Negative pressure pump and cylinder head cover

A negative pressure pump comprising:

• an electrically insulative casing that is formed in a tubular shape, an axial direction one end of the casing being closed off by a cap body;
• an electrically conductive rotary shaft that is disposed in the casing,
• the rotary shaft being mechanically and electrically connected to an earthed power source,
• the rotary shaft being rotated by power being transmitted from the power source, and
• a rotation center of the rotary shaft being disposed to be offset relative to a center of the casing;
• and
• an electrically conductive vane that is disposed in the casing,
• the vane being supported at the rotary shaft to freely reciprocate in a direction orthogonal to the rotary shaft and being electrically connected to the power source via the rotary shaft,
• the vane rotating integrally with the rotary shaft and end portions of the vane sliding over an inner wall face of the casing, and
• the vane dividing the interior of the casing into a plurality of spaces and generating negative pressure.