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Patent Abstract
A solenoid valve is provided which may be used to inject fuel into
an internal combustion engine for automotive vehicles. The solenoid
valve includes an armature and stator attracting the armature to
open a fluid passage. The solenoid valve also includes a retaining
nut and an end body. The retaining nut engages a housing to retain
a hollow cylindrical stator casing in the housing. The end body
is joined to the casing in alignment therewith to hold the stator
within the casing without subjecting the stator to the pressure
produced by the engagement of the retaining nut with the housing.
This minimizes undesirable loads on the stator.
Patent Claims
What is claimed is:
1. A solenoid valve comprising: a housing in which a fluid passage
and a valve seat is formed; a valve member disposed in said housing,
when resting on the valve seat, said valve member closing the fluid
passage, when leaving the valve seat, said valve member opening
the fluid passage; an armature connected to said valve member, said
armature being movable in the same direction as that of movement
of said valve member; a stator attracting said armature to move
said valve member, opening the fluid passage; a coil producing an
attractive force in said stator electromagnetically when said coil
is energized; a pressure-receiving mechanism provided in contact
with said housing; a fixing mechanism engaging said housing in contact
with said pressure-receiving mechanism to press said pressure-receiving
mechanism against said housing; and an engaging mechanism holding
said stator in engagement with said pressure-receiving mechanism
without transmitting an external force acting on said pressure-receiving
mechanism from said fixing mechanism and said housing.
2. A solenoid valve as set forth in claim 1, wherein said engaging
mechanism includes a holding member which is formed integrally with
said pressure-receiving mechanism on a side of a surface of said
pressure-receiving mechanism opposite a housing-contacting surface
and which has formed therein a groove with which said stator is
fitted.
3. A solenoid valve as set forth in claim 2, wherein said pressure-receiving
mechanism includes a cylindrical member having a flange which is
formed on a valve seat side of said holding member integrally with
said holding member and which is nipped between said housing and
said fixing mechanism.
4. A solenoid valve as set forth in claim 2, wherein said stator
has formed thereon a portion tapered toward the valve seat, and
wherein said holding member is made of a cylinder which has an end
portion remote from the valve seat, bent inwardly and a shoulder
formed on an inner wall thereof, inclined to contact with the tapered
portion of said stator.
5. A solenoid valve as set forth in claim 2, wherein said engaging
mechanism includes a stopper made of cylindrical member which hits
on one of said armature and said control valve when said armature
is attracted by said stator and which has a damper flange, and wherein
said stator is made of a hollow cylindrical member in which said
stopper is disposed in contact of an end remote from said armature
with the damper flange.
6. A fuel injector comprising: a nozzle valve working to open and
close a spray hole selectively; a nozzle body supporting said nozzle
valve slidably; a pressure chamber formed in said nozzle body, producing
therein a fuel pressure working to urge said nozzle valve in a spray
hole-closing direction; and a solenoid valve working to control
the fuel pressure in said pressure chamber, said solenoid valve
including, (a) a housing in which a fluid passage and a valve seat
is formed; (b) a valve member disposed in said housing, when resting
on the valve seat, said valve member closing the fluid passage,
when leaving the valve seat, said valve member opening the fluid
passage; (c) an armature connected to said valve member, said armature
being movable in the same direction as that of movement of said
valve member; (d) a stator attracting said armature to move said
valve member, opening the fluid passage; (e) a coil producing an
attractive force in said stator electromagnetically when said coil
is energized; (f) a pressure-receiving mechanism provided in contact
with said housing; (g) a fixing mechanism engaging said housing
in contact with said pressure-receiving mechanism to press said
pressure-receiving mechanism against said housing; and (h) an engaging
mechanism holding said stator in engagement with said pressure-receiving
mechanism without transmitting an external force acting on said
pressure-receiving mechanism from said fixing mechanism and said
housing.
7. A fuel injector as set forth in claim 6, wherein said engaging
mechanism includes a holding member which is formed integrally with
said pressure-receiving mechanism on a side of a surface of said
pressure-receiving mechanism opposite a housing-contacting surface
and which has formed therein a groove with which said stator is
fitted.
