JP2013232547A - On-vehicle circuit board accommodation housing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle circuit board accommodation housing which reduces influences of radiation noise while adopting a resin member.SOLUTION: An on-vehicle circuit board accommodation housing 100 according to this invention includes an on-vehicle circuit board 106 on which an electronic component is mounted and accommodates the on-vehicle circuit board. The on-vehicle circuit board accommodation housing 100 includes: a metal base member 102 on which the on-vehicle circuit board is placed; and a resin cover member 104 covering the on-vehicle circuit board and assembled to the base member. The base member includes: a rectangular bottom surface part 108; a frame body 110 which is erected around the bottom surface part and contacts with the on-vehicle circuit board thereby forming a cavity 140 between the bottom surface part and the on-vehicle circuit board; and at least one wall part 112 erected from the bottom surface part to the cavity.

Description

  The present invention relates to a vehicle-mounted circuit board housing case that houses a vehicle-mounted circuit board on which electronic components that operate at a specific frequency are mounted.

  In vehicles such as automobiles, a large number of electronic control units (ECUs) that control various in-vehicle devices such as airbags are arranged. The electronic control unit includes a control board (on-vehicle circuit board) that is an on-vehicle electronic device, and is mounted with a large number of electronic components that operate at a frequency of about 1.6 GHz, for example.

  The in-vehicle circuit board is accommodated in, for example, an aluminum die-cast box-shaped housing. By housing the in-vehicle circuit board in the metal casing, the rigidity and the like are improved, and the electronic components on the in-vehicle circuit board can be protected in the event of a vehicle collision.

  However, when a metal casing is used, there is a problem that the weight and manufacturing cost increase. On the other hand, Patent Document 1 describes a housing that employs a box-shaped resin case with an opening at the bottom in order to reduce weight and cost.

  The housing includes the resin case (cover member in the present application) and a metal cover (base member in the present application) that covers the opening of the case. A board on which electronic components are mounted (an in-vehicle circuit board in the present application) is housed and fixed in the case from the opening of the case.

JP 2012-28661 A

  By the way, radiation noise (electromagnetic wave) may be radiated from the outside to the casing that houses the on-vehicle circuit board due to the surrounding environment. In this case, the metal housing functions as an electrostatic shield. For this reason, the electronic component mounted on the in-vehicle circuit board is not affected by the radiation noise and is unlikely to malfunction.

  In patent document 1, since the resin-made case is employ | adopted as a part of housing | casing, a housing | casing does not function as an electrostatic shielding body but a radiation noise passes a case. Here, since the in-vehicle circuit board is, for example, a multilayer board on which electronic components are mounted, it can be regarded as a single metal plate (conductive wall) as a whole, but there is actually a gap between the electronic parts. In addition, there is a gap due to a pattern for wiring on the board on which the electronic component is mounted, and a gap between the metal cover and the mounting board. Therefore, the radiated noise that has passed through the case partially passes through these gaps, is reflected by the metal cover, and is partially reflected again by the in-vehicle circuit board.

  As a result, in the casing, a resonance phenomenon occurs in the space between the on-board circuit board and the metal cover. In particular, if the resonance frequency coincides with the frequency at which the electronic component malfunctions, there is a possibility that problems such as the airbag not being deployed normally occur.

  That is, when a resin member is used as a part of the housing in order to reduce the weight and cost of the housing, there is a problem that it becomes difficult to reduce the influence of radiation noise.

  In view of such problems, an object of the present invention is to provide an in-vehicle circuit board housing case that can reduce the influence of radiation noise while employing a resin member.

  In order to solve the above problems, a typical configuration of an in-vehicle circuit board housing case according to the present invention is an in-vehicle circuit board housing case that includes an in-vehicle circuit board on which electronic components are mounted and houses the in-vehicle circuit board. The base member includes a metal base member on which the in-vehicle circuit board is placed, and a resin cover member that covers the in-vehicle circuit board and is assembled to the base member. The base member has a rectangular bottom surface portion and a bottom surface portion. And a frame body that forms a cavity between the bottom surface portion and the in-vehicle circuit board by being in contact with the in-vehicle circuit board, and at least one wall portion that is erected in the cavity from the bottom surface portion. It is characterized by.

