JP2014086436A - On-vehicle circuit board housing case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle circuit board housing case which can reduce influence of not only radiation noise but also conduction noise while employing a resin member.SOLUTION: An on-vehicle circuit board housing case 100 accommodates an on-vehicle circuit board 106 on which an electronic component is mounted, and includes: a metal foundation member 102 on which the on-vehicle circuit board is placed; and a resin cover member 104 which is installed on the foundation member while covering the on-vehicle circuit board. The on-vehicle circuit board includes a first region 134 to which a plurality of terminals 117b of an external connector 117 are connected and which is positioned in the vicinity of one end 106a of the on-vehicle circuit board. The foundation member includes: a rectangular bottom surface part 108; a frame body 110 which is installed upright in the periphery of the bottom surface part and forms a cavity 140 between the bottom surface part and the on-vehicle circuit board by being brought into contact with the on-vehicle circuit board; and a wall part 112 which is installed upright from the bottom surface part into the cavity and partitions the first region.

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 high frequencies.

  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 increases or the manufacturing cost increases. 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, the housing that houses the in-vehicle circuit board may be exposed to radiation noise (electromagnetic waves) from the outside 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.

  Furthermore, an external connector for connecting other in-vehicle components is mounted on the in-vehicle circuit board. The external connector has a plurality of terminals, and these terminals are inserted into through holes arranged in a plurality of on-vehicle circuit boards, for example, and soldered. Since the terminals of the external connector serve as signal input / output lines, conduction noise may propagate from other in-vehicle components. As a result, in the case, the electronic component may malfunction due to the influence of conduction noise.

  The present invention has been made in view of such a problem, and an object thereof is to provide an in-vehicle circuit board housing case that can reduce not only radiation noise but also conduction 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. And 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 in-vehicle circuit board has a plurality of terminals of the external connector. It has a first region that is connected and is located near one end of the in-vehicle circuit board, and the base member is a rectangular bottom surface part, and stands on the periphery of the bottom surface part so as to be in contact with the in-vehicle circuit board. And a vehicle-mounted circuit board, and a wall portion that stands in the cavity from the bottom surface and divides the first region.

  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 above configuration, 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. Can be prevented, and the influence of external radiation noise can be reduced.

  Further, in the above configuration, the terminal of the external connector is a signal input / output line, and conduction noise may propagate from other in-vehicle components connected to the external connector. In this case, a plurality of terminals of the external connector located in the first region may function as an antenna, for example, and conduction noise may be radiated into the housing.

  Assuming such a case, in the present invention, the first region of the in-vehicle circuit board is partitioned by the wall portion. By dividing the first region, it is difficult for harmonics associated with conduction noise to propagate to other regions of the in-vehicle circuit board with the wall portion interposed therebetween. As a result, an electronic component mounted in another region is less likely to malfunction due to conduction noise. Therefore, according to the on-vehicle circuit board housing case, it is possible to reduce not only the radiation noise but also the influence of conduction noise while adopting a resin member. Here, partitioning the first region means that the first region is isolated from other regions so as to prevent propagation of conduction noise, and the first region and other regions are separated without gaps. However, the present invention is not limited to this, and there may be a gap between the frame and the wall itself.

  Said wall part is good to be formed without a gap so that it may cross from one edge part of the bottom face part to the other edge part. Thereby, in a vehicle-mounted circuit board, a 1st area | region and another area | region are divided by a wall part without a clearance gap. Therefore, the conduction noise is more difficult to propagate from the first region to the other region, and the malfunction due to the conduction noise of the electronic component mounted in the other region can be further prevented. Further, the space is divided by the wall portion, and the resonance frequency generated as noise greatly deviates from the frequency at which the electronic component malfunctions.

