JP2007262996A - Fuel injector for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine capable of compatibly securing a required flow rate of fuel and atomizing the fuel. <P>SOLUTION: When mixing of intake air and the fuel easily becomes insufficient such as when a flow rate of the intake air is small or the temperature of engine cooling water is low, a small quantity of fuel is injected from injectors 71 and 72 arranged in branch ports 61 and 62. Thus, nozzle ports 711 and 721 can be diametrically reduced, and atomization of the fuel is promoted. Thus, the intake air and the fuel are sufficiently mixed even when the flow rate of the intake air is small or the temperature of the engine cooling water is low. The fuel is injected from the injector 73 arranged in an intake port 26 when a flow rate of the fuel required by an engine body 20 is large such as when the flow rate of the intake air is large or the temperature of the engine cooling water is high. Thus, sufficient fuel is supplied to a combustion chamber 28 even when insufficient in only fuel injected from the injectors 71 and 72. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel injection device for an internal combustion engine, and is particularly suitable for application to an internal combustion engine in which a plurality of branch ports are branched from the combustion chamber side of the intake port.

  In recent years, the engine has a plurality of branch ports communicating with one cylinder, that is, one combustion chamber. As described above, in an engine having a plurality of branch ports per combustion chamber, a technique disclosed in Patent Document 1 is known as an injector that injects fuel into intake air flowing through each branch port. In the case of the technique disclosed in Patent Document 1, two fuel sprays formed by an injector are distributed to two branch ports. Thus, by forming two fuel sprays from an injector, the adhesion of the fuel to the wall part which partitions two branch ports is reduced.

JP 2004-225598 A

However, in the case of the technique disclosed in Patent Document 1, the injector is mounted away from the combustion chamber at the branch port. Therefore, depending on the shape of the branch port, the fuel injected from the injector may adhere to the wall surface forming the branch port.
In order to prevent the fuel from adhering to the wall surface forming the branch port, it is conceivable to provide an injector at each intake port. Incidentally, the intake air distributed to the intake port further flows into the combustion chamber via the branch port. Therefore, the flow rate of the intake air flowing through the branch port becomes small. Thus, when an injector is provided at each branch port, it is necessary to reduce the amount of fuel injected from the injector in accordance with a small intake air flow rate in order to promote atomization of the fuel. However, if the amount of fuel injected from each injector installed in the intake port is reduced, there is a problem that when the engine output is increased, the required fuel flow rate cannot be secured.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel injection device for an internal combustion engine that can ensure both the required flow rate of fuel and atomization of fuel.

  According to the first aspect of the present invention, in addition to the downstream injectors provided in each branch port, an upstream injector is provided on the opposite side of the branch port from the branch port, that is, on the upstream side in the flow direction of the intake air. For example, when the required fuel flow rate is small, such as when the output is relatively small, fuel is injected from the downstream injector. As a result, a relatively small amount of fuel is injected from the downstream injector into each branch port. Therefore, the fuel can be atomized. Further, for example, when the required flow rate of the fuel becomes large as in the case where the output is relatively large, the fuel is injected from the upstream injector in addition to the downstream injector. As a result, fuel that is insufficient in the downstream injector is injected from the upstream injector into the intake port. When a large fuel flow rate is required, the flow rate of the intake air flowing through the intake port and the branch port is large. Therefore, even if the fuel injected from the upstream injector provided on the upstream side of the branch portion adheres to the wall surface forming the branch port, the attached fuel is vaporized by the flow of the intake air. Therefore, the necessary fuel flow rate is ensured and the fuel sufficiently mixed with the intake air can be supplied to the combustion chamber.

