A novel type of temperature probe and method for manufacturing such a probe

Abstract

The invention relates to a method for manufacturing a temperature probe (1), the method comprising first providing an active subassembly comprising a pair of electrically conductive strips (11) and a heat-sensitive element (12) attached to each of these strips (11), the heat-sensitive element (12) being attached in the vicinity of one of the longitudinal ends (110; 111) of the strips, and then producing a first overmolding (20) around at least a portion of the active subassembly (10) by injecting material into a first mold. This first mold comprises a first portion in which the strips are held during injection, the strips being held in a region away from their longitudinal ends (110; 111), and a second portion comprising an axisymmetric, demoldable cavity, in which the heat-sensitive element (12) is positioned during injection. Finally, a second overmolding (30) is produced around at least a portion of the first overmolding (20) in order to obtain a casing (20; 30) in the form of an immersion body.

Description

[0001] A new type of temperature probe and a method for manufacturing such a probe

[0002] The invention relates to a method for manufacturing a temperature probe, particularly for measuring the temperature of a fluid, and more specifically, a thermal regulation fluid in a motor vehicle. This could include, in particular, a probe for measuring the temperature of the coolant in a battery pack. The invention further relates to such a temperature probe.

[0003] Probes of the aforementioned type generally comprise at least one pair of connecting blades, also called tabs in the technical field, a temperature-sensitive element electrically connected to each of these blades, and a casing that surrounds at least part of the connecting blades and the temperature-sensitive element. At least part of the casing may take the form of what is called a immersion body, that is, a shape that allows the probe to be mounted, via its body, in a pipe or tank, for example, in contact with the fluid whose temperature is to be measured.

[0004] Typically, temperature probes are made up of several parts or components. The temperature-sensitive element is inserted into a hollow body, most often made of metal or plastic. Thermally conductive material, in the form of a paste or resin, is generally added to fill the air gaps between the temperature-sensitive element and the body. This ensures efficient thermal conduction between the hollow body and the temperature-sensitive element, which greatly improves the probe's accuracy and responsiveness.

[0005] EP 1 707930 Al discloses, for example, a temperature sensor comprising a subassembly integrating the temperature-sensitive element, the connecting tabs, and a support for these tabs, which is inserted into the hollow body of the sensor. Thermally conductive material is then placed in the hollow body so as to enclose the temperature-sensitive element.

[0006] Temperature probes of this type have a relatively high manufacturing cost due to the significant time required for the various assembly steps. The use of a seal between the temperature-sensitive element and the hollow body can lead to leaks if the seal is not properly installed.

[0007] Furthermore, adding the thermally conductive material often proves problematic. It is a messy operation that must be carefully controlled to achieve proper filling without air bubbles. The time required for the material to polymerize further lengthens the probe's manufacturing process.

[0008] Recently, temperature probes have also become available in which the immersion-shaped body is molded around at least part of the connecting blades and the temperature-sensing element, in direct contact with them. Probes of this type are easier to manufacture, primarily because the number of assembly steps is reduced. Direct overmolding also eliminates the need for paste or resin, while ensuring good thermal conductivity between the body and the temperature-sensing element.

[0009] FR 3 035 212 Al, on behalf of the Applicant, discloses, for example, a manufacturing process for a temperature probe in which the temperature-sensitive element and the tabs undergo two overmoldings. The tabs are connected by a material bridge, such that the assembly has an H shape. This material bridge maintains the tabs at the correct mutual spacing during the first overmolding, which corresponds to shaping a connecting part of the probe near one longitudinal end of the tabs. After this first overmolding, the H-shaped bridge is cut. The second overmolding is then performed, which completes the casing, including the part protecting the temperature-sensitive element. Probes of this type are generally satisfactory, particularly with regard to their manufacturing process.

[0010] However, the material bridge corresponding to the horizontal bar of the H shape can sometimes pose difficulties during probe manufacturing. For example, cutting this bridge requires a specific tool within the mold, resulting in a more complex mold that is more likely to cause development or maintenance challenges. Furthermore, this cutting process generates a metal chip as waste, which must be properly disposed of. Otherwise, there is a risk of electrical contact between the tabs or damage to the mold. The H shape also creates significant material waste during its production, leading to inefficiency and increased manufacturing costs.

[0011] The Plaintiff sought to improve this situation.

[0012] A method for manufacturing a temperature probe is proposed, particularly for measuring the temperature of a thermal management fluid in a motor vehicle. This probe comprises at least one pair of connecting blades and a temperature-sensitive element electrically connected to each of the connecting blades, as well as a housing, at least partially shaped like a plunger, molded around at least a portion of the blades and the temperature-sensitive element, in direct contact with them. The method comprises the following steps:

[0013] a. provide an active sub-assembly comprising a pair of electrically conductive blades and at least one thermosensitive element attached to each of these conductive blades, in the vicinity of one of the longitudinal ends of these blades; b. carry out a first overmolding around at least part of the active sub-assembly by injecting material into a first mold, this first mold comprising at least a first part in which the blades are held during injection, in an intermediate zone, away from the longitudinal ends of these blades, and a second part, adjacent to the first, comprising an axisymmetric and demoldable cavity, in which the thermosensitive element is positioned during injection;

[0014] c. perform a second overmolding around at least part of the first overmolding, by injecting material into a second mold to obtain the envelope.

