Electromagnetic switching positive engagement clutch and method for actuation of an electromagnetic switching positive engagement clutch

Abstract

A positive engagement, electromagnetically commutated clutch (10) is shown, comprising an axially movable driven part (16), an axially fixed driven part (24), and a stator (32) having at least one drive coil (36) capable of being energized and switched with polarity reversal to move the axially movable part (16) along the shaft (12). The positive engagement clutch (10) further comprises a permanent magnet (38) for retaining the moving part (16) in a final position, and a spring return element (54) for transferring the moving part (16) from the final position to the initial position, the holding force exerted by the permanent magnet (38) on the moving part (16) in the final position being greater than the spring return force of the spring return element (54). A method for actuation of such a positive engagement, electromagnetically commutated clutch (10) is further shown. Figure 2

Description

Title of the invention: Positive engagement, electromagnetically commutated clutch and method for actuation of a positive engagement, electromagnetically commutated clutch

[0001] The invention relates to a positive engagement, electromagnetically commutated clutch. The invention further relates to a method for actuation of a positive engagement, electromagnetically commutated clutch.

[0002] Clutches are generally used when torque must be temporarily transmitted from one shaft to another shaft aligned coaxially with it without permanently connecting the two shafts. A distinction is made between friction clutches and positive engagement clutches. The present invention relates to clutches with positive engagement, referred to herein as positive engagement clutches. Positive engagement clutches include, for example, toothed clutches and dog clutches.

[0003] Sliding sleeves are often used for positive engagement clutches. These have teeth that mesh with counter teeth, so that a positive engagement occurs, which allows the transmission of torque from a first shaft to a second shaft.

[0004] It is known from the prior art of electromagnetic clutches in which the sliding sleeve is adjusted by a drive coil that exerts a magnetic force on the sliding sleeve. In clutches of this type, the sliding sleeve can be moved in one direction from a disengaged position in order to bring the sliding sleeve into engagement with a clutch body. This is then referred to as a unilateral clutch.

[0005] Positive engagement, electromagnetically commutated clutches generally include at least one drive coil for this purpose. Engaging the drive coil generates a magnetic field that can move the sliding sleeve. To maintain the displaced state, particularly in the final position of the sliding sleeve, the drive coil generally continues to be energized with a low current in the engaged state. Consequently, energy is constantly required to hold the sliding sleeve in the final position. Disengaging the drive coil causes the sliding sleeve to move back to its initial position, this switching operation generally being assisted by an elastic return element.

[0006] In addition to the current supply to the drive coil, which is also required in the final position, a magnetic force may remain after the drive coil is switched off due to remanence, so the elastic return element must be able to overcome a relatively large force. This can cause a delay in the switching process.

[0007] The invention therefore aims to provide a positive engagement, electromagnetically commutated clutch in which a continuous current supply to the drive coil is not required and in which no delay occurs in the commutation process due to remanence. A further objective is to provide a method for actuation of a positive engagement, electromagnetically commutated clutch that requires the least amount of energy possible.

[0008] The first objective is achieved, according to the invention, by a positive engagement, electromagnetically commutated clutch comprising an axially movable driven part, which is rotationally fixed to a driven shaft and is capable of being moved linearly along the shaft between an initial position and a final position. Furthermore, the positive engagement clutch comprises at least one axially fixed driven part, which is aligned coaxially with the shaft, and a stator having at least one drive coil capable of being energized and switched with polarity reversal to move the axially movable part along the shaft, a positive engagement being present between the axially movable part and the axially fixed part, and thus a rotational connection between the shaft and the axially fixed part in a clutched position.The positive engagement clutch further includes at least one permanent magnet to retain the moving part in the final position, and an elastic return element for transferring the moving part from the final position to the initial position, the holding force exerted by the permanent magnet on the moving part in the final position being greater than the return force of the return element.

[0009] In other words, at least one permanent magnet is provided, the magnetic force of which is sufficiently high to hold the moving part axially in the final position, so that the drive coil does not need to be energized during the holding process. Consequently, the positive engagement, electromagnetically commutated clutch consumes less energy, since the positive engagement connection between the axially moving part and the fixed part is sufficiently ensured by the permanent magnet, thus increasing the driving range, particularly in the case of an electric vehicle. Furthermore, no magnetic force remains in the drive coil when the moving part needs to be moved from the final position to the initial position, since the coil The training device does not need to be powered during the maintenance process.

