Normally closed thermal trip switch

Abstract

The normally-closed thermal trip switch comprises a first conductor and a second conductor which are arranged in a shell in a penetrating mode, the first conductor located in the shell has elasticity and is arranged in a cantilever mode, and the first conductor is in direct conductive contact with the second conductor under limiting of a limiting piece to form a series circuit. Current flows through a series circuit formed by direct conductive contact of the first conductor and the second conductor. Part of the material of the limiting piece limiting the first conductor is a low-melting-point material lower than the melting point of the material of the shell, when the temperature of the first conductor reaches the melting point of the low-melting-point material, the part, abutting against the first conductor, of the limiting piece is softened or melted, limiting is relieved, and the first conductor located in the shell is far away from the second conductor under the action of the elastic force of the first conductor. The first conductor and the second conductor are disconnected from the direct conductive contact. The normally-closed thermal trip switch is high in response speed and can protect a power semiconductor device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power control and electric vehicles, in particular to a device for protecting power semiconductor devices in the event of a fault current. BACKGROUND

[0002] Power devices are an important part of modern power electronic systems, mainly referring to electronic components designed to handle high voltage, large current, and achieve power conversion and control, such as MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor), IGBT (Insulated Gate Bipolar Transistor), power diode, etc. They have high efficiency, low loss and good switching characteristics, and are widely used in motor control, solar photovoltaic, new energy vehicles, etc. However, these devices may face overcurrent, overvoltage and short circuit failures in actual application, resulting in high temperature, reduced performance, reduced life and even damage to the device, so designing an efficient protection method for power devices is crucial to ensure the reliability and life of power devices.

[0003] There are several methods for protecting power devices at present:

[0004] 1. Fuse, fuse is a traditional protection method, fuse is often connected in series at the power input end of the circuit to control the total current of the entire circuit. Its working principle is that when the fault current increases after the circuit fails, it causes the fuse to heat up and melt to cut off the power supply to achieve the purpose of protection, with the advantages of simple implementation, easy maintenance, low cost, complete power cut-off during protection, etc. Therefore, it is widely used in all electronic circuits and electronic devices at present.

[0005] The defects of this method are: the total current of the circuit flows through the fuse, the change of the working current of a single power device is not enough to cause the fuse to melt quickly, and it cannot play a quick protection role for the power device, but only prevents the fault from further expanding.

[0006] 2. Detecting the main circuit current method or detecting the power device working current method, this method is to insert a detection element (resistor or current transformer, etc.) in the main circuit or power device working circuit path, and obtain a fault signal by detecting the current signal of the working current of the main circuit or power device path on the detection element, and controlling the off of the current path for protection.

[0007] The defects of this method are: it always responds after the fault current is formed, causing a lag in the detection result and protection action, and it cannot play a quick protection role for the power device, but only prevents the fault from further expanding.

[0008] 3. Parallel detection of working voltage drop method, which needs to design a protection circuit, and the protection circuit is connected in parallel with the protected power device, and the signal is obtained by detecting the voltage drop of the protected device during working, and the circuit failure is judged according to the voltage, and the protection method adopts the local protection mode, that is, the control signal of the protected power device is forcibly cut off to force it to stop working to realize the protection. The measurement of the working state and the judgment of the fault are more accurate, and the protection effect is ideal.

[0009] The defects of the method are that the design of the protection circuit is complex, electronic components need to be arranged and certain control logic needs to be designed, the production requirement is high, the cost is high, and the universality is poor. SUMMARY

[0010] The technical problem to be solved by the present application is to provide protection for the power semiconductor device when a fault current occurs by connecting a normally closed thermal trip switch in series in the circuit where the power semiconductor device is located, and triggering the normally closed thermal trip switch to act by using the heat energy generated by the power semiconductor device when a fault current occurs, and disconnecting the circuit where the power semiconductor device is located, or limiting the current of the power semiconductor device, and forcibly reducing the current of the circuit where the power semiconductor device is located, to realize the protection of the power semiconductor device.

