JP2018008611A - Electric power assisted bicycle and method of detecting driving torque - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and accurately detect a torque without causing a large increase in weight and without using complicated wiring.SOLUTION: An electric power assisted bicycle comprises: a frame; a wheel drive shaft provided on the frame and rotatably supporting a drive wheel; a crankshaft rotatably provided on the frame and applied with a driving torque; a belt-shaped drive transmission member annularly wound around to be capable of transmission of the driving torque from the crankshaft to the wheel drive shaft; an assist drive means for assisting rotational driving of the drive wheel by applying an assist torque to the wheel drive shaft; a torque detection means for detecting the driving torque added to the crankshaft; and a control means for controlling the assist drive means on the basis of the driving torque added to the crankshaft. The torque detection means is provided with a tension detection means capable of detecting the tension generated in the drive transmission member, and a torque calculation means for calculating the driving torque on the basis of the detected tension.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrically assisted bicycle and a method for calculating a driving torque applied to a crankshaft of the electrically assisted bicycle.

  In the electrically assisted bicycle described in Patent Document 1, a torque sensor is provided around the pedal crank of the pedal portion to detect torque generated in the pedal crank. Further, in the microcomputer, the pedal effort obtained from the detection signal from the torque sensor is calculated, and the assist amount is calculated based on this.

JP 2004-306818 A

However, the method of measuring the torque generated in the pedal crank at or around the crankshaft, like the torque sensor in Patent Document 1, has a problem that the torque sensor becomes larger or heavier in principle. In addition, when the measurement unit of the torque sensor is configured to rotate integrally with the crankshaft of the pedal crank, the transmission mechanism of the electrical signal transmitted from the measurement unit of the torque sensor, that is, the wiring routing and connection structure becomes complicated. There was a problem that it was easy.
In addition, conventional load sensors are installed in rotating systems such as sprockets that are supported on the crankshaft and pedals that are provided at both ends of the pedal crank. In this case, signal transmission is likely to be complicated. There was a problem.

  Therefore, the present invention provides an electrically assisted bicycle and a driving torque detection method capable of simply and accurately detecting torque without causing a significant increase in weight and without using complicated wiring. For the purpose.

In order to solve the above-mentioned problems, an electric assist bicycle according to the present invention is provided with a frame, a wheel drive shaft that is provided on the frame and rotatably supports a drive wheel, and is provided rotatably on the frame and imparts a drive torque. Of the drive wheel by applying an assist torque to the wheel drive shaft, a belt-like drive transmission member that is looped around the crankshaft to be able to transmit the drive torque from the crankshaft to the wheel drive shaft. An electrically assisted bicycle having assist drive means for assisting rotational drive, torque detection means for detecting drive torque applied to the crankshaft, and control means for controlling the assist drive means based on the drive torque applied to the crankshaft The torque detection means calculates the drive torque based on the tension detection means capable of detecting the tension generated in the drive transmission member and the detected tension. Is characterized by comprising a torque calculation unit for, a.
As a result, torque can be detected easily and accurately without causing a significant increase in weight and without using complicated wiring.

In the electric assist bicycle according to the present invention, the tension detecting means includes a deformable portion that can be elastically deformed in accordance with a change in tension, and a strain gauge that can measure the amount of strain generated in the deformed portion, and is driven based on the amount of strain. It is preferable to detect the tension generated in the transmission member.
As a result, the tension of the drive transmission member can be detected with a small and simple configuration, thereby enabling accurate torque detection.

In the electrically assisted bicycle according to the present invention, the tension detecting means has a gear portion that engages with the drive transmission member and is rotatable with the movement of the drive transmission member, and the deformation portion is at least the drive transmission member via the gear portion. It is preferable that it is connected to.
Thereby, the tension of the drive transmission member can be detected without greatly hindering the movement of the drive transmission member.

