Transmission

A transmission for a motor vehicle includes an electric motor. A rotor shaft is connected in a torque-proof manner to a rotor of the electric motor. At least one bearing directly supports the rotor shaft. A transmission shaft is connected in a torque-proof manner to the rotor shaft. Both the transmission shaft and the rotor shaft are supported directly on a transmission component by the at least one bearing.

FIELD OF THE INVENTION

The invention relates generally to a transmission for a motor vehicle, with a rotor shaft that is connected in a torque-proof manner to the rotor of an electric motor, at least one bearing that directly supports the rotor shaft, a transmission shaft that is connected in a torque-proof manner to the rotor shaft, a multi-speed transmission gearing in operative connection with the transmission shaft and an output shaft in operative connection with the transmission shaft by the transmission gearing.

The invention also relates generally to a hybrid drive and a motor vehicle with such a transmission.

BACKGROUND

A multitude of transmissions, which consist of a conventional multi-speed gear set and a hybrid unit, are known from the state of the art. Each of the two systems is self-supporting and has its own central axis of rotation. In the assembled state of the transmission, the two systems are connected to each other in a torque-proof manner. This necessarily results in a redundancy that, depending on the order of magnitude during operation, causes vibrations and noises or, in the worst case, even damages the bearing. The two central axes of rotation of the two systems can never be exactly superimposed on each other, due to the manufacturing tolerances of the participating components, such that the central axes of rotation are never perfectly aligned with each other. In most cases, they are crossed, parallel or crooked relative to each other. As a result of this defective arrangement of the central axes of rotation relative to each other, constraining forces arise in the transmission causing the aforementioned problems.

A transmission that features a hybrid module is known from DE 10 2014 202 621 A1. A rotor shaft, which is coupled to an electric motor of the hybrid module, is supported by a bearing on the transmission housing. In addition, the rotor shaft is connected in a torque-proof manner and is supported on a transmission shaft that is coupled to a multi-speed transmission gearing. The transmission shaft is supported on the transmission housing by two other bearings. The rotor shaft is supported on the transmission housing by the torque-proof connection between the rotor shaft and the transmission shaft, the transmission shaft and the other bearing. In this version as well, the problem exists that, due to manufacturing tolerances the central axes of rotation of the rotor shaft and the transmission shaft are not perfectly aligned with each other.

SUMMARY OF THE INVENTION

As such, exemplary aspects of the invention provide a transmission with which the central axes of rotation of the rotor shaft and the transmission shaft are arranged better relative to each other or are aligned with each other relative to known transmissions.

Exemplary aspects of the invention provide a transmission of the aforementioned type, which is characterized in that both the transmission shaft and the rotor shaft are supported directly on a transmission component by the at least one bearing.

The transmission in accordance with exemplary aspects of the invention has the advantage that the mounting of the the rotor shaft and the transmission shaft takes place in such a manner that a redundancy no longer exists, such that the central axes of rotation of the rotor shaft and the transmission shaft are better arranged relative to each other and, in the ideal case, are aligned with each other. This is realized by the fact that both the rotor shaft and the transmission shaft are supported on the transmission component by the same bearing. Thereby, the at least one bearing can absorb forces in the radial and/or axial direction, in particular in both axial directions.

The transmission component can be any component of the transmission, such as, for example, a transmission housing or the retainer explained below. In addition, one exemplary advantage of the invention is that the rotor shaft is no longer indirectly supported on the transmission housing by the transmission shaft, but is supported directly on the transmission component by the at least one bearing. This reduces the tolerance path between the bearing of the rotor shaft and the stator. The result is a transmission that has a better arrangement of the central axes of rotation of the rotor shaft and the transmission shaft relative to each other.

The direct mounting of the rotor shaft by the at least one bearing means that no other component is arranged between the rotor shaft and the at least one bearing. The support of the rotor shaft and the transmission shaft directly on the transmission component by the at least one bearing means that no other component is arranged between the at least one bearing and the transmission component. The transmission shaft can also be supported directly on the transmission component by the at least one bearing, that is, without the provision of additional components between the transmission shaft and the at least one bearing. Alternatively, the transmission shaft can be indirectly supported on the transmission component by the at least one bearing. In this case, one or more components can be arranged in the radial direction 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, such that the transmission shaft is supported on the transmission component by the rotor shaft and the at least one bearing.

Within the meaning of this invention, a shaft is not to be understood exclusively as, for example, a cylindrical, rotatably mounted machine element for transferring torque. Rather, it is understood to also include general connecting elements that connect individual components to each other, in particular connecting elements that connect multiple components in a torque-proof manner.

The electric motor includes at least of one stationary stator and the rotatably mounted rotor, and in engine mode is configured to convert electrical energy into mechanical energy in the form of rotational speed and torque, and in generator mode is configured to convert mechanical energy into electrical energy in the form of current and voltage. The electric motor can be arranged in a transmission housing.

