Pedal force meter for bicycle
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- MINEBEAMITSUMI INC
- Filing Date
- 2026-01-05
- Publication Date
- 2026-07-30
Smart Images
Figure JP2026000061_30072026_PF_FP_ABST
Abstract
Description
Bicycle pedal force meter
[0001] This invention relates to a bicycle pedal force meter.
[0002] A strain sensor is known to be used as a force meter for bicycles. For example, Patent Document 1 discloses a force measurement module applied to a bicycle, which includes a strain sensor for detecting the strain on the bicycle's crank.
[0003] International Publication No. 2012 / 053114
[0004] With the advancement of technologies such as electric assist bicycles, the performance requirements for pedal force meters are also changing. One example of the objectives of this invention is to provide a bicycle pedal force meter that is excellent in detection accuracy and mechanical strength, and has a structure that is easy to miniaturize.
[0005] The bicycle force meter of the present invention comprises, for example, a bearing, a shaft having a portion supported by the bearing, a holder having a holding portion for holding the bearing and a radially extending deformable surface, and a plurality of strain sensors, wherein the plurality of strain sensors include a first strain sensor attached to a first portion of the deformable surface, a second strain sensor attached to a second portion of the deformable surface, and a third strain sensor attached to a third portion of the deformable surface, wherein the first strain sensor, the second strain sensor, and the third strain sensor are arranged in the circumferential direction, and the second and third portions deform more than the first portion.
[0006] This is a view of a bicycle force meter according to one embodiment, as seen in the direction of the rotation axis. This is a perspective view showing a part of the configuration of a bicycle force meter according to one embodiment. This is a cross-sectional view showing a part of the configuration of a bicycle force meter according to one embodiment. This is a cross-sectional view of a bicycle force meter according to one embodiment. This is a perspective view of the case of a bicycle force meter according to one embodiment. This is a cross-sectional view of a bicycle force meter according to one embodiment. This is a perspective view of the frame of a bicycle force meter according to one embodiment, as seen in the direction of the rotation axis. This is a perspective view showing a modified case. This is a diagram showing a modified case in which the holder and the inner surface of the frame are connected via an elastic member. This is a perspective view showing a modified holder. This is a diagram showing a modified frame.
[0007] In describing embodiments of the present invention, for convenience of explanation, the direction along the rotation axis X of the shaft S is referred to as the rotation axis direction or axial direction. In the rotation axis direction, the direction of arrow a is referred to as one side, and the direction of arrow b is referred to as the other side. The directions of arrows cd perpendicular to the rotation axis X are referred to as the radial direction. In the radial direction, the direction of arrow c moving away from the rotation axis X is referred to as the outside or one side, and the direction of arrow d moving towards the rotation axis X is referred to as the inside or the other side. In a certain member or part, the outer surface in the radial direction may be referred to as the outer circumferential surface, and the inner surface in the radial direction may be referred to as the inner circumferential surface. The direction of rotation around the rotation axis X is referred to as the circumferential direction.
[0008] The direction in which a bicycle moves when riding is called the direction of travel, and is indicated by arrow T in Figure 1. The direction opposite to the direction of travel is called the direction of reversal, and is indicated by arrow R in Figure 1. For the sake of explanation, the direction perpendicular to the direction of travel and the axis of rotation, and away from the road surface, may be called the upward direction (arrow U), and the opposite direction may be called the downward direction (arrow D). However, the "upward direction" and "downward direction" may not coincide with the vertical up and down directions when riding on slopes or when the bicycle is tilted.
[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Figure 1 is a view of a bicycle force meter (hereinafter referred to as force meter 1) according to this embodiment, in the direction of the rotation axis. However, the case 30 is omitted in Figure 1. Figure 2 is a perspective view of the sensor device 10 provided in the force meter 1. Figure 3 is a cross-sectional view of the sensor device 10 along the rotation axis X. Figure 4 is a cross-sectional view of the force meter 1 along the rotation axis X. Figures 3 and 4 are cross-sectional views corresponding to the A-A cross-section in Figure 1. Figure 5 is a perspective view of the case 30.
[0010] As shown in Figures 1 and 4, the pedal force meter 1 comprises a shaft S, a sensor device 10, a frame 20, and a case 30. The shaft S is a bicycle crankshaft. The shaft S may also be a rod connected to the crankshaft. The shaft S rotates around a rotation axis X. The frame 20 and case 30 form a housing that accommodates the sensor device 10.
[0011] The sensor device 10 includes a holder 101. The material of the holder 101 is not particularly limited. The material of the holder 101 may be, for example, steel, stainless steel, aluminum alloy, titanium, plastic, carbon fiber reinforced plastic, ceramic, or other metallic or non-metallic material. The holder 101 has a deformable surface 101a that extends in the radial direction. As shown in Figures 1 and 2, the deformable surface 101a of the holder 101 has a first portion 101a1, a second portion 101a2, and a third portion 101a3. As will be described later, the first portion 101a1, the second portion 101a2, and the third portion 101a3 are arranged at a predetermined interval in the circumferential direction.