The electrically assisted bicycle according to the present invention has storage means capable of storing the tension detected by the tension detection means, and the torque calculation means is an average value of tensions for a plurality of times within a unit period stored by the storage means. The average tension can be calculated, and the tension used for calculating the driving torque by the torque calculating means is preferably the average tension.
As a result, even if there is an instantaneous irregular torque fluctuation, the assist torque is not suddenly changed every time the fluctuation occurs, so that the influence on the operation due to the sudden change of the assist torque can be suppressed.

The electrically assisted bicycle of the present invention has storage means capable of storing the drive torque calculated by the torque calculation means, and the torque calculation means is an average value of the drive torque for a plurality of times within the unit period stored by the storage means. The average driving torque can be calculated, and the driving torque used for controlling the assist driving means by the control means is preferably the average driving torque.
As a result, even if there is an instantaneous irregular torque fluctuation, the assist torque is not suddenly changed every time the fluctuation occurs, so that the influence on the operation due to the sudden change of the assist torque can be suppressed.

The drive torque detection method of the present invention is a drive torque detection method for calculating the drive torque applied to the crankshaft in an electrically assisted bicycle that transmits the drive torque applied to the crankshaft to the wheel drive shaft via the drive transmission member. A strain measurement step for measuring a strain amount generated in the deformed portion connected to the drive transmission member, a tension detection step for detecting a tension generated in the drive transmission member based on the measured strain amount, and a tension detection step. And a torque calculating step for calculating a driving torque applied to the crankshaft based on the tension detected in step (b).
As a result, torque can be detected easily and accurately without causing a significant increase in weight and without using complicated wiring.

  According to the present invention, an electrically assisted bicycle and a driving torque detection method capable of simply and accurately detecting torque without causing a significant increase in weight and without using complicated wiring are provided. can do.

1 is a side view showing a partially enlarged electric assist bicycle according to an embodiment of the present invention. It is a block diagram which shows the structure of the electrically assisted bicycle which concerns on embodiment of this invention. It is a front view which shows the structure of the tension | tensile_strength detection part in embodiment of this invention. It is a top view which shows the structure of the tension | tensile_strength detection part in embodiment of this invention. It is a figure which shows the circuit structure of the tension | tensile_strength detection part in embodiment of this invention.

Hereinafter, an electrically assisted bicycle and a driving torque detection method according to an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a side view showing a partially enlarged electric assist bicycle 10 according to the present embodiment. FIG. 2 is a block diagram showing a configuration of the electrically assisted bicycle 10. FIG. 3 is a front view showing the configuration of the tension detector 27 in the present embodiment. FIG. 4 is a plan view showing the configuration of the tension detection unit 27. FIG. 5 is a diagram illustrating a circuit configuration of the tension detection unit 27.
In FIG. 1, FIG. 3, and FIG. 4, XYZ coordinates are shown as reference coordinates. The Z direction is along the vertical direction, and the XY plane is a plane along the horizontal direction orthogonal to the Z direction.

As shown in FIG. 1, an electrically assisted bicycle 10 includes a frame 11, a rear wheel sprocket 12 as a wheel drive shaft, a drive chain 13 as a drive transmission member, a pedal sprocket 14, a crankshaft 15, and a pedal. 16 and a detection unit sprocket 21. Furthermore, as shown in FIG. 2, the electric assist bicycle 10 includes a torque detection unit 20 as a torque detection unit, a memory 32, a control unit 41, a power supply unit 42, a motor drive unit 43, a motor 44, An input unit 51 and a display unit 52 are provided. The torque detection unit 20 includes a tension detection unit 27 as a tension detection unit and a torque calculation unit 31 as a torque calculation unit. The power supply unit 42, the motor drive unit 43, and the motor 44 constitute assist drive means. Although not shown, the electrically assisted bicycle 10 includes a front fork assembled to the frame 11, a front wheel on which a drive shaft is rotatably supported with respect to the front fork, a saddle provided on the frame 11 so that the height can be adjusted, and the like. Is provided.
In FIG. 1, components of the torque detector 20 other than the detector sprocket 21 are not shown.

