JP2005207319A - Method and apparatus for regenerating exhaust gas purification filter for diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise exhaust temperature without deterioration of combustion when regenerating an exhaust gas purification filter provided in an exhaust gas system of a diesel engine. <P>SOLUTION: A glow plug for heating a suction air of the diesel engine is provided. A time of reproduction is determined based on the pressure difference between the upstream side and the downstream side of the exhaust gas purification filter. In case that the exhaust gas purification filter is regenerated during an operation of the diesel engine, at first a glow plug is turned on and then the diesel engine is operated in the condition that the exhaust gas temperature is raised higher than that in the normal combustion condition. the suction air throttling is made to raise the exhaust temperature. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a regeneration method and a regeneration device for an exhaust gas purification filter for a diesel engine.

  The exhaust gas (exhaust gas) of the diesel engine contains carbon particulates called diesel particulates, and an exhaust purification filter that collects the carbon particulates is provided in the exhaust system. The carbon fine particles collected in the exhaust purification filter are removed by combustion when the exhaust is exhausted at a high temperature (for example, 400 ° C. or higher), and the exhaust purification filter is regenerated.

  Since exhaust gas is discharged at a high temperature when the diesel engine is in a high-load operation state, if the diesel engine is continuously operated in a medium-to-low load state, the amount of carbon fine particles deposited on the exhaust purification filter increases and becomes clogged. There is a problem of causing. In order to prevent this clogging, a regenerator that raises the temperature of the exhaust gas in a medium and low load state is provided.

And as a method of raising the temperature of the exhaust gas in a medium and low load state, (1) a method of restricting the intake air, (2) a method of changing the fuel injection timing, and (3) a method of restricting the exhaust gas are conceivable. However, when one of the above methods is performed alone, there is a problem that hydrocarbons in the exhaust gas increase or the combustion state of the engine greatly changes from the normal combustion state. In order to solve this problem, when the exhaust purification filter is regenerated, the intake temperature to the engine is reduced to raise the exhaust temperature, and the fuel injection advance mechanism is operated to advance the fuel from the optimum standard fuel injection timing. Has been proposed (see Patent Document 1).
JP-A-6-137130 (paragraphs [0005] and [0006] in FIG. 3, FIG. 3)

  However, in order to regenerate the exhaust purification filter on which the carbon fine particles are accumulated, throttle of the intake air or operation of the exhaust throttle always deteriorates the combustion state of the engine. However, there is a limit to the technique for advancing the injection timing as described in. This is because if the intake air is reduced to reduce the amount of air, the oxygen concentration decreases, the combustion worsens, and the smoke worsens. And even if the advance of the injection timing is performed, the pressure in the combustion chamber does not recover, and it becomes very difficult to secure the ignition temperature necessary for combustion unless the compression ratio is increased.

Further, when the injection timing is shifted to the advance side, the premixing period is increased and abrupt combustion occurs, resulting in deterioration of combustion noise and impairing merchantability.
The present invention has been made in view of the above-described conventional problems, and its purpose is to increase the exhaust temperature without deteriorating combustion during the regeneration process of the exhaust purification filter provided in the exhaust system of the diesel engine. Another object of the present invention is to provide a regeneration method and a regeneration device for an exhaust gas purification filter for a diesel engine.

  In order to achieve the above object, an invention according to claim 1 is a method for regenerating an exhaust purification filter provided in an exhaust system of a diesel engine. Then, an intake air heating means for heating the intake air of the diesel engine is provided, and when the exhaust purification filter is regenerated during operation of the diesel engine, the intake air heating means is first operated, and then the standard combustion state The diesel engine is operated in a state where the exhaust temperature is further increased. Here, the “standard combustion state” means an appropriate combustion state corresponding to the operating state (load state) of the engine.

  As an operation method in a state where the exhaust temperature is raised from the standard combustion state, there are a method of restricting the intake air, delaying the fuel injection timing, or restricting the exhaust gas. In order to regenerate the exhaust purification filter, if the diesel engine is operated with the exhaust temperature simply raised from the standard combustion state, hydrocarbons and carbon monoxide in the exhaust will increase or smoke will deteriorate due to deterioration of combustion. To do. However, in the present invention, unlike the conventional method, when the exhaust purification filter is regenerated, first, the intake air heating means is actuated to raise the intake air temperature, and the exhaust gas temperature is raised from the standard combustion state. The diesel engine is operated at As a result, even if combustion is performed under conditions such as an intake throttle that would otherwise deteriorate combustion, the temperature necessary for combustion is ensured and stable combustion is performed.

