Absolute displacement measuring device for a spindle actuator of an actuating actuator

Abstract

Absolute displacement measuring device (1) for a spindle actuator (2) of an actuating actuator (3,60), wherein the absolute displacement measuring device (1) comprises at least the following components: - a rotor element (4) which is rotationally fixed to a rotor (5) of a rotary drive unit (6) for the operation of the spindle actuator (2); - a first measuring wheel (7) driven by the rotor element (4); - a second measuring wheel (8) which is driven by the first measuring wheel (7) with a different gear ratio, wherein the measuring wheels (7,8) each have a readable marking (9,10) of the respective rotational position (11,12), characterized by the fact that one of the measuring wheels (8) is designed as a ring gear, wherein the other measuring wheel (7) is arranged radially inside the ring gear.

Description

[0001] The invention relates to an absolute position measuring device for a spindle actuator of an actuating actuator, a spindle actuator for an actuating actuator, as well as a hydrostatic and a mechanical actuating actuator for a friction clutch.

[0002] Spindle actuators for hydrostatic actuation actuators are known from the prior art, in particular for an actuation device for a friction clutch of a motor vehicle. Such hydrostatic actuation actuators are also referred to as hydrostatic master units. For example, hydrostatic actuation actuators are known as clutch actuators for the hydraulic actuation of a friction clutch, which for this purpose comprise the master cylinder of a hydrostatic actuation system. In a hydrostatic actuation actuator, a master cylinder is generally provided for receiving a hydraulic fluid, wherein the receiving volume can be varied by means of a master piston. The master piston is moved translationally in the master cylinder, thereby changing the receiving volume of the master cylinder.A hydrostatic slave unit communicating with it, with a receiving volume in a slave cylinder with a movable slave piston, thereby experiences a correspondingly reversed change in the receiving volume.

[0003] To control the volume change in the hydrostatic actuation actuator, a rotary, preferably electric, drive is preferably used, and the rotary movement is translated into a translational movement of the master piston by means of a spindle drive. In a first variant, a rotationally fixed spindle nut is moved translationally by means of a drive spindle. Reference is made, for example, to DE 10 2010 047 801 A1. A second variant is known from WO 2011 / 050 766 A1, in which a master piston is arranged in a master cylinder and is translationally fixed by a drive spindle. The rotary drive, therein by means of a pitch-true planetary roller gear (S-PWG), translates this rotation into a translational movement of the drive spindle and thus of the master piston.

[0004] In order to control or regulate the position of the linear actuator element, for example in the first variant of a spindle nut or in the second variant of a drive spindle, the state of the art uses, for example, a translatory absolute position sensor to measure the translatory absolute position directly on the linear actuator element. Such an absolute position sensor can clearly determine the position of the linear actuator element at any time through direct (linear) measurement during operation, without the need for an additional reference. The absolute position sensor is expensive and, moreover, is usually only spatially separated from the measuring electronics and can therefore often be integrated into a spindle actuator via space-intensive additional plug connections and / or more complex encapsulation. In addition, the connection of the sensors is often susceptible to vibration and installation is complex.

[0005] Absolute position sensors, in particular for detecting angles of rotation greater than 360°, are known, for example, from DE 10 2009 041 232 A1 and DE 10 2015 214 435 A1.

[0006] Furthermore, a configuration is known in which only one rotor position sensor (or angle sensor) is provided. In this case, at the level of the readout electronics or evaluation electronics, the position of the linear actuator element is determined incrementally by counting each complete revolution of the rotary drive and indirectly by calculating the geometric relationship between the thread pitch and the relative translational displacement between the spindle nut and drive spindle. In this configuration, it is necessary to provide at least one reference stop or a reference sensor for which a zero position is defined. This means that in the event of a loss of (memory) in the control system or an error when counting the complete revolutions, and thus a loss of the relative reference to the reference stop, the reference stop or reference sensor must be approached.This is time-consuming, particularly due to the additional plausibility check that is usually required. This plausibility check is necessary, for example, to reliably distinguish between possible stiffness or other stops and the reference stop. Another disadvantage is that the mechanical requirements for such an actuator are particularly high, because high running quality and high stop strength are required for the reference stop.

[0007] Furthermore, indirect readout systems are known in which driven measuring shafts are used for reading. Such systems can be configured in such a way that no reference stop is required, because a unique measured value is assigned to each angular position, preferably over the entire travel range of the linear actuator element. Particularly in spindle actuators, where a central component (e.g., a translationally moved drive spindle) prevents the placement of a central measuring magnet rotating with the rotor, at least one mechanically connected off-axis measuring shaft has been used. This means that inaccuracies in the mechanical transmission, for example, via gears, are accepted and / or high manufacturing and assembly precision are required.

[0008] Based on this, the present invention is based on the object of at least partially overcoming the disadvantages known from the prior art. The features of the invention are derived from the independent claims, for which advantageous embodiments are presented in the dependent claims. The features of the claims can be combined in any technically reasonable manner, whereby the explanations from the following description as well as features from the figures, which comprise additional embodiments of the invention, can also be consulted for this purpose.

[0009] The invention relates to an absolute position measuring device for a spindle actuator of an actuating actuator, wherein the absolute position measuring device has at least the following components: - a rotor element which is rotationally fixedly connected to a rotor of a rotary drive unit for the operation of the spindle actuator; - a first measuring wheel driven by the rotor element; - a second measuring wheel, which is driven by the first measuring wheel with a gear ratio different from the first, wherein the measuring wheels each have a readable marking of the respective rotational position. The absolute position measuring device is characterized primarily by the fact that one of the measuring wheels is designed as a ring gear, with the other measuring wheel being arranged radially inside the ring gear.

