JP2010156275A - Control device for diesel engine - Google Patents

Abstract

Disclosed is a control technique for a diesel engine that can suppress the occurrence of cavitation in a high-pressure fuel supply pump and suppress oxidative deterioration of biodiesel fuel supplied to the high-pressure fuel supply pump.
A fuel supply system 5 of a diesel engine 10 sucks a fuel injection valve 80 from a low pressure side fuel passage (for example, a low pressure fuel passage 222) into a high pressure side fuel passage (for example, a fuel rail 88) to which fuel is supplied. A high-pressure fuel supply pump 100 that boosts and supplies fuel is provided. The ECU 200, which is a control device for the diesel engine 10, has an operation state (engine rotational speed and engine load) of the diesel engine 10 in a predetermined low load side region, and the concentration of the biodiesel fuel in the fuel is equal to or higher than the determination concentration. In some cases, the opening of the intake metering valve of the high-pressure fuel supply pump 100 is controlled to be larger so that the high-pressure side fuel pressure (rail pressure) becomes higher than when the concentration falls below the determination concentration.
[Selection] Figure 2

Description

  The present invention relates to a control technology for a diesel engine, and more particularly, to a high-pressure fuel supply pump that boosts and supplies fuel sucked from a low-pressure fuel passage to a high-pressure fuel passage through which a fuel injection valve receives fuel. The present invention relates to diesel engine control technology.

  A diesel-type internal combustion engine (hereinafter referred to as a diesel engine) usually has a fuel injection valve (injector) that injects fuel for each cylinder, a high-pressure side fuel passage through which the fuel injection valve receives fuel supply, and a low-pressure side. A high-pressure fuel supply pump is provided that boosts and supplies the fuel sucked from the fuel passage. The high-pressure side fuel passage includes a fuel chamber formed in a common fuel distribution pipe to which each fuel injection valve is connected.

  In a diesel engine, diesel fuel made using vegetable oil such as rapeseed oil as a raw material, so-called “biodiesel fuel” may be used. Biodiesel fuel is mainly composed of oxygenated compounds, specifically fatty acid methyl ester (FAME), and is a diesel fuel (hereinafter referred to as diesel oil) made by fractionating crude oil, a crude oil. It is known that it is more susceptible to oxidative degradation than

  The following Patent Document 1 discloses a technique of using gasoline mixed with alcohol (ethanol), so-called “biogasoline” for an internal combustion engine. Ethanol is an oxygen-containing compound. Patent Document 2 below discloses a technique for estimating an alcohol concentration in a mixed fuel in which alcohol and gasoline are mixed, that is, a concentration of an oxygen-containing compound. The technique described in Patent Document 2 can also be applied to estimate the concentration of biodiesel fuel mainly composed of fatty acid methyl ester, which is an oxygen-containing compound.

JP 2006-144736 A JP 2008-107098 A

  By the way, in the diesel engine as described above, depending on the operation state (engine load and engine speed), the fuel flow speed and pressure may vary greatly depending on the location within the high-pressure fuel supply pump. For example, when the high-pressure fuel supply pump is provided with an intake metering valve that controls the flow rate of fuel sucked into the booster chamber by a throttling action, the pressure may greatly decrease on the downstream side of the intake metering valve.

  When the pressure of the fuel flow path in the high-pressure fuel supply pump drops below the saturated vapor pressure, the generation and collapse of fuel bubbles at that portion, so-called cavitation may occur. In the high-pressure fuel supply pump as described above, when the above light oil is supplied as the fuel, when cavitation occurs, the light oil as the fuel locally becomes high temperature, but the properties of the light oil are almost changed. Absent.

  However, since biodiesel fuel is more susceptible to oxidative degradation than light oil, if high-pressure fuel supply pump is supplied with biodiesel fuel (neat fuel) or light oil mixed with high concentration of biodiesel fuel, high-pressure fuel When cavitation occurs in the fuel flow path in the supply pump, the biodiesel fuel component in the mixed fuel may be oxidized and deteriorated.

  This invention is made in view of the above, Comprising: It suppresses generation | occurrence | production of the cavitation in a high pressure fuel supply pump, and can suppress the oxidative degradation of the biodiesel fuel resulting from a cavitation, For diesel engines The purpose is to provide control technology.

  A control device for a diesel engine according to the present invention is a diesel engine equipped with a high-pressure fuel supply pump that boosts and supplies fuel sucked from a low-pressure side fuel passage to a high-pressure side fuel passage that is supplied with fuel by a fuel injection device. A control device that can control the high-pressure side fuel pressure, which is the fuel pressure in the high-pressure side fuel passage, wherein the operating state of the diesel engine is in a predetermined low-load side region, and the concentration of biodiesel fuel in the fuel is When the concentration is higher than the determination concentration, control is performed so that the high-pressure side fuel pressure becomes higher than when the concentration is lower than the determination concentration.

  In the control device for a diesel engine, the high-pressure fuel supply pump includes an intake metering valve that adjusts a flow rate of the fuel sucked into the booster chamber by a throttling action, and the operation state of the diesel engine is a predetermined low load side. When the concentration of the biodiesel fuel in the fuel is equal to or higher than the determination concentration, the opening of the intake metering valve may be controlled to be larger than when the concentration is below the determination concentration. it can.

  In the above diesel engine control device, when the operating state of the diesel engine is not in the predetermined low load side region and the concentration of the biodiesel fuel in the fuel is equal to or higher than the determination concentration, it is lower than the determination concentration. Control can be performed such that the high-pressure side fuel pressure becomes higher than the case.

  Further, the control device for a diesel engine according to the present invention has a high-pressure fuel supply pump that boosts and supplies the fuel sucked from the low-pressure side fuel passage to the high-pressure side fuel passage to which the fuel injection device is supplied with fuel, The high-pressure fuel supply pump is a control device that is used in a diesel engine having an intake metering valve that adjusts the flow rate of fuel sucked into the booster chamber by a throttling action, and that can control the opening of the intake metering valve. Thus, when the operating state of the diesel engine is in a predetermined low load side region and the concentration of biodiesel fuel in the fuel is equal to or higher than the determination concentration, the intake metering valve Control to increase the opening.

  According to the present invention, when the operating state is in the low load side region, it is caused by cavitation by suppressing the occurrence of cavitation due to the occurrence of a portion with low fuel pressure in the fuel flow path in the high-pressure fuel supply pump 100. It is possible to suppress oxidative degradation of biodiesel fuel.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments (hereinafter referred to as embodiments). In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

  First, schematic configurations of the diesel engine and the vehicle according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle including a diesel engine according to the present embodiment. In FIG. 1, only the main parts related to the present invention are schematically shown for the diesel engine and the vehicle.

  The diesel engine according to the present embodiment is a compression ignition type internal combustion engine that spontaneously ignites the fuel by supplying the fuel to the atmosphere in the combustion chamber that has been compressed to a high temperature. As shown in FIG. 1, the diesel engine 10 is mounted on a vehicle 1 as a prime mover, and the vehicle 1 is provided with a fuel tank 220 that stores fuel supplied. The vehicle 1 is provided with a diesel engine electronic control device (hereinafter referred to as ECU) 200 as a control means for controlling the entire vehicle 1 including the diesel engine 10. The ECU 200 has a ROM (not shown) as storage means for storing various control constants.

