JP2017022224A - Electronic device including easy to remove circuit board having high vibration resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an electronic device having high vibration resistance where a circuit board can be attached removably.SOLUTION: In an electronic device including a circuit board (102), and housings (100a, 100b) for holding the circuit board, the housings are constituted to hold the edge of the circuit board partially or entirely (Q part, R part), and to hold one part (P part) of the region on the circuit board farther inside than the edge.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an electronic device including a circuit board that can be easily attached and detached, and particularly to an electronic device including a circuit board having high vibration resistance.

  Conventionally, in an electronic device including a circuit board, a plurality of locations near the edge portion of the circuit board (for example, the vicinity of the four corner portions or the vicinity of four opposing edges) are screwed to the casing of the electronic device. Thus, the circuit board is fixed. As a result, the circuit board is firmly fixed to the housing of the electronic device. On the other hand, when it is desired to remove the circuit board for maintenance of the electronic device, the configuration using a large number of screws is required. Becomes complicated.

  For this reason, for example, the case of the electronic device has a case and a cover, and the circuit board is fixed by sandwiching the periphery of the edge portion of the circuit board in the case of the electronic device (that is, the case and the cover). The structure which performs is known (refer patent document 1). In general, in the configuration in which the edge portion of the circuit board is sandwiched and fixed in the casing, the circuit board portion sandwiched by the casing is subjected to stress along with changes in environmental temperature due to a difference in thermal expansion coefficient between the circuit board and the casing. May occur, or the contact portion between the circuit board and the housing may rub against each other to generate metal powder, resulting in malfunction of the electronic circuit. For this reason, in the configuration described in Patent Document 1, in particular, by providing a slit in the vicinity of the portion of the circuit board that is sandwiched between the casings to release the stress, damage to the board and generation of metal powder are prevented. Suppressed.

  However, in the configuration of Patent Document 1, since the edge portion of the circuit board is fixed, when the electronic device is installed in a vibration environment, the central portion of the circuit board is bent and damaged depending on the frequency of vibration applied. May occur. That is, in the conventional electronic device, there is room for further improvement in the vibration resistance of the circuit board attached inside the electronic device.

JP, 2014-099572, A

  From the above background, it is desired to realize an electronic device in which a circuit board can be easily attached and detached and has high vibration resistance.

One aspect of the present invention is an electronic device including a circuit board and a casing that holds the circuit board, and the casing holds part or all of an edge portion of the circuit board. In addition, it is configured to hold one part of the area inside the edge part on the circuit board.
According to another aspect of the present invention, the casing is made of a conductive material, and a ground pattern is formed in one part of the inner region of the circuit board held by the casing. The ground current of the electronic circuit configured on the circuit board flows out of the ground pattern to the housing and returns to the power source provided outside the electronic device.
According to another aspect of the present invention, the circuit board includes a plurality of ground patterns provided for one or a plurality of circuit blocks formed on the circuit board, and each of the plurality of ground patterns includes: It is directly connected to the ground pattern formed in one part of the inner region.
According to another aspect of the present invention, the electronic device is a control device that is mounted on a vehicle and controls the operation of the vehicle, wherein the housing is fixed to the vehicle body of the vehicle, It is electrically connected to a power supply ground terminal mounted on the vehicle.
According to another aspect of the present invention, the position of the contact portion between the portion of the inner region and the housing on the circuit board is such that the mechanical resonance frequency of the circuit board is higher than a predetermined frequency. Selected to be higher.
According to another aspect of the present invention, the casing grips the circuit board by a pressurizing tool provided in the vicinity of a contact portion between the casing and a portion of the inner region of the circuit board. Power is granted.
Another aspect of the present invention is an electronic device having the above-described configuration.
According to another aspect of the invention, the pressure tool is a screw.

It is a block diagram which shows the structure of the electronic device which concerns on one Embodiment of this invention. It is a figure which shows an example of the circuit board used for the electronic device shown in FIG. It is a figure for demonstrating the fixing structure of the circuit board in the housing | casing of the electronic device shown in FIG.

  Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, as an example, an electronic device that is a control device that is mounted on a vehicle and controls the operation of the vehicle is shown, but the electronic device according to the present invention is not limited to this application. In addition to a control device that performs vehicle control, the present invention can be widely applied as an electronic device having other uses or functions.

