Methods for the safe operation of an actuator

Abstract

Method for the safe operation of an actuator (1), wherein the actuator is provided for the provision of a torque, with a linear drive (2) and a gearbox (3) for converting a linear motion into a rotary motion of a shaft (5), wherein the gearbox (3) comprises a lever (4) which rotates the shaft (5) to be subjected to the torque, wherein the gearbox (3) further comprises a coupling element (6) and wherein the coupling element (6) is connected to the linear drive (2) via a first connection point (7) and to the lever (4) via a second connection point (8), so that energy transfer between the linear drive (2) and the lever (4) takes place exclusively via the coupling element (6), and wherein the coupling element (6) is rotatably connected at both connection points (7, 8), characterized in that the maximum force provided by the linear drive (2) is limited depending on a current value of a gear ratio of the gearbox (3).

Description

[0001] The present invention relates to a method for safely operating an actuator with the features according to the preamble of claim 1.

[0002] Such actuators are already known from DE 10 2016 207 827 A1 with a nonlinear actuating force for an actuating unit for an automatic transmission (preferably a PRND automatic transmission system) of a motor vehicle. A corresponding cam track is provided for generating the nonlinearity.

[0003] In general, such an actuator is already known from DE 10 2018 116 133 A1.

[0004] In the subsequently published DE 10 2023 115 292 A1 of the applicant, an actuator with a non-linear characteristic curve is also disclosed. Due to the toggle-lever kinematics used in this actuator concept, a constant drive torque of the electric motor in an end position results ( Fig. 1, Fig. 8) of the toggle lever mechanism, an actuating force (torque) on the output shaft (5) that tends towards infinity, which can lead to damage to the load being actuated or to parts of the actuator itself.

[0005] The present invention aims to operate such an actuator safely in a simple manner.

[0006] This problem of the invention is solved by a method having the features of claim 1.

[0007] A method for the safe operation of an actuator is provided, wherein the actuator is designed to provide torque and comprises a linear drive and a gearbox for converting linear motion into rotary motion of a shaft. The gearbox includes a lever that rotates the shaft to which the torque is applied. The gearbox further includes a coupling element, and the coupling element is connected to the linear drive via a first connection point and to the lever via a second connection point, such that energy transfer between the linear drive and the lever occurs exclusively via the coupling element. The coupling element is rotatably connected at both connection points. The maximum force provided by the linear drive is limited depending on the current value of the gearbox's gear ratio.

[0008] The current gear ratio of the gearbox depends on the travel position along the axis of motion of the linear drive, for example, a spindle of a spindle drive, and is either learned at the end-of-line or recalculated in a referencing or update process. The current gear ratio is therefore the value for the gear ratio at the current travel position.

[0009] In a preferred embodiment of the invention, it is provided that the lever is connected at a second lever end to the shaft via a third connection point in a rotationally fixed manner and at a first lever end rotatably to the coupling element via the second connection point, and the coupling element is rotatably connected to the linear drive via the first connection point, and the lever establishes a rigid connection between the two connection points.

[0010] In a further preferred embodiment of the invention, it is provided that in an initial position of the transmission a first, preferably housing-fixed stop is provided to determine the initial position and / or in an end position of the transmission a second, preferably housing-fixed stop is provided to determine the end position, and wherein the first lever end is designed to abut the lever against the first and / or second stop.

[0011] In an alternative preferred embodiment of the invention, it is provided that in an end position of the gearbox a second, preferably housing-fixed stop is provided for determining the end position, and wherein a spindle end or an end cap of a spindle of the linear drive is designed to stop the spindle against the second stop.

[0012] In a further preferred embodiment of the invention, it is provided that the value of the gear ratio at the travel position along the axis of motion of the linear drive is calculated from the ratio of a rotation angle Δφ to be determined, which results from the rotational movement of the shaft resulting from the movement of the linear drive, and a predetermined distance Δx, which the linear drive moves along the axis of motion of the linear drive, starting from the travel position.

[0013] The current travel position is the position between the start position and the end position at which a predetermined point of the spindle, for example the spindle center, the spindle end or the end cap of the spindle of the linear drive, is currently located during the movement of the spindle.

[0014] A predetermined spindle feed, for example denoted as Δx, results in a determined shaft rotation, for example denoted as Δφ. The gear ratio is calculated as the quotient Δφ / Δx of these two values.

[0015] Due to the non-linearity of the toggle lever kinematics, the gear ratio is not constant along the entire path between the initial and final positions, but rather assumes different values ​​at each position between these two positions. For each travel position between the initial and final positions, the gear ratio at that position is determined as the quotient Δφ / Δx. This is primarily done end-of-line, but can also be requested by a higher-level control system as needed or on a regular basis.

[0016] In a further preferred embodiment of the invention, it is provided that the course of the values ​​of the gear ratio is stored as a function of the travel position of the linear drive.

[0017] In a further preferred embodiment of the invention, it is provided that the dependence of the values ​​of the gear ratio on the travel position of the linear drive is not linear.

