JP2007023792A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of properly regenerating a DPF device even if embers of a particulate are generated. <P>SOLUTION: After finishing regeneration of the DPF device 13, differential pressure ΔP<SB>M</SB>in an exhaust gas flow rate M<SB>1</SB>is estimated from an oil ash quantity and a DPF characteristic F<SB>0</SB>stored in a memory 20a, and differential pressure ΔP<SB>11</SB>in the exhaust gas flow rate M<SB>1</SB>is determined from a differential pressure sensor 24. In (ΔP<SB>11</SB>-ΔP<SB>M</SB>)≥a, when (S<SB>1</SB>-S<SB>2</SB>)<b is realized, since there is no ember of the particulate, the oil ash quantity stored in the memory 20a is updated to a value calculated on the basis of (ΔP<SB>11</SB>-ΔP<SB>M</SB>), and when (S<SB>1</SB>-S<SB>2</SB>)≥b is realized, since there are the embers of the particulate, a fuel adding quantity is increased. While, in (ΔP<SB>11</SB>-ΔP<SB>M</SB>)<a, since there is no ember of the particulate, the fuel adding quantity is reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust purification device, and more particularly, to an exhaust purification device that processes particulates discharged from an engine.

Patent Document 1 discloses a DPF (diesel particulate filter) device that processes particulates (main components are carbon particles) discharged from a diesel engine. By providing this DPF device in the exhaust system of the vehicle, particulates in the exhaust gas are captured by the DPF device. The exhaust gas contains a small amount of oil ash generated when the engine oil burns, and is captured by the DPF device together with the particulates. When particulates and oil ash are captured by the DPF device, the differential pressure before and after the DPF device rises. Therefore, this differential pressure is monitored during operation of the diesel engine, and when the differential pressure exceeds a predetermined value, Perform playback.
In Patent Document 1, regeneration of the DPF device is performed by delaying the fuel injection timing, or by further injecting fuel once after normal fuel injection, thereby raising the exhaust gas temperature and removing the particulates by combustion. Done. However, oil ash derived from inorganic components and the like of engine parts cannot be burned and removed like particulates, and remains captured by the DPF device even after regeneration. For this reason, even if the particulates are completely removed by regeneration, the differential pressure before and after the DPF device becomes higher by the amount of oil ash that is captured. When the number of regenerations of the DPF device increases and the amount of oil ash captured by the DPF device increases, the amount of particulate actually captured is reduced, although the differential pressure before and after the DPF device exceeds a predetermined value. It ’s not too much. Then, in the regeneration of the DPF device, the regeneration time becomes longer than necessary, leading to a reduction in fuel consumption.
The ratio of particulates and oil ash trapped in the DPF device cannot be detected only by the differential pressure before and after the DPF device. Therefore, in Patent Document 1, a predetermined value to be compared with the differential pressure before and after the DPF device is corrected based on the oil ash accumulation amount estimated on the basis of the vehicle travel distance, the engine operation history, and the like. Thus, the regeneration process is performed when the amount of the particulates actually captured by the DPF device is always constant. Thereby, reproduction | regeneration is started at an appropriate timing and the deterioration of a fuel consumption can be prevented.
In addition to increasing the temperature of the exhaust gas discharged from the engine itself as described in Patent Document 1, as a means for incinerating particulates captured by the DPF device and regenerating the DPF device, As described in Patent Document 2, it is known that an electric heater is provided in a DPF device, and the DPF device is directly heated and regenerated by energizing the heater. Further, as described in Patent Documents 3 and 4, an oxidation catalyst is disposed upstream of the exhaust system DPF device, and post-injection in the combustion chamber or fuel injection by a fuel addition valve disposed in the exhaust system. A technique is known in which fuel is added to exhaust gas, fuel components are reacted on an oxidation catalyst, and high-temperature gas is supplied to a downstream DPF device.

JP 2002-303123 A JP-A-9-280036 JP 2003-83036 A JP 2005-90256 A

  However, depending on the operating condition of the diesel engine, the particulate matter may remain unburned due to the fact that the regeneration cannot be performed completely or the operation of the diesel engine is stopped during the regeneration. During regeneration of the DPF device, the particulates do not burn uniformly. For example, in the DPF device of the type as disclosed in Patent Document 1, since burning starts from the front end or the center of the filter, unburned residue is also biased inside the DPF device, resulting in uneven deposition of particulates. The differential pressure before and after the DPF device has different values between the state where the particulates are uniformly captured inside the DPF device and the state where there is uneven deposition inside the DPF device, so there is once a burning residue. Then, even with the method of Patent Document 1, there is a problem that the amount of captured particulates cannot be accurately reflected.

  The present invention has been made to solve such problems, and an object of the present invention is to provide an exhaust purification device that can appropriately regenerate a DPF device even if particulate burnout remains. .