[0015] According to the proposed process, the probe casing is planned to be produced in at least two successive overmolding stages. At each of these stages, the correct positioning of the heat-sensitive element within the overmolding is ensured.

[0016] This positioning is achieved in particular by maintaining, at least during the first overmolding, the electrically conductive blades in an intermediate zone of these blades, away from their longitudinal ends, and by providing an axisymmetric and demoldable cavity, in which the thermosensitive element, welded to a longitudinal end of these blades, is positioned during the injection of material.

[0017] In this respect, the proposed method differs from the prior art, in which the conductive blades are generally held only at one end. The Applicant highlighted a significant risk, in this case, of deformation of the metal blades, particularly due to the injection pressure of the plastic material.

[0018] If the blades are deformed, correct and / or repeatable positioning of the temperature-sensitive element within the casing cannot be guaranteed. This generally necessitates increasing the thickness of the casing, at least around the temperature-sensitive element, to ensure that the element does not ultimately come into contact with the probe's surface (risk of fluid ingress and short circuit). This additional thickness impairs heat exchange with the fluid being measured and reduces the probe's responsiveness and accuracy. By incorporating measurements that guarantee correct and repeatable positioning of the temperature-sensitive element within the casing, the proposed method results in improved probe performance, accuracy, and responsiveness.The proposed process further involves manufacturing the active subassembly of the probe, comprising a pair of electrically conductive blades and at least one temperature-sensitive element attached, notably by welding, to each of these conductive blades, prior to the overmolding process. This reduces the time between the first and second overmoldings: the material of the first overmolding thus retains a temperature close to its demolding temperature when the second overmolding is performed. This results in better adhesion of the second overmolding to the first. In this respect as well, the proposed process differs from conventional processes, for example, known from FR 3 035212 Al, in which the temperature-sensitive element is welded to the blades after the first overmolding and before the second. This welding requires handling the blank between overmoldings, which generally leads to complete cooling of the material of the first overmolding.To overcome this drawback, it is known to steam the blank before repositioning the part in the mold for the second overmolding. However, steaming lengthens and complicates the manufacturing process.

[0019] Optional features of the invention, complementary or alternative, are set out below.

[0020] The axisymmetric and demoldable cavity of the second part of the first mold includes an axial segment generally cylindrical, close to the first part of the first mold, and an axial segment generally frustoconical, which extends the cylindrical segment away from the first part of the first mold.

[0021] In step b., at least one area with reliefs is made in the first overmolding, and, in step c, the first overmolding is positioned in the second mold by means of at least one area of ​​the second mold whose shape is at least partially complementary to the area with reliefs of the first overmolding.

[0022] In step b., one or more ribs are made, and, in step c., these ribs are remelted in the second overmolding by the material injected during this second overmolding. In step b., the first overmolding leaves at least one area free of material giving access to at least part of the intermediate zone of the blades, and in step c., the second overmolding fills each area free of material from the first overmolding.

[0023] At step b., the axial segment, generally cylindrical, is able to form at least partially a cylindrical bearing surface in the first overmolding, while at step c., the second overmolding leaves at least part of this cylindrical bearing surface free of material.

[0024] In step b., a frustoconical portion is formed in the first overmolding, which at least partially surrounds the heat-sensitive element, and, in step c., the second mold includes a cavity having an axial segment which is generally frustoconical, while the frustoconical portion which surrounds the heat-sensitive element is positioned in this axial segment.

[0025] In step b., the first part of the first mold includes at least one cavity in which the blades are positioned during injection, and this first part further includes one or more pins which protrude into said cavity and hold the blades there.

[0026] In step c., the second overmolding surrounds a terminal portion of the first overmolding, in which the heat-sensitive element is located.

[0027] A temperature probe is also proposed, particularly for measuring the temperature of a thermal regulation fluid in a motor vehicle. This probe comprises at least one pair of connecting blades and a temperature-sensitive element electrically connected to each of the connecting blades, as well as a housing in the shape of a plunger body, molded around at least part of the blades and the temperature-sensitive element, in direct contact with them.The envelope consists of a first overmolding around at least part of the active subassembly, this first overmolding having at least one free area of ​​material giving access to at least one of the connecting blades and an axisymmetric and axially demoldable end portion surrounding at least the heat-sensitive element, and a second overmolding around at least part of the first overmolding, this second overmolding filling each free area of ​​material of the first overmolding and surrounding at least part of said end portion.

[0028] Optionally, the axially demoldable axisymmetric end portion of the first overmolding has a cylindrical bearing surface forming the bottom of an annular groove, while the second overmolding has a shoulder surface forming at least one of the flanks of this groove.

