Switching procedure in a purely electrically powered vehicle

Abstract

Switching method for a purely electrically driven vehicle comprising at least two electric machines (3, 5, 10, 11, 15, 21, 22), wherein at least one electric machine is coupled to a drive via a transmission (4, 6, 12, 13, 16, 23, 24) with interruption of traction force during switching, characterized in that the transmissions are switched in such a way that the interruption of traction force during switching leads to a yaw moment about the vehicle's vertical axis (14), which, due to the reduction of drive load or braking torque, assists cornering.

Description

[0001] The present invention relates to a switching method in a purely electrically powered vehicle comprising at least two electric machines, wherein at least one electric machine is coupled to a drive via a transmission with interruption of traction during switching, according to the preamble of claim 1.

[0002] Purely electrically powered vehicles are known from the prior art. In particular, electrically powered vehicles are known which have at least two electric motors, with at least one electric motor being connected to a drive via a transmission. These transmissions are generally designed as manual transmissions with at least two gears, where a gear change results in an interruption of traction.

[0003] Connecting an electric motor to a gearbox on the output side offers the advantage of increased torque during start-up. Furthermore, a wider speed range can be achieved while simultaneously improving efficiency, as the electric motor can operate within its most efficient range. Additionally, the design of the electric motor proves simpler, since there are hardly any conflicting design objectives in such a case. Moreover, the electric motor can be completely decoupled from the gearbox when it is in neutral, which advantageously avoids no-load losses.

[0004] By providing at least two electric motors to drive the vehicle, an all-wheel-drive function can be advantageously implemented with two driven axles, without the need for an all-wheel-drive transfer case. Furthermore, it is possible to implement a torque-vectoring function, i.e., a driving-dynamically motivated torque distribution to the drive axles or to individual driven wheels of an axle.

[0005] The basic sequence of a shift in a gearbox connected to an electric motor on the drive side, with interruption of traction during shifting, is known from the prior art as follows: A load reduction is performed on the electric motor connected to the gearbox, which marks the beginning of the interruption of traction. The gear is then selected, and the electric motor is actively synchronized before the new gear is engaged; subsequently, a load is applied to the electric motor, and the interruption of traction ends. The disadvantage of this approach is the traction interruption inherent in the gearbox design. These gearboxes are generally designed as automated manual transmissions.

[0006] For example, DE 41 33 060 C2 discloses a drive arrangement for a motor vehicle, comprising: an internal combustion engine, an electric generator arrangement driven by the internal combustion engine, an electric motor for each of the driven wheels, and an electronic control unit that controls the magnitude of the electrical power supplied to the individual electric motors from the generator arrangement, wherein the control unit includes wheel load sensing means that detect the magnitude of the instantaneous wheel load of each of the driven wheels, and wherein the control unit controls the electrical power supplied to each electric motor (9) depending on the detected instantaneous wheel load of the wheel driven by the electric motor, wherein the control unit includes meanswhich, depending on the wheel load, specify or determine a maximum value of the resulting wheel force transmissible by each driven wheel, and that the control system regulates the electrical power supplied to each electric motor so that the resulting wheel force is less than the maximum value, wherein, if the maximum value of the wheel force of one of the driven wheels is exceeded, the control system reduces the drive torque supplied by the electric motor of that wheel and increases the drive torque of the electric motor of at least one other wheel.

[0007] Furthermore, DE 40 11 291 A1 discloses a non-rail-bound vehicle with at least two electric drive motors, one of which is intended to drive a drive wheel on the left side of the vehicle and the other to drive a drive wheel on the right side of the vehicle, wherein each of the two electric motors has its own motor control for specifying the instantaneous target power and / or the instantaneous target speed of the respective electric motor;and that a higher-level central control unit connected to the motor controls is provided, which controls the two electric motors via the motor controls in the sense of preventing drive slippage and / or preventing brake lock-up and / or achieving a driving dynamically favorable right / left drive differential, whereby the central control unit and / or the motor controls take into account information about the current actual electrical power and / or the current actual rotational speed of the two electric motors;

[0008] Furthermore, a method for operating a vehicle with several drive motors is known from DE 196 19 321 A1, wherein each of the motors is downstream of a switchable transmission with at least two stages, and the switching of the downstream transmissions takes place depending on the overall efficiency of the respective drive motor when predetermined switching points, which depend on the overall efficiency, are reached, wherein the transmissions downstream of the drive motors are switched at different times, so that no interruption of traction occurs in the overall drive system.

