Electromagnetic clutch

Abstract

[Problem] To provide an electromagnetic clutch capable of preventing accumulation of foreign matter between a yoke and a magnetic circuit forming member. [Solution] An electromagnetic clutch (3) is provided with an annular electromagnetic coil (31), a yoke (32) that holds the electromagnetic coil (31), a magnetic circuit forming member (33) that forms a magnetic circuit of a magnetic flux generated by a current flowing through the electromagnetic coil (31), and an armature (34). The magnetic circuit forming member (33) rotates with respect to the yoke (32) in an oil bath state. The electromagnetic clutch (3) is provided with pump units (91, 92) for generating a flow of lubricating oil (8) between the yoke (32) and the magnetic circuit forming member (33). The pump sections (91, 92) have: inner tapered sections (911, 921) having tapered outer peripheral surfaces (911a, 921a); and an outer tapered portion (912, 922) having a tapered inner peripheral surface (912a, 922a), the inner tapered portion (911, 921) being formed on one of the magnetic circuit forming member (33) and the yoke (32), and the outer tapered portion (912, 922) being formed on the other of the magnetic circuit forming member (33) and the yoke (32).

Description

Technical Field

[0001] The present invention relates to an electromagnetic clutch used in an oil bath state. Background Art

[0002] Conventionally, for example, a vehicle driving force transmission system includes an electromagnetic clutch that operates an armature to interrupt torque by passing current through an electromagnetic coil held by a yoke. Patent Document 1 describes a driving force transmission device including an electromagnetic clutch as a pilot clutch mechanism.

[0003] The driving force transmission device described in Patent Document 1 includes an outer housing composed of a bottomed, cylindrical front housing with an opening at one end and a rear housing threadedly engaged with the opening of the front housing. The outer housing houses an inner shaft, a main clutch mechanism, a cam mechanism, and a pilot clutch mechanism. The main clutch mechanism includes a plurality of outer clutch plates splined to the inner circumference of the front housing and a plurality of inner clutch plates splined to the outer circumference of the inner shaft. The frictional sliding between these clutch plates is lubricated with lubricating oil.

[0004] The cam mechanism comprises a first cam member, a second cam member, and a plurality of cam bodies arranged between the first and second cam members. The relative rotation of the first and second cam members generates a cam thrust that presses against the main clutch mechanism. The pilot clutch mechanism comprises an electromagnet held by a yoke, a friction clutch, and an armature. The friction clutch is arranged between the rear housing and the armature, and is pressed toward the rear housing by the armature when current is supplied to the electromagnet. When the friction clutch is pressed, torque is transmitted from the front housing to the first cam member via the friction clutch, causing the first cam member to rotate relative to the second cam member, thereby pressing the second cam member against the main clutch mechanism.

[0005] The rear housing has an axially recessed annular portion, and the electromagnet is housed within this recess, supported by the yoke. Inner and outer gaps (clearances) are provided between the inner and outer circumferences of the yoke and the inner surface of the annular recess. When current is applied to the electromagnet, a magnetic circuit is formed, circulating through the yoke, the inner gap, the rear housing, the friction clutch, the armature, the friction clutch, the rear housing, the outer gap, and the yoke. An annular cylindrical body made of non-magnetic material is embedded in the radially middle portion of the rear housing, functioning as a magnetic path-forming member that forms the magnetic flux path.

[0006] Furthermore, in the driving force transmission device described in Patent Document 1, a hardened layer is formed on the surfaces of the rear housing and the yoke facing the two gaps through a soft nitriding process. The hardened layer has a hardness that prevents foreign matter such as iron powder from entering the gap from being bitten into. Even if foreign matter does enter the gap, it can prevent it from accumulating in the gap.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-219966 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] In the structure described in Patent Document 1, a hardened layer based on a soft nitriding process is formed on the rear housing and the magnetic yoke to suppress the negative effects of foreign matter entering the gap between them. However, since this hardened layer is non-magnetic, the magnetic resistance of the magnetic circuit increases due to the formation of the hardened layer, and the magnetic properties are reduced. In addition, the man-hours required for the soft nitriding process increase, and the manufacturing cost increases. Therefore, an object of the present invention is to provide an electromagnetic clutch that can prevent the accumulation of foreign matter between the magnetic yoke and the magnetic path forming member even without forming a hardened layer on the magnetic yoke and the magnetic path forming member.

[0012] Means for solving problems

[0013] In order to achieve the above-mentioned purpose, the present invention provides an electromagnetic clutch, comprising: an annular electromagnetic coil; a yoke that holds the electromagnetic coil; a magnetic path forming member that forms a magnetic path of a magnetic flux generated by current flowing through the electromagnetic coil; and an armature that is attracted by the magnetic flux toward the magnetic path forming member side, and the magnetic path forming member rotates relative to the yoke in an oil bath state, wherein a pump portion is constituted by a portion of each of the magnetic path forming member and the yoke, and the pump portion generates a flow of lubricating oil between the yoke and the magnetic path forming member, and the pump portion has: an inner cone portion having a tapered outer peripheral surface; and an outer cone portion having a tapered inner peripheral surface opposite to the tapered outer peripheral surface with a gap therebetween, the inner cone portion being formed on one side of the magnetic path forming member and the yoke, and the outer cone portion being formed on the other side of the magnetic path forming member and the yoke.

[0014] Effects of the Invention

[0015] According to the electromagnetic clutch of the present invention, it is possible to prevent foreign matter from accumulating between the yoke and the magnetic path forming member. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic configuration diagram schematically showing a configuration example of a vehicle equipped with a driving force transmission device including an electromagnetic clutch according to an embodiment of the present invention.

