TRANSMISSION ARRANGEMENT, DRIVE UNIT AND METHOD FOR OPERATING A DRIVE UNIT FOR A VEHICLE

Abstract

Gear arrangement for a vehicle, having an input shaft, a layshaft, an output shaft connected to a drive wheel of the vehicle, a plurality of shiftable first gear wheel sets which connect the input shaft and the layshaft and which are each associated with at least one gear stage, and a machine gear connected to one of the shafts and into which the drive torque of an electric machine can be introduced. The first gear wheel sets form a first part-gear mechanism, wherein at least one second shiftable gear wheel set connects the layshaft and the output shaft and forms a second part-gear mechanism, wherein the at least one second gear wheel set is associated with at least one gear stage and wherein the machine gear is arranged in an axial direction between the first part-gear mechanism and the second part-gear mechanism.

Claims

1. Gear arrangement for a vehicle, having an input shaft, a layshaft, an output shaft which can be connected to a drive wheel of the vehicle, a plurality of shiftable first gear wheel sets which connect the input shaft and the layshaft and which are each associated with at least one gear stage, a machine gear which is connected or can be connected to one of the shafts and into which the drive torque of an electric machine can be introduced, wherein the first gear wheel sets form a first part-gear mechanism, wherein at least one second shiftable gear wheel set connects the layshaft and the output shaft and forms a second part-gear mechanism, wherein the at least one second gear wheel set is associated with at least one gear stage and wherein the machine gear is arranged in an axial direction between the first part-gear mechanism and the second part-gear mechanism.

2. Gear arrangement according to claim 1, wherein the machine gear is connected by means of a free wheel to one of the shafts.

3. Gear arrangement according to claim 1, wherein the machine gear is securely connected to the layshaft, wherein the electric machine can be connected to the machine gear by means of a separating clutch or a free wheel.

4. Gear arrangement according to claim 1, wherein the machine gear is connected by means of a free wheel to an intermediate shaft which is securely connected to an idler wheel of a gear wheel set of the first gear wheel sets, which idler wheel is rotatably supported on the layshaft.

5. Gear arrangement according to claim 1, wherein the machine gear is connected or can be connected to an intermediate shaft which is arranged coaxially with respect to the input shaft.

6. Gear arrangement according to claim 5, wherein the intermediate shaft is connected to the input shaft by means of a shiftable free wheel or a separating clutch.

7. Gear arrangement for a vehicle, having: an input shaft, a layshaft, an output shaft which can be connected to a drive wheel of the vehicle, a plurality of shiftable first clear wheel sets which connect the input shaft and the layshaft and which are each associated with at least one clear stage, a machine clear which is connected or can be connected to one of the shafts and into which the drive torque of an electric machine can be introduced, wherein the electric machine is connected to the machine gear by means of a lead gear mechanism, wherein the lead gear mechanism is arranged so as to axially overlap with at least one gear wheel set of the first and/or second shiftable gear wheel sets.

8. Gear arrangement according to, wherein the electric machine is connected to the machine gear by means of a lead gear mechanism, wherein the lead gear mechanism has an intermediate wheel which is rotatably supported on an auxiliary shaft which is arranged offset in a parallel manner with respect to the input shaft and the layshaft.

9. Gear arrangement according to claim 1, wherein the input shaft is coupled to a drive shaft by means of a spring arrangement of a torque detection device.

10. Gear arrangement according to claim 1, wherein the wheel sets of the gear arrangement are arranged in a housing which defines a fluid sump for producing a lubrication for the wheel sets, wherein a heat source is arranged in the housing and wherein at least one (i) the arrangement of the heat source in the housing is selected or (ii) the housing is

11. Gear arrangement according to claim 1, wherein the wheel sets of the gear arrangement are arranged in a housing in which a fluid sump is arranged for at least one of lubrication or cooling, wherein a fluid pump draws from the fluid sump fluid which is used to cool the heat source.

12. Drive unit for a vehicle, having a gear arrangement which comprises: an input shaft, a layshaft, an output shaft which can be connected to a drive wheel of the vehicle, a plurality of shiftable first gear wheel sets which connect the input shaft and the layshaft and which are each associated with at least one gear stage, a machine gear which is connected or can be connected to one of the shafts and into which the drive torque of an electric machine can be introduced, wherein the first gearwheel sets form a first part-gear mechanism, wherein at least one second shiftable gear wheel set connects the lavshaft and the output shaft and forms a second part-gear mechanism, wherein the at least one second gear wheel set is associated with at least one gear stage and wherein the machine gear is arranged in an axial direction between the first part-gear mechanism and the second part-gear mechanism, and an electric machine which is connected to the machine gear of the gear arrangement.

13. Drive unit according to claim 12, wherein the electric machine has a stator which is cooled by means of a cooling arrangement.

