JP4802922B2 - Particulate filter regeneration system for internal combustion engine - Google Patents

Description

  The present invention relates to a regeneration technique for a particulate filter disposed in an exhaust passage of an internal combustion engine.

When the particulate filter is disposed in the exhaust passage of the internal combustion engine, it is necessary to perform PM regeneration processing on the particulate filter. As a technology related to the PM regeneration process, when the PM regeneration process is performed using post injection when the PM collection amount of the particulate filter exceeds a predetermined amount, the cooling water temperature is lower than a predetermined determination temperature. Is known to perform post-injection for PM regeneration processing (see, for example, Patent Document 1).
JP 2005-282478 A JP 2005-16345 A

  By the way, when the internal combustion engine repeats the operation for a short time, there is a possibility that the state where the operation of the internal combustion engine is stopped before the coolant temperature becomes equal to or higher than the determination temperature. In such a case, since the PM regeneration process is not executed even if the PM collection amount becomes a predetermined amount or more, the PM collection amount may be excessively increased.

  The present invention has been made in view of various circumstances as described above, and an object of the present invention is to provide a technique capable of suitably regenerating a particulate filter regardless of the use conditions of the internal combustion engine.

  In order to solve the above-described problems, the present invention allows the particulate regeneration filter to perform the PM regeneration process when the internal combustion engine is at a low temperature, so that the particulate filter can be used even when the internal combustion engine repeats the short-time operation. The amount of PM collected was not increased excessively.

  If post-injection for PM regeneration processing is performed when the internal combustion engine is at a low temperature, fuel post-injected from the fuel injection valve (hereinafter referred to as “post-injected fuel”) adheres to the cylinder bore wall surface and becomes lubricating oil. There is a possibility of inducing dilution and the like. For this reason, it is preferable that the execution frequency of the PM regeneration process when the internal combustion engine is low is reduced as much as possible.

  Therefore, the particulate filter regeneration system for an internal combustion engine according to the present invention has a longer PM regeneration processing interval (hereinafter referred to as “regeneration interval”) when the temperature of the internal combustion engine is low than when the temperature of the internal combustion engine is high. By doing so, the dilution of the lubricating oil was minimized.

Specifically, the present invention relates to a particulate filter disposed in the exhaust passage of the internal combustion engine, an acquisition means for acquiring the amount of PM collected by the particulate filter, and a physical quantity correlated with the temperature of the internal combustion engine. Acquired by the detection means for detecting, the regeneration means for performing PM regeneration processing for oxidizing and removing PM collected by the particulate filter by performing post injection from the fuel injection valve of the internal combustion engine, and the acquisition means A particulate filter regeneration system for an internal combustion engine, comprising: a control means for operating the regeneration means when the collected amount of PM is not less than a first predetermined amount and the physical quantity detected by the detection means is not less than a predetermined temperature. The PM trap acquired by the acquisition unit when the physical quantity detected by the detection unit is less than the predetermined temperature. There becomes a second predetermined amount or more greater than the first predetermined amount, said control means is so as to operate the reproducing device.

  According to such a configuration, even if the temperature of the internal combustion engine does not rise above the predetermined temperature, the PM regeneration process is performed on the condition that the PM collection amount exceeds the second predetermined amount. Therefore, even if the state where the operation of the internal combustion engine is stopped before the temperature of the internal combustion engine becomes equal to or higher than the predetermined temperature is repeated, the amount of PM trapped by the particulate filter is unlikely to be excessive.

  Further, since the second predetermined amount is set to an amount larger than the first predetermined amount, the regeneration interval when the temperature of the internal combustion engine is lower than the predetermined temperature is greater than the regeneration interval when the temperature of the internal combustion engine is equal to or higher than the predetermined temperature. become longer. As a result, it is possible to perform the PM regeneration process while minimizing the dilution of the lubricating oil.

  In the particulate filter regeneration system for an internal combustion engine according to the present invention, the second predetermined amount may be increased as the physical quantity detected by the detection means indicates a lower temperature.

  This means that the regeneration interval becomes longer as the temperature of the internal combustion engine becomes lower. The post-injected fuel is more likely to adhere to the cylinder bore wall surface as the temperature of the internal combustion engine becomes lower. However, if the regeneration interval is lengthened as the temperature of the internal combustion engine becomes lower, the frequency of occurrence of oil dilution can be minimized.

