Title of the Invention
ELECTROMAGNETIC FUEL INJECTION VALVE
5
Technical Field
[0001] The present invention relates to an electromagnetic fuel injection valve in which a
movable core is driven by controlling the energization of a coil provided on an outer
periphery of a fixed core to repeat the opening and closing of a valve.
10
Background Art
[0002] In the related art, an electromagnetic fuel injection valve that includes a movable
core that faces a fixed core and works in conjunction with a valve body, a coil housing that
surrounds a coil provided on an outer periphery of the fixed core and functions as a yoke
15 forming a magnetic circuit passing through the fixed core and the movable core, and a resin
loaded between the coil housing and the coil, in which the movable core and the valve body
are integrally driven by controlling the energization of the coil to repeat an open valve state
and a closed valve state, is known (see, for example, Patent Literature 1).
[0003] In the electromagnetic fuel injection valve of Patent Literature 1, the coil housing
20 includes two yokes that are disposed on both sides in the radial direction with the coil
interposed therebetween. Each yoke includes a partially cylindrical large-diameter
portion having an inner surface that faces a cylindrical side surface of the coil and a central
angle that is an obtuse angle. The large-diameter portion has a recessed portion formed
therein. In addition, the recessed portion in the large-diameter portion includes a loading
25 hole penetrating the recessed portion.
[0004] The loading of the resin into a space between the coil housing and the coil is
performed in response to the injection molding of a coating layer covering a main unit
including the coil housing and the like in the electromagnetic fuel injection valve with the
main unit considered as an insert member. That is, in this case, a space between the two
30 yokes serves as a loading port, and the resin is loaded into the space. In addition, the
2
loading is also performed through the loading hole.
[0005] In the case of loading the resin into this space, the above-mentioned recessed
portion and loading hole have a function of enhancing the loading property of the resin into
the space. This enables the injection molding of the coating layer at a lower pressure or
5 within a shorter period of time and improves the production efficiency.
Citation List
Patent Literature
[0006] Patent Literature 1: Japanese Patent No. 5546667
10
Summary of Invention
Technical Problem
[0007] However, in the electromagnetic fuel injection valve of Patent Literature 1, the
large-diameter portion in the yoke constituting the magnetic circuit includes the recessed
15 portion, but this measure cannot be said to be always appropriate from the viewpoint of
promoting size reduction while avoiding the degradation of the performance and the
deterioration of the yield attributed to the injection molding. That is, the recessed portion
enhances the loading property of the resin, but may adversely affect a magnetic path in the
yoke to degrade the performance or may increase the diameter of the yoke.
20 [0008] An object of the present invention is to provide an electromagnetic fuel injection
valve capable of ensuring favorable performance and promoting size reduction while
avoiding the deterioration of the yield attributed to injection molding in view of the abovementioned problem of the related art.
25 Solution to Problem
[0009] An electromagnetic fuel injection valve according to the present invention
includes a fixed core, a movable core configured to face the fixed core, a valve body
configured to work in conjunction with the movable core, a coil provided on an outer
periphery of the fixed core, a coil housing configured to surround the coil and form a
30 magnetic circuit passing through the fixed core and the movable core, and a resin loaded
3
between the coil and the coil housing, in which the coil housing includes a pair of coil
housing half bodies that are disposed on both sides in a radial direction with the coil
interposed therebetween, each coil housing half body includes a partially cylindrical portion
having an inner surface facing a cylindrical side surface of the coil and an obtuse central
5 angle, and in the electromagnetic fuel injection valve configured to be in an open valve
state and a closed valve state repeatedly by controlling energization of the coil to drive the
movable core and the valve body, the partially cylindrical portion of each coil housing half
body includes two communication holes having a predetermined diameter and penetrating
the partially cylindrical portion in the radial direction provided at a predetermined interval
10 in an axial direction.
[0010] In this configuration, it is possible to perform the loading of a resin that molds an
insulating portion between the coil housing and the coil at the same time as the injection
molding of a coating layer that covers a main unit including the coil housing and the like
of the electromagnetic fuel injection valve as an insert member. In this case, a space
15 between the two coil housing half bodies and the two communication holes serve as loading
ports of the resin into a space between the coil housing and the coil.
