Electromagnetic coupling and method for closing and opening an electromagnetic coupling

Description

[0001] The invention relates to an electromagnetic coupling and a method for closing and opening an electromagnetic coupling.

[0002] The term "electromagnetic clutch" is intended to indicate that the clutch is electromagnetically actuated. However, torque transmission when the clutch is engaged can occur via positive and / or frictional engagement.

[0003] If torque needs to be temporarily transmitted from one shaft to another coaxially aligned shaft without permanently connecting the two shafts, couplings are typically used. A distinction is made between friction-fit and positive-locking couplings. The present invention is limited to positive-locking couplings.

[0004] For positive-locking couplings, sliding coupling sleeves are frequently used. These have one or more different toothed sections that engage with mating teeth, creating a positive connection through which torque can be transmitted from one shaft to another.

[0005] Electromagnetic couplings are known from the prior art in which the adjustment of the movable coupling sleeve is effected by a coil that exerts a magnetic force on the coupling sleeve. The switching travel along which the movable coupling sleeve can be adjusted by the magnetic forces is limited. This is because the magnetic forces that can be applied to the coupling sleeve decrease with increasing distance from the coil. This means that the switching sleeve can only be adjusted along a certain section via the magnetic force of the coil, and thus the axial engagement of the teeth and mating teeth is also correspondingly limited.

[0006] However, the axial overlap of the gear teeth, in addition to the design of the gear teeth themselves, is crucial in determining the maximum amount of torque that can be transmitted between two shafts via the coupling. Consequently, in an electromagnetic coupling, the transmissible torque is limited due to the restricted travel of the shift sleeve.

[0007] If the switching path and thus the axial overlap of the gearing is to be increased, this inevitably entails the use of larger coils.

[0008] A disadvantage is that using larger coils increases the installation space required and material costs. Furthermore, using larger coils also increases the weight of the electromagnetic clutch. This has a particularly negative impact when the electromagnetic clutch is used in vehicles.

[0009] US Patent 2,969,134 A discloses an electromagnetic clutch in which the first and second gear teeth have inclined surfaces, so that the gear teeth initially slide past each other and do not form a positive connection until a predetermined differential speed between the shift sleeve and the clutch body is undershot. Then engagement is possible.

[0010] DE 10 2017 204 113 A1 discloses a coupling device with an electromagnetic coupling and a second coupling that is actuated by changing the viscosity of an active medium. The electromagnetic coupling has positive locking elements, such as internal and external teeth, on both the sliding sleeve and the two coupling parts.

[0011] US Patent 2021 / 0190150 A1 discloses an electromagnetically actuated positive-lock coupling, the sliding sleeve and coupling body of which have toothing, preferably provided by gears and / or spur gears. Furthermore, the positive-lock coupling has a locking mechanism consisting of two detent devices between which a ball can engage.

[0012] US 9 816 569 B2 discloses a power transmission device, preferably designed as an electromagnetically actuated claw coupling, such that the shift sleeve and the coupling body each have claw teeth.

[0013] Against this background, the object of the invention is to provide an electromagnetic coupling in which the largest possible axial overlap of the gear teeth can be achieved despite the limited magnetic switching travel of the shift sleeve. This is to be achieved without using a larger coil and without significantly increasing the weight of the electromagnetic coupling.

[0014] The object of the invention is solved by an electromagnetic clutch comprising a shift sleeve having a first toothed section which is arranged non-rotatably on a first shaft and is linearly adjustable along the shaft between an engaged and disengaged state, a first clutch body having a second toothed section which is aligned coaxially with the first shaft, a stator comprising a first coil which serves to adjust the shift sleeve linearly along the shaft directly or indirectly, wherein the first and / or second toothed section has undercut(s) in the direction of the engaged state which is / are designed such that a torque transmission between the shaft and the first clutch body generates a force on the shift sleeve in the direction of the engaged state, and wherein in the engaged state there is a positive locking connection between the shift sleeve and the first clutch body through the first and second toothed sections.Furthermore, an armature is provided which is coupled to the switching sleeve and is adjustable along the first shaft by energizing the first and / or second coil, wherein the armature and the switching sleeve are coupled so as to be axially displaceable relative to each other. The adjustment of the armature by at least one of the coils is limited by a stop provided on the coupling body to prevent contact with the stator, whereby when the armature is in contact with the stop while a coil is energized, a magnetic holding force may be present, acting on the armature.

[0015] The basic idea of ​​the invention is that the switching sleeve can be adjusted from the disengaged state to the engaged state by means of the first coil, thus creating a positive fit between the first and second teeth, since there is already a reduced axial overlap of the teeth in the axial direction.

[0016] If torque is transmitted between the first shaft and the clutch body, the first and / or second teeth, due to the undercuts, generate a force that acts on the shift sleeve in the direction of the engaged state.

[0017] This results in the shift sleeve being moved further towards the engaged position once a certain force is applied. This allows for a shift path that would not be possible solely through adjustment via the first coil. Consequently, when torque is transmitted, the shift sleeve is "pulled" towards the engaged position by the undercut first and / or second teeth.

[0018] The additional displacement of the shift sleeve during torque transmission is accompanied by an increase in the axial overlap of the first and second gear teeth, so that higher torques can be transmitted.