[0012] Multiple strain sensors 103s are attached to the holder 101. The multiple strain sensors 103s include a first strain sensor 103s1, a second strain sensor 103s2, and a third strain sensor 103s3. The first strain sensor 103s1 is attached to a first portion 101a1 of the deformable surface 101a of the holder 101. The second strain sensor 103s2 is attached to a second portion 101a2 of the deformable surface 101a of the holder 101. The third strain sensor 103s3 is attached to a third portion 101a3 of the deformable surface 101a of the holder 101. The first strain sensor 103s1, the second strain sensor 103s2, and the third strain sensor 103s3 are arranged at predetermined intervals in the circumferential direction.
[0013] As shown in Figure 1, the second portion 101a2 and the third portion 101a3 of the deformable surface 101a of the holder 101 are positioned on the side of the bicycle's direction of travel (arrow T) relative to the first portion 101a1. The first portion 101a1 is positioned on the side of the shaft S in the direction of reversal (arrow R), while the second portion 101a2 and the third portion 101a3 are positioned on the side of the shaft S in the direction of travel (arrow T). As will be described later, this arrangement allows the second portion 101a2 and the third portion 101a3 of the deformable surface 101a to deform more than the first portion 101a1 when the bicycle is being ridden.
[0014] In the circumferential direction, the angle between the rotation axis X and the first part 101a1 and the second part 101a2, and the angle between the rotation axis X and the first part 101a1 and the third part 101a3 are both obtuse angles. In this embodiment, the angle between the rotation axis X and the second part 101a2 and the third part 101a3 is also obtuse. Here, the "angle between the rotation axis X and the first part 101a1 and the second part 101a2" is the angle (angle θ in Figure 1) between a virtual line segment along the radial direction connecting the rotation axis X and the center of the first strain sensor 103s1 (the central position in the circumferential direction) and a virtual line segment along the radial direction connecting the rotation axis X and the center of the second strain sensor 103s2 (the central position in the circumferential direction). １)(The same applies to the "angle formed by the rotation axis X, the second part 101a2, and the third part 101a3". The "angle formed by the rotation axis X, the second part 101a2, and the third part 101a3" refers to the angle between a virtual line segment along the radial direction connecting the rotation axis X and the center (the central position in the circumferential direction) of the second strain sensor 103s2, and a virtual line segment along the radial direction connecting the rotation axis X and the center (the central position in the circumferential direction) of the third strain sensor 103s3 (the angle θ in FIG. 1). ２ )(The same applies to the "angle formed by the rotation axis X, the first part 101a1, and the third part 101a3". The "angle formed by the rotation axis X, the first part 101a1, and the third part 101a3" refers to the angle between a virtual line segment along the radial direction connecting the rotation axis X and the center (the central position in the circumferential direction) of the first strain sensor 103s1, and a virtual line segment along the radial direction connecting the rotation axis X and the center (the central position in the circumferential direction) of the third strain sensor 103s3 (the angle θ in FIG. 1). ３ )(It is as follows.)
[0015] The angle θ １ and the angle θ ３ may be, for example, within the range of 95° to 150°, may be within the range of 100° to 140°, or may be within the range of 110° to 130°. In the illustrated form, the angle θ １ and the angle θ ３ are both 120°. The difference (absolute value) between the angle θ １ and the angle θ ３ may be, for example, 30° or less, may be 15° or less, or may be 5° or less. In the illustrated form, the difference between the angle θ １ and the angle θ ３ is 0°.
[0016] [[ID=二十六]] The angle θ ２ may be, for example, within the range of 60° to 170°, may be within the range of 100° to 140°, or may be within the range of 110° to 130°. In the illustrated form, the angle θ ２ is 120°. That is, in the illustrated form, the first strain sensor 103s1, the second strain sensor 103s2, and the third strain sensor 103s3 are arranged at equal intervals in the circumferential direction.
[0017] The direction from the rotation axis X toward the center of the first strain sensor 103s1 coincides with the backward direction (arrow R). However, the direction from the rotation axis X toward the center of the first strain sensor 103s1 may be shifted circumferentially with respect to the backward direction (arrow R) by, for example, within a range of ±0 to 30°, ±0 to 15°, or ±0 to 5°.