[0011] To solve the above technical problems, the technical solution provided by the present application is a normally closed thermal trip switch, which comprises a shell with a cavity, a first conductor and a second conductor are arranged in the cavity of the shell, one end of the first conductor and the second conductor outside the shell is respectively connected as the connection end of the normally closed thermal trip switch, the first conductor inside the shell is elastically arranged in a cantilevered manner, and the first conductor arranged in a cantilevered manner is directly in conductive contact with the second conductor under the limiting of a limiting piece to form a series circuit, and when the thermal trip switch works, the current flows through the series circuit formed by the direct conductive contact of the first conductor and the second conductor; the limiting piece limiting the first conductor is made of a low-melting-point material lower than the melting point of the material of the shell, when the temperature of the first conductor reaches the melting point of the low-melting-point material, the part of the limiting piece in contact with the first conductor softens or melts, and the limiting is released, and the first conductor inside the shell moves away from the second conductor under the action of its own elastic force, so that the first conductor and the second conductor are disconnected from the direct conductive contact.

[0012] Preferably, the limiting piece comprises a fixed seat and a limiting rod connected with each other, the limiting rod is made of a low-melting-point material, the fixed seat is fixed in the shell, and the limiting rod limits the initial position of the first conductor.

[0013] Preferably, a limiting protrusion is provided on the outer periphery of the limiting rod, and the end of the limiting rod away from the fixed seat is inserted into the first conductor. The limiting protrusion abuts against the first conductor to restrict its initial position. When the temperature rises to a threshold range, the limiting protrusion melts, and the limiting rod softens or melts, thereby releasing the restriction on the first conductor.

[0014] Preferably, one side of the inner wall of the housing has a stepped structure, one end of the second conductor inside the housing is fixedly disposed at the lowest step surface of the stepped structure, one end of the first conductor which is cantilevered across the stepped structure and rests on the second conductor at the lowest step surface of the stepped structure, making conductive contact with the second conductor, and one end of the first conductor inside the housing is configured as an arc-shaped structure protruding toward the second conductor.

[0015] Preferably, the first conductor and the second conductor located within the housing are elastic and suspended. The limiting member passes through the suspended ends of the first conductor and the second conductor, connecting and fixing the suspended ends of the first conductor and the second conductor. When the limiting member melts, the connection between the suspended ends of the first conductor and the second conductor is released. Under the action of their own elastic force, the suspended ends of the first conductor and the second conductor are displaced in opposite directions, causing the first conductor and the second conductor to disconnect from the conductive connection.

[0016] Preferably, one end of the first and second conductors located outside the housing is provided outside the housing as a connection end of a thermal trip switch in a patch, bent-out flat-out, or straight-out quick-connect manner.

[0017] Preferably, a through-hole is provided in the shell wall of the housing, and an indicator is inserted through the mounting hole. One end of the indicator is located in the mounting hole, and the other end is located on the displacement path of one end of the first conductor in the housing. When one end of the first conductor is displaced, the indicator is driven to move towards the outside of the housing, so that the end of the indicator facing the outside of the housing extends out of the shell wall.

[0018] Preferably, the indicator has a T-shaped structure, with one end of the lateral feature of the T-shaped structure located inside the housing.

[0019] Preferably, the indicator is positioned by a limiting structure, wherein the limiting structure is: an elastic barb structure is provided on the outer periphery of the indicator, the barb structure elastically abutting against the mounting hole to form the limiting structure; or, the indicator is assembled in the mounting hole in an interference fit to form the limiting structure; or, a limiting spring is provided between the limiting member and the outer periphery of the housing wall of the mounting hole to form the limiting structure.

[0020] Preferably, a heating resistor is provided inside the housing; the two ends of the heating resistor are electrically connected to the first conductor and the second conductor respectively to form a current limiting circuit, or the heating resistor is connected in parallel with the first conductor to form a current limiting circuit, and the current limiting circuit is connected in parallel with a series circuit formed by direct conductive contact between the first conductor and the second conductor; the limiting member passes through the first conductor and contacts the heating resistor, or the heating resistor is close to the limiting member.

[0021] Preferably, the two ends of the heating resistor are inserted into the shell wall and electrically connected to the ends of the first conductor and the second conductor located outside the shell, respectively.

[0022] Preferably, the heating resistor has a coil-like structure and is wound around the outer periphery of the first conductor and connected in parallel with the first conductor.

