DRIVE ASSEMBLY FOR A BICYCLE

Description

Technical field

[0001] The present invention relates to a drive arrangement for a bicycle. Furthermore, the present invention relates to a bicycle. State of the art

[0002] It is common practice to incorporate a freewheel on bicycles. This allows, for example, the crank axle to be disengaged from a driven wheel. This enables the bicycle to roll without the pedals turning. On e-bikes, a freewheel can also be used to disengage a drive motor. In a locked position, the freewheel can connect two shafts in a rotationally fixed manner, for example, to enable the transmission of drive power.

[0003] By detecting the deformation of a component of the freewheel, the transmitted drive force can be measured, for example, to control a drive. However, depending on the freewheel's design and the relative position in which the two shafts are connected, disturbances can occur. For example, a radial force can act on the freewheel in the locked state, deforming it depending on the locked position. Consequently, the detected deformation may only correspond imprecisely to the transmitted drive force.

[0004] CN102644679 A discloses a pawl freewheel for asynchronous speed control in a bicycle. CN109421882 A discloses a torque sensing assembly and a mid-mounted motor and bicycle. US2021046992 A1 discloses a bicycle capable of measuring power, and in particular a sprocket of the bicycle capable of measuring the power transmitted through the sprocket. Description of the invention

[0005] A first aspect concerns the drive system for a bicycle. The drive system can, for example, include a gearbox, a crank axle, a wheel, and the respective power transmission elements to the wheel. The drive system can include a drive motor, for example, an electric motor. The drive system can be designed for a bicycle configured as a pedelec (pedal-assist electric bicycle). The drive system can be designed to transmit power from a cyclist and, optionally, from the drive motor to the wheel.

[0006] The drive assembly features a pawl freewheel. A pawl freewheel is also known as a locking pawl freewheel. A freewheel can, for example, transmit torque in only one direction of rotation, in which case the freewheel is in its locked position. When the direction of rotation is reversed, the connection is automatically disengaged, and the freewheel is then in its unlocked position. The pawl freewheel can, for example, be designed to decouple a drive, such as a crank axle, from an output. For instance, the pawl freewheel can decouple the crank axle from the drive motor, or vice versa. The pawl freewheel can also be designed to change the gear ratio within the drive assembly's transmission.

[0007] The pawl freewheel has at least a first ring and a second ring. The two rings can each be permanently and rotationally fixed to a shaft of the drive assembly. The first ring has teeth. The teeth can, for example, extend radially inside or outside along the circumference of the first ring. The pawl freewheel has at least one pawl movably mounted on the second ring. The pawl can also be referred to as a locking pawl. In a locked state, the pawl is engaged with the teeth of the first ring. The pawl can, for example, be spring-loaded with respect to this engagement. In a released state, the pawl is disengaged from the teeth. In the locked state, the two rings are rotationally fixed to each other via their engagement. In the released state, the pawl slides off the teeth, for example, and the two rings can rotate relative to each other.The pawl can, for example, allow the two rings to rotate relative to each other in one direction and prevent rotation in the opposite direction once the pawl engages with the teeth. The rings can also have non-ring-shaped sections. The pawls and the teeth can be located on opposite sides of the two rings. The two rings can be arranged coaxially. The two rings can be located in the same axial region. The two rings can each be rotatably mounted about a central axis.

[0008] The drive assembly includes a sensor device designed to detect deformation of the first ring of the pawl freewheel due to an applied drive force. This drive force can be transmitted, for example, to the second ring in the locked position, or from the second ring in the locked position to the first ring. The drive force can be applied to the drive assembly, for example, by a cyclist at the respective pedals. The detected deformation can, for example, provide information about the transmitted torque. This enables, for example, power measurement, automatic control of the bicycle's gear shifting, and, alternatively or additionally, control of the drive motor. Control can also be directly dependent on the detected deformation. The sensor device can, for example, include at least one sensor.The sensor device can be configured, for example, to determine deformation electroresistively, magnetically, optically, or acoustically. For instance, the sensor device can include one or more strain gauges attached to the first ring. The sensor device can also include an evaluation unit for processing the respective sensor signals. If multiple sensors are used, their signals can be fused to produce a single measured value.

[0009] The first ring has at least one toothed section and one toothless section in the circumferential direction. This allows the relative position of the pawl's engagement with the teeth to be defined relative to a deformation measurement point on the first ring. This avoids disturbances in the deformation measurement caused by the relative position of the two rings when the pawl engages with the teeth. For example, the engagement can cause a radial force. Furthermore, the measurement point cannot be located on a central axis of the first ring if it is hollow. If continuous teeth are used, the radial force would affect the deformation differently depending on the angle of engagement between the pawl and the teeth relative to the measurement point. Therefore, calculating an applied torque as a function of the measured deformation can be very inaccurate due to its strong positional dependence.

