JP2006046288A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device, capable of preventing temperature fall at a postprocessing means. <P>SOLUTION: This device is provided with a postprocessing means 5 installed in the middle of an exhaust tube 4 in which exhaust gas 2 from an engine 1 flows, a bypass passage 6 to send the exhaust gas 2 to bypass the postprocessing means 5 downstream, a passage changing means 7 provided on a branch position 4a to the exhaust tube 4 of the bypass passage 6, speed reduction detecting means 8 and 9 to detect speed reduction during drive, and a control device 10 to change the exhaust tube 4 on the side of the postprocessing means 5 into the bypass passage 6 by a passage changing means 7 when speed reduction is detected by the speed reduction detecting means 8 and 9. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust purification device applied to an engine such as a diesel engine.

  Particulate matter (particulate matter) discharged from a diesel engine as an internal combustion engine is mainly composed of carbonaceous soot and SOF (Soluble Organic Fraction) composed of high-boiling hydrocarbon components. As a component, it is composed of a small amount of sulfate (sulfate component), but as a measure to reduce this type of particulates, a particulate filter is installed in the middle of the exhaust pipe through which exhaust gas flows. It has been done conventionally.

  This type of particulate filter has a porous honeycomb structure made of a ceramic such as cordierite, and the inlets of the flow paths partitioned in a lattice pattern are alternately sealed, and the inlets are not sealed. About the flow path, the exit is sealed, and only the exhaust gas which permeate | transmitted the porous thin wall which divides each flow path is discharged | emitted downstream.

  Then, the particulates in the exhaust gas are collected and deposited on the inner surface of the porous thin wall, so that the particulates are appropriately burned and removed before the exhaust resistance increases due to clogging. It is necessary to regenerate, but in normal diesel engine operating conditions, there are few opportunities to obtain exhaust temperatures that are high enough for the particulates to self-combust. For example, an appropriate amount for platinum-supported alumina A catalyst regeneration type particulate filter in which an oxidation catalyst formed by adding a rare earth element such as cerium is integrally supported is being put to practical use.

  That is, if such a catalyst regeneration type particulate filter is employed, the oxidation reaction of the collected particulates is promoted to lower the ignition temperature, and the particulates can be burned and removed even at an exhaust temperature lower than the conventional one. It becomes possible.

  However, even when such a catalyst regeneration type particulate filter is used, the trapped amount exceeds the particulate processing amount in the operation region where the exhaust temperature is low, so such a low exhaust gas. If the operation state at the temperature continues, the particulate filter may not be regenerated well, and the particulate filter may fall into an excessive collection state, and the particulate filter is in a stage where the amount of accumulated particulates has increased. It has been considered to forcibly regenerate the particulate filter by adding fuel to the exhaust gas on the more upstream side.

  In other words, if fuel is added upstream from the particulate filter, the added fuel undergoes an oxidation reaction on the oxidation catalyst of the particulate filter, and the heat of the reaction raises the catalyst bed temperature to burn out the particulate. Thus, regeneration of the particulate filter is achieved.

  As for the method of actively regenerating this type of particulate filter, the non-ignition which is later than the compression top dead center is followed by the main injection of fuel performed near the compression top dead center for the fuel injection device of the engine. Some perform fuel addition by performing post-injection at a timing (see, for example, Patent Document 1).

Further, even in an operation state where the exhaust temperature is extremely low, there is also a type in which the exhaust gas is increased by increasing the exhaust throttle valve by narrowing the exhaust throttle valve, and the particulates are finally burned and removed (for example, , See Patent Document 2).
Japanese Patent Laid-Open No. 2003-222040 JP 2003-227330 A

  However, while the particulate filter is being regenerated in this way, when the driver decelerates while driving with the accelerator turned off, the addition of fuel injected into each cylinder of the engine is stopped and the engine is stopped. Since the intake throttle valve of the intake pipe that introduces fresh air into the exhaust pipe is fully opened, the fresh air does not burn and flows down directly to the post-processing means such as a particulate filter, causing the temperature of the post-processing means to drop, and the exhaust gas There was a problem that the purification ability of the water could not be suitably maintained.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an exhaust purification device that prevents a temperature drop of the post-processing means.

