Housing

Abstract

A resin housing for accommodating an electronic substrate in the interior thereof, the housing comprising a flame retardant material having a prescribed flame retardancy between the housing inner walls and the electronic substrate in the interior of the housing.

Description

Housing

[0001] The present invention relates to a housing for housing an electronic substrate therein.

[0002] In a power supply circuit for an in-vehicle electronic control device, when an overcurrent that causes overheating is detected from the detection result of a current detection circuit, a technique of turning off a transistor as a protection operation is known (Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2004-147391

[0004] However, the technique described in Patent Document 1 performs a protection operation against overcurrent to prevent overheating of the electronic substrate. However, when overheating of the electronic substrate cannot be prevented, there is a problem that the housing for housing the electronic substrate may melt or catch fire due to the overheating of the electronic substrate.

[0005] The problem to be solved by the present invention is to provide a housing that can prevent melting or ignition when the electronic substrate housed therein overheats.

[0006] The present invention is a resin housing for housing an electronic substrate therein, and solves the above problem by providing a flame-retardant material having a predetermined flame retardancy between the inner wall of the housing and the electronic substrate inside the housing.

[0007] According to the present invention, when the electronic substrate housed therein overheats, melting or ignition of the housing can be prevented.

[0008] FIG. 1 is a cross-sectional view of an electronic control device to which the housing according to the present embodiment is applied. FIG. 2 is a diagram for explaining an example when the housing according to the present embodiment is applied to an in-vehicle electronic control device. FIG. 3 is a cross-sectional view showing an example of the housing according to the present embodiment.

[0009] The following describes an electronic control device to which the housing according to this embodiment is applied, based on the drawings. The electronic control device is applied, for example, to the ECU (Electronic Control Unit) of a vehicle. Figure 1 is a cross-sectional view of the electronic control device to which the housing according to this embodiment is applied. Figure 1 shows a cross-sectional view of the electronic control device as seen from the side. In Figure 1, the X axis and Y axis are directions along the plane of the electronic circuit board. The Y axis is perpendicular to the X axis in the XY plane. The Z axis is perpendicular to the XY plane. In this embodiment, the electronic control device 1 comprises a housing 10 and an electronic circuit board 20. The housing 10 houses at least the electronic circuit board 20 inside.

[0010] The housing 10 is formed in the shape of a rectangular parallelepiped. The housing 10 is, for example, a case made of synthetic resin. The housing 10 is made of a flammable material. The housing 10 is composed of, for example, a box-shaped case with one side open and a substantially rectangular plate-shaped cover that closes the open side of the case. The case and cover are fastened together, for example, with screws. This creates an internal space in the housing 10 for housing the electronic circuit board 20. The housing 10 is not limited to separate components such as the case and cover, but may also be composed of a single integrated case.

[0011] The housing 10 has side walls 10a that surround the electronic circuit board 20 from all four sides, a top wall 10b that forms the top surface of the electronic circuit board 20, and a bottom wall 10c that forms the bottom surface of the electronic circuit board 20. The housing 10 may be partially made of metal material or the like. For example, the bottom wall 10c may be made of metal material.

[0012] The electronic circuit board 20 is a printed circuit board (PCB) formed from a known material such as a thermoplastic resin, a thermosetting resin, a ceramic, or a composite of glass and resin. The electronic circuit board 20 has a mounting surface 20a on which electronic components are mounted. Electronic components include microcontrollers, transistors, resistors, capacitors, etc. In particular, the electronic components include heat-generating elements, which are electronic components that generate heat. Heat-generating elements are components that generate a large amount of heat. The mounting surface 20a is the surface facing the top wall 10b of the housing 10. In other words, of the pair of main surfaces of the electronic circuit board 20, the surface located on the top wall 10b side becomes the mounting surface 20a for electronic components, and the surface located on the bottom wall 10c side becomes the surface of the electronic circuit board 20 opposite to the mounting surface 20a. This surface 20b is also called the non-mounting surface 20b.

[0013] Inside the housing 10, a flame retardant material 30 having a predetermined flame retardancy is provided between the inner wall of the housing 10 and the electronic circuit board 20. For example, the flame retardant material 30 is placed between the inner side surface 101b of the top wall 10b facing the mounting surface 20a and the mounting surface 20a. The thickness of the flame retardant material 30 may be configured to be less than the thickness of the inner wall of the housing 10 (main body). For example, the flame retardant material 30 is a film-shaped component. The film-shaped flame retardant material 30 is attached to each inner wall of the housing 10, including the inner side surface 101b. This protects the housing 10 no matter where overheating occurs on the electronic circuit board 20. The film-shaped flame retardant material 30 may be attached to the inner side surfaces of the side walls 10a, the top wall 10b, and the bottom wall 10c, or it may be attached to some of the inner side surfaces as long as it is attached to at least the top wall 10b.

