JP2005188334A - Fuel injection control device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device for an engine prevented from occurrence of worsening of emission even when a valve overlap period is increased for suppression of knocking. <P>SOLUTION: In an engine provided with at least cylinder fuel injection valve 33; a variable valve timing mechanism VTT to vary the switching timing of at least the one of a suction valve and an exhaust valve; and a supercharger 22, the engine is provided with a knocking occurrence suppressing means to suppress the occurrence of knocking by operating the variable valve timing mechanism at a given time for increasing a valve over lap; and a correction means to correct a fuel injection amount supplied from the cylinder fuel injection valve 33 to a fuel injection amount against a suction air amount before operation of the knocking occurrence suppressing means when knocking is detected by the knocking detecting means and knocking occurrence suppressing means is operated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an engine fuel injection control device, and more particularly, to an engine including at least an in-cylinder fuel injection valve, a variable valve timing mechanism that varies opening / closing timing of at least one of an intake valve and an exhaust valve, and a supercharger. The present invention relates to a fuel injection control device.

  2. Description of the Related Art Conventionally, an engine having a variable valve timing mechanism and a supercharger is provided with valve overlap control means for increasing an overlap period when the operating state of the engine is in a low rotation and high load state. For example, Patent Document 1 discloses a technique in which scavenging of the inside is promoted to reduce the in-cylinder temperature and suppress the occurrence of knocking due to supercharging.

JP-A-5-59975

  By the way, the technique as described in Patent Document 1 is provided with at least an in-cylinder fuel injection valve, and only air is sucked into the cylinder, and the in-cylinder fuel injection is directly performed on the air sucked into the cylinder. When applied to an engine having an operation region in which fuel is injected and supplied from a valve, the following problems occur. That is, when the valve overlap period is increased, scavenging is promoted as described above, which means that the blow-through of fresh air increases at the same time. Since the fuel injection amount is determined in accordance with the amount of air taken into the cylinder, as a result, it deviates from the desired air-fuel ratio and the emission deteriorates.

  An object of the present invention is to provide a fuel injection control device for an engine that eliminates such problems of the prior art and does not cause deterioration of emissions even when the valve overlap period is increased to suppress knocking.

  An engine fuel injection control apparatus according to an embodiment of the present invention that achieves the above object includes at least an in-cylinder fuel injection valve, a variable valve timing mechanism that varies an opening / closing timing of at least one of an intake valve and an exhaust valve, An engine comprising a feeder, wherein the variable valve timing mechanism is activated at a predetermined time to increase the valve overlap so that knocking is suppressed by knocking detection suppressing means and knocking detecting means detects knocking, and the knocking is detected. Correction means for correcting a fuel injection amount supplied from the in-cylinder fuel injection valve to a fuel injection amount with respect to an intake air amount before operation of the knocking generation suppression means when the generation suppression means is operated. It is characterized by.

  The engine further includes a port fuel injection valve. When knocking is detected by the knocking detection unit and the knocking generation suppression unit is activated, fuel from the in-cylinder fuel injection valve to the port fuel injection valve is detected. A fuel injection ratio changing means for increasing the injection ratio may be provided.

  The fuel injection ratio changing means preferably sets the fuel injection ratio from the in-cylinder fuel injection valve to 100%.

  According to the present invention having the above-described configuration, when knocking is detected by the knocking detection unit and the knocking generation suppression unit is activated, the variable valve timing mechanism is activated and the valve overlap is increased. At this time, the fuel injection amount supplied from the in-cylinder injection valve is corrected by the correction means to the fuel injection amount with respect to the intake air amount before the operation of the knocking occurrence suppression means. Even if the air amount is smaller than the intake air amount, the air-fuel ratio does not change greatly, and the emission is not deteriorated.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing the overall configuration of a variable valve timing mechanism and a supercharged engine according to an embodiment of the present invention.

