JP3938863B2 - Exhaust purification device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust emission control device.
[0002]
[Prior art]
Particulate matter (particulate matter) discharged from a diesel engine is mainly composed of soot made of carbonaceous matter and SOF content (Soluble Organic Fraction) made of high-boiling hydrocarbon components. The composition contains a small amount of sulfate (mist-like sulfuric acid component). As a measure to reduce this type of particulates, a particulate filter is installed in the middle of the exhaust pipe through which the exhaust gas flows. It has been done conventionally.
[0003]
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.
[0004]
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.
[0005]
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.
[0006]
However, even when such a catalyst regeneration type particulate filter is employed, the oxidation catalyst carried by the particulate filter has an active temperature range, and the exhaust temperature is below the lower limit of activation temperature. If the operation state continues, the oxidation catalyst is not activated, so that there is a possibility that the particulates are not burned and removed well.Therefore, a fuel addition means for adding fuel to the exhaust gas upstream from the particulate filter is used. Therefore, forced regeneration of the particulate filter by active heating has been studied.
[0007]
In this case, the fuel added on the upstream side of the particulate filter undergoes an oxidation reaction on the oxidation catalyst of the particulate filter, the catalyst bed temperature is raised by the reaction heat, and the particulates in the particulate filter are burned out. It will be.
[0008]
[Problems to be solved by the invention]
However, conventionally, for example, a pressure sensor is arranged before and after sandwiching the particulate filter and the differential pressure between the inlet side and the outlet side is obtained to determine the over-collection state, or the travel distance, the operation time, etc. As a guideline, the design philosophy of determining the excessive collection state of the particulate filter and forcibly regenerating the particulate filter automatically while driving has become mainstream. When curate has accumulated, there is a concern that the particulate filter cannot be immediately forcibly regenerated by the driver's intention.
[0009]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust emission control device capable of arbitrarily forcibly regenerating a particulate filter at the driver's intention.
[0010]
[Means for Solving the Problems]
The exhaust emission control device according to claim 1 of the present invention is an exhaust emission purification device equipped with a catalyst regeneration type particulate filter in the middle of an exhaust pipe through which exhaust gas flows, and the particulates collected by the particulate filter are collected. Forced regeneration means for forcibly removing combustion to regenerate the particulate filter, operation means provided in the driver's seat to arbitrarily operate the forced regeneration means, and forcibly removing particulates when idling stops If the engine speed is less than or equal to the specified speed, the accelerator is turned off, the gear is in neutral, the clutch is turned off, and all idling stop conditions are in place. Usually return to the mode, Seiwa not be any one of the idling stop condition after performing the forced regeneration when you're Can is one having a control means for stopping an emergency release which is adapted to immediately return to the normal mode.
[0011]
In the exhaust emission control device according to claim 2 of the present invention,
Forced regeneration means
A fuel injection device that injects fuel into each cylinder of the engine, and a control device that switches the control of the fuel injection device from a normal mode to a forced regeneration mode in response to a command from an operation means;
The control device
When the difference between the gas pressure at the inlet of the particulate filter and the gas pressure at the outlet exceeds the normal range and it is determined that the particulate filter has fallen into the excessive collection state, the control of the injection device is performed by operating the operating means. the is configured to provide an instruction for performing post injection at a slower timing than the continued compression top dead center the switch from the normal mode to the forced regeneration mode for each cylinder in the main injection of fuel to the fuel injection device.
[0012]
In the exhaust emission control device according to the third aspect of the present invention, the control device performs switching to the forced regeneration mode after the operation means is operated in a plurality of times, and the predetermined amount after switching to the first forced regeneration mode. In the forced regeneration mode of the number of times, the fuel post injection amount is suppressed, and in the forced regeneration mode after the predetermined number of times of the forced regeneration mode, the fuel injection device is controlled to release the suppression of the fuel post injection amount. Yes.
[0013]
In the exhaust emission control device according to claim 4, the control device is configured to give a command to the fuel injection device to perform after injection at a combustible timing immediately after the main injection of fuel in the forced regeneration mode prior to post injection. .