[0018] As shown in Figure 1, the frame 20 of the force meter 1 has portions h1, h2, and h3 that connect to an external device (for example, a bicycle frame). The portions h1, h2, and h3 that connect to the external device may be holes for inserting fastening members such as bolts. In the circumferential direction, one of the portions h1, h2, and h3 that connect to the external device is located between the first portion 101a1 and the second portion 101a2, or between the second portion 101a2 and the third portion 101a3. In the illustrated form, in the circumferential direction, the portion h1 that connects to the external device is located between the first portion 101a1 and the second portion 101a2, the portion h2 that connects to the external device is located between the second portion 101a2 and the third portion 101a3, and the portion h3 that connects to the external device is located between the third portion 101a3 and the first portion 101a1. In other words, in the circumferential direction, the first part 101a1 is positioned between parts h1 and h3 that connect to external devices, and the part h2 that connects to external devices is positioned between the second part 101a2 and the third part 101a3. This allows the first part 101a1 to be positioned in the direction of the bicycle moving backward (arrow R), and the second part 101a2 and the third part 101a3 to be positioned in the direction of the bicycle moving forward (arrow T). These parts h1, h2, and h3 that connect to external devices are formed as parts that protrude outward (radially) from the outer circumference of the frame 20. Note that the parts h1, h2, and h3 that connect to external devices may be holes formed in the outer circumference of the frame 20. However, the number of parts that connect to external devices may be one, two, or four or more.
[0019] Next, the configuration of the sensor device 10 will be described in detail with reference to Figures 2 and 3. The sensor device 10 comprises a holder 101, a bearing 102, a plurality of strain sensors 103s, a ring 104, and a substrate 105. The bearing 102 rotatably supports the shaft S relative to the holder 101.
[0020] In this embodiment, the bearing 102 is a ball bearing having an inner ring 102i and an outer ring 102o (Figure 3). The bearing 102 is not limited to a ball bearing, and may be any other type of bearing, such as a sleeve bearing. In the drawing, the bearing 102 is shown as a shielded bearing, but the bearing 102 does not have to have a shield. The ring 104 is configured to rotate together with the inner ring 102i of the bearing 102. Multiple strain sensors 103s and the substrate 105 are electrically connected.
[0021] As shown in Figure 3, the holder 101 has an inner circumferential portion (holding portion 110) that holds the bearing 102, an outer portion (outer circumferential portion 120) that surrounds the holding portion 110 in the radial direction, and a connecting portion 130 that connects the holding portion 110 and the outer circumferential portion 120. As will be described later, the connecting portion 130 is the portion of the strain generating body 101 that extends from the holding portion 110 toward the outer circumferential portion 120, and in this embodiment it is formed as a plate-shaped portion (plate). The holding portion 110 is a cylindrical portion that extends in the direction of the rotation axis. The holding portion 110 has a cylindrical shape around the rotation axis X and has an inner circumferential surface 110i. The holding portion 110 supports the shaft S via the bearing 102. In the direction of the rotation axis, one end of the holding portion 110 (direction of arrow a) is provided with a portion 111 that extends toward the shaft S.
[0022] In the direction of rotation, a plate-shaped, annular connecting portion 130 is connected to one end (direction of arrow a) of the holding portion 110. The connecting portion 130 extends radially outward. In the radial direction, an outer peripheral portion 120 is connected to the outside of the connecting portion 130. Therefore, the connecting portion 130 connects the holding portion 110 and the outer peripheral portion 120 in the radial direction. The connecting portion 130 is elastic and easily deformed with strain, partly due to the shape of the gap 140 described later. Deformation here includes curving and twisting in the directions of arrows a, b, c, and d. In the direction of rotation, the surface of the connecting portion 130 facing one side (direction of arrow a) constitutes a part of the deformable surface 101a of the holder 101.
[0023] The outer periphery 120 is a portion that can be used to attach the holder 101 to an external member, and has a bent shape and a substantially L-shaped cross-section. The outer periphery 120 is curved along the circumferential direction. As shown in Figure 2, the holder 101 has three outer peripheries 120. In this embodiment, the three outer peripheries 120 are arranged in positions that are three times symmetrical around the axis of rotation X. That is, the three outer peripheries 120 are arranged at predetermined intervals in the circumferential direction (every 120° in this embodiment). The arrangement of each of the three outer peripheries 120 corresponds to the arrangement of the first portion 101a1, the second portion 101a2, and the third portion 101a3 of the deformable surface 101a of the holder 101.
[0024] The outer periphery 120 has a portion 121 that extends in the direction of rotation axis and a flange 122. The flange 122 extends radially outward (arrow c direction) from the other end of the portion 121 that extends in the direction of rotation axis (direction of arrow b). The portion 121 of the outer periphery 120 that extends in the direction of rotation axis is provided with a first projection 123 (see Figure 2) that projects radially outward and a second projection 124 (see Figure 3) that projects radially inward.