[0010] The absolute position measuring device is designed to clearly detect the position of an actuator element, for example, the master piston of a hydrostatic actuating actuator or a mechanical actuating actuator, over the entire extent of the travel or actuating path. This does not require direct measurement of the actuator element's travel. A mechanical actuating actuator comprises an actuating connecting rod, which can be moved in a translational and, if necessary, tiltable manner. In one embodiment, an actuating device, for example, a piston for actuating a disc spring of a friction clutch, can be directly actuated by means of the actuating connecting rod. Alternatively, another transmission system, for example, a hydrostatic master-slave system, can be interposed.A hydrostatic actuator comprises a master piston in a master cylinder, by means of which a hydraulic fluid can be displaced or drawn into the master cylinder. The master cylinder is communicatively connected to a slave cylinder, so that a slave piston guided therein can be moved correspondingly by means of the master piston.

[0011] The absolute position measuring device proposed here is particularly suitable for a spindle actuator in which the spindle is rotationally fixed, for example, via a rail-like spindle guide. This spindle is axially movable by means of a rotor, which engages the spindle thread with the aid of a translationally fixed, pitch-true spindle nut. The spindle nut is particularly preferably a so-called pitch-true planetary roller gear (S-PWG) or a pitch-true ball screw (KGT). In one embodiment, a spindle nut has a transmission ratio between the rotor and the spindle that is not equal to one. When reference is made below to the rotation of the spindle nut, this means the rotation on the spindle side, i.e., the rotation acting directly on the spindle, whereby at the same time the transmission-transmitting spindle nut is rotationally fixed to the rotor, i.e., there is no transmission ratio deviating from one on the rotor side.Preferably, the transmission ratio between rotor and spindle is equal to one. The pitch accuracy describes that the relative movement between the spindle nut and the spindle is in a clear and reproducible relationship without unknown deviations. In a particularly simple spindle, the thread pitch is constant and the pitch accuracy ensures that the translational relative movement of the spindle after a full rotation (360°) of the rotor or the spindle nut corresponds exactly to the constant thread pitch. The absolute position measuring device proposed here can also be used for the variant with an axially fixed spindle and an axially movable spindle nut. To record the translational movement of the spindle or the spindle nut, it is therefore sufficient to record the rotational movement of the rotor and / or the axially fixed spindle or the axially fixed spindle nut.

[0012] For this purpose, a first measuring wheel and a second measuring wheel are provided, with the first measuring wheel rotating with the rotor element at a fixed gear ratio. In the normal operational assembly, the rotor element is firmly connected to the rotor and thus the first measuring wheel rotates with the rotor at a fixed gear ratio. The first measuring wheel is driven directly or indirectly by the rotor in the assembly. With an indirect gear ratio, intermediate elements such as wheels, gears and / or belts are provided. Furthermore, the second measuring wheel is configured such that it is directly or indirectly driven and rotates with the first measuring wheel and thus also with the rotor (element) at a fixed gear ratio. Particularly preferably, the second measuring wheel is driven directly by the first measuring wheel.The fixed transmission ratio between the first measuring wheel and the second measuring wheel is not equal to one, preferably close to one with the largest possible pitch over the entire length of the travel path of the actuator element, for example the master piston or the actuating connecting rod.

[0013] For measurement and installation space reasons, it is advantageous to set a gear ratio close to one. The following formula is suitable for this design: for: ψ(x)=2πxφ(x)=∓2πx(m+1N)+α0=∓ψ(x)(m+1N)+α0

[0014] While ψ describes the angular position of the first measuring wheel, φ describes the angular position of the second measuring wheel. x in integer intervals corresponds to a full revolution of the first measuring wheel. Typically, the starting angle is defined as the zero position or initial position at the beginning of the maximum travel distance with x0 = 0, and the end position at the end of the maximum travel distance of the spindle is defined as x maxset. For each full revolution (2π) of the first measuring wheel, the second measuring wheel moves through an angular amount greater or less than 360° in the same time. The rotational position is opposite, i.e. negative, in the case of, for example, indirect counter-rotating wheel transmission. This relationship is described by the factor of the sum of a first integer (modulor m ∈ ℤ0 - element of the integers with zero, i.e.: ..., -3, -2, -1, 0, 1, 2, 3, ...) and the inverse of a second integer (N ∈ ℤ - element of the integers without zero, i.e.: ..., -3, -2, -1, 1, 2, 3, ...). The second integer (N) is preferably greater in magnitude than the total number of revolutions of the rotor over the maximum translational travel of the spindle or the spindle nut, preferably one greater or less than the total number of revolutions.The angle α0 represents any phase shift between the zero position of the second measuring wheel and the first measuring wheel and is essentially any angle; this can be determined, for example, by manufacturing requirements. In the following examples, this phase shift is set as α0 = 0 for simplicity.

[0015] For a particularly space-saving configuration, the second measuring shaft runs only slightly backwards or forwards with a low-complexity translation device, so the modulor m = 1 is set for this.

[0016] With a transmission ratio according to the preceding description, due to the above-described relationship between the first angular position ψ(x) of the first measuring wheel and the second angular position φ(x) of the second measuring wheel, the second marking is always at a different angular position than the first marking over the entire travel path of the spindle for each (different) gear change. Particularly preferably, the first measuring wheel and the second measuring wheel are always arranged in different or metrologically distinguishable angular constellations to one another over the entire travel path for any intermediate travel positions of the spindle. In another embodiment, the markings are arranged in different or metrologically distinguishable angular constellations to one another only during a gear change.

