FUEL INJECTION VALVE

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The inventionλelates to fuel injection valves that inject fuel into combustion chambers of an engine.

2. Description of the Related Art

[0002] Conventionally, a fuel injection system is used to supply fuel to an engine. The injection performance and characteristics that such a fuel injection system is required to provide are different in each engine speed range. More specifically, fuel needs to be atomized in a low engine-speed range, and fuel needs to be injected at a high injection rate in a high engine-speed range. To satisfy such requirements regarding fuel injection, fuel injection valves have been proposed that vary the number of injection holes that open during each injection.

[0003] One such fuel injection valve is described in Japanese Patent Application Publication No. 2007-71093 (JP-A-2007-71093). The fuel injection valve has a body having first injection holes and second injection holes formed at the lower end portion of the body. During fuel injection, the fuel injection holes are opened in two separate stages, that is, the first injection holes are first opened, and then second injection holes are opened. A first needle, which is cylindrical, is provided in the body and it opens and closes the first injection holes that are opened in the first stage of fuel injection, and a second needle is provided in the first needle and it opens and closes the second injection holes that are opened in the second stage of fuel injection. The first needle has a communication passage through which the outer peripheral side and the inner peripheral side of the first needle communicate with each other. That is, the space between the inner peripheral face of the first needle and the outer peripheral face of the second needle and the space on the outer peripheral side of the first needle communicate with each other via the communication passage formed in the first needle. According to

this structure, even if the fuel in the space between the inner peripheral face of the first needle and the outer peripheral face of the second needle decreases after the first and second fuel injection holes are opened, fuel is immediately supplied from the outer peripheral side of the first needle, and this minimizes the fluctuation of the pressure in said space and thus minimizes changes of the operation states of the first and second needles.

[0004] In a fuel injection valve that incorporates two or more needles arranged coaxially, there is a possibility that either or both of the needles may become eccentric due to errors or variations of manufacturing processes and/or due to variations of fuel inflows. If the needle of such a fuel injection valve thus becomes eccentric, the positional relation between the needle and the nozzle body of the fuel injection valve changes. In such a case, the needle becomes closer to the nozzle body on one side, and thereby narrowing the fuel passage_on the affected side. In this case, there is a possibility that fuel injection through the injection hole or holes on the affected side is performed like so-called hollow-cone fuel injection, or there is even a possibility that the injection hole or holes are closed, failing to inject fuel therefrom. In such case, a nonuniform fuel spray is formed in the engine cylinder, and this may result in an increase of smoke. Further, even if the eccentricity of the needle is low, the resultant pressure decrease at the side where the needle is closer to the nozzle body makes the needle more eccentric.

SUMMARY OF THE INVENTION

[0005] The invention provides a fuel injection valve that prevents a needle from becoming more eccentric.

[0006] The first aspect of the invention relates to a fuel injection valve, having: a nozzle body that has a first injection hole and a second injection hole; a first needle that is movably arranged in the nozzle body and opens and closes the first injection hole by moving up and down in the nozzle body; and a second needle that is movably arranged in the first needle and opens and closes the second injection hole by

moving up and down in the first needle, wherein a groove is formed in at least one of an inner peripheral face of the first needle and an outer peripheral face of the second needle so as to extend circumferentially.

[0007] According to the fuel injection valve described above, even if the first needle or the second needle becomes eccentric, it is prevented from becoming more eccentric. Conventionally, if a needle of a fuel injection valve becomes eccentric, the fuel passage in the fuel injection valve becomes narrower on one side and the pressure in the fuel passage on said side decreases, and this pressure decrease makes the eccentric needle more eccentric. According to the fuel injection valve of the first aspect of the invention, on the other hand, even if the first needle or the second needle becomes eccentric, fuel moves along the groove formed at the first or second needle from the region of the fuel passage where the passage area has increased as a result of the first or second needle having become eccentric to the region of the fuel passage where the passage area has decreased as a result of the first or second needle having become eccentric. As a result of such fuel movement in the fuel passage, the pressure in the fuel passage become even throughout its circumference, and therefore the aforementioned local pressure decrease in the fuel passage is suppressed, which prevents the eccentric needle from becoming more eccentric. In particular, it is to be noted that the groove may be formed in any shape along the circumference of the needle as long as it can properly reduce or eliminate pressure differences in the circumferential direction of the fuel passage.

[0008] The above-described fuel injection valve may be such that the groove extends over the entire circumference of the at least one of the inner peripheral face of the first needle and the outer peripheral face of the second needle.

