Abstract: An oiling device includes a passage system that circulates and feeds oil to an oiling object. A control unit includes a storage unit that has stored therein a first abnormality pressure set value that differs according to oiling temperature; the first abnormality pressure set value is set to a lower pressure as the oiling temperature is higher. The control unit executes an abnormal stop of the oiling object when an oiling pressure detected by an oiling pressure detecting unit is equal to or lower than the first abnormality pressure set value corresponding to an oiling temperature detected by an oiling temperature detecting unit.

Abstract: A screw compressor 2 includes a compressor main body 4, a motor 8, and a gearbox 10. The compressor main body 4 includes screw rotors 5c, 5d, 6c, and 6d, rotor casings 5e and 6e accommodating therein the screw rotors 5c, 5d, 6c, and 6d, and main body casings 5a and 6a accommodating therein the rotor casings 5e and 6e, the main body casings being provided with first flanges 5b and 6b on respective ends thereof. The motor 8 drives the screw rotors 5c, 5d, 6c, and 6d via gears 10f and 10g. The gearbox 10 has an attachment surface Son which the first flange 6b to the main body casings 5a and 6a is attached, accommodates therein the gears 10f and 10g, and has a substantially rectangular shape. In a state where the compressor main body 4 is attached to the gearbox 10, a part of the first flange 6b extends to an outside of the attachment surface S, and projection regions of the rotor casings 5e and 6e onto the attachment surface S exist within the attachment surface S.

Abstract: The oil-free screw compressor includes: a screw rotor including a screw and a shaft; a bearing; a first shaft seal device disposed between the screw and the bearing, the first shaft seal device including: a first seal and a first communication section; a second shaft seal device disposed between the first shaft seal device and the bearing, the second shaft seal device including: a second seal and a second communication section; and a first seal member including a seal between the first communication section and the second communication section. The casing includes an atmosphere communication section configured to communicate the first communication section and the second communication section with an atmosphere. A sectional area in the first communication section is larger than a sectional area between the seal of the first seal member and the shaft.

Abstract: The screw compressor includes a first-stage compressor main body and a second-stage compressor main body for compressing fluid with screw rotors, a motor for driving the first-stage compressor main body and the second-stage compressor main body, and a gear box. The gear box is connected to the first-stage compressor main body, the second-stage compressor main body, and the motor; transmits a driving force of the motor to the screw rotors, and includes a first attachment hole for attaching the first-stage compressor main body and a second attachment hole for attaching the second-stage compressor main body; and is provided with an annular rib surrounding both of the first attachment hole and the second attachment hole. In the screw compressor, the vibration of the natural vibration mode which is most burdensome and should be reduced can be efficiently reduced.

Abstract: The oil-free screw compressor includes: a screw rotor, a bearing configured to support a rotor shaft, a shaft seal device including an oil seal arranged at a position closer to the bearing and a gas seal arranged on at a position closer to the rotor chamber, an atmosphere communication space communicating with an atmosphere communication hole, and an oil return groove including a return inclined surface inclined so as to expand in diameter radially outward from a gas seal-side end to an oil seal-side end. The oil seal portion is a viscoseal including a spiral groove portion. An inner peripheral surface of the oil seal includes an inner peripheral boundary portion that defines a part of the atmosphere communication space, on a side closer to the bearing in the atmosphere communication hole. The oil seal-side end is arranged in a vicinity of the inner peripheral boundary portion and at a position closer to the bearing.

Abstract: The oil-free screw compressor includes: a casing having a rotor chamber; a bearing supporting rotary shafts of screw rotors; a shaft seal device with an oil seal portion and an air seal portion; a ventilation gap positioned between the oil seal portion and the air seal portion; and an atmosphere open passage communicating an atmosphere side of the casing with the ventilation gap communicate. A most narrowed portion, an air seal portion, and oil seal portions are set such that the followings is established: (La/Sa2.5)/(Lh/Sh2.5)>|P2|/?Pb La: effective shaft seal length Sh: effective open cross-sectional area (most narrowed portion of atmosphere open passage) Lh: effective narrowed length (most narrowed portion of atmosphere open passage) Sa: shaft seal cross-sectional area |P2|: negative pressure in rotor chamber during unloading operation ?Pb: minimum differential pressure in the oil seal portion during the unloading operation.