The exhaust purification apparatus according to the present invention is an exhaust purification apparatus that processes particulates in exhaust gas. The exhaust purification apparatus detects a differential pressure before and after the DPF apparatus that captures the particulates and the DPF apparatus. Means for detecting the flow rate of the exhaust gas, and control means for storing reference DPF characteristics that are the relationship between the differential pressure and the flow rate in the DPF device without deposits. Compares the measured change rate of the differential pressure detected by the differential pressure detecting means with respect to the flow rate detected by the exhaust gas flow rate detecting means and the reference change rate obtained from the reference DPF characteristics, and compares the measured change rate and the reference change rate. Is less than a predetermined value, it is determined that there is no particulate burnout in the DPF device.
The actual change rate is the ratio of the differential pressure difference between the two flow rates detected by the differential pressure detection means to the difference between any two different flow rates of the exhaust gas, and the reference change rate is the difference between the two flow rates. , The ratio of the differential pressure difference between the two flow rates obtained from the reference DPF characteristics, the control means, when the difference between the two ratios is smaller than a predetermined value, there is no particulate burnout in the DPF device, May be determined.
The exhaust emission control device further includes a temperature detection means for detecting the temperature of the exhaust gas flowing into the DPF device, and the control means corrects the detection value by the exhaust gas flow rate detection means based on the temperature of the exhaust gas. Good.
The exhaust purification device includes a catalyst provided upstream of the DPF device, and fuel addition means provided upstream of the catalyst, and the control means determines whether or not the next time the particulates remain unburned in the DPF device. You may make it adjust the fuel addition amount injected from a fuel addition means in reproduction | regeneration of a DPF apparatus.
The exhaust emission control device includes an electric heating means for heating the DPF device, and the control means adjusts the heating condition of the electric heating means in the next regeneration of the DPF device based on the presence or absence of unburned particulates in the DPF device. It may be.

  According to the present invention, the control means compares the actual change rate with the reference change rate, and if the difference between the actual change rate and the reference change rate is smaller than the predetermined value, the particulate unburned residue remains in the DPF device. By determining that there is no burnout, even if particulate burnout occurs, conditions are set so that not only newly captured particulates but also unburned particulates can be burned and removed during the next regeneration. Therefore, the regeneration of the DPF device can be performed appropriately.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 shows the configuration of the exhaust gas purification apparatus according to the first embodiment. An intake manifold 3 and an exhaust manifold 4 are connected to the cylinder head 1 of the four-cylinder engine. Each of the four cylinders 2 is provided with an injection nozzle 9 for injecting fuel into the cylinders 2. The injection nozzle 9 is an electromagnetic valve that injects high-pressure fuel into the cylinder 2 in a fine spray state. Each injection nozzle 9 is connected to a common common rail 8. One end of the fuel passage 5 is connected to the common rail 8. The other end of the fuel passage 5 is connected to a fuel supply pump 6. The common rail 8 receives supply of high-pressure fuel from the fuel supply pump 6, discharges a part of the fuel by the relief valve 25, and returns it to a fuel supply system such as a fuel tank (not shown) via the discharge passage 26. A high pressure fuel of a predetermined pressure is always maintained inside. One end of a fuel passage 7 is connected to the fuel supply pump 6. The other end of the fuel passage 7 is connected to a fuel tank. A desired amount of fuel is injected into the cylinder 2 by using the pressure of the high-pressure fuel in the common rail 8 to control the opening and closing time of the injection nozzle 9.
An intake passage 14 is connected to the intake manifold 3. An air cleaner 15 for removing dust contained in the intake air is disposed at the inlet 14 a of the intake passage 14. A throttle valve 16 (throttle valve) for adjusting the intake air amount and a negative pressure sensor 21 for detecting the intake negative pressure are sequentially provided downstream of the air cleaner 15.

  An exhaust passage 11 through which exhaust gas flows is connected to the exhaust manifold 4. Further, the exhaust manifold 4 is provided with a fuel addition nozzle 10 for supplying fuel into the exhaust manifold 4. The fuel addition nozzle 10 communicates with the fuel supply pump 6 through the fuel passage 27 so that fuel having a lower pressure than that in the common rail 8 is supplied. An oxidation catalyst 12 and a DPF device 13 are provided in the exhaust passage 11 from upstream to downstream. Between the oxidation catalyst 12 and the DPF device 13, a temperature sensor 23 for detecting the temperature of the exhaust gas flowing into the DPF device 13 is provided. Further, a differential pressure sensor 24 for detecting the differential pressure before and after the DPF device 13 is provided. Here, the temperature sensor 23 constitutes a temperature detecting means, and the differential pressure sensor 24 constitutes a differential pressure detecting means.

