Shifting mechanism for a transmission

Abstract

The invention discloses a shifting mechanism (1) for a transmission, in particular a vehicle transmission, having: - an input interface (4) designed to receive an input variable; - an output interface (8) designed to output a manipulated variable (10) to a shifting element (9), the shifting mechanism (1) being designed to generate the manipulated variable (10) from the input variable, and - a friction-based limiting element (5) arranged between the input interface (4) and the output interface (8) and designed to limit the manipulated variable (10) if the input variable exceeds a predetermined threshold value. The invention further discloses a transmission and a vehicle.

Description

[0001] DESCRIPTION

[0002] Shifting mechanism for a gearbox

[0003] The present disclosure relates to a shifting mechanism for a transmission, in particular for a vehicle transmission, a transmission and a vehicle.

[0004] In switchable transmissions, a shifting element, such as a shift sleeve mounted on a transmission shaft, is axially displaced into a shift position, thereby creating a frictional connection between a gear mounted on the transmission shaft and the transmission shaft itself. To achieve this shift position, axially extended positive-locking elements of the shifting element must be inserted into corresponding gaps between the connecting elements of the gear to be connected to the transmission shaft. For this to occur, the rotational speeds of the transmission shaft and the gear to be connected must be brought to the same speed during a synchronization process before the positive-locking elements can be moved axially into the gaps, allowing the shifting element to reach the shift position.When moving the positive locking elements into the corresponding gaps, it can happen, for example, that the positive locking elements are not completely aligned with the gaps. This can lead to undesirable contact between the positive locking elements and the connecting elements (e.g., their end faces) during axial movement. This results in undesirably high counterforces in the switching mechanism, which is designed to move the switching element as described. Furthermore, there is a risk of damage to the contact between the positive locking element and the connecting element, or to the switching mechanism in general. This also leads to undesirably long switching times, as the switching element cannot engage in the switching position within the desired time.

[0005] To address this problem, switching mechanisms are known that incorporate a spring which deforms accordingly when subjected to excessively high opposing forces. While this introduces elasticity into the switching mechanism, allowing for reversible deformation of the spring under high opposing forces, this solution has the disadvantage of introducing oscillation into the switching mechanism, which must be additionally accounted for or suppressed.

[0006] Therefore, the purpose of the present disclosure is to provide a solution to the above-mentioned problem without revealing the disadvantages known from the prior art.

[0007] This task is solved by the subject matter of the independent claims. Advantageous further developments are the subject matter of the dependent claims, the following description, and the accompanying drawings.

[0008] A shifting mechanism for a transmission, in particular for a vehicle transmission, is disclosed. The shifting mechanism comprises the following elements:

[0009] - an input interface designed to receive an input quantity;

[0010] - an output interface configured to deliver a manipulated variable to a switching element, wherein the switching mechanism is configured to generate the manipulated variable from the input variable, and

[0011] - a friction-based limiting element that is arranged between the input interface and the output interface and is designed to limit the manipulated variable when the input variable exceeds a predetermined threshold.

[0012] The switching element can be designed in particular as a switching sleeve or as a switching finger.

[0013] The input variable can be, in particular, an input force or an input torque.

[0014] The manipulated variable can be, in particular, a manifold force or a manifold torque.

[0015] The input interface can be designed as a rotary element (e.g., a wave) or as a translationally movable element. The output interface can be designed as a rotary element (e.g., a wave) or as a translationally movable element.

[0016] The limiting element can be designed for force or moment transmission via static friction between the input interface and the output interface, as long as the input variable does not exceed the predetermined threshold.

[0017] A particular advantage of this switching mechanism compared to the prior art is that the friction-based limiting element, especially in force or torque transmission via static friction, represents a rigid or at least nearly rigid element within the force flow from the input interface to the output interface. This eliminates unnecessary elasticities or vibrations in the switching mechanism that would otherwise need to be considered during its design.

[0018] According to one embodiment, the limiting element therefore behaves like a rigid or stiff element, e.g., like a rigid or stiff part of a shaft or a rigid or stiff part of a rod, for input quantities that are below the predetermined threshold, so that essentially force or moment transmission is not affected or only affected to a limited extent.

[0019] Preferably, the switching mechanism includes a drive device configured to generate a drive variable. The drive device can be directly connected to the input interface to imprint the drive variable as the input variable. In this case, the input variable and the drive variable are identical. Alternatively, the drive device can be indirectly connected to the input interface via at least one intermediate element, wherein the at least one intermediate element is configured to generate the input variable from the drive variable and imprint it as the input variable on the input interface. The intermediate element can be, for example, a transmission stage with at least one gear stage, or a motion converter, for example, a switching drum, a spindle drive, or a combination of pinion and rack.

[0020] The drive device can be designed as an electric, pneumatic, or hydraulic drive. In particular, if the drive device is electric, it can be a rotary drive, for example, an electric motor. However, a translational electric drive, such as a linear motor, is also conceivable. A pneumatic or hydraulic drive device is typically implemented as a combination of a cylinder and a pressurized piston guided within it, which is designed to act on the input interface, for example, directly or via at least one intermediate element.

[0021] The limiting element can have a frictional contact designed to allow relative movement between the input interface and the output interface when the predetermined threshold value is exceeded by the input quantity.

