JP5573584B2 - Overcurrent detection element - Google Patents

Description

  The present invention relates to an overcurrent detection element.

  Conventionally, a fusible fuse has been used as an overcurrent interrupting device that is disposed in a conductive path connecting a power source and a load and interrupts an overcurrent flowing through the conductive path. However, since the fuse needs to be replaced by melting, an overcurrent interrupt device that does not use a fuse has been proposed for maintenance-free purposes. As this type of overcurrent interrupt device, for example, the one described in Patent Document 1 is known.

  In the above overcurrent interrupt device, the structure for detecting overcurrent is formed by winding a circuit conductor around temperature sensing means, and this temperature sensing means is connected to a signal line. When the overcurrent flows and the temperature of the circuit conductor rises, the temperature of the temperature sensing means rises. Then, the resistance value of the temperature sensing means changes and the voltage at both ends of the temperature sensing means (the current flowing through the temperature sensing means) changes. Overcurrent is generated by cutting off the circuit based on this voltage (current). Is to prevent.

JP-A-10-108357

  However, according to the above configuration, the circuit conductor generates heat due to an overcurrent flowing through the circuit conductor, and this heat is transmitted to the temperature sensing means, the temperature of the temperature sensing means rises, and the voltage across the temperature sensing means changes. To do. For this reason, if a large current flows in a very short time, a time delay occurs until the heat generated in the circuit conductor is transferred to the temperature sensing means, and this time delay causes overcurrent interruption at an appropriate timing. There is concern that it cannot be done.

  The present invention has been completed based on the above situation, and an object of the present invention is to provide an overcurrent detecting element capable of executing an overcurrent interruption with high accuracy.

The present invention is an overcurrent detection element that is arranged in a conductive path connecting a power source and a load and that is used in an overcurrent interrupting device that blocks overcurrent flowing through the conductive path, and is in series with the conductive path. A metal first plate portion to be connected, a metal second plate portion arranged adjacent to the first plate portion, a first electrode connected to the first plate portion, and the second plate A heat-sensitive part that has a second electrode connected to the part and has a characteristic according to the temperature of the first plate part during energization and generates a signal according to the temperature, and the second plate part has One corner portion, the corner portion is opposed to a side edge of the first plate portion via a gap portion set at a predetermined interval, and the corner portion of the side edge of the second plate portion On both sides of the gap part by two side edges forming a part and a side edge of the first plate part facing the corner part The are two narrow portions forming a V-shape comprising a narrow shape is formed toward the gap portion, wherein the thermosensitive portion is arranged so as to straddle one of the two said narrow portion.

  According to the present invention, the heat sensitive part is connected to the first plate part via the first electrode and is connected to the second plate part via the second electrode. For this reason, when an overcurrent flows through the conductive path, the overcurrent flows through the first plate portion connected in series with the conductive path. Then, the heat generated in the first plate part due to the overcurrent is directly transferred from the first electrode connected to the first plate part to the heat sensitive part. As a result, the heat sensitive part can generate a signal corresponding to the temperature at an appropriate timing and directly transmit it from the second electrode to the control part via the second plate part. Even when it flows through the conductive path, overcurrent interruption can be executed at an appropriate timing.

  Furthermore, if the heat sensitive part is downsized and the heat capacity of the heat sensitive part is reduced, the temperature of the heat sensitive part is likely to rise, so that it is considered that overcurrent interruption can be executed with higher accuracy. In order to reduce the size of the heat sensitive part, it is necessary to process the first plate part and the second plate part with high accuracy and to form a small gap so that a small heat sensitive part can be arranged. However, pressing the side edges of the first plate portion and the second plate portion while forming a relatively small gap over a relatively wide range is considered from the viewpoint of press processing accuracy. Difficult.

According to the present invention, the side edge of the first plate portion and the one corner portion of the second plate portion are arranged adjacent to each other via the gap portion set at a predetermined interval. Two narrow portions having a V shape are formed on both sides of the gap portion. As a result, by forming two narrow portions having a V shape by press working, a gap portion set at a relatively small interval can be easily formed. In the present invention, only the vicinity of the gap portion of the narrow portion may be controlled so as to have a relatively small gap, and therefore, it can be easily pressed. By disposing the heat sensitive part on one of the narrow parts formed on both sides of the gap part, a relatively small heat sensitive part can be connected to the first plate part and the second plate part. Thereby, the overcurrent interruption can be executed with higher accuracy.