[0025] As shown in Figure 3, in the radial direction, the outer periphery 120 faces the holding portion 110 with a gap 140 in between. In the rotation axis direction, the gap 140 is formed on the other side of the connecting portion 130 (in the direction of arrow b). Due to the presence of the gap 140, the outer periphery 120 and the holding portion 110 are separated by a predetermined distance in the radial direction. The gap 140 is formed to be a curved space along the circumferential direction.
[0026] Multiple strain sensors 103s are attached to the deformable surface 101a of the holder 101 to detect strain on the deformable surface 101a. Each of the multiple strain sensors 103s is positioned in the portion where the outer periphery 120 is connected.
[0027] The first strain sensor 103s1, the second strain sensor 103s2, and the third strain sensor 103s3, each included in the plurality of strain sensors 103s, are mounted on a deformable surface 101a such that the orientation of the grid (not shown) is in a predetermined direction (for example, radial, circumferential, or oblique to the radial direction, oblique to the circumferential direction, etc.). The first strain sensor 103s1, the second strain sensor 103s2, and the third strain sensor 103s3 may each have multiple grids with different orientations. The first strain sensor 103s1, the second strain sensor 103s2, and the third strain sensor 103s3 may each be strain gauges. Strain gauges can detect surface strain as a change in resistance. The plurality of strain sensors 103s may also be various other sensors such as resistive elements and piezoelectric elements.
[0028] In the radial direction, the bearing 102 is positioned inside the holding portion 110 of the holder 101 (in the direction of arrow d). The inner ring 102i of the bearing 102 is fixed to the outer circumferential surface of the shaft S by adhesive or press-fitting. The outer ring 102o of the bearing 102 is fixed to the inner circumferential surface 110i of the holding portion 110 of the holder 101 by adhesive or press-fitting. The portion 111 of the holder 101 that extends toward the shaft S is in contact with one end face (in the direction of arrow a) of the outer ring 102o of the bearing 102 in the axial direction. The holding portion 110 of the holder 101 and the portion 111 that extends toward the shaft S house the bearing 102 and restrict the movement of the bearing 102.
[0029] An annular substrate 105 is positioned on the deformable surface 101a of the holder 101. The substrate 105 is, for example, a flat printed circuit board (PCB) on which circuits and electronic components (neither shown) are arranged. The substrate 105 is positioned between the holder 101 and a plurality of strain sensors 103s. The substrate 105 surrounds the ring 104 from the radial outside (direction of arrow c). The substrate 105 extends parallel or substantially parallel to the deformable surface 101a of the holder 101. The substrate 105 has a surface (front) 105a and a surface (back) 105b. In the direction of rotation, surface 105a faces one side (direction of arrow a) and surface 105b faces the other side (direction of arrow b). Surfaces 105a and 105b extend radially.
[0030] Multiple strain sensors 103s are arranged between the substrate 105 and the holder 101 in the direction of rotation. The substrate 105 and the multiple strain sensors 103s are electrically connected by a conductive member or the like (not shown).
[0031] As shown in Figure 2, a sensor 105s is positioned on the surface 105a of the substrate 105. The sensor 105s is attached to the inner edge of the substrate 105 in the radial direction. As will be described later, this inner edge of the substrate 105 or the sensor 105s is positioned in a location that overlaps in the axial direction with the position (in the radial direction) of the outer ring 102o of the bearing 102 or the position (in the radial direction) of the holding portion 110 of the holder 101. In particular, the sensor 105s is positioned in the axial direction facing the outer ring 102o of the bearing 102 or the holding portion 110 of the holder 101 via the substrate 105. The sensor 105s is a sensor capable of detecting magnetic flux, and may be, for example, a Hall element, a Hall IC, or a magnetoresistive element. The sensor 105s detects the magnetic flux or change in magnetic flux of the magnet M, which will be described later and is located on the ring 104, in the radial direction. The sensor 105s is positioned in the radial direction facing the magnet M. The substrate 105 is provided with, for example, a circuit (not shown) for amplifying signals from the sensor 105s and a plurality of strain sensors 103s and communicating with the outside.
[0032] The ring 104 is an annular member that surrounds the shaft S from the outside in the radial direction. In the radial direction, the ring 104 is positioned inside the substrate 105. In the radial direction, the ring 104 and the substrate 105 are separated by a predetermined distance. The ring 104 and the substrate 105 have overlapping positions in the rotation axis direction and face each other in the radial direction.
[0033] As shown in Figure 3, the ring 104 comprises a flange 104a extending radially outward, a plate portion 104b extending radially inward, and a cylindrical portion 104c. The cylindrical portion 104c is a cylindrical part extending in the direction of the rotation axis. The flange 104a and the plate portion 104b are connected to the cylindrical portion 104c. In the direction of the rotation axis, the flange 104a is positioned to one side (in the direction of arrow a) of the plate portion 104b.
