JP2005113693A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device for an internal combustion engine which improves the startability of the engine and does not cause idle roughness.
In an internal combustion engine including an in-cylinder injector 11 and an intake manifold injector 12, a first or several injections of fuel at the start are injected into a cylinder in a compression stroke. 11, and the subsequent fuel injection during start-up in which the starter switch 49 is on is performed by the intake passage injection injector 12.
[Selection] Figure 1

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly, to an in-cylinder injector that injects fuel into a cylinder and an intake-path injector that injects fuel into an intake passage or an intake port. And a so-called dual injection internal combustion engine fuel injection control device.

  Generally, an in-cylinder injector for injecting fuel into the cylinder and an intake-path injector for injecting fuel into the intake passage or the intake port are provided according to the operating state of the engine. A so-called dual injection internal combustion engine that realizes stratified combustion in the low-load operation region and homogeneous combustion in the high-load operation region by improving the fuel efficiency and output characteristics by switching these injectors is known. It has been.

  However, in such a dual injection internal combustion engine, for example, a technique described in Patent Document 1 has been proposed in order to improve the startability.

  In this system, when the fuel injection pressure supplied from the high-pressure fuel pump is higher than a predetermined pressure, the compression stroke injection is performed by the in-cylinder injector, and when the fuel injection pressure is lower than the predetermined pressure, the intake stroke injection is performed by the in-cylinder injector. Or, if necessary, the fuel injection mode is switched and controlled so that the intake stroke injection is performed by the intake manifold injector.

Japanese Patent Laid-Open No. 10-176574

  However, in the technique described in Patent Document 1, the fuel injection mode is switched and controlled in accordance with the fuel injection pressure at the time of starting. However, if the in-cylinder direct injection by the in-cylinder injector is continued, Since the amount of direct fuel injection is large, the fuel injection pressure is lowered, and there is a risk of misfire. In particular, when the engine temperature is low, the injection amount is larger than the pumping amount of the fuel pump, and a long time is required until the predetermined set pressure is reached. On the other hand, when an intake manifold injector is used at the time of starting, it takes time from injection to ignition, and there is a problem that fuel followability peculiar to direct injection is lost and startability deteriorates.

  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 improves the startability of the engine and does not cause idle roughness.

  A fuel injection control device for an internal combustion engine according to an embodiment of the present invention that achieves the above object is provided for an internal combustion engine including an in-cylinder injector and an intake manifold injector, up to the first time or several times at start-up. The fuel injection is performed to the cylinder in the compression stroke by the in-cylinder injector, and fuel injection during start-up thereafter is performed by the intake passage injection injector.

  According to the fuel injection control device for an internal combustion engine according to one aspect of the present invention, in the internal combustion engine including the in-cylinder injector and the intake manifold injector, the first or several fuel injections at the start time are Since the injection to the cylinder in the compression stroke is performed by the in-cylinder injector, the start is quickly performed. Further, during the subsequent startup, fuel injection by the in-cylinder injector is not performed, but is performed by the intake passage injector, so that the fuel injection pressure of the in-cylinder injector is quickly increased, Idle roughness does not occur.

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, the engine 1 includes four cylinders 1a. Each cylinder 1 a is connected to a common surge tank 3 via a corresponding intake branch pipe 2. The surge tank 3 is connected to an air flow meter 4 a through an intake duct 4, and the air flow meter 4 a is connected to an air cleaner 5. A throttle valve 7 driven by a step motor 6 is disposed in the intake duct 4. The throttle valve 7 is closed to some extent only when the engine load is extremely low, and is kept fully open when the engine load is slightly increased. On the other hand, each cylinder 1 a is connected to a common exhaust manifold 8, and this exhaust manifold 8 is connected to a three-way catalytic converter 9.

  Each cylinder 1a is provided with an in-cylinder injector 11 for injecting fuel into the cylinder and an intake passage injector 12 for injecting fuel into the intake port. These injectors 11 and 12 are controlled based on the output signal of the electronic control unit 30. Further, each in-cylinder injector 11 is connected to a common fuel distribution pipe 13, and this fuel distribution pipe 13 is connected to a fuel distribution pipe 13 through a check valve 14, and is driven by an engine drive type. A high-pressure fuel pump 15 is connected.