  The diesel engine 10 has a plurality of cylinders and includes a fuel injection valve (injector) 80 for each cylinder. Each fuel injection valve 80 is provided from a common fuel chamber (fuel rail) formed in the fuel distribution pipe 82. This is a so-called “common rail type” diesel engine 10 that is supplied with fuel. The fuel supply system 5 that supplies fuel to the diesel engine 10 sucks fuel from the fuel tank 220, pressurizes the fuel, and supplies the fuel to a common fuel chamber formed in the fuel distribution pipe 82. It has a pump (high pressure supply pump) 100. A detailed configuration of the fuel supply system 5 including the high-pressure fuel supply pump 100 will be described later.

  The diesel engine 10 is provided with a cylinder block, a piston, a connecting rod, a crankshaft, a camshaft, and a cylinder head 20 (not shown) as parts of an engine body system in which a cylinder is formed. A cylinder bore is formed in the cylinder block, and the piston reciprocates in the cylinder bore. A cylinder head 20 is coupled to the cylinder block so as to face the top surface of the piston and close the cylinder bore. A space surrounded by the cylinder bore, the piston, and the cylinder head 20 is a “cylinder”. Note that the cylinder is denoted by reference numeral 12 in FIG.

  When the crankshaft rotates, the piston reciprocates and air is sucked into the cylinder. Further, fuel is supplied to the cylinder by a fuel injection valve 80. The supplied fuel is ignited by being exposed to a high temperature atmosphere in the cylinder. The reciprocating motion of the piston caused by the ignition and combustion of the fuel is converted into rotational motion via the connecting rod and output from the crankshaft. A crank angle sensor (not shown) for detecting a rotation angle position of the crankshaft (hereinafter referred to as a crank angle) is provided in the vicinity of the crankshaft, and a signal related to the detected crank angle is sent to the ECU 200. ing. The torque output from the crankshaft by the diesel engine 10 (hereinafter referred to as engine load) is controlled by the ECU 200.

  The cylinder head 20 is formed with an intake port 24 that guides intake air from an intake passage, which will be described later, to the cylinder on one side of the cylinder bore 20 with the axis of the cylinder bore interposed therebetween. An exhaust port 26 for discharging exhaust gas is formed. The cylinder head 20 is provided with intake and exhaust valves (not shown) corresponding to the cylinder side openings of the intake port 24 and the exhaust port 26. These intake valve and exhaust valve are driven by receiving mechanical power from a camshaft (not shown). The intake valve and the exhaust valve are configured to be openable and closable at a predetermined timing according to the crank angle.

  The diesel engine 10 according to the present embodiment is provided with a turbocharger 60 that compresses intake air by kinetic energy of exhaust gas discharged from a cylinder. In addition, the diesel engine 10 includes an outside air duct 41 that introduces air from outside air as an intake system component that guides air from outside air to the cylinder, and an air cleaner that removes dust from the drawn air (hereinafter referred to as intake air). 42, an air flow meter (not shown) for measuring the flow rate of the intake air, an intercooler 45 for cooling the air compressed by the turbocharger 60, a throttle valve 46 for adjusting the flow rate of the intake air, and an intake An intake manifold 48, which is a distribution pipe for distributing air to each cylinder, is provided.

  The downstream side of the intake manifold 48 is connected to the cylinder head 20, and a branch passage 49 formed in the intake manifold 48 communicates with the intake port 24. A surge chamber communicating with the branch passage 49 is formed on the upstream side of the branch passage 49. On the other hand, a throttle valve 46 is provided on the upstream side of the intake manifold 48. The throttle valve 46 adjusts the flow rate of intake air taken into the cylinder (hereinafter referred to as intake air amount). The opening degree of the throttle valve 46, that is, the intake air amount is controlled by the ECU 200.

  An intake pipe 47 is connected to the upstream side of the throttle valve 46. The passage in the intake pipe 47 communicates with the surge chamber in the intake manifold 48. An intercooler 45 is connected to the upstream side of the intake pipe 47. The intercooler 45 is configured as a heat exchanger, and cools the intake air (supply air) that has been compressed by a compressor 62 of the turbocharger 60 described later to become high temperature.

  An intake pipe 44 is connected to the upstream side of the intercooler 45. The passage in the intake pipe 44 communicates with the passage in the intake pipe 47 via the passage in the intercooler 45. A compressor 62 of the turbocharger 60 is connected to the upstream side of the intake pipe 44. The passage in the intake pipe 44 communicates with the compressor 62 of the turbocharger 60.

  An intake pipe 43 is connected to the upstream side of the compressor 62 of the turbocharger 60. The passage in the intake pipe 43 communicates with the compressor 62 of the turbocharger 60. An air cleaner 42 is connected to the upstream side of the intake pipe 43, and an outside air duct 41 is provided on the upstream side of the air cleaner 42. The passage in the intake pipe 43 communicates with the outside air duct 41 through the air cleaner 42.

  An air flow meter (not shown) is provided on the downstream side of the element of the air cleaner 42. The air flow meter detects the amount of intake air introduced from the outside air duct 41. The air flow meter sends a signal related to the detected intake air amount to the ECU 200.

  The fresh air introduced from the outside air duct 41 passes through the air cleaner 42, the flow rate is detected by the air flow meter, and is compressed by the compressor 62 of the turbocharger 60. The compressed intake air having a high temperature is cooled by the intercooler 45 and flows to the throttle valve 46. The intake air whose flow rate is adjusted by the throttle valve 46 flows into the surge chamber in the intake manifold 48, is distributed to each cylinder from the branch passage 49, and flows into the cylinder through the intake port 24.

  Further, the diesel engine 10 includes exhaust manifolds 52 that join exhaust gases from the cylinders and lead them to the turbocharger 60 as exhaust system parts that exhaust exhaust gases from the cylinders to the outside air. An exhaust aftertreatment device 55 for treating nitrogen oxides and particulate matter (PM), an oxidation catalyst 58 for purifying exhaust gas from the exhaust aftertreatment device 55 by an oxidation reaction, an oxidation catalyst 58 and an exhaust aftertreatment device 55, An A / F sensor 98 for detecting the oxygen concentration of the exhaust gas is provided.

  A branch passage 51 is formed on the upstream side of the exhaust manifold 52 corresponding to each cylinder, and communicates with the exhaust port 26 of each cylinder. Further, on the downstream side of the passage in the exhaust manifold 52, a merging portion where exhaust gases from the cylinders merge is formed. The exhaust manifold 52 joins exhaust gases discharged from the intake ports 26 of a plurality of cylinders of the diesel engine 10 at a joining portion and guides them to a turbine 64 of a turbocharger 60 described later.

  The turbocharger 60 includes a compressor 62 provided between the intake pipe 43 and the intake pipe 44, and a turbine 64 provided between the exhaust manifold 52 and the exhaust pipe 54. is doing. A compressor wheel that compresses air by rotating is accommodated in the housing of the compressor 62, and a turbine wheel that is rotationally driven by the flow of exhaust gas is accommodated in the housing of the turbine 64. The compressor wheel and the turbine wheel are joined together.

  In the turbocharger 60, the turbine wheel and the compressor wheel are rotationally driven by the kinetic energy of the exhaust gas flow flowing into the turbine 64 from the confluence portion of the exhaust passage in the exhaust manifold 52, and the air in the compressor 62 is compressed. To the intercooler 45. The exhaust gas in the turbine 64 flows downstream through the passage in the exhaust pipe 54 and flows into an exhaust aftertreatment device 55 described later.

