JP4356583B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a technique for appropriately controlling an internal combustion engine having a diesel particulate filter (DPF).

  In general, output control of an internal combustion engine is performed on the basis of smoke concentration (mainly concentration of particulate matter (abbreviated as PM)) in exhaust gas in consideration of recent environmental problems. That is, since the smoke density increases as the output increases, the output is controlled in a range where the smoke density is not more than a specified value.

  As a method for controlling the output in consideration of the smoke concentration, the smoke concentration in the tail pipe depends on the intake air amount of the internal combustion engine. For example, the maximum injection amount with respect to the boost pressure (intake manifold pressure) is given by a map or the like. Or, a method of correcting the basic injection amount with the supercharging pressure is common.

  On the other hand, exhaust gas discharged from a diesel engine contains a large amount of PM in addition to HC, CO, NOx and the like. Therefore, in recent years, a diesel particulate filter (abbreviated as DPF) that captures PM and burns and removes it has been put to practical use as an exhaust gas purification device for a diesel engine.

Japanese Patent Publication No. 5-34499

  However, since the DPF is a filter that captures PM and the like as described above, smoke is hardly discharged from the tail pipe in a vehicle equipped with such a DPF. Therefore, in an internal combustion engine equipped with a DPF, there is no need to limit the output reflecting the smoke concentration from the tail pipe, and it is possible to set a fuel injection amount that generates a maximum torque for a predetermined intake air amount. End up.

  However, in reality, smoke is discharged from the outlet of the internal combustion engine (engine out), and even if it is possible to set the fuel injection amount so as to generate the maximum torque, the internal combustion engine is discharged with excessive smoke. If the engine is continuously operated, the amount of accumulated PM in the DPF continues to increase, and the exhaust pressure increases due to an increase in the filter pressure loss of the DPF, resulting in a pumping loss and the like. Further, in a state where PM is excessively accumulated on the DPF, the DPF may be damaged when the PM self-ignites during high load operation or the like.

  On the other hand, even when the amount of accumulated PM in the DPF increases, the PM is burned and removed by natural regeneration of the DPF, or the PM is forcibly burned and removed (forced regeneration) by post injection or the like. However, natural regeneration cannot be expected with a diesel engine with a relatively low exhaust gas temperature, and increasing the frequency of forced regeneration causes problems such as worsening fuel consumption.

  On the other hand, when the output control is performed on the internal combustion engine equipped with the DPF based on the exhaust smoke concentration at the engine out, the above-mentioned problem due to excessive smoke discharge can be solved, but the output torque There is a problem that is suppressed.

  By the way, in the above cited reference 1, when the temperature of the DPF is higher than the temperature during normal combustion of PM, a relatively large amount of fuel is supplied to the combustion chamber, and the reaction of the oxidation catalyst provided on the upstream side of the DPF. A technique for reducing heat and preventing an abnormal temperature rise of the DPF is described.

  However, this technology only shows countermeasures when the DPF is abnormally hot, and achieves higher levels of both improving the output torque of the internal combustion engine under normal use conditions and suppressing excessive PM accumulation on the DPF. There is room for improvement from the point of view.

  The present invention has been made in view of the above situation, and relates to a fuel injection control device for an internal combustion engine, and provides a technique capable of improving the output of the internal combustion engine while suppressing excessive PM accumulation on the DPF. Objective.

A fuel injection control device for an internal combustion engine according to the present invention that solves the above problems is as follows.
Fuel injection means for supplying fuel to the internal combustion engine;
A filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in exhaust gas;
Filter state detecting means for detecting an exhaust temperature upstream of the filter and an exhaust temperature downstream of the filter;
Operating state detecting means for detecting the operating state of the internal combustion engine;
Injection control means for controlling the fuel injection means according to a target fuel injection amount equivalent value obtained from the detection output of the operating state detection means,
The injection control means increases the target fuel injection amount equivalent value on condition that the downstream exhaust temperature is equal to or higher than the first temperature and the upstream exhaust temperature is equal to or higher than the second temperature. A fuel injection control device for an internal combustion engine characterized by correcting.

