Glossary of Electromagnetic Clutch and Electromagnetic Brake Terms (Excerpt from JIS B 1404-1:2005)
2026/05/07
[
Scope] This standard specifies terminology related to electromagnetic clutches and electromagnetic brakes used to transmit, interrupt, or brake torque from one shaft to another on a straight line, or from the driving side to the driven side on coaxial shafts.
a) Terminology
| Number | Term | Definition | Corresponding English (for reference) |
|---|---|---|---|
| 101 | Electromagnetic Clutch | A clutch that transmits or cuts off torque from the driving side to the driven side on the same axis through electromagnetic operation. | electromagnetic clutch |
| 102 | Electromagnetic Friction Clutch | An electromagnetic clutch that engages via friction. | electromagnetic friction clutch |
| 103 | Micro electromagnetic friction clutch | An electromagnetic friction clutch with a static friction torque of less than 10 N·m. | electromagnetic friction micro-clutch |
| 104 | Electromagnetic Disc Clutch | An electromagnetic friction clutch with a circular friction surface. | electromagnetic disc clutch |
| 105 | Electromagnetic engagement clutch | An electromagnetic clutch that engages through meshing. | electromagnetic positive clutch |
| 106 | Electromagnetic tooth clutch | An electromagnetic clutch that engages via numerous V-shaped teeth on the opposing cylindrical end faces. | electromagnetic toothed clutch |
| 107 | Electromagnetic air-gap clutch | An electromagnetic clutch with a gap between the driving and driven sides. | electromagnetic gap-type clutch |
| 108 | Electromagnetic powder clutch | An electromagnetic clutch that uses powder enclosed within the gap as the medium for torque transmission. | electromagnetic particle clutch, electromagnetic powder clutch |
| 109 | Hysteresis Clutch | An electromagnetic clutch that utilizes the hysteresis characteristics of magnetic materials. | hysteresis clutch |
| 110 | Induction Clutch | An electromagnetic clutch that utilizes the principle of electromagnetic induction. | induction clutch |
| 111 | Electromagnetic Coil Spring Clutch | An electromagnetic clutch that utilizes the wrapping amplification effect, in which a coil-shaped spring clamps the input and output shafts, which are coaxial, to transmit or cut off torque. | electromagnetic wrap spring clutch |
| 121 | Electromagnetic Brake | A brake that uses electromagnetic actuation to decelerate, stop, or maintain a rotating body in a stationary or constant state. | electromagnetic brake |
| 122 | Electromagnetic Friction Brake | An electromagnetic brake that utilizes friction. | electromagnetic friction brake |
| 123 | Micro electromagnetic friction brake | An electromagnetic friction brake with a static friction torque of less than 10 N·m. | electromagnetic friction micro-brake |
| 124 | Electromagnetic disc brake | An electromagnetic friction brake with a circular friction surface. | electromagnetic disc brake |
| 125 | Electromagnetic engagement brake | An electromagnetic brake that operates by engagement. | electromagnetic positive brake |
| 126 | Electromagnetic tooth brake | An electromagnetic brake of the interlocking type featuring numerous V-shaped teeth on the opposing cylindrical end faces. | electromagnetic toothed brake |
| 127 | Electromagnetic air-gap brake | An electromagnetic brake with a gap between the stationary and rotating parts. | electromagnetic gap-type brake |
| 128 | Electromagnetic powder brake | An electromagnetic brake that uses powder enclosed within the gap as a medium for torque transmission. | electromagnetic particle brake, electromagnetic powder brake |
| 129 | Hysteresis Brake | An electromagnetic brake that utilizes the hysteresis characteristics of magnetic materials. | hysteresis brake |
| 130 | Induction Brake | An electromagnetic brake that utilizes the principle of electromagnetic induction. | induction brake |
| 131 | Electromagnetic Coil Spring Brake | An electromagnetic brake that utilizes a winding amplification effect, in which a coiled spring simultaneously clamps a rotating hub and a stationary hub on the same axis to transmit or interrupt torque. | electromagnetic wrap spring brake |
| 141 | Dry | A type in which the torque transmission section is in a dry state. | dry type |
| 142 | Wet | A type in which the torque transmission section is lubricated with oil. | wet type |
| 143 | Single-plate | A type with a single friction surface. | single disc |