14. Drive unit according to claim 12, having (i) a control device for at least one of controlling a shifting apparatus for the gear wheel sets controlling the electric machine, and having (ii) a sensor arrangement for detecting at least one status variable of the drive unit.

15. Drive unit according to claim 14, wherein the sensor arrangement comprises at least one of: a rotor position sensor for detecting a rotation position of a rotor of the electric machine a shifting position sensor a speed sensor for detecting a speed of the input shaft a rotation position sensor for detecting a relative rotation position of the input shaft a crank position sensor for detecting a rotation position of cranks which are connected to a drive shaft or a torque sensor for detecting a muscular force torque which is introduced into a drive shaft.

16. Drive unit according to claim 14, wherein a printed circuit board, on which the control device or at least one sensor of the sensor arrangement is arranged, is secured to a housing, wherein the control device has an electronic power unit for the electric machine or an electronic power unit for a shifting motor or a microprocessor.

17. Drive unit according to claim 15, wherein the rotor position sensor for detecting a rotation position of a rotor of the electric machine and the shifting position sensor are arranged on a common printed circuit board.

18. Drive unit according to claim 12, wherein the control device is constructed and configured to carry out a shifting operation of at least one of the wheel sets by means of the shifting apparatus during a second time period, within which a muscular force torque acting periodically on a drive shaft is at a minimum.

19. Drive unit according to claim 18, wherein the control device is constructed and configured, when a wish to shift is detected, to initially increase a torque provided by the electric machine for a first short time period in order to tension at least the gear arrangement and subsequently rapidly to decrease the torque provided by the electric machine in order to place the gear arrangement for the second time period briefly in a load-free state, wherein the shifting apparatus is temporally controlled in such a manner that a shifting of a gear wheel set falls within this second time period.

20. Drive unit according to claim 19, wherein the control device is constructed and configured so that the first short time period overlaps temporally with a time period in which a muscular force torque acting periodically on a drive shaft is at a maximum.

21.-22. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0104] Embodiments of the disclosure are illustrated in the drawing and are explained in greater detail in the following description. In the drawings:

[0105] FIG. 1 shows a bicycle frame with an embodiment of a drive unit according to the disclosure;

[0106] FIG. 2 is a perspective view of another embodiment of a drive unit according to the disclosure without a housing;

[0107] FIG. 3 is a schematic illustration of another embodiment of a drive unit according to the disclosure;

[0108] FIG. 4 is a schematic illustration of another embodiment of a drive unit according to the disclosure;

[0109] FIG. 5 is a schematic illustration of another embodiment of a drive unit according to the disclosure;

[0110] FIG. 6 is a schematic illustration of another embodiment of a drive unit according to the disclosure;

[0111] FIG. 7 is a schematic illustration of another embodiment of a drive unit according to the disclosure;

[0112] FIG. 8 is an exploded view of the drive unit illustrated in FIG. 2 with a housing;

[0113] FIG. 9 is a schematic longitudinal sectioned view through a portion of the drive unit of FIGS. 2 and 8;

[0114] FIG. 10 is a time flow chart of torques over time in a method according to the disclosure for operating the drive unit; and

[0115] FIG. 11 is a schematic illustration of another embodiment of a drive unit according to the disclosure.

DETAILED DESCRIPTION

[0116] FIG. 1 is a schematic illustration of a drive unit 10 for a vehicle such as a bicycle F. The drive unit 10 is integrated in a bicycle frame 12 in the region of a bottom bracket. The drive unit 10 may in this instance be integrated in the bicycle frame 12 in such a manner that the drive unit 10 forms the bottom bracket.

[0117] The drive unit 10 has a housing 14 which is connected at the outer periphery thereof to a saddle tube and a lower tube (main tube) of the bicycle frame 12.

[0118] In the housing 14, there is received a gear arrangement 16 which is constructed to convert a drive movement which is introduced via cranks 18 into the gear arrangement 16 into a rotation of a chain ring or belt wheel 20 with a number of different appropriate transmission or gear ratios.

[0119] In the housing 14, there is further received an electric machine 22 which can feed additional drive power into the gear arrangement.

[0120] The bicycle F is consequently configured as an E-bike or Pedelec. Preferably, the electric machine 22 can only be controlled to provide drive power when a torque is also introduced via at least one of the cranks 18.

[0121] FIG. 2 is a perspective illustration of a preferred embodiment of such a drive unit 10.

[0122] The drive unit 10 has a drive shaft 26 which is constructed as a crankshaft. At the axial ends thereof, the drive shaft 26 has crank insertion portions 28 onto which the cranks 18 can be axially inserted.

[0123] The drive unit 10 further has a layshaft 30 which is arranged offset in an axially parallel manner with respect to the drive shaft 26.

