Drive arrangement of a pedelec

Abstract

Drive arrangement of a pedelec with a manual drive shaft (13) and with an electric drive (EM 1), which are coupled to a common output (18) via a wave gear (WG 1), characterized in that a countershaft transmission with at least one switchable transmission stage is provided.

Description

[0001] The present invention relates to a drive arrangement of a pedelec according to the type defined in more detail in the preamble of patent claim 1.

[0002] Manually powered vehicles, especially bicycles or pedelecs, in which a pedalling rider drives the vehicle using muscle power and is assisted by an electric auxiliary motor, are well known.

[0003] Furthermore, wave gears are known, which are also referred to as stress wave gears or sliding wedge gears, among other things. The wave gear has a wave generator, an inner bushing and an outer bushing. The outer bushing has internal teeth and the inner bushing has external teeth, which mesh with each other, for example, over two circumferential sections. The cross-section of the outer bushing is circular. The inner bushing is designed to be deformable. The wave generator, which has an elongated or elliptical shape, presses the inner bushing with its external teeth into the internal teeth of the outer bushing, for example, over two circumferential sections. The number of teeth of the external teeth of the inner bushing and the internal teeth of the outer bush are different from one another.For example, if the outer bushing is used as the output element, power can be input to the wave gear drive via both the inner bushing and the wave generator on the drive side. In this way, a superposition function is realized by the wave gear drive.

[0004] DE 10 2013 003 108 A1 relates to a bicycle drive system with a pedal axle combined with a high-speed electric motor and a reduction gear, whereby a circular thrust gear with translatory movement is used for power transmission.

[0005] WO 2014 / 047 747 A1 relates to a pedal-operated device for an e-bicycle, in which both a pedal force via a pedal axle and a motor force via a separate drive shaft are transmitted to a common drive pinion, wherein freewheel mechanisms are provided in both power transmission paths in order to be able to use the drives separately or in combination.

[0006] DE 10 2013 206 710 A1 relates to an e-bicycle with a crank mechanism, an electric drive and a continuously adjustable conical ring gear, which is arranged on the crank mechanism and transmits the torque generated by the rider to a chainring.

[0007] DE 10 2013 206 713 A1 relates to an e-bicycle with a crank mechanism, an electric drive and a continuously adjustable friction gear, which is arranged on the crank mechanism and transmits the torque generated by the rider to a chainring.

[0008] JP 2014 - 113 912 A relates to a drive unit for a bicycle with pedal assistance, in which a motor with an opening for receiving the crank axle, a drive shaft arranged separately from the crank mechanism for transmitting the crank movement and an output unit for combining the motor power and the pedal force are provided.

[0009] JP 2015 - 189 468 A relates to a bicycle drive device with a motor arranged in the housing, in which a rotating vane element coupled to the crank axle generates an air flow in the housing in order to effectively cool the motor during operation.

[0010] DE 10 2015 100 676 B3 discloses a drive assembly for a manually driven vehicle with an electric auxiliary drive. The drive assembly has a first drive shaft as a pedal crank with a first pedal and a second pedal as a manual drive. Furthermore, a second drive shaft is provided, which is rotationally fixedly connected to a rotor of the electric auxiliary drive. The pedal crank and the rotor are coupled to an output element via a strain wave gear, wherein the output element is connected to a rear wheel of the vehicle. In the known drive assembly, a wave generator of the strain wave gear is rotationally fixedly connected to the rotor of the auxiliary drive, wherein a preformable inner bushing of the strain wave gear is rotationally fixedly connected to the pedal crank. The output element is connected to an outer bushing of the strain wave gear.

[0011] In such drive-assisted two- or multi-wheeled vehicles, such as pedelecs, the motor must reduce the rider's torque so that the rider feels resistance on the pedal. However, it is known that in pedelec vehicles, for example, motor assistance may only be provided up to a predetermined cut-off speed. If the motor assistance is reduced beyond a certain cut-off speed, this has the disadvantageous consequence of the rider pedaling into the void without resistance. This creates a negative riding experience for the rider. Furthermore, with the known drive assembly, it is not possible for the rider to no longer provide manual propulsion at speeds above the predetermined assistance or cut-off speed.In addition, a mechanical gearshift is required so that the motor support power can be varied when both the riding speed and cadence are specified.