  FIG. 1 is a diagram illustrating a configuration of an electronic device according to an embodiment of the present invention. FIG. 1A is a top view of the electronic device 10, and FIG. 1B is a front view of the electronic device 10. .

  The electronic device 10 is an electronic control unit (ECU, Electronic Control Unit) that is mounted on a vehicle and performs engine control of the vehicle, and includes a base 100a made of a conductive material (for example, a metal such as aluminum or a conductive resin). A conductive casing 100 constituted by a cover 100b, a circuit board 102 mounted inside the casing 100, a connector 104 mounted on the circuit board 102 and partially exposed outside the casing 100, Have The base 100a and the cover 100b are fastened by a screw 106 provided at a substantially central portion of the top view shown in FIG. 1A, and the circuit board 102 is fixed between the base 100a and the cover 100b by the fastening. The fixing structure of the circuit board 102 will be described later.

  2A and 2B are diagrams showing an example of the circuit board 102. FIG. 2A is a plan view of the circuit board 102, FIG. 2B is a cross-sectional view taken along the line TT, and FIG. FIG. A hole 200 through which the screw 106 is inserted is provided in the center portion of the circuit board 102, and the peripheral portion of the hole 200 of the circuit board 102 is thicker than the other parts on the front and back sides of the circuit board 102. Thin recesses 202 and 204 are provided in an annular shape (FIGS. 2B and 2C).

  In addition, a ground pattern 206 configured to come into contact with the cover 100b of the housing 100 when the circuit substrate 102 is accommodated in the housing 100 is provided in a central region including the hole 200 of the circuit substrate 102. Yes. Further, the circuit board 102 is provided with ground patterns 208, 210, 212 provided for each of a plurality of circuit blocks constituting an electronic circuit (not shown) formed on the circuit board 102. ˜212 are directly and electrically DC connected to the ground pattern 206 provided in the region including the hole 200 via the connection patterns 214, 216, and 218, respectively. In the following description, “connected” means electrically connected in a direct current unless otherwise specified.

  Here, the circuit block refers to a part of an electronic circuit that can be classified by a predetermined attribute such as a function or a signal to be handled, for example, a transistor that amplifies an analog minute signal from a sensor or the like input from the outside of the electronic device 10, for example. A small signal amplifier circuit block including an amplifier circuit, a logical operation block including a computer that performs a logical operation by converting an amplified analog signal output from the small signal amplifier circuit block into a digital signal, and the logical operation block A drive circuit block or the like that drives a load such as an actuator existing outside the electronic device 10 with a high voltage and / or a large current based on the calculation result.

  The ground patterns 208 to 212 provided for each of these circuit blocks are, for example, so-called signal ground (SG) signals provided in a small signal amplifier circuit block and so-called logic ground (LG) provided in a logic operation block. , Logic Ground) pattern, and so-called power ground (PG) provided in the drive circuit block.

  In the present embodiment, the ground patterns 208 to 212 are illustrated as being formed on the exposed surface (surface layer) of the circuit board 102 on which the ground pattern 206 is formed. Reference numeral 212 denotes a surface facing the surface on which the ground pattern 206 is formed, or an inner layer when the circuit board 102 is a multilayer substrate, and is electrically connected to the ground pattern 206 via a via or the like. can do.

  3 is a view for explaining a fixing structure of the circuit board 102 in the housing 100 of the electronic device 10 shown in FIG. 1, and FIG. 3A is a cross-sectional view taken along the SS line of the electronic device 10 shown in FIG. FIG. 3B is a partial detail view of the P portion shown in FIG. 3A, and FIG. 3C is a partial detail view of the Q portion shown in FIG. Since the R portion has a symmetrical structure with respect to the Q portion, only the partial detailed view of the Q portion is shown and described here.

  The circuit board 102 is sandwiched and gripped by the recesses 300 and 302 provided in the base 100a and the cover 100b at a substantially central portion in the horizontal direction in FIG. 3A and also in an edge portion in the horizontal direction in the drawing. It is sandwiched and held between the base 100a and the cover 100b. Note that the grip portion of the housing 100 at the edge portion of the circuit board 102 is, for example, a U-shape in parallel with the left and right edges and the upper edge of the cover 100b in the top view shown in FIG. It can be formed. The gripping at the edge of the circuit board 102 may be performed at a part of the edge of the circuit board 102 in this way. For example, when the connector 104 is not used, the entire edge of the circuit board 102 (entire circumference) ) Can be configured to be gripped by the housing 100.