[0011] Since the two communication holes also serve as the loading ports of the resin in
this way, the inflow rate of the resin from the outside to the inside of the coil housing half
bodies increases, and it is possible to avoid the generation of welds at both end portions of
20 the coil. This makes it possible to avoid the welds causing the disorder of winding at both
end portions of the coil and to improve the yield.
[0012] Therefore, this yield improvement is achieved simply by providing the two
communication holes in the coil housing half bodies constituting the magnetic circuit
without increasing the diameter of the coil housing while suppressing a change in the cross25 sectional area of the coil housing half bodies to the minimum extent. Therefore, according
to the present invention, it is possible to provide an electromagnetic fuel injection valve
capable of ensuring favorable performance and promoting size reduction while achieving
improvement in the yield.
[0013] In the present invention, a thickness of the coil housing half body may be constant.
30 This makes it possible to prevent a decrease in the magnetic force between the fixed core
4
and the movable core caused by the magnetic flux being limited in a portion with an uneven
thickness in the coil housing half bodies.
[0014] In the present invention, in each of the communication holes, a diameter of an
opening portion on the coil side may be larger than a diameter of an opening portion on the
5 opposite side. This makes the resin favorably diffuse to the inside of the coil housing half
bodies from the opening portions of the communication holes on the coil side in the case
of the resin being loaded through the communication holes from the outside of the coil
housing half bodies during the injection molding of the coating layer of the electromagnetic
fuel injection valve, and it is thus possible to more effectively suppress the generation of
10 the welds on both end portions of the coil.
Brief Description of Drawings
[0015] FIG. 1 is a cross-sectional view illustrating an electromagnetic fuel injection valve
according to an embodiment of the present invention.
15 FIG. 2 is an enlarged cross-sectional view illustrating a part of a coil assembly in
the electromagnetic fuel injection valve of FIG. 1.
FIG. 3 is a perspective view illustrating a coil housing half body in the
electromagnetic fuel injection valve of FIG. 1.
FIG. 4A is a view illustrating a resin flow analysis result regarding a weld
20 generation status in response to the loading of a resin into a space between a coil housing
and a coil in a case where there is no communication hole in the coil housing half body.
FIG. 4B is a view illustrating a resin flow analysis result regarding the weld
generation status in a case where there is one communication hole in the coil housing half
body.
25 FIG. 4C is a view illustrating a resin flow analysis result regarding the weld
generation status in the case of one embodiment of the present invention where there are
two communication holes in the coil housing half body.
FIG. 4D is a view illustrating a resin flow analysis result regarding the weld
generation status in a case where there are three communication holes in the coil housing
30 half body.
5
Description of Embodiments
[0016] Hereinafter, an embodiment of the present invention will be described using
drawings. FIG. 1 illustrates an electromagnetic fuel injection valve according to an
5 embodiment of the present invention. As illustrated in FIG. 1, this electromagnetic fuel
injection valve 1 includes a fixed core 2, a movable core 3 facing the fixed core 2, a valve
body 4 configured to work in conjunction with the movable core 3, a coil 5 provided on an
outer periphery of the fixed core 2, a coil housing 6 configured to surround the coil 5 and
form a magnetic circuit passing through the fixed core 2 and the movable core 3, and a resin
10 7 loaded between the coil 5 and the coil housing 6. In addition, the electromagnetic fuel
injection valve 1 is put into an open valve state and a closed valve state repeatedly by
controlling the energization of the coil 5 to drive the movable core 3 and the valve body 4.
[0017] A valve housing 8 of the electromagnetic fuel injection valve 1 is composed of a
cylindrical valve seat member 9, a magnetic cylindrical body 10 that is fitted and liquid15 tightly welded to a rear end portion outer peripheral surface of the valve seat member 9, a
non-magnetic cylindrical body 11 that abuts and liquid-tightly welded to a rear end of the
magnetic cylindrical body 10, the hollow cylindrical fixed core 2 that is liquid-tightly
welded to an inner peripheral surface of the non-magnetic cylindrical body 11 with a smalldiameter front end portion fitted to the non-magnetic cylindrical body 11, and a fuel inlet
20 tube 12 that is fitted and liquid-tightly welded to a rear end portion outer periphery of the
fixed core 2.