[0017] Figure 2 This is a cross-sectional view showing the driving force transmission device housed in the housing portion of the transformer case together with the first shaft and the second shaft.

[0018] Figure 3It will Figure 2 An enlarged view showing a portion of FIG.

[0019] Figure 4 It will Figure 3 Part A is an enlarged view of a main part showing a further enlargement. DETAILED DESCRIPTION

[0020] [Implementation Method]

[0021] Reference Figures 1 to 4 The embodiments of the present invention will be described. It should be noted that the embodiments described below are specific examples of preferred embodiments of the present invention, and some parts specifically illustrate various technically preferred technical matters, but the technical scope of the present invention is not limited to these specific forms.

[0022] Figure 1 This is a schematic diagram schematically illustrating an example of the structure of a vehicle 1 equipped with a driving force transmission device 2 including an electromagnetic clutch according to an embodiment of the present invention. This vehicle 1 is a four-wheel drive vehicle capable of driving left and right front wheels 101 and 102 and left and right rear wheels 103 and 104. Vehicle 1 includes an engine 11 as a driving source. The rotation of the output shaft of engine 11 is shifted by a transmission 12 and output to a transfer case 13. Alternatively, an electric motor or a so-called hybrid system combining an engine and an electric motor may be used as the driving source.

[0023] In this embodiment, the driving force of the engine 11 is always transmitted to the front wheels 101 and 102, and is then transmitted to the rear wheels 103 and 104 depending on the vehicle's state. That is, in this embodiment, the front wheels 101 and 102 serve as the main drive wheels, while the rear wheels 103 and 104 serve as auxiliary drive wheels. For example, during acceleration or when the front wheels 101 and 102 slip, the driving force is transmitted to the rear wheels 103 and 104.

[0024] The vehicle 1 includes a propeller shaft 14 for the front wheels and a differential 15. The propeller shaft 14 for the front wheels transmits the driving force output from the transfer case 13 to the front wheels to the differential 15. The differential 15 distributes the driving force input from the propeller shaft 14 to the left and right front wheels 101 and 102 via left and right drive shafts 151 and 152.

[0025] The vehicle 1 also includes a propeller shaft 16 on the rear wheel side and a differential device 17. The propeller shaft 16 on the rear wheel side transmits the driving force output from the transfer case 13 to the rear wheel side to the differential device 17. The differential device 17 distributes the driving force input from the propeller shaft 16 to the left and right rear wheels 103 and 104 via left and right drive shafts 161 and 162.

[0026] The transfer case 13 includes a transfer case housing 133 having a housing body 131 and a housing cover 132. The transfer case 133 includes a housing portion 130 for accommodating the driving force transmission device 2. Lubricating oil is enclosed in the housing portion 130. The driving force transmission device 2 is disposed in an oil bath within the housing portion 130 and is controlled by the control device 18. The control device 18 controls the driving force transmission device 2 based on the magnitude of the current supplied to the driving force transmission device 2.

[0027] The driving force transmission device 2 transmits the driving force corresponding to the current supplied from the control device 18 from the first shaft 134 to the second shaft 135. The first shaft 134 is connected to the output shaft 121 of the transmission 12, and the second shaft 135 is connected to the propeller shaft 16 on the rear wheel side. The first shaft 134 is the input shaft of the driving force transmission device 2, and the second shaft 135 is the output shaft of the driving force transmission device 2.

[0028] The driving force of the engine 11 is transmitted to the propeller shaft 14 on the front wheel side via a driving sprocket 136 fixed to the first shaft 134, a transmission chain 137 wound around the driving sprocket 136, a driven sprocket 138 around which the transmission chain 137 is wound, and a front wheel side output shaft 139 to which the driven sprocket 138 is fixed.

[0029] The driving force is transmitted to the rear-wheel propeller shaft 16 via the driving force transmission device 2. The amount of driving force not transmitted to the rear-wheel propeller shaft 16 is transmitted to the front-wheel propeller shaft 14. The greater the current supplied by the control device 18, the greater the driving force transmitted by the driving force transmission device 2. The control device 18 adjusts the current supplied to the driving force transmission device 2 to control the driving force transmission device 2 based on vehicle conditions such as the rotational speed of the front wheels 101, 102 and the rear wheels 103, 104, the vehicle speed, the amount of accelerator pedal operation, and the yaw rate.

[0030] Figure 2 1 is a cross-sectional view showing the driving force transmission device 2 housed in the housing portion 130 together with the first shaft 134 and the second shaft 135. Figure 2 , the driving force transmission device 2 is shown in a cross section along the rotation axis O of the first shaft 134 and the second shaft 135 . Figure 3 It will Figure 2 An enlarged view showing a portion of Figure 4 It will Figure 3 1 is an enlarged view of a main part showing a further enlarged portion A of FIG. Hereinafter, the direction parallel to the rotation axis O is referred to as the axial direction. When the driving force transmission device 2 is mounted on the vehicle 1 , the rotation axis O is horizontal.

[0031] Figures 2 to 4 The vertical direction of the drawing corresponds to the vertical direction of the driving force transmission device 2 mounted on the vehicle 1. Figure 2, an oil level 80 of the lubricating oil 8 is shown in a state where the vehicle 1 is stopped and the driving force transmission device 2 is not rotating. Figure 3 A portion of the driving force transmission device 2 located below the rotation axis O is shown. Oil seals 130a and 130b for preventing leakage of the lubricating oil 8 sealed in the accommodating portion 130 are attached to the case body 131 and the case cover 132 of the transfer case 133 .

