Connector housing and connector unit

1. A connector housing comprising:

a cylindrical side wall,

wherein the cylindrical side wall includes a concave surface on one side of an outer circumferential surface of the cylindrical side wall in a first direction,

wherein the concave surface curves inwards into an arc shape and extends in a second direction, so that the concave surface is to be pressed against a cylindrical member with the second direction aligned with a direction in which the cylindrical member extends,

wherein the concave surface includes a first arc portion and second arc portions, a first one of the arc portions provided on a first outer side of the first arc portion in a third direction which is perpendicular to both the first direction and the second direction, and a second one of the second arc portions provided on a second outer side of the first arc portion in the third direction,

wherein a radius of curvature of each of the second arc portions is larger than a radius of curvature of the first arc portion.

2. The connector housing according to claim 1 ,

wherein the first arc portion extends in the second direction and the second arc portions extend in the second direction.

3. The connector housing according to claim 1 , wherein the concave surface includes an engaging projection to be brought into engagement with a groove of a corrugated tube having a corrugated configuration.

4. The connector housing according to claim 3 , wherein the engaging projection includes a rib provided along a circumferential direction of the concave surface.

5. The connector housing according to claim 1 , further comprising:

two ribs provided on another side of the outer circumferential surface of the side wall which is different from said one side,

wherein the two ribs protrude outwards from said another side of the outer circumferential surface of the side wall and extend in a direction which crosses to the second direction.

6. A connector housing comprising:

a cylindrical side wall, wherein:

the cylindrical side wall includes a concave surface on one side of an outer circumferential surface of the cylindrical side wall in a first direction,

the concave surface curves inwards into an arc shape and extends in a second direction, so that the concave surface is to be pressed against a cylindrical member with the second direction aligned with a direction in which the cylindrical member extends; and

two ribs provided on another side of the outer circumferential surface of the side wall which is different from said one side,

wherein the two ribs protrude outwards from said another side of the outer circumferential surface of the side wall and extend in a direction which crosses to the second direction,

wherein said another side of the outer circumferential surface of the side wall is opposite in the first direction to said one side of an outer circumferential surface of the cylindrical side wall, and

wherein the concave surface is formed with cut-outs, wherein the cut-outs are configured to allow the ribs to enter the cut-outs when two connector housings are aligned in an identical direction so that the concave surface formed on said one side of one of the two connector housings faces the ribs formed on said another side of the other of the two connector housing.

7. A connector unit comprising:

a first connector housing that is the connector housing according to claim 6 ;

a second connector housing that is the connector housing according to claim 6 ; and

a connecting member configured to fix the first connector housing and the second connector housing together in a condition where the ribs formed on said another side of the second connector housing placed in the cut-outs formed on said one side of the first connector housing.