  In said structure, the case where radiation noise (electromagnetic wave) is irradiated toward the cover member from the outside is assumed. The electromagnetic wave passes from the outside through the resin cover member and further reaches the in-vehicle circuit board. The electromagnetic wave reaching the in-vehicle circuit board partially passes through the in-vehicle circuit board, reaches the cavity, and is reflected by the metal base member. The electromagnetic wave reflected by the base member is partially reflected by the in-vehicle circuit board and then again reflected by the base member.

  The cavity functions as a so-called cavity resonator because it is a space surrounded by a metal base member and an in-vehicle circuit board that can be regarded as a conductive wall. In general, a cavity resonator generates a resonance phenomenon in which only an electromagnetic field having a specific wavelength, which is determined by the size and shape of a space, is grown in a space surrounded by conductive walls. Note that there are a large number of resonance modes indicating the state of the electromagnetic field generated in the space due to the resonance phenomenon according to the resonance frequency of the electromagnetic wave in the space.

  In the cavity, the electromagnetic wave is repeatedly reflected between the base member and the on-vehicle circuit board, so that a resonance phenomenon occurs. Due to the resonance phenomenon, electromagnetic waves (for example, microwaves) having a resonance frequency (for example, about 1.64 GHz) at which an electronic component mounted on the on-vehicle circuit board malfunctions may be generated in the cavity. That is, in the casing having the above-described cavity, the operation of the electronic component may become unstable and malfunction may occur due to electromagnetic waves generated by the resonance phenomenon. As an example, the long side, the short side, etc. of the bottom surface of the rectangle has a half wavelength of an electromagnetic wave having a frequency at which the electronic component malfunctions (generally 1 / n wavelength, n is an integer of 2 or more). If they match, malfunction is likely to occur.

  Therefore, in the present invention, by forming a wall portion standing from the bottom surface portion of the base member toward the cavity, formation of an electric field and a magnetic field in a resonance mode, which is expected to occur in the cavity when the wall portion does not exist, is formed. Hinder. In other words, the wall has a function of shifting the resonance frequency of the electromagnetic wave in the cavity. Therefore, according to the on-vehicle circuit board housing case, it is possible to prevent an electromagnetic wave having a resonance frequency that matches the malfunction frequency of the electronic component from being formed in the cavity while adopting a resin cover member. It is possible to prevent malfunction of electronic components and reduce the influence of radiation noise from the outside.

  Said wall part is good to stand in the area | region except the short side of a bottom face part. As a result, the wall portion is present in an intermediate portion excluding the short side along the long side direction of the bottom surface portion, thereby preventing the formation of an electric field and a magnetic field in a resonance mode close to a resonance frequency at which the electronic component malfunctions. easy. Therefore, the influence of the radiation noise from the outside can be reduced more effectively.

  The wall portion may be provided so as to include a portion overlapping the center of the long side of the bottom surface portion when the bottom surface portion is viewed from the short side direction. As a result, the wall portion can more reliably prevent the formation of the electric field and magnetic field in the resonance mode, shift the problematic resonance frequency, and more effectively reduce the influence of radiation noise from the outside. In addition, when a wall part has two side surfaces which respectively face both short sides of a bottom face part, if a wall part overlaps the center of the long side of a bottom face part, each faces from two side faces The distance to both short sides may be different.

  The wall portion may have two side surfaces respectively facing both short sides of the bottom surface portion, and the distances from the two side surfaces to both short sides facing each other may be equal. As a result, the wall portion surely includes the central portion located at the center of the long side of the bottom surface portion when the bottom surface portion is viewed from the short side direction. The effect of radiation noise can be reduced more effectively.

  Said wall part is good to extend in the transversal direction of a bottom face part. Thereby, the wall portion is positioned in a direction orthogonal to the electric field and magnetic field along the long side direction generated in the resonance mode. Therefore, the wall portion can more reliably prevent the formation of the electric field and magnetic field in the resonance mode, shift the problematic resonance frequency more reliably, and can more effectively reduce the influence of external radiation noise.