  The index that correlates with the ability of the filter to burn and remove particulates is, for example, the DPF temperature (exhaust gas temperature) that determines the ability of the DPF to burn and remove PM, the oxygen concentration in the exhaust gas, and the like. Based on these indices, when the DPF has an excess PM removal capability, the fuel injection amount is not limited to the target fuel injection amount, but is increased and corrected to improve the output.

  The filter state is grasped from the exhaust gas temperature passing through the DPF, and an accurate determination of the increase correction is made.

In the fuel injection control device for an internal combustion engine,
Upper Symbol injection control means is a fuel injection control device for an internal combustion engine and performs increase correction in accordance with the exhaust temperature of the exhaust gas temperature and the upstream side of the downstream side.

  A DPF having a predetermined length in the exhaust gas flow direction may have a non-uniform temperature inside. Further, the PM removal capability of the DPF depends on the DPF temperature. Therefore, by performing an increase correction in accordance with the downstream exhaust temperature and the upstream exhaust temperature, the filter state is accurately grasped, and an accurate increase correction is performed.

In the fuel injection control device for an internal combustion engine,
The target fuel injection amount equivalent value is a fuel injection control device for an internal combustion engine, wherein the smoke concentration discharged from the internal combustion engine is limited to a predetermined concentration or less.

  Due to problems such as legal restrictions and the appearance of exhaust gas during vehicle travel, the smoke concentration in the exhaust gas may be provided with a predetermined regulation value. If the fuel injection control is performed according to this regulation value in all operating states, there is a problem that sufficient engine output cannot be obtained. Therefore, the engine output is improved by effectively utilizing the excess PM removal capability of the DPF.

In the fuel injection control device for an internal combustion engine,
The injection control means sets the target fuel injection amount equivalent value within a limit range corresponding to the boost pressure of the internal combustion engine, and exceeds the limit based on the detection output of the filter state detection means. A fuel injection control device for an internal combustion engine, wherein an injection amount equivalent value is corrected by increasing.

  The engine output can be improved by utilizing the PM purification ability of the DPF while appropriately suppressing smoke discharged from the internal combustion engine.

According to the fuel injection control device for an internal combustion engine according to the present invention, a fuel injection means for supplying fuel to the internal combustion engine, a filter provided in the exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust gas, A filter state detecting means for detecting an exhaust temperature upstream of the filter and an exhaust temperature downstream of the filter; an operating state detecting means for detecting an operating state of the internal combustion engine; and a detection by the operating state detecting means Injection control means for controlling the fuel injection means in accordance with a target fuel injection amount equivalent value obtained from the output, wherein the injection control means has the downstream exhaust gas temperature equal to or higher than a first temperature, and it on condition exhaust gas temperature on the upstream side is a second temperature above, since it was decided to increase correction of the target fuel injection amount corresponding value, the fuel injection amount in accordance with the PM removal capability of the filter It can be increased, thereby improving the output torque of the internal combustion engine while suppressing excessive accumulation of PM on the filter. Further, it is possible to accurately detect the situation where PM is stably burned and removed by the filter, and it is possible to prevent the PM from being excessively deposited on the filter due to an increase in the fuel injection amount in a situation where combustion removal is uncertain. .

Further, in the fuel injection control apparatus for an internal combustion engine, the upper Symbol injection control means, since to carry out the increment correction in accordance with the exhaust temperature of the exhaust gas temperature and the upstream side of the downstream, PM removal filter It is possible to achieve fuel increase correction that accurately corresponds to the capacity, and to efficiently improve the output torque of the internal combustion engine.

