JP5781982B2 - In-vehicle circuit board housing case and in-vehicle electronic control device - Google Patents

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, and a vehicle-mounted electronic control device that includes the vehicle-mounted circuit board housing case.

  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 addition, as represented by the metal cover of the casing shown in Patent Document 1, the metal cover tends to have a smaller dimension in the thickness direction from the viewpoint of weight reduction and space saving of the casing. It is expected to be. Therefore, it is considered that the dimension of the space where the resonance phenomenon occurs between the on-vehicle circuit board and the metal cover tends to be small.

  In view of such a problem, an object of the present invention is to provide an in-vehicle circuit board housing case and an in-vehicle electronic control device that can reduce the influence of radiation noise while adopting 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 that forms a cavity together with the bottom surface portion, and the distance between the bottom surface portion of the base member and the in-vehicle circuit board is about 5.5 mm or 5.5 mm or more.

  In the above configuration, a case is assumed where a cavity is formed between the bottom surface portion of the base member and the in-vehicle circuit board, and radiation noise (electromagnetic wave) is irradiated from the outside toward the cover member. 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. Further, since the resonance phenomenon is determined by the size and shape of the cavity, it is considered that the resonance phenomenon depends not only on the long side and the short side length of the rectangular bottom surface portion but also on the distance between the bottom surface portion and the in-vehicle circuit board.

  Therefore, in the present invention, contrary to the technical tendency of reducing the above-described cavity, the distance between the bottom surface portion of the base member and the in-vehicle circuit board is set to about 5.5 mm or 5.5 mm or more to widen the cavity. . As a result, it is believed that the formation of resonant mode electric and magnetic fields, which are expected to occur in the cavity when the distance is less than 5.5 mm, is prevented. In other words, by setting the above distance to 5.5 m or more among the dimensions of the cavity functioning as the cavity resonator, the resonance mode associated with the resonance phenomenon determined by the dimension and shape of the cavity is also changed. The resonance frequency of the electromagnetic wave can be shifted. 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 base member is good to contain the interposition member which contact | connects a vehicle-mounted circuit board and can change the distance of a bottom face part and a vehicle-mounted circuit board. As an example, a base member in which an interposition member having a thickness of 0.5 mm or more is prepared, the long side dimension of the bottom surface part is 105 mm, the short side dimension is 85 mm, and the dimension from the bottom surface part to the upper end of the frame body is 5 mm. Prepared. Therefore, the distance is increased by the thickness of the interposition member and is changed from 5 mm to 5.5 mm or more (in other words, the cavity depth is increased by 10% or more).

  And when the in-vehicle circuit housing | casing housing | casing using said base member was irradiated without the interposed member arrange | positioning the radiation noise of electric field strength 200V / m which has a frequency of 1.5 GHz vicinity, malfunction was confirmed. On the other hand, an interposition member having a thickness of 0.5 mm obtained by stacking copper foil tapes is interposed between the base member and the in-vehicle circuit board, and in that state, has a frequency in the vicinity of 1.5 GHz similarly to the above. When radiated noise with an electric field strength of 200 V / m was irradiated, no malfunction occurred. As the interposition member, if the thickness is 0.5 mm or more, a washer having a thickness of about 1 mm or a nut having a thickness of about 3 mm may be used. No malfunction occurred even when the housing in which these interposition members were arranged was irradiated with radiation noise having an electric field strength of 200 V / m having a frequency near 1.5 GHz. As described above, it has been clarified that the influence of electromagnetic waves, that is, the presence or absence of malfunctioning fluctuates by interposing the interposition member between the base member and the in-vehicle circuit board and changing the distance. In other words, if the above-mentioned distance is changed by the interposition member, as a result, the frequency of the electromagnetic wave can be prevented from matching the malfunction frequency of the electronic component, and malfunction of the electronic component can be prevented.

  The on-vehicle circuit board housing case may further include a polystyrene foam disposed in the cavity. Styrofoam is a dielectric material with a relative dielectric constant of 2 to 2.5, good radio wave transmission depending on the frequency band of electromagnetic waves, the resonance mode changes, and the resonance frequency that causes malfunction of electronic components It is thought that there is a case to shift. Therefore, the influence of the radiation noise from the outside can be reduced more effectively.

