Electromagnetic coupling

Abstract

Electromagnetic clutch (10), with a switching unit (16) which is arranged non-rotatably on a shaft (12) and is linearly displaceable along the shaft (12) between a disengagement position and an engagement position, a coupling body (20) which is arranged coaxially to the shaft (12) and which has an engagement geometry (22) into which the switching unit (16) engages in the engagement position to establish a rotationally fixed connection between the coupling body (20) and the shaft (12), and with a drive unit (23) for linearly moving the switching unit (16), which circumferentially surrounds the switching unit (16), wherein the drive unit (23) comprises at least three stators (25, 26, 27) with currentable coils (29, 30, 31) or has at least two stators (25, 27) with currentable coils (29, 30) and a permanent magnet (48) arranged between the two stators.

Description

[0001] The present invention relates to an electromagnetic coupling with a switching unit which is arranged non-rotatably on a shaft and is displaceable along the shaft, and a coupling body which has an engagement geometry into which the switching unit engages positively in the coupling position.

[0002] Electromagnetically switchable couplings with stators for moving a switching unit are generally known. The maximum possible switching travel of such couplings is limited by the attractive force that can be generated by a stator coil. The magnetic force acting on a switching unit, more precisely on an armature, decreases with increasing displacement until a force equilibrium is reached and the switching unit comes to a stop. To achieve higher attractive forces and thus longer switching travels, a correspondingly large stator with a correspondingly large coil is required. A disadvantage here is the increasing size of the stator with increasing switching travel, as this affects the overall size of the coupling. More precisely, the radially required installation space increases with the increasing size of the stator or coil.

[0003] It is therefore an object of the invention to provide an electromagnetic coupling with which large switching distances can be achieved while maintaining a compact design.

[0004] This problem is solved according to the invention by an electromagnetic coupling 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. The coupling comprises a coupling body that is arranged coaxially to the shaft and has an engagement geometry into which the switching unit engages in the engagement position to establish a non-rotatable connection between the coupling body and the shaft. The coupling also has a drive unit for linearly moving the switching unit, which circumferentially surrounds the switching unit, wherein the drive unit comprises at least three stators with energizable coils or at least two stators with energizable coils and a permanent magnet arranged between the two stators.

[0005] A drive unit with at least three stators operates in particular according to the reluctance principle or the alternating current principle, and a drive unit with a permanent magnet arranged between two stators operates, for example, according to the hybrid principle.

[0006] The reluctance principle utilizes magnetic reluctance force to pull the switching unit into the position of lowest magnetic reluctance. A drive unit operating on the reluctance principle does not require permanent magnets.

[0007] In alternating current (AC) operation, permanent magnets are used on the switching unit. A switching unit operating on the AC principle can generate both attractive and repulsive forces.

[0008] In a drive unit operating according to the hybrid principle, electromagnets and permanent magnets are arranged alternately. During operation, the coils are energized in such a way that the magnetic flux at one pole of the permanent magnets is amplified and largely balanced at the other pole. This results in a change in the magnetic field, which moves the switching unit. In other words, according to the hybrid principle, only half of the available coils contribute to force generation, while the other half serves to compensate for the magnetic forces of the permanent magnet. A drive unit operating according to the hybrid principle therefore requires more energy during operation; however, it can generate higher switching forces than a drive unit operating according to the reluctance principle or the alternating current principle.

[0009] Two stators and one permanent magnet are generally sufficient to generate a defined movement according to the hybrid principle; however, depending on the desired switching path, more than two stators and a corresponding number of permanent magnets may be present.

[0010] By using multiple stators based on the reluctance or hybrid principle, significantly larger switching travels can be achieved than with conventional electromagnetic clutches. In particular, multi-stage movement is possible, in which the switching unit can assume several defined intermediate positions between the disengagement and engagement positions. The clutch thus represents a multistable clutch.

[0011] A multi-stage movement, as defined in the application, is understood to mean a movement in which each stator causes a movement of the switching unit along a defined section of the movement. That is, the stators act sequentially and not simultaneously.

[0012] The multi-stage movement allows for significantly larger switching travels without requiring larger individual stators. According to the invention, large switching travels can thus be achieved with a compact design, particularly minimizing the installation space required in the radial direction. This represents a considerable advantage over conventional coupling systems. Theoretically, with a coupling according to the invention, arbitrarily large switching travels can be achieved through appropriate design, i.e., by using a corresponding number of coils or by appropriately designing the switching unit.