[0022] The friction contact can consist of a surface pairing of two surfaces that shift relative to each other as soon as the input variable exceeds the predetermined threshold. For example, one surface is connected directly or via intermediate elements to the input interface, and another surface is connected directly or via intermediate elements to the output interface. Alternatively, the friction contact can also have multiple surface pairings, for example, realized by individual lamellae in contact with each other. These can also be designed to shift relative to each other as soon as the input variable exceeds the predetermined threshold.

[0023] The relative movement occurs particularly immediately when the predetermined threshold value is exceeded by the input variable. In this way, the control variable is immediately limited, and there is a risk of damage to the switching mechanism. 1 or of the transmission is minimized. The limiting element can be designed to transmit force or torque from the input interface to the output interface via static friction in frictional contact, as long as the input variable does not exceed the predetermined threshold. The limiting element can then act as described above as a rigid or at least nearly rigid element within the force flow from the input interface to the output interface. Due to static friction, there is preferably no displacement of the surfaces of the surface pairing or multiple surface pairings when the input variable is below the predetermined threshold.

[0024] The resulting relative motion limits the force or torque flow in the switching mechanism between the input and output interfaces. Force or torque transmission from the input to the output interface then occurs via sliding friction in the frictional contact instead of static friction. This automatically limits the control variable applied to the switching element.

[0025] By appropriately designing the limiting element, for example by selecting suitable friction linings or their coefficients of friction, or by adjusting a spring element that exerts a contact force on the frictional contact, the predetermined threshold value for the input variable, above which the relative movement is to commence, can be influenced. Furthermore, gear ratios, motion conversions (e.g., from translational to rotational or from rotational to translational), and / or inertia acting in the switching mechanism or in the force and / or torque flow can be taken into account.

[0026] Preferably, the switching mechanism includes a transmission element that is directly connected to the limiting element between the limiting element and the output interface. This allows the output interface to be coupled to the limiting element, particularly when direct coupling is not possible. The transmission element can be designed as a rotary element (e.g., a shaft) or as a translationally displaceable element (e.g., a rod). The limiting element can be configured such that no relative movement occurs when the input variable is below or equal to the predetermined threshold, and that in this case, the input variable is transmitted to the transmission element without restriction.The limiting element can be configured so that relative movement occurs when the input variable is greater than the predetermined threshold, and that the input variable is transferred to the transfer element with a restriction to the magnitude of the threshold or less. The transfer element is configured to transfer the optionally restricted input variable to an intermediate element or directly to the output interface. In the case of direct transfer to the output interface, the optionally restricted input variable can simultaneously be the manipulated variable.

[0027] Preferably, the limiting element is configured such that the input variable is transmitted through the limiting element from the input interface to the transmission element or other intermediate elements by means of static friction, particularly within the frictional contact of the limiting element, as long as the input variable is below or equal to the predetermined threshold. If the input variable is above the predetermined threshold, the limiting element can be configured to transmit the input variable by means of sliding friction, particularly within the frictional contact, i.e., during relative movement within the frictional contact. The quantity then transmitted from the input variable is then at most equal to or below the predetermined threshold.

[0028] Especially when the drive device has relatively high moving masses during the generation of the drive signal, and thus relatively high inertial forces or moments of inertia are introduced into the switching mechanism, the friction-based limiting element provided in the switching mechanism is advantageous, particularly when relative movement begins upon exceeding the threshold value. This is because an input signal caused by the inertia of the drive device can be absorbed by the limiting element in the frictional contact as the relative movement begins. This advantage can be utilized for electric, hydraulic, and pneumatic drive devices. Particularly in electric drive devices, relatively high inertial forces or moments of inertia arise from the moving rotor, which can be limited in this way.

[0029] Even with drive devices that have relatively short response times, as is the case with electric drives, this problem does not need to be addressed with more moderate control or a limited acceleration speed to minimize the possibility of the drive device slowing down or a potential collision speed between the positive locking element and the connecting element. Instead, such an electric drive device can be accelerated to the maximum possible speed. If undesirably high counterforces occur, for example, due to contact between the positive locking element and the connecting element, as described above, the control variable is limited or reduced accordingly by the resulting relative movement in the frictional contact of the limiting element. This advantage can also be used for hydraulic and pneumatic drive devices.

[0030] Preferably, the input variable is an input torque and the relative motion is a rotary motion. This embodiment is suitable for a rotary drive device if it is connected directly or at least without motion conversion to the input interface. The input interface is then designed as a shaft. Preferably, the transmission element described above is also designed as a shaft.

[0031] In this case, the limiting element can be designed as a coupling. The coupling can have a friction pair that forms the frictional contact, or a lamellar pack that is part of or forms the frictional contact. The frictional contact of the coupling can be spring-loaded or pressed in order to set the predetermined threshold value via the contact force. Further parameters for setting the predetermined threshold value include, for example, the material and / or the dimensions of the corresponding friction surfaces, as well as their coefficient of friction. If the input variable remains below the predetermined threshold value, no relative movement takes place in the frictional contact. The coupling then rotates in the closed position.

[0032] With a spring-loaded friction contact of the clutch, the following torque T can be transmitted approximately:

[0033] T = F xr m x

[0034] F: Contact force on the friction contact, e.g. by the spring element rm : mean friction radius of the clutch p: coefficient of static or sliding friction (depending on whether static or sliding friction predominates in the friction contact)

[0035] Alternatively, the input variable is an input force and the relative motion is a translational motion. This embodiment is suitable for a translationally acting drive device, such as one of those mentioned above, which is directly connected to the limiting element. However, it is also possible for the switching mechanism to have a rotaryally acting drive device, such as an electric motor, which acts on the input interface of the limiting element via a motion converter designed to convert the rotary drive variable into a translational input variable.