With a particular version, the transmission features an input shaft that can be coupled to an internal combustion engine. The input shaft is connectable to the rotor shaft in a torque-proof manner by a shift element. The shift element can be a clutch, in particular a multi-disk clutch. Whether the torque provided by the internal combustion engine is transferred to the transmission shaft can be set by the shift element.

For the purposes of this invention, a torque-proof connection is understood as a connection between two components that is formed in such a manner that the two components connected to each other always feature the same rotational speed. This is possible if, for example, no shift element is arranged between the two components connected to each other, since, otherwise, the rotational speeds of the two components can differ from each other in the open state of the shift element. In addition, for the purposes of this invention, a connection between two components is designated as “connectable to the rotor shaft in a torque-proof manner” if a shift element is arranged between the two components connected to each other.

The multi-speed transmission gearing can feature multiple gear sets, such as, for example, planetary gear sets, by which different gears with different transmission ratios can be realized.

In addition, the transmission can feature a retainer for retaining the electric motor, in particular the stator. The retainer can be connected in a torque-proof manner to an intermediate housing, whereas the connection between the retainer and the intermediate housing can be formed to be detachable. The intermediate housing can be connected in a torque-proof manner to the transmission housing. Thus, the electric motor, in particular the stator, can advantageously be connected to the intermediate housing in a torque-proof manner solely by the retainer, thus, without the provision of additional connections. This simplifies the assembly of the electric motor in the transmission.

The assembly process is simplified particularly if the stator is connected to the retainer prior to installation in the transmission. In addition, the rotor shaft can be coupled to the electric motor prior to the installation of the rotor shaft in the transmission. As a result, at least the electric motor and the retainer form a hybrid module, which can be easily installed in the transmission or removed from the transmission.

The transmission shaft and the rotor shaft can be supported on the retainer by the at least one bearing. In this case, the retainer corresponds to the aforementioned transmission component. Since the retainer is connected in a torque-proof manner to the intermediate housing, and this is connected in a torque-proof manner to the transmission housing, the transmission shaft and the rotor shaft are supported on the transmission housing by the at least one bearing and the retainer through the intermediate housing. The retainer can have a different bearing that also supports the rotor shaft.

With a particularly preferred embodiment, the transmission shaft can be connected in a torque-proof manner to the rotor shaft by a positive-locking connection. The positive-locking connection preferably can be formed as a spline. A spline is a shaft-hub connection, wherein the torque is transferred by tooth flanks. The shaft is externally toothed, while the hub is internally toothed. Splines are characterized by a simple establishment of the connection. In addition, the shaft and hub can be displaced axially relative to each other, in particular in the unencumbered state.

The at least one bearing can be arranged in the radial direction, in particular in the radial direction starting from the transmission shaft, between a section of the retainer 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 connected in a torque-proof manner to the transmission shaft. Thus, the section of the rotor shaft can feature the hub of the aforementioned spline. Thus, there is a plane at which the transmission shaft, the section of the rotor shaft connected to the transmission shaft, the at least one bearing, and the retainer are arranged.

In addition to the at least one bearing, the transmission shaft can be supported by an additional bearing. In particular, the transmission shaft can be supported directly on the transmission housing or through the output shaft by the additional bearing. Thereby, the additional bearing can be arranged on the output shaft, such that the transmission shaft and the output shaft are supported, in particular directly, on the transmission housing by the bearing.

With a particular version, the at least one bearing can be formed as a rolling bearing that is configured to absorb forces in the axial direction. In particular, the at least one bearing can be formed in such a manner that it transfers forces to the transmission component in the axial and radial direction.

With one version, only a single bearing, which absorbs the axial and radial forces, can be provided. Thus, the rotor shaft and the transmission shaft can be supported in a radial and axial direction by a single bearing. Alternatively, the bearing can comprise first and second bearings, whereas the first and/or second bearings are able to absorb the axial and radial forces. In addition, the bearing can alternatively comprise first and second bearings, which can absorb only radial forces. In this case, the bearing can additionally comprise an axial bearing.

The bearing can be supported in the axial direction on one side on the rotor shaft, and on another side on a shoulder of the transmission shaft. Thereby, the one side can directly fit on the rotor shaft and the other side can directly fit on the shoulder of the transmission shaft. Thus, in a simple manner, it is ensured that the bearing absorbs the respective axial force of the transmission shaft independently of the direction of the axial movement of the transmission shaft. The one side of the bearing can face the other side with respect to a normal plane running perpendicular to the central axis of rotation of the rotor shaft.

