FR2723616A1 - Diesel engine fuel filter - Google Patents

Abstract

The filter consists of a housing (101) covered by a fuel inlet and outlet unit (108) and containing a central filtering sleeve (115) of a coalescent medium. The sleeve is positioned so that the fuel enters its inner channel (116) from the top and passes through its walls, while water droplets fall by gravity to the bottom (118) of the housing. The outer surface of the housing has a heating sleeve (120) which covers the major part of its height and raises the temperature of the filter to a predetermined level, controlled by a thermostat. The heating sleeve is made from an inner layer (120.2) of a woven resistance material and an outer insulation and protection layer of a resin, moulded directly onto the resistance material.

Description

 The invention relates to a filtration device for a diesel engine, capable of integrating at least one additional function in addition to its function of filtering diesel upstream of the engine.

 The term "diesel engine" must be understood in a broad sense, encompassing in particular all types of engines using diesel fuel as fuel, and both stationary engines and on-board engines for propelling vehicles.

 In conventional circuits supplying diesel fuel from the tank to the engine, a particle filter is provided, generally produced in the form of a cartridge containing a filtering medium, for example made of cellulose fibers, to stop solid particles. The cartridge is crimped into a filter body, with a diesel inlet and outlet.

 Conventional circuits also include a heating means, and sometimes also a water separator interposed between the supply (or booster) pump and the particle filter.

 Conventionally, two types of heating means are used, at one and / or the other end of the circuit for supplying diesel fuel to the engine. The first type consists of a coil arranged around the suction strainer in the diesel tank, this coil being supplied by the engine cooling water. This heating means only intervenes after a certain period of engine operation, and its action is actually imprecise and random. The second type, especially provided on board vehicles, consists of heating candles which heat a small volume of diesel in order to be able to start cold. This means has a relatively limited action insofar as the diesel continues to arrive cold during the engine start-up period. It generally takes at least ten minutes for the engine to be hot enough for the diesel to be regularly reheated, which causes the well-known phenomenon of emission of fumes during the start-up period.

 Neither of these two reheating means is currently capable of exerting a regulated reheating action, in particular during the start-up period.

 A water separator is also often (especially in hot countries) included in the supply circuit to improve the engine efficiency, because we know that the calorific value of diesel is improved if we extract the water present in addition or less quantity depending on the quality of the diesel coming from the refinery. It is then a separate device provided between the feed pump and the particulate filter, and operating according to a principle of cyclonic effect. Such an apparatus is nevertheless bulky and expensive, and the removal of water by centrifugation is imperfect.

 The diesel engine supply circuit is then organized in accordance with the diagram illustrated in Figure 5.

 The circuit 1 takes diesel fuel from the tank 2 through a tube 3 by means of a supply (or booster) pump 6. The tube 3 comprises a suction strainer 4, which is here surrounded by a heating coil 5 of the aforementioned type. Downstream of the feed pump 6, there is here a water separator 7, then a particle filter 8, the diesel fuel thus filtered arriving at an injection pump 9 supplying the engine by a line 10. A line of return 12, with a calibrated valve 11, channels excess diesel to tank 2.

 As an indication, the supply pump 6 delivers approximately 250 l / h, and the injection pump approximately 40 l / h. It is therefore understandable that the heating of diesel is complex, because the heating must relate to the quantity of diesel delivered by the feed pump, and the fact of heating this quantity of OOC to 400C for example would require a bulky and expensive installation. There are for example electric resistance heating rings, which are mounted around the supply pipe - such a system however requires that the engine is running, otherwise the ring or rings used would be subject to overheating. dangerous, so that their activation is designed to take place only after the start-up period.

 The object of the invention is to design an improved filtration device which makes it possible to ensure, in addition to its natural function as a particle filter, at least one additional function, while simplifying the arrangement of the supply circuit of the diesel engine. .

 The subject of the invention is therefore a filtration device, the structure of which makes it possible to carry out regulated heating of the diesel fuel to bring it to a temperature suitable for its injection, and this from the start of the engine.

 The invention also relates to a filtration device, the structure of which also makes it possible to achieve satisfactory water retention, thereby dispensing with the use of a separate additional device to perform this function.

