Motor Vehicles

Abstract

A motor vehicle comprises a drivable front axle, a drivable rear axle, an internal combustion engine, an automatic transmission connected to the internal combustion engine, and a torque distribution stage connected to the automatic transmission that is switchable and can realize all-wheel drive, the torque distribution stage being connected to the front axle and the rear axle, wherein the torque generated by the internal combustion engine can be guided to the front axle or the rear axle or distributed to both axles by the torque distribution stage, wherein an electric motor connected to the rear axle is provided, wherein the torque generated by the electric motor and transmitted to the rear axle is transmitted to the torque distribution stage via the coupling and can be additionally transmitted to the front axle by the torque distribution stage, and a freewheel mechanism is provided between the automatic transmission and the torque distribution stage, by means of which the automatic transmission is decoupled from the torque distribution stage when the internal combustion engine is not running and the axles are driven by the electric motor.

Description

Technical Field

[0001] The present invention relates to a motor vehicle, comprising a drivable front axle, a drivable rear axle, an internal combustion engine, an automatic transmission connected to the internal combustion engine, and a torque distribution stage connected to the automatic transmission, which is switchable and capable of realizing all-wheel drive, the torque distribution stage being connected or connectable to the front axle and the rear axle, wherein the torque generated by the internal combustion engine can be directed by the torque distribution stage to the front axle or the rear axle or distributed to both axles. Background Art

[0002] A conventional automatic transmission, which is also often referred to as a stepped automatic transmission, is connected to a conventional drive train, and a torque distribution stage, i.e. a switchable all-wheel drive stage, is connected downstream of the automatic transmission. This motor vehicle with a conventional drive train makes it possible to direct the torque generated by the internal combustion engine via an automatic transmission with, for example, seven or eight switching stages and via a downstream torque distribution stage either to only one axle, i.e. to the front axle or the rear axle, or to both axles, depending on the drive mode, so that all-wheel drive is then obtained. The torque distribution stage can be used to set the respective shares directed to the front axle and the rear axle in an all-wheel drive to be the same or different. This allows the driver to select different drive modes.

[0003] Motor vehicles are increasingly equipped with electric drives, wherein a so-called electric rear axle, i.e., a complete rear axle including a differential and an electric motor that directly drives the rear axle, is preferably provided. However, in a motor vehicle with a conventional drive train as described above, such an electric rear axle cannot be integrated, in which a torque distribution stage is connected downstream of the automatic transmission as described. Because in order to achieve all-wheel drive through the electric rear axle, the electric rear axle must be connected to the torque distribution stage so that the torque generated by the electric motor (which is mainly transmitted to the rear axle) is directed to the front axle in proportion, thereby also actively driving the front axle. However, because the torque distribution stage is connected to the front automatic transmission, in the case of pure electric drive, since the internal combustion engine-driven automatic transmission and the connected rear axle are attached to the same segment of the torque distribution stage, the automatic transmission will be driven together, i.e., driven together or loaded in the propulsion direction when driving purely electric. Because the internal combustion engine does not work when driving purely electric. This only leads to a drag torque in the best case, which produces power loss and has a negative impact on the electric driving range. However, it is much more serious that no lubricant is supplied to the transmission during pure electric driving because the internal combustion engine is not running. In conventional drive trains of the type mentioned at the beginning, the internal combustion engine supplies lubricant to the automatic transmission, that is, the internal combustion engine receives hydraulic supply and guides the lubricant to the transmission at a sufficient pressure and in a sufficient amount. However, in this case, since such lubricant supply is not available, the transmission may even be damaged during longer driving. Summary of the invention

[0004] It is therefore an object of the present invention to provide a motor vehicle which is improved therefrom.

