Ball screw drive with anti-rotation device

Abstract

Featuring an anti-rotation device: at least one locking element (2) provided on a moving element configured to move longitudinally without rotation and projecting outwards in a radial direction from the surface of the moving element at at least one point, and at least one guide element (5) having a groove and configured to be arranged in a recess of an enclosure of the moving element such that its groove is arranged substantially parallel to the longitudinal axis of the moving element, and to guide the protruding part of the locking element (2) in its groove during longitudinal movement of the moving element, wherein the at least one guide element (5) is designed such that it has no degree of freedom along the longitudinal axis of the groove, but at least the rotational degree of freedom about an axis parallel to the longitudinal axis of the groove.

Description

[0001] The present invention relates to a rotation protection device for an axially moving element and a ball screw drive with a rotation protection device, in particular for use in an automated manual transmission (AMT) for converting rotary into translational motion.

[0002] Electrically driven actuators can be used to actuate clutches and gears in AMT transmissions. The rotary output motion generated by an electric motor is typically first translated in a transmission stage and then converted into a linear motion. Ball screws are frequently used for this latter step in practice.

[0003] These typically consist of a spindle with a grooved raceway, balls embedded in the grooves, and a nut that rotates around the spindle with minimal friction thanks to the balls. The spindle slides longitudinally along the balls in the grooves through the inner diameter of the nut. The nut also features a ball recirculation system that returns balls from points where they would otherwise slip out of the contact area due to the movement of the nut and spindle to areas where they are needed to reduce friction. In other words, this system ensures that balls are always present between the nut and spindle, thus minimizing friction between them.

[0004] Furthermore, it must be ensured that the spindle does not rotate along with the nut. This is achieved by an anti-rotation device for the spindle. The anti-rotation device is usually achieved through a positive locking mechanism between the spindle and the housing of the ball screw drive. In the prior art, a transverse bolt is typically provided in the spindle to implement the anti-rotation device. This bolt projects radially beyond the spindle and is guided in corresponding elongated grooves in the housing along the direction of actuation. Thus, while the spindle can move longitudinally, its rotational degree of freedom is blocked by the anti-rotation device.

[0005] However, this design has the disadvantage that tolerances, different friction pairs, and uneven surface pressure cause significant wear between the locking element and the groove of the housing. Even slight play between the locking element and the housing means that a rotational movement of the nut also results in a slight rotational movement of the spindle, until contact between the locking element and the housing prevents the spindle from rotating.

[0006] In the described prior art arrangement, this process results in a very small contact area between the locking element and the housing, more precisely with the side surface of the groove of the housing in which the locking element is guided, causing high wear on both the side surface of the groove and the locking element.

[0007] In this context, DE 10 2008 051 544 B4 relates to a spindle drive with a rotatable spindle nut and a threaded spindle mounted on a reference body in a rotationally fixed and axially displaceable manner by means of a linear guide, wherein the axis of the threaded spindle is arranged parallel to the longitudinal direction of the linear guide, and wherein the linear guide has a groove and a guide element engaging in the groove, which includes an elastic area whose width transverse to the longitudinal direction of the linear guide is greater than the maximum groove width in the area used for the linear guide.

[0008] DE 20 2006 014 177 U1 relates to a device for extracting a component located in a bore of a component, which has a grippable forming section in the area of ​​its end protruding from the component, consisting of several radially adjustable gripper elements forming a conical outer surface, which are provided in their free end area with radially inwardly directed gripper webs with which the gripper elements can be brought into positive engagement with the forming section of the component, wherein a guide tube is provided which is adjustable relative to the gripper elements by means of a pulling device and by which the gripper elements can be fixed in their engagement position with the forming section.

[0009] The object of the present invention is therefore to provide a solution that reduces the wear of a described arrangement and thus achieves longer service life of the components and lower costs for maintenance activities.

[0010] This problem is solved by the subject matter of the independent claims according to the invention. Advantageous embodiments are included in the dependent claims.

[0011] An anti-rotation device according to the invention comprises a locking element arranged on a moving element configured to move along its longitudinal axis, i.e., in the longitudinal direction, without performing any rotational movement. The locking element projects radially outwards from the surface of the moving element at at least one point.

