U.S. patent application number 11/121915 was filed with the patent office on 2005-09-22 for welding machine and welding method.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Hokao, Takayuki, Kariya, Yoshiki, Murakami, Koji, Nishina, Hiroyuki, Shirai, Hideaki, Tanaka, Norio.
Application Number | 20050205535 11/121915 |
Document ID | / |
Family ID | 26610079 |
Filed Date | 2005-09-22 |
United States Patent
Application |
20050205535 |
Kind Code |
A1 |
Shirai, Hideaki ; et
al. |
September 22, 2005 |
Welding machine and welding method
Abstract
In a welding machine and welding method, for welding cylinder
members together about an outside diameter, which prevents the
cylinder members from being deformed and corrects the deformation
of a portion to be welded, a laser beam, generated by a laser
generator, is dispersed in two directions by a spectroscope. The
laser beams focus on an outer cylinder member using two optical
heads, respectively, in a plane perpendicular to a center axis of
outer cylinder member. The optical heads are separated from each
other by approximately 90 degrees in the plane. The outer and inner
cylinder members are welded to each other in the circular direction
using laser beams. Therefore, directions, in which the cylinder
members are deformed due to the laser beams, are perpendicular to
each other creating uniform radial deformation.
Inventors: |
Shirai, Hideaki;
(Okazaki-city, JP) ; Murakami, Koji; (Chiryu-city,
JP) ; Tanaka, Norio; (Kariya-city, JP) ;
Kariya, Yoshiki; (Nishio-city, JP) ; Nishina,
Hiroyuki; (Okazaki-city, JP) ; Hokao, Takayuki;
(Anjo-city, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
DENSO CORPORATION
Kariya city
JP
|
Family ID: |
26610079 |
Appl. No.: |
11/121915 |
Filed: |
May 5, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11121915 |
May 5, 2005 |
|
|
|
10081239 |
Feb 25, 2002 |
|
|
|
6919528 |
|
|
|
|
Current U.S.
Class: |
219/121.63 ;
219/121.76 |
Current CPC
Class: |
B23K 26/0619 20151001;
B23K 26/282 20151001; B23K 26/067 20130101 |
Class at
Publication: |
219/121.63 ;
219/121.76 |
International
Class: |
B23K 026/24 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 26, 2001 |
JP |
2001-50015 |
Jan 21, 2002 |
JP |
2002-11556 |
Claims
1-3. (canceled)
4. An injector to be assembled by welding, the injector comprising:
a valve body including a valve seat; a valve member for stopping
fuel injection when seated on the valve seat, and for permitting
fuel injection when separated from the valve seat; a movable core
connected to the valve member at an opposite side of the valve
seat, the movable core reciprocating together with the valve
member; a fixed core disposed opposite the valve member relative to
the movable core, the fixed core facing the movable core; an
electromagnetic driving device for generating magnetic force by
which the movable core is attracted to the fixed core; and a
housing member of which an inner peripheral wall is connected to an
outer peripheral wall of the valve body, the housing member
containing the movable core so as to reciprocate therein, wherein:
each of the housing member and the valve body is a cylinder member;
and the valve body is inserted into the housing member, and they
are welded to each other by melting them about a circumference of
the housing member.
5. The injector according to claim 4, wherein: each of the valve
member and the movable core is a cylinder member; and the valve
member is inserted into the movable core, and they are welded to
each other by melting them about the circumference of the movable
core.
6. The injector according to claim 5, wherein: the injector
includes a magnetic member, disposed outside the housing member and
the fixed core, for magnetically connecting the housing member and
the fixed core; the magnetic member is a cylinder member; and the
housing member is inserted into the magnetic member, and the
housing member and the magnetic member are welded to each other by
melting them about the circumference of the magnetic member.
7-21. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based on and incorporates herein by
reference Japanese Patent Application No. 2001-50015 filed on Feb.
