PNEUMATIC ACTUATOR WITH WEAR COMPENSATION

Description

[0001] The invention relates to a pneumatic actuator for actuating a functional element, in particular a pneumatic clutch actuator for a commercial vehicle for actuating a clutch of the commercial vehicle, comprising a pneumatic piston, a pneumatic housing, wherein the pneumatic piston is arranged displaceably in the pneumatic housing for executing a stroke along an actuating axis, an interface holder with an interface for connecting the pneumatic actuator to the functional element, and a wear compensation device which is designed to temporarily fix the pneumatic piston and the interface holder for transmitting an actuating force from the pneumatic piston to the interface holder and to release the temporary fixation between the pneumatic piston and the interface holder for compensating for a wear-related change in the stroke of the functional element.

[0002] In vehicles, particularly commercial vehicles, there are several options for implementing an automatic transmission. In addition to automatic transmissions (AT), automated manual transmission systems (AMT) are frequently used. AMT systems consist of a conventional manual transmission that is operated automatically. Modern AMT systems can also be based on transmissions developed specifically for this purpose. In an AMT system, a clutch that connects the transmission to the drive shaft of the vehicle engine is usually operated automatically to eliminate manual clutch operation. A clutch actuator opens the clutch, and then a transmission actuator changes the gear. After the gear change, the clutch actuator releases the clutch and engages the drive shaft and the transmission. Common types of clutch actuators are electromechanical, hydraulic, or pneumatic.

[0003] There are two common types of pneumatic clutch actuators. Linear pneumatic actuators have a pneumatic piston slidably mounted within a cylinder. When actuated, the cylinder is filled with air, moving the piston relative to the cylinder. The piston is connected to an actuating rod that actuates the clutch. Since the vehicle engine's drive shaft must be in line with the clutch and transmission, commercially available linear pneumatic clutch actuators are mounted offset from the clutch. The actuating rod is designed as a fork-like rod that extends perpendicular to the piston's actuating direction. To achieve the required mechanical strength, such an actuating system must generally be very large and heavy. Furthermore, multiple parts are required, resulting in complex and often expensive systems.

[0004] Concentric pneumatic clutch actuators consist of a pneumatic housing and a pneumatic piston, which is movably arranged in a pneumatic chamber of the pneumatic housing. The pneumatic piston can be moved back and forth within the pneumatic housing and can actuate a functional element. The pneumatic housing has a central opening to allow a shaft to pass through the pneumatic actuator. Pneumatic clutch actuators can therefore be arranged around a drive or output shaft, with the pneumatic piston directly actuating the clutch. The need for a deflection is eliminated. Because the pneumatic piston directly actuates the clutch coaxially, mechanical stresses are reduced, and concentric clutch actuators can be manufactured smaller. Furthermore, fewer parts are required, which reduces overall costs.

[0005] Functional elements wear out over their service life. For example, vehicle clutches typically have clutch plates fitted with friction linings that are pressed together with a clutch reaction force to transmit power. A force applied by the pneumatic actuator, which counteracts the clutch reaction force, allows the friction linings of the clutch plates to separate from each other. When the clutch is engaged, a relative movement occurs between the two clutch plates, also known as slippage. The friction linings rub against each other and transfer only a portion of the torque applied to the clutch from one clutch plate to the other. This friction causes the friction linings to wear.

[0006] To compensate for friction lining wear, an actuator operating the clutch must perform a longer stroke. In addition to an activation stroke, a wear stroke must also be performed. The wear stroke can exceed the stroke required to open the clutch. This wear stroke leads, on the one hand, to an increased demand for working fluid (especially air), resulting in increased operating costs, and, on the other hand, to reduced positioning accuracy.

[0007] To compensate for the wear of the functional element, pneumatic actuators with wear compensation mechanisms are known.

[0008] WO 2016 / 184569 A1 discloses a clutch actuator with automatic wear compensation. For this purpose, the clutch actuator has an actuating element designed as a piston and a piston rod. The piston rod transmits a release force applied to the actuating element to the clutch. The actuating element has a clamping element. When the release force is applied to the piston, it is supported on the clamping element in a form-fitting and force-fitting manner. The clamping element partially deflects the release force into a normal force, so that the actuating element and the piston rod are frictionally fixed. When the force acts in the opposite direction, the frictional engagement is released, and the piston rod can slide against the clamping element to compensate for length. A disadvantage is that the arrangement according to WO 2016 / 184569 A1 is only suitable for concentric pneumatic actuators.Furthermore, the small contact surfaces on the clamping element result in very high mechanical loads, which can lead to damage. Furthermore, the wing-like design of the clamping element means that frictional engagement cannot be permanently ensured under high loads.

[0009] EP 2 683 960 B1 discloses a self-adjusting clutch actuator for operating a vehicle clutch, comprising a piston configured to act on the vehicle clutch via a transmission member. A compensation mechanism is arranged between the piston and the transmission member, which is capable of switching between an unlocked state, in which the piston adjusts its length, and a locked state, in which it is locked to a fixed length.The compensation mechanism includes a positive gearing that converts any length adjustment movement into a corresponding relative movement of a first and a second component of the compensation mechanism, and vice versa. The compensation mechanism is configured to effect its locked state by bringing the first and second components into frictional engagement with each other, thereby preventing length adjustment movements of the compensation mechanism. The compensation mechanism is configured to respond to the state of movement of the piston, such that the change from the locked to the unlocked state occurs when the piston reaches its end-stop position due to a depressurization of the chamber, and that a change from the unlocked to the locked state is effected when it leaves its end-stop position due to the next pressurization of the chamber.The length compensation mechanism has a spring mechanism that drives a change in length using a preload force of the clutch. The clutch actuator according to EP 2 683 960 B1 is also unsuitable for concentric pneumatic actuators. Furthermore, the design is complex, and the achievable friction force is limited due to the low ratio of friction diameter to thread diameter. Furthermore, the compensation mechanism is subject to high mechanical loads, which can limit the service life of the clutch actuator.

[0010] DE102017210444A1 discloses an actuating device for a motor vehicle, comprising a working cylinder and a working piston, which form a pressure chamber for filling with a pressure medium, wherein the working piston has a main piston and an actuating piston, which are designed to be displaceable relative to one another in order to provide a variable effective length of the working piston, wherein a clamping device is formed on the working piston, which prevents displacement between the main piston and the actuating piston during a disengagement process of the actuating device and thereby fixes the effective length for the disengagement process.

[0011] DE102019204352A1 relates to a pressure fluid actuating arrangement for a friction clutch, comprising a first actuating element and a second actuating element which delimits a pressure fluid chamber with the first actuating element, wherein by introducing pressure fluid into the pressure fluid chamber, the second actuating element is movable from a basic positioning with respect to the first actuating element in an actuating direction along a movement axis.

[0012] DE102018210628A1 discloses a self-adjusting clutch actuator for actuating a clutch, comprising a transmission element which is provided for displacement in a displacement direction, a compensation mechanism with a piston which is provided for displacement in the displacement direction of the transmission element, wherein the compensation mechanism is designed to enable a relative displacement of the transmission element in the displacement direction with respect to the piston.

[0013] The object of the present invention is to provide a pneumatic actuator of the type mentioned above which can be used flexibly and which, compared to the prior art, allows a particularly safer and / or more reliable transmission of actuating forces.

[0014] The invention solves the problem in a pneumatic actuator of the type mentioned at the outset in a first aspect in that the wear compensation device has an extension sleeve. An extension sleeve is a sleeve whose diameter can be varied by applying a change in length. By stretching the extension sleeve in the longitudinal direction, the diameter of the extension sleeve can be reduced, i.e. the extension sleeve can be contracted. By compressing the extension sleeve, i.e. by shortening the extension sleeve in the longitudinal direction, the diameter of the extension sleeve increases or expands. It should be understood that the extension sleeve is further developed in order to bring about the contraction or expansion effect, and that not every tubular element represents an extension sleeve within the meaning of the invention. Thus, even the diameter of simple tubes contracts slightly when stretched in the longitudinal direction.However, this effect is extremely small, so a simple tube does not constitute an extension sleeve. The pneumatic actuator can be designed either as an (external) linear pneumatic actuator or as a concentric pneumatic actuator, with a concentric pneumatic actuator being preferred.

[0015] The contraction and expansion can also only occur partially and does not have to occur over the entire length of the extension sleeve in its longitudinal direction. The extension sleeve can preferably be open on both sides, i.e. tubular, or closed on one side. The extension sleeve does not have to be designed in a similar way to extension sleeves for medical applications. For example, the extension sleeve can be designed as a braid, but this is not necessary. Preferably, in the relaxed state, the length of the extension sleeve is smaller than its diameter. This achieves an axially short design and saves installation space. However, it can also be provided that the diameter of the extension sleeve in the relaxed state is smaller than its length. The extension sleeve can also preferably have jumps or steps in diameter.

