Pressure difference detection device for particulate matter collection filters

Abstract

To detect pressure differences with high accuracy, regardless of the condition of the particulate matter collection filter. [Solution] The pressure difference detection device includes a low-pass filter that reduces the pulsation width by reducing high-frequency components contained in the output signals of the upstream pressure sensor and the downstream pressure sensor; a processed differential pressure value acquisition unit that acquires a processed differential pressure value which is the difference between the processed upstream pressure value, which is the output signal of the upstream pressure sensor after passing through the low-pass filter, and the processed downstream pressure value, which is the output signal of the downstream pressure sensor after passing through the low-pass filter; an intake air volume correction unit that performs annealing on the intake air volume to acquire a corrected intake air volume so as to reflect the response delay that occurs in the processed upstream pressure value and the processed downstream pressure value after passing through the low-pass filter; and an actual differential pressure value acquisition unit that acquires the actual differential pressure value between the upstream pressure and the downstream pressure of the particulate matter collection filter based on the correspondence between the processed differential pressure value and the corrected intake air volume.

Description

Technical Field

[0001] The present invention relates to a pressure difference detection device for a particulate collection filter.

Background Art

[0002] Conventionally, there has been a proposal to detect the differential pressure before and after a particulate collection filter provided in an exhaust passage of an internal combustion engine (see, for example, Patent Document 1). The differential pressure before and after the particulate collection filter is used for controlling the regeneration process of the particulate collection filter or for determining an abnormality in the particulate collection filter itself. Therefore, it is required that the differential pressure before and after the particulate collection filter be detected as accurately as possible. Here, when comparing the upstream pressure and the downstream pressure of the particulate collection filter, a phase difference due to the difference in the detection position appears in the pressure waveforms of both. In Patent Document 1, in order to reduce the influence of this phase difference, the upstream pressure and the downstream pressure of the particulate collection filter are corrected based on the engine speed and other factors.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, expensive precious metals are used in particulate filters, and various theft prevention measures have been proposed. However, regardless of whether such theft prevention measures are in place, it is conceivable that vehicles will be operated with the particulate filters removed. The phase difference of the pressure waveform in the particulate filter differs between the state in which the particulate filter is installed and the state in which the particulate filter has been removed. Therefore, even if phase difference correction is performed as proposed in Patent Document 1, it is difficult to accurately detect the differential pressure across both the state in which the particulate filter is installed and the state in which the particulate filter has been removed.

[0005] Furthermore, exhaust pressure waveforms exhibit exhaust pulsations corresponding to the number of cylinders in the internal combustion engine. The period of these exhaust pulsations changes according to the engine speed. Therefore, the calculation period for the differential pressure across the particulate filter may coincide with the period of the exhaust pulsations. When the calculation period for the differential pressure across the particulate filter coincides with the period of the exhaust pulsations, an aliasing phenomenon may occur, where the detected signal is detected as a value different from the actual value. It is known that the effect of aliasing is greater when the pulsation amplitude is large. When aliasing occurs, the differential pressure across the particulate filter appears to change, making it impossible to detect the accurate differential pressure value. In the proposal of Patent Document 1, there is a possibility that accurate detection results cannot be obtained due to the aliasing phenomenon.

[0006] Therefore, the objective of the pressure difference detection device for particulate matter collection filters disclosed herein is to detect the pressure difference with high accuracy, regardless of the condition of the particulate matter collection filter. [Means for solving the problem]