26, 2001, and Japanese Patent Application No. 2002-11556 filed on
Jan. 21, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a welding machine and a
welding method, by which and in which cylinder members are
connected together. Specifically, one cylinder member is inserted
within another cylinder member and energy is applied to the outside
cylinder member, around an outside diameter of the cylinder member,
using an energy-applying unit(s), so that the cylinder members
become welded together.
[0004] 2. Description of Related Art
[0005] Generally, when multiple cylinder members are welded
together around their peripheries, energy is applied to the
cylinder members in a single direction using an energy source. An
example is shown in FIG. 8. First, an inner cylinder member 201
having a columnar shape is press-fitted into an outer cylinder
member 200 having a circular pipe-like shape. Then, a laser beam
211, generated by a laser generator, is focused on the outer
cylinder member 200 using an optical head 210 disposed outside the
outer cylinder member 200. Thus, the outer cylinder member 200 and
the inner cylinder member 201 become welded to each other at a
point of contact at an outer periphery while cylinder members 200
and 201 are rotated.
[0006] However, when both cylinder members are welded to each other
by applying energy to both at only one position, a problem occurs.
That is, relative thermal distortion is generated among a
non-melted portion, a melted portion due to the applied energy, and
a portion starting solidification. For this relative thermal
distortion, both cylinder members are deformed from a pre-weld
shape 220 shown in FIG. 9A to a post-weld shape 221 shown in FIG.
9B. As shown in FIG. 9B, both cylinder members are deformed in a
direction perpendicular to an energy-applying direction, and each
cylinder member is deformed to an elliptical shape when viewed in
cross-section.
[0007] Here, elliptical-deformation processes will be described
when the cylinder members are welded in the circular or
circumferential direction by applying energy in a single direction
using an energy source. Before welding, for example, when one
cylinder member is press-fitted into and attached to another
cylinder member, both cylinder members are deformed. Then, this
deformation is made larger by relative distortion between an
expanded portion and a contracted portion due to welding, and each
cylinder member is deformed to an elliptical shape in its cross
section. Even when the cylinder members are not deformed and
substantially have a complete circular shape before welding as
shown in FIG. 9A, they are deformed after welding as shown in FIG.
9B. The shape 220 substantially having a circular shape tends to
deform to the shape 221 having an elliptical shape in a direction
crossing the energy-applying direction at a weld-starting position.
In FIGS. 9A and 9B, larger and smaller circles described with
broken lines indicate the largest and smallest diameters among the
welded and deformed portions, respectively.
[0008] Irrespective of deformation before welding, when welding is
performed in an angle area from zero degrees to 90 degrees in a
circular direction, the cylinder members are deformed to an
elliptical shape due to thermal expansion, and an amount of
deformation increases. When the welding proceeds to an angle of 180
degrees, the elliptical deformation is relieved by expansion due to
welding progress in an angle area from 90 degrees to 180 degrees
and by shrinkage due to solidification in the angle area from zero
degree to 90 degrees. Then, the amount of the deformation is
decreased. When the welding proceeds to an angle of 270 degrees,
the relieved elliptical deformation is again enlarged by expansion
due to welding progress in an angle area from 180 degrees to 270
degrees. When the welding proceeds to an angle of 360 degrees, the
elliptical deformation is relieved by expansion due to welding
progress in an angle area from 270 degrees to 360 degrees and by
shrinkage due to solidification in the angle area from 180 degree
to 270 degrees. Then, the amount of the deformation decreases. As
the welding proceeds in the angle area, the amount of the
deformation increases and decreases. The cylinder members are
deformed to an elliptical shape due to welding. Even when the
welding proceeds beyond 360 degrees and the same portion is welded
many times, the above-described deformation process is repeated at
the previously-welded portions. In a member requiring metal
sealing, when the member is deformed by welding, sealing
performance is degraded.