[0019] The total switching path of the switching sleeve is thus divided into a first switching path, which is achieved by means of the coil, and a second switching path, which is caused by the undercuts of the first and / or second toothing in conjunction with an acting torque.

[0020] This design allows for a simple construction to accommodate higher switching distances and greater axial overlap of the gear teeth without changing the coil dimensions or increasing the air gap between the armature and stator.

[0021] Furthermore, adjusting the armature by means of the first and / or second coil along the first shaft also causes a displacement of the switching sleeve. Nevertheless, relative movement between the armature and the switching sleeve cannot be ruled out.

[0022] Furthermore, the material for the switching sleeve can be selected and treated independently of its magnetic properties. For example, torque-transmitting components can be hardened without having to consider the magnetic properties of the switching sleeve.

[0023] Furthermore, all torque-transmitting components can also be magnetically decoupled from the armature.

[0024] Furthermore, this design allows for extremely small gap dimensions between the armature and the stator, which makes it possible to achieve particularly high switching forces.

[0025] This results in a high magnetic holding force even with low current flow to the coil.

[0026] This allows the power loss when holding the armature at the stop to be significantly reduced by lowering the current, without the armature unintentionally detaching from the stop.

[0027] One aspect stipulates that the first coil serves to directly or indirectly adjust the shift sleeve linearly along the first shaft into the engaged state, and that the stator includes a second coil which serves to directly or indirectly adjust the shift sleeve linearly along the first shaft in the opposite direction to the engaged state. Additionally or alternatively to the second coil, a spring return mechanism can be provided, which applies a spring force to the shift sleeve linearly along the first shaft in the opposite direction to the engaged state.

[0028] Furthermore, it is conceivable that, depending on the switching direction, both coils serve to adjust the switching sleeve into the engaged and disengaged state.

[0029] Furthermore, when the shift sleeve is adjusted by means of the first coil in the engaged state, an axial overlap between the first and second teeth may occur, and the undercuts may shift the shift sleeve towards the engaged state during torque transmission.

[0030] Due to the additional displacement of the shift sleeve towards the engaged state, the axial overlap of the first and second teeth increases, as explained above, and is greater than if the shift sleeve is moved into the engaged state solely by the coil.

[0031] Preferably, the first and / or second toothing, which is provided with undercuts, may have teeth whose tooth flanks are wedge-shaped in the top view at least along a section of the tooth.

[0032] The wedge shape allows for a simple design of the undercuts and still provides a flat support of the teeth of the gears against each other, provided that the tooth flanks of the teeth are matched to each other.

[0033] For example, by using a wedge shape for the teeth that is only partially present, it can be achieved that when the shift sleeve moves towards the engaged state during torque transmission and the maximum overlap of the teeth is reached, further sections are provided along the teeth that lie flat on opposite surfaces of the teeth of the mating teeth.

[0034] This allows for a high axial overlap and, at the same time, a flat contact surface of the teeth of the gearing.

[0035] Preferably, the first and second toothing have undercuts, with the tapered ends of the wedge-shaped sections of the first and second toothing running in opposite directions.

[0036] If both gear teeth have wedge-shaped sections, the tooth flanks of the gear teeth can be aligned so that the wedge-shaped sections are present over a flat surface.

[0037] Advantageously, the armature and the switching sleeve are coupled in the axial direction via at least one elastic spring unit, which springs back when the switching sleeve and the armature are axially displaced relative to each other.

[0038] The spring unit thus allows relative movement between the shift sleeve and the armature. At the same time, it compresses, creating a spring force that returns the shift sleeve and the armature to their original relative position.

[0039] In addition, at least one spring unit can be arranged such that, with the first and second teeth contacting each other face-to-face and the shift sleeve not yet coupled to the first clutch body, the spring unit preloads the shift sleeve in the direction of the engaged state.

[0040] This brings the additional advantage that as soon as the teeth rotate relative to each other, the shift sleeve performs an accelerated movement towards the first clutch body and the teeth mesh together.

[0041] Preferably, the anchor can have a first axial contact surface, the switching sleeve a second axial contact surface, and the elastic spring unit can be supported in the axial direction on the first and second axial contact surfaces.

[0042] This allows the spring unit to be supported evenly between the armature and the shift sleeve, so that any spring forces acting on the shift sleeve and the armature are distributed evenly and tilting of the components is prevented.

[0043] The anchor can have a radial web on which the first axial bearing surface is provided. A web offers a particularly simple implementation for a bearing surface and is also stable.

[0044] Advantageously, a first spring unit can be located on one axial side of the bridge and a second spring unit on the opposite side of the bridge, with at least one of the spring units exerting a restoring force during relative displacement of the armature and the switching sleeve.

[0045] This ensures that the armature and the switching sleeve are coupled in both axial directions via the spring units, and that, in the case of pre-tensioned spring units and a relative movement between the armature and the switching sleeve, a restoring force is exerted by at least one spring unit.

[0046] If the shift sleeve is in the engaged state and a torque is applied, the elastic spring units still allow a relative displacement between the armature and the shift sleeve.

[0047] As soon as the torque application is reduced or no longer present, the restoring forces through at least one of the spring units cause the shift sleeve to move back to its initial state relative to the armature.

