JP2004014690A - Substrate housing box - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently radiate heat generated on a circuit board from a heat sink. <P>SOLUTION: In a substrate housing box 10, a heat sink 13 is provided on the bottom of a box main body 12, a placing part 12b is projected on a peripheral wall 12a, a power circuit board 14 is placed in the heat sink 13, and a control circuit board 15 is placed on the placing part 12b. In the placing part 12b, a through screw hole 12d is formed, and on the control circuit board 15 a through hole 15e communicated with the through screw hole 12d is formed. Then, a pressing screw 11 having a spring part 11c is inserted into the through hole 15e and screwed with the through screw hole 12d to fix the control circuit board 15 on the placing part 12d, and the power circuit board 14 is pressed to the heat sink 13 with a required energizing force and fixed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a board housing box for housing a circuit board in a box body having a heat radiating section, and more particularly to efficiently transferring heat generated in the circuit board to the heat radiating section.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, circuit boards for various controls have been housed in a board housing box in order to secure waterproof and dustproof in addition to protecting the boards themselves. When the amount of heat generated by the accommodated circuit board is large, a heat radiating portion is provided in the board housing box so as to radiate the generated heat to the outside in order to prevent a problem caused by heat. Such a board storage box is used in various places, and in particular, is often mounted on a vehicle and used for controlling various electric components of the vehicle.
[0003]
FIG. 7 is a cross-sectional view of a conventional substrate storage box 1. The board housing box 1 is for controlling an electric power steering device of a vehicle, and a power circuit board 4 for controlling power supply and a control circuit board 5 for controlling various signals inside the box body 2 are spaced apart from each other. The box 8 is accommodated in a stacked state, and the cover 8 covers the opening of the box body 2.
[0004]
The box body 2 is provided with a heat sink 3 made of aluminum at the bottom of a synthetic resin peripheral wall 2a formed by insert molding, and a mounting portion 2b for the control circuit board 5 protruding from the peripheral wall 2a. The power circuit board 4 has a power circuit conductor 4b formed on a ceramic substrate portion 4a and a power semiconductor 4c such as a power transistor for power control, which generates a large amount of heat, mounted thereon. On the other hand, the control circuit board 5 also has a control circuit conductor 5b formed on a board portion 5a and a control semiconductor 5c and the like mounted thereon.
[0005]
The power circuit board 4 is fixed in a state of being placed on the heat sink 3 with the synthetic adhesive 6, transmits generated heat to the heat sink 3, and radiates heat from the heat sink 3 to the outside. On the other hand, the control circuit board 5 is fixed to the mounting portion 2 a spaced apart from the power circuit board 4 with a synthetic adhesive 6 so as not to be affected by the heat generated in the power circuit board 4. The power circuit board 4 and the control circuit board 5 are connected to the relay line 7 with a connector to connect a required circuit between the boards 4 and 5.
[0006]
[Problems to be solved by the invention]
The board housing box 1 radiates the heat of the power circuit board 4 from the heat sink 3, but the synthetic adhesive 6 is interposed between the power circuit board 4 and the heat sink 3. The synthetic adhesive 6 is necessary to fix the power circuit board 4 to the heat sink 3, but because it contains a resin component and the like, it prevents heat generated in the power circuit board 4 from being transmitted to the heat sink 3, thereby reducing heat radiation efficiency. There is a problem to do.
[0007]
For such a problem, it is also conceivable to provide a screw hole in the heat sink 3 and fix the power circuit board 4 to the heat sink 3 with screws. However, in such a screw fixing structure, it is necessary to form a screw hole in the heat sink 3 having a complicated shape, and a crack is generated in the substrate portion 4a of the power circuit substrate 4 made of ceramic by a fastening force due to the screw. Therefore, such a fixing structure is not preferable.