[0012] Furthermore, the anti-rotation device according to the invention comprises at least one guide element, which in turn is provided with a groove. A groove is defined as an elongated recess in the guide element, which can have any cross-sectional shape and is designed to receive the locking element. The at least one guide element with the groove is arranged in a recess of a housing of the moving element such that the groove lies essentially parallel to the longitudinal axis of the moving element and guides the part of the locking element projecting from the surface of the moving element during longitudinal movement of the moving element. If the moving element experiences a moment that would cause it to rotate about its own longitudinal axis, this movement is prevented by the engagement of the locking element in the groove of the guide element.Furthermore, at least one guide element has no open degree of freedom along the longitudinal axis of the groove, but at least one open degree of freedom for rotation about an axis parallel to the longitudinal axis of the groove.

[0013] Due to the open rotational degree of freedom, the guide element can align itself with the guide element, depending on the rotation of the moving element and thus of the locking element, by means of the force exerted on it by the locking element. This increases the contact area between the locking element and the guide element, thereby reducing wear on the components involved.

[0014] In an advantageous embodiment, and to achieve a solution with the smallest possible installation space, the locking element is arranged at one end or in an end region of the moving element. This avoids an axially protruding section of the spindle and prevents an unnecessary increase in the overall installation space of the device.

[0015] Furthermore, in an advantageous embodiment, the number of guide elements corresponds to the number of points where the at least one locking element projects radially from the surface of the moving element. The advantage of this embodiment is that each end of the at least one locking element contributing to the anti-rotation mechanism has a guide element, thus ensuring optimal alignment of the respective guide element. On the other hand, this ensures that only the required number of guide elements are used, saving machining effort and costs.

[0016] In a further advantageous embodiment, the cross-section of the groove of the at least one guide element, perpendicular to the longitudinal axis of the guide element, has the same shape as the cross-section perpendicular to the longitudinal axis of the movement element through the part of the locking element projecting into the groove of the guide element. Several points of the locking element can project into the groove, and several locking elements and guide elements can be provided.

[0017] In a further advantageous embodiment of the invention, the anti-rotation device has at least 2 guide elements, preferably arranged uniformly around the moving element, in order to at least halve the force to be absorbed by the at least one guide element for each guide element and thus reduce the wear in each individual guide element.

[0018] A further advantage is an embodiment of the locking element as a bolt. This means that the cross-section of the at least one locking element has a circular shape perpendicular to the longitudinal axis of the locking element at a point where the locking element projects into the groove of the guide element.

[0019] In a further advantageous embodiment, the at least one guide element is rotatably mounted at its end faces or at its ends within the housing. Such a mounting prevents any movement of the guide element within the housing, except for rotation about an axis defined by the mounting and parallel to the longitudinal axis of the moving element. This design has the advantage of minimizing friction between the guide element and the housing when aligning the guide element with the locking element, thereby reducing wear on the components involved.

[0020] In a further advantageous embodiment of the invention, the at least one guide element is arranged in the recess of the housing in such a way that movement of the guide element in its longitudinal direction is limited on one side by the stop against the housing and movement of the guide element in the opposite direction is prevented by a retaining ring, so that no movements in the longitudinal direction of the guide element are possible.

[0021] A further advantage is an embodiment in which the guide element has a symmetrical, preferably circular, cross-section perpendicular to its longitudinal axis. In particular, a circular cross-section ensures a small size and simple implementation of the invention.

[0022] In a further advantageous embodiment, the guide element and the recess in the housing in which the guide element is accommodated have the same cross-sectional shape perpendicular to the longitudinal axis of the guide element. Such a design therefore requires no more installation space than anti-rotation devices according to the prior art.

[0023] In a further advantageous embodiment, the groove of the at least one guide element has a symmetrical cross-section in the longitudinal direction of the groove.

[0024] Furthermore, in an advantageous embodiment, the material of the at least one guide element and the material of the at least one locking element form a material pairing that exhibits low wear and / or low frictional resistance when the materials rub against each other. The material of the at least one guide element is preferably a hard material such as hard steel. In this way, increased wear of the groove and the at least one locking element can be avoided, and low maintenance requirements can be ensured.