  The invention according to claim 2 is a regeneration device for an exhaust purification filter provided in an exhaust system of a diesel engine. And an intake air heating means for heating the intake air of the diesel engine, a regeneration timing detection means for detecting the regeneration timing of the exhaust purification filter, and an exhaust purification filter based on a detection signal of the regeneration timing detection means. Judgment means for judging whether or not reproduction is necessary is provided. When it is determined that the exhaust purification filter needs to be regenerated, first, the intake air heating means is operated, and then the diesel engine is controlled to operate in a combustion state in which the exhaust temperature is raised from the standard combustion state. Control means.

  In the present invention, the regeneration timing of the exhaust purification filter is detected by the regeneration timing detection means, and based on the detection signal of the regeneration timing detection means, it is determined whether or not regeneration of the exhaust purification filter is necessary. When it is determined that regeneration is necessary, the intake air heating means is first activated to increase the intake air temperature of the engine. Then, the diesel engine is operated in a combustion state in which the exhaust gas temperature is raised from the standard combustion state with the intake air temperature rising. As a result, even if combustion is performed under conditions such as an intake throttle that would otherwise deteriorate combustion, the temperature necessary for combustion is ensured and stable combustion is performed.

  According to a third aspect of the present invention, in the second aspect of the present invention, the intake air heating means is a glow plug. In the present invention, when it is determined that the exhaust purification filter needs to be regenerated, the glow plug is heated, and then the diesel engine is operated in a combustion state in which the exhaust temperature is raised from the standard combustion state. When a glow plug is provided as the intake air heating means, it is easier to ensure the temperature required for combustion than the intake heater. This is because in the case of a glow plug, the intake air is heated in the combustion chamber, but since the intake heater heats the intake air in the intake pipe, the heated intake air may be cooled before entering the combustion chamber.

  According to a fourth aspect of the present invention, in the invention according to the second or third aspect, the control means controls the engine to operate the diesel engine in a state in which the exhaust temperature is raised from a standard combustion state. Control to throttle the intake air. Therefore, in the present invention, control is easier as compared with methods other than the intake throttle.

  ADVANTAGE OF THE INVENTION According to this invention, in the regeneration process of the exhaust gas purification filter provided in the exhaust system of the diesel engine, exhaust gas temperature can be raised without deteriorating the combustion in a diesel engine.

Hereinafter, an embodiment in which the present invention is applied to an automobile diesel engine will be described with reference to FIGS. 1 and 2.
FIG. 2 is a schematic configuration diagram of a diesel engine system. The diesel engine system includes a diesel engine 11 (hereinafter also simply referred to as the engine 11), a fuel injection pump 12, and an ECU 13 (electronic control unit) that electronically controls the diesel engine 11 and the fuel injection pump 12. Yes.

  The diesel engine 11 includes a cylinder head 14 and a cylinder block 15 formed with a plurality of cylinders 15a (only one is shown in FIG. 2). A piston 16 is provided in each cylinder 15a so as to be able to reciprocate. A combustion chamber 17 is formed for each cylinder by the piston 16, the cylinder 15 a and the cylinder head 14. The cylinder head 14 is provided with a fuel injection nozzle 18 with its nozzle portion exposed to the combustion chamber 17, and fuel pumped from the fuel injection pump 12 through a fuel passage (not shown) is supplied from the fuel injection nozzle 18. It is injected into the combustion chamber 17. The piston 16 reciprocates in the cylinder 15a by the propulsive force obtained from the explosion after the intake / compression stroke in the combustion chamber 17, and the reciprocating motion of the piston 16 rotates the crankshaft (output shaft) (not shown) via the connecting rod 19. It is converted into motion and output is obtained.

  An intake passage 20 connected to the intake port and an exhaust passage 21 connected to the exhaust port are connected to the combustion chamber 17 of the engine 11. An air cleaner 22 and a throttle valve 23 are provided in the intake passage 20. The throttle valve 23 is an electric type operated by a throttle motor (electric motor) 24, and the flow rate of the intake air introduced into the combustion chamber 17 is adjusted by adjusting the opening of the throttle valve 23.

  The exhaust passage 21 that constitutes the exhaust system of the diesel engine 11 contains exhaust gas (exhaust gas) of the engine 11 and collects carbon particulates (hereinafter referred to as PM) called diesel particulates. 25 is provided. The exhaust passage 21 is provided with a differential pressure sensor 26 that detects a differential pressure between the pressure upstream of the exhaust purification filter 25 and the pressure downstream. The differential pressure sensor 26 constitutes a regeneration timing detection unit that detects the regeneration timing of the exhaust purification filter 25.

