Abstract:
The heater system of a fuel filter includes: a power supply unit supplying power; a lead wire unit receiving power from the power supply unit and having a plurality of branch lines to divide current of the supplied power; and a fuel filter having a plurality of internal thermo switches connected to the branch lines of the lead wire unit, respectively, and a PTC heater heated by power supplied through the internal thermo switches.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to Korean Patent Application Number 10-2011-0126782 filed Nov. 30, 2011, the entire contents of which application is incorporated herein for all purposes by this reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a heater system of a fuel filter, and more particularly, to a heater system of a fuel filter, using a heater and a thermo switch. 
         [0004]    2. Description of Related Art 
         [0005]    A heater system  10  of a fuel filter according to the related art has a structure as illustrated in  FIG. 1 . In this structure, when a thermo switch  14  provided in a fuel filter  12  is turned on at a predetermined temperature or less, a PTC (Positive Temperature Coefficient) heater  16  is connected to a power source and then operates. When fuel is heated by PTC heater  16 , thermo switch  14  is turned off at a predetermined temperature or more so as to stop the heating. 
         [0006]    In heater system  10  of the fuel filter according to the related art, however, a large starting current (surge current) is generated as shown in  FIG. 2 , when a vehicle is started. Then, as illustrated in  FIG. 3 , a contact portion A may be burned out, or thermo switch  14  may be molten out. 
         [0007]    Further, heater system  10  of the fuel filter according to the related art has a limitation in design because the mounting position and structural size of thermo switch  14  are limited. More specifically, contact portion A of thermo switch  14  cannot be increased in size, in order to improve durability and increase the heating value of the heater. 
         [0008]    The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
       BRIEF SUMMARY 
       [0009]    Various aspects of the present invention are directed to providing a heater system of a fuel filter, which is capable of reducing a starting current by improving the design and wiring of thermo switches, thereby increasing durability. 
         [0010]    In an aspect of the present invention, a heater system of a fuel filter, may include a power supply unit supplying power, a lead wire unit receiving the power from the power supply unit and having a plurality of branch lines to divide current of the power from the power supply unit, and the fuel filter having a plurality of internal thermo switches connected to the branch lines of the lead wire unit, respectively, wherein the plurality of internal thermo switches is electrically-connected to a PTC (Positive Temperature Coefficient) heater heated by a power supplied through the respective internal thermo switches. 
         [0011]    The respective internal thermo switches may have operation temperature conditions which are sequentially set in different manners. 
         [0012]    When the number of branch lines is set to two, two internal thermo switches are provided so as to correspond to the two branch lines, one of the internal thermo switches may have an ON operation condition of 7° C.±4.5° C. and an OFF operation condition of 24° C.±3.5° C., and the other one of the internal thermo switches may have an ON operation condition of −2° C.±4.5° C. and an OFF operation condition of 5° C.±3.5° C. 
         [0013]    The power supply unit supplies a power applied from a battery disposed in a vehicle to the lead wire unit. 
         [0014]    The internal thermo switches are connected in parallel. 
         [0015]    In another aspect of the present invention, a heater system of a fuel filter, may include a power supply unit supplying power, a lead wire unit receiving the power from the power supply unit and having a plurality of branch lines to divide current of the power supplied from the power supply unit and an external thermo switch installed in one of the branch lines, and the fuel filter having an internal thermo switch connected to a branch line where the external thermo switch is not installed, among the branch lines of the lead wire unit, wherein the external thermo switch and the internal thermo switch are electrically-connected to a PTC (Positive Temperature Coefficient) heater heated by a power separately supplied through the external thermo switch and the internal thermo switch. 
         [0016]    When the number of branch lines is set to two, the external thermo switch is installed on one of the two branch lines, and the internal thermo switch is connected to the other one of the two branch lines. 
         [0017]    The internal thermo switch may have an ON operation condition of 7° C.±4.5° C. and an OFF operation condition of 24° C.±3.5° C., and the external thermo switch may have an ON operation condition of −2° C.±4.5° C. and an OFF operation condition of 5° C.±3.5° C. 
