PTC (Positive Temperature Coefficient) thermosensitive resistor

Abstract

The invention relates to the field of electronics, in particular to a PTC thermosensitive resistor which comprises a PTC thermosensitive resistor ceramic cavity, a first electrode plate, a second electrode plate and a metal spring piece, the first electrode plate is connected to a first electrode of the PTC thermosensitive resistor ceramic cavity, the second electrode plate is connected to a second electrode of the PTC thermosensitive resistor ceramic cavity, and the metal spring piece is connected to the PTC thermosensitive resistor ceramic cavity. The first electrode plate, the second electrode plate and the PTC thermistor ceramic cavity form a sealed cavity, the metal spring piece is arranged in the sealed cavity, one end of the metal spring piece is fixedly connected with the first electrode plate, and the other end of the metal spring piece abuts against the second electrode plate at the first temperature; and disconnecting from the electrode sheet at a second temperature, according to the scheme, the over-temperature protection function is achieved, when normal working large current flows through the metal spring piece and a protected object is in a normal temperature rising state, the temperature generated by the metal spring piece can be dissipated outwards through the first electrode plate and the second electrode plate, and over-temperature protection is prevented from being triggered by mistake.

Description

Technical Field

[0001] The present invention relates to the field of electronics, in particular to a PTC thermistor. Background Art

[0002] PTC thermistors are semiconductor ceramic devices primarily made from barium titanate. Their Curie temperatures vary depending on their formulation. When the maximum operating voltage or current is applied, or when the rated operating temperature is exceeded, the thermistor's resistance increases dramatically as its temperature exceeds the Curie temperature. When the operating voltage, current, and temperature return to normal, the resistance returns to its initial low resistance. Due to these characteristics, PTC thermistors are often used as resettable fuses or 10,000-cycle fuses. However, while maintaining a certain withstand voltage, these products are designed with a specific zero-power resistance. This resistance value generates a certain amount of heat when a normal current flows through them. Consequently, their rated operating current cannot reach the ampere level of conventional fuses, limiting their application.

[0003] Therefore, it is very important for those skilled in the art to design a PTC thermistor that can be applied to large current on-off protection scenarios and can self-recover. Summary of the Invention

[0004] The embodiment of the present invention provides a self-recovering PTC thermistor applicable to large current on-off protection scenarios, so as to solve the problem that existing PTC thermistors are difficult to meet the ampere-level current protection requirements.

[0005] The present invention discloses a PTC thermistor, which comprises: a PTC thermistor ceramic cavity, a first electrode sheet, a second electrode sheet, and a metal spring sheet, wherein the first electrode sheet is connected to the first electrode of the PTC thermistor ceramic cavity, and the second electrode sheet is connected to the second electrode of the PTC thermistor ceramic cavity, so that a sealed cavity is formed between the first electrode sheet, the second electrode sheet, and the PTC thermistor ceramic cavity, and the metal spring sheet is arranged in the sealed cavity, one end of the metal spring sheet is fixedly connected to the first electrode sheet, and the other end of the metal spring sheet abuts against the second electrode sheet at a first temperature and is disconnected from the electrode sheet at a second temperature, wherein the first temperature is less than or equal to the Curie temperature of the PTC thermistor, and the second temperature is greater than the Curie temperature of the PTC thermistor.

[0006] Optionally, the metal spring sheet includes two metal sheets, the two metal sheets are arranged in close proximity, and the thermal expansion coefficients of the two metal sheets are different.

[0007] Optionally, the metal spring sheet includes a plurality of metal sheets, the plurality of metal sheets are crimped and compositely arranged, and each of the metal sheets has a different thermal expansion coefficient.

[0008] Optionally, the metal spring sheet includes a first connecting portion for connecting to the first electrode sheet and a second connecting portion for connecting to the second electrode sheet, the first connecting portion is arranged parallel to the first electrode sheet, and the second connecting portion is arranged parallel to the second electrode sheet.

[0009] Optionally, the first electrode and the second electrode of the PTC thermistor ceramic cavity are respectively printed on two opposite ends of the PTC thermistor ceramic cavity.

[0010] Optionally, one end of the metal spring sheet is welded to the first electrode sheet.