[0018] In a further preferred embodiment of the invention, it is provided that the end position has a predetermined end position threshold value for the gear ratio.

[0019] In a particularly preferred embodiment of the invention, it is provided that the force of the linear drive is limited along the axis of movement of the linear drive when the direction of movement of the linear drive is towards the end position and the gear ratio at the current position exceeds the end position threshold.

[0020] In a preferred embodiment of the invention, it is provided that this limit stops the linear drive.

[0021] The linear drive, for example the spindle, can thus be advantageously brought to a stop just before reaching the end stop, so that the actuator comes to a halt at a stopping position shortly before actually reaching the end position. The actual end position can therefore be chosen so that the stopping position, i.e., the position of the actual stop, is also the desired stopping position, for example, just before reaching the end position or the stop. In this way, not only can the desired stopping position be reached, but it can also be avoided – as desired – thus advantageously preventing the actuator from hitting the stop or overloading the actuator or the load being moved.

[0022] The invention proposes to vary the drive torque of an energy converter, for example an electric motor, for driving a spindle nut of the linear drive, depending on the translation of the toggle lever mechanism determined by the kinematics, in particular a reduction in the direction of the end position ( Fig. 1, Fig. 6, Fig. 8) is provided for, so that no overload occurs.

[0023] This can occur directly depending on the translation of the toggle lever, which is the case with procedures towards the end position, shortly before reaching the end position ( Fig. 1, Fig, 6, Fig. 8) Active braking is required to compensate for actuator inertia. During active braking, the linear actuator generates a braking torque, if necessary by reversing the current. Active braking can also be implemented when moving towards the starting position shortly before reaching that position. In this way, depending on the application, maximum system dynamics can be achieved if required.

[0024] If maximum safety is required, the possibility of a power failure at the actuator can also be considered. For example, in a scenario where the power failure occurs precisely when the braking torque is required. Taking known inertias into account, only the braking torque without any current is considered, and the drive is switched off earlier in the direction of the end position than if an increased braking torque could be provided by reversing the current. In this way, overloading by the toggle-lever kinematics of the load being actuated or of the actuator itself can be prevented in any state of the actuator.

[0025] Depending on the downstream load to be actuated, the torque reduction according to the invention can also be provided in only one direction of movement. This is the case, for example, when actuation in one direction is against an elasticity, such as a spring, so that potential damage can be largely avoided.

[0026] It may be provided that, in addition to the lever and the linear drive, a third connecting component is supplied by means of the coupling element, which can be mounted in a particularly simple way and enables a non-linear characteristic curve of the actuator through a corresponding energy transfer from the linear drive to the lever and thus to the shaft.

[0027] Furthermore, it can be provided that the lever is connected at one end to the shaft via a third connection point, preventing rotation, and at the other end to the coupling element via a second connection point, creating a rigid connection between the two connection points. The non-linearity of the actuator can be easily adjusted by modifying the positions of the connection points and the length of the coupling element, since it is not the distance of the second lever end to the shaft that can be varied, but only the transmitted torque or the corresponding rotational speed. In other words, the fixed position of the third connection point on the housing, as a constraint, defines the movement of the lever in space, and the rotational speed and torque of the shaft are determined by the length of the coupling element in conjunction with its position on the linear actuator.

[0028] It can be provided that the coupling element establishes a rigid connection between the first and second connection points, such that a linear movement of the first connection point by the linear drive results in a first pivoting movement of the second connection point around the first connection point, as well as a second pivoting movement of the second connection point around the third connection point. Due to the rotationally fixed connection of the lever to the shaft, the second pivoting movement causes the shaft to rotate. The path traveled by the second connection point is predetermined by the constraint of the rigid lever. The corresponding superposition of the two pivoting movements to form a fixed curve determines the non-linearity of the rotational speed and the transmitted torque.

[0029] The coupling element can be configured to connect the lever and the linear actuator in such a way that the second connection point moves along a path. In a first working range around a first endpoint of the path, the movement of the first connection point by the linear actuator is translated into a first rotational movement of the shaft. In a second working range around a second endpoint, the movement of the first connection point by the linear actuator is reduced into a second rotational movement of the shaft. The first rotational movement covers a larger angular range with a smaller force transmission than the second rotational movement within a given time interval. In this way, specific operating points and an intermediate transition range for the shaft actuation force can be defined, corresponding to a desired non-linearity of the actuation and transitioning seamlessly into one another.

[0030] Furthermore, it can be arranged that at the second endpoint, the coupling element is perpendicular to the lever and the axis of movement of the linear actuator, and the lever is parallel to the axis of movement. Force transmission is difficult with such an arrangement. The force exerted by the linear actuator on the coupling element acts perpendicular to the tangent of the circular arc described by the second end of the lever; the transmitted torque is very small, and consequently, a high rotational speed can be achieved. In this arrangement, the actuator also exhibits self-locking. This is even more pronounced when friction points of the actuator are taken into account.

