Magnetic clutch device

A magnetic clutch device having improved durability and reliability without increasing a size in an axial direction. A fixed member, the first engagement element, and a second engagement element are arranged concentrically to one another in order from a rotational center axis. The first engagement element comprises a first magnet. The fixed member comprises a second magnet in which a polarity is switched between a straight polarity and a reversed polarity, and a coil that switches the polarity of the second magnet depending on a direction of the current applied thereto.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention claims the benefit of priority to Japanese Patent Application No. 2017-076385 filed on Apr. 7, 2017 with the Japanese Patent Office, the entire contents of which are incorporated herein by reference in its entirety.

BACKGROUND

Field of the Invention

Embodiment of the present disclosure relates to the art of a magnetic clutch device adapted to selectively transmit torque between rotary members by selectively establishing a magnetic circuit between the rotary members.

Discussion of the Related Art

An example of an electromagnetic brake that transmits torque by a magnetic force is described in JP-A-H01-303331. In the electromagnetic brake taught by JP-A-H01-303331, a rotary member and a fixed member are arranged coaxially while being opposed to each other. An armature is provided on the rotary member, and a yoke is provided on the fixed member. The yoke is provided with a first permanent magnet, a coil, and a second permanent magnet whose magnetic pole is inverted according to a direction of a pulse current flowing through the coil. When setting magnetic poles of the second permanent magnet in such a manner as to form a forward magnetic circuit in the yoke by the first permanent magnet, the magnetic circuit is closed in the yoke. In this situation, the magnetic circuit is not formed between the yoke and the armature. That is, torque does not act between the fixed member and the rotary member. Consequently, the electromagnetic brake is released. When the pulse current is supplied to the coil, magnetic poles of the second permanent magnet are inverted so that the magnetic circuit is formed between the yoke and the armature. Consequently, the fixed member and the rotary member are magnetically attracted to each other. That is, the electromagnetic brake is engaged.

Thus, the electromagnetic brake described in JP-A-H01-303331 is configured so as to selectively exert the torque between the fixed member and the rotary member without bringing those members into contact to each other. For this reason, the electromagnetic brake described in JP-A-H01-303331 may be used as a clutch to selectively connect two rotary members. However, in the electromagnetic brake described in JP-A-H01-303331, the permanent magnet and the coil are arranged in one of the rotary members. That is, if the electromagnetic brake described in JP-A-H01-303331 is used as the clutch, the coil is rotated together with one of the rotary member. In this case, a slip ring is used to supply electricity to the coil by bringing a carbon brush or a wire brush into contact to the ring. However, the slip ring would be frictionally worn thereby reducing a torque capacity of the clutch. For this reason, it is difficult to use the electromagnetic brake described in JP-A-H01-303331 as a clutch in a vehicular powertrain.

Further, in the electromagnetic brake described in JP-A-H01-303331, the rotary member and the fixed member are arranged coaxially while being opposed to each other. That is, the electromagnetic brake described in JP-A-H01-303331 is axially too large to be fitted the powertrain. In addition, is the electromagnetic brake described in JP-A-H01-303331 is used in the powertrain, areas of engagement surfaces are insufficient to ensure an engagement force.

SUMMARY

Aspects of preferred embodiments of the present application have been conceived noting the foregoing technical problems, and it is therefore an object of the present application is to provide a magnetic clutch device having improved durability and reliability without increasing a size in an axial direction.

The embodiment of the present disclosure relates to a magnetic clutch device that engages a first engagement element and a second engagement element with each other to transmit torque by establishing a magnetic circuit between the first engagement element and the second engagement element, and that disengages the first engagement element and the second engagement element from each other to interrupt torque transmission by eliminating the magnetic circuit between the first engagement element and the second engagement element. In order to achieve the above-explained objective, according to the embodiment of the present disclosure, the first engagement element and the second engagement element are arranged concentrically to each other. A fixed member that is not allowed to rotate is arranged in a radially inner side or radially outer side of the first engagement element and the second engagement element while being concentrically to the first engagement element and the second engagement element. The first engagement element includes a first magnet. The fixed member includes a second magnet in which a polarity is switched between a straight polarity and a reversed polarity in accordance with a direction of the magnetic circuit established by the first magnet between the first engagement element and the second engagement element, and a coil that switches the polarity of the second magnet depending on a direction of the current applied thereto. The second engagement element is situated in a radially opposite side of the fixed member across the first engagement element, and the second engagement element is formed of a magnetic body through which the magnetic circuit penetrates. The magnetic circuit circulating between the first engagement element and the second engagement element is eliminated when the polarity of the second magnet is set in the straight polarity.