[0048] The spring units can be housed in spaces which are radially bounded on the inside by a shift sleeve and radially on the outside by an anchor, as well as on one end face by the web and on the opposite end face by a gear fixedly connected to the shift sleeve, wherein the gear has the first toothing and engages in the second toothing provided on the clutch body in the engaged state.

[0049] By housing the spring units in compartments, it is ensured that they are guided on all sides. Furthermore, this ensures that when the switching sleeve moves relative to the armature in either of the two axial directions, at least one of the spring units is always compressed and exerts a restoring force.

[0050] Advantageously, at least one spring unit is at least a wave ring or a disc spring, or comprises a package of these.

[0051] Both disc springs and wave springs are particularly suitable because they act uniformly on the two axial contact surfaces along the entire circumference when they are preloaded or compressed.

[0052] Furthermore, at least one spring unit can be arranged such that, when the shift sleeve is not yet coupled to the clutch body, this spring unit is pre-tensioned to exert a spring force on the shift sleeve in the direction of the engaged state. If necessary, when the teeth engage head-to-head, the spring unit can pre-tension the shift sleeve in the direction of the engaged state. The displacement force is transmitted from the armature via the spring unit to the shift sleeve, and the spring unit compresses when there is sufficient resistance from the shift sleeve, so that the spring unit then continuously presses against the shift sleeve in the direction of the engaged state. With the initial head-to-head contact of the teeth, the spring unit presses the shift sleeve into the teeth on the clutch body as soon as a tooth gap is reached.

[0053] At least one spring unit can be arranged such that, when the shift sleeve is coupled to the first clutch body, this spring unit is pre-tensioned to exert a spring force on the shift sleeve in the direction of the disengagement state. This means the shift sleeve is pre-tensioned in the direction of the disengagement state. The spring force therefore continuously assists the disengagement process, even if the armature has not yet been moved.

[0054] In addition, a spring detent may be provided to exert a holding force on the shift sleeve in the engaged and / or disengaged state.

[0055] This makes it possible, for example, to avoid activating the coils if the armature, including the switching sleeve, is to be kept in the disengaged state.

[0056] Furthermore, this also allows the spring detent to exert a holding force on the shift sleeve in the engaged state when the armature, together with the shift sleeve, is moved towards the engaged state as soon as the armature has reached the stop, or as soon as the shift sleeve is additionally moved further towards the engaged state by a torque load.

[0057] According to one option, a second coupling body can be provided, which is aligned coaxially to the first shaft and is located on the axial side of the shift sleeve opposite the first coupling body, and can be coupled to the shift sleeve by actuating the second coil, wherein the toothing of the second coupling body and the associated toothing of the shift sleeve are designed like the toothing of the first coupling body and its associated toothing.

[0058] This allows the shift sleeve to be moved from its initial state into two different engagement states, so that torque transmission can also take place between the first shaft and the second clutch body.

[0059] Advantageously, when moving the shift sleeve into the engaged state with the second clutch body, the spring units can act on the shift sleeve before and after engagement in the direction of the engaged state or the disengaged state, as previously explained.

[0060] The corresponding advantages arise from the explanations above.

[0061] The aforementioned problem is also solved by a method for closing and opening an electromagnetic clutch, in particular an electromagnetic clutch according to the invention as explained above, comprising an armature and a coupling sleeve having a first toothed section, which is arranged non-rotatably on a first shaft and is linearly adjustable along the first shaft between an engaged and disengaged state, a first clutch body with a second toothed section, which is aligned coaxially with the first shaft, a first coil which serves to adjust the coupling sleeve linearly along the first shaft into the engaged state, and a second coil which serves to adjust the coupling sleeve linearly along the first shaft against the engaged state, comprising the following steps: a) Applying voltage to the first coil and generating a magnetic force acting on the armature towards the first clutch body; b) Moving the armature and engaging the shift sleeve with the armature from a disengaged state towards the engaged state, with a spring unit interposed between the armature and the shift sleeve; c) Moving the shift sleeve into the engaged state and forming a positive connection between the shift sleeve and the first clutch body through the first and second teeth, wherein the first and second teeth have a first axial overlap with each other; d) Transmitting a torque between the first clutch body and the first shaft and moving the shift sleeve relative to the armature towards the first clutch body, wherein the first and second teeth have a second axial overlap with each other that exceeds the amount of the first;e) Canceling or reducing the transmitted torque between the first coupling body and the first shaft, and displacing the shift sleeve relative to the armature away from the first coupling body, wherein the first and second teeth have the first axial overlap with each other; f) Canceling or reducing the magnetic force acting on the armature by the first coil; g) Applying voltage to the second coil and generating a magnetic force acting on the armature; and h) Displacing the armature and moving the shift sleeve with it from an engaged state to the disengaged state.

[0062] The first coil is energized, causing the armature to move the switching sleeve from the disengaged state to the engaged state. The coupling between the armature and the switching sleeve is achieved via spring units, which are preferably pre-tensioned by the movement of the armature, so that the movement of the armature results in a practically direct movement of the switching sleeve.

[0063] It is possible that the first and second teeth lie on top of each other and that the teeth of the shift sleeve do not engage directly with the teeth of the clutch body.

[0064] This results in the armature moving towards the clutch body due to the magnetic force, while movement of the shift sleeve is impossible due to the end-to-end contact of the teeth. Therefore, a relative movement occurs between the armature and the shift sleeve, which compresses and thus pre-tensions at least one of the spring units.

