JP2010209754A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently oxidize particulate matter in an exhaust gas purifier even at low temperatures while maintaining a temperature range in which active oxygen does not autolyze. <P>SOLUTION: An exhaust emission control device is disposed in an exhaust gas passage of an internal combustion engine, includes the exhaust gas purifier (10) collecting particulate matter in exhaust gas, and oxidizes (burns) collected particulate matter by supplying active oxygen to the exhaust gas purifier. The exhaust emission control device includes a first and a second supply passage which are two supply passages for supplying active oxygen to the exhaust gas purifier and are connected to an active oxygen supply source, and an on-off valve (24) changing an on/off state of the first or the second supply passage. An active catalyst (30) is disposed in the second supply passage. The exhaust emission control device controls to open the second supply passage by the on-off valve, and to supply active oxygen to the exhaust gas purifier through the second supply passage if the temperature of the exhaust gas purifier is lower than a prescribed activation reference temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine.

  For example, as disclosed in Patent Document 1 as a conventional technique, an exhaust purification device for an internal combustion engine including a DPF (Diesel Particulate Filter) and an ozone supply device is known. According to this exhaust gas purification apparatus, particulate matter (PM) contained in the exhaust gas can be oxidized and removed by active oxygen (ozone).

JP 2006-348888 A

  By the way, ozone generally self-decomposes rapidly at a temperature of 300 ° C. or higher. For this reason, when DPF becomes high temperature of 300 degreeC or more, PM which remains without being oxidized increases. On the other hand, even when the temperature of ozone is too low, the stability of ozone becomes high, so the oxidation rate of PM becomes slow, and PM cannot be oxidized efficiently.

  Accordingly, in order to solve the above-mentioned problems, the present invention is effective in the exhaust gas purifier (DPF) even at a low temperature while maintaining active oxygen (ozone) in a temperature range in which self-decomposition does not occur. The present invention provides an exhaust purification device for an internal combustion engine which is improved so that particulate matter (PM) can be oxidized.

In order to achieve the above object, a first invention is an exhaust purification device,
An exhaust gas purifier that is provided in an exhaust passage through which exhaust gas of the internal combustion engine flows and collects particulate matter in the exhaust gas;
Two supply paths for supplying active oxygen to the exhaust purifier, a first supply path and a second supply path connected to an active oxygen supply source;
An on-off valve for changing an open / close state of the first supply path or the second supply path;
An active catalyst installed in the second supply path for activating active oxygen;
Temperature detecting means for estimating or detecting the temperature of the exhaust purifier;
Activity discrimination means for discriminating whether or not the temperature of the exhaust gas purifier estimated or detected by the temperature detection means is lower than an activity reference temperature;
When it is determined that the temperature of the exhaust purifier is lower than the activation reference temperature, the second supply path is opened by the on-off valve, and the active oxygen is supplied to the exhaust purifier through the second supply path. Active control means for controlling to be supplied;
It is characterized by providing.

According to a second invention, in the first invention,
Heating means for heating the active catalyst;
Heating determination means for determining whether or not the temperature of the exhaust purifier estimated or detected by the temperature detection means is lower than a heating reference temperature that is lower than the activation reference temperature;
Heating control means for controlling the heating catalyst to heat the active catalyst when it is determined that the temperature of the exhaust gas purifier is lower than the heating reference temperature;
Is further provided.

  According to the first invention, when the temperature of the exhaust gas purifier is lower than the activation reference temperature, the active oxygen can be supplied to the exhaust gas purifier after passing through the active catalyst. Thereby, even if the temperature of the exhaust gas purifier is low, the particulate matter collected in the exhaust gas purifier can be efficiently oxidized by the activated oxygen.

  According to the second invention, when it is determined that the temperature of the exhaust purifier is lower than the heating reference temperature that is lower than the activation reference temperature, the active catalyst can be heated by the heating means. Thereby, even when the exhaust gas purifier is at a low temperature, the oxidation of the particulate matter by the active oxygen can be performed efficiently.

It is a figure for demonstrating the exhaust gas purification apparatus in Embodiment 1 of this invention. It is a figure for demonstrating the relationship between the catalyst temperature of DPF in Embodiment 1 of this invention, and PM reduction amount. It is a flowchart for demonstrating the control routine which a control apparatus performs in Embodiment 1 of this invention. It is a figure for demonstrating the exhaust gas purification apparatus in Embodiment 2 of this invention. It is a figure for demonstrating the relationship between the catalyst temperature of DPF in Embodiment 2 of this invention, and PM reduction amount. It is a flowchart for demonstrating the control routine which a control apparatus performs in Embodiment 2 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram for explaining an exhaust emission control device according to an embodiment of the present invention. The exhaust purification device shown in FIG. 1 is disposed downstream of the catalyst purifier 6 in the exhaust passage 4 of the internal combustion engine 2.