[0016] The actuating axis is the axis along which the pneumatic piston can be displaced during actuation. In a pneumatic housing that defines a cylindrical cavity for accommodating the piston, the actuating axis is defined, for example, by the central axis of the cylindrical cavity. Preferably, the actuating axis and an actuation axis of the functional element, along which the functional element is moved during actuation, are parallel, particularly preferably congruent.

[0017] The actuating force is preferably oriented along the actuating axis, in particular parallel to the actuating axis. If the pneumatic piston and the interface holder are temporarily fixed by the wear compensation device, then an actuating force acting on the pneumatic piston along the actuating axis preferably also acts along the actuating axis on the interface holder. The wear compensation device is preferably designed to release the temporary fixation between the pneumatic piston and the interface holder when no actuating force is transmitted. An extension sleeve enables simple and reliable transmission of high actuating forces. Furthermore, extension sleeves are robust against mechanical stress and can be manufactured cost-effectively. Furthermore, a bidirectional wear compensation device can be provided by means of an extension sleeve.For example, when installing a new clutch, a shortening or lengthening of the wear compensation device can be achieved in the opposite direction to the wear compensation.

[0018] In order to actuate the functional element, the pneumatic actuator must perform a stroke. A wear-related stroke change is the change in this stroke caused by wear of the functional element. If the functional element is a clutch, for example, the friction linings of this clutch can wear out and become smaller over its service life. To actuate the clutch, the pneumatic actuator must then perform a stroke that is longer or shorter than when the clutch was new. The pneumatic actuator must therefore perform a wear stroke in addition to or minus the working stroke required to actuate a new clutch. This change in the stroke to be performed by the pneumatic actuator is the wear-related stroke change.

[0019] In a first preferred embodiment, to create the temporary fixation between the extension sleeve and the interface holder, a radial force can be generated by radial contraction of the extension sleeve, which acts from the extension sleeve to the interface holder. To create the radial contraction of the extension sleeve, the extension sleeve is stretched longitudinally. For this purpose, when the actuating force is transmitted from the pneumatic piston to the interface holder, a longitudinal force, which is preferably identical to the actuating force, acts on the extension sleeve. The extension sleeve is therefore preferably stretched when the actuating force is transmitted. However, it can also be provided that the extension sleeve is compressed when the actuating force is transmitted. To temporarily fix the pneumatic piston and interface holder, the radial force is generated, which acts from the extension sleeve to the interface holder.The radial force creates a frictional connection between the extension sleeve and the interface holder. This frictional connection preferably prevents relative movement between the extension sleeve and the interface holder. The radial force preferably scales with the actuating force.

[0020] The radial force is preferably substantially directly proportional to the actuating force. The actuating force is preferably proportional to the radial force. The actuating force is particularly substantially directly proportional to the actuating force when a force component of a spring of the wear compensation device is neglected. If the actuating force transmitted from the pneumatic piston to the interface holder increases, the radial force also increases due to the directly proportional relationship. The radial force causes the frictional connection or the frictional force required for this. As the actuating force to be transmitted increases, the frictional force increases, so that the fixation between the pneumatic piston and interface holder is strengthened. By means of the extension sleeve, even high actuating forces can be transmitted reliably. Slipping or unintentional relative sliding of the interface holder to the pneumatic piston can be effectively prevented.Damage to the pneumatic actuator's components is prevented, and actuating forces can be transmitted reliably. Preferably, the radial force is linearly proportional to the actuating force. Doubling the actuating force, for example, will then also double the radial force.

[0021] In a further preferred embodiment, a force ratio between the radial force and the actuating force has a value of 10 or greater. The force ratio is determined by dividing the value of the radial force by the value of the actuating force. With a force ratio of 10, the radial force is ten times the value of the actuating force. The inventor has discovered that, in particular, a reliable transmission of actuating forces is possible with a force ratio of 10 or greater. Thus, slippage is effectively prevented with this force ratio, since typical friction values ​​are in the range of 0.1 or higher. Preferably, the force ratio is greater than or equal to an inverse value of a friction value between the extension sleeve and the interface holder.

[0022] In one variant, the extension sleeve has a first extension slot that extends helically around the adjustment axis in a first thread direction. It can also be provided that the first extension slot extends helically around a central axis of the extension sleeve. The first extension slot preferably extends in a side wall of the extension sleeve. Preferably, the first extension slot extends completely through the sleeve wall of the extension sleeve in the radial direction. The first extension slot therefore preferably extends completely from an inner diameter of the extension sleeve to an outer diameter. Synonymous with helical, the extension of the extension slot can also be described as helical or screw-shaped. The thread direction, which can also be referred to as the winding direction or helicity, is determined by viewing along the adjustment axis.The extension slit primarily causes the contraction or expansion effect of the extension sleeve. By providing the extension slit, the extension sleeve can be stretched more extensively in the longitudinal direction, with the extension slit then enabling improved contraction or expansion transverse to the longitudinal direction (in the diameter direction).

[0023] The extension slot preferably has at least half a turn, preferably one full turn, along the adjustment axis. The extension slot preferably has 0.25 to 4, preferably 0.5 to 3, preferably 0.5 to 2, particularly preferably 0.5 to 1.5 full turns. One turn extends circumferentially once over the entire circumference, so that the beginning and end of a full turn are only offset from one another in the longitudinal direction of the helix. A radial force that can be generated by the extension sleeve is directly proportional to the number of turns of the first extension slot. Thus, the radial force that can be generated for an identical longitudinal force with two full turns is twice as large as with one turn of the extension slot, but only half as large as with a total of four turns. The radial force provided by the extension sleeve can advantageously be scaled by selecting the number of turns.Preferably, the actuating force is transmitted to the extension sleeve as a longitudinal force. The number of windings can then advantageously be selected so that a frictional connection can always be reliably achieved when transmitting the actuating force.

[0024] It is further preferred that the first extension slot has a first pitch angle in a range of greater than 0° to 20°, preferably 1° to 20°, more preferably 1° to 15°, more preferably 1° to 12°, more preferably 1° to 10°, more preferably 2° to 10°, more preferably 2° to 8°, more preferably 2° to 6°, particularly preferably 3° to 6°. The pitch angle determines the pitch and the pitch ratio of the first extension slot. The pitch is the extension of one complete turn in the longitudinal direction of the extension sleeve. The pitch ratio is determined as the extension of one complete turn in the radial direction divided by the extension of one complete turn in the longitudinal direction. The radial force that can be generated by means of the extension sleeve is indirectly proportional to the pitch angle. The smaller the pitch angle, i.e. the flatter the pitch, the greater the radial force that can be provided by the extension sleeve.The inventor has discovered that a particularly safe and reliable transmission of actuating forces is possible by using a pitch angle within the preferred range. Preferably, the pitch or pitch angle of the first extension slot is constant. However, it can also be provided that the extension slot has a variable pitch. For example, central turns located between outer turns can have a greater or smaller pitch than the outer turns.

[0025] In a further preferred embodiment, the extension sleeve has a second extension slot which extends helically around the adjusting axis in a second thread direction. The extension sleeve can also have more than two, preferably 2 to 10, particularly preferably 3 to 6, extension slots. A plurality of extension slots allows loads to be distributed evenly across the extension sleeve. It should be understood that the second thread direction can also be identical to the first thread direction. The first extension slot and the second extension slot can, for example, both be right-handed. Preferably, the second extension slot has a second pitch angle which is identical to the first pitch angle. Furthermore, the second extension slot also preferably has at least half a turn, particularly preferably a full turn.However, it can also be provided that the first extension slot and the second extension slot have different thread directions, number of turns, and / or pitch angles. Preferably, the first extension slot and the second extension slot partially or completely overlap. It can also be provided that the first extension slot and the second extension slot are offset from one another in the direction of the adjustment axis.

[0026] In a preferred embodiment, the pneumatic actuator has a plurality of extension slots, wherein the plurality of extension slots extend around the actuating axis in the form of a multiple helix, in particular as a double helix, triple helix, or quadruple helix. It should be understood that in the case of a double helix, the pneumatic actuator must have at least two extension slots, and in the case of a triple helix, at least three extension slots, etc. A multiple helix arrangement enables a particularly reliable and uniform transmission of actuating forces. Furthermore, a multiple helix arrangement (double helix, triple helix, quadruple helix, etc.) can effectively prevent tilting moments that can arise when external forces are applied to the extension sleeve. It can also be provided that the ends of the extension slots are partially offset from one another along the actuating axis.The multiple helix is ​​particularly preferably a double helix, triple helix, quadruple helix, quintuple helix, sextuple helix, sevenfold helix, eightfold helix, ninefold helix, or tenfold helix. The deformation of the extension sleeve is more uniform the higher the number of extension slots in the helix arrangement. However, with the additional number of extension slots, the manufacturing costs also increase. The inventor has discovered that with a multiple helix arrangement from the aforementioned range (double helix to tenfold helix), particularly favorable application properties of the extension sleeve can be achieved at low manufacturing costs.