[0065] If the shift sleeve rotates relative to the clutch body, the pre-tensioned spring will accelerate the shift sleeve into the engaged position, forming a positive connection with the clutch body. The teeth then exhibit an initial axial overlap with each other.

[0066] This positive locking allows the transmission of torque between the clutch body and the first shaft, which results in the shift sleeve moving further towards the clutch body relative to the armature and increasing the axial overlap of the teeth, so that an additional torque can be transmitted.

[0067] Furthermore, due to this relative movement between the shift sleeve and the armature, compression in the axial direction of at least one spring unit also takes place.

[0068] This results in the restoring force that builds up, shifting the shift sleeve back to its original position relative to the armature as soon as the transmitted torque between the first shaft and the clutch body is sufficiently reduced or eliminated.

[0069] The shift sleeve remains in the engaged state. However, the gear engagement decreases to its original level. To move the armature and shift sleeve back into the disengaged state, the magnetic force exerted by the first coil must first be reduced or eliminated. Additionally, the second coil must be energized so that a magnetic force acts towards the disengaged state, displacing the armature and shift sleeve axially along the first shaft.

[0070] The further advantages arising from this can be found in the paragraphs above.

[0071] The invention is described below with reference to an embodiment illustrated in the accompanying drawings. These show: Figure 1 a sectional view of an electromagnetic coupling according to the invention with a switching sleeve in the disengagement state; Figure 2 a schematic top view of the gear teeth of the electromagnetic coupling according to the invention Figure 1 with the switching sleeve in the disengagement state; Figure 3 a sectional view of a further electromagnetic coupling according to the invention with a switching sleeve in the disengagement state according to a second option; Figure 4 a schematic top view of the gear teeth of the electromagnetic coupling according to the invention with the switching sleeve in the disengagement state according to a second option; Figure 5 a perspective exploded view of all relevant components of the electromagnetic coupling of Figure 3 ; Figure 6Detail A of the electromagnetic coupling of Figure 3 ; Figure 7 Detail A of the electromagnetic coupling of Figure 3 with the shift sleeve in the partially engaged state; Figure 8 the schematic representation of the gearing of Figure 4 with the shift sleeve in the partially engaged state; Figure 9 the detail of the electromagnetic coupling of Figure 3 with the shift sleeve in the fully engaged state and during torque transmission; and Figure 10 the schematic representation of the gearing of Figure 4 with the shift sleeve in the fully engaged state and during torque transmission.

[0072] Figure 1 Figure 10 shows an electromagnetic coupling 10, which serves to couple a first shaft 12 and a second shaft 14 aligned coaxially to the first shaft 12 by opening and closing.

[0073] The electromagnetic clutch 10 comprises a shift sleeve 16, which has a shift sleeve housing 17 and a first toothed section 18. The toothed section 18 is located radially outside the circumference on a gear 19 that is non-rotatably connected to the shift sleeve housing 17.

[0074] Alternatively, the switching sleeve 16 can also be made in one piece.

[0075] Furthermore, the shift sleeve 16 is arranged in a rotationally fixed manner on the first shaft 12 and is adjustable linearly along this shaft between an engaged and an disengaged state. Figure 1 The shift sleeve 16 is shown in the disengaged state.

[0076] A first coupling body 20 is assigned to the second shaft 14.

[0077] The coupling body 20 has a second toothing 22, here an internal toothing, and is rotationally fixed to the second shaft 14, so that the coupling body 20 is aligned coaxially to the first shaft 12.

[0078] However, it is also conceivable that the first coupling body 20 forms part of the second shaft 14 and is formed integrally with it.

[0079] The coupling body 20 comprises at least one annular section and the second toothing 22 runs along the radial inner side of the annular section.

[0080] The first and second teeth 18, 22 of the shift sleeve 16 and of the first clutch body 20 are positioned at the ends of the shafts 12, 14.

[0081] As in Figure 2 As shown, both the first and the second toothing 18, 22 have undercuts 23 and 25 when viewed in the axial direction.

[0082] Alternatively, it is also conceivable that only one of the toothings 18, 22 is provided with undercuts.

[0083] The first and second toothing 18, 22 serve to form a positive connection between the shift sleeve 16 and the first clutch body 20 in the engaged state of the shift sleeve 16.

[0084] A stator 24 is provided for adjusting the switching sleeve 16 between the engaged and disengaged states, comprising a first coil 26 and a second coil 28.

[0085] The first coil 26 serves to adjust the shift sleeve 16 linearly along the first shaft 12 into the engaged state (in Figure 1 to the left) and the second coil 28 for adjusting the shift sleeve 16 linearly along the first shaft 12 against the engaged state, i.e. away from the first clutch body 20.

[0086] In addition to or as an alternative to the second coil 28, a spring can also be provided (not shown in the figures) which applies a spring force linearly along the first shaft 12 to the shift sleeve 16 in the opposite direction to the engaged state.

[0087] The adjustment of the switching sleeve 16 by the first and second coils 26, 28 can be carried out directly by the coils 26, 28 exerting a magnetic force directly on the switching sleeve 16 itself.

