JP3671586B2 - Rotational torque sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to the technical field of a sensor that detects rotational torque applied to a driven rotor such as a wheel that is rotationally driven by a chain or the like, and particularly to the technical field of a rotational torque sensor that is suitable for use with a bicycle with an auxiliary motor.
[0002]
[Prior art]
As a conventional rotational torque sensor, JP-A-8-85491 discloses a rotational torque sensor for an electric bicycle. In this prior art, a spring that is expanded and contracted when a torque is applied from the chain to the rear wheel is disposed around the rotation axis, and a ferrite displacement fixed to one end of the spring is disposed around the coil. Is detected as a change in inductance.
[0003]
[Problems to be solved by the invention]
However, in the above-described prior art, since the ferrite and the spring are rotating bodies that rotate together with the chain sprocket and the rear wheel, it is necessary to measure the inductance of the coil in order to detect the displacement of the ferrite due to the expansion and contraction of the spring. Therefore, an electronic circuit for inductance detection is needed. In addition, since the mechanism for transmitting torque including the spring is complicated, not only is the number of parts large, but the weight must be increased to ensure precise measurement accuracy and mechanical strength. . As a result, the rotational torque sensor according to the conventional technique also has a disadvantage that it must be disadvantageous in terms of cost.
[0004]
Accordingly, an object of the present invention is to provide a torque sensor that has a simple configuration, is lightweight, small, and inexpensive.
[0005]
[Means for solving the problems and their functions and effects]
In order to solve the above problems, the inventor has invented the following means.
(First means)
The first means of the present invention includes a fixed shaft, a driven rotor that is rotatably supported around the fixed shaft, and an outer periphery that is held so as to be movable within a predetermined range within the rotation plane with respect to the driven rotor. A driving rotor that rotationally drives the driven rotor by receiving a force in a tangential direction at the portion, and the fixed shaft that is movable in a predetermined section in the tangential direction without rotating with respect to the fixed shaft And a non-rotating body that rotatably supports the drive rotor, and a sensor that measures one of a pressing force and a pulling force acting between the non-rotating body and the fixed shaft. This is a rotational torque sensor.
[0006]
In this means, when the drive rotor receives a tangential force (hereinafter referred to as a tangential force), the drive rotor moves in a predetermined range in the direction, and the opposite side of the fixed shaft at the point where the tangential force is applied. The driven rotor is driven on the side and the reaction force from the driven rotor is received. Then, a resultant force of a tangential force and a reaction force is generated in the tangential direction, and this resultant force presses the non-rotating body against the fixed shaft, so that a pressing force or a pull (on the opposite side) is generated between the non-rotating body and the fixed shaft. Force is generated and measured by the sensor. Since this force measured by the sensor is proportional to the tangential force, the tangential force can be calculated by measuring this force, and thus the torque can be calculated.
[0007]
In the above means, the components of the rotational torque sensor are roughly divided into five points: a fixed shaft, a driven rotor, a driving rotor, a non-rotating body, and a sensor, so the number of parts is small and the configuration is extremely simple. . Further, since there are no specially bulky components or expensive parts, the rotational torque sensor can be configured to be lightweight, small and inexpensive.
Therefore, according to this means, it is possible to provide a torque sensor that has a simple configuration, is lightweight, small, and inexpensive.
[0008]
(Second means)
According to a second means of the present invention, in the first means, the drive rotor is rotationally driven by receiving a force in the tangential direction by any one of a chain, a belt, a gear including a rack, and a friction surface. Features.
It has been clarified that the present invention includes almost any torque transmission means that generates a tangential force in the drive rotor.
[0009]
For example, if the drive rotor is a chain-driven sprocket, the tangential force generated by the chain on the pulling side is measured by a sensor, so that torque can be measured easily and precisely. Even when the drive rotor is a gear and a tangential force is generated by the gear including the rack, the torque can be easily and precisely measured by measuring the tangential force with a sensor. Even when the object that exerts a tangential force on the drive rotor is a friction surface, the torque can be measured easily and precisely by measuring the tangential force with a sensor, as in the case of the combination of the rack and the gear. . When the drive rotor is a belt-driven pulley, the sensor output when no torque is applied is regarded as the zero point, and the tangential force is measured by the sensor as in the case of a chain-driven sprocket. Can easily measure torque.
[0010]
Therefore, according to this means, in addition to the effect of the first means described above, there is an effect that it can be applied to almost any torque transmission means that generates a tangential force in the drive rotor.
(Third means)
According to a third means of the present invention, in the first means, the sensor is a strain gauge, which is fixed to one of the non-rotating body and the fixed shaft and is deformed by a force acting between the two. It is characterized by being joined to a leaf spring.
