Pressure difference detecting device for particulate trapping filter

Abstract

A pressure difference detection device for a particulate filter includes: a low-pass filter that reduces the high-frequency components in the output signals of an upstream pressure sensor and a downstream pressure sensor, thereby reducing the pulse width; a pressure difference acquisition unit that acquires the difference between the output signal of the upstream pressure sensor after passing through the low-pass filter (i.e., the processed upstream pressure value) and the output signal of the downstream pressure sensor after passing through the low-pass filter (i.e., the processed downstream pressure value), i.e., the pressure difference before and after processing; an intake air volume correction unit that smooths the intake air volume to reflect the amount of response delay generated in the processed upstream and downstream pressure values ​​due to passing through the low-pass filter, thereby acquiring a corrected intake air volume; and an actual pressure difference acquisition unit that acquires the actual pressure difference between the upstream and downstream pressures of the particulate filter based on the correspondence between the pressure difference before and after processing and the corrected intake air volume.

Description

Technical Field

[0001] This invention relates to a pressure differential detection device for particulate trap filters. Background Technology

[0002] Previously, methods for detecting the pressure difference across a particulate filter installed in the exhaust passage of an internal combustion engine have been proposed (for example, see Patent Document 1). The pressure difference across the particulate filter is used to control the regeneration process of the particulate filter or to determine any abnormalities in the particulate filter itself. Therefore, it is necessary to be able to detect the pressure difference across the particulate filter as accurately as possible. Here, if the upstream and downstream pressures of the particulate filter are compared, a phase difference appears in their pressure waveforms due to the different detection locations. In Patent Document 1, to reduce the impact of this phase difference, the upstream or downstream pressure of the particulate filter is corrected based on engine speed or other information.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2023 / 233605 Summary of the Invention

[0006] However, particulate filters use expensive precious metals, and various anti-theft measures have been proposed. However, it is foreseeable that the vehicle may operate with the particulate filter removed, regardless of the presence or absence of such anti-theft measures. The phase difference of the pressure waveform in the particulate filter differs between the state with the particulate filter installed and the state with the particulate filter removed. Therefore, as proposed in Patent Document 1, even with phase difference correction, it is difficult to detect an accurate pressure difference between the states with and without the particulate filter installed.

[0007] Furthermore, exhaust pulses corresponding to the number of cylinders in the internal combustion engine appear in the exhaust pressure waveform. The period of the exhaust pulses varies depending on the engine speed. Therefore, the calculation period for the pressure difference across the particulate filter may coincide with the period of the exhaust pulses. When the calculation period for the pressure difference across the particulate filter coincides with the period of the exhaust pulses, aliasing sometimes occurs, causing the detected signal to be detected as a different value than the actual value. It is known that the effect of aliasing increases with the pulse width. When aliasing occurs, the pressure difference across the particulate filter changes visually, making it impossible to detect an accurate pressure difference value. In the solution of Patent Document 1, due to aliasing, accurate detection results may not be obtained.

[0008] Therefore, the problem with the pressure difference detection device for particulate filters disclosed in this specification is to perform pressure difference detection with high accuracy regardless of the state of the particulate filter.

[0009] The aforementioned problem is achieved through a pressure differential detection device for a particulate filter. This device includes: an upstream pressure sensor disposed upstream of a particulate filter located in an exhaust passage connected to an internal combustion engine, detecting the upstream pressure of the particulate filter; a downstream pressure sensor disposed downstream of the particulate filter, detecting the downstream pressure of the particulate filter; an air flow meter disposed in an intake passage connected to the internal combustion engine, detecting the intake air volume; a low-pass filter that reduces the pulse width by reducing high-frequency components in the output signals of the upstream and downstream pressure sensors, respectively; and a pre- and post-processed pressure differential acquisition unit that acquires the pre- and post-processed pressure differential value. The pressure difference before and after processing is the difference between the processed upstream pressure value (the output signal of the upstream pressure sensor after passing through the low-pass filter) and the processed downstream pressure value (the output signal of the downstream pressure sensor after passing through the low-pass filter). The intake air volume correction unit performs smoothing processing on the intake air volume detected by the airflow meter to obtain a corrected intake air volume, in a manner that tracks the rate of change of the pressure difference before and after processing, reflecting the amount of response delay generated in the pressure difference before and after processing due to the low-pass filter. The actual pressure difference acquisition unit acquires the actual pressure difference between the upstream and downstream pressures of the particulate filter based on the correspondence between the pressure difference before and after processing and the corrected intake air volume.

