Abstract: A controllable brake (20) including a rotor (28) supported by a shaft (30) which is rotatably supported by bushings (42) received in housing (22). A coil assembly (48) creates a magnetic field within a pole piece (32), which is preferably manufactured from a powdered metal material, which preferably has a density of between about 6.8 and 7.0 gm/cm. A magnetically-soft medium is contained within first and second gaps (86, 88) located between pole piece (32) and rotor (28). In one aspect, a magnetic saturation zone (25) reduces the propensity of magnetizing the shaft (30). In another, the pole halves (24, 26) are received in radially-spaced pole pockets (37) formed in the housing (22) and include an axial bias spring (70) to ensure intimate contact. In another aspect, a lip projection (76) traps fluid (23) between the lip projection (76) and shaft (30) and minimizes fluid exposure to the shaft seal (44). In another aspect, cooling fins (55) or a projection (53) restrains rotation of the housing (22).

Abstract: A magnetorheological clutch for controllable torque transmission includes a housing defining a cavity with a rotary input element carrying at least one input clutch plate extending radially in the cavity. A rotary output element carrying at least one output clutch plate extends radially into the cavity adjacent the input clutch plate with a gap defined between the input clutch plate and the output clutch plate. A core formed of magnetically permeable material has a pair of side plates extending radially across the housing. A coil effective to establish an electromagnetic field is carried against the core. Magnetorheological fluid is carried in the cavity within the gap and is responsive to the electromagnetic field that is established by the coil through the core so that torque is transferred from the input clutch plate to the output clutch plate through the magnetorheological fluid.

Abstract: A cooling mechanism of an electromagnetic powder clutch comprises a drive member connected with an output shaft of an engine, a driven member connected with a main drive shaft through a pump drive shaft, a metal powder interposed in the gap between the drive member and the driven member for transmitting torque from the drive member to the driven member, a cooling fluid for cooling said electromagnetic clutch, a cooling passage provided in the driven member for letting flow the cooling fluid therein so as to cool the driven member, an oil supply passage provided in the driven member for supplying the cooling fluid to the cooling passage, an oil drain passage provided in the driven member for draining the cooling fluid from the cooling passage, a supply passage provided in a clearance between the main drive shaft and the pump drive shaft for supplying the cooling fluid to the oil supply passage, and a return passage provided in a center hole of the main drive shaft for returning the cooling fluid from the oil d

Abstract: A fluid-based torque transfer device modulates the amount of torque which is transmitted from an input shaft to an output shaft. The torque transfer device includes a first plate connected to the input shaft. A second plate is connected to the output shaft and spaced from the first plate. A magnetorheological fluid is provided between the first and second plates. A magnetic circuit, including a coil wound around a core material defining a gap, applies a magnetic field to the magnetorheological fluid to variably control the rotation of the second plate in response to the rotation of the first plate. A controller adjusts the current to the coil to vary the magnetic field. Sensors detect at least one of the rotational speed and the torque of the input shaft, the output shaft, vehicle speed, steering direction, throttle position, gear position and brake position. The controller varies the current provided to the coil based thereon.

Abstract: Tapering shallow notches are provided in the surface of a rotor of a magnetic brake or clutch to increase the torque-transmitting effect of the unit as compared to a conventional smooth torque-transmitting surface. The notches taper decreasingly toward the torque-transmitting surface in the direction opposite to the direction of rotation of the rotor.

Abstract: The electrically controlled force transmitting apparatus includes a drive member having an electrically conductive surface and a driven member having an electrically conductive surface, which are arranged to be opposed to each other with a small space therebetween, a fibrous member provided in the space between the opposed electrically conductive surfaces of the drive and driven members, and a voltage supply source connected across the electrically conductive surfaces, whereby by applying a voltage across the opposed surfaces, there is induced a shear stress and a force is transmitted from the drive member to the driven member. The space in which the fibrous member is arranged is preferably filled with an electrically insulating fluid medium.

Abstract: A fluid coupling device for coupling torque between two members and utilizing a magnetorheological fluid having a controllable yield strength in shear in response to a magnetic field and having a determinable viscosity in the absence of a magnetic field and with the coupling device having a rotor, rotatably supported in a cavity in a housing with the cavity filled with the magnetorheological fluid and with the cavity and rotor having similarly shaped contours and constructed to concentrate the magnetic coupling effect through the fluid at the radially outer end of the rotor and a torque load simulator system utilizing the fluid coupling for determining the performance of a torque tool or other torque related apparatus relative to a predetermined standard of performance.

