U.S. patent application number 12/167656 was filed with the patent office on 2009-01-15 for fuel injection valve.
This patent application is currently assigned to AISAN KOGYO KABUSHIKI KAISHA. Invention is credited to Takayoshi HAMANO, Yukinori KATO, Hikaru KIKUTA, Takashi OKADA.
Application Number | 20090014677 12/167656 |
Document ID | / |
Family ID | 40121706 |
Filed Date | 2009-01-15 |
United States Patent
Application |
20090014677 |
Kind Code |
A1 |
KIKUTA; Hikaru ; et
al. |
January 15, 2009 |
FUEL INJECTION VALVE
Abstract
A fuel injection valve is provided with a main body and a valve
member. The main body has a fuel passage and a fuel injection
opening formed at the downstream-end of the fuel passage. The valve
member is provided in the fuel passage. The valve member is
configured to move between a first position in which the valve
member closes the fuel injection opening and a second position in
which the valve member opens the fuel injection opening. The fuel
injection valve is further provided with a compression spring
disposed in the fuel passage and a spring pin. The compression
spring restrains the valve member toward the first position. The
spring pin is pressedly inserted into the fuel passage for keeping
the compression spring in the fuel passage. A surface of the spring
pin has a resistance against sulfur.
Inventors: |
KIKUTA; Hikaru;
(Takahama-shi, JP) ; OKADA; Takashi; (Nagoya-shi,
JP) ; KATO; Yukinori; (Toyoake-shi, JP) ;
HAMANO; Takayoshi; (Chita-shi, JP) |
Correspondence
Address: |
DENNISON, SCHULTZ & MACDONALD
1727 KING STREET, SUITE 105
ALEXANDRIA
VA
22314
US
|
Assignee: |
AISAN KOGYO KABUSHIKI
KAISHA
Obu-shi
JP
|
Family ID: |
40121706 |
Appl. No.: |
12/167656 |
Filed: |
July 3, 2008 |
Current U.S.
Class: |
251/337 ;
156/244.12 |
Current CPC
Class: |
F02M 2200/9061 20130101;
F02M 61/205 20130101; F02M 51/0667 20130101; F02M 61/166 20130101;
F02M 2200/9076 20130101 |
Class at
Publication: |
251/337 ;
156/244.12 |
International
Class: |
F01L 3/10 20060101
F01L003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 12, 2007 |
JP |
2007-183527 |
Claims
1. A fuel injection valve, comprising: a main body that comprises a
fuel passage and a fuel injection opening formed at a
downstream-end of the fuel passage; a valve member that is disposed
in the fuel passage, and configured to move between a first
position in which the valve member closes the fuel injection
opening and a second position in which the valve member opens the
fuel injection opening; a compression spring that is disposed in
the fuel passage, and configured to restrain the valve member
toward the first position; and a spring pin that is tightly
inserted into the fuel passage, and configured to keep the
compression spring within the fuel passage, wherein a surface of
the spring pin has a resistance against sulfur.
2. A fuel injection valve as in claim 1, wherein the spring pin is
made of material having a resistance against sulfur.
3. A fuel injection valve as in claim 1, wherein the spring pin is
made of a copper alloy having a resistance against sulfur.
4. A fuel injection valve as in claim 1, wherein the spring pin is
made of a copper alloy containing at least one of nickel, silicon,
aluminum, and chromium, and the at least one of nickel, silicon,
aluminum, and chromium is included in the copper alloy by at least
5 percent by weight.
5. A fuel injection valve as in claim 1, wherein the spring pin is
made of albata.
6. A fuel injection valve as in claim 1, wherein the surface of the
spring pin is covered with material having a resistance against
sulfur.
7. A fuel injection valve as in claim 6, wherein the surface of the
spring pin is covered with a Ni--P alloy.
8. A fuel injection valve as in claim 1, wherein an exterior
surface of the spring pin is roughened.
9. A fuel injection valve as in claim 8, wherein the exterior
surface of the spring pin is roughened by shot peening treatment.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to Japanese Patent
Application No. 2007-183527, filed on Jul. 12, 2007, the contents
of which are hereby incorporated by reference into the present
specification.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a fuel injection valve,
particularly to a fuel injection valve which injects fuel into an
internal combustion engine.
[0004] 2. Description of the Related Art
[0005] U.S. Pat. No. 5,165,656A discloses a fuel injection valve
which injects fuel into an internal combustion engine. This fuel
injection valve is provided with a main body and a valve member.