[0124] A first part-gear mechanism 32 connects the drive shaft 26 and the layshaft 30. A second part-gear mechanism 34 connects the layshaft 30 to an output shaft 36. The output shaft 36 is arranged coaxially relative to the drive shaft 26 in the form of a hollow shaft around the drive shaft 26. There is provided on the output shaft 36 a plug-type tooth arrangement 38 onto which the chain ring or belt wheel 20 can be axially pushed.

[0125] The gear arrangement 16 further contains a machine gear 40, via which drive power of the electric machine 22 can be introduced into the gear arrangement 16. The electric machine 22 is arranged axially parallel with respect to the layshaft 30 and the drive shaft 26. The electric machine 22 is connected to the machine gear 40 via a step-down gear mechanism or a lead gear mechanism 42.

[0126] The drive shaft 26 is coaxial relative to an axis Al. The layshaft 30 is coaxial relative to an axis A2. The electric machine 22 is coaxial relative to an axis A3. The step-down gear mechanism or the lead gear mechanism 42 has a lead gear shaft which is not described in greater detail and which is located on an axis A4.

[0127] A camshaft 44 is provided concentrically relative to the layshaft 30. The camshaft 44 is arranged radially inside the layshaft 30 and serves to shift shiftable gear wheel sets of the first part-gear mechanism 32 and the second part-gear mechanism 34. The camshaft 44 is coupled to the layshaft 30 by means of a speed modulation gearbox 46 in such a manner that the camshaft 44 generally rotates at the same speed as the layshaft during operation. Via the speed modulation gearbox 46, however, a relative rotation can also be produced in order in this manner to select and shift the individual gear wheel sets.

[0128] The gear arrangement 16 further has a torque detection device 48 for detecting a muscular force torque introduced into the drive shaft 26. The torque detection device 48 may be connected to a control device which is not illustrated in greater detail.

[0129] The control device which is not illustrated in greater detail is configured to control the electric machine 22 in accordance with a torque which is detected by the torque detection device 48 in order where necessary to provide additional drive torque.

[0130] FIG. 3 shows another embodiment of a drive unit according to the disclosure which, with regard to structure and function, generally corresponds to the drive unit 10 of FIG. 2. Elements which are identical are therefore denoted with the same reference numerals. The differences are substantially explained below.

[0131] As can be seen in FIG. 3, the drive shaft 26 is coupled by means of a torsion spring 52 of the torque detection device 48′ to an input shaft 50. The input shaft 50 is arranged as a hollow shaft around the drive shaft 26 in a state axially offset with respect to the output shaft 36.

[0132] A torsion angle sensor 56 of the torque detection device 48′ detects a relative rotation of the input shaft 50 with respect to the drive shaft 26. The rotation angle measured in this manner is preferably proportional to a torque which is introduced into the drive shaft 26.

[0133] Furthermore, there is provided a rotation position sensor or crank position sensor 54 which detects an absolute rotation position of the input shaft 50.

[0134] The first part-gear mechanism 32 has a plurality of four shiftable wheel sets R1, R2, R3, R4 which each contain a fixed wheel which is connected to the input shaft 50 in a rotationally secure manner and an idler wheel which is rotatably supported on the layshaft 30. The second part-gear mechanism 34 has another plurality of wheel sets R5, R6, R7. The wheel sets of the second part-gear mechanism each have a fixed wheel which is connected to the output shaft 36 in a rotationally secure manner and an idler wheel which is rotatably supported on the layshaft 30.

[0135] The camshaft 44 has a plurality of cams which correspond to the plurality of wheel sets of the first and second part-gear mechanisms. In FIG. 3, for reasons of clarity, only one shifting cam N2 for the wheel set R2 and the shifting cam N7 for the wheel set R7 are given reference numerals.

[0136] The idler wheels of the wheel sets R1 to R7 are in each case connected to the layshaft 30 by means of shiftable free wheels. The shiftable free wheels each have pawls which can be activated by means of the shifting cams (for example, N2, N7). In the relative rotation position shown of the cam shaft 44 with respect to the layshaft 30 of FIG. 3, the shifting cams N2 and N7 activate the pawls S2 and S7 so that, in the conventional forward rotation direction of the drive shaft 26 for driving the bicycle F, the idler wheels of the wheel sets R2 and R7 are coupled to the layshaft 30. The idler wheels of the other wheel sets R1, R3, R4, R5, R6 are in contrast uncoupled from the layshaft 30. In the illustration of FIG. 3, a drive torque which is introduced into the drive shaft 26 can consequently be introduced via the torsion spring 52 into the input shaft 50 and from there via the wheel set R2 into the layshaft 30. From the layshaft 30, the torque can be introduced via the wheel set R7 of the second part-gear mechanism 34 into the output shaft 36.

