Electromagnetic clutch

Abstract

To prevent a first slide surface where a resin and a resin slide over each other from being heated to a high temperature and melted even when an input shaft is rotationally driven at high speed.SOLUTION: An electromagnetic clutch of the invention includes: a resin relay shaft which integrally rotates with an input shaft which is rotationally driven by a motor; a rotor which integrally rotates with the input shaft; a resin coupling disposed at the outer periphery side of the relay shaft and having an armature which closely contacts with or separates from the rotor; and air supply means which supplies air to a first slide surface on which the relay shaft and the coupling slide over each other.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an electromagnetic clutch.

Background Art

[0002] As a conventional electromagnetic clutch, there is generally one having a drive member having a coupling member that can be brought into close contact with or separated from a rotor fixed to a shaft, a yoke that is rotatably fitted to the shaft and forms a magnetic path together with the rotor, and an exciting coil attached to the yoke (see, for example, Patent Document 1). In this electromagnetic clutch, a current is supplied to the exciting coil to attract the coupling member to the rotor so that the rotor and the yoke are fixed, and the coupling between the rotor and the yoke is disengaged by stopping the supply of current to the exciting coil.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As an electromagnetic clutch 801 similar to the electromagnetic clutch of Patent Document 1, as shown in FIG. 14, there are a relay shaft 803 fixed to an input shaft 2, a rotor 6 fixed to the relay shaft 803 via a hub 5, a coupling 8 having an armature 10 that can be brought into close contact with or separated from the rotor 6, a yoke 11 that is rotatably fitted to the relay shaft 803 and forms a magnetic path together with the rotor 6, and an electromagnet 18 (excitation device) formed by winding an exciting coil 16 around a bobbin 12 attached to the yoke 11. The yoke 11 is disposed on the outer periphery of the rotor 6 via bearings 11a and 11b fixed to its inner peripheral surface.

[0005] In the electromagnetic clutch 801, the intermediate shaft 803 and the coupling 8 are made of resin. Therefore, in the electromagnetic clutch 801, when the coupling 8 is disconnected from the rotor 6, the resin intermediate shaft 803 and the resin coupling 8 slide against each other. At the first sliding surface N1 where the resins slide against each other, the thermal conductivity of the resin is low and frictional heat does not easily dissipate. As a result, at high sliding speeds, the temperature becomes high and there is a problem that the first sliding surface N1 may melt.

[0006] Furthermore, in the electromagnetic clutch 801, the rotor 6 is made of steel, and the bearings 11a and 11b are made of resin. Therefore, in the electromagnetic clutch 801, the steel rotor 6 and the resin bearings 11a and 11b slide against each other. At the second sliding surface N2 where the steel and resin slide against each other, the thermal conductivity of the steel is high and frictional heat dissipates easily, but the thermal conductivity of the resin is low and frictional heat dissipates difficult to escape. As a result, when the sliding speed is very high, the surface becomes very hot and there is a problem that the second sliding surface may melt.

[0007] The present invention aims to provide an electromagnetic clutch that can prevent the first sliding surface, where two resins slide against each other, from melting. [Means for solving the problem]

[0008] To achieve this objective, the present invention employs the following means.

[0009] In other words, the electromagnetic clutch of the present invention is characterized by comprising: a resin intermediate shaft that rotates integrally with an input shaft that is rotationally driven by a driving means; a rotor that rotates integrally with the input shaft; a resin rotation transmission member that is arranged on the outer circumference of the intermediate shaft and has an armature that can be made in close contact with or separated from the rotor; and an air supply means that supplies air to a first sliding surface on which the intermediate shaft and the rotation transmission member slide.

[0010] In this configuration, air is supplied to the first sliding surface where the resin intermediate shaft and the resin rotation transmission member slide against each other. Therefore, even when the input shaft is driven to rotate at high speed, it is possible to prevent the first sliding surface where the resins slide against each other from becoming too hot and melting.

[0011] The electromagnetic clutch of the present invention is characterized in that the air supply means has a plurality of through grooves that penetrate from the outer circumferential surface of the intermediate shaft to the first sliding surface, a vane formed between two adjacent through grooves, and an intake hole that communicates with the through grooves and is formed on the end face of the intermediate shaft.

[0012] With this configuration, air can be easily supplied to the first sliding surface.

[0013] In the electromagnetic clutch of the present invention, the intake hole is characterized in that it communicates with the through groove on the side of the rotation axis of the input shaft that is closer to the first sliding surface.

[0014] With this configuration, forming the intake holes in the intermediate shaft prevents a decrease in the strength of the intermediate shaft.

[0015] The electromagnetic clutch of the present invention is characterized in that it is rotatably fitted to the relay shaft and forms a magnetic path together with the rotor, the yoke is fitted to the outer circumference of the rotor via a bearing, and the air supplied to the first sliding surface by the air supply means is subsequently supplied to the second sliding surface on which the rotor and the bearing slide.

[0016] With this configuration, air is supplied to the second sliding surface where the steel rotor and the resin bearing slide against each other. Therefore, even when the input shaft is driven to rotate at a very high speed, it is possible to prevent the second sliding surface where the steel and resin slide against each other from becoming too hot and melting.

