WO2006090513A1

WO2006090513A1 - Exhaust gas purification device and exhaust gas purification method

Info

Publication number: WO2006090513A1
Application number: PCT/JP2005/020580
Authority: WO
Inventors: Takashi Ikeda; Takao Onodera; Kenichi Nakaya; Tatsuo Mashiko
Original assignee: Isuzu Motors Limited
Priority date: 2005-02-24
Filing date: 2005-11-10
Publication date: 2006-08-31
Also published as: JP2006233832A

Abstract

An exhaust gas purification system (10) of a vehicle provided with an exhaust gas treatment device (3) having, in an exhaust path of an internal combustion engine (1), either or both of an oxidation catalyst (3a) and a diesel particulate filter (3b). The exhaust gas purification system has a control device provided with a HC separation control means for performing HC separation control by which HC that is accumulated in the exhaust gas treatment device is burnt and removed. The HC separation control is performed when an intake air temperature (Tin) detected by a suction air temperature detection means (32A) is not higher than a predetermined determination temperature (T0) and simultaneously the time duration of an idling state exceeds a predetermined determination value. The construction above solves a problem of HC accumulation caused by idling operation for many hours and minimizes deterioration in drivability and worsening of fuel consumption.

Description

Specification

Exhaust gas purification device and exhaust gas purification method

Technical field

The present invention relates to an exhaust gas purification system that includes an oxidation catalyst or a diesel particulate filter (DPF) and purifies exhaust gas from an internal combustion engine. More specifically, the present invention relates to an exhaust gas purification system that can prevent discharge of unburned hydrocarbon (HC) accumulated in an oxidation catalyst or diesel particulate filter into the atmosphere by idling for a long time.

Background art

[0002] In automobiles equipped with diesel engines, in order to purify particulate matter (PM: particulate matter) (hereinafter referred to as PM) in the exhaust gas, an oxidation catalyst or diesel is used in the exhaust path of the engine. A particulate matter reducing device such as a particulate filter (DPF: Diesel Particulate Filter: DPF) is placed.

[0003] However, in this diesel vehicle, unburned hydrocarbon (HC) discharged during idling, organic soluble components (SOF: Soluble Organic Fraction: hereinafter referred to as S0F) of PM, Steam or the like adheres to and accumulates on the surface of the oxidation catalyst or the surface of the filter.

[0004] That is, some vehicles, such as a freezer car, are idle for a long time. During this long idle operation, HC is stored in the oxidation catalyst and DPF. If the idling state continues and the accumulation of unburned HC or S0F continues for several hours, then the vehicle is started again and the accelerator is opened, for example, when the accelerator opening increases, the following occurs. A problem occurs.

[0005] In this case, the flow rate of the exhaust gas increases without the exhaust gas temperature being raised to the temperature range where the oxidation catalyst is activated. As a result, unburned HC and SOF adhering to the oxidation catalyst and filter are desorbed all at once and released into the atmosphere from the rear end of the exhaust pipe. Since these are emitted as white smoke, the visibility of the following vehicle is poor. They also cause odors. [0006] On the other hand, there is a DPF that has an electric heater for regeneration. In this DPF, the unheated HC adhering to the DPF is incinerated by heating the DPF using the electric heater during idling. Can be removed. However, in this case, the problem of increased power consumption arises.

[0007] Furthermore, a heating source such as an electric heater is provided, and the exhaust gas is controlled by fuel injection control such as after-rejection by fuel injection of the engine. There is a method to oxidize and remove unburned HC by raising the temperature of the oxidation catalyst and DPF by raising the temperature. However, in this case, there is a problem that a control program for implementing this method is required again.

[0008] And, for example, as described in Japanese Patent Laid-Open No. 9-222012 (page 3), Japanese Patent Laid-Open No. 9-264162 (page 2), etc., conventional diesel engines In a vehicle exhaust gas purification system equipped with a catalyst that oxidizes unburned components contained in engine exhaust, the amount of white smoke and odor generated at start-up is greatly reduced by the following method. Yes.

[0009] A throttle valve is provided on the upstream side of the catalyst in the engine exhaust passage, and an actuator for opening and closing the throttle valve is connected to the battery side via a parking brake switch. The catalyst is activated by increasing the exhaust temperature of the engine by applying an exhaust throttle while parking. This catalyst activation greatly reduces the amount of white smoke and odor generated when starting.

