JP2007032426A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

The present invention relates to a fuel injection control device for an internal combustion engine, and promotes atomization of injected fuel to improve startability.
SOLUTION: A first injector 50 and a heater 52 are arranged in air passages 40, 42, 44, 46 connected to an intake pipe 34. In addition to the first injector 50, a second injector 70 capable of injecting fuel into the intake port 18 is provided. When the internal combustion engine is started, fuel is injected from the second injector 70 while air heated by the heater 52 is supplied from the air passages 40, 42, 44, 46 to the intake pipe 34.
[Selection] Figure 1

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device for an internal combustion engine capable of supplying vaporized fuel at the time of starting.

There has been proposed a technique for stabilizing the combustion in the combustion chamber by supplying vaporized fuel when the internal combustion engine is cold started. For example, Patent Document 1 provides a bypass intake passage that connects an upstream portion of a throttle valve and an upstream portion of an injector (downstream injector) disposed in an intake port by bypassing the throttle valve, and this bypass intake passage is provided with this bypass intake passage. An internal combustion engine in which an injector (upstream injector) and a heater are arranged is disclosed. In the technique disclosed in Patent Document 1, at the time of cold start, the fuel injected from the upstream injector is heated and vaporized by a heater, and the vaporized fuel is supplied into the combustion chamber, thereby stabilizing the combustion at the time of cold start. We are trying to make it.
JP 2004-132241 A Japanese Patent Laid-Open No. 2-91437 JP 2002-39022 A

  However, there is a distance from the installation position of the upstream injector to the combustion chamber of each cylinder. For this reason, in a situation where the engine temperature is extremely low, such as during cold start in winter, there is a possibility that fuel heated by the heater and vaporized may be reliquefied in the bypass intake passage. If fuel that has become droplets by reliquefaction is supplied into the combustion chamber, startability and exhaust emissions will deteriorate. On the other hand, when the fuel is injected from the downstream injector without using the upstream injector, the fuel cannot be sufficiently atomized at the extremely low temperature, so that good startability cannot be obtained.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel injection control device for an internal combustion engine in which startability is improved by promoting atomization of injected fuel. .

In order to achieve the above object, the first invention provides
An air passage connected to an intake pipe provided for each cylinder;
A first injector capable of injecting fuel into the air passage;
A heater provided at a site where fuel is injected by the first injector in the air passage;
A fuel injection control device for an internal combustion engine having a second injector capable of injecting fuel into an intake port or directly into a combustion chamber,
When starting the internal combustion engine, fuel is injected from the second injector while supplying air heated by the heater to the intake pipe.

According to a second invention, in the first invention,
Prior to starting the internal combustion engine, heating of the air in the air passage by the heater is started.

According to a third invention, in the first or second invention,
When the temperature of the internal combustion engine exceeds a predetermined first warm-up temperature, or when it is predicted that the temperature exceeds the first warm-up temperature, fuel injection by the second injector is stopped, and the first injector It is characterized by starting the fuel injection by.

According to a fourth invention, in the third invention,
When the temperature of the internal combustion engine exceeds a predetermined second warm-up temperature that is higher than the first warm-up temperature, or when it is predicted that the temperature exceeds the second warm-up temperature, the heater heats the air. Is stopped, fuel injection by the first injector is stopped, and fuel injection by the second injector is started.

According to a fifth invention, in any one of the first to fourth inventions,
The air passage is a bypass intake passage that connects an upstream portion of a throttle valve and the intake pipe by bypassing the throttle valve.

  According to 1st invention, the fuel injected from the 2nd injector is atomized by mixing with the high temperature air heated with the heater. Since the second injector injects fuel into the intake port or directly into the combustion chamber, the ratio of atomized fuel droplets compared to the first injector installed away from the combustion chamber Is low. Therefore, according to the first invention, atomization of fuel can be promoted, startability can be improved, and exhaust emission can be improved by suppressing discharge of unburned HC. .

  According to the second invention, by heating the air with the heater prior to starting, high-temperature air can be supplied from the start of starting, and fuel atomization can be promoted.

  According to the third aspect of the invention, when the temperature of the internal combustion engine rises, the fuel injection by the second injector is switched to the fuel injection by the first injector, so that the unburned HC can be discharged by supplying vaporized fuel with better combustibility. Can be further suppressed.

  According to the fourth aspect of the present invention, when the temperature of the internal combustion engine further increases, the fuel injection by the first injector is switched to the fuel injection by the second injector, so that the exhaust emission is further improved by controlling the fuel supply amount for each cylinder. be able to.

