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 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE
MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
TECHNICAL FIELD
5 [0001]
The present disclosure relates to an electromagnetic fuel injection
valve to be mounted in an engine.
BACKGROUND ART
10 [0002]
As illustrated in each of FIGS. 1 and 2 of PLT 1, a conventional fuel
injection valve has a magnetic throttle portion 13 at the outer-diameter
side of an air gap 58 between an armature 17 and a core 2; the respective
both axis-direction ends of a yoke 45 disposed outside a coil are welded
15 to the core 2 and a valve holder 10.
[0003]
An fuel injection valve of this type is structured in such a way that
deformation of such an orifice plate 22 as illustrated in a drawing of PLT
2 displaces a valve seat 18 so that the lift amount of the valve body is
20 adjusted.
CITATION LIST
Patent Literature
[0004]
25 PLT 1: WO96/24763
3
PLT 2: WO92/03653
Technical Problem
[0005]
Due to strengthening of exhaust gas restrictions 5 on a vehicle,
high-accuracy air-fuel ratio control is required for an engine; thus, there
is required a fuel injection valve that can accurately inject even a minute
amount of fuel. When the spring load of a fuel injection valve is increased
so as to shorten the valve-closing time, the amount of fuel to be injection
10 when the valve is closed decreases and hence even a minute amount of fuel
can accurately be injected. On the other hand, when the spring load is
increased, the electromagnetic force at a time when the valve is opened
becomes insufficient; therefore, there has been a problem that under the
condition that the driving voltage at a time when the engine starts is low,
15 the valve cannot be opened. It is conceivable that in order to increase
the electromagnetic force, the armature is upsized; however, because the
increase in the armature mass prolongs the valve-closing time, the fuel
injection amount cannot be decreased.
[0006]
20 Meanwhile, when in the fuel injection valve of PLT 1, the magnetic
throttle portion 13 is made thinner, magnetic flux that passes in this
portion decreases and hence the magnetic flux that passes through the air
gap 58 increases; therefore, it is made possible to increase the
electromagnetic force without upsizing the armature 17. However, because
25 after welding of its both axis-direction ends, the yoke 45 contracts due
4
to coldness, a stress is imposed intensively on the magnetic throttle
portion 13, which is thinnest in the structure between the welding points,
and hence deformation may be caused. The valve holder 10 including the
magnetic throttle portion 13 contains the core 2 and the armature 17; thus,
the deformation of the magnetic throttle portion 13 changes 5 the relative
positional relationship between the core 2 and the armature 17 and hence
the valve lifting amount changes. In the fuel injection valve of PLT 1,
the inner circumferential surface of the magnetic throttle portion 13 is
the sliding surface between the magnetic throttle portion 13 and the
10 armature sliding portion 36; when the magnetic throttle portion 13 is
buckled, there exists no clearance between the armature sliding portion
36 and the inner circumferential surface of the magnetic throttle portion
13 and hence a sliding failure of the armature 17 is caused.
[0007]
15 Therefore, there is required a fuel injection valve that makes it
possible that even when in order to increase the magnetic flux that passes
through the gap between the core and the armature, the valve holder is thinned,
post-welding contraction of the yoke, for example, can be suppressed from
deforming the thinned portion of the valve holder.
20
Solution to Problem
[0008]
A fuel injection valve according to the present disclosure is provided
with
25 a valve seat in which a fuel path is formed,
5
a valve body that travels toward the axial-direction
valve-opening side and departs from the valve seat so as to open the fuel
path or travels toward the axial-direction valve-closing side and abuts
on the valve seat so as to close the fuel path,
5 a tubular coil,
a tubular core disposed at the inner-diameter side of the coil,
a tubular armature that is disposed at the axial-direction
valve-closing side of the core in such a way as to be spaced apart by a
gap from the core, that is attracted by magnetic flux, produced by
10 energization of the coil, to the axial-direction valve-opening side, and
that makes the valve body travel to the axial-direction valve-opening side,
a tubular valve holder that contains the valve seat, the valve
body, and the armature at the inner-diameter side thereof, and
a tubular yoke that covers the outside of the coil.
15 The yoke includes
a tubular yoke outer-diameter portion that covers the
outer-diameter side of the coil,
a tubular yoke valve-closing portion that extends from the yoke
outer-diameter portion toward the axial-direction valve-closing side, and
20 a yoke valve-opening portion that extends from the yoke
outer-diameter portion toward the axial-direction valve-opening side and
is welded to the outer circumferential surface of the core.