[0023] Preferably, the housing includes a cover with one open end and a base with one closed end. The base is disposed at the open end of the cover and closes the open end of the cover. The first conductor and the second conductor are respectively disposed between the cover and the base on opposite sides of the housing. One end of the first conductor and the second conductor are located inside the housing, and the other end is located outside the housing.

[0024] Preferably, the cover and the base are connected and fixed by a snap-fit ​​mechanism.

[0025] The normally closed thermal trip switch of this invention uses a limiting component made of a low-melting-point material. When the temperature rises, the limiting component melts or softens, losing its limiting force and thus releasing the limit, causing the first and second conductors to disengage from conductive contact. When the limiting component melts or softens, the shell material, due to its high melting point, retains its original hardness and structure, and does not soften or melt.

[0026] The normally closed thermal trip switch of the present invention has a simple structure. It is connected in series as a single device in the circuit of the power device and placed close to the power device. When a fault current occurs in the circuit where the power device is located, the temperature of the power device rises. The thermal trip switch disconnects under the combined action of its own heat and the heat of the power device, thereby disconnecting the circuit where the power device is located and realizing the protection of the power device.

[0027] The normally closed thermal trip switch of the present invention is low in cost and can effectively protect power semiconductor devices and improve their service life. Attached Figure Description

[0028] Figure 1 This is a cross-sectional view of the normally closed thermal trip switch in its initial state.

[0029] Figure 2 yes Figure 1 A side view structural diagram.

[0030] Figure 3 yes Figure 1 A schematic diagram of the structure after the action.

[0031] Figure 4 yes Figure 1 A schematic diagram of the structure after the action, showing the melting of the limiting protrusion.

[0032] Figure 5 yes Figure 1 A schematic diagram showing the structure after the action, in which the limit rod is completely melted.

[0033] Figure 6 This is a structural diagram of the snap-fit ​​structure between the cover and the base.

[0034] Figure 7 This is a structural diagram of the initial state with indicators set.

[0035] Figure 8 This is a structural diagram showing the action after the indicator is set.

[0036] Figure 9 yes Figure 1 A schematic diagram of a structure with a heating resistor added on top of the basic structure.

[0037] Figure 10 yes Figure 1 A schematic diagram of a structure with a heating resistor added on top of the basic structure.

[0038] Figure 11 yes Figure 1 A schematic diagram of a structure with a heating resistor added on top of the basic structure.

[0039] Figure 12 This is a schematic diagram of the structure of the first and second conductors, which are suspended in the air when the limiting component is in the initial state.

[0040] Figure 13 yes Figure 12 A schematic diagram of the structure after the limiting component melts following the action.

[0041] Figure 14 This is a schematic diagram of a thermal trip switch with a bent, flat-out connection.

[0042] Figure 15 This is a schematic diagram of a thermal trip switch with a direct-out quick-connect structure.

[0043] Figure label:

[0044] Cover 1, snap hole 11, base 5, borrow hole 51, snap protrusion 52, first conductor 3, one end of the first conductor located outside the shell 31, one end of the first conductor located inside the shell 32, second conductor 4, one end of the second conductor located outside the shell 41, one end of the second conductor located inside the shell 42, fixing seat 21, limiting rod 2, limiting protrusion 22, indicator 6, heating resistor 7, heating resistor 8, limiting member 9. Detailed Implementation

[0045] The normally closed thermal trip switch of the present invention includes a housing with a cavity, in which a first conductor and a second conductor are disposed. One end of the first conductor and the second conductor located outside the housing serves as the connection end of the normally closed thermal trip switch. The first conductor located inside the housing is elastic and cantilevered. Under the limitation of a limiting member, the cantilevered first conductor and the second conductor make direct conductive contact to form a series circuit. When the thermal trip switch is working, current flows through the series circuit formed by the direct conductive contact of the first conductor and the second conductor. The limiting member limiting the first conductor is made of a low-melting-point material with a melting point lower than that of the housing material. When the temperature of the first conductor reaches the melting point of the low-melting-point material, the part of the limiting member that abuts the first conductor softens or melts, releasing the limitation. The first conductor located inside the housing moves away from the second conductor under its own elastic force, causing the first conductor and the second conductor to disconnect from the direct conductive contact.

[0046] The following describes preferred embodiments in detail with reference to the accompanying drawings. The directional terms used are for reference only and do not constitute a limitation on the technical solutions of this invention.