Abstract: Polymeric systems are disclosed that exhibit the Johnsen-Rahbeck effect and an electrostatic clutch for using films of these polymeric systems. The films may be pressed from the polymeric reaction product of either a polymer having an anionic functionality reacted with cations, or a polymer having cationic functionality reacted with anions. The dielectric film may be interposed between nesting, or otherwise contacting, conductive surfaces to increase the frictional force between the surfaces by the Johnsen-Rahbeck effect when a voltage differential is applied across the surfaces.

Abstract: A selectively-operable drive device for drive action including a drive input member to put drive into the device, a drive output member to supply drive action from the device, the input and output members being electrically isolatingly spaced, the device being selectively operable to put the input member and output member into driving relation by electric field electrodes on the input and output members and between the spaced members a quantity of electric field responsive fluid subject, on energisation in operation, to an electric field between the electrodes, the output member being of material of lower density than the input member and the output member having a lower mechanical time constant than the input member.

Abstract: There is disclosed a fluid clutch device for controlling transmission of motive power of a vehicular engine to accessory equipment such as an oil pump for a power steering mechanism or an air compressor for an air conditioner. The clutch device includes first and second members arranged for relative rotation about a common axis. The first member is operated by the vehicular engine while the second member is constructed to operate the accessory equipment. The first and second members are accommodated in a hermetically sealed clutch casing which is filled with an electroviscous fluid. A source of high voltage potential is provided for applying a voltage to the electroviscous fluid, and various units for generating information regarding driving of the accessory equipment are also used.

Abstract: A gearbox comprises a row of parallely mounted disks. The mutually facing diametral planes of the disks are carrying cylindrical rings mounted coaxially to the rotation axes of the disks and provided with engaging elements on their internal and external cylindrical surfaces. Due to an offset between the neighboring disks providing for eccentricity between their parallel rotation axes all the rings located in the space between the diametral planes of the neighboring disks are in permanent engagement. Each ring is freely rotatable and is provided with means for its controlled interlocking with the disk carrying it.

Abstract: An electrically actuated valve for control of a pressurized fluid, particularly a sanitary valve, comprises a rotor (15) arranged in a housing (1) between an inlet passageway (6) and an outlet passageway (7). The rotor (15) is rotatable under the action of the pressurized fluid and transports portions of the fluid from the inlet passageway (6) to the outlet passageway (7). There is an operational connection between the rotor (15) and an element (19) rotatably arranged in a chamber (21) filled with an electro-viscous liquid (22). The electro-viscous liquid (22) is arranged between two electrodes (23, 24) to which as high voltage (25) can be applied. In one embodiment of the invention the rotor (15) also forms the closure element of the valve, which is braked to a various extent by the rotatable element (19) arranged in the electro-viscous liquid. In a further embodiment rotation of the rotor will supplied to a closure member via the rotatable element, which will then be an element of a clutch, and gear means.

Abstract: A device for controlling the magnitude of torque transmitted from a torque supply source to an output drive device utilizing a contained electrorheological fluid medium. A pair of wetted surface plates, each operably connected to one of the supply and drive device via a shaft, are immersed in the fluid medium. Electrical energy is applied to the fluid to cause a pseudo-solid to form between the plates thereby facilitating the transmission of torque.

Abstract: A limited slip differential includes a friction clutch mechanism, a viscous coupling, and a camming mechanism disposed between the friction clutch mechanism and the viscous coupling. The camming mechanism converts shearing forces within the viscous coupling to an axial force applied to engage the clutch mechanism. The camming mechanism includes annular discs having axially inclined ramps, and a roller bearing for movement along the ramps to provide for variable spacing between the annular discs, wherein increased spacing is used to apply the axial force.

Abstract: An apparatus for damping movement includes a housing and a blade which are movable relative to each other. The blade is cantilevered to an axis and has segments formed of magnetizable material which are separated by segments formed of nonmagnetizable material. Electromagnetic coils are connected with the housing and apply a magnetic field to a magnetic field responsive fluid through which the blade is movable. The blade has recesses which are formed in the segments of magnetizable material and hold magnetic field responsive fluid. A plurality of ribs separate the recesses and are at least partially formed of the nonmagnetizable material. In one embodiment of the invention, ribs and recesses are provided on opposite sides of the blade. In another embodiment of the invention, the ribs and recesses are provided on one side of the blade and the opposite side of the blade is flat.

