Cassette-based power meter

• US 7,775,128 B2
• Filed: 09/04/2008
• Issued: 08/17/2010
• Est. Priority Date: 09/04/2008
• Status: Active Grant

• Current Assignee: SRAM LLC (SRAM International Corp.)
• Original Assignee: Saris Cycling Group Incorporated
• Inventors: Roessingh, Jordan R., Wendt, David L.
• Primary Examiner(s): Caputo; Lisa M
• Assistant Examiner(s): Kirkland, III; Freddie
• Application Number:
  US12/204,578
• Publication Number:
  US 20100050785A1
• Time in Patent Office: 712 Days
• Field of Search: 738/621.91
• US Class Current: 73/862.191
• CPC Class Codes: B62J 45/411 Torque sensors
• CPC Class Codes: B62J 45/42 characterised by mounting
• CPC Class Codes: B62M 9/12 the chain, belt, or the like being laterally shiftable , e.g. using a rear derailleur
• CPC Class Codes: G01L 3/1457 involving resistance strain gauges

Abstract

A cassette-based power measuring apparatus includes a power sensing arrangement mounted within a cavity defined by a hollow bicycle cassette. The power sensing arrangement includes a torque sensing assembly including torque sensing elements configured to measure a user applied torque. The torque sensing elements are in communication with an electronics assembly configured to process the measured data and transmit it to a receiver. The torque sensing assembly may comprise a torque tube or a series of bending beams secured between a rear plate of the cassette and a freehub. The torque tube or bending beams may include strain gauges bonded thereto for measuring strain induced by application of forces in response to user-applied power.

Claims

1. A bicycle comprising:

a frame;

a pair of wheels including a driven wheel mounted to the frame;

a rotatable pedal assembly mounted to the frame;

a chain drive associated with the rotatable pedal assembly and configured to cause rotation of the driven wheel in response to rotation of the rotatable pedal assembly;

a drive gear arrangement drivingly interconnected with the driven wheel and driven by the chain drive during operation of the rotatable pedal assembly, wherein the drive gear arrangement includes an internal cavity; and

a torque sensing arrangement positioned within the internal cavity of the drive gear arrangement for measuring torque applied by a user to the drive gear arrangement through the chain drive and the pedal assembly;

wherein the drive gear arrangement comprises a hollow cassette defining the internal cavity, wherein the torque sensing arrangement is positioned within the internal cavity of the hollow cassette, and wherein the hollow cassette includes a series of concentric external gears.

2. The bicycle of claim 1, further comprising a hub assembly mounted within the driven wheel and including a freehub, wherein the hollow cassette is secured to the freehub.

3. The bicycle of claim 2 wherein the torque sensing arrangement is secured between the cassette and the freehub.

4. The bicycle of claim 3, wherein the torque sensing arrangement comprises a torque measurement assembly including at least one torque sensing element mounted between the cassette and the freehub.

5. The bicycle of claim 4, wherein the torque sensing arrangement includes a tubular member mounted to the freehub and connected to the cassette, and further includes a strain gauge coupled to the tubular member.

6. The bicycle of claim 1, wherein the torque sensing arrangement includes an electronics assembly configured to process signals provided thereto from a torque sensing element.

7. The bicycle of claim 1, wherein the hollow cassette includes a series of concentric external gears and a rear plate, and wherein a portion of the torque sensing arrangement is secured to the rear plate of the hollow cassette.

8. The bicycle of claim 7, wherein the torque sensing arrangement comprises a plurality of torque sensing elements mounted to the rear plate.

9. The bicycle of claim 8, wherein the torque sensing elements comprise a plurality of strain gauges.

10. A bicycle comprising:

a frame;

a pair of wheels including a driven wheel mounted to the frame wherein a hub assembly is carried by the driven wheel and includes a freehub;

a rotatable pedal assembly mounted to the frame;

a chain drive associated with the rotatable pedal assembly and configured to cause rotation of the driven wheel in response to rotation of the rotatable pedal assembly;

a drive gear arrangement drivingly interconnected with the driven wheel and driven by the chain drive during operation of the rotatable pedal assembly, wherein the drive gear arrangement comprises a hollow cassette secured to the freehub, wherein the hollow cassette defines an internal cavity, and wherein the hollow cassette includes a series of concentric external gears; and

a torque sensing arrangement positioned within the internal cavity of the hollow cassette for measuring torque applied by a user to the drive gear arrangement through the chain drive and the pedal assembly, wherein the torque sensing arrangement is secured between the cassette and the freehub and includes at least one torque sensing element, wherein the torque sensing arrangement comprises at least one torque transmission bending beam secured between the freehub and a rear plate defined by the cassette.

