The present invention relates to a fuel injection device used in an internal combustion engine, and more particularly, to a fuel injection device capable of forming diffusive spray and changing the spray shape.
Recently, there has been considerable activity in the technique of changing the sprayed shape of fuel injected through an injection aperture on the basis of the load state of an internal combustion engine such as a diesel engine or a gasoline engine. The optimized shape of sprayed fuel based on the load state of the internal combustion engine improves fuel economy and exhaust emission.
For example, Patent Document 1 discloses a fuel injection device with a swirl flow forming member and a cylindrical forming room, which are located an upstream side of a seat portion located between a needle valve and a nozzle body. The device alters the lift amount of the needle valve on the basis of the load state of the internal combustion engine to thus adjust the degree of opening in a fuel inlet passage connected to the swirl flow forming room. It is thus possible to change the shape of sprayed fuel injected via an injection aperture formed in a lower end of the nozzle body.
However, the device disclosed in Patent Document 1 needs a particular member (swirl flow forming member) for forming swirl flow arranged between the needle valve and the nozzle body, and thus has a complicated structure. Further, the device shown in Patent Document 1 has the single injection aperture provided in the lower end of the nozzle body. Patent Document 1 does not disclose any technique of controlling the shape of spayed fuel injected via multiple injection apertures provided on a side of the nozzle body.
An object of the present invention is to provide a fuel injection device having a simple structure equipped with multiple injection apertures via which fuel is diffusively spayed and capable of changing the shape of sprayed fuel.
The above object is achieved by a fuel injection device characterized by comprising a nozzle body equipped with multiple injection apertures, a needle valve arranged in the nozzle body, a fuel swirl portion in which fuel is swirled along an inner wall surface of the nozzle body, and a guide portion applying swirl force to the fuel and then guiding the fuel to the fuel swirl portion, the fuel swirl portion being arranged at a position at which the fuel swirl portion partially overlaps with the injection apertures.
The fuel swirl portion may include a first circumferential groove formed on one of the inner wall surface of the nozzle body and an outer circumferential surface of the needle valve. The guide portion may include a groove formed on the inner wall surface of the nozzle body and an outer circumferential surface of the needle valve.
A protrusion may be provided at an upstream side of the circumferential groove, and the guide grooves are formed in the protrusion. Another protrusion may be provided at a downstream side of the circumferential groove.
There may be provided a needle movement mechanism that moves the needle valve in its axial direction to thus change a lift amount of the needle valve, wherein: the needle valve is movable between a low lift position having a small lift amount and a high lift position having a large lift amount by the needle movement mechanism; and the first circumferential groove overlaps with parts of injection apertures when the needle valve is located at the low lift position.
The fuel swirl portion may include a ring-shaped s pacing formed between an outer circumferential surface of the needle valve and the inner wall surface of the nozzle body. The guide portion may include a groove formed on one of the inner wall surface of the nozzle body and the outer circumferential surface of the needle valve. There may be provided a needle movement mechanism that moves the needle valve in its axial direction to thus change a lift amount of the needle valve, wherein: the needle valve is movable between a low lift position having a small lift amount and a high lift position having a large lift amount by the needle movement mechanism; and a ring-shaped spacing is defined when the needle valve is at the low lift position.
The needle valve may have a column-shaped portion having a small size at a tip, and the ring-shaped spacing may be defined between the outer circumferential surface of the column-shaped portion and the inner wall surface of the nozzle body when the needle valve is at the low lift position. The protrusion may be at an upstream side of the column-shaped portion, and a groove included in the guide portion may be formed in the protrusion.
A second circumferential groove for rectification may be connected to an upstream side of the guide portion.
A swirl flow forming member may be provided so as to be spaced apart from the fuel swirl portion, wherein the swirl flow forming member has the guide portion. The fuel swirl portion may be a first circumferential groove formed on one of the inner wall surface of the nozzle body and an outer circumferential surface of the needle valve. A protrusion may be provided at a downstream side of the first circumferential groove. There may be provided a characterized by further comprising a needle movement mechanism that moves the needle valve in its axial direction to thus change a lift amount of the needle valve, wherein: the needle valve is movable between a low lift position having a small lift amount and a high lift position having a large lift amount by the needle movement mechanism; and the first circumferential groove overlaps with parts of injection apertures when the needle valve is located at the low lift position.
