JP6094735B2 - Engine fuel injection control device - Google Patents

Description

  The present invention relates to an engine fuel injection control device including an exhaust gas recirculation device that recirculates a part of engine exhaust gas to intake air.

  As a technique for reducing nitrogen oxide (NOx) contained in the exhaust gas of an engine (internal combustion engine), an exhaust circulation device (exhaust gas recirculation device) that introduces a part of the exhaust gas into the intake passage as exhaust gas circulation gas is known. ing. The introduction of the exhaust gas is appropriately performed according to the operating state of the engine. For example, during high load operation (for example, during acceleration of high load and high acceleration), a large amount of air must be introduced into the combustion chamber. Since smoke may be deteriorated, it is generally stopped during that time. However, even if the introduction of the exhaust gas is stopped, the exhaust gas remains in the intake passage for a while. In particular, when the exhaust circulation passage connecting the exhaust passage and the intake passage is relatively long, the exhaust circulation gas tends to remain in the intake passage. For this reason, smoke may increase with an increase in the fuel injection amount during a period in which the exhaust gas circulates during high load operation.

  In order to solve such a problem, for example, there is one in which the fuel injection amount is limited based on the amount of oxygen contained in the intake gas (see, for example, Patent Document 1). By limiting the fuel injection amount in this way, it is possible to suppress an increase in smoke.

JP 2006-249972 A

  However, if the fuel injection amount is limited, there is a possibility that a desired torque cannot be generated. In particular, during high-load operation, it is difficult to generate torque required by the driver, and drivability may be reduced.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fuel injection control device for an engine that can generate a desired torque and can also suppress the occurrence of smoke.

According to a first aspect of the present invention for solving the above problems, an exhaust circulation control means for introducing an exhaust circulation gas from an exhaust passage of an engine into an intake passage through an exhaust circulation passage, and an exhaust circulation gas remaining in the intake passage. And an injection control means for controlling fuel injection from the fuel injection valve. The injection control means is configured so that the engine is in a high load state and the exhaust circulation control means causes the exhaust circulation gas to be exhausted. When the introduction of the exhaust gas is stopped, the total amount of fuel injected from the fuel injection valve in one cycle in the exhaust gas circulation gas remaining period in which the exhaust gas circulation gas is detected by the exhaust gas detection means is the intake passage. wherein limiting the injection quantity due to the pre-injection before the main injection as a constant exhaust circulating gas remains in the normal operation period is a period that does not remain within, at the pre-injection Certain limited been injection amount to the fuel injection control apparatus for an engine, wherein the supplement in the main injection.

According to a second aspect of the present invention, in the fuel injection control device for an engine according to the first aspect, the injection control means stops the pre-injection and injects a predetermined amount of fuel only by the main injection. The fuel injection control device for the engine is characterized.

According to a third aspect of the present invention, in the fuel injection control device for an engine according to the first or second aspect, the injection control means is configured to adjust the pre-circulation gas according to a detection amount of the exhaust circulation gas by the exhaust circulation gas detection means. An engine fuel injection control device is characterized in that the injection amount by injection is changed.

  According to the fuel injection control device of the present invention, it is possible to generate the torque required by the driver even during the exhaust circulation gas remaining period, and to suppress the generation of smoke.

It is a schematic structure figure showing an engine concerning one embodiment of the present invention. It is a figure which shows an example of the aspect of the fuel injection which concerns on one Embodiment of this invention. It is a flowchart of the fuel injection control which concerns on one Embodiment of this invention. It is the schematic which shows the other example of the aspect of the fuel injection which concerns on one Embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  An engine 10 according to this embodiment shown in FIG. 1 is an in-line 4-cylinder diesel engine including four cylinders (combustion chambers) 11 arranged in series. An intake manifold 12 is connected to an intake port (not shown) of each cylinder 11, and an intake pipe (intake passage) 13 is connected to the intake manifold 12. On the other hand, an exhaust manifold 14 is connected to an exhaust port (not shown) of each cylinder 11, and an exhaust pipe (exhaust passage) 15 is connected to the exhaust manifold 14.

