A trip unit and circuit breaker

Abstract

The application discloses a kind of tripper and circuit breaker, specifically relates to low-voltage electrical technology field, including shell, the inside of shell is provided with electromagnetic mechanism, secondary amplification mechanism, adjusting mechanism.The application is through the setting of adjusting cavity and first piston structure, when the temperature in the circuit breaker rises, the expansion of thermal expansion gas is pushed to the direction of fixed plate by first piston, to provide greater thrust for the release of moving iron core, prevent the same thrust under the phenomenon of magnetic field weakening, delay or unable to trip, improve safety, and can be when the temperature in the circuit breaker is too high, release the attraction of moving iron core and static iron core, make circuit breaker trip, so as to play the role of fault protection, further improve safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-voltage electrical apparatus, and more particularly to a release and circuit breaker. BACKGROUND

[0002] The release is a device mechanically connected with the circuit breaker, used to release the holding mechanism under certain conditions, so that the circuit breaker is automatically disconnected, playing a circuit protection role.

[0003] A release and circuit breaker are disclosed in Chinese Patent No. CN202111128818.8, relating to the technical field of low-voltage electrical apparatus, comprising: a bracket; an electromagnetic mechanism including a coil, a coil skeleton, a moving iron core, a static iron core, and a permanent magnet; the static iron core is arranged in the coil skeleton, the moving iron core is movably arranged in the coil skeleton, and the permanent magnet is arranged at one end of the coil skeleton close to the static iron core; a secondary amplification mechanism including a push rod mechanism, an energy storage elastic element, and a lock catch mechanism; the energy storage elastic element is arranged on the push rod mechanism, the lock catch mechanism is arranged at one end of the energy storage elastic element, the lock catch mechanism is fixed on the bracket, one end of the energy storage elastic element close to the lock catch mechanism is fixedly connected with the bracket, and the push rod mechanism is in sliding connection with the bracket; one end of the moving iron core cooperates with the static iron core, and the other end of the moving iron core penetrates through the coil skeleton and cooperates with the lock catch mechanism. The release of the present application realizes the integration of the under-voltage release and the separate excitation release, reduces the overall structure size of the release, and expands the use range of the release.

[0004] Although the release of the above-mentioned application can expand the use range, the temperature of the coil inside the release may increase due to the external environment temperature and the working temperature of the electronic components inside the circuit breaker during use. Since the resistivity of the coil wire increases with the increase of temperature, the magnetic field strength under the same current will weaken, which may cause release delay or even failure to release, causing safety hazards. At the same time, the permanent magnet may demagnetize due to factors such as temperature and external interference during long-term use, causing the magnetic field strength to decay, so that the moving iron core cannot be normally attracted to the static iron core, affecting the normal use of the circuit breaker.

[0005] The present application provides a release and circuit breaker, aiming to solve the problems of temperature rise of the coil inside the release, causing release delay or even failure to release, causing safety hazards, and demagnetization of the permanent magnet during long-term use, causing the moving iron core to fail to be normally attracted to the static iron core, affecting the normal use of the circuit breaker. SUMMARY

[0006] The present application aims to provide a kind of tripping device and circuit breaker, to solve the coil temperature rise in the tripping device in the background art proposed, cause tripping delay even unable to trip, cause security risk, and permanent magnet appears demagnetization phenomenon in long time use, cause the normal attraction of moving iron core and static iron core, affect the normal use of circuit breaker problem.

[0007] To achieve the above object, the present application provides the following technical solutions: a kind of tripping device, including shell, electromagnetic mechanism and secondary amplification mechanism, the electromagnetic mechanism includes coil framework, moving iron core, static iron core, permanent magnet, magnetic yoke, fixed plate and first elastic piece,

[0008] Further comprising adjusting mechanism, the adjusting mechanism includes:

[0009] It is provided with the adjusting cavity of thermal expansion gas, for adjusting the moving iron core release thrust in response to temperature change;

[0010] Control cavity is used for generating negative pressure according to permanent magnet magnetic field attenuation;

[0011] With the storage cavity of adjusting cavity and control cavity communication, its inside is provided with piston piece, and the piston piece moves to suck adjusting cavity gas to adjust the first elastic piece thrust.

[0012] Preferably, first piston is slidably connected in the adjusting cavity, and the first elastic piece is connected with the fixed plate and the first piston at two ends respectively, thermal expansion gas can push the first piston to compress the first elastic piece after expansion.

