Information
-
Patent Grant
-
6601786
-
Patent Number
6,601,786
-
Date Filed
Friday, May 11, 200123 years ago
-
Date Issued
Tuesday, August 5, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Mar; Michael
- Gorman; Darren
Agents
-
CPC
-
US Classifications
Field of Search
US
- 239 5851
- 239 5853
- 239 5854
- 239 5855
- 239 5332
- 239 5339
- 239 5333
- 239 5337
- 251 127
- 251 12915
- 251 12921
-
International Classifications
- B05B130
- F02M5100
- F02M6120
- F16K3102
-
Abstract
In a fuel injection valve, a cylindrical valve body has a valve seat protruding radially inward out of an inner wall thereof and a needle supporting cylindrical inner wall. A nozzle needle is fixed to the armature so as to move together with the armature, while being supported slidably by the needle supporting cylindrical inner wall. The nozzle needle is provided with a valve portion to be seated on the valve seat when a coil is de-energized and inside thereof with a cavity into which fuel is introduced. A fuel accumulation bore is provided between inner circumference of the cylindrical valve body and outer circumference of the nozzle needle. With the construction mentioned above, the nozzle needle is provided with an opening through which the cavity communicates with the fuel accumulation bore.
Description
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority of Japanese Patent Application No. 2000-139702 filed on May 12, 2000, the content of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel injection valve for an internal combustion engine (hereinafter called as an engine).
2. Description of Related Art
As shown in
FIG. 6
, a conventional fuel injection valve
100
has a nozzle needle
101
that is slidably and reciprocatingly supported by a sliding portion
102
. The sliding portion
102
is provided with a plurality of cuts for forming fuel passages. The cuts of the sliding portion
102
also serve as vapor passages through which vapor generated by heat near injection holes moves toward a side of fuel upstream. A contact portion
103
formed at an end of the nozzle needle
101
on a side of fuel injection may be seated on a valve seat
105
a
formed in a valve body
105
.
An armature
111
is connected with the nozzle needle
101
at a position facing a stator
110
and is biased in a valve closing direction by a spring
112
. Since the armature
111
and the sliding portion
102
are slidably and reciprocatingly supported by the valve body
105
, the nozzle needle
101
can make a reciprocating movement accurately along a center axis thereof. Generally, the stator
110
and the armature
111
are made of lower toughness material and are plated with, for example, chromium to form thin film thereon. When a coil
115
is energized, the armature
111
is attracted toward the stator
110
against biasing force of the spring
112
. Accordingly, the nozzle needle
101
leaves the valve seat
105
a
so that fuel is injected from the injection holes. When the coil
115
is de-energized, the contacting portion
103
is seated on the valve seat
105
a
to finish fuel injection.
It is important for better fuel consumption that fuel is supplied to the engine at an adequate timing during a period when an intake port of the engine is opened. Therefore, the fuel injection valve is required to have quick response characteristic that is largely affected by mass of a moving member including the nozzle needle
101
.
According to the conventional fuel injection valve
100
, the nozzle needle
101
is integrally provided with the sliding portion
102
having the cuts, whose maximum outer diameter is larger than that of the contact portion
103
, for securing the fuel and vapor passages. Accordingly, among the nozzle needle
101
, the sliding portion
102
and the armature
111
, which constitute the moving member, the sliding portion
102
adversely affects on the quick response characteristic of the fuel injection valve because of larger mass thereof.
Further, formation of the chromium thin film on portions where the stator
110
and the armature
111
come in contact with each other results in higher manufacturing cost of the fuel injection valve.
SUMMARY OF THE INVENTION
An object of the invention is to provide a fuel injection valve in which weight of a nozzle needle is relatively light and mass of a movable member constituted by the nozzle needle and an armature is smaller so that quicker response characteristic of the injection valve is secured.
To achieve the above object, in the injection valve having a housing, a stator, an armature and a coil for exerting electromagnetic attracting force on the armature, a cylindrical valve body, which is provided with at least an injection hole, has a valve seat protruding radially inward out of an inner wall thereof, which is positioned on a side of the stator with respect to the injection hole, and a needle supporting cylindrical inner wall, which is positioned on a side of the stator with respect to the valve seat. A nozzle needle is fixed to the armature so as to move together with the armature in the cylindrical valve body, while being supported slidably by the needle supporting cylindrical inner wall. The nozzle needle is provided with a valve portion to be seated on the valve seat when the coil is de-energized and inside thereof with a cavity into which fuel is introduced. A fuel accumulation bore is provided between inner circumference of the cylindrical valve body extending axially from the valve seat to the needle supporting cylindrical inner wall and outer circumference of the nozzle needle.
With the construction mentioned above, the nozzle needle is further provided with an opening through which the cavity communicates with the fuel accumulation bore so that, when the valve portion leaves the valve seat upon energizing coil, the fuel accumulation bore communicates with the injection hole for fuel injection.
