FR2723202A1 - Temp. sensor for use in automobiles - Google Patents

Abstract

The device includes an electrical transducer(100), using a thermistor (102), a protective device (200) generally in form of dome around a thermistor, electrical connections (300) connected to the thermistor output and a plastic body (400) partially moulded over the dome (200), which has on its exterior surface, at the position where it is associated with the over mould (400), raised structures (210) which guarantee sealing and/or positioning between the protective element (200) and the moulded body (400).

Description

 The present invention relates to the field of sensors of physical quantities, in particular temperature sensors.

 Many types of temperature sensors have already been proposed.

 It has in particular been proposed temperature sensors of the type illustrated in Figure 1 attached.

 We see in this figure 1, a sensor comprising a capsule 10 formed of a metal tube 12 closed at one end 11 and which houses a thermistor pad 14 associated with two bristles 15 and 16 for electrical connection. The thermistor 14 is immobilized in the tube 12 by resin 18 or an equivalent overmolding. The bristles 15 and 16 are welded to respective electrically conductive plugs 20 and 22.

These welds are referenced 24 and 26. The same sheets 20 and 22 are welded at 28 and 30 on electrical connection wires 32 and 34. A body 40 of plastic material is overmolded on the assembly thus formed. Then the body 40 molded onto said assembly is placed in a metal case 50. The latter is immobilized on the body 40 by any appropriate means, such as for example by crimping at 52. An O-ring 54 provides sealing between the body 40 and the housing 50. The housing 50 preferably comprises a threaded barrel 56 and a part of hexagonal section 58 adapted for the tightening of the thread was 56 in a complementary bore. The housing 50 has bores 59 facing the zone of the tube 12 which houses the thermistor 14.

A mass of resin 60 seals the wires 32, 34, while a resin seal 70 seals between the tube 12 and the overmolded body 40.

 However, the sensors of the type shown in the attached FIG. 1 are not entirely satisfactory. In particular, these known sensors have a very complex structure.

 The present invention now aims to improve the known sensors.

 An important object of the present invention is to improve the sealing of the sensor.

 An important aim of the present invention is in particular to propose a new simplified structure sensor.

 Another important object of the present invention is to propose a new sensor making it possible to integrate into different types of assembly.

 Another important object of the present invention is to propose a new sensor of perfectly mastered dimensions for automatic mounting.

 Another important object of the present invention is to propose a new sensor making it possible to reduce its dimensions, therefore to improve the thermal gradient and the response time.

 Another important object of the present invention is to propose a new sensor which makes it possible to measure the temperature of a liquid or a gas without difference.

 These various aims are achieved within the framework of the present invention by means of a sensor, in particular of temperature, of the known type comprising an electrical transducer, for example a thermistor, a protection member in the general shape of a bulb which surrounds the electrical transducer electrical connection means connected to the output terminals of the electrical transducer and a plastic body overmolded at least partially on said protective member, characterized in that said protective member comprises on its outer surface and at its end associated with the overmolded body, relief structures which guarantee sealing and / or positioning between the protective member and the overmolded body.

 Other objects, characteristics and advantages of the present invention will appear on reading the detailed description which follows and with reference to the appended drawings given by way of nonlimiting examples and in which - Figure 1 previously described represents a schematic view in section of a sensor according to the state of the art, - Figure 2 shows a longitudinal section view of a bulb according to the present invention, - Figure 3 shows a cross-sectional view of the same bulb of the Figure 2, according to the sectional plane referenced III-III in Figure 2, - Figure 4 shows a longitudinal sectional view of a bulb according to another alternative embodiment of the present invention, - Figure 5 shows a view in cross section of the same bulb of FIG. 4, according to the cutting plane referenced VV in FIG. 4, - Figures 6, 7 and 8 represent three alternative embodiments of structures in relief provided on a bulb according to the present invention to ensure the seal between it and a molded plastic body, - Figure 9 shows an alternative embodiment of the end of a bulb according to the present invention comprising such relief structures, - Figure 10 shows an end view of the same bulb, - Figures 11, 12, 14 and 15 show views in longitudinal section of four sensor variants according to the present invention, Figure 13 showing a partial end view of a connector body used in the context of the embodiment of FIG. 12, - Figures 16 and 17 show two orthogonal views between them of connection strips used in the context of an embodiment of the present invention, while FIG. 18 represents a sectional view of the same lamellae according to the cutting plane referenced XVIII-XVIII in FIG. 16, - Figures 19 and 20 represent ent two orthogonal views between them of the same connection strips after sectioning of connecting bridges between them, and - Figures 21 and 22 show two views in longitudinal section of sensors according to the present invention before making the overmolded body.