In the invention according to claim 2, the control means controls the injection amount of the fuel injected from the upstream injector and the downstream injector. Thus, for example, the fuel injection amount from the upstream injector and the downstream injector can be controlled according to the flow rate of intake air or the required output.
In the invention according to claim 3, the control means injects fuel from the upstream injector when the fuel injection amount from the downstream injector is insufficient. For example, when the required fuel flow rate is small, such as when the output is relatively small, fuel is injected from the downstream injector. As a result, a relatively small amount of fuel is injected from the downstream injector into each branch port. For example, when the output becomes relatively large and the required fuel flow rate becomes large, the fuel is injected from the upstream injector in addition to the downstream injector. When a large fuel flow rate is required, the flow rate of the intake air flowing through the intake port and the branch port is large. Therefore, even if the fuel injected from the upstream injector provided on the upstream side of the branch portion adheres to the wall surface forming the branch port, the attached fuel is vaporized by the flow of the intake air. Therefore, the necessary fuel flow rate is ensured and the fuel sufficiently mixed with the intake air can be supplied to the combustion chamber.

  According to a fourth aspect of the present invention, the control means sets the fuel injection amounts from the upstream injector and the downstream injector in accordance with the intake air flow rate detected by the flow rate detection means. When the flow rate of the intake air increases, the required fuel increases, and the fuel is insufficient only by the fuel injection from the downstream injector. Therefore, the control means injects fuel from the upstream injector in addition to the downstream injector when the flow rate of the intake air increases. When a large fuel flow rate is required, the flow rate of the intake air flowing through the intake port and the branch port is large. Therefore, even if the fuel injected from the upstream injector provided on the upstream side of the branch portion adheres to the wall surface forming the branch port, the attached fuel is vaporized by the flow of the intake air. Therefore, the necessary fuel flow rate is ensured and the fuel sufficiently mixed with the intake air can be supplied to the combustion chamber.

  In the invention according to claim 5, the control means sets the fuel injection amount from the upstream injector and the downstream injector in accordance with the temperature of the engine coolant detected by the temperature detecting means. For example, when the engine coolant temperature is low, the intake port wall surface temperature is also low, and the fuel adhering to the port wall surface is difficult to vaporize. Therefore, when fuel is injected from the upstream injector, the fuel is likely to adhere to the wall surface forming the branch port on the downstream side of the branch portion. On the other hand, when the temperature of the engine cooling water is high, the intake port wall surface temperature is also high, and the fuel adhering to the port wall surface is easily vaporized. Therefore, even if fuel is injected from the upstream injector, the fuel is unlikely to adhere to the wall surface that forms the branch port on the downstream side of the branch portion. Thus, the control means sets the fuel injection amounts from the upstream injector and the downstream injector in accordance with the temperature of the engine coolant detected by the temperature detection means. Therefore, the necessary fuel flow rate is ensured and the fuel sufficiently mixed with the intake air can be supplied to the combustion chamber.

Hereinafter, an embodiment to which the present invention is applied will be described with reference to the drawings.
An engine to which a fuel injection device according to an embodiment of the present invention is applied is shown in FIG. The engine 10 includes an engine main body 20 and a control device 11 as control means. As shown in FIG. 3, the engine body 20 is a gasoline engine using gasoline as fuel, for example. The fuel may be alcohol, for example. The engine body 20 is not limited to a gasoline engine, and may be a diesel engine, for example.

  The engine body 20 includes a cylinder block 21 and a cylinder head 22. The cylinder block 21 forms a cylindrical cylinder 23. The engine body 20 has a cylinder 23 as one or a plurality of cylinders. The cylinder 23 accommodates the piston 24 inside. The piston 24 reciprocates in the axial direction of the cylinder 23 by the connecting rod 25.

  The cylinder head 22 is disposed on one end side of the cylinder block 21. The cylinder head 22 forms an intake port 26 and an exhaust port 27. The engine body 20 includes an intake valve 40 that opens and closes the intake port 26 through the cylinder head 22 and an exhaust valve 50 that opens and closes the exhaust port 27.

  The intake valve 40 penetrates the cylinder head 22. The intake valve 40 has a shaft portion 41 and a valve portion 42. The shaft portion 41 is slidably supported by the cylinder head 22 with the gasket 43 interposed therebetween. The shaft portion 41 has one end in the axial direction connected to the valve portion 42 and the other end in contact with the intake cam 45 with the tappet 44 interposed therebetween. A spring 46 as an elastic member is installed between the cylinder head 22 and the tappet 44. The spring 46 presses the tappet 44 in a direction away from the cylinder head 22. The tappet 44 moves integrally with the intake valve 40.

