Transmission for a motor vehicle

Abstract

Transmission for a motor vehicle, comprising a rotor shaft (3) non-rotatably connected to the rotor of an electric machine (EM), at least one bearing (4) directly supporting the rotor shaft (3), a transmission shaft (5) non-rotatably connected to the rotor shaft (3), a multi-start transmission (6) operatively connected to the transmission shaft (5), and an output shaft (7) operatively connected to the transmission shaft (5) by means of the transmission (6), wherein both the transmission shaft (5) and the rotor shaft (3) are directly supported on a transmission component by means of the at least one bearing (4), characterized in that the transmission has a clamping device for pre-tensioning the bearing (4).

Description

[0001] The invention relates to a transmission for a motor vehicle, comprising a rotor shaft non-rotatably connected to the rotor of an electric machine, at least one bearing directly supporting the rotor shaft, a transmission shaft non-rotatably connected to the rotor shaft, a multi-start transmission operatively connected to the transmission shaft, and an output shaft operatively connected to the transmission shaft by means of the transmission.

[0002] Furthermore, the invention relates to a hybrid drive and a motor vehicle with such a transmission.

[0003] Numerous gearboxes are known from the prior art, consisting of a conventional multi-start gear set and a hybrid unit. Each of the two systems is independently supported and has its own axis of rotation. When the gearbox is assembled, the two systems are fixedly connected to each other. This inevitably results in over-constraint, which, depending on its magnitude, causes vibrations and noise during operation, or in the worst case, even bearing damage. Due to manufacturing tolerances of the components involved, the two axes of rotation of the two systems can never be aligned exactly, meaning they are never perfectly aligned. In most cases, they are crossed, parallel, or misaligned. This faulty arrangement of the axes of rotation creates constraint forces within the gearbox, causing the aforementioned problems.

[0004] From DE 10 2014 202 621 A1, a gearbox is known that incorporates a hybrid module. A rotor shaft of the hybrid module, coupled to an electric machine, is supported on the gearbox housing by means of a bearing. Furthermore, the rotor shaft is non-rotatably connected to and supported on a gearbox shaft, which is coupled to a multi-start transmission. The gearbox shaft is supported on the gearbox housing by means of two other bearings. The rotor shaft is supported on the gearbox housing by the non-rotatable connection between the rotor shaft and the gearbox shaft, the gearbox shaft, and the other bearing. This design also suffers from the problem that, due to manufacturing tolerances, the axes of rotation of the rotor shaft and the gearbox shaft are not aligned.

[0005] DE 10 2014 208 799 A1 discloses a gearbox with an electric motor.

[0006] The subsequently published DE 11 2015 000 947 T5 discloses a vehicle drive device.

[0007] DE 11 2013 000 259 T5 discloses a hybrid drive device.

[0008] The object of the invention is therefore to provide a transmission in which the rotational axes of the rotor shaft and the transmission shaft are arranged better relative to each other or are aligned with each other.

[0009] This problem is solved by a gearbox of the type mentioned above, which is characterized in that both the gearbox shaft and the rotor shaft are directly supported on a gearbox component by means of at least one bearing.

[0010] The transmission according to the invention has the advantage that the rotor shaft and the transmission shaft are supported in such a way that no over-constraint exists, so that the rotational axes of the rotor shaft and the transmission shaft are better aligned with each other and ideally align with each other. This is achieved by supporting both the rotor shaft and the transmission shaft on the transmission component by means of the same bearing. The at least one bearing can absorb forces in the radial and / or axial direction, in particular both axial directions.

[0011] The transmission component can be any part of the transmission, such as a transmission housing or the retaining device described below. Furthermore, an advantage of the invention is that the rotor shaft is no longer indirectly supported on the transmission housing via the transmission shaft, but is supported directly on the transmission component by means of at least one bearing. This reduces the tolerance path between the rotor shaft bearing and the stator. The result is a transmission with an improved arrangement of the rotational axes of the rotor shaft and the transmission shaft relative to each other.