It is more particularly a filtration device for a diesel engine, characterized in that it comprises
- a filter housing surmounted by a diesel input and output element
- a central filter sleeve with coalescing media, said sleeve being arranged inside the housing so that the diesel fuel penetrates from above into the interior space of the sleeve then crosses the wall of the latter before rising to exit the housing, and the drops of water formed flow by gravity from the bottom of the filter sleeve to form a volume of residual water topped with diesel
- A heating sleeve arranged on the outer surface of the housing, extending over most of the height thereof, used to heat to a predetermined temperature the diesel filling the housing to form a reserve of hot diesel.

 Preferably, the diesel input and output element is equipped with a thermostat taking the temperature of said element, used to control the activation of the heating sleeve only when a caloric intake is necessary to maintain the diesel at the predetermined temperature. . For uses in countries where temperatures are low, an additional caloric intake is necessary, and this is ensured, in accordance with a particular embodiment, by providing a heating element interposed between the upper part of the housing and the element d 'input and output of diesel, so as to be crossed by the diesel leaving said housing; in particular, it will be an in-line heater equipped with at least one heating plug, the control of which is controlled by the aforementioned thermostat.

 Advantageously still, the central filtering sleeve includes, in addition to the coalescing media, an envelope forming a particle filter arranged around said media, and this sleeve is also suspended from an upper wall for closing the housing, which wall also has holes for outlet arranged radially beyond said sleeve.

 Preferably, the housing has, below the heating sleeve, transparent axial windows allowing visual control of the level of the volume of residual water, and this housing is also equipped below with a manual or automatic purge member, serving to drain the excess water from the residual water volume.

 According to an advantageous embodiment, the heating sleeve consists of a heating fabric, preferably formed of a woven resistance, and of an outer insulating and protective plastic envelope.

In particular, the outer casing is made of resin, in particular a charged polyurethane resin, which is molded directly on the heating fabric.

 According to a practical embodiment, the filter housing has an internal volume of 2 to 2.5 liters of capacity, and the thermostat is adjusted so that the reserve of diesel occupying this volume is heated and maintained at a temperature of about 400C.

Other characteristics and advantages of the invention will appear more clearly in the light of the description which follows and of the appended drawings, relating to a particular embodiment, with reference to the figures in which:
- Figure 1, and Figure 2 which is a view along II-II, illustrate a filtration device according to the invention, here with a heater element interposed between the filter housing and the input element and diesel outlet
- Figures 3 and 4 are complementary views of the device of Figures 1 and 2 highlighting the removable nature of the heater element
- Figure 6, which is to be compared to the diagram of Figure 5 previously described, illustrates a diesel engine supply circuit including the aforementioned filtration device, the structure of which allows a loop arrangement for this circuit, with recycling of the diesel already hot, which allows to heat only the quantity necessary corresponding to the consumption of the engine.

 Figures 1 and 2 illustrate a filtration device 100 for a diesel engine, according to the invention.

This device firstly comprises a filter housing 101, produced in the form of a metal casing, the capacity of which is for example of the order of two liters to two and a half liters, said housing being here produced with a shape cylindrical with axis X. In the upper part, that is to say at the top of FIGS. 1 and 2, the filter housing 101 has an upper closure wall 102, against which is supported, by means of a seal 105, a heater element 104 surmounted by an element 108 for entering and leaving diesel. The filter housing 101 thus constitutes a closed enclosure, the only communication bores of which consist, in the upper part, of holes 103 for the outlet of the filtered diesel fuel, and, in the lower part, at the level of a purge member 128 serving, as will be explained later, to remove excess water from a residual volume of water 108 formed with the drops which are reconstituted from the micro-drops contained in the diesel fuel. The element 108 comprises an orifice 109 for the entry of the diesel fuel into the filtration device 100, and an orifice 110 for the outlet of the diesel fuel, after filtration, separation of water, and heating of the latter. The element 108 comprises an internal end piece 111, onto which a connection tube 112 is screwed, which passes through a central bore 113 of the heater element 104 (when such a heater element is provided), to be screwed into the upper wall 102 of the filter housing 101. If reference is made to FIGS. 3 and 4, a better distinction is made between the diesel input and output members mounted on the element 108, with a nozzle 123 respectively associated with a pipe. inlet 124, and a nozzle 125 associated with an outlet pipe 126.

