Abstract:
This heating assembly comprises a thermally conductive tube ( 42 ), to be immersed in a thermally expandable material of a thermostatic element of a valve, an electric heating resistor disposed inside the tube and from which there extend electrically conductive wires ( 62 ), and a unitary housing ( 1 ) made from plastic, through which the fluid to be regulated flows via the valve, and which is secured by over-molding of a longitudinal end portion ( 44 ) of the tube. In order to make the molding of the over-molded housing simple and inexpensive to carry out, while being easy to adapt to various geometric forms of the heating assembly, the invention proposes that, before the housing is molded, a reinforcement ( 7 ) for supporting the wires outside the tube, which is separate from the housing, and to which the housing is secured by over-molding, can be securely mounted on the end portion of the tube and supports the wires outside the tube, said wires being externally mounted on the reinforcement, and, when the housing is being molded, keeps the wires in place while the plastic material of the housing coats these wires, the reinforcement and the end portion of the tube.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a heating assembly for a thermostatic valve, as well as a method for manufacturing such a heating assembly. It also relates to a thermostatic valve comprising one such heating assembly. 
       BACKGROUND OF THE INVENTION 
       [0002]    In many applications in the fluids field, in particular for cooling vehicle heat engines, thermostatic valves are used to distribute a fluid entering various circulation channels, based on the temperature of that fluid. These valves are said to be thermostatic because the movement of their inner closure member(s) is controlled by a thermostatic element, i.e., an element that comprises a cup containing a thermally expanding material and a piston able to slide relative to the cup under the action of the thermally expanding material when the latter expands. 
         [0003]    To distribute the fluid as a function of other parameters, in particular conditions outside the valve, such as the ambient temperature or the load of the vehicle propelled by the engine equipped with the valve, it is known to incorporate electric heating of the thermally expandable material into the valve, which makes it possible to control the valve from outside it, independently of or in addition to the temperature of the incoming fluid, in particular using an onboard computer in the vehicle programmed appropriately. In practice, a heating resistance is arranged inside the aforementioned piston or a similar tube: for example, by immobilizing the piston in the moving case of the valve, the power supply of the resistance causes the temperature of the thermally expanding material to increase, which, by extension of the latter, causes the cup to slide around the piston, a closure member being supported by that cup to act on the flow of fluid through the valve. 
         [0004]    To provide electricity to the heating resistance, one possibility, known from DE-A-103 03 133, consists of the electrically conductive wires, which extend from the resistance to the outside of the aforementioned tube while passing through a terminal part of the latter, and the free ends of which are electrically connected to connecting steps to be connected to an external current source, being directly coated with the plastic material of the housing during molding of the latter around the aforementioned terminal part of the tube. However, this solution is delicate to manufacture, since during molding of the case, the plastic material injected so as to overmold the terminal part of the tube tends to pull, or even pull out, the electrical wires, unless sophisticated and therefore expensive injection molds are used, which furthermore need to be modified when the arrangement of the wires is changed, typically depending on the position, on the case, of the aforementioned connecting pads. 
         [0005]    EP-A-0,853,267 proposes overmolding both the terminal part of a heating tube, similar to what is mentioned above, and the electrical wires that leave that tube, with a plastic coating material, so as to form a module, which is next attached in a single piece to the rest of the thermostatic valve, by screwing a thread formed by that plastic material in a complementary tapping, formed by the housing of the valve. The implementation of this solution has the same drawbacks as above, during the injection of the aforementioned plastic coating material. 
         [0006]    WO-A-2011/010051 mentions a possible pre-injection of plastic around electrical wires similar to those mentioned thus far, but only at the end of those wires, at which they are electrically connected to connecting studs. This pre-injection is followed by an injection of plastic to form the housing of the valve, then coating all of the rest of the wires, extending outside the tube, as well as the terminal part of the tube. 
       SUMMARY OF THE INVENTION 
       [0007]    The aim of the present invention is to propose a heating assembly in which molding of the overmolded housing is simple and cost-effective to perform, while being easy to adapt to various heating assembly geometries. 
