ELECTRIC HEATER ASSEMBLY FOR HEATING A DIESEL ENGINE FUEL FILTER

Abstract: Fuel oil clouding caused by formation of wax crystals in diesel fuel at low temperatures, which clouding restricts flow through and may plug the fuel filter of a diesel engine powered motor vehicle causing poor drivability, power loss and eventual flameout, is obviated by a fuel oil heater unit (10) which can readily convert a non-heated diesel engine spin-on type fuel filter (24) into one containing an electric heater for heating fuel above its cloud temperature. The heater unit (10) includes a spacer (22) insertable between the fuel manifold (12) and the filter (24) of the engine. The spacer (22) has a diameter comparable to that of the manifold (12) and filter (24) to present a flush overall outside surface and is provided with a star-shaped temperature self-limiting PTC heater (44) having radially extending finger-like portions (46) between each pair of which is provided a flow passage (26) through which the fuel flows and is heated enroute to the filter (24) from inlet (14) of the manifold. In an alternate arrangement a modified fuel manifold (12') is provided and includes an integralbowl-shaped recess (72) constituting a fuel reservoir in which is immersed a flat strip-like spirally coiled electric resistance heating element (78) connected in series with a combination thermostat/heating element (80) and defining a spiral heating passage for the fuel from manifold inlet (14') to the filter (24').

Description: ELECTRIC HEATER ASSEMBLY FOR HEATING A DIESEL ENGINE FUEL FILTER . This application is a continuation-in-part of my copending application U.S. Serial No. 456,072 (PCT- US 82/01646). This invention relates in general to a diesel engine. More particularly, it relates to a heater unit that can be readily applied to a diesel engine having a spin-on type fuel filter. The use of diesel engine fuel heaters to prevent fuel oil clouding is known. A drop in temperature below a predetermined level allows wax crystals to form, which restricts flow through and may plug the fuel filter, causing poor drivability, power loss, and eventual flame- out. The problem usually occurs after the operator has started the engine and driven a short distance before engine fuel starvation is realized by the engine faltering and flaming out. More often than not, the only method of restarting the engine is to tow the vehicle to a warm area where the fuel system may be defrosted. A common solution has been to provide an inline heater to maintain the fuel temperature above the cloud point. However, since the specifications for either cloud point or pour point (the temperature at which fuel ceases to flow) are not uniform among fuel suppliers, this type of heater is often only borderline effective. Heaters that are incorporated directly into the fuel filter also are known. However, these generally are complicated, costly constructions that are not suitable for retrofitting to a diesel engine that has a spin-on type fuel filter since the entire filter unit and manifold must be replaced as well as the mounting modified. Muller, U.S. 2,902,158, shows a unit fuel filter connected to a fuel manifold and having a centrally located heater unit surrounded by a number of candle type filter elements. The fuel flows from outside to inside the filter prior to being heated. Low temperature fuel may form wax crystals on the outside of the filter and plug it prior to the heater element being effective to prevent the same. King et al, U.S. 3,235,084, shows a one-piece fuel manifold-filter also having a centrally located heater element. Replacement of a filter unit would require replacement of the entire unit to retrofit it to a diesel engine, which is not practical or economical. Prier, U.S. 3,463,317, merely shows the use of an adapter or spacer between an oil manifold and a spin-on type oil filter to reroute incoming oil to a cooler prior to entering the filter. Barrow, U.S. 3,550,781, shows a fuel vaporizing unit having a spacer element between a filter and liquid fuel. The spacer contains a heater coil; however, the unit is not adaptable as a simple insert between a diesel engine fuel manifold and spin-on filter. Richards et al, U.S. 4,091,265, shows a filter assembly integral with a fuel manifold and having a tran¬ sistorized heat conducting ring for incoming fuel. Such a construction would be costly to manufacture, require a special installation, and would not be adaptable for a simple retrofit. van Koπynenfcurg , U.S. 4,304,987, shows an elec¬ trical heater including a positive temperature coefficient (PTC) element joined to a constant wattage (C ) element by a carbon black composition in a πanner such that when electrical current is supplied to the two elements, a relatively constant source of heat is produced up to a predetermined temperature level or switch point, whereupon the heater becomes self-regulating, thereby eliminating the need for a separate shut-off switch to control the heat outpu . None of the above constructions provide a simple cartridge type heater unit that can easily be inserted between a conventional diesel engine fuel manifold and its OMPI spin-on type fuel filter, or, alternatively, a heater unit that can easily be incorporated directly into the fuel filter fuel manifold, and made operative simply by connect¬ ing the leads from the heater to the engine electrical system. In each of the prior art cases above, the construc¬ tion generally requires a specific installation that does not lend itself to a retrofit installation on other vehicles without a complete modification of the original structure. It is a primary object of this invention, there¬ fore, to provide a diesel fuel oil heater unit that can readily be applied to diesel engine vehicles employing spin-on type fuel oil filters. It is another object of the invention to provide a heater unit of the type described