Electromagnetic clutch

Abstract

An object is to provide an electromagnetic clutch that can prevent water from entering the electromagnetic clutch from a foreign matter discharge portion when a waterproof cover member that covers a front side end surface of an armature plate is provided with the foreign matter discharge portion that discharges foreign matter such as wear powder to the outside even when the cover member is attached. A cover member (20) that covers a front side end surface (3b) of an armature plate (4) includes a top surface portion (20a) that is provided so as to face the front side end surface (3b) of the armature plate (4), and a cylindrical portion (20b) that extends from the top surface portion (20a). A foreign matter discharge portion (25) is formed so as to protrude toward the outside of the cylindrical portion (20b), and the foreign matter discharge portion (25) includes an opening (25a) that faces a side peripheral surface side of the armature plate (4), an opening (25b) that faces a rear side of a compressor, and an internal space (25c) that communicates with these openings (25a and 25b).

Description

TECHNICAL FIELD

[0001] The present application relates to an electromagnetic clutch for interrupting a rotational force transmitted from a rotational power source such as an engine and a motor to a compressor of an air conditioner for a vehicle, and more particularly to an electromagnetic clutch whose front side is covered with a cover member. BACKGROUND

[0002] For example, as disclosed in PTL 1, a general electromagnetic clutch used in a compressor of an air conditioner for a vehicle includes a rotor rotatably fitted from the outside on an outer periphery of a cylindrical portion of a housing that supports a drive shaft, and the rotor is rotated by receiving a rotational force from a rotational power source such as an engine or a motor; a hub coupled to the drive shaft so as to be unable to rotate with respect to the drive shaft and rotate together with the drive shaft; an armature plate coupled to the hub and disposed so as to face a side end surface of the rotor with a slight gap therebetween; and an exciting coil housed in an inside of an annular space of the rotor.

[0003] Depending on the type and purpose of the vehicle, the installation site of the compressor can be, for example, a severe water-exposed environment such as an environment in which the electromagnetic clutch is likely to be exposed to water because the compressor is installed next to the engine of a rear engine compartment of a bus and the electromagnetic clutch is oriented toward the outside of the vehicle. In this way, when the electromagnetic clutch is exposed to water, the water can enter the bearing for smoothly rotating the rotor, and thus the inside of the bearing can rust. In addition, in a bus, the inside of the rear engine compartment can be cleaned with high-pressure water by a high-pressure cleaning machine, in which case, because water is more likely to enter the bearing of the electromagnetic clutch, rust in the bearing can also be likely to be aggravated. Therefore, as shown in PTL 1, by covering the entire front side end surface of the armature plate of the electromagnetic clutch with a cover member, the electromagnetic clutch can be waterproof.

[0004] On the other hand, in the electromagnetic clutch, because the rotor and the armature plate are frictionally engaged with each other, abrasion powder is generated from the frictional surfaces of the rotor and the armature plate. In order to prevent the abrasion powder from accumulating in the electromagnetic clutch to cause problems related to the operation of the clutch, it is necessary to provide a configuration for discharging the abrasion powder from the inside of the electromagnetic clutch to the outside when the entire front side end surface of the armature plate of the electromagnetic clutch is covered with a cover member. Therefore, PTL 1 discloses a configuration in which a foreign matter discharge opening for discharging foreign matters such as abrasion powder generated in the electromagnetic clutch to the outside is provided in the cover member that covers the entire front side end surface of the armature plate of the electromagnetic clutch.

