FR2950968A1 - PROBE FOR MEASURING THE OIL LEVEL IN AN AUTOMOBILE HOUSING MADE OF POLYMERIC MATERIAL - Google Patents

Abstract

The invention relates to a sensor for measuring the oil level in a motor housing, comprising a plug (1) for fixing said probe on a wall (7) of said housing and a dip tube (2, 3) carried by said intake (1), intended to be immersed in the oil and equipped with a measuring element (8) sensitive to the height of the oil in the housing. The dip tube (2, 3) is made of polymer material. Thanks to the invention, the probe is manufactured at lower cost and less mass.

Description

Probe for measuring the oil level in a car casing made of polymer material

The field of the present invention is that of equipment for the automobile, and more particularly that of instruments for controlling the proper functioning of the engine. The invention more specifically relates to an oil level probe. Motor vehicles are designed to operate with a properly lubricated engine, which assumes, among other things, that the engine crankcase maintains a sufficient volume of oil at all times. To ensure compliance with this condition, vehicles have an oil gauging system that is present in this case. Such a system comprises a probe attached to the housing, associated with a dip tube which is immersed in the oil and allows the remaining level to be determined by means of an element sensitive to the height of the liquid carried by the tube.

The probe generally comprises a socket fixed on the housing and which passes through a piercing, the sealing being provided for example by O-rings surrounding the socket and interposed between it and the housing wall. This plug serves, on the outside of the housing, mechanical support and electrical connection for a connector that collects information from the sensing element and transmits it to the lubrication monitoring system, which will then shape them for a presentation to the driver or to trigger an alert. It comprises, on the inside of the housing, a connection element to the dip tube. The latter optionally comprises a first portion bent to take into account the shape and orientation of the housing where the plug is located and straighten the rest of the tube to place it in a vertical position in the oil; it thus comprises a second part which extends vertically in the oil until it exceeds the maximum level attainable by the oil. This second part has two opening windows whose height positioning corresponds to the two extreme limits of the level that one wishes to monitor.

Inside this tube is unwound a resistive electric wire, constituting the sensitive element, which starts from the socket and extends by making a return trip in the tube, passing in front of the window furthest from the socket . The wire is thus immersed in the oil, over part of its length which is a function of the level thereof in the housing. The principle of measuring the oil level is based on the measurement of the potential difference between the ends of the wire at the plug, when an electric current of a predefined intensity is injected. The passage of the current causes the creation of heat by Joule effect, which dissipates in the environment. The dissipation of this heat is different depending on whether the wire is more or less immersed in the oil. The temperature obtained, resulting from this greater or lesser dissipation, acts on the resistivity of the wire and therefore on the voltage that must be applied to the terminals to pass the predefined current. In the known probes, the tube immersed in the oil is made in two parts: a first part is made of metal to meet the requirements of mechanical strength and in particular the vibration requirements which are high because, on the one hand of the vibratory level in the zone considered, on the other hand the relative length of the tube; the second part is made of polymer material for obvious reasons of cost. The first part is fixed on the socket which is made of metallic material, and the second part of the tube is fixed on the first, the two connections being made by crimping the metal. The second part of the tube is in the form of two half-shells, one of which carries the two windows of entry of the oil; this conformation with two shells makes it possible to have access to the wire during its assembly and, among other things, to be able to tension it during its installation, before closing the shells. The two half-shells fit one against the other and their common end located on the side of the metal part of the tube, is positioned in the crimp zone of this first portion of metal material.

The use of these probes, because of the choice of the metal for their realization and the crimping operation, results in a relatively high cost. The replacement of the metal with a polymer material encounters the problem of the vibratory level to be supported and the method of fixing the tube to the socket, crimping being no longer possible. The method of attachment must indeed guarantee the absence of rotation of the tube relative to the plug, because its angular position conditions the vertical positioning of the second portion of the dip tube. The object of the present invention is to remedy these drawbacks by proposing an oil level measurement probe in a low cost engine casing which is resistant to vibrational stresses and which ensures proper positioning of the dip tube in the liquid. . For this purpose, the subject of the invention is a sensor for measuring the oil level in an engine casing, comprising a plug for fixing said probe on a wall of said casing and a dip tube carried by said plug, intended to be at least partially immersed in the oil and equipped with a measuring element sensitive to the height of the oil in the housing, characterized in that said dip tube is formed (made) of polymeric material.