Further, an ECU 20 is provided as a control means, and the ECU 20 includes a fuel supply pump 6, an injection nozzle 9, a fuel addition nozzle 10, a negative pressure sensor 21, an engine speed sensor 17, an accelerator sensor 18, a temperature sensor 23, and a differential pressure. The sensor 24 is electrically connected. The engine speed sensor 17 is a sensor that is disposed near the end of the crankshaft of the engine and detects the engine speed. The accelerator sensor 18 is a sensor that detects the depression angle of the accelerator pedal 19 operated by the driver. The ECU 20 adjusts the fuel supply amount by controlling the injection nozzle 9 based on the depression angle of the accelerator pedal 19 operated by the driver and the operating state of the engine.
The ECU 20 also adds a fuel addition amount (initial value = Q) calculated by a map that represents the relationship between the exhaust gas flow rate and the differential pressure before and after the DPF device 13 (hereinafter referred to as DPF characteristics), and a flowchart that will be described later. ₀ ), and a memory 20a that stores information for N times regarding whether or not to calculate increase or decrease of the added fuel, and an oil ash amount or a differential pressure (initial value = 0) corresponding to the oil ash amount. In the map, a DPF characteristic F ₀ before capturing particulates and oil ash as set forth in the graph of FIG. 2 is set. Thereby, for example, the differential pressures before and after the DPF device 13 at two arbitrary exhaust gas flow rates M ₁ and M ₂ (M ₁ <M ₂ ) are ΔP ₀₁ and ΔP ₀₂ , respectively. From this map, the ratio S ₀ of the differential pressure difference (ΔP ₁₂ −ΔP ₁₁ ) to the flow rate difference (M ₂ −M ₁ ) between (M ₁ , ΔP ₀₁ ) and (M ₂ , ΔP ₀₂ ) can be calculated. . Here, the DPF characteristic F ₀ constitutes a reference DPF characteristic. The exhaust gas flow rate is calculated from the intake negative pressure when air is sucked into the cylinder 2, the engine speed, and the amount of fuel injected into the cylinder 2 under the control of the ECU 20. Here, the negative pressure sensor 21, the engine speed sensor 17 and the ECU 20 constitute exhaust gas flow rate detection means. In order to determine the differential pressure from the exhaust gas flow rate based on the DPF characteristic F ₀ , it is necessary to correct the exhaust gas flow rate with respect to the exhaust gas temperature. This correction method will be described later. FIG. 2 shows a three-dimensional map to which one axis based on the exhaust gas temperature is added if it is strictly shown by reflecting such temperature correction. In this map, the DPF characteristic F ₀ is a curved surface shape. Make. However, in the first embodiment, only the comparison of the two driving states is performed, so there is no particular problem with the two-dimensional map shown in FIG.

Next, the operation of the exhaust gas purification apparatus according to the first embodiment will be described.
As shown in FIG. 1, when the engine is started, the fuel supply pump 6 supplies fuel from a fuel tank (not shown) to the common rail 8 via the fuel passages 7 and 5, and supplies a predetermined high-pressure fuel into the common rail 8. maintain.
When the engine is started, intake air is drawn into each cylinder 2 through the intake passage 14 and the intake manifold 3. At this time, the negative pressure sensor 21 detects the negative pressure of the air sucked into each cylinder 2. In each cylinder 2, air is compressed by a piston (not shown) and fuel is injected from each injection nozzle 9. The fuel supply amount is controlled by the ECU 20 and adjusted by changing the opening / closing time of the injection nozzle 9. Thereby, combustion occurs in each cylinder 2. Exhaust gas generated by combustion in each cylinder 2 is exhausted from each cylinder 2 and collected in the exhaust manifold 4 and flows through the exhaust passage 11. The exhaust gas flowing through the exhaust passage 11 passes through the oxidation catalyst 12 and then flows into the DPF device 13. After the fixed particulates such as particulates and oil ash contained in the exhaust gas are captured by the DPF device 13, To be discharged.

  After the engine has been operating for a predetermined time since the end of regeneration of the previous DPF device 13, the ECU 20 is suitable for regeneration of the DPF device 13, for example, under the condition that the exhaust gas temperature is equal to or higher than the predetermined temperature. If the conditions are satisfied, the fuel addition nozzle 10 is operated. As a result, supply of fuel into the exhaust manifold 4 is started, and regeneration of the DPF device 13 is started. As the fuel to be added, a predetermined set amount per injection is injected, and supply of a predetermined fuel addition amount is completed by a plurality of injections. The total amount of fuel added is adjusted by increasing or decreasing the number of injections. The fuel supplied into the exhaust manifold 4 flows into the oxidation catalyst 12 along with the exhaust gas. The fuel is oxidized by the oxidation catalyst 12, and the temperature of the exhaust gas flowing downstream increases due to the reaction heat of this oxidation reaction. When the exhaust gas temperature rises to a predetermined temperature or higher, the particulates captured by the DPF device 13 are removed by combustion. On the other hand, the oil ash trapped in the DPF device 13 is not burned and removed but remains trapped in the DPF device 13 and gradually accumulates every time regeneration is repeated. After the fuel is supplied into the exhaust manifold 4 by a predetermined amount, the ECU 20 stops the fuel injection of the fuel addition nozzle 10 and ends the regeneration of the DPF device 13. After the regeneration of the DPF device 13 is completed, the amount of fuel supplied in the next regeneration is determined by comparing the DPF characteristic after the regeneration with the reference DPF characteristic.

