A scroll compressor includes a first chamfered portion formed at a distal end portion of a spiral blade of a fixed scroll, a second chamfered portion formed at a distal end portion of a spiral blade of an orbiting scroll, a third chamfered portion formed at a bottom portion of the spiral blade of the fixed scroll, and a fourth chamfered portion formed at a bottom portion of the spiral blade of the orbiting scroll. An expression of 0<{(Av1+Av2)/2}/Ac<110.sup.4 is satisfied where a sectional area of a space between the first chamfered portion and the fourth chamfered portion is defined as Av1, a sectional area of a space between the second chamfered portion and the third chamfered portion is defined as Av2, and a sectional area of a compression chamber is defined as Ac.

A scroll vacuum pump includes an orbiting scroll having a wall extending axially from an orbiting scroll base towards a fixed scroll, the fixed scroll having a fixed scroll wall extending axially from a fixed scroll base towards the orbiting scroll; an axially extending drive shaft having an eccentric shaft portion so that rotation of the eccentric shaft portion imparts an orbiting motion to the orbiting scroll relative to the fixed scroll; and an axial thrust bearing arrangement including an array of ball bearings for bearing against the orbiting scroll base in an axial direction, each ball bearing describing a circular path over the orbiting scroll base during orbiting motion; at least one thrust surface for bearing against the array of ball bearings; and an adjustment mechanism for adjusting the axial position of said at least one thrust surface and thereby the axial position of the orbiting scroll base.

A roots pump includes a housing, a rotor chamber, a pair of rotary shafts, and a pair of rotors. The rotor chamber includes a rotor chamber peripheral surface facing a pair of distal end portions of each of the rotors. Each of the pair of the distal end portions includes: a pair of rotor peripheral surfaces facing the rotor chamber peripheral surface with a first radial clearance; and a distal end peripheral surface that is formed between the pair of the rotor peripheral surfaces in the rotational direction and faces the rotor chamber peripheral surface with a second radial clearance greater than the first radial clearance. A width of the rotor chamber peripheral surface facing the distal end peripheral surface in the rotational direction is greater than a sum of a pair of predetermined widths of the rotor chamber peripheral surface facing the pair of the rotor peripheral surfaces.

A scroll compressor, includes: a scroll compression mechanism including an orbiting scroll, a fixed scroll, and a thrust plate supporting a load of the orbiting scroll in a thrust direction; a back-pressure application mechanism that applies, as back pressure, the refrigerant gas compressed by the scroll compression mechanism to a rear surface of the thrust plate; and a floating amount restriction mechanism that restricts an amount of floating of the thrust plate caused by the back pressure. The floating amount restriction mechanism includes a restriction pin that includes a shaft part and a head part, and locks the thrust plate to the head part to restrict the amount of floating. The shaft part passes through the thrust plate and has a front end part fixed to a front housing, and the head part has a diameter larger than a diameter of the shaft part.

A dry-compressing vacuum pump, in particular a screw pump, has two rotor elements (14) which are arranged in a pump chamber (12) and which are each carried by a rotor shaft (22). Two shaft ends of the rotor shafts (22) project through a side wall (28) of the pump housing (10). On the two shaft ends (28) there is arranged in each case one toothed belt pulley (38). Furthermore, a drive device and an electric motor for driving the rotor shaft (22) are provided. According to the invention, the rotor shafts (22) are driven by means of a toothed belt (40). To be able to use a toothed belt for drive purposes, a rotational flank clearance between the two rotor elements (14) of greater than 0.75, in particular greater than 1, is provided.

A fluid pump includes a gear housing with a pocket wall and a base. The pocket wall and the base define a pocket that projects into the gear housing from a pocket surface. The fluid pump also includes a first gear rotatably positioned in the pocket. The first gear is spaced from the pocket surface by a first gap. The fluid pump also includes a second gear rotatably positioned in the pocket that engages the first gear. The second gear is spaced from the pocket surface by a second gap. The fluid pump also includes a selected shim that is selected from a plurality of shims in a shim set. The selected shim has a thickness that results in a desired clearance between the selected shim and the first face or the second face.

Provided is a scroll fluid machine that makes it possible to attenuate the bending stress applied to the base of a wall body having an inclined section. The scroll fluid machine is provided with a wall body inclined section in which the distance between the facing surfaces of an end plate of a fixed scroll and an end plate of a rotating scroll that face each other continuously decreases from the outer circumferential side toward the inner circumferential side. A mesh clearance that is a gap between wall bodies formed when the wall bodies mesh with each other is larger on the outer circumferential side of the inclined section than on the inner circumferential side of the inclined section. The mesh clearance is made larger by drawing the wall surface of a wall body further back toward the central side of the wall body in the thickness direction than the original wall surface profile thereof.

A scroll compressor including a first bearing rotatably supporting a rotary shaft relative to a casing at one side of the rotary shaft with respect to a motor, a second bearing rotatably supporting the rotary shaft relative to the casing at the other side of the rotary shaft with respect to the motor, and a third bearing rotatably supporting the rotary shaft relative to an orbiting scroll at the opposite side of the first bearing with respect to the second bearing. The distance between a first bearing center and a third bearing center is a predetermined distance, the distance between a motor center and the third bearing center is longer than the distance between the motor center and the first bearing center, and the distance between a second bearing center and the motor center is longer than the distance between the second bearing center and the third bearing center.

A scroll compressor includes a fixed scroll and a movable scroll. The fixed scroll has a spiral fixed-side wrap positioned upright on a surface of a fixed-side plate. The movable scroll is orbitably disposed to face the fixed scroll. The movable scroll has a spiral movable-side wrap positioned upright on a surface of a movable-side plate, with the movable-side wrap being configured to mesh with the fixed-side wrap. A side clearance is formed between a side surface of the fixed-side wrap and a side surface of the movable-side wrap so as to increase from an outer peripheral side toward an inner peripheral side of each of the wraps.

A screw pump includes a male screw, a female screw, a motor, a journal, a bearing member, and a case. The motor includes an output shaft, which transmits a torque to the male screw, and the motor is operable to drive the male screw to rotate the same through the output shaft. The journal is rotatably placed between the output shaft of the motor and the male screw. The bearing member rotatably supports the journal. The case includes a screw receiving hole that receives the male screw and the female screw. The journal and the male screw are coaxially and non-detachably integrated together. The output shaft and the journal are fitted together by clearance fit that enables transmission of the torque between the output shaft and the journal.