[0032] The driving force transmission device 2 includes an electromagnetic clutch 3; a cam mechanism 4, which is operated by the torque transmitted by the electromagnetic clutch 3 to generate a cam thrust; a main clutch 5, which is pressed axially by the cam thrust of the cam mechanism 4; and a cylindrical sleeve 6, which is interposed between the main clutch 5 and the first shaft 134. The torque transmitted by the electromagnetic clutch 3 is amplified by the cam mechanism 4 and the main clutch 5, and the driving force is transmitted from the first shaft 134 to the second shaft 135 via the sleeve 6 and the main clutch 5.

[0033] The sleeve 6 has a plurality of axially extending inner circumferential spline projections 6a formed on its inner circumferential surface, and a plurality of axially extending outer circumferential spline projections 6b formed on its outer circumferential surface. The first shaft 134 has a plurality of spline projections 134a formed on its outer circumferential surface for engagement with the plurality of inner circumferential spline projections 6a of the sleeve 6. The end portion of the first shaft 134 is non-rotatably fitted into the inner side of the sleeve 6.

[0034] The electromagnetic clutch 3 includes an annular electromagnetic coil 31, which is supplied with current from the control device 18; a yoke 32, which holds the electromagnetic coil 31; a magnetic path forming member 33, which forms a magnetic path for the magnetic flux generated by the current flowing through the electromagnetic coil 31; an armature 34, which is attracted toward the magnetic path forming member 33 by this magnetic flux; a pilot clutch 35, which is axially arranged between the magnetic path forming member 33 and the armature 34; a rotation receiving member 36, which rotates integrally with the magnetic path forming member 33; and a bearing 37, which is arranged between the magnetic path forming member 33 and the yoke 32. The bearing 37 supports the magnetic path forming member 33 so that it can rotate relative to the yoke 32.

[0035] The rotating housing member 36 houses the magnetic path forming member 33, the armature 34, the pilot clutch 35, the cam mechanism 4, the main clutch 5, and the sleeve 6. The yoke 32, the magnetic path forming member 33, the pilot clutch 35, and the armature 34 are arranged axially side by side, with the magnetic path forming member 33 and the pilot clutch 35 disposed between the yoke 32 and the armature 34. The rotating housing member 36 and the magnetic path forming member 33 are disposed within the housing portion 130 of the transfer case 133 while being bathed in lubricating oil 8, and rotate relative to the yoke 32 while in the oil bath.

[0036] The magnetic circuit forming member 33 includes an inner magnetic member 331 and an outer magnetic member 332, each made of a soft magnetic material, arranged concentrically around the rotation axis O, and an annular non-magnetic portion 333 disposed between the inner magnetic member 331 and the outer magnetic member 332. In this embodiment, the non-magnetic portion 333 is made of a non-magnetic metal such as austenitic stainless steel. The inner magnetic member 331 and the outer magnetic member 332 are made of, for example, a soft magnetic metal primarily composed of iron. The inner circumferential end of the non-magnetic portion 333 is fixed to the inner magnetic member 331 by welding, and the outer circumferential end is fixed to the outer magnetic member 332 by welding. A sliding bearing 70 is press-fitted into the inner circumferential surface of the inner magnetic member 331, and the first shaft 134 is inserted into the inner side of the sliding bearing 70.

[0037] An annular recess 330 centered on the rotation axis O is formed in the magnetic path-forming member 33. This recess accommodates a portion of the yoke 32 in the axial direction. The recess 330 is formed between the inner magnetic member 331 and the outer magnetic member 332 and is axially open toward the side opposite the pilot clutch 35 and the armature 34. The non-magnetic portion 333 is located at the innermost portion of the annular recess 330 in the axial direction.

[0038] The rotating receiving member 36 is a bottomed cylindrical member integrally formed with a cylindrical portion 361 and a disc-shaped bottom portion 362 disposed inside the cylindrical portion 361. A plurality of splined protrusions 361a extending in the axial direction are formed on the inner circumferential surface of the cylindrical portion 361. The bottom portion 362 is disposed inside one axial end of the cylindrical portion 361. The other axial end of the cylindrical portion 361 is screwed into the outer magnetic member 332 of the magnetic path forming member 33. A washer 71 is disposed between the bottom portion 362 and the sleeve 6.

[0039] A fitting hole 360 is formed in the center of the bottom portion 362, into which the second shaft 135 fits. A plurality of spline projections 362a extending in the axial direction are formed on the inner circumferential surface of the fitting hole 360. A plurality of spline projections 135a are formed on the outer circumferential surface of the second shaft 135. These spline projections 135a engage with the plurality of spline projections 362a formed on the inner circumferential surface of the fitting hole 360, thereby fitting the second shaft 135 to the rotation receiving member 36 in a relatively non-rotatable manner.

[0040] like Figure 3 As shown, the pilot clutch 35 includes a plurality of pilot outer clutch plates 351 and a plurality of pilot inner clutch plates 352. The pilot outer clutch plates 351 and the pilot inner clutch plates 352 are formed of a soft magnetic metal and are annular. The frictional sliding between the pilot outer clutch plates 351 and the pilot inner clutch plates 352 is lubricated by lubricating oil 8.

[0041] A plurality of engaging protrusions 351a are formed on the outer peripheral end of the pilot outer clutch plate 351, and a plurality of arc-shaped slits 351b are formed in a portion axially aligned with the non-magnetic portion 333 of the magnetic path forming member 33. The pilot outer clutch plate 351 is axially movable but non-rotatable relative to the rotating housing member 36 by virtue of the plurality of engaging protrusions 351a engaging with the plurality of spline protrusions 361a of the rotating housing member 36.

