JP2011169235A - Method for controlling dpf regeneration - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling DPF regeneration precisely determining regeneration timing by performing a pretreatment for eliminating a difference in the amount of SOF causing a dispersion in differential pressure before determining differential pressure between the front and rear of a DPF. <P>SOLUTION: Time from completion of the DPF regeneration to the next DPF regeneration is counted, the inlet temperature of the DPF during the time is detected, and SOF time (t<SB>L1-n</SB>) when the inlet temperature of the DPF is lower than temperature (T<SB>SOF</SB>) produced in PM by the SOF after the completion of the DPF regeneration is integrated. When the differential pressure between the front and rear of the DPF is equal to or higher than an upper limit, pretreatment time (t) for keeping the temperature of the DPF at the SOF temperature (T<SB>SOF</SB>) or higher is determined according to SOF integration time (t<SB>L</SB>), and the SOF is oxidized and removed under a pretreatment condition. After an appropriate time, the differential pressure between the front and rear of the DPF with a ratio of soot increased is detected. When the differential pressure is equal to or higher than the upper limit, the soot in the DPF is oxidized and removed to thereby regenerate the DPF. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a DPF regeneration control method for accurately judging clogging of a DPF connected to an exhaust pipe of a vehicle and regenerating the DPF.

  PM (particulate matter; particulate matter) purification equipment discharged from a diesel engine connects a DPF (diesel particulate filter) to the exhaust pipe of the diesel engine, collects PM with the DPF, and collects exhaust gas. Purify and discharge to the atmosphere.

  Since the PM collected by this DPF causes clogging of the filter, it is necessary to periodically oxidize, remove and regenerate the collected PM.

  The detection of the clogging of the DPF is performed automatically or manually by the ECU (engine control unit) when the exhaust pressure sensor detects the differential pressure before and after the DPF and the differential pressure reaches the upper limit value. In this case, the DPF warning lamp provided in the cabin is turned on, and when the driver presses the regeneration execution switch, the regeneration of the DPF is started.

  In the regeneration, the exhaust temperature is raised to 600 ° C., and the PM collected in the DPF is burned with this high-temperature exhaust gas, removed and regenerated.

  In this regeneration, when the exhaust throttle valve on the exhaust side of the engine is open and the injection pattern is performing multi-injection of pre-injection and main injection, the exhaust throttle valve is closed and pre-injection and after-injection before and after the main injection. The exhaust gas temperature rises by performing multi-injection (pilot injection, pre-injection, main injection, after-injection) increased by adding, and then rises above the activation temperature (250 ° C.) of the oxidation catalyst in the DPF. By adding post injection to multi-injection (pilot injection, pre-injection, main injection, after-injection), the temperature of exhaust gas is raised to 600 ° C by catalytic combustion with an oxidation catalyst in the DPF, and PM is burned I am letting.

  In this regeneration operation, it is important to accurately determine when to regenerate the DPF.

  In the conventional technology, as shown in Patent Documents 1 to 4, the relationship between the differential pressure before and after the DPF and the PM deposition amount is grasped in advance, and the regeneration timing is appropriately determined by the differential pressure using a map or a model. I was going.

  However, PM deposited on the DPF has a problem that the deposition state differs depending on the ratio of SOF (organic solvent soluble component) and SOOT (soot) and the relationship between the differential pressure and the PM deposition amount is not always constant. For this reason, there is a scene where the reproduction time cannot be determined accurately.

Japanese Patent No. 39951619 Japanese Patent No. 4100388 Japanese Patent No. 4140640 Japanese Patent No. 4232556

  That is, FIG. 7 shows a surface SEM image of PM of samples A to C discharged from the vehicle and deposited on the DPF. FIG. 7A shows sample A with 50% SOF, and FIG. Sample B with SOF of 25%, FIG. 7C shows sample C with SOF of 5% or less.

  As can be seen from FIG. 7, in PM, the ratio of SOF and SOOT is not constant under the use conditions. When the ratio of SOF is large, the number of pores is small, and when the ratio of SOF is small, the number of pores is large. Thus, the difference in the amount of SOF appears as a large difference in the deposit form (denseness). This becomes a variation factor of the differential pressure determination.

  For this reason, in PM with a large amount of SOF, since the SOOT is small, the regeneration operation of the DPF is excessively performed. When the amount of SOF is small, the regeneration of the SOOT becomes insufficient and the regeneration operation cannot be performed accurately. There's a problem.

