JP4046879B2 - Bicycle torque sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bicycle torque sensor that is installed to detect driving torque on a crankshaft that is useful when driving auxiliary power for a bicycle with auxiliary power, automatic shifting for a bicycle with an automatic transmission, or the like.
[0002]
[Prior art]
Conventionally, various methods have been employed to detect the driving torque on the crankshaft required for auxiliary power driving of a bicycle with auxiliary power or automatic shifting of a bicycle with an automatic transmission.
For example, in Japanese Patent Laid-Open No. 4-100790 shown as the first conventional example, a potentiometer or a strain gauge is provided on the surface of the crankshaft as a method of measuring the driving torque generated on the crankshaft by pedal depression. Using the affixed torsion bar, the amount of twist of the torsion bar is detected by the potentiometer or strain gauge, and the drive torque is measured.
However, in the first conventional example, since the detection unit is disposed on the crankshaft which is the rotating part, the detected data is transferred to the vehicle body side or the occupant side which is the non-rotating part by a slip ring or a brush. There is a possibility that noise may be mixed due to friction or wear of a slip ring, a brush, or the like, resulting in lack of reliability of the obtained data.
[0003]
In addition to the resistance to pedaling caused by the rotational resistance of slip rings and brushes, unpleasant noise was generated. In addition, the slip ring and the brush were forced to be replaced due to wear.
Furthermore, when the crankshaft itself is used as a sensor, the maximum strength of the crankshaft must be designed with a sufficient safety factor so that it can withstand the strong pedaling force of human power. On the other hand, since the normal measurement torque is very small, the S / N ratio, which is the accuracy of the measurement torque, decreases as a result, and the expansion ratio due to temperature change increases with respect to the strain amount in the normal torque. This has also been a cause of lowering the S / N ratio.
In addition, the “0 point” of the potentiometer or strain gauge is displaced due to the backlash of the torque transmission system, or a small load remains on the torsion bar due to the rotational resistance of the torque transmission system, so that the “0 point” is not correct when measuring the strain gauge. There was a risk of stabilization.
[0004]
Therefore, like the one disclosed in Japanese Patent Laid-Open No. 10-291494 shown as the second conventional example, it is made of a magnetostrictive material disposed between a crank arm and a sprocket pivotally supported with respect to the crank arm. A strain gauge is installed, and the crankshaft torque generated by pedal depression is detected as a compressive force between the crank arm and the sprocket, and a magnet corresponding to the compressive stress generated by the strain gauge made of a magnetostrictive material is detected. The change in impedance due to the change is transmitted by electromagnetic induction to the coil installed in a non-contact manner between the sprocket on the rotation side and the body hanger on the fixed side, and the crankshaft torque on the rotation side is fixed. It can now be transmitted to the car body on the side without contact.
[0005]
[Problems to be solved by the invention]
However, in the second conventional example configured as described above, the sensor made of the magnetostrictive material disposed between the crank arm and the sprocket is a relatively expensive material, and the sensor portion made of the magnetostrictive material. In addition, the body hanger, which is a non-contact transmission part for measuring torque, constitutes a part of a complicated electrical circuit, which makes the structure complicated and costly because it requires labor to assemble the parts. Invited.
[0006]
Therefore, the present invention solves the problems in the conventional bicycle torque sensor and can secure a high S / N ratio while being a low-cost and simple structure, and is easy to assemble, and between the non-rotating part and the rotating part. An object of the present invention is to provide a torque sensor for a bicycle that can easily transmit the data of the above.
[0007]
[Means for Solving the Problems]
For this reason, in the present invention, a strain gauge is attached to the outer circumferential arc surface of the substantially Ω-shaped sensor piece to detect the strain value, and both ends of the sensor piece are pivotally supported with respect to the crank arm and the crank arm. By being arranged between the sprocket and the sprocket, the compressive force acting between the crank arm and the sprocket is detected based on the stress value detected by the strain gauge. Is.
Further, the present invention provides a first member integral with a crank arm that restrains one end of the sensor piece, a second member integral with a sprocket that restrains the other end of the sensor piece and is rotatable coaxially with the crank arm, Is provided.
Further, the present invention is characterized in that when the compressive force acting on both ends of the sensor piece exceeds a specified value, the further strain amount is restricted by the close contact of the slit portion at the center of the sensor piece. It is what.
Further, the present invention is characterized in that an elastic body that biases the sensor piece in a compressing direction is interposed between the crank arm and the sprocket.
Further, the present invention is characterized in that an elastic body for biasing in a direction to release compression to the sensor piece is interposed between the crank arm and the sprocket.