[0012] The direct support of the rotor shaft by the at least one bearing means that no other component is located between the rotor shaft and the at least one bearing. Supporting the rotor shaft and the transmission shaft by means of the at least one bearing directly on the transmission component means that no other component is located between the at least one bearing and the transmission component. The transmission shaft can also be supported directly on the transmission component by means of the at least one bearing, i.e., without providing any further components between the transmission shaft and the at least one bearing. Alternatively, the transmission shaft can be supported indirectly on the transmission component by means of the at least one bearing. In this case, one or more components can be arranged radially between the transmission shaft and the at least one bearing.For example, the rotor shaft can be arranged between the transmission shaft and the at least one bearing, so that the transmission shaft is supported on the transmission component via the rotor shaft and the at least one bearing.

[0013] For the purposes of this invention, the term "shaft" is not limited to, for example, a cylindrical, rotatably mounted machine element for transmitting torques. Rather, it also includes general connecting elements that join individual components together, in particular connecting elements that join several components together in a rotationally fixed manner.

[0014] The electric machine consists of at least a stationary stator and a rotatably mounted rotor. In motor mode, it is designed to convert electrical energy into mechanical energy in the form of rotational speed and torque, and in generator mode, it is designed to convert mechanical energy into electrical energy in the form of current and voltage. The electric machine may be housed in a gearbox.

[0015] In a special design, the transmission has an input shaft that can be coupled to an internal combustion engine. The input shaft is connected to the rotor shaft in a rotationally fixed manner by means of a switching element. The switching element can be a clutch, in particular a multi-plate clutch. The switching element allows control over whether the torque supplied by the internal combustion engine is transmitted to the transmission shaft.

[0016] For the purposes of the invention, a rotationally fixed connection is understood to be a connection between two components that is designed such that the two connected components always have the same rotational speed. This is possible, for example, if no switching element is arranged between the two connected components, since otherwise, when the switching element is open, the rotational speeds of the two components could differ. Furthermore, for the purposes of the invention, a connection between two components is described as rotationally fixed if a switching element is arranged between the two connecting components.

[0017] The multi-speed transmission can have several sets of gears, such as planetary gear sets, which allow different gears with different ratios to be implemented.

[0018] Furthermore, the gearbox can include a retaining device for holding the electric machine, in particular the stator. The retaining device can be rotationally fixed to an intermediate housing, whereby the connection between the retaining device and the intermediate housing can be detachable. The intermediate housing can be rotationally fixed to the gearbox housing. The electric machine, in particular the stator, can thus advantageously be rotationally fixed to the intermediate housing solely by means of the retaining device, i.e., without the need for any further connections. This simplifies the installation of the electric machine in the gearbox.

[0019] The assembly process is significantly simplified if the stator is connected to the holding device before being installed in the gearbox. Furthermore, the rotor shaft can be coupled to the electric motor before the rotor shaft is installed in the gearbox. As a result, at least the electric motor and the holding device form a hybrid module that can be easily installed in or removed from the gearbox.

[0020] The transmission shaft and the rotor shaft can be supported on the retaining element by means of at least one bearing. In this case, the retaining element corresponds to the transmission component mentioned above. Since the retaining element is rotationally fixed to the intermediate housing, and the intermediate housing is rotationally fixed to the transmission housing, the transmission shaft and the rotor shaft are supported on the transmission housing via the intermediate housing by means of the at least one bearing and the retaining element. The retaining element may have another bearing that also supports the rotor shaft.

[0021] In a particularly preferred embodiment, the transmission shaft can be connected to the rotor shaft in a rotationally fixed manner by means of a positive-locking connection. This positive-locking connection can preferably be designed as a splined connection. A splined connection is a shaft-hub connection in which the torque is transmitted via tooth flanks. The shaft has external teeth, while the hub has internal teeth. Splined connections are characterized by their simple manufacturing process. Furthermore, the shaft and hub can be axially displaced relative to each other, particularly when unloaded.