[0007] The above problem is solved by an upstream pressure sensor located upstream of a particulate filter located in the exhaust passage connected to an internal combustion engine, which detects the upstream pressure of the particulate filter; a downstream pressure sensor located downstream of the particulate filter, which detects the downstream pressure of the particulate filter; an airflow meter located in the intake passage connected to the internal combustion engine, which detects the intake air volume; a low-pass filter that reduces the pulsation width by reducing the high-frequency components contained in the output signal of the upstream pressure sensor and the output signal of the downstream pressure sensor, respectively; a processed upstream pressure value which is the output signal of the upstream pressure sensor after passing through the low-pass filter; and the output of the low-pass filter This is achieved by a pressure difference detection device for a particulate collection filter, which comprises: a processed differential pressure value acquisition unit that acquires a processed differential pressure value that is the difference between the processed downstream pressure value, which is the output signal of the downstream pressure sensor after processing; an intake air volume correction unit that performs annealing on the intake air volume detected by the airflow meter to acquire a corrected intake air volume so as to reflect the response delay that occurs in the processed differential pressure value after passing through the low-pass filter and to follow the rate of change of the processed differential pressure value; and an actual differential pressure value acquisition unit that acquires the actual differential pressure value between the upstream pressure and the downstream pressure of the particulate collection filter based on the correspondence between the processed differential pressure value and the corrected intake air volume.

[0008] In the pressure difference detection device for the particulate collection filter with the above configuration, the annealing process can be carried out in such a manner that the waveform showing the change in intake air volume approaches the waveform of the differential pressure value before and after processing, which is experiencing a response delay.

[0009] In the pressure difference detection device for the particulate collection filter with the above configuration, the intake air volume correction unit can be configured such that the waveform showing the change in intake air volume is matched with the waveform of the processed differential pressure value before and after processing, which is experiencing a response delay.

[0010] Furthermore, in the pressure difference detection device for the particulate matter collection filter with the above configuration, the low-pass filter can be configured to receive the output signal from the upstream pressure sensor and the output signal from the downstream pressure sensor, respectively, and reduce the pulsation amplitude by reducing the high-frequency components contained in these output signals.

[0011] Furthermore, in the pressure difference detection device for the particulate matter collection filter with the above configuration, the low-pass filter can be configured to receive the difference between the output signal of the upstream pressure sensor and the output signal of the downstream pressure sensor, and reduce the pulsation amplitude by reducing the high-frequency components included in the difference. [Effects of the Invention]

[0012] The pressure difference detection device for particulate matter collection filters disclosed herein can detect the pressure difference with high accuracy regardless of the condition of the particulate matter collection filter. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1A is a schematic diagram of an engine system to which the pressure difference detection device of the particulate matter collection filter of the embodiment is applied. Figure 1B is a functional block diagram of the ECU in a modified example. [Figure 2] Figure 2A shows an example of the raw pressure waveform, which is the unprocessed detected value of the upstream pressure of the particulate matter collection filter, and the waveform after LPF processing by passing the signal through a low-pass filter. Figure 2B shows an example of the raw pressure waveform, which is the unprocessed detected value of the downstream pressure of the particulate matter collection filter, and the waveform after LPF processing by passing the signal through a low-pass filter. Figure 2C shows an example of the raw pressure waveform of the differential pressure across the particulate matter collection filter, calculated based on the unprocessed detected value, and the waveform after LPF processing by passing the signal through a low-pass filter. [Figure 3]Figure 3A is a graph showing the relationship between the intake air volume Ga and the differential pressure across the particulate filter before LPF treatment, and the relationship between the intake air volume Ga and the differential pressure across the particulate filter after LPF treatment. Figure 3B is a magnified graph showing the relationship between the intake air volume Ga and the differential pressure across the particulate filter after LPF treatment. Figure 3C is a graph showing the relationship between the corrected intake air volume Ga after annealing and the differential pressure across the particulate filter after LPF treatment, as well as illustrating the threshold for abnormality detection. [Figure 4] Figure 4A is an explanatory diagram of a model that reproduces the reaction delay that occurs in the upstream and downstream pressures of a particulate filter due to LPF treatment. Figure 4B is an explanatory diagram of a model in which annealing treatment is applied to the intake air volume in response to the reaction delay that occurs in the upstream and downstream pressures of a particulate filter. [Figure 5] Figure 5A is an explanatory diagram showing a model that reproduces the reaction delay occurring in the upstream or downstream pressure of the particulate matter collection filter shown in Figure 4A, and a model in which annealing treatment is applied to the intake air volume shown in Figure 4B, superimposed on each other. Figure 5B is an example of a graph showing the error between the two models superimposed in Figure 5A. [Figure 6] Figure 6 is an example of a flowchart for determining abnormalities in a particulate collection filter based on the pressure difference detected by the pressure difference detection device of the particulate collection filter in the embodiment. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the dimensions and proportions of each part in the drawings may not be shown to be exactly the same as those of the actual parts. Also, some details may be omitted in the drawings.