[0011] Optionally, the first electrode sheet is bonded to the first electrode of the PTC thermistor ceramic cavity by conductive adhesive.

[0012] Optionally, the first electrode sheet is welded to the first electrode of the PTC thermistor ceramic cavity.

[0013] Optionally, the second electrode sheet is bonded or welded to the first electrode of the PTC thermistor ceramic cavity by conductive adhesive.

[0014] Optionally, the first electrode sheet and the second electrode sheet are both provided with connecting pins for electrically connecting to a PCB board.

[0015] The PTC thermistor provided by the embodiment of the present invention has the beneficial effect of forming a sealed cavity for mounting a metal spring sheet by connecting a first electrode sheet to the first electrode of the ceramic cavity of the PTC thermistor and connecting a second electrode sheet to the second electrode of the ceramic cavity of the PTC thermistor. The metal spring sheet, which can shrink when heated and recover when cooled, serves as a temperature switch between the first and second electrode sheets. During normal operation, the metal spring sheet short-circuits the first and second electrode sheets, and the PTC thermistor is in a low-resistance state. When the temperature rises abnormally, the metal spring sheet shrinks due to heat, disconnecting the first and second electrode sheets, and the PTC thermistor enters a high-resistance state, thus achieving an over-temperature protection function. Moreover, when a high normal operating current flows through the metal spring sheet and the protected object is in a normal temperature rising state, the temperature generated by the metal spring sheet can also be dissipated to the outside through the first and second electrode sheets, effectively triggering the over-temperature protection, thereby enabling the PTC thermistor to be used in environments with high rated operating currents. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments, in which: Figure 1 The structure of the PTC thermistor in the embodiment of the present invention is shown in FIG. Figure 1 ; Figure 2 The structure of the PTC thermistor in the embodiment of the present invention is shown in FIG. Figure 2 .

[0017] The reference numerals in the figures are: 100 , PTC thermistor ceramic cavity; 200 , first electrode sheet; 300 , second electrode sheet; 400 , metal spring sheet; 500 , connecting pin; 110 , first electrode; 120 , second electrode; 410 , first connecting portion; 420 , second connecting portion. DETAILED DESCRIPTION

[0018] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. Now, in conjunction with the accompanying drawings, the preferred embodiments of the present invention will be described in detail.

[0019] Existing PTC thermistors require a specific zero-power resistance value to achieve a certain withstand voltage. According to the formula W=I²Rt, this resistance value will inevitably generate heat when a normal current flows through it. However, if a high current in the ampere range is passed through the PTC thermistor, the heat generated will increase significantly given a certain resistance value. This excessive heat cannot be dissipated through the PTC thermistor itself, causing it to heat up and trip prematurely before the set protection temperature is reached. This prevents its rated operating current from reaching the ampere level like a conventional fuse. Therefore, the following solution is needed to meet the high-current self-recovery protection requirements.

[0020] like Figure 1 and Figure 2 As shown, the present invention provides a specific embodiment of a PTC thermistor.

[0021] A PTC thermistor, reference Figure 1, including a PTC thermistor ceramic cavity 100, a first electrode sheet 200, a second electrode sheet 300 and a metal spring sheet 400, the first electrode sheet 200 is connected to the first electrode 110 of the PTC thermistor ceramic cavity 100, and the second electrode sheet 300 is respectively connected to the second electrode 120 of the PTC thermistor ceramic cavity 100, so that a sealed cavity is formed between the first electrode sheet 200, the second electrode sheet 300 and the PTC thermistor ceramic cavity 100, and the metal spring sheet 400 is arranged in the sealed cavity, one end of the metal spring sheet 400 is fixedly connected to the first electrode sheet 200, and the other end of the metal spring sheet 400 abuts against the second electrode sheet 300 at a first temperature and is disconnected from the electrode sheet at a second temperature; wherein the first temperature is less than or equal to the Curie temperature of the PTC thermistor, and the second temperature is greater than the Curie temperature of the PTC thermistor.

[0022] Specifically, the PTC thermistor ceramic cavity 100 is a semiconductor ceramic device using barium titanate as a main raw material. A first electrode 110 and a second electrode 120 are respectively provided on opposite sides of the PTC thermistor ceramic cavity 100. The first electrode 110 and the second electrode 120 can be provided by printing.

