Abstract: The polycarbonates of the present invention include those of sucrose series having a specific cyclic structure, those of oligosaccharide and monosaccharide series other than the sucrose series, those derived from specific saccharides having no cyclic structure, those having a skeletal structure of pentaerythritol, neopentyl glycol or trimethylolmethane, and specific dicarbonates.The lubricating oil and electrical insulating oil of the invention contain the above-mentioned polycarbonates.The polycarbonates of the invention are excellent in compatibility with Freon R-134a (HFC) as well as in lubricating properties, detergency and electrical insulating properties, and are capable of providing lubricating oil for refrigerator, automotive engine oil, automotive gear oil, lubricating oil for rolling and lubricating oil for fiber, especially lubricating oil for which electrical insulating properties are required, and electrical insulating oil.

Abstract: A spindle motor for a machine tool is required to operate at a low rotational speed and to deliver a high output in a machining mode, and is required to operate at a high rotational speed and to deliver a high output in another machining mode. An AC motor employing a winding arrangement of the present invention meets those operating conditions for different machining modes, in that the coils (X1, X2; X1', X2') of each winding for a phase are divided into a plurality of sets of coils, and the plurality of sets of coils are held in a slot (SL). The connection of terminals (U1, U2; V1, V2; W1, W2) for phase dividing the coils into the sets is changed selectively by switching unit (SW, SW') such as an electromagnetic relay, to thereby supply power selectively to the coils for the output regulation.

Abstract: The stator of a built-in motor must be firmly and accurately mounted on the spindle head housing or the like of a machine tool. A stator core (10), i.e., a principal component of the stator is welded partially at the circumference (14) thereof, and then the circumference of the stator core (10) held by a mandrel is finished to an accurate outside diameter by grinding. The stator core (10) thus constructed is subjected to a deformation with a lapse of time after the mandrel has been removed. To solve this problem, each lamination (12) of the stator core (10) is coated with a thermosetting adhesive, to be thereby joined together, and each lamination (12) is provided with a plurality of pressed projections (22) to be joined together by weld portions (20) on the circumference of the stator core (10), or each lamination (12) is joined together by pressing a serrated bar (26) into a bore (24) thereof, without a pressed projection (22).

Abstract: The stator of a built-in motor must be firmly and accurately mounted on the spindle head housing or the like of a machine tool. A stator core (10), i.e., a principal component of the stator is welded partially at the circumference (14) thereof, and then the circumference of the stator core (10) held by a mandrel is finished to an accurate outside diameter by grinding. The stator core (10) thus constructed is subjected to a deformation with a lapse of time after the mandrel has been removed. To solve this problem, each lamination (12) of the stator core (10) is coated with a thermosetting adhesive, to be thereby joined together, and each lamination (12) is provided with a plurality of pressed projections (22) to be joined together by weld portions (20) on the circumference of the stator core (10), or each lamination (12) is joined together by pressing a serrated bar (26) into a bore (24) thereof, without a pressed projection (22).

Abstract: An ac spindle motor (10) for driving a spindle motor of a machine tool provided with a rotor (14) having an output shaft (12) connected to the spindle, and a stator (16) surrounding the rotor and having a laminated core (20) serving as a yoke, and stator winding assemblies of three phases (U-phase, V-phase, W-phase). The stator winding assembly of each phase (18u, 18v, 18w) has: windings (C.sub.2, C.sub.4) of a first group which are energized for a rotation of the spindle in both a low-speed range not higher than a given speed, and a high-speed range above the given speed; windings (C.sub.1, C.sub.3) of a second group energized only for a rotation of the spindle in the low-speed range; and electrical contact means (S1, S2, S3, S4) controlled so that the windings (C.sub.1, C.sub.2, C.sub.3, C.sub.4) of the first and second groups are energized to generate a first multipolar revolving magnetic field for the rotation of the spindle in the low-speed range, and so that only the windings (C.sub.2, C.sub.

Abstract: Low rotational speed characteristics of a three-phase induction motor driven by a PWM inverter are improved by rapid .DELTA.-Y connection switching by semiconductor switches (1, 2, 3, 4, 5), for example, TRIAC's.

Abstract: Provided is a spindle drive control apparatus which is provided with a single three-phase spindle motor (60) for rotatingly driving a spindle (50) of a machine tool and a solenoid relay (70) for switching the phase windings (U, V, W) of the motor between a delta (.DELTA.) and star (Y) state and which switches the phase windings to the delta connection when rotating the spindle (50) at high speed for heavy duty cutting work and switches to the star connection for generating the high torque when rotating at a superlow speed (for example, 0.5 rpm) for contouring machining work etc. In this way, it becomes possible to handle the machining work performed in the past with two types of motor by using just a single motor, thus contributing to reduced costs.