  Accordingly, an object of the present invention is to solve the above-mentioned problems and perform a pre-processing for removing the difference in the SOF amount that causes the differential pressure variation before determining the differential pressure before and after the DPF, thereby determining the regeneration timing. An object of the present invention is to provide a DPF regeneration control method that can be performed precisely.

In order to achieve the above object, according to the first aspect of the present invention, a DPF is connected to an exhaust pipe of an engine, PM in the exhaust gas is collected by the DPF, the exhaust gas is purified and exhausted, and accumulated in the DPF. In the DPF control method for detecting the differential pressure before and after the DPF due to the PM and the DPF is regenerated when the differential pressure exceeds the upper limit value, the time from the end of the DPF regeneration until the next DPF regeneration is counted. In the meantime, the DPF inlet temperature is detected, and the DPF inlet temperature is equal to or lower than the temperature (T _SOF ) at which SOF (organic solvent soluble component) is generated in PM after the completion of DPF regeneration (t _L1 to _n ) are integrated, and when the differential pressure before and after the DPF becomes equal to or higher than the upper limit, the SOF temperature of the DPF temperature (t _L ) in accordance with the SOF integration time (t _L ) to oxidize and remove the SOF in PM coercive in T _SOF) more The pretreatment time (t) is determined, and the SOF is oxidized and removed under the pretreatment conditions. Thereafter, the differential pressure before and after the DPF in which the ratio of SOOT is increased is detected, and the differential pressure exceeds the upper limit value. In some cases, the DPF regeneration control method is characterized in that the SOPF in the DPF is oxidized and removed to regenerate the DPF.

According to the second aspect of the present invention, the pretreatment time (t) is the PM deposition amount judgment value W _PM , the PM mass after SOF removal is W _SOF , the PM oxidation rate is V _SOF , and the SOF integration time ( t _L ), where the playback interval is t _o
t = (W _PM × W _SOF ) / V _SOF × t _L / t _o
Determined by
Furthermore, pre-processing conditions (PC) are
PC = T _SOF × t
The DPF regeneration control method according to claim 1, which is set in step (1).

The invention according to claim 3 is the DPF regeneration control method according to claim 1 or 2, wherein the pretreatment condition is that the exhaust gas having an SOF temperature (T _SOF ) of 250 to 300 ° C. is passed through the DPF for a pretreatment time (t). It is.

  According to the present invention, when determining the differential pressure before and after the DPF, first, when the differential pressure reaches the upper limit value, the pretreatment operation for removing the SOF is performed, and then substantially based on the differential pressure due to SOOT deposition. By judging the regeneration time, an excellent effect that an accurate regeneration operation can be performed is exhibited.

It is a figure which shows the flowchart of the reproduction | regeneration control method of DPF of this invention. In this invention, it is a figure which shows mass change when PM deposited on DPF is heated. In this invention, it is a figure which shows the oxidation rate when PM deposited on DPF is heated. In this invention, it is a figure which shows an example of a time-dependent change of the DPF inlet_port | entrance temperature between DPF regeneration intervals. It is a figure which shows the relationship between PM deposition amount of DPF and pressure loss in this invention and a prior art example. In this invention, it is a figure which shows the DPF system integrated in the diesel engine exhaust system. It is a figure which shows the SEM image of the surface of PM deposited on DPF.

  A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

  First, with reference to FIG. 6, the DPF system incorporated in the diesel engine exhaust system of the present invention will be described.

  In FIG. 6, an intake manifold 11 and an exhaust manifold 12 are connected to the diesel engine 10. An intake pipe 13 is connected to the intake manifold 11, and an intake throttle valve 14 is connected to the intake pipe 13.

  An exhaust pipe 15 is connected to the exhaust manifold 12, and an exhaust throttle valve 16, a DPF 18, and a silencer 19 are sequentially connected to the exhaust pipe 15. The exhaust throttle valve 16 is an electric pressure control switching valve 17 that adjusts the air pressure from the air tank 20 and its opening degree is controlled.

  The DPF 18 is configured such that an oxidation catalyst 22 is provided in the front stage in the DPF main body 21 whose diameter of the exhaust pipe 15 is expanded, and a catalytic ceramic filter 23 is provided in the rear stage. The oxidation catalyst 22 in the front stage is used for the HC in the exhaust gas. (Hydrocarbon) and CO are oxidized and a part of PM is oxidized, and PM is collected by the catalytic ceramic filter 23 at the subsequent stage.

