Abstract: There is provided a scroll compressor having high overall efficiency and reliability in a wide pressure operating range. A backside excess-suction-pressure region is provided such that pressure higher than suction pressure by a constant value is applied to a backside of scroll members to produce an attractive force to attract both scroll members. A control bypass is also provided for communicating compression chambers with a discharge system only when pressure in the compression chambers is high.

Abstract: The invention relates to the design of backflow orifices for a rotary compressor serving as a compressor for an engine. One example of such a rotary compressor is a roots blower. The fluid conveyed by two oppositely rotating rotors from an inlet to an outlet of the compressor flows back partially via the backflow orifices. The edges of the backflow orifices are at a varying height from an inner surface contour of the pump casing. The height variation contributes to a reduction in the noise generated by the compressor.

Abstract: A pump assembly is provided that includes a gerotor pump and a manifold. An aspirating member is positioned between a pump inlet cavity in the manifold and a fluid reservoir. Fluid flow generated by operation of the pump is diverted by a flow control valve and accelerates as it passes between the aspirating member and the manifold. The resulting decrease in static pressure draws the fluid out of the reservoir where it mixes with the higher velocity fluid. As the combined fluid is slowed, the static pressure increases to “supercharge” the inlet cavity to improve the inlet fill and reduce cavitation. An inlet port in the gerotor pump corresponds to the inlet cavity in the manifold. The timing and geometry of an input port is optimized to prevent noise inducing pressure spikes while maintaining sufficient back pressure in the pump chambers to collapse entrapped vapor bubbles in the fluid.

Abstract: An oil pump apparatus includes an oil pump housing having a first suction port, a second suction port and a discharge port in the circumferential direction thereof. A shape of the end portion in the anti-rotational direction at the second suction port is formed to be along a shape of the end portion on the rotational direction side of one pump chamber which is sealed momentarily between the two suction ports, and a shape of the inner circumferential end portion of the first suction port is formed to be along the rotational trace of the end portion on the anti-rotational direction side of the pump chamber. A plural first pockets are formed on the driven rotor, and a second pocket is formed on the pump housing to communicate between the pump chamber and one of the first pockets when the pump chamber is communicated to the first suction port.

Abstract: A scroll-type compressor includes a fixed scroll member and an orbiting scroll member. The fixed scroll member has a first end plate and a spiral element formed on and extending from a first side of the first end plate. The orbiting scroll member has a second end plate and a spiral element formed on and extending from a first side of the second end plate. The spiral elements interfit with one other at an angular and radial offset to form a plurality of line contacts defining at least one pair of sealed-off, fluid pockets. A plurality of bypass apertures are formed through the first end plate of the fixed scroll member. A tip seal, which is made of Polyphenylene-sulfide or Polyetheretherketone, is embedded in a front end portion of the spiral element of the orbiting scroll member.

Abstract: The invention relates to the design of backflow orifices for a rotary compressor serving as a compressor for an engine. One example of such a rotary compressor is a roots blower. The fluid conveyed by two oppositely rotating rotors from an inlet to an outlet of the compressor flows back partially via the backflow orifices. The edges of the backflow orifices are at a varying height from an inner surface contour of the pump casing. The height variation contributes to a reduction in the noise generated by the compressor.

Abstract: A compressor valve comprising at least one valve port opening and a flexible valve member located over the at least one valve port for controlling gas flow therethrough, wherein the compressor valve is adapted to cause elements of the valve member to vibrate at least substantially out of phase during operation of the compressor valve.

Abstract: A sliding vane pump comprising a rotor housing having a pumping chamber, a rotor in the pumping chamber having a plurality of radially disposed slots, and a plurality of sliding vanes disposed in the slots configured to extend to follow an inner wall of said pumping chamber.

Abstract: Fixed throttle devices 36A, 36B, 36C, 36D are screw-engaged with a rotor housing 12. A fixed throttle device 37is screw-engaged with a front housing 13, and a fixed throttle device 38is screw-engaged with a rear housing 14. Inert gas is supplied to the respective throttle devices 36A, 36B, 36C, 36D, 37and 38via branch pipes 54 to 59. Each of the throttle devices 36A, 36B, 36C, 36D, 37and 38includes a check valve 44, a fixed throttle 45 screw-engaged with the check valve 44, and a pipe joint 46 screw-engaged with the check valve 44.

