Pedally propelled drive with torque relief system and method for controlling gear shifting

Abstract

A pedally propelled vehicle drive system (1) and method for controlling a gear shift, comprising a crankshaft (3), a gear system (10) with multiple selectable gear ratios, wherein the gear system has a gear input shaft (10a) and a gear output shaft (10b), and is configured to provide an output torque in an output torque direction on the gear output shaft (10b) when an input torque in an input torque direction is present on the gear input shaft (10a), and a torque relief mechanism (50) configured to operate in a free running mode wherein the torque relief mechanism (50) transfers a first torque from the crankshaft (3) to the gear input shaft (10a) in the input torque direction, and bypass mode where at least some of the first torque is transferred by the torque relief mechanism to the gear output shaft (10b) in the output torque direction.

Description

PEDALLY PROPELLED DRIVE WITH TORQUE RELIEF SYSTEM AND METHOD FOR CONTROLLING GEAR SHIFTING TECHNICAL FIELD

[0001] The present invention relates to an improved gear shift system for a vehicle. The invention is of specific relevance for vehicles with multiple gears, where shifting is performed under torque and / or where the performance of the vehicle is seriously affected by the torque loss during shifting. Such vehicles could be e.g., pedally propelled vehicles where the pedaling is assisted by a motor, such as for an electric bicycle, but it may also be implemented in relation to gear shifting of multi-speed gear systems where no such motor-assist is available, or for motor-only driven vehicles, e.g., tractors or other heavy machinery.BACKGROUND

[0002] As described initially, the invention can be used in a wide range of applications. One such application is pedally propelled vehicles.

[0003] Most pedally propelled vehicles, such as bicycles are equipped with some sort of selectable gear ratio to improve pedaling efficiency and comfort.

[0004] Different from gears in other types of vehicles that are motor driven, where a gear shift system and motor drive system can co-operate during the gear shift, a bicycle control system is not able to control the rider and the torque from the rider on the pedals in the same way.

[0005] Experienced riders have therefore developed their own understanding and application of a shifting scheme. The optimum shifting scheme will depend on the type of bicycle, the characteristics of the rider etc., which means that practically no shifting schemes will be the same.

[0006] This is cumbersome, and one can easily observe that less experienced, and even experienced riders struggle to shift gears efficiently in certain situations.

[0007] With the introduction of electrical bikes, where pedaling is supported by a motor drive, the same problem remains. The shift control system can control the contribution from the motor, but not from the rider.

[0008] While many experienced riders in the sport segment have accepted and even appreciate developing their own shifting scheme, shifting remains a hurdle for many riders, and for any pedally propelled vehicle with motorized support, such as standard pedelecs,moped style e-bikes, electric cargo vehicles with two or more wheels, mountain bikes, leisure bikes, commuter bikes etc., this problem is increasing with the number of such vehicles and riders affected.

[0009] The pedaling rate is defined as the number of revolutions of the crank shaft per unit time. This is also termed the cadence and is mostly defined as rounds per minute (rpm).

[0010] Although an optimal cadence is unique for every rider, it is clear that the human physiology in general does not allow large variations in cadence in order to maintain efficient power production and comfort.

[0011] Most modern bicycles are therefore equipped with some sort of variable gear mechanism to vary the relationship between the cadence and the rotational speed of the drive wheel. By changing the gear ratio, the desired cadence can be selected for different speeds and different cycling conditions, such as e.g. uphill or downhill.

[0012] The gear shift is performed by a gear shift mechanism. The type of gear shift mechanism will depend on the type of gear system used in the specific case.

[0013] However, efficient shifting of gears on a bicycle requires precision and timing. Experienced riders know that they should shift close to the dead point of the crank to reduce the torque from the riders feet present on the gear mechanism. A large torque makes shifting more difficult and will usually reduce the lifetime of the shift mechanism and the transmission.

[0014] E-bikes add more complexity to the gear shifting. In addition to the torque from the rider, the torque from the motor should be taken into account as well. If the experienced rider eases off the pedals for shifting, the shifting mechanism will still struggle if a large torque from the electric motor is present. Vice-versa will a large torque from the rider represent a problem for shifting, even in the event that the control system is able to reduce the torque from the motor during shifting temporarily. Automatic gear shifting may further complicate this, since the rider does not know when the control system is going to perform the gear shift.

[0015] High efficiency, dog clutch or pawl based mechanical stepped transmissions will have challenges during gear shifts. This will affect all down shifts, and depending on architecture, also some upshifts.

[0016] More specifically the following challenges remain to be solved:- Separate clutches under torque. The clutches will be harder to separate with increased torque. With a given shift mechanism, a certain torque threshold is given- Engage the correct gear after shifting. Shifting gears using high forces can result in high wear on shift mechanisms as well as host shifts.- Reduce shock loads in drive line components after completed high load gear shifts.

[0017] There might be two sources for the torque input, the controllable motor, as well as the less controllable rider. If the rider torque is low and the motor input is high, a gear shift can be performed quickly reducing the motor torque, perform the gear shift and reapply motor torque in a controlled manner. Low rider torque is often unpredictable, and to select pedal in a 12-6 position (i.e. vertical crank arms) is often chosen to increase the probability. The result is a delayed gear shift and a loss of output torque during the shift and the post shift torque reloading.

[0018] In situations with constant high rider input torque, a gear shift is not possible, thus, the rider torque into the transmission must be reduced if no other means are provided. This will reduce the performance of the bicycle.