Abstract: An oil-free screw compressor has a screw rotor including a screw and a shaft, a bearing supporting the shaft, a first shaft seal device disposed between the screw and the bearing and including a first seal opposite to the shaft, and a first communication portion communicating the inner periphery face and the outer peripheral face of the first shaft seal device, a second shaft seal device disposed between the first shaft seal device and the bearing and including a second seal opposite to the shaft, and a second communication portion communicating an inner periphery face and the outer peripheral face of the second shaft seal device, and a casing including an atmosphere communication portion connected to both of the first communication portion and the second communication portion on the inner peripheral face of a shaft accommodation space.

Abstract: A method for forming drilled cast which includes drilling with a drill so as to provide communication with a cast hole includes a casting step and a drilling step. The casting step is to cast a cast having a cast hole which includes a flat inner wall surface in which width of a position to be drilled with the drill is obtained by adding first length H1 serving as a manufacturing error range of the cast to a diameter D of the drill, which is a second length H2. The drilling step is to form a through hole providing communication between an interior of the cast hole and an exterior of the cast through the flat inner wall surface with the drill.

Abstract: An oil-free screw compressor includes: a casing having a rotor chamber; a bearing supporting rotary shafts of the screw rotors; a shaft seal device including an oil seal portion and an air seal portion; an atmosphere open hole formed in the shaft seal device; at least one communication hole formed in the rotary shaft; and an annular space communicating the atmosphere open hole with the at least one communication hole communicate with each other. The annular space includes an inner peripheral annular space formed on an inner peripheral side of the casing. Assuming an open cross-sectional area of the inner peripheral annular space as S1, a total open cross-sectional area of the communication holes as S2, an open cross-sectional area of the i-th communication hole out of the communication holes as S2i, and the number of communication holes as n (n being a natural number of 1 or more), a following relationship is satisfied.

Abstract: The oil-free screw compressor includes: a screw rotor including a screw and a shaft; a bearing; a first shaft seal device disposed between the screw and the bearing, the first shaft seal device including: a first seal and a first communication section configured to communicate the bearing side with respect to between the shaft and the first seal, and an outer peripheral face of the first shaft seal device; a second shaft seal device disposed between the first shaft seal device and the bearing, the second shaft seal device including: a second seal and a second communication section configured to communicate the screw side with respect to between the shaft and the second seal, and an outer peripheral face of the second shaft seal device; and a first seal member including a seal between the first communication section and the second communication section.

Abstract: The oil-free screw compressor includes: a screw rotor, a bearing configured to support a rotor shaft, a shaft seal device including an oil seal arranged at a position closer to the bearing and a gas seal arranged on at a position closer to the rotor chamber, an atmosphere communication space communicating with an atmosphere communication hole, and an oil return groove including a return inclined surface inclined so as to expand in diameter radially outward from a gas seal-side end to an oil seal-side end. The oil seal portion is a viscoseal including a spiral groove portion. An inner peripheral surface of the oil seal includes an inner peripheral boundary portion that defines a part of the atmosphere communication space, on a side closer to the bearing in the atmosphere communication hole. The oil seal-side end is arranged in a vicinity of the inner peripheral boundary portion and at a position closer to the bearing.

Abstract: A screw compressor 2 includes a compressor main body 4, a motor 8, and a gearbox 10. The compressor main body 4 includes screw rotors 5c, 5d, 6c, and 6d, rotor casings 5e and 6e accommodating therein the screw rotors 5c, 5d, 6c, and 6d, and main body casings 5a and 6a accommodating therein the rotor casings 5e and 6e, the main body casings being provided with first flanges 5b and 6b on respective ends thereof. The motor 8 drives the screw rotors 5c, 5d, 6c, and 6d via gears 10f and 10g. The gearbox 10 has an attachment surface Son which the first flange 6b to the main body casings 5a and 6a is attached, accommodates therein the gears 10f and 10g, and has a substantially rectangular shape. In a state where the compressor main body 4 is attached to the gearbox 10, a part of the first flange 6b extends to an outside of the attachment surface S, and projection regions of the rotor casings 5e and 6e onto the attachment surface S exist within the attachment surface S.

