Patent Grant
8919674
1. Field of the Invention
The present invention relates to a fuel injection valve mainly used for a fuel supply system of an internal-combustion engine, and specifically to an injection hole plate provided at the downstream side of a valve seat.
2. Description of the Related Art
Recently, with tighter exhaust emission regulation for vehicles and the like, improvements in the degree of freedom of the injection direction and atomization of the fuel spray injected from the fuel injection valve have been required, and particularly, various studies have already been made on the atomization of the fuel spray.
In a fuel injection valve in related art, a fuel injection valve in which a thin injection hole plate with plural injection holes formed therein is provided at the downstream side of a valve member and a valve seat for injecting fuel from the respective injection holes is known. In the fuel injection valve, generally, the injection hole has an equal diameter from its entrance to exit, and, when fuel flows into the injection hole having the equal diameter, the fuel does not spread along the injection hole inner surface but is injected as a liquid column. The fuel as the liquid column is hard to be atomized and may deteriorate combustion in the internal-combustion engine.
In this regard, for example, as shown in Patent Document 1, in order to obtain a liquid membrane sufficiently spread within the injection hole, it is conceivable that the injection hole is tapered. By forming a conical shape spreading at the exit side of the injection hole, it may be expected that the spray spreads along the inner wall surface of the injection hole, and the fuel turns into a thin membrane and is injected.
Further, for example, as shown in Patent Document 2, the fuel entrance is formed in an elliptical shape or plural circles and the fuel is injected from a belt-like exit that smoothly communicates with the entrance, and thus, the spray in the uniform liquid membrane may be injected from the exit and atomization of the fuel may be promoted.
Furthermore, for example, as shown in Patent Document 3, the fuel spray may be atomized by forming an oval injection hole with a major axis and a minor axis to have an injection hole shape with a straight elongated shape and arc shapes on both ends, and making the minor axis shorter. Further, as a modified example of the oval injection hole, three circular injection holes may be aligned on a straight line to form one injection hole.
However, in the case where the tapered injection holes as shown in Patent Document 1 are formed in the injection hole plate, the areas of injection hole entrances may easily vary in respect of working, and there is a problem of variations in flow rate and spray, and further, very complex steps are necessary in respect of manufacture and dimensional management, and there are problems that deterioration of productivity of the fuel injection valve and increase in cost may be caused.
In addition, the injection holes shown in Patent Document 2 and Patent Document 3 have a structure of injecting spray in a shape along a channel shape while filling the injection hole with fuel. Accordingly, there are problems that air bubbles produced in the fuel due to decompression boiling at the downstream side of the injection hole at a high temperature under negative pressure are clogged at the injection hole exit, and flow characteristics (static flow, dynamic flow) with changes in temperature, atmosphere pressure, etc. largely change.
A fuel injection valve according to the invention is to solve the above described problems for easier manufacturing, formation of thin membranes of fuel in injection holes, promotion of atomization of spray, and smaller changes in flow characteristics.
A fuel injection valve according to the invention has a valving element that opens and closes a valve seat, and, when opening the valve seat with the valving element, allows fuel to pass through between the valving element and a valve seat surface and to be injected from plural holes provided in an injection hole plate attached at a downstream side of the valve seat, wherein the holes provided in the injection hole plate are combined injection holes formed by partially overlapping two or more single injection holes from an upstream side to a downstream side of the injection hole plate, each of the single injection holes is a circular hole having the same diameter in an entrance part at the upstream side and an exit part at the downstream side of the injection hole plate, at least one of the single injection holes has an injection hole angle α defined by a tilt angle of a center axis line connecting an entrance part center and an exit part center relative to a plate thickness direction of the injection hole plate, intersection angles β are provided so that, if center axis lines of the respective single injection holes forming the combined injection holes are projected on a plane orthogonal to a valve seat axis, the center axis lines of the respective single injection holes may intersect, and thereby, areas of exit parts are larger than areas of entrance parts in the combined injection holes, and the combined injection holes are formed by press working.
