JP2014129818A - Engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve estimation accuracy of an amount of PM accumulation of a particulate filter in an engine with the particulate filter.SOLUTION: An engine 5 possessing a particulate filter 13 and PM accumulation amount estimation means 53 possesses: first estimation means 51 estimating an amount of PM accumulation on the basis of a filter differential pressure of an entrance and exit of the particulate filter 13; and second estimation means 52 estimating the amount of PM accumulation on the basis of operational status of the engine 5. The first estimation means 51 is selected if an elapsed time T passes more than an appointed time T1, and the second estimation means 52 is selected if the elapsed time T is shorter than the appointed time T1.

Description

  The present invention relates to an engine provided with a particulate filter.

  Conventionally, a black smoke purification device provided in a diesel engine is known. The black smoke purification device is a device that removes particulate matter (particulate matter, hereinafter referred to as PM) from the toxic exhaust gas of a diesel engine. The black smoke purification apparatus includes an oxidation catalyst and a particulate filter (hereinafter referred to as a filter). Since the filter has only a filter function, if it is used for a long time, clogging occurs and the exhaust load increases and efficiency is deteriorated. Thus, filter regeneration means for warming the filter and burning PM is also known.

  In the filter regeneration means, it is necessary to estimate the PM accumulation amount of the filter. However, there are two PM accumulation states in the filter: a state in which the PM is accumulated inside the filter and a state in which the PM is accumulated on the surface.

  Furthermore, these two states differ depending on the engine operating state and the PM accumulation amount. That is, since the correlation between the filter differential pressure and the PM deposition amount is not constant, it is known that the filter differential pressure and the PM deposition amount show a complicated correlation having a hysteresis loop.

  Conventionally, as the PM accumulation amount estimation means, the first estimation means for estimating the PM accumulation amount based on the differential pressure of the filter, and the PM based on the engine operation history, the PM emission amount, or the PM regeneration amount of the black smoke purification device. Second estimation means for estimating the amount of deposition is known.

  In the filter regeneration means, the first estimation means is used for an engine operation state (regeneration area) with a high engine speed or engine load, and the second estimation means is an engine operation state (non-regeneration area) with a low engine speed or engine load. (For example, Patent Document 1).

JP 2006-90224 A

  When the engine operating state shifts from the non-regeneration area to the regeneration area, the selection of the estimation means is also switched from the second estimation means to the first estimation means. However, the inventors have confirmed through tests that there is a sudden change in the filter differential pressure for a while in the correlation between the filter differential pressure and the PM deposit when the engine operating state shifts from the non-regeneration range to the regeneration range. did.

  For this reason, depending on the engine operating state, the estimated value of the PM accumulation amount varies even with the first estimation means with relatively high estimation accuracy. Therefore, the problem to be solved is to improve the estimation accuracy of the PM deposition amount of the particulate filter by improving the above-mentioned problem in the engine equipped with the particulate filter.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  In claim 1, in an engine (5) comprising a particulate filter (13) and a PM accumulation amount estimating means (53), PM accumulation is based on the filter differential pressure between the inlet and outlet of the particulate filter (13). First estimation means (51) for estimating the amount, and second estimation means (52) for estimating the PM accumulation amount based on the operating state of the engine (5), and the elapsed time (T) is a predetermined time ( If T1) or more has elapsed, the first estimation means (51) is selected, and if the elapsed time (T) is smaller than the predetermined time (T1), the second estimation means (52) is selected.

  In claim 2, in the engine according to claim 1, when the first estimating means (51) is switched to the second estimating means (52), the final value of the PM accumulation amount by the first estimating means (51). Is used as the initial value of the PM accumulation amount estimated by the second estimating means (52).

  As effects of the present invention, the following effects can be obtained.

  According to the first aspect, when the filter differential pressure fluctuates, the PM accumulation amount of the particulate filter can be estimated by estimating the PM accumulation amount using the second estimating means.

  In claim 2, each time the first estimating means is switched to the second estimating means, the second estimating means is initialized with the final value of the PM estimation amount with relatively good estimation accuracy as needed by the first estimating means. Thus, the estimation accuracy of the PM accumulation amount of the second estimation means can be improved.

