Electric motor, rotary drive system, and hydraulic excavator

An electric motor, comprising:

• a rotor including a rotary shaft provided so as to be rotatable around an axis thereof and a rotor core fixed to an outer peripheral surface of the rotary shaft;
• a stator including:
• a core main body having a cylindrical shape surrounding the rotor core from an outer peripheral side of the rotor core;
• a plurality of core convex portions provided at intervals in a peripheral direction, and each of which projects from an outer peripheral surface of the core main body and which extends in an axial direction of the rotary shaft;
• and
• a plurality of coils attached to the core main body;
• and
• a casing in which a first accommodating space accommodating the rotor and the stator is formed and which has an inner peripheral surface including an abutting inner peripheral surface on which a top portion of the core convex portion outside in a radial direction abuts,
• wherein an outer peripheral-side flow path on which lubricating oil is capable of flowing is formed between the core convex portions adjacent to each other in the peripheral direction by the outer peripheral surface of the core main body and the inner peripheral surface of the casing,
• wherein the abutting inner peripheral surface has a circular shape centered on the axis in a sectional view orthogonal to the axis,
• wherein the top portion of each of the core convex portions has an outer diameter corresponding to an inner diameter of the abutting inner peripheral surface and has a cylindrical surface shape fitting onto the abutting inner peripheral surface over the peripheral direction,
• wherein the casing includes:
• a first casing that has a first cylindrical portion having, as the inner peripheral surface, the abutting inner peripheral surface and a tapered inner peripheral surface expanding in diameter from the abutting inner peripheral surface toward the one side in the axial direction, and that has a first bottom portion closing the first cylindrical portion from the other side in the axial direction, and
• a second casing that has a second cylindrical portion fitted to the first cylindrical portion from an inside of the first cylindrical portion and a second bottom portion closing the second cylindrical portion from the one side in the axial direction;
• and
• wherein the second cylindrical portion includes:
• a fitting inner peripheral surface having an inner diameter corresponding to the outer peripheral surface of the core main body and fitted to the outer peripheral surface of the core main body.