 As indicated above, the sensor according to the present invention essentially comprises - an electrical transducer 100, preferably formed of a thermistor, - a protective member 200 in the general shape of a bulb which surrounds the electrical transducer 100, - means 300 for electrical connection, connected to the output terminals of the electrical transducer 100 and - a body 400 of plastic material molded at least partially on said protective member 200.

 Furthermore, according to an important characteristic of the present invention, said protective member 200 comprises on its outer surface and at its end associated with the overmolded body 400, structures 210 in relief which guarantee sealing and / or positioning between the protection body 200 and the overmolded body 400.

In the appended figures the thermistor 100 is composed of a disc or a plate 102 comprising two bristles 104, 106 for connection which constitute the output terminals thereof. These bristles 104, 106 are advantageously made of steel. The thermistor pad 102 can be of the CTN type (Negative Temperature Coefficient thermistor) or of the type
PTC (Positive Temperature Coefficient Thermistor).

 The bulb-shaped protective member 200 can be the subject of several alternative embodiments.

 According to the embodiment shown in Figure 2, this protective member 200 is formed of metal, for example stainless steel, aluminum or brass. More specifically, the protective member 200 shown in FIG. 2 is formed by a sleeve 201 closed at one end by a transverse wall 202 and comprising on its second end, ie near its opening contour 204, the means 210 cited above. According to Figure 2 these means 210 are thus formed of an annular collar, generally planar, transverse to the axis of the sleeve, projecting from its outer surface.

 In addition, this sleeve 201 is filled with an electrically insulating heat transfer product 206, for example with a resin, in which the thermistor 102 is placed.

 The thermistor 102 is placed in the sleeve 201, near the transverse wall 202 of the latter, inside the coolant 206. Of course the bristles 104 and 106 emerge outside of the coolant 206 and the sleeve 201, by the opening contour 204 thereof.

 As a variant, the sleeve 201 shown in FIG. 2 can be produced not from metal, but from plastic, for example from thermoplastic or thermosetting material.

 According to the embodiment shown in Figure 4, the protective member 200 may be formed not of a sleeve receiving a heat transfer product in which the thermistor 102 is bathed, but only of a body 208, for example made of plastic , overmolded on the thermistor 102 and part of the bristles 104 and 106. Here again this body 208 is provided with structures 210 designed to ensure the seal and / or the relative positioning between the protective member 200 and the overmolded body 400. According to the embodiment shown in FIG. 4, these structures 210 are formed of an annular flange molded on the outer periphery of the body 208.

Figures 3 and 5 illustrate the possibility of placing not a single thermistor 102 in a protective member 200, but several juxtaposed thermistors, for example two thermistors, such as a
CTN and a CTP. More precisely still, the two thermistors 102 can be placed in compartments separated by a partition 201 coming from the protective member 200, as seen in FIG. 5.

 The protective member 200 may typically have a length of the order of 15mm. It can moreover be symmetrical in revolution, for example with an average diameter of the order of 3 mm or else have an oblong cross section, for example of the order of 3 × 7 mm as seen in FIGS. 3 and 5.

 The aforementioned structures 210 intended to ensure the seal and / or the relative positioning between the protective member 200 and the overmolded body 400 can be the subject of numerous embodiments.