[0019] In a typical gearshift known from all types of dog brake and pawl operated transmissions as well as derailleurs, there is a short torque interruption where the rider will feel a short crank rotation without resistance. This is more pronounced with high torque shifts and larger gear steps, typically seen on eMTBs. This torque interruption is not only uncomfortable for the rider but will create an uncontrolled shock in the driveline - the typical reason for chain and sprocket damage and reduction of frame components and driveline service life. Thus, there is a need for an improved shifting mechanism that takes the responsibility for smooth and efficient shifting off the experienced or less experienced rider.

[0020] EP 3 655 316 Bl discloses a drive arrangement for a vehicle with a multi-stage planetary gearing system that allows for variable transmission ratios. Similarly, US 2024 / 0059372 Al describes a pedally propelled vehicle gear system that uses a control system to manage torque during gear shifts.SHORT SUMMARY

[0021] The present invention relates to a pedally propelled vehicle drive system that comprises a torque relief mechanism (TRM), a method and a control system for controlling gear shifting of a pedally propelled vehicle with a crankshaft 3 and a gear system 10 with multiple selectable gear ratios according to the independent claims.

[0022] One of the advantages of the drive system is enhanced gear shifting under load due to reduced shock loads in the driveline.

[0023] In some embodiments the invention may have other advantages over existing drive systems, such as reducing mechanical stress and enhancing the overall efficiency of the drive system. The configuration allows for smoother gear transitions, particularly under load conditions, improving the riding experience for users.

[0024] Smoother gearing may be obtained by the invention by reducing torque over the gear system while at the same time maintaining the torque on the drive wheel. Thus, output torque may be maintained during gear shift by torque filling.

[0025] Additionally, the invention may in some embodiments provide a practical solution for achieving a higher gear ratio than the maximum gear ratio of the gear system, further enhancing the vehicle's performance and the applicability of the gear system itself.

[0026] The invention ensures precise torque management, contributing to the system's reliability and durability.

[0027] Overall, the invention addresses the challenges of torque management in pedally propelled vehicles, offering a novel approach that enhances gear shifting efficiency and vehicle performance.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is a system diagram illustrating the pedally propelled vehicle drive system 1 with a torque relief mechanism 50 arranged in parallel with the multi-speed gear system 10.

[0029] FIG. 2 is a schematic diagram illustrating the pedally propelled vehicle drive system 1 with the torque relief mechanism 50 arranged concentrically with the crankshaft 3.

[0030] FIG. 3 is a schematic diagram illustrating the pedally propelled vehicle drive system 1 with the torque relief mechanism 50 and an electric motor 20 arranged concentrically with the crankshaft 3.

[0031] FIG. 4 is a schematic diagram illustrating the pedally propelled vehicle drive system 1 with the torque relief mechanism the torque relief mechanism 50 and an electric motor 20 arranged concentrically with the crankshaft 3.

[0032] FIG. 5 illustrates in a perspective view an embodiment of the torque relief mechanism 50 with its primary components.

[0033] FIG. 6 is a section view of the axial elements of the torque release mechanism 50 and its support elements.

[0034] FIG. 7 illustrates a perspective view of the torque release mechanism without the clutch basket and the clutch actuator.

[0035] FIG. 8 is an exploded view of Fig. 7.

[0036] FIG. 9 illustrates in a perspective view the basket 85 of the clutch assembly.

[0037] Fig. 10 illustrates in a side view drawing an arrangement of the drive elements on the input side of the gear system 10 and the torque relief system 50

[0038] FIG. 11 illustrates in a section view the clutch 80 assembly and the clutch actuator wherein the clutch is in a disengaged state.

[0039] FIG. 12 illustrates in a section view the clutch 80 assembly and the clutch actuator wherein the clutch is in an engaged state.

[0040] Fig. 13 and Fig. 14 illustrate details of the clutch actuation mechanism.

[0041] Fig. 15 illustrates in a schematic diagram a control system 110 communicating with the torque relief system 50 and other system elements of the pedally propelled drive system to control the torque relief system 50 based on the state of the other system elements.EMBODIMENTS OF THE INVENTION

[0042] In the following description, various examples and embodiments of the invention are set forth in order to provide the skilled person with a more thorough understanding of the invention. The specific details described in the context of the various embodiments and with reference to the attached drawings are not intended to be construed as limitations. Rather, the scope of the invention is defined in the appended claims.

[0043] The embodiments described below are numbered. In addition, dependent embodiments defined in relation to the numbered embodiments are described. Unless otherwise specified, any embodiment that can be combined with one or more numbered embodiments may also be combined directly with any of the dependent embodiments of the numbered embodiments referred to.

[0044] In general the term "wheel" is used in this document. A wheel may have different implementations depending on the context. In some configurations the wheel can be a pulley, and in other configurations it may be a gearwheel.

[0045] As used herein, "torque fill" denotes providing alternative or additional torque along another path or from another source during a temporary reduction of torque in the main path, so that output torque during a transient, e.g. gear shift, is kept substantially continuous.

[0046] In some embodiments, the torque fill is an operating mode of the pedally propelled vehicle drive system during a gear shift of the gear system, in which the torque transmitted through the gear system from the gear input shaft to the gear output shaft via the gear system is intentionally reduced, and at least a part of a first torque from the crankshaft, optionally including a torque contribution from a motor, is transferred directly to the gear output shaft via the torque relief mechanism in the output torque direction, such that a reduction of output torque on the gear output shaft and / or the drive wheel that would otherwise occur during the gear shift is at least partially compensated.