[0014]
Thus, in the present invention, when the particulate filter falls into an overcollected state and it is necessary to perform forced regeneration at an early stage or when the driver wants to perform periodic regeneration of the particulate filter periodically In this case, the driver can operate the operation means to operate the forced regeneration means, and the forced regeneration of the particulate filter can be arbitrarily performed by the driver's intention. Further, there is no possibility that the vehicle suddenly starts when the driver accidentally shifts the gear to a position other than neutral.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0016]
FIGS. 1 to 3 show an example of an embodiment of the present invention. In the exhaust emission control device of this embodiment, as shown in FIG. 1, an automobile diesel engine 1 (internal combustion engine) passes through an exhaust manifold 2. Exemplified is a case where a catalyst regeneration type particulate filter 6 integrally supporting an oxidation catalyst is accommodated in a muffler 5 of an exhaust pipe 4 through which exhaust gas 3 discharged in this way flows. A filter case 7 that holds the particulate filter 6 forms an outer cylinder of the muffler 5.
[0017]
That is, a particulate filter 6 as shown in an enlarged view in FIG. 2 is accommodated in a filter case 7 having front and rear inlet pipes 8 and outlet pipes 9. The particulate filter 6 is made of ceramic. It has a porous honeycomb structure, and the inlets of the flow paths 6a partitioned in a lattice pattern are alternately sealed, and the outlets of the flow paths 6a that are not sealed are sealed. Only the exhaust gas 3 that has permeated through the porous thin wall 6b that partitions each flow path 6a is discharged to the downstream side.
[0018]
The inlet pipe 8 and the outlet pipe 9 of the filter case 7 are equipped with pressure sensors 10 and 11 for measuring the inlet gas pressure and the outlet gas pressure of the exhaust gas 3. Detection signals 10a and 11a are input to a control device 12 constituting an engine control computer (ECU: Electronic Control Unit). In the control device 12, detection signals 10a from the pressure sensors 10 and 11 are detected. 11a, it is determined whether or not the pressure difference between the inlet side and the outlet side of the particulate filter 6 is within the normal range, and when the pressure difference exceeds the normal range, the particulate filter 6 is excessively collected. It is determined to have fallen into a state.
[0019]
Further, the control device 12 outputs a fuel injection signal 13a for instructing the fuel injection timing and the injection amount toward the fuel injection device 13 for injecting the fuel into each cylinder of the diesel engine 1.
[0020]
Here, the fuel injection device 13 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 the fuel injection signal 13a, and the fuel is supplied. The injection timing (injection start timing and injection end timing) and the injection amount (valve opening time) are appropriately controlled.
[0021]
Further, the accelerator of the driver's seat (not shown) is provided with an accelerator sensor 14 (load sensor) for detecting the accelerator opening as a load of the diesel engine 1, and the rotational speed is set at an appropriate position of the diesel engine 1. A rotation sensor 15 for detection is provided, and the accelerator opening signal 14a and the rotation speed signal 15a from the accelerator sensor 14 and the rotation sensor 15 are also input to the control device 12.
[0022]
Further, an alarm lamp or the like on the instrument panel in the driver's seat receives a warning signal 16a from the control device 12 when the control device 12 determines that the particulate filter 6 has fallen into an overcollected state. 16 and a regeneration button 17 that constitutes an operation means for arbitrarily operating a forced regeneration means described in detail later.
[0023]
In the control device 12, the fuel injection signal 13a in the normal mode is determined based on the accelerator opening signal 14a and the rotation speed signal 15a. On the other hand, the regeneration button 17 is operated by the driver and the regeneration command is issued. When the signal 17a is input, the mode is switched from the normal mode to the forced regeneration mode, and after the main injection of fuel performed near the compression top dead center (crank angle 0 °), the post injection is performed at a timing that does not ignite later than the compression top dead center. The fuel injection signal 13a for performing the above is determined.
[0024]
In other words, in the present embodiment, the forced regeneration means of the particulate filter 6 is configured by the control device 12 and the fuel injection device 13, and as described above, from the compression top dead center following the main injection. When the post-injection is performed at a timing that does not ignite slowly, unburned fuel (mainly HC: hydrocarbon) is added to the exhaust gas 3 by this post-injection, and this unburned fuel is added to the particulate filter 6. An oxidation reaction occurs on the oxidation catalyst on the surface, and the catalyst bed temperature rises due to the reaction heat, and the particulates in the particulate filter 6 are burned and removed.