[0137] For relative rotation of the camshaft 44 with respect to the layshaft 30, a shifting apparatus 60 is provided.

[0138] The shifting apparatus 60 has a planetary gear wheel set 64 which forms the speed modulation gearbox 46. The planetary gear wheel set arrangement 64 has a first planet wheel set whose sun wheel is connected to the layshaft 30, whose ring gear is coupled to the housing 14 and whose planetary carrier is connected to the planet carrier of a second planet wheel set. The sun wheel of the second planet wheel set is connected to the camshaft 44. The ring gear 66 of the additional planetary gear wheel set serves to introduce relative rotations between the camshaft 44 and the layshaft 30. The ring gear 66 is connected via a speed adaptation gear mechanism 70 to a shifting motor 68 in the form of an electric motor. The shifting motor 68 is arranged coaxially relative to an axis A5. The speed adaptation gear mechanism 70 has a speed adaptation shaft 71 which is located in an axis A6. A pinion which is connected to the shifting motor 68 is connected to a first fixed wheel of the speed adaptation shaft 71. A second fixed wheel of the speed adaptation shaft 71 is connected to a drive wheel which is connected to the ring gear 66 in a rotationally secure manner. A rotation position of the ring gear 66 can be detected by means of a shifting position sensor 72.

[0139] In the prior art, as mentioned in the introduction, such a ring gear 66 is generally activated by hand. In this instance, however, the shifting of gear stages in the drive unit 10 is carried out by means of an actuator via the shifting motor 68.

[0140] The electric machine 22 has a rotor which is not described in greater detail and whose rotor position can be established by means of a rotor position sensor 76.

[0141] The electric machine 22 provides a machine torque T.sub.M which is introduced into a machine shaft 78. The machine torque T.sub.M can be combined with a torque T.sub.F of a driver which is introduced into the drive shaft 26 in such a manner that at the output shaft 36 an output torque T.sub.A which is introduced into the chain ring or the belt wheel 20 is provided.

[0142] The gear arrangement 16 has, as mentioned above, a machine gear 40 which is rotatably supported on the layshaft 30. The machine shaft 78 is connected to the machine gear 40 by means of a lead gear mechanism 42. More specifically, the lead gear mechanism 42 has a lead gear shaft 80 which is located on the axis A4 and which is connected to the machine shaft 78 via a first constant wheel set and which has a fixed wheel which is in engagement with the machine gear 40.

[0143] The machine gear 40 can be connected to the layshaft 30 by means of a shiftable free wheel. FIG. 3 shows that the shiftable free wheel is activated, wherein a free wheel pawl SM connects the layshaft 30 to the machine gear 40. The free wheel pawl SM can be activated by means of a shifting cam NM of the camshaft 44. The shifting cam NM may be constructed on an individual portion of the camshaft 44 which is connected via a first carrier 82 which is dependent on the rotation position to a portion of the camshaft 44 which is associated with the first part-gear mechanism 32. The portion of the camshaft 44 on which the shifting cam NM is constructed is further connected via the second carrier 84 which is dependent on the rotation position to a portion of the camshaft 44 which is associated with the second part-gear mechanism 34.

[0144] The drive unit 10 further has a printed circuit board 86 on which a control device 88 is constructed. The control device 88 receives signals from the various sensors 54, 56, 72, 76 and provides control signals for an electronic power unit of the electric machine 22 and the shifting motor 68. Furthermore, the control device 88 is connected to a shifting unit or a shift 89 which can be arranged, for example, in the region of a handlebar of the bicycle F and via which shifting signals in the form of a wish to shift or the like can be initiated.

[0145] If such a wish to shift is obtained via the shifting unt 89, the control device 88 controls the shifting motor 68 in order to carry out the desired shifting operation in which the camshaft 44 is rotated relative to the layshaft 30. This is preferably carried out in a coordinated manner, as will be described below.

[0146] The control device 88 is further connected to an authorisation unit 90. The authorisation unit 90 may, for example, contain an input unit for an authorisation code, wherein, as a result of this code, an authorisation signal is then produced and is transmitted to the control device 88. Only when a correct authorisation signal has been obtained is the control device 88 (and/or the gear arrangement) activated.

[0147] The authorisation unit 90 may be integrated with the shifting unit 89 in a subassembly which can be mounted in the region of a handlebar of the bicycle.

[0148] With the drive unit 10, the following operating modes can be produced. On the one hand, a mode which is operated simply with muscular force is conceivable. To this end, the shiftable free wheel of the machine gear 40 is preferably deactivated by the camshaft 44 being rotated in such a manner that the shifting cam NM moves the free wheel pawl SM into a deactivation position so that the drive power of the electric machine 22 can no longer be introduced into the layshaft 30.