[0009] The present invention is based on the objective of providing a switching method for a purely electrically driven vehicle comprising at least two electric machines, wherein at least one electric machine is coupled to a drive via a transmission with interruption of traction force during switching, the implementation of which avoids an interruption of traction force on the vehicle.

[0010] This problem is solved by the features of claim 1. Further embodiments and advantages of the invention will become apparent from the dependent claims.

[0011] Accordingly, a switching method is proposed for a purely electrically powered vehicle comprising at least two electric motors, where at least one electric motor is coupled to a drive via a transmission with interruption of traction during shifting. The transmissions are switched in such a way that the interruption of traction during shifting results in a yaw moment about the vehicle's vertical axis, which, due to the reduction of drive load or braking torque, assists cornering. The total electrically generated torque of the electric motors can remain unchanged before and during the shifting process.

[0012] In a vehicle with two axles, each driven by an electric motor via a transmission, the transmissions are always switched alternately according to the invention, whereby the load of the electric motor assigned to the switching transmission before the switching, i.e. the load present before the switching, is additionally redistributed to the electric motor assigned to the non-switching transmission during the load reduction phase, so that the sum of the drive torque transmitted to both axles remains unchanged before and during the switching.

[0013] In this case, the electric motor associated with the non-switching side can be overloaded for the duration of the switching operation without overheating, since electric motors are generally capable of handling short-term overloads and a switching operation lasts approximately 1 to 2 seconds. The inventive design does not place any additional load on the energy storage device, as the total electrically generated torque remains unchanged before and during the switching operation.

[0014] In the event that the vehicle has a driven axle with two independent wheel drives, each comprising an electric motor and a transmission downstream of the electric motor, it is proposed to engage one of the two transmissions when it is known in advance that a yaw moment, i.e., a moment about the vehicle's vertical axis, which could lead to a steering input, is likely to be required during the shift, as is the case when cornering. This can be detected, for example, using the vehicle's steering angle in conjunction with vehicle environment sensors, including, for example, a camera and / or a digital map in conjunction with a GPS system.

[0015] According to the invention, the transmission is engaged whose interruption of traction during shifting leads to a yaw moment around the vehicle's vertical axis, which supports cornering in traction mode and reduces braking torque in deceleration mode.

[0016] Depending on the desired yaw moment, it can also be provided that the electric motor assigned to the non-shifting transmission takes on or reduces additional load.

[0017] In the event that the vehicle has two driven axles, one of which comprises two individual wheel drives, each including an electric motor and a downstream transmission, it is proposed that, when the transmission assigned to the axle without individual wheel drives is to be shifted, the drive or braking load from the electric motor assigned to this transmission is distributed to the electric motors assigned to the individual wheel drives in equal or different proportions before and during the shifting process, for the purpose of generating a desired yaw moment.

[0018] Furthermore, it is proposed that the gearboxes assigned to the individual wheel drives are always switched simultaneously, whereby the gearbox assigned to the axle without individual wheel drive is not switched, and whereby the load of the electric machines assigned to the individual wheel drives is redistributed to the electric machine assigned to the axle without individual wheel drive before switching in the load reduction phase, so that the sum of the drive torque transmitted to both axles remains unchanged.

[0019] If it is known in advance that a yaw moment is likely to be desired during the switching operation, then the gearboxes assigned to the individual wheel drives can be switched individually, whereby the drive or braking load of the electric machine connected to the gearbox to be switched is preferably redistributed to the electric machine assigned to the axle without individual wheel drive during the load reduction phase in order to avoid generating an excessively high yaw moment.

[0020] The need for a yaw moment can be detected, for example, based on the vehicle's steering angle in conjunction with vehicle environment sensors, including, for example, a camera and / or a digital map in conjunction with a GPS system. Preferably, the transmission is engaged whose interruption of traction during shifting results in a yaw moment around the vehicle's vertical axis, which, due to the reduction of drive load or braking torque, assists cornering.

