FR2858812A1 - Tank for auxiliary or operating liquid in Internal combustion (IC) engine is shaped with reducing section from base to top - Google Patents

Abstract

Tank (10) e.g. for containing urea or a solution (12) of urea and water, is made from a plastic material, especially by blow moldings. It has an outlet (14) in its base (16) and a vent (26) at the top (24), and is shaped so that it reduces in section between the base and top, being e.g. truncated conical or pyramidal. The tank (10) e.g. for containing urea or a solution (12) of urea and water, is made from a plastic material, especially by blow moldings. It has an outlet (14) in its base (16) and a vent (26) at the top (24), and is shaped so that it reduces in section between the base and top, being e.g. truncated conical or pyramidal. The tank is fitted with a heater (28), either a coil or a tube carrying a heated fluid, and can form part of a selective catalytic reduction system for purifying exhaust gases.

Description

Field of the invention

  The present invention relates to a reservoir for a liquid, in particular for an operating liquid and / or an auxiliary liquid for the operation of an internal combustion engine and / or to installations associated thereto or downstream thereof, having a sampling port near the bottom of the tank and a venting hole in the upper area of the tank.

  STATE OF THE ART As the limit values for pollutants should decrease more and more in recent years for internal combustion engines of motor vehicles, various processes have been developed for treating the exhaust gases of internal combustion engines. . To reduce the NOx components contained in the exhaust gas, in particular, reducing catalysts have been developed for diesel engines which can usually be classified as selective catalytic reduction catalysts equipped with a urea metering system and accumulator catalysts. Selective reduction catalysts (also known as SCR catalysts) are regenerated by a urea feed and / or an ammonia reducing agent while the accumulator catalysts are regenerated by cyclic hydrocarbon feed and combustion. These hydrocarbons are usually the fuel carried by the vehicle and supplying the internal combustion engine; in the operating phase with a rich mixture, the exhaust gases serve to regenerate the accumulator catalyst.

  Urea or water / urea solution for the operation of urea dosing systems is usually taken to a vehicle tank. As for the urea dosing system, the water / urea solution, usually used, freezes at temperatures below about 11 C, when used in a motor vehicle it is necessary to isolate or heat the tank to ensure low temperatures, reliable sampling in the fluid state. In the case of tank heating and removal of the water / urea solution at the bottom of the tank, the still frozen layer which is above the liquefied layer can interfere with the filling of the tank because it forms a watertight separating layer towards the bottom of the tank. low. The ventilation of the lower zone of the tank by a ventilation opening provided in the upper part is hampered for these reasons.

  To remedy this difficulty, it is possible to use a bypass air con-duce which connects the upper zone of the tank or its bottom and which bypasses the tank from the outside.

  Moreover, between the part of the water / urea solution already de-frozen and the part still frozen and which clings to the side walls of the tank, during defrosting, the formation of an air layer hindering the transport of the heat between the heated lower zone towards the still frozen upper zone of the solution. If necessary, this effect can lead to power cuts in the water / urea solution.

  With the help of Figure 2 will be described below a reservoir for a water / urea solution corresponding to the current state of the art. In the cylindrical or prismatic reservoir 10 there is a water / urea liquid solution 12 supplying a urea metering system (not shown) via a sampling orifice 14 provided in the bottom 16 of the reservoir. A bypass line 18 connects a bottom vent 20 of the bottom 16 of the tank to an upper vent 22 in the upper zone 24 of the tank 10. Furthermore, in the upper zone 24 of the tank 10 there is a upper ventilation 26 through which air can enter the reservoir 10 when the level of the water / urea solution 12 decreases by leakage of the sample.

  During winter operation, the temperature of the water / urea solution 12 in the tank may drop below 11 C so that the solution 12 may freeze in the tank 10.

  To avoid this, there is provided a heating installation 28 in the tank 10 which is usually in the lower zone 30 of the tank 10 and comprises for example an electric heating coil or a heating pipe traversed by a hot fluid, for example from the cooling water or other fluid heated by the heat released by the engine.

  The heating system 28 makes it possible to keep the solution 12 in the liquid state in the lower zone 30 of the tank 10. However, it can not prevent the upper layer 32 of the solution 12 from remaining frozen while the level of the solution 12 decreases as a result of the sampling through the sampling orifice 14. Thus an air layer 34 is formed between the upper level of the solution 12 and the frozen layer 32. This air layer functions on the one hand as insulation and hinders the heat transfer between the heated solution and / or the frozen top layer 32. In addition, the depression caused hinders the transfer of the solution from the sampling port 14. Due to the slight expansion of the solution in the frozen state, the upper layer 32, frozen, is blocked in the tank 10 and possibly requires a prolonged time for its disappearance.

  DESCRIPTION AND ADVANTAGES OF THE INVENTION For this purpose the invention relates to a tank of the type defined above characterized in that a tank geometry having a section which decreases from the bottom of the tank to the upper zone.

