JP5482717B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a pressure accumulating container capable of accumulating fuel in a high pressure state, a fuel pump for discharging fuel from a fuel tank to the pressure accumulating container, and an electronically controlled fuel to which fuel stored in the pressure accumulating container is supplied The present invention relates to a fuel injection control device for an internal combustion engine applied to a fuel injection system for an internal combustion engine configured to include an injection valve.

  As this type of control device, as can be seen in the following Patent Document 1, the area of the passage in the fuel injection valve that guides the fuel supplied from the pressure accumulating vessel to the injection hole changes depending on the temperature change of the fuel injection valve. Due to this, there is known one that suppresses a decrease in the adjustment accuracy of the fuel injection amount from the fuel injection valve. Specifically, the control device first estimates the temperature of the fuel flowing into the fuel injection valve based on the flow rate of the fuel flowing into the fuel injection valve from the fuel tank via the fuel pipe, and based on the estimated fuel temperature. Estimate the temperature of the fuel injector. Then, the fuel injection amount from the fuel injection valve is corrected based on the estimated temperature of the fuel injection valve. Thereby, suppression of the fall of the adjustment precision of the fuel injection quantity resulting from the temperature change of a fuel injection valve is aimed at.

JP 2005-180352 A

  By the way, while the fuel flowing into the fuel inlet of the fuel injection valve from the pressure accumulator flows through the fuel injection valve, heat is exchanged between the fuel flowing in the fuel injection valve (hereinafter referred to as fuel flow) and the fuel injection valve. Is done. For this reason, the temperature of the fuel flowing into the fuel inlet and the temperature of the circulating fuel can be different. In this case, due to the change in the viscosity of the circulating fuel, the influence of the circulating fuel on the nozzle needle of the fuel injection valve that opens and closes the nozzle hole may change. In this case, the behavior of the nozzle needle at the time of fuel injection from the fuel injection valve changes, so that the fuel injection amount from the fuel injection valve may deviate from the initially assumed amount.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel injection control device for an internal combustion engine that can suitably suppress a decrease in adjustment accuracy of the fuel injection amount from the fuel injection valve. It is to provide.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

A first aspect of the present invention is a pressure accumulation container capable of accumulating fuel in a high pressure state, a fuel pump that discharges fuel from a fuel tank to the pressure accumulation container, and a fuel injection valve that is supplied with fuel stored in the pressure accumulation container The fuel injection valve includes a fuel inlet into which fuel supplied from the pressure accumulating vessel flows, and a nozzle that opens and closes the injection hole of the fuel injection valve. A fuel injection valve, and when there is a difference between the temperature of the fuel injection valve and the temperature of the fuel flowing into the fuel inlet, the fuel flowing from the fuel inlet stays in the fuel injection valve The longer the residence time equivalent, which is the equivalent of time, is estimated by the fuel temperature estimation means for estimating the temperature of the fuel in the fuel injection valve so as to approximate the temperature of the fuel injection valve, and the fuel temperature estimation means Of spent fuel Correction means for correcting the fuel injection amount from the fuel injection valve based on the degree, and operating means for energizing the fuel injection valve based on the fuel injection amount corrected by the correction means. To do.

  When the fuel that has flowed into the fuel inflow port stays in the fuel injection valve, for example, flows through a passage in the fuel injection valve, heat exchange is performed between the fuel and the fuel injection valve in the fuel injection valve. When heat exchange is performed, the temperature of the fuel in the fuel injection valve changes, so that the viscosity of the fuel changes. When the fuel viscosity changes, the influence of the fuel in the fuel injection valve on the behavior of the nozzle needle may change due to the change in the flow rate of the fuel flowing through the passage in the fuel injection valve.

  Here, the heat exchanged between the fuel in the fuel injection valve and the fuel injection valve tends to increase as the time during which the fuel flowing in from the fuel inlet stays in the fuel injection valve is longer. For this reason, the amount of change in the temperature of the fuel in the fuel injection valve tends to increase as the residence time increases.

  In view of this point, in the above-described invention, the longer the equivalent amount of time that the fuel flowing in from the fuel inlet stays in the fuel injector (the equivalent amount of residence time) is, the longer the fuel injection is made to approximate the temperature of the fuel injector. Estimate the temperature of the fuel in the valve.

  Here, according to the temperature of the fuel in the fuel injection valve, it is possible to grasp a change in the influence of the fuel in the fuel injection valve on the behavior of the nozzle needle. That is, it is possible to grasp the deviation of the fuel injection amount from the fuel injection valve due to the temperature change of the fuel in the fuel injection valve.

  In view of this point, in the above invention, the fuel injection amount from the fuel injection valve is corrected based on the estimated value of the fuel temperature in the fuel injection valve, and the fuel injection valve is energized based on the corrected fuel injection amount. Thereby, the fall of the adjustment precision of the fuel injection quantity from a fuel injection valve can be suppressed suitably.

According to a second invention, in the first invention, the residence time equivalent amount is calculated based on one combustion cycle of the internal combustion engine and a fuel injection amount from the fuel injection valve required for the one combustion cycle. A residence time calculation means is further provided, wherein the fuel temperature estimation means estimates the temperature of the fuel in the fuel injection valve based on the residence time equivalent amount calculated by the residence time calculation means.

  When fuel is injected from the fuel injection valve, an amount of fuel corresponding to the fuel injection amount flows from the fuel inlet side toward the injection hole side in the fuel injection valve. In view of this point, in the above invention, the residence time equivalent amount is calculated based on one combustion cycle of the internal combustion engine and the fuel injection amount required for one combustion cycle. As a result, the residence time equivalent amount can be appropriately calculated, and the temperature of the fuel in the fuel injection valve can be appropriately estimated by the fuel temperature estimating means.

According to a third invention, in the first or second invention, the fuel injection valve is formed by an inner wall of the fuel injection valve, and accommodates the nozzle needle, the needle storage chamber and the fuel flow. A fuel passage connecting the inlet, a pressure control chamber for applying fuel pressure to the opposite side of the nozzle needle to the side facing the nozzle hole, the needle housing chamber, a high pressure fuel passage including the fuel passage, and the fuel tank A valve body that operates to connect any one of the low-pressure fuel passages connected to the pressure control chamber, and an electric actuator that is energized to operate the valve body, and is configured to energize the electric actuator. The fuel injection valve is configured to inject fuel from the nozzle hole through the high-pressure fuel passage by operating the nozzle needle. The fuel passage and the electric actuator are arranged in a direction perpendicular to the central axis direction of the fuel injection valve, and the pressure control chamber is disposed in the electric actuator in the central axis direction of the fuel injection valve. It is arrange | positioned rather than the said nozzle hole side.

  In the above-described invention, the pressure control chamber and the high-pressure fuel passage are communicated with each other by the operation of the valve body, so that the high-pressure fuel flows into the pressure control chamber from the high-pressure fuel passage and the fuel injection valve is closed. On the other hand, by connecting the pressure control chamber and the low-pressure fuel passage by the operation of the valve body, the high-pressure fuel flows out from the pressure control chamber to the low-pressure fuel passage to open the fuel injection valve.

