FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION [See section 10, Rule 13]
INJECTOR
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

Description
Technical Field
[0001] The present invention relates to an injector configured
to supply fuel to, for example, an internal combustion engine.
Background Art
[0002] There has hitherto been known a fuel injection device having the following configuration. Specifically, a valve member is accommodated inside a housing having a cylindrical shape so as to be movable in a reciprocating manner. An injection hole is closed by bringing the valve member into contact with a valve seat, and the injection hole is opened by separating the valve member away from the valve seat. A movable core that is movable integrally with the valve member is accommodated inside the housing. Further, a fixed core arranged on an upstream side of the movable core is fixed to the housing . A coil portion is provided around the housing . The coil portion is configured to generate an electromagnetic attraction force for attracting the movable core to the fixed core. The valve member is brought into contact with the valve seat when energization to the coil is stopped, and the valve member is separated away from the valve seat when energization to the coil is performed. [0003] There has hitherto been proposed a fuel injection

device having the following configuration in order to reduce operating noise at the time of opening the valve, which is generated when a movable core collides against a fixed core. Specifically, a gap between an inner peripheral surface of a housing and an outer peripheral surface of the movable core is adjusted, and a protruding portion having a cylindrical shape is formed on an end portion of the movable core on the fixed core side. In such related-art fuel injection device, a fluid damper effect obtained by resistance of fuel flowing through the gap between the inner peripheral surface of the housing and the outer peripheral surface of the movable core increases. With this, a speed of the movable core at the time of opening the valve is reduced, thereby reducing operating noise at the time of opening the valve (see, for example, Patent Literature 1) .
Citation List
Patent Literature
[0004] [PTL 1] JP 3882892 A
Summary of Invention Technical Problem
[0005] In the related-art fuel injection device disclosed in Patent Literature 1, when a valve opening operation is performed, most of fuel in a space on an upstream side with respect to the movable core moves from an inner peripheral side to an outer

peripheral side of the movable core, and then flows out to a downstream side with respect to the movable core from an outer peripheral portion of an end surface of the movable core on the upstream side through a gap between an inner peripheral surface of the housing and an outer peripheral surface of the movable core. In the related-art fuel injection device disclosed in Patent Literature 1, the gap between the inner peripheral surface of the housing and the outer peripheral surface of the movable core is minimum at the end surface of the movable core on the upstream side. Thus, a direction of movement of fuel changes sharply when the fuel flows into the gap between the inner peripheral surface of the housing and the outer peripheral surface of the movable core, with the result that there is increased variation in loss in the flow of fuel from product to product, which is caused by, for example, dimension errors. Consequently, a characteristic of an injection amount of fuel varies significantly from product to product. [0006] The present invention has been made to solve the above-mentioned problems, and has an object to obtain an injector, which is capable of reducing variation in characteristic of an injection amount of fuel, and reducing operating noise at the time of opening a valve.
Solution to Problem
[0007] According to one embodiment of the present invention,
there is provided an injector, including: a core having a

cylindrical shape; a valve seat, which has a seat surface formed therein, and is arranged on a downstream side of flow of fuel with respect to the core; a valve body, which is arranged between the core and the seat surface so as to be displaceable, and is configured to close a fuel passage when the valve body is brought into contact with the seat surface and open the fuel passage when the valve body is separated away from the seat surface; a holder having a cylindrical shape, which is configured to accommodate the valve seat and the valve body; an elastic body configured to urge the valve body in such a direction that the valve body is brought into contact with the seat surface; and a coil configured to generate an electromagnetic attraction force of displacing the valve body against an urging force of the elastic body in such a direction that the valve body is separated away from the seat surface, wherein the valve body includes an armature opposed to the core, wherein the armature includes: an armature sliding portion having a cylindrical shape; a core opposing portion having a cylindrical shape and protruding from the armature sliding portion toward the core; and a protruding portion having a cylindrical shape, which protrudes from an inner peripheral portion of the core opposing portion toward the core and is contactable with the core, wherein an outer diameter of the core opposing portion is smaller than an outer diameter of the armature sliding portion, and wherein an outer diameter of the protruding portion is smaller than the outer diameter of the core opposing portion.

Advantageous Effects of Invention
[0008] According to the fuel injection valve of the present invention, a first volume portion can be formed on a radially outer side of the protruding portion, and a second volume portion can be formed on a radially outer side of the core opposing portion. Thus, when fuel in the first volume portion moves to a downstream side of flow of fuel along with a valve opening operation, the flow of fuel is spread in the second volume portion, thereby being capable of suppressing turbulence of the fuel. In this manner, variation in characteristic of the injection amount of fuel of the injector can be reduced. Further, a ratio of fuel moving to the gap on the radially outer side through a space between the core and the core opposing portion at the time of the valve opening operation can be increased. Thus, an effect of decelerating the valve body can be increased, and operating noise at the time of opening the valve can be reduced.
Brief Description of Drawings
[0009] FIG. 1 is a sectional view for illustrating an injector
according to a first embodiment of the present invention.
FIG. 2 is an enlarged sectional view for illustrating an armature when the injector of FIG. 1 is in a valve closed state.
FIG. 3 is an enlarged sectional view for illustrating the armature when the injector of FIG. 2 is in a valve opened state.

