Electromagnetic coupling
The electromagnetic clutch addresses the issue of maintaining a defined position with reduced energy consumption and reliability by generating a remanent force to hold the switching unit, using a stator with optimized geometry and materials, ensuring stable operation even during power failures.
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Utility models
- Current Assignee / Owner
- Filing Date
- 2025-12-18
- Publication Date
- 2026-04-09
AI Technical Summary
Existing electromagnetic couplings face issues with maintaining a defined position of the switching unit without continuous energization, leading to increased power consumption and potential unintended movement during power failures.
An electromagnetic clutch design that generates a remanent force by magnetizing the surrounding material when energized, allowing the switching unit to be held in the engaged state without continuous energy input, using a stator with an optimized geometry and suitable materials to maintain the position.
Reduces energy consumption and ensures the switching unit remains in a defined position, even during power failures, without additional components like permanent magnets or mechanical holding devices, while providing a cost-effective and space-saving solution.
Smart Images
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Abstract
Description
[0001] The present invention relates to an electromagnetic clutch with a switching unit which is arranged non-rotatably on a shaft and which is linearly displaceable along the shaft between a disengagement position and an engagement position, a clutch body which has an engagement geometry into which the switching unit engages positively in the engagement position, and a currentable coil for adjusting the switching unit along the shaft.
[0002] To ensure trouble-free operation of such couplings, it is necessary to hold the switching unit in a defined end position until it is to be actively moved. A mechanical holding device can be provided for this purpose, which latches the switching unit in an end position. However, this solution involves increased manufacturing effort. Alternatively or additionally, a coil used to move the switching unit can be continuously energized to hold it in an end position, whereby the current can be reduced compared to the current required for switching. However, continuous energizing results in increased power consumption. Another disadvantage is that in the event of an unforeseen power failure, the switching unit can be unintentionally moved from its end position by the force of a normally present return element.
[0003] It is therefore an object of the invention to provide an improved electromagnetic coupling in which a defined position of the switching unit can be ensured in a simple manner.
[0004] This problem is solved according to the invention by an electromagnetic clutch with a switching unit that is arranged non-rotatably on a shaft and is linearly displaceable along the shaft between a disengagement position and an engagement position, a clutch body that is arranged coaxially to the shaft and has an engagement geometry into which the switching unit engages positively in the engagement position to establish a non-rotatable connection between the clutch body and the shaft, and at least one stator with a stator housing and an energizable coil arranged in the stator housing for direct or indirect adjustment of the switching unit along the shaft. The switching unit includes an armature that is displaceable along the shaft by energizing the coil.The clutch is designed to build up a remanent force during a switching operation by energizing the coil, which is sufficient to hold the switching unit in the switched state by remanent force alone.
[0005] The electromagnetic clutch according to the invention is characterized in particular by the fact that, when the clutch is engaged, a magnetic remanence is generated that is sufficient to maintain the engaged state without energizing the coil. In other words, the material surrounding the coil is magnetized when the coil is energized, and the residual magnetism remaining after the energization is switched off is sufficient to hold the switching unit in the engaged position. This significantly reduces the energy consumption of the clutch, as no continuous energization is required to maintain the engaged position. In particular, the engaged state can be maintained without any energy input. In the event of an unforeseen power failure, the switching unit is held in the desired position by the remanent force, thus preventing undefined or unwanted states.More precisely, a defined position of the switching unit is maintained in both the open and closed states of the clutch.
[0006] To generate a sufficiently large remanent force to hold the switching unit, the stator housing and / or the armature can have a geometry optimized for magnetic flux. Alternatively or additionally, sufficient remanent force can be achieved by using suitable materials, such as ferromagnetic materials.
[0007] Another advantage of the described coupling is its simple and therefore cost-effective design, without additional components such as permanent magnets, magnetic flux bridges, or mechanical holding devices. This results in a significant space saving compared to conventional systems.
[0008] The clutch can be either a normally open or a normally closed clutch. In a normally open clutch, the armature rests against the projection of the stator housing when the switching unit is engaged; in a normally closed clutch, the armature rests against the projection when disengaged.
[0009] The stator housing can be made in two parts, which simplifies manufacturing.