  The present invention provides post-processing means installed in the middle of an exhaust pipe through which exhaust gas from an engine flows, a bypass flow path for bypassing exhaust gas to the post-processing means and flowing downstream, A flow path switching means provided at a branch point with respect to the exhaust pipe, a deceleration detection means for detecting deceleration during traveling, and an exhaust pipe on the post-processing means side by the flow path switching means when the deceleration detection means detects deceleration. The present invention relates to an exhaust emission control device comprising a control device for switching to a bypass flow path.

  Further, the present invention preferably includes an exhaust throttle means for narrowing the flow path of the exhaust pipe, and the bypass flow path is closed by the flow path switching means when the flow path is narrowed by the exhaust throttle means.

  Furthermore, the present invention includes a post-treatment means as a particulate filter, and a fuel addition means capable of adding fuel from upstream of the particulate filter, and the fuel addition means adds the fuel to regenerate the particulate filter. It is preferable that the processing is performed by the control means.

  Thus, in this way, when the driver decelerates with the accelerator turned off while traveling, the flow switching means switches from the exhaust pipe on the post-processing means side to the bypass flow path. Even in the stopped state, it is possible to prevent the fresh air from flowing into the post-processing means and prevent the temperature of the post-processing means from decreasing.

  An exhaust throttle means for narrowing the flow path of the exhaust pipe is provided, and when the flow path is narrowed by the exhaust throttle means, the bypass flow path is closed by the flow path switching means. Since the exhaust gas is flowed to the exhaust pipe on the means side and the exhaust gas is boosted by the exhaust throttling means to raise the exhaust temperature, the temperature reduction of the post-processing means can be prevented.

  The post-processing means is a particulate filter, and a fuel addition means that can add fuel from the upstream of the particulate filter is provided. When the fuel is added by the fuel addition means to regenerate the particulate filter, the control means If it is configured to process, when the driver turns off the accelerator and decelerates while traveling, the flow path switching means switches from the exhaust pipe on the particulate filter side to the bypass flow path, so during the regeneration of the particulate filter Even if it exists, it can suppress that a fresh air flows in into a particulate filter, and can prevent the temperature fall of a particulate filter.

  According to the above-described exhaust purification device of the present invention, it is possible to prevent the fresh air from flowing into the post-processing means and prevent the temperature reduction of the post-processing means even when the fuel addition is stopped. An excellent effect can be achieved.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 and 2 show an embodiment of the present invention. Reference numeral 1 in FIG. 1 denotes a diesel engine. Exhaust gas 2 discharged from each cylinder (not shown) of the diesel engine 1 is shown in FIG. Is discharged from the exhaust manifold 3 through the exhaust pipe 4 to the outside of the vehicle.

  In the middle of the exhaust pipe 4, post-processing means 5 for purifying the exhaust gas 2 in a predetermined activation temperature range (temperature window) is provided. Here, one of the post-processing means 5 includes a particulate filter 5a that collects and burns particulates, and the other one is a predetermined part of DPNR (Diesel Particulate and NOx Reduction). Some have NOx once adsorbed on the catalyst, and have a NOx reduction catalyst that burns the particulates with highly reactive active oxygen generated at that time. Another is blowing in a reducing agent such as ammonia. Accordingly, some SCR (Selective Catalytic Reduction) includes a selective reduction catalyst that treats NOx by reacting with a reducing agent such as ammonia on the catalyst. Here, the post-processing means 5 is not limited to the above example, and is not particularly limited as long as the exhaust gas 2 is purified within a predetermined activation temperature range (temperature window). Further, the particulate filter 5a has a porous honeycomb structure made of ceramic as shown in FIG.