However, in this exhaust gas purification apparatus, the exhaust gas temperature is kept high even during parking, and unburned HC and the like are oxidized by the activated oxidation catalyst. Therefore, there is no adhesion and accumulation on the oxidation catalyst. However, when the parking brake is activated, the throttle valve always closes and the exhaust throttle works, so the exhaust throttle always continues during parking. In addition, exhaust throttling is also required when waiting for traffic lights or stopping for a short time. As a result, there arises a problem that fuel consumption is significantly deteriorated.

As a measure against white smoke, for example, as described in Japanese Unexamined Patent Publication No. 2004-100668, when the engine is left idle for a long time, the exhaust brake is closed to raise the temperature of the exhaust gas. An exhaust gas purification system that burns HC with an oxidation catalyst has also been proposed.

[0012] On the other hand, the accumulation of HC in the oxidation catalyst and DPF during long idle operation is caused by the intake air temperature. It occurs only when the temperature is low, and it has been concentrated that the temperature is high in warm regions and summer, and that it does not occur in the season. For this reason, simply monitoring idle operation for a long time and performing control to perform HC disengagement control such as exhaust throttling and idle rotation speed increase when the idle operation exceeds a predetermined judgment time, it is possible to switch to an oxidation catalyst or DPF. HC withdrawal control is performed even though there is no accumulation of HC. In addition, the driver pitility and fuel consumption associated with this HC departure control are suffered.

Disclosure of the invention

[0013] The present invention has been made to solve the above-described problems, and an object of the present invention is to monitor intake air temperature and determine intake air temperature for the problem of HC accumulation due to idling for a long time. By adding to the exhaust gas purification system, the exhaust gas purification system and the exhaust gas can be made to perform more rational HC departure control, and the deterioration of driver parity and fuel consumption accompanying the HC departure control can be minimized. The object is to provide a gas purification method.

[0014] An exhaust gas purification system for achieving the above object includes an exhaust gas treatment device having either or both of an oxidation catalyst and a diesel particulate filter in an exhaust passage of an internal combustion engine. In a vehicle exhaust gas purification system, an intake air temperature detecting means for detecting an intake air temperature, an idling state detecting means for detecting that the operating state of the internal combustion engine is in an idling state, and an idling state detected by the idling state detecting means. A duration measuring means for measuring a duration time of the idling state, and an intake air temperature detected by the intake air temperature detecting means is equal to or lower than a predetermined judgment temperature, and a duration time of the idling state exceeds a predetermined judgment time. A control device having HC removal control means for performing HC removal control for burning and removing HC accumulated in the exhaust gas treatment device. Bei was constructed.

[0015] In addition, an exhaust gas purification method for achieving the above object is provided for a vehicle including an exhaust gas treatment device having either or both of an oxidation catalyst and a diesel particulate filter in an exhaust passage of an internal combustion engine. In the exhaust purification system, when the intake air temperature is lower than the predetermined judgment temperature and the idling state duration exceeds the predetermined judgment time, the HC accumulated in the exhaust gas treatment device is burned and removed. It is characterized by performing HC withdrawal control. [0016] According to the exhaust gas purification system and the exhaust gas purification method of the present invention, by monitoring the intake air temperature and adding the intake air temperature to the determination items for the problem of HC accumulation due to the idling operation for a long time, Judgment for separation control can be made more rational. As a result, it is possible to minimize the deterioration of driver spirit and fuel consumption associated with HC departure control.

Brief Description of Drawings

FIG. 1 is a system configuration diagram of an exhaust gas purification system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a control device for an exhaust gas purification system according to an embodiment of the present invention.

FIG. 3 is a diagram showing a flow of HC adhesion countermeasure control.

FIG. 4 is a diagram showing an example of a time series of HC withdrawal control.

FIG. 5 is a diagram showing another example of time series of HC withdrawal control.

BEST MODE FOR CARRYING OUT THE INVENTION

[0018] The exhaust gas purification system and the exhaust gas purification method of the embodiment according to the present invention will be described below by taking an exhaust gas purification system including a continuous regeneration type DPF device of a combination of an oxidation catalyst and a filter with a catalyst as an example. This will be described with reference to the drawings.

FIG. 1 shows the configuration of an exhaust gas purification system 1 for an internal combustion engine according to this embodiment. This exhaust gas purification system 1 is configured by providing a continuous regeneration type DPF device 13 in an exhaust passage 12 connected to an exhaust manifold 11 of a diesel engine 10. This continuous regeneration type DPF device 13 is configured to have an oxidation catalyst 13a on the upstream side and a filter 13b with catalyst on the downstream side. Further, an exhaust throttle valve (exhaust brake) 16 is provided upstream of the continuous regeneration type DPF device 3.

