Patent Publication Number: US-11049683-B2

Title: High-voltage direct-current thermal fuse

Description:
CROSS REFERENCE TO THE RELATED APPLICATIONS 
     This application is the national phase entry of International Application No. PCT/CN2018/101788, filed on Aug. 22, 2018, which is based upon and claims priority of Chinese Patent Application No. 201720786629.2, filed to the China National Intellectual Property Administration on Jun. 30, 2017, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present application relates to a fuse, in particular to a high-voltage direct-current thermal fuse. 
     BACKGROUND 
     China&#39;s electric-car market has been growing fast since 2014. The next 5-10 years are expected to be an important period for the industrialization of electric vehicles, and the market is expected to boom in the future. As the largest electric-car market in the world, in the year of 2015, China&#39;s annual new energy vehicle output reached 340,000 units and annual sales volume reached 330,000 units, with year-on-year growth of 3.3 and 3.4 times, respectively. In the whole year of 2016, the total sales volume of new energy vehicles in China reached 507,000 units, with year-on-year growth of 53%. It is estimated that the sales volume of new energy vehicles in 2017 and 2020 will reach 750,000 and 2 million units, and the penetration rate is expected to reach 6% in the year of 2020. As new energy vehicles are being promoted nationwide, growth within the industry is promising. 
     Batteries have always been the part that people care about the most in an electric car. However, Chinese car manufacturers and foreign car manufacturers have vastly different battery selection criteria. At present, Nissan Leaf is a car model having the highest market share, which has a battery voltage of 360 Vdc. Mitsubishi&#39;s i-MiEV has a battery voltage of 300 Vdc. A Tesla battery pack of 7000 pieces of 18650 lithium batteries has a voltage of only 400 Vdc. Battery pack voltage of China&#39;s electric vehicles is much higher than the battery pack voltage of cars manufactured by foreign car manufacturers. For example, the battery pack voltage of BYD Qin is 560 Vdc, while the battery pack voltage of BYD Tang is 700 Vdc. 
     Battery pack with high voltage has two advantages, lower energy/power loss and higher motor drive efficiency. Increasing the voltage will be a trend and should be a development direction in the future. Increasing the voltage of the battery pack will result in reduced working current while the output power stays the same as before the change. However, this has a great impact on the performance requirement/cost of peripheral devices. By using a battery pack having higher voltage, the protection devices used in circuits should be able to operate under high voltage conditions. 
     Chinese patent NO. 201420230161.5 discloses a high-voltage direct-current temperature fuse, which is the only high-voltage direct-current thermal protection device in the industry that can reach 15A 450 Vdc. However, among China&#39;s mainstream car manufacturers, the voltage of battery packs are all set above 500 Vdc, as a result there is an urgent need for a high-voltage direct-current protection device in the market. 
     SUMMARY 
     In order to solve the existing problems mentioned above, one of the purposes of the present application is to provide a high-voltage direct-current thermal fuse to provide an effective thermal protection for a circuit by shutting of the current to the circuit. 
     One of the purposes of the present application is achieved by the following technical solutions. 
     A high-voltage direct-current thermal fuse includes a fusible component having two fusible alloy support arms parallel to each other; a fluxing agent; a fusing cavity, wherein the fusible component and the fluxing agent are sealed within the fusing cavity; and two pins, wherein the two pins are respectively connected to the two support arms. Technically, the fluxing agent only needs to have contact with the fusible alloy. Practically, the fluxing agent is usually coated over the fusible alloy. 
     Preferably, the fusible component has a U-shaped, M-shaped, S-shaped or trapezoid-shaped structure. 
     Preferably, the high-voltage direct-current thermal fuse further includes an insulation block, and the insulation block is arranged between the two support arms and separates the two pins. This setting acts to lengthen the arc to increase the insulation tolerance of the pins during an arc extinction. 
     Preferably, the high-voltage direct-current thermal fuse further includes a housing and a bottom plate. The insulation block is arranged on the bottom plate. The housing, the bottom plate, the insulation block, and the two pins form the fusing cavity. 
     Preferably, a fusible alloy connection segment is connected between the two support arms. 
     Preferably, n conductive members and n−1 fusible alloy connection segments arranged at intervals are connected between the two support arms, and n is a natural number. When n is greater than or equal to 2, each fusible alloy connection segment is arranged between two conductive members, so as to ensure that the fusible alloy material and the conductive members are arranged at intervals, in an alternating method. Theoretically, any conductive material can be used as the conductive member of the present disclosure. Preferably, the conductive member uses the same material as the pins. On reaching the operating temperature, the fusible alloy contracts toward the two pins, and the contraction rate of the fusible alloy with excessive length will be slower. As a result, if the fusible alloy is applied to a high voltage structure, the high voltage cannot be cut off in time. The fusible alloy can be configured as multiple segments that are alternatingly arranged with the conductive members to improve the contraction rate of the fusible alloy. 