The valve holder includes
a core connection portion whose inner circumferential surface
25 is fitted with and welded to the outer circumferential surface of the core,
6
a gap outer-diameter portion that is a portion closer to the
axial-direction valve-closing side than the core connection portion is and
that is disposed at the outer-diameter side of the gap between the core
and the armature,
an armature sliding portion that is a portion 5 closer to the
axial-direction valve-closing side than the gap outer-diameter portion is
and whose inner circumferential surface slides on the outer circumferential
surface of the armature, and
a holder press-fitting portion that is a portion closer to the
10 axial-direction valve-closing side than the armature sliding portion is
and whose outer circumferential surface is press-fitted with the inner
circumferential surface of the yoke valve-closing portion.
The gap outer-diameter portion is formed thinner than each of the
core connection portion, the armature sliding portion, and the holder
15 press-fitting portion is.
Axial-direction frictional force, produced between the inner
circumferential surface of the yoke valve-closing portion and the outer
circumferential surface of the holder press-fitting portion, is smaller
than an axial-direction deformation load with which plastic deformation
20 of the gap outer-diameter portion begins.
Advantage of Invention
[0009]
In a fuel injection valve according to the present disclosure, because
25 a gap outer-diameter portion, of a valve holder, that is disposed at the
7
outer-diameter side of a gap between a core and an armature is thinned,
it is made possible that magnetic flux that passes through the gap
outer-diameter portion is reduced so as to increase magnetic flux that
passes through the gap; thus, attractive force of the armature can be
increased. The core and a yoke valve-opening portion of 5 a yoke are welded
to each other; however, a holder press-fitting portion of the valve holder
and a yoke valve-closing portion of the yoke are coupled with each other
through press-fitting. Accordingly, because though frictional force
produced by a contact pressure between the press-fitting portions, the yoke
10 is coupled with the portion that is closer to the axial-direction
valve-closing side than the gap outer-diameter portion is, the
press-fitting portions slide on each other and hence the load in the axial
direction can be removed. In addition, axial-direction frictional force
at the press-fitting portion is smaller than the axial-direction
15 deformation load of the gap outer-diameter portion; therefore, before due
to, for example, post-welding contraction of the yoke, the axial-direction
load to be imposed on the gap outer-diameter portion reaches the deformation
load of the gap outer-diameter portion, the inner circumferential surface
of the yoke valve-closing portion and the outer circumferential surface
20 of the holder press-fitting portion slide on each other and hence the
axial-direction load can be reduced; thus, the deformation of the gap
outer-diameter portion can be suppressed.
[0010]
Moreover, the gap outer-diameter portion is thinned but the armature
25 sliding portion is not thinned; therefore, even if due to variations in
8
the production, the gap outer-diameter portion is deformed, the armature
sliding portion can be suppressed from being deformed. Thus, because it
can be suppressed that there occurs a failure in sliding between the armature
sliding portion and the armature, the risk of the operation failure in the
fuel injection valve can be reduced. In addition, the 5 armature sliding
portion is disposed at a position closer to the axial-direction
valve-opening side than the holder press-fitting portion is; thus, the
armature sliding portion is not press-fitted into the yoke valve-closing
portion. Therefore, because the armature sliding portion is not liable
10 to be deformed by press-fitting, it is made possible that deformation of
the inner circumferential surface of the armature sliding portion is not
liable to cause sliding failure.
BRIEF DESCRIPTION OF THE DRAWINGS
15 [0011]
FIG. 1 is a cross-sectional view of a fuel injection valve according
to Embodiment 1 of the present disclosure;
FIG. 2 is a principal-part cross-sectional view of the fuel injection
valve according to Embodiment 1 of the present disclosure;
20 FIG. 3 is a cross-sectional view of the fuel injection valve for
explaining adjustment of a valve lifting amount according to Embodiment
1 of the present disclosure;
FIG. 4 is a cross-sectional view for explaining machining of a yoke
according to Embodiment 1 of the present disclosure;
25 FIG. 5 is a cross-sectional view for explaining machining of the yoke
9
according to Embodiment 1 of the present disclosure; and
FIG. 6 is a cross-sectional view for explaining shaving machining
of a yoke valve-closing portion according to Embodiment 1 of the present
disclosure.
5
DESCRIPTION OF EMBODIMENTS
[0012]
Embodiment 1
A fuel injection valve 1 according to Embodiment 1 will be explained
10 with reference to the drawings. FIG. 1 is a cross-sectional view of the
fuel injection valve 1 according to the present embodiment, when taken along
a plane passing through the center axis Y. FIG. 2 is a principal-part
cross-sectional view of the fuel injection valve 1. Each of FIGS. 1 and
2 is a view of the fuel injection valve 1 at a time when the valve is closed.