[0029] Other features and advantages of the invention will become apparent from the reading of the detailed description below, made with reference to the attached drawings, in which: - figure 1 represents a temperature probe according to the invention, seen in isometric perspective;

[0030] - Figure 2 represents the temperature probe from Figure 1, seen in longitudinal section;

[0031] - Figure 3 represents a thermosensitive subset for the probe of Figure 1 and Figure 2, seen in isometric perspective;

[0032] - Figure 4 represents a draft of a temperature probe according to the invention, seen in isometric perspective;

[0033] - Figure 5 represents the draft of Figure 4, in isometric perspective and from a different angle of view;

[0034] - Figure 6 represents the draft of Figure 4 and Figure 5, seen in longitudinal section;

[0035] - Figure 7 represents part of a mold intended for the production of the rough draft of figures 4 to 6, seen in a cut isometric perspective;

[0036] - Figure 8 represents another part of the mold of Figure 7, seen in section; - Figure 9 represents the probe of Figure 1 and Figure 2, seen in isometric perspective; and - Figure 10 represents part of a mold intended for the production of the probe of Figure 9 in particular, seen in a cut isometric perspective.

[0037] The accompanying drawings contain, for the most part, elements of a definite nature. They can therefore not only serve to better explain the present invention, but also contribute to its definition, if necessary.

[0038] Figures 1 and 2 show a temperature probe 1, used, in particular, for measuring the temperature of a thermal management fluid in a motor vehicle. Specifically, this probe 1 can be used to measure the temperature of a coolant in a battery pack, particularly in an electric or hybrid motor vehicle. The probe 1 may also be referred to in the technical field as a "temperature sensor."

[0039] Typically, probe 1 comprises a temperature-sensitive element (not visible in Figures 1 and 2) and a pair of connecting blades 11, each electrically connected to the temperature-sensitive element. This temperature-sensitive element is, for example, based on NTC technology, for "Negative Temperature Coefficient," that is, a thermistor whose resistance varies according to the temperature of its environment.

[0040] Each of the connecting blades 11 is attached to the heat-sensitive element near a first longitudinal end, or proximal end 110 (shown as the lower end in the figures), for example by welding. In addition, each of the connecting blades 11 has a second longitudinal end, or distal end 111, opposite the proximal end 110, for electrically connecting the probe 1 to an electrical connector on the vehicle. In the embodiment shown in the figures, each connecting blade 11 is curved near its distal end 111, here at approximately 90 degrees. As a result, the distal ends 110 of the connecting blades 11 protrude from a plane containing the remaining blades 11. This curvature is optional. Different angles of curvature can also be considered.The probe 1 comprises a casing molded around at least a portion of the connecting blades 11 and the temperature-sensing element, in direct contact with them. A portion of this elongated casing forms a plunger body 60. The plunger body 60 surrounds the temperature-sensing element and at least a portion of the connecting blades near their proximal end 110. Here, the plunger body 60 surrounds the connecting blades 11 up to their curved portion. Furthermore, the plunger body 60 generally has an axisymmetric shape, with its axis corresponding to its longitudinal axis. In Figures 1 and 2, this plunger body 60 is shown extending vertically, as an example only, without this limiting the functional positions of the probe.

[0041] The probe casing 1 further has a portion shaped as an electrical connector 21, which surrounds the connecting blades 11, at least in the vicinity of their distal end 111. Here, the connector-shaped portion 21 surrounds the connecting blades 11 from their distal end 111 to their curved portion. In Figures 1 and 2, the portion of the casing forming connector 21 is shown extending horizontally, for illustrative purposes only. This connector portion 21 and the plunger body 60 connect to each other.

[0042] The plunger body 60 has an end portion 34, which surrounds the heat-sensitive element. Here, this end portion 34 generally has a frustoconical shape, which flares out as it moves away from the free end of the plunger body 60. This end portion 34 terminates in a hemispherical, or teardrop, shape.

[0043] Between the connector portion 21 and its end portion 34, the plunger body 60 has a portion shaped into an annular groove 25, intended to receive a sealing gasket, in particular a toroidal one. This groove 25 consists of a generally cylindrical surface forming a groove bottom 25a, and a pair of annular surfaces bordering this groove bottom 25a, namely a proximal flank 25b, close to the end portion 34 of the plunger body 60 and a distal flank 25c, far from this portion 34. Between the groove 25 and the connector portion 21, the plunger body 60 has a succession of circular ribs of a first type, or first ribs.Here, the diving body 60 has a rib of this type near the annular groove 25 (first proximal rib 37a), another away from this groove 25 (first distal rib 37c) and a last one between the first proximal rib 37a and the first distal rib 37c (first intermediate rib 37b).

[0044] These first ribs primarily serve to mechanically connect the probe to its mounting bracket in the vehicle. Specifically:

[0045] - the first distal rib 37c, here hexagonal in shape, is intended to fit into a support of complementary shape and to ensure an anti-rotation function of the probe;

[0046] - the first intermediate rib 37b helps to guide and / or center the probe in its support;

[0047] - the first proximal rib 37a jointly delimits with the first intermediate rib 37b an annular space, suitable for receiving a metallic clip or similar, which ensures the retention of the sensor on its support;

[0048] - the first intermediate rib 37b and the first distal rib 37c jointly delimit a space, here generally annular, used as a recess to limit the mass of material of the sensor.

[0049] We are interested in the manufacture of a temperature probe of the type of probe 1 described in relation to figures 1 and 2.

[0050] We first plan a thermosensitive subset 10 as shown in figure 3.