[0025] A further advantageous embodiment of the invention is in which the end of the locking element projects so far into the groove that the point of the locking element which comes into contact with one of the side surfaces of the groove when the locking element is rotated by a rotation of the moving element is further away from the surface of the spindle than the center of the cross-section of the guide element perpendicular to its longitudinal axis.

[0026] A ball screw drive according to the invention comprises a spindle with a raceway profile and a defined outer diameter, and a nut with a defined inner diameter that is slightly larger than the outer diameter of the spindle. Furthermore, it includes at least two balls arranged between the nut and the spindle in the latter's raceway profile to enable low-friction movement between the spindle and the nut. In this arrangement, the spindle moves longitudinally as the nut rotates around the spindle. The longitudinal axes of the nut and the spindle are aligned, and the nut rotates around the spindle without longitudinal movement.

[0027] To prevent rotational movement of the spindle, the ball screw drive is provided with an anti-rotation device according to the invention, wherein the spindle of the ball screw drive is the moving element of the anti-rotation device. The locking element, which is arranged on the spindle, engages with its protruding ends in the groove of the guide element arranged opposite the spindle and is guided therein. The guide element is arranged in a housing of the spindle as described above.

[0028] Another ball screw drive according to the invention represents the kinematic inversion of the ball screw drive described above. In this embodiment, the spindle rotates about its own longitudinal axis without moving in the axial direction. This causes the nut to undergo axial, i.e., translational, movement, for which its rotation must be prevented. The anti-rotation device is therefore provided on the nut, which in this ball screw drive constitutes the moving element of the anti-rotation device. The at least one guide element with the groove in which the locking element is guided is consequently arranged opposite the nut in the housing of the ball screw drive of this embodiment. Thus, the locking element can be guided in the groove of the guide element during translational movement, and rotation of the nut is prevented.

[0029] The invention will be explained in more detail below with reference to figures. The figures show, in detail: Fig. 1 Schematic diagram of the structure of an embodiment of the ball screw drive according to the invention Fig. 2 Cross-sectional view through the locking element of the spindle, the spindle itself and two guide elements of the embodiment made of Fig. 1 Fig. 3. Detailed view of the cross-sectional view from Fig. 2 to illustrate the operating principle of the ball screw drive according to the invention Fig. 4 more detailed views of the Fig. 2 to illustrate the functional principle for aligning the guide element. Fig. 5 Schematic representation to illustrate a further embodiment of a ball screw drive according to the invention with anti-rotation device

[0030] Fig. Figure 1 shows a schematic diagram of the construction of an embodiment of the ball screw drive according to the invention with an anti-rotation device according to the invention. The central components of the ball screw drive 1 are the spindle 3 and the nut 4, which rotates about the longitudinal axis of the spindle. Balls are arranged between the nut and the spindle to ensure the lowest possible friction in the rotation of the nut 4. The balls are located in a Fig. The nut 4 is guided in the spindle 3 by a groove profile (not shown). The nut 4 is rotatably mounted on its outer diameter by the ball bearings 6, so that rotation of the nut 4 around the spindle 3 is possible, but movement of the nut 4 in the longitudinal direction of the spindle 3 is prevented.

[0031] If the nut 4 is set into rotation, for example by an electric motor (not shown), the rotational movement of the nut 4 is converted into a translational movement (to the right or left in the plane of the drawing) of the spindle 3 by the balls guided in the raceway profile of the spindle 3. Since the balls would move out of the area between the nut 4 and the spindle 3 along the raceway profile due to the rotational movement of the nut 4 and the resulting translational movement of the spindle 3, the balls must be returned from one end of the nut 4 to the other end. This is achieved via a return system within the nut 4, which is not shown but is known in the prior art.