  The exhaust valve 50 penetrates the cylinder head 22. The exhaust valve 50 has a shaft portion 51 and a valve portion 52. The shaft portion 51 is movably supported by the cylinder head 22 with the gasket 53 interposed therebetween. The shaft portion 51 has one end in the axial direction connected to the valve portion 52 and the other end in contact with the exhaust cam 55 with the tappet 54 interposed therebetween. A spring 56 as an elastic member is installed between the cylinder head 22 and the tappet 54. The spring 56 presses the tappet 54 in a direction away from the cylinder head 22. The tappet 54 moves integrally with the exhaust valve 50.

  The inner wall surface of the cylinder block 21 forming the cylinder 23, the surface on the cylinder block 21 side of the cylinder head 22, the end surface on the cylinder head 22 side of the piston 24, the end surface on the piston 24 side of the intake valve 40, and the exhaust A space formed by the end surface of the valve 50 on the piston 24 side is a combustion chamber 28. The combustion chamber 28 can communicate with the intake port 26 and the exhaust port 27. As shown in FIG. 2, the intake port 26 communicates with the surge tank 31 at the end opposite to the combustion chamber 28. The end of the surge tank 31 opposite to the intake port 26 communicates with an intake introduction portion (not shown). The air introduced from the intake air introduction portion flows into the surge tank 31 via, for example, an air cleaner and a throttle (not shown). The surge tank 31 distributes the air introduced from the intake air introduction portion to the intake port 26 that communicates with each cylinder 23 of the engine body 20.

As shown in FIG. 3, the cylinder head 22 is provided with an ignition device 32 at a substantially central portion of the combustion chamber 28. The ignition device 32 is installed through the cylinder head 22. The ignition device 32 includes an ignition coil (not shown) and an ignition plug that are integrally formed. The ignition device 32 has an end on the ignition plug side exposed to the combustion chamber 28.
In the present embodiment, as shown in FIG. 1, two branch ports 61 and 62 branched from the intake port 26 communicate with the combustion chamber 28. Two exhaust ports 27 communicate with the combustion chamber 28. That is, the engine body 20 of the present embodiment is a so-called 4-valve engine. Note that three or more branch ports 61 and 62 and the exhaust port 27 of the engine body 20 may be configured to communicate with the combustion chamber 28. For example, the number of branch ports and exhaust ports may be different as in a so-called 5-valve engine having three branch ports communicating with the combustion chamber 28 and two exhaust ports.

  The intake port 26 branches into two branch ports 61 and 62 at a branch part 63 between the surge tank 31 and the combustion chamber 28. As a result, the intake air flowing from the surge tank 31 to the intake port 26 is distributed from the branch portion 63 to the two branch ports 61 and 62. In the present embodiment, the inner diameters of the two branch ports 61 and 62 are substantially the same. The branch port 61 and the branch port 62 are partitioned by a wall portion 64.

  The cylinder head 22 is provided with injectors 71, 72, 73 as shown in FIG. In the middle of each branch port 61, 62, one injector 71, 72 is installed as shown in FIG. Further, a single injector 73 is installed in the middle of the intake port 26. Accordingly, a total of three injectors are installed in the intake port 26 and the branch ports 61 and 62. All of the injectors 71, 72, 73 penetrate the cylinder head 22. In the injectors 71 and 72, one end in the axial direction is exposed to the branch ports 61 and 62, and the other end is connected to the fuel rail 74. One end of the injector 73 in the axial direction is exposed to the intake port 26, and the other end is connected to the fuel rail 75.

  The injectors 71 and 72 have injection holes 711 and 721 at the ends opposite to the fuel rail 74, respectively. The injector 73 has an injection hole 731 at the end opposite to the fuel rail 75. The fuel rail 74 and the fuel rail 75 are supported by the cylinder head 22, for example. Fuel is supplied to the fuel rail 74 and the fuel rail 75 from a fuel tank (not shown). The injectors 71 and 72 inject the fuel supplied to the fuel rail 74 into the intake air flowing through the branch ports 61 and 62 from the injection holes 711 and 721, respectively. Further, the injector 73 injects the fuel supplied to the fuel rail 75 into the intake air flowing through the intake port 26 from the injection hole 731.