  As shown in FIG. 1, the discharge side of the high-pressure fuel pump 15 is connected to the suction side of the high-pressure fuel pump 15 via a spill electromagnetic valve 15a. When the amount of fuel supplied from the pump 15 into the fuel distribution pipe 13 is increased and the spill electromagnetic valve 15a is fully opened, the fuel supply from the high pressure fuel pump 15 to the fuel distribution pipe 13 is stopped. ing. The spill electromagnetic valve 15a is controlled based on the output signal of the electronic control unit 30.

  On the other hand, each intake passage injector 12 is connected to a common fuel distribution pipe 16, and the fuel distribution pipe 16 and the high pressure fuel pump 15 are connected to a common fuel pressure regulator 17 through an electric motor drive type low pressure fuel pump. 18 is connected. Further, the low pressure fuel pump 18 is connected to the fuel tank 20 via the fuel filter 19. The fuel pressure regulator 17 returns a part of the fuel discharged from the low-pressure fuel pump 18 to the fuel tank 20 when the fuel pressure of the fuel discharged from the low-pressure fuel pump 18 becomes higher than a predetermined set fuel pressure. Accordingly, the fuel pressure supplied to the intake manifold injector 12 and the fuel pressure supplied to the high-pressure fuel pump 15 are prevented from becoming higher than the set fuel pressure. Further, as shown in FIG. 1, a flow valve 21 is provided between the high pressure fuel pump 15 and the fuel pressure regulator 17. The flow valve 21 is normally opened. When the flow valve 21 is closed, the fuel supply from the low pressure fuel pump 18 to the high pressure fuel pump 15 is stopped. The opening / closing of the flow valve 21 is controlled based on the output signal of the electronic control unit 30.

  The electronic control unit 30 is composed of a digital computer and includes a ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, and an input port which are connected to each other via a bidirectional bus 31. 35 and an output port 36. The air flow meter 4 a generates an output voltage proportional to the amount of intake air, and the output voltage of the air flow meter 4 a is input to the input port 35 via the AD converter 37. A water temperature sensor 38 that generates an output voltage proportional to the engine cooling water temperature is attached to the engine 1, and the output voltage of the water temperature sensor 38 is input to the input port 35 via the AD converter 39. A fuel pressure sensor 40 that generates an output voltage proportional to the fuel pressure in the fuel distribution pipe 13 is attached to the fuel distribution pipe 13, and the output voltage of the fuel pressure sensor 40 is supplied to the input port 35 via the AD converter 41. Entered. An oxygen concentration sensor 42 that generates an output voltage proportional to the oxygen concentration in the exhaust gas is attached to the exhaust manifold 8 upstream of the catalyst 9. The output voltage of the oxygen concentration sensor 42 is input to an input port 35 via an AD converter 43. Is input. The accelerator pedal 10 is connected to a load sensor 44 that generates an output voltage proportional to the depression amount of the accelerator pedal 10, and the output voltage of the load sensor 44 is input to the input port 35 via the AD converter 45. The input port 35 is connected to a rotational speed sensor 46 that generates an output pulse representing the engine rotational speed. Further, a cylinder discrimination sensor 48 that discriminates a cylinder to be controlled by detecting a predetermined crank angle and a starter switch 49 that detects a starter on / off signal are connected to the input port 35. In the ROM 32 of the electronic control unit 30, the value of the fuel injection amount and the engine cooling water temperature set corresponding to the operating state based on the engine load and the engine speed obtained by the load sensor 44 and the engine speed sensor 46 described above. Correction values and the like based on are previously mapped and stored.

  Furthermore, FIG. 2 shows a side sectional view of the cylinder 1a. Referring to FIG. 2, 61 is a cylinder block, 62 is a piston having a recess 62a formed on the top surface, 63 is a cylinder head secured on the cylinder block 61, and 64 is between the piston 62 and the cylinder head 63. The formed combustion chamber, 65 is an intake valve, 66 is an exhaust valve, 67 is an intake port, 68 is an exhaust port, and 69 is an ignition plug. The intake port 67 is formed so that the air flowing into the combustion chamber 64 generates a swirling flow around the cylinder axis. The recess 62 a extends from the peripheral edge of the piston 62 located on the in-cylinder injector 11 side toward the center of the piston 62 and extends upward below the spark plug 69.