[0027] Preferably, the pneumatic actuator has a torsion lock to prevent relative rotational movement between the extension sleeve and the interface holder. A torsion lock prevents the extension sleeve from performing a torsional movement during stretching and / or compression, which could counteract the contraction and / or expansion of the extension sleeve. The torsion lock thus allows for reliable transmission of actuating forces.

[0028] In a preferred embodiment, the first direction of the first extension slot and the second direction of the second extension slot are opposite to each other.

[0029] It is further preferred that the extension sleeve has a securing groove that extends in the direction of the adjustment axis, wherein the anti-twist device has a securing element that engages in the securing groove. The securing element preferably engages in the securing groove in a form-fitting manner. The securing groove is preferably arranged offset in the direction of the adjustment axis from the first and / or second extension slot. However, it can also be provided that the securing groove is arranged in the region of at least one of the extension slots. Particularly preferably, the securing groove extends in the direction of the adjustment axis completely through a helical region in which the extension slot extends along the adjustment axis through the extension sleeve. Torsion may occur in the section of the extension sleeve (viewed along the adjustment axis) in which the extension slot extends.The torsion lock can therefore preferably only be provided in this section (the helical region). However, it can also be provided that the extension slot extends completely through the extension sleeve. In the diameter direction, the securing groove preferably extends only partially through the extension sleeve. Preferably, the torsion lock can also have multiple securing elements, which preferably engage in different securing grooves in the extension sleeve. If the torsion lock has multiple securing elements, these are preferably offset from one another in the circumferential direction of the extension sleeve, particularly preferably regularly offset. The securing element is preferably a dowel pin or a key. However, the securing element can preferably also be a pin of the interface holder.

[0030] In a further embodiment, the extension sleeve comprises a first partial sleeve and a second partial sleeve, which are arranged coaxially with each other and connected to each other. Preferably, the first partial sleeve and the second partial sleeve have an identical diameter.

[0031] Preferably, the second partial sleeve is arranged radially within the first partial sleeve, wherein a first end of the first partial sleeve is connected to an adjacent first end of the second partial sleeve, and wherein a second end of the first partial sleeve, which is opposite the first end of the first partial sleeve along the adjustment axis, is connected to a second end of the second adjustment sleeve, which is opposite the first end of the second partial sleeve along the adjustment axis. The two partial sleeves are thus connected at two opposite ends. Between the connected ends, the partial sleeves are preferably free of connections. Connection-free partial sleeves are not connected by a material fit. The partial sleeves can abut one another, in particular on cylindrical outer surfaces.

[0032] The ends of the partial sleeves are preferably connected by a material bond. For example, the first partial sleeve and the second partial sleeve can be welded together. Furthermore, the first partial sleeve and the second partial sleeve can also be connected to one another by gluing, clamping, screwing, riveting, pressing and / or soldering. Extension slots in the partial sleeves preferably have oppositely oriented thread directions, so that the partial sleeves are at least partially designed as mutual torsion protection. The first partial sleeve and the second partial sleeve are preferably adapted to one another such that their contraction behavior under load is essentially identical. When a load is applied to the ends of the extension sleeve, the first partial sleeve should therefore contract essentially identically to the second partial sleeve.For this purpose, the partial sleeves can preferably be designed essentially identically, with the exception of different diameters and opposing thread directions. For example, the wall thicknesses, pitch angles of the extension slots, slot widths of the extension slots, and / or number of turns of the extension slots of both partial sleeves can be essentially identical. In particular, the slot width, number of turns, and / or pitch angle of the extension slots can also be different in order to match the contraction behavior of the first partial sleeve to the contraction behavior of the second partial sleeve.

[0033] The extension sleeve preferably has a first end and a second end opposite the first end along the adjustment axis, with the first end abutting the pneumatic piston in the direction of the adjustment axis. The first end is preferably designed as a collar that abuts the pneumatic piston in the direction of the adjustment axis. The first end is preferably circumferentially symmetrical. Alternatively or additionally, the extension sleeve can have one or more retaining lugs for engaging the pneumatic piston.

[0034] In a further embodiment, the pneumatic actuator comprises a spring that preloads the interface holder against the second end of the extension sleeve. If there is no frictional engagement between the extension sleeve and the interface holder, the spring can preferably move the interface holder relative to the extension sleeve. The spring is preferably arranged radially in the extension sleeve.

[0035] Furthermore, the pneumatic actuator preferably has a decoupling element designed to decouple the pneumatic piston from the interface holder in an end position and to connect the interface holder directly or indirectly to the pneumatic housing in a force-conducting manner. The end position of the pneumatic piston is the position the pneumatic piston assumes when no actuating force is to be transmitted. It should be understood that the pneumatic piston is decoupled (load-free) even when the interface holder and pneumatic housing are indirectly connected. For example, an indirect connection could be realized by an intermediate plate arranged between the pneumatic housing and the interface holder.In the end position, the decoupling element decouples the pneumatic piston so that forces applied to the interface holder via the interface are not transferred to the piston but are diverted directly via the housing. This can prevent loads on the piston in the end position. Wear and tear on the piston is reduced and damage is prevented. Preferably, the decoupling element additionally and / or alternatively decouples the extension sleeve so that no or reduced longitudinal forces act on the extension sleeve in the end position of the pneumatic piston. This can prevent or reduce frictional engagement between the extension sleeve and the interface holder. In the end position, the extension sleeve and the interface holder are therefore preferably movable relative to one another.Preferably, even in the end position, with the pneumatic cylinder decoupled, a preload force is transmitted to the interface unit. The preload force is preferably applied by the spring to the interface holder, with the preload force preferably being supported on the housing via the extension sleeve and the decoupling element. Particularly preferably, a preload force applied by the spring is in a range from 100N to 1kN, preferably 100N to 900N, preferably 100N to 800N, preferably 100N to 700N, preferably 100N to 600N, preferably 100N to 500N, preferably 200N to 500N, preferably 200N to 400N, particularly preferably 250N to 350N.

[0036] According to a preferred embodiment, the pneumatic piston is an annular piston which is guided in the housing on at least one outer guide surface and has an inner receiving space, wherein the interface holder and the wear compensation device are arranged at least partially in the inner receiving space. The outer guide surface can be arranged both radially inside and radially outside the inner receiving space. The outer guide surface is a surface of the pneumatic cylinder facing away from the inner receiving space. For example, an annular piston can be guided on a radially inner surface on a corresponding guide shaft of the pneumatic housing. Additionally or alternatively, the piston can be guided on a radially outer surface in the pneumatic housing.Arranging the wear compensation device and the interface holder in the inner receiving space enables a simple and particularly compact design of the pneumatic actuator. The pneumatic piston preferably has a substantially U-shaped cross-section that defines the receiving space. The outer guide surface can preferably be formed by one or more sliding bushings. The pneumatic piston is preferably designed as an annular piston, especially when the pneumatic actuator is a concentric pneumatic actuator.

[0037] The first extension slot preferably extends over a longitudinal section of 10% to less than 100%, preferably 10% to 90%, preferably 10% to 80%, preferably 20% to 80%, preferably 20% to 70%, preferably 30% to 70%, preferably 30% to 60%, preferably 30% to 50%, particularly preferably 40% to 60%, of an axial length of the extension sleeve. The axial length of the extension sleeve is determined along the longitudinal axis of the extension sleeve, which is preferably parallel to the adjustment axis. It can also be provided that several extension slots extend together over the preferred longitudinal section. For example, the first extension slot can extend over a longitudinal section of 30% and the second extension slot can extend over a longitudinal section of 30% offset in the longitudinal direction of the extension sleeve, so that the extension slots then extend together over a longitudinal section of 60%.With a first extension slot extending over the preferred longitudinal section, sufficient flexibility of the extension sleeve can be achieved.

[0038] It is further preferred that the frictional connection can be produced by radial contraction of the extension sleeve by 0% to 5%, preferably 0.01% to 4.5%, preferably 0.0% to 4.5%, preferably 0.01% to 4%, preferably 0.01% to 3%, preferably 0.01% to 1%, particularly preferably 0.01% to 0.05% of an inner diameter of the extension sleeve. The extension sleeve can already rest against the interface holder in the relaxed state. However, there is no frictional connection as long as the extension sleeve is relaxed. Nevertheless, in the case of an extension sleeve resting against the interface holder, only an infinitesimally small contraction (a contraction of 0%) is necessary to produce the frictional connection. To determine the contraction, the contracted inner diameter in comparison to the inner diameter in the unloaded state is decisive. For example, if an inner diameter of 100 mm decreases to 99 mm when contracted, this corresponds to a contraction of 1%.The preferential contraction to create the frictional connection ensures low stress on the extension sleeve. Furthermore, a large contraction allows for larger gaps, which facilitates the manufacturing and assembly of the pneumatic actuator.