The main body has a fuel passage and a fuel injection opening
formed at the downstream-end of the fuel passage. The valve member
is disposed in the fuel passage and is constructed so as to move
between a first position in which the valve member shuts the fuel
injection opening and a second position in which the valve member
opens the fuel injection opening. The fuel injection valve is
further provided with a compression spring and an actuator. The
compression spring is disposed in the fuel passage and biases the
valve member toward the first position. The actuator moves the
valve member toward the second position against bias force of the
compression spring. The actuator is constructed by using an
electromagnetic coil.
[0006] A spring pin (called an adjustment bushing in the above
literature) is arranged in the fuel passage of the main body. The
spring pin is pressed into the fuel passage for keeping the
compression spring in the fuel passage. The above literature
describes that anti-rust spring steel, bronze, brass, tombac and
copper beryllium are useful as material of which the spring pin is
made.
BRIEF SUMMARY OF THE INVENTION
[0007] Since the spring pin is exposed to the fuel which passes
through the fuel passage, the spring pin is required to have a
corrosion resistance against fuel. Therefore, material having
excellent characteristic of corrosion resistance against fuel is
used for the material of which the spring pin is made. However, in
the conventional fuel injection valve, it is confirmed that
corrosion of the spring pin progresses at an abnormal speed and the
functions of the fuel injection valve are lowered at an early
stage. There is a need for finding the cause of the above problem
and a need for a fuel injection valve taking countermeasures
against the problem.
[0008] The inventor of the present invention eagerly pursued the
above problem and found that the cause of the problem is in the
quality of the fuel. For example, to an automobile in which the
fuel injection valve is installed, petroleum (fuel) is repeatedly
supplied in unspecified gas stations. Therefore, the quality of the
fuel supplied to the automobile is not always constant. There may
be a case sometimes where fuel with inferior quality is supplied to
the automobile. The fuel with inferior quality often includes a
large amount of sulfur. In the case where the fuel with such an
inferior quality is frequently supplied, sulfidation corrosion of
the spring pin is unavoidably advanced at an abnormal speed. It is
found by the inventor of the present invention that the abnormal
corrosion of the spring pin is caused by the sulfidation corrosion
due to sulfur included in the fuel. Based on the aforesaid finding,
the possibility of effectively preventing the abnormal corrosion of
the spring pin has been realized by giving a resistance against
sulfur to a surface of the spring pin.
[0009] A fuel injection valve realized by the present teachings is
provided with a main body and a valve member. The main body has a
fuel passage and a fuel injection opening formed at the
downstream-end of the fuel passage. The valve member is disposed in
the fuel passage and is constructed so as to move between a first
position in which the valve member shuts the fuel injection opening
and a second position in which the valve member opens the fuel
injection opening.
[0010] The fuel injection valve is further provided with a
compression spring and a spring pin. The compression spring is
disposed in the fuel passage, and biases the valve member towards
the first position. The spring pin is tightly inserted into the
fuel passage for keeping the compression spring in the fuel
passage. The spring pin is made of material having a resistance
against sulfur, preferably a copper alloy having a resistance
against sulfur.
[0011] In the fuel injection valve according to the present
teachings, the spring pin is made of material having the resistance
against sulfur. Therefore, even in the case where fuel which
includes a relatively large amount of sulfur, as such as the fuel
with inferior quality, is used, the corrosion of the spring pin is
effectively suppressed. Thereby, the functions of the fuel
injection valve are maintained over a longer time period.
[0012] The spring pin is preferably made of a copper alloy
containing at least one of nickel, silicon, aluminum, and chromium
by at least 5 percent by weight.
[0013] This type of copper alloy is remarkably invulnerable to
corrosion caused by sulfur. Therefore, the spring pin made of this
type of copper alloy is able to suppress the corrosion of the
spring pin remarkably.
[0014] The spring pin is more preferably made of albata; a copper
alloy mainly composed of copper, nickel, and zinc.
[0015] After being tightly pressed into the fuel passage, the
position of the spring pin needs to be stably maintained against
the bias force from the compression spring. Therefore, the spring
pin is required to have sufficient strength and to be strongly
fitted into the fuel passage. Albata has the favorable resistance
against sulfur as well as the sufficient strength. Therefore, the
spring pin made of albata is able to restrain the corrosion of the
spring pin and is able to be tightly fitted into the fuel
passage.
