Temperature detecting apparatus

The invention relates to a temperature detecting apparatus and an automobile using the same, and is intended to improve the heat response characteristic. The apparatus comprises a first metal pipe, first and second metal wires accommodated in the first metal pipe, at least one end of each wire being projected from one end of the first metal pipe, an insulator for keeping an electric insulation of the first metal pipe and the first and second metal wires in the first metal pipe, a temperature detecting element projecting out of one end of the first metal pipe and disposed between ends of the first and second metal wires, and a metal cap fitted to one end of the first metal pipe for covering the temperature detecting element, wherein the temperature detecting element is in a substantially flat shape or in a flat shape longer in the length in the direction between the first and second metal wires than the length in the direction at right angle thereto, and a portion of the metal cap opposite to the temperature detecting element is in a flat shape in the same direction in a shape similar to the temperature detecting element.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a temperature detecting apparatus used in 
detection of temperature of various places and an automobile incorporating 
the same. 
2. Description of Related Art 
In the automobile, it has been attempted to purify emissions by installing 
an emission purifying system in the emission route including a catalytic 
purifying apparatus. To optimize the performance of the catalytic 
purifying apparatus to the maximum extent, it is necessary to detect the 
emission temperature in the emission route by a temperature detecting 
apparatus (or device). 
A conventional temperature detecting device comprises, as shown in FIG. 19 
through FIG. 23, a metal pipe 26, two, first and second, metal wires 27 
accommodated in the metal pipe 26, at least one end being projected from 
one end of the metal pipe 26, an insulator 28 for keeping an electric 
insulation of the metal pipe 26 and the first and second metal wires 27 
inside the metal pipe 26, a columnar temperature detecting element 29 
provided between ends of the first and second metal wires 27 projecting 
out of one end of the metal pipe 26, and a metal cap 30 fitted to one end 
of the metal pipe 26 so as to cover this temperature detecting element 29. 
The temperature detecting element 29 is known to be most sensitive to 
temperature in the portion between the first and second metal wires 27. In 
such conventional construction, however, since the columnar temperature 
detecting element 29 is disposed coaxially in the cylindrical metal cap 
30, the portion between the first and second metal wires 27 of the 
temperature detecting element 29 is at a position remote from the outer 
side of the metal cap 30, and the sensing of heat transmitted from the 
outer side of the metal cap 30 was dull (or inexact), and the heat 
response characteristic was poor. 
SUMMARY OF THE INVENTION 
It is hence an object of the invention to provide a temperature detecting 
apparatus having excellent heat response characteristic. 
To achieve this object, in the invention, the shape of the temperature 
detecting element has a substantially flat shape longer in the length in 
the direction between the first and second metal wires (i.e., width of the 
temperature detecting element) than the length in its right-angle 
direction, and the portion of the metal cap confronting (or facing) the 
temperature detecting element also has a substantially flat shape in 
substantially the same direction, and has a substantially similar shape to 
the temperature detecting element. 
In this construction, the portion of the temperature detecting element 
between the two metal wires mainly responsible for detecting temperature 
can be disposed at a position close to the side of the metal cap, and the 
heat can be detected sensibly (or more precisely), so that the heat 
response characteristic of the temperature detecting apparatus may be 
enhanced. 
The invention according to claim 1 of the invention relates to a 
temperature detecting apparatus which comprises a first metal pipe, a 
first metal wire and a second metal wire accommodated (or placed) in the 
first metal pipe, at least one end of the first metal wire and the second 
metal wire being projected from one end of the first metal pipe, an 
insulator for keeping an electric insulation of the first metal pipe and 
the first metal wire and the second metal wire in the first metal pipe, a 
temperature detecting element projecting out of one end of the first metal 
pipe and disposed between the ends of the first and second metal wires 
projected from the one end of the first metal pipe, and a metal cap fitted 
to one end of the first metal pipe for covering the temperature detecting 
element, in which the temperature detecting element has a substantially 
flat shape longer in the length in the direction between the first and 
second metal wires (width of the temperature detecting element) than the 
length in the direction at right angle thereof, and the portion of the 
metal cap confronting the temperature detecting element is in a 
substantially flat shape and in substantially the same direction and same 
shape (or substantially similar shape) as the temperature detecting 
element, whereby the heat response characteristic is improved as mentioned 
above. 