The oxidation catalyst 13a is formed by supporting an oxidation catalyst such as platinum (Pt) on a support such as a ceramic honeycomb structure. The filter with catalyst 13b is a monolith honeycomb wall flow type filter in which the inlet and outlet of a porous ceramic honeycomb channel are alternately sealed, or a felt-like filter in which inorganic fibers such as alumina are randomly laminated. Etc. are formed. A catalyst such as platinum or cerium oxide is supported on the filter.

[0021] Then, the monolith honeycomb type wall flow type finore is applied to the filter with catalyst 13b. When PM is used, PM (particulate matter) in the exhaust gas G is trapped by the porous ceramic wall. Further, when a fiber filter type is adopted for the filter with catalyst 13b, PM is collected by the inorganic fibers of the filter.

[0022] Then, in order to estimate the amount of PM accumulated on the filter with catalyst 13b, a differential pressure sensor 21 is provided in the conducting pipe connected before and after the continuous regeneration type DPF device 13. Further, an oxidation catalyst inlet exhaust temperature sensor 22 and a filter inlet exhaust temperature sensor 23 are provided for regeneration control of the filter with catalyst 13b. The oxidation catalyst inlet exhaust temperature sensor 22 is provided upstream of the oxidation catalyst 13a and the filter with catalyst 13b. The filter inlet exhaust temperature sensor 23 is provided between the oxidation catalyst 13a and the filter with catalyst 13b. Further, an intake air temperature sensor 24 is provided in the intake passage 17 leading from the air cleaner 18 to the intake manifold 15.

Output values of these sensors are input to a control device (ECU: engine control unit) 30. The control device 30 performs overall control of the operation of the engine 10 and also performs regeneration control of the continuous regeneration type DPF device 13. A control signal output from the control device 30 controls the fuel injection device (injection nozzle) 14 of the engine 10 and the exhaust throttle valve (exhaust brake) 16 provided in the exhaust passage 12. Furthermore, if necessary, an intake throttle valve (not shown) that adjusts the intake air amount to the intake manifold 15 or an EGR valve that adjusts the EGR amount installed in the EGR passage along with the EGR cooler (see Fig. This is controlled.

[0024] The fuel injection device 14 is connected to a common rail injection system (not shown) that temporarily stores high-pressure fuel that has been pressurized by a fuel pump (not shown). In order to operate the engine, the control device 30 includes information such as the accelerator opening from the accelerator position sensor (APS) 31 and the engine speed from the rotational speed sensor 32, as well as the parking brake switch ONZOFF and power take-off. Information such as (PT ○) switch ON / OFF, neutral switch ONZ ○ FF, vehicle speed, and coolant temperature Tw are also entered.

The control device 30 is also provided with a DP F regeneration control means 51 having a PM collection amount estimating means 51 A and a regeneration control means 51 B. The amount of PM collected by the filter 13b with catalyst of the continuous regeneration type DPF device 13 is matched by the PM collection amount estimation means 51A by matching the differential pressure ΔP before and after the filter 13b with catalyst with the amount of PM collected. Estimate the amount collected. The regeneration control means 51B performs regeneration control when the differential pressure ΔP is equal to or greater than a predetermined regeneration determination value ΔPa. [0026] This regeneration control is slightly different depending on the type of the continuous regeneration type DPF device 13. In this regeneration control, the timing of the main injection (main) of the fuel injection of the engine 10 is delayed (retarded), post-injected (post-injection), intake throttle is performed, and the exhaust gas temperature is adjusted. Raise. As a result, the PM collected in the continuous regeneration type DPF device 13 is oxidized and removed so that the temperature and environment are suitable for the oxidation removal of PM. In the apparatus shown in FIG. 1, the driver can be informed that the regeneration control of the filter 13b with catalyst is necessary by the blinking light 41 and the warning light 42. The driver sees these instructions and can manually force regeneration by pressing the manual regeneration switch 43.

In the present invention, as shown in FIG. 2, the control device 30 includes HC adhesion countermeasure control means 52 in addition to the engine control means 50 and the DPF control means. The HC attachment countermeasure control means 52 includes an intake air temperature detection means 52A, an idling state detection means 52B, a continuous time measurement means 52C, and an HC separation control means 52D.

