JP2008298028A - Fuel injection control device of in cylinder injection type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce adhered fuel adhering to the top face of a piston and the inner wall face of a cylinder by preventing fluctuations of injection fuel due to an intake flow in a spray guide type in cylinder injection engine. <P>SOLUTION: The fuel injection timing of a fuel injection valve 19 is changed to the timing when the injection fuel is hardly affected by the intake flow in response to an intake valve timing (valve timing of air intake valve 35) which is changed owing to the operation of a variable valve timing device 36. Thereby even if conditions (timing of generation, strength or the like) for generating the intake flow in the cylinder are changed by a change in intake valve timing, the fuel injection timing is changed in response to the intake valve timing to set the fuel injection timing to the timing when the injection fuel is hardly affected by the intake flow (for example, after intake valve 35 closing timing). Thereby fluctuations in the injection shape of the injection fuel by the intake flow is prevented to effectively reduce the adhered fuel adhering to the top face 33 of the piston and the inner wall face 34 of the cylinder. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for a spray guide type in-cylinder injection internal combustion engine that directly injects fuel into the fuel chamber from substantially above the center of the combustion chamber of the internal combustion engine.

  A conventional general in-cylinder internal combustion engine, for example, as described in Patent Document 1 (Japanese Patent Laid-Open No. 9-280092), fuel is introduced into the combustion chamber from the side of the combustion chamber (near the intake port). The fuel injection valve is arranged so as to directly inject the fuel, and the fuel injected from the fuel injection valve collides with a recess on the top surface of the piston so that the injected fuel is guided upward by the inner peripheral wall of the recess. Such an injection method is called a wall guide method.

  In this patent document 1, the fuel injection timing is changed in accordance with the valve timing (opening / closing timing) of the intake valve that is changed by the operation of the variable valve timing device, and the fuel injection is terminated earlier than the vicinity of the intake valve closing timing. Therefore, the mixing of the injected fuel and the intake air is promoted by utilizing the intake air flow in the cylinder that is generated when the air is sucked into the cylinder from the intake port during the opening period of the intake valve. Yes.

  By the way, when the fuel injected from the fuel injection valve adheres to the upper surface of the piston or the inner wall surface of the cylinder, the adhering fuel tends to remain as unburned HC. There is a tendency that exhaust emissions increase due to an increase in HC emissions.

As a countermeasure, a spray guide type in-cylinder internal combustion engine has been developed. As described in Patent Document 2 (Japanese Patent Laid-Open No. 2005-105877), this spray guide type in-cylinder injection internal combustion engine supplies fuel into the fuel chamber from substantially above the center of the combustion chamber (near the spark plug). Fuel adhering to the piston upper surface and cylinder inner wall surface by arranging the fuel injection valve so as to inject directly, and slowly injecting fuel so that the fuel injected from the fuel injection valve does not collide with the piston upper surface and cylinder inner wall surface Is trying to reduce.
JP-A-9-280092 JP 2005-105877 A

  However, since the spray injection type in-cylinder internal combustion engine has a relatively low fuel injection force (penetration force) so that the fuel injected by the fuel injection valve does not collide with the piston upper surface or the cylinder inner wall surface, Even if the fuel spray angle is set so that the injected fuel does not collide with the upper surface of the piston or the inner wall surface of the cylinder, the valve timing of the intake valve changes due to the operation of the variable valve timing device. When the intake air flow becomes stronger, the spray shape of the injected fuel is disturbed by the intake air flow, and the fuel adhering to the upper surface of the piston or the inner wall surface of the cylinder may increase, and the exhaust emission may deteriorate.

  The technique disclosed in Patent Document 1 occurs during the opening period of the intake valve in the wall guide type cylinder injection internal combustion engine by terminating the fuel injection earlier than the vicinity of the closing timing of the intake valve. This technique promotes the mixing of injected fuel and intake air by utilizing the intake air flow in the cylinder, and this wall guide technique solves the problems in the above-described spray guide type in-cylinder injection internal combustion engine. It is not possible.

