JP6163780B2 - Electromagnetic clutch - Google Patents

Description

  The present invention relates to a friction member and an electromagnetic clutch including the friction member.

  Conventionally, an electromagnetic clutch that frictionally engages a pair of friction members by the magnetic force of an electromagnetic coil is known. Some of such electromagnetic clutches have a configuration for reducing drag torque due to residual magnetism or the like of the friction member when the electromagnetic coil is not energized (see, for example, Patent Documents 1 and 2).

  In the electromagnetic clutch described in Patent Document 1, a disc spring is disposed via a bearing between a yoke that supports the electromagnetic coil and an armature that is attracted to the yoke by the magnetic force of the electromagnetic coil and frictionally engages the yoke. The disk spring is configured to urge the armature in a direction away from the yoke.

  In the electromagnetic clutch described in Patent Document 2, a rotor is disposed between a yoke supporting an electromagnetic coil and an armature, and the armature is frictionally engaged with the rotor by the magnetic force of the electromagnetic coil, whereby torque transmission coupled to the armature is performed. Torque is transmitted between the member and the rotor. A ring-shaped leaf spring is disposed between the armature and the torque transmission member, and the armature and the torque transmission member are connected by the leaf spring, and the armature is biased in a direction away from the rotor.

JP 2011-144834 A JP 2011-1112060 A

  All of these electromagnetic clutches can reduce drag torque by arranging spring members. On the other hand, the arrangement of spring members increases the number of assembly steps and the number of parts. End up.

  Accordingly, an object of the present invention is to provide a friction member and an electromagnetic clutch that can reduce drag torque without providing a dedicated component such as a spring member for reducing drag torque.

The present invention, in order to achieve the above object, provides a conductive magnetic clutch [1] to [2].

[1] An electromagnetic coil, a casing including a yoke made of a soft magnetic material that holds the electromagnetic coil, and a first friction member and a second friction member that are housed in the casing and frictionally engage with each other by the magnetic force of the electromagnetic coil. The first friction member is made of a soft magnetic material having an inner friction portion and an outer friction portion connected in a radial direction via two connection portions provided at positions symmetrical with respect to the rotation axis, The outer friction portion is composed of two semicircular arc portions having the two coupling portions at both ends in the circumferential direction, and at least a part protrudes toward the second friction member from the friction surface of the inner friction portion. The yoke is bent so that the inner peripheral surface thereof faces the outer peripheral surface of the outer friction portion in the radial direction, and a magnetic flux flows between the inner and outer peripheral surfaces when the electromagnetic coil is energized, so that the electromagnetic coil is not energized. Sometimes, the first Electromagnetic clutch and said second friction member and the inner friction of the member is spaced apart by the elasticity of the outer friction part.

[2] The electromagnetic clutch according to [1], wherein a gap formed between the inner friction portion and the outer friction portion functions as a magnetic shielding portion that prevents a short circuit of magnetic flux .

  According to the present invention, it is possible to reduce drag torque without providing a spring member for reducing drag torque.

Sectional drawing which shows the structural example (at the time of non-operation) of the electromagnetic clutch which concerns on embodiment. Sectional drawing which shows the structural example (at the time of an action | operation) of the electromagnetic clutch which concerns on embodiment. The input side clutch plate is shown, (a) is sectional drawing, (b) is a top view, (c) is a side view. The top view which shows an output side clutch plate. The graph which shows the experimental result for confirming the effect of the electromagnetic clutch which concerns on embodiment.

[Embodiment]
Embodiments of the present invention will be described with reference to FIGS.

  1 and 2 are cross-sectional views showing a configuration example of the electromagnetic clutch according to the present embodiment. 3A and 3B show an input side clutch plate of the electromagnetic clutch, in which FIG. 3A is a cross-sectional view, FIG. FIG. 4 is a plan view showing an output side clutch plate of the electromagnetic clutch. FIG. 1 shows the non-operating state of the electromagnetic clutch, and FIG. 2 shows the operating state of the electromagnetic clutch. Fig.3 (a) is sectional drawing of the input side clutch plate in the AA line of FIG.3 (b).

(Overall configuration of electromagnetic clutch 1)
As shown in FIGS. 1 and 2, the electromagnetic clutch 1 has an input side clutch plate 2 as a first friction member, an output side clutch plate 3 as a second friction member, and an electromagnetic coil 4 as main components. I have. This electromagnetic clutch 1 is configured as a single-plate clutch that detachably transmits torque between one input-side clutch plate 2 and one output-side clutch plate 3.

