FR2866151A1 - Seat occupant presence sensor for motor vehicle, has flexible units adapted so that conducting portions contact due to external pressure to circulate current, and opening to access internal space between inner sides of units from outside - Google Patents

Abstract

The sensor has two flexible units (9, 10), each with an inner side presenting an electrically conducting portion, and an outer side. The units are integrated to form an internal space between the inner sides. The units (9, 10) are adapted so that an external pressure makes the conducting portions to contact to allow the circulation of electrical current. An opening (20) permits the internal space to be accessed from outside. Independent claims are also included for the following: (A) a mould for manufacturing a vehicle seat cushioning that has a presence sensor (B) a process for manufacturing a vehicle seat cushioning (C) a vehicle.

Description

PRESENCE SENSOR, MATTRESSING EQUIPPED WITH SUCH A SENSOR,

  The present invention relates to presence sensors. BACKGROUND OF THE INVENTION

  More particularly, the invention relates to a presence sensor comprising a first flexible element and a second flexible element, each of which comprises: an inner face having an electrically conductive portion, said inner faces being disposed opposite one another and an external face opposite to said inner face, said flexible elements being integral with one another so as to form between said inner faces an internal space, said flexible elements being furthermore adapted, on the one hand, to an external pressure exerted on the outer face of at least one flexible element causes said electrically conductive portions in contact to allow the circulation of an electric current, and secondly, to prevent the flow of electric current when said portions electrically conductive are not in contact.

  When they are connected to a suitable electrical circuit, such presence sensors form a sensor capable of detecting that pressure is exerted on them. These are in particular often used in the motor vehicle seating elements, in particular the seat, as described in document US Pat. No. 5,896,090, in which they are installed in sheets between the seat padding and the covering cap.

  Nevertheless, such implantation near the surface is troublesome for several reasons. On the one hand, it can degrade both the comfort of an occupant seated in the seat that may feel under the sheet of sensors, and the appearance of the surface of the seat element, where protuberances can appear. On the other hand, the sensitivity of these sensors is very much related to the very nature of the covering cap which, for mainly aesthetic reasons, is often made in very varied materials that absorb the pressure exerted by the occupant very differently. in the seat. Finally, compatibility problems may arise if another sheet, for example a heating sheet, is located on the seat surface.

  To solve these problems, one could be trying to implant the sheet of sensors of the prior art deeper into the seat, that is to say for example under padding. Nevertheless, such a very deep implantation in the seat element makes it much less possible to detect the presence of an occupant since much of the pressure exerted by the occupant is absorbed by the padding.

  The present invention is intended to overcome these disadvantages.

  For this purpose, according to the invention, a sensor of the kind in question is essentially characterized in that it has an opening through which said internal space is accessible from the outside.

  Thanks to these arrangements, it is possible to maintain the presence sensor in the mold used to make the padding, keeping the inner faces spaced from each other by inserting a separator element in the internal space through the opening. This makes it possible to mold the padding around the sensor, and thus to incorporate the sensor to the desired depth in the seat.

  In preferred embodiments of the invention, one or more of the following provisions may be used: the sensor comprises an electrically insulating flexible element arranged between said first and second elements; flexible; said first and second flexible elements are each in the form of a thin film having a peripheral zone and a central zone, each electrically conductive portion extending in the respective central zone of the element which is associated with it, said element electrically insulating is in the form of a hollow film delimited by a peripheral zone similar to the peripheral zone of the first and second flexible elements, said electrically insulating element being devoid of central zone, and the peripheral zones of said flexible elements are each fixed on said peripheral zone of the electrically insulating element, except at the opening of said sensor for at least one of them; said flexible elements are made entirely of an electrically conductive material; - The inner face of each flexible element is made from an electrically insulating material on which is reported the electrically conductive portion associated therewith.

  In another aspect, the invention relates to a vehicle seat element padding comprising such a sensor.

  In a preferred embodiment, it may be possible to resort to the following arrangement: at least one of said outer faces of said sensor is fixed by overmolding in the padding.

