MOTOR CONTROL DEVICE AND ELECTRIC ASSISTED BICYCLE

Abstract

To suppress the risk that a motor may generate assist torque more than necessary.SOLUTION: A motor control device of a power-assisted bicycle comprises a torque sensor that detects torque based on tread force applied to a pedal, a motor that generates assist torque for driving a wheel in accordance with the torque detected by the torque sensor and a motor control part that controls the motor, where the torque sensor comprises a voltage output part that outputs a reference voltage when tread force is not applied to the pedal and outputs a detection voltage when tread force is applied to the pedal and a torque calculating part that calculates torque on the basis of a difference between the reference voltage and the detection voltage outputted from the voltage outputting part. The motor control device further comprises a reference voltage fluctuating part that fluctuates a value of the reference voltage in accordance with fluctuation caused by an external factor of a voltage outputted from the voltage output part, where when torque larger than zero is calculated although tread force is not applied to the pedal, the reference voltage fluctuating part increases the value of the reference voltage.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a motor control device and an electrically assisted bicycle. [Background technology]

[0002] Conventionally, there has been known an electrically assisted bicycle that includes a torque sensor that detects pedaling force and outputs a voltage corresponding to the pedaling force, and a motor that is driven based on the torque detected by the torque sensor to generate auxiliary power (see Patent Document 1). Patent Document 1 describes that the zero point of the torque sensor is measured when the drive control of the motor is started, and then the pedaling force is calculated by subtracting the zero point value from the detection data of the torque sensor. Patent Document 1 also describes that if the lowest point of the detection data of the torque sensor is greater than the threshold value for determining an abnormality of the torque sensor for a predetermined period of time or more, it is determined that an abnormality has occurred and the drive of the motor is stopped. Incidentally, the technology described in Patent Document 1 takes into consideration an abnormality in which the output voltage of the torque sensor increases, but does not take into consideration an abnormality in which the output voltage of the torque sensor decreases. Therefore, in the technology described in Patent Document 1, when an abnormality in which the output voltage of the torque sensor decreases occurs, the motor may not be appropriately controlled. In detail, in the technology described in Patent Document 1, when an abnormality in which the output voltage of the torque sensor decreases occurs, the value of the reference voltage corresponding to the zero point value of the output voltage of the torque sensor may drop too much, and the motor may generate more auxiliary power (assist torque) than necessary. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-041352 A Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the above-mentioned problems, an object of the present invention is to provide a motor control device and an electrically assisted bicycle that can reduce the risk of the motor generating more assist torque than necessary. [Means for solving the problem]

[0005] One aspect of the present invention is a motor control device provided on an electrically assisted bicycle which includes a wheel, a pedal to which a pedaling force is applied to drive the wheel, a torque sensor which detects a torque based on the pedaling force applied to the pedal, a motor which generates an assist torque to drive the wheel in accordance with the torque detected by the torque sensor, and a motor control unit which controls the motor, wherein the torque sensor comprises a voltage output unit which outputs a reference voltage when the pedaling force is not applied to the pedal, and outputs a detected voltage which has a value different from the reference voltage when the pedaling force is applied to the pedal, and a torque calculation unit which calculates the torque based on the difference between the reference voltage output from the voltage output unit and the detected voltage, and a reference voltage fluctuation unit which fluctuates the value of the reference voltage used in the calculation of the torque by the torque calculation unit in accordance with fluctuations due to external factors in the voltage output from the voltage output unit, and when the torque calculation unit calculates a value greater than zero as the torque value even though the pedaling force is not being applied to the pedal, the reference voltage fluctuation unit increases the value of the reference voltage used in the calculation of the torque by the torque calculation unit.

[0006] In one embodiment of the motor control device of the present invention, when the torque calculation unit calculates a torque value greater than zero even though no pressure is being applied to the pedal, the reference voltage fluctuation unit may increase the value of the reference voltage used in the calculation of the torque by the torque calculation unit to the value of the detected voltage currently output by the voltage output unit.

[0007] In one embodiment of the motor control device of the present invention, the slope of the reference voltage value increased by the reference voltage fluctuation unit when no pedal force is applied to the pedal may be greater than or equal to the slope of the reference voltage value decreased by the reference voltage fluctuation unit when no pedal force is applied to the pedal.

[0008] An electrically assisted bicycle according to one aspect of the present invention may include the motor control device. Effect of the Invention

[0009] According to the present invention, it is possible to provide a motor control device and an electrically assisted bicycle that can reduce the risk of the motor generating more assist torque than necessary. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing an example of the configuration of an electrically assisted bicycle according to a first embodiment. [Diagram 2] 2 is a diagram showing an example of functional blocks of a motor control device provided in the power-assisted bicycle of the first embodiment. FIG. [Diagram 3] 5A and 5B are diagrams for explaining a reference voltage, a detected voltage, and a difference when no force is being applied to a pedal and when a force is being applied to the pedal. [Figure 4] 4 is a diagram for explaining an example of fluctuation (increase and decrease) in the voltage output from the voltage output section of the torque sensor due to an external factor, and processing performed by the reference voltage fluctuation section when such fluctuation occurs. FIG. [Diagram 5] FIG. 13 is a diagram for explaining an example of a fluctuation (two decreases) in the voltage output from the voltage output unit of the torque sensor due to an external factor, and a process performed by the reference voltage fluctuation unit, the reference voltage lower limit value setting unit, the reference voltage lower limit value fluctuation unit, and the detection voltage monitoring unit when the fluctuation occurs. [Figure 6] 5 is a flowchart illustrating a first example of processing executed in the power-assisted bicycle of the first embodiment. [Figure 7]11 is a diagram for explaining a comparative example in which the motor generates more assist torque than necessary as a result of the reference voltage value decreasing too much. FIG. [Figure 8] 11 is a diagram for explaining the reference voltage, the detected voltage, and the difference when the crank is rotated in reverse by a rider of the power-assisted bicycle when the ratchet is deteriorated. FIG. [Figure 9] 6 is a flowchart illustrating a second example of the processing executed in the power-assisted bicycle of the first embodiment. [Figure 10] 4A to 4C are diagrams illustrating an example of processing performed by a reference voltage variation unit of the power-assisted bicycle of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a motor control device and an electrically assisted bicycle according to the present invention will be described.