[0010] The moving part may be a sliding sleeve or an armature, while the fixed part may be in the form of a clutch body. The armature and / or the sliding sleeve is / are preferably made of a ferromagnetic metal.

[0011] In one embodiment, the initial position is a disengaged position and the final position is the engaged position, whereas in an alternative embodiment, the initial position is the engaged position and the final position is the disengaged position. Consequently, the positive engagement, electromagnetically commutated clutch can be in a normally open (NO) state or a normally closed (NC) state. Thus, it is irrelevant whether the positive engagement clutch is a clutch in which the moving part is held by the permanent magnet in an engaged or disengaged position.

[0012] The stator of the positive engagement clutch may further include a magnetic bridge between the drive coil and said at least one permanent magnet. The magnetic bridge serves to stabilize and strengthen the magnetic field of the permanent magnet, in order to prevent any undesirable magnetic effects, particularly during the movement of the moving part. In other words, the magnetic bridge serves to prevent possible deviations in the magnetic field of the permanent magnet, particularly during the activation and deactivation process of the drive coil.

[0013] While the magnetic bridge is preferably arranged between the coil and said at least one permanent magnet, it is also possible to arrange the magnetic bridge on the side of the permanent magnet that is opposite to the drive coil.

[0014] According to one embodiment of the positive engagement clutch, said at least one drive coil, said at least one permanent magnet, and / or the magnetically conductive bridge are injection-molded 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 mass. This ensures that all the magnetic components, i.e., the drive coil, the permanent magnet, and / or the magnetically conductive bridge, are anchored in their intended location and that the magnetic attraction or repulsion of these parts does not cause any displacement of the intended arrangement.

[0015] Said at least one permanent magnet may, for example, be a ring magnet or comprise at least two ring segments. From an economic point of view in particular, ring segments are preferred to ring magnets, that is to say, parts of a ring that are not continuous at the periphery.

[0016] According to one embodiment, the stator and / or said at least one permanent magnet are arranged in a stator housing. Consequently, both the stator and the permanent magnet are protected from external influences by the stator housing.

[0017] If a magnetically conductive bridge is provided, it can also be arranged in the stator housing.

[0018] Preferably, the stator housing is made of a soft magnetic material and has an end portion projecting radially inwards, which is axially opposed to the moving part. Thus, the stator housing can stabilize and strengthen the magnetic field of said at least one permanent magnet, so that the moving part can be held in the final position without having to supply current to the drive coil.

[0019] According to one embodiment, the stator housing comprises two L-shaped cross-section rings, one ring having a socket-shaped inner wall and a side wall projecting radially outwards from it, and the other ring having a socket-shaped outer wall and a side wall projecting radially inwards, the radially inner end of which forms the end portion. A stop for the moving part can thus be provided by the stator housing, in particular the end portion, so that the final position of the moving part is defined by the end portion of the stator housing.

[0020] Preferably, the side wall projecting radially inwards projects radially further inwards than the inner socket-shaped wall. In other words, the end portion of the side wall projecting radially inwards is located outside the stator housing.

[0021] According to one embodiment, the stator, said at least one permanent magnet, and the elastic return element form a bistable system in which the axially moving part is locked in position in the initial position and in the final position when the coil is deactivated, on the one hand by said at least one permanent magnet and on the other hand by the elastic return element. The permanent magnet and the elastic return element create two stable states corresponding to the initial position and the final position, so that it is not necessary to supply the drive coil with current to maintain the moving part in the final or initial position.

[0022] According to another embodiment, an electronic circuit with an H-bridge is provided to reverse the polarity of the stator. Thus, the moving part can be moved to the final position or to the initial position depending on the polarity of the drive coil. The use of an electronic circuit with an H-bridge therefore eliminates the need for a second drive coil.

[0023] The elastic return element can preferably be a wave spring. Alternatively, a leaf spring or a spiral spring can also be used.

