JP2014007116A - Thermosensitive pellet type thermal fuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosensitive pellet type thermal fuse that prevents members from being fused and bonded with each other due to ark generated from a contact part without increasing the number of parts.SOLUTION: A thermosensitive pellet type thermal fuse comprises: a hollow metal case 18; a second lead 19 laid at one end of the metal case; an insulation pipe 12 for closing an opening end of the metal case; a thermosensitive pellet 15 which includes a first lead 11 passing through the insulation pipe and defining its inner end as a contact point, and which is laid in contact with the second lead; and a movable contact point 17 which makes contact with the inner end of the first lead via the thermosensitive pellet and is always biased to an opening direction. The thermosensitive pellet type thermal fuse limits an exposed area of the inner end of the first lead by encompassing the inner end peripheral border of the first lead with a peripheral wall 16 formed on the insulation pipe and by narrowing a gap L1 between the insulation pipe and the movable contact point, and shields metal parts such as a compression spring 13 placed outside the peripheral wall from arc discharge generated when the movable contact point making contact with the contact point of the first lead and the contact point of the first lead are separated.

Description

  The present invention relates to a temperature-sensitive pellet type thermal fuse that detects an overheating of an electric device and interrupts a circuit, and is capable of reducing welding resistance or insulation resistance between members due to an arc generated from a contact portion, particularly a case inner end portion of a first lead. The present invention relates to a temperature-sensitive pellet type thermal fuse improved so as to prevent it.

  In household electrical appliances or industrial electrical / electronic equipment, thermal fuses are used as protective parts that sense the temperature of the equipment and quickly shut down the circuit in the event of abnormal overheating. Thermal fuses are mounted on products such as home appliances, portable devices, communication devices, office equipment, in-vehicle devices, AC adapters, chargers, motors, and batteries. In general, there are various types of thermal fuses with rated current values ranging from about 0.5 A to about 15 A. Temperature-sensitive pellet type thermal fuses are preferably used particularly for high current ratings of 6 A or more. As one of the typical forms of the temperature-sensitive pellet type thermal fuse, for example, as shown in Patent Document 1 or Patent Document 2, a cylindrical metal case having a hollow portion inside, and both ends of the metal case are arranged. A temperature-sensitive pellet that has a first lead and a second lead that are provided and is disposed in contact with the second lead, and contacts the first lead through the temperature-sensitive pellet and is constantly urged in the opening direction. When the temperature of the mounted electrical equipment exceeds the specified temperature, the temperature sensitive pellet melts or softens, so that the movable contact is separated from the first lead by the urging force and the circuit is cut off. There is a temperature-sensitive pellet type thermal fuse. By connecting the temperature-sensitive pellet type thermal fuse in the above-mentioned configuration in series with the electrical equipment and placing it at the location where the abnormal temperature rise of the electronic or electrical equipment is desired to be detected, the temperature is supplied to the electrical equipment via the temperature-sensitive pellet-type thermal fuse. Can distribute power. The temperature-sensitive pellet is solid at normal temperature, and at this time, the movable contact is pressed against the inner end of the case of the first lead by the biasing force. Therefore, the first lead-metal case-movable contact-second lead is held in a conductive state. When the temperature of the installation location rises to the operating temperature of the temperature-sensitive pellet type temperature fuse due to abnormal energization such as a short circuit of the electrical equipment, the temperature-sensitive pellet melts and the movable contact is pressed against the end of the first lead. Therefore, the movable contact is separated from the case inner end portion of the first lead, and the first lead and the second lead are in a non-conductive state. As a result, the supply / distribution to the electrical equipment is stopped, the temperature rise of the electrical equipment is prevented, and accidents such as overheating damage to the electrical equipment or ignition due to the electrical equipment can be prevented.