[0009] In FIGS. 9A and 9B, large and small circles shown with
broken lines indicate the largest and smallest diameters among the
welded and deformed portions, respectively. The shape 220, being
substantially circular, tends to be deformed to the elliptical
shape 221 in a direction crossing the energy-applying direction at
a weld-starting position.
[0010] In order to restrict both cylinder members from being
deformed due to the method where energy is applied to both in a
single direction, the following method is considered. As shown in
FIG. 10, energy is applied to both cylinder members at two
positions simultaneously in directions opposing each other at 180
degrees. However, energy is applied to the outer and inner cylinder
members 200 and 201 at two positions opposing each other in the
radial direction, and both cylinder members are readily deformed at
two positions. Therefore, both cylinder members are readily
deformed in a direction perpendicular to the energy-applying
direction. Accordingly, a shape 230, substantially having a
complete circular shape before welding as shown in FIG. 11A, tends
to be deformed to a shape 231 having an elliptical shape after
welding, shown in FIG. 11B, in a direction crossing the
energy-applying directions at weld-starting positions. In FIGS. 11A
and 11B, large and small circles shown with broken lines indicate
the largest and smallest diameters among the welded and deformed
portions, respectively.
[0011] When foreign matter is mixed into a portion to be melted
with applied energy, the foreign matter may be evaporated by the
applied energy, so that pores are sometimes generated at the welded
portion. When pores are generated at the welded portion, welding
failure may occur.
SUMMARY OF THE INVENTION
[0012] It is a first object of an embodiment of the present
invention to provide a welding machine and a welding method, for
welding cylinder members together in the circular direction, which
prevents the cylinder members from being deformed and which
corrects the deformation of a portion to be welded. It is another
object of an embodiment of the present invention to provide a
welding method which prevents pores from being generated at a
welded portion. It is another object of an embodiment of the
present invention to provide a welding machine for reducing fuel
leakage of an injector.
[0013] For example, when a cylinder member is press-fitted into a
different cylinder member before welding, the deformation of the
cylinder members due to this press-fitting can be corrected by
welding.
[0014] According to a welding machine in an embodiment of the
present invention, energy-applying units, for applying energy
generated by an energy source to cylinder members, are disposed
outside the cylinder members at two positions. An angle by which
the energy-applying units are separated from each other in a
circular direction about the cylinder members is defined by .theta.
degrees, where 80.ltoreq..theta..ltoreq.100- . That is, the
energy-applying units melt the cylinder members at two positions
separated from each other at approximately 90 degrees in the
circular (circumferential or peripheral) direction. Therefore, the
cylinder members are deformed in two directions perpendicular to
each other, and the cylinder members are uniformly deformed at the
welded portions, thereby preventing the welded portions of the
cylinder members from being deformed overall. Further, the cylinder
members are uniformly deformed at the welded portions, thereby
correcting a shape of a portion to be welded, if it is deformed
before welding.
[0015] Additionally, energy-applying units, for applying energy
generated by an energy source to cylinder members, may be disposed
outside the cylinder members at multiple positions. When the number
of the energy-applying units is defined by "n" and an angle
".theta.", by which the neighboring energy-applying units are
separated from each other in a circular direction about the
cylinder members, a relationship exists such that
[(360/n)-10].ltoreq..theta..ltoreq.[(360/n)+10]. Therefore, three
or more energy-applying units may melt the cylinder members at
three or more positions separated from each other substantially by
the same angle in the circular direction, that is, around the
periphery of the circular members. Thus, the cylinder members are
uniformly deformed at the welded portions, thereby preventing the
welded portions of the cylinder members from being deformed
overall. Further, the cylinder members are uniformly deformed at
the welded portions, thereby correcting a shape of a portion to be
welded, if it is deformed before welding.
[0016] According to a welding machine in an embodiment of the
present invention, the energy-applying units are disposed in a
plane perpendicular to a center axis of the cylinder members, and
the energy is introduced from the energy-applying units to the
cylinder members along the intersection of the plane and the outer
cylinder member. Therefore, the direction in which the energy is
applied to the cylinder members does not change with respect to the
axis of the cylinder members, thereby uniformly welding the
cylinder members around their periphery.
