Method and device for detecting pressure difference of particulate filter

Abstract

An exhaust passage (14) of an internal combustion engine (1) is provided with a particulate filter (15). An upstream-side pressure sensor (16A) which detects the upstream-side pressure (Pin) of the particulate filter (15) and a downstream side pressure sensor (16B) which detects the downstream side pressure (Pout) of the particulate filter (15) are provided. Control of a regeneration treatment and the like are performed on the basis of an upstream / downstream pressure difference which is the difference between the upstream-side pressure and the downstream-side pressure. In order to reduce the phase difference between waveforms of both of the pressures based on an exhaust pulsation, a phase correction time (Δt) is calculated on the basis of the engine rotation speed (Ne), and, with regard to the upstream-side pressure (Pin), a pressure detection value which precedes by the phase correction time (Δt) is set as a corrected upstream-side pressure (Pinh) (S3 and S4). Then, the corrected upstream-side pressure (Pinh) and the downstream-side pressure (Pout) are used to calculate a corrected upstream / downstream pressure difference (DP) (S6).

Description

Particulate filter pressure differential detection method and apparatus

[0001] The present invention relates to a method and device for detecting a pressure difference across a particulate filter (GPF or DPF) provided in an exhaust passage of an internal combustion engine.

[0002] In both gasoline and diesel engines, a particulate filter is sometimes used to remove particulates from the exhaust. Patent Document 1 discloses a method for detecting the pressure difference between the upper and lower sides of a particulate filter using a differential pressure sensor to control a regeneration process for clogged particulate filters installed in an exhaust passage and to estimate particulate filter damage. It also discloses a method for correcting an error in the average differential pressure caused by exhaust pressure pulsation using a correction value determined from a map of engine required torque and engine speed.

[0003] However, Patent Document 1 does not take into consideration the phase difference between the pressure waveforms of the upstream and downstream pressures of the particulate filter. That is, although both the upstream and downstream pressures change in response to exhaust pulsation, their phases do not necessarily coincide. For example, if the passage length from the upstream pressure outlet to the differential pressure sensor in an exhaust passage equipped with a particulate filter differs from the passage length from the downstream pressure outlet to the differential pressure sensor, a relatively large phase difference can occur between the respective pressure waveforms (see, for example, FIG. 3 ). As a result, a pressure difference occurs between the upstream and downstream pressures due to the phase difference. That is, as is clear from FIG. 3 , the pressure difference between the upstream and downstream pressures changes significantly, reversing positive and negative values ​​microscopically, which is one factor that reduces the accuracy of measuring the pressure difference between the upstream and downstream pressures.

[0004] Japanese Patent Application Laid-Open No. 2002-371827

[0005] This invention provides a method for detecting a pressure difference in a particulate filter, which detects the pressures upstream and downstream of a particulate filter provided in an exhaust passage of an internal combustion engine using an upstream pressure sensor and a downstream pressure sensor, respectively, and calculates the pressure difference across the particulate filter. At least one of the detected pressure 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 becomes small, and the corrected pressure value is used to calculate the pressure difference across the particulate filter.

[0006] By applying a correction corresponding to the phase difference in this way, the component of the pressure difference between the upper and lower parts of the particulate filter due to the phase difference is eliminated or suppressed, and therefore, even if, for example, the passage length of the pipe for the upstream pressure sensor is different from the passage length of the pipe for the downstream pressure sensor, the pressure difference between the upper and lower parts of the particulate filter can be determined with high accuracy.

[0007] The present invention relates to an internal combustion engine having a particulate filter, a method for calculating a pressure difference between an upper and lower parts of a combustion chamber, and a method for correcting a phase difference between the upper and lower parts of a combustion chamber.

[0008] An embodiment of the present invention will now be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing a schematic configuration of an internal combustion engine 1 according to an embodiment of the present invention. The internal combustion engine 1 according to the embodiment is a four-stroke, spark-ignition internal combustion engine (a so-called gasoline engine), and each cylinder is provided with an intake valve 2, an exhaust valve 3, and an ignition plug 4. The illustrated example is configured as a direct-injection engine, and a fuel injection valve 5 that injects fuel into the cylinder is disposed, for example, on the intake valve 2 side. However, the engine may also be configured as a port injection type that injects fuel toward an intake port 6.

