Abstrict
An electrode structure includes a metallic electrode having a configuration
of a bending cylinder and having a plurality of members disposed
successively in an axial direction of the electrode and mutually
connected with adjacent member(s); a case for installing the metallic
electrode and one end of a lead wire for electrification therein;
and an insulating member which is positioned between the case and
the electrode and which the case from the electrode. An electric
heater includes a housing, a honeycomb structure installed in the
housing, and the electrode structure for electrifying the honeycomb
structure. The electrode structure exhibits excellent composability,
waterproof ability, and gas sealability.
Claims
What is claimed is:
1. An electrode structure comprising:
an angled cylindrical metallic electrode having a plurality of
members disposed successively in an axial direction of the electrode
mutually connected to each other;
a case for housing the metallic electrode and one end of a lead
wire for electrification therein; and
an insulating member positioned between the case and the electrode
for insulating the case from the electrode.
2. An electrode structure according to claim 1, wherein the electrode
comprises a first electrode member and a second electrode member,
each having a cylindrical configuration and the second cylindrical
member connecting with the lead wire at one end and the first electrode
member at the other end so as to form a predetermined angle.
3. An electrode structure according to claim 2, wherein the first
electrode member is threadedly engaged with the second electrode
member by means of a negative screw portion arranged in the first
electrode member and a positive screw portion arranged in the second
electrode member.
4. An electrode structure according to claim 2, wherein the first
electrode member is connected with the second electrode member by
welding.
5. An electrode structure comprising:
a metallic electrode having a columnar configuration and having
a lead wire connected at the top end of the electrode and forming
a predetermined angle with the electrode;
a case for housing the metallic electrode and one end of the lead
wire for electrification therein;
an insulating member positioned between the case and the electrode
for insulating the case from the electrode; and
a waterproof member positioned between the case and the lead wire
for avoiding permeation of water therebetween;
wherein the electrode is spaced from the waterproof member to protect
the waterproof member from deterioration due to a temperature increase
at the top end of the electrode.
6. An electrode structure according to claim 5, wherein the case
comprises:
a lower member for installing a lower portion of the electrode,
having a cylindrical portion covering a part or all of a peripheral
surface of the electrode; and
an upper member for installing an upper portion of the electrode,
closing an opening portion of the cylindrical portion near an upper
portion of the electrode.
7. An electrode structure according to claim 1, wherein a waterproof
member is positioned between the case and the lead wire so as to
avoid permeation of water from a gap between the case and the lead
wire.
8. An electrode structure according to claim 1, wherein the electrode
structure connects with a subject to be electrified, the subject
being installed in a metallic housing, and electrifies the subject.
9. An electrode structure according to claim 1, wherein the subject
to be electrified has a metallic honeycomb structure.
10. An electrode structure according to claim 7, wherein the waterproof
member comprises a thermal resistant, insulating organic composite
or a glass.
11. An electrode structure according to claim 10, wherein the insulating
organic composite contains fluorine.
12. An electrode structure according to claim 7, wherein a case
for installing the electrode is crimped from outside in the portion
where a waterproof member is positioned.
13. An electrode structure according to claim 7, wherein a gap
between at least (i) the case and the waterproof member and (ii)
the waterproof member and the lead wire is sealed with an adhesive.
14. An electrode structure according to claim 1, wherein the insulating
member comprises a first insulator, a second insulator, and an inorganic
powder packed into a gap between the first insulator and the second
insulator.
15. An electrode structure according to claim 1, wherein the insulating
member comprises the first insulator, the second insulator, and
a cement sealing material packed into the gap between the first
insulator and the second insulator.
16. An electrode structure according to claim 14, wherein each
of the first insulator and the second insulator comprises a ceramic
material.
17. An electrode structure according to claim 2, wherein an insulating
member is positioned between the second electrode member and the
case or between the electrode and the lower case member.
18. An electrode structure according to claim 1, wherein a gap
between the electrode and the insulating member and a gap between
the insulating member and the case are sealed with a metallic sealing
material.
19. An electrode structure according to claim 18, wherein an insulating
member is positioned between the electrode and the case, and a spring
member and a pressing member are positioned between the electrode
and the case, the spring member absorbing differences in thermal
expansion among the electrode, the case, and the insulating member,
and the pressing member transmitting a load to the spring member.
20. An electrode structure according to claim 19, wherein an insulating
member is positioned between the second electrode member and the
case, and a spring member and a pressing member are positioned between
the second electrode member and the case, the spring member absorbing
differences in the thermal expansion among the second electrode
member, the case, and the insulating member, and the pressing member
transmitting a load to the spring member.
21. An electrode structure according to claim 19, wherein the pressing
member is a nut mounted on the electrode.
22. An electrode structure according to claim 19, wherein the pressing
member is fixed to the electrode by welding.
23. An electrode structure according to claim 19, wherein the pressing
member is fixed to the electrode by crimping.
24. An electrode structure according to claim 1, wherein the insulating
member is an insulating coat covering at least one of the electrode
and the case.
25. An electrode structure according to claim 24, wherein a gap
between the electrode and the case is sealed with an inorganic powder.