  According to the fifth aspect of the invention, the dedicated bypass intake passage is used as a passage for supplying high-temperature air heated by the heater, so that the passage volume from the heater to the intake pipe is reduced, and the temperature of the air is increased by the heater. Efficiency can be increased.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 4.
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which a fuel injection control device as an embodiment of the present invention is applied. The internal combustion engine according to this embodiment includes a cylinder block 6 in which a piston 8 is disposed, and a cylinder head 4 assembled to the cylinder block 6. A space from the upper surface of the piston 8 to the cylinder head 4 forms a combustion chamber 10, and an intake port 18 and an exhaust port 20 are formed in the cylinder head 4 so as to communicate with the combustion chamber 10. An intake valve 12 for controlling the communication state between the intake port 18 and the combustion chamber 10 is provided at a connection portion between the intake port 18 and the combustion chamber 10. An exhaust valve 14 for controlling the communication state between the port 20 and the combustion chamber 10 is provided. A spark plug 16 is attached to the cylinder head 4 so as to protrude from the top of the combustion chamber 10 into the combustion chamber 10.

  An intake pipe 34 is connected to the intake port 18. An intake pipe 34 is provided for each cylinder (for each intake port 18), and each intake pipe 34 branches off from the surge tank 32. An intake manifold is formed by each intake pipe 34 and surge tank 32. An injector 70 is attached to each intake pipe 34 so as to face the intake port 18. The injector 70 provided for each cylinder is referred to as a MAIN injector (second injector). An intake passage 30 for introducing new gas is connected to the surge tank 32. An electronically controlled throttle valve 36 is disposed at the connection between the intake passage 30 and the surge tank 32.

  A bypass pipe 40 is provided upstream of the throttle valve 36 in the intake passage 30 and is branched from the intake passage 30. FIG. 2 is a top view of the internal combustion engine shown in FIG. As shown in FIGS. 1 and 2, the tip end portion (downstream end portion) of the bypass pipe 40 is connected to a delivery pipe 44, and a branch pipe 46 branches from the delivery pipe 44 for each cylinder. Each branch pipe 46 is connected to an upstream portion of the MAIN injector 70 in the intake pipe 34. In the present embodiment, the bypass pipe 40, the delivery pipe 44, and the branch pipe 46 form a bypass intake passage that bypasses the throttle valve 36 and supplies air to the intake pipe 34. An ISC valve 48 is attached to the bypass pipe 40. When the throttle valve 36 is fully closed, the ISC valve 48 is opened to bypass the throttle valve 36 and supply air to the intake pipe 34.

  A fuel vaporization portion 42 that is a volume portion is formed downstream of the ISC valve 48 in the bypass pipe 40. One injector 50 is attached to the fuel vaporization section 42. The injector 50 provided in the fuel vaporization unit 42 is referred to as a SUB injector (first injector). The SUB injector 50 is attached to the fuel vaporization unit 42 so as to inject fuel along the air flow direction in the fuel vaporization unit 42. A PCT heater (hereinafter simply referred to as a heater) 52 is provided in the fuel vaporization section 42 along the fuel injection direction of the SUB injector 50. By operating the SUB injector 50 with the heater 52 energized, the fuel injected from the SUB injector 50 is heated and vaporized by the heater 52 to become vaporized fuel.

  The fuel injected from the SUB injector 50 is the same type of liquid fuel as the fuel injected from the MAIN injector 70. As described above, the MAIN injector 70 is provided for each cylinder, and is connected to the delivery pipe 62 via the branch pipe 64. The delivery pipe 62 is connected to a fuel pump (not shown) via a fuel supply pipe 60. A fuel distribution pipe 66 is branched from the middle of the fuel supply pipe 60, and the fuel distribution pipe 66 is connected to the SUB injector 50. The fuel pumped to the fuel supply pipe 60 by the fuel pump is distributed to each branch pipe 64 by the delivery pipe 62 and supplied to each MAIN injector 70. Further, part of the fuel pumped to the fuel supply pipe 60 is supplied to the SUB injector 50 through the fuel distribution pipe 66.

  The internal combustion engine includes an ECU (Electronic Control Unit) 80 as its control device. Various devices such as the starter 26 are connected to the output side of the ECU 80 in addition to the ignition plug 16, the throttle valve 36, the ISC valve 48, the MAIN injector 70, the SUB injector 50, and the heater 52. The starter 26 rotationally drives the crankshaft 24 in response to an input of a start signal from the ECU 80.

