JP2006188988A - Low temperature continuous oxidation device of particulate matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high performance PM low temperature continuous oxidation device, particularly using strong oxidation reaction power of an oxygen negative ion, for stably and continuously oxidizing PM by the oxygen negative ion in the whole operation area, even if the exhaust gas temperature is the low temperature. <P>SOLUTION: A PM oxidation device promotes oxidation of the PM by the oxygen negative ion in an exhaust part of an internal combustion engine 1, and an oxygen negative ion discharge part 2A of an oxygen negative ion generator 2 is connected to an exhaust pipe 4 just before the exhaust upstream side of a DPF 3. The oxygen negative ion discharged to the exhaust pipe 4 generates a required oxygen negative ion quantity by controlling the temperature and impression voltage of an alumina cement constituting material 5 by determining its required quantity on the basis of a generating PM quantity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a low temperature of PM that can continuously oxidize particulate matter mainly composed of carbon (hereinafter referred to as “PM”) contained in the exhaust gas of an internal combustion engine even at a low temperature in the entire operation region. More particularly, the present invention relates to a low-temperature continuous oxidation apparatus for PM using a strong oxidation reaction force of oxygen negative ions.

  The treatment of PM contained in the exhaust gas of an internal combustion engine has become a major issue. As a conventional technique, there is Patent Document 1, which includes a charging unit that charges PM, a collection device that collects PM charged by the charging unit, and a combustion device that burns the PM collected by the collection device. In addition, a technology relating to an exhaust gas purification device is proposed in which the combustion device carries alumina cement, which is a substance that generates oxygen negative ions, and the combustion device incorporates a high voltage application device. According to the apparatus, by applying a high voltage to the combustion apparatus, PM is burned using the heat of discharge, and the alumina cement is heated to 600 ° C. or more by discharge and oxygen negative ions are generated. The oxidation reaction between the oxygen negative ions and the collected PM is accurately promoted.

  However, in the above technique, since the high voltage applying device is directly arranged in the exhaust gas, the safety and reliability of the entire device is increased due to the high temperature state of 600 ° C or higher and the large vibration. There is a problem in securing, and it is necessary to support alumina cement on the entire filter. As a result, the entire filter must be filled with oxygen negative ion generation conditions, and the required energy becomes extremely large.

Japanese Patent Laid-Open No. 2004-190529

  The present invention seeks to improve the above-mentioned drawbacks of the prior art, and does not arrange a high voltage application device directly in the exhaust, and does not employ a method of supporting alumina cement on the filter. Even if the gas temperature is low, PM can be stably and continuously oxidized by oxygen negative ions throughout the operating range, especially high-performance PM low-temperature continuous oxidation utilizing the strong oxidation reaction force of oxygen negative ions It is an object to realize an apparatus. The present invention also relates to the realization of a low-temperature continuous oxidation apparatus for PM that can stably generate a necessary and sufficient amount of oxygen negative ions in consideration of the generation amount of PM that changes every moment depending on the operation state.

  The low-temperature continuous oxidation apparatus for PM according to claim 1 is a PM oxidation apparatus that promotes oxidation of PM by oxygen negative ions in an exhaust part of an internal combustion engine, and an oxygen negative ion release part of the oxygen negative ion generator is connected to an exhaust pipe. It is characterized by being.

In ^{general, O -, O 2-, O} 2 -, O 3 -, O n - oxygen negative ions as defined is known to have about a thousand times the oxidation capacity than the oxygen molecule Yes. Therefore, even if the exhaust gas temperature is low, PM contained in the exhaust gas can be continuously oxidized. Therefore, since the PM low-temperature continuous oxidation apparatus has such a configuration, a high voltage application apparatus or the like is not directly disposed in the exhaust gas, and a method of supporting alumina cement on the filter is not employed. Even if the exhaust gas temperature is low, the entire operation region can be oxidized with oxygen negative ions so that PM can be continuously oxidized.

  Preferably, the exhaust pipe is an exhaust pipe immediately before the exhaust upstream side of a diesel particulate filter (hereinafter referred to as “DPF”).

  By configuring in this way, especially when a large amount of PM is discharged during warm-up operation, PM can be continuously oxidized and burned in front of the DPF, preventing a large amount of PM from accumulating on the filter. An increase in the pressure loss of the filter can be suppressed.