[0017] According to an embodiment of the present invention, the
welding machine is used as an injector welding machine. Using the
welding machine, a housing member and a valve body as a cylinder
member are welded to each other by melting them in a circular
direction. Since the housing member and the valve body are
uniformly deformed at all of their welded portions, they can be
prevented from overall deformation at their welded portions.
Further, if a shape of their portions to be welded are deformed
before welding, that can be corrected. An off-center situation
between the valve body and the valve member is reduced while the
complete-circle degree (circularity) of an inner peripheral surface
(forming a valve seat) of the valve body is improved. Further, when
the valve member is seated on the valve seat, a clearance between
the valve seat and the valve member becomes smaller. Therefore,
seat performance between the valve seat and the valve member is
improved. Accordingly, when the valve-member is seated on the valve
seat, an amount of fuel, leaked from the clearance between the
valve seat and the valve member, is reduced.
[0018] According to a welding machine of another embodiment of the
present invention, a movable core and the valve member as cylinder
members are welded to each other by melting them about their
peripheries. Since the movable core and the valve member are
uniformly deformed at all of their welded portions, overall
deformation can be prevented. Further, if a shape of their
portions, to be welded, is deformed before welding, that also can
be corrected. An off-center situation between the valve body and
the valve member is reduced while overall circularity of the valve
member is improved. Further, when the valve member is seated on the
valve seat, a clearance between the valve seat and the valve member
becomes smaller. Therefore, seat performance between the valve seat
and the valve member is improved. Accordingly, when the valve
member is seated on the valve seat, an amount of fuel, leaked from
the clearance between the valve seat and the valve member, is
reduced.
[0019] According to a welding machine in an embodiment of the
present invention, the housing member and a magnetic member as
cylinder members are welded to each other by melting them in a
circular direction (around a periphery). Since the housing member
and the magnetic member are uniformly deformed at all of their
welded portions, they can be prevented from being deformed at their
welded portions. Further, if a shape of their portions, to be
welded, are deformed before welding, that also can be corrected.
Further, circularity of the housing member is improved, thereby
reducing an off-center situation between the valve member and the
valve body welded to the housing member. Further, when the valve
member is seated on the valve seat, a clearance between the valve
seat and the valve member becomes smaller. Therefore, seat
performance between the valve seat and the valve member is
improved. Accordingly, when the valve member is seated on the valve
seat, an amount of fuel, leaked from the clearance between the
valve seat and the valve member, is reduced.
[0020] Further, the cylinder members may be welded together while
the cylinder members are rotated about the center axis of the
cylinder members, as a rotation axis, relative to the
energy-applying units. Then, a portion of the cylinder members,
melted by the energy applied from one of the neighboring
energy-applying units in the circular direction, is again melted by
the energy applied from another unit. This is a type of secondary
heat application. Therefore, even when pores are generated in a
portion of the cylinder members welded by the energy applied from
one of the energy-applying units, the portion is again melted by
energy applied from another unit, so that the pores are eliminated
during the second melting.