26. An electrode structure according to claim 1, wherein the insulating
member is an insulating coat covering the electrode, and a gap between
the case and the insulating coat is sealed with a metallic sealing
material.
27. An electrode structure according to claim 1, wherein the insulating
member is an insulating coat covering the case, and a gap between
the electrode and the insulating coat is sealed with a metallic
sealing material.
28. An electrode structure according to claim 24, wherein a material
of the insulating coat is plasma-sprayed alumina.
29. An electrode structure according to claim 24, wherein a material
of the insulating coat is a ceramic.
30. An electrode structure according to claim 14, wherein the inorganic
powder is packed under a pressure.
31. An electrode structure according to claim 1, wherein a coat
on the lead wire works as a waterproof member.
32. An electric heater comprising:
a housing;
a honeycomb structure installed in the housing; and
an electrode structure for electrifying the honeycomb structure
comprising:
an angled cylindrical metallic electrode having a plurality of
members disposed successively in an axial direction of the electrode
mutually connected to each other;
a case for housing the metallic electrode and one end of a lead
wire for electrification therein; and
an insulating member positioned between the case and the electrode
for insulating the case from the electrode.
33. An electric heater comprising:
a housing;
a honeycomb structure installed in the housing; and
an electrode structure for electrifying the honeycomb structure
comprising:
a metallic electrode having a columnar configuration and having
a lead wire connected at the top end of the electrode and forming
a predetermined angle with the electrode;
a case for housing the metallic electrode and one end of the lead
wire for electrification therein;
an insulating member positioned between the case and the electrode
for insulating the case from the electrode; and
a waterproof member positioned between the case and the lead wire
for avoiding permeation of water therebetween;
wherein the electrode is spaced from the waterproof member to protect
the waterproof member from deterioration due to a temperature increase
at the top end of the electrode.
Description BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to an electrode structure and to
an electric heater provided with the electrode. More specifically,
the present invention relates to an electrode structure for electrifying,
for example, a subject installed in a metallic housing and to an
electric heater provided with the electrode structure.
In the catalytic converter used for purifying an exhaust gas of
automobiles, etc., there has been known a technique to mount an
electric heater on a catalytic converter so as to raise a temperature
of a catalyst up to a working temperature in the early stage. The
electric heater generally has a structure that a metallic honeycomb
structure is installed and held in a metallic housing such as a
can and that the honeycomb structure to be electrified is provided
with an electrode for electrification.
As an electrode structure for such an electric heater, there has
conventionally been proposed an electrode structure shown in FIG.
10. In FIG. 10, the electrode structure has an electrode 6 made
of a metallic bolt. To the metallic bolt 6 are fixed insulating
members (insulators) 8 and 8' and a jig 26 for fixing the insulators
via a washer 10 by means of a nut 14. The insulating members insulate
a metallic housing (can) 2 from the electrode 6. The electrode structure
is inserted to a throughhole 12 arranged in the metallic housing
2 and fixed to the metallic housing by welding. One end of the electrode
6 inside the metallic housing 2 is connected with a part of a honeycomb
structure 4 by means of a connecting member 16. Additionally, a
gas sealability is maintained by a cement sealing material 28.
In an electric heater provided with such an electrode structure,
the electrode structure preferably contains a lead wire in view
of easy mounting on an exhaust gas pipe of automobiles, etc., one
end of the lead wire being unitarily mounted on the electrode structure
for convenience of composing. In this case, there sometimes happens
that water splashes the electrode during driving a car, for example,
in a rain, thereby causing an electric short, corrosion, etc., which
require to be avoided.
An electric heater preferably has a small size in view of a space
where the heater is fixed so as to actually use for an exhaust gas
pipe of automobiles, etc. Particularly, a length of an electrode
is preferably as short as possible. When a length of an electrode
is shortened, it is required to consider inconvenience such as deterioration
of a coat covering a lead wire because a temperature of an end portion
of the electrode rises up, workability upon composing the electrode,
and the like, when the length of the electrode is simply shortened.
Further, this electrode structure is required to ensure that a
gas sealability is maintained and that the metallic housing is insulated
from the electrode.
SUMMARY OF THE INVENTION
The present invention aims to solve the aforementioned problems.
The present invention provides an electrode structure comprising:
a metallic electrode having a configuration of a bending cylinder
and having a structure that a plurality of members disposed successively
in an axial direction of the electrode are mutually connected with
adjacent member(s); a case for installing the metallic electrode
and one end of a lead wire for electrification therein; and an insulating
member which is positioned between the case and the electrode and
which is insulating the case from the electrode.
In the aforementioned electrode structure, the electrode preferably
comprises a first electrode member and a second electrode member,
each having a cylindrical configuration and the second electrode
member connecting with the lead wire at one end and the first electrode
member at the other end so as to form a predetermined angle.
The present invention further provides an electrode structure comprising:
a metallic electrode having a columnar configuration and having
the lead wire at the top end of the electrode so as to form a predetermined
angle with the electrode; a case for installing the metallic electrode
and one end of a lead wire for electrification therein; and an insulating
member which is positioned between the case and the electrode and
which is insulating the case from the electrode.