8. A fuel injector as set forth in claim 7, wherein said pressure-receiving
mechanism includes a cylindrical member having a flange which is
formed on a valve seat side of said holding member integrally with
said holding member and which is nipped between said housing and
said fixing mechanism.
9. A fuel injector as set forth in claim 7, wherein said stator
has formed thereon a portion tapered toward the valve seat, and
wherein said holding member is made of a cylinder which has an end
portion remote from the valve seat, bent inwardly and a shoulder
formed on an inner wall thereof, inclined to contact with the tapered
portion of said stator.
10. A fuel injector as set forth in claim 7, wherein said engaging
mechanism includes a stopper made of cylindrical member which hits
on one of said armature and said control valve when said armature
is attracted by said stator and which has a damper flange, and wherein
said stator is made of a hollow cylindrical member in which said
stopper is disposed in contact of an end remote from said armature
with the damper flange.
11. A solenoid valve comprising: a housing in which a fluid passage
and a valve seat is formed; a valve member disposed in said housing,
when resting on the valve seat, said valve member closing the fluid
passage, when leaving the valve seat, said valve member opening
the fluid passage; an armature connected to said valve member, said
armature being movable in the same direction as that of movement
of said valve member; a stator attracting said armature to move
said valve member, opening the fluid passage; a coil producing an
attractive force in said stator electromagnetically when said coil
is energized; a stator-mounting member; a pressing member engaging
said housing to produce a nipping pressure working to nip said stator-mounting
member between said pressure member and said housing; and a stator-holding
member holding said stator in said stator-mounting member without
subjecting said stator to the nipping pressure produced by said
pressure member.
12. A solenoid valve as set forth in claim 11, wherein said stator-holding
member is disposed in alignment with said stator to urge said stator
into constant engagement with said stator-mounting member.
13. A solenoid valve as set forth in claim 11, wherein said stator-mounting
member is made of a hollow cylindrical member which has a flange
which is nipped between a step formed on an inner wall of said pressing
member and an end of said housing.
14. A solenoid valve as set forth in claim 13, wherein said stator-mounting
member has disposed therein said stator, said stator-mounting member
having formed on an inner wall thereof a tapered surface, and wherein
said stator has formed on an outer wall a tapered surface which
engages the tapered surface of said stator-mounting member.
15. A solenoid valve as set forth in claim 11, wherein said stator-mounting
member is made of a hollow cylindrical member which has an end portion
bent inward to engage a groove formed on an outer wall of said stator-holding
member to hold said stator within said stator-mounting member tightly.
Patent Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field of the Invention
[0002] The present invention relates generally to a solenoid valve
and a fuel injector which may be used to inject fuel into an internal
combustion engine for automotive vehicles, and more particularly
to an improved structure of a solenoid valve designed to minimizing
undesirable loads on parts of the solenoid valve and a fuel injector
using the same.
[0003] 2. Background Art
[0004] In general, solenoid valves are used in fuel injectors of
internal combustion engines. Such solenoid valves are designed to
magnetically energize a stator installed in a housing to attract
an armature, lifting up a valve member to open a valve hole. A maximum
amount of lift of the valve member is fixed upon installation of
the stator within the housing. For example, Japanese Patent First
Publication No. 10-122086 discloses such a solenoid valve. FIG.
6 shows one example of conventional solenoid valves for use in fuel
injectors. The shown solenoid valve is constructed to be installed
in a holder body 113 of a fuel injector. A control valve 106 is
press fit within an armature 105. The control valve 106 is disposed
slidably in a bearing 110 and moved to open a valve hole 108 formed
in a plate 111 when the armature 105 is attracted to a stator 104.
The bearing 110 is screwed into the holder body 113 to nip the plates
111 and 112 between the holder body 113 and the bearing 110. The
stator 104 is welded at portions, as indicated by A and B, to a
casing 114. A retaining nut 102 is screwed on a threaded cylinder
107 of the holder body 113 to hold the casing 114 and a spacer 109
between the end body 101 and the bearing 110, thereby positioning
the stator 104 relative to the plate 111. This fixes the interval
between the stator 104 and the valve hole 108, thereby setting the
maximum amount of lift of the control valve 106.