  Further, the exhaust pipe 4 is provided with a bypass flow path 6 so that the exhaust gas 2 is bypassed with respect to the post-processing means 5 and flows downstream, and the branch passage 4a of the bypass flow path 6 with respect to the exhaust pipe 4 is provided with exhaust gas. A flow path switching means 7 such as a switching valve is provided so that the flow of the gas 2 can be appropriately switched to the bypass flow path 6 side. Here, the flow path switching means 7 is not limited to the switching valve, and any flow path switching means 7 may be used as long as the flow path is switched.

  Further, the diesel engine 1 is equipped with a rotation sensor 8 (deceleration detection means) for detecting the engine rotation speed, and the rotation speed signal 8 a from the rotation sensor 8 and the accelerator opening are used as a load of the diesel engine 1. An accelerator opening signal 9a from an accelerator sensor 9 (deceleration detecting means) to be detected is input to a control device 10 constituting an engine control computer (ECU: Electronic Control Unit).

  The control device 10 outputs a fuel injection signal 11a to the fuel injection device 11 of the fuel addition means for injecting fuel into each cylinder of the diesel engine 1 based on the accelerator opening signal 9a and the rotation speed signal 8a. It has become so. Here, the fuel injection device 11 is composed of a plurality of injectors (not shown) provided for each cylinder, and the electromagnetic valves of these injectors are appropriately controlled to open by a fuel injection signal 11a. The injection timing (valve opening timing) and the injection amount (valve opening time) are appropriately controlled.

  Further, in the control device 10, the exhaust throttle opening command signal 12a is sent to the exhaust brake 12 of the exhaust throttle means provided on the upstream side of the flow path switching means 7 by the exhaust pipe 4 by the command signal 13a from the exhaust brake lever 13. Is output.

  Further, in the control device 10, an accelerator opening signal 9 a from the accelerator sensor 9, a rotation speed signal 8 a from the rotation sensor 8, and a command from the exhaust brake lever 13 are sent to the flow path switching means 7 such as a switching valve. Based on the signal 13a, the switching signal 7a of the flow path switching means 7 is output.

  Further, in the control device 10, the fuel injection signal 11a in the normal mode is determined based on the accelerator opening signal 9a and the rotational speed signal 8a. Depending on an example of the post-processing means 5, the particulate filter 5a When it becomes necessary to perform forced regeneration of the engine, the normal mode is switched to forced regeneration mode, and the non-ignition which is slower than the compression top dead center following the main injection of fuel performed near the compression top dead center (crank angle 0 °) The fuel injection signal 11a for performing the post injection at the timing is determined.

  The operation of the embodiment of the present invention will be described below.

  When the driver decelerates while turning off the accelerator while the post-processing means 5 is being regenerated, the fuel of the fuel addition means is based on the fuel injection signal 11a and the switching signal 7a from the control device 10. The addition of fuel is stopped by the injector 11 and the flow path switching means 7 switches the flow path from the exhaust pipe 4 on the post-processing means 5 side to the bypass flow path 6, and fresh air from the diesel engine 1 is transferred to the bypass flow path 6. By flowing, the inflow of fresh air to the post-processing means 5 is prevented and the post-processing means 5 is maintained at a high temperature. Here, the post-processing means 5 is the particulate filter 5a, and when the deceleration is performed while the particulate filter 5a is being regenerated, the particulate filter 5a is maintained at a high temperature by switching to the bypass passage 6. Yes. In the normal case, the particulate filter 5a appropriately collects the particulates in the exhaust gas 2 while the particulate filter 5a is not being regenerated.

  Further, when the exhaust brake lever 13 is turned on while the post-processing means 5 is being regenerated, the flow path switching means 7 bypasses the bypass flow based on the opening command signal 12a from the control device 10. The flow path is switched to the exhaust pipe 4 on the side of the post-processing means 5 so as to close the path 6, and the flow path is throttled by the exhaust brake 12 of the exhaust throttling means, the exhaust gas 2 is increased to raise the exhaust temperature, and the post-processing means Maintain 5 at a high temperature.