The guide portion may include a groove, which includes a groove width at a fuel inlet side greater than a groove width at a fuel outlet side. The guide portion may include a groove, which gradually becomes deeper from an upstream side in a fuel swirl direction to a downstream side.
The first circumferential groove may have a cross section taken along an axial line of the needle valve so that the cross section has a depth that gradually increases from a tip of the needle valve to a root end of the needle valve. The first circumferential groove may have a cross section taken along an axial line of the needle valve so that the cross section has a depth that gradually increases from a root end of the needle valve to a tip of the needle valve.
According to the present invention, the fuel swirl portion that swirls fuel is arranged so as to overlap with parts of the injection apertures, so that the spay of sprayed fuel can be formed into diffusive spray having a wide spray angle. When the fuel swirl portion becomes away from the injection apertures, the shape of sprayed fuel can be formed into column-shaped spray having a narrow spray angle. It is thus possible to change the shape of sprayed fuel only be adjusting the positional relationship between the fuel swirl portion and the injection apertures.
FIGS. 12(A) and 12(B) are diagrams for explaining differences between the fuel injection devices of different embodiments
FIGS. 14(A) and 14(B) are diagrams illustrating a peripheral portion of injection apertures of a fuel injection device 1I in accordance with Embodiment 9;
FIGS. 15(A) and 15(B) are diagrams illustrating a peripheral portion of injection apertures of a fuel injection device 1J in accordance with Embodiment 10;
FIGS. 16(A) and 16(B) are diagrams illustrating a peripheral portion of injection apertures of a fuel injection device 1K in accordance with Embodiment 11;
FIGS. 18(A) and 18(B) are diagrams of variations of guide grooves provided in a needle valve;
FIGS. 20(A) and 20(B) are diagrams of variations of the cross sections of guide grooves in a needle valve; and
FIGS. 21(A), 21(B) and 21(C) are diagrams of variations of the cross sections of circumferential in a needle valve.
A description will now be given, with reference to the accompanying drawings, of multiple embodiments of the present invention.
A tip (a lower side in
The tip of the needle valve 20 is formed into a conical shape, which corresponds to the inner wall surface 11 of the nozzle body 10. A seat portion 21 that is seated on the seat surface 11ST of the nozzle body 10 is formed in a tip portion of the conical shape. A closed state is defined when the needle valve 20 descends and the seat portion 21 is brought into contact with the seat surface 11ST. As will be described later, the fuel injection device 1A is equipped with a needle movement mechanism that moves the needle valve in the axial directions AX and changes the magnitude of movement (lift amount) of the needle valve. The following description is given assuming that a low lift position is defined as a position at which the needle valve 20 is moved upwards by a relatively small lift amount by means of the needle movement mechanism, and a high lift position is defined as a position at which the needle valve 20 is moved upwards by a relatively large lift amount.
The needle valve 20 has a fully circumferential groove (first circumferential groove) 24, which is located closer to the tip than the seat portion 21 and functions as a fuel swirling portion. The circumferential groove 24 is formed so as to circularly cut off an outer circumferential surface of the conical shape of the tip of the needle valve 20. Multiple guide grooves 22, which are slant to the axial directions AX, are connected to the upper portion of the circumferential groove 24. The multiple guide grooves 22 apply swirl force to fuel and introduce fuel to the fuel swirling portion. The multiple guide grooves 22 are formed by cutting off the outer circumferential surface of the needle valve 20 in strip fashion, and have lower ends connected to the upper end of the circumferential groove 24.
The circumferential groove 24 is positioned so as to overlap the upper-side portions of the injection apertures 12 (parts of the injection apertures) at the low lift position. That is, the circumferential groove 24 is positioned so as to overlap the upper side portions of the injection apertures 12 at the low lift position when viewed in the height direction along the axial direction AX. Preferably, the circumferential groove 24 is positioned so as to overlap ½ to ⅓ of the injection apertures 12 from the upper side.
