JP2015053840A - Electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To release connection between a drive shaft and a cooling fan when an unexpected external load acts on the cooling fan to prevent the cooling fan from being damaged due to the influence of the external load.SOLUTION: An electric motor includes: an electric motor main body 32 including a rotor 30 and a stator 31; and a cooling fan 33 for cooling the electric motor main body 32, and the electric motor main body 32 includes: a case 36 in which the rotor 30 and the stator 31 are inwardly installed; and a drive shaft 37 concentrically connected to the rotor 30. One end side 37a and the other end side 37b of the drive shaft 37 are respectively extended outwardly from the case 36, and the cooling fan 33 is connected to any one end of the drive shaft 37. The electric motor includes a clutch 400 for operatively connecting the drive shaft 37 and the cooling fan 33 in a normal state, and for, when an external load acts on the cooling fan 33, releasing operative connection between the drive shaft 37 and the cooling fan 33.

Description

  The present invention relates to an electric motor including an electric motor main body including a rotor and a stator, and a cooling fan for cooling the electric motor main body. More specifically, the present invention relates to an electric motor body in which a rotor and a stator are housed in a case, and one end side of a drive shaft concentrically connected to the rotor extends from the case to the outside as an output shaft, and the drive shaft An electric motor body extending from the case to the outside as a connecting shaft, and a cooling fan connected to the connecting shaft of the electric motor body, the cooling fan cooling the electric motor body as the drive shaft rotates Related to the motor.

  In general, as shown in FIG. 4, the electric motor 100 </ b> A includes an electric motor main body 102 including a rotor 100 and a stator 101, a cooling fan 103 that cools the electric motor main body 102, and a cover 104 that covers the cooling fan 103. And a cover 104 arranged so as to be able to take in outside air in an area where 103 is arranged (see, for example, Patent Document 1).

  The electric motor main body 102 includes a motor casing 106 that houses the rotor 100 and the stator 101, and a drive shaft 107 that is concentrically connected to the rotor 100.

  In this type of electric motor main body 102, one end side 107 a of the drive shaft 107 extends outside from the motor casing 106 as an output shaft connected to a load device (for example, a pump), and the other end side of the drive shaft 107. Reference numeral 107 b extends from the motor casing 106 to the outside as a connecting shaft connected to the cooling fan 103. In general, the drive shaft 107 is rotatably supported by a bearing 108 disposed in the motor casing 106.

  The cooling fan 103 is disposed outside the motor casing 106 of the electric motor main body 102 and is connected to the drive shaft 107 (connection shaft 107b). As a result, the cooling fan 103 takes in outside air and sends the outside air as cooling air to the side of the electric motor body 102 as the electric motor body 102 is driven (rotation of the drive shaft 107).

JP 2011-35950 A

  By the way, since the cooling fan 103 is disposed outside the motor casing 106 of the electric motor main body 102, an unexpected external load may act on the cooling fan 103 in this type of electric motor.

  For example, a foreign object such as a string may be sucked with the cooling fan 103 and the foreign object may be entangled with the cooling fan 103. In this case, although the electric motor main body 102 is driven, the entanglement of foreign matters may act as an unexpected external load that prevents the cooling fan 103 from rotating, resulting in damage to the cooling fan 103. .

  In addition, the electric motor 100A is provided with a flood-proof type in which the electric motor main body 102 has a watertight structure and the electric motor main body 102 can continue to be driven even if it is submerged by a flood or the like. As a result of the water pressure acting on the cooling fan 103 outside the electric motor body 102 as an unexpected external load that prevents the cooling fan 103 from rotating, the cooling fan 103 is damaged as in the above case. Sometimes.

  Therefore, the conventional electric motor 100A has a problem that it cannot be used as a result of the cooling function of the electric motor main body 102 being lost.

  Therefore, in view of the above problems, the present invention releases the connection between the drive shaft and the cooling fan when an unexpected external load acts on the cooling fan, and the cooling fan is damaged due to the external load. It aims at providing the electric motor which can prevent.

  An electric motor according to the present invention includes an electric motor main body including a rotor and a stator, and a cooling fan for cooling the electric motor main body, and the electric motor main body includes a case that houses the rotor and the stator, and a drive concentrically connected to the rotor. In a motor having a shaft, one end side and the other end side of the drive shaft extending from the case to the outside, and a cooling fan connected to one end of the drive shaft, the drive shaft and the cooling fan are normally connected. While being operatively connected, a clutch is provided that releases the operative connection between the drive shaft and the cooling fan when an external load acts on the cooling fan.