[0021] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The present invention will become more fully understood from
the detailed description and the accompanying drawings,
wherein:
[0023] FIG. 1 is a schematic perspective view showing a welding
machine in an embodiment of the present invention;
[0024] FIG. 2 is a schematic explanation view showing deformation
due to welding of both cylinder members;
[0025] FIG. 3A is a schematic explanation view showing a
cross-section of a cylinder member in a case of high working
accuracy before welding;
[0026] FIG. 3B is a schematic explanation view showing a
cross-section of a cylinder member in a case of high working
accuracy after welding;
[0027] FIG. 4A is a schematic explanation view showing a
cross-section of a cylinder member in a case of low working
accuracy before welding;
[0028] FIG. 4B is a schematic explanation view showing a
cross-section of a cylinder member in a case of low working
accuracy after welding;
[0029] FIG. 5A is a schematic sectional view showing a welded
portion with pores formed before invoking two-time welding
techniques;
[0030] FIG. 5B is schematic cross-sectional view showing
deformation of a welded portion with no pores after invoking
two-time welding techniques;
[0031] FIG. 6 is a cross-sectional view showing an injector welded
by a welding machine of an embodiment of the present invention;
[0032] FIG. 7 is a characteristic graph showing a relationship
between circularity of a cylinder member and oil-sealing
performance;
[0033] FIG. 8 is a schematic perspective view showing a welding
machine in a conventional example 1;
[0034] FIG. 9A is a schematic explanation view showing cross
section deformation of a cylinder member before welding in a
conventional example 1 of FIG. 8; and
[0035] FIG. 9B is a schematic explanation view showing the cross
section deformation of a cylinder member after welding in a
conventional example 1 of FIG. 8;
[0036] FIG. 10 is a schematic perspective view showing a welding
machine in a conventional example 2;
[0037] FIG. 11A is a schematic explanation view showing
cross-section deformation of both cylinder members before welding
in the conventional example 2 of FIG. 10; and
[0038] FIG. 11B is a schematic explanation view showing
cross-section deformation of both cylinder members after welding in
the conventional example 2 of FIG. 10.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] The following description of the preferred embodiments is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0040] FIG. 1 is a schematic view showing a welding machine in an
embodiment of the present invention. An outer cylinder member 10
and an inner cylinder member 11 have circular cross-sections, and
the inner cylinder member 11 is press-fitted into the outer
cylinder member 10. For example, the outer and inner cylinder
members 10, 11 could be a combination of a housing of an injector
and a nozzle body, respectively.
[0041] A laser generator 1 as an energy source generates a
high-energy laser beam such as an yttrium aluminum garnet (YAG)
laser beam and a carbon oxide (CO.sub.2) laser beam. A laser beam,
generated by the laser generator 1, is dispersed in two directions
by a spectroscope 2. Two dispersed laser beams are focused on the
outer cylinder member 10 by two optical heads 20 as energy-applying
units, respectively. The optical heads 20 are disposed outside the
outer and inner cylinder members 10, 11 in a plane perpendicular to
a center, longitudinal axis of both cylinder members 10, 11.
Further, the optical heads 20 are separated from each other by
approximately 90 degrees in a circular direction about the center,
longitudinal axis of the cylinder members 10, 11. The laser beams
30, focused on the outer cylinder member 10 by the optical heads
20, are introduced along a plane perpendicular to the center axis
of both cylinder members 10, 11. The outer and inner cylinder
members 10, 11 are completely welded to each other in the circular
direction using the laser beams 30 focused by the optical heads 20.
An arc discharge beam and an electron beam may be used as high
energy for welding both cylinder members together.
[0042] When the outer and inner cylinder members 10, 11 are
completely welded to each other in the circular direction, they are
rotated relative to the optical heads 20. When possible, the
optical heads 20 may be rotated about both cylinder members 10, 11.
Further, the outer and inner cylinder members 10, 11 may be rotated
more than one revolution. Thus, a portion, melted by the laser beam
30 at a front side in a rotational direction, is again melted by
the laser beam 30 at a rear side in the rotational direction.
[0043] Next, description will be made on welding operations of the
welding machine in an embodiment of the present invention. In FIGS.
3A-4B, large and small circles noted with broken lines indicate the
largest and smallest diameters among the welded and deformed
portions, respectively. The optical heads 20 are disposed outside
the outer cylinder member 10 and separated from each other
substantially by 90 degrees. The outer and inner cylinder members
10, 11 are welded to each other at two positions separated from
each other substantially by 90 degrees about the periphery of the
cylinder members 10, 11. When the welding is performed by applying
the laser beam 30 only in a single direction, relative thermal
distortion is generated among a non-melted portion, a melted
portion by applying the laser beam 30, and a portion starting
solidification. For this relative thermal distortion, both cylinder
members tend to deform in a direction crossing the applying
direction of the laser beam 30.