 Inside the filter housing 101, a central filter sleeve 115 is arranged, said sleeve being for example, as can be seen in FIGS. 2 and 3, suspended from the upper wall 102 for closing the housing, and extends thus inside said housing over most of the height thereof, with an arrangement coaxial with the aforementioned X axis. The central filter sleeve 115 includes a coalescing medium, denoted 115.1 and an envelope 115.2 forming a particle filter arranged around said medium. The casing 115.2 can be a metallic casing by which the central filter sleeve 115 is suspended from the upper wall 102 for closing the housing. Of course, the outlet holes 103 of this upper wall 102 are disposed radially beyond said sleeve, because this sleeve delimits the entry of the diesel fuel arriving through the orifice 109 of the element 108. The casing 115.2 forming a filter particles can be produced in the form of an adequate mesh grid, and the coalescing medium 115.1 can be made of fibrous material of conventional type, preferably with a filtration threshold of around 3 ssm to have satisfactory combustion with little unburnt. The diesel which arrives through the orifice 109 in the filtration device thus penetrates from the top of the casing 101, into the interior space, denoted 116, of the central filtering sleeve 115, and this diesel oil crosses the wall of the sleeve before rising for exit the filter housing 101 through the associated holes 103. By passing through the wall of the central filter sleeve, the diesel oil first undergoes a retention of its solid particles thanks to the envelope 115.2, then the micro-drops which it contained are gradually gathered in the coalescing medium 115.1 to form drops of water which can then flow by gravity. The reconstituted drops have a diameter of the order of 4 to 5 mm, and these drops flow by gravity from the bottom of the filter sleeve 115 to form a volume of residual water 118 surmounted by diesel in the lower part of the housing. The level of the separation surface between the volume of residual water 118 and the interior volume 117 of diesel fuel which fills all the remaining volume of the filter housing 101 has been noted 119.

 The central filtering sleeve 115 thus ensures, thanks to its coalescing medium, the water retention function, a function which was in the devices of the prior art provided by a separate device mounted in series on the supply circuit. The diesel which passes through the outlet holes 103 is thus rid of its water and its solid particles. It has thus been possible to elegantly resolve the problem of water retention, which in particular makes it possible to avoid the formation of sulfuric acid, the drawbacks of which are easily understood for the mechanical members.

There is further provided a heating sleeve 120, arranged on the outer surface of the filter housing 101, this sleeve serving to heat the diesel filling the housing to a predetermined temperature, to constitute a reserve of hot diesel. Therefore the heating sleeve 120 extends over the major part of the height of the filter housing 101, that is to say over the useful height of the latter for which it is necessary to exercise the heating action. Preferably, provision may be made for the heating sleeve 120 to be constituted by a heating cloth formed from a thickness of resin 120.1 in which a wire resistance 120.2 is embedded. This heating fabric will preferably be glued directly to the filter housing 101, so as to obtain optimum adhesion against the wall thereof. It will then be advantageous to provide an external envelope 122 ensuring both the electrical insulation and the mechanical protection of the heating fabric, this latter envelope being preferably made of plastic material such as charged polyurethane resin. For the production of the heating fabric 120.1, 120.2, reference may be made to documents FR-A-2,486,751 and
FR-A-2.493.090, emanating from the company R. MARCHOIS, in which the production of coated resistance structures is taught which is particularly suitable for the particular application which is made of it here. In Figure 1, there is shown the son 121 associated with the electrical supply of the heating fabric.

 If we want to organize a real control of the heating of the diesel reserve contained in the filter housing 101, it is advantageous to provide that the element 108 for entering and leaving the diesel is equipped with a thermostat serving to order activation of the heating sleeve 120 only when a caloric intake is necessary to maintain the diesel at the predetermined temperature. We distinguish in Figure 1 an appendage 129 formed on the element 108 of input and output of diesel, which appendix has a hole 129.1 whose inlet is threaded, so as to be able to mount a control thermostat.

