Electromagnetically switchable positive locking coupling and method for actuating an electromagnetically switchable positive locking coupling

Abstract

An electromagnetically switchable positive-lock coupling (10) is shown, comprising an axially movable driven part (16), an axially stationary driven part (24), and a stator (32) with at least one currentable, reversible drive coil (36) for adjusting the axially movable part (16) along a shaft (12). The positive-lock coupling (10) also includes a permanent magnet (38) for holding the movable part (16) in an end position and an elastic return element (54) for moving the movable part (16) from the end position to the initial position, wherein in the end position the holding force exerted by the permanent magnet (38) on the movable part (16) is greater than the return force of the return element (54). Furthermore, a method for actuating such an electromagnetically switchable positive locking coupling (10) is shown.

Description

[0001] The invention relates to an electromagnetically switchable positive-lock coupling. Furthermore, the invention relates to a method for actuating an electromagnetically switchable positive-lock coupling.

[0002] 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-lock couplings. The present invention relates to positive-lock couplings, which are referred to here as positive-lock couplings. Examples of positive-lock couplings include gear couplings and jaw couplings.

[0003] For positive-lock couplings, sliding shift sleeves are frequently used. These have teeth that engage with mating teeth, creating a positive lock through which torque can be transmitted from a first shaft to a second shaft.

[0004] Electromagnetic couplings are known from the prior art in which the adjustment of the shift sleeve is effected via a drive coil that exerts a magnetic force on the shift sleeve. In such couplings, the shift sleeve can be moved from a disengaged position in one direction to engage with a coupling body. This is referred to as a single-sided coupling.

[0005] Electromagnetically actuated positive-lock couplings typically have at least one drive coil. Switching on the drive coil generates a magnetic field that can move the coupling sleeve. To maintain the moved state, particularly in an end position of the coupling sleeve, the drive coil is usually continuously energized with a low current while in the holding position. Therefore, energy is continuously required to keep the coupling sleeve in its end position.

[0006] Switching off the drive coil causes the switching sleeve to move into a starting position, with this switching process usually being supported by an elastic return element.

[0007] In addition to the current required for the drive coil even in the end position, a magnetic force may remain after the drive coil is switched off due to remanence, meaning the elastic return element must overcome a relatively large force. This can lead to a delay in the switching process.

[0008] It is therefore an object of the invention to provide an electromagnetically switchable positive-lock coupling in which a continuous current supply to the drive coil is not required and in which no delays occur in the switching process due to remanence. Furthermore, it is an object to provide a method for actuating an electromagnetically switchable positive-lock coupling that requires as little energy as possible.

[0009] The first problem is solved according to the invention by an electromagnetically switchable positive-lock coupling with an axially movable, driven part that is rotationally fixed on a shaft and is linearly displaceable along the shaft between a starting position and an end position. Furthermore, the positive-lock coupling has at least one axially stationary, driven part that is aligned coaxially with the shaft, and a stator with at least one energizable, reversible drive coil for adjusting the axially movable part along the shaft, wherein in an engaged position there is a positive lock between the axially movable part and the axially stationary part, and thus a rotary connection between the shaft and the axially stationary part.The positive locking coupling also includes a permanent magnet for holding the moving part in the end position and an elastic return element for transferring the moving part from the end position to the starting position, wherein in the end position the holding force exerted on the moving part by the permanent magnet is greater than the return force of the return element.

[0010] In other words, at least one permanent magnet is provided, whose magnetic force is sufficient to hold the axially movable part in its end position, so that the drive coil does not need to be energized during the holding process. Accordingly, the electromagnetically switchable positive-lock coupling consumes less energy, since the positive-locking connection between the axially movable part and the stationary part is adequately secured by the permanent magnet, which can increase the range, particularly in an electric vehicle. Additionally, no magnetic force remains in the drive coil when the movable part is to be moved from its end position to its starting position, as the drive coil does not need to be energized during the holding process.

[0011] The moving part can be a shift sleeve or an armature, while the stationary part can be designed as a coupling body. The armature and / or the shift sleeve are preferably made of a ferromagnetic metal.