  An injector (fuel injection valve) 16 for injecting fuel is provided corresponding to each cylinder 11 and is connected to a common rail 17. The common rail 17 is connected to a fuel tank via a supply pump (high pressure pump) (not shown). Fuel is pumped from the fuel tank by this supply pump, and high-pressure fuel in the common rail 17 is injected into each cylinder 11 from the injector 16.

  A turbocharger (supercharging means) 18 is provided in the middle of the intake pipe 13 and the exhaust pipe 15. In the turbocharger 18, when exhaust gas flows from the exhaust pipe 15, the turbine is rotated by the flow of exhaust gas. As the turbine rotates, the compressor rotates, and air is sucked into the turbocharger 18 from the intake pipe 13 and pressurized.

  An air cleaner 19, an air flow sensor 20, and a first throttle valve 21 are provided in the intake pipe 13 on the upstream side of the turbocharger 18. The first throttle valve 21 adjusts the amount of fresh air (fresh air amount) that has passed through the air cleaner 19, and through this adjustment, the intake pipe 13 passes through a low-pressure exhaust circulation pipe (low-pressure exhaust circulation passage) described later. The amount of exhaust gas recirculated to the exhaust gas (low-pressure exhaust gas circulation amount) is indirectly adjusted.

  In the intake pipe 13 on the downstream side of the turbocharger 18, an intercooler 22 that cools intake air whose temperature has increased due to pressurization by the turbocharger 18 is disposed. The intake pipe 13 on the downstream side of the intercooler 22 is provided with a second throttle valve 23 that opens and closes the intake pipe 13 by driving an electric actuator.

  The second throttle valve 23 adjusts the intake air amount (fresh air amount + low pressure exhaust gas circulation amount) that has passed through the intercooler 22 and is introduced into the intake pipe 13 through the high pressure exhaust gas circulation tube described later by this adjustment. The amount of exhaust gas (high-pressure exhaust gas circulation) is adjusted indirectly.

  One end of a high-pressure exhaust circulation pipe 24 through which high-pressure exhaust gas (high-pressure exhaust circulation gas) circulates is connected to the intake pipe 13 downstream of the second throttle valve 23. The other end of the high pressure exhaust circulation pipe 24 is connected to the upstream side of the turbocharger 18 of the exhaust pipe 15. A high-pressure exhaust circulation cooler 25 is provided in the high-pressure exhaust circulation pipe 24, and a high-pressure exhaust circulation valve 26 is provided in a connection portion of the high-pressure exhaust circulation pipe 24 with the intake pipe 13. When the high-pressure exhaust circulation valve 26 is opened, a part of the high-pressure exhaust gas flowing upstream from the turbocharger 18 of the exhaust pipe 15 flows into the high-pressure exhaust circulation pipe 24 and is cooled by the high-pressure exhaust circulation cooler 25. After that, it is introduced into the intake pipe 13.

  A linear air-fuel ratio sensor (LAFS) 27 for detecting the air-fuel ratio of the intake gas is provided downstream of the high-pressure exhaust circulation pipe 24 of the intake pipe 13. The LAFS 27 also functions as exhaust circulation gas detection means for detecting exhaust circulation gas in the intake pipe 13. The intake manifold 12 is provided with a boost pressure sensor 28 that detects the pressure inside the intake manifold 12.

Further, on the downstream side of the turbocharger 18 of the exhaust pipe 15, a diesel oxidation catalyst (hereinafter simply referred to as “oxidation catalyst”) 31 that is an exhaust purification catalyst and a diesel particulate filter (diesel particulates) that is an exhaust purification filter. A collection filter: Diesel Particulate Filter (hereinafter referred to as “diesel particulate collection filter”) 32 is disposed in order from the upstream side. When the exhaust gas flows into the oxidation catalyst 31, nitrogen monoxide (NO) in the exhaust gas is oxidized and nitrogen dioxide (NO ₂ ) is generated. Further, particulate matter (PM) in the exhaust gas is collected by the diesel particulate collection filter 32.