[0051] This heat-sensitive subassembly 10 comprises a pair of electrically conductive blades 11 and a heat-sensitive element 12 electrically connected to each of the conductive blades 11. The heat-sensitive element 12 is attached to each of the conductive blades 11, in the vicinity of the proximal end 110 of these conductive blades 11. In particular, the heat-sensitive element 12 is here welded to each of the conductive blades 11, for example via a pair of pins 121 or electrically conductive wires.

[0052] Although Figure 3 shows conductive blades 11 extending substantially parallel to each other, it will be understood that in practice, nothing maintains these conductive blades 11 in this relative position.

[0053] Next, a rough draft of the temperature probe is produced, as shown in figures 4 to 6. This rough draft is obtained by making a first overmolding 20 around at least part of an insert formed of a thermosensitive sub-assembly of the type described in relation to figure 3.

[0054] This first overmolding 20 includes the portion of the probe's casing forming a connector 21, around the distal end 111 of the conductive blades 11. This first overmolding 20 also includes an elongated portion, which surrounds the remaining conductive blades 11 and the heat-sensitive element 12. This elongated portion connects to the portion forming the connector 21. The elongated portion of the first overmolding 20 includes an end segment 27 that extends longitudinally and surrounds at least the heat-sensitive element 12. This end segment 27 is generally shaped axisymmetrically and is axially demoldable. The axis of this end segment 27 corresponds to the longitudinal axis of the probe's plunger body.

[0055] This end segment 27 includes a shoulder surface 25c for forming the distal flank of the plunger body's groove, and a cylindrical bearing surface 25a, adjacent to the shoulder surface 25c, a portion of which is for forming the bottom of the plunger body's groove. The end segment 27 further includes a terminal portion 26, which extends along the axis of the end segment 27 and surrounds at least the heat-sensitive element 12. Here, the terminal portion 26 of the end segment 27 also encloses at least a portion of the pins, or analogs, that connect this heat-sensitive element 12 to the conductive blades 11. In particular, this terminal portion 26 is adjacent to the cylindrical bearing surface 25a.

[0056] This terminal portion 26 comprises a hemispherical part 26a that encloses most of the heat-sensitive element 12 and a frustoconical part 26b that projects longitudinally from the cylindrical bearing surface 25a and converges towards the hemispherical part 26a. This frustoconical part 26b of the terminal portion 26 encloses the remainder of the heat-sensitive element 12. The hemispherical part 26a can be seen as having the shape of a teardrop. The base of the frustoconical part 26b has a diameter substantially smaller than the diameter of the cylindrical bearing surface 25a.

[0057] Here, the end segment 27 includes a second terminal portion 28, opposite the first portion 26, which extends along the axis of the end segment 27 and connects to the cylindrical bearing surface 25a via the shoulder surface 25c. This second terminal portion 28 of the end segment 27 is generally cylindrical in shape, with a diameter substantially larger than that of the cylindrical bearing surface 25a. This second terminal portion 28 contributes, possibly in combination with the first intermediate rib 37b, to guiding and / or centering the probe in its support.

[0058] Because the cylindrical span 25a has a diameter smaller than the second terminal portion 28, and the first terminal portion 26 has a diameter smaller than the cylindrical span 25a, in the absence of an undercut surface on the end segment 27, the latter is shaped in such a way that it can be demolded along its longitudinal axis, in the direction of the first terminal portion 26.

[0059] The first overmolding 20 still includes at least one material-free area, or first recess 22a (Figures 4 and 6), providing access to at least one of the connecting blades 11 of the heat-sensitive subassembly. This first recess 22a provides access to each of the connecting blades 11 of this subassembly. Here, the first overmolding 20 further includes a second recess 22b (Figures 4 and 5), providing access to one of the connecting blades 11, and a third recess 22c (Figure 5) providing access to the other of these blades 11. In particular, the second recess 22b and the third recess 22c are each opposite the first recess 22a with respect to a respective connecting blade 11.

[0060] Here, the elongated portion of the first overmolding 20 further includes a connecting segment 23, which extends along the longitudinal axis of the elongated portion to the connector-shaped portion 21 of the first overmolding. This elongated portion also includes an intermediate segment 24, which connects the connecting segment 23 to the end segment 27. The cutouts, in particular the first 22a, the second 22b, and the third 22c, are formed on this intermediate portion. The connecting segment 23 and the intermediate segment 24 each surround a respective longitudinal section of each of the connecting blades 11.

[0061] In the embodiment shown in the figures, the connecting segment 23 is delimited by a pair of enlarged portions, namely a proximal enlarged portion 23a, near the heat-sensitive element 12, and a distal enlarged portion 23b, near the connector-shaped portion 21. Between the proximal enlarged portion 23a and the distal enlarged portion 23b, the connecting portion 23 has forms 23c that contribute to the positioning of the first overmolding in a mold. These forms 23c, here shaped like ribs, impart rigidity to the first overmolding 20, while limiting the volume and mass of plastic material of this first overmolding 20. The forms 23c have draft surfaces, so as to facilitate not only the ejection of the first overmolding 20 from the mold, but also its placement for the second overmolding.