[0016] In another fuel injection valve realized by the present
teachings, the surface of the spring pin may be covered with a film
having a resistance against sulfur. In this fuel injection valve,
the corrosion of the spring pin due to sulfur may also be
suppressed and its functions may be maintained over a longer time
period.
[0017] The above film having a resistance against sulfur may
preferably be a Ni--P alloy plated layer. The Ni--P alloy plated
layer has an employable corrosion resistance against sulfur. By
forming the Ni--P alloy plated layer on the surface of the spring
pin, it is possible to remarkably hinder the corrosion of the
spring pin.
[0018] An exterior surface of the spring pin may preferably be
roughened. In employing the material of the spring pin based on the
present teachings, there may be a case where the force required for
pressing the spring pin into the fuel passage increases. In this
case, with the exterior surface of the spring pin being roughened,
it is possible to reduce the force required for fitting the spring
pin into the fuel passage.
[0019] The above roughening treatment may preferably be a shot
peening treatment. By utilizing the shot peening treatment, proper
roughening of the exterior surface of the spring pin can be done in
a relatively easy process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a vertical sectional view of a fuel injection
valve.
[0021] FIG. 2 shows a state in which a valve member is at a first
position.
[0022] FIG. 3 shows a state in which the valve member is at a
second position.
[0023] FIG. 4 is a perspective view of a spring pin.
DETAILED DESCRIPTION OF THE DRAWINGS
[0024] Some of the characteristic features of an embodiment in
which the present invention may be carried out are listed
below.
(Feature 1) A main body may be provided with a body, a core fixed
in the body, and a valve seat fixed at one end of the body and
provided with a fuel injection opening. A valve member which may be
disposed in the main body may be formed between the core and the
valve seat. The valve member may be constructed so as to move
between a first position in which one end of the valve member is
brought in abutment with the valve seat so as to shut the fuel
injection opening and a second position in which one end of the
valve member is brought apart from the valve seat and the other end
is brought in abutment with the core.
[0025] (Feature 2) A shutter portion which is brought in abutment
with the valve seat so as to shut the fuel injection opening may be
provided in one end of the valve member.
[0026] (Feature 3) An actuator may be constructed by using an
electromagnetic coil. The core and the valve member may be formed
by using magnetic material. In a case where electricity is provided
to the electromagnetic coil, the core and the valve member are
magnetized.
[0027] (Feature 4) The spring pin may be a hollow cylindrical
member and may be provided with a slit which extends in the
longitudinal direction.
EMBODIMENT OF THE INVENTION
[0028] An unlimiting embodiment of a fuel injection valve
actualized with the present teachings will be described with
reference to the drawings. FIG. 1 shows a vertical sectional view
of a fuel injection valve 10 of the embodiment. As shown in FIG. 1,
the fuel injection valve 10 is provided with a main body 12, a
valve member 30, a compression spring 24 and an electromagnetic
coil 26.
[0029] Inside the main body 12, a fuel passage 20 through which the
fuel passes is formed. An arrow A in FIG. 1 shows the flowing
direction of the fuel. At the downstream-end 12d of the main body
12, a fuel injection opening 42 is formed. Further upstream to the
upstream-end 12c of the main body 12, a fuel pipe (not shown) which
extends from a fuel tank (not shown) is connected. The fuel passage
20 is communicates the fuel injection opening 42 and the
upstream-end 12c of the main body 12.
[0030] In the present specification, the expression "upstream"
means upstream with regard to the fuel flowing direction A, and the
expression "downstream" means downstream with regard to the fuel
flowing direction A. That is, the expressions "upstream side" and
"downstream side" correspond to the "upper side" and the "lower
side" as shown in FIG. 1 respectively.
[0031] A configuration of the main body 12 will be described in
detail. As shown in FIG. 1, the main body 12 is provided with a
body 14, a core 16, a spring pin 22, a valve seat holder 32 and a
valve seat 34.
[0032] The body 14 is a cylindrical member which constructs an
outer frame of the main body 12. The body 14 is made of resin. On
an exterior surface of the body 14, a connector 48 which is
connected to an external control unit (not shown) is formed. In the
connector 48, a plurality of terminal pins 50 which are
electrically connected to the electromagnetic coil 26 are
formed.