[0008]
On the other hand, in the board storage box 1 shown in FIG. 7, the power circuit board 4 and the control circuit board 5 are connected by a relay line 7 to form a required circuit. It is necessary to provide connectors for connection on the board 4 and the control circuit board 5, so that the cost of each board 4 and 5 is increased, and there is also a problem that connection of the relay line 7 is troublesome.
[0009]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a board housing box that can efficiently radiate heat generated on a circuit board such as a power circuit board from a heat sink.
It is another object of the present invention to provide a board storage box for securely fixing a circuit board such as a power circuit board to a heat sink with a configuration that does not cause a problem such as cracking in the board section.
Further, another object of the present invention is to provide a board housing box in which the labor and the like related to connecting circuits between a plurality of housed circuit boards are reduced.
[0010]
[Means for Solving the Problems]
A board housing box according to a first aspect of the present invention is a board housing box in which a circuit board is mounted on the heat radiating section and housed in a box body provided with a heat radiating section, wherein the first circuit board mounted on the heat radiating section is provided. A mounting portion projecting from the peripheral wall of the box main body in parallel to the first circuit board, and a mounting portion having a through screw hole formed therein; and a mounting portion mounted on the mounting portion, In a state where the second circuit board is fixed to the mounting portion by screwing the second circuit board having a through hole communicating with the through screw hole and the through screw hole through the through hole. And a pressing screw having a tip portion for pressing the first circuit board to the heat radiating portion.
[0011]
According to the first invention, the first circuit board is pressed against the heat radiating section by using a pressing screw for fixing the second circuit board to the mounting portion. Can be fixed in a state of being directly in contact with the heat radiating portion, and a state having excellent heat conductivity can be secured to improve heat radiating property. Further, since the pressing screw is screwed into the through screw hole of the mounting portion, it is not necessary to form a screw hole in the heat radiating portion.
[0012]
In order to prevent the first circuit board from being warped when pressed, at least the four corners and the center of the first circuit board are pressed by pressing screws to press the first circuit board uniformly to the heat radiating portion. Is preferred. When the board area of the first circuit board is large, it is preferable to further press the peripheral sides and the vicinity of the center with a pressing screw in addition to the above-mentioned five places in order to surely press the heat radiating portion. Further, depending on the surface roughness of each surface with which the first circuit board and the heat radiating portion abut, even if the first circuit board is pressed against the heat radiating portion, a gap may be formed between the two. It is preferable to fill with transmission grease or the like.
[0013]
In addition, it is preferable to apply a power circuit board or the like that generates a larger amount of heat than the second circuit board to the first circuit board. In this way, the heat generated by the first circuit board is radiated. The second circuit board such as the control circuit board that radiates heat from the unit and generates a small amount of heat can reduce malfunctions such as malfunction due to heat. Note that the number of second circuit boards that generate a small amount of heat is not limited to one, and a plurality of second circuit boards can be accommodated in a board storage box by providing a mounting portion on the box body in the stacking direction. Is also good.
[0014]
The board housing box according to the second invention is characterized in that the pressing screw includes an elastic portion for urging the first circuit board toward the heat radiating portion.
In the second invention, by providing the pressing screw with the elastic portion, the pressing load on the heat radiating portion of the first circuit board can be appropriately set, and the pressing load on the first circuit board can be reduced and the heat radiating portion can be reasonably reduced. Can be contacted. In addition, a leaf spring, a coil spring, or the like can be applied to the elastic portion.
[0015]
According to a third aspect of the present invention, in the board storage box, the first circuit board includes an exposed first circuit conductor, and a tip of the pressing screw abuts the first circuit conductor. .
According to the third aspect, the first circuit conductor is pressed by the pressing screw, so that the load on the first circuit board due to the pressing is further reduced, and the first circuit board is surely radiated with the required pressing force. Can be pressed against the part.
[0016]
According to a fourth aspect of the present invention, in the board housing box, the second circuit board includes an exposed second circuit conductor, and the pressing screw is formed of a conductive material, and is in contact with the second circuit conductor. There is a feature.