In a non-limiting embodiment, the magnetic circuit circulating between the first engagement element and the second engagement element may be eliminated by the second magnet to disengage the first engagement element and the second engagement element from each other. The magnetic circuit may be established between the first engagement element and the second engagement element by the second magnet to magnetically attract the first engagement element and the second engagement element to each other.

In a non-limiting embodiment, the fixed member may be situated in the radially inner side of the first engagement element and the second engagement element.

In a non-limiting embodiment, the first engagement element may include an engagement face, the second engagement element may include an engagement face, and the first engagement element and the second engagement element may be magnetically engaged with each other while maintaining a gap between the engagement face of the first engagement element and the engagement face of the second engagement element.

In a non-limiting embodiment, a plurality of protrusions may be formed on the engagement face of the first engagement element in such a manner as to protrude toward the engagement face of the second engagement element. A plurality of protrusions may also be formed on the engagement face of the second engagement element in such a manner as to protrude toward the engagement face of the first engagement element.

In a non-limiting embodiment, the first engagement element may include a first segment and a second segment being opposed to each other in an axial direction. The first magnet may be interposed between the first segment and the second segment. The first engagement element may further include a stopper portion formed on a radially outer portion of each of the first segment and the second segment.

In a non-limiting embodiment, the magnetic clutch device may be arranged in a powertrain of a vehicle. In this case, the fixed member may be fixed to a stationary member, the first engagement element may be connected to a first disc member, the second rotary member may be connected to a second disc member, the first disc member may be connected to a rotary shaft of a first rotary element of a differential mechanism, and the second disc member may be connected to a rotor shaft of a first motor.

In a non-limiting embodiment, the differential mechanism may include the first rotary element, a second rotary element, and a third rotary element. The first rotary element may be connected to the first motor by engaging the first engagement element and the second engagement element, the second rotary element may be connected to an engine, and the third rotary element may be connected to an output member that delivers a drive force to a drive wheel. The vehicle may comprise a second motor connected to a power transmission route between the drive wheel and the third rotary element. The second motor may be driven by an electric power generated by the first motor to generate a drive force to be delivered to the drive wheel.

Thus, the magnet clutch device according to the embodiment of the present disclosure comprises a fixed member that is not allowed to rotate, a first engagement element having the first magnet that is adjacent to the fixed member, and a second engagement element that transmits torque to/from the first engagement element without being contacted to the first engagement element. The fixed member, the first engagement element, and the second engagement element are arranged concentrically to one another. The fixed member comprises the second magnet that switches a direction of the magnetic circuit established between the first engagement element and the second engagement element, and a coil that switches the polarity of the second magnet when a current is applied thereto. Specifically, the polarity of the second magnet is reversed by supplying a current to the fixed member to transmit torque between the first engagement element and the second engagement element. That is, in the magnet clutch device according to the embodiment it is unnecessary to arrange an additional movable member such as a slip ring to supply current to one of the first engagement element and the second engagement. According to the embodiment, therefore, the magnetic clutch device will not be damaged frictionally and hence reliability of the magnetic clutch device can be improved to be used in a powertrain of automobiles.

In addition, since the fixed member, the first engagement element, and the second engagement element are arranged concentrically to one another, a size of the magnetic clutch device in the axial direction can be reduced. According to the embodiment, therefore, the magnetic clutch device may be can be fitted easily into the powertrain of automobiles without increasing a size of the powertrain.

Further, since the second engagement element is situated in the radially opposite side of the fixed member across the first engagement element, a circumferential area of the engagement face of each of the first engagement element and the second engagement element can be increased respectively. According to the embodiment, therefore, a torque transmitting capacity of the magnetic clutch device can be increased to improve the reliability of the magnetic clutch device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Embodiment of the present disclosure will now be explained with reference to the accompanying drawings. Referring now toFIG. 1, there is shown an example of a powertrain of a vehicle Ve using a magnetic clutch device according to the embodiment. A prime mover of the vehicle Ve includes an engine1as a main prime mover, a first motor2, and a second motor3. An output power of the engine1is distributed to the first motor2and to a driveshaft5through a power split mechanism4as a differential mechanism. An electric power generated by the first motor2may be supplied to the second motor3to generate torque, and output torque of the second motor3may be delivered to drive wheels6through the driveshaft5.