FIG. 4 is a sectional view taken along the line IV-IV of FIG. 2.
FIG. 5 is a sectional view taken along the line V-V of FIG. 3.
FIG. 6 is an enlarged sectional view for illustrating magnetic flux passing through the armature of FIG. 3.
Description of Embodiments
[0010] Now, an embodiment of the present invention is described with reference to the drawings. First Embodiment
FIG. 1 is a sectional view for illustrating an injector according to a first embodiment of the present invention. An injector 1 includes a drive device 2 and a valve device 3. The valve device 3 is operated by the drive device 2. The valve device 3 faces an intake passage of an engine. Fuel passes through fuel passages inside the drive device 2 and the valve device 3, and then is injected from the valve device 3 to the intake passage of the engine.
[0011] The drive device 2 includes a housing 4, a core 5, a coil 6, a bobbin 7, a cap 8, and a terminal 9. The housing 4 is made of metal and has a two-step circular cylindrical shape. The core 5 is made of metal, has a cylindrical shape, and is arranged inside the housing 4. The coil 6 is arranged inside the housing 4 under a state of surrounding the core 5. The bobbin 7 is made of resin, and the coil 6 is wound around the bobbin 7. The cap 8

is made of metal, and is fixed to a part of an outer peripheral portion of the housing 4 by welding so as to cover the bobbin 7 at a periphery of the core 5. The terminal 9 is configured to electrically connect the coil 6 to the outside. The housing 4, the core 5, the coil 6, the bobbin 7, the cap 8, and the terminal 9 are integrated with each other with a molded body 10 made of resin. Further, the housing 4, the core 5, the coil 6, the bobbin 7, and the cap 8 are arranged coaxially with an axial line P of the injector 1.
[0012] A fuel pipe (not shown) is connected to an end portion of the core 5 on an upstream side of flow of fuel. A gap between the core 5 and the fuel pipe is sealed by an O-ring 27. Further, a filter 28 is provided in a space inside the core 5. Fuel is supplied at a pressure of about 300 kPa from the fuel pipe into the fuel passages inside the injector 1. Further, fuel having passed through the filter 28 is filled into the fuel passages inside the injector 1.
[0013] The cap 8 has a cutout portion. The terminal 9 is connected to the coil 6 through the cutout portion of the cap 8. When energization to the coil 6 is performed through the terminal 9, an electromagnetic force is generated from the coil 6. [ 0014] The valve device 3 includes a valve seat 12, an injection-hole plate 13, a valve body 14, a holder 15, a fixed rod 16, and a spring 17. The valve seat 12 has a valve-seat internal space portion 11. The injection-hole plate 13 is arranged on a

downstream side of flow of fuel with respect to the valve seat 12. The valve body 14 is displaceable with respect to the valve seat 12 in a direction along the axial line P. The holder 15 is made of metal, has a cylindrical shape, and is configured to accommodate the valve seat 12, the injection-hole plate 13, and the valve body
14. The fixed rod 16 has a cylindrical shape, and is arranged on
an upstream side of flow of fuel with respect to the valve body
14 so as to be fixed to the core 5. The spring 17 is an elastic
body, and is arranged between the valve body 14 and the fixed rod
16.
[0015] The holder 15 is fixed to the housing 4 . The valve seat 12 is fixed to an inner peripheral surface of the holder 15. The injection-hole plate 13 is fixed to the valve seat 12. The valve seat 12, the injection-hole plate 13, the valve body 14, the holder
15, the fixed rod 16, and the spring 17 are arranged coaxially with
the axial line P of the injector 1.
[0016] The valve seat 12 is arranged on the downstream side of flow of fuel with respect to the core 5. The valve seat 12 has a through hole 12a as a fuel passage. The through hole 12a is formed from the valve-seat internal space portion 11 to the injection-hole plate 13 side. The through hole 12a is formed coaxially with the axial line P. An inner surface of the valve-seat internal space portion 11 includes a guide surface 18 and a seat surface 19. The guide surface 18 has a circular cylindrical shape, and extends along a direction in which the valve body 14 is displaced. The seat