[0028] The intake air temperature detecting means 52A is means for detecting the intake air temperature. This means includes an intake air temperature sensor 24 provided in the intake passage 17. Further, the idling state detecting means 52B is a means for detecting whether or not the engine is in an idling state. This means is here configured to be in an idling state when the parking brake switch is on.

[0029] It should be noted that, regarding the idling state determination by the idling state detecting means 52B, in addition to the parking brake switch, the engine speed detected by an accelerator brake for an exhaust brake, a magnetic sensor, etc., the accelerator detected by the accelerator sensor It is also possible to use the opening, vehicle speed, and the neutral position of the reduction gear. In addition, PTO (power take-off) is not used and DPF is not being replayed. Under these conditions, it is assumed that the engine is not idling.

[0030] The duration measuring means 52C is means for starting measurement when the idling state is established. This means is here configured to measure the idling duration tm with a timer. In addition, when monitoring the continuation of the idling state, it is intended to see the continuation of HC adhesion over a long period of time, so even if the idle state temporarily collapses, it is not considered to be the release of the idle state. It is preferable to configure so as not to exist. This one Temporary collapse of the idle state occurs due to vehicle movement at a low speed for a short time (for example, several minutes) or temporary strengthening of air conditioning.

[0031] Further, the HC desorption control means 52D is configured such that the intake air temperature Tin detected by the intake air temperature detection means 52A is equal to or lower than a predetermined determination temperature TO and the idling state duration tm exceeds a predetermined determination value tmO. Is configured to perform HC withdrawal control. The predetermined determination value tmO is a predetermined duration, and is set to 1 to 5 hours, for example.

This HC detachment control is configured to close the exhaust throttle valve 16. Further, the HC separation control is configured to release the state in which the exhaust throttle valve 16 is closed when the operating state of the engine 10 departs from the idling state, such as at the start of traveling or when the PT is operated.

[0033] Alternatively, in the HC separation control, the exhaust throttle valve 16 is closed and the idle speed is set to 10% to 130. It is configured to rise about / ο, that is, to idle up. Furthermore, in this Η C release control, the idle-up state with the exhaust throttle valve 16 closed is canceled when the engine 10 operating state deviates from the idling state, such as when starting running or ΡΤ〇 operation. Is done.

In FIG. 1, the exhaust throttle valve 16 is provided on the upstream side of the continuous regeneration type DPF device 13, but may be disposed on the downstream side of the continuous regeneration type DPF device 13. Les.

[0035] According to the exhaust gas purification system 1 configured as described above, HC adhesion countermeasure control is performed according to the flow illustrated in Fig. 3 regarding the accumulation and removal of unburnt HC and SOF in the oxidation catalyst 13a and the filter with catalyst 13b. Is done.

The HC adhesion countermeasure control in FIG. 3 is a control performed in parallel with the normal filter regeneration control. In this filter regeneration control, filter regeneration is performed when it is determined that the PM collection estimated amount by the PM collection amount estimating means 51A and the regeneration control means 51B exceeds a predetermined value.

[0037] When this control flow is called from the main control flow that also controls the engine and the like, it is first determined in step S51. In step S51, it is determined whether or not the intake air temperature Tin detected by the intake air temperature detection means 52A is equal to or lower than a predetermined determination temperature TO. In this determination, if the intake air temperature Tin is not equal to or lower than the predetermined determination temperature TO, the process returns and the HC disengagement control is not performed. [0038] If the intake air temperature Tin is equal to or lower than the predetermined determination temperature TO in step S51, the process proceeds to the next step S52. In step S52, the idling state detecting means 52B determines whether or not the idling state. If it is not idling in this determination, it returns and does not perform HC removal control.

[0039] If the engine is in the idling state in step S52, the duration is counted in step S53, and measurement of the duration tm in the idling state is started. After this count, it is determined in step S54 whether or not the duration tm exceeds a predetermined determination time tmO. If not, the process returns to step S52. Then, steps S52, S53, and S54 are repeated until the duration tm exceeds the predetermined determination time tmO, and when the idle state is not reached midway, the process returns. This predetermined judgment value (duration) tmO is set to 1 hour to 5 hours, preferably 2 hours to 3 hours.

[0040] Then, when the duration tm exceeds the predetermined determination time tmO in step S54, HC detachment control is performed in step S55. When this HC disengagement control is performed only with the exhaust throttle, as shown in FIG. 4, the valve closing control of the exhaust throttle valve 16 is continued for a predetermined first duration tml, and then the exhaust throttle valve 16 is opened. The valve control is continued for a predetermined second duration (rest time m2), and this is repeated until the idling state ends. If it is determined that the idling state has ended during this repetition, the exhaust throttle is The valve closing control or valve opening control of the valve 16 is also terminated.