         [0018]    The power supply unit supplies a power applied from a battery disposed in a vehicle to the lead wire unit. 
         [0019]    The external thermo switch and the internal thermo switch are connected in parallel. 
         [0020]    As such, the heater system of a fuel filter according to the exemplary embodiments of the present invention divides the current supplied from the power supply unit through the lead wire unit and supplies the divided currents to the internal thermo switches. Accordingly, it is possible to reduce an excessive starting current which may occur when one thermo switch is used as in the related art. Furthermore, it is possible to prevent the melt-out of the thermo switches. 
         [0021]    Further, the heater system of a fuel filter according to the exemplary embodiment of the present invention is operated by the plurality of internal thermo switches. Therefore, even when a problem occurs in any one internal thermo switch, the operation may be maintained by another internal thermo switch. Accordingly, the safety function may be strengthened. 
         [0022]    In addition, in the heater system of a fuel filter according to the exemplary embodiment of the present invention, since the internal thermo switches have different operation temperature conditions, the amount of currents supplied to the PTC heater may be sequentially controlled according to the temperature. Therefore, the heating value of the PTC heater may be sequentially controlled. 
         [0023]    Moreover, since the external thermo switch is installed in the lead wire unit, the heater system of a fuel filter according to the exemplary embodiment of the present invention may be more easily manufactured, and the manufacturing cost thereof may be reduced. 
         [0024]    The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a schematic circuit diagram of a heater system of a fuel filter according to the related art. 
           [0026]      FIG. 2  is a waveform diagram of a starting current generated by a thermo switch in the heater system of a fuel filter according to the related art. 
           [0027]      FIG. 3  is a diagram explaining damage which occurs in the thermo switch in the heater system of a fuel filter according to the related art. 
           [0028]      FIG. 4  is a schematic circuit diagram of a heater system of a fuel filter according to an exemplary embodiment of the present invention. 
           [0029]      FIG. 5  is a schematic circuit diagram of a heater system of a fuel filter according to another exemplary embodiment of the present invention. 
       
    
    
       [0030]    It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
         [0031]    In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
       DETAILED DESCRIPTION 
       [0032]    Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
         [0033]    Hereinafter, a heater system of a fuel filter according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.  FIG. 4  is a schematic circuit diagram of the heater system of a fuel filter according to the exemplary embodiment of the present invention. 
         [0034]    Referring to  FIG. 4 , a heater system  100  of a fuel filter according to the exemplary embodiment of the present invention may include a power supply unit  110 , a lead wire unit  120 , and a fuel filter  130 . 
         [0035]    Power supply unit  110  supplies power to fuel filter  130  through lead wire unit  120 , using a battery  112  disposed in a vehicle as a power source. 
         [0036]    Lead wire unit  120  may receive power from power supply unit  110 , divide current of the supplied power through a plurality of branch lines, and connect the divided currents to fuel filter  130 . 
         [0037]    In  FIG. 4 , two branch lines  122  are provided. Accordingly, the current of the power supplied from power supply unit  110  may be divided in half and then supplied to internal thermo switches  132 , respectively. 
         [0038]    Fuel filter  130  may include a plurality of internal thermo switches  132  connected to branch lines  122  of lead wire unit  120 , respectively, and a PTC heater  134  heated by the power supplied through internal thermo switches  132 . 
         [0039]    Internal thermo switches  132  may have operation temperature conditions which are sequentially set in different manners. For example, when two internal thermo switches  132  are provided as illustrated in  FIG. 4 , one disposed above between internal thermo switches  132  may have an ON operation condition of 7° C.±4.5° C. and an OFF operation condition of 24° C.±3.5° C., and the other one disposed below between internal thermo switches  132  may have an ON operation condition of −2° C.±4.5° C. and an OFF operation condition of 5° C.±3.5° C. 
         [0040]    Since two internal thermo switches  132  have different OFF operation temperature conditions, two internal thermo switches  132  are turned on in time so as to supply the divided currents to PTC heater  134 . Therefore, a starting current (surge current) may be lowered. 
         [0041]    Since two internal thermo switches  132  are independently turned on/off according to the operation temperature conditions, the supply of the power through branch lines  122  of lead wire unit  120  may be selectively performed. 