  According to yet another aspect, the invention relates to a mold for producing such a seat element padding, said padding having, once molded, a final shape, said mold having an inner wall similar to said final shape molding pad, said mold having at least one separator element extending from said wall, and having a shape adapted to: be introduced into the internal space of the sensor through said opening, before molding the padding, hold said internal faces spaced from each other, during the molding of the padding and be removed from the internal space of the sensor after molding the padding.

  In a preferred embodiment, it is possible to use the following arrangement: the mold comprises several separator elements having different shapes to each other.

  According to yet another aspect, the invention relates to a method for producing such a seat element padding comprising steps in which, (a) in such a mold, said separator element is inserted into the opening of the sensor (b) injecting into said mold a foam capable of solidifying which at least partially encompasses said sensors, and (c) once the foam has solidified, removing said separator element from said sensor.

  In a preferred embodiment, it may be possible to use the following arrangement: said separator element has a thickness corresponding to a desired distance between said two internal faces, said method further comprising a step prior to step (a) , during which said separator element thickness is determined according to a desired sensitivity for said sensor.

  According to yet another aspect, the invention relates to a seat element comprising such a padding, said seat member having a bearing surface for receiving an occupant in the seat member, said occupant thereby generating a pressure field in the padding, said sensor being arranged so that said outer face of one of said flexible elements of said sensor is oriented generally towards said occupant when it has taken place in the seat, so that said pressure field generated by the The occupant causes said external surface to cause said external pressure to bring said two electrically conductive portions of said sensor into contact.

  According to yet another aspect, the invention relates to a detection device comprising such a sensor, and further comprising an electric circuit which comprises an electric current generator, a first terminal connected to the electrically conductive portion of the first flexible element, a second terminal connected to the electrically conductive portion of the second flexible element, and current passage detection means adapted to detect the passage of an electric current between the first terminal and the second terminal.

  According to yet another aspect, the invention relates to a vehicle comprising such a device.

  Other features and advantages of the invention will become apparent from the following description of one of its embodiments, given by way of non-limiting example, with reference to the accompanying drawings.

  In the drawings: FIG. 1 is a partially sectional view of a vehicle seat equipped with presence sensors; FIG. 2 is a sectional view of a first embodiment of a sensor according to the invention; FIG. 3 is an exploded perspective view of a sensor according to a second embodiment of the invention; FIG. 4 is a perspective view of a mold used to produce a padding provided with presence sensors; FIG. 5 is a perspective view of a pinch sensor for installation in the mold, and FIG. 6 is a sectional view of a presence sensor according to a third embodiment, embedded in the padding.

  In the different figures, the same references designate identical or similar elements.

  Figure 1 shows a seat comprising a seat 1 of a seat on which an occupant 2 can take place. It should be noted that the invention described here is not limited to seats seats, and applies to any other seat element may be provided with a presence sensor, such as for example a seat back, a seat headrest, an armrest or other.

  The seat 1 comprises on its upper part a flexible covering cap 3, made of variable type materials depending on the seat considered (eg textile, leather, etc.). The seat 1 thus has a bearing surface 28 with which the occupant of the seat is in contact when seated in the seat and constituted by the upper face of the covering cap 3. The cap covers a lining 4 such as synthetic foam padding or the like, which is supported by a strong structure. This resistant structure comprises, for example, a rigid reinforcement (not shown) on which is for example mounted an elastic suspension sheet 21, made for example of metal son, and which carries the lining 4.

  Directly under the cap 3, or placed inside the lining 4, there are one or more sensors 6 of presence. The sensors 6 are, on the one hand, connected to the pole more than one electric generator 34 by a first electric wire 7 and, on the other hand, to the minus pole of the same electric generator by a second electric wire 8 (FIG. 2) . One or other of these son can also be connected to an ohmmeter 33. At rest, when not stressed, the presence sensors 6 have a large resistance, so that no current can pass through these sensors.

  A first embodiment of such a sensor is shown in Figure 2, which is for example taken in the same section as the seat in Figure 1. In this first embodiment, the sensor has for example a cylindrical shape when seen in the direction of the double arrow of Figure 2, and slightly domed in the plane of section.