  Another representative configuration of the 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 that houses the in-vehicle circuit board. And a resin cover member that covers the in-vehicle circuit board and is assembled to the base member. The base member is erected around the rectangular bottom surface portion and the bottom surface portion. It has the frame which forms a cavity with a bottom face part, and is provided with the expanded polystyrene arranged in the cavity.

  According to the said structure, it is thought that the situation equivalent to lengthening the path | route through which an electromagnetic wave passes substantially can be created by arrange | positioning dielectrics like a polystyrene foam in a cavity. Thereby, as an example, even when the distance between the bottom surface portion of the base member and the on-vehicle circuit board is 5 mm, the apparent resonance frequency can be shifted, and malfunction of electronic components can be prevented. It is thought that the influence of radiation noise from can be reduced.

  In order to solve the above-described problems, a typical configuration of an on-vehicle electronic control device according to the present invention includes the above-described on-vehicle circuit board housing case. In this way, it is possible to obtain a highly reliable on-vehicle electronic control device that reduces the influence of radiation noise.

  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, and the vehicle-mounted electronic control apparatus can be provided, employ | adopting resin members.

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 and interposition 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 state which has not arrange | positioned the interposition member in the base member of FIG. It is a schematic diagram explaining the resonance phenomenon which arises in the cavity formed with the base member of FIG. FIG. 8 is a diagram illustrating resonance modes expected to occur in the cavity of FIG. 7. It is a figure which illustrates the relationship between the distance from the base member of FIG. 7, and a vehicle-mounted circuit board, and the presence or absence of malfunction. It is sectional drawing which illustrates a part of vehicle-mounted circuit board housing | casing housing | casing which is other embodiment of this 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. .

  Moreover, the housing | casing 100 is provided with the interposed members 107a, 107b, 107c, and 107d interposed between the base member 102 and the vehicle-mounted circuit board 106, as shown in FIG. The interposition members 107a, 107b, 107c, and 107d all have the same shape, and a copper foil tape is stacked to a thickness of about 0.5 mm, a washer having a thickness of about 1 mm, or a thickness of about 3.5 mm. It can be a nut. Here, the interposed members 107a, 107b, 107c, and 107d are illustrated as washers.

  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 and a frame body 110 erected around 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 diagram illustrating the base member 102 and the interposition members 107a to 107d of the housing 100 of FIG. FIG. 3A is a top view of the base member 102 and the interposed members 107a to 107d. FIG.3 (b) is AA sectional drawing of Fig.3 (a).

  As illustrated in FIG. 3A, interposition members 107 a to 107 d are respectively disposed on the ground terminals 114 a to 114 d of the base member 102. These ground terminals 114a to 114d and interposition members 107a to 107d are perforated as shown. The ground terminals 114a to 114d are also used as fastening portions when assembling the in-vehicle circuit board 106 and the cover member 104 via the interposition members 107a to 107d.

  Here, the height of the frame 110 of the base member 102 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 was set to 5 mm. Further, as illustrated in FIG. 3B, the dimension Lb in the thickness direction of the interposed member 107d that is arranged on the ground terminal 114d and is typically shown is 0.5 mm.

  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 dimension Lc illustrated in FIG. 3B of the long sides 118a and 118b is about 105 mm, and the dimension Ld of the short sides 120a and 120b illustrated in FIG.

  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 130 and a power supply line 132 connected to the power supply IC 130 are mounted on the back surface of the in-vehicle circuit board 106. The power supply line 132 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).

  The interposition members 107a to 107d illustrated by dotted lines in FIG. 5A are in contact with the ground terminals 114a to 114d on the lower surface (see FIG. 3A), and are in contact with the in-vehicle circuit board 106 on the upper surface. For this reason, as illustrated in FIG. 5B, the upper end 110a of the frame 110 and the in-vehicle circuit board 106 are separated by 0.5 mm as a dimension Lb in the thickness direction of the interposed members 107a to 107d. Become.

  As described above, the height of the frame 110 is 5 mm, which is the dimension La from the bottom surface portion 108 to the upper end 110a of the frame 110. Therefore, the distance from the bottom surface portion 108 to the in-vehicle circuit board 106 is a distance obtained by adding the dimension Lb to the dimension La, that is, 5.5 mm. In other words, the presence of the interposition members 107 a to 107 d causes the distance from the bottom surface portion 108 to the in-vehicle circuit board 106 to be 10% larger than the dimension La from the bottom surface portion 108 to the upper end 110 a of the frame 110. That is, the interposition members 107a to 107d are members that come into contact with the in-vehicle circuit board 106 and allow the distance between the bottom surface portion 108 and the in-vehicle circuit board 106 to be changed. The dimension La is set so that the power supply IC 130 and the like can be mounted on the back surface of the in-vehicle circuit board 106.

