JP2006183602A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an internal combustion engine capable of suppressing the excessive temperature rise of a filter when the filter collecting particulates is regenerated. <P>SOLUTION: A DPF device having first and second DPFs 21a and 21b collecting particulates in exhaust emission and first and second heaters Ha and Hb heating the first and second DPFs 21a and 21b is disposed in the exhaust passage 11 of the engine 10. A first temperature detection part THa formed of first to third heat resistors THa1 to THa3 is installed in the first DPF 21a, and an electric current to the first heater Ha is controlled by utilizing the characteristic change of the first temperature detection part THa. In the same manner, a second temperature detection part THb formed of fourth to sixth resistors THb1 to THb3 is installed in the second DPF 21b, and an electric current to the second heater Hb is controlled by utilizing the characteristic change of the second temperature detection part THb. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  In recent years, exhaust passages of some internal combustion engines such as diesel engines are provided with exhaust purification members such as filters that collect particulate matter (hereinafter referred to as PM (Particulate Matter)) in the exhaust.

  In such a filter, the exhaust resistance increases as the amount of collected PM increases. Therefore, it is necessary to perform a process of reducing the amount of collected PM by heating the filter to promote the oxidation of the collected PM, that is, a so-called filter regeneration process.

Therefore, in the exhaust gas purification apparatus described in Patent Document 1, a heater is provided in the filter, and when the integrated value of the PM amount in the exhaust gas estimated based on the engine operating state increases or is detected by a pressure sensor. When the back pressure immediately before the filter is increased due to an increase in the amount of collected PM, the heater is energized for a predetermined time.
JP-A-11-141327

  By the way, in the apparatus described in the above document, when the integrated value of the PM amount in the exhaust gas, the back pressure immediately before the filter, or the like is increased, that is, when the PM trapping amount of the filter is estimated to be increased to some extent. The heater is energized.

  Here, during filter regeneration, the temperature of the filter rises due to heating by the heater and the oxidation heat of PM, but the actual amount of collected PM is greater than the estimated amount of collected PM. Since a large amount of PM is oxidized, the temperature of the filter may be excessively increased. In some cases, the filter may be burned out.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an internal combustion engine that can suppress an excessive increase in temperature of the filter when performing regeneration processing of the filter that collects particulate matter. An object is to provide an exhaust emission control device.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 is an exhaust gas purification apparatus for an internal combustion engine comprising a filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust gas, and a heater for heating the filter. The gist of the invention is that a thermal resistor is disposed on the filter, and the amount of current supplied to the heater is controlled by utilizing the characteristic change of the thermal resistor.

  According to this configuration, the filter is heated by energizing the heater, thereby regenerating the filter. Here, in the above configuration, a thermal resistor whose resistance value changes according to the temperature is arranged in the filter, and the amount of current supplied to the heater is controlled using the characteristic change (resistance value change) of the thermal resistor. I have to. Therefore, when there is a possibility that the temperature of the filter will rise excessively during the regeneration process of the filter, the amount of heating by the heater can be reduced, and the PM oxidation rate can be suppressed by reducing the amount of heating by the heater. Will be able to. Therefore, when the filter regeneration process is performed, an excessive temperature rise of the filter can be suppressed. Examples of the thermal resistor include a thermistor.

  In controlling the energization amount using the characteristic change of the thermal resistor, the control current to the current control element is changed using the characteristic change of the thermal resistor, as described in claim 2. By adopting a configuration in which the energization amount to the heater controlled by the current control element is changed, the energization amount of the heater can be controlled with a simple configuration. Examples of the current control element include a transistor.

  The gist of a third aspect of the present invention is the exhaust gas purification apparatus for an internal combustion engine according to the first or second aspect, wherein a plurality of the thermal resistors are provided from an upstream portion to a downstream portion of the filter. .

  According to this configuration, since it becomes possible to detect a local temperature rise of the filter, an excessive temperature rise of the filter can be more suitably suppressed. In this configuration, it is desirable to provide thermal resistors at the upstream, middle and downstream portions of the filter.