Abstract: In a hydraulic vane motor having at least two working chambers (13, 14) and having flow in both directions, sealing strips (12), in a way that is known per se, are arranged loose in the respective vane slots (11) and are spring-loaded from the vane (11) towards the pathway (15). Each working chamber (13, 14) is provided with at least four ports (16a, 16b) in the pathway (15). In addition to the ports, grooves (20, 21, 22) are advantageously arranged parallel to the ports.

Abstract: In order to simultaneously generate pressure and negative pressure with a single-stage pump, said pump has a pump chamber (18) that is formed in a housing and that is provided with a suction port, a pressure port and a charging port. There is a pair of rotors (30, 32) in the pump chamber (18) that has at least three blades and that rotates in opposite directions around parallel spaced axes and the rotors intermesh free of contact and, together with the peripheral wall of the pump chamber (18), they define cells (60, 62a, 62b, 64) that are separate from each other.

Abstract: A positive displacement rotary pump including a housing having an internal chamber and inlet and discharge ports, a sealing land on the housing between a downstream end of the inlet port and an upstream end of the discharge port, and a rotating group in the internal chamber defining a plurality of pump chambers. The pump chambers traverse in succession and at regular intervals the inlet port and the sealing land and the discharge port. The housing has a stationary pre-charging passage which communicates with the discharge port and overlaps the sealing land. The rotating group includes a plurality of rotating pre-charging passages which communicate with respective ones of the pump chambers.

Abstract: The invention relates to an internal gear machine for reversed operation in a closed circuit comprising an outer-toothed pinion, an inner-toothed ring gear meshing with the pinion; a housing; a filing that fills the sickle-shaped space between the pinion and the ring gear; the filling comprises two identical filler pieces; a stop pin is provided that is mounted in the housing and against which the filler pieces are supported by their front faces; the housing has two pressure lines and a drain outlet; the filler pieces are symmetrically disposed relative to a plane (symmetrical plane) extending through the center points of the pinion and the ring gear; the two pressure lines are located on both sides of the symmetrical plane viewed in axial direction.

Abstract: A pump has meshing inner and outer rotors mounted eccentrically in a housing. The pump also has an inlet and a main outlet. The main outlet communicates via a control gap with a secondary outlet. The control gap provides a filtering action for some of the fluid pumped.

Abstract: A scroll compressor is provided that has greater control over the compressed volume by having a plurality of sequentially spaced unloader valves and associated holes. By providing the plurality of valves, a control achieves greater variation over the final compressed volume. The present invention is most preferably utilized in the type of scroll compressor having a hybrid wrap geometry to provide an increased volume of refrigerant adjacent the suction area of the compressor.

Abstract: A rotary vane pump for delivering a fluid, having a delivery device accommodated in a casing (2), a casing cover (3) arranged on one end face, and optionally with a bearing flange (4) adjoining the casing (2) on the side opposite to the casing cover (3). A seal (5,6) is arranged between the casing (2) and the casing cover (3) and optionally between the casing (2) and the bearing flange (4), and the seal (5,6) is inserted into a groove (8,9) formed in the casing cover (3), and optionally in the bearing flange (4), and/or in the respective end face (7) of casing (2). Also a leakage path (13) for the fluid extends between a delivery side (11) and suction side (12). The leakage path (13) extends on the inner side (14) of the seal at least in sections parallel to the seal (5,6).

Abstract: A scroll-type compressor includes a fixed scroll member and an orbiting scroll member. The fixed scroll member has a first end plate and a spiral element formed on and extending from a first side of the first end plate. The orbiting scroll member has a second end plate and a spiral element formed on and extending from a first side of the second end plate. The spiral elements interfit with one other at an angular and radial offset to form a plurality of line contacts defining at least one pair of sealed-off, fluid pockets. A plurality of bypass apertures are formed through the first end plate of the fixed scroll member. A tip seal, which is made of Polyphenylene-sulfide or Polyetheretherketone, is embedded in a front end portion of the spiral element of the orbiting scroll member.

Abstract: A scroll compressor has a unique oil supply port for supplying lubricant to both the seals and the Oldham coupling. The oil supply port is positioned at a location such that it will not likely result in undue amounts of lubricant being entrained into the refrigerant leading into the compression chambers. The present invention is thus an improvement over the prior art.