[0005] To achieve this object, according to the present invention, an electric motor connected to the rear axle is provided in a motor vehicle of the type mentioned at the outset, wherein the torque generated by the electric motor and transmitted to the rear axle is transmitted to a torque distribution stage via a coupling and can be additionally transmitted from the torque distribution stage to the front axle, wherein a freewheel mechanism / overrunning clutch mechanism is provided between the automatic transmission and the torque distribution stage, via which the automatic transmission is decoupled from the torque distribution stage when the internal combustion engine is not running and the axle is driven by the electric motor.

[0006] In the motor vehicle according to the invention, an electric rear axle is provided, in which the electric machine together with the rear axle differential is a fixed component of the rear axle. In order to be able to realize all-wheel drive in principle also in electric operation, the electric machine is permanently coupled to the torque distribution stage, that is, the electric machine or its transmission is permanently mechanically coupled to the corresponding input segment of the torque distribution stage, for example via a corresponding cardan shaft, which connects the differential of the rear axle to the torque distribution stage.

[0007] Therefore, in pure electric operation, only the rear axle can be driven when the switchable torque distribution stage is not switched to all-wheel drive. When all-wheel drive is desired, the torque distribution stage is switched accordingly, and the torque transmitted from the rear axle to the torque distribution stage is also transmitted to the front axle in proportion.

[0008] Now, in order to prevent the automatic transmission from being entrained in the disadvantageous manner described at the beginning in two different operating modes, a freewheel mechanism is provided according to the present invention, which is arranged between the automatic transmission and the torque distribution stage. This freewheel mechanism, which acts on one side, can achieve that the automatic transmission stage is decoupled from the torque distribution stage in the purely electric operating condition. Because the input segment of the torque distribution stage, which is loaded with torque from the rear axle in the electric operating condition, is also connected to the automatic transmission, so that the torque on the internal combustion engine side can be transmitted to the rear axle through the automatic transmission and the torque distribution stage in the operation of the internal combustion engine. However, according to the present invention, this connection is now guided by the intermediate freewheel mechanism, which works in such a way that the freewheel mechanism decouples the torque distribution stage from the automatic transmission when the internal combustion engine is not working or is decoupled from the automatic transmission, so that the rear axle torque applied to the torque distribution stage cannot be guided to the automatic transmission due to the decoupling.

[0009] By means of this decoupling, it is now possible to "electrify" the conventional drive train, since it is possible to operate the internal combustion engine as well as the electric motor without adversely affecting the automatic transmission. Because in pure internal combustion engine operation the freewheel mechanism acts in a coupled manner, that is, the torque on the internal combustion engine side is transmitted to the torque distribution stage and is directed by the torque distribution stage to either the front axle or the rear axle, or to both axles in the case of all-wheel drive, depending on the drive mode. Since the torque is directed through the automatic transmission and since the internal combustion engine is operating, the corresponding automation of the lubricant supply of the transmission is ensured. However, in pure electric operation, the automatic transmission is decoupled so that the automatic transmission is not driven along and therefore cannot be damaged due to lack of lubricant supply. However, in mixed operation, when both the internal combustion engine and the electric motor are operating, the torque on the internal combustion engine side is transmitted by the automatic transmission via the then coupled freewheel mechanism to the torque stage, which also receives the torque generated on the rear axle side, wherein the total torque generated is then distributed in all-wheel operation via the torque distribution stage. Since the internal combustion engine is operating and thus both provides torque and operates the hydraulic supply device, automation of the lubricant supply to the transmission is ensured.

[0010] The freewheel mechanism itself, i.e. the central, optionally coupled component, is a clamping roller freewheel mechanism or a clamping body freewheel mechanism. Such a clamping roller freewheel mechanism or a clamping body freewheel mechanism has corresponding clamping rollers or clamping bodies on the inner part of the freewheel mechanism that is coupled to the transmission output, while the outer part of the freewheel mechanism is coupled to the corresponding input segment of the torque distribution stage. In one direction of rotation, the outer part can rotate relative to the inner part without mechanical coupling, and in the other direction of rotation, a corresponding mechanical, torque-stable coupling is directly obtained. If the internal combustion engine is switched on, it also provides torque to the automatic transmission, so that the transmission output shaft must rotate and the inner part of the freewheel mechanism also rotates with the transmission output shaft, so that a mechanical coupling with the outer part is immediately produced and the delivered torque is further transmitted to the torque distribution stage. In pure internal combustion engine operation, the torque on the internal combustion engine side is the only torque applied, while in additional operation of the electric motor, the torque on the internal combustion engine side forms a total torque together with the torque on the electric motor side - the total torque is then distributed via the torque distribution stage when the torque distribution stage is switched accordingly - or acts only on the driven rear axle together with the torque on the electric motor side.