[0017] In the electromagnetic clutch of the present invention, the relay shaft and the rotary transmission member are formed of super engineering plastic, which is characterized by this.

[0018] With such a configuration, by forming the resin relay shaft and the resin rotary transmission member with super engineering plastic having a high melting point, even when the input shaft is rotationally driven at high speed, it is possible to further prevent the first sliding surface where the resins slide against each other from becoming so hot as to melt.

Effect of the Invention

[0019] According to the present invention described above, even when the input shaft is rotationally driven at high speed, it is possible to prevent the first sliding surface where the resins slide against each other from becoming extremely hot and melting.

Brief Description of the Drawings

[0020] [Figure 1] It is a cross-sectional view of an electromagnetic clutch 1 according to an embodiment of the present invention. [Figure 2] It is a perspective view of a relay shaft 3 of the electromagnetic clutch 1 in FIG. 1. [Figure 3] It is a cross-sectional view taken along line a1 - a1 in FIG. 1. [Figure 4] It is a side view of the relay shaft 3 in FIG. II. [Figure 5] It is a partially enlarged view of the electromagnetic clutch 1 in FIG. 1. ~ [Figure 6] It is a partially enlarged view of the electromagnetic clutch 1 in FIG. 1. [Figure 7] ~ FIG. 7(a) is a perspective view of a relay shaft 103 according to a modification, and FIG. 7(b) is a side view of the relay shaft 103. [Figure 8] FIG. 8(a) is a perspective view of a relay shaft 203 according to a modification, and FIG. 8(b) is a side view of the relay shaft 203. [Figure 9] [[ID=!]] [Figure 10] Figure 10(a) is a front view of the relay shaft 403 according to a modified example, and Figure 10(b) is a side view of the relay shaft 403. [Figure 11] Figure 11(a) is a front view of the relay shaft 503 according to a modified example, and Figure 11(b) is a side view of the relay shaft 503. [Figure 12] Figure 12(a) is a front view of the relay shaft 603 according to a modified example, and Figure 12(b) is a side view of the relay shaft 603. [Figure 13] This figure shows the case where a groove 5N is formed between the outer circumferential surface of the hub 5 and the inner circumferential surface of the rotor 6. [Figure 14] This is a cross-sectional view of a conventional electromagnetic clutch 801. [Modes for carrying out the invention]

[0021] Embodiments of the present invention will be described below with reference to the drawings. The configuration of the electromagnetic clutch 1 according to this embodiment is substantially the same as that of the conventional electromagnetic clutch 801, except for the configuration of the relay shaft 3.

[0022] As shown in Figure 1, the electromagnetic clutch 1 according to this embodiment comprises a relay shaft 3 fixed to an input shaft 2, a rotor 6 fixed to the relay shaft 3 via a hub 5, a coupling 8 having an armature 10 that can be made to be in close contact with or separated from the rotor 6, a yoke 11 that is rotatably fitted to the relay shaft 3 and forms a magnetic path together with the rotor 6, and an electromagnet 18 (excitation device) formed by winding an excitation coil 16 around a bobbin 12 attached to the yoke 11.

[0023] The electromagnetic clutch 1 of this embodiment is used, for example, in opening and closing devices such as automobile doors. Therefore, the operating environment of the electromagnetic clutch 1 is -30℃ to 80℃, and the sliding speed is very high, at 5000 to 20000 rpm (2 to 8 m / s).

[0024] The input shaft 2 is a roughly cylindrical member made of steel and is rotationally driven by a motor 2a (driving means). The intermediate shaft 3 is a roughly cylindrical member made of resin and is fitted and fixed to the outer surface of the input shaft 2. The intermediate shaft 3 rotates integrally with the input shaft 2.

[0025] The hub 5 is a substantially cylindrical member made of steel, and has a through hole 5a through which the intermediate shaft 3 passes, and a flange portion 5b extending radially outward from one end in the axial direction. The hub 5 is fitted and fixed to the outer surface of the intermediate shaft 3 and is also fitted into the central hole 6n of the cylindrical portion 6a of the rotor 6. The hub 5 rotates integrally with the input shaft 2, the intermediate shaft 3, and the rotor 6.

[0026] The rotor 6 is a substantially bottomed cylindrical member made of steel. The rotor 6 is made of a magnetic material and has a cylindrical portion 6a, a plate-like portion 6b extending outward from the cylindrical portion 6a, and a cylindrical portion 6c integrally formed on the outer peripheral edge of the plate-like portion 6b. The cylindrical portion 6a of the rotor 6 is positioned on the outer circumference of the hub 5, and the plate-like portion 6b is positioned opposite the armature 10.

[0027] The rotor 6 is positioned to cover one end of the electromagnet 18. The rotor 6 is configured to form a magnetic path when the electromagnet 18 is activated, and is also configured to divert the magnetic flux toward the armature 10 through a notch 6n formed in the plate-shaped portion 6b.

[0028] The coupling 8 is a substantially bottomed cylindrical member made of resin. The cylindrical portion 8a of the coupling 8 is made of a non-magnetic material and is positioned to cover the rotor 6. A boss portion 8b that protrudes in the axial direction is integrally provided on the outer periphery of the cylindrical portion 8a.