  Said vehicle-mounted circuit board contains an external connector, and a wall part is good to overlap with an external connector when the vehicle-mounted circuit board is seen from the normal line direction. Thereby, formation of the electric field and magnetic field of a resonance mode which become a problem can be prevented in the vicinity of the external connector expected to be easily affected by radiation noise in the in-vehicle circuit board. Therefore, malfunction of the electronic component is less likely to occur.

  Said vehicle-mounted circuit board contains a power supply line, and a wall part is good to overlap with a power supply line when the vehicle-mounted circuit board is seen from the normal line direction, or is located in the vicinity of a power supply line. Thereby, formation of the electric field and magnetic field of the resonance mode which become a problem can be prevented in the vicinity of a power supply line expected to be easily affected by radiation noise in the in-vehicle circuit board. Therefore, malfunction of the electronic component is less likely to occur.

  The height of the wall portion is preferably lower than the height of the frame. Thereby, a wall part does not contact a vehicle-mounted circuit board, and a vehicle-mounted circuit board does not receive a mechanical stress. In addition, when a wall part contacts a vehicle-mounted circuit board, it is preferable as a noise countermeasure.

  The bottom surface portion is formed with a first ground terminal formed at a location where one long side intersects with one short side, and a second formed at a location where one long side intersects with the other short side. A location where the ground terminal is separated from the location where the other long side and one short side intersect, and the third ground terminal formed on one short side, and the other long side and the other short side intersect And a fourth ground terminal formed on the other short side. Thereby, the distance between the first ground terminal and the second ground terminal is different from the distance between the third ground terminal and the fourth grant terminal. Therefore, it is assumed that the resonance of electromagnetic waves is somewhat hindered and the influence of external radiation noise can be reduced.

  You may provide an electromagnetic wave absorption sheet between said vehicle-mounted circuit board and a base member. If it does in this way, electromagnetic waves will be absorbed with an electromagnetic wave absorption sheet, and resonance of electromagnetic waves can be prevented somewhat.

  ADVANTAGE OF THE INVENTION According to this invention, the vehicle-mounted circuit board housing | casing housing | casing which can reduce the influence of radiation noise can be provided, employ | adopting a resin member.

It is a figure which shows the vehicle-mounted circuit board accommodation housing | casing in embodiment of this invention. It is a disassembled perspective view of the vehicle-mounted circuit board accommodation housing | casing of FIG. It is a figure which shows the base member of the vehicle-mounted circuit board accommodation housing | casing of FIG. It is a figure which shows the back surface of the vehicle-mounted circuit board of the vehicle-mounted circuit board accommodation housing | casing of FIG. It is a figure which shows the state which mounted the vehicle-mounted circuit board on the base member of FIG. It is a top view which shows the base member used as a comparative example. It is a schematic diagram explaining the resonance phenomenon which arises in the cavity formed with the base member of FIG. It is a figure which illustrates the resonance mode which arises in the cavity of FIG. It is a schematic diagram explaining the principle which shifts a resonant frequency. It is a top view which illustrates other foundation members which are other embodiments of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  FIG. 1 is a diagram showing an in-vehicle circuit board housing case according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of the on-board circuit board housing case of FIG. As shown in the figure, the in-vehicle circuit board housing case (hereinafter referred to as the housing 100) includes a metal base member 102 and a resin cover member 104, in which the in-vehicle circuit board 106 is housed. .

  The base member 102 is a member that serves as a base on which the in-vehicle circuit board 106 is placed, and is formed by, for example, aluminum die casting. As illustrated in FIG. 2, the base member 102 includes a rectangular bottom surface portion 108, a frame body 110 erected around the bottom surface portion 108, and a wall portion 112 erected on the bottom surface portion 108. The base member 102 includes ground terminals 114a, 114b, 114c, and 114d formed by using the bottom surface portion 108 and the frame body 110, and flanges 116a and 116b that project outward to fix the housing 100 to the vehicle. 116c.

  As illustrated in FIG. 2, the cover member 104 is a member having a box shape with an open bottom, and houses the in-vehicle circuit board 106 therein. Then, the cover member 104 covers the in-vehicle circuit board 106 and is assembled to the base member 102, whereby the housing 100 illustrated in FIG. 1 is assembled.

  A large number of electronic components that operate at a predetermined frequency are mounted on the in-vehicle circuit board 106. However, FIG. 2 shows only the external connector 117 installed on the in-vehicle circuit board 106.