  In the case of this embodiment, the injector 71 and the injector 72 are installed in the branch ports 61 and 62, respectively, and the injector 73 is installed in the intake port 26. Thereby, the end of the injector 73 on the injection hole 731 side is installed on the side opposite to the combustion chamber 28 with respect to the branching portion 63, that is, on the upstream side in the flow direction of the intake air. Thereby, the injector 73 is an upstream injector in a claim. Further, the end portions of the injector 71 and the injector 72 on the side of the injection holes 711 and 721 are installed on the combustion chamber 28 side of the branching portion 63, that is, on the downstream side in the flow direction of the intake air. Thereby, the injector 71 and the injector 72 are downstream injectors in the claims.

  Both the end portion on the injection hole 711 side of the injector 71 and the end portion on the injection hole 721 side of the injector 72 are installed closer to the combustion chamber 28 than the branch portion 63. The injection angle of the fuel injected from the injector 71 and the injector 72 is set according to the inner diameter of each branch port 61, 62. That is, the injection angle is set such that the fuel injected from the injector 71 and the injector 72 does not adhere to the inner wall of the cylinder head 22 that forms the branch port 61 and the branch port 62. Therefore, the fuel injected from the injector 71 and the injector 72 does not adhere to the wall portion 64 that partitions the branch port 61 and the branch port 62.

  A control device (ECU) 11 shown in FIG. 2 is a microcomputer including a CPU, a ROM, and a RAM, for example. The control device 11 is connected to the injectors 71 and 72 and the injector 73 of the engine body 20. The control device 11 outputs drive signals to the injectors 71 and 72 and the injector 73 to control the timing of fuel injection from the injectors 71 and 72 and the injector 73. The control device 11 is connected to a throttle sensor 12 that detects a throttle opening (not shown). The flow rate of intake air at the intake port 26 and the branch ports 61 and 62 correlates with the opening of a throttle (not shown). Therefore, the control device 11 detects the flow rate of the intake air flowing through the intake port 26 and the branch ports 61 and 62 by detecting the opening of a throttle (not shown) by the throttle sensor 12. Therefore, the throttle sensor 12 is a flow rate detecting means in the claims.

  The control device 11 is connected not only to the injectors 71 and 72, the injector 73 and the throttle sensor 12 but also to the ignition device 32 and the temperature sensor 13. The control device 11 outputs a drive signal to the ignition device 32 and ignites the air-fuel mixture in the combustion chamber 28 at a predetermined time. The temperature sensor 13 detects the temperature of engine cooling water (not shown). Therefore, the temperature sensor 13 is a temperature detection means in the claims.

  The control device 11 is further connected to a rotational speed sensor (not shown). A rotation speed sensor (not shown) detects the rotation speed of the engine body 20. The control device 11 detects the operating state and load state of the engine body 20 from the throttle sensor 12, the temperature sensor 13, the rotation speed sensor, and the like, and sets the fuel injection amounts from the injectors 71 and 72 and the injector 73.

Next, the operation of the injectors 71 and 72 and the injector 73 by the control device will be described.
(Control based on intake flow rate)
When controlling the injectors 71 and 72 and the injector 73 based on the flow rate of intake air, the control device 11 detects the opening of a throttle (not shown) from the throttle sensor 12. As described above, the opening degree of the slot correlates with the intake air flow rate at the intake port 26 and the branch ports 61 and 62. For example, when the throttle is hardly open, that is, when the engine body 20 is idling, the flow rate of the intake air at the intake port 26 and the branch ports 61 and 62 is minimized. On the other hand, when the throttle opening increases and the throttle is fully opened, the engine main body 20 enters a high output state, and the intake air flow rate at the intake port 26 and the branch ports 61 and 62 increases. In this way, the control device 11 detects the flow rate of the intake air in the intake port 26 and the branch ports 61 and 62 by detecting the opening of the throttle (not shown) by the throttle sensor 12.