[0021] According to a further variant of the inventive method, it is proposed that, in a vehicle comprising two driven axles, each with two individual wheel drives comprising an electric motor and a downstream transmission, when switching a single transmission, the drive or braking load of the electric motor connected to the transmission to be switched is redistributed to the electric motor of the other axle located on the same side of the vehicle before the switching in the load reduction phase, in order to avoid generating a yaw moment through the switching.

[0022] Furthermore, it is proposed to shift both gearboxes of the same axle simultaneously and, in doing so, to redistribute the drive or braking load of the electric machines connected to the gearboxes to be shifted to the respective electric machine of the other axle located on the same side of the vehicle during the load reduction phase before the shift, so that no yaw moment is generated.

[0023] Furthermore, it is proposed to switch the gearboxes of two diagonally opposite single-wheel drives simultaneously and to distribute the drive or braking load of the electric machines connected to the gearboxes to be switched to the other two electric machines during the load reduction phase, so that no yaw moment is generated.

[0024] The inventive design largely avoids the loss of traction; in addition, a "torque vectoring" function is implemented during gear changes if at least one axle has two individual wheel drives.

[0025] The invention is explained in more detail below with reference to the accompanying figures. These figures depict: Fig. 1: A schematic view of the components relevant to the invention of an electrically powered vehicle, in the case that the vehicle has two axles, each driven by an electric machine via a transmission; Fig. 2: A schematic view of the components relevant to the invention of an electrically powered vehicle, in the case that the vehicle has a driven axle with two individual wheel drives, each comprising an electric motor and a transmission; Fig. 3: A schematic diagram of the components relevant to the invention of an electrically powered vehicle, in the case that the vehicle has two driven axles, one of the axles comprising two individual wheel drives, each comprising an electric motor and a transmission; and Fig. 4: A schematic representation of the invention-relevant components of an electrically powered vehicle, in the case that the vehicle has two driven axles, each with two individual wheel drives, comprising an electric machine and a downstream transmission.

[0026] The figures shown do not depict the components of electrical energy storage, inverters, control and power electronics of the electric machines, as well as the controls of the gearboxes and the overall drive train.

[0027] In Fig. 1 denotes the front axle and 2 the rear axle of an electrically powered vehicle. The front axle 1 is driven by an electric motor 3 via a transmission 4 with interruption of traction during gear changes, while the rear axle 2 is driven by an electric motor 5 via a transmission 6 with interruption of traction during gear changes.

[0028] According to the invention, the transmissions 4 and 6 are always switched alternately, i.e., never simultaneously. During the load reduction phase, the load of the electric motor associated with the switching transmission is additionally redistributed to the electric motor associated with the non-switching transmission, so that the sum of the drive torque transmitted to both axles remains unchanged before and during the switching operation. For example, when transmission 4 is switched, the load of electric motor 3 is redistributed to electric motor 5 before the switching operation. This prevents overheating of electric motor 5, which is taking on the additional load, due to the overload capacity of electric motors and the short duration of the switching operation.

[0029] In Fig. Figure 2 shows a further embodiment of the invention-relevant components of an electrically driven vehicle. Here, the vehicle comprises a driven axle 7, in this case the rear axle, with two individual wheel drives 8, 9, each comprising an electric motor 10, 11 and a transmission 12, 13 downstream of the respective electric motor 10, 11. The vertical axis of the vehicle is in Fig. 2 with the reference number 14.

[0030] According to the invention, in such a vehicle configuration, it is proposed to engage one of the two transmissions 12, 13 when it is known in advance that a yaw moment, i.e., a moment about the vehicle's vertical axis, which can lead to a steering input of the vehicle, is likely to be required during the shifting process, as is the case when cornering. The need for a yaw moment can be detected based on the vehicle's steering angle in conjunction with vehicle environment sensors, comprising, for example, a camera and / or a digital map in conjunction with a GPS system.

[0031] According to the invention, the transmission is engaged whose interruption of traction during shifting leads to a yaw moment around the vehicle's vertical axis, which, due to the reduction of drive load or braking torque, supports cornering.