Next, a procedure for determining the supply amount of the added fuel supplied in the regeneration of the DPF device 13 will be described using the flowchart of FIG.
Immediately after the regeneration of the DPF device 13 is completed, the calculation of the fuel addition amount at the next regeneration is started. First, in step S1, the ECU 20 determines the differential pressure ΔP ₁₁ before and after the DPF device 13 at the exhaust gas flow rate M ₁ and the exhaust gas temperature from the detection values by the differential pressure sensor 24 and the temperature sensor 23 in an arbitrary operation state. Is detected. At the same time, a differential pressure ΔP _M at the exhaust gas flow rate M ₁ is estimated based on the oil ash amount and the DPF characteristic F ₀ stored in the memory 20a. In the process of estimating ΔP _M , it is necessary to obtain the differential pressure ΔP ₀₁ at the exhaust gas flow rate M ₁ from the DPF characteristic F _0. At this time, the exhaust gas flow rate M ₁ is set to the exhaust gas temperature detected by the temperature sensor 23. It is necessary to correct it. A map used for this correction is shown in FIG. The horizontal axis indicates the exhaust gas flow rate detected by the negative pressure sensor 21, the engine speed sensor 17 and the ECU 20, and the vertical axis indicates the exhaust gas temperature detected by the temperature sensor 23. By dividing each of the horizontal axis and the vertical axis at arbitrary intervals, a plurality of grid-like sections are defined on the graph. Each section is assigned a value corresponding to a differential pressure before and after the DPF device 13 with respect to the exhaust gas flow rate corrected by the exhaust gas temperature. In FIG. 4, all of the plurality of sections have a square shape, but an interval for dividing each of the horizontal axis and the vertical axis is arbitrary, and the sections need not necessarily be square. In FIG. 4, a section indicated by diagonal lines is determined from the exhaust gas flow rate M ₁ and the exhaust gas temperature T ₁ , and the differential pressure ΔP ₀₁ assigned to this section is the differential pressure obtained from the DPF characteristic F _0. It becomes. From the differential pressure ΔP ₀₁ and the oil ash amount stored in the memory 20a, the differential pressure ΔP _{M at the} exhaust gas flow rate M ₁ is estimated.

Next, the ECU 20 determines whether (ΔP ₁₁ −ΔP _M ) is equal to or greater than a predetermined value a (step S2). If it is determined in step S2 that (ΔP ₁₁ −ΔP _M ) is equal to or greater than the predetermined value a, the process proceeds to step S3. As preparation, the exhaust flow rate is newly increased to M ₂ (M ₁ ≠ M _{2. In} this example, the differential pressure ΔP ₁₂ and the exhaust gas temperature when M ₁ <M ₂ ) are detected. As shown in FIG. 5, the ECU 20 plots (M ₁ , ΔP ₁₁ ) and (M ₂ , ΔP ₁₂ ) on a map stored in the memory 20a, and the flow rate difference (M ₂ ) between the two points. calculating the _{S 1} is the ratio of the difference of the differential pressure (ΔP ₁₂ -ΔP ₁₁₎ for -M _1). Thereafter, the ECU 20 determines whether (S ₁ -S ₀ ) is equal to or greater than a predetermined value b (step S3). Here, S ₀ and S ₁ constitute a reference change rate and an actually measured change rate, respectively.
The DPF characteristics during engine operation are affected by the accumulated state of solid particulates such as trapped particulates and oil ash. Since the accumulation state of the solid fine particles captured by the DPF device 13 continues to change while the engine is running, the detection values obtained by the exhaust gas flow rate detection means and the differential pressure detection means are used on the map stored in the memory 20a. It is difficult to accurately represent the DPF characteristics during engine operation. Therefore, the virtual DPF properties during engine operation at any given time and F _1. Here, it is assumed that the DPF characteristic F ₁ includes two points (M ₁ , ΔP ₁₁ ) and (M ₂ , ΔP ₁₂ ). When the solid fine particles are uniformly deposited in the DPF device 13, as shown in FIG. 5, the DPF characteristic F ₁ does not change the line shape and the line does not change compared to the DPF characteristic F _0. Slide up. On the other hand, when the solid fine particles are deposited in the DPF device 13 with uneven deposition unevenness, as shown in FIG. 6, the DPF characteristic F ₁ is on the side where the exhaust gas flow rate is large. Compared to ₀ , the line shape changes so that the differential pressure before and after the DPF device 13 tends to increase. Oil ash that is not affected by the regeneration of the DPF device 13 is uniformly deposited in the DPF device 13, so if the line shape of the DPF characteristic changes, it is caused by unburned particulates. I understand.
If particulates are completely incinerated by regeneration and only oil ash accumulation affects the differential pressure, S ₁ and S ₀ are almost equal, and (S ₁ -S ₀ ) is predetermined. It becomes smaller than the value b. On the other hand, when the particulates remain unburned, the particulates are accumulated in the DPF device 13 with uneven deposition, so (S ₁ −S ₀ ) is equal to or greater than the predetermined value b.

