Patent Application
20130256428
1. Field of the Invention
The present invention relates to a fuel injection valve used for an internal combustion engine and in particular to a fuel injection valve that has a plurality of fuel injection holes and can improve atomizing performance by jetting swirl fuel from the fuel injection holes.
2. Description of the Related Art
The fuel injection valve disclosed in JP-2004-278464-A is known as a conventional technology for promoting the atomization of fuel jetted from the fuel injection holes by the use of swirl flow.
The fuel injection valve includes a valve seat member having a valve seat which cooperates with a valve body and has an opening at its downstream end toward the front end face of the valve seat member, and includes an injector plate joined to the front end face of the valve seat member. There are provided lateral-directional passages communicating with the downstream end of the valve seat and swirl chambers each formed by tangentially opening the corresponding downstream ends of the lateral-directional passages, between the valve seat member and the injector plate. The injector plate is bored with fuel injection holes each adapted to jet the fuel subjected to swirl in the swirl chamber. The curvature radius of the inner circumferential surface of the swirl chamber is gradually reduced from the upstream side toward the downstream side in the direction along the inner circumferential surface of the swirl chamber. In other words, the curvature is gradually increased from the upstream side toward the downstream side in the direction along the inner circumferential surface of the swirl chamber. In addition, the inner circumferential surface of the swirl chamber is formed along an involute curve having a base circle in the swirl chamber.
In this fuel injection valve, an overlapping surface between the thick-walled portion of a passage plate and the injector plate is formed to have two slope faces inclined in a V-shape with respect to the axis of the valve seat. In addition, the fuel injection holes are divided into two sets each arranged at a slant in directions opposite to the other.
With the configuration described above, the atomization of fuel from each of the fuel injection holes can effectively be promoted. In addition, the injecting direction of fuel can be varied.
The fuel injection valve described in JP-7-35001-A is known as a conventional technology for promoting the atomization of fuel by the use of swirl force and for distributing fuel into a plurality of holes to make mixing with air satisfactory.
It is known that when fuel subjected to swirl force is jetted, fuel spray is formed in a hollow conical shape. Such a fuel spray is changed into liquid droplets from a liquid membrane state via liquid ligament break-up and becomes an atomized fuel spray.
If mounting on an engine, a fuel injection valve is required to be slim in view of mounting performance. Accordingly, since the injection portion is configured as a nozzle portion with small dimensions, various devices are needed to extract injection performance in consideration of a performance aspect, manufacturing and assembly and so on.
In the conventional technology described in JP-2004-278464-A, the passage plate is configured such that a portion having the lateral-directional passage and the swirl chamber communicating therewith is formed as the thick-walled portion. In addition, the outer circumferential portion of the thick-walled portion is formed as a thin-walled portion. A thin plate-like injector plate having fuel injection holes is put on and circumferentially fixed to the thin-walled portion. For fixation, the energy applied to the outer circumferential portion is efficiently used during welding (laser welding is known). In addition, a method of increasing the degree of freedom of injection characteristics involves forming the overlapping surface between the thick-walled portion and the injection plate into the V-shape, thereby making it possible to change an injection direction.
According to the configuration described above, although the outer circumferential portion can be fixedly secured as designed, it is difficult to prevent the deformation (curving) of the thinned injector plate.
As a result, a minute clearance will occur above the lateral-directional passages and the swirl chambers.
In particular, the lateral-directional passage is an important region to produce swirl fuel. Because of the occurrence of the clearance, fuel leakage occurs, which reduces the swirl force. Because of variations in clearances, variations in the swirling strength of the fuel supplied to the fuel injection holes occur. Further, there is concern that the symmetry of a swirl flow at the outlet of the injection hole may be impaired.
As a result, atomization performance is impaired or the shape of fuel spray is varied. Further, robustness is impaired in terms of injecting-direction control.
The conventional technology described in JP-7-35001 includes the configuration for distributing atomized fuel; however, it does not disclose methods for processing and assembling a swirling passage and a swirl chamber, which require high-accurate processing.
The present invention has been made in view of such situations and aims to provide a fuel injection valve that is superior in atomization performance and in shape controllability by solving a problem about minute deformation occurring when a plate-like member having fuel injection holes adapted to jet swirl fuel is assemble to a nozzle body, and by eliminating the interference of fuel sprays, which poses a problem when fuel injection holes are arranged close to each other.