[0010] The measuring point can, for example, correspond to the position of a sensor on the sensor device on the first ring. For instance, the first ring might have only a single toothed section with just one tooth, ensuring the engagement point is always aligned identically with the measuring point. However, more toothed sections can also be provided. Alternatively or additionally, more teeth can be provided in the respective toothed sections. This allows, for example, faster engagement and thus locking of the pawl freewheel in a corresponding direction of rotation. The toothed section can form the toothing. The first ring can also have several toothed sections that together form the toothing. Furthermore, if multiple pawls are provided that can be engaged simultaneously, component stress can be minimized.The toothless area allows for minimal variance in the alignment of the respective engagement points relative to the deformation measurement points, thus minimizing the influence of disturbances such as radial forces. For example, the relative alignment of the pawl's engagement with the toothing to the sensor can lie within a predetermined angular range relative to the respective sensors of the sensor device.

[0011] Several toothed sections and, alternatively or additionally, several toothless sections can be provided. A toothless section can be arranged between each toothed section, for example, circumferentially. The respective toothed sections can be spaced apart from each other circumferentially, for example, by respective toothless sections. Each toothed section has at least one tooth designed for engagement with the pawl. If several teeth are provided per toothed section, they can be located next to each other circumferentially and, for example, directly adjoin one another. The toothed sections and the toothless sections extend, for example, circumferentially on the outside or inside of the first ring. The respective pawls and alternatively or additionally, toothed sections can be identical.Individual pawls and alternative or additional toothing areas can be arranged uniformly, in particular symmetrically. The following descriptions for only one toothing area and alternatively or additionally only one pawl also apply equally to multiple toothing areas or pawls, where applicable.

[0012] In one embodiment of the drive arrangement, the first ring can have at least a first toothed section and a second toothed section. The two toothed sections can be spaced apart circumferentially by a first toothless section and a second toothless section. Each toothed section can thus form a separate tooth segment of the gearing. For example, two pawls can be provided, each of which engages one of the two toothed sections in the locked position. This enables high torque transmission with a compact design. The two toothed sections can be arranged opposite each other on the circumference of the first ring. This allows for symmetrical force application.

[0013] In one embodiment of the drive arrangement, the drive arrangement may have at least two pawls. However, the drive arrangement may also have three or more pawls. The pawls may, for example, be spaced apart from one another on the inside or outside of the second ring. The angular extent of the respective toothed areas may be greater than or equal to the angular distance between the two pawls. If three or more pawls are provided, the angular extent of the respective toothed areas may be greater than or equal to the maximum angular distance between two pawls. The pawls may be arranged uniformly along the circumference of the second ring.The angular extent of a toothed section can be the angle between a first end of the toothed section in the circumferential direction and a second end of the toothed section in the circumferential direction, measured from a center point or axis of rotation of the first ring. An angular distance between two pawls can be the angle between a first pawl and a second pawl adjacent to it in the circumferential direction, measured from a center point or axis of rotation of the second ring. Measurements can be taken, for example, from a bearing point or a point of engagement between the two pawls. For instance, the angular distance between two pawls can be measured from the same point on each pawl.For example, a toothed section can extend at least 25° along the circumference of the first ring if each bearing point, around which two adjacent pawls are rotatably mounted, is also spaced 25° apart along the circumference of the second ring. This allows the pawls to engage, and thus the locking state, regardless of the relative position of the two rings, making it predictable for the driver. If, for instance, the toothed sections are shorter than the distance between the pawls, the first ring must rotate further or less, depending on its position, before the respective pawls engage.

[0014] In one embodiment of the drive arrangement, the sensor device can be configured to detect the deformation of the first ring in an area where the torque applied by a cyclist at the pedals of the bicycle drive has already been summed. This makes the detected deformation particularly suitable for controlling the drive train and, alternatively or additionally, for power measurement. For example, appropriate sensors are arranged on the first ring, such as axially in the area of ​​the second ring and the pawls attached to it. For example, all torques from both pedals of the bicycle may already be summed at the first ring. If the crank axle forms the first ring, the applied torque may, for example, be summed axially in the area of ​​the second ring or the pawls. For example, the torque from both pedals may be summed for the first time at the point of contact with the crank axle.Alternatively or additionally, the sensor device is designed to detect the deformation of the first ring in an area where a torque applied by the cyclist at the pedals of the bicycle drive is not yet superimposed on a drive torque of the drive motor. This allows, for example, the drive motor to be easily controlled depending on the cyclist's driving force.