When the seat portion 21 of the needle valve 20 is seated on the seat surface 11ST of the nozzle body 10, passages of fuel FE to the injection apertures 12 are closed. When the needle valve 20 moves to the low lift position having a small lift amount from the above position, a slight gap is formed between the inner wall surface 11 of the nozzle body 10 and the needle valve 20. Thus, some of the fuel FE flows into the circumferential groove 24 via the slant guide grooves 22. The slant guide grooves 22 apply swirl force (force for swirling leftwards in
As shown in the left side half and
In contrast, in the high lift position shown in the right side half of
As described above, the fuel injection device 1A enables diffusive spray at the low lift position, and easily changes the spray shape only by changing the lift amount of the needle valve 20. Next, the needle movement mechanism provided in the fuel injection device 1A is described.
The fuel injection device 1A has a fuel feed port 13 that is formed at an upper end and is connected to a not shown fuel pipe. The fuel injection device 1A includes the nozzle body 10 and the needle valve 20 arranged therein, as has been described previously. The nozzle body 10 is made up of a hollow cylindrical main body 10a, and a nozzle portion 10b integrally connected to an end of the main body 10a. The nozzle body 10 internally has a space 14, which continuously extends from the main body 10a to the nozzle portion 10b. The fuel FE entering into the fuel feed port 13 from the fuel pipe moves down in the space 14 and is finally injected via the multiple injection apertures 12 arranged at the lower end.
The needle valve 20 is arranged within the space 14. A first magnetic circuit M1 and a second magnetic circuit M2 are arranged in the space in the main body 10a of the nozzle body 10. The first magnetic circuit M1 has a first electromagnet (M1a, M1c) composed of a first magnetic core M1a of a hollow cylindrical shape and a first coil M1c buried in the first magnetic core M1a. The first magnetic circuit M1 is equipped with a ring-shaped magnetic body (armature) M1b. The needle valve 20 is positioned in an opening of the armature M1b with relative movement. The armature M1b is connected to a stopper member 15 fixed to the needle valve 20 via a first spring S1, and is elastically coupled with the needle valve 20.
The second magnetic circuit M2 having the same configuration as that of the first magnetic circuit M1 is provided at the upper side of the first magnetic circuit M1. The second magnetic circuit M2 has a second electromagnet (M2a, M2c) composed of a second magnetic core M2a of a hollow cylindrical shape and a second coil M2c buried in the second magnetic core M2a. The second magnetic circuit M2 is equipped with a ring-shaped magnetic body (armature) M2b. The needle valve 20 is fixed in an opening of the armature M2b. The armature M2b is elastically coupled with the upper portion of the injector main body 10a via a second spring S2.
The fuel injection device 1A is equipped with a connector 16 for making an electrical connection with an outside thereof. The fuel injection device 1A is connected, via the connector 16, to an ECU (Electronic Control Unit) 17 of a diesel engine on which the fuel injection device 1A is mounted. The fuel injection device 1A is driven under the control of the ECU 17 on the basis of the load state of the diesel engine. When only the first magnetic circuit M1 is driven by the ECU 17, the aforementioned low lift state is realized. When both the first magnetic circuit M1 and the second magnetic circuit M2 are driven by the ECU 17, the aforementioned high lift state is realized.
The fuel injection device 1A with the above-mentioned structure is capable of controlling the shape of sprayed fuel only by forming the circumferential groove 24 and the guide grooves 22 at given positions in the needle valve 20 and moving the needle valve 20 to the low and high lift positions. The fuel injection device 1A of Embodiment 1 may be manufactured at low cost because the grooves are merely formed on the needle valve 20 at given positions.
The above-mentioned fuel injection device 1A may be used in various applications. For example, the fuel injection device 1A may be used to realize an application in which the engine is operated with pre-mixed compression natural ignition combustion in a first operating range having a relative low engine load and is operated with normal combustion (diffusive combustion) in a second operating range having a relatively high engine load. In this application, the needle valve is set at the low lift position in the first operating range so that fuel can be injected with high diffusion and low complete penetration force. In the second operating range, the needle valve is set at the high lift position so that fuel can be injected with low diffusion and high complete penetration force.