[0088] Alternatively, as in Figure 1 As shown, an additional armature 30 is provided, which is coupled to the switching sleeve 16 in the axial direction. The adjustment of the switching sleeve 16 is effected indirectly via the armature 30. The armature 30 can therefore be adjusted along the first shaft 12 by energizing the first or second coil 26, 28 and can move the switching sleeve 16 along with it.

[0089] To prevent magnetic stray fluxes, the armature 30 can be magnetically decoupled from the switching sleeve 16.

[0090] This can be achieved, for example, by coating the switching sleeve 16 with a plastic, at least in the area facing the armature 30. Alternatively, it is also possible to choose a non-ferromagnetic material for the switching sleeve 16.

[0091] Furthermore, a stop 32 can be provided, which is located on the first coupling body 20 and limits the adjustment of the armature 30 by the first coil 26 in the direction of the first coupling body 20.

[0092] Furthermore, a first elastic spring unit 34 and a second elastic spring unit 36 ​​are provided, via which the armature 30 and the switching sleeve 16 are coupled in an axially displaceable manner relative to each other.

[0093] The elastic spring units 34, 36 are arranged between the armature 30 and the switching sleeve 16 in such a way that a relative displacement in the axial direction results in at least one of the spring units 34, 36 springing into place.

[0094] Alternatively, a design using only one spring unit is also conceivable.

[0095] The first elastic spring unit 34 and the second elastic spring unit 36 ​​are housed in rooms 38, 40.

[0096] Both spaces 38 and 40 are radially bounded on the inside by the switching sleeve 17. Radially on the outside, the two spaces 38 and 40 are defined by the armature 30.

[0097] In the axial direction, the space 38 for the spring unit 34 is bounded by a first axial contact surface 42, which is provided on a radial web 44 of the anchor 30. Furthermore, the space 38 is bounded on the side opposite the first axial contact surface 42 by a second axial contact surface 46.

[0098] The second axial contact surface 46 is provided on the end face of the gear 19.

[0099] Consequently, the first elastic spring unit 34 is supported in the axial direction on the first axial contact surface 42 and the second axial contact surface 46 and can optionally be pre-tensioned between the axial contact surfaces 42, 46.

[0100] The space 40 is defined by a third axial contact surface 48, which is provided on the side of the web 44 opposite the second axial contact surface 46, and a fourth axial contact surface 50, which is provided on the switching sleeve 16.

[0101] The second elastic spring unit 36 ​​is supported axially on the third axial contact surface 48 and the fourth axial contact surface 50. Optionally, it can also be pre-tensioned between the contact surfaces 48 and 50.

[0102] Both of the spring units 34, 36 each comprise at least one wave ring. Alternatively, they can each comprise a package of several wave rings.

[0103] Alternatively, it is also conceivable that each of the spring units 34, 36 comprises a disc spring or a disc spring package.

[0104] Instead of the two elastic spring units 34, 36, it is also conceivable to implement the electromagnetic coupling only with the first elastic spring unit 34 or only with the second elastic spring unit 36.

[0105] Furthermore, the electromagnetic clutch 10 can include a spring detent 52 which has a spring ring 54 which is guided within a groove 56 provided on the first shaft 12 and can engage in recesses 58 provided on the shift sleeve 16, so that the spring detent 52 exerts a holding force on the shift sleeve 16 in the disengaged state.

[0106] As explained above, Figure 2The first and second toothing 18, 22, each with undercuts 23, 25, shown in detail. The first toothing has teeth 60 and the second toothing 22 has teeth 62.

[0107] The respective undercuts 23, 25 of the teeth 18, 22 are formed by the wedge-shaped tooth flanks 64 of the teeth 60 and the wedge-shaped tooth flanks 66 of the teeth 62, thereby forming wedge-shaped sections 68, i.e. gaps.

[0108] Accordingly Figure 2 The respective tooth flanks 64, 66 are wedge-shaped over the entire axial length of the teeth 60, 62. Thus, the wedge-shaped sections 68 correspond to the entire tooth flank.

[0109] However, it is also conceivable that the wedge-shaped sections 68 correspond only to a part of the entire tooth flank.

[0110] Due to the wedge-shaped tooth flanks 64, the teeth 60 have tapered ends 70, and the teeth 62 have tapered ends 72 due to the wedge-shaped tooth flanks 66. The tapered ends 70 extend in the opposite direction to the tapered ends 72, so that the ends 70 and 72 point in opposite directions.

[0111] The tapered ends 70 are arranged on the side of the wedge-shaped section 68 of the first toothing 18 facing away from the coupling body 20, and the tapered ends 72 are arranged on the side of the wedge-shaped section 68 of the second toothing 22 facing away from the shift sleeve 16.

[0112] The Figures 3 to 10 The electromagnetic coupling 10 is shown according to a second option. Unlike the one in Figure 1The electromagnetic coupling 10 shown in the second option additionally comprises a second coupling body 74, which is aligned coaxially to the first shaft 12 and is arranged on a third shaft 78.

[0113] The second coupling body 74 has a third toothing 76.

[0114] In accordance with the previous explanations regarding the first coupling body 20, the second coupling body 74 can also be provided as an independent component on the third shaft 78 or be manufactured as one piece with it.

[0115] Furthermore, a second gear 80 is additionally arranged on the side of the shift sleeve 16 facing the second clutch body 74, the end face of which facing the web 44 forms the fourth axial contact surface 50. The second gear 80 is provided with a fourth tooth 82.