As embodiments of the present invention, the following embodiments are preferable.
It is preferable that a portion of the first plate portion to which the first electrode is connected is a heat generating portion that generates heat when energized, and the heat generating portion and the heat sensitive portion are integrally covered with a synthetic resin portion.

  It is not only when a large current flows in a short time that it is necessary to interrupt the overcurrent. For example, when the overcurrent flows only for a short time, such as a so-called inrush current, the wire does not smoke because it does not reach the smoke generation temperature, but the wire reaches the smoke generation temperature as the overcurrent flows longer. Makes it easier to smoke.

  According to this aspect, the heat generated in the heat generating part of the first plate part due to the overcurrent flowing in the first plate part is not only directly transmitted to the heat sensitive part, but also transmitted to the heat sensitive part via the synthetic resin part. Is done. For this reason, it becomes possible to adjust the thermal time constant of the temperature-time characteristic acquired by the heat sensitive part by the synthetic resin part. Thereby, an overcurrent interruption with high accuracy can be performed.

  According to the present invention, it is possible to execute an overcurrent interruption with high accuracy.

The figure which shows the electrical constitution of the overcurrent interruption apparatus which concerns on Embodiment 1. Top view showing overcurrent detection element Side view showing overcurrent detection element The top view which shows the process of performing press processing to a metal plate material The top view which shows the press process which forms a 2nd narrow part The top view which shows the process of connecting a heat sensitive part The top view which shows the process of cut | disconnecting a board part side tie bar The top view which shows the process of forming a synthetic resin part FIG. 5 is a plan view showing an overcurrent detection element according to the second embodiment. FIG. 5 is a plan view showing an overcurrent detection element according to the third embodiment.

<Embodiment 1>
A first embodiment in which an overcurrent detection element 20 according to the present invention is applied to an overcurrent interrupt device 10 will be described with reference to FIGS. The overcurrent interrupt device 10 is arranged in a conductive path 11 that connects a power source B mounted on a vehicle (not shown) and a load M. As the load M, an arbitrary load M such as a motor, a heater, or the like can be adopted as necessary. The conductive path 11 includes an arbitrary conductive path 11 such as an electric wire, a terminal fitting, a bus bar, or a conductor pattern formed on the circuit board 12 by a printed wiring technique.

(Overcurrent interrupt device 10)
As shown in FIG. 1, the overcurrent interrupt device 10 includes a circuit board 12 having a conductive path 11 connected to a path from a power supply B to a load M, an overcurrent detection element 20 mounted on the circuit board 12, and And a switching element 13 for energizing or disconnecting the conductive path 11 and a control unit 14 for controlling on / off of the switching element 13. As the control unit 14, for example, a CPU that executes a predetermined program stored in a memory (not shown) may be used, or the control unit 14 may be configured by a circuit.

  In the present embodiment, the switching element 13 is a semiconductor relay. Specifically, an N-type MOSFET is used. In this case, the supply of power to the load M can be cut off by connecting the source and drain to the conductive path 11 that supplies power to the load M and supplying a signal from the control unit 14 to the gate.

  An overcurrent detection element 20 is connected to the switching element 13 via the conductive path 11. The overcurrent detection element 20 is connected in series to the conductive path 11 and is connected to the load M. The overcurrent detection element 20 includes a heat sensitive part 24 that is branched from the conductive path 11 and connected thereto. Although not shown in detail, the overcurrent detection element 20 is connected to the conductive path 11 of the circuit board 12 by a known method such as soldering.

  The heat sensitive part 24 of the overcurrent detection element 20 is grounded via a resistor R mounted on the circuit board 12. The heat sensitive unit 24 has a characteristic corresponding to the temperature and generates a signal corresponding to the temperature. In the present embodiment, the heat sensitive unit 24 changes the voltage according to the temperature. The control unit 14 acquires the voltage output from the heat sensitive unit 24, compares this voltage with a predetermined threshold value, and turns off the switching element 13 when the voltage exceeds the predetermined threshold value.

(Overcurrent detection element 20)
As shown in FIG. 2, the overcurrent detection element 20 includes a metal first plate portion 30 connected in series to the conductive path 11 and a metal disposed adjacent to the side of the first plate portion 30. The second plate portion 31 is connected to the first plate portion 30 and the second plate portion 31 and has a characteristic corresponding to the temperature of the first plate portion 30 during energization, and a signal corresponding to this temperature is provided. And a heat-sensitive part 24 to be generated.