[0023] The first electrode sheet 200 can be made of a copper sheet of a certain thickness, and its surface is nickel-plated to enhance its corrosion resistance. The shape of the first electrode sheet 200 is adapted to the combined shape of the side surface of the first electrode 110 of the PTC thermistor ceramic cavity 100. The first electrode sheet 200 is arranged on the side surface of the first electrode 110 of the PTC thermistor ceramic cavity 100 and is electrically connected to the first electrode 110. The second electrode sheet 300 is the same as the first electrode sheet 200 and can also be made of a copper sheet of a certain thickness, and its surface is nickel-plated to enhance its corrosion resistance. The shape of the second electrode sheet 300 is adapted to the combined shape of the side surface of the second electrode 120 of the PTC thermistor ceramic cavity 100. The second electrode sheet 300 is arranged on the side surface of the second electrode 120 of the PTC thermistor ceramic cavity 100 and is electrically connected to the second electrode 120.

[0024] The first electrode sheet 200, the second electrode sheet 300, and the PTC thermistor ceramic cavity 100 can collectively enclose a sealed cavity. The metal spring sheet 400 is disposed within the sealed cavity, and one end of the metal spring sheet 400 is fixedly connected to the first electrode sheet 200. When the circuit operates normally, the other end of the metal spring sheet 400 abuts against the second electrode sheet 300 to short-circuit the first electrode sheet 200 and the second electrode sheet 300, thereby causing the PTC thermistor to operate in a low-resistance state. When a circuit fault occurs and the protected object abnormally heats up, the increased temperature is transferred to the metal spring sheet 400 through thermal coupling. The metal spring sheet 400 contracts and deforms upon heating, causing the other end of the metal spring sheet 400 to be disconnected from the second electrode sheet 300, thereby causing the PTC thermistor to operate in a high-resistance state.

[0025] Among them, when the protected object is at the first temperature, that is, the temperature does not exceed the Curie temperature, the metal spring sheet 400 is in a natural state, that is, the other end of the metal spring sheet 400 is in close contact with the second electrode sheet 300. At this time, the current can pass through the first electrode sheet 200, the metal spring sheet 400, and the second electrode sheet 300 in sequence to form a loop to keep the first electrode sheet 200 and the second electrode sheet 300 short-circuited. At the same time, the PTC thermistor ceramic cavity 100 is also in a short-circuit state, so that the PTC thermistor is in a low-resistance state, allowing current to pass normally, and the system is in a normal power supply state.

[0026] When the protected object is at the second temperature, that is, the temperature exceeds the Curie temperature, the metal spring piece 400 expands due to the temperature increase, and will shrink and deform, thereby disconnecting from the second electrode piece 300. At this time, the circuit between the first electrode piece 200, the metal spring piece 400, and the second electrode piece 300 is cut off, and the PTC thermistor quickly enters a high-resistance state and enters a thermal equilibrium state. The temperature in the thermal equilibrium state maintains the necessary temperature for the metal spring piece 400 to be in the disconnected state, so that the PTC thermistor enters a continuous protection state. In the continuous protection state, current cannot pass, realizing the over-temperature protection function, effectively preventing the equipment from being damaged by excessive temperature. When the temperature drops to the first temperature, the metal spring piece 400 returns to its original state and re-contacts the second electrode piece 300. The circuit is connected again, allowing current to pass normally, and the system resumes normal operation.

[0027] In this embodiment, the first electrode sheet 200 is connected to the first electrode 110 of the PTC thermistor ceramic cavity 100, and the second electrode sheet 300 is connected to the second electrode 120 of the PTC thermistor ceramic cavity 100 to form a closed cavity for installing the metal spring sheet 400. The metal spring sheet 400, which can shrink when heated and recover when cooled, serves as a temperature switch between the first electrode sheet 200 and the second electrode sheet 300. During normal operation, the metal spring sheet 400 connects the first electrode sheet 200 and the second electrode sheet 300. The electrode sheet 300 is short-circuited, and the PTC thermistor is in a low-resistance state. When the temperature rises abnormally, the metal spring sheet 400 contracts due to the heat, and the first electrode sheet 200 and the second electrode sheet 300 are disconnected, and the PTC thermistor enters a high-resistance state, realizing the over-temperature protection function. Moreover, when the metal spring sheet 400 flows with a high current of normal operation and the protected object is in a normal temperature-rising state, the temperature generated by the metal spring sheet 400 can also be dissipated to the outside through the first electrode sheet 200 and the second electrode sheet 300, and the over-temperature protection will not be mistakenly triggered.