[0149] For a Pedelec operating mode, in contrast, the free wheel pawl SM is activated. Via the torque detection device 48, a torque T.sub.F which is introduced into the drive shaft 26 by means of muscular force is detected. The control device then controls the electric machine 22 in such a manner that it additionally provides an electric drive torque T.sub.M, preferably depending on various support modes (Eco, Normal or Turbo, to mention a few examples). In this instance, the torque T.sub.M is adjusted in such a manner that there is provided in the region of the output shaft 36 an overall output torque T.sub.A which is composed of the driver torque T.sub.F and an electric drive torque T.sub.M which typically represents a value of from 0.5 times to 4 times the driver torque TF.

[0150] In many countries, the electromotive support is limited to a specific speed threshold, for example, 25 km/h. If the driver produces a higher vehicle speed by means of muscular force, the layshaft 30 overtakes the machine gear 40. If the shifting clicking of the shiftable free wheel is perceived to be disruptive in this case, the control device 88 can deactivate the free wheel.

[0151] The control device 88 can also activate the shiftable free wheel with the pawl SM, for example, only when a valid authorisation signal has been detected.

[0152] If in an error state an impermissible torque is provided by the electric machine 22, the control device 88 can also deactivate the shiftable free wheel with the pawl SM.

[0153] If a wish to shift has been detected by the shifting unit 89, the control device 88 initiates a shifting operation of at least one of the wheel sets by means of the shifting apparatus 60 in such a manner that this shifting operation is carried out during a time period in which a muscular force torque T.sub.F acting periodically on a drive shaft is minimal. Alternatively or additionally, when such a shifting wish is detected, a torque which has been provided by the electric machine is initially increased for a first short time period in order to tension at least the gear arrangement and subsequently the torque provided by the electric machine is rapidly reduced in order to move the gear arrangement for a second short time period into a load-free state. The shifting apparatus is in this instance temporally controlled in such a manner that a shifting of the gear wheel set falls within this second short time period.

[0154] FIGS. 4 to 7 illustrate additional embodiments of drive units which with regard to structure and operating method generally correspond to the drive unit 10 of FIG. 3. Elements which are the same are therefore given the same reference numerals. The differences are substantially explained below.

[0155] In the drive unit 10′ of FIG. 4, the rotor of the electric machine 22 is connected to the machine shaft 78′ by means of a separating clutch or free wheel which can be shifted by means of the control device 88. The machine gear 40′ is in this instance connected to the layshaft 30 in a rotationally secure manner. The camshaft 44′ may be constructed as a continuous shaft or, between a portion which is associated with the first part-gear mechanism 32 and a portion which is associated with the second part-gear mechanism 34, a carrier 82′ which is dependent on the rotation position may be provided.

[0156] The separating clutch 92 may be a clutch which is normally open and which is closed by means of an actuator which is not illustrated in greater detail when the electric machine 22 is intended to provide drive torque. Alternatively, the separating clutch 92 may also be a clutch which is normally closed and which is opened by means of an actuator if necessary. Such an actuator is typically connected to the control device 88. The actuator may, for example, be an electromagnet actuator or another actuator.

[0157] FIG. 4 further shows that the shifting position sensor 72′ is connected to a rotor of the shifting motor 68. This embodiment of a shifting position sensor 72 can be produced in a structurally simple manner. However, the shifting position is potentially influenced by play in the speed adaptation gear mechanism 70 so that a detection of the shifting position of the ring gear 66 by means of a shifting position sensor 72, as shown in FIG. 3, is preferred.

[0158] FIG. 5 illustrates another embodiment of a drive unit 10″ which is based on the embodiment of FIG. 3.

[0159] In place of the shiftable free wheel with the pawl SM, the machine gear 40″ is connected by means of a non-shiftable free wheel 98 to an intermediate shaft 96 which is arranged coaxially around the layshaft 30. The intermediate shaft 96 is connected in a rotationally secure manner to the idler wheel of one of the wheel sets of the first part-gear mechanism (or the second part-gear mechanism). The non-shiftable free wheel may also be fitted at the end face to the machine gear 40″. In this instance, the free wheel may act directly between the machine gear 40″ and the idler wheel of one of the wheel sets of the first part-gear mechanism (or the second part-gear mechanism). The intermediate shaft 96 may be dispensed with in this instance. In this instance, the intermediate shaft 96 is connected to the idler wheel of the wheel set R1.

[0160] Furthermore, the fixed wheels R1 to R4 of the first part-gear mechanism 32 are secured to a fixed wheel shaft 100 which is arranged coaxially around the input shaft 50″. The fixed wheel shaft 100 is coupled to the input shaft 50″ by means of another non-shiftable free wheel 102. It can thereby be ensured that no inadmissible torques are transmitted from the electric machine 22 to the drive shaft 26 which, as in the previous embodiments, is coupled by means of a torsion spring 52 to the input shaft 50″.

