DE102018221601A1 - Drive axle of an electric vehicle - Google Patents

Abstract

The invention relates to a drive axle (1) of an electrically drivable vehicle, comprising two drivable vehicle wheels (R1, R2), two electrical machines (EM1, EM2), two multi-speed manual transmissions (G1, G2) with transmission output shafts (GAW1, GAW2), whereby the first electrical machine (EM1) and the first manual transmission (G1) have a first drive train (A1) for driving the first vehicle wheel (R1) and the second electrical machine (EM2) and the second manual transmission (G2) have a second drive train (A2) Form the drive of the second vehicle wheel (R2). It is proposed that an electronically controllable friction clutch (K), in particular a multi-plate clutch, be arranged between the transmission output shafts (GAW1, GAW2, 9, 10) of the first and second manual transmissions (G1, G2) is.

Description

The invention relates to a drive axle of an electrically drivable vehicle, comprising two drivable vehicle wheels, two electrical machines, two multi-speed manual transmissions with transmission output shafts, the first electrical machine and the first manual transmission having a first drive train for driving the first vehicle wheel and the second electrical machine and the like second gearbox form a second drive train for driving the second vehicle wheel. The invention also relates to a method for driving an electric vehicle.

Such a drive is known and is referred to as a wheel-specific drive. Both drivetrains are separate, identical and mirror images. For cost reasons, dog clutches are used as shift elements, which causes an interruption in traction when shifting, which affects shifting comfort and driving performance. If you only switch on one side, there is a yaw moment for the vehicle due to an interruption in tractive power on the one hand and full drive torque on the other, which the driver must compensate for by taking countermeasures.

Starting from a wheel-specific drive of the type mentioned at the outset, it is an object of the invention to improve the performance and shifting comfort of the vehicle.

The invention comprises the features of independent claims 1 and 5. Advantageous refinements result from the subclaims.

According to a first aspect of the invention, in the case of a drive axle of the type mentioned at the outset, an electronically controllable friction clutch, in particular a multi-plate clutch, is arranged between the first transmission output shaft of the first manual transmission and the second transmission output shaft of the second manual transmission. By means of the adjustable multi-plate clutch, a non-positive connection between the right and the left wheel side can be established if necessary, which is particularly advantageous when shifting on only one side, either in the right or in the left manual transmission. In this case, for example, there is an interruption in traction on the right-hand side, so that the right wheel would be without drive. This is prevented by the clutch being closed and the drive torque being transmitted from the left, still driven side to the right (unpowered) wheel. This avoids an interruption in tractive power, and gearshift comfort and driving performance are increased.

According to a preferred embodiment, the manual transmission has two gear stages, i. H. a first gear and a second gear, which takes into account the need of the vehicle, in particular a commercial vehicle, for the approach climbing ability and the final speed.

According to a further preferred embodiment, for the switching process, i. H. the gear change from the first to the second or from the second to the first gear provided a positive shift element, in particular a dog clutch. The claw coupling has the advantage that, due to its simple construction, it can be manufactured at relatively low cost and is highly efficient.

According to a further preferred embodiment, a first fixed transmission stage is arranged between the first transmission output shaft and the first or left wheel and a second fixed transmission stage is arranged between the second transmission output shaft and the second or right wheel, both transmission stages having the same transmission ratio. Both gear ratios serve to further reduce the speed of the electrical machines.

According to a further aspect of the invention, in a method for driving an electric vehicle by means of the drive axle described above, it is provided that the switching operation is fundamentally only on one side, ie. H. is carried out either on the side of the left wheel or on the side of the right wheel and that at the same time, ie during the switching process, a torque is transmitted from the driven wheel side to the non-driven side via the clutch. As mentioned above, when switching, e.g. B. on the right side an interruption of traction, so that the right wheel is without drive. During the switching process, the clutch is closed or partially closed, so that a torque is transmitted from the left side, on which there was no shifting, to the right side - this means that both wheels are driven with the same torque during the switching process, and it occurs during the Switching no interruption of traction.