  Here, since the fuel passage and the electric actuator are arranged in the above-described manner in the direction perpendicular to the central axis direction of the fuel injection valve, the fuel passage from the fuel inlet to the pressure control chamber becomes long. For this reason, the amount of change in the temperature of the fuel before the fuel flowing into the fuel inlet reaches the pressure control chamber is likely to increase, and the amount of change in the flow rate of the fuel flowing into the pressure control chamber is likely to increase. In this case, when the pressure change rate in the pressure control chamber changes, the behavior of the nozzle needle changes, and the adjustment accuracy of the fuel injection amount tends to decrease. For this reason, the above-mentioned invention in which the adjustment accuracy of the fuel injection amount is likely to be lowered has a great merit of including the fuel temperature estimating means and the correcting means.

According to a fourth invention, in the third invention, the correction means corrects the fuel injection amount to be increased as the temperature of the fuel in the fuel injection valve is higher.

  The fuel injection valve in the above invention has a characteristic that the fuel injection amount from the fuel injection valve decreases as the fuel temperature in the fuel injection valve increases. For this reason, for example, when the fuel temperature in the fuel injection valve is higher than the assumed temperature, there is a concern that the actual fuel injection amount from the fuel injection valve is less than the assumed amount. In view of this point, in the above invention, the fuel injection amount can be appropriately corrected in the above aspect.

According to a fifth invention, in any one of the first to fourth inventions, the fuel injection valve is formed by an inner wall of the fuel injection valve, and the needle storage chamber for storing the nozzle needle, and the needle The nozzle needle further includes a fuel passage that connects the storage chamber and the fuel inlet, and the nozzle needle includes an enlarged portion whose outer diameter is enlarged at an intermediate portion in the axial direction thereof.

  In the said invention, the said enlarged part is provided in the nozzle needle. For this reason, the part by which the area of the channel | path formed with the outer peripheral surface of a nozzle needle and the said inner wall is made small by an enlarged part will be formed. Due to this, the flow rate of the fuel flowing through the passage formed by the outer peripheral surface of the nozzle needle and the inner wall changes due to the temperature change of the fuel, and the differential pressure before and after passing through the portion where the area of the passage is reduced Can change. In this case, due to a change in the force acting on the nozzle needle, the behavior of the nozzle needle changes, and the adjustment accuracy of the fuel injection amount tends to decrease. In particular, when the fuel temperature becomes excessively low, there is a concern that the influence becomes remarkably large. For this reason, the above-mentioned invention in which the adjustment accuracy of the fuel injection amount is likely to be lowered has a great merit of including the fuel temperature estimating means and the correcting means.

A sixth invention is characterized in that, in the fifth invention, the correction means corrects the fuel injection amount to be increased as the fuel temperature is lower in a region where the fuel temperature in the fuel injection valve is lower. To do.

  The fuel injection valve in the above invention has a characteristic that the fuel injection amount from the fuel injection valve decreases as the fuel temperature decreases in the region where the fuel temperature in the fuel injection valve is low. For this reason, for example, when the fuel temperature in the fuel injector is excessively lower than the assumed temperature, there is a concern that the actual fuel injection amount from the fuel injector is less than the assumed amount. In view of this point, in the above invention, the fuel injection amount can be appropriately corrected in the above aspect.

According to a seventh invention, in any one of the first to sixth inventions, control means for injecting fuel from the fuel injection valve a plurality of times into one cylinder of the internal combustion engine in one combustion cycle of the internal combustion engine; Means for calculating the amount of fuel required for one combustion cycle of the internal combustion engine based on the required torque of the internal combustion engine, and means for dividing the required amount of fuel and assigning it to each of the multiple injections Further, the correction means corrects the fuel amount allocated to each of the plurality of injections based on the temperature of the fuel estimated by the fuel temperature estimation means.

  Due to the temperature change of the fuel in the fuel injection valve, the fuel injection amount corresponding to each of the multiple injections may deviate from the initially assumed amount. Here, the fuel injection amount corresponding to each of the multiple injections does not necessarily deviate at the same rate, for example.

  In view of this point, in the above invention, the correction accuracy of the fuel injection amount can be improved by correcting the fuel amount assigned to each of the multiple injections by the correcting means.

The system block diagram concerning one Embodiment. The figure which shows the relationship between the fuel temperature and fuel injection quantity concerning one Embodiment. The enlarged view of the fuel injection valve concerning one Embodiment. The figure which shows the relationship between fuel temperature and the viscosity of a fuel. The figure which shows the outline | summary of an annular clearance flow. The figure which shows the change of the injection rate resulting from the fuel temperature concerning one Embodiment. The flowchart which shows the procedure of the correction process of the fuel injection quantity concerning one Embodiment. The figure which shows the outline | summary of the estimation method of the fuel temperature in the fuel injection valve concerning one Embodiment. The figure which shows the outline | summary of the correction method of the fuel injection amount concerning one Embodiment. The figure which shows the structure of the fuel injection valve concerning other embodiment. The figure which shows the relationship between the fuel temperature and fuel injection quantity concerning other embodiment.

  Hereinafter, the control apparatus according to the present invention is a pressure accumulating fuel equipped with a four-stroke multi-cylinder (four-cylinder) on-board diesel engine (hereinafter referred to as an engine) whose intake / compression / expansion / exhaust stroke is one combustion cycle (720 ° C.). An embodiment applied to an injection system will be described with reference to the drawings.

  FIG. 1 shows a system configuration according to the present embodiment.

  As shown in the drawing, the fuel (light oil) in the fuel tank 10 is pumped up by an engine-driven fuel pump 14 that is driven as the crankshaft 12 rotates, and is discharged from the fuel pump 14. Specifically, the fuel pump 14 includes a trochoid feed pump that pumps the fuel in the fuel tank 10 through the low-pressure pipe 16, and a plunger-type high-pressure pump that pressurizes and supplies (pumps) the pumped fuel to the common rail 18. It is configured with.

  The fuel pump 14 further includes an intake metering valve, which is an electronically controlled valve body that adjusts the discharge amount of the fuel pump 14 by adjusting the amount of fuel sucked into the high-pressure pump, and the fuel pump 14. A fuel temperature sensor 20 is provided for detecting the temperature of the internal fuel (pump inlet fuel temperature, which is the temperature of the fuel pumped up by the feed pump).

  The fuel discharged from the fuel pump 14 is pumped to the common rail 18. The common rail 18 is a pressure accumulating container for storing the fuel pumped from the fuel pump 14 in a high pressure state and supplying the stored fuel to the electronically controlled fuel injection valve 24 of each cylinder via the high pressure pipe 22. The common rail 18 is provided with a fuel pressure sensor 25 for detecting the fuel pressure (rail pressure) inside the common rail 18.

  The fuel injection valve 24 includes a body 26 (a member including a nozzle body and a holder body) and a pressure chamber forming member 28, and a plurality of injection holes 30 formed in the body 26 include a combustion chamber of the engine. 32 so as to protrude to 32.