[0017] Particularly advantageous for the largest possible distances between the individual angular positions of the second measuring wheel during the respective gear changes is set to m = 1 and N = G + 1, where G is the number of threads, so with x0 = 0, x max = G. However, significantly faster and significantly slower ratios are also possible according to this relationship. For example, with 32 threads on the spindle, the second integer (N) is set to 33. Only at the theoretical 33rd thread does the periodicity factor of the second measuring wheel become an integer again: (xmax+1)(1N)=(G+1)(1G+1)=1

[0018] Only then would a double angular constellation (as with the zeroth thread) of the two measuring wheels be repeated, but the spindle does not have a 33rd thread.

[0019] The first measuring wheel and the second measuring wheel each have a marking which has a fixed orientation to the respective measuring wheel. The respective marking can be read automatically by a corresponding measuring device. This allows the angular position of the respective measuring wheel to be detected by a respective angle sensor using the known, fixed orientation of the marking. For example, a magnet arrangement is provided for marking on at least one measuring wheel, and its magnetic flux density is used to detect the angular position. The magnetic flux density changes with the angular position of the respective measuring wheel relative to a fixed location at which the associated angle sensor is arranged. Using various previously known angle sensors, the change can easily be detected as an electronic measurement variable.

[0020] The recorded angular constellation of the two measuring wheels is always different over the entire length of the travel path of the actuator element and thus allows an automated control-based conclusion to be drawn about the absolute translational position of the actuator element.

[0021] Here, it is proposed to design one of the measuring wheels as a ring gear, with the other measuring wheel being arranged as a drive wheel inside the ring gear. To achieve the appropriate gear ratio, which is different from one, the orbital lengths of the two measuring wheels are different, so that the ring gear is arranged eccentrically to the drive wheel. The eccentricity of the two measuring wheels is fixed and therefore does not rotate with the rotation of the rotor element. Particularly preferably, the inner radius of the ring gear is only larger than the outer radius of the drive wheel by so much that a relative movement between the ring gear and the drive wheel is possible.

[0022] Due to the arrangement of the first measuring wheel and the second measuring wheel near the rotor of the drive unit, a particularly space-saving design is possible, while at the same time a precise and reliable reading of the absolute angular position is possible.

[0023] In a further advantageous embodiment of the absolute position measuring device, the ring gear is formed by the second measuring wheel.

[0024] This configuration allows for a particularly space-saving design, as the driven second measuring wheel forms the ring gear arranged eccentrically to the spindle axis, allowing the eccentric peripheral bearing to be set up on the outer circumference of the ring gear. Particularly preferably, the ring gear is mounted directly on the stator overmolding of the electric drive unit of the spindle actuator. This allows for cost savings, especially for large production runs, and also simplifies and ensures reliable installation of the absolute position measuring device on the spindle actuator.

[0025] In a further advantageous embodiment of the absolute position measuring device, the first measuring wheel is firmly connected to the rotor element, preferably formed in one piece therewith.

[0026] This embodiment avoids inaccuracies due to play in a transmission drive, especially in the one-piece design. Particularly preferably, the second measuring wheel is driven directly by the first measuring wheel. This avoids further inaccuracies due to the direct transmission from the first measuring wheel to the second measuring wheel. Particularly preferably, the second measuring wheel is the ring gear.

[0027] In a further advantageous embodiment of the absolute position measuring device, the first measuring wheel has a first marking and the second measuring wheel has a second marking and the respective readable marking is formed by means of one of the following devices: - an optical barcode; - an inductive barcode; - a magnetic position encoding; and - a ring magnet, wherein the principle of the first marking and the principle of the second marking are preferably free from interference with each other.

[0028] Optical bar coding is designed to optically read the angular position. At least two different bar types, for example, a dark and a light bar, are arranged adjacent to each other around the circumference, and these can be automatically distinguished optically, for example, by different reflections. Inductive bar coding follows the same basic principle, but here the at least two different bar types influence an inductive field in a distinguishably different way, so that this can be detected by an inductive measuring device. Magnetic position coding, for example, is designed using a plurality of magnets distributed around the circumference.In a preferred embodiment, two magnets are provided which are spaced apart from each other around the circumference by, for example, 180° and are each aligned opposite to each other, so that, for example, the north pole of a first magnet and the south pole of the second magnet is detected by the measuring device. With a ring magnet, a comparable effect is achieved in that the north pole is spaced apart from the south pole by 180° around the circumference. With sufficient field strength, the ring magnet can generally be implemented in a more space-saving manner than magnetic position coding. According to a preferred embodiment, two mutually interference-free principles are used, thus enabling a space-saving design without the need for extensive measuring effort. Particularly preferably, the drive wheel has a ring magnet and the ring gear has optical or inductive bar coding.This takes advantage of the fact that the largest possible circumferential length is desired for bar coding, which in this embodiment is maximized for the ring gear. Furthermore, the precision of measuring the angular position of the ring magnet depends primarily on the measuring position of the measuring device, because the magnetic field extends beyond the radial extent of the ring magnet.

[0029] In a further advantageous embodiment of the absolute position measuring device, the measuring wheels are designed as gears.

[0030] To ensure a reliable and, for most applications, sufficiently accurate transmission between the first and second measuring wheels, it is advantageous to design the measuring wheels as intermeshing gears. This eliminates any relative slippage.