surface 19 has a conical shape inclined in a direction of approaching the axial line P continuously from the guide surface 18 to the through hole 12a. That is, on the inner peripheral portion of the valve seat 12, there are provided the guide surface 18 extending along the axial line P and the seat surface 19 inclined with respect to the axial line P.
[0017] The valve body 14 is arranged between the core 5 and the seat surface 19 so as to be displaceable. Further, the valve body 14 includes an armature 21, a ball 22, and a coupling member 23. The armature 21 has a cylindrical shape, and is a movable core arranged inside the holder 15. The ball 22 has a spherical shape, and is inserted in the valve-seat internal space portion 11. The coupling member 23 has a cylindrical shape, and is configured to couple the armature 21 and the ball 22 to each other. The valve body 14 is displaced with respect to the valve seat 12 while the ball 22 is guided along the guide surface 18.
[0018] The ball 22 is rotatable in the valve-seat internal space portion 11. With this configuration, inside the holder 15, inclination of the axial line of the valve body 14 with respect to the axial line of the holder 15 is allowed. Further, a fuel passage is formed between an inner surface of the valve-seat internal space portion 11 and the ball 22.
[0019] The armature 21 is opposed to the core 5 in a direction along the axial line P of the injector 1. When the valve body 14 is displaced with respect to the valve seat 12, the ball 22 is brought

into contact with the seat surface 19 or separated away from the seat surface 19. The ball 22 is brought into contact with the seat surface 19 through displacement of the armature 21 in the direction of being separated away from the core 5. The ball 22 is separated away from the seat surface 19 through displacement of the armature 21 in a direction of approaching the core 5. The valve body 14 is brought into contact with the seat surface 19 to close the fuel passages, thereby bringing the injector 1 into a valve closed state. The valve body 14 is separated away from the seat surface 19 to open the fuel passages, thereby bringing the injector 1 into a valve opened state. When the injector 1 is brought into the valve closed state, the armature 21 is separated away from the core 5. When the injector 1 is brought into the valve opened state, the armature 21 is brought into contact with the core 5. Fuel flows through the fuel passage defined between the inner surface of the valve-seat internal space portion 11 and the ball 22 in the order of the guide surface 18 and the seat surface 19, and then flows to the injection-hole plate 13 via the through hole 12a. [0020] The injection-hole plate 13 has a plurality of fuel injection holes 26 formed through the injection-hole plate 13. Fuel flowing to the injection-hole plate 13 via the through hole 12a of the valve seat 12 is injected to the intake passage of the engine through the plurality of fuel injection holes 26. [0021] The spring 17 generates an elastic restoring force under a state of being compressed between the fixed rod 16 and the

coupling member 23. With this, the spring 17 urges the valve body 14 in such a direction that the ball 22 is brought into contact with the seat surface 19.
[0022] The coil 6 generates an electromagnetic attraction force of attracting the armature 21 to the core 5 through energization to the coil 6. When the electromagnetic attraction force of the coil 6 is generated, the valve body 14 is displaced in a direction of being separated away from the seat surface 19 against the urging force of the spring 17.
[0023] FIG. 2 is an enlarged sectional view for illustrating the armature 21 when the injector 1 of FIG. 1 is in the valve closed state. Further, FIG. 3 is an enlarged sectional view for illustrating the armature 21 when the injector 1 of FIG. 2 is in the valve opened state. A joining member 2 9 is fixed to the armature 21. The joining member 2 9 has a cylindrical shape, and is configured to join the coupling member 23 to the armature 21. In this example, the joining member 29 and the armature 21 are formed of a single integrated member.
[0024] The armature 21 includes an armature sliding portion 31, a core opposing portion 32, and a protruding portion 33. The armature sliding portion 31 has a cylindrical shape. The core opposing portion 32 has a cylindrical shape, and protrudes from the armature sliding portion 31 toward the core 5. The protruding portion 33 has a cylindrical shape, and protrudes from an inner peripheral portion of the core opposing portion 32 toward the core

5.
[0025] A first volume portion A being a space is defined as a fuel passage between an outer peripheral surface of the protruding portion 33 and an inner peripheral surface of the holder 15. A second volume portion B being a space is defined as a fuel passage between an outer peripheral surface of the core opposing portion 32 and the inner peripheral surface of the holder 15. A gap C is defined as a fuel passage between an outer peripheral surface of the armature sliding portion 31 and the inner peripheral surface of the holder 15. Therefore, in a space surrounded by the armature 21, the holder 15, and the core 5, the first volume portion A, the second volume portion B, and the gap C are continuously defined in the stated order from the upstream side to the downstream side of flow of fuel.
[0026] An end surface of the armature sliding portion 31 on the valve seat 12 side corresponds to an end surface of the entire armature 21 on the valve seat 12 side. The end surface of the armature sliding portion 31 on the valve seat 12 side is orthogonal to the axial line of the valve body 14.
[0027] An outer diameter of the armature sliding portion 31 is constant in a direction along the axial line of the valve body 14. Therefore, a shape of the outer peripheral surface of the armature sliding portion 31 is a circular cylindrical shape having a center extending along the axial line of the valve body 14. Further, the outer diameter of the armature sliding portion 31 is