The invention according to claims 2 and 9 of the invention relates to a 
temperature detecting apparatus as set forth in claim 1 or 8 wherein the 
closed end side of the metal cap, ahead of the open end side fitted to the 
outer periphery of one end of the first metal pipe, is in a flat shape, 
whereby it is not necessary to flatten also the first metal pipe, and the 
first metal pipe of a generally cylindrical shape can be used, thereby 
minimizing the cost, but also maintaining the strength of the apparatus. 
The invention according to claims 3 and 10 of the invention relates to a 
temperature detecting apparatus as set forth in claim 2 or 9 wherein the 
opening end of the metal cap (i.e., the open end side of the metal cap) is 
plastically deformed to the first metal pipe side, so that the opening end 
of the metal cap is reduced in diameter, and the metal cap and the first 
metal pipe are welded in this reduced portion, whereby the metal cap and 
the first metal pipe contact with each other almost in the entire 
periphery in this reduced portion by reducing the diameter of the metal 
cap, and the welded state of the both parts (i.e., the first metal pipe 
and the metal cap) is stable on the whole periphery, and hence the 
temperature detecting element in the metal cap is kept airtight from the 
ambient atmosphere so as to be protected. 
The invention according to claims 4 and 11 of the invention relates to a 
temperature detecting apparatus as set forth in claim 3 or 10 wherein the 
opening of the metal cap is formed by expanding the metal cap from the 
closed end side toward this opening, whereby the metal cap can be fitted 
to one end of the first metal pipe. 
The invention according to claims 5 and 12 of the invention relates to a 
temperature detecting apparatus as set forth in claim 3 or 10 wherein the 
forward side of the metal cap from the fitting portion to the first metal 
pipe is in a shape gradually flat toward the closed end, whereby, 
different from immediate flat processing of the metal cap at one end of 
the first metal pipe, it is effective to prevent lowering of insulation 
resistance due to too close distance (undue proximity) between the metal 
cap and the first and second metal wires at one end side of the metal 
pipe. 
The invention according to claims 6 and 13 of the invention relates to a 
temperature detecting apparatus as set forth in claim 5 or 12 wherein the 
metal cap is gradually reduced in wall thickness from the opening toward 
the closed end, whereby heat can be transmitted to the temperature 
detecting element more quickly as the wall thickness is thin at the closed 
end of the metal cap accommodating the temperature detecting element, and 
hence heat response performance is improved, and such reduction of wall 
thickness can be easily formed by a drawing process. 
The invention according to claim 7 of the invention relates to a 
temperature detecting apparatus as set forth in claim 1 wherein at least 
one of the metal cap and the first metal pipe is heat treated at a higher 
temperature than the maximum operating temperature before welding of the 
metal cap and the first metal pipe, whereby a rigid oxide film is formed 
on the heat treated surface of the metal cap or the first metal pipe, and 
therefore the characteristic of the temperature detecting element does not 
deteriorate due to forming of an oxide film by depriving of oxygen in the 
temperature detecting element during use or release of undesired gas from 
the metal cap or from the first metal pipe surface. 
The invention according to claim 8 of the invention relates to a 
temperature detecting apparatus as set forth in claim 1 wherein a bump is 
formed in one of a fitting portions of the first metal pipe or the metal 
cap and a recess to be fitted with the bump is formed in the other of the 
fitting portions of the first metal pipe or the metal cap, whereby the 
metal cap of flat shape can be mounted correctly on the temperature 
detecting element of a same substantially flat shape, and hence damage of 
the temperature detecting element can be prevented and the improvement of 
heat response performance obtained by combination of the flat shapes will 
not be impeded. 