[0013] For example, a shift travel of more than 4 mm can be achieved with a clutch according to the invention.

[0014] A significant advantage of the switching system according to the invention is the stable state in both the open and closed states as well as in several conceivable intermediate positions.

[0015] The clutch can be a normally open or a normally closed clutch.

[0016] From one perspective, the drive unit, together with the switching unit, forms a reluctance linear motor, thus achieving particularly efficient and precise motion control. A reluctance linear motor is characterized in particular by its high dynamics, resulting in short switching times.

[0017] According to one embodiment, the switching unit is a one-piece rotor, which enables simple and cost-effective manufacturing. The one-piece manufacturing also minimizes tolerance chains.

[0018] The runner, for example, is made of iron, which ensures optimal magnetic properties of the runner.

[0019] For example, in cross-section, the rotor has a row of teeth on the side facing the drive unit, with several teeth spaced apart in the direction of movement. These teeth function as pole shoes. The spacing and number of teeth determine how many defined intermediate positions the rotor can assume between the engagement and disengagement positions; in other words, the teeth enable controlled movement of the rotor.

[0020] For example, the teeth have a rectangular cross-section; in other words, the teeth are cinder-shaped and arranged at regular intervals from each other.

[0021] In one variant, the stators are magnetically isolated from each other, with the axial spacing between the stators being a maximum of one-quarter of the tooth pitch. The pole offset of the energized coils is therefore also one-quarter of the tooth pitch. This design ensures that a sufficiently large magnetic force is generated in every position of the switching unit to move it at a controlled, uniform speed. Generally, the smallest possible distance between the coils is advantageous with regard to the performance of the drive unit.

[0022] The tooth spacing can be adjusted to the position of the at least three stators such that the teeth of the first of the two outer stators form a closed magnetic circuit, while the teeth of the second outer stator are positioned with a gap. This configuration can be present in both the engagement and disengagement positions. The tooth spacing is determined primarily by the distance between the stators. By adjusting the tooth positions to the stator positions in this way, an optimal arrangement is achieved with regard to magnetic friction, ensuring that the leakage flux between the switching unit or rotor and the drive unit remains low compared to the useful flux through the working air gap.

[0023] The outer stators are those furthest out in the axial direction. The remaining stators are evenly distributed between the outer stators.

[0024] In one variant, the switching unit comprises a rotor and several permanent magnets arranged on the rotor, thereby generating both attractive and repulsive forces between the stators and the rotor to cause the rotor to move in a desired direction. This allows the switching unit to be moved to any position along its path of travel.

[0025] According to one aspect, the coupling includes a control unit configured to alternately energize the stator coils to continuously move the switching unit, thus enabling precise motion control. In full-step operation, for example, one-third of the coils are switched on, possibly with a slight time overlap. In half-step operation, the average duty cycle of the coils increases to two-thirds, meaning the coils are switched on with a greater time overlap than in full-step operation. However, the motor power does not increase proportionally in half-step operation, as only smaller reluctance changes can be achieved in this mode.

[0026] For example, the control unit is configured to alternately energize the stator coils according to a predetermined sequential order, meaning that the duty cycle of the coils remains constant. This allows for simpler control with fewer electronic components.

[0027] Alternatively, the control unit can be configured to energize the stator coils in such a way that the maximum possible magnetic force acts on the switching unit in every position, thereby achieving particularly smooth movement of the switching unit and avoiding detent forces or vibration. The energization is specifically tailored to the current relative position between the stators and the switching unit, with feedback between the switching unit's position and the energization. This means that the duty cycle of the coils can vary.

[0028] According to another alternative, the control unit can be configured, provided the drive unit has at least two stators with current-carrying coils and a permanent magnet arranged between the two stators, to energize the stator coils in such a way that a magnetic flux is amplified at one pole of the at least one permanent magnet and balanced at the other pole. As previously explained in connection with the hybrid principle, the magnetic flux of the permanent magnet is thus influenced in such a way that a magnetic force can be generated to move the switching unit.

[0029] For example, the coupling includes a holding device designed to keep the switching unit in the disengaged and / or engaged position when the coils are de-energized. This holding device enables energy-efficient operation, as the end positions can be maintained without continuous power supply.

[0030] The holding device secures the switching unit in particular against unintentional displacement, while movement of the switching unit is possible without hindrance if a force is applied to the switching unit in the direction of movement that is greater than the holding force of the holding device.

