Electrically assisted bicycles

Abstract

To achieve cost down by reducing the number of components in a power-assisted bicycle comprising a motor which applies a torque to a wheel.SOLUTION: A power-assisted bicycle (1) comprising an assist drive unit (10) for applying an assist torque to a rear wheel (7) from an assist motor (15) comprises: an acceleration sensor (57) which detects an acceleration acting on a vehicle body; a cadence sensor (55) which detects a pedal rotation speed; and a control part (53) which controls drive of the assist motor (15). The control part (53) calculates a vehicle speed from the detection results of the cadence sensor (55) and the acceleration sensor (57), and on the basis of the calculation result of the vehicle speed, detects sliding of the rear wheel (7), and performs control for suppressing this sliding.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to an electrically assisted bicycle. [Background technology]

[0002] For example, Patent Document 1 describes a technique in which an inertial sensor is used to detect the pitch angle or roll angle of an electrically assisted bicycle, and this is used to control the assist motor. Patent Document 2 describes that in an electrically assisted bicycle, the occurrence of slippage is detected when the motor output remains unchanged while the rotation speed of the drive wheels increases. Patent Document 3 and the like disclose that in an electrically assisted bicycle, when slippage is detected, the auxiliary driving force of the front wheel motor is limited, and then the limit is lifted when the number of times the pedal is depressed reaches a predetermined number. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-81343 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-159754 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-128992 Summary of the Invention [Problem to be solved by the invention]

[0004] As described in the above patent documents, various types of assist systems are used in electrically assisted bicycles. Electrically assisted bicycles typically have many components in addition to the assist drive unit, such as a device for detecting the vehicle speed (wheel speed) on the wheel. For this reason, a new configuration is needed to prevent the cost from increasing compared to a regular bicycle without assist.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to reduce the number of parts and thereby reduce costs in an electrically assisted bicycle equipped with an electric motor that applies torque to a wheel. [Means for solving the problem]

[0006] As a means for solving the above problems, a first aspect of the present invention is an electrically assisted bicycle (1) equipped with an assist drive unit (10) that applies assist torque from an assist motor (15) to a rear wheel (7), and further equipped with an acceleration sensor (57) that detects acceleration acting on the vehicle body, a cadence sensor (55) that detects the number of pedal revolutions, and a control unit (53) that controls the drive of the assist motor (15), and the control unit (53) calculates the vehicle speed from the detection results of the cadence sensor (55) and the acceleration sensor (57), detects slippage of the rear wheel (7) based on the calculated vehicle speed, and performs control to suppress this slippage. With this configuration, rear wheel traction control for electrically assisted bicycles can be achieved by detecting rear wheel slippage based on changes in pedal rotation speed, vehicle speed, and acceleration, and then controlling the system to suppress said slippage. Because vehicle speed is calculated from the detection results of the cadence sensor and acceleration sensor, there is no need to use the vehicle speed (wheel speed) detection device provided on conventional electrically assisted bicycles, which reduces the manufacturing costs of electrically assisted bicycles.

[0007] In a second aspect of the present invention, in the first aspect, the control unit (53) determines that the rear wheel (7) is slipping when the vehicle speed and acceleration decrease while the pedal rotation speed increases. According to this configuration, if both the vehicle speed and acceleration decrease while the pedal rotation speed is increasing, it is determined that the rear wheel is slipping, and the rear wheel slip determination can be made with high accuracy based on multiple parameters.

[0008] In a third aspect of the present invention, in the first or second aspect, the acceleration sensor (57) includes an inertial measurement unit (57a) for detecting accelerations in the vehicle longitudinal direction, the vehicle lateral direction, and the vehicle vertical direction. According to this configuration, by providing an inertial measurement unit that detects acceleration in multiple directions, various motor controls can be realized, such as control related to vehicle acceleration / deceleration, control related to wheel skid, and control related to the vertical direction of the vehicle.

[0009] A fourth aspect of the present invention is the third aspect, wherein the inertial measurement unit (57a) is provided integrally with the assist drive unit (10). According to this configuration, by providing the inertial measurement unit integrally with the assist drive unit, the inertial measurement unit can be easily positioned, and the power-assisted bicycle can be easily configured.