[0012] According to one embodiment, the initial position is a disengagement position and the final position is the engagement position, while according to an alternative embodiment, the initial position is the engagement position and the final position is the disengagement position. Accordingly, the electromagnetically switchable positive-lock coupling can be either normally open (“NO”) or normally closed (“NC”). Therefore, it is irrelevant whether the positive-lock coupling is a coupling in which the moving part is held in an engagement position or in the disengagement position by the permanent magnet.

[0013] The stator of the positive-lock coupling can additionally include a magnetic bridge between the drive coil and the at least one permanent magnet. This magnetic bridge serves to stabilize and strengthen the magnetic field of the permanent magnet, preventing undesirable magnetic effects, particularly during the movement of the moving part. In other words, the magnetic bridge prevents any deviations in the magnetic field of the permanent magnet, especially during the switching-on and switching-off of the drive coil.

[0014] While the magnetic bridge is preferably arranged between the coil and the at least one permanent magnet, the magnetic bridge can also be arranged on the side of the permanent magnet that is facing away from the drive coil.

[0015] According to one embodiment of the positive-locking coupling, the at least one drive coil, the at least one permanent magnet, and / or the magnetically conductive bridge are overmolded with a non-conductive material or encapsulated in a non-conductive material. The non-conductive material is, in particular, a magnetically non-conductive material such as a plastic compound. This ensures that all magnetic components, i.e., the drive coil, the permanent magnet, and / or the magnetically conductive bridge, are anchored in their intended positions and that the magnetic attraction or repulsion of these parts does not cause any displacement of the intended arrangement.

[0016] The at least one permanent magnet can, for example, be a ring magnet or comprise at least two ring segments. Particularly from an economic perspective, ring segments are preferred over a ring magnet; that is, sections of a ring that are not continuous around the circumference.

[0017] According to one embodiment, the stator and / or the at least one permanent magnet are arranged in a stator housing. Accordingly, both the stator and the permanent magnet are protected from external influences by the stator housing.

[0018] If a magnetically conductive bridge is provided, it can also be located in the stator housing.

[0019] Preferably, the stator housing is made of a soft magnetic material and has a radially inwardly projecting end section that is axially opposite the moving part. This allows the stator housing to stabilize and amplify the magnetic field of the at least one permanent magnet, so that the moving part can be held in the end position without the need to energize the drive coil.

[0020] According to one embodiment, the stator housing is composed of two rings with an L-shaped cross-section, one ring having a sleeve-shaped inner wall and a side wall projecting radially outwards, and the other ring having a sleeve-shaped outer wall and a side wall projecting radially inwards, the radially inner end of which forms the end section. Thus, the stator housing, and in particular the end section, can provide a stop for the moving part, so that the end position of the moving part is defined by the end section of the stator housing.

[0021] Preferably, the radially inwardly projecting side wall extends further radially inward than the sleeve-shaped inner wall. In other words, the end section of the radially inwardly projecting side wall is located outside the stator housing.

[0022] According to one embodiment, the stator, the at least one permanent magnet, and the elastic restoring element form a bistable system in which the axially movable part is secured in its starting and end positions when the coil is switched off, on the one hand by the at least one permanent magnet and on the other hand by the elastic restoring element. The permanent magnet and the elastic restoring element create two stable states corresponding to the starting and end positions, so that energizing the drive coil to hold the movable part in either the starting or end position is not required.

[0023] According to another embodiment, an electronic circuit with an H-bridge is provided for reversing the polarity of the stator. Thus, the moving part can be moved to its end position or its starting position depending on the polarity of the drive coil. By using an electronic circuit with an H-bridge, a second drive coil can therefore be omitted.

[0024] The elastic return element can preferably be a wave spring. Alternatively, a leaf spring or a coil spring can also be used.

[0025] The problem is also solved according to the invention by a method for actuating an electromagnetically switchable positive-lock coupling, as described above. The method comprises the following steps: a) Energizing the stator to move the moving part from a starting position to a final position; b) Switching off the drive coil after the moving part has reached the end position; c) Holding the movable part in the end position by means of at least one permanent magnet; and d) Reversing the polarity of the stator and energizing the reversed stator to move the moving part from the end position to the starting position with at least the support of the restoring element.

