JP2006336620A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device for an internal combustion engine, which does not impair performance of the engine. <P>SOLUTION: The internal combustion engine comprises: a cylinder injection injector 140 for injecting fuel toward the inside of a cylinder, and an intake port injection injector 150 for injecting fuel toward the inside of an intake port. The engine further comprises a change control means for changing an injection sharing ratio from both of the injectors depending on engine loads, when the injection sharing ratio from both of the injectors are changed depending on operational statuses, and an injection amount of fuel from the cylinder injection injector 140 is below its minimum fuel injection amount. This change control means sets the fuel injection amount of the cylinder injection injector to be zero when the engine load is a predetermined value or less, and sets the fuel injection amount of the cylinder injection injector 140 to be the minimum fuel injection amount when the engine load exceeds the predetermined value, and then corrects the fuel injection amount of the intake port injection injector 150 to correspond to each of the fuel injection amounts. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more specifically, includes an in-cylinder injector that injects fuel into a cylinder and an intake port injector that injects fuel into an intake port. The present invention relates to a fuel injection control device for a so-called dual injection type internal combustion engine.

  Generally, an in-cylinder injector for injecting fuel into a cylinder and an intake port injector for injecting fuel into an intake passage or an intake port are provided, depending on the operating state of the engine. By switching and using these injectors, for example, stratified combustion in the low load operation region and homogeneous combustion in the high load operation region are realized, or fuel is injected at a predetermined injection ratio according to the operation state. A so-called dual injection type internal combustion engine that improves fuel consumption characteristics and output characteristics is known (Patent Documents 1, 2, etc.).

  By the way, in such a dual injection type internal combustion engine, when the fuel injection is performed at a predetermined injection ratio according to the operating state, the required injection amount from the in-cylinder injector may vary depending on the operating condition. Sometimes it is below the minimum injection amount. If the required injection amount is below the minimum injection amount in this way, the control of the fuel injection amount set by the valve opening time may become unstable. Therefore, in order to satisfy the required injection amount while maintaining the minimum valve opening time, it is conceivable to reduce the fuel pressure supplied to the injector. However, if the fuel pressure is reduced in this way, atomization of the injected fuel is not promoted. There is a possibility that a new problem of worsening combustion and emission may occur.

  Therefore, although it is not a dual injection type internal combustion engine in Patent Document 3, when the required injection amount falls below the minimum injection amount of the fuel injection valve, the fuel injection valve injects once every two cycles. Have been disclosed.

  Also, in Patent Document 4, although not a dual injection type internal combustion engine, when the required injection time interrupts the minimum injection time, the fuel injection time is changed to the minimum injection time and the ignition timing is retarded. This technique is disclosed.

  Further, in Patent Document 5, in a two-cycle internal combustion engine including an in-cylinder injector and an out-cylinder injector, an in-cylinder injector is used to suppress air-fuel mixture blowout and control an air-fuel ratio at the time of ignition. Discloses a technique for controlling the fuel injection timing and the injection amount from and the injection amount from the in-cylinder injector. However, there is no mention of a case where the required injection amount is lower than the minimum injection amount of the injector.

JP 2001-20837 A JP-A-5-2321221 JP 2003-120379 A JP-A-8-165972 Japanese Patent Application Laid-Open No. 11-13510

  However, when the required injection amount from the in-cylinder injector is less than the minimum injection amount as described above, the injection from the in-cylinder injector is simply performed once every two cycles as described in Patent Document 3, In other words, simply setting the injection amount to zero in one cycle or setting the minimum injection amount as described in Patent Document 4 is not appropriate for a dual injection type internal combustion engine. For example, if the injection from the in-cylinder injector is zero in a high load region, the in-cylinder injector has no cooling effect due to its own injection despite being exposed to high-temperature combustion gas. As a result of deposit depositing around the nozzle hole, the in-cylinder injector may be clogged. On the other hand, if the minimum injection amount is set in the low load region, fuel exceeding the required injection amount is injected into the cylinder, and as a result, a large amount of unburned components may remain, leading to deterioration of emissions.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fuel injection control device for an internal combustion engine that eliminates such conventional problems and does not impair engine performance.

  A fuel injection control device for an internal combustion engine according to an embodiment of the present invention that achieves the above object includes an in-cylinder injector that injects fuel into a cylinder and an intake port injection that injects fuel into an intake port. In an internal combustion engine equipped with an injector, when the injection ratio from both injectors changes according to the operating state and the fuel injection amount from the in-cylinder injector is below the minimum fuel injection amount, it depends on the engine load. And a change control means for changing the ratio of spraying from both injectors.