[0031] Further advantages and features will become apparent from the following description and the accompanying drawings. The drawings show: - Fig. 1 by way of example an electromagnetic coupling not according to the invention, - Fig. 2 a switching unit and a drive unit operating according to the reluctance principle of an electromagnetic clutch according to the invention, wherein the switching unit is arranged in a disengagement position, - Fig. 3 the unit from Fig. 2, wherein the switching unit is arranged in an intermediate position, - Fig. 4 the unit from Fig. 2, wherein the switching unit is arranged in a clutch-in position, - Fig. 5 a switching unit and a drive unit operating according to the hybrid principle of an electromagnetic coupling according to the invention, and - Fig. 6 a switching unit and a drive unit operating according to the alternating current principle of an electromagnetic coupling according to the invention.

[0032] Fig. Figure 1 shows the basic structure of an electromagnetic coupling 10, wherein the embodiment shown is a normally open coupling 10.

[0033] The coupling 10 comprises a first rotatable shaft 12 and a second rotatable shaft 14.

[0034] 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.

[0035] The switching unit 16 includes an armature 18, which is usually made of a ferromagnetic material.

[0036] 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.

[0037] 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.

[0038] 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 exemplary embodiment according to Fig. 1 is formed in one piece with the anchor 18.

[0039] An engagement geometry 22 within the meaning of the application refers to a structure, for example a toothing or claw geometry, which enables a positive locking connection.

[0040] Furthermore, the coupling 10 comprises a drive unit 23 with a stator 26, which includes 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.

[0041] 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 from the disengaged position to the engaged position.

[0042] 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.

[0043] The Fig. Figures 2 to 4, 5 and 6 each illustrate a unit with a switching unit 16 and a drive unit 23. Each of the in the Fig. The 2 to 6 units shown can be arranged as in Fig. 1 illustrated coupling 10 can be integrated.

[0044] For identical structures with identical functions known from the above embodiment, the same reference numerals are used below, and reference is made to the preceding explanations, with the differences of the respective embodiments being discussed below to avoid repetition.

[0045] During the Fig. In the illustrated embodiment 2 to 4, the drive unit 23 together with the switching unit 16 forms a reluctance linear motor.

[0046] The drive unit 23 comprises three magnetically isolated stators 25, 26, 27 with currentable coils 29, 30, 31.

[0047] The switching unit 16 is formed by a one-piece rotor 36, which is made primarily of iron.

[0048] As already mentioned in connection with Fig. As explained in section 1, the switching unit 16 is mounted on the first shaft 12 in a rotationally fixed and linearly displaceable manner.

[0049] The shift claw 24 is manufactured as a single unit with the rotor 36.

[0050] In cross-section, the runner 36 has a row of teeth 38 on the side facing the drive unit 23, with several teeth 40 spaced apart from each other in the direction of movement. The teeth 40 function as pole shoes.

[0051] In the exemplary embodiment, the teeth 40 have a rectangular cross-section. In other words, the teeth 40 form a ridged structure. However, other tooth shapes are also conceivable.

[0052] All teeth 40 are identically shaped and the individual teeth 40 have the same distance between them.

[0053] The distance between teeth 40 and the distance between stators 25, 26, 27 are coordinated. Specifically, the distance between stators 25, 26, 27 is a maximum of one quarter of the tooth pitch.

[0054] More precisely, the spacing of the teeth 40 is such that it is matched to the position of the three stators 25, 26, 27 in the Fig. In the depicted state 2, the first of the two outer stators 27 with teeth 40 forms a closed magnetic circuit, and a second outer stator 25 with teeth 40 is arranged with gaps between them. This allows for continuous movement of the switching unit, which will be explained in more detail below.

[0055] The control unit 32 is designed to move the switching unit 16 by alternately energizing the coils 29, 30, 31 of the stators 25, 26, 27.

[0056] The coupling 10 further comprises a holding device 42, which is designed to hold the switching unit 16 in the disengagement position or in the engagement position when the coils 29, 30, 31 are de-energized.

[0057] The holding device 42 is a mechanical holding device comprising a holding element 44 mounted in the shaft 12 and elastically acted upon against the switching unit 16, which in the exemplary embodiment is a ball.

[0058] The switching unit 16, in particular the rotor 36, has two axially spaced recesses 46 in the area of ​​the retaining element 44, wherein the retaining element 44 projects at least partially into a corresponding recess 46 in the engagement position and in the disengagement position of the switching unit 16.