[0010] In the pressure difference detection device of the particulate trap filter with the above structure, the smoothing process can be implemented in such a way that the waveform representing the change in the amount of intake air is close to the waveform of the pressure difference value before and after the processing that caused the response delay.

[0011] In the pressure difference detection device of the particulate trap filter with the above structure, the intake air volume correction unit can be made to make the waveform representing the change in intake air volume consistent with the waveform of the pressure difference value before and after the processing, which has a response delay, through the smoothing process.

[0012] Furthermore, in the pressure difference detection device of the particulate trap filter with the above structure, the low-pass filter can be used to reduce the high-frequency components contained in the output signals of the upstream pressure sensor and the downstream pressure sensor respectively, thereby reducing the pulse width.

[0013] Furthermore, in the pressure difference detection device of the particulate trap filter with the above structure, the low-pass filter can be used to reduce the high-frequency components contained in the difference value between the output signal of the upstream pressure sensor and the output signal of the downstream pressure sensor, thereby reducing the pulse width.

[0014] The pressure difference detection device for particulate filters disclosed in this specification can detect pressure differences with high accuracy regardless of the state of the particulate filter. Attached Figure Description

[0015] Figure 1 (A) is a simplified structural diagram of the engine system of the pressure difference detection device of the particulate trap filter in the application implementation method. Figure 1 (B) is the functional block diagram of the ECU in the variant example.

[0016] Figure 2 (A) is an example of the raw pressure waveform, which is the unprocessed detected value of the upstream pressure of the particulate trap filter, and the waveform after passing through the LPF low-pass filter. Figure 2 (B) is an example of the raw pressure waveform, which is the unprocessed detected value of the downstream pressure of the particulate trap filter, and the waveform after passing through the LPF low-pass filter. Figure 2 (C) is an example of the raw pressure waveform of the pressure difference before and after the particulate trap filter calculated based on the unprocessed detection value, and the waveform after LPF processing through a low-pass filter.

[0017] Figure 3 This is a graph showing the relationship between the intake air volume Ga and the pressure difference across the particulate filter before LPF treatment, and the relationship between the intake air volume Ga and the pressure difference across the particulate filter after LPF treatment. Figure 3 (B) is an enlarged graph showing the relationship between the intake air volume Ga and the pressure difference before and after the LPF-treated particulate filter. Figure 3 (C) represents the relationship between the corrected intake air volume Ga after smoothing and the pressure difference before and after the LPF-treated particulate trap filter, and illustrates the threshold for anomaly detection.

[0018] Figure 4 (A) is an illustration of a model that reproduces the reaction delay generated by upstream and downstream pressures of a particulate trap filter through LPF treatment. Figure 4 (B) is an illustration of a model that smooths the intake air volume in response to the reaction delay caused by the upstream and downstream pressures of the particulate trap filter.

[0019] Figure 5 (A) is to reproduce Figure 4 The model of the reaction delay caused by upstream or downstream pressure in the particulate trap filter shown in (A), and the model of the reaction delay caused by upstream or downstream pressure in the particulate trap filter. Figure 4 The diagram (B) shows an overlay representation of the model with the air intake volume smoothed out. Figure 5 (B) indicates that in Figure 5 An example of an overlay graph showing the errors of the two models in (A).

[0020] Figure 6 This is an example of a flowchart for determining anomalies in a particulate filter based on the pressure difference detected by the pressure difference detection device of the particulate filter according to the embodiment. Detailed Implementation

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, in the drawings, the dimensions, ratios, etc., of various parts are sometimes not shown to be exactly the same as the actual dimensions, ratios, etc. In addition, detailed parts are sometimes omitted in the description based on the drawings.

[0022] (Implementation Method) First, refer to Figure 1 (A) Briefly describes the structure of the engine system 100 of the pressure differential detection device for the particulate filter in the application embodiment. 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 in the intake passage 12 and is introduced into the internal combustion engine 10. A mixture of air and fuel is formed in the combustion chamber of the internal combustion engine 10. Power is generated by burning the mixture. The exhaust gas produced by combustion is discharged through the exhaust passage 14.

[0023] The internal combustion engine 10 is a gasoline engine that uses gasoline as fuel. Alternatively, the internal combustion engine 10 can also be a diesel engine that uses light oil as fuel.