[0009] An electronically controlled throttle valve 10, the opening of which is controlled by a control signal from an engine controller 9, is disposed upstream of a collector section 8 in an intake passage 7 connected to an intake port 6 of each cylinder. An air flow meter 11, which detects the amount of intake air, is disposed upstream of the throttle valve 10, and an air cleaner 12 is disposed further upstream.

[0010] The exhaust ports 13 of each cylinder are joined together to form a single exhaust passage 14, which is provided with a particulate filter (so-called gasoline particulate filter: GPF) 15 that collects exhaust particulates. The particulate filter 15 is made of, for example, a so-called plugged ceramic filter in which one end of a large number of fine passages formed in a monolithic ceramic body are alternately plugged, and the surface is coated with a three-way catalyst.

[0011] An air-fuel ratio sensor 19 for detecting the exhaust air-fuel ratio is disposed in the exhaust passage 14 at a position upstream of the particulate filter 15. Note that a separate three-way catalytic converter may be provided in series with the particulate filter 15.

[0012] The particulate filter 15 is equipped with a pressure sensor unit 16, which includes an upstream pressure sensor 16A and a downstream pressure sensor 16B configured as a single package to detect the pressure difference between above and below the particulate filter 15. These upstream and downstream pressure sensors 16A and 16B are, for example, semiconductor pressure sensors of an appropriate type, and essentially the same pressure sensors are used. An upstream sensor pipe 17, branching off from the upstream side (inlet side) of the particulate filter 15 in the exhaust passage 14, is connected to the upstream pressure sensor 16A, and the exhaust pressure upstream of the particulate filter 15 is guided via this upstream sensor pipe 17. A downstream sensor pipe 18, branching off from the downstream side (outlet side) of the particulate filter 15 in the exhaust passage 14, is connected to the downstream pressure sensor 16B, and the exhaust pressure downstream of the particulate filter 15 is guided via this downstream sensor pipe 18. In one embodiment, the passage length of the upstream sensor pipe 17 and the passage length of the downstream sensor pipe 18 are different from each other due to the mounting position of the pressure sensor unit 16. For example, the passage length of the upstream sensor pipe 17 is relatively shorter. Due to this difference in 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, as will be described later.

[0013] 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 from a number of sensors, such as a crank angle sensor 21 for detecting the engine speed, a water temperature sensor 22 for detecting the coolant temperature, and an accelerator position sensor 23 for detecting the amount of depression of the accelerator pedal. Based on these input signals, the engine controller 9 optimally controls the amount and timing of fuel injection by the fuel injection valve 5, the ignition timing by the spark plug 4, the opening of the throttle valve 10, etc.

[0014] Furthermore, the engine controller 9 determines the pressure difference between the upper and lower parts of the particulate filter 15 based on the pressure detection by the upstream pressure sensor 16A and the downstream pressure sensor 16B, and controls the regeneration process for clogging of the particulate filter 15 and estimates whether the particulate filter 15 is damaged based on this pressure difference.

[0015] That is, when excessive particulates accumulate in the particulate filter 15, the airflow resistance increases, necessitating forced regeneration, for example, by temporarily raising the exhaust temperature. This increase in airflow resistance is detected as an increase in the pressure difference between the upper and lower sides of the particulate filter 15. Furthermore, if a ceramic filter is damaged due to an impact or the like, its exhaust particulate collection performance decreases, and when such damage occurs, the airflow resistance decreases relatively significantly. This decrease in airflow resistance is detected as a decrease in the pressure difference between the upper and lower sides of the particulate filter 15.

[0016] FIG. 3 shows 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. The horizontal axis represents crank angle or time. As the exhaust valve 3 opens and closes with each cycle, exhaust pulsation occurs in the exhaust passage 14 with a period or frequency corresponding to the number of cylinders and engine speed. This exhaust pulsation appears in both the upstream pressure Pin and the downstream pressure Pout. However, as mentioned above, because the passage length of the upstream sensor pipe 17 is shorter than the passage length of the downstream sensor pipe 18, a phase difference occurs in which the pressure waveform of the upstream pressure Pin is relatively advanced. Such a phase difference results in a large upper and lower pressure difference due to this phase difference, which reduces the accuracy of estimating the clogging state and filter damage based on the airflow resistance.