Since the nozzle needle is provided inside thereof with the cavity and with the opening through which the cavity communicates with the fuel accumulation bore, weight of the nozzle needle is lighter than that of the conventional fuel injection valve in which the nozzle needle has the cuts for forming the fuel and vapor passages between the armature accommodation bore and the fuel accumulation bore.
Preferably, the opening of the nozzle needle is opened to the highest position in the fuel accumulation bore to evacuate vapor smoothly.
It is preferable that the housing has a hollow into which fuel is flown from outside and the stator is provided with a penetrating bore communicating with the hollow of the housing at an axial end thereof and communicating with an armature accommodation bore at another axial end thereof, and the armature has a through-hole for making the armature accommodation bore on a side of the stator communicate with the cavity so that fuel is introduced from the hollow of the housing into the cavity. With this construction, the fuel injection valve becomes further lighter and more compact.
It is preferable that the nozzle needle penetrates axially along the through-hole of the armature until an axial end thereof protrudes out of an axial end of the armature toward the stator so that fuel is introduced into the cavity from the hollow of the housing via the penetrating bore. This will make it possible to manufacture the fuel injection valve at lower cost, since an air gap is automatically formed between the stator and the armature by the axial end of the nozzle needle protruding out of the end of the armature and coming in contact with the stator and, further, it is not necessary to cover the axial end of the nozzle needle with chromium thin film for reinforcement because the nozzle needle is inherently made of material having relatively higher stiffness.
Preferably, the opening of the nozzle needle is formed to axially stride over the needle supporting cylindrical inner wall so that the cavity communicates not only with the fuel accumulation bore but also with the armature accommodation bore on a side of the cylindrical valve body. With this construction, vapor generated by heat is easily evacuated from the fuel accumulation bore to the armature accommodation bore through the opening. Accordingly, fluctuation of injection characteristic due to vapor is limited.
Further, it is preferable that the needle cylindrical inner wall, whose diameter is larger than a diameter of the valve seat, is formed to protrude radially inward out of the inner wall of the cylindrical valve body. Since a diameter of the valve seat are smaller than that of the needle supporting cylindrical inner wall, the seat valve, on which the valve portion of the nozzle needle is seated, is easily and accurately machined by inserting a cutting tool from a side of the needle supporting cylindrical inner wall into an inside of the cylindrical valve body.
Moreover, preferably, the nozzle needle is provided with a small diameter column portion whose axial end on a side of the injection hole constitutes the valve portion and with a large diameter column portion whose diameter is larger than that of the small diameter column portion and which is slidably supported by the needle supporting cylindrical inner wall.
BRIEF DESCRIPTION OF THE DRAWING
Other features and advantages of the present invention will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following detailed description, the appended claims, and the drawings, all of which form a part of this application. In the drawings:
FIG. 1
is across sectional part view of a fuel injection valve according to a first embodiment of the present invention;
FIG. 2
is a cross sectional whole view of the fuel injection valve according to the first embodiment;
FIG. 3
is a cross sectional part view of a fuel injection valve according to a second embodiment of the present invention;
FIG. 4
is a cross sectional part view of a modified fuel injection valve according to the second embodiment;
FIG. 5
is a cross sectional part view of a fuel injection valve according to a third embodiment of the present invention; and
FIG. 6
is a cross sectional whole view of a conventional fuel injection valve as a prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
(First Embodiment)
A fuel injection valve according to a first embodiment is described with reference to
FIGS. 1 and 2
.
As shown in
FIG. 2
, a valve body
29
, a nozzle needle
26
, an armature
25
, a stator
22
, an adjusting pipe
21
, a spring
24
and a filter
11
are accommodated in a cylindrical member
14
.
The cylindrical member
14
, for example, made of composite magnetic material, is formed in pipe shape to have both of magnetic and non-magnetic portions. The cylindrical member
14
has the non-magnetic portion partly changed by heating and is provided with a magnetic pipe portion
14
c
, a non-magnetic pipe portion
14
b
and a magnetic pipe portion
14
a
, which are positioned upward in order from a lower end thereof on a side of fuel injection. The armature
25
is housed in an armature accommodation bore
14
e
of the cylindrical member
14
in a vicinity of a boundary between the non-magnetic pipe portion
14
b
and the magnetic pipe portion
14
c
. The valve body
29
and an injection hole plate
28
are housed in the magnetic pipe portion
14
c
on a side of fuel injection. The filter
11
, which filters foreign material in fuel, is installed in the cylindrical member
14
at an upper end on a fuel upstream side.
