FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION [See section 10, Rule 13]
FUEL INJECTION VALVE;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

DESCRIPTION TECHNICAL FIELD
[0001] The present invention relates to a fuel injection valve that is used to supply fuel to an internal combustion engine of an automobile, etc., and particularly relates to a fuel injection valve that achieves promotion of atomization in spraying characteristics.
BACKGROUND ART
[0002] In recent years, with exhaust gas regulations for internal combustion engines of automobiles, etc., having been tightened, there is a demand for atomization of fuel sprays that are emitted from fuel injection valves. Various studies have been made on methods for achieving atomization with use of a swirl flow.
Patent Document 1 discloses the following fuel injection. That is, in a type in which a valve closing member that cooperates with a valve seat surface is disposed in a valve casing, a center opening is provided downstream of the valve seat surface, at least two tangential passages extend in a radial direction from the center opening, the respective tangential passages are open at respective swirl chambers in a tangential direction, and a constant-quantity opening for fuel leads from the center of each swirl chamber to the outside.

CITATION LIST
PATENT DOCUMENT
[0003] Patent Document 1: Japanese Laid-Open Patent
Publication No. 1-271656
SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION
[0004] In the case of the fuel injection valve using a swirl flow as in the conventional example described above, if impurities contained in the fuel are accumulated in a fuel passage, the fuel flow is stagnated, and thus, the speed of the fuel flowing into a swirl chamber is decreased. Accordingly, the angular velocity at the time of swirling of the fuel is decreased. The angular velocity in the swirl chamber influences performances such as the spray spread angle and spray atomization after fuel injection. Consequently, if impurities contained in the fuel are deposited in the fuel passage, variation in the spray spread angle and deterioration of spray atomization could be caused. [0005] The present invention has been made in consideration of the above circumstances. An object of the present invention is to provide a fuel injection valve in which a recess that allows impurities to be deposited therein is provided in a swirl chamber, whereby spraying

characteristics are maintained in a favorable state even when impurities have been deposited.
SOLUTION TO THE PROBLEMS
[0006] A fuel injection valve according to the present invention has a valve body for opening and closing a valve seat. In the fuel injection valve, as a result of operation of the valve body, fuel is injected through a plurality of injection holes provided in an injection hole plate mounted to a downstream-side opening portion of the valve seat. The injection hole plate includes: a swirl chamber for providing swirling force to the fuel and for injecting the fuel through each injection hole to outside; and a fuel passage for introducing the fuel into the swirl chamber. The fuel passage has, at a place where a side wall portion and a bottom portion thereof cross each other, a recess obtained by recessing the side wall portion of the fuel passage in a direction in which the fuel passage is expanded.
EFFECT OF THE INVENTION
[0007] In the fuel injection valve according to the present invention, fuel having flowed through the valve seat opening portion into each swirl chamber flows into the injection hole while causing a swirl flow. By the swirl flow being maintained also within the injection hole, a thin

liquid film is formed along the inner wall of the injection hole, and the thin liquid film is injected in a hollow conical shape through the injection hole, whereby atomization of the fuel is promoted.
Further, at a place where the side wall portion and the bottom portion of the fuel passage cross each other, the fuel passage has a recess obtained by recessing the side wall portion of the fuel passage in a direction in which the fuel passage is expanded. Accordingly, in the recess, the flow velocity becomes lower than that in the center portion of the fuel passage. Therefore, impurities in the fuel are easily deposited in the recess. Since the flow velocity is low in the recess, even if impurities are deposited in the recess, the mean flow velocity in the fuel passage is not varied substantially. Thus, the influence on the angular velocity of the fuel flowing in and swirling in the swirl chamber is small. The angular velocity in the swirl chamber influences the spraying characteristics after the fuel injection.
Therefore, by the provision of the recess in the fuel passage, occurrence of variation in the spray spread angle and deterioration of spray atomization due to deposition of impurities in the fuel can be suppressed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] [FIG. 1] FIG. 1 is a cross-sectional view showing

a fuel injection valve of Embodiment 1 of the present invention.
[FIG. 2] FIG. 2 is a diagram showing a tip portion of the fuel injection valve in Embodiment 1, in which (a) is a cross-sectional view of the tip portion of the fuel injection valve, and (b) is a plan view viewed in a line A-A arrow direction.
[FIG. 3] FIG. 3 is an enlarged plan view of FIG. 2(b), and a cross-sectional view viewed in a line B-B arrow direction.
[FIG. 4] FIG. 4 is a cross-sectional view showing a fuel passage in Embodiment 1.
[FIG. 5] FIG. 5 is a cross-sectional view showing a fuel passage in Embodiment 2 of the present invention.
[FIG. 6] FIG. 6 is a diagram showing a tip portion of a fuel injection valve in Embodiment 3 of the present invention, in which (a) is a cross-sectional view of the tip portion of the fuel injection valve, and (b) is a plan view viewed in a line C-C arrow direction.
[FIG. 7] FIG. 7 is a cross-sectional view showing a fuel passage in Embodiment 3.
[FIG. 8] FIG. 8 is a cross-sectional view showing a fuel passage in Embodiment 4 of the present invention.
[FIG. 9] FIG. 9 is a diagram showing a tip portion of a fuel injection valve in Embodiment 5 of the present