[0029] The armature 10 is attached to the rotor 6 side of the cylindrical portion 8a by a coupling 8, biased by a spring (not shown) in the direction toward the cylindrical portion 8a along the axial direction. The coupling 8 holds the armature 10 so that it can move in the axial direction and rotate as a whole.

[0030] The outer circumference of the coupling 8 is equipped with a gear (not shown) for transmitting driving force to an external device. By connecting an output drum (not shown) or the like so as to mesh with this gear, it becomes possible to open and close the car door.

[0031] The armature 10 is a plate-shaped member made of steel and has an outer diameter smaller than the inner diameter of the boss portion 8b of the coupling 8. The armature 10 is attracted in the direction of the rotor 6 by the magnetic flux diverting from the notch portion 6n of the rotor 6 when the electromagnet 18 is activated. Since the coupling 8 and the armature 10 are not fixed to the intermediate shaft 3, they are rotatable relative to the intermediate shaft 3.

[0032] A yoke 11 made of steel is positioned on the outer circumference of the cylindrical portion 6a of the rotor 6. The yoke 11 is made of a magnetic material, and bearings 11a and 11b are fixed to its inner surface. Therefore, the yoke 11 is configured not to rotate even when the rotor 6 rotates together with the input shaft 2.

[0033] Inside the rotor 6, a bobbin 12 is positioned on the outer circumference of the yoke 11. The bobbin 12 has a cylindrical portion 12a that fits onto the yoke 11, and flange portions 12b and 12c that extend radially outward from both ends of the cylindrical portion 12a. The excitation coil 16 is wound between the flange portions 12b and 12c on the outer surface of the cylindrical portion 12a.

[0034] In the electromagnetic clutch 1 of this embodiment, the relay shaft 3, coupling 8, and bearings 11a and 11b are made of resin, and a super engineering plastic with a high melting point is used as the resin. Examples of super engineering plastics include PPS (polyphenylene sulfide) resin and PEEK (polyether ether ketone) resin.

[0035] In conventional electromagnetic clutches 801, the intermediate shaft 803 and coupling 8 are made of POM (polyacetal) resin. The heat resistance temperature of POM is approximately 90-100°C, while the heat resistance temperature of PPS, a super engineering plastic, is approximately 240°C, and the heat resistance temperature of PEEK is approximately 300°C.

[0036] Therefore, in the electromagnetic clutch 1 of this embodiment, the heat resistance temperature of the relay shaft 3 and coupling 8 is very high compared to the heat resistance temperature of the relay shaft 803 and coupling 8 of a conventional electromagnetic clutch 801.

[0037] The configuration of the relay shaft 3 of the electromagnetic clutch 1 in this embodiment will be described with reference to Figures 2 to 4.

[0038] As shown in Figure 2, the relay shaft 3 has a first portion 30 located inside the coupling 8, a second portion 31 located inside the hub 5, and a third portion 32 extending outward from the end of the first portion 30 (the end opposite to the second portion 31) and facing the side surface of the coupling 8.

[0039] The first part 30 has an outer surface with a substantially circular cross-sectional shape. Four through grooves 33 are formed on the outer surface of the first part 30. The through grooves 33 are substantially rectangular in shape and penetrate from the outer surface to the inner surface of the first part 30. The through grooves 33 are formed to extend in the circumferential direction of the first part 30. The four through grooves 33 are formed at equal intervals in the circumferential direction, as shown in Figure 3. A wing portion 35 is formed between two adjacent through grooves 33. Therefore, the first part 30 of the relay shaft 3 has four through grooves 33 and four wing portions 35 arranged alternately in the circumferential direction.

[0040] As shown in Figure 4, four intake holes 36 are formed in the third part 32. The four intake holes 36 each penetrate from the side of the third part 32 to the four through grooves 33 formed in the first part 30. Therefore, the four through grooves 33 formed in the first part 30 communicate with the outside through the four intake holes 36 formed in the third part 32. A tapered portion 36a is formed at the entrance of the intake holes 36 during resin processing. The tapered portion 36a is positioned along the outer circumference of the intake holes 36. Therefore, outside air is easily drawn into the intake holes 36.

[0041] In the electromagnetic clutch 1 of this embodiment, four through grooves 33, four vane portions 35, and four intake holes 36 formed on the relay shaft 3 constitute the air supply means 50.

[0042] The operation of the electromagnetic clutch 1 of this embodiment will now be described. Figure 5 is an enlarged view of the portion enclosed by the dashed-dotted circle in the electromagnetic clutch 1 of Figure 1, and Figure 6 is an enlarged view of the portion enclosed by the dashed-dotted rectangle in the electromagnetic clutch 1 of Figure 1.

[0043] When the motor 2a is driven and the input shaft 2 is rotated, the excitation coil 16 is energized, forming a magnetic closed loop between the yoke 11, rotor 6, and armature 10. The armature 10 is then magnetically attracted to the rotor 6, compressing the spring (not shown) against its biasing force, thereby engaging the electromagnetic clutch 1. At this time, the coupling 8 rotates integrally with the armature 10 attracted to the rotor 6, and therefore rotates together with the input shaft 2.