[0047] See Figures 1 to 3 A normally closed thermal trip switch mainly includes a housing, a first conductor, a second conductor, and a limiting component. The housing is made of an insulating material with a high melting point and includes a cover 1 and a base 5. The cover 1 is a cap-shaped structure with one open end and one closed end. The base 5 is located at the open end of the cover 1 and closes the open end, forming a relatively sealed housing with a cavity inside. The base 5 is a stepped structure with a certain thickness, located inside the housing. A borrow hole 51 is provided on the inner surface of the base 5. The side walls of the base 5 and the cover 1 are provided with a snap-fit ​​structure, and the base 5 is connected and fixed to the cover 1 by snap-fit, for example: see... Figure 6 A protruding snap-fit ​​protrusion 52 is provided on the side wall of the base 5 that mates with the cover 1, and a snap-fit ​​hole 11 is provided on the corresponding side wall of the cover 1. During assembly, the snap-fit ​​protrusion 52 of the base 5 snaps into the snap-fit ​​hole 11 of the cover 1, forming a fixed connection. The cover 1 and the base 5 can also be connected and fixed by bolts, rivets, laser welding or adhesive bonding.

[0048] The second conductor 4 passes between the lowest step surface of the stepped structure of the base 5 and the cover 1. One end 42 of the second conductor 4 located inside the housing is bent and fixed to the lowest step surface of the stepped structure of the base 5. One end 41 of the second conductor 4 located outside the housing is set on the outer surface of the base 5 in a patch-type structure as one of the connection ends of the normally closed thermal trip switch.

[0049] The first conductor 3 passes between the highest step surface of the stepped structure of the cover 1 and the base 5. One end 31 of the first conductor 3, located outside the housing, is attached to the outer surface of the base 5 as one of the connection terminals of a normally closed thermal trip switch. The first conductor 3, located inside the housing, is bent above the highest step of the base 5 and cantilevered. This cantilevered portion of the first conductor 3 has a certain degree of elasticity. Under its own elastic force, one end 32 of the first conductor 3 is suspended near the top of the cover 1, maintaining sufficient insulation distance from the second conductor 4 located at the lowest step surface of the base 5. A limiting hole is provided at the location of the first conductor 3 corresponding to the borrow hole 51 of the base 5. One end 32 of the first conductor 3 extends from the highest step surface on one side of the stepped structure of the base 5 to the lowest step surface on the other side of the base 5 in a suspended manner. Under the limiting action of the limiting member 2, it overlaps the end 42 of the second conductor 4 located on the lowest step surface of the base 5, so that the first conductor 3 and the second conductor 4 make conductive contact, forming a series circuit in which the first conductor and the second conductor are in direct conductive contact. One end 32 of the first conductor 3 has an arc-shaped structure that protrudes towards the base 5, which improves the reliability and stability of the contact.

[0050] When the first conductor 3 inside the shell loses the limit of the limiting member 2, one end 32 of the first conductor 3 moves toward the top of the cover 1 under its own elastic force, the first conductor 3 and the second conductor 4 lose their conductive contact, and the series circuit formed by the direct conductive contact between the first conductor and the second conductor is broken.

[0051] The limiting member 2 is disposed on the top side of the cover 1 inside the housing, opposite to the second conductor 4. The limiting member 2 includes a fixing seat 21 and a limiting rod 2. The fixing seat 21 is fixed to the cover 1 by means of adhesive, bolts, etc. The limiting rod 2 is disposed perpendicular to the inner surface of the base 5. A limiting protrusion 22 is provided on the outer peripheral surface of the limiting rod 2 near the free end. The limiting rod 2 passes through the limiting hole on the first conductor 3 and is located in the insertion hole of the base 5. The limiting protrusion on the limiting rod 2 presses against the outer periphery of the limiting hole of the first conductor 3, pressing one end 32 of the first conductor 3 tightly against the second conductor 4 of the base 5.

