Abstract: A disk-shaped cover has a first toothed portion at one surface thereof. A housing is coupled with the cover such that a space is defined therebetween. The housing has a second toothed portion at one surface thereof, facing the first toothed portion. A shaft is rotatably disposed through a middle portion of the housing. A fan is fixedly connected to the housing and rotatable with the housing. A rotor is mounted in the space between the cover and the housing, engaged with and rotatable with the shaft, with third and fourth toothed portions at both surfaces thereof, engaged with the first and second toothed portions, respectively. An operation unit controls an amount of fluid supplied to the space between the cover and the housing to control a frictional force generated between the rotor, the housing, and the cover. A control unit controls the operation unit based on a coolant temperature.

Abstract: A power transmission for a compressor includes a driven member rotable by an engine. The power transmission includes a drive member rotable coaxially with the driven member to rotate a shaft of a compressor for regulating displacement of the compressor. The power transmission includes a link interconnecting the driven member and the drive member with each other in a crossing direction relative to the drive shaft. The link is disengageable from one member of the driven member and the drive member.

Abstract: A pneumatic compressor capable of supplying compressed gas to a pneumatic tool. The compressor can be powered alternatively by either a battery or an AC power source. The compressor comprises a permanent magnet DC electric motor and circuitry for converting the AC power source to DC power. The compressor includes a receptacle for accommodating one or more of a plurality of batteries and includes circuitry for using batteries having different voltages. The AC power source may also be used to charge a battery connected to the compressor.

Abstract: The invention relates to a device for driving a coolant pump (2) for the coolant circuit of an internal combustion engine in a motor vehicle comprising a drive train that encompasses a drive wheel (7), a viscous coupling (11), and a drive shaft (3). The inventive driving device is provided with a second coupling (15) which is embodied as a clutch and can be connected to the drive train parallel to the viscous coupling (11), resulting in increased redundancy and two-step rev control.

Abstract: A portable haze sprayer having a multi-function that can spray powder chemicals or a fertilizer, spray chemicals in a high pressure, and widely spray chemicals is provided.

Abstract: A split-pressure, dual-pump system for supplying hydraulic fluid to a multi-speed transmission is provided. The system includes a low-pressure work circuit operatively connected to a fixed displacement pump, and a high-pressure work circuit operatively connected to a variable displacement pump. The system also includes a regulator valve fluidly coupled to the variable displacement pump via a decrease circuit and an overage circuit for regulating the flow of fluid to the high-pressure work circuit. The invention consists of separating the high-pressure needs of the system into a separate work circuit from the low-pressure needs of the system, and optimizing pump design separately for each work circuit to maximize transmission efficiency and reduce parasitic losses. A method of supplying hydraulic fluid to a multi-speed transmission at variable flow and pressure is also provided.

Abstract: A complex fluid machine has an expansion-compressor device, a pump, and a motor generator, wherein the expansion-compressor device, the pump, and the motor generator are operatively connected and arranged in series, and a power transmitting device for disconnecting the pump from the motor generator, when the expansion-compressor device is driven by the motor generator so as to be operated as a compressor device.

Abstract: The invention relates to a method for control of a pressurised air supply system for a motor vehicle (10), said system comprising a drive motor (1) for driving the motor vehicle, which drives an air compressor (3) by means of a drive connection (2), or said drive connection for driving the air compressor may be switched on. Said method comprises the following method steps: in a supply condition, the air compressor is driven by the drive motor and connected with the air supply side (3.

Abstract: A power transmission mechanism for transmitting driving power between a shaft and a rotor connected to the shaft includes a cylindrical adapter located between the shaft and the rotor and a screw seat arranged on the shaft. The adapter has a first internally threaded portion in its inner peripheral surface and a first externally threaded portion in its outer peripheral surface. The first internally threaded portion is engaged with a second externally threaded portion of the shaft, and the first externally threaded portion is engaged with a second internally threaded portion of the rotor. The screw seat has a screw seat surface. The adapter is screwed onto the shaft such that the adapter is pressed against the screw seat surface, and the rotor is screwed onto the adapter such that the rotor is pressed against the screw seat surface.