[0017] In this embodiment, the phase difference is corrected in advance, and then the upper and lower pressure difference is calculated using the upstream pressure Pin and the downstream pressure Pout. Fig. 2 is a flowchart showing the flow of a process for calculating the upper and lower pressure difference executed by the engine controller 9, and this process is repeatedly executed at predetermined calculation cycles.

[0018] In the first step 1, the pressure detection value Pin of the upstream pressure sensor 16A at that time is read in. This reading of the pressure detection value Pin is repeated for each calculation cycle, resulting in time-series data such as the pressure waveform Pin shown in FIG.

[0019] In the next step 2, the rotation speed Ne of the internal combustion engine 1 is read. Then, in step 3, a 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 is longest when the rotation speed Ne is an idle rotation speed, and has the characteristic of becoming shorter as the rotation speed Ne increases.

[0020] Next, in step 4, the corrected upstream pressure Pinh is calculated. Specifically, the pressure value before the phase correction time Δt is calculated from the time series data of the upstream pressure Pin obtained as shown in the pressure waveform Pin in Fig. 3, and this is set as the corrected upstream pressure Pinh at that time.

[0021] Next, in step 5, the pressure detection value Pout of the downstream pressure sensor 16B at that time is read. Then, in step 6, the vertical pressure difference DP is calculated as the difference between the corrected upstream pressure Pinh and the downstream pressure detection value Pout. That is, the vertical pressure difference DP is calculated as "DP = Pinh - Pout".

[0022] 4 shows the relationship between the pressure waveform of the corrected upstream pressure Pinh and the downstream pressure Pout. The corrected upstream pressure Pinh is obtained by delaying the pressure waveform of the upstream pressure Pin shown in FIG. 3 by a phase correction time Δt, and this correction reduces the phase difference between the two. Therefore, the upper and lower pressure difference based on the phase difference is reduced, and the accuracy of estimating clogging and the like based on the upper and lower pressure difference is improved. Note that the upper and lower pressure difference DP calculated for each calculation cycle in step 6 is ultimately used to control the regeneration process of the particulate filter 15 after undergoing appropriate averaging processing.

[0023] In the above embodiment, the phase difference is reduced by delaying the pressure waveform of the upstream pressure Pin, which is relatively on the leading side. However, it is also possible to obtain both the pressure waveform of the upstream pressure Pin and the pressure waveform of the downstream pressure Pout as time series data, and then correct the downstream pressure Pout, which is relatively on the lagging side, to the leading side. Furthermore, the phase difference may be reduced by bringing the two closer together.

[0024] Furthermore, in the above embodiment, the phase correction time Δt is calculated based on the engine rotation speed Ne, but a correction based on the exhaust gas temperature may be added to the phase correction time Δt based on the engine rotation speed Ne. The higher the exhaust gas temperature, the faster the sonic velocity becomes, and therefore the required phase correction time Δt becomes shorter. A map may be created in advance in which optimal phase correction times Δt are assigned using the engine rotation speed Ne and the exhaust gas temperature as parameters, and the phase correction time Δt may be read from this map. The exhaust gas temperature may be detected using a temperature sensor, or may be estimated based on the operating state of the internal combustion engine 1 (load, rotation speed, etc.).

[0025] Furthermore, a correction based on the exhaust gas flow rate may be added to the phase correction time Δt based on the engine rotation speed Ne. The larger the exhaust gas flow rate, the higher the flow velocity, and therefore the shorter the required phase correction time Δt. A map may be created in advance in which optimal phase correction times Δt are assigned using the engine rotation speed Ne and the exhaust gas flow rate as parameters, and the phase correction time Δt may be read from this map. For simplicity, the exhaust gas flow rate may be calculated by considering the intake air volume as the exhaust gas flow rate, or may be calculated based on the intake air volume and taking combustion into consideration.

[0026] Furthermore, the phase correction time Δt based on the engine rotation speed Ne may be corrected using both the exhaust gas temperature and the exhaust gas flow rate.