[0032] According to the invention, when the vehicle is in towing mode, the transmission 12 on the right wheel of the rear axle 7 is engaged when a right turn is driven. Similarly, the transmission 13 on the left wheel of the rear axle 7 is engaged when a left turn is driven.

[0033] During a right-hand curve in train operation, a shift at the gearbox 12 results in a load reduction at the electric motor 10 associated with this gearbox, leading to a yaw moment about the vehicle's vertical axis 14, which assists the curve. According to one embodiment of the invention, the load on the electric motor 11 associated with the gearbox 13 is reduced only to the extent necessary to prevent an excessively high yaw moment; during straight-ahead travel, the load on the electric motor 11 would have to be completely reduced to avoid the generation of a yaw moment altogether. In another embodiment of the invention, if a particularly high yaw moment is desired, the electric motor 11 can also assume additional load.

[0034] According to the invention, when the vehicle is in overrun mode, the transmission 12 on the right wheel of the rear axle 7 is engaged when a left turn is driven. Similarly, the transmission 13 on the left wheel of the rear axle 7 is engaged when a right turn is driven. This means that the reduction in load on the electric motor associated with the transmission being engaged reduces the braking torque and acts in the opposite direction to the effect in traction mode, where a reduction in load means a reduction in drive torque.

[0035] In the event that the cornering maneuver is completed during the shifting process and therefore no yaw moment is required, the load on the electric motor not involved in the shifting process is also reduced according to the invention, and the loss of traction is accepted, since the stabilization of the vehicle is prioritized.

[0036] subject of the Fig. 3 are the components relevant to the invention of an electrically powered vehicle, in the case that the vehicle has two driven axles, wherein one of the axles has two individual wheel drives, each comprising an electric motor and a transmission

[0037] In the example shown, the front axle 17 is driven by an electric motor 15 via a transmission 16; the rear axle 7 comprises two independent wheel drives 8, 9, each with an electric motor 10, 11 and a transmission 12, 13 downstream of the respective electric motor 10, 11. The vertical axis of the vehicle is as shown in Fig. 2 with the reference number 14.

[0038] According to the invention, for a configuration of the vehicle according to Fig. 3. It is proposed that when the gearbox 16 assigned to axle 17 without individual wheel drive is to be engaged, the drive or braking load from the electric machine 15 assigned to this gearbox 16 is to be distributed to the electric machines 10, 11 assigned to the individual wheel drives 8, 9 in equal or different proportions for the purpose of generating a desired yaw moment about the vertical axis 14. The gearboxes 12, 13 of the individual wheel drives 8, 9 are not engaged in this process.

[0039] Furthermore, the gearboxes 12, 13 assigned to the individual wheel drives 8, 9 are always engaged simultaneously, while the gearbox 16 assigned to axle 17 without individual wheel drive is not engaged. During the load reduction phase, the load of the electric motors 10, 11 assigned to the individual wheel drives 8, 9 is redistributed to the electric motor 15 assigned to axle 17 without individual wheel drive, so that the sum of the drive torque transmitted to both axles 7, 17 remains unchanged before and during the engagement.

[0040] If it is known in advance that a yaw moment will likely be desired during the switching operation, then analogous to the exemplary embodiment from Fig. 2 the gearboxes 12, 13 assigned to the individual wheel drives 8, 9 are switched individually, wherein the drive or braking load of the electric machine connected to the gearbox to be switched is preferably fully or partially redistributed to the electric machine 15 assigned to the axle 17 without individual wheel drive during the load reduction phase in order to avoid generating an excessively high yaw moment.

[0041] The need for a yaw moment can be detected, for example, based on the vehicle's steering angle in conjunction with vehicle environment sensors, such as a camera and / or a digital map in conjunction with a GPS system. In this case, the transmission is selected whose interruption of traction during the shift results in a yaw moment around the vehicle's vertical axis, which, due to the reduction in drive load or braking torque, assists cornering.

[0042] In the event that the transmission 16 assigned to the axle 17 without individual wheel drive is to be shifted, the gear is left in the transmissions 12, 13 of the individual wheel drives 8, 9 according to the invention and the drive or braking load present before the shifting of the electric machine 15 assigned to the axle 17 without individual wheel drive is redistributed to the electric machines 10, 11 assigned to the individual wheel drives 8, 9 in equal proportions or in different proportions for the purpose of generating a yaw moment about the vehicle's vertical axis 14.