 According to the embodiment shown in Figure 6, these structures 210 are formed of annular corrugations 212 distributed over the length of the sleeve 201 in the vicinity of the end thereof through which emerge the bristles 104, 106. It can s 'Act for example two corrugations generally sinusoidal section as shown in Figure 6, without the invention being limited to this form or this particular number. Such undulations 212 or waves make it possible to improve the adhesion and the seal between the protective member 200 and the overmolded body 400. They also serve to delimit the stop of overmolding, that is to say the end of the overmolded body 400, avoiding that the material of the overmolding goes beyond these corrugations 212. Of course such corrugations can also be provided on the external surface of a protective member 208 formed by molding of plastic material as illustrated in Figure 4.

 According to the embodiment shown in FIG. 7, these structures 210 are formed by a flange 214. This flange 214 has the shape of a flat crown, perpendicular to the axis of the protective member 200 (which axis is referenced 0-0 in the appended figures) projecting from the external surface of this member 200, in the vicinity of its end through which the bristles 104, 106 emerge. Such a flange 214 can be provided both on a sleeve 201 conforming to the mode of embodiment of FIG. 2, that on an overmolded body 208 according to the embodiment of FIG. 4. Such a flange 214 makes it possible in particular to ensure the positioning and the centering of the protective member 200 during the overmolding operation of the body 400, as well as stopping the plastic material composing this body 400.

 We find in the embodiment shown in Figure 8, a flange 214 conforming to that of Figure 7. However according to Figure 8, the means 210 are complemented by an annular rib 215 projecting from the outer surface of the member protection 200, at a distance from the flange 214. The flange 2 14 and the rib 215 thus delimit between them an annular groove 216 designed to allow hooking on a connection (for example of the type illustrated in FIGS. 16 to 20) or a equivalent member, so as to form a rigid sub-assembly, easy to introduce into a mold for the production of the overmolded body 400.

 We find in the embodiment of Figures 9 and 10, a flange 214 projecting from one end of the protective member 200. However according to this embodiment of Figures 9 and 10, said flange 214 is not symmetrical of revolution but, on the contrary, has localized cutouts 217. These cutouts 217 are designed to allow harpooning connections or equivalent means on the bulb 200 in order to form a rigid and moldable sub-assembly in a manner comparable to FIG. 8. It can for example, two diametrically opposite cutouts 217 which open onto the outer periphery of the flange 214, without however the invention being limited to this arrangement or to this particular number.

 The mounting of the protective member 200 itself in the final sensor, in particular in the overmolded body 400, can be the subject of numerous variants.

 Found in the embodiment shown in Figure 11, a sensor according to the present invention comprising the protective member 200 which houses the thermistor 100, the connecting strips 300 and the molded body 400. However, this sensor further comprises a threaded insert 500 and a connector body 600 preformed. The insert 500 is preferably made of metal, although as a variant it may if necessary be made of plastic. The connector body 600 is advantageously made of plastic. The insert 500 is generally symmetrical in revolution. On its outer surface it includes a threaded barrel 502 which remains accessible on the outer surface of the sensor after the overmolded body 400 has been made to allow said sensor to be fixed by screwing in a complementary tapped bore, and a flange 504 projecting from its outer surface and comprising localized lights 505 designed to receive latching structures 610 coming from the connector body 600. Internally the insert 500 has a chamber 506 whose internal diameter is complementary to the external diameter of the flange 214 provided on a protective member 200 , to receive the latter, which chamber 506 opens onto an axial end of the insert 500 and is extended by a channel 508 which opens onto the second axial end of the insert 500 and has a diameter complementary to the external envelope of the protective member 200, as can be seen in FIG. 11. Thus when the bulb of the protection 200 is engaged in the insert 500, this bulb emerges outside said insert 500, through the channel 508, and the collar 610 rests on the recess formed between the bottom of the chamber 506 and this channel 508. The collar 610 consequently makes it possible to center the protective member in the insert 500. It also makes it possible to limit the flow of the plastic material making up the overmolded body 400, inside the chamber 506, that is to say that it prevents this material from flowing between the outer wall of the protective member 200 and the wall of the channel 508, as can be seen in FIG. 11. The connector body 600 is itself molded onto the strips 300. Of course these strips 300 must emerge respectively on either side of this connector body 600, on one side in a connector chamber 602 accessible outside of the latter for connection with a member on the other side e n view of a connection on the bristles 104, 106 of the thermistor 100. The connector body 600 further comprises the aforementioned snap-fastening structures 610 capable of cooperating with the insert 500.