  A front stage (upstream side) of the exhaust aftertreatment device 55 is provided with a NOx occlusion reduction type catalyst 55a that is an exhaust purification catalyst that occludes nitrogen oxide in exhaust gas and reduces it to nitrogen. On the other hand, a downstream (downstream) side is provided with a DPNR catalyst system 55c which is an exhaust purification catalyst with a filter mechanism and simultaneously purifies PM (particulate matter) and nitrogen oxides.

  The NOx occlusion reduction type catalyst 55a occludes nitrogen oxides in the exhaust gas in the form of nitrate when the exhaust gas flowing through the NOx storage reduction catalyst 55a is in an oxygen-excess atmosphere (lean atmosphere) containing a large amount of oxygen. On the other hand, when the exhaust gas flowing through the NOx storage reduction catalyst 55a has a reducing atmosphere (rich atmosphere) containing a large amount of unburned hydrocarbons (hereinafter simply referred to as “HC”), The stored nitrogen oxides are reduced to nitrogen by HC as a reducing agent contained. In this way, the NOx storage reduction catalyst 55a purifies nitrogen oxides in the exhaust gas.

  On the other hand, the DPNR catalyst system 55c has a function of a diesel particulate filter (hereinafter referred to as DPF) that collects PM, burns the collected PM, and regenerates the filter by releasing it as carbon dioxide. This is a combination of the functions of the NOx storage reduction catalyst described above, and it is possible to simultaneously purify PM and nitrogen oxides. Specifically, the DPNR catalyst system 55c collects PM in the exhaust gas flowing through the filter, and changes the nitrogen oxides to nitrates when the exhaust gas is in an oxygen-excess atmosphere (lean atmosphere). The collected PM is oxidized by the active oxygen generated at this time and the oxygen in the exhaust gas. On the other hand, when the exhaust gas flowing through the DPNR catalyst system 55c is in a reducing atmosphere (rich atmosphere), the stored nitrogen oxides are reduced to nitrogen by HC as a reducing agent contained in the exhaust gas. At the same time, the active oxygen generated at this time oxidizes PM. In this way, the DPNR catalyst system 55c can oxidize and burn PM continuously to regenerate the filter in which PM is collected.

  An exhaust pipe 56 is connected to the downstream side of the exhaust aftertreatment device 55 described above, and exhaust gas in which nitrogen oxides and PM are reduced by the exhaust aftertreatment device 55 is connected to an exhaust passage in the exhaust pipe 56. Gas flows. The exhaust pipe 56 is equipped with an A / F sensor 98 that detects the oxygen concentration of the exhaust gas in the exhaust passage. The A / F sensor 98 sends a signal related to the oxygen concentration in the exhaust gas flowing into the oxidation catalyst 58 to the ECU 200 after nitrogen oxides and PM are reduced by the exhaust aftertreatment device 55.

  An oxidation catalyst 58 is provided on the downstream side of the exhaust pipe 56. The oxidation catalyst 58 oxidizes and purifies hydrocarbons and carbon monoxide contained in the exhaust gas that has passed through the exhaust aftertreatment device 55. The exhaust gas purified by the oxidation catalyst is released to the outside air.

  Further, the diesel engine 10 is provided with a so-called exhaust gas recirculation device 70 (hereinafter referred to as an EGR device) that takes a part of the exhaust gas discharged from the cylinder from the exhaust passage and flows it into the intake passage. . The EGR device 70 includes an EGR passage that connects the exhaust passage and the intake passage, an EGR valve 77 that adjusts the flow rate of exhaust gas that flows through the EGR passage (hereinafter referred to as EGR gas), an EGR cooler 74 that cools the EGR gas, have.

  The exhaust manifold 52 described above is provided with an EGR gas intake 71, and an EGR pipe 72 is connected to the intake 71. An EGR cooler 74 is connected to the EGR pipe 72 on the downstream side in the EGR gas flow direction. The EGR cooler 74 is constituted by a heat exchanger, and can cool the inflow EGR gas. An EGR pipe 76 is connected to the downstream side of the EGR cooler 74.

  An EGR valve 77 is disposed at the downstream end of the EGR pipe 76. The EGR valve 77 is composed of an electromagnetic flow control valve. An EGR pipe 78 is connected to the downstream side of the EGR valve 77. The EGR pipe 78 connects an EGR gas outlet 79 provided in the intake manifold 48 and an EGR valve 77. The opening degree of the EGR valve 77, that is, the flow rate of the EGR gas flowing through the EGR passage is controlled by the ECU 200.

  The diesel engine 10 is provided with an exhaust fuel addition valve 89 for adding fuel to the exhaust passage, in addition to the fuel injection valve 80 for supplying fuel into the cylinder. The exhaust fuel addition valve 89 is configured by an electromagnetically driven fuel injection valve, and is supplied with fuel from the high-pressure fuel supply pump 100 via the fuel passage 87 at a predetermined fuel pressure (for example, 1 MPa). . The exhaust fuel addition valve 89 is provided in the vicinity of the exhaust port 26 of the cylinder having the shortest exhaust path from the exhaust port 26 to the turbine 64 among a plurality of cylinders in the diesel engine 10. The exhaust fuel addition valve 89 is capable of adding fuel to the exhaust passage by injecting fuel from the injection hole exposed in the exhaust port 26.

  Next, the structure of the fuel supply system of the diesel engine which concerns on this embodiment is demonstrated using FIG. FIG. 2 is a schematic diagram showing the configuration of the fuel supply system according to the present embodiment. In FIG. 2, only the main part related to the present invention is schematically shown in the configuration of the fuel supply system.

  The fuel supply system 5 is provided for each cylinder, and a fuel injection valve 80 that directly injects fuel into the cylinder, a fuel distribution pipe 82 that distributes and supplies the fuel to each fuel injection valve 80, and a fuel distribution pipe 82 The fuel rail 88 includes a high-pressure fuel supply pump 100 that supplies pressurized fuel, and a fuel tank 220 that stores the supplied fuel.

  The fuel injection valve 80 is a fuel injection valve in which a piezo element (piezoelectric element) is used as a valve opening actuator, and can perform a plurality of fuel injections in one cycle, so-called multistage injection. . The injection period of the fuel injection valve 80 in each cycle, that is, the injection timing and the injection time length (valve opening time) are controlled by the ECU 200 via a driver unit (not shown). Each fuel injection valve 80 is supplied with fuel from a common fuel rail 88 at a predetermined fuel pressure (for example, 120 MPa).

  The fuel distribution pipe 82 has a fuel rail 88 that is a high-pressure fuel storage chamber capable of storing high-pressure fuel and suppressing pressure fluctuations of the fuel. The fuel distribution pipe 82 distributes and supplies fuel from the fuel rail 88 to each fuel injection valve 80. The fuel pressure in the fuel rail 88 is referred to as “rail pressure” in the following description.

  A fuel pressure sensor 81 for detecting the fuel pressure in the fuel rail 88 is provided at one end of the fuel distribution pipe 82. The fuel pressure sensor 81 sends a signal related to the fuel pressure in the fuel rail 88, that is, the high-pressure side fuel passage, to the ECU 200. The other end of the fuel distribution pipe 82 is provided with a pressure limiter 83 that limits the pressure of the fuel rail 88 to a maximum allowable pressure or less. The pressure limiting valve 83 opens when the rail pressure exceeds the maximum allowable pressure, and returns the fuel in the fuel rail 88 to the fuel tank 220 through the return passage 86. The fuel rail 88 in the fuel distribution pipe 82 is supplied with pressurized fuel (high pressure fuel) from the high pressure fuel supply pump 100 through the high pressure fuel passage 84 (high pressure side fuel passage).