  Specifically, the exhaust purification device includes a DPF 10 (exhaust purification device) disposed in the exhaust passage 4. The DPF 10 collects PM mixed in the exhaust gas from the internal combustion engine, and purifies the exhaust gas by oxidizing (combusting) the PM by receiving supply of ozone through a path described later.

  In the vicinity of the DPF 10 inlet of the exhaust passage 4, a temperature sensor 12 that outputs an output corresponding to the circulating exhaust temperature is installed. An ozone supply path 14 for supplying ozone (active oxygen) to the DPF 10 is connected upstream of the temperature sensor 12 in the exhaust passage 4.

  An air filter 16 is attached to the upstream end of the ozone supply path 14. A pressure sensor 18 that emits an output corresponding to the pressure in the ozone supply path 14 is installed downstream of the air filter 16 in the ozone supply path 14. A pump 20 is installed downstream of the pressure sensor 18 for taking outside air into the ozone supply path 14 and circulating it. An ozone generator 22 (active oxygen supply means) is installed downstream of the pump 20. The ozone generator 22 generates ozone from oxygen in the air taken in from the outside.

  A two-way valve 24 (open / close valve) is attached downstream of the ozone generator 22 in the ozone supply path 14. The ozone supply path 14 branches in two directions, a first flow path 26 and a second flow path 28, downstream from the installation position of the two-way valve 24.

  An ozone activation catalyst 30 for activating ozone is attached to the second flow path 28. The ozone active catalyst 30 is composed of noble metals such as Pt, Pd, Rh, Ag, transition metals such as Fe, Mn, Co, Zr or oxides thereof, rare earth elements or oxides thereof, or oxides of Al or Si. A catalyst containing one or more.

  The first flow path 26 and the second flow path 28 of the ozone supply path 14 are assembled again at the downstream end. The downstream end of the ozone supply path 14 is connected upstream of the temperature sensor 12 in the exhaust passage 4.

  This exhaust purification device has a control device 32. The control device 32 is electrically connected to the temperature sensor 12, the pressure sensor 18, etc., and receives these outputs to detect necessary information regarding the operating state of the device. In addition, it is electrically connected to the pump 20, the ozone generator 22, the two-way valve 24, and the like, and by supplying control signals to these, the ozone supply amount by the ozone generator 22, the first flow path 26 or the second flow path 28. Can be controlled.

  In this system, air is taken in from outside through the air filter 16, and ozone is generated from oxygen in the air in the ozone generator 22. The ozone generated here is supplied to the DPF 10 through either the first supply path or the second supply path.

  The first supply path of ozone is a flow path that is supplied from the exhaust passage 4 to the DPF 10 after joining the ozone supply path 14 from the ozone supply path 14 through the first flow path 26 side that is the branch path. The second supply path flows from the ozone supply path 14 to the second flow path 28, which is the branch path, passes through the ozone activation catalyst 30, and then merges with the ozone supply path 14, and from the exhaust path 4 to the DPF 10. It is a flow path to be supplied. That is, the first supply path is a flow path that flows through the first flow path 26 side, and the second supply path is a flow path that flows through the second flow path 28 side and passes through the ozone activation catalyst 30.

  Switching between the first supply path and the second supply path is performed by a two-way valve 24 installed at the upstream end of the first flow path 26 and the second flow path 28. That is, by operating the two-way valve 24, the first flow path 26 is opened and the second flow path 28 is closed as necessary, and the first flow path 26 is closed and the second flow path 28 is opened. You can switch between

  By the way, ozone causes self-decomposition at temperatures of 300 ° C. or higher, while stability is increased at low temperatures of 150 ° C. or lower. Therefore, when the DPF 10 is not maintained in an appropriate temperature range, the oxidation of PM in the DPF 10 may not proceed efficiently. However, since the temperature of the DPF 10 greatly depends on the exhaust gas temperature flowing in from the exhaust passage 4, it is difficult to control the temperature of the DPF 10 within an appropriate temperature range.

  Therefore, in the system according to the first embodiment, when the temperature of the DPF 10 is expected to be low, control is performed so that ozone is supplied through the second supply path side, that is, the ozone active catalyst 30. The ozone activation catalyst 30 can activate ozone. Therefore, even when the temperature of the DPF 10 is low, the oxidation of PM can be efficiently advanced by passing the ozone active catalyst.

  FIG. 2 is a diagram for explaining the relationship between the temperature of the DPF 10 and the amount of decrease in PM in Embodiment 1 of the present invention. In FIG. 2, the horizontal axis represents the temperature [° C.] of the DPF 10, and the vertical axis represents the PM reduction amount [g]. In FIG. 2, a solid line (a) indicates a case where ozone is supplied from the first supply path side, and a broken line (b) indicates a case where ozone is supplied from the second supply path side through the ozone active catalyst 30. .