[0034] An annular, plate-shaped magnet M is arranged on the ring 104. In the direction of rotation, the magnet M is attached to one side of the flange 104a (direction of arrow a). The magnet M is arranged coaxially with the shaft S. The magnet M is, for example, alternately magnetized in the circumferential direction, and the inner surface of the magnet M has multiple sets of two different magnetic poles (N pole, S pole) arranged alternately. The positions of the magnet M and the sensor 105s, which is placed on the substrate 105, overlap in the axial direction. In the radial direction, the distance between the magnet M and the sensor 105s is within the range in which the sensor 105s can detect the magnetic flux of the magnet M. Note that the magnet M does not have to be annular, and may be multiple magnets M arranged in an annular shape. In this case, the inner surfaces of two adjacent magnets M have different magnetic poles. In this case, the magnet M may be attached to one or more locations in the circumferential direction of the ring 104. The sensor device 10 can detect the rotational speed or rotational position of the shaft S using the sensor 105s and the magnet M. However, the presence of the sensor 105s, ring 104, and magnet M in the force meter 1 is optional. Furthermore, if the sensor 105s can detect magnetic flux, a magnet M magnetized in the axial direction or multiple magnets M arranged in a ring shape may be used.
[0035] In the direction of rotation, the ring 104 is positioned on one side of the bearing 102 (in the direction of arrow a). The inner ring 102i of the bearing 102 protrudes further in the axial direction (in the direction of arrow a) than the outer ring 102o. The plate portion 104b and the cylindrical portion 104c of the ring 104 are connected to the inner ring 102i of the bearing 102. As a result, the ring 104 rotates together with the inner ring 102i of the bearing 102.
[0036] Next, with reference to Figure 4, the sensor device 10 will be described in detail as to how it is housed in the frame 20 and case 30. In the direction of rotation, the sensor device 10 is housed between the frame 20 and case 30. The frame 20 may also serve as the housing for an actuator, for example, which includes a reduction gear and a motor that rotates the gears of the reduction gear. The material of the frame 20 and case 30 is not particularly limited. The material of the frame 20 and case 30 may be, for example, an aluminum alloy, a magnesium alloy, steel, stainless steel, plastic, carbon fiber reinforced plastic, a metal matrix composite, or other metallic or non-metallic material. The material of the frame 20 may be the same as or different from the material of the case 30.
[0037] In the radial direction, the shaft S is surrounded by the sensor device 10, the frame 20, and the case 30. The shaft S has a portion Sa supported by the bearing 102. A groove Sb extending in the circumferential direction is formed in portion Sa of the shaft S. Portion Sa of the shaft S is fixed to the inner ring 102i of the bearing 102 on one side (direction of arrow a) and the other side (direction of arrow b) of the groove Sb in the rotation axis direction. The shaft S has an annular portion Sc that protrudes radially outward. In the rotation axis direction, the annular portion Sc is in contact with the other end face (direction of arrow b) of the inner ring 102i of the bearing 102.
[0038] The frame 20 comprises a bottom portion 21, an inner wall 22, and an outer wall 23. In the direction of rotation axis, the sensor device 10 is positioned on one side (direction of arrow a) of the bottom portion 21 of the frame 20. In this embodiment, in the direction of rotation axis, the sensor device 10 is positioned on the side of the bottom portion 21 opposite to the space MS through which a drive device such as a motor is housed. A hole 21h is formed in the bottom portion 21 of the frame 20 through which a shaft S is inserted. The inner wall 22 and outer wall 23 of the frame 20 protrude from the bottom portion 21 to one side (direction of arrow a) in the direction of rotation axis. The outer wall 23 of the frame 20 extends in the direction of rotation axis and is formed in a cylindrical shape. In the radial direction, the outer periphery 120 (particularly the flange 122) of the holder 101 of the sensor device 10 is positioned between the inner wall 22 and the outer wall 23 of the frame 20.
[0039] The case 30 is a member that covers the sensor device 10 and the frame 20 from one side (in the direction of arrow a) in the rotation axis direction. The case 30 includes a lid 31 that faces the bottom 21 of the frame 20 in the rotation axis direction, and a cylinder 32 that extends in the rotation axis direction. A hole 31h through which the shaft S is inserted is formed in the lid 31 of the case 30. The cylinder 32 protrudes from the outer peripheral portion of the lid 31 to the other side (in the direction of arrow b) in the rotation axis direction. In the radial direction, the cylinder 32 is sandwiched between the outer peripheral portion 120 of the holder 101 and the outer wall 23 of the frame 20. And the cylinder 32 is disposed in a space formed between the outer peripheral portion 120 (the portion 121 extending in the rotation axis direction) of the holder 101 and the outer wall 23 of the frame 20.
