JP2012089594A - On-vehicle electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle electronic apparatus which smoothly flows air generated by natural convection even if a connector protrudes from an upper part of a surface, in which radiation fins are disposed, within a housing.SOLUTION: An on-vehicle electronic apparatus includes a housing which houses a circuit board 2 therein, a connector 3 protruding toward the exterior from an upper part of a front surface of the housing, and radiation fins 4 protruding toward the exterior from a part of the front surface of the housing which is located below the connector 3. Each radiation fin 4 has a linear part 4a extending along the housing from a lower part to an upper part and a bent part 4b bent obliquely toward a closer side 1c, out of left and right sides of the housing, at a middle part of the radiation fin 4.

Description

  The present invention relates to an on-vehicle electronic device having a function of radiating heat of an electronic component.

  2. Description of the Related Art Conventionally, with the digitization of vehicles, there is an increasing need for heat generation countermeasures for electronic components inside in-vehicle electronic devices. In order to dissipate the heat of the electronic component, a linear heat dissipating fin is provided in the housing of the in-vehicle electronic device. (For example, see Patent Documents 1 and 2).

JP 2007-273807 A JP 2010-57345 A

  In order to improve the heat dissipation efficiency of the heat dissipation fins, it is preferable that the surrounding natural convection air flows along the heat dissipation fins. When the vehicle is stopped, air naturally convects from below to above in an enclosed space such as an engine room. For this reason, the radiating fins are generally arranged along the upper side from the lower side with respect to the mounting position of the in-vehicle electronic device on the vehicle.

  However, due to the structure, the connector sometimes protrudes to the outside from the upper part of the same surface as the surface on which the heat dissipating fins are provided in the casing of the in-vehicle electronic device. At this time, air generated by natural convection in the vehicle flows from below to above along the heat dissipating fins, but there is a problem that the connector acts as a shield to block the air flow and the heat dissipating efficiency is lowered.

  The present invention has been made to solve the conventional problems, and even if a connector protrudes from the upper part of the same surface of the housing as the surface on which the radiating fins are arranged, the air generated by natural convection is stagnated. It is an object of the present invention to provide an in-vehicle electronic device that can be made to flow without any problem.

  In order to achieve the above-mentioned object, the on-vehicle electronic device according to the present invention includes a linear part in which a heat radiating fin extends from the lower side to the upper side of the casing, and a side closer to the left and right sides of the casing. And a bent portion that is bent obliquely toward the surface.

  According to the present invention, there is provided an in-vehicle electronic device capable of flowing air generated by natural convection without stagnation even when a connector protrudes from an upper portion of the same surface as the surface on which the heat dissipating fins are disposed. Can be provided.

The perspective view of the vehicle-mounted electronic device in this embodiment 1 is a perspective view of the in-vehicle electronic device of FIG. The front view of the housing | casing which is the principal part of the same FIG. Sectional view when the AA cross section of FIG. 3 is seen from the B direction

  Hereinafter, an in-vehicle electronic device according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view of an in-vehicle electronic device according to this embodiment. FIG. 2 is a perspective view of the on-vehicle electronic device of FIG. 1 when viewed from another viewpoint. FIG. 3 is a front view of the housing of FIG. 4 is a cross-sectional view of the AA cross section of FIG. 3 as viewed from the B direction. The vertical and horizontal relationships visible in FIGS. 1 to 3 are the actual vertical and horizontal relationships.

  As shown in FIGS. 1 to 4, the in-vehicle electronic device includes a housing 1, a circuit board 2, a connector 3, and heat radiating fins 4.

  The housing 1 is made of metal such as aluminum die casting, for example, and a first case 1a provided in the front direction and a second case 1b provided in the back direction are coupled to have a space inside. An opening 1c is provided at the upper front of the first case 1a. The opening 1c extends from the left side 1d side of the housing 1 to the right side 1e side. A circuit board 2 is provided in an internal space formed by the first case 1 a and the second case 1 b of the housing 1. The first case 1a has a recessed portion 1f in which a part of the front surface is recessed and a protruding portion 1g in which a part of the front surface protrudes.

  The circuit board 2 is electrically connected to an external electronic device via the connector 3. The circuit board 2 includes a heat generation region 2a mainly composed of heat generation system components (for example, transistors and semiconductors) that generate a relatively large amount of heat generation, and signal system components (for example, logic ICs, crystal oscillators, and the like) that generate a relatively small amount of heat generation. The area is divided into a signal area 2b mainly composed of a ceramic capacitor.

  A large amount of electric power is applied to the heat generation system parts compared to the signal system parts. Further, the heat generation system parts provided in the heat generation area 2a are denser than the signal system parts provided in the signal area 2b. For this reason, the heat generation region 2a generates larger heat than the signal region 2b.