[0012] First Embodiment Fig. 1 is a diagram showing an example of the configuration of an electrically assisted bicycle 1 according to the first embodiment. Fig. 2 is a diagram showing an example of functional blocks of a motor control device provided in the electrically assisted bicycle 1 according to the first embodiment. In the example shown in Figures 1 and 2, the electric assisted bicycle 1 of the first embodiment includes a wheel 11, pedals 12, a crank 13, a ratchet 14, a motor 1M, a torque sensor 1A, a crank rotation sensor 1B, a motor control unit 1L, and a torque correction unit 1N. The wheels 11 include a front wheel 11A and a rear wheel 11B. A pedaling force of a rider of the power-assisted bicycle 1 that drives the wheels 11 (rear wheel 11B in the example shown in FIG. 1) is applied to the pedals 12. The cranks 13 are connected to the pedals 12. The cranks 13 convert the pedaling force of the rider of the power-assisted bicycle 1 that is applied to the pedals 12 into a force that drives the rear wheel 11B. The ratchet 14 is a mechanism that transmits the pedaling force applied to the pedals 12 to the rear wheel 11B when the cranks 13 are rotating forward, and prevents the pedaling force applied to the pedals 12 from being transmitted to the rear wheel 11B when the cranks 13 are rotating reversely. The motor 1M generates an assist torque that drives the wheels 11 (front wheel 11A in the example shown in FIG. 1). In the example shown in FIG. 1, the motor 1M drives the front wheels 11A, but in other examples, the motor 1M may drive the rear wheels 11B.

[0013] 1 and 2, torque sensor 1A detects torque (≈ pedaling force × length of crank 13) based on the pedaling force applied by the rider of power-assisted bicycle 1 to pedal 12. Torque sensor 1A includes a voltage output unit 1A1 and a torque calculation unit 1A2. The voltage output unit 1A1 outputs a voltage. As will be described in detail later, the voltage output from the voltage output unit 1A1 may fluctuate (increase or decrease) due to the influence of external factors (such as the temperature around the torque sensor 1A, electromagnetism, etc.). When the voltage output from the voltage output unit 1A1 does not fluctuate due to the influence of external factors, the voltage output unit 1A1 outputs the reference voltage RV when no force is being applied to the pedal 12, and outputs a detection voltage DV whose value is different from the reference voltage RV when force is being applied to the pedal 12. On the other hand, when the voltage output from the voltage output unit 1A1 fluctuates due to the influence of external factors, the voltage output from the voltage output unit 1A1 when no force is being applied to the pedal 12 is no longer the reference voltage RV. Based on the difference ΔV between the reference voltage RV and the detected voltage DV output from the voltage output unit 1A1, the torque calculation unit 1A2 calculates a torque based on the pedal force applied to the pedal 12. The torque calculation unit 1A2 calculates a larger value as the torque based on the pedal force applied to the pedal 12 as the difference ΔV between the reference voltage RV and the detected voltage DV becomes larger. The motor 1M generates an assist torque for driving the wheels 11 in accordance with the torque detected by the torque sensor 1A (the torque calculated by the torque calculation unit 1A2 of the torque sensor 1A). The motor 1M generates a larger assist torque as the torque detected by the torque sensor 1A increases. The motor control device provided in the power-assisted bicycle 1 includes, for example, a torque sensor 1A, a crank rotation sensor 1B, a motor M, a motor control unit 1L, and a torque correction unit 1N, all of which are shown in FIG.

[0014] Fig. 3 is a diagram for explaining the reference voltage RV, the detected voltage DV, and the difference ΔV when no pedal force is applied to the pedal 12 and when a pedal force is applied to the pedal 12. In detail, Fig. 3 shows an example of the time waveform of the detected voltage DV output from the voltage output unit 1A1 of the torque sensor 1A when a pedal force is applied to the pedal 12 so that the crank 13 rotates forward. In the example shown in FIG. 3, the voltage output from the voltage output unit 1A1 is not affected by external factors (such as the temperature around the torque sensor 1A, electromagnetism, etc.). During the period from time t1 to time t2, no pedaling force is applied to the pedal 12. Then, during the period from time t2 onwards, a pedaling force is applied to the pedal 12 so that the crank 13 rotates forward (that is, so that the power-assisted bicycle 1 moves forward). When the value of the detected voltage DV output from the voltage output unit 1A1 fluctuates at a period that is half the rotation period of the crank 13 when the power-assisted bicycle 1 is traveling, the torque sensor 1A estimates that a pedaling force is being applied to the pedal 12. On the other hand, when the value of the detected voltage DV output from the voltage output unit 1A1 does not fluctuate at a period that is half the rotation period of the crank 13 when the power-assisted bicycle 1 is traveling, the torque sensor 1A estimates that no pedaling force is being applied to the pedal 12. In another example, whether or not a pedal force is being applied to the pedal 12 may be determined based on the detection result of the torque sensor 1A and the detection result of the crank rotation sensor 1B.

[0015] 3, during the period from time t1 to time t2, the value of the detected voltage DV output from the voltage output unit 1A1 does not fluctuate in a period that is half the rotation period of the crank 13 when the power-assisted bicycle 1 is traveling. Therefore, the torque sensor 1A estimates that no pedal force is being applied to the pedal 12 during the period from time t1 to time t2. Specifically, for example, at time t1, the torque sensor 1A estimates that no pedal force is being applied to the pedal 12 based on the time waveform of the detected voltage DV output from the voltage output unit 1A1 before time t1. Furthermore, the torque sensor 1A sets the detected voltage DV output from the voltage output section 1A1 at the time t1 when it is estimated that no pedal force is being applied to the pedal 12 as the reference voltage RV. During the period after time t1, the reference voltage RV is maintained at a constant value.

[0016] 3, during the period from time t1 to time t2, the detected voltage DV output from the voltage output unit 1A1 coincides with the reference voltage RV, and the difference ΔV between the reference voltage RV and the detected voltage DV becomes zero. Therefore, the torque calculation unit 1A2 calculates zero as the torque based on the pedaling force applied to the pedal 12. As a result, the motor 1M does not generate an assist torque that drives the wheels 11. Next, during the period from time t2 onwards, the detection voltage DV output from the voltage output unit 1A1 becomes higher than the reference voltage RV, and the difference ΔV between the reference voltage RV and the detection voltage DV (=detection voltage DV-reference voltage RV) becomes greater than zero. As a result, the motor 1M generates an assist torque that drives the wheels 11.