[0012] The present invention is based on the object of proposing a drive arrangement of the type described above, which avoids a negative driving experience and expands the operating possibilities.

[0013] This object is achieved according to the invention by the features of patent claim 1, wherein advantageous and claimed developments result from the subclaims and the description as well as the drawings.

[0014] Thus, a drive arrangement is proposed, preferably for a pedelec or the like, which comprises a manual drive, for example, a manual drive shaft embodied as a pedal crankshaft or the like, and at least one electric drive. The drives are coupled via at least one harmonic drive to a common output for implementing a superposition function. To avoid a negative driving experience for the rider and to expand the operating options, a countershaft transmission with at least one switchable gear ratio is provided.

[0015] The drive arrangement with the electric drive connected via a wave gear to realize the superposition function is expanded according to the invention by a countershaft transmission with a switchable mechanical gear or a switchable transmission stage.

[0016] Preferably, the shiftable mechanical gear is connected parallel to the override function. According to an advantageous development, this is achieved by arranging a countershaft of the countershaft transmission axially parallel to the manual drive shaft.

[0017] The intended gear ratio is translated into high-speed and designed in such a way that a suitable cadence is achieved at the legally prescribed limiting speed for pedelecs, for example 60 revolutions / min or similar. To implement the gear ratio, at least one shifting element or the like for shifting the gear ratio is assigned to the countershaft, for example, with which a spur gear designed as a switchable idler gear of one of the spur gear stages assigned to the countershaft can be connected to the countershaft. A cost-effective positive-locking shifting element, for example in the form of a claw clutch or the like, can preferably be used as the shifting element. However, other clutches, for example frictional clutches, can also be used as shifting elements.

[0018] The shifting element can, for example, be operated manually by the rider using a corresponding shift lever or twist grip on the pedelec's handlebar. It is also conceivable for the shifting element to be operated automatically via a suitable actuator.

[0019] With manual gear shifting, the pedaling resistance for the rider is reduced and the cadence tends to increase as the electric drive reduces torque upon reaching the cut-off speed. This signals the rider to engage the mechanical gear shift. This corresponds to the usual riding behavior on a bicycle with conventional gear shifting, where a shift to a higher gear occurs as the cadence increases.

[0020] With automatic gearshift operation, the engagement or actuation of the shifting element takes place at the synchronization point of the shifting element, so that the transition from overlay operation to mechanical gear takes place unnoticed by the rider and there is no change in the cadence when the shifting element is actuated.

[0021] When the mechanical gear or gear ratio is engaged, the riding behavior is similar to that of a pedelec with a parallel electric drive. If the speed exceeds the limiting speed, the rider can continue riding using muscle power alone. If the speed is below the limiting speed, the electric drive can provide variable torque assistance, whereby the speed overlay on the strain wave gear can be fixed at a defined ratio by the mechanical gear.

[0022] The parallel connection of the countershaft to the mechanical gear ratio is preferably achieved via two spur gear stages, with the shifting element assigned to one of the spur gear stages. Actuating the shifting element connects a switchable idler gear of the spur gear stage to the countershaft to achieve the predetermined gear ratio. One of the spur gear stages can be connected or is connected to the manual drive shaft, and the other spur gear stage is connected to the output of the pedelec. The spur gears of the spur gear stages are coupled to each other either directly or indirectly via intermediate gears, chain or belt drives, or the like.

[0023] According to a further development of the present invention, the high-speed transmission can be realized using a planetary gear set or the like. The provided planetary gear set is also associated with the countershaft, and to realize the transmission step when using a planetary gear set, a cost-effective brake can advantageously be used as a shifting element. In this case, a positive-locking or frictional brake can be used as the shifting element.