According to FIG. 11, these structures 610 consist of two tongues, each provided at the end with a snap-toothing 612 capable of cooperating with the aforementioned slots 505 of the insert 500. These structures 610 provide temporary support and positioning of the body connector 600 on the insert 500. These snap-fastening structures 610 can be the subject of numerous variant embodiments. They can for example be formed as a variant of teeth tongues integral with the insert 500 and designed to penetrate into complementary slots provided on the connector body 600. To produce the sensor shown in FIG. 11, the procedure is essentially as follows. After placing the thermistor 100 in the protective member 200 and making the insert 500 and the connector body 600, the protective member 200 is engaged on the insert 500 as indicated above, then the bristles 104 and 106 of the thermistor 100 are fixed respectively on the strips 300 of connector body 600 at 105 and 107. I1 can for example be a fixing by welding by adding metal or by electric welding.

The assembly thus obtained is then placed in the cavity of a mold for the production of the overmolded body 400. Preferably this body 400 fills the chamber 506 with the insert 500 and the space between the insert 500 and the connector body 600. It also at least partially covers the external surface of this insert 500 and of the connector body 600, as can be seen in FIG. 11. Preferably this body 400 has locally a non-symmetrical hexagonal or equivalent section 410 of revolution, facilitating the rotational training of the sensor for its assembly by screwing.

 We find in Figure 12 an alternative embodiment of the sensor comprising a protective member 200 which houses a thermistor 100, a connector body 600 molded on strips 300, a molded body 400 and a threaded insert 500. However according to Figure 12 the insert 500 is formed by a simple threaded sleeve on a part of its outer surface and which receives in its internal chamber 506 an extension 620 of the connector body 600 on which the protective member 200 is mounted. This extension 620 thus that the shape adapted to support the protective member 200 can be the subject of numerous embodiments. It may be for example, without this form being limiting, of two arms 622 coming from the connector body 600 and which carries an open or closed ring 624 whose internal diameter is complementary to the external envelope of the member protection 200. To form the sensor of FIG. 12, the protection member 200 is first placed on the shape 624 of the connector body 600, then after having welded the bristles 104 and 106 on the strips 300, the sub-assembly thus formed is placed in the insert 500 and this assembly is itself introduced into the overmolding cavity for the production of the overmolded body 400. This body 400 fills the internal chamber of the insert 500. It also covers the area of connection between the insert 500 and the connector body 600. Preferably the body 400 has a hexagonal or equivalent cross section 410, on a part of its outer surface.

 FIG. 14 shows an alternative embodiment of a sensor according to the present invention comprising a connector body 600 comparable to FIG. 12, but on the other hand devoid of a threaded insert 500. According to this variant, the protective member 200 is positioned on the connector body 600 and the bristles 104 and 106 are welded to the strips 300, as described above with reference to FIG. 12. Then the assembly obtained is placed directly in the overmoulding cavity for the production of the overmolded body 400. And this body 400 itself has, from molding, fixing forms, such for example and without this provision being limiting, snap-fitting structures 430. De such snap-on structures 430 can be the subject of numerous variant embodiments. They will therefore not be described in detail below.

 FIG. 15 shows another variant embodiment of the sensor according to the present invention comprising neither connector body 600 nor threaded insert 500. According to the variant embodiment of FIG. 15, the bulb 200 of the protection member is supported by a plug 310 which can be secured at the origin of the connection strips 300. After having placed the bulb 200 on this sheet 3 10 and having welded the bristles 104 and 106 on the strips, the sub-assembly thus formed is introduced into the cavity of a mold for the production of the overmolded body 400. Preferably the latter comprises fixing structures which have come from molding, such as snap-fastening structures, as indicated above for FIG. 14. The body overmoulded 400 thus produced can be the subject of numerous variant embodiments.

For this reason, the geometry of the body 400 shown in FIG. 15 will not be described in more detail below.