  First, the overall configuration of a variable valve timing mechanism and a supercharged engine to which the present invention is applied will be described with reference to FIG. In the figure, reference numeral 10 denotes an engine with a variable valve timing mechanism and a supercharger (hereinafter simply referred to as “engine”), and in the figure, a port fuel injection valve and an in-cylinder fuel injection valve are provided. Indicates a gasoline engine. The cylinder block 11 of the engine 10 is provided with a cylinder head 12, and an intake port 13 and an exhaust port 14 are formed in the cylinder head 12 for each cylinder.

  As an intake system of the engine 10, an intake manifold 15 communicates with each intake port 13, and a throttle chamber 18 in which a throttle valve 17 is interposed via a surge tank 16 in which intake passages of the respective cylinders gather in the intake manifold 15. It is communicated. The throttle valve 17 is driven by a throttle motor 19. An intercooler 20 is interposed upstream of the throttle chamber 18, and the intercooler 20 communicates with a compressor 22 </ b> C of a turbocharger 22 as an example of a supercharger via an intake pipe 21, and further communicates with an air cleaner 23. Has been.

  A port injector 31 as a port fuel injection valve is disposed immediately upstream of the intake port 13 of each cylinder of the intake manifold 15, and the cylinder head 12 is directly in the combustion chamber of each cylinder in the cylinder block 11. An in-cylinder injector 33 is disposed as an in-cylinder fuel injection valve that injects fuel. Each in-cylinder injector 33 communicates with a fuel delivery pipe 35 to which high-pressure fuel is supplied from a high-pressure fuel pump 34. Further, a spark plug 36 is provided for each cylinder of the cylinder head 12.

  On the other hand, as an exhaust system of the engine 10, exhaust is joined by an exhaust manifold 25 communicating with each exhaust port 14 of the cylinder head 12, and an exhaust pipe 26 is connected to the exhaust manifold 25. Then, the turbine 22T of the turbocharger 22 is interposed in the exhaust pipe 26, and a catalyst, a muffler, etc. are disposed downstream thereof and released to the atmosphere. In the turbocharger 22, the compressor 22C is rotationally driven by the energy of the exhaust gas introduced into the turbine 22T, and sucks and pressurizes the air to supercharge the turbocharger 22 on the side of the turbine 22T. A wastegate valve 28 having an actuator 27 is provided.

  The actuator 27 for operating the wastegate valve is divided into two chambers by a diaphragm, one of which forms a pressure chamber communicating with the supercharging pressure control solenoid valve 29, and the other is a spring that urges the wastegate valve 28 in the closing direction. And a spring chamber is formed in which a rod connecting the diaphragm and the wastegate valve 28 is extended, and the spring chamber is released to the atmosphere.

  Further, the supercharging pressure control solenoid valve 29 has a port communicating with the pressure chamber of the actuator 27 for operating the wastegate valve and the surge tank 16 downstream of the compressor 22C of the turbocharger 22, and will be described later. (Referred to as ECU), the opening degree of the wastegate valve 28 is adjusted according to the duty ratio of the control signal output from the control signal 100 to control the supercharging pressure.

  Here, the variable valve timing mechanism of the engine 10 will be described. As is well known, rotation of the crankshaft 51 of the engine 10 is performed by a crank pulley, a timing belt, an intake cam pulley fixed to the crankshaft 51 on an intake camshaft and an exhaust camshaft respectively disposed in the cylinder head 12. It is transmitted through an exhaust cam pulley or the like, and the crankshaft 51 and the camshaft are set to have a 2-to-1 rotation angle. The intake cam provided on the intake camshaft and the exhaust cam provided on the exhaust camshaft (both not shown) are rotated at a rotation angle of 2: 1 with the crankshaft 51, respectively. Based on this, the intake valve 40 and the exhaust valve 41 are opened and closed.

  Between the intake camshaft and the intake cam pulley, a hydraulically driven variable that continuously changes the rotation phase (displacement angle) of the intake camshaft with respect to the crankshaft 51 by relatively rotating the intake cam pulley and the intake camshaft. A valve timing mechanism InVVT is provided. As is well known, this variable valve timing mechanism InVVT is hydraulically switched by an oil control valve 42 such as a linear solenoid valve or a duty solenoid valve, and operates according to a drive signal from an ECU 100 for engine control described later. .