When it is determined in step S3 that the value of (S ₁ −S ₀ ) is smaller than the predetermined value b, the ECU 20 has no particulate burnout remaining in the DPF device 13 and only oil ash is accumulated. Judge that In this case, the oil ash amount can be calculated from (ΔP ₁₁ −ΔP _M ), and the calculated value is overwritten and stored in the memory 20a. (Step S4). Then, it moves to step S1 and repeats the same operation based on the oil ash amount memorize | stored in the memory 20a. Since the oil ash amount is used only for calculating the differential pressure, the corresponding differential pressure value itself may be stored without converting the differential pressure into the oil ash amount.
On the other hand, when it is determined in step S3 that the value of (S ₁ −S ₀ ) is equal to or greater than the predetermined value b, the ECU 20 determines that there is no particulate burnout in the DPF device 13. In this case, since it is necessary to burn and remove the unburned particulates at the time of the next and subsequent regenerations, the ECU 20 performs a calculation to increase the amount of fuel added to the exhaust manifold 4 by a predetermined amount ( In step S5), the increased fuel addition amount is overwritten and stored in the memory 20a (step S6). The reason why the increment of the fuel addition amount is set to a predetermined amount will be described later.

If it is determined in step S2 that (ΔP ₁₁ −ΔP _M ) is smaller than the predetermined value a, the process proceeds to step S7, and the fuel addition amount is increased after the regeneration of the DPF device 13 in the past N times. Or, it is determined whether or not weight reduction has been performed. N is an arbitrary number of times determined in advance, and an arbitrary value can be set. If it is determined that there is no increase or decrease in fuel, the process proceeds to step S8. The N-time role will be described later. In step S8, the ECU 20 performs a calculation for reducing the fuel addition amount by a predetermined amount, and in the subsequent step S6, the fuel addition amount after the reduction is overwritten and stored in the memory 20a. If it is determined in step S7 that there is an increase or decrease in fuel, step S8 is omitted and the process proceeds to step S6. In this case, since the calculation for changing the fuel addition amount is not performed, the previous fuel addition amount is maintained in the memory 20a as it is.

Thereafter, when the engine is operated for a predetermined time after the regeneration of the DPF device 13 is completed, the fuel supply is started with the fuel addition amount stored in the memory 20a, whereby the regeneration of the DPF device 13 is performed again. When the regeneration of the DPF device 13 is completed again, the amount of fuel to be supplied in the next regeneration is determined according to the procedure described above.
In step S5, the increment of the fuel injection amount is set to a predetermined amount. This is to prevent the fuel injection amount from being increased unnecessarily when erroneous detection of the amount of unburned particulates occurs, and to prevent deterioration of fuel consumption and catalyst deterioration due to overheating. The purpose is to limit the increase in the fuel injection amount. Since the form of unburned particulates is not necessarily uniform, it is difficult to accurately calculate the amount of unburned residue even if it is recognized in step S3 that there is unburned particulates. Further, each sensor may cause a false detection due to a transient state of the engine operating state. Therefore, the fuel injection amount is increased by an amount corresponding to the amount of unburned fuel, and the unburned residue is not incinerated at a time when the DPF device 13 is regenerated next time. In the first embodiment, multiple times including the next time are performed. The processing method which eliminates the unburned residue is taken.
Specifically, when it is determined that there has been no unburned particulates (corresponding to “NO” in step S3), the processing of step S2, step S3, step S7, etc. at the next calculation of the fuel addition amount is exemplified. To do. After completion of regeneration of the DPF device 13, calculation of the fuel addition amount in the next regeneration is started. Since the amount of fuel added is increased, at the next regeneration of the DPF device 13, in addition to the newly captured particulates, part of the previous unburned residue is also incinerated. If the remaining unburned last time a small amount, the differential pressure [Delta] P ₁₁ becomes a small value, the step S2 is "NO". In step S7, since the previous fuel addition amount has been increased, the answer is “YES”, step S8 is omitted, and the fuel addition amount in which the predetermined amount is increased by one time is maintained. This is a consideration for completely burning the unburned residue. For example, when N = 3 is set, the regeneration of the DPF device 13 is performed three times with the fuel addition amount increased by a predetermined amount for one time. The amount of fuel added is reduced.
On the other hand, if the previous unburned residue is large, the process goes to step S5 through step S2 and step 3, and the fuel addition amount is further increased by a predetermined amount.