[0024] The arrangement of the shifting element near the countershaft is advantageous, as there is sufficient space for actuation of the shifting element. Internal shifting is also possible, for example, because the front faces of the countershaft are accessible from the sides.

[0025] The present invention is further explained below with reference to the drawings. They show: Fig. 1 a schematic view of a first embodiment of a drive arrangement of a pedelec according to the invention with a switching element assigned to a first spur gear stage; Fig. 2 a schematic view of a second embodiment of the drive arrangement with a switching element assigned to a second spur gear stage; Fig. 3 a schematic view of an alternative embodiment, by way of example based on the second embodiment variant according to Fig. 2 with intermediate gears for coupling the respective spur gears of the spur gear stages; Fig. 4 a schematic view of a further alternative embodiment, by way of example based on the second embodiment variant according to Fig. 2 with a chain or belt drive for coupling the respective spur gears of the spur gear stages; Fig. 5 a schematic view of a third embodiment of the arrangement according to the invention with a planetary gear set assigned to a countershaft transmission; Fig. 6 a schematic view of an alternative embodiment according to Fig. 5 with a different connection of the planetary gear set; and Fig. 7 a schematic view of an alternative embodiment by way of example based on the first embodiment variant according to Fig. 1 with a freewheel between an outer bushing of a strain gear and an output of the pedelec.

[0026] In the Fig. 1 to 7 show various design variants and alternative versions of the drive arrangement, which can also be combined with each other.

[0027] The drive arrangement of a pedelec according to the invention comprises a manual drive shaft 13, for example, as a pedal crankshaft, and an electric drive EM 1, for example, as an electric machine that can be operated as a generator or as a motor. Both the manual drive and the electric drive are coupled to a common output 18 via a strain wave gear WG 1. In addition to the superposition function generated by the strain wave gear WG 1, a countershaft transmission with at least one switchable gear ratio is provided.

[0028] Regardless of the various design variants and alternative embodiments, the countershaft transmission is provided with a countershaft 8 arranged axially parallel to the manual drive shaft 13. To connect the countershaft 8, the countershaft 8 is coupled or can be coupled to the manual drive shaft 13 via a first spur gear stage ST1 and to the output 18 via a second spur gear stage ST2. The output 18 of the two- or multi-wheel pedelec is connected, for example, via a sprocket or a belt pulley to the rear or front wheel to be driven. It is also possible for the output 18 to be designed as a hub output.

[0029] Advantageously, all required components are housed in a common housing 14. Preferably, the electric drive EM 1 is arranged coaxially with the pedal crankshaft or the manual drive shaft 13, with the strain wave gear WG 1 being arranged axially next to the electric drive EM 1 and also associated with the manual drive shaft 13.

[0030] As already described at the beginning, the wave gear WG 1 usually has a mounted wave generator 1 inside, which is provided with an elliptical or longitudinally drawn outer race, which is coupled to a deformable inner bush 2, wherein the inner bush 2 has an external toothing, which is in engagement with an outer bush 3 having a circular diameter and having an internal toothing.

[0031] To realize the mechanical transmission stage, it is provided that a switching element K, K', B for switching the transmission stage or gear is assigned to the countershaft 8, with which a spur gear 5, 6 designed as a loose gear of one of the spur gear stages ST 1, ST 2 can be connected to the countershaft 8.

[0032] Regardless of the respective design variants and versions, it is provided that a pedal crankshaft as a manual drive shaft 13 is connected to the deformable inner bushing 2 of the wave gear WG 1 and the wave generator 1 of the wave gear WG 1 is connected to a rotor 19 of the electric drive EM 1, wherein the outer bushing 3 of the wave gear WG 1 is connected to the output 18 of the pedelec.