[0040] FIG. 5 is a perspective view of the case 30. In the radial direction, a flange 33 is formed on the outside of the cylinder 32. The flange 33 is provided with portions (in the illustrated form, four holes 33h) for connecting the case 30 to the frame 20. The four holes 33h of the case 30 are formed at positions corresponding to the four holes 24 (see FIG. 8) of the frame 20. By inserting a fastening member such as a bolt through the holes 33h and the holes 24, the case 30 is fixed to the frame 20.
[0041] As shown in FIG. 5, on the inner surface 34 (the inner peripheral surface of the cylinder 32) of the case 30, three protruding portions 34p protruding inward in the radial direction are provided. The protruding portion 34p protrudes toward the outer peripheral portion 120 of the holder 101.
[0042] FIG. 6 is a cross-sectional view of the pedometer 1 in a cross-sectional plane perpendicular to the rotation axis X (the cross-sectional plane indicated by B - B in FIG. 4). In FIG. 6, the cross-sectional surface of the outer peripheral portion 120 (the portion 121 extending in the rotation axis direction) of the holder 101 is visible. As shown in FIG. 6, a part (the first protruding portion 123) of the outer peripheral portion 120 of the holder 101 and the inner surface 34 of the case 30 are connected in the radial direction. The first protruding portion 123 of the holder 101 protrudes toward the inner surface 34 of the case 30 and is in contact with the protruding portion 34p of the inner surface 34 of the case 30 in the radial direction. A gap G is formed between the other part of the outer peripheral portion 120 of the holder 101 and the inner surface 34 of the case 30.
[0043] Figure 7 is a perspective cross-sectional view of the same cross-section as in Figure 6. Figure 7 shows an enlarged view of the area enclosed by the dashed line in Figure 6. As shown in Figure 7, the outer periphery 120 of the holder 101 is also connected to the inner wall 22 of the frame 20. The second projection 124 of the holder 101 protrudes toward the inner wall 22 of the frame 20 and is in contact with the inner wall 22 in the radial direction.
[0044] The first protrusion 123 on the outer circumference 120 of the holder 101 and the protrusion 34p on the case 30 may be provided only by one of them. Also, the second protrusion 124 is not required to be provided on the outer circumference 120 of the holder 101.
[0045] Figure 8 is a view of the frame 20 from one side to the other in the direction of the rotation axis (in the direction of arrow b in Figure 4). The inner surface 25 of the frame 20 (the inner circumferential surface of the outer wall 23) is provided with a plurality of protrusions 25p (five in the illustrated configuration) that project inward in the radial direction. As shown in Figures 6 and 7, the plurality of protrusions 25p contact the outer circumferential portion 120 of the holder 101 in the circumferential direction. The plurality of protrusions 25p include one or more protrusions 25pe on one side of the outer circumferential portion 120 of the holder 101 (in the direction of arrow e in Figures 6 and 8) and one or more protrusions 25pf on the other side (in the direction of arrow f in Figures 6 and 8) in the circumferential direction. In this way, the plurality of protrusions 25p of the frame 20 restrict the rotation of the holder 101.
[0046] Alternatively, the force meter 1 may have a structure that restricts the rotation of the holder 101 by the case 30a shown in Figure 9. The inner surface 34a of the case 30a (the inner circumferential surface of the cylinder 32a) is provided with a plurality of (two in the illustrated example) protrusions 30ap that project inward in the radial direction. The plurality of protrusions 30ap contact the outer circumferential portion 120 of the holder 101 in the circumferential direction. In the circumferential direction, the rotation of the holder 101 is restricted if one of the plurality of protrusions 30ap is on one side of the outer circumferential portion 120 of the holder 101 and the other of the plurality of protrusions 30ap is on the other side of the outer circumferential portion 120 of the holder 101.
[0047] Alternatively, the rotation of the holder 101 of the force meter 1 may be restricted by the structure shown in Figure 10. In the modified example shown in Figure 10, the holder 101 and the inner surface 25 of the frame 20 are connected radially via a plurality of elastic members 40. The plurality of elastic members 40 include elastic members 41, 42, and 43. In the circumferential direction, elastic member 41 is positioned between the first portion 101a1 and the second portion 101a2 of the holder 101, elastic member 42 is positioned between the second portion 101a2 and the third portion 101a3 of the holder 101, and elastic member 43 is positioned between the third portion 101a3 and the first portion 101a1 of the holder 101. In the circumferential direction, elastic members 41, 42, and 43 are in contact with the outer periphery 120 of the holder 101. The plurality of elastic members 40 are, for example, resin members. The plurality of elastic members 40 restrict the rotation of the holder 101. Furthermore, the elasticity of the multiple elastic members 40 shortens the time it takes for the deformed holder 101 to return to its original shape, thereby suppressing the effects of hysteresis in the force meter 1.