  Specifically, in the body 26, the nozzle hole 30, the annular needle seat portion 34, the substantially cylindrical needle housing chamber 36, and the central axis direction of the fuel injection valve 24 are sequentially formed from the front end side of the fuel injection valve 24. A fuel passage 38 extending in the (vertical direction) and connected to the needle housing chamber 36 and a fuel inlet 40 connecting the high-pressure fuel from the common rail 18 and connecting to the fuel passage 38 are formed.

  The needle accommodation chamber 36 accommodates a nozzle needle 42 that is displaceable in the direction of the central axis of the fuel injection valve 24. The nozzle needle 42 is a substantially cylindrical valve member (needle valve) extending in the direction of the central axis of the fuel injection valve 24, and a tip portion for opening and closing the nozzle hole 30 in order from the nozzle hole 30 side in the central axis direction. 42a, the guide part 42b, and the back pressure part 42c are comprised integrally. Incidentally, an annular fuel passage extending in the central axis direction of the fuel injection valve 24 is formed between the inner wall of the body 26 that forms the needle housing chamber 36 and the outer peripheral surface of the nozzle needle 42.

  The tip end portion 42 a is seated on the needle seat portion 34, thereby blocking the needle accommodation chamber 36 and the combustion chamber 32. On the other hand, the tip end portion 42 a is separated from the needle seat portion 34, thereby communicating the needle accommodation chamber 36 and the combustion chamber 32.

  The guide portion 42 b is a substantially cylindrical portion that is larger than the outer diameter of the tip end portion 42 a and extends in the central axis direction of the fuel injection valve 24. Specifically, the guide portion 42b is provided at a position corresponding to the annular fuel passage in the nozzle needle 42. The guide portion 42b is in contact with the inner wall of the body 26 forming the needle housing chamber 36, thereby stabilizing the vertical displacement of the nozzle needle 42 and preventing the tip portion 42a from being seated at a position displaced from the needle seat portion 34. Has an operation stability function.

  Incidentally, in the present embodiment, hereinafter, the fuel passage 38 and the annular fuel passage are collectively referred to as a high pressure fuel passage. The fuel flowing in from the fuel inlet 40 is guided to the injection hole 30 by the high-pressure fuel passage.

  The nozzle needle 42 is applied with a force toward the nozzle hole 30 by a needle spring 44.

  The back pressure portion 42 c is provided on the opposite side (back side) of the nozzle needle 42 to the side facing the needle seat portion 34. Further, the back pressure part 42 c faces the pressure control chamber 46.

  The pressure control chamber 46 is partitioned by the back pressure portion 42 c (the rear end of the nozzle needle 42) and the pressure chamber forming member 28, and communicates with the control valve housing chamber 50 through the orifice 48.

  The control valve accommodating chamber 50 is communicated with either the high pressure fuel passage or the low pressure fuel passage 54 connected to the fuel tank 10 by the operation of the control valve 52 accommodated therein. Specifically, the control valve 52 is applied with a force in a direction to shut off the control valve housing chamber 50 and the low-pressure fuel passage 54 by a valve spring 56.

  Further, the control valve 52 can be displaced by an electric actuator 62 via a piston 58 and a displacement enlarging unit 60.

  The displacement enlarging unit 60 has a function of increasing the displacement amount of the piston 58 by a predetermined fluid (for example, fuel for injection) filled in the displacement enlarging unit 60.

  The electric actuator 62 is a member that extends in the central axis direction of the fuel injection valve 24, and is arranged in the body 26 so as to be aligned with the fuel passage 38 in a direction perpendicular to the central axis direction of the fuel injection valve 24. According to such an arrangement, the pressure control chamber 46 is arranged closer to the injection hole 30 than the electric actuator 62 in the central axis direction of the fuel injection valve 24.

  Here, in the present embodiment, a piezoelectric stack in which a plurality of piezoelectric elements and electrode plates are alternately stacked is assumed as the electric actuator 62. Note that the piezo element is a capacitive load that expands and contracts due to the piezoelectric effect, and is switched between an expanded state and a contracted state by charging and discharging. In addition, the piezo stack extends in the direction of the central axis of the fuel injection valve 24. In order to ensure the displacement of the control valve 52 required for the fuel injection function, it is necessary to alternately stack a plurality of piezo elements and electrode plates. Because there is.

  In such a configuration, when the electric actuator 62 is not energized and the piezo element is in the contracted state, the control valve 52 shuts off the control valve housing chamber 50 and the low pressure fuel passage 54 by the force of the valve spring 56 and accommodates the control valve. The chamber 50 and the high-pressure fuel passage are displaced so as to communicate with each other. For this reason, high pressure fuel is supplied to the pressure control chamber 46 from the high pressure fuel passage through the orifice 48, and the pressure applied to the nozzle needle 42 by the high pressure fuel in the pressure control chamber 46 and the high pressure fuel in the needle housing chamber 36. Becomes substantially equal to the pressure applied to the nozzle needle 42. Thus, the force of the needle spring 44 displacing the nozzle needle 42 toward the nozzle hole 30 of the fuel injection valve 24 causes the nozzle needle 42 to be seated on the needle seat portion 34 (the fuel injection valve 24 is closed). Become. Therefore, fuel injection from the nozzle hole 30 is stopped.

  On the other hand, when the electric actuator 62 is energized and the piezo element is in the extended state, the control valve 52 overcomes the force applied from the valve spring 56 to shut off the control valve housing chamber 50 and the high-pressure fuel passage. Further, the control valve accommodating chamber 50 and the low pressure fuel passage 54 are displaced so as to communicate with each other. Therefore, the high pressure fuel in the pressure control chamber 46 flows out to the low pressure fuel passage 54 through the orifice 48 and the control valve storage chamber 50. The pressure applied to the nozzle needle 42 by the fuel in the pressure control chamber 46 is smaller than the pressure applied to the nozzle needle 42 by the high-pressure fuel in the needle housing chamber 36. When the force due to the pressure difference becomes larger than the force by which the needle spring 44 displaces the nozzle needle 42 toward the injection hole 30 of the fuel injection valve 24, the nozzle needle 42 is separated from the needle seat portion 34 (fuel). The injection valve 24 is opened). Thereby, high-pressure fuel is injected from the injection hole 30.

  The fuel injection valve 24 having such a structure is referred to as a center feed fuel injection valve. According to the center-feed type fuel injection valve, the amount of static leak can be greatly reduced (or made zero). Here, the static leak means fuel that always flows out to the low-pressure fuel passage 54 through a gap or the like in the fuel injection valve 24 when the fuel injection valve 24 is closed.

  The electronic control unit (ECU 64) is a control unit that operates various actuators necessary for various controls of the accumulator fuel injection system, and includes a microcomputer, a memory 64a (nonvolatile memory), and the like. The ECU 64 includes an accelerator sensor 66 that detects the amount of accelerator operation by the driver, a water temperature sensor 68 that detects the temperature (cooling water temperature) of cooling water for cooling the engine, and an oil temperature that detects the temperature (oil temperature) of engine oil. Detection signals of the sensor 70, the intake air temperature sensor 72 that detects the temperature of the intake air supplied to the combustion chamber 32, and the intake pressure sensor 74 that detects the pressure of the intake air supplied to the combustion chamber 32 are sequentially input. The ECU 64 also detects an outside air temperature sensor 76 that detects the outside air temperature, a vehicle speed sensor 78 that detects the traveling speed of the vehicle, a crank angle sensor 80 that detects the rotation angle of the crankshaft 12, the fuel temperature sensor 20, and the fuel pressure sensor 25. Such detection signals are sequentially input. Based on these input signals, the ECU 64 performs engine combustion control such as energizing the intake metering valve of the fuel pump 14 to control the rail pressure to the target value.