[0036] In this case, the limiting element can be designed as a translational friction element. A translational friction element can essentially have a frictional contact extending parallel to the direction of the translational relative motion. This can be realized, for example, by a cylindrical surface of a friction piston that is in internal contact with the cylindrical surface of a friction cylinder in which the friction piston is guided. This can be a radially elastic friction piston that clamps onto the inner surface of the cylindrical surface of the friction cylinder and thus presses its side or cylindrical surface against the cylindrical surface of the friction cylinder from the inside.If a force is applied to the friction piston via the input interface, which is designed here as a translational interface, the relative movement begins as soon as the force exceeds the predetermined threshold and can no longer be fully transmitted by the friction contact. If the input value is equal to or below the predetermined threshold, the relative movement must be reversed. A return spring element can be provided for this purpose, which then moves the friction piston back to its starting position. This can be a disadvantage compared to the previously described coupling, as the latter does not require a return spring for the relative movement. Nevertheless, such a translational friction element can be useful if, for example, a translationally acting drive device is used and no further motion conversion is planned.This applies when the entire switching mechanism consists exclusively of translationally moving elements between the input interface or the drive device and the output interface. The axes of the friction piston and the friction cylinder are specifically oriented in the direction of the translational relative movement.

[0037] If the switching mechanism has a transmission element, as described above, which is directly connected to the limiting element and is provided between the limiting element and the output interface, or which can be directly understood as the output-side interface of the limiting element opposite the input interface, the switching mechanism is preferably designed such that (e.g., in the case of a translational input interface and a translational transmission element) a ground referenced to the input interface of all elements of the switching mechanism 1, located on the input interface side, is equal to or greater than a mass of all elements of the switching mechanism related to the transmission element 1 , which are located on the side of the transmission element. Alternatively, the switching mechanism can be designed such that (e.g., in the case of a rotary input interface and a rotary transmission element) a moment of inertia of all elements of the switching mechanism relative to the input interface is given by 1 , which are located on the side of the input interface, is equal to or greater than the moment of inertia of all elements of the switching mechanism related to the transmission element 1 , which are located on the side of the transmission element. This is advantageous because it reduces the inertia of the switching mechanism. 1Behind the limiting element, i.e., on the side of the transmission element and thus on the side of the output interface beyond the input interface, the inertial forces are less than or at most equal to the inertial forces in front of the limiting element, i.e., on the side of the input interface. Inertial forces of the switching mechanism that should not act on the switching element, and in particular not on an unwanted contact between the positive locking and connecting elements, can thus be absorbed by the limiting element. This means that elements of the switching mechanism 1Components positioned on the input interface side, which are set in motion, for example, by a drive device as described above, or even the drive device itself, exert an inertial force or moment of inertia on the input interface, particularly when the counterforce in the switching mechanism becomes too high, for example, when undesired contact occurs between the positive locking element and the connecting element. This inertial force or moment of inertia is then limited in the limiting element by the resulting relative movement as soon as the predetermined threshold is exceeded. Therefore, it is advantageous to use as many elements of the switching mechanism as possible. 1to be arranged on the side of the input interface. These elements may include, in particular, the following (other elements not mentioned are not excluded): a drive device (e.g., as described above), a transmission stage, a motion converter, a shaft, and / or a rod. In particular, these elements are to be understood as those elements through which the force or torque flow to the input interface, i.e., especially from the drive device to the input interface, to the output interface. It is particularly preferred that the limiting element is directly connected to the output interface without any further element being arranged between them.

[0038] Disclosed is a transmission, in particular a vehicle transmission. The transmission has a shifting element and a shifting mechanism, as described above. The output interface of the shifting mechanism 1The switching element is connected so that the actuating variable can be applied to the switching element, thus enabling the setting of a switching stage in the transmission. The switching element can be designed as a switching sleeve. Features already described above in connection with the switching mechanism and relating to the transmission are to be understood as at least optional features of the transmission disclosed herein. In particular, the switching stage can include a switching position of the switching element in which a force transmission is established between a gear arranged on a transmission shaft and the transmission shaft.

[0039] Disclosure relates to a vehicle, in particular a commercial vehicle, with a transmission as described above. The vehicle may be electrically, hybrid, or conventionally powered. Features already described above in connection with the shifting mechanism and relating to the vehicle are to be understood as at least optional features of the vehicle disclosed herein.

[0040] The following are embodiments of the disclosed switching mechanism. 1 described in more detail using the attached drawings.

[0041] They show:

[0042] Fig. 1 shows a first embodiment of the switching mechanism. 1 ,

[0043] Fig. 2 shows a second embodiment of the switching mechanism. 1 ,

[0044] Fig. 3 shows a third embodiment of the switching mechanism 1 ,

[0045] Fig. 4 shows a further development of the embodiment shown in Fig. 2,

[0046] Fig. 5 shows a further development of the embodiment shown in Fig. 1,

[0047] Fig. 6 shows a further development of the embodiment shown in Fig. 1,

[0048] Fig. 7 shows a schematic representation of a boundary element,

[0049] Fig. 8 shows a schematic representation of another limiting element, and Fig. 9 shows time profiles of the manipulated variable.

[0050] Fig. 1 shows a first embodiment of the switching mechanism. 1 .