[0052] The limiting rod 2 is made of a low-melting-point material. Here, "low-melting-point" refers to a material with a lower melting point than the shell structure material. Specifically, the melting point of the limiting rod 2 is lower than that of the cover 1 and base 5. This ensures that the shell structure maintains its original structure and strength even when the limiting rod 2 softens or melts. For example, the limiting rod might be made of low-melting-point plastic, such as PP (polypropylene), with a melting point of approximately 190 degrees Celsius. The shell (cover and base) might be made of nylon, with a melting point of approximately 280 degrees Celsius. Even when the limiting rod melts, the shell still maintains its original structure and strength. When the temperature of the first conductor reaches the melting point of the low-melting-point material, refer to... Figure 4 The limiting protrusion 22 melts, and the limiting rod 2 softens, partially melts, or completely melts. (See attached image) Figure 5 When the limiting rod 2 is completely melted, it loses its limiting and suppressing effect on the first conductor. Under the action of the elastic force, the first conductor 3 moves towards the top of the cover 1, losing its conductive contact with the second conductor 4, thus causing the normally closed thermal trip switch to open. When the limiting rod 2 softens or melts, the cover 1 and the base 5 remain unchanged and will not soften or melt.

[0053] Working principle:

[0054] Under normal operating conditions, the first conductor 3 and the second conductor 4 make conductive contact to form a series circuit, and the thermal trip switch is normally closed.

[0055] When the temperature of the first conductor reaches the melting point of the low-melting-point material, the limiting protrusion of the limiting rod melts, the limiting rod softens or melts, the first conductor 3 is released from the limit, and the first conductor 3 is displaced under the action of elastic force and disengages from the conductive contact with the second conductor 4. The conductive contact between the first conductor 3 and the second conductor 4 forms a series circuit that is broken, causing the thermal trip switch to open.

[0056] In use, the normally closed thermal trip switch is connected in series in the circuit where the power device is located. The normally closed thermal trip switch is set close to the power device. When a fault current occurs in the circuit where the power device is located, the temperature of the thermal trip switch rises, the limiting protrusion of the limiting member melts, and the limiting rod softens or melts, releasing the limiting of the first conductor 3. The first conductor 3 is displaced under the action of elastic force and loses conductive contact with one end of the second conductor 4 inside the housing, causing the thermal trip switch to open and disconnecting the circuit where the power device is located, thus protecting the power device.

[0057] In other embodiments, an indicator 6 may also be provided to indicate to the operator that the thermal trip switch has been activated. Figure 1 Based on this, an indicator 6 is installed on one side of the top of the cover 1 where the second conductor 4 is located, see [reference]. Figures 7 to 8A mounting hole is provided on the top of the cover 1, and the indicator 6 is installed in the mounting hole. One end of the indicator 6 passes through and is fixed in the mounting hole on the top of the cover 1, while the other end is located on the displacement path of one end 32 of the first conductor 3 in the cavity of the housing. To further define the initial position of the indicator 6, a resilient barb structure (not shown) is provided on the outer periphery of the end of the indicator 6 located in the mounting hole. The resilient barb structure and the mounting hole are interference-fitted to form a limiting structure. The indicator 6 is configured as an inverted "T" shape. One end of the lateral feature of the inverted "T" shape, i.e., the wider end, is located inside the housing. When the indicator 6 is displaced toward the outside of the housing, the lateral feature of the inverted "T" shape can be locked inside the housing, preventing the indicator 6 from completely detaching from the housing. In some embodiments, a retaining spring is provided on the indicator 6.

[0058] When the limiting member 2 is released, and the first conductor 3 moves away from the top of the cover 1 away from the second conductor 4, the driving indicator 6 moves towards the outside of the housing. The indicator 6 overcomes the limitation of the barbed structure, and one end of the indicator 6 extends out of the outer surface of the housing wall, indicating to the operator that the normally closed thermal trip switch has been activated and that the circuit containing the power device has failed. After the indicator 6 is activated, the elastic barbed structure moves to the outside of the housing, forming a termination position limit to prevent the indicator 6 from re-entering the housing.

[0059] The initial position of indicator 6 can also be limited by the following methods: indicator 6 is assembled in the mounting hole in an interference fit to form a limiting structure to limit the initial position of indicator 6; or, a limiting spring is provided between the limiting member of indicator and the inner wall of the cover around the mounting hole to form a limiting structure to limit the initial position of indicator.