[0017] Returning to the explanation of the example shown in Figures 1 and 2, the crank rotation sensor 1B detects the rotation of the crank 13. The crank rotation sensor 1B has a configuration similar to that described in paragraph 0024 of JP-A-9-286377, for example, and has a function of determining whether the crank 13 connected to the pedal 12 is rotating forward or backward. The motor control unit 1L controls the motor 1M based on the torque detected by the torque sensor 1A and the like. The torque correction unit 1N corrects the reference voltage RV when the voltage output from the voltage output unit 1A1 is affected by external factors (such as the temperature around the torque sensor 1A, electromagnetism, etc.) The torque correction unit 1N includes a reference voltage fluctuation unit 1N1, a reference voltage lower limit value setting unit 1N2, a reference voltage lower limit value fluctuation unit 1N3, and a detected voltage monitoring unit 1N4. The reference voltage variation unit 1N1 varies the value of the reference voltage RV used in the torque calculation by the torque calculation unit 1A2. The reference voltage lower limit setting unit 1N2 sets a lower limit value RVmin of the reference voltage RV varied by the reference voltage variation unit 1N1. The reference voltage lower limit variation unit 1N3 varies the lower limit value RVmin of the reference voltage RV set by the reference voltage lower limit setting unit 1N2. The reference voltage lower limit variation unit 1N3 varies the lower limit value RVmin of the reference voltage RV based on, for example, the detection voltage DV and the reference voltage RV output from the voltage output unit 1A1. The detected voltage monitor 1N4 monitors the detected voltage DV output from the voltage output unit 1A1.

[0018] As described above, the technology described in Patent Document 1 takes into consideration an abnormality in which the output voltage of the torque sensor increases, but does not take into consideration an abnormality in which the output voltage of the torque sensor decreases. The present inventors have found through extensive research that the voltage output from the voltage output section 1A1 of the torque sensor 1A not only increases but also decreases due to the influence of external factors. If the voltage output from the voltage output section 1A1 of the torque sensor 1A decreases due to the influence of an external factor, and if the value of the reference voltage RV is not decreased but maintained as it is, the difference ΔV between the reference voltage RV and the detected voltage DV (= reference voltage RV - detected voltage DV) will become abnormally large, and accordingly the torque calculated by the torque calculation section 1A2 will become abnormally large, which may result in the motor 1M generating more assist torque than necessary.

[0019] Therefore, in the example shown in Figures 1 and 2, the reference voltage variation unit 1N1 varies the value of the reference voltage RV used for calculating torque by the torque calculation unit 1A2 in response to fluctuations in the voltage output from the voltage output unit 1A1 of the torque sensor 1A due to external factors (e.g., the temperature around the torque sensor 1A, electromagnetism, etc.).

[0020] FIG. 4 is a diagram for explaining an example of fluctuation (increase and decrease) in the voltage output from voltage output section 1A1 of torque sensor 1A in response to an external factor, and a process performed by reference voltage fluctuation section 1N1 when such fluctuation occurs. In the example shown in FIG. 4, no pedal force is applied to the pedal 12 during the period from time t11 to time t16. Specifically, during the period from time t11 to time t12, the value DV1 of the detected voltage DV output from the voltage output section 1A1 of the torque sensor 1A is constant. Specifically, for example, at time t11, the torque sensor 1A estimates that no pedal force is being applied to the pedal 12 based on the time waveform of the detected voltage DV output from the voltage output unit 1A1 before time t11. Furthermore, the torque sensor 1A sets the value DV1 of the detected voltage DV output from the voltage output unit 1A1 at the time t11 when it is estimated that no pedal force is being applied to the pedal 12 as the value RV1 of the reference voltage RV. During the period from time t11 to time t12, the reference voltage RV is maintained at a constant value RV1. The torque sensor 1A calculates zero as the torque based on the pedal force applied to the pedal 12, based on the difference ΔV (=value RV1-value DV1) between the reference voltage RV and the detected voltage DV.

[0021] In the example shown in FIG. 4, next, during the period from time t12 to time t13, the detection voltage DV output from the voltage output section 1A1 of the torque sensor 1A increases from the value DV1 to the value DV2 due to an external factor. At time t13, the torque sensor 1A estimates that no pressure is being applied to the pedal 12 based on the time waveform of the detected voltage DV output from the voltage output unit 1A1, for example, during the period from time t12 to time t13 (i.e., the time waveform of the detected voltage DV indicating that although the detected voltage DV is increasing, there is no increase or decrease in the detected voltage DV due to the rotation of the crank 13). The reference voltage variation unit 1N1 varies (more specifically, increases) the reference voltage RV from a value RV1 to a value RV2 (= a value DV2) at time t13 when it is estimated that no pedal force is being applied to the pedal 12. That is, the reference voltage variation unit 1N1 sets the value DV2 of the detected voltage DV output from the voltage output unit 1A1 at time t13 as the value RV2 of the reference voltage RV after the variation. During the period from time t13 to time t14, the reference voltage RV is maintained at a constant value RV2. The torque sensor 1A calculates zero as the torque based on the pedal force applied to the pedal 12, based on the difference ΔV (=value RV2-value DV2) between the reference voltage RV and the detected voltage DV.

[0022] In the example shown in FIG. 4, next, during the period from time t14 to time t15, the detection voltage DV output from the voltage output section 1A1 of the torque sensor 1A decreases from the value DV2 to the value DV3 due to an external factor. At time t15, the torque sensor 1A estimates that no pressure is being applied to the pedal 12 based on the time waveform of the detected voltage DV output from the voltage output unit 1A1, for example, during the period from time t14 to time t15 (i.e., the time waveform of the detected voltage DV indicating that although the detected voltage DV is decreasing, there is no increase or decrease in the detected voltage DV due to the rotation of the crank 13). The reference voltage variation unit 1N1 varies (more specifically, decreases) the reference voltage RV from a value RV2 to a value RV3 (= a value DV3) at time t15 when it is estimated that no pedal force is being applied to the pedal 12. That is, the reference voltage variation unit 1N1 sets the value DV3 of the detected voltage DV output from the voltage output unit 1A1 at time t15 as the value RV3 of the reference voltage RV after the variation. During the period from time t15 to time t16, the reference voltage RV is maintained at a constant value RV3. The torque sensor 1A calculates zero as the torque based on the pedal force applied to the pedal 12, based on the difference ΔV (=value RV3−value DV3) between the reference voltage RV and the detected voltage DV.