[0022] The at least one bearing can be arranged radially, particularly radially extending from the transmission shaft, between a section of the retaining device and a section of the rotor shaft. In particular, the at least one bearing can be attached to the section of the rotor shaft that is non-rotatably connected to the transmission shaft. This section of the rotor shaft can thus include the hub of the aforementioned splined connection. This creates a plane in which the transmission shaft, the section of the rotor shaft connected to the transmission shaft, the at least one bearing, and the retaining device are arranged.

[0023] The transmission shaft can be supported by at least one additional bearing. In particular, the transmission shaft can be supported directly against the transmission housing or via the output shaft by means of the additional bearing. The additional bearing can be arranged on the output shaft, so that the transmission shaft and the output shaft are supported, in particular directly, against the transmission housing by means of the bearing.

[0024] In a particular embodiment, the at least one bearing can be designed as a rolling bearing, which is configured to absorb forces in the axial direction. In particular, the at least one bearing can be designed such that it transmits forces in the axial and radial directions to the transmission component.

[0025] In one design, there may be only a single bearing that absorbs both axial and radial forces. This allows the rotor shaft and the transmission shaft to be supported radially and axially by a single bearing. Alternatively, the bearing may comprise a first and a second bearing, with the first and / or second bearing capable of absorbing both axial and radial forces. Furthermore, the bearing may alternatively comprise a first and a second bearing that absorb only radial forces. In this case, the bearing may additionally include a thrust bearing.

[0026] The bearing can be supported axially on one side by the rotor shaft and on the other side by a shoulder of the gearbox shaft. One side can be in direct contact with the rotor shaft and the other with the shoulder of the gearbox shaft. This ensures, in a simple manner, that the bearing absorbs the respective axial force of the gearbox shaft, regardless of the direction of its axial movement. One side of the bearing can be oriented opposite the other side with respect to a normal plane perpendicular to the rotor shaft's axis of rotation.

[0027] It is particularly advantageous if at least one bearing is a double-row angular contact ball bearing. In this case, only a single bearing is required. The double-row angular contact ball bearing can be configured in an O-arrangement and has the advantage of being able to absorb the axial forces generated when the shifting element is actuated very effectively. Furthermore, the transmission shaft is very well supported axially and therefore exhibits minimal axial movement. This is essential for shifting elements actuated by a release bearing to ensure consistently good shifting performance.

[0028] Alternatively, the bearing can comprise a single-row angular contact ball bearing and a second single-row angular contact ball bearing. Using two single-row angular contact ball bearings is advantageous because they are more cost-effective than a single double-row angular contact ball bearing. The first and second single-row angular contact ball bearings can be spaced axially apart and / or arranged in an O-arrangement. An adjusting element, such as an adjusting washer, can be positioned between the first and second single-row angular contact ball bearings. This adjusting element serves to increase the bearing base, i.e., the axial distance between the first and second angular contact ball bearings, and to compensate for any play between the two angular contact ball bearings, the rotor shaft, and the transmission shaft.

[0029] Any play between the rotor shaft, the at least one bearing, and the transmission shaft is compensated for by a clamping device that preloads the at least one bearing. The clamping device may include a slotted nut screwed onto the transmission shaft. The clamping device exerts an axial force on the at least one bearing via the rotor shaft, pressing the bearing against the shoulder of the transmission shaft. In the embodiment using two single-row angular contact ball bearings, the axial force exerted by the clamping device is transmitted via the rotor shaft, the first single-row angular contact ball bearing, and the adjusting element to the second single-row angular contact ball bearing. Preloading the at least one bearing also offers the advantage of improved bearing arrangement stiffness, increased running accuracy, and the prevention of bearing damage.

[0030] In an alternative design, the bearing can comprise a first radial bearing, in particular a first plain bearing, and a second radial bearing, in particular a second plain bearing. The use of plain bearings is particularly advantageous in gearboxes where limited installation space is available in the radial direction. Furthermore, plain bearings provide excellent damping of the rotor shaft. The radial bearings serve exclusively to absorb radial forces. Therefore, the bearing can include at least one thrust bearing, which can be a needle roller bearing.