  The tank for liquids according to the invention is such that in the installed state, its section decreases in the direction opposite to the direction of gravity. This makes it possible to guarantee that for a medium frozen in the feed tank, at low temperatures, the upper, frozen layer does not remain attached to the side walls of the tank but falls or falls into the lower liquefied regions of the thawed medium and then floats. on the liquid parts of the medium.

  In particular for a tank intended for a urea solution for operating an exhaust gas cleaning system of a motor vehicle, in winter mode very low temperatures can be encountered for which the solution contained in the tank may freeze. If the solution is thawed by means of a suitable heating system which is typically located in the lower zone of the tank, the result is that the still frozen top layer is not likely to remain attached to the side walls due to the geometry of the reservoir widens and at any moment it slides so that the whole medium liquefies in a relatively short time.

  The heating system of the tank may for example be an electric heating coil or a heating pipe or a tube through which a hot medium passes. The hot medium may be in particular the coolant of the internal combustion engine that can be heated with the heat generated by the operation of the internal combustion engine.

  The reservoir may in particular have a geometry in the form of a truncated cone or truncated pyramid with a flattened top zone and preferably a flattened or slightly curved bottom zone. The reservoir may also have other symmetrical or unsymmetrical geometries with a reduction of the section upwards.

  Advantageously, the plastic reservoir is produced, in particular, by a blow molding process. This makes it possible to achieve all the desired shapes in a simple and economical way, and that one can if necessary also adapt to the existing conditions of use in a vehicle. In this way the tank may for example be bulged inwardly on one side or have a substantially perpendicular sidewall while the other sides may be formed according to the invention to have a generally reduced section upward.

  The feed tank according to the invention is particularly suitable as a urea storage tank or for a solution of water and urea. The tank may be part of a catalytic selective reduction system for cleaning the exhaust gases of an internal combustion engine, in particular a motor vehicle.

  Drawings The present invention will be described hereinafter with the aid of preferred embodiments shown in the accompanying drawings in which: - Figure 1 shows a tank according to the invention for liquids; - Figure 2 shows a reservoir for liquids as known according to the state of the art.

  Description of the embodiments

  Figure 1 shows a possible embodiment of a tank 10 according to the invention shown in schematic longitudinal section. The reservoir 10 has in this case, in the installed state, a truncated cone or truncated pyramid shape decreasing upwards that is to say in the direction opposite to the direction of gravity. The side walls 36 of the tank 10 may be inclined at an angle of a few degrees with respect to the vertical direction; these walls do not necessarily have an inclination as strong as that presented in an exaggerated manner in FIG. 1. It is sufficient for a few degrees to prevent the upper layer 32, frozen from the water / urea solution 12, from becoming wedged against the walls. In the case of the tank 10 according to the invention, the bypass line of FIG. 2 can be omitted by heating the solution 12 with the aid of the heating installation installed in the lower zone. From the tank, the entire solution 12 is defrosted very quickly because the frozen top layer 32 can not separate from the already frozen, liquid part of the solution and remain hooked in the upper zone of the tank. The removal of the solution 12 through the sampling orifice 14 of the bottom 16 of the reservoir is thus disturbed in no way and at any time. The ventilation of the upper ventilation opening 26 is not disturbed.

  The heating installation 28 may for example be an electric heating coil or a heating tube traversed by a hot fluid. This hot fluid can be heated for example by the heat released by the internal combustion engine. The bottom 16 of the tank may optionally be curved downwards. Side walls 36 may optionally have a contour different from that shown for example if it is intended to adapt to predetermined installation conditions in a vehicle. A side wall 36 may be domed or straight and the other sidewall 36 is born with a proper inclination to generally have a geometry of the tank 10 that tapers upwardly.

Claims (7)

  1) Tank for a liquid, in particular for an operating liquid and / or an auxiliary liquid for the operation of an internal combustion engine and / or installations associated thereto or downstream thereof, comprising an orifice sampling device (14) near the bottom (16) of the reservoir and a ventilation opening (26) in the upper zone (24) of the reservoir (10), characterized by a reservoir geometry having a section which decreases from the bottom 10 of the tank (16) to the upper zone (24).   2) Tank according to claim 1, characterized in that the tank (10) is equipped with a heating system (28).   3) Tank according to claim 1, characterized by a frustoconical shaped tank geometry.   4) Tank according to claim 1, characterized by a reservoir geometry of pyramidal shape.   5) Tank according to claim 1, characterized in that the reservoir (10) is made of plastic material inc inc inc especially by a blowing process.   6) Tank according to claim 1, characterized in that the reservoir (10) is intended to receive urea or a solution (12) of water and urea.   7) Tank according to claim 6, characterized in that the reservoir (10) is part of a selective catalytic reduction system for purifying the exhaust gas of an internal combustion engine including those of a motor vehicle.