[0014] The flame retardancy of the flame retardant 30 is evaluated in advance by flammability tests, etc. Flame retardancy is defined by several different classifications that represent the degree of resistance to burning of a material. The flame retardancy of the flame retardant 30 is higher than that of the housing 10 (main body). For example, the flame retardant 30 is classified into the category that represents the highest flame retardancy according to a predetermined evaluation standard. Specifically, flame retardancy is defined by standards such as the UL94 standard. The flame retardant 30 is, for example, 5VA resin. In the following explanation, 5VA resin is used as an example of the flame retardant 30, but the flame retardant 30 is not limited to this and may be fire-resistant paper, ceramics, or metal foil. If the flame retardant 30 is in film form, the flame retardant 30 is attached to the inner side surface of the housing 10 by film insert molding. The application method of the flame retardant 30 can be, for example, adhesive application, film insert molding, or two-color molding. By applying the flame retardant 30 using film insert molding or two-color molding, the number of work steps can be reduced compared to adhesive application. If the flame retardant 30 is a material to which it can be bonded, the flame retardant 30 may also be attached to the inner side surface of the housing 10 by adhesive application. If the flame retardant 30 is 5VA resin, the flame retardant 30 is attached to the inner side surface of the housing 10 by two-color molding.

[0015] In this embodiment, by attaching a fire-resistant and heat-insulating material to the inner wall of the housing 10, it is possible to prevent fire generated from the electronic circuit board 20 from coming into contact with the housing 10 (main body). This prevents ignition of resin drip generated from the housing 10 even if the housing 10 melts due to heat. Furthermore, by using a flame-retardant material 30 processed into a film shape, film insert molding can be performed, allowing the housing 10 to have fire-resistant properties while reducing the amount of expensive fire-resistant material used.

[0016] The flame retardant 30 may be a resin member that forms a carbonized layer on its surface that is generated and expands due to heat. The carbonized layer is also called char. The carbonized layer of the flame retardant 30 is formed by the overheating of the electronic substrate 20. The carbonized layer has heat insulating and gas barrier properties. When the flame retardant 30 carbonizes, it expands, and the heat insulating properties of the expanded carbonized layer reduce melting that extends to the outside of the housing 10. Furthermore, the gas barrier properties of the expanded carbonized layer prevent ignition at the flash point of the flammable gas generated when the resin is overheated.

[0017] The flame retardant 30 may be positioned such that the carbonized layer comes into contact with the electronic substrate 20 when a carbonized layer is formed. This prevents the spread of fire to the electronic substrate 20 due to the gas barrier properties of the carbonized layer in contact with the electronic substrate 20, even if the electronic substrate 20 is on fire. For example, by bringing the inner side surface 101b of the top wall 10b closer to the electronic substrate 20, the flame retardant 30 attached to the inner side surface 101b is positioned closer to the electronic substrate 20. For example, the distance between the inner side surface 101b of the top wall 10b and the electronic substrate 20 is designed according to the thickness of the carbonized layer that is generated. The thickness of the carbonized layer during expansion is calculated by multiplying the thickness of the flame retardant 30 before expansion by the expansion rate of the carbonized layer. For example, the carbonized layer expands to three times the thickness of the flame retardant 30. Alternatively, the flame retardant 30 may be positioned closer to the electronic substrate 20 by having a predetermined thickness.

[0018] Furthermore, the flame retardant 30 may be arranged to cover the electronic circuit board 20. For example, the flame retardant 30 may be laminated so as to be in contact with a pair of surfaces of the electronic circuit board 20 (mounting surface 20a and non-mounting surface 20b), or the entire electronic circuit board 20 may be sealed with the flame retardant 30. Methods for covering the electronic circuit board 20 with the flame retardant 30 include injection molding, pouching, and heat shrinkage. Moreover, it is not limited to covering the electronic circuit board 20 with the flame retardant 30; the flame retardant 30 may be laminated on the mounting surface 20a of the electronic circuit board 20. By arranging the flame retardant 30 so as to be in direct contact with the electronic circuit board 20, even if the electronic circuit board 20 overheats, a carbonized layer will be generated in the portion of the flame retardant 30 corresponding to the overheated area of ​​the electronic circuit board 20, and the resulting carbonized layer can extinguish the fire. In this embodiment, the flame retardant 30 may be placed on the electronic circuit board 20 side, on the housing 10 side, or on both the electronic circuit board 20 and the housing 10.