15 [0013]
The front-end portion of the fuel injection valve 1 is mounted in
an engine in such a way as to be exposed in the air-intake path
(unillustrated) of the engine, so that fuel is supplied to the rear-end
portion of the fuel injection valve 1. The fuel injection valve 1 opens
20 the valve in response to an electric signal from a control apparatus so
as to inject fuel into the air-intake path.
[0014]
The fuel injection valve 1 has a valve seat 3 in which a fuel path
3a is formed and a valve body 2 for opening and closing the fuel path 3a.
25 When traveling toward the axial-direction valve-opening side X1, the valve
10
body 2 departs from the valve seat 3 so as to open the fuel path 3a; when
traveling toward the axial-direction valve-closing side X2, the valve body
2 abuts on the valve seat 3 so as to close the fuel path 3a. The valve
body 2 is disposed at the axial-direction valve-opening side X1 of the fuel
path 3a. The valve body 2 is a needle valve having a sphere-5 shaped front-end
portion 2a for blocking the fuel path 3a and a tubular (cylindrical tubular,
in this example) pipe 2b that extends from the front-end portion 2a toward
the axial-direction valve-opening side X1. The pipe 2b is provided with
a plurality of holes in the side face thereof and is fixed to the front-end
10 portion 2a through welding. The fuel injection valve 1 has an orifice plate
4 that is provided at the axial-direction valve-closing side X2 of the valve
seat 3 and in which injection holes 4a are formed.
[0015]
In the present disclosure, the direction in which the valve body 2
15 travels is define as the axial direction X. The axial direction X is in
parallel with the center axis Y of each of tubular members. The
axial-direction valve-closing side X2 is at the front-end side of the fuel
injection valve 1; the axial-direction valve-opening side X1 is at the
rear-end side of the fuel injection valve 1. The respective tubular members
20 are arranged around the center axis Y.
[0016]
The valve seat 3 and the orifice plate 4 are arranged at the end portion
(the front-end portion) of the fuel injection valve 1 at the axial-direction
valve-closing side X2; fuel is injected from the end portion. The end
25 portion (the rear-end portion) of the fuel injection valve 1 at the
11
axial-direction valve-opening side X1 opens toward the axial-direction
valve-opening side X1; fuel of substantially 300 kPa is supplied from a
fuel pipe (unillustrated) to the opening portion. An O-ring 13 is embedded
in the outer circumferential surface of the rear-end portion of the fuel
injection valve 1 and seals the connection with 5 the fuel pipe.
[0017]
The fuel injection valve 1 is provided with a tubular coil 5; a tubular
core 7 disposed at the inner-diameter side of the coil 5; an armature 8
that is disposed at the axial-direction valve-closing side X2 of the core
10 7 in such a way as to be spaced apart by a gap 6 from the core 7 and is
attracted by magnetic flux, produced by energization of the coil 5, to the
axial-direction valve-opening side X1; and a tubular yoke 11 that covers
the outside of the coil 5. Each of the core 7, the yoke 11, and the armature
8 is formed of a magnetic material such as iron. The coil 5 has a bobbin
15 5a on which copper wire is wound. The bobbin 5a is formed integrally with
a supporting member for an after-mentioned terminal 12. The core 7 extends
up to the end portion (the rear-end portion) of the fuel injection valve
1 at the axial-direction valve-opening side X1.
[0018]
20 The armature 8 is provided with a cylindrical tubular main body
portion 8a and a cylindrical tubular boss portion 8b that is a portion
extending from the main body portion 8a toward the axial-direction
valve-closing side X2, that has an inner diameter the same as that of the
main body portion 8a, and that has an outer diameter smaller than that of
25 the main body portion 8a. The endface of the core 7 (an after-mentioned
12
core small-diameter portion 7a) at the axial-direction valve-closing side
X2 and the endface of the armature 8 (the main body portion 8a) at the
axial-direction valve-opening side X1 face each other in the axial direction
X. The gap 6 between the core 7 and the armature 8 in the axial direction
X is produced when the valve is closed; when the valve 5 is opened, the gap
6 is not produced. The portion of the main body portion 8a at the
axial-direction valve-closing side X2 has an outer diameter larger than
that of the portion thereof at the axial-direction valve-opening side X1
and is a sliding surface that slides on the inner circumferential surface
10 of an armature sliding portion 9c of a valve holder 9. Through press-fitting,
the inner circumferential surface of the armature 8 fits with and is fixed
to the outer circumferential surface of the end portion of the pipe 2b at
the axial-direction valve-opening side X1.
[0019]
15 The fuel injection valve 1 is provided with a spring 15 that is disposed
at the inner-diameter side of the core 7 and presses the armature 8 toward
the axial-direction valve-closing side X2. The end portion of the spring
15 at the axial-direction valve-opening side X1 is supported by a tubular
(cylindrical tubular, in this example) rod 16; the end portion of the spring
20 15 at the axial-direction valve-closing side X2 presses the pipe 2b fixed
to the armature 8 toward the axial-direction valve-closing side X2. The
rod 16 is fitted with and fixed to the inner circumferential surface of
the core 7 through press-fitting.