         [0008]    To that end, the invention relates to a heating assembly for a fluid control thermostatic valve, comprising: 
         [0009]    a tube, being thermally conductive, having a longitudinal central axis and being able to be plunged in a thermally expandable material of a thermostatic element of the valve, 
         [0010]    an electric heating resistance, which is positioned inside the tube and from which electrically conducting wires extend outside the tube, 
         [0011]    a single-piece housing made from a plastic material, through which the fluid flows and which is secured by overmolding to a terminal longitudinal part of the tube, and 
         [0012]    a framework for supporting the conductive wires outside the tube, the framework being separate from the housing, the tube being secured to the framework by overmolding. 
         [0013]    The framework is suitable, before molding of the housing, for being fixedly attached to the terminal longitudinal part of the tube and for supporting the conductive wires outside the tube, those conductive wires being outwardly assembled on the framework. The frame work is also suitable, during molding of the housing, for keeping the conductive wires in place while the plastic material of the housing coats those conductive wires, the framework and the terminal longitudinal part of the tube. 
         [0014]    One of the ideas at the base of the invention is to keep the electrical wires leaving the tube in place, at least during the injection of plastic material to overmold the housing. 
         [0015]    The invention is thus based on the presence of a framework for supporting the wires outside the tube, which is placed before molding the housing, while being fixedly attached to the terminal part of the tube, for example by cooperating with that terminal part through complementary shapes. During the molding of the housing, the framework keeps the wires in place outside the tube, thus protecting them from any excess stress applied by the injected plastic material. This framework, jointly with the wires and the terminal part of the tube, is then coated by the injected plastic material. Owing to the invention, the overmolding of the housing may be done simply and quickly, using a standard mold and in an automated manner, without running the risk of damaging the wires and/or separating them from their pre-molding position. Advantageously, the framework according to the invention makes it possible to modify the arrangement of the wires before molding to adapt to various geometries of heating assemblies. 
         [0016]    According to other advantageous features of the heating assembly according to the invention: 
         [0017]    the framework is made in a single piece; 
         [0018]    the framework has an elongated overall shape, which extends lengthwise, at least for a part thereof turned toward the tube, in a transverse or substantially radial direction with respect to the axis; 
         [0019]    an end part of the framework, turned toward the tube, is configured to surround and fasten itself, in particular by cooperating through complementary shapes, to a free, outwardly flared end of the terminal longitudinal part of the tube; 
         [0020]    between an end part of the framework turned opposite the tube and a running part of the framework, the framework includes a flexible zone, in particular thinner, suitable for being deformed so as to adjust the relative positioning between that end part and the rest of the framework before molding the housing; 
         [0021]    in an end part of the framework turned opposite the tube, the framework has through holes for complementary reception of electrical connecting studs that are respectively electrically connected to the conductive wires before molding of the housing; 
         [0022]    a running part of the framework, which connects end parts thereof turned toward and opposite the tube, respectively, to each other, delimits a longitudinal trough for receiving the conductive wires, in which the wires run lengthwise between the end parts of the framework and which is provided with means for keeping those conductive wires in place before molding the housing; 
         [0023]    the heating assembly further comprises a single sealing gasket, which is an O-ring or a four-lobed seal, which is both inserted radially between the housing and the tube and arranged axially against an end part of the framework, turned toward the tube. 
         [0024]    The invention also relates to a fluid control thermostatic valve, comprising: 
         [0025]    a heating assembly as defined above, 
         [0026]    a valve housing consisting at least partially of the housing of the heating assembly, 
         [0027]    a closure member for regulating the flow of a fluid through the valve housing, and 
         [0028]    a thermostatic element, comprising a stationary part fixedly connected to the valve housing, and a moving part that bears the closure member and is movable relative to the stationary part under the expansion action of a thermally expanding material in which the tube of the heating assembly is plunged. 
         [0029]    The invention further relates to a method for manufacturing a heating assembly for a fluid control thermostatic valve, wherein a tube is provided, that is thermally conductive, has a longitudinal central axis and is suitable for being plunged in a thermally expanding material of a thermostatic element of the valve and in which an electrical heating resistance is positioned from which electrically conductive wires extend outside the tube. A framework, on which the conductive wires outside the tube are outwardly assembled so as to support those conductive wires, is fixedly attached to a terminal longitudinal part of the tube. Then a single-piece housing, that is made from a plastic material and through which a fluid is intended to flow, is secured simultaneously to the terminal longitudinal part of the tube, the framework and the conductive wires outside the tube, by coating the terminal longitudinal part of the tube, the framework and the conductive wires outside the tube, those conductive wires being kept in place by the framework during molding of the plastic material. 