  Next, each member of the housing 100 will be described with reference to FIGS. FIG. 3 is a view showing the base member 102 of the housing 100 of FIG. FIG. 3A is a top view of the base member 102. FIG.3 (b) is AA sectional drawing of Fig.3 (a).

  As illustrated in FIG. 3A, the bottom surface portion 108 of the base member 102 has a rectangular shape defined by long sides 118 a and 118 b and short sides 120 a and 120 b. Here, as an example, the long sides 118a and 118b are about 105 mm, and the short sides 120a and 120b are about 85 mm. Further, the height of the frame 110 illustrated in FIG. 3B, that is, the dimension La from the bottom surface portion 108 to the upper end 110 a of the frame 110 is set to 5 mm. Furthermore, the height of the wall portion 112 illustrated in FIG. 3B, that is, the dimension Lb from the bottom surface portion 108 to the upper end 112a of the wall portion 112 is 4 mm. Therefore, the height of the wall portion 112 is lower than the height of the frame body 110.

  As illustrated in FIG. 3A, the wall portion 112 includes side surfaces 122 and 124 parallel to the short sides 120a and 120b. Further, the wall portion 112 overlaps the central portion 126 indicated by the dotted line in FIG. The central portion 126 is a portion located at the center of the long side 118a of the bottom surface portion 108 when the bottom surface portion 108 is viewed from the short side direction (short direction). The side surface 122 is separated from the short side 120a by a dimension Lc as illustrated in FIG. The side surface 124 is separated from the short side 120b by a dimension Ld as illustrated in FIG. Further, the dimension Lc is larger than the dimension Ld.

  As illustrated in FIG. 3A, the first ground terminal (ground terminal 114a) is set at a location where the long side 118b and the short side 120a intersect. The second ground terminal (ground terminal 114b) is set at a location where the long side 118b and the short side 120b intersect.

  The third ground terminal (ground terminal 114c) is set to the short side 120a. The ground terminal 114c is separated from the location where the long side 118a and the short side 120a intersect, and is located slightly closer to the intersecting location from the center of the short side 120a. The fourth ground terminal (ground terminal 114d) is set to the short side 120b. The ground terminal 114d is located in the vicinity of a location where the long side 118a and the short side 120b intersect. These ground terminals 114a to 114d have holes as shown in the figure, and are also used as fastening portions when the in-vehicle circuit board 106 and the cover member 104 are assembled.

  Since the ground terminal 114c is set to the short side 120a, as illustrated in FIG. 3A, the dimension Le between the ground terminals 114a and 114b is smaller than the dimension Lf between the ground terminals 114c and 114d. Here, the dimension Lf was about 90 mm. That is, the dimension Lf was a dimension close to 91.4 mm, which is a half wavelength of 1.64 GHz, at which many electronic components mounted on the in-vehicle circuit board 106 malfunction. The wavelength is calculated from the equation (1).

Wavelength = velocity of electromagnetic wave / frequency≈3 × 10 ¹¹ /1.64×10 ⁹ = 182.8 mm (1)
FIG. 4 is a view showing the back surface of the in-vehicle circuit board 106 of the housing 100 of FIG. As illustrated in FIG. 4, for example, a power supply IC 128 and a power supply line 130 connected to the power supply IC 128 are mounted on the back surface of the in-vehicle circuit board 106. The power supply line 130 exists at a position overlapping with a part of the external connector 117 indicated by a dotted line in the figure mounted on the surface of the in-vehicle circuit board 106.

  FIG. 5 is a diagram illustrating a state in which the in-vehicle circuit board 106 is placed on the base member 102 in FIG. 3. FIG. 5A is a top view showing the surface of the in-vehicle circuit board 106 together with the base member 102. FIG.5 (b) is BB sectional drawing of Fig.5 (a). As illustrated in FIG. 5A, the wall portion 112 has a region that overlaps the external connector 117 and the region that overlaps the power supply line 130 or the vicinity thereof when the in-vehicle circuit board 106 is viewed from the normal direction (here, upward). Is located. As illustrated in FIG. 5B, the upper end 110 a of the frame 110 is in contact with the in-vehicle circuit board 106, and a cavity 140 is formed between the bottom surface 108 and the in-vehicle circuit board 106.