  In particular, the ECU 64 performs fuel injection control in which the electric actuator 62 is energized so that fuel is injected and supplied from the fuel injection valve 24 a plurality of times (multistage injection) to one cylinder during one combustion cycle (720 ° C. A). In the present embodiment, pilot injection and main injection are performed as the multistage injection. Here, the pilot injection promotes the mixing of the fuel and air immediately before ignition by injection of a very small amount of fuel, and shortens the ignition timing delay after the main injection to suppress the generation of nitrogen oxides (NOx). However, this is done for the purpose of reducing combustion noise and vibration. On the other hand, the main injection contributes to engine torque generation and has the maximum injection amount during multi-stage injection.

  Specifically, the fuel required in one combustion cycle to realize generation of the engine required torque based on the accelerator operation amount based on the output value of the accelerator sensor 66 and the engine speed based on the output value of the crank angle sensor 80. A fuel injection amount (required injection amount) from the injection valve 24 is calculated. Next, the required injection amount is divided into injection amounts for pilot injection and main injection, and these injection amounts are set as command values (command injection amounts) for the fuel injection valve 24. Further, a time interval (interval) between the end timing of the pilot injection and the start timing of the main injection is calculated from the required injection amount, the engine rotation speed, the cooling water temperature based on the output value of the water temperature sensor 68, and the like. Then, based on the command injection amount, the interval, the rail pressure based on the output value of the fuel pressure sensor 25, and the like, a command injection period (drive signal) for the fuel injection valve 24 for performing multi-stage injection is calculated. Then, by energizing the electric actuator 62 based on the drive signal, the fuel injection valve 24 is opened, and an amount of fuel corresponding to the required injection amount is injected from the injection hole 30.

  The drive signal is usually calculated using a map associated with the rail pressure and the fuel injection amount from the fuel injection valve 24. This map is normally created by an adaptation operation under a reference temperature condition (for example, the cooling water temperature is 80 ° C.) and stored in the memory 64a of the ECU 64.

  By the way, when the temperature of the fuel flowing through the high-pressure fuel passage changes, the viscosity of the fuel changes, and the fuel injection amount from the fuel injection valve 24 may deviate from the initially assumed amount (the amount assumed at the time of adaptation). This is because the temperature of the fuel flowing through the high-pressure fuel passage deviates from the temperature corresponding to the temperature condition that is the reference for adaptation. When such a change in fuel temperature occurs, even if the drive signals are the same, as shown in FIG. 2, the fuel injection amount Q increases in the low temperature region as the fuel temperature increases, and then the high temperature region. In this case, the injection characteristic changes such that the fuel injection amount Q decreases. Hereinafter, in addition to FIG. 2, the mechanism by which the fuel injection amount Q changes due to the change in the temperature of the fuel flowing through the high-pressure fuel passage will be described with reference to FIGS.

  FIG. 3 shows a partially enlarged view of the fuel injection valve 24. In FIG. 3, the gap between the back pressure portion 42c of the nozzle needle 42 and the pressure chamber forming member 28, and the gap between the inner wall of the body 26 forming the needle housing chamber 36 and the outer peripheral surface of the guide portion 42b. Is displayed larger. Further, illustration of the needle spring 44 and the valve spring 56 is omitted.

  First, the mechanism by which the fuel injection amount Q decreases as the fuel temperature increases when the fuel temperature is in the high temperature region will be described. Note that the high temperature region refers to a region where the increase in the viscosity of the fuel accompanying a decrease in the fuel temperature is moderate (see FIG. 4).

When the temperature of the fuel flowing through the high-pressure fuel passage increases, the fuel viscosity μ decreases, so that the fuel from the high-pressure fuel passage passes through the annular gap (flow passage A) between the back pressure portion 42c and the pressure chamber forming member 28. The flow rate of fuel flowing into the pressure control chamber 46 increases. As the fuel flow rate increases, the differential pressure before and after the fuel passes through the flow path A decreases. Here, the fuel viscosity μ, the fuel flow rate, and the differential pressure are determined by the following equation (c1) for the annular gap flow.
Q = (π × d × h ^ 3) / (12 × μ × L) × (P1-P2) (c1)
However,
Q: Flow rate of fluid passing through the annular gap π: Circumferential ratio d: Inner diameter of the annular gap h: Gap μ: Fluid viscosity (absolute viscosity)
L: Length of the annular gap P1-P2: Differential pressure before and after passing through the annular gap FIG. 5 is a diagram showing an outline of the annular gap. Specifically, FIG. 5A is a plan view showing a model of an annular gap, and FIG. 5B is a cross-sectional view taken along the line AA in FIG.

  Returning to FIG. 3, when the flow rate of the fuel flowing into the pressure control chamber 46 increases, the following phenomenon occurs under the situation where the fuel injection valve 24 opens or closes.

  In a situation where the fuel injection valve 24 is opened from the closed state, that is, in a situation where the pressure control chamber 46 and the low pressure fuel passage 54 are communicated, the fuel injection valve 24 flows into the pressure control chamber 46 via the flow path A. As the amount of fuel to be increased, the rate of pressure decrease in the pressure control chamber 46 decreases, and the rate at which the nozzle needle 42 operates in the direction away from the needle seat portion 34 decreases. Thereby, the valve opening timing of the fuel injection valve 24 is delayed, and the fuel injection amount Q from the fuel injection valve 24 decreases.

  On the other hand, in the situation where the fuel injection valve 24 is changed from the open state to the closed state, that is, in the situation where the pressure control chamber 46 and the high pressure fuel passage communicate with each other, in addition to the passage A, the high pressure fuel passage The amount of fuel flowing into the pressure control chamber 46 through the flow path (flow path B) through the control valve accommodating chamber 50 and the orifice 48 increases. For this reason, the speed at which the pressure in the pressure control chamber 46 increases is increased, and the speed at which the nozzle needle 42 operates in the direction of seating on the needle seat portion 34 increases. Thereby, the valve closing timing of the fuel injection valve 24 is advanced, and the fuel injection amount Q from the fuel injection valve 24 is reduced.

  In the high temperature region, the fuel injection amount Q from the fuel injection valve 24 with respect to the same drive signal decreases as the fuel temperature increases due to such a mechanism.