[0041] The predetermined first duration (removal time) tml is set to 1 hour to 5 hours, preferably 2 hours to 3 hours. The predetermined second duration (the pause time m2 is set to 1 to 10 seconds, preferably 4 to 7 seconds.

[0042] When performing HC separation control with exhaust throttling and idling up, as shown in FIG. 5, the valve closing control and idling up of the exhaust throttling valve 16 are continued for a predetermined third duration tm3. To do. Thereafter, the valve opening control of the exhaust throttle valve 16 and no idle up are continued for a predetermined fourth duration (rest time) tm4. This is repeated until the idling state is completed. When it is determined that the idling state has ended, the valve closing control of the exhaust throttle valve 16 and the idle up or the valve opening control of the exhaust throttle valve 16 are also ended. If this exhaust throttling and idle up are performed, the following can be achieved. The exhaust gas temperature can be raised by idling up, so HC combustion removal can be promoted. The time for exhaust throttling can be shortened compared to the case of exhaust throttling alone. In addition, exhaust throttling HC can be prevented from adhering to and accumulating in the oxidation catalyst 13a.

[0043] The predetermined third duration (removal time) tm3 is 5 minutes to 50 minutes, preferably 10 minutes to 2

Set to 0 minutes. The predetermined fourth duration (rest time) tm4 is set between 0.5 hours and 4 hours, preferably between 0.5 hours and 2 hours.

[0044] Here, the end of the valve closing control or valve opening control of the exhaust throttle valve 16 means that the use of the exhaust throttle valve 16 as a countermeasure for HC separation is stopped, and It should be used for exhaust brake operation.

[0045] By reducing the amount of exhaust gas with this exhaust throttle, unburned HC, S0F, etc. flowing into the oxidation catalyst 13a or the filter with catalyst 13b are reduced. Further, by increasing the exhaust gas temperature with this exhaust throttle, unburned HC, S0F, etc. accumulated on the oxidation catalyst 13a or the filter with catalyst 13b can be oxidized and removed.

[0046] After making this return, this HC withdrawal countermeasure control is called again and started, and steps S51 to S55 are repeated. This process is repeated while the engine 10 is running, and the accumulation and monitoring of unburned HC and SOF on the oxidation catalyst 13a and the filter 13b with catalyst are monitored and removed.

[0047] According to the above exhaust gas purification system and HC separation countermeasure control, monitoring the intake air temperature Tin and adding the intake air temperature Tin to the judgment items for the problem of HC accumulation due to long-term idle operation. This makes it possible to make the judgment for HC withdrawal control more rational. As a result, it is possible to minimize the deterioration in drivability and fuel consumption associated with HC departure control.

Industrial applicability

[0048] The exhaust gas purifying apparatus and the exhaust gas purifying method of the present invention having the above-described excellent effects include not only exhaust gases of internal combustion engines mounted on automobiles, but also exhaust gases of various industrial machines and stationary internal combustion engines. It can be used very effectively as an exhaust gas purification device and exhaust gas purification method for factory gas, power plant gas, etc.

Claims

The scope of the claims

[1] In an exhaust gas purification system for a vehicle including an exhaust gas processing device having one or both of an oxidation catalyst and a diesel particulate filter in an exhaust passage of an internal combustion engine, an intake air temperature detecting means for detecting an intake air temperature; An idling state detecting means for detecting that the operating state of the internal combustion engine is an idling state, a duration measuring means for measuring the duration of the idling state detected by the idling state detecting means, and the intake air temperature detecting means When the detected intake air temperature is equal to or less than a predetermined determination temperature and the duration of the idling state exceeds a predetermined determination time, HC desorption control is performed to burn and remove HC accumulated in the exhaust gas processing device. An exhaust gas purification system comprising a control device having an HC detachment control means.

[2] In an exhaust gas purification system for a vehicle provided with an exhaust gas treatment device having one or both of an oxidation catalyst and a diesel particulate filter in an exhaust passage of an internal combustion engine, the intake air temperature is not more than a predetermined judgment temperature, and An exhaust gas purification method comprising performing HC separation control for burning and removing HC accumulated in the exhaust gas processing device when the duration of the idling state exceeds a predetermined determination time.