         [0042]    That is, when the one disposed above between internal thermo switches  132  is turned on and the other disposed below is turned off depending on the temperature of fuel filter  130  according to the exemplary embodiment of the present invention, the power may be supplied to PTC heater  134  only by internal thermo switch  132  disposed above. 
         [0043]    As such, heater system  100  of a fuel filter according to the exemplary embodiment of the present invention may divide the current supplied from power supply unit  110  through lead wire unit  120 , and supply the divided currents to internal thermo switches  132 . Accordingly, it is possible to reduce an excessive starting current which may occur when one thermo switch is used as in the related art. Therefore, it is possible to prevent the melt-out of the thermo switches. 
         [0044]    Heater system  100  of a fuel filter according to the exemplary embodiment of the present invention is operated by the plurality of internal thermo switches  132 . Therefore, even when a problem occurs in any one internal thermo switch  132 , the operation may be maintained by another internal thermo switch  132 . Accordingly, the safety function may be strengthened. Internal thermo switches  132  are connected in parallel to each other. 
         [0045]    In heater system  100  of a fuel filter according to the exemplary embodiment of the present invention, since internal thermo switches  132  have different operation temperature conditions, the amount of currents supplied to PTC heater  134  may be sequentially controlled according to the temperature. Therefore, the heating value of PTC heater  134  may be sequentially controlled. 
         [0046]    Hereinafter, a heater system  200  of a fuel filter according to another exemplary embodiment of the present invention will be described with reference to  FIG. 5 . In heater system  200  of a fuel filter according to the exemplary embodiment of the present invention, the current division using the parallel connection of thermo switches that is the main gist of the present invention is performed in the same manner as the above-described exemplary embodiment of the present invention. Therefore, the detailed descriptions thereof will be omitted herein. 
         [0047]    Referring to  FIG. 5 , heater system  200  of a fuel filter according to the exemplary embodiment of the present invention may include a power supply unit  210 , a lead wire unit  220 , and a fuel filter  230  as in the above-described exemplary embodiment of the present invention. 
         [0048]    Heater system  200  of a fuel filter according to the exemplary embodiment of the present invention is different from the heater system of a fuel filter according to the above-described exemplary embodiment of the present invention in that an external thermo switch  224  is installed on a part of branch lines  222  of lead wire unit  220 . An internal thermo switch  232  disposed in fuel filter  230  is connected to branch line  222  where external thermo switch  224  is not installed, among branch lines  222  of lead wire unit  220 . 
         [0049]    As illustrated in  FIG. 5 , when two branch lines  222  of lead wire unit  220  are provided, external thermo switch  224  is installed on one of branch lines  222 , and internal thermo switch  232  is connected to the other branch line  222 . 
         [0050]    Internal thermo switch  232  and external thermo switch  224  may have operation conditions which are sequentially set in different manners. For example, internal thermo switch  232  may have an ON operation condition of 7° C.±4.5° C. and an OFF operation condition of 24° C.±3.5° C., and external thermo switch  224  may have an ON operation condition of −2° C.±4.5° C. and an OFF operation condition of 5° C.±3.5° C. 
         [0051]    That is, in the exemplary embodiment illustrated in  FIG. 4 , two internal thermo switches  132  selectively perform the current division according to the temperature. In the exemplary embodiment illustrated in  FIG. 5 , external thermo switch  224  and internal thermo switch  232  selectively perform the current division according to the temperature. That is, external thermo switch  224  and internal thermo switch  232  are connected in parallel. 
         [0052]    In heater system  200  of a fuel filter according to the exemplary embodiment of the present invention, as external thermo switch  224  operating according to the temperature condition is installed in lead wire unit  220 , the addition of internal thermo switch  232  to fuel filter  230  is unnecessary, unlike the above-described exemplary embodiment of the present invention. Therefore, heater system  200  according to the exemplary embodiment of the present invention may be more easily manufactured and the manufacturing cost thereof may be further reduced than in the exemplary embodiment illustrated in  FIG. 4 . 
         [0053]    The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.