         [0030]    The method according to the invention makes it possible to manufacture a heating assembly as defined above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    The invention will be better understood upon reading the following description, provided solely as an example and done in reference to the drawings, in which: 
           [0032]      FIG. 1  is a longitudinal cross-section of a thermostatic valve according to the invention; 
           [0033]      FIGS. 2 and 3  are perspective, cross-sectional quarter views of the valve of  FIG. 1 ; 
           [0034]      FIG. 4  is an enlarged view of the circled detail IV in  FIG. 1 ; 
           [0035]      FIGS. 5 and 6  are cross-sections along lines V-V and VI-VI of  FIG. 1 , respectively; and 
           [0036]      FIG. 7  is a perspective view, showing a subassembly to be overmolded, belonging to the valve of  FIG. 1  and comprising a thermally conductive tube positioned in a framework so as to be inserted into a mold for producing the housing of the valve. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0037]      FIGS. 1 to 6  show a thermostatic valve comprising a housing  1  made from plastic, in which a fluid is designed to flow, in a manner regulated by the other components of the valve, in particular oil or a coolant liquid when the valve belongs to a cooling circuit for a heat engine. 
         [0038]    The housing  1  comprises a tubular single-piece main body  11 , here with a globally rectilinear shape centered around an axis X-X belonging to the cutting plane of  FIG. 1 . During use, the aforementioned fluid flows through the body  11 , between its two longitudinal ends, while being regulated, here at one of said ends, by a closure disk  2  centered on the axis X-X and translatable along the axis: when this closure member is pressed tightly against a seat  12  delimited by the aforementioned end of the body  11 , as shown in  FIG. 1 , the flow of the fluid is interrupted, whereas when the closure member  2  is separated from the seat  12 , the fluid can flow freely around the closure member and thus enter or leave the body  11 . 
         [0039]    In practice, various embodiments can be considered regarding the body  11  and the closure member  2 , without limiting the invention. Advantageously, the housing  1  comprises an annular flange  13  orthoradially surrounding the body  11 , while being made in a single piece with that body. 
         [0040]    In order to control the movement of the closure member  2 , the thermostatic valve comprises a thermostatic element  4  comprising, in a manner well known in the field, a cup  41  on the one hand, which contains a thermally expandable material, not shown in figures, and around which the closure member  2  is securely fastened, for example by fitting, and a piston  42  on the other hand, which is partially plunged in the cup  41  and translatable along its central longitudinal axis under the action of the expansion of the thermally expandable material contained in that cup. The thermostatic element is arranged across from the housing  1  such that on the one hand, its piston  42  is substantially centered on the axis X-X, and on the other hand, that piston is fixedly connected to the body  11 , here at a plastic arm  14  that is a single piece with the body  11  and that extends, through the inside of the body  11 , from a portion of that body  11 , as clearly shown in  FIGS. 2 and 3  and as specified in more detail below. Thus, during use, the piston  42  is stationary relative to the housing  1 , while the cup  41  and the closure member  2  that it supports are movable along the axis X-X relative to the housing, under the effect of the thermally expandable material when the latter expands, or when that material contracts, under the opposite effect of a returns spring  5  interposed between the closure member  2  and a stirrup  3  which, during use, is fixedly connected to two tabs  15  integral with the flange  13 . In a manner known in itself, these movements are guided along the piston  42 , typically by a guide part secured to the cup  41 . 
         [0041]    For convenience, the rest of the description is oriented relative to the axis X-X: the terms “lower” and “bottom” describe an axial direction oriented toward the cup  41  of the thermostatic element  4 , while the terms “upper” and “top” describe an opposite direction. 
