Level indicator, in particular for a combustion engine cooling circuit of a motor vehicle

0001The present invention relates to a liquid level sensor, in particular for a cooling system of the engine of a motor vehicle.

0002A sensor verifies the presence of liquid cooling in the cooling radiator of a vehicle automobile and provoguer igniting a bright light on the instrument edge to alert the driver in case of absence or level Insufficient fluid. It typically includes a probe consisting of two closely spaced parallel electrodes, plunging vertically for example in the radiator expansion tank, between which is circulated an electrical signal.

0003As the liquid, which is conductive, bathes the two electrodes, the signal may flow from one electrode to the other. In case of lower the liquid level below the lower end of electrodes, the signal path between the electrodes is interrupted.

0004A simple electronic circuit controls the transmission of the signal in the probe and can distinguish the two situations above, for achieving a continuity sensor.

0005In Figure 1, a partial view is shown of a sensor liquid level according to the prior art, with a partial section the detail of the means of mounting and fastening on an upper wall 10 the radiator expansion tank.

0006A main part 30 to hold the housing forming sensor electronics, partially shown in Figure 1, is extended by two electrodes 21 and 22, said main portion and said electrodes being separated by the mounting means and fixing of the sensor on the wall 10 of the radiator expansion tank. These means will be described in more detail in the following description.

0007The electrodes 21 and 22 comprise two conductors or rods conductive, 23 and 24 respectively, made of a copper alloy and zinc and whose ends are tinned to still make better conductive. These conductors are covered except for their end by an insulating cladding, respectively 25 and 26, directed to integrally with the main part 30, for example by overmolding plastic on the conductors.

0008The insulating sheathing 25 and 26 primarily serve a function for holding the conductors 23 and 24 of the electrodes 21 and 22.

0009Indeed, the diameter of the conductors is of the order of 2 mm and their length can reach 126 mm depending on the application, and depending in particular on the shape of the expansion tank of the radiator and the mounting location of the sensor thereon.

0010Insulating sheathings thus possible to prevent the conductors are twisted when transporting the sensor and manipulations before being mounted on the radiator, which could prohibit the fitting of the sensor and even cause a short circuit between the two conductors.

0011The rigidity of the electrodes 21 and 22 is further enhanced by presence of a central rib 27 made integral with the sheathings insulators 25 and 26 and with the main portion 30.

0012However, it has been found that a sensor such as that shown in Figure 1, once assembled on the cooling radiator of a motor vehicle, and in the absence of any malfunction electronic circuit, does not always work satisfactorily.

0013In particular, when the engine cooling circuit emptied abruptly, for example when a hose breaks or disconnected, and therefore the end of the electrodes 21 and 22 is more bathed in the liquid, the warning light on the dashboard sometimes remains off. This is obviously very damaging since the driver is not informed that the cooling circuit of the motor is defective, can not stop in time to the vehicle prevent the destruction of the engine by increasing its temperature beyond a destruction temperature.

0014It seems that this sensor malfunction can be attributed to the formation of a drop of liquid, referenced 50 in FIG 1, between the conductors 23 and 24 and the chamfered ends of insulating sheaths 25 and 26 of the two electrodes 21 and 22. Indeed, Such a drop maintains electrical contact between the conductors 23 and 24 despite the absence of liquid in the radiator.

0015For reasons relating to the space available for mounting the sensor on the upper wall 10 of the radiator expansion tank, the hole therein presents a diameter D of 18 mm.

0016This leads to dispose the electrodes 21 and 22 so enough close. Indeed, the distance between their respective axes is only about 6 mm.

0017Gold, wherein the coolant is generally composed of a mixture of water, glycol and alcohol which gives a viscous structure, we understand that it is indeed possible that 50 drop of liquid forms between the electrode tips when the radiator empty abruptly.

0018The present invention aims to overcome this drawback of the state art.

0019Indeed, the invention relates to a liquid level sensor, in particular for an engine cooling system of a vehicle automobile, of the type comprising at least two electrodes substantially parallel intended to penetrate into a cavity containing liquid normal and having two apparent conductive portions of electrodes disposed substantially at the same level, and a circuit own electronic circulating an electrical signal between said electrodes so as to achieve a continuity sensor.

0020According to the invention, the sensor includes anti-drip means that would prevent the retention of one or more liquid drops connecting the exposed conductive portions of the electrodes.

0021According to a first embodiment of the invention, each electrode comprises a conductive rod covered except at its end apparent with an insulating sheath of maintenance, and the insulating sheath of an first electrode is shorter than that of the second electrode to provide said anti-drip means.

0022In this first embodiment, the conductive rods the first and second electrodes may be of the same length.

0023The visible part of the conductive rod of said first electrode which is not covered by the insulating sheath may be substantially two times longer than the corresponding portion of said second electrode.

0024Alternatively, the conductive rod of said first electrode can be shorter than the conductive rod of said second electrode.

0025According to a second embodiment of the present invention, each electrode comprises conductive rods having portions exposed, and exposed conductive portions are arranged away from one another and connected to one another by a solid material electrically insulating forming a common insulating sheath whose surface external is continuous and generally convex, concave possible said outer surface having sufficiently small dimensions and large enough spacing to prevent retention drops liquid contiguous.