  The cylinder head 14 is provided with a glow plug 27 in a state where the tip is disposed in the combustion chamber 17. The glow plug 27 constitutes intake air heating means for heating the intake air during the regeneration process of the exhaust purification filter 25.

  The diesel engine 11 and the fuel injection pump 12 are provided with various sensors as detection means for detecting an engine load, an operating state, and the like. As the various sensors, for example, the cylinder block 15 is provided with a water temperature sensor 28 for detecting the water temperature in the engine 11. An air flow meter 29 for detecting the amount of intake air is provided on the downstream side of the air cleaner 22 provided in the intake passage 20. Further, an accelerator opening sensor 31 that detects the amount of depression of the accelerator pedal 30 is used as a detection unit that detects the operating state of the engine 11 and the like.

  On the other hand, the fuel injection pump 12 is driven by rotational input from the output shaft of the engine 11, and includes an electromagnetic spill valve 32 for adjusting the fuel injection amount and a timer device for controlling the fuel injection timing ( Timer control valve) 33 is provided. The energization time during the control of the electromagnetic spill valve 32 is controlled to adjust the overflow flow rate (spill amount), whereby the fuel injection amount injected from the fuel injection nozzle 18 is adjusted. Further, the fuel injection timing is determined by adjusting the start timing of the plunger that reciprocates in the pump housing by the duty control of the timer device 33. Further, the fuel injection pump 12 is provided with an engine rotation speed sensor 34 for detecting the engine rotation speed NE and a fuel temperature sensor 35 for detecting the fuel temperature in the fuel injection pump 12.

  The differential pressure sensor 26, the water temperature sensor 28, the air flow meter 29, the accelerator opening sensor 31, the engine speed sensor 34, and the fuel temperature sensor 35 are all connected to the input side (input interface) of the ECU 13. Data detected by each sensor is input to the ECU 13.

  The throttle motor 24, the glow relay 27a of the glow plug 27, the electromagnetic spill valve 32, and the timer device 33 are electrically connected to the output side (output interface) of the ECU 13, respectively. The ECU 13 determines the operating state of the diesel engine 11 based on detection signals output from the sensors, and the throttle valve 23 (throttle motor 24) is set so that the standard combustion state is obtained except during the regeneration process of the exhaust purification filter 25. ), The electromagnetic spill valve 32 and the timer device 33 are controlled. The “standard combustion state” means an appropriate combustion state corresponding to the operating state (load state) of the engine.

The ECU 13 incorporates a microcomputer (hereinafter referred to as “microcomputer”) 36. The microcomputer 36 includes a memory (ROM and RAM) 37.
The memory 37 should be commanded for engine control on the basis of the operation state grasped from the detection signals of the water temperature sensor 28, the air flow meter 29, the accelerator opening sensor 31, the engine speed sensor 34, and the fuel temperature sensor 35. Maps, formulas, and the like used for determining various command values (control values) are stored. The map, formula, etc. include, for example, a map, formula, etc. for determining the fuel injection amount, throttle opening, and the like.

  The memory 37 stores a program for performing the regeneration process of the exhaust purification filter 25. The ECU 13 constitutes determination means for determining whether or not the exhaust purification filter 25 needs to be regenerated based on the detection signal of the differential pressure sensor 26. When it is determined that the exhaust purification filter 25 needs to be regenerated, the ECU 13 first controls the engine 11 so that the engine 11 is operated in a state in which the exhaust temperature is raised from the standard combustion state after the glow plug 27 is operated. Configure the means.

Next, the operation of the apparatus configured as described above will be described.
The ECU 13 responds to the engine operating state (load state) based on the operating state grasped from the detection signals of the water temperature sensor 28, the air flow meter 29, the accelerator opening sensor 31, the engine speed sensor 34, and the fuel temperature sensor 35. The throttle motor 24, the electromagnetic spill valve 32, and the timer device 33 are controlled so that the proper combustion state is obtained. This control is performed in a state where the regeneration process of the exhaust purification filter 25 is not performed.

  The ECU 13 performs control for regeneration processing of the exhaust purification filter 25 according to the flowchart of FIG. This control is performed every predetermined time set in advance. In step S1, the ECU 13 reads a detection signal of the differential pressure sensor 26 and obtains a differential pressure Pd between the upstream pressure and the downstream pressure of the exhaust purification filter (DPF) 25 (DPF differential pressure detection). Next, in step S2, the ECU 13 compares the DPF regeneration determination reference pressure P1 and the differential pressure Pd to determine whether or not it is time to regenerate the exhaust purification filter 25. Specifically, the ECU 13 determines whether or not the differential pressure Pd is greater than the regeneration determination reference pressure P1. If it is greater, the ECU 13 determines that regeneration is necessary, and proceeds to step S3. If not greater, the regeneration control ends. Therefore, if not large, the engine 11 is operated in the standard combustion state.