[0031] In a particular embodiment, the positive-locking connection can be arranged at least partially between the first and second radial bearings, and especially between the first and second plain bearings. The transmission shaft can be centered on the rotor shaft by means of a fit. The friction-locking connection can be arranged further away from the input shaft and / or the internal combustion engine in the axial direction than the positive-locking connection.

[0032] A hybrid drive in which the internal combustion engine is coupled to the input shaft is particularly advantageous. Furthermore, a motor vehicle equipped with the transmission or hybrid drive according to the invention is advantageous.

[0033] The invention is schematically depicted in the figures and described below, with identical or equivalent elements generally being designated by the same reference numerals. The figures show: Fig. 1 a schematic representation of a first embodiment of the transmission according to the invention for a motor vehicle, Fig. 2 an enlarged section of the transmission according to the invention for a motor vehicle according to a second embodiment, Fig. 3 an enlarged section of the transmission according to the invention for a motor vehicle according to a third embodiment and Fig. 4 an enlarged section of the transmission according to the invention for a motor vehicle according to a fourth embodiment.

[0034] The in Fig. The transmission shown in Figure 1 for a motor vehicle comprises an electric machine EM, which is rotationally fixed to a rotor shaft 3, and a bearing 4, which directly supports the rotor shaft 3. Furthermore, the transmission comprises a transmission shaft 5, which is rotationally fixed to the rotor shaft 3. The transmission shaft 5 is operatively connected to a multi-start reduction gear 6. The transmission also comprises an output shaft 7, which is operatively connected to the transmission shaft 5 via the reduction gear 6. Both the transmission shaft 5 and the rotor shaft 3 are supported by the bearing 4 on a transmission component described in more detail below.

[0035] In the Fig. In the embodiment shown in Figure 1, the gearbox component corresponds to a holding element 8, which serves to hold a stator 1 of the electric machine EM. The holding element 8 is detachably connected to an intermediate housing 9, in particular by screws. The intermediate housing 9 is rotationally fixed to a gearbox housing 19, in particular by screws. The intermediate housing 9 has lines through which the individual components of the gearbox can be supplied with fluid, in particular oil. In particular, the fluid can be supplied to an actuating device 14, which will be discussed below. In addition to the stator 1, the electric machine EM has a rotor 2, which is rotationally fixed to the rotor shaft 3.

[0036] Bearing 4 is a double-row angular contact ball bearing in an O-arrangement and is arranged radially between the rotor shaft 3 and the retaining element 8. Bearing 4 is in direct contact with both the rotor shaft 3 and the transmission shaft 5. Specifically, an inner ring of the double-row angular contact ball bearing rests against both the rotor shaft 3 and the transmission shaft 5. The axial position of the inner ring is fixed by the transmission shaft 5 and the rotor shaft 3, so that relative movement between the inner ring and the rotor shaft 3 and / or transmission shaft 5 is not possible. Specifically, the inner ring abuts a shoulder 10 of the transmission shaft 5 on one side. On the opposite side, the inner ring abuts a radially projecting section of the rotor shaft 3.

[0037] An outer ring of the double-row angular groove ball bearing is in direct contact with the holding element 8. The outer ring of the double-row angular groove ball bearing is fixed in its axial position by the holding element 8. This means that the outer ring cannot move axially relative to the holding element 8.

[0038] The rotor shaft 3 is non-rotatably connected to the transmission shaft 5 by means of a splined connection. The bearing 4 is arranged on a section of the rotor shaft 4 which has the internally toothed hub of the splined connection.

[0039] The gearbox has a clamping device in the form of a slotted nut 11. The slotted nut 11 is screwed onto the drive shaft 5 and exerts an axial force on the rotor shaft 3 and thus on the bearing 4. In particular, as a result of the force exerted by the slotted nut 11, the bearing 4 is pressed against the shoulder 10 of the gearbox shaft 5.