[0051] A shifting mechanism 1 is shown, which is intended for a transmission, in particular for a vehicle transmission.

[0052] The switching mechanism 1 features:

[0053] - an input interface 4 designed to receive an input quantity;

[0054] - an output interface 8 configured to output a manipulated variable 10 to a switching element 9, wherein the switching mechanism 1 is configured to generate the manipulated variable 10 from the input variable, and

[0055] - a friction-based limiting element 5, which is arranged between the input interface 4 and the output interface 8 and is designed to limit the manipulated variable 10 when the input variable exceeds a predetermined threshold.

[0056] For this purpose, the limiting element 5 can have a frictional contact which is designed to allow relative movement between the input interface 4 and the output interface 8 when the predetermined threshold value is exceeded by the input quantity.

[0057] The input interface 4 is designed as a rotatable shaft and connected to a drive device 2, which is configured to apply a torque to the input interface 4 as a drive variable. The drive device 2 can, in particular, be designed as an electric drive device, e.g., as a rotary electric motor, as described above.

[0058] The drive device 2 is directly connected to the input interface 4. This means that the drive quantity is directly applied as drive torque to the friction-based limiting element 5. The limiting element 5 is designed as a friction clutch and is connected on the output side to a transmission element 6, which, like the input interface 4 on the drive side, is designed as a rotatable shaft.

[0059] A motion converter 7 is connected to the transmission element 6 and is configured to convert a torque of the transmission element 6 into a force. The motion converter 7 is configured to transmit this force to the output interface 8 of the switching mechanism. 1The output interface 8 in this embodiment of the switching mechanism 1 has a switching fork 8.1, which is shown schematically from the side. The output interface 8 is designed to transmit the force applied by the motion transducer 7 via the switching fork 8.1 to a switching element 9, e.g., a switching sleeve, which is shown here from the side and is designed to be horizontally displaceable. The force applied to the switching element 9 to displace it acts here as the actuating variable 10 in the horizontal direction. The actuating variable 10 can act as a force to the left and to the right, as shown by the two arrows acting on the switching element 9. Thus, the switching element 9, which is displaceable to the left and right, can be moved according to the applied actuating variable 10.

[0060] Thus, with the switching mechanism 1 shown, a control variable 10 can be generated and applied to a switching element 9, wherein the control variable 10 is generated from an input variable that is applied to the input interface 4 or from a drive variable of the drive device 2 (here a drive torque).

[0061] The motion converter 7 can, for example, have a switching drum, a spindle drive or a combination of pinion and rack.

[0062] The limiting element 5 is designed to transmit the input variable applied to the input interface 4 to the transmission element 6 if the input variable does not exceed the predetermined threshold. Since the limiting element 5 is designed as a coupling, the frictional contact is formed between the friction surfaces of the coupling. The threshold up to which an input variable can be fully applied from the input interface 4 to the transmission element 6 can be determined, in particular, by the choice of materials in the frictional contact, the coefficient of friction or surface roughness in the frictional contact, the size and number of friction surfaces, and the contact force of the friction surfaces.

[0063] If a drive torque is applied as an input variable to the input interface 4, and this torque is below or equal to the predetermined threshold value, the limiting element 5 behaves like part of a shaft consisting of the input interface 4, the limiting element 5, and the transmission element 6. That is, the input variable is simply transmitted to the transmission element 6, since a state of static friction prevails within the limiting element 5, i.e., in the frictional contact. This means that no relative movement occurs in the frictional contact. The input variable is therefore not limited by the limiting element 5.

[0064] If a drive torque is applied as an input variable to the input interface 4 that is above the predetermined threshold value, the limiting element 5 limits the torque transmitted to the transmission element 5 to the predetermined threshold value or below. For this purpose, the limiting element 5 is designed such that a relative movement between the input interface 4 and the transmission element 6 occurs within the limiting element or within the frictional contact. This means that the input variable is now only transmitted to the transmission element 6 at or below the predetermined threshold value. A sliding friction state now prevails in the frictional contact.

[0065] Ultimately, limiting the drive torque or input variable during transmission from input interface 4 to transmission element 6 in the further course of the switching mechanism results in 11 to output interface 8 also that the actuating variable 10, which is imposed on the switching element 9, is limited.

[0066] If the switching element 9 encounters resistance, e.g. because the positive locking elements located on the switching element 9 collide with the connecting elements of a gear of the transmission to which the switching element 9 belongs when the switching element 9 is moved into a switching position and must first slip off in order to bring the switching element 9 into the switching position, a control variable 10, which acts on the switching element 9 and thus on the contact between the positive locking element and the connecting element, can be limited so that damage can be avoided.

[0067] Fig. 2 shows a second embodiment of the switching mechanism. 1 .

[0068] This switching mechanism 1 differs from the switching mechanism 1 shown in Fig. 1 essentially in that an intermediate element, namely a motion converter 7, is provided between the drive device 2 and the input interface 4, and thus the friction-based limiting element 5, wherein the limiting element 5 is designed here as a translational friction element. The motion converter behind the limiting element 5 has been omitted. Otherwise, the switching mechanism 1 shown corresponds to the switching mechanism from Fig. 1. For the description of the drive device 2, the output interface 8, the switching fork 8.1, and the switching element 9, reference is therefore made to the description of Fig. 1.