The invention according to claim 14 of the invention relates to a 
temperature detecting apparatus wherein a recess is formed between the 
first and second metal wires of the temperature detecting element in a 
substantially flat shape, wherein the recess formed on the surface of the 
temperature detecting element can prevent significant drop of insulation 
resistance between the metal wire and metal cap which may be caused as a 
result of contact of the surface of the temperature detecting element with 
the inner surface of the metal cap in a plane state. 
The invention according to claim 15 of the invention relates to a 
temperature detecting apparatus forming a protrusion projecting toward the 
temperature detecting element side in a flat portion of the metal cap 
confronting the temperature detecting element, wherein such formation of a 
protrusion in the metal cap does not allow this protrusion to contact in a 
plane state if contacting with the temperature detecting element in a spot 
state, thereby preventing significant lowering of insulation resistance 
between the metal cap and metal wire. 
The invention according to claim 16 of the invention relates to an 
automobile comprising a temperature detecting apparatus as set forth in 
claim 1 disposed in an emission route, wherein various adequate controls 
can be effected corresponding to the emission temperature detected by the 
temperature detecting apparatus of excellent heat response performance. 
The invention according to claim 17 of the invention relates to an 
automobile as set forth in claim 16 wherein the temperature detecting 
apparatus is disposed so that the width direction (longitudinal direction) 
of the temperature detecting element in a flat shape confronting the 
emission route coincides with the flow direction of emission, whereby the 
emission flows at both sides of the first metal pipe of flat shape, and 
the first metal cap receives heat in a wide area, so that the heat 
response performance may be further enhanced, thereby realizing a more 
adequate control for the automobile. 
The invention is also directed to a method of detecting temperature of our 
(an) environment with the apparatus of the invention. The environment may 
be automobile emissions, liquid or gas. The invention according to claim 
19 relates to such a method, comprising inserting the temperature 
detecting apparatus into the environment and recording the temperature by 
visual observation or electronic or mechanical means, such as by a 
computer or mechanical sensor. The apparatus comprises a first metal pipe, 
a first metal wire and a second metal wire placed in the first metal pipe, 
at least one end of the first metal wire and at least one end of the 
second metal wire being projected from one end of the first metal pipe, an 
insulator for keeping an electric insulation of the first metal pipe and 
the first metal wire and the second metal wire in the first metal pipe, a 
temperature detecting element projecting out of one end of the first metal 
pipe and disposed between the ends of the first metal wire and the second 
metal wire, and a metal cap fitted to one end of the first metal pipe for 
covering the temperature detecting element, wherein the temperature 
detecting element has a substantially flat shape longer in the length in 
the direction between the first and second metal wires (width dimension) 
than the length in the direction at right angle to the width dimension, 
and a portion of the metal cap confronting the temperature detecting 
element has a substantially flat shape in substantially the same direction 
and a shape substantially similar to the temperature detecting element. 
The invention according to claim 21 is directed to a method, as set forth 
in claim 19 wherein in the apparatus a bump is formed in one of a fitting 
portions of the first metal pipe or the metal cap and a recess to be 
fitted with the bump is formed in the other of the fitting portions of the 
first metal pipe or the metal cap, whereby the metal cap of flat shape can 
be mounted correctly on the temperature detecting element of a same 
substantially flat shape, and hence damage of the temperature detecting 
element can be prevented and the improvement of heat response performance 
obtained by combination of the flat shapes will not be impeded. 
The invention according to claim 12 is directed to such a method wherein in 
the apparatus a recess is formed between the first and second metal wires 
of the temperature detecting element in a substantially flat shape, 
wherein the recess formed on the surface of the temperature detecting 
element can prevent significant drop of insulation resistance between the 
metal wire and metal cap which may be caused as a result of contact of the 
surface of the temperature detecting element with the inner surface of the 
metal cap in a plane state. 
The invention according to claim 25 is directed to such a method wherein in 
the apparatus there is formed a protrusion projecting toward the 
temperature detecting element side in a flat portion of the metal cap 
confronting the temperature detecting element, wherein such formation of a 
protrusion in the metal cap does not allow this protrusion to contact in a 
plane state if contacting with the temperature detecting element in a spot 
state, thereby preventing significant lowering of insulation resistance 
between the metal cap and metal wire.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, embodiments of the invention are described 
in detail below. 