  Various sensors such as a crank angle sensor 84 and a water temperature sensor 82 and various switches such as an ignition switch 86 and a door switch 88 are connected to the input side of the ECU 80. The crank angle sensor 84 is a sensor that outputs a signal corresponding to the rotation angle of the crankshaft 24, and the water temperature sensor 82 is a sensor that outputs a signal corresponding to the cooling water temperature of the internal combustion engine. The door switch 88 is a switch that is provided on the driver side door of the vehicle and outputs an open signal to the ECU 80 when the driver side door is opened. The ECU 50 drives each device according to a predetermined control program based on the output of each sensor or switch.

  FIG. 3 is a flowchart showing the contents of the fuel injection control at the time of start executed by the ECU 80 in the present embodiment. FIG. 4 is a time chart showing the execution results of the routine shown in FIG. In FIG. 4, engine speed (NE), heater 52 energized state, ISC valve 48 open / close state, throttle valve 36 open / close state, MAIN injector 70 operating state, SUB injector 50 operating state, cooling water temperature, ignition switch. 86 output signals (IG) and an operation command (STA) to the starter 26 are shown on the same time axis. Hereinafter, with reference to FIG. 3 and FIG. 4, the content of the fuel injection control at the time of start according to the present embodiment will be described.

  In the first step 100 of the routine shown in FIG. 3, it is determined whether or not the door switch 88 has been turned on. In the present embodiment, the act of the driver opening the driver's seat side door is regarded as a manifestation of the driver's intention to start the internal combustion engine. A door switch 88 is used as means for detecting an intention to start the internal combustion engine. Until the door switch 88 is detected to be turned on, the energization of the heater 52 is kept off (step 128).

When the on-door switch 88 is detected (time point t ₁ in FIG. 4), power from a battery (not shown) to the heater 52 is turned on it as a trigger (step 102). When the energization is turned on, the heater 52 generates heat. Thereby, heating of the air in the fuel vaporization part 42 is started prior to starting of the internal combustion engine.

  In the next step 104, it is determined whether or not the ignition switch 86 is turned on. It will be in a standby state until the ignition switch 86 is turned on. During this time, the energization of the heater 52 is kept on, and the air in the fuel vaporization section 42 is warmed by the heater 52. Although omitted in the routine shown in FIG. 3, if the ignition switch 86 is not detected to be turned on even after a predetermined time has elapsed since the door switch 88 was detected to be turned on, the heater 52 is turned off. It may be.

When it is detected that the ignition switch 86 is turned on (time t _{2 in} FIG. 4), the ISC valve 48 is opened (step 106), and the throttle valve 36 is fully closed (step 108). This opens an air passage that connects the upstream portion of the throttle valve 36 and the upstream portion of the MAIN injector 70 in the intake pipe 34 by bypassing the throttle valve 36.

  In the next step 104, it is determined whether or not supply of an operation command to the starter 26 (ON) is detected. The operation command to the starter 26 is turned on, and the engine is on standby until cranking of the internal combustion engine by the starter 26 is started. During this time as well, energization of the heater 52 is kept on, and the air in the fuel vaporization section 42 is warmed by the heater 52.

When cranking of the internal combustion engine by the starter 26 is started (time point t _{3 in} FIG. 4), the engine temperature such as the water temperature, the intake air temperature, the oil temperature, etc. is set as a state quantity indicating the current state of the internal combustion engine (engine state). A representative state quantity is acquired (step 112). Here, the coolant temperature THW is measured from the signal of the water temperature sensor 82.

  In the next step 114, the cooling water temperature THW is compared with a predetermined first reference water temperature THW1. The first reference water temperature THW1 is a temperature range in which fuel vaporized by heating by the heater 52 may be reliquefied in the bypass pipe 40, the delivery pipe 44, or the branch pipe 46, specifically, a minus temperature of zero degrees or less. Is set to

  As a result of the comparison in step 114, when the cooling water temperature THW is lower than the first reference water temperature THW1, that is, when the liquefied fuel can be reliquefied, the fuel injection from the SUB injector 50 is not performed. In this case, fuel is injected from the MAIN injector 70 of the first explosion cylinder toward the intake port 18 of the cylinder (step 116). At this time, since cranking by the starter 26 has started, the high-temperature air heated by the heater 52 in the fuel vaporization section 42 passes through the delivery pipe 44 and the branch pipe 46 and enters the intake pipe 34 of the first explosion cylinder. To be introduced. The delivery pipe 44 and the branch pipe 46 are dedicated passages for supplying high-temperature air heated by the heater 52. Therefore, the passage volume from the heater 52 to the intake pipe 34 is reduced so that the air generated by the heater 52 is reduced. The temperature elevating efficiency can be increased.

