Abstract: An engine cooling assembly 10 includes an electric motor 12, a fan 14 driven by the electric motor, and a shroud 16 at least partially surrounding the fan. First, resilient decoupling structure 20 mounts the motor to the shroud in a manner to isolate vibration between the motor and the shroud. Second, flexible decoupling structure 22 is associated with the shroud and is constructed and arranged to mount the shroud to the shroud mounting structure in a manner to isolate vibration between the shroud and the shroud mounting structure when the shroud is coupled to the shroud mounting structure.

Abstract: A spindle motor includes a rotor case in which a shaft support is located at the center of the rotor and disc mounting guides are located around the shaft support at a predetermined interval, a shaft installed at the shaft support, a disc chuck spring having at least one disc inner hole chucking portion and arranged at the rotor case such that at least one disc inner hole chucking portion slightly protrudes between the disc mounting guides, a magnet inside the rotor case, an armature stator facing the magnet via a gap, and a stator base where the armature stator is located, the stator base supporting the shaft inside the armature stator.

Abstract: In one aspect of the present invention discloses a dual-stiffness damping system for an evacuated energy storage system, the damping system comprising one or more flexible dampers and a plurality of more rigid bumpers, and a method of damping an evacuated energy storage system using dual-stiffness damping. Indeed, under normal operating conditions, a flexible damper, having a stiffness of about 500 lb/in to about 4000 lb/in, minimizes the rigid body critical speed of the rotor assembly of the energy storage system, allowing relative displacement between the stator assembly and rotor assembly but preventing the assemblies from physically contacting each other. Under more extreme external loading conditions, e.g., during an earthquake, the plurality of more rigid bumpers, having a stiffness of about 50,000 to 250,000 lb/in, engages the outer race of the bearing assembly to arrest further relative displacement substantially.

Abstract: A vehicular AC generator comprising a pair of cores included in a rotor and supported by a rotating shaft, a plurality of trapezoidal-shaped claws as magnetic poles protruding on the outer periphery edges of the pair of cores, and a pair of fans attached to the front side and the rear side of the cores, at least one of the fans having an outer diameter in the range between 85% and 96% of the outer diameter of each of the cores, each of the claws having a tapered portion for gradually decreasing the outer diameter of a shoulder portion of the claw in the direction toward the end surface of the core so that the outer diameter of at least one of the cores faced to the at least one of the fans becomes substantially the same as the outer diameter of the at least one of the fans, whereby the sound caused by cutting wind by the rotation of the centrifugal fans can be reduced without deteriorating the cooling efficiency of the coil ends of the stator.

Abstract: A rotation stabilizing device includes a rotary member rotated around a rotating center axis, an inertia member vibrating in accordance with a change of rotating speed of the rotary member, and a viscoelastic connector for detachably connecting the inertia member to the rotary member. The viscoelastic connector has viscosity and elasticity so as to change form in accordance with vibration of the inertia member. The inertia member is connected to at least one of an outer side and an inner side of the rotary member at a same phase in a direction of the rotating center axis of the rotary member by the viscoelastic connector.

Abstract: A vehicular AC generator comprising a pair of cores included in a rotor and supported by a rotating shaft, a plurality of trapezoidal-shaped claws as magnetic poles protruding on the outer periphery edges of the pair of cores, and a pair of fans attached to the front side and the rear side of the cores, at least one of the fans having an outer diameter in the range between 85% and 96% of the outer diameter of each of the cores, each of the claws having a tapered portion for gradually decreasing the outer diameter of a shoulder portion of the claw in the direction toward the end surface of the core so that the outer diameter of at least one of the cores faced to the at least one of the fans becomes substantially the same as the outer diameter of the at least one of the fans, whereby the sound caused by cutting wind by the rotation of the centrifugal fans can be reduced without deteriorating the cooling efficiency of the coil ends of the stator.

Abstract: An electric motor accommodated fixedly in position within its own casing or a housing of a compressor is provided with a non-conductive member between its stator and the casing or the housing, for preventing the stator and the casing or housing from making contact with each other. The non-conductive member is made of a material having a thermal expansion coefficient greater than that of the stator, such as resin.