As shown in FIG. 1 to FIG. 3, the temperature detecting apparatus of the 
invention has construction similar to the conventional construction and, 
comprises a first metal pipe 5, a first metal wire and a second metal wire 
3 (also referred to here as "first and second metal wires") accommodated 
in the first metal pipe 5, at least one end of each metal wire being 
projected from one end of the first metal pipe 5, an insulator 4 for 
keeping an electric insulation of the first metal pipe 5 and the first and 
second metal wires 3 in the first metal pipe 5, a temperature detecting 
element 2 projecting out of one end of the first metal pipe 5 and disposed 
between ends of the first and second metal wires 3, and a metal cap 1 
fitted to one end of the first metal pipe 5 for covering the temperature 
detecting element 2. Reference numeral 3 denotes two metal wires, which 
are preferably 0.3 mm in diameter. Substantially around and on the entire 
periphery (or length) of the two metal wires, excluding both ends of the 
two metal wires 3, there is disposed the first metal pipe 5, preferably 
having a cylindrical shape, 2.8 mm in outside diameter, and the spacing 
between the metal wires 3 and the first metal pipe 5 is filled with the 
insulator 4, preferably made of MgO, to form a two-core tube. At each end 
of these two metal wires 3, as shown in FIG. 4 and FIG. 5, the temperature 
detecting element 2 of a substantially flat, and preferably flat shape, is 
connected as shown in FIG. 2 and FIG. 3, and an opening 100 (FIG. 3) of 
the metal cap 1 of a tubular form with a bottom of the opening closed at 
one end so as to accommodate the temperature detecting element 2 is fitted 
by a flange 101 to the outer periphery of one end of the first metal pipe 
5. In one preferred embodiment, the metal cap 1 is made of a material of 
SUS310S of 0.5 mm in thickness. The opening of the metal cap is 
cylindrical, and the closed end side (opposite the opening 100) is in a 
flat shape substantially corresponding to the shape of the temperature 
detecting element 2 as shown in FIG. 2 to FIG. 4. The opening of this 
metal cap 1 is fitted to the outer periphery of one end of the first metal 
pipe 5, and the first metal pipe 5 and the metal cap 1 are joined on the 
circumference by any suitable means, preferably by a weld zone 6 by laser 
welding, and the inside of the metal cap 1 is kept airtight. In one 
specific embodiment, the metal cap 1 has a flat shape as mentioned above, 
and measures 3.8 mm in the width direction (i.e., longitudinal direction 
or direction along axis "x" in FIG. 4), and 2.9 mm in the thickness 
direction (i.e., direction along axis "y" in FIG. 4 which is perpendicular 
to the width direction). Moreover, as shown in FIG. 4 and FIG. 5, in the 
temperature detecting element 2, two tubular electrodes 2b, preferably 
made of platinum material, are buried in the portion of a thermistor 2a of 
a flat shape, and the electrodes 2b penetrate through the thermistor 2a. 
The temperature detecting element 2 is constructed so that the central 
axis of the portion of the thermistor 2a may be parallel to the central 
axis of the electrodes 2b. The temperature detecting element 2 is in a 
flat shape longer in the length (width) in the direction between the first 
and second metal wires (i.e., a direction along the axis "x" in FIG. 4) 
than the length (thickness) in the direction at right angle thereto. In 
one preferred embodiment, the flat shape of the temperature detecting 
element measures 2.4 mm in the width direction (longitudinal direction) 
and 1.5 mm in the thickness direction. As shown in FIG. 2 and FIG. 3, the 
metal wires 3 penetrate inside of the electrodes 2b of the temperature 
detecting element 2, and are electrically connected by welding at the 
leading end of the electrodes 2b. The thickness direction of the 
temperature detecting element 2 in flat shape is designed to substantially 
correspond to (or coincide with) the thickness direction of the metal cap 
1 which has a flat shape. 