  A screw 106 is inserted into the hole 306 (FIG. 3B) provided in the recess 300 of the base 100a, the hole 308 provided in the recess 302 of the cover 100b, and the hole 200 provided in the circuit board 102. Then, the screw 106 and the nut 304 are fastened to function as a pressurizing tool, and the circuit board 102 is gripped with respect to the housing 100 at the center portion and the edge portion by the fastening force of the screw 106 and the nut 304. To be fixed.

  On the other hand, when the circuit board 102 is held between the recesses 300 and 302 of the base 100a and the cover 100b, the ground pattern 206 (FIG. 2A) of the circuit board 102 comes into contact with and electrically connects to the cover 100b. Will be. As a result, the ground pattern 206 is connected to the power supply provided in the vehicle via the cover 100b and the metal body of the vehicle when the casing 100 of the electronic device 10 is attached to the metal body or the like of the vehicle. It will be electrically connected to the ground terminal of the device. That is, a ground current of an electronic circuit (not shown) configured on the circuit board 102 flows from the ground pattern 206 to the housing 100 and returns to a power source provided outside the electronic device 10.

  The recesses 202 and 204 of the circuit board 102 are filled with a waterproof adhesive 320 so that moisture and water do not enter the housing 100 through the holes 200, 306, and 308 (FIG. 3 ( b)). Further, the base 100a and the cover 100b are respectively formed with recesses 310 and 312 so as to form an annular shape substantially concentric with the recesses 202 and 204 provided in an annular shape on the circuit board 102. 312 is also filled with a waterproof adhesive 320.

  Further, as shown in FIG. 3C, a concave portion 314 is also formed on the left and right sides of the cover 100b in FIG. 3A, and the concave portion 314 is filled with the waterproof adhesive 320. As a result, airtightness inside the housing 100 is established. Here, for example, in the top view shown in FIG. 1A, the recess 314 can be formed in a U-shape along the left and right edges and the upper edge of the cover 100b. . In FIG. 3C, the folded portion 330 provided at the end of the cover 100b is such that when the vehicle on which the electronic device 10 is mounted is washed, for example, the water pressure of the high pressure car wash water is waterproof. It functions as a defense wall to prevent the agent 320 from being directly applied.

  In the electronic device 10 having the above configuration, the circuit board 102 is held and fixed by the housing 100 (that is, the base 100a and the cover 100b). That is, the circuit board 102 is gripped by the casing 100 at the edge portion of the circuit board 102, and particularly in the central region of the circuit board 102, the casing 100 (specifically, the recesses 300 of the base 100 a It is configured to be held between the cover 100b and the concave portion 302).

  In this way, the electronic device 10 has a shorter distance between the gripping portions than the conventional structure that grips only the opposite edges of the circuit board 102 due to the gripping portion in the central region of the circuit board 102. The resonance frequency in the vibration in the direction orthogonal to the surface direction of the circuit board 102 can be increased (for example, higher than the maximum frequency of the environmental vibration), and the vibration resistance can be improved.

  In addition, since the circuit board 102 is gripped by the fastening force of the screw 106 in the central region of the circuit board 102, when thermal expansion / contraction of the circuit board 102 and the casing 100 occurs, The expansion and contraction of the circuit board 102 occurs centering on the grip portion of the central region. For this reason, in the grip part in the center area | region of the circuit board 102 which is the center of the said expansion / contraction, the friction resulting from thermal expansion / contraction between the circuit board 102 and the housing | casing 100 hardly arises. In addition, since the distance between the gripping portion in the central region of the circuit board 102 and the edge portion of the circuit board 102 is shorter than the distance between the opposing edges of the circuit board 102, it occurs in the gripping portion at the edge of the circuit board 102. The amount of rubbing between the circuit board 102 and the housing 100 (the amount of displacement of the circuit board 102 with respect to the housing 100) is reduced compared to the conventional structure that grips only the facing edges.