According to the fourth invention, the pressing screw formed of a conductive material is brought into contact with each circuit conductor of both circuit boards, so that the pressing screw itself can be used as a relay conductive member. The relay line required for the circuit connection can be eliminated, and the circuit connection between the circuit boards can be easily performed.
[0017]
In addition, as a conductive material forming the pressing screw, a material such as aluminum, copper, gold, or silver can be used. Further, in addition to forming the pressing screw with the above-described various materials, the pressing screw may be formed of a non-conductive material, and the pressing screw may be covered with the above-described various materials to secure conductivity.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings showing the embodiments.
FIG. 1 is a sectional view of a substrate storage box 10 according to an embodiment of the present invention. The board storage box 10 of this embodiment is mounted on a vehicle and connected to a steering assist motor 22 and a torque sensor 23 in the electric power steering device 21 shown in FIG. 2 to control the rotation of the motor 22. .
[0019]
The board housing box 10 includes a power circuit board 14 for controlling power supply and a control circuit board 15 for controlling signals related to rotation of the motor 22 inside a box body 12 provided with a heat sink 13 as a heat radiating section at the bottom. The box body 12 is covered with a cover 18 while being fixed and accommodated by a pressing screw 11 in a stacked state with an interval.
[0020]
As shown in FIG. 3, the box body 12 is provided with a peripheral wall 12 a surrounding three sides, and four corners inside the peripheral wall 12 a are parallel to the upper surface 13 a of the heat sink 13 at locations spaced from the heat sink 13. The mounting portions 12b are projected in the respective directions, and a central mounting portion 12c is provided on one of the three peripheral walls 12a so as to protrude from the center in the side direction to the center of the box body 12. . Each of the mounting portion 12b and the central mounting portion 12c is formed with a through screw hole 12d.
[0021]
The box body 12 is made of synthetic resin, and is formed integrally with the heat sink 13 by insert molding with the heat sink 13 made of aluminum. The cover 18 is formed in a substantially L-shape that covers the upper opening 12e and the side opening 12f of the box body 12.
[0022]
On the other hand, in the power circuit board 14 shown in FIG. 1, the first circuit conductor 14b is exposed on the upper surface 14d according to the circuit shape by performing an etching process on the ceramic substrate portion 14a, and the power for controlling the power supply is provided. The semiconductor 14c is mounted. The power circuit board 14 according to the present embodiment, in a state where the power circuit board 14 is accommodated in the box body 12 shown in FIG. 3, opposes each through screw hole 12 d of the mounting portion 12 b and the central mounting portion 12 c in a plan view direction. The circuit shape is such that the first circuit conductor 14b exists.
[0023]
The above-described power circuit board 14 corresponds to a first circuit board, and a current formed by a power supply (vehicle battery) having a high voltage value flows through a circuit formed by the first circuit conductors 14b and the like. The amount of heat generated at 14c and the like is larger than that of the control circuit board 15 corresponding to the second circuit board.
[0024]
In the control circuit board 15 shown in FIG. 1, the second circuit conductor 15b is exposed on the upper surface 15d of the board portion 15a according to the circuit shape, and various control semiconductors 15c are mounted. Further, as shown in FIG. 4, the control circuit board 15 has a circuit shape in which the second circuit conductor 15b exists at a position facing the through screw hole 12d in a state of being housed in the box main body 12 similarly to the power circuit board 14. And a through hole 15e is formed at a position corresponding to each through screw hole 12d.
[0025]
The current value of the current flowing through the second circuit conductor 15b of the control circuit board 15 is smaller than the current value flowing through the first circuit conductor 14b of the power circuit board 14. Further, a part of the circuit formed by the second circuit conductor 15b of the control circuit board 15 needs to be connected to a required circuit formed by the first circuit conductor 14b of the power circuit board 14 for power supply and the like. The pressing screw 11 is used for circuit connection between the control circuit board 15 and the power circuit board 14.