[0060] In other embodiments, to improve the response speed of the normally closed thermal trip switch, in Figure 1 Based on this, a heating resistor 7 is installed on the base 5 corresponding to the limiting rod 2 to accelerate heat accumulation. Simultaneously, the heating resistor 7 serves as a current-limiting component. The heating resistor can be a finished surface-mount resistor or a resistor in other package forms. See [link / reference] Figure 9A heating resistor 7 is installed on the base 5. The limiting rod 2 of the limiting member 2 passes through the first conductor 3 and contacts the upper surface of the heating resistor 7. Both ends of the heating resistor 7 pass through the base 5 and are conductively connected to one end of the first conductor 3 and the second conductor 4 located outside the base in a patch-like manner. The connection can be made by welding, conductive contact, or other conductive connection methods. The heating resistor 7 forms a current-limiting circuit between the first conductor 3 and the second conductor 4. Because the resistance of the heating resistor 7 is much greater than the resistance of the first and second conductors, under normal operating conditions, the current mainly flows through the series circuit formed by the direct conductive contact of the first conductor 3 and the second conductor 4. The current flowing through the series-connected heating resistor is very small, and the heat generated is insufficient to soften the limiting protrusion of the limiting rod and the limiting rod itself; therefore, the limiting cannot be released. When a fault current occurs in the circuit containing the power device, the current increases through the current-limiting circuit with the heating resistor. Under the combined action of the heat from the heating resistor, the heat from the thermal trip switch, and the heat from the power device, the limiting protrusion of the limiting rod 2 melts rapidly, releasing the limiting and causing the first conductor and the second conductor to separate from conductive contact.

[0061] Figure 9 Working principle:

[0062] Under normal operating conditions, because the resistance of the heating resistor is very large, the current flows through the series circuit formed by the direct conductive contact of the first and second conductors. The heat generated by the heating resistor cannot soften or melt the limiting protrusion of the limit rod, and the thermal trip switch does not work.

[0063] When a fault current occurs in the circuit containing the power device, the current through the thermal trip switch increases, the temperature of the heating resistor rises rapidly, and the temperature generated by the power device also rises, causing the limiting protrusion of the limit rod to melt rapidly. Under the action of the elastic force, the first conductor 3 is separated from the conductive contact with the second conductor 4, and the series circuit formed by the direct conductive contact between the first conductor 3 and the second conductor 4 is broken. The current in the power device flows through the current limiting circuit with the heating resistor in series. Due to the current limiting effect of the heating resistor, the current flowing through the power device is reduced to a safe range, thus protecting the power device.

[0064] Integrating a heating resistor can improve the response speed of the thermal trip switch and shorten the response time.

[0065] The heating resistor can also be directly connected in parallel with the first conductor 3, see [link / reference] Figure 10A coil-type heating resistor 8 is wound around the first conductor 3 on the side of the limiting rod 2 near the limiting member 2. The two ends of the heating resistor 8 are electrically connected to the first conductor 3, forming a current-limiting circuit connected in parallel to the series circuit formed by the conductive contact of the first conductor 3 and the second conductor 4. During normal operation, the current mainly flows through the series circuit formed by the direct conductive contact of the first and second conductors. Because the resistance of the heating resistor is much greater than the resistance of the first and second conductors, the current passing through the heating resistor is very small and insufficient to soften the limiting protrusion. When the first and second conductors are disconnected, the current-limiting circuit also disconnects.

[0066] For another structural form where the coil-type heating resistor 8 is directly connected in parallel with the first conductor 3, please refer to [the original text]. Figure 11 The heating resistor 8 is located at the insertion hole 51 of the base 5. One end of the limiting rod 2 passes through the limiting hole on the first conductor 3 and is inserted into the hollow part of the coil-type heating resistor 8. A gap is maintained between the heating resistor 8 and the outer periphery of the limiting rod 2, which does not affect the release of the limiting of the first conductor 3. The two ends of the heating resistor 8 are respectively connected to the first conductor 3 located on both sides of the limiting rod 2. Figure 11 and Figure 10 The working principle is the same. Figure 11 The heating efficiency of the heating resistor 8 for the limiting rod 2 is higher than that of the heating resistor 8. Figure 10 The heating resistor 8 has high heating efficiency.