[0010] The stator housing can have a radially inward projection that extends further radially inward than the coil. Viewed axially, the armature overlaps this projection radially in sections. This means that when the coupling is engaged, the armature rests axially against the stator housing. Due to the residual magnetism present after the coil has been energized, the armature adheres to the projection even after the coil has been de-energized, thus providing a holding force sufficiently high to retain the switching unit.
[0011] According to one aspect, the armature is stepped in the area of the projection, such that in a switched state of the coupling, the armature rests axially against the projection with a first, radially outer section and axially overlaps the projection with a second, radially inner section. Such a shape of the armature represents a magnetically optimized geometry, which promotes the generation of sufficiently high remanent forces.
[0012] According to one aspect, the armature has a bevel in a region axially adjacent to the end faces of the step, thereby achieving improved axial attraction of the armature. Specifically, this geometry results in an increased attractive force on the armature as the switching unit is progressively moved towards the switched position, since the bevel ensures that a certain axial distance between the projection and the armature can be maintained even as the armature approaches the projection.
[0013] According to one embodiment, the slope between the end faces of the step extends continuously from one end face to the next, thereby maximizing the previously described effect with regard to the improved attractive force.
[0014] For example, the slopes have different angles of inclination, which allows the magnetic force characteristics to be specifically influenced.
[0015] According to one variant, both bevels form an acute angle with the central axis of the clutch, for example, an angle of a maximum of 20°, and in particular a maximum of 10°. This optimizes the geometry of the armature with regard to switching speed and holding force, which in turn reduces energy consumption during shifting.
[0016] According to one aspect, the electromagnetic clutch has an elastic return element that applies a restoring force to the switching unit. This elastic return element is, for example, a spring. Thanks to this elastic return element, the switching unit can be easily moved back to its initial position without electrical energy.
[0017] With a normally open clutch, the restoring force acts in the direction of the disengagement position, with a normally closed clutch in the direction of the engagement position.
[0018] The return element is designed in such a way that the return force of the return element is less than the magnetic remanence force in the switched state of the clutch, in order to ensure that the switching unit is held securely in the switched position.
[0019] To reset the switching unit, a short, initial switching pulse is sufficient to release the switching unit from the switched position, allowing the reset element to move the switching unit.
[0020] According to one aspect, the stator housing has a hole on a side facing the switching unit, which optimizes the magnetic flux in such a way that an increased attractive force acts on the armature during switching.
[0021] The breakthrough can overlap with the armature in an area adjacent to the step in the armature when the clutch is disengaged. This has a beneficial effect on the magnetic field distribution, thereby reducing the force required for switching and thus further lowering energy consumption during the switching process.
[0022] For example, the opening is located in an area adjacent to the radially outer end face of the anchor.
[0023] The coupling can include a control unit configured to energize the coil of at least one stator to move the switching unit, in particular from the disengagement position to the engagement position, and to switch off or reduce the energization when the switching unit has reached an end position. This can occur immediately or with a certain time delay after reaching the end position. This achieves an energy-efficient mode of operation for the coupling, in which energy is only required for the switching itself.
[0024] According to one variant, the control unit is configured to pulse the current through the coil of at least one stator in order to maintain a remanent force at the contact surface of the armature with the projection of the stator housing. This ensures a stable switching position even over extended periods, while simultaneously minimizing energy consumption through the pulsating current. In particular, the pulsating current prevents the remanent force from dissipating.
[0025] The control unit can further be configured to energize the coil of at least one stator with reversed polarity in order to release the switching element from its end position when the clutch is engaged. In this case, the remanent force decreases due to the reduction of the magnetic field, and the spring force of the return element becomes greater than the remanent force. This allows the switching unit to be moved back to its initial position solely by the axial force exerted by the elastic return element. This results in an increased switching speed when downshifting. In other words, when the switching element is reset, demagnetization prevents any further remanent force from acting on the switching unit and thus prevents any delay in its movement.
[0026] According to one aspect, electronics for energizing the coil include a full bridge, an H-circuit or a four-quadrant converter, which enables precise control of the current direction and thus polarity reversal.
[0027] According to one embodiment, the switching unit comprises a switching claw complementary to the engagement geometry of the clutch body, which is formed in one piece with the armature, ensuring a compact design and reliable power transmission.