[0044] In contrast, under normal non-energized conditions, a magnetic closed loop is not formed between the yoke 11, rotor 6, and armature 10. Therefore, the armature 10 is biased by a spring (not shown) toward the cylindrical portion 8a of the coupling 8 and released from the rotor 6, resulting in a state where the armature 10 and rotor 6 do not rotate together, i.e., a disconnected state. At that time, the coupling 8 rotates freely while sliding against the relay shaft 3.

[0045] In the electromagnetic clutch 1 of this embodiment, when the relay shaft 3 rotates freely against the cylindrical portion 8a of the coupling 8 during normal non-energized operation, the resin relay shaft 3 and the resin coupling 8 slide against each other on the first sliding surfaces N1a and N1b, as shown in Figure 5. At that time, as the relay shaft 3 rotates integrally with the input shaft 2, the vane portion 35 formed on the relay shaft 3 rotates, forming an airflow in which air drawn in from the outside through the intake hole 36 flows towards the through groove 33.

[0046] The first sliding surface N1a includes a sliding surface located between the outer circumferential surface of the first portion 30 of the intermediate shaft 3 and the inner circumferential surface of the coupling 8, and a sliding surface located between the inner surface of the third portion 32 of the intermediate shaft 3 and the side surface of the coupling 8. The first sliding surface N1b is a sliding surface located between the outer circumferential surface of the first portion 30 of the intermediate shaft 3 and the inner circumferential surface of the coupling 8.

[0047] Therefore, as shown in Figure 5, outside air is drawn into the through groove 33 of the intermediate shaft 3 through the intake hole 36 of the intermediate shaft 3. This air flows over the first sliding surface N1a between the intermediate shaft 3 and the coupling 8 (the sliding surface located on the intake hole 36 side of the through groove 33), and then passes between the third portion 32 of the intermediate shaft 3 and the side surface of the coupling 8 before being discharged to the outside. Thus, the first sliding surface N1a is cooled by the convection of the air passing over it, and the contact pressure between the resins is reduced by the fluid pressure, thereby suppressing heat generation at the first sliding surface N1a.

[0048] Similarly, air drawn into the through groove 33 from the outside via the intake hole 36 of the intermediate shaft 3 flows over the first sliding surface N1b between the intermediate shaft 3 and the coupling 8 (the sliding surface located on the opposite side of the intake hole 36 from the through groove 33), and then flows towards the rotor 6. As a result, the first sliding surface N1b is cooled by the convection of air passing over it, and the contact pressure between the resins is reduced by the fluid pressure, thereby suppressing heat generation at the first sliding surface N1b.

[0049] Furthermore, in the electromagnetic clutch 1 of this embodiment, when the rotor 6 rotates freely against the bearings 11a and 11b during normal non-energized operation, the steel rotor 6 and the resin bearings 11a and 11b slide against each other on the second sliding surfaces N2a and N2b, as shown in Figure 6. At that time, air that has flowed over the first sliding surface N1b and then flowed toward the rotor 6 is supplied to the second sliding surface N2a between the rotor 6 and the bearing 11a.

[0050] The second sliding surface N2a includes a sliding surface positioned between the outer circumferential surface of the cylindrical portion 6a of the rotor 6 and the inner circumferential surface of the portion of the bearing 11a along the cylindrical portion 6a, and a sliding surface positioned between the inner surface of the plate-shaped portion 6b of the rotor 6 and the outer surface of the portion of the bearing 11a along the plate-shaped portion 6b. The second sliding surface N2b includes a sliding surface positioned between the outer circumferential surface of the cylindrical portion 6a of the rotor 6 and the inner circumferential surface of the portion of the bearing 11b along the cylindrical portion 6a, and a sliding surface positioned between the inner surface of the flange portion 5b of the hub 5 and the outer surface of the portion of the bearing 11b along the flange portion 5b.

[0051] Therefore, the air that flows over the first sliding surface N1b and then towards the rotor 6 flows over the second sliding surface N2a between the rotor 6 and the bearing 11a, as shown in Figure 6. As a result, the second sliding surface N2a between the rotor 6 and the bearing 11a is cooled by the convection of air passing over the second sliding surface N2a, and the contact pressure between the resins is reduced by the fluid pressure, thereby suppressing heat generation at the second sliding surface N2a.

[0052] The air that flows over the second sliding surface N2a between the rotor 6 and the bearing 11a is supplied to the second sliding surface N2b between the rotor 6 and the bearing 11b. As a result, the second sliding surface N2b between the rotor 6 and the bearing 11b is cooled by the convection of air passing over the second sliding surface N2b, and the contact pressure between the resins is reduced by the fluid pressure, thereby suppressing heat generation at the second sliding surface N2b.

[0053] The electromagnetic clutch 1 of this embodiment can employ a sliding bearing structure in which resins slide against each other even under high-speed sliding conditions, enabling a significant reduction in the manufacturing cost of clutches for electric doors of automobiles. In the electromagnetic clutch 1, not only is there a cooling effect from the air flowing into the internal space from the vane portion 35 of the relay shaft 3, but even when the clutch is not energized, the input shaft 2 rotates at high speed, allowing air to flow into the gaps between parts, creating gaps on the sliding surfaces and reducing friction between parts. Furthermore, dust such as shavings generated between the armature 10 and rotor 6 can be removed, thus maintaining the friction surface. Therefore, it not only cools the parts but also extends the lifespan of other parts.