In the aforementioned electrode structure, the case for insulating
the electrode preferably comprises a lower member for installing
a lower portion of the electrode, having a cylindrical portion covering
a part or all of a peripheral surface of the electrode, and an upper
member for installing an upper portion of the electrode, closing
an opening portion of the cylindrical portion near an upper portion
of the electrode.
The electrode structure preferably has a waterproof member positioned
between the case for installing an electrode and the lead wire so
as to avoid permeation of water from a gap between the case for
installing an electrode and the lead wire.
Preferably, the electrode structure connects with a subject to
be electrified, the subject being installed in a metallic housing,
and is used to electrify the subject. The subject to be electrified
preferably has a metallic honeycomb structure.
The present invention furthermore provides an electric heater comprising:
a housing; a honeycomb structure installed in the housing; and one
of the aforementioned electrode structures for electrifying the
honeycomb structure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view showing an embodiment of an electrode
structure of the present invention.
FIG. 2 is a cross-sectional view showing an embodiment of a waterproof
structure of an electrode of the present invention.
FIG. 3 is a cross-sectional view showing another embodiment of
a waterproof structure of an electrode of the present invention.
FIG. 4 is a cross-sectional view showing still another embodiment
of a waterproof structure of an electrode of the present invention.
FIG. 5 is a cross-sectional view showing another embodiment of
an electrode structure of the present invention.
FIG. 6 is a cross-sectional view showing still another embodiment
of an electrode structure of the present invention.
FIG. 7 is a cross-sectional view showing an embodiment of fixing
a pressing member to an electrode of the present invention.
FIG. 8 is a cross-sectional view showing yet another embodiment
of an electrode structure of the present invention.
FIG. 9 is a cross-sectional view showing yet another embodiment
of an electrode structure of the present invention.
FIG. 10 is a cross-sectional view showing an embodiment of a conventional
electrode structure.
FIG. 11 is a partial explanatory view showing an embodiment of
connecting a lead wire with an electrode.
FIG. 12 is a partial explanatory view showing another embodiment
of connecting a lead wire with an electrode.
FIG. 13 is a partial explanatory view showing still another embodiment
of connecting a lead wire with an electrode.
FIG. 14 is a partial explanatory view showing yet another embodiment
of connecting a lead wire with an electrode.
FIG. 15 is a partial explanatory view showing yet another embodiment
of connecting a lead wire with an electrode.
FIG. 16 is a partial explanatory view showing yet another embodiment
of connecting a lead wire with an electrode.
FIG. 17 is an explanatory view showing an embodiment of a pressing
member.
FIG. 18 is a cross-sectional view showing yet another embodiment
of an electrode structure of the present invention.
FIG. 19(a) is a cross-sectional view showing yet another embodiment
of an electrode structure of the present invention.
FIG. 19(b) is a plan view from the top of the electrode structure
shown in (a) in which the upper case member for installing the upper
portion of the electrode is removed.
FIG. 20 is a cross-sectional view showing yet another embodiment
of an electrode structure of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
When only a length of an electrode is just shortened, heat of an
exhaust gas or the like is easily transmitted to an end of the electrode
through case for holding an electrode and through the electrode.
As a result, a temperature of the end of the electrode is prone
to exceed a thermal resistant temperature of the aforementioned
waterproof member and coating material covering a lead wire. Accordingly,
the electrode structure is required to have a predetermined or larger
distance from a connecting portion of the electrode and the substance
to be electrified to the waterproof member.
In the present invention, an electrode has a bending configuration.
Alternatively, a lead wire is connected to the upper end of an electrode
so as to have a predetermined angle between the lead wire and the
electrode, thereby imparting a bending configuration to the electrode
structure. Thus, the electrode can have a practical size and a predetermined
or larger distance from the connecting portion of the electrode
and the subject to be electrified to the waterproof member can be
maintained, thereby preventing the waterproof member or the like
from deteriorating by an increase of a temperature at the top end
of the electrode.
When an electrode having a bending configuration is prepared by
only bending a unitarily formed electrode itself, attachment of
a case for installing an electrode to the electrode becomes difficult.
Accordingly, in the present invention, the electrode is composed
of a plurality of members disposed successively in the axial direction
of the electrode, each of the members being mutually connected to
adjacent member(s), thereby overcoming difficulty in production.
A member constituting the electrode is preferably a metallic stick
or a metallic cylinder. Each of the metallic stick and the metallic
cylinder may have a bending configuration. The members are connected
by welding, threaded engagement, etc.
The number of members constituting the electrode is preferably
two. One end of one (the second electrode member) of the two members
is connected with a lead wire, and one end of the other member (the
first electrode member) is connected with a subject to be electrified.
The other end of the first cylindrical member is connected with
the other end of the second electrode member. The two members are
connected so as to form an angle preferably smaller than 180.degree.,
more preferably within the range from 45.degree. to 135.degree.,
furthermore preferably within the range from 80.degree. to 100.degree..
When the first electrode member is connected with the second electrode
member by threaded engagement, preferably the first electrode member
has a negative screw portion and the second electrode member has
a positive screw portion.