[0032] To prevent rotation of the spindle 3 due to the dynamic rotation of the nut 4, it is necessary to prevent the rotation of the spindle 3 by means of an anti-rotation device. The anti-rotation device consists of the following: Fig. The embodiment shown in Figure 1 consists of three components. Firstly, a locking element 2 is provided at the end of the spindle 3, which here is understood as the moving element. This locking element 2 is arranged perpendicular to the longitudinal axis of the spindle 3. Furthermore, the locking element 2 has a circular cross-section in a cutting direction perpendicular to the longitudinal axis of the locking element 2. It can thus be described as a cylindrical bolt that stands perpendicular to the longitudinal axis of the spindle 3. In addition, the bolt projects clearly outwards from the surface of the spindle 3 in a radial direction at both ends. In this embodiment, the end faces of the bolt are designed as flat surfaces.

[0033] The other two components of the anti-rotation device are guide elements 5, which are arranged directly opposite each other, in the plane of the drawing above and below the spindle 3, parallel to the longitudinal axis of the spindle 3. Like the spindle 3 and the locking element 2, the guide elements 5 also have a circular cross-section and can therefore be described as cylinders with flat end faces.

[0034] On the side facing the spindle 3, the two guide elements 5 have a groove (in Fig. (1 not shown), which each receive the ends of the locking element 2. The grooves are arranged in the guide elements 5 such that, during a translational movement of the spindle 3 to the left (in the plane of the drawing), the spindle 3 moves over the locking element 2 in the grooves over the entire actuation length L. bguided movement and rotation of the spindle 3 can be avoided. In addition, the cross-sectional shapes of the grooves correspond to the respective guided ends of the locking element 2, so that the cross-sections of the grooves are filled as completely as possible by the ends of the locking element 2 without hindering the translational movement of the locking element 2 along the grooves.

[0035] The guide elements 5 are each arranged in a recess of a housing 8 of the ball screw drive 1. The recesses and the guide elements 5 have the same cross-sectional shape perpendicular to the longitudinal axis of the guide elements 5. It should be noted that the radius of the described cross-section of the guide elements 5 is slightly smaller than the radius of the cross-sections of the respective recesses. Longitudinal movement is limited on one side by the stop of the guide elements 5 against the housing 7 (right side in the plane of the drawing) and on the other side by a retaining ring 8 (left side in the plane of the drawing). Thus, the guide elements 5 can rotate about their longitudinal axes in their recesses, while translational movement of the guide elements in the longitudinal direction is not possible.

[0036] Fig. Figure 2 shows a cross-sectional view of the embodiment of the ball screw drive made of Fig. 1. The section is taken at the level of the locking element, showing the spindle 3, the locking element 2, and the two guide elements 5. The circular cross-sections of the spindle 3 and the two guide elements 5 are visible. The locking element 2 engages with its respective ends in the groove of the guide element 5. In this view, the movement of the spindle, and thus of the locking element 2, is into or out of the plane of the drawing.

[0037] Fig. Figure 3 shows a detailed view of the cross-sectional view from Fig. 2, where only the lower guide element 5 and the lower part of the spindle 3 and the locking element 2 are considered. It should be noted that, in order to better explain the principle of the invention, the groove of the guide element 5 has been shown to be significantly larger than the end of the locking element 2, so that a clear clearance can be seen between the groove and the locking element 2.

[0038] The spindle 3, and therefore also the locking element 2, exhibits a slight angle of rotation relative to the guide element 5. This results from a slight rotation of the spindle 3 caused by the torque M. sThis was caused by the rotation of the nut 4, which in turn acts on the spindle 3. Since the groove has a larger cross-section than the locking element 2 in the area of ​​the groove, the end of the locking element 2 can initially move within the groove. From a certain angle of rotation, the locking element comes into contact with a side surface of the groove (as shown). The contact point of the end of the locking element 2 lies, in the plane of the drawing, below the center point of the essentially circular cross-section of the guide element 5. This is shown in Fig. 3 through the distance L a between the center point of the cross-section of the guide element and the point of contact between the groove and the locking element 2.

[0039] After the locking element makes contact with the guide element, the torque M is now applied. stransferred to the guide element 5. Since this is located in the recess of the housing (not shown in Fig. 3) can move and especially rotate slightly in the plane of the drawing, resulting in the moment M s of the safety element 2 at a moment M f of the guide element 5, which in particular results in a rotation of the guide element 5 in the recess.