  Similarly, between the exhaust camshaft and the exhaust cam pulley, a hydraulic drive that continuously changes the rotational phase (displacement angle) of the exhaust camshaft with respect to the crankshaft 51 by relatively rotating the exhaust cam pulley and the exhaust camshaft. A variable valve timing mechanism ExVVT of the type is provided. The variable valve timing mechanism ExVVT, as with the intake side variable valve timing mechanism InVVT, is switched in oil pressure by an oil control valve 43 and is operated by a drive signal from an ECU 100 for engine control described later.

  Next, various sensors for detecting the engine operating state will be described. An air flow meter 101 is interposed immediately downstream of the air cleaner 23 of the intake pipe 21 and a temperature sensor 102 is interposed immediately downstream of the intercooler 20. Further, a throttle position sensor 103 is connected to the throttle valve 17 disposed in the throttle chamber 18, and an intake pipe pressure sensor 104 is provided to the surge tank 16. Further, a fuel pressure sensor 105 for detecting fuel pressure is provided in the fuel delivery pipe 35, a knocking sensor 106 is attached to the cylinder block 11 of the engine 10, and a cooling water temperature sensor 107 is provided in the cylinder block 11. Further, a back pressure sensor 108 is disposed downstream of the joining portion where the exhaust manifold 25 joins.

  The intake-side variable valve timing mechanism InVVT and the exhaust-side variable valve timing mechanism ExInVVT are arranged on the outer periphery of a cam rotor that is fixed to the intake camshaft and the exhaust camshaft and rotates synchronously as a sensor for detecting the operation position. An intake-side cam position sensor 109 and an exhaust-side cam position sensor 110 that detect a plurality of formed protrusions at equal angles and output a cam position pulse representing the cam position are provided. In addition, a crank position sensor 111 is provided that detects protrusions at predetermined crank angles formed on the outer periphery of the crank rotor 52 that is attached to the crankshaft 51 and rotates synchronously, and outputs a crank pulse representing the crank angle. .

  In FIG. 1, reference numeral 100 denotes an electronic control unit (hereinafter referred to as “ECU”), which processes signals from the various sensors described above to calculate control amounts for the various actuators, and performs fuel injection control, ignition It performs timing control, idle speed control, supercharging pressure control, valve timing control for intake valves and exhaust valves, and the like. The ECU 100 is composed mainly of a microcomputer to which a CPU, ROM, RAM, backup RAM, counter / timer group, and I / O interface are connected via a bus line, and a constant voltage circuit for supplying a stabilized power source to each part, Peripheral circuits such as a drive circuit and an A / D converter connected to the I / O interface are incorporated. The input port of the I / O interface includes an air flow meter 101, a temperature sensor 102, a throttle position sensor 103, an intake pipe pressure sensor 104, a fuel pressure sensor 105, a knocking sensor 106, a cooling water temperature sensor 107, a back pressure sensor 108, a cam. Position sensors 109 and 110, a crank position sensor 111, a vehicle speed sensor for detecting the vehicle speed, and the like are connected.

  On the other hand, the output port of the I / O interface includes a throttle motor 19, a supercharging pressure control solenoid valve 29, a port injector 31, an in-cylinder injector 33, a high-pressure fuel pump 34, an ignition coil 36, oil control valves 42 and 43, and the like. Are connected via a drive circuit.

  The ECU 100 processes detection signals from the sensors input via the I / 0 interface according to a control program stored in the ROM, and stores various data stored in the RAM and the backup RAM. Engine operation control such as fuel injection amount and timing control, ignition timing control, supercharging pressure control, and valve timing control is performed based on various learning value data and fixed data such as a control map stored in the ROM.