invention, in which (a) is a cross-sectional view of the tip portion of the fuel injection valve, and (b) and (c) are cross-sectional views respectively viewed in a line E-E arrow direction and a line F-F arrow direction.
DESCRIPTION OF EMBODIMENTS [0009] Embodiment 1
FIGS. 1 to 4 each show a fuel injection valve of Embodiment 1 of the present invention. In FIG. 1, reference character 1 denotes a fuel injection valve. The fuel injection valve 1 is composed of: a solenoid device 4; a housing 5 that is a yoke portion of a magnetic circuit; a core 6 that is a fixed core portion of the magnetic circuit; a coil 7; an armature 8 that is a movable core portion of the magnetic circuit; and a valve device 9. The valve device 9 includes a valve body 10, a valve main body 11, and a valve seat 12.
The valve main body 11 is press-fitted onto an outer diameter portion of the core 6 and then welded thereto. The armature 8 is press-fitted onto the valve body 10 and then welded thereto. An injection hole plate 13 is connected to the valve seat 12 through weld portions 13a. The injection hole plate 13 is provided with a plurality of injection holes 14 that penetrate the injection hole plate 13 in the plate thickness direction thereof.

The injection hole plate 13 includes: swirl chambers 18 that provide swirling force to the fuel and that inject the fuel through the injection holes 14 to the outside; and a fuel passage 17 that introduces the fuel into the swirl chambers 18.
As shown in FIGS. 2 to 4, the fuel passage 17 has, at a place where a side wall portion and a bottom portion thereof cross each other, a recess 19 that has a rectangular-shaped cross section obtained by recessing the side wall portion of the fuel passage 17 in a direction in which the fuel passage 17 is expanded.
The fuel passage 17 is formed in a cross shape, and the swirl chambers 18 are disposed at four places, on the downstream side, of the fuel passage 17. The injection holes 14 are provided at positions that correspond to the center portions of the respective swirl chambers 18. [0010] In the fuel injection valve 1 configured as above, when an actuating signal is sent from a controller of an engine to a drive circuit of the fuel injection valve 1, an electric current is applied to the coil 7 of the fuel injection valve 1, and a magnetic flux occurs in the magnetic circuit, which is composed of the armature 8, the core 6, the housing 5, and the valve main body 11, so that the armature 8 is attracted and moved to the core 6 side, and the valve body 10, which is integrated with the armature 8, is separated

from a valve seat portion 12a to form a gap therebetween.
The fuel flows from chamfered portions 15a of a ball 15 that is welded to a tip portion of the valve body 10, through the gap between the valve seat portion 12a and the valve body 10, and is injected through the plurality of injection holes 14 to an engine air intake passage.
Next, when an operation stop signal is sent from the controller of the engine to the drive circuit of the fuel injection valve 1, the application of the electric current to the coil 7 stops, and the magnetic flux in the magnetic circuit decreases, so that the gap between the valve body 10 and the valve seat portion 12a is closed by a compression spring 16 that presses the valve body 10 in a valve-closing direction, whereby the fuel injection ends.
The valve body 10 slides at an armature side surface 8a relative to a guide portion of the valve main body 11, and an armature upper surface 8b comes into contact with the lower surface of the core 6 in a valve-opened state. [0011] In Embodiment 1, as shown in FIGS. 2 to 4, a plurality of (four in the drawings) swirl chambers 18 that provide swirling force to the fuel are formed by recessing the upstream side of the injection hole plate 13. The fuel passage 17 that introduces the fuel into the swirl chambers 18 is provided so as to correspond to the swirl chambers 18. The fuel passage 17 is in communication with a valve seat

opening portion 12b.
Accordingly, the fuel having flowed through the valve seat opening portion 12b into each swirl chamber 18 flows into the injection hole 14 while causing a swirl flow. By the swirl flow being maintained also within the injection hole 14, a thin liquid film is formed along the inner wall of the injection hole, and the thin liquid film is injected in a hollow conical shape through the injection hole 14, whereby atomization of the fuel is promoted.
The closer to a wall surface the fuel flowing in the fuel passage 17 is, the lower the flow velocity is, in general. Therefore, impurities are easily deposited at corner sections of the fuel passage 17. If impurities contained in the fuel are accumulated in the fuel passage 17, the fuel flow is stagnated, and thus, the speed of the fuel flowing into the swirl chamber 18 is decreased.
Accordingly, the angular velocity at the time of swirling of the fuel is decreased. The angular velocity in the swirl chamber 18 influences performances such as the spray spread angle and spray atomization after the fuel injection. Therefore, impurities contained in the fuel are deposited in the fuel passage, whereby variation in the spray spread angle and deterioration of spray atomization could be caused. [0012] Thus, as shown in FIGS. 2 to 4, the fuel injection