[0069] The switching mechanism 1 is designed to convert the drive torque generated by the rotary drive device 2, e.g., an electric motor, into a force via the motion converter 7. This force can then be introduced on the input side into the limiting element 5 via an input interface 4, which here is designed as a translationally displaceable element, such as a rod. On the output side, the limiting element 5 has a transmission element 6, which can also be designed as a rod. The transmission element 6 is connected to the output interface 8 in order to ultimately impose the manipulated variable 10 onto the switching element 9 via the switching fork 8.1.

[0070] The translational limiting element 5 is designed to transfer the input quantity, in this case a force, from the input interface 4 to the transmission element 6, whereby a limitation of the input quantity occurs when the input quantity exceeds a predetermined threshold value specified by the limiting element 5.

[0071] The limiting element 5 can essentially have a frictional contact extending parallel to the direction of the translational relative motion. This can be realized, for example, by a cylindrical surface of a friction piston that is in internal contact with the cylindrical surface of a friction cylinder in which the friction piston is guided. This can be a radially elastic friction piston that clamps itself against the inner surface of the cylindrical surface of the friction cylinder and thus presses against the cylindrical surface of the friction cylinder from the inside. If a force is applied as an input variable via the input interface, which here is designed as a translational interface, the relative motion begins as soon as the input variable exceeds the predetermined threshold and can no longer be fully transmitted by the frictional contact.The limiting element is then in a sliding friction state, in which sliding friction is present in the frictional contact.

[0072] If the input value is again below or equal to the predetermined threshold, the relative movement must be reversed. A return spring element can be provided for this purpose, which then moves the friction piston back to its starting position. If the input value is equal to or below the predetermined threshold, a static friction state exists in the frictional contact. In this case, an applied input value is transmitted from the input interface 4 without limitation via the limiting element 5 to the transmission element 6.

[0073] The switching mechanism 1 is designed to transmit the input variable directly from the transmission element 6 to the output interface 8. The transmission element 6 and the output interface 8 are directly connected, so that a force acting on the transmission element 6, such as an input variable limited or unlimited by the limiting element 5, can be applied to the output interface 8, ultimately applying the manipulated variable 10 to the switching element 9. The switching mechanisms 1, shown in Figures 1 and 2, have rotary drive devices 2. The limiting element 5, shown in Fig.

[0074] Figure 1 shows a rotary limiting element 5 that is directly connected to the input interface 4. In contrast, Figure 2 shows a translational limiting element 5. Here, an intermediate element, namely the motion converter 7, is required to connect the rotary drive device 2 to the translational limiting element 5. The motion converter 7 can, for example, comprise a switching drum, a spindle drive, or a rack and pinion combination. An embodiment of a switching mechanism is described below. 1 shown, in which a translationally acting drive device 2 is provided.

[0075] Fig. 3 shows a third embodiment of the switching mechanism. 1 .

[0076] Here, a translationally acting drive device 2 is directly connected to the input interface 4. The drive device 2 can be designed as a hydraulic or pneumatic drive device, which has a piston that is displaceable in a cylinder by means of pressure and which is designed to apply an axial piston force or drive force as an input variable to the input interface 4.

[0077] The limiting element 5 and the elements 6, 8, 8.1 and 9 located behind it correspond to those shown in Fig. 2. Therefore, reference is made to the preceding description. Ultimately, this switching mechanism 1 allows a control variable 10 to be applied to the switching element 9, which essentially corresponds to the driving force generated by the drive device 2, whereby the force can be limited accordingly by the limiting element 5.

[0078] Further developments of the switching mechanisms are explained in Figures 4 to 6 below.

[0079] Fig. 4 shows a further development of the embodiment shown in Fig. 2. Reference is made to the description of Fig. 2, and the differences of this embodiment are discussed below.

[0080] A transmission stage 3 is provided between the drive device 2 and the motion converter 7. This stage comprises a pinion 3.1 and a gear 3.2. The pinion 3.1 is connected to the drive device 2. The motion converter 7 is designed as a spindle drive, comprising an axially rotatable threaded spindle 7.1 and an axially displaceable spindle nut 7.2 that interacts with it. The gear 3.2 is connected to the threaded spindle 7.1, enabling it to rotate axially. The motion converter 7 is designed to exert an axial displacement or force on the spindle nut 7.2 in accordance with the rotation of the threaded spindle 7.1. The spindle nut 7.2 is connected to the input interface 4, allowing the force to be introduced as an input variable into the limiting element 5.

[0081] The switching mechanism 1 shown here comprises several intermediate elements, namely the transmission stage 3 and the motion converter 7, which are arranged between the drive device 2 and the input interface 4 and are thus positioned on the input side relative to the limiting element 5. On the output side of the limiting element 5, only the transmission element 6 and the associated output interface 8 are provided. This configuration of the switching mechanism offers the following advantages: 11. A design in which the input-side inertias, which can be determined here, for example, as the input-side mass relative to the input interface 4, are equal to or greater than the inertias on the output side of the limiting element 5, i.e., greater than the output-side mass relative to the transmission element 6. This prevents excessively large inertial forces from acting on an undesired contact between the positive locking element and the connecting element. Instead, these forces are limited, if necessary, in the limiting element 5 when relative movement begins. This is achieved, for example, by arranging as many or all of the elements required for conversion or translation in the switching mechanism—in order to generate the manipulated variable 10 from the input variable or the drive variable—on the input side of the limiting element 5.

[0082] Fig. 5 shows a further development of the embodiment shown in Fig. 1.

