Differential device

A differential device comprising

• a differential case that has a hollow case main body and an annular flange part projectingly provided integrally with an outer peripheral face of the case main body and that is rotatable around a predetermined axis,
• a differential mechanism that is housed within the case main body,
• an access window that is provided in the case main body on one side, in a direction along the axis, of the flange part in order to allow the differential mechanism to be assembled into the case main body, and
• a ring gear that meshes with a drive gear linked to a power source and transmits power from the drive gear to the differential case,
• the ring gear having a tooth part that receives a thrust load in a direction along the axis by meshing with the drive gear,
• an outer peripheral part of the flange part having a joining part joined to an inner peripheral face of the ring gear by welding, a fitting face part fitted into the inner peripheral face of the ring gear, and a space-forming part positioned between the joining part and the fitting face part and forming a blocked space between the outer peripheral part of the flange part and the inner peripheral face of the ring gear,
• a degassing passage being provided in the flange part, and the degassing passage providing communication between the blocked space and an outer face of the differential case,
• wherein the flange part comprises a first flange part and a second flange part, the first flange part being positioned outside a region sandwiched by a pair of imaginary straight lines passing through the axis and inner ends, on one side and on an other side in a peripheral direction of the differential case, of the access window when viewed on a projection plane orthogonal to the axis, and the second flange part being positioned in the region,
• the second flange part includes a predetermined region spaced in the peripheral direction from a border part with the first flange part, the predetermined region being a region that can avoid a concentration of stress in an area around the degassing passage present in the predetermined region when a thrust load acts on the flange part so as to give rise to stress resisting inclination of the flange part toward the axis side, and
• the degassing passage is disposed only in the first flange part, or only in the predetermined region of the second flange part, or only in the first flange part and the predetermined region out of an entire periphery of the flange part.