  Further, when a plurality of thermal resistors are provided, the wiring system can be simplified by connecting the thermal resistors in series as in the fourth aspect of the invention. Incidentally, if at least one of the resistance values of the plurality of thermal resistors connected in series changes, the combined resistance value changes. Therefore, even when a local temperature rise occurs in the filter, the amount of current supplied to the heater is controlled using the change in the characteristics of multiple thermal resistors connected in series, in other words, the change in their combined resistance value. can do.

  The gist of the fifth aspect of the present invention is the exhaust gas purification apparatus for an internal combustion engine according to any one of the first to fourth aspects, wherein the heater is provided upstream of the filter.

  According to this configuration, the exhaust gas is heated by the heater provided on the upstream side of the filter, and the heated exhaust gas passes through the inside of the filter. As a result, the temperature of the entire filter can be increased efficiently. For example, compared to the case where the entire filter is directly heated by a heater, the heater can be reduced in size and power consumption can be reduced. become.

Hereinafter, an embodiment of an exhaust emission control device for an internal combustion engine according to the present invention will be described with reference to FIGS. 1 and 2 together.
FIG. 1 is a schematic configuration diagram showing an engine 10 as a diesel engine including an exhaust purification device according to the present embodiment, and a peripheral configuration thereof.

Exhaust gas discharged from the engine 10 is discharged to the atmosphere through the exhaust passage 11, the turbine chamber of the turbocharger 12, the DPF (Diesel Particulate Filter) device 20, and the like.
A DPF 21 that is divided into two in the exhaust flow direction is provided inside the DPF device 20, and one first DPF 21a and the other second DPF 21b are arranged in parallel to the exhaust flow direction. Yes. The first DPF 21a and the second DPF 21b are filters made of a porous ceramic structure, and the PM in the exhaust gas is collected when passing through the porous wall, so that it passes through the first DPF 21a and the second DPF 21b. Exhaust gas purification is achieved.

A partition plate 22 is provided between the first DPF 21a and the second DPF 21b to block the flow of exhaust gas between the first DPF 21a and the second DPF 21b.
Further, a switching plate 23 is provided on the upstream side of the DPF 21 to limit the amount of exhaust gas flowing into the first DPF 21a and the second DPF 21b. The switching plate 23 is a member driven by an actuator such as a motor, and is provided with a plurality of holes. The sizes and positions of the plurality of holes are appropriately set so that the exhaust gas flows almost uniformly on the cross section of the DPF on the side where the exhaust gas flow rate is limited.

  When the switching plate 23 is driven to the first DPF 21a side, most of the exhaust gas flows into the second DPF 21b. When the switching plate 23 is driven to the second DPF 21b side, most of the exhaust gas flows into the first DPF 21a. Further, when the switching plate 23 is driven so as to be parallel to the flow direction of the exhaust gas, that is, when the switching plate 23 is in the neutral position, the exhaust gas is divided into two parts so that the first DPF 21a and the second DPF 21b are almost equally distributed. Inflow.

  A first heater Ha is provided on the upstream side of the first DPF 21a, more specifically on the upstream end surface of the first DPF 21a, and on the upstream side of the second DPF 21b, more specifically on the upstream end surface of the second DPF 21b. A heater Hb is provided. The first heater Ha and the second heater Hb are provided with a plurality of holes through which exhaust gas passes. The first heater Ha and the second heater Hb generate heat by supplying power from the battery 15 of the vehicle. In addition, you may make it provide the 1st heater Ha and the 2nd heater Hb in the part spaced apart from the upstream end surface of each DPF.

  Further, the engine 10 is provided with a generator 14 that generates electric power by utilizing engine output and wheel rotation during deceleration, and the battery 15 is charged by supplying electric power from the generator 14.

