Differential device

Abstract

Differential device comprising: an input housing (1) which is rotatable about an axis (C) and has an end surface (3) that is directed in one direction of the axis (C); a differential gear set (7) with a first and a second lateral gear (75, 77) each rotatable about the axis (C), wherein the differential gear set (7) enables differential movement between the first and the second lateral gear (75, 77); Claw teeth (13) which are directed towards the end surface (3) and are provided on an output housing (5) carrying the differential gear set (7) or on the second side gear (77); a coupling structure (11) which can be engaged with the claw teeth (13) and is designed to couple the output housing (5) or the second side gear (77) with the input housing (1) in the engaged state; a coupling element (15) which is movable in the direction of the axis (C) and has an inner end (17) which is connected to the coupling element (15) and an outer end (19) which is projected through the end surface (3) to an outer part of the inlet housing (1); an armature (23) movable in the direction of the axis (C), wherein the armature (23) is at least partially made of a magnetic material and is in contact at least indirectly with the outer end (19); an electromagnet (25) which is supported axially spaced from the end surface (3), wherein the electromagnet (25) is configured to generate a magnetic flux in the axial direction in order to attract the armature (23) and, via the coupling element (15), to engage the coupling structure (11) with the claw teeth (13); and a spring (31) which biases the clutch element (15) in a direction to disengage the claw teeth (13).

Description

TECHNICAL AREA

[0001] The present disclosure relates to a differential device and in particular to a differential device equipped with an actuator controlled by an attracting electromagnet to enable the actuation of a clutch. BACKGROUND

[0002] When a four-wheeled vehicle travels on an uneven road, the drive power is preferably distributed to all four wheels for traction stability, rather than just the front or rear wheels. However, when the vehicle is traveling on a well-paved road, all-wheel drive (AWD) is disadvantageous in terms of fuel efficiency and other factors. Therefore, systems are often used that allow the driver to consciously select between two-wheel and all-wheel drive modes, also known as "part-time all-wheel drive."

[0003] While various drivetrains are possible that achieve temporary all-wheel drive, for example, a combination of a differential gear that enables differential movement between the axles and a clutch that temporarily couples an input shaft to the differential gear can be used. A device referred to as a "free-running differential" is proposed that incorporates such a combination in a single unit. Publication JP 2011-112 114 A discloses an example of a free-running differential.

[0004] The actuator for operating the clutch can be a motor with a gearbox, a hydraulic device, an electromagnet, or similar, with the electromagnet being particularly effective in terms of responsiveness. In the JP 2011 112 114 A, the electromagnet generates a magnetic flux that flows around the core, and this magnetic flux is directed to the piston to create a pressure force on the piston, thus actuating the clutch. While such electromagnets generate a relatively low force, they allow for low-energy operation. However, attracting electromagnets are advantageous in terms of their ability to generate higher power.

[0005] Examples are known from JP HO2 - 286 944 A and WO 2017 / 100 550 A1, although these are not for a free-running differential but for a locked differential motion, where the electromagnet magnetically attracts the armature and the return spring is used for disengagement. Since the electromagnet in both cases requires wiring to the vehicle body, the electromagnet and its associated components should be designed to be rotationally fixed while the differential is rotating.

[0006] WO 2011 / 064 364 A1 discloses a differential arrangement for an electrically driven drive axle of a motor vehicle. The differential arrangement comprises a drive wheel and a differential drive with one input section and two output sections. The output sections are connected to the input section and exhibit a differential action relative to each other. A clutch is effectively arranged between the drive wheel and the differential drive. When the clutch is engaged, torque is transmitted from the drive wheel to the differential drive, and when the clutch is disengaged, torque transmission is interrupted. The differential arrangement also includes a controllable actuator for actuating the clutch and a sensor for detecting at least three clutch positions.

[0007] From US patent 10,267,400 B2, a differential device is known comprising a differential mechanism, a differential housing, and a coupling mechanism that transmits a drive force between the differential housing and the differential mechanism. The coupling mechanism includes a side element that is axially movable within the differential housing and an actuator for moving the sliding element axially.