[0033] According to a first embodiment of the drive arrangement according to the invention, which is shown in Fig. 1, it is provided that a first spur gear 5 of the first spur gear stage ST 1 is designed as an idler gear of the countershaft 8, which idler gear is connected to the countershaft 8 when the shifting element K is in the closed state and is coupled to a second spur gear 4 of the first spur gear stage ST 1, wherein the second spur gear 4 is designed as a fixed gear of the manual input shaft 13. The shifting element K is designed as a clutch, preferably as a dog clutch. The first spur gear 6 A of the second spur gear stage ST 2 is designed as a fixed gear of the countershaft 8 and is coupled to a second spur gear 7 of the second spur gear stage ST 2, which is designed as a fixed gear of the output 18.

[0034] A second variant according to Fig. 2 differs essentially from the first embodiment in that the shifting element K' is assigned to the countershaft 8 in the area of ​​the second spur gear stage ST 2. In detail, it is provided that the first spur gear 5 of the first spur gear stage ST 1 is designed as a fixed gear of the countershaft 8 and is coupled to the second spur gear 4 of the first spur gear stage ST 1, which is designed as a fixed gear of the manual input shaft 13. A first spur gear 6 of the second spur gear stage ST 2 is designed as an idler gear of the countershaft 8, which is connected to the countershaft 8 when the shifting element K' is closed and is coupled to a second spur gear 7 of the second spur gear stage ST 2, which is designed as a fixed gear of the output 18. If, for example, the spur gear 6 has a larger diameter than the spur gear 5 A, more abdominal space is available for the idler gear bearing in this embodiment.

[0035] As an alternative to the design variants according to Fig. 1 and Fig. 2, it is also possible for the spur gears 4 and 7 to be designed as loose gears and for the switching element K or K' to be assigned to the manual drive shaft 13 or the wear ring 18. However, this alternative design is only advantageous if sufficient installation space is available in the area of ​​the output 18 or the manual drive shaft 13 for actuation of the switching element K or K'.

[0036] In Fig. 3 is an alternative embodiment only by way of example based on the second embodiment variant according to Fig. 2. In the alternative embodiment, the spur gears 4, 5, 5A of the first spur gear stage ST1 are coupled to one another via an intermediate gear 9. Furthermore, the spur gears 6, 6A, 7 of the second spur gear stage ST2 are coupled to one another via a second intermediate gear 10. Accordingly, the intermediate gears 9, 10 are used to bridge the center distance between the pedal crankshaft or the manual drive shaft 13 and the countershaft 8. This has the advantage that a smaller housing 14 can be realized, since the spur gears 5, 5A, 6, 6A can have a smaller diameter.

[0037] Alternatively, it can also be provided that only one intermediate gear 9, 10 is provided on one side and two intermediate gears 9, 10 are provided on the other side in order to obtain the correct direction of rotation so that the manual drive shaft 13 and the output 18 rotate in the same direction.

[0038] In Fig. 4 shows a further alternative embodiment, using the second embodiment variant as an example only. Here, the spur gears 4, 5, 5A of the first spur gear stage ST1 are coupled to one another via a first chain drive or belt drive 11. Furthermore, the spur gears 6, 6A, 7 of the second spur gear stage ST2 are coupled to one another via a second chain drive or belt drive 12. Accordingly, the chain or belt drive 11, 12 is used to bridge the centerline distance between the manual drive shaft 13 and the output 18. This allows for a smaller housing 14, since the gears 5, 5A, 6, 6Art can be made smaller.

[0039] It is also entirely conceivable that the proposed chain drive or belt drive 11, 12 and the intermediate gears 9, 10 could be combined. For example, a chain drive or belt drive 11, 12 could be provided on one side and an intermediate gear 9, 10 on the other side.

[0040] In Fig. 5 shows a third embodiment variant in which a planetary gear set PS is assigned to the countershaft 8, which is coupled to a shifting element B designed as a brake, by means of which an element of the planetary gear set PS can be locked or connected to the housing 14. In this case, a planetary gear carrier 20 of the planetary gear set PS is connected to the countershaft 8, wherein a ring gear 21 of the planetary gear set PS is connected to the shifting element B designed as a brake, such that the ring gear 21 is connected to the housing 14 when the shifting element B is closed. Furthermore, a sun gear 22 of the planetary gear set PS is connected to the first spur gear 6 A of the second spur gear stage ST 2, wherein the spur gear 6 A is mounted as a ring gear on the countershaft 8. The high-speed transmission stage is thus essentially realized with the aid of the planetary gear set PS.The spur gears 5 A, 6 A and the planetary gear set PS each have small diameters, so that a particularly small-sized housing 14 can be realized.