[0015] In one embodiment of the drive arrangement, the sensor device can be configured to detect the deformation of the first ring in at least one area adjacent to at least one of the gear teeth. The detection area can be radially adjacent and, alternatively or additionally, circumferentially adjacent. For example, the detection area can lie in the same circumferential region as the nearest gear teeth. The detection area can be defined, for example, by an arrangement of a strain gauge or by the orientation of an optical deformation sensor. Due to the proximity of the detection area, a deformation can be particularly pronounced, and thus a measurement signal can be generated.

[0016] In one embodiment of the drive arrangement, the sensor device can be configured to detect the deformation of the first ring in at least one region opposite to at least one of the gear teeth. For example, the detection area can be located in a different circumferential region than the nearest gear teeth. For example, the detection area can be located in a circumferential region between two nearest gear teeth. For example, the detection area can be located adjacent to a toothless region. For example, the detection area can be located in the same circumferential region as the nearest toothless region. This reduces the measurement's susceptibility to interference signals, such as radial forces from the pawl engagement.

[0017] It can also be provided that the deformation of the first ring is detected in at least a first area, which is opposite to at least one of the gear teeth, and in a second area, which is adjacent to at least one of the gear teeth. This makes filtering out interference signals easy. For example, a sensor of the sensor device can be arranged in each detection area.

[0018] In one embodiment of the drive arrangement, the sensor device may include at least one strain gauge as a sensor, which is arranged on the first ring. A strain gauge allows for the particularly simple detection of deformation in a specific area. Furthermore, the strain gauge can be easily integrated into the drive arrangement. Two or more strain gauges may also be provided, for example, on different areas of the first ring. For instance, individual strain gauges may be attached to an end face of the first ring.

[0019] In one embodiment of the drive arrangement, the sensor device can be configured to determine the drive torque transmitted by the pawl freewheel as a function of the deformation. For this purpose, the sensor device can include an evaluation unit designed to calculate the drive torque as a function of the detected deformation. Multiple measured deformations, for example in different areas, can also be taken into account. The transmitted drive torque can be particularly well used as a control variable for other functions of the drive arrangement or the bicycle as a whole.

[0020] According to the invention, the drive arrangement has a greater number of pawls than gear teeth. This allows for rapid locking of the freewheel when the direction of rotation changes. Furthermore, the gear teeth can be small while still ensuring fast and position-independent pawl engagement. With small gear teeth, the engagement position of the pawls relative to the sensors can be very similar each time the freewheel locks. For example, the number of pawls can be a multiple of the number of gear teeth.

[0021] In one embodiment of the drive arrangement, the respective gear sections can have a multitude of teeth arranged side by side in the circumferential direction. This allows for a small number of pawls while still ensuring fast and position-independent pawl engagement. Alternatively, all or only some gear sections can have only one tooth.

[0022] In one embodiment of the drive arrangement, the first ring can be recessed in the respective toothless areas. This allows, for example, the first ring to extend less radially in the toothless areas than in the toothed areas. The radial extent can be measured, for example, up to the tooth root. The first ring can also be thinner in the toothless areas. This allows deformation to occur more intensely in the toothed areas, where it can then be detected particularly well.

[0023] In one embodiment of the drive arrangement, the first ring can be designed as the inner ring and the second ring as the outer ring. The second ring can be arranged radially outside the first ring. The toothing can then be arranged radially outside the first ring. This makes manufacturing particularly cost-effective and simple. The respective pawls can, for example, be mounted radially inside the second ring.

[0024] In one embodiment of the drive arrangement, the first ring can be designed as the outer ring and the second ring as the inner ring. The first ring can be arranged radially outside the second ring. The toothing can then be arranged radially inside the first ring. The respective pawls can, for example, be mounted radially outside the second ring. This simplifies the assembly of the pawls.