As shown in
FIG. 1
, the valve body
29
, which is formed in pipe shape, is press fitted into and fixed by laser welding to an inner wall of the magnetic pipe portion
14
c
. An inner circumferential wall of the valve body
29
has a conical surface wall
29
a
, a large diameter cylindrical surface wall
29
b
, a conical surface wall
29
c
, a small diameter cylindrical surface wall
29
d
and a conical surface wall
29
e
, which are positioned in order from a side of fuel injection toward a side of fuel upstream. The conical surface wall
29
a
, whose diameter is smaller toward a side of fuel injection, is provided to form a valve seat on which a contact portion
26
c
of the nozzle needle
26
can be seated. The large diameter cylindrical surface wall
29
b
is provided to form a fuel accumulation bore
29
f
. A diameter of the conical surface wall
29
is smaller toward a side of fuel upstream. The small diameter cylindrical surface wall
29
d
constitutes a nozzle needle supporting hole whose diameter is smaller than that of the fuel accumulation bore
29
f
. A diameter of the conical surface wall
29
e
is larger toward a side of fuel upstream.
The injection hole plate
28
in cup shape is press fitted into and fixed by laser welding to an inner wall of the magnetic pipe portion
14
c
. The injection hole plate
28
is in contact with an end of the valve body
29
on a side of fuel injection. The injection hole plate
28
is formed in thin plate shape and provided in a center thereof with a plurality of injection holes
28
a.
The nozzle needle
26
is made of stainless steel and formed in cylindrical shape having a bottom. The nozzle needle
26
is provided on a side of fuel upstream with a large diameter column portion
26
e
whose diameter is slightly smaller than an inner diameter of the small diameter cylindrical surface wall
29
d
and provided on a side of fuel injection with a small diameter column portion
26
d
whose diameter is smaller than that of the large diameter column portion
26
e
on a side of fuel upstream. It is preferable that a diameter difference between the large and small diameter column portions
26
e
and
26
d
is more than 0.1 mm in view of obtaining lighter weight of the nozzle needle
26
and easily manufacturing the valve seat.
An end corner of the small diameter column portion
26
d
on a side of fuel injection is chamfered or tapered to form a conical surface that constitutes the contact portion
26
c
. A diameter of the contact portion
26
c
, that is, a seat diameter, is smaller than that of the small diameter cylindrical surface wall
29
d
. To bring an outer wall of the large diameter column portion
26
e
in slidable contact with the small diameter cylindrical surface wall
29
d
, a slight clearance is formed therebetween. Most part of the large diameter column portion
26
e
is formed in thin cylinder shape and an inner circumferential wall
26
a
thereof constitutes an interior passage
26
f
. The interior passage
26
f
is formed by drilling a hole from an end of the large diameter column portion
26
e
on a side of fuel upstream. Length of the drilled hole is deep to an extent that a bottom of the nozzle needle
26
sufficiently endures a shock caused on seating itself on the valve seat.
An axial length of the large diameter column portion
26
e
is long to an extent that, when centerless machining forms the small diameter column portion
26
d
and the contact portion
26
c
, an outer circumferential wall of the large diameter column portion
26
e
can be held tightly by a chuck so that a center axis of the valve body does not deviate throughout a whole axial length thereof.
The large diameter column portion
26
e
is provided with outlet holes
26
b
that constitute openings of the interior passage
26
f
. The outlet holes
26
b
are positioned circumferentially at 180-degree angular intervals so as to perforate the large diameter column portion
26
e
radially. One outlet hole
26
b
, instead of the two outlet holes
24
, is sufficient enough to perform an operation of the present invention. Each of the outlet holes
26
b
is formed in shape of oval or flat oval whose major axis extends axially and whose major axis length is longer than axial length of the small diameter cylindrical surface wall
29
d
. A periphery of the outlet hole
26
b
on a side of fuel injection is located at a position lower than an axial end of the small diameter cylindrical surface wall
29
d
on a side of fuel injection and opened to the fuel accumulation bore
29
f
. Another periphery of the outlet hole
26
b
on a side of fuel upstream is located at a position higher than an axial end of the small diameter cylindrical surface wall
29
d
on a side of fuel upstream and opened to the armature accommodation bore
14
e
. The shape of the outlet hole
26
b
is not limited to oval or flat oval but may be circular.
The armature
25
is fixed by laser welding to an outer wall of the large diameter column portion
26
on a side of fuel upstream. The armature
25
is made of ferromagnetic material such as magnetic stainless steel and is formed in pipe shape having steps. Inner circumferential wall
25
b
of the armature
25
is provided in middle thereof with a ring shaped projection so as to form steps on axially opposite sides thereof. Inner diameter of the armature
25
at the ring shaped projection is smallest. The step of the armature
25
on a side of fuel upstream serves as a spring seat
25
c
. An interior passage
25
e
of the armature
25
and the interior passage
26
f
of the nozzle needle
26
communicate with each other. The armature is further provided at an end on a side of fuel upstream with a flange
25
a
. An outer circumferential wall of the flange
25
a
and an inner circumferential wall of the cylindrical member
14
are in slidable contact with each other so that a slight clearance is formed therebetween.