Abstract: An improved scroll compressor having a full thrust surface at which a face of the non-orbiting scroll is in contact with the base of the orbiting scroll is provided with two suction passages. The suction passages extend along circumferential directions at which a substantial portion of the direction of the suction port is tangential. The two suction passages are circumferentially spaced to each be associated with independent compression chambers within the scroll compressor. Due to the tangential component, the refrigerant leaving the ports tends to merge into the compression chambers more rapidly. This results in improved flow, and a reduction in heat transfer.

Abstract: In order to simultaneously generate pressure and negative pressure with a single-stage rotary piston machine, said machine has a chamber (18) that is formed in a housing and that is provided with a suction connection, a pressure port and a charging port. In the pump chamber (18), there are two three-blade rotors (30, 32) that work with internal compression and internal expansion and that rotate in opposite directions around parallel spaced axes and these rotors intermesh so as to be free of contact so that, together with the peripheral wall of the pump chamber (18), they define cells (60, 62a, 62b, 64) that are separate from each other.

Abstract: An oil pump apparatus includes an oil pump housing having a first suction port a second suction port and a discharge port in the circumferential direction thereof. A shape of the end portion in the anti-rotational direction at the second suction port is formed so as to be along a shape of the end portion in the rotational direction at the pump chamber which is sealed momentarily between the first suction port and the second suction port, and a shape of the inner circumferential end portion of the first suction port is formed so as to be along the rotational trace of the end portion on the side of the anti-rotational direction at the pump chamber which is sealed momentarily between the first suction port and the second suction port. A plural first pockets are formed on the driven rotor, and a second pocket is formed on the pump housing.

Abstract: Apertures through each face of a planetary rotor, volutes for low loss delivery and collection of fluid to and from the working volumes of a planetary rotary pump, compressor, or turbine, and zero clearance seals by using continuous carbon fiber reinforced polyetheretherketone (PEEK) or other self-lubricating materials significantly improve the volumetric flow rate of such rotary pumps compressors or turbines.

Abstract: A rotary piston internal combustion engine comprises a substantially circular-cylindrical compression space (3) and a substantially circular-cylindrical working space (4), rotary pistons (7, 8) which can rotate together about an axis of the compression space (3) and the working space (4), being disposed in the compression space (3) and the working space (4) are slides (19) which are arranged so as to be movable in the radial direction in order to abut sealingly the surface of the respective rotary piston (7, 8). The periphery of the working space has a first exhaust aperture (26). The working space has further exhaust apertures (27) which can be closed by exhaust valves (15) which can be closed and opened successively by means of an adjusting arrangement (17).

Abstract: Fixed throttle devices 36A, 36B, 36C, 36D are screw-engaged with a rotor housing 12. A fixed throttle device 37 is screw-engaged with a front housing 13, and a fixed throttle device 38 is screw-engaged with a rear housing 14. Inert gas is supplied to the respective throttle devices 36A, 36B, 36C, 36D, 37 and 38 via branch pipes 54 to 59. Each of the throttle devices 36A, 36B, 36C, 36D, 37 and 38 includes a check valve 44, a fixed throttle 45 screw-engaged with the check valve 44, and a pipe joint 46 screw-engaged with the check valve 44.

Abstract: A highly reliable scroll compressor adapted to make the amount of a refrigerant taken in through a first suction inlet of a scroll compression element as equal as possible to that taken in through a second suction inlet of the scroll compression element so as to improve the intake efficiency, thereby suppressing pulsation and noise. If the sectional area of the inlet of a refrigerant passage through which a refrigerant taken in flows from an end of a swivel lap via the outer periphery thereof to the second suction inlet is denoted as A1, the sectional area of the inlet of the first suction inlet is denoted as A2, and the sectional area of the inlet of a communication groove is denoted as A3 when the gap between a stationary lap and the swivel lap of the scroll compression element reaches its maximum, then A1, A2, and A3 stay within a range defined by 1.5≦A2/(A1+A3)≦2.5.

Abstract: A positive displacement, recirculating Root's type rotary compressor which operates on a constant volume, near isothermal cycle is disclosed. The compressor includes a pair of involutely lobed impellers and a discharge pressure reflux flow loop. The flow loop includes a discharge port, a flow distributor, an output port, and one or two pair of low impedance rectangular conduits terminating in linear nozzles that serve as reflux ports. Reflux flow through the nozzles is directed with impeller rotation. It isentropically expands into the constant volume displacement cavities so that the contained pressure approaches discharge level. The final pressure increase into discharge is gained through adiabatic compression at a low pressure ratio. The resulting process is inherently non-contaminating, as there are no valves and no contacting or rubbing parts in the flow stream. It can be applied wherever gases or vapors must be compressed.

