Patent Application
20130255640
The present invention relates to a fuel injection valve for use with an internal combustion engine and, more particularly, to a fuel injection valve which has plural fuel injection holes, each injecting swirling fuel to promote atomization of the fuel, and which can control the spray pattern.
A fuel injection valve set forth in JP-A-2008-280981 is known as a conventional technique for achieving promotion of atomization of fuel sprayed from plural fuel injection holes and controlling the spray pattern by making use of swirling stream.
This fuel injection valve has a valve body capable of being opened and closed to permit and stop injection of fuel, a seat portion capable of being brought into intimate contact with the valve body to stop injection of fuel, and an orifice plate disposed downstream of both the valve body and the seat portion and having fuel injection holes from which fuel is ejected. Atomized, curved swirling spray is ejected from the fuel injection holes.
Furthermore, in this fuel injection valve, the orifice plate has the fuel injection holes from which fuel is sprayed, a swirling chamber in which fuel is swirled, and a fuel intake passage for introducing fuel into the swirling chamber. The center of each fuel injection hole is offset a different amount from the center axis of the fuel intake passage. The fuel injection hole having a smaller amount of offset sprays atomized fuel over a smaller angle. The fuel injection holes having larger amounts of offset provide plural sprays of swirling and curved atomized fuel. Owing to this configuration, the amount of fuel adhering to the intake valve (bottom) of the engine and to the inner wall surface of the cylinder is reduced. As a result, a homogeneous air-fuel mixture is produced. Hence, a decrease in the amount of soot contained in the exhaust gas and higher engine output can be accomplished.
On the other hand, a fuel injection valve set forth in JP-A-2001-317434 is known as a conventional technique for obtaining a highly atomized spray by making use of a swirling force.
In this fuel injection valve, the outer surface of each fuel injection hole for ejecting swirled fuel on the exit side is formed by first and second surfaces. The first surface includes the exit of the fuel injection hole. The second surface is spaced from the fuel injection hole, has a wall opposite to the ejected spray, and protrudes from the first surface. Thus, the ejected spray consists of a central portion and an outer portion. The outer portion is composed of a thick spray portion having a wide spread circumferentially and a thin spray portion having a narrow spread. As a result, the spray is shaped in an integrated flattened form.
This flattened spray form permits the thick spray portion having a wide spread to be directed toward the inner wall surface that is opposite to the inner wall of the intake pipe on which a fuel injection valve is disposed. Furthermore, the thick spray portion can be symmetrically directed toward the central partition wall located in the center of the intake valve. Consequently, fuel and air can be mixed efficiently while suppressing fuel deposition on the inner wall surface of the intake pipe. Thus, purification of exhaust emission and improvement of the fuel consumption can be accomplished.
It is known that if swirled fuel is sprayed, the spray assumes a hollow conical form. Since this kind of spray has a high degree of atomization, the ejected spray shows a less penetration. Furthermore, the spray is easily biased in a certain direction under the influences of motion of air within the ambient into which the spray is injected and of flow of the gas. In consequence, the spray structure needs to be designed ingeniously. For example, a desired function needs to be imparted to arbitrary portions of the spray.
In the conventional technique set forth in the above-cited JP-A-2008-280981, the center of each fuel injection hole is offset relative to the center axis of the fuel intake passage. A spray of a narrow angle is produced from each fuel injection hole having a smaller amount of offset. On the other hand, a curved spray of a wide angle is created from each fuel injection hole having a larger amount of offset. The curved sprays are plural in number and directed in different directions without in contact with each other. With such a spray structure, sprays narrow angle and sprays of wide angle minimally affect each other. Accordingly, when the spray structure (such as spread of each spray or penetration) is modified, it follows that the amount of offset of the fuel intake passage is varied. In this technique, the diameters of grain particles of spray are varied or the spray pattern is varied greatly. It can be said that this is undesirable for the design.
In the conventional technique set forth in the above-cited JP-A-2001-317434, it is possible to vary the shape of the spray structure consisting of thick spray portions of wide angle and thin spray portions of narrow angle but it is difficult to greatly vary the spray pattern.
In view of the foregoing circumstances, the present invention has been made. It is an object of the present invention to provide a fuel injection valve capable of better controlling the shape of a fuel spray structure by appropriately adjusting the injection characteristics of fuel injection holes (such as direction, strength of swirling motion, and distance) from which swirled fuel is ejected.
