Differential pressure detection method and device for particulate filter

Abstract

A particulate filter (15) is provided in an exhaust passage (14) of an internal combustion engine (1). An upstream-side pressure sensor (16A) for detecting the upstream-side pressure (Pin) of the particulate filter (15) and a downstream-side pressure sensor (16B) for detecting the downstream-side pressure (Pout) are provided, and control of regeneration processing is performed on the basis of the difference between the upstream-side pressure sensor (16A) and the downstream-side pressure sensor (16B). In order to reduce the phase difference between pressure waveforms based on both exhaust pulsation, a phase correction time ([delta] t) is obtained on the basis of an engine rotational speed (Ne), and a pressure detection value before the phase correction time ([delta] t) is set as a corrected upstream pressure (Pinh) with respect to an upstream pressure (Pin) (S3, S4). The vertical pressure difference (DP) is calculated using the corrected upstream pressure (Pinh) and the corrected downstream pressure (Pout) (S6).

Description

Technical Field

[0001] The present invention relates to a detection method and device for detecting the upper and lower pressure differences of a particulate filter (GPF or DPF) provided in an exhaust passage of an internal combustion engine. Background Art

[0002] In order to remove particulates contained in exhaust gas, a particulate filter is sometimes used for both gasoline internal combustion engines and diesel internal combustion engines. Patent document 1 discloses the following scheme:

[0003] That is, in order to control the regeneration process for the clogging of the particulate filter provided in the exhaust passage and to estimate the defect of the particulate filter, the upper and lower pressure differences of the particulate filter are detected by using a pressure difference sensor. In addition, a method is disclosed in which a pressure difference average value error caused by the pressure pulsation of the exhaust gas is corrected by using a correction value defined in a map of the engine required torque and the engine speed.

[0004] However, Patent Document 1 does not consider the phase difference between the pressure waveform of the upstream side pressure of the particulate filter and the pressure waveform of the downstream side pressure. That is, the upstream side pressure and the downstream side pressure both change in response to the exhaust pulsation, but the phases of the two are not necessarily consistent. For example, if the length of the passage from the upstream side pressure outlet to the differential pressure sensor of the exhaust passage with the particulate filter is different from the length of the passage from the downstream side pressure outlet to the differential pressure sensor, a large phase difference may occur between the pressure waveforms (for example, refer to Figure 3 ). As a result, a pressure difference is generated between the upstream pressure and the downstream pressure due to the phase difference. Figure 3 It is clearly shown that, microscopically, the positive and negative of the upper and lower pressure differences are reversed and vary greatly, which becomes a factor in reducing the measurement accuracy of the upper and lower pressure differences.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2002-371827 Summary of the invention

[0006] The present invention relates to a method for detecting a pressure difference of a particulate filter, wherein an upstream pressure sensor and a downstream pressure sensor are used to detect the pressure on the upstream side and the pressure on the downstream side of a particulate filter arranged in an exhaust passage of an internal combustion engine, respectively, and the upper and lower pressure differences of the particulate filter are calculated, wherein:

[0007] At least one of the pressure detection values ​​is corrected so that the phase difference between the pressure waveform detected by the upstream pressure sensor and the pressure waveform detected by the downstream pressure sensor is reduced, and the upper and lower pressure differences are calculated using the corrected pressure value.

[0008] By performing the correction corresponding to the phase difference in this way, the component of the upper and lower pressure difference based on the phase difference is removed or suppressed. Therefore, even if the passage length of the piping for the upstream pressure sensor is different from the passage length of the piping for the downstream pressure sensor, the upper and lower pressure difference of the particulate filter can be obtained with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a diagram for explaining the structure of an internal combustion engine equipped with a particulate filter according to an embodiment.

[0010] Figure 2 1 is a flowchart showing a process flow for calculating the upper and lower pressure differences according to one embodiment.

[0011] Figure 3 1 is a characteristic diagram showing pressure waveforms on the upstream side and the downstream side of a reference example in which the phase difference correction is not performed.