  The control device 11 controls fuel injection from the injectors 71 and 72 and the injector 73 from the detected flow rate of the intake air. When the flow rate of intake air is relatively small, the control device 11 outputs a drive signal to the injectors 71 and 72. Thereby, the fuel is injected from the injectors 71 and 72 installed in the two branch ports 61 and 62. The fuel injected from the injectors 71 and 72 is injected into the intake air flowing through the branch ports 61 and 62, respectively.

  When the flow rate of intake air is relatively small, the flow rate of intake air at the branch ports 61 and 62 is also small. Therefore, when the amount of fuel injected from the injectors 71 and 72 increases, the fuel is not sufficiently mixed with the intake air, and a part of the injected fuel is formed as droplets on the inner wall of the cylinder head 22 forming the branch ports 61 and 62. It becomes easy to adhere. The fuel adhering as droplets flows into the combustion chamber 28 in a liquid state along the inner wall of the cylinder head 22. Since the liquid fuel is not mixed with the intake air sucked into the combustion chamber 28, the combustion in the combustion chamber 28 becomes insufficient. As a result, the fuel efficiency is deteriorated without contributing to the output of the engine 10, and the unburned hydrocarbon (HC) contained in the exhaust increases.

  In this embodiment, when the flow rate of intake air is relatively small, fuel is injected from the injectors 71 and 72 installed in the branch ports 61 and 62, respectively. Therefore, the flow rate of the fuel injected from the injectors 71 and 72 can be reduced. By reducing the flow rate of the fuel injected from the injectors 71 and 72, the diameter of the injection holes 711 and 721 of the injectors 71 and 72 can be reduced. Atomization of fuel injected from the injectors 71 and 72 is promoted as the nozzle holes 711 and 721 have a smaller diameter. As a result, the flow rate of the fuel injected from the injectors 71 and 72 is reduced, and the diameter of the injection holes 711 and 721 of the injectors 71 and 72 is reduced, thereby promoting atomization of the fuel injected from the injectors 71 and 72. . As a result, the fuel injected from the injectors 71 and 72 to the branch ports 61 and 62 is sufficiently mixed with the intake air flowing through the branch ports 61 and 62. Thereby, even when the flow rate of the intake air is relatively small, the atomized fuel is sufficiently mixed with the intake air, so that the fuel burns sufficiently in the combustion chamber 28. Therefore, HC contained in the exhaust gas can be reduced without causing deterioration of fuel consumption.

  By the way, when the flow rate of intake air is relatively small, the control device 11 does not output a drive signal to the injector 73. Thereby, the injector 73 does not inject fuel into the intake air flowing through the intake port 26. When the flow rate of the intake air is relatively small, the fuel required for the operation of the engine body 20 is injected from the injectors 71 and 72 installed in the branch ports 61 and 62. Therefore, the fuel required for the engine body 20 is sufficiently supplied by injection from the injectors 71 and 72. Therefore, the engine body 20 can be operated stably without injecting fuel from the injector 73 installed in the intake port 26.

  Further, when fuel is injected from the injector 73 when the flow rate of the intake air is relatively small, a part of the fuel injected from the injector 73 may adhere to the wall portion 64 that partitions the branch ports 61 and 62. When the flow rate of the intake air is small, the fuel adhering to the wall portion 64 becomes droplets and flows into the combustion chamber 28 along the wall portion 64 via the branch ports 61 and 62. As described above, the fuel in droplet form is insufficiently combusted. Therefore, when the flow rate of the intake air is relatively small, the control device 11 stops the fuel injection from the injector 73. Thereby, the adhesion of fuel to the wall portion 64 and the inflow of the adhered fuel to the combustion chamber 28 are reduced. Therefore, HC contained in the exhaust gas can be reduced without causing deterioration of fuel consumption.