[0009] Further, the above-described fuel injection valve may be such that the groove is formed to face a gap that is provided between the inner peripheral face of the first needle and the outer peripheral face of the second needle. According to this structure, the eccentric needle may be more effectively prevented from becoming more eccentric. If the first or second needle is eccentric, the pressure of fuel flowing in the

gap between the first and second needle becomes uneven in the circumferential direction. However, in the fuel injection valve described above, because fuel is evenly distributed all around the axes of the first and second needles through the groove, fuel pressure differences between respective circumferential positions of the gap between the first and second needles are minimized, and therefore the eccentric needle can be more effectively prevented from becoming more eccentric.

[OOIO] Further, the above-described fuel injection valve may be such that: a gap is provided between the inner peripheral face of the first needle and the outer peripheral face of the second needle, wherein the gap has a wide portion and a narrow portion, in which the distance between the inner peripheral face of the first needle and the outer peripheral face of the second needle of the wide portion is greater than that of the narrow portion; and the groove is formed facing the short-distance portion (29a) of the gap, and the groove is formed so as to face the short-distance portion of the gap .

[0011] According to this structure, the eccentric needle may be more effectively prevented from becoming more eccentric. As the first or second needle becomes eccentric, the pressure at the short-distance portion changes more largely than the pressure at the long-distance portion does, and such a pressure change in the short-distance portion makes the eccentric needle more eccentric. In view of this fact, in the fuel injection valve described above, the groove is formed so as to face the short-distance portion of the gap, and this more effectively suppresses changes in the pressure in the gap and thus more effectively prevents the eccentric needle from becoming more eccentric.

[0012] Further, the above-described fuel injection valve may be such that: a gap is formed between the inner peripheral face of the first needle and the outer peripheral face of the second needle; and the groove is formed in a region where the first needle maintains a specified clearance from the second needle and there is no point of contact between the first and second needles within the region. Further, the groove may face the gap wherever the first needle is located within a movement range of the first needle while the first needle is moving and wherever the first needle and the second

needle are located within movement ranges of the first needle and the second needle, respectively, while the first needle and the second needle are together moving.

[0013] According to this structure, because the groove is formed facing the gap wherever the first needle and the second needle are located while they are moving, an eccentric needle can be more effectively prevented from becoming more eccentric

[0014] Further, the above-described fuel injection valve may be such that a plurality of grooves are provided.

[0015] According to this structure, the grooves provide an increased flow of fuel, and this facilitate making the pressures around the needle even, and therefore the eccentric needle can be more effectively prevented from becoming more eccentric. Note that such an effect can be obtained also by increasing the width of the groove.

[0016] As such, the fuel injection valve of the invention prevents the eccentric needle from becoming more eccentric by making the pressure of fuel between the first and second needles even.

BRIEF DESCRIPTION QF THE DRAWINGS

[0017] The features, advantages, and technical and industrial significance of this invention will be described in the following detailed description of example embodiments of the invention with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG 1 is a view schematically showing a fuel injection valve according to the first example embodiment of the invention;

FIG. 2 is an enlarged view of the lower end portion of the fuel injection valve of the first example embodiment;

FIG. 3 A is an enlarged view of a portion of a second needle where grooves are formed;

FIG. 3B is a cross-sectional view taken along A-A in FIG. 3A, showing the grooves formed at the second needle;

FIG 4 is an enlarged view of the lower end portion of a fuel injection valve

according to the second example embodiment of the invention;

FIG. 5 is an enlarged view of the lower end portion of a fuel injection valve according to the third example embodiment of the invention;

FIG. 6A is a view showing grooves formed in a fuel injection valve according to other example embodiment; and

FIG. 6B is a cross-sectional view taken along B-B in FIG 6A, showing the grooves of the fuel injection valve in FIG. 6 A.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] Hereinafter, example embodiments of the invention will be described with reference to the drawings. FIG. 1 schematically shows the structure of a fuel injection valve 1 according to the first example embodiment of the invention. The fuel injection valve 1 has a nozzle body 4. First injection holes 2 and second injection holes 3 are formed at the lower end of the nozzle body 4. More specifically, the first injection holes 2 are radially formed around the axis of the nozzle body 4, and the inside of the nozzle body 4 communicates with the outside through the first injection holes 2. Likewise, the second injection holes 3 are also radially formed around the axis of the nozzle body 4, and the inside of the nozzle body 4 communicates with the outside through the second injection holes 3 as well. A first needle 5, which is cylindrical, is slidably arranged in the nozzle body 4. The fuel injection valve 1 is urged toward the lower end of the fuel injection valve 1 by a first spring 6. Fuel is supplied from the upper side of the nozzle body 4 to the outer peripheral side of the first needle 5. Further, a second needle 7, which is pointed on the lower side, is slidably arranged in the first needle 5. A flange 7a is formed at the upper portion of the second needle 7. The flange 7a is adapted to fit on an upper face 5 a of the first needle 5. The second needle 7 is urged toward the lower end of the fuel injection valve 1 by a second spring 8.