[0047] As used herein, a "shift torque threshold" (STT) denotes a torque limit associated with a particular gear shift, below which the gear shift is permitted to occur. The STT is in particular selected to achieve a desired shifting experience for the rider, including smooth torque transitions and avoidance of objectionable shocks or interruptions in pedalling resistance, and may be set differently for different upshifts and / or downshifts. Above the STT, torque-transmitting elements in the gear system (10), such as dog clutches, friction clutches, pawls or similar coupling devices, can be subjected to such high contact forces and friction that they become effectively locked in their engaged state, so that separation and / or re-engagement would require excessive actuator force or would risk jamming or damage and / or cause undesired shock loads in the drivetrain and vehicle frame. The STT is therefore chosen such that the torque across the relevant torque-transmitting elements is low enough to allow reliable disengagement and engagement while maintaining the desired shifting comfort for the rider.

[0048] "Torque zero crossing" of the gear system (10) is in the following understood to mean a condition in which a torque transmitted through the gear system (10) changes sign between the input torque direction and an opposite direction, and in particular the instant at which the transmitted torque passes through zero.

[0049] When the speed of axles or shafts is mentioned, this should be understood as rotational speed.

[0050] In an independent embodiment ED01-01, the invention is a pedally propelled vehicle drive system 1 comprising;- a crankshaft 3,- a gear system 10 with multiple selectable gear ratios, wherein the gear system has a gear input shaft 10a and a gear output shaft 10b, and is configured to provide an output torque in an output torque direction on the gear output shaft 10b when an input torque in an input torque direction is present on the gear input shaft 10a, and- a torque relief mechanism 50 configured to operate in a free running mode wherein the torque relief mechanism 50 transfers a first torque from the crankshaft 3 to the gear input shaft 10a in the input torque direction, and bypass mode where at least a part of the first torque is transferred by the torque relief mechanism to the gear output shaft 10b in the output torque direction.

[0051] ED01-02: The pedally propelled vehicle drive system 1 of ED01-01, wherein a gear ratio between the crankshaft 3 and the gear input shaft 10a is identical in the input torque direction in the free running mode and the bypass mode.

[0052] ED01-03: The pedally propelled vehicle drive system 1 of ED01-01 or ED01-02, wherein the torque relief mechanism 50 is configured to overrun the rotational speed of the gear output shaft 10b provided by the input torque on the gear input shaft 10b in the bypass mode.

[0053] Overrun in this context means that the gear output shaft 10b obtains a higher speed in the bypass mode with regards to the speed in the free running mode.

[0054] ED01-04: The pedally propelled vehicle drive system 1 of any of ED01-01 to ED01-03, wherein the gear system 10 with multiple selectable gear ratios has a maximum gear ratio, wherein the torque relief mechanism 50 is configured to overrun the maximum gear ratio in the bypass mode with an overdrive speed.

[0055] ED01-05: The pedally propelled vehicle drive system 1 of ED01-04, wherein the gear system 10 with multiple selectable gear ratios has an average gear ratio difference between neighboring gear ratios, wherein the torque relief mechanism 50 is configured to overrun the maximum gear ratio with an additional overdrive speed corresponding to between 0.5 and 1.5, preferably 0.7 to 1.3 of the average gear ratio difference of the gear system 10.

[0056] I.e., for a 7-drive gear with a range of 428%, the average gear ratio interval may be e.g. 28%, corresponding to the an overdrive speed of 546%.

[0057] ED01-06: The pedally propelled vehicle drive system 1 of any of ED01-01 to ED01-05, comprising a motor 20 configured to contribute to the first torque.

[0058] ED01-07: The pedally propelled vehicle drive system 1 of any of ED01-06, comprising a gear shift actuator configured to shift gears of the motor 20.

[0059] ED01-08: The pedally propelled vehicle drive system 1 of any of ED01-07, wherein the torque relief mechanism 50 is configured to gradually transferring at least part of the first torque to the gear output shaft 10b in the output torque direction before a gear shift of the gear system 10 and gradually transferring the first torque back to the input shaft 10a in the input torque direction after the gear shift.

[0060] ED02-01: The pedally propelled vehicle drive system 1 of any of ED01-01 to ED01-07, wherein the torque relief mechanism 50 comprises a speed-up gear 51.

[0061] ED02-02: The pedally propelled vehicle drive system 1 of ED01-01, wherein the speed-up gear 51 is an epicyclic gear train 70.

[0062] ED02-03: The pedally propelled vehicle drive system 1 of ED01-02, wherein the epicyclic gear train 70 comprises a sun gear 71, planet gears 72, a ring gear 73 and a planet carrier 74

[0063] ED02-04: The pedally propelled vehicle drive system 1 of ED01-03, wherein the planet carrier 74 is driven by the crankshaft 3.

[0064] ED02-05: The pedally propelled vehicle drive system 1 of ED02-03 or ED02-04, wherein the ring gear 73 is configured to be restricted to rotate with full speed with regards to a housing of the pedally propelled vehicle drive system 1 in the bypass mode.