valve 1 of Embodiment 1 has, at a place where the side wall portion and the bottom portion of the fuel passage 17 cross each other, a recess 19 that has a rectangular-shaped cross section obtained by recessing the side wall portion of the fuel passage 17 in a direction in which the fuel passage 17 is expanded.
In the recess 19, the flow velocity becomes lower than that in the center portion of the fuel passage 17, and thus, impurities in the fuel are easily deposited in the recess 19. Since the flow velocity in the recess 19 is low, even if impurities are deposited in the recess 19, the mean flow velocity in the fuel passage 17 is not varied substantially. Thus, the influence on the angular velocity of the fuel flowing in and swirling in the swirl chamber 18 is small.
By the provision of the recess 19 in the fuel passage 17 in this manner, occurrence of variation in the spray spread angle and deterioration of spray atomization due to deposition of impurities in the fuel can be suppressed. [0013] As described above, the present invention provides a fuel injection valve that has a valve body 10 for opening and closing a valve seat 12, and in which, as a result of operation of the valve body 10, fuel is injected through a plurality of injection holes 14 provided in an injection hole plate 13 mounted to a downstream-side opening portion of the

valve seat 12, wherein the injection hole plate 13 includes: a swirl chamber 18 for providing swirling force to the fuel and for injecting the fuel through each injection hole 14 to outside; and a fuel passage 17 for introducing the fuel into the swirl chamber 18, and the fuel passage 17 has, at a place where a side wall portion and a bottom portion thereof cross each other, a recess 19 obtained by recessing the side wall portion of the fuel passage 17 in a direction in which the fuel passage 17 is expanded. In the recess 19, the flow velocity becomes lower than that in the swirl chamber 18. Thus, impurities in the fuel are easily deposited in the recess 19. Since the flow velocity is low in the recess 19, even if impurities are deposited in the recess 19, the mean flow velocity in the swirl chamber 18 is not varied substantially. Thus, the influence on the angular velocity of the swirling fuel is reduced, and occurrence of variation in the spray spread angle and deterioration of spray atomization due to deposition of impurities in the fuel can be suppressed. [0014] Embodiment 2
FIG. 5 is a cross-sectional view of the fuel passage 17 in Embodiment 2 of the present invention. Since the closer to a wall surface the fuel flow is, the smaller the flow velocity is, the distance between wall surfaces in the recess 19 needs to be reduced to some degree in order to

attain a flow velocity reduction effect in the recess 19.
If the proportion of the length of the recess 19 to the length of the side wall portion of the fuel passage 17 exceeds half, the distance between wall surfaces in the recess 19 is increased, and the flow velocity reduction effect in the recess 19 is reduced.
[0015] Therefore, in Embodiment 2, the following relationship is realized. That is, when the fuel passage 17 is viewed in a cross section perpendicular to the side wall portion and the bottom portion of the fuel passage 17, the distance from the ceiling portion to the bottom portion of the fuel passage 17 is defined as h, and the length corresponding to the portion obtained by excluding the recess 19 from the side wall portion of the fuel passage 17 is defined as d, d/h>0.5 is established.
Accordingly, the effect of reducing the flow velocity in the recess 19 is enhanced. Thus, it is possible to attain the effect of suppressing occurrence of variation in the spray spread angle and deterioration of spray atomization due to deposition of impurities in the fuel as described in Embodiment 1.
An example is shown for reference. In the case of h=0.12 mm, d=0.08 mm can be set to realize d/h=0.67. In this case, the height (h-d) of the recess 19 is 0.04 mm. Since large impurities in the fuel are removed by a filter provided

on the upstream side, the height of the recess 19 may be set to a value about the mesh size of the filter. [0016] Embodiment 3
FIG. 6 and FIG. 7 show a fuel injection valve of Embodiment 3 of the present invention. The injection hole plate 13 is composed of: an upstream-side plate 20 that forms side wall portions of the fuel passage 17 and the swirl chambers 18; and a downstream-side plate 21 that forms bottom portions of the fuel passage 17 and the swirl chambers 18 and in which the injection holes 14 are open.
After the upstream-side plate 20 is machined to form the fuel passage 17, the swirl chambers 18, and the recess 19, the upstream-side plate 20 and the downstream-side plate 21 are joined together by a method such as welding, brazing, or diffusion bonding.
When the injection hole plate 13 is configured as divided members in this manner, formation of the recess 19 is facilitated, and productivity is improved. [0017] Embodiment 4
FIG. 8 is a cross-sectional view of the fuel passage 17 in Embodiment 4 of the present invention. In Embodiments 1 to 3, the recess 19 has a rectangular-shaped cross section, but in the present embodiment, the recess 19 has an R shape cross section that is continuously enlarged in a side wall direction of the fuel passage 17.

