JP2006077761A - Pm deposition quantity estimation control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correctly grasp PM deposition quantity so as to realize regeneration of a DPF 1 at correct timing. <P>SOLUTION: This device for estimating PM deposition quantity of the DPF 1 provided in an exhaust passage 7 in a diesel engine 10 is provided with a differential pressure sensor 2 to detect differential pressure of exhaust gas pressure in the exhaust passage between the upstream and the downstream of the DPF 1, operation states detection means 12 and 14 to detect operation conditions of the diesel engine 10, a parameter detection means 13 to detect a parameter interlocked with exhaust gas flow of the DPF 1, a first estimation means 3 to compute PM deposition quantity based on the differential pressure, a second estimation means 3 to compute increase quantity of the PM deposition quantity in each specified period based on the operation conditions, and accumulate the increase quantity for computing the PM deposition quantity, and a control means to compute the PM deposition quantity by selectively applying the first estimation means 3 and the second estimation means 3 in accordance with the parameter, and apply the PM deposition quantity estimated by the first estimation means 3 to an initial value in starting accumulation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a diesel particulate filter (DPF) that collects particulates contained in exhaust gas from a diesel engine, and more particularly to a technique for estimating the amount of PM accumulated in the DPF.

  In order to trap the particulates contained in the exhaust gas of the diesel engine, the DPF provided in the exhaust passage of the diesel engine passes the exhaust gas through the porous filter material, so that the particulate is put on the wall surface of the hole of the filter material. Deposit.

  However, as the PM deposition amount increases, the DPF flow resistance increases and the particulate trap capacity of the DPF also decreases. Therefore, when the particulate deposition amount reaches a predetermined amount, the temperature of the exhaust gas is increased and the DPF is increased. The particulates accumulated inside are removed from the DPF by burning. This process is generally referred to as DPF regeneration.

  The particulate accumulation amount of the DPF can be detected from the differential pressure of the exhaust gas upstream and downstream of the DPF. However, the differential pressure changes depending on the flow rate of the exhaust gas passing through the DPF, and the detection accuracy of the differential pressure sensor that detects the differential pressure may also be affected by the change in the flow rate of the exhaust gas.

Patent Document 1 discloses a method of detecting the rate of change in exhaust gas flow rate and correcting the sensor output value based on this rate of change as a method of accurately estimating the accumulation amount from the differential pressure across the DPF. .
JP 2003-166411 A

  However, the differential pressure sensor that detects the differential pressure across the DPF has a characteristic that the error increases as the exhaust gas flow rate decreases. Prior art corrections that depend on the rate of change of the exhaust gas flow rate do not address the difference in the exhaust gas flow rate itself. Therefore, for example, even if the conventional technique is applied to a diesel engine for driving a vehicle, it is inevitable that a detection error of the differential pressure becomes large when the vehicle is traveling at a low vehicle speed.

  An increase in the differential pressure detection error decreases the accuracy of determining the regeneration timing of the DPF. As a result, when the regeneration frequency of the DPF increases, the fuel consumption of the diesel engine increases.

  In view of this, an object of the present invention is to accurately grasp the amount of DPF particulate accumulation and realize DPF regeneration at an appropriate timing.

  The particulate accumulation amount estimation control apparatus according to the present invention is an apparatus for estimating a particulate accumulation amount of a diesel particulate filter provided in an exhaust passage of a diesel engine, wherein the exhaust gas pressure in the exhaust passage upstream of the filter and the downstream of the filter. A differential pressure sensor for detecting a differential pressure with respect to the exhaust gas pressure in the exhaust passage, an operating state detecting means for detecting an operating condition of the diesel engine, and a parameter detecting means for detecting a parameter linked to the exhaust gas flow rate of the filter; A first estimating means for calculating the particulate deposition amount based on the differential pressure; and calculating an increase amount of the particulate deposition amount per fixed period based on the operating condition; Second estimating means for calculating the amount of curated deposition, the first estimating means and the second estimating means Is selectively applied in accordance with the parameter to calculate the particulate deposition amount, and when applying the second estimation unit, the particulate deposition amount estimated by the first estimation unit is cumulatively started. And a control means applied to the initial value.

