The present invention relates to a fuel injection valve used in an engine and, more specifically, to a fuel injection valve in which atomization of fuel spray is improved while restraining excessive spray diffusion.
Recently, improvement of flexibility of direction of fuel spray injection injected from a fuel injection valve and atomization of fuel spray is required in a circumstance in which exhaust gas regulation for automotive vehicles or the like is tightened. In particular, atomization of fuel spray has been studied in various manner, and, for example, disclosed in Patent Publication No. 3183156 (hereinafter, referred to as Patent Document 1) is a fluid injection nozzle in which injection holes are arranged inside an imaginary envelope along an intersection between the main flow direction of fluid on the downstream side of a seat portion of a valve seat and an injection hole plate, a portion of the distal end of a valve element, which is located inwardly of the seat portion and opposes the injection holes is formed into a flat plane parallel to the injection hole plate, the injection holes are inclined with respect to the injection hole plate by a predetermined angle and satisfy a relation h<1.5d where d represents the diameter of the injection hole, and h represents the vertical distance between the flat plane of the valve element and the injection hole plate with the valve opened.
According to this injection nozzle, after fuel is flowed out from the seat portion of the valve seat, the flow is converted to a flow along the injection hole plate in a cavity interposed between the flat plane of the valve element and the injection hole plate, and a flow proceeding directly to the injection holes and a flow passing between the injection holes, making a U-turn at the center of the injection hole plate by the opposing flow and proceeding to the injection holes are generated, whereby flows which proceed uniformly toward the injection holes may be obtained. Accordingly, collision between the fuel flows may be induced immediately above the injection holes, whereby atomization is accelerated.
Patent Document 1: Japanese Patent No. 3183156
In the technology disclosed in Patent Document 1, conversion of the flow of fuel flowed out from the seat portion of the valve seat into the flow parallel to the injection hole plate in the cavity interposed between the flat plane of the valve element and the injection hole plate is used for atomization of fuel spray. However, the flow rate of the fuel entering into the injection holes is subjected to variation in height of the cavity. Therefore, since the height of the cavity defined in Patent Document 1 is affected by variation in machining or the inclination of the valve element with the valve opened, it has a disadvantage such that flow rate accuracy or spray characteristic tend to vary from one fuel injection valve to another.
Means to cause the flow toward the center of the injection hole plate and the flow passing between the injection holes, making the U-turn at the center of the injection hole plate by the opposing flow and proceeding to the injection holes to collide with each other immediately above the injection holes is effective for atomization. However, the spray tends to diffuse easily, and hence directivity of spray is deteriorated. Therefore, the spray adheres to the wall surface of an inlet port, and enters a combustion chamber in the form of a liquid film, whereby there is a possibility to cause degradation of exhaust gas or degradation of controllability of engine output.
In order to solve the above-described problems, in the device in the related art, it is an object of the present invention to provide a fuel injection valve for a gasoline engine in which atomization of fuel spray is improved while restraining variation in flow rate accuracy or spray characteristic, and maintaining the directivity of spray.
A fuel injection valve according to the present invention including a valve element for opening and closing a valve seat and the valve element being driven upon reception of an operation signal from a control unit and causing fuel to be injected from a plurality of injection holes formed on an injection hole plate mounted on the downstream side of the valve seat, wherein the valve element is formed at a distal end thereof with a flat plane which is substantially parallel with the injection hole plate, wherein injection hole entrances of the injection holes are arranged inside an imaginary envelop along an intersection between an extension of a downstream inner wall of a seat portion of the valve seat and an upstream plane of the injection hole plate, and outside the flat plane at the distal end of the valve element, and wherein the relation between the vertical distance h between the flat plane at the distal end of the valve element and the upstream plane of the injection hole plate with the valve opened and the diameter d of the injection hole entrance is h<d, and the injection hole is formed to be inclined by a predetermined angle with respect to the direction of the thickness of the injection hole plate.
A fuel injection valve according to the present invention including a valve element for opening and closing a valve seat and the valve element being driven upon reception of an operation signal from a control unit and causing fuel to be injected from a plurality of injection holes formed on an injection hole plate mounted on the downstream side of the valve seat, wherein a projection which projects toward the downstream so as to extend substantially in parallel with the distal end of the valve element is formed at the center of the injection hole plate, and a flat portion is formed out side of the projection, wherein the relation between the minimum distance r from the distal end of the valve element to the center of the injection hole plate with the valve opened and the diameter d of the injection hole entrance is r<d, and wherein injection hole entrances of the injection holes are arranged inside the minimum inner diameter of the valve seat on the flat portion.
According to the fuel injection valve of the present invention, the injection hole entrances are arranged inside the main stream of fuel flow from the seat portion of the valve seat, and the surface area of the cavity flow path immediately above the injection holes suddenly reduces. Therefore, the fuel flow entering the injection hole entrances at a large angle is enhanced, and hence the atomized fuel spray is obtained while restraining excessive spray diffusion.
Since one surface of the flow path immediately above the injection holes in the cavity is configured by a high-accuracy ball, the dimensional variation of the flow path immediately above the injection holes is small, and uneven height of the cavity due to inclination of the valve element when the valve is opened may be prevented. Therefore, variation in flow rate in the cavity immediately above the injection holes is small, and variations inflow rate accuracy (static flow rate) and spray characteristics (spray shape, diameter of spray particle) are restrained.