In the fuel injection control device for an internal combustion engine,
The target fuel injection amount equivalent value is limited so that the smoke concentration discharged from the internal combustion engine is not more than a predetermined concentration.
It is possible to improve the engine output by effectively utilizing the excess PM removal ability of the DPF by eliminating the output shortage caused by performing the fuel injection control in consideration of the smoke concentration in all operating states. .

In the fuel injection control device for an internal combustion engine,
The injection control means sets the target fuel injection amount equivalent value within a limit range corresponding to the boost pressure of the internal combustion engine, and exceeds the limit based on the detection output of the filter state detection means. Since we decided to correct the injection amount equivalent value,
The engine output can be improved efficiently while appropriately suppressing the smoke discharged from the internal combustion engine.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. However, the following embodiments do not limit the present invention. FIG. 1 is a schematic configuration diagram showing a fuel injection control device for an internal combustion engine according to an embodiment of the present invention.

  As shown in FIG. 1, an engine 1 that is an internal combustion engine is, for example, a common rail in-line four-cylinder diesel engine. In the common rail type engine 1, an electromagnetic fuel injection nozzle 3 (fuel injection means) is provided in each cylinder facing the combustion chamber 2, and each fuel injection nozzle 3 is connected to a common rail 5 by a high-pressure pipe 4. Yes. The common rail 5 is connected to the fuel tank 8 via a high-pressure pipe 6 in which a high-pressure pump 7 is interposed. Since engine 1 is a diesel engine, light oil is used as the fuel.

  An electromagnetic intake throttle valve 10 is provided in the intake passage 9 of the engine 1. An EGR passage 13 extends from the upstream portion of the exhaust passage 12, and the end of the EGR passage 13 is connected to a portion of the intake passage 9 downstream of the intake throttle valve 10. An electromagnetic EGR valve 14 is interposed in the EGR passage 13.

Further, an exhaust purification device is interposed in the downstream portion of the exhaust passage 12. The exhaust emission control device is configured by providing an oxidation catalyst (DOC) 20 upstream of a diesel particulate filter (DPF) 21. The exhaust purification device is configured to generate an oxidant (NO ₂ ) in the oxidation catalyst 20 and continuously oxidize and remove particulate matter (PM) deposited on the downstream DPF 21 by the generated oxidant. ing.

On the input side (operating state detection means) of the electronic controller (ECU) 15 are an airflow sensor 11 for detecting the intake air amount Qa, a pre-DFF temperature sensor 23a for detecting the temperature of the exhaust gas upstream and downstream of the DPF 21, and DPF post-temperature sensor 23b (filter state detecting means), accelerator pedal 16 depression amount, that is, accelerator opening sensor 17 for detecting accelerator opening APs, sensor for detecting engine 1 rotational speed Ne, intake manifold pressure P _B And various devices such as the fuel injection nozzle 3, the high pressure pump 7, the intake throttle valve 10, and the EGR valve 14 are connected to the output side.

  Thereby, various devices are controlled based on various input information, and the engine 1 is appropriately controlled. The fuel injection control device for an internal combustion engine according to the present embodiment has a function of controlling the target fuel injection amount of the fuel injection nozzle 3 based on the operating state of the engine 1, and the temperature of the DPF 21 is less than a predetermined temperature. In this case, the target fuel injection amount is limitedly controlled so that the smoke concentration discharged from the engine 1 is equal to or lower than the predetermined concentration. When the temperature of the DPF 21 is equal to or higher than the predetermined temperature, the target fuel injection amount is determined according to the temperature of the DPF 21. The fuel injection amount is corrected to increase.

  The control of the target fuel injection amount is divided depending on whether the DPF 21 is lower than the predetermined temperature or higher than the predetermined temperature. The predetermined temperature set here is an index corresponding to the ability of the DPF 21 to burn and remove the PM deposited thereon. It is an example. That is, although the PM removal capability of the DPF 21 depends on the temperature of the DPF 21, for example, the temperature at which the DPF 21 is in a filter state that allows the DPF 21 to continue to completely remove the PM accumulated with the operation of the engine 1 (continuous regeneration). The lower limit value is set as the predetermined temperature.