According to an aspect of the present invention, there is provided a fuel injection valve including a valve body openable and closable to jet fuel and block the jet of fuel; a nozzle body having a valve seat surface capable of coming into close contact with the valve body to block the jet of fuel; and an orifice plate disposed downstream of the valve seat surface and has a plurality of fuel injection holes adapted to jet swirl fuel; wherein the nozzle body has an end face portion with a downwardly convex inclined surface, the inclined surface is formed stepwise such that a plane corresponding to a swirling passage is located slightly lower than a plane corresponding to a swirl chamber, and the orifice plate having the swirling passage and the swirl chamber is fixedly inserted into the nozzle body by being guided by a concave groove-outer circumferential wall portion provided in an outer circumferential portion of the nozzle body.
In this case, the convex lower inclined surface formed on the nozzle body may have a first inclined surface portion corresponding to the swirling passage of the orifice plate and a second inclined surface portion corresponding to the swirl chamber of the orifice plate, the first inclined surface being located upper portion than the second inclined surface portion.
The convex upper inclined surface formed on the orifice plate may have a first inclined surface portion corresponding to the swirling passage of the nozzle body and a second inclined surface corresponding to the swirling chamber of the nozzle body, the first inclined surface being located lower portion than the second inclined surface.
Further, the swirl chamber has a cross-section formed with an involute curve or a helical curve.
According to the aspect of the present invention, the inclined surface of the orifice plate, which corresponds to the swirling passage, is secured to the corresponding inclined surface of the nozzle body in a close contact manner. Therefore, the fuel flowing in the swirling passage can be prevented from leaking. Thus, the fuel can effectively be supplied to the swirl chamber, thereby applying sufficiently swirl force to each of the fuel injection holes.
The nozzle body and the orifice body covering the nozzle body are formed convexly; therefore, the fuel sprays jetted from the fuel injection holes machined perpendicularly to the inclined surface of the orifice plate can effectively be atomized without mutual interference (interference in a liquid-film state) and jetted in predetermined directions.
Preferred embodiments of the present invention will be described with reference to
A first embodiment of the present invention is described with reference to
Referring to
The fuel injection valve 1 includes a yoke 10 composed of a magnetic body surrounding the electromagnetic coil 11; a core 7 located at the center of the electromagnetic coil 11 and having one end in magnetic contact with the yoke 10; the valve body 6 to be lifted at a predetermined amount; a valve seat surface 3 in contact with the valve body 6; a fuel injection chamber 4 adapted to admit the passage of fuel flowing through the gap between the valve body 6 and the valve seat surface 3; and an orifice plate 20 having a plurality of fuel injection holes 23a, 23b, 23c (see
The core 7 has a spring 8 as an elastic member at its central portion. The spring 8 is adapted to press the valve body 6 toward the valve seat surface 3. The elastic force of the spring 8 is adjusted by the pressing amount of a spring adjuster 9 toward the valve seat surface 3.
In the state of the non-energization of the coil 11, the valve body 6 and the valve seat surface 3 are in close contact with each other. In this state, since a fuel passage is closed, fuel stays inside the fuel injection valve 1. That is, fuel is not jetted from each of the plurality of fuel injection holes 23a, 23b, 23c provided on the orifice plate.
On the other hand, if the coil 11 is energized, the valve body 6 is shifted by the electromagnetic force until it comes into contact with the lower end face of the core 7, to which the valve body 6 faces.
In the opened state, a clearance is produced between the valve body 6 and the valve seat surface 3; therefore, the fuel passage is opened so that fuel is jetted from the plurality of fuel injection holes 23a, 23b, 23c.
Incidentally, the fuel injection valve 1 is provided with a fuel passage 12 having a filter 14 disposed at its inlet portion. The fuel passage 12 includes a through-hole portion penetrating the central portion of the core 7 and is a passage adapted to lead the fuel pressurized by a fuel pump not shown to the fuel injection holes 23a, 23b, 23c through the inside of the fuel injection valve 1. The fuel injection valve 1 is coated on its outside portion with a resin mold 15 for electrical insulation.
The fuel injection valve 1 is operated by the energization (injection pulses) of the coil 11 as described above to switch the position of the valve body 6 between the opened state and the closed state, thereby controlling the supply quantity of fuel.
To control the supply quantity of fuel, the valve body is designed to prevent the leakage of fuel particularly in the closed state.
