Steel lamella for a friction switching element of a motor vehicle powertrain

Abstract

Oil-lubricated wet friction switching element of a motor vehicle powertrain, wherein the friction switching element has several lamellae arranged in series, which are alternately designed as a steel lamella and friction lining lamella, and wherein the steel lamella (10) is unlined on both sides, wherein • the steel lamella (10) has first recesses (12a, 12b) which are elongated in the direction of a first extension (14a) of the first recesses (12a, 12b) and extend along a curve (17a, 17b) in relation to the first extension (14a), wherein each curve (17a, 17b) corresponds substantially to a circumferential line (18a, 18b) on which the first recesses (12a, 12b) are arranged relative to a reference point, and • a first number of first recesses (12a) are arranged according to a reference point on a first circumferential line (18a) with a first diameter (D1) and further numbers of first recesses (12b) are arranged according to a reference point on further circumferential lines (18b) of a different diameter (D2), and • Second recesses (13a, 13b) of significantly smaller first and / or second extent (16a, 16b) are provided, wherein at least between a first pair of adjacent first recesses (12a, 12b) and between a second such pair, exactly one second recess (13a) is arranged according to a reference point on a circumferential line (19a, 19b) which coincides with the first circumferential line (18a), and exactly one further second recess (13b) is arranged according to a reference point on a further circumferential line (19b) which coincides with the second circumferential line (18b).

Description

[0001] The invention relates to a steel lamella for a friction switching element running in oil in a motor vehicle drive train with the features of the preamble of claim 1.

[0002] AT 220 893 B discloses a friction clutch with oil-lubricated plates and counter plates, wherein the counter plates each have a plurality of axially through openings. These have the form of elongated holes.

[0003] From DE 20 2018 002 101 U1 a friction lining lamella with openings for weight reduction is known.

[0004] The invention is based on the objective of providing a steel lamella for a friction switching element of a motor vehicle drive train, with which improved heat dissipation in the friction switching element can be achieved.

[0005] This problem is solved according to the invention by a steel lamella with the features of claim 1.

[0006] The invention relates to a steel lamella for a friction switching element running in oil in a motor vehicle powertrain. The friction switching element has several lamellae arranged in series, which are alternately designed as steel lamellae and friction lining lamellae. The steel lamella according to the invention is unlined on both sides. The steel lamella according to the invention further has first recesses, which are elongated and extend along a curve in a first dimension. A friction switching element within the meaning of the invention can, for example, be a multi-plate clutch or a friction switching element with lamellae designed as a brake. The friction switching element can, in particular, be designed as a friction switching element of a transmission, such as, in particular, a torque converter automatic transmission, a dual-clutch transmission, or a hybrid transmission, for a motor vehicle powertrain.The friction switching element can also be configured as a friction switching element in an electric vehicle powertrain or as a friction switching element in an electric drive system of a motor vehicle with an electric motor as the drive unit. Within the scope of the invention, the extension of first recesses of a first extension along a line of curvature is to be understood, in particular, geometrically and not in the sense of a fixed number of lines of curvature. Several first extensions of first recesses can extend along different lines of curvature. A line of curvature can, for example, be a circular arc, a segment of an ellipse, an oval, or any other curved line, in particular of a continuously convex or concave nature. The first recesses generally also reduce the component weight.

[0007] The first recesses advantageously allow for the creation of sealed volumes by bringing the steel plate into contact with a friction lining plate on each side of the steel plate when the friction switching element is closed. The friction lining plates can be, in particular, double-sided friction lining plates, also known as double-sided plates.

[0008] The possible formation of oil reservoirs in the closed volumes of the first recesses of the steel lamellae, caused by the enclosed volumes, advantageously leads to improved heat dissipation from the lamellae, especially at the beginning of an opening process of the friction switching element.

[0009] Furthermore, in the open state of the switching element, the first recesses according to the invention create oil pressure cushions, which lead to a reduction in drag torques. This is particularly advantageous for an electric or electrified motor vehicle powertrain with a drive unit designed as an electric machine. During a cold start operation of the friction switching element, the friction switching element with the steel lamella according to the invention reduces or even prevents creeping of the motor vehicle without a gear engaged.