[0005] The positioning of the stator 104 relative to the plate
111, however, requires welding of the casing 114 and the stator
104. The stator 104, thus, needs to be made of a heat resisting
material If the stator 104 is positioned in direct contact with
the end body 101 and the spacer 109 in order to avoid thermal loads
on the stator 104, the compressive pressure produced by tightening
the retaining nut 102 acts on the stator 104. The stator 104, thus,
needs to be made of material which is tough and hard. Specifically,
it is necessary to make the stators 104 of limited materials, which
will be disadvantages in increasing the attractive force produced
by the stator 104 and which may result in undesirable thermal deformation
and physical breakage of the stator 104.
SUMMARY OF THE INVENTION
[0006] It is therefore a principal object of the invention to avoid
the disadvantages of the prior art.
[0007] It is another object of the invention to provide an improved
structure of a solenoid valve designed to minimize undesirable loads
on a stator and a fuel injector using the same.
[0008] According to one aspect of the invention, there is provided
a solenoid valve which comprises: (a) a housing in which a fluid
passage and a valve seat is formed; (b) a valve member disposed
in the housing, when resting on the valve seat, the valve member
closing the fluid passage, when leaving the valve seat, the valve
member opening the fluid passage; (c) an armature connected to the
valve member, the armature being movable in the same direction as
that of movement of the valve member; (d) a stator attracting the
armature to move the valve member, opening the fluid passage; (e)
a coil producing an attractive force in the stator electromagnetically
when the coil is energized; (f) a pressure-receiving mechanism provided
in contact with the housing; (g) a fixing mechanism engaging the
housing in contact with the pressure-receiving mechanism to press
the pressure-receiving mechanism against the housing; and (h) an
engaging mechanism holding the stator in engagement with the pressure-receiving
mechanism without transmitting an external force acting on the pressure-receiving
mechanism from the fixing mechanism and the housing.
[0009] In the preferred mode of the invention, the engaging mechanism
includes a holding member which is formed integrally with the pressure-receiving
mechanism on a side of a surface of the pressure-receiving mechanism
opposite a housing-contacting surface and which has formed therein
a groove with which the stator is fitted.
[0010] The pressure-receiving mechanism includes a cylindrical
member having a flange which is formed on a valve seat side of the
holding member integrally with the holding member and which is nipped
between the housing and the fixing mechanism.
[0011] The stator has formed thereon a portion tapered toward the
valve seat. The holding member is made of a cylinder which has an
end portion remote from the valve seat, bent inwardly and a shoulder
formed on an inner wall thereof, inclined to contact with the tapered
portion of the stator.
[0012] The engaging mechanism includes a stopper made of cylindrical
member which hits on one of the armature and the control valve when
the armature is attracted by the stator and which has a damper flange.
The stator is made of a hollow cylindrical member in which the stopper
is disposed in contact of an end remote from the armature with the
damper flange.
[0013] According to the second aspect of the invention, there is
provided a fuel injector which comprises: (a) a nozzle valve working
to open and close a spray hole selectively; (b) a nozzle body supporting
the nozzle valve slidably; (c) a pressure chamber formed in the
nozzle body, producing therein a fuel pressure working to urge the
nozzle valve in a spray hole-closing direction; and (d) a solenoid
valve working to control the fuel pressure in the pressure chamber.
The solenoid valve includes: (a) a housing in which a fluid passage
and a valve seat is formed; (b) a valve member disposed in the housing,
when resting on the valve seat, the valve member closing the fluid
passage, when leaving the valve seat, the valve member opening the
fluid passage; (c) an armature connected to the valve member, the
armature being movable in the same direction as that of movement
of the valve member; (d) a stator attracting the armature to move
the valve member, opening the fluid passage; (e) a coil producing
an attractive force in the stator electromagnetically when the coil
is energized; (f) a pressure-receiving mechanism provided in contact
with the housing; (g) a fixing mechanism engaging the housing in
contact with the pressure-receiving mechanism to press the pressure-receiving
mechanism against the housing; and (h) an engaging mechanism holding
the stator in engagement with the pressure-receiving mechanism without
transmitting an external force acting on the pressure-receiving
mechanism from the fixing mechanism and the housing.