  When the fuel temperature increases, the annular gap (flow path) between the tip 42a and the needle seat 34 immediately after the tip 42a starts to be separated from the needle seat 34 by the opening operation of the fuel injection valve 24. Due to the change in the amount of fuel flowing through C), the fuel injection amount Q increases. In other words, as the amount of fuel flowing through the flow path C increases, the pressure acting on the lower end of the nozzle needle 42 increases due to a decrease in the differential pressure before and after passage through the flow path C. For this reason, the speed at which the nozzle needle 42 operates in the direction away from the needle seat portion 34 increases, and the fuel injection amount Q increases. However, the degree of shift of the fuel injection amount Q due to the influence of the flow path C is smaller than the degree of shift of the fuel injection amount Q due to the influence of the flow paths A and B. For this reason, in the high temperature region, the fuel injection amount Q decreases as the fuel temperature increases.

  Next, the mechanism by which the fuel injection amount Q decreases when the fuel temperature is low when the fuel temperature is in the low temperature region will be described. Note that the low temperature region refers to a region where the amount of increase in the viscosity of the fuel accompanying a decrease in the fuel temperature suddenly increases (see FIG. 4 above).

  When the temperature of the fuel flowing through the high-pressure fuel passage becomes excessively low, the viscosity μ of the fuel suddenly increases, so that an annular gap between the outer peripheral surface of the guide portion 42b and the inner wall of the body 26 forming the needle housing chamber 36 is obtained. The fuel injection amount Q decreases due to the influence of (channel D).

  That is, in a situation where the fuel injection valve 24 is changed from the open state to the closed state, the amount of fuel flowing into the pressure control chamber 46 from the high pressure fuel passage via the flow paths A and B decreases, and the pressure control chamber 46 The rate of increase in pressure decreases.

  On the other hand, when the viscosity of the fuel becomes excessively high, the degree of decrease in the amount of fuel flowing through the flow path D increases, so that the degree of decrease in the fuel pressure in the vicinity of the tip 42a is less than the degree of decrease in the pressure in the pressure control chamber 46. Become big enough. In particular, the length of the guide portion 42b (the length in the central axis direction of the fuel injection valve 24) tends to be increased in order to ensure the operation stabilizing function of the nozzle needle 42. The pressure difference at is increased, and the degree of decrease in the fuel pressure in the vicinity of the tip 42a tends to increase.

  When the degree of pressure decrease near the tip end portion 42a is greater than the degree of pressure decrease in the pressure control chamber 46, the pressure difference acting on the upper and lower ends of the nozzle needle 42 increases, so that the needle seat portion 34 is seated in the direction of seating. The speed at which the nozzle needle 42 operates increases. Thereby, the valve closing timing of the fuel injection valve 24 is advanced, and the fuel injection amount Q from the fuel injection valve 24 is reduced.

  In the low temperature region, the fuel injection amount Q from the fuel injection valve 24 with respect to the same drive signal decreases as the fuel temperature decreases due to such a mechanism.

  Note that the length of the guide portion 42b (the length in the direction of the central axis of the fuel injection valve 24) is shortened (in FIG. 5 above) in order to mitigate the influence of the deviation in the injection characteristics due to the influence of the flow path D in the low temperature region. (L can be shortened). However, it is difficult to adopt this method. This is because it is difficult to provide an alternative means for ensuring the operation stabilizing function of the nozzle needle 42 for the fuel injection valve 24 according to the present embodiment. Incidentally, it is difficult to ensure the operation stabilizing function by extending the length of the back pressure portion 42c in the central axis direction. This is because, for example, the coaxiality required for the operation of the nozzle needle 42 cannot be secured because the body 26 and the pressure chamber forming member 28 are separate members.

  FIG. 6 shows an example of a change in the fuel injection amount (injection rate) per unit time from the fuel injection valve 24 due to a change in the temperature of the fuel flowing through the high-pressure fuel passage. Specifically, FIG. 6A shows the transition of the drive signal to the electric actuator 62, and FIG. 6B shows the transition of the injection rate.

  In the illustrated example, when the fuel temperature decreases in the high temperature region, the transition of the injection rate changes from the waveform shown by the solid line to the waveform shown by the broken line. This is because, as described above, the opening timing of the fuel injection valve 24 is advanced and the closing timing is delayed.

  On the other hand, when the fuel temperature further decreases and shifts from the high temperature region to the low temperature region, the transition of the injection rate changes from a waveform indicated by a broken line in the figure to a waveform indicated by a one-dot chain line. This is because the valve opening timing of the fuel injection valve 24 is further advanced and the valve closing timing is changed from the delay side to the earlier side as described above.

  In the present embodiment, the command injection amount correction process is performed based on the estimated value of the temperature of the fuel flowing through the high-pressure fuel passage in order to compensate for the deviation in the injection characteristics caused by the change in the fuel temperature.

  FIG. 7 shows the procedure of the correction processing according to this embodiment. This process is executed by the ECU 64 at a predetermined cycle, for example.

  In this series of processes, first, in step S10, the temperature of the fuel flowing into the fuel inlet 40 (INJ inlet fuel temperature Tin) is estimated. In the present embodiment, the INJ inlet fuel temperature Tin, the pump inlet fuel temperature Tpmp calculated from the output value of the fuel temperature sensor 20, and the heat between the fuel and the outside in the path from the inlet of the fuel pump 14 to the fuel inlet 40. This is estimated based on the change in the temperature of the fuel due to the transfer of fuel. More specifically, the temperature change amount is defined so that the temperature rise side is positive, and the INJ inlet fuel temperature Tin is calculated as an added value of the pump inlet fuel temperature Tpmp and the temperature change amount.

  Here, the temperature change amount is calculated based on the following parameters (A) to (D).

  (A) Energy Ein input to the fuel as the fuel is compressed by the plunger in the fuel pump 14: The greater the energy Ein, the greater the temperature rise of the fuel. In addition, what is necessary is just to let the said energy Ein be the energy at the time of assuming that the compression aspect of the fuel by a plunger is adiabatic compression, for example. Moreover, what is necessary is just to grasp | ascertain the said energy Ein based on an engine speed, rail pressure, etc., for example.

  (B) Cooling water temperature THw: The higher the cooling water temperature THw, the more heat that is transmitted from the engine body to the fuel piping and the common rail 18 tends to increase. Therefore, the amount of temperature change tends to increase.

  (C) Outside temperature Tair: As the outside temperature Tair is higher than the temperature of the fuel, while the fuel flows through the path from the fuel pump 14 to the fuel inflow port 40, the fuel flows from the periphery of the path to the fuel via a pipe or the like. Since the transferred heat tends to increase, the temperature change amount tends to increase. The outside air temperature Tair may be calculated from the output value of the outside air temperature sensor 76, for example.

  (D) Vehicle travel speed SPD: The higher the vehicle travel speed SPD, the greater the amount of air blown to piping or the like through which fuel flows as the vehicle travels. It tends to make it. The traveling speed SPD of the vehicle may be calculated from the output value of the vehicle speed sensor 78, for example.

  In subsequent steps S12 to S16, the temperature of the fuel flowing through the high-pressure fuel passage (INJ internal fuel temperature Tij) is estimated. In the present embodiment, as the INJ internal fuel temperature Tij, the fuel temperature in the vicinity of the connection portion between the fuel passage 38 and the needle storage chamber 36 in the high-pressure fuel passage (α portion in FIG. 3 above, hereinafter, the estimated position α) is assumed. doing. This is because the high-pressure fuel that passes through this position passes through the flow path A to flow path D shown in FIG. 3, and therefore the fuel temperature at the estimated position α and the injection characteristics of the fuel injection valve 24 It is based on the fact that it can be related appropriately.