The engine1is a conventional internal combustion engine such as a gasoline engine and a diesel engine. Each of the first motor2and the second motor3is a motor-generator that is operated not only as a motor to generate torque by applying electricity thereto, but also as a generator to generate electricity by applying torque thereto. For example, a permanent magnet synchronous motor and an AC motor such as an induction motor may be used individually as the first motor2and the second motor3. The first motor2and the second motor3are connected to a storage device such as a battery and a capacitor through an inverter (neither of which are shown) so that electric power may be supplied to the first motor2and the second motor3from the storage device. The storage device may also be charged with electric powers generated by the first motor2and the second motor3.

The power split mechanism4as a single-pinion planetary gear unit is connected to an output shaft of the engine1to distribute output power of the engine1to the first motor2and to the drive wheels6. The power split mechanism4comprises a sun gear7as a first rotary element, a ring gear8as a third rotary element arranged concentrically with the sun gear7, a plurality of pinion gears10interposed between the sun gear7and the ring gear8, and a carrier9as a second rotary element supporting the pinion gears10in a rotatable manner.

In the power split mechanism4, the carrier9is connected to the output shaft of the engine1. That is, the output shaft of the engine1also serves as an input shaft of the power split mechanism4.

The first motor2is disposed in an opposite side of the engine1across the power split mechanism4, and in the first motor2, a rotor shaft2bthat is rotated integrally with a rotor2ais connected to the sun gear7of the power split mechanism4through an after-mentioned engagement device.

A first drive gear11as an external gear is formed integrally with the ring gear8of the power split mechanism4to serve as an output member, and a countershaft12is arranged in parallel with a common rotational axis of the power split mechanism4and the first motor2. A counter driven gear13is fitted onto one end of the countershaft12(i.e., right side inFIG. 1) to be rotated integrally therewith while being meshed with the first drive gear11, and a counter drive gear (i.e., a final drive gear)14is fitted onto the other end of the countershaft12(i.e., left side inFIG. 1) in such a manner as to be rotated therewith while being meshed with a differential ring gear (i.e., a final driven gear)16of a differential gear unit15as a final reduction. Thus, the ring gear8of the power split mechanism4is connected to the driveshaft5and the drive wheels6through the first drive gear11, the countershaft12, the counter driven gear13, the counter drive gear14, and an output gear train17including the differential ring gear16.

In the powertrain of the vehicle Ve, an output torque of the second motor3can be added to the torque delivered from the power split mechanism4to the drive wheels6through the driveshaft5. To this end, a rotor3aof the second motor3is connected to a rotor shaft3bextending in parallel with the countershaft12to rotate integrally therewith, and a second drive gear18is fitted onto a leading end of the rotor shaft3bto be rotated integrally therewith while being meshed with the counter driven gear13. Thus, the ring gear8of the power split mechanism4and the second motor3are individually connected to the drive wheels6through the second drive gear18, the output gear train17, and the driveshaft5.

In order to selectively connect a rotary shaft7aof the sun gear7to the rotor shaft2b, a clutch device19is arranged in the powertrain of the vehicle Ve. According to the embodiment, a magnetic clutch in which an engagement state is switched by energizing a coil is used as the clutch device19. Specifically, the rotary shaft7aof the sun gear7and the rotor shaft2bare connected to each other to rotate integrally by engaging the clutch device19. InFIG. 1, an upper half of the clutch device19indicates disengagement of clutch device19, and a lower half of the clutch device19indicates engagement of the clutch device19.

Here will be explained a principle for activation of the clutch device19. In the clutch device19, polarity of one of magnets is reversed by applying current to a coil wound around the magnet. Consequently, magnetic attraction is established so that the engagement elements are engaged to each other. That is, the clutch device19may also be called a variable field engagement device. In the clutch device19, rotary members are engaged to each other while keeping an air gap20, that is, without being contacted to each other.