Patent Document 1: Japanese Patent Laid-Open No. 01-154422 Patent Document 2: Japanese Utility Model Registration No. 3161636 Patent Document 3: Japanese Utility Model Publication No. 57-052841 Patent Document 4: Japanese Patent Laid-Open No. 08-0454404

  As described above, the temperature-sensitive pellet type temperature fuse is a non-recoverable protection element, and it is necessary to prevent re-conduction after operation and to make the current-canceling property more complete and reliable. After the operation, it is desirable that the withstand voltage between the first lead and the second lead is as high as possible and that the insulation resistance after the operation is higher. For this reason, for example, the distance between the inner end of the first lead and the movable contact is increased after the operation of the temperature-sensitive pellet type temperature fuse for the purpose of further improving the withstand voltage between both leads of the temperature-sensitive pellet type temperature fuse. Thus, Patent Document 3 proposes a method for improving the withstand voltage. Further, in Patent Document 4, a floating contact member serving as an intermediate electrode is added between the first lead and the movable contact to separate the contact opening portion and the movable contact, and the contact opening portion that is likely to generate arc discharge. Is used as a contact surface between the first lead and the floating contact member, and a temperature-sensitive pellet having a structure in which arc discharge is unlikely to occur between the first compression lead and the weak compression spring that applies a biasing force to the movable contact. There is a mold temperature fuse.

  However, in the temperature-sensitive pellet type thermal fuse configuration described in Patent Document 3 in which the withstand voltage is improved by increasing the distance between the first lead end and the movable contact, for example, the conventional example (a) shown in FIG. As shown in the product cross-sectional view of (b), since the metal compression spring that bears the biasing force is conductive, the movable contact can be obtained even if the distance between the inner end of the first lead and the movable contact is increased. Since the weak compression spring elastically connected to the first lead end is located closer to the first lead end than the movable contact, the distance between the lead end and the weak compression spring is greater than the distance between the lead end and the movable contact. The arc discharge greatly affects the withstand voltage between the first and second leads, and the arc discharge generated at or after the contact opening easily forms a discharge path from the end of the lead to the nearby weak compression spring, Weak compression spring and movable contact are exposed to arc discharge The contact may stop in a half-open state before the contacts are completely separated, or the separation operation may be interrupted in the middle with insufficient insulation distance. There is a problem that some of the thermal fuses have poor withstand voltage and insulation resistance. Further, the temperature-sensitive pellet type thermal fuse of Patent Document 4 requires a new floating contact member to be newly added between the first lead and the movable contact, which makes the configuration more complicated and requires extra manufacturing cost. Therefore, the economic disadvantage is great.

  Therefore, the present invention does not require an additional part such as a floating contact member, and can effectively shield the metal member around the movable contact including the compression spring from an arc generated when the contact is opened or after the contact is released. An object of the present invention is to provide a temperature-sensitive pellet type thermal fuse that prevents welding and has a reliable shut-off without re-conduction after operation, and is excellent in safety and economy.

  According to the present invention, a temperature-sensitive pellet that melts or softens at least at a specific temperature, a strong compression spring that presses the temperature-sensitive pellet, and a cylindrical case inside a cylindrical case that has good conductivity and good thermal conductivity An insulating tube that closes the open end of the wire, a weak compression spring that is in contact with the insulating tube, a first lead that has an inner end penetrating the insulating tube as a contact portion, and the first lead and the cylindrical case. In a temperature-sensitive pellet type thermal fuse having a connected movable contact and further comprising a second lead disposed at one end of the cylindrical case, the inner end of the first lead between the insulating tube and the movable contact A temperature-sensitive pellet type thermal fuse having a reduced exposed area is provided. More preferably, at least a temperature-sensitive pellet that melts or softens at a specific temperature, a strong compression spring that presses the temperature-sensitive pellet, and an opening in the cylindrical case, inside the cylindrical case that has good conductivity and good heat conductivity An insulating tube that closes the end; a weak compression spring that is in contact with the insulating tube; a first lead that penetrates the insulating tube; and a movable contact that is electrically connected to the first lead and the cylindrical case; In the temperature-sensitive pellet type thermal fuse provided with the second lead arranged at one end of the first lead, the inner periphery of the first lead is surrounded by a peripheral wall formed in the insulating tube, and a gap between the insulating tube and the movable contact is formed. By reducing the width, the exposed area of the inner end of the first lead is suppressed, and a compression spring or the like disposed outside the peripheral wall from the arc discharge generated when the movable contact and the contact of the first lead are separated or after the separation. Shielded metal parts Thermal fuse, wherein is provided.