[0020]
25 The fuel injection valve 1 is provided with the terminal 12 for
13
connecting the coil 5 with the external control apparatus. The terminal
12 is disposed at a side portion of the fuel injection valve 1. When the
control apparatus supplies the terminal 12 with electric power, the coil
5 generates magnetic flux; then, the magnetic flux of the coil 5 produces
attractive force for attracting the armature 8 toward the 5 axial-direction
valve-opening side X1. When the magnetic-flux attractive force to the
axial-direction valve-opening side X1 exceeds the pressing force of the
spring 15 to the axial-direction valve-closing side X2, the armature 8 and
the valve body 2 travel toward the axial-direction valve-opening side X1;
10 then, the valve body 2 departs from the valve seat 3, and hence the valve
is opened. In contrast, when the supply of electric power from the control
apparatus to the terminal 12 is stopped, the magnetic-flux attractive force
to the axial-direction valve-opening side X1 is extinguished and due to
the pressing force of the spring 15 to the axial-direction valve-closing
15 side X2, the armature 8 and the valve body 2 travel toward the axial-direction
valve-closing side X2; then, the valve body 2 abuts on the valve seat 3,
and hence the valve is closed.
[0021]
The fuel injection valve 1 is provided with the tubular valve holder
20 9 that contains the valve seat 3, the valve body 2, and the armature 8 at
the inner-diameter side thereof. The valve holder 9 contains also the
orifice plate 4 at the inner-diameter side thereof.
[0022]
The orifice plate 4 has welding portions 4c welded to the portions
25 of the valve seat 3 at the axial-direction valve-closing side X2 and welding
14
portions 4b welded to the valve holder 9. That is to say, the valve seat
3 is fixed to the valve holder 9 through the intermediary of the orifice
plate 4.
[0023]
The yoke 11 is provided with a tubular yoke outer-5 diameter portion
11a that covers the outer-diameter side of the coil 5, a tubular yoke
valve-closing portion 11b that extends from the yoke outer-diameter portion
11a toward the axial-direction valve-closing side X2 and supports the valve
holder 9, and a yoke valve-opening portion 11c that extends from the yoke
10 outer-diameter portion 11a toward the axial-direction valve-opening side
X1 and is welded to the outer circumferential surface of the core 7.
[0024]
In the present embodiment, the yoke outer-diameter portion 11a and
the yoke valve-closing portion 11b are respective members that are
15 integrated with each other; they are formed in the shape of a two-step
cylindrical tube in which the diameter of the yoke valve-closing portion
11b decreases in two steps from the diameter of the yoke outer-diameter
portion 11a. The yoke valve-opening portion 11c is a plate-shaped member
and has a welding portion 11d welded to the outer circumferential surface
20 of the core 7 and a welding portion 11e welded to the yoke outer-diameter
portion 11a. The yoke valve-opening portion 11c is an annular-plate-shaped
member; a portion thereof in the circumferential direction along which the
terminal 12 is disposed is cut out therefrom; the yoke valve-opening portion
11c blocks the opening, at the axial-direction valve-opening side X1, of
25 a cylindrical tubular space between the outer circumferential surface of
15
the core 7 and the inner circumferential surface of the yoke outer-diameter
portion 11a.
[0025]
The valve holder 9 is provided with a core connection portion 9a
whose inner circumferential surface is fitted with and welded 5 to the outer
circumferential surface of the core 7; a gap outer-diameter portion 9b that
is a portion closer to the axial-direction valve-closing side X2 than the
core connection portion 9a is and that is disposed at the outer-diameter
side of the gap 6 between the core 7 and the armature 8; the armature sliding
10 portion 9c that is a portion closer to the axial-direction valve-closing
side X2 than the gap outer-diameter portion 9b is and whose inner
circumferential surface slides on the outer circumferential surface of the
armature 8 (the portion of the main body portion 8a at the axial-direction
valve-closing side X2); and a holder press-fitting portion 9d that is a
15 portion closer to the axial-direction valve-closing side X2 than the
armature sliding portion 9c is and whose outer circumferential surface is
press-fitted with the inner circumferential surface of the yoke
valve-closing portion 11b. In addition, the valve holder 9 has a holder
front-end portion 9e that is a portion closer to the axial-direction
20 valve-closing side X2 than the holder press-fitting portion 9d is and that
contains the valve seat 3, the valve body 2, and the orifice plate 4 at
the inner-diameter side thereof.