According to the fuel injection valve of the invention, since the combined injection holes are formed by partially overlapping the two or more single injection holes from the upstream side to the downstream side of the injection hole plate, manufacturing is easy, and, since the area of the inner circumferential surface of the combined injection hole becomes larger toward the exit side, formation of thin membranes of fuel may be promoted within the combined injection holes and atomization of spray may be promoted. Further, depending on the shapes of the combined injection holes to be formed, various spray forms may be realized without the expense of atomization. Furthermore, if air bubbles are produced in the fuel due to decompression boiling of part of the fuel, when the fuel enters from the entrances within the combined injection holes, the fuel is pressed against the wall surfaces within the combined injection holes, turns into thin membranes. In addition, compared to the injection hole having the equal diameter from the injection hole entrance to the exit, the area of the inner circumferential surface of the combined injection hole becomes larger toward the exit side, and thus, air bubbles may be easily ejected from the combined injection hole and the changes in characteristics (static flow, dynamic flow) with changes in atmosphere may be made smaller.
The foregoing and other object, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
Next, an operation will be explained. When an operation signal is sent from a controller of an engine to a drive circuit (not shown) of the fuel injection valve 1, a current is conducted in the coil 5 of the fuel injection valve 1, magnetic flux is generated in the magnetic circuit including the armature 6, the core 4, the housing 3, and the valve main body 9 is attracted to the core 4, and an upper surface 6a of the armature 6 is brought into contact with the lower surface of the core 4. When the valving element 8 integrated with the armature 6 moves away from a valve seat surface 10a to form a clearance, the fuel passes from plural grooves 13a provided at a leading end part (ball) 13 of the valving element 8 through the clearance between the valve seat surface 10a and the valving element 8, and is injected from the plural holes 12 to an engine intake pipe.
When a stop signal of the operation is sent from the controller of the engine to the drive circuit of the fuel injection valve 1, the conduction of the current from a connector 51 to the coil 5 is stopped, the magnetic flux in the magnetic circuit is reduced, the clearance between the valving element 8 and the valve seat surface 10a is closed by the elastic force of a compression spring 14 that pushes the valving element 8 in the valve closing direction, and the fuel injection ends. At opening and closing operation of the valving element 8, the valving element 8 slides along a guide part 9a projecting inward in the radial direction of the valve main body 9, and a guide part 13b of the ball 13 of the valving element 8 slides along a valve seat sliding part 10b. The guide part 13b is means for regulating non-coaxiality (waggle) of the valving element 8 in the radial direction relative to the valve seat sliding part 10b. Therefore, it is preferable to set the clearance as small as possible, and the clearance is set to 10 μm or less (the clearance at one side is 5 μm or less) to make the wear resistance of the valving element 8 within the acceptable limit.
In order that the area of the exit part may be larger than the area of the entrance part in the combined injection hole 16, predetermined angles β are provided between the adjacent single injection holes so that, if the center axis lines in the single injection holes 15a, 15b, 15c are projected on a plane orthogonal to a valve seat axis 34, the center axis lines of the respective single injection holes 15a, 15b, 15c may intersect. It is not necessary that the angle between the single injection holes 15a, 15b and the angle between the single injection holes 15b, 15c are the same, or it is not necessary that the center axis lines of the respective single injection holes 15a, 15b, 15c intersect at one point.
The mainstream of the fuel flow from the valve seat surface 10a flows from the outside to the inside in the radial direction of the valve seat axis 34 of the fuel injection valve into the entrance part 16a of the combined injection hole 16, and a liquid membrane is formed by the separation of the flow in the entrance part 16a of the combined injection hole 16, the fuel is pressed toward the valve seat axis 34 within the combined injection hole 16, the flow within the combined injection hole 16 becomes a flow along the curvature of the combined injection hole 16, and injected from the exit part 16b of the combined injection hole 16. Note that, in embodiment 1, all of the holes forming the combined injection hole 16 have the injection angle α, however, it is necessary at least one of the plural single injection holes forming the combined injection hole 16 has the injection angle α.