[0039] The extension sleeve is preferably made at least in sections from steel, particularly preferably from a steel and / or spring steel suitable for deep-drawing processes. The interface holder is preferably made at least in sections from steel, particularly preferably from cast steel or cast iron. Furthermore, the pneumatic piston and / or the pneumatic housing are preferably made at least in sections from aluminum, preferably die-cast, sand-cast, or cold-forming alloys. Alternatively or additionally, the pneumatic housing is made at least in sections from steel, particularly a steel suitable for deep-drawing processes. It should be understood that the terms steel and aluminum also include alloys.

[0040] In a second aspect, the object mentioned at the outset is achieved by a clutch arrangement for a commercial vehicle, comprising a clutch and a pneumatic actuator according to the first aspect of the invention, wherein the pneumatic actuator is provided for opening and / or closing the clutch.

[0041] In a third aspect, the invention achieves the object mentioned above by means of a commercial vehicle having a clutch arrangement according to the second aspect of the invention. It should be understood that the pneumatic actuator according to the first aspect of the invention, the clutch arrangement according to the second aspect of the invention, and the vehicle according to the third aspect of the invention have identical or similar sub-aspects, as set out in particular in the dependent claims. In this respect, reference is made in full to the above description for these aspects.

[0042] Embodiments of the invention will now be described below with reference to the drawings. These are not necessarily intended to depict the embodiments to scale; rather, the drawings are presented in a schematic and / or slightly distorted form where this is useful for explanation. For supplements to the teachings immediately apparent from the drawings, reference is made to the relevant prior art.

[0043] It should be noted that various modifications and changes to the form and detail of an embodiment can be made within the scope of protection defined by the claims.

[0044] For the sake of simplicity, the same reference numerals are used below for identical or similar parts or parts with identical or similar functions.

[0045] Further advantages, features and details of the invention will become apparent from the following description of the preferred embodiment and from the drawings, which show: Figure 1a a schematic coupling arrangement with a pneumatic actuator and a closed coupling; Figure 1b the coupling arrangement according to Figure 1a , wherein the clutch is open; Figure 2a a sectional view of a pneumatic actuator in an initial state, wherein the pneumatic actuator is not actuated; Figure 2b the sectional view according to Figure 2b , wherein the pneumatic actuator is actuated; Figure 2c a sectional view of a pneumatic actuator in a state with maximum wear compensation, wherein the pneumatic actuator is actuated; Figure 2d the sectional view according to Figure 2d, wherein the pneumatic actuator is unactuated; Figure 3a shows a sectional view through a first embodiment of an extension sleeve; Figure 3b shows a sectional view through an alternative embodiment of an extension sleeve; Figure 3c shows a double half-sectional view of an alternative embodiment of an extension sleeve; Figure 4 shows a coupling arrangement with a linear actuator, and Figure 5 shows a commercial vehicle with a coupling arrangement.

[0046] A coupling arrangement 100 comprises a pneumatic actuator 1 and a functional element 101, which in this case is a clutch 102. The pneumatic actuator is designed as a concentric pneumatic actuator 1. The clutch 102 and the pneumatic actuator 1 are connected by an actuating lever 104. In particular, in the case of a linear pneumatic actuator 5 (cf. Figure 4 ), the adjusting lever 104 can also have several lever segments and / or joints. In the Figures 1a and 1bIn the illustrated embodiment, the adjusting lever 104 extends from a first clutch disc 106 to a ball bearing 108, which forms an interface 110 between the pneumatic actuator 1 and the clutch 102. The interface 110, designed as a ball bearing 108, enables a rotational movement of the first clutch disc 106 relative to the pneumatic actuator 1. The pneumatic actuator 1 can thus preferably be designed to be rotationally fixed, which enables simple attachment.

[0047] A restoring force FR of the clutch 102 presses the first clutch disc 106 against a second clutch disc 112. The restoring force FR can be applied to the clutch 102, for example, by a closing spring (not shown). The restoring force presses a first friction lining 114 of the first clutch disc 106 against a second friction lining 116 of the second clutch disc 112, creating a frictional engagement between the friction linings 114, 116. This allows a torque M to be transmitted from an input shaft 118 to an output shaft 120.

[0048] In order to shift a transmission (not shown) that is connected to the input shaft 120, the input shaft 118 and the output shaft 120 must be separated. To separate the shafts 118, 120, the pneumatic actuator 1 applies an actuating force FS to the first clutch disc 106, which acts counter to the restoring force FR. The actuating force FS is greater in magnitude than the restoring force FR, so that the first clutch disc 106 is moved in the actuating direction RS. To apply the actuating force FS, a pneumatic piston 10 of the pneumatic actuator 1 is moved along an actuating axis AS of the pneumatic actuator in the actuating direction RS. The pneumatic piston executes a stroke H. The actuating direction RS of the pneumatic actuator 1 can, in principle, be different from a direction of movement of the first clutch disc 106, for example, through the use of deflection rods.

[0049] By moving the first clutch disc 106 in the actuating direction RS, the friction linings 114, 116 are separated from each other, so that no more torque M is transmitted from the input shaft 118 to the output shaft 120. In the then load-free state, a gear of the transmission can be changed. Subsequently, the actuating force FS is reduced, so that the restoring force FR of the clutch 102 moves the first clutch disc 106 toward the second clutch disc 112, opposite the actuating direction RS.

[0050] If the input shaft 118 and the output shaft 120 have different speeds, these speeds must be adjusted. To achieve this, the friction linings 114, 116 are brought into contact, rotating relative to each other until the output shaft 120 has been accelerated or decelerated to the speed of the input shaft 118. The relative movement of the first friction lining 114 to the second friction lining 116 is also referred to as slippage.

[0051] As soon as the shafts 118, 120 have identical speeds, slippage no longer occurs and the torque M of the input shaft 118 is transmitted frictionally from the second clutch disc 112 to the first clutch disc 106. Over its life cycle, the clutch 102 is opened and closed many times, whereby different speeds of the input shaft 118 and output shaft 120 usually have to be compensated by slippage. This leads to wear of the friction linings 114, 116 occurring over the service life of the clutch 102. Due to the wear of the friction linings 114, 116, the clutch discs 106, 112 move towards each other (in Figure 1a and Figure 1bthe first clutch disc 106 moves to the right). This movement is caused by the restoring force FR. In order to compensate for the wear-related change in a clutch length LK, measured in the adjustment direction RS between the clutch discs 106, 112, a wear compensation device 3 is provided on the pneumatic actuator 1, which with reference to the Figures 2a to 2d is explained in more detail.

[0052] The wear of the friction linings 114, 116 causes the first clutch disc 106 to move towards the pneumatic actuator 1, so that the pneumatic actuator 1 must be shortened in this embodiment to compensate for wear.

[0053] The structure of the pneumatic actuator 1 will now be described with reference to Figure 2a explained in more detail. Figure 2ashows the pneumatic actuator 1 in an actuated state. The pneumatic actuator 1 is therefore shown in a state in which a clutch 102 connected to it is open (compare Figure 1b ). In this embodiment, the pneumatic actuator 1 is designed as a ring actuator 2. The pneumatic actuator 1 has a pneumatic housing 4 that defines a pneumatic cylinder 6. A guide shaft 8 of the concentric pneumatic actuator 2 is tubular, so that the drive shaft 118 can be passed through the pneumatic actuator 1 in the actuating direction RS.

[0054] A pneumatic piston 10 is slidably arranged in the pneumatic cylinder 6 of the pneumatic housing 4. The pneumatic piston 10 is guided by the guide shaft 8 of the pneumatic housing 4, so that it can be moved in the adjustment direction RS along the adjustment axis AS. However, it can also be provided that the pneumatic piston 10 is alternatively or additionally guided on an outer circumference of the pneumatic piston 10 (see in particular also Figure 4). An outer guide surface 12 is in contact with the guide shaft 8 for guiding the pneumatic piston 10. It can be provided that the pneumatic piston 10 has guide rings (not shown). These guide rings can be made of particularly wear-resistant and / or lubricious material. Alternatively or additionally, it can also be provided that the pneumatic piston 10 is guided on a second outer guide surface 14 arranged on the outer diameter. Furthermore, the pneumatic cylinder 6 can be sealed by seals (not shown) so that pressure medium introduced into the pneumatic cylinder 6, preferably air, cannot escape through gaps formed between the pneumatic piston 10 and the pneumatic housing 4.