  As in the invention of claim 3, the oxygen negative ion generator includes a container, and an alumina cement constituent material in which at least part of the oxygen negative ion generator is disposed in the container and the outer surface of which is an oxygen negative ion generator, A heater for heating the alumina cement constituent material; an oxygen supply electrode formed on at least a part of an inner surface of the alumina cement constituent material; a gas containing at least oxygen gas supplied to the oxygen supply electrode; An oxygen negative ion extraction electrode installed in the container apart from the negative ion generation unit, and a power source capable of applying a higher voltage to the oxygen negative ion extraction electrode than the oxygen supply electrode.

  The conventional oxygen negative ion generator requires a high vacuum device and an energy source for discharge, and thus has disadvantages such as an increase in size and power consumption. On the other hand, in a compact type, Although there was a drawback that the amount of oxygen negative ions produced was very small, this configuration eliminates the need for a high vacuum device or an energy source for discharge, and allows compact oxygen and oxygen from alumina cement. Negative ions can be generated stably and continuously. As a result, even if the exhaust gas is at a low temperature, there is an effect that PM can be stably and continuously oxidized by oxygen negative ions in the entire operation region.

  According to a fourth aspect of the present invention, the oxygen negative ion generation device includes a generated PM amount detecting means, and when the generated PM amount is equal to or greater than a certain value, the power source and the heater drive switch are turned on, and not greater than a certain amount. In some cases, control means for controlling the drive switches to be turned off is provided.

  With this configuration, when the amount of generated PM is small and the PM can be processed only by the DPF function, oxygen negative ions are not generated, and the generated amount of PM is equal to or greater than a certain amount during warm-up operation. In this case, oxygen negative ions can be generated. As a result, generation of useless oxygen negative ions can be prevented and generation of useless power consumption can be suppressed.

  The apparatus according to claim 5 is characterized in that the oxygen negative ions released from the oxygen negative ion emission part of the oxygen negative ion generator into the exhaust pipe is a necessary oxygen negative ion amount determined based on the generated PM amount. It is what.

  With this configuration, it is possible to generate only a necessary and sufficient amount of oxygen negative ions with respect to the constantly changing amount of generated PM, thereby preventing generation of wasted oxygen negative ions, resulting in unnecessary consumption. Generation of electric power can be suppressed.

  According to a sixth aspect of the present invention, the required amount of negative oxygen ions is generated by controlling the temperature of the alumina cement constituent and the applied voltage.

  According to experiments, it has been found that the generation of oxygen negative ions starts when the temperature of the alumina cement is around 650 ° C. and increases linearly from 700 ° C. to over 800 ° C. Thus, it has been found that the generation of oxygen negative ions starts when the electric field strength is 35 V / cm, and the generation increases linearly from 1000 V / cm to 2000 V / cm. Therefore, by configuring in this way, a related data map of the oxygen negative ion generation amount, the temperature of the alumina cement constituent material, and the applied voltage is prepared in advance, and the temperature and applied voltage are based on these data. By properly controlling the above, it is possible to reliably generate the amount of each necessary oxygen minus ion.

  According to a seventh aspect of the invention, the generated PM amount is calculated based on engine operation state detection data including at least the internal combustion engine speed and the fuel injection amount.

  In general, the amount of generated PM varies greatly depending on the engine operating state, particularly the internal combustion engine speed and the fuel injection amount. Therefore, with this configuration, it is possible to calculate the change in the amount of generated PM more accurately. As a result, there is an effect that the required oxygen minus ion amount can be calculated more accurately.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the overall configuration of the internal combustion engine system, and the oxygen negative ion generator 2 is disposed in the middle of the exhaust pipe 4 from the internal combustion engine (engine) 1, specifically at a position immediately before the exhaust upstream side of the DPF 3. An overall view of a low-temperature continuous oxidation apparatus for PM according to the present invention, in which an oxygen negative ion emitting portion 2A is connected, is shown.

  FIG. 2 is an enlarged view of the oxygen negative ion generator 2 shown in FIG. Reference numeral 2 denotes an oxygen negative ion generator, an alumina cement constituent 5 that can contain oxygen negative ions, a container 8 that holds the alumina cement constituent 5, a heater 9 that heats the alumina cement constituent 5, and an alumina cement. An oxygen supply electrode 6 provided in the structure 5, a gas 12 containing at least oxygen gas supplied to the oxygen supply electrode 6, and an extraction electrode 10 for extracting oxygen negative ions from the alumina cement structure 5; And a power source 11 that can apply a higher voltage to the extraction electrode 10 than the oxygen supply electrode 6.