a maximum outer diameter in the armature 21. With this configuration, when the axial line of the valve body 14 is inclined with respect to the axial line of the holder 15, the outer peripheral surface of the armature sliding portion 31 is brought into contact with a part of the inner peripheral surface of the holder 15. [0028] In this example, the outer peripheral surface of the armature sliding portion 31 is formed of hard chromium plating covering the armature sliding portion 31 made of electromagnetic stainless steel. With this configuration, abrasion of the armature sliding portion 31 caused through contact of the outer peripheral surface of the armature sliding portion 31 with the inner peripheral surface of the holder 15 is suppressed.
[0029] The end surface of the core opposing portion 32 on the core 5 side is opposed to the core 5 in the direction along the axial line P of the injector 1. Further, the end surface of the core opposing portion 32 on the core 5 side is orthogonal to the axial line of the valve body 14 . A dimension Lb of the core opposing portion 32 in the direction along the axial line of the valve body 14 is smaller than a dimension Lc of the armature sliding portion 31 in the direction along the axial line of the valve body 14. With this configuration, a dimension of the second volume portion B in the direction along the axial line P of the injector 1 is smaller than a dimension of the gap C in the direction along the axial line P of the injector 1. [0030] An outer diameter of the core opposing portion 32 is

smaller than the outer diameter of the armature sliding portion 31. With this configuration, a distance between the outer peripheral surface of the core opposing portion 32 and the inner peripheral surface of the holder 15 is larger than a distance between the outer peripheral surface of the armature sliding portion 31 and the inner peripheral surface of the holder 15. That is, a radial dimension of the second volume portion B is larger than a radial dimension of the gap C.
[0031] The outer peripheral surface of the core opposing portion 32 includes a tapered surface 32a and a cylindrical surface 32b. The tapered surface 32a has an annular shape, and is continuous with the outer peripheral surface of the armature sliding portion 31. The cylindrical surface 32b is formed between the end surface of the core opposing portion 32 on the core 5 side and the tapered surface 32a.
[0032] The tapered surface 32a extends from the outer peripheral surface of the armature sliding portion 31 toward the protruding portion 33 side so as to be inclined with respect to the axial line of the valve body 14 in a direction of approaching the axial line of the valve body 14. A shape of the cylindrical surface 32b has a circular cylindrical shape having a center extending along the axial line of the valve body 14. [0033] The protruding portion 33 can be brought into contact with the end surface of the core 5 on the downstream side. When the injector 1 is in the valve opened state, as illustrated in FIG.

3, while the core opposing portion 32 is separated away from the core 5, the protruding portion 33 is brought into contact with the core 5. Further, when the injector 1 is in the valve closed state, as illustrated in FIG. 2, the protruding portion 33 is separated away from the core 5 through intermediation of a gap g. [0034] An outer diameter of the protruding portion 33 is smaller than the outer diameter of the core opposing portion 32. With this configuration, a distance between the outer peripheral surface of the core opposing portion 32 and the inner peripheral surface of the holder 15 is larger than a distance between the outer peripheral surface of the armature sliding portion 31 and the inner peripheral surface of the holder 15. That is, a radial dimension of the first volume portion A is larger than the radial dimension of the second volume portion B.
[0035] A part of the holder 15 is formed into a thin portion 15a. A thickness of the thin portion 15a is smaller than a thickness of a portion of the holder 15 other than the thin portion 15a. When the protruding portion 33 is held in contact with the core 5, the thin portion 15a is positioned on a radially outer side of the protruding portion 33. When the protruding portion 33 is held in contact with the core 5, the portion of the holder 15 other than the thin portion 15a, namely, a thick portion of the holder 15 having a thickness larger than that of the thin portion 15a is positioned on a radially outer side of the armature sliding portion 31. In this example, an entire periphery of the portion of the holder 15

positioned on the radially outer side of the protruding portion 33 when the protruding portion 33 is held in contact with the core 5 corresponds to the thin portion 15a.
[0036] An end portion of the coupling member 23 is inserted along the inner peripheral surface of the joining member 29. An outer diameter of the joining member 29 is smaller than an outer diameter of the protruding portion 33. With this configuration, a distance between the outer peripheral surface of the joining member 29 and the inner peripheral surface of the holder 15 is larger than a distance between the outer peripheral surface of the protruding portion 33 and the inner peripheral surface of the holder 15.
[0037] FIG. 4 is a sectional view taken along the line IV-IV of FIG. 2. FIG. 5 is a sectional view taken along the line V-V of FIG. 3. Under a state in which the axial line of the valve body 14 matches with the axial line of the holder 15, as illustrated in FIG. 4, a sectional shape of the gap C is annular, and the radial dimension of the gap C has a constant value 5 over an entire periphery of the armature 21. In contrast, under a state in which the axial line of the valve body 14 is inclined with respect to the axial line of the holder 15 and the outer peripheral surface of the armature sliding portion 31 is held in contact with the inner peripheral surface of the holder 15, as illustrated in FIG. 5, the sectional shape of the gap C is crescent, a maximum value of the radial dimension of the gap C is twice the value 5, and a minimum