  In the temperature-sensitive pellet type thermal fuse of the present invention, the inner peripheral edge of the first lead is surrounded by a peripheral wall formed in an insulating tube, and the gap from the peripheral wall end to the movable contact, that is, the exposed area of the first lead inner end. By suppressing the exposure length, metal parts placed outside the peripheral wall can be shielded from arc discharge that occurs when the contact between the movable contact and the first lead is separated, and the number of parts can be increased. In addition, there is no need to change the materials and materials of parts such as temperature-sensitive pellets, and further, without increasing the outer diameter and length of the cylindrical case, it is possible to prevent a decrease in insulation resistance and dielectric breakdown after operation. Therefore, the voltage / current rating can be maintained even if the device is downsized.

  The inner edge of the first lead where the electric field strength increases due to the edge effect and the discharge concentrates is surrounded by a peripheral wall formed in the insulating tube, or at the same time, the corner of the inner edge of the first lead is rounded. Dispersion and reduction of the electric field strength at the inner end of one lead makes it difficult to generate arc discharge.

1 is a cross-sectional view of a temperature-sensitive pellet type thermal fuse 10 according to a first embodiment of the present invention. Sectional drawing of the temperature sensitive pellet type | mold thermal fuse 20 of Example 2 which concerns on this invention is shown. Sectional drawing of the conventional temperature sensitive pellet type | mold thermal fuse (a) and (b) is shown.

  According to the present invention, at least a temperature-sensitive pellet that melts or softens at a specific temperature, a strong compression spring that presses the temperature-sensitive pellet, and a cylindrical case that has good conductivity and good heat conductivity. An insulating tube that closes the open end, a weak compression spring that is in contact with the insulating tube, a first lead that has an inner end penetrating the insulating tube as a contact portion, and a movable that is electrically connected to the first lead and the cylindrical case In a temperature-sensitive pellet type thermal fuse having a contact and further comprising a second lead disposed at one end of the cylindrical case, the inner end periphery of the first lead is surrounded by a peripheral wall formed in an insulating tube. The gap L1 between the insulating tube and the movable contact is suppressed to a predetermined dimension or less to suppress the exposed area of the inner end of the first lead, so that the movable contact contacting the first lead and the first lead are separated. Wall from arc discharge generated during and after breaking Thermal fuse shielded from metal components such as a weak compression spring arranged outside is provided. In one preferred configuration, the gap from the peripheral wall end provided in the insulating tube inserted through the first lead to the movable contact (that is, the length of the portion where the first lead tip is exposed from the end surface of the insulating tube) is set to L1. When the distance from the first lead end to the weak compression spring is X, and the ratio of X / L1 is at least 0.6 or more, the metal parts can be separated from the arc discharge generated after the opening between the two contacts and the opening. Can be effectively shielded. More preferably, the ratio of X / L1 is 1.0 or more. In addition, it is preferable to round off the corners of the outer periphery of the first lead inner end to disperse the electric field concentrated on the inner end of the first lead.