The block diagram which showed the whole structure of the diesel engine which concerns on the Example of this invention. The graph which shows the correlation of an engine driving | running state and PM regeneration area | region. The graph which shows the correlation with filter differential pressure | voltage and PM deposition amount. The schematic diagram which shows the time of PM deposition in a filter, and the time of PM reproduction | regeneration. The flowchart which shows PM deposition amount estimation means.

  Next, embodiments of the invention will be described. First, a schematic configuration of a diesel engine according to an embodiment of the present invention will be described.

  As shown in FIG. 1, a diesel engine (hereinafter referred to as an engine) 5 has an exhaust path including a black smoke purification device 10 that removes an engine body 20, an air supply path, and a particulate matter (hereinafter referred to as PM). And an Exhaust Gas Recirculation device (hereinafter referred to as an EGR device) and an Engine Control Unit (hereinafter referred to as an ECU) 100. The engine 5 is assumed to be mounted on the vehicle in this embodiment.

  The engine main body 20 is a four-cylinder diesel engine, and includes a fuel injection device (not shown), cylinders 25, 25, 25, 25, an air supply manifold 21, and an exhaust manifold 22.

  The air supply path includes an air cleaner 23 that removes dust and the like contained in the air, and an air supply throttle valve 24 that adjusts the air supply flow rate by being controlled to open and close. The supply air throttle valve 24 is a device that raises the exhaust gas temperature by reducing the supply air flow rate, and promotes combustion of PM in the oxidation catalyst 12 described later to prevent clogging.

  The exhaust path includes a black smoke purification device 10 to be described later in detail, an additive introduction device 14 for introducing a reducing agent or a combustion aid into the exhaust gas, and an exhaust throttle valve 15 for adjusting the exhaust flow rate by being controlled to open and close. , And is configured. The additive charging device 14 raises the exhaust gas temperature by oxidizing the oxidation catalyst 12 by introducing a reducing agent into the exhaust gas, or combustion of PM by introducing an auxiliary combustion agent such as a catalyst. It is a device that lowers the temperature than usual. The exhaust throttle valve 15 is a device that raises the exhaust gas temperature by restricting the exhaust flow rate and promotes PM combustion in the oxidation catalyst 12 described later to prevent clogging.

  Further, an exhaust gas temperature sensor 34 and an exhaust flow sensor 35 are provided in the exhaust path downstream of the black smoke purification device 10.

  The EGR device is a device that suppresses the generation of nitrogen oxides (NOx) by lowering the oxygen concentration in the intake air and gradually burning the fuel, and returns a part of the exhaust gas to the supply side. An EGR path 71 and an EGR valve 72 that adjusts the EGR amount by being controlled to open and close are provided.

  The black smoke purification apparatus 10 is separately provided on the upstream side of the filter 13 with a particulate filter (hereinafter referred to as a filter) 13 for passing the introduced exhaust gas through a porous partition wall and filtering PM contained in the exhaust gas. And an oxidation catalyst 12 that raises the temperature of the oxidation catalyst and warms the filter 13 by bringing it into contact with unburned material (fuel) and burning it (oxidation reaction).

  Further, the black smoke purification device 10 includes a filter inlet pressure sensor 31 provided at the inlet of the filter 13, a filter outlet pressure sensor 32 provided at the outlet of the filter 13, and a filter temperature sensor 33 provided at the filter 13. Is provided.

  The engine speed sensor 41 is provided in the vicinity of the crankshaft of the engine body 20. The rack position sensor 42 is provided in the vicinity of the rack position of the fuel injection device. An accelerator opening sensor 43 that detects the set position of the accelerator is provided in the vicinity of the accelerator of the vehicle. The vehicle speed sensor 44 is provided near the transmission of the vehicle.

  The ECU 100 includes a controller 50 and a storage unit 60. The controller 50 has functions as first estimation means 51, second estimation means 52, PM accumulation amount estimation means 53, and filter regeneration means 54, which will be described in detail later. The storage unit 60 can store constants and maps described later in advance.

  The ECU 100 detects the filter inlet pressure sensor 31 that can detect the inlet pressure of the filter 13, the filter outlet pressure sensor 32 that can detect the outlet pressure of the filter 13, the filter temperature sensor 33 that can detect the temperature of the filter 13, and the exhaust gas temperature. An exhaust gas temperature sensor 34 that can detect, an exhaust gas flow sensor 35 that can detect the flow rate of the exhaust gas, an engine speed sensor 41 that can detect the engine speed, a rack position sensor 42 that can detect the rack position of the fuel injection device, It is connected to an accelerator opening sensor 43 that can detect the accelerator opening and a vehicle speed sensor 44 that can detect the traveling speed of the vehicle.