[0031] According to a further aspect of the invention, a spindle actuator for an actuating actuator is proposed, wherein the spindle actuator has at least the following components: - an electric drive unit comprising a stator and a rotor; - a spindle with a spindle axis which can be driven by means of the rotor; - an absolute position measuring device according to an embodiment as described above, which is connected to the rotor by means of the rotor element and by means of which the absolute angular position of the rotor can be detected; - a measuring device for recording the markings of the absolute position measuring device; - control electronics by means of which the spindle can be moved in a controlled manner based on the measurements of the measuring device.

[0032] The spindle actuator has a spindle that executes a translational movement via a plurality of threads with a defined, i.e., known, thread pitch as a result of the rotation of a driving spindle nut, or moves a spindle nut driven by the spindle along the spindle axis. In the first variant, the spindle nut is firmly connected to the rotor of the rotary drive unit, and the spindle is firmly connected in translational fashion to an actuator element, for example, a master piston or (articulated) an actuating connecting rod. In the second variant, the spindle is firmly connected in rotational fashion to the rotor, and the spindle nut is firmly connected in translational fashion to an actuator element.In both variants, there is therefore a clear geometric relationship between a rotational movement of the rotor and the translational movement of the actuator element or of an existing thread and the translational, or axial, (absolute path) position of the spindle or the spindle nut. The actuator element can be moved axially back and forth between an initial position and an end position along a predetermined maximum travel path by means of the spindle. A fixed transmission ratio between the rotor and the first and second measuring wheels is set up for this maximum travel path in such a way that the second measuring wheel is aligned at a different angle compared to all other gear changes over a complete rotation of the rotor. A gear change is defined at a predetermined angular position of the first measuring wheel and the rotor and is therefore repeated after each full rotation of the rotor.Preferably, the first measuring wheel and the rotor are rotationally fixed or integrally connected to one another, so that the angular position of the first measuring wheel is identical to the angular position of the rotor. Consequently, the actuator element is moved axially by the amount of the thread pitch for one full rotation of the rotor, or, in the case of a multiplying spindle nut, by a multiplying multiple of the thread pitch. It should be noted that in preferred embodiments with the arrangement described above, even intermediate positions of the spindle between gear changes can be read off absolutely unambiguously.

[0033] As described above, the second measuring wheel is connected via a fixed gear ratio, which results in a different periodicity. This means that the second measuring wheel completes a full rotation either faster or slower than the first measuring wheel. This gear ratio is preferably configured such that, over the entire travel of the actuator element, for example, the master piston or the actuating connecting rod, the second measuring wheel is never at the same angular position on the spindle at the time of a gear change as it is during another gear change. For details of possible embodiments, reference is made to the preceding explanations.As a result of this defined deviating periodicity, with a detected second angular position of the second measuring wheel and a detected first angular position of the first measuring wheel, the adjacent thread, i.e. the translational (axial) absolute path position of the actuator element, can be clearly determined and the rotary drive unit, preferably an electric drive unit, for example a servo motor, can be directly controlled and / or regulated with this measured variable, preferably directly commutated according to a predetermined manipulated variable.

[0034] The measuring device for detecting the markings on the measuring wheels can be reduced to small-scale sensors, which can be manufactured using the same technology even if the marking principles are preferably different, and can therefore be mounted on a common circuit board. The associated control electronics, by means of which the spindle can be moved in a controlled manner based on the measurements from the measuring device, are preferably also integrated into the circuit board or housed in a central processing unit, for example in a motor vehicle. In the simplest version, the control electronics comprise the target input and the control variable provided by the measuring device. Alternatively, other parameters and / or servo properties can be taken into account, whereby a desired input is determined and implemented instead of outputting the actual user input unprocessed as a manipulated variable.For example, if the user sets the clutch to engage too quickly, this will be converted into a clutch engagement process that is as fast as possible but with minimal wear.

[0035] This allows for a very small absolute position measuring device, combined with simple and error-free measurement electronics. Furthermore, the absolute position of the actuator element can be determined at any time without memory requirements at any angular position of the first measuring wheel, provided that no duplicate angular positions of the first measuring shaft and the second measuring shaft occur over the entire travel path, preferably according to the above specification. Thus, the spindle does not need to be moved to a different absolute position in order to (exactly) determine the current absolute position.

[0036] In a further advantageous embodiment of the spindle actuator, the stator has a stator overmolding and the second measuring wheel is mounted on the stator overmolding.

[0037] In this preferred embodiment, the stator overmolding is used to simultaneously form a bearing for the second measuring wheel. Particularly preferably, the second measuring wheel is designed as a ring gear, and the stator overmolding forms an eccentric circumferential bearing for the ring gear. For low-friction relative movement between the second measuring wheel and the stator overmolding, suitable material pairings are preferably selected that have a low coefficient of friction in direct contact with one another or exhibit lubricating properties during relative movement.

[0038] In a further advantageous embodiment of the spindle actuator, the spindle is rotationally fixed and axially movable by means of a spindle nut, wherein the spindle nut preferably comprises a pitch-accurate planetary roller gear for transmitting the rotation to the spindle, and the measuring wheels are arranged around the spindle axis, wherein preferably the first measuring wheel is arranged concentrically and the second measuring wheel is arranged eccentrically to the spindle axis.

[0039] This preferred embodiment takes advantage of the fact that the arrangement of the measuring wheels allows for the formation of a central passage through which the axially moving spindle can pass. This makes it possible to implement a compact design while simultaneously ensuring reliable reading of the angular positions of the measuring wheels and thus the absolute angular position of the rotor. Particularly preferably, the corresponding measuring device is also designed with a central passage. This means that both the absolute position measuring device and the reading-out measuring device can be arranged axially close to the drive unit.