[0042] A plurality of engaging protrusions 352a are formed on the inner circumferential end of the pilot inner clutch plate 352, and a plurality of arc-shaped slits 352b are formed in a portion axially aligned with the non-magnetic portion 333 of the magnetic path forming member 33. The pilot inner clutch plate 352 is engaged with the pilot cam 41 of the cam mechanism 4, described later, via the plurality of engaging protrusions 352a, allowing axial movement relative to the pilot cam 41 but preventing relative rotation.

[0043] The armature 34 is made of a soft magnetic metal formed into an annular plate shape and has a plurality of engaging protrusions 34a formed on its outer peripheral end. The engaging protrusions 34a engage with the spline protrusions 361a of the rotating housing member 36, and the armature 34 is axially movable but non-rotatable relative to the rotating housing member 36.

[0044] The electromagnetic coil 31 has a winding 311 through which current supplied from the control device 18 flows. The winding 311 is sealed by a resin-molded sealing member 312. The winding 311 is made of, for example, an enameled wire, and current is supplied from the control device 18 via an electric wire 310.

[0045] The yoke 32 is made of a soft magnetic metal formed into an annular shape, and integrally includes an inner portion 321 axially parallel to the inner magnetic member 331 of the magnetic path forming member 33, an outer portion 322 axially parallel to the outer magnetic member 332 of the magnetic path forming member 33, and a side wall portion 323 axially parallel to the electromagnetic coil 31. Figure 2 As shown, the yoke 32 is locked against rotation relative to the transfer case 133 by engaging with a locking portion 131a provided on the case body 131 of the transfer case 133. A housing portion 320 for housing and retaining the electromagnetic coil 31 is formed between the inner portion 321 and the outer portion 322. The housing portion 320 is axially open toward the non-magnetic portion 333 of the magnetic path forming member 33.

[0046] The bearing 37 is a shielded rolling bearing having an inner ring 371 and an outer ring 372, a plurality of rolling elements 373 disposed between the inner ring 371 and the outer ring 372, a retaining frame 374 for retaining the plurality of rolling elements 373, and a pair of shield members 375 disposed between the inner ring 371 and the outer ring 372. Figure 4As shown, the shield member 375 is formed into an annular shape and integrally includes a fixed portion 375a fixed to the outer ring 372, an opposing portion 375b that faces the outer circumferential surface 371a of the inner ring 371 with a gap therebetween, and a wall portion 375c between the fixed portion 375a and the opposing portion 375b. Annular grooves 372a are formed at both axial ends of the outer ring 372, and the fixed portions 375a of the shield member 375 engage with these annular grooves 372a.

[0047] In this embodiment, the rolling element 373 is spherical, but the present invention is not limited thereto and the rolling element 373 may also be cylindrical, for example. In addition, in this embodiment, the shielding member 375 is respectively arranged at both axial ends of the bearing 37, but the shielding member 375 may be arranged only at one axial end of the bearing 37.

[0048] In this embodiment, the shield member 375 is fixed to the outer ring 372, and a gap is formed between the shield member 375 and the inner ring 371. However, conversely, the shield member 375 may be fixed to the inner ring 371, and a gap may be formed between the shield member 375 and the outer ring 372. In other words, the shield member 375 may be fixed to one of the inner ring 371 and the outer ring 372, and a gap may be formed between the shield member 375 and the other of the inner ring 371 and the outer ring 372.

[0049] An inner ring fitting portion 331a that fits into the inner ring 371 of the bearing 37 is provided at the axial ends of the magnetic circuit forming member 33 on the yoke 32 side. The inner ring fitting portion 331a is a portion of the inner magnetic member 331 and is pressed into the inner ring 371. A shim 72 is arranged axially between the inner ring 371 and the inner magnetic member 331 to adjust the axial gap between the yoke 32 and the magnetic circuit forming member 33. The shim 72 is axially aligned with the inner ring 371 and is sandwiched between the side surface 371b of the inner ring 371 and the shim contact surface 331b formed on the inner magnetic member 331.

[0050] The cam mechanism 4 includes a pilot cam 41 positioned inside the pilot clutch 35; a main cam 42 positioned closer to the main clutch 5 than the pilot cam 41; a plurality of rolling elements 43 positioned between the pilot cam 41 and the main cam 42; and a retainer 44 that holds the rolling elements 43. The outer circumference of the pilot cam 41 is formed with a plurality of splined protrusions 41a that engage with the plurality of engaging protrusions 352a of the pilot inner clutch plate 352. The pilot cam 41 rotates relative to the main cam 42 by torque transmitted from the rotation receiving member 36 via the pilot clutch 35.

[0051] The main cam 42 integrally includes a cam portion 421 axially opposed to the pilot cam 41, and a pressing portion 422 for pressing the main clutch 5. Multiple cam grooves 41b are formed on the surface of the pilot cam 41 that faces the cam portion 421 of the main cam 42. Multiple cam grooves 421a are formed on the surface of the cam portion 421 of the main cam 42 that faces the pilot cam 41. The cam grooves 41b and 421a extend in an arc shape along the circumference, with the axial depth being greatest at the circumferential center and gradually decreasing in depth toward the circumferential ends.

[0052] The axial movement of the pilot cam 41 in the direction away from the main cam 42 is restricted by the thrust roller bearing 73. The thrust roller bearing 73 is arranged between the inner magnetic member 331 of the magnetic path forming member 33 and the back surface 41c of the pilot cam 41.