  The input side clutch plate 2 and the output side clutch plate 3 are made of, for example, a soft magnetic material mainly composed of iron. Further, the input side clutch plate 2 and the output side clutch plate 3 share the rotation axis O, and can be relatively rotated on the rotation axis O.

  The electromagnetic clutch 1 also includes a yoke 11 that holds the electromagnetic coil 4 and a case element 12 that forms a receiving space S for the input side clutch plate 2 and the output side clutch plate 3 together with the yoke 11. The yoke 11 and the case element 12 are fixed to each other by a plurality of bolts 80 to constitute the casing 10. The yoke 11 and the case element 12 are made of a soft magnetic material such as iron. The housing space S of the casing 10 is filled with lubricating oil (not shown) at a filling rate of 50%, for example.

  The yoke 11 is formed with an annular recess 11 a that houses the electromagnetic coil 4. The electromagnetic coil 4 accommodated in the annular recess 11 a is prevented from coming off by a snap ring 111. A current is supplied to the electromagnetic coil 4 from a control device (not shown) via an electric wire 41.

  The electromagnetic clutch 1 has an input member 5 to which the input shaft 91 is fitted and an output member 6 to which the output shaft 92 is fitted. The input member 5 includes a bottomed cylindrical tube portion 50 having a spline fitting portion 50a formed on the inner peripheral surface, and a flange portion that protrudes outward from the tube portion 50 at one end portion on the output member 6 side. 51 in an integrated manner. A screw hole that is screwed into a bolt 82 for fixing a bearing support member 81 described later is formed in the bottom portion 500 of the tube portion 50.

  A spline fitting portion 91a formed on the outer peripheral surface of the input shaft 91 is fitted to the spline fitting portion 50a of the cylindrical portion 50 so as to be movable in the axial direction and not relatively rotatable. A spline fitting portion 51 a for connecting the input member 5 and the input side clutch plate 2 so as not to be relatively rotatable is formed on the outer peripheral surface of the flange portion 51.

  The output member 6 includes a bottomed cylindrical tube portion 60 having a spline fitting portion 60a formed on the inner peripheral surface, and a flange portion that protrudes outward from the tube portion 60 at one end portion on the input member 5 side. 61 is integrated. A spline fitting portion 92a formed on the outer peripheral surface of the output shaft 92 is fitted to the spline fitting portion 60a of the cylindrical portion 60 so as to be movable in the axial direction and not relatively rotatable. In the accommodation space of the output shaft 92 in the cylindrical portion 60, the end portion on the flange portion 61 side is plugged with a bottom portion 600.

  A spline fitting portion 61 a for connecting the output member 6 and the output side clutch plate 3 so as not to be relatively rotatable is formed on the outer peripheral surface of the flange portion 61. The inside of the collar portion 61 is formed hollow, and a bottomed cylindrical bearing support member 81 and two ball bearings 731 and 732 disposed on the outer periphery of the bearing support member 81 are accommodated in the space inside the collar portion 61. Has been. The bearing support member 81 integrally includes a bottom portion 811 and a cylindrical portion 812, and the bottom portion 811 is fixed to the bottom portion 500 of the input member 5 with a bolt 82. In the ball bearings 731 and 732, each inner ring is fitted to the outer peripheral surface of the cylindrical portion 812 of the bearing support member 81, and each outer ring is fitted to the inner peripheral surface of the flange portion 61.

  The input member 5 is rotatably supported by the yoke 11 via a seal bearing 71. A cylindrical spacer 83 is disposed between the inner ring of the seal bearing 71 and the input side clutch plate 2.

  The output member 6 is rotatably supported by the case element 12 via a seal bearing 72. A cylindrical spacer 84 is disposed between the inner ring of the seal bearing 72 and the output side clutch plate 3. Between the output side clutch plate 3 and the spacer 84 and between the spacer 84 and the inner ring of the seal bearing 72, a plurality of shims 851, 852, 861, and 862 for adjusting the gap are interposed. The spacer 84 and the plurality of shims 851, 852, 861, 862 regulate the axial movement of the output side clutch plate 3 toward the output shaft 92 side.