  According to the present invention, for example, the first estimation unit is applied in an operation region where the detection accuracy of the differential pressure sensor is high, and the second estimation unit is applied in an operation region where the detection error of the differential pressure sensor is large, When switching from the first estimation means to the second estimation means, the particulate accumulation amount estimated by the first estimation means is used as the initial value of the cumulative start, so that the particulates with high accuracy can be obtained over a wide range of operation. It is possible to estimate the accumulation amount, and as a result, it is possible to prevent wasteful regeneration and reduce fuel consumption deterioration and the like.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic diagram of a system according to the first embodiment. The diesel engine 10 includes an exhaust passage 7. A DPF 1 is provided in the middle of the exhaust passage 7. The DPF 1 allows the exhaust gas in the exhaust passage 7 to pass through a porous filter material, thereby depositing particulates in the exhaust gas in the DPF 1. The exhaust gas from which the particulates have been removed is discharged from the DPF 1.

When the accumulated amount of particulates in the DPF 1 reaches a predetermined amount, the controller 3 (control means) outputs a regeneration signal to the regeneration device 9, and the regeneration device 9 raises the exhaust gas temperature of the diesel engine 1 to enter the DPF 1. In order to raise the exhaust gas temperature of the diesel engine 1 that burns the accumulated particulates, a method by fuel injection control such as retarding the fuel injection timing or performing post injection, or a method of heating the exhaust gas using a heating device Any known method may be applied. The regeneration device 9 is constituted by a fuel injection device when the former method is used, and is constituted by a heating device when the latter method is applied.

  The controller 3 includes a microcomputer including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a nonvolatile memory 20 and an input / output interface (I / O interface). It is also possible to configure the controller with a plurality of microcomputers.

  The controller 3 estimates the amount of particulates accumulated in the DPF 1 for outputting a reproduction signal (first and second estimation means). For this purpose, the controller 3 includes a differential pressure sensor 2 that detects a differential pressure ΔP upstream and downstream of the DPF 1, an upstream temperature sensor 4 that detects exhaust gas temperature upstream of the DPF 1, and a downstream that detects exhaust gas temperature downstream of the DPF 1. A temperature sensor 5, an air flow meter 11 that detects the intake air flow rate of the diesel engine 10, a rotation speed sensor 12 (operation state detection means, rotation speed detection means) that detects the rotation speed of the diesel engine 10, and a traveling speed of the vehicle. Detection data is input as signals from a vehicle speed sensor 13 (parameter detection means), a load sensor 14 (driving state detection means) that detects the load of the diesel engine 10, and an odometer 15 that detects the travel distance of the vehicle. Exhaust gas pressures upstream and downstream of the DPF 1 are respectively guided to the differential pressure sensor 2 through the pipe 6. The load of the diesel engine 10 can be represented by the depression amount of an accelerator pedal provided in the vehicle or the fuel injection amount Q of the diesel engine 10.

  The controller 3 estimates the particulate deposition amount of the DPF 1 using the above signals. The estimation is performed by selectively applying the following two estimation methods, the differential pressure method and the operation history method, according to the operation conditions of the diesel engine 1.

  The differential pressure method is a method for estimating the particulate deposition amount from the differential pressure ΔP upstream and downstream of the DPF 1. As shown in FIG. 8, the amount of particulates accumulated in the DPF 1 can be expressed by a function having the differential pressure ΔP upstream and downstream of the DPF 1 and the exhaust gas flow rate Qexh of the DPF 1 as parameters. When the exhaust gas flow rate Qexh is constant, the differential pressure ΔP increases as the particulate accumulation amount increases. Therefore, with respect to a plurality of different particulate accumulation amounts, the relationship between the exhaust gas flow rate Qexh and the differential pressure ΔP is defined in advance from the differential pressure ΔP and the exhaust gas flow rate Qexh using the characteristic map shown in FIG. The amount of curate deposition can be determined. This estimation method is called a differential pressure method.

  The exhaust gas flow rate Qexh is calculated from the intake air flow rate detected by the air flow meter 11, the exhaust temperature in the DPF 1, the differential pressure ΔP, and the fuel injection amount Q of the diesel engine 10. Since the calculation method of the exhaust gas flow rate Qexh using these parameters is known, the description thereof is omitted. The exhaust temperature in the DPF 1 is obtained as an average value of the detected temperatures of the upstream temperature sensor 4 and the upstream temperature sensor 5.

The operation history method is a method of calculating the accumulated amount of particulates by integrating the accumulated amount of particulates per time determined by the operating conditions of the diesel engine 10.
As operating conditions, the load of the diesel engine 1 and the rotational speed are applied. The particulate deposition amount of DPF1 per hour is calculated using a map of the characteristics shown in FIG. 9 that prescribes the relationship between these parameters and the particulate deposition amount of DPF1 per hour.

