| JP04292571 | FUEL FEED DEVICE |
| JP3732395 | VEHICULAR CONTROL DEVICE |
| JP2010084728 | HEAT EXCHANGER AND FUEL SUPPLY SYSTEM |
DOLENC, Igor (Brunov drevored 24, 5220 Tolmin, SI)
BIZJAK, Aleš (Volče 40, 5220 Tolmin, SI)
SKOČIR, Iztok (Muceniška 1c, 5222 Kobarid, SI)
DOLENC, Igor (Brunov drevored 24, 5220 Tolmin, SI)
BIZJAK, Aleš (Volče 40, 5220 Tolmin, SI)
| Patent Claims 1. Diesel fuel heater for road vehicles, wherein the heater is secured to the housing of the fuel filter and PTC heating elements are positioned by means of guides between two electrically and thermally conductive plates, the top plate thereof being pressed upon by springs, characterized in that, extending vertically, i. e. axially, from the bottom of the housing (1), there are guides (6) which are of a preferably cylindrical shape, exhibiting a larger diameter in the portion proximal to the housing (1) and then tapering off stepwise to a smaller diameter, the height of the guides (6) in the smaller-diameter portion being lower than the height of the heating elements (5), and further guides (7) which are of a preferably cylindrical shape and of a diameter preferably equal or similar to the smaller diameter of the guides (6), the height of the guides (7) being such as to protrude slightly, preferably about 1 mm, above the height of the heating elements (5), wherein the structure of the bottom plate (3) , the heating elements (5) and the top plate (4) is being pressed - against by legs (8b) of a torsion spring (8). 2. Diesel fuel heater according to Claim 1, characterized in that the plate (3) has bores aligned with the guides (6, 7) and the plate (4) has bores aligned with the guides (7) . 3. Diesel fuel heater according to Claim 1, characterized in that the guides (6) on the bottom of the housing (1) are positioned such as to allow the bottom plate (3) to be positioned, and the heating elements (5) to be positioned on the bottom plate (3) . 4. Diesel fuel heater according to Claim 1, characterized in that the guides (6) on the bottom of the housing (1) are positioned in groups, each group defining a circumference, so that the top portions of the guides (3) encircle the respective heating elements (5) . 5. Diesel fuel heater according to Claim 1, characterized in that the torsion spring (8) is fitted over the column (9), said spring (8) having alternating down- bent legs (8b) and up-bent legs (8c), wherein the number of down-bent legs (8b) is equal to the number of heating elements (5), the legs (8b) being shaped such as to press against the top plate (4) in spots located directly above the underlying heating elements (5) . |
The present invention relates to a diesel fuel heater for road vehicles. It is a problem with diesel-powered vehicles that the fuel gels at low temperatures, obstructing the unhindered flow of the fuel, particularly through the fuel filter. Therefore, the fuel has to be heated prior to entering the filter.
Most prior-art heaters are secured to the fuel filter and they mostly employ PTC (Positive Temperature Coefficient) elements as heating elements. PTC elements are convenient in that they allow the heating power to be self-regulated in dependence of temperature.
Typical prior-art heater designs are disclosed in patents US 4,479,477, EP 0 367 631, EP 0 162 939 and EP 0 581 176. It is characteristic of all these designs that the heaters are secured to the fuel filter and that PTC elements are utilized as heating elements. The PTC elements are placed in electrical and thermal contact with at least one metal plate which increases the effective heating surface area of the PTC heating elements. The electrical and thermal contact between the metal plate and the PTC element is ensured by means of springs. In all prior-art designs the effective heating surface area is reduced by the various cutouts in the metal surfaces, neither do the auxiliary elements, the springs in particular, help increase the heating surface area.
In order for the heater to function most efficiently, the effective heating surface, i. e. the surface area of the metal heating plates, should be as large as possible and the auxiliary elements should contribute to the overall extent thereof.
It is therefore a primary object of the instant invention to increase the effective heating surface area. At the same time, the structure should facilitate the discharge of static electricity from the heater cover.
As per the invention, the said object is achieved according to the independent patent claim.
The invention shall hereinafter be described according to an embodiment thereof and with reference to the accompanying drawings, representing:
Figure 1: the heater in cross-section,
Figure 2: the heater in front view,
Figure 3: the heater in projection.