[0054] As described above, the electromagnetic clutch 1 of this embodiment comprises a resin intermediate shaft 3 that rotates integrally with an input shaft 2 which is rotationally driven by a motor 2a, a rotor 6 that rotates integrally with the input shaft 2, a resin coupling 8 arranged on the outer circumference of the intermediate shaft 3 and having an armature 10 that can be made to be in close contact with or separated from the rotor 6, and an air supply means 50 that supplies air to the first sliding surfaces N1a and N1b on which the intermediate shaft 3 and the coupling 8 slide.

[0055] In this configuration, air is supplied to the first sliding surfaces N1a and N1b where the resin intermediate shaft 3 and the resin coupling 8 slide against each other. Therefore, even when the input shaft 2 is driven to rotate at high speed, it is possible to prevent the first sliding surfaces N1a and N1b, where the resins slide against each other, from becoming too hot and melting.

[0056] In the electromagnetic clutch 1 of this embodiment, the air supply means 50 has a plurality of through grooves 33 that penetrate from the outer circumferential surface of the relay shaft 3 to the first sliding surfaces N1a and N1b, a vane portion 35 formed between two adjacent through grooves 33, and an intake hole 36 that communicates with the through grooves 33 and is formed on the end face of the relay shaft 3.

[0057] With this configuration, air can be easily supplied to the first sliding surfaces N1a and N1b.

[0058] In the electromagnetic clutch 1 of this embodiment, the intake hole 36 communicates with the through groove 33 on the rotation axis side of the input shaft 2, relative to the first sliding surfaces N1a and N1b.

[0059] With this configuration, forming the intake holes 36 in the intermediate shaft 3 prevents a decrease in the strength of the intermediate shaft 3.

[0060] In the electromagnetic clutch 1 of this embodiment, multiple vane portions 35 are formed on the relay shaft 3 in the circumferential direction.

[0061] With this configuration, air can be supplied around the entire circumference of the first sliding surfaces N1a and N1b.

[0062] In the electromagnetic clutch 1 of this embodiment, a yoke 11 is provided which is rotatably fitted to the relay shaft 3 and forms a magnetic path together with the rotor 6. The yoke 11 is fitted to the outer circumference of the rotor 6 via bearings 11a and 11b. Air supplied to the first sliding surface N1b by the air supply means 50 is then supplied to the second sliding surface N2 on which the rotor 6 and the bearings 11a and 11b slide.

[0063] With this configuration, air is supplied to the second sliding surface N2 where the steel rotor 6 and the resin bearings 11a and 11b slide against each other. Therefore, even when the input shaft 2 is driven to rotate at high speed, it is possible to prevent the second sliding surface N2 where the steel and resin slide against each other from becoming too hot and melting.

[0064] In the electromagnetic clutch 1 of this embodiment, the relay shaft 3 and the coupling 8 are made of super engineering plastic.

[0065] With this configuration, by forming the resin intermediate shaft 3 and resin coupling 8 from a super engineering plastic with a high melting point, it is possible to better prevent the first sliding surfaces N1a and N1b, where the resins slide against each other, from becoming too hot and melting, even when the input shaft 2 is rotated at high speed.

[0066] Furthermore, the specific configuration of each part is not limited to the embodiments described above.

[0067] In the above embodiment, the air supply means 50 is composed of four through grooves 33, four vane portions 35, and four intake holes 36 formed in the relay shaft 3, but is not limited thereto. For example, the number, shape, size, and arrangement of the through grooves 33, vane portions 35, and intake holes 36 are arbitrary. The air supply means of the present invention only needs to supply air to the first sliding surfaces N1a and N1b where the relay shaft 3 and the coupling 8 (rotation transmission member) slide against each other.

[0068] A modified version of the relay shaft 3 of the above embodiment, the relay shaft 103, will be described with reference to Figure 7. As shown in Figure 7(a), four through grooves 331 are formed on the outer circumferential surface of the first portion 30 of the relay shaft 103. The through grooves 331 are substantially circular in shape and penetrate from the outer circumferential surface to the inner circumferential surface of the first portion 30. The four through grooves 331 are formed at equal intervals in the circumferential direction. A wing portion 351 is formed between two adjacent through grooves 331. Therefore, in the first portion 30 of the relay shaft 103, the four through grooves 331 and the four wing portions 351 are arranged alternately in the circumferential direction. As shown in Figure 7(b), four intake holes 361 are formed in the third portion 32. The four intake holes 361 penetrate from the side surface of the third portion 32 to the four through grooves 331 formed in the first portion 30. Therefore, the four through grooves 331 formed in the first portion 30 communicate with the outside through the four intake holes 361 formed in the third portion 32. In this modified example, the four through grooves 331, four vane portions 351, and four intake holes 361 formed in the relay shaft 103 constitute the air supply means 50.