The heat response characteristic of the temperature detecting apparatus in 
the above embodiment and the characteristic of the conventional 
temperature detecting apparatus are shown in Table 1. 
TABLE 1 
__________________________________________________________________________ 
Heat Constituent of Tested Sample 
Response Dimension or 
Time Name of Components 
Item Material 
__________________________________________________________________________ 
This 10-11 sec 
metal wire (3): 
diameter 0.3 mm 
Invention first metal pipe (5): 
outer diameter 
2.8 mm 
metal cap (1): material SUS310S 
thickness of material 
0.5 mm 
width 3.8 mm 
thickness 2.9 mm 
temperature detecting element (2): 
width 2.4 mm 
thickness 1.5 mm 
Prior Art 
28-30 sec 
metal wire (27): 
diameter 0.5 mm 
metal pipe (26): 
outer diameter 
4.8 mm 
metal cap (30): 
material SUS310S 
thickness of material 
0.5 mm 
outer diameter 
6.0 mm 
temperature detecting element (29): 
diameter 3.6 mm 
__________________________________________________________________________ 
As known from Table 1, the heat response time is 28 to 30 seconds in the 
prior art, and 10 to 11 seconds in the embodiment of the invention. The 
improved response is achieved by lowering of thermal capacity by reducing 
the size of the metal wires 3, the insulator 4, the first metal pipe 5, 
the metal cap 1, and temperature detecting element 2, flat shape of the 
closed end side of the metal cap 1, and flat shape of the section of the 
temperature detecting element 2 accommodated in the space of the metal cap 
1, so that the heat response performance of 11 seconds or less may be 
assured. The heat response characteristic of 11 seconds or less is 
sufficient to enable the temperature detecting apparatus to be used in 
conjunction with an emission purifying system. 
Next, as schematically shown in FIGS. 1, 6 and 7, each one of the other 
ends of the metal wires 3 is electrically connected with one end of a lead 
wire 10 through a relay terminal 8. Two relay terminals 8 are integrated 
on a terminal fixing element 9 in a state of the leading ends bent at 
right angle as shown in FIG. 6 and FIG. 7. The terminal fixing element 9 
is formed of an insulating resin, and a receiving port 11 in which the 
other end of the first metal pipe 5 is inserted is formed at its leading 
end side, and when the other end of the first metal pipe 5 is inserted 
into this receiving port 11, four ribs 12 shown in FIG. 7 provided inside 
are deformed, and this action causes to fix the other end of the first 
metal pipe 5. That is, the rear end of the first metal pipe 5 is 
press-fitted and fixed in this receiving port 11. Two penetration holes 13 
are provided in the receiving port 11 of the terminal fixing element 9, 
and a partition 14 is provided between them, and the leading ends of the 
penetration holes 13 are expanded toward the partition 14. More 
specifically, the rear ends of the metal wires 3 are separated in the 
partition 14, and penetrate through the penetration holes 13 along the 
slope, and are pushed out onto the respective relay terminals 8. In the 
portions of the relay terminals 8 in which the metal wires 3 are extruded, 
as shown in FIG. 6, two weld zones 15, 16 differing in length are 
provided, and these weld zones 15, 16 are formed by extruding the relay 
terminals 8 at specific interval to the surface sides. Therefore, by 
resistance welding of these extruded metal wires 3, the welding resistance 
in the weld zones 15, 16 is higher than when the weld zones 15, 16 are 
integrated, and the welding resistance of the weld zones 15, 16 is also 
different, and portions having two different weld strengths are obtained, 
so that a secure and redundant structure is realized. Meanwhile, a leading 
end of the lead wire 10 is fixed to the junction 17 at the rear end of the 
relay terminal 8 by welding. 