  The present invention has been made in view of such circumstances, and the object of the present invention is therefore to prevent the spray shape of the injected fuel from being disturbed by the intake air flow in a spray-guided direct injection internal combustion engine. An object of the present invention is to provide a fuel injection control device for a direct injection internal combustion engine that can reduce the amount of attached fuel effectively.

  In order to achieve the above object, an invention according to claim 1 is directed to a variable valve device that changes the valve opening / closing characteristics of an intake valve and / or an exhaust valve of an internal combustion engine, and fuel to the fuel chamber from substantially above the center of the combustion chamber. In a fuel injection control device for a spray guide type in-cylinder injection internal combustion engine having a fuel injection valve for direct injection, the fuel injection timing of the fuel injection valve is determined by the fuel injection timing control means according to the operating state of the variable valve device. The injection fuel is changed at a time when it becomes difficult to be influenced by the intake air flow.

  In this way, even if the generation state (generation time, strength, etc.) of the intake air flow in the cylinder changes due to the change of the valve opening / closing characteristics due to the operation of the variable valve device, the fuel injection timing is set according to the valve opening / closing characteristics. By changing the fuel injection timing, it is possible to set the fuel injection timing when the injected fuel is hardly affected by the intake air flow. As a result, it is possible to prevent the spray shape of the injected fuel from being disturbed by the intake air flow, to effectively reduce the fuel adhering to the piston upper surface and the cylinder inner wall surface, and to improve the exhaust emission. it can.

  The present invention is preferably applied to a system including a variable valve timing device that changes the valve timing and / or a variable valve lift device that changes the valve lift amount. In this way, even if the intake air flow is changed due to a change in the valve timing due to the operation of the variable valve timing device or a change in the valve lift amount due to the operation of the variable valve lift device, the valve timing or the valve lift amount is reduced. Accordingly, the fuel injection timing can be changed to set the fuel injection timing at a time when the injected fuel is hardly affected by the intake air flow.

  Further, when the fuel injection timing is changed according to the operating state of the variable valve device, the fuel injection timing is set so that the fuel injection start timing is after the closing timing of the intake valve as in the third aspect. You may do it. In this way, since the fuel injection can be started after the intake of air into the cylinder is completed after the intake valve is closed, the injected fuel is hardly affected by the intake air flow. Can do.

  The present invention is not limited to setting the fuel injection timing so that the fuel injection start timing is after the intake valve closing timing, and can be made small enough to ignore the influence of the intake air flow received by the injected fuel. In this case, the fuel injection start timing may be slightly earlier than the intake valve closing timing.

  In the present invention, the current valve opening / closing characteristics (valve timing and valve lift amount) may be detected by a sensor or the like, and the fuel injection timing may be calculated according to the current valve opening / closing characteristics. When the valve opening / closing characteristics change rapidly, the valve opening / closing characteristics change between the calculation timing of the fuel injection timing and the fuel injection execution timing, so the response delays in controlling the fuel injection timing according to the change in the valve opening / closing characteristics. Will occur.

  Therefore, as in claim 4, the future valve opening / closing characteristics that change due to the operation of the variable valve device are predicted by the valve opening / closing characteristics predicting means, and the fuel injection timing is calculated based on the predicted future valve opening / closing characteristics. May be. In this way, at the stage of calculating the fuel injection timing, the valve opening / closing characteristics at the time of future fuel injection execution are predicted, and the fuel injection timing according to the predicted valve opening / closing characteristics at the time of fuel injection execution is calculated. Therefore, even when the valve opening / closing characteristic changes rapidly, the fuel injection timing can be changed with good response to the change in the valve opening / closing timing, and the control accuracy of the fuel injection timing can be improved.

Hereinafter, an embodiment embodying the best mode for carrying out the present invention will be described.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.

  An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the cylinder injection engine 11 which is a cylinder injection internal combustion engine, and a throttle valve whose opening degree is adjusted by a motor 14 on the downstream side of the air cleaner 13. 15 is provided. Further, a surge tank 16 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 17 for detecting the intake pipe pressure is provided in the surge tank 16. The surge tank 16 is provided with an intake manifold 18 that introduces air into each cylinder of the engine 11.