  Referring to FIG. 7, the error of the differential pressure sensor 2 that detects the differential pressure ΔP in the differential pressure method decreases as the exhaust gas flow rate Qexh increases. Therefore, when the vehicle is traveling at a low vehicle speed, the accuracy of estimating the particulate accumulation amount of the DPF 1 by the differential pressure method is low, which is lower than the driving history method.

  Further, although the detected temperatures of the upstream temperature sensor 4 and the upstream temperature sensor 5 are used for calculating the exhaust gas flow rate Qexh by the differential pressure method, the temperature sensor is generally low in responsiveness. Generally, fluctuations in the exhaust gas flow rate are accompanied by changes in the exhaust gas temperature. Since the exhaust gas flow rate Qexh uses the exhaust gas temperature as a parameter, a time lag occurs in the calculation result in a situation where the exhaust gas flow rate changes suddenly. As a result, in a situation where the exhaust gas flow rate changes abruptly, the estimation accuracy of the particulate deposition amount of the DPF 1 by the differential pressure method is lowered.

  Corresponding to these characteristics of the differential pressure method and the operation history method, the controller 3 selectively applies the estimation by the differential pressure method and the estimation by the operation history method to the estimation of the particulate accumulation amount of the DPF 1 according to the operation conditions. . Here, the differential pressure method can calculate the particulate deposition amount only from the data of the operating conditions at that time, but the operation history method adds the particulate deposition amount per hour to the past particulate deposition amount, thereby reducing the particulate deposition amount. calculate. Therefore, when switching from the differential pressure method to the operation history method, the operation history method is applied by adding the deposition amount per hour to the particulate deposition amount by the differential pressure method at the time of switching. When switching from the operation history method to the differential pressure method, the particulate deposition amount calculated by the differential pressure method is immediately applied instead of the particulate deposition amount calculated by the operation history method.

  Next, a particulate deposition amount estimation routine executed by the controller 3 for estimating the particulate deposition amount will be described with reference to FIG. The controller 3 executes this routine at intervals of 10 milliseconds during operation of the diesel engine 1.

  In step S1, the controller 3 determines whether or not the vehicle speed detected by the vehicle speed sensor 13 exceeds 40 kilometers per hour. As described above, the estimation of the particulate accumulation amount by the differential pressure method decreases as the vehicle speed decreases, and is lower than the estimation accuracy of the particulate accumulation amount by the driving history method at a vehicle speed lower than a certain vehicle speed. 40 km / h applied to step S1 represents an example of this boundary vehicle speed. Since the boundary vehicle speed depends on the characteristics of the differential pressure sensor 2 and the diesel engine 1, it is actually determined by experiments and simulations.

  If the determination in step S1 is affirmative, the controller 3 performs the process of step S2, and if negative, it executes steps S12 to S14 to calculate the particulate deposition amount by the operation history method.

  In step S2, the controller 3 determines whether or not the vehicle speed change rate ΔVSP is below the threshold value TS2. As described above, when the exhaust gas flow rate changes abruptly, the estimation accuracy of the particulate deposition amount of the DPF 1 by the differential pressure method decreases. Here, the exhaust gas flow rate changes linearly in response to changes in the vehicle speed. Therefore, when the differential pressure method and the operation history method are compared with respect to the estimation accuracy of the particulate accumulation amount, the change rate of the exhaust gas flow rate which becomes a boundary where the accuracy is reversed is represented by the change rate of the vehicle speed, and this is set as the threshold value TS2. Set. The change rate of the vehicle speed is used because the calculation is easier than the change rate of the exhaust gas flow rate. The specific value of the threshold value TS2 is determined by experiments or simulations. For example, it is 1 to 2 kilometers per hour per second.

  If the determination in step S2 is affirmative, the controller 3 performs the process of step S3. If the determination is negative, the controller 3 executes steps S12 to S14 to calculate the particulate deposition amount by the operation history method.

  In step S3, the controller 3 determines whether or not the vehicle speed VSP is equal to or lower than the set vehicle speed Vtc. The set vehicle speed Vtc is a vehicle speed stored in the nonvolatile memory 20 in step S9 described later. Here, the controller 3 reads and determines the set vehicle speed Vtc stored in the nonvolatile memory 20 at the previous execution of step S9.

  The controller 3 performs the process of step S4 when the determination of step S3 is affirmative, and performs the process of step S8 to S10 when negative, and calculates the particulate deposition amount by the differential pressure method.