[0062] Furthermore, the first overmolding 20 preferably includes one or more ribs of a second type, or second ribs, which project from at least one of the segments of the first overmolding 20, axially or radially. In particular, the first overmolding 20 here includes:

[0063] - a rib that projects radially from the intermediate segment 24, near the connecting segment 23 (second distal rib 24a);

[0064] - a rib that projects radially from the intermediate segment 24, near the end segment 27 (second intermediate rib 24b);

[0065] - a rib that projects axially from the cylindrical span 25a towards the end of the end segment 27 (second proximal rib 24c).

[0066] Optionally, this second proximal rib 24c is flush with the cylindrical span 25a, as is the case here.

[0067] Figures 7 and 8 show a first mold 40, as an example of a mold suitable for carrying out a first overmolding of the type described in relation to figures 4 to 6. There is a thermosensitive sub-assembly 10 installed inside the cavity of the first mold 40.

[0068] This first mold 40 includes at least a first part, or upper part 40a, shaped to receive the blades 11 of the heat-sensitive sub-assembly 10 and to hold them there, at least in an intermediate zone 112, away from both their proximal end 110 and their distal end 111.

[0069] The upper part 40a of the first mold 40 has a molding cavity comprising a first cavity 421, arranged to form the connecting portion of the first overmolding, and a second cavity 410, arranged to form its elongated portion. The second cavity 410 communicates with the first. Here, the second cavity 410 is arranged to form the connecting segment of the first overmolding and its intermediate segment. Within this second cavity 410, recessed sections are arranged to form these different segments. Each portion is referenced with the number of the corresponding segment, plus four hundred. The first mold 40 also includes at least one second part, here in the form of a drawer 40b, shown here below the upper part 40a of the first mold 40. This drawer 40b has a third cavity 427, arranged to form the end segment of the first overmolding.

[0070] This third cavity 427 is arranged to receive the element 12 of the heat-sensitive subassembly 10, while the conductive blades 11 are installed in the upper part 40a of the mold. The drawer 40b has a first face, or upper face, through which the drawer 40b joins the upper part 40a of the mold. The cavity 427 of the drawer 40b is open on this upper face, while the second cavity 410 of the upper part of the mold is open on the corresponding face. When the drawer 40b is in place under the upper part 40a of the mold, the second cavity 410 and the third cavity 427 are aligned.

[0071] The end segment of the first overmolding can be demolded by moving the drawer 40b along the longitudinal direction of the cavity, away from the upper part 40a of the mold.

[0072] In the recessed cavity 427 of drawer 40b, there are portions arranged to form the end segment of the elongated part of the first overmolding. These portions are referenced there with the numbers of the corresponding portions of the end segment, plus four hundred.

[0073] In particular, this cavity 427 has a terminal section 426 with a generally frustoconical portion 426b that opens into a generally hemispherical end portion 426a. This hemispherical portion 426a is arranged to receive the heat-sensitive element 12. The shape and dimensions of the frustoconical portion 426b, where it connects to the hemispherical portion 426a, correspond, by their larger values, to the heat-sensitive element 12. The latter is thus guided by the frustoconical portion 426b, and then positioned centrally with respect to the hemispherical portion 426a, when the cavity 427 is filled with material (see Figure 8).

[0074] Here, the upper part 40a of the mold 40 is itself made in two parts, each comprising a respective half of the second cavity 410. Here, a first part 40a-l (visible in figures 7 and 8) includes in particular the essential part of the first cavity 421, while the second part 40a-2 includes the remainder of this cavity 421. In figures 4 and 5, a line PJ represents, in an exaggerated manner, the mark left by the parting line between the first part 40a-l and the second 40a-2 of the upper part 40a of the mold 40.

[0075] In the second impression 410, the blades 11 of the thermosensitive subset 10 are held, including during injection (see figure 8), in an intermediate zone 112 of these blades 11, away from their distal end 111 and their proximal end 110. For example, these blades are held by one or more pins.

[0076] Here, a first portion 43a of a first pin 43 protrudes into the second cavity 410, in the area 424 corresponding to the intermediate segment of the first overmolding. This first portion 43a of the first pin 43 has an end arranged to contact the two conductive blades 11 on one face thereof. Here, the end of this first portion 43a is further partially shaped into a spacer, capable of maintaining a gap between the two conductive blades 11. Here, the first pin 43 further comprises two additional portions 43b and 43c, which protrude into the second cavity 410, at the level of the first portion 43a of this pin. These additional portions 43b and 43c are opposite each other and are each arranged to contact a respective conductive blade 11 on its edge.The additional portions 43b and 43c cooperate with the first portion 43a of the first spindle 43 to maintain the conductive blades 11 at a predetermined distance (center distance). Here, the first spindle 43 belongs to the same half of the upper portion 40a of the mold 40, for example, the first part 40a-l. Here, a single spindle is arranged in this first part 40a-l.

[0077] Here, a second pin (not visible in Figure 8) is positioned in the second section 40a-2 of the upper part 40a of the first mold 40, for example, opposite the first pin 43 positioned in the first section 40a-1 of this upper part 40a. This second pin is arranged to ensure proper retention of the conductive blades 11 in conjunction with the first pin, including during injection. One of the first and second pins can be mounted in the first mold 40 by means of one or more springs to further improve the retention of the conductive blades 11.

