BACKGROUND AND SUMMARY

[0001] This application is claims priority to a U.S. Application Serial No.

12/271,011, filed on November 14, 2008, the disclosure of which is incorporated herewith by reference in its entirety.

[0002] The disclosure of the present application relates to a fuse assembly with integrated current sensing, primarily for use in the drive system of an electric or hybrid-electric vehicle.

[0003] With the electrification of the drive systems of vehicles, there are several problems with the state of the art in current sensing methodologies. Given the high currents present and the need to sense the DC current, there are basically two options:

(1) Non-contact Hall effect sensors or (2) Inline current shunt resistors.

[0004] Hall effect sensors have three primary problems. First, the sensors rely on sensing a static magnetic field. This static magnetic field can be affected by an external field imposed on the drive system and also by switching noise on the lines themselves. Second, depending on the design, Hall effect sensors are sensitive to the mechanical mounting of the system and can exhibit variation base on their installation methods. Third, Hall effect sensors are less accurate that equivalent current shunt methodologies.

[0005] Inline current shunt resistors have their own limitations. The dissipation power caused by the current requires that the resistance of the resistive element be of an extremely small value. This means that a metalized shunt is required to maintain a reasonable size. This thermal profile generally also requires the shunt to be mounted off-board or in a leaded device, i.e., a device with electrical conductors connected to the device.

[0006] Second, it is necessary to physically insert the resistance of the current shunt resistor into the current path. This both adds to the mechanical complexity, and adds additional impedance into the drive system. The impedance comes as both the resistance of the element, as well as in additional connection points in the system.

Third, if the shunt becomes thermally stressed due to an over current conditions, its electrical resistance changes.

[0007] There is a constant for improved sensing devices that will eliminate one or more problems associated with the prior art sensing devices. [0008] A fuse assembly includes a main component. The main component is partially encased in a protective sheath formed of an electrically insulating, i.e., non- conductive, material. The main component includes a pair of connectors formed of an electrically conductive material, such as a metal. The connectors allow the fuse assembly to be electrically connected into a larger system, such as an electric vehicle drive system. A fusible link is electrically connected between the connectors and is preferably encased in the protective sheath. The fusible link melts or otherwise dissipates when subjected to current flowing through the fuse assembly in excess of a predetermined current for a predetermined time, as is well known to those skilled in the art. A current sensing element is also electrically connected between the connectors. The current sensing element includes a resistor which is commonly referred to as a current shunt resistor. The current sensing element includes a pair of terminals electrically connected on either side of the resistor such that the voltage across the resistor may be measured. By measuring the voltage, and knowing the resistance of the resistor, the current flowing through the current sensing element, and the fuse assembly as a whole, may be easily calculated.

[0009] Typically, electric vehicle drive systems require the fusible link for short circuit safety protection. In the event that the fusible link blows, the fuse assembly will be required to be replaced. In replacing the fuse assembly, the current sensing element is also replaced. Therefore, the current sensing element will be maintained within tolerances. In the illustrated embodiment, the fusible link is connected to one of the connectors, the current sensing element is connected to the other connector, and a linking piece formed of an electrically conductive material, such as metal, is connected between the fusible link and the current sensing element. [0010] A pair of external terminals is electrically connected to the terminals of the current sensing element. The external terminals are disposed at least partially on an exterior of the protective sheath to allow connection of a voltage sensor (not shown) or other such measurement apparatus (not shown) to the fuse assembly. [0011] At least one advantage of the disclosure of the present application is to provide a fuse assembly that is simple to design and manufacture. [0012] At least one additional advantage of the disclosure of the present application is to provide a fuse assembly that reduces additional impedance into the drive system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Advantages of the present disclosure will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

[0014] FIG. 1 shows a perspective view of an exemplary embodiment of a fuse assembly according to the present disclosure; and

[0015] FIG. 2 shows a perspective view of an exemplary embodiment of a fuse assembly showing the main component of the fuse assembly according to the present disclosure.

DETAILED DESCRIPTION

[0016] Referring to the figures, wherein like numerals indicate corresponding parts throughout the several views, a fuse assembly with integrated current sensing is shown at 10.

[0017] As shown in FIG. 1, the fuse assembly 10 includes a main component 12.

Preferably, as shown in FIG. 2, the main component 12 is partially encased in a protective sheath 14 formed of an electrically insulating, i.e., non-conductive, material.

[0018] The main component 12 includes a pair of connectors 16A, 16B formed of an electrically conductive material, such as a metal. The connectors 16A, 16B allow the fuse assembly 10 to be electrically connected into a larger system (not shown), such as an electric vehicle drive system (not shown).

[0019] A fusible link 18 is electrically connected between the connectors 16 A, 16B and is preferably encased in the protective sheath 14. The fusible link 18 melts or otherwise dissipates when subjected to current flowing through the fuse assembly 10 in excess of a predetermined current for a predetermined time, as is well known to those skilled in the art.

[0020] A current sensing element 20 is also electrically connected between the connectors 16 A, 16B. The current sensing element 20 includes a resistor (not shown) which is commonly referred to as a current shunt resistor. The current sensing element 20 includes a pair of terminals 22 electrically connected on either side of the resistor such that the voltage across the resistor may be measured. By measuring the voltage, and knowing the resistance of the resistor, the current flowing through the current sensing element 20, and the fuse assembly 10 as a whole, may be easily calculated.

[0021] In one embodiment, the current sensing element 20 may be implemented using a SPR3004 manufactured by Vishay Intertechnology, Inc. of Malvern, Pa., USA. Of course, other sources and configurations for the current sensing element 20 may be realized by those skilled in the art.

[0022] Typically, electric vehicle drive systems require the fusible link 18 for short circuit safety protection. In the event that the fusible link 18 blows, the fuse assembly 10 will be required to be replaced. In replacing the fuse assembly 10, the current sensing element 20 is also replaced. Therefore, the current sensing element 20 will be maintained within tolerances.

[0023] In the illustrated embodiment, the fusible link 18 is connected to one of the connectors 16A, the current sensing element 20 is connected to the other connector 16B, and a linking piece 24 formed of an electrically conductive material, such as metal, is connected between the fusible link 18 and the current sensing element 20. [0024] A pair of external terminals 26 is electrically connected to the terminals 22 of the current sensing element 10. The external terminals 26 are disposed at least partially on an exterior of the protective sheath 14 to allow connection of a voltage sensor (not shown) or other such measurement apparatus (not shown) to the fuse assembly 10.

[0025] While various embodiments of fuse assemblies been described in considerable detail herein, the embodiments are merely offered by way of non- limiting examples of the disclosure described herein. It will therefore be understood that various changes and modifications may be made, and equivalents may be substituted for elements thereof, without departing from the scope of the disclosure. Indeed, this disclosure is not intended to be exhaustive or to limit the scope of the disclosure.