Abstract: A variable capacity rotary compressor having a slot defined between eccentric bushes, a latch pin fitted to a rotary shaft so as to be latched to the slot, and a restraint unit for restraining the eccentric bushes upon rotation of the rotary shaft. The restraint unit includes a restraint member mounted in the rotary shaft, a supporting shaft extending from the latch pin to be inserted into the hollow portion of the restraint member, and a return spring interposed between an outer circumference of the supporting shaft and the restraint member to move the restraint member inward toward the center of the rotary shaft when the rotary shaft is not rotated. The restraint unit is easy to manufacture and install and to ensure smooth operation thereof.

Abstract: In one embodiment, a pump system includes a motor-to-pump transmission having a planetary gear assembly and a clutch. In another embodiment, a pump system includes a transmission having a housing with a motor mount and a pump mount, a central gear disposed in the housing, a plurality of planet gears disposed in the housing, wherein the plurality of planet gears is disposed about and engaged with the central gear. The transmission also includes an outer ring gear disposed in the housing, wherein the outer ring gear is disposed about and engaged with the plurality of planet gears.

Abstract: In a hybrid compressor for a vehicle where a vehicle engine is stopped when the vehicle is temporally stopped, a pulley, a motor and a compressor can be driven in independent from each other, and are connected to a sun gear, planetary carriers and a ring gear of a planetary gear. A rotational speed of the motor is adjusted by a controller, so that a rotational speed of the compressor is changed with respect to a rotational speed of the pulley. Accordingly, production cost of the hybrid compressor and the size thereof can be reduced, while a cooling function can be ensured even when the vehicle engine is stopped.

Abstract: A vacuum pump and a vacuum system can be stopped when necessary when an engine is operating.

Abstract: A compressor device compresses refrigerant of a refrigeration cycle system and is connected to an engine and a motor to selectively receive drive force from one or both of the engine and the motor. When the engine is operated in an idling mode, a control apparatus energizes the motor to drive the compressor device alone or in cooperation with the engine and controls the energization of the motor to adjust load on the engine.

Abstract: A portable pneumatic fastening tool has an onboard compressor assembly to alleviate the need for an external air compressor. The onboard compressor assembly includes a motor and a compressor mounted to the tool body. The motor can be powered by a detachable battery mounted to a cover for covering the onboard compressor assembly. A portable pneumatic fastening tool may also be powered by a portable compressor assembly which can be borne by the user.

Abstract: A variable capacity rotary compressor to prevent eccentric bushes from rotating faster than a rotating shaft, and includes upper and lower compression chambers having different interior capacities thereof, and the rotating shaft with upper and lower eccentric cams being provided thereon to be eccentric from the rotating shaft in a common direction. Upper and lower eccentric bushes are fitted over the upper and lower eccentric cams, respectively, with a slot provided there between. A locking pin changes a position of the upper or lower eccentric bush to a maximum eccentric position. Upper and lower brake units are, respectively, provided between the upper eccentric cam and the upper eccentric bush, and between the lower eccentric cam and the lower eccentric bush. The upper and lower brake units, respectively, include first and second upper brake balls, and first and second lower brake balls, to restrain the upper and lower eccentric bushes.

Abstract: In a centrifugal pump (10) for liquids comprising an impeller casing (50) inside which a centrifugal impeller (40) is rotatably mounted including a hub (42) from which a plurality of curved blades (44) delimited by two curved edges (44a,44b) extend, from one of the curved edges (44a) of the curved blades (44) a tab (48) extends on the side of the concavity of the blades (44) and is folded in the opposite direction to the blade (44) with respect to a radial plane.

Abstract: A variable capacity rotary compressor including first and second compression chambers having different capacities, and a rotating shaft. First and second eccentric cams are mounted to the rotating shaft to be eccentric in a same direction. First and second eccentric bushes are fitted over the first and second eccentric cams to make an angle between eccentric lines of the first and second eccentric bushes be less than 180°. A locking pin functions to change a position of the first or second eccentric bush to a maximum eccentric position. Further, a slot is formed on the rotating shaft between the first and second eccentric bushes. In this case, the slot having a predetermined length is formed to have a same angle as the angle between the eccentric lines of the first and second eccentric bushes. The locking pin is inserted into the slot.

