D'HERRIPON, Bastiaan Andreas (Sporenring 136, EE GOIRLE, NL-5053, NL)
SCHEPERS, René Guillaume François (Hyacintstraat 7, RW Kerkrade, NL-6466, NL)
ROOVERS, Gijsbertus Cornelis Franciscus (Bankven 35, BA GOIRLE, NL-5052, NL)
D'HERRIPON, Bastiaan Andreas (Sporenring 136, EE GOIRLE, NL-5053, NL)
SCHEPERS, René Guillaume François (Hyacintstraat 7, RW Kerkrade, NL-6466, NL)
| CLAIMS 1. Detection system (40) for detecting a direction of rotation of an axle (11) rotating with respect to a frame (2) , the detection system comprising: a dragging element (32; 132) for being arranged in slidable contact with the axle (11), the dragging element (32) being provided with a friction coupling for operating between the dragging element (32) and the axle (11) such that rotation of the axle causes a tangential dragging force on the dragging element; wherein the dragging element can be displaced circumferentially with respect to the frame; wherein the system further comprises at least one stop (33, 34; 134) for being fixed with respect to the frame (2) such as to restrict the freedom of circumferential travel of the dragging element; and wherein the system further comprises at least one sensor (41, 42) for being fixed with respect to the frame (2) to detect a position of the dragging element with respect to the frame (2) . 2. Detection system (40) for detecting a direction of rotation of an axle (11) rotating with respect to a frame (2), the detection system comprising: a dragging element (32; 132) for being arranged in slidable contact with the axle (11), the dragging element (32) being provided with a friction coupling for operating between the dragging element (32) and the axle (11) such that rotation of the axle causes a tangential dragging force on the dragging element ; wherein the friction force is speed-related; and wherein the system further comprises at least one sensor for being fixed with respect to the frame (2) to sense the direction of the dragging force and preferably also the magnitude of the dragging force. 3. Detection system according to claim 1 or 2, wherein. the dragging element (32) comprises a magnet for being magnetically clamped to the axle, and/or wherein the dragging element (132) has a shape in the form of a clamp, or is provided with clamping means', for extending around the axle (11) over more than 180°. 4. · Bicycle (1), comprising a frame (2) and- a set of pedals (12, 13) mounted on a crank axle (11) that is mounted for rotation with respect to the frame, the bicycle being provided with a rotation detection system (40) for detecting a rotation direction of the pedals; wherein the rotation detection system comprises: a dragging element (32; 132) arranged in slidable contact with the axle (11) such as to be capable of sliding over the axle surface in the axle's circumferential direction; a friction coupling operating between the dragging element (32; 132) and the axle (11) such that rotation of the axle causes a tangential dragging force on the dragging element; wheren the dragging element can be displaced circumferentially with respect to the frame; wherein the rotation detection system further comprises at least one stop (33, 34; 134) fixed with respect to the frame, restricting the freedom of circumferential travel of the dragging element; and wherein the rotation detection system further comprises at least one sensor (41, 42) fixed with respect to the frame for detecting a position of the dragging element with respect to the frame. 5. Bicycle (1), comprising a frame (2) and a set of pedals (12, 13) mounted on a crank axle (11) that is mounted for rotation with respect to the frame, the bicycle being provided with a rotation detection system (40) for detecting a rotation direction of the pedals; wherein the rotation detection system comprises: a dragging element (32; 132) arranged in slidable contact with the axle (11) such as to be capable of sliding over the axle surface in the axle's circumferential direction; a friction coupling operating between the dragging element (32; 132) and the axle (11) such that rotation of the axle causes a tangential dragging force on the dragging element; wherein the friction force is speed-related; and wherein the rotation detection system further comprises at least one sensor fixed with respect to the frame to sense the direction of the dragging force and preferably also the magnitude of the dragging force. 6. Bicycle according to claim 4 or 5, wherein the dragging element (32) comprises a magnet and is magnetically clamped to the axle (11) . 7. Bicycle according to claim 6, wherein the sensor (41, 42) comprises a magnet sensor. 8. Bicycle according to any of claims 4-7, wherein the dragging element (132) has a shape in the form of a clamp, or is provided with clamping means, engaging around the axle (11) over more than 180° and exerting a mechanical clamping force on the axle. 9. Bicycle according to any of claims 4-8, further comprising pressing means pressing the dragging element against the axle for increasing the friction such as to increase the dragging force . 10. Bicycle according to any of claims 4-9, wherein the sensor (41, 42) comprises an optical sensor or a mechanical sensor or an inductive electrical sensor or a capacitive electrical sensor . 11. Bicycle according to any of claims 4-10, wherein the at least one stop defines two extreme tangential positions of the dragging element, and further comprising bias means (43) cooperating with the dragging element for exerting on the dragging element a tangential bias force towards one of said two extreme tangential positions. 