Abstract: A gear pump for delivering liquid media has a pump housing with at least two bores, in which at least two meshing gears with tooth tips are contained. The gears are radially mounted by bearing surfaces which on one side consist of areas of the tooth tips and on the other side, of areas of the interior of the bores. This arrangement requires no slide bearings in the conventional sense, which results in a smaller number of pump parts and hence to reduced manufacturing costs.

Abstract: It is an object of the present invention to improve the efficiency of a scroll gas compressor by operating a bypass at a proper compression ratio. To achieve the object, the present invention is constituted so that at least one pair of bypass holes whose one ends are opened in a compression chamber currently performing compression nearby a discharge vent and whose other ends communicate with a discharge chamber are asymmetrically arranged on a panel board. This structure makes it possible to improve the efficiency of the compressor by operating the bypass at an optimum compression ratio even if a difference is observed between pressure rises of a pair of symmetric compressed spaces under the compression process.

Abstract: Screw-spindle vacuum pump with at least three closed-off feed chambers located one behind the other along each rotor and method for operating this compressor. The chamber which is last on the delivery side is brought virtually to the compression limit pressure by means of pre-admission, shortly before it opens towards the delivery side, by supplying a pre-admission stream which is at least five times as great as the intake mass stream. A precondition, in this case, is a minimum ratio of external compression to internal compression of five.

Abstract: The required larger than normal pressure drop between the infeed and pump inlets of a positive displacement gear or lobe type pump pumping a high viscosity fluid such as pastry dough is obtained by the introduction of a vacuum inside the pump at or near the rotary nip points of the gear or lobe type pump to provide a means for the removal of any gas present in the vicinity of the nip point.

Abstract: A fluid flow device and method are provided according to which one or more impellers are mounted for rotation in a chamber formed in a casing. Fluid to be processed is introduced into an inlet formed in the casing and at least one impeller is mounted for rotation in the chamber to flow the fluid through the casing and through an outlet in the casing. The impeller also draws atmospheric air into the chamber through an air inlet formed in the casing, and any backflow of the fluid from the fluid outlet into the air inlet is prevented.

Abstract: The invention relates to a roller vane pump for operating an automatic transmission for motor vehicles. The pump is provided with a pump housing (12), a rotor (4), a cam ring (2) and roller elements (7), which define a number of pump chambers (13). Fluid is communicated between a hydraulic channel (24) and a pump chamber (13) through suction ports (11 and 16) and discharge ports (17 and 18). According to the invention the pump is provided with a suction port (26) for allowing a predominantly radial flow of fluid to a pump chamber (13) and/or with a rotor (4) with slots (6) with a circumference (32) which is partly curved with a curvature substantially matching the curvature of the roller elements (7) and/or with a rotor (4) with a circumference segment (30) deviating at least partly from a circle, in order to decrease the amount of wear of pump parts as well as the noise level generated during pumping.

Abstract: A hydraulic vane pump (10), including a top section (12), a middle section (14), a vane rotor assembly (16) and a bottom section (18) secured together to form a single assembly. The vane pump (10) has a fluid feed chamber (20) to supply fluid directly to the top of a bore (32) formed in the middle section (14). Fluid from the feed chamber (20) also passes through a bypass chamber (28) into a fluid pocket (24) in the bottom section (18) and into the bottom of the bore (32). A vane rotor assembly (16) is used to force fluid from the bore (32) out the outlet chamber (26). By supplying fluid to both the top and bottom of the bore (32) cavitation is reduced. By feeding fluid from a single side of the hydraulic vane pump (10), packaging requirements are minimized.

Abstract: The invention concerns an oil-sealed vane-type rotary vacuum pump (1) with a rotor (3) and an oil pump (45, 46) whose suction chamber is fitted with feeds (64, 65) for gas and oil. In order to simplify the supply of a gas/oil mixture to the vacuum pump, the invention proposes that the gas and oil feeds (64, 65) are disposed in such a way that initially only oil and subsequently both oil and air are aspirated into the volume swept by the oil pump (45, 46) as it rotates.

Abstract: An improved scroll compressor utilizes a crossing economizer passage which is defined between an outer end face of the fixed scroll and a mating end face of an overlying cover. Since the economizer passage is formed in a face which is exposed before assembly, it is relatively easy to machine the complex crossing passage into the end face. The passage is machined into the end face, and the cover and fixed scroll are secured together closing the passage. The invention simplifies formation of the relatively complex economizer crossing passage.