  In step S3, the ECU 13 outputs an energization instruction command to the glow relay 27a. Then, the glow plug 27 is turned on (glow energization ON). After the glow plug 27 is turned on and the tip temperature of the glow plug 27 has risen sufficiently, the ECU 13 proceeds to step S4, where the throttle motor 24 makes the opening of the throttle valve 23 smaller than the standard combustion state of the engine 11. A command signal is output. Then, the throttle motor 24 is driven to throttle the intake air. As a result, the exhaust temperature rises (step S5). When the exhaust temperature rises above the PM combustion temperature, the exhaust purification filter 25 is regenerated (step S6).

  If the engine 11 is operated in a state where the exhaust temperature is simply raised from the standard combustion state, hydrocarbons and carbon monoxide in the exhaust will increase or smoke will deteriorate due to deterioration in combustion. However, when the exhaust purification filter 25 is regenerated, the engine 11 is first operated in a state where the exhaust temperature is increased from the standard combustion state with the glow plug 27 turned on and the intake air temperature increased. Is called. As a result, even if combustion is performed under conditions such as intake throttling that would otherwise deteriorate combustion, the temperature necessary for fuel combustion is ensured and stable combustion is performed.

  Next, in step S7, the ECU 13 reads the detection signal of the differential pressure sensor 26 and obtains the differential pressure Pd between the upstream pressure and the downstream pressure of the exhaust purification filter 25. In step S8, the DPF regeneration completion determination reference pressure P2 is compared with the differential pressure Pd to determine whether the regeneration of the exhaust purification filter 25 is completed. Specifically, the ECU 13 determines whether or not the differential pressure Pd is smaller than the regeneration completion determination reference pressure P2. If it is smaller, the ECU 13 determines that regeneration is completed, and proceeds to step S9. If not smaller, it returns to step S7.

  In step S <b> 9, the ECU 13 outputs a command signal for returning the opening of the throttle valve 23 to a value corresponding to the standard combustion state of the engine 11 to the throttle motor 24. Then, the throttle motor 24 is driven to release the intake throttle. Next, after the intake air is recovered, the ECU 13 outputs an energization release instruction command to the glow relay 27a in step S10, and the glow plug 27 is turned off (glow energization OFF). Then, the regeneration control of the exhaust purification filter 25 ends.

This embodiment has the following effects.
(1) Intake air heating means (glow plug 27) for heating the intake air of the diesel engine 11 is provided, and when the exhaust purification filter 25 is regenerated during operation of the engine 11, the intake air heating means is first activated. Thereafter, the engine 11 is operated in a state where the exhaust temperature is raised from the standard combustion state. Therefore, even if combustion is performed under conditions that would otherwise deteriorate combustion, such as an intake throttle, the temperature necessary for combustion is ensured and stable combustion is performed.

  (2) A glow plug 27 is used as the intake air heating means. Therefore, it is easier to secure the temperature required for combustion than when an intake heater is provided as the intake air heating means. This is because, in the case of the glow plug 27, the intake air is heated in the combustion chamber 17, but the intake heater heats the intake air in the intake passage 20 (intake pipe), so that the heated intake air cools before entering the combustion chamber 17. there is a possibility.

  (3) A differential pressure sensor 26 that detects the differential pressure between the pressure upstream of the exhaust purification filter 25 and the pressure downstream is provided as a regeneration timing detection means for detecting the regeneration timing of the exhaust purification filter 25. . Then, the ECU 13 determines whether or not the exhaust purification filter 25 needs to be regenerated based on the differential pressure Pd detected by the differential pressure sensor 26. Therefore, the determination of whether or not regeneration is necessary is more accurate than when the amount of PM accumulated on the exhaust purification filter 25 is estimated based on the usage time of the exhaust purification filter 25 to determine whether or not regeneration is necessary. become.

  (4) The ECU 13 throttles intake air to the engine 11 as control for operating the engine 11 in a state where the exhaust temperature is raised from the standard combustion state. Therefore, control is easier compared to methods other than the intake throttle.

(5) After the glow plug 27 is turned on for reproduction processing, the glow plug 27 is kept on until reproduction is completed. Therefore, there is also an effect of helping increase the exhaust temperature.
The embodiment is not limited to the above, and may be embodied as follows, for example.