In addition, the present invention is characterized in that a transmitting member is installed on the sprocket or crank arm side, and the compression force data detected by the sensor piece is received on the vehicle body side or on the passenger side. These are the means for solving the problems.
[0008]
Embodiment
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1, 2 and 4B show a first embodiment of a bicycle torque sensor according to the present invention. FIG. 1 is a side view of a crankshaft and a sprocket pivotally supported by the crankshaft, and FIG. The exploded perspective view and FIG. 4 (B) are BB sectional views of FIG. 5 and 6 show control block diagrams of the sensor piece employed in the bicycle torque sensor of the present invention and the transmitting and receiving parts to which the measured torque data is transmitted.
As shown in FIG. 1, in the present invention, a strain gauge 19 is attached to the outer circumferential arc surface of a substantially Ω-shaped sensor piece 6 to detect a strain value, and both ends of the sensor piece 6 are connected to the crank arm 1 and the crank arm 1. By being arranged between the crank arm 1 and the sprocket 2 pivotally supported with respect to the crank arm 1, the stress value detected by the sensor piece 6 is relatively between the crank arm 1 and the sprocket 2. The present invention is characterized in that it is configured to detect an acting compressive force.
[0009]
In the present embodiment, as shown in FIGS. 1 and 2, a sensor seat 10 which is a first member integral with the crank arm 1 for restraining the piece convex portion 20 at one end of the sensor piece 6, The crank arm is provided with a second sensor receiving seat 7 which is a second member integrated with a sprocket 2 which is constrained by a piece convex portion 29 at the other end of the sensor piece 6 and can rotate coaxially with the crank arm 1. A tension coil spring 8, which is an elastic body that urges the sensor piece 6 in a compressing direction, is interposed between the sprocket 1 and the sprocket 2.
More specifically, the axial center of the crank arm 1 is provided with a main first arm 12 projecting in the radial direction, a male spline 13 extending in the axial direction, and a male screw part 14 carved at the end thereof. . On the other hand, a sprocket 2 for transmitting a driving force generated in the crank arm 1 by a pedal depression (not shown) to the rear wheel side (not shown) by a chain or the like includes a sprocket outer ring 2A having a tooth portion on the outer periphery, and the sprocket It is composed of a starfish-like sprocket inner ring 3 attached to the inner peripheral side of the outer ring 2A, and each outward leg 16 in the sprocket inner ring 3 is attached to each inward leg 15 in the sprocket outer ring 2A with a screw or the like. Positioning in the radial direction is reliably performed by the stopper 18 of each outward leg 16 in the ring 3 of the sprocket.
[0010]
A second sensor receiving seat 7 as a second member is attached to and attached to the side surface of the sprocket inner ring 3. In that case, the bearing 5 is mounted | worn with the inner peripheral side of those members.
Further, the male spline 13 of the crank arm 1 is fitted with the female spline 25 of the first sensor receiving seat 10 as the first member, and the female screw portion 26 of the ring nut 11 disposed on the outer side thereof is connected to the crank arm. The crank arm 1 and the first sensor seat 10 as the first member are integrated with each other by screwing into a male screw portion 14 carved at the end of one male spline 13, and the outer peripheral portions thereof Is pivotally supported by a bearing 5 mounted on the inner peripheral side of the inner ring 3 of the sprocket. This state is clearly shown by the BB cross-sectional view of FIG.
A frame receiver 9 is attached to a first arm composed of a main first arm 12 in the crank arm 1 and a sub first arm 23 in a first sensor receiving seat 10 as a first member. A piece convex portion 20 that is one end portion of the sensor piece 6 is engaged with a piece concave portion 21 formed in the piece receiver 9, and a piece convex portion 29 that is the other end portion of the sensor piece 6 is the second member. The sprocket inner ring 3 is attached to the second arm 22 of the second sensor seat 7 so as to be locked and restrained.
[0011]
In the first sensor seat 10 which is a first member integrated with the crank arm 1, a spring arm 24 which protrudes in a radial direction on the substantially opposite side to the sub first arm 23 is provided on a tension coil spring 8 which is an elastic body. The other end of the tension coil spring 8 is attached to the outward leg 16 of the sprocket inner ring 3 by the second spring receiving bolt 28.
Thus, as shown in FIG. 1, the sensor disposed between the first arm 23 (and 12) on the crank arm 1 side and the second arm 22 on the sprocket 2 side by the restoring force f0 of the tension coil spring 8. The piece 6 is compressed at f0. That is, the sensor piece 6 is compressed in the driving direction of the crank arm 1 (arrow f).