[0059] Alternatively or in addition to the mechanical holding device 42, the switching unit 16 can be held in the coupling position by a continuous current supply to the stator 27.

[0060] The following describes an actuation process of a clutch 10 with a drive unit 23 and a switching unit 16 according to Fig. 2 described, with particular attention paid to the temporal sequence of the current supply to the individual coils 29, 30, 31 by the control unit 32.

[0061] In Fig. Figure 2 shows the switching unit 16 in an initial position that corresponds to the disengagement position.

[0062] In the illustrated embodiment, a magnetic equilibrium exists between the stator 27 and the teeth 40-1, 40-3 in the disengaged position. This means that the stator 27 cannot contribute to the movement of the switching unit 16 as long as it is in the disengaged position.

[0063] However, there is an offset between the stators 25, 26 and the teeth 40-4, 40-6, 40-7, 40-9, so that these stators can in principle provide a force component for moving the switching unit 16 out of the disengaged position.

[0064] By alternately energizing the stators 25, 26, 27, or more precisely the corresponding coils 29, 30, 31, which is effected by the control unit 32, the stators 25, 26, 27 alternately contribute to the movement of the switching unit 16. In particular, by moving the switching unit 16 out of the disengaged position, the magnetic equilibrium between the teeth 40-1, 40-3 and the stator 27 is broken. Instead, a magnetic equilibrium is established between one of the other stators 25, 26 and the teeth 40 of the rotor 36.

[0065] Starting from the in Fig. In the position illustrated in Figure 2, with increasing displacement of the switching unit 16, a magnetic equilibrium is initially created between the stator 26 and the teeth 40-4, 40-6, as shown in Figure 2. Fig. Figure 3 illustrates this. In this state, the switching unit 16 is arranged in an intermediate position between the disengagement position and the engagement position.

[0066] Upon further displacement, particularly when the switching unit 16 reaches the engagement position, a magnetic equilibrium is established between the stator 25 and the teeth 40-7, 40-9, as shown in Fig. 4 is illustrated.

[0067] In the engagement position and the disengagement position, the switching unit 16 is locked by the holding device 42.

[0068] To move the switching unit 16 from the engagement position back to the disengagement position, the energizing of the stators 25, 26, 27 or the corresponding coils 29, 30, 31 can be carried out in the same way in reverse order.

[0069] Alternatively, the return can be achieved by the elastic return element 34, which is located in the Fig. 2 to 4 are not shown for the sake of simplicity.

[0070] It is also conceivable that a short current pulse is necessary for resetting in order to reduce any existing remanent forces and overcome the holding force of the holding device 42, and that the resetting movement is further effected by the elastic resetting element 34.

[0071] There are basically two ways in which the coils 29, 30, 31 can be energized by the control unit 32. The two alternatives differ in the programming stored in the control unit 32.

[0072] According to a first alternative, the coils 29, 30, 31 are alternately energized according to a predetermined sequential order. In other words, the duty cycle of the coils 29, 30, 31 is constant, and all coils 29, 30, 31 have the same duty cycle.

[0073] According to a second alternative, the duty cycle of coils 29, 30, 31 can be controlled based on their position. This means that the position of the switching unit 16 is detected by a suitable sensor, and the current applied to coils 29, 30, 31 is then controlled based on the current position of the switching unit 16. In other words, the position of the switching unit 16 serves as a control variable for regulating the current applied to coils 29, 30, 31. This type of control ensures that the maximum possible magnetic force is applied to the switching unit 16 in every position. This results in particularly smooth movement of the switching unit 16; however, the electronic complexity is increased compared to the first alternative.

[0074] Fig. Figure 5 illustrates an embodiment in which the drive unit 23 operates according to the hybrid principle.

[0075] Compared to the one associated with the Fig. In the embodiment described in sections 2 to 4, the coupling 10 differs in the shape of the drive unit 23; the switching unit 16 is identical to that described in section 2. Fig. 2 to 4 described switching unit 16.

[0076] The drive unit according to Fig. 5 comprises two stators 25, 27 with currentable coils 29, 31 and a permanent magnet 48 arranged between the two stators 25, 27.

[0077] To switch the clutch 10, the coils 29, 31 of the stators 25, 27 are energized in such a way that a magnetic flux is increased at one pole of the permanent magnet 48 and balanced at the other pole of the permanent magnet 48.