[0014] In the preferred mode of the invention, the engaging mechanism
includes a holding member which is formed integrally with the pressure-receiving
mechanism on a side of a surface of the pressure-receiving mechanism
opposite a housing-contacting surface and which has formed therein
a groove with which the stator is fitted.
[0015] The pressure-receiving mechanism includes a cylindrical
member having a flange which is formed on a valve seat side of the
holding member integrally with the holding member and which is nipped
between the housing and the fixing mechanism.
[0016] The stator has formed thereon a portion tapered toward the
valve seat. The holding member is made of a cylinder which has an
end portion remote from the valve seat, bent inwardly and a shoulder
formed on an inner wall thereof, inclined to contact with the tapered
portion of the stator.
[0017] The engaging mechanism includes a stopper made of cylindrical
member which hits on one of the armature and the control valve when
the armature is attracted by the stator and which has a damper flange.
The stator is made of a hollow cylindrical member in which the stopper
is disposed in contact of an end remote from the armature with the
damper flange.
[0018] According to the third aspect of the invention, there is
provided a solenoid valve which comprises: (a) a housing in which
a fluid passage and a valve seat is formed; (b) a valve member disposed
in the housing, when resting on the valve seat, the valve member
closing the fluid passage, when leaving the valve seat, the valve
member opening the fluid passage; (c) an armature connected to the
valve member, the armature being movable in the same direction as
that of movement of the valve member; (d) a stator attracting the
armature to move the valve member, opening the fluid passage; (e)
a coil producing an attractive force in the stator electromagnetically
when the coil is energized; (f) a stator-mounting member; (g) a
pressing member engaging the housing to produce a nipping pressure
working to nip the stator-mounting member between the pressure member
and the housing; and (h) a stator-holding member holding the stator
in the stator-mounting member without subjecting the stator to the
nipping pressure produced by the pressure member.
[0019] In the preferred mode of the invention, the stator-holding
member is disposed in alignment with the stator to urge the stator
into constant engagement with the stator-mounting member.
[0020] The stator-mounting member is made of a hollow cylindrical
member which has a flange which is nipped between a step formed
on an inner wall of the pressing member and an end of the housing.
[0021] The stator-mounting member has disposed therein the stator.
The stator-mounting member has formed on an inner wall thereof a
tapered surface. The stator has formed on an outer wall a tapered
surface which engages the tapered surface of the stator-mounting
member.
[0022] The stator-mounting member is made of a hollow cylindrical
member which has an end portion bent inward to engage a groove formed
on an outer wall of the stator-holding member to hold the stator
within the stator-mounting member tightly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The present invention will be understood more fully from
the detailed description given hereinbelow and from the accompanying
drawings of the preferred embodiments of the invention, which, however,
should not be taken to limit the invention to the specific embodiments
but are for the purpose of explanation and understanding only.
[0024] In the drawings:
[0025] FIG. 1 is a vertical sectional view which shows a fuel injector
equipped with a solenoid valve according to the embodiment of the
invention;
[0026] FIG. 2 is a partial sectional view which shows an internal
structure of the solenoid valve installed in the fuel injector of
FIG. 1;
[0027] FIG. 3 is a partial sectional view which shows a stator
and an armature of the solenoid valve of FIG. 2;
[0028] FIG. 4 is an exploded perspective view which shows an end
body, a stator, and a casing of the solenoid valve of FIG. 2;
[0029] FIG. 5 is an exploded perspective view which shows assembling
processes of parts of the solenoid valve of FIG. 2; and
[0030] FIG. 6 is a partial sectional view which shows a conventional
solenoid valve.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] Referring to the drawings, wherein like reference numbers
refer to like parts in several views, particularly to FIGS. 1 and
2, there is shown a fuel injector 1 according to the invention.
[0032] The fuel injector 1 is installed in a head of an internal
combustion engine (not shown) and inject fuel directly into one
of cylinders of the engine.
[0033] The fuel injector 1 includes a holder body 11 (i.e., an
injector body) and a nozzle body 12 which are joined by a retaining
nut 14.
[0034] The holder body 11 has a needle chamber 11d formed therein.
Similarly, the nozzle body 12 has a needle chamber 12e formed therein.