The fuel injection valve of this type uses a ball (a steel ball for a ball bearing as a JIS standard product) that has high circularity and is subjected to mirror finish. This ball is useful for improving seat performance.
On the other hand, the valve seat surface 3 in close contact with the ball is set at an optimum valve seat angle of 80° to 100° so as to have satisfactory abradability and circularity with a high degree of accuracy. Dimensional conditions that can maintain extremely high seat performance with the above-mentioned ball are selected for the valve seat surface 3.
Incidentally, the nozzle body 2 having the valve seat surface 3 is increased in hardness by quenching. Further, unnecessary magnetism is removed from the nozzle body 2 by demagnetization.
The configuration of the valve body 6 enables injection amount control without the leakage of fuel.
Incidentally, the vertical direction in the present specification and claims is based on
The nozzle body 2 is provided at its lower end portion with a fuel introduction hole 5 having a diameter smaller than an diameter φS of a seat portion 3a of the valve seat surface 3. The valve seat surface 3 is formed into a conical shape and has the fuel introduction hole 5 at the central portion of the downstream end thereof. The valve seat surface 3 and the fuel introduction hole 5 are formed so that the centerline of the valve seat surface 3 and the centerline of the fuel introduction hole 5 may coincide with the axis of the fuel injection valve. The fuel introduction hole 5 is formed at the lower end face of the nozzle body 2 as an opening communicating with a central hole (a central bore) 25 of the orifice plate 20.
The configuration of a plurality of fuel passages formed in the orifice plate 20 is previously described with reference to
The central hole 25 is a concavely shaped groove portion provided at the central portion of the orifice plate 20. Swirling passages 21a, 21b, 21c radially extend from the central hole 25. The swirling passages 21a, 21b, 21 have respective upstream ends communicating with the inner circumferential surface of the central hole 25.
The swirling passages 21a, 21b and 21c are connected at respective downstream ends to swirl chambers 22a, 22b and 22c, respectively, for communication with each other. The swirling passages 21a, 21b and 21c are respective fuel passages adapted to supply fuel to the swirl chambers 22a, 22b and 22c, respectively. In this sense, the swirling passages 21a, 21b, 21c may be called swirl fuel supply passages 21a, 21b, 21c.
The wall surfaces of the swirl chambers 22a, 22b, 22c are each formed such that its curvature is gradually increased (its curvature radius is gradually reduced) from the upstream side toward the downstream side. In this case, the curvature may continuously be increased. Alternatively, the curvature may gradually be increased stepwise from the upstream side toward the downstream side while it is made constant in a predetermined range. Representative examples of a curve line whose curvature is continuously increased from the upstream side toward the downstream side include an involute curve (shape) and a helical curve (shape). In the present embodiment, the swirl chambers 22a, 22b, 22c are formed based on the helical curve; however, the fuel injection holes 23a, 23b, 23c are each opened at the center of the helix (the center of a swirl).
Incidentally, if the involute curve line is used for each of the swirl chambers 22a, 22b, 22c, it is preferable that the center of a basic circle of the involute curve line be coincident with the center of the fuel injection hole 23a.
The downstream end of the sidewall of each of the swirling passages 21a, 21b, 21c and the terminal end of the inner circumferential wall of a corresponding one of the swirl chambers 22a, 22b, 22c are formed to have a connection surface (an R-portion) with a predetermined thickness. This thick portion is permitted to have a size in a range from approximately 0.01 mm to 0.1 mm. Preferably, a range from approximately 0.02 mm to 0.06 mm may preferentially be adopted.
Because of forming the thick portion as mentioned above, collision is alleviated between the fuel turning around each of the swirl chambers 22a, 22b, 22c and the fuel flowing into a corresponding one of the swirling passages 21a, 21b, 21c. Thus, the smooth flow of fuel along the helical wall surface of each of the swirl chambers 22a, 22b, 22c is formed.
The cross-sectional shape, vertical to the flow direction, of each of the swirling passages 21a, 21b, 21c is oblong (rectangular). The swirling passages 21a, 21b, 21c are each made to have height smaller than each width thereof, whereby they are designed to have dimensions advantageous to press forming.
Since the oblong portion is restricted in size (the minimum cross-sectional area), the fuel flowing into the swirling passages 21a, 21b, 21c can ignore a pressure loss from the seat portion 3a of the valve seat surface 3 via the fuel injection chamber 4, the fuel introduction hole 5, the central hole 25 of the orifice plate 20 to a corresponding one of the swirling passages 21a, 21b, 21c.