[0065] ED02-05: The pedally propelled vehicle drive system 1 of any of ED02-03 to ED02-05, wherein the ring gear 73 is configured to gradually reduce speed with regards to a housing of the pedally propelled vehicle drive system 1 when the torque relief mechanism 50 shifts from the free running mode to the bypass mode.

[0066] ED03-01: The pedally propelled vehicle drive system 1 of ED01-01 to ED02-06, wherein the torque relief mechanism 50 comprises a clutch 80.

[0067] ED03-02: The pedally propelled vehicle drive system 1 of ED03-01, wherein the clutch is configured to reduce or stop rotation of the ring gear 73.

[0068] ED03-03: The pedally propelled vehicle drive system 1 of ED03-01 or ED03-02, wherein the clutch 80 is a friction clutch.

[0069] ED03-04: The pedally propelled vehicle drive system 1 of ED03-01 or ED03-03, wherein the clutch is a multi-plate clutch.

[0070] ED03-05: The pedally propelled vehicle drive system 1 of ED03-04, wherein the clutch comprises alternating steel and friction plates 81, 82 arranged inside a basket 85.

[0071] ED03-06: The pedally propelled vehicle drive system 1 of ED03-05, wherein the steel plates 81 or friction plates 82 are rotationally fixed to the basket 85.

[0072] ED03-07: The pedally propelled vehicle drive system 1 of any of ED03-01 to ED03-06, wherein the clutch 80 is configured to provide a variable torque transfer from the crankshaft 3 to the gear output shaft 10b.

[0073] ED03-08: The pedally propelled vehicle drive system 1 of any of ED03-01 to ED03-04, wherein the clutch 80 comprises a clutch actuator system configured to disconnect and connect the plates in the multi-plate clutch.

[0074] ED03-09: The pedally propelled vehicle drive system 1 of ED03-08, wherein the clutch actuator system comprises a pressure plate 184 arranged on top of the multiple clutch plates inside the basket and a lever arm 188 arranged to push the pressure plate 184 to compress the multiple clutch plates to engage the clutch.

[0075] ED03-10: The pedally propelled vehicle drive system 1 of ED03-09, wherein the pressure plate 184 is arranged to release the support plate 184 to de compress the multiple clutch plates to disengage the clutch.

[0076] ED03-11: The pedally propelled vehicle drive system 1 of any of ED03-09 to ED03-10, wherein the clutch actuator system further comprises a resilient torque restrictor configured to restrict maximum torque from the lever arm 188 to the pressure plate 184.

[0077] ED04-01: The pedally propelled vehicle drive system 1 of any of ED01-01 to ED03-11, wherein the torque on the gear output shaft 10b remains substantially constant or within a predetermined deviation range in both the free running mode and the bypass mode.

[0078] ED04-02: The pedally propelled vehicle drive system 1 of ED01-01 or ED04-01, wherein, in the bypass mode, the torque transmitted through the gear system 10, between the gear input shaft 10a and the gear output shaft 10b, is reduced to below a shift torque threshold (STT) associated with the gear shift.

[0079] ED04-03: The pedally propelled vehicle drive system 1 of any of ED01-01 to ED04-02, wherein, during a gear shift, the torque relief mechanism 50 is configured toprovide a torque fill to the gear output shaft 10b so as to maintain the output torque on the gear output shaft 10b substantially constant or within a predetermined deviation range.

[0080] ED04-04: The pedally propelled vehicle drive system 1 of ED04-03, further comprising a motor, wherein the torque relief mechanism 50 is configured to provide the torque fill by transferring torque from the motor to the gear output shaft 10b.

[0081] ED04-05: The pedally propelled vehicle drive system 1 of any preceding embodiment, wherein, in the bypass mode, the torque relief mechanism 50 is configured to gradually increase the part of the first torque transferred to the gear output shaft 10b.

[0082] ED04-06: The pedally propelled vehicle drive system 1 of any preceding embodiment, wherein the torque relief mechanism 50 comprises an epicyclic gear train having a planet carrier, a sun gear, and a ring gear, wherein the planet carrier is arranged to receive torque from the crankshaft 3 and the sun gear is arranged to deliver torque to the gear output shaft 10b.

[0083] ED04-07: The pedally propelled vehicle drive system 1 of ED04-06, wherein the torque relief mechanism 50 comprises a torque-transmitting element configured to control a rotational speed of the ring gear of the epicyclic gear train.

[0084] ED04-08: The pedally propelled vehicle drive system 1 of ED04-07, wherein the torque-transmitting element is configured to permit slip to regulate the rotational speed of the ring gear.

[0085] ED04-09: The pedally propelled vehicle drive system 1 of ED04-07 or ED04-08, wherein the torque-transmitting element is configured to transmit torque between the ring gear and a housing of the pedally propelled vehicle drive system.

[0086] ED04-10: The pedally propelled vehicle drive system 1 of ED04-09, wherein the torque-transmitting element is configured to apply a braking torque to the ring gear by coupling the ring gear to the housing.

[0087] In an independent embodiment EM01-01, the invention is a method for controlling gear shifting of a pedally propelled vehicle with a crankshaft 3 and a gear system 10 with multiple selectable gear ratios, wherein the gear system has a gear input shaft 10a and a gear output shaft 10b, and is configured to provide an output torque in an output torque direction on the gear output shaft 10b when an input torque comprising a first torque from the crankshaft 3 in an input torque direction is present on the gear input shaft 10a, the method comprising;- transferring at least part of the first torque to the gear output shaft 10b in the output torque direction. The part of the first torque can be transferred to the output shaft during a gear shift operation.