[0011] The coupling of the automatic transmission to the torque distribution stage is advantageously realized via a hollow shaft. For this purpose, the transmission output is coupled to a hollow shaft via a toothing, which is coupled to the input segment of the torque distribution stage via a freewheel mechanism. The hollow shaft allows a central, rotationally symmetrical coupling to the input segment of the torque distribution stage, for example, the outer friction plate carrier of a multi-plate clutch, which will be discussed below. The hollow shaft itself is in turn coupled or connected to the inner part of the freewheel mechanism, while the outer part of the freewheel mechanism is coupled to the input segment of the torque distribution stage.

[0012] The input segment itself is connected to the output segment inside the torque distribution stage or forms the output segment at the output end of the distribution stage, and the torque distribution stage is connected to the cardan shaft connected to the rear axle through the output segment. Therefore, when the internal combustion engine is used alone for driving, the torque generated on the internal combustion engine side is further transmitted to the rear axle through the output segment, but the output segment is also used as an input segment for the motor torque provided on the rear axle side to a certain extent.

[0013] The torque distribution stage itself is preferably a multi-plate clutch or includes such a multi-plate clutch. The front axle can be switchably connected to the rear axle drive in a simple manner by means of such a multi-plate clutch, which is also called an additional clutch / hang-on clutch (Hang-On-Kupplung). Such a multi-plate clutch usually has at least one outer friction plate carrier, which is an input segment for the torque on the internal combustion engine side and also for the torque on the motor side. The multi-plate clutch also includes an inner friction plate carrier, which is connected to the drive shaft extending to the front axle differential via a shaft, so that the torque to be distributed is transmitted to the front axle. The corresponding friction plates are arranged on the outer friction plate carrier and on the inner friction plate carrier, which are meshed with each other, wherein the friction plate group can be axially pressed together by a suitable adjustment element, such as a hydraulic CSC adjuster (CSC=Concentric Slave Cylinder, concentric slave cylinder), so that the torque introduced on the input segment, that is, the outer friction plate carrier, is transmitted to the inner friction plate carrier in a friction-locked, pressed-together state.

[0014] The outer friction plate carrier is therefore the input segment of the torque distribution stage. The friction plate carrier is coupled to the already described hollow shaft via a freewheel mechanism, wherein a mechanical, rotationally fixed connection is only produced when the hollow shaft actively rotates and thus when the internal combustion engine is running, otherwise the freewheel mechanism acts in a decoupled manner. The outer friction plate carrier is also coupled to an output shaft forming an output segment, which is attached to a cardan shaft leading to the rear axle. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Further advantages and details of the invention emerge from the exemplary embodiments described below and with reference to the drawings.

[0016] Figure 1 A motor vehicle according to the invention is shown. DETAILED DESCRIPTION

[0017] Figure 1 The motor vehicle 1 according to the invention is shown, which comprises a driven front axle 2 and a driven rear axle 3. Furthermore, an internal combustion engine 4 and an automatic transmission 5 coupled thereto, ie a stepped automatic transmission, are provided, which has, for example, seven or eight shifting stages.

[0018] A torque distribution stage 6 is connected downstream of the automatic transmission 5, by means of which, depending on the specific drive mode of the motor vehicle, the torque can be directed only to the front axle 2 or only to the rear axle 3, or in the case of all-wheel drive to both axles 2, 3. For this purpose, the torque distribution stage 6 is coupled on the one hand to a front axle differential 7, which will be described in more detail below, and via a cardan shaft 8 to a rear axle differential 9, which will also be described in more detail below.