[0040] Furthermore, the transmission has an input shaft 12, which is coupled to an internal combustion engine VM, and a switching element 13 in the form of a clutch. The input shaft 12 can be connected to the rotor shaft 3 in a rotationally fixed manner by means of the switching element 13.

[0041] The switching element 13 can be actuated by an actuating device 14, which may, for example, be a release bearing. The actuating device 14 exerts an axial force on the switching element 13 to close it. A lever 16 of the actuating device, through which the switching element 13 is actuated, extends through the rotor shaft 3. Furthermore, the actuating device 14 has a piston 23 coupled to the lever 16. When the actuating device 14 is activated, the piston 23 is pressurized with a fluid and consequently moves in an axial direction. As a result of the axial movement of the piston, the lever 16 presses against the switching element 13 and thus exerts the axial force on the switching element 13.

[0042] The transmission has several planetary gear sets and switching elements, by means of which different gears with different ratios can be implemented.

[0043] The transmission shaft 5 is supported by a further bearing 15 in addition to the bearing 4. The further bearing 15 is arranged on the output shaft 7 and supports the output shaft 7 directly against the transmission housing 19.

[0044] Fig. Figure 2 shows an enlarged section of the transmission according to the invention for a motor vehicle according to a second embodiment. The in Fig. The embodiment shown in 2 differs from the one in Fig. 1 shown embodiment in the design of bearing 4.

[0045] This indicates that in Fig. Figure 2 shows a second embodiment with two single-row angular contact ball bearings in an O-arrangement. The two single-row angular contact ball bearings are spaced apart axially. An adjusting washer 17 is arranged between the two angular contact ball bearings. The adjusting washer 17 is in direct contact with the inner rings of the two angular contact ball bearings.

[0046] The two angular contact ball bearings are preloaded by the slotted nut 11. In particular, an axial force exerted by the slotted nut 11 is transmitted via the rotor shaft 3, a first angular contact ball bearing, the adjusting washer 17 to a second angular contact ball bearing, thereby pressing the second angular contact ball bearing against the shoulder 10 of the transmission shaft 3.

[0047] Furthermore, there is a difference to the one in Fig. The embodiment shown in Figure 1 differs in that only one inner ring of the angular contact ball bearing, which is located further away from the input shaft and / or internal combustion engine, is arranged on both the transmission shaft 5 and the rotor shaft 3.

[0048] Fig. Figure 3 shows an enlarged section of the transmission according to the invention for a motor vehicle according to a third embodiment. The third embodiment differs from the second embodiment in the design of a larger bearing base.

[0049] Fig. Figure 4 shows an enlarged section of the transmission according to the invention for a motor vehicle according to a fourth embodiment. In the Fig. In the embodiment shown in Figure 4, a first plain bearing 24 and a second plain bearing 25 are provided, by means of which the rotor shaft 3 and the transmission shaft 5 are supported on the holding element 8. The rotor shaft 3 is directly supported on the holding element 8 by means of the first and second plain bearings 24, 25. The two plain bearings 24, 25 can only absorb radial forces. In addition, two axial bearings 21, 22 are provided, which can only absorb axial forces.

[0050] In addition to the plug connection, the rotor shaft 3 is centered on the transmission shaft 5 by means of a fit. The fit is located in a region of the transmission shaft 5 that is axially further away from the internal combustion engine VM than the plug connection. In particular, the fit is located in the area of ​​the two axial bearings 21, 22.

[0051] The plug connection and the fit support the gearbox shaft 5 radially on the rotor shaft 3. This means that in this embodiment the gearbox shaft 5 is supported on the retaining means 8 by means of the plug connection and the fit, the rotor shaft 3 and the first and second plain bearings 24, 25.