  The DPF 18 is provided with exhaust temperature sensors 24 and 25 for detecting the exhaust gas temperature before and after the oxidation catalyst 22, and the exhaust pressure sensor 26 for detecting the differential pressure between the exhaust gases before and after the catalytic ceramic filter 23. These detected values are input to an ECU (engine control unit) 30.

  The ECU 30 receives the vehicle speed from the vehicle speed sensor 27, the engine speed and the engine coolant temperature from the various sensors 28, and the ECU 30 determines the fuel injection amount of the engine 10 based on these and various multi-injection patterns ( A fuel injection device (not shown) is controlled so as to inject fuel by appropriately selecting pilot injection, pre-injection, main injection, after-injection, and post-injection.

  Further, the ECU 30 controls the opening degree of the intake throttle valve 14 based on the differential pressure detected by the exhaust pressure sensor 26 and the detected values of the exhaust temperature sensors 24 and 25, and the opening degree signal to the electric pressure control switching valve 17. Is output to control the opening degree of the exhaust throttle valve 16 to adjust the amount of intake air supplied to the engine 10 and the amount of exhaust gas from the engine 10, and by controlling the exhaust gas temperature, the exhaust gas flowing into the DPF 18 is controlled. The DPF 18 can be continuously regenerated by increasing the gas temperature.

In the present invention, when the differential pressure detected by the exhaust pressure sensor 26 is equal to or greater than the upper limit (ΔP _limit ), the ECU 30 determines the amount of SOF in the PM accumulated in the DPF 18 over time at the DPF inlet temperature before the regeneration operation. Determine from change, perform pre-processing operation to remove SOF, remove SOF from PM, detect differential pressure before and after DPF with increased SOOT ratio, and whether the differential pressure is more than upper limit (ΔP _limit ) By determining whether or not, an appropriate regeneration time can be determined, and thus an accurate regeneration operation can be performed.

  The DPF regeneration control method of the present invention will be described in detail below.

  As described with reference to FIG. 7, the PM discharged from the vehicle does not have a constant ratio of SOF and SOOT under use conditions, and the difference in the amount of SOF appears as a large difference in deposition form (denseness). This becomes a variation factor of the differential pressure determination.

  Therefore, differential thermal analysis of sample A in FIG. 7A (SOF amount 50%), sample В in FIG. 7B (SOF amount 25%, sample C in FIG. 7C (SOF amount 5% or less)). The result of performing is shown in FIG.

  FIG. 2 shows changes in temperature and PM mass when samples A to C are subjected to thermal mass spectrometry using a differential thermal analyzer.

  When PM is heated to 250 to 300 ° C., the PM mass change is Sample A> Sample B> Sample C. However, when the temperature is 300 ° C. or higher, each sample A to C has the same mass change, and the mass change is up to 500 ° C. It turns out that it becomes the same mass change when it becomes 500 degreeC or more, and PM is lose | eliminated at 600 degreeC.

Therefore, from the results of FIG. 2, if the temperature at the time of W _{SOF in which} the samples A to C have the same mass change is T _SOF , the mass decrease up to T _SOF is the amount of moisture and the amount of SOF in the PM of each sample A to C. Shows the difference between the sums of In T _SOF above also be considered by drawing mass reduction certain curves in each PM, above T _SOF, i.e. composition in PM by heating the SOF elimination temperature became substantially uniform and (W _SOF) Can do.

The SOF removal temperature T _SOF is about 250 ° C. to 300 ° C., and W _SOF is 0.2 to 0.5, although there are some widths depending on the engine model.

  FIG. 3 shows the PM oxidation rate calculated from FIG.

From FIG. 3, the oxidation rate of SOF shows the maximum value (V _SOF ) at the SOF removal temperature T _SOF , and then the oxidation rate becomes slow, and the oxidation rate is increased by oxidation of SOOT above 500 ° C. Obtained.

  As described above, even if there is a variation in the amount of SOF in the PM deposited on the DPF, if the SOF in the PM is removed, the PM is made up of substantially SOOT with a small amount of SOF as in the sample C in FIG. It can be PM.

  Therefore, it is understood that the SOF can be efficiently removed by estimating the amount of SOF generated in the PM.

  FIG. 4 shows the change over time in the temperature of the DPF inlet when PM is collected by the exhaust temperature sensors 24 and 25 immediately after the DPF regeneration in the DPF system described in FIG.

The SOF generated in the exhaust gas is generated when the SOF removal temperature T _SOF or lower is reached, and it is considered that oxidation combustion occurs at the SOF removal temperature T _SOF or higher. _Therefore , the DPF inlet temperature becomes the SOF removal temperature T _SOF or lower. The time (t _{L1 to} t _Ln ) is integrated.