[0116] In the electromagnetic coupling 10 according to the second option, the shift sleeve 16 can be moved directly or indirectly via the armature 30 by means of the second coil 28 towards the second coupling body 74 into a coupling state in which a positive locking is formed by the third toothing 76 and the fourth toothing 82 between the third shaft 78 and the shift sleeve 16.

[0117] Furthermore, a stop 84 is provided on the second coupling body 74, which limits the adjustment of the armature 30.

[0118] Furthermore, the explanations regarding the second tooth 22 apply analogously to the third tooth 76, and the explanations regarding the first tooth 18 apply analogously to the fourth tooth 82.

[0119] Accordingly Figure 4The third and fourth toothed sections 76 and 82 have teeth 86 and 88, which are shaped analogously to those of the first and second toothed sections 18 and 22 and also have undercuts. Consequently, the third and fourth toothed sections 76 and 82 have wedge-shaped sections 90.

[0120] The following will be based on the Figures 4 and 6 to 10 The function and operation of the electromagnetic coupling 10 will be explained. In the Figures 5 to 10 The electromagnetic coupling 10 is shown according to the second option; however, these statements also apply to those in the Figure 1 and 2 electromagnetic coupling shown 10.

[0121] The function of the electromagnetic clutch is further described exclusively by means of coupling the shift sleeve 16 with the first clutch body 20. However, the explanations can be applied equally to coupling the shift sleeve 16 with the second clutch body 74.

[0122] The initial state is the disengaged state of the shift sleeve 16, as shown in the Figures 4 and 6 shown.

[0123] Therefore, there is no positive locking between any of the teeth of the shift sleeve and the teeth of the clutch bodies 20, 74.

[0124] To hold the shift sleeve 16 in this open state and to ensure that it remains open, the spring detent 52 exerts a holding force on the shift sleeve in the disengaged state.

[0125] Alternatively or additionally, by energizing the first and second coils 26, 28, the switching sleeve 16 can exert a holding force in the disengaged state via the armature 30, to which the switching sleeve is coupled via the elastic spring units 34, 36.

[0126] If the shift sleeve 16 is to be moved from the disengaged state towards the first clutch body 20, a voltage must soon be applied to the first coil.

[0127] If the switching sleeve 16 is held in the disengaged state by the first and second coils 26, 28, the applied voltage to the second coil 28 must also be reduced or eliminated.

[0128] Applying voltage to the first coil 26 creates a magnetic flux, which exerts a magnetic force on the armature 30 in the direction of the first coupling body 20.

[0129] The magnetic force displaces the armature 30, which in turn is coupled to the switching sleeve 16 via the first and second elastic spring units 34, 36. Thus, a displacement of the armature 30 with pre-tensioned elastic spring units 34, 36 directly results in the switching sleeve 16 being moved along with it.

[0130] In the case of non-preloaded elastic spring units 34, 36, at least one of the spring units 34, 36 must first be compressed so that a spring force builds up. The spring force builds up and acts on the switching sleeve 16, so that the switching sleeve 16 is indirectly driven by the armature 30 via the spring unit as soon as the magnitude of the spring force exceeds the magnitude of any holding force that may be acting.

[0131] This displacement of the armature 30 towards the first coupling body 20 continues until the armature 30 reaches the stop 32 provided on the first coupling body 20. When the coil 26 is energized, a magnetic holding force acts on the armature 30.

[0132] Here, the first toothing 18 of the shift sleeve 16 can either be, as in the Figure 7 and 8As shown, before reaching the stop 32, the coupling body engages directly into the second toothing 22 of the first coupling body 20, so that a positive locking connection is formed.

[0133] However, it is also possible for the first and second teeth 18, 22 to make end-to-end contact before the stop 32 is reached. In this case, the teeth 18, 22 are tooth-to-tooth, and further axial movement of the shift sleeve 16 towards the first clutch body 20 is prevented.

[0134] This results in a relative movement between the shift sleeve 16, which contacts the front face of the first clutch body 20, and the armature 30, on which a magnetic force continues to act, causing it to move further until it reaches stop 32.

[0135] This results in the first spring unit 34 being compressed between the first axial contact surface 42 and the second axial contact surface 46, as the dimensions of the space 38 decrease in the axial direction.

[0136] At the same time, the space 40 increases in the axial direction, so that the third and fourth axial contact surfaces 48, 50 move away from each other.

[0137] An end-face contact of the first and second teeth 18, 22 therefore results in an additional preloading of the first elastic spring unit 34, so that an additional spring force acts on the shift sleeve 16 towards the first clutch body 20.

[0138] If a relative rotation occurs between the shift sleeve 16 and the first clutch body 20, the shift sleeve 16 moves into the engaged state, whereby the shift sleeve 16, due to the applied spring force, moves in an accelerated motion towards the engaged state according to Figure 7will be postponed.

[0139] This creates a positive fit between the shift sleeve 16 and the first clutch body 20, formed by the first and second teeth 18, 22. A first axial overlap U1 exists between the first and second teeth 18, 22 (see Figure 8 ).

[0140] If a torque transmission takes place between the first clutch body 20 and the first shaft 12, this results in a force on the shift sleeve 16 in the direction of the engaged state, i.e. towards the first clutch body 20, due to the wedge-shaped teeth 18, 22.