The PM collected by the diesel particulate collection filter 32 is oxidized (combusted) by NO ₂ in the exhaust gas and discharged as CO ₂ , and the NO ₂ remaining in the diesel particulate collection filter 32 is decomposed into N _2. Discharged. That is, the exhaust gas is purified by the oxidation catalyst 31 and the diesel particulate filter 32, and the PM and NOx emissions can be greatly reduced.

  Further, on the downstream side of the turbocharger 18 of the exhaust pipe 15, that is, on the downstream side of the diesel particulate filter 32 in this embodiment, a low-pressure exhaust circulation pipe 33 in which a part of the low-pressure exhaust gas (low-pressure exhaust circulation gas) circulates. One end is connected. The other end of the low-pressure exhaust circulation pipe 33 is connected to the intake pipe 13 between the turbocharger 18 and the first throttle valve 21. As in the case of the high pressure exhaust circulation pipe 24, the low pressure exhaust circulation pipe 33 is provided with a low pressure exhaust circulation cooler 34 and a low pressure exhaust circulation valve 35. When the low-pressure exhaust circulation valve 35 is opened, a part of the low-pressure exhaust gas (low-pressure exhaust circulation gas) flowing downstream from the turbocharger 18 of the exhaust pipe 15 is cooled by the low-pressure exhaust circulation cooler 34 and is taken into the intake pipe. 13 is introduced.

  Note that differential pressure sensors 36 are provided at both ends of the low-pressure exhaust circulation pipe 33. The differential pressure sensor 36 detects the differential pressure between the pressure upstream of the turbocharger 18 in the intake pipe 13 and the pressure downstream of the turbocharger 18 in the exhaust pipe 15. That is, the flow rate and flow rate of the low-pressure exhaust gas circulating through the low-pressure exhaust gas circulation pipe 33 are obtained from the detection result of the differential pressure sensor 36.

  Such an engine 10 is controlled by an ECU (electronic control unit) 40. The ECU 40 includes an input / output device, a storage device (ROM, RAM, etc.), a central processing unit (CPU), a timer counter, and the like, and performs overall control of the engine 10 based on signals from the various sensors described above.

  Various sensors such as a crank angle sensor for detecting the crank angle of the engine 10 are connected to the input side of the ECU 40 in addition to the air flow sensor 20, the LAFS 27, the boost pressure sensor 28, and the differential pressure sensor 36 described above. Detection information from the sensors is input. On the other hand, various output devices such as the injector 16, the first and second throttle valves 21, 23, the high pressure exhaust circulation valve 26, and the low pressure exhaust circulation valve 35 are connected to the output side of the ECU 40. These various output devices output various information such as the fuel injection amount and valve opening calculated by the ECU 40 based on the detection information detected by the various sensors as described above. The engine fuel injection control apparatus according to the present embodiment includes such an ECU 40 and various sensors including LAFS 28 as exhaust circulation gas detection means.

  The ECU 40 constituting the fuel injection control device includes an exhaust circulation control means 41 and an injection control means 42. The exhaust circulation control means 41 introduces exhaust circulation gas from the exhaust passage to the intake passage through the exhaust circulation passage according to the operating state of the engine. For example, in this embodiment, the exhaust circulation control means 41 controls the opening and closing of the high pressure exhaust circulation valve 26 to introduce the high pressure exhaust gas into the intake pipe 13 via the high pressure exhaust circulation pipe 24 at a predetermined timing. In addition, the opening and closing of the low-pressure exhaust circulation valve 35 is controlled to introduce the low-pressure exhaust circulation gas into the intake pipe 13 through the low-pressure exhaust circulation pipe 33 at a predetermined timing.

  The injection control means 42 controls the fuel injection from each fuel injection valve 16 based on, for example, the engine speed (Ne) of the engine 10 and a load (intake amount, etc.). In addition, the injection control means 42 performs one cycle from the fuel injection valve 16 during the exhaust circulation gas remaining period in which the exhaust circulation gas is detected when the engine 10 is in a high load state and the introduction of the exhaust circulation gas is stopped. The injection amount by the pre-injection before the main injection is limited with the total fuel amount to be injected constant. In the present embodiment, when the high-pressure exhaust circulation valve 26 and the low-pressure exhaust circulation valve 35 are fully closed and the introduction of the high-pressure exhaust circulation gas and the low-pressure exhaust circulation gas is stopped, the injection control means 42 performs the pre-injection as described above. The injection amount from the fuel injection valve 16 is limited.