That is, the total time (t _L ) that is equal to or less than T _SOF in the DPF regeneration interval (time t ₀ ) in FIG.
t _L = t _L1 + t _L2 + t _L3 + t _L4 + t _L5 + t _L6
Thus, the time t _L in the regeneration interval time t ₀ represents the amount of SOF contained in the PM.

  Therefore, pretreatment conditions (PC) for removing SOF in PM in order to homogenize the composition of PM actually deposited on the DPF will be described.

When most of the PM deposited on the DPF is SOOT and reaches the upper limit value (ΔP _limit ) of the differential pressure, the judgment value of the PM deposition amount is W _PM , the PM mass after SOF removal is W _SOF , When the oxidation rate is V _SOF , the SOF integration time (t _L ), and the regeneration interval is t _o , the pretreatment time (t) is
t = (W _PM × W _SOF ) / V _SOF × t _L / t _o (1)
Determined by
The pre-processing conditions (PC) are
PC = T _SOF × t (2)
To decide.

The PM deposition amount determination value W _{PM in} Equation 1 is obtained in advance from the engine type and DPF type, and at the same time, the PM oxidation rate V _SOF is obtained based on the value when actually oxidized, These values are stored in the ECU 30 in FIG. Further, T _SOF can be appropriately determined by the ECU within a value of 250 to 300 ° C. obtained in the engine exhaust system.

In this way, the pretreatment condition (PC) considering the pretreatment time (t) and the SOF removal temperature T _SOF is determined, and the SPF removal temperature T of the exhaust gas actually flowing to the DPF in the DPF system described in FIG. By adjusting the _SOF , holding the preprocessing time (t), and preprocessing based on this, PM can be homogenized to the state of the sample C shown in FIG. After the treatment, when the upper limit value (ΔP _limit ) of the differential pressure is reached, the exhaust gas temperature is set to 600 ° C., so that an accurate regeneration treatment can be performed.

  FIG. 5 shows the relationship between the PM deposition amount and the pressure loss before and after the DPF. The line A shows the sample A of the SOF amount shown in FIG. 7A, and the line C shows the relationship shown in FIG. 7C. FIG. 5A shows the relationship between the PM deposition amount of the present invention and the pressure loss, and FIG. 5B shows the relationship between the conventional PM deposition amount and the pressure loss.

  As shown in FIG. 5A, the pressure loss when an appropriate amount of PM is deposited can be almost the same between the max of line A and the min of line C, whereas FIG. In the conventional example shown in FIG. 2, the pressure loss difference between the max of the line A and the min of the line C is large, and the SOF ratio increases in a state close to the line A.

  As described above, the present invention can be refined by adding the above-described pre-processing before performing the regeneration determination based on the differential pressure, which has a large variation in the conventional method.

  The regeneration control method of the present invention is programmed in the ECU 30 described with reference to FIG. 6, and the ECU 30 determines the regeneration timing based on the differential pressure detected by the exhaust pressure sensor 26 and the detected values of the exhaust temperature sensors 24 and 25. At the same time, playback control is executed.

  A flowchart of the regeneration control by the ECU 30 will be described with reference to FIG.

After the DPF regeneration operation is completed, the next DPF clogging determination 40 is started, and the measurement 41 of the DPF inlet temperature (T) and time (t) is performed. At this time, the time t is counted, and the count value (Σt ₀ ) is stored in the internal memory 42.

The temperature (T) is a step1, T> T whether _SOF is determined, T> if T _SOF, the time (t _L) between on which it is T> T _SOF, automatically be credited Is stored in the internal memory 43.

Then measure 44 of the differential pressure ([Delta] P) is performed, the differential pressure ([Delta] P) is obtained by the differential pressure measured in step2, it is determined whether [Delta] P _limit> [Delta] P, if [Delta] P _limit> [Delta] P, the DPF clogging determination 40 side In step 1, it is determined again whether or not the DPF temperature (T) is T> T _SOF . If T> T _SOF , the time (t _L ) is accumulated.

Next, when it is determined in step 2 that ΔP _limit ≦ ΔP, preprocessing (PC) 45 is performed. At this time, based on the accumulated time (t ₀ ) stored in the internal memories 42 and 43 and the accumulated time (t _L ) while T> T _SOF , the calculations described in the expressions 1 and 2 are performed. That is,
t = (W _PM × W _SOF ) / V _SOF × t _L / t _o (1)
PC = T _SOF × t (2)
Is calculated and the pretreatment 45 is performed to remove the SOF in the PM deposited on the DPF.