Abstract: A method for facilitating damping torsional or ring vibrations of a dynamoelectric machine including a rotor assembly with a first amortisseur bar and a second amortisseur bar extending therefrom and terminating at an endring is provided. The method includes providing a damping assembly, and positioning the damping between the first amortisseur bar and the second amortisseur bar such that the damping assembly contacts the first and second amortisseur bars, and is substantially proximate the endring or alternatively the damping assembly is positioned only over one amortisseur bar.

Abstract: A rotor assembly for an electric device comprising includes a hub fixedly connectable to a crankshaft of an engine and a rotor fixedly connected to said hub for operational engagement with a stator of the electric machine. An elastomeric dampener is disposed between and interconnects the hub and the rotor to dampen torsional vibration from the engine.

Abstract: A brushless motor having a turntable including a rotor in which a turntable is integrally formed on the outer side of a rotor case and a magnet is arranged on the inner side thereof, a shaft for supporting the rotor, a stator base for supporting the shaft, and a stator formed on a portion of the stator base for driving the rotor, in which the turntable which has a media mounting portion at least partly formed of resin, includes a media installation guide formed of the same resin to support a medium, and at least one media inner diameter chucking spring member integrally formed of resin to have a diameter slightly greater than the media installation guide and the inner diameter of the media.

Abstract: An axial ventilator has an external-rotor drive motor having an external rotor with a rotor shaft and an internal stator, wherein the external rotor rotates about the internal stator during operation of the external-rotor drive motor. A ventilator wheel driven by the external rotor is provided. A bearing support tube is arranged in the internal stator. A radial plain bearing is arranged in the bearing support tube and supports the rotor shaft. An axial bearing formed by a free end of the rotor shaft and a stationary counter member, against which the free end of the rotor shaft rests, are provided. The stationary counter member comprises a thrust element and an elastomeric shaped member. The thrust element is connected to the elastomeric shaped member.

Abstract: The invention provides a commutator motor capable of reducing vibration and noise generated in commutator motor and improving durability against breakage of armature. A commutator 3 having a conductive section 32 mounted on a rotary shaft 1 through an insulating section 31 is provided with a vibration-isolating member 33 made of rubber by adhesion or integral formation at the location between the conductive section 32 and the rotary shaft 1, for example, between the insulating section 31 and the rotary shaft 1 or between the conductive section 32 and the insulating section 31. In one aspect of the invention, another vibration-isolating member supports a brush holder 4 for holding a brush 41 coming in contact with the commutator 3.

Abstract: A method and apparatus are provided for modeling an electric motor. The method includes the steps of interpolating a flux density for each angular position within an air gap of the electric motor from a predetermined air gap and tooth magnetization magnetomotive force versus air gap flux density curve, decomposing the interpolated flux density into a set of harmonic components using a fast Fourier transform and determining a flux density error function from the decomposed set of harmonic components.

Abstract: The present invention provides internally damped stators, rotors, and transformers; internally damped cores from which they may be made; and a method of making the aforementioned.

Abstract: An image forming apparatus includes a developing unit implemented as a revolver or rotary unit driven by a revolver motor, which includes a motor case. A motor support member supports the surface of the motor case at a position beneath the center of gravity of the revolver motor. The motor support member reduces a moment acting on a motor mount about the apparent center of rotation of the revolver motor due the weight of the motor to substantially zero. This configuration enhances the durability of the motor mount or vibration preventing member and thereby protects the revolver from defective rotation.

Abstract: A power generation system (10) including an apparatus for attaching a generator stator core (20) to a frame support (30) and associated methods are provided. The system (10) preferably includes a stator core frame support member (30) and a generator stator core (20) including a plurality of keybars (22) positioned spaced-apart and extending along outer peripheral portions of the generator stator core (20). The generator stator core (20) is positioned to overlie the stator core frame support member (30). The system (10) further includes a core supporter (40) connected to the stator core frame support member (30) and positioned to contact the generator stator core (20). The core supporter (40) includes first (43) and second (44) core connectors (42) for low tuning the natural frequency of a generator stator core (20) and for stabilizing the power generation system during operation.

Abstract: A cylindrical case provided with a chamber is coaxially attached to a rotary shaft of a motor. A plurality of balancers are movably provided within the chamber so as to cancel a rotation eccentricity of the motor. A viscous member such as high viscosity fluid is provided on at least one of the surfaces of the balancers and an inner face of the chamber.