[0013] Preferably, second piston is slidably connected in the control cavity, magnetic piece is fixedly embedded on the side of the second piston close to the permanent magnet, second elastic piece is connected between the second piston and the permanent magnet, and negative pressure is generated when the second elastic piece pushes the second piston when the permanent magnet magnetic field attenuates.

[0014] Preferably, driving block and multiple friction pieces are arranged in the piston piece, the driving block is locked by extruding multiple friction pieces through wedge surface, and the driving block can be unlocked by negative pressure suction.

[0015] Preferably, one end of the piston piece is provided with a communication groove, the communication groove is communicated with the control cavity, multiple limit grooves are equidistantly arranged on the side wall of the piston piece, multiple friction pieces are slidably connected in the corresponding limit grooves, and the driving block is slidably connected in the communication groove.

[0016] Preferably, third elastic piece is arranged between the driving block and the communication groove, and the driving block is attracted by negative pressure by overcoming the elastic force of the third elastic piece.

[0017] Preferably, the adjusting cavity is arranged on the side of the magnetic yoke close to the fixed plate, and the magnetic yoke is fixedly connected with the coil frame.

[0018] Preferably, the contact area of the friction member with the inner wall of the storage cavity can be increased according to the increase of the gas pressure.

[0019] Preferably, the control cavity is provided with an air exhaust for air flow on the side away from the permanent magnet.

[0020] A circuit breaker comprising the above-mentioned tripping device.

[0021] Technical effects and advantages of the present application:

[0022] 1. The adjusting cavity and the first piston are arranged, when the temperature in the circuit breaker rises, the thermal expansion gas expands to push the first piston to move towards the fixed plate, providing greater thrust for the release of the moving iron core, preventing the tripping delay or failure under the same thrust after the magnetic field weakens, improving safety, and when the temperature in the circuit breaker is too high, the attraction between the moving iron core and the static iron core is released, the circuit breaker is tripped, thereby playing a role in fault protection, further improving safety.

[0023] 2. The driving block and the friction member are arranged, when the permanent magnet appears demagnetization phenomenon and the magnetic field weakens, negative pressure is generated in the storage cavity, the driving block no longer presses the plurality of friction members to contact the inner wall of the storage cavity, the limiting of the piston member is released, and the piston member can draw part of the thermal expansion gas in the adjusting cavity to the storage cavity, so that the thrust of the first elastic member is weaker, thereby adjusting the thrust of the first elastic member on the moving iron core according to the attenuation degree of the magnetic field of the permanent magnet, preventing the moving iron core from being normally attracted to the static iron core under the same thrust after the magnetic field strength of the permanent magnet attenuates, avoiding affecting the normal use of the circuit breaker, thereby improving the service life of the tripping device. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a schematic diagram of the overall structure of the present application.

[0025] Figure 2 It is a schematic diagram of the secondary amplification mechanism structure of the present application.

[0026] Figure 3 It is a schematic diagram of the adjusting mechanism structure of the present application.

[0027] Figure 4 It is an explosion entity of the internal structure of the piston member.

[0028] Figure 5 It is a sectional view of the piston member structure.

[0029] Figure 6The schematic diagram of the push rod mechanism structure of the application.

[0030] Figure 7 The schematic diagram of the lock catch mechanism structure of the application.

[0031] Figure 8 The schematic diagram of the position of the limiting rod of the application.

[0032] Figure 9 The schematic diagram of the electromagnetic mechanism structure of the application.

[0033] The reference signs are as follows: 1, shell; 2, electromagnetic mechanism; 21, coil; 22, coil skeleton; 23, moving iron core; 24, static iron core; 25, permanent magnet; 26, magnetic yoke; 27, fixed plate; 28, first elastic member; 29, mounting frame; 3, secondary amplification mechanism; 31, push rod mechanism; 311, base; 312, push rod; 313, lock catch groove; 314, extension part; 315, slide; 316, passage; 317, hook part; 318, side plate; 319, connecting rod; 32, energy storage elastic member; 33, lock catch mechanism; 331, lock catch; 332, lock catch elastic member; 333, lock catch shaft; 334, first lock arm; 335, second lock arm; 336, limiting rod; 337, support member; 4, adjusting mechanism; 41, adjusting cavity; 42, first piston; 43, control cavity; 44, second piston; 45, magnetic member; 46, second elastic member; 47, storage cavity; 48, piston member; 49, communication groove; 410, limiting groove; 411, friction member; 412, driving block; 413, third elastic member. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the application.

