JP4905947B2 - Protective device - Google Patents

Description

  The present invention relates to a contact-type circuit breaker having a movable contact body, for example, a non-recoverable protection that prevents contact welding accompanying opening of the movable contact body in a protection device using a temperature-sensitive pellet type thermal fuse. In particular, the present invention relates to a one-shot type protection device that safely shuts off an electric circuit in combination with a non-contact type circuit breaker using a fusible alloy when a contact-type thermal fuse having a movable contact is used in a DC circuit. .

A protection device such as a thermal fuse is widely used to protect damages caused by overheating of household or industrial electronics and electric equipment. A thermal fuse is a non-return type circuit breaker that detects abnormal temperature rise and quickly shuts down the circuit to prevent equipment damage and fire. It is a circuit interruption element which interrupts an electric circuit. As a typical thermal fuse, there is known a fusible alloy type thermal fuse that uses a low melting point fusible alloy that does not contain harmful metals having environmental problems as disclosed in Patent Document 1 as a temperature sensitive material. . FIG. 2 shows a cross-sectional view of this type of fusible alloy type thermal fuse 20, in which a low melting point fusible alloy 23 is joined and connected between a pair of leads 21 and 22, and a flux 24 is coated on the surface thereof. The fusible alloy 23 covered with the flux 24 is accommodated in an insulating case 25, and a pair of leads 21 and 22 are led out from the case 25 sealed with resin sealing materials 26 and 27. On the other hand, there is also known a temperature sensitive pellet type thermal fuse having a movable contact body which can be set widely in a nominal rated current of 0.5 A to 15 A and can be used for a high current of 6 A or more. As shown in FIG. 3, a temperature-sensitive pellet type temperature fuse 30 that is operated at a predetermined operating temperature using a temperature-sensitive material molded body as a temperature-sensitive material has a temperature-sensitive pellet 31 as a strong compression spring 32, a movable contact. The body 33 and the weak compression spring 34 are accommodated in a metal case 35, and a pair of leads 36 and 37 are fixedly attached to the case 35 with one of the insulators 38 and the resin sealant 39, and the other directly attached to the case 35. Yes. In Patent Documents 2 and 3, as a high-load temperature fuse, a contact spring is operated by sliding the operating pin using a fusible solder tablet filled in the casing and a sliding operating pin, and cut off. A temperature safety switch is disclosed.
JP 2005-276577 A Japanese Patent Laid-Open No. 04-212234 JP 56-067130

  Conventionally, when a circuit of a contact-type thermal fuse having the above-described movable contact body is interrupted at a predetermined operating temperature, the contact portion may be welded to cause a failure in circuit disconnection. In particular, when a contact temperature fuse protector is connected in series to a DC power supply and a load circuit, plasma or arc discharge occurs during the interruption operation, and the movable contact electrode is heated and the contact member is welded. It becomes. Such a problem becomes a problem in a load circuit such as a high voltage and a high current, which may hinder use as a protection device. As a countermeasure, it is conceivable to use a high-current protection device that prevents sparks by placing a high-resistance or current fuse in parallel with the temperature-sensitive pellet-type thermal fuse. Or the malfunction of the contact member accompanying the separation cannot be prevented. In particular, when the temperature sensitive material is moderately deformed under a high voltage and high current load, if the movable contact body is gradually opened, the contact part at the time of interruption will be melted and damaged. This becomes noticeable when using a thermal fuse, and the larger the load current, the more problematic. For example, when shutting off at the operating temperature, the operating current may cause welding of the contact portion, making reliable and safe shutting operation difficult.

  In particular, when a contact-type thermal fuse having a movable contact body is used in a high-current DC circuit, plasma discharge continues due to circuit interruption and cannot be safely interrupted. Further, a fusible alloy type thermal fuse, which is a non-contact type thermal fuse without a movable contact body, has a problem that the rated current is small and cannot be used for a high current load. Further, when the current fuse is arranged in parallel with the movable contact type circuit breaker element, there is a problem that when an abnormal overheating not caused by the current occurs, only the current fuse is conducted, and the circuit is not cut at an abnormal temperature. Therefore, some measures to avoid troubles that occur when the circuit is opened when using contact-type thermal fuses that can be used in high-load circuits are required, and a non-recoverable temperature safety switch or thermal fuse that can always safely shut off the circuit is required. It has been desired to provide a one-shot type protective device.

