automotive transmission

Abstract

Motor vehicle transmission (1) with a transmission housing (8) and means for translating a first rotary motion into a second rotary motion of different speeds and / or different directions of rotation, wherein the motor vehicle transmission (1) comprises a first transmission shaft (2) and a second transmission shaft (3) which are rotatably mounted in the transmission housing (8) by means of rolling bearings (6, 7, 15, 16), wherein the first transmission shaft (2) carries a first gear (4) and the second transmission shaft (3) carries a second gear (5) which engages with the first gear (4) or can be brought into engagement with the first gear (4), wherein the motor vehicle transmission (1) has a bearing plate (9) which comprises at least two bearing points (14) for supporting transmission shafts (2, 3), wherein a plurality of slots (27) are provided in the bearing plate (9) to reduce the stiffness of the bearing plate (9) in partial areas of the bearing plate (9),wherein the bearing plate (9) further comprises a first opening (10) and a second opening (11), wherein rolling bearings (25, 26) are arranged in the openings (10, 11) of the bearing plate (9), characterized in that the slots (27) are arranged in a circular shape (28) around the respective openings (10, 11) in the bearing plate (9).

Description

The invention relates to a motor vehicle transmission with a bearing plate and to a method for manufacturing such a bearing plate according to the preamble of the independent claims. In motor vehicle transmissions, internal vibration excitations lead to system-related noise generation. A primary noise source is the rolling tooth flanks of meshing gears under load, as the forces and torques generated during rolling cause vibrations that are perceived by the vehicle's occupants as transmission rattle or whine. Noise can also originate from other parts of the transmission, such as the rolling noise of the bearings. These noises generated within the transmission are transmitted as structure-borne sound via gears, transmission shafts, and bearings to the transmission housing, from where they are either emitted as airborne sound into the surrounding environment or introduced into the vehicle structure as structure-borne sound. A crucial component in this transmission chain is the transmission bearing, which is in direct contact with the transmission housing. To reduce noise generation in a vehicle transmission, measures can be taken to minimize vibration excitation; these are referred to as primary measures. Secondary measures can also be implemented to reduce the transmission of sound waves to the transmission housing or the emission of sound waves from the transmission housing. Primary measures include, for example, optimizing the stiffness profile of the gear teeth and reducing the deviations between them. However, these measures typically lead to a significant increase in manufacturing costs, as they involve tighter manufacturing tolerances and consequently longer machining times for the components. Furthermore, these measures cannot minimize noise in all load cases, so they are generally not suitable as the sole means of noise reduction. Secondary measures aimed at minimizing the transmission of sound waves to the housing and the radiation of sound waves include various types of insulation and damping, as well as measures that aim to modify the natural vibration behavior of the components primarily involved in structure-borne noise generation and conduction. One way to reduce noise is to insulate the bearing points from the gearbox housing. From DE 195 02 560 A1, a motor vehicle transmission is known in which at least two gears are arranged that are rotatable relative to each other and mesh with each other. The gears are mounted at at least one end in a common bearing plate, with an elastic spring ring made of a polymer material provided between the bearing plate and the transmission housing to reduce the transmission of sound into the transmission housing. From DE 20 2017 104 746 U1, a bearing support is known which carries a first outer ring and a second outer ring of two rolling bearings. The outer rings of the rolling bearings each have a groove that extends completely around the respective outer ring in the circumferential direction. Furthermore, the bearing support comprises a base body in which the outer rings of the rolling bearings are embedded. A flexible coupling element is provided between the outer rings and the base body to reduce the transmission of vibrations from the outer rings to the bearing support. DE 10 2007 006 228 A1 discloses a gearbox with a housing in which at least two shafts can be coupled to each other via a gear set to set a desired gear ratio, the shafts being rotatably mounted in the housing by means of bearing plates. The bearing