In this way, after the regeneration of the DPF device 13 is completed, the ECU ₂₀ detects the flow rate detected by the differential pressure sensor 24 with respect to the flow rate difference (M ₂ −M ₁ ) at the _two flow rates M ₁ and M ₂ with different exhaust gases. the ratio _{S 1} of the difference of the differential pressure (ΔP ₁₂ -ΔP ₁₁₎ in _{M 1,} M _2, for the difference of the flow rate _(M 2 -M _1), in the flow rate _M 1, _{M 2} obtained from DPF characteristic _{F 0} Based on the difference (S ₁ -S ₀ ) between the differential pressure difference (ΔP ₀₂ -ΔP ₀₁ ) and the ratio S _0, it is determined whether there is any unburned particulates. In this case, not only newly captured particulates but also unburned particulates can be combusted and removed in the next and subsequent regenerations.
Further, based on the exhaust gas flow rate calculated from the intake negative pressure when the air is sucked into the cylinder 2, the engine speed and the injection amount of the fuel injected into the cylinder 2, and detected by the temperature sensor 23. By correcting according to the exhaust gas temperature, the differential pressure before and after the DPF device 13 in consideration of the change in the exhaust gas pressure loss can be obtained, so that it is possible to accurately determine whether particulates remain unburned.
When the ECU 20 determines that there is no particulate unburned residue in the DPF device 13, the ECU 20 reduces the amount of fuel supplied during regeneration of the DPF device 13, and when it determines that there is unburned fuel, Since the amount is increased, the supply amount of fuel consumed in the regeneration of the DPF device 13 can be optimized, and the fuel efficiency can be improved.

  In the first embodiment, the exhaust gas flow rate is calculated from the intake negative pressure, the engine speed, and the fuel injection amount. However, the present invention is not limited to this. In an engine having an air flow meter in the intake passage 11, the exhaust gas flow rate can be calculated from the intake flow rate detected by the air flow meter and the fuel injection amount. In this case, the air flow meter and the ECU 20 serve as exhaust gas flow rate detection means.

Embodiment 2. FIG.
Next, an exhaust purification system according to Embodiment 2 of the present invention will be described. In the following embodiments, the same reference numerals as those in FIG. 1 are the same or similar components, and detailed description thereof will be omitted.
The exhaust purification device according to Embodiment 2 of the present invention regenerates the DPF device 13 by heating the DPF device 13 with electric heating means instead of the fuel addition nozzle 10 and the catalyst 12 as compared with Embodiment 1. It is what I did. As shown in FIG. 7, an electric heater 30 that is electric heating means is provided upstream of the DPF device 13, and the electric heater 30 is electrically connected to the ECU 20. Other configurations are the same as those in the first embodiment.

  Next, the operation of the exhaust gas purification apparatus according to the second embodiment will be described with reference to FIG. After the engine has operated for a predetermined time, the ECU 20 operates the electric heater 30 to heat the DPF device 13 so that the DPF device 13 has a preset temperature. Thereby, the particulates captured by the DPF device 13 are burned and removed, and the DPF device 13 is regenerated. Further, as in the first embodiment, the oil ash captured by the DPF device 13 remains captured by the DPF device 13 without being removed by combustion. After the regeneration of the DPF device 13 is completed, the ECU 20 determines whether there is any unburned particulates in the same manner as in the first embodiment. Further, based on the presence or absence of the unburned particulates, in the next regeneration of the DPF device 13, the conditions under which the electric heater 30 heats the DPF device 13, for example, the heating temperature is adjusted.

Next, the procedure for adjusting the heating conditions will be described with reference to the flowchart of FIG.
Steps S10 to S13 are the same as steps S1 to S4 in the float chart of FIG. 3 in the first embodiment. If it is determined in step S12 that (S ₁ -S ₀ ) is equal to or greater than the predetermined value b, the ECU 20 needs to burn and remove unburned particulates at the next regeneration. Then, a calculation is performed to decrease the set temperature of the electric heater 30 by a certain temperature (step S14), and the set temperature after the decrease is stored in the memory 20a (step S15). Here, the reason why the set temperature of the electric heater 30 is lowered when there is unburned particulate is because the amount of the particulate is larger by the amount of unburned. That is, when the heating condition is adjusted so that the set temperature of the electric heater 30 is relatively low, only a part of the particulates burns. When some of the particulates start to burn, the combustion is sequentially transmitted to the remaining particulates, and the particulates are gradually burned. As a result, it is possible to prevent a large amount of particulates from burning at once and generating high heat, thereby damaging the DPF device 13.
If it is determined in step S11 that (ΔP ₁₁ −ΔP _M ) is smaller than the predetermined value a, the process proceeds to step S16, and after the past N regenerations of the DPF device 13, the setting of the electric heater 30 is performed. Determine if the temperature has increased or decreased. If the set temperature has not been increased or decreased, the ECU 20 performs a calculation to increase the set temperature of the electric heater 30 by a certain temperature (step S17), and stores the increased set temperature in the memory 20a (step S17). S15). Here, the reason why the set temperature of the electric heater 30 is raised when there is no unburned particulate is because the amount of the particulate is small by the amount of oil ash. That is, when there are few particulates, even if a part of the particulates are burned, the combustion is not easily transmitted to the remaining particulates. For this reason, ECU20 adjusts a heating condition so that the temperature of the electric heater 30 may become comparatively high so that the captured particulate can be burned at a stretch. If there are few particulates, high heat will not generate | occur | produce even if it burns at a stretch, and the DPF apparatus 13 will not be damaged. The role of step S16 is the same as that of step S7 in the flowchart of FIG.
Other operations are the same as those in the first embodiment.