0026Preferably, the outer surface of the common sheath is smooth, to reduce the adhesion of liquid, and it may advantageously be cylindrical to facilitate evacuation.

0027In all embodiments, the insulating sheaths may advantageously be made integral with a main portion forming the sensor housing, by overmolding the conductive rods.

0028The invention also concerns an installation for cooling the heat engine of a motor vehicle, comprising a radiator provided with an expansion vessel, which is characterized in that it includes a level sensor as defined above, in particular arranged in said expansion tank, which alerts the driver by via an indicator light on the dashboard of the vehicle, when the coolant level in the system is insufficient.

0029Other features and advantages of the present invention apparent on reading the nonlimiting description which follows, with reference to the accompanying drawings in which:<ul><li>Figure 1, already partially analyzed, shows schematically a level sensor according to the prior art;</li><li>Figure 2 and Figure 3 illustrate, in front view and in side view, a level sensor according to a first embodiment of the invention;</li><li>Figures 4, 5, 6, 7 and 8 illustrate, respectively in a view Front, side view, in section AA, BB section and in perspective, the downwardly directed portion of a sensor according to a second embodiment of the present invention; and</li><li>9 illustrates, in perspective, the plunging part a two-level sensor according to the second embodiment of the invention.</li></ul>

0030Figure 1 depicts a level sensor the prior art detailing the means for mounting and fixing the sensor on the wall 10 of the radiator expansion tank. These means are represented as a partial section of the portion of the sensor between the main part 30 and the electrodes 21 and 22.

0031The wall 10 of the vessel to the cooling radiator expansion has a stepped hole for passage and fixing of the sensor according to a bayonet mount. This hole comprises, on the outer face side of the wall 10, a portion of cylindrical bore and on the side of the internal face of the wall 10, a portion of shaped bore overall rectangular.

0032The means for mounting and fixing of the sensor on the wall 10 include, starting from the main part 30 forming a housing sensor:<ul><li>an annular groove 41, the upper sidewall 46 connects to the main part 30 forming the sensor housing and whose flank less than 47 is chamfered to permit the mounting of an O-ring 45;</li><li>a cylindrical portion 43 having two flats not visible in Figure 1, and whose largest dimension does not exceed the smallest dimension of the bore portion to form overall rectangular of the stepped hole of the wall 10;</li><li>and a chamfered shoulder 44 extending said portion cylindrical comprising two own radial tabs to cooperate with the inner surface of the wall 10.</li></ul>

0033These means to achieve a tight installation of the sensor on the expansion tank, and are not in themselves the subject of the invention.

0034To Figures 2 and 3, in which the same elements as in Figure 1 bear the same references, a sensor is shown as a first embodiment of the invention. 2 is e.g. a front view and Figure 3 is for example a left side view.

0035The main part 30 forming the sensor housing includes a upper half case 32 and a lower housing half extended 31 radially forming part 33 connector for connection to outside the electronic circuit in the sensor, via a complementary connector and a not shown wiring harness. The part 33 forming the connector for this purpose comprises at least three connecting pins 34, the first of which is intended to be connected to the mass of the vehicle, the second to the supply voltage of the battery, and the third to a first terminal of an indicator lamp disposed on the dashboard of the vehicle and whose second terminal is connected to the mass.

0036The electronic circuit located inside the part 30 forming main sensor housing comprises means such as a voltage oscillator for generating an AC signal between the two conductors 23 and 24 to which these means are connected, and to detect the passage or non-passage of the signal between the conductors 23 and 24 via the coolant. An alternating signal allows overcome the problems of electrolytic liquid through which said signal.

0037Upon detection of a non-electrical continuity between the two conductors 23 and 24, a DC voltage is generated on the third connecting connector pin 33 to light the lamp witness.

0038Accordance with the principle of the invention, the sensor comprises anti-drop means for preventing the retention of one or more drops liquid between the conductor exposed ends of the electrodes, especially when the cooling system is emptied abruptly.

0039In this first embodiment, the anti-drip means made in the way that is described below. Each electrode 21, 22 respectively, comprises a conductive rod 23, respectively 24, covered, except at its exposed end, an insulating sheath maintenance 55, respectively 56, the insulating sheath of the first electrode 22 is shorter than that of the second electrode 21.

0040According to a first adaptation of this embodiment, shown in Figure 2, the conductive rods of the first and second electrodes are of the same length. Preferably, the portion apparent from the conductive rod 24 of the electrode 22 which is not covered by the insulating sheath 56 is then substantially twice longer than the corresponding portion of the electrode 21.

0041In another adaptation of this embodiment, not shown in the figures, the conductive rod 24 of the electrode 22 is shorter than the conductor rod 23 of the electrode 21. In this case, the exposed parts of the conductive rod 24 of the electrode 22 which is not covered with the insulating sheath 56, and the corresponding exposed portion of the conductive rod 23 of the electrode 21, are preferably same length.