[0041] Overall, the advantage is that the switching element B, designed as a brake, is easier to operate than a clutch because a fixed actuator is possible. A positive-locking or friction-locking brake can be used.

[0042] In Fig. 6 is an alternative design based on the design variant according to Fig. 5, in which a different connection of the planetary gear set PS is realized. Here, it is provided that the planetary gear carrier 20 of the planetary gear set PS is also connected to the countershaft 8. However, the ring gear 21 of the planetary gear set PS is connected to the first spur gear 6 A of the second spur gear stage ST 2, while the sun gear 22 of the planetary gear set PS is connected to the switching element B designed as a brake, so that the sun gear 22 can be connected to the housing 14 when the brake is engaged. In this alternative embodiment, the planetary gear set PS has a lower transmission ratio than in the embodiment according to Fig. 5.

[0043] In Fig. 7 is a schematic view of an alternative embodiment, by way of example based on the first embodiment variant according to Fig.1 with a freewheel 15 between the outer bushing 3 of the strain wave gear WG1 and the output 18 of the pedelec. This has the advantage that the electric machine or the electric drive EM 1 is not forced to undesirably high speeds when the mechanical gear is engaged during travel, for example at the throttle stop. This results in fewer losses. Furthermore, when the electric machine EM 1 is stationary, the outer bushing 3 of the strain wave gear WG 1 rotates slightly slower than the manual drive shaft 13, i.e., no losses occur in the electric machine EM 1. Since the mechanical gear is geared to high speed, for example, gear ratio i equal to 0.5, the output 18 with the fixed gear 7 rotates faster than the outer bushing 3 of the strain wave gear WG 1. This also applies if the electric drive EM 1 is speed-controlled in such a way that the strain wave gear WG 1 is in block circulation, i.e.There is no rolling of the gearing in the wave gear WG 1. This results in only minimal losses in the electric drive EM 1 and no losses at all in the wave gear WG 1. Reference symbol 1 wave generator of the wave gear 2 deformable inner bushing of the strain wave gear 3 Outer bushing of the strain wave gear 4 second spur gear as fixed gear of the first spur gear stage 5 first spur gear as idler gear of the first spur gear stage 5 A first spur gear as fixed gear of the first spur gear stage 6 first spur gear as idler gear of the second spur gear stage 6A first spur gear as fixed gear of the second spur gear stage 7 second spur gear as fixed gear of the output 8 Countershaft 9 first intermediate gear 10 second intermediate gear 11 first chain or belt drive 12 second chain or belt drive 13 manual drive shaft or pedal crank shaft 14 housings 15 Freewheel 16 left pedal 17 right pedal 18 Output of the Pedelec 19 Rotor of the electric drive or electric machine 20 Planet gear carrier of the planetary gear set 21 Ring gear of the planetary gear set 22 Sun gear of the planetary gear set ST 1 first spur gear stage ST 2 second spur gear stage EM 1 electric drive WG 1 wave gear K,K' switching element as clutch claw B Switching element as brake PS planetary gear set