[0040] Fig. Figure 4 shows the orientation of the guide element 5 as a result of the moment M f The left illustration shows the one in Fig. Situation 3 already described. The locking element 2 is in contact with a side surface of the groove, such that the moment M s is transferred to the guide element 5 and the moment M fThis causes the guide element 5 to rotate about an axis parallel to its longitudinal axis. As a result, the guide element 5 aligns itself such that the locking element 2, with its entire side surface located within the groove, is in contact with the side surface of the groove.

[0041] In this position, the moment M s not be transmitted further to the guide element 5, whereby the moment M f The force no longer acts on the guide element 5. The rotation of the guide element 5 therefore stops and the guide element 5 has reached its end position.

[0042] In this final position, compared to the position shown in the left-hand illustration, a line contact instead of a point contact has formed between locking element 2 and guide element 5. The torque M sThe force acting on the locking element 2 is thus distributed over a larger area than in the left-hand illustration. Fig. 4.

[0043] In conventional state-of-the-art solutions, as described above, a locking element is guided in a groove in the housing of the ball screw drive. The state-of-the-art solution is thus represented by the left-hand illustration of the Fig. 4 represents. By aligning the guide element 5 (see right-hand illustration) and the associated force transmission into the guide element 5 or the housing (not shown in Fig. 4) Due to the larger contact area of ​​the locking element 2 on the side surface of the groove, less wear can be achieved between locking element 2 and guide element 5, and rotation of the spindle can still be ensured.

[0044] Fig. Figure 5 shows a schematic representation of another ball screw drive according to the invention with anti-rotation device. The in Fig. The embodiment shown in Figure 5 represents the kinematic inversion of the embodiment according to Figure 5. Fig. 1 dar.

[0045] A drive device 9 is connected to a spindle 3 via a coupling 10. The spindle 3 has a grooved profile 3a on at least part of its circumference and is rotatably mounted via bearings 11. A nut 4 engages with the spindle via balls (not shown) inserted in the grooved profile 3a. The spindle 3 passes through the nut 4, as in the embodiment described above, with the two components being oriented coaxially to each other. The nut is also mounted such that it can perform translational movement along the longitudinal direction of the spindle 3. Rotation of the nut 4 is prevented by the anti-rotation device 12, which is arranged at both axial ends of the nut. As described above, the anti-rotation device according to the invention consists of a locking element 2 and a guide element 5, wherein the locking element 2 engages in a groove of the guide element 5.The nut 4 remains connected to an actuating element 13. The guide element and groove are as in the ball screw drive of the embodiment according to . Fig. 1 opposite the safety element in a recess of the housing 7.

[0046] The ball screw drive operates as follows. When the drive device 9 applies a drive movement (rotation) to the spindle 3 via the coupling 10, the spindle is set into a rotary motion. The positive locking achieved via the balls between the nut 4 and the spindle 3 allows the nut to move translationally in an axial direction, while the anti-rotation device 12 prevents rotation of the nut 4. Thus, the actuating element can be moved parallel to a longitudinal axis of the spindle 3. REFERENCE MARK LIST 1 ball screw drive 2 safety element 3 spindles 3a Running groove profile 4 Mother 5 guide element 6 ball bearings 7 Enclosure 8 retaining ring 9 Drive device 10 Clutch 11 warehouses 12 Anti-rotation device 13 Actuating element L b Actuation length M s torque acting on the spindle M f torque acting on guide element