[0024] According to the invention, the objective is also achieved by a method of actuation of a positive engagement, electromagnetically commutated clutch, as described above. The method comprises the following steps:

[0025] a) supply the stator with current to move the moving part from an initial position to a final position;

[0026] b) deactivate the drive coil after the moving part has reached the final position;

[0027] c) maintain the moving part in the final position by means of said at least one permanent magnet; and

[0028] d) reverse the polarity of the stator and supply the reversed polarity stator with current to move the moving part from the final position to the initial position at least by means of the return element.

[0029] Thus, the basic idea of ​​the invention is that the drive coil only needs to be powered to move the moving part, which saves energy and avoids delays due to remanence.

[0030] As already indicated previously, the magnetic force of said at least one permanent magnet is sufficient to maintain the moving part in its final position, so that the drive coil does not need to be energized when the moving part is in the final position or in its initial position.

[0031] According to an embodiment of the method, the moving part is moved in step d) from the final position to the initial position by means of the elastic return element. The spring force of the elastic return element then exceeds the magnetic force of said at least one permanent magnet when the polarity of the stator is reversed and the moving part is axially displaced from its final position. In other words, by supplying the stator with reversed polarity, the magnetic field of said at least one permanent magnet can be reduced, so that the magnetic force acting on the moving part is reduced. By reducing the magnetic force of said at least one permanent magnet, the spring force of the elastic return element can exceed the magnetic force and thus move the moving part from its final position to its initial position.Depending on the magnitude of the spring force of the elastic return element, the energy required to supply current to the drive coil can thus be reduced, even during movement out of the final position.

[0032] The reversal of the polarity of the stator in step d) can be achieved, for example, by an electronic circuit having an H-bridge.

[0033] Other advantages and features of the invention will become apparent from the following description and the drawings to which reference is made, which show:

[0034] - [Fig. 1] a schematic cross-sectional view of a positive engagement clutch and electromagnetic switching according to the invention in the disengaged position;

[0035] - [Fig.2] a detailed cross-sectional view of the positive engagement clutch represented on [Fig.1] in the stator area;

[0036] - [Fig.3] a magnetic simulation of the cross-sectional view shown in [Fig.3]; and

[0037] - [Fig.4] a magnetic simulation of the positive engagement clutch in a Cross-sectional view in a clutch position.

[0038] Fig. 1 shows a positive engagement electromagnetically commutated clutch 10, which serves to couple a first shaft 12 and a second shaft 14 aligned coaxially with respect to the first shaft 12 by opening and closing.

[0039] The positive engagement clutch 10 shown in [Fig.1] is an electromagnetic tooth clutch having teeth that protrude radially inwards and radially outwards and that engage with each other.

[0040] The positive engagement, electromagnetically commutated clutch 10 can, however, also be any other type of toothed clutch. It is only important that the connection be established by positive engagement.

[0041] The positive engagement and electromagnetically commutated clutch 10 includes an axially movable driven part 16, which, in this example of an embodiment of the positive engagement clutch 10, is a sliding sleeve 18 which has radially inside, along the circumference, a first toothing 20 which is engaged with an external toothing on the first shaft 12.

[0042] Furthermore, the sliding sleeve 18 is fixed to the rotation on the first shaft 12 and is able to be moved axially along it between a clutch position and a disengagement position. [Fig. 1] shows the sliding sleeve 18 in the disengagement position.

[0043] The second shaft 14 is axially fixed and, in this example of an embodiment of the positive engagement clutch 10, is a clutch body 26 which is rotationally coupled to the second shaft 14. The shaft 14 can carry a part 24 which is fixed to it and which, together with the shaft 14, forms the clutch body 26.

[0044] The clutch body 26 has a second set of teeth 28 which is arranged along the outer circumference of the clutch body 26 (here of the part 24).

[0045] The first tooth 20 and the second tooth 28 together form a clutch tooth 30 and serve to create, in the clutch position of the sliding sleeve 18, a positive engagement between the sliding sleeve 18 and the clutch body 26.

[0046] The clutch teeth 30 formed by the first and second teeth 20, 28 may have, at least at the teeth of the first teeth 20 and / or at the teeth of the second teeth 28, undercuts such that, when the sliding sleeve 18 is in the engaged position and a torque is applied to the positive engagement clutch 10, an additional displacement of the sliding sleeve 18 towards the clutch body 26 occurs, since the circumferential force is partially converted into an axial displacement force. This can be achieved, for example, by undercuts widening in a wedge shape, so that a wedge effect occurs in the direction of the engaged position when a torque is transmitted.