Claims

[1] Drive arrangement of a pedelec with a manual drive shaft (13) and with an electric drive (EM 1), which are coupled to a common output (18) via a wave gear (WG 1), characterized by that a countershaft transmission with at least one switchable gear ratio is provided. [2] Drive arrangement according to claim 1, characterized by that the countershaft transmission has a countershaft (8) which is arranged axially parallel to the manual drive shaft (13). [3] Drive arrangement according to claim 1 or 2, characterized by that the countershaft (8) of the countershaft transmission is or can be coupled to the manual drive shaft (13) via a first spur gear stage (ST 1) and to the output (18) via a second spur gear stage (ST 2). [4] Drive arrangement according to claim 2 or 3, characterized bythat the countershaft (8) is assigned a switching element (K, K', B) for switching the transmission stage, with which a spur gear (5, 6) designed as a loose gear of one of the spur gear stages (ST 1, ST 2) can be connected to the countershaft (8). [5] Drive arrangement according to one of the preceding claims, characterized by that a pedal crankshaft as a manual drive shaft (13) is connected to a deformable inner bushing (2) of the wave gear (WG 1) and a wave generator (1) of the wave gear (WG 1) is connected to a rotor (19) of the electric drive (EM 1), wherein an outer bushing (3) of the wave gear (WG 1) is connected to the output (18) of the pedelec. [6] Drive arrangement according to one of claims 3 to 5, characterized bythat a first spur gear (5) of the first spur gear stage (ST 1) is designed as a loose gear of the countershaft 8, which is connected to the countershaft (8) in the closed state of the shift element (K) and is coupled to a second spur gear (4) of the first spur gear stage (ST 1), wherein the second spur gear (4) is designed as a fixed gear of the manual drive shaft (13), and that a first spur gear (6 A) of the second spur gear stage (ST 2) is designed as a fixed gear of the countershaft (8) and is coupled to a second spur gear (7) of the second spur gear stage (ST 2), which is designed as a fixed gear of the output (18). [7] Drive arrangement according to one of claims 3 to 5, characterized bythat the first spur gear (5 A) of the first spur gear stage (ST 1) is designed as a fixed gear of the countershaft (8) and is coupled to a second spur gear (4) of the first spur gear stage (ST 1), which is designed as a fixed gear of the manual drive shaft (13), and that a first spur gear (6) of the second spur gear stage (ST 2) is designed as a loose gear of the countershaft (8), which is connected to the countershaft (8) in the closed state of the switching element (K') and is coupled to a second spur gear (7) of the second spur gear stage (ST 2), which is designed as a fixed gear of the output (18). [8] Drive arrangement according to one of claims 6 or 7, characterized by that the spur gears (4, 5, 5 A) of the first spur gear stage (ST 1) are coupled to one another via a first intermediate gear (9). [9] Drive arrangement according to one of claims 6 to 8, characterized bythat the spur gears (6, 6 A, 7) of the second spur gear stage (ST 2) are coupled to one another via a second intermediate gear (10). [10] Drive arrangement according to one of claims 6 or 7, characterized by that the spur gears (4, 5, 5 A) of the first spur gear stage (ST 1) are coupled to one another via a first chain or belt drive (11). [11] Drive arrangement according to one of claims 6, 7 or 10, characterized by that the spur gears (6, 6 A, 7) of the second spur gear stage (ST 2) are coupled to one another via a second chain or belt drive (12). [12] Drive arrangement according to one of the preceding claims, characterized by that the countershaft (8) is assigned a planetary gear set (PS), to which a brake is assigned as a switching element (B), by means of which an element of the planetary gear set (PS) can be locked. [13] Drive arrangement according to claim 12, characterized bythat a planetary gear carrier (20) of the planetary gear set (PS) is connected to the countershaft (8), that a ring gear (21) of the planetary gear set (PS) is connected to the switching element (B) designed as a brake, and that a sun gear (22) of the planetary gear set (PS) is connected to the first spur gear (6 A) of the second spur gear stage (ST 2). [14] Drive arrangement according to claim 12, characterized by that a planet gear carrier 20 of the planetary gear set (PS) is connected to the countershaft (8), that a ring gear (21) of the planetary gear set (PS) is connected to the first spur gear (6 A) of the second spur gear stage (ST 2), and that a sun gear (22) of the planetary gear set (PS) is connected to the switching element (B) designed as a brake. [15] Drive arrangement according to one of the preceding claims, characterized by that a freewheel (15) is provided between the outer bush (3) of the strain gear (WG 1) and the output (18).

Images