  As shown in FIG. 1, the temperature-sensitive pellet type thermal fuse 10 of the present invention has a silver plated copper alloy cylindrical case 18 provided with a second lead 19 of a silver plated copper material fixed by caulking at one end. A chemical temperature-sensitive pellet 15 that melts at a specific temperature, two metal plates 80, a strong compression spring 14 that is interposed between both metal plates 80 and presses the temperature-sensitive pellet 15, and one side The silver alloy movable contact 17 that is in contact with the metal plate 80 and is in sliding contact with the inner wall of the cylindrical case 18, the ceramic insulating tube 12 that closes the opening end of the cylindrical case 18, and the central portion of the insulating tube 12 A first lead 11 made of silver-plated copper with a penetrating inner end as a contact, a weak compression spring 13 sandwiched between the insulating tube 12 and the movable contact 17, and the inside of the cylindrical case 18 is epoxy Airtight sealing with resin sealing material 70 and sealing And a ceramic porcelain bushing 90 to 70 ends. The insulating tube 12 is fixed to the lead sandwiched between the protrusion 101 provided on the first lead and the flange portion 100, and the inner end peripheral edge of the first lead 11 contacting the movable contact 17 at the same time is the insulating tube. It is arranged so as to be surrounded by 12 peripheral walls 16. At this time, by setting the ratio X / L1 between the gap L1 from the end of the peripheral wall 16 to the movable contact 17 and the distance X from the first lead end to the weak compression spring to be at least 0.6 or more, Metal parts can be effectively shielded from arc discharge generated after breaking. More preferably, X / L1 is 1.0 or more. Thereby, metal parts such as the weak compression spring 13 disposed outside the peripheral wall 16 are shielded from arc discharge generated when the contact of the first lead 11 and the movable contact 17 are separated and after the separation. In the temperature-sensitive pellet type thermal fuse 10 of the first embodiment, a counterbore which has been shallowly provided at the distal end portion of the insulating tube 12 for the purpose of improving the seating of the flange portion provided exclusively on the distal end side of the first lead is conventionally used. 16 so that the contact-side end of the first lead 11 can be shielded by the peripheral wall 16 of the insulating tube 12, and the outer corner of the inner end of the first lead is rounded to round the electric field. Prevents concentration on corners. At this time, instead of making the countersink of the insulating tube 12 shallower than before, the flange portion provided on the first lead tip side is made closer to the first lead tip side so that the gap L1 from the end of the peripheral wall 16 to the movable contact 17 is increased. It may be shortened.

  Here, as Example 1 of the present invention, the temperature-sensitive pellet type temperature fuse according to the present invention and the temperature-sensitive pellet type temperature fuse 10 of the comparative example are manufactured by the SEFUSE (registered trademark) SF-E series, and this is energized. Results of comparison and evaluation by counting the number of specimens whose insulation resistance value was below the standard value by placing them in the furnace while applying a load and forcibly operating them under severe temperature loads exceeding the practical upper limit. Post.

  The maximum diameter of the exposed portion of the first lead of the thermal pellet type thermal fuse 10 shown in FIG. 1 is fixed to 1.0 mm, and the shortest distance X from the first lead surface to the weak compression spring 13 is fixed to 0.7 mm. In a high-temperature bath in which 50 temperature-sensitive pellet type temperature fuses each having a gap L1 from the end of the peripheral wall 16 to the movable contact 17 adjusted to 0.3 mm to 2.0 mm were prepared and adjusted to + 100K higher than the operating temperature. Table 1 shows data obtained by measuring the insulation resistance at 500 V DC using a superinsulator and counting and comparing the number of insulation resistance values below 0.2 MΩ. In Comparative Example 1-1 in Table 1, since L1 is 2 mm and the distance X to the weak compression spring is 0.7 mm, X / L1 is 0.35 times. In accordance with this, X / L1 of Comparative Example 1-2 is 0.44 times, X / L1 of Comparative Example 1-3 is 0.54 times, and X / L1 of Example 1-1 is 0.60 times. X / L1 of Example 1-2 is 0.70 times, X / L1 of Example 1-3 is 1.00 times, and X / L1 of Example 1-4 is 1.40 times. It shows that.

  As a result of counting the number of each of the 50 test temperature fuses in Table 1 whose insulation resistance value was less than 0.2 MΩ, Comparative Example 1-1 to Comparative Example 1 in which both X / L1 were less than 0.6 -3, 3 to 7 were generated that were less than 0.2 MΩ within 1 minute, but in Example 1-1 where X / L1 was 0.6, the number was less than 0.2 MΩ within 1 minute. Was zero. Further, in Example 1-2 in which X / L1 is 0.7, the total number of 0.2 MΩ or more can be maintained for 5 minutes, and Examples 1-3 and 1-4 in which X / L1 is 1.0 or more can be maintained. Then, the insulation resistance value could be maintained for 15 minutes.