     Preferably, one conductive member is connected between the two support arms. 
     Preferably, two conductive members and one fusible alloy connection segment arranged between the two conductive members are connected between the two support arms. 
     Preferably, when n is greater than or equal to 3, the cross-sectional areas of the fusible alloy connection segments may differ from one another, and the operating temperature of the fusible alloy connection segment having a smaller cross-sectional area is higher than the operating temperature of the fusible alloy connection segment having a larger cross-sectional area. By doing so, while improving the current handling capability in per unit volume, the ability of cutting of the circuit with high voltage is also improved. After other fusible alloys are disconnected, The fusible alloy having a high operating temperature and a small cross-sectional area can contract faster to cut off the arc under the action of the temperature and the current after other fusible alloys are disconnected. 
     Preferably, a place at which the support arms, the fusible alloy connection segment, and the conductive member are connected is provided with connection holes, and the conductive member is placed in the connection hole for welding. This welding mode is better than welding the fusible alloy and conductive member with flat surfaces. 
     Preferably, the two pins are perpendicular to the support arms. 
     Preferably, a non-metallic partition film is arranged inside the fusing cavity to divide the fusing cavity into an inner cavity and an outer cavity, and the inner cavity and the outer cavity are mutually sealed; the fluxing agent is arranged inside the inner cavity, and quartz sand is arranged inside the outer cavity. In high voltage application, arc cutting process easily gasifies and expands the fluxing agent. The quartz sand can absorb the impact of gasification and block the transmission path of the arc, which is favorable for improving the insulation withstanding voltage of the opening points. 
     Preferably, the high-voltage direct-current thermal fuse includes a plurality fusible components connected in parallel. 
     Preferably, conductive members having equal electric potential in the plurality of fusible components connected in parallel can be integrated into one body. When a plurality of fusible components having one conductive member are connected in parallel, all of the conductive members can be integrated into one body. By doing so, the structure is simplified and the processing is easier. 
     Preferably, the fusible component may have a hollow tube structure, and the fluxing agent is placed inside the tube. By doing so, the surface oxide layer of fusible alloy can be activated more effectively, and the arc can be cut off quickly. 
     Preferably, an external connection part of each pin is wavy on one side, near the fusing cavity and is flat on the other side away from the fusing cavity. 
     The present application has the following advantages. 
     The fusible components of the high-voltage direct-current thermal fuse in this application is a U-shaped structure having two support arms parallel to each other. A high electric field intensity is generated when an arc is being cut off, as a result, the electrons repel each other, and the arc is lengthened, thereby increasing the speed of cutting off the arc. Therefore, this invention can be used to provide thermal protection for high-voltage direct-current power devices. When an abnormal heating condition occurs and the temperature reaches the operating temperature point of the fusible alloy, the cutting off operation can be performed quickly to protect the circuit, therefore providing a safe operating condition. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present application will be further described below with reference to the following drawings. 
         FIG. 1  is a cross-sectional view of the high-voltage direct-current thermal fuse according to Embodiment 1 in the present application; 
         FIG. 2  is an exploded view of the high-voltage direct-current thermal fuse according to Embodiment 1 in the present application; 
         FIG. 3  is a cross-sectional view of the high-voltage direct-current thermal fuse according to Embodiment 2 in the present application; 
         FIG. 4  is an exploded view of the high-voltage direct-current thermal fuse according to Embodiment 2 in the present application; 
         FIG. 5  is a cross-sectional view of the high-voltage direct-current thermal fuse according to Embodiment 3 in the present application; 
         FIG. 6  is a cross-sectional view of the high-voltage direct-current thermal fuse according to Embodiment 4 in the present application; 
         FIG. 7  is a cross-sectional view of the high-voltage direct-current thermal fuse according to Embodiment 5 in the present application; and 
         FIG. 8  shows one embodiment of the pins according to the present disclosure. 