Abstract: The screw compressor includes a first-stage compressor main body and a second-stage compressor main body for compressing fluid with screw rotors, a motor for driving the first-stage compressor main body and the second-stage compressor main body, and a gear box. The gear box is connected to the first-stage compressor main body, the second-stage compressor main body, and the motor; transmits a driving force of the motor to the screw rotors, and includes a first attachment hole for attaching the first-stage compressor main body and a second attachment hole for attaching the second-stage compressor main body; and is provided with an annular rib surrounding both of the first attachment hole and the second attachment hole. In the screw compressor, the vibration of the natural vibration mode which is most burdensome and should be reduced can be efficiently reduced.

Abstract: An oil-free screw compressor with good assemblability of a shaft seal device that reduces leakage of a compressed gas, where the oil-free screw compressor accommodates male and female screw rotors in a rotor chamber of a casing, supports each screw rotor by a bearing through a rotor shaft, and has shaft seal devices in a shaft seal space. The shaft seal devices include an oil seal on the side of the bearing, a packing case on the side of the rotor chamber, and a gas seal. An end of the packing case on the side of the bearing and an end of the oil seal on the side of the rotor chamber are fitted and fixed by interference fit to form a gas seal accommodation space, the gas seal accommodation space accommodating the seal ring.

Abstract: An oil-free screw compressor has a screw rotor including a screw and a shaft, a bearing supporting the shaft, a first shaft seal device disposed between the screw and the bearing and including a first seal opposite to the shaft, and a first communication portion communicating the bearing side with respect to between the shaft and the first seal and the outer peripheral face of the first shaft seal device, and a second shaft seal device disposed between the first shaft seal device and the bearing and including a second seal opposite to the shaft, and a second communication portion communicating the screw side with respect to between the shaft and the second seal and the outer peripheral face of the second shaft seal device.

Abstract: An oil-free screw compressor includes: a casing having a rotor chamber; a bearing supporting rotary shafts of the screw rotors; a shaft seal device including an oil seal portion and an air seal portion; an atmosphere open hole formed in the shaft seal device; at least one communication hole formed in the rotary shaft; and an annular space communicating the atmosphere open hole with the at least one communication hole communicate with each other. The annular space includes an inner peripheral annular space formed on an inner peripheral side of the casing. Assuming an open cross-sectional area of the inner peripheral annular space as S1, a total open cross-sectional area of the communication holes as S2, an open cross-sectional area of the i-th communication hole out of the communication holes as S2i, and the number of communication holes as n (n being a natural number of 1 or more), a following relationship is satisfied.

Abstract: The oil-free screw compressor includes: a casing having a rotor chamber; a bearing supporting rotary shafts of screw rotors; a shaft seal device with an oil seal portion and an air seal portion; a ventilation gap positioned between the oil seal portion and the air seal portion; and an atmosphere open passage communicating an atmosphere side of the casing with the ventilation gap communicate. A most narrowed portion, an air seal portion, and oil seal portions are set such that the followings is established: (La/Sa2.5)/(Lh/Sh2.

Abstract: An oil-free screw compressor with good assemblability of a shaft seal device that reduces leakage of a compressed gas, where the oil-free screw compressor accommodates male and female screw rotors in a rotor chamber of a casing, supports each screw rotor by a bearing through a rotor shaft, and has shaft seal devices in a shaft seal space. The shaft seal devices include an oil seal on the side of the bearing, a packing case on the side of the rotor chamber, and a gas seal. An end of the packing case on the side of the bearing and an end of the oil seal on the side of the rotor chamber are fitted and fixed by interference fit to form a gas seal accommodation space, the gas seal accommodation space accommodating the seal ring.

Abstract: A method for forming drilled cast which includes drilling with a drill so as to provide communication with a cast hole includes a casting step and a drilling step. The casting step is to cast a cast having a cast hole which includes a flat inner wall surface in which width of a position to be drilled with the drill is obtained by adding first length H1 serving as a manufacturing error range of the cast to a diameter D of the drill, which is a second length H2. The drilling step is to form a through hole providing communication between an interior of the cast hole and an exterior of the cast through the flat inner wall surface with the drill.