| 144 | Multi-disc | A type with two or more friction surfaces. A type with two friction surfaces is sometimes called a double disc. | multiple disc (multi-disc) |
| 145 | Stationary Coil Type | A type in which the coil is stationary. | stationary coil type |
| 146 | Rotating coil type | A type in which the coil rotates. | rotating coil type |
| 147 | Excitation-operated type (direct-acting type) | A type in which the clutch engages or the brake is applied when electricity is applied. | electromagnetic actuated type (electromagnetic engaged type) |
| 148 | Non-electromagnetic actuated type (negative actuation type) | A type in which the clutch engages or the brake is applied when power is cut off. | Spring-actuated type / Permanent magnet-actuated type (negative-actuated type) (spring-negative type) (fail-safe type) |
| 149 | Wear-Adjustable Type | A type that requires adjustment to maintain functionality when the wear of the friction plates reaches a certain level. | Wear-adjusting type |
| 150 | Non-wear-adjusting type | A type that does not require adjustment until the friction plate is completely worn out. | wear non-adjusting type |
| 151 | Magnetized friction plate type | A type in which the friction plate serves as the magnetic path. | Flux-traversed disc type |
| 152 | Non-magnetized friction plate type | A type in which the friction plate does not form the magnetic path. | non-flux traversed disc type |
| 153 | Butt-joint shaft type | A type used for butt-jointed shafts. | split shaft type |
| 154 | Solid shaft type | Type used for through shafts. | through shaft type |
| 155 | Spline Drive Type | A type used in dry single-plate clutches and brakes, as well as dual-plate clutches and brakes, in which the armature is moved axially by splines while simultaneously transmitting torque. | spline drive type |
| 156 | Pin-driven type | In dry single-plate clutches and brakes, as well as two-plate clutches and brakes, a type in which the armature is moved axially by pins while simultaneously transmitting torque. | pin drive type |
| 157 | Leaf Spring Drive Type | In dry single-plate clutches and brakes, as well as two-plate clutches and brakes, a type in which the armature is moved axially by disc springs, simultaneously transmitting torque. | disc spring drive type |
| 158 | Fixed-position engagement type | A type of structure in which opposing teeth engage only at a specific position during one revolution. | synchro position type |
| 159 | Free-meshing type | A type of structure in which opposing teeth mesh at any position. | full position type |
| 160 | Tooth-surface magnetization type | A type in which a portion of the tooth acts as a magnetic path. | flux traversed tooth type |
| 161 | Non-magnetized tooth type | A type in which the tooth portion does not form a magnetic path. | non-flux traversed tooth type |
| 162 | Water-cooled type | A type in which the generated heat is cooled by water. | water-cooled type |
| 163 | Air-cooled type | A type in which generated heat is cooled by air. | air cooling type |
b) Component terminology
| Number | Term | Definition | Corresponding English (for reference) |
|---|---|---|---|
| 201 | Coil | A loop of wire that generates a magnetic field. | magnetic coil |
| 202 | Yoke | A piece of iron that forms part of a magnetic circuit. *At Miki Pulley, this is called a "clutch stator." | yoke |
| 203 | Field | A component with a coil embedded in the yoke. *At Miki Pulley, this is called a "stator." | field |
| 204 | Field retainer | A component that prevents the field from rotating. | holding arm |
| 205 | Magnet body | A component that incorporates a coil within the yoke and has a friction surface. | magnet body |
| 206 | Armature | A movable iron plate that forms a magnetic circuit. | armature |
| 207 | Armature adapter | A component fixed to the armature that meshes with the armature hub to transmit power. | armature adapter |
| 208 | Armature Hub | A component fixed to the shaft that connects to the armature or armature adapter to transmit power. | armature hub |
| 209 | Drive pin | A component that slides the armature axially while simultaneously transmitting power. | drive pin |
| 210 | Rotor | A component that forms part of the magnetic circuit; a rotating body that rotates relative to the coil and transmits power. | rotor |
| 211 | Disc (friction plate) | A plate that generates friction. | friction disc |
| 212 | Inner Disc | A friction plate that transmits torque between the outer disc and the inner driver when the inner circumference is engaged with the inner driver. | inner disc |