The present invention provides a fuel injection valve having: swirl chambers having inner walls whose curvature is gradually increased from upstream to downstream along flow of fuel; passages for swirling motion, the passages permitting introduction of fuel into the swirl chambers; fuel injection holes opening into the swirl chambers and including at least two narrow-angle injection holes and a wide-angle injection hole from which at least two narrow-angle sprays and a wide-angle spray are respectively ejected; and an orifice plate provided with the injection holes and having a center. The narrow-angle injection holes are spaced a given distance from the center of the orifice plate. The wide-angle injection hole is formed on a line perpendicularly intersecting a line segment that interconnects the centers of the narrow-angle injection holes.
According to the present invention, the narrow-angle sprays are ejected from weakly swirling chambers where weakly swirled fuel is created. The wide-angle spray where higher levels of atomization are achieved is ejected from a strongly swirling chamber in which strongly swirled fuel is created. The narrow-angle sprays can prevent scattering of the wide-angle spray and urge the wide-angle spray downward. In consequence, a spray structure which has good levels of atomization and whose shape or pattern can be controlled well can be formed.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.
The preferred embodiments of the present invention are hereinafter described with reference to
The first embodiment (embodiment 1) of the present invention is described below by referring to
The fuel injection valve 1 has a yoke 10 made of a magnetic material around the electromagnetic coil 11, a core 7 located at the center of the coil 11 and having its one end magnetically coupled to the yoke 10, the aforementioned valve body 6 capable of being lifted a given distance, a valve seat surface 3 in contact with the valve body 6, a fuel injection chamber 4 (see
A spring 8 acting as a resilient member pushing the valve body 6 against the valve seat surface 3 is mounted in the center of the core 7. The resilient force of the spring 8 is adjusted by the extent to which a spring adjuster 9 is pushed in toward the valve seat surface 3.
When the coil 11 is not electrically energized, the valve body 6 is kept in intimate contact with the valve seat surface 3. Under this condition, the fuel passage is closed and, therefore, fuel stays in the fuel injection valve 1 and is prevented from being ejected from the fuel injection holes 23a, 23b, 23c.
On the other hand, when the coil 11 is electrically energized, the resulting electromagnetic force moves the valve body 6 into contact with the opposite, lower end surface of the core 7.
When the valve is open in this way, a gap is created between the valve body 6 and the valve seat surface 3 and so the fuel passage is opened to permit fuel to be ejected from the fuel injection holes 23a, 23b, 23c.
The fuel passage 12 having a filter 14 in its entrance is formed in the fuel injection valve 1. The passage 12 includes a hole portion extending through the center of the core 7. The fuel passage 12 guides fuel under pressure by a fuel pump (not shown) through the fuel injection valve 1 into the fuel injection holes 23a, 23b, 23c. The fuel injection valve 1 is coated on its outside with a molded plastic part 15 such that the valve is electrically insulated.
As described previously, the position of the valve body 6 is switched in response to injection pulses to the coil 11 such that it is electrically energized, whereby the fuel injection valve 1 is opened and closed. Thus, the amount of supplied fuel is controlled.
To control the amount of supplied fuel, the valve body is designed so that fuel does not leak, especially when the valve is closed.
In this type of fuel injection valve, a mirror-finished ball (such as a steel ball adapted as a ball bearing conforming with the Japanese Industrial Standards) having a high degree of circularity is used as the valve body 6. This is advantageous for improvement of the seatability.
The valve seat angle of the valve seat surface 3 with which the ball makes intimate contact is set to an optimum angle, from 80 degrees to 100 degrees, at which good grindability can be obtained and which permits the degree of circularity to be achieved accurately. The dimensions of the valve seat surface are so set that the ball can be kept seated on it quite well.
The hardness of the nozzle body 2 having the valve seat surface 3 has been enhanced by quenching. Furthermore, unwanted magnetism has been removed from the nozzle body by demagnetization.
This structure of the valve body 6 permits leakproof control of fuel delivery rate.
In the present specification including the claims, the up and down direction is defined as shown in
A fuel intake hole 5 having a diameter smaller than the diameter φS of the seat portion 3a of the valve seat surface 3 is formed in the lower end of the nozzle body 2. The valve seat surface 3 is conical in shape. The fuel intake hole 5 is formed in the center of the downstream end of the valve seat surface 3. The valve seat surface 3 and the fuel intake hole 5 are so formed that the center line of the valve seat surface 3 and the center line of the fuel intake hole 5 are coincident with the axial center Z of the valve. The fuel intake hole 5 forms an opening in the lower end surface of the nozzle body 2, the opening being in communication with a central hole 24 in the orifice plate 20.
The central hole 24 is concave and formed in the top surface 20a of the orifice plate 20. Passages 21a, 21b, and 21c for swirling motion extend radially from the central hole 24. The passages 21a, 21b, and 21c for swirling motion have upstream ends which open into the inner surface of the central hole 24 and are in communication with the central hole 24.