The fuel injection device 1A may also be used in another application in which the engine is operated with the pre-mixed compression natural ignition combustion at an initial state of combustion and with the normal combustion at the later stage of combustion. In this application, the needle valve is set at the low lift position in the initial state of combustion so that fuel can be injected with high diffusion and low complete penetration force. In the later stage of combustion, the needle valve is set at the high lift position so that fuel can be injected with low diffusion and high complete penetration force. By spraying fuel in different ways by the fuel injection device 1A as mentioned above, fuel economy can be improved and exhaust emission can be improved.
Preferably, the circumferential groove 24 overlaps with the upper ½ to ⅓ of the injection apertures 12 at the time of low lift. In this case, the circumferential groove 24 may totally or partially overlap with the upper portions of the injection apertures 12.
Even the fuel injection device 1B of Embodiment 2 brings about advantages similar to those of the fuel injection device 1A. That is, it is possible to easily change the shape of sprayed fuel in such a manner that the circumferential groove 18 and the guide grooves 19 are formed at given positions on the nozzle body 10, and the needle valve 20 is merely moved to the low and high lift positions.
Embodiment 1 has an exemplary structure in which the circumferential groove and the guide grooves are formed on the needle valve, and Embodiment 2 ahs an exemplary structure in which the circumferential groove an the guide grooves are formed on the inner wall of the nozzle body 10. However, the formation of the circumferential groove and the guide grooves are not limited to the above structures. The circumferential groove may be formed on the needle valve 20 and the guide grooves may be formed on the inner wall of the nozzle body 10. In contrast,, the guide grooves may be formed on the needle valve 20, and the circumferential groove may be formed on the inner wall of the nozzle body 10. That is, the circumferential groove and the guide grooves are not formed on the same surface but may be separately formed on the needle valve 20 and the inner wall of the nozzle body 10.
The fuel FE that unevenly drops from the upstream side of the fuel injection device 1C flows into the guide grooves 22 via the second circumferential groove 25. The fuel FE in the circumferential groove 25 is temporarily reserved therein, and has restored pressure (the liquid phase is homogenized). The multiple guide grooves 22 are connected to the lower side of the second circumferential groove 25. Thus, the fuel FE that is rectified within the second circumferential groove 25 evenly flows into the multiple guide grooves 22. Since the fuel evenly flows into the multiple guide grooves 22, the fuel FE can be smoothly introduced to the first circumferential groove 24 from the guide grooves 22. The use of the circumferential groove 25 having the rectifying function allows the guide grooves 22 to be formed with a slightly lowered precision in processing. It is thus possible to employ plastic forming such as rolling and improve the productivity.
The fuel injection device 1C of Embodiment 3 provides effects similar to those of the fuel injection device 1A. That is, the shape of sprayed fuel can be changed by merely moving the needle valve 20 to the low and high lift positions. Particularly, the fuel injection device 1C is so configured that the fuel FE is rectified in the second circumferential groove 25 and is introduced into the guide grooves 22. It is thus possible to form the guide grooves 22 with a lowered precision.
Embodiment 3 has an exemplary structure in which the first circumferential groove, guide grooves and second circumferential groove are formed on the needle valve 20, and Embodiment 4 has an exemplary structure in which the first circumferential groove, guide grooves and second circumferential groove are formed on the inner wall of the nozzle body 10. However, the formation of the first circumferential groove, guide grooves and second circumferential groove is not limited to the above. For example, the first circumferential groove, guide grooves and second circumferential groove are not required to be formed on an identical surface, but may be separately formed on the needle valve 20 and the inner wall of the nozzle body 10.
