An electric compressor includes a compression portion, an electric motor, an inverter, a housing, a support bracket, a vibration insulator, and a soundproofing cover. The compression portion is configured to compress a fluid. The electric motor is configured to drive the compression portion. The inverter is configured to drive the electric motor. The housing includes an outer peripheral surface that has a cylindrical shape and accommodates the compression portion, the electric motor, and the inverter. The support bracket is fastened to the housing and supports the housing to an object to which the electric compressor is mounted. The vibration insulator is interposed between the support bracket and the object. The soundproofing cover is made of an elastically deformable sound absorbing material and covers the housing and the support bracket.

Provided is a gear pump and a gear motor in which noise is reduced. A gear pump includes: gears which mesh and pair with each other; a casing including a gear housing chamber for housing the gears; and at least one hollow layer which is configured in the casing and divides the casing into at least inner walls and outer walls. Coincidence critical frequency of the inner walls and coincidence critical frequency of the outer walls are different. The hollow layer is formed between the gear housing chamber in the casing and an outer surface of the casing.

A compressor unit includes a compressor body including a compression mechanism, and an accumulator connected to the compressor body. The compression mechanism includes a cylinder, a piston to rotate eccentrically in the cylinder, and a blade partitioning an interior of a compression chamber of the cylinder into low and high pressure chambers. A frequency one time an operation frequency n of the compressor body and a frequency three times the operation frequency n of the compressor body are a 1n frequency and a 3n frequency, respectively. A phase difference between a phase of a transfer function of the 1n frequency of the accumulator and a phase of a transfer function of the 3n frequency of the accumulator is 2060 with respect to a peak of the 1n frequency where the phase lag is positive, at a maximum number of revolutions of the compressor body.