[0047] In addition, a stator 32 is provided radially with respect to the sliding sleeve 18, which includes a stator housing 34 and a drive coil 36 at least partially housed in the stator housing 34.

[0048] A permanent magnet 38 made in the form of a disc-shaped annular magnet is further arranged at an axial end in the stator housing 34. Alternatively, however, it is also possible to provide at least two annular segments to reduce the cost of the permanent magnet 38.

[0049] The stator housing 34, which is shown in more detail in [Fig.2], is composed of two rings 40, 42 with L-shaped cross-section. The first ring 40 has an inner wall 44 in the shape of a socket and a side wall 46 projecting radially outwards from it, while the second ring 42 has an outer wall 48 in the shape of a socket and a side wall 50 projecting radially inwards.

[0050] As can be seen in particular on [Fig.2], the radially inner end of the inwardly projecting side wall 50 extends beyond the inner wall 44 and forms an end part 52 which is axially opposite to the movable part 16.

[0051] Preferably, the stator housing 34, i.e. the first ring 40 and the second ring 42, is made of a soft magnetic material.

[0052] The drive coil 36 arranged in the stator housing 34 serves for the linear movement of the sliding sleeve 18 along the first shaft 12 in the direction of the clutch position towards the clutch body 26.

[0053] It is also conceivable as an alternative that the drive coil 36 is used to move the sliding sleeve 18 along the first shaft 12 towards the disengagement position of the sliding sleeve 18.

[0054] In principle, the drive coil 36 is used to move the sliding sleeve 18 along the first shaft 12 from an initial position to a final position.

[0055] Depending on the type of positive engagement clutch 10, the initial position is either the disengaged position or the engaged position. Positive engagement clutches Clutches 10 whose initial position is the disengagement position and whose final position is the engagement position are called "normally open," while positive engagement clutches 10 whose initial position is the engagement position and whose final position is the disengagement position are called "normally closed."

[0056] The movement of the sliding sleeve 18 from the initial position to the final position is effected by a magnetic force exerted on the sliding sleeve 18 when the drive coil 36 is energized. The magnetic field generated by the drive coil 36 is then reinforced by the magnetic field of the permanent magnet 38.

[0057] In order to return the sliding sleeve 18 to its initial position, an elastic return element 54 is provided, through which the sliding sleeve 18 is coupled to the first shaft 12 so as to be able to move in the axial direction.

[0058] In the positive engagement clutch 10 shown in the figures, the elastic return element 54 is a wave spring 56.

[0059] The wave spring 56 is arranged between the sliding sleeve 18 and the first shaft 12 such that a relative displacement of the sliding sleeve 18 in the axial direction towards the final position, here the clutch position, causes a compression of the wave spring 56. This results in a restoring force that the wave spring 56 exerts on the sliding sleeve 18.

[0060] The restoring force or the spring force then acts in the opposite direction to the magnetic force of the permanent magnet 38.

[0061] However, in order to be able to maintain the sliding sleeve 18 in the final position, i.e. the clutch position, the holding force exerted by the permanent magnet 38 on the sliding sleeve 18 in the final position is greater than the restoring force of the wave spring 56.

[0062] The stator 32, the permanent magnet 38, and the wave spring 56 thus form a bistable system capable of locking the sliding sleeve 18 in its initial and final positions. When the drive coil 36 is deactivated, the sliding sleeve 18 is locked in its final position by the permanent magnet 38 and in its initial position by the wave spring 56.

[0063] The wave spring 56 is arranged in a recess in the first shaft 12 and bears axially on one side against a wall of the first shaft 12 and on the other side against a disc 58 fixed to the sliding sleeve 18.

[0064] Consequently, the wave spring 56 is housed in a space delimited radially on the inside by the first shaft 12 and radially on the outside by the sliding sleeve 18.

[0065] As shown in particular in the detailed view of [Fig.2], the positive engagement clutch 10 further comprises a magnetic bridge 60 which is arranged between the drive coil 36 and the permanent magnet 38 inside the stator housing 34. The magnetic bridge 60 can alternatively also be arranged on the side of the permanent magnet 38 away from the drive coil 36. The magnetic bridge 60 serves to strengthen and stabilize the magnetic field of the permanent magnet 38.