[0019] The rear axle 3 itself is an electric rear axle which has an electric machine 10 and a downstream electric motor transmission 11 as fixed axle components which is coupled to the differential 9 .

[0020] The specific design of the entire drive train can realize all-wheel drive by pure internal combustion engine drive of the rear axle 3 or by internal combustion engine drive of the front axle 2 and the rear axle 3. In addition, pure electric drive only by the rear axle 3 and all-wheel drive by the rear axle 3 and the front axle 2 can also be realized. In the case of pure electric drive, whether it is rear axle drive or all-wheel drive, it is ensured that the automatic transmission 5 is decoupled from the torque distribution stage 6 in any case, so that it is not driven together when the internal combustion engine 4 is not working. In order to achieve this, the output shaft 12 of the automatic transmission 5 is connected to the hollow shaft 14 via the gear transmission stage 13, and the hollow shaft itself is connected to the input section 16 of the torque distribution stage 6 designed as a multi-plate clutch 18 via a freewheel mechanism 15, preferably a clamping roller freewheel mechanism or a clamping body freewheel mechanism, which is in the form of an outer friction plate carrier 17 here. The outer friction plate carrier 17 is connected to the output shaft 19 of the torque distribution stage, which is in turn connected to the cardan shaft 8, which is in turn connected to the rear axle differential 9.

[0021] The multi-plate clutch 18 also comprises an inner friction plate carrier 20 . An outer friction plate 21 is axially displaceably arranged on the outer friction plate carrier 17 , and an inner friction plate 22 is axially displaceably arranged on the inner friction plate carrier 20 , wherein the axial displacement is indicated by two arrows P. The friction plate package can thus be pressed together axially by means of an adjusting element, for example a hydraulically operated concentric slave cylinder (CSC), and moved toward a support, so that the friction plates 21 , 22 form a friction lock and a torque applied to the rotating outer friction plate carrier 17 can be transmitted to the inner friction plate carrier 20 .

[0022] The inner friction plate carrier 20 is connected to an output shaft 23 , which in turn is connected via a gear stage 24 to a shaft 25 extending to the front axle differential 7 , via which a torque, ie a torque of the drive device, is transmitted to the front axle 2 .

[0023] As described, the cardan shaft 8 is connected to the rear axle differential 9 , so that the torque delivered by the automatic transmission 5 can be transmitted to the rear axle differential 9 , thereby driving the rear axle 3 .

[0024] The electric machine 10, in which the stator 26 and the rotor 27 are shown here by way of example, is connected with its output shaft 28 via a toothing 29 to an intermediate shaft 30, which extends to the actual rear axle transmission 31, which in turn is connected to the differential 9. As a result, the torque generated by the electric machine 10 can be transmitted to the wheels.

[0025] As shown, the automatic transmission 5 as well as the gear transmission stages 13 and 24, the hollow shaft 14, the drive shaft 25 and the differential 7 can be integrated in a compact housing, which is connected to the internal combustion engine 4 with a housing flange on the one hand and to which the torque distribution stage 6 is connected with its housing flange on the other hand. Similarly, the motor transmission 11 with its transmission stage 31 and the rear axle differential 9, the compact components of the electric rear axle 3 are integrated in a common housing, to which the motor 10 is connected with its housing flange, so that a very compact axle design is also obtained here.

[0026] The central element that can realize variable internal combustion engine drive and electric motor drive in combination with decoupling from the automatic transmission 5 while enabling all-wheel engagement / drive is the freewheel mechanism 15. As described, the freewheel mechanism is a clamping roller freewheel mechanism or a clamping body freewheel mechanism. The inner part of the freewheel mechanism 15, on which the clamping rollers or clamping bodies are arranged, is connected to the hollow shaft 14, while the outer part of the freewheel mechanism 15 is connected to the input segment 16, here, the outer friction plate carrier 17. This arrangement is such that when the hollow shaft 14 is actively driven by the automatic transmission 5 when the internal combustion engine 4 is running, the freewheel mechanism 15 is engaged. The transmitted torque is transmitted to the output shaft 19 via the outer friction plate carrier 17, and thus transmitted to the differential 9 via the cardan shaft 8, so that the rear axle 3 is driven by the internal combustion engine 4.