It is particularly advantageous if the at least one bearing is a double-row angular ball bearing. In this case, only one bearing is required. The double-row angular ball bearing can be formed in an O-arrangement, and features the advantage that, upon an actuation of the shift element, it can very easily absorb the axial forces. In addition, the transmission shaft is mounted very easily in axial manner, and thus can perform only a small axial movement. This is absolutely necessary with shift elements that are actuated by a release bearing, such that a good shifting quality is guaranteed.

Alternatively, the bearing can comprise a single-row angular ball bearing and a second single-row angular ball bearing. The provision of two single-row angular ball bearings is advantageous to the extent that it is more cost-effective than a single double-row angular ball bearing. The first single-row angular ball bearing and the second single-row angular ball bearing can be spaced apart from each other in the axial direction and/or can be arranged in an O-arrangement. An adjusting element, such as, for example, an adjusting disk, can be arranged between the first single-row angular ball bearing and the second angular ball bearing. The adjusting element serves to enlarge the bearing base (that is, the distance between the first angular ball bearing and the second angular ball bearing in the axial direction), and to compensate for any backlash between the two angular ball bearings, the rotor shaft and the transmission shaft.

Moreover, a backlash between the rotor shaft, the at least one bearing and the transmission shaft can be compensated for by the provision of a clamping device, which causes the at least one bearing to be preloaded. The clamping device can feature a groove nut, which is screwed onto the transmission shaft. By the rotor shaft, the clamping device exerts an axial force on the at least one bearing, such that the at least one bearing is pressed against the shoulder of the transmission shaft. With the version with which two single-row angular ball bearings are provided, the axial force exerted by the clamping device is transferred through the rotor shaft, the first single-row angular ball bearing, the adjusting element to the second single-row angular ball bearing. The preloading of the at least one bearing also has the advantage that the rigidity of the bearing arrangement is improved, the running accuracy increases and damages to the bearing can be avoided.

With an alternative version, the bearing can comprise a first radial bearing, in particular a first slide bearing, and a second radial bearing, in particular a second slide bearing. The provision of slide bearings is particularly suitable for transmissions with which little installation space is available in the radial direction. In addition, slide bearings enable an excellent damping of the rotor shaft. The radial bearings serve exclusively to absorb a radial force. Therefore, the bearing can at least comprise an axial bearing, whereas the axial bearing can be an axial needle bearing.

With a particular version, the positive-locking connection can be arranged at least partially between the first and second radial bearings, in particular between the first and second slide bearings. The transmission shaft can be centered on the rotor shaft by a fitting. The force-fitting connection can be arranged, with respect to the input shaft and/or the internal combustion engine, further away in the axial direction than the positive-locking connection.

A hybrid drive, with which the internal combustion engine is coupled to the input shaft, is particularly advantageous. In addition, a motor vehicle that features the transmission in accordance with exemplary aspects of the invention or the hybrid drive is advantageous.

DETAILED DESCRIPTION

The transmission for a motor vehicle shown inFIG. 1features an electric motor EM that is coupled in a torque-proof manner to a rotor shaft3, and a bearing4that directly supports the rotor shaft3. In addition, the transmission features a transmission shaft5, which is connected in a torque-proof manner to the rotor shaft3. The transmission shaft5is in operative connection with a multi-speed transmission gearing6. In addition, the transmission features an output shaft7, which is in operative connection with the transmission shaft5by the transmission gearing6. Both the transmission shaft5and the rotor shaft3are supported on a transmission component described in more detail below by the bearing4.

In the version shown inFIG. 1, the transmission component corresponds to a retainer8, which serves to retain a stator1of the electric motor EM. The retainer8is detachably connected (in particular, screwed) to an intermediate housing9. The intermediate housing9is connected in a torque-proof manner (in particular, screwed) to a transmission housing19. The intermediate housing9features lines through which the individual components of the transmission can be supplied with fluid, in particular oil. In particular, the fluid can be fed to an actuating device14, which is discussed further below. The electric motor EM features, in addition to the stator1, a rotor2that is connected to the rotor shaft3in a torque-proof manner.

The bearing4is a double-row angular ball bearing in an O-arrangement, and is arranged in the radial direction between the rotor shaft3and the retainer8. In this case, the bearing4is in direct contact with the rotor shaft3and the transmission shaft5. In particular, an inner ring of the double-row angular ball bearing is attached to both the rotor shaft3and the transmission shaft5. The inner ring is fixed in its axial position by the transmission shaft5and the rotor shaft3, such that a relative movement between the inner ring and the rotor shaft3and/or the transmission shaft5is not possible. In particular, the inner ring abuts against a shoulder10of the transmission shaft5on one side. On an opposite side of the inner ring, the inner ring abuts against a section of the rotor shaft3projecting in the radial direction.

An outer ring of the double-row angular ball bearing is in direct contact with the retainer8. The outer ring of the double-row angular ball bearing is fixed in its axial position by the retainer8. This means that the outer ring cannot move in the axial direction relative to the retainer8.