  In the particulate filter regeneration system for an internal combustion engine according to the present invention, the control means may shorten the execution time of the PM regeneration process as the physical quantity detected by the detection means indicates a lower temperature.

  In this case, the lower the temperature of the internal combustion engine, the shorter the execution period of post injection for PM regeneration processing. As a result, the PM regeneration process can be executed while minimizing the amount of fuel adhering to the cylinder bore wall surface.

  As a method of determining the execution end timing of the PM regeneration process, when the amount of PM remaining in the particulate filter is acquired during the execution of the PM regeneration process, and the acquired PM remaining amount falls below the reference amount A method of terminating the execution of the PM regeneration process is conceivable.

  When the above-described method is adopted, the reference amount may be increased as the physical amount detected by the detecting unit shows a lower temperature.

  In this case, the execution time of the PM regeneration process becomes shorter as the temperature of the internal combustion engine becomes lower. Therefore, it is possible to execute the PM regeneration process while minimizing the amount of fuel adhering to the cylinder bore wall surface.

  In the present invention, examples of the physical quantity correlated with the temperature of the internal combustion engine include the temperature of cooling water and the temperature of lubricating oil.

  According to the present invention, the particulate filter can be suitably regenerated regardless of the use conditions of the internal combustion engine.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

<Example 1>
First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. An internal combustion engine 1 shown in FIG. 1 is a compression ignition type internal combustion engine (diesel engine) having a plurality of cylinders 2.

  A fuel injection valve 3 is attached to each cylinder 2 of the internal combustion engine 1. The fuel injection valve 3 directly injects the fuel boosted in the common rail 30 into the cylinder 2.

  An intake passage 4 communicates with each cylinder 2. A compressor housing 50 and an intercooler 6 of the turbocharger 5 are disposed in the intake passage 4. The intake air supercharged by the compressor housing 50 is cooled by the intercooler 6 and then introduced into each cylinder 2. The intake air introduced into each cylinder 2 is ignited and burned in the cylinder 2 together with the fuel injected from the fuel injection valve 3.

  Gas burned in each cylinder 2 (burned gas) is discharged to the exhaust passage 7. The exhaust discharged into the exhaust passage 7 is released into the atmosphere via the turbine housing 51 and the exhaust purification device 8 disposed in the middle of the exhaust passage 7.

  The exhaust purification device 8 is a particulate filter on which a catalyst having oxidation ability is supported. Instead of supporting the catalyst having oxidation ability on the particulate filter, the oxidation catalyst may be arranged immediately upstream of the particulate filter. Hereinafter, the exhaust purification device 8 is referred to as a particulate filter 8.

  A portion of the intake passage 4 downstream of the intercooler 6 and a portion of the exhaust passage 7 upstream of the turbine housing 51 are connected to each other by an EGR passage 9. In the middle of the EGR passage 9, an EGR valve 10 that adjusts the flow rate of exhaust gas (hereinafter referred to as “EGR gas”) flowing through the EGR passage 9, and an EGR cooler for cooling the EGR gas flowing through the EGR passage 9 11 is arranged.

  The amount of EGR gas is adjusted by the opening degree of the intake throttle valve 12 and / or the opening degree of the EGR valve 10 disposed at a site downstream of the intercooler 6 of the intake passage 4 and upstream of the connection portion of the EGR passage 9. It has come to be.

  The fuel injection valve 3, the EGR valve 10, and the intake throttle valve 12 described above are electrically controlled by the ECU 13. The ECU 13 is electrically connected to various sensors such as an air flow meter 14, a water temperature sensor 15, a crank position sensor 16, and a differential pressure sensor 17.

  The air flow meter 14 is a sensor that measures the amount of intake air flowing through the intake passage 4. The water temperature sensor 15 is a sensor that measures the temperature of cooling water circulating in the internal combustion engine 1. The crank position sensor 16 is a sensor that detects the rotational position of the crankshaft of the internal combustion engine 1. The differential pressure sensor 17 is a sensor that measures the difference between the exhaust pressure upstream of the particulate filter 8 and the exhaust pressure downstream of the particulate filter 8 (hereinafter referred to as “filter differential pressure before and after”).