value of the radial dimension of the gap C is zero. [0038] When the dimension of the annular gap C formed when the axial line of the valve body 14 matches with the axial line of the holder 15 has the same value <5 for each product, the dimension of the crescent gap C formed when the outer peripheral surface of the armature sliding portion 31 is held in contact with the inner peripheral surface of the holder 15 is also the same for each product. Further, when the annular sectional shape of the annular gap C formed when the axial line of the valve body 14 matches with the axial line of the holder 15 is the same for each product, the crescent sectional shape of the gap C formed when the outer peripheral surfaec of the armature sliding portion 31 is held in contact with the inner peripheral surface of the holder 15 is also the same for each product. Therefore, through contact of the outer peripheral surface of the armature sliding portion 31 with the inner peripheral surface of the holder 15, variation in the dimension and the sectional shape of the gap C from product to product is suppressed, and variation in flow velocity distribution of fuel flowing through the gap C is also suppressed.
[0039] Meanwhile, when whether or not the outer peripheral surface of the armature sliding portion 31 is brought into contact with the inner peripheral surface of the holder 15 varies from product to product, the sectional shape of the gap C varies significantly from product to product. [0040] FIG. 6 is an enlarged sectional view for illustrating

magnetic flux passing through the armature 21 of FIG. 3. The magnetic flux induced by the coil 6 mainly flows back through a main magnetic path Q generated around the coil 6. The main magnetic path Q extends from the housing 4 to the core 5 via the holder 15, the armature sliding portion 31, the core opposing portion 32, and the protruding portion 33 in the stated sequential order. Owing to presence of the thin portion 15a of the holder 15, the number of magnetic flux lines passing directly between the holder 15 and the core 5 is reduced by the thin portion 15a, with the result that the number of magnetic flux lines passing through the main magnetic path Q is increased.
[0041] Thus, the number of magnetic flux lines passing through the holder 15 and the armature sliding portion 31 is increased so that an intense electromagnetic attraction force acts in a radial direction between the inner peripheral surface of the holder 15 and the outer peripheral surface of the armature sliding portion 31. In this embodiment, through increase in the electromagnetic attraction force acting between the inner peripheral surface of the holder 15 and the outer peripheral surface of the armature sliding portion 31, a state in which the outer peripheral surface of the armature sliding portion 31 is held in contact with the inner peripheral surface of the holder 15 is stably obtained in terms of mechanics.
[0042] Further, a length L of the spring 17 illustrated in FIG. 1, which is given when the protruding portion 33 is held in contact

with the core 5, that is, when the injector is in the valve opened state, and the radial dimension 5 of the gap C, which is given when the axial line of the valve body 14 matches with the axial line of the holder 15, satisfies the following relation. Specifically, when 5/L=tanG, 8 has a value of 0.1° or more, that is, a relation of θ>0.1 is satisfied. A radial misalignment amount of the end portion of the spring 17 on the downstream side is determined depending on the radial dimension 5 of the gap C. Therefore, through the setting of the value of θ to 0.1° or more when 5/L=tanθ is given, the spring 17 in the valve opened state is easily inclined with respect to the axial line of the holder 15. Thus, unbalanced load generated by the spring 17 is easily applied to the armature 21, and the outer peripheral surface of the armature sliding portion 31 is more easily brought into contact with the inner peripheral surface of the holder 15.
[0043] Next, an operation is described. Under a state in which energization to the coil 6 is stopped, the ball 22 is held in contact with the seat surface 19 of the valve seat 12 by the urging force of the spring 17. With this, the fuel passages are closed, and supply of the fuel from the valve seat 12 to the injection-hole plate 13 is stopped.
[004 4 ] When energization to the coil 6 is performed, the electromagnetic attraction force is generated, and the armature 21 is attracted to the core 5. With this, the valve body 14 is displaced toward the core 5 against the urging force of the spring

17 . With this, the ball 22 is separated away from the seat surface 19 of the valve seat 12 so that the injector is brought into the valve opened state in which the fuel passages are opened. [0045] On this occasion, the magnetic flux induced by the coil 6 mainly flows through the main magnetic path Q passing through the holder 15 and the armature sliding portion 31. Thus, the outer peripheral surface of the armature sliding portion 31 is attracted to the inner peripheral surface of the holder 15, and the axial line of the valve body 14 is inclined with respect to the axial line of the holder 15 . In this manner, the outer peripheral surface of the armature sliding portion 31 is brought into contact with the inner peripheral surface of the holder 15.
[0046] Further, at the time of a valve opening operation of the injector 1, along with movement of the armature 21 to the core 5 side, fuel in the space surrounded by the armature 21, the holder 15, and the core 5 flows out to the downstream side of flow of fuel with respect to the armature 21. When the armature 21 approaches the core 5, the gap g between the protruding portion 33 and the core 5 is reduced. On this occasion, with the configuration in which the protruding portion 33 is formed on the inner peripheral portion of the armature 21, a ratio of fuel flowing into the armature 21 is reduced, and a ratio of fuel flowing through the gap C to the downstream side of flow of fuel with respect to the armature 21 is increased. [0047] Of the fuel in the space surrounded by the armature 21,