The combined injection hole 16 is formed by respectively press working the single injection holes 15a, 15b, 15c in the injection hole plate 11 and overlapping the circular holes of the single injection holes 15a, 15b, 15c. Alternatively, the shape of the combined injection hole 16 may be press-worked. In either case, manufacturing is easy because the combined injection hole 16 is formed by combining the circular holes.
Since the fuel injection valve in embodiment 1 has the above described configuration and the area of the inner circumferential surface of the combined injection hole becomes larger toward the exit side compared to the injection hole having the equal diameter from the injection hole entrance to the exit, formation of the thin membrane of the fuel within the combined injection hole is promoted toward the exit part 16b, and the spray may be atomized. Further, as described above, since the combined injection hole is not filled with the fuel and the fuel turns into the thin liquid membrane while pressed against inside of the combined injection hole and is injected from the exit part 16b of the combined injection hole 16, the air bubbles produced within the combined injection hole 16 may be easily ejected and the changes in flow characteristics (static flow, dynamic flow) with changes in atmosphere may be made smaller.
The single injection holes 17a, 17b, 17c are circular holes having the same diameters (cylindrical holes) from the entrance parts at the upstream side to the exit parts at the downstream side of the injection hole plate 11, and the injection hole diameters of the three single injection holes 17a, 17b, 17c are different from one another. In the case of part B in
Since the different combined injection holes 18 (part B, part C as shown in
Generally, the angle of the spray formed by the edge line of the collective spray (hereinafter, referred to as “spray angle”) and the particle size of the collective spray have a trade-off relation, and, larger the spray angle, the smaller the particle size. In the fuel injection type internal-combustion engine, by supplying the atomized fuel, ignition is promptly completed, the combustion efficiency becomes higher, the emission concentration of the exhaust gas, particularly, carbon hydride is reduced, and thus, atomization of the fuel is necessary for raising the combustion efficiency.
In the fuel injection valve in related art, the spray having a nearly uniform particle size within a collective spray is injected to the intake valve and, in this regard, a certain fixed amount of the outside part with respect to the center axis of the spray adheres to the inner wall of the intake port. If the spray angle is made larger in order to atomize the collective spray having the nearly uniform particle size, the adhesion to the inner wall of the intake port increases, the fuel moving along the inner wall, turning into a liquid membrane, and flowing into an air cylinder with a delay increases, and thereby, the combustion efficiency becomes lower, and, as a result, the concentration of carbon hydride HC in the exhaust gas becomes higher and the engine controllability becomes deteriorated.
The rest of the configuration is the same as that in embodiment 1, and the single injection holes 23a, 23b, 23c have injection hole angles α defined by tilt angles of center axis lines connecting the respective entrance part centers and the exit part centers relative to the plate thickness direction of the injection hole plate, and the area of the exit part is larger than the area of the entrance part in the combined injection hole 22, the combined injection hole 22 is formed by combining the circular holes, and thereby, manufacturing is easy. Note that, in the single injection holes 23a, 23b, 23c, the injection hole angles α may be different from one another.
According to embodiment 3, as is the case of embodiment 1, the atomization of the fuel spray may be promoted. Further, the area of the entrance part 22a in the combined injection hole 22 is made equal to the area of the entrance part of the single injection hole 23b having the maximum injection hole diameter of the three single injection holes 23a, 23b, 23c, and thus, variations in flow rate due to variations in work position of the other single injection holes 23a, 23c may be suppressed.
The rest of the configuration is the same as that in embodiment 1, and the area of the exit part is larger than the area of the entrance part in the combined injection hole 24, the combined injection hole 24 is formed by combining the circular holes, and thereby, manufacturing is easy. Further, the locations of the entrance parts of the single injection holes 25a, 25b, 25c are overlapped and the area of the entrance part in the combined injection hole 24 is equal to the area of the entrance part of the single injection hole.