[0024] An air flow meter 20 and a throttle valve 22 are sequentially arranged from the upstream side in the intake passage 12. A catalyst 25, an upstream pressure sensor 27, a gas particulate filter (GPF) 26, and a downstream pressure sensor 28 are sequentially arranged from the upstream side in the exhaust passage 14.

[0025] Air flow meter 20 detects the airflow rate within intake passage 12. Throttle valve 22 regulates the airflow rate. When the opening of throttle valve 22 increases, the airflow rate increases. When the opening decreases, the amount of air drawn in decreases.

[0026] Catalyst 25 is, for example, a three-way catalytic converter. GPF 26 traps particulate matter in the exhaust gas. Furthermore, in the case where the internal combustion engine 10 is a diesel engine, a DPF (Diesel Particulate Filter) is installed instead of GPF 26. Upstream pressure sensor 27 detects the exhaust pressure upstream of GPF 26. Downstream pressure sensor 28 detects the exhaust pressure downstream of GPF 26.

[0027] ECU 30 functions as a pressure differential detection device. ECU 30 includes a CPU (Central Processing Unit) and other computing units, RAM (Random Access Memory) and ROM (Read-Only Memory) and other storage devices. ECU 30 performs various controls by executing programs stored in ROM or the storage devices. 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 upstream and downstream pressure differential value acquisition unit 35, an intake air volume correction unit 36, and an actual upstream and downstream pressure differential acquisition unit 37.

[0028] 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 the processed upstream pressure value, which is obtained by processing the upstream pressure detection value through a low-pass filter (LPF) 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 the processed downstream pressure value, which is obtained by processing the downstream pressure detection value through an LPF 34a. The pressure difference value acquisition unit 35 acquires the difference between the processed upstream pressure value and the processed downstream pressure value, i.e., the pressure difference value before and after processing. Additionally, as a variation, such as... Figure 1 As shown in (B), the differential pressure value acquisition unit 54 before and after processing can be used instead of the differential pressure value acquisition unit 35 before and after processing. Modifications will be explained later. In this embodiment, the cutoff frequency of LPF32a and 34a is set to 1Hz, but this is just one example; other frequencies are also possible.

[0029] The intake air volume correction unit 36 ​​performs smoothing processing on the actual intake air volume obtained by the airflow meter 20, corresponding to the amount of response delay generated in the processed upstream pressure value accompanying the processing based on LPF32a. Furthermore, smoothing processing can be performed in a manner corresponding to the amount of response delay generated in the processed downstream pressure value accompanying the processing based on LPF34a. The actual pressure difference acquisition unit 37 acquires the processed pressure difference value corresponding to the corrected intake air volume as the actual pressure difference value. The intake air volume correction unit 36 ​​can perform smoothing processing on the actual intake air volume obtained by the airflow meter 20, corresponding to the amount of response delay generated in the processed downstream pressure value accompanying the processing based on LPF34a. Furthermore, in this embodiment, the ECU 30 functions as LPF32a and 34a, but LPF32a and 34a can also be configured as a circuit combining resistors, capacitors, etc.

[0030] The pressure difference detection device of this embodiment includes an air flow meter 20, an upstream pressure sensor 27, a downstream pressure sensor 28, and an ECU 30.

[0031] <Pressure Differential Detection Principle and Detection Policy>

[0032] Next, refer to Figures 2 to 3 Section (C) explains the pressure detection principle and detection policy.

[0033] exist Figure 2 In (A), the unprocessed detection value of the upstream pressure of PDF26, i.e., the raw pressure waveform of the upstream pressure detection value, is plotted as a solid line. Additionally, in Figure 2 In (A), the waveform of the upstream pressure detection value after being processed by the LPF through a low-pass filter, i.e. the processed upstream pressure value, is depicted by dashed lines.

[0034] exist Figure 2 In (B), the unprocessed detected value of the downstream pressure of PDF26, i.e., the raw pressure waveform of the downstream pressure detected value, is plotted as a solid line. Additionally, in Figure 2 In (B), the waveform of the downstream pressure detection value after being processed by the low-pass filter LPF is depicted by dashed lines, i.e., the processed downstream pressure value.

[0035] exist Figure 2 In (C), the pressure difference between the upstream and downstream pressure detection values, i.e., the original pressure waveform of the pressure difference detection value, is depicted by a solid line. Additionally, in Figure 2 In (C), the waveform of the differential pressure detected before and after the LPF processing through the low-pass filter is depicted by dashed lines, i.e., the differential pressure before and after processing.