         [0042]    The thermostatic valve comprises an electric heating resistance  61  which, as shown in dotted lines in  FIG. 1 , is arranged inside the piston  42 , made to that end in the form of a metal tube, here with a circular base, such that said resistance  61  occupies the lower terminal part  43  of the piston  42 , i.e., its terminal part plunged in the cup  41 , so that the resistance  61  can heat the thermally expandable material contained in that cup. 
         [0043]    In its upper terminal part  44 , the piston  42  is configured with an outwardly flared free end  45 : as clearly shown in  FIG. 4 , this flared end  45  is made up of a stepped wall  46 , globally fitted into a plane perpendicular to the axis X-X, and a horn-shaped wall  47 , connecting, while gradually narrowing, the inner end of the stepped wall  46  to the upper end of the rest of the terminal part  44 . Advantageously, the stepped wall  46  and the horn-shaped wall  47  here form a single piece with the rest of the terminal part  44 , while in particular being obtained by stamping the free end  45 . As an alternative that is not shown, the stepped wall  46  can be extended or even replaced by a wall with a raised shape, for example cylindrical, centered on the axis X-X. 
         [0044]    In order to electrically connect the heating resistance  61  and external current source, two electrically conductive wires  62  are connected to that resistance  61  and extend from the latter to the outside of the piston  42 , while passing through the upper terminal part  44  of the latter, in which the wires  62  emerge upwardly, as clearly shown in  FIG. 2  and  FIG. 7 , in which several components of the thermostatic valve have been omitted for greater clarity related to the following considerations. The respective parts of the wires  62  outside the piston  42  extend from the terminal part  44  of the latter to the connecting studs  63 , to which the wires  62  are respectively electrically connected and the free ends  64  of which, i.e., those turned opposite the wires  62 , are accessible outside the housing  1  to be connected to the aforementioned external current source. It will be noted that, for visibility reasons, only one of the studs  63  is shown in  FIGS. 2 and 3 . In practice, the respective ends  65  of the studs  63 , opposite their end  64 , are respectively connected to the ends of the wires  62 , opposite the heating resistance  61 , by any appropriate means, for example by welding, crimping or brazing. The stud ends  64  are left stripped, advantageously remotely surrounded by a base  16  for connecting to the external current source, that base  16  advantageously being made in a single piece with the body  11  of the housing  1 . 
         [0045]    According to the invention, the portion of the conductive wires  62  outside the piston  42  is not embedded alone in the plastic material making up the housing  1 . On the contrary, as clearly shown in  FIGS. 2 to 7 , the thermostatic valve further comprises a framework  7  designed to support the wires  62  outside the piston  42 , that framework  7  being separate from the housing  1 , inasmuch as, as shown in  FIG. 7 , that framework  7  is made in the form of one or more parts, in the case at hand a single part, which are not integral with the housing  1 . 
         [0046]    This framework  7  has an elongated overall shape that extends lengthwise in a direction transverse to the axis X-X, or a substantially radial direction, as in the example considered in the figures. Thus, the framework  7  includes, in its longitudinal direction, an end part  71  turned toward the axis X-X, a running part  72  and an end part  73 , opposite its end part  71 . 
         [0047]    The end part  71  of the frame  7  is designed to be fixedly attached to the upper terminal part  44  of the tube  42  independently of the other components of the thermostatic valve, in particular for molding of the housing  1 . In the example embodiment considered in the figures, this end part  71  comprises a globally tubular body  71 . 1 , which is suitable for being arranged all around the flared end  45  of the upper terminal part  44  of the piston  42  and which has, at its lower axial end, a stepped rim  71 . 2 , turned toward the axis X-X and forming an axial downward bearing for the stepped wall  46  and the horn-shaped wall  47  of that piston end  45 , as clearly shown in  FIG. 4 . Furthermore, in its upper end part, the tubular body  71 . 1  is provided with hooks  71 . 3 , of which there are three in the example embodiment considered here and which are suitable for clipping to the piston end  45 , while cooperating with respective portions of the stepped wall  46  of the piston end  45  so as to axially upwardly block that stepped wall  46  and thereby maintaining that stepped wall and the horn-shaped wall  47  bearing axially downward against the rim  71 . 2  of the end part  71  of the framework  7 . 