[0066] The operating mode and use of the positive engagement clutch 10 are described below.

[0067] In the embodiment of the positive engagement clutch 10 presented here, the initial state is formed by the disengagement position of the sliding sleeve 18, as shown in Figures 2, 3 and 4.

[0068] There is then no positive engagement between the first tooth 20 of the sliding sleeve 18 and the second tooth 28 of the clutch body 26.

[0069] In this disengaged and open state, the sliding sleeve 18 is held by the wave spring 56 as long as no external force whose intensity exceeds the elastic force of the wave spring 56 acts on the sliding sleeve 18.

[0070] We also refer to a positive engagement clutch 10 which is "normally open".

[0071] As long as the sliding sleeve 18 is in the initial position, here the disengagement position, the spring force of the wave spring 56 is greater than the magnetic force of the permanent magnet 38.

[0072] If the sliding sleeve 18 is to be moved from the disengagement position to the clutch body 26, sufficient tension must first be applied to the drive coil 36 of the stator 32.

[0073] The power supply to the drive coil 36 is generally achieved by a control.

[0074] Supplying current to the drive coil 36 generates a magnetic field that is superimposed on and reinforces the magnetic field of the permanent magnet 38. In other words, activating the drive coil 36 generates a magnetic field whose field lines are parallel to the field lines of the magnetic field generated by the permanent magnet 38, so that the magnetic flux density, and therefore also the magnetic field acting on the sliding sleeve 18, is reinforced.

[0075] If the amount of the magnetic force of the drive coil 36 and the permanent magnet 38 exceeds the amount of the spring force of the wave spring 56 acting on the sliding sleeve 18, the latter moves towards the clutch body 26.

[0076] Once the sliding sleeve 18 has reached its final position, here the clutch position, the drive coil 36 is deactivated. This is possible because, in the final position of the sliding sleeve 18, the magnetic force, i.e., the holding force exerted by the permanent magnet 38 on the sliding sleeve 18, 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 teeth 20, 28.

[0077] The sliding sleeve 18 is therefore held in the final position only by the permanent magnet 38. The drive coil 36 is not supplied with current.

[0078] In order to then return the sliding sleeve 18 from the final position to the initial position, i.e. to perform a disengagement operation, the polarity of the stator 32 is first reversed.

[0079] The polarity reversal of the stator 32, in particular of the drive coil 36, is carried out by an electronic circuit 62 which includes an H-bridge 64. The circuit 62 can for example be housed in a control 65.

[0080] When the reverse polarity drive coil 36 is energized, the magnetic field of the drive coil 36 again overlaps with the magnetic field of the permanent magnet 38. This time, however, the magnetic force acting on the sliding sleeve 18 decreases, since the respective magnetic field lines of the drive coil 36 and the permanent magnet 38 overlap destructively.

[0081] The magnetic force acting on the sliding sleeve 18 is reduced until the spring force of the wave spring 56 exceeds the magnetic force, so that the wave spring 56 can return the sliding sleeve 18 from the final position to the initial position.

[0082] Figures 3 and 4 show respectively the magnetic field of the permanent magnet 38 in the disengaged position and in the engaged position, i.e., the initial and final positions. It can be seen that the magnetic field acting on the sliding sleeve 18 is significantly stronger in the final position than in the initial position, because the sliding sleeve is held in the final position by the permanent magnet 38, while the wave spring 56 holds the sliding sleeve 18 in the initial position.

[0083] The figures do not show any embodiment in which said at least one drive coil 36, the permanent magnet 38, and the magnetically conductive bridge 60 are injection-coated or encapsulated with a non-conductive material. Encapsulating or injection-coating the magnetic components of the bistable system prevents any undesired movement of the components due to magnetic attraction or repulsion depending on the polarity of the drive coil 36.

[0084] The positive engagement clutch 10 shown is characterized in that the drive coil 36 must not be energized in the final state of the sliding sleeve 18 to hold the sliding sleeve 18 in its final position.