When a bending configuration of the electrode structure is formed
by connecting a lead wire to the top end of the electrode so as
to have a predetermined angle, the angle between the lead wire and
the electrode is preferably 50-150.degree., more preferably 60-120.degree.,
furthermore preferably 75-105.degree.. The lead wire can be connected
to the top end of the electrode by various kinds of means such as
a direct welding, a connecting member, etc.
A case for installing an electrode is composed of the lower member
for installing the lower portion of the electrode and the upper
member installing the upper portion of the electrode. The lower
member has a cylindrical portion covering a part or all of a peripheral
surface of the electrode, and the upper member close an opening
portion of the cylindrical portion near an upper portion of the
electrode. This structure overcomes difficulty in production. That
is, the top end of the electrode is exposed when the electrode is
equipped with the lower member of the case for installing an electrode
because the lower member does not cover the top end of the electrode,
and therefore a lead wire is easily connected to the top end of
the electrode. Incidentally, the upper member of the case for installing
an electrode is attached to the lower member after the lead wire
is connected to the electrode.
An electrode structure of the present invention preferably has
a waterproof member positioned between a case for installing an
electrode and a lead wire so as to avoid water permeation from the
gap between the case for installing an electrode and the lead wire.
The aforementioned waterproof member is preferably an insulating
organic composite having a thermal resistance or a glass. Specifically,
the insulating organic composite is preferably poly(tetrafluoroethylene)
(commercial name: Teflon) or an organic composite containing fluorine
such as fluoro-rubber. However, Teflon is more preferable because
Teflon has a less weight decrease at a high temperature. Further,
a glass may be mixed with Teflon so as to enhance thermal resistance.
A waterproof member preferably has a thermal resistance of 100.degree.0
C. or more, more preferably 150.degree. C. or more.
The waterproof member is preferably fixed by crimping the case
for installing an electrode from outside the case for installing
an electrode in the portion where the waterproof member is disposed
in view of ensuring to avoid water permeation into the electrode.
Alternatively, sealing with an adhesive a gap between the case for
installing an electrode and the waterproof member and/or a gap between
the waterproof member and the lead wire can ensure to avoid water
permeation into the electrode. The electrode structure preferably
has a waterproof ability of 1 cc/min or less of water permeation
under 0.5 atm. The adhesive preferably has a large expansion coefficient
so as to endure the repeated temperature change between high temperature
and low temperature as in an automobile exhaust gas system. Additionally,
the adhesive preferably has a water-repellent ability because the
adhesive contacts with water. From these view points, an organic
adhesive, specifically polyimide or the like, is preferably used.
A lead wire is usually covered with a coating material. The coating
material preferably has a thermal resistance of 100.degree. C. or
more. Specifically, a core wire with Teflon coating, a core wire
with polyimide tape winding therearound and with a woven glass fiber
covering the polyimide tape, or the like is used as a lead wire
covered with a coating material. The core wire preferably has a
diameter of 1.0-5.0 mm. Further, the core wire is preferably composed
of thin wires each having a diameter of 0.5 mm or less, the wires
being twisted into a core wire.
An electrode structure of the present invention has an insulating
member between the electrode and the case for installing an electrode.
The insulating member ensure the insulation of the case for installing
an electrode from the electrode.
The insulating member is preferably composed of the first insulator,
the second insulator, and an inorganic powder packed in a gap between
the first insulator and the second insulator because of an excellent
gas sealability. Further, such an insulating member hardly deteriorate
in gas sealability and insulating ability even if a solid comes
flying from outside the exhaust gas pipe and collides with the electrode.
An inorganic powder is packed in the gap preferably under a pressure.
Specifically, an inorganic powder is preferably talc, kaolin, or
the like. Each of the first insulator and the second insulator preferably
has a structure which can hold an inorganic powder between the electrode
and the case for installing the electrode. Alternatively, a ceramic
material having a predetermined strength, specifically an alumina
material, a porcelain material, or the like can be used for each
of the first and the second insulators. Incidentally, the inorganic
material is preferably packed in a gap between the first insulator
and the second insulator with a load of, for example, 200 kgf or
more. The second insulator directly contacting the inorganic powder
preferably has a difference in level because a packed inorganic
powder is not loosen even if heat cycles and vibrations are transmitted
to the inorganic powder.
Incidentally, when an electrode having a bending configuration
is used and the electrode is composed of two members, an insulating
member composed of the first insulator, the second insulator, and
an inorganic powder packed in a gap between the first and the second
insulators are preferably disposed between the second electrode
member and the case for installing an electrode in view of workability
upon composing the electrode structure, preventing temperature increase
in the waterproof member, etc.
Additionally, a gap between the insulating member and the electrode
and a gap between the electrode and the case for installing an electrode
may be sealed with a metallic sealing material. Preferably, a spring
member and a pressing member are positioned between the electrode
and the case for installing an electrode. The spring member absorbs
differences in thermal expansion among the electrode, the case for
installing an electrode, and the insulating member. The pressing
member transmits a load to the spring member. Such a structure can
maintain gas sealability by a metallic sealing material and absorb
differences in thermal expansion among members by the spring member.
The pressing member may be fixed to the electrode by forming the
pressing member so as to have a configuration of a nut and being
engaged with the electrode. Alternatively, the pressing member may
be fixed to the electrode by crimping a part of the pressing member
against the electrode or by being welded directly to the electrode.