  The ECU 13 controls the fuel injection valve 3, the EGR valve 10, and the intake throttle valve 12 based on the measurement values of the various sensors described above. For example, the ECU 13 executes PM regeneration control that is the gist of the present invention in addition to known control such as fuel injection control.

  In the PM regeneration control, the ECU 13 determines whether or not the PM amount (PM collection amount) ΣPM collected by the particulate filter 8 is equal to or greater than a predetermined amount A. For example, the predetermined amount A is an amount determined so that the back pressure acting on the internal combustion engine 1 falls within an allowable range.

  As a method of acquiring the PM collection amount ΣPM of the particulate filter 8, a method of converting the elapsed time from the previous PM regeneration processing execution time into the PM collection amount ΣPM, and the vehicle running from the previous PM regeneration processing execution time A method of converting the distance into the PM trapping amount ΣPM, a method of integrating the PM discharge amount (PM amount discharged by the internal combustion engine 1) from the previous execution of the PM regeneration process, or the measured value of the differential pressure sensor 17 is PM trapped. The method etc. which convert into collection amount ΣPM can be illustrated.

  When the ECU 13 determines that the PM collection amount ΣPM of the particulate filter 8 is equal to or greater than the predetermined amount A, the ECU 13 executes PM regeneration processing. In the PM regeneration process, the ECU 13 raises the temperature of the particulate filter 8 to a temperature range where PM can be oxidized by causing the fuel injection valve 3 to perform post injection.

  The ECU 13 acquires a PM amount (hereinafter referred to as “PM residual amount”) ΣPMremaining in the particulate filter 8 when the PM regeneration process is executed, and the PM residual amount ΣPMremain is a predetermined regeneration end value B (for example, zero). ) The PM regeneration process is terminated when the following occurs.

  As a method for obtaining the PM residual amount ΣPMremain described above, a product of PM oxidation rate (PM amount oxidized per unit time) and PM regeneration processing execution time is obtained by collecting PM at the start of PM regeneration processing execution. A method of subtracting from the quantity ΣPM can be exemplified.

  The PM oxidation rate increases as the temperature of the particulate filter 8 increases and the amount of exhaust gas flowing into the particulate filter 8 (the amount of oxygen flowing into the particulate filter 8) increases. It can be obtained as a parameter.

  By the way, if post injection is performed when the temperature of the internal combustion engine 1 is low, the post-injected fuel may adhere to the cylinder bore wall surface and cause dilution of the lubricating oil. For this reason, the ECU 13 executes the PM regeneration process on condition that the temperature of the internal combustion engine 1 is equal to or higher than a predetermined temperature.

  However, a vehicle equipped with the internal combustion engine 1 may be mainly used for short-distance movement. In such a case, the internal combustion engine 1 repeats the operation for a short time. Therefore, there is a high possibility that the internal combustion engine 1 repeats a state where the operation is stopped before the temperature is raised to a predetermined temperature or higher.

  If the state where the operation is stopped before the internal combustion engine 1 is heated to a predetermined temperature or higher is repeated, the PM regeneration process is not performed even if the PM trapping amount ΣPM of the particulate filter 8 exceeds the predetermined amount A. The PM trapping amount ΣPM of the particulate filter 8 becomes excessive, and the back pressure of the internal combustion engine 1 may become excessively high.

  Therefore, in the PM regeneration control of the present embodiment, the ECU 13 performs the PM regeneration process while making the regeneration interval longer when the temperature of the internal combustion engine 1 is lower than the predetermined temperature than when the temperature of the internal combustion engine 1 is equal to or higher than the predetermined temperature. Was allowed to run.

As a method of lengthening the regeneration interval, a method of setting the aforementioned predetermined amount to a larger value than when the internal combustion engine 1 is at a predetermined temperature or higher can be exemplified. According to such a method, even when the internal combustion engine 1 is repeatedly shut down before the temperature rises to a predetermined temperature or higher, the PM regeneration process is performed while reducing the opportunity for dilution of the lubricating oil. Can be done.

  Hereinafter, PM regeneration control in the present embodiment will be described with reference to FIG. FIG. 2 is a flowchart showing a PM regeneration control routine. This PM regeneration control routine is a routine stored in advance in the ROM of the ECU 13, and is repeatedly executed by the ECU 13 at predetermined intervals.

