JP2012021783A - Torque detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a torque detector that is easily assembled, lightweight, and inexpensive, without using special parts or heavy parts.SOLUTION: The torque detector of the present invention is provided with a roughly rectangular slot 30 inside a housing 25a supporting a rolling bearing 26a of a shaft 24 in a case 22 and mounts a distortion detecting element 32 on a side wall 31 positioned inside the slot 30 and facing the rolling bearing 26a, so as to detect a pedaling force applied to a pedal as a torque.

Description

  The present invention relates to a torque detection device for detecting the torque of a shaft driven by a pedal of a bicycle.

  In an electric bicycle, the pedaling force of the person acting on the pedal is detected as torque, and when this torque value exceeds a preset value, the electric motor is automatically driven to add auxiliary driving force, It is configured so that it can be easily driven on slopes. Further, even in a general bicycle, the pedaling force of a person acting on the pedal is detected as a torque, and when this torque value exceeds a preset value, the gear can be automatically switched to run at an optimum gear ratio. There is something that is configured as follows.

  FIG. 5A is a cross-sectional view of a bottom bracket portion of an electric bicycle equipped with a conventional torque detection device, and FIG. 5B is an enlarged view of portion A in FIG. 5A (see Patent Document 1). 5 (a) and 5 (b), reference numeral 1 denotes a bottom bracket portion of an electric bicycle. A shaft 4 having screw holes 3a and 3b at both ends is inserted into the housing 2, and is freely rotatable through rolling bearings 5a and 5b. It is supported by. Reference numeral 6a denotes a crank having a fitting hole at the base, which is fitted to one end of the shaft 4 and fixed by a bolt 7a screwed into the screw hole 3a. (Not shown) is rotatably mounted. Reference numeral 6b denotes a crank provided with a cylindrical boss 8 having a fitting hole at the base, and the fitting hole is fitted to the other end of the shaft 4 and fixed by a bolt 7b screwed into the screw hole 3b. A pedal (not shown) is rotatably mounted at the tip. Reference numeral 10 denotes a torque detection device, which includes a cylindrical portion 11 and a flange 12, and includes a detection portion 13 that generates a torsional stress when a pedal is depressed, and a bottomed cylindrical coil unit having detection coils 14a and 14b mounted on the inner periphery. It consists of 15. The detection unit 13 is made of a magnetic alloy such as an Fe—Ni alloy, and a hole through which the shaft 4 is inserted is provided at the center of the cylindrical unit 11. The detector 13 is fixed to the boss 8 of the crank 6b by bolts 16a and 16b. The flange 12 of the detection unit 13 is fixed to the gear holding unit 17 by bolts 18a and 18b, and a gear 19 having a chain (not shown) is attached to the gear holding unit 17 by bolts 20a and 20b. It is fixed. Furthermore, magnetic anisotropies in opposite directions are given to portions of the cylindrical portion 11 of the detection portion 13 that face the detection coils 14a and 14b.

  When the pedal 6 is depressed and the crank 6b is rotated in the forward direction of the bicycle, the rotational force is transmitted to the gear 19 via the crank 6b, the boss 8, the detection unit 13, and the gear holding unit 17. At this time, torsional stress is generated in the detection unit 13 integrally coupled with the crank 6b due to the rotational force of the crank 6b and the tension of the chain. As a result, tensile stress is applied to the portion of the cylindrical portion 11 of the detection portion 13 that faces the detection coil 14a, and compressive stress is applied to the portion that faces the detection coil 14b. Increases or decreases the permeability. As a result, the self-inductances of the detection coils 14a and 14b change, and an output voltage corresponding to the torque applied to the shaft 4 can be obtained from the bridge circuit including these detection coils.

JP-A-8-338773

  However, in an electric bicycle or the like using the above conventional torque detection device, a crank having a cylindrical boss having a fitting hole in the base, and a magnetic alloy having a portion having magnetic anisotropy in opposite directions. Since a special part such as a detection part and a detection coil have to be used, there is a problem that not only the assembly is complicated and the weight reduction is difficult, but also the cost becomes high.

  The present invention solves the above-described conventional problems, and provides a torque detector that is configured without using special parts or heavy parts, is easy to assemble, is lightweight, and is inexpensive.

  In order to achieve the above object, the present invention has the following configuration.

