DRIVE TRAIN AND MOTOR VEHICLE

Abstract

A drive train for a vehicle comprises an input shaft, an output shaft, a first planetary gearing unit, a second planetary gearing unit and a third planetary gearing unit, each having a sun wheel, a carrier wheel and an annulus. The carrier wheel of the first planetary gearing unit is coupled to the sun wheel of the second planetary gearing unit. The annulus of the first planetary gearing unit is coupled to the carrier wheel of the second planetary gearing unit and to the annulus of the third planetary gearing unit. The annulus of the second planetary gearing unit is coupled to the carrier wheel of the third planetary gearing unit. The drive train has a first clutch device and a second clutch device, wherein the first and second clutch devices are connected by input sides thereof to the input shaft. The drive train has a first braking device, a second braking device and a third braking device. The drive train further includes an electric machine having an output coupled to the sun wheel of the first planetary gearing unit and to the first braking device.

Claims

1. A drive train for a vehicle, comprising: an input shaft, an output shaft a first planetary gearing unit, a second planetary gearing unit and a third planetary gearing unit, each having a sun wheel, a carrier wheel and an annulus, wherein: the carrier wheel of the first planetary gearing unit is coupled in a rotationally fixed manner to the sun wheel of the second planetary gearing unit, the annulus of the first planetary gearing unit is coupled in a rotationally fixed manner to the carrier wheel of the second planetary gearing unit and to the annulus of the third planetary gearing unit, the annulus of the second planetary gearing unit is coupled or can be coupled in a rotationally fixed manner to the carrier wheel of the third planetary gearing unit, and the drive train has a first clutch device and a second clutch device, wherein the first and second clutch devices are connected by input sides thereof to the input shaft, and an output side of the first clutch device is coupled in a rotationally fixed manner to the sun wheel of the third planetary gearing unit, an output side of the second clutch device is coupled in a rotationally fixed manner to the carrier wheel of the second planetary gearing unit, and the drive train has a first braking device, a second braking device and a third braking device, wherein the first braking device is coupled in a rotationally fixed manner to the sun wheel of the first planetary gearing unit, the second braking device is coupled in a rotationally fixed manner to the carrier wheel of the first planetary gearing unit, the third braking device is coupled in a rotationally fixed manner to the annulus of the first planetary gearing unit, to the carrier wheel of the second planetary gearing unit, to the annulus of the third planetary gearing unit, and wherein the output shaft is coupled in a rotationally fixed manner to the carrier wheel of the third planetary gearing unit, and an electric machine having an output coupled in a rotationally fixed manner to the sun wheel of the first planetary gearing unit and to the first braking device.

2. The drive train as claimed in claim 1, further comprising: a third clutch device connected by an input side thereof to the input shaft, wherein: an output side of the third clutch device is coupled in a rotationally fixed manner to the sun wheel of the first planetary gearing unit, the first braking device is coupled in a rotationally fixed manner to the output side of the third clutch device, and the output of the electric machine is coupled to the output side of the third clutch device.

3. The drive train as claimed in claim 2, wherein operation of the third clutch device is based on positive engagement.

4. The drive train as claimed in claim 1, wherein the electric machine and the first braking device are arranged structurally directly adjacent to one another.

5. The drive train as claimed in claim 1, further comprising: an internal combustion engine with an internal combustion engine torque capacity, and wherein an electric torque capacity of the electric machine is at least 40% of the internal combustion engine torque capacity.

6. The drive train as claimed in claim 1, further comprising: an internal combustion engine with an internal combustion engine torque capacity, and the second clutch device is configured to transmit at least 150% of the internal combustion engine torque capacity.

7. The drive train as claimed in claim 1, further comprising: an internal combustion engine with an internal combustion engine torque capacity, and the first clutch device is configured to transmit at least 140% of the internal combustion engine torque capacity.

8. The drive train as claimed in claim 1, further comprising: an internal combustion engine with an internal combustion engine torque capacity, and the second braking device is configured to absorb at least 250% of the internal combustion engine torque capacity.

9. The drive train as claimed in claim 1, wherein operation of the first, second, or third braking device is based on one or more of the following principles of action: switchable freewheel, self-energizing mechanism, positive engagement, and blocking synchronization.

10. A motor vehicle having at least one driven wheel, which can be driven by a drive train as claimed in claim 1.

11. The drive train as claimed in claim 1, wherein the electric machine is an electric motor.

12. The drive train as claimed in claim 1, further comprising: an internal combustion engine with an internal combustion engine torque capacity, and the second clutch device is configured to transmit more than 250% of the internal combustion engine torque capacity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The present disclosure described above is explained in detail below in relation to the relevant technical background, with reference to the associated drawings, which show preferred embodiments. The present disclosure is not in any way restricted by the purely schematic drawings, and it should be noted that the illustrative embodiments shown in the drawings are not restricted to the dimensions illustrated.