[0023] FIG. 5 is a diagram for explaining an example of a fluctuation (two decreases) in the voltage output from the voltage output unit 1A1 of the torque sensor 1A in response to an external factor, and an example of the processing performed by the reference voltage fluctuation unit 1N1, the reference voltage lower limit value setting unit 1N2, the reference voltage lower limit value fluctuation unit 1N3, and the detected voltage monitoring unit 1N4 when this fluctuation occurs. 5, the value of the detected voltage DV output from the voltage output unit 1A1 at a predetermined time before time t21 when it is estimated that no pedal force is being applied to the pedal 12 is set as the value RV21 of the reference voltage RV. A lower limit value RVmin of the reference voltage RV reduced by the reference voltage fluctuation unit 1N1 is set by a reference voltage lower limit value setting unit 1N2. Furthermore, an abnormality determination threshold voltage TV of the detected voltage DV output from the voltage output unit 1A1 is set by a detected voltage monitoring unit 1N4.

[0024] During the period from time t21 to time t22, the detection voltage DV output from the voltage output unit 1A1 is not affected by external factors (such as the temperature around the torque sensor 1A, electromagnetism, etc.) because these factors are small compared to the pedaling force. Therefore, there is no need to take the influence of external factors into consideration. During the period from time t21 to time t22, the value of the detected voltage DV output from the voltage output unit 1A1 fluctuates with a period that is half the rotation period of the crank 13 when the power-assisted bicycle 1 is traveling. Therefore, the torque sensor 1A estimates that a pedaling force is being applied to the pedal 12. As a result, during the period from time t21 to time t22, the reference voltage RV is not varied by the reference voltage variation section 1N1, but is maintained at a constant value RV21. During the period from time t21 to time t22, the torque calculation unit 1A2 of the torque sensor 1A calculates the torque based on the difference ΔV between the value RV21 of the reference voltage RV and the detected voltage DV, and the motor 1M generates an assist torque according to the torque calculated by the torque calculation unit 1A2 of the torque sensor 1A. In other words, the power-assisted bicycle 1 is driven normally.

[0025] In the example shown in FIG. 5, next, during the period from time t22 to time t23, the detection voltage DV output from the voltage output section 1A1 of the torque sensor 1A decreases due to an external factor. Furthermore, during the period from time t22 to time t23, the torque sensor 1A estimates that no pressure is being applied to the pedal 12 based on the time waveform of the detected voltage DV output from the voltage output unit 1A1 (i.e., the time waveform of the detected voltage DV which indicates that although the detected voltage DV is decreasing, there is no increase or decrease in the detected voltage DV due to the rotation of the crank 13). During the period from time t22 to time t23, reference voltage variation unit 1N1 reduces the reference voltage RV from value RV21 to a lower limit value RVmin.

[0026] In the example shown in FIG. 5, the lower limit value RVmin of the reference voltage RV is maintained at a constant value during the period from time t23 onwards, but in other examples, the lower limit value RVmin of the reference voltage RV set by the reference voltage lower limit value setting unit 1N2 may be varied (increased or decreased) by the reference voltage lower limit value variation unit 1N3.

[0027] In the example shown in FIG. 5, next, during the period from time t23 to time t24, the detection voltage DV output from the voltage output unit 1A1 is not affected by external factors (e.g., the temperature around the torque sensor 1A, electromagnetism, etc.) because the influence of these external factors is negligible compared to the pedaling force, so there is no need to take the influence of external factors into consideration. During the period from time t23 to time t24, the value of the detected voltage DV output from the voltage output unit 1A1 fluctuates with a period that is half the rotation period of the crank 13 when the power-assisted bicycle 1 is traveling. Therefore, the torque sensor 1A estimates that a pedaling force is being applied to the pedal 12. As a result, during the period from time t23 to time t24, the reference voltage RV is maintained at the lower limit value RVmin without being varied by the reference voltage variation section 1N1. During the period from time t23 to time t24, the torque calculation unit 1A2 of the torque sensor 1A calculates the torque based on the difference ΔV between the lower limit value RVmin of the reference voltage RV and the detected voltage DV, and the motor 1M generates an assist torque according to the torque calculated by the torque calculation unit 1A2 of the torque sensor 1A. In other words, the assist by the motor 1M continues. In detail, since the difference ΔV between the lower limit value RVmin of the reference voltage RV and the detected voltage DV during the period from time t23 to time t24 is smaller than the difference ΔV between the value RV21 of the reference voltage RV and the detected voltage DV during the period from time t21 to time t22, the assist torque generated by motor 1M during the period from time t23 to time t24 is smaller than the assist torque generated by motor 1M during the period from time t21 to time t22.

[0028] In the example shown in FIG. 5, next, during the period from time t24 to time t25, the detection voltage DV output from the voltage output section 1A1 of the torque sensor 1A decreases due to an external factor. Specifically, at time t25, the detection voltage DV output from the voltage output section 1A1 reaches the abnormality determination threshold voltage TV. Furthermore, during the period from time t24 to time t25, the torque sensor 1A estimates that no pressure is being applied to the pedal 12, based on, for example, the time waveform of the detected voltage DV output from the voltage output unit 1A1 (i.e., the time waveform of the detected voltage DV indicating that although the detected voltage DV is decreasing, there is no increase or decrease in the detected voltage DV due to the rotation of the crank 13). During the period from time t24 to time t25, the detected voltage DV output from the voltage output unit 1A1 is lower than the lower limit value RVmin of the reference voltage RV, so the reference voltage RV is maintained at the lower limit value RVmin without being fluctuated by the reference voltage fluctuation unit 1N1, and the detected voltage monitoring unit 1N4 continues to monitor the detected voltage DV output from the voltage output unit 1A1. In detail, during the period from time t24 to time t25, the detection voltage monitoring unit 1N4 determines whether the detection voltage DV output from the voltage output unit 1A1 is equal to or lower than the abnormality determination threshold voltage TV, and outputs a determination result indicating that the detection voltage DV output from the voltage output unit 1A1 is not equal to or lower than the abnormality determination threshold voltage TV (i.e., there is no error).