[0161] FIG. 5 further shows a variant of a shifting position sensor 72″ which is arranged on a sensor shaft 104 which is located on an axis A7. The sensor shaft 104 is connected to a fixed wheel which is in engagement with the gear onto which a drive torque of the shifting motor 68 is also introduced and which is connected in a rotationally secure manner to the ring gear 66 of the speed modulation gearbox 46. Generally, however, a shifting position sensor, also in the embodiment of FIG. 5, may be configured in any one of the other manners as described above, that is to say, for example, also without a sensor shaft or in an integral manner.

[0162] The sensor shaft 104 may in this instance be produced together with a fixed wheel which is secured thereto from plastics material since it does not have to transmit any torque.

[0163] FIG. 6 illustrates another embodiment of a drive train which is based on the embodiment of FIG. 5. In the drive unit 10′″, there is rotatably supported on the lead gear shaft 80′″ an idler wheel which is in engagement with the machine gear 40″. The idler wheel of the lead gear shaft 80′″ is coupled to the lead gear shaft 80 by means of a non-shiftable free wheel 98″. The machine gear 40′″ is rotatably supported on the layshaft 30 and is in engagement with a fixed wheel 105 which is placed on the fixed wheel shaft 100. Consequently, drive power of the electric machine 22 can be introduced into the fixed wheel shaft 100 and from there via the first part-gear mechanism 32 and the second part-gear mechanism 34 onto the output shaft 36.

[0164] As in the embodiment of FIG. 5, the fixed wheel shaft 100 is coupled to the input shaft 50″ by means of a second, non-shiftable free wheel 102.

[0165] FIG. 7 shows another embodiment of a drive unit 10.sup.IV which is based on the embodiment of FIGS. 3 and 6. In the drive unit 10.sup.IV, the lead gear mechanism 42.sup.IV contains a planetary gear wheel set 106 which has three members, of which one (in this instance, the ring gear) is connected to the housing 14. Another member is connected to the machine shaft 78 (in this instance, the sun wheel). A third member (in this instance, the planetary carrier) is connected to a lead gear mechanism shaft 80.sup.IV which is arranged in this instance as a hollow shaft 80.sup.IV around the machine shaft 78. The lead gear mechanism shaft 80.sup.IV is connected to a fixed wheel which is in engagement with an intermediate wheel 109 which is secured to an auxiliary shaft 108. In FIG. 7, the auxiliary shaft 108 is illustrated as being coaxial relative to the layshaft 30. In a preferred embodiment, however, the auxiliary shaft 108 is arranged axially parallel with the layshaft 30. The intermediate wheel 109 is in engagement with a machine gear 40.sup.IV which is rotatably supported on an intermediate shaft/fixed wheel shaft 100 which is arranged coaxially relative to the drive shaft 26. The fixed wheel shaft 100 is coupled to the machine gear 40.sup.IV by means of a non-shiftable free wheel 98.sup.IV. Furthermore, the fixed wheel shaft 100 is coupled to the input shaft 50″ by means of a second, non-shiftable free wheel 102, as in the embodiments of FIGS. 5 and 6.

[0166] In terms of function, the embodiment of FIG. 7 consequently corresponds to that of FIG. 6.

[0167] FIG. 8 is an exploded view of a drive unit 10.sup.V which corresponds in terms of structure to the drive unit 10 of FIGS. 2 and 3. It can be seen that the housing 14 has a basic housing 110 and a first housing cover 112 and a second housing cover 114.

[0168] A region between the basic housing 110 and the first housing cover 112 is constructed for receiving the printed circuit board 86 with the rotor position sensor 76 which is secured thereto and the shift position sensor 72 which is secured thereto. The space between the basic housing 110 and the first housing cover 112 is preferably fluid-free. In the basic housing 110, suitable seals are provided for this purpose.

[0169] The first housing cover 112 and the second housing cover 114 are placed on the basic housing 110 in an axial direction.

[0170] In a space which is formed by the basic housing 110 and the second housing cover 114, the gear arrangement 16 is received together with the electric machine 22. The electric machine 22 is, however, preferably received therein in such a manner that at least the stator or the connections thereof (preferably also the rotor) is/are sealed with respect to a fluid space which is formed by the basic housing 110 and the second housing cover 114. The stator of the electric machine 22 is contacted with the printed circuit board 86 by means of plug-type contacts. The rotor of the electric machine 22 preferably has permanent magnets which require no electrical contacting. On the rotor of the electric machine 22, however, there is preferably provided a portion of the rotor position sensor 76 which cooperates with the other portion on the printed circuit board 86.