  Accordingly, the present invention has been proposed to eliminate the above-mentioned drawbacks, and in a one-shot type circuit breaker that is a one-time operation, an electric circuit is subjected to a chemical change under a predetermined operating condition. It is intended to provide a new and improved protection device that prevents the occurrence of defects such as welding due to sparks or plasma discharge when it is opened by dissociation or separation by physical change, and can safely shut off the electric circuit. is there.

  In particular, when the circuit breaker element is a thermal fuse, if the switching member is operated using the physical deformation of the temperature sensitive material and the deformation characteristic of the temperature sensitive material is not steep, the heating is slow and the deformation is gradually made. As an effective means for unstable operation such as when used in high voltage / high current load circuits or DC circuits, it is improved to safely disconnect circuits by connecting different types of circuit interrupting elements in parallel. Another purpose is to provide a one-shot type protection device.

According to the present invention, a protective device connected between a pair of protective terminals provided in series with a power source and a load, the protective device comprising a temperature sensitive pellet and having a first operating temperature. A fuse and a non-contact type thermal fuse having a second operating temperature that is higher than the first operating temperature and is connected in parallel with the contact type thermal fuse with a fusible alloy; A protection device is provided that is operated prior to an operating condition of the non-contact type thermal fuse . That is, a protection device is provided in which a contact-type circuit breaker element operating at a first operating temperature is connected in parallel with a non-contact-type circuit breaker element having a fusible alloy that operates at an overcurrent or a second operating temperature. The protection device is a contact-type thermal fuse in which a power source and a load are configured by a DC circuit, and the contact-type circuit breaker element has a movable contact member that operates at a first operating temperature. Desirably, it comprises a contactless thermal fuse that operates at a second operating temperature that is higher than the first operating temperature , thereby providing a safe and reliable shut-off protection device. Further, when the resistance value of each thermal fuse connected between the pair of protection terminals is an internal resistance, the internal resistance (r1) of the contact-type thermal fuse is the internal resistance (r2) of the non-contact-type thermal fuse. It is smaller and the relationship r1 <r2 is set. Preferably, this relational expression is set as (r2 / r1)> 5, and more preferably, 5 times or more of this ratio is made 10 times or more, and it has been found that a more reliable blocking function is exhibited. In other words, when a current is passed through a non-contact type thermal fuse having a fusible alloy, the resistance value is high, so that the operating temperature is reached by self-heating and is cut. By making the contact-type thermal fuse high resistance, current during operation is induced to the contact-type thermal fuse side having the movable contact body. Since the internal resistance of the thermal fuse is originally low for the contact-type thermal fuse and high for the non-contact-type thermal fuse, the protection device with the bypass circuit can be effectively achieved by connecting different types of thermal fuses in parallel. Here, the resistance value, which is the internal resistance, can be adjusted using the lead portion and the element portion of the thermal fuse as necessary. For example, in order to increase the resistance value of a non-contact type thermal fuse, the resistance value naturally increases due to downsizing, and can also be adjusted by the length of the lead wire.

  In the specific structure of the protective device described above, it is advantageous that the different types of circuit breaker elements are insulated from each other by an insulating tube or a coating film. For example, in the case of a contact-type thermal fuse, electrical insulation can be obtained satisfactorily even if a non-contact-type thermal fuse is provided in a bypass manner by insulating the external surface to make contact with the temperature sensing unit. When disposing these different types of circuit breaker elements in an environment with a temperature difference, place the contact-type thermal fuse on the high-temperature side, the non-contact-type thermal fuse on the low-temperature side, and the contact-type thermal fuse on the non-contact side. Enable operation prior to the shape thermal fuse. In order to allow a high current, a plurality of contact-type thermal fuses are connected in parallel to distribute the energization current, and the allowable current can be increased. Furthermore, the effectiveness of the non-contact type thermal fuse can be enhanced by delaying the operation by molding it with an insulating material and allowing the protective device to operate stably and reliably.