[0141] The force acting on the shift sleeve 16 depends significantly on the geometry of the undercuts 23, 25 and the torque present.

[0142] Above a certain torque, the force acting on the shift sleeve 16 increases in such a way that the shift sleeve 16 is moved relative to the armature 30 located at the stop 32 towards the first clutch body 20, so that the axial overlap of the first and second teeth 18, 22 increases further until a second axial overlap U 2 is reached, which corresponds to a maximum axial overlap and exceeds the amount of the first axial overlap U 1.

[0143] This condition is in the Figure 9 and 10 shown.

[0144] The relative movement between the shift sleeve 16 and the armature 30 increases the space 38 in the axial direction, causing the elastic spring unit 34 to relax in the axial direction (provided it was previously in a pre-tensioned state). Simultaneously, the space 40 decreases in the axial direction, compressing the second elastic spring unit 36 ​​between the third axial contact surface 48 of the web 44 and the fourth axial contact surface 50 of the second gear 80.

[0145] Furthermore, additionally, accordingly Figure 9 The spring detent 52 acts in this state and exerts a holding force on the shift sleeve 16, since in this position there is another groove on the inside of the shift sleeve 16 into which the spring ring 56 can engage.

[0146] If the torque transmitted between the first clutch body 20 and the first shaft 12 is canceled or reduced, the shift sleeve 16 is displaced away from the first clutch body 20, at least from a certain torque threshold, due to the spring force acting on the shift sleeve 16 by the highly compressed second elastic spring unit 36, so that the first and second teeth 18, 22 again assume the first axial contact U 1, as shown in the Figure 7 and 8 shown.

[0147] If the switching sleeve is to be moved back into the disengaged state, the magnetic force generated by the voltage applied to the first coil 26 must first be reduced or eliminated.

[0148] Furthermore, a voltage must be applied to the second coil 28, which exerts a magnetic force on the armature 30, acting away from the first coupling body 20.

[0149] This results in a displacement of the armature 30, whereby the shift sleeve 16, via the interposition of the first and second elastic spring units 34, 36, is moved from the engaged state back to the disengaged state according to the Figures 5 and 6 is being moved.

[0150] In this state, the switching sleeve can again be held in place by the spring detent 52 and / or via the armature 30 by energizing the first and second coils 26, 28, as explained above.

Claims

1. An electromagnetic clutch, comprising a shifting sleeve (16) which has a first toothing (18), is arranged in a rotationally fixed manner on a first shaft (12) and can be displaced linearly along the first shaft (12) between an engaged and a disengaged state, a first clutch body (20), which has a second toothing (22) and which is aligned coaxially with the first shaft (12), a stator (24), which comprises a first coil (26), which serves for the direct or indirect displacement of the shifting sleeve (16) linearly along the first shaft (12), wherein the first and / or the second toothing (18, 22) has / have undercuts (23, 25) in the direction of the engaged state, which are configured such that a torque transmission between the first shaft (12) and the first clutch body (20) generates a force on the shifting sleeve (16) in the direction of the engaged state, wherein, in the engaged state, there is a positive fit due to the first and the second toothing (18, 22) between the shifting sleeve (16) and the first clutch body (20), wherein an armature (30) is provided which is coupled to the shifting sleeve (16), and wherein the armature (30) is adapted to be displaced along the first shaft (12) by energizing the first and / or the second coil (28), the armature (30) and the shifting sleeve (16) being coupled so as to be displaceable relative to each other in the axial direction, characterized in that a displacement of the armature (30) by at least one of the coils (26, 28) is limited by a stop (32) which is provided on the first clutch body (20), and in that, when the armature (30) rests against the stop (32) when the coil (26, 28) is energized, there is a magnetic holding force which acts on the armature (30).

2. The electromagnetic clutch according to claim 1, characterized in that the first coil (26) serves for direct or indirect displacement of the shifting sleeve (16) linearly along the first shaft (12) into the engaged state, and in that the stator (24) comprises a second coil (28), which serves for direct or indirect displacement of the shifting sleeve (16) linearly along the first shaft (12) in the direction opposite to the engaged state and / or in that a spring return is provided which applies a spring force to the shifting sleeve (16) linearly along the first shaft (12) in the direction opposite to the engaged state.

3. The electromagnetic clutch according to claim 1 or 2, characterized in that when the shifting sleeve (16) is displaced by means of the first coil (26) into the engaged state, there is an axial overlap (U1, U2) between the first and the second toothing (18, 22) and the undercuts (23, 25) move the shifting sleeve (16) towards the engaged state when torque is transmitted.

4. The electromagnetic clutch according to any of the preceding claims, characterized in that the first and / or the second toothing (18, 22) provided with undercuts (23, 25) has / have teeth (60, 62) the tooth flanks (64, 66) of which are wedge-shaped at least along a section of the tooth (60, 62) in a plan view, in particular in that the first and the second toothing (18, 22) have undercuts (23, 25) and the tapered ends (70, 72) of the wedge-shaped sections (68) of the first and the second toothing (18, 22) extend in opposite directions.