[0019] The second needle 7 has a large-diameter portion 7b and a small-diameter portion 7c. The large-diameter portion 7b is formed on the upper side of the second needle 7 and is slidable along an inner peripheral face 5b of the first needle 5.

The small-diameter portion 7c is formed on the lower side of the large-diameter portion 7b. A gap 9 that serves as a fuel passage is provided between the outer peripheral face of the small-diameter portion 7c of the second needle 7 and the inner peripheral face 5b of the first needle 5. Two grooves 10 are formed at the small-diameter portion 7c of the second needle 7 and extend over the entire circumference of the small-diameter portion 7c.

[0020] The first needle 5 has passages 5c through which the gap 9 and the outer peripheral side of the first needle 5 communicate with each other. Fuel flows from the outer side of the first needle 5 to the gap 9 through the passages 5c.

[0021] FIG. 2 is an enlarged view of the lower end portion of the fuel injection valve 1. Referring to FIG 2, sealing portions 5b, 5e are formed at the lower end of the first needle 5. In operation, as the first needle 5 moves downward, the sealing portions 5b, 5e are seated on seat faces 4a on the inner side of the nozzle body 4, whereby the first injection holes 2 are closed. A sealing portion 7d is provided at the lower end of the second needle 7. In operation, as the second needle 7 moves downward, the sealing portion 7d is seated on a seat face 4a on the inner side of the nozzle body 4, whereby the second injection holes 3 are closed.

[0022] Next, the operation of the fuel injection valve 1 will be described. Fuel is supplied from the upper side of the nozzle body 4 to the outer peripheral side of the first needle 5, and the pressure of the fuel produces force that is strong enough to lift the first needle 5 up against the urging force of the first spring 6. As the first needle 5 is lifted up, the sealing portions 5d, 5e move away from the respective seat faces 4a of the nozzle body 4, so that the first injection holes 2 are opened and fuel is injected from the first injection holes 2. Then, the first needle 5 stops when it hits the flange 7a. Then, as the pressure of the fuel on the outer peripheral side of the first needle 5 further increases from this state, the first needle 5 and the second needle 7 are both lifted up while being in contact with each other. As the second needle 7 is lifted up, the sealing portion 7d of the second needle 7 moves away from the seat faces 4a of the nozzle body 4, whereby the second injection holes 3 are opened and fuel may be injected through the

second injection holes 3.

[0023] Fuel enters the gap 9 both when the first needle 5 is moved and when the first needle 5 and the second needle 7 are together moved. Further, if fuel has been injected from the first injection holes 2 only as described above, the fuel in the lower side of the gap 9 flows out from the first injection holes 2. Likewise, if fuel has been injected from the first injection holes 2 and the second injection holes 3 as described above, the fuel in the lower side of the gap 9 flows out from the first injection holes 2 and the second injection holes 3. Further, fuel enters the gap 9 from the outer peripheral side of the first needle 5 through the passages 5c. As such, fuel flows through the gap 9. The grooves 10 are positioned so that the grooves 10 face the gap 9 wherever the first needle 5 is located within its movement range while the first needle 5 is moving and wherever the first needle 5 and the second needle 7 are located in their movement ranges while the first needle 5 and the second needle 7 are together moving. That is, the grooves 10 face the inner peripheral face 5b of the first needle 5 even when the second needle 7 is at the position where it closes the injection holes 3 while the upper face 5a of the first needle 5 is in contact with the flange 7a of the second needle 7.

[0024] Next, the effects of the fuel injection valve 1 structured as described above will be described with reference to FIG 3 A and FIG 3B. Note that the arrows in FIG 3A and 3B indicate the movement directions of fuel. FIG 3A is an enlarged view of where the grooves 10 are formed. FIG 3B is a cross sectional view taken along the line A-A in FIG 3A. That is, the cross section shown in FIG 3B shows the structure on a plane extending through one of the grooves 10. The first needle 5 or the second needle 7 may become eccentric due to errors and variations in the processes for manufacturing the fuel injection valve 1 and/or due to variations of fuel inflows. If the first needle 5 or the second needle 7 becomes eccentric, referring to FIG 3B, a wide-gap region 9a and a narrow-gap region 9b of the gap 9 are created in the radial direction of the needles 5, 7 [NOTE: Please confirm that 9a and 9b are indicated in the Figure. They are absent in the copy I have (it appears to be marked 9 (wide) and 9 (narrow) instead.]. If the grooves 10 are not formed, and the first needle 5 or the second needle 7

becomes eccentric and the wide-gap region 9a and the narrow-gap region 9b of the gap 9 are thus created, the pressure in the narrow-gap region 9b decreases to an extent that said pressure decrease attracts the eccentric needle, which increases the eccentricity of the needle. On the other hand, if the grooves 10 are formed as described above, fuel moves along the grooves 10 as shown in FIG. 3B and this fuel movement cancels the pressure difference between the wide-gap region 9a and the narrow-gap region 9b that may arise if the needle becomes eccentric, and this prevents the eccentric needle from becoming more eccentric.