[0008] US Patent 2018 / 0038422A1 discloses an interrupter comprising an intermittent element with a meshing tooth that engages with a second rotating element and moves axially between a coupled position and a decoupled position, and an actuator that moves the intermittent element axially. The actuator includes a coil that generates a magnetic flux and a piston that moves axially with the intermittent element.

[0009] US 9,695,922 B2 discloses a coupling device comprising an end wall rotatable about an axis, an extended wall extending as a single body from a first face of the end wall along the axis and defining a circular slot, a coupling with a coupling element movable along the axis and able to rest on a second face of the end wall, and a solenoid configured to drive the coupling element along the axis. SUMMARY OF THE INVENTION

[0010] Since the clutch is also immersed in lubricating oil for the differential, the viscosity of the lubricating oil acts as a resistance that prevents the clutch from disengaging. Furthermore, when torque is applied, the friction between the engaged clutch teeth strongly opposes disengagement. Therefore, to ensure clutch disengagement, the return spring must exert a corresponding elastic force. The electromagnet, in turn, must exert sufficient pressure against this reinforced return spring, which is why an embodiment in which the electromagnet attracts the armature is advantageous. However, due to its residual magnetization, the armature tends to stick to the electromagnet, so the return spring must exert a greater repulsive force to remove it. The attracting electromagnet and the return spring must therefore be synergistically reinforced.

[0011] The manner in which the force and reaction force are absorbed is in itself a technical challenge, and the manner in which the force is transmitted to the coupling also requires considerable consideration. Furthermore, if a larger magnetic flux is to be generated, the influence of magnetic flux leakage into the environment must be carefully taken into account. For example, increasing the cross-sectional area of ​​the core's magnetic path to reduce leakage flux inevitably necessitates a larger device. That is to say, the arrangement and mounting of the associated components in an attracting electromagnet can introduce many potential technical problems. The device described below was developed with these problems in mind.

[0012] Based on this, the present invention aims to provide a differential device that reduces energy loss due to magnetic scattering while maintaining a compact design.

[0013] The problem is solved by a differential device having the features of claim 1. Further developments of the differential device are specified in the dependent claims.

[0014] According to one aspect, a differential device is provided with an input housing rotatable about an axis and having an end face directed in one direction of the axis; a differential gear set comprising a first and a second lateral gear, each rotatable about the axis, and enabling differential movement between the first and second lateral gears; claw teeth directed towards the end face and provided on an output housing supporting the differential gear set or on the second lateral gear; a coupling structure capable of engaging with the claw teeth and designed to couple the output housing or the second lateral gear to the input housing when engaged;a coupling element movable in the axial direction and having an inner end connected to the coupling element and an outer end projecting through the end face to an exterior of the input housing; an axially movable armature, wherein the armature is at least partially formed of a magnetic material and is in contact with the outer end; an electromagnet supported axially away from the end face, wherein the electromagnet is configured to generate an axial magnetic flux to attract the armature and, via the coupling element, to engage the coupling structure with the claw teeth; and a spring biasing the coupling element in a disengagement direction from the claw teeth. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a sectional view of a differential device according to one embodiment, in a section plane along the differential axis. Fig. 2A is an enlarged sectional view of an actuator and its surroundings. Fig. 1. Fig. 2B is an enlarged sectional view of a modified example that Fig. 2A corresponds to this. Fig. 3A is a partial view of a structure for preventing the actuator from rotating, according to an example. Fig. 3B is a partial view of a structure for preventing the actuator from rotating, according to another example. Fig. Figure 4 is a partial sectional view showing an example where the actuator acts on a coupling element via a piston. Fig. 5A is a partial sectional view of another example showing the interaction between a sensor and the actuator. Fig. 5B is a partial section view showing another example that Fig. 5A is equivalent. Fig. 5C is a partial sectional view of an example with a contact sensor that Fig. 5A is equivalent. Fig. Figure 6 is a partial sectional view showing an example where a combination with a side wheel forms a coupling. DESCRIPTION OF THE EXECUTION FORMS

[0015] Exemplary embodiments are described below with reference to the accompanying drawings. In the following description and accompanying claims, unless otherwise specified, an axis means a rotational axis of a differential device, an axial direction means a direction parallel to the axis, and a radial direction means a direction perpendicular to it. The following description distinguishes between right and left, but this is done only for the sake of simplicity. Of course, there are also embodiments in which right and left are reversed.