[0029] In the example shown in FIG. 5, next, during the period from time t25 to time t26, the detection voltage DV output from the voltage output section 1A1 of the torque sensor 1A further decreases from the abnormality determination threshold voltage TV due to an external factor. Furthermore, during the period from time t25 to time t26, the torque sensor 1A estimates that no force is being applied to the pedal 12, based on, for example, the time waveform of the detected voltage DV output from the voltage output unit 1A1 (i.e., the time waveform of the detected voltage DV indicating that although the detected voltage DV is decreasing, there is no increase or decrease in the detected voltage DV due to the rotation of the crank 13). During the period from time t25 to time t26, since the detection voltage DV output from the voltage output unit 1A1 is lower than the lower limit value RVmin of the reference voltage RV, the reference voltage RV is maintained at the lower limit value RVmin without being fluctuated by the reference voltage fluctuation unit 1N1, and the detection voltage monitoring unit 1N4 continues to monitor the detection voltage DV output from the voltage output unit 1A1. In detail, during the period from time t25 to time t26, the detection voltage monitoring unit 1N4 determines whether the detection voltage DV output from the voltage output unit 1A1 is equal to or lower than the abnormality determination threshold voltage TV, and outputs a determination result indicating that the detection voltage DV output from the voltage output unit 1A1 is equal to or lower than the abnormality determination threshold voltage TV (i.e., that a malfunction has occurred). At time t25, for example, when the detected voltage monitor 1N4 first determines that the detected voltage DV output from the voltage output unit 1A1 is equal to or lower than the abnormality determination threshold voltage TV (that is, a failure has occurred), the assist by the motor 1M is stopped.

[0030] FIG. 6 is a flowchart for explaining a first example of the processing executed in the power-assisted bicycle 1 of the first embodiment. In the example shown in FIG. 6, in step S11, the voltage output section 1A1 of the torque sensor 1A outputs the detection voltage DV. Next, in step S12, for example, the detection voltage monitoring unit 1N4 of the torque correction unit 1N determines whether the detection voltage DV is higher than the reference voltage RV. If the detection voltage DV is equal to or lower than the reference voltage RV, the process proceeds to step S13, and if the detection voltage DV is higher than the reference voltage RV, the process proceeds to step S19.

[0031] In step S13, the detection voltage monitoring unit 1N4 of the torque correction unit 1N judges whether the detection voltage DV is equal to or greater than the lower limit RVmin of the reference voltage RV. If the detection voltage DV is lower than the lower limit RVmin of the reference voltage RV, the process proceeds to step S14. If the detection voltage DV is equal to or greater than the lower limit RVmin of the reference voltage RV, the process proceeds to step S17. In step S14, the detection voltage monitoring unit 1N4 of the torque correction unit 1N judges whether or not the detection voltage DV is higher than the abnormality determination threshold voltage TV. If the detection voltage DV is equal to or lower than the abnormality determination threshold voltage TV, the process proceeds to step S15, and if the detection voltage DV is higher than the abnormality determination threshold voltage TV, the process proceeds to step S18.

[0032] In step S15, the detected voltage monitoring unit 1N4 of the torque correction unit 1N determines that a malfunction has occurred in the power-assisted bicycle 1. Next, in step S16, the motor control unit 1L stops (ends) the assist by the motor 1M.

[0033] In step S17, the reference voltage variation unit 1N1 varies the value of the reference voltage RV to the value of the detection voltage DV output from the voltage output unit 1A1 in step S11. Then, the process proceeds to step S19. In step S18, the reference voltage variation unit 1N1 maintains the value of the reference voltage RV at the lower limit value RVmin, rather than varying the value of the reference voltage RV to the value of the detection voltage DV as in step S17. Then, the process proceeds to step S19.

[0034] In step S19, the torque calculation unit 1A2 of the torque sensor 1A calculates the torque based on the pedal force applied to the pedal 12 (≒ pedal force × length of the crank 13) based on the difference ΔV between the reference voltage RV and the detected voltage DV output from the voltage output unit 1A1 in step S11.

[0035] FIG. 7 is a diagram for explaining a comparative example in which the motor 1M generates more assist torque than necessary as the value of the reference voltage RV drops too much. In the comparative example shown in FIG. 7, at time t31, the torque sensor 1A estimates that no pedal force is being applied to the pedal 12, based on the time waveform of the detected voltage DV output from the voltage output unit 1A1 before time t31. Furthermore, the torque sensor 1A sets the value DV31 of the detected voltage DV output from the voltage output unit 1A1 at the time t31 when it is estimated that no pedal force is being applied to the pedal 12 as the value RV31 of the reference voltage RV.

[0036] 7, next, during the period from time t32 to time t33, the rider of the power-assisted bicycle 1 rotates the crank 13 in reverse. In the power-assisted bicycle 1 of the comparative example, because the ratchet 14 has deteriorated, part of the pedaling force applied to the pedal 12 to rotate the crank 13 in reverse is detected by the torque sensor 1A. As a result, the detection voltage DV output from the voltage output unit 1A1 of the torque sensor 1A decreases from a value DV31 to a value DV32. At time t33 when the reverse rotation of the crank 13 stops (i.e., time t33 when the pedal force is no longer applied to the pedal 12), the reference voltage variation unit 1N1 varies the reference voltage RV from value RV31 to value RV32 (=value DV32). That is, the reference voltage variation unit 1N1 sets the value DV32 of the detected voltage DV output from the voltage output unit 1A1 at time t33 as the value RV32 of the reference voltage RV after the variation. During the period from time t33 to time t34, the reference voltage RV is maintained at a constant value RV32. The torque sensor 1A calculates zero as the torque based on the pedal force applied to the pedal 12, based on the difference ΔV (=value RV32-value DV32) between the reference voltage RV and the detected voltage DV.