[0005] REFERENCE LIST

[0006] PATENT LITERATURE

[0007] PTL 1: JP-A-2009-281579 SUMMARY

[0008] TECHNICAL PROBLEM

[0009] However, in the configuration of the cover disclosed in PTL 1, as shown in FIG. 1 of PTL 1, the outer edge portion of the circular plate portion extends from the foreign matter discharge opening toward the outer periphery of the electromagnetic clutch. Therefore, for example, when the engine compartment of a bus is cleaned by a high-pressure cleaning machine as described above, high-pressure water can hit the surface of the outer edge portion of the circular plate portion of the cover on the outer periphery of the cover with respect to the foreign matter discharge opening, and enter the electromagnetic clutch from the foreign matter discharge opening of the cover. Figure 3 A, Figure 3 B and Figure 4 As shown, the outer edge portion of the circular plate portion extends from the foreign matter discharge opening toward the outer periphery of the electromagnetic clutch. Therefore, for example, when the engine compartment of a bus is cleaned by a high-pressure cleaning machine as described above, high-pressure water can hit the surface of the outer edge portion of the circular plate portion of the cover on the outer periphery of the cover with respect to the foreign matter discharge opening, and enter the electromagnetic clutch from the foreign matter discharge opening of the cover.

[0010] The present application has been made to solve the above problem, and an object of the present application is to provide an electromagnetic clutch that is capable of preventing water from entering the electromagnetic clutch from a foreign matter discharge portion when the cover is attached, even when the cover that covers the front side end surface of the armature plate is provided with the foreign matter discharge portion that discharges foreign matters such as abrasion powder to the outside.

[0011] PROBLEM SOLUTION

[0012] To achieve the above object, the electromagnetic clutch according to claim 1 includes a rotor that is rotatably supported by a housing of a compressor and is configured to receive a rotational force from a rotational power source to rotate, a hub that is coupled to a drive shaft of the compressor so as to be unable to rotate with respect to the drive shaft and rotate together with the drive shaft, an armature plate that is coupled to the hub and has a rear side end surface that is disposed to face a friction wall of the rotor while having a gap therebetween, an exciting coil that is supported by the housing of the compressor, housed inside the rotor, and configured to generate an electromagnetic attractive force between the armature plate and the rotor, and a cover that is attached to the rotor and configured to cover a front side end surface of the armature plate, the cover including a top surface portion that is disposed to face a front side end surface of the armature plate opposite to the rear side end surface, and a cylindrical portion that extends from the top surface portion. A foreign matter discharge portion that discharges foreign matters in the cover to the outside of the cover toward a rear side of the compressor is formed on the cylindrical portion of the cover. The rotational power source is, for example, an engine or a motor of an automobile. The foreign matter is, for example, abrasion powder generated due to frictional engagement between the rotor and the armature plate.

[0013] Accordingly, since the cover member covering the front side end surface of the armature plate of the electromagnetic clutch forms the foreign matter discharge portion on the cylindrical portion rather than on the top surface portion which can be exposed to water from the front side, it is possible to prevent water from the front side of the electromagnetic clutch from entering the cover member and further entering the electromagnetic clutch from the foreign matter discharge portion.

[0014] In the electromagnetic clutch according to claim 2, the foreign matter discharge portion of the cover member is formed to protrude outward from the cylindrical portion, and includes a first opening facing the side peripheral surface side of the armature plate, a second opening facing the rear side of the compressor, and an internal space communicating with the first opening and the second opening.

[0015] Accordingly, foreign matter in the cover member of the electromagnetic clutch enters the internal space of the foreign matter discharge portion from the first opening and is then discharged to the outside of the electromagnetic clutch from the second opening, and the two openings of the foreign matter discharge portion of the cover member through which foreign matter enters and exits are directed to the side peripheral surface side of the armature plate and the rear side of the compressor, respectively, so it is possible to prevent water from entering the cover member and further entering the electromagnetic clutch from the foreign matter discharge portion even if the electromagnetic clutch is covered with water from the front side end surface side of the armature plate of the electromagnetic clutch.

[0016] In the electromagnetic clutch according to claim 3, the rotor includes a plurality of annular constituent members, and adjacent constituent members among the plurality of constituent members are coupled to each other via an annular magnetic shield portion made of a non-magnetic body. The plurality of annular constituent members are, for example, a friction wall constituent member having a friction surface facing a friction surface of the armature plate, an outer peripheral wall constituent member positioned on an outer side with respect to the friction wall constituent member, and an inner peripheral wall constituent member positioned on an inner side with respect to the friction wall constituent member. Accordingly, it is possible to prevent wear powder generated due to frictional engagement between the rotor and the armature plate from entering a space between the rotor and the coil housing.