[0028] Further advantages and features of the invention will become apparent from the following description and from the accompanying drawings, to which reference is made. The drawings show: - Fig. 1 by way of example an electromagnetic coupling not according to the invention, - Fig. 2 an electromagnetic coupling according to the invention in the area of a switching unit, - Fig. 3 a magnetic flux diagram of the coupling Fig. 2 with the coil energized, and - Fig. 4 a magnetic flux diagram of the coupling Fig. 2 with the coil unenergized in the switched state.
[0029] Fig. Figure 1 shows the basic structure of an electromagnetic coupling 10, wherein the embodiment shown is a normally open coupling 10.
[0030] The coupling 10 comprises a first rotatable shaft 12 and a second rotatable shaft 14.
[0031] A switching unit 16 is arranged in a rotationally fixed manner on the first shaft 12 and is linearly displaceable along the first shaft 12 between a disengagement position and an engagement position. Fig. Figure 1 shows the switching unit 16 in a disengaged position.
[0032] The switching unit 16 includes an armature 18, which is usually made of a ferromagnetic material.
[0033] The coupling 10 further comprises a coupling body 20, which is arranged coaxially to the first shaft 12 and which is fixed against rotation on the second shaft 14.
[0034] The clutch body 20 has an engagement geometry 22 into which the switching unit 16 engages positively in the engagement position to create a rotationally fixed connection between the clutch body 20 and the first shaft 12 and consequently also between the clutch body 20 and the second shaft 14.
[0035] For this purpose, the switching unit 16 has a switching claw 24 complementary to the engagement geometry 22 of the clutch body 20, which in the illustrated embodiment is formed in one piece with the armature 18.
[0036] Furthermore, the coupling 10 comprises a stator 26 with a stator housing 28 and an energizable coil 30 arranged in the stator housing 28 for direct or indirect adjustment of the switching unit 16 along the first shaft 12. In particular, the armature 18 can be moved along the first shaft 12 by energizing the coil 30.
[0037] The stator housing 28 is made of two parts.
[0038] The current flow to coil 30 is regulated by a control unit 32, which is located in Fig. Figure 1 is shown schematically. Specifically, the control unit 32 is configured to energize the coil 30 of the stator 26 to move the switching unit 16, in particular from the disengagement position to the engagement position.
[0039] An elastic return element 34, which in the exemplary embodiment is a spring, applies a return force to the switching unit 16, which in the illustrated exemplary embodiment corresponds to the disengagement position.
[0040] The return element 34 is axially supported by a block 36 which is fixedly mounted on the first shaft 12.
[0041] The in Fig. The embodiment shown in 2 differs from the one in Fig. The embodiment shown in 1 is essentially distinguished by the shape of the anchor 18, which according to the Fig. The embodiment shown in section 2 has a geometry optimized for magnetic flux technology, which will be explained in more detail below.
[0042] As in Fig. As can be seen in Figure 2, the stator housing 28 has a radially inward projecting projection 38, which extends further radially inward than the coil 30. In addition, the stator housing 28 has an opening 40 on a side facing the switching unit 16.
[0043] Viewed axially, the anchor 18 overlaps the projection 38 radially in sections, with the anchor 18 being stepped in the region of the projection 38, more precisely at its axial end facing the coupling body 20. Due to the step 42, the anchor 18 has two axially offset end faces 44, 46 on its side facing the coupling body 20.
[0044] The stage 42 is shaped such that, in a switched state of the clutch 10, the armature 18 rests axially against the projection 38 with a first, radially outer section 48 and axially overlaps the projection 38 with a second, radially inner section 50 (see Fig. 3 and Fig. 4). In Fig. 2. For better illustration, sections 48 and 50 are separated by a dashed line.
[0045] In the unactuated state of the clutch 10, the opening 40 overlaps with the armature 18 in an area adjacent to the stage 42.
[0046] In a region axially adjacent to the end faces 44, 46 of the step 42, the anchor 18 has a chamfer 52, 54. This gives the anchor 18 two conically shaped sections.
[0047] A first inclined plane 52 extends continuously between the end faces 44, 46 from a first end face 44 to the second end face 46. Thus, the second conical section borders directly on the first conical section in the axial direction.