  In this case, the target fuel injection amount is limited so that the smoke concentration is equal to or lower than the predetermined concentration under the condition that the DPF 21 is lower than the predetermined temperature and PM is not completely removed and PM accumulates in the DPF 21. By controlling the control, smoke emission is suppressed and the problem of PM accumulation in the DPF 21 is solved.

  On the other hand, when the DPF 21 is at a predetermined temperature or higher and the DPF 21 can be continuously regenerated, the output of the engine 1 is improved by making use of the excess PM removal capability of the DPF 21 by increasing the target fuel injection amount. Can do. When the temperature is equal to or higher than the predetermined temperature, the DPF 21 has the ability to remove the PM amount further exceeding the exhausted PM amount determined by the target fuel injection amount. Even if the injection amount is increased to increase the smoke concentration, the DPF 21 Processed and will not break smoke regulations. Therefore, by controlling in this way, the output of the engine 1 can be improved while suppressing smoke discharge.

  FIG. 2 is a graph showing the relationship between the DPF temperature and the change with time in the differential pressure across the DPF, obtained from the test. In the figure, the vertical axis represents the differential pressure between the exhaust gas pressure upstream of the DPF and the downstream exhaust gas pressure (unit: KPa), and the horizontal axis represents time (unit: seconds). The time-dependent change in the differential pressure across the DPF when 20% exhaust gas is discharged is shown for DPF temperatures of 426 ° C., 556 ° C., and 647 ° C.

  Note that the DPF is a filter having a predetermined length in the exhaust gas flow direction, and there are cases where the temperature on the DPF inlet side and the temperature on the DPF outlet side are different. The test was conducted with the same inlet temperature and outlet temperature.

  As shown in the figure, it can be seen that when the temperature of the DPF is 426 ° C., the differential pressure across the DPF increases with time. This is because since the temperature of the DPF is relatively low, PM having a concentration of 20% contained in the exhaust gas cannot be completely removed by combustion, and PM continues to accumulate in the DPF. Since this PM deposition degree is remarkable, it is thought that a differential pressure rises notably.

  On the other hand, when the temperature of the DPF is 556 ° C. and 647 ° C., it can be seen that the differential pressure across the DPF is stable. This is because the temperature of the DPF is relatively high, so that the 20% concentration PM contained in the exhaust gas can be completely burned and removed, and at the same time the PM flows into the DPF, it is burned off or This is because even when PM is deposited in the DPF, it is not excessively deposited and does not affect the differential pressure across the DPF.

  FIG. 3 is a graph showing the PM accumulation amount in the DPF from the relationship between the smoke concentration discharged from the engine and the temperature of the DPF. In the figure, the vertical axis represents smoke concentration in exhaust gas exhausted from the engine (unit:%), and the horizontal axis represents DPF temperature (unit: ° C). The amount of PM (unit: g / h) is plotted. Similarly to FIG. 2, the test was performed with the DPF inlet temperature and outlet temperature being the same by setting the operation state to a steady state.

  An example of how to view FIG. 3 shows that when the temperature of the DPF is 650 ° C., for example, when exhaust gas having a smoke concentration of 20% is introduced, the inflow amount of PM is equal to the combustion removal amount in the DPF, so the deposition rate is 0 g. When exhaust gas having a smoke concentration of 35% is introduced, the inflow amount of PM is larger than the combustion removal amount in the DPF, the deposition rate is 10 g / h, and the exhaust gas having a smoke concentration of less than 20% When it is made to flow, it can be seen that the inflow amount of PM is smaller than the combustion removal amount in the DPF, the deposition rate is 0 g / h, and it has an excess PM removal capability (continuous regeneration region).