  In the PM regeneration control routine, the ECU 13 first calculates the PM collection amount ΣPM of the particulate filter 8 in S101.

  In S102, it is determined whether or not the temperature of the internal combustion engine 1 is equal to or higher than a predetermined temperature Tmp. In the PM regeneration control routine of FIG. 2, the temperature of the internal combustion engine 1 is substituted by the measured value (cooling water temperature) thw of the water temperature sensor 15, but the temperature of the cylinder bore wall surface and the temperature in the cylinder 2 are directly measured. Alternatively, the temperature of the lubricating oil may be substituted.

  If an affirmative determination is made in S102 (thw ≧ Tmp), the ECU 13 executes normal PM regeneration processing in S103 and thereafter.

  Specifically, the ECU 13 first determines in S103 whether or not the PM trapping amount ΣPM calculated in S101 is equal to or greater than a predetermined amount A.

  If a negative determination is made in S103 (ΣPM <A), the ECU 13 ends this routine without executing the PM regeneration process. On the other hand, if a positive determination is made in S103 (ΣPM ≧ A), the ECU 13 proceeds to S104.

  In S104, the ECU 13 starts executing the PM regeneration process by causing the fuel injection valve 3 to perform post injection.

  In S105, the ECU 13 calculates the PM residual amount ΣPMremain. Subsequently, the ECU 13 proceeds to S106, and determines whether or not the PM residual amount ΣPMremain calculated in S105 has decreased to the regeneration end value B or less.

  If a negative determination is made in S106, the ECU 13 returns to S104 described above and continues to execute the PM regeneration process. On the other hand, if an affirmative determination is made in S106, the ECU 13 proceeds to S107 and ends the execution of the PM regeneration process. That is, in S107, the ECU 13 controls the fuel injection valve 3 to stop post injection for PM regeneration processing.

  If a negative determination is made in S102 described above (thw <Tmp), the ECU 13 proceeds to S108. In S108, the ECU 13 compares the PM collection amount ΣPM calculated in S101 with the amount obtained by adding the correction value α to the predetermined amount A (= A + α). The correction value α is a fixed value larger than zero.

  Here, the predetermined amount A corresponds to the first predetermined amount according to the present invention, and the amount obtained by adding the correction value α to the predetermined amount A (= A + α) corresponds to the second predetermined amount according to the present invention. .

If it is determined in S108 that the PM collection amount ΣPM is less than the second predetermined amount (= A + α) (ΣPM <(A + α)), the ECU 13 ends this routine without executing the PM regeneration process. . On the other hand, when it is determined in S108 that the PM collection amount ΣPM is equal to or larger than the second predetermined amount (= A + α) (ΣPM ≧ (A + α)), the ECU 13 performs S104 to S1.
In 07, PM regeneration processing is executed.

  As described above, when the ECU 13 executes the PM regeneration control routine of FIG. 2, the acquisition means, detection means, regeneration means, and control means according to the present invention are realized. Therefore, when the state in which the operation of the internal combustion engine 1 is stopped before the temperature of the internal combustion engine 1 becomes equal to or higher than the predetermined temperature Tmp is repeated, the PM regeneration process is performed while making the regeneration interval longer than normal. become. As a result, it is possible to prevent the PM collection amount ΣPM of the particulate filter 8 from becoming excessive while reducing the opportunity for dilution of the lubricating oil.

<Example 2>
Next, a second embodiment of the present invention will be described with reference to FIG. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  In the first embodiment described above, an example in which the correction value α is a fixed value has been described, but in this embodiment, an example in which the correction value α is changed according to the temperature of the internal combustion engine 1 will be described.

  FIG. 3 is a diagram showing the relationship between the temperature (cooling water temperature) thw of the internal combustion engine 1 and the correction value α. In FIG. 3, the correction value α becomes zero when the cooling water temperature thw is equal to or higher than the predetermined temperature Tmp, but increases as the cooling water temperature thw decreases when the cooling water temperature thw is lower than the predetermined temperature Tmp. Yes.

  When the correction value α is determined in this way, when the temperature of the internal combustion engine 1 is lower than the predetermined temperature Tmp, the regeneration interval becomes longer as the temperature of the internal combustion engine 1 becomes lower.