The merit of the inventors is to overcome the prejudice that one could not manufacture a "all-polymer" tube by providing, contrary to the teaching of the prior art that required that at least a portion of the tube be made of metallic material in the purpose of damping the vibrations, that the whole of this tube is in polymer (one speaks fluently of plastic material). The manufacture of a polymer tube allows a significant reduction in the mass and cost of the probe. According to a preferred embodiment, the tube comprising an end portion (or distal portion) intended to be at least partly immersed in the oil and a connecting portion between the end portion and the socket, the connecting portion and the terminal portion of the tube are formed (made) of polymeric material. This configuration allows, thanks to the connecting portion, to place the socket at a preferential location on the housing, while maintaining a vertical orientation for the terminal portion.

Preferably the plug is also formed (made) of polymer material. In this case a connector can be fixed on the socket, outside the housing, by a welding which can be of the type welding by vibration, ultrasonic welding or infrared welding. The use of polymeric material for setting also further increases the cost and mass reduction of the probe. According to a preferred embodiment, the end portion has two half-shells nested one inside the other. The invention further infringes the prejudices of the prior art according to which, if the end tube had two half-shells, it was impossible not to support them by a metal coupling portion because of the vibrations to which a motor housing. According to a preferred embodiment, the coupling portion comprises a monoblock tube portion. Such a portion of integral tube can dampen vibrations. According to a preferred embodiment in this case, the coupling portion supports, preferably in one piece, a half-shell, a half-shell being adapted to be fitted on the half-shell supported by the connecting portion to form with it the terminal portion. Thus, the mounting of the probe is simplified, the connecting portion 35 supporting even before mounting a portion of the terminal portion.

Preferably, the plunger tube comprises a male end cooperating with a cavity of the socket, the plunger tube being connected to the socket by a plugging force of said male end into said cavity. The ramming force makes it possible to ensure a good rotational retention of the dip tube on the plug. It also ensures a translational hold, avoiding inadvertent withdrawal of the dip tube from the socket. Preferably said cavity has an inner surface with a knurled area cooperating with a knurled area of an outer surface of said male end for their engagement in force. The use of knurling ensures a good retention of the dip tube in the cavity, against inadvertent translation of the tube and especially against any rotation. In a particular embodiment, the male endpiece comprises hooking means, said socket comprising retaining means capable of cooperating with said hooking means for holding the male end in the socket. These hooking means further improve the translational holding of the dip tube in the cavity. Preferably, the attachment means comprise lugs protruding from the male end and the receptacle comprises a groove for receiving said lugs. Advantageously, the male endpiece comprises at least one elastically deformable zone for reversibly reducing the section of the male endpiece when introduced into the cavity. The introduction of the tip into the cavity and the passage thereof through the first knurled zone of the latter are optionally facilitated. In a particular embodiment, said deformable zone is made elastically deformable by cuts made in the direction of insertion of the male end into the cavity. Preferably the notches are in number equal to the number n of clipping means and shifted by 7t / n relative to them. The invention also relates to a motor vehicle engine comprising a housing equipped with an oil level measuring probe as described above and a vehicle equipped with such a motor. The invention will be better understood, and other objects, details, features and advantages thereof will become more clearly apparent from the following detailed explanatory description of an embodiment of the invention given by way of purely illustrative and non-limiting example, with reference to the accompanying schematic drawings. In these drawings: - Figure 1 is a partial sectional view of a plug and a plunger tube according to the preferred embodiment of the probe of the invention, in front view; FIG. 2 is a perspective view of a dip tube according to the preferred embodiment of the probe of the invention, in profile view; FIGS. 3 and 4 are sectional views, respectively from the front and from the side, of a receptacle serving to support the dip tube of FIG. 2 for a measuring probe according to the preferred embodiment of the invention; FIGS. 5 and 6 are sectional views, respectively front and side, of the male end of the plunger tube of FIG. 2 and FIG. 7 is an isometric view of the male end of the plunger tube 15. FIG. 2. Referring to FIG. 1, an oil level probe comprising a plug 1 on which is mounted by crimping a first part, called a tube or connecting portion 2, of a dip tube, is seen first part being itself a carrier of a second portion, said portion or end tube 3. This tube 20 plunger is, according to the invention, made entirely of polymeric material; in this case therefore, the connecting tube 2, just like the end tube 3, are formed of polymer material. According to an alternative embodiment not shown, the plunger tube can be formed in one piece. In FIG. 1, the tap 1 is partially seen in section, as is the connecting tube 2, while the end tube 3 is shown in front view. The end tube 3 comprises two half-shells of which one, which appears in FIG. 1, comprises two openings, in this case called lower window 4 and upper window 5 because of their position in FIG. penetrate the oil whose level is to be measured. The plug 1 comprises a thread 6 intended to allow its attachment to the wall 7 of the casing in which is the oil whose level is to be measured. The connecting tube 2 is an intermediate piece whose primary function is to ensure correct positioning of the end tube 3, that is to say, in the first place to position it vertically regardless of the orientation of the housing to the where the plug 1 is mounted, and secondly to place it at a height such that the lower window 4 is placed below the lowest oil level that we want to measure. The upper window is then, by the choice made when defining the dimensions of the end tube 3, at or above the highest level of oil that is to be measured. The connecting tube 2 fulfills a second vibration damping function between the socket 1 and the end tube 3.