  In other words, a low-melting-point fusible alloy is used for the non-contact type thermal fuse having a fusible alloy as the temperature sensitive material of the thermal fuse, and the thermosensitive material molded body is a pellet for the contact type thermal fuse having a movable contact body. Used. In the latter contact-type temperature fuse, the internal resistance is small, so that a low resistance circuit is formed between the connection terminals. On the other hand, a circuit breaker element of a non-contact type thermal fuse that melts at an overcurrent or melts at a predetermined operating temperature as a high resistance circuit is connected between a pair of protective terminals. A parallel circuit is formed between a pair of terminals forming the protective device by a circuit breaker element of a low resistance circuit and a circuit breaker element of a high resistance circuit. When the operating temperature is reached at an abnormal temperature, the low-resistance circuit of the contact-type circuit breaker opens the low-resistance circuit at the predetermined operating temperature, and immediately after that, the high-resistance circuit of the non-contact-type circuit breaker temporarily Provided is a non-returnable protection device that allows and opens electricity and completely disconnects between protective terminals. Here, the low-resistance circuit is a contact-type thermal fuse using a temperature sensitive material, and the high-resistance circuit is a non-contact-type thermal fuse having a fusible alloy. The element opens to completely shut off the circuit. Preferably, the low-resistance circuit is a temperature-sensitive pellet type thermal fuse using a temperature-sensitive pellet, and the high-resistance circuit temporarily allows energization after the operation of the low-resistance circuit and dissociates or opens by current blowing to interrupt the circuit. It is a non-contact type circuit breaker.

  The present invention is a protection device using a contact-type circuit breaker element, which is configured by connecting non-contact-type circuit breaker elements in parallel, thereby stabilizing the circuit breakage and causing problems due to sparks and plasma discharges. Prevents the occurrence of the occurrence of a safe and reliable shut-off operation. In other words, the circuit breaking operation is safely and reliably achieved through the two steps of the opening and closing operation by the temperature sensitive material and the subsequent opening and closing operation by energizing the current fusing element. In particular, it has a great practical effect as a wide range of use of contact-type thermal fuses in a high-voltage and high-current high-load circuit in a DC circuit, and to solve problems at the time of interruption.

  In an embodiment of the present invention, a contact-type circuit breaker element and a non-contact-type circuit breaker element are connected in parallel between a pair of protective terminals to constitute a protection device. In particular, this protection device is used in series connection with a DC power source and a load, and effectively exhibits the high voltage and high current response characteristic of the contact-type circuit breaker element. Here, the contact-type circuit breaker element is a temperature-sensitive pellet type thermal fuse having a movable contact member that operates at the first operating temperature. On the other hand, the non-contact type circuit breaker element is a fusible alloy type thermal fuse having a low melting point fusible alloy that operates at a predetermined overcurrent or a second operating temperature. In this case, the first operating temperature is set lower than the second operating temperature, and in the state of being connected in parallel, the contact-type circuit breaker element is first activated to be shut off, and then the non-contact type. The circuit breaker element is actuated to be cut open, and the protective terminals are completely cut off. The pair of protective terminals function as terminals for connecting the protective device in series with the power supply and the load circuit. Further, since the fusible alloy type thermal fuse generates heat due to self-resistance, even if it operates by detecting an overcurrent, it is shut off in an open state.