Abstract: An electromagnetic powder coupling device which can be used either as a brake or a clutch. In order to remove undesirable heat in the device, one attributable to Joule heat mainly emanated by field member, a rotor and a cylinder, and to other to frictional heat, especially inevitable for this kind of electromagnetic powder coupling device which is emanated by the friction between the rotor, cylinder and the magnetic powder filled in the space between the cylinder and the rotor, the coupling device incorporates a forced air draft cooling system. Two variations of cooling systems are disclosed, both of which have, in common with, at least a blower and a plurality of passages for forced draft air cooling not only to the external part but also to the inner part of the field member and the cylinder.

Abstract: A magnetic particle type electromagnetic clutch has two clutch discs so disposed that the two discs can be electromagnetically connected together and disconnected. In a space between the two discs are charged magnetic particles. When an excitation current is run through the excitation coil disposed near the two discs to produce a magnetic flux, the two discs and magnetic particles are magnetized to be connected in unison, thereby transmitting a torque from the drive shaft to the driven shaft. The two discs are each secured to the tip end of the shafts. The shaft has two groups of magnetic layers which are rigidly affixed to the shaft and axially spaced. Each of the groups of magnetic layers is directed + 45 degrees or - 45 degrees with respect to the axis of the shaft. When the shafts start to rotate, magnetostriction is developed in the respective magnetic layers resulting in a change in permeability.

Abstract: An article feeding apparatus comprising a driven roller and a pressure roller resiliently urged toward the driven roller. Movement of the pressure roller toward the driven roller is controlled by means of a damper containing material having electro-rheological properties. An electric potential of controlled magnitude is applied selectively to the material to control movement of the pressure roller. The apparatus is described in relation to a print drum and impression roller of a franking machine.

Abstract: A clutch and brake mechanism for a mechanical drive of print drum in a franking machine is disclosed which utilizes a clutch and brake operated by means of electric potentials applied across an electro-rheological fluid. Elements of the clutch and brake are formed with annular walls which are interposed to form opposed electrodes between which the electro-rheological fluid is contained. Application of electric potentials to the fluid is controlled by a microprocessor.

Abstract: An electrorheological fluid e.g. for selectively coupling clutch members consists of silicone oil containing 30 volume % of dispersed polyaniline. The polyaniline is acidically oxidised aniline subsequently treated with base.

Abstract: A damper device of a clutch has an annular driven member comprising a pair of disk members, a hub disposed in an annular space formed in the driven member, damper springs disposed between the driven member and the hub, and stopper pins, each secured to the driven member at both end portions thereof. The stopper pin comprises a pin body and a cylindrical collar mounted on the pin body. The pin body is made of soft steel and the collar is made of steel harder than the pin body and disposed to be abutted against the hub.

Abstract: An apply system for clutches employing electro-rheological fluid to transmit torque between two sets of interleaved plates. The plates are disposed within a stationary housing. The first set of plates is fixed to the stationary housing. The second set of plates is fixed to a shaft rotatable relative to the housing. A piston is coaxially disposed against the plates at one end of the interleaved plates. A piston apply chamber is located in the stationary housing on the opposite side of the piston. The electro-rheological fluid is circulated through the system by a pump, passing by the apply side of the piston, then between the plates, and then back to the pump. When there is a voltage potential between the plates, the flow between the plates is restricted and the pressure of the fluid on the piston builds, displacing the piston toward the plates. The plates are moved closer together by the piston. Contact between the plates is prevented by insulating elements mounted to alternate surfaces of the plates.

Abstract: An electrophoretic fluid torque transmission apparatus in which cooperable electrodes are connected respectively to drive and driven elements. An electrophoretic fluid capable of separating into particle-rich and particle-deficient phases by electrophoresis operates in surface contact with the electrodes. An electrically non-conductive material having raised surface areas and spaces between the surface areas is associated with one or more of the electrodes. When a voltage is applied between the electrodes in a first direction, the particle-rich phase of the fluid collects on one of the electrodes and also makes contact with the spaces and the raised surface areas of the material associated with the other electrode thereby engaging or locking the electrodes together and transmitting force between the elements.

Abstract: A transmission includes a control unit which controls engagement/disengagement of an electromagnetic clutch such that it is disengaged when it is detected that a vehicle is at a stop, and such that the vehicle creeps at a predetermined speed when pressing of an accelerator pedal is detected.