(Configuration of input side clutch plate 2)
As shown in FIG. 3, the input side clutch plate 2 is formed with an inner slit 201 and an outer slit 202 concentrically around the rotation axis O. The inner slit 201 and the outer slit 202 are formed as gaps that penetrate the input side clutch plate 2 in the thickness direction (axial direction).

  The input side clutch plate 2 is frictionally engaged with the output side clutch plate 3 on the inner side of the inner slit 201 and the base portion 20 formed with the spline fitting portion 20a to be fitted to the spline fitting portion 51a of the input member 5. The first friction portion 21 formed with the first friction surface 21a and the second friction portion 22 formed with the second friction surface 22a frictionally engaged with the output side clutch plate 3 between the inner slit 201 and the outer slit 202. And a third friction portion 23 formed with a third friction surface 23 a that frictionally engages with the output side clutch plate 3 outside the outer slit 202.

  In the input side clutch plate 2, the first to third friction portions 21 to 23 have a thickness of 5 mm, for example, and the third friction portion 23 has an outer diameter of 137 mm, for example. The radial width of the inner slit 201 and the outer slit 202 is, for example, 4 mm.

  The input side clutch plate 2 rotates integrally with the input member 5 when the spline fitting portion 20 a of the base portion 20 is fitted to the spline fitting portion 51 a of the input member 5. The outer peripheral surface 23b of the third friction portion 23 in the input side clutch plate 2 faces the inner peripheral surface of the casing 10 (see FIGS. 1 and 2). The third friction part 23 is an aspect of the outer friction part in the present invention, and the second friction part 22 is an aspect of the inner friction part in the present invention.

  The first friction part 21 and the second friction part 22 are connected in the radial direction via two connection parts 241 and 242. The second friction part 22 and the third friction part 23 are connected in the radial direction via two connection parts 251 and 252. One connecting portion 241 and the other connecting portion 242 that connect the first friction portion 21 and the second friction portion 22 are provided at positions symmetrical with respect to the rotation axis O. In addition, one connecting portion 251 and the other connecting portion 252 that connect the second friction portion 22 and the third friction portion 23 are provided at positions symmetrical with respect to the rotation axis O. In the present embodiment, the connecting portions 241, 242, 251, 252 are arranged so that the straight line connecting the two connecting portions 241, 242 and the straight line connecting the two connecting portions 251, 252 are orthogonal to each other in the rotation axis O. Is provided.

  The inner slit 201 includes a first arc-shaped slit 201a and a second arc-shaped slit 201b. The first arcuate slit 201a and the second arcuate slit 201b are terminated by connecting portions 241 and 242 at both ends in the circumferential direction, respectively. The central angles of the first arcuate slit 201a and the second arcuate slit 201b are each approximately 180 °.

  Similarly, the outer slit 202 includes a first arc-shaped slit 202a and a second arc-shaped slit 202b. The first arcuate slit 202a and the second arcuate slit 202b are terminated by connecting portions 251 and 252 at both ends in the circumferential direction. The central angles of the first arcuate slit 202a and the second arcuate slit 202b are each approximately 180 °.

  The third friction portion 23 is bent so that at least a part thereof protrudes toward the output side clutch plate 3 (see FIG. 1) with respect to the friction surface 22 a of the second friction portion 22. In the present embodiment, the third friction portion 23 includes a semicircular first arc portion 231 and a second arc portion 232 having the connecting portions 251 and 252 as both end portions in the circumferential direction. The first arc portion 231 and the second arc portion 232 can be formed by, for example, forming the outer slit 202 and applying an external force to cause plastic deformation.

  The third friction part 23 (the first arc part 231 and the second arc part 232) presses the output side clutch plate 3 away from the input side clutch plate 2 due to its elasticity. Accordingly, when the electromagnetic coil 4 is not energized, the first friction portion 21 and the second friction portion 22 of the input side clutch plate 2 and the output side clutch plate 3 are connected to each other as shown in FIG. They are separated in the axial direction by elasticity. In this case, only the central portions in the circumferential direction of the first arc portion 231 and the second arc portion 232 are elastically contacted with the output side clutch plate 3.