A nozzle valve 20 is disposed within the needle chambers 11d and
12e.
[0035] The holder body 11 has an inlet 11f which works as a connector
to a fuel pump (not shown) The inlet 11f has a fuel inlet passage
11a formed therein. A bar filter 13 is installed in the fuel inlet
passage 11a. The fuel inlet passage 11a communicates with a fuel
passage 12d formed in the nozzle body 12 through a fuel passage
11b. The fuel passage 12d communicates with the needle chamber 12e
through a fuel sump 12c. The needle chamber 12e communicates with
spray holes 12b formed in a head of the nozzle body 12. The fuel
supplied from the fuel pump to the inlet 11f flows through the bar
filter 13 to the fuel inlet passage 11a, the fuel passages 11b and
12d, the fuel sump 12c, and the needle chamber 12e and is injected
from the spray holes 12b into a cylinder of the engine. The holder
body 11 also has a leak passage 11c leading to the needle chamber
11d.
[0036] The nozzle valve 20 consists of a needle 20c, a rod 20b,
and a control piston 20a. The needle 20c is made up of a seating
portion (i.e., a valve head), a small-diameter portion, a tapered
portion, and a large-diameter portion. The large-diameter portion
is disposed hermetically within the needle chamber 12e to be movable
in a lengthwise direction of the nozzle valve 20. The tapered portion
is urged upward, as viewed in FIG. 1, by the fuel pressure in the
fuel sump 12c. An annular gap is formed between an outer wall of
the small-diameter portion and an inner wall of the needle chamber
12e. The seating portion is of a conical shape and rests on a valve
seat 12a to close the spray holes 12b. The rod 20b abuts at one
end on the needle 20c and at the other end on the control piston
20a. A coil spring 15 is disposed around the rod 20b and urges the
needle 20c through the rod 20b into constant engagement with the
valve seat 12a. The control piston 20a is disposed within the needle
chamber 11d hermetically to be movable in the lengthwise direction
thereof.
[0037] A first annular plate 16, as shown in FIG. 2, is disposed
within a cylindrical end chamber which is formed in an end portion
of the holder body 11 in communication with an upper end of the
needle chamber 11d. The first plate 16 has formed therein a through
hole 16a leading to the needle chamber 11d and an inlet orifice
16b communicating between the through hole 16a and the fuel inlet
passage 11a through a fuel passage 11j. A pressure chamber 16c is
defined by the end of the control piston 20a, the inner wall of
the needle chamber 11d, and an inner wall of the through hole 16a.
[0038] A second annular plate 18 and a third annular plate 17 are
laid on the first plate 16 to overlap each other. The second annular
plate 18 has a seat 18a formed on a flat surface thereof facing
the third annular plate 17. The third plate 17 is screwed into the
end chamber of the holder body 11 to hold the first plate 16 and
the second plate 18 therewithin. The third plate 17 has through
holes 17a and 17b formed therein. A bush 60 is press fit within
the through hole 17a. The bush 60 is made of a thin-walled hollow
cylindrical member having a relatively high hardness and defines
a valve chamber 70 between a lower end thereof and the second plate
18. The second plate 18 has formed therein a valve hole 18b which
establishes communication between the pressure chamber 16c and the
valve chamber 70. A clearance 11e is, as clearly shown in FIG. 2,
formed in a circumferential direction between side walls of the
first and second plates 16 and 18 and the inner wall of the end
chamber of the holder body 11. The clearance 11e leads to the leak
passage 11c and to the hole 17b through a recess 17c formed in a
surface of the third plate 17 facing the second plate 18. The holder
body 11 has a cylindrical threaded portion 11g. The cylindrical
threaded portion 11g, the second plate 18, and the third plate 17
form a housing for a solenoid valve 2 as will be described below.