Thus, the clutch device19may be activated without requiring hydraulic pressure, and may be maintained in engagement without supplying current thereto. In addition, since the engagement elements are engaged while maintaining a clearance therebetween, the clutch device19may be prevented from being frictionally damaged without requiring lubrication.

Structure of the clutch device19is illustrated inFIG. 2in more detail. The clutch device19comprises a fixed member21, a first rotary member22as a first engagement element, and a second rotary member23as a second engagement element. In the clutch device19, the first rotary member22and the second rotary member23are selectively rotated integrally with each other and relatively to each other. To this end, a magnetic field is selectively established between the first rotary member22and the second rotary member23to selectively transmit torque between the first rotary member22and the second rotary member23. Specifically, the fixed member21, the first rotary member22, and the second rotary member23are arranged concentrically to one another in order from a rotational center axis O.

The fixed member21as an innermost member of the clutch device19comprises a cylindrical member24, a pair of permanent magnets25, and a coil26interposed between the magnets25to establish a magnetic field. For example, an alnico magnet may be used as individually as each of the magnets25, and polarity of each of the magnets25is individually reversed by energizing the coil26. That is, the North pole and the South pole the magnet25is switched by energizing the coil26. Accordingly, each of the magnets25will be respectively called the “reversible magnet” hereinafter. In other words, the polarity of the reversible magnet25is switched between a straight polarity and a reversed polarity in accordance with a direction of the magnetic field established by another magnet27between the first rotary member22and the second rotary member23. For example, a neodymium magnet which can establish a stronger magnetic force and in which polarity cannot be reversed may be used as the magnet27, and accordingly the magnet27will be called the “non-reversible magnet” hereinafter. Specifically, the polarity of the reversible magnet25is switched by switching a direction of the current supplied to the coil26. Alternatively, the fixed member21may also be arranged in radially outer side of the first rotary member22and the second rotary member23.

The first rotary member22is also a cylindrical member, and situated in radially outer side of the fixed member21. The first rotary member22is divided into a first segment22aand a second segment22bbeing opposed to each other in the axial direction, and the non-reversible magnet27is interposed between the first segment22aand the second segment22b. The non-reversible magnet27is subjected to a centrifugal force resulting from rotation of the first rotary member22. In order to hold the non-reversible magnet27between the first segment22aand the second segment22bof the first rotary member22, a stopper portion28is formed respectively on a radially outer portion of each of the first segment22aand the second segment22bin such a manner as to reduce a clearance between the first segment22aand the second segment22b. In the embodiment, accordingly, the non-reversible magnet27serves as a “first magnet”, and the reversible magnet25serves as a “second magnet”.

An air gap29is maintained between the fixed member21and the first rotary member22, and a magnetic attraction acts between the fixed member21and the first rotary member22. That is, in the clutch device19, the first rotary member22is engaged with the fixed member21while keeping the air gap29, that is, without being contacted to the fixed member21. Here, when the clutch device19is in disengagement, the fixed member21and the first rotary member22may serve as a brake mechanism.

The second rotary member23is also a cylindrical member, and the second rotary member23is situated in radially outer side of the first rotary member22. As describes, the air gap20is also maintained between the first rotary member22and the second rotary member23. Specifically, the air gap20is maintained between an outer circumferential face30aas an engagement face of the first rotary member22and an inner circumferential face30bas an engagement face of the second rotary member23. Both of the first rotary member22and the second rotary member23are formed of magnetic material or magnetic body at least partially so that the magnetic flux created by the non-reversible magnet27penetrates through the outer circumferential face30aof the first rotary member22and the inner circumferential face30bof the second rotary member23. A direction of the magnetic flux is switched by supplying current to the coil26so that a closed magnetic circuit is established between the first rotary member22and the second rotary member23thereby attracting the first rotary member22and the second rotary member23to each other. Thus, in the embodiment, the outer circumferential face30aand the inner circumferential face30bserve as an engagement portion30.

As described, the first rotary member22is engaged with the fixed member21while keeping the air gap29, and with the second rotary member23while keeping the air gap20. Each of the air gaps20and29are individually set as narrow as possible to increase magnetic density thereby generating strong magnetic force. As also described, according to the embodiment, the fixed member21and the second rotary member23are situated radially outer side, and hence the air gap20between the fixed member21and the second rotary member23is also situated radially outer side. That is, a radial distance R between the rotational center axis O and the air gap20is increased. For this reason, a circumferential area S of each of the outer circumferential face30aof the first rotary member22and the inner circumferential face30bof the second rotary member23can be increased respectively. In other words, the circumferential area S of the engagement portion30can be increased. The circumferential area S can be expressed by the following expression:
S=2πR·L;
where L is an axial length of the air gap20.