Accordingly, the distance between wall surfaces in
rectangular-shaped cross section. Thus, the fuel flow velocity reduction effect in the recess 19 is enhanced. Therefore, it is possible to attain the effect of suppressing occurrence of variation in the spray spread angle and deterioration of spray atomization due to deposition of purities in the fuel as described in Embodiment 1. [0018] Embodiment 5
A formula based on the potential theory is applicable to prediction of an injection flow rate of a fuel injection valve employing a general swirl method, and an injection flow rate q, a cross-sectional area Si of a fuel passage, an injection hole diameter re, a swirl chamber diameter ri, and a ratio k of the injection hole diameter and the diameter of a hollow portion formed within the injection
hole have a relationship of q∝k, Si, re/ri.
Here, there is a problem that, when impurities in the fuel have been accumulated in the recess 19, the cross-sectional area Si of the fuel passage 17 is varied, and thus, the injection flow rate q is varied.
[0019] Therefore, in Embodiment 5, as shown in FIG. 9, a region that does not have the recess 19 is provided in a part of the fuel passage 17. In addition, the region, of the fuel passage 17, that does not have the recess 19 is provided on

the downstream side with respect to the region, of the fuel passage 17, that has the recess 19.
When the region having the recess 19 in which impurities in the fuel are easily deposited is disposed on the upstream side, impurities in the fuel are less likely to be deposited in the fuel passage 17 in the region on the downstream side that does not have the recess 19. Thus, the cross-sectional area Si of the fuel passage 17 can be maintained to be constant.
Accordingly, even when impurities in the fuel have been accumulated in the recess 19, it is possible to prevent the injection flow rate from being varied.
[0020] The present invention is not limited to the above embodiments, and various design modifications can be made. Accordingly, within the scope of the present invention, the above embodiments may be freely combined with each other, or each of the above embodiments may be modified or simplified as appropriate.
DESCRIPTION OF THE REFERENCE CHARACTERS [0021] 1 fuel injection valve
4 solenoid device
5 housing
6 core
7 coil

8 armature
8a armature side surface 8b armature upper surface
9 valve device
10 valve body
11 valve main body
12 valve seat
12a valve seat portion
12b valve seat opening portion
13 injection hole plate
14 injection hole
15 ball
15a chamfered portion
16 compression spring
17 fuel passage
18 swirl chamber
19 recess
20 upstream-side plate
21 downstream-side plate

We Claim:
[1] A fuel injection valve that has a valve body for opening and closing a valve seat and in which, as a result of operation of the valve body, fuel is injected through a plurality of injection holes provided in an injection hole plate mounted to a downstream-side opening portion of the valve seat, wherein
the injection hole plate comprises:
a swirl chamber for providing swirling force to the fuel and for injecting the fuel through each injection hole to outside; and
a fuel passage for introducing the fuel into the swirl chamber, and
the fuel passage has, at a place where a side wall portion and a bottom portion thereof cross each other, a recess obtained by recessing the side wall portion of the fuel passage in a direction in which the fuel passage is expanded.
[2] The fuel injection valve according to claim 1, wherein
when the fuel passage is viewed in a cross section perpendicular to the side wall portion and the bottom portion thereof, a distance from a ceiling portion of the fuel passage to the bottom portion of the fuel passage is defined

as h, and a length corresponding to a portion obtained by excluding the recess from the side wall portion of the fuel passage is defined as d, the fuel passage has a relationship of d/h>0.5.
[3] The fuel injection valve according to claim 1 or 2, wherein
the injection hole plate is composed of: an upstream-side plate that forms side wall portions of the fuel passage and the swirl chamber; and a downstream-side plate that forms bottom portions of the fuel passage and the swirl chamber and in which the injection hole is open.
[4] The fuel injection valve according to any one of claims 1 to 3, wherein
the recess has a rectangular cross section.
[5] The fuel injection valve according to any one of claims 1 to 3, wherein
the recess has an R shape cross section that is continuously enlarged in a side wall direction of the fuel passage.
[6] The fuel injection valve according to any one of claims 1 to 5, wherein

a region that does not have the recess is provided in a part of the fuel passage.
[7] The fuel injection valve according to claim 6, wherein
the region, of the fuel passage, that does not have the recess is provided on a downstream side in the fuel passage with respect to a region, of the fuel passage, that has the recess.
[8] The fuel injection valve according to any one of
claims 1 to 7, wherein
the fuel passage is formed in a cross shape, and the swirl chamber is disposed at four places, on a
downstream side, of the fuel passage.