Bicycle gearing having a noncircular chainring

Abstract

The invention relates to a bicycle gearing, comprising: a cylindrical-gear gearing (10), which has a stationary sun gear (11) having a central bearing axis (y.sub.1) extending centrally therein and a planet gear (12), which travels on the sun gear (11) and rotates about a planet-gear bearing axis (y.sub.2); a four-bar linkage (20), which interacts with the cylindrical-gear gearing (10) and which comprises a crank (21), which is fixedly connected to the planet gear (12) and is rotatably connected to a pedal crank (22); and a toothed wheel (30), by means of which a traction means (31) can be driven. The problem addressed by the invention is that of improving a bicycle gearing of the type in question in such a way that a rounder pedaling feel is perceived by the bicycle rider. The problem is solved according to the invention in that the toothed wheel (30) has an oval shape.

Claims

1. A bicycle transmission comprising: a spur gear having a fixed sun gear having a central bearing axis extending thorough a center of the sun gear and a rotating planet gear running on the fixed sun gear and rotates around a planet gear bearing axis that is parallel to the central bearing axis; a gear wheel having an oval shape, via which a traction element is drivable, and a four-bar linkage connected to the gear wheel and which interacts with the spur gear, the four-bar linkage comprising a pedal crank and a crank, the crank fixedly connected to the planet gear and connected in a rotationally-movable manner to the pedal crank.

2. A bicycle transmission according to claim 1, wherein the oval gear wheel has a major axis diameter and a minor axis diameter and the major axis diameter is always offset at an angle of 60 to 130 from a connecting line between the central bearing axis and the planet gear bearing axis.

3. A bicycle transmission according to claim 1 wherein the four-bar linkage rotates around the central bearing axis and is comprised of a carrier plate rotatably mounted around the central bearing axis, such that planetary gear can rotate eccentrically around the central bearing axis.

4. A bicycle transmission according to claim 1 wherein the linkage has three pivot joints and a sliding joint.

5. A bicycle transmission according to claim 1 wherein the linkage has four pivot joints.

6. A bicycle transmission according to claim 3 also comprising a pivot joint between the planet gear and the carrier plate.

7. A bicycle transmission according to claim 3, wherein the linkage comprises a coupling having at least one pivot joint which is arranged between the carrier plate and the crank.

8. A bicycle transmission according to claim 3, wherein the linkage comprises a coupling comprised of a sliding joint.

9. A bicycle transmission according to claim 3, wherein the linkage comprises a coupling having a third pivot joint, a fourth pivot joint and a pendulum arm.

10. A bicycle transmission according to claim 9 wherein the third pivot joint is between the crank and the pendulum arm and the fourth pivot joint is between the pendulum arm and the carrier plate.

11. A bicycle transmission according to claim 1 also comprising a central shaft on the central bearing axis and the gear wheel is rotatably connected to the central shaft.

12. A bicycle transmission according to claim 1, wherein the spur gear further comprises a frame element, a fixed second sun gear, wherein the sun gear and the second sun gear are on opposite sides of the frame element, and a second planet gear rotating about a second planet gear bearing axis and engaging the second sun gear, and further comprising a second linkage, wherein the second four-bar linkage comprises a second crank, which is fixedly connected to the second planet gear and is connected in a rotationally-movable manner to a second pedal crank.

13. A bicycle transmission comprising: a spur gear that has a stationary sun gear with a central bearing axis that intersects its center and a planet gear, running on the sun gear, that rotates around a planet gear bearing axis, a four-bar linkage, interacting with the spur gear, the four-bar linkage comprising a crank connected rigidly to the planet gear and connected rotatably to a pedal crank, and a gear wheel that can drive a traction element, the gear wheel connected to the four-bar linkage, wherein the gear wheel has an oval shape with a greater main axis diameter and a small secondary axis diameter so that the main axis diameter in a rotation direction of the gear wheel is always offset at an angle of 60 to 130 from a connecting line running between the central bearing axis and the planet gear bearing axis.