[0078] In the first impression 421, the blades 11 of the thermosensitive subassembly 10 are held, including during injection (see figure 8), in an area near their distal end 111. In figures 7 and 8, an upper pin 44 engaged in the first impression 421, along it, is arranged to hold the distal ends 111 of the connecting blades 11.

[0079] Figure 8 shows the cavity of the first mold 40 filled with plastic material. The first spindle 43 and the upper spindle 44 hold the blades 11 of the heat-sensitive subassembly during the first overmolding.

[0080] The first mold 40 is arranged to ensure correct positioning of the heat-sensitive sub-assembly 10 in the molding cavity and maintenance of this position during the first overmolding, in particular because:

[0081] - the thermosensitive element 12 is recentered by the frustoconical portion 426b which acts as a centering cone;

[0082] - the conductive blades 11 are held at their distal end 111, in particular by the upper pin 44;

[0083] - the conductive blades 11 are held in an intermediate zone 112 by the first pin 43 and, where applicable, the second. The first overmolding fixes the spacing (center distance) between the conductive blades 11. This first overmolding also includes reliefs which result from holding the connecting blades 11 in the molding cavity during the first overmolding, in particular by means of pins such as the first pin 43 and the second described above.

[0084] The first overmolding also creates centering shapes 23. These shapes are used to correctly position the blank in a second mold 50 via the first overmolding, in order to carry out a second overmolding.

[0085] Figures 1, 2 and 9 show probe 1 in the finished, or semi-finished, state after a second overmolding 30.

[0086] The probe 1 consists of a blank of the type described in relation to figures 4 to 6 and of this second overmolding 30 around at least part of the blank, that is to say at least part around the first overmolding 20 and, where appropriate, at least part of the thermosensitive subassembly left free by the first overmolding 20.

[0087] This second overmolding 30 includes here an intermediate portion 32 which surrounds the intermediate segment 24 of the first overmolding 20. In this intermediate portion 32, the second overmolding 30 fills each of the spaces of the first overmolding 20. This is, in particular, the first space 22a (figure 2), the second 22b (figure 9) and the third 22c (figures 2 and 9).

[0088] This second overmolding 30 further includes a terminal portion 34, which encloses at least the terminal portion 26 of the end segment of the first overmolding 20. This terminal portion 34 of the second overmolding 30 forms the terminal portion of the probe 1. In particular, this terminal portion 34 extends over a part of the cylindrical bearing surface 25a of the terminal segment 27 of the first overmolding 20. This portion 34 has an annular terminal surface that forms the proximal flank 25b of the groove 25 of the plunger body 60. The connector portion 21 is part of the first overmolding 20. The plunger body 60 of the probe 1 consists of the first overmolding 20, around at least a part of the blades 11 and the heat-sensitive element, and the second overmolding 30, around at least a part of the first overmolding 20 and, where applicable, a part of the blades 11. left free of material by the first overmolding 20. Finally, the plunger body 60 of the probe 1 is in one piece.

[0089] Figures 2 and 9 show that the second overmolding 30 covers the second ribs formed on the first overmolding 20. In practice, these ribs create raised areas that are melted by the plastic injected during the second overmolding. In particular, the second proximal rib 24c fuses with the terminal portion 34 of the second overmolding 30, while the second distal rib 24a and the second intermediate rib 24b fuse with the intermediate portion 32 of the second overmolding 30. The fusion of the second ribs 24a, 24b, and 24c during the second overmolding contributes to the seal between the first molding 20 and the second molding 30.

[0090] The second overmolding 30 joins the first overmolding 20 at bonding lines. These consist of a first line 35a between the terminal portion 34 of the second overmolding and the cylindrical bearing surface 25a of the first, a second line 35b between the second terminal portion 28 of the first overmolding 20 and the intermediate portion 32 of the second, and a third line 35c between the intermediate portion 32 of the second overmolding 30 and the proximal enlarged portion 23a of the first.

[0091] Figure 10 shows an example of a mold for making the second overmolding, or second mold 50.

[0092] For the second overmolding, the blank is installed in the mold cavity 530 of this second mold 50. The blank is positioned using the first overmolding 20. This second mold has a cavity in which at least a portion of the impression has shapes complementary to at least some of the segments of the first overmolding 20. In particular, the cavity 530 includes a projecting portion 523 shaped to correspond with the centering shapes 23c of the first overmolding 20. The cavity 530 of the second mold 50 includes a first portion of the impression 524 that surrounds at least the intermediate segment 24 of the first overmolding 20. As a result, the reliefs of this first overmolding 20 are located inside the first portion of the impression 524 when the projecting portion 523 of the cavity 530 engages the centering shapes 23c of the first overmolding 20. A volume of material comes to fill the savings during the second overmolding 30.

[0093] The impression of the second mold 50 also has a terminal portion 534, consisting here of a frustoconical portion 534b and a hemispherical portion 534a which extends this frustoconical portion 534b. This hemispherical portion 534a surrounds the hemispherical portion 26a of the first overmolding 20.