  The sensor comprises a first layer 9, consisting for example of a flexible electrically insulating synthetic material, intended to receive on its outer face 29, oriented towards the bearing surface 28, a pressure in a direction generally normal to the surface of this first layer 9, and further having an inner face 24 facing the inside of the sensor 6. The sensor also has a second layer 10, for example made of a flexible plastic material electrically insulating, having an outer face 25 and a face internal 26 facing the inside of the sensor 6.

  The internal faces 24, 26 respectively of the first flexible element 9 and the second flexible element 10 are respectively provided with a first 13 and a second 14 electrically conductive element in an internal space 12 between the first 9 and second 10 flexible elements . These first 13 and second 14 conductive elements are respectively connected to the plus pole and the minus pole of the electrical generator via respectively the first wire 7 and the second electrical wire 8.

  Of course, all forms of sensors for matching at a given distance two conductive elements can be used in the context of the invention, and in particular a parallelepiped shape.

  According to a second embodiment (FIG. 3), the first 9 and second 10 flexible elements are made directly from an electrically conductive material, and consist, for example, of woven metal wires. It is then not necessary to report on the first 9 and second 10 flexible elements of the first 13 and second 14 conductive elements, but it is a portion of the inner face 24, 26, the first 9 and second 10 flexible metal elements which serves as an electrically conductive element. The first 9 and second 10 flexible elements are then directly connected respectively to the plus and minus pole of the generator respectively via the electric wires 7 and 8. In this case, the sensor 6 also has a flexible intermediate element 11, consisting of for example a flexible synthetic material, placed between the first 9 and second 10 flexible elements. It is expected that the first 9 and second 10 flexible elements have a similar shape comprising a central zone 30 and a peripheral zone 31, and that the flexible intermediate element 11 has a shape devoid of central zone, and therefore only having a zone 32. It is useful that the flexible intermediate member 11 is made of an electrically insulating material.

  In the case of first 9 and second 10 cylindrical flexible elements, this flexible element may for example be annular, thus defining the free internal space 12.

  According to a third embodiment, the second embodiment is modified in that the flexible elements 9, 10 of the sensor are not made from wire, but can each be made of an electrically insulating flexible material, on the face inside which a conductive element 13, 14 is attached.

  The operating principle of such sensors, according to any one of the first, second and third embodiments presented above is now described.

  When a strong pressure is exerted on the sensor 6, it deforms and the free inner space 12 is compressed until the first 13 and second 14 electrically conductive elements come into contact, which allows a current to flow between the first 7 and second 8 electrical wires. The ohmmeter then detects a resistance drop of the sensor 6, which means that the seat is occupied.

  Nevertheless, in the sensors of the prior art, when a too weak pressure is exerted on the sensor 6, the first flexible element 9 is not sufficiently deformed to compensate for the displacement or the deformations of the second flexible element 10, so that the first 13 and second 14 electrically conductive elements do not come into contact, and no current can pass. This phenomenon is particularly common in sensors of the prior art when they are implanted under the padding 4 of the seat, which absorbs almost completely the pressure exerted by the user on the seat.

  The method of producing a presence sensor according to the invention is now presented, in FIGS. 3 and 4, for a sensor of rectangular shape according to the second embodiment of the sensor. The same method can nevertheless be implemented for the various embodiments of the sensor.

  Thus, this sensor is in the form of two thin rectangular films 9, 10 made in the form of an electrically conductive fabric, and a flexible intermediate element 11 in the form of a rectangular frame hollowed out in its shape. center made from an electrically insulating material.

  The first 9 and second 10 electrically conductive flexible elements are each fixed on either side of the flexible insulating element 11, for example by gluing, sewing, or any other appropriate means. At least one of the first 9 and second 10 electrically conductive flexible elements is attached to the flexible insulating element on a portion of its periphery, for example on the three sides 9a, 9b, 9c, so that the fourth side 9d n it is not fixed on the flexible insulating element 11, but simply rests on it, thereby providing an opening 20 through which the internal space 12 can be accessed from outside the sensor 6.