  Here, the change control means sets the fuel injection amount from the in-cylinder injector to 0 when the engine load is a predetermined value or less, and from the in-cylinder injector when the engine load exceeds the predetermined value. The fuel injection amount is set to the minimum fuel injection amount, and the fuel injection amount from the intake port injection injector is corrected corresponding to each of the fuel injection amounts.

  According to a fuel injection control device for an internal combustion engine according to an aspect of the present invention, an in-cylinder injector that injects fuel into a cylinder and an intake port injector that injects fuel into an intake port. In the internal combustion engine provided, when the injection ratio from both injectors changes according to the operating state and the fuel injection amount from the in-cylinder injector is below the minimum fuel injection amount, the change control means The injection ratio is changed according to the engine load. Accordingly, since it is avoided that fuel below the minimum fuel injection amount is injected from the in-cylinder injector, it is possible to prevent the fuel injection amount from becoming unstable and prevent the engine performance from being impaired.

  Here, the change control means sets the fuel injection amount from the in-cylinder injector to 0 when the engine load is equal to or less than a predetermined value, and from the in-cylinder injector when the engine load exceeds the predetermined value. According to the mode of correcting the fuel injection amount from the intake port injection injector in correspondence with the minimum fuel injection amount, the total fuel injection amount is less than a predetermined value, for example, when the engine load is low. The amount is injected from the intake port injector, and it is easy to obtain a homogeneous mixture, and there are few unburned components, so the deterioration of emissions is suppressed. In addition, since the minimum fuel injection amount is injected from the in-cylinder injector when the engine load exceeds a predetermined value, for example, when the engine load is high, the cooling effect by the injection of itself is also achieved despite being exposed to high-temperature combustion gas. Yes, deposit adhesion is suppressed and clogging is suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, referring to FIG. 1 showing a schematic configuration diagram of a fuel injection control device for a dual injection type internal combustion engine according to the present invention, a plurality of engines (hereinafter also referred to as engines) 100 are arranged in a cylinder block 101 (FIG. 1). Are provided with only one cylinder 102). 103 is a piston having a cavity formed on the top surface, 104 is a cylinder head fixed on the cylinder block 101, 105 is a combustion chamber formed between the piston 103 and the cylinder head 104, 106 is an intake valve, 107 Is an exhaust valve, 108 is an intake port, 109 is an exhaust port, and 110 is a spark plug. The piston 103 is connected to the crankshaft 112 via a connecting rod 111.

  Each cylinder 102 is connected to a common surge tank 114 via a corresponding intake manifold 113. The surge tank 114 is connected to an air flow meter 116 via an intake duct 115, and the air flow meter 116 is connected to an air cleaner 117. A throttle valve 119 driven by an electric motor 118 is disposed in the intake duct 115. The throttle valve 119 is electronically controlled to open and close by an electronic control unit (ECU) 200 described later independently of an operation of an accelerator pedal 160 described later. On the other hand, each cylinder 102 is connected to a common exhaust manifold 120, and this exhaust manifold 120 is connected to a three-way catalytic converter 122.

  For each cylinder 102, an in-cylinder injector 140 for injecting fuel into the cylinder and an intake port injection injector 150 for injecting fuel toward the intake port 108 (or in the intake passage). And are attached respectively. These injectors 140 and 150 are controlled based on the output signal of the electronic control unit 200, respectively. Each in-cylinder injector 140 is connected to a common delivery pipe 142, and this delivery pipe 142 is connected to an engine-driven high-pressure pump via a check valve (not shown). The discharge side of the high pressure pump is connected to the suction side of the high pressure pump via a spill solenoid valve. The smaller the opening of the spill solenoid valve, the more fuel is supplied from the high pressure pump into the delivery pipe 142. When the spill solenoid valve is fully opened, the fuel supply from the high pressure pump to the delivery pipe 142 is stopped. This spill solenoid valve is controlled based on the output signal of the electronic control unit 200.

  On the other hand, each intake port injection injector 150 is connected to a common delivery pipe 152, and the delivery pipe 152 and the high pressure pump are connected to an electric motor driven low pressure pump via a common fuel pressure regulator (not shown). ing. Furthermore, the low pressure pump is connected to the fuel tank via a fuel filter. The fuel pressure regulator is configured to return a part of the fuel discharged from the low pressure pump to the fuel tank when the fuel pressure of the fuel discharged from the low pressure pump becomes higher than a predetermined set fuel pressure. The fuel pressure supplied to the intake port injector 150 and the fuel pressure supplied to the high-pressure pump are prevented from becoming higher than the set fuel pressure.