[0053] The inner circumferential end of the pressing portion 422 of the main cam 42 is formed with a plurality of engaging protrusions 422a that engage with the plurality of outer circumferential spline protrusions 6b formed on the sleeve 6. The engagement of the engaging protrusions 422a with the outer circumferential spline protrusions 6b allows the main cam 42 to move axially relative to the sleeve 6 but prevents relative rotation. Furthermore, an elastic member 74 is disposed between the back surface 421b of the cam portion 421 of the main cam 42 and the sleeve 6 to bias the main cam 42 toward the pilot cam 41. The elastic member 74 is formed, for example, of a wave washer and is compressed in the axial direction.

[0054] When no current is supplied to the electromagnetic coil 31, the rolling element 43 is located in the center of the cam grooves 41b and 421a, and no cam thrust is generated by the cam mechanism 4, and the main clutch 5 is not pressed. Figure 3 , and the armature 34 is attracted toward the magnetic path forming member 33. The magnetic path 30 includes an inner gap 301, which is the gap between the inner magnetic member 331 of the magnetic path forming member 33 and the inner portion 321 of the yoke 32, and an outer gap 302, which is the gap between the outer magnetic member 332 of the magnetic path forming member 33 and the outer portion 322 of the yoke 32. The sizes of the inner gap 301 and the outer gap 302 vary depending on the thickness of the gasket 72. The gasket 72 is selected so that the sizes of the inner gap 301 and the outer gap 302 are appropriate values.

[0055] When the armature 34 is attracted toward the magnetic path forming member 33, the pilot clutch 35 is compressed, and the multiple pilot outer clutch plates 351 and pilot inner clutch plates 352 come into frictional contact, transmitting torque to the pilot cam 41. As the pilot cam 41 rotates relative to the main cam 42, the rolling elements 43 roll in the cam grooves 41b and 421a, generating a cam thrust, which causes the main cam 42 to press the main clutch 5. The greater the current supplied to the electromagnetic coil 31, the greater the cam thrust.

[0056] The main clutch 5 includes a plurality of main outer clutch plates 51 and a plurality of main inner clutch plates 52. The plurality of main outer clutch plates 51 and the plurality of main inner clutch plates 52 are alternately arranged in the axial direction.

[0057] like Figure 3 As shown, a plurality of engagement protrusions 51a are formed on the outer peripheral end of the main outer clutch plate 51. The main outer clutch plate 51 is axially movable but non-rotatable relative to the rotation receiving member 36 by engaging the plurality of engagement protrusions 51a with the plurality of spline protrusions 361a of the rotation receiving member 36.

[0058] A plurality of engagement protrusions 52a are formed on the inner peripheral end of the main inner clutch plate 52. The main inner clutch plate 52 is axially movable and non-rotatable relative to the sleeve 6 by engagement of the plurality of engagement protrusions 52a with the plurality of outer peripheral spline protrusions 6b of the sleeve 6.

[0059] The frictional sliding between the main outer clutch plate 51 and the main inner clutch plate 52 is lubricated by the lubricating oil 8. The main outer clutch plate 51, the pressing portion 422 of the main cam 42, and the bottom 362 of the rotation receiving member 36 are respectively formed with oil holes 51b, 422b, and 362b for flowing the lubricating oil 8.

[0060] The cylindrical portion 361 of the rotating housing member 36 has a maximum outer diameter portion 361b at one end located on the outer periphery of the magnetic path forming member 33, and has a smaller diameter portion 361c located closer to the other end than the maximum outer diameter portion 361b. The smaller diameter portion 361c corresponds to the outer periphery of the main clutch 5 and the main cam 42.

[0061] When the rotating receiving member 36 rotates around the rotation axis O, in the receiving portion 130 of the transfer case housing 133, the lubricating oil 8 is biased toward the yoke 32 side due to the difference in outer diameter between the maximum outer diameter portion 361b and the small diameter portion 361c of the rotating receiving member 36. That is, when the rotating receiving member 36 rotates, the circumferential speed of the maximum outer diameter portion 361b is faster than the circumferential speed of the small diameter portion 361c, so the lubricating oil 8 flows from the small diameter portion 361c side to the maximum outer diameter portion 361b side with a faster circumferential speed, and further flows from the portion corresponding to the outer periphery of the maximum outer diameter portion 361b to the yoke 32 side. The lubricating oil 8 flowing toward the yoke 32 side flows between the side wall portion 323 of the yoke 32 and the housing body 131, and is supplied to the bearing 37. Figure 2 In FIG. 1 , the flow of the lubricating oil 8 is indicated by a plurality of arrows.

[0062] The lubricating oil 8 supplied to the bearing 37 flows through the gap between the shield member 375 and the inner ring 371 of the bearing 37 and flows into the inner gap 301 and the outer gap 302. In order to reduce the magnetic resistance of the magnetic flux in the magnetic circuit 30, the inner gap 301 and the outer gap 302 are adjusted to be narrow. Figure 4 As shown, if foreign matter 81 is mixed with lubricating oil 8 and remains in inner gap 301 or outer gap 302, there is a possibility of blockage in inner gap 301 or outer gap 302, or a change in the magnetic resistance of the magnetic flux in magnetic circuit 30. In particular, if foreign matter 81 is iron powder, foreign matter 81 is likely to adhere to yoke 32 or magnetic circuit forming member 33 due to magnetic force.