  On the other hand, when the driver accelerates by turning on the accelerator from off to on the way while the post-processing means 5 is being regenerated, the fuel addition is performed based on the fuel injection signal 11a and the switching signal 7a from the control device 10. The fuel injection device 11 of the means starts the addition of fuel, and the flow path switching means 7 switches the flow path from the bypass flow path 6 to the exhaust pipe 4 on the post-processing means 5 side, and the high-temperature exhaust gas from the diesel engine 1 By flowing 2 to the post-processing means 5, the post-processing means 5 is maintained at a high temperature. Here, the post-processing means 5 is the particulate filter 5a, and when the accelerator is turned on and the vehicle is switched from deceleration to acceleration, the regeneration of the particulate filter 5a is caused by the inflow of hot exhaust gas 2 into the particulate filter 5a. Has resumed.

  Thus, in this way, when the driver decelerates while turning off the accelerator during traveling while the post-processing means 5 is being regenerated, the flow path switching means 7 causes the post-processing means 5 side. Since the exhaust pipe 4 is switched to the bypass flow path 6, fresh air is prevented from flowing into the post-processing means 5 even when the fuel addition is stopped, thereby preventing the temperature of the post-processing means 5 from decreasing. As a result, the purification ability of the exhaust gas 2 can be suitably maintained.

  When the exhaust brake 12 of the exhaust throttle means for narrowing down the flow path of the exhaust pipe 4 is provided and the flow path is narrowed down by the exhaust brake 12 of the exhaust throttle means, the bypass flow path 6 is closed by the flow path switching means 7. The exhaust gas 2 is caused to flow to the exhaust pipe 4 on the post-processing means 5 side by the flow path switching means 7 and the exhaust gas 2 is boosted by the exhaust brake 12 of the exhaust throttle means to raise the exhaust temperature. A temperature drop can be prevented.

  The post-processing means 5 is a particulate filter 5a, and is provided with a fuel injection device 11 as a fuel addition means capable of adding fuel from the upstream of the particulate filter 5a, and the fuel is added by the fuel injection device 11 as a fuel addition means. If the control means is used to regenerate the particulate filter 5a, when the driver decelerates with the accelerator turned off during traveling, the exhaust pipe 4 on the particulate filter 5a side is switched by the flow path switching means 7. Therefore, even when the particulate filter 5a is being regenerated, the fresh air is prevented from flowing into the particulate filter 5a, and the temperature of the particulate filter 5a is prevented from being lowered. In addition, the regeneration of the particulate filter 5a can be restarted promptly.

  Note that the exhaust emission control device of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

It is the schematic which shows an example of the form which implements this invention. It is sectional drawing which shows the detail of the particulate filter of FIG.

Explanation of symbols

1 Diesel engine (engine)
2 Exhaust gas 4 Exhaust pipe 4a Branch location 5 Post-processing means 5a Particulate filter 6 Bypass flow path 7 Flow path switching means 8 Rotation sensor (deceleration detection means)
9 Accelerator sensor (deceleration detection means)
DESCRIPTION OF SYMBOLS 10 Control apparatus 11 Fuel injection apparatus (fuel addition means)
12 Exhaust brake (exhaust throttle means)

Claims (3)

  Post-processing means installed in the middle of an exhaust pipe through which exhaust gas from the engine circulates, a bypass passage that bypasses the exhaust gas with respect to the post-treatment means and flows downstream, and a branch of the bypass passage to the exhaust pipe A flow path switching means provided at a location, a deceleration detection means for detecting deceleration during traveling, and a bypass flow path from the exhaust pipe on the post-processing means side by the flow path switching means when the deceleration detection means detects the deceleration. An exhaust purification device comprising a control device for switching to   The exhaust according to claim 1, further comprising an exhaust throttle means for narrowing a flow path of the exhaust pipe, wherein the bypass flow path is closed by the flow path switching means when the flow path is narrowed by the exhaust throttle means. Purification equipment.   The post-processing means is a particulate filter, and a fuel addition means that can add fuel from the upstream of the particulate filter is provided. When the fuel is added by the fuel addition means to regenerate the particulate filter, the control means The exhaust emission control device according to claim 1, wherein the exhaust gas purification device is configured to process.

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