  Of course, for a sensor of cylindrical shape, the flexible conductive element will be fixed to the flexible insulating element 11 only over part of their periphery.

  Figure 4 now shows a mold adapted for molding the padding 4 to be mounted on the seat member (seat, backrest, headrest, or other) shown in Figure 1. The mold 15, for example here a mold for a headrest is in the form of a tank 16 on which is hinged a lid 17 which can be folded down on the tank 16 so as to form a closed space comprising a cavity 18 whose wall has the shape of the padding 4 to foam. In the context of the invention, the mold 15 also comprises at least one separating element 19, for example in the form of an oblong element fixed or mounted on the inner wall of the cavity, and extending inwards of the mold. The position of the free portion 19b of the separator element in the mold defines the position that the sensor 6 is intended to occupy in the padding 4.

  As shown in more detail in FIG. 5, the free part 19b of the separating element 19 has, in particular, a shape adapted to be able to be introduced into the opening 20 formed for this purpose in the sensor 6 at the edge 9d of the first element flexible 9. This introduction is facilitated when, as shown grossicially caricature in Figure 5, the sensor is gripped, for example with his fingers, at its sides 9a and 9c to spread the side 9d of the first flexible element 9 of the corresponding part of the flexible insulating element 11. Thus it is possible to thread the sensor 6 onto the free part 19b of the separating element 19 so that this free part 19b keeps the electrically conductive portions 13, 14, respectively of the first 9 and the second 10 flexible elements.

  Although the mold is shown in FIG. 4 provided with a single separating element 19, several separating elements may be provided, the free portion 19b of which may or may not be at the level of the wall of the cavity 18. The free part 19b at the wall allows the sensors to be placed on the padding surface.

  A foam capable of solidifying, such as polyurethane, or the like, can then be conventionally injected into the mold under pressure. The foam then extends around the presence sensors 6 fitted on the separating elements 19, but the pressure exerted by the foam on the outer faces 29, 25 of the first and second flexible elements 9, 10 can not push back towards the the other the internal faces 24, 26 of said flexible elements, since these are kept at a distance by the separating element 19.

  The separator element 19 is introduced into the sensor 6 in a foam-tight manner, so that the foam can not penetrate into the internal space 12 during the molding operation.

  We can then close the lid and the foam will gradually expand and adhere to the outer faces 29, 25 of the sensor 6. In the solidified state, the foam and the sensor provided with its separator element 19 are then in a state mechanical balance.

  By removing the padding formed of the mold, the separating element 19 is removed from the inside of the internal space 12 by the opening in the sensor 6. Either the separating elements 19 are permanently mounted in the mold 15, and the simple action of removing the padding from the mold removes the separating elements 19 from the inside of the sensors 6, or the separating elements 19 are removably mounted on the mold 15, and these are disassembled in order to be removed from the mold 15 with the padding, and are subsequently removed therefrom.

  FIG. 6 shows a view of the third embodiment of the sensor according to the same section as FIG. 2, after its formation and incorporated in the padding 4. The effective shape of the sensor 6 in the foam formed depends on the shape of the free part 19b of the separator element 19. The height at which the sensor 6 in the padding 4 is located depends on the position in the mold of the free part 19b of the separating element 19. In the rest state shown in FIG. 6, in which no occupant is seated on the seat, the first 9 and second 10 flexible elements are kept at a distance because their respective outer faces 29, 25 are fixed at equilibrium in the padding 4.

  By choosing the shape and the position of the free parts 19b of the separating elements 19, the shape of the sensor 6 is chosen, and in particular the distance between the first 9 and second 10 flexible elements, which is directly related to the sensitivity of the sensor 6 For example, it would be possible, for example, to deposit, in the vicinity of the surface of the seat, less sensitive sensors, and / or deeper in the padding, more sensitive sensors, to determine more precisely the presence or not, or even possibly , the weight of the occupant of the seat. It will also be possible to select or design the type of sensor to be used specifically for a given seat, knowing the predetermined type of use of the seat.