[0035] Embodiment one

[0036] Reference Figures 1 to 9 An undertripping device in an embodiment of the application comprises a shell 1, and the inside of the shell 1 is provided with an electromagnetic mechanism 2, a secondary amplification mechanism 3 and an adjusting mechanism 4.

[0037] The electromagnetic mechanism 2 comprises a coil 21, a coil frame 22, a moving iron core 23, a static iron core 24, a permanent magnet 25, a magnetic yoke 26, a fixed plate 27 and a first elastic member 28, the coil 21 is mounted on the coil frame 22, the static iron core 24 is mounted in the coil frame 22, the moving iron core 23 is slidingly connected in the coil frame 22, the permanent magnet 25 is arranged at one end of the coil frame 22 close to the static iron core 24, the magnetic yoke 26 is arranged at the other end of the coil frame 22, the fixed plate 27 is fixedly connected with the moving iron core 23, the first elastic member 28 is sleeved on the moving iron core 23 and located between the magnetic yoke 26 and the fixed plate 27, and the two ends of the coil frame 22 are fixedly connected with mounting frames 29, each mounting frame 29 is fixedly connected with the shell 1, and the electromagnetic mechanism 2 is prior art and will not be described in detail here.

[0038] Reference Figure 2 Figures 6 to 9 The secondary amplification mechanism 3 is slidingly connected in the shell 1 and comprises a push rod mechanism 31, an energy storage elastic member 32 and a lock catch mechanism 33, the push rod mechanism 31 comprises a base 311 and a push rod 312, the base 311 is slidingly connected with the shell 1 through a sliding block arranged on the side surface, the electromagnetic mechanism 2 is arranged below the base 311, the energy storage elastic member 32 is arranged on the base 311, the base 311 is provided with a lock catch groove 313 matched with the lock catch mechanism 33, one end of the base 311 is provided with an extension 314, the extension 314 is arranged perpendicularly to the base 311, the push rod 312 is arranged on the extension 314, a slide way 315 is arranged on one side of the base 311 close to the extension 314, a channel 316 is arranged through the extension 314, the channel 316 is communicated with the slide way 315, one end of the base 311 away from the extension 314 is provided with a side plate 318, the side plate 318 is provided with a connecting rod 319 parallel to the base 311, the lock catch groove 313 is arranged at one end of the connecting rod 319 away from the side plate 318, and the push rod 312 is arranged at one side of the channel 316 and provided with a hook portion 317 at the end portion.

[0039] A handle and a lever (not shown in the figure) are arranged on the circuit breaker, the handle is used for realizing the closing and opening of the circuit breaker, the handle can drive the lever to move, the lever can cooperate with the push rod mechanism 31 through a lever shaft, and the structure principle of the circuit breaker is prior art and will not be described in detail here.

[0040] Figures 6 to 9 ​The locking mechanism 33 comprises a locking buckle 331, a locking elastic member 332 and a locking shaft 333, the upper portion of the base 311 is provided with a support member 337 fixedly connected with the shell 1, one end of the energy storage elastic member 32 is connected with the support member 337, and the other end is connected with the side plate 318, the two ends of the locking shaft 333 are fixedly connected with the support member 337, the locking elastic member 332 is sleeved on the locking shaft 333, one end of the locking elastic member 332 is connected with the support member 337, and the other end is connected with the locking buckle 331, the locking buckle 331 is rotationally connected with the locking shaft 333, the locking buckle 331 has a first locking arm 334 and a second locking arm 335, the first locking arm 334 is provided with a limiting rod 336 clamped with the locking groove 313 on the base 311, and the end face of the second locking arm 335 is used for being connected with the moving iron core 23, the secondary amplification mechanism 3 is a prior art, and will not be described in detail here.

[0041] Specific working principle, in the initial state, the push rod mechanism 31 is driven by the energy storage elastic member 32 to move the moving iron core 23 in the coil framework 22 to the direction of the static iron core 24, and the moving iron core 23 is attracted to the static iron core 24 under the action of the permanent magnet 25;

[0042] When the push handle is used to buckle the circuit breaker, the lever shaft arranged on the circuit breaker drives the base 311 to move in the shell 1 and compresses the energy storage elastic member 32, when the base 311 drives the connecting rod 319 to move to the position of the limiting rod 336, the second locking arm 335 drives the limiting rod 336 to be clamped into the locking groove 313 under the action of the locking elastic member 332, thereby limiting the push rod mechanism 31, preventing the push rod mechanism 31 from moving away from the locking mechanism 33 under the action of the energy storage elastic member 32, at this time, the energy storage elastic member 32 is in an energy storage state, and the moving iron core 23 and the static iron core 24 are still in the attracted state under the action of the permanent magnet 25;