[0043] In a system according to Fig.4, in which the electrically driven vehicle comprises two driven axles 7, 18, each with two individual wheel drives 8, 9 and 19, 20 respectively, wherein the individual wheel drives 8, 9, 19, 20 each have an electric machine 10, 11, 21, 22 and a transmission 12, 13, 23, 24 downstream of the respective electric machine, it is proposed according to the invention to redistribute the drive or braking load to the electric machine assigned to an individual wheel drive on the same side of the vehicle when a single transmission is engaged, thereby preventing the generation of a yaw moment.

[0044] For example, when a gear is shifted in the transmission 23 of the individual wheel drive 19 of the front axle 18, the load on the electric motor 21 is reduced, thereby eliminating the drive torque at the front right wheel. According to the invention, during the shifting process, the drive or braking load on the electric motor 21 upstream of the shift is redistributed to the electric motor 10 assigned to the individual wheel drive 8, thereby increasing the drive torque at the rear right wheel and keeping the total torque about the vertical axis 14 of the vehicle constant.

[0045] According to the invention, it is proposed to switch both transmissions of the same axle, for example the transmissions 12 and 13, simultaneously and thereby to redistribute the drive or braking load of the electric machines 10, 11 connected to the transmissions 12, 13 to be switched, in the load reduction phase, completely or partially to the respective electric machine 21, 22 of the other axle 18 arranged on the same side of the vehicle, so that no yaw moment is generated.

[0046] As part of a further training, the gearboxes of two diagonally opposite individual wheel drives, for example gearboxes 12 and 24, are switched simultaneously, and the drive or braking load of the electric machines 10, 22 connected to the gearboxes 12, 24 that are present before the switching is redistributed completely or partially to the other two electric machines 11, 21 during the load reduction phase, so that no yaw moment is generated.

[0047] It is also possible that, if it is known in advance that a yaw moment is likely to be desired during the shifting process, at least one transmission should be used whose interruption of traction during shifting leads to a yaw moment around the vehicle's vertical axis, which, due to the reduction of drive load or braking torque, supports cornering. Reference sign 1 Front axle 2 Rear axle 3 Electric machine 4 gearboxes 5 Electric machine 6 gearboxes 7 axle, rear axle 8 Individual wheel drive 9 Individual wheel drive 10 Electric machine 11 Electric machine 12 gearboxes 13 gearboxes 14 Vertical axis of the vehicle 15 Electric machine 16 gearboxes 17 axle 18 axle 19 Individual wheel drive 20 Individual wheel drive 21 Electric machine 22 Electric machine 23 gearboxes 24 gearboxes