5. The electromagnetic clutch according to any of the preceding claims, characterized in that the armature (30) and the shifting sleeve (16) are coupled via at least a first spring unit (34) which is elastic in the axial direction and which deflects when the shifting sleeve (16) and the armature (30) are displaced axially relative to each other.

6. The electromagnetic clutch according to any of the preceding claims, characterized in that at least one spring unit (34, 36) is arranged such that when the first and the second toothing (18, 22) are in contact on the end face and the shifting sleeve (16) is not yet coupled to the first clutch body (20), the spring unit (34, 36) pretensions the shifting sleeve (16) in the direction of the engaged state.

7. The electromagnetic clutch according to claim 5 or 6, characterized in that the armature (30) has a first axial abutment surface (42) and the shifting sleeve (16) has a second axial abutment surface (46), and in that the first elastic spring unit (34) is supported in the axial direction on the first and the second axial abutment surfaces (42, 46).

8. The electromagnetic clutch according to claim 7, characterized in that the armature (30) has a radial web (44) on which the first axial abutment surface (42) is provided, in particular in that the first spring unit is present on an axial side of the web (44) and a second spring unit (36) is present on the opposite side of the web (44), at least one of the spring units (34, 36) exerting a restoring force when the armature (30) and the shifting sleeve (16) are displaced relative to each other.

9. The electromagnetic clutch according to claim 8, characterized in that the spring units (34, 36) are accommodated in spaces (38, 40) which are delimited radially on the inside by a shifting sleeve bushing (17) and radially on the outside by the armature (30) and on one end face by the web (44) and on the opposite end face by a toothed wheel (19) firmly connected to the shifting sleeve bushing (17), wherein the toothed wheel (19) has the first toothing (18) and engages in the second toothing (22) provided on the first clutch body (20) in the engaged state.

10. The electromagnetic clutch according to any of claims 5 to 9, characterized in that the at least one spring unit (34, 36) comprises at least one wave ring or a disk spring or an assembly thereof.

11. The electromagnetic clutch according to any of claims 5 to 10, characterized in that at least one spring unit (34, 36) is arranged such that, when the shifting sleeve (16) is not yet coupled to the first clutch body (20), this spring unit (34, 36) is preloaded to exert a spring force on the shifting sleeve in the direction of the engaged state.

12. The electromagnetic clutch according to any of claims 5 to 11, characterized in that at least one spring unit (34, 36) is arranged such that, when the shifting sleeve (16) is coupled to the first clutch body (20), this spring unit (34, 36) is preloaded to exert a spring force on the shifting sleeve in the direction of the disengaged state.

13. The electromagnetic clutch according to any of the preceding claims, characterized in that a second clutch body (74) is provided, which is aligned coaxially with the first shaft (12) and is provided on the axial side of the shifting sleeve (16) opposite to the first clutch body (20) and can be coupled to the shifting sleeve (16) by actuating the second coil (28), wherein the toothing (76) of the second clutch body (74) and the associated toothing (82) of the shifting sleeve (16) are formed like the toothing (22) of the first clutch body (20) and the associated toothing (18) thereof, in particular in that, when the shifting sleeve (16) is moved into the engaged state along with the second clutch body (74), the spring units (34, 36) act on the shifting sleeve (16) before and after the engagement in the direction of the engaged state or the disengaged state.

14. A method of closing and opening an electromagnetic clutch (10) according to any of the preceding claims, comprising an armature (30) and a shifting sleeve (16) coupled thereto, which has a first toothing (18), is arranged in a rotationally fixed manner on a first shaft (12) and can be displaced linearly along the first shaft (12) between an engaged and a disengaged state, a first clutch body (20) having a second toothing (22), which is aligned coaxially with the first shaft (12), a first coil (26), which serves to displace the shifting sleeve (16) linearly along the first shaft (12) into the engaged state, and a second coil (28), which serves to displace the shifting sleeve (16) linearly along the first shaft (12) against the engaged state, comprising the following steps: a) applying a voltage to the first coil (26) and generating a magnetic force acting on the armature (30) towards the first clutch body (20); b) displacing the armature (30) and entraining the shifting sleeve (16) by means of the armature (30) from a disengaged state in the direction of the engaged state with the interposition of a spring unit (34, 36) between the armature (30) and the shifting sleeve (16); c) moving the shifting sleeve (16) into the engaged state of the shifting sleeve (16) and forming a positive fit between the shifting sleeve (16) and the first clutch body (20) by means of the first and the second toothing (18, 22), the first and the second toothing (18, 22) having a first axial overlap (U1) with respect to each other; d) transmitting a torque between the first clutch body (20) and the first shaft (12) and displacing the shifting sleeve (16) relative to the armature (30) towards the first clutch body (20), the first and the second toothing (18, 22) having a second axial overlap (U2) with respect to each other, which exceeds the amount of the first one; e) canceling or reducing the transmitted torque between the first clutch body (20) and the first shaft (12) and displacing the shifting sleeve (16) relative to the armature (30) away from the first clutch body (20), the first and the second toothing (18, 22) having the first axial overlap (U1) with respect to each other; f) canceling or reducing the magnetic force acting on the armature (30) by the first coil (26); g) applying a voltage to the second coil (28) and generating a magnetic force acting on the armature (30); and h) displacing the armature (30) and entraining the shifting sleeve (16) by means of the armature (30) from an engaged state to the disengaged state.