  As shown by the solid line (a) in FIG. 2, when ozone is supplied through the first flow path 26, the amount of PM decrease is the largest when the temperature of the DPF 10 is around 200 ° C., in particular, 100 ° C. or less, When the temperature exceeds 300 ° C., the amount of decrease is small. On the other hand, as shown by the broken line (b), when supplying ozone that has passed through the ozone active catalyst 30 from the second flow path 28, the peak of the PM decrease amount is that the temperature of the DPF 10 is around 80 ° C. That is, the PM removal amount can be greatly improved even when the temperature of the DPF 10 is low.

  Therefore, the system of the second embodiment has a temperature at which the solid line (a) when supplied from the first flow path 26 side intersects with the broken line (b) when supplied from the second flow path 28 side, that is, the second line. The boundary temperature at which the PM decrease amount when supplied from the flow path 28 side is larger than the PM decrease amount when supplied from the first flow path 26 is set as the activation reference temperature T1, and is used for switching determination.

  More specifically, assuming that the exhaust temperature flowing into the DPF 10 correlates with the temperature of the DPF 10, the exhaust temperature is detected by the temperature sensor 12 installed near the inlet of the DPF 10. When it is determined that the exhaust temperature is lower than the activation reference temperature T1, the second flow path 28 side is opened, and ozone is supplied through the ozone supply catalyst 30 through the second supply path. On the other hand, when the exhaust temperature is equal to or higher than the activation reference temperature T1, ozone is supplied through the first supply path. The activation reference temperature T1 is obtained in advance by experiments or the like and stored in the control device 32.

  FIG. 3 is a flowchart for illustrating a control routine executed by the control device in the first embodiment of the present invention. The routine of FIG. 3 is a routine that is repeatedly executed. In the routine of FIG. 3, it is first determined whether or not there is a request for ozone supply (S102). If the request for ozone supply is not recognized in step S102, the current process ends.

  On the other hand, if a request for ozone supply is recognized in step S102, ozone supply is started (S104). Specifically, the pump 20 and the ozone generator 22 are operated, outside air is taken in, ozone is generated in the ozone generator 22, and ozone supply is started.

  Next, the exhaust temperature is detected (S106). The exhaust temperature is detected according to the output of the temperature sensor 12 installed immediately before the DPF 10. The detected exhaust gas temperature is estimated as representing the temperature of the DPF 10. Next, it is determined whether or not the exhaust temperature is lower than the activation reference temperature T1 (S108). The reference temperature is stored in the control device in advance as described above.

  If it is determined in step S108 that the exhaust gas temperature <the activation reference temperature T1 is established, the two-way valve 24 is switched to close the first flow path 26 and open the second flow path 28 (S110). Switching of the two-way valve 24 is performed by a control signal from the control device 32. Thereby, ozone is activated in the ozone activation catalyst 30 and then supplied to the DPF 10.

  On the other hand, if the establishment of the exhaust gas temperature <the activation reference temperature T1 is not recognized in step S108, the two-way valve 24 is switched to open the first flow path 26 and close the second flow path 28 (S112). . Thus, ozone is supplied to the DPF 10 through the first supply path without passing through the ozone activation catalyst 30.

  Thereafter, it is determined whether or not the ozone supply is terminated (S114). If the end of ozone supply is not recognized in step S114, the process returns to step S106 again, the exhaust gas temperature is detected again, and the determination of switching of the two-way valve 24 is repeated (S106 to S112). On the other hand, when the end of the ozone supply switching is recognized in step S114, the current process ends.

  As described above, according to the first embodiment, when the temperature of the DPF 10 is low, ozone can be activated and supplied. Therefore, a high PM removal rate in the DPF 10 can be ensured over a wide temperature range.

  In the first embodiment, the case where only one of the first flow path 26 and the second flow path 28 is opened and the other is closed has been described. For example, when the temperature is below a certain reference temperature, the first flow Both the path 26 and the second flow path 28 may be opened so that only a part of ozone passes through the ozone active catalyst 30.

  In the routine of FIG. 3, the “temperature detecting means” of the present invention is realized by executing the process of step S106, and the “activity determining means” is realized by executing the process of step S108. The “activity control unit” is realized by executing the process of step S110.

Embodiment 2. FIG.
FIG. 4 is a diagram for explaining a system according to the second embodiment of the present invention. The system in FIG. 4 is the same as the system in FIG. 1 except that a heater 40 (heating means) for heating the ozone active catalyst 30 is provided around the ozone active catalyst 30. In the system of FIG. 4, the heater 40 is electrically connected to the control device 32. In response to a control signal from the control device 32, an electric current is supplied, whereby the ozone activation catalyst 30 is heated.