the holder 15, and the core 5, fuel f1 in the first volume portion A moves to the radially outer side along with movement of the armature 21 to the core 5 side, and flows into the second volume portion B in a spreading manner. In this manner, turbulence of flow of the fuel fl is suppressed. Fuel f2 in the second volume portion B moves to the radially outer side along with movement of the armature 21 to the core 5 side, and flows into the gap C together with the fuel f1 having flowed into the second volume portion B through the first volume portion A. On this occasion, the fuel fl and the fuel f2 smoothly flow into the gap C along the tapered surface 32a while accelerating.
[0048] The fuel having flowed into the gap C flows out through the gap C to the downstream side of flow of fuel with respect to the armature 21. On this occasion, the dimension of the gap C in the direction along the axial line is larger than the dimension of the second volume portion B in the direction along the axial line, and hence the fuel is easily rectified in the gap C. In this manner, the fuel in a state of being rectified in the gap C flows out to the downstream side with respect to the armature 21. The fuel having flowed out through the gap C to a free space on the downstream side of flow of fuel is changed into a vortex at an outlet of the gap C due to an action of expansion loss in the flow passage. As a result, fluid loss occurs.
[004 9] Energy generated by the fluid loss reduces kinetic energy of the valve body 14. In particular, under a state

immediately before completion of the valve opening operation, almost all the fuel discharged through the first volume portion A and the second volume portion B passes through the gap C. Thus, an effect of decelerating the valve body 14 is large, and a damping action on the valve opening operation is increased. When the injector 1 is brought into the valve opened state, the protruding portion 33 is brought into contact with the core 5. [0050] Under the valve opened state of the injector 1, the fuel having flowed out to the downstream side with respect to the armature
21 flows into the valve-seat internal space portion 11. After that, the fuel flows through the fuel passage defined between the ball
22 and the guide surface 18, the fuel passage defined between the ball 22 and the seat surface 19, and the through hole 12a in the stated order. After that, the fuel having passed via the through hole 12a is injected to the intake passage of the engine through the plurality of fuel injection holes 26 of the injection-hole plate 13.
[0051] Meanwhile, when energization to the coil 6 is stopped, the electromagnetic attraction force is lost, and the valve body 14 is displaced by the urging force of the spring 17 in a direction of approaching the seat surface 19 of the valve seat 12. After that, the ball 22 is brought into contact with the seat surface 19, and the fuel passages are closed. In this manner, supply of the fuel via the through hole 12a of the valve seat 12 to the injection-hole plate 13 is stopped.

[0052] In such injector 1, the outer diameter of the core opposing portion 32 is smaller than the outer diameter of the armature sliding portion 31, and the outer diameter of the protruding portion 33 is smaller than the outer diameter of the core opposing portion 32. Thus, the first volume portion A can be formed on the radially outer side of the protruding portion 33, and the second volume portion B can be formed on the radially outer side of the core opposing portion 32 . With this configuration, when the fuel in the first volume portion A moves to the downstream side of flow of fuel along with the valve opening operation, the flow of fuel is spread in the second volume portion B, thereby being capable of suppressing turbulence of the fuel. In this manner, the flow of fuel flowing into the gap C between the outer peripheral surface of the armature sliding portion 31 and the inner peripheral surface of the holder 15 and passing through the gap C can be stabilized, thereby being capable of reducing variation in loss in the flow of fuel from product to product. That is, variation in characteristic of an injection amount of fuel of the injector 1 can be reduced. Further, the protruding portion 33 protrudes from the inner peripheral portion of the core opposing portion 32 toward the core 5, and hence the ratio of fuel moving to the gap C on the radially outer side through the space between the core 5 and the core opposing portion 32 at the time of the valve opening operation can be increased. In this manner, the effect of decelerating the valve body 14 can be increased, and operating noise at the time

of opening the valve can be reduced.
[0053] Further, the outer diameter of the armature sliding portion 31 is constant in the direction along the axial line of the valve body 14, and the end surface of the armature sliding portion 31 on the valve seat 12 side is orthogonal to the axial line of the valve body 14 . Thus, the fluid loss of fuel, which occurs due to expansion loss when the fuel flows through the narrow gap C to the free space, can be increased. In this manner, the valve body 14 can be effectively decelerated at the time of the valve opening operation, and operating noise at the time of opening the valve can be further reduced.
[0054] Further, the outer peripheral surface of the armature sliding portion 31 is brought into contact with the inner peripheral surface of the holder 15 through inclination of the axial line of the valve body 14 with respect to the axial line of the holder 15. Thus, a state in which a fixed sectional shape of the gap C is obtained in each product by bringing the outer peripheral surface of the armature sliding portion 31 into contact with the inner peripheral surface of the holder 15 can be easily ensured at the time of the valve opening operation. In this manner, the distribution of fuel flowing through the gap C can be stabilized, thereby being capable of further reducing variation in characteristic of the injection amount of fuel from product to product.
[0055] Further, a part of the holder 15 is formed into the thin portion 15a, and the thin portion 15a is positioned on the radially