plates are mounted to the housing via at least one damping element for sound and vibration damping. A switching device for setting the gear ratio is attached to at least one of the bearing plates, which are decoupled from the housing. Another way to reduce noise is to isolate various bearing points of the transmission shafts from the transmission housing. However, this measure significantly reduces bearing stiffness in the radial direction. This reduction in stiffness at the bearing points leads to increased shaft displacement when transmitting torque within the transmission. In spur gear transmissions, this significantly affects the contact pattern of the gear teeth. This can potentially lead to reduced durability and increased excitation, thereby increasing noise generation. A further disadvantage arises if only a few bearing points can be isolated.Due to the reduced stiffness of the isolated bearing points compared to the non-isolated bearing points, the forces and moments are more strongly supported at the non-isolated bearing points, thereby increasing the load at these bearing points and increasing the structure-borne noise transmission at these bearing points. The object of the invention is to minimize noise generation in a motor vehicle transmission and to overcome the disadvantages known from the prior art. According to the invention, this problem is solved by a motor vehicle transmission comprising a transmission housing and means for translating a first rotary motion into a second rotary motion of different speeds and / or different directions of rotation. The motor vehicle transmission includes a first transmission shaft and a second transmission shaft, which are rotatably mounted in the transmission housing by means of rolling bearings. The first transmission shaft carries a first gear, and the second transmission shaft carries a second gear, which engages with, or can be brought into engagement with, the first gear. The motor vehicle transmission is provided to have a bearing plate comprising at least two bearing points for supporting the transmission shafts. The bearing plate has a plurality of slots to reduce the stiffness of the bearing plate in certain areas.The slots in the bearing plate allow for changes to its stiffness and thus to the range of its natural frequency. Furthermore, the slots dampen vibrations, thereby reducing the transmission of structure-borne sound waves from the transmission shafts to the transmission housing. The features listed in the dependent claims enable advantageous improvements and further developments of the motor vehicle transmission proposed in the independent claim. In a preferred embodiment of the automotive transmission, the bearing plate has a first opening and a second opening, in which rolling bearings for supporting the transmission shafts are arranged. This allows for coupling of the transmission shafts, thereby increasing the stiffness of the transmission assembly and reducing the deflection of the transmission shafts. This reduces the bearing load on the rolling bearings, thus decreasing the transmission of vibrations to the transmission housing. Furthermore, the reduced deflection of the transmission shafts allows for the inclusion of additional damping elements, which further reduce the transmission of vibrations from the rolling bearings to the bearing plate and / or from the bearing plate to the transmission housing. In a preferred embodiment of the invention, the slots are arranged in a circular shape around the respective opening in the bearing plate. For a multitude of applications, it has proven advantageous to arrange the slots in the bearing plate in such a way that they form a circular shape around the respective opening. This minimizes the transmission of structure-borne noise from the rolling bearing housed in the opening to the gearbox housing. For other applications, it is advantageous for the slots to have a meandering shape. In this case, the slots are placed at appropriate locations on the bearing plate to achieve a local reduction in stiffness. In a beneficial improvement, the bearing plate is composed of multiple sheets. This multi-sheet construction creates additional slots between the individual sheets, which also dampen vibrations. Furthermore, manufacturing is simplified, as the individual sheets can be produced easily and cost-effectively as stamped parts. Additionally, designers gain more freedom in the bearing plate's design, since the slots do not need to extend completely through the entire plate but can be present only in individual sheets. This allows for better tuning of the bearing plate to the specific vibrations to be damped. In a preferred embodiment of the automotive transmission, the bearing plate is provided with at least two mounting openings through which it can be fixed to another transmission