[0011]
In this means, since the sensor is a strain gage in which the sensor is fixed to the leaf spring, the structure of the sensor is extremely simple, light and small, inexpensive, and highly accurate and reliable. In addition, the circuit for taking out the sensor output may be a simple bridge circuit, which is similarly lightweight, small, inexpensive, and highly accurate and reliable.
Therefore, according to this means, in addition to the effect of the first means described above, there is an effect that the rotational torque sensor of the present invention can be configured with high accuracy and high reliability in addition to being lighter, smaller and cheaper.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
The embodiments of the rotational torque sensor of the present invention will be described clearly and sufficiently in the following examples so that those skilled in the art can understand that they can be implemented.
[Example 1]
(Configuration of Example 1)
As shown in FIG. 1, the rotational torque sensor according to the first embodiment of the present invention includes a sprocket 42 that is driven by the chain 5 and rotates around the fixed shaft 1, and a rear wheel (not shown) of the electric bicycle. It has been incorporated. That is, the rotational torque sensor of the present embodiment includes the fixed shaft 1, the driven rotor 4, the driving rotor 2, the non-rotating body 12, the pressing force sensors 13 and 14, and the like. The rotor 2 is rotationally driven.
[0013]
The fixed shaft 1 is an axle of the rear wheel of the bicycle, and rotatably supports a driven rotor 2 that forms a central portion of the rear wheel around the axle. That is, the fixed shaft 1 rotatably supports the driven rotor 2 via the ball bearing 61 at the intermediate portion, and the rotational axis of the driven rotor 2 always coincides with the center line of the fixed shaft 1.
As shown in FIG. 2, the distal end portion of the fixed shaft 1 is formed by a rectangular bar portion 11, and holds a non-rotating body 12 that can move in a predetermined range in the front-rear direction. A ball bearing 62 is fixed to the outer periphery of the non-rotating body 12, and the drive rotor 4 is rotatably supported via the ball bearing 62. Accordingly, the drive rotor 4 is movable in a predetermined range in the front-rear direction with respect to the fixed shaft 1 and is rotatably supported around the fixed shaft 1. However, although the rotation axis of the drive rotor 4 and the central axis of the fixed shaft 1 are parallel, they do not necessarily coincide with each other, and are usually shifted in the front-rear direction.
[0014]
As shown in FIG. 1 again, the drive rotor 4 is held by the driven rotor 2 so as to be movable within a predetermined range within its rotational surface, and is driven to rotate by receiving a tangential force on the outer peripheral portion. As a result, the driven rotor 2 is rotationally driven. That is, the drive rotor 4 includes a flange member 41 that is supported around the non-rotating body 12 via a ball bearing 62, and a sprocket 42 that is coaxially fixed to the outer periphery of the flange member 41. Teeth 43 that mesh with the chain 5 are formed on the outer periphery of the sprocket 42, and the sprocket 42 receives a pulling force (tangential force) in the tangential direction (in this case, forward) from the chain 5 via the teeth 43. Driven.
[0015]
Torque is transmitted from the drive rotor 4 to the driven rotor 2 through the eight joint pins 3 penetrating through the through hole 40 of the drive rotor 4 and the through hole 20 of the driven rotor 2. As shown in FIGS. 1 and 3, the inner diameters of the through holes 20 and 40 are about 0.1 mm larger than the outer diameter of the joint pin 3, and the drive rotor 4 can move within a predetermined range with respect to the driven rotor 2. I have to.
[0016]
As shown in FIGS. 1 and 2, the non-rotating body 12 is fixed to the fixed shaft 1 so as to be movable in a predetermined section in the tangential direction (that is, the front-rear direction) without rotating with respect to the square bar portion 11 of the fixed shaft 1. Is held by the square bar portion 11. The non-rotating body 12 pivotally supports the drive rotor 4 via a ball bearing 62. Further, as shown in FIG. 1, the square bar portion 11 of the fixed shaft 1 protrudes from the through hole 420 of the non-rotating body 12 with an appropriate gap, and when the bicycle falls to the right side, the sprocket 42 or the like is It comes to protect.
[0017]
As shown in FIG. 1 again, the pressing force sensors 13 and 14 are fixed to the rear surface of the square bar portion 11 of the fixed shaft 1 and measure the pressing force acting between the non-rotating body 12 and the fixed shaft 1. Sensor. This sensor comprises a U-shaped leaf spring 13 and a strain gauge 14 as shown in FIG. The leaf spring 13 includes a leaf spring portion 131 that forms an intermediate portion, and a pair of legs that protrude forward from both the left and right sides of the leaf spring portion 131 and are fixed on a square rod portion 11 (not shown). This is an integral member composed of the portion 12 and a ridge 133 that protrudes rearward from the central portion of the leaf spring portion 131. A strain gauge 14 that detects expansion and contraction in the left-right direction is fixed to the front surface of the central portion of the leaf spring portion 131 that faces the ridge 133.