(Configuration of output side clutch plate 3)
As shown in FIG. 4, the output side clutch plate 3 is formed with an inner slit 301 and an outer slit 302 concentrically around the rotation axis O. The inner slit 301 is formed as an annular recess that is recessed in the axial direction from the surface facing the input side clutch plate 2. The outer slit 302 is formed as a gap passing through the output side clutch plate 3 in the thickness direction (axial direction). The outer slit 302 includes a first arc-shaped slit 302a and a second arc-shaped slit 302b.

  The output side clutch plate 3 is frictionally engaged with the input side clutch plate 2 on the inner side of the inner slit 301 and the base portion 30 formed with the spline fitting portion 30a to be fitted to the spline fitting portion 61a of the output member 6. The first friction portion 31 formed with the first friction surface 31a and the second friction portion 32 formed with the second friction surface 32a that frictionally engages the input side clutch plate 2 between the inner slit 301 and the outer slit 302. And a third friction portion 33 formed with a third friction surface 33a that frictionally engages with the input side clutch plate 2 outside the outer slit 302.

  More specifically, the first friction surface 31a of the output side clutch plate 3 is in contact with the first friction surface 21a of the input side clutch plate 2, and the second friction surface 32a of the output side clutch plate 3 is in contact with the input side clutch plate 2. The second friction surface 22a comes into contact with the inner peripheral portion. Further, the third friction surface 33a of the output side clutch plate 3 has its inner peripheral side portion in contact with the outer peripheral side portion of the second friction surface 22a of the input side clutch plate 2, and the outer peripheral side of the third friction surface 33a. Is in contact with the third friction surface 23 a of the input side clutch plate 2.

  Between the first arc-shaped slit 302a and the second arc-shaped slit 302b, two coupling portions 341 and 342 that couple the second friction portion 32 and the third friction portion 33 in the radial direction are provided. The two connecting portions 341 and 342 are provided at positions that are symmetric with respect to the rotation axis O.

  The output side clutch plate 3 rotates integrally with the output member 6 when the spline fitting portion 30 a of the base portion 30 is fitted to the spline fitting portion 61 a of the output member 6. Thus, when the input side clutch plate 2 and the output side clutch plate 3 are frictionally engaged, torque is transmitted from the input member 5 to the output member 6, that is, from the input shaft 91 to the output shaft 92.

  The input side clutch plate 2 and the output side clutch plate 3 are frictionally engaged by the magnetic force of the electromagnetic coil 4. When the electromagnetic coil 4 is energized, a magnetic flux flows through the magnetic path M shown in FIG. 2, and the output side clutch plate 3 is attracted to the input side clutch plate 2.

  The magnetic path M includes the yoke 11, the first friction part 21 of the input side clutch plate 2, the first friction part 31 and the second friction part 32 of the output side clutch plate 3, the second friction part 22 of the input side clutch plate 2, It is formed in the 3rd friction part 33 of the output side clutch plate 3, and the 3rd friction part 23 of the input side clutch plate 2, and a rotation magnetic flux flows in this order. The inner and outer slits 201 and 202 of the input-side clutch plate 2 and the inner and outer slits 301 and 302 of the output-side clutch plate 3 function as magnetic shields that prevent short-circuiting of magnetic flux.

  When the electromagnetic coil 4 is energized, as shown in FIG. 2, the third friction portion 23 of the input side clutch plate 2 is elastically deformed, and the third friction surface 23 a is the friction surface 21 a of the first friction portion 21 and the second friction portion. It is located on the same plane as the friction surface 22 a of the portion 22 and is in surface contact with the third friction surface 33 a of the third friction portion 33 of the output side clutch plate 3.

  FIG. 5 is a graph showing the results of an experiment conducted to confirm the effect of the electromagnetic clutch 1 according to the present embodiment.

  In this experiment, an electromagnetic clutch having an input side clutch plate in which the third friction portion is not bent is used as a comparative example, and the drag torque between the electromagnetic clutch according to this comparative example and the electromagnetic clutch 1 according to the present embodiment is calculated. It was measured. The electromagnetic clutch according to the comparative example has the same configuration as that of the electromagnetic clutch 1 according to the present embodiment except that the third friction portion is not bent. The output member 6 was fixed so as not to rotate, and the torque acting on the output member 6 when the input member 5 was rotated while the electromagnetic coil 4 was not energized was measured as drag torque.