The fuel injection device 1E is designed so that a ring-shaped spacing SP functioning in a manner similar to that of the circumferential groove can be formed only when the needle valve 20 is located at the low lift position as shown in
The needle valve 20 of Embodiment 5 has a column-shaped portion 30 at the tip thereof. The column-shaped portion 30 has a bottom surface slightly smaller than the bottom surface of an lower-end surface 20FP of the needle valve main body so as to allow the downward flow of the fuel FE guided by the guide grooves 22. That is, the circumferential portion of the low-end surface 20FP to which the column-shaped portion 30 is connected has a step portion 31. The step portion 31 is positioned so as to overlap the upper portions of the inlets 12NP of the injection apertures 12. A member 32 added to the end of the column-shaped portion 30 is a volume adjustment member for restraining the dead volume.
The upper portions of the inlets 12NP are shaped so as to easily receive the step portion 31. That is, the upstream side portions of the inlets 12NP are inclined so as to continue with the seat surface 11ST.
Turning to the reference circle CR in
At the time of high lift shown in
As described above, the fuel injection device 1E of Embodiment 5 provides effects similar to those of the fuel injection devices of Embodiments 1 through 4. Particularly, there is no need to form the circumferential groove on the needle valve 20 and the nozzle body 10, so that the number of production steps can be reduced and productivity can be improved. The guide grooves of the fuel injection device 1E may be formed on the inner wall surface 11 of the nozzle body 10.
In the fuel injection device 1G, the fuel FE passing through the guide grooves 41 of the swirl forming member 40 flows down while being swirled along the inner wall surface 11 of the nozzle body 10, and enters into the circumferential groove 24. Then, the fuel FE is swirled in the circumferential groove 24. The following operation is the same as that of Embodiments 1 through 4. The fuel FE swirled flows into the injection apertures 12 so that drift flow can be caused, and a swirl flow of fuel FE is produced in the injection apertures 12. Thus, the fuel discharged from an outlet 12TP of the injection aperture 12 is brought into a state of diffusive spray of fine particles and a wide spray angle. In this manner, the fuel injection device 1A is capable of forming a spray shape of diffusive spray at the low lift position. The fuel injection device 1G is capable of changing the shape of sprayed fuel to column-shaped spray having a relatively small spray angle by merely moving the needle valve 20 from the low lift position to the high lift position. The fuel injection device 10 of Embodiment 7 utilizes the separate swirl forming member 40, so that the production process can be simplified and the cost can be reduced. Alternatively, the circumferential groove may be arranged so as to partially overlap with the upper portions of the injection apertures 12 of the nozzle body 10.
In Embodiments 1 through 6 mentioned above, the slant guide grooves 22 or 19 are provided on the outer circumferential surface of the needle valve 20 or the inner wall surface 11 of the nozzle body 10. Fuel is caused to flow into the circumferential groove 24 or the like through the guide grooves 22 or the like, and to be swirled therein. In order to produce a stronger swirl flow in the circumferential groove, a larger quantity of fuel may be vigorously entered into the guide grooves. In the aforementioned embodiments, there is some fuel that passes through the spacing between the outer circumference of the needle valve 20 and the inner wall surface of the nozzle body 10 without entering into the guide grooves. If such fuel passing rough the spacing is introduced into the guide grooves, stronger swirl flow can be produced in the circumferential groove. The following description is directed to a fuel injection device capable of introducing a larger quantity of fuel into the guide grooves.
In order to facilitate easy understanding, a description will now be given, with reference to FIGS. 12(A) and 12(B), of differences between the aforementioned embodiments and the present embodiment.
The fuel injection device shown in
The guide grooves 22 are formed so that only downstream-side portions or the entire guide grooves 22 engage the upstream-side protrusion 27. It is desired that the protrusion 27 faces the upper end of the circumferential groove 24. As shown, the protrusion 27 may be slightly shortened so that the downstream-side portions of the guide grooves 22 can be formed in the protrusion 27. Alternatively, the protrusion may be lengthened.
The protrusion 27 arranged on the upstream side of the circumferential groove 24 results in a state in which fuel flowing down is dammed when the needle valve 20 is at the low lift position. The dammed fuel FE concentrates on the guide grooves 22 that are cutoff portions on the protrusion 27. Thus, in the structure shown in
The protrusion 28 provided at the downstream side of the circumferential groove 24 restrains fuel entering into the circumferential groove 24 from flowing out of the groove 24 downwards. Although the protrusion 28 is preferably employed taking the above into consideration, but may be omitted. The protrusion 28 may be omitted in such a manner that a portion (lower portion) of the needle valve 20 closer to the tip than the circumferential groove 24 is enlarged so as to reduce the spacing and restrain the fuel from flowing out of the circumferential groove 24 downwards.