  On the other hand, when the flow rate of intake air becomes relatively large, that is, when a large output is required for the engine body 20, the control device 11 is installed in the intake port 26 in addition to the injectors 71 and 72 installed in the branch ports 61 and 62. A drive signal is also output to the injector 73 that has been operated. When the engine body 20 is required to have a large output, the intake air flow rate increases and the required fuel flow rate also increases. At this time, the flow rate of the fuel that can be injected from the injectors 71 and 72 installed in the branch ports 61 and 62 is limited. Therefore, the flow rate of fuel injected from the injectors 71 and 72 is insufficient with respect to the required flow rate of fuel. Therefore, the control device 11 outputs a drive signal to the injector 73 when the fuel injection amount from the injectors 71 and 72 is insufficient. Thereby, in addition to the injectors 71 and 72, fuel is injected from the injector 73 into the intake air flowing through the intake port 26.

  When the output of the engine body 20 increases, the flow rate of the intake air flowing through the intake port 26 and the branch ports 61 and 62 increases. Therefore, even if the fuel injected from the injector 73 adheres to the wall portion 64 that partitions the branch ports 61 and 62, the attached fuel is vaporized by the flow of intake air. As a result, the vaporized fuel is easily mixed with the intake air flowing through the intake port 26 and the branch ports 61 and 62. Therefore, mixing of the fuel and the intake air can be promoted while ensuring the fuel flow rate.

(Control based on intake air temperature)
When controlling the injectors 71 and 72 and the injector 73 based on the temperature of the engine coolant, the control device 11 detects the temperature of engine coolant (not shown) from the temperature sensor 13. The control device 11 controls fuel injection from the injectors 71 and 72 and the injector 73 from the detected temperature of the engine coolant. When the temperature of the engine cooling water is relatively low, the control device 11 outputs a drive signal to the injectors 71 and 72. Thereby, the fuel is injected from the injectors 71 and 72 installed in the two branch ports 61 and 62. The fuel injected from the injectors 71 and 72 is injected into the intake air flowing through the branch ports 61 and 62, respectively.

  When the engine coolant temperature is relatively low, the intake port wall surface temperature is also low, and the fuel adhering to the port wall surface is difficult to vaporize. Therefore, when the amount of fuel injected from the injectors 71 and 72 increases, the injected fuel is not mixed with the intake air, and a part of the injected fuel is formed as droplets on the inner wall of the cylinder head 22 forming the branch ports 61 and 62. It becomes easy to adhere. The fuel adhering as droplets flows into the combustion chamber 28 in a liquid state along the inner wall of the cylinder head 22. Since the liquid fuel is not mixed with the intake air sucked into the combustion chamber 28, the combustion in the combustion chamber 28 becomes insufficient. As a result, fuel efficiency is deteriorated without contributing to the output of the engine 10, and unburned HC contained in the exhaust increases.

  In the case of this embodiment, when the temperature of the engine cooling water is relatively low, fuel is injected from the injectors 71 and 72 installed in the branch ports 61 and 62, respectively. Therefore, the flow rate of the fuel injected from the injectors 71 and 72 can be reduced. By reducing the flow rate of the fuel injected from the injectors 71 and 72, the diameters of the injection holes 711 and 721 of the injectors 71 and 72 can be reduced. Atomization of fuel injected from the injectors 71 and 72 is promoted as the nozzle holes 711 and 721 have a smaller diameter. As a result, the flow rate of the fuel injected from the injectors 71 and 72 is reduced, and the diameter of the injection holes 711 and 721 of the injectors 71 and 72 is reduced, thereby promoting atomization of the fuel injected from the injectors 71 and 72. . As a result, the fuel injected from the injectors 71 and 72 to the branch ports 61 and 62 is sufficiently mixed with the intake air flowing through the branch ports 61 and 62. Thereby, even when the temperature of the engine coolant is relatively low, the atomized fuel is sufficiently mixed with the intake air, so that the fuel burns sufficiently in the combustion chamber 28. Therefore, HC contained in the exhaust gas can be reduced without causing deterioration of fuel consumption.