[0031] In a second possible arrangement, the coupling element at the first endpoint can be aligned parallel to the axis of movement of the linear drive and perpendicular to the lever. This results in maximum torque and minimum rotational speed. Accordingly, a stable position of the actuator is also ensured here.

[0032] It can be provided that a first, preferably housing-mounted, stop is provided at the first endpoint to define the first endpoint and / or a second, preferably housing-mounted, stop is provided at the second endpoint to define the second endpoint, wherein the second lever end is designed to abut the lever against the first and / or second stop. In this way, the two stable endpoints of the actuator can be reliably approached and held in position even against vibrations.

[0033] The stops can be provided, for example, as an extension of a spindle of the linear drive on an actuator housing and in the opposite end position as a stop for the lever.

[0034] It may be provided that the first and / or second stop is integrally formed from an actuator housing.

[0035] The advantage of positioning the stops on the housing, rather than limiting the linear adjustment range of the linear actuator within the actuator itself, lies in the fact that, in this further development, a rotor bearing of the linear actuator is positioned between the actuator and the lever. Consequently, the cumulative coefficient of friction, which is primarily determined by the sliding friction within the linear actuator and the stops, and only negligibly by the rolling friction of the rotor bearing, does not fluctuate as much as with a combination of solely sliding friction points. This allows for a more precise determination of the required drive torque of the linear actuator, necessary to ensure secure clamping at the stops.

[0036] The method for safely clamping the actuator at its end points involves a slow approach of the linear drive to its respective end stop. This brings, for example, a spindle enclosed by the linear drive to one of the stops and / or the lever to the other. Subsequently, the linear drive continues to move in the same direction, or the corresponding spindle continues to rotate even after reaching its respective end stop. The linear drive, spindle, or lever is then moved with a defined torque, which is reliably below the maximum possible torque of any motor or electric motor driving the linear drive or spindle. This ensures that the clamping can be safely released even under changing conditions (fluctuations in lubrication, temperature, or power supply, etc.) to allow a return to normal operating conditions.

[0037] To enable particularly controlled approach to the stops for setting or calibrating the actuator, it may be provided that the first and / or second stop has a targeted softness, so that a predetermined linear movement of the linear drive is enabled.

[0038] The required locking torque can also be predetermined to a reasonable value by considering the effective radius of the stops for the spindle or lever, or their variation during the design process.

[0039] Since no additional components are required for the stops, but only an adapted geometry of the actuator housing, the securing of the end stops can be implemented almost cost-neutrally.

[0040] An actuator can comprise a linear drive and a gearbox for converting linear motion into rotary motion. In principle, various types of linear drives based on different principles are well known to those skilled in the art, be they mechanical or hydraulic linear drives. The linear drive can, for example, be a ball screw drive or a planetary roller screw drive. The linear motion can be provided accordingly by a nut on a spindle or by the spindle itself. The rotary motion of a shaft is generated by a lever that is fixed to the shaft. A rigid connection is established between the lever and the linear motion element (nut or spindle, etc.) of the linear drive by means of a coupling element.The connection point of the coupling element on the linear actuator moves linearly along a straight path, while the connection point of the coupling element on the lever pivots along a circular path with a predefined radius r around the axis of the shaft. The distance between the two connection points on the lever and the linear actuator remains constant. This creates a trajectory for the second connection point on the lever that provides a higher angular velocity with lower torque in a first operating range and a lower angular velocity with higher torque in a second operating range for driving the shaft. A corresponding transition range exists between the two operating ranges.

[0041] In this way, the shaft can provide a rotational motion with a variable characteristic curve, i.e., a higher angular velocity in a first angular range than in a second angular range, and a correspondingly lower torque in the first angular range than in the second. This rotational motion can be used to actuate disconnect units, clutches, brakes, or parking locks within the powertrain of a motor vehicle or commercial vehicle.

[0042] The toggle lever mechanism described here creates a non-linear characteristic curve between the linear drive of the linear actuator, e.g., a spindle travel, and the rotation of the lever or the drive force of the linear actuator, or between the spindle force and the torque of the lever. Therefore, such an actuator is particularly suitable for actuating loads that also have a non-linear actuation force characteristic curve. A parking lock actuation can be cited as an example.

[0043] This arrangement allows the shaft for actuating loads to be positioned very close to the linear drive - significantly closer than if a comparably large actuating torque were generated solely by an actuating lever.