[0083] Therefore, reference is made to the description of Fig. 1, and only the differences are discussed.

[0084] The drive device 2 is connected to a pinion 3.1 of a transmission stage 3, which meshes with a gear 3.2 of the transmission stage 3. The gear 3.2 is connected to the input interface 4 of the limiting element 5, which, as explained with reference to Fig. 1, is designed as a coupling. On the output side, the coupling 5 is connected to the transmission element 6, which is designed as a shaft and is connected to an axially rotatable threaded spindle 7.1 of the motion converter 7, which interacts with an axially displaceable spindle nut 7.2. The motion converter 7 is designed here as a spindle drive.

[0085] A torque generated as a drive variable by the drive device 2 can thus be translated by the transmission stage 3 and converted into a force by the motion converter 7. The limiting element 5 is provided as a coupling between these stages to limit the torque. In this way, the actuating variable 10, which is applied to the switching element 9 by the switching mechanism 1 as an actuating force, can be limited. The embodiment shown here demonstrates a possibility of arranging the limiting element 5 between several elements 3, 7, which are provided for the conversion and translation of the drive variable.

[0086] Fig. 6 shows a further development of the embodiment shown in Fig. 1.

[0087] This embodiment essentially corresponds to that shown in Fig. 5. The only difference is the motion converter 7. Therefore, reference is made to the preceding descriptions, and only the differences are discussed below. The motion converter 7 is located on the output side of the limiting element 5 and is connected to the transmission element 6, which is designed as a rotatable shaft. The motion converter 7 has an axially rotatable switching drum 7.3, on the surface of which a switching cam is provided. The output interface 8 engages in the switching cam and, with the switching fork 8.1, can apply a control variable 10 to the switching element 9. The control variable 10 is generated by the rotation of the switching drum 7.3, which then interacts with the output interface 8 via the switching cam. The rotation of the switching drum 7.3 is generated by the rotation of the transmission element 6.

[0088] Further embodiments, not shown, can be formed based on the embodiments shown in Figures 2, 4, 5, and 6 if corresponding limiting elements are connected directly to the drive device 2 instead of at the position shown. Based on Figure 2, a rotary limiting element can therefore be provided between the drive device 2 and the motion converter 7, while the limiting element 5 shown in Figure 2 is omitted. Based on Figure 4, a rotary limiting element can be provided between the drive device 2 and the transmission stage 3, while the limiting element 5 shown in Figure 4 is omitted. Based on Figure 5, a rotary limiting element can be provided between the drive device 2 and the transmission stage 3, while the limiting element 5 shown in Figure 5 is omitted. Based on Figure 5, a rotary limiting element can be provided between the drive device 2 and the transmission stage 3, while the limiting element 5 shown in Figure 5 is omitted.6 A rotary limiting element can be provided between the drive device 2 and the transmission stage 3, while the limiting element 5 shown in Fig. 6 is omitted.

[0089] Fig. 7 shows a schematic representation of a boundary element.

[0090] A section of a limiting element 5 is shown, designed as a rotary limiting element, specifically as a clutch. On the left is an input interface 4, designed as a shaft, which is connected to a rotatable friction disc 5.1 of the clutch. The friction disc 5.1, with its side facing away from the input interface 4, faces a mating surface of a clutch basket 5.2. The surface of this side, together with the mating surface of the clutch basket 5.2, forms a frictional contact 5.4. For easier differentiation, the two surfaces are shown spaced apart. In reality, however, these surfaces are in contact with each other to form the frictional contact 5.4. This contact is transmitted via the torque input from the input interface 4 to the clutch basket 5.2 and further to a connected transmission element 6 (designed as a shaft) or to an output interface 8 of the switching mechanism. 1 can be transferred.

[0091] The friction contact 5.4 is subjected to a spring force generated by a spring element 5.3, which is supported on one side by a designated collar in the clutch basket 5.2 and on the other side by the side of the friction disc 5.1 facing the input interface 4. The spring element is designed as a compression spring and is pre-tensioned in its installed position, so that the corresponding contact force is applied to the friction contact 5.4.

[0092] The friction contact 5.4 can transmit a torque (i.e., an input variable) up to a predetermined threshold value from the input interface 4 to the transmission element 6 or the output interface 8. The predetermined threshold value can be set by the contact force of the spring element 5.3 and thus by the design of the spring. Further parameters for setting the predetermined threshold value include, for example, the material and / or the dimensions and number of the corresponding friction surfaces, as well as their coefficient of friction.

[0093] The limiting element 5 is designed such that, when the predetermined threshold value is exceeded by the input variable, a relative movement begins in the friction contact 5.4 between the friction disc 5.1 and the clutch basket 5.2. This causes the friction contact 5.4 to switch from static to sliding friction, whereby a torque is transmitted that is less than or at most equal to the predetermined threshold value. In this way, the transmitted torque or input variable can be limited from the input interface 4 to the transmission element 6 or further to the output interface 8. The limiting element 5 shown here, which is designed as a clutch, has the advantage that no resetting of the limiting element 5 is necessary after such a limiting process, i.e., after the relative movement begins. Instead, the limiting element 5 is designed such that the friction contact 5...4. When the input variable is reduced below or to the predetermined threshold value, the friction disc 5.1 returns to a static friction state, so that the friction disc 5.1 is again rigidly coupled to the clutch basket 5.2, and thus the input interface 4 is coupled to the transmission element 6. In the static friction state, the limiting element 5 therefore acts as a shaft connection between the input interface 4 and the transmission element 6 or the output interface 8.