[0043] When the circuit breaker needs to be tripped, the coil 21 is energized, and the coil 21 generates a magnetic field opposite to the permanent magnet 25 after being energized, thereby overcoming the attraction of the permanent magnet 25 to the moving iron core 23, so that the moving iron core 23 is released, and the moving iron core 23 is released and impacts the second locking arm 335 of the locking buckle 331 under the action of the thrust of the first elastic member 28, so that the locking buckle 331 drives the first locking arm 334 to be deflected, and the limiting rod 336 is separated from the locking groove 313, thereby releasing the limitation of the push rod mechanism 31, so that the push rod mechanism 31 is released under the action of the energy storage elastic member 32, and quickly slides to the initial position, and in the process of returning to the initial position, the hook part 317 drives the tripping lever on the circuit breaker to be deflected, thereby making the circuit breaker trip, and in the process of returning to the initial position, the push rod mechanism 31 drives the moving iron core 23 to be attracted to the static iron core 24 again, thereby completing the action cycle.

[0044] Embodiment two

[0045] In use, due to the external environment temperature and the working temperature of the internal electronic components of the circuit breaker, the temperature of the coil 21 in the release device is increased, and the resistivity of the coil 21 wire increases with the increase of the temperature, which will cause the weakening of the magnetic field intensity under the same current, and the weakening of the magnetic field intensity may cause the delay of the release or even the failure of the release, which will cause the safety hazard. Therefore, the device described in the above embodiment is improved in the present embodiment.

[0046] With reference to Figure 2 and Figure 3 , the adjusting mechanism 4 comprises an adjusting cavity 41 arranged on the side of the magnetic yoke 26 close to the fixed plate 27, a first piston 42 is slidingly connected in the adjusting cavity 41, one end of the first elastic member 28 is connected with the first piston 42, and the other end is connected with the fixed plate 27, and a thermal expansion gas is arranged on the side of the adjusting cavity 41 away from the fixed plate 27.

[0047] In actual use, when the temperature in the circuit breaker is increased, the thermal expansion gas in the adjusting cavity 41 will expand due to the heat, and after the expansion of the thermal expansion gas, the first piston 42 will be pushed to move towards the fixed plate 27, so as to further compress the first elastic member 28, so as to increase the pushing force of the moving iron core 23 when it is released, so as to provide greater pushing force when the magnetic field is weakened.

[0048] The higher the temperature is, the greater the resistivity of the coil 21 wire is, and the greater the expansion volume of the thermal expansion gas is, so as to adapt to the change of the temperature and increase the pushing force of the moving iron core 23 when it is released, and compensate for the weakening of the magnetic field caused by the temperature, so as to prevent the delay of the release or the failure of the release under the same pushing force after the weakening of the magnetic field of the coil 21, and improve the safety.

[0049] It should be noted that when the temperature in the circuit breaker is too high due to the fault, the thermal expansion gas will expand sharply, and the first elastic member 28 will cooperate with the thermal expansion gas to enable the moving iron core 23 to overcome the magnetic force of the permanent magnet 25, so as to release the attraction between the moving iron core 23 and the static iron core 24, and enable the circuit breaker to release, so as to play a role in fault protection, and further improve the safety.

[0050] In summary, through the arrangement of the adjusting cavity 41, the first piston 42 and other structures, when the temperature in the circuit breaker is increased, the thermal expansion gas will expand to push the first piston 42 to move towards the fixed plate 27, so as to provide greater pushing force for the release of the moving iron core 23, prevent the delay of the release or the failure of the release under the same pushing force after the weakening of the magnetic field, improve the safety, and when the temperature in the circuit breaker is too high, release the attraction between the moving iron core 23 and the static iron core 24, so as to release the circuit breaker, so as to play a role in fault protection, and further improve the safety.

[0051] Embodiment three

[0052] In use, the permanent magnet 25 may demagnetize due to temperature, external interference and other factors during long-term use, resulting in attenuation of the magnetic field strength, causing the moving iron core 23 to fail to normally attract the static iron core 24, and affecting the normal use of the circuit breaker. Therefore, the device described in the above embodiment is improved in this embodiment.

