Electronic control device

1. An electronic control device, comprising:

a housing having a plurality of housing members joined together to define therein an inner space;

a circuit board accommodated in the inner space of the housing and mounting thereon various electronic components; and

a connector attached to one end of the circuit board,

wherein at least one of the housing members includes an upper step portion covering the connector, a lower step portion covering the circuit board and an inclined wall portion connecting the upper and lower step portions, the inclined wall portion having a housing vent hole formed therethrough in a thickness direction of the inclined wall portion, the housing vent hole being inclined relative to the upper and lower step portions and the circuit board;

wherein the electronic control device comprises a protection wall arranged on the inclined wall portion and having a wall surface covering an outer opening of the housing vent hole, with a gap left between the wall surface of the protection wall and the outer opening of the housing vent hole and communicating with the housing vent hole, the protection wall having a closed connection at upper and lower sides thereof to the inclined wall portion and defining protection-wall vent holes at both sides in a horizontal direction thereof, each of the protection-wall vent holes extending along the wall surface of the protection wall from the gap to the outside in a radial direction of the housing vent hole and being open to the outside;

wherein the electronic control device further comprises an air-permeable waterproof membrane fixed to an inner opening of the housing vent hole, whereby there is a vent passage defined between the air-permeable waterproof membrane and each of the protection-wall vent holes such that the vent passage has a bent part from the housing vent hole to the gap so as to be in communication with the protection-wall vent holes; and

wherein a relational expression of tan θ 2 >tan θ 1 is satisfied where θ 1 is an angle between an entering water S flowing in the vent passage through the protection-wall vent hole to the inside of the housing vent hole and the inner opening of the housing vent hole; W is an opening width of the inner opening in a direction perpendicular to two vertical lines intersecting the inner opening of the housing vent hole at right angles from the entering water S; D is an axial length of the housing vent hole; and tan θ 2 is a ratio of D/W.

2. The electronic control device according to claim 1 ,

wherein the housing has a fixing surface for fixing on a vehicle body;

wherein the at least one of the housing members has the inclined wall portion inclined relative to the fixing surface; and

wherein the housing vent hole is formed in the inclined wall portion of the at least one of the housing members such that the air-permeable waterproof membrane is inclined at a predetermined angle relative to the fixing surface.

3. The electronic control device according to claim 1 ,

wherein the protection wall is formed integral with the housing member.

4. An electronic control device, comprising:

a housing having a plurality of housing members joined together to define therein an inner space; and

a circuit board accommodated in the inner space of the housing and mounting thereon various electronic components; and

a connector attached to one end of the circuit board;

wherein at least one of the housing members includes an upper step portion covering the connector, a lower step portion covering the circuit board and an inclined wall portion connecting the upper and lower step portions, the inclined wall portion having a housing vent hole formed therethrough in a thickness direction of the inclined wall portion, the housing vent hole being inclined relative to the upper and lower step portions and the circuit board;

wherein the electronic control device comprises a protection wall arranged on the inclined wall portion and having a wall surface covering an outer opening of the housing vent hole, with a gap left between the wall surface of the protection wall and the outer opening of the housing vent hole and communicating with the housing vent hole, the protection wall having a closed connection at upper and lower sides thereof to the inclined wall portion and defining protection-wall vent holes at both sides in a horizontal direction thereof, each of the protection-wall vent holes extending along the wall surface of the protection wall from the gap to the outside in a radial direction of the housing vent hole and being open to the outside;

wherein the electronic control device further comprises an air-permeable waterproof membrane fixed to an inner opening of the housing vent hole, whereby there is a vent passage defined between the air-permeable waterproof membrane and each of the protection-wall vent holes such that the vent passage has a bent part from the housing vent hole to the gap so as to be in communication with the protection-wall holes;

wherein the housing has a fixing surface for fixing on a vehicle body;

wherein the inclined wall portion is inclined relative to the fixing surface;

wherein the air-permeable waterproof membrane is inclined at a predetermined angle relative to the fixing surface; and

wherein there is a predetermined angle formed between a direction of cross section of the housing vent hole and the horizontal direction.

5. An electronic control device, comprising:

a housing having a plurality of housing members joined together to define therein an inner space;

a circuit board accommodated in the inner space of the housing and mounting thereon various electronic components; and

a connector attached to one end of the circuit board,

wherein at least one of the housing members includes an upper step portion covering the connector, a lower step portion covering the circuit board and an inclined wall portion connecting the upper and lower step portions, the inclined wall portion having a housing vent hole formed therethrough in a thickness direction of the inclined wall portion, the housing vent hole being inclined relative to the upper and lower step portions and the circuit board;

wherein the electronic control device comprises a protection wall arranged on the inclined wall portion and having a wall surface covering an outer opening of the housing vent hole, with a gap left between the wall surface of the protection wall and the outer opening of the housing vent hole and communicating with the housing vent hole, the protection wall having a closed connection at upper and lower sides thereof to the inclined wall portion and defining protection-wall vent holes at both sides in a horizontal direction thereof, each of the protection-wall vent holes extending along the wall surface of the protection wall from the gap to the outside in a radial direction of the housing vent hole and being open to the outside;

wherein the electronic control device further comprises an air-permeable waterproof membrane fixed to an inner opening of the housing vent hole, whereby there is a vent passage defined between the air-permeable waterproof membrane and each of the protection-wall vent holes such that the vent passage has a bent part from the housing vent hole to the gap so as to be in communication with the protection-wall vent holes; and

wherein a protrusion is formed in the housing vent hole.