Abstract: An electrophoretic fluid torque transmission apparatus and method in which cooperable electrodes are connected respectively to drive and driven elements. An electrophoretic fluid capable of separating into particle-rich and particle-deficient phases by electrophoresis operates in surface contact with the electrodes. An electrically non-conductive material having raised surface areas and spaces between the surface areas is associated with one or more of the electrodes. When a voltage is applied between the electrodes in a first direction, the particle-rich phase of the fluid collects on one of the electrodes and also makes contact with the spaces and the raised surface areas of the material associated with the other electrode thereby engaging or locking the electrodes together and transmitting force between the elements.

Abstract: In a variable inertial mass flywheel having a main flywheel member coupled to an engine crankshaft and a subflywheel member rotatably arranged relative to the main flywheel member, an electrorheological fluid whose viscosity changes according to intensity of electric field at high response speed is enclosed between electrodes formed on the main flywheel member and the subflywheel member. At engine idling, a higher voltage is applied to the electrodes to increase the viscosity of the fluid, that is, to increase inertial mass of the flywheel so that engine torque ripple can effectively be absorbed. At engine acceleration, a lower (or zero) voltages is applied to the electrodes to decrease the viscosity of the fluid, that is to decrease inertial mass of the flywheel so that high engine torque response characteristics can stably be obtained.

Abstract: An apparatus for controlling the transmission of torque between drive elements using an electroactive fluid which is sealed within an enclosed chamber. A housing defines the chamber and includes at least one end defining an opening. Spaced electrodes are provided in the chamber in contact with the fluid and are respectively connected to the drive elements. A controllable power source applies a variable electric field to the fluid such that force is transmitted between the electrodes by the fluid according to the strength of the field. A shaft connects one of the electrodes to one of the elements and extends through the opening. A ferrofluid seal assembly prevents leakage of the fluid from the chamber through the opening. The assembly defines with the shaft an annular space in communication with the fluid. A magnetic circuit is provided in the assembly by a permanent magnet for applying a concentrated magnetic field in one or more regions across the annular space.

Abstract: A ball joint including a socket defining a chamber and having an opening. The ball joint also includes a ball stud having a ball portion and a shank portion. The ball portion is located in the chamber of the socket. The shank portion of the ball stud projects through the opening in the socket. The chamber has a shape generally conforming to the shape of the ball portion of the ball stud. Electrorheological fluid is interposed between the ball portion of the ball stud and the socket for resisting relative movement between the ball stud and socket. The viscosity of the electrorheological fluid is variable as a function of the magnitude of an electric field applied thereto to vary the resistance to relative movement between the ball stud and the socket. The electric field applied to the electrorheological fluid is controlled to control the viscosity of the electrorheological fluid and thereby control the relative movement between the ball stud and the socket.

Abstract: A system for disengaging an electromagnetic clutch upon selection of an opposite driving range of an automatic transmission. When a forward driving range is selected during rearward driving or a rearward driving range is selected during forward driving, a loading shift signal is produced. In response to the loading shift signal at a vehicle speed higher than a clutch engaging vehicle speed, the electromagnetic clutch is disengaged in order to prevent the engine from stalling.

Abstract: Disclosed is a control method and controller for a magnetic powder clutch system including a magnetic powder clutch having an input shaft connected to an engine and an output shaft. In the method, the magnetic powder clutch is energized by an energizing strength which is determined based on a target transmitting torque. The energizing strength is compensated with a predetermined correction factor to realize high accuracy control. Moreover, the correction factor is always updated in response to an error between the target transmitting torque and the detected actual transmitting torque.

Abstract: A soft start, self-powered coupling for connecting a motor to a load, the coupling including a magnetic particle clutch, a generator having a rotor carried by the clutch and a stator, and an electronic control circuit assembly carried by the generator rotor, the magnetic particle clutch being connector to the motor and to the load, the generator powering the electronic control circuit assembly and the clutch to provide linear timed acceleration of the load.

Abstract: An engine cooling fan includes a first member adapted to be drivingly connected to the engine and a second member mounted rotatably relative to the first member, a series of fan blades are provided on the second member, the first and second members having opposed parallel faces separated from one another, the space between the faces being filled with a fluid the viscosity of which may be varied by applying a magnetic or electric field, the first and second members being arranged such that an electric or magnetic field may be applied therebetween. The electric or magnetic field is controlled by a control unit in response to signals corresponding to coolant temperature and engine speed.