[0012] Figure 4 1 is a characteristic diagram showing pressure waveforms on the upstream side and the downstream side in an embodiment in which the phase difference is corrected. DETAILED DESCRIPTION

[0013] Hereinafter, one embodiment of the present invention will be described in detail based on the drawings. Figure 1 1 is an explanatory diagram showing a schematic structure of an internal combustion engine 1 to which an embodiment of the present invention is applied. The internal combustion engine 1 of one embodiment is a spark ignition type internal combustion engine (so-called gasoline internal combustion engine) of a four-stroke cycle, and has an intake valve 2 and an exhaust valve 3, and a spark plug 4 in each cylinder. In addition, the illustrated example is configured as a direct-injection type internal combustion engine, and a fuel injection valve 5 that injects fuel into the cylinder is, for example, arranged on the side of the intake valve 2. In addition, a port injection type structure that injects fuel into the intake port 6 may also be used.

[0014] An electronically controlled throttle valve 10 is installed on the upstream side of a manifold portion 8 of an intake passage 7 connected to an intake port 6 of each cylinder, the opening of which is controlled by a control signal from an engine controller 9. An air flow meter 11 for detecting the amount of intake air is arranged on the upstream side of the throttle valve 10, and an air filter 12 is arranged further upstream.

[0015] The exhaust ports 13 of the cylinders are combined into an exhaust passage 14, and a particulate filter (so-called gasoline particulate filter: GPF) 15 for collecting exhaust particulates is provided in the exhaust passage 14. The particulate filter 15 is composed of, for example, a so-called sealed-pore ceramic filter in which one end of a plurality of fine passages formed in a monolithic ceramic body is alternately sealed, and a three-way catalyst is coated on the surface.

[0016] An air-fuel ratio sensor 19 for detecting the exhaust air-fuel ratio is disposed at a position upstream of the particulate filter 15 in the exhaust passage 14. In addition, another three-way catalyst device may be provided in series with the particulate filter 15.

[0017] The particulate filter 15 has a pressure sensor unit 16 which is composed of an upstream pressure sensor 16A and a downstream pressure sensor 16B in order to detect the upper and lower pressure difference of the particulate filter 15. The upstream pressure sensor 16A and the downstream pressure sensor 16B are composed of, for example, semiconductor pressure sensors of appropriate types, and basically the same pressure sensors are used. The upstream pressure sensor 16A is connected to an upstream sensor pipe 17 branched from the upstream side (inlet side) of the particulate filter 15 in the exhaust passage 14, and the exhaust pressure on the upstream side of the particulate filter 15 is guided through the upstream sensor pipe 17. The downstream pressure sensor 16B is connected to a downstream sensor pipe 18 branched from the downstream side (outlet side) of the particulate filter 15 in the exhaust passage 14, and the exhaust pressure on the downstream side of the particulate filter 15 is guided through the downstream sensor pipe 18. Here, in one embodiment, the passage length of the upstream sensor piping 17 and the passage length of the downstream sensor piping 18 are different from each other according to the relationship of the installation position of the pressure sensor unit 16. For example, the passage length of the upstream sensor piping 17 is relatively short. As described later, due to the difference in the passage length, a phase difference occurs between the pressure waveform detected by the upstream pressure sensor 16A and the pressure waveform detected by the downstream pressure sensor 16B.

[0018] The detection signals of the upstream pressure sensor 16A and the downstream pressure sensor 16B are input to the engine controller 9. In addition to the detection signals of the air flow meter 11 and the air-fuel ratio sensor 19, the engine controller 9 also receives detection signals of a plurality of sensors such as a crank angle sensor 21 for detecting the rotation speed of the internal combustion engine, a water temperature sensor 22 for detecting the temperature of the cooling water, and an accelerator opening sensor 23 for detecting the amount of depression of the accelerator pedal. The engine controller 9 controls the fuel injection amount and injection timing of the fuel injection valve 5, the ignition timing of the spark plug 4, and the opening of the throttle valve 10 to be optimal based on the above input signals.

[0019] The engine controller 9 obtains the upper and lower pressure differences of the particulate filter 15 based on the pressure detections of the upstream pressure sensor 16A and the downstream pressure sensor 16B, and controls the regeneration process for the clogging of the particulate filter 15 and estimates the defect of the particulate filter 15 based on the upper and lower pressure differences.