         [0048]    Of course, forms other than those described above can be considered for the end part  71  of the framework  7 , as long as that end part  71  has arrangements allowing it to be fixedly connected to the upper terminal part  44  of the piston  42  before molding of the housing  1 , if applicable by adapting to geometries other than that of the flared end  45  shown in the figures. 
         [0049]    The running part  72  of the framework  7  is designed so as, before molding of the housing  1 , to allow the part of the conductive wires  62  outside the piston  42  to be outwardly attached on that running part  72  and thus to be kept in place relative to the framework  7 . In the example embodiment considered in the figures, this running part  72  delimits, on its upper face, a trough  72 . 1  for receiving wires  62  outside the piston  42 , in which trough those wires run lengthwise between the opposite end parts  71  and  73  of the framework  7 . Furthermore, as clearly shown in  FIG. 5 , the trough  72 . 1  is provided with at least one raised portion  72 . 2  that is configured, by itself or jointly with the rest of the trough  72 . 1 , to keep the wires  62  inside the trough  72 . 1  and thus participate in keeping those wires in place outside the piston  42 . Thus, for the example embodiment considered in the figures, the trough  72 . 1  is provided with several of these raised portions  72 . 2 , which are distributed in the longitudinal direction of the framework  7 , and at each of which each wire  62  is transversely jammed between the raised portion and the bottom of the trough  72 . 1 . 
         [0050]    Of course, embodiments other than the trough  72 . 1  and/or the raised portions  72 . 2  can be considered as long as they consist of arrangements, in particular but not exclusively in terms of shape, of the running part  72  seeking to keep the wires in place outwardly attached on the framework  7  and running along that running part  72 . 
         [0051]    The end part  73  of the framework  7  is advantageously designed to fixedly receive the connecting studs  63 . Thus, in the example embodiment considered in the figures and as shown in  FIG. 6 , this end part  73  is provided with through holes  73 . 1 , in each of which one of the studs  63  is received, in a complementary manner so as to connect the studs  63  and the framework  7  to each other. 
         [0052]    Optionally and advantageously, the end part  73  is more openworked than the rest of the framework  7 , so as to facilitate access to the electrical connection zone between the ends  65  of the studs  63  and the conductive wires  62 : thus, in the example embodiment considered in the figures, the end part  73  is openworked both upwardly and downwardly, while the running part  72  and the opposite end part  71  are only upwardly open, as shown by comparing  FIGS. 2 and 3 . Thus, in  FIG. 3 , a downwardly through window, delimited by the end part  73  and upwardly emerging on the connecting zone between the studs  63  and the wires  62 , is referenced  73 . 2 . 
         [0053]    Furthermore, independently of the immediately preceding considerations, the framework  7  advantageously includes a flexible zone  74  connecting its running part  72  and the end part  73  to each other. In the example embodiment considered in the figures, this flexible zone  74  consists of two parallel strands of material, which each connect the end  73  and running  72  parts to each other and which have respective cross-sections, the sum of which is significantly smaller than the minimum cross-section of the parts  72  and  73 . In other words, and more generally, the flexible zone  74  is thinner compared to the rest of the framework  7 . It will be understood that, owing to its flexibility, the zone  74  is easily deformable relative to the rest of the framework  7 , such that said flexible zone  74  makes it possible to adjust the relative position between the end part  73  and the running part  72 . In particular, as an example, the end part  73  can, subject to deformation of the flexible zone  74 , extend in an inclined direction relative to the longitudinal direction of the running part  72 . 
         [0054]    In light of the preceding explanations, it will be understood that the framework  7  is a part making it possible to support the conductive wires  62 , for the part of the latter outside the piston  42 , said part being designed to cooperate with the piston, the wires  62  and the connecting studs  63  before molding of the housing  1 . Furthermore, according to one manufacturing example of the thermostatic valve, the aforementioned components, in other words the piston  42 , inwardly equipped with the heating resistance  61  from which the conductive wires  62  extend, the framework  7  and the connecting studs  63  are assembled to one another to form an assembly as shown in  FIG. 7 . Then, secondly, the housing  1  is molded, more specifically overmolded, around that preassembled assembly. 