[0044] An embodiment of the method according to the invention, to which it is not limited, and from which further features of the invention may emerge, is described in the Fig. 8, Fig. 9 and Fig. 10 are shown. They show: Fig. 1 an actuator in a partial sectional view Fig. 2: Symbolic representation of a trajectory curve of the second connection point 8 of the lever 4 for actuating the shaft 5 of the actuator according to Fig. 1 Fig. 3 alternative designs of the actuator Fig. 4 Symbolic representation of an alternative trajectory of the second connection point 8 of the lever 4 for actuating the shaft 5 when the actuator is actuated according to Fig. 3 Fig. 5 Actuator according to the Fig. 1. Additional stops on the actuator housing (second connection point 8 in the first endpoint 21) Fig. 6 Actuator according to the Fig. 1. Additional stops on the actuator housing (second connection point 8 at the second endpoint 22) (near endpoint 22: maximum torque on shaft 5 when moving the spindle 5 towards or away from endpoint 22) Fig. 7 one half of an actuator housing Fig. 8 Explanation of the method according to the invention: Actuator in end position of the toggle lever ( Fig. 8 identical to Fig. 1 (but without reference mark) Fig. 9 Explanation of the method according to the invention: Actuator according to Fig. 8 in a middle position of the toggle lever Fig. 10 Explanation of the method according to the invention: Actuator according to Fig. 8 in the starting position of the knee lever

[0045] The Fig. Figure 1 shows an actuator 1 for converting a linear movement of a linear drive 2 into a rotational movement 23,24 of a shaft 5.

[0046] The linear drive 2 comprises a spindle 50. The spindle 50 has an end cap 51, which is connected on one side via a support roller 52 to a coupling element 6. Instead of only one support roller 52 as shown here, support rollers can also be connected on both sides, each with its own coupling element.

[0047] The support roller 52 provides a first connection point 7 for the rotatable mounting of the coupling element 6.

[0048] The coupling element 6 is designed as a linearly extending, rigid sheet metal part, which is connected at one end to the spindle 50 via the first connection point 7 and at the other end to a lever 4 via a second connection point 8. The coupling element 6 is also rotatably mounted on the lever 4 via the second connection point 8.

[0049] The lever 4 extends from its first lever end 9 with the second connection point 8 to a third connection point 10 at the second lever end 11. The lever 4 is non-rotatably connected to a shaft 5 at the third connection point 10. For this purpose, the lever 4 has a hole 53 with an internal toothing 54 at this point. The shaft 5 has corresponding external teeth 55 which engage with the internal toothing 54. The shaft 5 is rotatably mounted in an actuator housing 40 and extends through the actuator housing 40 in the direction of a shaft axis 56. The shaft axis 56 runs perpendicular to both the axis of movement 41 of the spindle 50 and the direction of extension 57 of the coupling element 6.

[0050] Outside the actuator housing 40, the shaft 5 is connected to an actuating element 60. This can be an eccentric disc, a contour disc, or similar component, which is set in rotation by means of the shaft 5. A parking lock, a brake, a clutch, or similar device can be actuated via this actuating element 60.

[0051] Spindle 50, end cap 51, coupling element 6 and lever 4 are components of a gearbox 3, which converts a linear movement of the spindle 50 of the linear drive 2 into a rotational movement 23,24 of the shaft 5 to drive the actuating element 60.

[0052] In Fig. In position 1, the spindle 50 is in position P1, whereby the extension direction 57 of the coupling element 6 is practically perpendicular to the axis of movement 41 of the spindle 50 and to the lever 4. In position P1, the spindle 50 is practically fully extended, and the second connection point 8 is located at a second endpoint 22. When the spindle 50 is retracted, the corresponding travel path of the spindle 50 is coupled to a smaller travel path of the second connection point 8 perpendicular to it via the coupling element 6. That is, in this case, the linear movement of the linear drive 2 is converted into a second rotational movement 24. Here, a maximum torque is transmitted to the shaft 5 at a minimum rotational speed.

[0053] An illustration of the transmitted torque and the associated rotational speed is shown in Fig. 2 shown. In the left part of the Fig. 2 the second connection point 8 is located in the second endpoint 22, as also in Fig. As shown in Figure 1, the lever 4 is located at a first endpoint 21 on the right. At the second endpoint 22 of the second connection point 8, the first connection point 7 of the coupling element 6 is located on the axis of movement 41 of the spindle 50. A linear movement to retract the spindle 50 in direction 61 pulls the lever 4 via the second connection point 8 into a second rotational movement 24 around the third connection point 10. The second connection point 8 follows a path 20 with a distance r between the second connection point 8 and the third connection point 10. This movement of the lever 4 is characterized at the second endpoint 22 by a minimum rotational speed and a maximum torque.

[0054] In the right part of the Fig. The second connection point 8 is located at a first endpoint 21. Here, the spindle 50 is retracted so far that the lever element 4 lies practically completely parallel to the spindle 50 on the axis of movement 41. Extending the spindle 50 then results in a maximum rotational speed and minimum torque of the lever 4.

[0055] In the area between the two endpoints 21 and 22, the lever 4 is thus driven with a non-linear torque characteristic. The shaft 5 is driven accordingly, and the non-linear characteristic of the shaft 5 can be used to actuate a non-linear load, such as a parking lock.