  Hereinafter, with reference to FIGS. 6 to 9, a description will be given of a case where a resonance phenomenon occurs in the cavity under a situation where radiation noise (electromagnetic wave) is irradiated to the casing 100 from the outside. In addition, as a situation where radiation noise is irradiated, for example, when radiation noise is generated from a wireless device placed in the passenger compartment or various devices installed along the road, this radiation noise is irradiated to a traveling vehicle, etc. Can be considered.

  FIG. 6 is a top view showing a base member as a comparative example. FIG. 7 is a schematic diagram illustrating the principle of a resonance phenomenon that occurs in a cavity formed by the base member of FIG. FIG. 7A shows a state in which a resonance phenomenon occurs in the cavity when the base member of the comparative example is used. FIG.7 (b) has shown the mode of the radiation noise in the structure which abbreviate | omitted the base member from Fig.7 (a). FIG.7 (c) has shown the mode of the radiation noise in the structure which added the electromagnetic wave absorption sheet | seat to Fig.7 (a).

  As illustrated in FIG. 6, the base member 202 of the comparative example is different from the base member 102 in that the wall portion 112 is not formed on the bottom surface portion 208. As illustrated in FIG. 7A, the base member 202 forms a cavity 140 </ b> A with the in-vehicle circuit board 106.

  First, assuming a situation where radiation noise is irradiated from the outside, radiation noise was irradiated toward the housing 100 before the ECU was started. The ECU includes the on-board circuit board 106 housed in the housing 100 using the base member 202 of the comparative example. And when ECU was started during radiation noise irradiation, the malfunction that ECU did not start was confirmed. Moreover, when the ECU noise during operation was irradiated, a malfunction that the operation of the ECU stopped was also confirmed. This malfunction is considered to be because the resonance frequency of the radiated noise generated in the cavity 140A due to the resonance phenomenon coincides with the operation frequency of about 1.6 GHz of the electronic component mounted on the in-vehicle circuit board 106.

  Specifically, the radiation noise 142 applied to the housing 100 from the outside passes through the resin cover member 104 (not shown) and reaches the in-vehicle circuit board 106 as illustrated in FIG. 7A. . The on-board circuit board 106 is, for example, a multilayer board on which electronic components are mounted, and can be regarded as a single metal plate (conductive wall) as a whole, but actually there are many gaps between the electronic parts.

  Therefore, the radiated noise 142 reaching the in-vehicle circuit board 106 partially passes through the in-vehicle circuit board 106 and reaches the cavity 140A, and is reflected by the metal base member 202. As illustrated in FIG. 7A, the radiation noise 144 reflected by the base member 202 is partially reflected by the in-vehicle circuit board 106 and then reflected again by the base member 202.

  In other words, the cavity 140A is a space surrounded by the metal base member 202 and the in-vehicle circuit board 106 that can be regarded as a conductive wall in part. Therefore, it is considered that the cavity 140A functions as a so-called cavity resonator. In general, a cavity resonator generates a resonance phenomenon in which only an electromagnetic field having a specific wavelength, which is determined by the size and shape of a space, is grown in a space surrounded by conductive walls.

  On the other hand, as illustrated in FIG. 7B, in the configuration excluding the base member 202, the radiated noise 142 only partially passes through the in-vehicle circuit board 106, and no malfunction of the electronic component was confirmed. Therefore, it was confirmed that the radiation noise 142 irradiated from the upper surface of the in-vehicle circuit board 106 does not directly affect the electronic components of the in-vehicle circuit board 106.

  Further, as illustrated in FIG. 7C, the malfunction of the electronic component was not confirmed even in the configuration in which the electromagnetic wave absorbing sheet 146 was disposed in the cavity between the in-vehicle circuit board 106 and the base member 202.

