TEMPERATURE SENSOR

Abstract

Method for the manufacture of a temperature sensor with a thermocouple comprising the following successive steps: a) introduction, in a support tube made of a ceramic material, of two thermocouple wires until they extend beyond said support tube; b) welding the ends of said thermocouple wires extending beyond said support tube so as to form a thermocouple hot point; c) introduction, at least partially, of the support tube into a reinforcement tube made of a stainless steel; d) fixing a cap onto said reinforcement tube so as to protect said hot point.

Claims

1. A method for the manufacture of a temperature sensor with a thermocouple comprising the following, performed successively: introducing, in a support tube made of a ceramic material, two thermocouple wires until they extend beyond said support tube; welding the ends of said thermocouple wires extending beyond said support tube to form a thermocouple hot point; independently of introducing and welding the thermocouple wires, introducing, at least partially, of the support tube into a reinforcement tube made of a stainless steel; and fixing a cap onto said reinforcement tube to protect said hot point.

2. The method according to claim 1, wherein the support tube is partitioned.

3. The method according to claim 1, wherein the cap is swaged before being fixed onto the support tube.

4. The method according to claim 1, wherein the cap is shaped so as to cover over 90% of the outer lateral surface of the support tube.

5. The method according to claim 1, wherein before fitting the cap, the cap is filled with an insulating material of a material chosen from aluminum and/or magnesium.

6. The method according to claim 1, wherein the cap is made of Inconel.

7. The temperature sensor manufactured by method according to claim 1.

8. The temperature sensor according to claim 7, wherein the temperature sensor is used in an environment at a temperature above 1000° C. and/or in which the temperature can vary between −40° C. and 1200° C.

9. A heat engine of a motor vehicle comprising a temperature sensor according to claim 7.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0055] Further features and advantages of the invention will emerge from the following detailed description and an examination of the accompanying drawings, in which:

[0056] FIG. 1 is a schematic representation of a temperature sensor connected to a measuring device;

[0057] FIG. 2 is a schematic illustration of the principle of operation of a thermocouple;

[0058] FIG. 3 (FIGS. 3a to 3d) shows the method of manufacture of a temperature sensor according to the prior art;

[0059] FIG. 4 (FIGS. 4a to 4d) shows the different steps of a manufacturing method according to the invention.

DEFINITIONS

[0060] “Proximal” and “distal” distinguish the two ends of a temperature sensor according to the invention. The “distal” end is that of the hot point.

[0061] “Hot point” conventionally describes the connection between the two thermocouple wires, regardless of its temperature.

[0062] “Comprising a,” “having a,” or “including a,” means “comprising at least one,” unless stated otherwise.

[0063] Identical reference numerals are used to identify the same parts in the different Figures.

DETAILED DESCRIPTION

[0064] As FIGS. 1 to 3 have been described in the preamble; reference will now be made to FIG. 4.

[0065] Step a) involves passing the two thermocouple wires 10 and 12, designed to form a thermocouple, through one or more longitudinal bores 28 of a support tube 30 made of a ceramic material (FIG. 4a).

[0066] The support tube 30 is shaped so as to guide the thermocouple wires when they are introduced.

[0067] Preferably, the support tube 30 is a profile section, preferably shaped so that the bore or bores 28 have a cross section substantially identical to that of the thermocouple wires that they are designed to receive.

[0068] The support tube 30 can in particular be manufactured by extrusion.

[0069] Preferably, the support tube is partitioned. The partitioning of the support tube 30 advantageously enables any risk of electrical contact between the parts of the thermocouple wires introduced into said support tube to be avoided, even if they are not insulated by means of an electrically insulating sleeve.

[0070] In a variation not shown, the support tube 30 comprises one bore and the thermocouple wires are sheathed by means of an electrically insulating sleeve, thus avoiding any electrical contact between the thermocouple wires inside the support tube 30.

[0071] The thermocouple wires can be flexible or rigid. Preferably they have a substantially circular cross section.

[0072] The thermocouple wires are pushed until they project beyond the distal end 32 of the support tube 30. The projecting parts 40 and 42 of the thermocouple wires are completely or partially stripped so as to allow, in step b), the two thermocouple wires to come into contact.

[0073] The projecting parts 50 and 22 [sic!] of the thermocouple wires 10 and 12 that extend beyond the proximal end 44 can have a length greater than 5 cm, greater than 10 cm, greater than 20 cm, greater than 50 cm. Advantageously, these wires can thus serve as an extension cable 3 so as to electrically connect the temperature sensor 2 to the measuring device 4. Clearly, if the thermocouple wires are used as an extension cable, their projecting proximal end parts 50 and 52 must be electrically insulated. At their proximal end, the thermocouple wires 10 and 12 preferably comprise electrical connection means, for example connection terminals enabling their connection to the measuring device 4.

[0074] At step b), as shown in FIG. 4b, the distal terminal parts 40 and 42 of the thermocouple wires 10 and 12 are then connected to each other, i.e. placed in physical contact and electrically connected, in a final manner, so as to form a hot point 13. The connection is preferably achieved by hot welding.

[0075] At step c), the support tube is introduced into a stainless steel reinforcement tube 60. Step c) can precede step b), or even precede step a).

[0076] At step d), as shown in FIG. 4c, the thermocouple resulting from the connection of the two thermocouple wires is protected by means of a cap 20, preferably made of Inconel.

[0077] The cap 20 can be rigidly fixed to the reinforcement tube by any means, for example by means of an appropriate adhesive, so as to define a hermetic chamber 54 housing the projecting distal parts 40 and 42 of the thermocouple wires. Preferably, the chamber 54 is filled with an insulating material, preferably of powder, arranged in the cap before it is fixed onto the reinforcement tube. The powder insulating material can be in particular an aluminum powder or a magnesium powder.

[0078] Even more preferably, the cap 20 has a swaging 56 preferably extending to the distal end 32 of the support tube 30, as shown. Advantageously, a swaging 56 improves the response time of the sensor.

[0079] Advantageously, the creation of the swaging by means of a cap also improves mechanical strength, and particularly resistance to vibrations, compared to the prior art.

[0080] The swaging 56 can also serve as a mechanical stop facilitating fitting of the cap 20 onto the support tube 30. Even more preferably, the cap 20 comprises, in the extension of the swaging 56, a widened part 58 of a shape substantially complementary to the support tube 30, so that the support tube 30 can guide the cap 20 when it is being fitted.

[0081] Preferably, the support tube 60 extends the cap 20 in order to cover with it at least part, preferably all of the outer lateral surface of the protective sleeve. Preferably, the cap and the reinforcement tube together define an enclosure around the support tube. Preferably, this enclosure is sealed at least in the part of the temperature sensor that extends from the proximal end of the mineral insulated cable to the distal end 62 of the temperature sensor.

[0082] Even more preferably, the bore of the reinforcement tube 60 is of a shape that is substantially complementary to the outer lateral surface of the support tube 30.

[0083] In an embodiment, the cap 20 is fixed to the edge 24 of the distal end of the reinforcement tube 60, as shown in FIG. 4c. In an embodiment, the cap 20 and the reinforcement tube 60 form a monolithic assembly, i.e. the reinforcement tube 60 is made in one piece with the cap 20.

[0084] As it is now clear, the steps of a manufacturing method according to the invention are simple and can be automated. This results in a significant reduction in manufacturing costs.

[0085] Obviously, the invention is not limited to the embodiment described and represented, provided purely for illustrative purposes.