[0017] Advantageous Effects

[0018] As described above, according to the present application, the foreign matter discharge portion of the cover member covering the front side end surface of the armature plate of the electromagnetic clutch is formed on the side peripheral surface of the cylindrical portion. In addition, the two openings of the foreign matter discharge portion of the cover member face the side peripheral surface side of the armature plate and the rear side of the compressor, respectively. Therefore, unlike the case where the foreign matter discharge portion is formed on the top surface portion of the cover member, it is possible to prevent water from entering the cover member and further entering the electromagnetic clutch from the foreign matter discharge portion to rust the bearing even if the electromagnetic clutch is covered with water from the front side of the electromagnetic clutch.

[0019] In particular, according to the present application as claimed in claim 3, it is possible to prevent wear powder generated due to frictional engagement between the rotor and the armature plate from entering a space between the rotor and the coil housing. BRIEF DESCRIPTION OF DRAWINGS

[0020] [ Figure 1 ] Figure 1 is a side view showing the appearance of the configuration in which the cover according to the present application is attached to the electromagnetic clutch in an example of a compressor equipped with the electromagnetic clutch to which the present application is applied.

[0021] [ Figure 2 ] Figure 2 is a cross-sectional view of the configuration in which the cover according to the present application is attached to the electromagnetic clutch, as viewed obliquely from the front side.

[0022] [ Figure 3 ] Figure 3 is a cross-sectional view of the configuration in which the cover according to the present application is attached to the electromagnetic clutch, as viewed from one side.

[0023] [ Figure 4 ] Figure 4 is an explanatory diagram showing the outline of the configuration of the rotor according to the present application used in the electromagnetic clutch, in which, Figure 4 (a) of FIG. 6 is a front view of the rotor, and Figure 4 (b) of FIG. 6 is a cross-sectional view taken along the line I-I in (a) of FIG. 6. Figure 4

[0024] [ Figure 5 ] Figure 5 is an explanatory diagram showing the outline of the configuration of the armature plate used in the electromagnetic clutch, in which, Figure 5 (a) of FIG. 7 is a front view of the armature plate, and Figure 5 (b) of FIG. 7 is a cross-sectional view taken along the line II-II in (a) of FIG. 7. Figure 5

[0025] [ Figure 6 ] Figure 6 (a) of FIG. 8 is a front view of the cover according to the present application, and Figure 6 (b) of FIG. 8 is a rear view of the cover according to the present application.

[0026] [ Figure 7 ] Figure 7 (a) of FIG. 9 is a perspective view of the cover according to the present application, as viewed obliquely from the front side, and Figure 7 (b) of FIG. 9 is a perspective view of the cover according to the present application, as viewed obliquely from the rear side. DETAILED DESCRIPTION

[0027] Hereinafter, an embodiment of the present application will be described with reference to the accompanying drawings.

[0028] Figure 1 ​​The illustrated compressor 100 is a refrigerant compressor for an air conditioner of a large vehicle such as a bus or a truck. It should be noted that the type of compressor according to the present application is not limited to such a refrigerant compressor for an air conditioner of a large vehicle. Although not illustrated, the present application is also applicable to a compressor that constitutes a refrigeration cycle of an air conditioner of a passenger vehicle, for example. In Figure 1 In the figures, the left side of the figure is the front side, and the right side of the figure is the rear side.

[0029] Figure 1 The illustrated compressor 100 will be described as an example of a compressor equipped with the electromagnetic clutch 1 to which the present application is applied, and the compressor includes a cylinder block 101, a front cylinder head 102 assembled to the front side of the cylinder block 101 via a valve plate, and a rear cylinder head 103 assembled to the rear side of the cylinder block 101 via a valve plate. The cylinder block 101, the front cylinder head 102, and the rear cylinder head 103 are fastened along the axial direction thereof by fastening bolts 104 (only the heads of these fastening bolts are illustrated) to form a housing 105 of the compressor 100.