  The high-pressure fuel supply pump 100 operates by receiving mechanical power from a camshaft, a crankshaft or the like of the diesel engine 10. The high pressure fuel supply pump 100 sucks the fuel stored in the fuel tank 220 from the low pressure fuel passage 222 (low pressure side fuel passage). A fuel filter 224 for removing dust in the fuel is provided in the middle of the low pressure fuel passage 222. The high-pressure fuel supply pump 100 pressurizes the fuel from the fuel tank 220 that has been sucked in, and supplies the fuel by feeding it to the fuel rail 88 through the high-pressure fuel passage 84 (high-pressure side fuel passage). The surplus fuel in the high-pressure fuel supply pump 100 is returned into the fuel tank 220 through the return passages 130 and 226. In this way, the high-pressure fuel supply pump 100 can increase the pressure of the fuel sucked from the low-pressure side fuel passage and supply the fuel to the high-pressure side fuel passage where the fuel injection valve 80 receives the supply of fuel.

  The “high-pressure side fuel passage” means a fuel passage through which high-pressure fuel pressurized by the high-pressure fuel supply pump 100 flows. In the present embodiment, the high pressure side fuel passage includes a fuel chamber (fuel rail) 88 in the fuel distribution pipe 82 in addition to the high pressure fuel passage 84. The fuel pressure in these high pressure side fuel passages will be referred to as “high pressure side fuel pressure” in the following description. That is, in the present embodiment, the above-described rail pressure becomes the “high pressure side fuel pressure”.

  On the other hand, the “low pressure side fuel passage” means a fuel passage through which the low pressure fuel sucked by the high pressure fuel supply pump 100 flows. In the present embodiment, the low pressure side fuel passage includes the low pressure fuel passage. In addition to 222, return passages 130, 226 and the like are included.

Next, the configuration of the high-pressure fuel supply pump according to the present embodiment will be described with reference to FIG.
FIG. 3 is a schematic diagram showing the configuration of the high-pressure fuel supply pump according to the present embodiment. FIG. 4 is a cross-sectional view showing the structure of the intake metering valve of the high-pressure fuel supply pump. FIG. 3 schematically shows only the main part related to the present invention with respect to the high-pressure fuel supply pump. In the following description, the upstream side in the fuel flow direction is simply referred to as “upstream side”, and the downstream side in the fuel flow direction is simply referred to as “downstream side”.

  As shown in FIG. 3, the high-pressure fuel supply pump 100 feeds fuel sucked from the low-pressure side fuel passage by preloading it, sucks the fuel sent from the feed pump 102, and boosts the pressure by boosting the fuel. A high-pressure pump 110 that sends the fuel to the side fuel passage, and an intake metering valve 105 that adjusts the flow rate of the fuel that is sent from the feed pump 102 and sucked into the high-pressure pump 110. Note that a description of the return passage for returning excess fuel from the high-pressure pump 110 and the feed pump 102 to the fuel tank 220 will be omitted.

  The feed pump 102 is an internal gear pump of a type in which two gears having different rotation axes are in mesh with each other. The feed pump 102 is rotationally driven by mechanical power from a camshaft or the like of the diesel engine 10. The feed pump 102 sucks fuel from the low-pressure fuel passage in the low-pressure fuel passage 222 and sends the fuel to the fuel passage 103 toward the intake metering valve 105.

  The high-pressure pump 110 is a positive displacement pump, and more specifically, a rotary / eccentric outer cam type fuel pump. The high-pressure pump 110 includes plungers 116 and 117 that reciprocate in cylinders 114 and 115, an eccentric cam 112 that rotates around a rotation center axis (indicated by a point C in FIG. 3), a plunger 116, and a plunger 117. The ring cam 113 is provided between the ring cam 113 and the eccentric cam 112 to convert the rotational motion of the eccentric cam 112 into the reciprocating motion of the plungers 116 and 117. The eccentric cam 112 is rotationally driven by mechanical power from a camshaft or the like of the diesel engine 10. The ring cam 113 and portions of the plungers 116 and 117 that are in contact with the ring cam 113 are accommodated in the housing 111. A cylinder 114 and a cylinder 115 are extended in the housing 111 so as to face each other. Inside the cylinder 114 and the cylinder 115, fuel is sucked and repressed by reciprocation of the plunger 116 and the cylinder 117, respectively. Chambers 120 and 121 (hereinafter referred to as boost chambers) are configured. The pressurizing chamber 120 and the pressurizing chamber 121 communicate with each other through a fuel passage (not shown) formed inside the plunger 116 and the plunger 117 and the inside of the housing 111.

  In the cylinder 114, a fuel chamber 120 (hereinafter referred to as a boosting chamber) 120 is formed in which the volume is changed by the reciprocating motion of the plunger 116 and the boosted fuel can be boosted. A passage 107 that guides the metered fuel to the high-pressure pump 110 is connected to the upstream side of the boosting chamber 120, and a passage that boosts the pressure and guides the fuel toward the fuel rail 88 on the downstream side of the boosting chamber 120. 126 is connected. A check valve 122 that allows only the flow of fuel from the passage 107 toward the pressure increasing chamber 120 is provided between the pressure increasing chamber 120 and the passage 107. A check valve between the pressure increasing chamber 120 and the passage 126 opens when the pressure difference of the pressure increasing chamber 120 with respect to the passage 126 exceeds a predetermined value, and allows only the flow of fuel from the pressure increasing chamber 120 toward the passage 126. 124 is provided.

  Similarly, a pressure increasing chamber 121 whose volume is changed by the reciprocating motion of the plunger 116 is formed in the cylinder 115. A passage 108 that leads the metered fuel to the high-pressure pump 110 is connected to the upstream side of the boosting chamber 121, and a passage that boosts the pressure and guides the fuel toward the fuel rail 88 on the downstream side of the boosting chamber 121. 127 is connected. A check valve 123 that allows only the flow of fuel from the passage 108 toward the booster chamber 121 is provided between the booster chamber 121 and the passage 108. A check valve between the booster chamber 121 and the passage 127 is opened when the pressure difference of the booster chamber 121 with respect to the passage 127 exceeds a predetermined value, and allows only the flow of fuel from the booster chamber 121 toward the passage 127. 125 is provided.

  In the high-pressure pump 110 configured as described above, when the eccentric cam 112 rotates and the ring cam 113 and the plungers 116 and 117 move in the direction indicated by the arrow A in the figure, the volume of the boosting chamber 120 decreases and the pressure increases. As the pressure rises, the volume of the pressure increasing chamber 121 increases and the pressure decreases. The high-pressure pump 110 sucks the fuel in the passage 108 into the pressurizing chamber 121, boosts the fuel in the pressurizing chamber 121, and sends the fuel from the check valve 124 to the passage 126.

  Thereafter, the fuel sucked into the pressurizing chamber 121 is guided to the pressurizing chamber 120 through a fuel passage formed inside the plungers 116 and 117. When the ring cam 113 and the plungers 116 and 117 move in the direction indicated by the arrow B in the figure, the volume of the boosting chamber 121 decreases and the pressure increases, and the volume of the boosting chamber 120 increases and the pressure decreases. The high-pressure pump 110 sucks the fuel in the passage 107 into the pressurizing chamber 120, boosts the fuel in the pressurizing chamber 120, and sends the fuel from the check valve 125 to the passage 127.