[0026] Accordingly, the basic idea of ​​the invention is that the drive coil only needs to be energized to move the movable part, so that energy can be saved and delays due to remanence can be avoided.

[0027] As previously stated, the magnetic force of the at least one permanent magnet is sufficient to hold the moving part in its end position, so that the drive coil does not need to be energized while the moving part is within the end position or in its starting position.

[0028] According to one variant of the method, in step d), the movable part is moved from its end position to its starting position by means of the elastic return element. The spring force of the elastic return element exceeds the magnetic force of the at least one permanent magnet when the stator is reversed and the axially movable part has been moved from its end position. In other words, by energizing the reversed stator, the magnetic field of the at least one permanent magnet can be reduced, thus reducing the magnetic force acting on the movable part. By reducing the magnetic force of the at least one permanent magnet, the spring force of the elastic return element can exceed the magnetic force and thus move the movable part from its end position to its starting position.Depending on the size of the spring force of the elastic return element, the energy required to power the drive coil can also be reduced during the movement out of the end position.

[0029] The reversal of the stator polarity in step d) can be achieved, for example, by an electronic circuit with an H-bridge.

[0030] Further advantages and features of the invention will become apparent from the following description and from the referenced drawings. The drawings show: - Fig. 1 a schematic sectional view of an electromagnetically switchable positive locking coupling according to the invention in the disengagement position; - Fig. 2 a detailed view of the in Fig. 1. Positive locking coupling shown in the area of ​​the stator in section; - Fig. 3 a magnetic simulation of the in Fig. 3 shown section view; and - Fig. 4 a magnetic simulation of the positive locking coupling in a sectional view in an engagement position.

[0031] Fig. Figure 1 shows an electromagnetically switchable positive locking 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.

[0032] At the in Fig. The positive locking coupling 10 shown in Figure 1 is an electromagnetic tooth coupling with radially inward and radially outward projecting teeth that interlock.

[0033] However, the electromagnetically switchable positive locking coupling 10 can also be any other type of gear coupling.

[0034] The only important thing is that the connection is made by a positive fit.

[0035] The electromagnetically switchable positive locking coupling 10 comprises an axially movable, driven part 16, which in this embodiment of the positive locking coupling 10 is a switching sleeve 18 having a first toothing 20 radially inside along the circumference, which engages with an external toothing on the first shaft 12.

[0036] Furthermore, the shift sleeve 18 is arranged in a rotationally fixed manner on the first shaft 12 and is axially adjustable along this shaft between an engagement position and an disengagement position. Fig. Figure 1 shows the shift sleeve 18 in the disengaged position.

[0037] The second shaft 14 is axially fixed and, in this embodiment of the positive-locking coupling 10, is a coupling body 26 that is rotationally fixed to the second shaft 14. The shaft 14 can carry a part 24 rigidly connected to it, which together with the shaft 14 forms the coupling body 26.

[0038] The coupling body 26 has a second toothing 28 which is arranged along the outer circumference of the coupling body 26 (here part 24).

[0039] The first toothing 20 and the second toothing 28 together form a coupling toothing 30 and serve to form a positive locking connection between the shift sleeve 18 and the coupling body 26 in the engagement position of the shift sleeve 18.

[0040] The coupling teeth 30 formed by the first and second toothing 20, 28 can have undercuts at least on the teeth of the first toothing 20 and / or on the teeth of the second toothing 28. These undercuts are designed such that, when a shift sleeve 18 is in the engaged position and a torque is applied to the positive-locking coupling 10, an additional displacement of the shift sleeve 18 towards the coupling body 26 occurs because the circumferential force is partially converted into an axial displacement force. This can be achieved, for example, by wedge-shaped undercuts, so that a wedge effect is created in the direction of the engaged position when a torque is transmitted.

[0041] In addition, a stator 32 is provided radially to the switching sleeve 18, which includes a stator housing 34 and a drive coil 36, which is at least partially enclosed in the stator housing 34.

[0042] Furthermore, a permanent magnet 38, designed as a disc-shaped ring magnet, is arranged at one axial end of the stator housing 34. Alternatively, at least two ring segments can be provided to reduce the cost of the permanent magnet 38.