  By the way, when the temperature of the engine coolant is relatively low, the control device 11 does not output a drive signal to the injector 73. Thereby, the injector 73 does not inject fuel into the intake air flowing through the intake port 26. When the temperature of the engine body 20 is low, such as immediately after the engine body 20 is started, the temperature of the members constituting the intake system that supplies intake air to the engine body 20 is also low. Further, when the temperature of the engine body 20 is low, such as immediately after the engine 10 is started, the rotational speed of the engine body 20 and the load on the engine body 20 are also small. Therefore, even if fuel is not injected from the injector 73 installed in the intake port 26, the engine body is stably operated by the fuel injected from the injectors 71 and 72 installed in the branch ports 61 and 62.

  Further, when the fuel is injected from the injector 73 not only immediately after the engine 10 is started but also when the temperature of the engine coolant is low, part of the fuel injected from the injector 73 adheres to the wall portion 64 that partitions the branch ports 61 and 62. There is a risk. When the temperature of the engine cooling water is low, the fuel adhering to the wall 64 becomes droplets and flows into the combustion chamber 28 along the wall 64 via the branch ports 61 and 62. As described above, the fuel in droplet form is insufficiently combusted. Therefore, when the temperature of the engine coolant is low, the control device 11 stops the fuel injection from the injector 73. Thereby, the adhesion of fuel to the wall portion 64 and the inflow of the adhered fuel to the combustion chamber 28 are reduced. Therefore, HC contained in the exhaust gas can be reduced without causing deterioration of fuel consumption.

  On the other hand, when the output of the engine body 20 increases and the temperature of the engine body 20 rises, the temperature of the intake system also rises, and the temperature of the engine cooling water also rises. When the output of the engine body 20 increases, the fuel flow rate required for the engine body 20 increases. Therefore, the control device 11 outputs a drive signal to the injector 73 installed in the intake port 26 in addition to the injectors 71 and 72 installed in the branch ports 61 and 62.

  The injectors 71 and 72 installed in the branch ports 61 and 62 are limited in the flow rate of fuel that can be injected. For this reason, when the flow rate of fuel required by the engine body 20 increases, the fuel injected from the injectors 71 and 72 alone is insufficient. Therefore, the control device 11 outputs a drive signal to the injector 73 when the temperature of the engine cooling water is high and the fuel injection amount from the injectors 71 and 72 is insufficient with respect to the intake air flow rate detected from the throttle opening. . Thereby, in addition to the injectors 71 and 72, fuel is injected from the injector 73 into the intake air flowing through the intake port 26.

  When the temperature of the engine cooling water is high, the intake port wall surface temperature is also increased. Therefore, even if the fuel injected from the injector 73 adheres to the wall portion 64 that partitions the branch ports 61 and 62, the attached fuel is vaporized. As a result, the vaporized fuel is easily mixed with the intake air flowing through the intake port 26 and the branch ports 61 and 62. Therefore, mixing of the fuel and the intake air can be promoted while ensuring the fuel flow rate.

  In the above embodiment, the control of the injectors 71 and 72 and the injector 73 based on the flow rate of the intake air and the control of the injectors 71 and 72 and the injector 73 based on the temperature of the engine cooling water have been individually described. However, the injection of fuel from the injectors 71 and 72 and the injector 73 may be controlled by combining the flow rate of intake air and the temperature of engine cooling water. The flow rate of intake air and the temperature of engine cooling water that determine whether or not to inject fuel from the injector 73 depend on, for example, the performance of the engine body 20, the flow rates of fuel injected from the injectors 71 and 72 and the injector 73, and the like. Can be determined arbitrarily.

  Furthermore, in the above-described embodiment, the configuration in which fuel is injected from the injector 73 installed in the intake port 26 when the fuel injection amount from the injectors 71 and 72 installed in the branch ports 61 and 62 is insufficient will be described. did. However, when the flow rate of intake air is large or the temperature of engine cooling water is high, fuel is injected only from the injector 73 installed in the intake port 26, and from the injectors 71, 72 installed in the branch ports 61, 61. The fuel injection may be stopped. That is, the fuel injection amount by the injector 73 installed in the intake port 26 may be set larger than the sum of the fuel injection amounts by the injectors 71 and 72 installed in the branch ports 61 and 62.