  Here, the fuel post-injected from the fuel injection valve 3 (post-injected fuel) is more likely to adhere to the cylinder bore wall surface as the temperature of the internal combustion engine 1 becomes lower. This means that the lower the temperature of the internal combustion engine 1, the easier the dilution of the lubricating oil occurs.

  On the other hand, when the regeneration interval becomes longer as the temperature of the internal combustion engine 1 becomes lower, the PM regeneration process is performed while reducing the opportunity for dilution of the lubricating oil even when the temperature of the internal combustion engine 1 is significantly lower than the predetermined temperature Tmp. Can be performed.

<Example 3>
Next, a third embodiment of the present invention will be described with reference to FIG. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  In the first embodiment described above, an example in which the regeneration end value B is a fixed value has been described. In this embodiment, an example in which the regeneration end value B is changed according to the temperature of the internal combustion engine 1 will be described.

  FIG. 4 is a diagram showing the relationship between the temperature (cooling water temperature) thw of the internal combustion engine 1 and the regeneration end value B. In FIG. 4, the regeneration end value B becomes zero when the cooling water temperature thw is equal to or higher than the predetermined temperature Tmp, but increases as the cooling water temperature thw decreases when the cooling water temperature thw is lower than the predetermined temperature Tmp. ing.

  When the regeneration end value B is determined in this way, when the temperature of the internal combustion engine 1 is lower than the predetermined temperature Tmp, the execution period of the PM regeneration process becomes shorter as the temperature of the internal combustion engine 1 becomes lower.

Here, the post-injected fuel from the fuel injection valve 3 (post-injected fuel) is more likely to adhere to the cylinder bore wall surface as the temperature of the internal combustion engine 1 becomes lower, but when the regeneration end value B is determined as described above, Even when the temperature of the internal combustion engine 1 is significantly lower than the predetermined temperature Tmp, the PM regeneration process can be performed while suppressing dilution of the lubricating oil.

  The second embodiment described above and this embodiment may be combined. In that case, as the temperature of the internal combustion engine 1 becomes lower, the regeneration interval becomes longer and the execution period of the PM regeneration process becomes shorter. As a result, it is possible to perform the PM regeneration process while minimizing the dilution of the lubricating oil.

1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. It is a flowchart which shows PM regeneration control routine. It is a figure which shows the relationship between the temperature of an internal combustion engine, and correction value (alpha). FIG. 3 is a diagram showing the relationship between the temperature of an internal combustion engine and a regeneration end value B.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 4 ... Intake passage 7 ... Exhaust passage 8 ... Particulate filter 13 .... ECU
15 .... Water temperature sensor 16 .... Crank position sensor 17 .... Differential pressure sensor

Claims (4)

A particulate filter disposed in the exhaust passage of the internal combustion engine;
An acquisition means for acquiring the amount of PM collected by the particulate filter;
Detecting means for detecting a physical quantity correlated with the temperature of the internal combustion engine;
Regenerating means for performing PM regeneration processing for oxidizing and removing PM collected by the particulate filter by performing post injection from the fuel injection valve of the internal combustion engine;
An internal combustion engine comprising: control means for operating the regeneration means when the amount of PM collected by the obtaining means is greater than or equal to a first predetermined amount and the physical quantity detected by the detection means is greater than or equal to a predetermined temperature. In the particulate filter regeneration system of
When the PM collection amount acquired by the acquisition unit when the physical amount detected by the detection unit is less than the predetermined temperature is equal to or greater than a second predetermined amount greater than the first predetermined amount, the control unit is configured to regenerate the regeneration unit. A particulate filter regeneration system for an internal combustion engine, wherein   2. The particulate filter regeneration system for an internal combustion engine according to claim 1, wherein the second predetermined amount is increased as the physical quantity detected by the detection means indicates a lower temperature.   3. The particulate filter regeneration system for an internal combustion engine according to claim 1, wherein the control unit shortens the execution time of the PM regeneration process as the physical quantity detected by the detection unit indicates a lower temperature. 3. The control means according to claim 1 or 2, wherein the control means controls the regeneration means to end the PM regeneration process when the amount of PM collected by the obtaining means during execution of the PM regeneration process falls below a reference amount. Is what
The particulate filter regeneration system for an internal combustion engine, further comprising a correction unit that increases the reference amount as the physical quantity detected by the detection unit indicates a lower temperature.

Images