  In step S4, the controller 3 determines whether or not the elapsed time from the set time Ttc to the current time T is less than the threshold value TS1. The set time Ttc is the time stored in the nonvolatile memory 20 in step S9 described later. Here, the controller 3 reads the set time Ttc stored in the non-volatile memory at the previous execution of step S9 and makes a determination. The threshold value TS1 means a time range in which the change in the particulate deposition amount does not show a substantial change. The threshold value TS1 is set to a few minutes.

  If the determination in step S4 is affirmative, the controller 3 executes steps S5 to S7 to calculate the particulate accumulation amount by the operation history method. If the determination in step S4 is negative, steps S8 to S10 are executed to calculate the particulate deposition amount by the differential pressure method.

  In step S5, the controller 3 refers to the characteristic map shown in FIG. 9 stored in advance in the ROM based on the fuel injection amount Q and the rotational speed N of the diesel engine 1, and calculates the particulate deposition amount ΔPM per unit time. Ask. By setting the unit time equal to the routine execution interval in advance, ΔPM becomes the particulate accumulation amount during the period from the previous routine execution to the current routine execution. The map is set so as to give a value slightly larger than the actual deposition amount per unit time in consideration of the error. If the particulate accumulation amount is estimated to be too small, the particulate deposition amount at the start of regeneration of the DPF 1 exceeds a predetermined amount that should be originally regenerated, and an excessive heat generation amount due to combustion of excessively accumulated particulates is a filter of the DPF 1. There is a possibility of damaging the material. Giving the map a slightly higher value helps to prevent these problems.

  In the next step S6, the controller 3 calculates an estimated value PMb of the particulate deposition amount by adding the particulate deposition amount ΔPM per unit time obtained in step S5 to the previous value PMbz stored in the nonvolatile memory 20. .

  In the next step S7, the controller 3 stores the estimated value PMb in the nonvolatile memory 20 as the previous value PMbz used in the next routine execution.

After the process of step S7, the controller 3 performs the process of step S11.
On the other hand, estimation of the particulate deposition amount by the differential pressure method in steps S8 to S10 is performed as follows.

  In step S8, the controller 3 obtains the exhaust gas flow rate Qexh of the DPF 1 from the differential pressure ΔP upstream and downstream of the DPF 1, the intake air flow rate, the exhaust temperature in the DPF 1, and the fuel injection amount Q of the diesel engine 10 as described above. calculate. Based on the differential pressure ΔP and the exhaust gas flow rate Qexh, an estimated value PMa of the particulate deposition amount is obtained with reference to the characteristic map shown in FIG. 8 stored in advance in the ROM. The map is set in advance so as to give a slightly larger value than the actual deposition amount.

  In the next step S9, the controller 3 stores the current vehicle speed VSP and the time T in the nonvolatile memory 20 as the set vehicle speed Vtc and the set time Ttc, respectively. Step S9 is executed only when the particulate deposition amount is estimated by the differential pressure method. Therefore, the set time Ttc means the time when the particulate deposition amount is estimated last by the differential pressure method. The above-described step S4 determines whether or not the elapsed time since the last estimation of the particulate deposition amount by the differential pressure method has reached the threshold value TS1, that is, whether or not the differential pressure method has just been applied. Is executed.

  In the next step S10, the controller 10 stores the estimated value PMa of the particulate accumulation amount in the nonvolatile memory 20 as the previous value PMbz used in the next routine execution. In addition, the estimated value PMa of the particulate accumulation amount itself is stored in the nonvolatile memory 20 because it may be used in the next routine execution.

  After the process of step S7 or step S10, the controller 3 sets the estimated value PMa of the particulate deposition amount obtained in step S8 to the output value PM of the particulate deposition amount in step S11. The meaning of the process in step S11 will be described in detail later. After step S11, the controller 3 ends the routine.

  The calculation process of the particulate accumulation amount by the operation history method of steps S12 to S14 is the same as the process of steps S5 to S7, and thus the description thereof is omitted.

  After the process of step S14, the controller 3 sets the particulate deposition amount estimated value PMb calculated in step S13 to the particulate deposition amount output value PM in step S15. After the process of step S15, the controller 3 ends the routine.

In this routine, the differential pressure method of steps S8 to S10 is applied to the estimation of the particulate accumulation amount when the vehicle speed exceeds 40 km / h and the vehicle speed change rate ΔVSP is smaller than the threshold value TS2. Even in that case, if the vehicle speed VSP falls below the set vehicle speed Vtc stored in the nonvolatile memory 20 before the elapsed time after applying the differential pressure method reaches the threshold value TS1, the operation is performed in steps S5 to S7. The amount of particulate deposition is calculated by the hysteresis method. In other words, when the vehicle speed VSP decreases during application of the differential pressure method, the estimated value PMa of the particulate deposition amount by the differential pressure method is not calculated until the duration time of the state reaches the threshold value TS1, instead of However, the particulate deposition amount estimated value PMb calculated by the operation history method is not output in steps S5 to S7, and the output value PM is not calculated. An estimated value PMa of the particulate accumulation amount stored in the nonvolatile memory 20 is set.