  According to such a configuration, the clutch operatively connects the drive shaft and the cooling fan in a normal state. As a result, the rotational torque of the drive shaft of the electric motor main body is transmitted to the cooling fan. As a result, the cooling fan rotates and sends cooling air to the electric motor main body. Therefore, even if the motor body generates heat due to the rotation of the rotor in the case, it is effectively cooled and the performance of the motor can be maintained. On the other hand, when an unexpected external load acts on the cooling fan, the clutch releases the operative connection between the drive shaft and the cooling fan. Thereby, the rotational torque of the drive shaft of the electric motor main body is not transmitted to the cooling fan, and it is possible to prevent the cooling fan to which an external load is applied from being damaged.

  Moreover, as one aspect of the electric motor according to the present invention, the electric motor main body is preferably a submersible type in which the case is formed liquid-tight and the space between the case and the drive shaft is liquid-tight.

  According to such a configuration, water intrusion into the case is prevented, so that the electric motor main body can be continuously driven even during flooding.

  Further, as another aspect of the electric motor according to the present invention, the clutch is connected to the first clutch body connected to either the drive shaft or the cooling fan of the electric motor main body, and to either the drive shaft or the cooling fan of the electric motor main body. A second clutch body to be coupled, the second clutch body provided to be movable in the axial direction of the drive shaft, and an urging member that urges the second clutch body toward the first clutch body. The first clutch body and the second clutch body are in close contact with each other by the urging force of the urging member to transmit the rotational torque of the drive shaft, while the external load acts on the cooling fan. A slip occurs between the closely contacting surfaces to make it impossible to transmit the rotational torque of the drive shaft.

  According to such a configuration, the clutch (the first clutch body and the second clutch body) normally transmits the rotational torque of the drive shaft to the cooling fan to rotate the cooling fan. On the other hand, when an external load is applied to the cooling fan, slippage occurs between the close contact surfaces of the first clutch body and the second clutch body, thereby preventing the rotational torque of the drive shaft from being transmitted to the cooling fan. . When the external load on the cooling fan is removed, the second clutch body is urged toward the first clutch body by the urging member, and the rotational torque of the drive shaft is changed between the first clutch body and the second clutch body. Communicated in close proximity. Thereby, a drive shaft and a cooling fan rotate integrally. That is, the clutch self-returns the connection between the electric motor main body and the cooling fan. Accordingly, the drive can be continuously performed without any human intervention during normal state or return from an emergency.

  As described above, according to the present invention, when an unexpected external load acts on the cooling fan, the connection between the drive shaft and the cooling fan is released, and the cooling fan is damaged due to the external load. Can prevent such an excellent effect.

FIG. 1 is a cut front view of an electric pump including an electric motor according to an embodiment of the present invention as a drive source. FIG. 2 is an enlarged cross-sectional view of a main part of the electric motor according to the embodiment. 3A and 3B are enlarged cross-sectional views showing a modification of the main part of the electric motor according to the embodiment. FIG. 4 is a cross-sectional view showing a conventional electric motor.

  An electric motor according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. In this embodiment, an electric pump including an electric motor as a drive source will be described as an example. For example, as shown in FIG. 1, the electric pump 1 includes a pump 2, an electric motor 3 that drives the pump 2, and a connecting member 4 that connects the pump 2 and the electric motor 3.

  The pump 2 is a centrifugal pump. The pump 2 includes a blade body 20 and a shaft body 21 connected to the blade body 20. The shaft body 21 is a rotation center of the blade body 20, a blade housing chamber 22 for housing the blade body 20, and a blade. The pump casing 25 includes a suction port 23 and a discharge port 24 that communicate with the storage chamber 22, and includes a pump casing 25 that supports the shaft body 21 connected to the blade body 20.