Claims

[1] Having a twist-proof feature: at least one locking element (2) provided on a moving element configured to move longitudinally without rotation and projecting outwards in a radial direction from the surface of the moving element at at least one point, and at least one guide element (5) having a groove and configured to be arranged in a recess of an enclosure of the moving element such that its groove is arranged substantially parallel to the longitudinal axis of the moving element, and to guide the protruding part of the locking element (2) in its groove during longitudinal movement of the moving element, wherein the at least one guide element (5) is designed such that it has no degree of freedom along the longitudinal axis of the groove, but at least the rotational degree of freedom about an axis parallel to the longitudinal axis of the groove. [2] Anti-rotation device according to one of the preceding claims, wherein the number of guide elements (5) corresponds to the number of places at which the at least one locking element (2) projects out of the surface of the moving element in a radial direction. [3] Anti-rotation device according to one of the preceding claims, wherein the cross-section of the groove of the at least one guide element (5) has the same shape perpendicular to its longitudinal direction as the cross-section perpendicular to the longitudinal direction of the movement element of the at least one end of the at least one locking element (2) projecting into the groove of the guide element (5). [4] Anti-rotation device according to one of the preceding claims, wherein in the case of several guide elements (5) these are evenly distributed over the circumference of the movement element. [5] Anti-rotation device according to one of the preceding claims, wherein the at least one end of the at least one locking element (2) which projects into the groove of the at least one guide element (5) has a circular cross-section perpendicular to the longitudinal direction of the at least one locking element (2). [6] Anti-rotation device according to one of the preceding claims, wherein the at least one guide element (5) is mounted in the housing at its ends in the longitudinal direction, wherein the mounting is configured to allow low-friction rotation of the guide element (5) about an axis parallel to the longitudinal axis of the movement element and to prevent any translational movement of the at least one guide element (5). [7] Anti-rotation device according to one of the preceding claims, wherein the at least one guide element (5) has a symmetrical and preferably a circular cross-section perpendicular to its longitudinal direction. [8] Anti-rotation device according to one of the preceding claims, wherein the at least one guide element (5) and the recess of the housing have substantially the same cross-sectional shape perpendicular to their longitudinal direction. [9] Anti-rotation device according to one of the preceding claims, wherein a material of the at least one guide element (5) and a material of the at least one locking element (2) form a material pairing which exhibits low wear and / or low frictional resistance when friction occurs between the materials, wherein the material of the at least one guide element (5) is preferably a hard material such as steel. [10] Anti-rotation device according to one of the preceding claims, wherein the moving element has an enclosure which surrounds at least the moving element and serves as a housing, wherein the at least one guide element (5) is arranged in the enclosure such that it abuts the enclosure on one side and is fixed on the other side with a retaining ring, so that no movement in the longitudinal direction of the guide element (5) is possible. [11] Anti-rotation device according to one of the preceding claims, wherein the groove of the at least one guide element (5) has a symmetrical cross-section in the longitudinal direction of the groove. [12] Anti-rotation device according to one of the preceding claims, wherein the locking element (2) projects at at least one point so far into the groove of the at least one guide element (5) that the point of the at least one locking element (2) which comes into contact with one of the side surfaces of the groove when the locking element (2) is rotated with the groove is further away from the surface of the moving element than the center of the cross-section of the guide element (5). [13] Ball screw drive with anti-rotation device: a spindle (3) with a running groove profile and defined outer diameter, a nut (4) with a defined inner diameter that is slightly larger than the outer diameter of the spindle (3), at least two balls arranged between the nut (4) and the spindle (3) in the latter's raceway profile and configured to enable low-friction movement of the spindle (3) along the longitudinal direction of the nut (4), wherein the central axes of the inner diameter of the nut (4) and the outer diameter of the spindle (3) are superimposed and the nut (4) is configured to rotate around the spindle (3) without longitudinal movement and the spindle (3) is configured to move longitudinally without rotation, and a rotation lock according to one of the preceding claims, wherein the spindle (3) of the ball screw drive is configured to function as a motion element of the anti-rotation device. [14] Ball screw drive with anti-rotation device: a spindle (3) with a running groove profile and defined outer diameter, a nut (4) with a defined inner diameter that is slightly larger than the outer diameter of the spindle (3), at least two balls arranged between the nut (4) and the spindle (3) in the latter's raceway profile and configured to enable low-friction movement of the spindle (3) along the longitudinal direction of the nut (4), wherein the central axes of the inner diameter of the nut (4) and the outer diameter of the spindle (3) are superimposed, and the nut (4) is configured to move in the longitudinal direction of the spindle without rotation about the spindle (3), and the spindle (3) is configured to rotate in the nut (4) without movement in its longitudinal direction, and a rotation lock according to any one of the preceding claims 1 to 12, wherein the nut (4) of the ball screw drive is configured to act as a movement element of the anti-rotation device.

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