[0053] With reference to Figures 2 to 5 The adjusting mechanism 4 further comprises a control cavity 43 and a storage cavity 47, the permanent magnet 25 is fixedly connected in the control cavity 43, the second piston 44 is slidingly connected in the control cavity 43, the magnetic member 45 is fixedly embedded on the side of the second piston 44 close to the permanent magnet 25, the second elastic member 46 is connected between the second piston 44 and the permanent magnet 25, and the exhaust hole for air circulation is arranged on the side of the control cavity 43 away from the permanent magnet 25.

[0054] With reference to Figures 3 to 5 The two ends of the storage cavity 47 are in communication with the adjusting cavity 41 and the control cavity 43, respectively, the piston member 48 is slidingly connected in the storage cavity 47, the communication groove 49 is arranged on the side of the piston member 48 close to the control cavity 43, the plurality of limiting grooves 410 in communication with the communication groove 49 are uniformly arranged on the outer side of the piston member 48, the friction member 411 is slidingly connected in each limiting groove 410, the driving block 412 is slidingly connected in the communication groove 49, the wedge surfaces capable of cooperating with each other are arranged between one end of the plurality of friction members 411 inside the communication groove 49 and the driving block 412, the third elastic member 413 is sleeved in the communication groove 49, one end of the third elastic member 413 is connected with the driving block 412, and the other end of the third elastic member 413 is connected with the communication groove 49, and the elastic coefficient of the second piston 44 is greater than that of the third elastic member 413.

[0055] In actual use, in the initial state, the driving block 412 is pressed against the plurality of friction members 411 under the thrust of the third elastic member 413, so that the friction heads of the plurality of friction members 411 can be in contact with the inner wall of the storage cavity 47 and limit the piston member 48, preventing the piston member 48 from moving in the storage cavity 47.

[0056] When the permanent magnet 25 appears demagnetization phenomenon, the magnetic field is weakened, the attraction of the permanent magnet 25 to the magnetic part 45 is weakened, at this time, the second elastic part 46 can push the second piston 44 to move away from the permanent magnet 25, in the process of moving, the second piston 44 can draw the air in the storage cavity 47 into the control cavity 43, so that the negative pressure is generated in the storage cavity 47, the negative pressure of the storage cavity 47 can drive the driving block 412 to compress the third elastic part 413, so that the driving block 412 no longer extrudes the plurality of friction parts 411 to contact the inner wall of the storage cavity 47, the limiting of the piston part 48 is released, so that the piston part 48 can move in the storage cavity 47, at this time, the negative pressure in the storage cavity 47 can drive the piston part 48 to move towards the control cavity 43, and part of the thermal expansion gas in the adjusting cavity 41 is drawn into the storage cavity 47, so that the first piston 42 can further move away from the fixed plate 27 in the adjusting cavity 41, so that the pushing force of the first elastic part 28 is weakened;

[0057] The weaker the magnetic field of the permanent magnet 25 is, the stronger the negative pressure in the storage cavity 47 is, the farther the piston part 48 moves, and the more thermal expansion gas is drawn in the adjusting cavity 41, so that the pushing force of the first elastic part 28 to the moving iron core 23 is weaker, so that the pushing force of the first elastic part 28 to the moving iron core 23 can be adjusted according to the attenuation degree of the magnetic field of the permanent magnet 25, to prevent the moving iron core 23 from being unable to normally attract the static iron core 24 under the same pushing force after the magnetic field strength of the permanent magnet 25 is attenuated, to avoid affecting the normal use of the circuit breaker, thereby improving the service life of the trip unit.

[0058] It should be noted that since the adjusting cavity 41 is communicated with the storage cavity 47, the thermal expansion gas will generate a pushing force on the piston part 48 after being heated and expanded, if the other side of the piston part 48 does not generate negative pressure, the driving block 412 will extrude the plurality of friction parts 411 under the simultaneous action of the third elastic part 413 and the positive pressure, so that the friction heads of the plurality of friction parts 411 can further contact the inner wall of the storage cavity 47, to improve the limiting of the piston part 48, to prevent the piston part 48 from moving in the storage cavity 47, so that only when the permanent magnet 25 demagnetizes to generate negative pressure in the storage cavity 47, the friction parts 411 can release the limiting of the piston part 48, to prevent the thermal expansion gas from moving the piston part 48 when the permanent magnet 25 does not demagnetize.