  That is, when the vehicle decelerates during the application of the differential pressure method, the estimated value PMa of the particulate accumulation amount estimated by the differential pressure method before the deceleration is output as it is until the time corresponding to the threshold value TS1 elapses. Output as PM. As described above, the estimated value PMa of the particulate deposition amount calculated by the differential pressure method is numerically set on the map so as to give a slightly larger value to the actual deposition amount. Therefore, if the deceleration is finished in a short time, even if the estimated PMa value of the particulate deposition amount before deceleration is output, a large error does not occur with the actual deposition amount.

  When the duration of the deceleration state exceeds the threshold value TS1, the calculation of the particulate deposition amount estimated value PMa by the differential pressure method in steps S8 to S10 is resumed, and the calculation result is set to the output value PM.

  In the period until the elapsed time after applying the differential pressure method reaches the threshold value TS1, the calculation result is not output in steps S5 and S6. The calculation is performed for the following reason.

  Steps S5 to S7 are performed only when the determination in step S4 is positive. In this case, the previous value PMbz in step S10 is not updated. In this state, if the determination in step S1 or S2 turns negative, thereafter, calculation of the particulates by the operation history method is performed in steps S12 to S14. As the previous value PMbz used in step S12 immediately after the switching, the value PMbz updated in step S7 immediately before is higher in accuracy than the value PMbz in step S10 in the update stop state. That is, in order to ensure the accuracy of the previous value PMbz as an initial value when the operation history method of steps S12 to S15 is applied, the calculation of the particulate deposition amount estimated value PMb of steps S5 and S6 and the calculation of step S7 are performed. The result is stored in the nonvolatile memory 20.

  The execution of steps S5 to S7 is limited to a short period until the duration of the deceleration state of the vehicle reaches the threshold value TS1. Therefore, steps S5 to S7 may be omitted, and if step S4 is positive, the process of step S11 may be performed immediately. In this case, when switching from the differential pressure method of steps S8 to S10 to the operation history method of steps S12 to S14, the previous value PMbz used for calculating the estimated PMb of the particulate accumulation amount in step S13 performed immediately after the switching is When the differential pressure method is applied, the value stored in the nonvolatile memory 20 in step S10 is used.

  With reference to FIGS. 3A and 3B, the change in the particulate deposition amount of the DPF 1 estimated by the above routine execution will be described.

  It is assumed that the diesel engine 1 is started at time t0 and the vehicle starts. Until the vehicle speed reaches 40 km / h, the particulate accumulation amount is estimated using the driving history method by executing steps S12 to S15. The previous value PMbz used first in step S13 at time t0 is a value stored in the nonvolatile memory 20 when the previous operation of the diesel engine 1 is stopped. Here, the previous value PMbz at time t0 is set to zero.

  If the vehicle speed exceeds 40 kilometers per hour, the determination in step S1 turns positive. Further, the vehicle speed change rate ΔVSP falls below the threshold value TS2 in step S2, and the vehicle speed VSP exceeds the set vehicle speed Vtc in step S3, so that the particulate deposition amount estimation method is switched at time t1. Specifically, the particulate deposition amount is estimated using the differential pressure method in steps S8 to S10 instead of steps S12 to S15.

  Since the differential pressure method is an estimation method that does not depend on the previous value PMbz, by switching, the estimated value of the particulate deposition amount changes stepwise from the deposition amount PMb1 by the operation history method to the deposition amount PMa1 by the differential pressure method.

  The particulate accumulation amount is estimated by the differential pressure method until time t2 when the vehicle speed falls below 40 kilometers per hour. As described above, since the map of the estimated value PMa of the particulate deposition amount used in the differential pressure method gives a slightly larger value than the actual value, the straight line connecting the estimated values PMa1 and PMb2 always slightly exceeds the actual deposition amount Y.

  After the vehicle speed falls below 40 kilometers per hour at time t2, the accumulation amount of particulates is estimated using the operation history method by executing steps S12 to S15 again. At time t2, the previous value PMbz applied in step S13 is the value set in step S10 of the differential pressure method that was completed immediately before. In the operation history method, the accumulation amount is integrated starting from the previous value PMbz. Therefore, when switching from the differential pressure method to the operation history method, a step does not occur in the estimated particulate accumulation amount.