  Here, the correlation between the PM deposition amount and the filter differential pressure will be described in detail. The PM accumulation amount is the amount of PM accumulated in the filter 13, and the filter differential pressure as the differential pressure of the black smoke purification device is the difference between the inlet pressure and the outlet pressure of the filter 13.

  As shown in FIG. 2, the black smoke purification device 10 is divided into a regeneration region and a non-regeneration region according to the engine operating state. In FIG. 2, the engine operating state is determined by the engine speed and the engine load. Regeneration means that the PM accumulated on the filter 13 is burned into the harmless carbon dioxide in the black smoke purification device 10. The regeneration region is a region where the engine speed and engine load are high, the exhaust gas temperature is high, and PM can be combusted. In the regeneration zone, PM will continue to be regenerated without being deposited. The non-regeneration region is a region where the engine speed and the engine load are low, the exhaust gas temperature is low, and PM cannot be combusted. In the non-regeneration area, PM will continue to be deposited.

  As shown in FIGS. 3A and 3B, when PM is deposited on the filter 13 and when PM accumulated on the filter 13 is regenerated, the inside and the surface of the filter 13 are regenerated stepwise. Will be deposited. FIG. 3A shows in a stepwise manner the PM is deposited on the filter 13 in the non-regeneration area described above. That is, in the non-regeneration region, first, PM is deposited on the inside and the surface of the filter 13, and eventually accumulates only on the surface of the filter 13 when it does not accumulate inside the filter. FIG. 3B shows a case where PM accumulated on the filter 13 is regenerated in the above-described regeneration region. That is, in the regeneration region, first, the PM inside the filter 13 through which the exhaust gas flows is regenerated first, and eventually the regeneration of the PM on the filter 13 surface becomes dominant.

  In this way, the inside and the surface of the filter 13 are regenerated or deposited in stages, so that the PM deposition state is not always constant. Therefore, the PM deposition amount and the filter differential pressure have the following characteristics.

  As shown in FIG. 4, the transition of the PM deposition amount and the filter differential pressure shows a complex correlation having a hysteresis loop represented by the upper stage characteristic line and the continuous regeneration deposition line (thick solid line in FIG. 4). Here, the accumulation limit (the one-dot chain line in FIG. 4) is a threshold in consideration of a safety factor (80% in the present embodiment) in the limit of the PM accumulation amount that can be deposited on the filter 13 in the black smoke purification apparatus 10.

  As indicated by an arrow a in FIG. 4, when the engine 5 is operated in a non-regeneration region from a state where PM does not accumulate on the filter 13, PM is gradually accumulated inside and on the surface of the filter 13 as described above. Therefore, the amount of PM deposited inside increases, and the filter differential pressure increases rapidly due to the resistance. If the accumulation amount further increases and does not accumulate in the filter, PM accumulates only on the surface of the filter 13, and the filter differential pressure gradually increases with the increase in the PM accumulation amount as indicated by the upper characteristic line. .

  As shown by the arrow b in FIG. 4, when the engine 5 is operated in the regeneration region from the state where PM has accumulated on the filter 13, as described above, the PM in the filter 13 in which the exhaust gas flows is regenerated first. Therefore, first, the filter differential pressure decreases more rapidly than the upper characteristic line. When the PM in the filter 13 is almost regenerated, the regeneration of the PM on the surface of the filter 13 becomes dominant. Therefore, as shown in the accumulation line at the time of continuous regeneration, the filter differential pressure becomes gradual with respect to the decrease in the PM accumulation amount. . As shown by the arrow b 'in FIG. 4, when the PM in the filter 13 is almost regenerated, the PM proceeds to the left or right on the accumulation line during continuous regeneration and the accumulation and regeneration of the surface of the filter 13 are balanced depending on the engine operating state. Stable at the point. After that, as long as it is in the regeneration zone, the state transits on the continuous regeneration deposition line.