[0044] In the present example, the laser beams 30 are focused on
the outer cylinder member 10 at two positions separated from each
other by approximately 90 degrees. Therefore, the laser beam 30 is
focused on the outer cylinder member 10 by one of the two optical
heads 20 in a direction where the outer and inner cylinder members
10, 11 are deformed due to the laser beam 30 focused by the other
of the two optical heads 20. Accordingly, as shown in FIG. 2, the
directions, in which the outer and inner cylinder members 10, 11
are deformed due to the laser beams 30, are perpendicular to each
other. Thus, both cylinder members are uniformly deformed in radial
directions.
[0045] As shown in FIG. 3A, when a pre-welding shape 50 of both
cylinder members is substantially a circle due to a high working
accuracy for both cylinder members, a post-welding shape 51 thereof
shown in FIG. 3B can also be maintained to be substantially a
circle. As shown in FIG. 4A, even when a pre-welding shape 60 of
both cylinder members is deformed due to a low working accuracy for
both cylinder members, both cylinder members are uniformly deformed
in two directions perpendicular to each other. Therefore, the
deformation of the pre-welding shape 60 is corrected to a
post-welding shape 61 of both cylinder members, shown in FIG. 4B,
which is substantially a circle.
[0046] When foreign matter and the like are mixed into a portion of
both cylinder members 10, 11 to be welded, the following problem
occurs. That is, as shown in FIG. 5A, when the portion containing
the foreign matter is melted by the laser beam focused with one of
the optical heads 20, pores 71 are generated in the welded portion
70 containing the foreign matter. However, the laser beam 30 is
focused on the welded portion 70 by the other of the optical heads
20, and the welded portion is again melted, so that the pores 71
are eliminated as shown in FIG. 5B.
[0047] For example, the welding machine of the present example is
used to weld cylinder members of an injector 100 shown in FIG. 6.
The cylinder members described above may correspond to a valve
housing 101, a valve body 110, a valve member 120, a movable core
and a magnetic member 135 of the injector 100. In FIG. 6, welded
portion locations 142, 144 are indicative of weld locations but
welding is not limited to those locations. At first, a structure of
the injector 100 will be described.
[0048] In FIG. 6, the valve housing 101 as a housing member of the
injector 100 is integrally formed so that a first magnetic portion
102, a non-magnetic portion 102 as a magnetic resistance portion
and a second magnetic portion 104 are disposed from a fuel
injection side in this order. The valve housing 101 is magnetized,
and thereafter the non-magnetic portion 103 is non-magnetized by
heating a portion of the valve housing 101. Thus, the first and
second magnetic portions 102 and 104 remain magnetized. An inner
peripheral wall of the first magnetic portion 102 is welded to an
outer peripheral wall of the valve body 110. The valve housing 101
contains the valve member 120 and the movable core 122 being
capable of reciprocating therein. A cup-shaped injection hole plate
112 is welded to the outer peripheral wall of the valve body 110,
and is sandwiched between the valve body 110 and a supporting
member. The injection hole plate 112, formed in a thin plate shape,
defines plural holes (injection holes) in its center portion.
[0049] The valve member 120, formed in a cylindrical shape having a
bottom, includes a contacting portion 121 at the bottom. The
contacting portion 121 can be seated onto a valve seat provided on
the inner peripheral wall of the valve body 110. The cylindrical
movable core 122 is welded to the valve member 120 at an opposite
side of the injection holes. A side wall of the valve member 120
defines plural fuel through holes 120a at an upstream side of the
contacting portion 121. Fuel passes through the fuel through holes
120a from the inside to the outside, and flows toward a seat
portion constructed by the contacting portion 121 and the valve
seat 111. When the contacting portion 121 is seated onto the valve
seat 111 using force applied by a spring 125, the injection holes
are closed, and fuel injection is stopped. The movable core 122 is
attracted to a fixed core 130 by energizing a coil 140 as an
electromagnetic driving device, and the valve member 120 is
separated from the valve seat 111 together with the movable core
122. The injection holes are released, and the fuel injection is
permitted.