The fuel injection device shown in
FIGS. 15(A) and 15(B) are enlarged views of a peripheral portion of injection apertures of a fuel injection device 1J in accordance with Embodiment 10. The fuel injection device 1J is configured by varying the fuel injection device 1E having the column-shaped portion 30 at the tip of the needle valve 20 in Embodiment 5. The needle valve 20 has the step portion 31 on the circumference of the lower end surface 20FP to which the column-shaped portion 30 is connected. The fuel injection device 1J of the present embodiment has the protrusion 27 added to the step portion 31.
FIGS. 16(A) and 16(B) are enlarged views of a peripheral portion of injection apertures of a fuel injection device 1K in accordance with Embodiment 11. The fuel injection device 1K is configured by varying the fuel injection device 1F of Embodiment 6. The needle valve 20 with the column-shaped portion 30 has the circumferential groove (second circumferential groove) 25 for rectification at the upper ends of the guide grooves 22. The present fuel injection device 1K has the protrusion 27 in the region in which the guide grooves 22 are formed.
The fuel injection devices of the aforementioned embodiments can change the shape of sprayed fuel by changing the lift amount of the needle valve 20. When the axial position of the the needle valve 20 is fixed to the low lift position, the fuel injection device permanently forms diffusive spray. The fuel injection device of permanent diffusive spray type may be applied to direct injection type gasoline engines.
(Variation 1)
A description will now be given of a variation applicable to the aforementioned embodiments. FIGS. 18(A) and 18(B) show variations of the guide grooves 22 provided on the needle valve 20.
In FIGS. 18(A) and 18(B), the depth of the guide grooves 22ST and 22PR may be varied so that the depth on the fuel FE inlet side is deeper than that on the fuel FE outlet side. This variation enhances the flow rate at which the fuel FE goes out. Although FIGS. 18(A) and 18(B) are directed to the guide grooves 22 provided on the needle valve 20, the variation shown therein may be applied to the guide grooves 19 provided on the nozzle body 10 as well. As shown in FIGS. 19(A) and 19(B), when the protrusions 27 and 28 are added to the upper and lower portions of the circumferential groove 24, the flow rate at which the fuel FE that goes out can be enhanced for both the cases of FIGS. 19(A) and 19(B). The case shown in
(Variation 2)
FIGS. 20(A) and 20(B) show variations of the cross sections of the guide grooves 22 provided on the needle valve 20.
(Variation 3)
FIGS. 21(A), 21(B) and 21(C) show variations of the cross section of the circumferential groove 24 provided on the needle valve 20.
The deeper the groove, the greater the flow rate of fuel FE therein. FIGS. 21(B) and 21(C) show flow rate distributions CB in the circumferential grooves on the right-hand sides. In the structure shown in
As described above, the shape of sprayed fuel can be controlled by changing the cross section of the circumferential groove. The circumferential groove is not limited to the arc shape cross sections shown in FIGS. 21(A) through 21(C), but may have a V-shaped cross section or a C-shaped cross section. Although FIGS. 21(A) through 21(C) are directed to the circumferential groove 24 provided on the needle valve 20, the present variation may be applied to the guide grooves 19 provided on the nozzle body 10.
In Embodiment 8 and the other embodiments subsequent thereto, the protrusion is added to the needle valve 20. When the guide grooves 19 are provided to the inner wall surface 11 of the nozzle body 10, a similar protrusion may be applied to the nozzle body 10.
The preferred embodiments of the present invention have been described. The present invention is not limited to these specific embodiments, but variations and modifications may be made within the scope of the claimed invention.
Number | Date | Country | Kind |
---|---|---|---|
2004-276205 | Sep 2004 | JP | national |
2005-135643 | May 2005 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/JP05/17448 | 9/22/2005 | WO | 3/19/2007 |