Abstract: A housing (7") of the displacement machine for compressible media includes an end wall (28). Placed onto the housing (7") in the axial direction is a hood (50), which, together with the end wall (28), bounds a space (51). The two inlets (12, 12'), which are located on the outside in the radial direction, are connected to each other by this space. For its part, the hood (50) has a nozzle-like connection (52), via which the displacement machine can be connected to an upstream air filter. The displacement machine needs little space, as viewed in the radial direction.

Abstract: The invention relates to a fluid-conveying machine, in particular, a pump having a component rotating in a stationary housing part inside an annular gap. The stationary housing part separates an interior having a higher product pressure from an exterior having a lower pressure. A rotating component is mounted in an external bearing which is sealed with respect to the interior via a sealing system. In order to improve the sealing, the invention provides that the annular gap is formed between two sliding bearing shells which comprise extremely hard, wear-resistant materials and, in accordance with the operating principle of a radial sliding bearing, form a first pressure-reducing stage. A feedback device, which feeds back the leakage from this first sealing stage into the conveying process of the machine, is connected downstream of the first pressure-reducing stage. A second sealing stage is arranged axially downstream of the feedback device.

Abstract: A method of improving the efficiency of a pair of first and second scroll refrigeration compressors, at least the second of which includes an intermediate port is characterized in that the delivery of the first scroll compressor is fed into the intermediate port of the second compressor at a pressure corresponding to the intermediate port in the compression process occurring in the second scroll compressor.

Abstract: A positive displacement gear rotor fuel pump with a plurality of spaced apart outlet ports through which fuel is discharged from a fuel pumping assembly and a valve which prevents any fuel downstream of the outlet ports which is at outlet pressure, from reentering portions of the pumping assembly which are at a lower pressure to prevent the higher pressure fuel from rapidly compressing and collapsing the fuel vapor in the pumping assembly to greatly reduce the noise of the operating fuel pump. This reduces the magnitude of the cavitation noise in the fuel pump which is the noise caused by the collapsing of the fuel vapor in the pump. The outlet ports are also constructed and arranged to prevent adjacent pumping chambers of the pumping assembly from communicating with each other to prevent the fuel at an increased pressure in a downstream pumping chamber from flowing into a lower pressure pumping chamber upstream thereof to also reduce cavitation noise in the fuel pump.

Abstract: A gas blower and method according to which the gas is introduced into the inlet of a housing where it is pressurized by rotating impellers. The pressurized gas is directed to a discharge plenum from which a first portion of the gas is discharged. The remaining portion of the gas is passed from the discharge plenum through a plurality of openings to a recirculating chamber for recirculating the gas back to the housing. The gas is passed from the recirculating chamber back to the housing through two radially-spaced sets of angularly-spaced openings formed in the housing.

Abstract: The locations of economizer ports in a scroll compressor are optimized such that the ports supply supplemental fluid to compression chambers prior to the outer seal points closing the compression chambers. Thus, the economizer port supplies fluid against a low average pressure and the amount of fluid injected from the economizer port is maximized. The location of the economizer port is preferably selected such that a wave caused in the compression chamber due to the injection of fluid from the economizer port does not reach the outer seal point until the outer seal point closes the compression chamber. Thus, there is no back flow from the economizer port toward the main suction chamber, and no corresponding reductions in the main suction flow.

Abstract: A fuel pump comprises a pump unit and a motor unit. The pump unit is a trochoid gear type having rotors in a pump chamber defined by a pair of side plates and a cylindrical housing. A disk plate is attached to the side plate to provide an arcuate-shaped pressure pulsation reducing passage jointly with the side plate. Protrusions or recesses are provided in the passage to cause turbulence in fuel flowing through the passage. This turbulence scatters pressure pulsation in the fuel thereby to reduce the pressure pulsation.

Abstract: A scroll-type compressor has multiple discharge ports and blocks to prevent undesired movement of the non-orbiting scroll plate and an improved lubrication system.