As the outer circumferential wall of the large diameter column portion
26
e
and the small diameter cylindrical wall
29
d
are in slidable contact with each other and the outer circumferential wall of the flange
25
a
and the inner circumferential wall of the cylindrical member
14
are in slidable contact with each other, the nozzle needle
26
moves reciprocatingly along a predetermined orbit. The armature
25
is provided at an axial end thereof on a side of fuel upstream with a ring shaped projection
25
d
which comes in contact with the stator
22
with an air gap between the axial end of the armature
25
other than the ring shaped projection
25
d
and an axial end of the stator
22
. A surface of the ring shaped projection
25
d
that comes in contact with the stator
22
is coated with chromium thin film.
As shown in
FIG. 2
, the stator
22
is made of ferromagnetic material such as magnetic stainless steel and is formed in cylindrical shape. A surface of the stator
22
that comes in contact with the armature
25
is coated with chromium thin film. The adjusting pipe
21
is press fitted and fixed into an inner wall of the stator
22
. Adjusting a press fitting amount of the adjusting pipe
21
allows to change preset biasing force of the spring
24
, whose one end contacts the spring seat
25
c
of the armature
25
and whose another end contacts an end of the adjusting pipe
21
. The adjusting pipe
21
may be fastened to stator
22
by screws instead of being press fitted thereto.
As shown in
FIG. 2
, a resin spool
30
is attached to outer circumference of the cylindrical member
14
. A coil
31
is wound on outer circumference of the spool
30
. An outer circumference of the cylindrical member
14
is covered with a resin mold
13
and provided with a connector portion
16
protruding out of the outer wall of the resin mold
13
. A terminal
12
, which is connected in circuit with the coil
31
, is embedded in the connector portion
16
. The terminal is partly covered with a resin rib
17
.
A magnetic member
23
covers around outer circumference of the coil
31
. A fan shaped magnetic member
18
is disposed on a fuel upstream side of the coil
31
circumferentially at an angle of about 250 degrees not to interfere with the rib
17
. A resin mold
15
is formed around outer circumferences of the magnetic members
18
and
23
and connected with the resin mold
13
. The nozzle needle
26
, the stator
22
, the magnetic pipe portions
14
a
and
14
c
and the magnetic members
18
and
23
constitute a magnetic circuit through which magnetic flux passes on energizing the coil
31
.
Fuel, which is flown into the cylindrical member
14
through the filter
11
, is introduced to the fuel accumulation bore
29
f
from the outlet hole
26
b
via an interior of the adjusting pipe
21
, an interior of the stator
22
, the interior passage
25
e
of the armature
25
and the inner passage
26
f
of the nozzle needle
26
so that fuel reaches a portion where the contact portion
26
c
of the nozzle needle
26
is seated on the valve seat. When the contact portion
26
c
is seated on the valve seat, communication between the fuel accumulation bore
29
f
and the injection holes
28
a
is interrupted and, when the contact portion
26
c
leaves the valve seat, the fuel accumulation bore
29
f
communicates with the injection holes
28
a.
Next, an operation of the fuel injection valve
1
is described.
Upon energizing the coil
31
, the nozzle needle
26
is attracted toward the stator
22
against the biasing force of the spring
24
. Accordingly, the contact portion
26
c
leaves the valve seat so that fuel is injected from the injection holes
28
a.
Upon de-energizing the coil
31
, the nozzle needle
26
receives the biasing force of the spring
24
acting in the valve closing direction so that the contact portion
26
c
is seated on the valve seat to finish the fuel injection from the injection holes
28
a.
According to the fuel injection valve
1
mentioned above, As the outer circumferential wall of the large diameter column portion
26
e
and the small diameter cylindrical wall
29
d
are in slidable contact with each other and the outer circumferential wall of the flange
25
a
and the inner circumferential wall of the cylindrical member
14
are in slidable contact with each other, the nozzle needle
26
moves reciprocatingly along the predetermined orbit without offsetting the center axis thereof. Accordingly, the contact portion
26
c
of the small diameter column portion
26
d
comes in contact accurately with a predetermined seat position on the conical surface wall
29
a.
During engine operation, vapor tends to be generated in fuel by heat in the fuel accumulation bore
29
f
. According to the fuel injection valve
1
, the vapor moves toward the fuel upstream side from the fuel accumulation bore
29
f
through the outlet hole
26
b
so that generation of the vapor does not affect adversely on fuel injection characteristic. Further, the outlet hole
26
b
makes it possible to reduce frictional resistance between the nozzle needle
26
and the valve body
29
so that the quick response characteristic of the nozzle needle
26
is secured since a surface area where the nozzle needle
26
and the valve body
29
are in slidable contact with each other is relatively small.