[0037] In the comparative example shown in FIG. 7, next, during the period from time t34 to time t35, the detection voltage DV output from the voltage output section 1A1 of the torque sensor 1A increases from the value DV32 to the value DV33 due to an external factor (for example, the temperature around the torque sensor 1A, electromagnetism, etc.). 7, for example, at time t35, the value DV33 of the detected voltage DV output from the voltage output unit 1A1 becomes higher than the value RV32 of the reference voltage RV, and the difference ΔV between the reference voltage RV and the detected voltage DV (= the value DV33 of the detected voltage DV - the value RV32 of the reference voltage RV) becomes greater than zero. As a result, the motor 1M generates an assist torque that drives the wheels 11.

[0038] In consideration of this, in the power-assisted bicycle 1 of the first embodiment, as described above, the reference voltage lower limit setting section 1N2 sets the lower limit value RVmin of the reference voltage RV varied by the reference voltage variation section 1N1. Specifically, the reference voltage lower limit setting unit 1N2 sets a value higher than the value RV32 of the reference voltage RV shown in FIG. 7 as the lower limit value RVmin of the reference voltage RV. Therefore, according to the power-assisted bicycle 1 of the first embodiment, it is possible to reduce the risk of the motor 1M generating more assist torque than necessary when the value of the reference voltage RV drops too much, as in the comparative example shown in FIG. In other words, the power-assisted bicycle 1 of the first embodiment can reduce the risk of the motor 1M generating an inappropriate assist torque.

[0039] Even when the reference voltage lower limit value setting unit 1N2 sets the lower limit value RVmin of the reference voltage RV, there are cases where the torque calculation unit 1A2 calculates a torque value greater than zero even though no pedal force is being applied to the pedal 12, as in the case of time t35 in the comparative example shown in FIG. 7. Therefore, in one example of an electrically assisted bicycle 1 of the first embodiment, when the torque calculation unit 1A2 calculates a torque value greater than zero even though no force is being applied to the pedal 12, the reference voltage fluctuation unit 1N1 performs a correction to increase the value of the reference voltage RV used in the calculation of torque by the torque calculation unit 1A2.

[0040] Specifically, when the torque calculation unit 1A2 calculates a torque value greater than zero even though no force is being applied to the pedal 12, such as at time t35 in the comparative example shown in Figure 7, in one example of an electrically assisted bicycle 1 of the first embodiment, the reference voltage fluctuation unit 1N1 increases the value of the reference voltage RV used in the calculation of torque by the torque calculation unit 1A2 to the value of the detected voltage DV currently output by the voltage output unit 1A1 (value DV33 in the comparative example shown in Figure 7).

[0041] In addition, in one example of the electrically assisted bicycle 1 of the first embodiment, when a force is applied to the pedal 12, such as during the period from time t32 to t33 in the comparative example shown in Figure 7, the torque calculation unit 1A2 calculates the torque value to be zero when the detected voltage DV output from the voltage output unit 1A1 is lower than the reference voltage RV.

[0042] Fig. 8 is a diagram for explaining the reference voltage RV, the detected voltage DV, and the difference ΔV when the crank 13 is rotated in reverse by the rider of the power-assisted bicycle 1 when the ratchet 14 is in a deteriorated state. In detail, Fig. 8 shows an example of the time waveform of the detected voltage DV output from the voltage output unit 1A1 of the torque sensor 1A when a pedaling force is applied to the pedal 12 so as to rotate the crank 13 in reverse when the ratchet 14 is in a deteriorated state. In the example shown in FIG. 8, the voltage output from the voltage output unit 1A1 is not affected by external factors (such as the temperature around the torque sensor 1A, electromagnetism, etc.). During the period from time t41 to time t42, no pedaling force is applied to the pedal 12. Next, during the period from time t42 onwards, a pedaling force is applied to the pedal 12 so that the crank 13 rotates in the reverse direction.

[0043] 8, during the period from time t41 to time t42, the value of the detected voltage DV output from the voltage output unit 1A1 does not fluctuate in a period that is half the rotation period of the crank 13 when the power-assisted bicycle 1 is traveling. Therefore, the torque sensor 1A estimates that no pedal force is being applied to the pedal 12 during the period from time t41 to time t42. Specifically, for example, at time t41, the torque sensor 1A estimates that no pedal force is being applied to the pedal 12, based on the time waveform of the detected voltage DV output from the voltage output unit 1A1 before time t41. Furthermore, the torque sensor 1A sets the detected voltage DV output from the voltage output unit 1A1 at the time t41 when it is estimated that no pedal force is being applied to the pedal 12 as the reference voltage RV. During the period from time t41 to time t42, the reference voltage RV is maintained at a constant value.

[0044] 8, during the period from time t41 to time t42, the detected voltage DV output from the voltage output unit 1A1 coincides with the reference voltage RV, and the difference ΔV between the reference voltage RV and the detected voltage DV becomes zero. Therefore, the torque calculation unit 1A2 calculates zero as the torque based on the pedaling force applied to the pedal 12. As a result, the motor 1M does not generate an assist torque that drives the wheels 11. Next, during the period from time t42 onwards, in an electrically assisted bicycle 1 in which the ratchet 14 has deteriorated, part of the force applied to the pedal 12 to rotate the crank 13 in reverse is detected by the torque sensor 1A, the detected voltage DV output from the voltage output section 1A1 of the torque sensor 1A becomes lower than the reference voltage RV, and the difference ΔV between the reference voltage RV and the detected voltage DV (= reference voltage RV - detected voltage DV) becomes a value greater than zero.

[0045] In the example shown in Figure 8, similar to the example of the electric assisted bicycle 1 of the first embodiment described with reference to Figure 7, the torque calculation unit 1A2 calculates a torque value of zero during the period from time t42 onwards when the detection voltage DV output from the voltage output unit 1A1 becomes lower than the reference voltage RV when a force is applied to the pedal 12.

[0046] In the example shown in FIG. 8, during the period from time t42 onwards when the crank rotation sensor 1B determines that the crank 13 is rotating in reverse, the reference voltage variation section 1N1 does not vary the value of the reference voltage RV. That is, during the period after time t42, the reference voltage RV is maintained at a constant value, similarly to the period from time t41 to time t42. Therefore, in the example shown in Figure 8, when the crank 13 is rotated in reverse while the ratchet 14 is deteriorated, as in the comparative example shown in Figure 7, the reference voltage fluctuation unit 1N1 reduces the value of the reference voltage RV, thereby reducing the risk of the motor 1M generating more assist torque than necessary.