[0040] According to a further aspect of the invention, a hydrostatic actuating actuator for a friction clutch is proposed, wherein the hydrostatic actuating actuator has at least the following components: - a spindle actuator according to an embodiment as described above; - a master piston which can be driven by the spindle for translational movement and is preferably firmly connected to a rotationally fixed and axially movable spindle; - a master cylinder for receiving the master piston and a hydrostatic fluid, wherein the master cylinder can be connected to a slave cylinder by means of the hydraulic fluid, wherein the measuring device and the control electronics are preferably arranged on a common circuit board, preferably for end arrangement at the rotor behind the electric drive unit as seen from the master piston.

[0041] The spindle of the spindle actuator is driven by the rotary drive unit, e.g., a servo motor, and the rotary drive unit is controlled by measuring the first angular position of the first measuring wheel and the second angular position of the second measuring wheel as a controlled variable, as described above. The spindle in the first variant, or the spindle nut in the second variant, is firmly connected to a master piston. The master piston thus performs a translational movement along the spindle axis by axially displacing the master piston along the spindle axis using the thread pitch of the spindle threads in interaction with the spindle nut. Thus, a hydraulic fluid in the master cylinder can be displaced or sucked in by the master piston, so that a slave cylinder communicating with it can be controlled, and a force can be transferred from the master cylinder to the slave cylinder.This particularly advantageously enables fast and precise actuation of the master piston or slave piston, as required, for example, when actuating a friction clutch assembly. Furthermore, high forces, such as those required for applying pressure to a friction clutch, can be generated.

[0042] In the previously known devices for detecting the absolute position of the master piston, it is necessary to provide at least one additional sensor or stop, which is arranged in the region of the travel path of the spindle. Alternatively, according to the prior art, a complex and possibly slow calibration process is necessary. Here, it is now possible to arrange the entire measuring arrangement at the end, i.e. outside the region of the travel path of the spindle, whereby even the entire measuring electronics, and preferably also the control electronics, can be arranged combined on a single circuit board at the end, and optionally as a separate component. Particularly preferably, the first measuring wheel and the second measuring wheel are arranged behind the rotary bearings for the spindle nut and for the spindle, respectively, viewed from the master piston, preferably behind the rotary drive unit.

[0043] According to a further aspect of the invention, a mechanical actuating actuator for a friction clutch is proposed, wherein the mechanical actuating actuator has at least the following components: - a spindle actuator according to an embodiment as described above; - an actuating connecting rod which can be driven by means of the spindle for translational movement, preferably being directly connected to a rotationally fixed and axially movable spindle, wherein the actuating connecting rod can preferably be connected to an actuating device of a friction clutch, wherein furthermore preferably the measuring device and the control electronics are arranged on a common circuit board, preferably for end arrangement at the rotor as seen from the actuating connecting rod behind the electric drive unit.

[0044] The spindle of the spindle actuator can be driven by the rotary drive unit, for example a servo motor, and the rotary drive unit is controlled by measuring the first angular position of the first measuring wheel and the second angular position of the second measuring wheel as a controlled variable, as described above. The spindle in the first variant or the spindle nut in the second variant is connected, preferably directly, to an actuating connecting rod. The actuating connecting rod can thus be driven in a translationally controlled manner. For some applications, the actuating connecting rod is designed to tilt during the translational movement. This is particularly advantageous for applications in the automotive sector. In one embodiment, the actuating connecting rod is directly connected to an actuating device, for example a piston for actuating a disc spring, for a friction clutch.Alternatively, another transmission system, for example a hydrostatic master-slave system, is interposed.

[0045] This particularly advantageously enables fast and precise actuation of the actuating connecting rod, as required, for example, when actuating a friction clutch assembly. Furthermore, high forces, such as those required for pressing a friction clutch, can be generated.

[0046] In the previously known devices for detecting the absolute position of the actuating connecting rod, it is necessary to provide at least one additional sensor or stop arranged in the region of the spindle travel path. Alternatively, according to the prior art, a complex and possibly slow calibration process is necessary. Here, it is now possible to arrange the entire measuring arrangement at the end, i.e. outside the region of the spindle travel path, whereby even the entire measuring electronics, and preferably also the control electronics, can be arranged combined on a single circuit board at the end, and optionally as a separate component. Particularly preferably, the first measuring wheel and the second measuring wheel are arranged behind the rotary bearings for the spindle nut and for the spindle, respectively, viewed from the actuating connecting rod, preferably behind the rotary drive unit.

[0047] According to a further aspect of the invention, a friction clutch with a clutch axis for releasably connecting an output shaft to a consumer is proposed, wherein the friction clutch has at least the following components: - at least one friction package with at least one friction plate and at least one corresponding friction disc, via which a torque can be transmitted in the pressed state; - at least one actuating device for pressing the at least one friction package; and - at least one actuating actuator according to an embodiment as described above for the controlled actuation of the actuating device.

[0048] The friction clutch is designed to releasably transmit torque from an output shaft to a consumer and vice versa. This is generally achieved via at least one friction assembly, which has an axially displaceable pressure plate, generally rotationally fixed to the output shaft, which can be pressed against at least one corresponding friction disc. The contact force results in a friction force across the friction surface, which, when multiplied by the mean radius of the friction surface, results in a transmittable torque. In a dual clutch, two separately actuated friction assemblies are provided, each connected to its own output shaft, preferably one of the transmission shafts of a dual transmission, so that torque can be transmitted uninterruptedly or at least with minimal interruption via one output shaft each.