[0016] Mainly on Fig. Referring to paragraph 1, the differential device is suitable for the purpose of temporarily transmitting torque from an input shaft to axles, thereby enabling differential movement between the axles rotating about axis C (this may be referred to as a "free-running differential" or similar). The differential device could be used for an all-wheel-drive vehicle, although its application is not limited to this.

[0017] The differential gear generally consists of an input housing 1, which receives torque from the input shaft, a clutch 11 for acting on a differential gear set 7, and an actuator 21 for actuating the clutch 11. The differential gear may be provided with an output housing 5, which carries the differential gear set 7, and the output housing 5 is rotatable relative to the input housing 1.

[0018] The input housing 1 and the output housing 5 are coaxial and nested inside each other, and normally, but not necessarily, the former accommodates the latter.

[0019] The input housing 1 is permanently drive-connected to the input shaft to receive torque from it and rotate it about the axis C. The input housing 5 is equipped with claw teeth 13 to form the clutch 11. When the clutch 11 is disengaged, no torque is transmitted to the output housing 5, allowing the output housing 5 to rotate freely about the axis C. When the actuator 21 engages the clutch 11, the input housing 1 is drive-connected to the output housing 5 to transmit torque to the output housing 5, causing both to rotate together.

[0020] Alternatively, as in Fig. As shown in Figure 6, one of the lateral gears 77 of the differential gear set 7 is provided on the back side of its teeth with the dog teeth 13 to form the clutch 11. In this example, the differential gear set 7 is not supported by the output housing 5, but directly by the input housing 1. When the clutch 11 is engaged, the lateral gear 77 is coupled to the input housing 1. If one of the lateral gears 77 is locked, the other 77 cannot perform differential movement, so the clutch 11 in this example is used to lock / unlock the differential movement by the differential gear set 7. A differential device according to this example may be called a 'locking differential' or similar.

[0021] Referring again to Fig. The input housing 1 is generally cylindrical, and its end faces roughly separate the interior from the exterior. The connection between the input housing 1 and the input shaft can be achieved, for example, by a toothed ring, and a flange projecting radially from the cylinder can be used to connect the toothed ring, although of course other embodiments are also possible.

[0022] Hub sections project axially outwards from each of the two end faces of the inlet housing 1, and the inlet housing 1 is thereby supported by a carrier 81. Bearings 83, such as roller bearings, can be arranged between the inlet housing 1 and the carrier 81, although ball bearings or other bearing arrangements can be used instead of roller bearings. The actuator 21 is arranged around one of the end faces 3.

[0023] The output housing 5 is equipped with the differential gear set 7 and can therefore deliver torque to both axles, allowing differential movement between them. According to the in Fig. In the example shown, the differential gear set 7 is a bevel gear type and comprises compensating gears 71 rotatably mounted on a compensating gear axle 73, and side gears 75, 77 which mesh with these.

[0024] Of course, any other type, such as a spur gear or a planetary gear drive, can also be used. The side gears 75, 77 can be provided with teeth on their inner circumferences for coupling to the shafts, although any other coupling form can be used.

[0025] The output housing 5 is provided at one end 9 with claw teeth 13, which mesh axially and in the direction of the end surface 3 of the input housing 1. The claw teeth 13 form the coupling 11, which drives the output housing 5 to the input housing 1 when it is engaged, as already described. The coupling structure for drives the output housing 5 to the input housing 1 can be, as in Fig. 1 shown as an example, can be realized by means of a coupling element 15, or alternatively the input housing 1 can be provided with corresponding claw teeth to form the coupling 11 in combination with the claw teeth 13.