  As described above, when the ECU 20 determines that there is no unburned particulate matter in the DPF device 13, the ECU 20 increases the set temperature of the electric heater 30 in the next regeneration of the DPF device 13, and determines that there is unburned residue. Since the set temperature of the electric heater 30 is lowered, the heating conditions of the electric heater 30 in the regeneration of the DPF device 13 can be optimized, so that the DPF device 13 may be damaged by inappropriate heating conditions. Can be prevented.

  In the second embodiment, the heating condition of the electric heater 30 is described as the heating temperature. However, the present invention is not limited to this. The heating condition may be the operating time of the electric heater 30. In this case, when there is unburned particulates, the operation time is shortened in order to burn some of the particulates. On the other hand, when there is no unburned particulate matter, even if some of the particulates are burned, the combustion is not easily transmitted to the remaining particulates, so that all of the particulates can be burned by heating by the electric heater 30. , Extend the operating time.

Embodiment 3 FIG.
Next, an exhaust emission control apparatus according to Embodiment 3 will be described. The exhaust emission control device according to the third embodiment is different from the first embodiment in that the fuel injection amount is adjusted while particulates and oil ash are captured by the DPF device 13. The configuration of the exhaust gas purification apparatus according to the third embodiment is the same as that of the first embodiment. Therefore, the procedure for adjusting the fuel injection amount will be described below with reference to the flowchart of FIG.
When this procedure is started, the ECU 20 determines whether or not the travel distance has exceeded a predetermined value (step S20). Thereby, the reproduction start timing is determined. When the travel distance exceeds a predetermined value, that is, when it is time to regenerate the DPF device 13, the ECU 20 determines whether or not the value detected by the temperature sensor 23 exceeds the predetermined value (step S21). This is because when the engine load is low, the exhaust gas temperature is low, so even if fuel is supplied to the exhaust gas, the catalyst is not activated and the particulates captured by the DPF device 13 may not burn. Because. Therefore, step S21 is a step for performing regeneration after determining whether or not the operating state of the engine is a state in which the DPF device 13 can be regenerated.
If the detected value by the temperature sensor 23 exceeds the predetermined value and the DPF device 13 can be regenerated, the process proceeds to step S22, and the ECU 20 performs the differential pressure sensor 24 and the temperature sensor 23 in any operation state. From the detected value, the differential pressure ΔP ₁₁ before and after the DPF device 13 at the exhaust gas flow rate M ₁ and the exhaust gas temperature are detected. At the same time, the differential pressure ΔP _M at the exhaust gas flow rate M ₁ is estimated in the same manner as in the method described in the first embodiment.

Subsequent steps S23 to S26 and S29 to S30 are the same as steps S2 to S5 and S7 to S8 of FIG. 3 in the first embodiment. In step S26 or S30, when the amount of fuel added in the previous DPF device 13 is increased or decreased, the fuel is added into the exhaust manifold 4 with the amount of fuel added, whereby regeneration of the DPF device 13 is started. (Step S27). In subsequent step S28, the fuel addition amount is stored in the memory 20a, the travel distance data is reset, and the series of procedures is completed.
When a predetermined time has elapsed since the start of fuel addition, the ECU 20 ends the regeneration of the DPF device 13 by stopping the fuel addition. Thereafter, the above procedure is repeated to adjust the fuel injection amount in the next regeneration.
Also in the exhaust gas purification apparatus according to the third embodiment, the same effect as in the first embodiment can be obtained.

Embodiment 4 FIG.
Next, an exhaust emission control apparatus according to Embodiment 4 will be described. The exhaust purification apparatus according to the fourth embodiment adjusts the fuel injection amount in a state where particulates and oil ash are captured by the DPF device 13 as compared with the second embodiment. The configuration of the exhaust emission control device according to the fourth embodiment is the same as that of the second embodiment. Therefore, the procedure for adjusting the fuel injection amount will be described below with reference to the flowchart of FIG.
When this procedure is started, the ECU 20 determines whether or not the travel distance exceeds a predetermined value (step S40). Thereby, the reproduction start timing is determined. Subsequent steps S41 to S44 are the same as steps S22 to S25 of FIG. 9 in the third embodiment. In addition, in steps S45 to S49, the decrease in the fuel addition amount is changed to the increase in the set temperature of the electric heater 30 with respect to the steps S26 to S30 in FIG. 9, and the increase in the fuel addition amount is set to the set temperature of the electric heater 30. It has been changed to decline.
Also in the exhaust gas purification apparatus according to the fourth embodiment, the same effect as in the second embodiment can be obtained.