  For this reason, even when the temperature of the circuit board 102 and the casing 100 fluctuates due to a change in environmental temperature, heat generation of an electronic component (not shown) mounted on the circuit board 102, the circuit board 102 and the casing 100 The amount of metal powder (black powder) generated by rubbing each other can be greatly reduced.

  In the electronic device 10, a plurality of ground patterns 206 to 212 are formed on the circuit board 102. Thus, when a plurality of ground patterns are formed on the circuit board, the ground patterns are not connected in cascade in order to minimize the potential difference generated between the ground patterns due to the flow of the ground current. It is desirable that each ground pattern is connected to the power supply ground only through a common ground pattern portion (see, for example, Japanese Patent Application Laid-Open No. 2014-099554).

  In the electronic device 10, since the ground pattern 206 that is electrically connected to the housing 100 when the circuit substrate 102 is accommodated in the housing 100 is provided in the central portion of the circuit substrate 102, the center By arranging the other ground patterns 208 to 212 from the portion to the outside, the above-mentioned “each ground pattern (208 to 212) is connected to the power supply ground only through the common ground pattern portion (206)”. Can be easily realized.

  Further, in the electronic apparatus 10, since the assembly of the casing 100 and the fixing of the circuit board 102 are performed by a single screw 106, the structure is simple and the work time during assembly is shortened. Cost can be reduced.

  In the present embodiment, the substantially central portion of the circuit board 102 is gripped by the housing 100. However, the present invention is not limited to this, and the circuit board 102 is located in one part of the area inside the edge portion of the circuit board 102. By adopting a configuration in which is held, the same effect as described above can be obtained. Further, the position of the grip portion provided in one part of the inner region is determined by the elasticity of the material used for the circuit board 102, the arrangement of electronic components mounted on the circuit board 102 (that is, the mass distributed on the circuit board 102). The distribution frequency of the circuit board 102 in a state of being fixed to the housing 100 can be selected so as to be higher than a desired (and therefore predetermined) lower limit value.

  In the present embodiment, the screw 106 and the nut 304 are used as a pressurizing tool, and the gripping force of the housing 100 with respect to the circuit board 102 is obtained by the fastening force between the screw 106 and the nut 304. Not limited to this, a leaf spring or a coil spring may be used as the pressurizing tool.

  DESCRIPTION OF SYMBOLS 10 ... Electronic device, 100 ... Case, 100a ... Base, 100b ... Cover, 102 ... Circuit board, 104 ... Connector, 106 ... Screw, 200, 306, 308 ... Hole, 202, 204, 300, 302, 310, 312, 314 ... Recess, 206, 208, 210, 212 ... Ground pattern, 214, 216, 218 ... Connection pattern, 304 ... -Nuts, 320 ... waterproof adhesive, 330 ... folded portion.

Claims (7)

A circuit board;
A housing for holding the circuit board;
With
The housing is configured to grip a part or all of the edge portion of the circuit board and to grip one part of the area on the circuit board from the edge portion.
Electronic equipment. The casing is made of a conductive material,
A ground pattern is formed in one part of the inner region of the circuit board held by the housing,
The ground current of the electronic circuit configured on the circuit board flows out from the ground pattern to the housing and returns to the power source provided outside the electronic device.
The electronic device according to claim 1. The circuit board includes a plurality of ground patterns provided for each one or a plurality of circuit blocks formed on the circuit board, and each of the plurality of ground patterns is formed in a part of the inner region. Directly connected to the ground pattern formed,
The electronic device according to claim 2. The electronic device is a control device that is mounted on a vehicle and controls the operation of the vehicle,
The housing is fixed to the vehicle body of the vehicle, and is electrically connected to a ground terminal of a power source mounted on the vehicle via the vehicle body.
The electronic device according to claim 1. On the circuit board, the position of the contact portion between the one portion of the inner region and the housing is selected so that the mechanical resonance frequency of the circuit board is higher than a predetermined frequency.
The electronic device according to claim 1. The pressing force provided in the vicinity of the contact portion between the casing and one part of the inner region of the circuit board gives a force for the casing to grip the circuit board.
The electronic device according to claim 1.   The electronic device according to claim 5, wherein the pressurizing tool is a screw.

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