The rotor shaft3is connected in a torque-proof manner to the transmission shaft5by a spline. Thereby, the bearing4is arranged on a section of the rotor shaft4, which features the internally toothed hub of the spline.

The transmission features a clamping device in the form of a groove nut11. The groove nut11is screwed onto the drive shaft5and exerts an axial force on the rotor shaft3and thus the bearing4. In particular, as a result of the force exerted by the groove nut11, the bearing4is pressed against the shoulder10of the transmission shaft5.

In addition, the transmission features an input shaft12, which is coupled to an internal combustion engine VM, and a shift element13in the form of a clutch. The input shaft12is connectable in a torque-proof manner to the rotor shaft3by the shift element13.

An actuation of the shift element13can take place by an actuating device14, which can be, for example, a release bearing. In doing so, the actuating device14exerts an axial force for closing the shift element13on it. A lever16of the actuating device, through which the shift element13is actuated, extends through the rotor shaft3. In addition, the actuating device14features a piston23that is coupled to the lever16, which piston, upon the actuation of the actuating device14, is subjected to a fluid and consequently moves in the axial direction. As a result of the axial movement of the piston, the lever16presses against the shift element13and thus exerts the axial force on the shift element13.

The transmission gearing features a multiple number of planetary gear sets and shift elements, by which different gears can be realized with different transmission ratios.

The transmission shaft5is supported next to the bearing4by an additional bearing15. The additional bearing15is arranged on the output shaft7and supports the output shaft7directly on the transmission housing19.

FIG. 2shows an enlarged section of the transmission in accordance with exemplary aspects of the invention for a motor vehicle in accordance with a second embodiment. The embodiment shown inFIG. 2differs from the embodiment shown inFIG. 1in the formation of the bearing4.

Thus, the second embodiment shown inFIG. 2features two single-row angular ball bearings in an O-arrangement. The two single-row angular ball bearings are arranged in a manner spaced apart in the axial direction. An adjusting disk17is arranged between the two angular ball bearings. The adjusting disk17is in direct contact with the inner rings of the two angular ball bearings.

The two angular ball bearings are preloaded by the groove nut11. In particular, an axial force exerted by the groove nut11is transferred through the rotor shaft3, a first angular ball bearing, the adjusting disk17to the second angular ball bearing, by which the second angular ball bearing is pressed against the shoulder10of the transmission shaft3.

In addition, there is a difference with the embodiment shown inFIG. 1in that only one inner ring of the angular ball bearing located further away from the input shaft and/or internal combustion engine is arranged both on the transmission shaft5and on the rotor shaft3.

FIG. 3shows an enlarged section of the transmission in accordance with exemplary aspects of the invention for a motor vehicle in accordance with a third embodiment. The third embodiment differs from the second embodiment in the formation of a larger bearing base.

FIG. 4shows an enlarged section of the transmission in accordance with exemplary aspects of the invention for a motor vehicle in accordance with a fourth embodiment. With the embodiment shown inFIG. 4, a first slide bearing24and a second slide bearing25are present, by which the rotor shaft3and the transmission shaft5are supported on the retainer8. The rotor shaft3is directly supported on the retainer8by the first and second slide bearings24,25. The two slide bearings24,25are able to absorb radial forces exclusively. In addition, two axial bearings21,22, which absorb exclusively axial forces, are provided.

In addition to the plug connection, the rotor shaft3is centered on the transmission shaft5by a fitting. The fitting is arranged in an area of the transmission shaft5, which is turned away from the internal combustion engine VM in the axial direction further than the plug connection. In particular, the fitting takes place in the area of the two axial bearings21,22.

The plug connection and the fitting support the transmission shaft5in the radial direction on the rotor shaft3. This means that, in this version, the transmission shaft5is supported on the retainer8by the plug-in connection and the fitting, the rotor shaft3and the first and second slide bearings24,25.

The two axial bearings21,22serve to absorb the axial forces acting on the transmission shaft5, and are formed as axial needle bearings. Thereby, a first axial bearing21absorbs an axial force of the transmission shaft5in a first axial direction. This axial force can arise, for example, if the shift element13is actuated. A second bearing22absorbs an axial force in a second direction opposite to the first axial direction. This axial force can arise if, for example, one or more shift elements present in the transmission gearing6is closed.

Thereby, the axial force acting on the transmission shaft5is transferred to the first and/or second axial bearing21,22through a transfer element20. The transfer element20is arranged in the axial direction between the two axial bearings21,22and is in operative connection with the transmission shaft5. Thereby, the transfer element20is arranged free of backlash on the transmission shaft5. In addition, the transfer element is in direct contact with the two axial bearings21,22and the transmission shaft5.

REFERENCE SIGNS

EM Electric motor

VM Internal combustion engine