[0026]
The outer diameter of the armature sliding portion 9c is smaller than
25 that of the holder press-fitting portion 9d; the outer circumferential
16
surface of the armature sliding portion 9c neither makes contact with nor
is press-fitted with the inner circumferential surface of the yoke
valve-closing portion 11b.
[0027]
The end portion of the core 7 at the axial-direction 5 valve-closing
side X2 is the cylindrical tubular core small-diameter portion 7a whose
outer diameter is smaller than that of the portion of the core 7 at the
valve-opening side X1; a gap 7b (hereinafter, referred to as a core
small-diameter portion gap 7b) that opens toward the axial-direction
10 valve-closing side X2 is produced between the inner circumferential surface
of the coil 5 (the bobbin 5a) and the outer circumferential surface of the
core small-diameter portion 7a. The core connection portion 9a of the valve
holder 9 is disposed in the core small-diameter portion gap 7b. The core
connection portion 9a of the valve holder 9 is formed in the shape of a
15 cylindrical tube; in a state that the inner circumferential surface of the
core connection portion 9a is fitted with the outer circumferential surface
of the core small-diameter portion 7a through press-fitting, the core
connection portion 9a is welded to the core small-diameter portion 7a
through a welding portion 9f.
20 [0028]

The gap outer-diameter portion 9b is formed thinner than each of the
core connection portion 9a, the armature sliding portion 9c, and the holder
press-fitting portion 9d is. In other words, the radial-direction
25 thickness of the gap outer-diameter portion 9b is formed thinner than that
17
of each of the core connection portion 9a, the armature sliding portion
9c, and the holder press-fitting portion 9d is. Through the thinning, the
magnetic flux that passes through the gap outer-diameter portion 9b is
reduced so as to increase the magnetic flux that passes through the gap
6 between the core 7 and the armature 8; thus, the attractive 5 force of the
armature 8 can be increased.
[0029]
However, when thinned, the gap outer-diameter portion 9b becomes
liable to be deformed. Because the portion that is closer to the
10 axial-direction valve-opening side X1 than the gap outer-diameter portion
9b and the portion that is closer to the axial-direction valve-closing side
X2 than the gap outer-diameter portion 9b are coupled with each other through
the intermediary of the yoke 11, a load in the axial direction X is imposed
on the gap outer-diameter portion 9b when due to cooling after the welding,
15 the yoke 11 contracts. When the load in the axial direction X exceeds the
axial-direction deformation load B with which plastic deformation of the
gap outer-diameter portion 9b begins, the gap outer-diameter portion 9b
is deformed; the space in the gap 6 becomes narrower; when the valve opens,
the traveling amount of the armature 8 to the axial-direction valve-opening
20 side X1 decreases; then, a failure in valve opening is caused. Therefore,
there is desired the fuel injection valve 1 that can suppress the gap
outer-diameter portion 9b from being deformed, even when, for example,
cooling after welding makes the yoke contract and hence a load in the axial
direction X is imposed on the gap outer-diameter portion 9b.
25 [0030]
18

In the present embodiment, in the portion that is closer to the
axial-direction valve-opening side X1 than the gap outer-diameter portion
9b is, the core connection portion 9a of the valve holder 9 and the core
7 are welded to each other through the welding portion 5 9f, and the core
7 is welded to the yoke 11 (the yoke valve-opening portion 11c) through
the welding portion 11d. Accordingly, because through welding, the yoke
11 is coupled with the portion that is closer to the axial-direction
valve-opening side X1 than the gap outer-diameter portion 9b is, the load
10 in the axial direction X cannot be removed. In contrast, in the portion
that is closer to the axial-direction valve-closing side X2 than the gap
outer-diameter portion 9b is, the holder press-fitting portion 9d of the
valve holder 9 and the yoke 11 (the yoke valve-closing portion 11b) are
coupled with each other through press-fitting. Accordingly, because
15 though frictional force A produced by a contact pressure between the
press-fitting portions, the yoke 11 is coupled with the portion that is
closer to the axial-direction valve-closing side X2 than the gap
outer-diameter portion 9b is, the press-fitting portions slide on each other
and hence the load in the axial direction X can be removed.
20 [0031]
Thus, the frictional force A in the axial direction X, produced
between the inner circumferential surface of the yoke valve-closing portion
11b of the yoke 11 and the outer circumferential surface of the holder
press-fitting portion 9d of the valve holder 9, is set to be smaller than
25 the axial-direction deformation load B with which plastic deformation of
19
the gap outer-diameter portion 9b of the valve holder 9 begins (A  B).