[0094] Such a rotary limiting element 5 can, for example, be provided as a limiting element in the switching mechanisms shown in Figures 1, 5 and 6.

[0095] Fig. 8 shows a schematic representation of another boundary element.

[0096] The limiting element 5 shown here is designed as a translational limiting element and is shown in a sectional view. It has a friction piston 5.5 which is axially connected to an input interface 4, which is designed as a rod. The friction piston 5.5 itself is axially guided in a friction cylinder 5.6. The friction cylinder 5.6 is in turn connected to a transmission element 6 extending to the right or to an output interface 8. The friction cylinder 5.6 is designed to be axially displaceable and can thus transmit displacements or forces to the transmission element 6 or the output interface 8. A friction contact 5.8 is provided between the outer surface of the friction piston 5.5 and the inner surface of the friction cylinder 5.6. The friction piston 5.5 is designed to contact the outer surface of the friction piston 5.5 with the inner surface of the friction cylinder 5.6 under its own radially elastic preload.to bring the friction contact 5.8 into contact with the friction piston 5.5 and the friction cylinder 5.6. For clarity, the friction contact 5.8 is represented here as the gap between the friction piston 5.5 and the friction cylinder 5.6. In reality, the friction piston 5.5 and the friction cylinder 5.6 are in contact within the friction contact 5.8, with static friction prevailing as long as the input quantity, i.e., a force applied to the input interface 4, remains below or equals a predetermined threshold. If the force applied to the input interface 4 exceeds the predetermined threshold, sliding friction begins, and the friction piston 5.5 slides within the friction cylinder 5.6, i.e., it moves relative to the friction cylinder 5.6.

[0097] The contact force with which the friction piston 5.5 presses from the inside against the inside of the friction cylinder 5.6 is primarily determined by the elasticity of the material of the friction piston 5.5, as well as the radial dimensions of the friction piston 5.5 and the bore of the friction cylinder 5.6. The friction piston 5.5 may incorporate a radially elastic spring element or be made of, or consist of, an elastic material such as plastic.

[0098] The contact force influences the force (input parameter) at which the relative movement between friction piston 5.5 and friction cylinder 5.6 begins, i.e., at which point the friction contact 5.8 switches from static to sliding friction. Other parameters that can be considered for setting the predetermined threshold value include, for example, the extent of the outer surface of the friction piston 5.5, the materials of the friction piston 5.5 and friction cylinder 5.6 in the friction contact 5.8, and the surface roughness in the friction contact 5.8.

[0099] The limiting element 5 shown is designed to transmit a force acting axially on the input interface 4 without limitation to the transmission element 6 or the output interface 8, as long as the input quantity does not exceed a predetermined threshold value, which is defined by the static friction limit of the friction contact 5.8. If the input quantity exceeds the predetermined threshold value, the friction contact 5.8 switches to a sliding friction state, and the friction piston 5.5 and friction cylinder 5.6 move relative to each other. Only a limited force is now transmitted via the friction contact 5.8 to the transmission element 6 or the output interface 8. This force depends on the sliding friction state in the friction contact 5.8. If the input quantity is again below or equal to the threshold value, a return spring element 5, arranged axially between the friction cylinder 5.6 and the friction piston 5.5, must be used to limit the force.9. A return movement is used to return the friction piston 5.5 to its initial position. In the configuration shown, corresponding return spring elements 5.9 are provided on both sides of the friction piston 5.5 to return it to the initial position shown.

[0100] Such a translational limiting element 5 can, for example, be provided as a limiting element in the switching mechanisms shown in Figures 2, 3 and 4.

[0101] Fig. 9 shows time profiles of the manipulated variable.

[0102] Shown here are curves 14 of the manipulated variable 10 (vertical axis), e.g., from Figures 1 to 6, over time t (vertical axis), so that the effect of the limiting element 5, as shown, for example, in the figures described above or generally above, can be explained. The manipulated variable 10 can, for example, act as an axial force on a switching element, which is designed, for example, as a switching sleeve.

[0103] The dashed horizontal line 1 1 indicates a control variable limit that should not be exceeded by a switching mechanism, because, for example, exceeding the control variable limit could result in damage to the transmission or the switching mechanism. 1 to be expected.

[0104] The dashed control variable curve 12 represents an ideal control variable curve, which is approximately achieved when the switching element does not introduce excessively high or undesirable counterforces into the switching mechanism, as would be the case, for example, if there is contact between the positive locking and connecting elements when the switching element is moved in the gearbox.

[0105] In the manipulated variable profiles 13 and 14, such an undesirable contact now takes place between the positive locking and connecting elements, so that the force on the switching element or the manipulated variable is further increased by the switching mechanism, so that the manipulated variable profiles 13 and 14 deviate from the horizontal plateau of the manipulated variable profile 12 when the contact is initiated and are increased.