[0010] According to an advantageous embodiment of the invention, the first extent of the first recesses is at least approximately eight times the size of a second extent, and the first recesses have rounded outlets. According to the invention, the contours of the recesses have rounded outlets extending to an outermost point in the direction of their greatest extent. These rounded outlets can be formed, for example, by a circular arc, a segment of an ellipse, an oval, or the like.

[0011] According to the invention, each curve essentially corresponds to a circumferential line on which the first recesses are arranged relative to a reference point. The term circumferential line refers not only to the inner or outer circumference of the steel lamella, but also to all intervening concentric circumferential lines. Different curves can correspond to different circumferential lines. A reference point can, for example, be the center point of a first recess. If the first recesses are located relative to a reference point on a first circumferential line, this can therefore mean that the centers of the first recesses are located on a specific circumferential line.The possible extension of the first extension of the first recesses according to the invention along a curve running essentially in the circumferential direction advantageously ensures that the inert oil is accelerated in a correspondingly advantageous manner as soon as the rotational movement begins.

[0012] According to the invention, a first set of first recesses is arranged relative to a reference point on a first circumferential line with a first diameter, and further sets of first recesses are arranged relative to a reference point on further circumferential lines of a different diameter. Within the scope of this invention, a set generally refers to a group with one or more elements. A first circumferential line can be understood as the circumferential line closest to the inner circumference of the steel lamella. The further circumferential lines of a different diameter are, accordingly, circumferential lines of a larger diameter. Deviating definitions are not excluded. A reference point can, for example, be the center point of a recess. If a first set of first recesses is located relative to a reference point on a first circumferential line, this can therefore mean that the centers of the first recesses of the first set are located on a specific circumferential line.The same applies in this case to the further number of first recesses on further circumferential lines. This aspect of the invention advantageously allows the stiffness of the steel lamella to be maintained despite comparatively large first recesses and a comparatively large number of first recesses, and thus a large total oil reservoir.

[0013] The arrangement of the first recesses relative to a reference point on the first and subsequent circumferential lines can advantageously be arranged in a regular alternation. For example, the arrangement can alternate simply, twice, or generally multiple times between two circumferential lines. With these arrangements, sufficient stiffness can be achieved even with a comparatively large number of first recesses in the steel lamella.

[0014] According to a further advantageous embodiment of the invention, a web remains between each of the two first recesses, the width of which corresponds at least to the value of the second dimension. Several webs of varying widths can be provided, taking this minimum dimension into account. This ensures sufficient stiffness of the steel lamella.

[0015] According to a further advantageous embodiment of the invention, the first extension is at least approximately 15 millimeters, wherein the oil has a kinematic viscosity between 3 and 4 centistokes at a temperature of 100 degrees Celsius. With first recesses having an extension of at least 15 millimeters, when using an oil for the friction switching element with a kinematic viscosity at 100 degrees Celsius of at most 4 centistokes, it is advantageous that, particularly at the very first moment at the beginning of an opening process of the friction switching element, an acceleration of the oil along the first extension can be achieved even within the recess, thus enabling a comparatively rapid oil flow. This allows the flowing oil to absorb frictional heat from the lamellae and leads to improved cooling of the lamellae.

[0016] According to the invention, second recesses of significantly smaller first and / or second extent are provided, wherein at least one second recess is arranged between a first pair of adjacent first recesses and between a second such pair, along a circumferential line and a reference point. This also means that at least one second recess need not be arranged between every adjacent first recess. The first and second pairs can be adjacent to each other, but need not be. If only two first recesses are arranged in total, these constitute both the first and second pairs within the meaning of the invention. A significantly smaller first and / or second extent is to be understood in relation to the first and / or second extent of the first recesses.The circumferential line on which the second set of recesses are arranged relative to a reference point can have the same or a different diameter than the circumferential lines on which the first set of recesses are arranged relative to a reference point. The second set of recesses can be, for example, circular, elliptical, oval, or have another shape. These second set of recesses serve to further reduce the component weight without negatively impacting stiffness too much.

[0017] A further advantageous embodiment of the invention provides that the first extent of the second recesses is at least twice the extent of the second recesses. The second recesses can, for example, have rounded outlets of the type described.

