FORCE SENSOR FOR THE BOTTOM BRACKET OF A BICYCLE

Abstract

The present invention refers to a bottom bracket load sensor designed to measure the deformation of the end bearings of the bottom bracket as a result of the pedalling force. This sensor requires a special, customized design with deformation sensors arranged to measure the effective force ignoring parasitic forces. It is very important to have a true measurement, among other cases, for the optimization of the performance of electric motors on bicycles.

Claims

1. A force sensor for a bicycle bottom bracket (14) comprising; an outer ring (2) with a slit all around perimeter (11) thereof as a housing for at least one mechanical stop (12), an inner ring (3), a central ring (4) between the outer ring and the inner ring, with at least four openings (5) arranged around a perimeter thereof, arranged to form four arms, two of the arms having a same length of a major arch (6) on a vertical axis and the other two arms having a same length of a minor arch (7) on a horizontal axis, arranged symmetrically, at least one shear deformation sensor (8) placed on each of the minor arch arms matching the horizontal axis and at least one deflection deformation sensor (9) on each of the major arch arms matching the vertical axis.

2. The force sensor for a bicycle bottom bracket (14) according to claim 1, wherein the outer ring (2) of the cylindrical part (1) is used as a housing for a bearing (10).

3. The force sensor for a bicycle bottom bracket (14) according to claim 1, wherein the outer ring (2) and the bottom bracket (14) have a gap (13) therebetween so that the outer ring (2) has radial movement freedom.

4. The force sensor for a bicycle bottom bracket (14) according to claim 1, wherein the mechanical stop (12) is made of an elastic material.

5. The force sensor for a bicycle bottom bracket (14) according to claim 1, wherein the inner ring (3) of the cylindrical part (1) has suitable facilities for being mounted and fixed to the bottom bracket (14).

6. The force sensor for a bicycle bottom bracket (14) according to claim 1, wherein the shear deformation sensors (8) are placed on the horizontal axis, and the deflection deformation sensors (9) are on the vertical axis.

7. The force sensor for a bicycle bottom bracket (14) according to claim 1, wherein the shear deformation sensors (8) and the deflection deformation sensors (9) are connected to form a full Wheatstone bridge circuit to compensate the temperature changes.

8. The force sensor for a bicycle bottom bracket (14) according to claim 1, wherein the force sensor is installed on a drive side where a chain ring (15) is placed for detecting and compensating chain ring (15) or sprocket changes.

9. The force sensor for a bicycle bottom bracket (14) according to claim 1, wherein the force sensor is installed on an opposite side to a chain ring (15).

10. The force sensor for a bicycle bottom bracket (14) according to claim 1 wherein the force sensor calculates a force applied by each of a rider's legs at a same time.

11. The force sensor for a bicycle bottom bracket (14) according to claim 1, wherein data obtained by the deformation sensors are interpreted and converted into readable data on external devices after applying an algorithm.

Description

DESCRIPTION OF THE DRAWINGS

[0027] To have a better understanding of this invention, the annexed drawing represents a preferred practical embodiment of it.

[0028] FIG. 1.—Shows the cylindrical part (1) as designed to measure shear and deflection.

[0029] FIG. 2.—Shows the cylindrical part (1) with the shear deformation sensors (8), the deflection deformation sensors (9) and the embedded bearing (10).

[0030] FIG. 3.—Shows a detail of the cylindrical part (1) with the mechanical stop (12).

[0031] FIG. 4.—Shows the force sensor installed in the bottom bracket (14) and its position on the axle (16) in relation to the cranks (17) and chain ring (16).

PREFERRED EMBODIMENT OF THE INVENTION

[0032] The device of this invention shows in FIG. 1 the hollow cylindrical part (1) with three differentiated rings or parts. In the outer ring (2) a bearing (10) is fitted on its inner perimeter. Along the outer perimeter there is a slit (11) which houses the mechanical stop (12). The inner ring (3) has the function of being mounted and fixed to the bottom bracket. The central ring (4) is specially designed to measure the shear and deflection caused by the deformation of the bearing (10) integrated in the sensor, due to the force applied by the rider while pedalling. The reading must be accurate, free of parasitic forces, that is, it must be able to detect the deformation with very different applied forces.

[0033] We would like to emphasize that the perimeter of the central ring (4) has four openings (5). The arrangement of these openings (5) is not equidistant around the perimeter of the central ring (4), but they are arranged so that they form four arms. Two of them have the same of a major arch (7) and the other two have the same length of a minor arch (6).

[0034] The device, object of the present invention shows in the FIG. 2 the cylindrical part (1) graded, with the inserted bearing (10) described in the previous paragraph. It also shows in the central ring (4) the minor arch arms (6) positioned on the horizontal axis, where the shear deformation sensors (8) are placed matching the mentioned horizontal axis. On the vertical axis the major arch arms (7), where the deflection deformation sensors (9) are positioned, matching the vertical axis. It must be emphasized that the characteristic design of this cylindrical part (1), which measures the shear in the horizontal axis and the deflection in the vertical one, has as main purpose the elimination of the parasitic forces produced in the deformation of the bearings (10) of the bottom bracket (14), when applying the pedalling force.

[0035] The detail of FIG. 3 shows a sectional view of the outer ring (2) with the bearing (10) fitted and mounted on the bottom bracket (14). This detail shows the radial movement freedom of the outer ring with that gap (13) between the bottom bracket (14) and the outer ring (2). It is also shown the detail of the mechanical stop (12) inserted in the slit (11).

[0036] The FIG. 4 of the device object of the present invention shows the load sensor mounted on the same side of the chain ring (15). The force sensor is fixed to the bottom bracket (14) and covered by an outer housing. The bottom bracket (14) with the force sensor mounted on the frame between the cranks (17) and with the axle (16) passing through the interior. This figure contributes to the understanding of the fact that when the crank (17) axle (16) rotates as a result of the pedalling action, the load sensor remains fixed, while the bearing (10) also rotates and is deformed under the action of the applied forces. It can also be seen the matching position to the horizontal axis of the shear deformation sensors (8) and the matching position to the vertical axis of the deflection deformation sensors (9). The characteristics of this sensor make that it is suitable for the measuring of output at both high and low speeds and for the compensation of sprocket or chain ring changes.

[0037] An algorithm converts the data collected by the shear deformation sensors (8) and the bending deformation sensors (9) making them usable for the correct performance of an electric motor incorporated in a bicycle or for the reading of the output developed by the rider at every moment.

[0038] The specialized person in this technology will easily understand that it is possible to combine features of different embodiments with features of other possible embodiments, provided that such a combination is technically supported.