[0033] The core 16 is a hollow cylindrical member which is made of
magnetic material, and is fixed to a through hole 14a of the body
14. A part of the core 16 protrudes from the through hole 14a of
the body 14 to the upstream side. That is, a part of the core 16
rises out in the upstream direction from the uppermost edge of the
body 14. The downstream-end 16d of the core 16 is arranged within
the through hole 14a of the body 14 at the downstream side. A
through hole 16a formed inside the core 16 constructs a part of the
fuel passage 20. In the through hole 16a of the core 16, a filter
18 for removing a foreign substance from the fuel is provided. The
core 16 is formed on the opposite side of fuel injection opening 42
with regard to the valve member 30. It can also be said that the
core 16 is formed on the upstream side of the valve member 30,
while the fuel injection opening 42 is formed on the downstream
side of the valve member 30.
[0034] The spring pin 22 is a hollow cylindrical member of which a
through hole 22a is formed in the midst. The spring pin 22 thus has
an exterior surface on the outside of the spring pin 22, and an
interior surface on the inside of the through hole 22a. The through
hole 22a constructs a part of the fuel passage 20. The spring pin
22 is pressedly inserted into the through hole 16a of the core 16.
In such condition, the exterior surface of the spring pin 22 makes
tight contact with the surface of the through hole 16a (that is,
the interior surface of the core 16). The spring pin 22 is arranged
on the upstream side of the compression spring 24, and is abutted
with the upstream-end 24c of the compression spring 24. The spring
pin 22 is for adjusting the amount to which the compression spring
24 is to be compressed. The degree of compression of the
compression spring 24 can be changed by changing the position into
which the spring pin 22 is inserted. The inserting position of the
spring pin 22 can also be described as the depth to which the
spring pin is thrust into towards the downstream-end 16d of the
core 16. The spring pin 22 will be described further in detail
later.
[0035] The valve seat holder 32 is a cylindrical member with a
through hole 32a formed in the midst thereof. The valve seat holder
32 is fixed into the through hole 14a of the body 14. The valve
seat holder 32 is formed on the downstream side of the core 16, and
a part of the valve seat holder 32 protrudes from the through hole
14a of the body 14 towards the downstream side. Inside the through
hole 32a of the valve seat holder 32, the valve member 30 is
disposed. A clearance is formed between the interior surface of the
through hole 32a of the valve seat holder 32 and the valve member
30. The clearance formed thereof constructs a part of the fuel
passage 20. The clearance may be partially formed among the border
between the through hole 32a and the valve member 30. At the
upstream-end of the valve seat holder 32, a cylindrical sleeve 28
made of non-magnetic material is provided. A through hole 28a is
formed in the midst of the cylindrical sleeve 28. In the through
hole 28a of the sleeve 28, the downstream-end 16d of the core 16
and the upstream-end 30c of the valve member 30 are inserted. The
valve member 30 is slidably arranged with regard to the interior
side surface of the through hole 28a of the sleeve 28.
[0036] The valve seat 34 is a cylindrical member and is fixed into
the through hole 32a of the valve seat holder 32. A cavity 34b is
formed inside the valve seat 34 with a bottom surface residing on
the downstream side. A through hole 34a is formed on the bottom
surface of the valve seat 34. The downstream part of the valve
member 30 is arranged inside the internal cavity 34b of the valve
seat 34. A clearance is formed between the interior side and bottom
surfaces of the cavity 34b of the valve seat 34 and the valve
member 30. The clearance formed thereof constructs a part of the
fuel passage 20. Over a part of an exterior surface of the valve
seat 34 at its downstream side, an orifice plate 38 is provided. A
through hole 38a is formed on the orifice plate 38 at a location
that corresponds to the position at which the through hole 34a is
formed on the valve seat 34. The valve seat 34 and the orifice
plate 38 are formed at the downstream-end 12d of the main body 12.
Of the valve seat 34 and the orifice plate 38, through holes 34a
and 38a construct the fuel injection opening 42.
[0037] Next, a construction of the valve member 30 will be
described more in detail. The valve member 30 is a cylindrical
member made of magnetic material. The valve member 30 is hollowly
formed, with a bottom surface residing on the downstream side; a
through hole 30a is formed within the valve member 30. The valve
member 30 is disposed in the through hole 32a of the valve seat
holder 32, and is slidably supported so as to slide in the
direction parallel to the fuel flowing direction A. The
downstream-end 24d of the compression spring 24 is abutted with the
valve member 30.
[0038] The upstream-end 30c of the valve member 30 faces the
downstream-end 16d of the core 16 which serves as a part of the
main body 12. At the downstream-end of the valve member 30, a plug
portion 36 for closing the fuel injection opening 42 is provided.
The internal through hole 30a of the valve member 30 is
communicated with the through hole 16a of the core 16, and
constructs a part of the fuel passage 20. On the lower side surface
of the valve member 30, a plurality of through holes 30b is formed.