Abstract: There is provided an apparatus for regulating the position of an adjustably positionable vehicle part such as a window or movable roof. The apparatus includes an electric drive motor having a drive shaft which is axially displaceable within a fixed limit during driving operation of the shaft. The apparatus also includes a power transfer assembly having a driven member operatively connected to the drive shaft of the electric drive motor for driving movement thereby and a damping member for damping the axial displacement of the drive shaft of the electric motor in one axial direction. The apparatus further includes a housing having a chamber compatibly dimensioned with respect to the damping member for receiving the damping member therein in a press fit disposition.

Abstract: A motor comprises a base plate with an axle seat to which a stator bobbin is mounted. The stator bobbin comprises an axle hole for rotatably receiving a shaft of a rotor. The rotor comprises a permanent ring magnet. A balance ring is mounted to the base plate and comprises an upright annular wall and an annular bottom wall. The upright annular wall of the balance ring and a lower section of the permanent ring magnet attract each other while the annular bottom wall of the balance ring and a lower end face of the permanent ring magnet attract each other.

Abstract: An automatic balancing apparatus which includes a support shaft which is rotated by a drive; a case body which is fixed to the support shaft and which rotates together with the support shaft; a ring magnet which is placed at the inside corner, in the radial direction, of an inner space of the case body; and a balancing member. The balancing member further includes a plurality of magnetic bodies which are movable in the inner space of the case body and which can be drawn up by the magnetic field of the ring magnet. When the rotational frequency of a rotor, which rotates together with the case body, exceeds the resonant frequency, the automatic balancing apparatus reduces vibrations of the rotor; and the outer circumference of the ring magnet has a flat portion.

Abstract: An air treatment appliance for treating surrounding air including a body. A spider-mount mounted to the body has a motor mounted thereto in cantilever fashion. A fan attached to the motor may be a radial fan, and is operable to draw in surrounding air and cause it to flow through the appliance. A grommet between the motor and the spider-mount dampens vibrations from the motor. A filtering mechanism in the path of the airflow helps filter out undesirable material from the surrounding air. A radial airflow guide downstream from the fan efficiently guides the airflow to be expelled in a predetermined direction. The motor is at least partially accommodated by the spider-mount and the fan. The apparatus results in reduced noise and vibration during operation of the appliance.

Abstract: To present a motor brush structure capable of decreasing the current ripple and torque ripple substantially while minimizing the cost increase, and, by using the same motor, a motor-driven power steering device capable of suppressing generation of working sound, magnetostriction sound, radio noise, and cogging feel during steering operation. In a motor-driven power steering device used as a steering device for turning wheels such as front wheels of an automobile, a pair of shunt brushes for shunting are added to a pair of main brushes, these shunt brushes are disposed at positions for geometrically inverting the brush contact positions with segments, and it is composed so that the waveforms of the current flowing in the main brushes 11 from each segment of a commutator to each coil, the current into the shunt brushes, and the shunted current may be mutually inverted in phase to cancel each other.

Abstract: A chamfered portion 100 on three points, being a point B formed on a peripheral end surface of a root shoulder portion of magnetic pole pieces 8a or 9a and being on a line, from which a taper formed on an outer peripheral surface of the root shoulder portion starts, a point C on a skew slanted portion of the magnetic pole pieces 8a and 9a, and a point A on the peripheral end surface of the magnetic pole pieces 8a or 9a apart from an end surface of a stator core 4 by a distance between L1/4 and 7×L1/8, is formed in the magnetic pole piece of an a.c. generator for vehicle, whereby noises such as wind noise and electromagnetic sound can be reduced, a magnetic circuit of a rotor is improved, the amount of magnetic flux is increased, whereby an output becomes high.

Abstract: The invention relates to means and methods by which a rotor is rotationally journalled relative to a stator in a magnetic field provided concentrically about a longitudinal axis, coincident with the rotor and the stator axis such that an annular gap is formed between the rotor and the stator. A flexible, sheet metal foil of non-magnetic and electrically conductive material is arranged for insertion in the annular gap in relative rotation to the rotor. The foil is shaped for generating a fluid film in cooperation with the revolving periphery of the rotor, and effective to counteract oscillating rotation of said rotor due to the formation of eddy currents that are induced in the sheet metal foil upon displacement within the magnetic field.

Abstract: In a vehicle alternator, a bobbin around which a coil is wound is mounted in a Lundell-type poles, an auxiliary oscillating body is mounted to the poles so as to constitute a vibration system having a two-degree of freedom which is composed of the poles and the auxiliary oscillating body and the auxiliary oscillating body has a natural frequency approximately equal to that of the poles.