[0010] In a fifth aspect of the present invention, in the third aspect, the control unit (53) determines that the vehicle is jumping when the change in acceleration measured by the inertial measurement unit (57a) is in the vertical direction of the vehicle. According to this configuration, it is possible to determine whether the vehicle is jumping, thereby suppressing unnecessary assistance to the rear wheel that is suspended in the air.

[0011] In a sixth aspect of the present invention, in the third aspect, the control unit (53) determines that the wheels are skidding when the change in acceleration measured by the inertial measurement unit (57a) is in the left-right direction of the vehicle. According to this configuration, it is possible to determine whether the wheels are skidding, and therefore it is possible to provide appropriate drive assistance that suppresses skidding of the wheels. [Effects of the Invention]

[0012] According to the present invention, in an electrically assisted bicycle equipped with an electric motor that applies torque to a wheel, the number of parts can be reduced, thereby reducing costs. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a left side view of an electrically assisted bicycle according to an embodiment of the present invention. [Figure 2]3 is a cross-sectional view taken along the axial direction of the assist drive unit of the electrically assisted bicycle. FIG. [Figure 3] (A) is a side view of the electrically assisted bicycle when gripping the handlebars, and (B) is a graph showing the time course of cadence, vehicle speed, and vehicle acceleration when gripping the handlebars. [Figure 4] 1A is a side view of the electrically assisted bicycle when slipping occurs during acceleration, and FIG. 1B is a graph showing the time changes in cadence, vehicle speed, and vehicle acceleration when slipping. [Figure 5] 10 is a flowchart showing a process of rear wheel traction control. [Figure 6] 1A is a side view of the electrically assisted bicycle during grip braking, and FIG. 1B is a graph showing the time changes in front wheel rotation speed, vehicle speed, and vehicle acceleration during grip braking. [Figure 7] 1A is a side view of the electrically assisted bicycle when slippage occurs during deceleration, and FIG. 1B is a graph showing the time variation of the front wheel rotation speed, vehicle speed, and vehicle acceleration during slippage. [Figure 8] 10 is a flowchart showing a process of front wheel antilock regenerative brake control. [Figure 9] FIG. 1 is a diagram illustrating the configuration of a rear wheel traction control system. [Figure 10] FIG. 1 is a diagram illustrating the configuration of a front wheel antilock regenerative braking system. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, directions such as front, rear, left, and right are the same as directions in the vehicle described below unless otherwise specified. In addition, an arrow FR indicating the front of the vehicle, an arrow LH indicating the left side of the vehicle, and an arrow UP indicating the top of the vehicle are shown in appropriate locations in the drawings used in the following description. The term "middle" used in this embodiment refers not only to the center between both ends of an object, but also to the range inside the both ends of an object. In the following description, it is assumed that the body of the vehicle is in an upright position without tilting left or right.

[0015] <Electric Assist Bicycle 1> FIG. 1 is a left side view of an electrically assisted bicycle 1 according to an embodiment. The electrically assisted bicycle 1 shown in Fig. 1 is equipped with an assist motor 15 that generates assist power in response to the force applied to pedals 2. The electrically assisted bicycle 1 is mounted with an assist drive unit 10 around a pedal crankshaft 3 that runs along the left-right direction, and a battery 5 that is mounted, for example, along a body frame 4. In the figure, reference numeral 6 denotes the front wheel, reference numeral 7 denotes the rear wheel, reference numeral 8 denotes the handlebars, reference numeral 9 denotes the seat, reference numeral 2a denotes the pedal crank arm, line C1 denotes the central axis of rotation of the pedal crankshaft 3, and reference numeral 60 denotes the front-wheel electric drive unit. Hereinafter, the direction along axis C1 is referred to as the axial direction, the direction perpendicular to axis C1 as the radial direction, and the direction around axis C1 as the circumferential direction.