[0039] The solenoid valve 2 has a stator 31 disposed within a hollow
cylindrical casing 33. The casing 33 has, as shown in FIG. 2, formed
on an inner wall thereof an inner shoulder 33b which has a conical
surface inclined downward, as viewed in the drawing. The casing
33 has formed on an outer wall thereof below the inner shoulder
33b a flange 33a which is held between an inner step 52a of a retaining
nut 52, as clearly shown in FIG. 5, and the end of the threaded
portion 11g of the holder body 11 through an annular spacer 19 to
join the casing 33 to the holder body 11. Specifically, the retaining
nut 52 is tightened on the threaded portion 11g of the holder body
11, thereby nipping the flange 33a between the inner step 52a of
the retaining nut 52 and the end of the threaded portion 11g of
the holder body 11 through the annular spacer 19 to secure the casing
33 on the holder body 11 firmly. The annular spacer 19 is made of
a disc whose thickness is so selected as to adjust a maximum lift
of the control valve 40 to a desired value. The maximum lift may
alternatively be adjusted by changing the thickness of the flange
33a without use of the annular spacer 19. Instead of the spacer
19, a disc spring may also be disposed between the flange 33a and
the end of the threaded portion 11g to adjust the amount of lift
of the control valve 40 by turning the retaining nut 52. The casing
33 has an upper opening closed by an end body 53. The casing 33
has a thin-walled end 33c curved inwardly to engage an annular groove
53a formed in an outer wall of the end body 53. The outer wall of
the end body 53 is opposed to the inner wall of the retaining nut
52 in a radius direction thereof, and not in a longitudinal direction
thereof.
[0040] A stopper 35 is disposed in the cylindrical stator 31 in
contact with the lower end of the end body 53. The stopper 35 consists
of a hollow cylinder 35b and a damper flange 35a formed on an end
of the cylinder 35b. A small annular gap is provided between the
inner wall 31a of the stator 31 and the outer wall of the stopper
35. Specifically, the stator 31 is not in direct contact with the
stopper 35. The stator 31 consists of a large-diameter portion,
a tapered portion (i.e., a shoulder) 31b, as clearly shown in FIG.
4, a small-diameter portion. The end 31c of the large-diameter portion
is in contact with the damper flange 35a. The outer diameter of
the large-diameter portion is substantially equal to that of the
damper flange 35a. The tapered portion 31b is in contact with the
inner shoulder 33b of the casing 33. In the stator 31, a bobbin
34 and a coil 32 wound around the bobbin 34 are fixed through resin.
The coil 32 leads electrically to a terminal 51 extending into a
connector 50.
[0041] A control valve 40 is disposed slidably within the stator
31 and the third plate 17. The control valve 40 consists of a spherical
member 40a, a stem 40b, and a spring seat 40c. The spherical member
40a, the stem 40b, and the spring seat 40c may be connected together
in press-fits or formed by machining a single member. The spherical
member 40a has a flat surface which works to close the valve hole
18b. The stem 40b is press fit at a base thereof within a central
hole formed in an armature 41 to be slidable along with the armature
41 in contact with the inner wall of the bush 60. The armature 41
is disposed between the stator 31 and the third plate 17. The armature
41, as clearly shown in FIG. 3, has an annular protrusion 41a formed
on the center of the end surface facing the stator 31. The protrusion
41a projects from the end surface of the armature 41 by approximately
50 .mu.m in order to establish an air gap H between the armature
41 and the stator 31 when the armature 41 is lifted up fully. The
protrusion 41a is located in co-axial alignment with the cylinder
35b of the stopper 35 so that the end of the protrusion 41a hits
on the lower end of the cylinder 35b when the armature 41 is lifted
up fully.
[0042] A second coil spring 38 is, as shown in FIG. 2, disposed
in the cylinder 35b of the stopper 35 between an end of a spring
pressure-adjusting pipe 37 forced into the end body 53 and the spring
seat 40c to urge the spherical member 40a into constant engagement
with the second plate 18 through the stem 40b to close the valve
hole 18b.
[0043] The manner in which the casing 33, the stator 31, the stopper
35, the end body 53, and the retaining nut 52 are joined to the
holder body 11 will be discussed below with reference to FIGS. 4
and 5.
[0044] First, the stator 31 equipped with the coil 32 and the terminal
51 is inserted into the casing 33 until the tapered portion 31b
hits on the inner shoulder 33b of the casing 33, thereby positioning
the stator 31 coaxially with the casing 33. The stopper 35 is inserted
into the stator 31 until the damper flange 35a hits on the end 31c
of the stator 31. The cylinder 35b of the stopper 35 is fitted in
contact with the inner wall 31a of the stator 31, thereby positioning
the stopper 35 coaxially with the stator 31. The terminal 51 is
inserted into a hole (not shown) formed in the end body 53.