[0056] In Fig. Figure 3 shows an alternative arrangement of the coupling element 6 between the lever 4 and the spindle 50. Here, the spindle 50 is in the retracted position P2, with the second connection point 8 located at the second endpoint 22. In the parallel position of the coupling element 6, it is positioned so that it covers the spindle 50 in the direction of the axis of movement 41. In contrast to the design according to the Fig. 1 and Fig. 2 tilted by 90°. An illustration of the torques generated by this actuator can be found in Fig. 4. Here, on the left, a first endpoint 21 of the second connection point 8 is shown, while on the right, a corresponding second endpoint 22 is depicted. Between these points, the second connection point 8 is moved along the path 20'. Again, a maximum torque is transmitted to the shaft 50 at the second endpoint 22 (right), and a minimum torque at the first endpoint 21. Accordingly, the shaft 50 is subjected to a first rotational movement 23 at the first endpoint 21 and to a second rotational movement 24 at the second endpoint 22. The lengths of the arrows representing the rotational movements 23 and 24 symbolize the transmitted torque.

[0057] The trajectories 20 and 20' of the two alternatives in the Fig. 2 and Fig. 4 are practically mirror images and otherwise identical. However, the directions of rotation are reversed at minimum and maximum torque of shaft 5, i.e., the rotational movements 23 and 24' are each reversed and equal in magnitude. In the first example of the Fig. 2. The maximum torque is transmitted when the spindle is pulled in 50, in the second alternative according to Fig. 4, however, when extending the spindle 50.

[0058] The in Fig. 3 shown alternative design of an actuator 1 according to Fig. 1 also features a coupling element 6' with two parallel partial coupling elements 6a on both sides of the spindle 50. Actuation according to the alternative from such a coupling element 6' is then also possible. Fig. 4 possible.

[0059] The same principles apply here for generating the nonlinear characteristic curve of wave 5 as already described above. Fig. 1 described.

[0060] In the Fig. 5 and Fig. 6 is an actuator according to the Fig. Figure 1 shows the drive by a spindle drive in a sectional view and further stops 30, 31 for the lever 4 and the spindle 50 are provided on the actuator housing 40.

[0061] In Fig. 5 the lever 4, or the second connection point 8, is located in a first endpoint 21, in Fig. 6 is the second connection point 8 in the second endpoint 22 shown. Starting from an actuator position according to Fig. 6, therefore a maximum torque is generated when the spindle 50 is pulled in towards the linear drive 2 on the shaft 5.

[0062] In Fig. In position 5, the lever 4 is positioned at the first endpoint 21 against the first stop 30. The first stop 30 is designed as an integrated component of the actuator housing 40. If a predetermined torque is now applied by the spindle 50 or the spindle drive 70, which presses the lever 4, or the first lever end 9, against the first stop 30 with a predetermined force, then the position of the lever 4 and thus the angular position of the shaft 5 can be uniquely determined, and the actuator 1 can generally be secured against adjustments, for example, due to vibrations.

[0063] In Fig. Lever 4, or the second connection point 8, is located at the second endpoint 22. The second stop 31 is now provided for the spindle 50, or rather the end cap 51 of the spindle 50. Similarly, the spindle 50 can now be pressed against the second stop 31 with a predetermined torque. Here, too, the position of lever 4, and thus the angular position of shaft 5, can be clearly defined, and the actuator 1 can generally be secured against adjustments, for example, due to vibrations.

[0064] In Fig. 5 and Fig. Figure 6 further shows that the spindle 50 is driven via a nut 71. This nut is connected to the spindle via a toothed connection 72. Since the spindle 50 is fixedly mounted in the actuator housing 40, the rotational movement of the nut 71 is converted into the linear movement of the spindle 50. The spindle 50 is supported on the actuator housing 40 via the nut 71 and a rotor bearing 73. The drive of the nut 71 is realized via a rotor 74 of an electric motor 75.

[0065] Since, as shown here, the rotor bearing 73 is arranged axially between the stops 30, 31 and the rotor 74, the torque required for a secure clamping of the lever 4 or the spindle 50 on the first or second stop 30, 31 can be determined more precisely, because the summed coefficient of friction, which is mainly determined by the sliding friction coefficients (spindle / nut, stop surfaces) and only negligibly by the rolling friction coefficient of the rotor bearing, does not fluctuate as much as a combination of only sliding friction points.

[0066] In Fig. Figure 7 shows one half of an actuator housing 40. The actuator housing 40 has an internal contour 42. This contour 42 is embossed into the actuator housing 40 parallel to the spindle 50 and serves to receive a bearing element 43. The bearing element 43 is, as shown in Fig. 1 is shown arranged at one end of the spindle 50 and supports the spindle 50 on the actuator housing 40. As shown in Fig. As shown in Figure 1, it is preferably designed as a support roller 52. The bearing element 43 coincides with the first connection point 7. Preferably, this bearing element 43 consists of two support rollers 52, which are arranged around the articulated first connection point 7 between the spindle 50 and the coupling element 6, preferably on both sides at the end of the spindle 50, and which are supported on corresponding frame-fixed support surfaces 44 of the contour 42 in the actuator housing 40 and can roll there. In this way, the efficiency of the actuator 1 can be improved (in principle, one- or two-sided sliding bearings are also conceivable). The support surfaces 44 preferably run parallel to the axis of movement 41 of the spindle 50 or of the linearly displaceable element of the linear drive 2.