[0088] The gear shift operation may comprise a pre-shift period, a shift period, and a post shift-period.

[0089] EM01-02: The method of EM01-01, wherein gear output shaft 10b is speeded-up to an overdrive speed above the speed of the gear output shaft 10b when the gear system 10 is shifted to its maximum gear ratio.

[0090] EM01-03: The method of EM01-02, wherein the additional overdrive speed corresponds to between 0.5 and 1.5, preferably 0.7 to 1.3 of the average interval between gear ratios of the gear system 10.

[0091] As an example, for a 7-drive gear with a range of 428%, the average gear ratio interval may be e.g. 28%, corresponding to an overdrive speed of 546%.

[0092] EM01-04: The method of any of EM01-01 to EM01-03, comprising;- initiating a gear shift in the gear system 10- gradually transferring at least part of the first torque to the gear output shaft 10b in the output torque direction,- complete the gear shift.- gradually transferring the first torque back to the in the input shaft 10a in the input torque direction.

[0093] This will ensure a soft engagement of the next gear.

[0094] EM01-05: The method of EM01-04, wherein the step of initiating the gear shift comprises providing a gear shift signal to a gear shift actuator 11 of the gear system 10.

[0095] EM01-06: The method of any of EM01-01 to EM01-05, wherein the steps of gradually transferring at least part of the first torque to the gear output shaft 10b in the output torque direction, and gradually transferring the first torque back to the gear input shaft 10a in the input torque direction after the completed gear shift comprises;- controlling a friction clutch 80 arranged between the crankshaft and the gear output shaft 10b to gradually engage until a shiftable torque across the gear system 10 is sufficiently small for a gear shift to be carried out by the gear shift actuator 11, and thereafter to gradually disengage until all the first torque is transferred back to the gear input shaft 10a.

[0096] The shiftable torque is the maximum torque across the gear system 10 for which the shift actuator is able to carry out a gear shift. This may vary with the type of gearsystem, the shift interval and direction, the shift actuator etc. The shift actuator may inform a control system that a shift has been carried out. The shiftable torque may optionally be a value set in a control system 100 that is lower than the maximum torque in order to smooth the shifting experience and allow the shift only to be carried out once the set value has been reached. The set value may also vary with the type of gear system, the shift interval and direction, the shift actuator etc.

[0097] EM01-07: The method of any of EM01-01 to EM01-05, wherein the steps of gradually transferring at least part of the first torque to the gear output shaft 10b in the output torque direction, and gradually reducing the first torque to the gear output shaft 10b in the output torque direction after the completed gear shift comprises;- controlling a friction clutch 80 arranged between the crankshaft and the gear output shaft 10b to gradually engage,- carry out the gear shift before the friction clutch is fully engaged.

[0098] EM01-08: The method of any of EM01-03 to EM01-07, wherein the step of initiating a gear shift comprises;- determining the cadence of the crankshaft 3,- determining the input torque on the gear input shaft 10a,- determining the next gear shift based on at least the cadence and the input torque.

[0099] EM02-01: The method of any of EM01-01 to EM01-08, comprising controlling the transfer of torque such that the torque on the gear output shaft 10b remains substantially constant or within a predetermined deviation range while transferring at least a part of the first torque to the gear output shaft 10b during the gear shift.

[0100] EM02-02: The method of EM01-01 or EM02-01, comprising reducing, while performing the gear shift, a torque transmitted through the gear system 10, between the gear input shaft 10a and the gear output shaft 10b, below a shift torque threshold (STT) associated with the gear shift.

[0101] EM02-03: The method of any of EM01-01 to EM02-02, comprising, during a gear shift operation, operating the torque relief mechanism 50 to provide a torque fill to the gear output shaft 10b to maintain an output torque on the gear output shaft 10b substantially constant or within a predetermined deviation range.

[0102] EM02-04: The method of EM02-03, wherein the pedally propelled vehicle further comprises a motor, and wherein providing the torque fill comprises transferring torque from the motor via the torque relief mechanism 50 to the gear output shaft 10b.

[0103] EM02-05: The method of any of EM01-01 to EM02-04, comprising gradually increasing, during the gear shift, a proportion of the first torque that is transferred to the gear output shaft 10b.

[0104] EM02-06: The method of any of EM01-01 to EM02-05, wherein transferring at least a part of the first torque to the gear output shaft 10b comprises transmitting torque through an epicyclic gear train having a planet carrier, a sun gear, and a ring gear, wherein the planet carrier receives torque from the crankshaft 3 and the sun gear delivers torque to the gear output shaft 10b.

[0105] EM02-07: The method of EM02-06, comprising controlling a rotational speed of the ring gear of the epicyclic gear train by engaging a torque-transmitting element.

[0106] EM02-08: The method of EM02-07, comprising:- in a pre-shift period, initiating a gear shift in the gear system 10, and gradually transferring at least part of the first torque to the gear output shaft 10b in the output torque direction,- in a shift period, completing the gear shift, and- in a post-shift period, gradually transferring the first torque back to the gear input shaft 10a in the input torque direction.