  More specifically, the first DPF 21a is provided with a plurality of thermal resistors for detecting the temperature of the first DPF 21a from the upstream portion to the downstream portion of the first DPF 21a between the first DPF 21a and the partition plate 22. It has been. This thermal resistor has a characteristic that the resistance value increases rapidly in a predetermined temperature atmosphere. For example, a thermistor used as a temperature detecting element can be used. A first thermal resistor THa1 is provided in the upstream portion of the first DPF 21a, a second thermal resistor THa2 is provided in the midstream portion, and a third thermal resistor THa3 is provided in the downstream portion. 3 forms a first temperature detector THa.

  Similarly, the second DPF 21b is also provided with a plurality of thermal resistors for detecting the temperature of the second DPF 21b from the upstream portion to the downstream portion of the second DPF 21b. A fourth thermal resistor THb1 is provided in the upstream portion of the second DPF 21b, a fifth thermal resistor THb2 is provided in the midstream portion, and a sixth thermal resistor THb3 is provided in the downstream portion. 3 forms a second temperature detection unit THb.

FIG. 2 shows an electrical schematic configuration for controlling the energization amount of the first heater Ha and the second heater Hb using the characteristic change (resistance value change) of each thermal resistor.
First, one terminal of the first heater Ha and one terminal of the second heater Hb are common, and the current detector AM1 and the power supply circuit breaker 41c that forcibly cuts off the power to each heater are used. And connected to the positive terminal of the battery 15. The other terminal of the first heater Ha is connected to the emitter terminal of the first transistor TRa, and the amount of current supplied to the first heater Ha depends on the control current input to the base terminal of the first transistor TRa. Be controlled. Similarly, the other terminal of the second heater Hb is connected to the emitter terminal of the second transistor TRb, and the energization amount to the second heater Hb according to the control current input to the base terminal of the second transistor TRb. Is controlled.

  The first thermal resistor THa1, the second thermal resistor THa2, and the third thermal resistor THa3 constituting the first temperature detector THa are connected in series, and the combined resistance value of the first temperature detector THa. Is equal to the sum of the resistance values of the first to third thermal resistors THa1 to THa1. Thus, by connecting the thermal resistors in series, the wiring system is simplified as compared with the case of connecting in parallel. A predetermined voltage V1 is applied to one terminal of the first temperature detector THa, and the other terminal is connected to the base terminal of the first transistor TRa. The other terminal is connected to the other end of the pull-down first resistor Ra whose one end is grounded and a first switching circuit 41a for switching energization / non-energization to the first heater Ha. Yes.

  Similarly, the fourth thermal resistor THb1, the fifth thermal resistor THb2, and the sixth thermal resistor THb3 that constitute the second temperature detector THb are also connected in series, and the second temperature detector THb The combined resistance value is equal to the sum of the resistance values of the fourth to sixth thermal resistors THb1 to THb1. A predetermined voltage V1 is applied to one terminal of the second temperature detector THb, and the other terminal is connected to the base terminal of the second transistor TRb. The other terminal is connected to the other end of the pull-down second resistor Rb whose one end is grounded, and a second switching circuit 41b for switching between energization and non-energization of the second heater Hb. Yes.

  The first and second transistors TRa and TRb, the first and second resistors Ra and Rb, the first and switching circuits 41a and 41b, the power breaker 41c, and the like constitute a heater control circuit 40.

The output terminal of the generator 14 is connected to the plus terminal of the battery 15 via the current detection unit AM2.
A control device 30 including a central processing unit and a storage device grasps the engine operating state based on detection signals from various sensors, and performs various controls of the engine 10 according to the operating state.

Further, the control device 30 detects the current consumption of the first heater Ha and the second heater Hb based on a signal from the current detection unit AM1, detects the amount of power generated by the generator 14 based on the signal from the current detection unit AM2, 14, control of power generation amount, switching control of the first switching circuit 41 a and the second switching circuit 41 b,
The power cutoff control by the power breaker 41c, the drive control of the switching plate 23, etc. are performed.