[0045] The end body 53 is placed on the damper flange 35a of the
stopper 35. The edge 33d of the thin-walled end 33c of the casing
33 is located on a level with the groove 53a of the end body 53.
The edge 33d of the thin-walled end 33c of the casing 33 is pressed
inwardly into the groove 53a to join the casing 33 to the end body
53. When the edge 33d of the casing 33 is forced into the groove
53a of the end body 53, it will cause the end body 53 to be shifted
downwardly, as viewed in FIGS. 4 and 5, to move the damper flange
35a and the stator 31 in the same direction. This causes the tapered
portion 31b of the stator 31 to be pressed against the inner shoulder
33b of the casing 33, thus positioning the stator 31 in the longitudinal
direction thereof within the casing 33. The damper flange 35a is
nipped between the end body 53 and the stator 31.
[0046] After the stator 31, the stopper 35, and the end body 53
are installed in the casing 33 in the above manner, the casing 33
is put in the threaded portion 11g of the holder body 11 through
the spacer 19. Next, the retaining nut 52 is put on the casing 33
and the end body 53 and then screwed on the threaded portion 11g
to holding the spacer 19 and the flange 33a between the inner step
52a of the retaining nut 52, as shown in FIG. 5, and the end surface
11h of the threaded portion 11g of the holder body 11, thereby positioning
the assembly of the casing 33, the stator 31, the stopper 35, and
the end body 53 within the holder body 11. This fixes the interval
between the second plate 18 installed in the body holder 11 and
the stator 31, setting a maximum amount of lift of the control valve
40.
[0047] A fuel injection operation of the fuel injector 1 will be
discussed below.
[0048] When it is required to inject the fuel into the internal
combustion engine, an ECU (electronic control unit), not shown,
actuates a fuel injection pump and delivers the fuel to an accumulator
pipe. The fuel is stored in the accumulator pipe at a constant high
pressure level and supplied to the fuel injector 1 through a supply
pipe connected to the inlet 11f.
[0049] The ECU produces a control valve-actuating current as a
function of an operating condition of the engine and outputs it
to the coil 32 of the stator 31 in the form of a pulse signal. When
the coil 32 is energized, it will cause the stator 31 to produce
an attractive force. When the sum of the attractive force and the
fuel pressure within the pressure chamber 16c acting on the control
valve 40 exceeds the spring pressure of the second spring 38, the
armature 41 is attracted to the stator 31, thereby causing the control
valve 40 to be lifted upward, as viewed in FIGS. 1, 2, and 3 until
the protrusion 41a of the armature 41 hits on the end of the cylinder
35b of the stopper 35, so that the spherical member 40a of the control
valve 40 leaves the seat 18a to open the valve hole 18b. When the
valve hole 18a is opened, it establishes the fluid communication
between the pressure chamber 16c and the pressure chamber 70, thereby
causing the fuel to flow from the pressure chamber 16c to the pressure
chamber 70. The fuel entering the pressure chamber 70 is drained
to a fuel tank through the through hole 17b, the inside of the cylinder
35b of the stopper 35, and the inside of the adjusting pipe 37.
[0050] When the pressure chamber 16c communicates with the pressure
chamber 70, it will cause the fuel flowing out of the pressure chamber
16c through the valve hole 18b to be greater than that flowing into
the pressure chamber 16c from the inlet orifice 16b, so that the
fuel pressure within the pressure chamber 16c drops. When the fuel
pressure in the pressure chamber 16c decreases, and the sum of the
spring pressure of the first spring 15 and the fuel pressure in
the pressure chamber 16c urging the needle 20c in the spray hole-closing
direction overcomes the fuel pressure in the fuel sump 12c urging
the needle 20c in the spray hole-opening direction, it will cause
the needle 20c to be moved away from the valve seat 12a to open
the spray holes 12b, thereby producing a fuel jet.