Abstract: A system for controlling clutch current of an electromagnetic clutch at acceleration of a vehicle on a downhill. The clutch is engaged when vehicle speed is higher than a first reference speed. When the vehicle is accelerated on a downhill at a speed higher than a second reference speed which is lower than the first reference speed, the clutch is engaged to provide an engine braking effect.

Abstract: A control system for an electromagnetic clutch for a vehicle has an engine speed sensor, a clutch driven member speed sensor and a throttle position sensor. The system has a memory storing first torque capacities increasing with increase of engine speed and storing second torque capacities at clutch engagement rate 100% in accordance with engine speed and throttle position. The actual clutch engagement rate is calculated based on output signals of the engine speed sensor and the clutch driven member speed sensor. A first torque capacity and a second capacity are derived from the memory in accordance with output signals of the sensors. A torque capacity Tc for engaging the clutch is calculated as follows,Tc=Re.multidot.TcL+(1-Re).multidot.Tcswhere Re is the clutch engagement rate, Tcs is the first torque capacity and TcL is the second torque capacity.

Abstract: An electroviscous fan clutch (10) is employed as an accessory drive mechanism within a truck or automobile. A shaft (36), either driven by the engine or driving a load (31), carries a clutch member (14) arranged for fluid engagement with a body member (12) for the transmission of torque therebetween when electroviscous fluid is disposed in an operating chamber (45) defined by complimentary shear surfaces (40 and 44) in the clutch and body members. The clutch and body members are electrodes, connected to a source of high voltage potential (86), which establish an electrostatic field within the operating chamber to selectively vary the characteristic viscosity of fluid flowing therethrough.

Abstract: An electroviscous fan clutch (10) is employed as an accessory drive mechanism within a truck or automobile. A shaft (36), either driven by the engine or drivig a load (31), carries a clutch member (14) arranged for fluid engagement with a body member (12) for the transmission of torque therebetween when electroviscous fluid is disposed in an operating chamber (45) defined by complimentary shear surfaces (40 and 44) in the clutch and body members. The clutch and body members are electrodes, connected to a source of high voltage potential (86), which establish an electrostatic field within the operating chamber to selectively vary the characteristic viscosity of fliud flowing therethrough.

Abstract: An electrorheological fluid torque transmission and conversion system provides for variable control of torque in clutch and brake applications. Communication of mechanical energy between the drive elements is accomplished by magnetic coupling to eliminate the need for a dynamic fluid seal for interface of moving parts to the interior portion of the electrorheological fluid containment chamber. Permanent magnets are associated respectively with each of a first member and a second member which are magnetically coupled through a surface with low magnetic permeability such that the first member and second members rotate in unison. A variety of permanent arrangements may be utilized. Further, the drive element internal to the electrorheological fluid chamber may be both mechanically and electrically decoupled. A floating electrode may be capacitively coupled through the fluid to the power supply. Also provided are inner and outer conductive plates are provided for increased fluid surface contact area.

Abstract: A magnetic particle-type electromagnetic coupling apparatus is cooled by a plurality of heat pipes which are partially embedded in the outer periphery of a rotating coupling member near the portion of the coupling member which is in contact with magnetic particles during operation. Heat is removed from the coupling member by a working fluid which is sealed within the heat pipes and is dissipated to the atmosphere through cooling fins attached to the heat pipes.

Abstract: A system for controlling an electromagnetic clutch for a motor vehicle at transient state of driving condition of the motor vehicle. An actual engagement ratio is obtained in dependence on speeds of a drive member land a driven member of the clutch. A desired engagement ratio of the clutch is obtained in accordance with the speeds of the drive member and driven member. Clutch current is controlled so as to converge the actual engagement ratio on the desired engagement ratio. The transition of the change of the actual engagement ratio is observed and a correction signal is generated when the actual engagement ratio does not change in a converging direction. The clutch current is corrected by the correction signal.

Abstract: A magnetic-particle-type coupling device for transmitting the rotation of an engine to a transmission. One end portion of a heat pipe is embedded in a driven body, the other end portion of the heat pipe is inserted in the internal opening of the input shaft of the transmission, and cooling oil is supplied into the internal opening, so that the driven body and a driving body are efficiently cooled although the coupling device is made compact.