[0063] Therefore, in this embodiment, if Figure 4 As shown, two inner and outer pump sections 91 and 92 are formed by parts of the yoke 32 and the magnetic path forming member 33 to generate a flow of lubricating oil 8 between the yoke 32 and the magnetic path forming member 33. Of the two inner and outer pump sections 91 and 92, one pump section 91 provided radially inwardly of the yoke 32 and the magnetic path forming member 33 is formed by parts of the inner magnetic member 331 of the magnetic path forming member 33 and the inner portion 321 of the yoke 32, and the other pump section 92 provided radially outwardly of the yoke 32 and the magnetic path forming member 33 is formed by parts of the outer magnetic member 332 of the magnetic path forming member 33 and the outer portion 322 of the yoke 32.

[0064] These pump units 91 and 92 apply flow pressure from the radial inner side to the outer side of the magnetic path forming member 33 to the lubricating oil 8 between the yoke 32 and the magnetic path forming member 33, and can also be said to be flow pressure applying units. Hereinafter, one pump unit 91 is referred to as the inner pump unit 91, and the other pump unit 92 is referred to as the outer pump unit 92. Figure 4 In FIG. 1 , the inner pump portion 91 and the outer pump portion 92 are enclosed by dotted lines.

[0065] The inner pump portion 91 includes an inner conical portion 911 having a conical outer peripheral surface 911a and an outer conical portion 912 having a conical inner peripheral surface 912a opposite to the conical outer peripheral surface 911a across a gap. The inner conical portion 911 is formed on the inner magnetic member 331 of the magnetic path forming member 33, and the outer conical portion 912 is formed on the inner portion 321 of the yoke 32. The conical outer peripheral surface 911a and the conical inner peripheral surface 912a are inclined relative to the axial direction and parallel to each other, and are opposite to each other across the inner gap 301. The conical outer peripheral surface 911a is a conical inclined surface whose outer diameter increases as it approaches the inner side of the annular recess 330. The conical inner peripheral surface 912a is a conical inclined surface whose inner diameter increases as it approaches the inner side of the annular recess 330.

[0066] The outer pump portion 92 includes an inner conical portion 921 having a conical outer peripheral surface 921a and an outer conical portion 922 having a conical inner peripheral surface 922a opposite to the conical outer peripheral surface 921a across a gap. The inner conical portion 921 is formed on the outer portion 322 of the yoke 32, and the outer conical portion 922 is formed on the outer magnetic member 332 of the magnetic path forming member 33. The conical outer peripheral surface 921a and the conical inner peripheral surface 922a are inclined relative to the axial direction and are parallel to each other. The conical outer peripheral surface 921a is a conical inclined surface whose outer diameter decreases as it approaches the inner side of the annular recess 330. The conical inner peripheral surface 922a is a conical inclined surface whose inner diameter decreases as it approaches the inner side of the annular recess 330.

[0067] When the magnetic path forming member 33 rotates, the lubricating oil 8 in the inner gap 301 generates centrifugal force, causing the lubricating oil 8 to flow along the tapered inner circumferential surface 912a toward the inner side of the annular recess 330. Furthermore, the lubricating oil 8 in the outer gap 302 generates centrifugal force, causing the lubricating oil 8 to flow along the tapered inner circumferential surface 922a from the inner side of the annular recess 330 toward the opening. This flow of lubricating oil 8 prevents foreign matter 81 from accumulating in the inner gap 301 or the outer gap 302 and clogging them. Furthermore, it prevents foreign matter 81 from flowing back into the space between the yoke 32 and the magnetic path forming member 33, along with the lubricating oil 8, from the outlet 300 of the lubricating oil 8 flow path between the yoke 32 and the magnetic path forming member 33. The outlet 300 is the portion between the axial end of the outer magnetic member 332 of the magnetic path forming member 33 and the outer portion 322 of the yoke 32.

[0068] The length L1 of the flow path for lubricating oil 8 between the tapered outer circumferential surface 911a and the tapered inner circumferential surface 912a of the inner pump section 91, and the length L2 of the flow path for lubricating oil 8 between the tapered outer circumferential surface 921a and the tapered inner circumferential surface 922a of the outer pump section 92 are preferably 5 mm or more, and more preferably 10 mm or more. By setting L1 and L2 to 5 mm or more, the increase in magnetic resistance in the inner pump section 91 and the outer pump section 92 can be suppressed. In addition, if L1 and L2 are 10 mm or more, the increase in magnetic resistance in the inner pump section 91 and the outer pump section 92 can be sufficiently suppressed, and torque can be ensured.

[0069] Furthermore, the taper angle θ1 of the tapered outer circumferential surface 911a of the inner pump section 91 and the taper angle θ2 of the tapered inner circumferential surface 912a are preferably the same, and the taper angle θ3 of the tapered outer circumferential surface 921a of the outer pump section 92 and the taper angle θ4 of the tapered inner circumferential surface 922a of the outer pump section 92 are preferably the same. Consequently, the separation distance between the tapered outer circumferential surface 911a and the tapered inner circumferential surface 912a of the inner pump section 91 is the same distance throughout the entire length L1 of the flow path. This prevents a significant difference in magnetic resistance between the inner and outer diameters of the inner pump section 91, thereby suppressing magnetic saturation in the inner pump section 91. Furthermore, the separation distance between the tapered outer circumferential surface 921a and the tapered inner circumferential surface 922a of the outer pump section 92 is the same distance throughout the entire length L2 of the flow path. This prevents a significant difference in magnetic resistance between the inner and outer diameters of the outer pump section 92, thereby suppressing magnetic saturation in the outer pump section 92. The taper angles θ1 to θ4 are angles formed by the tapered outer circumferential surface 911 a and the tapered inner circumferential surface 912 a of the inner pump portion 91 and the tapered outer circumferential surface 921 a and the tapered inner circumferential surface 922 a of the outer pump portion 92 relative to the axial direction.