[0018] The valve seat member 9 has a valve hole 13 that is open at a front end surface, a
conical valve seat 14 that continues to an inner peripheral end of the valve hole 13, and a
cylindrical guide hole 15 that continues to a large-diameter portion of the valve seat 14.
25 An injector plate 16 made of a steel plate and having a plurality of fuel injection holes that
communicate with the valve hole 13 is liquid-tightly welded to a front end surface of the
valve seat member 9.
[0019] A portion that does not fit with the fixed core 2 is left at a front end portion of the
non-magnetic cylindrical body 11, the above-mentioned hollow cylindrical movable core 3
30 that faces a front end surface of the fixed core 2 throughout the magnetic cylindrical body
6
10 from the portion is fitted, and the valve body 4 is coupled to the movable core 3. The
fixed core 2 and the movable core 3, which have a hollow cylindrical shape, have a thicker
thickness than the magnetic cylindrical body 10 and the non-magnetic cylindrical body 11.
[0020] The valve body 4 is composed of a spherical valve portion 17 capable of sliding
5 the guide hole 15 to open and close the valve hole 13 in cooperation with the valve seat 14
and a valve stem 18 having a front end portion fixed to the valve portion 17, and a rear end
portion of the valve stem 18 is press-fitted and welded to the inner peripheral surface of the
movable core 3. Therefore, the valve body 4 is integrally formed with the movable core
3 and can be raised and lowered in the valve housing 8.
10 [0021] The valve stem 18 is made of a pipe material with a slot 19, and an inner portion
of the valve stem 18 communicates with a hollow portion of the movable core 3, and an
inside and an outside of the valve stem 18 communicate with each other via the slot 19.
In addition, a plurality of flat surfaces allowing the passage of fuel are formed around the
spherical valve portion 17.
15 [0022] In addition, the fuel inlet tube 12, the fixed core 2, a retainer 20 described below,
the respective hollow portions of the movable core 3 and the valve stem 18, the slot 19 of
the valve stem 18, the guide hole 15 of the valve seat member 9, the valve hole 13, and the
fuel injection holes of the injector plate 16 constitute a series of fuel flow passages F in the
valve housing 8.
20 [0023] In the hollow portion of the fixed core 2, the retainer 20 made of a slotted pipe
material is press-fitted and fixed to an intermediate portion of the fixed core 2, and a front
end portion of the retainer 20 serves as a first spring seat. On the other hand, the rear end
portion of the valve stem 18 is finished in the middle of the hollow portion of the movable
core 3, and an upper end portion of the valve stem 18 serves as a second spring seat. A
25 valve spring 21 is compressed between the first spring seat and the second spring seat.
The movable core 3 is actuated in a direction in which the movable core 3 is separated
downward from the fixed core 2, that is, in a seating direction of the valve seat 14 of the
valve body 4, by a set load of the valve spring 21. The set load of the valve spring 21 is
adjusted by the fitting depth of the retainer 20 into the fixed core 2.
30 [0024] A ring-shaped stopper member 22 made of a non-magnetic material and slightly
7
protruding from a rear end surface is embedded in the inner peripheral surface of the
movable core 3. A coil assembly 23 is fitted to an outer periphery of the valve housing 8
to correspond to the fixed core 2 and the movable core 3.
[0025] The coil assembly 23 is composed of a bobbin 24 made of a synthetic resin that is
5 fitted to an outer peripheral surface of the fixed core 2 from the rear end portion of the
magnetic cylindrical body 10 throughout the fixed core 2 and the above-mentioned coil 5
that is wound around the bobbin 24. A terminal support arm 26 that supports a proximal
end portion of a power supply terminal 25 protruding to one side is integrally formed at a
rear end portion of the bobbin 24. A terminal of the coil 5 is connected to the power supply
10 terminal 25. The coil assembly 23 is covered with the above-mentioned coil housing
(yoke) 6 on an approximately half circumferential surface thereof.