  Further, when exhaust gas having a smoke concentration of 20% is caused to flow into the DPF, if the temperature of the DPF is 650 ° C., the inflow amount of PM is equal to the combustion removal amount in the DPF, so the deposition rate is 0 g / h. When the temperature of the DPF is 575 ° C., the amount of inflow of PM is larger than the amount of combustion removal in the DPF, the deposition rate is 10 g / h, and when the temperature of the DPF is higher than 650 ° C., the amount of inflow of PM is It can be seen that it is less than the amount of combustion removal in the DPF, the deposition rate is 0 g / h, and has an excess PM removal capability (continuous regeneration region).

  Particularly useful from FIG. 3 is that the inflow of PM and the amount of combustion removal in the DPF are equal and the region below the condition where the PM deposition rate is 0 g / h (continuous regeneration region), that is, the DPF. Has a PM removal capability, and even if the engine output is increased to increase the smoke concentration, there is an area where the smoke regulation can be cleared while solving the problem caused by PM accumulation in the DPF. is there.

  In addition, the PM inflow rate is larger than the combustion removal amount in the DPF, and the deposition rate is such that it does not affect the differential pressure across the DPF even under conditions where the PM deposition rate is several g / h. If so, there is an area where smoke regulation can be cleared while solving the problem caused by PM accumulation in the DPF even if the engine output is further increased to increase the smoke concentration.

  In this embodiment, this beneficial region is used to perform control for improving the output of the internal combustion engine while suppressing excessive accumulation of PM on the DPF. FIG. 4 is a diagram illustrating a control method in the fuel injection control device for the internal combustion engine according to the present embodiment.

As shown in the figure, the basic fuel injection amount Q _B is obtained from the accelerator opening APs and the engine speed Ne (reference number 31), and the intake manifold boost pressure P _B and the engine speed Ne are used to determine the smoke concentration. The fuel injection amount Q _SMOKE by regulation is obtained (reference numeral 32), and the minimum value is selected from these injection quantities to be the injection quantity Q ₀ (reference numeral 33).

That is, when the engine 1 is operated with the basic fuel injection amount Q _B , the smoke concentration discharged from the engine 1 may be higher than a predetermined concentration, so the fuel injection obtained from the map of the supercharging pressure P _B and the rotational speed Ne. Volume Q Regulated by _SMOKE . The control method for the internal combustion engine based on the injection amount Q ₀ obtained in this way is a conventional output control method considering the smoke concentration.

In the present embodiment, when the temperature of the DPF 21 is lower than the predetermined temperature, the engine 1 is controlled based on the injection amount Q ₀ , while when the temperature of the DPF 21 is equal to or higher than the predetermined temperature, the injection amount Q ₀ is set. On the other hand, the engine 1 is controlled by performing an increase correction (reference numeral 34) according to the DPF temperature.

The increase correction of the injection amount Q ₀ corresponding to the temperature of the DPF 21 is performed as follows. Basically, the increase correction is performed based on the outlet side temperature (reference numeral 35) of the DPF 21 detected by the sensor 23b (reference numeral 34). That is, when the DPF outlet temperature reaches a temperature at which PM can be burned and removed, the injection amount Q ₀ is corrected to increase according to the temperature to obtain the injection amount Q _F.

  This is because when the DPF outlet temperature is high, the DPF inlet temperature is also generally high, and the entire DPF 21 is in a filter state suitable for burning and removing PM. On the other hand, even if the inlet temperature is high, the outlet temperature may be low. In this case, PM may not be removed at the low temperature portion of the DPF 21.

As an auxiliary control, correction is performed based on the inlet side temperature (reference numeral 36) of the DPF 21 detected by the sensor 23a (reference numeral 34). This is because even if the DPF outlet temperature is high, the inlet temperature may be low. Such a filter state is not a filter state suitable for the entire DPF 21 to burn and remove PM. Therefore, the increase correction performed according to the outlet temperature is canceled, and the injection amount as the corrected injection amount Q _F is cancelled. Q ₀ is given.