[0032]
In this configuration, before due to, for example, the post-welding
contraction of the yoke 11, the load in the axial direction X to be imposed
on the gap outer-diameter portion 9b reaches the deformation 5 load B of the
gap outer-diameter portion 9b, the inner circumferential surface of the
yoke valve-closing portion 11b and the outer circumferential surface of
the holder press-fitting portion 9d slide on each other and hence the load
in the axial direction X can be reduced; thus, the deformation of the gap
10 outer-diameter portion 9b can be suppressed.
[0033]
In addition, as described above, the gap outer-diameter portion 9b
is thinned but the armature sliding portion 9c is not thinned; therefore,
even if due to variations in the production, the gap outer-diameter portion
15 9b is deformed, the armature sliding portion 9c can be suppressed from being
deformed. Thus, because it can be suppressed that there occurs a failure
in sliding between the armature sliding portion 9c and the armature 8 (the
portion of the main body portion 8a at the axial-direction valve-closing
side X2), the risk of the operation failure in the fuel injection valve
20 1 can be reduced.
[0034]
In addition, as described above, the armature sliding portion 9c is
disposed at a position closer to the axial-direction valve-opening side
X1 than the holder press-fitting portion 9d is; thus, the armature sliding
25 portion 9c is not press-fitted into the yoke valve-closing portion 11b.
20
Therefore, because the armature sliding portion 9c is not liable to be
deformed by press-fitting, it is made possible that deformation of the inner
circumferential surface of the armature sliding portion 9c is not liable
to cause sliding failure.
5 [0035]
In the present embodiment, the inner circumferential surface of the
valve holder 9 from the gap outer-diameter portion 9b to the armature sliding
portion 9c is a cylindrical tubular face having one and the same diameter.
In this configuration, the respective inner diameters of the gap
10 outer-diameter portion 9b and the armature sliding portion 9c are
concurrently managed; therefore, it is made possible that as is the case
with the armature sliding portion 9c, the inner diameter of the gap
outer-diameter portion 9b is accurately managed so that the deformation
load B of the gap outer-diameter portion 9b is suppressed from varying.
15 [0036]

At first, the outer circumferential surface of the core
small-diameter portion 7a of the core 7 is press-fitted with the inner
circumferential surface of the core connection portion 9a of the valve
20 holder 9; then, the core connection portion 9a and the core small-diameter
portion 7a are welded to each other so that the welding portions 9f is formed.
[0037]
Then, the outer circumferential surface of the holder press-fitting
portion 9d of the valve holder 9 that is integrated with the core 7 is
25 press-fitted with the inner circumferential surface of the yoke
21
valve-closing portion 11b that is integrated with the yoke outer-diameter
portion 11a. After that, the coil 5 integrated with the terminal 12 is
inserted into the cylindrical tubular space between the outer
circumferential surface of the core 7 and the inner circumferential surface
of the yoke outer-diameter portion 11a. Then, the annular-5 plate-shaped
yoke valve-opening portion 11c in which the terminal 12 is not provided
is disposed in the opening portion of the cylindrical tubular space at the
axial-direction valve-opening side X1; the welding portion 11e is formed
by applying welding to the boundary between the yoke outer-diameter portion
10 11a and the yoke valve-opening portion 11c; then, the welding portion 11d
is formed by applying welding to the boundary between the core 7 and the
yoke valve-opening portion 11c.
[0038]
When the core 7 and the yoke valve-opening portion 11c are welded
15 to each other, laser irradiation causes metal melting in parts of the core
7 and the yoke valve-opening portion 11c, and hence the temperatures of
the surrounding metal members rise. When the laser irradiation is ended,
metal contraction caused by solidification and temperature fall of the
melted metal produces a stress that makes the yoke 11 travel toward the
20 axial-direction valve-opening side X1 with respect to the core 7. At this
time, as described above, the inner circumferential surface of the yoke
valve-closing portion 11b of the yoke 11 and the outer circumferential
surface of the holder press-fitting portion 9d of the valve holder 9 slide
on each other and hence the load in the axial direction X to be imposed
25 on the thinned gap outer-diameter portion 9b of the valve holder 9 can be
22
suppressed from reaching the deformation load B; thus, deformation of the
gap outer-diameter portion 9b can be suppressed.
[0039]
Then, the foregoing assembled components are molded out of resin 18.
Then, the outer circumferential surface of the rod 16 is 5 press-fitted with
the inner circumferential surface of the core 7. After that, the spring
15, the armature 8 press-fitted with the pipe 2b, and the valve body 2 are
inserted into the core 7 and the valve holder 9. The orifice plate 4 and
the valve seat 3, which are welded to each other through the welding portion
10 4c, are inserted into the valve holder 9 so as to be positioned with respect
to the valve holder 9; then, the welding portion 4b is formed by welding
the outer circumferential portion of the orifice plate 4 to the inner
circumferential surface of the valve holder 9 over the entire circumference.