[0061] FIG. 1: shows a conventional drive train illustrating the geometric positions of the individual devices,

[0062] FIG. 2: shows a drive train according to the present disclosure illustrating the logical positions of the individual devices,

[0063] FIG. 3: shows a drive train according to the present disclosure illustrating the geometric positions of the individual devices,

[0064] FIG. 4: shows a diagram intended to illustrate the torque loading of the first braking device B1,

[0065] FIG. 5: shows a diagram intended to illustrate the torque loading of the second braking device B2,

[0066] FIG. 6: shows a diagram intended to illustrate the torque loading of the first clutch device K1,

[0067] FIG. 7: shows a diagram intended to illustrate the torque loading of the second clutch device K2,

[0068] FIG. 8: shows a diagram intended to illustrate the torque loading of the third braking device B3,

[0069] FIG. 9: shows a diagram intended to illustrate the torque loading of the third clutch device K3,

[0070] FIG. 10: shows a diagram intended to illustrate a control method for carrying out the gear change from 2 to 3,

[0071] FIG. 11: shows a diagram intended to illustrate a control method for carrying out driving away using the electric machine.

DETAILED DESCRIPTION

[0072] The logical configuration of the drive train in accordance with the present disclosure is illustrated in FIG. 2.

[0073] The electric machine EM is arranged logically downstream of the third clutch device K3 and in parallel with the first braking device B1 and the sun wheel S of the first planetary gearing unit P1.

[0074] Corresponding to the logical position is a structural association with a geometric location, this being illustrated by way of example in FIG. 3.

[0075] Here, the installation position is between the third clutch device K3 and the first braking device B1. In this case, however, the present disclosure is not restricted to this geometric location of the electric machine EM; on the contrary, the electric machine EM could also be arranged in a functionally equivalent way between the first braking device B1 and the second braking device B2. The arrangement of the electric machine in direct proximity to the brake B1 is structurally advantageous because owing to its large mass and the applied magnetic forces, the rotor requires good support, the bearing support frame of which is also capable of supporting the nonrotating side of a brake B1. In the drive train according to the present disclosure, individual devices must be designed in accordance with the dependencies illustrated for each device in FIGS. 4-9, wherein a torque reserve should preferably be included in addition in each case.

[0076] FIGS. 4-9 illustrate the respective loading M_r of a device by a torque as a function of the maximum torque of the internal combustion engine M_ICE and that of the electric motor M_EM.

[0077] It can be seen here in the case of each device that the degree of hybridization, which is plotted on the X axis, has a major effect on which gear requires the maximum torque of the respective device, wherein the torque value which acts on the respective device in the respective gear and accordingly is relevant to design is plotted on the Y axis.

[0078] In other words, FIGS. 4-9 illustrate how the respective torque M_r acting on the device is as a function of the total torque composed of the individual torques of the internal combustion engine and the electric machine, depending on the gear implemented.

[0079] FIG. 4 shows this for gears 3 and 5, wherein the function M_r=|(0.18M_ICE+M_EM)| applies to gear 3 and the function M_r=|(0.41M_ICE+M_EM)| applies to gear 5.

[0080] FIG. 5 shows this for gears 2 and 6, wherein the function M_r=|(0.84M_ICE+2.06M_EM)| applies to gear 2 and the function M_r=|(0.38 M_ICE+2.06M_EM)| applies to gear 6.

[0081] FIG. 6 shows this for gears 3 and 4, wherein the function

[0082] M_r=|(M_ICE)| applies to gear 3, and the function M_r=|(0.31M_ICE+1.69M_EM)| applies to gear 4.

[0083] FIG. 7 shows this for gears 4 and 6, wherein the function

[0084] M_r=|(0.69M_ICE+1.69M_EM)| applies to gear 4, and the function M_r=|(M_ICE)| applies to gear 6.

[0085] FIG. 8 shows this for gears 1 and Rev (reverse gear) wherein the function

[0086] M_r=|(2.23M_ICE+5.46M_EM)| applies to gear 1, and the function M_r=|(5.46M_ICE+5.46M_EM)| applies to reverse gear.

[0087] FIG. 9 shows this for reverse gear, wherein the function M_r=|(M_ICE)| applies.

[0088] From FIG. 4, it can be seen that the first braking device B1 can be made more compact and/or can be designed for a lower power than conventional embodiments since it is substantially load-free at 40% of the torque M_EM provided by the electric machine in relation to the torque of the internal combustion engine M_ICE. Thus, the first braking device B1 can, for example, be fitted with a switchable freewheel 20, optionally with rollers, pawls, wedging disks, screw cone elements, or with static friction elements with a high coefficient of friction, e.g. ceramic pads, hard fiber linings, hook and loop bands, or with friction elements with a self-energizing effect, e.g. band brakes, wrap springs, boost ramps; or can be of positive-locking configuration, e.g. in the form of a dog clutch, if appropriate in combination with friction synchronization. In this case, the first braking device B1 should be designed for 30-60% of the maximum torque that can be provided by the internal combustion engine, in particular to 40-50% of this maximum torque.