According to a further preferred method variant, the degree of torque transmission of the clutch, that is to say the size of the torque transmitted by the clutch, is variable on account of the electronic control and is dependent on a shift process, on the direction of travel, for. B. driving straight or driving through a right or left curve and depending on a vehicle acceleration or deceleration regulated. When switching on The clutch is closed on one side, the clutch is not fully closed when cornering and, depending on the direction of the curve, shifting is only permitted on the right or left side. These parameters, which must be recognized by a control device, are the input variables for regulating the multi-plate clutch.

According to a further preferred variant of the method, the clutch is completely closed, which corresponds to a degree of transmission of one hundred percent when a switching operation is carried out on one side. In this case, the full engine torque of the driving side is transferred to the non-driven side, which applies to the vehicle traveling straight ahead.

According to a further preferred variant of the method, the clutch is not fully closed when the vehicle is cornering, but is adjusted to the transmission of half an engine torque on the driving wheel side.

According to a further preferred method variant, the gearshift operation is to be carried out on the left-hand side of the wheel when the vehicle is accelerating in a left-hand turn or decelerated in a right-hand turn. This results in a yaw moment, which causes the vehicle to oversteer, i. H. steers into the curve.

According to a further preferred variant of the method, a shift operation or a gear change is to be carried out on the right-hand side of the wheel when the vehicle is accelerating in a right-hand bend or decelerated in a left-hand bend. This also creates a yaw moment that oversteers the vehicle. Due to the tendency to oversteer, i. H. into the curve, the safety when switching in a curve is increased.

• 1 eine Antriebsachse für ein Elektrofahrzeug in schematischer Darstellung und
• 2 die Antriebsachse gemäß 1 in detaillierter Darstellung.

An embodiment of the invention is shown in the drawing and will be described in more detail below, wherein further features and / or advantages may result from the description and / or the drawing. Show it

• 1 a drive axle for an electric vehicle in a schematic representation and
• 2nd the drive axle according to 1 in a detailed representation.

1 shows a schematic representation of a drive axle 1 of an electrically drivable vehicle, hereinafter also referred to as an electric vehicle. The drive axle 1 includes a first or left vehicle wheel R1 and a second or right vehicle wheel R2 , hereinafter also the first or left wheel R1 and second or right wheel R2 called. The first or left wheel R1 is powered by a first powertrain A1 driven, which is a first electrical machine EM1 , in the following also electric machine EM1 called a manual transmission G1 , a transmission output shaft GAW1 , a first axle shaft AW1 and a fixed translation level Ü1 includes. The second or right wheel R2 is powered by a second powertrain A2 driven, which is a mirror image of the first drive train A1 is built and a second electrical machine EM2 , also for short electric machine EM2 called a second manual transmission G2 , a second transmission output shaft GAW2 , a second axle shaft AW2 and a second fixed translation level Ü2 having. Between the first and the second axle shaft AW1 , AW2 is an electronically adjustable friction clutch K arranged, which preferably as a multi-plate clutch K is trained. Through the clutch K can create a positive connection between the two axle shafts AW1 , AW2 respectively between the left wheel R1 and the right wheel R2 be made, which is through the clutch K transmitted torque is adjustable in terms of its degree of transmission from zero (clutch open) to one hundred percent (clutch closed). The coupling K can thus be operated fully closed, fully separated or partially closed in certain situations, which are explained below. The first and the second manual transmission G1 , G2 are preferably designed as a two-speed manual transmission, ie the speeds of the two electric machines EM1 , EM2 can be geared down in two gear steps. With the clutch open K work the first powertrain A1 and the second powertrain A2 completely independent of each other, ie the left wheel R1 and the right wheel R2 can each be driven at different speeds and different torques, which can generate a yaw moment (torque around the vertical axis of the vehicle) - so-called torque vectoring, which makes the vehicle more agile.