outer side of the protruding portion 33 when the protruding portion 33 is held in contact with the core 5. Thus, the number of magnetic flux lines directly passing the holder 15 and the core 5 can be reduced by the thin portion 15a, thereby being capable of increasing the number of magnetic flux lines passing through the holder 15 and the armature sliding portion 31. In this manner, magnitude of the electromagnetic attraction force of attracting the outer peripheral surface of the armature sliding portion 31 to the inner peripheral surface of the holder 15 can be increased, and the outer peripheral surface of the armature sliding portion 31 can be more reliably brought into contact with the inner peripheral surface of the holder 15 at the time of the valve opening operation. As a result, at the time of every valve opening operation, a state in which the outer peripheral surface of the armature sliding portion 31 is held in contact with the inner peripheral surface of the holder 15 can be more reliably reproduced, thereby being capable of further reducing variation in characteristic of the injection amount of fuel from product to product. [0056] Further, the length L of the spring 17, which is given when the protruding portion 33 is held in contact with the core 5, and the radial dimension 5 of the gap C between the outer peripheral surface of the armature sliding portion 31 and the inner peripheral surface of the holder 15, which is given when the axial line of the valve body 14 matches with the axial line of the holder 15, satisfies a relation of θ>0.1 when 5/L=tanθ. Accordingly, the

spring 17 in the valve opened state can be easily inclined with respect to the axial line of the holder 15, and unbalanced load generated by the spring 17 can be easily applied to the armature 21. Thus, a state in which the outer peripheral surface of the armature sliding portion 31 is held in contact with the inner peripheral surface of the holder 15 can be more reliably reproduced, thereby being capable of further reducing variation in characteristic of the injection amount of fuel from product to product.
[0057] Further, the outer peripheral surface of the core opposing portion 32 includes the tapered surface 32a continuous with the outer peripheral surface of the armature sliding portion 31. Accordingly, the fuel in the first volume portion A and the second volume portion B can be caused to smoothly flow into the gap C along the tapered surface 32a. In this manner, variation in loss in the flow of fuel during inflow into the gap C from product to product can be further reduced, thereby being capable of further reducing variation in characteristic of the injection amount of fuel of the injector 1. Further, speed of the fuel flowing through the gap C is increased, and hence there can be increased fluid loss, which occurs due to expansion loss when the fuel flows out through the gap C to the downstream side of flow of fuel with respect to the armature 21. In this manner, operating noise at the time of opening the valve can be further reduced. [0058] Further, the dimension Lc of the armature sliding

portion 31 in the direction along the axial line of the valve body
14 is larger than the dimension Lb of the core opposing portion
32 in the direction along the axial line of the valve body 14.
Accordingly, a section of the gap C for rectifying fuel can be
increased, and the fuel rectified in the gap C at high speed can
be caused to flow out through the gap C to the downstream side.
In this manner, there can be increased fluid loss, which occurs
due to expansion loss when the fuel flows out through the gap C
to the downstream side, and operating noise at the time of opening
the valve can be further reduced.
[0059] Further, the outer peripheral surface of the armature sliding portion 31 is formed of hard chromium plating covering the armature sliding portion 31. Accordingly, hardness of the outer peripheral surface of the armature sliding portion 31 can be increased, and abrasion of the armature sliding portion 31 due to long-term use of the injector 1 can be suppressed. Thus, a state of the gap C between the outer peripheral surface of the armature sliding portion 31 and the inner peripheral surface of the holder
15 can be stabilized, and a change in characteristic of the injection
amount of fuel can be prevented for a long period of time.
[0060] In the above-mentioned example, the outer peripheral
surface of the armature sliding portion 31 is brought into contact
with the inner peripheral surface of the holder 15 through
inclination of the axial line of the valve body 14 with respect
to the axial line of the holder 15. However, inclination of the

axial line of the valve body 14 with respect to the axial line of the holder 15 may be inhibited. Even with this configuration, turbulence of the fuel flowing into the gap C can be suppressed, thereby being capable of reducing variation in characteristic of the injection amount of fuel from product to product. [0061] Further, in the above-mentioned example, the thin portion 15a of the holder 15 is formed over the entire periphery of the holder 15, but only a part of a peripheral portion of the holder 15 may be formed into the thin portion 15a. With this configuration, an imbalance of the electromagnetic attraction force for attracting the outer peripheral surface of the armature sliding portion 31 to the inner peripheral surface of the holder 15 can be forcibly caused in a peripheral direction of the holder 15, and the outer peripheral surface of the armature sliding portion 31 can be more reliably brought into contact with the inner peripheral surface of the holder 15 at the time of the valve opening operation. [0062] Further, in the above-mentioned example, the outer peripheral surface of the armature sliding portion 31 is formed of hard chromium plating, but the present invention is not limited thereto. A surface of the armature 21 made of the electromagnetic stainless steel may be exposed as the outer peripheral surface of the armature sliding portion 31.
0063; Further, in the above-mentioned example, the outer peripheraL surface of the core opposing port ion 32 includes the annular tapered surface 32a continuous with the outer peripheral