[0030] A plurality of cylinder bores and one crank chamber (not illustrated) are defined in the cylinder block 101 of the housing 105. A drive shaft 106 (illustrated by a broken line in Figure 5 ) that passes through the crank chamber is rotatably supported in the cylinder block 101 so that a swash plate (not illustrated) provided in the crank chamber is rotated by the rotation of the drive shaft 106 to reciprocate a double-headed piston (not illustrated) in each of the cylinder bores. As Figure 3 Illustrated is that the electromagnetic clutch 1 is attached to one end portion of the drive shaft 106.

[0031] Figure 2 and Figure 3 The illustrated electromagnetic clutch 1 is used to interrupt the rotational force transmitted from a rotational power source (not illustrated) such as an engine or a motor to the compressor 100. In Figure 2 and Figure 3 In the figures, the left side of the figure is the front side, and the right side of the figure is the rear side.

[0032] As Figure 2 and Figure 3 Illustrated is that the electromagnetic clutch 1 includes a rotor 3 that is supported by a cylindrical portion 102a (in Figure 3The compressor 100 includes a hub 8 (shown in FIG. 1 ), a cylindrical portion of which protrudes from an end portion of the front cylinder head 102 and surrounds the drive shaft 106 of the compressor 100 and is rotatably supported; a hub 8, which is coupled to the drive shaft 106 of the compressor 100 so as to be non-rotatable relative to the drive shaft but rotates together with the drive shaft 106; an armature plate 4, which is disposed facing the rotor 3 with a slight gap therebetween in the axial direction and is fixed to the hub 8; and an excitation coil 7, which is supported by the housing 105 of the compressor 100, housed inside the rotor 3, and generates an electromagnetic attractive force between the armature plate 4 and the rotor 3. In the embodiment, a leaf spring mechanism 11 that urges the armature plate 4 in a direction away from the rotor 3 is used as a mechanism between the hub 8 and the armature plate 4 to prevent the armature plate 4 from coming into contact with the rotor 3 when the excitation coil 7 is not energized.

[0033] Figure 4 The rotor 3, shown as a single body in the figure, is a magnetic body except for non-magnetic bodies 34 and 35 described below. The rotor is provided with a bearing 2 on its inner periphery and is rotatably mounted, via the bearing 2, on the outer periphery of a cylindrical portion 102a extending from the front cylinder head 102 of the compressor 100 to allow the drive shaft 106 to be inserted therethrough. The rotor 3 has a friction wall 3a on the side opposite to the compressor 100 (the front side). The front end surface of the friction wall 3a is formed in a flat shape, is substantially perpendicular to the axial center of the rotor 3, and has a friction surface facing the armature plate 4.

[0034] In addition, in the embodiment, Figures 2 to 4 (in particular Figure 4 ), the rotor 3 includes: an annular friction wall constituent member 31 having a friction wall 3a; an annular outer peripheral wall constituent member 32, which is arranged on the outer peripheral side relative to the friction wall constituent member 31 and has an outer peripheral wall 3b extending laterally toward the rear side (in the axial direction of the drive shaft 106); an annular inner peripheral wall constituent member 33, which is arranged on the inner peripheral side relative to the friction wall constituent member 31 and has an inner peripheral wall 3c extending laterally toward the rear side (in the axial direction of the drive shaft 106); an annular outer non-magnetic body 34, which connects the friction wall constituent member 31 and the outer peripheral wall constituent member 32; and an annular outer non-magnetic body 35, which connects the friction wall constituent member 31 and the inner peripheral wall constituent member 33. The constituent members 31, 32 and 33 are made of an iron-based magnetic material. The non-magnetic bodies 34 and 35 are made of, for example, a non-magnetic metal such as copper.