[0040]
15 Next, as illustrated in FIG. 3, in a state that the end portion (the
rear-end portion) of the fuel injection valve 1 at the axial-direction
valve-opening side X1 is fixed, the orifice plate 4 is pressed by a
cylindrical columnar jig 19 toward the axial-direction valve-opening side
X1. The front end of the jig 19 has a cylindrical tubular protruding portion
20 19a protruding toward the axial-direction valve-opening side X1. The
protruding portion 19a presses the vicinity of the welding portions 4c,
thereby causing plastic deformation of the portion of the orifice plate
4 between the welding portion 4c and the welding portion 4b, so that the
valve seat 3 is displaced toward the axial-direction valve-opening side
25 X1 with respect to the valve holder 9; then, the valve lifting amount is
23
adjusted by adjusting the distance of the gap 6 between the core 7 and the
armature 8 in the axial direction X.
[0041]
In the present embodiment, in order to increase the attractive force
of the armature 8, the gap outer-diameter portion 9b (the 5 radial-direction
thickness) of the valve holder 9 is thinned more than the orifice plate
4 (the thickness of the plate) is; therefore, the axial-direction
deformation load B with which plastic deformation of the gap outer-diameter
portion 9b of the valve holder 9 begins is smaller than the axial-direction
10 deformation load C with which plastic deformation of the orifice plate 4
begins.
[0042]
Accordingly, if the pressing force of the jig 19 for causing plastic
deformation of the orifice plate 4 is directly transferred to the gap
15 outer-diameter portion 9b, the gap outer-diameter portion 9b may be
deformed.
[0043]
Therefore, the deformation load C in the axial direction X, with which
plastic deformation of the orifice plate 4 begins, is set to be smaller
20 than the total value of the frictional force A in the axial direction X,
produced between the inner circumferential surface of the press-fitted yoke
valve-closing portion 11b and the outer circumferential surface of the
holder press-fitting portion 9d, and the deformation load B, in the axial
direction X, with which plastic deformation of the thinned gap
25 outer-diameter portion 9b of the valve holder 9 begins (C  A  B).
24
[0044]
In this configuration, in the case where the jig 19 presses the orifice
plate 4 with pressing force of the deformation load C of the orifice plate
4 or thereabouts, the pressing force can be blocked by the total value of
the frictional force A between the yoke valve-closing portion 5 11b and the
holder press-fitting portion 9d and the deformation load B of the gap
outer-diameter portion 9b; thus, the gap outer-diameter portion 9b can be
suppressed from being deformed. Therefore, the valve lifting amount can
be adjusted by deforming the orifice plate 4 without deforming the thinned
10 gap outer-diameter portion 9b.
[0045]
The yoke outer-diameter portion 11a and the yoke valve-closing
portion 11b, which are integrated members formed in the shape of a two-step
cylindrical tube, are formed through drawing machining and shaving
15 machining. Specifically, as illustrated in FIG. 4, the drawing machining
is performed by pressing a plate material with a punch (unillustrated) whose
front end is formed in the shape of a two-step cylindrical column. After
that, the state illustrated in FIG. 5 is obtained by cutting unnecessary
parts through cutting machining. In this situation, as illustrated in FIG.
20 4, in order to open the lower end, the central portion is punched with a
punching tool 20; however, at this time, as illustrated in FIG. 5, an
inner-diameter expansion portion 11f in which the inner diameter is expanded
is produced. Accordingly, as illustrated in FIG. 6, there is performed
shaving machining in which the inner circumferential surface of the yoke
25 valve-closing portion 11b is shaved with a shaving tool 21 so that the inner
25
circumferential surface thereof becomes a straight cylindrical tubular face.
As a result, the yoke valve-closing portion 11b is not only a drawing
machining portion formed through drawing machining, but also a shaving
machining portion whose inner circumferential surface is formed in the shape
of a cylindrical tube through 5 shaving machining.
[0046]
As described above, the yoke valve-closing portion 11b, which becomes
a press-fitting portion, can be manufactured at low cost, through drawing
machining and shaving machining. The shaving machining makes it possible
10 that the inner circumferential surface of the yoke valve-closing portion
11b is made to be a straight cylindrical tubular face and that the inner
diameter thereof is accurately adjusted. As a result, because the contact
pressure and the frictional force A at the press-fitting portion can
accurately be adjusted, deformation of the gap outer-diameter portion 9b
15 can be suppressed.
[0047]
Within the scope of the present disclosure, the embodiments thereof
can appropriately be modified or omitted.