[0106] Control variable curve 13 shows the case where no limiting element is effective in the switching mechanism. Here, the control variable 10 continues to increase until the positive locking and connecting elements slip against each other, allowing the switching element to engage. The control variable 10 is held above the control variable limit 11 for a relatively long time. Furthermore, as shown, undesirable oscillations can occur in the control variable curve 13, such as those caused by stick-slip effects between the positive locking and connecting elements. Only when the contact between the positive locking and connecting elements is overcome or released does the control variable curve 13 decrease again below the control variable limit 11. In contrast, control variable curve 14 shows the case where a limiting element is effective in the switching mechanism. Here, the control variable 10 only increases until the control variable limit 11 is reached. After that, for example...Sliding friction occurs in the limiting element or its frictional contact, so that force transmission or control variable generation can now only occur based on the input variable transmitted through the sliding frictional contact, and no longer through static friction. As a result, the control variable 10 in the control variable curve 14 is reduced again and remains completely below the control variable limit 11 designed for this case.

[0107] The control variable limit 11 can be used in the design of the switching mechanism. 1 The predetermined threshold at which the frictional contact switches from static to sliding friction and relative movement begins, as described above, is determined. This applies to the design of the switching mechanism. 1Preferably, the reverse approach is conceivable, namely that the manipulated variable limit 11, which results from the component properties of the transmission, in particular the positive locking and connecting elements, is used to calculate a predetermined threshold value. The present disclosure shows a way of generating a manipulated variable from an input variable, wherein the manipulated variable is limited by the fact that a static friction state in a limiting element changes to a sliding friction state as soon as the input variable exceeds a predetermined threshold value. It is advantageous here that the disclosed switching mechanism behaves like a drive train with maximum rigidity as long as the input variable does not exceed the threshold value. Only when the threshold has been exceeded does relative motion begin, or the limiting element is designed to then switch to a sliding friction state.This provides an advantage over the vibration-prone solutions known from the prior art, which use a spring element.

[0108] REFERENCE MARK LIST

[0109] 1. Switching mechanism

[0110] 2 Drive device

[0111] 3rd translation stage

[0112] 3.1 Sprocket

[0113] 3.2 Gear

[0114] 4 Input interface

[0115] 5 Boundary element

[0116] 5.1 Friction disc

[0117] 5.2 Clutch basket

[0118] 5.3 Spring element

[0119] 5.4 Friction contact

[0120] 5.5 Friction piston

[0121] 5.6 Friction cylinder

[0122] 5.8 Friction contact

[0123] 5.9 Return spring element

[0124] 6 transmission element

[0125] 7 motion converters

[0126] 7.1 Threaded spindle

[0127] 7.2 Spindle nut

[0128] 7.3 Switching drum

[0129] 8 Output interface

[0130] 8.1 Shift fork

[0131] 9 Switching element

[0132] 10 Control variable

[0133] 11 Control parameter limit

[0134] 12 ideal control variable profile

[0135] 13 Control variable curve without limiting element

[0136] 14 Control variable curve with limiting element t time

Claims

PATENT CLAIMS 1. Shifting mechanism (1) for a transmission, in particular a vehicle transmission, comprising: - an input interface (4) designed to receive an input quantity; - an output interface (8) configured to output a manipulated variable (10) to a switching element (9), wherein the switching mechanism (1) is configured to generate the manipulated variable (10) from the input variable, and - a friction-based limiting element (5) arranged between the input interface (4) and the output interface (8) and designed to limit the manipulated variable (10) when the input variable exceeds a predetermined threshold.

2. Switching mechanism (1) according to claim 1, further comprising: - a drive device (2) designed to generate a drive quantity and which is directly connected to the input interface (4) in order to imprint the drive quantity on the input interface (4) as an input quantity, or which is indirectly connected to the input interface (4) via at least one intermediate element (3, 7), wherein the at least one intermediate element (3, 7) is designed to generate the input quantity from the drive quantity and to imprint it on the input interface (4) as an input quantity.

3. Switching mechanism (1 ) according to claim 1 or 2, wherein the limiting element (5) has a frictional contact (5.4, 5.8) which is configured to allow relative movement between the input interface (4) and the output interface (8) when the predetermined threshold value is exceeded by the input quantity.

4. Switching mechanism (1) according to claim 3, wherein the input variable is an input torque and the relative motion is a rotary motion.

5. Switching mechanism (1) according to claim 3, wherein the input variable is an input force and the relative motion is a translational motion.

6. Switching mechanism (1) according to one of the preceding claims, further comprising - a transmission element (6) that is directly connected to the limiting element (5) between limiting element (5) and output interface (8).

7. Switching mechanism (1) according to claim 6, wherein a mass of all elements of the switching mechanism is related to the input interface (4). 1 (1 ), which are located on the side of the input interface (4), is equal to or greater than a mass of all elements of the switching mechanism related to the transmission element (6). 1(1) which are located on the side of the transmission element (6), or wherein a moment of inertia of all elements of the switching mechanism is related to the input interface (4). 1 (1 ), which are located on the side of the input interface (4), is equal to or greater than a moment of inertia of all elements of the switching mechanism related to the transmission element (6). 1 (1) which are located on the side of the transmission element (6).

8. Switching mechanism (1) according to claim 6 or 7, wherein the limiting element (5) is configured to transmit the input quantity to the transmission element (6) by means of static friction when the input quantity is below the predetermined threshold.

9. Transmission, in particular vehicle transmission, comprising: - a switching element (9) and - a switching mechanism (1) according to one of the preceding claims, wherein the output interface (8) of the switching mechanism 1 (1) with the The switching element (9) is connected so that the actuating variable (10) can be applied to the switching element (9) so that a switching stage can be set in the transmission.

10. Vehicle, in particular commercial vehicle, with a transmission according to claim 9, wherein the vehicle is designed as an electrically, hybrid or conventionally powered vehicle.

Images