[0048] Alternatively, the rotation of the holder 201 of the force meter 1 may be restricted by the holder 201 shown in Figure 11 and the frame 20a shown in Figure 12. As shown in Figure 11, the holder 201 has an inner circumference 210 and an outer circumference 220. The outer circumference 220 has a portion 221 that extends in the direction of rotation axis and a flange 222. The flange 222 extends radially outward (arrow c direction) from the other end (direction of arrow b) in the direction of rotation axis of the portion 221 that extends in the direction of rotation axis. In the direction of rotation axis, the other side (direction of arrow b) of the flange 222 is provided with a curved protrusion 222p. The protrusion 222p projects outward (arrow b direction) in the direction of rotation axis. As shown in Figure 12, three curved holes 20ah are formed in the bottom portion 21a of the frame 20a. The hole 20ah has a shape corresponding to the protrusion 222p of the holder 201. The outer circumference 220 (protrusion 222p) of the holder 201 and the frame 20a (hole 20ah) are fitted together, thereby restricting the circumferential rotation of the holder 201.
[0049] The pedal force meter 1 according to this embodiment has the above configuration. Crank arms (not shown) are connected to one end (direction of arrow a) and the other end (direction of arrow b) in the rotation axis direction of the shaft S. A pedal is attached to each crank arm. When the rider presses down on one side of the bicycle pedal, one end of the shaft S (first end) closer to the pressed pedal tries to tilt in the direction of the pedaling force, and the other end of the shaft S on the opposite side (second end) tries to tilt in the opposite direction of the pedaling force. As a result, a part of the holder 101 is pressed radially outward by the bearing 102, and another part of the holder 101 is pulled radially inward by the bearing 102. Since the outer circumference 120 of the holder 101 is attached to the frame 20 and the case 30, stress is concentrated near the outer circumference 120. As a result, strain occurs on the deformable surface 101a of the holder 101, and this strain is detected by a plurality of strain sensors 103s. The sensor device 10 can obtain the pedaling force acting on the shaft S from the strain detected by the multiple strain sensors 103s.
[0050] The deformable surface 101a of the force meter 1 has a first portion 101a1, a second portion 101a2, and a third portion 101a3, to which a first strain sensor 103s1, a second strain sensor 103s2, and a third strain sensor 103s3 are attached, respectively. In the circumferential direction, the angles between the rotation axis X and the first portion 101a1 and the second portion 101a2, and the angles between the rotation axis X and the first portion 101a1 and the third portion 101a3 are both obtuse angles. The arrangement of the first portion 101a1, the second portion 101a2, and the third portion 101a3 ensures that when a certain force is applied, the magnitude and direction of deformation in the first portion 101a1, the second portion 101a2, and the third portion 101a3 are different. Therefore, by combining the strain information detected by the first strain sensor 103s1, the second strain sensor 103s2, and the third strain sensor 103s3, information on the direction and strength of the pedaling force acting on the shaft S can be obtained with high accuracy. Depending on the detected direction and strength of the pedaling force, the output of the motor of, for example, an electric assist bicycle may be controlled.
[0051] The pedaling force when cycling is predominantly in the downward direction (direction D in Figure 1). In the force meter 1, the first part 101a1, the second part 101a2, and the third part 101a3 of the deformable surface 101a are arranged as described above. As a result, the first part 101a1 is less deformable by pedaling force compared to the second part 101a2 and the third part 101a3. In other words, the second part 101a2 and the third part 101a3 of the deformable surface 101a are positioned to deform more than the first part 101a1 during normal use of the bicycle. By arranging them in this way, the majority of the pedaling force applied to the shaft S can be received by the two parts (second part 101a2 and third part 101a3), thereby improving mechanical strength.
[0052] The pedal force meter 1 has a simple configuration comprising a holder 101 and multiple strain sensors 103s. Furthermore, since it is possible to detect pedal force information in all directions using the first strain sensor 103s1, the second strain sensor 103s2, and the third strain sensor 103s3, the overall size of the device can be reduced.
[0053] In the force meter 1, when the outer circumference 120 of the holder 101 is pushed radially outward in response to the pedaling force, the first projection 123 of the holder 101 is pressed against the projection 34p of the case 30, and stress concentrates near the first projection 123. Conversely, when the outer circumference 120 of the holder 101 is pulled radially inward, the second projection 124 of the holder 101 is pressed against the inner wall 22 of the frame 20, and stress concentrates near the second projection 124. In this way, because the points where stress concentrates are limited, the force meter 1 has, for example, a high signal-to-noise ratio and excellent detection accuracy.
[0054] In the force meter 1, the rotation of the holders 101 and 201 is restricted by the above-described configuration or a modified configuration. By adopting such a configuration, the rotation of the holders 101 and 201 can be suppressed without using fastening members, thus reducing the number of parts.