[0016] <Assist drive unit 10> FIG. 2 is a cross-sectional view taken along the axial direction of the assist drive unit 10 of the power-assisted bicycle 1. As shown in FIG. 2, the assist drive unit 10 includes an assist motor 15 arranged coaxially with the pedal crankshaft 3, a reducer 40 also arranged coaxially with the pedal crankshaft 3 and transmitting the driving force (torque) of the assist motor 15 to the pedal crankshaft 3, and a unit case 11 that houses the assist motor 15 and the reducer 40 and is supported by the body frame 4. The assist drive unit 10 is a compact, single-axis electric drive unit in which the assist motor 15 and the reducer 40 are arranged coaxially with the pedal crankshaft 3, and is a drive unit that can be suitably used in an electrically assisted bicycle 1.

[0017] The unit case 11 is divided into left and right case bodies 12 and 13 in the vehicle width direction. The left case body 12 is formed in a cylindrical shape with a bottom that opens to the right, and the right case body 13 is formed in a cylindrical shape with a bottom that opens to the left. The right case body 13 is deeper in the vehicle width direction than the left case body 12. An assist motor 15 and a reducer 40 are housed in a closed space formed by the left and right case bodies 12 and 13 butting their open portions against each other. In particular, the assist motor 15 and the reducer 40 are housed inside the right case body 13, and control system components such as a control board 36, a power supply board 37, and various sensors are housed inside the left case body 12. The left and right case bodies 12 and 13 are each integrally formed as a cast part made of, for example, an aluminum alloy.

[0018] The left case body 12 has a left side wall 12a facing the left side of the vehicle, and a left outer peripheral wall 12b extending rightward (toward the right case body 13) from the outer periphery of the left side wall 12a. A left bearing portion 22 is provided in the center of the left side wall 12a to support the left side of the pedal crankshaft 3 and a sensor shaft 18 (described later) via a left bearing 22a. The right case body 13 includes a right side wall 13a facing the right side of the vehicle, and a right outer peripheral wall 13b extending leftward (toward the left case body 12) from the outer periphery of the right side wall 13a. A right bearing portion 23 is provided in the center of the right side wall 13a to support the right side of the pedal crankshaft 3 and an output shaft (unit output member) 19 (described later) via a right bearing 23a.

[0019] The assist motor 15 is an inner rotor type motor and includes a cylindrical stator 15b fixed to the inside of the right outer peripheral wall 13b of the right case body 13, and a similarly cylindrical rotor 15a disposed on the inner periphery of the stator 15b. The assist motor 15 in this embodiment is, for example, a DC motor, but the type of motor is not particularly limited. A plurality of permanent magnets 15a1 are fixed to the outer periphery of the rotor 15a and arranged in the circumferential direction. An input gear 41 of a reducer 40 is supported on the inner periphery of the rotor 15a via an eccentric oscillation bearing 42. The reducer 40 is composed of, for example, a pair of axially adjacent internal planetary gear mechanisms 40a. The pair of internal planetary gear mechanisms 40a are arranged so as to fit within the overall width of the assist motor 15 in the axial direction and so as to overlap the assist motor 15 as viewed in the radial direction. Each internal planetary gear mechanism 40a is a mechanism including an input gear (ring gear, internal gear) 41 and an output gear (planet gear, external gear) 45 that meshes with the inner gear teeth of the input gear 41. For example, a mechanism disclosed by the present applicant in Japanese Patent Publication No. 6910197 can be suitably used.

[0020] The rotor 15a is attached to the right case body 13 via a pair of support rings 16 in the axial direction. The rotor 15a is supported by the left and right support rings 16 via rotor bearings 16a, respectively. A pair of swing bearings 42 are arranged axially between the pair of rotor bearings 16a. Axially adjacent rotor bearings 16a and swing bearings 42 are in contact with each other via thrust plates 16b. A thrust receiver 40b attached to the inner periphery of the rotor 15a is arranged axially outward of each rotor bearing 16a. Each thrust receiver 40b is in contact with the adjacent rotor bearing 16a from the axial outside, thereby receiving the thrust force of the swing bearing 42 via the rotor bearing 16a and thrust plate 16b.