  The above-described on-board circuit board includes the other end of the on-board circuit board, has a second region located on the opposite side of the first region across the wall portion, and the wall portion faces the first region. The first side surface has a side surface and a second side surface facing the second region, and the bottom surface portion has a first side facing the first side surface and a second side facing the second side surface. The distance from the first side to the first side is preferably smaller than the distance from the second side surface to the second side. As a result, the second region is not only less susceptible to conduction noise, but is wider than the first region. For this reason, more electronic components can be mounted in the second region, and the influence of conduction noise on these electronic components can be reduced.

  The height of the wall portion is preferably equal to the height of the frame. Thereby, a wall part and a vehicle-mounted circuit board contact directly, and the ground and wall part of a vehicle-mounted circuit board become equipotential as an example, and it is preferable as a noise countermeasure. Moreover, if it is the structure which contacts the low impedance line on a vehicle-mounted circuit board, the same effect can be expected.

  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, and is preferable. Although the wall portion is not in direct contact with the in-vehicle circuit board, the wall portion is in indirect contact with the in-vehicle circuit board through a frame body in contact with the in-vehicle circuit board. For this reason, the wall portion is preferably equipotential with the ground of the in-vehicle circuit board. Similarly to the above, it may be connected to a low impedance line.

  ADVANTAGE OF THE INVENTION According to this invention, the vehicle-mounted circuit board accommodation housing | casing which can reduce not only radiation noise but the influence of conduction noise can be provided, 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 sectional drawing which illustrates the other base member which is other embodiment of this invention. It is a top view which illustrates other foundation members which are further 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. Note that the ground terminals 114a to 114d of the base member 102 have holes formed as illustrated in FIG. 2, and are also used as fastening portions when the in-vehicle circuit board 106 and the cover member 104 are 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. The external connector 117 is used to connect other appropriate on-vehicle components, and is mounted in the vicinity of one end portion 106a of the on-vehicle circuit board 106. An electronic component as a main circuit is mounted on the other end 106b side of the in-vehicle circuit board 106. Here, examples of the main circuit include a signal processing circuit including a semiconductor element, an interface circuit, and a power supply circuit.

  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 112 a of the wall portion 112 is also 5 mm, which is equal to the height of the frame body 110.

  As illustrated in FIG. 3A, the wall portion 112 includes a first side surface (side surface 122) and a second side surface (side surface 124). The side surfaces 122 and 124 are substantially parallel to the first side (long side 118a) and the second side (long side 118b) of the bottom surface part 108, respectively. Further, the wall portion 112 is formed without a gap so as to cross from the ground terminal 114c set at the short side 120a serving as one end portion of the bottom surface portion 108 to the short side 120b serving as the other end portion of the bottom surface portion 108. Has been.

  The length of the wall portion 112, that is, the dimension Lc from the ground terminal 114c to the short side 120b was set to about 95 mm. Moreover, the thickness dimension Ld of the wall part 112 was 1.0-2.0 mm. Further, in the wall portion 112, the dimension Le from the side surface 122 to the long side 118a is about 30 mm, and the dimension Lf from the side surface 124 to the long side 118b is about 55 mm, so that the dimension Le is smaller than the dimension Lf. did.

  Here, the dimension Lg between the ground terminals 114c and 114d was about 90 mm. This dimension Lg was a dimension close to 91.4 mm, which is a ½ wavelength of a frequency of 1.64 GHz, at which many electronic components mounted on the on-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. 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. 4, a power supply IC 128 is mounted on the back surface of the in-vehicle circuit board 106 as one of electronic components serving as main circuits. The power supply line 130 illustrated in the figure is connected to the power supply IC 128 and exists at a position overlapping with a part of the external connector 117 indicated by the dotted line in the figure mounted on the surface of the in-vehicle circuit board 106.