[0027] If all-wheel drive is desired, the multi-plate clutch 18 is actuated to press the friction plate group consisting of the outer friction plate 21 and the inner friction plate 22 together and form a friction lock, so that the torque transmitted on the internal combustion engine side is also transmitted to the inner friction plate carrier 20 and from the inner friction plate carrier via the output shaft 23 and the drive shaft 25 to the front axle differential 7 and via the front axle differential to the front wheels.

[0028] In the pure motor operation, that is, when the internal combustion engine 4 is not working, the torque is generated only by the electric motor 10 and transmitted to the differential 9 through the motor transmission 11 and transmitted to the rear wheels through the differential. However, due to the connection between the cardan shaft 8 and the differential 9, the cardan shaft 8 also rotates here and due to the connection between the cardan shaft and the output shaft 19, the outer friction plate carrier 17 is also forced to rotate. However, the outer friction plate carrier is decoupled from the stationary hollow shaft 14 by the freewheel 15, that is, the hollow shaft 14 is not driven and the automatic transmission 5 is not driven together. Therefore, it is possible to achieve a pure motor drive of the rear axle 3 without the automatic transmission 5 being loaded together in the propulsion.

[0029] If all-wheel drive is to be realized in a purely electric drive, the friction plate group consisting of the outer friction plate 21 and the inner friction plate 22 can also be easily pressed together axially toward the support and form a friction lock, so that the currently stationary inner friction plate carrier 20 is also driven in rotation. The branched torque is then directed to the front axle 2 again via the output shaft 23 and the drive shaft 25. The proportion of the torque applied to the front axle and the torque applied to the rear axle can be adjusted accordingly, similar to the pure internal combustion engine drive.

[0030] However, a hybrid drive consisting of an internal combustion engine drive and an electric motor drive can also be realized. That is, the internal combustion engine 4 can be connected when the electric motor is driven, so that the internal combustion engine provides torque to the automatic transmission 5, and the automatic transmission transmits the torque through the hollow shaft 14. Because the hollow shaft rotates actively, a force lock is automatically generated inside the freewheel mechanism 15, that is, the internal parts exceed the external parts to a certain extent, and an additional torque is applied in addition to the torque on the motor side. Therefore, a total torque consisting of the torque on the internal combustion engine side and the torque on the motor side is obtained, which is then applied to the torque distribution stage 6. This total torque can be branched on the two axles 2 and 3, that is, a kind of all-wheel drive is obtained. However, it is also conceivable that the total torque is then only transmitted to the rear axle 3.

[0031] Therefore, by decoupling the automatic transmission according to the present invention, pure electric operation is possible, because the transmission of the conventional powertrain is stationary by decoupling the freewheel mechanism 15. Therefore, there is no damage to the transmission, because the internal combustion engine 4 is not working, so there is no active lubricant supply to the transmission. Another advantage is that the torque of the electric drive rear axle 3 does not run through the automatic transmission in principle, because the torque is also distributed in advance through the torque distribution stage 6 even in the all-wheel electric drive. This results in that the transmission only needs to be designed with respect to the torque provided by the internal combustion engine 4 in terms of its effective power. In terms of efficiency or drive efficiency, the decoupling of the freewheel mechanism according to the present invention is also advantageous, because the automatic transmission is not driven together during pure electric drive, which otherwise will lead to a relatively large drag torque and thus a reduction in the electric driving range. More precisely, it is only necessary to drive the freewheel mechanism 15 with its external parts, but this will not lead to a drag torque worthy of attention.