  The cylinder head of the engine 11 is provided with a fuel injection valve 19 that directly injects fuel into the cylinder for each cylinder. The fuel discharged from the high-pressure fuel pump 21 is sent to the delivery pipe 23 through the high-pressure fuel pipe 22, and the high-pressure fuel is distributed from the delivery pipe 23 to the fuel injection valve 19 of each cylinder. A fuel pressure sensor 24 that detects the pressure of the fuel supplied to the fuel injection valve 19 is attached to the delivery pipe 23. Further, a spark plug 20 (see FIG. 2) is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 20.

  As shown in FIG. 2, the in-cylinder injection engine 11 of this embodiment is a spray-guided in-cylinder injection engine, and is a fuel disposed approximately above the center of the combustion chamber 32 (near the spark plug 20). By directly injecting fuel into the fuel chamber 32 from the injection valve 19 and slowly injecting the fuel from the fuel injection valve 19 so as not to collide with the piston upper surface 33 or the cylinder inner wall surface 34, the piston upper surface 33 or The fuel adhering to the cylinder inner wall surface 34 is reduced. Further, the in-cylinder injection engine 11 is provided with a variable valve timing device 36 that changes the valve timing (opening / closing timing) of the intake valve 35.

  On the other hand, as shown in FIG. 1, the exhaust pipe 25 of the engine 11 is provided with an exhaust gas sensor 26 (an air-fuel ratio sensor, an oxygen sensor, or the like) that detects an air-fuel ratio or rich / lean of the exhaust gas. Between the upstream side of the exhaust gas sensor 26 in the exhaust pipe 25 and the surge tank 16 on the downstream side of the throttle valve 15 in the intake pipe 12, an EGR pipe 27 for returning a part of the exhaust gas to the intake side. And an EGR valve 28 for adjusting the exhaust gas recirculation amount (EGR amount) is provided in the middle of the EGR pipe 27.

  A cooling water temperature sensor 29 that detects the cooling water temperature and a crank angle sensor 30 that outputs a pulse signal each time the crankshaft of the engine 11 rotates a predetermined crank angle are attached to the cylinder block of the engine 11. Based on the output signal of the crank angle sensor 30, the crank angle and the engine speed are detected. Further, the accelerator operation amount (depressed amount of the accelerator pedal) is detected by the accelerator sensor 31.

  Outputs of these various sensors are input to a control circuit (hereinafter referred to as “ECU”) 37. The ECU 37 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 19 according to the engine operating state. The ignition timing of the spark plug 20 is controlled.

  At that time, the ECU 37 switches the combustion mode between the stratified combustion mode and the homogeneous combustion mode according to the engine operating state (engine rotational speed, required torque, etc.). In the stratified combustion mode, a small amount of fuel is directly injected into the cylinder in the compression stroke, and a stratified mixture is formed in the vicinity of the spark plug 20 for stratified combustion (lean combustion), thereby improving fuel efficiency. On the other hand, in the homogeneous combustion mode, the engine output is increased by increasing the fuel injection amount and directly injecting fuel into the cylinder during the intake stroke to form a homogeneous mixture and performing homogeneous combustion (stoichiometric or rich combustion).

  Further, the ECU 37 executes a valve timing control routine (not shown) to set the target valve timing (target advance angle from the reference position) of the intake valve 35 based on the engine operating state (engine speed, required torque, etc.). The variable valve timing device 36 is controlled so as to make the actual valve timing (actual advance angle amount from the reference position) of the intake valve 35 coincide with the target valve timing.