[0025] A second aspect concerns a bicycle with a drive system as described in the first aspect and a crank axle with pedals mounted to it, designed to transmit a driving force from the cyclist into the drive system. The pedals are, for example, rotatably mounted on crank arms, which are permanently and rotationally fixed to the crank axle. The respective advantages and further features can be found in the description of the first aspect, whereby embodiments of the first aspect also form embodiments of the second aspect and vice versa. Brief description of the characters

[0026] Fig. 1 illustrates how different engagement positions in a pawl freewheel can change the detection of a transmitted drive torque. Fig. 2 illustrates a first embodiment of a drive arrangement for a bicycle. Fig. 3illustrates a second embodiment of a drive arrangement for a bicycle. Fig. 4 illustrates a third embodiment of a drive arrangement for a bicycle. Detailed description of embodiments

[0027] Fig. 1 Figure 1 shows a section of a pawl freewheel with an inner ring 10 and an outer ring 12. The inner ring 10 has radial external teeth extending along its entire circumference. Pawls 14 are rotatably mounted on the inside of the outer ring 12. In a locked position, the pawls 14 engage with the nearest teeth of the inner ring 10. Such a state, with two possible relative positions of the two rings 10 and 12, is shown in Figure 1. Fig. 1illustrated. In addition, a strain sensor 16 is shown, which is eccentrically attached to an end face of the inner ring 10 and by means of which a drive torque transmitted via the pawl freewheel in the locked state is measured.

[0028] A first relative position of the two rings 10, 12 and thus of the only latch 14 shown relative to the strain sensor 16 corresponds to the position of the latch 14 on the right in the image plane of Fig. 1 This results in an alignment of the engagement of the latch 14 with the strain sensor 16, which is illustrated by an arrow 18. A second relative position of the two rings 10, 12, and thus of the only latch 14 shown, relative to the strain sensor 16, corresponds to the position of the latch 14 on the left in the image plane. Fig. 1This results in a changed orientation of the engagement of the pawl 14 with the strain sensor 16, which is illustrated by an arrow 20. An angular distance between these two arrows 18, 20 is illustrated by an arrow 22 and corresponds to the extent of two teeth of the toothing of the inner ring 10 in the circumferential direction.

[0029] The transmitted drive torque corresponds to a deformation or torsion of the inner ring 10 in the circumferential direction. The strain sensor 16 is designed as a strain gauge, which can only detect deformation along one axis. Simultaneously, the transmitted drive torque also causes a radial force at the engagement point. Depending on the relative position of the engagement point and the strain sensor 16 to each other, the proportion of this radial force along the measuring axis of the strain sensor 16 varies. This results in a disturbance variable in the measurement, which depends on the relative position of the two rings 10 and 12 to each other.

[0030] This effect is present in the first embodiment of a drive arrangement for a bicycle, which is in Fig. 2The drive assembly has a pawl freewheel 50. The pawl freewheel 50 has a first hollow ring 52 with teeth and a second hollow ring 54 with several pawls 56 movably mounted on it. The pawl freewheel 50 is in a locked state in which two of the pawls 56 are engaged with the teeth of the first ring 52. The first ring 52 is designed as an inner ring and the teeth are arranged radially outside its circumference. The second ring 54 is designed as an outer ring, with the pawls 56 projecting radially inside the second ring 54 towards the teeth. The two rings 52, 54 are arranged coaxially. The pawls 56 are spring-loaded with respect to the teeth.

[0031] The drive assembly includes a sensor device designed to detect deformation of the first ring 52 of the pawl freewheel 50 due to an applied drive force. This allows the measurement of the drive torque transmitted via the pawl freewheel 50 in the locked state. For this purpose, the sensor device has two sensors 58 designed as strain gauges.

[0032] The toothing of the first ring 52 comprises a first toothed section 60 and a second toothed section 62, which are spaced apart circumferentially by a first toothless section 64 and a second toothless section 66. This limits the variance of the relative position of the engagement of the pawls 56 relative to the sensors 58 to the circumferential extent of the toothed sections 60 and 62. This, in turn, limits any potential influence of the relative position on the detected deformation compared to a continuously toothed inner ring.

[0033] The angular extent of the respective toothed sections 60, 62 is greater than or equal to the angular distance between two adjacent pawls 56. Each toothed section 60, 62 has several teeth arranged side by side in the circumferential direction. This ensures that the locking behavior of the pawl freewheel 50 is position-independent despite the toothless sections 64, 66. The pawls 56 are evenly distributed around the circumference of the second ring 54. The toothed sections 60, 62 are located on opposite sides of the first ring 52. The toothed sections 60, 62 are identical. The toothless sections 64, 66 are identical. This results in a symmetrical design.

[0034] The sensor device of the first embodiment is designed to detect the deformation of the first ring 52 in two areas, which are opposite to the toothed areas 60, 62. These areas correspond to the position of the sensors 58. The sensors 58 are arranged in the same circumferential area as each adjacent toothless area 64, 66.