[0019] In this embodiment, if the electronic circuit board 20 has a small circuit, the flame retardant material 30 may be provided to cover the electronic circuit board 20. The small circuit is, for example, an electronic circuit used in components such as a map lamp, steering wheel heater, and seat heater. If the electronic circuit board 20 has a large circuit, the flame retardant material 30 may be provided to cover the inner wall of the housing 10. The large circuit is, for example, an electronic circuit used in components such as a USM, BCM, PIU, Meter, and navigation system. Furthermore, if the electronic circuit board 20 is an integrated unit with a vehicle component, the flame retardant material 30 may be provided to cover the inner wall of the housing 10. If the electronic circuit board 20 is an integrated unit with a vehicle component, the housing 10 may be partially made of resin. In this case, the resin portion of the housing 10 is covered with the flame retardant material 30.

[0020] Here, using Figure 2, an example of applying the housing according to this embodiment to an in-vehicle electronic control device will be described. Figure 2 is a diagram illustrating an example of applying the housing according to this embodiment to an in-vehicle electronic control device. The left side of Figure 2 shows the state immediately after the electronic circuit board 20 overheats and ignites. In the left side of Figure 2, a fire 3 is generated on the electronic circuit board 20. The right side of Figure 2 shows the state after some time has passed since the electronic circuit board 20 ignited. In the right side of Figure 2, the housing 10 has melted and resin drip 4 has occurred. In Figure 2, the electronic control device 1 with the housing 10 applied is applied to a vehicle. When the electronic control device 1 is mounted in a vehicle, it is positioned vertically (so that the direction of gravity is parallel to the electronic circuit board 20 and the top wall 10b). In the example of Figure 2, the Y-axis direction is the direction of gravity. That is, the negative direction of the Y-axis is the upper direction of the vehicle, and the positive direction of the Y-axis is the lower direction of the vehicle. Inside the vehicle, flammable materials 2 are present around the electronic control device 1. Specifically, the flammable material 2 inside the vehicle is located in a downward direction relative to the electronic control unit 1.

[0021] In the example shown in Figure 2, the electronic circuit board 20 overheats and ignites inside the housing 10. At this time, as shown in the left diagram of Figure 2, a flame retardant 30 is attached to the inner wall of the housing 10, so even if a fire 3 is generated on the electronic circuit board 20, the fire 3 does not come into contact with the housing 10. Also, as shown in the right diagram of Figure 2, the overheating of the electronic circuit board 20 causes a carbonized layer 31 to form on the inner surface of the flame retardant 30 and expand. The expanded carbonized layer 31 comes into contact with the ignited electronic circuit board 20, extinguishing the fire 3. Furthermore, even if the outer side surface of the housing 10 melts and resin drip 4 is generated due to the overheating of the electronic circuit board 20, the fire 3 from the electronic circuit board 20 does not come into contact with the housing 10, preventing the resin drip 4 from igniting. Therefore, even if the resin drip 4 falls onto flammable materials 2 inside the vehicle, ignition of the flammable materials 2 inside the vehicle can be prevented.

[0022] Furthermore, in this embodiment, the outer wall of the housing 10 may be provided with ribs. Here, an example of ribs provided on the outer wall of the housing according to this embodiment will be described using Figure 3. Figure 3 is a cross-sectional view showing an example of the housing according to this embodiment. Figure 3 shows a modified version of the housing described in Figure 1. Figure 3 shows the electronic control device 1 mounted on a vehicle, similar to Figure 2. The electronic control device 1 is arranged vertically (so that the direction of gravity is parallel to the electronic circuit board 20 and the top wall 10b). In the example of Figure 3, the Y-axis direction is the direction of gravity. That is, the negative direction of the Y-axis is the upper direction of the vehicle, and the positive direction of the Y-axis is the lower direction of the vehicle. Except for the differences between the modified version shown in Figure 3 and the housing described in Figure 1, the description of the housing described in Figure 1 will be appropriately referenced. The difference from the housing described in Figure 1 is that ribs 40 are provided on the outer side surface 102b of the top wall 10b of the housing 10.