  One end portion of the shaft body 21 is connected to the blade body 20 in the blade housing chamber 22, and the other end side of the shaft body 21 extends outward from the pump casing 25. More specifically, in the pump 2, the suction port 23 and the shaft body 21 are disposed concentrically, and the shaft body 21 extends to the outside from the side opposite to the suction port 23 in the pump casing 25. Accordingly, a bearing 26 that supports the shaft body 21 is mounted at a position symmetrical to the suction port 23 of the pump casing 25. Further, as the shaft body 21 extends from the pump casing 25 to the outside, the gland packing P <b> 1 is disposed between the shaft body 21 and the pump casing 25. Thereby, the liquid sucked into the blade accommodating chamber 22 from the suction port 23 is led out to the discharge port 24 without leaking outside.

  The electric motor 3 includes an electric motor main body 32 including a rotor 30 and a stator 31, and a cooling fan 33 that cools the electric motor main body 32. Furthermore, the electric motor 3 includes an inner cover 34 that covers the electric motor main body 32 and the cooling fan 33, and an outer cover 35 that covers the inner cover 34.

  The electric motor main body 32 includes a motor casing 36 that houses the rotor 30 and the stator 31, and a drive shaft 37 that is concentrically connected to the rotor 30.

  Bearings 38 and 39 that support the drive shaft 37 are mounted on the motor casing 36. A plurality of fins 36 a extending in the same direction as the drive shaft 37 are disposed on the outer peripheral surface of the motor casing 36 in the circumferential direction. A connection flange 360 for connecting the connecting member 4, the inner cover 34, and the outer cover 35 is provided at one end of the motor casing 36.

  More specifically, the motor casing 36 includes a casing body 361 that accommodates the rotor 30 and the stator 31, and a connection flange 360 that is connected to the casing body 361. The casing body 361 includes a cylindrical outer peripheral wall portion 361a, a first closing portion 361b that closes one end opening of the outer peripheral wall portion 361a, and a second closing portion 361c that closes the other end opening of the outer peripheral wall portion 361a. .

  The stator 31 is fixed to the inner periphery of the outer peripheral wall portion 361a, and the rotor 30 is disposed in the stator 31. On the outer periphery of the outer peripheral wall portion 361a, a plurality of fins 36a are provided protruding at intervals in the circumferential direction.

  Bearings 38 and 39 are fitted to the first closing portion 361b and the second closing portion 361c so as to be concentric or substantially concentric with the outer peripheral wall portion 361a. In addition, annular gland packings P2 and P3 are fitted to the first closing portion 361b and the second closing portion 361c so as to be concentric with the bearings 38 and 39. Thus, the bearings 38 and 39 rotatably support the drive shaft 37, and the gland packings P2 and P3 allow liquid (mainly water) to enter the motor casing 36 from between the drive shaft 37 and the motor casing 36. Prevent inflow. That is, the electric motor 3 according to the present embodiment is a submersion type that can prevent the water in the electric motor main body 32 (motor casing 36) from being flooded and can continue driving even during submergence.

  The connecting flange 360 is connected to the first closing portion 361b and extends outward from the outer periphery of the outer peripheral wall portion 361a. The inner cover 34 and the outer cover 35 are coupled to the first surface of the coupling flange 360 on the motor casing 36 side. On the other hand, the connecting member 4 is connected to the second surface opposite to the first surface of the connecting flange 360.

  The connection flange 360 includes a first ventilation hole H1 formed between the outer cover 35 and the inner cover 34, which will be described later, and a first ventilation hole H1 that communicates with the outside, an outer peripheral wall portion 361a, and the inner cover 34. And a second ventilation hole H2 that communicates the secondary side ventilation path R2 (described later) and the outside.

  As described above, the drive shaft 37 is rotatably supported by the bearings 38 and 39 attached to the motor casing 36. One end side 37a of the drive shaft 37 extends from one end of the motor casing 36 to the outside as an output shaft connected to the input shaft of the load device (in this embodiment, the shaft body 21 of the pump 2). . The other end side 37 b of the drive shaft 37 extends from the other end of the motor casing 36 to the outside as a connecting shaft connected to the cooling fan 33.

  One end side (output shaft) 37 a of the drive shaft 37 is disposed concentrically with the shaft body 21 of the pump 2, and is connected to the shaft body 21 via a coupling C.

  The cooling fan 33 includes a main shaft portion 330 and a fan portion 331 connected to the main shaft portion 330. The fan portion 331 includes a disc portion 331a disposed concentrically with the main shaft portion 330, and a plurality of surfaces extending from one surface of the disc portion 331a (a surface opposite to the surface connected to the main shaft portion 330). And a blade 331b.