  As illustrated in FIGS. 5A and 5B, the external connector 117 includes a housing 117a and a plurality of terminals 117b held by the housing 117a. As illustrated in FIG. 5A, the plurality of terminals 117b extend in parallel to each other from the housing 117a to the vicinity of the side surface 122 of the wall portion 112 indicated by a dotted line in the drawing. Further, as illustrated in FIG. 5B, the terminal 117 b is bent downward from the vicinity of the side surface 122 of the wall portion 112 and reaches the surface of the in-vehicle circuit board 106. When this state is viewed from the back surface of the in-vehicle circuit board 106, as illustrated in FIG. 4, the plurality of terminals 117a are inserted into the through holes 132 of the in-vehicle circuit board 106, and are soldered, for example. For example, the through holes 132 are located on the end portion 106a side of the in-vehicle circuit board 106, and a plurality of through holes 132 are arranged in parallel to the end portion 106a (here, three rows).

  Hereinafter, the connector connection area including the portion where the external connector 117 is mounted and the plurality of terminals 117 a are connected in the in-vehicle circuit board 106 is referred to as a first area 134. In addition, a main circuit mounting area in which the power supply IC 128 shown as the main circuit in the in-vehicle circuit board 106 is mounted is referred to as a second area 136. The second region 136 is a region surrounded by a dotted line illustrated in FIG. 4 and FIG. 5A and is located on the end portion 106b side of the in-vehicle circuit board 106. In addition to the above, other major circuits are also installed.

  Further, when the in-vehicle circuit board 106 is viewed from the normal direction (here, upward) in a state where the in-vehicle circuit board 106 is placed on the base member 102 as illustrated in FIG. Thus, the first region 134 is partitioned. As illustrated in FIG. 3A, the wall portion 112 is erected without a gap so as to cross from the ground terminal 114 c formed on the bottom surface portion 108 of the base member 102 to the short side 120 b. For this reason, in the in-vehicle circuit board 106, the first region 134 and the second region 136 are partitioned by the wall portion 112 without a gap.

  Further, in the state illustrated in FIGS. 5A and 5B in which the in-vehicle circuit board 106 is placed on the base member 102, the long sides 118 a and 118 b of the base member 102 are end portions of the in-vehicle circuit board 106. It is located in the vicinity of 106a and 106b, and further faces the first region 134 and the second region 136, respectively. In the base member 102, as described above, the side surfaces 122 and 124 of the wall portion 112 face the first region 134 and the second region 136, respectively, and the dimension Le illustrated in FIG. Smaller than. Therefore, in the in-vehicle circuit board 106, in the above state, the second area 136 is wider than the first area 134 defined by the wall portion 112.

  Further, as illustrated in FIG. 5B, the frame member 110 of the base member 102 has an upper end 110 a that 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. Forming. Furthermore, since the height of the wall 112 is equal to the height of the frame 110 as described above, the upper end 112a of the wall 112 and the in-vehicle circuit board 106 are in direct contact as illustrated in FIG. 5B. ing.

  Hereinafter, with reference to FIGS. 6 to 8, 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 from the outside to the housing 100. 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. In addition, when noise was applied to the operating ECU, it was confirmed that the ECU stopped operating. 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 frequency at which the electronic component mounted on the in-vehicle circuit board 106 malfunctions.

  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 at the problematic frequency 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 an electromagnetic field different from the electromagnetic fields shown in the resonance modes 150, 152, and 154 is formed although illustration is omitted. As a result, the resonance frequency of the electromagnetic wave in the cavity 140 can be shifted.

  Furthermore, in this embodiment, not only the influence of the radiation noise irradiated to the housing | casing 100 from the outside but the influence of conduction noise is also considered. That is, the plurality of terminals 117b of the external connector 117 mounted on the in-vehicle circuit board 106 are signal input / output lines, and conduction noise may propagate from other in-vehicle components connected to the external connector 117. . In this case, the plurality of terminals 117 b located in the first region 134 may function as, for example, an antenna, and conduction noise may be radiated into the cavity 140 of the housing 100.

  Assuming such a case, in the present embodiment, the first region 134 of the in-vehicle circuit board 106 is partitioned by the wall portion 112 described above. By partitioning the first region 134, harmonics associated with conduction noise or the like are difficult to propagate to the second region 136 of the in-vehicle circuit board 106 sandwiching the wall portion 112.