The plurality of through holes 30b align orthogonal to the fuel
flowing direction between the internal through hole 30a and the
plug portion 36. The internal through hole 30a of the valve member
30 is communicated with the internal hole 34b of the valve seat 34
through the aforementioned through holes 30b.
[0039] The valve member 30 is configured to move between a first
position in which the valve member 30 shuts the fuel injection
opening 42 as shown in FIG. 2, and a second position in which the
valve member 30 opens the fuel injection opening 42 as shown in
FIG. 3. It should be noted that the first position is the limit to
which the valve member 30 is able to move towards the downstream
side; approaching the side of the fuel injection opening 42, and
the second position is the limit to which the valve member 30 is
able to move towards the upstream side; receding from the side of
the fuel injection opening 42. In the case where the valve member
30 is at the first position as shown in FIG. 2, the plug portion 36
serving as the downstream-end of the valve member 30 is brought in
contact with the valve seat 34 so as to close the fuel injection
opening 42. At this moment, the upstream-end 30c of the valve
member 30 is parted from the downstream-end 16d of the core 16.
Meanwhile, in the case where the valve member 30 is at the second
position as shown in FIG. 3, the plug portion 36 serving as the
downstream-end of the valve member 30 is brought apart from the
valve seat 34 so as to open the fuel injection opening 42. At this
moment, the upstream-end 30c of the valve member 30 is in contact
with the downstream-end 16d of the core 16.
[0040] Next, the details of the configurations of the compression
spring 24 and the electromagnetic coil 26 will be described. As
aforementioned, the compression spring 24 is disposed in the
through hole 16a of the core 16. The compression spring 24 is
formed between the spring pin 22 and the valve member 30, in a
state that the compression spring 24 is compressed. The
upstream-end 24c of the compression spring 24 is abutted with the
exterior bottom surface of the spring pin 22, and the
downstream-end 24d of the compression spring 24 is abutted with a
surface protruding within the through hole 30a of the valve member
30. The compression spring 24 biases the valve member 30 towards
the first position by its elastic force, which is the movement
limit in the downstream direction (refer to FIG. 2).
[0041] The electromagnetic coil 26 is fixed in the through hole 14a
of the body 14. The electromagnetic coil 26 surrounds part of the
core 16 including the downstream-end 16d. Electricity is provided
to the electromagnetic coil 26 from the external control unit (not
shown) through the terminal pins 50 of the connector 48. The
electricity is provided at the timing at which the fuel is to be
injected. The electromagnetic coil 26 generates a magnetic field by
the electricity provided thereto.
[0042] Next, The manner in which the fuel injection valve 10
operates will be described. Fuel flows from the fuel pipe (not
shown) which is connected to the upstream-end 12c into the main
body 12 of the fuel injection valve 10. The flowing fuel flows
through the fuel passage 20 and reaches the fuel injection opening
42 formed at the downstream-end 12d of the main body 12. In the
case where the electricity is not provided to the electromagnetic
coil 26, the valve member 30 is maintained at the first position by
the bias force of the compression spring 24 (refer to FIG. 2). In
this case, since the fuel injection opening 42 is shut by the plug
portion 36 of the valve member 30, the fuel is not injected from
the fuel injection opening 42.
[0043] Meanwhile, when the electricity is turned on and provided to
the electromagnetic coil 26, the electromagnetic coil 26 generates
a magnetic field, thus magnetizing the core 16 and the valve member
30. In such condition, the core 16 and the valve member 30 attract
each other such that the valve member 30 shifts its posture to the
second position, moving upward against the bias force of the
compression spring 24 (refer to FIG. 3). The plug portion 36 of the
valve member 30 is brought apart from the valve seat 34, such that
the fuel injection opening 42 is opened. At this moment, the fuel
is injected from the fuel injection opening 42. The electricity is
intermittently provided to the compression spring 24 and the fuel
is intermittently injected from the fuel injection opening 42.
[0044] The schematic structure and operation of the fuel injection
valve 10 of the present embodiment is described above. Next, a
detailed description of the configuration of the spring pin 22 will
be described.