Abstract: Device for controlling the means (1) for recirculating a cooling fluid in engines (11a) in particular for vehicles and like, comprising a shaft (2) actuating the impeller, means (3,3b) for generating the movement of said shaft and means for transmitting the movement from the said generating means (3,3b) to the said shaft (2) of the impeller (1), in which said movement transmission means comprise a double-action coupling (30,40) comprising: magnetic means (31) integral with a rotor (30;130;230) and able to cooperate with corresponding magnetizable means (41;141;241) of a support (40;140;240) rotationally connected to the shaft (2) of the recirculating means and movable in an axial direction with respect thereto, so as to determine a first speed of rotation of the recirculating means (1), and electromagnetic means (22,22a) able to co-operate with a ring (41a;141a;241a) integral with said support (40;140;240) so as to determine a second and different speed of rotation of the pump impeller (1).

Abstract: A variable capacity rotary compressor including upper and lower compression chambers having different interior capacities, and a rotating shaft. Upper and lower eccentric cams are provided on the rotating shaft to be eccentric from the rotating shaft in a same direction. Upper and lower eccentric bushes are fitted over the upper and lower eccentric cams, respectively, in such a way that a maximum eccentric part of the upper eccentric bush is opposite to that of the lower eccentric bush, with a slot provided between the upper and lower eccentric bushes. A locking pin functions to change a position of the upper or lower eccentric bush to a maximum eccentric position. Further, upper and lower brake units are respectively provided between the upper eccentric cam and the upper eccentric bush, and between the lower eccentric cam and the lower eccentric bush.

Abstract: A variable capacity rotary compressor including a housing to define therein two compression chambers having different capacities, a rotating shaft transmit ting a rotating force from a drive unit to the two compression chambers, two eccentric parts are provided on an outer surface of the rotating shaft to be placed in the two compression chambers, respectively. Two eccentric bushes, having different weights respectively fitted over the eccentric parts to rotate relative to the rotating shaft within predetermined angles, a pair of force transmission parts, provided on opposite sides of the eccentric unit, to receive the rotating force of the rotating shaft so that one of the two eccentric bushes rotates while being eccentric from the rotating shaft and a remaining one of the two eccentric bushes rotates while being released from eccentricity from the rotating shaft, according to a rotating direction of the rotating shaft.

Abstract: A liquid dispensing device includes at least one piston pump (7), which sucks liquid to be dispensed from a container in a filling cycle and applies the liquid to a target in an emptying cycle and which is driven by an actuator comprising an actuating element (1) that is arranged to move a piston rod (2) between two extreme positions, and a gripper (3) attached to the actuating means (1), which gripper is able to engage with the piston rod (2) so as to move it along with the actuating element. The gripper (3) is made able to engage with the piston rod (2) only in its first extreme position and arranged to disengage automatically from the piston rod in its second extreme position.

Abstract: The present invention provides a hybrid compressor system in which its configuration is simplified, its cost and size are reduced, and its reliability is enhanced. In the hybrid compressor system which selectively transmits a driving force of an engine and a driving force of a motor being mounted on a vehicle to a compressor of a vehicle air conditioning device to drive the compressor, the motor is provided with a one-way clutch which selectively transmits the driving force of the motor to the compressor 1.

Abstract: Method and apparatus for reducing the pumping duty cycle of a pump assembly associated with an oil, natural gas, or water well with a concomitant reduction in the wear associated with the pump down hole components. An engine is connected with a pump assembly through a pneumatically actuated clutch and a selected event is determined to actuate the clutch to connect the engine with the pump assembly. The selected events may be a timed cycle determined from observations or a direct determination of liquid level in the well bore so that hydrocarbon production is maintained from the well bore. A pressurized gas is supplied on the occurrence of the selected event to actuate the clutch to connect the pump assembly with the engine to remove liquid from the gas well to maintain hydrocarbon production from the well.

Abstract: A variable capacity rotary compressor to prevent an eccentric bush and a locking pin from being deformed or worn out due to a variance in a pressure of a compression chamber as a rotating shaft rotates. The compressor includes upper and lower compression chambers having different interior capacities thereof, and a rotating shaft. Upper and lower eccentric cams are provided on the rotating shaft to be eccentric from the rotating shaft in a common direction. Upper and lower eccentric bushes are fitted over the upper and lower eccentric cams, respectively, with a slot provided at a position between the upper and lower eccentric bushes. The locking pin operates to change a position of the upper or lower eccentric bush to a maximum eccentric position. Further, surfaces of parts around first and second ends of the slot are heat-treated, thus increasing a hardness thereof.