[0070] The taper angles θ1 to θ4 are preferably 5 degrees or greater to achieve a sufficient pumping effect to expel foreign matter that has intruded into the inner and outer gaps 301 and 302. To ensure sufficient magnetic path area within the inner and outer gaps 301 and 302, they are preferably 40 degrees or less. If the taper angles θ1 to θ4 are approximately 45 degrees or greater, the magnetic path area within the inner and outer gaps 301 and 302 decreases, increasing the magnetic resistance.

[0071] Lubricating oil 8 is supplied to the inner pump unit 91 and the outer pump unit 92 from between the inner end of the magnetic path forming member 33 on the yoke 32 side and the yoke 32. In this embodiment, the end of the magnetic path forming member 33 on the yoke 32 side is the inner ring fitting portion 331a, and the bearing 37 is disposed between this inner ring fitting portion 331a and the yoke 32. Furthermore, the lubricating oil 8 that passes through the gap between the shield member 375 and the inner ring 371 of the bearing 37 is supplied to the inner pump unit 91 and the outer pump unit 92. Therefore, the shield member 375 and the inner ring 371 of the bearing 37 function as a filter that prevents foreign matter 81 in the lubricating oil 8 from flowing toward the inner pump unit 91 and the outer pump unit 92. In other words, the shield member 375 and the inner ring 371 of the bearing 37 constitute a filter that prevents foreign matter 81 in the lubricating oil 8 from flowing toward the inner pump unit 91 and the outer pump unit 92.

[0072] When the gap between the facing portion 375b of the shield member 375 in the bearing 37 and the outer circumferential surface 371a of the inner ring 371 is defined as D0, the gap between the tapered outer circumferential surface 911a and the tapered inner circumferential surface 912a of the inner pump portion 91 is defined as D1, and the gap between the tapered outer circumferential surface 921a and the tapered inner circumferential surface 922a of the outer pump portion 92 is defined as D2, D0 is smaller than D1 and D2. For example, D0 is smaller than 0.2 mm, and D1 and D2 are, for example, not less than 0.2 mm and not more than 0.3 mm.

[0073] Thus, the foreign matter passage diameter of the gap between shield member 375 and inner race 371 in bearing 37 is smaller than the size of the gap between tapered outer circumferential surface 911a and tapered inner circumferential surface 912a in inner pump section 91, and the size of the gap between tapered outer circumferential surface 921a and tapered inner circumferential surface 922a in outer pump section 92. Here, the foreign matter passage diameter refers to the maximum diameter of a foreign object that can pass through the gap between shield member 375 and inner race 371 in bearing 37, assuming a spherical foreign object. This structure prevents foreign matter 81, which is too large to pass through inner gap 301 or outer gap 302, from entering inner gap 301 or outer gap 302.

[0074] (Effects of Implementation Methods)

[0075] According to the embodiment described above, the pumping action of the inner pump unit 91 and the outer pump unit 92 causes the lubricating oil 8 between the yoke 32 and the magnetic path forming member 33 to flow toward the outlet portion 300, thereby preventing foreign matter from becoming lodged between the yoke 32 and the magnetic path forming member 33. Furthermore, due to the outer diameter difference between the maximum outer diameter portion 361b and the smaller diameter portion 361c of the cylindrical portion 361 of the rotating housing member 36, when the rotating housing member 36 rotates in an oil bath, the lubricating oil 8 is concentrated on the yoke 32 side within the housing portion 130, thereby supplying a sufficient amount of lubricating oil 8 between the yoke 32 and the magnetic path forming member 33. Furthermore, the bearing 37 functions as a filter, thereby preventing large foreign matter 81 from entering between the yoke 32 and the magnetic path forming member 33. Furthermore, since a hardened layer is not formed on the yoke and the magnetic path forming member as described in Patent Document 1, the driving force transmission device 2 can be made inexpensive and have excellent magnetic properties.

[0076] (Note)

[0077] The present invention has been described above based on the embodiments, but these embodiments do not limit the invention according to the claims. Furthermore, it should be noted that the combinations of features described in the embodiments are not necessarily all necessary for solving the problems of the invention. Furthermore, the present invention can be implemented by omitting some structures, adding or replacing structures, or by appropriately modifying the present invention without departing from its main purpose. For example, the present invention can be implemented by modifying the following (1) to (5).

[0078] (1) In the above embodiment, based on Figure 1 The structure of the vehicle 1 in which the driving force transmission device 2 is used for the transfer case 13 is described, but the structure of the vehicle is not limited to this. For example, the driving force transmission device 2 can be arranged between the rear end portion of the drive shaft extending from the transmission and the differential device 17 on the rear wheel side, or the driving force transmission device 2 can be arranged between the differential device 17 and the left drive shaft 161 or the right drive shaft 162.

[0079] (2) In the above embodiment, the electromagnetic clutch 3 includes the inner pump unit 91 and the outer pump unit 92 . However, the present invention is not limited thereto, and one of the inner pump unit 91 and the outer pump unit 92 may be omitted.

[0080] (3) In the above embodiment, the bearing 37 is used as a filter. However, the present invention is not limited thereto. For example, a mesh filter may be used to prevent large foreign matter 81 from entering between the yoke 32 and the magnetic path forming member 33 .

[0081] (4) In the above embodiment, the electromagnetic clutch 3 is combined with the cam mechanism 4 and the main clutch 5 to form the driving force transmission device 2 . However, the electromagnetic clutch 3 may be used alone depending on the application and torque transmission capacity.