[0026] Referring to Fig. 2A, for example in combination with Fig. In this case, the coupling element 15 is a generally annular element that fits loosely into the inner surface of the input housing 1 and is movable in the axial direction of axis C. Its inner end 17 is located inside the input housing 1 to connect with the coupling structure. From the surface opposite the inner end 17, a plurality of legs project axially outwards, the respective outer ends 19 of which penetrate the end surface 3 and are exposed to the outside of the input housing 1. Since openings in the end surface 3 engage with the legs of the coupling element 15, the coupling element 15 is able to transmit torque from the input housing 1 to the output housing 5.

[0027] The inner end 17 can be provided with second claw teeth 14, and the claw teeth 13 and the second claw teeth 14 are designed to interlock and thus together form the coupling 11. In this case, as already described, the coupling structure is formed integrally with the coupling element 15.

[0028] The outer ends 19 can further be provided with a contact plate 27 which communicates with the actuator 21. The contact plate 27 has a plate-like shape that forms a ring generally continuous in the circumferential direction and can be provided with a curved and raised section for attachment to the outer ends 19 and / or a suitable projection to come into contact with the actuator 21. The material applied to the contact plate 27 can, without being particularly limited, be different from the materials of the input housing 1 and the coupling element 15, as well as from an armature 23 and a core 53, which are described later.

[0029] The actuator 21 generally comprises an armature 23, an electromagnet 25, and a return spring 31. The armature 23 consists at least partially of a magnetic material and is therefore attracted by the magnetic flux generated by the electromagnet 25. The armature 23 is arranged such that it is in contact with the outer ends 19, thereby enabling the coupling element 15 to move axially along axis C. The return spring 31 pushes the coupling element 15 in the opposite direction.

[0030] The electromagnet 25 is arranged circularly around the axis C and comprises a coil 51, which generates a magnetic flux in the axial direction, and a core 53, which surrounds the coil 51 and conducts the magnetic flux. The coil 51 is a wound wire made of a good conductor such as copper, with the winding direction preferably oriented such that the magnetic flux is generated most strongly in the axial direction of the axis C. The core 53 can be made of a material with high magnetic permeability, such as ferrite, so that the magnetic flux is conducted with high efficiency to improve energy efficiency and also to reduce the negative effect caused by magnetic flux leakage into the environment. The core 53 surrounds most of the coil 51 but leaves a portion facing the armature 23 axially open, thereby effectively directing the magnetic flux onto the armature.

[0031] The armature 23 is provided with a radial surface 41 that receives and is attracted to the aforementioned magnetic flux, and which can be a disk-shaped surface extending in a radial direction. To extend the area for receiving the magnetic flux, as shown in Fig. As shown in Figure 2B, the anchor can also be provided with a chamfer 45 inclined towards the core 53, which can be located not only on the radial inner side but also on the outer side. The core 53 can have a shape complementary to the chamfers.

[0032] The armature 23 is further provided with an axial section 43 which is elongated to such an extent that it is in contact with the outer ends 19 or the contact plate 27 and thus transmits the driving force to them. The axial section 43 can be, as exemplified in Fig. 3A in combination with Fig. 2A and Fig. As shown in Figure 2B, the rim is a cylindrical edge extending axially from the outer circumference of the radial surface 41. The rim at least partially covers the core 53 and extends over its outer surface to the outer ends 19 or to the contact plate 27. This shape can be formed piecewise by pressing or drawing a flat plate and is therefore easy to manufacture. Of course, it can also be produced by casting or forging, or an axial section 43 can be joined as a separate body to a flat radial surface 41. Although thin, such a shape is sufficient for driving the coupling element 15 and is advantageous insofar as the cross-section of the core 53 does not need to be reduced.

[0033] Alternatively, the anchor 23 can be provided with columns 49 instead of or in addition to the cylindrical rim, as shown in Fig. Figure 4 illustrates this. The columns 49 penetrate the electromagnet 25, particularly the core 53, and extend axially to contact the outer ends 19 or the contact plate 27. As shown, the columns 49 can extend radially inward from the coil 51 or radially outward from it. Since the columns 49 prevent the armature 23 from rotating, a recess described later can be omitted in these embodiments. Alternatively, the columns 49 can extend around the outer circumference of the core 53. In this case, the columns 49 can be secured against rotation by engaging a pin 85, as described later, or they can have an individual anti-rotation device.