[0021] The pedal crankshaft 3 has base ends of left and right pedal crank arms 2a fixed to its left and right ends so as to rotate integrally with it. The shafts of the left and right pedals 2 are fixed to the distal ends of the left and right pedal crank arms 2a, respectively. A cylindrical transmission tube 17 is supported on the outer periphery of the pedal crankshaft 3. The transmission tube 17 is divided axially within the right case body 13. The left side of the transmission tube 17 serves as a sensor shaft 18 that is inserted into the left case body 12, and the right side of the transmission tube 17 serves as an output shaft 19 that is inserted into the right case body 13.

[0022] An expanded diameter portion 19a is formed at the left end of the output shaft 19, surrounding the outer periphery of the right end of the sensor shaft 18 with a gap therebetween. Reference numeral 19b in the figure denotes a flange-shaped stepped wall formed radially at the base end (right end) of the expanded diameter portion 19a. A first one-way clutch 26 is disposed between the inner circumferential surface of the expanded diameter portion 19a and the outer circumferential surface of the right end of the sensor shaft 18. The right end of the output shaft 19 protrudes to the right of the right bearing portion 23 (outside the case), and a drive sprocket 31 is attached to this right end so as to rotate integrally with the right end. The drive sprocket 31, together with a driven sprocket 32 ​​attached to the rear wheel 7 (drive wheel) and an endless drive chain 33 wound around both sprockets 31, 32, are included in a chain-type power transmission mechanism 34 that connects the pedal crankshaft 3 and the rear wheel 7.

[0023] The inner periphery of the left end (one axial end) of the sensor shaft 18 is supported by being fitted to the outer periphery of the left side of the pedal crankshaft 3 by a spline or the like. The sensor shaft 18 can rotate integrally with the pedal crankshaft 3 in both forward and reverse rotation directions. The inner periphery of the right end (the other axial end) of the sensor shaft 18 is supported via a needle bearing 27 on the outer periphery of a left-right intermediate portion (not limited to the center portion) of the pedal crankshaft 3 so as to be relatively rotatable. The needle bearing 27 is located in the intermediate portion of the pedal crankshaft 3 in the axial direction (lengthwise direction) and between the outer peripheral protrusions of the pedal crankshaft 3, and therefore has a half-split structure and is attached to the pedal crankshaft 3. By disposing the needle bearing 27 between the end of the sensor shaft 18 and the pedal crankshaft 3, runout of the end of the sensor shaft 18 is suppressed, improving the accuracy of torque detection (described later) and the accuracy of operation of the first one-way clutch 26. The right end of the sensor shaft 18 is disposed inside the expanded diameter portion 19a of the output shaft 19. The outer periphery of the right end of the sensor shaft 18 is supported on the inner periphery of the expanded diameter portion 19a of the output shaft 19 via a first one-way clutch 26.

[0024] When the pedal crankshaft 3 attempts to rotate relative to the output shaft 19 in the forward direction (the direction in which the electrically assisted bicycle 1 moves forward), the first one-way clutch 26 enables torque to be transmitted from the pedal crankshaft 3 to the output shaft 19, allowing the electrically assisted bicycle 1 to be driven by the rider's pedaling force. On the other hand, when the output shaft 19 attempts to rotate relative to the pedal crankshaft 3 in the forward direction (i.e., when the pedal crankshaft 3 attempts to rotate relative to the output shaft 19 in the reverse direction), the cam built into the first one-way clutch 26 does not engage and the first one-way clutch 26 spins freely, making it impossible to transmit torque.

[0025] A cylindrical reducer output member 47 that supports an output gear 45 of the reducer 40 is disposed on the inner peripheral side of the reducer 40. The reducer output member 47 is either formed integrally with the output gear 45 or has a configuration in which a separate output gear 45 is fixed integrally thereto. The reducer output member 47 is disposed so as to surround the outer periphery of the output shaft 19 with a gap therebetween. A second one-way clutch 28 is disposed between the inner peripheral surface of the reducer output member 47 and the outer peripheral surface of the output shaft 19.