  In particular, in the case of an in-vehicle electronic device for a direct injection engine, a component for direct injection engine control is newly provided. Direct injection engine control parts require drive power and generate a large amount of heat. Further, since the in-vehicle electronic device for the direct injection engine is provided in the engine room, the in-vehicle electronic device is likely to accumulate heat. For this reason, the direct-injection engine control component is provided in the heat generating region 2a, and a heat dissipation countermeasure described later is performed. In this case, for example, at most about several watts of power is applied to the signal region 2b, but about ten watts of power is applied to the heat generating region 2a. The power that can be dissipated by the general circuit board 2 itself used in the in-vehicle electronic device for the direct injection engine is about 10 watts at most. For this reason, it is not necessary to consider the influence of heat generation in the signal area 2b, but it is necessary to take measures for heat dissipation in the heat generation area 2a. This is to prevent the circuit board 2 and components on the board from being damaged beyond the upper limit temperature.

  The heat generation system components are provided on the back surface of the circuit board 2 corresponding to the heat generation region 2a. On the other hand, the signal system components are provided on both surfaces of the circuit board 2 corresponding to the signal region 2b. As a result, the heat generated in the heat generating region 2a is thermally conducted to the recessed portion 1f of the first case 1a in contact with the circuit board 2 and radiated. On the other hand, since signal system components are placed on both sides in the signal system region 2b, the mounting area on the circuit board 2 can be improved. Thus, by providing the heat generating region 2a and the signal system region 2b on the circuit board 2, it is possible to achieve both heat dissipation and improvement of the mounting area.

  The connector 3 is provided above the front of the first case 1a. The connector 3 protrudes from the opening 1c to the outside (front direction). The connector 3 extends from the left side 1d side of the housing 1 to the right side 1e side, and contacts the inner periphery of the opening 1c.

  The radiating fin 4 is made of the same material as that of the housing 1. The heat radiating fins 4 are formed integrally with the housing 1. The radiating fin 4 is composed of a plurality of metal protrusions. Adjacent metal protrusions are set at substantially equal intervals. Natural convection air in the vehicle flows from below to above in a region sandwiched between adjacent metal protrusions of the radiating fin 4. The entrance of each path is provided on the bottom side of the housing 1. Each route has only one exit. The heat radiating fins 4 protrude outward from the front surface of the housing 1 below the connector 3. As shown in FIG. 4, the height of the radiating fin 4 in the protruding direction is lower than the height of the connector 3 in the protruding direction. Moreover, the radiation fin 4 is provided in the area | region projected by the heat_generation | fever area | region 2a of the circuit board 2 among the housing | casing 1 front. Here, the front surface of the circuit board 2 is in contact with the rear of the recessed portion 1f in the heat generation region 2a.

  The radiating fin 4 includes a straight portion 4a and a bent portion 4b continuous with the straight portion 4a. The straight portion 4 a extends upward from the bottom side of the housing 1. The bent portion 4b is bent obliquely toward the left side 1d, which is the closer side of the left and right sides 1d and 1e of the housing 1, in the middle of the heat radiation fin 4. The bent portion 4b extends continuously upward from the upper end of the linear portion 4a. The bending angle of the bent portion 4b is preferably set to about 45 degrees (35 to 55 degrees) with respect to the straight portion 4a. At other angles, the flow of natural convection air tends to be hindered by the side wall of the bent portion 4 b and the lower wall of the connector 3.

  Natural convection air in the vehicle passes through the straight portion 4 a from the bottom side of the housing 1. For example, natural convection air moves right above each path from the lower end of each path formed by the valleys between adjacent metal protrusions of the straight line portion 4a.

  The natural convection air that has reached the upper end of the straight portion 4a passes through the bent portion 4b. For example, natural convection air that has reached the upper end of each path constituted by the valleys of the adjacent metal protrusions of the straight portion 4a flows into the lower end of each path constituted by the valleys of the adjacent metal protrusions of the bent part 4b. To do. As a result, the natural convection air that has passed straight along the path of the straight line portion 4a changes its course in the bending angle direction by the bending portion 4b. In addition, the path of the bent portion 4b is inclined by approximately 45 degrees (35 degrees to 55 degrees) with respect to the path of the straight portion 4a, and is not a sudden angle change, so the course is changed without disturbing the flow of natural convection air. can do. And the air of natural convection moves diagonally upward along each path | route comprised by the valley of the metal protrusion which adjoins the bending part 4b.