[0047] FIG. 9 is a flowchart for explaining a second example of the processing executed in the power-assisted bicycle 1 of the first embodiment. In the example shown in FIG. 9, in step S21, the voltage output section 1A1 of the torque sensor 1A outputs the detection voltage DV. Next, in step S22, for example, the detection voltage monitoring unit 1N4 of the torque correction unit 1N determines whether the detection voltage DV is higher than the reference voltage RV. If the detection voltage DV is equal to or lower than the reference voltage RV, the process proceeds to step S23, and if the detection voltage DV is higher than the reference voltage RV, the process proceeds to step S27.

[0048] In step S23, the detection voltage monitoring unit 1N4 of the torque correction unit 1N judges whether the detection voltage DV is equal to or greater than the lower limit RVmin of the reference voltage RV. If the detection voltage DV is lower than the lower limit RVmin of the reference voltage RV, the process proceeds to step S24, and if the detection voltage DV is equal to or greater than the lower limit RVmin of the reference voltage RV, the process proceeds to step S30. In step S24, the detection voltage monitoring unit 1N4 of the torque correction unit 1N judges whether or not the detection voltage DV is higher than the abnormality determination threshold voltage TV. If the detection voltage DV is equal to or lower than the abnormality determination threshold voltage TV, the process proceeds to step S25. If the detection voltage DV is higher than the abnormality determination threshold voltage TV, the process proceeds to step S31.

[0049] In step S25, the detected voltage monitoring unit 1N4 of the torque correction unit 1N determines that a malfunction has occurred in the power-assisted bicycle 1. Next, in step S26, the motor control unit 1L stops (ends) the assist by the motor 1M.

[0050] In step S27, the torque calculation unit 1A2 of the torque sensor 1A calculates the torque based on the pedal force applied to the pedal 12 (≒ pedal force × length of the crank 13) based on the difference ΔV between the reference voltage RV and the detected voltage DV output from the voltage output unit 1A1 in step S21. Next, in step S28, the torque sensor 1A determines whether or not a pedal force is being applied to the pedal 12. If a pedal force is being applied to the pedal 12, the process returns to step S21. On the other hand, if no pedal force is being applied to the pedal 12, the process proceeds to step S29.

[0051] In step S29, the reference voltage variation unit 1N1 varies the value of the reference voltage RV to the value of the detection voltage DV output from the voltage output unit 1A1 in step S21 (more specifically, increases the value to the value of the detection voltage DV). Then, the process returns to step S21.

[0052] In step S30, the reference voltage variation unit 1N1 varies the value of the reference voltage RV to the value of the detection voltage DV output from the voltage output unit 1A1 in step S21. Then, the process proceeds to step S32. In step S31, the reference voltage change unit 1N1 maintains the value of the reference voltage RV at the lower limit value RVmin, rather than changing the value of the reference voltage RV to the value of the detection voltage DV as in steps S29 and S30. Next, the process proceeds to step S32.

[0053] In step S32, the torque calculation unit 1A2 of the torque sensor 1A calculates the torque (≈push force × length of the crank 13) based on the push force applied to the pedal 12, based on the difference ΔV between the reference voltage RV and the detection voltage DV output from the voltage output unit 1A1 in step S21. Then, the process returns to step S21.

[0054] FIG. 10 is a diagram for explaining an example of the processing performed by the reference voltage change unit 1N1 of the power-assisted bicycle 1 of the first embodiment. In the example shown in FIG. 10, no pedal force is applied to the pedal 12 during the period from time t51 to time t55. Specifically, during the period from time t51 to time t52, the value DV51 of the detected voltage DV output from the voltage output section 1A1 of the torque sensor 1A is constant. Specifically, for example, at time t51, the torque sensor 1A estimates that no pedal force is being applied to the pedal 12 based on the time waveform of the detected voltage DV output from the voltage output unit 1A1 before time t51. Furthermore, the torque sensor 1A sets the value DV51 of the detected voltage DV output from the voltage output unit 1A1 at the time t51 when it is estimated that no pedal force is being applied to the pedal 12 as the value RV51 of the reference voltage RV. During the period from time t51 to time t52, the reference voltage RV is maintained at a constant value RV51. The torque sensor 1A calculates zero as the torque based on the pedal force applied to the pedal 12, based on the difference ΔV (=value RV51-value DV51) between the reference voltage RV and the detected voltage DV.

[0055] In the example shown in FIG. 10, next, during the period from time t52 to time t53, the detection voltage DV output from the voltage output section 1A1 of the torque sensor 1A decreases from the value DV51 to the value DV52 due to an external factor. At time t52A, the torque sensor 1A estimates that no force is being applied to the pedal 12 based on, for example, the time waveform of the detected voltage DV output from the voltage output unit 1A1 during the period from time t52 to time t52A (i.e., the time waveform of the detected voltage DV indicating that although the detected voltage DV is decreasing, there is no increase or decrease in the detected voltage DV due to the rotation of the crank 13). The reference voltage variation unit 1N1 starts varying (specifically, starts decreasing) the reference voltage RV from the value RV51 at time t52A when it is estimated that no pedal force is being applied to the pedal 12. Furthermore, the reference voltage variation unit 1N1 ends the variation (decrease) of the reference voltage RV at time t53 when the detected voltage DV becomes the value DV52 and the decrease in the detected voltage DV ends, and sets the value DV52 of the detected voltage DV to the value RV52 of the reference voltage RV. In other words, the reference voltage variation unit 1N1 sets the value DV52 of the detected voltage DV output from the voltage output unit 1A1 at time t53 as the value RV52 of the reference voltage RV after the variation. During the period from time t53 to time t54, the reference voltage RV is maintained at a constant value RV52. The torque sensor 1A calculates zero as the torque based on the pedal force applied to the pedal 12, based on the difference ΔV (=value RV52-value DV52) between the reference voltage RV and the detected voltage DV.