  The invention according to claim 1 is a housing, a front wheel side shaft that passes through the housing, a rolling bearing that is fitted to the front wheel side shaft, a housing portion that supports an outer side surface of the rolling bearing, and the front wheel side One end is fixed to the shaft, and a pedal is rotatably provided at the other end, and a crank that transmits a pedaling force applied to the pedal, a gear that is fixed to the front wheel shaft, and a rotational movement of the gear are transmitted to the rear. A chain for driving the wheel, and a slot having a substantially rectangular shape extending in the vertical direction is provided in the housing portion in the vicinity of the outer side surface on the rear wheel side of the rolling bearing, and is opposed to the rolling bearing in the slot. A strain detecting element is mounted on the side wall, and when the pedal moves in the rear wheel direction by depressing the pedal, it is generated on the side wall facing the rolling bearing in the slot. In this configuration, the pedal force applied to the pedal is detected, and according to this configuration, the distortion generated on the side wall facing the rolling bearing in the slot provided in the housing portion is detected and applied to the shaft. Because it is possible to directly detect the treading force that is applied, a crank with a cylindrical boss with a fitting hole in the base and a magnetic alloy detector with parts with magnetic anisotropy in opposite directions are used. It is configured without using parts, heavy detection coils, and the like, and has the effect of providing a torque detection device that is easy to assemble, lightweight, and inexpensive.

  According to a second aspect of the present invention, in particular, the rear wheel side of the outer side surface of the rolling bearing is only in the vicinity of a horizontal line passing through the center of the rolling bearing and in the vicinity of a vertical line passing through the center of the rolling bearing. According to this configuration, when the shaft moves in the rear wheel direction by stepping on the pedal, stress concentrates on the side wall facing the rolling bearing in the slot. Distortion occurs. Thereby, it has the effect that the pedal effort applied to a pedal can be detected more accurately as torque.

  In the invention according to claim 3 of the present invention, in particular, the strain detecting element is a MEMS strain detecting element. According to this configuration, a large electrical output can be obtained for a certain strain. A large electrical output can be obtained even when the applied pedaling force is small, and this has the effect that the pedaling force applied to the pedal can be detected with higher accuracy as torque.

  As described above, the torque detection device of the present invention includes a housing, a front wheel side shaft that passes through the housing, a rolling bearing that is fitted to the front wheel side shaft, a housing portion that supports an outer side surface of the rolling bearing, One end is fixed to the front wheel side shaft, and a pedal is rotatably provided at the other end, and a crank for transmitting a pedaling force applied to the pedal, a gear fixed to the front wheel side shaft, and a rotational movement of the gear are transmitted. A slot for driving a rear wheel, and a slot having a substantially rectangular shape extending in the vertical direction in the housing portion and extending in the vertical direction in the vicinity of the outer side surface of the rolling bearing on the rear wheel side, and the rolling bearing in the slot A strain detecting element is mounted on the side wall facing the wheel, and when the shaft moves in the rear wheel direction by stepping on the pedal, it is attached to the rolling bearing in the slot. Detects the pedal force applied to the pedal by detecting the strain generated on the facing side wall, and detects the strain generated on the side wall facing the rolling bearing in the slot provided in the housing. Special parts such as a crank with a cylindrical boss with a fitting hole in the base and a magnetic alloy detector with parts with opposite magnetic anisotropy Further, it is configured without using a heavy detection coil and the like, and this provides an excellent effect that it is possible to provide a torque detection device that is easy to assemble, lightweight, and inexpensive.

(A) Sectional drawing of the bottom bracket part of the electric bicycle carrying the torque detection apparatus in Embodiment 1 of this invention, (b) BB sectional drawing of (a) (A) The figure which shows the state of the distortion which generate | occur | produces in the side wall facing the rolling bearing in the slot provided in the housing part when the tension | tensile_strength to the rear-wheel side by a chain is applied to a shaft, The figure which shows the state of the distortion which generate | occur | produces in the side wall facing the rolling bearing in the slot provided in the housing part when torque is applied. (A) Sectional drawing of the bottom bracket part of the electric bicycle carrying the torque detection apparatus in Embodiment 2 of this invention, (b) B'-B 'sectional view taken on the line of (a). (A) Top view of a MEMS strain detection element used in the torque detection device according to Embodiment 3 of the present invention, (b) A cross-sectional view taken along the line CC of (a), (c) A DD line of (a) Sectional drawing, (d) Detailed view of part E in (b) (A) Sectional view of the bottom bracket part of an electric bicycle equipped with a conventional torque detection device, (b) A part enlarged view of (a)