[0107] In an independent embodiment EC01-01, the invention is a control system 100 for controlling gear shifting of a pedally propelled vehicle with a crankshaft 3 and a gear system 10 with multiple selectable gear ratios, wherein the gear system has a gear input shaft 10a and a gear output shaft 10b, and is configured to provide an output torque in an output torque direction on the gear output shaft 10b when an input torque comprising a first torque from the crankshaft 3 in an input torque direction is present on the gear input shaft 10a, wherein the control system is configured for performing the steps in any of the method embodiments above.

[0108] The gear shift as a result of an embodiment of the invention can be explained as follows: A larger and larger part of the torque will be transferred to the gear output shaft 10b. When all the torque from the crankshaft 3 and optionally the motor 20 is transferred, the speed of the gear output shaft 10b will start to increase. This allows for an overdrive gear but there is no speed increase during normal gear shifts - only transfer and balancing of momentum.

[0109] After the gear shift has been carried out, the clutch opens in a controlled manner and gradually transfers the torque back to the gear input shat 10a. Since the clutch canslip the torque transfer back to the gear becomes "soft" and shock loads in the driveline are avoided.

[0110] From the riders perspective the speed of the bike does not change during a gear shift - only the speed of the crankshaft, which gradually changes to a new speed after the gear change has been completed.

[0111] In the following sections, specific embodiments will be presented with reference to the figures provided.

[0112] In the embodiment illustrated in Fig. 1, the pedally propelled vehicle drive 1 comprises a crankshaft 3 with first and second crank arms 3a, 3b and a gear system 10 with multiple selectable gear ratios. The crank shaft 3 provides input torque to the gear input shaft 10a of the gear system via a first cog drive comprising crank wheel 41 arranged on the crank shaft, trm input wheel 43, and gear input wheel 42 rotationally fixed on the input shaft 10a. The trm input wheel 43 rotates in the opposite direction with regards to the two other wheels.

[0113] The output torque from the gear system 10 on the gear output shaft 10b is transferred to the drive wheel 52, driving a drive transfer element 53, such as e.g., a belt or a chain.

[0114] A gear output wheel 61 fixed concentrically to the gear output shaft 10b, meshes with a trm output gear 62 on the output of the torque relief system 50. Thus, the drive torque relief system is here arranged non-concentrically and in parallel with reference to the crankshaft 3. It is also non-concentrically arranged with regards to the gear input shaft 10a and gear output shaft 10b.

[0115] Fig. 2 illustrates another embodiment of the pedally propelled vehicle drive system 1. Here the torque relief system 50 is arranged concentrically about the crankshaft 3 where the input of the torque relief system 50 is connected directly to the crankshaft. Chain drives on the input and output sides transfers torque from the crank wheel 41 to the gear input wheel 42 and from the trm output gear 62 to the gear output wheel 61, respectively.

[0116] Fig 3 illustrates an embodiment where the pedally propelled vehicle drive system 1 comprises a motor 20. Both the crankshaft 3 and electric motor 20 can provide input torque to the gear input shaft 10a of the gear system via first and second one-way clutches 31, 21, respectively, and the crank wheel 41 and the gear input wheel 42 interconnected by an input element 45, such as a chain or belt. In addition, the trm input wheel 43 is also driven by the input element 45, however, in the opposite direction of thetwo other wheels. The side view of Fig. 10 illustrates an advantageous and compact configuration of these wheels. The output side of the drive system is similar to Fig. 1.

[0117] The embodiment in Fig. 4 is similar to the embodiment in Fig. 3, but illustrates in more detail an embodiment of the torque relief system 50. As can be seen, the torque relief system 50 here comprises a clutch and a speed-up gear, in this case an epicyclic gear, wherein the ring gear is connected to the clutch and the planet carrier is connected to the trm input wheel 43. The features of the torque relief system 50 will be further explained below.

[0118] Fig. 5 illustrates in a perspective view an embodiment of the torque relief system 50, comprising a clutch 80, a speed-up gear 70, a trm input wheel 43 and a trm output wheel 62. The trm output wheel 62 is integrated with a trm shaft 51 and a clutch actuator servo 190 can be seen outside the clutch.

[0119] Fig. 6 is a section view of the torque relief system 50 of Fig. 5. The clutch and speed-up gear are not shown, except for the planet carrier 74 that is integrated with the trm input wheel 43 and the sun gear 71 that is integrated with the trm shaft 51. The trm shaft 51 and sun gear 71 rotate with regards to the trm input wheel 43 and the planet carrier 74, supported by the third bearing 93, here a needle roller bearing. Further, the trm input wheel 43 and the planet carrier 74 rotate with regards to a housing of the pedally propelled vehicle drive system 1, supported by first and second bearings 91, 92.

[0120] Fig. 7 and 8 illustrate the torque relief system 50 in more detail, where some inner elements of the clutch 80 and the speed-up gear 70 are shown.

[0121] The epicyclic gear train 70 comprises a sun gear 71, planet gears 72, a ring gear 73 and a planet carrier 74, wherein the planet carrier 74 is connected to the trm input wheel 43 and the sun gear 71 is connected to the trm output wheel 62.

[0122] Further, the ring gear 73 is integrated with a clutch hub 83 of the clutch, where the clutch is a multi-plate friction clutch with a clutch assembly comprising alternating steel plates 81 and friction plates 82 as seen in Fig. 8. The steel plates have teeth along the circumference that are interlocked with slits 86 in a clutch basket 85 illustrated in Fig.9, while the friction plates have inner teeth interlocked with corresponding grooves 87 on the clutch hub 83. The steel plates and the friction plates can slide along the slits and grooves in the direction perpendicular to the plates.

