JPH04272419A - Filter regeneration controlling device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a filter regeneration control device which does not fail to judge a regeneration timing irrespective of individual characteristic of a pressure sensor. CONSTITUTION:During idling of an engine, an atmospheric pressure P is detected by pressure sensors 16, 17, and a deviation is obtained by comparison of outputs. After judgment of an actual regeneration timing of a filter, an output Vf of the pressure sensor 16 is corrected by the deviation, and a pressure difference P in respect to the filter is optimized, and filter regeneration timing is normally judged.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an internal combustion engine in which a filter for collecting particulates (exhaust particles) in the exhaust gas is installed in the exhaust system. Regarding.

0002

[Prior Art] For example, the exhaust of an internal combustion engine such as a diesel engine contains many exhaust particulates, that is, particulates. filter is installed. As this filter is used, as the amount of particulates collected increases, the collection efficiency also decreases, so the particulates are incinerated periodically by, for example, generating heat by energizing an electric heater placed at the end of the filter. It is designed to be played.

[0003] In determining when to regenerate this filter, for example, two pressure sensors are placed upstream and downstream of the filter to determine the differential pressure across the filter, that is, the filter pressure loss value. A device for measuring the amount of trapped particulates has already been proposed, which determines when to regenerate a filter based on the value of the increasing differential pressure (see Japanese Patent Application Laid-Open No. 60-47937).

0004

However, even if the two pressure sensors used in the above-mentioned conventional apparatus are of the same model, there is a slight difference in sensor characteristics (ie, output voltage-pressure characteristics). In addition, there is a tendency for sensor characteristics to gradually differ depending on the installation location and changes over time, so the above differential pressure values calculated from the output values of pressure sensors with different sensor characteristics are not reliable. Therefore, it is not possible to accurately determine when to regenerate the filter. This tendency is particularly noticeable in light load operating regions where the exhaust pressure is relatively small and the output voltage value of each pressure sensor is small (the degree of influence due to characteristic deviation is large), and there is a possibility of misjudging the filter regeneration time. expensive.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a filter regeneration control device that can avoid the erroneous judgment of filter regeneration timing caused by the characteristic deviation of the pressure sensor as described above.

[0006]

[Means for Solving the Problems] To achieve the above object, the present invention, as shown in FIG. In an internal combustion engine, the differential pressure before and after the filter is determined using multiple pressure sensors, and the time for regeneration of the filter is determined based on the magnitude of the differential pressure. Pressure detection operation in which each pressure sensor simultaneously detects a predetermined standard pressure. a sensor output deviation calculation means for calculating the deviation of each pressure sensor output with respect to the predetermined pressure detected at the same time; and a sensor output correction means for correcting the output of one pressure sensor based on the calculated deviation. Provides a playback control device.

[0007]

[Operation] By calculating the output deviation of the two pressure sensors with respect to a standard predetermined pressure, and correcting the output of one of the pressure sensors during actual pressure detection using the above deviation, the two pressure sensors Eliminate the difference in pressure detection characteristics between

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described with reference to the drawings. FIG. 2 shows, as a first embodiment of the present invention, a filter regeneration control device that supplies atmospheric pressure to both pressure sensors and determines the deviation of the sensor outputs when the engine is idling.

Referring to FIG. 2, 1 is a filter that collects particulates, 2 is an exhaust pipe that guides exhaust gas from the engine body (not shown) to filter 1 when collecting particulates, and 3 is an exhaust pipe that guides exhaust gas from the engine body (not shown) when collecting particulates. Filter gas 1
This is a bypass pipe that allows for a more detour.

Inside each of the exhaust pipe 2 and the bypass pipe 3, a first exhaust control valve 4 and a second exhaust control valve 5 are provided to achieve the exhaust gas flow during particulate collection and filter regeneration as described above. is provided, and its operation is controlled by a control circuit (ECU) 6 so that, for example, when collecting particulates, the valve occupies the position shown in the figure, and when regenerating the filter, it occupies the position shown by the dotted line around the valve. .

Between the first exhaust control valve 4 disposed inside the exhaust pipe 2 and the filter 1, a regeneration gas (for example, secondary air) for particulate combustion is supplied to the exhaust gas of the filter 1 during filter regeneration. An electric air pump 7 is provided for supplying air to the upstream side (hereinafter referred to as the upstream side), and is powered by a battery 9 together with a filter regeneration electric heater 8 disposed at the front end of the filter 1 . Regarding these filter regeneration elements, reference numerals 10 and 11 refer to the control circuit 6.
12 is an air pump filter, and 13 is a stop valve that prevents exhaust gas from flowing back into the air pump 7.