component. These mounting openings allow for easy fixation of the bearing plate. Additional damping elements can be provided at the mounting openings to reduce the transmission of structure-borne noise. The bearing plates can be attached directly to the transmission housing or to another transmission component. The slots in the bearing plate provide sufficient damping to minimize transmission noise. According to an advantageous embodiment of the invention, the first and second transmission shafts are each supported at a first and a second bearing point in the transmission housing, with the bearing plate forming at least one of the bearing points. Since the installation space in motor vehicle transmissions is often limited, and at the same time there is a desire for the lowest possible weight of the transmission, bearing plates are used in such transmissions to enable a compact and space-saving mounting of the two transmission shafts. Because such a bearing plate can, by its very nature, be excited by the vibrations of both transmission shafts, these bearing plates are particularly critical with regard to the transmission of structure-borne noise from the transmission shafts to the transmission housing.The slots in the bearing plate allow for appropriate vibration damping, so that structure-borne noise is only transmitted to the gearbox housing to a very limited extent. Alternatively, in a further embodiment of the invention, the first and second transmission shafts are each supported at a first and a second bearing point in the transmission housing, the bearing plate being a coupling plate that forms an additional bearing point between the first and second bearing points. This additional bearing point reduces the deflection of the transmission shafts, particularly in transmissions with long transmission shafts and many gear pairs. This reduces the overall load at the bearing points, thereby minimizing structure-borne noise excitation.Although the coupling plate, if it has direct contact with the gearbox housing, forms another transmission path for structure-borne noise, the corresponding damping through the slots in the coupling plate and the reduced deflection of the gearbox shafts and the resulting reduced bearing forces result in an overall reduction of gearbox noise. According to the invention, a bearing plate for a motor vehicle transmission is proposed, wherein a plurality of slots are incorporated into the bearing plate to reduce the stiffness of the bearing plate in certain areas. By using such a bearing plate to support the transmission shafts in a motor vehicle transmission, the transmission of vibrations from the transmission shaft bearings to the transmission housing is reduced, thereby minimizing transmission noise. In an advantageous embodiment of the invention, the slots in the bearing plate are filled with a damping filling material, in particular a plastic or a foam. The damping effect of the slots can be enhanced by using a suitable highly damping filling material. The invention also proposes a method for manufacturing a bearing plate for a motor vehicle transmission, wherein slots are incorporated into the bearing plate to locally reduce its stiffness. By incorporating these slots, the bearing plate can be adapted to the vibrations occurring, in order to minimize the transmission of structure-borne sound waves. In a preferred embodiment of the method, the bearing plate is composed of a plurality of sheets, the slots preferably being introduced into the sheets by means of a punching or fine-blanking process. By using a bearing plate composed of stacked sheets, the individual sheets can be made correspondingly thin, making the introduction of the slots by a punching or fine-blanking process cost-effective and requiring comparatively little tooling. Furthermore, the individual sheets can be clamped together using a suitable clamping device, resulting in elastic and / or plastic deformation of the sheets. This allows the natural frequency of the bearing plate to be changed, thereby optimizing its damping behavior. Unless otherwise stated in individual cases, the various embodiments of the invention mentioned in this application can be advantageously combined with one another. The invention is explained below with reference to preferred embodiments and the accompanying figures. Identical components or components with the same function are identified by the same reference numerals. Figure 1 shows an embodiment of a motor vehicle transmission according to the invention with two transmission shafts, wherein the transmission shafts are rotatably mounted in the transmission housing at least at one bearing point by means of a bearing plate; Figure 2 shows an embodiment of a bearing plate for a motor vehicle transmission according to the invention; and Figure 3 shows a further embodiment