[0056] In the example shown in FIG. 10, next, during the period from time t54 to time t55, the detection voltage DV output from the voltage output section 1A1 of the torque sensor 1A increases from the value DV52 to the value DV53 due to an external factor. At time t55, the torque sensor 1A estimates that no pressure is being applied to the pedal 12 based on the time waveform of the detected voltage DV output from the voltage output unit 1A1, for example, during the period from time t54 to time t55 (i.e., the time waveform of the detected voltage DV indicating that although the detected voltage DV is increasing, there is no increase or decrease in the detected voltage DV due to the rotation of the crank 13). The reference voltage variation unit 1N1 varies (more specifically, increases) the reference voltage RV from value RV52 to value RV53 (=value DV53) at time t55 when it is estimated that no pedal force is being applied to the pedal 12. That is, the reference voltage variation unit 1N1 sets the value DV53 of the detected voltage DV output from the voltage output unit 1A1 at time t55 as the value RV53 of the reference voltage RV after the variation. During the period after time t55, the reference voltage RV is maintained at a constant value RV53. The torque sensor 1A calculates zero as the torque based on the pedal force applied to the pedal 12, based on the difference ΔV (=value RV53−value DV53) between the reference voltage RV and the detected voltage DV.

[0057] In other words, in the example shown in FIG. 10, the slope of the value of the reference voltage RV that the reference voltage variation unit 1N1 increases when no force is applied to the pedal 12 (i.e., the slope of the value of the reference voltage RV at time t55 (≒∞)) is greater than or equal to the slope of the value of the reference voltage RV that the reference voltage variation unit 1N1 decreases when no force is applied to the pedal 12 (i.e., the slope of the value of the reference voltage RV during the period from time t52A to time t53). This is to prevent the motor 1M from generating an assist torque when the difference ΔV between the reference voltage RV and the detected voltage DV (=detected voltage DV-reference voltage RV) becomes greater than zero during the period from time t55 onwards, even though no force is being applied to the pedal 12.

[0058] <Second embodiment> A second embodiment of the motor control device and power-assisted bicycle of the present invention will now be described. Except for the points described below, the motor control device and power-assisted bicycle 1 of the second embodiment are configured similarly to the motor control device and power-assisted bicycle 1 of the first embodiment described above. Therefore, the motor control device and power-assisted bicycle 1 of the second embodiment can achieve the same effects as the motor control device and power-assisted bicycle 1 of the first embodiment described above, except for the points described below.

[0059] As described above, in the power-assisted bicycle 1 of the first embodiment, the torque correction unit 1N is provided with the reference voltage variation unit 1N1, the reference voltage lower limit value setting unit 1N2, the reference voltage lower limit value variation unit 1N3, and the detected voltage monitoring unit 1N4. In the power-assisted bicycle 1 of the second embodiment, the reference voltage variation section 1N1, the reference voltage lower limit value setting section 1N2, the reference voltage lower limit value variation section 1N3, and the detected voltage monitoring section 1N4 may be provided in, for example, the motor control section 1L.

[0060] Although the present invention has been described above using the embodiments, the present invention is not limited to these embodiments, and various modifications and substitutions can be made without departing from the scope of the present invention. The configurations described in the above-mentioned embodiments and examples may be combined.

[0061] Note that all or part of the functions of each part of the electrically power-assisted bicycle 1 in the above-mentioned embodiment may be realized by recording a program for realizing these functions on a computer-readable recording medium, and having a computer system read and execute the program recorded on the recording medium. Note that the "computer system" referred to here includes hardware such as the OS and peripheral devices. In addition, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage units such as hard disks built into computer systems. Furthermore, the term "computer-readable recording medium" may also include those that dynamically hold a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and those that hold a program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or client in such cases. Furthermore, the above program may be one that realizes part of the above-mentioned functions, or may be one that can realize the above-mentioned functions in combination with a program already recorded in the computer system. [Explanation of symbols]

[0062] 1...electrically assisted bicycle, 11...wheel, 11A...front wheel, 11B...rear wheel, 12...pedal, 13...crank, 14...ratchet, 1A...torque sensor, 1A1...voltage output section, 1A2...torque calculation section, 1B...crank rotation sensor, 1L...motor control section, 1M...motor, 1N...torque correction section, 1N1...reference voltage fluctuation section, 1N2...reference voltage lower limit value setting section, 1N3...reference voltage lower limit value fluctuation section, 1N4...detected voltage monitoring section

Claims

1. Wheels and A pedal to which a stepping force is applied to drive the wheel; a crank rotation sensor having a function of determining whether a crank connected to the pedal is rotating forward or backward; a torque sensor that detects a torque based on the pedal force applied to the pedal; a motor that generates an assist torque for driving the wheels in response to the torque detected by the torque sensor; A motor control device provided in an electric assisted bicycle including a motor control unit that controls the motor, The torque sensor is a voltage output unit that outputs a reference voltage when the pedal force is not being applied to the pedal, and outputs a detection voltage having a value different from the reference voltage when the pedal force is being applied to the pedal; a torque calculation unit that calculates the torque based on a difference between the reference voltage and the detection voltage output from the voltage output unit, a reference voltage variation unit that varies a value of the reference voltage used for the calculation of the torque by the torque calculation unit in response to a variation due to an external factor of the voltage output from the voltage output unit, When the torque calculation unit calculates a value greater than zero as the torque value even though the pedal force is not being applied to the pedal, the reference voltage variation unit increases the value of the reference voltage used in the calculation of the torque by the torque calculation unit, and when the crank rotation sensor determines that the crank is rotating in reverse, the reference voltage variation unit does not vary the value of the reference voltage. Motor control device.

2. When the torque calculation unit calculates a value greater than zero as the torque value even though the pedal force is not applied to the pedal, the reference voltage variation unit increases a value of the reference voltage used in the calculation of the torque by the torque calculation unit to a value of the detection voltage currently output by the voltage output unit. The motor control device according to claim 1 .

3. a slope of the value of the reference voltage increased by the reference voltage varying unit when the pedal force is not applied to the pedal is equal to or greater than a slope of the value of the reference voltage decreased by the reference voltage varying unit when the pedal force is not applied to the pedal; The motor control device according to claim 1 or 2.

4. An electrically assisted bicycle comprising the motor control device according to any one of claims 1 to 3.

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