Drive train of a motor vehicle that can be driven in a purely electric manner

Abstract

A drive train (6) is provided for a motor vehicle which can be driven in a purely electric manner. A gear mechanism (7, 15) has a standardized housing (8) for accommodating an electrical machine (16) or two electrical machines (10, 11) and for accommodating two gear mechanism output shafts (9) which are associated with a vehicle axle (2, 4). A large number of drive topologies for various vehicle sectors with purely electric drives can be formed by configuring the drive train in this way.

Claims

1. A drive train of a motor vehicle that can be driven in a purely electric manner, the motor vehicle having a front axle and a rear axle and opposite first and second lateral sides, the drive train comprising: a front gear mechanism having a front housing, a front electrical machine located between the front and rear axles and being flange mounted to the front housing at a position between the front housing and the first lateral side of the motor vehicle, no electrical machine being mounted to the front housing at a position between the front housing and the second lateral side of the motor vehicle, and two front gear mechanism output shafts extending from the front housing and associated with the front axle; and a rear gear mechanism having a rear housing, a rear electrical machine located between the front and rear axles and being flange mounted to the rear housing at a position between the rear housing and the second lateral side of the motor vehicle, no electrical machine being mounted to the rear housing at a position between the rear housing and the first lateral side of the motor vehicle, and two rear gear mechanism output shafts extending from the rear housing and associated with the rear axle, wherein the front housing and the rear housing are identical but are reversed relative to one another in a front-rear direction, wherein a size of the front electrical machine is different from a size of the rear electrical machine, and wherein a first of the electrical machines is an asynchronous machine and a second of the electrical machines is a permanent-magnet synchronous machine.

2. The drive train of claim 1, wherein the gear mechanism is a summing gear mechanism.

3. The drive train of claim 1, wherein at least one of the front and rear gear mechanisms is connected to an electrical machine of high power, or two electrical machines of low power, or an electrical machine of high power and an electrical machine of low power.

4. The drive train of claim 1, wherein the gear mechanism has two separate gear mechanism units having the two gear mechanism output shafts for a single-wheel drive of the road wheels.

5. The drive train of claim 4, wherein identical electrical machines are connected to the gear mechanism units in each case.

6. The drive train of claim 1, wherein each of the respective electrical machines has a rotor shaft arranged transverse to a forward direction of travel of the motor vehicle.

7. The drive train of claim 1, wherein each of the respective gear mechanism output shafts is arranged transverse to a forward direction of travel of the motor vehicle.

8. The drive train of claim 1, wherein the gear mechanism is in a central region of the motor vehicle with respect to a width of the motor vehicle.

9. The drive train of claim 1, comprising two electrical machines and the gear mechanism are between the electrical machines.

10. The drive train of claim 1, wherein at least one of the gear mechanisms is a two-stage gear mechanism.

11. The drive train of claim 10, wherein at least one of the gear mechanisms is of three-shaft design with an intermediate shaft.

12. The drive train of claim 10, wherein at least one of the gear mechanisms has a first stage of planetary design and a second stage of spur-gear design.

13. The drive train of claim 1, wherein at least one of the gear mechanisms has a decoupling device for decoupling at least one of the electrical machines.

14. The drive train of claim 1, wherein the front housing is closer to the second lateral side of the vehicle than to the first lateral side of the vehicle, and the rear housing is closer to the first lateral side of the vehicle than to the second lateral side of the vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1 to 7 show drive trains for a front and a rear axle of a motor vehicle, illustrated for drive topologies.

(2) FIG. 8 shows the influence of different sizes of electrical machines used in the drive train in a torque/rotation speed graph.

(3) FIG. 9 shows the influence of different types of electrical machines used in the drive train in a torque/rotation speed graph.

(4) FIG. 10 is an embodiment of the drive train when the gear mechanism is a summing gear mechanism, as seen from above.

(5) FIG. 11 shows the drive train of FIG. 10, as seen in the direction of the vehicle axle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) FIG. 1 is a schematic plan view of a motor vehicle, such as a passenger car, with the outer corner contour of the motor vehicle which illustrated by the four curved line sections 1. Two front wheels are associated with a front axle 2 of the motor vehicle, and two rear wheels 5 are associated with a rear axle 4 of the motor vehicle. The front axle 2 forms a constituent part of an independent drive train 6, and the rear axle 4 forms a constituent part of an independent drive train 6. The drive trains 6 are of different configurations, and the design thereof is described in greater detail below.

(7) A gear mechanism 7 has a gear mechanism housing 8 and is associated with the rear axle 4. The gear mechanism housing 8 is a standardized housing. It is therefore of identical design for all the drive topologies that are discussed below. The housing 8 accommodates an electrical machine or two electrical machines and two gear mechanism output shafts 9 that are associated with the rear axle 4 and the rear wheels 5. Specifically, the housing 8 accommodates two electrical machines 10 and 11 that are flange-connected on sides of the housing 8 that are averted from one another and the gear mechanism 7 is arranged between the two electrical machines 10 and 11. Output shafts 12 of the electrical machines 10 and 11 have pinions 13 that mesh with a gear wheel 14 of the gear mechanism 7. Thus, the gear mechanism 7 is a summing gear mechanism. As an alternative, the output shafts 12 of the electrical machines 10 and 11 are fixed to a gear mechanism input shaft that has a pinion 13 meshed with the gear wheel 14 of the gear mechanism 7. In addition, it is possible, in both cases, for an intermediate shaft to also be arranged between the pinion 13 and the gear wheel 14 to form a required transmission ratio.