[0025] Next, the second example embodiment of the invention will be described. FIG. 4 is an enlarged view of the lower end portion of a fuel injection valve 21 according to the second example embodiment of the invention. The structure of the fuel injection valve 21 is identical to the structure of the fuel injection valve 1 of the first example embodiment except that the fuel injection valve 21 incorporates a second needle 27 instead of the second needle 7 of the fuel injection valve 1. The second needle 27 has a small-diameter portion 27c that corresponds to the small-diameter portion 7c of the second needle 7 of the first example embodiment. The second needle 27 differs from the second needle 7 in that the small-diameter portion 27c has a first small-diameter portion 27cl and a second small-diameter portion 27c2. The diameter of the first small-diameter portion 27cl of the second needle 27 is equal to the diameter of the small-diameter portion 7c of the second needle 7, and two grooves 37 are formed at the first small-diameter portion 27cl so as to extend over the entire circumference of the first small-diameter portion 27cl. The diameter of the second small-diameter portion 27c2 is smaller than the first small-diameter portion 27cl. A sealing portion 27d is provided at the lower end of the second needle 27. Because other portions of the fuel injection valve 21 are identical to those of the fuel injection valve 1 of the first example embodiment, the structures are denoted by the same reference numerals in FIG 4 and their details are not described here again.

[0026] A gap 29 that serves as a fuel passage is provided between the inner peripheral face 5b of the first needle 5 and the small-diameter portion 27c of the second

needle 27. The gap 29 is composed of a short-distance portion 29a that is located between the inner peripheral face 5b of the first needle 5 and the first small-diameter portion 27cl of the second needle 27 and a long-distance portion 29b that is located between the inner peripheral face 5b of the first needle 5 and the second small-diameter portion 27c2 of the second needle 27. Grooves 30 are formed so as to face the short-distance portion 29a of the gap 29.

[0027] According to the the fuel injection valve 21 of the second example embodiment, fuel moves through the grooves 30 that face the gap 29, and this fuel movement cancels the pressure difference that is caused by the needle having become eccentric, and this prevents the eccentric needle from becoming more eccentric.

[0028] Next, the third example embodiment of the invention will be described. FIG. 5 is an enlarged view of the lower end portion of a fuel injection valve 41 according to the third example embodiment of the invention. The structure of the fuel injection valve 41 is similar to the structure of the fuel injection valve 1 of the first example embodiment except that the fuel injection valve 41 incorporates a first needle 45 and a second needle 47 in place of the first needle 5 and the second needle 7 of the fuel injection valve 1 of the first example embodiment.

[0029] The second needle 47 has a large-diameter portion 47b a small-diameter portion 47c. The large-diameter portion 47b is provided at the upper side of the second needle 47 and is slidable along the inner peripheral face 45b of the first needle 45. The small-diameter portion 47c is provided below the large-diameter portion 47b. A gap 49 is formed between the small-diameter portion 47c and the inner peripheral face 45b of the first needle 45. Two grooves 50 formed in the inner peripheral face 45b of the first needle 45 extend over the entire circumference of the inner peripheral face 45b. The first needle 45 has passages 45c through which the gap 49 is communicated with the outer peripheral side of the first needle 45. Sealing portions 45d, 45e are provided at the lower end of the first needle 45, and a sealing portion 47d is provided at the lower end of the second needle 47. Note that other structures of the fuel injection valve 41 are identical to those of the fuel injection valve 1 of the first example

embodiment and therefore said structures are denoted by the same reference numerals in FIG 5 and their details are not described here again.

[0030] According to the above-described structure of the fuel injection valve 41, fuel moves through the grooves 50 that face the gap 49, and this fuel movement cancels the pressure difference that is caused by the needle having become eccentric, and this prevents the eccentric needle from becoming more eccentric.

[0031] While the invention has been described with reference to the foregoing example embodiments, it should be understood that the invention is not restricted to the described embodiments. To the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the example embodiments are shown in various example combinations and configurations, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the invention. For example, while two grooves are formed in each of the foregoing example embodiments, only a single groove may be formed, or three or more grooves may be formed. Further, the grooves may be formed in both the first and second needles.

[0032] Further, the grooves formed in each needle may be C-shaped grooves as in the example illustrated in FIG 6A and FIG 6B. FIG. 6A and FIG 6B illustrate a portion of a first needle 57 having C-shaped groves 60. FIG 6A shows a front view of the first needle 57, and FIG 6B shows the cross section taken along the line B-B in FIG. 6 A. The C-shaped grooves may be formed in any of the above-described fuel injection valves of the invention. Note that the grooves 60 are formed such that non-grooved portions 61 of the respective grooves 60 do not overlap each other in any radial direction of the first needle 57.