  In this configuration, the radiated noise 142 partially passing through the in-vehicle circuit board 106 is absorbed by the electromagnetic wave absorbing sheet 146, reaches the base member 202 as the radiated noise 148a, is reflected by the base member 202, and becomes the radiated noise 148b. . The radiation noise 148b is absorbed by the electromagnetic wave absorbing sheet 146, reaches the in-vehicle circuit board 106 as the radiation noise 148c, is partially reflected by the in-vehicle circuit board 106, and becomes the radiation noise 148d. The radiation noise 148d reaches the cavity as radiation noise 148e while being absorbed by the electromagnetic wave absorbing sheet 146. That is, it is considered that the resonance phenomenon did not occur because the electromagnetic wave was absorbed by the electromagnetic wave absorbing sheet 146.

  Therefore, in the case 100 using the base member 202 of the comparative example schematically shown in FIG. 7A, the in-vehicle circuit board 106 and the base member 202 form a parallel plate via the cavity 140A, and the so-called parallel plate. It is assumed that a resonance phenomenon that causes resonance occurs.

  FIG. 8 is a diagram illustrating a resonance mode generated in the cavity of FIG. The resonance mode indicates a state of an electromagnetic field generated in the space due to the resonance phenomenon, and there are a large number according to the resonance frequency of the electromagnetic wave in the space. 8A and 8B, the electric field at a certain moment is indicated by a solid line, and the magnetic field is indicated by a dotted line.

  FIG. 8A schematically shows resonance modes 150, 152, and 154 generated in the cavity 140A of the casing 100 using the base member 202 of the comparative example. FIG. 8B is a schematic diagram showing the electromagnetic field indicated by the resonance modes 150, 152, and 154 and the base member 102 in an overlapping manner. 8A and 8B illustrate the resonance modes on the upper side when the cavity 140A is viewed from above. In addition, the diagrams illustrated below as the resonance modes show the state where the cavity 140A is viewed from the side, and is further enlarged in the height direction.

  The resonance modes 150, 152, and 154 are all representative modes, and it is assumed that the resonance frequency is about 1.6 GHz that is a malfunction frequency of the electronic component. As calculated by the above equation (1), a half wave of an electromagnetic wave having a frequency of 1.64 GHz, that is, a harmonic that is an integral multiple of 91.4 mm exists as a standing wave in the cavity 140A and resonates. Electromagnetic fields shown in resonance modes 150, 152, and 154 are formed. Note that whether the state of the electromagnetic field generated in the cavity 140A is classified into any of the resonance modes 150, 152, and 154 depends on the size and shape of the cavity 140A.

  Here, when the length between the long sides 118a and 118b, the short sides 120a and 120b or the ground terminals 114c and 114d of the bottom surface portion 208 of the base member 202 substantially matches the half wavelength of the electromagnetic wave, Electronic components are likely to malfunction. As described above, the dimension Lf between the ground terminals 114c and 114d illustrated in FIG. 3A is about 90 mm, and is 91.4 mm, which is a half wavelength of the electromagnetic wave having a malfunctioning frequency of 1.64 GHz. The dimensions were close.

  Therefore, in this embodiment, by erecting the wall portion 112 on the bottom surface portion 108 of the base member 102, the resonance frequency of the radiation noise is shifted so that the electronic component malfunctions differently from the frequency at which the electronic component malfunctions. It is preventing.

  That is, as illustrated in FIG. 8B, when the wall portion 112 indicated by the dotted line is erected on the long side 118 a of the bottom surface portion 108, the electric field and magnetic field shown in the resonance modes 150, 152, and 154 are formed. Is disturbed. That is, an electric field and a magnetic field are not formed in the region occupied by the wall portion 112, and although not illustrated, an electromagnetic field different from the electromagnetic fields shown in the resonance modes 150, 152, and 154 is formed. The frequency will shift.

  FIG. 9 is a schematic diagram for explaining the principle of shifting the resonance frequency. FIG. 9A representatively shows one wavelength of the standing wave 160 having a resonance frequency of 1.64 GHz. The standing wave 160 is formed from an electromagnetic field indicated by the resonance modes 150, 152, and 154 illustrated in FIG. FIG. 9B shows a state where the standing wave 160 illustrated in FIG.

  Assuming that the positions of the nodes appearing every 1/2 wavelength of the standing wave 160 are the ground terminals 114c and 114d as illustrated in FIG. 9B, the wall portion 112 is positioned between the ground terminals 114c and 114d. . Therefore, the standing wave 160 is reflected at the point C of the wall portion 112 illustrated in FIG. 9B, and becomes a new standing wave having a wavelength different from the wavelength λ in the drawing. Therefore, the frequency of the new standing wave is assumed to be different from the malfunction frequency 1.64 GHz of the electronic component.