[0028] In one embodiment, reference Figure 1 The metal spring piece 400 includes two metal sheets. By laminating and pressing two metal sheets with different thermal expansion coefficients together, when the temperature changes, the different thermal expansion coefficients of the two metal sheets will cause the composite metal spring piece 400 to deform differently and bend. In addition, the metal spring piece 400 also has a certain high resistivity. Under a certain high fault current, it will generate a certain temperature rise, accelerate the deformation difference, and trigger the protection more timely.

[0029] In one embodiment, reference Figure 1 The metal spring piece 400 includes multiple metal sheets. By laminating and pressing multiple metal sheets with different thermal expansion coefficients, when the temperature changes, the different thermal expansion coefficients of the multiple metal sheets will cause the composite metal spring piece 400 to deform differently and bend. In addition, the metal spring piece 400 also has a specific high resistivity. Under a specific high fault current, it will generate a certain temperature rise, accelerate the deformation difference, and trigger the protection more timely.

[0030] When assembling the PTC thermistor, the metal spring piece 400 can be installed close to the heat source to be protected to achieve better heat coupling, thereby triggering reliable protection of the metal spring piece 400.

[0031] In one embodiment, reference Figure 1The metal spring sheet 400 includes a first connecting portion 410 for connecting to the first electrode sheet 200 and a second connecting portion 420 for connecting to the second electrode sheet 300. The first connecting portion 410 is arranged parallel to the first electrode sheet 200, and the second connecting portion 420 is arranged parallel to the second electrode sheet 300.

[0032] Specifically, refer to Figure 1 The first connecting portion 410 of the metal spring piece 400 is spot-welded on the first electrode piece 200, and the second connecting portion 420 of the metal spring piece 400 is in contact with the second electrode piece 300. The second connecting portion 420 serves as a moving contact, and the second electrode piece 300 serves as a static contact. The moving contact and the static contact are in contact with each other with a certain elastic force. By welding the first connecting portion 410 to the first electrode piece 200, the contact area between the first connecting portion 410 and the first electrode piece 200 can be effectively increased. On the one hand, the connection stability between the first connecting portion 410 and the first electrode piece 200 can be improved. On the other hand, when the rated working current flows through the metal spring piece 400 and the protected object is in a normal temperature rising state, the temperature generated by the current flowing through the metal spring piece 400 can be dissipated to the outside through the first connecting portion 410 and the first electrode piece 200, thereby preventing the over-temperature protection from being falsely triggered.

[0033] Further, refer to Figure 1 By arranging the second connecting portion 420 in parallel with the second electrode sheet 300, the contact area between the second connecting portion 420 and the second electrode sheet 300 can be effectively increased under normal working conditions. On the one hand, the connection stability between the second connecting portion 420 and the second electrode sheet 300 can be improved. On the other hand, when the rated working large current flows through the metal spring sheet 400 and the protected object is in a normal temperature rising state, the temperature generated by the current flowing through the metal spring sheet 400 can be dissipated to the outside through the second connecting portion 420 and the second electrode sheet 300, thereby preventing the over-temperature protection from being falsely triggered.

[0034] In one embodiment, reference Figure 1 One end of the metal spring sheet 400 is welded to the first electrode sheet 200. The metal spring sheet 400 and the first electrode sheet 200 are fixedly connected by welding to achieve electrical connection. The welding strength is high and can withstand certain mechanical stress and vibration, which can ensure that they will not loosen or fall off during long-term use. The solder has excellent electrical conductivity and low contact resistance, which can reduce energy loss during current transmission and ensure stable conduction of the circuit.