[0023] Ribs 40 are attached to the outer side surface 102b of the top wall 10b of the housing 10. There may be one rib 40 or multiple ribs 40. Multiple ribs 40 are arranged in a line along the Y-axis. In the example in Figure 3, three ribs 40 are attached, but the number of ribs 40 is not limited to this; there may be two or fewer, or four or more. The strength of the housing 10 can be increased by attaching the ribs 40. In Figure 3, the outer side surface 102b of the top wall 10b is shown as an example of an "outer wall," but the outer wall on which the ribs 40 are provided is not limited to this. For example, when the housing 10 is positioned on a vehicle, the outer wall on which the ribs 40 are provided may be any outer side surface parallel to the direction of gravity, such as the side wall 10a or the bottom wall 10c.

[0024] The rib 40 protrudes outward (in the positive Z-axis direction) from the outer surface 102b of the top wall 10b. The rib 40 is provided to extend along the X-axis direction. That is, the rib 40 is composed of ribs along a plane (XZ plane) that includes the X-axis and Z-axis. For example, in a cross-sectional view of the housing 10 viewed from the side, the rib 40 protrudes perpendicularly to the outer surface 102b. Note that the rib 40 is not limited to protruding perpendicularly to the outer surface 102b in a cross-sectional view of the housing 10 viewed from the side; it may also be inclined in the negative Y-axis direction (upward direction of the vehicle) relative to the outer surface 102b. In this embodiment, since the rib 40 protrudes along a plane substantially perpendicular to the direction of gravity (Y-axis direction), even if resin drip occurs from the outer surface 102b of the top wall 10b on which the rib 40 is provided, the resin drip will get caught on the rib 40, so the rib 40 can stop the resin drip from falling in the direction of gravity. This prevents the vehicle from catching fire due to resin dripping.

[0025] As described above, the housing according to this embodiment is a resin housing for housing an electronic circuit board, and a flame retardant having a predetermined flame retardancy is provided between the inner wall of the housing and the electronic circuit board inside the housing. This prevents the housing from melting or igniting if the electronic circuit board housed inside overheats.

[0026] Furthermore, in the housing according to this embodiment, the electronic circuit board has a mounting surface on which heat-generating electronic components are mounted, and the flame retardant is placed between the inner wall facing the mounting surface and the mounting surface. This prevents the housing from melting or igniting if the mounting surface on the electronic circuit board on which the electronic components are mounted overheats.

[0027] Furthermore, in the housing according to this embodiment, the flame retardant is a film-shaped component attached to the inner wall. This makes it possible to reduce the amount of flame retardant used.

[0028] Furthermore, in the housing according to this embodiment, the flame retardant is a resin component that generates a carbonized layer on its surface that expands with heat. This prevents the flame from coming into contact with the housing if the electronic circuit board ignites.

[0029] Furthermore, in the housing according to this embodiment, the flame retardant is arranged so that when a carbonized layer is formed, the carbonized layer comes into contact with the electronic substrate. This allows the fire that has occurred on the electronic substrate to be extinguished.

[0030] Furthermore, the enclosure according to this embodiment is constructed from flammable materials. This allows the enclosure to be made from less expensive materials.

[0031] Furthermore, the outer wall of the housing according to this embodiment is provided with ribs. This increases the strength of the housing.

[0032] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Accordingly, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0033] 1...Electronic control unit 10...Enclosure 20...Electronic circuit board 30...Flame retardant material 40...Ribs

Claims

1. A resin housing for housing an electronic circuit board, wherein the housing is provided with a flame-retardant material having a predetermined flame retardancy between the inner wall of the housing and the electronic circuit board.

2. The housing according to claim 1, wherein the electronic substrate has a mounting surface on which heat-generating electronic components are mounted, and the flame retardant material is disposed between the inner wall facing the mounting surface and the mounting surface.

3. A housing according to claim 1 or 2, wherein the flame retardant is a film-shaped member attached to the inner wall.

4. A housing according to any one of claims 1 to 3, wherein the flame retardant is a resin member that generates a carbonized layer on the surface of the flame retardant that expands with heat.

5. The housing according to claim 4, wherein the flame retardant is arranged such that the carbonized layer comes into contact with the electronic substrate when the carbonized layer is formed.

6. A housing according to any one of claims 1 to 5, wherein the housing is made of a flammable material.

7. A housing according to any one of claims 1 to 6, wherein the housing is provided with ribs on its outer wall.

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