  According to the present embodiment, by forming the wall portion 112 standing from the bottom surface portion 108 of the base member 102 toward the cavity, the resonance mode 150 is expected to be generated in the cavity 140A where the wall portion 112 does not exist. , 152 and 154 are prevented from being formed, and the resonance frequency of the radiation noise can be shifted. Therefore, in the case 100, the radiated noise that matches the frequency at which the electronic component malfunctions is not formed in the cavity while the resin cover member 104 is employed. As a result, malfunction of the electronic component can be prevented, and the influence of external radiation noise can be reduced.

  As illustrated in FIG. 3A, the wall portion 112 has side surfaces 122 and 124 parallel to the short side direction of the bottom surface portion 108, so that the electric field along the long side direction (longitudinal direction) generated in the resonance mode and Located in a direction perpendicular to the magnetic field. Therefore, the wall 112 reliably prevents the formation of the resonance mode electric field and magnetic field, reliably shifts the resonance frequency, and can more effectively reduce the influence of radiation noise from the outside.

  As illustrated in FIG. 3B, the wall portion 112 includes the central portion 126 of the bottom surface portion 108. Therefore, the wall portion 112 reliably prevents the formation of an electric field and a magnetic field in the resonance mode, and shifts the resonance frequency. The influence of external radiation noise can be reduced more effectively.

  As illustrated in FIG. 5A, the wall portion 112 is located in a region overlapping the external connector 117, a region overlapping the power supply line 130, or the vicinity thereof when the in-vehicle circuit board 106 is viewed from above. The external connector 117 and the power supply line 130 are expected to be easily affected by radiation noise in the in-vehicle circuit board 106. For example, if a current is generated in the power supply line 130 by an electric field, it is considered that the circuit operation becomes unstable. Therefore, the wall 112 can prevent the formation of an electric field and a magnetic field in the resonance mode in the vicinity of the external connector 117 or the power supply line 130, and can prevent malfunction of the electronic component.

  Since the dimension Le between the ground terminals 114a and 114b and the dimension Lf between the ground terminals 114c and 114d are different from each other, it is assumed that the resonance of electromagnetic waves is somewhat prevented and the influence of radiation noise from the outside can be reduced.

  Since the height of the wall portion 112 is lower than the height of the frame 110, the wall portion 112 does not contact the in-vehicle circuit board 106, and the in-vehicle circuit board 106 is not subjected to mechanical stress. In addition, it is preferable as a noise countermeasure when the wall part 112 contacts the vehicle-mounted circuit board 106.

  In the above embodiment, one wall portion 112 is erected on the long side 118a of the bottom surface portion 108 of the base member 102. However, if the formation of the electric field and magnetic field in the resonance mode can be prevented, the arrangement of the wall portion 112 is possible. Is not limited to this.

  FIG. 10 is a diagram illustrating another foundation member which is another embodiment of the present invention. Fig.10 (a) is a figure which shows the example which installed many wall parts. FIG.10 (b) is a figure which illustrates the base member different from Fig.10 (a).

  As illustrated in FIG. 10A, the base member 102 </ b> A has a large number (in this case, nine walls) 112, 162 a to 162 h erected in a region excluding the short sides 120 a and 120 b of the bottom surface portion 108 </ b> A. doing. In other words, the wall portions 112 and 162a to 162h are present in an intermediate region excluding the short sides 120a and 120b along the long side direction of the bottom surface portion 108, and the formation of the resonance mode electric field and magnetic field is likely to be hindered.

  As illustrated in FIG. 10B, the base member 102 </ b> B has two wall portions 164 a and 164 b erected on the short side of the bottom surface portion 108 </ b> B. These wall portions 164a and 164b are erected so as to be parallel to the long sides 118a and 118b of the bottom surface portion. Thereby, the wall part 112 is located in the direction orthogonal to the electric field and magnetic field along the short side direction produced in a resonance mode. Therefore, the wall portion 112 can reliably prevent the formation of an electric field and a magnetic field in the resonance mode, and can reliably shift the resonance frequency. Therefore, even when the base members 102 </ b> A and 102 </ b> B are used for the housing 100, the influence of radiation noise from the outside can be more effectively reduced.