[0018] According to the invention, a first number of second recesses are arranged relative to a reference point on a first circumferential line, and further numbers of second recesses are arranged relative to a reference point on further circumferential lines of a different diameter. The diameters of these circumferential lines may, but need not, coincide with the diameters of the circumferential lines along which the first recesses are arranged relative to a reference point. A first circumferential line can be understood as the circumferential line closest to the inner circumference of the steel lamella. The further circumferential lines of a different diameter are, accordingly, circumferential lines of a larger diameter. Deviating specifications are not excluded. A reference point can, for example, be the center point of a recess.If a first set of second cutouts is located on a first circumferential line with respect to a reference point, this can mean that the centers of the second cutouts of the first set are located on a specific circumferential line. The same applies in this case to the further sets of second cutouts on further circumferential lines. This ensures sufficient stiffness of the steel lamella.

[0019] A further advantageous embodiment of the invention provides that webs with a width at least equal to the second dimension of the first recesses remain between the first and second recesses. This can also apply to webs between the second recesses. Several webs of varying widths can be provided, taking this minimum dimension into account. This ensures sufficient stiffness of the steel lamella.

[0020] The invention can be further characterized in that the steel lamella has indentations at specific angular intervals. The position of a first indentation can be defined by the space between two adjacent first indentations, and the angular intervals by the maximum number of indentations around the entire circumference, determined by stiffness considerations. For example, the number of indentations can be evenly distributed over a full circle of 360 degrees, i.e., for instance, a total of 3 indentations at angular intervals of 120 degrees. The indentations can be arranged on both the outer and inner circumference of the steel lamella and can be designed in different shapes. The indentations serve to further reduce weight.

[0021] Furthermore, the invention can be characterized in that the number of secondary recesses is reduced in the area of ​​the indentations. For example, if two secondary recesses are arranged in the space between further adjacent first recesses without an associated indentation, then only one or even no secondary recess may be provided in the area of ​​an indentation. This serves to maintain stiffness.

[0022] The invention can further be characterized in that the ratio of recesses to solid surface is not less than 25 percent.

[0023] The invention can be further characterized in that the steel lamella according to the invention is installed in a motor vehicle powertrain comprising one or more electric motors. Very high torques are present in a motor vehicle powertrain comprising one or more electric motors, even immediately at the start of an acceleration process. In this case, the steel lamella according to the invention is particularly advantageous because the oil pressure cushions created by the design of the recesses can effectively reduce drag torques and improve heat dissipation.

[0024] In one embodiment of the invention, the friction radius of the steel lamella is at least approximately 110 millimeters, and the inner radius of the steel lamella is more than approximately 200 millimeters. Advantageously, this embodiment of the invention allows for the creation of a switching element with high torque capacity, which is particularly necessary in a gearshift transmission of an electric or electrified motor vehicle powertrain with one or more electric motors as the drive motor. Furthermore, good heat dissipation, especially during the initial opening process of the friction switching element, and operation of the friction switching element in the open position with comparatively low drag torques can still be ensured.

[0025] Furthermore, according to the invention, a friction switching element designed as a lamellar friction switching element with several lamellae arranged in series is proposed, wherein the lamellae are alternately designed as steel lamellae and friction lining lamellae, and wherein the friction switching element has at least one friction lining lamella which has an end face facing an axially adjacent steel lamella, which is free of grooves. The friction switching element has at least one steel lamella according to the invention. Advantageously, all friction lining lamellae of the friction switching element according to the invention have end faces in both axial directions which are free of grooves. Advantageously, all steel lamellae of the friction switching element according to the invention are designed according to the invention. Within the scope of the invention, an end face of a friction lining lamella free of grooves is understood to mean a friction lining lamella that is completely ungrooved.The friction switching element according to the invention advantageously exhibits at least substantially stable friction coefficient behavior, so that, for example, the hydrodynamic friction component, especially at low pressures, can be kept at least substantially constant. This minimizes the typical break-in behavior of a friction switching element, particularly one designed as a wet-running lamellar friction switching element, especially at low pressures. Furthermore, it has been found that when a groove pattern is incorporated into the friction lamella, this groove pattern is subject to continuous change, resulting in a constant change in the friction coefficient. This can now be avoided by the friction switching element according to the invention. The result is stable friction coefficient behavior of the friction switching element, particularly over its service life.