[0034] The axial section 43 or the columns 49 can be made of the same material as the radial surface 41 and can also be formed as a single body with it, or they can be made of a non-magnetic material and formed as separate bodies. In the case of the non-magnetic material, the leakage flux of the magnetic flux can be reduced and its negative effect suppressed.

[0035] Furthermore, a bushing, as a separate body, can be inserted between the axial section 43 or the columns 49 and the outer ends 19 or the contact plate 27. The bushing is annular and therefore remains in contact with these two elements when the input housing 1 rotates. The bushing can be made of a non-magnetic material, for example, a resin with a low coefficient of friction, to reduce friction.

[0036] Since the inner circumference of the core 53 fits onto the hub section 57, the entire actuator 21 is supported by it. Except for the inner circumference, the core 53 is located away from the input housing 1, and in particular, a considerable gap exists between the rear of the core 53 and the end face 3 of the input housing 1. This helps to reduce the leakage flux of the magnetic flux from the core 53 towards the end face 3. The hub section 57 can be provided with a shoulder 59 that extends slightly radially outward to hold the core 53 in position. The extension of the shoulder 59 is at least shorter than to the rear of the coil 51, so that a gap is maintained at least radially outside the inner circumference of the coil 51.

[0037] The inner circumference of the core 53 can be extended in the axial direction opposite to the shoulder 59, as shown in the Fig. 2A and Fig. Figure 4 illustrates this. This elongated section can essentially have a cylindrical shape and is normally formed as a single body with the core 53, but it can also be a separate body attached to the core 53. Its end can rest against the bearing 83 and thus be prevented from coming loose. Alternatively, the hub section 57 can be provided with a locking element to prevent the core 53 from coming loose. Such an element is, for example, a ring that engages in the hub section 57 and can be made of a non-magnetic material to prevent leakage of the magnetic flux. However, the inner circumference of the core 53 need not necessarily be in contact with the hub section 57 over its entire surface. To reduce the contact area, the inner circumference of the core 53 can be provided with a groove or recess.This is also helpful to reduce the leakage of magnetic flux and to reduce the sliding resistance between the core 53 and the hub section 57.

[0038] The armature 23 can be mounted on the hub section 57 or on the extended section of the core 53. In either case, they are in a sliding connection, allowing the armature 23 to move axially. A connection of the armature 23 to the core 53, both of which are non-rotatable, is advantageous for smooth axial movement. To prevent the armature 23 from coming loose, a ring 33 can be used, which engages with either the core 53 or the hub section 57. The ring can be made of a non-magnetic material to reduce the loss of magnetic flux.

[0039] Alternatively, a support element 35 can be used to support the core 53 and the anchor 23, as shown in Fig. Figure 2B shows that the support element 35 can, for example, be essentially cylindrical, and one end of it can rest against the bearing 83 to prevent it from loosening. The support element 35 is in contact with the core 53, and both are non-rotatable, thus preventing the core from loosening. Alternatively, the support element 35 can form a tight fit on the hub section 57 or have a structure for engaging with the hub section 57. The armature 23 can slide on the support element 35, which is helpful in suppressing the escape of magnetic flux from the armature 23 to the hub section 57. To prevent the armature 23 from loosening, the support element 35 can be provided with any anti-loosening structure; an example of this is a short flange formed by bending its end outwards, as shown. The support element 35 can also be made of a non-magnetic material to reduce magnetic flux leakage.

[0040] The return spring 31 can be arranged in the gap between the back of the core 53 and the end face 3 of the input housing 1. In particular, it can be arranged between the contact plate 27 and the end face 3. The return spring 31 can be slightly compressed beforehand to bias the coupling element 15 in a direction that assists its disengagement.