Furthermore, as the interior passage
26
f
of the nozzle needle
26
constitutes a fuel passage, the outer diameter of the large diameter column portion
26
e
is relatively small and is slightly larger than or nearly equal to that of the contact portion
26
c
. A large part of the nozzle needle
26
is constituted by the large diameter column portion
26
e
whose wall thickness is relatively thin. Accordingly, mass of the movable member integrally composed of the nozzle needle
26
and the armature
25
becomes smaller, resulting in improving the quick response characteristic of the nozzle needle
26
.
Moreover, as the small diameter column portion
26
d
is formed on the nozzle needle
26
on a side of fuel injection, the valve seat can be easily and accurately manufactured. In more details, it is generally required to highly accurately machine the seat portion on the conical surface wall
29
a
on which the contact portion
26
c
is fluid-tightly seated. Since the seat diameter is smaller than an inner diameter of the small diameter cylindrical surface wall
29
d
of the valve body which slidably supports the nozzle needle
26
, the seat portion on the conical surface wall
29
a
can be accurately machined by inserting a cutting tool into the fuel accumulation bore
29
f
from a side of fuel upstream after the small diameter cylindrical surface wall
29
d
, the conical surface wall
29
c
, the large diameter cylindrical surface wall
29
b
and conical surface wall
29
a
are machined.
As the fuel injection valve
1
has a construction that the valve body
29
supports the large diameter column portion
26
e
of the nozzle needle
26
on a side of fuel upstream, the nozzle needle
26
can be easily and accurately machined. That is, it is necessary to machine coaxially and accurately the large diameter column portion
26
e
and the contact portion
26
c
for securing valve fluid-tightness. Since the large diameter column portion
26
e
, whose axial length is relatively long, is firmly fixed by the chuck, centerless machining can accurately form the contact portion
26
c.
(Second Embodiment)
A fuel injection valve according to a second embodiment is described with reference to
FIG. 3. A
construction of the fuel injection valve not shown in
FIG. 3
is substantially same as the fuel injection valve
1
of the first embodiment. The construction of the second embodiment substantially similar as that of the first embodiment is described with the same reference number as the first embodiment.
A valve body
41
is formed in shape of a cylinder whose peripheries of both opening ends protrude radially and inwardly. An inner circumferential wall of the valve body
41
has a conical surface wall
41
a
, a large diameter cylindrical surface wall
41
b
, a step surface wall
41
c
and a small diameter cylindrical surface wall
41
d
, which are positioned in order from a side of fuel injection toward a side of fuel upstream. The conical surface wall
41
a
, whose diameter is smaller toward a side of fuel injection, is provided to form a valve seat on which a contact portion
42
b
of the nozzle needle
42
can be seated. The large diameter cylindrical surface wall
41
b
is provided to form a fuel accumulation bore
41
e
. The small diameter cylindrical surface wall
41
d
constitutes a nozzle needle supporting hole whose diameter is smaller than that of the fuel accumulation bore
41
e.
The nozzle needle
42
is made of stainless steel and formed in cylindrical shape having a bottom. The nozzle needle
42
has a column wall
42
d
whose diameter is identical from a side of fuel injection to a side of fuel upstream. To bring the column wall
42
d
in slidable contact with the small diameter cylindrical surface wall
41
d
, a slight clearance is formed therebetween. An interior passage
42
c
is formed by drilling a hole from an end of the nozzle needle
42
on a side of fuel upstream. Length of the drilled hole is deep to an extent that a bottom of the nozzle needle
42
sufficiently endures a shock caused on seating itself on the valve seat. An outlet hole
42
, which constitute an opening of the interior passage
42
c
, is formed in oval or flat oval shape.
An interior space
40
d
, which is formed by an inner circumferential wall
40
b
of an armature
40
, and the interior passage
42
c
of the nozzle needle
42
communicate with each other. Outer circumference of a flange
40
c
on the outer circumference of the armature
40
is in slidable contact with the inner circumferential wall
14
d
of the cylindrical member
14
A. The armature
40
is provided at a step portion thereof with vapor passages
40
a
, through which an armature accommodation bore
14
e
and the interior space
40
d
of the armature
40
communicate with each other. The vapor passages
40
a
serve to move vapor included in fuel toward a side of fuel upstream in the armature accommodation bore
14
e.
According to the second embodiment, it is easy to form accurately the contact portion
42
b
by centerless machining since the nozzle needle
42
has the column wall
42
d
whose diameter is identical axially. Further, as the fuel passage extending from the interior space
40
d
of the armature
40
to the fuel accumulation bore
41
e
is formed through the interior passage
42
c
and the outlet hole
42
a
of the nozzle needle
42
, the mass of the nozzle needle
42
is smaller so that the quicker response of the nozzle needle
42
may be secured.
As an alternative, the nozzle needle
43
may be formed to penetrate axially the armature
40
, as shown in FIG.