2nd shows a drive axle 2nd which in the construction of the drive axle 1 according to 1 corresponds and a representation of individual components of the two manual transmissions G1 , G2 ( 1 ) shows. The first drive train A1 comprises a first electrical machine EM1 (in short: electric machine EM1 ) with a rotor 3rd and a rotor shaft 3a on which gears 5a , 7a (Fixed wheels 5a , 7a ) a first gear 5 and a second gear 7 are rotatably arranged, and a first transmission output shaft 9 on which idler wheels 5b , 7b the first and second gear 5 , 7 are arranged. The idler gears 5b , 7b are through a switching element 11 switchable ie you can alternate with the transmission output shaft 9 be connected in a rotationally fixed The switching element 11 is preferably a positive coupling, especially a claw coupling 11 educated. On the first transmission output shaft 9 is a first gear on the output side 13a a fixed translation level 13 arranged which between the first transmission output shaft 9 and a first axle shaft 15 is effective. On the first axle shaft 15 is a second gear 13b arranged, which with the first gear 13a is engaged. The first axle shaft 15 drives the first or left wheel R1 on. The second drive train is analogous and a mirror image A2 built which is a second electrical machine EM2 (in short: electric machine EM2 ) with a rotor 4th and a rotor shaft 4a , a first gear 6 , a second gear 8th , a preferably as a claw coupling 12 trained switching element 12 and a second transmission output shaft 10th includes. Between the second transmission output shaft 10th and a second axle shaft 16 is a second fixed translation level 14 arranged. Both translation levels 13 , 14 serve to further reduce the speeds of the two e-machines EM1 , EM2 . Between the first transmission output shaft 9 and the second transmission output shaft 10th is an electronically adjustable friction clutch 17th , preferably a multi-plate clutch 17th arranged, which can transmit a torque adjustable in size between the right and left wheel sides.

The coupling 17th or. K in 1 has the task of interrupting the traction (on the wheels R1 , R2 ) when shifting gears, ie to avoid shifting. Without the clutch 17th would when the first dog clutch was actuated 11 or the second dog clutch 12 an interruption in traction in the first or in the second drive train occurs for engaging a gear. According to the invention is only on one side, either on the side of the right wheel R2 or on the side of the left wheel R1 switched, that is, a switching operation for engaging the first or second gear is carried out. This has the result that on one side of the wheel, for. B. the side of the left wheel R1 an interruption in traction occurs during the switching process, on the other side of the wheel, for. B. the side of the right wheel R2 but still a drive on the wheel ( R2 ) he follows. Now the clutch 17th closed, so is from the driven wheel side, for example the side of the right wheel R2 from the second transmission output shaft 10th a torque on the first transmission output shaft 9 and thus on the left axle shaft 15 and the left wheel R1 transfer. The result is that there is no interruption in tractive power. When the vehicle is driving straight ahead, the clutch is 17th fully closed, ie one hundred percent of the torque of the driving electric machine is transmitted.

When the vehicle is cornering, the clutch may 17th not be closed completely, but must be half the engine torque of the driving electric machine, EM1 or EM2 , are regulated. The electronically controlled clutch 17th includes a control, not shown, which must recognize whether the vehicle is accelerating or decelerating and whether the vehicle is moving through a strong left or right curve. If the control system recognizes that the vehicle is accelerating into a left-hand bend, the gearshift should only take place on the left-hand side, ie on the inside of the bend. In this case, a yaw moment turning to the left occurs, ie the vehicle tends to oversteer. If the control system recognizes that the vehicle is decelerating in a right-hand bend, gearshifts should also only be made on the left-hand side, whereby a right-turning yaw moment is generated, ie the vehicle tends to oversteer.

A shift on the right-hand side should only take place if you accelerate into a right-hand curve or decelerate into a left-hand curve. In the case of acceleration in the right-hand curve, a right-turning yaw moment arises when shifting, and in the case of deceleration in a left-hand curve, a left-turning yaw moment is generated, so that the vehicle oversteers in both cases. Seen in terms of time, the build-up of the clutch torque, ie that of the clutch 17th transmitted torque take place synchronously with the reduction of the drive torque of the switching drive train. For example, the switching element 11 of the first drive train A1 is actuated, the drive torque, which is from the first electric machine EM1 runs out, gradually or abruptly (claw clutch) dismantled. In the same way, that of the second electric machine EM2 outgoing engine torque the torque to be transmitted in the clutch 17th build up. The regulation of the torque of the clutch 17th is said to cause both wheels R1 , R2 the same wheel torques act so that a yaw moment, which the driver would have to compensate for, is avoided. The circuit of the second electric machine EM2 should only be done again when driving straight ahead.