Then, in the space between the inner and outer rings 3 and 2 in the sprocket 2 or on the back side of the sprocket 2, a transmitting member 4 in which a battery, a control circuit, and a transmitting unit are housed as shown in FIG. 6 is installed.
[0012]
When climbing a steep hill, etc., when the pedaling force by human power exceeds a predetermined magnitude and the compressive force acting on both ends of the sensor piece 6 having the substantially Ω shape exceeds a specified value, the center of the sensor piece 6 When the slit portion 17 of this portion is in close contact (see FIGS. 5A and 5B), the amount of further strain is restricted.
When the behavior of the stress σ corresponding to the compressive force generated in the sensor piece 6 at this time is analyzed with reference to FIG. 5, the slit of FIG. In the first embodiment, the compression force f0 (see FIG. 1) due to the presence of the tension coil spring 8 biased in the direction of compressing the sensor piece 6 until the portion 17 comes into close contact. Therefore, the sensor piece 6 is compressed by the resultant force F = f + f0 with the driving force f generated by human power by stepping on the pedal.
[0013]
FIG. 5 (C) illustrates the relationship between the driving force f generated by manpower by depressing the pedal and the stress σ generated in the strain gauge 19 attached to the outer periphery of the sensor piece 6. ). With reference to the case of F = f at the center of FIG. 5 (C), the parallel movement above this by the amount of the additional compression force f0 by the tension coil spring 8 shows the compression characteristics of the present embodiment. is there. The specified value of the maximum measured stress σ1 is reached when the slit portion 17 in FIG.
The sensor piece 6 has a substantially Ω shape, so that a large spring constant can be obtained although the size as a sensor is small, and the length of the outer peripheral surface can be taken sufficiently, and a large arc-shaped gauge surface can be obtained. Since a uniform stress distribution can be obtained in any part of the arcuate outer peripheral surface, highly accurate measurement is possible, and there is no problem even if the position where the strain gauge 19 is attached is somewhat shifted. When the compression force due to human power reaches a predetermined specified value, the slit portion 17 at the center portion of the sensor piece 6 is brought into close contact with each other so that a further amount of distortion is regulated. The characteristic only needs to be accurate within the range up to the predetermined specified value σ1, and when a compressive force higher than that is applied, a greater proof strength can be obtained by the close contact of the slit portion 17.
Further, since the width of the slit portion is narrow and the elastic deformation of the sensor piece 6 is very small, the direct feeling at the time of pedaling is not impaired.
[0014]
FIG. 3 shows a bicycle torque sensor according to a second embodiment of the present invention. In this embodiment, the compression of the sensor piece 6 is released between the crank arm 1 and the sprocket 2. A tension coil spring 8 that is an elastic body to be biased is interposed.
The present embodiment is also assembled in the same manner as the exploded perspective view shown in FIG. 2, and FIG.
In the present embodiment, the tension coil spring 8 intervenes to act as a force f1 in the opposite direction to the driving force f generated in the crank arm 1 by the human force that depresses the pedal. That is, since it acts as a force f1 for returning the crank arm 1, the stress σ corresponding to the compressive force generated in the sensor piece 6 at this time is shown in FIG. 5 as in the first embodiment described above. In the second embodiment, the sensor in the second embodiment until the slit portion 17 in FIG. 5 (B) comes into close contact before the assembly in FIG. 5 (A) is assembled. By interposing the tension coil spring 8 which is an elastic body biasing in the direction to release the compression to the piece 6, the characteristic of reducing the force f <b> 1 by the tension coil spring 8 is shown, and by depressing the pedal The sensor piece 6 is compressed by the compression characteristic of F = f−f1 subtracted from the driving force f generated by human power. In FIG. 5 (C), the reference value of F = f is translated downward by f1, and when the slit portion 17 in FIG. 5 (B) comes into close contact, the specified value of the maximum measured stress σ1 is reached.
[0015]
In the present invention, the transmitting member 4 is installed on the sprocket 2, and the compressive force data detected by the sensor piece 6 is received on the vehicle body side or on the passenger side. As shown in the block configuration diagram of FIG. 6, appropriate transmission members and reception members are employed. However, in the illustrated embodiment, the transmission member 4 detects the traveling of the bicycle by the vibration detection unit. Then, power is turned on by the power control unit. The stress value detected by the strain gauge 19 affixed to the sensor piece 6 that is compressed according to the driving torque by the crank arm 1 is taken out as a voltage signal by the signal amplifying unit and converted into a voltage by the voltage-frequency converting unit. The frequency is converted to a corresponding frequency, and is transmitted to the air by the high frequency output unit through the carrier wave transmission unit.