Claims

[1] Switching method in a purely electrically powered vehicle comprising at least two electric machines (3, 5, 10, 11, 15, 21, 22), wherein at least one electric machine is coupled to a drive via a transmission (4, 6, 12, 13, 16, 23, 24) with interruption of traction force during switching, characterized by , that the transmissions are shifted in such a way that the interruption of traction during shifting leads to a yaw moment around the vehicle's vertical axis (14), which, due to the reduction of drive load or braking torque, supports cornering. [2] Switching method according to claim 1, characterized by , that the total electrically generated torque of the electric machines remains unchanged before and during the switching process. [3] Switching method according to claim 1 or 2, characterized by, that in the event that the vehicle has two axles (1, 2) each driven by an electric machine (3, 5) via a transmission (4, 6), the transmissions (4, 6) are always switched alternately, whereby the load of the electric machine (3) or (5) assigned to the switching transmission (4) or (6) is additionally redistributed to the electric machine assigned to the non-switching transmission during the load reduction phase, so that the sum of the drive torque transmitted to both axles (1, 2) remains unchanged before and during the switching, whereby overheating of the electric machine taking over the load is avoided due to the overload capacity of electric machines and the short duration of the switching. [4] Switching method according to claim 1 or 2, characterized by, that in the event that the vehicle has a driven axle (7) with two independent wheel drives (8, 9) each comprising an electric machine (10, 11) and downstream transmission (12, 13), one of the two transmissions (12, 13) is engaged if it is known in advance that a yaw moment is likely to be desired during the time of the engagement, the transmission is engaged whose interruption of traction during the engagement leads to a yaw moment about the vehicle's vertical axis (14), which, due to the reduction of drive load or braking torque, assists cornering. [5] Switching method according to claim 4, characterized by , that depending on the desired yaw moment, the electric motor assigned to the non-shifting gearbox takes on or reduces additional load. [6] Switching method according to claim 1 or 2, characterized by, that in the event that the vehicle has two driven axles (7, 17), wherein one axle (7) comprises two individual wheel drives (8, 9), each comprising an electric machine (10, 11) and a transmission (12, 13) downstream of the respective electric machine (10, 11), and the other axle (17) is driven by an electric machine (15) via a transmission (16), when shifting the transmission (16) assigned to the axle (17), the gear is retained in the transmissions (12, 13), and the drive or braking load is distributed from the electric machine (15) assigned to this transmission (16) to the electric machines (10, 11) assigned to the individual wheel drives (8, 9) in equal or different proportions for the purpose of generating a desired yaw moment about the vertical axis (14). [7] Switching method according to claim 1 or 2, characterized by, that in the case that the vehicle has two driven axles (7, 17), wherein one axle (7) comprises two individual wheel drives (8, 9), each comprising an electric machine (10, 11) and a transmission (12, 13) downstream of the respective electric machine (10, 11), and the other axle (17) is driven by an electric machine (15) via a transmission (16), the transmissions (12, 13) assigned to the individual wheel drives (8, 9) are always switched simultaneously, wherein the transmission (16) assigned to the axle (17) is not switched, and wherein the load of the electric machines (10, 11) assigned to the individual wheel drives (8, 9) is redistributed to the electric machine (15) assigned to the axle (17) during the load reduction phase, so that the sum of the drive torque transmitted to both axles (7, 17) remains unchanged before and during the switching. [8] Switching method according to claim 1 or 2, characterized by, that in the event that the vehicle has two driven axles (7, 17), wherein one axle (7) has two individual wheel drives (8, 9) each comprising an electric machine (10, 11) and a transmission (12, 13) downstream of the respective electric machine (10, 11), and the other axle (17) is driven by an electric machine (15) via a transmission (16), if it is known in advance that a yaw moment is likely to be desired during the time of the shift, the transmission (12, 13) is shifted whose interruption of traction during the shift leads to a yaw moment about the vehicle's vertical axis (14), which, due to the reduction of drive load or braking torque, assists cornering. [9] Switching method according to claim 8, characterized by, that the drive or braking load of the electric machine (10, 11) connected to the transmission (12, 13) to be switched is redistributed in the load reduction phase to the electric machine assigned to the axle (17) without individual wheel drive in whole or in part (15) in order to avoid generating an excessively high yaw moment. [10] Switching method according to claim 1 or 2, characterized by, that in the event that the vehicle comprises two driven axles (7, 18) each with two individual wheel drives (8, 9) or (19, 20), wherein the individual wheel drives (8, 9, 19, 20) each have an electric machine (10, 11, 21, 22) and a transmission (12, 13, 23, 24) downstream of the respective electric machine, the transmissions of two diagonally opposite individual wheel drives are switched simultaneously, wherein the drive or braking load present before the switching of the electric machines connected to the transmissions to be switched is redistributed to the two other electric machines during the load reduction phase. [11] Switching method according to claim 1 or 2, characterized by, that in the event that the vehicle comprises two driven axles (7, 18) each with two individual wheel drives (8, 9) or (19, 20), wherein the individual wheel drives (8, 9, 19, 20) each have an electric machine (10, 11, 21, 22) and a transmission (12, 13, 23, 24) downstream of the respective electric machine, if it is known in advance that a yaw moment is likely to be desired during the time of the shift, at least one transmission is shifted, the interruption of which tractive force during the shift leads to a yaw moment about the vehicle's vertical axis, which, due to the reduction of drive load or braking torque, assists cornering. [12] Switching method according to one of claims 3, 5, 7, 11, characterized by , that the need for a yaw moment is detected based on the steering angle of the vehicle in conjunction with vehicle environment sensors, comprising a camera and / or a digital map in conjunction with a GPS system.

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