  The upper end 110a of the frame 110 is in contact with the in-vehicle circuit board 106 via the interposition members 107a to 107d, and as illustrated in FIG. 5B, there is a cavity between the bottom surface portion 108 and the in-vehicle circuit board 106. 140 is formed. That is, the dimension of the cavity 140 is such that the long side is 105 mm, the short side is 85 mm, and the height (thickness) is 5.5 mm, and the height is 0 than the height of the frame 110 by the interposition members 107a to 107d. .5mm higher.

  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 state where the interposition members 107a to 107d are not arranged on the base member 102 of FIG. Here, the dimension Le between the ground terminals 114c and 114d was about 90 mm. As shown in the figure, 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. As shown in the figure, the ground terminal 114d is located in the vicinity of a location where the long side 118a and the short side 120b intersect.

  FIG. 7 is a schematic diagram for explaining the principle of the resonance phenomenon that occurs in the cavity formed by the base member 102 of FIG. FIG. 7A shows a state in which a resonance phenomenon occurs in the cavity when the base member 102 is used without the interposed members 107a to 107d being arranged. FIG.7 (b) has shown the mode of the radiation noise in the structure which abbreviate | omitted the base member 102 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. 7A, the base member 102 forms a cavity 140A with the in-vehicle circuit board 106 in a state where the interposition members 107a to 107d are not disposed on the ground terminals 114a to 114d. doing.

  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. It is assumed that the ECU includes an in-vehicle circuit board 106 accommodated in the casing 100, and no interposition members 107a to 107d are disposed between the in-vehicle circuit board 106 and the base member 102. 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 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 radiation 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 102. As illustrated in FIG. 7A, the radiation noise 144 reflected by the base member 102 is partially reflected by the in-vehicle circuit board 106 and then reflected again by the base member 102.

  That is, since the cavity 140A is a space surrounded by the metal base member 102 and the in-vehicle circuit board 106 that can be considered as a conductive wall, it is considered to function 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 102, 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 102.

  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 102 as the radiated noise 148a, is reflected by the base member 102, 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 140A as the 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.

  Accordingly, in the casing 100 using the base member 102 without the interposed members 107a to 107d schematically shown in FIG. 7A, the in-vehicle circuit board 106 and the base member 102 are parallel through the cavity 140A. It is assumed that a resonance phenomenon that forms a flat plate and causes so-called parallel plate resonance occurs.

  FIG. 8 is a diagram illustrating a resonance mode expected to occur in the cavity. 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 illustrated in FIG. In addition, the figure illustrated to the upper side as each resonance mode in Fig.8 (a) has shown the state which looked at the cavity 140A from upper direction. 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.

  On the other hand, FIG. 8B shows that the interposed members 107a to 107d are arranged between the base member 102 and the in-vehicle circuit board 106, and the height is higher than the cavity 140A by the thickness dimension Lb of the interposed members 107a to 107d. It is assumed that the cavity 140 illustrated in 5 (b) is formed. That is, as illustrated in the lower side of FIG. 8B, in the cavity 140, the distance from the bottom surface 108 to the in-vehicle circuit board 106 is a distance obtained by adding the dimension Lb to the dimension La. .

  The resonance modes 150, 152, and 154 illustrated in FIG. 8A and FIG. 8B are all representative modes, assuming that the resonance frequency is about 1.6 GHz, which is a malfunction frequency of the electronic component. Yes. The wavelength of the electromagnetic wave having a frequency of 1.64 GHz is calculated from the equation (1).

Wavelength = velocity of electromagnetic wave / frequency≈3 × 10 ¹¹ /1.64×10 ⁹ = 182.8 mm (1)
Resonance mode is achieved when a half wave of an electromagnetic wave having a frequency of 1.64 GHz calculated by the above formula (1), that is, a harmonic of an integral multiple of 91.4 mm, exists as a standing wave in the cavity 140A and resonates. Electromagnetic fields indicated by 150, 152, and 154 are formed, respectively. 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 108 of the base member 102 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. 6 is about 90 mm, and is ½ of the frequency of 1.64 GHz at which many electronic components mounted on the in-vehicle circuit board 106 malfunction. The size was close to the wavelength of 91.4 mm.