surface of the armature sliding portion 31, but the tapered surface 32a may be a surface orthogonal to the axial line of the valve body
■; 4.
[0064] Further, in the above-mentioned example, the dimension Lc of the armature sliding portion 31 in the direction along the axial line of the valve body 14 is larger than the dimension Lb of the core opposing portion 32 in the direction along the axial line of the valve body 14 . However, the dimension Lc of the armature sliding portion 31 may be equal to the dimension Lb of the core opposing portion 32, or the dimension Lc of the armature sliding portion 31 may be smaller than the dimension Lb of the core opposing portion 32.
[0065] Further, in the above-mentioned example, the holder 15 includes the thin portion 15a, but the thin portion 15a may be omitted.
Reference Signs List
[0066] 1 injector, 5 core, 6 coil, 12 valve seat, 14 valve body, 15 holder, 15a thin portion, 17 spring (elastic body), 19 seat surface, 21 armature, 31 armature sliding portion, 32 core opposing portion, 32a tapered surface, 33 protruding portion

We Claim :
[Claim 1] An injector, comprising:
a core having a cylindrical shape;
a valve seat, which has a seat surface formed therein, and is arranged on a downstream side of flow of fuel with respect to the core;
a valve body, which is arranged between the core and the seat surface so as to be displaceable, and is configured to close a fuel passage when the valve body is brought into contact with the seat surface and open the fuel passage when the valve body is separated away from the seat surface;
a holder having a cylindrical shape, which is configured to accommodate the valve seat and the valve body;
an elastic body configured to urge the valve body in such a direction that the valve body is brought into contact with the seat surface; and
a coil configured to generate an electromagnetic attraction force of displacing the valve body against an urging force of the elastic body in such a direction that the valve body is separated away from the seat surface,
wherein the valve body includes an armature opposed to the core,
wherein the armature includes:
an armature sliding portion having a cylindrical shape; a core opposing portion having a cylindrical shape and

protruding from the armature sliding portion toward the core; and a protruding portion having a cylindrical shape, which protrudes from an inner peripheral portion of the core opposing portion toward the core and is contactable with the core,
wherein an outer diameter of the core opposing portion is smaller than an outer diameter of the armature sliding portion, and
wherein an outer diameter of the protruding portion is smaller than the outer diameter of the core opposing portion.
[Claim 2] The injector according to claim 1,
wherein the outer diameter of the armature sliding portion is constant in a direction along an axial line of the valve body, and
wherein an end surface of the armature sliding portion on the valve seat side is orthogonal to the axial line of the valve body.
[Claim 3] The injector according to claim 1 or claim 2,
wherein inclination of the axial Line of the valve body with respect to an axial line of the holder is allowed in the holder, and
wherein an outer peripheral surface of the armature sliding portion is brought into contact with an inner peripheral surface of the holder through inclination of the axial line of the valve body with respect to the axial line of the holder.

[Claim 4] The injector according to claim 3,
wherein a part of the holder is formed into a thin portion,
wherein a thickness of the thin portion is smaller than a thickness of a portion of the holder other than the thin portion,
wherein the thin portion is positioned on a radially outer side of the protruding portion when the protruding portion is held in contact with the core, and
wherein the portion of the holder other than the thin portion is positioned on a radially outer side of the armature sliding portion when the protruding portion is held in contact with the core .
[Claim 5] The injector according to any one of claims 1 to 4, wherein a length (L) of the elastic body, which is given when the protruding portion is held in contact with the core, and a radial dimension
(5) of a gap between the outer peripheral surface of the armature sliding portion and the inner peripheral surface of the holder, which is given when the axial line of the valve body matches with the axial line of the holder, satisfies a relation of G^0.1c when 5/L=tanG.
[Claim 6] The injector according to any one of claims 1 to 5,
wherein an outer peripheral surface of the core opposing portion includes a tapered surface that has an annular shape and

is continuous with the outer peripheral surface of the armature sliding portion, and
wherein the tapered surface extends from the outer peripheral surface of the armature sliding portion to the protruding portion side so as to be inclined with respect to the axial line of the valve body in a direction of approaching the axial line of the valve body.
[Claim 7] The injector according to any one of claims 1 to 6, wherein a dimension of the armature sliding portion in the direction along the axial line of the valve body is larger than a dimension of the core opposing portion in the direction along the axial line of the valve body.
[Claim 8] The injector according to any one of claims 1 to 7, wherein the outer peripheral surface of the armature sliding portion is formed of hard chromium plating covering the armature sliding portion.