When an electrode having a bending configuration is used and the
insulating member is positioned between the second electrode member
and the case for installing an electrode, the spring member and
the pressing member are positioned between the second electrode
member and the case for installing an electrode.
The case for installing an electrode may be insulated from the
electrode by coating an insulating coating material on one or both
of the electrode and the case for installing an electrode. The electrode
with an insulating coat is preferably inserted into the case for
installing an electrode under a pressure in view of an airtightness.
Alumina, ceramics, or the like, is suitably used as an insulating
coating material. However, plasma-sprayed alumina is preferable
as an insulating coat.
Incidentally, when an electrode having a bending configuration
is used and the electrode is composed of two members, either of
the first electrode member and the second electrode member may be
provided with an insulating coating material.
When the electrode is covered with an insulating coating material,
a gap between the case for installing an electrode and the insulating
coating material is preferably sealed with a metallic sealing material.
When the case for installing an electrode is covered with an insulating
coating material, a gap between the electrode and the insulating
coating material is preferably sealed with a metallic sealing material.
The reason is that gas sealability is imparted to the electrode.
A gap between the electrode and the case for installing an electrode
is preferably sealed with an inorganic powder because gas sealability
and impact resistance are imparted to the electrode. The inorganic
powder is preferably packed in the gap under a pressure as described
above.
Gaps formed mutually by the insulator, the case for installing
an electrode, and the electrode may be sealed with a cement sealing
material, thereby imparting gas sealability to the electrode.
In an electrode structure of the present invention, an electrode
is fixed to a metallic housing via an insulating member and a case
for installing an electrode. One end of the electrode located inside
the metallic housing is connected with a part of a subject to be
electrified directly or via a metallic connecting member by means
of welding, or the like.
A subject to be electrified is, for example, a metallic honeycomb
structure. A metallic honeycomb structure connected with an electrode
of the present invention forms an electric heater which is mounted
on a catalytic converter for purifying automobile exhaust gas, or
the like. Not only a metallic honeycomb structure but also various
subjects to be electrified can be used for an electrode structure
of the present invention.
The present invention is hereinbelow described in more details
with reference to the illustrated embodiments. However, the present
invention is by no means limited to these embodiments.
FIG. 1 is an explanatory view showing an embodiment of an electrode
structure in which the electrode has a bending configuration of
the present invention. In FIG. 1, reference numerals 2, 4, 6, 16,
18a, 18b, 18d, 20, 22, and 24 denote a metallic housing, a case
for installing an electrode, an electrode made of metallic stick,
a metallic connecting member, the first insulator, the second insulator,
an inorganic powder, a lead wire, a waterproof member, and a caulking
ring, respectively.
In the electrode structure shown in FIG. 1, the electrode 6 is
composed of the first electrode member 6a and the second electrode
member 6b, each having a cylindrical configuration. The second electrode
member 6b is threadedly engaged with the first electrode member
6a so as to form an angle of about 90.degree. to each other. The
first electrode member 6a has a negative screw portion, and the
second electrode member 6b has a positive screw portion. The first
electrode member 6a is inserted into a throughhole 12 arranged in
a metallic housing 2. The second electrode member 6b is fixed to
the case 4 for installing the electrode via the insulating member
18 composed of the first insulator 18a, the second insulator 18b,
and an inorganic powder 18dpacked in a gap between the first and
the second insulating members 18a, and 18b. The case 4 for installing
an electrode is successively connected with the metallic housing
2. In the embodiment shown in FIG. 1, the first case member 4a is
the outer side and the second case member 4b in the inner side are
partially laminated to form a dual structure in the case 4 for installing
an electrode. The second case member 4b is caulked in the top periphery
of the second insulator 18bvia the caulking ring 24. The use of
the caulking ring 24 enables to pack the inorganic powder 18dunder
a pressure without excessively stressing the second insulator 18b.
Preferably, the caulking ring 24 has a larger thermal expansion
coefficient than the second case member 4b because the caulking
ring 24 absorbs a difference of thermal expansion between the second
case member 4b and the insulating member 18 upon being heated, thereby
avoiding deterioration of sealability. Preferably, the first case
member 4a and the second case member 4b are airtightly connected
with each other in the all periphery of the laminated portion by
welding or the like, preferably by laser welding, so as to prevent
the electrode structure from permeation of water from a gap between
the first case member 4a and the second case member 4b.
The waterproof member 22 is placed between the case 4 for installing
an electrode and the lead wire 20. The case 4 for installing an
electrode is crimped in the portion where the waterproof member
22 is connected, thereby avoiding forming a gap between the case
4 for installing an electrode and the waterproof member 22 and a
gap between the waterproof member 22 and the lead wire 20 so as
to have a structure of ensuring that water permeation from a gap
between the case 4 for installing an electrode and the lead wire
20 does not happen. The lead wire 20 is electrically connected with
the electrode 6 by a connecting member 30 at the bottom end of the
lead wire 20 and the upper end of the electrode 6. The other end
of the electrode 6, which is inside the metallic housing 2, is connected
with a subject to be electrified in a part there of, which is not
illustrated, by means of a metallic connecting member 16.