4
. An axial end
43
a
of the nozzle needle
42
protrudes out of the end of the armature
40
on a side of the stator so as to come in contact with stator
22
. With this construction, as it is not necessary to cover the axial end
43
a
with the chromium thin film for reinforcement, the fuel injection valve is manufactured at lower cost.
(Third Embodiment)
A fuel injection valve according to a third embodiment is described with reference to
FIG. 5. A
construction of the fuel injection valve not shown in
FIG. 5
is substantially same as the fuel injection valve
1
of the first embodiment. The construction of the third embodiment substantially similar as that of the first embodiment is described with the same reference number as the first embodiment.
A valve body
52
is formed in shape of a cylinder whose opening end on a side of fuel injection protrudes radially and inwardly. The valve body
52
is provided on an inner circumferential wall thereof with a conical surface wall
52
b
on a side of fuel injection and a cylindrical surface wall
52
a
on a side of fuel upstream. The conical surface wall
52
b
, whose inner wall diameter is smaller toward a side of fuel injection, constitutes a valve seat on which a contact portion
51
c
of a nozzle needle
51
is seated. The cylindrical surface wall
52
constitutes a fuel accumulation bore
52
c.
The nozzle needle
42
, which is made of stainless steel, is formed in cylindrical shape having a bottom. The nozzle needle
51
is provided on a side of fuel upstream with a large diameter column portion
51
e
whose diameter is slightly smaller than an inner diameter of the cylindrical surface wall
52
a
and provided on a side of fuel injection with a small diameter column portion
51
d
whose diameter is smaller than that of the large diameter column portion
51
e
. An end corner of the small diameter column portion
51
d
on a side of fuel injection is chamfered or tapered to form a conical surface that constitutes the contact portion
51
c
. A diameter of the contact portion
51
c
, that is, a seat diameter, is smaller than that of the cylindrical surface wall
52
a.
An axial end
51
g
of the large diameter column portion
51
e
on a side of fuel upstream penetrates an armature
50
so as to protrude out of the end of the armature on a side of the stator. The axial end
51
g
comes in contact with the stator
22
with an air gap between the axial end of the armature and an axial end of the stator
22
. An outer circumferential wall of the large diameter column portion
51
e
and the cylindrical surface wall
52
a
are in slidable contact with each other so that a slight clearance is formed therebetween. An interior passage
51
a
is formed by drilling a hole from an end of the large diameter column portion
51
e
on a side of fuel upstream. Length of the drilled hole is deep to an extent that a bottom of the nozzle needle
51
sufficiently endures a shock caused on seating itself on the valve seat.
Outlet holes
51
b
, which extends from the large diameter column portion
51
e
to the small diameter column portion
51
d
, are positioned circumferentially at 180-degree angular intervals so as to perforate the large diameter column portion
51
e
radially. The outlet hole
51
b
is formed in oval or flat oval shape. A periphery of the outlet hole
51
b
on a side of fuel injection is formed on an outer circumferential wall of the small diameter column portion
51
d
and another periphery thereof on a side of fuel upstream is formed on an outer circumferential wall of the large diameter column portion
51
e
at a position on a side of fuel upstream with respect to an axial end
52
d
of an valve body
52
.
According to the third embodiment, the interior passage
51
a
of the nozzle needle
51
communicates with injection holes
28
a
via a fuel accumulation bore
52
which is formed between the valve body
52
and the small diameter column portion
51
d
. Wall thickness of most part of the nozzle needle
51
is thinner. Accordingly, mass of a movable member composed of the nozzle needle
51
and the armature
50
is relatively small so that the nozzle needle
51
has quicker response characteristic.
Claims
- 1. A fuel injection valve comprising:a housing; a stator fixed to the housing; a cylindrical valve body fixed to the housing, the cylindrical valve body being provided at an axial end thereof on a side opposite to the stator with at least an injection hole and having a valve seat protruding radially inward out of an inner wall thereof, which is positioned on a side of the stator with respect to the injection hole, and a needle supporting cylindrical inner wall, which is positioned on a side of the stator with respect to the valve seat; an armature accommodation bore provided in the housing between the stator and the cylindrical valve body; an armature movable in the armature accommodation bore; a coil for exerting an electromagnetic attracting force on the armature so as to be attracted toward the stator when energized; a nozzle needle fixed to the armature and movable together with the armature in the cylindrical valve body and the armature accommodation bore, while being supported slidably by the needle supporting cylindrical inner wall, the nozzle needle being provided with a valve portion to be seated on the valve seat when the coil is de-energized and inside thereof with a cavity into which fuel is introduced; and a fuel accumulation bore provided between an inner circumference of the cylindrical valve body extending axially from the valve seat to the needle supporting cylindrical inner wall and an outer circumference of the nozzle needle; wherein the nozzle needle is provided with an opening through which the cavity communicates with the fuel accumulation bore so that, when the valve portion leaves the valve seat upon energizing the coil, the fuel accumulation bore communicates with the injection hole for fuel injection; and the housing has a hollow into which fuel is flown from outside and the stator is provided with a penetrating bore communicating with the hollow of the housing at an axial end thereof and communicating with the armature accommodation bore at another axial end thereof, and the armature has a through-hole for making the armature accommodation bore on a side of the stator communicate with the cavity so that fuel is introduced from the hollow of the housing into the cavity.