  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 140, the resonance mode is expected to occur in the cavity 140A where the wall portion 112 does not exist. The formation of the electric and magnetic fields 150, 152, and 154 is prevented, and the resonance frequency of the radiation noise can be shifted. For this reason, the housing 100 does not form radiated noise in the cavity 140 that matches the frequency at which the electronic component malfunctions, while employing the resin cover member 104. As a result, malfunction of the electronic component can be prevented, and the influence of external radiation noise can be reduced.

  Furthermore, according to the present embodiment, since the first region 134 of the in-vehicle circuit board 106 is partitioned by the wall portion 112, conduction noise generated in the first region 134 is difficult to propagate to the second region 136. As a result, an electronic component as a main circuit mounted in the second region 136 is less likely to malfunction due to conduction noise. The main circuit includes not only the power supply IC 128 but also an electronic circuit that is generally considered to be easily affected by conduction noise, such as a signal processing circuit including a semiconductor element and an interface circuit as described above. On the other hand, in the first region 134, a circuit element that is hardly affected by conduction noise, such as a capacitor or a resistor, may be mounted. Therefore, according to the casing 100, by forming the wall portion 112 on the base member 102, not only the radiation noise but also the influence of the conduction noise can be reduced while adopting the resin cover member 104.

  As described above, the wall portion 112 partitions the first region 134 and the second region 136 without a gap. For this reason, the conduction noise is more difficult to propagate from the first region 134 to the second region 136, and malfunction caused by the conduction noise of the electronic component mounted on the second region 136 can be further prevented.

  In the base member 102, the wall 112 defines the first region 134, and the dimension Le is smaller than the dimension Lf. For this reason, the second region 136 is not only less susceptible to conduction noise, but is wider than the first region 134, so that more electronic components as main circuits can be mounted, and conduction to these electronic components can be increased. The influence of noise can be reduced.

  Since the height of the wall 112 is equal to the height of the frame 110, the wall 112 and the in-vehicle circuit board 106 are in direct contact, and the ground or low impedance line of the in-vehicle circuit board 106 and the wall 112 are equipotential. Therefore, it is preferable as a noise countermeasure.

  FIG. 9 is a cross-sectional view illustrating another foundation member which is another embodiment of the present invention. Fig.9 (a) is a figure corresponding to the AA cross section of FIG.3 (b). FIG. 9B is a view corresponding to the BB cross section of FIG. The base member 102A is different from the base member 102 in that the height of the wall portion 112A is lower than the height of the frame 110.

  As an example, the height of the wall portion 112A, that is, the dimension Lb ′ from the bottom surface portion 108 to the upper end 112a ′ of the wall portion 112A is larger than the height dimension La of the frame body 110 as illustrated in FIG. For example, it was reduced by about 0.1 to 1 mm. For this reason, as illustrated in FIG. 9B, the in-vehicle circuit board 106 and the wall portion 112A are not in contact with each other, and a gap 160 is generated between them.

  Thereby, the in-vehicle circuit board 106 is preferable because it is not subjected to mechanical stress from the wall 112A, for example. Here, although the wall portion 112 </ b> A is not in direct contact with the in-vehicle circuit board 106, the wall portion 112 </ b> A is in indirect contact with the in-vehicle circuit board 106 through the frame body 110 in contact with the in-vehicle circuit board 106. For this reason, the wall portion 112A is equipotential with the ground or low impedance line of the in-vehicle circuit board 106, which is preferable as a noise countermeasure.

  In the above embodiment, the first region 134 and the second region 136 are partitioned by the wall portion 112 without a gap, but the present invention is not limited to this. That is, if the resonance frequency is shifted by preventing the formation of the electric field and magnetic field in the resonance mode, and further, it is possible to prevent the conduction noise from propagating from the first region 134 to the second region 136, the position of the wall portion 112. The shape and shape may be set as appropriate.