[0049] To ensure the most precise pressing process possible for a friction package, which above all enables fast and low-wear coupling, actuation of the actuating device using the hydrostatic or mechanical actuating actuator described above is particularly advantageous. This allows the absolute travel position of the master piston or the actuating connecting rod to be determined in any situation and, at the same time, adjusted very precisely. The design is particularly advantageous in that it is space-saving, easy to install, reliable, and consumes very little energy for reading. In a particularly preferred embodiment according to the above description, no movement of the master piston or the actuating connecting rod and the inevitably associated actuation input are required to (exactly) determine the absolute travel position of the spindle nut. Rather, the absolute travel position can be determined at any time and in any position.Furthermore, in a preferred embodiment, only an exact assignment of the angular positions of the measuring wheels to a (single) absolute travel position of the actuator is necessary, for example, by means of precise assembly or initial calibration. Calibration of further relationships is not necessary; rather, they can be determined geometrically with sufficient accuracy and predictability.

[0050] According to a further aspect of the invention, a drive train for a motor vehicle is proposed, wherein the drive train has a drive unit with an output shaft and a friction clutch according to an embodiment according to the above description, wherein the output shaft is detachably connectable to at least one consumer for torque transmission by means of the friction clutch.

[0051] The drive train is designed to releasably transmit, i.e., connectable and disconnectable, a torque provided by a drive unit, for example, an energy conversion machine, preferably an internal combustion engine or an electric motor, and output via its output shaft to at least one consumer. An exemplary consumer is at least one drive wheel of a motor vehicle and / or an electric generator for providing electrical energy. Conversely, inertial energy introduced by, for example, a drive wheel can also be absorbed. The at least one drive wheel then forms the drive unit, wherein its inertial energy can be transferred by means of the friction clutch to an electric generator for recuperation, i.e., for electrically storing the braking energy, with a correspondingly configured drive train.Furthermore, in a preferred embodiment, a plurality of drive units are provided, which can be connected in series or in parallel or decoupled from one another by means of the friction clutch, or whose torque can be detachably made available for use. Examples include hybrid drives consisting of an electric motor and an internal combustion engine, but also multi-cylinder engines in which individual cylinders (groups) can be switched on.

[0052] To transmit torque in a targeted manner and / or via a manual transmission with different gear ratios, or to disengage a transmission, the use of the friction clutch described above is particularly advantageous because even high transmittable torques can be switched precisely and with low wear. At the same time, the absolute travel position of the actuator element can be determined at any time, even after a power interruption to the measuring electronics, and the overall precision of the actuation is high.

[0053] According to a further aspect of the invention, a motor vehicle is proposed, wherein the motor vehicle has at least one drive wheel which can be driven by means of a drive train according to an embodiment according to the above description.

[0054] Most motor vehicles today have front-wheel drive, and therefore the drive unit, such as an internal combustion engine or an electric motor, is preferably positioned in front of the driver's cab and perpendicular to the main direction of travel. The installation space is particularly limited with such an arrangement, making it particularly advantageous to use a small friction clutch. The use of a friction clutch is similar in motorized two-wheelers, which require significantly increased performance while maintaining the same installation space.

[0055] This problem is exacerbated in small-car passenger cars according to the European classification. The functional units used in a small-car passenger car are not significantly smaller than in larger passenger cars. Nevertheless, the available installation space is considerably smaller in small cars. The drivetrain described above features a friction clutch or a particularly compact hydrostatic actuator. At the same time, the absolute position of the actuator element can be measured at any time, regardless of power outages in the measurement electronics.

[0056] Passenger cars are assigned to a vehicle class based on factors such as size, price, weight, and performance, although this definition is subject to constant change according to market needs. In the US market, vehicles in the small car and subcompact car classes are classified as subcompact cars according to the European classification, while in the British market they correspond to the supermini and city car classes, respectively. Examples of the subcompact car class include a Volkswagen up! or a Renault Twingo. Examples of the compact car class include an Alfa Romeo Mito, Volkswagen Polo, Ford Fiesta, or Renault Clio.

[0057] The invention described above is explained in detail below against the relevant technical background with reference to the accompanying drawings, which show preferred embodiments. The invention is in no way limited by the purely schematic drawings, whereby it should be noted that the drawings are not to scale and are not suitable for defining proportions. It is shown in Fig. 1: a spindle actuator with absolute position measuring device in section; Fig. 2: a sectioned absolute position measuring device with rotor in spatial representation; Fig. 3: a dual clutch with hydrostatic actuation actuator; Fig. 4: a single clutch with mechanical actuation actuator; and Fig. 5: a drive train in a motor vehicle with a friction clutch.