[0035] In one embodiment, reference Figure 1The first electrode sheet 200 and the first electrode 110 of the PTC thermistor ceramic cavity 100 can be connected by welding or by conductive adhesive. The welding strength is high and can withstand certain mechanical stress and vibration, which can ensure that they will not loosen or fall off during long-term use. The solder has excellent conductivity and low contact resistance, which can reduce energy loss during current transmission and ensure stable conduction of the circuit. The conductive adhesive bonding can achieve uniform bonding over a large area, so that the force between the first electrode sheet 200 and the first electrode 110 is more uniform, avoiding damage to the PTC thermistor ceramic cavity 100 due to excessive local stress, and less damage to brittle materials such as the PTC thermistor ceramic cavity 100, which can better protect the structural integrity of the PTC thermistor ceramic cavity 100.

[0036] In one embodiment, reference Figure 1 The second electrode sheet 300 and the second electrode 120 of the PTC thermistor ceramic cavity 100 can be connected by welding or by conductive adhesive. The welding strength is high and can withstand certain mechanical stress and vibration, which can ensure that it will not loosen or fall off during long-term use. The solder has excellent conductivity and low contact resistance, which can reduce energy loss during current transmission and ensure stable conduction of the circuit. The conductive adhesive bonding can achieve uniform bonding over a large area, so that the force between the second electrode sheet 300 and the second electrode 120 is more uniform, avoiding damage to the PTC thermistor ceramic cavity 100 due to excessive local stress, and less damage to brittle materials such as the PTC thermistor ceramic cavity 100, which can better protect the structural integrity of the PTC thermistor ceramic cavity 100.

[0037] In one embodiment, reference Figure 2 The first electrode sheet and the second electrode sheet are both provided with connecting pins 500 for electrically connecting to an external PCB board.

[0038] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Those skilled in the art may modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein; and all these modifications and replacements should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A PTC thermistor, characterized in that: include: A PTC thermistor ceramic cavity, a first electrode sheet, a second electrode sheet, and a metal spring sheet, wherein the first electrode sheet is connected to the first electrode of the PTC thermistor ceramic cavity, and the second electrode sheet is connected to the second electrode of the PTC thermistor ceramic cavity, so that a sealed cavity is formed between the first electrode sheet, the second electrode sheet, and the PTC thermistor ceramic cavity, and the metal spring sheet is disposed in the sealed cavity, one end of the metal spring sheet is fixedly connected to the first electrode sheet, and the other end of the metal spring sheet abuts against the second electrode sheet at a first temperature and is disconnected from the electrode sheet at a second temperature, wherein the first temperature is less than or equal to the Curie temperature of the PTC thermistor, and the second temperature is greater than the Curie temperature of the PTC thermistor.

2. The PTC thermistor according to claim 1, characterized in that: The metal spring sheet includes two metal sheets, the two metal sheets are arranged in close contact, and the thermal expansion coefficients of the two metal sheets are different.

3. The PTC thermistor according to claim 1, characterized in that The metal spring sheet includes a plurality of metal sheets, the plurality of metal sheets are crimped and compositely arranged, and each of the metal sheets has a different thermal expansion coefficient.

4. The PTC thermistor according to claim 1, characterized in that: The metal spring sheet includes a first connecting portion for connecting to the first electrode sheet and a second connecting portion for connecting to the second electrode sheet. The first connecting portion is arranged parallel to the first electrode sheet, and the second connecting portion is arranged parallel to the second electrode sheet.

5. The PTC thermistor according to claim 1, characterized in that: The first electrode and the second electrode of the PTC thermistor ceramic cavity are respectively printed on two opposite ends of the PTC thermistor ceramic cavity.

6. The PTC thermistor according to claim 1, characterized in that: One end of the metal spring sheet is welded to the first electrode sheet.

7. The PTC thermistor according to claim 1, characterized in that: The first electrode sheet is bonded to the first electrode of the PTC thermistor ceramic cavity by conductive adhesive.

8. The PTC thermistor according to claim 1, characterized in that: The first electrode sheet is welded to the first electrode of the PTC thermistor ceramic cavity.

9. The PTC thermistor according to claim 1, characterized in that: The second electrode sheet is bonded or welded to the first electrode of the PTC thermistor ceramic cavity by conductive adhesive.

10. The PTC thermistor according to claim 1, characterized in that: The first electrode sheet and the second electrode sheet are both provided with connecting pins for electrically connecting to a PCB board.

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