In order to detect the state of particulate collection in the filter 1, the exhaust pipes 1 upstream and downstream of the filter 1 are
are connected to pressure introduction pipes 14 and 15, respectively, and are provided with a pressure sensor 16 (filter upstream side) and a pressure sensor 17 (filter downstream side) that detect the exhaust pressure in the exhaust pipe area.

Further, according to this embodiment, rotary pressure detection line switching valves 18 and 1 driven by the control circuit 6 are installed in the middle of the pressure introduction pipes 14 and 15.
9 are interposed respectively. These pressure detection line switching valves 18 and 19 determine the pressure introduced into each pressure sensor 16 and 17, either the exhaust pressure from the exhaust pipe 1 or the atmospheric pressure shown by the arrow. , the operation of the control circuit 6 which controls its operating position will be described later. Furthermore, 20 and 21
is a pressure sensor filter.

On the input side of the control circuit 6, in addition to the analog signals from the pressure sensors 16 and 17, there is also a filter on the input side.
Analog signals from exhaust temperature sensors 22 and 23 provided downstream, a signal indicating the intake air amount Ga detected by an air flow meter (not shown), and engine speed N
Various signals indicating the current operating state of the engine, such as a signal indicating e, are input. The control circuit 6 controls the engine based on the operating information obtained from these various sensors, and in the case of the filter 1, outputs signals to drive the electric air pump 7 and electric heater 8 during filter regeneration. Pressure detection line switching valve 18, 1 which is a feature of the invention
Outputs a signal to activate 9.

The operation of the filter regeneration control device according to the present invention will be specifically explained below with reference to FIGS. 3 and 4.

FIGS. 3 and 4 show that each pressure sensor 16, 17 receives a standard predetermined pressure (in the case of this embodiment, This is a flowchart for detecting the atmospheric pressure (atmospheric pressure), determining the deviation of the sensor outputs, and correcting the output value of the pressure sensor based on this deviation.
This is a time interrupt routine that is processed every predetermined time such as sec. In addition, in this flowchart, the standard pressure (atmospheric pressure) detection timing is limited to idling operation because the pressure detection line is switched in an operating state where the exhaust pressure is low, and the exhaust gas introduced into the pressure introduction pipes 14 and 15 at this time is This is to reduce the amount of gas and keep the pressure detection line as clean as possible, but basically it is possible to calculate the sensor output deviation in any operating state.

Referring to FIG. 3, first, in step 31, it is determined whether a sensor output calibration completion flag F2 (described later) is set to 1. It is assumed that this flag is initialized to 0, for example, when the ignition switch (IG) is turned on (engine start). Therefore, in the case of No in this step, the routine proceeds to step 32, and this time it is determined whether an atmospheric pressure introduction flag F1 (described later) is set to 1 or not. Incidentally, like the flag F2, this flag F1 is also initialized to 0 at the time of engine start.

If No in step 32, the routine proceeds to step 33. In step 33, whether or not the engine is currently in an idling state is determined based on, for example, the engine speed Ne and the accelerator opening Accp (or the intake air flow rate Ga).
(It's okay, though). And yes in this step
If it is determined that this is the case, the process proceeds to step 34, where it is determined whether or not this idle operating state continues for a predetermined period of time (for example, 2 minutes). This is because the output characteristics of the pressure sensors 16 and 17 do not change so suddenly, so the execution condition for the output deviation calculation process is limited to an operating state in which idling continues for a predetermined period of time, so that the deviation calculation is not performed so frequently. (Even once a day is fine).

If the determination in step 34 is Yes, the routine then proceeds to step 35, in which a drive signal from the control circuit 6 is output, the pressure detection line switching valves 18 and 19 are rotated, and the pressure sensor 16 is turned on. , 17 to introduce atmospheric pressure. In reality, this valve switching takes a certain amount of time, so in the following step 36, a predetermined period of time (for example, 10 seconds) is set after the valve switching signal is output.
It is determined whether atmospheric pressure has been introduced into the pressure sensor detection section (not shown) after the elapse of time. If it is determined that the positions of the switching valves 18 and 19 have changed and atmospheric pressure is introduced into both pressure sensors 16 and 17 (Yes), the process proceeds to step 37, and the output V1 of both pressure sensors 16 and 17 is changed.
, V2.