[0043] The stator housing 34, which is in Fig. Figure 2, shown in more detail, is composed of two rings 40 and 42 with L-shaped cross-sections. The first ring 40 has a sleeve-shaped inner wall 44 and a side wall 46 projecting radially outwards, while the second ring 42 has a sleeve-shaped outer wall 48 and a side wall 50 projecting radially inwards.

[0044] As particularly in Fig. As can be seen in Figure 2, the radially inner end of the inwardly projecting side wall 50 extends beyond the inner wall 44 and forms an end section 52 which is axially opposite the movable part 16.

[0045] Preferably the stator housing 34, i.e. the first ring 40 and the second ring 42, is made of a soft magnetic material.

[0046] The drive coil 36 arranged in the stator housing 34 serves to linearly adjust the switching sleeve 18 along the first shaft 12 in the direction of the coupling position towards the coupling body 26.

[0047] Alternatively, it is also conceivable that the drive coil 36 serves to adjust the shift sleeve 18 along the first shaft 12 towards the disengagement position of the shift sleeve 18.

[0048] In principle, the drive coil 36 serves to adjust the switching sleeve 18 along the first shaft 12 from a starting position to an end position.

[0049] Depending on the type of positive-lock coupling 10, the initial position is either the disengagement position or the engagement position. Positive-lock couplings 10 whose initial position is the disengagement position and whose final position is the engagement position are referred to as normally open, while positive-lock couplings 10 whose initial position is the engagement position and whose final position is the disengagement position are referred to as normally closed.

[0050] The adjustment of the switching sleeve 18 from the initial position to the end position is effected by a magnetic force exerted on the switching sleeve 18 when the drive coil 36 is energized. The magnetic field generated by the drive coil 36 is thereby amplified by the magnetic field of the permanent magnet 38.

[0051] To move the switching sleeve 18 back to its starting position, an elastic return element 54 is provided, via which the switching sleeve 18 is coupled to the first shaft 12 in an axially displaceable manner.

[0052] In the positive locking coupling 10 shown in the figures, the elastic return element 54 is a wave spring 56.

[0053] The wave spring 56 is arranged between the shift sleeve 18 and the first shaft 12 in such a way that a relative displacement of the shift sleeve 18 in the axial direction towards the end position, here the engagement position, results in a compression of the wave spring 56. This creates a restoring force that the wave spring 56 exerts on the shift sleeve 18.

[0054] The restoring force or spring force acts in the opposite direction to the magnetic force of the permanent magnet 38.

[0055] However, in order for the shift sleeve 18 to be held in the end position, i.e. the engagement position, the holding force exerted on the shift sleeve 18 by the permanent magnet 38 is greater than the restoring force of the wave spring 56 in the end position.

[0056] The stator 32, the permanent magnet 38, and the wave spring 56 thus form a bistable system that can secure the switching sleeve 18 in both the starting and end positions. In the end position, when the drive coil 36 is switched off, the switching sleeve 18 is secured by the permanent magnet 38, and in the starting position by the wave spring 56.

[0057] The wave spring 56 is arranged within a recess in the first shaft 12 and presses axially on one side against a wall on the first shaft 12 and on the other side against a disk 58 attached to the switching sleeve 18.

[0058] Accordingly, the wave spring 56 is housed in a space which is radially limited on the inside by the first shaft 12 and radially on the outside by the switching sleeve 18.

[0059] As seen particularly in the detailed view in Fig. As shown in Figure 2, the positive-lock coupling 10 also includes a magnetic bridge 60, which is arranged between the drive coil 36 and the permanent magnet 38 inside the stator housing 34. Alternatively, the magnetic bridge 60 can also be arranged on the side of the permanent magnet 38 facing away from the drive coil 36. The magnetic bridge 60 serves to amplify and stabilize the magnetic field of the permanent magnet 38.

[0060] The following describes the function and operation of the positive locking coupling 10.

[0061] In the embodiment of the positive-locking coupling 10 shown here, the initial state is the disengagement position of the switching sleeve 18, as shown in Fig. 2, Fig. 3 and Fig. 4 shown.