[0055] To introduce air into the pneumatic cylinder 6 or the volume enclosed between the pneumatic piston 10 and the pneumatic housing 4, the pneumatic housing 4 has supply and discharge channels (not shown). To move the pneumatic piston 10, air or another suitable pressurized pressure medium is introduced into the pneumatic cylinder 6, so that the pneumatic piston 10 is moved out of the pneumatic cylinder 6 in the actuating direction RS along the actuating axis AS. By removing the pressure or venting the pneumatic cylinder 6, the pneumatic piston 10 can be moved into the pneumatic piston 6 against the actuating direction RS along the actuating axis AS. During operation, the pneumatic piston 10 can be moved back and forth into the pneumatic cylinder 6 by supplying and discharging pressure medium.

[0056] The movement of the pneumatic piston 10 is at least partially caused by the restoring force FR acting on the interface 110 along the actuating axis AS. To move the pneumatic piston 10 in the actuating direction RS, the pressure medium exerts the actuating force FS on an active surface 16 of the pneumatic piston 10, which in this case is an underside of the pneumatic piston 10.

[0057] The interface 110, designed as a ball bearing 108, is arranged on an interface holder 18 of the pneumatic actuator 1. Preferably, an outer ring 108a of the ball bearing 108 is fixed to the interface holder 18 of the pneumatic actuator by means of fastening means not shown in detail. It can also be provided that an inner ring 108b of the ball bearing 108 is fixedly connected to the interface holder 18 and an outer ring 108a is connected to the coupling 102. In this exemplary embodiment, the interface holder 18 is cylindrical and has a radially inwardly projecting shoulder 20 on which the outer ring 108a of the ball bearing 108 is arranged.

[0058] The interface holder 18 is partially inserted into an extension sleeve 22. In the Figure 2aIn the actuated state shown, an outer surface 24 of the interface holder 18 is in contact with an inner surface 26 of the extension sleeve 22. The extension sleeve 22 applies a radial force Frad to the outer surface 24 of the interface holder 18 via the inner surface 26. This radial force Frad creates a frictional connection between the extension sleeve 22 and the interface holder 24. A first end 28 of the extension sleeve 22 rests against the pneumatic piston 10, so that the actuating force FS can be transmitted via the pneumatic piston 10, the extension sleeve 22, the frictional connection between the inner surface 26 and the outer surface 24 to the interface holder 18 and finally to the interface 110. The first end 28 of the extension sleeve 22 is designed here as a radially circumferential collar 30. The extension sleeve 22 can also have hook-shaped projections or noses for engagement with the pneumatic piston 10.Furthermore, the pneumatic piston 10 can also be in contact with the pneumatic housing 4 in another way, for example in a form-fitting manner.

[0059] To prevent relative rotation of the extension sleeve 22 and / or the interface holder 18 about the adjustment axis AS, the pneumatic actuator 1 has a torsion lock 32. In this exemplary embodiment, the torsion lock 32 has two securing elements 34, which are designed as locating pins 36. The locating pins 36 are inserted into corresponding retaining grooves 38 of the interface holder 18 and engage in a form-fitting manner in corresponding securing grooves 40 of the extension sleeve 22. The locating pins are positively received in the holding grooves 38 and the securing grooves 40 and thus prevent twisting of the extension sleeve 22 relative to the interface holder 18. At the same time, however, the locating pins 36 are displaceable in the securing grooves 40 so that the torsion lock 32 allows a relative movement of the interface holder 18 to the extension sleeve in the adjustment direction RS or opposite to the adjustment direction RS.

[0060] In this exemplary embodiment, the longitudinal axis AL of the extension sleeve 22 is identical to the adjustment axis AS. The securing grooves 40 extend parallel to the longitudinal axis AL of the extension sleeve 22 in a helical region 45. The helical region 45 is the section of the extension sleeve 22 along the longitudinal axis AL in which an extension slot 56 extends. The securing grooves 40 preferably extend from the first end 28 to a second end 42 of the extension sleeve 22. The securing grooves 40 therefore preferably extend in the longitudinal direction RL of the extension sleeve 22 essentially completely through the helical region 45, and particularly preferably through the entire extension sleeve 22.

[0061] In the radial direction RR of the extension sleeve 22, which is also the radial direction RR of the pneumatic piston 10, the locking groove 40 does not extend completely through the extension sleeve 22, but only in sections from the inner surface 26 into a side wall 44 of the extension sleeve 22.

[0062] The second end 42 of the extension sleeve 22 is designed as a collar 46, so that the extension sleeve 22 is open on both sides. However, the extension sleeve 22 can also have a cup-shaped cross-section with a closed second end 42 (see FIG. Figure 4 ).

[0063] Between the second end 42 of the extension sleeve 22 and the shoulder 20 of the interface holder 18, a spring 48 is arranged, which preloads the second end 42 against the interface holder 18. To bring the shoulder 20 closer to the second end 42, the spring 48 must be compressed, which in turn requires a force to be applied. In the non-fixed state, when the extension sleeve 22 and the interface holder 18 are not or not fully frictionally connected to one another, an actuating force FS applied to the interface 110 can be applied via the interface holder 18 and the spring 48 to the second end 42 of the extension sleeve 22. The first end 28 of the extension sleeve 22 rests against the pneumatic piston 10.

[0064] The actuating force FS then causes the extension sleeve 22 to stretch in its longitudinal direction RL, which is parallel to the actuating axis AS. The stretch in the longitudinal direction RL results in a contraction of the extension sleeve 22 in the radial direction RR, so that the inner surface 26 of the extension sleeve 22 comes into contact with the outer surface 24 of the interface holder 18, and a radial force Frad is transferred from the extension sleeve 22 to the outer surface 24 of the interface holder 18. This radial force Frad causes a frictional connection between the extension sleeve 22 and the interface holder 18.

[0065] As soon as the frictional connection between the interface holder 18 and the extension sleeve 22 is established, actuating forces FS applied to the pneumatic piston 10 and restoring forces FR applied to the interface 110 are directly transferred from the interface holder 18 to the extension sleeve 22 and the spring 48 is decoupled so that a spring length LF is constant in the fixed state.

[0066] Furthermore, the pneumatic actuator 1 has a decoupling element 50, which is arranged in the radial direction between the pneumatic piston 10 and the extension sleeve 22. A first decoupling element end 52 extends through the pneumatic piston 10 and protrudes radially from the pneumatic piston 10. The first decoupling element end 52 is not in contact with the pneumatic piston 10, so that no forces are transmitted from the first decoupling element end 52 to the pneumatic piston 10.

[0067] A second decoupling element end 54 abuts the second end 42 of the extension sleeve 22. In the Figure 2bIn the end position 55 of the pneumatic piston 10 shown, the first decoupling element end 52 rests against the pneumatic housing 4, so that restoring forces FR applied to the interface 110 can be transmitted to the housing 4 via the interface holder 18, the spring 48, the extension sleeve 22, and the decoupling element end 52. In the end position 55, the decoupling element 50 is in contact neither with the base 16 of the pneumatic cylinder 10 nor with that section of the pneumatic cylinder 10 against which the first end 28 of the extension sleeve 22 rests. The pneumatic piston 10 is decoupled by the decoupling element 50, so that no restoring force FR acts on the pneumatic piston 10. Rather, the restoring force FR is guided past the pneumatic piston 10 via the decoupling element 50. The piston 10 does not transfer any force to the interface 110.However, a force is preferably still transmitted to the interface 110 by the spring 48. The force FF transmitted by the spring 48 opposes the restoring force FR and, in the end position 55 (and after wear compensation), is in equilibrium with the restoring force FR. Preferably, the spring 48 is preloaded such that the spring rate of the spring 48 is essentially independent of its length LF. Thus, despite the length compensation of the wear compensation device 3, a substantially constant spring force FF can be provided. Since the pneumatic piston 10 is decoupled, no force is transmitted from the first end 28 of the extension sleeve 22 to the pneumatic piston 10 or from the pneumatic piston 10 to the first end 28. Therefore, no longitudinal force FL acts on the extension sleeve 22 along the adjustment axis AS.Although the spring 48 is supported on the extension sleeve 22, the force is transmitted directly to the decoupling element 50 via the second end 42. The extension sleeve 22 does not create a (complete) frictional connection, and the interface holder 18 is movable relative to the extension sleeve 22.

[0068] In this embodiment, the pneumatic piston 10 has a U-shaped cross-section. The wear compensation device 3 is arranged in an inner receiving space 51 defined by the U-shaped cross-section and protrudes from this inner receiving space 51 in the adjustment direction RS. The U-shape allows for large guide surfaces 14 of the pneumatic piston 10, enabling precise and play-free guidance of the pneumatic cylinder along the adjustment axis AS. (Despite the large guide surfaces 14, a compact design is achieved by arranging the wear compensation device 3 in the inner receiving space 51.)

[0069] The Figures 2a and 2b show the pneumatic actuator 1 in a state with maximum length along the actuating axis AS. This state of the pneumatic actuator 1 results when the friction linings 114, 116 of the clutch 102 are in a new condition. As explained above, the pneumatic piston 10 can be moved in the actuating direction RS against the restoring force FR by introducing a pressure medium into the pneumatic cylinder 6.