  As described above, in the high-pressure pump 110, the eccentric cam 112 is rotationally driven, so that the fuel fed from the feed pump 102 and the flow rate of which is adjusted by an intake metering valve 105 described later is supplied from the passage 106 to the boosting chamber 120. Alternatively, the air can be sucked into the pressurizing chamber 121, boosted, and sent to the high-pressure side fuel passage 84 toward the fuel rail 88. Since the eccentric cam 112 rotates at a rotational speed proportional to the engine rotational speed of the diesel engine 10, the volume of the booster chambers 120 and 121 periodically changes at a frequency proportional to the engine rotational speed. The fuel flow rate sent from the high-pressure pump 110 to the high-pressure side fuel passage 84, that is, the fuel flow rate from the feed pump 102 toward the high-pressure pump 110 is adjusted by the intake metering valve 105.

  The intake metering valve 105 is a flow rate control valve that adjusts the flow rate of fuel that passes therethrough, and is a throttle valve that adjusts the flow rate by a throttle action. The intake metering valve 105 adjusts the flow rate of fuel passing therethrough by changing the cross-sectional area of the flow path inside. The suction metering valve 105 is a linear solenoid type electromagnetically driven valve, and has a valve body 310 that can slide in the housing 300 as shown in FIG. The housing 300 is formed with a through hole 302 that allows the passage 106 (see FIG. 3) toward the high-pressure pump 110 to communicate with the inside of the housing 300. On the other hand, the valve body 310 is formed with an internal passage 311 that communicates with the passage 103 and a through hole 312 that allows the internal passage 311 and the through hole 302 to communicate with each other. The internal passage 311 receives the fuel delivered from the feed pump 102 as indicated by an arrow F1 in the figure.

  In the intake metering valve 105, the valve body 310 slides relative to the housing 300, so that the through hole 302 on the valve body 310 side and the through hole 312 on the housing 300 side overlap, that is, the arrow F2 in the figure. It is possible to change the cross-sectional area of the fuel channel (hereinafter simply referred to as “channel cross-sectional area”). The position of the valve body 310 relative to the housing 300 is controlled by the ECU 200.

  The intake metering valve 105 reduces the cross-sectional area of the flow path between the through hole 302 and the through hole 312, that is, forms a “throttle”, thereby generating flow path resistance in the fuel flow. It is possible to adjust the flow rate of fuel flowing from the passage 106 that strengthens the “throttle” toward the high-pressure pump 110. The intake metering valve 105 can reduce the flow rate of the fuel supplied to the high-pressure pump 110 by reducing the cross-sectional area of the flow path between the through hole 302 and the through hole 312, that is, by strengthening the throttle. On the other hand, the flow rate of the fuel delivered toward the high-pressure pump 110 can be increased by increasing the cross-sectional area of the flow path, that is, by reducing the throttle. That is, the intake metering valve 105 can adjust the flow rate of the fuel delivered toward the high-pressure pump 110 by a throttling action.

  In the following description, in the intake metering valve 105, reducing the flow passage cross-sectional area (that is, increasing the throttle) is referred to as “increasing the opening degree”. On the other hand, increasing the channel cross-sectional area (that is, reducing the aperture) is referred to as “decreasing the opening degree”. That is, as the opening of the intake metering valve 105 is increased, the flow rate of the fuel delivered toward the high pressure pump 110 is increased, and the pressure in the high pressure side fuel passage, that is, the high pressure side fuel pressure is increased. The opening of the intake metering valve 105, that is, the high-pressure side fuel pressure is controlled by the ECU 200.

  In the vehicle 1 including the fuel supply system 5 configured as described above, the ECU 200 performs a signal related to a crank angle from a crank angle sensor (not shown) and a signal related to an intake air amount (fresh air amount) from an air flow meter. And a signal related to the rail pressure (high-pressure side fuel pressure) from the fuel pressure sensor 81. Further, the ECU 200 detects a signal related to the accelerator operation amount from the accelerator pedal position sensor 96 that detects the operation amount of the accelerator pedal by the driver, and between the exhaust aftertreatment device 55 and the oxidation catalyst 58 from the A / F sensor 98. And a signal relating to the oxygen concentration in the exhaust gas.

  Based on these detection signals, the ECU 200 estimates the engine rotation speed and the engine load, which are the operating states of the diesel engine 10, as control variables. Further, the ECU 200 estimates the oxygen concentration in the exhaust gas after passing through the exhaust aftertreatment device 55 as a control variable. In addition, the ECU 200 has “bio concentration estimation means” which is a function of detecting the concentration of biodiesel fuel in the fuel supplied to the high-pressure fuel supply pump 100 and estimating the concentration as a control variable. Will be explained.

  As shown in FIGS. 1 and 2, the fuel tank 220 includes not only diesel fuel (hereinafter referred to as light oil) produced by fractionating crude oil, which is a mineral oil, but also vegetable oil such as rapeseed oil as methanol and the like. Diesel fuel mainly composed of fatty acid methyl ester (FAME) esterified by reaction (hereinafter referred to as “biodiesel fuel”) is mixed and supplied at a desired concentration. The fuel in which light oil and biodiesel fuel are mixed in the fuel tank 220 is hereinafter referred to as “mixed fuel”.

  The fuel tank 220 is provided with a fuel property detection sensor 228 capable of detecting information related to the fuel property of the mixed fuel in the fuel tank 220 in order to estimate the concentration of biodiesel fuel in the fuel. Examples of the information related to the fuel property include the light transmittance, the light refractive index, and the dielectric constant of the mixed fuel. The fuel property detection sensor 228 sends a signal related to the detected fuel property information to the ECU 200.

  The ECU 200 detects a signal related to the fuel property information from the fuel property detection sensor 228, and estimates information related to the fuel property such as light transmittance and dielectric constant as a control variable. Based on these control variables, the ECU 200 is configured to be able to estimate the concentration of biodiesel fuel in the mixed fuel stored in the fuel tank 220.

  Specific methods for detecting and estimating the concentration of biodiesel fuel in the fuel are disclosed, for example, in paragraphs 0034 to 0096 of Japanese Patent Application Laid-Open No. 2008-107098 of the present applicant. In the publication, a fuel property sensor capable of detecting the light transmittance and refractive index of fuel is provided in a delivery pipe (fuel distribution pipe), and signals relating to the light transmittance and refractive index are transmitted to an electronic control unit (ECU). ). There is a correlation between the light transmittance of the fuel and the alcohol concentration in the fuel. The ECU estimates the alcohol concentration in the fuel, that is, the concentration of the oxygen-containing compound, based on the correlation between the light transmittance and the alcohol concentration obtained in advance and the detected light transmittance. Fatty acid methyl ester, which is the main component of biodiesel fuel, and alcohol contained in so-called biogasoline are also oxygenated compounds, and the concentration of biodiesel fuel in the mixed fuel is detected based on almost the same principle as the alcohol concentration. Can be estimated. The contents of Japanese Patent Application Laid-Open No. 2008-107098 are incorporated herein as part of the present specification.

  In addition, the method of estimating the density | concentration of biodiesel fuel is not limited to the above-mentioned thing. For example, the fuel property detection sensor 228 detects the viscosity, temperature, and the like of the fuel supplied into the fuel tank 220, and the ECU 200 estimates the concentration of biodiesel fuel in the fuel based on these detected signals. It is good as a thing.