In particular, the fuel introduction hole 5 and the central hole 25 of the orifice plate 20 are each designed to provide the fuel passage with a desired size so as to prevent the occurrence of a pressure loss caused by sharp curve.
Accordingly, the pressure energy of fuel is efficiently converted into swirl velocity energy at a portion corresponding to each of the swirling passages 21a, 21b, 21c.
Additionally, the fuel flow accelerated by the oblong portion is led to each of the fuel injection holes 23a, 23b, 23c downstream of the corresponding swirling passages 21a, 21b, 21c while maintaining sufficient swirl strength, i.e., sufficient swirl velocity energy.
Incidentally, the swirl chambers 22a, 22b, 22c are each sized to have such a diameter as to reduce an influence of a friction loss resulting from a fuel flow and of a friction loss on the inside wall thereof as much as possible. The size of the diameter is such that about four to six times of the hydraulic diameter will be an optimum value. Also the present embodiment adopts this method.
In the present embodiment, the fuel passages each combined of the swirling passage 21, the swirl chamber 22 and the fuel injection hole 23 are installed so as to be divided equally among three. However, the fuel passages may be installed so as to be divided equally among the further increased number, thereby increasing the degree of freedom of variation in the shape of fuel spray and in injection quantity.
A method of processing the swirling passages 21a, 21b, 21c and the swirl chambers 22a, 22b, 22c and a method of assembling them are next described with reference to
The nozzle body 2 is formed with: the fuel introduction hole 5 located at its central portion; a mating surface 2a for the swirling passages and a mating surface 2b for the swirl chambers, the mating surface 2a and the mating surface 2b being inclined toward the upstream side from the fuel introduction hole 5; and a concave inside wall surface 2c, a bottom wall surface 2d and an outside wall surface 2e, which are continuous with the mating surface 2b for the swirl chambers.
The mating surface 2a for the swirling passages is a plane corresponding to the swirling passages 21a, 21b, 21c which are formed when the orifice plate 20 is fixedly inserted into the nozzle body 2.
The mating surface 2a for the swirling passages is not formed flush with the mating surface 2b for the swirl chambers. Specifically, the mating surface 2b side for the swirl chambers is located slightly higher than the mating surface 2a for the swirling passages. Thus, a slight step (about several ten microns) is formed between the mating surface 2a and the mating surface 2b.
The position of the step is indicated by an imaginary circle 26a illustrated in
In this way, the swirling passages 21a, 21b, 21c can be covered up to the terminal ends thereof by the mating surface 2a for the swirling passages. Thus, fuel leakage from the swirling passages 21a, 21b, 21c can be reduced.
The orifice plate 20 is formed in a convex shape toward the downside so as to have a lowest external surface at its central portion. In addition, the orifice plate 20 has a pressing surface 26 formed at the central portion on a lowest external surface thereof. The pressing surface 26 has a diameter smaller than that of the central hole 25 located at the central portion.
The pressing surface 26 is a pressing portion which is used during the stroke adjustment with the valve body 6 after the orifice plate 20 has been assembled to the nozzle body 2.
A pressing surface 29 is formed at the outer circumferential portion of an inclined surface.
The pressing surface 29 is a pressing portion which is used when the orifice plate 20 is assembled to the nozzle body 2.
On the other hand, the orifice plate 20 is formed, on an upper inside thereof, with the radially extending swirling passages 21a, 21b, 21c communicating with the central hole 25 and with the corresponding swirl chambers 22a, 22b, 22c.
A mating surface 20a for the swirling passages may be flush with a mating surface 20b for the swirl chambers. However, it is preferred that a slight step be formed between the mating surface 20a for the swirling passages and the mating surface 20b for the swirl chambers. In this case, it is preferred that the mating surface 20b for the swirl chambers be designed to be slightly offset toward the downside direction of the mating surface 2a for the swirling passages.
In this way, the mating surface 20a for the swirling passages and the mating surface 2a for the swirling passages come into contact with each other, which can reduce fuel leakage from the swirling passages 21a, 21b, 21c.
The orifice plate 20 has an outer shape portion formed to have a size in which the orifice plate fits to an outside wall surface 2e of the concave portion formed on the nozzle body 2. The orifice plate 20 is fixedly inserted into the nozzle body 2 by its outer shape portion being guided by the outside wall surface 2e. When the orifice plate 20 is fixedly press-fitted to the nozzle body 2, a flat surface portion on the outer circumferential side thereof is used as a pressing surface.