  By the way, in the in-cylinder injection engine 11 of the spray guide system, the fuel injection force (penetration force) is set relatively weak so that the fuel injected from the fuel injection valve 19 does not collide with the piston upper surface 33 or the cylinder inner wall surface 34. Therefore, even if the fuel spray angle is set so that the injected fuel does not collide with the piston upper surface 33 or the cylinder inner wall surface 34, the intake valve timing (valve timing of the intake valve 35) is activated by the operation of the variable valve timing device 36. If the intake air flow in the cylinder during the fuel injection period becomes strong and the spray shape of the fuel is disturbed by the intake air flow, the attached fuel adhering to the piston upper surface 33 or the cylinder inner wall surface 34 may increase. is there. In particular, in the stratified combustion mode in which fuel is injected in the compression stroke, since the period from fuel injection to ignition is shorter than in the homogeneous combustion mode, the attached fuel cannot be vaporized and tends to remain as unburned HC, and the attached fuel increases. HC emissions may increase and exhaust emissions may deteriorate.

  As a countermeasure, in this embodiment, the fuel injection timing of the fuel injection valve 19 is changed according to the intake valve timing which is changed by the operation of the variable valve timing device 36 by executing a fuel injection timing control routine of FIG. The injection fuel is changed at a time when it becomes difficult to be influenced by the intake air flow. As a result, even if the generation state (generation timing, strength, etc.) of the intake air flow in the cylinder changes due to a change in the intake valve timing, the fuel injection timing is changed according to the intake valve timing, and the injected fuel is drawn into the intake air. The fuel injection timing is set at a time that is not easily affected by the flow.

  The control of the fuel injection timing according to the intake valve timing may be executed only in the stratified combustion mode, but may be executed in both the stratified combustion mode and the homogeneous combustion mode.

  Hereinafter, the processing contents of the fuel injection timing control routine of FIG. 3 executed by the ECU 37 will be described. The fuel injection timing control routine shown in FIG. 3 is executed at a predetermined cycle while the ECU 37 is powered on, and serves as fuel injection timing control means in the claims. When this routine is started, first, at step 101, the engine rotational speed Ne detected by the crank angle sensor 30 is read, and then the routine proceeds to step 102 where the required torque set based on the accelerator operation amount or the like is read.

  Thereafter, the process proceeds to step 103, and a reference is made to a map of the target intake valve timing TVVT (target valve timing of the intake valve 35), and the intake valve 35 corresponding to the current engine operating state (for example, the engine speed Ne and the required torque). Target valve timing TVVT is calculated. Thereby, the variable valve timing device 36 is controlled so that the actual intake valve timing (actual valve timing of the intake valve 35) matches the target intake valve timing TVVT.

  Thereafter, the routine proceeds to step 104, where the target fuel injection timing TSOI corresponding to the current engine operating state (for example, engine speed Ne and required torque) is calculated with reference to the map of the target fuel injection timing TSOI.

  Thereafter, the routine proceeds to step 105, where the intake valve timing PVVT at the time of executing the fuel injection is predicted based on the current engine speed Ne and the fuel injection timing SOI by a map or a mathematical formula. The process of step 105 serves as valve opening / closing characteristic prediction means in the claims.

  Thereafter, the routine proceeds to step 106, where the final fuel injection timing SOI is calculated by a map or a mathematical formula based on the predicted intake valve timing PVVT at the time of fuel injection execution and the target fuel injection timing TSOI. The fuel injection timing SOI is changed according to the intake valve timing PVVT at the time of executing the injection to a time when the injected fuel is hardly affected by the intake air flow.

  For example, in the stratified combustion mode, the fuel injection timing SOI is set so that the fuel injection start timing is after the valve closing timing of the intake valve 35. As a result, fuel injection can be started after the intake of air into the cylinder is completed after the intake valve 35 is closed, so that the injected fuel can be hardly affected by the intake air flow. .

  However, the fuel injection start timing may be slightly earlier than the closing timing of the intake valve 35 as long as the influence of the intake air flow received by the injected fuel can be made small enough to be ignored.