[0015] (Embodiment) First, referring to FIG. 1A, the schematic configuration of an engine system 100 to which a pressure difference detection device for a particulate collection filter according to an embodiment is applied will be described. The engine system 100 includes an internal combustion engine 10, an intake passage 12, an exhaust passage 14, and an ECU (Electronic Control Unit) 30. Air flows through the intake passage 12 and is introduced into the internal combustion engine 10. The air forms an air-fuel mixture in the combustion chamber of the internal combustion engine 10. Power is generated by the combustion of the air-fuel mixture. The exhaust gas generated by combustion flows through the exhaust passage 14 and is discharged.

[0016] The internal combustion engine 10 is a gasoline engine that uses gasoline as fuel. Note that the internal combustion engine 10 may be a diesel engine that uses light oil as fuel.

[0017] An air flow meter 20 and a throttle valve 22 are provided in the intake passage 12 in order from the upstream side. The exhaust passage 14 includes a catalyst 25, an upstream pressure sensor 27, a GPF (Gasoline Particulate Filter) 26 as a particulate collection filter, and a downstream pressure sensor 28 in order from the upstream side.

[0018] The air flow meter 20 detects the flow rate of the intake air in the intake passage 12. The throttle valve 22 adjusts the flow rate of the intake air. When the opening degree of the throttle valve 22 increases, the flow rate of the intake air increases. When the opening degree decreases, the intake air volume decreases.

[0019] The catalyst 25 is, for example, a three-way catalyst. The GPF 26 collects particulate matter in the exhaust gas. Note that when the internal combustion engine 10 is a diesel engine, a DPF (Diesel Particulate Filter) is installed instead of the GPF 26. The upstream pressure sensor 27 detects the pressure of the exhaust gas on the upstream side of the GPF 26. The downstream pressure sensor 28 detects the pressure of the exhaust gas on the downstream side of the GPF 26.

[0020] The ECU 30 functions as a pressure difference detection device. The ECU 30 includes an arithmetic unit such as a CPU (Central Processing Unit), and storage units such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The ECU 30 performs various controls by executing programs stored in the ROM or the storage unit. The ECU 30 functions as an upstream pressure detection value acquisition unit 31, a processed upstream pressure value acquisition unit 32, a downstream pressure detection value acquisition unit 33, a processed downstream pressure value acquisition unit 34, a processed differential pressure value acquisition unit 35, an intake air amount correction unit 36, and an actual differential pressure acquisition unit 37.

[0021] The upstream pressure detection value acquisition unit 31 acquires the upstream pressure detection value detected by the upstream pressure sensor 27. The processed upstream pressure value acquisition unit 32 acquires a processed upstream pressure value obtained by subjecting the upstream pressure detection value to a process of passing it through a low-pass filter (LPF: Low-Pass Filter) 32a. The downstream pressure detection value acquisition unit 33 acquires the downstream pressure detection value detected by the downstream pressure sensor 28. The processed downstream pressure value acquisition unit 34 acquires a processed downstream pressure value obtained by subjecting the downstream pressure detection value to a process of passing it through the LPF 34a. The processed differential pressure value acquisition unit 35 acquires a processed differential pressure value that is the difference between the processed upstream pressure value and the processed downstream pressure value. As a modification, as shown in FIG. 1B, a processed differential pressure value acquisition unit 54 can be employed instead of the processed differential pressure value acquisition unit 35. The modification will be described later. The cut-off frequencies of the LPFs 32a and 34a in the present embodiment are set to 1 Hz, but this is an example, and other frequencies may be used.