[0059] In summary, by the arrangement of the driving block 412 and the friction piece 411, when the magnetic field is weakened due to demagnetization of the permanent magnet 25, the negative pressure is generated in the storage cavity 47, the driving block 412 no longer presses the plurality of friction pieces 411 to contact the inner wall of the storage cavity 47, the limiting of the piston piece 48 is released, and the piston piece 48 can draw a part of the thermal expansion gas in the adjusting cavity 41 into the storage cavity 47, so that the pushing force of the first elastic piece 28 is weaker, thereby adjusting the pushing force of the first elastic piece 28 on the moving iron core 23 according to the attenuation degree of the magnetic field of the permanent magnet 25, preventing the moving iron core 23 from being normally attracted to the static iron core 24 under the same pushing force after the attenuation of the magnetic field strength of the permanent magnet 25, avoiding affecting the normal use of the circuit breaker, and improving the service life of the release.

[0060] Embodiment Four

[0061] The embodiment provides a circuit breaker comprising the above release, which can adjust the pushing force of the iron core 23 according to the temperature change, prevent the circuit breaker from being delayed or unable to release, adjust the pushing force of the iron core 23 according to the change of the magnetic field of the permanent magnet 25, avoid affecting the normal use of the circuit breaker, and improve the safety of the circuit breaker.

[0062] Finally, the above only describes the preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A trip unit, characterized in that: The device includes a housing (1), an electromagnetic mechanism (2), and a secondary amplification mechanism (3). The electromagnetic mechanism (2) includes a coil frame (22), a moving iron core (23), a stationary iron core (24), a permanent magnet (25), a magnetic yoke (26), a fixing plate (27), and a first elastic element (28). The coil (21) is mounted on the coil frame (22), the stationary iron core (24) is mounted inside the coil frame (22), and the moving iron core (23) is slidably connected inside the coil frame (22). The permanent magnet... (25) is set at one end of the coil frame (22) near the stationary iron core (24), the magnetic yoke (26) is set at the other end of the coil frame (22), the fixing plate (27) is fixedly connected to the moving iron core (23), the first elastic element (28) is sleeved on the moving iron core (23) and located between the magnetic yoke (26) and the fixing plate (27), and the two ends of the coil frame (22) are fixedly connected to the mounting brackets (29), each of the mounting brackets (29) is fixedly connected to the housing (1); It also includes an adjustment mechanism (4), which includes: A regulating chamber (41) for thermally expanding gas is provided to adjust the thrust of the moving iron core (23) in response to temperature changes; The control cavity (43) is used to generate negative pressure based on the attenuation of the magnetic field of the permanent magnet (25); The storage chamber (47) is connected to the regulating chamber (41) and the control chamber (43), and a piston (48) is provided inside it. The piston (48) moves to draw gas from the regulating chamber (41) to adjust the thrust of the first elastic element (28). The first piston (42) is slidably connected in the adjustment cavity (41). The two ends of the first elastic element (28) are respectively connected to the fixed plate (27) and the first piston (42). After the thermal expansion gas expands, it can push the first piston (42) to compress the first elastic element (28). A second piston (44) is slidably connected inside the control cavity (43). A magnetic element (45) is fixedly embedded on the side of the second piston (44) near the permanent magnet (25). A second elastic element (46) is connected between the second piston (44) and the permanent magnet (25). When the magnetic field of the permanent magnet (25) decays, the second elastic element (46) pushes the second piston (44) to generate a negative pressure. The adjustment cavity (41) is located on the side of the magnetic yoke (26) near the fixing plate (27), and the magnetic yoke (26) is fixedly connected to the coil frame (22).

2. The trip unit according to claim 1, characterized in that: The piston (48) is provided with a drive block (412) and a plurality of friction elements (411). The drive block (412) locks the piston (48) by squeezing the plurality of friction elements (411) with a wedge-shaped surface, and can release the lock by attracting the drive block (412) with negative pressure.

3. The trip unit according to claim 2, characterized in that: The piston (48) has a connecting groove (49) at one end, which is connected to the control cavity (43). The piston (48) has multiple limiting grooves (410) at equal intervals on its side wall. Multiple friction elements (411) are slidably connected in the corresponding limiting grooves (410). The drive block (412) is slidably connected in the connecting groove (49).

4. The trip unit according to claim 3, characterized in that: A third elastic element (413) is provided between the drive block (412) and the connecting groove (49), and the negative pressure attracts the drive block (412) by overcoming the elastic force of the third elastic element (413).

5. The trip unit according to claim 4, characterized in that: The contact area between the friction element (411) and the inner wall of the storage cavity (47) can be increased as the gas pressure increases.

6. The trip unit according to claim 5, characterized in that: The control cavity (43) has an exhaust vent on the side away from the permanent magnet (25) for air circulation.

7. A circuit breaker, characterized in that: Includes the trip unit as described in any one of claims 1 to 6.

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