12. Bicycle according to any of claims 4-11, wherein the at least one stop defines two extreme tangential positions of the dragging element, and wherein the at least one sensor is capable of detecting the presence. of the dragging element at one of .said two extreme tangential positions. 13. Bicycle according to any of claims 4-12, further comprising a housing (30) fixed with respect to the frame and mounted adjacent the crank axle; wherein the housing, in its surface facing the crank axle, has a tangential recess (31); wherein the dragging element is accommodated in said recess; and wherein the recess (31) has tangential end faces (33, 34) acting as said stops. 14. Bicycle according to claim 13, wherein the sensor (s) (41, 42) is/are mounted in the said housing (30) . 15. Bicycle according to claim 13 or 14, wherein two sensors (41,' 42) are arranged close to respective ones of said tangential end faces (33, 34) . 16. Bicycle according to any of the previous claims 4-15, further comprising means for providing a speed-dependency of the friction between the dragging element and the axle, these means preferably comprising a friction fluid between the dragging element and the axle, or eddy current generating means . 17. Bicycle according to any of the previous claims 4-16, further comprising a controller (50) having at least one input for receiving sensor signals from the at least one sensor; wherein the bicycle further comprises an electrical assistance motor (60), wherein the controller (50) is designed for actuating the motor, wherein the controller is designed to inhibit actuation of the motor when the detection signals indicate rotation of the pedals in the rearward direction; and/or wherein the bicycle further comprises a break light (70) , wherein the controller is designed to actuate the break light when the detection signals indicate rotation of the pedals in the rearward direction; nd/or wherein the controller is designed to control the motor on the basis of the drive force as represented by the friction force. |
The present invention relates in general to a detector for detecting the direction of rotation of an axle. Such detector may be useful in several application. One
particularly useful application is the case of bicycle pedals, which can be rotated forwards in order to drive the bicycle, and which can be rotated backwards, for braking, in which case the detector can be used for actuating a brake light. Such detector is especially useful in so-called electrical
bicycles, i.e. bicycles having an electrically powered motor, where the motor is only allowed to give power when the cyclist is rotating the pedals forwards, the motor power being
proportional to the pedal force exerted by the cyclist, and/or where the motor is controlled by pedal rotation and/or
pedalling speed (cadence) . In many electrical bicycles, this pedal force is measured by measuring the chain force, namely by measuring the horizontal force exerted on the driven wheel and/or its suspension. In the case of a bicycle with a coaster brake, i.e. a brake actuated by back-pedalling, there is also such horizontal force when the cyclist is using the brake, and it is vital that the electric motor is not actuated in this situation. In cadence-controlled electric bikes, the reaction time to the stopping of the pedal action is often quite long, and a direction detector could allow for a faster stopping reaction of the motor.
Known solutions for detection the rotation direction of an axle include for instance a carrier disc fixed to the axle and carrying one or more magnets, and a plurality of Hall sensors detecting the passage of the magnet: the order in which the sensors are actuated determines the direction of rotation. Such solution, however, is relatively complicated, and requires a processor for processing and analysing the Hall sensor signals. Further, a problem is that the axle must travel a relatively large angle before such known system has reliably detected its direction of rotation.
A specific objective of the present invention is to provide a very simple implementation of such detector without the above drawbacks .
According to an important aspect of the present
invention, a rotation direction detector comprises an axle following element, being in friction contact with the axle surface and capable of sliding over the axle surface. Due to the friction, the axle following element tends to rotate along with the axle, "sitting" on the surface. Its path, however, is limited by two stops, and when being stopped by one of these stops the element is necessarily stationary so that it slides over the rotating axle. Its position, which determines the direction of rotation and which is determined by the stop it contacts, can easily be detected.
The invention will be explained in more detail with reference to the drawings, in which:
figure 1 schematically shows a bicycle;
figure 2 schematically shows a longitudinal section of a pedal axle to illustrate the detector of the present invention;
figure 3 schematically shows a cross-section of the pedal axle to illustrate the detector of the present invention;
figure 4 is a block diagram schematically illustrating the control of an electrical assistance motor;
figures 5-7 illustrate more details of emmodiments of the detector of the present invention.
