Metal fusion bonding – Process – With measuring – testing – indicating – inspecting – or...
Reexamination Certificate
2001-03-05
2002-09-10
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
With measuring, testing, indicating, inspecting, or...
C228S131000, C228S175000, C219S061000, C219S091200
Reexamination Certificate
active
06446856
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of welding a hollow member and an insertion member to form a composite member comprised of a hollow member such as a valve structure of a fuel injection system and an insertion member which is inserted into and joined to the hollow member and, more particularly, relates to a method of welding a hollow member and an insertion member to form a composite member comprised of a hollow member and insertion member where a high dimensional accuracy is required in the axial end-to-end distance of the end faces and where a reliable concentricity is required in the center axes of the hollow member and insertion member.
2. Description of the Related Art
An example of the valve structure of a fuel injection system in an internal combustion engine of the related art where concentricity is required will be explained first. As shown in FIG.
14
(
a
) and FIG.
14
(
b
), the valve structure
3
of the related art is comprised of a cylindrical hollow member
11
having a closed bottom, that is, a holder, a cylindrical body
315
to be inserted into and accommodated in the hollow member
11
, and an insertion member
12
to be inserted in the hollow member
11
.
The overlap portion
13
where the hollow member
11
and the insertion member
12
overlap and the overlap portion
331
where the hollow member
11
and the body
315
overlap are circumferentially welded together.
Next, another example of the valve structure of a fuel injection system in an internal combustion engine of the related art where a high dimensional accuracy is required in the end-to-end distance of the end faces will be explained.
As shown in FIG.
13
(
a
) and FIG.
13
(
b
), the valve structure is comprised of a cylindrical housing
1091
, a nozzle receiver
9200
comprised to be able to receive the nozzle portion
1500
, a body
1092
provided with an injection bore
9290
communicating with the nozzle holder
9200
, a needle
1015
provided with the nozzle portion
1500
, and a holding member
1016
provided with a spring
1600
for holding the needle
1015
.
In the related art, the body
1092
is inserted into one end of the housing
1091
and the needle
1015
held in the holding member
1016
is inserted into the other end to thereby assemble the parts and form the valve structure
1009
.
The overlap portion
1093
of the housing
1091
and the body
1092
is circumferentially welded together. Reference numeral
094
indicates the weld.
Thermal strain occurs at the time of circumferentially welding the overlap portion
1093
and sometimes results in deviation of the dimensions of the valve structure in the axial direction from the desired values.
In the valve structure
1009
, the clearance C shown in FIG.
13
(
b
) has to be of a predetermined dimension.
Therefore, in the related art, a spacer
1097
was arranged behind the body
1092
as shown in FIG.
13
(
b
) to absorb the thermal strain at the time of circumferential welding and thereby ensure a suitable clearance C and a suitable range of operation of the needle
1015
.
In the related art, the dimensions of A and B shown in FIG.
13
(
b
) are measured at the time of assembling the parts, and the body
1092
etc. are ground to obtain the suitable clearance C. Next, the housing
1091
and the body
1092
are circumferentially welded to join them. The thermal strain accompanying the circumferential welding is absorbed by the spacer
1097
.
Therefore, it is possible to obtain a valve structure
1009
resistant to the effects of changes in dimensions due to thermal strain and having precise dimensional accuracy.
Summarizing the problem to be solved by the invention, since thermal strain occurs at the time of circumferential welding in a valve structure of a fuel injection system of the related art where concentricity is required, even if the hollow member
11
and the insertion member
12
are assembled to have the same center axes G
1
and G
2
, there is the problem that the center axes G
1
and G
2
become misaligned as shown in the later explained FIG.
18
(
a
), FIG.
18
(
b
), and
FIG. 19
in the later circumferential welding. Note that from here on, the state where the center axes G
1
and G
2
are correctly aligned will be referred to as “good concentricity”, while the state where they are not aligned will be referred to as “poor concentricity”.
Further, in the valve structure of the other related art where a high dimensional accuracy is required in the axial end-to-end distance, the spacer
1097
has to be separately provided. Not only is the trouble of assembly increased, but also, while it is possible to absorb the thermal strain by the spacer
1097
in the structure of FIG.
13
(
a
) and FIG.
13
(
b
) shown in the related art, this technique does not work well with other structures. Further, there is a limit to how far the dimensional changes caused by thermal strain can be minimized.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of welding a hollow member and an insertion member to form a composite member giving a superior concentricity and a high dimensional accuracy in the axial direction.
According to a first aspect of the present invention, there is provided a method of welding a hollow member and an insertion member to form a composite member comprising preparing a hollow member and an insertion member, inserting the insertion member in the hollow member, and partially welding an overlap portion where the hollow member and the insertion member overlap to correct an axial end-to-end distance of the hollow member and the insertion member in a corrective welding step.
Preferably, the method further comprises that the hollow member and the insertion member are joined together by a partial weld provided in the corrective welding step.
Alternatively, the method further comprises circumferentially welding the entire circumference of the overlap portion of the hollow member and the insertion member in a regular welding step.
More preferably, the method further comprises simultaneously performing the corrective welding step and the regular welding step by a plurality of welding heads.
Still more preferably, the method further comprises that said insertion member is press-fitted in the hollow member.
Still more preferably, the method further comprises that at least one set of partial welds are provided at axially symmetric positions (A-H) at the overlap portion in the corrective welding step.
Still more preferably, the method further comprises measuring the axial end-to-end distance of the composite member for each corrective welding step in a measurement step and continuing the corrective welding step until the axial end-to-end distance reaches a predetermined length.
Alternatively, still more preferably, the method further comprises determining an amount of melting before the corrective welding step in a melting determination step and performing the corrective welding step in accordance with the amount of melting determined in the melting determination step.
According to a second aspect of the present invention, there is provided a method of welding a hollow member and an insertion member to form a composite member comprising preparing a hollow member and an insertion member, inserting the insertion member in the hollow member, and partially welding an overlap portion of the hollow member and the insertion member correct the concentricity of the composite member in a corrective welding step.
Preferably, the method further comprises that the hollow member and the insertion member are joined together by a partial weld provided in the corrective welding step.
Alternatively, the method further comprises circumferentially welding the entire circumference of the overlap portion of the hollow member and the insertion member in a regular welding step.
Alternatively, the method further comprises consecutively performing the corrective welding step and the regular welding step.
More preferably, the method further comprises measuring
Iwanari Eiji
Ohmi Yoshinori
Sato Takafumi
Shirai Hideaki
Denso Corporation
Dunn Tom
Harness Dickey & Pierce PLC
Stoner Kiley
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