[0035] The non-magnetic bodies 34 and 35 are formed in a concentric shape, are provided at a predetermined interval around the central axis of the rotor 3, so that the non-magnetic body 34 is located on the outer side, and the non-magnetic body 35 is located on the inner side. A thin annular friction member 36 is provided on the front side of the outer non-magnetic body 34. The front side end surface of the friction member 36 is flat, and is located on the same plane as the friction surface of the friction wall 3a. The front side end surface of the inner non-magnetic body 35 is located at a position recessed from the friction surface of the friction wall 3a and the front side end surface of the outer peripheral wall constituting member 32, so that a stepped portion is formed between the friction wall constituting member 31 and the outer peripheral wall constituting member 32 of the rotor 3.

[0036] In addition, the bearing 2 is fixed to the inner peripheral side of the inner peripheral wall 3c of the inner peripheral wall constituting member 33 constituting the rotor 3. A ring-shaped space 5 open on the rear side is formed between the outer peripheral wall 3b of the outer peripheral wall constituting member 32 and the inner peripheral wall 3c of the inner peripheral wall constituting member 33, and the ring-shaped space 5 accommodates the coil housing 12 accommodating the field coil 7 via a predetermined gap. Accordingly, the rotor 3 can rotate along the field coil 7 (coil housing 12) without sliding contact with the coil housing 12. In addition, a grooved belt 9 (on which a belt (not shown) for transmitting a rotational force from a rotational power source is wound) including a plurality of V-shaped grooves is formed in the outer peripheral side of the outer peripheral wall 3b of the outer peripheral wall constituting member 32.

[0037] Figure 5 The armature plate 4 shown as a single body is formed in a disc shape, is coupled to the leaf spring mechanism 11, and has a rear side end surface 4a provided to face the friction surface of the friction wall 3a of the rotor 3 while having a slight gap therebetween. The rear side end surface 4a is formed in a flat shape, is substantially perpendicular to the axial center of the rotor 3, and forms a friction surface facing the friction surface of the friction wall 3a, etc. In addition, in the armature plate 4, a plurality of arc-shaped slit holes 41 are formed as a magnetic shielding portion that shields the magnetism generated by energization of the field coil 7 described below. The slit holes 41 penetrate the armature plate 4 in the axial direction of the drive shaft 106, and thus are provided along the circumference of a circle centered on the central axis of the armature plate 4.

[0038] The field coil 7 is accommodated in a coil housing 12. The coil housing 12 is formed of a ring-shaped iron container, has a ring-shaped groove 12a open at one end, and accommodates the field coil 7 in the ring-shaped groove 12a. The ring-shaped groove 12a is filled with an epoxy resin material 13 to fix the field coil 7. The coil housing 12 is attached to the front cylinder head 102 of the compressor 100.

[0039] In the present embodiment, in order to prevent the bearing 2 from rusting due to the electromagnetic clutch 1 being exposed to water from the front side, the rotor 3 is provided with a flange-like protruding wall 3d further protruding to the outer peripheral side with respect to the outer peripheral wall 3b on the outer peripheral wall forming member 32, and the waterproof cover member 20 is attached mainly to the front side of the protruding wall 3d. That is, in the protruding wall 3d of the rotor 3, a plurality of (six in this embodiment) screw holes 37 (shown in Figure 4 FIG. 6) are formed, through which the fixing means 23 such as screws described below are inserted.

[0040] As shown in Figures 1 to 3 , Figure 6 and Figure 7 , the cover member 20 attached to the rotor 3 generally includes a top surface portion 20a whose inner peripheral surface faces the side end surface of the armature plate 4 and the side end surface of the hub 8, a cylindrical portion 20b extending from the peripheral edge of the top surface portion 20a toward the rear side, and a flange 20c protruding outward in the extending direction from the end of the cylindrical portion 20b, and the cover member covers the entire front side end surface 4b and the side peripheral surface of the armature plate 4.