[0022] The intake air volume correction unit 36 ​​performs annealing on the actual intake air volume acquired by the airflow meter 20 to correspond to the response delay in the processed upstream pressure value resulting from processing by the LPF 32a. The annealing may also be performed to correspond to the response delay in the processed downstream pressure value resulting from processing by the LPF 34a. The actual differential pressure acquisition unit 37 acquires the corrected intake air volume and the processed differential pressure value corresponding to it as the actual differential pressure value. The intake air volume correction unit 36 ​​may also perform annealing on the actual intake air volume acquired by the airflow meter 20 to correspond to the response delay in the processed downstream pressure value resulting from processing by the LPF 34a. In this embodiment, the ECU 30 functions as LPF 32a and 34a, but LPF 32a and 34a may be configured as electrical circuits combining resistors, capacitors, etc.

[0023] The pressure difference detection device of this embodiment includes an airflow meter 20, an upstream pressure sensor 27, a downstream pressure sensor 28, and an ECU 30.

[0024] <Pressure difference detection principle and detection policy> Next, the pressure detection principle and detection strategy will be explained with reference to Figures 2 to 3C.

[0025] Figure 2A shows the raw, unprocessed upstream pressure waveform of PDF26, represented by a solid line. Figure 2A also shows the waveform of the processed upstream pressure after passing it through a low-pass filter (LPF), represented by a dotted line.

[0026] Figure 2B shows the raw, unprocessed downstream pressure waveform of PDF26, represented by a solid line. Figure 2B also shows the waveform of the processed downstream pressure after passing through a low-pass filter (LPF), represented by a dotted line.

[0027] Figure 2C shows the raw pressure waveform of the differential pressure between the upstream and downstream pressure detection values, i.e., the differential pressure detection value, as a solid line. Figure 2C also shows the waveform of the differential pressure detection value after LPF processing, i.e., the processed differential pressure value, as a dotted line.

[0028] Referring to Figure 2A, the waveform of the processed upstream pressure value shows a reduction in the pulsation amplitude compared to the raw pressure waveform of the upstream pressure detection value. Referring to Figure 2B, the waveform of the processed downstream pressure value also shows a similar reduction in the pulsation amplitude compared to the raw pressure waveform. Furthermore, referring to Figure 2C, the waveform of the processed differential pressure value also shows a similar reduction in the pulsation amplitude compared to the raw pressure waveform. By reducing the pulsation amplitude in this way, the occurrence of aliasing can be suppressed.

[0029] Next, referring to Figure 3A, the relationship between the intake air volume Ga and the differential pressure across the particulate filter before LPF treatment is shown. In Figure 3A, the plot distribution area labeled "before LPF treatment" (indicated in black) extends over a wide range of the differential pressure across the GPF. Furthermore, the plot distribution area before LPF treatment shows a tendency for the differential pressure across the GPF to increase with increasing intake air volume Ga. In contrast, the plot distribution area labeled "after LPF treatment" (indicated in gray) shows a narrower distribution range of the differential pressure across the GPF compared to the plot distribution area before LPF treatment. This is related to the reduction in the pulsation amplitude of the treated differential pressure value, as shown in Figure 2C. Thus, it can be confirmed that even when the pulsation amplitude of the treated differential pressure value after LPF treatment is reduced, the tendency for the differential pressure across the GPF to increase with increasing intake air volume Ga is maintained.

[0030] Next, referring to Figure 3B, the relationship between the intake air volume Ga and the differential pressure across the particulate matter collection filter after LPF treatment is shown in an enlarged view. According to Figure 3B, variability is observed in the distribution range of the differential pressure across the GPF. In other words, plots are seen that fall outside the upward-sloping band-shaped region. This is thought to be due to the fact that the differential pressure across the GPF has undergone LPF treatment. That is, the processed upstream pressure value and processed downstream pressure detection value used to obtain the processed differential pressure value are affected by the LPF treatment and experience a response delay. In contrast, the intake air volume Ga is not subjected to any treatment. This effect is thought to be reflected in the variability in the distribution range of the differential pressure across the GPF. Therefore, in this embodiment, a corrected intake air volume is obtained by applying an annealing process to the actual intake air volume to correspond to the response delay occurring in the processed upstream pressure value and processed downstream pressure detection value.

