CRANKSET BASED BICYCLE POWER MEASUREMENT

• US 20090120208A1
• Filed: 11/06/2007
• Published: 05/14/2009
• Est. Priority Date: 11/06/2006
• Status: Active Grant

• Current Assignee: SRAM LLC (SRAM International Corp.)
• Original Assignee: SRAM LLC (SRAM International Corp.)
• Inventors: Meyer, James Isaac
• Granted Patent: US 8,065,926 B2
• Time in Patent Office: Days
• US Class Current: 73/862.45
• CPC Class Codes: A63B 2071/0652 Visualisation or indication relating to symmetrical exercise, e.g. right-left performance related to spinal column
• CPC Class Codes: B62J 45/411 Torque sensors
• CPC Class Codes: B62J 45/421 at the pedal crank
• CPC Class Codes: B62M 3/00 Construction of cranks operated by hand or foot
• CPC Class Codes: B62M 9/00 Transmissions characterised by use of an endless chain, belt, or the like cycle chain guards B62J13/00
• CPC Class Codes: G01L 3/1471 using planet wheels or conical gears
• CPC Class Codes: G01L 3/1478 involving hinged levers

Abstract

The present application relates to an input torque measuring device for a drive train of a bicycle. The drive train includes a first crank arm and a second crank arm. An inboard end of each crank arm is rotatably mounted to the bicycle at a bottom bracket of the bicycle. At least one chain ring is configured to rotate a driven wheel of the bicycle. A spider is connected to the first crank arm adjacent the bottom bracket and extends out to the at least one chain ring. The spider is configured to transmit force applied to the crank arms directly to the at least one chain ring. The spider may include a plurality of sensors configured to respond to the force applied by the spider to the at least one chain ring. The sensors produce an electronic signal relative to the force transmitted by the spider to the at least one chain ring and a processor configured to receive the electronic signals from each sensor of the spider.

Claims

1. An input torque measuring device for a drive train of a bicycle, the drive train including a first crank arm and a second crank arm configured to be engaged by a rider of the bicycle at an outboard end, an inboard end of each crank arm rotatably mounted to the bicycle at a bottom bracket of the bicycle, at least one generally planar chain ring oriented generally perpendicular to the bottom bracket and configured to rotate about the bottom bracket and to rotate a driven wheel of the bicycle, the device comprising:

a spider connected to a first crank arm adjacent the bottom bracket and extending out to and directly supporting the at least one chain ring, the spider configured to transmit force applied to the crank arms directly to the at least one chain ring;

the spider including a plurality of sensors configured to respond to the force applied by the spider to the at least one chain ring and produce an electronic signal relative to the force transmitted by the spider to the at least one chain ring, each sensor oriented to be generally parallel to a plane of the at least one chain ring;

an electronic circuit configured to receive the electronic signals from each sensor of the spider.

2. The input torque measuring device of claim 1, further comprising the spider including a plurality of arms extending from a center of the spider out to the at least one chain ring, each spider arm including a sensor.

3. The input torque measuring device of claim 2, wherein each spider arm includes an opposed pair of sensors.

4. The input torque measuring device of claim 1, wherein each sensor is a responds to a deflection of a portion of the spider when the force is transmitted from the spider to the at least one chain ring.

5. An input torque measuring device for a drive train of a bicycle, the drive train including a first crank arm and a second crank arm configured to be engaged by a rider of the bicycle at an outboard end, an inboard end of each crank arm rotatably mounted to the bicycle at a bottom bracket of the bicycle, at least one generally planar chain ring oriented generally perpendicular to the bottom bracket and configured to rotate about the bottom bracket and to rotate a driven wheel of the bicycle, the device comprising:

a spider connected to a first crank arm adjacent the bottom bracket, the spider including a plurality of spider arms extending out to and directly supporting the at least one chain ring, the spider configured to transmit force applied to the crank arms through the spider arms to the at least one chain ring;

the spider including a plurality of sensors configured to respond to the force applied by the spider to the at least one chain ring and produce an electronic signal relative to the force transmitted by the spider to the at least one chain ring;

each sensor mounted to a spider arm and comprising a strain grid oriented parallel to a plane of the at least one chain ring;

an electronic circuit configured to receive the electronic signals from each sensor of the spider.

6. The input torque measuring device of claim 5, further comprising each spider arm including at least one sensor.

7. The input torque measuring device of claim 5, each sensor further comprising a pair of strain grids, the strain grids of each pair oriented perpendicular to each other.

8. The input torque measuring device of claim 5, each sensor mounted to a shear web defined in the spider arm.

9. The input torque measuring device of claim 8, further comprising each shear web having a pair of perpendicularly arranged strain grids mounted on opposite sides of the shear web.

10. The input torque measuring device of claim 9, the shear web further including an opening permitting electrical connection of the sensors on opposite sides of the shear web.

11. The input torque measuring device of claim 5, wherein each spider arm is symmetrical about at least one axis.

12. The input torque measuring device of claim 8, further comprising the shear web defined in a recess on the spider arm, the sensor mounted within the recess, and a protective covering provided over the sensor within the recess.

13. The input torque measuring device of claim 12, wherein the protective covering is formed from an material at least partially filling the recess and laying directly on the sensor.

14. An input torque measuring device for a drive train of a bicycle, the drive train including a first crank arm and a second crank arm configured to be engaged by a rider of the bicycle at an outboard end, an inboard end of each crank arm rotatably mounted to the bicycle at a bottom bracket of the bicycle, at least one chain ring mechanically connected to the crank arms and configured to rotate a driven wheel of the bicycle, the device comprising:

at least one of the crank arms including at least one strain measurement device configured to generate an electronic signal when a force is applied to the crank arm, the electronic signal relative to the force applied to the crank arm;

circuitry configured to receive the electronic signal from the strain gage.

15. The input toque measuring device of claim 14, further comprising the at least one strain measurement device includes at least one strain gage oriented generally perpendicular to a rotational axis of the crank arm.

16. The input torque measurement device of claim 15, further comprising the at least one strain gage including a pair of strain grids oriented generally perpendicular to each other.

17. The input torque measurement device of claim 15, further comprising a shear web defined in the crank arm with the at least one strain gage mounted on opposite sides of the shear web.

18. The input torque measuring device of claim 14, further comprising a pair of strain measurement devices mounted on opposite each other on opposite sides of the crank arm and generally parallel to each other.

19. The input torque measuring device of claim 18, further comprising both strain measurement devices oriented generally perpendicular to the rotational axis of the crank arm

20. The input torque measuring device of claim 18, wherein the crank arm is generally symmetrical about at least one axis adjacent the location of the strain measurement devices.

21. The input torque measuring device of claim 18, further comprising a shear web defined in the crank arm and the strain measurement devices are mounted on opposite sides of the shear web.

22. The input torque measuring device of claim 18, wherein the crank arm is a hollow member defining an internal recess and the strain measurement devices are positioned within the recess on opposite sides.