 In FIG. 4, a thermostat 130 is thus distinguished, taking the temperature of the metallic mass of the element 108, and the end of which is adjacent to the flow of diesel oil leaving the filter housing 101. It will be noted that the position of the thermostat 130 is chosen close to the diesel outlet nozzle, so that the temperature measurement is as significant as possible.

 Thanks to this system, it is possible to optimally ensure a third function, which is a regulated heating function of the diesel, making it possible to bring and maintain this fuel at the desired injection temperature, for example a temperature close to 400C. . The diesel reserve contained in the filter housing 101, which corresponds to approximately 2 to 2.5 liters, is thus permanently maintained at the desired temperature by the heating sleeve 120, the activation of which is controlled by the thermostat 130.

 The housing 101 has, below the heating sleeve 120, transparent axial windows 127 allowing visual control of the level of the volume of residual water 118 at the bottom of said housing. The housing 101 is also equipped with a purge member 128, which may be manual or automatic, serving to remove the excess water from the volume of residual water. In this case, a manual tap has been shown, but it goes without saying that an automatic purge system with float can be provided, intervening as soon as the water level exceeds a predetermined threshold, which avoids the need for '' visual monitoring of the volume of water retention.

 This provides a constant volume filter, occupied by a large volume of diesel which is permanently maintained at the desired temperature. Therefore, when starting the engine, the preheating of the diesel reserve thus constituted makes it possible to ensure the supply of the engine during the entire starting period, with optimal injection and an extremely reduced quantity of fumes emitted.

 In the case of operation at relatively low temperatures, that is to say equal to or lower than 50C, the aforementioned heating cloth is not powerful enough to ensure sufficiently quickly the heating of the diesel fuel contained in the housing. filter. It is then advisable to organize an additional caloric intake, which is ensured here by providing a heater element 104 interposed between the upper part of the filter housing 101 and the element 108 for entering and leaving the diesel fuel, this heater element being crossed by the diesel oil leaving said housing.

 In this case, an in-line heater will preferably be provided, which may consist of a stack of three elements 104.1, 104.2, 104.3 as illustrated in FIGS. 1 and 2, or even a one-piece element that cannot be dismantled as was illustrated in Figures 3 and 4. In all cases, the heater element 104 has a central bore 113 associated with the passage of the tube 112 for communication and connection. The in-line heater 104 has reliefs defining a labyrinth with an important route for the heat exchange, making it possible to rapidly heat the diesel which passes through it. When the heater consists of several stacked elements, it is advantageous to provide a centering stud such as the stud 107 shown in FIG. 1, this stud also constituting a key for mounting the heater. The central element 104.2 is equipped with two heating candles 106 of the conventional type allowing the heating element 104 to be brought to the desired temperature. Preferably then, the control of these heating candles 106 is controlled by the above-mentioned thermostat 130, which makes it possible to have the desired temperature permanently at the outlet of the filtration device.

It should be noted that the organization of the heating of diesel by passing through a heating plate whose temperature is controlled, provides optimum security, insofar as the diesel is never in contact with an electrical element.

 In hot or temperate countries, it will be useless to provide such a heating element 104, as is suggested in FIGS. 3 and 4, in which case the element 108 for input and output of diesel fuel will be mounted directly on the upper part of the filter housing 101. FIGS. 3 and 4 also make it possible to understand that the filtration device thus designed is versatile, insofar as it is easy to remove the heating element 104 if it proves unnecessary. , or to add it for climatic periods of low temperatures.

 In all cases, a supply of hot fuel is obtained as soon as the engine is started, which was not possible with the use of conventional systems such as the aforementioned heating rings. In addition, the fact of centralizing the control by a special single thermostat, which takes for example the temperature of the metallic mass of the element of input and output of diesel, allows to have an optimal security both for the order heating candles and to order the heating cloth.

 It has thus been possible to produce a filtration device, the structure of which allows regular heating of the diesel fuel to bring it to a temperature suitable for its injection, and this from the start of the engine.

 The structure of the filtration device according to the invention also makes it possible to achieve satisfactory water retention, thereby dispensing with the use of a separate additional device to perform this function.

 Finally, the structure of the filtration device according to the invention allows a loop arrangement for the supply circuit of the diesel engine, which previously could not be used for conventional type circuits.