| 213 | Outer Disc | A friction plate that transmits torque between the inner disc and the outer driver when the outer circumference is combined with the outer driver. | outer disc |
| 214 | Driver | A component that meshes with the disc to transmit power. | driver |
| 215 | Inner Driver | A component that transmits torque in combination with the inner disc. | inner driver |
| 216 | Outer Driver | A component that transmits torque in combination with the outer disc. | outer driver |
| 217 | Facing | A friction material for clutches and brakes that is affixed to a disc surface or cylindrical end face. *At Miki Pulley, this is referred to as "lining." | facing |
| 218 | Brake plate | A component that forms part of the magnetic circuit, providing braking action, and a friction plate equipped with a brake facing. | brake plate |
| 219 | Automatic gap adjustment device | A device that automatically compensates for the increase in clearance between friction surfaces due to wear. | autogap device |
| 220 | Release Spring | A spring used in clutches and brakes to maintain the necessary clearance between friction surfaces or between tooth tips. | release spring |
| 221 | Actuating spring | A spring used to apply operating pressure in non-magnetically operated clutches and brakes. | actuating spring |
| 222 | Wrap spring | A spring that transmits or interrupts torque in combination with input and output hubs located on the same axis. | wrap spring |
| 223 | Powder | Magnetic iron powder (magnetic powder) used as a medium for torque transmission. | magnetic particle, magnetic powder |
c) Operational terms
| Number | Term | Definition | Quantity symbol (for reference) | Unit (Reference) | Corresponding English (Reference) |
|---|---|---|---|---|---|
| 301 | Synchronization | The state in which the driven side is synchronized with the driving side through the engagement of the clutch. | engaging of clutch | ||
| 302 | Braking | The state in which the brakes are applied to decelerate or stop the movement of a moving object. | braking | ||
| 303 | Holding | A state in which a moving object is held in its current stationary position. | holding | ||
| 304 | Release | The state in which the clutch or brake is disengaged. | disengaging of clutch, release of brake | ||
| 305 | Electromagnetic operation | The action of engaging or disengaging the clutch and applying or releasing the brake using electromagnetic force. | electromagnetic operation, electromagnetic actuation | ||
| 306 | Cushioned engagement | Engagement in which torque is gradually transmitted from the driving side to the driven side via the clutch, allowing the driven side to synchronize without impact | shockless engaging of clutch (cushioned start) | ||
| 307 | Cushioned braking | The action of decelerating or stopping a target object using brakes without impact. | shockless braking | ||
| 308 | Continuous Slipping Operation | The operation of continuously slipping the clutch or brake. | slip service | ||
| 309 | Incomplete meshing | A state in which the opposing teeth of a gear engage only partially along the tooth surface. | incomplete tooth engagement | ||
| 310 | Cusp-to-cusp engagement | A connection made when the tips of opposing teeth come into contact. | Engaging with tooth top | ||
| 311 | Stationary engagement | Engagement performed while the clutch is stationary. | stationary engagement of clutch | ||
| 312 | Rotating engagement | Engagement performed while the clutch is rotating. | rotating engagement of clutch | ||
| 313 | Engagement Frequency | The number of times the clutch engages per unit of time. | Ne | times/s times/min | engaging frequency |
| 314 | Braking frequency | The number of times the brake operates per unit of time. | Nb | times/s times/min | braking frequency |
| 315 | Duty cycle | The ratio of the time the coil is energized by the clutch or brake to the duration of one cycle, expressed as a percentage. | ％ | Excitation time ratio | |
| 316 | Rotation time ratio | The ratio of the time the rotating element is rotating to the duration of one cycle, expressed as a percentage. | ％ | rotating time ratio | |
| 317 | Over-excitation | Excitation performed by momentarily applying a voltage higher than the rated voltage to improve the response of a clutch or brake or to increase the generated torque. | over-excitation | ||
| 318 | Under-excitation | Excitation performed by applying a voltage lower than the rated voltage to provide cushioning in the clutch/brake or to reduce the generated torque. | weak excitation | ||