(Embodiment 1)
Hereinafter, the first aspect of the present invention will be described with reference to the first embodiment. Fig.1 (a) shows sectional drawing when the bottom bracket part 21 of the electric bicycle carrying the torque detection apparatus in Embodiment 1 of this invention is cut | disconnected horizontally. In FIG. 1 (a), a shaft 24 having screw holes 23a, 23b at both ends is inserted into the housing 22, and the rolling is held in housing portions 25a, 25b attached to the openings at both ends of the housing 22. The bearings 26a and 26b are rotatably supported. Reference numeral 27a denotes a crank having a fitting hole at the base, which is fitted to one end of the shaft 24 and fixed by a bolt 28a screwed into the screw hole 23a. (Not shown) is rotatably mounted. Reference numeral 27b denotes a crank having a fitting hole in the base, and the fitting hole is fitted to the other end of the shaft 24 and fixed by a bolt 28b screwed into the screw hole 23b. A pedal (not shown) is rotatably mounted. A gear 29 is fixed to the shaft 24.

  FIG.1 (b) shows the BB sectional drawing in Fig.1 (a). In FIG. 1B, the arrow direction indicates the rear wheel side, and the housing portion 25a supports the outer side surface of the rolling bearing 26a over the entire circumference. The housing portion 25a is provided with a substantially rectangular slot 30 extending in the vertical direction in the vicinity of the outer side surface on the rear wheel side of the rolling bearing 26a, and a side wall facing the rolling bearing 26a in the slot 30. A strain detecting element 32 made of a strain gauge is mounted on 31. Similarly, the housing portion 25b supports the outer side surface of the rolling bearing 26b over the entire circumference.

  When a chain (not shown) is applied to the gear 29 and a tension is applied between the gear 29 and the rear wheel, the shaft 24 moves to the rear wheel side, so that the slot as shown in FIG. Distortion is generated on the side wall 31 facing the rolling bearing 26 a in 30. As a result, tensile strain acts on the strain detection element 32 and the resistance value increases. Therefore, an output voltage corresponding to the tension is generated in a bridge circuit composed of the strain detection element 32 and three fixed resistors. Next, when the pedal is depressed to rotate the crank 27b in the forward direction of the bicycle, the rotational force is transmitted to the crank 27b and the shaft 24, so that the shaft 24 moves to the rear wheel side, and FIG. As shown in b), a larger strain is generated on the side wall 31 facing the rolling bearing 26 a in the slot 30. As a result, the resistance value of the strain detection element 32 changes, and an output voltage corresponding to the torque applied to the shaft 24 is obtained in the bridge circuit composed of the strain detection element and the three fixed resistors.

  As described above, the torque detection device according to the first embodiment of the present invention can directly detect the pedaling force applied to the shaft by detecting the distortion generated in the side wall facing the rolling bearing in the slot provided in the housing portion. Therefore, special parts such as a crank with a cylindrical boss having a fitting hole in the base, a magnetic alloy detector having parts with magnetic anisotropies in opposite directions, a heavy detection coil, etc. Thus, the number of parts can be reduced, and a torque detector that is easy to assemble, lightweight, and inexpensive can be provided.

  In the torque detector according to the first embodiment of the present invention, housing portions 25a and 25b are attached to the opening portions at both ends of the housing 22, and the shafts are provided via the rolling bearings 26a and 26b held in the housing portions 25a and 25b. 24, the rolling bearings 26a and 26b for supporting the shaft 24 rotatably on the casing 22 are directly attached to the casing 22 without using the housing portions 25a and 25b, and the rolling bearing 26a is mounted in the casing 22. A substantially rectangular slot 30 extending in the vertical direction close to the outer side surface on the rear wheel side may be provided.

(Embodiment 2)
The second aspect of the present invention will be described below with reference to the second aspect of the present invention. FIG. 3A is a cross-sectional view when the bottom bracket portion 21 of the electric bicycle equipped with the torque detection device according to Embodiment 2 of the present invention is cut horizontally, and FIG. 3B is B ′ in FIG. -B 'sectional view taken on the line is shown. In the second embodiment of the present invention, components having the same configuration as the configuration of the first embodiment of the present invention described above are denoted by the same reference numerals, and the description thereof is omitted.