  The electrically assisted bicycle 10 generates assist torque by driving the motor 44, and applies the assist torque to the rear wheel sprocket 12, thereby reducing the force Tr (FIG. 1) for stepping on the pedal 16. The torque detecting unit 20 detects the driving torque applied to the crankshaft 15, and the control unit 41 controls the driving of the motor 44 based on the driving torque. The assist torque generated by the drive of the motor 44 is applied to the rear wheel sprocket 12, thereby assisting the rotational drive of the rear wheel as the drive wheel.

  Assist on / off by the motor 44, mode setting, and the like are performed by operating the input unit 51, and the setting content is displayed on the display unit 52 and stored in the memory 32. The input unit 51 and the display unit 52 are provided on a handlebar (not shown). Further, the memory 32 stores the detection result of the tension, the calculation result of the torque, and various settings related thereto, for example, the radius r of the pedal part sprocket 14, the distance R between the center 14 c of the pedal part sprocket 14 and the connection position 16 c of the pedal 16. Etc. are saved.

  The rear wheel sprocket 12 as a wheel drive shaft is rotatably supported by the frame 11 and rotatably supports a rear wheel (not shown) as a drive wheel.

  Further, the frame 11 rotatably supports the pedal portion sprocket 14 and the two crankshafts 15 via a rotation shaft (not shown). The rotating shaft extends in the left-right direction (X direction) and is rotatably supported by the frame 11.

  The pedal part sprocket 14 has a radius r and is attached to the end of the rotating shaft in the left-right direction. The pedal portion sprocket 14 has a center 14c disposed on the central axis of the rotating shaft.

  The two crankshafts 15 extend in an arm shape, and one end thereof is locked to the center 14c from the left and right sides of the pedal portion sprocket 14, respectively. The two crankshafts 15 extend in directions opposite to each other across the center 14 c in the radial direction of the pedal portion sprocket 14. With the above configuration, the two crankshafts 15 and the pedal portion sprocket 14 are supported by the frame 11 via the rotating shaft, and are rotatable about the rotating shaft.

  The other end of the two crankshafts 15 is provided with a pedal shaft portion 15a extending in the left-right direction, and the two pedal shaft portions 15a extend in directions away from each other. The pedals 16 are respectively held on the pedal shaft portions 15a. The length from the center 14c of the pedal sprocket 14 to the connecting position 16c between the pedal shaft 15a extending from the crankshaft 15 and the pedal 16 is R. The connection position 16c is located at the approximate center of the pedal 16 in the YZ plane.

A drive chain 13 composed of a belt-like roller chain is looped around the rear wheel sprocket 12 and the pedal part sprocket 14, and a plurality of rollers of the drive chain 13 are arranged in the rear wheel sprocket 12 and the pedal part sprocket 14. It fits into each of a plurality of tooth bottoms. As described above, the drive chain 13 is wound around each of the rear wheel sprocket 12 and the pedal portion sprocket 14, so that a tension acts on the drive chain 13. In the electrically assisted bicycle 10, when the user steps on the pedal 16, the pedal sprocket 14 rotates via the crankshaft 15, and the roller of the drive chain 13 on which the tension is exerted thereby has the rear wheel sprocket 12 and the pedal. Each sprocket 14 is driven without being disengaged from the tooth bottom, and power is transmitted to the drive wheel supported by the rear wheel sprocket 12.
As the drive transmission member, instead of the drive chain formed of a roller chain, a form in which a belt-like belt is looped and hung around the rear wheel sprocket 12 and the pedal portion sprocket 14 is also possible.

  In addition to the rear wheel sprocket 12 and the pedal part sprocket 14, the drive chain 13 is hung around the detection part sprocket 21 of the torque detection part 20 in the upper part 13 a on the upper side in the Z direction. As shown in FIG. 3, the detection unit sprocket 21 as a gear unit is held by a holder 22, and the holder 22 is fixed to a support plate 23.