  In addition to the above configuration, the electric pump (electric motor) 1 according to the present embodiment operatively connects the drive shaft 37 and the cooling fan 33 in a normal state while an external load acts on the cooling fan 33. A clutch 400 for releasing the operative connection between the drive shaft 37 and the cooling fan 33 is provided.

  As shown in FIG. 2, the clutch 400 includes a first clutch body 401 connected to the cooling fan 33 and a second clutch body 402 connected to the drive shaft 37 of the electric motor body 32, and the shaft center of the drive shaft 37. A second clutch body 402 movably provided in the direction, and a biasing member 403 that biases the second clutch body 402 toward the first clutch body 401.

  In the normal state, the first clutch body 401 and the second clutch body 402 are in close contact with each other by the urging force of the urging member 403 to transmit the rotational torque of the drive shaft 37, while when an external load is applied to the cooling fan 33. Then, slip occurs between the close contact surfaces so that the rotational torque of the drive shaft 37 cannot be transmitted.

  This will be described more specifically. As shown in FIG. 2, the first clutch body 401 is connected to the main shaft portion 330 of the cooling fan 33 and has a close contact surface (clutch surface) S <b> 1 facing the electric motor main body 32 side. Accordingly, in the present embodiment, the other end side (the connecting shaft 37b) of the drive shaft 37 is inserted into the main shaft portion 330 of the first clutch body 401 and the cooling fan 33. Further, the cooling fan 33 is rotatably supported by a bearing 404 fitted on the drive shaft 37. The cooling fan 33 is fixed by a bolt B as a retaining stopper.

  The second clutch body 402 has a close contact surface (clutch surface) S2 facing the first clutch body 401 side. The second clutch body 402 is inserted through the other end side of the drive shaft 37 (connection shaft 37b). The second clutch body 402 is provided so as to be movable in the axial direction with respect to the drive shaft 37 and immovable in the circumferential direction. The second clutch body 402 includes a plurality of grooves 402b formed in the axial direction on the inner surface of the cylindrical portion 402a of the second clutch body 402, and a plurality of radially protruded projections on the outer peripheral surface of the drive shaft 37. The locking piece 370 is freely movable in the axial direction with respect to the drive shaft 37 by the locking piece 370 loosely inserted in the groove 402b, and is configured to rotate integrally with the drive shaft 37.

  A coil spring is employed for the urging member 403. The coil spring 403 is fitted on the other end side (the connecting shaft 37 b) of the drive shaft 37 and biases the second clutch body 402 toward the first clutch body 401. In the present embodiment, the biasing member 403 is provided between the step portion formed by forming the other end side (the connecting shaft 37 b) of the drive shaft 37 with a smaller diameter than the one end side and the second clutch body 402. , And the urging force of the urging member 403 acts on the second clutch body 402.

  Returning to FIG. 1, the inner cover 34 includes an inner cylindrical wall portion 340 that covers the outer periphery of the motor casing 36, and an annular portion 341 that is connected to one end of the inner cylindrical wall portion 340. The inner cylindrical wall portion 340 of the inner cover 34 is set to have a larger diameter than the outer peripheral wall portion 361 a of the motor casing 36. The other end of the inner cylindrical wall 340 is connected to the first surface of the connecting flange 360 so that the inner cylindrical wall 340 is concentric with the outer peripheral wall 361 a of the motor casing 36. Thereby, secondary side ventilation path R2 is formed by the clearance gap between the outer peripheral wall part 361a and the inner side cover 34. FIG.

  The outer cover 35 includes an outer cylindrical wall portion 350 that covers the outer periphery of the inner cylindrical wall portion 340 of the inner cover 34, and a side wall portion 351 that closes one end opening of the outer cylindrical wall portion 350. The outer cylindrical wall portion 350 of the outer cover 35 is set to have a larger diameter than the inner cylindrical wall portion 340 of the inner cover 34 and is longer in the axial direction than the inner cylindrical wall portion 340 of the inner cover 34. Is set longer. The outer cover 35 has the other end of the outer cylindrical wall 350 coupled to the first surface of the coupling flange 360 so that the outer cylindrical wall 350 is concentric with the inner cylindrical wall 340 of the inner cover 34. Is done. Thereby, the primary side ventilation path R1 is formed by the gap between the inner cover 34 and the outer cover 35. Since the annular portion 341 is connected to one end portion of the inner cylindrical wall portion 340 of the inner cover 34, the primary side ventilation path R1 and the secondary side ventilation path R2 are connected via holes defined by the annular portion 341. The air flow path R for cooling the fins 36a of the motor casing 36 is formed.