Since bicycles are known per se, a general description with reference to figure 1 will be kept brief. A bicycle 1 comprises a frame 2, a rear wheel 3, a front wheel 4, handle bars 5, and a saddle 6. For forward motion, the rear wheel 3 is provided with a rear chain wheel 7, which through a chain 8 is coupled to a front chain wheel 9, which is rotated by the cyclist using the pedal mechanism 10. Other transmission systems are also possible. The pedal mechanism 10 comprises a crank axle 11 mounted horizontally in crank bearings (not shown in this figure) allowing for rotation. Pedals 12 and 13 are mounted at
opposite ends of the crank axle 11.
Figure 2 schematically shows a longitudinal section of the crank axle. The axle 11 is. held in bearings 21, 22 with respect to the frame 2. Close to the axle 11, or around the axle 11, a plastic housing 30 is mounted. This housing can be inside the bottom bracket 2A that contains the pedal crank, as shown in figure 2, but it can also be outside the bearings, i.e. between a bearing and the corresponding pedal .
Figure 3 is a schematic cross section of the axle 11 and the housing 30. The housing 30 has a recess 31 facing the axle 11. Apart from this recess 31, the housing 30 may completely fill the space between the axle 11 and the bottom bracket 2A, but this is not necessary, as shown. A magnet 32 is placed on the axle 11. The axle 11 comprises a magnetizable material, typically iron or steel, so that the magnet 32 sticks to the axle 11. The magnet 32 is located in the housing recess 31. It can be seen that the recess 31 has a tangential size larger than the size of the magnet 32, so that the magnet 32 can travel over some distance in the recess 31. When the pedals are rotated in the forward direction (clockwise in- figure 3), the magnet 32 rotates with the- axle 11 until it reaches a first end 33 of the recess 31; from that moment on, the magnet is stationary with respect to the housing 30, sliding over the rotating axle 11. When the pedals are rotated in the backward direction, the magnet 32 rotates with the -axle 11 until it reaches the second end 34 of the recess 31; from that moment on, the magnet is stationary with respect to the housing 30, sliding over the rotating axle 11.
In the housing 30, a first magnet sensor 41 is located adjacent the first end 33 of the recess 31, and a second magnet sensor 42 is located adjacent the second end 34 of the recess 31. The magnet sensor may for instance comprise a Hall sensor or a Reed relays. It should be clear that the first magnet sensor 41 is actuated when the pedals are rotated in the forward direction, and that the second magnet sensor 42 is ,
4
actuated when the pedals are rotated in the .backward
direction. As shown schematically in figure 4, the magnet sensors provide their output signals to a controller 50 for controlling an electric assistance motor 60, which may for instance be a hub motor of the rear wheel 3. The controller 50 is designed to actuate the motor 60 only when the pedals are rotated in the forward direction, i.e. when the first magnet sensor 41 is actuated while the second magnet sensor 42 is not, and to positively switch off the motor when the pedals are rotated in the opposite direction, i.e. when the first magnet sensor 41 is not actuated.
Alternatively, or additionally, the controller 50 may be equipped for actuating a brake light 70 when the second magnet sensor 42 is actuated.
In a more economical embodiment, it may suffice that the system comprises only one sensor, either only the first sensor or only the second sensor. In the first case, the controller 50 actuates the motor 60 when the one sensor is actuated, in the second case the controller 50 actuates the motor 60 when the one sensor is not actuated.
Figure 5 is a cross-section comparable to figure 3, wherein the system comprises only one magnet sensor 44 located asymmetrically with respect to the recess 31. In contrast to the embodiment of figure 3, where the magnet sensor 41 is located in a tangential end wall, the magnet sensor 44 is now located in a radial side wall 35 of the recess 31.
It should be clear that the tangential size of the recess
31 should be determined in relation to the size of the magnet
32 and the desired play for the magnet to obtain a reliable discrimination between detection of one rotation direction and the other.
A problem may be that the system can not reliably detect that the pedals are held stationary. After all, the pedals can be held stationary immediately after having been rotated in the forward direction, in which case the first magnet sensor 41 will continue to be actuated, or immediately after having been rotated in the backwards direction, in which case the second magnet sensor 42 will continue to be actuated. This problem can be solved by adding a spring 43, exerting a bias force on the magnet 32 to urge the magnet towards the second magnet sensor 42. The bias force should be chosen just high enough to overcome the friction between magnet and axle when the axle is held stationary, but low enough to allow the rotating axle to take the magnet along toward the first recess end. In such embodiment, the first magnet sensor 41 is
actuated when the pedals are being rotated in the forward direction while the second magnet sensor 42 is actuated when the pedals are held still or are rotated in the backward direction. It is noted that such embodiment requires that the friction between the magnet and the exle when stationary is lower than when the axle is rotating.