Claims (14)

  A presence sensor comprising a first flexible member (9) and a second flexible member (10), each of which comprises: an inner face (24, 26) having an electrically conductive portion (13, 14), said inner faces being disposed opposite one another, and an outer face (29, 25) opposite to said inner face, said flexible elements being integral with each other so as to form between said internal faces an internal space ( 12), said flexible elements being furthermore adapted, on the one hand, so that an external pressure exerted on the external face of at least one flexible element causes said electrically conductive portions in contact to allow the circulation of an electric current. and, on the other hand, to prevent the flow of electric current when said electrically conductive portions are not in contact, characterized in that the sensor has an opening (20) through which said internal space (12) is accessible from the outside.   The sensor of claim 1, further comprising an electrically insulating flexible member (11) disposed between said first and second flexible members.   The sensor according to claim 2, wherein said first and second flexible elements (9, 10) are each in the form of a thin film having a peripheral zone (31) and a central zone (30), each electrically conductive member (13, 14) extending into the respective central zone of the element associated therewith, wherein said electrically insulating member is in the form of a hollow film delimited by a peripheral zone (32) similar to the peripheral zone of the first and second flexible elements, said electrically insulating element being devoid of central zone, and wherein the peripheral zones of said flexible elements are each fixed (31) on said peripheral zone (32) of the electrically insulating element, except for level of the opening of said sensor for at least one of them.   4. Sensor according to any one of claims 1 to 3, wherein said flexible elements (9, 10) are made entirely of an electrically conductive material.   5. Sensor according to any one of claims 1 to 3, wherein the inner face of each flexible element (9, 10) is made from an electrically insulating material on which is reported the electrically conductive portion associated therewith .   6. Vehicle seat element padding 20 comprising a sensor (6) according to any of the preceding claims.   The seat element pad according to claim 6, wherein at least one of said outer faces (29, 25) of said sensor is overmolded in the padding.   8. Mold for the realization of a seat element padding according to claim 6 or 7, said padding (4) having, when molded, a final shape, said mold having a wall internal device (18) similar to said final form of the padding to be molded, characterized in that said mold comprises at least one separating element (19) extending from said wall, and having a shape adapted to: - be introduced into the internal space (12) of the sensor through said opening (20), before molding the padding, keeping said inner faces at a distance from each other, during the molding of the padding and - being removed from the internal space (12) of the sensor after molding the padding.   9. Mold according to claim 8, comprising a plurality of separating elements (19) having shapes different from each other.   10. A method of producing a seat element padding according to claim 6 or 7, comprising steps in which, (a) in a mold according to claim 8 or claim 9, said separator element (19) is inserted into the opening (20) of the sensor (6), (b) a mold capable of solidifying which at least partially encompasses said sensors is injected into said mold (15), and (c) once the foam has solidified, said separator element (19) is removed from said sensor (6).   11.The method of claim 10, wherein said separator element (19) has a thickness corresponding to a desired distance between said two inner faces, said method further comprising a step prior to step (a), during which said separator element thickness is determined as a function of a desired sensitivity for said sensor (6).   A seat member comprising a padding (4) according to claim 6 or claim 7, said seat member having a bearing surface (28) for receiving an occupant in the seat member, said occupant thereby generating a pressure field in the padding (4), said sensor (6) being arranged such that said outer face (29) of one of said flexible elements (9) of said sensor is oriented globally towards said occupant when it has taken in the seat, so that said pressure field generated by the occupant causes on said outer face (29) said external pressure which brings into contact said two electrically conductive portions (13, 14) of said sensor.   13. Detection device comprising a sensor according to any one of claims 1 to 5 and further comprising an electric circuit which comprises a generator (34) of electric current, a first terminal connected to the electrically conductive portion (13, 25). the first flexible element (9), a second terminal connected to the electrically conductive portion (14, 25) of the second flexible element (10), and means for detecting the current flow adapted to detect the passage of an electric current between the first terminal and the second terminal.   14.A vehicle comprising a device according to claim 13.