[0171] FIG. 8 further shows a torque detection device 48 which contains a permanent magnet 120 which is secured, for example, to the input shaft 50 or to the drive shaft 26. Furthermore, the torque detection device 48 has at least one Hall sensor 122 which is secured to a sensor unit 118 which is arranged coaxially relative to the drive shaft 26 and which is connected via indicated cables to a control device 88.

[0172] FIG. 8 further shows that the shifting position sensor 72 may be constructed in a similar manner to that shown in FIG. 5, having a sensor shaft 104 which is arranged on an axis A7.

[0173] FIG. 9 is a longitudinal sectioned view of the drive unit 10v. It can be seen here that the shaft arrangement is rotatably supported with the drive shaft 26 and the input shaft 50 by means of a first bearing 124 and a second bearing 126, wherein the first bearing 124 is arranged in the region of the basic housing 110 and wherein the second bearing 126 is arranged in the region of the second housing cover 114.

[0174] The layshaft 30 is rotatably supported at least by means of a third bearing 128 which is constructed on the second housing cover 114 and preferably by means of a needle bearing which is not illustrated in greater detail at the axially opposite side.

[0175] FIG. 10 is a time flowchart of a torque over time.

[0176] FIG. 10 shows a shifting operation, which can be carried out under load.

[0177] FIG. 10 first shows that a torque T.sub.F which is provided by a driver is applied in an approximately sinusoidal manner to the drive shaft 26, with a period P.

[0178] It can further be seen that prior to a shifting operation there is provided by the electric machine a torque T.sub.M which extends in an approximately synchronous manner with the driver torque T.sub.F and which, for example, is approximately from 70% to 80% of the driver torque T.sub.F. In other embodiments, however, the torque T.sub.M may also be significantly greater.

[0179] At a time ti, a wish to shift is detected by the control device, for example, via the shifting unit 89.

[0180] In this instance, the torque T.sub.M of the electric machine is then initially increased, preferably in a synchronous manner with a maximum of the driver torque T.sub.F.

[0181] The increase of the torque is carried out for a first time period E1, for example, from a time t.sub.1 to a time t.sub.4. At a time t.sub.3, a maximum of the driver torque T.sub.F is reached.

[0182] A shifting operation should be carried out at a time t.sub.7. At the time t.sub.4, the torque T.sub.M of the electric machine is then decreased in such a manner that it reaches a minimum value T.sub.M-MIN at a time t.sub.6, that is to say, is not reduced to 0. This time t.sub.6 is temporally slightly before the minimum of the driver torque T.sub.F. The reduction of the torque from the time t.sub.4 is consequently temporally placed in such a manner that the time t.sub.6 is shortly before the planned shifting time t.sub.7.

[0183] After the shifting operation, from a time ts, the electric drive torque T.sub.M can be increased again and raised to a normal support level which was also present before the shifting operation. This is achieved at the time tio.

[0184] For the second short time period E.sub.2, the torque is consequently decreased.

[0185] As a result of the fact that the torque was initially increased for the time period E.sub.1 so that the drive train as a whole was tensioned, and subsequently the torque was rapidly or abruptly decreased, the drive train is on the whole non-tensioned so that a load-free state occurs. This is, for example, provided in a time period of approximately t.sub.5 to t.sub.9. Preferably, a shifting operation is carried out within a timeframe of t.sub.6 to t.sub.8, in particular at a time t.sub.7.

[0186] The shifting operation can consequently be carried out at a time at which the drive train is in a substantially load-free state. Consequently, a shifting can be carried out under load.

[0187] The increase of the torque T.sub.M does not act on the speed of the vehicle, as a result of the inertias. Accordingly, the reduction of the torque T.sub.M does not act on the drive behaviour of the vehicle, also as a result of the inertias.

[0188] The driver in a manner of speaking does not notice that this brief increase of torque and subsequently a torque reduction have taken place.

[0189] FIG. 11 shows another embodiment of a drive unit 10.sup.VI which with regard to the function is based on the drive unit 10′ of FIG. 4. Elements which are the same are consequently given the same reference numerals. The differences are substantially explained below.

[0190] FIG. 11 shows that, in order to cool the electronic power unit on the printed circuit board 86 and/or the stator 22S of the electric machine 22, a cooling arrangement 130 may be provided.

[0191] The cooling arrangement 130 initially makes use of the fact that there is located in the housing 14 a fluid sump 132 which by way of a splash lubrication lubricates the wheel sets of the first and the second part-gear mechanism. The fluid sump 132 has a fluid level 134. Below the fluid level 134, there is arranged a fluid pump 136 which is operated in an electromotive manner, for example, controlled via the control device 88, or driven by coupling to a shaft which is provided.

[0192] The fluid pump 136 pumps fluid into a fluid line 138, which leads to a plurality of cooling locations and which is finally returned to the fluid sump 132.