Here, FIGS. 5(a) and 5(b) show an example of the output characteristics of each pressure sensor 16, 17 as one model, and (a) shows the pressure-sensor output of the pressure sensor 16 on the upstream side of the filter. Characteristic diagram (b) is a pressure-sensor output characteristic diagram of the pressure sensor 17 on the downstream side of the filter. These figures also show the sensor outputs of both sensors when they measure atmospheric pressure P0, and the sensor output V1 of the first pressure sensor 16 is a larger value than the sensor output V2 of the second pressure sensor 17. This indicates that there is a deviation in the output from the so-called standard predetermined pressure.

In step 38 following step 37, the deviation α=V1 − of each sensor output obtained in this way is
A process is performed to calculate V2 (see FIG. 5) and update and store the previous deviation α stored in the memory of the control circuit 6. Then, in the next step 39, a flag F1 is set to 1, which means that atmospheric pressure is actually introduced into each pressure sensor 16, 17 for the first time. In the routine after the flag F1 is set through the steps described above, the determination in step 32 described above is Yes, and steps 33 to 39 described above are not executed.

By the way, when the determination in step 32 is Yes, that is, both pressure sensors 16, 1 by atmospheric pressure measurement are
When the sensor output calibration in step 7 is completed, the routine proceeds to step 40, and a signal is outputted to return the pressure detection line switching valves 18 and 19 to the positions shown in FIG. 2 again. Then, in the following step 41, as in the previous step 36, it is checked whether the time required for valve operation has elapsed, and it is determined that the exhaust pressure upstream and downstream of the filter is guided to both pressure sensors 16 and 17. If so, the process proceeds to step 42, sets the sensor output calibration completion flag F2 to 1, and proceeds to step 43. still,
Naturally, in the case of No in step 41, this flag is not set and step 42 is skipped.

[0023] Once again, the sensor output calibration end flag F2
In the routine after is set to 1, it is determined that there is no need to calibrate the sensor output until the engine is stopped, so the determination in step 31 is Yes, and the processes in steps 32 to 42 described above are skipped. . still,
Steps 33, 34, and 36 mentioned above, although they are different for the sake of explanation.
If it is determined as No in any of the above, the sensor output calibration process has not yet been executed, so step 3
5 and steps 37 to 39 are skipped and the process proceeds to step 43.

In step 43 shown in succession in FIG. 4, first, it is determined whether or not the current engine operating state is under the conditions for determining the filter regeneration time. In other words, in general, when the engine is in transition, the filter regeneration time is determined. Therefore, it is determined whether or not it is not a transient period, for example. If the condition is not transient and the filter regeneration timing determination condition is satisfied (Yes), the routine proceeds to step 44 and reads the outputs Vf and Vu from the pressure sensors 16 and 17.

In the following step 45, the filter downstream exhaust pressure Pu and the filter upstream exhaust pressure Pf are determined from the outputs Vu and Vf read in the above manner, as follows: Pu = k・Vu Pf =k・(Vf −α)= k・[Vf −(V1
-V2)] where k: constant α: Calculated using an equation for inter-sensor output deviation.

That is, as explained using FIG. 5, the pressure sensor 1 obtained by detecting the atmospheric pressure Po
Using an output deviation α between 6 and 17, for example, depending on the installation environment,
By subtracting this deviation α from the output Vf of the pressure sensor 16 on the upstream side of the filter, using the output of the pressure sensor 17 on the downstream side of the filter, which is expected to have a relatively small change in output over time, as a reference, the output characteristic difference between the sensors can be calculated. The output of the excluded pressure sensor 16 can be determined. As a result, the reliability of the calculated filter upstream exhaust pressure Pf is improved, and the differential pressure across the filter ΔP=(Pf
-Pu) detection accuracy can be improved.

In the following step 46, the filter front and rear differential pressure ΔP is calculated from each of the exhaust pressures Pf and Pu obtained as described above, and is calculated from the filter regeneration reference value β which is predetermined according to the operating state at that time. In comparison, the differential pressure ΔP
, that is, if the pressure loss is larger than the filter regeneration reference value (Yes), it is determined that it is now the regeneration time. In this case, the routine proceeds to step 47, where a filter regeneration flag Fs is used as a reference for executing a filter regeneration processing program (not shown).
This routine ends by executing the process of setting 1 to 1.