  The connecting member 4 includes a cylindrical main body 40 that surrounds one end side (driving shaft 37 a side) of the drive shaft 37 that extends outward from the motor casing 36, and a flange-shaped first member that is connected to one end of the main body portion 40. A first connecting portion 41 connected to the pump casing 25 of the pump 2, and a flange-like second connecting portion 42 connected to the other end of the main body portion 40. A second connecting portion connected to the motor casing. In the present embodiment, the connecting member 4 includes a bearing 43 that partially supports the drive shaft 37 in the main body 40.

  The connecting member 4 according to the present embodiment connects the second connecting portion 42 to the connecting flange 360 in a state where the second connecting portion 42 is overlapped with the second surface of the connecting flange 360 of the motor casing 36. Yes. Accordingly, the second connection portion 42 has ventilation holes H3 and H4 at positions corresponding to the first ventilation hole H1 and the second ventilation hole H2 of the coupling flange 360.

  Thus, when the cooling fan 33 rotates, the outside air is taken into the primary side ventilation path R1, and the outside air is discharged to the outside through the secondary side ventilation path R2. That is, outside air passes through the outer periphery of the motor casing 36 and cools the plurality of fins 36a.

  Next, a usage mode of the electric motor according to the present embodiment will be described. In a normal state, the clutch 400 operatively connects the drive shaft 37 and the cooling fan 33. More specifically, the first clutch body 401 and the second clutch body 402 are brought into close contact with each other by the urging force of the urging member 403, and the rotational torque of the drive shaft 37 is transmitted to the cooling fan 33. As a result, the cooling fan 33 rotates and sends cooling air to the electric motor main body 32. That is, outside air is taken into the primary side ventilation path R1, the outside air is discharged to the outside through the secondary side ventilation path R2, and the outside air passes through the outer periphery of the motor casing 36 to cool the plurality of fins 36a. ing. Therefore, even if the motor main body 32 generates heat due to the rotation of the rotor 30 in the motor casing 36, the motor 3 is effectively cooled and the performance of the motor 3 can be maintained. Further, by the rotation of the blade body 20 of the pump 2, the liquid sucked into the blade housing chamber 22 from the suction port 23 of the pump casing 25 is led out to the discharge port 24 without leaking outside.

  On the other hand, when an unexpected external load acts on the cooling fan 33, the clutch 400 releases the operative connection between the drive shaft 37 and the cooling fan 33. More specifically, slip occurs between the close contact surfaces of the first clutch body 401 and the second clutch body 402, and the rotational torque of the drive shaft 37 cannot be transmitted. Thereby, the rotational torque of the drive shaft 37 of the electric motor main body 32 is not transmitted to the cooling fan 33, and it is possible to prevent the cooling fan 33 on which an external load is applied from being damaged.

  When the external load on the cooling fan 33 is removed, the second clutch body 402 is biased toward the first clutch body 401 by the biasing member 403, and the rotational torque of the drive shaft 37 is changed to the first clutch body 401. And the second clutch body 402 are transmitted in close contact. Thereby, the drive shaft 37 and the cooling fan 33 rotate integrally. That is, the clutch 400 causes the motor main body 32 and the cooling fan 33 to self-recover. Accordingly, the drive can be continuously performed without any human intervention during normal state or return from an emergency.

  Thus, according to the electric motor according to the present embodiment, when an unexpected external load acts on the cooling fan 33, the connection between the drive shaft 37 and the cooling fan 33 is released, and the influence of the external load It is possible to prevent the cooling fan 33 from being damaged. Further, the clutch 400 self-recovers the connection between the electric motor main body 32 and the cooling fan 33, so that continuous driving is possible at the time of normal state or emergency return.

  In addition, this invention is not limited to the said embodiment, Of course, a various change can be added in the range which does not deviate from the summary of this invention.

  For example, in the case of the above embodiment, the self-returning clutch is used. However, when an unexpected external load acts on the cooling fan 33 without returning, the motor body 32 and the cooling fan 33 A clutch 400A that simply releases the connection may be used.