[0082] (5) In the above-mentioned embodiment, the electromagnetic clutch 3 is described as a multi-plate friction clutch having a plurality of pilot outer clutch plates 351 and a plurality of pilot inner clutch plates 352. However, the present invention is not limited thereto. The electromagnetic clutch 3 may be a single-plate friction clutch in which the pilot clutch 35 is omitted and torque is transmitted by friction between the armature 34 and the magnetic path forming member 33.

[0083] Description of labels

[0084] 3…Electromagnetic clutch

[0085] 301…Inside gap

[0086] 302…outer gap

[0087] 31…Solenoid coil

[0088] 32…Yoke

[0089] 321…Inner part

[0090] 322…outer part

[0091] 33…Magnetic circuit forming member

[0092] 331…Inner magnetic member

[0093] 332…Outer magnetic member

[0094] 333…Non-magnetic part

[0095] 34…Armature

[0096] 36...rotating receiving member

[0097] 361b…maximum outer diameter

[0098] 361c…Trail section

[0099] 37…Bearings

[0100] 371…Inner Circle

[0101] 372…outer ring

[0102] 375…Shielding component

[0103] 8…Lubricating oil

[0104] 81…Foreign matter

[0105] 91…Inner pump

[0106] 911…Inner cone

[0107] 911a…conical outer surface

[0108] 912…Outer cone

[0109] 912a…conical inner surface

[0110] 92…Outer pump

[0111] 921…Inner cone

[0112] 921a…conical outer surface

[0113] 922…Outer cone

[0114] 922a…conical inner surface

Claims

1. An electromagnetic clutch comprising: an annular electromagnetic coil; a yoke for holding the electromagnetic coil; a magnetic path forming member for forming a magnetic path of magnetic flux generated by current flowing through the electromagnetic coil; and an armature attracted by the magnetic flux toward the magnetic path forming member, the magnetic path forming member rotating relative to the yoke in an oil bath state, wherein: A pump portion is formed by a portion of each of the magnetic path forming member and the yoke, and the pump portion generates a flow of lubricating oil between the yoke and the magnetic path forming member. The pump portion includes: an inner tapered portion having a tapered outer peripheral surface; and an outer tapered portion having a tapered inner peripheral surface facing the tapered outer peripheral surface with a gap therebetween. The inner tapered portion is formed on one of the magnetic path forming member and the yoke, and the outer tapered portion is formed on the other of the magnetic path forming member and the yoke.

2. The electromagnetic clutch according to claim 1, wherein: The magnetic path forming member comprises: an inner magnetic member and an outer magnetic member, each of which is made of a soft magnetic body; and an annular non-magnetic portion, which is provided between the inner magnetic member and the outer magnetic member. The yoke includes an inner portion axially aligned with the inner magnetic member of the magnetic path forming member and an outer portion axially aligned with the outer magnetic member of the magnetic path forming member. The inner and outer pump parts are formed by a portion of each of the magnetic circuit forming member and the magnetic yoke. The pump portion on one side is composed of a portion of each of the inner magnetic member of the magnetic path forming member and the inner portion of the yoke, and the pump portion on the other side is composed of a portion of each of the outer magnetic member of the magnetic path forming member and the outer portion of the yoke.

3. The electromagnetic clutch according to claim 1 or 2, wherein: The yoke, the magnetic path forming member, and the armature are arranged in parallel in the axial direction, and the magnetic path forming member is arranged between the yoke and the armature. The electromagnetic clutch includes a rotating housing member that houses the magnetic path forming member and the armature and rotates integrally with the magnetic path forming member, wherein the rotating housing member is arranged in an oil bath state in a housing. The rotating housing member rotates in an oil bath state, thereby forming a biased state in which the lubricating oil is biased toward the yoke side in the housing. Lubricating oil is supplied to the pump portion from between an end portion of the magnetic path forming member on the yoke side and the yoke.

4. The electromagnetic clutch according to claim 3, wherein: The rotating receiving member has one end portion located on the outer circumference side of the magnetic path forming member as a maximum outer diameter portion with the largest outer diameter, and has a small diameter portion with a smaller outer diameter than the maximum outer diameter portion at the other end side relative to the maximum outer diameter portion. Due to the outer diameter difference between the maximum outer diameter portion and the small diameter portion of the rotation housing member, when the rotation housing member rotates in the oil bath state, lubricating oil in the housing is biased toward the yoke side.

5. The electromagnetic clutch according to claim 3, wherein: A filter portion is provided between the end portion of the magnetic path forming member and the yoke portion, and the filter portion suppresses foreign matter in the lubricating oil from flowing toward the pump portion.

6. The electromagnetic clutch according to claim 5, wherein: A foreign matter passage diameter of the filter portion is smaller than a size of a gap between the tapered outer peripheral surface and the tapered inner peripheral surface of the pump portion.

7. The electromagnetic clutch according to claim 5, wherein: The electromagnetic clutch includes a bearing that supports the magnetic path forming member so as to be rotatable relative to the yoke, wherein the bearing is arranged between the end portion of the magnetic path forming member and the yoke. The bearing comprises: an inner ring and an outer ring; a plurality of rolling elements arranged between the inner ring and the outer ring; and a shield member fixed to one of the inner ring and the outer ring, and forming a gap between the shield member and the other of the inner ring and the outer ring. The other of the inner ring and the outer ring and the shielding member constitute the filter portion. A size of a gap between the other of the inner ring and the outer ring and the shield member in the radial direction of the bearing is smaller than a size of a gap between the tapered outer peripheral surface and the tapered inner peripheral surface of the pump portion.

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