  For example, when the vehicle is decelerated, the generator 14 is operated, whereby the rotational force of the wheels is converted into electric energy and collected by the battery 15. Further, the balance between the power consumed by energizing the first heater Ha and the second heater Hb and the power generated by the generator 14 is calculated, and when the charge amount of the battery 15 is insufficient, the engine output or the like Is used to operate the generator 14 so that a sufficient amount of power can be supplied to the first heater Ha and the second heater Hb.

  In this embodiment, PM in exhaust gas is collected by the DPF 21, but the exhaust resistance increases as the amount of PM collected by the DPF 21 increases, which affects engine output and the like. To give. Therefore, in the present embodiment, a process for promoting the oxidation of PM collected in the DPF 21 in the following manner, a so-called regeneration process for the DPF 21 is performed.

  First, the amount of PM collected by the DPF 21 is estimated through processing executed by the control device 30. Here, based on the engine load and engine speed calculated based on the accelerator operation amount, etc., the exhaust amount per unit time is estimated for the PM amount discharged from the engine 10, and this estimated PM discharge amount Is accumulated, the amount of PM collected by the DPF 21 is estimated. Then, when the estimated amount of collected PM exceeds a predetermined amount, regeneration processing of the DPF 21 is performed.

  When this regeneration process is executed, the switching plate 23 is driven to the first DPF 21a side and energization to the first heater Ha is performed for a predetermined time, whereby the first DPF 21a is heated and the PM collected in the first DPF 21a. The oxidation of is promoted. The energization time for the first heater Ha is set to a time necessary for sufficiently reducing the collected PM.

  In the regeneration process performed in this manner, the exhaust gas flowing into the first DPF 21a passes through the first DPF 21a while being heated by the first heater Ha. As a result, the temperature of the entire first heater Ha can be efficiently increased. For example, the size of the first heater Ha can be reduced and the power consumption can be reduced as compared with the case where the entire filter is directly heated by the heater. Can be achieved. Further, since the amount of exhaust flowing into the first DPF 21a is limited by the switching plate 23, the amount of heat that moves from the first DPF 21a toward the exhaust is suppressed. Therefore, compared with the case where the amount of exhaust is not limited, the first DPF 21a can be heated with a smaller amount of power.

  Incidentally, a regeneration process is also performed in which the fuel of the engine is added and burned on the filter so as to heat the filter. However, in such a regeneration process, oxygen is consumed in the combustion of the fuel and the like. Therefore, the oxidation rate of PM may be reduced. In this respect, in the present embodiment, the filter is heated by the heater, so that the reduction in the PM oxidation rate due to the addition of fuel or the like can be avoided.

  When the regeneration of the first DPF 21a is completed in this way, the switching plate 23 is driven to the second DPF 21b side, the second heater Hb is energized for a predetermined time, and the regeneration of the second DPF 21b is performed in the same manner as the regeneration of the first DPF 21a. The

  By the way, in this embodiment, when the amount of PM trapped by the DPF 21 is estimated and the estimated value reaches a specified amount, the regeneration process of the DPF 21 (the first DPF 21a and the second DPF 21b) is performed.

  Here, the temperature of the first DPF 21a during the regeneration of the first DPF 21a rises due to the heating by the first heater Ha and the heat of oxidation of PM, but the actual amount of collected PM rather than the estimated amount of collected PM. A large amount of PM is oxidized when there are more of these. For this reason, the temperature of the first DPF 21a may be excessively increased, and in some cases, the first DPF 21a may be burned out. The occurrence of such a problem is the same for the second DPF 21b.

  In this respect, in the present embodiment, the first DPF 21a and the second DPF 21b are provided with the first temperature detection unit THa and the second temperature detection unit THb, respectively. Therefore, an excessive temperature rise of the first DPF 21a and the second DPF 21b is caused. It is suppressed. Hereinafter, the suppression mode will be described. In addition, since the suppression aspect in 1st DPF21a and the suppression aspect in 2nd DPF21b are the same, below, it demonstrates taking the example of the suppression aspect of 1st DPF21a.