Description

(1) For better comprehension, the invention is explained in more detail below based on 5 figures. The figures show:

(2) FIG. 1: a side view of the bicycle gearing system according to a first embodiment, with the pedal crank in a 0 position;

(3) FIG. 2: a side view of the bicycle gearing system according to FIG. 1, with the pedal crank in a 90 position and the second pedal crank in a 270 position;

(4) FIG. 3: a lengthwise view through the bicycle gearing system with the pedal crank in the 0 position and the second pedal crank in a 180 position;

(5) FIG. 4: a side view of the bicycle gearing system according to a second embodiment, with the pedal crank in a 0 position; and

(6) FIG. 5: a side view of the bicycle gearing system according to FIG. 4, with the pedal crank in a 90 position.

(7) FIG. 1 shows a side view of the bicycle gearing system per the invention, according to a first embodiment, with a pedal crank 22 in a 0 position, and FIG. 2 shows the pedal crank 22 rotated 90 in the corresponding clockwise rotation direction M to the 90 position.

(8) Both FIGS. 1 and 2 show the bicycle gearing system per the invention in an installation position, in which it is connected by means of a frame element 60 to a bicycle frame that is not shown here. For this purpose, the frame element 60 has three mounting flanges 63, 64, 65 for mounting on a front pipe (mounting flange 63), a saddle pipe (mounting flange 64), and a rear pipe (mounting flange 65).

(9) On a first side 61 of the frame element 60, a stationary sun gear 11 can be seen, which together with a planet gear 12 forms a spur gear 10, as well as a four-bar linkage 20 interacting with the spur gear 10. On a second (covered here) side 62 of the frame element 60 there is a second sun gear 11a that interacts with a second four-bar linkage 20a (see FIG. 3). The drawing references for the assemblies lying behind the frame element 60 in the drawing plane of FIGS. 1 and 2 are marked with the letter a and can be seen predominantly in the lengthwise view in FIG. 3.

(10) Both four-bar linkages 20, 20a relate to a central shaft 14, which runs crosswise through the frame element 60, with its front face visible. The central shaft 14 defines a central bearing axis y.sub.1 of the bicycle gearing system.

(11) A carrier plate 23, 23a is mounted on each axial end section of the central shaft 14 in such a way that it cannot twist, and it rotates in a circle together with the central shaft 1 when the bicycle gearing system is in operation. The connection between the carrier plate 23 and the central shaft 14 is made in a centrally located section of the carrier plate 23. In a section of the carrier plate 23 lying outside of that, the planet gear 12 is supported against the carrier plate 23 by a first pivot joint 40 in such a way that it can rotate.

(12) A crank 21, 21a is either attached to the planet gear 12, 12a in such a way that it cannot rotate or forms part of a one-piece assembly together with said planet gear. The crank 21, 21a protrudes radially, offset axially, from the planet gear 12, 12a, and engages the pedal crank 22, 22a rotatably by means of a second pivot joint 41 (see FIG. 3).

(13) A kinematic coupler 24, 24a in the shape of a pendulum arm 25, 25a is also connected rotatably to the carrier plate 23. A first end of the pendulum arm 25, 25a engages the pedal crank 22 on the side related to the frame element 2 by means of a third pivot joint 42. The opposite end of the pendulum arm 25 is fastened rotatably to the carrier plate 23 by means of a fourth pivot joint 43.

(14) Power is provided by the bicycle rider through pedals (not shown) to the two pedal cranks 22, 22a located axially to the central shaft 14 on the outsides of the bicycle gearing system (see FIG. 3). FIGS. 1, 3, and 4 show the pedal cranks 22, 22a and the four-bar linkages 20, 20a related to each of them in a 0 position, in which the pedal crank(s) 22, 22a and the related crank 21, 21a are extended, meaning that the crank 21, 21a is shown going out from a planet gear bearing axis y.sub.2, y.sub.2a of the planet gear 12, 12a radially inward towards the central shaft 14. This puts the free end of the pedal crank 22, 22a in its farthest outward position.