Abstract: A variable capacity rotary compressor including a hermetic casing, and a housing installed in the hermetic casing to define therein first and second compression chambers having different capacities. A compressor is placed in the first and second compression chambers and operated to execute a compression operation in either the first or second compression chamber according to a rotating direction of a rotating shaft which drives the compressing unit. A pressure controller applies the outlet pressure of the compressor to the first or second compression chamber where an idle operation is executed, and has a path control chamber provided at a portion of the housing outside the first and second compression chambers. First and second inlet channels connect both ends of the path control chamber to inlet ports of the first and second compression chambers, respectively. A communicating channel connects an outlet side of the compressor to the path control chamber.

Abstract: A compressor provided with a torque limiter constructed such that, in view of possible occurrence of accidental locking of the compressor, in the case where a one-way clutch is used in place of an electromagnetic clutch in order to permit a refrigerant compressor for a vehicle air-conditioning system to be driven by an electric motor instead of an internal combustion engine, when an excessive torque is to be transmitted by the one-way clutch, rollers ride over wedge surfaces and fall into pocket sections, or sprags are reversed to roll-over.

Abstract: This invention relates to a pumping system. The design of the system is such that bi-directional operation can be achieved using a significantly smaller and hence lighter unit than those currently available. It uses the direction of rotation of the drive shaft to control the opening and closure of the by-pass means for controllably returning the fluid to the first reservoir.

Abstract: A compressor for a vehicle air conditioner includes a pressure sensor and a torque computing unit for computing the compressor torque. The compressor also has a communication unit that allows data communication with other devices based on vehicle data communication protocols. The torque computing unit and the communication unit are integral with the compressor. Therefore, it is possible to calculate the driving torque quickly, and an engine electronic control unit can control an engine such that the torque required for the compressor can be quickly generated.

Abstract: A hybrid compressor includes a first compression mechanism, which is driven by a first drive source, and a second compression mechanism, which is driven by a second drive source. A first discharge port of the first compression mechanism and a second discharge port of the second compression mechanism are connected to a single discharge path.

Abstract: A hybrid compressor system affords maximum cooling capability by making full use of an additional motor to improve the fuel consumption efficiency of a vehicle while ensuring passenger compartment cooling when the engine is stopped. The hybrid compressor system includes a compression unit for compressing a refrigerant, a motor for driving the compression unit, and disconnection means for disconnecting the drive force of a vehicle engine. In the hybrid compressor system, when the thermal load of the refrigeration cycle system lies within a predetermined range in a higher load region, the control means connects the disconnection means to allow the vehicle engine to drive the compression unit. When the thermal load of the refrigeration cycle system lies within a lower load region of the predetermined range, the control means disconnects the disconnection means to allow the motor to drive the compression unit even while the vehicle engine is running.

Abstract: A system for maintaining hydraulic pressure in a vehicle hydraulic system when the vehicle is stopped or idling. A hydraulic pressure reserve system includes a primary hydraulic circuit that includes a hydraulic pump and a hydraulic sump and that provides hydraulic pressure to at least a hydraulically actuated transmission and an accumulator tank and control valve connected from the primary hydraulic circuit for storing a reserve of hydraulic fluid at an accumulator pressure. An accumulator control valve, such as a bi-directional valve, allows a flow of hydraulic fluid between the primary circuit and the accumulator tank according to the primary circuit pressure to raise the primary circuit pressure towards a desired pressure.

Abstract: A variable capacity rotary compressor is designed to make a pressure of a high-pressure side be uniformly applied to upper and lower ends of a roller of a low-pressure side, allowing the roller of the low-pressure side to be smoothly rotated. The compressor includes a housing to define two compression chambers which are partitioned by a partition plate. Two flanges are mounted to predetermined positions of the compression chambers to close openings of the compression chambers. A rotating shaft passes through the compression chambers and the partition plate. Two eccentric units are mounted to the rotating shaft to be placed in the compression chambers. One of the eccentric units is eccentric from the rotating shaft to execute a compression operation while a remaining one of the eccentric units is released from eccentricity from the rotating shaft to execute an idle rotation, according to a rotating direction of the rotating shaft.

Abstract: In a hybrid compressor for a vehicle where a vehicle engine is stopped when the vehicle is temporally stopped, a pulley, a motor and a compressor can be driven in independent from each other, and are connected to a sun gear, planetary carriers and a ring gear of a planetary gear. A rotational speed of the motor is adjusted by a controller, so that a rotational speed of the compressor is changed with respect to a rotational speed of the pulley. Accordingly, production cost of the hybrid compressor and the size thereof can be reduced, while a cooling function can be ensured even when the vehicle engine is stopped.