     
    
    
     The reference numerals in the drawings are illustrated below:
           101  housing     102  bottom plate     1021  insulation block     103  left pin     104  right pin     105  fusible alloy     106  fluxing agent     107  encapsulation adhesive     108  non-metallic partition film     109  quartz sand     201  housing     202  bottom plate     203  left pin     204  right pin     205  first support arm     206  conductive member     207  second support arm     208  fluxing agent     209  encapsulation adhesive     210  non-metallic partition film     211  quartz sand     301  housing     302  bottom plate     303  left pin     304  right pin     305  first support arm     306  first conductive member     307  fusible alloy connection segment     308  second conducive member     309  second support arm     310  fluxing agent     311  encapsulation adhesive     401  connection hole       

     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Embodiment 1 
     As shown in  FIG. 1  and  FIG. 2 , the high-voltage direct-current thermal fuse includes the non-metallic housing  101 , the bottom plate  102 , and the insulation block  1021  arranged on the bottom plate  102 . The housing  101  and the bottom plate  102  are sealed with the encapsulation adhesive  107 . The housing  101 , the bottom plate  102 , the left pin  103 , the right pin  104 , and the insulation block  1021  form the fusing cavity, and two fusible components coated with the fluxing agent  106  are hermetically arranged in the fusing cavity. The fusible component is a U-shaped structure having two fusible alloy support arms parallel to each other and fusible alloy connection segments connecting the two support arms. Namely, the fusible component is a U-shaped fusible alloy  105 . The left pin  103  and the right pin  104  are perpendicular to the fusible alloy support arms. An end of the left pin  103  is connected to a support arm at a side and the other end of the left pin  103  extends out of the housing  101 . One end of the right pin  104  is connected to the other support arm at the other side and the other end of the right pin  104  extends out of the housing  101 . The insulation block  1021  is arranged between the parallel support arms and separates the left pin  103  and the right pin  104 . The left pin  103 , the fusible alloy  105 , and the right pin  104  form the fusing component of an electrical connection. 
     When the high-voltage direct-current thermal fuse is applied in the thermal protection of a power device in high-voltage circuits, when the power device operates in unusual conditions, the temperature would rise abnormally. The heat is transferred to the fluxing agent  106  and the fusible alloy  105  through the left pin  103 , the right pin  104 , and the housing  101 , the temperature transfer the fluxing agent  106  from solid state to liquid state and activate the surface oxide layer of the fusible alloy  105 . When the temperature reaches the operating temperature point of the fusible alloy  105 , the fusible alloy  105  starts to creep and contract toward the left pin  103  and the right pin  104 . When the fusible alloy  105  is broken, a high-voltage arc is generated, and the opening point of the fusible alloy  105  is rapidly eroded by electricity. When the fusible alloy  105  reaches the two parallel support arms after contraction and electrical erosion, the high electric field intensity generated by the breaking of the fusible alloy  105  makes the electrons of the two support arms repel each other, the arc is lengthened, and the arc is rapidly cut off, thus cutting off the circuit. The insulation block  1021  of the bottom plate  102  functions to lengthen the arc and increase the insulation voltage withstanding capability of the left pin  103  and the right pin  104  in the arc extinction. 
     Embodiment 2 
     As shown in  FIG. 3  and  FIG. 4 , the high-voltage direct-current thermal fuse includes the non-metallic housing  201 , the bottom plate  202 , and the insulation block arranged on the bottom plate  202 . The housing  201  and the bottom plate  202  are sealed with the encapsulation adhesive  209 . The housing  201 , the bottom plate  202 , the left pin  203 , the right pin  204 , and the insulation block form the fusing cavity, and two fusible components coated with the fluxing agent  208  are hermetically arranged in the fusing cavity. The fusible component is a U-shaped structure having the first support arm  205  and the second support arm  207  which are made of fusible alloy and are parallel to each other. The first support arm  205  and the second support arm  207  are connected by the conductive member  206 . The insulation block is arranged between the first support arm  205  and the second support arm  207  and separates the left pin  203  and the right pin  204 . The left pin  203  and the right pin  204  are perpendicular to the first support arm  205  and the second support arm  207 . An end of the left pin  203  is connected to the first support arm  205  of the fusible component and the other end of the left pin  203  extends out of the housing  201 . An end of the right pin  204  is connected to the second support arm  207  of the fusible component and the other end of the right pin  204  extends out of the housing  201 . The left pin  203 , the first support arm  205 , the conductive member  206 , the second support arm  207 , and the right pin  204  are electrically connected successively to form a structure with two breaking points. 
     On reaching the operating temperature, the fusible alloy contracts toward the two pins, and the fusible alloy with an excessive length will have a slower contraction rate. As a result, if the fusible alloy is applied to a high voltage structure, the high voltage cannot be cut off in time. The fusible component may be configured as two fusible alloy segments that are separate and parallel to each other. The conductive member is connected between the two fusible alloy segments as a bridge to form an electrical connection. 