  Further, the method of estimating the concentration of biodiesel fuel is not limited to the method of detecting / estimating directly from the fuel by the fuel property detection sensor 228. For example, in a predetermined operation state of the diesel engine 10, the fuel injection valve 80 and the like are operated in the same manner as when only light oil is supplied. At this time, the exhaust gas between the exhaust aftertreatment device 55 and the oxidation catalyst 58 is operated. It is also possible to estimate the concentration of biodiesel fuel in the fuel by comparing the behavior of oxygen concentration (time history) with the behavior of oxygen concentration when only light oil is supplied.

  The ECU 200 determines the injection characteristics of the fuel injection valve 80 according to the concentration of the biodiesel fuel in the fuel estimated as described above and the operating state of the diesel engine 10 (engine speed and engine load). It is possible to control the high-pressure side fuel pressure (rail pressure) that is the fuel pressure in the high-pressure side fuel passage, that is, the opening of the intake metering valve 105.

  In the diesel engine 10 configured as described above, depending on the operating state, that is, the engine load and the engine rotation speed, the fuel pressure may be greatly reduced locally in the high-pressure fuel supply pump 100. As a result, the flow rate of the fuel may increase and the pressure may decrease in the intake metering valve 105 that adjusts the fuel flow rate. At this time, when the pressure is reduced to the saturated vapor pressure, cavitation may occur.

  When high concentration biodiesel fuel is contained in the fuel from the fuel tank 220, when cavitation occurs in the high-pressure fuel supply pump 100, the biodiesel fuel component in the fuel is oxidized and deteriorated, and the pollutant is contained in the fuel. May occur.

  In particular, when the operating state of the diesel engine 10 is in the operating region on the low load side, the amount of intake air per cycle of each cylinder is small, and the amount of fuel injected by the fuel injection valve 80 per cycle is also small. For this reason, in the low load side operation region, the high-pressure fuel supply pump 100 has a small amount of fuel to be delivered per cycle toward the fuel rail 88, and the opening of the intake metering valve 105 is reduced (throttling). Need to be strong). When the opening of the intake metering valve 105 is reduced, there is a problem that the fuel pressure is reduced in the vicinity of the throttle and cavitation is likely to occur.

  Therefore, in the present embodiment, when the operation state of the diesel engine is in a predetermined low load side region and the concentration of biodiesel fuel in the fuel is equal to or higher than a predetermined determination concentration, the determination concentration The control is performed so that the high-pressure side fuel pressure becomes higher than that in the case where the pressure is lower than 1. The following description will be made with reference to FIGS. 2 and 5 to 7.

  FIG. 5 is a flowchart showing target high-pressure side fuel pressure setting control executed by the diesel engine control device (ECU) according to the present embodiment. FIG. 6 is a diagram showing the relationship between the operating range of the diesel engine according to the present embodiment and the target value of the high-pressure side fuel pressure. FIG. 7 is a table showing the relationship between the concentration of biodiesel fuel in the fuel supplied to the diesel engine according to this embodiment and the target value of the high-pressure side fuel pressure.

  As shown in FIGS. 2 and 5, the ECU 200 sets a target value for the high-pressure side fuel pressure (hereinafter referred to as a target high-pressure side fuel pressure) according to the operating state of the diesel engine 10, that is, the engine speed and the engine load. “Target high-pressure side fuel pressure setting control” is executed. The target high-pressure side fuel pressure setting control is repeatedly executed by the ECU 200 when the diesel engine 10 is in operation.

  As shown in FIG. 5, first, the ECU 200 acquires various control variables in step S100. The control variables include the engine speed and the engine load indicating the operating state of the diesel engine 10 and the biodiesel fuel concentration (hereinafter simply referred to as “bioconcentration”).

  In step S102, the ECU 200 determines whether or not the bio concentration is equal to or higher than a predetermined determination concentration. The determination concentration is a bioconcentration threshold value for determining whether or not oxidative degradation of the biodiesel fuel becomes a problem when cavitation occurs. In the present embodiment, the determination concentration is set to 50%. The determination concentration is obtained in advance by a matching experiment or the like, and is stored in the ROM of the ECU 200 as a control constant.

  When the bioconcentration is lower than the determination concentration (S102: No), the ECU 200 determines that the bioconcentration is relatively “low” and that the oxidative deterioration of the biodiesel fuel does not matter so much even if cavitation occurs. The target high-pressure side fuel pressure is set to “normal target high-pressure side fuel pressure”, and the opening of the intake metering valve 105 of the high-pressure fuel supply pump 100 is adjusted according to the “normal target high-pressure side fuel pressure”. The rail pressure is controlled (S104).

As shown in FIGS. 6 and 7, the “normal target high-pressure side fuel pressure” is set as follows depending on which operating region the diesel engine 10 is in.
"Low rotation and low load range" = "Low pressure"
When the operating state of the diesel engine 10 is in an operating region in which the engine rotational speed is lower than a predetermined determination rotational speed and the engine load is lower than a predetermined determination concentration (hereinafter referred to as a low rotation low load region), Set the target high-pressure side fuel pressure to a relatively low pressure.
"Low rotation high load range" = "Medium pressure"
When the operating state of the diesel engine 10 is in an operating region where the engine rotational speed is lower than a predetermined determination rotational speed and the engine load is higher than a predetermined determination concentration (hereinafter referred to as a low rotation high load region), Set the target high-pressure side fuel pressure to a relatively "medium pressure".
"High rotation and low load area" = "Medium pressure"
When the operation state of the diesel engine 10 is in an operation region where the engine rotation speed is higher than a predetermined determination rotation speed and the engine load is lower than a predetermined determination concentration (hereinafter referred to as a high rotation low load region), Set the target high-pressure side fuel pressure to a relatively "medium pressure".
"High rotation and high load range" = "High pressure"
When the operating state of the diesel engine 10 is in an operating region where the engine rotational speed is higher than a predetermined determination rotational speed and the engine load is higher than a predetermined determination concentration (hereinafter referred to as a high rotation high load region), Set the target high-pressure side fuel pressure to a relatively high pressure.
The ECU 200 controls the opening degree of the intake metering valve 105 of the high-pressure fuel supply pump 100 in accordance with the target high-pressure side fuel pressure set in this way.

  On the other hand, when the bioconcentration is equal to or higher than the determination concentration (S102: Yes), the ECU 200 determines that the biodegradation of the biodiesel fuel becomes a problem when the bioconcentration is relatively “high concentration” and cavitation occurs. Then, the process proceeds to step S106.

  In step S106, the ECU 200 determines whether or not the operating state (engine rotational speed and engine load) of the diesel engine 10 is in a predetermined low load side region. That is, ECU 200 determines whether or not the engine load of diesel engine 10 is equal to or greater than a predetermined determination load corresponding to each engine rotation speed. The low load side region is an operating region in which the fuel injection amount per cycle of the fuel injection valve 80 is relatively small, and the opening of the intake metering valve 105 of the high-pressure fuel supply pump 100 is small (the throttle is increased). Is set. That is, the low load side region is set to an operation region where cavitation is relatively likely to occur in the high pressure fuel supply pump 100. The low load side region is obtained in advance by a matching experiment or the like, and is stored in the ROM of the ECU 200 as a control constant (determination load for each engine rotation speed).