The downstream end of the passage 21a for swirling motion, the downstream end of the passage 21b for swirling motion, and the downstream end of the passage 21c for swirling motion are communicatively connected to the swirl chambers 22a, 22b, and 22c, respectively. The passages 21a, 21b, and 21c for swirling motion are fuel passages permitting fuel to be supplied into the swirl chambers 22a, 22b, and 22c, respectively. In this meaning, the swirl passages 21a, 21b, and 21c may be referred to as swirling fuel supply passages 21a, 21b, and 21c, respectively.
The wall surfaces of the swirl chambers 22a, 22b, and 22c are so formed that they gradually increase in curvature (decrease in radius of curvature) from upstream to downstream. The curvatures may continuously increase. Alternatively, the curvatures may increase in steps from upstream to downstream, i.e., the curvatures are kept constant within a given range.
One typical example of a curve whose curvature increases gradually from upstream to downstream is an involute curve. Another example is a spiral curve. In the present embodiment, a spiral curve is taken as an example. A different curve as described above which gradually increases in curvature from upstream to downstream may similarly be adopted.
The narrow-angle injection holes 23a and 23b and the wide-angle injection hole 23c open into the centers of the swirl chambers 22a, 22b, and 22c, respectively.
The nozzle body 2 and orifice plate 20 are so configured that they can be placed in position easily and that they can be assembled together at enhanced dimensional accuracy.
The orifice plate 20 is fabricated by press forming that is advantageous for mass productivity. It is conceivable that other method such as electric discharge machining, electroforming, or etching which gives high machining accuracy without applying large stresses could be adopted.
The structure of the orifice plate 20 is next described in detail by referring to
The orifice plate 20 is provided with the central hole 24 in communication with the fuel intake hole 5. The three passages 21a, 21b, and 21c for swirling motion extend radially outwardly, are connected to the central hole 24, and are arranged in an opposite relation to each other.
If the outside diameter of the central hole 24 is set equal to the width of the passages 21a-21c for swirling motion, the flow through the passages 21a-21c is not hindered at all.
The downstream end of one passage 21a for swirling motion communicatively opens into the entrance of the swirl chamber 22a. The narrow-angle injection hole 23a opens into the center of the swirl chamber 22a.
In the present embodiment, the inner wall of the swirl chamber 22a is formed so as to draw a spiral curve on a plane (cross section) perpendicular to the center axis (Z in
Where the swirl chamber 22a is formed as an involute curve, the center of the basic circle of the involute curve is preferably coincident with the center of the narrow-angle injection hole 23a.
The narrow-angle injection hole 23a is spaced a given distance from the center O of the orifice plate 20.
The swirl chamber 22b and the narrow-angle injection hole 23b are in communication with the downstream end of the other passage 21b for swirling motion. This swirl chamber 22b is designed in the same way as the swirl chamber 22a.
The narrow-angle injection hole 23b is spaced a given distance from the center O of the orifice plate 20.
The swirl chamber 22c and wide-angle injection hole 23c are in communication with the downstream end of the further passage 21c for swirling motion. This swirl chamber 22c is designed in the same way as the swirl chamber 22a.
The wide-angle injection hole 23c is formed on a line that is at right angles to a line segment intersecting the center of the narrow-angle injection hole 23a and the center of the narrow-angle injection hole 23b.
The swirl chambers 22a and 22b are arranged on the Y-axis as shown in
The swirl chamber 22a is arranged on the Y-axis. Therefore, the narrow-angle injection hole 23a located at the (vortical) center of the swirl chamber 22a drawing a spiral curve and the narrow-angle injection hole 23b located at the center of the swirl chamber 22b are arranged on the Y-axis.
As shown in
Because of this structure, the axial length l1 (
As a result, a stream that draws in air is generated as indicated by arrows 26 in
Patterns of sprays of the ejected fuel, the positional relationship between the sprays, and their mutual interaction are next described by referring to
Narrow-angle sprays 30 and 31 have been ejected from the narrow-angle injection holes 23a and 23b, respectively. A wide-angle spray 32 has been ejected from the wide-angle injection hole 23c.
Since the swirl chambers 22a and 22b weakly swirl fuel, the sprays 30 and 31 are narrow-angle sprays. The narrow-angle sprays 30 and 31 consist of filmy liquid regions 30a, 31a formed over relatively long ranges, split regions 30b, 31b generated by filamentary liquid caused by flapping caused by the velocity difference with the atmosphere, and atomized spray regions 30c, 31c, respectively.