  In the present embodiment described above, the fuel injection timing of the fuel injection valve 19 is changed to a time when the injected fuel is hardly affected by the intake air flow in accordance with the intake valve timing that is changed by the operation of the variable valve timing device 36. Therefore, even if the intake air flow generation situation (occurrence timing, strength, etc.) changes due to changes in the intake valve timing, the fuel injection timing is changed according to the intake valve timing, and the injected fuel is sucked The fuel injection timing can be set at a time that is not easily affected by the air flow. Thereby, the disturbance of the spray shape of the injected fuel due to the intake air flow can be prevented, the attached fuel adhering to the piston upper surface 33 and the cylinder inner wall surface 34 can be effectively reduced, and the exhaust emission is improved. be able to.

  In addition, in this embodiment, at the stage of calculating the fuel injection timing, the intake valve timing at the time of executing the future fuel injection is predicted, and the fuel injection timing corresponding to the predicted intake valve timing at the time of executing the fuel injection is calculated. As a result, even when the intake valve timing changes rapidly, the fuel injection timing can be changed with good response to the change of the intake valve timing, and the control accuracy of the fuel injection timing can be improved. .

  However, the current intake valve timing may be detected by a sensor or the like, and the fuel injection timing may be calculated according to the current intake valve timing. Even in this case, if the change in the intake valve timing is relatively gradual, The fuel injection timing can be changed according to the intake valve timing to a time when the injected fuel becomes less susceptible to the intake air flow.

  Further, in the above embodiment, the fuel injection timing is changed according to the intake valve timing which is changed by the operation of the variable valve timing device 36, but information on the operating state of the variable valve timing device 36 (for example, hydraulic type In this case, the fuel injection timing may be changed in accordance with a hydraulic pressure command value, and in the case of an electric type, a current command value.

  In the above embodiment, the present invention is applied to a system including the variable valve timing device 36 that changes the valve timing of the intake valve 35. However, the system includes a variable valve timing device that changes the valve timing of the exhaust valve. The present invention may be applied. Furthermore, the present invention may be applied to a system including a variable valve lift device that changes the valve lift amount of the intake valve and a variable valve lift device that changes the valve lift amount of the exhaust valve.

It is a schematic block diagram of the whole engine control system in one Example of this invention. It is a longitudinal cross-sectional view of a fuel injection valve and its peripheral part. It is a flowchart explaining the flow of a process of a fuel injection timing control routine.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Cylinder injection type engine (cylinder injection type internal combustion engine), 12 ... Intake pipe, 15 ... Throttle valve, 19 ... Fuel injection valve, 20 ... Spark plug, 25 ... Exhaust pipe, 32 ... Combustion chamber, 35 ... Intake Valve, 36 ... variable valve timing device, 37 ... ECU (fuel injection timing control means, valve opening / closing characteristic prediction means)

Claims (4)

A spray guide type in-cylinder having a variable valve device that changes valve opening / closing characteristics of an intake valve and / or an exhaust valve of an internal combustion engine, and a fuel injection valve that directly injects fuel into the fuel chamber from substantially above the center of the combustion chamber In a fuel injection control device for an injection internal combustion engine,
A cylinder comprising fuel injection timing control means for changing the fuel injection timing of the fuel injection valve to a timing at which the injected fuel is hardly affected by the intake air flow in accordance with the operating state of the variable valve device. A fuel injection control device for an internal injection internal combustion engine.   The variable valve device is a variable valve timing device that changes a valve timing as the valve opening / closing characteristic and / or a variable valve lift device that changes a valve lift amount as the valve opening / closing characteristic. A fuel injection control device for an in-cylinder internal combustion engine.   3. The fuel injection timing control unit according to claim 1, wherein the fuel injection timing control unit sets the fuel injection timing so that a fuel injection start timing of the fuel injection valve is after a closing timing of the intake valve. 4. A fuel injection control device for a cylinder injection internal combustion engine. A valve opening / closing characteristic predicting means for predicting a future valve opening / closing characteristic that changes due to the operation of the variable valve device;
The in-cylinder engine according to any one of claims 1 to 3, wherein the fuel injection timing control means calculates the fuel injection timing based on a future valve opening / closing characteristic predicted by the valve opening / closing characteristic prediction means. A fuel injection control device for an injection type internal combustion engine.

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