  During the regeneration of the first DPF 21a, when the temperature of the first DPF 21a becomes higher than a predetermined temperature, the resistance value of the first temperature detector THa increases rapidly. More specifically, an atmosphere of at least one of the first thermal resistor THa1, the second thermal resistor THa2, and the third thermal resistor THa3 that configures the first temperature detector THa and is connected in series. When the temperature (local temperature of the first DPF 21a) becomes higher than a predetermined temperature, the resistance value of the thermal resistor rapidly increases. Therefore, the combined resistance value of the first temperature detection unit THa also increases rapidly, and the control current input to the base terminal of the first transistor TRa decreases. When the control current decreases, the energization amount to the first heater Ha also decreases according to the degree of decrease, and the energization to the first heater Ha is limited or stopped. Incidentally, when the temperature of the first DPF 21a decreases and the resistance value of the first temperature detector THa decreases, energization to the first heater Ha is started or the energization amount is increased.

  As described above, even when a local temperature rise occurs in the first DPF 21a, a change in characteristics of the plurality of thermal resistors connected in series, in other words, a change in their combined resistance value is utilized to the first heater Ha. When the temperature of the first DPF 21a is likely to rise excessively during the regeneration process of the first DPF 21a, the amount of heating by the first heater Ha is reduced. In addition, since the oxidation rate of PM can be suppressed as the amount of heating by the first heater Ha decreases, an excessive temperature rise of the first DPF 21a can be appropriately suppressed when the regeneration process of the first DPF 21a is performed.

  Since the engine load increases and the exhaust temperature rises when the generator 14 is operated, the temperature of the first DPF 21a and the second DPF 21b is increased by the increase of the exhaust temperature and the heating by the first heater Ha and the second heater Hb. It becomes easy to be maintained. Accordingly, in such a case, the regeneration efficiency of the first DPF 21a and the second DPF 21b can be increased.

  When the engine load is higher than a certain level, the switching plate 23 is held in the neutral position. For this reason, it is possible to suppress a decrease in engine output due to an increase in exhaust resistance and a deterioration in emissions due to the introduction of excess exhaust gas recirculation gas.

As described above, according to the present embodiment, the following effects can be obtained.
(1) A thermal resistor is disposed in a filter (first DPF 21a and second DPF 21b) that collects PM, and heaters (first heater Ha and second heater) provided in the DPF 21 by utilizing the characteristic change of the thermal resistor. The energization amount to the heater Hb) is controlled. Therefore, when there is a possibility that the temperature of the filter will rise excessively during the regeneration process of the filter, the amount of heating by the heater can be reduced, and the PM oxidation rate can be suppressed by reducing the amount of heating by the heater. Will be able to. Therefore, when the filter regeneration process is performed, an excessive temperature rise of the filter can be suppressed.

  (2) A control current to the current control element (first transistor TRa and second transistor TRb) is changed using the characteristic change of the thermal resistor, and thereby a heater (first heater) controlled by the current control element The energization amount to Ha and the second heater Hb) is changed. Therefore, the energization amount of the heater can be controlled with a simple configuration.

  (3) A plurality of thermal resistors are provided from the upstream portion to the downstream portion of the filter. Therefore, a local temperature rise of the filter can be detected, and an excessive temperature rise of the filter can be more suitably suppressed.

  (4) Since the plurality of provided thermal resistors are connected in series, the wiring system can be simplified. Incidentally, if at least one of the resistance values of the plurality of thermal resistors connected in series changes, the combined resistance value changes. Therefore, even when a local temperature rise occurs in the filter, the amount of current supplied to the heater is controlled using the change in the characteristics of multiple thermal resistors connected in series, in other words, the change in their combined resistance value. can do.