[0055] The pedal force meter 1 can detect not only pedal force information but also the rotational speed or rotational position of the shaft S using the sensor 105s and magnet M. Here, the substrate 105 to which the sensor 105s is attached is positioned on the deformable surface 101a of the holder 101. Therefore, the overall thickness of the device can be reduced.
[0056] Although preferred embodiments of the bicycle force meter of the present invention have been described above, the bicycle force meter of the present invention is not limited to the configuration of the above-described embodiments. For example, the first portion of the deformable surface of the holder may be positioned on the side of the shaft S in the direction of travel, and the second and third portions may be positioned on the side of the shaft S in the direction of reversal. Also, if necessary, the first portion 101a1 may be positioned in the circumferential direction between portions h1 and h2 that connect to an external device, and the portion h2 that connects to an external device may be positioned between the second portion 101a2 and the third portion 101a3. Thus, the third portion 101a3 may be positioned in the direction of travel of the bicycle (arrow T), and the second portion 101a2 and the third portion 101a3 may be positioned in the direction of reversal of the bicycle (arrow R), or these arrangements may not be made, and can be selected as appropriate. The outer circumference of the holder and the housing or case may be connected without a protruding portion. The force meter of the present invention may not have a case. The sensor device may be located in the space of the frame where the drive device, such as the motor, is housed. The sensor device may omit the sensor and magnet capable of detecting magnetic flux. The circuit board may be separated from the holder. The end of the shaft may have a spline (a shape with circumferentially aligned bumps and grooves) as shown in the figure, or it may have another shape. The bicycle may be an electric assist bicycle, an electric bicycle, or any other type of bicycle.
[0057] Furthermore, those skilled in the art can modify the bicycle force meter of the present invention as appropriate, and change the shape, dimensions, and combinations of various components, in accordance with conventionally known knowledge. As long as such modifications still possess the configuration of the present invention, they are of course included within the scope of the present invention.
[0058] 1...force meter, 10...sensor device, 20...frame, 30...case, 41, 42, 43...elastic members, 101...holder, 101a...deformable surface, 101a1...first part, 101a2...second part, 101a3...third part, 102...bearing, 103s...multiple strain sensors, 103s1...first strain sensor, 103s2...second strain sensor, 103s3...third strain sensor, 110...holding part, S...shaft, Sa...part supported by the bearing, X...rotating shaft, h1, h2, h3...parts connected to external devices.
Claims
1. A bicycle force meter comprising: a bearing; a shaft having a portion supported by the bearing; a holder having a holding portion for holding the bearing and a radially extending deformable surface; and a plurality of strain sensors, wherein the plurality of strain sensors include: a first strain sensor attached to a first portion of the deformable surface; a second strain sensor attached to a second portion of the deformable surface; and a third strain sensor attached to a third portion of the deformable surface, wherein the first strain sensor, the second strain sensor, and the third strain sensor are arranged in the circumferential direction, and the second and third portions deform more than the first portion.
2. The bicycle force meter according to claim 1, wherein in the circumferential direction, the angle between the axis of rotation of the shaft and the first and second portions, and the angle between the axis of rotation of the shaft and the first and third portions are both obtuse angles.
3. The bicycle force meter according to claim 1 or 2, wherein a portion for connecting to an external device is arranged between the first portion and the second portion, or between the second portion and the third portion, in the circumferential direction.
4. The bicycle force meter according to any one of claims 1 to 3, wherein the second and third parts are positioned on the side of the bicycle in the direction of travel relative to the first part.
5. A bicycle force meter according to any one of claims 1 to 4, comprising a frame and a case covering the frame, wherein a portion of the outer circumference of the holder is connected to the inner surface of the case.
6. A gap is formed between the other part of the outer circumference of the holder and the inner surface of the case, the bicycle force meter according to claim 5.
7. The portion of the outer circumference of the holder is a projection that protrudes toward the inner surface of the case, the bicycle force meter according to claim 6.
8. The bicycle force meter according to claim 5, wherein the inner surface of the case has a projection that protrudes toward the outer circumference of the holder.
9. A bicycle force meter according to any one of claims 1 to 4, comprising a frame, or a housing formed by the frame and a case covering the frame, wherein the inner surface of the frame or the inner surface of the case has a protrusion that contacts the holder in the circumferential direction.
10. A bicycle force meter according to any one of claims 1 to 4, comprising a frame, wherein in the radial direction, the holder and the inner surface of the frame are connected via an elastic member, and in the circumferential direction, the outer periphery of the holder and the elastic member are in contact.
11. A bicycle force meter according to any one of claims 1 to 4, comprising a frame, wherein the outer circumference of the holder and the frame are fitted together.