20 REFERENCE SIGNS LIST
[0048]
1: fuel injection valve
2: valve body
3: valve seat
25 3a: fuel path
26
4: orifice plate
4a: injection hole
5: coil
6: gap
5 7: core
8: armature
9: valve holder
9a: core connection portion
9b: gap outer-diameter portion
10 9c: armature sliding portion
9d: holder press-fitting portion
11: yoke
11a: yoke outer-diameter portion
11b: yoke valve-closing portion
15 11c: yoke valve-opening portion
X: axial direction
X1: axial-direction valve-opening side
X2: axial-direction valve-closing side
27
We Claim :
1. A fuel injection valve comprising:
a valve seat in which a fuel path is formed;
a valve body that travels toward an axial-direction valve-opening
side and departs from the valve seat so as to open the fuel 5 path or travels
toward an axial-direction valve-closing side and abuts on the valve seat
so as to close the fuel path;
a tubular coil;
a tubular core disposed at an inner-diameter side of the coil;
10 a tubular armature that is disposed at the axial-direction
valve-closing side of the core in such a way as to be spaced apart by a
gap from the core, that is attracted by magnetic flux, produced by
energization of the coil, to the axial-direction valve-opening side, and
that makes the valve body travel to the axial-direction valve-opening side;
15 a tubular valve holder that contains the valve seat, the valve body,
and the armature at an inner-diameter side thereof; and
a tubular yoke that covers an outside of the coil,
wherein the yoke includes
a tubular yoke outer-diameter portion that covers an
20 outer-diameter side of the coil,
a tubular yoke valve-closing portion that extends from the yoke
outer-diameter portion toward the axial-direction valve-closing side, and
a yoke valve-opening portion that extends from the yoke
outer-diameter portion toward the axial-direction valve-opening side and
25 is welded to an outer circumferential surface of the core,
28
wherein the valve holder includes
a core connection portion whose inner circumferential surface
is fitted with and welded to the outer circumferential surface of the core,
a gap outer-diameter portion that is a portion closer to the
axial-direction valve-closing side than the core connection 5 portion and
that is disposed at an outer-diameter side of the gap between the core and
the armature,
an armature sliding portion that is a portion closer to the
axial-direction valve-closing side than the gap outer-diameter portion and
10 whose inner circumferential surface slides on the outer circumferential
surface of the armature, and
a holder press-fitting portion that is a portion closer to the
axial-direction valve-closing side than the armature sliding portion and
whose outer circumferential surface is press-fitted with an inner
15 circumferential surface of the yoke valve-closing portion,
wherein the gap outer-diameter portion is formed thinner than each
of the core connection portion, the armature sliding portion, and the holder
press-fitting portion, and
wherein axial-direction frictional force, produced between the inner
20 circumferential surface of the yoke valve-closing portion and the outer
circumferential surface of the holder press-fitting portion, is smaller
than an axial-direction deformation load with which plastic deformation
of the gap outer-diameter portion begins.
25 2. The fuel injection valve according to claim 1, further comprising an
29
orifice plate in which an injection hole is formed,
wherein the orifice plate has a welding portion welded to a portion
of the valve seat at the axial-direction valve-closing side and a welding
portion welded to the valve holder, and the valve seat is fixed to the valve
holder through the intermediary of the 5 orifice plate, and
wherein an axial-direction deformation load with which plastic
deformation of the orifice plate begins is smaller than a total value of
the axial-direction frictional force, produced between the inner
circumferential surface of the yoke valve-closing portion and the outer
10 circumferential surface of the holder press-fitting portion, and the
axial-direction deformation load with which plastic deformation of the gap
outer-diameter portion begins.
3. The fuel injection valve according to claim 2, wherein the
15 axial-direction deformation load with which plastic deformation of the gap
outer-diameter portion begins is smaller than the axial-direction
deformation load with which plastic deformation of the orifice plate begins.
4. The fuel injection valve according to any one of claims 1 through 3,
20 wherein the yoke outer-diameter portion and the yoke valve-closing
portion are respective members that are integrated with each other and are
formed in a shape of a two-step cylindrical tube in which a diameter of
the yoke valve-closing portion decreases in two steps from a diameter of
the yoke outer-diameter portion, and the yoke valve-closing portion is not
25 only a drawing machining portion formed through drawing machining but also
a shaving machining portion whose inner circumferential surface is formed
in a shape of a cylindrical tube through shaving machining, and
wherein the yoke valve
has a welding portion welded to the outer circumferential surface of the
core and a welding portion welded 5 to the yoke outer
5. The fuel injection valve according to any one of claims 1 through 4,
wherein the inner circumferential surface of the valve holder from the gap
outer-diameter portion to the armature sliding portion is a cylindrical
10 tubular face having one and the same diameter.