JP5304402B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine.

  Conventionally, for example, Patent Document 1 discloses an exhaust fuel addition control device for an internal combustion engine that includes an exhaust fuel addition valve in an exhaust passage near an exhaust valve in a specific cylinder. In this conventional control device, predetermined clogging suppression control for suppressing clogging of the exhaust fuel addition valve is performed. In addition, when the biofuel concentration is equal to or higher than a predetermined value, the period without addition until clogging suppression control is set short.

JP 2009-13847 A JP 2006-177313 A

  When a mixed fuel of a biofuel and a hydrocarbon fuel such as light oil is used, the properties of the mixed fuel change when the biofuel concentration in the mixed fuel changes. Specifically, when the biofuel concentration increases, for example, the fuel distillation characteristic deteriorates, so the evaporability of the fuel spray added to the exhaust passage deteriorates. As a result, there is a possibility that trouble may occur in catalyst control (NOx reduction, catalyst temperature rise, etc.) using fuel addition by the exhaust fuel addition valve.

  The present invention has been made to solve the above-described problems, and controls an internal combustion engine capable of satisfactorily improving the evaporability of fuel added to an exhaust passage when using a high biofuel concentration fuel. An object is to provide an apparatus.

A first invention is a control device for an internal combustion engine,
An exhaust fuel addition valve that is disposed in an exhaust passage near the exhaust valve in the specific cylinder and adds fuel to the exhaust passage;
Biofuel concentration detection means for detecting the biofuel concentration in the fuel added by the exhaust fuel addition valve;
A fuel addition period setting means for setting a fuel addition period by the exhaust fuel addition valve according to the biofuel concentration,
When the spray injected from the exhaust fuel addition valve receives an exhaust gas flow from a cylinder adjacent to the specific cylinder, the exhaust fuel addition valve in the direction toward the exhaust valve of the specific cylinder In the distance relationship where spray spraying occurs, it is arranged near the exhaust valve in the specific cylinder,
The fuel addition period setting means lengthens the fuel addition period in the exhaust stroke of a cylinder adjacent to the specific cylinder as the biofuel concentration increases.

According to the first aspect of the invention, the higher the biofuel concentration, the longer the fuel addition period during the exhaust stroke of the cylinder adjacent to the cylinder to which the exhaust valve is located in the vicinity of the exhaust fuel addition valve. Thus, when using a low biofuel concentration fuel, while avoiding blowback spray that by the influence of the exhaust gas discharged from the adjacent cylinder, when using fuel of high biofuel concentration is discharged from the adjacent cylinder The evaporability of the fuel added to the exhaust passage can be satisfactorily improved by the heat of the exhaust gas.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure for demonstrating the influence which the fuel added by the exhaust fuel addition valve receives from exhaust gas. It is a figure for demonstrating the setting of the fuel addition period according to the biofuel density | concentration in Embodiment 1 of this invention.

Embodiment 1 FIG.
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system of this embodiment includes a diesel engine 10 mounted on an automobile. Here, it is assumed that the diesel engine 10 is an in-line four-cylinder engine having four cylinders # 1 to # 4, and the explosion order of the diesel engine 10 is # 1 → # 3 → # 4 → # 2. Shall.

  The fuel of the diesel engine 10 is stored in the fuel tank 12. It is assumed that the fuel tank 12 is supplied with 100% light oil or a mixed fuel of light oil and biofuel. The fuel in the fuel tank 12 is transferred to the diesel engine 10 through the fuel pipe 14.

  A fuel pump 16 is installed in the middle of the fuel pipe 14. The high-pressure fuel pressurized by the fuel pump 16 is stored in the common rail 18 and distributed from the common rail 18 to the fuel injection valve 20 of each cylinder.

  The high-pressure fuel pressurized by the fuel pump 16 is also supplied to the exhaust fuel addition valve 24 disposed in the exhaust passage 22. In the configuration shown in FIG. 1, the exhaust fuel addition valve 24 is disposed in the exhaust passage 22 near the exhaust valve (not shown) in the # 4 cylinder.

  The fuel tank 12 is provided with a biofuel concentration sensor 26 for detecting the biofuel concentration in the mixed fuel in the fuel tank 12. As such a biofuel concentration sensor 26, for example, an optical sensor, a sensor of a type using a property in which the dielectric constants of hydrocarbon fuel and biofuel are different, or the like can be used.

  On the downstream side of the turbocharger 28 in the exhaust passage 22 of the diesel engine 10, an NSR (NOx Storage Reduction) catalyst 30 for purifying NOx, a catalyst for purifying NOx, and particulate matter in order from the upstream side. A DPNR (Diesel Particulate NOx Reduction) catalyst 32 including a particulate filter (DPF) 32a for removing PM and an oxidation catalyst 34 are arranged.