Moreover, the leading ends of the two relay terminals 8 and two lead wires 
10 are respectively put into two penetration holes of a waterproof tube 18 
of rubber material in order to keep waterproof. This waterproof structure 
is described below, and as shown in FIG. 1, the leading end of the 
waterproof tube 18 abuts against the rear end of the terminal fixing 
element 9, and an aluminum metal fixing tube 19 thinner than the 0.3 mm 
thick second metal pipe 7 is mounted on the outer circumference of this 
portion. In this case, the second metal pipe 7 positioned at the leading 
end side of the terminal fixing element 9 is processed by drawing so that 
the leading end side is reduced in diameter as compared with the terminal 
fixing element 9 as shown in FIG. 1, and hence the leading end of the 
terminal fixing element 9 abuts against the step of the second metal pipe 
7. Therefore, by processing by drawing the second metal pipe 7 positioned 
at the rear end side of the metal fixing tube 19 so as to be reduced in 
diameter over the entire circumference as shown in FIG. 1, the terminal 
fixing element 9 is pressed and fixed to the step 21 through the metal 
fixing tube 19 by this drawn portion 20. In this state, the internal 
waterproof tube 18 is compressed by the drawn portion 20, and hence the 
drawn portion 20, waterproof tube 18, and armor of lead wire 10 are 
compressed. The reduced diameter end portion of the second metal pipe 7 is 
positioned outside of the first metal pipe 5 as shown in FIG. 1, and the 
both are fixed by laser welding 22, and are also kept airtight. In this 
way, the inside of the second metal pipe 7 is kept waterproof. In the 
constitution of fixing the terminal fixing element 9 on the second metal 
pipe 7, if a tensile force is applied to the lead wire 10, its force 
reaches only up to the relay terminal 8 integrated with the terminal 
fixing element 9, and hence no force is applied to the thin metal wire 3 
of 0.3 mm in diameter with the strength of 10 kgf (98N), so that the wire 
may not be broken. 
Incidentally, the rear end of the metal fixing tube 19 is deformed inward 
by the drawn portion 20, and the waterproof tube 18 is provided inside, 
and the portion corresponding to the deformed portion extends up to the 
leading end of the armor of the lead wire 10, so that contact with the 
relay terminal 8 never occurs. 
In FIG. 1, reference numeral 23 is a tube for protection of lead wire. 
Reference numeral 24 is a mounting screw fitted to the second metal pipe 
7, and the temperature detecting element 2 is mounted by this mounting 
screw 24 to confront the high temperature emission. Reference numeral 25 
is a gasket used at this time. 
In FIG. 8, a temperature detecting apparatus A is installed in a catalytic 
purifying apparatus of an emission route B of an automobile, and it is 
intended to control adequately by a controller C in response to the 
emission temperature detected by the temperature detecting apparatus A of 
excellent heat response characteristic. 
The temperature detecting apparatus A is installed so that the width 
direction (longitudinal direction) of the temperature detecting element in 
flat shape may coincide with the flow direction of emission in the 
emission route B, whereby the emission flows at both sides of the first 
metal pipe of flat shape. In this way, the first metal cap 1 receives heat 
in a wide area, and thereby the heat response characteristic may be 
further enhanced, so that a more adequate control for the automobile may 
be realized. 
FIG. 9 and FIG. 10 show a different embodiment relating to a temperature 
detecting apparatus. The metal cap 1 has a portion whose diameter is 
gradually spreading from the closed end side to the opening, and in this 
construction the metal cap 1 can be easily fitted to one end of the first 
metal pipe 5. 
Meanwhile, what is shown in FIG. 9 and FIG. 10 is the temperature detecting 
apparatus in which the forward side of the junction of the metal cap 1 to 
the first metal pipe 5 is in a shape of a flat shape gradually toward the 
closed end, and different from the flat processing of the metal cap 1 
immediately at one end of the first metal pipe 5, which can prevent 
lowering of insulation resistance due to too close of a distance of the 
metal cap 1 and the first and second metal wires 3 at one end of the first 
metal pipe 5. 
Moreover, in the construction in FIG. 9 and FIG. 10, the metal cap 1 is 
gradually reduced in wall thickness from the opening toward the closed 
portion, and since the closed portion side of the metal cap 1 
accommodating the temperature detecting element 2 is thin, the heat can be 
transmitted to the temperature detecting element more quickly, and hence 
the heat response characteristic can be improved also from this respect, 
and such thin wall thickness can be easily formed by drawing process of 
the metal cap 1. 