 FIGS. 16 to 18 show a strip 350 comprising clusters of connection strips 300 and of plug 310 capable of supporting a protective member 200. More precisely, each cluster preferably comprises two connection strips 300 and a plug 310.

The plug 310 has a structure 312, such as an open or closed ring of internal diameter complementary to the external envelope of the protective member 200, to support the latter. More precisely, this structure 312 is adapted to allow precise positioning of the bulb 200 on the plug 310 while eliminating all the degrees of relative freedom between them. The use of such a strip 350 makes it possible to set up the protective members 200, automatically, on the sheets 310, as well as an automatic connection by welding the bristles 104 and 106 on the strips 300. Of course the bridges of connection 320 and 322 which exist between two adjacent connection clusters on the one hand and between the plug 310 and the strips 300 on the other hand must be broken before the closing of the mold used for the production of the overmolded body 400. The strips 300 and the plug 310 are shown in a separate position in FIGS. 19 and 20.

 FIG. 21 shows another alternative embodiment of a sensor according to the present invention devoid of insert 500 and connector body 600. According to FIG. 21, the bulb of the protective member 200 is supported not by a sheet 310 independent of the strips 300, but by these strips 300 themselves. More precisely in this case the bulb of the protective member 200 is advantageously of the type illustrated in FIGS. 9 and 10 and each of two connection strips 300, initially connected together by a breakable connecting bridge 320, has a toothing 302 for attachment by snap-fitting or harpooning in a slot 217 of the flange 214.

After having operated an assembly of the bulb 200 on the lamellae and having fixed the bristles 104 and 106 on the lamellae 300, the assembly thus formed is positioned in a mold with a view to producing the body 400 by overmolding. Again it is necessary to break the bridge 320 before closing the mold. All these operations are preferably carried out automatically.

 FIG. 22 shows another alternative embodiment of a sensor sub-assembly intended to be placed in a molding cavity for the formation of an overmolded body 400 for the production of a sensor conforming to the present invention. According to FIG. 22, this sub-assembly comprises a protective member 200, the bulb 201/208 of which can be metallic or plastic, a cassette 700 and two connection blades 300. According to FIG. 22, the exterior surface of the bulb 201/208 has the particularity of having annular grooves 209. These, which can be the subject of a large number of variants as to their geometry and / or their dimensions, are intended mainly to improve the heat exchange, to guarantee a good resistance in the mold used for the subsequent production of the overmolded body 400 and guarantee a good seal. The strips 300 can be fixed to the cassette 700 by any suitable means, for example by spear-fishing as seen in FIG. 22, or even by any equivalent means. As a variant, the cassette 700 can for example be overmolded on the strips 300.

The protective member 200 is also supported on the cassette 700 by any suitable means, for example by means comparable to those shown in Figures 16 to 20. After placing the member 200 on the cassette 700, fixed the strips 300 on the cassette 700 and welded the bristles 104 and 106 on these strips 300, the sub-assembly thus obtained is placed in the cavity of a mold for the production of the overmolded body 400. Preferably this overmolded body 400 also incorporates various forms of fastening, such as snap-on, snap-on fastening forms, or a groove for receiving a fastening clip. Again, the operations of assembling the member 200 on the cassette 700, of welding the bristles 104 and 106 and of assembling the strips 300 as well as the operation of overmolding the body 400 can be carried out entirely automatically.

 Of course the present invention is not limited to the particular embodiments which have just been described, but extends to all variants in accordance with its spirit.

 According to the embodiment shown in FIG. 11, the overmolded body 400 covers only the rear face of the flange 214 and of the protective member 200. On the other hand, according to the embodiment shown in FIGS. 12, 14, 15, 21 and 22 the overmolded body 400 covers a larger part of the rear region of the protection member. Of course, the methods of covering the protective member 200 by the overmolded body 400 can be the subject of other alternative embodiments.

 According to a variant, the thread used for fixing the sensor can be obtained by molding on the body 400.