  One end of an EGR passage 36 for recirculating exhaust gas to the intake side is connected to the exhaust passage 22, and an EGR cooler 38 for cooling the gas passing through the inside of the EGR passage 36. Is arranged.

  The system of this embodiment further includes an ECU (Electronic Control Unit) 40. Various sensors for controlling the operating state of the diesel engine 10 are connected to the ECU 40 together with the biofuel concentration sensor 26. In addition to the fuel pump 16, the fuel injection valve 20, and the exhaust fuel addition valve 24, various actuators for controlling the operating state of the diesel engine 10 are connected to the ECU 40.

  In the system of the present embodiment configured as described above, during the operation of the diesel engine 10, the regeneration of the particulate filter 32 a in which PM is collected and the regeneration of the sulfur-poisoned catalyst 32 and the like are performed. Temperature increase control for increasing the temperature of the filter 32a, the catalyst 32, and the like is performed. In the present embodiment, for such temperature increase control or for supply of fuel as a reducing agent to the NSR catalyst 30, fuel is supplied into the exhaust passage 22 as needed by the exhaust fuel addition valve 24. Is added.

  When a mixed fuel of biofuel and light oil is used as in the system of the present embodiment described above, the properties of the mixed fuel change when the biofuel concentration in the mixed fuel changes. Specifically, since biodiesel fuel is composed only of heavy components containing oxygen (components having 16 or more carbon atoms), the calorific value per unit injection amount is small, and the vaporization of the spray is good. Absent.

  For this reason, when the biofuel concentration is increased, the distillation characteristics of the mixed fuel are deteriorated, so that the evaporability of the fuel spray added to the exhaust passage is deteriorated. Further, since the calorific value of the mixed fuel decreases as the biofuel concentration increases, it is necessary to add more fuel in order to obtain a calorific value equivalent to that when using light oil. Furthermore, since the oxygen ratio in the fuel increases as the biofuel concentration increases, more fuel must be added when the exhaust passage 22 is made rich for the temperature increase control, NOx reduction, or the like. Will occur.

  As described above, when the biofuel concentration is increased, the fuel addition amount (fuel injection amount) is increased and the vaporization of the fuel spray is deteriorated. Therefore, the catalyst control using the fuel addition by the exhaust fuel addition valve ( NOx reduction, temperature rise control, etc.) may be hindered.

FIG. 2 is a view for explaining the influence of the fuel added by the exhaust fuel addition valve 24 from the exhaust gas.
As shown in FIG. 2, the exhaust gas discharged from each cylinder is directed to the catalyst (NSR 30 etc.) side and the EGR cooler 38 side. For this reason, if the EGR control is being executed, the exhaust gas discharged from each cylinder flows toward both the catalyst side and the EGR cooler 38 side as indicated by arrows in FIG.

  As described above, the exhaust fuel addition valve 24 is disposed in a portion close to the # 4 cylinder in the exhaust passage 22. Further, according to the explosion sequence of the diesel engine 10, at the timing when the exhaust valve of the # 4 cylinder is opened (that is, during the expansion stroke of the # 4 cylinder), the # 3 cylinder is in the exhaust stroke.

  In the description of FIG. 2, the fuel added to the exhaust passage 22 is assumed to be 100% light oil (B0). If fuel addition is performed using light oil (B0) at the timing as described above, the spray of the added fuel is blown back as shown in FIG. 2 due to the influence of exhaust gas discharged from the # 3 cylinder. It tends to occur. In addition, when such spray spraying occurs, fuel adheres to the wall surface of the exhaust passage 22 and deposits are easily generated. As a result, it becomes difficult to obtain the original effect of the exhaust system fuel addition for the purpose of the catalyst control (NOx reduction, temperature increase control, etc.).

FIG. 3 is a diagram for explaining the setting of the fuel addition period according to the biofuel concentration in the first embodiment of the present invention.
The fuel addition by the exhaust fuel addition valve 24 leads the fuel downstream (catalyst side) using the flow of exhaust gas discharged from the # 4 cylinder. Therefore, as shown in FIG. 3, the fuel addition period is set so that fuel addition is always performed in the exhaust stroke of the # 4 cylinder, which is the cylinder with the fuel addition valve, regardless of the biofuel concentration.

  For the reasons already described, it is necessary to increase the amount of fuel added as the biofuel concentration increases. For this reason, as shown in FIG. 3, the fuel addition period is set to become longer as the biofuel concentration becomes higher.