[0016]
When a radio wave signal is detected by the input switch detection unit in the reception unit installed on the vehicle side or the occupant side, the display control unit is turned on to turn on the reception circuit, and at the same time, the liquid crystal display unit is turned on to transmit the transmission member. The signal from can be displayed.
In the receiving circuit to which the power is turned on, the received signal is received by the high frequency amplifying unit, demodulated to a low frequency by the low frequency demodulating unit, and a voltage corresponding to the frequency is generated by the frequency-voltage converting unit. The stress value detected on the transmitting member side is displayed on the liquid crystal display unit.
At this time, although not shown, the voltage generated according to the frequency by the frequency-voltage conversion unit is used as a control value for auxiliary power drive control of a bicycle with auxiliary power (not shown) or automatic shift of a bicycle with automatic transmission. A control value for control or the like is input to the control circuit.
[0017]
FIG. 7 shows a third embodiment of a bicycle torque sensor according to the present invention. In this embodiment, as the sensor piece 6 disposed between the crank arm 1 side and the sprocket 2 side, In the first and second embodiments, an approximately Ω-shaped sensor piece 6 is used which is vertically opposed to each other.
Therefore, the sensor piece 6 is composed of an upper piece 6A and a lower piece 6B. According to this, a strain gauge is attached to each of the upper piece 6A and the lower piece 6B, and the respective measured values are averaged. A more accurate control value can be obtained.
[0018]
Although the embodiments of the present invention have been described above, the shape of the crank arm and sprocket (mounting form of the inner and outer rings, etc.), the installation form of the sensor piece, the interposed form of the elastic body, the crank arm within the scope of the present invention And sprocket shaft support form, crank arm and first member connection form, sprocket and second member connection form, signal transmission form between sensor piece and transmitting member, transmitting member mounting position and mounting The form, strain gauge type, and the like can be selected as appropriate.
[0019]
【The invention's effect】
As described above, according to the present invention, a strain gauge is attached to the outer circumferential arc surface of a substantially Ω-shaped sensor piece to detect a strain value, and both ends of the sensor piece are connected to the crank arm and the crank arm. It is arranged between the sprocket that is pivotally supported and configured to detect the compressive force acting between the crank arm and the sprocket based on the stress value detected by the strain gauge. Therefore, by arranging the sensor piece in the transmission path of the drive torque generated by the crank arm, it is possible to measure by directly converting the torque into the sensor piece stress value, and the mechanical configuration is simple In addition to a small torque transmission loss, the sensor piece has a substantially Ω shape, so that a large spring constant can be obtained although the size of the sensor is small.
Furthermore, the length of the outer peripheral surface can be taken sufficiently, and when the outer peripheral wall thickness of the sensor piece central part is increased, the outer circumference of the sensor piece can be reduced when receiving a compressive load input from both ends of the sensor piece. A uniform stress distribution can be obtained over a wide range in the arc portion, and measurement with high accuracy is possible, and there is no problem even if the placement position of the strain gauge is slightly shifted.
When the compressive force acting on both ends of the sensor piece exceeds a specified value, the slit portion at the center of the sensor piece is in close contact and the amount of further strain is regulated. When the value reaches a predetermined specified value, as described above, the amount of distortion beyond that is restricted, and the compression characteristic of the sensor piece only needs to be accurate within the range up to the predetermined specified value. When the / N ratio is improved and a compressive force higher than that is applied, a greater yield strength can be obtained by the close contact of the slit portion. Moreover, since the width of the slit portion is narrow and the elastic deformation of the sensor piece is very small, the direct feeling during pedaling is not impaired.
[0020]
In addition, if the sensor piece is designed so that the maximum stress value of the sensor piece generated within the measurement torque range required in the sensor piece shape design is within the fatigue limit, and both sides of the slit part at the center are in close contact with each other Even if a torque exceeding the measurement torque range is input, the sensor piece is not destroyed. With such a design, the maximum amount of strain within the fatigue limit of the sensor piece can be secured, and the S / N ratio with the normal torque can be improved to ensure measurement accuracy.
As a result, the influence of linear expansion due to temperature change, circuit temperature drift, etc. can be within the range of measurement error.