Claims (24)

 1. Sensor of physical quantity, in particular of temperature, of the known type comprising an electrical transducer (100), a protection member (200) in the general shape of a bulb which surrounds the electrical transducer (100), means (300) of connection electric connected to the output terminals of the electric transducer (100) and a body (400) of plastic material molded at least partially on said protection member (200), characterized in that said protection member (200) comprises on its surface exterior and at its end associated with the overmolded body (400), raised structures (210) which guarantee sealing and / or positioning between the protective member (200) and the overmolded body (400).  2. Sensor according to claim 1, characterized in that the electrical transducer (100) comprises at least one thermistor (102).  3. Sensor according to one of claims 1 or 2, characterized in that the protective member (200) is formed of a sleeve (201) closed at one end by a transverse wall (202) and comprising on its second end, that is to say near its opening contour (204), the projecting structures (210) ensuring the sealing and / or positioning and of a heat-transfer product (206) such as a resin, which fills the sleeve (201) and in which the transducer (100) is placed.  4. Sensor according to one of claims 1 or 2, characterized in that the protective member (200) is formed of a body (208) molded onto the electrical transducer (100) and part of the output terminals (104, 106) of it.  5. Sensor according to one of claims 1 to 4, characterized in that the protective member (200) is formed of metal, for example stainless steel, aluminum or brass, or plastic, for example material thermoplastic or thermosetting.  6. Sensor according to one of claims 1 to 5, characterized in that the structures (210) sealing and / or positioning are formed of annular corrugations (212) distributed over the length of the member protection (200).  7. Sensor according to one of claims 1 to 5, characterized in that the structures (210) ensuring the tightness and / or the positioning are formed of a collar (214) in the form of a flat, perpendicular crown to the axis of the protective member (200) projecting from the outer surface of this member (200).  8. Sensor according to one of claims 1 to 7, characterized in that the structures (210) sealing and / or positioning comprise at least one annular groove (216) on the outer surface of the member protection (200), adapted for attachment to a complementary member (312).  9. Sensor according to claim 8, characterized in that the groove (216) is formed between an annular rib (215) and a flange (214) projecting from the outer surface of the protection member (200).  10. Sensor according to one of claims 1 to 9, characterized in that the structures (210) ensuring the sealing and / or positioning comprise cutouts (217) formed in a flange (214) projecting to allow a fixing of the protection member (200) on a support (300).  11. Sensor according to one of claims 1 to 10, characterized in that it further comprises a connector body (600) overmolded on contact strips (300) to which the output terminals (104, 106) of the electrical transducer (100).  12. Sensor according to one of claims 1 to 11, characterized in that it further comprises a threaded insert (500).  13. Sensor according to claim 11 taken in combination with claim 12, characterized in that the connector body (600) is fixed to the threaded insert (500).  14. Sensor according to claim 13, characterized in that the connector body (600) is fixed to the insert (500) by harpooning.  15. Sensor according to claim 12, characterized in that the protective member (200) is placed on the insert (500).  16. Sensor according to claim 11, characterized in that the protective member (200) is placed on the connector body (600).  17. Sensor according to one of claims 1 to 16, characterized in that the body (400) of plastic material is molded onto a threaded insert (500) and a connector body (600).  18. Sensor according to one of claims 1 to 16, characterized in that the body (400) of plastic material is molded onto a connector body (600).  19. Sensor according to one of claims 1 to 16, characterized in that the plastic body (400) is molded onto a set of strips (300) to which the output terminals (104, 106) of the electrical transducer (100).  20. Sensor according to one of claims 1 to 16, characterized in that the body (400) of plastic material is overmolded on a cassette (700) adapted to receive the protective member (200) and connecting strips (300).  21. Sensor according to one of claims 1 to 20, characterized in that the protective member (200) is fixed on at least one strip (300, 310) initially connected to a strip of strips (300) by l 'via a breakable bridge (320).  22. Sensor according to claim 21, characterized in that the protective member (200) is fixed on at least one strip (300) by harpooning.  23. Sensor according to claim 21, characterized in that the protective member (200) is engaged on a ring (312) linked to a strip (300).  24. Sensor according to one of claims 1 to 23, characterized in that the protective member (200) has ridges (209) on its outer surface.