[0027] While one embodiment in which the present invention is applied to a gasoline particulate filter (GPF) has been described above, the present invention can also be similarly applied to a diesel particulate filter (DPF) for a diesel engine.

[0028] In the above embodiment, the phase difference is caused by the difference between the passage length of the upstream sensor pipe 17 and the passage length of the downstream sensor pipe 18. However, the phase difference may be caused by other factors such as the influence of the exhaust passage volume. In such cases, the present invention can be applied in the same way.

Claims

1. A method for detecting a pressure difference in a particulate filter, the method comprising: detecting an upstream pressure sensor and a downstream pressure sensor, respectively, of a particulate filter provided in an exhaust passage of an internal combustion engine, and calculating a pressure difference between above and below the particulate filter, At least one of the pressure detection values ​​is corrected so that a phase difference between a phase of the pressure waveform detected by the upstream pressure sensor and a phase of the pressure waveform detected by the downstream pressure sensor becomes small, and the pressure difference between the upstream and downstream pressure sensors is calculated using the corrected pressure value. Where: The length of the sensor pipes branching from the exhaust pipe equipped with the particulate filter to each pressure sensor is different between the upstream pressure sensor and the downstream pressure sensor, A corrected pressure value is obtained by delaying the pressure detection value of the pressure sensor having the relatively shorter passage length. Particulate filter pressure differential sensing method.

2. A method for detecting a pressure difference in a particulate filter, the method comprising: detecting an upstream pressure sensor and a downstream pressure sensor, respectively, of a particulate filter provided in an exhaust passage of an internal combustion engine, and calculating a pressure difference between above and below the particulate filter, At least one of the pressure detection values ​​is corrected so that a phase difference between a phase of the pressure waveform detected by the upstream pressure sensor and a phase of the pressure waveform detected by the downstream pressure sensor becomes small, and the pressure difference between the upstream and downstream pressure sensors is calculated using the corrected pressure value. Where: determining a phase correction time corresponding to the phase difference based on a rotation speed of the internal combustion engine; For one pressure whose phase is relatively leading, the pressure detection value before the phase correction time is used as the pressure value after correction. Particulate filter pressure differential sensing method.

3. Obtain the exhaust gas temperature, The phase correction time is corrected based on the exhaust gas temperature.

3. The method of claim 2, wherein the pressure difference in a particulate filter is detected by the pressure sensor.

4. Obtain the exhaust gas flow rate, The phase correction time is corrected based on the exhaust gas flow rate.

3. The method of claim 2, wherein the pressure difference in a particulate filter is detected by the pressure sensor.

5. (delete)

6. The calculated pressure difference is used to determine whether the particulate filter is defective.

3. A method for detecting a pressure difference in a particulate filter as claimed in claim 1 or 2.

7. The calculated pressure difference is used to control the regeneration of the particulate filter.

3. A method for detecting a pressure difference in a particulate filter as claimed in claim 1 or 2.

8. an upstream pressure sensor for detecting a pressure upstream of a particulate filter provided in an exhaust passage of the internal combustion engine, and a downstream pressure sensor for detecting a pressure downstream of the particulate filter; 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 becomes small; a pressure difference calculation unit that calculates a pressure difference between above and below the particulate filter using the corrected pressure value; Equipped with The length of the sensor pipes branching from the exhaust pipe equipped with the particulate filter to each pressure sensor is different between the upstream pressure sensor and the downstream pressure sensor, The phase correction unit obtains a corrected pressure value by delaying the pressure detection value of the pressure sensor having a relatively shorter passage length, in the pressure difference detection device for a particulate filter.

9. an upstream pressure sensor for detecting a pressure upstream of a particulate filter provided in an exhaust passage of the internal combustion engine, and a downstream pressure sensor for detecting a pressure downstream of the particulate filter; 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 becomes small; a pressure difference calculation unit that calculates a pressure difference between above and below the particulate filter using the corrected pressure value; Equipped with The phase correction unit is determining a phase correction time corresponding to the phase difference based on a rotation speed of the internal combustion engine; A pressure difference detection device for a particulate filter, in which a pressure detection value before a phase correction time is used as a corrected pressure value for one pressure whose phase is relatively leading.