[0018]
As shown in FIG. 4B, a pressing force F directed forward from the non-rotating body 12 (only part of which is shown) opposed to the protrusion 133 to the square bar portion 11 (not shown) of the fixed shaft 1 is applied. As a result, the rib 133 of the leaf spring 13 is pushed and the leaf spring 131 is bent. Then, the strain gauge 14 is stretched in the left-right direction, causing a change in resistance value that is substantially proportional to the pressing force F. If this change is detected by a known bridge circuit or the like (not shown) provided separately, The pressure F can be measured.
[0019]
(Operational effect of Example 1)
Since the rotational torque sensor of the present embodiment is configured as described above, the following action is produced.
That is, as shown in FIG. 5A, when a tangential force F <b> 1 is applied to the outer peripheral portion of the sprocket 42 by the chain 5, the non-rotating body 12 that pivotally supports the drive rotor 4 including the sprocket 42 is Move forward a distance corresponding to the deformation. Torque is applied to the drive rotor 4 including the flange member 41 in the clockwise direction in the drawing, so that the drive rotor 4 not only moves forward, but also clockwise in the allowable range of the joint pin 3 with respect to the driven rotor 2. Rotate relatively. Then, only the lowermost joint pin 3 is sandwiched between the inner peripheral surfaces of both the through holes 20 and 40 described above, and torque is transmitted from the drive rotor 4 to the driven rotor 2 via the lowermost joint pin 3. . At that time, a reaction force F <b> 2 from the driven rotor 2 is generated in the driving rotor 4 via the lowermost joint pin 3.
[0020]
As a result, as shown in FIG. 5B, a tangential force F1 from the chain 5 and a reaction force F2 from the joint pin 3 are applied to the drive rotor 4, and the resultant force F = F1 + F2 is applied to the non-rotating body 12 (not shown). ) Through the leaf spring 13. In other words, the tangential force F1 and reaction force F2 applied to both ends of the insulator 4 are supported by the leaf spring 13 as a fulcrum, and the reaction force of the resultant force F = F1 + F2 is generated to support the insulator 4. The ratio of the reaction force F2 to the tangential force F1 is determined by the lever principle based on the ratio of the two moment arms r1 and r2. Therefore, the torque applied to the drive rotor 4 is easily calculated with the measured values of the pressing force F applied to the two moment arms r1 and r2 and the leaf spring 13 that are apparent in design.
[0021]
Note that it is considered that the load L shown in FIG. 5A is output as much as the torque.
Here, as the driving rotor 4 and the driven rotor 2 rotate, the joint pins 3 that transmit torque from the lowermost joint pin 3 to the next joint pin 3 change one after another. There is no discontinuous jump, and torque is transmitted continuously. However, the moment arm from the leaf spring 13 to which the sensor 14 is attached to the joint pin 3 shifts the phase little by little (by the angular interval of the joint pin 3), and the tops of adjacent sine wave functions are continuous. The output is accompanied by pulsation. The width of the pulsation is about ± 3% when eight joint pins 3 are arranged at regular intervals as in this embodiment, and a smooth output can be obtained. When there is a request to further reduce the amount of pulsation, the pulsation can be easily reduced by increasing the number of joint pins 3 and reducing the angular interval.
[0022]
The rotational torque sensor of the present embodiment can be implemented with the above-described configuration while having the above-described torque measurement function, and therefore does not require special parts, parts that are heavy in weight and volume, and the configuration is extremely simple. Therefore, according to this embodiment, there is an effect that it is possible to provide a torque sensor with a simple configuration, a light weight and a small size, and with high reliability and measurement accuracy at low cost.
[0023]
(Modification of Example 1)
With respect to the joint pin 3 portion of the first embodiment, a slightly different configuration can be used.
For example, as a modified embodiment 1, as shown in FIG. 6A, the joint pin 3 is inserted into the through hole 20 ′ of the driven rotor 2 ′ with an interference fit, and the through hole 20 (burst hole) of the drive rotor 4 is inserted. ) Can be inserted with an extreme loose fit. Other parts of the rotational torque sensor of this modification are the same as those in the first embodiment.
[0024]
Also according to this modification, the same effects as in the first embodiment can be obtained, and even if vibration or the like is applied, the joint pin 3 is not disturbed and is firmly held by the driven rotor 2 ′, and noise is generated. It has the effect of being suppressed. In addition, even if the relationship between the through hole 20 ′ and the through hole 40 is reversed, the same effects as those of the present modification can be obtained.