Abstract: Disclosed is a control method for a magnetic powder clutch system including a magnetic powder clutch having an input shaft connected to an engine and an output shaft. In the method, the magnetic powder clutch is energized by an energizing strength which is determined based on a transmitting torque. The energizing strength is compensated with a predetermined correction factor to realize the control in high accuracy. Moreover, the correction factor is always updated in response to an error between the target engagement revolution speed and the detected actual engagement revolution speed. By correcting the energizing strength to diminish the error, the magnetic powder clutch is correctly engaged at the target engagement revolution speed.

Abstract: A torque limited of permanent magnet coupling type is disclosed, in which the value of transmitted torque is varied from a near zero minimum to a maximum. The torque limiter comprises a disk of magnetic material fixed to the output cylinder, and a pair of annular members disposed on both axial sides of the disk with small gaps filled with a powder of magnetic material. The annular members are rotatably supported on the output cylinder. An annular disk-shaped permanent magnet is fixed to one of the annular members at the side surface thereof opposite to the surface facing the disk. Further, an annular disk-shaped plate of magnetic material having an outer diameter greater than that of the permanent magnet is fixed on the outer side surface of the permanent magnet projecting radially from the outer circumferential surface of the permanent magnet.

Abstract: A system for controlling a drag torque of an electromagnetic clutch at releasing of an accelerator pedal of a motor vehicle with a continuously variable belt drive transmission. A detector is provided for detecting whether vehicle speed is lower than a predetermined low speed. At the low vehicle speed, the drag current is gradually reduced as the vehicle speed increases.

Abstract: This invention disclosed a new ferrofluid and the use of ferrofluids in magnetically controllable couplings such as electromagnetic clutches and brakes. The new ferrofluid is comprised of a stable suspension of magnetizable particles having a size of at least one micron, a fluid carrier and a complexing agent. The complexing agent maintains the magnetizable particles in suspension within the carrier fluid.

Abstract: A system for controlling a drag torque of an electromagnetic clutch at idling operation of an engine for a motor vehicle with a continuously variable belt drive transmission. A detector is provided for detecting whether engine speed is higher or lower than a predetermined minimum idling speed. When the engine speed is at a higher engine speed, a standard current is passed in a coil of the clutch. At a lower idling speed, the drag current is gradually reduced until the engine speed increases to the predetermined minimum idling speed.

Abstract: A system for controlling an electromagnetic clutch for a motor vehicle at starting of the motor vehicle. An actual engagement rate is obtained in dependency on speeds of a drive member and a driven member of the clutch. A desired output-input speed ratio of the clutch is obtained in accordance with load on the engine and the speed of the driven member, the output-input speed ratio representing a decreasing function of the engine load and an increasing function of the speed of the driven member. Clutch current is controlled so as to converge the actual output-input speed ratio to the desired engagement rate, thereby smoothly engaging the clutch at the start of the vehicle.

Abstract: A system for disengaging an electromagnetic clutch of a vehicle at rapid deceleration of the vehicle. The rapid deceleration is detected by changing rate of engine speed when the magnitude of deceleration is larger than a reference value, the electromagnetic clutch is disengaged at an engine speed which is higher than idling speed.

Abstract: A system for controlling a drag torque of an electromagnetic clutch at releasing of an accelerator pedal of a motor vehicle. A detector is provided for detecting whether vehicle speed is lower than a predetermined low speed. At the low vehicle speed, drag current is corrected in dependency on engine speed so as to provide a constant drag torque.

Abstract: A system for controlling an electromagnetic clutch for a motor vehicle at a transient state of a driving condition of the motor vehicle. An actual engagement rate (actual engagement ratio is obtained in dependency on speeds of a drive member and a driven member of the clutch. A desired engagement rate (desired engagement ratio) of the clutch is provided in accordance with conditions of the transient state and driving conditions. Clutch current is controlled so as to converge the actual engagement rate to the desired engagement rate, allowing the clutch to slip in dependency on the transient state conditions.

Abstract: A method and an apparatus of controlling an electromagnetic clutch incorporated in a power transmission system of a vehicle to transmit an output of an engine to the drive wheels of the vehicle is disclosed. An amount of electric current applied to the clutch is regulated to control an engaging action of said electromagnetic clutch, based on either a variation in rotating speed or torque of an output shaft of the electromagnetic clutch, or based on the frequency or number of variations per unit time in rotating speed or torque of the output shaft, as compared with the frequency or number of ignitions or combustions per unit time of the engine. In this way a variation in output torque of the engine is absorbed by the electromagnetic clutch for improved drivability, while a transmission power loss in the clutch is kept to a minimum for maximum fuel economy.