In the first to fourth embodiments, when determining the unburned particulate matter from the difference between the reference change rate and the actually measured change rate, two slopes S ₀ and S ₂ between two different exhaust gas flow rates M ₁ and M ₂ are used. _{Although the} determination is made based on the difference from ₁ , the present invention is not limited to this. The determination may be made from the difference in the change rate of the differential pressure before and after the DPF device 13 at three or more exhaust gas flow rates.

  In the first to fourth embodiments, the fuel supply pump 6 and the negative pressure sensor 21 are used as the exhaust gas flow rate detection means. However, the present invention is not limited to these. The exhaust gas flow rate can be calculated using not only the intake negative pressure and the fuel injection amount but also the engine speed, the engine coolant temperature, and the like. Accordingly, in addition to the fuel supply pump 6 and the negative pressure sensor 21, an appropriate number of devices including a rotational speed sensor for detecting the rotational speed of the engine and a temperature sensor for measuring the engine coolant temperature are appropriately selected. A device may be selected.

  In the first to fourth embodiments, the reference DPF characteristics are stored in the memory 20a in the form of a map, but the present invention is not limited to this. The reference DPF characteristic may be stored in the memory 20a in the form of an equation. In this case, no map is needed.

1 is a configuration diagram of an exhaust purification apparatus according to Embodiment 1 of the present invention. 3 is a map representing a reference DPF characteristic incorporated in the ECU of the exhaust gas purification apparatus according to the first embodiment. 5 is a flowchart showing a procedure for adjusting the amount of fuel added in the exhaust emission control device according to the first embodiment. It is a map used when correct | amending exhaust gas flow volume with respect to exhaust gas temperature. It is a map for demonstrating the method of determining the difference of a reference | standard change rate and measured change rate. It is a map for demonstrating the method of determining the difference of a reference | standard change rate and measured change rate. FIG. 3 is a configuration diagram of an exhaust purification device according to a second embodiment. 6 is a flowchart showing a procedure for adjusting the heating condition of the electric heating means in the exhaust purification apparatus according to the second embodiment. 7 is a flowchart showing a procedure for adjusting the amount of fuel added in an exhaust purification apparatus according to Embodiment 3. 6 is a flowchart showing a procedure for adjusting heating conditions of an electric heating means in an exhaust purification apparatus according to a fourth embodiment.

Explanation of symbols

  6 Fuel supply pump (exhaust gas flow detection means), 10 Fuel addition nozzle (fuel addition means), 12 Oxidation catalyst, 13 DPF device, 17 Engine speed sensor (exhaust gas flow detection means), 20 ECU (control means, exhaust) Gas flow detection means), 21 negative pressure sensor (exhaust gas flow detection means), 23 temperature sensor (temperature detection means), 24 differential pressure sensor (differential pressure detection means), 30 electric heater (electric heating means).

Claims (5)

In an exhaust purification device that processes particulates in exhaust gas,
The exhaust purification device includes:
A DPF device for capturing the particulates;
Differential pressure detecting means for detecting a differential pressure before and after the DPF device;
Exhaust gas flow rate detecting means for detecting the flow rate of the exhaust gas;
Control means in which a reference DPF characteristic, which is a relationship between the differential pressure and the flow rate, is stored in the DPF device without deposits;
The control means compares the actual change rate of the differential pressure detected by the differential pressure detection means with respect to the flow rate detected by the exhaust gas flow rate detection means, and a reference change rate obtained from a reference DPF characteristic, and An exhaust emission control device, wherein when the difference between a change rate and the reference change rate is smaller than a predetermined value, it is determined that there is no unburned particulate matter in the DPF device. The actual change rate is a ratio of the difference between the two pressures detected by the differential pressure detection means to the difference between two different flow rates of the exhaust gas.
The reference change rate is a ratio of a difference between the differential pressures at the two flow rates obtained from the reference DPF characteristics to a difference between the two flow rates.
2. The exhaust emission control device according to claim 1, wherein when the difference between the two ratios is smaller than a predetermined value, the control unit determines that there is no unburned particulate matter in the DPF device. . The exhaust purification device further includes a temperature detection means for detecting the temperature of the exhaust gas flowing into the DPF device,
3. The exhaust gas purification apparatus according to claim 1, wherein the control unit corrects a detection value by the exhaust gas flow rate detection unit according to a temperature of the exhaust gas. The exhaust purification device includes:
A catalyst provided upstream of the DPF device;
Fuel addition means provided upstream of the catalyst,
The said control means adjusts the fuel addition amount injected from the said fuel addition means in the reproduction | regeneration of the said DPF apparatus next time based on the presence or absence of the unburnt of the said particulate matter in the said DPF apparatus. The exhaust emission control device according to any one of Items 1 to 3. The exhaust purification device includes an electric heating means for heating the DPF device,
The said control means adjusts the heating conditions of the said electric heating means in the reproduction | regeneration of the said DPF apparatus next time based on the presence or absence of the unburned residue of the said particulate matter in the said DPF apparatus. The exhaust emission control device according to any one of the above.

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