  Specifically, during the period when the introduction of the exhaust gas circulation is stopped but the exhaust gas does not remain in the intake pipe 13 (normal operation period), the injection control means 42 responds to the requested torque. As shown in FIG. 2, as the fuel injection by the fuel injection valve 16, the main injection Ma and the pre-injection Pu that is the injection before the main injection Ma are performed as necessary (normal control).

  The total amount of fuel injected during one cycle from the fuel injection valve 16 is the sum of the injection amount by the pre-injection Pu and the injection amount by the main injection Ma. For example, when the injection amount by the main injection Ma is 90 and the injection amount by the pre-injection Pu is 10, the total fuel amount is 100.

  In the normal operation period, by performing the pre-injection Pu together with the main injection Ma in this way, it is possible to improve the ignition performance and generate the torque requested by the driver while suppressing, for example, combustion noise. . Usually, the pre-injection Pu tends to increase the smoke while relaxing the combustion noise. This is because after the pre-injection spray burns, the combustion is continued by the main injection spray in an oxygen-deficient atmosphere. However, when the exhaust gas does not remain, necessary and sufficient oxygen can be ensured, so that the combustion temperature becomes sufficiently high and the generation of smoke is suppressed.

  In contrast, when the introduction of the low-pressure exhaust gas is stopped and the exhaust gas remains in the intake pipe 13 (exhaust gas remaining period), the same torque request as that in the normal operation period occurs. In addition, as shown in FIG. 2, the injection control means 42 stops the pre-injection Pu, sets the injection amount by the pre-injection Pu to 0, and sets the injection amount by the main injection Ma to 100. That is, although the injection amount by the pre-injection Pu is limited, the control (pre-injection restriction control) is executed to maintain the total injection amount as 100 by supplementing the limited injection amount with the main injection Ma.

  When the above-described normal control is executed during the exhaust gas remaining period, the torque required by the driver can be generated, but the combustion temperature does not rise sufficiently and the amount of smoke increases. On the other hand, by executing the pre-injection restriction control, the torque required by the driver can be generated even during the remaining period of the exhaust gas circulation, and the occurrence of smoke is suppressed by eliminating the pre-injection Pu. You can also

  Hereinafter, the injection control of the fuel injection valve according to the present embodiment will be further described with reference to the flowchart of FIG.

  When the engine 10 is in a high load state and the exhaust circulation control means 41 closes the high pressure exhaust circulation valve 26 and the low pressure exhaust circulation valve 35 (step S1: Yes), the injection control means 42 then starts from, for example, the LAFS 28. Based on the information, the presence / absence of the exhaust circulation gas in the intake pipe 13 is detected (step S2). That is, in the present embodiment, the presence or absence of the exhaust circulation gas is detected based on the oxygen concentration of the intake air flowing in the intake pipe 13. If no exhaust gas circulation is detected from the intake pipe 13 (step S2: Yes), the process proceeds to step S3. In step S3, the injection control means 42 performs the normal control described above. The injection control means 42 controls the fuel injection valve 16 with reference to a normal control map, for example. On the other hand, when exhaust circulation gas is detected from the intake pipe 13 in step S2 (step S2: No), the process proceeds to step S4. In step S4, the injection control means 42 performs the pre-injection restriction control described above. The injection control means 42 controls the fuel injection valve 16 with reference to a map for pre-injection control control, for example. Thereafter, when no exhaust gas is detected from the intake pipe 13 (step S2: Yes), the process proceeds to step S3 and normal control is executed. Thereafter, when the exhaust circulation control means 41 opens the high-pressure exhaust circulation valve 26 and the low-pressure exhaust circulation valve 35 according to the operating state of the engine 10 (step S5: Yes), a series of processing ends.