By forming the combined injection hole 24 as shown in
The respective single injection holes 27a, 27b are circular holes having the same diameters (cylindrical holes) from the entrance parts at the upstream side to the exit parts at the downstream side of the injection hole plate 11, and the injection hole diameters of the single injection holes 27a, 27b are equal. The single injection holes 27a, 27b respectively have injection hole angles α1, α2 defined by tilt angles of center axis lines connecting the entrance part centers and the exit part centers relative to the plate thickness direction of the injection hole plate, and the injection hole angle α1 and the injection hole angle α2 are different from each other. Note that the rest of the configuration is the same as that in embodiment 1, and the area of the exit part is larger than the area of the entrance part in the combined injection hole 26, the combined injection hole 26 is formed by combining the circular holes, and thereby, manufacturing is easy. Further, the locations of the entrance parts of the single injection holes 27a, 27b are overlapped and the area of the entrance part in the combined injection hole 26 is equal to the area of the entrance part of the single injection hole. The injection hole diameters of the single injection holes 27a, 27b may not necessarily be equal.
By forming the combined injection hole 26 as shown in
The respective single injection holes 29a, 29b, 29c are circular holes having the same diameters (cylindrical holes) from the entrance parts at the upstream side to the exit parts at the downstream side of the injection hole plate 11, and all of the injection hole diameters D of the single injection holes 29a, 29b, 29c are the same. The single injection holes 29a, 29b, 29c have the injection hole angles α defined in the above description, and all of the injection hole angles α may be the same or different from one another. Note that the rest of the configuration is the same as that in embodiment 1, and the area of the exit part is larger than the area of the entrance part in the combined injection hole 28, the combined injection hole 28 is formed by combining the circular holes, and thereby, manufacturing is easy. Further, the locations of the entrance parts of the single injection holes 29a, 29b, 29c are overlapped and the area of the entrance part in the combined injection hole 28 is equal to the area of the entrance part of the single injection hole.
According to experiments, given that the distance between the centers in the exit parts of the adjacent single injection holes 29a, 29b is ds (mm), as shown in
The respective single injection holes 31a, 31b, 31c are circular holes having the equal diameters (cylindrical holes) from the entrance parts at the upstream side to the exit parts at the downstream side of the injection hole plate 11, and the injection hole diameters of the adjacent single injection holes 31a, 31b and single injection holes 31b, 31c are different from each other. In the case of embodiment 7, the injection hole diameters of the single injection holes 31a, 31c are the same, however, they may be different. The single injection holes 31a, 31b, 31c have the injection hole angles α defined in the above description, and all of the injection hole angles α may be the same or different from one another. Note that the rest of the configuration is the same as that in embodiment 1, and the area of the exit part is larger than the area of the entrance part in the combined injection hole 30, the combined injection hole 30 is formed by combining the circular holes, and thereby, manufacturing is easy.
According to experiments, given that the injection hole diameter of 31b having the larger injection hole diameter of the adjacent single injection holes 31b, 31c is D and the distance between the centers in the exit parts of the adjacent single injection holes 31b, 31c is ds (mm), as shown in
The respective single injection holes 35a, 35b, 35c are circular holes having the equal diameters (cylindrical holes) from the entrance parts at the upstream side to the exit parts at the downstream side of the injection hole plate 11, and the injection hole diameters of the adjacent single injection holes 35a, 35b, 35c may be different or the same. The single injection holes 35a, 35b, 35c have the injection hole angles α defined in the above description, and all of the injection hole angles α may be the same or different from one another. Note that the rest of the configuration is the same as that in embodiment 1, and the area of the exit part is larger than the area of the entrance part in the combined injection hole 32, the combined injection hole 32 is formed by combining the circular holes, and thereby, manufacturing is easy.
In embodiment 8, the entrance part of the combined injection hole 32 is provided inside a hypothetical envelope curve 33 at which the extension of the valve seat surface 10a of the valve seat 10 that forms a fuel path and has a diameter reduced toward the downstream side and an upstream side plane 11c of the injection hole plate 11 intersect, and the exit part of the combined injection hole 32 is provided outside in the radial direction of the valve seat axis 34 relative to the entrance part.
As shown in
Note that the invention is not limited to the examples shown in the embodiments, but various design changes may be made without departing the scope thereof.
While the presently preferred embodiments of the present invention have been shown and described. It is to be understood that these disclosures are for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.
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