  The holder 22 includes a shaft portion 22b extending in the X direction in the internal space of the main body portion 22a. The shaft portion 22b is rotatably inserted into a hole portion 21a penetrating the detection portion sprocket 21 in the thickness direction (X direction), so that the detection portion sprocket 21 is engaged with the upper portion 13a of the drive chain 13. It can be rotated. A cylindrical coupling portion 22 c extends upward from the upper surface of the main body portion 22 a of the holder 22. The holder 22 and the support plate 23 are coupled to each other by inserting and fixing the coupling portion 22c into a hole 23a that penetrates the support plate 23 in the thickness direction (Z direction).

  As shown in FIGS. 3 and 4, the support plate 23 is fixed to the center in the longitudinal direction (X direction) of the elastically deformable long plate-shaped deformable portion 24 (strain body). Fixing portions 25 and 26 are fixed to both ends of the deformation portion 24 in the longitudinal direction. These fixing portions 25 and 26 are respectively fixed to the frame 11. With this configuration, the detection unit sprocket 21 is held at the center in the longitudinal direction of the deformation unit 24 via the holder 22, and the tension of the drive chain 13 that meshes with the detection unit sprocket 21 by the elastic force of the deformation unit 24. It can be displaced in the Z direction according to the change.

  The detection unit sprocket 21 is disposed at a height that can be displaced above the position of the upper portion 13a of the drive chain 13 in the state C1 (FIG. 1) in which the detection unit sprocket 21 is not provided. As a result, a force F (FIG. 1) along the Z direction is applied to the upper portion 13a of the drive chain 13 in accordance with the tension of the drive chain 13 that varies depending on the drive torque.

  As shown in FIG. 4, strain gauges G <b> 1 and G <b> 3 are provided in order from the support plate 23 side on the upper surface 24 a of the region between the support plate 23 and the fixed portion 25 in the deformed portion 24. Strain gauges G4 and G2 are provided in order from the support plate 23 side on the upper surface 24b of the region between the fixed portion 26 and the upper surface 24b. In FIG. 4, the detailed pattern display of the strain gauges G1 to G4 is omitted. The strain gauges G <b> 1 to G <b> 4 are obtained by printing a predetermined metal pattern on an insulating base material, for example, and are used by being attached to a predetermined position of the deformable portion 24.

  As shown in FIG. 5, the strain gauges G1 to G4 have resistance values R1 to R4, respectively, and form a bridge circuit. That is, the first strain gauge G1 and the third strain gauge G3 are arranged in series, and the fourth strain gauge G4 and the second strain gauge G2 are arranged in series, and the strain gauges G1, G3 and The strain gauges G4 and G2 are connected in parallel to the power source S having the voltage V1. Further, an amplifying unit U is provided, and a voltage V2 at a connection point P1 between the first strain gauge G1 and the third strain gauge G3 is input to the positive electrode input, and a fourth strain gauge G4 is input to the negative electrode input. And the voltage V3 at the connection point P2 of the second strain gauge G2.

  When driving torque is applied to the pedal sprocket 14 by the user stepping on the pedal 16, a pulling force is applied to the driving chain 13, so that the tension of the driving chain 13 changes. That is, when the driving torque changes according to the change in the driving situation, the tension generated in the driving chain 13 also changes. Due to this change in tension, the force F (FIG. 1) applied to the detection unit sprocket 21 along the Z direction also changes, whereby the support plate 23 holding the detection unit sprocket 21 is displaced in the Z direction. Accordingly, the deformation portion 24 is deformed. Since the strain gauges G1 to G4 are respectively deformed along with this deformation, the respective resistance values R1 to R4 are changed, so that the output from the amplifying unit U is changed as the resistance value is changed. Basically, the greater the driving torque applied to the pedal sprocket 14, the closer the drive chain 13 is to the state of C1 shown in FIG. When the value of F increases, the deformation amount (deflection amount) of the deformation unit 24 increases, the resistance values R1 to R4 change, and the output from the amplification unit U changes. For example, as shown in FIG. 1 or FIG. 4, when a downward force F is applied, the strain gauges G <b> 1 and G <b> 2 provided on the fixing portions 25 and 26 side contract as compared with a case where the force F is not applied. For this reason, the corresponding resistance values R1 and R2 are reduced, and the strain gauges G3 and G4 on the support plate 23 side are expanded, so that the corresponding resistance values R3 and R4 are increased. Therefore, the output from the amplifier U is larger than in the state where the force F is not applied.