  (5) A heater is provided on the upstream side of the filter. As a result, the temperature of the entire filter can be increased efficiently. For example, compared to the case where the entire filter is directly heated by a heater, the heater can be reduced in size and power consumption can be reduced. become.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the PM emission amount per unit time is estimated, and the estimated amount is integrated by integrating the estimated values. However, the PM collection amount is calculated based on the back pressure immediately before the DPF 21. You may make it estimate.

  In the above embodiment, the PM collection amount of the first DPF 21a and the PM collection amount of the second DPF 21b may be estimated separately, and the first DPF 21a and the second DPF 21b may be regenerated based on the estimation result.

  In the above embodiment, a plurality of thermal resistors are provided, but one thermal resistor may be provided for each of the first DPF 21a and the second DPF 21b. Even in this case, the effects described in the above (1), (2), and (5) can be obtained. In this case, it is desirable to provide a thermal resistor at a portion where the temperature is most likely to rise in each filter.

  In the above embodiment, three thermal resistors are provided in each filter. However, the number of the thermal resistors can be arbitrarily changed. Further, when a plurality of thermal resistors are provided, each thermal resistor may be provided biased (intensively) at an arbitrary part of the filter.

-You may make it connect each thermal resistor in parallel. Also in this case, the effects other than the above (4) can be obtained.
The heater control circuit 40 described in the above embodiment is an example, and in short, any circuit can be used as appropriate as long as it is a circuit that controls the amount of current supplied to the heater using the change in characteristics of the thermal resistor.

  In the above embodiment, the heater is provided on the upstream side of the filter. However, the present invention can be similarly applied to a filter in which the heater is provided in other arrangement modes. Even in the case, the effects described in the above (1) to (4) can be obtained.

  -Although the said DPF apparatus 20 was an apparatus provided with the switching board 23, two DPF, etc., if it is an apparatus provided with at least 1 DPF, this invention can be applied similarly.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the engine to which this is applied, and its periphery structure about one Embodiment of the exhaust gas purification apparatus of the internal combustion engine concerning this invention. Schematic which shows the electrical structure for controlling the energization amount of a heater in the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 11 ... Exhaust passage, 12 ... Turbocharger, 14 ... Generator, 15 ... Battery, 20 ... DPF device, 21 ... DPF, 21a ... 1st DPF, 21b ... 2nd DPF, 22 ... Partition plate, 23 ... Switching Plate, 30 ... Control device, 40 ... Heater control circuit, 41a ... First switching circuit, 41b ... Second switching circuit, 41c ... Power circuit breaker, Ha ... First heater, Hb ... Second heater, THa ... First temperature Detection part (THa1 ... 1st thermal resistor, THa2 ... 2nd thermal resistor, THa3 ... 3rd thermal resistor), THb ... 2nd temperature detection part (THb1 ... 4th thermal resistor, THb2 ... 5th thermal resistance) Body, THb3 ... sixth thermal resistor), TRa ... first transistor, TRb ... second transistor, Ra ... first resistor, Rb ... second resistor, AM1, AM2 ... current detector.

Claims (5)

In an exhaust gas purification apparatus for an internal combustion engine comprising a filter provided in an exhaust passage of the internal combustion engine and collecting particulate matter in the exhaust gas, and a heater for heating the filter,
An exhaust gas purification apparatus for an internal combustion engine, wherein a thermal resistor is disposed in the filter, and an energization amount to the heater is controlled using a characteristic change of the thermal resistor. 2. The internal combustion engine according to claim 1, wherein an energization amount to the heater controlled by the current control element is changed by changing a control current to the current control element using a characteristic change of the thermal resistor. Exhaust purification equipment. The exhaust purification device for an internal combustion engine according to claim 1, wherein a plurality of the thermal resistors are provided from an upstream portion to a downstream portion of the filter. The exhaust gas purification apparatus for an internal combustion engine according to claim 3, wherein the plurality of thermal resistors are connected in series. The exhaust purification device for an internal combustion engine according to any one of claims 1 to 4, wherein the heater is provided on an upstream side of the filter.

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