[0070] As soon as pressure medium is introduced into the pneumatic cylinder 6 at a pressure that is greater than the ambient pressure, the actuating force FS acts on the effective area 16 of the pneumatic piston 8. If the actuating force FS is greater than the restoring force, the pneumatic piston 10 moves in the actuating direction RS (in Figure 2a up).

[0071] The actuating force FS acting on the active surface 16 of the pneumatic cylinder 10 is transmitted to the first end 28 of the extension sleeve 22, which rests against the pneumatic piston 10. The restoring force FR acting on the interface 110 is transmitted from the interface 110 to the interface holder 20. In the initial movement state (at the moment compressed air is introduced into the pneumatic cylinder 6), the pneumatic piston 10 and the interface holder 18 are not yet frictionally fixed by the extension sleeve 22. It should be understood that the extension sleeve 22 can already rest radially against the interface holder 18 without creating a (complete) frictional connection. For example, the gap may already be closed while the radial force is still too small to create a frictional connection.In this non-fixed state, when there is no frictional engagement between the extension sleeve 22 and the interface holder 18, the restoring force FR cannot be transmitted to the extension sleeve 22 via the surfaces 24, 26. In this case, the restoring force FR is applied by the interface holder 18 to the second end 42 of the extension sleeve 22 via the spring 48.

[0072] Opposing forces then act on the ends 28 and 42 of the extension sleeve 22. The actuating force FS acts on the first end 28 of the extension sleeve 22, while the restoring force FR, directed opposite to the actuating force FS, acts on the second end 42. The forces FR, FS acting in opposite directions stretch the extension sleeve 22 in its longitudinal direction RL, which is parallel to the actuating axis AS here. The stretching of the extension sleeve 22 leads to the contraction of the extension sleeve 22 in the radial direction RR. An inner diameter DI of the extension sleeve 22 is reduced so that the inner surface 26 of the extension sleeve 22 comes into secure contact with the outer surface 24 of the interface holder 18. When the surfaces 24, 26 come into contact, the extension sleeve 22 transfers the radial force Frad to the interface holder 18, since this essentially prevents further contraction of the extension sleeve 22.This creates a frictional connection between the extension sleeve 22 and the interface holder 18 immediately after the pressure medium is introduced into the pneumatic cylinder 6. The actuating force FS acting on the pneumatic cylinder 10 can now be transmitted via the surfaces 26, 24 to the interface holder 22 and the interface 110. If the actuating force FS is greater in magnitude than the opposing restoring force FR, the pneumatic piston 10 is moved out of the pneumatic cylinder 6 in the actuating direction RS.

[0073] Even if the extension sleeve 22 and the interface holder 18 are frictionally connected to one another, forces FS, FR acting along the adjustment axis AS are still transmitted by the extension sleeve 22. The radial force Frad is merely a resultant force that is always generated by the extension sleeve 22 when the extension sleeve 22 is stretched in its longitudinal direction RL due to acting forces FS, FR.

[0074] The restoring force FR can increase during the movement of the pneumatic piston 10 in the actuating direction RS. This is the case, for example, when the restoring force FR is provided by a closing spring of the clutch 102. As the restoring force FR increases, the actuating force SF must also increase in order to move the pneumatic piston 10 further. A load on the extension sleeve 22 along the actuating axis AS increases, so that it is stretched further in the longitudinal direction RL. The radial force Frad generated by the extension sleeve 22 is proportional to the force acting on the extension sleeve in the longitudinal direction RL, so that the increased load in the longitudinal direction RL also results in a higher radial force Frad of the extension sleeve 22. The radial force Frad therefore scales with the actuating force FS. The higher the actuating force FS, the higher the radial force FR applied by the extension sleeve 22 to the interface holder 18.The frictional engagement between the extension sleeve 22 and the interface holder becomes stronger the higher the forces FS, FR to be transmitted in the adjustment direction RS or along the adjustment axis AS. Even when transmitting high adjustment forces FS, a secure frictional engagement between the extension sleeve 22 and the interface holder 18 can be ensured, and relative sliding of the interface holder 18 to the extension sleeve 22 can be prevented.

[0075] When the clutch 102 is to be closed again, the pressure in the pneumatic cylinder 6 is reduced so that the actuating force SF acting on the pneumatic piston 10 becomes smaller than the restoring force FR. In this case, the restoring force SR moves the pneumatic piston 10 against the actuating direction RS into the pneumatic cylinder 6. The movement of the pneumatic piston 10 against the actuating direction RS continues until no more restoring force FR is applied to the interface 110, or until the pneumatic piston 10 is in the end position 55, which in Figure 2b As explained above, in the end position 55, the restoring force FR is transmitted directly to the pneumatic housing 4 via the decoupling element 52, so that the pneumatic piston 10 is decoupled.

[0076] The case that a restoring force FR is applied to the interface 110 even in the end position 55 of the pneumatic piston 10 generally occurs when the clutch length LK of the clutch 102 is reduced due to wear of the friction linings 114, 116 of the clutch discs 106, 112. The first clutch disc 106 can move closer to the second clutch disc 112 than in a new state. The restoring force FR, which is provided for closing the clutch 102 and is transmitted to the interface 110 by means of the actuating lever 104, acts over a longer path of the interface 110 counter to the actuating direction RS, since the restoring force FR is only supported at a later point in time via the clutch discs 106, 112.

[0077] Wear of the friction linings 114, 116 of the clutch 102 thus results in a restoring force FR acting on the interface 110 even when the pneumatic cylinder 10 is in the end position 55. In the end position 55, the second end 42 of the extension sleeve 22 rests against the second decoupling element end 54 of the decoupling element 52. Due to the decoupling of the pneumatic cylinder 10, no longitudinal force FL acts on the extension sleeve 22 in the longitudinal direction RL, and the frictional connection between the extension sleeve 22 and the interface holder 18 is released. When the longitudinal force FL is removed from the extension sleeve 22, it contracts in the longitudinal direction LR, so that its inner diameter DI expands.

[0078] The restoring force SR is transmitted in the end position 55 from the interface 110 via the interface holder 18 or its shoulder 20, the spring 48, the second end 42 of the extension sleeve 22, the second decoupling element end 54 and the first decoupling element end 52 to the housing 4. The spring 48 is transmitted from the Figures 2a and 2b In the relaxed state shown, the spring 48 is compressed along the adjusting axis AS, reducing its spring length LF. Spring 48 counteracts this compression with a spring force FF. Spring 48 is compressed until the resulting spring force FF is in equilibrium with the restoring force FR.

[0079] By compressing the spring 48, the spring length LF is shortened and the interface holder 18 is moved counter to the actuating direction RS into the inner receiving space 51 of the pneumatic piston 10. In this case, the interface holder 18 is moved along the actuating axis AS relative to the extension sleeve 22. The total length LG of the pneumatic actuator 1 is shortened. Thus, the total length LG1 of the pneumatic actuator 1 in the Figure 2b shown initial state is greater than a total length LG2 of the pneumatic actuator 1 in the Figure 2cThe wear-compensated state shown. The spring 48 has the lowest possible spring rate and is preloaded such that a spring force FF, preferably approximately 300 N, is provided over the entire clutch wear path. This is particularly advantageous because a diaphragm spring of the clutch 102, which preloads the clutch discs 106, 112 against each other, is so dominant (stiff) that wear always occurs on the spring 48 of the pneumatic actuator. Due to the low spring rate, the spring provides a substantially constant spring force FF over the entire adjustment range of the wear compensation device 3.

[0080] When the pneumatic actuator 1 is actuated again by introducing compressed air or pressure medium into the pneumatic cylinder 6, the frictional connection between the extension sleeve 22 and the interface holder 18 is restored and the spring 48 is prevented from relaxing. Upon further actuation, the pneumatic piston 10 is thus moved in the actuation direction RS together with the compressed spring 48 or the interface holder 18 inserted into the extension sleeve 22. Figures 2c and 2d show the wear compensation device 3 of the pneumatic actuator 1 at maximum wear compensation. The interface holder 18 is fully inserted into the extension sleeve 22. The spring 48 is maximally compressed, so that its spring length FL in comparison to the Figures 2a and 2b is significantly shortened. Figure 2dshows the pneumatic actuator 1 with the wear compensation device 3 compressed to its maximum in the actuated state, in which the pneumatic cylinder 6 is filled with pressure medium. Due to the frictional engagement between the extension sleeve 22 and the interface holder 18 caused when the pressure medium is introduced into the pneumatic cylinder 6, the spring 48 is not relieved and the wear-compensated state is maintained. The wear of the friction linings 114, 116 is compensated by moving the interface holder 18 relative to the extension sleeve 22. In an analogous manner, the wear compensation device 3 can also be used to adjust against a wear direction. For example, if a new clutch 102 is used, the pneumatic actuator 1 can be moved from the Figures 3c and 3d shown wear-compensated state to the initial state according to the Figures 3a and 3breturn. Thus, after installing a new clutch 102, the restoring force FR is supported earlier via the clutch discs 106, 112. The spring 48 lengthens accordingly until the spring force FF is in equilibrium with the restoring force FR.