Claims

Demands

1. Positive engagement, electromagnetically commutated clutch (10), comprising an axially movable driven part (16), which is rotationally fixed to a driven shaft (12) and is capable of being moved linearly along the shaft (12) between an initial position and a final position, at least one axially fixed part (24), which is aligned coaxially with the shaft (12), a positive engagement being present between the axially movable part (16) and the axially fixed part (24) and thus a rotational connection between the shaft (12) and the axially fixed part (24) in a clutched position, a stator (32) having at least one drive coil (36) capable of being energized and switched with polarity reversal to move the axially movable part (16) along the shaft (12), at least one permanent magnet (38) for retaining the movable part (16) in the final position,and an elastic return element (54) for transferring the moving part (16) from the final position to the initial position, the holding force exerted by the permanent magnet (38) on the moving part (16) in the final position being greater than the return force of the return element (54).

2. Positive engagement electromagnetically commutated clutch (10) according to claim 1, characterized in that the initial position is a disengagement position and the final position is the engagement position, or in that the initial position is the engagement position and the final position is a disengagement position.

3. Positive engagement electromagnetically commutated clutch (10) according to any one of the preceding claims, characterized in that the stator (32) further comprises a magnetic bridge (60) between the drive coil (36) and said at least one permanent magnet (38).

4. Positive engagement, electromagnetically commutated clutch (10) according to claim 3, characterized in that that said at least one drive coil (36), said at least one permanent magnet (38) and / or the magnetically conductive bridge (60) are injection coated with a non-conductive material or encapsulated in a non-conductive material.

5. Positive engagement electromagnetically commutated clutch (10) according to any one of the preceding claims, characterized in that said at least one permanent magnet (38) is an annular magnet or comprises at least two annular segments.

6. Positive engagement electromagnetically commutated clutch (10) according to any one of the preceding claims, characterized in that the stator (32) and / or said at least one permanent magnet (38) is / are arranged in a stator housing (34).

7. Positive engagement electromagnetically commutated clutch (10) according to claim 6, characterized in that the stator housing (34) is made of soft magnetic material and has an end portion (52) projecting radially inwards which is axially opposite to the moving part (16).

8. Positive engagement electromagnetically commutated clutch (10) according to claim 7, characterized in that the stator housing (34) is composed of two L-shaped cross-section rings (40, 42), one ring (40) having a sleeve-shaped inner wall (44) and a side wall (46) projecting radially outwards from thereon, and one ring (42) having a sleeve-shaped outer wall (48) and a side wall (50) projecting radially inwards, the radially inner end of which forms the end portion (52).

9. Positive engagement electromagnetically commutated clutch (10) according to any one of the preceding claims, characterized in that the stator (32), said at least one permanent magnet (38) and the elastic return element (54) form a bistable system in which the axially movable part (16) is locked in position in the initial position and in the final position when the drive coil (36) is deactivated, on the one hand by said at least one permanent magnet and on the other hand by the elastic return element (54).

10. Positive engagement, electromagnetically commutated clutch (10) according to any one of the preceding claims, characterized in that an electronic circuit (62) having an H-bridge (64) is provided to reverse the polarity of the stator (32).

11. Positive engagement electromagnetically commutated clutch (10) according to any one of the preceding claims, characterized in that the elastic return element (54) is a wave spring (56).

12. A method for actuation of a positive engagement, electromagnetically commutated clutch (10) according to any one of the preceding claims, the method comprising the following steps: a) supplying the stator (32) with current to move the moving part (16) from an initial position to a final position; b) de-energizing the drive coil (36) after the moving part (16) has reached the final position; c) holding the moving part (16) in the final position by means of said at least one permanent magnet (38); and d) reversing the polarity of the stator (32) and supplying the reverse-polarity stator (32) with current to move the moving part (16) from the final position to the initial position by means of the return element (54).

13. A method according to claim 12, characterized in that, in step d), the moving part (16) is moved from the final position to the initial position by means of the elastic return element (54), the spring force of the elastic return element (54) exceeding the magnetic force of said at least one permanent magnet (38) when the polarity of the stator (32) is reversed and the axially movable part (16) is moved out of its final position.

14. Method according to claim 12 or 13, characterized in that the polarity reversal of the stator (32) in step d) is carried out by an electronic circuit (62) having an H-bridge (64).

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