  As shown in FIG. 2, the alumina cement structure 5 is formed as a cylindrical body having one end closed by, for example, pressure molding and firing, and the closed one end side is disposed in the container 8. Yes. An oxygen supply electrode 6 is formed on at least a part of the inner surface of the alumina cement structure 5, and a gas 12 containing at least oxygen gas is supplied to the oxygen supply electrode 6 as will be described later. Electrons are supplied from the power supply 11. The oxygen supply electrode 6 is formed, for example, by applying a metal paste inside the alumina cement structure 5 and sintering it, and is formed porous so that the supplied oxygen can react with the alumina cement. Further, the outer surface of the closed end of the alumina cement constituting body 5 in the container 8 is an oxygen negative ion generating portion 7. Furthermore, the alumina cement structure 5 is heated to 600 ° C. or more by the heater 9 and is not shown, but the temperature of the alumina cement is controlled by using an appropriate temperature sensor that has been conventionally used.

  The container 8 is made of stainless steel, glass or the like, and the internal atmosphere is kept in a vacuum or filled with an inert gas such as argon, but is preferably kept dry.

  As shown in the drawing, the extraction electrode 10 is arranged at a predetermined distance d from the oxygen negative ion generator 7. Further, the extraction electrode 10 is made of a stainless steel plate or the like, and a hole is provided at the center thereof so that the generated oxygen negative ions can pass.

  The power source 11 is a power source that applies a voltage higher than that of the oxygen supply electrode 6 to the extraction electrode 10 in order to extract the oxygen negative ions 14 from the alumina cement, and may be either direct current or alternating current. Reference numeral 13 denotes a switch for turning on / off the power.

Next, a method for generating oxygen negative ions will be described. As a first step, it is preferable that the alumina cement constituting body 5 is heated by the heater 9 and heated to 650 ° C. or higher, for example, 700 to 810 ° C. As a second stage, the power supply 11 applies a voltage of 100 to 2500 V between the extraction electrode 10 and the oxygen supply electrode 6, and supplies a gas 12 containing oxygen gas to the oxygen supply electrode 6. For this reason, electrons are supplied from the oxygen supply electrode 6 and exchange of electrons occurs between the O ⁻ , O ²⁻ , and O ₂ ⁻ ions contained in the alumina cement, and so-called ion conduction occurs. As a result, oxygen negative ions 14 are generated from the oxygen negative ion generator 7 and released to the outside, and pass through the hole of the extraction electrode 10. On the other hand, the amount of oxygen negative ions stored in the alumina cement decreases because of the release of oxygen negative ions from the oxygen negative ion generator 7, but the gas 12 containing oxygen gas is used as the oxygen supply electrode. 6 is supplied to the alumina cement and reacts to compensate for the decrease.

FIG. 5 shows the relationship between the amount of oxygen negative ions generated and the temperature of the alumina cement. The vertical axis represents current density, and the horizontal axis represents temperature. The applied voltage is 375V. It is understood that oxygen negative ions begin to be generated when the temperature of the alumina cement structure 5 is approximately 650 ° C., and the current density starts to increase linearly when the temperature exceeds 700 ° C. At 810 ° C., the current density of oxygen negative ions is 0.25 μA / cm ² .

FIG. 6 shows the relationship between the amount of oxygen negative ions generated and the applied voltage. The vertical axis represents current density, and the horizontal axis represents electric field strength. Moreover, the temperature of the alumina cement structure 5 is 800 degreeC. It is understood that oxygen negative ions are generated when the electric field strength is 35 V / cm, 0.1 μA / cm ² is generated at 100 V / cm, and the current density starts to increase linearly from around 500 V / cm. Further, 1, ² , 2.7 μA / cm ^{2 are} generated at 1100, 1700, and 2130 V / cm, respectively.

  Further, the current density of the generated oxygen negative ions by the oxygen negative ion generator 2 according to the present invention is about 2000 times or more compared with the current density of the generated oxygen negative ions by the solid electrolyte material YSZ (stabilized zirconia) of the conventional example. It has become.