  As described above, in one embodiment of the present invention, when the intake air flow rate is small, or when the temperature of the engine coolant is low, when the mixing of intake air and fuel tends to be insufficient, the branch ports 61 and 62 A small amount of fuel is injected from the injectors 71 and 72 respectively installed in. When a small amount of fuel is injected from the injectors 71 and 72, the nozzle holes 711 and 721 are reduced in diameter, and fuel atomization is promoted. Therefore, even when the flow rate of the intake air is small or the temperature of the engine coolant is low, the intake air flowing through the branch ports 61 and 62 and the fuel are sufficiently mixed. Accordingly, the fuel is sufficiently combusted in the combustion chamber 28, and the HC contained in the exhaust gas can be reduced without causing deterioration of fuel consumption.

  On the other hand, when the flow rate of fuel required by the engine body 20 is large, such as when the flow rate of intake air is high or when the temperature of engine cooling water is high, the fuel is injected from the injector 73 installed in the intake port 26. Therefore, even when the fuel injected from the injectors 71 and 72 installed in the branch ports 61 and 62 is insufficient, sufficient fuel is supplied to the combustion chamber 28. Further, when the flow rate of intake air is large or the temperature of engine cooling water is high, the wall surface temperature of the intake port is also high, and fuel is injected from the injector 73 upstream of the branching portion 63 of the branch ports 61 and 62. Even if the fuel adheres to the wall portion 64, the attached fuel is vaporized because the port wall surface temperature is high. Therefore, the fuel in which the fuel and the intake air are sufficiently mixed flows into the combustion chamber 28, and both the securing of the fuel flow rate and the sufficient combustion of the fuel can be achieved.

  In the embodiment of the present invention described above, the example in which the flow rate of the intake air is detected from the throttle opening by the throttle sensor 12 has been described. However, the flow rate of intake air may be detected from the opening of the accelerator, for example. Further, a flow rate sensor may be installed in the intake port 26 or the branch ports 61 and 62, and the flow rate of intake air may be detected by the flow rate sensor.

  The present invention described above is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

The schematic diagram which shows schematic structure of the principal part of the engine to which the fuel-injection apparatus by one Embodiment of this invention is applied. 1 is a block diagram showing a schematic configuration of an engine to which a fuel injection device according to an embodiment of the present invention is applied. 1 is a cross-sectional view schematically showing an engine to which a fuel injection device according to an embodiment of the present invention is applied.

Explanation of symbols

  10: engine (fuel injection device), 11: control device (control means), 12: throttle sensor (flow rate detection means), 13: temperature sensor (temperature detection means), 20: engine body, 23: cylinder (cylinder), 26: Intake port, 28: Combustion chamber, 61, 62: Branch port, 63: Branch part, 71, 72: Injector (downstream injector), 73: Injector (upstream injector)

Claims (5)

An intake port through which intake air distributed to each cylinder flows,
A branch port branched into two or more from a branch portion provided on the combustion chamber side of the intake port;
An upstream injector provided on the opposite side of the branch port from the branch portion of the intake port and capable of injecting fuel into the intake air flowing through the intake port;
A downstream injector provided at each of the branch ports and capable of injecting fuel into the intake air flowing through the branch ports;
A fuel injection device for an internal combustion engine.   The fuel injection device for an internal combustion engine according to claim 1, further comprising a control unit that controls an injection amount of fuel injected from the upstream injector and the downstream injector.   The fuel injection device for an internal combustion engine according to claim 2, wherein the control means injects fuel from the downstream injector and injects fuel from the upstream injector when a flow rate of fuel injected from the downstream injector is insufficient. . The control means includes flow rate detection means for detecting a flow rate of intake air flowing through the intake port,
The said control means sets the injection quantity of the fuel injected from the said upstream injector and the said downstream injector according to the flow volume of the intake air which flows through the said intake port detected by the said flow volume detection means. A fuel injection device for an internal combustion engine. The control means includes temperature detection means for detecting the temperature of engine cooling water,
4. The internal combustion engine according to claim 2, wherein the control unit sets an injection amount of fuel injected from the upstream injector and the downstream injector in accordance with a temperature of engine cooling water detected by the temperature detection unit. Fuel injection device.

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