Abstract: A rotary compressor having a plurality of compression chambers and adapted to vary a compression capacity according to a direction of rotation of roller pistons within the compression chambers. A rotating shaft provided with a plurality of eccentric parts drives the roller pistons to compress refrigerant in the compression chambers by eccentric rotations of the eccentric parts. A reversible motor selectively rotates the rotating shaft in opposite directions, and a clutch engages the roller pistons such that the roller pistons perform a compressing action or an idle action according to a rotating direction of the rotating shaft, thus varying the compression capacity of the compressor according to a rotating direction of the rotating shaft. Thus, the compression capacity may be varied without using an inverter circuit.

Abstract: A compressor includes a housing, a rotary shaft, a pulley, an electric motor, a pulley one-way clutch, and a motor one-way clutch. The shaft is rotatably supported by the housing. The pulley is operably connected to the shaft and includes a power transmission portion. When power is transmitted from a vehicular engine to the power transmission portion, the pulley is rotated. The electric motor rotates the shaft and includes a rotor, which is operably connected to the shaft. At least part of the electric motor overlaps the power transmission portion in the axial direction of the shaft. The pulley one-way clutch is located between the pulley and the shaft and selectively permits and prevents power transmission between the pulley and the shaft. The motor one-way clutch is located between the rotor and the shaft and selectively permits and prevents power transmission between the rotor and the shaft.

Abstract: A control device for a hybrid compressor includes a motor driver for driving an electric motor, a clutch controller for driving an electromagnetic clutch and an engine drive timing controller. Power is transmitted from an engine to the compressor when the electromagnetic clutch is connected. The clutch controller sets a connecting force of the electromagnetic clutch to transmit a second starting torque of the compressor. The engine drive timing controller is electrically connected to the motor driver and the clutch controller. The engine drive timing controller commands the motor driver to activate the electric motor to discharge liquid refrigerant from the compression chambers to a predetermined level so that the compressor reduces its starting torque to the second starting torque before commanding the clutch controller to connect the electromagnetic clutch to transmit the power from the engine to the compressor.

Abstract: In a hybrid compressor for a vehicle where a vehicle engine is stopped when the vehicle is temporally stopped, a pulley, a motor and a compressor can be driven in independent from each other, and are connected to a sun gear, planetary carriers and a ring gear of a planetary gear. A rotational speed of the motor is adjusted by a controller, so that a rotational speed of the compressor is changed with respect to a rotational speed of the pulley. Accordingly, production cost of the hybrid compressor and the size thereof can be reduced, while a cooling function can be ensured even when the vehicle engine is stopped.

Abstract: This invention relates to a pumping system. The design of the system is such that bi-directional operation can be achieved using a significantly smaller and hence lighter unit than those currently available. It uses the direction of rotation of the drive shaft to control the opening and closure of the by-pass means for controllably returning the fluid to the first reservoir.

Abstract: In a hybrid compressor for a vehicle where a vehicle engine is stopped when the vehicle is temporally stopped, a pulley, a motor and a compressor can be driven in independent from each other, and are connected to a sun gear, planetary carriers and a ring gear of a planetary gear. A rotational speed of the motor is adjusted by a controller, so that a rotational speed of the compressor is changed with respect to a rotational speed of the pulley. Accordingly, production cost of the hybrid compressor and the size thereof can be reduced, while a cooling function can be ensured even when the vehicle engine is stopped.

Abstract: A power transmission for a compressor includes a driven member rotatable by an engine. The power transmission includes a drive member rotatable coaxially with the driven member to rotate a shaft of a compressor for regulating displacement of the compressor. The power transmission includes a link interconnecting the driven member and the drive member with each other in a crossing direction relative to the drive shaft. The link is disengageable from one member of the driven member and the drive member.

Abstract: A viscous coupling, or clutch system, is either coupled to a water pump or combined with a water pump and is used for controlling the coolant flow rate in a cooling system. At engine idle or low speeds, wherein the water pump is driven at very close speeds to the input speed, the viscous coupling would have little effect on the speed of the pump. However, due to the presence of the viscous coupling, a larger water pump may be used, resulting in good coolant flow at engine idle or lower speeds. As engine speeds are increased, the viscous coupling slips, resulting in lower input speeds for the water pump, thereby reducing the risk of pump cavitation. By increasing the water pump speed at lower engine speeds and decreasing the water pump speed at higher engine speeds, the engine likely will operate at ideal temperatures, and thus fuel economy may be improved and emissions minimized.