Note that the previous step 43 or step 46
If it is determined No in step 48, it means that the condition for determining the filter regeneration time is not satisfied or that the filter 1 has not collected enough particulates to require regeneration, so the routine proceeds to step 48. The filter regeneration flag Fs is reset to 0, filter regeneration processing is not performed, and this routine ends.

Next, a second embodiment of the present invention will be described with reference to FIG. The configuration of the present device shown in FIG. 6 is the same as the device of the first embodiment shown in FIG. 2, except that the switching valves 18 and 19 are removed, and the other configurations are the same. Therefore, the same components are given the same numbers.

In this embodiment, the illustrated filter regeneration control device reads the output from the pressure sensors 16 and 17 when the ignition switch is turned on, and uses this as V1 and V2 in the previous embodiment. be. That is,
This utilizes the fact that when the engine is stopped, the inside of the exhaust passage is at atmospheric pressure regardless of whether it is upstream or downstream of the filter, and when the engine is started, specifically before the starter is driven, each pressure sensor 16 , 17 to determine the output deviation α from the respective outputs V1 and V2 relative to the atmospheric pressure P0.

The flowchart shown in FIG. 7 is related to the operation of the apparatus described above and is a routine for calculating a deviation that is executed once each time the ignition switch is turned on. The sensor outputs V1 and V2 from 17 are read, and in the subsequent step 72, the deviation α=V1 - V2 is calculated, and this is updated in the memory in the control circuit 6 instead of the previously stored deviation.
It is to be memorized and terminated. Regarding the determination of filter regeneration time using the deviation α determined in this way,
This can be executed by the routine shown in FIG. According to the second embodiment, a filter regeneration control device that can achieve the same effects as the first embodiment without providing a switching valve for introducing atmospheric pressure and is more cost effective is provided. can do.

[0032] So far, two embodiments have been described in which atmospheric pressure is introduced in order to determine the output deviation between pressure sensors, but the present invention is of course not limited to these embodiments. For example, a value other than atmospheric pressure (such as positive pressure supplied from a pump) may be used as the standard predetermined pressure for calculating the deviation. In addition, in a device like the present invention that detects the same pressure to determine the difference in the output characteristics of both pressure sensors, in addition to the above-mentioned effect of optimizing the filter regeneration timing judgment, it is possible to If there is a large output difference between the two, it can be determined that one of the pressure sensors is faulty, or that the pressure detection line (switching valve, etc.) is faulty, which also has the effect of so-called fault diagnosis.

[0033]

[Effects of the Invention] As explained above, according to the present invention, when detecting the pressure before and after the filter when determining the time to regenerate the filter, each exhaust pressure can be obtained with the output deviation between pressure sensors corrected. The reliability of the calculated differential pressure across the filter is increased, and erroneous determination of filter regeneration timing due to individual pressure sensor differences can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a diagram corresponding to claims of the present invention.

FIG. 2 is a schematic configuration diagram of a filter regeneration control device as a first embodiment of the present invention.

FIG. 3 is a part (upper half) of a flowchart explaining the operation of the control circuit shown in FIG. 2, and is a diagram showing a process for determining an output deviation between pressure sensors.

FIG. 4 is the lower half of the flowchart following FIG. 3, showing processing for determining filter regeneration timing from the obtained output deviation.

FIG. 5 is a model diagram showing the output characteristics of each pressure sensor, in which (a) is a diagram showing a pressure sensor on the upstream side of the filter, and (b) is a diagram showing a pressure sensor on the downstream side of the filter.

FIG. 6 is a schematic device configuration diagram showing a second embodiment of the present invention.

FIG. 7 is a flowchart for determining sensor output deviation using the apparatus shown in FIG. 6;

[Explanation of symbols]

1...Filter 6...Control circuit 16, 17...Pressure sensor

Claims (1)

[Claims] Claim 1: Using two pressure sensors that detect exhaust pressure upstream and downstream of a filter that is installed in the exhaust system of an internal combustion engine and that collects particulates, the differential pressure before and after the filter is determined, and the magnitude of this differential pressure is determined. In the filter regeneration control device for an internal combustion engine, the filter regeneration control device for an internal combustion engine determines the regeneration timing of the filter based on the pressure detection operation means for causing each pressure sensor to simultaneously detect a predetermined pressure as a standard, and each pressure sensor corresponding to the predetermined pressure detected simultaneously. A filter regeneration control device comprising: a sensor output deviation calculation means for calculating an output deviation; and a sensor output correction means for correcting the output of one pressure sensor based on the calculated deviation.