[0026] A synthetic resin-made coating layer 27 that covers the outer peripheral surface of
the magnetic cylindrical body 10 and the fuel inlet tube 12 and embeds the coil assembly
23 is injection-molded. In this case, the power supply terminal 25 is accommodated and
15 held, and a coupler 28 protruding to one side of the coil assembly 23 is integrally molded
with the coating layer 27. The above-mentioned resin 7 loaded between the coil 5 and the
coil housing 6 is formed as a part of the coating layer 27.
[0027] A fuel filter 29 is mounted on an inlet of the fuel inlet tube 12. In addition, a fuel
cap connected to a fuel pump (not illustrated) is fitted to an upper end portion outer
20 periphery of the fuel inlet tube 12 via a seal member 30.
[0028] FIG. 2 illustrates a vicinity of the coil assembly 23 in an enlarged manner. As
illustrated in FIG. 2, the coil housing 6 is composed of a pair of coil housing half bodies 31
disposed on both sides in the radial direction with the coil assembly 23 interposed
therebetween. The above-mentioned resin 7 that forms an insulating portion between the
25 coil 5 and the coil housing half body 31 is loaded between the coil 5 and the coil housing
half body 31.
[0029] FIG. 3 illustrates the coil housing half body 31. As illustrated in FIG. 3, the coil
housing half body 31 includes a partially cylindrical portion 32 that is a partially cylindrical
part having an inner surface facing a cylindrical side surface of the coil and an obtuse central
30 angle θ. For example, 145° can be employed as the central angle. The thickness t of the
8
coil housing half body 31 is constant. For example, 1 mm is employed as the thickness t.
[0030] As illustrated in FIG. 2, two communication holes 33 that penetrate the partially
cylindrical portion 32 in the radial direction and have a predetermined diameter φ are
provided in the partially cylindrical portion 32 at a predetermined interval d in the axial
5 direction so that the position of the center point between the communication holes 33 is
positioned at the center position of the partially cylindrical portion 32. For example, 2
mm is employed as the predetermined diameter φ. For example, 8.4 mm is employed as
the predetermined interval d.
[0031] The loading of the resin between the coil housing 6 and the coil 5 is performed at
10 the same time as the injection molding of the coating layer 27. This injection molding is
performed with a main unit of the electromagnetic fuel injection valve 1 including the coil
housing 6, the valve housing 8, the power supply terminal 25, and the like, which have been
completely assembled, regarded as an insert member. In this case, regarding the loading
of the resin between the coil housing 6 and the coil 5, the space between the two coil
15 housing half bodies 31 and the two communication holes 33 serve as loading ports of the
resin.
[0032] In a case where the coating layer 27 is thus formed and the coil 5 is not energized
in the completed electromagnetic fuel injection valve 1, the valve portion 17 is pressed in
the front end direction with the valve spring 21, and the electromagnetic fuel injection valve
20 1 is in a closed valve state where the valve portion 17 is seated on the valve seat 14. In a
case where the fuel is pumped from a fuel pump (not illustrated) through a fuel distribution
pipe to the fuel inlet tube 12 in this state, the fuel fills the fuel flow passages F in the valve
housing 8 and further applies a fluid pressure to the valve portion 17.
[0033] In a case where the coil 5 is excited by energization through the coupler 28 in this
25 state, a magnetic flux generated by the excitation passes through the coil housing 6, the
magnetic cylindrical body 10, the movable core 3, and the fixed core 2, and a magnetic
attraction force is generated between the movable core 3 and the fixed core 2.
Accordingly, the movable core 3 is attracted to the fixed core 2 against the set load of the
valve spring 21, and the movable core 3 abuts on the fixed core 2.
30 [0034] This makes the valve portion 17 separated from the valve seat 14 and puts the
9
electromagnetic fuel injection valve 1 into an open valve state. Accordingly, the highpressure fuel in the fuel flow passages F is injected in a mist form from a fuel nozzle of the
injector plate 16 to an intake pipe of an internal combustion engine through the valve hole
13. In addition, in a case where the energization of the coil 5 is blocked, the
5 electromagnetic fuel injection valve 1 is returned to the closed valve state where the valve
portion 17 is seated on the valve seat 14.