Abstract: An air conditioner for air conditioning the interior of a compartment includes a compressor and an electric motor. The compressor compresses refrigerant gas and changes the displacement. The electric motor drives the compressor. A motor controller rotates the motor at a constant reference speed. A detection device detects information related to the thermal load on the air conditioner. A current sensor detects the value of current supplied to the electric motor. A controller controls the compressor based on the detected thermal load information and the detected current value. The controller computes a target torque of the compressor based on the thermal load information. In accordance with the computed target torque, the controller computes a target current value to be supplied to the electric motor. The controller further controls the displacement of the compressor such that the detected current value matches the target current value.

Abstract: A rotary compressor having a plurality of compression chambers and adapted to vary a compression capacity according to a direction of rotation of roller pistons within the compression chambers. A rotating shaft provided with a plurality of eccentric parts drives the roller pistons to compress refrigerant in the compression chambers by eccentric rotations of the eccentric parts. A reversible motor selectively rotates the rotating shaft in opposite directions, and a clutch engages the roller pistons such that the roller pistons perform a compressing action or an idle action according to a rotating direction of the rotating shaft, thus varying the compression capacity of the compressor according to a rotating direction of the rotating shaft. Thus, the compression capacity may be varied without using an inverter circuit.

Abstract: A compressor has a pulley for transmitting torque from an external drive source to a rotary shaft to drive a compression mechanism. The pulley has a pulley body. The compressor has a mass body located in a range that is radially inward of the outer circumference of the pulley. The mass body swings about an axis that is spaced from the rotation axis of the pulley body by a predetermined distance and is substantially parallel to the rotation axis of the pulley body.

Abstract: The present invention provides a rotating apparatus. The rotating apparatus includes a rotor and a motor generator. The rotor includes a belt holder on its outer circumferential surface. The belt holder transmits power between an engine and the rotor. The motor generator is accommodated in and operably connected to the rotor. The motor generator selectively functions as at least one of a motor and a generator. The motor generator is arranged inside the belt holder such that the motor generator is surrounded by the belt holder.

Abstract: A compressor includes a compressor main body and a power transmission mechanism. The power transmission mechanism includes a pulley and a hub. The pulley has a first inner cylinder and a second inner cylinder, which are apart from each other in the axial direction of the pulley. A one-way clutch is located on a power transmission path between the first inner cylinder and the hub. A bearing is located between the first inner cylinder and the hub. A bearing is located between the second inner cylinder and a housing of the compressor main body. A power transmission pin for discontinuing an excessive power transmission is located on a power transmission path between an engine of a vehicle and a drive shaft.

Abstract: A torque transmission apparatus absorbs torque fluctuations (vibrations) while limiting the size of the outside dimensions of a pulley. Elastomeric dampers and pendulum type vibration-absorbing mechanisms are located between an outer tube and an inner tube of a pulley body.

Abstract: A positive displacement hydraulic pump/motor assembly (1) includes a rotary cylinder block (3) having a central axis (5) and a generally circular array of cylinders (6) disposed around the axis. A corresponding plurality of pistons (10) is reciprocably disposed within the respective cylinders. A drive shaft (12) extends through a bore (13) formed in the cylinder block to effect rotation of the cylinder block about the central axis. A drive plate (15) is disposed at one end of the cylinder block to effect sequentially staggered reciprocation of the pistons in response to rotation of the cylinder block. A stationary valve plate (20) is disposed at an opposite end of the cylinder block, the valve plate having a valve face (21) adapted for sliding rotational engagement with a complementary mating face (22) formed on the cylinder block.

Abstract: A power transmitting mechanism transmits power from an engine to a drive shaft of a compressor. A pulley is supported by the compressor and is coupled to the engine. A hub is attached to the drive shaft. Rollers are located on the pulley. Elastic transmission arms are located between the pulley and the hub. The distal end of each arm is curved, and the proximal end is coupled to the hub. When the rollers are engaged with the arms, power is transmitted between the pulley and the hub. When, due to excessive torque, the rollers escape from the corresponding arm, power transmission between the pulley and the hub is disconnected. The distal ends of the arms are movable in the radial direction. When the rollers disengage from the corresponding arms, the distal ends of the arms move radially such that the pulley and the hub relatively rotate without interference by the arms.