Thus, the circumferential area S of the engagement portion30is changed depending on the radial distance R, and a torque transmitting capacity of the clutch device19is changed depending on the circumferential area S. In addition, the torque transmitting capacity of the clutch device19may also be changed by altering arrangements of the reversible magnet25and the non-reversible magnet27. To this end, for example, a plurality of the reversible magnet25and the non-reversible magnet27may be arranged in the circumferential direction (i.e., a rotational direction) while keeping predetermined intervals. In addition, numbers and arrangements of the reversible magnet25and the non-reversible magnet27may be altered depending on a desired torque transmitting capacity of the clutch device19.

As depicted inFIG. 3, the outer circumferential face30aof the first rotary member22and the inner circumferential face30bof the second rotary member23form a salient pole structure31. Specifically, a plurality of protrusions31aindividually having a triangle cross-section are formed on the outer circumferential face30aof the first rotary member22and the inner circumferential face30bof the second rotary member23. In the outer circumferential face30aof the first rotary member22, each of the protrusions31ais tapered toward the inner circumferential face30bof the second rotary member23. On the other hand, in the inner circumferential face30bof the second rotary member23, each of the protrusions31ais tapered toward the outer circumferential face30aof the first rotary member22. In other words, the air gap20is narrowed by the protrusions31a. In the clutch device19, therefore, the magnetic attraction acting between the outer circumferential face30aand the inner circumferential face30bis enhanced by the salient pole structure31to firmly engage the first rotary member22with the second rotary member23.

Here, shape of the protrusion31amay be altered e.g., to have a truncated trapezoidal cross-section. Optionally, the salient pole structure31may also be applied to the air gap29between the fixed member21and the first rotary member22.

FIG. 4shows an example to apply the clutch device19to the powertrain shown inFIG. 1. In the example shown inFIG. 4, the clutch device19is arranged between the casing33as a stationary member and the housing34to selectively engage the rotary shaft7aof the sun gear7with the rotor shaft2b. As described, the fixed member21, the first rotary member22, and the second rotary member23are arranged concentrically to one another in order from the rotational center axis. In the fixed member21, the coil26is interposed between the pair of reversible magnets25, and in the first rotary member22, the non-reversible magnet27is interposed between the first segment22aand the second segment22b.

Specifically, the fixed member21is fixed to the casing33by a fixing member37such as a bolt. The rotary shaft7aof the sun gear7is spliced into a center hole of a first disc member35, and a circumferential edge of the first disc member35is attached to the first rotary member22. The rotor shaft2bis spliced into a center hole of a second disc member36, and a circumferential edge of the second disc member36is attached to the second rotary member23. When the clutch device19is in engagement, the first rotary member22and the second rotary member23are rotated integrally with each other so that the rotary shaft7aof the sun gear7and the rotor shaft2bare rotated integrally with each other. By contrast, when the clutch device19is in disengagement, the first rotary member22and the second rotary member23are rotated relatively to each other so that the rotary shaft7aof the sun gear7and the rotor shaft2bare rotated relatively to each other.

In order to receive an axial load, a thrust bearing39is interposed individually between the first disc member35and the casing33, between the first disc member35and the second disc member36, and between the second disc member36and a rib38formed integrally with the housing34. The first segment22aand the second segment22bare fixed to each other by a fixing member40such as a bolt.

As described, in the clutch device19, polarity of the reversible magnet25is reversed by energizing the coil26to engage the first rotary member22with the second rotary member23. Turning toFIGS. 5A and 5B, there are shown magnetic fluxes in the clutch device19in engagement and in the clutch device19in disengagement. Specifically,FIG. 5Ashows a situation in which the clutch device19is in disengagement, and inFIG. 5A, a magnetic field is indicated by arrows. As known in the art, a magnetic flux flows from the North pole toward the South pole. In the situation shown inFIG. 5A, current is not supplied to the coil26so that the polarities of the reversible magnets25are set in such a manner that the magnetic fluxes flow only between the fixed member21and the first rotary member22. That is, a forward closed magnetic circuit circulating between the fixed member21and the first rotary member22is established. In the vehicle Ve shown inFIG. 1, for example, the clutch device19is brought into engagement when the operating mode of the vehicle Ve is switched from a single-motor mode in which the vehicle Ve is powered only by the second motor3while disconnecting the first motor from the powertrain, to a hybrid mode in which the vehicle Ve is powered by both of the engine1and the motor(s).