  The intake valve 65 and the exhaust valve 66 are linked to an intake valve drive mechanism 70 and an exhaust valve drive mechanism 71, respectively. The intake valve drive mechanism 70 and the exhaust valve drive mechanism 71 are configured by electromagnetic drive mechanisms that drive the intake valve 65 and the exhaust valve 66 forward and backward, respectively, using electromagnetic force generated when an excitation current is applied. Based on the signal of the electronic control unit 30, the opening / closing timing and the lift amount can be arbitrarily controlled. Therefore, for example, when the intake valve driving mechanism 70 and / or the exhaust valve driving mechanism 71 is operated based on a signal from the electronic control unit 30, the opening / closing timing of the intake valve 65 and / or the intake valve 65, and thus the opening period. Is variably controlled to be long or short.

  Here, the output port 36 of the electronic control unit 30 is connected to the step motor 6, each in-cylinder injector 11, each intake passage injector 12, the spill solenoid valve 15 a, the flow valve 21, via the corresponding drive circuit 47. The intake valve drive mechanism 70 and the exhaust valve drive mechanism 71 are connected.

  Next, the control at the start of the embodiment of the present invention having the above configuration will be described below with reference to the flowchart shown in FIG. First, when control is started by turning on an accessory switch (not shown), the electric motor driven low-pressure fuel pump 18 is started to drive, the flow valve 21 is opened, and the spill electromagnetic valve 15a is kept closed. Therefore, when the starter switch 49 is turned on in the determination in step S31 in the fuel injection mode determination routine, the process proceeds to step S32, and it is determined whether or not the determination is the first time after entering the routine. Here, if it is the first time, the process proceeds to step S33, and in-cylinder direct injection (hereinafter referred to as D4 injection) is performed by the in-cylinder injector 11 described in detail later. Further, when the determination in step S32 is not the first time and after step S33 described above, the process proceeds to step S34, and intake passage injection (hereinafter referred to as PFi injection) by the intake passage injection injector 12 described later is performed. Is executed.

  On the other hand, when the starter switch 49 is not turned on in the determination of step S31 described above, that is, when the starter switch 49 is turned off after being turned on once, the process proceeds to step S35, where the fuel component detected by the fuel pressure sensor 40 is detected. It is determined whether or not the actual fuel pressure in the pipe 13 has reached the target fuel pressure. If it is determined in step S35 that the actual fuel pressure has not reached the target fuel pressure, the process proceeds to step S36, and the PFi injection by the intake passage injector 12 is forcibly executed. When the actual fuel pressure has reached the target fuel pressure, the routine proceeds to step S37, where it is determined whether or not the engine is in the PFi injection range from the engine operating state based on the engine load and the engine speed as described later. If it is determined that this is not the PFi injection region, the routine proceeds to step S38, where the in-cylinder injector 11 performs D4 injection toward the in-cylinder combustion chamber 64, and the stratified combustion operation is performed. On the other hand, if it is in the PFi injection region, the process proceeds to step S36 described above, and PFi injection in the intake manifold injector 12 is executed to perform a homogeneous combustion operation.

  Here, the execution routine of D4 injection in step S33 described above will be further described. FIG. 4 shows the D4 injection possible range from the # 1 cylinder to the # 4 cylinder in relation to the crank angle. In FIG. 4, a straight arrow indicates a period during which the intake valve 65 is open, a black portion indicates a D4 injectable region or period, and a serpentine arrow indicates an ignition timing. Considering the crank angle 0 as a reference, at the crank angle 0 to 180 A °, the # 1 cylinder may be in the combustion stroke, the # 2 cylinder is in the exhaust stroke, the # 3 cylinder is in the compression stroke, and the # 4 cylinder is in the intake stroke. It can be seen (in FIG. 4, A means later and B means front).

  Therefore, in the execution routine of D4 injection in step S33, since the D4 injection is the first D4 injection after the start of the routine after the starter switch 49 is turned on, the cylinder angle can be detected and the cylinder discrimination sensor 48 can perform D4 injection. Is determined. That is, for example, if the crank angle is at a position of 180 A °, since the # 4 cylinder is in the compression stroke, D4 injection is performed to the # 4 cylinder. The fuel injection amount in this D4 injection is determined based on the map shown in FIG. That is, the fuel injection amount is determined so that the amount is reduced as the engine water temperature increases in response to the detection of the engine water temperature by the water temperature sensor 38. This is because the higher the engine water temperature is, the more fuel vaporization is promoted, so that ignition combustion is possible with a smaller amount of fuel. Then, the determined fuel injection amount is D4 injected only into the # 4 cylinder in the above example as the first or first fuel injection.