in which the heater is self -limiting in output temperature level to eliminate the need for a separate shut-off switch. It is also an object of the invention to provide a heater unit as described in which the heater element is star shaped in cross-section with radially extending finger¬ like portions circumferentially spaced from one another to provide maximum heating area exposure to the incoming fuel flow. It is a still further object of the invention to provide a fuel oil heater unit consisting of a self- contained cartridge type spacer unit adapted to be inserted between the usual fuel manifold and the fuel filter. A further object of the invention is to provide a fuel oil heater unit totally contained in the fuel πanifold itself. Other objects, features and advantages of the invention will become more apparent upon reference to the succeeding detailed description thereof, and by reference to the drawings illustrating the preferred embodiment thereof; wherein, OMPI F igure 1 is a cross-sectional view of a diesel engine fuel filter/heater unit embodying the invention; Fig ure 2 is a cross-sectional view taken on a plane indicated by and viewed in the direction of the ar rows II-II of Figure 1; Figure 3 is a cros s-sectional view of an alter na¬ tive embodiment of the invention taken on a plane indicated by and viewed in the dir ection of the arrows II I-III of Fig ure 4; and , Figures 4 and 5 are cross-sectional views taken on planes indicated by and viewed in the direction of the arrows IV- IV and V-V of Figures 3 and 4 , respect ively . Figure 1 shows a diesel engine fuel f ilter assembly 10 . It includes a base cover unit 12 that def ines a fuel mani fold having a fuel inlet passage 14 and an outlet passage 16. Inle t passage 14 is intersected by an annular plenum chamber 18 that is matingly aligned with a fuel annulus 20 formed in the top of a spacer element 22. The spacer is a unitary cartr idge type adapted to be inserted between manifo ld 12 and a spin-on type fuel f iler 24 to be exposed to the flow of fuel between the manifold and filter in a manner to be descr ibed . More particularly, the spacer 22 is of a diameter comparable to that of the manifold and filte r to present a flush overall outs ide surface . It is provided with a number of coaxially extending , circu fer ential ly spaced passages 26 that extend at their upper end from fuel annulus 20 to the annular fuel inlet plenum 28 at the outer per iphery of fuel filter 24. The fuel f ilter 24 is of conventional paper pleated type construction consisting of a base plate 30 having a central bore 32 def ining an outlet 34 for the filtered fuel . A flanged portion 36 contains circum¬ ferentially spaced holes 38 for receiving the fuel from spacer 22. An 0-ring seal 40 abuts the lower face of spacer 22 to seal against the leak of fuel outwardly. OMPI The fuel filter 24 is adapted to be screwed or spun on against the lower face of spacer 22 in the same manner as the filter is attached to the fuel manifold in the case where no spacer is present. That is, a threaded nipple 41 is attached to the adapter by a nut 42 to a second nipple that normally depends from the fuel manifold 12 to secure the spacer element to the manifold, and the nipple 41 is threaded into the fuel filter 24 at the opposite end of the filter being spun on it in the usual manner. Turning now to the invention, spacer or adapter 22 contains in this case a star shaped heater 44 that is defined by radially extending fingerlike portions 46 that are equally circumferentially spaced from one another to provide clearances 48 between. As best seen in Figure 2, the passages 26 extend between the spokes or fingers 46 of the heater to provide the greatest area of exposure to the flowing fuel. The heater in this instance is a self-output temperature limiting heater consisting of a positive temperature coefficient (PTC) element 50 connected to a constant wattage (CW) element 52 by an intervening carbon black composition 54, as shown and fully described in U.S. 4,304,987 mentioned previously. A pair of leads 56 and 58 extend outwardly of the adapter to a suitable connection to the diesel engine electrical system (not shown) to be energized whenever the engine is operating. The characteristics of the heater are such that the internal temperature of the heater increases at a fairly constant level with application of electrical current up to a certain temperature level, i.e., switch point, such as, for example. 250°F (121.1° Celsius), at which point the internal resistance of the heater increases markedly to a point where no further increase in heat output is provided. Thus, the element has a built-in or self-contained shutoff device that eliminates the need - B UREA OMPI for a separate switch to accomplish the same purpose. In operation, therefore, as soon as the engine is started, current is supplied to element 44 which begins heating. Therefore, when fuel flows through inlet 14, 18 and into adapter 22, fuel flow between the finger¬ like portions of the heater will absorb the heat therefrom and maintain the fuel at a temperature level preventing waxing, etc., as it prepares to enter the filter unit 24. The fuel flow then continues through paper-pleated filter portion 60 passing radially inwardly into the center core wherefrom it progresses upwardly back through adapter 22 and into the outlet passage portion 16 of the fuel manifold 12. An alternative solution to adding a heater between the fuel manifold and the conventional spin-on type fuel filter is to incorporate the fuel heater into the top of the manifold itself. This would require no special mount¬ ing bracket to attach the filter assembly to the engine, in contrast to the construction shown in Figure 1. In the case of Figures 3-5 showing, only a modification of the fuel manifold itself would be required plus a means to connect the heater electrically to the