[0021]
In addition, a first member integrated with a crank arm that constrains one end of the sensor piece, and a second member integrated with a sprocket that constrains the other end of the sensor piece and can rotate coaxially with the crank arm are provided. Therefore, in order to arrange the sensor piece between the crank arm and the sprocket, the first member and the second member can be freely designed and configured, so that the degree of freedom of design is greatly improved. be able to.
Further, an elastic body that urges the sensor piece in a compressing direction is interposed between the crank arm and the sprocket, or compression to the sensor piece is released between the crank arm and the sprocket. When the sensor “0 point adjustment” is performed without pedal input torque due to the elastic body biasing in the direction, the compression load of the sensor piece is not completely released due to mechanical frictional resistance, etc. Even in such a case, these residual loads are completely released or become constant as the preload compression load, and the sensor piece always obtains “0 point” by stable preload. Therefore, an accurate input torque can always be obtained by canceling or adding the preload in the final calculation process from the provisional “0 point” by preload.
[0022]
Furthermore, a transmission member is installed on the sprocket, and the compression force data detected by the sensor piece is received on the vehicle body side or on the occupant side. Therefore, stable measurement data can be obtained, maintenance is not required, and rotation resistance is not increased. Further, the transmitting member can be arranged on the inside or the back surface of the sprocket so that it is not easily damaged from the outside, and can be made inconspicuous.
In this way, a low-cost and simple structure can ensure a high S / N ratio, easy assembly, and reliable transmission of data between the non-rotating part and the rotating part. Is done.
[Brief description of the drawings]
FIG. 1 shows a first embodiment of a bicycle torque sensor according to the present invention, and is a side view of a crankshaft and a sprocket pivotally supported by the crankshaft.
FIG. 2 is an exploded perspective view of a first embodiment of a bicycle torque sensor according to the present invention.
FIG. 3 shows a second embodiment of a bicycle torque sensor according to the present invention, and is a side view of a crankshaft and a sprocket pivotally supported by the crankshaft.
4A is a cross-sectional view taken along the line AA in FIG. 3, and FIG. 4B is a cross-sectional view taken along the line BB in FIG.
FIG. 5 is a diagram illustrating a sensor piece employed in the bicycle torque sensor of the present invention and its compression characteristics.
FIG. 6 is a control block diagram of a transmission unit and a reception unit to which measurement torque data employed in the bicycle torque sensor of the present invention is transmitted.
FIG. 7 is a diagram showing a third embodiment of a bicycle torque sensor according to the present invention.
[Explanation of symbols]
1 Crank arm 2 Sprocket 2A Sprocket outer ring 3 Sprocket inner ring (second member)
4 Transmission member 5 Bearing 6 Sensor piece 7 Second sensor seat (second member)
8 Tensile coil spring (elastic body)
9 piece holder (first member)
10 First sensor seat (first member)
11 Ring nut 12 Main first arm (first member)
13 Male spline 14 Male screw part 15 Inward leg 16 Outward leg 17 Slit part 18 Stopper 19 Strain gauge 20 Frame convex part (one end part)
21 Recess for frame 22 Second arm 23 Sub first arm 24 Spring arm 25 Female spline 26 Female screw part 27 First spring receiving bolt 28 Second spring receiving bolt 29 Frame convex part (other end part)
Recess for 30 pieces

Claims (6)

A strain gauge is affixed to detect the strain value on the outer circumferential arc surface of the approximately Ω-shaped sensor piece, and both ends of the sensor piece are arranged between the crank arm and a sprocket pivotally supported with respect to the crank arm. A bicycle torque sensor configured to detect a compressive force acting relatively between the crank arm and the sprocket based on a stress value detected by the strain gauge. A first member integrated with a crank arm that constrains one end of the sensor piece, and a second member integrated with a sprocket that constrains the other end of the sensor piece and rotates coaxially with the crank arm. The bicycle torque sensor according to claim 1. 2. The structure according to claim 1, wherein when the compressive force acting on both ends of the sensor piece exceeds a specified value, a further strain amount is regulated by the close contact of the slit portion at the center of the sensor piece. Or the torque sensor for bicycles of 2. 4. The bicycle torque sensor according to claim 1, wherein an elastic body that urges the sensor piece in a compressing direction is interposed between the crank arm and the sprocket. The bicycle torque sensor according to any one of claims 1 to 3, wherein an elastic body for biasing the sensor piece in a direction to release compression is interposed between the crank arm and the sprocket. 6. The transmission device according to claim 1, wherein a transmitting member is installed on the sprocket or crank arm side, and the compression force data detected by the sensor piece is received on the vehicle body side or on the passenger side. Torque sensor for bicycles according to the above.

Images