  Thereafter, the particulate accumulation amount is estimated while switching between the driving history method and the differential pressure method according to the change in vehicle speed. In this way, the output value PM of the particulate accumulation amount reaches a predetermined amount at which regeneration is to be started at time t6, so that the controller 3 performs regeneration of the DPF 1 by executing another routine.

  3A and 3B do not show a process related to temporary deceleration of a vehicle to which the differential pressure method is applied. As described above, even if the vehicle decelerates during the application of the differential pressure method, the output value PM is maintained at the value PMa before deceleration until the deceleration duration reaches the threshold value TS1, while steps S5 to S7 are performed. As a result, the previous value PMbz is updated using the driving history method. Therefore, even if the vehicle speed frequently fluctuates during application of the differential pressure method, the output value PM changes stably, while the accuracy of the previous value PMbz used when switching to the driving history method is not impaired.

  The broken line in the figure shows the change in the amount of particulate deposition estimated using only the operation history method. The driving history method has a preferable estimation accuracy in the low vehicle speed range, but the estimation accuracy is lower than the differential pressure method at the high vehicle speed. Therefore, if the particulate accumulation amount is continuously estimated using the driving history method even after the vehicle speed exceeds 40 km / h, as shown by the broken line in the figure, the estimation error of the accumulation amount is accumulated, and the estimated accumulation amount Reaches a predetermined amount at which playback should be started at time t3. On the other hand, preferable estimation accuracy of the particulate accumulation amount can be realized by selectively applying the driving history method and the differential pressure method according to the vehicle speed.

  Next, a second embodiment of the present invention will be described with reference to FIG.

  The hardware configuration of the second embodiment is the same as that of the first embodiment, and differs from the first embodiment in that the routine of FIG. 4 is executed instead of the particulate deposition amount estimation routine of FIG. The execution conditions of this routine are the same as those in FIG. The difference between this routine and the routine of FIG. 2 relates to the switching conditions between the operation history method and the differential pressure method. Specifically, in this routine, step S22 is provided instead of step S2 of the routine of FIG. 2, step S23 is provided instead of step S3, and step S29 is provided instead of step S9. Other steps are the same as the routine of FIG.

  In step S22, the controller 3 determines whether or not the engine rotation speed change rate ΔN is lower than the threshold value TS3. The threshold value TS3 has the same meaning as the threshold value TS2 regarding the vehicle speed change rate ΔVSP. That is, when the differential pressure method and the operation history method are compared with respect to the estimated accuracy of the particulate accumulation amount, the change rate of the exhaust gas flow rate that becomes a boundary where the accuracy is reversed is a value expressed by the change rate ΔN of the engine rotation speed. A specific numerical value of the threshold value TS3 is determined by experiment or simulation.

  In step S23, it is determined whether or not the engine speed N is equal to or lower than the set speed Ntc.

  In step S29, the controller 3 stores the current engine speed N and time T in the nonvolatile memory 20 as the set vehicle speed Vtc and the set time Ttc, respectively.

  In this embodiment, as a parameter for switching between the driving history method and the differential pressure method, the engine speed change rate ΔN is used instead of the vehicle speed change rate ΔVSP used in the first embodiment. As described above, when the exhaust gas flow rate changes abruptly, the estimation accuracy of the differential pressure method is lowered, so that the operation history method is preferably applied. In this embodiment, this condition is determined by the engine speed change rate ΔN instead of the vehicle speed change rate ΔVSP.

  Also in this embodiment, the same operation as that of the first embodiment shown in FIGS. 3A and 3B can be obtained with respect to the estimation of the particulate accumulation amount of the DPF 1.

  Next, a third embodiment of the present invention will be described with reference to FIG.

  The hardware configuration of the third embodiment is the same as that of the first embodiment, and differs from the first embodiment in that the routine of FIG. 5 is executed instead of the particulate deposition amount estimation routine of FIG. The execution conditions of this routine are the same as those in FIG. The difference between this routine and the routine of FIG. 2 relates to processing when the operating condition changes to the application condition of the operation history method immediately after application of the differential pressure method. Specifically, in this routine, step S44 is provided instead of step S4 of the routine of FIG. 2, and step S49 is provided instead of step S9. Other steps are the same as the routine of FIG.