[0069] A modified version of the relay shaft 3 of the above embodiment, the relay shaft 203, will be described with reference to Figure 8. As shown in Figure 8(a), six through grooves 332 and six recessed grooves 332a are formed on the outer circumferential surface of the first portion 30 of the relay shaft 203. The through grooves 332 are substantially rectangular in shape and penetrate from the outer circumferential surface to the inner circumferential surface of the first portion 30. The six through grooves 332 are formed at equal intervals in the circumferential direction. The six recessed grooves 332a are formed concavely on the outer circumferential surface of the first portion 30 and extend over the entire axial area of ​​the first portion 30. The six recessed grooves 332a are each in communication with the six through grooves 332. The recessed grooves 332a are inclined such that the portion adjacent to the third portion 32 is located on the upstream side in the rotational direction of the input shaft 2, and as they move away from the third portion 32, they are located on the downstream side in the rotational direction of the input shaft 2. A wing portion 352 is formed between two adjacent recessed grooves 332a. Therefore, in the first portion 30 of the relay shaft 203, six grooves 332a (six through grooves 332) and six vane portions 352 are arranged alternately in the circumferential direction. In the third portion 32, as shown in Figure 8(b), six intake holes 362 are formed. The six intake holes 362 each penetrate from the side surface of the third portion 32 to the six through grooves 332 formed in the first portion 30. Therefore, the six through grooves 332 formed in the first portion 30 communicate with the outside through the six intake holes 362 formed in the third portion 32. In this modified example, the six through grooves 332, six vane portions 352, and six intake holes 362 formed in the relay shaft 203 constitute the air supply means 50.

[0070] A modified example of the relay shaft 3 of the above embodiment, the relay shaft 303, will be described with reference to Figure 9. As shown in Figure 9(a), eight through grooves 333 are formed on the outer circumferential surface of the first portion 30 of the relay shaft 303. The through grooves 333 are substantially circular in shape and penetrate from the outer circumferential surface to the inner circumferential surface of the first portion 30. The eight through grooves 333 are formed at equal intervals in the circumferential direction. A wing portion 353 is formed between two adjacent through grooves 333. Therefore, the first portion 30 of the relay shaft 303 has eight through grooves 333 and eight wing portions 353 arranged alternately in the circumferential direction. As shown in Figure 9(b), eight protrusions T3 and eight recesses N3 are arranged on the outer surface of the third portion 32. The eight protrusions T3 are formed at equal intervals in the circumferential direction. The eight protrusions T3 are arranged over the entire area from the inner circumferential side to the outer circumferential side of the third portion 32. The protrusion T3 is a narrow convex portion extending radially from the intermediate shaft 303. The radial center of the protrusion T3 is curved so as to be convex toward the upstream side in the rotational direction of the input shaft 2. The recess N3 is located between two adjacent protrusions T3. Eight intake holes 363 are formed in the third portion 32. The eight intake holes 363 each penetrate from the side surface of the third portion 32 to eight through grooves 333 formed in the first portion 30, radially inward from the recess N3. Therefore, the eight through grooves 333 formed in the first portion 30 communicate with the outside through the eight intake holes 363 formed in the third portion 32. In the intermediate shaft 303, since eight protrusions T3 are formed on the outer surface of the third portion 32, when the intermediate shaft 303 rotates, the eight protrusions T3 collect air radially inward on the outer surface of the third portion 32 and flow into the through grooves 333 from the intake holes 363. In this modified example, the eight through grooves 333, eight wing portions 353, eight intake holes 363, eight protrusions T3, and eight recesses N3 formed on the relay shaft 303 constitute the air supply means 50.

[0071] A modified example of the relay shaft 3 of the above embodiment, the relay shaft 403, will be described with reference to Figure 10. As shown in Figure 10(a), eight through grooves 334 and eight recessed grooves 334a are formed on the outer circumferential surface of the first portion 30 of the relay shaft 403. The through grooves 334 are substantially circular in shape and penetrate from the outer circumferential surface to the inner circumferential surface of the first portion 30. The eight through grooves 334 are formed at equal intervals in the circumferential direction. The eight recessed grooves 334a are formed concavely on the outer circumferential surface of the first portion 30 and extend along the axial direction of the first portion 30. The eight recessed grooves 334a are in communication with each of the eight through grooves 334. A wing portion 354 is formed between two adjacent recessed grooves 334a. Therefore, the eight recessed grooves 334a (eight through grooves 334) and the eight wing portions 354 are alternately arranged in the circumferential direction on the first portion 30 of the relay shaft 403. As shown in Figure 10(b), eight protrusions T4 and eight recesses N4 are arranged on the outer surface of the third part 32. The eight protrusions T4 are formed at equal intervals in the circumferential direction. The eight protrusions T4 are arranged across the entire area of ​​the third part 32, from the inner circumference to the outer circumference. The upstream end of each protrusion T4 in the rotational direction of the input shaft 2 is curved to be convex toward the downstream end of the input shaft 2 in the rotational direction. The downstream end of each protrusion T4 in the rotational direction of the input shaft 2 is curved to be convex toward the upstream end of the input shaft 2 in the rotational direction. The recesses N4 are arranged between two adjacent protrusions T4. Eight intake holes 364 are formed in the third part 32. The eight intake holes 364 each penetrate from the side surface of the third part 32 to eight through grooves 334 formed in the first part 30, radially inward of the recesses N4. Therefore, the eight through grooves 334 formed in the first portion 30 communicate with the outside through the eight intake holes 364 formed in the third portion 32. In the intermediate shaft 403, eight protrusions T4 are formed on the outer surface of the third portion 32. As the intermediate shaft 403 rotates, the eight protrusions T4 collect air radially inward on the outer surface of the third portion 32 and flow into the through grooves 334 from the intake holes 364. In this modified example, the eight through grooves 334, eight fins 354, eight intake holes 364, eight protrusions T4, and eight recesses N4 formed on the intermediate shaft 403 constitute the air supply means 50.In the intermediate shaft 403 shown in Figure 10, the eight intake holes 364 are connected to eight through grooves 334, but this is not the only option. For example, multiple intake holes 364 may be connected to one through groove 334. For instance, the intermediate shaft 403 may have four through grooves 334, four recessed grooves 334a, and eight intake holes 364, with two intake holes 364 connected to one through groove 334, allowing air to flow from the eight intake holes 364 to the four through grooves 334 and then to the four recessed grooves 334a. Alternatively, one intake hole 364 may be connected to multiple through grooves 334. For example, the relay shaft 403 may have eight through grooves 334, eight recessed grooves 334a, and four intake holes 364, with one intake hole 364 connected to two through grooves 334, so that air flows from the four intake holes 364 to the eight through grooves 334 and then to the eight recessed grooves 334a.