  Then, the INJ internal fuel temperature Tij, the INJ inlet fuel temperature Tin, and the amount of temperature change (hereinafter referred to as the temperature change amount due to heat exchange between the high pressure fuel and the fuel injection valve 24 from the fuel inlet 40 to the estimated position α). It is estimated as an addition value with the internal temperature change amount ΔT). Here, the internal temperature change amount ΔT is a value defined with the temperature rising side as positive.

  Specifically, first, in step S12, a considerable amount of time (residence time tlong) that the fuel flowing in from the fuel inlet 40 stays in the fuel injection valve 24 is calculated. In the present embodiment, the residence time tlong is a time that is assumed to be required for the fuel that has flowed into the fuel inlet 40 to reach the estimated position α. Then, the residence time tlong is defined as one combustion cycle (calculated from the volume V from the fuel inlet 40 to the estimated position α in the high-pressure fuel passage, the required injection amount Qtotal, the dynamic leak amount Qleak, and the engine speed). And a time corresponding to 720 ° C. A). More specifically, the residence time tlong is calculated by multiplying the value obtained by dividing the volume V by the added value of the required injection amount Qtotal and the dynamic leak amount Qleak by a time corresponding to one combustion cycle.

  Incidentally, the dynamic leak is caused by the operation of the nozzle needle 42 and the control valve 52 during fuel injection, and the fuel in the pressure control chamber 46 flows out to the low-pressure fuel passage 54 through the orifice 48 and the control valve storage chamber 50. It is the fuel to be used.

  In the subsequent step S14, the temperature of the fuel injection valve 24 (INJ inner wall temperature Tbody which is the temperature near the inner wall of the high-pressure fuel passage) is calculated. In this embodiment, the INJ inner wall temperature Tbody is an external parameter for grasping the influence of heat exchange between the fuel injection valve 24 and the outside on the INJ inner wall temperature Tbody, and the heat generated inside the fuel injection valve 24 is the INJ inner wall temperature Tbody. It is calculated based on internal parameters that grasp the influence on More specifically, in the present embodiment, the following (E) to (H) are adopted as external parameters, and the following (I) is adopted as internal parameters.

  (E) Cooling water temperature THw: Since the fuel injection valve 24 is in contact with the engine body, the cooling water temperature THw serves as a reference parameter for calculating the INJ inner wall temperature Tbody. Specifically, the INJ inner wall temperature Tbody tends to increase as the coolant temperature THw increases.

  (F) Combustion heat: The greater the combustion heat is, the more heat is transmitted to the fuel injection valve 24 protruding into the combustion chamber 32, and the INJ inner wall temperature Tbody tends to increase. In addition, what is necessary is just to grasp | ascertain combustion heat based on the request | requirement injection quantity, for example.

  (G) Intake air temperature Ts: The lower the intake air temperature Ts, the greater the degree of cooling of the fuel injection valve 24 protruding into the combustion chamber 32, and the INJ inner wall temperature Tbody tends to be lower. The intake air temperature Ts may be calculated from the output value of the intake air temperature sensor 72, for example.

  (H) Intake pressure Ps: When the intake pressure Ps changes, the combustion heat may change due to a change in the combustion state in the combustion chamber 32. For this reason, the intake pressure Ps can be adopted as an external parameter. The intake pressure Ps may be calculated from the output value of the intake pressure sensor 74, for example.

  (I) Dynamic leak amount Qleak, rail pressure Pr: When the fuel injection valve 24 is opened, high pressure fuel flows out from the pressure control chamber 46 into the low pressure fuel passage 54. Since there is a throttle portion between the path from the pressure control chamber 46 to the low pressure fuel passage 54, when the high pressure fuel passes through the throttle, the fuel is depressurized and the fuel flow rate is greatly increased. Here, heat is generated due to, for example, that the fuel whose flow rate has increased stirs the surrounding gas. This heat increases as the amount of dynamic leak Qleak increases or the rail pressure Pr increases. For this reason, the dynamic leak amount Qleak and the rail pressure Pr can be adopted as internal parameters. Here, the dynamic leak amount Qleak may be grasped in relation to the operating state of the engine, for example.

  As an external parameter, an oil temperature Toil that has a positive correlation with the cooling water temperature THw and is somewhat higher than the cooling water temperature THw may be employed. This is because by using the oil temperature Toil together with the coolant temperature THw, it is possible to more accurately grasp the influence of the heat transferred from the engine body to the fuel injection valve 24 on the INJ inner wall temperature. Here, the oil temperature Toil may be calculated from the output value of the oil temperature sensor 70, for example.

  Further, as an internal parameter, a parameter capable of grasping the influence of heat generation of the piezo stack itself due to energization to the piezo stack may be adopted.

  In the subsequent step S16, the INJ internal fuel temperature Tij is estimated based on the INJ inlet fuel temperature Tin, the INJ inner wall temperature Tbody, and the residence time tlong. In this estimation method, as shown in FIG. 8, the temperature of the fuel flowing into the fuel inlet 40 (INJ inlet fuel temperature Tin) gradually approaches the INJ inner wall temperature Tbody with time, and finally the INJ inner wall temperature Tbody. It is based on the convergence.

  Specifically, when the INJ inlet fuel temperature Tin is lower than the INJ inner wall temperature Tbody, the internal temperature increases as the temperature difference between the INJ inlet fuel temperature Tin and the INJ inner wall temperature Tbody increases or the residence time tlong increases. The amount of change ΔT increases and the INJ internal fuel temperature Tij tends to increase.

  Incidentally, the estimation method of the INJ internal fuel temperature Tij will be specifically described. For example, first, the temperature difference between the INJ inner wall temperature Tbody and the INJ inlet fuel temperature Tin and the internal temperature change amount ΔT related to the residence time tlong are expressed as follows. An internal temperature change amount ΔT is calculated using a prescribed map. Then, the INJ internal fuel temperature Tij may be estimated as an added value of the calculated internal temperature change amount ΔT and the INJ inlet fuel temperature Tin. Further, for example, the INJ internal fuel temperature Tij may be estimated using a map or a mathematical formula in which the INJ inlet fuel temperature Tin, the INJ inner wall temperature Tbody, the residence time tlong, and the INJ internal fuel temperature Tij are related.

  Returning to the description of FIG. 7, in the following step S18, a correction amount ΔQ of the command injection amount corresponding to each of the pilot injection and the main injection is calculated based on the INJ internal fuel temperature Tij. Here, the reason why the correction amount ΔQ of the command injection amount corresponding to each of the multi-stage injections is calculated is to improve the correction accuracy of the fuel injection amount. That is, due to the change in the INJ internal fuel temperature Tij, the fuel injection amount corresponding to each of the multistage injections may deviate from the amount assumed at the time of adaptation. Here, each of the fuel injection amounts corresponding to each of the multistage injections does not necessarily deviate at the same rate. That is, the deviation amount of the fuel injection amount can be different according to the drive signal (command injection period). For this reason, if the corrected required injection amount is divided and assigned after correcting the required fuel amount, the injection accuracy of each injection may be lowered.