[0035] Therefore, the electromagnetic fuel injection valve 1 is put into the closed valve
state and the open valve state repeatedly by controlling the energization of the coil 5, and it
is possible to perform appropriate supply of fuel to the internal combustion engine to which
10 the electromagnetic fuel injection valve 1 is attached.
[0036] As described above, according to the present embodiment, since the two
communication holes 33 are provided in the coil housing half bodies 31, the adverse
influence on the magnetic circuit in the coil housing half bodies 31 is suppressed to the
minimum extent, and the yield improves without increasing the diameter of the coil housing
15 6. Therefore, it is possible to provide an electromagnetic fuel injection valve capable of
ensuring favorable performance and promoting size reduction while improving the yield.
[0037] That is, it is possible to perform the loading of the resin between the coil housing
6 and the coil 5 in parallel at the same time as the formation of the coating layer 27 with
the resin by injection molding with the main unit of the electromagnetic fuel injection valve
20 1 including the coil housing 6 and the like regarded as an insert member. In this case, the
space between the two coil housing half bodies 31 and each of the two communication
holes 33 serve as the loading ports of the resin into the space between the coil housing 6
and the coil 5.
[0038] Since this makes the inflow rate of the resin into the coil housing half bodies 31,
25 from the outside to the inside of the coil housing half bodies 31, fast and makes it possible
to avoid the generation of welds in both end portions of the coil 5, it is possible to avoid the
disorder of winding being caused by the welds at both end portions of the coil 5 and to
improve the yield.
[0039] This yield improvement can be achieved simply by providing the two
30 communication holes 33 in the coil housing half bodies 31 without providing a recessed
10
portion or the like. Therefore, it is possible to avoid an increase in the diameter of the coil
housing 6 while suppressing the adverse influence on the magnetic circuit in the coil
housing half bodies 31 to the minimum extent.
[0040] FIG. 4A to FIG. 4D are views illustrating resin flow analysis results for describing
5 an effect of these two communication holes 33. FIG. 4A to FIG. 4D illustrate the
generation status of a weld 34 in a case where the loading of the resin between the coil
housing 6 and the coil 5 is performed in response to the injection molding of the abovementioned coating layer 27. FIG. 4A to FIG. 4D illustrate the generation status of this
weld 34 in cases where the number of the communication holes 33 provided in the coil
10 housing half bodies 31 is “0” (none), “1”, “2” (the case of the present embodiment), and
“3”.
[0041] In a case where the number of the communication holes 33 is “0” (none) as
illustrated in FIG. 4A, since the resin is loaded only from between the two coil housing half
bodies 31, the weld 34 is generated in a substantially linear shape along the length direction
15 of the coil housing half bodies 31. Therefore, it is understood that the end portions of this
weld 34 coincide with coil line switching positions in the end portions of the coil 5 and thus
serves as a cause of disorder in a coil line.
[0042] In a case where the number of the communication hole 33 is “1” as illustrated in
FIG. 4B, a status where the weld 34 is pressed and spread around the communication hole
20 33 due to the resin being loaded from this communication hole 33 is exhibited, but the weld
34 in this pressed and spread state is in a status of being closed at both end portions of the
coil 5. Therefore, it is understood that the generation of the weld 34 is not avoided at the
coil line switching positions in both end portions of the coil 5 and thus serves as a cause of
disorder in the coil line.
25 [0043] In a case where the number of the communication holes 33 is “2” as illustrated in
FIG. 4C, a status where the weld 34 is pressed and spread around each communication hole
33 on one and the other end portion sides of the coil 5 due to the resin being loaded from
the communication holes 33 is exhibited, and this status extends up to both end portions 35
of the coil 5. Therefore, it is understood that the generation of the weld 34 at the coil line
30 switching positions in both end portions 35 of the coil 5 is avoided and disorder being
11
caused in the coil line is prevented.