  The first plate portion 30 and the second plate portion 31 are formed by pressing a metal plate material into a predetermined shape. The first plate portion 30 has an elongated plate shape and is bent near the center in the longitudinal direction (left-right direction in FIG. 2). Also, the second plate portion 31 has a long and narrow rectangular shape. The length dimension of the second plate portion 31 is set shorter than that of the first plate portion 30. The second plate portion 31 has four corner portions 32. Among the corner portions 32, one corner portion 32 </ b> A is arranged to face the side edge of the first plate portion 30. A gap portion 33 set at a predetermined interval is formed between the corner portion 32 </ b> A and the first plate portion 30. The first plate portion 30 and the second plate portion 31 are generally arranged in a Y shape when viewed from above.

The two side edges forming the corner portion 32A of the second plate portion 31 and the side edges of the first plate portion 30 opposed to the corner portion 32A are both sides of the gap portion 33 (both sides in the left-right direction in FIG. 2). ) Are formed with a first narrow portion 34 and a second narrow portion 35 having a V shape that becomes narrower as the gap portion 33 is approached.

  The heat-sensitive part 24 is arranged in the first narrow part 34 located on the left side in FIG. 2 among the narrow parts. In the present embodiment, the heat sensitive part 24 uses an NTC thermistor. The NTC thermistor is a thermistor whose resistance decreases with increasing temperature, and is formed by covering a longitudinal end portion of a rectangular parallelepiped thermistor body having an internal electrode with a metal plating made of Pb or the like. The heat sensitive part 24 includes a first electrode 36 connected to the first plate part 30 and a second electrode 37 connected to the second plate part 31. The first plate portion 30 and the first electrode 36 and the second plate portion 31 and the second electrode 37 are connected by known brazing (in this embodiment, soldering). The heat sensitive part 24 is arranged so as to straddle the first narrow part 34.

  A region of the first plate portion 30 to which the first electrode 36 of the heat sensitive portion 24 is connected is a heat generating portion 38 that generates heat when energized. The heat generating portion 38 and the heat sensitive portion 24 are integrally covered with a synthetic resin portion 39. As shown in FIGS. 2 and 3, the synthetic resin portion 39 has a rectangular parallelepiped shape. The synthetic resin portion 39 is in close contact with the heat generating portion 38 and the heat sensitive portion 24 without any gap. As the synthetic resin constituting the synthetic resin portion 39, various known materials such as a thermosetting resin (such as an epoxy resin) and a thermoplastic resin (such as polyolefin, polyamide, and polyester) can be used.

  A portion of the first plate portion 30 that protrudes from the synthetic resin portion 39 is connected to the conductive path 11 of the circuit board 12 by a known method such as soldering. Further, a portion of the second plate portion 31 that protrudes from the synthetic resin portion 39 is electrically connected to the control portion 14.

(Production method)
Next, an example of a method for manufacturing the overcurrent detection element 20 will be described with reference to FIGS. First, as shown in FIG. 4, by pressing a metal plate material, the frame 50, the first plate portion 30 connected to the frame 50 by a frame-side tie bar 51, and the frame 50 And the second plate portion 31 connected to the first plate portion 30 by the plate portion side tie bar 52 while being connected by the frame side tie bar 51. At this stage, the first narrow portion 34 is formed between the first plate portion 30 and the second plate portion 31, but the second narrow portion 35 is not yet formed. For this reason, the gap part 33 is not formed yet. Further, the first plate portion 30 and the second plate portion 31 are connected by a plate portion side tie bar 52 having a shape that straddles the first narrow portion 34. In FIG. 4, a plurality of first plate portions 30 and second plate portions 52 are connected to the frame pair 50. In addition, the code | symbol was attached | subjected with respect to the 1st board part 30 and the 2nd board part 52 which were described in the uppermost part in FIG. 4, and it abbreviate | omitted about the other thing. The same applies to FIGS. 5 to 8 below.

  Subsequently, as shown in FIG. 5, the second narrow portion 35 is formed between the first plate portion 30 and the second plate portion 31 by further pressing. As a result, a gap portion 33 is formed between the first plate portion 30 and the second plate portion 31 with a predetermined interval.

  Next, solder is printed at predetermined positions on the first plate portion 30 and the second plate portion 31. Next, as shown in FIG. 6, the heat sensitive portion 24 is disposed between the first plate portion 30 and the second plate portion 31 so as to straddle the first narrow portion 34, and reflow soldering is performed.

  Subsequently, as shown in FIG. 7, the plate portion tie bar 52 is cut by further pressing.