  The horizontal axis represents the ratio of the number of rotations to the reference number of rotations, where the reference number of rotations (for example, 1000 rpm) is 1. The vertical axis shows the ratio of the drag torque to the reference torque, where 1 is the drag torque at the reference rotational speed of the electromagnetic clutch according to the comparative example (hereinafter, this drag torque is referred to as “reference torque”). Moreover, in FIG. 5, the measurement result of the drag torque of the electromagnetic clutch which concerns on a comparative example is shown with the broken line, and the measurement result of the drag torque of the electromagnetic clutch 1 which concerns on this Embodiment is shown with the continuous line.

  As shown in FIG. 5, in the electromagnetic clutch according to the comparative example, the drag torque increases as the rotation speed increases. When the rotation speed is 1.75 times the reference rotation speed, the drag torque is 1.61 times. Thus, when the rotational speed is 2.5 times the reference rotational speed, the drag torque is 2.06 times.

  On the other hand, in the electromagnetic clutch 1 according to the present embodiment, when the rotation speed is the reference rotation speed, the drag torque is 0.96 times the reference torque, and when the rotation speed is 1.75 times the reference rotation speed. When the drag torque is 0.86 times the reference torque and the rotation speed is 2.5 times the reference rotation speed, the drag torque is 0.89 times the reference torque.

  As is clear from the experimental results, the drag torque reduction effect by bending the third friction portion 23 is exhibited in all the rotational speed ranges in the measurement range. Further, in the electromagnetic clutch 1 according to the present embodiment, the increase in drag torque due to the increase in the rotational speed is suppressed because of the dynamic pressure effect of the lubricating oil enclosed in the accommodation space S and the input side clutch plate 2. This is considered because the output side clutch plate 3 is separated from each other. That is, as the input side clutch plate 2 rotates, the pressure of the lubricating oil between the third friction surface 23a of the input side clutch plate 2 and the third friction surface 33a of the output side clutch plate 3 is changed to the third friction portion. 23 increases in the vicinity of the center in the circumferential direction of the first arc portion 231 and the second arc portion 232, and the pressure of this lubricating oil separates the input side clutch plate 2 and the output side clutch plate 3 from each other, reducing drag torque. I think that.

(Operation and effect of the embodiment)
According to the above embodiment, when the electromagnetic coil 4 is not energized, that is, when the electromagnetic clutch 1 is not operated, the input side clutch plate 2 and the output side clutch plate 3 are connected to the third friction portion 23 of the input side clutch plate 2. It is spaced apart in the axial direction by the elasticity of. Thus, the drag torque can be reduced without providing a dedicated member for reducing the drag torque (for example, a spring member that separates the input side clutch plate 2 and the output side clutch plate 3).

  The third friction portion 23 of the input side clutch plate 2 includes a semicircular first arc portion 231 and a second arc portion 232, and the first arc portion 231 and the second arc portion 232 are connected to the connecting portions 251, 251. Since it continues in 252, the third friction surface 23 a in the third friction portion 23 is smoothly curved in the circumferential direction. Thereby, even if the input side clutch plate 2 and the output side clutch plate 3 rotate relatively when the electromagnetic coil 4 is not energized, the third friction part 23 is not scratched by the output side clutch plate 3. Furthermore, the input side clutch plate 2 and the output side clutch plate 3 can be separated by the dynamic pressure effect of the lubricating oil sealed in the accommodation space S.

  Further, since the first arc portion 231 and the second arc portion 232 and the output side clutch plate 3 are in contact with each other at two positions sandwiching the rotation axis O when the electromagnetic coil 4 is not energized, the first arc portion 231 and the second arc portion 231. It is possible to prevent the center axis of the output side clutch plate 3 or the input side clutch plate 2 from being inclined with respect to the rotation axis O by the pressing force of the arc portion 232 or the reaction force thereof. Thereby, even when the electromagnetic clutch 1 is not operated, the input shaft 91 or the output shaft 92 can be smoothly rotated.

  Since the third friction part 23 of the input side clutch plate 2 is composed of a semicircular first arc part 231 and a second arc part 232, for example, when the third friction part 23 is composed of three or more arc parts. In comparison, the first arc portion 231 and the second arc portion 232 can be easily bent. Further, the amount of protrusion at the center of the first arc portion 231 and the second arc portion 232 with respect to the bending angle (the amount of protrusion in the axial direction of the second friction portion 22 from the second friction surface 22a) may be made relatively large. It is possible to reliably prevent the input side clutch plate 2 and the output side clutch plate 3 from coming into contact with each other due to, for example, residual magnetism when the electromagnetic coil 4 is not energized.