[0048] The second inclined plane 54 is at most as long in the axial direction as the first inclined plane 52. In the illustrated embodiment, the second inclined plane 54 is shorter in the axial direction than the first inclined plane 52.
[0049] In the illustrated embodiment, the inclined surfaces 52, 54 have different angles of inclination.
[0050] In the exemplary embodiment, both inclined planes 52, 54 form an acute angle with a central axis of the coupling 10, in particular an angle of a maximum of 20°. However, in the exemplary embodiment, the second inclined plane 54 is shallower than the first inclined plane 52, that is, it forms a smaller angle with a central axis of the coupling 10 than the first inclined plane 52.
[0051] The following describes an actuation process of the clutch 10, whereby the effect of the magnetic flux-optimized geometry of the armature 18 becomes clear from the following description.
[0052] As mentioned previously, the control unit 32 is configured to energize the coil 30 of the at least one stator 26 to move the switching unit 16 from the disengaged position to the engaged position. With a normally closed clutch, the direction of movement would be reversed.
[0053] Furthermore, the control unit 32 is configured to switch off or reduce the power supply when the switching unit 16 has reached an end position. The end position of the switching unit 16 is for the normally open clutch in the Fig. 3 and Fig. 4 is shown and corresponds to the coupling position.
[0054] In Fig. Figure 3 shows the magnetic flux density distribution with the coupling 10 engaged while the coil 30 is energized, where the magnetic flux density is greater the higher the point density in the regions. In the Fig. The state shown in Figure 3 is a state at a time immediately after the switching unit 16 has reached the engagement position. In this state, a high magnetic flux density is present in the stator housing 28. The highest magnetic flux density is present in the area of the optimized geometry of the armature 18, more precisely in the area of the step 42, especially at the contact surface between the end face 46, which is set back from the first, axially outermost end face 44, and the projection 38.
[0055] The power supply can be switched off immediately or with a certain time delay after reaching the coupling position by the control unit 32.
[0056] Fig. Figure 4 shows the magnetic flux density distribution with the coupling 10 engaged and with the coil 30 unenergized.
[0057] As demonstrated by Fig. As can be seen in Figure 4, when coil 30 is switched off, a magnetic remanence is present which also causes an attractive force on the armature 18 when coil 30 is not energized. This is the case, for example, in the areas at the end of the reference lines to reference numerals 18 and 46, to the right of the end of reference numeral 38, to the right of the arrow of reference numeral 16 in the stator housing 28 and, to a somewhat lesser extent, at the upper and lower right corners of the stator housing 28.
[0058] The remanence force is favored by the stepped shape of the anchor 18.
[0059] Due to the magnetic flux-optimized geometry of the armature 18, a remanent force can be generated that is greater than the restoring force exerted by the restoring element 34, even when the coil 30 is unenergized. This allows the switched state of the coupling to be maintained even without energizing the coil 30. In this way, the coupling 10 is designed as a bistable electromagnetic actuator system.
[0060] However, it is also possible to achieve a sufficiently high remanent force by a suitable selection of the materials for the stator housing 28 and / or the armature 18, or to further increase the remanent force by a suitable material selection. In other words, the invention is not limited to the invention described in the Fig. The embodiment of the anchor 18 shown in Figures 2 to 4 is not limited; other forms of the anchor 18 are also possible. For example, the stage 42 of the anchor 18 can be omitted if a suitable material is selected.
[0061] To maintain the switched state over a longer period of time, the control unit 32 can be configured to pulse the current to the coil 30 of the at least one stator 26. This pulsating current maintains the remanent force at the contact surface of the armature 18 with the projection 38 of the stator housing 28.
[0062] To release the switching unit 16 from its end position after the clutch 10 has been actuated, the control unit 32 is configured to energize the coil 30 of the stator 26 with reversed polarity. For this purpose, the electronics for energizing the coil 30 include a full bridge, an H-circuit, or a four-quadrant converter. The reversed current reduces the remanent force, allowing the return element 34 to move the switching unit 16 back to its initial position.
[0063] The preceding description refers to a normally open coupling 10, but the same principle can be applied analogously to a normally closed coupling.