[0031] Referring to Figure 3C, the distribution range of the differential pressure across the GPF is generally within a band-shaped region that slopes upward to the right. Thus, by adopting the corrected intake air volume, an appropriate correspondence between the differential pressure across the GPF and the intake air volume Ga can be obtained. Based on the relationship between the differential pressure across the GPF and the intake air volume Ga shown in Figure 3C, the actual differential pressure value can be obtained.

[0032] Here, with reference to Figures 4A to 5B, an example of the annealing process for the intake air volume in this embodiment will be described. In this embodiment, the response delay caused by GPF processing of the upstream pressure detection value and the downstream pressure detection value is reproduced by simulation using a model. Then, the number of annealing iterations for the intake air volume is set to correspond to this response delay.

[0033] Figure 4A shows a model where LPF processing is applied to the upstream pressure detection value, but the downstream pressure detection value can also be used as the target of LPF processing instead of the upstream pressure detection value. Alternatively, the differential pressure value obtained by subtracting the downstream pressure detection value from the upstream pressure detection value may be used as the target of LPF processing. In the following explanation, we will assume that LPF processing is applied to the upstream pressure detection value. Figure 4A shows a model in which information corresponding to the upstream pressure detection value is provided as a step waveform, and an annealed waveform with a response delay is obtained by processing this with an LPF. Here, the cutoff frequency of the LPF is set to 1 Hz. Note that the cutoff frequency is not limited to 1 Hz and may be other frequencies. Figure 4B shows a state in which information corresponding to the intake air volume is provided as a step waveform, similar to the step waveform given in Figure 4A, and this is subjected to multiple annealing processes. Figure 5A shows the annealed waveforms shown in Figure 4A and Figure 4B superimposed. Figure 5B shows the error between the upstream pressure detection value after LPF processing, that is, the processed upstream pressure value and the intake air volume after annealing. The number of annealing cycles for the intake air volume is set to the number that minimizes the absolute value of the error. By performing annealing multiple times, the difference between the processed upstream pressure value and the processed intake air volume, i.e., the corrected intake air volume, is reduced. As a result, the waveform showing the change in intake air volume and the waveform of the processed differential pressure value, which is experiencing a response delay, gradually coincide. The set number of annealing cycles is stored in the ECU30. The stored number of annealing cycles is used in the pressure difference detection control performed by the ECU30.

[0034] The annealing process described here is merely an example, and various conventionally known methods may be used for annealing. Furthermore, the number of annealing cycles may be determined by calculations performed by the ECU30.

[0035] <Pressure difference detection and control> Next, with reference to Figure 6, an example of pressure difference detection control before and after the GPF26 will be described.

[0036] In step S1, the upstream pressure detection value acquisition unit 31 acquires the upstream pressure detection value detected by the upstream pressure sensor 27. The downstream pressure detection value acquisition unit 33 acquires the downstream pressure detection value detected by the downstream pressure sensor 28. The intake air volume correction unit 36 ​​acquires the actual intake air volume value obtained by the airflow meter 20. After step S1, the process proceeds to step S2.

[0037] In step S2, the processed upstream pressure value acquisition unit 32 passes the upstream pressure detection value through the LPF 32a to acquire the processed upstream pressure value. The processed downstream pressure value acquisition unit 34 passes the downstream pressure detection value through the LPF 34a to acquire the processed downstream pressure value. After step S2, the process proceeds to step S3. Since the processed upstream pressure value that has passed through the LPF 32a and the processed downstream pressure value that has passed through the LPF 34a have reduced pulsation amplitude, the occurrence of aliasing can be suppressed.

[0038] In step S3, the processed differential pressure value acquisition unit 35 acquires the processed differential pressure value, which is the difference between the processed upstream pressure value and the processed downstream pressure value. After step S3, the process proceeds to step S4.