  Thereafter, the heat generating portion 38 and the heat sensitive portion 24 are arranged in a mold (not shown), and a synthetic resin is injected into the mold cavity and solidified. Thereby, the synthetic resin part 39 which covers the heat generating part 38 and the heat sensitive part 24 integrally is formed.

  Subsequently, the frame side tie bar 51 is cut by pressing. Thereby, the overcurrent detecting element 20 is completed.

(Function, effect)
Then, the effect | action and effect of this embodiment are demonstrated. According to the present embodiment, the thermosensitive part 24 is connected to the first plate part 30 via the first electrode 36 and is connected to the second plate part 31 via the second electrode 37. For this reason, when an overcurrent flows through the conductive path 11, the overcurrent flows through the first plate portion 30 connected in series to the conductive path 11. Then, the heat generated in the first plate portion 30 due to this overcurrent is directly transmitted to the heat sensitive portion 24 from the first electrode 36 connected to the first plate portion 30. As a result, the heat sensitive unit 24 can generate a signal corresponding to the temperature at an appropriate timing, and can directly transmit the signal from the second electrode 37 to the control unit 14 via the second plate unit 31. Even when a large current flows through the conductive path 11, overcurrent interruption can be performed at an appropriate timing.

  Furthermore, if the heat-sensitive part 24 is downsized to reduce the heat capacity of the heat-sensitive part 24, the temperature of the heat-sensitive part 24 is likely to rise, so it is considered that overcurrent interruption can be executed with higher accuracy. In order to reduce the size of the heat sensitive part 24, it is necessary to process the first plate part 30 and the second plate part 31 with high accuracy and to form a small gap so that the small heat sensitive part 24 can be disposed. However, pressing the side edge of the first plate part 30 and the side edge of the second plate part 31 over a relatively wide range while forming a relatively small gap is an accuracy of the pressing process. Difficult to see from.

According to this embodiment, the side edge of the first plate portion 30 and one corner portion 32 of the second plate portion 31 are arranged adjacent to each other via the gap portion 33 set at a predetermined interval. . On both sides of the gap portion 33, two narrow portions having a V shape are formed. As a result, the gap portion 33 set at a relatively small interval can be easily formed by forming two V-shaped narrow portions by press working. In the present invention, only the vicinity of the gap portion 33 in the narrow portion only needs to be controlled so as to have a relatively small gap, so that it can be easily pressed. By disposing the heat sensitive portion 24 on one of the narrow portions formed on both sides of the gap portion 33, the relatively small heat sensitive portion 24 can be connected to the first plate portion 30 and the second plate portion 31. Thereby, the overcurrent interruption can be executed with higher accuracy.

  Moreover, it is not only when a large current flows in a short time that it is necessary to interrupt the overcurrent. For example, when the overcurrent flows only for a short time, such as a so-called inrush current, the wire does not smoke because it does not reach the smoke generation temperature, but the wire reaches the smoke generation temperature as the overcurrent flows longer. Makes it easier to smoke.

  For this reason, in the case of the overcurrent detection element 20 in which the heat sensitive part 24 is immediately heated by the heat generated by the overcurrent flowing through the conductive path 11 and the resistance value changes, the electric wire is still at the smoke generation temperature. There is a concern that the circuit may be shut off despite the allowance.

  According to the present embodiment, the heat generated in the heat generating portion 38 of the first plate portion 30 due to the overcurrent flowing in the first plate portion 30 is not directly transmitted to the heat sensitive portion 24 but also via the synthetic resin portion 39. However, it is transmitted to the heat sensitive part 24. For this reason, it becomes possible to adjust the thermal time constant of the temperature-time characteristic acquired by the heat sensitive part 24 by the synthetic resin part 39. Thereby, it is possible to perform overcurrent interruption with high accuracy even for an electric wire that tends to emit smoke as the overcurrent flow time becomes longer.

<Embodiment 2>
Next, Embodiment 2 of the present invention will be described with reference to FIG. In the present embodiment, the heat sensitive part 24 is disposed closer to the gap part 33 than the heat sensitive part 24 according to the first embodiment. Since the configuration other than the above is substantially the same as that of the first embodiment, the same members are denoted by the same reference numerals, and redundant description is omitted.

  Since the first narrow portion 34 is formed to become narrower as it approaches the gap portion 33, in order to arrange the smaller heat sensitive portion 24 in the first plate portion 30 and the second plate portion 31, the heat sensitive portion 24 should be close to the gap 33. As described above, according to the present embodiment, since the heat-sensitive part 24 of various sizes can be arranged without changing the shapes of the first plate part 30 and the second plate part 31, an overcurrent detection element About 20, the freedom degree of design can be improved. Further, by selectively using the heat-sensitive parts 24 having different sizes, it is possible to perform overcurrent interruption with high accuracy according to the characteristics of the conductive path 11.