Abstract: A scroll is provided which can be operated as either a vacuum pump, a low pressure compressor or a high pressure compressor. The scroll includes a housing, a fixed scroll plate having a continuous fixed involute wrap and an orbiting scroll plate having a continuous orbiting involute wrap. The wraps are of constant width and pitch. The fixed and orbiting scroll plates are mounted in the housing with their involute wraps extending toward each other to define a series of chambers. The fixed involute wrap and orbiting involute wrap each have at least a first section of one height and a second section of a second different height. Additionally, the scroll includes a first port proximate a peripheral edge of the housing, a second port proximate the center of the housing, and at least one mid-port; the mid-port being located proximate the change in height between the first and second sections of the involute wraps.

Abstract: A suction pump (22) suitable for use in a fuel dispensing system (20) or other fluid delivery system for volatile liquids. The suction pump includes a pump casing that defines a pump chamber (52) with inlet and outlet ports. A rotor (54) with vanes (58) is seated in the pump chamber. The vanes define fluid cavities (96a, 96b, 96c, . . . 96f) that rotate between the inlet and outlet ports. During each turn of the rotor, each fluid cavity passes through a section of the pump chamber in which it is isolated from both the inlet port and outlet port. A bleed duct (102) extends from the outlet port. A bleed port (104) extends from the bleed duct to the section of the pump chamber that defines the isolated position of the fluid cavities. During operation of the pump, pressurized fluid discharged from the outlet port flows through the bleed duct and bleed port into the isolated fluid cavity.

Abstract: A multi-rotor type compressor including plural compression elements each of which includes a rotor eccentrically rotating in a cylinder and a vane which is in sliding contact with the outer peripheral surface of the rotor and partitions the inside space of the cylinder into a suck-in space in which a suck-in operation is performed and a compression space in which a compressing operation is performed, and a power save mechanism including an intercommunication path through which the compression space of a compression element is allowed to intercommunicate with the suck-in space of another compression element at a predetermined phase, an interception valve for intercepting flow of fluid in the intercommunication path, and a check valve which is provided in the intercommunication path and allows the fluid to flow therethrough in only one direction. The compression may be equipped in an air conditioner.

Abstract: An oil-free two-stage vacuum pump includes first and second pump stages coupled in series. The first and second pump stages have discharge spaces capable of communicating with each other via a bypass passage. The bypass passage is provided with a pressure control valve which is closed when pressure in the bypass passage is lower than a predetermined pressure. This permits a reduction in scroll size. In addition, the pump is free from problems present in pumps with large scroll sizes such as drive shaft vibrations due to warping thereof at high speed rotation, noise and heat generation, and durability reduction due to causes such as non-uniform contact between stationary and revolving scrolls. Moreover, in a compression step in the first pump stage, withdrawn gas is under high pressure; the gas pressure in a sealed vessel is close to the atmospheric pressure in an initial stage of driving.

Abstract: Apparatuses are described for cooling the rotors of, improving the sealing of, and improving the power efficiency of twin-screw pumps. Such methods include (1) injecting liquid onto the rotor and into the rotor chambers at the point of greatest temperature accumulation, (2) implanting a heat transfer device within the rotor enclosure that can transfer heat outside of the rotor enclosure, and (3) injecting liquid into rotor chambers via energy recovery devices which reduce the total power consumption of the system.

Abstract: A scroll compressor has a check valve assembly for selectively opening and closing a discharge port and allowing a fluid to flow only from the discharge port towards a discharge chamber. A stationary end plate mounted in the scroll compressor has a plurality of bypass holes defined therein at locations symmetrical in terms of pressure. The plurality of bypass holes are open to compression chambers closest to the discharge port and communicate with the discharge chamber. The stationary end plate also has at least one bypass valve for selectively opening and closing the bypass holes and allowing the fluid to flow only from the compression chambers towards the discharge chamber through the bypass holes. The bypass holes are serviceable to prevent an excessive compression and are positioned so as not to be closed by an orbiting scroll wrap immediately after the compression chambers closest to the discharge port have communicated with the discharge port.

Abstract: In a screw fluid machine including male and female rotors which are engaged with each other, a casing for accommodating both the male and female rotors, fluid working rooms which are formed by the male and female rotors and the casing, and fluid inlet and outlet ports which are provided in the casing so as to intercommunicate with one end portion and the other end portion of the working rooms, the helix angle of the screw gear constituting each of the male and female rotors is set to be continuously varied in a helix advance direction. Further, the screw gear is designed so that the peripheral length of a pitch cylinder in a helix advance direction on a development of a tooth-trace rolling curve on the pitch cylinder of the screw gear can be expressed by a substantially monotonically increasing function.