  As mentioned above, although the friction member and electromagnetic clutch of this invention were demonstrated based on said embodiment, this invention is not limited to said embodiment, In various aspects in the range which does not deviate from the summary. It is possible to implement.

  For example, in the above-described embodiment, the case where the third friction portion 23 of the input side clutch plate 2 is bent so as to protrude toward the output side clutch plate 3 has been described. The third friction portion 33 may be bent so as to protrude toward the input side clutch plate 2.

  Moreover, although the said embodiment demonstrated the case where the inner side slit 201 and the outer side slit 202 were formed in the input side clutch plate 2, and the inner side slit 301 and the outer side slit 302 were formed in the output side clutch plate 3, There is no particular limitation on the number. That is, one slit may be formed in each of the input side clutch plate 2 and the output side clutch plate 3. One slit may be formed only in the input side clutch plate 2.

DESCRIPTION OF SYMBOLS 1 ... Electromagnetic clutch, 2 ... Input side clutch plate, 3 ... Output side clutch plate, 4 ... Electromagnetic coil, 5 ... Input member, 6 ... Output member, 10 ... Casing, 11 ... Yoke, 11a ... Annular recessed part, 12 ... Case Element, 20 ... base, 20a ... spline fitting part, 21 ... first friction part, 21a ... first friction surface, 22 ... second friction part, 22a ... second friction surface, 23 ... third friction part, 23a ... 3rd friction surface, 23b ... outer peripheral surface, 30 ... base, 30a ... spline fitting part, 31 ... 1st friction part, 31a ... 1st friction surface, 32 ... 2nd friction part, 32a ... 2nd friction surface, 33 ... 3rd friction part, 33a ... 3rd friction surface, 41 ... Electric wire, 50 ... Cylinder part, 50a ... Spline fitting part, 51 ... Spear part, 51a ... Spline fitting part, 60 ... Cylinder part, 60a ... Spline fitting Joint part, 61 ... Buttocks, 61a ... Splice Fitting portion 71, 72 ... Seal bearing, 80 ... Bolt, 81 ... Bearing support member, 82 ... Bolt, 83, 84 ... Spacer, 91 ... Input shaft, 91a ... Spline fitting portion, 92 ... Output shaft, 92a ... Spline fitting portion, 111 ... snap ring, 201 ... inner slit, 201a ... first arc-shaped slit, 201b ... second arc-shaped slit, 202 ... outer slit, 202a ... first arc-shaped slit, 202b ... second arc-shaped Slit, 231 ... first arc portion, 232 ... second arc portion, 241, 242, 251,252 ... connecting portion, 301 ... inner slit, 302 ... outer slit, 302a ... first arc-shaped slit, 302b ... second circle Arc-shaped slit, 500, 600 ... bottom, 731, 732 ... ball bearing, 811 ... bottom, 812 ... cylinder, 851, 852, 861, 862 ... shim M ... path, O ... Rotation axis, S ... accommodation space

Claims (2)

An electromagnetic coil;
A casing including a yoke made of a soft magnetic material for holding the electromagnetic coil;
Accommodated in the casing, and a first friction member and the second friction member frictionally engaging by the magnetic force of the electromagnetic coil,
The first friction member is made of a soft magnetic material to have the inner friction portion and an outer friction part connected to the radial direction via the two connection portions provided at symmetrical positions with respect to the rotation axis,
The outer friction portion is composed of two semicircular arc portions having the two connecting portions at both ends in the circumferential direction, and at least a part thereof is closer to the second friction member side than the friction surface of the inner friction portion. Bent to protrude,
The yoke has an inner circumferential surface facing the outer circumferential surface of the outer friction portion in a radial direction, and a magnetic flux flows between the inner and outer circumferential surfaces when the electromagnetic coil is energized,
An electromagnetic clutch in which the inner friction portion and the second friction member of the first friction member are separated by elasticity of the outer friction portion when the electromagnetic coil is not energized.   A gap formed between the inner friction portion and the outer friction portion functions as a magnetic shielding portion that prevents a short circuit of magnetic flux,
  The electromagnetic clutch according to claim 1.

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