[0067] Using the actuator 1 shown here, based on the toggle lever principle, a non-linear actuation characteristic can thus be easily implemented on an actuating element 60 via a linear drive 2. The provided stops 30, 31 prevent accidental adjustment due to vibrations or similar factors, and also ensure a defined position of the actuator 1, e.g., in the event of a power failure.

[0068] The support surfaces 44 in conjunction with the support rollers 52 enable safe operation with good efficiency.

[0069] The toggle lever mechanism therefore consists of spindle 50, coupling element 6, lever 4 and shaft 5, wherein the end of the spindle 50 is rotatably connected to one end of the coupling element 6 at the first connection point 7 and the other end of the coupling element 6 is rotatably connected to the second connection point 8 with one end 9 of the lever 4 and the other end 11 of the lever 4 is connected to the rotatably mounted shaft 5 at the third connection point 9 in a rotationally fixed manner.

[0070] The following will be the in Fig. The position of the toggle lever or actuator shown in section 8 is referred to as the end position. (see also Fig. 1 and Fig. 6).

[0071] The in Fig. The position of the toggle lever or actuator shown in section 10 is referred to below as the initial position. (see also Fig. 5).

[0072] Fig. Figure 9 shows a position between the initial and final positions, which is referred to below as the middle position of the knee lever or actuator.

[0073] In Fig. 8 ( Fig. Figure 2, left) shows the toggle lever or actuator in the aforementioned end position. The end position (see also Fig. 1 and Fig. 6) also corresponds to position P1 in Fig. 1. As the spindle approaches its end position – coming from a central position – the uniform movement of the spindle along its axis of motion 41, with a constant maximum available force of the spindle 50 in the direction of movement, results in an increasingly smaller and slower rotation of the shaft 5 relative to its bearing and the load being actuated, while the maximum available torque on the shaft 5 increases. This applies to both directions of movement of the spindle along its axis of motion 41, both – as described above – coming from a central position towards the end position, and also from the end position towards a central position, when the spindle 50 is retracted towards the linear drive 2.

[0074] Put another way, compared to the initial position ( Fig. 10, Fig. 2, right) or a middle position ( Fig. 9) - again in both directions, to achieve a relatively high torque on shaft 5, accepting an ever smaller and slower rotation of shaft 5 over only a few degrees, in the area of ​​the end position ( Fig. 8, Fig. 2, left) only a relatively small spindle force or only a minimal drive torque of the spindle nut 72 of the linear drive 2 is required with increased spindle travel.

[0075] The toggle lever kinematics used in this actuator concept result in - coming from the initial position ( Fig. 10) or a middle position ( Fig. 9) - with a constant drive torque of the linear drive 2 or the spindle nut 71 of the spindle drive 70 and thus with a constant force of the spindle 50 in the direction of movement, when approaching or reaching the end position ( Fig. 1, Fig. 6, Fig. 8) the toggle lever mechanism produces an actuating torque on the shaft 5 that tends towards infinity in principle, which can lead to damage to the load to be actuated by means of the actuating element 60 or to parts of the actuator itself.

[0076] The actuating torque on the shaft 5, which tends towards infinity, results when the spindle 50 is extended to such an extent that the coupling element 6 is preferably arranged perpendicular to the linear axis of movement 41 of the linear drive 2, and the lever 4 is in turn preferably arranged perpendicular to the coupling element 6 (facing the actuator 2) and parallel to the axis of movement 41. This toggle lever position is also used in Fig. 2, shown on the left at the second endpoint 22. The coupling element 6 is perpendicular to the lever 4 and to the axis of movement 41 of the spindle 50 of the linear drive 2, and the lever 4 is aligned parallel to the axis of movement 41.

[0077] Since an actuating torque on shaft 5 that tends towards infinity is undesirable, and the increased spindle travel – with uniform spindle movement – ​​increases the running time, the approach to the position at the second endpoint 22 is generally not fully completed, but – as in Fig. 8 shown - the above end position is arranged a few degrees before reaching the position at the second end point 22 and is usually provided with a stop 31 on the housing, for example for the spindle 50 to strike ( Fig. 6).

[0078] In Fig. 10 ( Fig. 2, right) is the toggle lever or the actuator in the above initial position. A relatively large drive torque of the spindle nut 72 of the linear drive or a relatively high spindle force is possible and leads to a small actuating torque at shaft 5 with a relatively large rotation angle of shaft 5, compared, for example, to a middle position of the toggle lever.

[0079] As the spindle approaches its initial position – approaching from a central position – the uniform movement of the spindle along its axis of motion 41, with a constant maximum available force of the spindle 50 in the direction of movement, leads to an increasingly larger and faster rotation of the shaft 5 over several degrees relative to its bearing and the load being actuated, while the maximum available torque on the shaft 5 decreases. This applies to both directions of movement of the spindle along its axis of motion 41: both – as previously described – approaching from a central position towards the initial position, and also from the initial position towards a central position when the spindle 50 extends away from the linear drive 2.