The above-described and other objects, characteristics and advantages of the present invention will be apparent from the detailed description and drawings in the following embodiments.
First Embodiment
In
The valve body 9 is press-fitted into an outer diameter portion of the core 4 and is welded thereto. The armature 6 is press-fitted into the valve element 8, and is welded thereto. An injection hole plate 11 is joined to the downstream side of the valve seat 10 at a welding portion 11a, and then inserted into the valve element 9 and joined thereto by a welded portion 11b. The injection hole plate 11 is formed with a plurality of injection holes 12 therethrough in the direction of the thickness as shown in
Subsequently, opening and closing movement of the fuel injection valve will be described.
When an operation signal is sent to a drive circuit of the fuel injection valve in
Subsequently, when an operation stop signal is sent to the drive circuit of the fuel injection valve from the engine control unit, distribution of the electric current in the coil 5 is stopped, and the magnetic flux in the magnetic circuit is reduced. Then, the clearance between the valve element 8 and the seat portion 10a of the valve seat is brought into a closed state by a compression spring 14 which urges the valve element 8 to the closing direction, whereby the fuel injection is terminated.
The valve element 8 slides with the side surface 6a of the armature and a guide 13b on the guide portion of the valve body 9, and with the valve opened, an upper surface 6b of the armature comes into abutment with the lower surface of the core 4. The guide 13b serves to regulate radial non-coaxiality (deflection) of the valve element 8 with respect to the valve seat plane, and hence it is preferable to set the clearance as small as possible. In the first embodiment, in order to keep the durable abrasion of the valve element within an allowable limit, the clearance is set to 10 μm or smaller (5 μm or smaller clearance on one side).
Referring now to
As shown in
The relation between the vertical distance h between the flat portion 13c at the distal end of the valve element and the upstream plane of the injection hole plate with the valve opened and the diameter d of the injection hole entrance is h<d, and the injection hole 12 is formed to be inclined by a predetermined angle with respect to the direction of the thickness of the injection hole plate.
In the fuel injection valve according to the first embodiment configured as described above, as shown in
Therefore, as shown in
Since one surface of the flow path immediately above the injection holes in the cavity 17 is configured by a ball, the dimensional variation is smaller than the flat portion 13c at the distal end of the valve element, and occurrence of uneven height of the cavity due to inclination of the valve element when the valve is opened may be prevented. Therefore, variation in flow rate in the cavity immediately above the injection holes is small, and variation in flow rate characteristic (static flow rate) and spray characteristics (spray shape, diameter of spray particle) are also small.
According to the fuel injection valve in the first embodiment, since the dead volume on the downstream of the seat portion of the valve seat is small, the amount of injection of initial spray injected without being accelerated at the beginning of injection and hence having a large particle diameter of the spray is small, and the amount of evaporation of fuel in the dead volume under high-temperature negative-pressure is also small. Therefore, change in flow rate characteristics (static flow rate, dynamic flow rate) and spray characteristics (shape of splay, particle diameter of the spray) in association with the change of atmosphere may be restrained.
As described thus far, according to the first embodiment of the present invention, with the spray characteristics such as good directivity of spray for aiming the induction valve and good mixing ability with air, a fuel injection valve which can provide the fuel spray with reduced exhaust emission and fuel consumption can be obtained.
Second Embodiment
As shown in
According to the second embodiment as well, as in the first embodiment, atomization is accelerated while restraining excessive diffusion of the fuel spray and the same effect as the first embodiment can be obtained.
Third Embodiment
As shown in
Other configurations are the same as those in the first embodiment and description will be omitted.
According to the third embodiment, the main flow 16a of fuel flow toward the injection hole plate 11 is guided toward, and caused to collide with, the outer periphery with respect to the injection hole entrances 12a, so that the flow 16a can be converted to a flow 16c along the injection plate, and the entrance angle γ into the injection hole entrances 12a is increased. Therefore, separation of flow at the injection hole entrances is further enhanced, and the thickness of the liquid films is reduced, so that atomization of fuel spray is effectively accelerated.
The third embodiment is also applicable to the fuel injection valve in the second embodiment as well as the first embodiment, as a matter of course.
Fourth Embodiment
As shown in
Other configurations are the same as those in the first embodiment, and description is omitted.
According to the fourth embodiment, since a small eddy current 20 is generated on the tapered plane 18, and the fuel flow passed through the seat surface 10c of the valve seat by the eddy current can hardly be separated on the tapered plane 18, the main flow 16a of the fuel flow can be further guided toward the taper surface. Consequently, collision with the injection hole plate 11 can be guided further to the side of the outer periphery with respect to the injection hole entrances 12a, and the fuel flow which flows into the injection hole entrances 12a is converted into a flow which is parallel to the injection hole plate 11, whereby the entrance angle γ to the injection hole entrances 12a may be further increased, so that atomization of fuel spray is enhanced.
The fourth embodiment is also applicable to the fuel injection valve in the second embodiment as well as the first embodiment, as a matter of course.
Fifth Embodiment
As shown in
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Indian Office Action issued Aug. 26, 2014 in Counterpart Patent Application No. 2827/CHENP/2009. |
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