[0041] A gap having a predetermined width is formed between the inner surface of the top surface portion 20a of the cover member 20 and the side end surface of the armature plate 4 and the side end surface of the hub 8, and between the inner peripheral surface of the cylindrical portion 20b of the cover member 20 and the outer peripheral surface of the armature plate 4, so as not to bring the cover member 20 into contact with the armature plate 4 and the hub 8 when the cover member 20 rotates in synchronization with the rotor 3.

[0042] The top surface portion 20a of the cover member 20 is formed with a plurality of (five in this embodiment) protruding portions 21 protruding in a substantially elliptical shape from the end surface of the top surface 20a toward the front side. The protruding portions 21 extend radially from the center of the top surface portion 20a of the cover member 20 toward the outer periphery, and the gap between the protruding portions 21 is uniform. In this way, by forming the protruding portions 21 on the top surface portion 20a of the cover member 20, the rigidity of the top surface portion 20a is improved, and abnormal noise is prevented from being generated from the top surface portion 20a. In the flange 20c, a plurality of (six in this embodiment) through holes 22 through which the fixing means 23 are inserted are formed, which are on the same axis as the screw holes 37 of the rotor 3 and in the extending direction of the protruding portions 21.

[0043] Further, in the electromagnetic clutch according to the present application, as a configuration for discharging the wear powder generated due to the friction coupling between the armature plate 4 and the rotor 3 to the outside of the electromagnetic clutch 1, a plurality of (six in this embodiment) foreign matter discharging portions 25 are formed on the cover member 20. In the embodiment, each of the foreign matter discharging portions 25 is formed between the adjacent protruding portions 21 from the viewpoint of facilitating the formation of the cover member 20.

[0044] In the embodiment, as shown in (a) of FIG. 10, the six foreign matter discharging portions 25 formed on the cylindrical portion 20b of the cover member 20 are provided at equal intervals, but the number and arrangement of the foreign matter discharging portions 25 are not necessarily limited thereto. In view of the balance when the cover member 20 rotates together with the rotor 3, it is preferable that three or more foreign matter discharging portions 25 are provided at equal intervals. Figure 6

[0045] Each of the foreign matter discharging portions 25 is formed to protrude outward from the cylindrical portion 20b of the cover member 20, and includes an armature plate 4 side opening 25a that opens to the front side of the side end surface of the armature plate 4, a rear side opening 25b that faces the rear side, and an internal space 25c that communicates with both the opening 25a and the opening 25b. A sufficient gap is provided between the opening 25b of the foreign matter discharging portion 25 and the flange 20c of the cover member 20 so that the wear powder can be smoothly discharged from the opening 25b. In order to form the internal space 25c having the openings 25a and 25b in this way, in the embodiment, a thin-walled portion that stands in a U shape blocks the front side and leaves the rear side open from the peripheral edge of the opening 25a formed in the cylindrical portion 20b, and then extends toward the rear side in a manner of covering the opening 25a to provide a function like a eave. That is, the outer shape of the foreign matter discharging portion 25 is a substantially ¼ spherical shape that is internally hollow.

[0046] In order to prevent the foreign matter discharging portion 25 from becoming an obstacle when the fixing device 23 is inserted into the through hole 22 of the cover member 20 in a state of abutting against the rotor 3 from the front side, as shown in (a) of FIG. 10, the foreign matter discharging portion 25 and the through hole 22 are provided to be offset from each other in the circumferential direction of the cover member 20. Figure 6

[0047] By forming such foreign matter discharging portions 25 on the cylindrical portion 20b of the cover member 20, the wear powder can be brought into the internal space 25c from the opening 25a of each of the foreign matter discharging portions 25 and then discharged from the opening 25b.

[0048] ​​In addition, because the wall portion of the inner space 25c of each of the foreign matter discharge portions 25 functions as a eave that blocks the front side of the inner space 25c (the front side of the opening 25b), even if the electromagnetic clutch 1 is exposed to water from the front side, it is possible to prevent the water from entering the cover 20 from the foreign matter discharge portions 25 and further entering the electromagnetic clutch 1.