| 319 | Rapid excitation | Excitation performed using a circuit with a reduced time constant to improve the response of the clutch-brake. | quick response excitation | ||
| 320 | Rapid over-excitation | Excitation that combines over-excitation and quick response excitation to further improve responsiveness with the clutch/brake or to increase the generated torque. | quick response over-excitation | ||
| 321 | Drag | A state or phenomenon in which, due to drag torque (slip torque), the driven side rotates in a clutch or braking occurs in a brake. | drag | ||
| 322 | Torque Interference (Torque Lap) | A phenomenon that occurs when two clutches or brakes are operated simultaneously, in which the damping torque and the generated torque interfere with each other, affecting engagement time, braking time, or wear. | torque wrap |
d) Performance terminology
| Number | Term | Definition | Quantity symbol (for reference) | Unit (Reference) | Corresponding English (Reference) |
|---|---|---|---|---|---|
| 401 | Rated Torque | The torque specified for the clutch and brake. | Tr | N·m | rated torque |
| 402 | Static friction torque | The friction torque generated when the friction surfaces of a friction clutch or friction brake are at rest. | Ts | N·m | static friction torque |
| 403 | Dynamic friction torque | Friction torque generated when the friction surfaces of a friction clutch or friction brake are in a slipping state. | Td | N·m | dynamic friction torque |
| 404 | Rated static friction torque | The static friction torque specified for the clutch and brake. | N·m | rated static friction torque | |
| 405 | Rated dynamic friction torque | Dynamic friction torque specified for the clutch and brake. | N·m | rated dynamic friction torque | |
| 406 | Average dynamic friction torque | For clutches, the average value of the dynamic friction torque generated during the actual engagement time. For brakes, the average value of the dynamic friction torque generated during the actual braking time. | Ta | N·m | average dynamic friction torque |
| 407 | Initial torque | Torque generated when the friction surfaces of a friction clutch or friction brake have not yet been run in. | Ti | N·m | initial torque |
| 408 | Load torque | A general term for the torque on the load side that appears as resistance torque or braking torque when the clutch or brake is engaged. | Tl | N·m | load torque |
| 409 | Damping torque | Transient torque during the transition from current interruption by the clutch or brake to drag torque. | decreasing torque | ||
| 410 | Drag torque (idling torque) | Torque generated when the clutch or brake is disengaged and the wheel is spinning freely. | Tdg | N·m | drag torque, residual torque |
| 411 | Breakaway torque | The torque just before the teeth begin to slip due to overload under rated excitation. | N·m | pull-out torque | |
| 412 | Static pull-out torque | The torque required to break free from a stationary state. | N·m | static pull-out torque | |
| 413 | Rotational pull-out torque | Pull-out torque in a rotating state. | N·m | rotating pull-out torque | |
| 414 | Tooth-to-tooth torque | Torque transmitted when the teeth are in mesh. | N·m | torque under tooth-top engagement | |
| 415 | Engagement torque | Torque transmitted by contact prior to full engagement. | N·m | Rubbing torque in synchro position type | |
| 416 | Braking force | Force applied to decelerate or stop the object being braked. | Fn | N | braking force |
| 421 | Total coupling time | Time from operation input to completion of coupling. | tte | s | total engaging time |
| 422 | Engaging time | Time from operation input to completion of coupling. | te | s | engaging time |
| 423 | Actual engagement time | Time from torque generation to completion of coupling. | tae | s | actual engaging time |
| 424 | Total braking time | Time from the application of the control signal to the completion of braking. | ttb | s | total braking time |
| 425 | Braking time | The time from the activation signal to a complete stop. | tb | s | braking time |
| 426 | Actual braking time | The time from torque generation to the completion of braking. | tab | s | actual braking time |
| 427 | Response time | A collective term for coupling time and braking time. | tr | s | response time |
| 428 | Initial delay time | The time from input to unit activation. | tid | s | initial delay time |
| 429 | Armature suction time | Time from power-up to torque generation. | ta | s | armature pull-in time |