[0036] Reference Figure 2In (A), the pulse width in the original pressure waveform of the upstream pressure detection value is reduced in the processed upstream pressure value waveform. (Refer to...) Figure 2 In (B), the pulse width in the original pressure waveform is also reduced in the processed downstream pressure waveform. Furthermore, referring to... Figure 2 In (C), the pulse width in the original pressure waveform is also reduced in the waveform of the pressure difference before and after processing. In this way, by reducing the pulse width, the occurrence of aliasing can be suppressed.

[0037] Next, refer to Figure 3 Figure (A) shows the relationship between the intake air volume Ga and the pressure difference before and after the particulate trap filter before LPF treatment. Figure 3 In (A), the plotted distribution area before LPF treatment (the area shown in black) expands to a large range of the pressure difference before and after GPF. Furthermore, in the scatter plot area before LPF treatment, it was found that the pressure difference before and after GPF also increases with the increase of the intake air volume Ga. In contrast, the scatter plot area after LPF treatment (the area shown in gray) shows a smaller distribution range of the pressure difference before and after GPF compared to the scatter plot area before LPF treatment. This is consistent with... Figure 2 As shown in (C), the pulse width of the pressure difference before and after treatment is reduced. Thus, it can be confirmed that even if the pulse width of the pressure difference before and after treatment is reduced after LPF treatment, the pressure difference before and after GPF maintains the trend of increasing with the increase of the intake air volume Ga.

[0038] Next, refer to Figure 3 (B) shows, with magnification, the relationship between the intake air volume Ga and the pressure difference before and after the LPF-treated particulate filter. According to Figure 3 In (B), a deviation was observed in the distribution range of the pressure difference before and after the GPF. Specifically, scattered points deviating from the monotonically increasing banded region can be observed. This is generally considered to be caused by the LPF processing of the pressure difference before and after the GPF. That is, the upstream and downstream pressure values ​​used to obtain the processed pressure difference are delayed due to the LPF processing. In contrast, no processing is applied to the intake air volume Ga. This effect is generally considered to manifest as a deviation within the distribution range of the pressure difference before and after the GPF. Therefore, in this embodiment, a corrected intake air volume is obtained by applying a smoothing process to the actual intake air volume corresponding to the amount of response delay generated in the processed upstream and downstream pressure values.

[0039] Reference Figure 3 The distribution range of the pressure difference across the GPF (Ga) roughly converges within a monotonically increasing band-shaped region. Thus, by employing the corrected intake air volume, a suitable correspondence between the pressure difference across the GPF and the intake air volume Ga can be obtained. Based on... Figure 3 The relationship between the pressure difference before and after the GPF and the intake air volume Ga shown in (C) can be used to obtain the actual pressure difference value.

[0040] Here, we will refer to Figure 4 (A) to Figure 5 (B) describes an example of the smoothing process for the intake air volume according to this embodiment. In this embodiment, the response delay caused by GPF processing of the upstream and downstream pressure detection values ​​is reproduced by using model simulation. Then, the number of smoothing cycles for the intake air volume is set in a manner corresponding to this response delay.

[0041] Figure 4 (A) represents the model where the upstream pressure detection value is processed using LPF (Limited Pressure Filter), but the downstream pressure detection value can also be used instead of the upstream pressure detection value for LPF processing. Alternatively, the pressure difference obtained by subtracting the downstream pressure detection value from the upstream pressure detection value can also be used as the object of LPF processing. In the following explanation, LPF processing of the upstream pressure detection value will be described. Figure 4 (A) shows a model for obtaining a smooth waveform that provides information corresponding to the upstream pressure detection value in a stepped waveform and generates a response delay by performing LPF processing on this information. Here, the cutoff frequency of the LPF is set to 1 Hz. However, the cutoff frequency is not limited to 1 Hz and can be other frequencies. Figure 4 (B) indicates that it is related to Figure 4 Similarly, the stepped waveform given in (A) provides information corresponding to the intake air volume in a stepped waveform, and the state after multiple smoothing processes is applied to it. Figure 5 The (A) overlap shows Figure 4 The smooth waveform shown in (A) and Figure 4 The smooth waveform shown in (B). Figure 5 (B) shows the upstream pressure detection value after LPF processing, i.e., the error between the processed upstream pressure value and the intake air volume after smoothing. The number of smoothing operations on the intake air volume is set to minimize the absolute value of the error. By performing multiple smoothing operations, 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 representing the change in intake air volume gradually matches the waveform of the pressure difference value before and after processing, which caused a response delay. The set number of smoothing operations is stored in ECU30. The stored number of smoothing operations is used for pressure difference detection control performed by ECU30.