  In view of these points, the correction accuracy of the fuel injection amount is improved by calculating the correction amount ΔQ corresponding to each of the multistage injections.

  Here, the calculation method of the correction amount ΔQ will be described. Using a map in which the drive signal, the rail pressure, the INJ internal fuel temperature Tij, and the fuel injection amount Q are related for each injection of the multi-stage injection, As shown in FIG. 9, the reference temperature (in the figure, near the boundary between the low temperature region and the high temperature region) that is the INJ internal fuel temperature at the estimated position α when the injection characteristics of the fuel injection valve 24 are adapted (during a reference temperature condition). The difference between the command injection amount Qt corresponding to the temperature of the fuel injection amount corresponding to the estimated INJ internal fuel temperature Tij may be calculated as the correction amount ΔQ. More specifically, the correction amount ΔQ may be calculated by subtracting the fuel injection amount corresponding to the INJ internal fuel temperature Tij estimated from the command injection amount Qt corresponding to the reference temperature. According to such correction, the correction amount ΔQ increases as the INJ internal fuel temperature Tij is higher in the high temperature region or the INJ internal fuel temperature Tij is lower in the low temperature region.

  The map is information indicating that the fuel injection amount Q decreases as the INJ internal fuel temperature Tij increases in the high temperature region, and the fuel injection amount Q decreases as the INJ internal fuel temperature Tij decreases in the low temperature region. It is stored in the memory 64a.

  Returning to the description of FIG. 7, in the subsequent step S20, the final command injection amount Qtfin corresponding to each of the multistage injections is obtained by adding the correction amount ΔQ to the command injection amount Qt corresponding to each of the multistage injections. calculate. Thereafter, multistage injection from the fuel injection valve 24 is performed based on the final command injection amount Qtfin.

  In addition, when the process of step S20 is completed, this series of processes is once complete | finished.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) The INJ internal fuel temperature Tij was estimated based on the INJ inlet fuel temperature Tin, the INJ inner wall temperature Tbody, and the residence time tlong. Then, based on the estimated INJ internal fuel temperature Tij, a correction process for correcting the command injection amount Qt of the fuel injection valve 24 was performed. Thereby, it is possible to suppress the occurrence of a situation in which the fuel injection amount from the fuel injection valve 24 deviates from the amount assumed at the time of adaptation due to the change in the INJ internal fuel temperature Tij. That is, it is possible to suitably suppress a decrease in the adjustment accuracy of the fuel injection amount from the fuel injection valve 24.

  (2) The command injection amount Qt corresponding to each of the pilot injection and the main injection is corrected. As a result, the correction accuracy of the fuel injection amount from the fuel injection valve 24 can be improved.

  (3) The fuel injection valve 24 is provided with a piezo stack and a center feed type. When the piezo stack is provided, the high-pressure fuel passage tends to be long, and the INJ internal fuel temperature Tij tends to change. Under such circumstances, the deviation of the fuel injection amount due to the change in the INJ internal fuel temperature Tij is increased by the guide portion 42b provided in the nozzle needle 42. For this reason, this embodiment which employs the fuel injection valve 24 in which the deviation of the fuel injection amount due to the change in the INJ internal fuel temperature Tij is large is highly worth performing the correction process.

(Other embodiments)
The above embodiment may be modified as follows.

  The fuel injection valve is not limited to the one provided with a piezo stack as the electric actuator 62. For example, an electromagnetic solenoid may be provided as the electric actuator 62. Even in this case, if the electric actuator 62 is arranged so as to be aligned with the fuel passage 38 in a direction perpendicular to the central axis direction of the fuel injection valve, the high-pressure fuel passage becomes longer and the INJ internal fuel temperature Tij becomes smaller. Since the configuration easily changes, the application of the present invention is effective.

  Further, for example, a fuel injection valve that does not have a pressure control chamber and directly operates the nozzle needle by an electric actuator may be used. Even in this case, when the fuel injection valve is opened, the adjustment accuracy of the fuel injection amount can be lowered due to the flow path C shown in FIG. 3, so that the application of the present invention is effective. .

  -In the said embodiment, although the thing of the center feed system was employ | adopted as a fuel injection valve, it is not restricted to this. For example, as shown in FIG. 10, a side feed type fuel injection valve 24a may be employed in which the fuel passage 38a is directly connected to the vicinity of the tip end portion 82a of the nozzle needle 82 (needle storage chamber 36a). Hereinafter, the structure of the fuel injection valve 24a will be described.

  High-pressure fuel that has flowed from the fuel inlet 40 a is supplied to the pressure control chamber 46 a of the fuel injection valve 24 a through the in-orifice 84.

  On the other hand, the pressure control chamber 46 a can communicate with the low-pressure fuel passage 54 via the out orifice 86. The pressure control chamber 46a and the low pressure fuel passage 54 are communicated and blocked by the control valve 52a. That is, the out-orifice 86 is blocked by the control valve 52a, so that the pressure control chamber 46a and the low-pressure fuel passage 54 are shut off. On the other hand, when the out orifice 86 is opened, the pressure control chamber 46a and the low pressure fuel passage 54 are communicated with each other.

  The control valve 52a is applied with a force in a direction to close the out orifice 86 by a valve spring 56a.

  The control valve 52a can be displaced by an electromagnetic solenoid as the electric actuator 62a. When the control valve 52a is attracted by the electromagnetic force of the electromagnetic solenoid, the control valve 52a is displaced in a direction to open the out orifice 86.

  In such a configuration, when the electromagnetic solenoid is not energized and no attractive force is generated by the electromagnetic solenoid, the out orifice 86 is blocked by the control valve 52a by the force of the valve spring 56a. For this reason, the difference of the pressure which each high pressure fuel in the pressure control chamber 46a and the needle accommodation chamber 36a applies to the nozzle needle 82 becomes substantially equal. For this reason, the fuel injection valve 24a is closed by the force by which the needle spring 44a displaces the nozzle needle 82 toward the injection hole 30a.

  On the other hand, when the electromagnetic solenoid is energized and a suction force is generated by the electromagnetic solenoid, the control valve 52a is displaced in a direction to open the out orifice 86. As a result, the high-pressure fuel in the pressure control chamber 46 a flows out to the low-pressure fuel passage 54 through the out orifice 86. For this reason, the pressure applied to the nozzle needle 82 by the high pressure fuel in the pressure control chamber 46a is smaller than the pressure applied to the nozzle needle 82 by the high pressure fuel in the needle housing chamber 36a. And if the force by this pressure difference becomes larger than the force by which the needle spring 44a displaces the nozzle needle 82 to the injection hole 30a side, the fuel injection valve 24a will be in a valve opening state.

  Here, in the side feed type fuel injection valve 24a, as shown in FIG. 11, the fuel injection amount Q from the fuel injection valve 24a decreases as the INJ internal fuel temperature Tij increases. This deviation in the injection characteristics is because the high-pressure fuel passage is not narrowed by a member corresponding to the guide portion, and thus there is no influence due to the flow path D in FIG. 3 in the low temperature region.