The dip tube is traversed by a resistive wire 8, U-shaped, which constitutes the measuring element and which goes back and forth inside the connecting tube 2 and the end tube 3. It is connected to its ends with two contacts 9 and 10 located in the socket, at which the desired voltage measurement takes place, and it extends throughout the length of the dip tube, to exceed the height of the upper window 5. In Referring now to Figure 2 there is shown the dip tube according to the preferred embodiment of the invention in profile view; it is noted that the junction between the connecting tube 2 and the end tube 3 is bent. The dip tube is shown in the configuration of an upwardly extending tube, the end tube 3 being located above the connecting tube 2 and the dip tube thus dipping into the oil from below; in another embodiment it could be oriented with the end tube located below the connecting tube, the dip tube then dipping into the oil from above. Again, the connecting tube 2 has the function of connecting the end tube 3 to a socket 1 fixed in a wall of the housing 7 containing the oil whose level is to be measured. The connecting tube 2 also makes it possible to position the end tube 3 in a vertical direction at the desired height, bypassing any obstacles in the volume of the casing. Since the connecting tube 2 according to the invention is no longer made of metal but of plastic, it is possible to compensate for the lack of stiffness of the plastic by increasing its thickness relative to that of an equivalent metal tube. The separation of the dip tube in two portions thus makes it possible to stiffen only the connecting portion 2 and to keep the same characteristics, for the end portion 3, as in the prior art. The connecting tube 2 has, at its end connected to the socket 1, in this case its lower end, a male end 21 intended to allow the attachment of the dip tube to a corresponding female portion 11 of the socket 1 and to ensure its holding in position, the socket 1 (not shown in Figure 2) being mounted on the housing 7 by a known fastening device. The male end 21 is in this case cylindrical and therefore extends globally along an axis.

Referring to Figures 3 to 6 we see the detail of the assembly means of the male end 21 of the connecting tube 2 on the female part 11 of the socket 1.