[0035] Fig. 3 Figure 1 shows a second embodiment of the drive arrangement, which is similar to the first embodiment. Only the differences are explained.

[0036] In the second embodiment, the first ring 52 is recessed in the area of ​​the two toothless regions 64, 66. The sensors 58 are now located adjacent to the toothed regions 60, 62 and thus in the same circumferential region of the respective adjacent toothed region 60 or 62. The sensor device is therefore now designed to detect the deformation of the first ring 52 in two regions, each of which is adjacent to at least one of the toothed regions 60, 62.

[0037] Fig. 4 Figure 1 shows a third embodiment of the drive arrangement, which is similar to the first embodiment. Only the differences are explained.

[0038] In the third embodiment, the number of pawls 56 is reduced. Instead of eight pawls 56, only four pawls 56 are provided. This makes the pawl freewheel 50 more cost-effective. To still achieve a position-independent locking behavior of the pawl freewheel 50, the two toothed sections 60, 62 have a greater circumferential extent and thus also more teeth than in the first embodiment. The angular extent of the respective toothed sections 60, 62 is also greater than or equal to the angular distance between two adjacent pawls 56. Therefore, in the third embodiment, the influence of disturbances on the measurement of the transmitted drive torque is subject to a greater influence of disturbances or the relative position of the two rings 52, 54 than in the first embodiment. Reference sign

[0039] 10 Inner ring 12 Outer ring 14 Pawl 16 Strain sensor 18 Arrow 20 Arrow 22 Arrow 50 Pawl freewheel 52 First ring 54 Second ring 56 Pawls 58 Sensors 60 Toothed area 62 Toothed area 64 Toothless area 66 Toothless area

Claims

1. Drive arrangement for a bicycle, having a pawl-type freewheel (50) which has a first ring (52) with a toothing (60, 62) and has a second ring (54) with at least one pawl (56) mounted movably thereon, wherein, in a blocking state, the pawl (56) is in engagement with the toothing, wherein the first ring (52) has in a circumferential direction at least one toothing region (60, 62) and one tooth-free region (64, 66), characterized in that the drive arrangement has a sensor device, wherein the sensor device is configured to detect a deformation of the first ring (52) of the pawl-type freewheel (50) due to an acting drive force, wherein the drive arrangement has a larger number of pawls (56) than toothing regions (60, 62).

2. Drive arrangement according to Claim 1, characterized in that the first ring (52) has at least a first toothing region (60) and a second toothing region (62), which are spaced apart from one another in the circumferential direction by a first tooth-free region (64) and a second tooth-free region (66).

3. Drive arrangement according to Claim 1 or 2, characterized in that the drive arrangement has at least two pawls (56), wherein an angular extent of the respective toothing regions (60, 62) is greater than or equal to an angular spacing between the two pawls (56).

4. Drive arrangement according to one of the preceding claims, characterized in that the sensor device is configured to detect the deformation of the first ring (52) in a region in which torque introduced by a cyclist at pedals of the bicycle drive has already been summed.

5. Drive arrangement according to one of the preceding claims, characterized in that the sensor device is configured to detect the deformation of the first ring (52) in at least one region which is adjacent to at least one of the toothing regions (60, 62).

6. Drive arrangement according to one of the preceding claims, characterized in that the sensor device is configured to detect the deformation of the first ring (52) in at least one region which is opposite at least one of the toothing regions (60, 62).

7. Drive arrangement according to one of the preceding claims, characterized in that the sensor device has at least one strain gauge as a sensor (58), which is arranged on the first ring (52).

8. Drive arrangement according to one of the preceding claims, characterized in that the sensor device is configured to determine a drive torque, which is transmitted by way of the pawl-type freewheel (50), according to the deformation.

9. Drive arrangement according to one of the preceding claims, characterized in that the respective toothing regions (60, 62) have a multiplicity of teeth which are arranged one next to the other in the circumferential direction.

10. Drive arrangement according to one of the preceding claims, characterized in that the first ring (52) is cut away in the respective tooth-free region (64, 66).

11. Drive arrangement according to one of the preceding claims, characterized in that the first ring (52) is in the form of an inner ring and the second ring (54) is in the form of an outer ring.

12. Drive arrangement according to one of preceding Claims 1 to 10, characterized in that the first ring is in the form of an outer ring and the second ring is in the form of an inner ring.

13. Bicycle having a drive arrangement according to one of the preceding claims, and having a pedal crank shaft which has pedals mounted thereon and is configured for introduction of a drive force into the drive arrangement by a cyclist.