A positive displacement pump for pumping oil in a motor vehicle transmission comprises a pump stage that has a central kidney-shaped suction cavity and two kidney-shaped pressure cavities. Oil is selectively pumped via one kidney-shaped pressure cavity or the other kidney-shaped pressure cavity in accordance with the direction of rotation of the pump stage. This makes it possible to create, with little complexity, two operating stages for the positive displacement pump.

A rotary compressor, including a cylinder, an inner peripheral surface of which is defined in an annular shape to define a compression space, provided with a suction port configured to communicate with the compression space to suction and provide refrigerant to the compression space; a roller rotatably provided in the compression space of the cylinder, and including with a plurality of vane slots at predetermined intervals along an outer peripheral surface, the plurality of vanes each providing a back pressure at one side thereinside; a plurality of vanes slidably inserted into the plurality of vane slots, respectively, to rotate together with the roller, front end surfaces of the plurality of vanes coming into contact with an inner periphery of the cylinder due to the back pressure to partition the compression space into a plurality of compression chambers; and a main bearing and a sub bearing provided at both ends of the cylinder, respectively.

A rotary compressor, including a cylinder, an inner peripheral surface of which is defined in an annular shape to define a compression space, provided with a suction port configured to communicate with the compression space to suction and provide refrigerant to the compression space; a roller rotatably provided in the compression space of the cylinder, and including with a plurality of vane slots at predetermined intervals along an outer peripheral surface, the plurality of vanes each providing a back pressure at one side thereinside; a plurality of vanes slidably inserted into the plurality of vane slots, respectively, to rotate together with the roller, front end surfaces of the plurality of vanes coming into contact with an inner periphery of the cylinder due to the back pressure to partition the compression space into a plurality of compression chambers; and a main bearing and a sub bearing provided at both ends of the cylinder, respectively.

A method of operating a rolling piston compressor includes determining a pressure difference (ΔP) between a discharge pressure (P.sub.d) within a compression volume and a suction pressure (P.sub.s) within a suction volume; determining a pressure ratio (r.sub.p) equal to the discharge pressure (P.sub.d) over the suction pressure (P.sub.s); estimating a discharge pressure (P.sub.d) based at least in part on the pressure difference (ΔP) and the pressure ratio (r.sub.p); determining that the discharge pressure (P.sub.d) is greater than a predetermined pressure limit (P.sub.d-limit); and lowering a target speed (ω.sub.target) of the rolling piston compressor.

A method of operating a rolling piston compressor includes determining a pressure difference (ΔP) between a discharge pressure (P.sub.d) within a compression volume and a suction pressure (P.sub.s) within a suction volume; determining a pressure ratio (r.sub.p) equal to the discharge pressure (P.sub.d) over the suction pressure (P.sub.s); estimating a discharge pressure (P.sub.d) based at least in part on the pressure difference (ΔP) and the pressure ratio (r.sub.p); determining that the discharge pressure (P.sub.d) is greater than a predetermined pressure limit (P.sub.d-limit); and lowering a target speed (ω.sub.target) of the rolling piston compressor.

A scroll compressor may include a compressor chamber, a back pressure chamber, a first intermediate pressure hole, a second intermediate pressure hole, a third intermediate pressure hole, a back pressure switching unit configured to selectively connect the first intermediate pressure hole and the back pressure chamber or the second intermediate pressure hole and the back pressure chamber, a capacity variable unit configured to selectively open and close a capacity variable passage, and a mode switching unit provided outside of the casing and configured to control opening and closing operations of the back pressure switching unit and the capacity variable unit. This may simplify the structure of the back pressure switching unit and the mode switching unit, thereby maintaining compactness of the compressor while installing the back pressure switching unit inside of the casing, and thus, operation reliability of the mode switching unit may be secured and maintenance facilitated.

A variable displacement pump according to the present invention is notably configured such that the opening area of a variable metering orifice (MO) is variably controlled by a second control valve (6) as a spool valve having a second spool valve body (61). According to this type of the second control valve (6), a larger amount of movement (stroke movement) of the second spool valve body (61) can be ensured. Consequently, the opening area of the variable metering orifice (MO) can be controlled without being restricted by a range of variation in a proper discharge amount based on an amount of movement of a cam ring (2), thereby achieving sufficient energy conservation of the pump.

A variable displacement pump according to the present invention is notably configured such that the opening area of a variable metering orifice (MO) is variably controlled by a second control valve (6) as a spool valve having a second spool valve body (61). According to this type of the second control valve (6), a larger amount of movement (stroke movement) of the second spool valve body (61) can be ensured. Consequently, the opening area of the variable metering orifice (MO) can be controlled without being restricted by a range of variation in a proper discharge amount based on an amount of movement of a cam ring (2), thereby achieving sufficient energy conservation of the pump.

A pump body assembly, a compressor and an air conditioner are provided. The pump body assembly includes a cylinder assembly, which is connected to a first flange and a second flange respectively and is disposed between the first flange and the second flange; a rotation shaft, which is provided and passes through the first flange, the cylinder assembly and the second flange in sequence, and which is provided thereon with sliding vane grooves; and a sliding vane, which is provided inside the sliding vane groove and fits the cylinder assembly to form a working cavity in the cylinder assembly. The first flange is provided thereon with an exhaust channel which is in communication with the working cavity, and the second flange is provided thereon with a gas flow balance portion.

A pump body assembly, a compressor and an air conditioner are provided. The pump body assembly includes a cylinder assembly, which is connected to a first flange and a second flange respectively and is disposed between the first flange and the second flange; a rotation shaft, which is provided and passes through the first flange, the cylinder assembly and the second flange in sequence, and which is provided thereon with sliding vane grooves; and a sliding vane, which is provided inside the sliding vane groove and fits the cylinder assembly to form a working cavity in the cylinder assembly. The first flange is provided thereon with an exhaust channel which is in communication with the working cavity, and the second flange is provided thereon with a gas flow balance portion.