On the other hand, the spray 32 is a wide-angle spray because the swirl chamber 22c strongly swirls fuel. Since the liquid film of this wide-angle spray 32 is thinned, the liquid film region 32a is short and thus filamentary liquid is created quickly in the split region 32b. Consequently, a transition to an atomized region 32c is made quickly. Also, the distance traveled to this atomized region is short.
The air guide hole 25 formed at the exit of the wide-angle injection hole 23c acts to stabilize flow of air created by the generation of the wide-angle spray 32 and to supply the flow to the liquid film region 32a. The guide hole contributes to splitting of the liquid film region 32a, i.e., contributes to promotion of atomization.
As is obvious from the figure, considerations are given to the narrow-angle sprays 30, 31 and to the wide-angle spray 32 such that no collision occurs among the filmy liquid regions 30a, 31a, and 32a. This indicates that the grain diameters are prevented from increasing. That is, our experimental analysis has demonstrated that if the liquid film regions collide against each other as they are, the energy causing atomization of fuel made into a thin film by swirling force will be lost and that the film will be thickened conversely, leading to increases in grain diameters.
The cross sections of the swirling passages 21a, 21b, and 21c taken perpendicularly to the direction of flow are rectangular. The swirling passages 21a, 21b, and 21c are so designed that their heights are made small compared with their widths. This is advantageous for press forming.
Since fuel flowing into the passages 21a, 21b, and 21c for swirling motion is restricted by their rectangular portions having their minimum areas, the loss of pressure of the fuel experienced when flowing from the seat portion 3a of the valve seat surface 3 to the swirling passages 21a, 21b, and 21c through the fuel injection chamber 4, fuel intake hole 5, and central hole 24 in the orifice plate 20 can be neglected.
Especially, the fuel intake hole 5 and the central hole 24 in the orifice plate 20 are so designed that they form fuel passageways of a desired size to prevent occurrence of pressure loss due to steep bending.
Accordingly, the pressure energy of the fuel is efficiently converted into velocity energy of swirling motion by the passages 21a, 21b, and 21c for swirling motion.
The flow of fuel accelerated by these rectangular portions is guided into the downstream narrow-angle injection holes 23a, 23b and wide-angle injection hole 23c, while the strength of the swirling motion, i.e., swirling velocity energy, is maintained sufficiently.
The diameter of the swirl chambers 22a, 22b, and 22c is so determined that the effects of frictional loss caused by the flow of fuel and frictional loss on the inner wall are minimized. It is said that optimum values of the diameter are approximately 4 to 6 times the hydraulic diameter. In the present embodiment, this principle is adopted.
The relationship among the swirling passages 21b, 22b, and narrow-angle injection hole 23b and the relationship among the swirling passages 21c, 22c, and wide-angle injection hole 23c are the same as the aforementioned relationship among the swirling passage 21a, 22a, and narrow-angle injection hole 23a. Therefore, a description of the former relationship is omitted here.
In the present embodiment, the center axes of the narrow-angle injection holes 23a, 23b, and wide-angle injection hole 23c are parallel to the axis of the fuel injection valve. The center axes may be tilted to provide wider latitude in determining the shapes or pattern of the sprays.
A fuel injection valve associated with a second embodiment (embodiment 2) of the present invention is described below by referring to
The difference with the fuel injection valve associated with the first embodiment is that the exit surface of the wide-angle injection hole 42 varies in stepwise manner, thus forming a step 43.
As shown in
Because of this structure, the spray ejected from the wide-angle injection hole 42 forms a wide-angle spray in the same way as in the first embodiment. Flow of air is generated in the liquid film region of this spray (at the outer fringes of the exit of the spray) as indicated by arrow 44 in
The air guide wall 41 operates to stably generate the flow of air at the outer fringes of the spray. Splitting into liquid films is maintained. As a result, the same advantageous effects as the first embodiment can be obtained.
A fuel injection valve associated with a third embodiment (embodiment 3) of the present invention is described below by referring to
The difference with the fuel injection valve associated with the first embodiment is that the surface of the wide-angle injection hole 52 which is located on the exit side is tilted.
As shown, the tilted portion 51 serves to shorten the axial length of the wide-angle injection hole 52. Substantially, the length of the wide-angle injection hole 52 is laterally nonuniform as shown.
Because of this structure, the spray ejected from the wide-angle injection hole 52 is a wide-angle spray in the same way as in the first embodiment. This spray is tilted to the left through angle a as viewed in
A deflected spray 57 has been ejected from the wide-angle injection hole 52. Narrow-angle sprays 55 and 56 have been ejected from the narrow-angle injection holes 53 and 54, respectively.