  3 (a) and 3 (b), the second embodiment of the present invention differs from the first embodiment of the present invention described above in that the rear wheel side of the rolling bearing 26a is centered on the rolling bearing 26a. A notch portion 33 is provided in the housing portion 25a so as to come into contact with the housing portion 25a only in the vicinity of the horizontal portion H passing through and the portion V near the vertical line passing through the center of the rolling bearing 26a.

  In the torque detection device according to the second embodiment of the present invention, when stepping on the pedal and rotating the crank 27b in the forward direction of the bicycle, the notch 33 is formed in the housing 25a on the rear wheel side of the outer side surface of the rolling bearing 26a. Since the shaft 24 can move freely in the horizontal direction and stress concentrates on the side wall 31 facing the rolling bearing 26 a in the slot 30, a large strain is generated on the side wall 31. As a result, the torque detection device according to the second embodiment of the present invention has an operational effect that the pedaling force applied to the pedal can be detected with higher accuracy as the torque.

(Embodiment 3)
The third aspect of the present invention will be described below with reference to the third aspect of the present invention. In the third embodiment of the present invention, the strain detection element is a MEMS strain detection element to which a micromachining technology called MEMS (Micro Electro Mechanical System) technology is applied, and the frequency and impedance greatly fluctuate even if the applied load is small. It is a highly accurate vibrator. The load and strain can be measured simply and with high accuracy simply by sticking such a micromechanical vibrator to a strained object.

4A is a top view of the MEMS strain sensing element 40, FIG. 4B is a cross-sectional view taken along line CC of FIG. 4A, and FIG. 4C is a DD line of FIG. 4A. FIG. 4D is a detailed sectional view of a portion E in FIG. 4B. 4A to 4D, reference numeral 41 denotes a semiconductor substrate made of silicon or the like, and an insulating layer made of a silicon oxide layer or a silicon nitride layer is formed on the surface of the semiconductor substrate 41. Reference numeral 42 denotes a beam portion formed by etching the semiconductor substrate 41, and this beam portion 42 constitutes a beam-like vibrating body whose natural frequency changes due to the action of a mechanical quantity. Reference numeral 43 denotes a fixed portion surrounding the beam portion 42, and the fixed portion 43 supports both ends of the beam-like vibrating body. In addition, a lower electrode, a piezoelectric layer made of PZT or the like, and a drive element 44 made of an upper electrode are formed in the center of the surface of the beam portion 42 in order, and both ends of the beam portion 42 Similarly, a lower electrode, a piezoelectric layer made of PZT or the like, and detection elements 45 and 46 made of an upper electrode are formed at positions symmetrical with respect to the center, and the drive element 44 and the detection elements 45 and 46 are arranged in a wiring pattern ( (Not shown) is electrically connected to the land 47. Further, in the MEMS strain detecting element, the strain generated in the side wall 31 facing the rolling bearing 26a in the slot 30 provided in the housing portion 25a is transmitted to the vibrator in the fixing portions 43 at both ends of the beam portion 42 in the semiconductor substrate 41. As described above, it is connected and fixed by a metal-based bonding material such as Au-Au bonding or a rigid material 48 such as an epoxy resin. In FIG. 4D, the drive element 44 is connected to the output side of the amplifier 50, and the detection elements 45 and 46 are connected to the input side of the amplifier 50 via the gain adjustment / phase shifter 51. The resonance frequencies of the drive element 44 and the detection elements 45 and 46 are selected in the vicinity of the natural frequency _fe of the beam portion 42. The semiconductor substrate of the MEMS strain sensing element created by the inventors has a rectangular shape with a length of 2 mm, a width of 1.5 mm, and a thickness of 0.3 mm, and the beam portion has a length of 1.2 mm, a width of 0.2 mm, and a thickness. 10 μm.