  The fuel injected from the MAIN injector 70 is atomized by mixing with high-temperature air introduced into the intake pipe 34 from the branch pipe 46, and is taken into the combustion chamber 10 as an air-fuel mixture. Thereby, combustion in the first explosion cylinder is improved, startability is improved, and discharge of unburned HC is also suppressed.

  Even after the first explosion, until the cooling water temperature THW becomes equal to or higher than the first reference water temperature THW1, fuel is injected from the MAIN injector 70 of the cylinder in the next intake stroke toward the intake port 18 of the cylinder. In the intake stroke of the cylinder, high-temperature air heated by the heater 52 and warmed is introduced into the intake pipe 34. Therefore, the fuel injected from the MAIN injector 70 is atomized by mixing with high-temperature air. The Thereby, in spite of low temperature, combustion in the combustion chamber 10 is improved and discharge of unburned HC is suppressed.

When the internal combustion engine is started, the engine temperature rises due to the combustion heat generated in the combustion chamber 10. The cooling water temperature THW gradually increases, and eventually increases to the first reference water temperature THW1 or higher. When the cooling water temperature THW becomes equal to or higher than the first reference water temperature THW1 (time t4 in FIG. ₄ ), even if the vaporized fuel is supplied by driving the SUB injector 50, it may be reliquefied in the passage. Becomes lower. Therefore, when the cooling water temperature THW becomes equal to or higher than the first reference water temperature THW1, the fuel injection by the MAIN injector 70 is stopped, and the fuel injection by the SUB injector 50 is started.

  In step 118, the cooling water temperature THW is compared with a predetermined second reference water temperature THW1. The second reference water temperature THW2 is a temperature at which it can be considered that the internal combustion engine has been warmed up. If the cooling water temperature THW is equal to or lower than the second reference water temperature THW2, it is further determined whether or not the internal combustion engine is idling (step 120). If the throttle opening θth is fully closed (θth <0) and the vehicle is stopped (vehicle speed SPD <0), it can be determined that the internal combustion engine is idling.

  If the result of the determination in steps 118 and 120 is before the warm-up of the internal combustion engine is completed and the engine is idling, fuel injection by the SUB injector 50 is performed (step 122). Since the energization of the heater 52 is kept on, the fuel injected from the SUB injector 50 is heated and vaporized by the heater 52 and is mixed with the high-temperature air in the fuel vaporization section 42 to become an air-fuel mixture. The air-fuel mixture containing vaporized fuel is introduced into the intake pipe 34 of the cylinder in the intake stroke via the delivery pipe 44 and the branch pipe 46, and is sucked into the combustion chamber 10 of the cylinder from the intake pipe 34. In this way, after the internal combustion engine has warmed to some extent, the vaporized fuel having excellent combustibility is supplied, so that the emission of unburned HC is further suppressed.

In the fuel injection by the SUB injector 50, the condition of step 118 is satisfied (that is, the warm-up of the internal combustion engine is completed), or the condition of step 120 is not satisfied (that is, the idling is stopped and acceleration is started). To continue). When the warm-up of the internal combustion engine is completed (time t _{5 in} FIG. 4) or when acceleration is started, the energization to the heater 52 is turned off (step 124). Then, fuel injection by the SUB injector 50 is stopped, and fuel injection by the MAIN injector 70 is started (step 126). When fuel injection is performed by the MAIN injector 70 upon completion of warm-up of the internal combustion engine, exhaust emission can be further improved by controlling the fuel supply amount for each cylinder. Further, when fuel injection is performed by the MAIN injector 70 at the start of acceleration, an amount of fuel corresponding to the required load can be accurately supplied to each cylinder.