  When the operation state of the diesel engine 10 is not in the predetermined low load side region (S106: No), the ECU 200 determines that there is almost no possibility of cavitation occurring in the high-pressure fuel supply pump 100. The high pressure side fuel pressure (rail pressure) is controlled by adjusting the opening of the intake metering valve 105 of the high pressure fuel supply pump 100 in accordance with “normal target high pressure side fuel pressure”.

  On the other hand, when the operation state of the diesel engine 10 is in the predetermined low load side region (S106: Yes), the ECU 200 determines that cavitation may occur in the high pressure fuel supply pump 100, and the target high pressure The side fuel pressure is switched to a new target high-pressure side fuel pressure (hereinafter referred to as a new target high-pressure side fuel pressure) corrected by multiplying the above-mentioned “normal target high-pressure side fuel pressure” by a predetermined multiple K. The ECU 200 adjusts the opening of the intake metering valve 105 of the high-pressure fuel supply pump 100 in accordance with the “new target high-pressure side fuel pressure” when the operating state is in the low load side region, so that the high-pressure side fuel pressure (rail pressure) is adjusted. Is controlled (S108).

  As shown in FIGS. 6 and 7, this “new target high-pressure side fuel pressure” is set as follows depending on which operating region the diesel engine 10 is in. The multiple K is obtained in advance by a fitting experiment or the like below, and is stored in the ROM of the ECU 200 as a control constant.

"Low rotation and low load range" = "Medium pressure"
The ECU 200 changes the target high-pressure side fuel pressure to “medium pressure” that is higher than the normal target high-pressure side fuel pressure (low pressure) when the operating state of the diesel engine 10 is in the low rotation and low load region. Since this is a low load side region, the amount of fuel that the high pressure fuel supply pump 100 should send out to the fuel rail 88 per cycle is small, and if it is set to the same value as the normal target high pressure side fuel pressure, the high pressure fuel This is because cavitation occurs in the supply pump 100 and there is a risk of oxidative degradation of the biodiesel fuel. The ECU 200 increases the high-pressure side fuel pressure compared to the normal target high-pressure side fuel pressure when the operating state is in the low rotation and low load region and the bioconcentration is high, that is, the opening of the intake metering valve 105 As a result, the occurrence of cavitation in the high-pressure fuel supply pump 100 is suppressed, and the oxidative deterioration of the biodiesel fuel is suppressed.

"Low rotation and high load range" = "Medium pressure / Low pressure"
The ECU 200 sets the target high-pressure side fuel pressure to “medium pressure” that is the same value as the normal target high-pressure side fuel pressure (intermediate pressure) when the operating state of the diesel engine 10 is in the low rotation and high load region. Since this is a high load region, the amount of fuel that the high-pressure fuel supply pump 100 should deliver to the fuel rail 88 per cycle is relatively large, and the possibility of cavitation occurring in the high-pressure fuel supply pump 100 is small. It is. When the operating state is in the low rotation high load region and the bioconcentration is high, the target high pressure side fuel pressure is changed to “low pressure” that is a value lower than the normal target high pressure side fuel pressure (intermediate pressure). It is good as a thing. This is because, when the bioconcentration is high, the combustion of the fuel is promoted by the oxygen-containing compound in the fuel, so the necessity for atomizing the fuel is relatively low, and the injection pressure of the fuel injection valve 80 That is, even if the high-pressure side fuel pressure is reduced compared to the normal target high-pressure side fuel pressure (intermediate pressure), the injected fuel injected from the fuel injection valve 80 can be sufficiently burned in the cylinder.

"High rotation and low load range" = "High pressure"
The ECU 200 changes the target high-pressure side fuel pressure to “high pressure”, which is a higher value than the normal target high-pressure side fuel pressure (intermediate pressure), when the operating state of the diesel engine 10 is in the high rotation and low load region. Since this is a low load side region, the amount of fuel that the high pressure fuel supply pump 100 should send out to the fuel rail 88 per cycle is small, and in addition, because it is a high rotation speed region, the high pressure pump 110 The eccentric cam 112 is rotationally driven at a relatively high speed, and the volumes of the pressure-increasing chambers 120 and 121 periodically change at a relatively high frequency, and the suction generated in the passages 106, 107 and 108 on the downstream side of the suction metering valve 105. This is because the negative pressure is large and cavitation is likely to occur particularly in the high-pressure fuel supply pump 100. When the operation state is in the high rotation and low load region and the bio concentration is high, the ECU 200 sets the target high pressure side fuel pressure to the same value as the normal target high pressure side fuel pressure. Occurrence of cavitation is determined by determining that the oxidative degradation of biodiesel fuel is likely to occur due to the occurrence, and increasing the high-pressure side fuel pressure compared to the normal target high-pressure side fuel pressure, that is, increasing the opening of the intake metering valve 105 This suppresses the oxidative degradation of biodiesel fuel.

"High rotation and high load range" = "High pressure / Medium pressure"
The ECU 200 sets the target high-pressure side fuel pressure to “high pressure”, which is the same value as the normal target high-pressure side fuel pressure (high pressure), when the operating state of the diesel engine 10 is in the high rotation high load region. Since this is a high load region, the amount of fuel that the high-pressure fuel supply pump 100 should deliver to the fuel rail 88 per cycle is relatively large, and the possibility of cavitation occurring in the high-pressure fuel supply pump 100 is small. It is. When the operating state is in the high rotation and high load region and the bioconcentration is high, the target high-pressure side fuel pressure is set to “medium pressure” that is lower than the normal target high-pressure side fuel pressure (high pressure). It is good as a thing. This is because, when the bioconcentration is high, the combustion of the fuel is promoted by the biodiesel fuel component (oxygen-containing compound) in the fuel, so the necessity for atomizing the fuel is relatively low. Even if the injection pressure of the injection valve 80, that is, the high-pressure side fuel pressure is reduced compared to the normal target high-pressure side fuel pressure (high pressure), the injected fuel injected from the fuel injection valve 80 can be sufficiently burned in the cylinder. is there.

  As described above, as shown in FIG. 2 and FIG. 5 to FIG. And when the operating state of the diesel engine 10 is in a predetermined low load side region (that is, a low rotation low load region and a high rotation low load region), the “low concentration” is lower than the determination concentration. Control is performed so that the high-pressure side fuel pressure rises. Specifically, the opening of the intake metering valve 105 of the high-pressure fuel supply pump 100 is increased. As a result, when the bioconcentration is relatively high and oxidative degradation of biodiesel fuel due to the occurrence of cavitation becomes a problem, oxidative degradation of biodiesel fuel is suppressed by suppressing the occurrence of cavitation in the high-pressure fuel supply pump. can do.

  In the present embodiment, the ECU 200 determines whether or not the bioconcentration in the fuel is equal to or higher than a predetermined determination concentration. When the ECU 200 determines that the “high concentration” is equal to or higher than the determination concentration, the ECU 200 When the operating state is in a predetermined low load side region, the high pressure side fuel pressure is controlled to be increased compared to the case where the low concentration is lower than the determination concentration, but the control mode of the high pressure side fuel pressure is It is not limited to this.

  For example, the ECU 200 determines whether the bioconcentration in the fuel is any one of “low concentration”, “medium concentration”, and “high concentration”, and the operation state of the diesel engine 10 falls within a predetermined low load side region. In some cases, when the bioconcentration is “medium concentration”, the fuel pressure on the high-pressure side is controlled to be higher than when it is “low concentration”, and when the bioconcentration is “high concentration”, “ Control may be performed such that the high-pressure side fuel pressure is further increased as compared with the case of “medium concentration”.

