Thermal measuring and testing – Temperature measurement – Combined with diverse art device
Reexamination Certificate
1999-08-27
2001-09-11
Gutierrez, Diego (Department: 2859)
Thermal measuring and testing
Temperature measurement
Combined with diverse art device
C374S208000
Reexamination Certificate
active
06286995
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a temperature sensor comprising a temperature sensitive element arranged in a fluid passage for detecting the temperature of the object fluid flowing in the fluid passage.
2. Description of the Related Art
A well-known temperature sensor of this type is used on an automobile (for example, Japanese Unexamined Patent Publications No. 7-201523, No. 9-126910, etc.). This type of temperature sensor is used as an exhaust gas temperature sensor and includes a temperature sensitive element (such as a thermistor element) for detecting the temperature of an exhaust gas (object fluid) flowing in an exhaust gas passage (flow passage). The sensor is generally mounted in the exhaust gas passage in the manner shown in FIG.
1
A.
This temperature sensor
200
comprises a wiring member (sheath pin)
1
including a metal outer cylinder
1
a
and a pair of conductive core wires
1
b
held in the metal outer cylinder
1
a
through an insulating material, a temperature sensitive element (such as a thermistor element) connected to the ends of the core wires
1
b
at an end of the wiring member
1
, and a pair of lead wires
4
connected to the other ends of the core wires
1
b
at the other end of the wiring member
1
for connecting an external circuit, wherein the wiring member
1
is inserted in a hole A
3
formed in a wall portion A
2
defining the exhaust gas passage A
1
thereby to set the temperature sensitive element
2
in position in the exhaust gas passage A
1
.
In this configuration, the connecting portions (lead wire coupling portions) B
1
between the core wires
1
b
and the lead wires
4
are protected by being covered with a cylindrical protective member (sleeve) J
6
. This protective member J
6
is coupled around the whole periphery of the weld zone (coupling portion) D
1
along the outer peripheral surface of the outer cylinder
1
a.
Also, a seal member J
5
for preventing the leakage of the exhaust gas from the hole A
3
is coupled around the whole outer peripheral surface of the protective member J
6
in the weld zone (coupling portion) D
2
.
This seal member J
5
, as shown in
FIG. 1A
, includes a tapered seat surface J
5
a
corresponding to the tapered surface of the hole A
3
. By bringing the seat surface J
5
a
in close contact with the tapered surface of the hole A
3
by a screw A
5
, the exhaust gas is prevented from leaking from the hole A
3
.
Also, a metal cap
3
made of a heat-resistant metal is coupled around the whole outer peripheral surface of the outer cylinder
1
a
at an end of the wiring member
1
. The temperature sensitive element
2
is housed in the metal cap
3
and thus is protected from the exhaust gas. The output of the temperature sensitive element
2
is retrieved by an external circuit, not shown, by way of the lead wires
4
from the core wires
1
b
of the wiring member
1
thereby to detect the temperature of the exhaust gas.
In the case where the temperature sensitive element
2
is disposed in the exhaust gas passage A having this constitution, however, the weld zones D
1
and D
2
are exposed to the exhaust gas in the exhaust gas passage A
1
, and therefore the exhaust gas is required to be sealed from the outside of the passage at three points including the seat surface J
5
a
of the seal member J
5
and the weld zones D
1
and D
2
. Especially, since there are two coupling portions where maintenance of air-tightness is required, the resulting constitution is extremely unreliable from the viewpoint of the sealing of the exhaust gas.
Also, from the viewpoint of the improvement of the sensor response, the component members of the temperature sensitive portion of the sensor, i.e. the temperature sensitive element
2
, the metal cap
3
and the wiring member
1
are preferably reduced in diameter. In that case, the protective member J
6
coupled to the outer cylinder
1
a
of the wiring member
1
is also required to be reduced in diameter. The portion of the protective member J
6
for protecting the lead wire coupling portions B
1
, on the other hand, is required to secure a sufficient space for welding or arranging a connector for connecting the core wires
1
b
and the lead wires
4
. Therefore, the diameter of the portion of the protective member J
6
for protecting the lead wire coupling portions B
1
constitutes a controlling factor for determining the diameter of the protective member J
6
.
As is shown in
FIG. 1A
, however, the protective member J
6
is straight in shape. The diameter of the protective member J
6
cannot be reduced more than necessary, therefore, for securing the diameter of the protective portion of the lead wire coupling portions B
1
. Also, the diameter of the wiring member
1
, which is coupled to the inner peripheral surface of the protective member J
6
on the outer peripheral surface of the outer cylinder
1
a
thereof, is determined by the diameter of the protective member J
6
and therefore cannot be easily reduced.
For improving the response of the temperature sensor, a deformed protective member (stepped sleeve) J
6
shown in
FIG. 1B
may be employed in which the portion for protecting the lead wire coupling portions B
1
and the portion D
1
for coupling with the outer cylinder
1
a
of the wiring member
1
have different diameters. This constitution requires, however, not only the cutting of the pipe but the drawing on machining of the protective member, thereby leading to a considerably increased machining cost for an increased production cost.
The problems of sealing and the protective member described above are not confined to the temperature sensor for detecting the exhaust gas temperature. Specifically, the problems are shared by temperature sensors comprising a wiring member with one end connected to a temperature sensitive element and the other end connected to lead wires and a cylindrical protective member for covering the connecting portion of the lead wires, wherein the wiring member is arranged in the fluid passage by being inserted in a hole formed in the wall portion of a fluid passage.
SUMMARY OF THE INVENTION
In view of the problem points of the prior art described above, the object of the present invention is to provide a temperature sensor comprising a temperature sensitive element arranged in a fluid passage through the wall portion of the fluid passage for detecting the temperature of the object fluid, wherein the sealing of the object fluid is reliably improved while at the same time reducing the diameter of the sensor without increasing the cost.
In order to achieve the object described above, according to the present invention, there is provided a temperature sensor wherein a seal member for preventing the leakage of the object fluid is arranged in close contact with a hole formed in wall portion defining a fluid passage and is coupled over the entire outer peripheral surface of an outer cylinder constituting protective member covering the connecting portions between core wires of the wiring member and lead wires for connecting an external circuit is coupled to the seal member at a portion farther away from the temperature sensitive element than the coupling portion between the seal member and the outer cylinder.
As a result, the coupling portion of the protective member exposed to the object fluid in the prior art is not exposed to the object fluid, since the protective member is coupled to the seal member at the portion further away from the temperature sensitive element than the coupling portion between the seal member and the outer cylinder. Only one coupling portion between the seal member and the outer cylinder is exposed to the object fluid, thereby improving the reliability of sealing.
Also, the wiring member is coupled to the seal member on the outer peripheral surface of the outer cylinder
1
a
and the protective member is coupled to the seal member. The diameter of one of the wiring member and the protective member, therefore, is not affected by the diameter of the other. Thus, the cyli
Fukaya Matsuo
Takahashi Sotoo
Denso Corporation
Gutierrez Diego
Pillsbury Winthrop LLP Intellectual Property Group
Verbitsky Gail
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