[0026] Further advantages, features and details of the invention will become apparent from the following description of exemplary embodiments and from the figures.

[0027] This shows Fig. 1 Top view of a first embodiment of a steel lamella according to the prior art Fig. 2 Partial view of a second embodiment of a steel lamella according to the prior art Fig. 3 Partial view of an embodiment of the invention

[0028] Fig. Figure 1 shows an exemplary first embodiment of a steel lamella 10 for a friction switching element of a motor vehicle. The steel lamella 10 has first recesses 12a, 12b. The first recesses 12a, 12b extend along a first dimension 14a, each along a curve 17a. In the present embodiment, the curve 17a essentially corresponds to a circumferential line 18a, on which the first recesses 12a, 12b are arranged relative to a reference point. A number of 24 first recesses 12a, 12b are arranged along the circumferential line 18a of first diameter D1, with their centers relative to the first dimension 14a. Fig. For clarity, only the diameter D1 is designated as an example. All further details are explained in the accompanying figure description. Pairs of first recesses 12a, 12b are evenly distributed at angular intervals of 30° around a full circle. Also at angular intervals of 30°, two second recesses 13a, 13b are arranged between each pair of adjacent first recesses 12a, 12b. This results in a sequence of two first recesses 12a, 12b and two second recesses 13a, 13b. A first set of second recesses 13a are arranged with their centers on a first circumferential line 19a of the first diameter D3, and a second set of second recesses 13b are arranged on a second circumferential line 19b of the larger diameter D4. The first dimension 16a of the second recesses 13a, 13b is 4 mm in this embodiment. The second recesses 13a, 13b have an elliptical shape.Between the first recesses 12a, 12b and the second recesses 13a, 13b, as well as between the second recesses 13a, 13b, webs 20 are visible, the width of which corresponds at least to the value of the first dimension 14a of the first recesses 12a, 12b. The ratio of recesses 12a, 12b, 13a, 13b to solid surface 24 is not less than 25 percent. The inner diameter of the steel lamella 10 is, for example, 230 mm, and the outer diameter is 252 mm, which corresponds to an outer-to-inner diameter ratio of approximately 1.10. The exemplary steel lamella 10 shown is therefore particularly suitable for use in a drive train which has one or more electric motors. Fig. Figure 2 shows, by way of example, a part of a second embodiment of a steel lamella 10 for a friction switching element of a motor vehicle. The first extension 14a of the first recesses 12a, 12b is 10 times the second extension 14b. The extensions 14a and 14b are in the Fig. Figure 2 is shown as solid lines, which do not belong to the illustration of the invention itself but serve only for illustrative purposes. In the present embodiment, the first extension 14a is specifically 20 mm to ensure functionality for the use of an oil with a viscosity of approximately 4 centistokes. Between two adjacent first recesses 12a, 12b, in the area of ​​indentations 22 arranged at a distance of 120 degrees, there is no second recess 13a, 13b; in the other areas, two second recesses 13a, 13b are arranged. The first extension 16a of the second recesses 13a, 13b is twice the length of a second extension 16b. Indentations 22 are arranged on both the inner and outer circumference of the steel lamella. In the exemplary embodiment shown, they have a contour corresponding to a partial ellipse.