  Here, an embodiment of the engine control routine having the above-described configuration will be described with reference to the flowchart of FIG. In this control routine, the intake valve and the exhaust gas are controlled by the fuel injection control in which the fuel injection amount and the timing are obtained mainly based on the engine load and the engine speed, and the valve timing control through the variable valve timing mechanisms InVVT and ExVVT. As part of a normal control routine for controlling the engine to an optimal state, such as valve overlap amount control in which both valves are opened and supercharging pressure control via the turbocharger 22, the crankshaft 51 It is executed every 180 ° rotation.

  Therefore, first, in step S201, it is determined whether or not knocking has occurred. If knocking has not occurred, the process proceeds to step S202, and it is determined whether or not the VVT advance amount is a map value.

  Here, the VVT advance amount is an advance amount for increasing the overlap by advancing the variable valve timing mechanism InVVT on the intake camshaft side, and the variable valve timing mechanism on the exhaust camshaft side. When the overlap is increased by ExVVT, this is the VVT retardation amount. The intent of the present invention is to either advance the variable valve timing mechanism InVVT on the intake camshaft side, retard the variable valve timing mechanism ExVVT on the exhaust camshaft side, or to perform both simultaneously In order to simplify the explanation, in the following description, the overlap amount is controlled only by operating the variable valve timing mechanism InVVT on the intake camshaft side. Will be described.

  The VVT advance amount map value is a value of the VVT advance amount in a normal driving state in which knocking does not occur. As described above, an appropriate VVT advance amount is stored in advance in the form of a map in the table based on the engine load and the engine speed as described above. In step S202, it is determined whether or not the VVT advance amount is a map value, as will be described later, when knocking does not occur as a result of the knocking suppression control, the VVT advance amount is rapidly increased. This is for “annealing” control that avoids the occurrence of a surge due to the restoration.

  In step S202, if the VVT advance amount is a map value, that is, "Yes", the process proceeds to step S203, and normal fuel injection control is performed. That is, the fuel injection amount is obtained from the map value based on the engine operating state based on the engine load and the engine speed detected by the air flow meter 101. At the same time, depending on the operating state of the engine, the ratio between the fuel injection amount from the port injector 31 and the fuel injection amount from the in-cylinder injector 33 is determined.

  On the other hand, if it is determined in step S201 that knocking has occurred, the process proceeds to step S204, where it is determined whether the intake pressure is greater than the back pressure. That is, a determination is made based on the detection values of the intake pipe pressure sensor 104 and the back pressure sensor 108, and when the intake pressure (supercharging pressure) is higher than the back pressure, that is, “Yes”, the process proceeds to step S205 and overshoots. VVT advance control is performed to enlarge the lap. By controlling the oil control valve 42, the variable valve timing mechanism InVVT on the intake camshaft side is advanced by a predetermined angle as described above.

  Then, after the overlap is enlarged by a predetermined angle, the process proceeds to step S208, and fuel injection amount correction control is performed.

  This fuel injection amount correction control corrects the fuel injection amount to the amount of intake air before the intake camshaft side variable valve timing mechanism InVVT serving as the knocking occurrence suppression means starts operating. Therefore, as a result of expanding the overlap, even if the actual air amount in the cylinder is smaller than the intake air amount measured by the air flow meter 102 due to the blow-through of fresh air, the air-fuel ratio is prevented from changing greatly.

  In this fuel injection amount correction control, the actual air amount existing in the cylinder may be obtained by calculation and corrected as the fuel injection amount corresponding thereto. That is, “in-cylinder air amount” = “air flow meter measured air amount” − “blow-off air amount” and “blow-off air amount” = (intake pressure−back pressure) × (overlap time). The actual amount of air present in the cylinder is obtained and corrected as a fuel injection amount for this amount of air.

In step S204 described above, if the back pressure is greater than the intake pressure, that is, “No”, the process proceeds to step S206, where normal knock control such as ignition timing retardation, EGR increase, supercharging pressure reduction, or the like is performed. Control is performed, and the process proceeds to step S203 described above. On the other hand, if the VVT advance amount is not a map value in step S202 described above, that is, “No”, the process proceeds to step S207, where “smoothing” control is performed to gradually reduce the overlap amount. For example, when the current VVT advance amount is VVTn and the map value is a VVT _{map value} , VVT _{(n + 1)} , which is a new VVT advance amount, causes N to be knocked out as a result of knock suppression control. Assuming that the number of control routine cycles after the determination in step S201 is given by the following equation.
VVT _{(n + 1)} = (VVT _{map value} −VVTn) / N + VVTn

  In step S207, after the overlap amount is decreased by a predetermined angle, the process proceeds to step S208, and the above-described fuel injection amount correction control is performed.

