Negative pressure pump and cylinder head cover

A negative pressure pump comprising:

• a casing inside of which a drive shaft driven to rotate by a motive power source is inserted and disposed;
• a pump portion that is formed in the casing, is equipped with a driven shaft, and produces negative pressure as a result of the rotation of the drive shaft being transmitted to the driven shaft;
• a drive-side clutch plate that is attached to the drive shaft, is movable in an axial direction of the drive shaft, rotates integrally with the drive shaft, and is magnetic;
• a driven-side clutch plate that is attached to the driven shaft, is movable in an axial direction of the driven shaft, rotates integrally with the driven shaft, and transmits the rotation from the drive shaft to the driven shaft as a result of the drive-side clutch plate becoming engaged with the driven-side clutch plate;
• an elastic body which, by means of its elastic force, presses the drive-side clutch plate against the driven-side clutch plate to cause the drive-side clutch plate to engage with the driven-side clutch plate;
• an electromagnet that is fixed to the casing, produces a magnetic force counter to a pressing force of the elastic body, and pulls the drive-side clutch plate away from the driven-side clutch plate to cancel a state of engagement therebetween;
• a first wall portion that is disposed on a pump portion side of the casing and receives the pressing force of the elastic body in a direction toward the first wall portion transmitted from the drive-side clutch plate to the driven-side clutch plate, via a first bearing rotatably supporting the driven shaft;
• and
• a second wall portion that is disposed on an opposite side from the pump portion side of the casing and supports an end portion, on the opposite side, of the elastic body via a second bearing rotatably supporting the drive shaft.