[0067] In other embodiments, the limiting member may be disposed at the conductive contact between the first conductor 3 and the second conductor 4. See also Figure 12 and Figure 13The first conductor 3 and the second conductor 4, located within the housing, are elastic and cantilevered. The first conductor 3 is bent into a cantilever shape near the top of the cover 1, and the second conductor 4 is bent into a cantilever shape near the inner surface of the base 5. The suspended ends of the first conductor 3 and the second conductor 4 within the housing are in conductive contact, and a limiting member 9 passes through the conductive contact point of the first conductor 3 and the second conductor 4 to connect and fix them in the cavity of the housing. After being connected by the limiting member 9, both the ends of the first conductor 3 and the second conductor 4 and the limiting member 9 are in a suspended state, that is, the limiting member 9 is supported by the suspended ends of the first conductor 3 and the second conductor 4. This forms a series circuit in which the first conductor 3 and the second conductor 4 are directly connected in series. The limiting member 9 includes a T-shaped pin and a rod-shaped pin. The T-shaped pin passes through the suspended ends of the first conductor and the second conductor, so that the lateral feature of the T-shaped structure is located on the first conductor side. The pin passes through the vertical feature of the pin on the second conductor side, connecting and fixing the suspended ends of the first conductor and the second conductor in a conductive contact manner. The limiting component 9 is made of low-melting-point material. When the temperature of the first conductor reaches the melting point of the low-melting-point material, the limiting component 9 melts, releasing the connection between the first conductor 3 and the second conductor 4. The first conductor 3 and the second conductor 4 then move in opposite directions under their own elastic force. That is, one end 32 of the first conductor 3 moves toward the top of the cover 1, and one end 42 of the second conductor 4 moves toward the base 5. The first conductor 3 and the second conductor 4 are no longer in conductive contact, thus breaking the series circuit directly connected to the first conductor 3 and the second conductor 4, and the thermal trip switch is turned off.

[0068] Figure 1 One end of the first and second conductors, serving as the connection terminals of the thermal trip switch, is a surface-mount structure. In other embodiments, it can also be a bent, flat-out structure. See [link / reference needed]. Figure 14 It can also be a direct-output quick-connect structure, see [link / reference] Figure 15 The thermal trip switch is designed to adapt to different usage environments, making it suitable for a wider range of applications.

[0069] The advantage of the normally closed thermal trip switch of the present invention is that it is a single device with a simple structure. It is only connected to a cooling fan, heat sink or cooling system when the device power cannot be dissipated normally by itself during fault circuit current, thereby reducing power loss.

Claims

1. A normally closed thermal trip switch, characterized by, The utility model discloses a thermal release switch, comprising a shell with a cavity, a first conductor and a second conductor are arranged in the cavity of the shell, one end of the first conductor and the second conductor outside the shell is connected as the connection end of the normally closed thermal release switch, the first conductor inside the shell is elastically arranged in a cantilever mode, the first conductor arranged in a cantilever mode is directly in conductive contact with the second conductor under the limiting of a limiting piece to form a series circuit, when the thermal release switch works, the current flows through the series circuit formed by the direct conductive contact of the first conductor and the second conductor, the limiting piece limiting the first conductor is made of a low melting point material with a melting point lower than that of the shell, when the temperature of the first conductor reaches the melting point of the low melting point material, the part of the limiting piece in contact with the first conductor softens or melts to release the limiting, and the first conductor inside the shell moves away from the second conductor under the action of its own elastic force, so that the first conductor and the second conductor are disconnected from the direct conductive contact.

2. The normally closed thermal trip switch of claim 1, wherein, The limiting piece comprises a fixing base and a limiting rod connected with each other, the limiting rod is made of a low melting point material, the fixing base is fixed in the shell, and the limiting rod limits the initial position of the first conductor.

3. The normally closed thermal trip switch of claim 2, wherein: A limiting protrusion is arranged on the outer periphery of the limiting rod, one end of the limiting rod away from the fixing base is inserted into the first conductor, the limiting protrusion limits the initial position of the first conductor by contacting the first conductor, and when the temperature rises to a threshold range, the limiting protrusion melts, and the limiting rod softens or melts to release the limiting of the first conductor.