[0193] At a first cooling location 140 of the housing, the fluid can be cooled, for example, from the exterior by a flow of air (not illustrated in greater detail) against the housing 14.

[0194] At a second cooling location 142, heat of the stator 22S of the electric machine 22 is discharged into the fluid flowing in the fluid line 138.

[0195] To this end, the stator is provided with cooling channels between windings or winding heads. Alternatively, the housing region may also be provided with cooling channels around the stator.

[0196] At a third cooling location 144, heat is discharged from the printed circuit board 86 to the fluid flowing in the fluid line 138.

[0197] At a fourth cooling location 146, the fluid line 138 may lead through a cooling member 148, via which heat contained in the fluid is discharged again before it is supplied to the fluid sump again.

[0198] FIG. 11 further schematically illustrates that there may be provided in the housing 14 a fluid redirection sheet 150 via which the fluid 152 which has been thrown up by the wheel sets can be directed to heat sources, for example, onto the printed circuit board 86 or a cooling member which is connected thereto, and/or, for example, onto stator winding heads of the stator 22S or cooling members which are connected thereto.

LIST OF REFERENCE NUMERALS

[0199] 10 Drive unit [0200] 12 Bicycle frame [0201] 14 Housing [0202] 16 Gear arrangement [0203] 18 Cranks [0204] 20 Chain ring/belt wheel [0205] 22 Electric machine [0206] 26 Drive shaft/Crankshaft [0207] 28 Plug-type crank portions [0208] 30 Layshaft [0209] 32 1.sup.st part-gear mechanism [0210] 34 2.sup.nd part-gear mechanism [0211] 36 Output shaft [0212] 38 Plug-type tooth arrangement for 20 [0213] 40 Machine gear [0214] 42 Step-down gear mechanism/lead gear mechanism [0215] 44 Camshaft [0216] 46 Speed modulation gearbox [0217] 48 Torque detection device [0218] 50 Input shaft (16) [0219] 52 Torsion spring (48) [0220] 54 Rotation angle sensor (48) [0221] 56 Rotation position sensor/crank position sensor [0222] 60 Shifting apparatus [0223] 64 Planetary gear wheel set arrangement [0224] 66 Ring gear [0225] 68 Shifting motor [0226] 70 Speed adaptation gear mechanism [0227] 71 Speed adaptation shaft [0228] 72 Shifting position sensor [0229] 76 Rotor position sensor [0230] 78 Machine shaft [0231] 79 Machine pinion [0232] 80 Lead gear mechanism shaft [0233] 81 Gear [0234] 82 1.sup.st rotation-position-dependent carrier [0235] 84 2.sup.nd rotation-position-dependent carrier [0236] 86 Printed circuit board [0237] 88 Control device [0238] 89 Shifting unit [0239] 90 Authorisation unit [0240] 91 Authorisation signal [0241] 92 Separating clutch [0242] 96 Intermediate shaft [0243] 98 1.sup.st non-shiftable free wheel [0244] 100 Intermediate shaft/fixed wheel shaft [0245] 102 2.sup.nd non-shiftable free wheel [0246] 104 Sensor shaft [0247] 105 Fixed wheel [0248] 106 Planetary gear wheel set (42) [0249] 108 Auxiliary shaft [0250] 109 Intermediate wheel (108) [0251] 110 Basic housing [0252] 112 1.sup.st housing cover [0253] 114 2.sup.nd housing cover [0254] 118 Sensor unit (48) [0255] 120 Permanent magnet [0256] 122 Hall sensor [0257] 124 1.sup.st bearing [0258] 126 2.sup.nd bearing [0259] 128 3.sup.rd bearing [0260] 130 Cooling arrangement [0261] 132 Fluid sump [0262] 134 Fluid level [0263] 136 Fluid pump [0264] 138 Fluid line [0265] 140 1.sup.st cooling location [0266] 142 2.sup.nd cooling location [0267] 144 3.sup.rd cooling location [0268] 146 4.sup.th cooling location [0269] 148 Cooling member [0270] 150 Fluid redirection sheet [0271] 152 Fluid [0272] F Bicycle (E-bike) [0273] A1-A6 Axes [0274] R1-R4 First shiftable wheel sets (32) [0275] R5-R7 Second shiftable wheel sets (34) [0276] S1-S7 Pawls (R1-R7) [0277] N1-N7 Shifting cams (R1-R7) [0278] SM Free wheel pawl (40) [0279] NM Shifting cam (40) [0280] TF Torque of driver [0281] TM Torque of electric machine [0282] TM-MIN Minimum torque of the electric machine [0283] TA Output torque [0284] TF Drive torque at 20 [0285] P Period TF [0286] E1 First time period [0287] E2 Second time period