| 430 | Armature release time | The time it takes to return to the original position from the input. | tar | s | armature release time |
| 431 | Torque rise time | Time from input to 80% of rated torque. | tp | s | torque build-up time |
| 432 | Actual torque rise time | Time from torque generation to 80%. | tap | s | actual torque build-up time |
| 433 | Torque decay time | Time to reach 10% of release input. | td | s | torque decaying time |
| 434 | Release time | Time from input to release. | tre | s | release time |
| 435 | Inertial stopping time | Time to reach zero velocity after release. | s | Time to zero speed | |
| 441 | Work done during coupling | Work during coupling. | Ee | J | engaging energy |
| 442 | Coupling work rate | Work per unit time. | Pe | W | engaging energy rate |
| 443 | Permissible coupled work | Permissible coupling work. | Eeal | J | allowable engaging energy |
| 444 | Allowable engaging power | Permissible power. | Peal | W | allowable engaging energy rate |
| 445 | Braking work | Work during braking. | Eb | J | braking energy |
| 446 | Braking power | Braking work per unit time. | Pb | W | braking energy rate |
| 447 | Permissible braking energy | Permissible braking work. | Ebal | J | allowable braking energy |
| 448 | Allowable braking power | Permissible power. | Pbal | W | allowable braking energy rate |
| 449 | Heat dissipation capacity | The ability to dissipate generated heat. | Cd | W | heat dissipation capacity |
| 450 | Slip power | Power during continuous sliding. | Ps | W | continuous heat dissipation |
| 451 | Permissible slip power | Permissible power rating. | Psal | W | allowable continuous heat dissipation |
| 452 | Connection limit | Allowable load conditions for coupling. | allowable engaging load condition | ||
| 461 | Rated voltage | Reference voltage. | V | rated voltage | |
| 462 | Minimum suction voltage | Minimum voltage that can be drawn. | V | minimum pull-in voltage | |
| 463 | Maximum release voltage | Maximum release voltage. | V | maximum release voltage | |
| 464 | Hold voltage | Voltage in the held state. | V | holding voltage | |
| 465 | Rated current | Current at rated voltage. | A | rated current | |
| 466 | Minimum draw current | Minimum current that can be drawn. | A | minimum pull-in current | |
| 467 | Maximum release current | Maximum release current. | A | maximum release current | |
| 468 | Hold current | Current in the holding state. | A | holding current | |
| 471 | Average friction radius | The radius calculated as (D + d)/4. | Rm | m cm | mean friction radius |
| 472 | Coefficient of static friction | The ratio of static friction force to normal force. | μs | coefficient of static friction | |
| 473 | Coefficient of kinetic friction | The ratio of kinetic friction force to normal force. | μd | coefficient of dynamic friction | |
| 474 | Sliding velocity | Velocity of the working surface. | V | m/s | sliding velocity |
| 475 | Moment of inertia | A value expressed as m×R². | J | kg·m² | moment of inertia |
| 476 | Friction surface pressure | Force per unit area. | Pe | Pa | contact pressure |
| 477 | Allowable contact pressure | Permissible contact pressure. | Pcal | Pa | allowable pressure |
| 478 | Wear rate | Amount of wear per unit of work. | w | cm³/J | wear rate |
| 481 | Speed-torque characteristics | Torque characteristics as a function of slip speed. | torque-slip characteristic | ||
| 482 | Rotational Speed-Torque Reduction Characteristics | Torque characteristics as a function of rotational speed. | torque-speed characteristic | ||
| 483 | Current-Torque Characteristics | Relationship between current and torque. | torque-current characteristic |
e) Safety terms
| Number | Term | Definition | Corresponding English (for reference) |
|---|---|---|---|
| 501 | Danger | Safety precautions indicating that improper handling may result in death or serious injury to the user. | danger |
| 502 | Caution | Safety precautions for situations where improper handling could result in injury to the user or cause only property damage. | caution |
| 503 | Warning | Signs indicating precautions and inspection items to warn of danger and prevent personal injury and equipment damage. | warning signs |
| 504 | Warning labels | Labels designed to warn of hazards and prevent personal injury and equipment damage, affixed directly to or near the clutch or brake unit. | warning labels |
| 505 | Safety Cover | Covers installed to prevent personal injury caused by machinery and equipment. | safety covers |
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