  Another embodiment of the present invention is a protection device for a DC circuit, which uses thermal fuses as contact type and non-contact type circuit breaker elements, respectively. Here, the contact-type thermal fuse operates at the first operating temperature, and the first operating temperature is set equal to or lower than the second operating temperature of the non-contact-type thermal fuse. For example, a DC power supply and a load circuit are provided with a pair of protective terminals connected in series, and different types of thermal fuses are connected in parallel between the terminals. A contact type circuit breaker such as a temperature sensitive pellet type thermal fuse is a low resistance circuit having a small internal resistance (r1) which is a resistance value between connection terminals, and is a non-contact type such as a low melting point soluble alloy type thermal fuse. The circuit breaker element constitutes a high resistance circuit having a larger internal resistance (r2), which is the resistance value between the connection terminals. In operation, when the first operating temperature is first detected at an abnormal temperature, the contact-type temperature fuse of the low resistance circuit is disengaged from the movable contact body and is opened. Next, the second operating temperature is detected, and the non-contact type circuit breaker of the high resistance circuit is opened due to melting of the fusible alloy and is operated in the open cut-off state. As a result, the connection state between the protective terminals is completely The circuit is cut off and the circuit is made safe. That is, when the movable contact body of the low resistance circuit moves due to the dissociation of the temperature-sensitive substance, the contact is released. At that time, no spark or plasma discharge occurs due to the energization of the high resistance circuit, and the following second operation is performed smoothly. Move to step. In the second step, the non-contact type thermal fuse is activated by the second operating temperature that detects self-heating due to overcurrent or ambient temperature due to the energizing current to the fusible alloy, and the protective terminals are cut off safely and securely. To. Thus, a one-shot type non-returnable protective device is provided.

  The second embodiment of the present invention is a structural modification in the case of utilizing the arrangement structure and internal resistance of the thermal fuse used as the circuit breaker described above. That is, it is to provide a safe and secure protection device by appropriately adjusting and setting the internal resistance, which is the lead resistance value between connected terminals, for the thermal fuse used as each circuit breaker element. Specifically, when the internal resistance of the contact-type circuit breaker element is (r1) and the internal resistance of the non-contact-type circuit breaker element is (r2), the respective internal resistances are maintained in a relational expression r1 <r2, , (R2 / r1)> 5 was found to be advantageous. Furthermore, it has been experimentally revealed that this relationship can be safely blocked by setting (r2 / r1)> 10. It has been found that the larger the value of the relational ratio (r2 / r1) of the resistance values of different types of thermal fuses, the more useful the stabilization, and the results of this operation test are shown in Table 1 together with the test conditions.

  In the third embodiment of the present invention, when a thermal fuse is used for the circuit breaker element described above, the surface of the circuit breaker element is covered with an insulating tube or an insulating coating film for insulation. This structure is effective for securing insulation in a circuit configuration in a narrow space. Also, in the circuit breaker layout, contact type thermal fuses should be placed on the high temperature side, non-contact type thermal fuses should be placed on the low temperature side, and the contact type thermal fuses can be operated prior to the non-contact type thermal fuses. To ensure the safety of operation. Furthermore, a protection device is disclosed in which a plurality of contact-type thermal fuses are connected in parallel to distribute the energization current and increase the allowable current. As a result, the regulation of the thermal fuse especially when used in a DC circuit can be relaxed and a large capacity can be realized. As another modified example, there is a protection device that performs an operation delay by performing molding of an insulating material with respect to the use of a non-contact type thermal fuse. In the operation at the abnormal temperature in these embodiments, the contact-type circuit breaker element is opened and shut off in advance, and then the low-resistance circuit temperature-sensitive pellet type temperature fuse is used, and then the contactless circuit type fusible alloy type as the high-resistance circuit. The thermal fuse blows, including the heat generated by heating, and switches the circuit to a completely disconnected state. This type of interrupting operation requires a high-load circuit to have some delay operation, and prevents sparking at the time of cut-off and prevents the occurrence of problems associated with discharge or prevents contact welding during operation. A one-shot type non-returnable protective device that achieves reliable switching to a cut-off state is disclosed.

  As shown in FIG. 1, a protection device 10 according to an embodiment of the present invention includes a temperature-sensitive pellet type thermal fuse 30 as a contact-type circuit breaker between protection terminals 16 and 18 in series with a DC power supply 12 and a load 14. A fusible alloy type thermal fuse 20 is connected as a non-contact type circuit breaker element in parallel with the temperature sensitive pellet type thermal fuse 30. Here, the operating temperature of each temperature fuse is a commercial product of a contact-type temperature fuse whose operating temperature of the temperature sensitive pellet type temperature fuse 30 is 109 ° C., and the operating temperature of the fusible alloy type temperature fuse 20 is 182 ° C. A non-contact thermal fuse commercial product was used. That is, the latter operating temperature is set higher than the former operating temperature. Therefore, no spark or plasma discharge occurs during the operation of the contact-type thermal fuse, no welding of the movable contact body occurs, and there is no problem. In addition to thermal fuses that use various temperature sensitive materials, contact type circuit breaker elements have thermoswitches, and non-contact type circuit breaker elements have various fusible alloy type temperatures such as axial, radial, and thin types. In addition to fuses, PTC polyswitches and thermistors are applicable.