[0041] While the return spring 31, together with the contact plate 27 and similar components, is rotatable, the armature 23 and the electromagnet 25 are not rotatable and are preferably secured against rotation. The core 53 can be provided with a radially outwardly projecting pin 85, as e.g. in Fig. Figure 3A shows that the anti-rotation device for the electromagnet 25 can be achieved by engaging the pin 85 with the carrier 81. The armature 23 can be provided with any structure that engages with the electromagnet 25, for example, with a recess in the axial section 43 for engagement with the pin 85. Alternatively, pins 87 extending from the core 53 and passing through the armature 23 can be used, as shown in Figure 3A. Fig. Figure 3B shows that in any case, the armature 23, together with the electromagnet 25, can be secured against rotation by the pins 85 and 87. The pins 85 and 87 can be integrally formed with the core 53, or they can be separate bodies made of a non-magnetic material. If they are made of a non-magnetic material, magnetic flux leakage can be reduced and its negative effects suppressed.

[0042] Returning to Fig. 1. The differential device can be equipped with essentially any means to detect whether the clutch 11 is engaged or not, an example being a non-contact sensor 91. Examples of the non-contact sensor 91 include, but are not limited to, a sensor that uses high-frequency vibrations to detect the proximity of metal, a sensor that detects changes in electrostatic capacitance, electric field, or magnetic field, and a sensor that uses optical means. Such non-contact sensors successfully avoid energy losses caused by contact between rotating components.

[0043] The non-contact sensor 91 can be arranged to detect whether the contact plate 27 is near or far. As described above, the contact plate 27 is located freely outside the outer circumference of the differential device and moves within the gap between the core 53 and the input housing 1, allowing the non-contact sensor 91 to perform precise detection without interference from surrounding components. The contact plate 27 is rotatable, but, as already described, ring-shaped, so that during rotation it is constantly facing the non-contact sensor 91 and thus available for detecting its axial position. Since, as already described, any material can be used for the contact plate 27, a material suitable for detection by the non-contact sensor 91 can be selected.Of course, instead of the contact plate 27, any other part of the coupling element 15 can also be used, or, as in . Fig. As shown in Figure 5A, any part of the anchor 23 can be selected as the object for detection. Since the anchor 23 is not rotatable, it is constantly facing the likewise non-rotatable non-contact sensor 91 and is therefore available for position detection. Furthermore, these components can additionally include any suitable element to facilitate detection.

[0044] As described above, the non-contact sensor 91 is oriented orthogonally to an axially moving component, but the non-contact sensor 91 can also be oriented axially, as shown in Fig. Figure 5B shows the object to be captured. The object can be the armature 23 or, as shown, the contact plate 27. In the latter case, these components can be partially cut out to avoid interference from the armature 23 and the core 53. It is not necessary to cut them out completely, since the armature 23 and the core 53 are non-rotating components, and only a portion can be cut out. Alternatively, the diameter of the contact plate 27 can be enlarged so that it projects radially outwards from the outer edges of the armature 23 and the core 53.

[0045] Alternatively, a contact sensor 93 can be used instead of the non-contact sensor, as shown in Fig.Figure 5C shows that a mechanical push-button switch or a pull-button switch is suitable for the contact sensor 93. Of course, a sensor using electrical, magnetic, or optical means can also be used. The object of detection includes the armature 23 and the contact plate 27, as described above, or any other part of the coupling element 15 can be the object.

[0046] Instead of or in addition to one of the aforementioned sensors, a speed sensor or any other sensor can also be provided for the differential device. The contact plate 27 can accordingly be provided with notches or teeth formed around its circumferential edge, which cause the sensor to generate pulses corresponding to their speed. Since the contact plate 27 is a rotating element that rotates synchronously with the input housing 1, it is suitable not only for determining whether the clutch 11 is engaged, but also for determining the rotational speed.

[0047] In the differential device described here, the leakage flux from the electromagnet to the input housing, particularly from the side face of the core to the end face of the input housing, is reduced. With attractor magnets, the magnetic flux is densest in this direction, and the input housing is strongly attracted. This can lead to significant energy loss due to friction when the rear face of the core and the end face of the input housing are in contact. Furthermore, since the input housing rotates perpendicular to the magnetic flux, the generation of an induced current also results in energy losses, which can increase with increasing magnetic force. The differential device described here could reduce both of these energy losses. Since the cross-sectional area of ​​the core does not need to be increased to counteract the leakage flux, the device can also be designed more compactly.On the other hand, since the relatively wide gap between the rear surface of the core and the end surface of the input housing provides space for the return spring, there is greater freedom in designing the return spring, and it is helpful to ensure sufficient restoring force and sufficient length for expansion and contraction. Furthermore, because the contact plate is radially exposed in the gap, the condition of the coupling can be easily monitored using sensors.

