the control device 47 of the exhaust purification device 40 according to this embodiment includes the sensor values of the oxygen concentration sensors 45a and 45b disposed on the inlet side and the outlet side of the oxidation catalyst 41, and the NOx concentration sensor 46a. 46b, the actual value of the amount of oxygen used for HC oxidation is calculated. Accordingly, it is possible to determine whether or not the unreacted HC slip state has occurred in the oxidation catalyst 41 with higher accuracy.

(Other embodiments)
The present invention is not limited to the above embodiment, and various modifications can be considered.

  For example, in the above-described embodiment, as a more preferable example of the heater control unit 47c, the outer peripheral portion of the oxidation catalyst 41 is limited to a case where an unreacted HC slip state occurs in the oxidation catalyst 41 during forced regeneration. It was set as the aspect heated. However, from the viewpoint of reducing the calculation load of the ECU 47, the heater control unit 47c may be configured to heat the outer peripheral portion of the oxidation catalyst 41 without determining whether or not the unreacted HC slip state has occurred. On the other hand, the heater control unit 47c detects the temperature of the outer peripheral portion of the oxidation catalyst 41, and determines whether or not a slip state of unreacted HC in the oxidation catalyst 41 has occurred from the temperature of the outer peripheral portion. Good.

  Moreover, in the said embodiment, it was set as the aspect which heats only the outer peripheral part of the oxidation catalyst 41 in the case of forced regeneration as a more suitable example of the heater control part 47c. However, depending on the configuration of the electric heater 43 and the like, the heater control unit 47c may be configured to heat not only the outer peripheral portion of the oxidation catalyst 41 but also the entire oxidation catalyst 41.

  In the above-described embodiment, as an example of the filter regeneration control unit 47b, the continuous regeneration of the PM filter 42 is not particularly controlled by the engine body 10 and the like. However, when performing the continuous regeneration of the PM filter 42, the filter regeneration control unit 47b reduces the EGR rate in the EGR device 31 and continuously regenerates the amount of NOx contained in the exhaust gas discharged from the engine body 10. You may perform control of increasing more than before.

  Moreover, in the said embodiment, the differential pressure sensor 44, oxygen concentration sensor 45a, 45b, and NOx concentration sensor 46a, 46b were shown as an example of the various sensors which the exhaust gas purification apparatus 40 has. However, the method for detecting the PM accumulation amount in the PM filter 42 and the slip state of the unreacted HC in the oxidation catalyst 41 is arbitrary, and indirectly by calculation processing using sensor information of other sensors. It may be sought.

  In the above embodiment, as an example of the configuration of the ECU 47, the functions of the PM amount estimation unit 47a, the filter regeneration control unit 47b, and the heater control unit 47c are described as being realized by one computer. Of course, it may be realized. On the other hand, it is a matter of course that the functions of the ECU 47 and the engine ECU may be realized by one ECU.

  Moreover, in the said embodiment, the aspect applied to a vehicle was shown as an example of the exhaust gas purification apparatus 40 of an internal combustion engine. However, the exhaust emission control device 40 according to the present invention can be applied not only to a vehicle but also to a device including another internal combustion engine such as a ship or an aircraft.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

  According to the exhaust gas purification apparatus for an internal combustion engine according to the present disclosure, it is possible to suppress unburned PM in the PM filter during forced regeneration of the PM filter.

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Engine main body 20 Intake passage 21 Air cleaner 22 Turbocharger 23 Intake throttle valve 30 Exhaust passage 31 EGR device 40 Exhaust purification device 41 Oxidation catalyst 42 PM filter 43 Electric heater 44 Differential pressure sensor 45a, 45b Oxygen concentration sensor
46a, 46b NOx concentration sensor 47 ECU
47a PM amount estimation unit 47b Filter regeneration control unit 47c Heater control unit

Claims (9)

An exhaust purification device for an internal combustion engine,
An oxidation catalyst and a PM filter disposed in order from the upstream side to the downstream side in the exhaust passage of the internal combustion engine;
An electric heater disposed adjacent to the oxidation catalyst;
A controller for controlling the electric heater so that the outer peripheral portion of the oxidation catalyst is heated during forced regeneration of the PM filter;
An exhaust purification device comprising: The control device, during the forced regeneration,
When the occurrence of a slip state of unreacted HC in the oxidation catalyst is detected, the control of the electric heater is executed,
The exhaust emission control device according to claim 1, wherein when the occurrence of a slip state of the unreacted HC is not detected, the control of the electric heater is not executed. The controller is
Based on the oxygen concentration detected at the inlet side and the outlet side of the oxidation catalyst, the actual value of the amount of oxygen used for HC oxidation in the oxidation catalyst is calculated, and the upstream side of the oxidation catalyst is injected. Based on the fuel injection amount, calculate a predicted value of the oxygen amount used for HC oxidation in the oxidation catalyst
The exhaust emission control device according to claim 2, wherein when the actual value is smaller than the predicted value, it is determined that a slip state of the unreacted HC has occurred. The controller is
Based on the sensor value of the oxygen concentration sensor disposed on each of the inlet side and the outlet side of the oxidation catalyst, and the sensor value of the NOx concentration sensor disposed on each of the inlet side and the outlet side of the oxidation catalyst, The exhaust emission control device according to claim 3, wherein an actual value is calculated. The control device, during the forced regeneration,
The control of the electric heater is performed so that the temperature of the outer peripheral portion of the oxidation catalyst is equal to or higher than an activation temperature at which the oxidation catalyst promotes HC oxidation. Exhaust purification device. The control device is further configured to continuously regenerate the PM filter.
The exhaust gas purification according to any one of claims 1 to 5, wherein when a decrease in the oxidation reaction of NO at the outer peripheral portion of the oxidation catalyst is detected, the electric heater is controlled to heat the outer peripheral portion of the oxidation catalyst. apparatus. The exhaust emission control device according to any one of claims 1 to 6, wherein the electric heater is disposed adjacent to an outer peripheral portion of the oxidation catalyst. The electric heater is configured to include an electrode pair that allows current to flow to the oxidation catalyst, and heats the outer peripheral portion of the oxidation catalyst by resistance heating using the current. The exhaust emission control device according to one item.   A vehicle comprising the exhaust emission control device according to any one of claims 1 to 8.

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