  A temperature-sensitive pellet type thermal fuse 20 according to the second embodiment of the present invention is a cylindrical case made of a silver-plated copper alloy provided with a second lead 29 of a tin-plated copper material that is caulked and fixed to one end as shown in FIG. 28, a chemical temperature sensitive pellet 25 that melts at a specific temperature, two metal plates 80, and a strong compression spring provided between the metal plates 80 so as to press the temperature sensitive pellet 25. 24, a silver alloy movable contact 27 that is in contact with one metal plate 80 and slidably in contact with the inner wall of the cylindrical case 28, a ceramic insulating tube 22 that closes the open end of the cylindrical case 28, and the insulating tube 22 A first lead 21 made of a silver-plated copper material having an inner end penetrating through the central portion thereof as a contact head 100, and a weak compression spring 23 sandwiched between the insulating tube 22 and the movable contact 27, and Epoxy resin sealing for hermetically sealing the inside of the cylindrical case 28 Equipped with a 70. The insulating tube 22 is sandwiched between the protrusion 101 provided on the first lead 21 and the contact head 100 and fixed to the lead. At the same time, the contact head 100 contacting the movable contact 27 is connected to the insulating tube 22. It is arranged so as to be surrounded by the peripheral wall 26. At this time, by setting the ratio X / L1 of the gap L1 from the end of the peripheral wall 26 to the movable contact 27 and the distance X from the first lead end to the weak compression spring to be at least 0.6 or more, Metal parts can be effectively shielded from arc discharge generated after breaking. More preferably, X / L1 is 1.0 or more. Thereby, metal parts such as the weak compression spring 23 arranged outside the peripheral wall 26 are shielded from arc discharge generated when and after the contact of the first lead 21 and the movable contact 27 are separated. The temperature-sensitive pellet type thermal fuse 20 according to the second embodiment is improved so that the contact head portion 100 that has been conventionally provided inside the first lead end in a completely exposed state can be shielded by the peripheral wall 26 provided in the insulating tube 22. doing. In this case, it is not necessary to change the shape and size of the first lead, and the product can be improved only by providing the peripheral wall 26 in the insulating tube 22. Although not particularly shown, the protrusion 101 has a plurality of protrusions having an outer diameter slightly larger than the inner diameter of the through hole of the insulating tube 22 arranged in advance in the first lead, and these are inserted into the through hole of the insulating tube 22. Therefore, the insulating tube 22 may be fixed so as not to come off.

  Next, as shown in FIG. 2, the SEFUSE (registered trademark) SF-L series member is applied to the temperature-sensitive pellet type thermal fuse 20 of the second embodiment in which the contact head 100 is surrounded by the peripheral wall 26 of 0.3 mm. It is manufactured by applying it to the furnace while energizing it and subjecting it to a severe temperature load exceeding the practical upper limit, forcing it to operate, and counting the number of specimens with insulation resistance values below the standard value The results of comparative evaluation are posted.

  The first lead diameter φ1 of the temperature-sensitive pellet type thermal fuse 20 shown in FIG. 2 is in the range of 0.6 mm to 2.0 mm, and the distance X from the first lead surface to the weak compression spring is 0.3 mm to 1.0 mm. In this range, each of the 50 temperature-sensitive pellet type temperature fuses prepared by fixing the gap L1 from the end of the peripheral wall 26 to the movable contact 27 to 1.0 mm was adjusted to a temperature + 100K higher than the operating temperature. Table 2 shows data obtained by measuring the insulation resistance at 500 V DC using a superinsulator after counting for 1 to 15 minutes, and counting and comparing the number of insulation resistance values less than 0.2 MΩ. In Comparative Example 2-1 in Table 2, since L1 is 1.00 mm and the distance X to the weak compression spring is 0.30 mm, X / L1 is 0.3 times. In accordance with this, X / L1 of Comparative Example 2-2 is 0.4 times, X / L1 of Comparative Example 2-3 is 0.5 times, and X / L1 of Example 2-1 is 0.6 times. X / L1 of Example 2-2 is 0.7 times, X / L1 of Example 2-3 is 0.8 times, and X / L1 of Example 2-4 is 1.0 times. It shows that.

  As a result of counting the number of each of the 50 test temperature fuses in Table 2 whose insulation resistance value was less than 0.2 MΩ, Comparative Example 2-1 to Comparative Example 2 in which both X / L1 were less than 0.6 -3, 7 to 48 counts were generated that were less than 0.2 MΩ within 1 minute, but in Example 2-1 where X / L1 was 0.6, the number fell below 0.2 MΩ within 5 minutes. There were 0 things. In Example 2-2 and Example 2-3 in which X / L1 is 0.7 or more, the total number of 0.2 MΩ or more can be maintained for 10 minutes, and further, Example 2- in which X / L1 is 1.0 or more. In No. 4, the insulation resistance value could be maintained for 15 minutes or more.