of a bearing plate for a motor vehicle transmission according to the invention. Figure 1 shows an embodiment of a motor vehicle transmission 1 according to the invention, comprising a first transmission shaft 2 and a second transmission shaft 3. The first transmission shaft 2 is rotatably mounted in a transmission housing 8 of the motor vehicle transmission 1 by means of two rolling bearings 6, 7. The first transmission shaft 2 carries a first gear 4, which is arranged between the two bearing points of the transmission shaft 2. The rolling bearings 6, 7 are preferably designed as ball bearings, tapered roller bearings, or cylindrical roller bearings. The first gear 4 meshes with a second gear 5, which is arranged on and supported by the second transmission shaft 3. A tooth 20 on the end face 22 of the first gear 4 meshes with a tooth 21 on the end face 23 of the second gear 5.The second transmission shaft 3 is rotatably mounted in the transmission housing 8 of the motor vehicle transmission 1 by means of a third rolling bearing 15 and a fourth rolling bearing 16. The gears 4, 5 are non-rotatably connected to the respective transmission shafts 2, 3 or can be non-rotatably connected to these transmission shafts 2, 3, in particular by means of a shift fork. The rolling bearings 6, 7, 15, 16 each have an inner ring 18 and an outer ring 19, with a plurality of rolling elements 24 arranged between the inner ring 18 and the outer ring 19. At least one bearing plate 9 with a first opening 10 and a second opening 11 is arranged in the transmission housing 8, with the first transmission shaft 2 being guided through the first opening 10 and the second transmission shaft 3 through the second opening 11 of the bearing plate 9. In the openings 10, 11 a rolling bearing 25, 26 is provided in which the transmission shafts 2, 3 can be rotatably mounted.The transmission shafts 2, 3 are supported by rolling bearings 25, 26 at an additional bearing point 14 between the respective rolling bearings 6, 7, 15, 16 to reduce the deflection of the transmission shafts 2, 3. Alternatively, the bearing plate 9 can also replace one bearing point 6, 7, 15, 16 of each of the first and second transmission shafts 2, 3. The bearing plate 9 can be fixed to the transmission housing 8 or to another transmission component via mounting openings 12. Alternatively, the bearing plate 9 can be in no direct contact with the transmission housing 8, thus preventing sound transmission from the bearing plate 9 to the transmission housing 8.In this embodiment, the bearing plate 9 is preferably designed without mounting openings 12 and is slid onto the two transmission shafts 2, 3 such that, in the assembled state, the bearing plate 9 is located between the first bearing point 6, 15 and the second bearing point 7, 16 for the two transmission shafts 2, 3, thus forming an additional bearing point 14. This provides additional support for the transmission shafts 2, 3, thereby reducing their deflection and increasing the stiffness of the vehicle transmission 1. This increase in stiffness can be used to provide corresponding elastic receiving elements 17 at the bearing points of the rolling bearings 6, 7, 15, 16, which decouple the outer rings 19 of the rolling bearings 6, 7, 15, 16 from the transmission housing 8. The rolling action of the teeth 20 of the first gear 4 against the teeth 21 of the second gear 5 generates vibrations, which are transmitted via the gears 4, 5, the transmission shafts 2, 3, and the rolling bearings 6, 7, 15, 16 to the gearbox housing 8. This causes the gearbox housing 8 itself to vibrate. The structure-borne noise is transmitted from the gearbox housing 8 to the vehicle components connected to it, particularly the chassis, and is radiated from the gearbox housing 8 as sound waves. The slots 27 in the bearing plate 9 dampen the propagation and transmission of structure-borne noise waves, thereby minimizing gearbox noise. Figure 2 shows an embodiment of a bearing plate 9 for a motor vehicle transmission 1 according to the invention. The bearing plate 9 has a plurality of slots 27, which locally weaken the bearing plate 9. This changes the natural vibration behavior of the bearing plate 9 and allows the vibrations transmitted to the bearing plate 9 from the rolling bearings 25, 26 to be dampened. The bearing plate 9 has a first opening 10 for receiving the first transmission shaft 2 and a second opening 11 for receiving the second transmission shaft 3. A fifth rolling bearing 25 is provided in the first opening 10 and a sixth rolling bearing 26 in the second opening 11, each providing an additional bearing point 14 for the transmission shafts 2, 3 between the first bearing point 6, 15 and the second bearing point 7, 16.The slots 27 can be arranged in a circular pattern around the openings 10, 11, thereby interrupting the