[0049] In addition, because the magnetic shield portion of the rotor 3 is made of a ring-shaped non-magnetic body, it is possible to prevent foreign matter such as abrasion powder from entering the space between the rotor 3 and the coil housing 12. Although the space between the rotor 3 and the cover 20 is surrounded, because the foreign matter discharge portions 25 are formed on the cover 20, it is not possible for foreign matter to remain inside the cover 20.

[0050] In addition, because the magnetic shield portion of the rotor 3 can be formed in a ring shape, compared to a case in which the magnetic shield portion of the rotor 3 is formed by slit holes having a through-hole shape, it is possible to eliminate the problem of magnetic leakage due to bridges provided between the slit holes.

[0051] Although the case in which the magnetic shield portion of the rotor 3 is formed by the non-magnetic bodies 34 and 35 shown as a single body in the above-described embodiment has been described, Figure 4 Although the case in which the magnetic shield portion of the rotor 3 is formed by the non-magnetic bodies 34 and 35 shown as a single body in the above-described embodiment has been described,

[0052] List of Reference Signs

[0053] 1 electromagnetic clutch

[0054] 3 rotor

[0055] 3a friction wall

[0056] 31 friction wall constituent member (constituent member)

[0057] 32 outer peripheral wall constituent member (constituent member)

[0058] 33 inner peripheral wall constituent member (constituent member)

[0059] 34 outer non-magnetic body (non-magnetic body)

[0060] 35 inner non-magnetic body (non-magnetic body)

[0061] 4 armature plate

[0062] 4a Rear end surface

[0063] 4b Front end surface

[0064] 7 Excitation coil

[0065] 8 hub

[0066] 20 Cover

[0067] 20a Top surface portion

[0068] 20b Cylindrical part

[0069] 25 Foreign body removal section

[0070] 25a opening (first opening)

[0071] 25b opening (second opening)

[0072] 25c interior space

[0073] 100 compressors

[0074] 105 housing

[0075] 106 drive shaft

Claims

1. An electromagnetic clutch (1), comprising: a rotor (3) rotatably supported by a housing (105) of the compressor (100) and configured to receive a rotational force from a rotational power source to rotate; a hub (8) coupled to a drive shaft (106) of the compressor (100) so as to be non-rotatable relative to the drive shaft and to rotate together with the drive shaft (106); an armature plate (4) coupled to the hub (8) and having a rear end surface (4a) disposed to face the friction wall (3a) of the rotor (3) with a gap therebetween; an excitation coil (7) supported by the housing (105) of the compressor (100), housed inside the rotor (3), and configured to generate an electromagnetic attraction force between the armature plate (4) and the rotor (3); as well as A cover member (20) attached to the rotor (3) and configured to cover the front end surface (4b) of the armature plate (4), the cover member (20) comprising a top surface portion (20a) and a cylindrical portion (20b), the top surface portion being arranged to face the front end surface (4b) of the armature plate (4) opposite to the rear end surface (4a), the cylindrical portion extending from the top surface portion (20a), characterized in that A foreign matter discharge portion (25) is formed on the cylindrical portion (20b) of the cover member (20), and the foreign matter discharge portion discharges foreign matter in the cover member (20) to the outside of the cover member (20) toward the rear side of the compressor (100).

2. The electromagnetic clutch (1) according to claim 1, wherein: The foreign matter discharge portion (25) of the cover member (20) is formed to protrude outward from the cylindrical portion (20b), and includes a first opening (25a) facing the side peripheral surface side of the armature plate (4), a second opening (25b) facing the rear side of the compressor (100), and an internal space (25c) communicating with the first opening and the second opening (25a, 25b).

3. The electromagnetic clutch (1) according to claim 1 or 2, wherein: The rotor (3) includes a plurality of annular constituent members (31, 32, 33), and adjacent constituent members of the plurality of annular constituent members (31, 32, 33) are coupled to each other via annular magnetic shielding portions (34, 35) made of a non-magnetic body.

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