[0072] A modified example of the relay shaft 3 of the above embodiment, the relay shaft 503, will be described with reference to Figure 11. As shown in Figure 11(a), eight grooves 335a are formed on the outer circumferential surface of the first portion 30 of the relay shaft 503. The grooves 335a are narrow grooves that extend in the axial direction of the relay shaft 503. The eight grooves 335a are formed at equal intervals in the circumferential direction. The grooves 335a are inclined such that the portion adjacent to the third portion 32 is positioned on the upstream side in the rotational direction of the input shaft 2, and as they move away from the third portion 32, they are positioned on the downstream side in the rotational direction of the input shaft 2. A wing portion 355 is formed between two adjacent grooves 335a. Therefore, the eight grooves 335a and the eight wing portions 355 are alternately arranged in the circumferential direction on the first portion 30 of the relay shaft 503. As shown in Figure 11(b), eight protrusions T5 and eight recesses N5 are arranged on the inner surface of the third portion 32. The eight protrusions T5 are formed at equal intervals in the circumferential direction. The eight protrusions T5 are arranged across the entire inner surface of the third portion 32, from the inner circumference to the outer circumference. The protrusions T5 are narrow convex portions that extend radially from the relay shaft 503. The radial central portion of each protrusion T5 is curved so as to be convex toward the upstream side in the rotational direction of the input shaft 2. The recesses N5 are arranged between two adjacent protrusions T5. The eight recesses N5 communicate with the eight grooves 335a formed in the first portion 30 on the radially inner side of the recesses N5. Therefore, the eight grooves 335a formed in the first portion 30 communicate with the outside together with the eight recesses N5 formed in the third portion 32. In the intermediate shaft 503, eight protrusions T5 are formed on the inner surface of the third portion 32. As the intermediate shaft 503 rotates, the eight protrusions T5 cause air to be collected radially inward on the inner surface of the third portion 32 and flow into the grooves 335a. In this modified example, the eight grooves 335a, eight fins 355, eight protrusions T5, and eight recesses N5 formed on the intermediate shaft 503 constitute the air supply means 50.

[0073] A modified example of the relay shaft 3 of the above embodiment, the relay shaft 603, will be described with reference to Figure 12. As shown in Figure 12(a), eight grooves 336a are formed on the outer circumferential surface of the first portion 30 of the relay shaft 603. The grooves 336a are narrow grooves that extend in the axial direction of the relay shaft 603. The eight grooves 336a are formed at equal intervals in the circumferential direction. The grooves 336a are formed such that their width increases as they move away from the third portion 32 in the axial direction. A wing portion 356 is formed between two adjacent grooves 336a. Therefore, the first portion 30 of the relay shaft 603 has eight grooves 336a and eight wing portions 356 arranged alternately in the circumferential direction. As shown in Figure 12(b), eight protrusions T6 and eight recesses N6 are arranged on the inner surface of the third portion 32. The eight protrusions T6 are formed at equal intervals in the circumferential direction. The eight protrusions T6 are arranged over substantially the entire area of ​​the third portion 32, from the inner circumference to the outer circumference. The protrusions T6 are narrow convex portions extending radially from the relay shaft 603. The upstream end of the protrusion T6 on the input shaft 2 in the rotational direction is curved to be convex toward the downstream end of the input shaft 2 in the rotational direction. The downstream end of the protrusion T6 on the input shaft 2 in the rotational direction is curved to be convex toward the upstream end of the input shaft 2 in the rotational direction. The recesses N6 are arranged between two adjacent protrusions T6. The eight recesses N6 communicate with the eight grooves 336a formed in the first portion 30 on the radially inward side of the recesses N6. Therefore, the eight grooves 336a formed in the first portion 30 communicate with the outside together with the eight recesses N6 formed in the third portion 32. In the intermediate shaft 603, eight protrusions T6 are formed on the inner surface of the third portion 32. As the intermediate shaft 603 rotates, the eight protrusions T6 cause air to be collected radially inward on the inner surface of the third portion 32 and flow into the grooves 336a. In this modified example, the eight grooves 336a, six vane portions 356, eight protrusions T6, and eight recesses N6 formed on the intermediate shaft 603 constitute the air supply means 50.