[0094] A process for manufacturing a temperature-controlled caustic soda by overmolding has been described, comprising the following steps:

[0095] - welding a heat-sensitive element onto a pair of conductive blades to form a heat-sensitive sub-assembly;

[0096] - placement of this thermosensitive sub-assembly in a first mold and creation of a first overmolding by injection of material into the first mold; - taking the first overmolding to form a blank, and placing the blank in a second mold, by cooperation of shape between the cavity of the second mold and at least part of the first overmolding, and creation of a second overmolding by injection of material into the second mold.

[0097] The proposed temperature probe, manufactured primarily through successive overmolding of a heat-sensitive subassembly, resolves most of the drawbacks encountered with temperature probes made by assembling components. In particular, the proposed probe eliminates the need for a seal between the sensing element and the immersion body. Furthermore, the initial overmolding eliminates the need for a thermally conductive material between the sensing element and its casing, since the plastic overmolding allows the heat-sensitive element to be completely and directly enclosed without air bubbles.

[0098] Securing the conductive blades in two zones during the initial overmolding—near their distal end and in an intermediate zone away from both the distal and proximal ends—eliminates the need for the prior art H-shape. Thanks to the manufacturing process described above, these connecting blades are held securely enough to eliminate the need for support from the product itself. This avoids the prior art cutting of the H-shape and its associated drawbacks, such as chip removal.

[0099] The described process ensures correct positioning of the sensing element within the mold: this element is recentered in the first mold by means of the truncated conical portion of the cavity corresponding to the terminal portion. The conductive blades are also held in place during the first overmolding near their distal end. The first overmolding creates centering shapes that help to correctly position the first overmolding in the mold for the second overmolding. The first overmolding has ribs that are remelted during the second overmolding by the injected material. The first overmolding forms the bottom of the probe body's groove by demolding along the longitudinal axis of the body. This ensures the absence of any parting line marks in this groove.

[0100] Because the heat-sensitive element is welded to the conductive blades before the first and second overmoldings, the time required to handle the blank between the first and second overmoldings is quite short, particularly shorter than in the state-of-the-art process. As a result, the material from the first overmolding is still hot during the second overmolding.

[0101] Furthermore, the fusion ribs created during the first overmolding are small. As a result, these ribs have virtually no thermal inertia. These ribs heat up rapidly upon contact with the injected material during the second overmolding, until they melt. This creates a perfect seal between the first and second overmoldings.

[0102] The process described above is remarkable due to the positioning of the heat-sensitive subassembly, and in particular the sensitive element of this subassembly, during overmolding. This positioning results from:

[0103] - securing the connecting blades at two points during the initial overmolding; - centering the sensing element within a truncated conical portion of the mold cavity, ensuring optimal and repeatable positioning. The plastic thickness around the sensing element during the initial overmolding is controlled and can therefore be minimized. The sensor's response time can then be reduced to the maximum.

[0104] - the use of recentering shapes for the correct positioning of the first overmolding during the second overmolding stage.

[0105] All of this guarantees precise and repeatable positioning of the sensitive element during the second overmolding, thus ensuring accuracy and responsiveness of the probe.

[0106] In the probe described above, the bottom of the groove for the sealing gasket is formed by the first overmolding, on a portion of which is demolded along the longitudinal axis of the immersion body. The bottom of the groove is thus free of any parting line marks, eliminating the risk of burrs. This design ensures a good seal between the probe and its support.

[0107] In a variant not shown here, the sensing element could be positioned against a stop in the cavity of the first mold along the longitudinal axis of that cavity. In this way, the truncated cone of the cavity centers the temperature-sensitive element in a plane perpendicular to the longitudinal axis of the cavity, while the vertical stop optimizes its positioning along this axis. The temperature-sensitive element is thus restricted from moving during the initial overmolding. The thickness of the plastic material around the element can be reduced, thereby further reducing the probe's sensitivity.

[0108] Another optional feature concerns the degassing of the first mold cavity. In conventional plastic injection molding processes, filling small areas can sometimes be problematic due to trapped air bubbles. To allow these air bubbles to escape, degassing zones are commonly incorporated into the molds. These are very small gaps between the mold parts, allowing air to escape while preventing molten plastic from leaking out. However, there is a risk of these degassing zones gradually becoming clogged with plastic residue.

[0109] With reference to Figure 8, a movable pin 41 is planned to be installed at the end of the cavity 410 of the first mold 40, in the area receiving the heat-sensitive element, namely its terminal portion 426. The adjustment of this pin 41 in its bore allows the evacuation of gases and thus the proper filling of the cavity 410. In addition, the movement of this pin 41, consisting of back-and-forth translational movements, promotes the cleaning and evacuation of plastic residues, thus guaranteeing repeatable and stable degassing over time.

[0110] The invention is not limited to the embodiment described above, by way of example only, but encompasses all variations that a person skilled in the art could conceive. In particular:

[0111] - The first and second overmolding can be done with different types and / or compositions of plastics.

[0112] - The axis of the electrical connector 21 is not necessarily perpendicular to the axis of the plunger body 60, but can take any angle, including being aligned with the body 60.