  The output from the amplifying unit U is converted into a digital signal by an analog-digital converter (ADC) and output as a change in tension. The output signal is sent to the torque calculation unit 31 via the control unit 41 and is stored in the memory 32.

The torque calculator 31 calculates drive torque based on the output signal from the ADC. The output signal from the ADC corresponds to the amount of change in tension. Based on this signal, the deviation angle θ (FIG. 1) of the upper part 13a of the drive chain 13 of C1 when the detector sprocket 21 is used and when it is not used. And the force F concerning the detection part sprocket 21 is computable. From these calculation results and the radius r of the pedal part sprocket 14 and the length R of the crankshaft 15 from the center 14c of the pedal part sprocket 14 to the coupling position 16c of the pedal 16, the pedal 16 is expressed by the following equation (1). The stepping force Tr can be calculated. This calculation result is stored in the memory 32.
Tr = (F · r) / (R · sin θ) (1)
Based on the force Tr and the length R calculated in this way, the driving torque applied to the crankshaft 15 can be calculated.

Here, it is preferable that the torque calculation unit 31 calculates an average tension that is an average value of a plurality of tensions stored in the memory 32 and is calculated based on the average tension. For example, detection by the tension detection unit 27 is performed every second, and an average value of tensions for a plurality of times of 15 seconds as a unit period is calculated to obtain an average tension.
Further, the torque calculation unit 31 calculates an average drive torque, which is an average value of the drive torques for a plurality of times within the unit period, stored in the memory 32, and the control unit 41 determines the motor 44 based on the average drive torque. It is preferable to perform control. For example, the calculation by the torque calculation unit 31 is performed every second, and the average value of the driving torque for a plurality of times for 15 seconds as a unit period is calculated and set as the average driving torque.

The drive torque detection method of this embodiment detects the drive torque applied to the crankshaft 15 by the following steps.
(1) The amount of strain generated in the strain gauges G1 to G4 on the deformation portion 24 connected to the drive chain 13 is measured (strain measurement step).
(2) The tension generated in the drive chain 13 is detected based on the measured strain amount (tension detection step).
(3) Based on the tension detected in the tension detection step of (2), the drive torque applied to the crankshaft 15 is calculated (torque calculation step).

With the configuration described above, the following effects are achieved according to the above embodiment.
(1) The tension of the drive chain 13 is changed by the force of depressing the pedal. That is, the tension of the drive chain 13 is changed by the drive torque generated on the crankshaft 15. Therefore, by measuring the change in the tension of the drive chain 13, the drive torque in the crankshaft 15 can be calculated, and the control unit 41 drives the motor 44 according to the calculated drive torque to apply the assist torque. be able to. Therefore, the driving torque can be calculated easily and accurately without being incorporated in the mechanical portion of the tachometer as in the prior art, without causing a significant increase in weight, and without using complicated wiring. . Therefore, it is possible to provide an electrically assisted bicycle that can easily transmit drive torque as an electrical signal.
(2) By detecting the strain amount of the deforming portion 24 with the strain gauges G1 to G4, the change in the tension of the drive chain 13 can be measured, and the rotational torque can be calculated easily and accurately.
(3) By connecting the deformable portion 24 to the drive chain 13 via the detection portion sprocket 21 as a gear portion, it is possible to detect torque without greatly hindering the movement of the drive chain 13.
(4) Assuming that the tension used for calculating the drive torque is the average tension and / or that the control of the motor 44 by the control unit 41 is performed based on the average drive torque, thereby causing instantaneous irregular torque fluctuations. However, since the assist torque is not suddenly changed every time it fluctuates, the influence on the operation due to the sudden change of the assist torque can be suppressed.