  As such a clutch 400A, as shown in FIGS. 3A and 3B, for example, a first shaft extending from the main shaft portion 330A toward the drive shaft 37 extends to the main shaft portion 330A of the cooling fan 33A. A clutch body 401A, and a second clutch body 402A fitted to the drive shaft 37 of the electric motor 3, the second clutch body 402A extending from the front end portion of the drive shaft 37 toward the cooling fan 33A. An annular key groove 500 formed in the circumferential direction of the drive shaft 37A of the electric motor 3 and a through hole 501 formed in a direction orthogonal to the key groove 500, the first clutch body 401A and the second clutch A through hole 501 formed through the body 402A and a shear pin 502 inserted through the through hole 501 are provided. In the figure, 331aA is a disk portion of the cooling fan 33A, and 331bA is a blade of the cooling fan 33A.

  Then, the convex first clutch body 401A is inserted into the concave portion 403A formed by the distal end portion of the drive shaft 37 and the second clutch body 402A, and the shear pin 502 is inserted through the through hole 501. The cooling fan 33A rotates together with the cooling fan 33A.

  The shear pin 502 is provided in such a size that it is cut or deformed from the keyway 500 by a shearing stress applied to the shear pin 502 when an unexpected external load is applied. Although not shown, the shear pin 502 has an annular O-ring groove formed at both ends exposed from the through hole 501 of the drive shaft 37A of the electric motor 3, and an O-ring is attached to the O-ring groove. Thus, the shear pin 502 is prevented from coming off from the drive shaft 37A.

  According to the clutch 400A having such a configuration, when an unexpected external load acts on the drive shaft 37, the shear pin 502 is cut by the unexpected external load, so that the main shaft portions of the drive shaft 37 and the cooling fan 33A are cut. The integral rotation with 330A is released. Thereby, damage to the cooling fan 33A can be prevented.

  In the above embodiment, a centrifugal pump has been described as an example of the pump 2. However, not only a centrifugal pump but also an axial flow pump, a mixed flow pump, and a cross flow pump may be used.

  Further, in the case of the above-described embodiment, annular ground packings P2 and P3 are fitted so as to be concentric with the bearings 38 and 39, so that the motor casing 36 is inserted between the drive shaft 37 and the motor casing 36. Although the liquid (mainly water) is prevented from flowing in, this submerged structure can also be applied to the structure of the bearing portion of the drive shaft 107 of the general electric motor 100A shown in FIG.

  DESCRIPTION OF SYMBOLS 1 ... Electric pump, 3 ... Electric motor, 33, 33A ... Cooling fan, 330, 330A ... Main shaft part, 36 ... Case (motor casing), 37 ... Drive shaft, 400, 400A ... Clutch, 401, 401A ... First clutch body 402, 402A ... second clutch body, 403 ... urging member, 403A ... concave portion, 500 ... keyway, 501 ... through hole, 502 ... shear pin

Claims (3)

  An electric motor main body including a rotor and a stator, and a cooling fan for cooling the electric motor main body. The electric motor main body includes a case that houses the rotor and the stator, and a drive shaft that is concentrically connected to the rotor. Each of the one end side and the other end side of the motor extends outside from the case, and in the motor in which the cooling fan is connected to one end of the drive shaft, while the drive shaft and the cooling fan are operatively connected in a normal state, An electric motor comprising a clutch for releasing the operative connection between the drive shaft and the cooling fan when an external load acts on the cooling fan.   2. The electric motor according to claim 1, wherein the electric motor main body is a submersible type in which a case is formed in a liquid-tight manner and a space between the case and the drive shaft is formed in a liquid-tight manner.   The clutch is a first clutch body connected to either the drive shaft of the motor body or the cooling fan, and a second clutch body connected to either the drive shaft of the motor body or the cooling fan, and is driven A second clutch body movably provided in the axial direction of the shaft, and a biasing member that biases the second clutch body toward the first clutch body, the first clutch body and the second clutch body are In a normal state, the rotational torque of the drive shaft is transmitted in close contact with the urging force of the urging member. On the other hand, when an external load is applied to the cooling fan, slippage occurs between the close contact surfaces of the drive shaft. The electric motor according to claim 1 or 2, wherein rotational torque cannot be transmitted.

Images