- 2. A fuel injection valve according to claim 1, wherein the nozzle needle penetrates axially along the through-hole of the armature until an axial end thereof protrudes out of an axial end of the armature toward the stator so that fuel is introduced into the cavity from the hollow of the housing via the penetrating bore.
- 3. A fuel injection valve according to claim 1, wherein the through hole of the armature communicates with the armature accommodation bore on the side of the stator at an axial end thereof and communicates with the cavity at another axial end thereof so that fuel is introduced into the cavity from the hollow of the housing via the penetrating bore and the through-hole.
- 4. A fuel injection valve according to claim 3, wherein the armature is provided at an axial end thereof on a side of the nozzle needle with an aperture through which the armature accommodation bore communicates with the through-hole.
- 5. A fuel injection valve comprising:a housing; a stator fixed to the housing; a cylindrical valve body fixed to the housing, the cylindrical valve body being provided at an axial end thereof on a side opposite to the stator with at least an injection hole and having a valve seat protruding radially inward out of an inner wall thereof, which is positioned on a side of the stator with respect to the injection hole, and a needle supporting cylindrical inner wall, which is positioned on a side of the stator with respect to the valve seat; an armature accommodation bore provided in the housing between the stator and the cylindrical valve body; an armature movable in the armature accommodation bore; a coil for exerting an electromagnetic attracting force on the armature so as to be attracted toward the stator when energized; a nozzle needle fixed to the armature and movable together with the armature in the cylindrical valve body and the armature accommodation bore, while being supported slidably by the needle supporting cylindrical inner wall, the nozzle needle being provided with a valve portion to be seated on the valve seat when the coil is de-energized and inside thereof with a cavity into which fuel is introduced; and a fuel accumulation bore provided between an inner circumference of the cylindrical valve body extending axially from the valve seat to the needle supporting cylindrical inner wall and an outer circumference of the nozzle needle; wherein the nozzle needle is provided with an opening through which the cavity communicates with the fuel accumulation bore so that, when the valve portion leaves the valve seat upon energizing the coil, the fuel accumulation bore communicates with the injection hole for fuel injection; and the opening is formed to axially stride over the needle supporting cylindrical inner wall so that the cavity communicates not only with the fuel accumulation bore but also with the armature accommodation bore on a side of the cylindrical valve body.
- 6. A fuel injection valve comprising:a housing; a stator fixed to the housing; a cylindrical valve body fixed to the housing, the cylindrical valve body being provided at an axial end thereof on a side opposite to the stator with at least an injection hole and having a valve seat protruding radially inward out of an inner wall thereof, which is positioned on a side of the stator with respect to the injection hole, and a needle supporting cylindrical inner wall, which is positioned on a side of the stator with respect to the valve seat; an armature accommodation bore provided in the housing between the stator and the cylindrical valve body; an armature movable in the armature accommodation bore; a coil for exerting an electromagnetic attracting force on the armature so as to be attracted toward the stator when energized; a nozzle needle fixed to the armature and movable together with the armature in the cylindrical valve body and the armature accommodation bore, while being supported slidably by the needle supporting cylindrical inner wall, the nozzle needle being provided with a valve portion to be seated on the valve seat when the coil is de-energized and inside thereof with a cavity into which fuel is introduced; and a fuel accumulation bore provided between an inner circumference of the cylindrical valve body extending axially from the valve seat to the needle supporting cylindrical inner wall and an outer circumference of the nozzle needle; wherein the nozzle needle is provided with an opening through which the cavity communicates with the fuel accumulation bore so that, when the valve portion leaves the valve seat upon energizing the coil, the fuel accumulation bore communicates with the injection hole for fuel injection; and the nozzle needle is provided with a small diameter column portion whose axial end on a side of the injection hole constitutes the valve portion and with a large diameter column portion whose diameter is larger than that of the small diameter column portion and which is slidably supported by the needle supporting cylindrical inner wall.