  Next, the first lead diameter φ1 of the temperature sensitive pellet type thermal fuse 20 shown in FIG. 2 is 1.8 mm, the distance X from the first lead surface to the weak compression spring is 0.7 mm, and the end of the peripheral wall 26 (Comparative Example 3). -1 is an insulating tube end corresponding to the end of the peripheral wall 26) to the movable contact 27, and the peripheral wall 16 is compared with the comparative example 3-1 of the conventional structure in which the peripheral wall 16 is not provided on the condition that the gap L1 is fixed to 0.8 mm. 50 each of the temperature-sensitive pellet type temperature fuses of Example 3-1 provided were prepared and held in a high-temperature bath adjusted to + 100K higher than the operating temperature for 1 to 15 minutes, and then a superinsulator was used. Table 3 shows data obtained by measuring the insulation resistance at a direct current of 500 V and counting and comparing the number of insulation resistance values less than 0.2 MΩ.

  As a result of counting the number of each of the 50 test temperature fuses in Table 3 whose insulation resistance value was less than 0.2 MΩ, X / L1 was 0.6 or more in Comparative Example 3-1, which does not have a peripheral wall structure. Even though 0.8 was less than 0.2 MΩ within 5 minutes, 7 were generated after 15 minutes, but in Example 3-1, 0 was within 10 minutes. 0 were below 0.2 MΩ, and 2 were below 0.2 MΩ within 15 minutes. From the result of the comparative test described above, it is not necessary to change the shape and dimensions of the first lead, and the product can be improved only by providing the peripheral wall 26 in the insulating tube 22.

  INDUSTRIAL APPLICABILITY The present invention can be used for a high-current contact-opening type thermal fuse that has a movable contact and senses an abnormal temperature to open the contact, and is particularly suitable for a temperature-sensitive pellet-type temperature fuse.

10, 20 ... the temperature sensitive pellet type thermal fuse of the embodiment,
11, 21 ... first lead, 12, 22 ... insulating tube,
13, 23 ... weak compression springs, 14, 24 ... strong compression springs,
15, 25 ... temperature-sensitive pellets, 16, 26 ... peripheral walls,
17, 27 ... movable contact, 18, 28 ... cylindrical case,
19, 29 ... second lead, 70 ... sealing material,
80 ... Metal plate, 90 ... Steel pipe,
100 ... flange or contact head, 101 ... projection,
L1: A gap between the insulating tube and the movable contact,
X: Distance from the first lead end to the weak compression spring,
φ1: Maximum wire diameter of the exposed portion of the first lead end.

Claims (4)

  Inside the cylindrical case having good conductivity and good thermal conductivity, at least a temperature-sensitive pellet that melts or softens at a specific temperature, a strong compression spring that presses the temperature-sensitive pellet, and an opening end of the cylindrical case An insulating tube to be closed, a weak compression spring in contact with the insulating tube, a first lead having an inner end penetrating the insulating tube as a contact portion, and the first lead and the cylindrical case are electrically connected. In the temperature-sensitive pellet type thermal fuse having a movable contact and further comprising a second lead disposed at one end of the cylindrical case, an inner end of the first lead between the insulating tube and the movable contact Temperature-sensitive pellet type thermal fuse with reduced exposed area.   The inner periphery of the first lead is surrounded by a peripheral wall formed in the insulating tube, and the gap L1 between the insulating tube and the movable contact is narrowed to suppress the exposed area of the inner end of the first lead. The temperature-sensitive pellet type thermal fuse according to claim 1.   The temperature-sensitive pellet according to claim 1 or 2, wherein a distance from the gap L1 and the first lead end to the weak compression spring is X, and a ratio of X / L1 is at least 0.6 or more. Mold temperature fuse. The temperature-sensitive pellet mold according to claim 1 or 2, wherein a distance from the gap L1 and the first lead end to the weak compression spring is X, and a ratio of X / L1 is 1.0 or more. Thermal fuse.

Images