     The first support arm  205  and the second support arm  207  having the same operating temperature would absorb heat and contract toward the metal members at the two sides at the same time on reaching the operating temperature, thereby ensuring that the breaking point falls within the region of the parallel structure, improving the electric field intensity, accelerating the diffusion speed of the charged ions, shortening the length of the fusible alloy, forming multiple breaking points at the same time, increasing the voltage drop and loss, reducing the energy of the arc, and facilitating to cut off the high voltage circuit. 
     Embodiment 3 
     As shown in  FIG. 5 , the high-voltage direct-current thermal fuse is a variant of Embodiment 1. On the basis of Embodiment 1, on the outer layer of the fusible alloy  105  coated with the fluxing agent  106 , the non-metallic partition film  108  is used to divide the fusing cavity into an inner cavity and an outer cavity that are mutually sealed. The quartz sand  109  is arranged in the outer cavity, and the fluxing agent  106  is arranged in the inner cavity. The inner cavity and the outer cavity are partitioned to prevent the fluxing agent  106  from penetrating into the quartz sand  109  at a high temperature, and to prevent the quartz sand  109  from penetrating the fluxing agent  106  to destroy the surface structure of the fusible alloy  105 . 
     When the fusible alloy  105  contracts and melts to break, a high-voltage arc is generated. The arc instantaneously and electrically erodes the opening point of the fusible alloy  105 , causing instantaneous gasification and expansion of the fusible alloy which impacts the non-metal partition film  108 . Under the action of the impact wave, the non-metal partition film  108  gets fractured, and the quartz sand  109  falls down to cover the fusible alloy  109 , thereby interrupting the high-voltage arc, forming multiple breaking points, and extinguishing the arc instantaneously, which can effectively cut off the circuit. 
     Embodiment 4 
     As shown in  FIG. 6 , the high-voltage direct-current thermal fuse is a variant of Embodiment 2. On the basis of Embodiment 2, the partition film structure is used in a double breaking point structure. On the outer layer of the first support arm  205  and the second support arm  207  coated with the fluxing agent  208 , the partition film  210  is used to separate the quartz sand  211  and the fluxing agent  208 . In the fusing process, the arc is cut off at multiple breaking points to prevent further development of the arc. 
     Embodiment 5 
     As shown in  FIG. 7 , according to the level of the voltage to be cut, the fusible alloy may be configured as more segments, and a conductive member is used as a bridge between every two fusible alloy segments to form a linear electrical connection in sequence. 
     High-voltage direct-current thermal fuse includes the non-metallic housing  301 , the bottom plate  302 , and the insulation block arranged on the bottom plate  302 . The housing  301  and the bottom plate  302  are sealed with the encapsulation adhesive  311 . The housing  301 , the bottom plate  302 , the left pin  303 , the right pin  304 , and the insulation block form the fusing cavity, and the fusible component coated with the fluxing agent  310  is hermetically arranged inside the fusing cavity. The fusible component is a U-shaped structure having the first support arm  305  and the second support arm  309  that are made of fusible alloy and are parallel to each other. The first support arm  305  and the second support arm  309  are connected by the first conductive member  306 , the fusible alloy connection segment  307 , and the second conductive member  308  that are arranged at intervals. The insulation block is arranged between the first support arm  305  and the second support arm  309  and separates the left pin  303  and the right pin  304 . The left pin  303  and the right pin  304  are perpendicular to the first support arm  305  and the second support arm  309 . An end of the left pin  303  is connected to the first support arm  305  of the fusible component and the other end of the left pin  303  extends out of the housing  301 . An end of the right pin  304  is connected to the second support arm  309  of the fusible component and the other end of the right pin  304  extends out of the housing  301 . The left pin  303 , the first support arm  305 , the first conductive member  306 , the fusible alloy connection segment  307 , the second conductive member  308 , the second support arm  309 , and the right pin  304  are electrically connected successively to form a multiple breaking point structure. The fluxing agent  310  is coated on the surfaces of the first support arm  305 , the fusible alloy connection segment  307 , and the second support arm  309 . The first support arm  305 , the fusible alloy connection segment  307 , and the second support arm  309  have the same operating temperature and form a multiple breaking point structure when fusing simultaneously, thereby increasing the voltage drop and loss and reducing the energy of the arc, so the thermal protection can be effectively performed. 
       FIG. 8  shows one embodiment of the pins. It is shown in the drawing that an external connection part of each pin is wavy at a side near the fusing cavity and is flat at a side away from the fusing cavity. 
     The present application has been described in detail in the form of embodiments with reference to the drawings. Described embodiments are merely preferred embodiments of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the embodiments, for those skilled in the art, the technical solutions described in the foregoing embodiments may be modified, or some of the technical features may be equivalently replaced. Any changes, equivalent substitution, improvement, and so on made without departing from the spirit and principle of this application shall be considered as falling within the scope of this application.