  Further, when the operation state of the diesel engine 10 is in a predetermined low load side region, the ECU 200 increases the high-pressure side fuel pressure as the bioconcentration in the fuel increases even if the operation state of the diesel engine 10 is the same. May be controlled to be higher (that is, the opening of the intake metering valve 105 is increased).

  As described above, the diesel engine 10 according to the present embodiment has a plurality of cylinders, and includes the fuel injection valve 80 for each cylinder, and each fuel injection valve 80 receives a supply of fuel. Is provided with a high-pressure fuel supply pump 100 that boosts and supplies fuel sucked from a low-pressure side fuel passage (for example, the low-pressure fuel passage 222), and an ECU 200 as a control device for a diesel engine includes: The high pressure side fuel pressure (rail pressure), which is the fuel pressure in the high pressure side fuel passage, can be controlled. The ECU 200 has the operating state (engine speed and engine load) of the diesel engine 10 in a predetermined low load side region, and the “bio concentration” that is the concentration of biodiesel fuel in the fuel is equal to or higher than a predetermined determination concentration. In such a case, control is performed so that the high-pressure side fuel pressure (rail pressure) becomes higher than that in the case where it falls below the determination concentration. When the operating state is in the low load side region, it is possible to suppress the occurrence of a cavitation in the portion where the fuel pressure is low in the fuel flow path in the high-pressure fuel supply pump 100 and the cavitation is caused in the portion. Oxidative degradation of biodiesel fuel can be suppressed.

  In the present embodiment, the high-pressure fuel supply pump 100 is provided with an intake metering valve 105 that adjusts the flow rate of fuel sucked into the booster chamber by a throttling action, and the ECU 200 operates the diesel engine 10 at a predetermined low level. When it is in the load side region and the bioconcentration is equal to or higher than the determination concentration, the opening of the intake metering valve 105 is controlled to be larger than when the bioconcentration is lower than the determination concentration. In the low load side region where the amount of fuel to be sent to the high pressure side fuel passage per cycle by the high pressure fuel supply pump 100 is small, and when the bioconcentration in the fuel is high, the intake is in comparison with the case where the fuel concentration is below the determination concentration By increasing the opening of the metering valve 105, the pressure drop due to the “throttle” of the intake metering valve 105 is suppressed and the occurrence of cavitation is suppressed, so that the oxidative degradation of biodiesel fuel due to the occurrence of cavitation Can be suppressed.

  Further, in this embodiment, when the operation state of the diesel engine is not in the predetermined low load side region (that is, in the high load side region) and the bioconcentration in the fuel is equal to or higher than the determination concentration, the determination concentration is set. The fuel pressure is controlled so that the fuel pressure on the high-pressure side is higher than the lower limit. When the bioconcentration is high, the combustion of fuel in the cylinder is promoted by oxygenated compounds in the fuel. Therefore, the injection pressure of the fuel injection valve 80, that is, the high-pressure side fuel pressure can be reduced. By reducing the high-pressure fuel pressure, the mechanical power used to drive the high-pressure fuel supply pump 100 can be reduced.

  In the present embodiment, the diesel engine 10 includes the EGR device 70 and the turbocharger 60, and includes the NOx occlusion reduction type catalyst 55a and the DPNR catalyst system 55c as exhaust aftertreatment devices. The configuration of the applicable diesel engine is not limited to this aspect. The high-pressure fuel supply pump 100 that boosts and supplies the fuel sucked from the low-pressure side fuel passage (for example, the low-pressure fuel passage 222) to the high-pressure side fuel passage (for example, the fuel rail 88) to which the fuel injection valve 80 is supplied with fuel. The present invention can be applied to any diesel engine provided with

  As described above, the control device for a diesel engine according to the present invention includes the high pressure fuel supply pump that boosts and supplies the fuel sucked from the low pressure side fuel passage to the high pressure side fuel passage where the fuel injection valve receives the supply of fuel. Useful for equipped diesel engines.

It is a mimetic diagram showing a schematic structure of vehicles containing a diesel engine concerning this embodiment. It is a mimetic diagram showing the composition of the fuel supply system concerning this embodiment. It is a schematic diagram which shows the structure of the high pressure fuel supply pump which concerns on this embodiment. It is sectional drawing which shows the structure of the intake metering valve of the high pressure fuel supply pump which concerns on this embodiment. It is a flowchart which shows the target high pressure side fuel pressure setting control which the control apparatus (ECU) for diesel engines which concerns on this embodiment performs. It is a figure which shows the relationship between the driving | running area | region of the diesel engine which concerns on this embodiment, and the target value of a high side fuel pressure. It is a graph which shows the relationship between the density | concentration of the biodiesel fuel in the fuel supplied to the diesel engine which concerns on this embodiment, and the target value of a high side fuel pressure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 5 Fuel supply system 10 Diesel engine 80 Fuel injection valve 82 Fuel distribution pipe 88 Fuel rail (fuel chamber, high pressure side fuel passage)
98 A / F sensor 100 High pressure fuel supply pump (High pressure supply pump)
102 Feed Pump 105 Suction Metering Valve for High Pressure Fuel Supply Pump 200 Electronic Control Device for Diesel Engine (ECU, Control Unit, Storage Unit, Bio Concentration Estimation Unit)
220 Fuel tank 222 Low pressure fuel passage (low pressure side fuel passage)
228 Fuel property detection sensor

Claims (4)

The fuel injection device is used in a diesel engine having a high-pressure fuel supply pump that supplies a high-pressure side fuel passage to which fuel is supplied by boosting fuel sucked from the low-pressure side fuel passage. A control device capable of controlling a certain high-pressure side fuel pressure,
When the operation state of the diesel engine is in a predetermined low load side region and the concentration of biodiesel fuel in the fuel is equal to or higher than the determination concentration,
A control device for a diesel engine that controls the fuel pressure on the high-pressure side to be higher than when the concentration falls below the determination concentration. The control device for a diesel engine according to claim 1,
The high-pressure fuel supply pump includes an intake metering valve that adjusts the flow rate of fuel drawn into the booster chamber by a throttling action.
When the operation state of the diesel engine is in a predetermined low load side region and the concentration of biodiesel fuel in the fuel is equal to or higher than the determination concentration,
A control device for a diesel engine that controls the opening of the intake metering valve to be larger than when the concentration is lower than the determination concentration. The control device for a diesel engine according to claim 1,
When the operation state of the diesel engine is not in the predetermined low load side region and the concentration of the biodiesel fuel in the fuel is equal to or higher than the determination concentration,
A control device for a diesel engine that controls the fuel pressure on the high-pressure side to be higher than when the concentration is lower than the determination concentration. The fuel injection device has a high-pressure fuel supply pump that boosts and supplies the fuel sucked from the low-pressure fuel passage to the high-pressure fuel passage that receives the supply of fuel. A control device that is used in a diesel engine equipped with an intake metering valve that adjusts the amount of fuel sucked, and that can control the opening of the intake metering valve,
When the operation state of the diesel engine is in a predetermined low load side region and the concentration of biodiesel fuel in the fuel is equal to or higher than the determination concentration,
A control device for a diesel engine that controls the opening of the intake metering valve to be larger than when the concentration is lower than the determination concentration.

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