[0078] The reset will be carried out as before in connection with the Fig. 2 to 4 explained by reverse polarity current flow to the coils and / or by the elastic energy stored in the restoring element 34.

[0079] Fig. Figure 6 illustrates an embodiment in which the drive unit 23 operates according to the alternating current principle.

[0080] The drive unit 23 is identical in this case to the one in the Fig. 2 to 4 illustrated drive unit 23, in particular with three magnetically isolated stators 25, 26, 27, each having a currentable coil 29, 30, 31.

[0081] The switching unit 16 comprises a rotor 36, which includes a carrier 50 and several permanent magnets 52 arranged on the carrier 50.

[0082] The switching claw 24 is formed as a single unit with the carrier 50.

[0083] By appropriately energizing the coils 29, 30, 31, both repulsive and attractive forces can be generated between the coils 29, 30, 31 and the permanent magnets 52, by which the switching unit 16 can be moved between the disengagement position and the engagement position.

[0084] The preceding description refers to a normally open coupling 10, but the same drive principles can be applied analogously to a normally closed coupling.

Claims

[1] Electromagnetic coupling (10), with a switching unit (16) which is arranged non-rotatably on a shaft (12) and is linearly displaceable along the shaft (12) between a disengagement position and an engagement position, a coupling body (20) which is arranged coaxially to the shaft (12) and which has an engagement geometry (22) into which the switching unit (16) engages in the engagement position to establish a rotationally fixed connection between the coupling body (20) and the shaft (12), and with a drive unit (23) for linearly moving the switching unit (16), which circumferentially surrounds the switching unit (16), wherein the drive unit (23) comprises at least three stators (25, 26, 27) with currentable coils (29, 30, 31) or has at least two stators (25, 27) with currentable coils (29, 30) and a permanent magnet (48) arranged between the two stators. [2] Electromagnetic coupling (10) according to claim 1, characterized by , that the drive unit (23) together with the switching unit (16) forms a reluctance linear motor. [3] Electromagnetic coupling (10) according to claim 1 or 2, characterized by , that the switching unit (16) is a one-piece rotor (36). [4] Electromagnetic coupling (10) according to claim 3, characterized by , that the runner (36) in cross-section has on the side facing the drive unit (23) a row of teeth (38) with several teeth (40) spaced apart from each other in the direction of movement. [5] Electromagnetic coupling (10) according to claim 4, characterized by , that the stators (25, 26, 27) are magnetically isolated from each other, wherein the distance between the stators (25, 26, 27) in the axial direction is at most one quarter of the tooth pitch. [6] Electromagnetic coupling according to claim 5, characterized by, that the spacing of the teeth (40) is such that the position of the at least three stators (25, 26, 27) is adjusted such that a first of the two outer stators (25, 27) forms a closed magnetic circuit with the teeth (40) and a second outer stator (25, 27) is arranged with the teeth (40) in a gap. [7] Electromagnetic coupling (10) according to claim 1, characterized by , that the switching unit (16) comprises a rotor (36) and several permanent magnets (52) arranged on the rotor. [8] Electromagnetic coupling (10) according to any one of the preceding claims, characterized by , that the coupling (10) includes a control unit (32) which is configured to alternately energize the coils (29, 30, 31) of the stators (25, 26, 27) in order to continuously move the switching unit (16). [9] Electromagnetic coupling (10) according to claim 8, characterized by, that the control unit (32) is set up to alternately energize the coils (29, 30, 31) of the stators (25, 26, 27) according to a predetermined sequential sequence. [10] Electromagnetic coupling (10) according to claim 8, characterized by , that the control unit (32) is configured to energize the coils (29, 30, 31) of the stators (25, 26, 27) in such a way that in every position a maximum possible magnetic force acts on the switching unit (16). [11] Electromagnetic coupling (10) according to any one of claims 1 to 4, characterized by , that the coupling (10) comprises a control unit (32) which is configured to energize the coils (29, 30, 31) of the stators (25, 26, 27) in such a way that a magnetic flux is increased at one pole of the at least one permanent magnet (48) and balanced at the other pole of the at least one permanent magnet (48). [12] Electromagnetic coupling (10) according to any one of the preceding claims, characterized by, that the coupling (10) includes a holding device (42) which is configured to hold the switching unit (16) in the disengaged position and / or in the engaged position when the coils (29, 30, 31) are de-energized.

Images