Metal working – Method of mechanical manufacture – Assembling or joining
Reexamination Certificate
2002-03-27
2004-01-06
Bryant, David P. (Department: 3726)
Metal working
Method of mechanical manufacture
Assembling or joining
C029SDIG003, C204S424000, C204S431000, C073S031050
Reexamination Certificate
active
06671942
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method for manufacturing a gas sensor having a tubular housing and a sensing element disposed in this housing.
For example, an oxygen sensor or a comparable gas sensor is equipped in an internal combustion engine to measure an oxygen concentration. This sensor comprises a tubular housing and a sensing element disposed in the housing. The housing has an inner cylindrical stepped portion protruding radially inward from an inner cylindrical surface thereof. The sensing element has a flange portion protruding radially outward from an outer surface thereof. The flange portion of the sensing element is placed on the inner cylindrical stepped portion of the housing. Talc powder or other inorganic powder is stuffed into a contact portion between the sensing element and the housing.
In stuffing such inorganic powder into the contact portion, a hardened powder ring is inserted into an annular end space defined between the inner cylindrical surface of the housing and the outer surface of the sensing element. The hardened powder ring is a hardened block of inorganic powder configured into a ring shape. The hardened powder ring is pressed and crushed.
However, according to the above-described conventional gas sensor manufacturing method, it is difficult to uniformly apply a pressing force to the hardened powder ring or the inorganic powder stuffed into the annular end space. This leads to nonuniform density distribution of the inorganic powder in the annular end space. Airtightness will be worsened.
Furthermore, in the pressing operation of the hardened powder ring, the pushing member may accidentally hit or collide with the sensing element or the housing and accordingly may damage the sensing element or the housing. If the sensing element is damaged, the output characteristics of the gas sensor will possibly deteriorate. If the housing is damaged, a small or sliced piece of housing material may mix into the inorganic powder. This will cause insulation defectiveness or other problem.
SUMMARY OF THE INVENTION
In view of the foregoing problems of the prior art, the present invention has an object to provide a manufacturing method for a gas sensor according to which no damage is given to the sensing element or the housing and the inorganic powder can be uniformly stuffed into the annular end space between the sensing element and the housing.
To accomplish the above and other related objects, the present invention provides a first method for manufacturing a gas sensor having a tubular housing and a sensing element disposed in the housing. The first manufacturing method of this invention comprises a step of inserting the sensing element into the tubular housing from a rear end toward a front end of the housing. The sensing element has a flange portion protruding radially outward from an outer surface thereof, and the housing has an inner cylindrical stepped portion protruding radially inward from an inner cylindrical surface thereof. The first manufacturing method of this invention further comprises a step of placing the flange portion of the sensing element on the inner cylindrical stepped portion of the housing, and a step of inserting a hardened powder ring into an annular end space defined between the inner cylindrical surface of the housing and the outer surface of the sensing element. The hardened powder ring is a hardened block of inorganic powder configured into a ring shape. The first manufacturing method of this invention further comprises a step of pressing the hardened powder ring toward the front end of the housing by a tubular pushing member and crushing the hardened powder ring into inorganic powder by the tubular pushing member so that the annular end space is stuffed by the inorganic powder. According to the first manufacturing method of this invention, the following relationship is satisfied
0.275 mm≦
r
p
−R
e
≦0.375 mm,
and
0.15 mm≦
r
h
−R
p
≦0.25 mm,
where r
p
represents an inner radius of the pushing member, R
p
represents an outer radius of the pushing member, r
h
represents an inner radius of the housing, and R
e
represents an outer radius of the sensing element at a portion substantially defining the annular end space.
This invention has the following functions and effects.
According to this invention, the inner radius r
p
and the outer radius R
p
of the pushing member satisfy the relationship 0.275 mm≦r
p
−R
e
and 0.15 mm≦r
h
−R
p
with respect to the outer radius R
e
of the sensing element and the inner radius r
h
of the housing. With this arrangement, it becomes possible to secure a sufficient clearance necessary for smoothing the insertion of the pushing member which is inserted into the annular end space. Namely, it becomes possible to secure a sufficient clearance between the pushing member and the housing and also secure a sufficient clearance between the pushing member and the sensing element.
Furthermore, the inner radius r
p
and the outer radius R
p
of the pushing member satisfy the relationship r
p
−R
e≦
0.375 mm and r
h
−R
p
≦0.25 mm with respect to the outer radius R
e
of the sensing element and the inner radius r
h
of the housing. With this arrangement, it becomes possible to sufficiently reduce or narrow the clearance between the pushing member and the housing as well as the clearance between the pushing member and the sensing element, when the pushing member is inserted into the annular end space. Accordingly, it becomes possible to uniformly press the hardened powder ring or the inorganic powder in the entire region of the annular end space.
As described above, this invention provides a method for manufacturing a gas sensor capable of uniformly stuffing the inorganic powder into the annular end space defined between the sensing element and the housing without damaging the sensing element and the housing.
According to the above-described first manufacturing method of the present invention, it is preferable that the pushing member has a press portion consisting of a flat surface, an inner curved surface having a curvature radius of 0.3~0.4 mm, and an outer curved surface having a curvature radius of 0.3~0.5 mm. The inner curved surface is formed at a radially inner end of the press portion. The outer curved surface is formed at a radially outer end of the press portion.
When the press portion of the pushing member has inner and outer curved surfaces having the above-described curvature radiuses, the press portion of the pushing member does not hit or collide against the outer surface of the sensing element as well as against the inner surface of the housing. No damage is given to the sensing element and the housing.
As described above, the inner radius r
p
and the outer radius R
p
of the pushing member satisfy the above-described conditions. The press portion of the pushing member has the inner and outer curved surfaces having the above-described curvature radiuses. Thus, it becomes possible to uniformly stuff the inorganic powder into the annular end space without damaging the sensing element and the housing.
The present invention provides a second method for manufacturing a gas sensor having a tubular housing and a sensing element disposed in the housing, comprising:
a step of inserting the sensing element into the tubular housing from a rear end toward a front end of the housing, the sensing element having a flange portion protruding radially outward from an outer surface thereof, and the housing having an inner cylindrical stepped portion protruding radially inward from an inner cylindrical surface thereof;
a step of placing the flange portion of the sensing element on the inner cylindrical stepped portion of the housing;
a step of inserting a hardened powder ring into an annular end space defined between the inner cylindrical surface of the housing and the outer surface of the sensing element, the hardened powder ring being a hardened block of talc powder configured into a ring shape;
a step of inserting a packing ring in
Nishimatsu Akira
Ohba Yukio
Bryant David P.
Denso Corporation
LandOfFree
Method for manufacturing a gas sensor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for manufacturing a gas sensor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for manufacturing a gas sensor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3259855