[0032] Therefore, the design of the drive train according to the invention or the integration of the freewheel mechanism 15 between the automatic transmission 5 and the torque distribution stage 6 according to the invention allows a conventional drive train consisting of an internal combustion engine and a conventional automatic transmission 5 and a conventional torque distribution stage to be combined with an electric rear axle without any disadvantages arising with respect to the automatic transmission 5.

[0033] In addition, all forward and backward movements can also be realized. When driving purely forward with the internal combustion engine, the freewheel is engaged, that is, the freewheel is connected and the torque is transmitted on. Driving backward with the internal combustion engine is not possible, because in this case, although the hollow shaft 14 rotates, the freewheel is separated, that is, decoupled. However, since the hollow shaft rotates in the opposite direction when driving backward, the freewheel is not engaged.

[0034] In the case of pure electric drive in the forward direction, the freewheel is disengaged, which results in the decoupling according to the invention of the automatic transmission which is not supplied with lubricant. Reverse travel by means of the electric machine is also possible, but here the freewheel is engaged due to the reversed direction of rotation of the input segment of the torque distribution stage, i.e. the freewheel is coupled to the automatic transmission, which is exceptionally entrained. However, this is not a disadvantage here, since such reverse travel only takes place very briefly and at low speed, so that damage to the transmission is avoided.

[0035] In the case of hybrid drive both by the internal combustion engine and by the electric motor, the freewheel is forced to close because the torque is introduced and transmitted by the internal combustion engine. If reverse travel is to be carried out in a given hybrid operation, the internal combustion engine is briefly turned off and reverse travel is achieved only by the electric motor.

Claims

1. A motor vehicle comprising a drivable front axle (2), a drivable rear axle (3), an internal combustion engine (4), an automatic transmission (5) connected to the internal combustion engine, and a torque distribution stage (6) connected to the automatic transmission (5) and capable of realizing all-wheel drive, the torque distribution stage being connected or capable of being connected to the front axle (2) and the rear axle (3), wherein: The torque generated by the internal combustion engine (4) can be directed to the front axle (2) or the rear axle (3) or distributed to the two axles (2, 3) by the torque distribution stage. It is characterized in that An electric motor (10) coupled to a rear axle (3) is provided, wherein the torque generated by the electric motor (10) and transmitted to the rear axle (3) is transmitted to a torque distribution stage (6) via the coupling and can be additionally transmitted from the torque distribution stage to the front axle (2), and a freewheel mechanism (15) is provided between the automatic transmission (5) and the torque distribution stage (6), by means of which the automatic transmission (5) is decoupled from the torque distribution stage (6) when the internal combustion engine (4) is not running and the axle is driven by the electric motor (10).

2. The motor vehicle according to claim 1, It is characterized in that The freewheel mechanism (15) is a clamping roller freewheel mechanism.

3. The motor vehicle according to claim 1, characterized in that: The freewheel mechanism (15) is a clamping body freewheel mechanism.

4. A motor vehicle according to any one of claims 1 to 3, It is characterized in that The transmission output end (12) is connected to a hollow shaft (14) via a toothed section (13), and the hollow shaft is connected to an input section (16) of a torque distribution stage (6) via a freewheel mechanism (15).

5. The motor vehicle according to claim 4, It is characterized in that The input segment (16) is connected to the output segment (19), and the torque distribution stage (6) is connected to the cardan shaft (8) connected to the rear axle (3) through the output segment.

6. A motor vehicle according to any one of claims 1 to 3, It is characterized in that The torque distribution stage (6) is a multi-plate clutch (18) or includes a multi-plate clutch (18).

7. The motor vehicle according to claim 5, It is characterized in that The torque distribution stage (6) is a multi-plate clutch (18) or includes a multi-plate clutch (18), The multi-plate clutch (18) comprises an outer friction plate support (17), which is connected to a hollow shaft (14) via a freewheel mechanism (15) and is connected to an output shaft (19) forming an output section.

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