 FIG. 6 illustrates such a supply circuit 200, the diagram shown being close to that of FIG. 5 relating to a supply circuit of conventional type.

 The diesel is taken from a tank 201 by a pipe 202 equipped with a suction strainer 203, by means of a booster pump 204 downstream of which is provided a filtration device 100 such as that which has just be described. The filtered diesel, freed of its water, and heated, arrives via a line 205 to an injection pump 206 allowing the associated engine to be supplied by a corresponding line 207. The return of the excess diesel is carried out by a line 209 equipped with a calibrated valve 208, this pipe 209 arriving in the suction circuit, upstream of the booster pump 204. The branches 205 and 209 thus constitute a circulation loop, with recycling of the already hot diesel fuel. We can then be satisfied with using a booster pump with a flow rate set on the necessary flow rate, for example 40 liters per hour, so that we inject only the quantity consumed as soon as the engine is running. This allows to heat only the quantity strictly necessary, corresponding for example to 40 liters per hour. This avoids the presence of a coil around the suction strainer, and the presence of a device specially designed to ensure water retention.

 The filtration device which has just been described thus makes it possible to considerably reduce the smoke emissions, especially when the engine is started cold, and it provides a significant saving compared to the existing supply circuits. The removal of water finally makes it possible to avoid the formation of sulfuric acid, as has been indicated above.

 The invention is not limited to the embodiment which has just been described, but on the contrary encompasses any variant incorporating, with equivalent means, the essential characteristics set out above.

Claims (10)

 1-. Filtration device for diesel engine, characterized in that it comprises  - a filter housing (101) surmounted by an element (108) for entering and leaving diesel  - a central filter sleeve (115) with coalescing media, said sleeve being arranged inside the housing (101) so that the diesel fuel penetrates from above into the interior space (116) of the sleeve and then passes through the wall of before rising to exit the housing, and the drops of water formed flow by gravity from the bottom of the filter sleeve (115) to form a volume of residual water (118) surmounted by diesel  - a heating sleeve (120) arranged on the outer surface of the housing (101), extending over the major part of the height thereof, serving to heat to a predetermined temperature the diesel fuel filling the housing to constitute a reserve hot diesel.  2. Device according to claim 1, characterized in that the element (108) of input and output of diesel is equipped with a thermostat (130) taking the temperature of said element, used to control the activation of the heating sleeve (120) only when a caloric intake is necessary to keep the diesel at the predetermined temperature.  3. Device according to claim 2, characterized in that a heating element (104) is interposed between the upper part of the housing (101) and the element (108) for input and output of diesel, so as to be crossed by the diesel oil leaving said housing.  4. Device according to claim 3, characterized in that the heater element (104) is an in-line heater equipped with at least one heating plug (106), the control of which is controlled by the above-mentioned thermostat (130).  5. Device according to one of claims 1 to 4, characterized in that the central filtering sleeve (115) includes, in addition to the coalescing medium (115.1), an envelope (115.2) forming a particle filter arranged around said medium.  6. Device according to one of claims 1 to 5, characterized in that the central filter sleeve (115) is suspended from an upper wall (102) for closing the housing, which wall also has outlet holes (103) arranged radially beyond said sleeve.  7. Device according to one of claims 1 to 6, characterized in that the housing (101) has, below the heating sleeve (120), transparent axial windows (127) allowing visual control of the water volume level residual (118).  8. Device according to one of claims 1 to 7, characterized in that the housing (101) is equipped below with a purge member (128) manual or automatic, used to remove excess water from the volume of residual water.  9. Device according to one of claims 1 to 8, characterized in that the heating sleeve (120) consists of a heating fabric (120.1, 120.2), preferably formed of a woven resistance, and an outer envelope (122) insulating and protective plastic material.  11. Device according to one of claims 2 to 10, characterized in that the filter housing (101) has an internal volume of 2 to 2.5 liters of capacity, and the thermostat (130) is adjusted so that the reserve of diesel occupying this volume is heated and maintained at a temperature of about 400C.  10. Device according to claim 9, characterized in that the outer casing (122) is made of resin, in particular a charged polyurethane resin, which is molded directly on the heating fabric (120.1, 120.2)