[0074] In the above embodiments and modifications, the air supply means 50 is formed on the intermediate shaft 3, but is not limited thereto. The air supply means of the present invention only needs to supply air to the first sliding surfaces N1a and N1b on which the intermediate shaft 3 and the coupling 8 (rotation transmission member) slide. Therefore, the air supply means may be formed on a component other than the intermediate shaft 3, such as a hub 5 or a rotor 6. Furthermore, the air supply means may be formed on multiple components, such as the intermediate shaft 3, the hub 5, and the rotor 6. For example, a resin hub 5 may be used, and grooves may be formed on the inner circumferential surface of the hub 5 to supply air to the first sliding surfaces N1a and N1b. As shown in Figure 8, in an intermediate shaft 203 having six intake holes 362, six through grooves 332, and six recessed grooves 332a, if spiral through grooves in the opposite direction to the spiral through grooves 332 are formed on the inner circumferential surface of the hub 5, air can be easily supplied to the first sliding surfaces N1a and N1b.

[0075] For example, as shown in Figure 13, if a groove 5N is formed on the outer surface of the hub 5 (the surface in contact with the rotor 6), the groove 5N can be used as an air passage for heat dissipation from the metal rotor 6. In the cases of Figures 8, 9, and 11, the helix is ​​wound in one direction, so it is also possible to make it a helix in the opposite direction to match the rotation direction of the input shaft 2. For example, in Figure 8(a), the groove 332a may be inclined such that the part adjacent to the third part 32 is positioned on the downstream side in the rotation direction of the input shaft 2, and as it moves away from the third part 32, it is positioned on the upstream and downstream sides in the rotation direction of the input shaft 2. For example, in Figure 11, if the input shaft 2 is rotated in the opposite direction, the direction of airflow will be reversed, and air will still flow inside.

[0076] In the above embodiment, the intermediate shaft 3, coupling 8, and bearings 11a and 11b are formed of super engineering plastic, but are not limited to this. The materials of the intermediate shaft 3, coupling 8, and bearings 11a and 11b are arbitrary and may be formed of resins other than super engineering plastic. The input shaft 2 is not limited to being made of steel and may be made of resin.

[0077] In the above embodiment, a gear is provided on the outer circumference of the coupling 8 for transmitting driving force to an external device, but it is not limited to this. For example, a structure that transmits driving force to an external device by connecting with splines, serrations, or other shapes other than gears is also possible. [Explanation of symbols]

[0078] 1. Electromagnetic clutch 2 Input shafts 2a Motor (driving means) 3. Intermediate shaft 6 rotors 8. Coupling (rotational transmission member) 10 Armature 11 York 11a Bearing 11b bearing 33 Through groove 35 Wings 36 intake holes 50 Air supply means 103 Intermediate shaft 331 Through groove 351 Wings 361 intake holes 203 Intermediate shaft 332 Through groove 352 Wings 362 intake holes 303 Intermediate shaft 333 Through groove 353 Hanebe 363 intake holes 403 Intermediate shaft 334 Through groove 354 Wings 364 intake holes 503 Intermediate shaft 335 Through groove 355 Wings 603 Intermediate shaft 336 Through groove 356 Wings N1a, N1b 1st sliding surface N2a, N2b 2nd sliding surface

Claims

1. An input shaft that is rotationally driven by a drive mechanism and a resin intermediate shaft that rotates integrally with it, A rotor that rotates integrally with the input shaft, A resin rotation transmission member having an armature positioned on the outer circumference of the relay shaft and which can be made to be in close contact with or separated from the rotor, An electromagnetic clutch characterized by comprising an air supply means for supplying air to a first sliding surface on which the relay shaft and the rotation transmission member slide.

2. The electromagnetic clutch according to claim 1, characterized in that the air supply means has a plurality of through grooves penetrating from the outer circumferential surface of the intermediate shaft to the first sliding surface, a vane formed between two adjacent through grooves, and an intake hole communicating with the through grooves and formed on the end face of the intermediate shaft.

3. The electromagnetic clutch according to claim 2, characterized in that the intake hole communicates with the through groove on the rotation axis side of the input shaft more than the first sliding surface.

4. The relay shaft is rotatably fitted with a yoke that, together with the rotor, forms a magnetic path. The yoke is fitted to the outer circumference of the rotor via a bearing, The electromagnetic clutch according to any one of claims 1 to 3, characterized in that the air supplied to the first sliding surface by the air supply means is subsequently supplied to the second sliding surface on which the rotor and the bearing slide.

5. The electromagnetic clutch according to any one of claims 1 to 3, characterized in that the relay shaft and the rotation transmission member are made of super engineering plastic.

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