[0058] In Fig. 1 shows a cross-sectional view of a spindle actuator 2 with an absolute position measuring device 1. The first variant shown here is a spindle 18 movable along the spindle axis 19 and rigidly connected to a master piston 26 (shown here additionally). The master piston 26 is shown in the fully retracted position, in which the receiving volume in the master cylinder is at its maximum. As a result, the spindle 18 is located, as shown, at its maximum left end stop. A spindle guide 56 is also provided in this area, by means of which the spindle 18 is rotationally fixed. The spindle nut 23 for driving the spindle 18 is axially fixed to the rotor 5 of the drive unit 6 and is designed as a pitch-accurate planetary roller gear 24. The rotor 5 itself is also axially fixed, for example, by means of the rotor bearing 57.This establishes a reproducible relationship between the axial movement of the spindle 18 and the rotation of the rotor 5. The rotor 5 is set in rotation under the control of the stator 17 of the drive unit 6. To detect the absolute position of the master piston 26, the absolute position measuring device 1 has a first measuring wheel 7 and a second measuring wheel 8. The first measuring wheel 7 is integrally integrated into a rotor element 4, which is a component of the rotor 5 of the drive unit 6. In this exemplary embodiment of the drive unit 6, the stator 17 has a stator overmolding 22. The second measuring wheel 8 is mounted eccentrically about its outer circumference around the eccentric axis 58 directly in the stator overmolding 22.In this example, the first marking 9 of the first measuring wheel 7 is formed by a ring magnet 16, and the second marking 10 of the second measuring wheel 8 is formed by two magnets offset by 180° with reversed polarity, which form a magnetic position coding 15. The angular positions of the respective measuring wheels 7 and 8 can be detected by a measuring device 20, which is integrated into a common circuit board 29.

[0059] In Fig. 2 is an absolute position measuring device 1 in a similar configuration as in Fig. 1, wherein the first measuring wheel 7 and the second measuring wheel 8 are designed as gears and the second marking 10 has an optical bar code 13 or an inductive bar code 14. This illustration schematically indicates that with one rotation of the rotor 5, the first measuring wheel 7 moves ahead of the second measuring wheel 8, so that the first measuring wheel 7 is in a first rotational position 11 and the second measuring wheel 8 is in a second rotational position 12, which, starting from a common zero position, have a different angular amount. These different rotational positions 11 and 12 are characteristic of the axial position of the spindle 18, so that the position of the spindle 18 can be reliably detected at any time.

[0060] In Fig. 3 shows an example of a friction clutch 25 as a (dry) double clutch, which, by means of a slave cylinder 28 and a respective first actuating device 46 and a second actuating device 47, outputs a torque input via an output shaft 31 about the clutch axis 30 via the first friction assembly 34 to the first output shaft 54 ​​and via the second friction assembly 35 to the second output shaft 55. The first friction assembly 34 is composed of several friction plates, namely a first pressure plate 36, a first intermediate plate 37 and a first counterplate 38, as well as several friction discs, namely a first pressure friction disc 42 and a first counterplate friction disc 43, for which friction plates can also be used.The second friction assembly 35 is also composed of several friction plates, namely a second pressure plate 39, a second intermediate plate 40, and a second counterplate 41, as well as several friction discs, namely a second pressure friction disc 44 and a second counterplate friction disc 45, for which friction plates can also be used. The friction assemblies 34 and 35 can be actuated via a hydrostatic actuation actuator 3 with a spindle actuator 2, preferably according to an embodiment shown above, by means of a hydraulic line 59, preferably automatically, via the slave cylinder 28. For this purpose, a master piston 26 in the master cylinder 27 can be moved back and forth by means of the spindle 18, so that a hydraulic fluid is displaced in the hydrostatic actuation actuator 3 and pressed into the slave cylinder 28.The drive unit 6 of the hydrostatic actuation actuator 3 can be controlled by means of a measuring device 20 and a control electronics 21, which is shown externally here.

[0061] In Fig. 4, a friction clutch 25 is shown as a (dry) single clutch. The friction clutch 25 comprises a friction assembly 34 with a pressure plate 36, a counter plate 38, and a pressure friction disc 42 arranged axially therebetween. A torque about the clutch axis 30 is transmitted, for example, by means of the output shaft 31 of a drive unit 50 (see Fig. 5) to the counterplate 38 and a rotationally fixed clutch cover 62, as well as the rotationally entrained but axially movable pressure plate 36. If the pressure plate 36 is pressed as shown, the torque is transmitted to the output shaft 54 ​​by means of the friction force generated between the friction plates 36, 38 and the pressure friction disc 42. In the released state, i.e., when the pressure plate 36 is displaced to the right in the illustration, transmission is interrupted or sufficiently reduced. The clutch configuration shown is, for example, a normally engaged friction clutch 25. In this case, the required contact force is applied by the disc spring 63 of the actuating device 46.To release, the diaphragm spring 63 is pressed centrally toward the output shaft 31 by means of the releaser 64 of the actuating device 46, so that the diaphragm spring 63 is moved radially outward toward the clutch cover 62, on which the diaphragm spring 63 is tiltably mounted. This enables the pressure plate 36 to be spaced apart from the pressure friction disc 42. This spacing may be assisted by a spring system, for example, leaf springs on the outer edge of the pressure plate 36, which are preloaded and connected to the clutch cover 62. A mechanical actuating actuator 60 with an actuating connecting rod 61 is provided here to directly actuate the actuating devices 46 or the releaser 64. Here, the actuating connecting rod 61 is mounted so that it can be tilted, so that a movement of the spindle 18 of the spindle actuator 2 away from the output shaft, i.e. to the right in the illustration, moves the releaser 64 towards the output shaft 31.This deflects the disc spring 63 as described above. Otherwise, the spindle actuator 2 corresponds to the illustration in the preceding figures, and in this respect, reference is made to the previous description.

[0062] In Fig. 5 schematically shows a drive train 48 comprising a drive unit 50, depicted here as an internal combustion engine, an output shaft 31, a friction clutch 25, and a torque-transmitting left drive wheel 32 and right drive wheel 33. The drive train 48 is arranged in a motor vehicle 49, with the drive unit 50 arranged with its engine axis 53 transverse to the longitudinal axis 52 in front of the driver's cab 51.