  As described above, in the present invention, the introduction of the exhaust gas to the intake pipe 13 is stopped, but in the exhaust gas circulation period in which the exhaust gas remains in the intake pipe 13, one cycle from the fuel injection valve 16. The total amount of fuel injected into the inside is constant, and the injection amount by the pre-injection Pu is limited. As a result, it is possible to suppress the occurrence of smoke while generating the torque required by the driver regardless of whether it is the normal operation period or the exhaust circulation gas remaining period. While pre-injection restriction control is being performed (exhaust gas circulation remaining period), there is a risk that the combustion noise will temporarily increase slightly. However, since the exhaust gas does not remain, the control is switched to normal control. The loudness is kept within an acceptable range.

  Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment.

  For example, in the above-described pre-injection restriction control, the injection amount by the pre-injection Pu is set to 0 in the exhaust gas remaining period, but the fuel amount to be restricted by the pre-injection Pu may be determined as appropriate. For example, as shown in FIG. 4, when the injection amount by the pre-injection Pu in the normal operation period is 10, and the injection amount by the main injection Ma is 90, the injection amount by the pre-injection Pu in the exhaust circulation gas remaining period is 5, the injection amount by the main injection Ma may be 95.

  Further, the amount of fuel limited by the pre-injection Pu during the exhaust gas circulation remaining period may be a fixed value, but the amount of exhaust gas remaining in the intake pipe 13 is obtained based on the detection result of the LAFS 28, and the amount of exhaust gas remaining It may be changed appropriately according to the above. Specifically, the amount of fuel limited by the pre-injection Pu is increased as the amount of exhaust gas circulation increases. Thereby, generation | occurrence | production of smoke can be suppressed more effectively.

  In the present embodiment, the example in which the pre-injection Pu and the main injection Ma are performed as the fuel injection by the fuel injection valve 16 has been described. For example, the post-injection is performed at a timing at which combustion can be continued after the main injection Ma. May be implemented. In this case, the total injection amount may be made constant by supplementing the injection amount limited by the pre-injection Pu with the main injection and the post-injection during the exhaust gas circulation remaining period.

DESCRIPTION OF SYMBOLS 10 Engine 11 Cylinder 12 Intake manifold 13 Intake pipe 14 Exhaust manifold 15 Exhaust pipe 16 Injector (fuel injection valve)
DESCRIPTION OF SYMBOLS 17 Common rail 18 Turbocharger 19 Air cleaner 20 Air flow sensor 21 1st throttle valve 22 Intercooler 23 2nd throttle valve 24 High pressure exhaust circulation pipe 25 High pressure exhaust circulation cooler 26 High pressure exhaust circulation valve 27 Linear air-fuel ratio sensor (LAFS)
28 Boost pressure sensor 31 Oxidation catalyst 32 Diesel particulate collection filter 33 Low pressure exhaust circulation pipe 34 Low pressure exhaust circulation cooler 35 Low pressure exhaust circulation valve 36 Differential pressure sensor 40 ECU
41 Exhaust circulation control means 42 Injection control means

Claims (3)

Exhaust circulation control means for introducing exhaust circulation gas from the exhaust passage of the engine to the intake passage through the exhaust circulation passage;
Exhaust gas detection means for detecting the exhaust gas remaining in the intake passage;
Injection control means for controlling fuel injection from the fuel injection valve;
With
The injection control means is configured such that when the engine is in a high load state and the introduction of the exhaust gas is stopped by the exhaust gas control means, the exhaust gas remaining is detected by the exhaust gas detection means. During the period, the total amount of fuel injected from the fuel injection valve during one cycle is kept constant in the normal operation period in which the exhaust gas circulation gas does not remain in the intake passage. Limit the injection amount ,
A fuel injection control device for an engine, characterized in that the injection amount limited by the pre-injection is supplemented by the main injection . The engine fuel injection control apparatus according to claim 1 ,
The fuel injection control device for an engine, wherein the injection control means stops the pre-injection and injects a predetermined amount of fuel only by the main injection. The engine fuel injection control device according to claim 1 or 2 ,
The engine fuel injection control device according to claim 1, wherein the injection control means changes an injection amount by the pre-injection in accordance with a detected amount of the exhaust circulation gas by the exhaust circulation gas detection means.

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