[0042] Furthermore, the smoothing process described here is just one example; various previously known smoothing methods can also be applied. Additionally, the number of smoothing iterations can be set based on calculations performed by the ECU30.

[0043] <Pressure Differential Detection and Control>

[0044] Next, refer to Figure 6 An example of pressure difference detection and control before and after GPF26 is illustrated.

[0045] In step S1, the upstream pressure detection value acquisition unit 31 acquires the upstream pressure detection value detected by the upstream pressure sensor 27. Additionally, the downstream pressure detection value acquisition unit 33 acquires the downstream pressure detection value detected by the downstream pressure sensor 28. Furthermore, 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.

[0046] In step S2, the upstream pressure value acquisition unit 32 passes the upstream pressure detection value through LPF 32a to obtain the processed upstream pressure value. Similarly, the downstream pressure value acquisition unit 34 passes the downstream pressure detection value through LPF 34a to obtain the processed downstream pressure value. After step S2, the process proceeds to step S3. The pulse widths of the processed upstream pressure value passing through LPF 32a and the processed downstream pressure value passing through LPF 34a are reduced, thus suppressing aliasing.

[0047] In step S3, the pressure difference acquisition unit 35 acquires the difference between the upstream pressure value and the downstream pressure value, i.e., the pressure difference before and after processing. After step S3, the processing proceeds to step S4.

[0048] In step S4, the intake air volume correction unit 36 ​​performs a predetermined number of smoothing processes on the actual intake air volume to obtain the corrected intake air volume. After step S4, the process proceeds to step S5. Alternatively, the process in step S4 can be performed simultaneously with steps S2 and S3 or before these processes. In short, the process up to step S4 can be completed before proceeding to step S5.

[0049] In step S5, the actual pressure difference acquisition unit 37 acquires the value corresponding to the corrected intake air volume acquired in step S4 from the processed pressure difference acquired in step S3, as the actual pressure difference value. This eliminates the inconsistency caused by response delay between the processed pressure difference and the corrected intake air volume. Therefore, an accurate actual pressure difference value can be obtained. Furthermore, the acquisition of the actual pressure difference value in step S5 can be performed when the actual intake air volume or the corrected intake air volume is above a predetermined value. This is because if the intake air volume increases, the actual pressure difference value increases accordingly, making it easier to obtain an accurate actual pressure difference value. That is, if the value is acquired in a region with a small actual pressure difference value, the proportion of error relative to the actual pressure difference value is considered to increase. Therefore, by acquiring the actual pressure difference value when the actual intake air volume or the corrected intake air volume is above a predetermined value, a more accurate actual pressure difference value can be obtained.

[0050] Through the processing up to step S5, the actual pressure difference between the upstream and downstream pressures of PDF26 can be obtained. In this embodiment, the ECU30 determines whether PDF26 is functioning correctly based on the obtained actual pressure difference. Therefore, in this embodiment, after step S5, the process proceeds to step S6.

[0051] In step S6, ECU 30 determines whether the acquired actual differential pressure value is above a preset threshold. The threshold is preset based on simulation or experimentation. If ECU 30 makes a positive determination (determined as "yes") in step S6, it proceeds to step S7. In step S7, ECU 30 performs a normal judgment on GPF26. This concludes the series of processes. On the other hand, if a negative determination (determined as "no") is made in step S6, it proceeds to step S8. In step S8, ECU 30 performs an abnormal judgment on GPF26. This concludes the series of processes. Furthermore, the acquired actual differential pressure value can also be used for other purposes, such as determining whether PDF26 regeneration is required.

[0052] (Modified Example) Next, a modified example will be described. In the modified example, ECU50 is used instead of ECU30. Figure 1 (B) shows a functional block diagram of ECU 50. ECU 50 functions as a differential pressure detection value acquisition unit 51. The 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. ECU 50 functions as a processed differential pressure value acquisition unit 54, an intake air volume correction unit 55, and an actual differential pressure value acquisition unit 56.