(8) The drive train 6 of the front axle 2 of the motor vehicle has an associated gear mechanism 15 with a housing 8 that corresponds to the housing 8 of the gear mechanism 7 so that the kinematics of this gear mechanism 15 are modified. For example, only one electrical machine 16 is connected to the bearing flange of the housing 8, and the bearing flange on the other side of the housing 8 remains free for another electrical machine. Thus, the housing 8 is closed in this region by a cover. The output shaft 12 of the electrical machine 16 is connected to a pinion 13 that meshes with a gear wheel 14 that can be narrower than the gear wheel 14 provided for the rear axle 4.

(9) The two electrical machines 10 and 11 of the rear axle 4 can be identical or different. The electrical machine 16 of the front axle 2 can be identical to or different from the electrical machines 10, 11 of the rear axle 4.

(10) This drive concept described in FIG. 1 preferably is used in the mid-range sector, in particular in sports cars.

(11) In the description of the following figures, parts of the respective drive train 6 that correspond to those of FIG. 1 with respect to structure or functionality are provided with the same reference numerals for the sake of simplicity.

(12) The FIG. 2 version of the motor vehicle, which likewise is used in the mid-range sector and/or in sports cars, differs from FIG. 1 only in that the rear drive train 6 of FIG. 1 is implemented for both the rear axle 4 and the front axle 2 in FIG. 2. In this respect, the front axle 2 is driven by the two electrical machines 10 and 11.

(13) The drive concept of FIG. 3 is used in the luxury sector and/or in sports cars in that sector and differs from FIG. 1 in that a gear mechanism 18 with a housing 8 that allows a single-wheel drive is used for the rear axle 4. Therefore, the rear axle 4 of the embodiment in FIG. 3 has electrical machines 10 and 11 with two pinions 13 that engage separate gear wheels 16, 17, and the gear wheel 17 is connected to a gear mechanism output shaft 9. The gear mechanism 18 therefore has two component gear mechanisms.

(14) The refinement of the drive train of FIG. 4 also is used in the luxury sector and in sports cars in that sector. In this case, both the front axle 2 and the rear axle 4 have the single-wheel drive with the gear mechanism 18 described in FIG. 3. Accordingly, four electrical machines 10, 11 are provided in this vehicle.

(15) The same housing 8 is used in the embodiment of FIGS. 3 and 4. On the basis of the variants of FIGS. 1 to 4, an increase in functionality and/or power in drive concepts of the respective motor vehicle that can be driven in a purely electric manner can be formed by choosing the number of electrical machines and the type of machine.

(16) The drive train of FIG. 5 is modified in relation to FIG. 1 in that, given an identical design of the drive train 6 of the front axle 2, the drive train 6 of the rear axle 4 also has only one electrical machine 16 connected to the housing 8 of the gear mechanism 15. However, the electrical machine 16 is on the left side and the gear mechanism 15 is on the right side in the region of the front axle 2, while the electrical machine 16 is on the right side and the gear mechanism 15 is on the left side in the region of the rear axle 4. The two electrical machines 16 are arranged between the axles 2 and 4. The same housing 8 is used again in FIG. 5, but different electrical machines 16 can be flange-connected to the housing. Therefore, the machine connection dimensions in the region of the electrical machine/gear mechanism interface are the same. As a result, different sizes of machine and types of machine can be used for power and function adjustment. For example, it is possible to choose the type of motor, for example an asynchronous machine or a permanent-magnet synchronous machine.

(17) FIG. 6 shows the configurations of the two drive trains of the motor vehicle for achieving symmetrical power distribution, when the same housing 8 is used. FIG. 7 shows the modification to the effect that asymmetrical power distribution takes place.

(18) The graph of FIG. 8 shows the influence of the size of the used electrical machine in terms of the torque that is output by the electrical machines, as a function of the rotation speed of the machine. The graph shows that the region of a high degree of efficiency in the characteristic maps for the degree of efficiency of the large electrical machine and the small electrical machine. The characteristic map 19 for the degree of efficiency of the large permanent-magnet synchronous machine and the characteristic map 20 for the efficiency of the small permanent-magnet synchronous machine overlap. Advantages in the degree of efficiency are produced in cyclical operation due to a relatively small electrical machine with the option of turning off or decoupling the machine.

(19) In a corresponding diagram, FIG. 9 shows the influence of the type of machine. The characteristic map 19 for the degree of efficiency of the permanent-magnet synchronous machine and the characteristic map 21 for the degree of efficiency of the asynchronous machine. In cyclical operation, advantages with respect to the degree of efficiency are produced by the combination of these different types of electrical machine and the changeover between the types of electrical machine as a function of the speed or load range. It is also possible to switch off or decouple a machine.

(20) FIGS. 10 and 11 show one possible configuration of the gear mechanism 7, which is a summing gear mechanism. The gear mechanism 7 is a two-stage gear mechanism. The gear mechanism 7 is of three-shaft design with an intermediate shaft. The two electrical machines 10 and 11 interact with the gear mechanism 7. A mechanical differential 22 is associated with the output drive of the gear mechanism 7. The figure does not illustrate a decoupling device, which is associated with the gear mechanism 7, for decoupling one of the two electrical machines 10, 11. Reference numeral 23 denotes the power electronics associated with an electrical machine 10 or 11.

(21) The configuration of the drive train 6 illustrated in FIGS. 10 and 11 allows a compact gear mechanism 7 to be formed in the center of the vehicle, with respect to an orientation transverse to the forward direction 24 of travel of the motor vehicle which is illustrated by the arrow. An efficient tooth system is possible with two gear wheel stages. The drive train can also be operated by one machine. To this end, the machine is decoupled by the decoupling device if the machine is in the form of an asynchronous machine. If the machine is in the form of a permanent-magnet synchronous machine, the decoupling device is not required. Immersion lubrication preferably is used in the gear mechanism 7, and therefore an oil pump is not required.