In this situation, polarities of the reversible magnets25are reversed by applying current to the coil26as shown inFIG. 5Bso that directions of the magnet fluxes are reversed to establish a reversed closed magnetic circuit P circulating between the first rotary member22and the second rotary member23, and to establish another reversed closed magnetic circuit circulating between the fixed member21and the second rotary member23via the first rotary member22. Consequently, the first rotary member22and the second rotary member23are magnetically attracted to each other, that is, the clutch device19is brought into engagement. In this situation, the clutch device19is brought into disengagement by applying current to the coil26again to reverse the polarities of the reversible magnets25as shown inFIG. 5A.

Here will be explained advantages to be achieved by the clutch device19according to the embodiment. As described, the clutch device19is a reversible magnetic engagement device, and the first rotary member22and the second rotary member23are engaged with each other without being contacted to each other. In the clutch device19, the reversible magnets25are arranged in the fixed member21, and the non-reversible magnet27is arranged in the first rotary member22. In the clutch device19thus structured, current may be supplied to the coil26through a conventional lead wire, and it is unnecessary to supply current to one of the first rotary member22and the second rotary member23using a slip ring or the like. In the clutch device19, therefore, an engagement force of the clutch device19will not be reduced by an unstable contact between the slip ring and a brush. For the reason, reliability of the clutch device19can be improved.

As described, in the clutch device19, the fixed member21, the first rotary member22, and the second rotary member23are arranged concentrically to one another in order from the rotational center axis O. In the clutch device19, therefore, the radial distance R between the rotational center axis O and the air gap20can be increased so that the circumferential area S of the engagement portion30between the fixed member21and the second rotary member23is increased. That is, the torque transmitting capacity of the clutch device19can be increased. The circumferential area S of the engagement portion30is also increased to further increase the torque transmitting capacity of the clutch device19by the stopper portions28formed on the first segment22aand the second segment22bof the first rotary member22.

In addition, since the fixed member21, the first rotary member22, and the second rotary member23are arranged concentrically to one another, a size of the clutch device19in the axial direction can be reduced. In the powertrain shown inFIG. 1, there is an available space in the radial direction and hence the clutch device19can be fitted easily in the powertrain shown inFIG. 1. Thus, according to the embodiment, the torque transmitting capacity of the clutch device19can be increased without increasing a size in the axial direction, and the clutch device19can be fitted easily especially into a powertrain of a vehicle in which an engine is mounted transversely.

Further, the clutch device19may also serve as a brake device in which one of the engagement elements is fixed. For example, the clutch device19adapted to serve as the brake device may be engaged when shifting the operating mode from the hybrid mode in which the vehicle Ve is powered by the engine1and the first motor2to an engine mode in which the vehicle Ve is powered only by the engine1while stopping the rotation of the first motor2. In addition, the clutch device19adapted to serve as the brake device may also be engaged to stop the rotation of the first motor2when the first motor2has to be cooled and when the first motor2has to be protected.

Although the above exemplary embodiments of the present disclosure have been described, it will be understood by those skilled in the art that the present application should not be limited to the described exemplary embodiments, and various changes and modifications can be made within the scope of the present disclosure. For example, the first rotary member22and the second rotary member23may also be contacted to each other when engaged. The clutch device19thus modified may be suitable to be arranged transversely. In this case specifically, the fixed member21, the first rotary member22, and the second rotary member23are arranged in the axial direction.

In addition, the clutch device19may also be used in a vehicle having a geared transmission in which a gear stage is shifted by manipulating a clutch and a brake, or a belt-driven continuously variable transmission in which a speed ratio is varied continuously by varying an effective running diameter of a belt applied to pulleys. Further, the clutch device19may also be used in an electric vehicle powered by a motor, or other industrial machines for transmitting power.