  ○ Instead of the configuration in which the differential pressure between the pressure upstream of the exhaust purification filter 25 and the pressure on the downstream side is detected by one differential pressure sensor 26, a pressure sensor for detecting the pressure on the upstream side, A pressure sensor for detecting pressure may be provided, and the differential pressure may be obtained from detection signals of both pressure sensors.

  ○ As a regeneration timing detection means, instead of means for detecting the pressure difference between the upstream side and the downstream side of the exhaust purification filter 25, a timer that simply measures the operating time of the engine 11 is provided, and the exhaust purification filter 25 is provided every predetermined time. May be reproduced.

  As a regeneration timing detection means, a PM accumulation amount estimation means for estimating the PM accumulation amount on the exhaust purification filter 25 may be provided. The PM accumulation amount estimation means estimates the amount accumulated on the exhaust purification filter 25 from the PM amount in the exhaust discharged from the engine 11, for example. The amount of PM in the exhaust gas is measured by, for example, a light transmission type smoke meter.

  ○ The PM accumulation amount may be estimated from the operating state and time. For example, the PM accumulation amount at the time of high load operation, medium load operation, and low load operation is obtained in advance by a test, and accumulated during each operation from the start of reuse of the exhaust purification filter 25 or the end of regeneration. PM accumulation amount is estimated from time. Since the temperature becomes higher than the temperature at which PM is combusted without performing the process of increasing the exhaust temperature during high load operation, the PM accumulation amount may be estimated only from the operation time in the middle and low load state.

  The method for raising the exhaust temperature during the regeneration process of the exhaust purification filter 25 is not limited to the intake throttle. For example, the exhaust gas may be throttled or the fuel injection timing may be delayed. When exhaust throttling is performed, the intake air is throttled as a result, and the load increases, so that the exhaust temperature rises.

○ An intake heater may be provided as the intake air heating means. Further, both the glow plug 27 and the intake heater may be provided as the intake air heating means.
O Heating by the intake air heating means may be performed only at medium and low loads without heating by the intake air heating means at high load. For example, in the flowchart of FIG. 1, a step (high load determination process) for determining whether or not the vehicle is in a high load state is provided before any of steps S1, S2, and S3. If the load is not high, proceed to the next step. In this case, unnecessary intake air heating is not necessary, and the life of the intake air heating means is extended.

○ The fuel supply may be configured to employ a common rail fuel injection system.
○ The present invention may be applied to a diesel engine equipped with an exhaust gas recirculation device (EGR device).

The following technical idea (invention) can be understood from the embodiment.
(1) In the invention according to any one of claims 2 to 4, the regeneration timing detection means is based on a differential pressure between a pressure upstream of the exhaust purification filter and a downstream pressure. Is detected.

  (2) The invention according to any one of claims 2 to 4 and the technical idea (1), further comprising a high load determination means for determining whether or not the operating state is a high load state, The control means controls the diesel engine to operate in the standard combustion state even when the judgment means judges that regeneration of the exhaust purification filter is necessary in a high load state.

The flowchart which shows the reproduction | regeneration procedure of an exhaust gas purification filter. The schematic block diagram of a diesel engine system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Diesel engine (engine), 13 ... ECU as judgment means and control means, 25 ... Exhaust purification filter, 26 ... Differential pressure sensor as regeneration time detection means, 27 ... Glow plug as intake air heating means.

Claims (4)

A method for regenerating an exhaust purification filter provided in an exhaust system of a diesel engine,
Intake air heating means for heating the intake air of the diesel engine is provided, and when the exhaust gas purification filter is regenerated during operation of the diesel engine, the intake air heating means is first activated and then the exhaust gas is discharged from the standard combustion state. A method for regenerating an exhaust gas purification filter for a diesel engine that operates the diesel engine with the temperature raised. An exhaust purification filter regeneration device provided in an exhaust system of a diesel engine,
Intake air heating means for heating the intake air of the diesel engine;
Regeneration timing detection means for detecting the regeneration timing of the exhaust purification filter;
Determination means for determining whether or not regeneration of the exhaust gas purification filter is necessary based on a detection signal of the regeneration timing detection means;
When it is determined that the exhaust purification filter needs to be regenerated, first, the intake air heating unit is operated, and then the control unit controls the diesel engine to operate in a state in which the exhaust temperature is raised from the standard combustion state. Regeneration device for exhaust gas purification filter for diesel engine equipped with   The regeneration device for an exhaust gas purification filter for a diesel engine according to claim 2, wherein the intake air heating means is a glow plug.   The diesel engine according to claim 2 or 3, wherein the control means controls the intake engine to be throttled as control for operating the diesel engine in a state in which an exhaust temperature is raised from a standard combustion state. Device for exhaust gas purification filter.

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