When the protection device according to the present invention is applied to a DC load circuit in the embodiment shown in FIG. 1, the operation state was confirmed by testing with each combination of the power supply voltages 25V and 50V and the load currents 5A and 30A. The temperature fuse used here is a temperature-sensitive temperature fuse of the contact type circuit breaker element 30 made of NEC / SCHOTTT type SFH109E, and the contactless circuit breaker element 20 is a fusible alloy type temperature of the type SM182A made of NEC / SCHOTTT. A fuse was used. As shown in Table 1, the results of this operation test confirmed that all of the four types of operation tests operate normally without any defects due to welding or the like on the movable contacts of the temperature-sensitive temperature fuse. It was.

On the other hand, Table 2 shows a contact-type thermal fuse having an operating temperature of 109 ° C. and a non-contact having four different operating temperatures when the ratio of the internal resistance r2 / r1 of different types of thermal fuses is different. The quality of the operation result was judged by the combination using each commercial product of the form temperature fuse. The result is indicated by a circle when it is normal, but the interruption operation is abnormal only when the operating temperature is the test voltage 50V, the current 10A, the internal resistance ratio is 3, and the first and second operating temperatures are the same. However, all other cases were good. From these results, it has been found that the internal resistance ratio (r2 / r1) is preferably set to 5 or more. As an example of using a contact-type thermal fuse, in the comparison between an AC circuit and a DC circuit, when a bypass circuit is not provided and a parallel circuit is not used as in the conventional method, a 50V / 5A and 75V / 5A circuit of a DC circuit is used. The test results revealed that there was a problem due to welding, but no problem occurred in an AC circuit under similar conditions. From this, it was found that the effectiveness in the DC circuit is remarkable.

It is a circuit diagram which shows the protection apparatus which is an Example of this invention. FIG. 2 is a cross-sectional view of a typical fusible alloy type thermal fuse used as the non-contact type circuit breaker of FIG. 1. It is sectional drawing of the typical temperature-sensitive pellet type | mold thermal fuse similarly utilized as a contact-type circuit interruption element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Protection device, 12 ... Power supply, 14 ... Load, 16, 18 ... Protection terminal,
20 ... Fusible alloy type thermal fuse (non-contact type circuit breaker),
30 ... Temperature-sensitive pellet type thermal fuse (contact type circuit breaker).

Claims (5)

A protective device connected between a pair of protective terminals provided in series with a power source and a load, the protective device comprising a temperature sensitive pellet and a contact-type thermal fuse having a first operating temperature, a fusible alloy And a non-contact type thermal fuse having a second operating temperature higher than the first operating temperature and connected in parallel with the contact type thermal fuse, the contact type thermal fuse being the non-contact type thermal fuse A protective device characterized by being operated prior to the operating conditions .   When the resistance value of each of the thermal fuses connected between the pair of protective terminals is an internal resistance, the internal resistance (r1) of the contact-type thermal fuse is the internal resistance (r2) of the non-contact-type thermal fuse. The protection device according to claim 1, wherein the protection device is set smaller.   When the thermal fuse is arranged at a location where there is a temperature difference between the protective terminals, the contact-type thermal fuse is set to the high temperature side, the non-contact type thermal fuse is set to the low-temperature side, and the contact-type thermal fuse is set to the non-contact type temperature. 3. The protective device according to claim 2, wherein the protective device is operated prior to the fuse.   3. The protection device according to claim 2, wherein the contact-type thermal fuse includes a plurality of parallel-connected fuses, and an allowable current is increased by dispersion of an energization current. 3. The protection device according to claim 2, wherein the non-contact type thermal fuse is molded with an insulating material, thereby delaying its operation.

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