         [0055]    In practice, this means that the aforementioned preassembled assembly is positioned inside a molding mold, inside which the plastic material is injected so as simultaneously to coat the upper terminal part  44  of the piston  42 , the framework  7  and the conductive wires  62 . More specifically, at the terminal part  44  of the piston  42 , the plastic material coats the flared end  45  of the terminal part  44  of the piston  42 , as well as the end part  71  of the framework  7 : the plastic then spreads inside the piston part  44 , covers the upper face of the stepped wall  46 , and coats the entire end part  71  of the framework  7 , advantageously except for the inner periphery of the lower face of the rim  71 . 2  of that end part  71 , as clearly shown in  FIGS. 1 ,  3  and  4 . Likewise, the plastic material coats the entire running part  72  of the framework  7 , in particular by spreading on the wires  62  running over that running part  72 , inside the trough  72 . 1 . During the injection of the plastic material, the aforementioned wires are kept in place inside the trough  72 . 1 , ensuring that they are reliably coated, without risking pulling them, or even pulling them out. 
         [0056]    It will be understood that the plastic material that overmolds the upper terminal part  44  of the piston  42  and the framework  7  and is arranged inside the body  11 , molded jointly with the rest of the housing  1 , forms the aforementioned arm  14 . 
         [0057]    Of course, the overmolding of the housing  1  around the framework  7  is also done around the end part  73  of that framework, as clearly shown in  FIGS. 1 to 3 , in particular coating the electrical connections between the studs  63  and the wires  62 . Advantageously, beyond the end part  73 , moving away from the axis X-X, the overmolding is done so as to form the connecting base  16  around the free end  64  of the studs  63 . Of course, as an alternative that is not shown, before molding the housing  1 , the flexible zone  74  of the framework  7  can be deformed so as to modify the relative positioning of the end part  73  with respect to the rest of the framework  7 , to adapt to other positional geometries of the studs  63  within the thermostatic valve: the overmolding of the housing  1  then freezes the deformation of the flexible zone  74 , by coating. 
         [0058]    At the end of molding of the housing  1 , the latter is secured to the aforementioned preassembled assembly, by overmolding of the upper terminal part  44  of the piston  42 , the framework  7  and the conductive wires  62  outside the piston  42 . The valve  1  is then in the configuration shown in  FIGS. 1 to 6 . 
         [0059]    Advantageously, the manufacture of the thermostatic valve ends by attaching a single O-ring  8 , which is arranged coaxially around the piston  42 , radially interposed between the piston and a part  17  across from the arm  14  of the housing  1 , and situated axially upwardly bearing against the rim  71 . 2  of the end part  71  of the frame  7 , as clearly shown in  FIGS. 1 ,  3  and  4 . As an alternative that is not shown, the O-ring  8  has a four-lobed shape. 
         [0060]    When the thermostatic valve is in use, the piston  42  is pressed against the transverse arm  14  under the action of the thermostatic element  4  and the return spring  5 : the corresponding axial stresses are transmitted through the upper face of the stepped wall  46 . The first radial dimension of the space guarantees a reliable force transmission, without damaging the arm  14 , and more generally, the housing  1 . Furthermore, the seal  8  makes the inside of the piston  42  tight with respect to the fluid flowing in the body  11  of the housing  1 . 
         [0061]    Various arrangements and alternatives to the heating assembly and the thermostatic valve described thus far may also be considered. For example: 
         [0062]    in the embodiment described thus far, the single-piece housing  1 , which is attached by overmolding, constitutes the entire external housing of the illustrated valve; alternatively, this single-piece housing may correspond only to part of the valve housing, while in particular being provided to be assembled to another ad hoc housing element; and/or 
         [0063]    in the example embodiment considered in the figures, the tube of the heating cartridge, in which the heating resistance  61  is arranged, constitutes the piston  42  of the thermostatic element  4 ; for other thermostatic valve construction forms, this tube of the heating cartridge and the piston of the thermostatic element, the thermally expandable material of which is heated by the heating resistance belonging to the heating assembly, may consist of two separate parts; in that case, generally, the tube of the heating assembly extends through the bottom of the cup of the thermostatic element, opposite the piston of that element.