[0026]
As shown in FIG. 5A, the pressing screw 11 is formed integrally with a screw head 11a, a screw part 11b, and a leaf spring-like spring part 11c which is an elastic part having a required urging force. The material is copper, which is a conductive material. Note that the screw portion 11b is set to a size that can be screwed with each of the through screw holes 12d of the box body 12, and the spring portion 11c under no load is gently fitted within the hole diameter of the through screw hole 12d. It has a curved shape so that the direction of deflection under load is uniform.
[0027]
Next, an assembling procedure of the substrate storage box 10 according to the present embodiment will be described.
First, the heat transfer grease 20 is applied to the upper surface 13a of the heat sink 13 of the box body 12 shown in FIG. 3, as shown in FIGS. After the application of the heat transfer grease 20, the power circuit board 14 is inserted through the side opening 12f of the box body 12, and is placed on the upper surface 13a of the heat sink 13. In addition, the control circuit board 15 is housed inside the opening 12e above the box main body 12, and is placed on the placing portion 12b and the central placing portion 12c.
[0028]
By mounting the control circuit board 15 in this manner, as shown in FIGS. 1, 5A and 5B, the through holes 15e of the control circuit board 15, the mounting portion 12b and the center mounting Each of the through holes 12d of the mounting portion 12c is in communication with each other. Next, when the pressing screw 11 is inserted into each of the through-holes 15e and the through-screw holes 12d and rotated in the screwing direction, as shown in FIG. Contact the first circuit conductor 14b. In this state, the screw head 11a of the pressing screw 11 is not in contact with the second circuit conductor 15b of the control circuit board 15.
[0029]
When the pressing screw 11 is further rotated in the screwing direction from the above-described state, the spring portion 11c is bent and completely screwed into the through screw hole 12d, and as shown in FIG. 15 and makes contact with the second circuit conductor 15b to fasten and fix the control circuit board 15 to the mounting portion 12b and the central mounting portion 12c. On the other hand, the pressing screw 11 that has been screwed presses the power circuit board 14 uniformly with a required urging force to the heat sink 13 with the heat transfer grease 20 interposed therebetween due to the bending of the spring portion 11c, and an appropriate load is applied. It is fixed with. After the power circuit board 14 and the control circuit board 15 are fixed to the box main body 12 in this way, the cover 18 is put on the board housing box 10 to complete it.
[0030]
The completed circuit board housing box 10 has no gap between the power circuit board 14 and the heat sink 13 because the power circuit board 14 is pressed against the heat sink 13 with the heat transfer grease 20 interposed therebetween. The heat generated in the circuit board 14 is reliably transmitted to the heat sink 13 and radiated to the outside. In addition, since the power circuit board 14 is pressed against the rigid first circuit conductor 14b by the pressing screw 11 having the spring portion 11c, the load on the pressing of the substrate portion 14a is smaller than that when the power circuit board 14 is directly fixed by the screw. It is less likely to cause problems such as cracks.
[0031]
Further, the pressing screw 11 comes into contact with the first circuit portion 14 of the power circuit board 14 with the spring portion 11c, and also contacts the second circuit conductor 15b of the control circuit board 15 with the screw head 11a. The required circuit connection between the two boards is performed by conducting itself, and the board housing box 10 eliminates the connecting relay wire, thereby reducing the labor and the like related to the relay of the circuit.
[0032]
Note that the substrate storage box 10 according to the present invention is not limited to the above-described embodiment, and various modifications can be applied. For example, like a pressing screw 31 shown in FIG. 6A, a coil spring-shaped one can be applied to the spring portion 31c, and the spring portion 31c may rotate separately from the screw portion 31b, or may rotate together. You may do so. Further, a spring 41c may be provided in the middle of the screw portion 41b like the pressing screw 41 shown in FIG. 6B, and further, as shown in FIG. It is also possible to apply a plunger type pressing screw 51 having a built-in spring portion 51c.