Abstract: When tapping is effected by a tap driven by a built-in spindle motor (12) and another motor (22), which built-in spindle motor directly drives the tap (14) to rotate without a transmission mechanism, and which other motor drives the tap (14) with the built-in spindle motor (12) to proceed along a longitudinal direction (Z), the two motors (12, 22) are synchronously controlled, and the difference between a commanded rotational speed output to the built-in spindle motor (12) from a synchronous control unit (36) and an actual rotational speed of the built-in spindle motor detected by a detector (16) is calculated by a difference calculator (32), and an alarm is output, for example, by a light-emitting diode (40), when the difference is higher than a prescribed value. Thereby, a high-speed tapping can be effected, the number of defective products can be reduced, and the threads accurately tapped.

Abstract: The invention relates to a motor output changeover control apparatus used for the spindle motor of machine tools. Conventionally, since a constant output over a wide range is realized by gears, a spindle motor is constituted by a single winding. The amount of heat produced by the winding is great, and a speed-change mechanism employing the gears is large in size.With the motor output changeover control apparatus of the invention, output characteristics over a wide range from high to low speeds is stabilized by changing over the connection of the power lines of an AC motor.

Abstract: When a spindle (10) of a machine tool is rotated and moved relative to a workpiece linearly along an axis (Z) thereof during a machining process such as screw cutting, a spindle servomotor (12) and a feed servomotor (22), each of which is the primary drive, must be rotated synchronously. In general, the spindle servomotor directly drives the spindle without a reduction gear, and the feed servomotor feeds a spindle head (18) through reduction gears (26, 28). Therefore, in general, the synchronous work is controlled in accordance with an acceleration and deceleration capacity of the spindle servomotor. Consequently, the spindle servomotor is rotated along the torque limit curve line (L1, L2) to drive the spindle, to thereby effect the synchronous work at a high efficiency.

Abstract: A rotor for high speed induction motor, having a stacked-lamination type rotor core (23) provided with axial opposite ends on which aluminum end rings (24) are assembled or fused by die casting, and balancing rings (25) provided as iron coverings enclosing the aluminum end rings (24), the iron balancing ring (25) being assembled or fused together with the above-mentioned end rings on the stacked-lamination type rotor core (23) by die casting.

Abstract: A motor cooling system in which the stator (1) of a motor is coated with a coating layer (11), and a cooling liquid is applied to the projecting portions (10) of stator coils and to the side portions of the rotor (2) to cool the motor. The motor cooling system is advantageously applicable to a spindle motor for a machine tool.

Abstract: A molding process for coating a motor stator (1) having coils (2) projecting outside from the opposite ends of the motor stator (1) with a synthetic resin. The stator having coils (2) projecting from the opposite ends thereof is placed in an upright position in combination with a built-up mold core. The synthetic resin is poured from the upper end of the mold core and the initially poured resin flowing around the outside of the coil projecting downward is discharged together with gas. The stator is thus coated entirely with the resin containing only a few pores through a single molding cycle. The stator can be readily separated from the mold core.

Abstract: An induction motor has a stator formed by inserting and holding piled steel plates (12) between end plates (11a, 11b) and welding support bars (13) consisting of nonmagnetic metal along the external surface of said piled steel plates.

Abstract: A motor-incorporated spindle head unit is provided with a rotatable spindle on which a rotor assembly of the drive motor is fixedly mounted. A stator assembly of the drive motor is arranged around the rotor assembly and is fixed to a housing of the spindle head unit. A heat insulating system for preventing heat transfer from the stator assembly of the drive motor to the spindle as well as the bearings supporting the spindle is arranged between the drive motor and the front part of the spindle. The heat insulating system uses the flow of air for forming a heat insulator during the operation of the spindle head unit. A cooling system for cooling the stator assembly of the drive motor is also incorporated in the housing of the spindle head unit.

Abstract: A motor-incorporated spindle head unit is provided with a rotatable spindle on which a rotor assembly of the motor is fixedly mounted. A stator assembly is arranged around the rotor assembly and is fixed to an outer framework of the spindle head unit in a cantilever fashion. A cooling system for cooling the stator assembly is formed by providing an annular gap between the outer framework and the periphery of the stator assembly and is adapted to permit cooling air introduced into the annular gap through air ports formed in an end of the outer framework to flow through at least a throughbore formed in the stator assembly.

Abstract: A device for cooling a reversible motor comprising: a plurality of blade-type cooling fins (17) attached to the protrusion (13b) of a rotary shaft (13) which protrusion is protruded into a cooling chamber (5) formed on the outside of a motor case (10); an exhaust blower (25) provided on the outer side of the cooling chamber (5) in the axial direction to expel the cooling air, and; a fixed rectifying vane (29), consisting of a plurality of radially arrayed guide vanes (29a), provided in the exhaust space (28) between the blade-type cooling fins (17) and the exhaust blower. In the cooling device, the cooling air stream, moving in a spiral manner, passes through the blade-type cooling fins (17), is rectified in the axial direction via the fixed rectifying vane (29) and is expelled by the exhaust blower (25), when the motor runs in both the forward and the reverse directions.