[0052] The two axial bearings 21, 22 serve to absorb the axial forces acting on the transmission shaft 5 and are designed as axial needle bearings. A first axial bearing 21 absorbs an axial force from the transmission shaft 5 in a first axial direction. This axial force can occur, for example, when the switching element 13 is actuated. A second bearing 22 absorbs an axial force in a second direction, opposite to the first axial direction. This axial force can occur, for example, when one or more switching elements in the transmission 6 are closed.

[0053] The axial force acting on the transmission shaft 5 is transmitted via a transmission element 20 to the first and / or second axial bearings 21, 22. The transmission element 20 is arranged axially between the two axial bearings 21, 22 and is operatively connected to the transmission shaft 5. The transmission element 20 is arranged on the transmission shaft 5 without play. Furthermore, the transmission element is in direct contact with the two axial bearings 21, 22 and the transmission shaft 5.

Claims

[1] Transmission for a motor vehicle, comprising a rotor shaft (3) non-rotatably connected to the rotor of an electric machine (EM), at least one bearing (4) directly supporting the rotor shaft (3), a transmission shaft (5) non-rotatably connected to the rotor shaft (3), a multi-start transmission (6) operatively connected to the transmission shaft (5), and an output shaft (7) operatively connected to the transmission shaft (5) by means of the transmission (6), wherein both the transmission shaft (5) and the rotor shaft (3) are directly supported on a transmission component by means of the at least one bearing (4), characterized by , that the gearbox has a tensioning device for pre-tensioning the bearing (4). [2] Gearbox according to claim 1, characterized by , that the transmission has an input shaft (12) that can be coupled to an internal combustion engine (VM) and which can be connected to the rotor shaft (3) in a rotationally fixed manner by means of a switching element (13). [3] Gearbox according to claim 1 or 2, characterized by , that the gearbox has a holding means (8) for holding the electric machine (EM) and the gearbox shaft (5) and the rotor shaft (3) are supported on the holding means (8) by means of the at least one bearing (4). [4] Gearbox according to any one of claims 1 to 3, characterized by , that the transmission shaft (5) is connected to the rotor shaft (3) in a rotationally fixed manner by means of a positive locking connection. [5] Gearbox according to claim 3 or 4, characterized by , that at least one bearing (4) is arranged in a radial direction between a section of the holding means (8) and a section of the rotor shaft (3). [6] Gearbox according to any one of claims 1 to 5, characterized by , that the transmission shaft (5) is supported on a transmission housing (19) directly or via the output shaft (7) via a further bearing (15). [7] Gearbox according to any one of claims 1 to 6, characterized by, that at least one bearing (4) is supported in the axial direction on one side on the rotor shaft (3) and on another side on a shoulder (10) of the transmission shaft (5). [8] Gearbox according to any one of claims 1 to 7, characterized by , that at least one bearing (4) is designed as a rolling bearing which is designed to absorb forces in the axial and radial directions. [9] Gearbox according to claim 8, characterized by , that a. that at least one bearing (4) is a double-row angular contact ball bearing or that b. the bearing (4) comprises a first single-row angular contact ball bearing and a second single-row angular contact ball bearing, wherein an adjusting element (17) is arranged between the first single-row angular contact ball bearing and the second single-row angular contact ball bearing. [10] Gearbox according to any one of claims 1 to 7, characterized by, that the bearing (4) comprises a first radial bearing, in particular a first plain bearing (24), and a second radial bearing, in particular a second plain bearing (25). [11] Gearbox according to claim 10, characterized by , that at least one bearing (4) includes at least one axial bearing (21, 22). [12] Gearbox according to claim 10 or claim 11, characterized by , that the positive locking connection of the rotor shaft (3) with the transmission shaft (5) is at least partially arranged between the first and second radial bearings. [13] Gearbox according to any one of the preceding claims 1 to 11, characterized by , that the transmission shaft (5) is centered on the rotor shaft (3) by means of a fit. [14] Hybrid drive with a transmission according to any one of claims 1 to 13, characterized by , that the internal combustion engine (VM) is coupled to the input shaft (12). [15] Motor vehicle with a transmission according to any one of claims 1 to 13 or a hybrid drive according to claim 14.

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