- 7. A fuel injection valve comprising:a housing; a stator fixed to the housing; a cylindrical valve body fixed to the housing, the cylindrical valve body being provided at an axial end thereof on a side opposite to the stator with at least an injection hole and having a valve seat protruding radially inward out of an inner wall thereof, which is positioned on a side of the stator with respect to the injection hole, and a needle supporting cylindrical inner wall, which is positioned on a side of the stator with respect to the valve seat; an armature accommodation bore provided in the housing between the stator and the cylindrical valve body; an armature movable in the armature accommodation bore; a coil for exerting an electromagnetic attracting force on the armature so as to be attracted toward the stator when energized; a nozzle needle fixed to the armature and movable together with the armature in the cylindrical valve body and the armature accommodation bore, while being supported slidably by the needle supporting cylindrical inner wall, the nozzle needle being provided with a valve portion to be seated on the valve seat when the coil is de-energized and inside thereof with a cavity into which fuel is introduced; and a fuel accumulation bore provided between an inner circumference of the cylindrical valve body extending axially from the valve seat to the needle supporting cylindrical inner wall and an outer circumference of the nozzle needle; wherein the nozzle needle is provided with an opening through which the cavity communicates with the fuel accumulation bore so that, when the valve portion leaves the valve seat upon energizing the coil, the fuel accumulation bore communicates with the injection hole for fuel injection; and the needle supporting cylindrical inner wall, whose diameter is larger than a diameter of the valve seat, is formed to protrude radially inward out of the inner wall of the cylindrical valve body.
- 8. A fuel injection valve comprising:a housing; a stator fixed to the housing; a cylindrical valve body fixed to the housing, the cylindrical valve body being provided at an axial end thereof on a side opposite to the stator with at least an injection hole and having a valve seat protruding radially inward out of an inner wall thereof, which is positioned on a side of the stator with respect to the injection hole, and a needle supporting cylindrical inner wall, which is positioned on a side of the stator with respect to the valve seat; an armature accommodation bore provided in the housing between the stator and the cylindrical valve body; an armature movable in the armature accommodation bore; a coil for exerting an electromagnetic attracting force on the armature so as to be attracted toward the stator when energized; a nozzle needle fixed to the armature and movable together with the armature in the cylindrical valve body and the armature accommodation bore, while being supported slidably by the needle supporting cylindrical inner wall, the nozzle needle being provided with a valve portion to be seated on the valve seat when the coil is de-energized and inside thereof with a cavity into which fuel is introduced; and a fuel accumulation bore provided between an inner circumference of the cylindrical valve body extending axially from the valve seat to the needle supporting cylindrical inner wall and an outer circumference of the nozzle needle; wherein the nozzle needle is provided with an opening through which the cavity communicates with the fuel accumulation bore so that, when the valve portion leaves the valve seat upon energizing the coil, the fuel accumulation bore communicates with the injection hole for fuel injection; and an outer circumference of the armature is in slidable contact with a circumferential wall constituting the armature accommodation bore in the housing so that the armature is slidably supported by axially spaced two supporting points.
- 9. A fuel injection valve comprising:a housing; a stator fixed to the housing; a cylindrical valve body fixed to the housing, the cylindrical valve body being provided at an axial end thereof on a side opposite to the stator with at least an injection hole and having a valve seat protruding radially inward out of an inner wall thereof, which is positioned on a side of the stator with respect to the injection hole, and a needle supporting cylindrical inner wall, which is positioned on a side of the stator with respect to the valve seat; an armature accommodation bore provided in the housing between the stator and the cylindrical valve body; an armature movable in the armature accommodation bore; a coil for exerting an electromagnetic attracting force on the armature so as to be attracted toward the stator when energized; a nozzle needle fixed to the armature and movable together with the armature in the cylindrical valve body and the armature accommodation bore, while being supported slidably by the needle supporting cylindrical inner wall, the nozzle needle being provided with a valve portion to be seated on the valve seat when the coil is de-energized and inside thereof with a cavity into which fuel is introduced; and a fuel accumulation bore provided between an inner circumference of the cylindrical valve body extending axially from the valve seat to the needle supporting cylindrical inner wall and an outer circumference of the nozzle needle, wherein the nozzle needle is provided on an outer circumference thereof with an opening at least part of which is opened to the fuel accommodation bore from the cavity so that the fuel introduced into the cavity flows through the opening to the fuel accumulation bore, and when the valve portion leaves the valve seat upon energizing the coil, the fuel accumulation bore communicates with the injection hole for fuel injection.
- 10. A fuel injection valve according to claim 9, wherein another part of the opening is radially opposed to the needle supporting cylindrical wall.
- 11. A fuel injection valve according to claim 9, wherein the valve seat and the needle supporting cylindrical inner wall are integrally formed into a single piece.
- 12. A fuel injection valve according to claim 9, wherein another part of the opening is opened to the armature accommodation bore from the cavity so that the opening axially strides over the needle supporting cylindrical inner wall.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2000-139702 |
May 2000 |
JP |
|
US Referenced Citations (12)
Foreign Referenced Citations (2)
Number |
Date |
Country |
0 602 001 |
Jun 1994 |
EP |
8-303327 |
Nov 1996 |
JP |