[0081] The Figures 3a , 3b and 3c show cross-sections through three alternative embodiments of the extension sleeve 22. In both variants, the extension sleeve 22 has the first end 28 and the second end 42, which is opposite the first end 28 in the longitudinal direction LR of the extension sleeve 22. The longitudinal direction LR runs along the longitudinal axis AL of the extension sleeve 22, which is parallel to the adjustment axis AS when installed. The side wall 44 of the extension sleeve 22 extends between the ends 28, 42.

[0082] The extension sleeve 22 has a first extension slot 56 which extends helically around the adjustment axis AS in a first direction G1 ( Figure 3a). In this embodiment, the first extension slot 56 is right-handed. In the radial direction RR, the extension slot 56 extends completely through the side wall 44 of the extension sleeve 22.

[0083] The first extension slot 56 has approximately two and a half complete turns 58. One complete turn 58 extends completely in the circumferential direction (in a planar projection along the longitudinal axis AL by 360°) in the side wall 44. Since the variant shown has two and a half complete turns 58, a first slot end 60 of the extension slot 56 and a second slot end 62 (concealed by side wall 44) of the first extension slot 56 are offset from each other in the longitudinal direction LR and in the circumferential direction (approximately 180°). The first extension slot 56 extends two and a half times completely in the circumferential direction (i.e., by 900°) through the side wall 44 of the extension sleeve 22. In the longitudinal direction RL of the extension sleeve 22, the extension slot in this embodiment extends over approximately 45% of an axial length of the extension sleeve 22, measured in the longitudinal direction RL between the first slot end 60 and the second slot end 62.

[0084] A pitch angle α of the first extension slot 56 has a value of approximately 5° in this exemplary embodiment. The pitch angle α is determined between the radial direction RR and a central slot axis 64 of the first extension slot 56. The number of turns N of the turns 58 of the first extension slot 56 and the pitch angle α determine the radial force Frad that can be generated by the extension sleeve 22. The pitch angle α can be converted into a pitch ratio of the extension slot 56 using trigonometric relationships. The pitch ratio (B / A) corresponds to the ratio of the extension slot's extension (B) in the radial direction RR to the extension (A) in the longitudinal direction RL and is Figure 3aThe pitch ratio (B / A) can be determined from the pitch angle α using trigonometric relationships. By applying the longitudinal force FL, a tangential force FT is generated that is oriented tangentially to the first extension slot 56 and corresponds to the product of the axial longitudinal force FL and the pitch ratio (B / A). The tangential force FT generates the radial force FR through the radial wrapping of the extension sleeve 22. The radial force is directly proportional to the tangential force FT and the number of turns N. The friction force Freib generated between the extension sleeve 22 and the interface holder 18 corresponds to the product of the radial force FR and a friction coefficient µ determined by the materials of the extension sleeve 22 and the interface holder. The following formulas [1] to [4] essentially clarify the relationship: FT = FL ∗ B A FR = FT ∗ 2 π ∗ N Freib = FR ∗ μ Freib > FL , vorzugsweise Freib ≫ FL Reibschlussbedingung

[0085] The radial force FR can be determined by appropriately selecting the pitch angle α and the number of turns N. To achieve frictional engagement, the frictional force Freib must be greater than the longitudinal force FL (formula

[04] ). It should be understood that the equations only represent the real relationship in a simplified manner. For example, the radial force FR may only scale approximately with the number of turns N.

[0086] Figure 3bshows an alternative embodiment of the extension sleeve 22. In this variant, the extension sleeve 22 has a second extension slot 66 in addition to the first extension slot 56. A second thread direction RG2 of the second extension slot 66 is oriented opposite to the first thread direction RG1 of the first extension slot 56. In this exemplary embodiment, the first extension slot 56 is right-handed and the second extension slot 66 is left-handed. Both the first extension slot 56 and the second extension slot 66 each have a complete turn 58. The first extension slot 56 is arranged in a first partial sleeve 68 of the extension sleeve 22, while the second extension slot 66 extends in a second partial sleeve 70. The partial sleeves 68, 70 are integrally connected to one another in a connecting region 72.However, the partial sleeves 68, 70 could also be connected, for example, by means of screws and / or rivets in an overlapping connection area 72. The first end 28 of the extension sleeve 22 is arranged on the first partial sleeve 68, while the second end 42 of the extension sleeve 22 is arranged on the second partial sleeve 70.

[0087] As explained above, the application of a longitudinal force FL causes a tangential force FT oriented parallel to the extension slots 56, 66. A first tangential force FT1, generated by the first extension slot 56, has a component along the longitudinal axis AL and a component in the circumferential direction. Similarly, a second tangential force FT2 of the second extension slot 66 also has a component along the longitudinal axis AL and a circumferential component.

[0088] Figure 3cshows a third embodiment of the extension sleeve 22, which also has two partial sleeves 68, 70. The left half of Figure 3c shows the first part of the sleeve 68 and the right half of Figure 3cshows the second partial sleeve 70. The second partial sleeve 70 has a smaller diameter and is inserted into the first partial sleeve 68 concentrically to the first partial sleeve 68. An outer diameter DAT of the second partial sleeve 70 essentially corresponds to an inner diameter DIT of the first partial sleeve 68. As illustrated by the line 72, a first end 74 of the first partial sleeve 68 and a first end 76 of the second partial sleeve 70 are materially connected. Along the longitudinal axis AL opposite the first end 74, the first partial sleeve 68 has a second end 78. Analogously, the second partial sleeve 70 also has a second end 80. A second line 82 illustrates that the second ends 78, 80 of the partial sleeves 68, 70 are also materially connected. Side walls 44a, 44b of the partial sleeves 68, 70 are in contact, but not integrally connected.

[0089] In the order pursuant to Figure 3aThe circumferential component of the tangential force FT would cause torsion of the extension sleeve 22 in the helical region 45 if the extension sleeve 22 is not prevented from this rotational movement. As explained above, the rotational movement can be prevented by the dowel pin 36, which positively engages the locking groove 40.

[0090] In the embodiment according to Figure 3c, which has two extension slots 56, 66, the torsion lock 32 can also be formed entirely or partially by the extension slots 56, 66. The extension slots 56, 66 are essentially identical and differ from one another only in the opposite thread directions RG1, RG2. While the longitudinally acting components of the tangential forces FT1, FT2 are oriented in the same direction, the circumferential components of the tangential forces FT1, FT2 point opposite one another. Due to the essentially identical design of the extension slots 56, 66, the tangential forces FT1, FT2 are equal in magnitude, so that the circumferential components cancel each other out. The oppositely oriented extension slots 56, 66 thus form the torsion lock 32.

[0091] It should be understood that the extension slots 56, 66 for forming the torsion lock 32 do not need to be substantially identical. Thus, a partial torsion lock 32 or a partial compensation of the circumferential component of the tangential force FT may also be sufficient. For example, the dowel pin 36 can be provided in addition to the extension slots 56, 66 with opposite thread directions RG1, RG2.

[0092] Figure 4 shows a clutch arrangement 100 with a linear actuator 5, which is not arranged concentrically to the clutch 102, but laterally offset from the clutch 102. The linear actuator 5 has a pneumatic piston 10, which is guided on second outer guide surfaces 14 in the pneumatic housing 4. However, the pneumatic piston 10 is not annular here, but essentially cup-shaped. The extension sleeve 22 is also cup-shaped (ie in Figure 4closed at the bottom), since here no shaft 118, 120 is guided through the linear actuator 5. However, an extension sleeve 22 open on both sides could also be provided. Otherwise, the linear pneumatic actuator 5 is essentially analogous to the concentric ring actuator 2 according to the Figures 1 and 2 formed, the functionality being also essentially the same. The interface 110 arranged on the interface holder 18 is according to Figure 4However, no ball bearing 108, but has a cup-shaped recess 122 into which the adjusting lever 104 engages. The adjusting lever 104 is formed by articulated lever segments 124. A stroke of the pneumatic piston 10 is transmitted via the interface holder 18, the interface 110 and the adjusting lever 104 to the clutch 102 or its first clutch disc 106. The cup-shaped recess 122 enables tilting of the lever segment 124a, which engages in the interface 110. The restoring force FR is provided here by means of a restoring spring 126 and transmitted to the interface 110 by the adjusting lever 104. To open the clutch 102 (as in Figure 4shown) pressure medium is introduced into the pneumatic cylinder 6, thereby moving the pneumatic piston 10 upward. The extension sleeve 22 is loaded in the longitudinal direction, creating a frictional connection between the extension sleeve 22 and the interface holder 18. The actuating force FS can thus be transmitted directly to the coupling 102 via the pneumatic piston 10, the extension sleeve 22, the interface holder 18, the interface 110, and the actuating lever 104.