[0033]
Further, the pressing screw 11 (including the pressing screw of the modified example; the same applies hereinafter) can be made of aluminum, gold, or silver as a material other than copper in order to secure conductivity. In the case of manufacturing with a material having low conductivity, the surface may be coated with aluminum, copper, gold, or silver by plating or the like to secure conductivity. When it is not necessary to connect a circuit between the power circuit board 14 and the control circuit board 15, it is not necessary to secure the conductivity of the pressing screw 11, and the pressing screw 11 and the second circuit conductor of the control circuit board 15 may be omitted. There is no need to make contact with 15b.
[0034]
In addition, the substrate portion 14a of the power circuit board 14 may be formed of a metal such as aluminum having an insulating layer, instead of being formed of ceramic. When it is not necessary to connect a circuit between the control circuit board 14 and the control circuit board 15, the board 14a may be directly pressed by the pressing screw 11.
[0035]
Further, the board housing box 10 houses a plurality of control circuit boards 15 with respect to one power circuit board 14 by providing a plurality of mounting portions 12b and the like in the board stacking direction on the peripheral wall 12a of the box body 12. You may make it.
[0036]
【The invention's effect】
As described in detail above, according to the first aspect of the invention, the first circuit board can be fixed to the heat radiating portion in a state having excellent thermal conductivity, so that the heat radiating property can be improved as compared with the related art.
According to the second invention, the first circuit board can be pressed against the heat radiating portion with an appropriate load, the load of pressing the first circuit board against the board can be reduced, and the first circuit board can be radiated well. Can be pressed against the radiator.
[0037]
According to the third aspect, the burden on the first circuit board due to the pressing can be further reduced.
According to the fourth aspect of the invention, required circuits between the circuit boards can be connected by pressing screws that ensure conductivity, and the connection between the circuit boards can be made more efficient.
[Brief description of the drawings]
FIG. 1 is a sectional view of a substrate storage box according to an embodiment of the present invention.
FIG. 2 is an overall schematic diagram of an electric power steering device to which a substrate housing box is applied.
FIG. 3 is a perspective view of a disassembled state of a box main body and a cover of the substrate storage box.
FIG. 4 is a perspective view of a main part of a control circuit board.
5A is a schematic view showing a state before a pressing screw is inserted into a through hole and a through screw hole, and FIG. 5B is a diagram showing a state where the pressing screw is screwed into the through screw hole and a control circuit board is placed. FIG. 4 is a schematic view of a state before being fixed to.
FIGS. 6A, 6B, and 6C are schematic front views of a pressing screw according to a modified example.
FIG. 7 is a sectional view of a conventional substrate storage box.
[Explanation of symbols]
Reference Signs List 10 Substrate storage box 11 Pressing screw 11c Spring part (elastic part)
12 Box body 12a Peripheral wall 12b Mounting part 12d Through screw hole 13 Heat sink (radiator)
14 power circuit board 14b first circuit conductor 15 control circuit board 15b second circuit conductor 15e through hole

Claims (4)

In a board housing box for mounting and housing a circuit board on the heat radiating section in a box body provided with a heat radiating section,
A first circuit board mounted on the heat radiating section;
A mounting portion projecting from the peripheral wall of the box main body in parallel with the first circuit board and having a through screw hole formed therein;
A second circuit board mounted on the mounting portion and having a through-hole communicating with the through-screw hole;
A pressing screw having a distal end portion pressing the first circuit board toward the heat radiating portion in a state where the second circuit board is fixed to the mounting portion by inserting the through hole and screwing with the through screw hole; A substrate storage box, comprising: The board housing box according to claim 1, wherein the pressing screw includes an elastic part that urges the first circuit board toward the heat radiating part. The first circuit board includes an exposed first circuit conductor,
3. The substrate housing box according to claim 1, wherein a tip of the pressing screw is in contact with the first circuit conductor. The second circuit board includes an exposed second circuit conductor;
4. The board storage box according to claim 3, wherein the pressing screw is formed of a conductive material, and is in contact with the second circuit conductor. 5.

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