[0063] With the absolute position measuring device proposed here, the absolute position of a master piston can be read in any condition in a small installation space. List of reference symbols 1 absolute position measuring device 2 spindle actuators 3 hydrostatic actuator 4 Rotor element 5 Rotor 6 Drive unit 7 first measuring wheel 8 second measuring wheel 9 first marking 10 second marking 11 first rotation position 12 second rotation position 13 optical bar coding 14 inductive bar coding 15 magnetic position coding 16 ring magnet 17 Stator 18 spindle 19 Spindle axis 20 measuring device 21 Control electronics 22 Stator overmolding 23 Spindle nut 24 pitch-accurate planetary roller gears 25 Friction clutch 26 master pistons 27 master cylinders 28 slave cylinders 29 circuit board 30 Coupling axle 31 Output shaft 32 left drive wheel 33 right drive wheel 34 first friction package 35 second friction package 36 first pressure plate 37 first intermediate plate 38 first counter plate 39 second pressure plate 40 second intermediate plate 41 second counter plate 42 first friction disc 43 first counter plate friction disc 44 second friction disc 45 second counter plate friction disc 46 first actuating device 47 second actuating device 48 Drivetrain 49 Motor vehicle 50 drive unit 51 Driver's cab 52 Longitudinal axis 53 Motor axle 54 first output shaft 55 second output shaft 56 spindle guide 57 rotor bearings 58 Eccentric axis 59 Hydraulic line 60 mechanical actuation actuator 61 actuating connecting rod 62 clutch cover 63 disc spring 64 releasers

Claims

[1] Absolute position measuring device (1) for a spindle actuator (2) of an actuating actuator (3,60), wherein the absolute position measuring device (1) has at least the following components: - a rotor element (4) which is rotationally fixedly connected to a rotor (5) of a rotary drive unit (6) for the operation of the spindle actuator (2); - a first measuring wheel (7) driven by the rotor element (4); - a second measuring wheel (8) which is driven by the first measuring wheel (7) with a different gear ratio from one, wherein the measuring wheels (7,8) each have a readable marking (9,10) of the respective rotational position (11,12), characterized by , that one of the measuring wheels (8) is designed as a ring gear, wherein the other measuring wheel (7) is arranged radially inside the ring gear. [2] Absolute position measuring device (1) according to claim 1, wherein the ring gear is formed by the second measuring wheel (8). [3] Absolute position measuring device (1) according to claim 1 or 2, wherein the first measuring wheel (7) is fixedly connected to the rotor element (4), preferably formed in one piece therewith. [4] Absolute position measuring device (1) according to one of the preceding claims, wherein the first measuring wheel (7) has a first marking (9) and the second measuring wheel (8) has a second marking (10), and wherein the respective readable marking (9, 10) is formed by means of one of the following devices: - an optical bar code (13); - an inductive bar code (14); - a magnetic position coding (15); and - a ring magnet (16), wherein preferably the principle of the first marking (9) and the principle of the second marking (10) are free from interference with each other. [5] Absolute position measuring device (1) according to one of the preceding claims, wherein the measuring wheels (7, 8) are designed as gear wheels. [6] Spindle actuator (2) for an actuating actuator (3,60), wherein the spindle actuator (2) has at least the following components: - an electric drive unit (6) comprising a stator (17) and a rotor (5); - a spindle (18) with a spindle axis (19) which can be driven by means of the rotor (4); - an absolute position measuring device (1) according to one of the preceding claims, which is connected to the rotor (5) by means of the rotor element (4) and by means of which the absolute angular position of the rotor (4) can be detected; - a measuring device (20) for detecting the markings (9,10) of the absolute position measuring device (1); - control electronics (21) by means of which the spindle (18) can be moved in a controlled manner on the basis of the measurements of the measuring device (20). [7] Spindle actuator (2) according to claim 6, wherein the stator (17) has a stator overmolding (22) and the second measuring wheel (8) is mounted on the stator overmolding (22). [8] Spindle actuator (2) according to claim 6 or 7, wherein the spindle (18) is rotationally fixed and is axially movable by means of a spindle nut (23), wherein the spindle nut (23) preferably comprises a pitch-accurate planetary roller gear (24) for transmitting the rotation to the spindle (18), and the measuring wheels (7, 8) are arranged around the spindle axis (19), wherein preferably the first measuring wheel (7) is arranged concentrically and the second measuring wheel (8) is arranged eccentrically to the spindle axis (19). [9] Hydrostatic actuating actuator (3) for a friction clutch (25), comprising at least the following components: - a spindle actuator (2) according to one of claims 6 to 8; - a master piston (26) which can be driven by the spindle (18) for translational movement; - a master cylinder (27) for receiving the master piston (26) and a hydraulic fluid, wherein the master cylinder (27) can be connected to a slave cylinder (28) in a communicating manner by means of the hydraulic fluid, wherein the measuring device (20) and the control electronics (21) are preferably arranged on a common circuit board (29), preferably for end-side arrangement at the rotor (4) behind the electric drive unit (6) as seen from the master piston (26). [10] Mechanical actuating actuator (60) for a friction clutch (25), comprising at least the following components: - a spindle actuator (2) according to one of claims 6 to 8; - an actuating connecting rod (61) which can be driven by means of the spindle (18) for translational movement, wherein the actuating connecting rod (61) is preferably connectable to an actuating device (46, 47) of a friction clutch, wherein the measuring device (20) and the control electronics (21) are preferably arranged on a common circuit board (29), preferably for end arrangement at the rotor (4) behind the electric drive unit (6) as seen from the actuating connecting rod (61).

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