[0050] The fixed core 130 is disposed opposite the injection holes
relative to the movable core 122, and faces the movable core 122.
One end of the spring 125 is engaged to an adjusting pipe 131, and
the other end thereof is engaged to the movable core 122. Force of
the spring 125 is applied toward the valve seat 111.
[0051] Magnetic members 135, 136 are disposed at an outer
peripheral side of the coil 140 as an electromagnetic driving
device. The first magnetic portion 102 and the fixed core 130 are
magnetically connected to each other by the magnetic members 135,
136 through the second magnetic portion 104. A magnetic circuit is
constructed by the fixed core 130, the movable core 122, the first
magnetic portion 102, the second magnetic portion 104 and the
magnetic members 135, 136.
[0052] The valve body 110 is inserted into the first magnetic
portion 102, and they are welded to each other by the welding
machine shown in FIG. 1 in the above-described welding manner. The
first magnetic portion 102 is inserted into the magnetic member
135, and they are welded to each other by the welding machine shown
in FIG. 1 in the above-described welding manner. The valve member
120 is inserted into the movable core 122, and they are welded to
each other by the welding machine shown in FIG. 1 in the
above-described welding manner.
[0053] Since the circularity of each cylinder member constructing
the injector 100 is improved, an off-center condition between the
valve body 110 and the valve member 120 is reduced. That is,
coaxial alignment is improved. Further, when the valve member 120
is seated on the valve seat 111, a clearance between the valve seat
111 and the valve member 120 becomes smaller. Since seat
performance between the valve seat 111 and the valve member 120 is
improved, oil-tight or oil-sealing performance is improved as shown
in FIG. 7. In FIG. 7, the oil-sealing performance indicates an
amount of fuel leaked from the clearance between the valve seat 111
and the valve member 120 when the valve member 120 is seated on the
valve seat 111. As can be seen from FIG. 7, as deviation from
circular form increases, oil-sealing performance is degraded, that
is, a higher flow rate of fluid results from between the clearance
between the valve seat 111 and the valve member 120, for
example.
[0054] In the example of an embodiment of the present invention
described above, two optical heads 20, as the energy-applying
units, are disposed outside the outer cylinder member 10 at two
positions separated from each other by an angle .theta. of 90
degrees. However, the angle .theta. is not limited to 90 degrees,
but it is permitted that 80.ltoreq..theta..ltoreq.90. Further, the
laser beams 30 are focused in directions perpendicular to the
center axis of both cylinder members. However, the laser beams 30
may be focused in directions that are not perpendicular to the
center axis of the cylinder members.
[0055] The number of the optical heads 20 is not limited to two,
but three or more optical heads 20 may be disposed outside the
outer cylinder member 10 at three or more positions separated from
each other substantially by the same angle. Then, the outer and
inner cylinder members 10, 11 may be welded to each other. When
three or more energy-applying units are disposed, the number of the
energy-applying units is defined by "n", and an angle ".theta.", by
which the neighboring optical heads 20 are separated from each
other in the circular direction about both cylinder members, is
defined. At this time, the optical heads 20 are disposed so that
[(360/n)-10].ltoreq..theta.23 [(360/n)+10]. When the structure of
the welding machine is considered, the number of the optical heads
20 is unlikely to exceed ten.
[0056] The description of the invention is merely exemplary in
nature and, thus, variations that do not depart from the gist of
the invention are intended to be within the scope of the invention.
Such variations are not to be regarded as a departure from the
spirit and scope of the invention.
* * * * *