A modification will be described below.
In the above embodiment, the support plate 23 is arranged in the center of the deformable portion 24 and both ends of the deformable portion 24 are fixed to the frame 11 by the two fixing portions 25 and 26. Thus, a cantilever structure in which only one end of the deformable portion 24 is fixed to the frame 11 may be employed. As a result, a simple and compact configuration can be achieved.

In the above-described embodiment, the detector sprocket 21 is rotatably attached to the upper part 13a of the drive chain 13. However, the detector sprocket 21 is rotatably attached to the lower part 13b of the drive chain 13 and the tension of the drive chain 13 is measured. You can also
Although the present invention has been described with reference to the above embodiment, the present invention is not limited to the above embodiment, and can be improved or changed within the scope of the purpose of the improvement or the idea of the present invention.

  In the above embodiment, the drive chain 13 is a ring chain, but a method of transmitting a driving force with a belt may be used.

  As described above, the electrically assisted bicycle and the drive torque detection method according to the present invention are useful in that torque detection can be performed easily and accurately.

DESCRIPTION OF SYMBOLS 10 Electric assist bicycle 11 Frame 12 Rear wheel sprocket 13 Drive chain (drive transmission member)
DESCRIPTION OF SYMBOLS 14 Pedal part sprocket 15 Crankshaft 15a Pedal shaft part 16 Pedal 20 Torque detection part 21 Detection part sprocket 22 Holder 23 Support plate 24 Deformation part 25, 26 Fixing part 27 Tension detection part 31 Torque calculation part 32 Memory 41 Control part 42 Power supply Unit 43 Motor drive unit 44 Motor 51 Input unit 52 Display unit G1, G2, G3, G4 Strain gauge S Power supply Tr Pedal force U Amplification unit

Claims (6)

Frame,
A wheel drive shaft provided on the frame and rotatably supporting a drive wheel;
A crankshaft rotatably provided on the frame and provided with a driving torque;
A belt-like drive transmission member that is looped around so that the drive torque can be transmitted from the crankshaft to the wheel drive shaft;
Assist driving means for assisting rotational driving of the drive wheels by applying assist torque to the wheel drive shaft;
Torque detecting means for detecting drive torque applied to the crankshaft;
An electrically assisted bicycle having control means for controlling the assist drive means based on drive torque applied to the crankshaft;
The torque detection means comprises: a tension detection means capable of detecting a tension generated in the drive transmission member; and a torque calculation means for calculating the drive torque based on the tension.   The tension detecting means includes a deformable portion that can be elastically deformed in accordance with a change in the tension, and a strain gauge that can measure the amount of strain generated in the deformed portion, and based on the strain amount, the drive transmission member The power-assisted bicycle according to claim 1, wherein the generated tension is detected.   The tension detecting means has a gear portion that engages with the drive transmission member and is rotatable with the movement of the drive transmission member, and the deformation portion is connected to the drive transmission member through at least the gear portion. The electrically assisted bicycle according to claim 2, wherein Storage means capable of storing the tension detected by the tension detection means;
The torque calculation means can calculate an average tension, which is an average value of the tensions for a plurality of times in a unit period, stored in the storage means,
The electrically assisted bicycle according to any one of claims 1 to 3, wherein the tension used to calculate the driving torque by the torque calculating means is the average tension. Storage means capable of storing the drive torque calculated by the torque calculation means;
The torque calculating means can calculate an average driving torque that is an average value of the driving torque for a plurality of times within a unit period stored in the storage means,
The electrically assisted bicycle according to any one of claims 1 to 3, wherein the driving torque used for controlling the assist driving means by the control means is the average driving torque. A drive torque detection method for calculating a drive torque applied to the crankshaft in an electrically assisted bicycle that transmits a drive torque applied to the crankshaft to a wheel drive shaft via a drive transmission member,
A strain measuring step for measuring the amount of strain generated in the deformed portion connected to the drive transmission member;
A tension detecting step for detecting a tension generated in the drive transmission member based on the measured strain amount;
And a torque calculating step of calculating a driving torque applied to the crankshaft based on the tension detected in the tension detecting step.

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