The housing 1 of the heater is shaped so that it can be attached to the upper part of the housing of the fuel filter. The heater has an inlet for the fuel entering the heater, and an outlet for the fuel flowing out into the filter. While passing through the heater housing, the fuel flows over the bottom metal heating plate 3, the top metal heating plate 4, the PTC heating elements 5 and the torsion spring 8, whereby it is heated. There are two types of guides extending vertically, i. e. axially, from the bottom of the housing 1: the guides 6 and the guides 7. The guides 6 are of a preferably cylindrical shape, exhibiting a larger diameter in the portion proximal to the housing 1 and then tapering off stepwise to a smaller diameter. The larger diameter is of the order of magnitude of 2.5 to 4 mm, whereas the smaller diameter is of the order of magnitude of 1 to 2 mm. The stepped tapering-off serves as support for the bottom heating plate 3 which is provided with bores, said bores being aligned with the guides 6 and being just slightly larger than the smaller diameter of the guide 6. When fitted onto the guides 6, the bottom plate 3 is vertically, horizontally, as well as rotationally positioned. The guides 6 are positioned on the bottom of the housing 1 such as to also allow the heating elements 5 to be positioned on the bottom plate 3. The heating elements 5 have the shape of a button, which is to say, a short cylinder. The guides 6 on the bottom of the housing 1 are positioned in groups, each group defining a circumference, so that the top portions of the guides 3 encircle the respective heating element 5. As per the invention, three guides 6 are employed for each heating element 5. The heating elements 5 in the heater are disposed along a circumference, the center whereof coincides with the center of the circular housing 1. The embodiment at hand represents a design with four heating elements 5, but there may be three or more. The height of the guide 6 in the smaller-diameter portion is lower than the height of the heating elements 5.
The guides 7 are of a cylindrical shape, and of a diameter preferably equal or similar to the smaller diameter of the guides 6. The embodiment being discussed envisions two guides 7, however there can be more than two. The height of the guides 7 is such as to protrude slightly, preferably about 1 mm, above the height of the heating elements 5. The guides 7 on the bottom of the housing 1 are positioned in such a way as not to coincide with the heating elements 5 or the guides 6. The bottom plate 3 and the top plate 4 are provided with two bores, said bores being aligned with the guides 7 and being just slightly larger than the diameter of the guide 7. The top plate 4 with its two bores is fitted over the two guides 7, resting on the heating elements 5.
At the bottom center of the housing 1 there is a column 9 rising almost to the height of the cover 2 of the housing 1. According to the disclosed and preferred embodiment, said column 9 is cylindrically shaped, in which case it is also provided with a vertical groove to allow the positioning of the spring 8. The spring 8 is fitted over the column 9 in a positionally defined manner. The spring 8 is shaped as a torsion spring having alternating down-bent legs 8b and up-bent legs 8c. The torsion spring 8 is made of a flexible, thermally and electrically conductive metal having a rim 8e, from which a positioning leg 8d extends inwards toward the column 9, and the above-described legs 8b and 8c extend outwards. The number of down-bent legs 8b is equal to the number of heating elements 5. The legs 8b are shaped such as to press against the top plate 4 in spots located directly above the underlying heating elements 5. The legs 8b are additionally horizontally bent on their bottom end so as to rest upon the top plate 4 with the largest surface possible, ensuring thermal contact and increasing the effective heating surface area of the heater .
The position of the down-bent legs 8b is such that the said legs 8b press against the top plate 4 in spots located directly above the centers of the underlying heating elements 5.
As a result, the heating elements 5 are squeezed between the bottom plate 3 and the top plate 4, having electrical and thermal contact with both plates. The spring 8 may be vertically fixed to the column 9, or it may be vertically movable and fixed by means of the cover 2 on which it rests. The cover 2 is secured to the housing of the fuel filter by means of friction welding. With this type of welding, an electrostatic charge is generated, which is removed to the plate 4 via the spring 8. The plates 3 and 4 are electrically connected in ways known in the art to a source of electric power for powering the heating bodies 5.
The present invention ensures that the effective heating surface area is maximized, and allows the static electricity to be removed.
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