[0025]
Thus, the control device 12 determines that the particulate filter 6 has fallen into an excessive collection state based on the detection signals 10a and 11a from the pressure sensors 10 and 11, and receives a warning signal 16a from the control device 12. When the warning lamp 16 is turned on and the driver who has confirmed this presses the regeneration button 17, the control of the fuel injection device 13 by the control device 12 is switched from the normal mode to the forced regeneration mode, and the main injection is followed. As a result of post injection being performed at a timing that does not ignite later than the compression top dead center, unburned fuel is added to the exhaust gas 3, and the fuel undergoes an oxidation reaction on the oxidation catalyst on the surface of the particulate filter 6, and its reaction heat. As a result, the catalyst bed temperature rises and the particulates in the particulate filter 6 are burned and removed.
[0026]
However, forcibly regenerating under the conditions that are already over trapped in this way includes the possibility that a large amount of particulates will burn rapidly at high temperatures and the particulate filter may be melted. Switching to the forced regeneration mode after the regeneration button 17 is pressed is performed in a plurality of times, and in the initial several forced regeneration modes, the particulates remain on the oxidation catalyst so as not to cause rapid high-temperature combustion. It is preferable to suppress the post-injection of the fuel to a level at which it is gently oxidized and decomposed into carbon dioxide and water, and to perform full-scale post-injection from the subsequent forced regeneration mode.
[0027]
Further, when the operation is performed in an operation region where the exhaust temperature is so low that the fuel added by the post injection cannot be oxidized on the oxidation catalyst of the particulate filter 6, the following details will be given. You may make it use the after injection as described together.
[0028]
That is, with respect to the forced regeneration mode by the control device 12, a fuel that performs after-injection at a combustible timing immediately after the main fuel injection and performs post-injection at a non-ignition timing later than the compression top dead center following the after-injection. The injection signal 13a is determined.
[0029]
Thus, if after-injection is performed at a combustible timing immediately after main injection, the thermal efficiency of the diesel engine 1 is reduced by burning at a timing at which the fuel of the after-injection is difficult to be converted to output, and the amount of heat generated by the fuel The amount of heat not used for the power of the engine increases and the exhaust gas temperature rises, so that the temperature necessary for the oxidation reaction of the fuel added in the subsequent post injection on the oxidation catalyst of the particulate filter 6 is secured. Become.
[0030]
Therefore, according to the above embodiment, the particulate filter 6 can be forcibly regenerated arbitrarily by the driver's intention by operating the regeneration button 17 on the driver's seat. If the particulates are accumulated, the forced regeneration means is immediately activated to regenerate the particulate filter 6, or the driver periodically performs the forced regeneration of the particulate filter 6. It is possible to avoid falling into an overcollected state.
[0031]
Here, there are two possible timings for pressing the regeneration button 17 when traveling and when idling is stopped. However, when forced regeneration is performed when idling is stopped, the temperature and flow rate of the exhaust gas 3 are too low and good. Since it is difficult to remove the particulates by burning, when the regeneration button 17 is pressed when the vehicle is idling, it is necessary for the control device 12 to automatically increase the rotational speed of the diesel engine 1 to about the middle speed.
[0032]
However, if the speed of the diesel engine 1 is automatically set to increase when the vehicle is idling, the vehicle suddenly starts when the driver accidentally shifts the gear to a position other than neutral. Therefore, an emergency release control logic as described in detail below is preferably incorporated in the control device 12.
[0033]
That is, as shown in FIG. 3, after the transition from the normal mode in step S1 to the state in which the regeneration button 17 in step S2 is pressed, the idling stop conditions are confirmed in step S3, and all conditions are satisfied. In step S4, the forced regeneration mode is continued for a predetermined time T to return to the normal mode. On the other hand, if any of the idling stop conditions in step S3 is not satisfied, the control is immediately returned to the normal mode. Build logic.
[0034]
In addition, as an idling stop condition in step S3, for example,
(I) The engine speed is not more than a predetermined speed.
(II) The accelerator is off.
(III) The gear is in neutral.
(IV) The clutch is off.
Ru conditions is considered such.