[0093] Figure 5shows a commercial vehicle 200 with an engine 202, a clutch assembly 100, and a transmission 204. The engine 202 is connected to the drive shaft 118, and the transmission 204 is connected to the output shaft 120. A torque M provided by the engine 202 can be transmitted from the drive shaft 118 to the output shaft 118 by means of the clutch 102. The pneumatic actuator 1 is a pneumatic clutch actuator 206 and is provided for opening the clutch 102 to enable a gear change on the transmission 204. The output shaft 118 extends through the pneumatic actuator 1, thus realizing a preferred in-line arrangement. The in-line arrangement of the pneumatic actuator 1 and clutch 102 eliminates the need for complex and failure-prone deflection rods. List of reference symbols (part of the description)

[0094] 1 pneumatic actuator 2 ring actuator 3 wear compensation device 4 pneumatic housing 5 linear actuator 6 pneumatic cylinder 8 guide shaft 10 pneumatic piston 12 outer guide surface 14 second outer guide surface 16 effective surface 18 interface holder 20 shoulder 22 extension sleeve 24 outer surface 26 inner surface 28 first end 30 collar 32 torsion lock 34 locking element 36 dowel pin 38 retaining groove 40 locking groove 42 second end 44, 44a,44bSide wall 45Helix region 46Collar 48Spring 50Decoupling element 51Inner receiving space 52First decoupling element end 54Second decoupling element end 55End position 56First extension slot 58Coil 60First slot end 62Second slot end 64First slot axis 66Second extension slot 68First partial sleeve 70Second partial sleeve 72Line 74First end of first partial sleeve 76First end of second partial sleeve 78Second end of first partial sleeve 80Second end of second partial sleeve 82Second line 100Coupling arrangement 101Functional element 102Coupling 104Adjusting lever 106First clutch disc 108Ball bearing 108aOuter ring 108bInner ring 110Interface 112Second clutch disc 114First friction lining 116Second friction lining 118Input shaft 120Output shaft 122Cup-shaped recess 124a, 124b,124cLever segments 126Return spring 200Commercial vehicle 202Engine 204Gearbox 206Pneumatic clutch actuator AExtension in longitudinal direction BExtension in circumferential direction ASAdjusting axis ALLongitudinal axis of the extension sleeve DIInner diameter DITInner diameter of first partial sleeve DATAOuter diameter of second partial sleeve FLLongitudinal force FL FRResetting force FRadial force Free friction force FSAdjusting force FT, FT1, FT2Tangential force HStroke LG, LG1, LG2Total length of the pneumatic actuator LAaxial length of the extension sleeve LFFease length LKCoupling length LSFease length MTorque NThorque of turns RG1First gear direction RG2Second gear direction RSAdjusting direction RLLongitudinal direction of the extension sleeve RRradial direction αInner pitch angle,

Claims

1. Pneumatic actuator (1) for actuating a functional element (101), in particular a pneumatic clutch actuator (206) for a commercial vehicle (200) for actuating a clutch (102) of the commercial vehicle (200), comprising a pneumatic piston (10), a pneumatic housing (4), wherein the pneumatic piston (10) is arranged in the pneumatic housing (4) so as to be displaceable along an adjusting axis (AS) for executing a stroke (H), an interface holder (18) with an interface (110) for connecting the pneumatic actuator (1) to the functional element (101), and a wear compensation device (3) which is designed to temporarily fix the pneumatic piston (10) and the interface holder (18) in order to transmit an adjusting force (Fs) from the pneumatic piston (10) to the interface holder (18) and to release the temporary fixation between the pneumatic piston (10) and the interface holder (18) in order to compensate for a wear-related stroke change of the functional element (101), characterized in that the wear compensation device (3) has an extension sleeve (22).

2. Pneumatic actuator (1) according to claim 1, wherein a radial force (Frad), which acts from the extension sleeve (22) on the interface holder (18), can be generated by radial contraction of the extension sleeve (22) in order to produce the temporary fixation between the extension sleeve (22) and the interface holder (18).

3. Pneumatic actuator (1) according to claim 2, wherein the radial force (Frad) is substantially directly proportional to the adjusting force (Fs).

4. Pneumatic actuator (1) according to claim 3, wherein a force ratio between the radial force (Frad) and the adjusting force (Fs) has a value of 10 or greater.

5. Pneumatic actuator (1) according to any one of the preceding claims, wherein the extension sleeve (22) has a first extension slot (56) which extends helically around the adjusting axis (AS) in a first running direction (RG1).

6. Pneumatic actuator (1) according to claim 5, wherein the first extension slot (56) has at least a half turn (58), preferably a complete turn (58), along the adjusting axis (AS).

7. Pneumatic actuator (1) according to claim 5 or 6, wherein the first extension slot (56) has a first pitch angle (α) in a range of greater than 0° to 20°, preferably 2° to 8°, particularly preferably 3° to 6°.

8. Pneumatic actuator (1) according to any one of claims 5 to 7, wherein the extension sleeve (22) has a second extension slot (66) which extends helically around the adjusting axis (AS) in a second running direction (RG2).

9. Pneumatic actuator (1) according to claim 8, comprising a plurality of extension slots, wherein the plurality of extension slots extend around the adjusting axis in the form of a multiple helix, in particular as a double helix, triple helix or quadruple helix.

10. Pneumatic actuator (AS) according to any one of the preceding claims, further comprising a torsion lock (32) for preventing relative movement between the extension sleeve (22) and the interface holder (18).

11. Pneumatic actuator (1) according to claim 8 or 10, wherein the first running direction (RG1) and the second running direction (RG2) are opposite to each other.

12. Pneumatic actuator (1) according to claim 10 or 11, wherein the extension sleeve (22) has a securing groove (40) which extends in the adjusting direction (RS) of the adjusting axis (AS), and wherein the torsion lock (32) has a securing element (34) which engages in the securing groove (40).

13. Pneumatic actuator (1) according to any one of the preceding claims, wherein the extension sleeve (22) has a first partial sleeve (68) and a second partial sleeve (70) which are arranged coaxially with one another and are connected to one another.

14. Pneumatic actuator (1) according to claim 13, wherein the second partial sleeve (70) is arranged radially inside the first partial sleeve (68), wherein a first end of the first partial sleeve (68) is connected to an adjacent first end of the second partial sleeve (70), and wherein a second end of the first partial sleeve (68), which is opposite the first end of the first partial sleeve (68) along the adjusting axis (AS), is connected to a second end of the second adjusting sleeve (70), which is opposite the first end of the second partial sleeve (70) along the adjusting axis (AS).

15. Pneumatic actuator (1) according to any one of the preceding claims, wherein the extension sleeve (22) has a first end (28) and a second end (42) opposite the first end (28) along the adjusting axis (AS), wherein the first end (28) rests against the pneumatic piston (10) in the direction of the adjusting axis (AS).

16. Pneumatic actuator (1) according to claim 15, comprising a spring (48) which biases the interface holder (18) against the second end (42) of the extension sleeve (22).

17. Pneumatic actuator (1) according to any one of the preceding claims, comprising a decoupling element (50) which is designed to decouple the pneumatic piston (10) from the interface holder (18) in an end position (55) and to connect the interface holder (18) directly or indirectly to the pneumatic housing (4) in a force-conducting manner.

18. Pneumatic actuator (1) according to any one of the preceding claims, wherein the pneumatic piston (10) is an annular piston which is guided on at least one outer guide surface (12, 14) in the pneumatic housing (4) and has an inner receiving space (51), wherein the interface holder (18) and the wear compensation device (32) are arranged at least partly in the inner receiving space (51).

19. Pneumatic actuator (1) according to claim 17, wherein the pneumatic piston (10) has a substantially U-shaped cross section defining the receiving space (51).

20. Pneumatic actuator (1) according to claim 5, wherein the first extension slot (56) extends over a longitudinal section of from 10% to less than 100%, preferably 30% to 70%, particularly preferably 40% to 60%, of an axial length (LA) of the extension sleeve (22).

21. Pneumatic actuator (1) according to claim 2, wherein the frictional connection can be produced by radial contraction of the extension sleeve (22) by 0% to 5% of an inner diameter (DI) of the extension sleeve (22).

22. Clutch arrangement (100) for a commercial vehicle (200), comprising a clutch (102) and a pneumatic actuator (1) according to any one of the preceding claims 1 to 21, wherein the pneumatic actuator (1) is provided for opening and / or closing the clutch (102).

23. Commercial vehicle (200) comprising a clutch arrangement (100) according to claim 22.