[0062] There is no positive locking between the first toothing 20 of the shift sleeve 18 and the second toothing 28 of the clutch body 26.

[0063] The shift sleeve 18 is held in this disengaged and open state by the wave spring 56 as long as no external forces act on the shift sleeve 18 whose magnitude exceeds the spring force of the wave spring 56.

[0064] This is also referred to as a positive locking coupling 10, which is “normally open”.

[0065] As long as the shift sleeve 18 is in the starting position, here the disengagement position, the spring force of the wave spring 56 is greater than the magnetic force of the permanent magnet 38.

[0066] If the switching sleeve 18 is to be moved from the disengagement position towards the coupling body 26, a sufficient voltage must first be applied to the drive coil 36 of the stator 32.

[0067] The drive coil 36 is usually energized via a control unit.

[0068] By energizing the drive coil 36, a magnetic field is generated through the drive coil 36, which superimposes itself on the magnetic field of the permanent magnet 38 and reinforces it. In other words, by switching on the drive coil 36, a magnetic field is generated whose field lines run parallel to the field lines of the magnetic field generated by the permanent magnet 38, so that the magnetic flux density and thus also the magnetic field acting on the switching sleeve 18 are increased.

[0069] If the magnitude of the magnetic force of the drive coil 36 and the permanent magnet 38 exceeds the magnitude of the spring force of the wave spring 56 acting on the shift sleeve 18, the shift sleeve 18 will move towards the clutch body 26.

[0070] Once the shift sleeve 18 has reached its end position, here the engagement position, the drive coil 36 is switched off. This is possible because, in the end position of the shift sleeve 18, the magnetic force, i.e., the holding force exerted on the shift sleeve 18 by the permanent magnet 38, is greater than the spring force of the wave spring 56. The magnetic force of the permanent magnet 38 is therefore sufficient to securely maintain the positive engagement formed by the first and second gear teeth 20, 28.

[0071] The switching sleeve 18 is therefore held in the end position solely by the permanent magnet 38. The drive coil 36 is not energized.

[0072] In order to move the switching sleeve 18 back from the end position to the starting position, i.e. to perform a disengagement process, the stator 32 is first reversed.

[0073] The polarity reversal of the stator 32, in particular of the drive coil 36, is effected by an electronic circuit 62, which includes an H-bridge 64. The circuit 62 can, for example, be housed in a controller 65.

[0074] If the reversed drive coil 36 is now energized, the magnetic field of the drive coil 36 again superimposes on the magnetic field of the permanent magnet 38. This time, however, the magnetic force acting on the switching sleeve 18 is reduced, since the respective magnetic field lines of the drive coil 36 and the permanent magnet 38 superimpose destructively.

[0075] The magnetic force acting on the switching sleeve 18 is reduced until the spring force of the wave spring 56 exceeds the magnetic force, so that the wave spring 56 can move the switching sleeve 18 from the end position back to the starting position.

[0076] In Fig. 3 and Fig. Figure 4 shows the magnetic field of the permanent magnet 38 in the disengagement position and the engagement position, i.e., the starting position and the end position. It can be seen that the magnetic field acting on the shift sleeve 18 is significantly stronger in the end position than in the starting position, since the shift sleeve is held in the end position by the permanent magnet 38, while the wave spring 56 holds the shift sleeve 18 in the starting position.

[0077] Not shown in the figures is an embodiment in which the at least one drive coil 36, the permanent magnet 38, and the magnetically conductive bridge 60 are overmolded or potted with a non-conductive material. By potting or overmolding the magnetic parts of the bistable system, it can be ensured that there is no unwanted displacement of the parts due to magnetic attraction or repulsion depending on the polarity of the drive coil 36.

[0078] The illustrated positive locking coupling 10 is characterized by the fact that the drive coil 36 does not need to be energized in the final state of the switching sleeve 18 in order to hold the switching sleeve 18 in its final position.