FIG. 11 to FIG. 13 show another embodiment, in which a bump 1a is formed in 
one of a fitting portion of the first metal pipe and the metal cap, and a 
recess 5a to be fitted with the bump 1a is formed in another of the 
fitting portion of the first metal pipe and the metal cap, at the junction 
of the metal cap 1 and the first metal pipe 5. By a convex-concave 
fitting, the metal cap 1 of flat shape can be correctly mounted on the 
temperature detecting element 2 of similar flat shape, and not only damage 
of the temperature detecting element 2 is avoided, but also it does not 
impede improved heat response characteristic obtained by the combination 
of mutual flat shapes. 
FIG. 14 and FIG. 15 show a further different embodiment of the invention, 
in which a recess 2c is formed in the portion of the temperature detecting 
element 2 between the first and second metal wires 3. The formation of the 
recess 2c in the surface of the temperature detecting element 2, prevents 
the contact of the recess 2c with the inside of the metal cap 1, and hence 
it is effective to prevent significant lowering of insulation resistance 
between the metal wires 3 and metal cap 1 which may result from the 
contact of the surface of the temperature detecting element 2 with the 
inside of the portion of the metal cap 1 in a plane state. 
FIG. 16 to FIG. 18 show another different embodiment, in which a protrusion 
1b projecting toward the side of the temperature detecting element 2 is 
provided in the flat portion of the metal cap 1 confronting the 
temperature detecting element 2, and by thus forming the protrusion 1b on 
the metal cap 1, this protrusion 1b may possibly contact with the 
temperature detecting element 2 in spot state, but will not contact in 
plane state, thereby preventing significant lowering of insulation 
resistance between the metal cap 1 and the metal wires 3. 
Moreover, in all embodiments of the invention, at least one of the metal 
cap 1 and the first metal pipe 5 should be preferably heat treated, before 
welding of metal cap 1 and the first metal pipe 5, at a temperature higher 
than the maximum operating temperature to which the temperature detecting 
apparatus is likely to be subjected. By heat treatment, a rigid oxide film 
can be formed on the heat treated surface of the metal cap 1 or the first 
metal pipe 5. Generally, when a metal is heated in an emission route, 
characteristically, it is oxidized by depleting oxygen from the 
surrounding, or it releases the gas adsorbed on the surface. However, the 
metal on which an oxide film is formed depletes a very small amount of 
oxygen from the surrounding or releases a very small amount of surface 
adsorption gas, as compared with the original metal surface. As a result, 
such a formation of the oxide film is effective to prevent problems 
associated with the deterioration of characteristics of the temperature 
detecting element 2 due to formation of an oxide film when metal is heated 
in the emission route by depleting of oxygen in the temperature detecting 
element 2 during use or release of unnecessary gas from the surface of the 
metal cap 1 or the first metal pipe 5. 
In all embodiments of the invention, it is contemplated that a portion of 
the metal cap which faces the temperature detecting element may have the 
shape and may be located on the metal cap so that it would substantially 
correspond to the shape and location of the temperature detecting element. 
It is also contemplated in all embodiments that the temperature detecting 
element (and thus the portion of the metal cap confronting the temperature 
detecting element) may have either a substantially flat or a flat shape. 
The application of the temperature detecting apparatus of the invention in 
the automobile is described specifically, but various other applications 
are possible. For example, when used in liquid or gas, the temperature 
detecting apparatus may be used as a temperature detecting apparatus 
excellent in thermal response. The invention may be also changed and 
modified in various manners. For example, materials of construction of the 
temperature detecting element and/of the insulator 4 may be changed if 
desired, depending on the environment in which the temperature detecting 
apparatus is used or other factors, apparent to those skilled in the art. 
Furthermore, the shape of the temperature detecting element may be 
changed. Thus, the temperature detecting element may be, triangular, 
trapezoidal or circular in shape. Therefore, modified examples existing in 
the true spirit and scope of the invention are all included in the scope 
of the claims.