  As described above, in the fuel injection control at the start according to the present embodiment, the fuel is injected from the MAIN injector 70 when the engine temperature at the start is extremely low. The fuel injected from the MAIN injector 70 is atomized by mixing with high-temperature air heated by the heater 52. Since the MAIN injector 70 injects fuel into the intake port 18, the proportion of atomized fuel droplets is low compared to the SUB injector 50 installed away from the combustion chamber 10. Further, since the heating of the air by the heater 52 is started prior to the start of the internal combustion engine, high-temperature air can be supplied to the intake pipe 34 immediately after the start of the start. Therefore, according to the fuel injection control at the time of starting according to the present embodiment, atomization of fuel can be promoted even when the engine temperature at the time of starting is extremely low, and the startability can be improved. In addition, the emission of unburned HC can be suppressed and the exhaust emission can be improved.

  Further, in the fuel injection control at the time of starting according to the present embodiment, when the temperature of the internal combustion engine rises to some extent, the fuel injection by the MAIN injector 70 is switched to the fuel injection by the SUB injector 50. The supply of unburned HC can be further suppressed by the supply. Further, when the temperature of the internal combustion engine further rises and the warm-up is completed, the fuel injection by the SUB injector 50 is switched again to the fuel injection by the MAIN injector 70, so that the exhaust emission is further controlled by controlling the fuel supply amount for each cylinder. Can be improved.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the above embodiment, the fuel is injected from the MAIN injector 70 to the intake port 18. However, the MAIN injector 70 is incorporated in the cylinder head 4 so that the fuel is directly injected into the combustion chamber 10 from the MAIN injector 70. It may be. That is, the fuel injection control device of the present invention can be applied not only to a port injection type internal combustion engine but also to a cylinder injection type internal combustion engine.

  In the above embodiment, the bypass intake passage that bypasses the throttle valve 36 is provided, and the SUB injector 50 and the heater 52 are arranged in the bypass intake passage. However, the SUB injector is disposed upstream of the throttle valve 36 in the intake passage 30. 50 and heater 52 may be arranged. In this case, the air-fuel mixture including high-temperature air and vaporized fuel heated by the heater 52 is introduced into the intake pipe 34 of each cylinder through the throttle valve 36 opened to a predetermined idle opening.

  Moreover, in the said embodiment, although the door switch 88 is used as a means to detect the driver's intention to start the internal combustion engine, you may detect using another means. For example, a sensor or switch for detecting that the driver is seated in the driver's seat may be provided, and it may be assumed that the driver intends to start the internal combustion engine when the driver is seated in the driver's seat.

1 is a diagram showing a schematic configuration of an internal combustion engine to which a fuel injection control device as an embodiment of the present invention is applied. It is a top view of the internal combustion engine shown in FIG. It is a flowchart of the fuel-injection control routine performed in embodiment of this invention. The execution result of the routine shown in FIG. 3 is shown with the time chart.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Combustion chamber 12 Intake valve 14 Exhaust valve 18 Intake port 20 Exhaust port 26 Starter 30 Intake passage 32 Surge tank 34 Intake pipe 36 Throttle valve 40 Bypass pipe 42 Fuel vaporization part 44 Delivery pipe 46 Branch pipe 48 ISC valve 50 SUB injector 52 Heater 60 Fuel supply pipe 62 Delivery pipe 70 MAIN injector 80 ECU
82 Water temperature sensor 84 Crank angle sensor 86 Ignition switch 88 Door switch

Claims (5)

An air passage connected to an intake pipe provided for each cylinder;
A first injector capable of injecting fuel into the air passage;
A heater provided at a site where fuel is injected by the first injector in the air passage;
A fuel injection control device for an internal combustion engine having a second injector capable of injecting fuel into an intake port or directly into a combustion chamber,
A fuel injection control device for an internal combustion engine, wherein when the internal combustion engine is started, fuel is injected from the second injector while supplying air heated by the heater to the intake pipe.   2. The fuel injection control device for an internal combustion engine according to claim 1, wherein heating of the air in the air passage by the heater is started prior to starting the internal combustion engine.   When the temperature of the internal combustion engine exceeds a predetermined first warm-up temperature, or when it is predicted that the temperature exceeds the first warm-up temperature, fuel injection by the second injector is stopped, and the first injector 3. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel injection is started.   When the temperature of the internal combustion engine exceeds a predetermined second warm-up temperature that is higher than the first warm-up temperature, or when it is predicted that the temperature exceeds the second warm-up temperature, the heater heats the air. 4. The fuel injection control device for an internal combustion engine according to claim 3, wherein the fuel injection by the first injector is stopped and the fuel injection by the second injector is started. 5. The internal combustion engine according to claim 1, wherein the air passage is a bypass intake passage that connects an upstream portion of a throttle valve and the intake pipe by bypassing the throttle valve. 6. Fuel injection control device.

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