Abstract: A brushless D.C. motor having a tolerance band that is used to retain the stator in the motor housing. The tolerance band has a plurality of waves formed along its length. The tolerance band is mounted within a housing groove, through which the stator is pressed. The tolerance band waves are compressed as the stator is pressed into motor housing. The compressed waves act as a radial spring to retain the stator in the housing with a minimal amount of radial force.

Abstract: A regulated permanent magnet generator incorporating a “tapered” or conical design for improved voltage regulation. The tapered faces of the rotor and stator are axially displaced from one another as the demand for voltage changes. In addition, this design allows for the stator and rotor to be used as a braking mechanism when placed into frictional contact with one another such as to prevent windmilling. This design offers better space efficiency when used with certain engine applications.

Abstract: The present invention is to obtain a vehicle alternator capable of effectively reducing an electromagnetic noise. The vehicle alternator includes steel sheet fans mounted to poles by being welding to the end surfaces of the poles on the inner peripheral sides of the fans at a plurality of positions in a peripheral direction and a bobbin around which a coil is wound and which is attached in the poles and further includes elastic matters interposed between the fans and the poles on the outer peripheral side of the welding portions where the fans are welded to the poles.

Abstract: According to the invention, the controller cascades are suitably divided up and the oscillation damped only in the load rotational-speed controller. Here, a motor rotational-speed setpoint value (z) of a quickly regulated motor rotational-speed controller (9) and not the motor torque, is selected as the connection point for a load acceleration (i). In order to achieve a shorter transient response time, according the invention the difference between a setpoint rotational speed (x) and load rotational speed (y) is connected to the motor rotational-speed setpoint value (z). The solution in principle according to the invention which is presented has, in contrast to other known methods, the advantage that the actuation of the corresponding controllers is comparatively simple with very good control results.

Abstract: A hybrid synchronous motor comprising a rotor and stators, wherein the stator has at least one assembly (7) having a structure in which ferromagnetic rings (2, 3) formed with cogs on the both inner and outer circumferences thereof, are arranged coaxially, and a coil winding (8) is wound on the assembly (7) so as to be positioned between cogs. The hybrid synchronous motor exhibits a high magnetic flux density in the air gap as the result of transverse magnetic flux of the permanent magnets combined with longitudinal magnetic flux of the coils and high active surface at the air gap due to double (inner and outer) air gaps. Further, since it contains only a single set of stator coils and it has merely a small number of assembling parts and conventional techniques of fabrication may be applied, the motor is cheap in construction. Furthermore, the motor exhibits an excellent energy efficiency due to only small ohmic losses in the coils.

Abstract: A motor is provided which is configured to have at least a portion thereof received in an interior of a cover to reduce noise of the motor. The interior is defined by an inner peripheral surface of the cover. The motor includes a generally cylindrical housing having a closed end and an opened end disposed opposite the closed end. A brush card assembly is provided and includes a brush card and a cover support structure coupled with the brush card. The brush card and cover support structure close the opened end of the housing. The cover support structure has a plurality of resilient members extending from the opened end towards the closed end of the housing, with each resilient member being generally adjacent to an outer surface of the housing and being biased away from the outer surface of the housing.

Abstract: A rotational balancing structure for an A.C. motor comprises a casing having an axle seat for rotatably holding a shaft of a rotor. A balancing sheet and a stator are mounted in the casing. The stator comprises plural stacked silicon steel plate wound around by a winding. An insulating ring is mounted to an end of the stator. Each of the stator and the insulating ring has a central hole. The rotor comprises an induction ring that is received in the central hole of the stator with an end face of the induction ring extending through the central hole of the stator for mutual attraction with the balancing sheet fixed on the casing.

Abstract: An active balance system is provided for counterbalancing vibrations of an axially reciprocating machine. The balance system includes a support member, a flexure assembly, a counterbalance mass, and a linear motor or an actuator. The support member is configured for attachment to the machine. The flexure assembly includes at least one flat spring having connections along a central portion and an outer peripheral portion. One of the central portion and the outer peripheral portion is fixedly mounted to the support member. The counterbalance mass is fixedly carried by the flexure assembly along another of the central portion and the outer peripheral portion. The linear motor has one of a stator and a mover fixedly mounted to the support member and another of the stator and the mover fixedly mounted to the counterbalance mass. The linear motor is operative to axially reciprocate the counterbalance mass. A method is also provided.