The electrode structure is excellent in composability, productivity,
and gas seatability. Further, even if a solid comes flying from
outside the exhaust gas pipe and collides with the electrode, gas
sealability and insulating ability hardly deteriorate, and the electrode
structure is structurally strong and has high safety.
Incidentally, since the first insulating member 18a, has a difference
in level 32 in the electrode structure shown in the FIG. 1, the
inorganic powder 18d packed in a gap between the first insulator
18a, and the second insulator 18b is hardly loosened even if heat
cycles and vibrations are transmitted to the electrode.
FIG. 5 shows an embodiment of sealing a gap between the insulating
member, which is positioned between the case for installing an electrode
and electrode, and an electrode and a gap between the insulating
member and the case for installing an electrode with a metallic
sealing material. In the electrode structure, the electrode has
a bending configuration.
In the electrode structure shown in FIG. 5, the insulator 18c is
positioned between the second case member 46 and the first electrode
member 6a. A gap between the insulator 18c and the first electrode
member 6a and a gap between the insulator 18c and the second case
member 46 for installing the electrode are sealed with a metallic
sealing member 56. In this embodiment, the first electrode member
6a is connected with the second electrode member 6b by welding.
This embodiment has the same waterproof structure as in the embodiment
shown in FIG. 1.
FIG. 6 shows another embodiment of sealing a gap between the insulating
member, which is positioned between the case and the electrode,
and the electrode and a gap between the insulating member and the
case. In the electrode structure, the electrode has a bending configuration.
In the electrode structure shown in FIG. 6, the insulating members
18a, and 18c are positioned between the second electrode member
6b and the case 4 for installing an electrode. A gap between the
second insulator 18c and the case member 4a and a gap between the
second insulator 18c and the second electrode member 6b are sealed
with a metallic scaling material 56.
A belleville spring 58 is supported from the top and bottom by
pressing members 60. The upper pressing member 60 is supported by
a flange 62 formed in the lower opening portion of the connecting
member 30.
The waterproof structure is the same as in the embodiment shown
in FIG. 1. The flange 62 effectively transmits a load applied to
the electrode caused by a difference in thermal expansion to the
belleville spring 58 in the same manner as the pressing members
60 do.
The electrode structure in FIG. 6 has differences from the electrode
structure in FIG. 5. The differences are that the electrode structure
in FIG. 6 is provided with the insulating member around the second
electrode member 6b, that the electrode structure is provided with
the spring structure for absorbing difference in thermal expansion,
that the case 4 for installing an electrode is composed of two members,
and that the case 4 for installing an electrode is provided with
a supporting portion 64 for the insulator 18a.
As shown in FIG. 7, the pressing member 60 may be fixed to the
electrode 6 by arranging a holding portion 64 in the pressing member
60 in the predetermined portion and keying an inner bank portion
of the pressing member 60, which has a configuration of a partially
cut ring, to the holding portion 64 in the electrode 6.
FIGS. 8 and 9 show embodiments of insulating the case for installing
an electrode from the electrode by plasma-spraying alumina on the
electrode. Each of the embodiments employs an electrode having a
bending configuration. In FIG. 8 the insulating coating material
18f is coated on the first electrode member 6a, while in FIG. 9
the insulating coating material 18f is coated on the second electrode
member 6b. The electrode with the insulating coating material 18f
being coated thereon is inserted under a pressure in the second
case 46 for installing an electrode. The waterproof structure of
these embodiments is the same as that of the embodiment in FIG.
1.
FIG. 18 is an explanatory view showing an embodiment of connecting
a lead wire to an electrode so as to form a predetermined angle
of the present invention.
In the electrode structure shown in FIG. 18, a lead wire 20 is
welded to the top end of the electrode 6 so as to have an angle
of about 90.degree. by means of a connecting member 70. The electrode
6 has a flat top portion, where a flat portion of the connecting
member 70 is welded. The electrode 6 is fixed to the case 4 for
installing an electrode via the insulating member 18 composed of
the first insulator 18a, the second insulator 18b, and the talc
18c packed between the first and the second insulators 18a, and
18b. The case 4 for installing an electrode is successively connected
with a metallic housing 2 and composed of the lower case member
31 and the upper case member 33. The lower case member 31 is composed
of the first cylindrical portion 80 and the second cylindrical portion
81. The first cylindrical portion 80 covers the periphery of the
electrode 6. The second cylindrical portion 81 covers the lead wire
20. The first cylindrical portion 80 is connected with the second
cylindrical portion 81 so as to form an angle of about 90.degree..
The upper case member 33 has a discoidal configuration and closes
the upper opening portion 82 of the first cylindrical portion 80.
The lower case member 31 has a dual structure formed by laminating
the first member 31a in the outside and the second member 31b in
the inside. The second member 31b is caulked by means of the caulking
ring 24 from outside in the periphery of the upper end of the first
insulator 18a. The role of the caulking ring 24 is the same as in
the electrode structure shown in FIG. 1. The laminated portion formed
of the first member 31a and the second member 31b is preferably
welded to ensure airtightness in every part of the laminated portion
so as to avoid permeation of water between the first and second
members 31a and 31b. A waterproof structure between the case 4 for
installing an electrode and the lead wire 20 is the same as that
of the embodiment in FIG. 1.
