FR2713285A1 - Device for limiting hydrocarbon emissions by evaporation for a vehicle equipped with an internal combustion engine. - Google Patents

Abstract

Device for limiting hydrocarbon emissions for a vehicle equipped with an internal combustion engine in which the return line (7, 7 ') to the tank (1) of the engine fuel supply circuit passes through a heat exchanger (8) placed in a filter (4) for recovering fuel vapors, said exchanger being adapted to simultaneously, on the one hand, cool the fuel returning to the tank in order to limit evaporation, and on the other hand, heat the activated carbon in the filter to facilitate desorption of fuel vapors.

Description

The present invention relates to a device for limiting

  emissions of hydrocarbon vapors from the fuel supply system of a vehicle fitted with an internal combustion engine and from a fuel filter

  these vapors used in this device.

  The anti-pollution regulations in force in certain countries impose the limitation of air pollution by hydrocarbon vapors emitted by motor vehicles with internal combustion engines. These vapors are mainly generated in the fuel tank of vehicles, during variations in the level or temperature of the fuel in the latter. Means have been proposed in the prior art to avoid the rejection of these vapors to the atmosphere. We know for example the use of a filter, generally made up of particles of activated carbon or not, interposed between the tank and the atmosphere, which traps hydrocarbon vapors while allowing gas exchanges for pressure balancing. . In order to remain effective, these filters must be regenerated to prevent them from becoming saturated. This regeneration is obtained by the circulation in the filter of a flow of air drawn in outside under the effect of the vacuum prevailing in the intake manifold of the engine. Such a filter is for example described in US patents US 4,598,686 and US 4,732,588 which further describe an electric heating device associated with this filter to improve the regeneration thereof. In fact, during the regeneration of the filter, the destocking of the fuel vapors, a phenomenon called desorption, results in a notable lowering of the temperature of the carbon contained in the filter, which has the consequence of slowing down, if not preventing regeneration. However, the use of a heating medium

  Electric is expensive, both for its realization and for energy consumed.

  Another way is also known to limit this pollution. One of the causes of fuel evaporation in the tank is linked to the return, in the tank, of part of the fuel supplied by the petrol pump to the engine, and not consumed by the latter. This fuel having stayed in the vicinity of the engine has been strongly heated by it and contributes to its return to the tank, to raise the temperature of the fuel and thus to increase the production of hydrocarbon vapors. American patent US Pat. No. 5,237,975 therefore proposes to limit this evaporation by suppressing the return of fuel to the tank by means of a pump whose flow rate is controlled by the consumption of the engine. Such a system is however complex and costly, and has many disadvantages for engine management. The present invention therefore aims to provide a device for limiting emissions of hydrocarbon vapors which advantageously combines the advantage of the preceding devices without having the drawbacks, and which is economical,

  both for its realization and for its functioning.

  These objects of the invention are achieved, as well as others which will appear in

  the rest of this description, with a device for limiting emissions

  of hydrocarbons for a vehicle equipped with an internal combustion engine, of the type comprising a fuel supply circuit comprising a tank, a supply line for an injector rail and a line for returning fuel to the tank , and a fuel vapor recovery circuit comprising an activated carbon filter connected by vapor lines to the tank and to the intake manifold of the engine. According to the invention, the line for returning fuel to the tank passes through a heat exchanger situated in the filter, said exchanger being adapted to simultaneously, on the one hand, cool the fuel returning to the tank in order to limit its evaporation, and secondly, warm the

  activated carbon in the filter to facilitate the desorption of fuel vapors.

  According to the invention also, a filter is proposed for recovering fuel vapors from a vehicle equipped with an internal combustion engine, comprising a heat exchanger intended to be inserted in the return circuit of the

fuel to the tank.

  Other characteristics and advantages will appear on reading the

  description which follows and on examination of the appended drawing in which FIG. 1

  shows a schematic view of the device according to the invention.