Next, the differential pressure is determined at step 3, and it is determined again whether ΔP _limit > ΔP.

When the SOF in the PM accumulated in the DPF is removed in the pre-processing 45, since SOF is removed, ΔP _limit > ΔP, and the process returns to the DPF clogging determination 40 side, and the determination of step 1 and step 2 is performed. If necessary, pre-processing is performed again.

When the SOF in the PM decreases and the amount of SOOT that accumulates in the DPF exceeds the differential pressure upper limit (ΔP _limit ) based on the SOOT amount (PM estimated value), it is determined in step 3 that ΔP _limit ≦ ΔP The actual DPF regeneration 46 is started. The determination in step 3 is based on the PM estimated value and pressure loss accumulated in the DPF described with reference to FIG. 5A, and ΔP _limit ≦ ΔP is the differential pressure ΔP of the PM having a large SOOT from which the SOF has been removed. Thus, the reproduction process can be accurately performed under the same conditions.

In the flow of FIG. 1, the upper limit value is set to be equal to ΔP _{limit in} the differential pressure determination of step 2 and step 3, but the upper limit value ΔP _{limit of step 2} is set to a value lower than the upper limit value ΔP _{limit of step 3} . May be.

Next, pre-processing (PC) 45 control by the ECU 30 is performed when the exhaust throttle valve 16 on the exhaust side of the engine 10 described with reference to FIG. 6 is opened and the injection pattern is subjected to multi-injection of pre-injection and main injection. In addition, exhaust gas temperature rises by closing the exhaust throttle valve 16 and performing multi-injection (pilot injection, pre-injection, main injection, after-injection) by adding pre-injection and after-injection before and after main injection. Then, the temperature is raised to the activation temperature (250 ° C.) or higher of the oxidation catalyst 22 in the DPF, and this is set as the SOF removal temperature T _SOF, and the SOF is removed by continuing the pretreatment PC time (= T _SOF × t).

  The DPF regeneration 46 closes the exhaust throttle valve 16 and performs multi-injection (pilot injection, pre-injection, main injection, after-injection, and post-injection), so that the exhaust gas is 600 by catalytic combustion by the oxidation catalyst 22 in the DPF 18. This is done by raising the temperature to 0 ° C. and oxidizing and burning PM. In this regeneration, the PM deposited on the catalyzed ceramic filter 23 is substantially SOOT, and the deposition amount is substantially constant, so that the regeneration time can be set accurately.

10 Engine 15 Exhaust pipe 18 DPF
45 Pretreatment (PC)
46 DPF regeneration

Claims (3)

DPF is connected to the exhaust pipe of the engine, PM in the exhaust gas is collected by the DPF, the exhaust gas is purified and exhausted, and the differential pressure before and after the DPF due to the PM accumulated in the DPF is detected. In the DPF control method for regenerating the DPF when the pressure exceeds the upper limit value, the time from the end of the DPF regeneration to the next DPF regeneration is counted, the inlet temperature of the DPF during that time is detected, and the DPF inlet The SOF time (t _L1 to _n ) where the temperature is equal to or lower than the temperature (T _SOF ) at which SOF (organic solvent soluble component) is generated in PM after the completion of DPF regeneration is integrated, and the differential pressure before and after the DPF When the value exceeds the upper limit, in order to oxidize and remove the SOF in the PM, the pretreatment time (t) for maintaining the DPF temperature at or above the SOF temperature (T _SOF ) is determined according to the SOF integration time (t _L ). And its pre-processing conditions SOF is oxidized and removed, and then the pressure difference before and after the DPF with a high SOOT ratio is detected. When the pressure difference exceeds the upper limit, the SOOT in the DPF is oxidized and removed to regenerate the DPF. A method for controlling regeneration of a DPF, comprising: The pretreatment time (t) is the PM deposition amount judgment value W _PM , the PM mass after SOF removal is W _SOF , the PM oxidation rate is V _SOF , the SOF integration time (t _L ), and the regeneration interval When t _o
t = (W _PM × W _SOF ) / V _SOF × t _L / t _o
Determined by
Furthermore, pre-processing conditions (PC) are
PC = T _SOF × t
The DPF regeneration control method according to claim 1, which is set in step (1). The DPF regeneration control method according to claim 1 or 2, wherein the pretreatment condition is performed by flowing an exhaust gas having an SOF temperature (T _SOF ) of 250 to 300 ° C through the DPF for a pretreatment time (t).

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