The female part 11 of the socket 1 comprises a cavity 12 with a cylindrical portion, for receiving the male end-piece 21, whose internal diameter substantially corresponds to the outside diameter of the male end 21 of the connecting tube 2, the inside diameter of the cavity 12 of the socket 1 being arranged relative to the outer diameter of the male end 21 in order to impose a force plug for the introduction of the male end 21 in the cavity 12. The entrance of the cavity 12 is longitudinally flat, without this feature is imperative, while the bottom of the cavity flares radially to create a circular groove 13 whose diameter is greater than that of its cylindrical portion. A chamfer 15 is also present at the bottom of the cavity and forms a connection between the cylindrical portion of the cavity 12 and the groove 13, in order to facilitate the passage of the cylindrical portion of the cavity 12 to its circular groove 13 for means of hooking, such as lugs 22, placed at the insertion end of the male end 21 and which are described in more detail below. The cavity 12 has, along a length, denoted L, of its cylindrical portion, a knurled zone 14, with a knurling projecting slightly inside this cavity 12. For its part, the male end 21 has a shape cylindrical complementary to that of the cavity 12 and has on its outer face a knurled zone 24, of a length substantially equal to the length L of the knurled zone 14 of the cavity 12 and positioned opposite this knurled zone 14 when the two parts are in position one in the other. Here, the knurling 24 projects slightly towards the outside of the cylinder, the tip 21 of which has the shape, the diameters of the two knurled zones being adapted so as to cause the two parts to be clamped together when the male end 21 is inserted into the cavity 12 of the socket 1, to prevent any rotation of the plunger tube relative to the socket 1; because of the interlocking knurling, any rotation of the male end 21 in the cavity 12 of the socket 1 would indeed cause a seizing knurling 14, 24 against each other, which would prohibit this rotation. At its insertion end in the cavity 12, the male end 21 has two protuberances or lugs 22, diametrically opposite with respect to the axis of the end piece 21, for maintaining the endpiece in translation 21. These lugs 22 form hooking means. These lugs 22 project, at the end of the nozzle 21, on its periphery, that is to say that they project out of its cross section. The lugs 22 have a first inclined face (bevel) with respect to a plane perpendicular to the insertion direction of the nozzle 21 in the cavity 12, so as to facilitate the introduction thereof into the cavity 12 of take 1; they also have a stop face perpendicular (transverse) to the axis of the nozzle 21 so as to ensure a locking in translation thereof when fully inserted into the cavity 12. When the tip 21 is in this position the lugs 22 penetrate into the groove 13 and prevents the removal of the tip 21, by the cooperation of the stop face of the lugs 22 with a radially extending face 16 of the groove 13, which fills and a function of retaining the attachment means 22, by abutment of the latter on it. In the insertion end of the male end 21 in the cavity 12 are formed two notches 23, diametrically opposite one another and offset by a quarter of a turn relative to the two lugs 22. These notches 23 are through the entire thickness of the nozzle 21 and cut along two generatrices of the cylinder whose tip 21 has the shape; they extend from the end of the nozzle 21 to its knurled portion 24; their length and their width are defined in a manner known to those skilled in the art to give sufficient flexibility to the two remaining half-cylinders (because of the cuts 23), thus defining an elastically deformable zone 25, and to allow the erasure of the lugs 22 when introducing the end of the nozzle 21 into the cavity 12 of the socket 1. We will now describe the mounting of an oil level measuring probe according to the embodiment described of the invention, on an oil retention housing. The operator first mounts the socket 1, alone, on the housing, by a suitable method and conventional for a skilled person. The plug 1 may have been previously provided with its dip tube if it is able to pass through the hole made in the wall 7. In the following description it is assumed that the dip tube is mounted after the fixing of the tube. the socket 1 on the casing 7; the principle of mounting the dip tube on the socket 1 remains unchanged in the case of a prior assembly of the tube on the socket 1. The method of fixing the socket 1 to the wall 7 of the housing can be screwing on a threading on the wall of a hole (piercing) drilled in the thickness of the wall 7 or a plugging force in such a hole. Seals are generally positioned, in a known manner, between the socket 1 and the casing wall 7. The connecting tube 2 and the end tube 3 are pre-assembled, with the resistive wire extending from the connection terminals with the contacts 9 and 10, at the foot of the connecting tube, up to exceed the upper window 5. This operation is in this case made possible by the constitution of the end tube 3 which is made in two half-shells , detachable one from the other, and which are assembled (fitted) before their common attachment to the connecting tube 2. In a particular embodiment, the connecting tube 2 is made in one piece with one of the two half-shells, a half-shell then being fitted on the half-shell of the connecting tube 2 to form with it the end tube 3. The operator then approaches the connecting tube 2 of the socket 1 and has the male end 21 in front of the inner cavity ure 12 of the socket 1. It then engages in force the male end 21 in this cavity 12. The pressure exerted on the lugs 22 during the support of the tip 21 on the insertion face of the cavity 12, associated with their bevel shape, forces them to return towards the interior of the cavity 12, which is made possible by the flexibility generated by the notches 23 formed in the tip 21; thus, the male end 21 is deformed elastically to be able to pass into the cavity 12. The end of the male end 21 then engages in the cavity 12, passes through the knurled zone 14 of the socket 1 and moves forward that the lugs 22 open at the groove 13. The half-cylinders carrying the lugs 22 then resume their position, since they form an elastically deformable zone 25, and engage the stop face of the lugs 22 against the radial extension face 16 of the groove. In this position the two knurled areas 14, 24 of the socket 1 and the nozzle 21 are engaged and cooperate to maintain the nozzle 21 in position in the socket 1; the pressure exerted on the surfaces in contact, associated with the interlocking of the two knurls 14, 24, ensures a good holding of the dip tube on the socket 1 and prevents its rotation. The dip tube is thus maintained both in rotation, by the cooperation of the two knurls 14, 24, and in translation, firstly by the two knurls 14, 24 and then, in a complementary and non-imperative manner, by the cooperation of pins 22 with the radial extension face 16. In the embodiment described, the male end 21 and the cavity 12 have been shown as cylinders of revolution; they may take any other form, provided that it allows them to be fixed to each other. Preferably, they are arranged to fit one into the other, preferably such that this interlocking is effected by fitting, thus generating a pressure between the surfaces in contact, so as to ensure their joining. Finally, the lugs 22, like the notches 23, have been represented in number of two; this number n of lugs 22 may be different from 2, the number of notches 23 then preferably being equal to the number of lugs 22 and each of them being positioned between two lugs 22. Preferably lugs 22 are distributed regularly on the periphery of the tip 21 and the notches 23 are offset by 7c / n relative to the lugs 22. Although the invention has been described in connection with a particular embodiment, it is obvious that it n It is in no way limited and includes all the technical equivalents of the means described and their combinations if they fall within the scope of the invention.