  Further, in the setting shown in FIG. 3, when a fuel with a low biofuel concentration such as a fuel with 100% light oil (B0) or a fuel with a biofuel concentration of 20% (B20) is used, the cylinder with fuel addition valve (# 4) is used. It is prohibited to add fuel while the # 3 cylinder adjacent to is in the exhaust stroke. The reason for this is that fuel with a low biofuel concentration has a relatively good spraying evaporability, so that the blowback shown in FIG. 2 is likely to occur due to the flow of exhaust gas from the # 3 cylinder. It is.

  On the other hand, when using a high biofuel concentration fuel such as B50 or B100, as shown in FIG. 3, during the period in which the # 3 cylinder adjacent to the exhaust fuel addition valve arranged cylinder (# 4) is in the exhaust stroke, The fuel addition is started.

  In addition, the fuel addition period during the exhaust stroke of the adjacent cylinder (# 3) is set longer as the biofuel concentration becomes higher. In other words, the fuel addition period is determined so that the proportion of the amount of fuel added during the exhaust stroke of the # 3 cylinder increases as the biofuel concentration increases.

  When using a fuel with a high biofuel concentration such as B50 or B100, the fuel addition period is increased (in terms of control) and the evaporation of the added fuel becomes difficult due to deterioration of the distillation characteristics of the fuel. Penetrating power increases. As a result, even when the fuel is added while the # 3 cylinder is in the exhaust stroke, it is more influenced by the exhaust gas from the adjacent cylinder (# 3) than when the low biofuel concentration fuel is used. Blowback will be alleviated. Furthermore, when using fuel with a high biofuel concentration, the evaporability of the spray deteriorates as described above, but the evaporability of the spray can be improved by the heat of the hot exhaust gas from the # 3 cylinder. it can.

  As described above, when using fuel with a low biofuel concentration, if the addition of fuel is performed when the # 3 cylinder is in the exhaust stroke, the adverse effect of blowback is large, but when using a fuel with a high biofuel concentration, The merit of wiping off the distilling characteristics of fuel, which has become worse as the biofuel concentration becomes higher, is greater. That is, according to the control of the present embodiment, the evaporability of the fuel added to the exhaust passage 22 can be satisfactorily improved when using a high biofuel concentration fuel.

  The exhaust fuel addition control based on the fuel addition period shown in FIG. 3 can be realized, for example, when the ECU 40 performs control of the following procedure on the actual machine. That is, after the ECU 40 detects the biofuel concentration in the fuel by the biofuel concentration sensor 26, a map of the fuel addition period and the fuel addition timing according to the biofuel concentration (for example, the fuel addition period as shown in FIG. 3). And a fuel addition based on a map in which the setting of the fuel addition time is stored in advance).

  Incidentally, in the first embodiment described above, the exhaust fuel addition valve 24 is arranged in the exhaust passage 22 near the exhaust valve of the # 4 cylinder. However, the location of the exhaust fuel addition valve in the present invention is not limited to this, and may be an exhaust passage near the exhaust valve in a specific cylinder. In addition, if the cylinders in which the exhaust fuel addition valves are arranged close to each other are different, the adjacent cylinders for using the exhaust heat are also different. For example, when the exhaust fuel addition valve is arranged in the exhaust passage near the exhaust valve of the # 1 cylinder, the adjacent cylinder for using the exhaust heat is the # 2 cylinder.

  In the first embodiment described above, the # 4 cylinder corresponds to the “specific cylinder” in the first invention, and the biofuel concentration sensor 26 corresponds to the “biofuel concentration detection means” in the first invention. doing. Further, the “fuel addition period setting means” in the first aspect of the present invention is realized by the ECU 40 adjusting the fuel addition period according to the biofuel concentration according to the setting of the fuel addition period as shown in FIG.

DESCRIPTION OF SYMBOLS 10 Diesel engine 12 Fuel tank 14 Fuel pipe 16 Fuel pump 18 Common rail 20 Fuel injection valve 22 Exhaust passage 24 Exhaust fuel addition valve 26 Biofuel concentration sensor 40 ECU (Electronic Control Unit)

Claims (1)

An exhaust fuel addition valve that is disposed in an exhaust passage near the exhaust valve in the specific cylinder and adds fuel to the exhaust passage;
Biofuel concentration detection means for detecting the biofuel concentration in the fuel added by the exhaust fuel addition valve;
A fuel addition period setting means for setting a fuel addition period by the exhaust fuel addition valve according to the biofuel concentration,
When the spray injected from the exhaust fuel addition valve receives an exhaust gas flow from a cylinder adjacent to the specific cylinder, the exhaust fuel addition valve in the direction toward the exhaust valve of the specific cylinder In the distance relationship where spray spraying occurs, it is arranged near the exhaust valve in the specific cylinder,
The control device for an internal combustion engine, wherein the fuel addition period setting means lengthens a fuel addition period in an exhaust stroke of a cylinder adjacent to the specific cylinder as the biofuel concentration increases.

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