By the way, the low-temperature continuous oxidation apparatus for PM according to the present invention is characterized in that in addition to the conventional PM supplementation and combustion function by DPF3, a continuous oxidation function by oxygen negative ions is added when a certain amount or more of PM is generated. Therefore, in the case where the amount of PM generated is small and it can be handled only by the DPF3 function, it is not necessary to generate oxygen negative ions. On the other hand, the amount of generated PM varies variously from warm-air operation to operation in a steady state. Therefore, it is very wasteful to always generate a large amount of oxygen negative ions in the plateau state, and it is desirable to generate only a necessary and sufficient amount of oxygen negative ions for the constantly changing amount of generated PM. By doing so, generation of wasted oxygen negative ions is prevented, and as a result, generation of wasted power consumption is suppressed.
In general, the amount of generated PM varies greatly depending on the engine operating state, particularly, the internal combustion engine speed and the fuel injection amount. Therefore, it is possible to more accurately calculate the change in the generated PM amount using the data regarding the engine operating state. As a result, the required oxygen minus ion amount can be calculated more accurately.

On the other hand, if the analysis results of FIGS. 5 and 6 are arranged, the generation of oxygen negative ions starts when the temperature of the alumina cement is about 650 ° C., and the generation increases linearly from 700 ° C. to over 800 ° C. It was also found that the generation of oxygen negative ions began when the electric field strength was 35 V / cm, and the generation increased linearly from 1000 V / cm to 2000 V / cm.
Therefore, the relevant data of the amount of oxygen negative ions generated, the temperature of the alumina cement constituent 5 and the applied voltage are acquired in advance, and the relevant map is prepared, and the alumina cement is prepared by ECU (not shown). By appropriately controlling the temperature and applied voltage of the constituent material 5, the amount of each necessary oxygen minus ion can be reliably generated.

  FIG. 3 is a flowchart relating to operation control of the oxygen negative ion generator 2 by an ECU (not shown), which will be described along the stage numbers S1 to S6. At the same time as the internal combustion engine (engine) 1 is started, the oxygen negative ion generator 2 is started, and at least data relating to the engine speed and fuel injection amount among the data relating to the engine operating state is measured by the engine system. Transferred (S1). The ECU calculates the amount of PM contained in the exhaust gas based on the engine speed and the fuel injection amount (S2). In this way, in the ECU, data regarding the generation amount of PM contained in the exhaust gas every moment is always grasped.

  Next, it is determined whether the amount of PM is a certain amount, i.e., greater than or less than the amount that can be processed only by PDF3 (S3). The switches 13 and heater 9 (not shown) are turned off, and the production of oxygen negative ions is stopped (S6). On the other hand, when it is above a certain amount, the switch 13 of the power source 11 and the switch of the heater 9 are turned on, and the application of voltage and the overheating of the alumina cement component 5 are started. At the same time, a map relating to the amount of PM and the amount of necessary oxygen negative ions prepared in advance is input to the ECU, and the amount of necessary oxygen negative ions is calculated based on the amount of PM and the map (S4).

  Further, the ECU is input with a map relating to the required amount of oxygen minus ions (current density of oxygen minus ions) and the temperature and applied voltage (electric field density) of the alumina cement constituent 5 prepared in advance. (Not shown) based on temperature data of the alumina cement structure 5 being transferred to the ECU and data and maps from ammeters and voltmeters (not shown respectively) installed in the circuit of the power supply 11 Thus, by controlling the temperature and applied voltage of the alumina cement structure 5, the necessary oxygen minus ion amount is reliably generated (S5).

  On the other hand, during this time, the calculation of the PM amount based on the data related to the engine operating state is continued, and when it is determined that the amount of generated PM is equal to or less than a certain amount due to the engine shifting to a steady operation state (S3). Will turn off the switch 13 of the power source 11 and the switch of the heater 9 to stop the generation of oxygen negative ions (S6).

  FIG. 4 is an image diagram showing the relationship between the exhaust gas temperature and the PM combustion rate when oxygen negative ions are used and when they are not used, based on experimental data. As can be seen from FIG. 4, when oxygen negative ions are not used, the PM combustion rate finally increases from around 600 ° C., but when oxygen negative ions are used, It can be seen that a fast combustion rate occurs and then continues stably.