[0045] FIG. 4 shows a single body of the spring pin 22. As shown in
FIG. 4, a slit 22e which extends in the longitudinal direction is
formed in the spring pin 22. An exterior surface 22f of the spring
pin 22 is to be tightly in contact with the interior surface of the
core 16. The exterior surface 22f is roughened by shot peening
treatment so as to be an remarkably uneven and rough surface. When
the exterior surface 22f of the spring pin 22 is uneven and rough,
it is possible to reduce the pressing force required at the time of
pressing the spring pin 22 into the through hole 16a of the core
16. It should be noted that the exterior surface 22f of the spring
pin 22 can be formed as an uneven surface by roll dicing or the
like with using a pattern die for transferring the unevenness.
[0046] The spring pin 22 is repeatedly exposed to the fuel which
passes through the through hole 16a of the core 16. The spring pin
22 needs to be able to tolerate corrosion that may be caused by the
fuel. Thus, a corrosion resistance against fuel is essential to the
spring pin 22. As the quality of the fuel to be used may not always
be of a high standard, and there may be a case where the fuel
includes a large amount of foreign substance such as inferior
gasoline, and LPG may be used. Accordingly, the spring pin 22 is
also required to have a high corrosion resistance against such
foreign substance included in the fuel.
[0047] The present inventor has confirmed that abnormal corrosion
of the spring pin 22 is caused particularly due to sulfur among the
foreign substance included in the fuel. Sulfide generated by
sulfidation corrosion of the spring pin 22 easily accumulates
between the valve member 30 and the valve seat 34, often causing
defect in closing the fuel injection opening 42. As a result of
experimenting the corrosion resistance against sulfur (a tolerance
against sulfur) of various materials, the present inventor has
confirmed that a copper alloy containing at least one of nickel,
silicon, aluminum, and chromium by at least 5 percent by weight has
the favorable corrosion resistance against sulfur (a favorable
tolerance against sulfur). These elements easily react with an
oxygen ion in the air or in the fuel, and the layer of their
oxidized film(s) is easily formed on the surface of the spring pin
22 covering the surface thereof. Particularly, when one or more of
these elements are contained by at least 5 percent by weight, their
oxidized film(s) is sufficiently formed on the surface of the
spring pin 22 so as to significantly retard the corrosion of the
spring pin 22 due to sulfur. Accordingly, when the spring pin 22 is
made of a copper alloy containing at least one of nickel, silicon,
aluminum, and chromium by at least 5 percent by weight, even in the
case where the fuel with inferior quality is frequently utilized,
for example, the corrosion of the spring pin 22 is even more
effectively suppressed, and functions of the fuel injection valve
10 can be maintained for a longer time period. That is, rise of the
problem such as the defect in hindering the fuel injection opening
42 to close caused by the accumulated sulfide between the valve
member 30 and the valve seat 34 may be prevented. Furthermore, a
decrease in the fuel injection amount caused by the accumulated
sulfide in the fuel injection opening 42 may also be prevented.
[0048] A copper alloy containing at least one of nickel, silicon,
aluminum, and chromium by at least 5 percent by weight may include,
cupronickel (containing 9 to 11 weight percent of nickel) and
albata (containing 16.5 to 19.5 weight percent of nickel), for
example. It should be noted that a relatively large amount of zinc
may also be included in albata (approximately 20 percent by
weight).
[0049] In the present embodiment, the spring pin 22 is made of
albata. Albata has a favorable resistance against sulfur as well as
relatively high strength as in having a high scale of Young's
modulus. Therefore, the spring pin 22 which is made of albata may
be strongly fitted to the through hole 16a of the core 16, into
which the spring pin 22 is pressed so as to constantly restrain the
upstream-end 24c of the compression spring 24.
[0050] Instead of the above copper alloy having a resistance
against sulfur, the surface of the spring pin 22 may be covered
with material which has excellent characteristic in a resistance
against sulfur. The material for covering the spring pin 22 may not
be limited to the above copper alloy having a resistance against
sulfur, but may be a Ni--P alloy. With a Ni--P alloy, it is
possible to easily form a stable film by plating. In this case, the
material with which the spring pin 22 is made may be selected from
group of materials having the desired rigidness or other
characteristic as desired in the spring pin 22.
[0051] The specific embodiments of the present invention are
described above, but these merely illustrate some possibilities of
the invention and do not restrict the claims thereof. The art set
forth in the claims includes various transformations and
modifications to the specific embodiment set forth above.
[0052] Furthermore, the technical elements disclosed in the present
specification or figures may be utilized separately or in all types
of conjunctions and are not limited to the conjunctions set forth
in the claims at the time of filing of the application.
Furthermore, the art disclosed in the present specification or
figures may be utilized to simultaneously realize a plurality of
aims or to realize one of these aims.
* * * * *