  FIG. 10 is a top view illustrating another foundation member, which is still another embodiment of the present invention. Fig.10 (a) is a figure which shows the example which changed the position of the wall part. FIG.10 (b) is a figure which shows the example which changed the shape of the wall part.

  The base member 102B is different from the base member 102 in that the wall portion 112B is located on the longer side 118a side as compared with the wall portion 112 described above. As illustrated in FIG. 10A, the wall 112B is formed without a gap from the short side 120a to the short side 120b.

  Since the wall portion 112B defines the first region 134 of the in-vehicle circuit board 106, if the first region 134 is narrow, the wall portion 112B may be formed so as to be closer to the long side 118a. In addition, as a case where the 1st area | region 134 becomes narrow, the case where the number of the columns of the through-hole 132 provided in the vehicle-mounted circuit board 106 illustrated to Fig.4 (a) is small, or the distance between columns is small is mentioned. . In such a case, among the rows of through holes 132, the row farthest from the end portion 106a is close to the end portion 106a, thereby narrowing the first region 134. As a result, the position of the wall portion 112B is also long. Near the side 118a. And the 2nd field 136 becomes a wider field, and can mount more electronic parts as a main circuit.

  As illustrated in FIG. 10B, the base member 102C is different from the base member 102 in that a gap 162 is formed in the wall 112C itself. The wall portion 112 </ b> C includes, for example, a large number of wall pieces 164 arranged adjacent to each other with a gap 162. The wall piece 164 may also have a gap 162 formed between the ground terminal 114C on the short side 120a and the short side 120b, as shown.

  Even in the wall portions 112A, 112B, and 112C, the resonance frequency is shifted by preventing the formation of the electric field and magnetic field in the resonance mode, and conduction noise is propagated from the first region 134 to the second region 136. Expected to interfere. Therefore, even when the base members 102A, 102B, and 102C are used for the housing 100, not only the radiation noise from the outside but also the influence of the conduction noise from the first region 134 can be reduced.

  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 ... Case, 102, 102A, 102B, 102C ... Base member, 104 ... Cover member, 106 ... In-vehicle circuit board, 108 ... Bottom surface part, 110 ... Frame body, 112, 112A, 112B, 112C ... Wall part, 114a- 114d: ground terminal, 116a to 116d ... flange, 117 ... external connector, 117a ... housing, 117b ... terminal, 118a, 118b ... long side, 120a, 120b ... short side, 122, 124 ... side, 128 ... power supply IC, DESCRIPTION OF SYMBOLS 130 ... Power supply line, 132 ... Through hole, 134 ... 1st area | region, 136 ... 2nd area | region, 140 ... Cavity, 142, 144, 148a-148e ... Radiation noise (electromagnetic wave), 146 ... Electromagnetic wave absorption sheet, 150, 152, 154 ... Resonance mode, 160, 162 ... Gap, 164 ... Wall piece

Claims (5)

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 in-vehicle circuit board has a first region that is connected to a plurality of terminals of an external connector and is located near one end of the in-vehicle circuit board;
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: a wall portion standing upright in the cavity from the bottom portion and partitioning the first region.   The on-vehicle circuit board housing case according to claim 1, wherein the wall portion is formed without a gap so as to cross from one end portion to the other end portion of the bottom surface portion. The in-vehicle circuit board includes the other end of the in-vehicle circuit board, and has a second region located on the opposite side of the first region across the wall portion,
The wall portion has a first side surface facing the first region and a second side surface facing the second region;
The bottom surface portion includes a first side facing the first side surface and a second side facing the second side surface,
The in-vehicle circuit board housing case according to claim 1, wherein a distance from the first side surface to the first side is smaller than a distance from the second side surface to the second side.   4. The on-board circuit board housing case according to claim 1, wherein a height of the wall portion is equal to a height of the frame body.   4. The on-board circuit board housing case according to claim 1, wherein a height of the wall portion is lower than a height of the frame body.

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