The friction between the magnet 32 and the axle 11 can be engineered to be speed-sensitive by applying a laminar
friction fluid 37 or fat between the magnet 32 and the axle 11. Another method to create speed-sensitive friction force is to use the magnet and a steel shaft to create an eddy-current brake. This speed-sensitivity can be increased by placing the magnet 32 in a magnet slide 36 having a larger friction area with the axle 11, as schematically illustrated in figure 6.
In cases- where the friction force is speed-related, for instance proportional to the speed, it is possible to provide the dragging element with a force sensor, for instance an inductive or capacitive sensor, and it is even possible to implement the system such that the dragging - element is not displaced or is only displaced over a very small distance, such as 1 mm or less. An electrical output signal of such friction force sensor contains the direction of the friction force, and hence the rotation direction of the pedals, so a controller receiving this output signal can respond quickly by switching off the electric motor if the pedal are stopped or if the pedalling reaction is reversed. Further, the electrical output signal of such friction force sensor is representative for (or even proportional to) the rotation speed of the pedals, so a controller receiving this output signal can control the electric motor (more power / less power) on the ■basis of this output signal. It should be clear to a person skilled in the art that the present invention is not limited to the exemplary
embodiments discussed above, but that several variations and modifications are possible within the protective scope of the invention as defined in the appending claims. For instance, it is not necessary that the recess 31 in the housing 30 is located above the axle 11: the recess 31 may be located below the axle 11, or in fact may have any orientation with respect to the axle 11.
In the above, an embodiment has been described on the basis of a magnet. More generally, the gist of the invention involves an element which on the one hand allows the pedal axle to rotate freely while it on the other hand receives a dragging force from the rotating axle. Such element will hereinafter be indicated as a dragging element. The dragging element is provided with pressing means exerting a pressing force on the dragging element, pressing it in mechanical contact with the pedal axle, so that a friction force is generated depending on said pressing force. The pressing force is selected to be high enough so that during operation said friction force will cause the dragging of the dragging
element, but on the other hand the pressing force is selected to be low enough so that, once the dragging block abuts the end of the recess 31, the dragging block can slide over the axle without hindering the axle's rotation and without causing wear .
In the above-described embodiment, the pressing force is a magnetic attraction force. In another embodiment, a spring or another type of resilient member may be provided, pressing the dragging element onto the axle .
In another emodiment, schematically illustrated in figure 7, the dragging element 132 is implemented in the form of a clamp, or provided with clamping means, extending around the axle 11 over more than 180°, and possibly arranged in a circumferential groove in the axle, in which case the clamping means exert a clamping force on the axle 11.
In the above, the sensors 41, 42 are described as
magnetic sensors. However, the sensors may be of different type, for instance optical sensors in which case the dragging element may reflect or interrupt a light beam, or mechanical sensors such as pressure-sensitive sensors, or even micro- switches .
In the above, the dragging element is described as travelling in a recess in the housing 30. Although this is a preferred embodiment, indeed, it is sufficient if the rotation detector comprises two stops 33, 34 at the same axial position (considered with respect to the axle 11) and at an angular distance from each other, defining a restriction for the freedom of the dragging element to travel in angular direction with the axle 11. This angular distance may be relatively small, for cooperating with a dragging element having
relatively small tangential size or cooperating with a
protrusion of a dragging element, where the dragging element may have larger tangential size than the protrusion. It is also possible that the dragging element has relatively large tangential size, such as for instance the dragging element 132 in the embodiment illustrated in figure 7: in such case, the angular distance between the two stops may approach 360°, and the design may also be described as having two stops mounted close together, or having one stop element 134 (see figure 7), positioned between the tangential end faces of the dragging element 132. It is further possible that the stop element and the sensor element are integrated; for instance, in the embodiment of figure 7, stop element 134 may be the actuation lever of a switch. It is further possible that the sensor element is located at a position other than between the tangential end faces of the dragging element 132; for
instance, in the embodiment of figure 7, the dragging element 132 may comprise a protrusion face 135 acting as interrupting element or reflecting element cooperating with an optical sensor (not shown) .
Features described in relation to a particular embodiment can also be applied to other embodiments described. Features of different embodiments may be combined to achieve another embodiment. Features not explicitly indicated as being
essential may be omitted. o
The reference numerals used in the claims only serve as clarification when understanding the claims with a view to the exemplary embodiments described, and should not be interpreted in any way limiting.
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