  In step S44, the controller 3 determines whether or not the difference between the current travel distance D of the vehicle detected by the odometer 15 and the set travel distance Dtc is less than the threshold value TS4. The difference between the current travel distance D and the set travel distance Dtc indicates the travel distance of the vehicle since the particulate deposition amount is finally estimated by the differential pressure method. In step S4 of the routine of FIG. 2, it is determined whether or not it is immediately after application of the differential pressure method based on the elapsed time since the particulate deposition amount was finally estimated by the differential pressure method. In this routine, the same determination is made based on the travel distance of the vehicle. The threshold value TS4 corresponds to the threshold value TS1 related to the elapsed time expressed by the travel distance of the vehicle.

  In step S8, the controller estimates the particulate accumulation amount PMa using the differential pressure method. In step S49, the controller sets the current vehicle speed VSP and the vehicle travel distance D as the set vehicle speed Vtc and the set travel distance Dtc in the nonvolatile memory 20, respectively. Store.

  Also in this embodiment, the same operation as that of the first embodiment shown in FIGS. 3A and 3B can be obtained with respect to the estimation of the particulate accumulation amount of the DPF 1.

  Next, a fourth embodiment of the present invention will be described with reference to FIG.

  This example relates to calculation of the particulate deposition amount by the differential pressure method performed in step S8 of each of the third to third embodiments. In this embodiment, the subroutine shown in FIG. 5 is executed in step S8.

  First, in step S31, it is determined whether or not the previous value PMbz of the particulate deposition amount stored in the nonvolatile memory 20 exceeds the threshold value TS5. The threshold value TS5 is set to a value slightly smaller than a predetermined amount set as a particulate deposition amount for the DPF 1 to start regeneration. Here, the threshold value TS5 is set to 90% of a predetermined amount for starting reproduction. The determination in step S31 has a meaning of determining whether or not the regeneration time of the DPF 1 is approaching.

  If the determination in step S31 is affirmative, in step S32, the controller 3 increases the gear ratio of the transmission provided in the vehicle. That is, a downshift is performed. By performing the downshift, the rotational speed of the diesel engine 1 increases and the exhaust gas flow rate increases.

  When the determination of step S31 is negative and after performing the process of step S32, the controller 3 estimates the particulate deposition amount by the differential pressure method in step S33 in the same process as step S8 of the first to third embodiments. To do.

  According to this embodiment, when the differential pressure method is applied, it is determined whether or not the regeneration time of the DPF 1 is close. If the regeneration time is approaching, the exhaust gas flow rate is increased by downshifting. Like the tactics, the differential pressure method exhibits a preferable estimation accuracy when the exhaust gas flow rate is large. Therefore, when the regeneration timing of the DPF 1 is approaching, by estimating the particulate deposition amount after increasing the exhaust gas flow rate, the estimation accuracy of the deposition amount can be increased and the regeneration timing can be correctly determined.

  This embodiment can be combined with any of the first to third embodiments.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

It is a schematic block diagram of the particulate deposition amount estimation apparatus of 1st Embodiment. 4 is a flowchart illustrating a particulate accumulation amount estimation routine executed by a controller in the first embodiment. (A), (B) is a timing chart explaining the change of the vehicle speed and the particulate accumulation amount estimated value by execution of the particulate accumulation amount estimation routine. It is a flowchart explaining the particulate deposition amount estimation routine which a controller performs in 2nd Embodiment. It is a flowchart explaining the particulate accumulation amount estimation routine which a controller performs in 3rd Embodiment. It is a flowchart explaining the particulate deposition amount estimation subroutine by the differential pressure method of 4th Embodiment. It is a figure showing the relationship between the detected value of a differential pressure sensor, and exhaust gas flow volume. It is a figure explaining the map characteristic of the particulate deposition amount which a differential pressure method uses. It is a figure explaining the map characteristic of the particulate deposition amount per unit time which an operation history method uses.

Explanation of symbols

1 Diesel particulate filter (DPF)
2 Differential pressure sensor 3 Controller 4 Upstream temperature sensor 5 Downstream temperature sensor 7 Exhaust passage 9 Regeneration device 10 Diesel engine 11 Air flow meter 12 Rotational speed sensor 13 Vehicle speed sensor 14 Load sensor 15 Odometer

Claims (16)