[0025]
Further, as a modification 2, as shown in FIG. 6 (b), a bolt 3 'in which a male screw is formed only at the tip portion is used instead of the joint pin 3, and the driven rotor 2 "is replaced with the through hole 20. It is also possible to adopt a configuration in which it is screwed into the formed female screw hole 20 ″. Also in this modified mode, the through hole 40 of the drive rotor 4 is a fool hole, so that the same effect as that of the modified mode 1 described above can be obtained, and the tip of the bolt 3 'passes through the driven rotor 2 "on the opposite side. Therefore, there is an effect that it can be configured more compactly.
[0026]
[Example 2]
As shown in FIGS. 7A to 7B, the rotational torque sensor as the second embodiment of the present invention is an embodiment in which gear driving is used instead of the chain driving in the first embodiment. In this embodiment, the drive rotor 4A is a gear and is rotationally driven by another gear 5 'meshing therewith, and rotationally drives the driven rotor 2A via a plurality of joint pins 3. The driven rotor 2A is also rotatably supported by a fixed shaft 1A. As shown in FIG. 7B, the non-rotating body 12A that also serves as the fixed shaft of the drive rotor 4A includes strain gauges 14 on both sides of the neck as a pressing force sensor.
[0027]
Therefore, by taking the difference between the resistance values of the two strain gauges 14, the pressing force F applied to the non-rotating body 12A can be measured relatively accurately. As shown in FIG. 7C, if the pressing force F is measured, the torque acting on the drive rotor 4A can be calculated by the same method as in the first embodiment.
Therefore, this embodiment of the gear drive also has an effect that, like the first embodiment, a torque sensor that has a simple configuration, is light and small, and has high reliability and high measurement accuracy can be provided at low cost.
[Brief description of the drawings]
FIG. 1 is a horizontal cross-sectional view showing a configuration of a rotational torque sensor as a first embodiment. FIG. 2 is an end view showing a configuration of a rotational torque sensor as a first embodiment. FIG. 4 is an assembled view showing the configuration and operation of the pressing force sensor of Example 1. (a) Cross-sectional view schematically showing the shape of the pressing force sensor when there is no load. (B) Pushing force under pressing force. FIG. 5 is a sectional view schematically showing the operation of the pressure sensor. FIG. 5 is a group diagram showing the operation of the rotational torque sensor as the first embodiment. FIG. 6B is a principle diagram of the pressing force sensor. FIG. 7 is a sectional view showing a configuration in the vicinity of the joint pin of the modified embodiment 1; FIG. 7B is a sectional view showing a configuration in the vicinity of the joint pin of the modified embodiment 2; Assembly diagram showing configuration and operation of rotational torque sensor (a) Driving low of Example 2 Side view showing a configuration (b) Description of the code is a schematic view showing the action of the torque sensor as a rotating horizontal sectional view showing the configuration of a torque sensor (c) Example 2 as Example 2
DESCRIPTION OF SYMBOLS 1,1A: Fixed axis | shaft 11: Square-bar part 12: Non-rotating body 12A: Non-rotating body which serves as a fixed axis 13: U-shaped leaf spring 14: Strain gauge 2, 2 ', 2 ", 2A: Driven Rotor 20, 20 ': Through hole 20 ": Screw hole 3: Pin 3': Bolt 4: Drive rotor 40: Through hole 420: Through hole 41: Flange member 42: Sprocket 43: Teeth 5: Chain 51: Pull side chain 52: Slack side chain 4A: Gear as drive rotor 5 ': Gear F: Pressing force F1: Tangent force F2: Reaction force L: Load r1, r2: Moment arm

Claims (3)

A fixed shaft;
A driven rotor that is rotatably supported around the fixed shaft;
A driving rotor that is held so as to be movable within a predetermined range in a rotation plane with respect to the driven rotor, and that is driven to rotate by receiving a tangential force on an outer peripheral portion;
A non-rotating body which is held by the fixed shaft so as to be movable in a predetermined section in the tangential direction without rotating with respect to the fixed shaft, and which rotatably supports the drive rotor;
A sensor for measuring one of a pressing force and a pulling force acting between the non-rotating body and the fixed shaft;
A rotational torque sensor comprising: The rotational torque sensor according to claim 1, wherein the drive rotor is rotationally driven by receiving a force in the tangential direction by any one of a chain, a belt, a gear including a rack, and a friction surface. 2. The rotational torque sensor according to claim 1, wherein the sensor is a strain gauge, and is fixed to one of the non-rotating body and the fixed shaft and joined to a leaf spring that is deformed by a force acting between the two. .

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