  The electronic control unit 200 is a digital computer and is connected to each other via a bidirectional bus such as a ROM (read only memory), a RAM (random access memory), a CPU (microprocessor), an input port, an output port, and the like. It has. The air flow meter 116 generates an output voltage proportional to the amount of intake air, and the output voltage of the air flow meter 116 is input to the input port via the AD converter.

  Further, the engine 100 is provided with a water temperature sensor 202 that generates an output voltage proportional to the cooling water temperature, and the output voltage of the water temperature sensor 202 is input to the input port 35 via an AD converter. An air-fuel ratio sensor 204 that generates an output voltage proportional to the air-fuel ratio in the exhaust gas is attached to the exhaust manifold 120 upstream of the three-way catalyst 122. The output voltage of the air-fuel ratio sensor 204 is also passed through an AD converter. Input to the input port.

  The accelerator pedal 160 is connected to an accelerator opening sensor 206 that generates an output voltage proportional to the depression amount of the accelerator pedal 160, and the opening of the throttle valve 119 is detected by a throttle opening sensor 208. . The output voltages of the accelerator opening sensor 206 and the throttle opening sensor 208 are input to the input port via the AD converter. Further, a crank angle sensor 210 that generates an output pulse representing the engine speed is connected to the input port. In the ROM 32 of the electronic control unit 200, the fuel injection amount set corresponding to the operating region based on the engine load and the engine speed obtained by the air flow meter 116, the accelerator opening sensor 206, and the crank angle sensor 210 described above. And the injection ratio are previously mapped and stored.

  Here, the output port of the electronic control unit 200 is connected to the igniter of the electric motor 118, each in-cylinder injector 140, each intake port injector 150, and the spark plug 110 via a corresponding drive circuit.

  Next, an example of the control of the embodiment of the present invention having the above configuration will be described below with reference to the flowchart of FIG. First, when the control is started, the electronic control unit 200 is requested by the driver in step S201 based on the engine required load and the engine speed obtained by the accelerator opening sensor 206 and the crank angle sensor 210 every predetermined time. It detects the operating conditions or areas of the engine being operated. Based on this detection, the total fuel injection amount Q stored in the map is determined in the next step S202. Next, the process proceeds to step S203, and the injection ratio k1st from the in-cylinder injector 140 and the intake port injector 150 under the above operating conditions is also obtained from the map. This spray distribution ratio k1st is set in advance, for example, as in the map shown in FIG.

  Specifically, in the present embodiment, for example, k1st = 0 in an extremely low load efficiency region such as an idling and / or deceleration operation region of engine 100, that is, from in-cylinder injector 140 The fuel injection ratio is 0, and the fuel injection ratio from the intake port injector 150 is 1. In the low load efficiency region of engine 100 with low load, k1st = 1, that is, the fuel injection ratio from in-cylinder injector 140 is 1, and the fuel injection ratio from intake port injector 150 is 0. Yes. Further, in the high load high efficiency region of engine 100, the fuel injection ratio from intake port injector 150 increases from the low load region to the maximum load (WOT) region, and fuel is simultaneously supplied from both injectors. Is set to be injected. In the maximum charging efficiency region of the maximum load (WOT) of engine 100, k1st = 1 is set so that fuel is injected only from in-cylinder injector 140.

Therefore, returning to the flowchart of FIG. 3 again, in step S204, based on the injection ratio k1st obtained in step S203, the in-cylinder fuel injection amount Qd and the port in-cylinder fuel injection amount Qp are expressed by the following equation (1) and It is calculated by (2).
(1) Qd = Q × k1st
(2) Qp = Q × (1-k1st)

  In the next step S205, based on the in-cylinder fuel injection amount Qd and the port fuel injection amount Qp obtained in step S204 described above, the in-cylinder injector 140 and the intake port injection injector 150 are subjected to a predetermined fuel pressure. The in-cylinder injector injection time taud and the intake port injector injection time taup, which are valve opening times, are calculated, respectively, and the process proceeds to step S206.

  In step S206, the in-cylinder injector injection time taud is greater than 0 and smaller than the in-cylinder injector minimum fuel injection time taumin corresponding to the minimum fuel injection amount of the in-cylinder injector 140, that is, It is determined whether it is below. If the in-cylinder injector injection time taud is longer than the in-cylinder injector minimum fuel injection time taumin, the process proceeds to step S217, and the in-cylinder injector injection time taud calculated in step S205 and the intake port injector injection. At time taup, fuel injection is executed and this control routine ends.