[0053] 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 front-to-back pressure difference detection value acquisition unit 51 acquires the difference between the upstream pressure detection value and the downstream pressure detection value, i.e., the front-to-back pressure difference detection value. The processed front-to-back pressure difference value acquisition unit 54 acquires the processed front-to-back pressure difference value obtained by processing the front-to-back pressure difference detection value through LPF 54a. The intake air volume correction unit 55 performs smoothing processing on the actual intake air volume acquired by the air flow meter 20, corresponding to the amount of response delay generated in the processed front-to-back pressure difference value accompanied by the LPF 54a processing. The actual front-to-back pressure difference acquisition unit 56 acquires the processed front-to-back pressure difference value corresponding to the corrected intake air volume as the actual pressure difference value.

[0054] In one implementation, the upstream and downstream pressure detection values ​​before obtaining the pressure difference of GPF26 are subjected to LPF processing, and then the difference between them is calculated to obtain the processed pressure difference value. In contrast, in a modified example, the difference between the upstream and downstream pressure detection values ​​(i.e., the pressure difference detection value) is calculated, and then LPF processing is performed on it to obtain the processed pressure difference value. Even in this method, pressure difference detection can be performed with high accuracy.

[0055] According to this embodiment, pressure difference detection is performed using the pressure difference value before and after processing with LPF. Since the pulse width of the pressure difference value before and after processing is reduced, aliasing can be suppressed. Furthermore, in this embodiment, the pressure difference detection uses a corrected intake air volume obtained by smoothing the amount of response delay generated in the value being processed due to the accompanying LPF-based processing. Therefore, pressure difference detection can be performed with high accuracy.

[0056] The above-described embodiments are merely examples for implementing the present invention, and the present invention is not limited thereto. Various modifications to these embodiments are within the scope of the present invention, and furthermore, various other embodiments can be implemented within the scope of the present invention, as is evident from the above description.

[0057] [Symbol Explanation]

[0058] 10…Internal combustion engine, 12…Intake passage, 14…Exhaust passage, 20…Air flow 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 pressure difference value acquisition unit, 36, 55…Intake air volume correction unit, 37, 56…Actual pressure difference acquisition unit.

Claims

1. A pressure differential detection device for a particulate filter, comprising: An upstream pressure sensor is configured on the upstream side of a particulate filter located in the exhaust passage connected to an internal combustion engine to detect the upstream pressure of the particulate filter. A downstream pressure sensor is configured on the downstream side of the particulate filter to detect the downstream pressure of the particulate filter; An air flow meter is configured in the intake passage connected to the internal combustion engine to detect the amount of air drawn in. A low-pass filter reduces the pulse width by decreasing the high-frequency components contained in the output signals of the upstream pressure sensor and the downstream pressure sensor, respectively. The unit that acquires the pressure difference value before and after processing acquires the pressure difference value before and after processing, which is the difference between the processed upstream pressure value as the output signal of the upstream pressure sensor after passing through the low-pass filter and the processed downstream pressure value as the output signal of the downstream pressure sensor after passing through the low-pass filter. The intake air volume correction unit performs smoothing processing on the intake air volume detected by the air flow meter to obtain the corrected intake air volume, in a manner that reflects the rate of change of the pressure difference before and after processing, by tracking the amount of response delay generated in the pressure difference before and after processing through the low-pass filter. as well as The actual pressure difference acquisition unit acquires the actual pressure difference between the upstream and downstream pressures of the particulate filter based on the correspondence between the pressure difference before and after processing and the corrected intake air volume.

2. The pressure difference detection device for the particulate trap filter as described in claim 1, wherein, The smoothing process is performed in such a way that the waveform representing the change in the amount of air drawn in is close to the waveform of the pressure difference before and after the processing, which produces the response delay.

3. The pressure difference detection device for the particulate trap filter as described in claim 2, wherein, The intake air volume correction unit uses the smoothing process to make the waveform representing the change in intake air volume consistent with the waveform of the pressure difference value before and after processing, which has generated a response delay.

4. The pressure differential detection device for the particulate trap filter as described in claim 1, wherein, The low-pass filter is input to the output signals of the upstream pressure sensor and the downstream pressure sensor, respectively, to reduce the high-frequency components contained in these output signals and reduce the pulse width.

5. The pressure differential detection device for the particulate trap filter as described in claim 1, wherein, The low-pass filter is input to the difference between the output signal of the upstream pressure sensor and the output signal of the downstream pressure sensor, reducing the high-frequency components contained in the difference and reducing the pulse width.

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