The clutch can be used when driving off-road 17th fully closed at low speeds, resulting in increased traction for the vehicle.

Reference symbol list

1

Drive axle ( 1 )

2nd

Drive axle ( 2nd )

3rd

first rotor

3a

first rotor shaft

4th

second rotor

4a

second rotor shaft

5

first gear stage (first drive train)

5a

Fixed gear

5b

Idler gear

6

first gear stage (second drive train)

7

second gear stage (first drive train)

7a

Fixed gear

7b

Idler gear

8th

second gear stage (second drive train)

9

first transmission output shaft

10th

second transmission output shaft

11

first switching element (dog clutch)

12

second switching element (dog clutch)

13

first translation stage

13a

first gear

13b

second gear

14

second stage of translation

15

first axle shaft

16

second axle shaft

17th

coupling

A1

first drive train

A2

second drive train

AW1

first axle shaft

AW2

second axle shaft

EM1

first electric machine

EM2

second electric machine

G1

first manual transmission

G2

second manual transmission

GAW1

first transmission output shaft

GAW2

second transmission output shaft

K

Multi-plate clutch

R1

first (left) wheel

R2

second (right) wheel

Ü1

first translation stage

Ü2

second stage of translation

Claims (10)

Drive axis of an electrically drivable vehicle, comprising - two drivable vehicle wheels (R1, R2), - two electrical machines (EM1, EM2), - two multi-speed manual transmissions (G1, G2) with transmission output shafts (GAW1, GAW2, 9, 10), - The first electrical machine (EM1) and the first manual transmission (G1) having a first drive train (A1) for driving the first vehicle wheel (R1) and - The second electrical machine (EM2) and the second manual transmission (G2) form a second drive train (A2) for driving the second vehicle wheel (R2) and wherein - An electronically controllable friction clutch (K, 17), in particular a multi-plate clutch, is arranged between the transmission output shafts (GAW1, GAW2, 9, 10) of the first and second manual transmissions (G1, G2). Drive axis after Claim 1 , characterized in that the manual transmission (G1, G2) each have two gear stages (5, 7; 6, 8). Drive axis after Claim 1 or 2nd , characterized in that the gearboxes (G1, G2) for shifting the gear stages (5, 7; 6, 8) each have a positive shifting element (11, 12), in particular a dog clutch. Drive axis after Claim 1 , 2nd or 3rd , characterized in that between the transmission output shafts (GAW1, GAW2, 9, 10) and the vehicle wheels (R1, R2) a fixed gear ratio (Ü1, Ü2, 13, 14) is arranged. Method for driving an electric vehicle by means of a drive axle (1, 2) according to one of the preceding claims, characterized in that a switching operation when driving straight ahead or cornering is carried out only on one side, the right or left wheel side, and during the switching operation by the clutch (K) a torque is transmitted from the driven wheel side to the non-driven wheel side. Procedure according to Claim 5 , characterized in that the degree of torque transmission of the clutch (K) is regulated as a function of a gearshift operation, the direction of travel (straight-ahead, right-hand or left-hand turn) and / or the vehicle acceleration or deceleration. Procedure according to Claim 5 , characterized in that the clutch (K) is closed (degree of transmission 100%) when a switching operation is carried out on one side, the right wheel side (R1) or the left wheel side (R2). Method according to claim Claim 5 or 6 , characterized in that the clutch (K) is not fully closed when cornering the vehicle, but on the transmission of the half engine torque of the driving wheel side is adjusted. Procedure according to Claim 5 , 6 or 8th , characterized in that a shift operation is to be carried out on the left wheel side when the vehicle is accelerating in a left turn or decelerating in a right turn. Procedure according to Claim 5 , 6 or 8th , characterized in that a shift operation is to be carried out on the right-hand side of the wheel when the vehicle is accelerating in a right-hand bend or decelerated in a left-hand bend.

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