11. The bicycle of claim 10, wherein the torque sensing element comprises a strain gauge bonded to the torque transmission bending beam.

12. A bicycle comprising:

a frame;

a pair of wheels including a driven wheel mounted to the frame wherein a hub assembly is carried by the driven wheel and includes a freehub;

a rotatable pedal assembly mounted to the frame;

a chain drive associated with the rotatable pedal assembly and configured to cause rotation of the driven wheel in response to rotation of the rotatable pedal assembly;

a drive gear arrangement drivingly interconnected with the driven wheel and driven by the chain drive during operation of the rotatable pedal assembly, wherein the drive gear arrangement comprises a hollow cassette secured to the freehub, wherein the hollow cassette defines an internal cavity, and wherein the hollow cassette includes a series of concentric external gears; and

a torque sensing arrangement positioned within the internal cavity of the hollow cassette for measuring torque applied by a user to the drive gear arrangement through the chain drive and the pedal assembly, wherein the torque sensing arrangement is secured between the cassette and the freehub and includes at least one torque sensing element, wherein the torque sensing arrangement comprises a pair of orthogonally coupled torque transmission beams, wherein a first torque transmission beam is secured to a rear plate of the cassette and a second torque transmission beam is secured to the freehub.

13. The bicycle of claim 12, wherein the torque sensing element comprises a compressive force sensing element secured between the first torque transmission beam and the second torque transmission beam.

14. A power sensing assembly for use with an apparatus powered by a user applied force to a pedal assembly for driving a wheel of the apparatus, wherein the wheel includes a hub, the power sensing assembly comprising:

a gear arrangement secured to the hub and drivingly interconnected with the pedal assembly, wherein the gear arrangement includes a body defining an internal cavity;

a torque sensing assembly contained within the internal cavity defined by the body of the gear arrangement and including one or more torque sensing elements, wherein the torque sensing assembly is configured to measure the torque applied by a user to the pedal assembly;

a velocity sensor that detects rotation of a wheel of the apparatus; and

a processor that determines power associated with the applied force to the pedal assembly from the torque measured by the torque sensing assembly and angular velocity information provided by the velocity sensor.

15. The power sensing assembly of claim 14, wherein the one or more torque sensing elements comprises one or more strain gauges.

16. The power sensing assembly of claim 14, further comprising a tubular member having a set of torque sensing elements affixed thereon, and wherein the tubular member is configured to fit over the hub.

17. The power sensing assembly of claim 14, wherein the body of the gear arrangement includes a rear plate that functions in part to define the internal cavity of the gear arrangement, and wherein the torques sensing assembly is configured for engagement with the rear plate.

18. A power sensing assembly for use with an apparatus powered by a user applied force to a pedal assembly and including a gear arrangement for driving a wheel of the apparatus, wherein the gear arrangement includes a freehub, the power sensing assembly comprising:

a torque sensing assembly mounted within an internal cavity defined by the gear arrangement and having a plurality of torque sensing elements in communication therewith, wherein the torque sensing assembly is configured to measure the torque applied by a user to the pedal assembly, wherein the torque sensing assembly is configured for engagement with a rear plate that functions in part to define the internal cavity of a gear arrangement, and wherein the torque sensing assembly comprises a plurality of bending beams secured between the rear plate and the freehub, wherein the plurality of bending beams includes at least one torque sensing element bonded thereto;

a velocity sensor that detects rotation of a wheel of the apparatus; and

a processor that determines power associated with the applied force to the pedal assembly from the torque measured by the torque sensing assembly and angular velocity information provided by the velocity sensor.

19. The power sensing assembly of claim 18, wherein the at least one torque sensing element comprises a strain gauge, and wherein each strain gauge is in communication with an electronics assembly configured to process the measured torque.

20. A bicycle wheel, comprising:

a rim;

an inner hub area;

a drive gear arrangement drivingly interconnected with the inner hub area, wherein the drive gear arrangement includes an internal cavity; and

a torque sensing arrangement positioned within the internal cavity of the drive gear arrangement for measuring torque applied by a user to the drive gear arrangement;

wherein the drive gear arrangement comprises a hollow cassette defining the internal cavity, wherein the torque sensing arrangement is positioned within the cavity of the hollow cassette, and wherein the hollow cassette includes a series of concentric external gears.

21. The bicycle wheel of claim 20, wherein the torque sensing arrangement includes at least one torque sensing element.

22. The bicycle wheel of claim 21, wherein the torque sensing element is interconnected between the inner hub area and a rear wall of the hollow cassette, wherein the rear wall at least in part defines the internal cavity of the hollow cassette.