[0089] The same applies to the third clutch device K3, which can be seen in FIG. 9.

[0090] It can furthermore be seen from FIG. 4, that the torque capacity of the electric machine is advantageously approximately at least 40% of the torque capacity of the internal combustion engine.

[0091] From FIG. 5, it can be seen that the torque capacity of the second braking device B2 should advantageously be designed for about 250% of the maximum torque provided by the internal combustion engine.

[0092] From FIG. 6, it can be seen that the first clutch device K1 should advantageously be designed for at least 140% of the maximum torque provided by the internal combustion engine.

[0093] From FIG. 7, it can be seen that the torque capacity of the second clutch device K2 should advantageously be around at least 150% of the maximum torque provided by the internal combustion engine. Detailed analysis subject to the boundary condition of a constant output torque shows that as much as about 250% of the maximum torque provided by the internal combustion engine is required for the second clutch device K2.

[0094] The following shift diagram can be obtained by means of the drive train according to the present disclosure illustrated in FIGS. 2 and 3.

TABLE-US-00002 Gear K1 K2 K3 B2 B1 B3 M_Out/M_ICE M_Out/M_EM M_ICE/M_EM 1 X X 3.23 4.46 2 X X 1.84 1.06 3 X X 1.41 CVT1 X 1.41 3.45 2.45 4 X X 1.00 1.00 5 X X 0.82 CVT2 X 0.82 4.45 5.45 6 X X 0.62 1.06 Rev X X 4.46 4.46 E1 X 4.46 E2 X 1.06 L X 1.00

[0095] Here, M_Out is the output torque of the drive train.

[0096] M_EM is the torque provided by the electric machine. M_ICE is the torque provided by the internal combustion engine.

[0097] Of relevance here are, on the one hand, the advantageous additional operating modes CVT 1, CVT 2, E1, E2 and L added by virtue of the arrangement of the electric machine EM and, on the other hand, the additional mode transitions resulting therefrom. These additional mode transitions make it possible to ensure comfort, even without frictional shift elements, since less friction energy arises in the clutch devices K1, K2, K3 and, at the same time, a constant torque at the outlet is ensured.

[0098] The CVT1 mode, in which the first clutch device K1 is closed and the rotor of the electric machine EM rotates, can be used to improve comfort and/or reduce frictional losses and/or synchronize rotational speeds in all gear changes between gears 1, 2, 3 and 4.

[0099] Another option for the use of the CVT1 mode is to allow a charging driveaway when the battery is empty but the internal combustion engine is running while the vehicle is stationary. In this context, the internal combustion engine turns the electric machine EM with a negative rotational speed, thus enabling the electric machine EM to charge the battery while operating as a generator. At the same time, the power flow from the internal combustion engine to the electric machine EM produces a transmission output torque, which can be used to drive away the vehicle.

[0100] The CVT2 mode, in which the second clutch device K2 is closed, can be used to improve comfort and/or reduce frictional losses and/or, where applicable, for complete rotational speed synchronization in all gear changes between gears 4, 5 and 6.

[0101] Moreover, the CVT2 mode allows continuously variable or stepped-ratio driving with rotational speed ratios beyond sixth gear and thus forms a widening of the spread of the transmission similar to an additional gear 7.

[0102] The E1 mode allows forward and reverse electric driving at low speeds.

[0103] The E2 mode allows purely electric forward driving or coasting with a relatively low amount of tractive effort (relatively small electric transmission), e.g. at relatively high road speeds.

[0104] Thanks to this new hybrid function, it is possible in one particular embodiment of the drive train to dispense with the third clutch device K3 when the reverse gear is implemented by means of the E1 mode.

[0105] While driving in the E1 mode, the internal combustion engine can be started at any time, either by using a separate starter motor, e.g. as a belt drive machine, or by engaging the first clutch device K1 to implement gear 1 with corresponding simultaneous activation, for the purpose of increasing the torque, of the electric machine EM assigned to the transmission, thus ensuring that the output torque of the transmission remains as far as possible constant in order to enhance comfort. Furthermore, the E mode can also be used for purely electric reversing, particularly when there is not supposed to be a third clutch device K3.

[0106] The charging mode L can be used when the vehicle is stationary, if appropriate when the brakes are actuated, or when traveling slowly for the purpose of coupling the battery to the internal combustion engine, with the output otherwise decoupled, i.e. with the vehicle being capable of rolling.