[0123] In order for the torque relief system 50 to overrun the torque provided through the gear input shaft 10a, the total gear ratio should be calculated from the following formula based on the number of teeth or circumference of the wheels:Total gear ratio = crank wheel 41* trm input wheel 43* gear output wheel 61 / gear input wheel 42* trm output wheel 62.

[0124] By keeping the clutch fully engaged and configuring the total gear ratio correctly, an extra gear ratio can be obtained. This can be seen as an overdrive. The extra gear ratio may e.g., be in the order of an average interval gear ratio for the gear system 10.

[0125] Fig. 11 and Fig. 12 illustrate in section views the clutch in disengaged and engaged states, respectively. A pressure plate 184 is arranged on top of the clutch packet consisting of steel plates 81 and the friction plates 82. When the pressure plate is forced against the clutch packet, friction will increase between the plates and the clutch hub 83 will be locked to the clutch basket 85. Since the clutch hub is integrated with the ring gear 73, the ring gear will rotate with about the same speed, but the torque through the clutch will increase as friction increases. When the ring gear slows down, the planets 72 inside the ring gear are forced to rotate since the planet carrier 74 is driven by the crankshaft. The rotating planets will then force the sun gear 71 to transfer momentum. The sun gear is rotationally connected to the trm output wheel 62, which again drives the gear output shaft 10b. In this configuration the sun gear will rotate faster than the planet carrier, which means that it acts like a speed-up gear.

[0126] When the pressure on the pressure plate is released, the ring gear 73 being in constant mesh with the transmission output will continue to rotate, but without transferring torque.

[0127] The pressure on the pressure plate 184 is in this embodiment provided by a clutch lever 193 connected to a clutch actuator servo 191 with an actuator shaft 192. Here the actuator servo is an electrically powered linear actuator with a lead screw connected to a corresponding nut on the clutch lever 193.

[0128] The clutch lever comprises first and second lever elements 194, 195 that are linked together by a moving lever pivot 196.

[0129] The first lever element has the shape of an L where the long leg is connected to the actuator shaft 192 and the short end is abutting the pressure plate in a first recess 185. Further, the lever pivot 196 is arranged where the two leg meets and the second lever element 195 with a pyriform shape is pivotally connected to the lever pivot such that the two lever elements can pivot with regards to each other. The tapered end of the second lever element 195 abuts a second recess 186 of a spring support plate 181 arranged inside the clutch basket 85, opposite the clutch packet with regards to the clutchlever 193. The first and second recesses 185, 186 ensures that the clutch lever do not slide on the pressure plate and the spring support plate during operation.

[0130] In disengaged state, the lever pivot 196 is arranged to the side of an axis c through the first and second recesses as illustrated in Fig. 11. This could be the center line of the clutch 80.

[0131] In the engaged state, the lever pivot 196 has moved to the axis c, as seen in Fig.12. This means that the effective height of the clutch lever has increased, and the pressure plate 184 has been moved towards the clutch packet and that the friction between the clutch plates has increased. In this position the clutch engagement forces go directly through the lever pivot. Thus, little or no force is needed to keep the clutch engaged. This is beneficial if the clutch should be engaged for a longer time, such as when the torque relief system is used to achieve an additional gear step overrunning the highest gear ratio of the gear system 10.

[0132] As a precautionary measure, the clutch has in one embodiment a torque limiter comprising a pre-loaded disk spring 182 outside the spring support plate 181. When the axial engagement force from the clutch lever reaches the counterforce of the preloaded disk spring, the disk spring will start to compress to prevent damage to the clutch or other components in the system.

[0133] Upper and lower retaining rings 187, 188 arranged in circumferential slits in the clutch basket 85 are used to secure the disk spring and the spring support plate in the axial direction of the clutch basket 85.

[0134] Fig. 13 and 14 illustrates the members involved in engagement and disengagement of the clutch where other components have been left out for readability.

[0135] Fig. 15 illustrates an embodiment of a control system 110 controlling the torque relief system 50. However, this should preferably involve other components of the drive system as well. In general the control system 110 may communicate with any of the clutch actuator 190 of the torque relief system 50, a gear shift actuator 11 of the gear system 10, a gear shift selector 6 operated by the rider in the case of manual gear shift, the motor control of the electric motor 20, a torque sensor 4 of the crankshaft, a gear output torque sensor 5, etc.

[0136] In the exemplary embodiments, various features and details are shown in combination. The fact that several features are described with respect to a particular example should not be construed as implying that those features by necessity have to be included together in all embodiments of the invention. Conversely, features that aredescribed with reference to different embodiments should not be construed as mutually exclusive. As those with skill in the art will readily understand, embodiments that incorporate any subset of features described herein and that are not expressly interdependent have been contemplated by the inventor and are part of the intended disclosure. However, explicit description of all such embodiments would not contribute to the understanding of the principles of the invention, and consequently some permutations of features have been omitted for the sake of simplicity or brevity.

Claims

CLAIMS1. A pedally propelled vehicle drive system (1) comprising;- a crankshaft (3),- a gear system (10) with multiple selectable gear ratios, wherein the gear system has a gear input shaft (10a) and a gear output shaft (10b), and is configured to provide an output torque in an output torque direction on the gear output shaft (10b) when an input torque in an input torque direction is present on the gear input shaft (10a), and- a torque relief mechanism (50) configured to operate in a free running mode wherein the torque relief mechanism (50) transfers a first torque from the crankshaft (3) to the gear input shaft (10a) in the input torque direction, and a bypass mode where at least a part of the first torque is transferred by the torque relief mechanism to the gear output shaft (10b) in the output torque direction.