Abstract: A rotary electrical actuator for mounting to a support surface in industrial applications having integral electronics that are isolated by vibration isolators from vibrations. The rotary actuator comprises a stator housing supporting a lamination stack and coils. The actuator housing has a mounting structure for mounting to the support surface (such as the mounting surface of an engine or a turbine for example) for support thereby. A rotor is carried for rotation in the stator housing. The actuator further comprises an electronics housing containing the electronics that control output of the electrical actuator. Vibration isolators supported by the stator housing in turn support the electronics housing, whereby vibrations received at mounting structure and traveling through the stator housing are dampened prior to traveling to the electronics housing. A number of embodiments are disclosed utilizing a tie rod assembly concept for the vibration isolators.

Abstract: The present invention is directed to a high speed spindle motor comprising a stator assembly including a stator having multiple conductors that create a plurality of magnetic fields when electrical current is conducted by the conductors and a body of a phase change material such as a thermoplastic substantially encapsulating the stator. A rotatable hub having a magnet connected thereto is in operable proximity to the stator. The high speed motor also includes a shaft, a bearing surrounding the shaft and one of the bearing or shaft being fixed to the stator assembly and the other of the bearing or shaft being fixed to the rotatable hub. Hard disc drives using the motor, and methods of developing and constructing the motor and hard disc drives are also disclosed.

Abstract: A drive system for a motor vehicle includes an electric machine arranged for driving a driveshaft of a drive unit and obtaining electrical energy during rotation of the driveshaft. The electric machine has a stator arrangement and a rotor arrangement which is connectable to the driveshaft for common rotation. The rotor arrangement is connectable to the driveshaft via an elastic connecting arrangement.

Abstract: The flux producing current limit of the motor control is adjusted to control the vibration of a motor. The flux producing current may be profiled in relation to the speed of the motor to compensate for excessive motor vibration.

Abstract: A support assembly for supporting a rotating shaft relative to a structure in which a first magnetized member is attached to the shaft for rotation therewith, a support member is connected to the structure and at least one damper member connects the support member to a second magnetized member for supporting the second magnetized member in a portion relative to the first magnetized member. The respective magnetic fields of the first and second magnetized members are such that radial deflective movement of the shaft, and therefore the first magnetic member, causes corresponding radial movement of the second magnetized member which is dampened by the damping member.

Abstract: The present invention proposes a control method of the auto-balancing system of an optical disk drive. The present invention adds a procedure of constant rotation speed in the acceleration process of the spindle motor when the rotation speed is below a critical speed. When the rotation speed of the spindle motor is below the critical speed, the position of added mass will be situated at a position at the same side of the unbalance vector of the original optical disk. Thereby the balancing mass will remain at the position of worst balancing effect in the procedure of constant rotation speed. After the procedure of constant rotation speed, the spindle motor will be accelerated to pass the critical speed of the system by the largest torque.

Abstract: A vehicular AC generator comprising a pair of cores included in a rotor and supported by a rotating shaft, a plurality of trapezoidal-shaped claws as magnetic poles protruding on the outer periphery edges of the pair of cores, and a pair of fans attached to the front side and the rear side of the cores, at least one of the fans having an outer diameter in the range between 85% and 96% of the outer diameter of each of the cores, each of the claws having a tapered portion for gradually decreasing the outer diameter of a shoulder portion of the claw in the direction toward the end surface of the core so that the outer diameter of at least one of the cores faced to the at least one of the fans becomes substantially the same as the outer diameter of the at least one of the fans, whereby the sound caused by cutting wind by the rotation of the centrifugal fans can be reduced without deteriorating the cooling efficiency of the coil ends of the stator.

Abstract: An electrical noise suppressing device has a pair of parallel first connecting terminals connectable to terminals of a motor and a pair of parallel second connecting terminals connectable to an external power source. The first connecting terminals and the second connecting terminals are raised on opposite surfaces of an insulating plate, respectively, at the same position of the insulating plate. A pair of choke coils and a capacitor are disposed between and connected to the second connecting terminals to suppress electrical noise.

Abstract: The present invention relates to a method and apparatus for reducing noise and vibration generated by a variable reluctance motor. The relative positions of paired opposing modules in each phase unit are adjusted relative to a stator, even after assembly of the motor, to reduce the noise and vibration.