Claims

[1] Electromagnetically switchable positive locking coupling (10), with an axially movable, driven part (16) which is arranged non-rotatably on a driven shaft (12) and is linearly displaceable along the shaft (12) between a starting position and an end position, at least one axially fixed part (24) which is aligned coaxially with the shaft (12), wherein in a coupling position there is a positive locking between the axially movable part (16) and the axially fixed part (24) and thus a rotary connection of the shaft (12) and the axially fixed part (24), a stator (32) with at least one currentable, reversible drive coil (36) for adjusting the axially movable part (16) along the shaft (12), at least one permanent magnet (38) for holding the movable part (16) in the end position, and an elastic restoring element (54) for transferring the movable part (16) from the end position to the starting position, wherein in the end position the holding force exerted on the movable part (16) by the permanent magnet (38) is greater than the restoring force of the restoring element (54). [2] Electromagnetically switchable positive locking coupling (10) according to claim 1, characterized by , that the starting position is a disengagement position and the end position is the engagement position, or that the starting position is the engagement position and the end position is a disengagement position. [3] Electromagnetically switchable positive locking coupling (10) according to one of the preceding claims, characterized by , that the stator (32) additionally comprises a magnetic bridge (60) between the drive coil (36) and the at least one permanent magnet (38). [4] Electromagnetically switchable positive locking coupling (10) according to claim 3, characterized by, that the at least one drive coil (36), the at least one permanent magnet (38) and / or the magnetically conductive bridge (60) are overmolded with a non-conductive material or encapsulated in a non-conductive material. [5] Electromagnetically switchable positive locking coupling (10) according to one of the preceding claims, characterized by , that the at least one permanent magnet (38) is a ring magnet or comprises at least two ring segments. [6] Electromagnetically switchable positive locking coupling (10) according to one of the preceding claims, characterized by , that the stator (32) and / or the at least one permanent magnet (38) are arranged in a stator housing (34). [7] Electromagnetically switchable positive locking coupling (10) according to claim 6, characterized by , that the stator housing (34) is made of soft magnetic material and has a radially inwardly projecting end section (52) which is axially opposite the moving part (16). [8] Electromagnetically switchable positive locking coupling (10) according to claim 7, characterized by , that the stator housing (34) is composed of two rings (40, 42) with an L-shaped cross-section, wherein one ring (40) has a sleeve-shaped inner wall (44) and a side wall (46) projecting radially outwards therefrom, and one ring (42) has a sleeve-shaped outer wall (48) and a side wall (50) projecting radially inwards, the radially inner end of which forms the end section (52). [9] Electromagnetically switchable positive locking coupling (10) according to one of the preceding claims, characterized by , that the stator (32), the at least one permanent magnet (38) and the elastic restoring element (54) form a bistable system in which the axially movable part (16) is secured in the starting and end positions when the drive coil (36) is switched off by the at least one permanent magnet on the one hand and by the elastic restoring element (54) on the other. [10] Electromagnetically switchable positive locking coupling (10) according to one of the preceding claims, characterized by , that an electronic circuit (62) with an H-bridge (64) is provided for reversing the polarity of the stator (32). [11] Electromagnetically switchable positive locking coupling (10) according to one of the preceding claims, characterized by , that the elastic restoring element (54) is a wave spring (56). [12] Method for actuating an electromagnetically switchable positive locking coupling (10) according to one of the preceding claims, wherein the method comprises the following steps: a) Energizing the stator (32) to move the movable part (16) from a starting position to a final position; b) Switching off the drive coil (36) after the moving part (16) has reached the end position; c) Holding the movable part (16) in the end position by means of the at least one permanent magnet (38); and d) Reversing the polarity of the stator (32) and energizing the reversed stator (32) to move the movable part (16) from the end position to the starting position with at least the support of the restoring element (54). [13] Method according to claim 12, characterized by , that in step d) the movable part (16) is moved from the end position to the starting position by means of the elastic restoring element (54), wherein the spring force of the elastic restoring element (54) exceeds the magnetic force of the at least one permanent magnet (38) when the stator (32) is reversed and the axially movable part (16) is moved out of its end position. [14] Method according to claim 12 or 13, characterized by , that the reversal of the polarity of the stator (32) in step d) is carried out by an electronic circuit (62) with an H-bridge (64).

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