[0080] Put another way, compared to the end position or a middle position, to achieve a relatively large and relatively fast rotation of shaft 5 while accepting a progressively lower torque on shaft 5, in the area of ​​the initial position ( Fig. 8, Fig. 2, left) - in both directions - an increased spindle force or increased drive torque of the spindle nut 72 of the linear drive 2 is permissible with a smaller spindle travel.

[0081] The starting position ( Fig. 10) occurs when the spindle 50 is retracted until the coupling element 6 is pulled approximately parallel to the axis of movement 41 of the spindle 50 and the lever 4 is pivoted to its maximum extent. This toggle lever position is also in Fig. 2, shown on the right at the first endpoint 21. The coupling element 6 is aligned parallel to the axis of movement 41 of the linear drive 2 and perpendicular to the lever 4.

[0082] Often, the approach to the position at the first endpoint 21 is not fully completed, for example due to the increased spindle force, but rather – as in Fig. 10 shown - the initial position is arranged a few degrees before reaching the position at the first endpoint 21 and is usually provided with a stop 30 on the housing, for example for the impact of the lever 40 ( Fig. 5).

[0083] Fig. 9 shows the actuator in a middle position of the toggle lever between end position ( Fig. 8) and starting position ( Fig. 10). The spindle nut 72 of the linear drive 2 is actuated with a lower drive torque compared to the initial position and with a higher drive torque compared to the final position.

[0084] The inventive solution to the problem is to limit the force of the spindle along the axis of motion 41 in the direction of movement, and thus to limit the drive torque of the spindle nut 71 and therefore of the spindle drive, i.e., for example, an electric motor of the linear drive 2. This limitation is to be dependent on the position of the actuator, i.e., dependent on the transmission of the toggle lever, i.e., dependent on the position of the toggle lever, or dependent on the spindle position, for example, the position on the axis of motion 41.

[0085] According to the invention, it is proposed to vary the drive torque of the energy converter, for example of an electric motor, for driving the spindle nut 72 of the linear drive 2, depending on the translation of the toggle lever mechanism determined by the kinematics, wherein in particular a reduction in the direction of the end position ( Fig. 1, Fig, 6, Fig. 8) is provided for, so that no overload occurs.

[0086] This can occur directly depending on the translation of lever 50, which is the case when moving towards the end position, shortly before reaching the end position ( Fig. 1, Fig, 6, Fig. 8) Active braking is required to compensate for actuator inertia. Active braking can also be implemented during movements towards the initial position shortly before reaching the initial position. In this way, maximum system dynamics could be achieved as needed, depending on the application.

[0087] This can also be achieved by taking into account the (known) inertias, so that an overload is prevented in any state, even in the event of a power failure (maximum safety).

[0088] Depending on the downstream load to be actuated, the torque reduction according to the invention can also be provided in only one direction of movement. This is the case, for example, when actuation in one direction is against an elasticity, such as a spring, so that potential damage can be largely avoided.

[0089] The exact value of a limit depends on many characteristics of the actuator as well as the load to be actuated and must therefore be determined by a person skilled in the art in each specific case. For example, the simple size of the actuator and its precise dimensions are important, such as the angle between the axis of movement 41 of the spindle 50 and the direction of extension 57 of the coupling element 6 ( Fig. 1) is selected in the final position.

[0090] In this way, referencing of the actuator, for example the spindle position, can be carried out at one or both stops (30, 31) without wearing out or even destroying the actuator through excessive torques or forces.

[0091] It is proposed to use a linear actuator 2 as the basic actuator, e.g. an electromechanical spindle actuator 1 with rotating, rotor-fixed nut 71 and linearly movable spindle 50, to which a toggle lever mechanism is connected.

[0092] For this purpose, the end of the spindle 50 is pivotally connected to a coupling element 6, the other end of which is pivotally connected to the end of a drive lever 4. The drive lever 4, in turn, is connected at its bearing point to an actuating shaft 5, to which it transmits its torque. The actuating shaft 5 extends from the actuator housing 40 and can be used to control an actuating function. The coupling element 6 can preferably be designed in two parts on both sides of the spindle 50 in order to transmit the forces symmetrically.

[0093] The end of the spindle 50 is connected to a bearing element supported in the housing 40. This bearing element preferably consists of two rollers arranged around the joint, preferably on both sides at the end of the spindle 50. These rollers bear against corresponding fixed support surfaces 44, e.g., in the actuator housing 40, and can roll along them to improve efficiency. A single- or double-sided sliding bearing is conceivable. The support surfaces 44 preferably run parallel to the axis of movement 41 of the linearly displaceable spindle 50 of the linear actuator 2, i.e., parallel to the spindle axis.