  On the other hand, since the resonance phenomenon is determined by the size and shape of the space, the bottom surface portion 108 is not limited to the length between the long sides 118a and 118b, the short sides 120a and 120b or the ground terminals 114c and 114d of the rectangular bottom surface portion 108. It is considered that this also depends on the distance between the circuit board 106 and the in-vehicle circuit board 106.

  Therefore, in the present embodiment, against the technical trend of reducing the cavity 140A from the viewpoint of weight reduction and space saving of the housing 100, the interposed members 107a to 107d are provided between the base member 102 and the in-vehicle circuit board 106. And a cavity 140 was formed in which the distance between the bottom surface portion 108 and the in-vehicle circuit board 106 was increased. As a result, in the present embodiment, the malfunction frequency of the electronic component is prevented by shifting the resonance frequency of the radiation noise to be different from the frequency at which the electronic component malfunctions. This will be specifically described below.

  As illustrated in FIG. 8B, the distance between the bottom surface portion 108 and the in-vehicle circuit board 106 is a distance obtained by adding the dimension Lb in the thickness direction of the interposition members 107a to 107d to the dimension La. For this reason, the above-mentioned cavity 140 is formed, which is different from the size and shape of the cavity 140A formed when the interposed members 107a to 107d are not present. Note that the distance between the bottom surface portion 108 and the in-vehicle circuit board 106 is 5.5 mm as described above, and the dimension La is 5 mm, which is 10% larger than the dimension La.

  That is, since the dimension of the space functioning as the cavity resonator changes depending on the presence of the interposed members 107a to 107d, it is considered that the resonance mode accompanying the resonance phenomenon determined by the size and shape of the space also changes. For this reason, in the cavity 140 schematically shown in FIG. 8B, a resonance mode different from the resonance modes 150, 152, and 154 in the figure formed in the cavity 140A is formed although illustration is omitted. is expected. Therefore, in the cavity 140, the formation of the electric field and magnetic field shown in the resonance modes 150, 152, and 154 is prevented, and an electromagnetic field different from the electromagnetic field shown in the resonance modes 150, 152, and 154 is formed. As a result, the resonance frequency of the electromagnetic wave in the cavity 140 can be shifted.

  FIG. 9 is a diagram illustrating the relationship between the distance from the base member 102 to the in-vehicle circuit board 106 and the presence or absence of malfunction. Here, as an example, as a result of radiating noise having a frequency of 1 to 2 GHz to the casing 100 in which the distance from the bottom surface portion 108 of the base member 102 to the in-vehicle circuit board 106 is changed, the presence or absence of malfunction is confirmed. Is shown. The distance is 5 mm when the interposed members 107a to 107d are not arranged. Further, when a 3.5 mm thick nut or a 1 mm thick washer is respectively disposed as the interposition members 107a to 107d, the above distance becomes 8.5 mm or 6 mm by adding 3.5 mm or 1 mm to 5 mm. Furthermore, when the interposed members 107a to 107d having a thickness of 0.5 mm formed by stacking the copper foil tapes are arranged, the above distance becomes 5.5 mm by adding 0.5 mm to 5 mm.

  In the figure, when the in-vehicle circuit housing case 100 is irradiated with radiation noise having an electric field strength of 200 V / m having a frequency of about 1.5 GHz without placing the interposition members 107a to 107d, the above distance is 5 mm. In this case, the malfunction was confirmed and the result was “NG”. However, when the interposition members 107a to 107d were arranged and the distances were increased to 5.5 mm, 6 mm, and 8.5 mm, no malfunction occurred and the result was “OK”. In addition, said distance is 10% or more larger compared with the case where interposition member 107a-107d is not arrange | positioned. Thus, it becomes clear that the influence of electromagnetic waves fluctuates by the interposed members 107a to 107d, and as a result, the frequency of the electromagnetic waves is also considered to change.