If the orifice plate 20 is fixedly press-fitted to the nozzle body 2, the mating surface 20a for the swirling passages of the orifice plate 20 comes into close contact with the mating surface 2a for the swirling passages of the nozzle body 2. The mating surfaces are formed to increase the degree of adhesion so as to have practically no gap therebetween.
On the other hand, the mating surface 20b for the swirl chambers of the orifice plate 20 and the mating surface 2b for the swirl chambers of the nozzle body 2 are formed to have a slight gap therebetween.
With the configuration described above, all the fuel flowing through the swirling passages 21a, 21b, 21c are supplied toward the corresponding swirl chambers 22a, 22b, 22c without leakage at least from the swirling passages 21a, 21b, 21c. Thus, the fuel flows into each of the swirl chambers 22a, 22b, 22c while keeping its pressure, thereby increasing swirl force.
A slight clearance δ3 (see
An inner circumferential-side wall surface 20c of the orifice plate 20 is formed to have a diameter greater than that of a concave inside wall surface 2c of the nozzle body 2. Because of this, a clearance δ1 is defined between the wall surface 20c and the inside wall surface 2c when the orifice plate 20 is fixedly inserted into the nozzle body 2.
A slight clearance δ2 is defined also between an outer circumferential end face 20d on an upper portion of the orifice plate 20 and a concave bottom face 2d of the nozzle body 2.
These clearances δ1, δ2 have the relationship of δ2>δ1. That is to say, the clearances are design to accommodate unnecessary deformation occurring when the orifice plate 20 is fixedly press-fitted to the nozzle body 2.
A description is given with reference to
In this case, although the wall surface 20c is slightly deformed, the clearance δ1 can accommodate the amount of the deformation.
Incidentally, the step is formed between the mating surface 2a for the swirling passages of the nozzle body 2 and the mating surface 2b for the swirl chambers. However, it is no problem that the mating surface 2a for the swirling passages of the nozzle body 2 and the mating surface 2b for the swirl chambers may continuously be connected to each other via a minute corner R or the like.
A fuel injection valve according to a second embodiment of the present invention is hereinafter described with reference to
The fuel injection valve of the second embodiment is different from that of the first embodiment in that a plurality of fuel introduction holes are provided at a lower end portion of the fuel injection valve. Thus, a fuel flow path from a fuel injection chamber is provided at a plurality of locations.
As shown in
The configuration described above can prevent the sharp curve of the fuel passage; therefore, a flow loss is extremely small and fuel flows from the fuel introduction holes 35a via the swirling passages 31a and reaches corresponding swirl chambers provided on the downstream thereof. Therefore, since swirling force is effectively applied to the fuel, a uniform fuel thin-film is jetted at the outlet of the fuel injection hole. As a result, the atomization characteristics of fuel are extremely superior and the same functions and effects as those of the first embodiment can be produced.
The embodiment described above concurrently has also the following functions and effects.
The volume of the fuel passage determined by the fuel injection chamber 4 and the fuel introduction holes 35a can sufficiently be reduced. Therefore, an extra route for flow from the fuel injection chamber 4 and the fuel introduction holes 35a to swirl chambers is eliminated. Thus, turbulence such as swirls or the like does not occur, thereby remarkably improving the robustness of an injection quantity and the shape control of fuel spray.
As described above, the fuel injection valve according to the embodiment of the present invention is such that the inclined surface for the swirling passages adapted to form swirl fuel in the orifice plate and the inclined surface of the nozzle body corresponding to the former inclined surface are brought into close contact with each other for fixation. This prevents the fuel passing through the swirl passages from leaking outwardly therefrom. Fuel is effectively supplied to the swirl chambers. Thus, the uniform and sufficient swirl force can be applied to the fuel for each of the fuel injection holes.
The nozzle body and the orifice plate covering the nozzle body are formed convexly. Accordingly, fuel sprays jetted from the fuel injection holes machined perpendicularly to the corresponding inclined surfaces do not interfere with each other. The interfere in a liquid membrane state, which poses a problem when the fuel injection holes are arranged close to each other, can be avoided. Thus, the fuel injection valve can be provided that is superior in atomization performance and in shape controllability.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-078785 | Mar 2012 | JP | national |