Claims

[1] Differential device comprising: an input housing (1) which is rotatable about an axis (C) and has an end surface (3) that is directed in one direction of the axis (C); a differential gear set (7) with a first and a second lateral gear (75, 77) each rotatable about the axis (C), wherein the differential gear set (7) enables differential movement between the first and the second lateral gear (75, 77); Claw teeth (13) which are directed towards the end surface (3) and are provided on an output housing (5) carrying the differential gear set (7) or on the second side gear (77); a coupling structure (11) which can be engaged with the claw teeth (13) and is designed to couple the output housing (5) or the second side gear (77) with the input housing (1) in the engaged state; a coupling element (15) which is movable in the direction of the axis (C) and has an inner end (17) which is connected to the coupling element (15) and an outer end (19) which is projected through the end surface (3) to an outer part of the inlet housing (1); an armature (23) movable in the direction of the axis (C), wherein the armature (23) is at least partially made of a magnetic material and is in contact at least indirectly with the outer end (19); an electromagnet (25) which is supported axially spaced from the end surface (3), wherein the electromagnet (25) is configured to generate a magnetic flux in the axial direction in order to attract the armature (23) and, via the coupling element (15), to engage the coupling structure (11) with the claw teeth (13); and a spring (31) which biases the clutch element (15) in a direction to disengage the claw teeth (13). [2] Differential device according to claim 1, wherein the armature (23) has a radial surface (41) extending radially to receive the magnetic flux and an axial section (43) extending axially from the radial surface (41) towards the outer end (19), and the axial section (43) is at least indirectly in contact with the outer end (19). [3] Differential device according to claim 2, wherein the axial section (43) is a body separated from the radial surface (41) and is made of a non-magnetic material. [4] Differential device according to claim 2, wherein the axial section (43) comprises a cylinder which at least partially covers an outer circumference of the electromagnet (25) and is in contact at least indirectly with the outer end (19). [5] Differential device according to claim 2, wherein the axial section (43) comprises a column (49) which penetrates the electromagnet (25) and is in contact at least indirectly with the outer end (19). [6] Differential device according to any one of claims 1 to 5, wherein the input housing (1) has a hub section (57) extending axially from the end surface (3), wherein the electromagnet (25) has a coil (51) for generating the magnetic flux and a core (53) surrounding the coil (51) to guide the magnetic flux, and wherein the core (53) is slidably mounted on the hub section (57) so that the electromagnet (25) is supported by the input housing (1). [7] Differential device according to claim 6, wherein the core (53) as an integral body or as a separate body has a support section which is slidably mounted on the hub section (57) and extends axially in such a way that it is in contact with a bearing (83) for supporting the hub section (57). [8] Differential device according to claim 7, wherein the anchor (23) is mounted on the support section in such a way that it is axially movable. [9] Differential device according to claim 6, wherein the core (53) has a pin (85, 87) for preventing the electromagnet (25) from rotating, wherein the pin (85, 87) extends radially or axially and the armature (23) engages with the pin (85, 87) so that the armature (23) together with the electromagnet (25) is prevented from rotating. [10] Differential device according to one of claims 1 to 5, wherein the outer end (19) of the coupling element (15) has a contact plate (27) forming a ring which extends continuously around the axis (C), and the contact plate (27) is arranged between the electromagnet (25) and the end surface (3) and is in contact with the armature (23). [11] Differential device according to claim 10, wherein the spring (31) is arranged between the end surface (3) and the contact plate (27) to preload the contact plate (27). [12] Differential device according to claim 10, wherein the contact plate (27) is exposed radially outwards, whereby the contact plate (27) can be detected by a sensor (91). [13] Differential device according to any one of claims 1 to 5, wherein the coupling structure (11) forms an integral body with the coupling element (15) so that they move together, and has second claw teeth (14) to engage with the claw teeth (13).

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