  According to the present embodiment, the interposition members 107a to 107d having the above thickness are interposed between the base member 102 having the above dimensions and the in-vehicle circuit board 106, so that the dimensions of the space functioning as a cavity resonator are obtained. And change shape. As a result, it is possible to prevent the formation of electric and magnetic fields in the resonance modes 150, 152, and 154, which are expected to occur in the cavity 140A in which the interposition members 107a to 107d do not exist, and to shift the resonance frequency of the radiation noise. 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. In the above embodiment, the distance between the bottom surface portion 108 of the base member 102 and the in-vehicle circuit board 106 is changed via the interposition members 107a to 107d. However, the present invention is not limited to this. As an example, the distance from the bottom surface portion 108 of the base member 102 to the upper end 110a of the frame 110 is set in advance so that the above-mentioned distance is about 5.5 mm or 5.5 mm or more without using the interposition members 107a to 107d. May be. In short, in the in-vehicle circuit board housing case, the above-described distance may be set so that radiated noise matching the frequency at which the electronic component malfunctions is not formed in the cavity.

  FIG. 10 is a cross-sectional view illustrating a part of an in-vehicle circuit board housing as another embodiment of the present invention. Note that the cross-sectional view of FIG. 10A corresponds to FIG. 5B. In the above embodiment, the resonance frequency of the radiation noise is shifted by arranging the interposed members 107a to 107d. However, the present invention is not limited to this. That is, as illustrated in FIG. 10, the flat foam polystyrene 160 may be disposed in the cavity 140 after the interposition members 107 a to 107 d are disposed.

  The expanded polystyrene 160 is a dielectric having a relative dielectric constant of 2 to 2.5. For this reason, by disposing the polystyrene foam 160 in the cavity 140, radio wave transmission is improved depending on the frequency band of radiation noise, the above-described resonance mode is changed, and as a result, the electronic component malfunctions. It is considered that the resonance frequency may be shifted. Therefore, even if it is such a housing | casing, the influence of the radiation noise from the outside can be reduced more effectively. From this fact, by disposing a dielectric material such as polystyrene foam, it is possible to create a situation equivalent to substantially extending the path through which the radio wave passes. Thus, unlike the case illustrated in the cross-sectional view of FIG. 10B, the base member 102 does not have the length of the dimension Lb in the thickness direction illustrated in FIG. 5B or FIG. Even if the distance from the bottom surface portion 108 to the in-vehicle circuit board 106 is set to 5 mm, for example, by disposing the foamed polystyrene 160 in the cavity 140, the apparent resonance frequency can be shifted, and the influence of radiation noise can be reduced. Although the foamed polystyrene 160 has a flat plate shape, it may have an appropriate shape. In addition, by using the on-vehicle circuit board housing case according to each of the above-described embodiments, it is possible to obtain a highly reliable on-vehicle electronic control device in which the influence of radiation noise is 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 for housing an in-vehicle circuit board on which an electronic component that operates at a specific frequency is mounted, and an in-vehicle electronic control device.

DESCRIPTION OF SYMBOLS 100 ... Housing | casing 102 ... Base member, 104 ... Cover member, 106 ... In-vehicle circuit board, 107a-107d ... Interposition member, 108 ... Bottom part, 110 ... Frame, 114a-114b ... Ground terminal, 116a-116d ... Flange DESCRIPTION OF SYMBOLS 117 ... External connector, 118a, 118b ... Long side, 120a, 120b ... Short side, 130 ... Power supply IC, 132 ... Power supply line, 140 ... Cavity, 142, 144, 148a-148e ... Radiated noise (electromagnetic wave), 146 ... Electromagnetic wave absorbing sheet, 150, 152, 154 ... resonance mode, 160 ... styrene foam

Claims (4)

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 has a rectangular bottom surface, a frame standing around the bottom surface and forming a cavity together with the bottom surface, and a plurality of ground terminals formed using the bottom surface and the frame And
The length of the long side of the bottom portion, the length of the short side, or a ground terminal located in the vicinity of a location where the long side and the short side intersect with another ground located at a position away from the intersecting location The length between the terminals is substantially equal to a half wavelength of the electromagnetic wave of the malfunction frequency of the electronic component, and the distance between the bottom surface portion of the base member and the in-vehicle circuit board is 5.5 mm or more. An on-vehicle circuit board housing case characterized by the above.   2. The on-board circuit board housing case according to claim 1, wherein the base member includes an interposition member that comes into contact with the on-board circuit board and allows a distance between the bottom surface portion and the on-board circuit board to be changed.   The on-vehicle circuit board housing case according to claim 1, further comprising a polystyrene foam disposed in the cavity.   An in-vehicle electronic control device comprising the in-vehicle circuit board housing case according to any one of claims 1 to 3.

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