  A specific increase correction will be described. For example, when the temperature of the DPF 21 is 680 ° C. (both the outlet temperature and the inlet temperature), the conventional smoke concentration is controlled with respect to the allowable smoke concentration of 30% (PM deposition rate is 0 g / h). Control was performed at an allowable smoke concentration or less, for example, a smoke concentration of 15%. Accordingly, the engine output is increased by correcting the fuel injection amount to increase from 15% to 30%.

  In the case described above, the allowable smoke concentration may be 30% or more within a range of the deposition rate that does not affect the differential pressure across the DPF 21. In this case, the engine output can be further improved.

In the above-described embodiment, the fuel control is performed based on the injection amount Q _F obtained by performing the correction by the temperature of the DPF 21 with respect to the injection amount Q ₀ subjected to the smoke restriction process. it may be a fuel control directly based on the minimum value of the injection quantity and the basic fuel injection amount Q _B which was corrected by the temperature with respect to smoke concentration regulation injection amount Q _sMOKE.

1 is a schematic configuration diagram showing a fuel injection control device for an internal combustion engine according to an embodiment of the present invention. It is a graph which shows the relationship between the temperature of DPF obtained with the test, and the time-dependent change of DPF front-back differential pressure. It is the graph shown from the relationship between the smoke density | concentration discharged | emitted from an engine, and the temperature of DPF about PM deposition amount in DPF. It is a figure which shows the control method in the fuel-injection control apparatus of the internal combustion engine which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diesel engine 2 Combustion chamber 3 Fuel injection nozzle 4 High pressure pipe 5 Common rail 6 High pressure pipe 7 High pressure pump 8 Fuel tank 9 Intake passage 10 Intake throttle valve 11 Air flow sensor 12 Exhaust passage 13 EGR passage 14 EGR valve 15 Electronic controller (ECU)
16 Accelerator pedal 17 Accelerator opening sensor 20 Oxidation catalyst (DOC)
21 Diesel particulate filter (DPF)
23a Temperature sensor before DPF 23b Temperature sensor after DPF 31 Basic fuel injection amount Q _B
32 Fuel injection quantity due to smoke concentration regulation Q _SMOKE
33 correction by the correction 36 DPF inlet temperature due to the correction 35 DPF outlet temperature by DPF temperature determination 34 injection amount Q ₀ of the injection quantity Q ₀

Claims (4)

Fuel injection means for supplying fuel to the internal combustion engine;
A filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in exhaust gas;
Filter state detecting means for detecting an exhaust temperature upstream of the filter and an exhaust temperature downstream of the filter;
Operating state detecting means for detecting the operating state of the internal combustion engine;
Injection control means for controlling the fuel injection means according to a target fuel injection amount equivalent value obtained from the detection output of the operating state detection means,
The injection control means increases the target fuel injection amount equivalent value on condition that the downstream exhaust temperature is equal to or higher than the first temperature and the upstream exhaust temperature is equal to or higher than the second temperature. A fuel injection control device for an internal combustion engine characterized by correcting. The fuel injection control device for an internal combustion engine according to claim 1,
Upper Symbol injection control means, fuel injection control device for an internal combustion engine and performs increase correction in accordance with the exhaust temperature of the exhaust gas temperature and the upstream side of the downstream side. The fuel injection control device for an internal combustion engine according to claim 1 or 2 ,
The fuel injection control device for an internal combustion engine, wherein the target fuel injection amount equivalent value is limited so that a smoke concentration discharged from the internal combustion engine is a predetermined concentration or less. The fuel injection control device for an internal combustion engine according to claim 1,
The injection control means sets the target fuel injection amount equivalent value within a limit range corresponding to the boost pressure of the internal combustion engine, and exceeds the limit based on the detection output of the filter state detection means. A fuel injection control device for an internal combustion engine, wherein an injection amount equivalent value is corrected to increase.

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