vehicle engine for operation whenever the engine is operative. More specifically. Figures 3-5 show a fuel filter assembly similar in construction to that illustrated in Figure 1. The fuel manifold 12' includes a horizontal fuel oil inlet 14', a horizontally disposed fuel outlet passage 16', a vertically inclined fuel inlet passage 18' leading to the outer periphery of the fuel filter, and an adapter nipple 70 onto which is screwed the spin-on type fuel filter 24'. Manifold 12* in this case is provided at its top with an integral bowl shaped recess 72 constituting a fuel reservoir and adapted to be closed by a suitable disc shaped cover. For clarity, the cover has been removed. As best seen in Figure 3, the fuel oil inlet 14' connects to an intersecting passage 74 that angles upwardly as indi¬ cated in Figure 5 to the bottom of the recess or fuel reservoir 76. Adapted to be immersed in the fuel oil is a flat strip-like coiled electric heater 78 connected to a combination thermostat/heating element 80 contained in one end of the manifold. Element 80 would be electrically connected by wiring not shown to the vehicle electrical system so as to be energized or rendered electrically operative at all times when the vehicle engine is opera¬ tive. The heater 78 is coiled as shown and is of a depth or width equal to that of the depth of the reservoir so as to provide a spiral passage for flow of the fuel oil inwardly to a central outlet 82. The latter is connected by an angled passage 84 to the inlet 18' to filter assembly 24'. A toothpick-like pin 86 extends through the coils of the heater element 78 to secure it in place without obstructing flow. The curved wall portion 90, defining a portion of the fuel reservoir, also acts as a guide for the incoming fuel oil in passage 74. In operation, fuel oil entering the inlet passage 14' travels diagonally upwardly as shown in Figure 4 to the end of the guide wall 90. At this point, the strap- like coil of heater 78 forms a wall to force the flow between it and the manifold and force fuel oil flow in a spiral path toward the outlet 82. The heater being energized as soon as the vehicle engine becomes operative, the fuel oil is warmed prior to its discharge into the inlet passage 18'. In this case, the combination thermostat/heating element 80 becomes inoperative above a predetermined temperature level and, therefore, shuts off the current to the heater element 78 when it is not needed to warm the fuel oil above the cloud point. From the foregoing , it will be seen that the O PI vr wiPo invention provides several embodiments of a self-limiting output temperatur e fuel oil heater that readily can be adapted to most diesel engines that have a spin-on type filter attached to the fuel manifold . While the invention has been shown and descr ibed in its pr eferred embodiments, it wil l be clear to those skilled in the arts to which it pertains that many modif i¬ cations and changes may be made thereto wi thout departing from the scope of the invention .

Claims: C L IMS 1. A self-contained unitary fuel oil heater unit for use with a diesel engine having a fuel manifold and a spin-on type fuel filter attached thereto, comprising a cartridge type heater unit adapted to be inserted axially between and attached to both the fuel manifold and filter and of a diameter comparable to that of the manifold and filter to be flush mounted with respect thereto, the unit having a plurality of coaxially extending fuel flow entry passages and an exit passage extending therethrough aligned with the normal mating entry and exit fuel flow passages in the manifold and filter permitting the inflow of fuel from the manifold through the spacer to the filter and the filtered outflow therefrom in a reverse direction from the filter through the spacer to the manifold, the unit contain- ing an electrically operative heater element connected to the engine electrical system and extending radially out¬ wardly in the plane of the unit to overlie the fuel flow passages to heat the fuel as it traverses the flow path from the manifold to the filter to prevent fuel clouding and waxing . 2. An oil heater unit as in Claim 1, the heater including a self-output temperature limiting element. 3. A unit as in Claim 1, the heater having a star shape in cross-section with radially extending finger-like portions circumferentially spaced from one another, the fuel flow entry passages flowing the fuel between the finger portions. 4. A unit as in Claim 3, including means connect¬ ing the heater electrically to the vehicle engine for operation at all times when the engine is operative. - REA OMPI 5. A self-contained fuel oil heater unit for use with a diesel eng ine, the uni t including a fuel manifold and a spin-on cartr idge type fuel f ilter attached thereto , the manifold having a bowl shaped fuel reservoir integ rated therewith on top thereof, and including an electr ically operative heater element immersed in the reservoir for warming the fuel oil , the f uel inlet and outlet to the manifold consisting of a pa ir of passag es each communi¬ cating with other passages connected respectively both to an inlet to the reservoir and to the outlet of the fuel filter , a f urther fuel outlet passage connecting the warmed fuel from the reservoir through the manifold to the top of the fuel f ilter for flow through the peripheral edges thereof into the filter proper and out through the filter outlet to the fuel outlet, and means connecting the heater to the electr ical system of the eng ine to be operative upon the engine being rendered operative . OMPI

Inventors: PAKULA BENJAMIN JOHN, PAKULA, BENJAMIN, JOHN
Applicants: FORD MOTOR CANADA, FORD MOTOR CO, FORD WERKE AG, FORD MOTOR COMPANY, FORD MOTOR COMPANY LIMITED, FORD MOTOR COMPANY OF CANADA, LIMITED, FORD-WERKE AKTIENGESELLSCHAFT
Application year: 1983
Main classification: H05B3
IPC codes: F02B3, F02M31, F02M37