Since fuel is swirled weakly, the narrow-angle sprays 55 and 56 form only narrow angles. The narrow-angle sprays 55 and 56 consist of liquid film regions 55a and 56a formed over relatively long ranges, split regions 55b and 56b generated by filamentary liquid generated by flapping caused by a velocity difference with the atmosphere, and atomized spray regions 55c and 56c, respectively.
On the other hand, the deflected spray 57 becomes a wide-angle spray because fuel is swirled strongly. This deflected spray 57 forms a thinned liquid film and so the liquid film region 57a is short. Accordingly, filamentary liquid is generated quickly in the split region 57b. Fuel makes a quick transition to the atomized region 57c. As a result, the spray travels a shorter distance.
As is obvious from
Consequently, the same advantageous effects as the first embodiment can be obtained. In any of the above-described embodiments, the diameter of the fuel injection holes is sufficiently large. If the diameter is increased, the cavities formed inside can be increased in size. This can contribute to thinning of film generated by ejected fuel without losing the swirling velocity energy at the injection holes.
If the ratio of the diameter of the injection holes to the depth of the injection holes is reduced, the loss of the swirling velocity energy is reduced to a minimum. Accordingly, the atomization characteristics of fuel are quite excellent.
Furthermore, if the ratio of the diameter of the injection holes to the depth of the fuel injection holes is reduced, the press formability is improved. Of course, this structure contributes to a cost reduction. Additionally, dimensional variations are suppressed by improvement of machinability. Consequently, the robustness of the spray pattern and the spray rate is improved greatly.
An example in which the sprays of the present embodiment is applied to a multicylinder internal combustion engine is next described.
Indicated by 101 is one cylinder of the multicylinder internal combustion engine. The fuel injection valve 100 has two intake valves arranged to be directed toward an intake port 108. Also shown are a combustion chamber 102, a piston 103 including a cavity 104, another cylinder 105, and a cylinder head 106. Also shown are intake valves 107, an intake passage 111, exhaust valves 109, an ignition plug 110, and an intake flow controller 112. The intake passage 111 has a central partition wall 108a that separates the intake port 108, and is connected on its upstream side. Each fuel injection valve 100 is mounted one by one on the upstream side. A fuel injection system employing multipoint injection is constituted. The fuel injection valves 100 are driven by control signals produced from an engine controller (not shown).
In order to improve the quality and state of the formed air-fuel mixture within the cylinders, the sprays 30, 31, and 32 are more atomized. Furthermore, in order to reduce adhesion of fuel to the inner wall surface of the cylinder head 106 and of the intake passage 111, the directionality and shapes of the sprays are optimized. That is, the sprays from the fuel injection valves 100 of the present embodiment are slightly spread on the inner wall surface of the intake passage 111. Furthermore, as shown in
Especially, high-density portions of the narrow-angle sprays 30 and 31 are directed to the centers of the stems and float near the central partition wall 108a of the intake passage 111 to prevent adhesion to the inner wall 108b. The wide-angle spray 32 is directed to the wall surface opposite to the wall surface to which the fuel injection valves 100 are mounted. Thus, this spray is carried by the intake flow into the cylinder 105.
Experiments on combustions in the internal combustion engine have shown that the emission performance and fuel consumption have been improved. It has been confirmed that the sprays from the fuel injection valves 100 suppress adhesion of fuel to the inner wall surface of the intake pipe, thus improving the quality and state of the formed air-fuel mixture.
As described so far, a fuel injection valve associated with each embodiment of the present invention has: swirl chambers having inner walls whose curvature increases gradually from upstream to downstream along flow of fuel; passages for swirling motion, the passages permitting introduction of fuel into the swirl chambers; fuel injection holes opening into the swirl chambers; and an orifice plate provided with the injection holes. The fuel injection holes include at least two narrow-angle injection holes and a wide-angle injection hole from which at least two narrow-angle sprays and a wide-angle spray are respectively ejected. The narrow-angle injection holes from which the narrow-angle sprays are ejected are spaced a given distance from the center O of the orifice plate. The wide-angle injection hole from which the wide-angle spray is ejected is formed on a line that perpendicularly intersects a line segment interconnecting the centers of the narrow-angle injection holes.
As a consequence, the narrow-angle spray ejected from the weak swirl chambers 22a and 22b can prevent scattering of the wide-angle spray, which is ejected from the strong swirl chamber 22c and is well atomized, and urge the wide-angle spray downward. Hence, a spray structure having excellent atomization characteristics and shape controllability can be formed.
It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-078786 | Mar 2012 | JP | national |