In the above configuration, when an AC voltage having a frequency in the vicinity of the natural frequency _fe of the beam portion 42 is applied from the amplifier 50 to the drive element 44, the drive element 44 provided in the center of the beam portion 42 has the beam portion 42. Stretching vibration is started in a direction parallel to the longitudinal direction. Due to this stretching vibration, the beam portion 42 starts string vibration up and down at the natural frequency _fe . The string vibration is received by the detection elements 45 and 46, and an AC signal having a frequency equal to the natural frequency _fe of the beam portion 42 is generated from the detection elements 45 and 46. These AC signals are phase-adjusted by a gain adjuster / phase shifter 51 and fed back to the input side of the amplifier 50. Thereby, the beam part 42 continues a string vibration with the frequency equal to the natural frequency _fe . At this time, the AC signals from the detection elements 45 and 46 may be added by an adder, and then fed back to the input side of the amplifier 50 via the gain adjustment / phase shifter 51. When tensile strain is exerted on the side wall 31 facing the rolling bearing 26a in the slot 30 provided in the housing portion 25a in a state where the beam portion 42 vibrates vertically in this manner, the inherent property of the beam portion 42 is obtained. The frequency _fe increases. In this manner, by measuring the natural frequency _fe output to the terminal, it is possible to detect and measure the strain generated in the side wall 31 facing the rolling bearing in the slot 30 provided in the housing portion 25a. is there.

  As described above, the torque detection device according to the third embodiment of the present invention particularly uses the strain detection element as a MEMS strain detection element. According to this configuration, a large electrical output can be obtained for a certain strain. Therefore, a large electrical output can be obtained even when the pedaling force applied to the pedal is small, thereby providing a torque detection device that can detect the pedaling force applied to the pedal with high accuracy.

  The torque detector according to the present invention includes a housing, a front wheel side shaft that passes through the housing, a rolling bearing that is fitted to the front wheel side shaft, a housing portion that supports an outer side surface of the rolling bearing, and the front wheel side. One end is fixed to the shaft, and a pedal is rotatably provided at the other end, and a crank that transmits a pedaling force applied to the pedal, a gear that is fixed to the front wheel shaft, and a rotational movement of the gear are transmitted to the rear. A chain for driving the wheel, and a slot having a substantially rectangular shape extending in the vertical direction is provided in the housing portion in the vicinity of the outer side surface on the rear wheel side of the rolling bearing, and is opposed to the rolling bearing in the slot. A strain detection element is mounted on the side wall, and the shaft faces the rolling bearing in the slot when the shaft moves in the rear wheel direction when the pedal is depressed. It detects the force applied to the pedal by detecting the distortion generated on the wall, and it is applied to the shaft by detecting the distortion generated on the side wall facing the rolling bearing in the slot provided in the housing part. Because it is possible to directly detect the treading force that is applied, a crank with a cylindrical boss with a fitting hole in the base and a magnetic alloy detector with parts with magnetic anisotropy in opposite directions are used. It is possible to reduce the number of parts, heavy detection coils, etc., thereby reducing the number of parts, and providing an effect of providing a torque detection device that is easy to assemble, lightweight, and inexpensive. In particular, electric bicycles and automatic transmissions It is useful when applied to the attached bicycle.

22 Housing 24 Shaft 25a, 25b Housing part 26a, 26b Rolling bearing 27a, 27b Crank 29 Gear 30 Slot 32 Strain detecting element

Claims (3)

A housing, a front wheel side shaft passing through the housing, a rolling bearing fitted to the front wheel side shaft, a housing portion supporting an outer side surface of the rolling bearing, and one end fixed to the front wheel side shaft; A crank that transmits a pedaling force applied to the pedal while rotatably providing a pedal at the end, a gear fixed to the front wheel side shaft, and a chain that transmits a rotational movement of the gear and drives a rear wheel; A substantially rectangular slot extending in the vertical direction is provided in the housing portion in the vicinity of the outer side surface on the rear wheel side of the rolling bearing, and a strain detecting element is mounted on a side wall facing the rolling bearing in the slot. Then, when the shaft moves in the rear wheel direction by depressing the pedal, the distortion generated on the side wall facing the rolling bearing in the slot is detected and the shaft is moved. Torque detecting apparatus for detecting a depression force applied to the dull. The rear wheel side of the outer side surface of the rolling bearing is in contact with the housing portion only in the vicinity of a horizontal line passing through the center of the rolling bearing and in the vicinity of a vertical line passing through the center of the rolling bearing. Torque detection device. The torque detection device according to claim 1, wherein the strain detection element is a MEMS strain detection element.

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