  On the other hand, when the in-cylinder injector injection time taud is less than the in-cylinder injector minimum fuel injection time taumin, the routine proceeds to step S207, where it is determined whether or not the charging efficiency KL of the engine 100 is greater than or equal to the boundary charging efficiency KLb.

  The charging efficiency KL is obtained based on the intake air amount obtained by the air flow meter 116 in the present embodiment. The boundary filling efficiency KLb is set in a boundary region between the low load region and the high load region in correspondence with the load of the engine 100.

  If it is determined in step S207 that the charging efficiency KL is greater than or equal to the boundary charging efficiency KLb, the process proceeds to step S208, where the in-cylinder injector injection time taud is changed to the in-cylinder injector minimum fuel injection time taumin. Is done. Thereafter, in step S209, the in-cylinder fuel injection amount Qd is recalculated, and the re-calculated in-cylinder fuel injection amount Qd and the total fuel injection amount Q are also recalculated (= Qd / Q) is performed (step S210). In step S211, the port fuel injection amount Qp is obtained using the recalculated injection division ratio k1st, and the intake port injector injection time taup is obtained again (step S212). In other words, the fuel injection amount Qp from the intake port injector 150 is corrected. Thereafter, the process proceeds to step S218, where fuel injection is executed by the in-cylinder injector injection time taud set in step S208 and the intake port injector injection time taup recalculated in step S212, and this control routine ends. To do.

  On the other hand, if it is determined in step S207 that the charging efficiency KL is less than the boundary charging efficiency KLb, the process proceeds to step S213, where the in-cylinder injector injection time taud is changed to 0 and set. Thereafter, in step S214, the in-cylinder fuel injection amount Qd is set to 0, and the injection ratio k1st is also set to 0 corresponding to the in-cylinder fuel injection amount Qd set to 0 (step S215). In step S216, the port fuel injection amount Qp is set to the total fuel injection amount Q, and the intake port injection injector injection time taup is obtained again (step S217). Thereafter, the process proceeds to step S218, where fuel injection is executed by the in-cylinder injector injection time taud set to 0 in step S213 and the intake port injector injection time taup recalculated in step S217, and this control routine is executed. Ends.

  Thus, according to the present embodiment, when the in-cylinder injector injection time taud is less than the in-cylinder injector minimum fuel injection time taumin, the engine load exceeds a predetermined value, that is, the charging efficiency of the engine 100 When KL is equal to or higher than the boundary filling efficiency KLb, since the minimum fuel injection amount is injected from the in-cylinder injector 140, there is also a cooling action by its own injection despite being exposed to high-temperature combustion gas, Deposit adhesion is suppressed and clogging is suppressed. When the engine load is equal to or lower than the predetermined value, that is, when the charging efficiency KL of the engine 100 is less than the boundary charging efficiency KLb, the total fuel injection amount is injected from the intake port injection injector 150, and it is easy to obtain a homogeneous mixture and unburned Since there are few components, the deterioration of emission is suppressed.

  Needless to say, the present invention can be similarly applied not only to a so-called four-valve engine having two intake ports and exhaust ports per cylinder, but also to a so-called two-valve engine.

1 is a schematic diagram showing a schematic configuration diagram of a fuel injection control device for a dual injection internal combustion engine according to the present invention. It is a flowchart which shows an example of the control form of the fuel-injection control apparatus of the dual injection type internal combustion engine which concerns on this invention. It is a map which shows the example of 1 setting of the injection division ratio in embodiment of this invention.

Explanation of symbols

116 Air Flow Meter 119 Throttle Valve 140 In-Cylinder Injector 150 Intake Port Injection Injector 200 Electronic Control Unit 206 Accelerator Opening Sensor 208 Throttle Opening Sensor 210 Crank Angle Sensor (Rotation Speed Sensor)

Claims (2)

In an internal combustion engine comprising an in-cylinder injector that injects fuel into the cylinder and an intake port injector that injects fuel into the intake port,
When the injection ratio from both injectors changes according to the operating state and the fuel injection amount from the in-cylinder injector is below the minimum fuel injection amount, the injection ratio from both injectors is set according to the engine load. A fuel injection control device for an internal combustion engine, comprising change control means for changing. The change control means sets the fuel injection amount from the in-cylinder injector to 0 when the engine load is equal to or less than a predetermined value, and the fuel injection from the in-cylinder injector when the engine load exceeds the predetermined value. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel injection amount from the intake port injection injector is corrected in accordance with a minimum fuel injection amount corresponding to each amount.

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