  FIG. 5 is a diagram for explaining the relationship between the catalyst temperature of the DPF 10 and the PM reduction amount according to Embodiment 2 of the present invention. In FIG. 5, the horizontal axis indicates the catalyst temperature [° C.] of the DPF 10, and the vertical axis indicates the PM reduction amount [g]. Moreover, in FIG. 5, a solid line (a) is a case where ozone is supplied from the first supply path, a broken line (c) is a case where ozone is supplied from the second supply path, and the region is at a temperature T2 or lower. Thus, the heater 40 is turned on and the ozone activated catalyst 30 is heated.

  As shown in FIG. 5, in the region lower than the activation reference temperature T1, the amount of PM reduction is larger when supplied from the second supply path. Further, comparing the broken line (b) in FIG. 2 and (c) in FIG. 5, even if the temperature of the DPF 10 is considerably low by turning on the heater 40 in a region below the temperature T2, A higher PM removal rate can be ensured. The heating reference temperature T2, which is a discriminating value for determining ON / OFF of the heater 40, is obtained in advance through experiments or the like and stored in the control device 32.

  FIG. 6 is a flowchart for illustrating a control routine executed by control device 32 in the second embodiment of the present invention. The routine of FIG. 6 is a routine that is repeatedly executed in place of the routine of FIG. The routine of FIG. 6 is the same as the routine of FIG. 3 except that the processing of steps S202 to S206 is included.

  In the routine shown in FIG. 6, in step S108, it is determined whether or not the exhaust temperature <the activation reference temperature T1 is satisfied, and then it is determined whether or not the exhaust temperature <the heating reference temperature T2 is satisfied (S202). ). The heating reference temperature T2 is a temperature previously stored in the control device.

  If it is determined in step S202 that the exhaust gas temperature <the heating reference temperature T2 is established, the heater 40 is turned on (S204). Here, a current is supplied to the circuit of the heater 40 by a control signal from the control device 32, and the ozone activation catalyst 30 is heated. On the other hand, if it is not recognized in step S202 that the exhaust gas temperature <the heating reference temperature T2 is not established, the heater 40 is turned off (S206).

  Thereafter, in step S110, the two-way valve 24 is set so as to open the second flow path 28 side, and the process is executed in accordance with the subsequent routine from S114.

  As described above, in the second embodiment of the present invention, the ozone active catalyst 30 can be heated when the temperature of the ozone active catalyst 30 is considerably low. Thereby, ozone can be activated more reliably and PM of DPF10 can be removed efficiently.

  In the routine of FIG. 6, the “heating determination unit” of the present invention is realized by executing the process of step S202, and the “heating control unit” is realized by executing the process of step S204.

  In the above embodiment, when referring to the number of each element, quantity, quantity, range, etc., the reference is made unless otherwise specified or the number is clearly specified in principle. The invention is not limited to the numbers. Further, the structure and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

2 Internal combustion engine 4 Exhaust passage 6 Catalyst purifier 12 Temperature sensor 14 Ozone supply path 16 Air filter 18 Pressure sensor 20 Pump 22 Ozone generator 24 Two-way valve 26 First flow path 28 Second flow path 30 Ozone active catalyst 32 Control device 40 heater

Claims (2)

An exhaust gas purifier that is provided in an exhaust passage through which exhaust gas of the internal combustion engine flows and collects particulate matter in the exhaust gas;
A first supply path and a second supply path that are connected to an active oxygen supply source and are two supply paths for supplying active oxygen to the exhaust gas purifier;
An on-off valve for changing an open / close state of the first supply path or the second supply path;
An active catalyst installed in the second supply path for activating active oxygen;
Temperature detecting means for estimating or detecting the temperature of the exhaust purifier;
Activity discrimination means for discriminating whether or not the temperature of the exhaust gas purifier estimated or detected by the temperature detection means is lower than an activity reference temperature;
When it is determined that the temperature of the exhaust purifier is lower than the activation reference temperature, the on-off valve opens the second supply path, and the active oxygen is supplied to the exhaust purifier through the second supply path. Active control means for controlling
An exhaust emission control device comprising: Heating means for heating the active catalyst;
Heating determination means for determining whether or not the temperature of the exhaust purifier estimated or detected by the temperature detection means is lower than a heating reference temperature that is lower than the activation reference temperature;
Heating control means for controlling the heating catalyst to heat the active catalyst when it is determined that the temperature of the exhaust gas purifier is lower than the heating reference temperature;
The exhaust emission control device according to claim 1, further comprising:

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