[0039] In step S4, the intake air volume correction unit 36 ​​performs a preset annealing process on the actual intake air volume to obtain the corrected intake air volume. After step S4, the process proceeds to step S5. Note that the process in step S4 may be performed simultaneously with or before steps S2 and S3. In short, it is sufficient that the processes up to step S4 are completed before proceeding to step S5.

[0040] In step S5, the actual differential pressure acquisition unit 37 acquires the value corresponding to the corrected intake air volume acquired in step S4 from the processed differential pressure acquired in step S3 as the actual differential pressure value. The discrepancy due to response delay between the processed differential pressure and the corrected intake air volume has been eliminated. Therefore, an accurate actual differential pressure value can be obtained. Note that the acquisition of the actual differential pressure value in step S5 can be performed when the actual intake air volume or the corrected intake air volume is greater than or equal to a predetermined value. This is because as the intake air volume increases, the actual differential pressure value increases accordingly, making it easier to obtain an accurate actual differential pressure value. In other words, if one attempts to acquire it in a region where the actual differential pressure value is small, the proportion of error relative to the actual differential pressure value is likely to increase. Therefore, by acquiring the actual differential pressure value when the actual intake air volume or the corrected intake air volume is greater than or equal to a predetermined value, a more accurate actual differential pressure value can be obtained.

[0041] The processing up to step S5 allows the actual differential pressure value between the upstream and downstream pressures of the PDF26 to be obtained. In this embodiment, the ECU30 determines whether the PDF26 is normal or not based on the obtained actual differential pressure value. Therefore, in this embodiment, after step S5, the process proceeds to step S6.

[0042] In step S6, the ECU30 determines whether the acquired actual differential pressure value is equal to or greater than a preset threshold. The threshold is set in advance based on simulations or experiments. If the ECU30 makes a positive determination (Yes) in step S6, it proceeds to step S7. In step S7, the ECU30 determines that the GPF26 is normal. This completes the series of processes. On the other hand, if the ECU30 makes a negative determination (No) in step S6, it proceeds to step S8. In step S8, the ECU30 determines that the GPF26 is abnormal. This completes the series of processes. The acquired actual differential pressure value may also be used for other purposes, such as determining whether or not to process the PDF26.

[0043] (Modified Version) Next, a modified version will be described. In the modified version, ECU50 is used instead of ECU30. Figure 1B shows a functional block diagram of ECU50. ECU50 functions as a front-to-rear differential pressure detection value acquisition unit 51. The front-to-rear differential pressure detection value acquisition unit 51 includes an upstream pressure detection value acquisition unit 52 and a downstream pressure detection value acquisition unit 53. ECU50 functions as a processed front-to-rear differential pressure value acquisition unit 54, an intake air volume correction unit 55, and an actual front-to-rear differential pressure acquisition unit 56.

[0044] The upstream pressure detection value acquisition unit 52 acquires the upstream pressure detection value detected by the upstream pressure sensor 27. The downstream pressure detection value acquisition unit 53 acquires the downstream pressure detection value detected by the downstream pressure sensor 28. The upstream / downstream differential pressure detection value acquisition unit 51 acquires the upstream / downstream differential pressure detection value, which is the difference between the upstream pressure detection value and the downstream pressure detection value. The processed upstream / downstream differential pressure value acquisition unit 54 acquires the processed upstream / downstream differential pressure value, which is the upstream / downstream differential pressure detection value that has been processed to pass through the LPF 54a. The intake air volume correction unit 55 performs annealing processing on the actual intake air volume acquired by the airflow meter 20 to correspond to the response delay that occurred in the processed upstream / downstream differential pressure value due to processing by the LPF 54a. The actual upstream / downstream differential pressure acquisition unit 56 acquires the corrected intake air volume and the processed upstream / downstream differential pressure value corresponding to it as the actual differential pressure value.