[0051] When it is required to stop the fuel injection, the ECU
deenergizes the coil. 32. When the coil 32 is deenergized, it will
cause the attractive force to disappear from the stator 31, so that
the spring pressure of the second spring 38 overcomes the fuel pressure
in the pressure chamber 16c to move the control valve 40 downward,
thereby closing the valve hole 18b through the spherical member
40a. The fuel continues flowing into the pressure chamber 16c through
the inlet orifice 16b, so that the fuel pressure in the pressure
chamber 16c is elevated. When the sum of the spring pressure of
the first spring 15 and the fuel pressure in the pressure chamber
16c acting on the needle 20c in the spray hole-closing direction
overcomes the fuel pressure in the fuel sump 12c in the spray hole-opening
direction, it will cause the needle 20c to move downward, as viewed
in FIG. 1, so that the needle 20c rests on the valve seat 12a to
close the spray holes 12b, thereby stopping the fuel injection.
[0052] The pressure produced by fastening the retaining nut 52
acting on the flange 33a of the casing 33 exerts the compressive
stress on the upper and lower surfaces 33e and 33f of the flange
33a, as clearly shown in FIG. 5, but does not substantially act
on the thin-walled portion 33c of the casing 33. Specifically, the
pressure produced by the retaining nut 52 acting on the flange 33a
of the casing 33 is not transmitted to the stator 31. Therefore,
external pressures substantially acting on the stator 31 when the
control valve 40 is at rest are only the pressure exerted by the
stopper 35 on the stator 31 toward the nozzle body 12 which is produced
by staking the edge 33d of the casing 33 and the reactive pressure
from the surface of the inner shoulder 33b. The outer diameter of
the tapered portion 31b of the stator 31 and the inner diameter
of the inner shoulder 33b of the casing 33 are decreased in a direction
in which the stator 31 is pressed, that is, downward, as viewed
in FIG. 5, therefore, the pressure exerted by the end body 53 on
the stator 31 does not concentrate on a specified portion of the
tapered portion 31b of the stator 31. Moreover, the pressure exerted
on the stator 31 by pressing or staking the edge 33d of the casing
on the end body 53 is much smaller than the pressure exerted on
the flange 33a of the casing 33 by fastening the retaining nut 52.
The stator 31 is not welded to any parts of the solenoid valve 2
and thus not subjected to the thermal stress during the assembly.
[0053] Further, the maximum lift of the control valve 40 is, as
described above, set by the contact of the protrusion 41a of the
armature 41 with the end of the cylinder 35b of the stopper 35.
The impact acting on the stopper 35 when the protrusion 41a hits
on the cylinder 35b of the stopper 35 is transmitted to the casing
33 from the damper flange 35a through the end body 53 and to the
body holder 11 from the flange 33a of the casing 33 through the
retaining nut 52. The impact is, however, not exerted on the stator
31 because the stopper 35 is disposed only within the stator 31
and not joined directly to the stator 31 at all.
[0054] Specifically, the static load acting on the stator 31 is
very low, and the impact load is not exerted on the stator 31, thereby
allowing the stator 31 to be made of a relatively low tenacity material.
Additionally, the stator 31 is not welded to any parts of the solenoid
valve 2 and thus may be made of a low thermal resistance material.
[0055] While, in the above embodiment, the casing 33, the stator
31, the stopper 35, and the end body 53 are joined by bending or
staking the edge 33d of the casing 33 into the groove 53a of the
end body 53, it may be accomplished by fastening screws into the
side walls of the casing 33 and the end body 53 in the lateral direction
thereof.
[0056] The maximum lift of the control valve 40 is restricted by
the direct engagement of the armature 41 with the stopper 35, however,
it may be set by providing a flange on the stem 40b of the control
valve 40 which hits on a member fixed on a given portion of the
holder body 11 when the control valve 40 is lifted up to a desired
level.
[0057] The stator 31 is not joined to the casing 33, however, may
be connected directly to the casing 33 by staking or using screws.
[0058] While the present invention has been disclosed in terms
of the preferred embodiments in order to facilitate better understanding
thereof, it should be appreciated that the invention can be embodied
in various ways without departing from the principle of the invention.
Therefore, the invention should be understood to include all possible
embodiments and modifications to the shown embodiments witch can
be embodied without departing from the principle of the invention
as set forth in the appended claims. |