[0029] Fig.Figure 3 shows an exemplary part of an embodiment of a steel lamella 10 according to the invention for a friction switching element of a motor vehicle. The first dimension 14a of the first recesses 12a, 12b is 10 times the second dimension 14b. Curvature lines 17a and 17b correspond essentially to circumferential lines 18a and 18b in the present embodiment, respectively, for a first number of first recesses 12a and a second number of first recesses 12b. On a first circumferential line 18a of first diameter D1, a first number of 12 first recesses 12a are arranged with their centers facing [missing information]. On a further circumferential line 18b of larger diameter D2, a further number of 12 first recesses 12b are arranged with their centers facing [missing information]. The arrangement is simply alternating between the circumferential lines 18a and 18b. Pairs of first recesses 12a, 12b are evenly distributed at an angular interval of 30 degrees over the full circle.At an angular interval of 30°, two second recesses 13a, 13b are arranged between each pair of adjacent first recesses 12a, 12b. This results in a sequence of two first recesses 12a, 12b and two second recesses 13a, 13b. The first dimension 16a of the second recesses 13a, 13b is twice the dimension 16b. A first set of 12 second recesses 13a are arranged with their centers on the first circumferential line 19a of first diameter D3, and a second set of 12 second recesses 13b are arranged on the second circumferential line 19b of larger diameter D4. In the illustrated embodiment, the diameters of the circumferential lines 19a and 19b correspond to the diameters of the circumferential lines 18a and 18b. In the area of ​​the indentations 22, no second recesses 13a, 13b are arranged. The first dimension 16a of the second recesses 12b is 4 millimeters in the present embodiment.The second recesses 13a, 13b have an elliptical shape. Between the first recesses 12a, 12b and the second recesses 13a, 13b, as well as between the second recesses 13a, 13b, webs 20 are visible, the width of which corresponds at least to the value of the first dimension 14a of the first recesses 12a, 12b. The inner diameter of the steel lamella 10 is, for example, 230 mm, and the outer diameter is 252 mm, which corresponds to an outer-to-inner diameter ratio of approximately 1.10. The steel lamella 10 shown as an example is therefore particularly suitable for use in a drive train that is wholly or partially powered by an electric motor. Reference symbol list 10 steel lamellae 12a First exemptions 12b First exemptions 13a Second exemptions 13b Second exemptions 14a First extension 14b Second Expansion 15 Rounded outlet 16a First extension 16b Second Extension 17a Curvature line 17b Curvature line 18a First circumferential line 18b Further perimeter lines 19a First circumferential line 19b Further perimeter lines 20 Bridge 22 indentation 24 full surface D1 First diameter D2 Other diameters D3 First Diameter D4 Other diameters

Claims

[1] Oil-lubricated wet friction switching element of a motor vehicle powertrain, wherein the friction switching element has several lamellae arranged in series, which are alternately designed as a steel lamella and friction lining lamella and wherein the steel lamella (10) is unlined on both sides, wherein • the steel lamella (10) has first recesses (12a, 12b) which are elongated in the direction of a first extension (14a) of the first recesses (12a, 12b) and extend along a curve (17a, 17b) in relation to the first extension (14a), wherein each curve (17a, 17b) corresponds substantially to a circumferential line (18a, 18b) on which the first recesses (12a, 12b) are arranged relative to a reference point, and • a first number of first recesses (12a) are arranged according to a reference point on a first circumferential line (18a) with a first diameter (D1) and further numbers of first recesses (12b) are arranged according to a reference point on further circumferential lines (18b) of a different diameter (D2), and • Second recesses (13a, 13b) of significantly smaller first and / or second extent (16a, 16b) are provided, wherein at least between a first pair of adjacent first recesses (12a, 12b) and between a second such pair, exactly one second recess (13a) is arranged according to a reference point on a circumferential line (19a, 19b) which coincides with the first circumferential line (18a), and exactly one further second recess (13b) is arranged according to a reference point on a further circumferential line (19b) which coincides with the second circumferential line (18b). [2] Oil-lubricated wet friction switching element of a motor vehicle powertrain according to claim 1, characterized by , that a first extension (14a) of the first recesses (12a, 12b) is at least approximately 8 times the size of a second extension (14b) and that the first recesses (12a, 12b) have rounded outlets (15). [3] Oil-lubricated wet friction switching element of a motor vehicle powertrain, according to one of the preceding claims, characterized by , that between two first recesses (12a, 12b) a bridge (20) remains with a width which corresponds at least to the value of the second extension (14b). [4] Oil-lubricated wet friction switching element of a motor vehicle powertrain, according to one of the preceding claims, characterized by , that the first expansion (14a) is at least approximately 15 millimeters, the oil having a kinematic viscosity between 3 and 4 centistokes at a temperature of one hundred degrees Celsius. [5] Oil-lubricated wet friction switching element of a motor vehicle powertrain, according to one of the preceding claims, characterized by , that a first extension (16a) of the second recesses (13a, 13b) is at least 2 times the length of a second extension (16b). [6] Oil-lubricated wet friction switching element of a motor vehicle powertrain, according to one of the preceding claims, characterized by , that between the first recesses (12a, 12b) and the second recesses (13a, 13b) there remain webs (20) with a width which is at least equal to the value of the second extension (14b).

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