  Further, in the PFi injection execution routine in step S34, the fuel injection amount in the PFi injection is determined based on the map shown in FIG. That is, the engine water temperature is detected by the water temperature sensor 38 and the engine rotational speed (cranking rotational speed) is detected by the rotational speed sensor 46, so that the engine water temperature increases and the amount increases as the rotational speed increases. The fuel injection amount is determined based on the reduced relationship. In the above-described example, the determined fuel injection amount is PFi injection in the order of # 2, # 1, # 3, and # 4 cylinders as fuel injection during start-up after the first shot.

  The control of the present invention at the time of starting described above will be further described with reference to the time chart shown in FIG. First, as described above, when the accessory switch is turned on, the electric motor driven low-pressure fuel pump 18 is started to drive, and the fuel pressure P1 is generated in the fuel distribution pipes 13 and 16. Therefore, at time t1, when the starter switch 49 is turned on and cranking by the starter is performed and at the same time a starter signal is input, D4 injection that is direct in-cylinder injection by the in-cylinder injector 11 is performed. Only the first cylinder (for example, # 4 cylinder) is performed in the compression stroke, and the other cylinders (# 2, # 1, # 3 cylinder, # 4 cylinder of the second cycle, etc.) are the intake passage injection injectors 12. PFi injection that is injection in the intake passage is performed in the intake stroke. This first D4 injection is performed under the fuel pressure P1, but since it is a direct injection into the cylinder, it is quickly started. Further, during the subsequent start when the starter signal is on, fuel injection by the in-cylinder injector 11 is not performed, but is performed by the intake passage injector 12. Therefore, by driving the high-pressure fuel pump 15 by cranking, The fuel pressure in the fuel distribution pipe 13 is quickly raised to the target fuel pressure P2. This state is shown by a solid line in FIG.

  On the other hand, when the entire amount is directly injected into the cylinder during start-up as in the prior art, it takes time for the fuel pressure to rise to the target fuel pressure P2, as shown by the broken line. However, there is a period in which the target fuel pressure P2 is not reached in idling after starting. As a result, if the D4 injection is continuously performed, a predetermined fuel amount cannot be obtained, resulting in idle roughness. By the way, in the present invention, since the fuel pressure in the fuel distribution pipe 13 is quickly increased to the target fuel pressure P2, after the time t2 when the starter signal is turned off, that is, idling roughness after starting is generated. There is no.

  Further, in the determination of whether or not it is the PFi injection range in the above-described step S37, based on the control region map shown in FIG. It is determined whether the D4 injection region or the PFi injection region from the operating state. Generally, in idling after starting, as is apparent from the control region map of FIG. 8, D4 injection is performed.

  In the above-described embodiment of the present invention, the example in which the first fuel injection at the time of starting is performed by the in-cylinder injector 11 to one cylinder in the compression stroke has been described. This is the target fuel pressure P2. As long as the rapid increase to the engine is not hindered, the cylinder injection in the cylinder 11 in the compression stroke may be performed by the in-cylinder injector 11 for the second and / or third injections. Good. Furthermore, it goes without saying that the control according to the present invention described above is not limited to a four-cylinder engine but can be performed by a multi-cylinder engine having more cylinders.

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 sectional side view of the engine shown in FIG. It is a flowchart which shows an example of the fuel-injection mode determination routine in one Embodiment of this invention. In one Embodiment of this invention, it is explanatory drawing which shows the in-cylinder direct injection possible area in # 1 cylinder to # 4 cylinder in relation to a crank angle. In one Embodiment of this invention, it is a graph which shows the relationship between the in-cylinder direct injection amount and water temperature. In one Embodiment of this invention, it is a graph which shows the relationship between the injection quantity in an intake passage, water temperature, and engine speed. In one Embodiment of this invention, it is a time chart which shows the mode of the control at the time of starting. It is a graph which shows the control area map in one Embodiment of this invention.

Explanation of symbols

11 In-cylinder injector 12 Intake passage injector 30 Electronic control unit 40 Fuel pressure sensor 44 Load sensor 46 Rotation speed sensor 48 Cylinder discrimination sensor 49 Starter switch

Claims (1)

In an internal combustion engine comprising an in-cylinder injector and an intake manifold injector,
The first or several fuel injections at the time of start-up are performed by the in-cylinder injector to the cylinder in the compression stroke, and fuel injection during the subsequent start-up is performed by the intake passage injection injector. A fuel injection control device for an internal combustion engine characterized by comprising:

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