[0045] In other words, in the embodiment, LPF processing was performed on both the upstream pressure detection value and the downstream pressure detection value before obtaining the differential pressure across the GPF26, and then the difference between these values ​​was calculated to obtain the processed differential pressure value across the GPF26. In contrast, in the modified example, the differential pressure detection value, which is the difference between the upstream pressure detection value and the downstream pressure detection value, is calculated, and then LPF processing is performed on this value to obtain the processed differential pressure value across the GPF26. Even with this configuration, the pressure difference can be detected with high accuracy.

[0046] [Effects] According to this embodiment, pressure difference detection is performed using the processed differential pressure value before and after processing by the LPF. Since the pulsation amplitude of the processed differential pressure value before and after processing is reduced, the occurrence of aliasing can be suppressed. Furthermore, in this embodiment, the corrected intake air volume, which has undergone annealing to correspond to the response delay that occurred in the value processed by the LPF, is used for pressure difference detection. Therefore, pressure difference detection can be performed with high accuracy.

[0047] The embodiments described above are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention, and it is obvious from the above description that various other embodiments are possible within the scope of the present invention. [Explanation of Symbols]

[0048] 10...Internal combustion engine, 12...Intake passage, 14...Exhaust passage, 20...Airflow meter, 22...Throttle valve, 25...Catalyst, 26...Particulate filter (GPF), 27...Upstream pressure sensor, 28...Downstream pressure sensor, 30...ECU, 31,52...Upstream pressure detection value acquisition unit, 32...Processed upstream pressure value acquisition unit, 32a,34a,54a...Low-pass filter (LPF), 33,53...Downstream pressure detection value acquisition unit, 34...Processed downstream pressure value acquisition unit, 35,54...Processed front-to-back differential pressure value acquisition unit, 36,55...Intake air volume correction unit, 37,56...Actual front-to-back differential pressure acquisition unit

Claims

1. An upstream pressure sensor is positioned upstream of a particulate filter located in the exhaust passage connected to an internal combustion engine, and detects the upstream pressure of the particulate filter. A downstream pressure sensor is positioned downstream of the particulate matter collection filter and detects the downstream pressure of the particulate matter collection filter, An airflow meter is placed in the intake passage connected to the internal combustion engine and detects the amount of intake air. A low-pass filter that reduces the pulsation amplitude by reducing the high-frequency components contained in the output signal of the upstream pressure sensor and the output signal of the downstream pressure sensor, respectively. A processed differential pressure value acquisition unit acquires a processed differential pressure value which is the difference between the processed upstream pressure value, which is the output signal of the upstream pressure sensor after passing through the low-pass filter, and the processed downstream pressure value, which is the output signal of the downstream pressure sensor after passing through the low-pass filter. An intake air volume correction unit performs annealing on the intake air volume detected by the airflow meter to obtain a corrected intake air volume, so that the response delay that occurs in the processed differential pressure value after passing it through the low-pass filter is reflected and the unit follows the rate of change of the processed differential pressure value. Based on the correspondence between the processed differential pressure values ​​and the corrected intake air volume, the actual differential pressure value acquisition unit acquires the actual differential pressure value between the upstream pressure and the downstream pressure of the particulate matter collection filter. A pressure difference detection device for a particulate matter collection filter equipped with the following features.

2. The annealing process is performed so that the waveform showing the change in intake air volume approaches the waveform of the processed differential pressure value where a response delay is occurring. A pressure difference detection device for a particulate matter collection filter according to claim 1.

3. The intake air volume correction unit, through the annealing process, matches the waveform showing the change in intake air volume with the waveform of the processed differential pressure value, which is experiencing a response delay. A pressure difference detection device for a particulate matter collection filter according to claim 2.

4. The aforementioned low-pass filter is The output signals from the upstream pressure sensor and the downstream pressure sensor are input, and the high-frequency components contained in these output signals are reduced to reduce the pulsation amplitude. A pressure difference detection device for a particulate matter collection filter according to claim 1.

5. The low-pass filter described above is The difference between the output signal of the upstream pressure sensor and the output signal of the downstream pressure sensor is input, and the high-frequency components included in the difference are reduced to reduce the pulsation amplitude. A pressure difference detection device for a particulate matter collection filter according to claim 1.

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