[0094] Thus, when actuated, for example when the linear actuating element, i.e., the spindle 50, is retracted, the coupling element 6 is pivoted, which in turn rotates the lever 4. This can occur until the coupling element 6 has been pulled approximately parallel to the axis of movement 41 and the lever 4 has pivoted to its maximum extent. The return stroke occurs analogously.

[0095] This toggle lever mechanism creates a non-linear characteristic curve between the spindle travel and the rotation of the lever 4, or between the spindle force and the torque of the lever 4. Therefore, such an actuator according to the invention is particularly suitable for actuating loads that also have a non-linear actuating force characteristic curve. A parking lock actuation can be cited as an example. This arrangement allows the actuating axis 5 to be positioned very close to the actuator 1 – significantly closer than if a comparably large actuating torque had to be generated solely by an actuating lever, since in that case the actuator itself would have to be positioned far outside the rotary actuation point, resulting in an unfavorable installation space requirement.

[0096] It is therefore an actuator with an actuating mechanism that can provide a high leverage ratio, but is located close to the actuating point.

[0097] The method according to the invention limits the strength of the torque so that no damage occurs to the actuator or the device to be operated. Reference symbol list 1 actuator 2 Linear drives 3 gearboxes 4 levers 5 wave 6, 6' coupling element 6a Partial coupling element 7 first junction 8 second junction 9 first lever end 10 third liaison point 11 second lever end 20, 20' track curve 21, 21' first endpoint 22, 22' second endpoint 23, 23' first rotational movement 24, 24' second rotational movement 25, 25' first swivel movement 26, 26' second swivel movement 30 first attack 31 second attack 40 actuator housings 41 Axis of movement 42 contour 43 Bearing element 44 support surfaces 50 spindle 51 End cap 52 Support roller 53 holes 54 Internal teeth 55 External gearing 56 Shaft axle 57 Direction of extension 60 Actuating element 61 direction 70 Spindle drive 71 mother 72 Interlocking point 73 rotor bearings 74 Rotor 75 electric motor 80 End position of the actuator or gearbox 90 middle position of the actuator or gearbox 100 Initial position of the actuator or gearbox P1, P2 spindle positions

Claims

[1] Method for safely operating an actuator (1), wherein the actuator is provided for providing a torque, with a linear drive (2) and a gearbox (3) for converting a linear motion into a rotary motion of a shaft (5), wherein the gearbox (3) comprises a lever (4) which rotates the shaft (5) to be subjected to the torque, wherein the gearbox (3) further comprises a coupling element (6) and wherein the coupling element (6) is connected to the linear drive (2) via a first connection point (7) and to the lever (4) via a second connection point (8), so that energy transfer between the linear drive (2) and the lever (4) takes place exclusively via the coupling element (6), and wherein the coupling element (6) is rotatably connected at both connection points (7, 8), characterized by , that the maximum force provided by the linear drive (2) is limited depending on a current value of a gear ratio of the gearbox (3). [2] Method according to claim 1, characterized by , that the lever (4) is connected at a second lever end (11) via a third connection point (10) to the shaft (5) in a rotationally fixed manner and at a first lever end (9) is rotatably connected via the second connection point (8) to the coupling element (6) and the coupling element (6) is rotatably connected via the first connection point (7) to the linear drive (2) and the lever (4) establishes a rigid connection between the two connection points (8, 10). [3] Method according to claim 1 or 2, characterized by , that in an initial position (100) of the transmission (3) a first, preferably housing-fixed stop (30) is provided for fixing the initial position (100) and / or in an end position (80) of the transmission (3) a second, preferably housing-fixed stop (31) is provided for fixing the end position (80), and wherein the first lever end (9) is designed to stop the lever (4) against the first and / or second stop (30, 31). [4] Method according to claim 1 or 2, characterized by , that in an end position (80) of the gearbox (3) a second, preferably housing-fixed stop (31) is provided for fixing the end position (80), and wherein a spindle end or end cap (51) of a spindle (50) of the linear drive (2) is designed to stop the spindle (50) against the second stop (31). [5] Method according to any one of the preceding claims, characterized by , that the value of the gear ratio at a travel position along the axis of motion (41) of the linear drive (2) is calculated from the ratio of a rotation angle Δφ to be determined, which results from the rotational movement of the shaft (5) resulting from the movement of the linear drive (2) and a predetermined distance Δx, which the linear drive (2) moves along the axis of motion (41) of the linear drive (2), starting from the travel position. [6] Method according to any one of the preceding claims, characterized by , that the course of the values ​​of the gear ratio is stored as a function of the travel position of the linear drive (2). [7] Method according to any one of the preceding claims, characterized by , that the dependence of the values ​​of the gear ratio on the travel position of the linear drive (2) is not linear. [8] Method according to any one of the preceding claims, characterized by , that the end position (80) has a predetermined end position threshold value for the gear ratio. [9] Method according to any one of the preceding claims, characterized by , that the force of the linear drive (2) along the axis of movement (41) of the linear drive (2) is limited when the direction of movement of the linear drive (2) is towards the end position (80) and the gear ratio at the current position exceeds the end position threshold.

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