(15) A gear wheel 30 engages the carrier plate 23 from the outside and transfers the rotational motion of the bicycle gearing system to a traction element in the form of a chain 31.

(16) The gear wheel 30 has an oval shape spanned by a main axis diameter D.sub.H and a secondary axis diameter DN, with the main axis diameter D.sub.H intersecting a connecting line 13 at an angle of about 90. The connecting line 13 always intersects the central bearing axis y.sub.1 of the central shaft 14 and the planet gear bearing axis y.sub.2, y.sub.2a of the planet gear 12, 12a, regardless of the orientation of the spur gear 10. This orientation of the oval gear wheel 30 is especially effective in reducing accelerations of the foot, in particular around the area of the 90 position.

(17) The lengthwise view in FIG. 3 also shows the second sun gear 11a, which is stationary with respect to the frame element 60 and located on the second side 62 of the frame element 2. The sun gear 11 and the second sun gear 11b are connected rigidly to each other and form a single one-piece assembly. A single one-piece assembly is understood to involve a connection that cannot be separated other than by destroying it.

(18) The central shaft 14 runs concentrically inside the sun gears 11, 11a, and in the area of the first and second sun gears 11, 11a it is attached to each of them by means of a central shaft bearing 15 that allows it to pivot.

(19) FIGS. 4 and 5 show a 0 position (FIG. 4) and a 90 position of the pedal crank 22 by comparison in a second embodiment. The second embodiment involves a four-bar linkage 20, 20a with three pivot joints 40, 41, 42 and a coupler 24 in the form of a slide joint 50. The slide joint 50 is configured as a linear guide 51, which includes two parallel guideways 53 and a slide 52 that moves axially along the extent of the guideways 53. The guideways 53 are aligned parallel to the axial extent of the pedal crank 22 at the 0 position and the 90 position.

(20) The guideways 53 are fastened permanently to the carrier plate 23 and rotate around the central bearing axis y.sub.1 when the bicycle gearing system is operating in rotation direction M. The slide 52 is also connected rotatably to the pedal crank 22 through the third pivot joint 42.

(21) In FIG. 4, with a pedal crank 22 aligned in the 0 position, the connecting line 13 runs out from the central bearing axis y.sub.1 perpendicularly through the second pivot joint 41 and to the planet gear bearing axis y.sub.2. In addition, the main axis diameter D.sub.H is offset from the gear wheel 30 at an angle of about 90 in rotation direction M.

(22) In the 90 position of the pedal crank 22 according to FIG. 5, the connecting line 13 runs horizontally in the image plane between the central bearing axis y.sub.1 and the planet gear bearing axis y.sub.2. The main axis diameter D.sub.H is rotated by angle of about 90 to the perpendicular position.

LIST OF REFERENCE INDICATORS

(23) 10 Spur gear 11 Sun gear 11a Second sun gear 12 Planet gear 12a Second planet gear 13 Connecting line 14 Central shaft 15 Central shaft bearing 20 Four-bar linkage 20a Second four-bar linkage 21 Crank 21a Second crank 22 Pedal crank 22a Second pedal crank 23 Carrier plate 23a Second carrier plate 24 Coupler 24a Second coupler 25 Pendulum arm 25a Second pendulum arm 30 Gear wheel 31 Traction element, chain 40 First pivot joint 41 Second pivot joint 42 Third pivot joint 43 Fourth pivot joint 50 Slide joint 51 Linear guide 52 Slide, linear guide 53 Guideway 60 Frame element 61 First side frame element 62 Second side frame element 63 Mounting flange, front pipe 64 Mounting flange, saddle pipe 65 Mounting flange, rear pipe Main axis diameter/connecting line angle D.sub.H Main axis diameter D.sub.N Secondary axis diameter M Gear wheel rotation direction y.sub.1 Central bearing axis y.sub.2 Planet gear bearing axis y.sub.2a Second planet gear bearing axis