[0035]
In the description of the present embodiment described above, as the forced regeneration means of the particulate filter 6, a means for switching the mode of the injection pattern of the fuel injection device 13 by the control device 12 is illustrated. As the regeneration means, for example, a fuel addition injector is separately provided at any location in the exhaust flow path from the exhaust manifold 2 to the exhaust pipe 4, and fuel is added to the exhaust gas 3 by this injector. It is also possible to adopt a means for attaching a heating device such as an electric heater to the particulate filter 6.
[0036]
The exhaust emission control device of the present invention is not limited to the above-described embodiment. The operation means may be a switch type other than the regeneration button, and does not depart from the gist of the present invention. Of course, various changes can be made within the range.
[0037]
【The invention's effect】
According to the exhaust gas purification apparatus of the first to fourth aspects of the present invention described above, the particulate filter can be arbitrarily forcibly regenerated by the driver's intention by operating the driver's operating means. If a large amount of particulate is accumulated in the particulate filter, the forced regeneration means is immediately activated to regenerate the particulate filter, or the driver periodically performs the forced regeneration of the particulate filter. By executing this, it is possible to avoid an overcollection state, and according to the exhaust emission control device of claim 1, even if the driver accidentally shifts the gear to a position other than neutral, the vehicle In the exhaust emission control device according to claim 3, the particulates are rapidly heated in a plurality of regeneration modes in the initial stage. In the exhaust emission control device according to claim 4, the after-injection fuel is burned at a timing that is difficult to be converted into output, so that the thermal efficiency of the engine is lowered and the heat generation amount of the fuel is reduced. heat is not used for power is increased by the exhaust gas temperature rise of, as a result, fuel added by the post-injection temperature required to oxidation reaction in the particulate filter is secured, and the like various excellent The effects can be achieved.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing details of the particulate filter of FIG.
FIG. 3 is a flowchart showing an example of control logic related to an emergency release of forced regeneration.
[Explanation of symbols]
3 Exhaust gas 4 Exhaust pipe 6 Particulate filter 12 Control device (forced regeneration means)
13 Fuel injection device (forced regeneration means)
17 Playback button (operation means)

Claims (4)

An exhaust purification device equipped with a catalyst regeneration type particulate filter in the middle of an exhaust pipe through which exhaust gas circulates, forcibly burning and removing particulates collected by the particulate filter, and removing the particulate filter When the forced regeneration means to regenerate, the operation means provided in the driver's seat to operate the forced regeneration means arbitrarily, and when the particulates are forcibly burned off when the vehicle is idling stopped, the engine speed is set to a predetermined speed. is less than or equal to the number, the accelerator is turned off, the gear is in the neutral, the normal mode after performing the forced regeneration when the clutch is equipped with all the idle stop condition such, are off return, and immediately returns to the normal mode when not Seiwa in any one of the idling stop conditions Exhaust gas purification apparatus characterized by comprising control means stop emergency release you. Forced regeneration means
A fuel injection device that injects fuel into each cylinder of the engine, and a control device that switches the control of the fuel injection device from a normal mode to a forced regeneration mode in response to a command from an operation means;
The control device
When the difference between the gas pressure at the inlet of the particulate filter and the gas pressure at the outlet exceeds the normal range and it is determined that the particulate filter has fallen into the excessive collection state, the control of the injection device is performed by operating the operating means. an instruction for performing post injection in claim 1, which is configured to provide to said fuel injector at a timing later than the continued compression top dead center the switch from the normal mode to the forced regeneration mode for each cylinder in the main injection of fuel The exhaust emission control device described.   The control device performs the switching to the forced regeneration mode after the operation means is operated in a plurality of times, and in the forced regeneration mode for a predetermined number of times after switching to the first forced regeneration mode, the control unit determines the fuel post-injection amount. 3. The exhaust emission control device according to claim 2, wherein the exhaust gas control device is configured to control the fuel injection device so as to release the suppression of the fuel post-injection amount in the forced regeneration mode after the predetermined number of forced regeneration modes.   4. The exhaust gas purification according to claim 2, wherein the control device is configured to give a command to perform after injection at a combustible timing immediately after main injection of fuel in the forced regeneration mode prior to post injection. apparatus.

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