In an apparatus for estimating the particulate accumulation amount of a diesel particulate filter provided in an exhaust passage of a diesel engine,
A differential pressure sensor for detecting a differential pressure between an exhaust gas pressure in an exhaust passage upstream of the filter and an exhaust gas pressure in an exhaust passage downstream of the filter;
An operating state detecting means for detecting an operating condition of the diesel engine;
Parameter detecting means for detecting a parameter linked to the exhaust gas flow rate of the filter;
First estimating means for calculating a particulate deposition amount based on the differential pressure;
A second estimating means for calculating an increase amount of the particulate deposition amount per fixed period based on the operating condition, and calculating the particulate deposition amount by accumulating the increase amount;
When the first estimation unit and the second estimation unit are selectively applied according to the parameter to calculate the particulate deposition amount, and the second estimation unit is applied, the first estimation unit and the second estimation unit are applied. And a control unit that applies the particulate deposition amount estimated by the estimation unit to the initial value of the cumulative start.   2. The particulate accumulation amount estimation control according to claim 1, wherein the first estimation unit is applied when the parameter is larger than a predetermined value, and the second estimation unit is applied when the parameter is not larger than a predetermined value. apparatus.   The predetermined value is obtained when the estimation accuracy of the first estimation unit when the parameter is larger than the predetermined value exceeds the estimation accuracy of the second estimation unit, and the first value when the parameter is smaller than the predetermined value. The particulate accumulation amount estimation control device according to claim 2, wherein the estimation accuracy of the estimation means is set to be lower than the estimation accuracy of the second estimation means.   The particulate deposition amount estimation control device according to claim 2 or 3, wherein the parameter is a vehicle speed.   5. The patty according to claim 4, wherein the control means applies the second estimating means when the rate of change of the vehicle speed exceeds a predetermined threshold value, even when the vehicle speed is greater than the predetermined value. Curate deposition amount estimation control device. A rotation speed detecting means for detecting an engine rotation speed of the diesel engine;
The control means applies the second estimation means when the rate of change of the engine rotation speed exceeds a predetermined threshold value, even when the vehicle speed is larger than the predetermined value. Particulate deposition amount estimation control device according to claim 1.   The particulate deposition amount estimation control apparatus according to any one of claims 4 to 6, wherein the control unit further includes a nonvolatile memory that stores the estimated particulate deposition amount.   The particulate matter according to claim 7, wherein the control means outputs the value stored in the non-volatile memory as the particulate accumulation amount when the vehicle speed decreases within a predetermined time from the execution of the first estimating means. Accumulation control device.   The control means applies the second estimation means to estimate the second particulate accumulation amount when the vehicle speed falls within a predetermined time from the execution of the first estimation means, and the vehicle speed is predetermined. The particulate accumulation amount estimation control device according to claim 8, wherein when the value is less than the value, the increase amount by the second estimation means is integrated with the second particulate accumulation amount as an initial value.   The particulate matter according to claim 7, wherein the control means outputs the value stored in the non-volatile memory as the particulate deposition amount when the engine speed decreases within a predetermined time from the execution of the first estimating means. Curate deposition amount estimation control device.   The control means estimates the second particulate accumulation amount by applying the second estimation means when the engine speed decreases within a predetermined time from the execution of the first means, and the vehicle speed is The particulate deposition amount estimation control device according to claim 10, wherein when the value falls below the predetermined value, the amount of increase by the second estimation unit is integrated using the second particulate deposition amount as an initial value.   The particulate matter according to claim 7, wherein the control means outputs the value stored in the nonvolatile memory as the particulate deposition amount when the vehicle speed falls within a predetermined distance from the execution of the first estimating means. Accumulation control device.   When the vehicle speed falls within a predetermined distance from the execution of the first estimating means, the control means applies the second estimating means to estimate the second particulate accumulation amount, and the vehicle speed is predetermined. 13. The particulate accumulation amount estimation control device according to claim 12, wherein when the value is lower than the value, the increase amount by the second estimation means is integrated with the second particulate accumulation amount as an initial value.   The first estimation means estimates based on the differential pressure and the exhaust gas flow rate so that the exhaust gas flow rate decreases and the particulate deposition amount increases as the differential pressure increases. The particulate deposition amount estimation control apparatus according to any one of 13.   The operating state detecting means comprises means for detecting the engine load and means for detecting the engine speed, and the second estimating means is configured to determine the engine based on the engine load and the engine speed. The particulate accumulation amount is estimated by estimating the increase amount so as to increase as the engine rotation speed increases and integrating the estimated increase amount. The particulate accumulation amount estimation control apparatus according to one.   The diesel engine is an engine that drives a vehicle via a transmission, and the control means determines whether or not the particulate accumulation amount of the nonvolatile memory exceeds a predetermined accumulation amount prior to execution of the first estimation means. The particulate matter accumulation amount estimation control according to any one of claims 1 to 15, wherein the transmission is downshifted when the particulate matter accumulation amount of the nonvolatile memory exceeds a predetermined accumulation amount. apparatus.

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