  At least a part of the natural convection air that has reached the upper end of the bent portion 4 b is released to the left side 1 d side of the housing 1. For example, the end of at least a part of each path constituted by the valleys of the adjacent metal protrusions of the bent portion 4 b is provided on the left side 1 d of the housing 1. The natural convection air that reaches the end and is discharged to the outside is not obstructed by the lower end of the connector 3. Therefore, natural convection air does not stay on the housing 1 of the in-vehicle electronic device, and new natural convection air can be made to easily flow through the radiating fins 4.

  In addition, a recess 1 f is provided in a part of the heat generation area in which the radiation fins 4 are formed in the front surface of the housing 1. Since the circuit board 2 and the housing 1 are in contact with each other by the recess 1f, the heat generated in the heat generating region 2a is thermally conducted to the first case 1a. The heat accumulated in the first case 1 a by this heat conduction is radiated by natural convection flowing upward through the radiation fins 4. Here, by providing the recessed portion 1f, the surface area of the side wall of the metal protrusion of the radiating fin 4 can be made larger than when the recessed portion 1f is not provided. Therefore, by providing the recessed portion 1f, the heat dissipation effect by natural convection can be further improved and the weight of the housing 1 can be reduced. That is, it is possible to achieve both improvement in heat dissipation effect and weight reduction of the in-vehicle electronic device.

As described above, according to the present invention, the natural convection of air flowing from the lower side to the upper side is the straight portion 4a.
Enter. In the straight line portion 4a, the metal projection extends upward from the bottom side of the housing 1 along the top, and is the same as the flow of natural convection. For this reason, natural convection can smoothly enter the straight portion 4 a and form a flow in the heat radiation fin 4. Once the flow in the radiating fin 4 can be formed at the straight portion 4a, the air flow is not disturbed even if the natural convection path is bent thereafter. Therefore, even if the flow of air that has passed through the straight portion 4a is bent by the bent portion 4b that is bent toward the closer side of the left and right sides 1d and 1e of the housing 1, the natural air that has entered the heat radiating fin 4 is bent. The convection air is discharged outside without disturbing the air flow. And even if the connector 3 protrudes from the upper part of the same surface as the surface where the radiation fin 4 is arrange | positioned among the housing | casings 1, the air which generate | occur | produced by the natural convection can be flowed without stagnation.

  In the embodiment of the present invention, the connector 3 protruding from the housing 1 has been described as preventing natural convection air flow, but the same surface as the surface of the housing 1 on which the heat dissipating fins 4 are disposed. An object other than the connector 3 may be used as long as it is a shield provided on the top and prevents the flow of natural convection air. For example, the protrusion part protruded from the housing | casing 1 for heat dissipation etc. may be sufficient.

  Further, the heat radiating fins 4 are provided in an area projected by the heat generating area 2 a of the circuit board 2 in the front surface of the housing 1. As a result, the heat generating area 2a having a large amount of heat generation is radiated by the heat radiation fins 4, and the signal area 2b having a small amount of heat generation is not provided with the heat radiation fins 4, thereby reducing the weight of the in-vehicle electronic device. . That is, in an in-vehicle electronic device that is required to cope with a thermal environment and further reduce weight, it is possible to achieve both improvement in heat dissipation effect and weight reduction.

  The vehicle-mounted electronic device according to the present invention is useful when there is a shield on the surface of the housing on which the heat dissipating fins are provided.

DESCRIPTION OF SYMBOLS 1 Case 2 Circuit board 3 Connector 4 Radiation fin 4a Straight line part 4b Bending part

Claims (6)

A housing containing a circuit board inside;
A shield projecting outward from above the front of the housing;
A heat dissipating fin projecting outward from the front of the housing below the shield,
The radiating fin includes a linear portion extending from the lower side to the upper side of the housing and a bent portion that is bent obliquely toward the closer side of the left and right sides of the housing. An on-vehicle electronic device characterized by the above. The shield is composed of a connector,
The upper front of the housing is open,
The in-vehicle electronic device according to claim 1, wherein the connector is electrically connected to the circuit board and protrudes from an opening of the housing. The circuit board is divided into a signal region mainly composed of signal system components with a relatively small amount of heat generation, and a heat generation region mainly composed of heat generation system components with a relatively large amount of heat generation,
The in-vehicle electronic device according to claim 2, wherein the radiating fin is provided in a region projected by a heat generating region of the circuit board in the front surface of the housing.   The in-vehicle electronic device according to claim 3, wherein the heat generation area of the circuit board is included in one of left and right areas divided at the center of the circuit board.   The in-vehicle electronic device according to claim 4, wherein a recess is provided in a part of a region of the front surface of the housing where the heat dissipating fins are formed.   The in-vehicle electronic device according to claim 5, wherein the bent portion is bent approximately 45 degrees with respect to the straight portion.

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