Claims (15)

REVENDICATIONS1. A sensor for measuring the oil level in a motor housing, comprising a plug (1) for fixing said probe on a wall (7) of said casing and a dip tube (2, 3) carried by said plug (1), intended to be at least partly immersed in the oil and equipped with a measuring element (8) sensitive to the height of the oil in the casing, characterized in that said dip tube (2, 3) is formed in polymeric material. 2. Measuring probe according to claim 1 wherein the tube (2,3) having an end portion (3) intended to be at least partially immersed in the oil and a connecting portion (2) between the terminal portion. (3) and the plug (1), the connecting portion (2) and the end portion (3) of the tube are formed of polymer material. 3. Measuring probe according to one of claims 1 or 2 wherein the plug (1) is formed of polymeric material. 4. Measuring probe according to one of claims 1 to 3, combined with claim 2, wherein the end portion (3) comprises two half-shells nested one inside the other. The measurement probe of claim 4, wherein the connector portion (2) comprises a one-piece tube portion. 6. Measuring probe according to claim 5, wherein the connecting portion (2) supports, preferably integrally, a half-shell, a half-shell being adapted to be fitted on the half-shell supported by the portion fitting (2) to form with it the end portion (3). 25 7. Measuring probe according to one of claims 1 to 6 wherein the dip tube (2, 3) comprises a male end (21) cooperating with a cavity (12) of the socket (1), the dip tube (2). , 3) being connected to the socket (1) by a plugging force of said male end (21) in said cavity (12). 8. Measuring probe according to claim 7 wherein said cavity (12) has an inner surface with a knurled area (14) cooperating with a knurled area (24) of an outer surface of said male end (21) for their mating in strength. 9. Measuring probe according to one of claims 7 or 8 wherein the male end (21) comprises means (22) for attachment, said socket (1) 35 having retaining means (16) adapted to cooperate with said hooking means for holding the spigot (21) in the socket (1). 10. Measuring probe according to claim 9 wherein the attachment means comprise lugs (22) projecting from the male end (21) and the socket (1) comprises a groove (13) for receiving said lugs (22). ). 11. Measuring probe according to one of claims 7 to 10 wherein the spigot (21) comprises at least one elastically deformable zone (25) for reversibly reducing the section of the spigot (21) during from its introduction into the cavity (12). 12. Measuring probe according to claim 11 wherein said deformable zone (25) is made elastically deformable by notches (23) made in the direction of introduction of the male end (21) in the cavity (12). 13. Measuring probe according to claims 9 and 12 wherein the notches (23) are in number equal to the number n of hooking means (22) and offset by iu / n relative thereto. Motor vehicle engine comprising a housing equipped with an oil level measuring probe according to one of claims 1 to 13. 15. Motor vehicle equipped with a motor according to the preceding claim.