CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Italian Application No. 102018000005299, filed on May 11, 2018, which is incorporated herein by reference as if fully set forth.

FIELD OF INVENTION

The invention relates in general to a bicycle component provided with a temperature-compensated stress/strain sensor. In particular, the invention relates to a bicycle component comprising at least one stress/strain sensor and at least one temperature sensor.

BACKGROUND

The general knowledge in the field of the detection of stresses in a bar, as typically used in the context of the measurement of the torque applied to a crankarm of a crankset of a bicycle, typically provides for the use of at least one strain gage, typically of two strain gages, one positioned on one side with respect to the neutral plane of the crankarm with respect to the useful component of the pedaling force, and the other positioned on the opposite side with respect to the neutral plane.

Considering the crankarm with the pedal axis in front position (in the travel direction) with respect to the rotation axis, and therefore in the “downstroke” (the most effective part of the pedaling cycle), the strain gage that is in top position is subjected to and detects a dilation or elongation, while the strain gage that is in bottom position detects a contraction or compression when the cyclist applies a force on the pedal.

In case of other components of the bicycle and in particular of the crankset, such as the spider of the right (more in general on the transmission chain/belt side) crankarm or the bottom bracket spindle or the free wheel body of a monolithic cogset associated with the hub of the rear wheel, it is similarly known to use two strain gages (or two pairs of strain gages) positioned in two different positions, such that when one is subjected to and detects a dilation or elongation, the other one detects a contraction or compression.

It is also known in general to provide, in each measuring position, for a further strain gage the tracks of which are oriented parallel with respect to the tracks of the active strain gage, the role of this parallel strain gage being that of increasing the precision of the measurement reading; or a further strain gage the tracks of which are oriented at 90° with respect to the tracks of the active strain gage, the role of this orthogonal strain gage being that of compensating for the changes in resistance in the active strain gage caused by changes in temperature and/or that of increasing the precision of the measurement reading, by detecting the elongations/shortenings due to the Poisson effect.

A reading device, typically comprising a Wheatstone bridge circuit, takes care of reading the outputs of the strain gage or of the strain gages, suitably combining them.

It is also in general known to compensate a measurement of stresses/strains with a temperature measurement.

U.S. Pat. No. 7,647,837 B2 and EP1407239B1 disclose temperature-compensated strain gage detection systems, without however any reference to the application to bicycles. In both cases, a temperature sensor is arranged at each strain gage. The U.S. document recognizes that the temperature can change not only the properties of a strain gage element, rather also the properties of the base material to which the strain gage is attached, and that differences in the expansion coefficient between the strain gage and the base material can cause errors in the measurement. InFIG. 2, such a document suggests to position the temperature sensors in the same plane as the strain gages. In the European document, the strain gage and the temperature sensor overlap each other and are therefore in planes parallel and immediately adjacent to one another.

The Applicant observes that, while for a strain gage (or other stress/strain sensor) that has to detect mechanical stresses/strains, the detection capability is maximized when it is positioned on surfaces—and more in general in planes—of the component under measurement subjected to high mechanical stresses, vice-versa it is appropriate for the temperature sensor to be affected as little as possible by the mechanical stresses/strains acting on the component, since its reading could otherwise be changed and not very reliable.

The technical problem at the basis of the invention is therefore to provide a bicycle component comprising such sensors that allows a measurement of stresses/strains that is particularly accurate and independent from the temperature.

SUMMARY

The present solution provides a bicycle component with a stress or strain sensor and an associated temperature sensor that are arranged so that the stress or strain sensor and an associated temperature lie in planes that do not coincide with one another and are not parallel to each another.