<Embodiment 3>
Next, Embodiment 3 of the present invention will be described with reference to FIG. In the present embodiment, the width dimension of the heat generating portion 38 to which the first electrode 36 of the heat sensitive portion 24 is connected is formed narrower than the other portions of the first plate portion 30. Since the configuration other than the above is substantially the same as that of the first embodiment, the same members are denoted by the same reference numerals, and redundant description is omitted.

  According to the present embodiment, the amount of heat generated by the heat generating portion 38 is greater than that of other portions of the first plate portion 30 during energization. As a result, when an overcurrent flows through the heat generating portion 38, the temperature of the heat sensitive portion 24 is likely to rise, so that the overcurrent can be interrupted with higher accuracy.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.
(1) In the present embodiment, the heat sensitive part 24 and the heat generating part 38 are integrally covered with the synthetic resin part 39, but the present invention is not limited to this, and the heat sensitive part 24 and the heat generating part 38 are exposed. Also good. Further, the heat-sensitive part 24 and the heat-generating part 38 may be integrally covered with an arbitrary material such as glass.
(2) In this embodiment, although the 1st board part 30 was made into the form bent, it is not restricted to this, It may be made into the shape which makes straight shape, and can be made into arbitrary shapes as needed.
(3) In the present embodiment, the second plate portion 31 has a rectangular shape, but is not limited thereto, and may be a polygonal shape such as a triangular shape or a pentagonal shape. Moreover, if the one corner | angular part 32 is formed, the 2nd board part 31 can be made into arbitrary shapes.
(4) In the present embodiment, the heat sensitive part 24 is arranged in the first narrow part 34, but the heat sensitive part 24 may be arranged in the second narrow part 35.
(5) In the present embodiment, the switching element 13 is a semiconductor relay, but is not limited thereto, and may be a mechanical relay.
(6) In the present embodiment, an NTC thermistor is used for the heat sensitive part 24, but a PTC thermistor may be used.
(7) In the third embodiment, the width dimension of the heat generating part 38 is formed to be narrower than other parts of the first plate part 30, but the present invention is not limited to this, and the thickness dimension of the heat generating part 38 is not limited thereto. May be formed to be thinner than other portions of the first plate portion 30. On the contrary, the width dimension of the heat generating part 38 is formed wider than the other part of the first plate part 30, or the thickness dimension of the heat generating part 38 is made thicker than the other part of the first plate part 30. It may be formed thick. By adjusting the thickness dimension and the width dimension of the heat generating portion 38 in this way, it is possible to execute overcurrent interruption with higher accuracy.

DESCRIPTION OF SYMBOLS 10 ... Overcurrent interrupting device 11 ... Conductive path 20 ... Overcurrent detection element 24 ... Heat sensitive part 30 ... 1st board part 31 ... 2nd board part 32 ... Corner | angular part 33 ... Gap part 34 ... 1st narrow part 35 ... 2nd narrow part 36 ... 1st electrode 37 ... 2nd electrode 38 ... Heat generating part 39 ... Synthetic resin part B ... Power supply M ... Load

Claims (3)

An overcurrent detection element used in an overcurrent interrupting device that is arranged in a conductive path connecting a power source and a load and interrupts an overcurrent flowing through the conductive path,
A metal first plate portion connected in series to the conductive path, a metal second plate portion disposed adjacent to the first plate portion, and a first connected to the first plate portion. A heat-sensitive part that has a second electrode connected to the electrode and the second plate part and has a characteristic according to the temperature of the first plate part during energization and generates a signal according to the temperature;
The second plate portion has one corner portion, and the corner portion faces a side edge of the first plate portion through a gap portion set at a predetermined interval,
Of the side edges of the second plate portion, two side edges forming the corner portion and a side edge of the first plate portion facing the corner portion are provided on both sides of the gap portion on the gap portion. Two narrow portions having a V shape that become narrower as the distance from
The thermosensitive element is an overcurrent detection element arranged so as to straddle one of the two narrow parts. The portion of the first plate portion to which the first electrode is connected is a heat generating portion that generates heat when energized, and the heat generating portion and the heat sensitive portion are integrally covered with a synthetic resin portion. Element for overcurrent detection. The overcurrent detection element according to claim 2, wherein the heat generating portion is formed narrower than other portions of the first plate portion.

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