  The device includes a fuel tank I in which a pump 11 is installed. Of course, this arrangement is given by way of example, the pump can also be installed outside the tank, in series with the latter. This pump supplies fuel under a predetermined pressure to an injector manifold 2 provided with a pressure regulator 21 via a supply line 6. The injector manifold and its pressure regulator 21 are mounted on the cylinder head of an internal combustion engine (not shown). For the correct operation of the pressure regulator, the fuel flow rate provided by the pump 11 is greater than the flow rate consumed by the engine. Therefore part of the fuel

  arriving at the regulator 21 is returned to the reservoir by a return line 7.

  The fuel flowing in the supply line 6, the regulator 21 and the return line 7 stays in the immediate vicinity of the engine and is therefore seen

warmed by it.

  The circuit used by the fuel vapors has also been shown in dotted lines in this figure. These, generated in the tank 1, for example under the effect of prolonged parking of the vehicle in the sun, are guided to a filter 4 by a pipe 41. The pipe 41 opens into the filter inside the active part of the filter constituted by granules of carbon 40. The vapors are then trapped in the carbon, while the gas exchange allowing the pressure to be balanced between the tank 1 and the external atmosphere is carried out by cleaned air hydrocarbon vapors via the vent pipe 43. When the engine is running, the filter 4 is regenerated by connecting it to the vacuum which prevails in the intake manifold 3 of the engine via a pipe 42 and a valve 5 then open. Air is then sucked through the conduit 43, scans the carbon 40 of the filter and becomes charged with fuel vapors, causing significant cooling of the carbon linked to the evaporation of the fuel which was trapped there. Note the particular embodiment of the filter 4. It comprises a heat exchanger 8 embedded in the carbon constituting the active part of the filter. This exchanger could advantageously be produced in the form of a tube provided with fins snaking inside the carbon, or in any other form adapted to allow a heat exchange between a hot fluid circulating in the exchanger and the surrounding carbon. The return line 7 for hot fuel from the engine is connected to the inlet of this exchanger 8, the outlet of which is connected to the

  tank 1 via a pipe 7 '.

  It is then understood that the hot fuel coming from the engine, passing through the exchanger 8, gives up its calories to carbon 40 inside the filter 4. This then gives an advantageous double effect. On the one hand, the carbon of the filter 4 is heated, which improves the efficiency of the desorption of the vapors trapped therein. On the other hand, the fuel which circulates in the exchanger is cooled, which makes it possible to return fuel to the tank at a much lower temperature than in the devices of the prior art, and thus to prevent the heating of the fuel in the tank. As a result, the generation of hydrocarbon vapors inside the tank is limited, thereby reducing the risks of saturation of the filter 4, and consequently the risks of rejection of vapors to the atmosphere. The object of the invention is thus achieved, thanks to this simultaneous double effect, and this is particularly economical. This eliminates the need for an electric heater in the filter, as well as its associated control system. Similarly, the device according to the invention operates without requiring any input

extra energy.

  Of course, the invention is not limited to the embodiment described and shown which has been given only by way of example. The exchanger 8 could be, for manufacturing reasons, around the active part of the filter and not inside. Likewise, a filter using a means other than carbon to trap fuel vapors, for example synthetic fibers, could be adapted to receive

  an exchanger without departing from the spirit of the invention.

Claims (2)

  1. Device for limiting hydrocarbon emissions for a vehicle equipped with an internal combustion engine, of the type comprising a fuel supply circuit comprising a tank (1), a supply line (6) of a injector rail (2) and a return pipe (7,7 ') from the fuel to the tank, and a fuel vapor recovery circuit comprising a filter (4) connected by steam pipes (41,42) to the tank and to the engine intake manifold, device characterized in that the line for returning the fuel to the tank passes through a heat exchanger (8) located in the filter, said exchanger being adapted, simultaneously, on the one hand to cool the fuel returning to the tank in order to limit its evaporation, and on the other hand, heating the filter in order to facilitate the desorption of the fuel vapors.   2. Filter for recovering fuel vapors from a vehicle equipped with an internal combustion engine, characterized in that it comprises a heat exchanger (8) intended to be inserted in the return circuit (7,7 ' ) fuel at 1 5 tank.