0042In all cases, the beveled ends of the claddings 55 and 56 does not in the same horizontal plane, they do not offer taken for the formation of a liquid drop between the rods conductor 23 and 24. Indeed, when the cooling circuit dry, even when empty abruptly, the liquid slides all first along the insulating sheaths 55 and 56, then along the sheath insulator 55 and the conductive pin 24, and finally along the rods conductors 23 and 24, without that no place may form and to maintain a drop of liquid capable of shorting the two conductive rods.

0043Figures 4 to 8 illustrate the downwardly directed portion of a sensor according to a second embodiment of the invention.

0044This downwardly directed portion sensor is intended to be connected to a major portion of sensor similar to that of modes embodiment of Figures 1 to 3, the main portion 30 providing the mounting tight on expansion vessel wall and containing the circuit internal electronic sensor.

0045In this second embodiment, there are two electrodes including two conductive rods 23 and 24 generally parallel. The conductive rods 23 and 24 comprise conductive portions exposed, respectively 63 and 64, disposed apart from each other and connected to each other by a solid electrically insulating material forming a common insulating sheath 60.

0046The outer surface 61 of the common insulating sheath 60 is continuous and generally convex. Any concavities of this outer surface 61 must have sufficiently small dimensions and sufficiently wide spacing between the relative to each other to avoid touching drops of liquid retention can provide electrical continuity between the conductive portions 63 and 64 exposed when the coolant level is lowered below the level occupied by the conductive portions Exposed 63 and 64. Thus, the common insulating cover 60 to outer surface 61 continuous and generally convex forms the anti-drop way in this second embodiment. This method is particularly effective, and provides high reliability.

0047Preferably, the outer surface 61 of the sheath 60 is common smooth, to reduce the adhesion of the liquid.

0048Figures 4 to 8 illustrate this embodiment in view of front view in FIG 4, in right side view of Figure 5, in section cross on plane in Figure 6, in cross section along plane BB in Figure 7, and in perspective in Figure 8. It Note that the exposed conductive portions 63 and 64 are portions outer cylindrical surface of the two conductive rods 23 and 24 cylindrical. The exposed conductive portions 63 and 64 are oriented in non convergent respective directions, preferably in opposite directions.

0049In the illustrated embodiment, the outer surface 61 of the sheath joint 60 is generally cylindrical, that is to say formed by generating remaining parallel to the common axis of the conductive rods 23 and 24. In cross section, illustrated in Figures 6 and 7, the Plunge sensor portion may have a general shape of a diamond to rounded tops.

0050The edges of each of the exposed conductive portions 63 and 64 are connected to the outer surface 61 of the collective casing 60 by a flared peripheral wall 65, as shown in the figures, favoring the flow of coolant at its lower level.

0051The outer surface 61 of the sheath 60 forms a common end 62 insulating convex downwardly directed portion of the sensor. portions exposed conductor 63 and 64 remain away from said end 62 insulating convex. This way, when the diving portion of sensor is disposed in a substantially vertical orientation, the liquid cooling, lowering level, leaving the contact Exposed conductive portions 63 and 64 before leaving contact with the outer surface 61 of the collective casing 60 forming the end 62 of downwardly directed portion of the sensor.

0052The insulating sheaths 55, 56 and 60 respectively, in the two embodiments, can advantageously be made of material with the main part 30 forming the sensor housing, by overmolding on the conductive rods 23 and 24 of the electrodes. Similarly, the portion 33 A connector can be realized integrally with said portion main 30 during the same operation, by overmolding on the pin Connection 34. All these can be achieved in a matter plastics such as polyamide 66 (PA66).

0053The invention also concerns an installation for cooling the heat engine of a motor vehicle, comprising a radiator provided with an expansion vessel. A level sensor such as defined above, is arranged for example in said expansion tank, and alerts the driver via an indicator light on the dashboard of the vehicle when the liquid level cooling in the system is inadequate.

0054The sensor of the invention has been described in two modes individual achievement but not limiting. In particular, the sensor may include more than two electrodes to detect a plurality of levels liquid, the means of the invention to prevent the formation of a drop between the pairs of electrodes being broken down so adapted.

0055For example, in the variant of the second embodiment illustrated in Figure 9, there is provided a sensor having four electrodes substantially parallel, two first electrodes being opposite one other, for example, first two opposite vertices of the section cross diamond, and having two first conductive portions exposed 63 and 64 located in a first level, two seconds electrodes being angularly offset relative to the first and electrodes opposed to each other, for example the other two peaks of the cross-sectional diamond, and having two seconds Similar exposed conductive portions such that the second portion apparent conductor 163, located at a second level different from the first level. Thus, a two-level sensor, the first two electrodes capable of generating a first electrical signal when the liquid reaches the first level, the second two electrodes capable of generating a second electrical signal when the liquid reaches the second level.

0056The electrodes can dip substantially vertically in a cavity as the expansion vessel of the cooling radiator engine of a motor vehicle. But it is obvious that other applications are possible, in which the electrodes are Non oriented vertically, especially with the second embodiment.

0057The present invention is not limited to the embodiments that have been explicitly described but includes the various variants and generalizations thereof within the scope of the claims below.