[0020] That is, if the particulates are excessively accumulated, the ventilation resistance increases, and the particulate filter 15 needs to be forcibly regenerated by, for example, temporarily raising the exhaust temperature. The increase in the ventilation resistance is detected as an increase in the upper and lower pressure difference of the particulate filter 15. In addition, if the filter made of ceramics is damaged by impact or the like, the exhaust particulate collection performance is reduced, but if such a defect occurs, the ventilation resistance is greatly reduced. The reduction in the ventilation resistance is detected as a reduction in the upper and lower pressure difference of the particulate filter 15.

[0021] Figure 3 The pressure waveforms of the upstream pressure Pin detected by the upstream pressure sensor 16A and the downstream pressure Pout detected by the downstream pressure sensor 16B are shown. The horizontal axis represents the crank angle or time. The exhaust valve 3 is opened and closed in each cycle, and as a result, exhaust pulsation of a period or frequency corresponding to the number of cylinders and the rotation speed of the internal combustion engine is generated in the exhaust passage 14. The exhaust pulsation appears in both the upstream pressure Pin and the downstream pressure Pout, but as mentioned above, the passage length of the upstream sensor piping 17 is shorter than the passage length of the downstream sensor piping 18, so a phase difference is generated in such a way that the pressure waveform of the upstream pressure Pin is relatively advanced. If such a phase difference exists, a large upper and lower pressure difference is generated based on the phase difference, and the accuracy of the estimation of the hole blockage state based on the ventilation resistance and the estimation of the filter defect is reduced.

[0022] In the present embodiment, calculation of the upper and lower pressure differences using the upstream pressure Pin and the downstream pressure Pout is performed after the phase difference is corrected in advance. Figure 2 This is a flowchart showing the flow of processing for calculating the upper and lower pressure differences executed in the engine controller 9. This processing is repeatedly executed at each predetermined calculation cycle.

[0023] In the first step 1, the pressure detection value Pin of the upstream pressure sensor 16A at that time is read. The reading of the pressure detection value Pin is repeated in each calculation cycle, so as a result, Figure 3 The time series data shown as the pressure waveform Pin in FIG.

[0024] In the next step 2, the rotation speed Ne of the internal combustion engine 1 is read. Then, in step 3, the phase correction time Δt corresponding to the phase difference is calculated based on the rotation speed Ne using a predetermined table or a predetermined relational expression. The phase correction time Δt has the following characteristics: it is longest when the rotation speed Ne is the idle rotation speed, and shortens as the rotation speed Ne increases.

[0025] Next, in step 4, the corrected upstream pressure Pinh is obtained. Specifically, Figure 3From the time series data of the upstream pressure Pin obtained as shown in the pressure waveform Pin, the pressure value before the phase correction time Δt is obtained and is set as the corrected upstream pressure Pinh at that time point.

[0026] Next, the pressure detection value Pout of the downstream pressure sensor 16B at that time is read in step 5. Then, the upper and lower pressure difference DP is calculated as the difference between the corrected upstream pressure Pinh and the downstream pressure detection value Pout in step 6. That is, the upper and lower pressure difference DP is obtained as "DP = Pinh - Pout".

[0027] Figure 4 FIG. 2 shows the relationship between the pressure waveform of the corrected upstream pressure Pinh and the downstream pressure Pout. The corrected upstream pressure Pinh is formed by the phase correction time Δt. Figure 3 The shape of the pressure waveform of the upstream pressure Pin shown in FIG. 1 is lagging behind, and the phase difference between the two is reduced by this correction. Therefore, the upper and lower pressure differences based on the phase difference are reduced, and the estimation accuracy of the pore clogging based on the upper and lower pressure differences is improved. In addition, the upper and lower pressure differences DP obtained in each calculation cycle in step 6 are finally used for the control of the regeneration process of the particulate filter 15 after being appropriately averaged.

[0028] In addition, in the above-mentioned embodiment, the phase difference is reduced by lagging the pressure waveform of the upstream side pressure Pin relatively on the advance side, but it is also possible to correct the downstream side pressure Pout relatively on the lag side toward the advance side based on both the pressure waveform of the upstream side pressure Pin and the pressure waveform of the downstream side pressure Pout obtained as time series data, and the phase difference can be reduced in a manner that makes the two close to each other.