4. The normally closed thermal trip switch of claim 3, wherein, One side inner wall in the shell is in a stepped structure, one end of the second conductor in the shell is fixedly arranged at the lowest step surface of the stepped structure, one end of the first conductor arranged in a cantilever mode is arranged on the second conductor on the lowest step surface of the stepped structure in a bridging mode and in conductive contact with the second conductor, and the one end of the first conductor in the shell is arranged as an arc structure protruding towards the second conductor.

5. The normally closed thermal trip circuit breaker of claim 2 wherein, The first conductor and the second conductor in the shell are respectively elastically arranged in a cantilever mode, the limiting piece is arranged at one end of the first conductor and the second conductor arranged in a cantilever mode to connect and fix the one end of the first conductor and the second conductor arranged in a cantilever mode, when the limiting piece melts to release the connection of the one end of the first conductor and the second conductor arranged in a cantilever mode, the one end of the first conductor and the second conductor arranged in a cantilever mode respectively moves in a direction away from each other under the action of its own elastic force, so that the first conductor and the second conductor are disconnected from the conductive connection.

6. The normally closed thermal trip circuit breaker of claim 1, wherein, One end of the first conductor and the second conductor outside the shell is arranged outside the shell in a patch type, a bending flat type or a straight out quick plug type as the connection end of the thermal release switch.

7. A normally closed thermal trip switch according to any one of claims 1 to 6, wherein A through-wall mounting hole is formed in the shell wall of the shell, an indicator is arranged in the mounting hole, one end of the indicator is located in the mounting hole, and the other end of the indicator is located on the displacement path of one end of the first conductor in the shell; when one end of the first conductor is displaced, the indicator is driven to displace towards the outside of the shell, and the one end of the indicator extending towards the outside of the shell protrudes out of the shell wall.

8. The normally closed thermal trip circuit breaker of claim 7, wherein: The indicator has a T-shaped structure, and one end of the transverse feature of the T-shaped structure is located inside the shell.

9. The normally closed thermal trip circuit breaker of claim 7 wherein, The initial position of the indicator is limited by a limiting structure, the limiting structure is that a elastic barb structure is arranged on the outer periphery of the indicator, the barb structure elastically abuts against the mounting hole to form the limiting structure, or the indicator is assembled in the mounting hole in an interference fit to form the limiting structure, or a limiting spring is arranged between the limiting member and the shell wall of the shell outside the outer periphery of the mounting hole to form the limiting structure.

10. The normally closed thermal trip switch according to any one of claims 1 to 6, wherein A heating resistor is arranged in the shell; the two ends of the heating resistor are respectively electrically connected with the first conductor and the second conductor to form a current limiting circuit, or the heating resistor is connected in parallel with the first conductor to form a current limiting circuit, the current limiting circuit is connected in parallel with a series circuit formed by direct electrical contact between the first conductor and the second conductor; the limiting member contacts the heating resistor through the first conductor, or the heating resistor is close to the limiting member.

11. The normally closed thermal trip circuit breaker of claim 10 wherein, The two ends of the heating resistor are arranged in the shell wall and are respectively electrically connected with one end of the first conductor and the second conductor located outside the shell.

12. The normally closed thermal trip circuit breaker of claim 10 wherein, The heating resistor has a coil structure and is connected in parallel with the first conductor by being arranged around the outer periphery of the first conductor.

13. The normally closed thermal trip circuit breaker of claim 7 wherein, A heating resistor is arranged in the shell; the two ends of the heating resistor are respectively electrically connected with the first conductor and the second conductor to form a current limiting circuit, or the heating resistor is connected in parallel with the first conductor to form a current limiting circuit, the current limiting circuit is connected in parallel with a series circuit formed by direct electrical contact between the first conductor and the second conductor; the limiting member contacts the heating resistor through the first conductor, or the heating resistor is close to the limiting member.

14. The normally closed thermal trip circuit breaker of claim 1, wherein: The shell includes a cover body with one open end and one closed end and a base, the base is arranged at the open end of the cover body and closes the open end of the cover body, the first conductor and the second conductor are respectively arranged between the cover body and the base on opposite sides of the shell, one end of the first conductor and the second conductor is located inside the shell, and the other end is located outside the shell.

15. The normally closed thermal trip circuit breaker of claim 14, wherein: The cover body and the base are connected and fixed in a snap-fit manner.

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