Thus, since this invention is the above structures, there exist the following effects.
In ^{general, O -, O 2-, O} 2 -, O 3 -, O n - oxygen negative ions as defined is known to have about a thousand times the oxidation capacity than the oxygen molecule Yes. Therefore, even if the exhaust gas temperature is low, PM contained in the exhaust gas can be continuously oxidized. Therefore, in the low-temperature continuous oxidation apparatus for PM according to the present invention, oxygen negative ions are stably and continuously generated from alumina cement with a compact facility without arranging a high voltage application apparatus directly in the exhaust. Therefore, even if the exhaust gas temperature is low, PM can be continuously oxidized by oxygen negative ions throughout the operation region.
In addition, when a large amount of PM is discharged, especially during warm-up operation, PM can be continuously oxidized and combusted before DPF3, preventing a large amount of PM from accumulating in the filter and increasing the pressure loss of the filter. Can be suppressed.
Furthermore, by always calculating the amount of generated PM based on the engine operating state, especially the internal combustion engine speed and fuel injection amount, it is possible to realize a rational use of the conventional DPF function combined with the oxygen negative ion function. In addition, by appropriately controlling the temperature and applied voltage of the alumina cement structure 5, only a necessary and sufficient amount of oxygen negative ions can be generated with respect to the constantly changing amount of generated PM, and wasted oxygen. Generation | occurrence | production of a negative ion can be prevented and generation | occurrence | production of useless power consumption can be suppressed as a result.

It is a schematic block diagram of the internal combustion engine system incorporating the continuous low-temperature oxidation apparatus for PM in the embodiment of the present invention. 1 is an overall configuration diagram of an oxygen negative ion generator in an embodiment of the present invention. It is a flowchart about the operation control regarding the oxygen negative ion generator of the continuous low-temperature oxidation apparatus of PM in embodiment of this invention. It is the image figure which showed the relationship between the combustion speed of PM and exhaust gas temperature in embodiment of this invention. It is the image figure which showed the relationship between the oxygen negative ion generation amount and the temperature of an alumina cement in embodiment of this invention. It is the image figure which showed the relationship between the oxygen negative ion generation amount and applied voltage in other embodiment of this invention.

Explanation of symbols

1 Engine 2 Oxygen Negative Ion Generator 2A Oxygen Negative Ion Release Part 3 DPF
4 Exhaust pipe 5 Alumina cement component 6 Oxygen supply electrode 7 Oxygen negative ion generator 8 Container 9 Heater 10 Extraction electrode 11 Power source 12 Gas containing oxygen gas 13 Switch 14 Oxygen negative ion

Claims (7)

  In an exhaust part of an internal combustion engine, an oxygen negative ion emission part of an oxygen negative ion generator is connected to an exhaust pipe in a particulate matter oxidation apparatus that promotes oxidation of particulate matter mainly composed of carbon by oxygen negative ions. A low-temperature continuous oxidation apparatus for particulate matter characterized by the above.   2. The particulate matter low-temperature continuous oxidation apparatus according to claim 1, wherein the exhaust pipe is an exhaust pipe immediately before the upstream side of the exhaust of the diesel particulate filter.   The oxygen negative ion generator includes a container, an alumina cement constituent material at least part of which is disposed in the container and having an outer surface serving as an oxygen negative ion generator, and a heater for heating the alumina cement constituent material. An oxygen supply electrode formed on at least a part of the inner surface of the alumina cement constituent material, a gas containing at least an oxygen gas supplied to the oxygen supply electrode, and the oxygen negative ion generating part spaced apart from the above The particulate negative electrode according to claim 1 or 2, comprising an oxygen negative ion extraction electrode installed in a container and a power source capable of applying a higher voltage to the oxygen negative ion extraction electrode than the oxygen supply electrode. Low-temperature continuous oxidation equipment for substances.   The oxygen negative ion generator includes a generated particulate matter amount detecting means, and when the generated particulate matter amount is a certain amount or more, the power source and the heater drive switch are turned on. The low-temperature continuous oxidation apparatus for particulate matter according to any one of claims 1 to 3, further comprising control means for controlling each of the drive switches to be off.   The oxygen negative ion released from the oxygen negative ion emission part of the oxygen negative ion generator into the exhaust pipe is a necessary oxygen negative ion amount determined based on the generated particulate matter amount. The low-temperature continuous oxidation apparatus for particulate matter according to any one of 1 to 4.   6. The low-temperature continuous oxidation apparatus for particulate matter according to claim 5, wherein the necessary oxygen negative ion amount is generated by controlling the temperature of the alumina cement constituent and the applied voltage.   7. The particle according to claim 4, wherein the generated particulate matter amount is calculated based on engine operation state detection data including at least an internal combustion engine speed and a fuel injection amount. Low-temperature continuous oxidation equipment for gaseous substances.

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