  As shown by an arrow c in FIG. 4, when transitioning between the regeneration region and the non-regeneration region, the transition is suddenly made from one of the upper characteristic line and the continuous regeneration deposition line to the other line. When the PM in the filter 13 is completely clogged or regenerated, it moves on the gentle upper stage characteristic line or the continuous regeneration deposition line. In other words, the filter differential pressure always varies rapidly except when it is on the upper characteristic line or the continuous regeneration deposition line.

  Here, each means of the present embodiment will be described based on the above-described correlation between the accumulation amount and the transition of the filter differential pressure. The first estimation means 51 is a means for estimating the PM accumulation amount based on the filter differential pressure, and is an estimation means used when the engine operating state is in the regeneration range. In this embodiment, the filter differential pressure detected by the filter inlet pressure sensor 31 and the filter outlet pressure sensor 32 is corrected for temperature, gas amount, etc., and the deposition limit differential pressure obtained in advance through experiments and calculations is obtained. By comparing, the PM deposition amount is estimated. The first estimating means 51 may estimate the PM accumulation amount based on the pressure before the filter 13.

  The second estimation means 52 is a means for estimating the PM accumulation amount based on the engine operation state such as the engine operation history, the PM emission amount, or the PM regeneration amount of the black smoke purification device 10, and the engine is in a non-regeneration area. It is an estimation means used when driving. In the present embodiment, the second estimation means 52 estimates the PM accumulation amount by adding a coefficient to the operation time of the engine 5 (which may be a travel distance when mounted on the vehicle).

  The PM accumulation amount estimation unit 53 is a unit that estimates the PM accumulation amount by selecting and using the first estimation unit 51 or the second estimation unit 52 based on whether the operation is the filter regeneration region operation or the non-regeneration region operation. It is. Here, as a matter of special mention, when the PM accumulation amount estimation means 53 of this embodiment switches from the second estimation means 52 to the first estimation means 51, the second estimation means 52 is continuously used for a predetermined time. Later, the first estimation means 51 is used.

  As described above, when the engine operation is switched from the non-regeneration region to the regeneration region, a sudden change in the filter differential pressure occurs. Therefore, the second estimating means 52 is continuously used for a predetermined time when switching, so that the estimated value of the PM accumulation amount does not fluctuate greatly. That is, in the black smoke purification apparatus 10, the estimation accuracy of the PM accumulation amount of the filter 13 is improved.

  In this embodiment, the PM accumulation amount estimation means 53 determines whether the operation is the filter regeneration region operation or the non-regeneration region operation based on the exhaust gas temperature and the exhaust gas flow rate. Specifically, the PM accumulation amount estimation means 53 sets threshold values for both the exhaust gas temperature and the exhaust gas flow rate, and determines whether the filter regeneration zone operation or the non-regeneration zone operation is performed based on whether or not the threshold values are exceeded. To do. At this time, if the threshold regeneration is exceeded and it is determined that the filter regeneration zone operation is performed, the first estimation means 51 is selected to estimate the PM deposition amount.

  In this way, the accuracy of determination as to whether the operation is in the filter regeneration region or the non-regeneration region operation is improved, the regeneration region of the PM is reliably determined, the estimation means suitable for the regeneration region of the PM is selected, and the PM The estimation accuracy of the deposition amount is improved.

  Here, in determining whether the operation is the filter regeneration region operation or the non-regeneration region operation, without being limited to the exhaust gas temperature and the exhaust gas flow rate, the rack position of the fuel injection device as the engine load, the engine speed, Change rate of engine speed which is the rate of change of engine speed, exhaust gas flow rate, filter temperature, filter differential pressure, rate of change of filter differential pressure which is rate of change of filter differential pressure, PM accumulation amount, accelerator opening, accelerator open The determination may be made based on any one of the accelerator opening change rate, the vehicle speed, the vehicle speed change, which is the rate of change in the vehicle speed, or a plurality of these.

  Here, the predetermined time during which the second estimating means 52 is continuously used is calculated based on the PM accumulation amount or the engine operating state. In this embodiment, the engine operating state is calculated using the exhaust gas temperature (see FIG. 5).

  Further, the exhaust gas temperature as the engine operating state is not limited to use, and any of the rack position of the fuel injection device as the engine load, the engine speed, the exhaust gas flow rate, the filter temperature, the accelerator opening, and the vehicle speed. One or a plurality of them may be used.