Abstract: An internally loaded universal motor has a stator, a rotor, brushes and a loading device for generating an internal load on the universal motor. The shaft has a commutator, and a rotor core adjacent to the commutator. The rotor core is electrically connected to the commutator and rotates within the stator. The brushes deliver electrical power to the commutator. The loading device prevents excessive rotation of the rotor when the universal motor has a low external load.

Abstract: A type of passive magnetic bearing that provides for both positive radial stiffness and significant levels of passive radial damping. Axial damping and axial forces can also be generated with minor modifications to the basic configuration. The bearing is comprised of a series of magnet, damping, and rigid non-magnetic elements essentially defining a laminated or composite structure. The damping material is directly mounted between the magnets and a rigid material, resulting in constrained layer damping. The range of motion of these floating, or soft mounted, magnets may also be restricted to generate higher stiffness in response to large vibrations.

Abstract: A power generation system (10) including an apparatus for attaching a generator stator core (20) to a frame support (30) and associated methods are provided. The system (10) preferably includes a stator core frame support member (30) and a generator stator core (20) including a plurality of keybars (22) positioned spaced-apart and extending along outer peripheral portions of the generator stator core (20). The generator stator core (20) is positioned to overlie the stator core frame support member (30). The system (10) further includes a core supporter (40) connected to the stator core frame support member (30) and positioned to contact the generator stator core (20). The core supporter (40) includes first (43) and second (44) core connectors (42) for stabilizing the power generation system and relieving vibration and eliminating lateral movement of the generator stator core (20) during operation.

Abstract: A spindle motor comprises a central axis fixed to a housing base. A core body is cantilevered by an annular member so as to support a coil of a stator. The coil is fixed to the housing base by an adhesion. The cantilevered core body is also supported by the housing base, so that the movement of the core body and coil is reliably restrained. The stator is prevented from vibrating during rotation of the rotor. Accordingly, reduction in the vibration of the spindle motor can be achieved.

Abstract: An automotive ac generator is provided which may be used in passenger vehicles and trucks and which is designed to minimize vibrations of coils of a stator during operation. The generator includes a hollow cylindrical stator core and a plurality of electrical conductors. The stator core surrounds the periphery of the rotor and has formed therein a plurality of slots in which the electrical conductors are disposed. The electrical conductors disposed in one of the slots are connected to those in another slot through conductive bridges, respectively, to form the coils of the stator. The conductive bridges project from the opposed ends of the stator core and are so designed as to resonate outside a normal speed range of the ac generator to minimize the vibrations of the coils of the stator inducing unwanted magnetic noises.

Abstract: A direct current motor according to the present invention is provided with a stator 2 in which coils 4 corresponding to N phases are arranged almost at equal intervals in a circle-circumferential direction of stator cores 3, a rotor 8 in which a plurality of permanent magnets 9 are respectively arranged at positions corresponding to the coils 4 of the stator 2, and a current carrying device, having a commutator 11, for commutating direct current supplied from a power source to N-phase current in cooperation with the rotor 8 and carrying the N-phase current to each coil of the stator 2. In the internal space of the current carrying device, a plurality of noise eliminating members 23 connected with a plurality of brush holding plates corresponding to the coil phases are arranged.

Abstract: A disc drive spindle motor for reducing the idle noise of a disc drive includes a stator having a first cylindrical surface for contacting a motor mount of the spindle motor. The motor mount includes a second cylindrical surface for contacting only a portion of the first cylindrical surface of the stator to reduce the transmission of vibrations from the stator to a base plate of the disc drive. The motor mount may be attached to a base plate of the disc drive when the spindle motor is formed separately from the disc drive. Alternatively, the motor mount may be formed integrally with the base plate of the disc drive.

Abstract: The invention provides a commutator motor capable of reducing vibration and noise generated in commutator motor and improving durability against breakage of armature. A commutator 3 having a conductive section 32 mounted on a rotary shaft 1 through an insulating section 31 is provided with a vibration-isolating member 33 made of rubber by adhesion or integral formation at the location between the conductive section 32 and the rotary shaft 1, for example, between the insulating section 31 and the rotary shaft 1 or between the conductive section 32 and the insulating section 31. In one aspect of the invention, another vibration-isolating member supports a brush holder 4 for holding a brush 41 coming in contact with the commutator 3.