2. The pedally propelled vehicle drive system (1) of claim 1, wherein the torque on the gear output shaft (10b) remains substantially constant or within a predetermined deviation range in the free running mode and the bypass mode.

3. The pedally propelled vehicle drive system (1) of claim 1 or 2, wherein, in the bypass mode, the torque transmitted through the gear system (10), between the gear input shaft (10a) and the gear output shaft (10b), is reduced below a shift torque threshold (STT) associated with the gear shift.

4. The pedally propelled vehicle drive system (1) of any of claims 1-3, wherein, during a gear shift, the torque relief mechanism (50) is configured to provide a torque fill to the gear output shaft (10b) to maintain an output torque on the gear output shaft (10b) substantially constant or within a predetermined deviation range.

5. The pedally propelled vehicle drive system (1) of claim 4, further comprising a motor, wherein the torque relief mechanism (50) is configured to provide the torque fill by transferring torque from the motor to the gear output shaft (10b).

6. The pedally propelled vehicle drive system (1) of any preceding claim, wherein, in the bypass mode, the torque relief mechanism (50) is configured to gradually increase the part of the first torque transferred to the gear output shaft (10b).

7. The pedally propelled vehicle drive system (1) of any preceding claim, wherein the torque relief mechanism (50) comprises an epicyclic gear train having a planet carrier, a sun gear and a ring gear, wherein the planet carrier is arranged to receive torque from the crankshaft (3) and the sun gear is arranged to deliver torque to the gear output shaft (10b).

8. The pedally propelled vehicle drive system (1) of claim 7, wherein the torque relief mechanism (50) comprises a torque-transmitting element configured to control a rotational speed of the ring gear of the epicyclic gear train.

9. The pedally propelled vehicle drive system (1) of claim 8, wherein the torquetransmitting element is configured to permit slip to regulate the rotational speed of the ring gear.

10. The pedally propelled vehicle drive system (1) of claim 8 or 9, wherein the torquetransmitting element is configured to transmit torque between the ring gear and a housing of the pedally propelled vehicle drive system.

11. The pedally propelled vehicle drive system (1) of claim 10, wherein the torquetransmitting element is configured to apply a braking torque to the ring gear by coupling the ring gear to the housing.

12. A method for controlling gear shifting of a pedally propelled vehicle with a crankshaft (3) and a gear system (10) with multiple selectable gear ratios, wherein the gear system has a gear input shaft (10a) and a gear output shaft (10b), and is configured to provide an output torque in an output torque direction on the gear output shaft (10b) when an input torque comprising a first torque from the crankshaft (3) in an input torque direction is present on the gear input shaft (10a), the method comprising;- transferring at least a part of the first torque to the gear output shaft (10b) in the output torque direction.

13. The method of claim 12, comprising controlling the transfer of torque such that a torque on the gear output shaft (10b) remains substantially constant or within a predetermined deviation range while transferring at least a part of the first torque to the gear output shaft (10b) when performing the gear shift.

14. The method of claim 12 or 13, comprising reducing, while performing the gear shift, a torque transmitted through the gear system (10), between the gear input shaft (10a) and the gear output shaft (10b), below a shift torque threshold (STT) associated with the gear shift.

15. The method of any of claims 12-14, comprising, during a gear shift operation, operating a torque relief mechanism (50) to provide a torque fill to the gear output shaft (10b) to maintain an output torque on the gear output shaft (10b) substantially constant or within a predetermined deviation range.

16. The method of claim 15, wherein the pedally propelled vehicle further comprises a motor, and wherein providing the torque fill comprises transferring torque from the motor via the torque relief mechanism (50) to the gear output shaft (10b).

17. The method of any of claims 12-16, comprising gradually increasing, during the gear shift, a proportion of the first torque that is transferred to the gear output shaft (10b).

18. The method of any of claims 12-17, wherein transferring at least a part of the first torque to the gear output shaft (10b) comprises transmitting torque through an epicyclic gear train having a planet carrier, a sun gear and a ring gear, wherein the planet carrier receives torque from the crankshaft (3) and the sun gear delivers torque to the gear output shaft (10b).

19. The method of claim 18, comprising controlling a rotational speed of the ring gear of the epicyclic gear train by engaging a torque-transmitting element.

20. The method of claim 19, comprising;- in a pre-shift period initiating a gear shift in the gear system (10), and- gradually transferring at least part of the first torque to the gear output shaft (10b) in the output torque direction,- in a shift period completing the gear shift, and- in a post-shift period gradually transferring the first torque back to the gear input shaft (10a) in the input torque direction.

21. A control system (100) for controlling gear shifting of a pedally propelled vehicle with a crankshaft (3) and a gear system (10) with multiple selectable gear ratios, wherein the gear system has a gear input shaft (10a) and a gear output shaft (10b), and is configured to provide an output torque in an output torque direction on the gear output shaft (10b) when an input torque comprising a first torque from the crankshaft (3) in an input torque direction is present on the gear input shaft (10a), wherein the control system is configured for performing the steps in any of claims 12 to 20.

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