  Here, when the change rate of the filter differential pressure as the engine operating state is used, it is possible to determine a sudden change in the filter differential pressure in the correlation between the filter differential pressure and the PM deposition amount. That is, it is possible to move to the first estimation means 51 having relatively higher estimation accuracy than the second estimation means 52 in a short time.

  The filter regeneration means 54 is a means for regenerating the filter 13 by burning in accordance with the PM accumulation amount estimated using the PM accumulation amount estimation means 53. In this embodiment, as the filter regeneration means 54, at least the supply throttle valve 24 or the exhaust throttle valve 15 is used to reduce the supply air flow rate, the exhaust pressure is increased to increase the exhaust gas temperature, and the reducing agent is added to the exhaust gas. The PM is combusted by oxidizing the reducing agent with the oxidation catalyst 12 by introducing it, or by introducing the auxiliary combustion agent into the exhaust gas. These filter regeneration means 54 are known techniques.

  Here, the control flow of the PM accumulation amount estimation means 53 will be described in detail. As shown in FIG. 5, in S101, the controller 50 starts the PM accumulation amount estimation control by the PM accumulation amount estimation means 53 when the engine is started. In S102, the controller 50 reads the exhaust gas temperature Tex assuming that PM is not deposited, that is, operating in the filter regeneration region. In S103, the controller 50 determines whether or not the exhaust gas temperature Tex is equal to or higher than a predetermined temperature Tex1. At this time, if the exhaust gas temperature Tex is lower than the predetermined temperature Tex1 in S103, the process proceeds to S107, and the second estimation means 52 is selected to estimate the PM accumulation amount. In S104, if the exhaust gas temperature Tex is equal to or higher than the predetermined temperature Tex1 in S103, the controller 50 calculates an elapsed time T after the exhaust gas temperature Tex becomes equal to or higher than the predetermined temperature Tex1. In S105, the controller 50 determines whether or not the elapsed time T is equal to or longer than the predetermined time T1. At this time, if the elapsed time T is shorter than the predetermined time T1, the process proceeds to S107, and the second estimation means 52 is selected to estimate the PM deposition amount. In S107, if the elapsed time T is equal to or longer than the predetermined time T1, the controller 50 proceeds to S106, selects the first estimation means 52, and estimates the PM accumulation amount.

  In S107, the controller 50 is configured to estimate the PM accumulation amount by the operation time of the engine 5 after the transition to S107 in the second estimation means 52. In this way, when the filter differential pressure fluctuates, the second estimation means 52 is used to improve the PM deposition amount estimation accuracy.

  Although not shown in FIG. 5, when the selection of the PM accumulation amount estimation unit 53 is switched from the first estimation unit 51 to the second estimation unit 52, the final value of the PM accumulation amount by the first estimation unit 51 is changed. Is the initial value of the PM deposition amount estimated by the second estimating means 52. In this way, every time the selection of the PM accumulation amount estimation means 53 is switched from the first estimation means 51 to the second estimation means 52, the second estimation means 52 is initialized, and the first estimation means 51 is relatively accurate as needed. This can be done by the final value of the estimated PM amount. That is, the PM accumulation amount estimation accuracy of the second estimation means 52 can be improved.

5 Diesel Engine 10 Black Smoke Purifier 12 Oxidation Catalyst 13 Particulate Filter 14 Additive Feeder 15 Exhaust Throttle Valve 20 Engine Body 24 Supply Throttle Valve 34 Exhaust Gas Temperature Sensor 51 First Estimating Means 52 Second Estimating Means 53 PM Accumulation Quantity estimating means 54 Filter regeneration means 60 Storage section 100 ECU

Claims (2)

In the engine (5) including the particulate filter (13) and the PM accumulation amount estimation means (53),
First estimation means (51) for estimating the PM accumulation amount based on the filter differential pressure at the inlet and outlet of the particulate filter (13), and second for estimating the PM accumulation amount based on the operating state of the engine (5). An estimation means (52),
If the elapsed time (T) has exceeded the predetermined time (T1), the first estimation means (51) is selected. If the elapsed time (T) is smaller than the predetermined time (T1), the second estimation means (52 ) Is selected.   The engine according to claim 1, wherein when the first estimating means (51) is switched to the second estimating means (52), the final value of the PM accumulation amount by the first estimating means (51) is determined by the second estimating means. An engine characterized by being used as an initial value of the PM accumulation amount estimated by the means (52).

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