This electrode structure is composed as follows:
The second member 31b of the lower case member 31 is fixed to the
electrode 6 via the insulating member 18. The second member 31b
is caulked by means of the caulking ring 24. A gap formed among
the insulating members 18a, and 18band the second member 31b may
be sealed with a metallic sealing material.
Then, the first member 31a of the lower case member 31 is fixed
to the second member 31b by press-inserting and welding (laser welding
or Tig, i.e., Tungsten-insert-gas welding) all the connecting portion.
Subsequently, a lead wire 20 provided with a connecting member
70 is inserted into the second cylindrical portion 81 of the lower
case member 31 from the opening portion. The lead wire 20 is welded
(by Tig welding or projection welding) to the top end of the electrode
6.
Then, the upper case member 32 is welded so as to cover the upper
opening portion 82 of the first cylindrical portion 80.
The waterproof member 22 is positioned between the second cylindrical
portion 81 of the lower case member 31 and the lead wire 20. The
second cylindrical portion 81 is crimped from outside to fix the
waterproof member 22 to the lead wire 20 and the second cylindrical
portion 81.
This electrode structure is excellent in composability, productivity,
and gas sealability. Further, even if a solid comes flying from
the outside the exhaust gas pipe and collides with the electrode,
gas sealability and insulating ability hardly deteriorates, and
the electrode structure is structurally strong and has high safety.
FIG. 19 shows another embodiment of connecting a lead wire to an
electrode in the top portion thereof of the present invention.
In the electrode structure shown in FIG. 19, a lead wire 20 is
welded to the top portion of the electrode 6 as to form an angle
of about 90.degree. by means of connecting member 70. The connecting
member 70 has a hole portion 54 having a configuration matching
the top portion of the electrode 6 so that the electrode 6 is engaged
with the hole portion 54 of the connecting member 70. The lower
case member 31 is composed of a cylindrical portion 83 and a half
cylindrical portion 84. The cylindrical portion 83 covers the lower
periphery of electrode 6. The half cylindrical portion 84 covers
the lower periphery of a lead wire 20 and is oriented so as to form
an angle of about 90.degree. with the cylindrical portion 83. The
upper case member 33 closes the opening portion of the cylindrical
portion 83 and has a half cylindrical portion 85. The upper case
member 33 covers the upper periphery of the lead wire 20. Each of
the lower case member 31 and the upper case member 33 has a flange
86 so as to connect with each other by welding at the flange 86.
An insulating structure and a waterproof structure of the embodiment
in FIG. 19 are the same as those of the embodiment in FIG. 18.
The electrode structure in FIG. 19 is composed as follows:
The insulating member 18 and the lower case member 31 are fixed
to the electrode 6 in the same manner as in FIG. 18.
Then, the lead wire 20 provided with the connecting member 70 covering
the electrode 6 is welded to the top portion of the electrode 6
by spot welding.
Subsequently, the upper case member 33 is connected with the lower
case member 31 at their flanges 86 by Tig welding or seam welding
all around the periphery.
Then, a portion 88 for covering the waterproof member is fixed
to the cylindrical portion of the case for installing an electrode.
The case for installing an electrode is formed of the lower case
member 31 and the upper case member 33, each having a half cylindrical
configuration, by Tig welding all around the periphery. A waterproof
member is fixed to the electrode structure in the same manner as
in FIG. 18.
FIG. 20 shows still another embodiment of connecting a lead wire
to the top portion of an electrode so as to form a predetermined
angle of the present invention.
In the electrode structure shown in FIG. 20, each of the lower
case member 31 and the upper case member 33 has a surface end having
an angle of about 45.degree. to the axis. The surface end has a
flange 86. The lower case member 31 and the upper case member 33
is connected at the flanges 86 so as to form an angle of 90.degree.
in the case 4 for installing an electrode.
The lead wire 20 is connected with the electrode 6 in the same
manner as in the embodiment in FIG. 18. An insulating structure
and an waterproof structure are also the same as in the embodiment
in FIG. 18.
The electrode structure in FIG. 20 is composed according to the
method applied to the electrode structures in FIG. 18 and FIG. 19.
That is, first, the lower case member 31 is fixed to the electrode
6. Subsequently, the lead wire 20 is connected with the electrode
6. Finally, the upper case member 33 is fixed to the lower case
member 31. Incidentally, the lower case member 31 is Tig welded
to the upper case member 33.
Incidentally, a spring structure such as a belleville spring 55
can be arranged between the electrode 6 and the case 4 for installing
an electrode as in an embodiment in FIG. 6 even when a lead wire
is connected to the top portion of the electrode so as to form a
predetermined angle, thereby absorbing a difference in thermal expansion
between the electrode 6 and the case 4 for installing an electrode.
In this case, the pressing members 60 are preferably arranged on
and beneath the belleville spring 58.
Incidentally, the waterproof structure in the electrode structure
in FIG. 20 may be the same as in FIGS. 2, 3, or 4.
In the embodiment in FIG. 2, the first waterproof member 40 surrounds
the lead wire 20. The first waterproof member 40 is held by the
case 4 for installing an electrode in the lower portion thereof.