transmission path between the rolling bearings 6, 7, 15, 16, 25, 26 and the gearbox housing 8. The bearing plate 9 can be designed as a stack of sheets 30, which simplifies the creation of the slots 27. The stack of sheets 30 is subjected to a corresponding preload force, which can be applied to the stack by suitable clamping devices, in particular a clamping screw. Alternatively or additionally, further clamping devices, in particular clamping bands or metal clamps placed around the stack, can be provided to bring the individual sheets 30 of the stack closer together and thus prevent them from shifting relative to each other. The preload can influence the strength of the stack, enabling the stack to dampen different natural frequencies.Multiple identical sheets 30, as well as sheets of varying thicknesses and / or materials, can be stacked together to adapt the damping properties to the frequency range to be damped. The bearing plate 9 has mounting openings 12, which allow it to be fixed to the gearbox housing 8 or another gearbox component. Damping elements 31 can be provided at the mounting openings 12 to achieve appropriate decoupling or damping between the bearing plate 9 and the gearbox housing 8. In an alternative embodiment, the slots 27 can be filled with a damping filling material 32, which further enhances the damping effect of the slots 27. Figure 3 shows a further embodiment of a bearing plate 9 according to the invention for a motor vehicle transmission 1 according to the invention. With essentially the same construction as shown in Figure 2, the slots 27 in this embodiment are designed in a meandering shape. This shape of the slots 27 reduces the propagation of sound waves, thus reducing the structure-borne noise transmission from the bearing plate 9 to the transmission housing 8. Reference symbol list 1 Motor vehicle transmission 2 (first) transmission shaft 3 (second) transmission shaft 4 (first) gear 5 (second) gear 6 Rolling bearing 7 Rolling bearing 8 Transmission housing 9 Bearing plate 10 First opening 11 Second opening 12 Mounting opening 13 Damping element 14 Bearing point 15 Rolling bearing 16 Rolling bearing 17 Mounting element 18 Inner ring 19 Outer ring 20 Toothing 21 Toothing 22 End face 23 End face 24 Rolling element 25 Rolling bearing 26 Rolling bearing 27 Slot 28 Circular shape 29 Meander shape 30 Sheet metal 31 Damping element 32 Filling material

Claims

Motor vehicle transmission (1) with a transmission housing (8) and means for translating a first rotary motion into a second rotary motion of different speeds and / or different directions of rotation, wherein the motor vehicle transmission (1) comprises a first transmission shaft (2) and a second transmission shaft (3) which are rotatably mounted in the transmission housing (8) by means of rolling bearings (6, 7, 15, 16), wherein the first transmission shaft (2) carries a first gear (4) and the second transmission shaft (3) carries a second gear (5) which engages with the first gear (4) or can be brought into engagement with the first gear (4), wherein the motor vehicle transmission (1) has a bearing plate (9) which comprises at least two bearing points (14) for supporting transmission shafts (2, 3), wherein a plurality of slots (27) are provided in the bearing plate (9) to reduce the stiffness of the bearing plate (9) in partial areas of the bearing plate (9),wherein the bearing plate (9) further comprises a first opening (10) and a second opening (11), wherein rolling bearings (25, 26) are arranged in the openings (10, 11) of the bearing plate (9), characterized in that the slots (27) are arranged in a circular shape (28) around the respective openings (10, 11) in the bearing plate (9). Motor vehicle transmission (1) according to claim 1, characterized in that the slots (27) have a meander shape (29). Motor vehicle transmission (1) according to one of claims 1 or 2, characterized in that the bearing plate (9) is composed of a plurality of sheets (30). Motor vehicle transmission (1) according to one of claims 1 to 3, characterized in that at least two fastening openings (12) are provided on the bearing plate (9) via which the bearing plate (9) can be fixed to a further transmission component. Motor vehicle transmission (1) according to one of claims 1 to 4, characterized in that the first transmission shaft (2) and the second transmission shaft (3) are each mounted at a first bearing point (6, 15) and at a second bearing point (7, 16) in the transmission housing (8), wherein the bearing plate (9) forms at least one of the bearing points (6, 7, 15, 16). Motor vehicle transmission (1) according to one of claims 1 to 5, characterized in that the slots (27) in the bearing plate (9) are filled with a damping filling material (32), in particular a plastic or a foam.

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