  In the wall portion 112, as illustrated in FIG. 3B, the dimension Lc between the side surface 122 and the short side 120a does not coincide with the dimension Ld between the side surface 124 and the short side 120b. (Dimension Lc> dimension Ld), but not limited to this, the dimension Lc may be equal to the dimension Ld. In this way, the wall 112 necessarily overlaps the central portion 126 when the bottom surface 108 is viewed from the short side direction. Therefore, formation of the electric field and magnetic field in the resonance mode can be reliably prevented, the resonance frequency can be reliably shifted, and the influence of radiation noise from the outside can be reduced more effectively.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  INDUSTRIAL APPLICABILITY The present invention can be used for an in-vehicle circuit board housing case that houses an in-vehicle circuit board on which electronic components that operate at a specific frequency are mounted.

DESCRIPTION OF SYMBOLS 100 ... Housing | casing, 102, 102A, 102B ... Base member, 104 ... Cover member, 106 ... In-vehicle circuit board, 108, 108A, 108B ... Bottom part, 110 ... Frame, 112, 162a-162h, 164a, 164b ... Wall 114a to 114b ... ground terminals, 116a to 116d ... flanges, 117 ... external connectors, 118a, 118b ... long sides, 120a, 120b ... short sides, 122, 124 ... side surfaces, 126 ... central portion, 128 ... power supply IC, DESCRIPTION OF SYMBOLS 130 ... Power supply line 140 ... Cavity 142, 144, 148a-148e ... Radiation noise (electromagnetic wave), 146 ... Electromagnetic wave absorption sheet, 150, 152, 154 ... Resonance mode, 160 ... Standing wave

Claims (10)

An in-vehicle circuit board housing case that includes an in-vehicle circuit board on which electronic components are mounted and that houses the in-vehicle circuit board,
A metal base member on which the in-vehicle circuit board is placed;
A resin cover member that covers the in-vehicle circuit board and is assembled to the base member;
The base member is
A rectangular bottom,
A frame that stands up around the bottom portion and forms a cavity between the bottom portion and the in-vehicle circuit board by contacting the in-vehicle circuit board;
An in-vehicle circuit board housing case comprising: at least one wall portion standing in the cavity from the bottom surface portion.   The on-vehicle circuit board housing case according to claim 1, wherein the wall portion is erected in a region excluding a short side of the bottom surface portion.   The in-vehicle circuit board according to claim 1, wherein the wall portion is provided so as to include a portion that overlaps a center of a long side of the bottom surface portion when the bottom surface portion is viewed from the short side direction. Containment housing. The wall portion has two side surfaces respectively facing both short sides of the bottom surface portion,
The in-vehicle circuit board housing case according to claim 1, wherein the distances from the two side surfaces to the both short sides facing each other are equal.   5. The on-vehicle circuit board housing case according to claim 1, wherein the wall portion extends in a short direction of the bottom surface portion. The in-vehicle circuit board includes an external connector,
6. The on-board circuit board housing case according to claim 1, wherein the wall portion overlaps with the external connector when the on-board circuit board is viewed from a normal direction thereof. The on-vehicle circuit board includes a power line,
The said wall part overlaps with the said power supply line when the said vehicle-mounted circuit board is seen from the normal line direction, or is located in the vicinity of this power supply line. The vehicle-mounted circuit board housing case described in 1.   8. The on-vehicle circuit board housing case according to claim 1, wherein a height of the wall portion is lower than a height of the frame body. The bottom portion is
A first ground terminal formed at a location where one long side and one short side intersect;
A second ground terminal formed at a location where the one long side and the other short side intersect;
A third ground terminal formed on the one short side, separated from a point where the other long side and the one short side intersect,
9. The device according to claim 1, further comprising: a fourth ground terminal that is positioned in the vicinity of a location where the other long side intersects with the other short side and is formed on the other short side. The on-board circuit board housing case according to claim 1.   10. The on-board circuit board housing case according to claim 1, wherein an electromagnetic wave absorbing sheet is provided between the on-board circuit board and the base member.

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