A waterproof tube 42 such as Teflon tube is wound on the upper portion
of the first waterproof member 40. The waterproof tube 42 is surrounded
by the waterproof-member holder 47. The waterproof-member holder
47 is crimped from outer periphery at the points A and B.
In this structure, the waterproof tube 42 is positioned between
the case 4 for installing an electrode and the waterproof-member
holder 47 at the point A, thereby ensuring to avoiding water permeation
because of the difference in thermal expansion. Since the waterproof-member
holder 47 is crimped at the point B together with the first waterproof
member 40 and the waterproof tube 42, water does not permeate at
this point. Accordingly, this structure ensures every high waterproof
ability.
In the embodiment shown in FIG. 3, one-piece type of case 4 for
installing an electrode is employed instead of the two-piece type
of case 4 shown in FIG. 1. An insulating member is positioned between
the case 4 for installing an electrode and the electrode 6. The
waterproof member 22 is positioned between the case 4 for installing
an electrode and the lead wire 20. In this structure, the case 4
for installing an electrode is caulked from outside with employing
a caulking member 48 in the side of the lead wire of the second
insulator 18b.
FIG. 4 is an embodiment showing another waterproof structure between
the case for installing an electrode and the lead wire. In this
embodiment, the coating material 50 covering the lead wire 20 also
works as a waterproof member. The coating material 50 is directly
crimped from outside the case 4 for installing an electrode. In
this case, the coating material 50 of the lead wire 20 should have
or preferably has a waterproof ability as described above. This
structure requires less number of parts, and therefore, the composability
enhances.
The electrode can be connected with a lead wire in various kinds
of methods. FIGS. 11-16 show the embodiments.
In FIG. 11, the lead wire 20 is connected with the electrode 6
by means of the connecting member 30. The connecting member 30 is
fixed to the lead wire 20 by means of protrusions 68 formed at one
end of the connecting member 30. The other end of the connecting
member 30 is curving toward outside to form a holding portion 70
where the connecting member 30 is projection welded to the electrode
6.
In FIG. 12, the connecting member 30 is fixed to the lead wire
20 by means of protrusions 68 formed at one end of the connecting
member 30 and to the electrode 6 by caulking the connecting member
in the holding portion 70 formed at the other side. The connecting
member 30 may be spot welded to the electrode 6.
In FIG. 13, the connecting member 30 is fixed to the lead wire
20 by means of protrusions 68 formed at one end of the connecting
member 30 and to the electrode 6 by threadedly engaging each other
by means of a negative screw portion formed at the other end of
the connecting member 30 and the positive screw portion formed on
the electrode.
In FIG. 14, the lead wire 20 is directly connected with the electrode
6. In FIG. 15, one end of the electrode 6 is formed so as to have
a cylindrical configuration. One end of the lead wire 20 is inserted
in the cylindrical portion of the electrode 6. Then, the cylindrical
portion of the electrode 6 is caulked from outside to fix the lead
wire 20 to the electrode 20.
FIG. 16 perpendicularly shows an example of connecting a lead wire
20 to the electrode 6. The connecting member 30 having a configuration
of the nut is connected to one end of the lead wire 20. The connecting
member 30 is fixed to the end of the electrode 6 by means of a bolt
52.
Evaluation
The electrode structure of the present invention shown in FIG.
1 and the conventional electrode structure in FIG. 10 were measured
for hygroscopicity and waterproof ability.
For measuring hygroscopicity of the electrode structures, the electrode
structures were left in a condition having a humidity of 100%. For
each electrode, there is measured a change of an insulating resistance
between the electrode and the case for installing an electrode according
to the time.
As a result, it was found that the electrode structure of the present
invention maintained a high insulating resistance of 1M.OMEGA. even
after 200 minutes passed, while the insulating resistance of the
conventional electrode structure decreased to lower than 1M.OMEGA.
after 30 minutes passed.
For measuring waterproof ability, an exhaust gas pipe is heated
so that the temperature of the waterproof member rises up to 200.degree.
C. Water having a flow rate of 20 cc/min. is poured to the electrode
for 5 seconds. This cycle was repeated 7 times. Then, the condition
of water permeation into the case for installing an electrode was
observed. As a result, there was no water permeation caused.
As described above, the present invention provides an electrode
structure including one end of a lead wire and having an excellent
convenience of composability, or the like, and an electric heater
provided with the electrode structure. An electrode structure of
the present invention is excellent in waterproof ability and gas
sealability. Since a whole electrode of an electrode structure of
the present invention has a bending configuration, the electrode
has a practical size and a sufficient length to avoid a temperature
rise in the end portion of the electrode. Therefore, the electrode
structure can avoid deterioration of a waterproof member, etc.,
by a temperature rise in the end portion of the electrode structure.
When the electrode itself has a bending structure, the electrode
is composed of a plurality of members each successively oriented
in the direction toward the axis of the electrode, each member being
connected mutually with adjacent member(s). When a lead wire is
connected with the electrode at the top end so as to form a predetermined
angle, a case for installing an electrode is composed of the lower
case member and the upper case member, thereby the electrode structure
is excellent in workability upon composing.
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