[0044] In a case where the number of the communication holes 33 is “3” as illustrated in
FIG. 4D, a status where the weld 34 is pressed and spread around each communication hole
33 due to the resin being loaded from each communication hole 33 is exhibited, and it can
5 be seen that, as in a case where the number of the communication holes 33 is “2”, the
generation of the weld 34 at the coil line switching positions in both end portions of the coil
5 is avoided.
[0045] On the other hand, it has been confirmed that, as the number of the communication
holes 33 increases, the magnetic characteristics in the coil housing half bodies 31 further
10 deteriorate and the attraction force between the fixed core 2 and the movable core 3 further
decreases.
[0046] As described above, it can be seen that the generation of the weld 34 in both end
portions of the coil 5 can be avoided without causing the deterioration of the magnetic
characteristics by disposing the two communication holes 33 having an appropriate
15 diameter φ in an intermediate position of the coil housing half bodies 31 at an appropriate
interval d along the length direction of the coil housing half bodies 31. Here, the diameters
φ and the interval d of the two communication holes 33 are selected so that no weld is
generated at the coil line switching position in the end portion of the coil 5 as shown in FIG.
4C.
20 [0047] Further, according to the present embodiment, since the thickness of the coil
housing half body 31 is constant, the magnetic flux is limited in a portion where the
thickness of the coil housing half body is not uniform, and it is thus possible to prevent the
magnetic force between the fixed core 2 and the movable core 3 from being decreased.
[0048] Hitherto, the embodiment of the present invention has been described above, but
25 the present invention is not limited thereto. For example, the diameter of the opening
portion on the coil 5 side may be larger than the diameter of the opening portion on the
opposite side in each of the communication holes 33. This makes the resin favorably
diffuse from the communication holes 33 to the inside of the coil housing half bodies 31 in
a case where the resin is loaded through the communication holes 33 from the outside of
30 the coil housing half bodies 31, and it is thus possible to more effectively suppress the
12
generation of the welds 34 in both end portions of the coil 5.
Description of Reference Numerals
[0049] 1: electromagnetic fuel injection valve
5 2: fixed core
3: movable core
4: valve body
5: coil
6: coil housing
10 7: resin
8: valve housing
9: valve seat member
10: magnetic cylindrical body
11: non-magnetic cylindrical body
15 12: fuel inlet tube
13: valve hole
14: valve seat
15: guide hole
16: injector plate
20 17: valve portion
18: valve stem
19: slot
20: retainer
21: valve spring
25 22: stopper member
23: coil assembly
24: bobbin
25: power supply terminal
26: terminal support arm
30 27: coating layer
13
28: coupler
29: fuel filter
30: seal member
31: coil housing half body
5 32: partially cylindrical portion
33: communication hole
34: weld
35: both end portions
F: fuel flow passage
10
14
1. An electromagnetic fuel injection valve, comprising:
a fixed core;
5 a movable core configured to face the fixed core;
a valve body configured to work in conjunction with the movable core;
a coil provided on an outer periphery of the fixed core;
a coil housing configured to surround the coil and form a magnetic circuit passing
through the fixed core and the movable core; and
10 a resin loaded between the coil and the coil housing,
wherein the coil housing includes a pair of coil housing half bodies that are
disposed on both sides in a radial direction with the coil interposed therebetween,
each coil housing half body includes a partially cylindrical portion having an inner
surface facing a cylindrical side surface of the coil and an obtuse central angle, and
15 the electromagnetic fuel injection valve configured to be in an open valve state
and a closed valve state repeatedly by controlling energization of the coil to drive the
movable core and the valve body,
the partially cylindrical portion of each coil housing half body includes two
communication holes having a predetermined diameter and penetrating the partially
20 cylindrical portion in the radial direction provided at a predetermined interval in an axial
direction.
2. The electromagnetic fuel injection valve according to claim 1,
wherein a thickness of the coil housing half body is constant.
25
3. The electromagnetic fuel injection valve according to claim 1,
wherein, in each of the communication holes, a diameter of an opening portion
on a coil side is larger than a diameter of an opening portion on the opposite side.