[0113] - The heat-sensitive element 12 can be provided without connecting pins 121. In this case, the heat-sensitive element 12 can be fixed directly between the two conductive blades 11. - The heat-sensitive element can be attached to the conductive blades by means other than welding, in particular by crimping. In this case, the proximal ends of these blades may have a thinner area to facilitate crimping.

Claims

Demands 1. A method for manufacturing a temperature probe (1), in particular for measuring the temperature of a thermal regulation fluid in a motor vehicle, this probe (1) comprising at least one pair of connecting blades (11) and a temperature-sensitive element (12) electrically connected to each of the connecting blades (11), as well as a housing at least partially in the shape of a immersion body (20; 30) molded around at least a portion of the blades (11) and the temperature-sensitive element (12), in direct contact with them, the method comprising the following steps: a. provide an active sub-assembly (10) comprising a pair of electrically conductive blades (11) and at least one thermosensitive element (12) attached to each of these conductive blades (11), in the vicinity of one of the longitudinal ends (110; 111) of these blades (11); b. carry out a first overmolding (20) around at least part of the active sub-assembly (10) by injecting material into a first mold (40), this first mold (40) comprising at least a first part (40a) in which the blades (11) are held during the injection, in an intermediate zone (112), away from the longitudinal ends (110; 111) of these blades (11), and a second part (40b), adjacent to the first (40a), comprising an axisymmetric and demoldable cavity (427), in which the thermosensitive element (12) is positioned during the injection; c. carry out a second overmolding (30) around at least part of the first overmolding (20), by injecting material into a second mold (50) to obtain the envelope (20;30).

2. A method according to claim 1, wherein the axisymmetric and demoldable cavity (427) of the second part (40b) of the first mold (40) comprises a generally cylindrical axial segment (425a), near the first part (40a) of the first mold (40), and a generally frustoconical axial segment (426b), which extends the cylindrical segment (425a) away from the first part (40a) of the first mold (40).

3. A method according to any one of claims 1 and 2, wherein, in step b, at least one relief zone (23) is formed in the first overmolding (20), and, in step c, the first overmolding (20) is positioned in the second mold (50) by means of at least one zone (523) of the second mold (50) having a shape at least partially complementary to the relief zone (23) of the first overmolding (20).

4. A method according to any one of the preceding claims, wherein, in step b., one or more ribs (24a, 24b, 24c) are made, and, in step c., these ribs (24a, 24b, 24c) are remelted in the second overmolding (30) by the material injected during this second overmolding.

5. A method according to any one of the preceding claims, wherein, in step b., the first overmolding (20) leaves at least one area (22a, 22b, 22c) free of material giving access to at least part of the intermediate area (112) of the blades (11), and in step c., the second overmolding (30) fills each area free of material (22a, 22b, 22c) of the first overmolding (20).

6. Method according to claim 2, wherein, in step b., the generally cylindrical axial segment (425a) is able to form at least partially a cylindrical bearing surface (25a) in the first overmolding (20), while in step c., the second overmolding (30) leaves at least a part of this cylindrical bearing surface (25a) free of material.

7. A method according to any one of the preceding claims, wherein, in step b, a frustoconical portion is formed in the first overmolding (20), which at least partially surrounds the heat-sensitive element (12), and, in step c, the second mold (50) comprises a cavity (530) having a generally frustoconical axial segment, while the frustoconical portion surrounding the heat-sensitive element (12) is positioned in this axial segment.

8. A method according to any one of the preceding claims, wherein, in step b, the first part (40a) of the first mold (40) comprises at least one cavity (410) in which the blades (11) are positioned during injection, and this first part (40a) further comprises one or more pins (43) which project into said cavity (410) and retain the blades (11) therein.

9. A method according to any one of the preceding claims, wherein, in step c, the second overmolding (30) surrounds a terminal portion (26) of the first overmolding (20), in which the heat-sensitive element is located.

10. A method according to any one of the preceding claims, wherein, in step b., at least one bore opening axially into the axisymmetric cavity and axially demoldable is provided, and a spindle (41) is moved in translation in this bore.

11. A temperature probe (1), particularly for measuring the temperature of a thermal control fluid in a motor vehicle, this probe (1) comprising at least one pair of connecting blades (11) and a temperature-sensing element (12) electrically connected to each of the connecting blades (11), and a housing in the form of a plunger body (10; 30) molded around at least a portion of the blades (11) and the temperature-sensing element (12), in direct contact therewith, characterized in that the housing consists of a first overmolding (20) around at least a portion of the active subassembly (10), this first overmolding (20) having at least one material-free zone (22a, 22b, 22c) providing access to at least one of the connecting blades (11) and an axisymmetric and axially demoldable end portion surrounding at least the temperature-sensing element (12), and a second overmolding (30) around of at least part of the first overmolding (20),this second overmolding (30) filling each free area of ​​material (22) of the first overmolding (20) and surrounding at least a part of said end portion.

12. Probe according to claim 11, wherein the axisymmetric and axially demoldable end portion (27) of the first overmolding (20) has a cylindrical bearing surface (25a) forming the bottom (25a) of an annular groove (25), while the second overmolding (30) has a shoulder surface (25c) forming at least one of the flanks (25b, 25c) of this groove (25).

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