  Incidentally, the INJ internal fuel temperature Tij may be, for example, the fuel temperature in the pressure control chamber 46a as a passage in the fuel injection valve 24a. In this case, the residence time tlong may be set, for example, as the main injection execution interval. This is because in the main injection, most of the fuel in the pressure control chamber 46a flows out to the low pressure fuel passage 54 side, so that the internal temperature change amount ΔT can be initialized. Further, the amount of static leak may be used together with the calculation of the residence time tlong.

  In the above embodiment, the INJ inlet fuel temperature Tin is estimated using various parameters including the coolant temperature THw, but is not limited thereto. For example, a sensor that directly detects the INJ inlet fuel temperature Tin may be provided, and the INJ inlet fuel temperature Tin may be detected by this sensor. The sensor may be provided in the vicinity of the fuel inlet 40 of the common rail 18, the high-pressure pipe 22, or the fuel injection valve 24, for example.

  The method for calculating the residence time tlong is not limited to the one exemplified in the above embodiment. For example, a flow rate sensor that detects the flow rate of the fuel flowing through the high-pressure fuel passage is provided, and is calculated by dividing the length from the fuel inlet 40 to the estimated position α by the flow rate calculated from the output value of the flow rate sensor. Also good.

  The INJ inner wall temperature Tbody estimation method is not limited to that exemplified in the above embodiment. For example, an estimation method using at least only the cooling water temperature THw may be adopted without using all the parameters exemplified in the above embodiment as external parameters. Further, for example, an exhaust temperature sensor may be provided on the exhaust passage of the engine, and an estimation method using combustion heat calculated from the exhaust temperature based on the output value of the exhaust temperature sensor may be employed.

  In the above embodiment, the situation in which the INJ internal fuel temperature Tij increases with time has been mainly described, but the present invention can be applied even in a situation in which the INJ internal fuel temperature Tij decreases with time.

  The multi-stage injection mode is not limited to two injections of main injection and minute injection performed prior to main injection. For example, the micro injection performed prior to the main injection may be performed twice or more, or the micro injection may be performed once or a plurality of times after the main injection.

  The engine is not limited to a compression ignition type internal combustion engine, and may be, for example, a cylinder injection type spark ignition type internal combustion engine. In this case, the fuel injection system is provided with an electric pump that pumps up fuel (gasoline) in the fuel tank and a delivery pipe that stores fuel pumped from the electric pump in a high-pressure state.

  Further, the engine is not limited to one using fossil fuel, and may be an engine using alcohol fuel such as alcohol or methanol, or a mixed fuel of fossil fuel and alcohol fuel, for example.

  DESCRIPTION OF SYMBOLS 10 ... Fuel tank, 14 ... Fuel pump, 18 ... Common rail, 24 ... Fuel injection valve, 30 ... Injection hole, 36 ... Needle storage chamber, 38 ... Fuel passage, 40 ... Fuel inlet, 42 ... Nozzle needle, 46 ... Pressure Control chamber, 62... Electric actuator, 64... ECU (an embodiment of a fuel injection control device for an internal combustion engine).

Claims (6)

A pressure accumulating container capable of accumulating fuel in a high pressure state, a fuel pump for discharging and supplying fuel from a fuel tank to the pressure accumulating container, and a fuel injection valve to which the fuel stored in the pressure accumulating container is supplied Applied to the internal combustion engine fuel injection system
The fuel injection valve includes a fuel inlet into which fuel supplied from the pressure accumulating vessel flows, and a nozzle needle that opens and closes a nozzle hole of the fuel injection valve,
A residence time equivalent amount, which is a considerable amount of time that the fuel flowing in from the fuel inlet port stays in the fuel injection valve, is passed from the fuel inlet port to a predetermined position connected to the fuel inlet port in the fuel injection valve. , The amount of fuel injection from the fuel injection valve required for one combustion cycle of the internal combustion engine, and the fuel that has flowed into the fuel injection valve from the fuel inlet is caused by the fuel injection operation by the fuel injection valve. A residence time calculating means for calculating based on a dynamic leak amount that is an amount flowing out to the fuel tank side and a time corresponding to one combustion cycle of the internal combustion engine;
Based on the difference between the temperature of the fuel injection valve and the temperature of the fuel flowing into the fuel inlet , and the residence time equivalent amount calculated by the residence time calculation means, the temperature of the fuel in the fuel injection valve is determined. A fuel temperature estimating means to estimate;
Correction means for correcting the fuel injection amount from the fuel injection valve based on the temperature of the fuel estimated by the fuel temperature estimation means;
A fuel injection control device for an internal combustion engine, comprising: operating means for energizing the fuel injection valve based on the fuel injection amount corrected by the correcting means. The fuel injection valve is formed by an inner wall of the fuel injection valve and includes a needle storage chamber that stores the nozzle needle, a fuel passage that connects the needle storage chamber and the fuel inlet, and the injection hole of the nozzle needle Any one of a pressure control chamber for applying fuel pressure to the side opposite to the pressure chamber, a high pressure fuel passage including the needle housing chamber and the fuel passage, and a low pressure fuel passage connected to the fuel tank is provided in the pressure control chamber. A valve element that operates to communicate with the valve body, and an electric actuator that is energized to operate the valve element, and the nozzle needle is operated by energizing the electric actuator, thereby Through which the fuel is injected from the nozzle hole,
In the fuel injection valve, the fuel passage and the electric actuator are arranged in a direction perpendicular to the central axis direction of the fuel injection valve, and the pressure control is performed in the central axis direction of the fuel injection valve. chamber fuel injection control apparatus for an internal combustion engine according to claim 1, characterized in that arranged on the injection hole side of the electric actuator. 3. The fuel injection control apparatus for an internal combustion engine according to claim 2 , wherein the correction means corrects the fuel injection amount to be increased as the temperature of the fuel in the fuel injection valve is higher. The fuel injection valve further includes a needle storage chamber that is formed by an inner wall of the fuel injection valve and that stores the nozzle needle, and a fuel passage that connects the needle storage chamber and the fuel inlet.
The fuel injection control device for an internal combustion engine according to any one of claims 1 to 3 , wherein the nozzle needle includes an enlarged portion whose outer diameter is enlarged at an intermediate portion in the axial direction thereof. 5. The fuel injection control for an internal combustion engine according to claim 4 , wherein the correction means corrects the fuel injection amount to be increased as the temperature of the fuel is lower in a region where the temperature of the fuel in the fuel injection valve is lower. apparatus. Control means for injecting fuel from the fuel injection valve a plurality of times into one cylinder of the internal combustion engine in one combustion cycle of the internal combustion engine;
Means for calculating the amount of fuel required for one combustion cycle of the internal combustion engine based on the required torque of the internal combustion engine;
Means for dividing the required amount of fuel and assigning it to each of the multiple injections;
The correction unit, the fuel temperature based on the temperature of the fuel estimated by the estimating means, any one of claims 1 to 5, characterized in that for correcting the fuel amount allocated to each of the plurality of times injection A fuel injection control device for an internal combustion engine according to claim 1.

Images