[0029] In addition, in the above-mentioned embodiment, the phase correction time Δt is calculated based on the internal combustion engine rotation speed Ne, but the phase correction time Δt based on the internal combustion engine rotation speed Ne may be further corrected based on the exhaust gas temperature. The higher the exhaust gas temperature, the higher the sound velocity, so the required phase correction time Δt is shortened. A correspondence map in which the optimal phase correction time Δt is assigned using the internal combustion engine rotation speed Ne and the exhaust gas temperature as parameters may be prepared in advance, and the phase correction time Δt may be read from the correspondence map. The exhaust gas temperature may be detected by a temperature sensor, or may be estimated based on the operating state (load, rotation speed, etc.) of the internal combustion engine 1.

[0030] Furthermore, the phase correction time Δt based on the engine rotation speed Ne can be corrected based on the exhaust gas flow rate. The greater the exhaust gas flow rate, the higher the flow velocity, so the required phase correction time Δt is shortened. A correspondence map that allocates the optimal phase correction time Δt using the engine rotation speed Ne and the exhaust gas flow rate as parameters can be prepared in advance, and the phase correction time Δt can be read from the correspondence map. With regard to the exhaust gas flow rate, the intake air amount can be simply regarded as the exhaust gas flow rate, or it can be calculated based on the intake air amount in consideration of combustion.

[0031] Furthermore, the phase correction time Δt based on the engine rotation speed Ne can be corrected using both the exhaust gas temperature and the exhaust gas flow rate.

[0032] An embodiment in which the present invention is applied to a gasoline particulate filter (GPF) has been described above, but the present invention can also be applied to a diesel particulate filter (DPF) for a diesel internal combustion engine.

[0033] In addition, in the above-mentioned embodiment, the case where the phase difference is caused by the difference in the passage length of the upstream sensor pipe 17 and the passage length of the downstream sensor pipe 18 is described, but the phase difference may also be caused by other factors such as the influence of the exhaust passage volume. The present invention can also be applied in this case.

Claims

1. A method for detecting a pressure difference of a particulate filter, wherein an upstream pressure sensor and a downstream pressure sensor are used to detect the pressure on the upstream side and the pressure on the downstream side of a particulate filter arranged in an exhaust passage of an internal combustion engine, respectively, and the upper and lower pressure differences of the particulate filter are calculated, wherein: At least one of the pressure detection values ​​is corrected in such a way that the phase difference between the pressure waveform detected by the upstream pressure sensor and the pressure waveform detected by the downstream pressure sensor is reduced, and the upper and lower pressure differences are calculated using the corrected pressure value.

2. The method for detecting the differential pressure of a particulate filter according to claim 1, wherein: The phase correction time corresponding to the phase difference is obtained based on the rotation speed of the internal combustion engine. Regarding the pressure of the one whose phase is relatively on the advanced side, the pressure detection value before the phase correction time is used as the pressure value after correction.

3. The method for detecting the differential pressure of a particulate filter according to claim 2, wherein: Find the exhaust gas temperature, The phase correction time is corrected based on the exhaust gas temperature.

4. The method for detecting the differential pressure of a particulate filter according to claim 2, wherein: Find the exhaust gas flow rate, The phase correction time is corrected based on the exhaust gas flow rate.

5. The method for detecting differential pressure of a particulate filter according to claim 1, wherein: The length of the sensor piping branching from the exhaust pipe having the particulate filter and reaching each pressure sensor is different between the upstream pressure sensor and the downstream pressure sensor. The corrected pressure value is obtained by lagging the pressure detection value of the pressure sensor having a relatively short path length.

6. The method for detecting differential pressure of a particulate filter according to claim 1, wherein: The calculated upper and lower pressure differences are used to determine whether the particulate filter is defective.

7. The method for detecting differential pressure of a particulate filter according to claim 1, wherein: The calculated upper and lower pressure differences are used for regeneration control of the particulate filter.

8. A pressure difference detection device for a particulate filter, wherein: The pressure difference detection device is configured to include: an upstream pressure sensor for detecting pressure on the upstream side of a particulate filter provided in an exhaust passage of the internal combustion engine, and a downstream pressure sensor for detecting pressure on the downstream side; a phase correction unit that corrects at least one of the pressure detection values ​​so that a phase difference between a phase of a pressure waveform detected by the upstream pressure sensor and a phase of a pressure waveform detected by the downstream pressure sensor is reduced; and The differential pressure calculation unit calculates the differential pressure between the upper and lower sides of the particulate filter using the corrected pressure value.

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