  The fuel injection amount determined in step S203 described above is injected and supplied to the engine 1 corresponding to the fuel injection mode set according to the operating state. In the engine 1 having both the port injector 31 and the in-cylinder injector 33 shown in FIG. 1, the port injector 31 and the in-cylinder injector 33 are switched according to the operation region and used for homogeneous combustion. It is also possible to realize stratified mixture combustion or use both at the same time. In such an engine that uses the port injector 31 and the in-cylinder injector 33 at the same time, when supplying the corrected fuel injection amount determined in step S208 described above, the port injector at the normal time when knocking has not occurred. The ratio of the fuel injection amount from the in-cylinder injector 33 is changed to be larger than that of the port injector 31 with respect to the ratio between the fuel injection amount from 31 and the fuel injection amount from the in-cylinder injector 33. This is to reduce as much as possible the possibility that a part of the fuel injected from the port injector 31 will be blown out by increasing the overlap amount for suppressing knocking. Therefore, from this point of view, when changing the fuel injection ratio from the port injector 31 and the in-cylinder injector 33, the injection from the port injector 31 is stopped and the fuel injection ratio from the in-cylinder injector 33 is set to 100%. It is preferable to do.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, the example in which the variable valve timing mechanism is disposed on both the intake camshaft side and the exhaust camshaft side has been described. However, the present invention is not limited to this, and the variable valve is not limited thereto. Any timing mechanism may be used as long as it is disposed on at least one of the intake camshaft and the exhaust camshaft. Further, the variable valve timing mechanism is not limited to the one that continuously switches, and the valve timing may be changed stepwise by selectively switching between the low speed cam and the high speed cam.

  Furthermore, in the above-described embodiment, an example in which the present invention is applied to an engine including both the port injector 31 and the in-cylinder injector 33 has been described. However, any engine having at least an in-cylinder injector may be used as another embodiment.

1 is a schematic configuration diagram showing an overall configuration of a variable valve timing mechanism and a supercharged engine according to an embodiment of the present invention. It is a flowchart which shows one form of the control routine which concerns on embodiment of this invention.

Explanation of symbols

1 Engine with variable valve timing mechanism and turbocharger 22 Turbocharger (supercharger)
31 Port injector 33 In-cylinder injector InVVT Intake side variable valve timing mechanism ExVVT Exhaust side variable valve timing mechanism 100 ECU
106 Knocking sensor 109 Intake side cam position sensor 110 Exhaust side cam position sensor

Claims (3)

In an engine including at least a cylinder fuel injection valve, a variable valve timing mechanism that varies opening and closing timings of at least one of an intake valve and an exhaust valve, and a supercharger,
Knocking occurrence suppression means for operating the variable valve timing mechanism at a predetermined time and suppressing the occurrence of knocking by increasing the valve overlap;
When knocking is detected by the knocking detection means and the knocking generation suppression means is operated, the fuel injection amount supplied from the in-cylinder fuel injection valve is set to the fuel injection amount relative to the intake air amount before the operation of the knocking generation suppression means. Correction means for correcting the quantity;
An engine fuel injection control device comprising:   The engine further includes a port fuel injection valve. When knocking is detected by the knocking detection unit and the knocking generation suppression unit is activated, a fuel injection ratio from the in-cylinder fuel injection valve to the port fuel injection valve is determined. 2. The fuel injection control device for an engine according to claim 1, further comprising a fuel injection ratio changing means for increasing. The fuel injection control device for an engine according to claim 2, wherein the fuel injection ratio changing means sets the fuel injection ratio from the in-cylinder fuel injection valve to 100%.

Images