[0107] This mode is also suitable for coasting when driving in gear 4. The speed of the internal combustion engine when charging or coasting is a matter of free choice and can be the idling speed or, alternatively, higher, i.e. closer to the rotational speed at which gear 4 is reengaged, this having advantages as regards acoustics and driving dynamics.

[0108] FIG. 10 illustrates a control method, showing how the gear change from 2 to 3 is carried out using the electric machine EM, thus enabling the first braking device B1 to be actuated in a positive-locking manner but nevertheless comfortably. The control method can also be used with a frictional braking device B1 and then reduces the frictional losses.

[0109] It can be seen here that, when operating in gear 2, a certain torque is present at the second braking device B2. For the purpose of changing gear, this is reduced, and the torque of the electric machine M_EM is raised, this corresponding to the CVT1 mode. After the brake B2 is opened, the initially negative rotational speed n EM of the electric machine EM is reduced toward 0 by corresponding operation (braking) of the electric machine. This means that the torque is produced by the electric machine EM, allowing gear 3 to be engaged, namely by closing or engaging the first braking device B1, which can be designed in a corresponding manner to be positive-locking. As a result, the rotational speed n_Fzg of the entire drive train rises in a comfortable manner during this sequence of operations.

[0110] FIG. 11 illustrates a control method, showing how driveaway is carried out using the electric machine EM, wherein the third braking device B3 is actuated, and how the change to gear 1 takes place (under power from the internal combustion engine).

[0111] First of all, the amount of torque from the electric machine M_EM is increased in response to driver demand, e.g. through actuation of a pedal, in order to drive the vehicle away.

[0112] The effect of this is the rise in the rotational speed n_Fzg of the entire drive train. Depending on the state of charge of the battery or road speed or, alternatively, a driver demand, the use of the internal combustion engine can be initiated.

[0113] A friction torque is built up at the first clutch device K1 in order to crank the internal combustion engine. The effect of this is a rise in the rotational speed of the internal combustion engine n_ICE and, once the internal combustion engine has started, there is likewise a rise in the torque M_ICE made available by the internal combustion engine. When the rotational speed of the internal combustion engine n_ICE and the rotational speed of the sun wheel S of the third planetary gearing unit P3 are uniform, the clutch device K1 can be fully engaged. Depending on the state of charge of the battery and, if appropriate, driver demand when accelerating the vehicle and consequently increasing the rotational speed of the drive train n_Fzg in gear 1, the torque M_ICE made available by the internal combustion engine can be increased and the torque M_EM made available by the electric motor can be reduced.

[0114] As an alternative to cranking with the aid of the clutch device K1, there is the possibility of starting the internal combustion engine by means of a belt or pinion starter. This enables synchronization by the first clutch device K1 to take place at a low differential rotational speed.

[0115] Development, modification and even simplification of the drive train described with an integrated electric machine EM is conceivable in many respects.

[0116] The third clutch device K3 can be of positive-locking design or can even be omitted completely. In this case of complete omission of the third clutch device K3, the operating modes Rev (reverse gear) and L (charging mode) are eliminated. The elimination of the operating mode Rev is compensated for by the operating mode E1, in which the electric machine EM allows reversing by means of reverse rotation. The elimination of the operating mode L can be compensated, for example, by a battery of correspondingly large dimensions or by means of a charging function of a generator or of a belt-type starter generator.

[0117] Another refinement is to make the third braking device B3 of positive-locking design. It requires a high torque capacity in the E1 mode and also in gear 1. Since it is only required in these gears, a very much more compact positive-locking design can be implemented.

[0118] It is likewise possible to employ a combined construction which unites a freewheel 20 with a positive-locking principle of operation or which unites a freewheel 20 with a frictional principle of operation.

[0119] With the present disclosure proposed here, it is thus possible to make available a drive train having electric or hybrid driving functions which, by virtue of the logical position of the electric machine EM within the transmission, makes it possible to dimension individual devices of the drive train in accordance with the respective torque requirements made upon it and thus to reduce the installation space for these devices and consequently for the entire drive train.

LIST OF REFERENCE SIGNS

[0120] P1 first planetary gearing unit [0121] P2 second planetary gearing unit [0122] P3 third planetary gearing unit [0123] S sun wheel [0124] T carrier wheel [0125] H annulus [0126] K1 first clutch device [0127] K2 second clutch device [0128] K3 third clutch device [0129] B1 first braking device [0130] B2 second braking device [0131] B3 third braking device [0132] EM electric machine [0133] EMA output (of the electric machine) [0134] M_r loading of a device by a torque [0135] M_ICE torque of the internal combustion engine [0136] M_EM torque of the electric machine [0137] 1 first gear [0138] 2 second gear [0139] 3 third gear [0140] 4 fourth gear [0141] 5 fifth gear [0142] 6 sixth gear [0143] Rev reverse gear [0144] 10 frame [0145] 20 freewheel [0146] 30 input shaft [0147] 40 output shaft