[0026] The second one-way clutch 28 enables the assist torque of the assist motor 15 to be transmitted from the reducer output member 47 to the output shaft 19. When the reducer output member 47 attempts to rotate relative to the output shaft 19 in the forward direction (the direction in which the power-assisted bicycle 1 moves forward), the cam built into the second one-way clutch 28 engages, enabling the torque to be transmitted to the output shaft 19. This makes it possible to impart the assist torque of the assist motor 15 to the output shaft 19. On the other hand, if the output shaft 19 attempts to rotate at a speed exceeding the legally permitted speed (for example, 24 km / h), a command is output from the control board 36 to the power supply board 37 to not generate torque to the assist motor 15. As a result, the rotor 15a, the reducer 40, and the reducer output member 47 do not rotate, the built-in cam of the second one-way clutch 28 does not engage and spins freely, and the pedal force assistance by the assist motor 15 is no longer provided.

[0027] When the rider pedals 2 to ride the electrically assisted bicycle 1, the driving force of the pedal crankshaft 3 is transmitted in this order to the sensor shaft 18, the first one-way clutch 26, and the output shaft 19, and then to the rear wheel 7 via the chain transmission mechanism 34. At this time, when the assist motor 15 rotates forward, the driving force is transmitted to the reducer output member 47 via the reducer 40, and then to the output shaft 19 via the second one-way clutch 28, thereby assisting the rider in reducing the pedal effort.

[0028] When the electrically assisted bicycle 1 coasts with the pedals 2 stopped, the chain-type transmission mechanism 34 does not rotate due to a one-way clutch disposed on the shaft of the rear wheel 7. When the electrically assisted bicycle 1 is stopped from coasting and an attempt is made to rotate the pedal crankshaft 3 in the reverse direction relative to the pedals 2, the built-in cam of the first one-way clutch 26 does not engage and the first one-way clutch 26 spins freely, making it impossible to transmit torque.

[0029] A magnetic alloy ribbon 35a is wound integrally around the outer circumferential surface of the axially intermediate portion of the sensor shaft 18. A torque detection coil 35b, supported by the left case body 12, is disposed on the outer circumferential side of the ribbon 35a. The ribbon 35a and the torque detection coil 35b constitute a magnetostrictive torque sensor 35. That is, a torque difference between both axial ends of the sensor shaft 18 generates shear strain in the ribbon 35a, and the torque detection coil 35b detects a change in the magnetic permeability of the ribbon 35a due to this strain, thereby detecting the torque acting on the sensor shaft 18.

[0030] Torque is input to the left end of the sensor shaft 18 by the pedal crankshaft 3, and this torque is output from the right end of the sensor shaft 18 to the output shaft 19 via the first one-way clutch 26. At this time, if the magnetostrictive torque sensor 35 detects torque equal to or greater than a specified value, the assist motor 15 is driven to apply an assist torque to the output shaft 19. This reduces the rotational torque of the pedal crankshaft 3 and, ultimately, the pedaling force.

[0031] The drive control of the assist motor 15 is performed by a control board 36 and a power supply board 37 housed in the left case body 12. The control board 36 has an MCU (Management Controller Unit), and the power supply board 37 has a PDU (Power Drive Unit). The MCU outputs a control signal to the PDU to drive the assist motor 15 based on inputs from the magnetostrictive torque sensor 35 and a rotation sensor (not shown) that detects the rotation of the pedal crankshaft 3. When the vehicle speed of the electrically assisted bicycle 1 is below a specified value and a predetermined or greater forward torque of the pedal crankshaft 3 is detected, the MCU drives the assist motor 15 to assist the pedaling force.

[0032] <Rear Wheel Traction Control System S1> FIG. 8 is a diagram showing the configuration of a rear wheel traction control system S1 that is applied to the power-assisted bicycle 1. 8, the rear wheel traction control system S1 has its main components in the assist drive unit 10. The rear wheel traction control system S1 has a drive unit 51 including the assist motor 15 and an electric control unit 51a, an ECU (hereinafter referred to as a first control unit 53) included in the MCU of the control board 36, a cadence sensor 55 that detects the pedal rotation speed, and an acceleration sensor 57 (inertial measurement unit 57a) that detects the acceleration acting on the vehicle body.

[0033] The first control unit 53 generates an assist torque from the assist motor 15 according to the pedal force of the rider and the rotation speed of the pedal crankshaft 3. The first control unit 53 calculates the vehicle speed from the detection results of the cadence sensor 55 and the acceleration sensor 57, detects slippage of the rear wheel 7 based on the calculation result of the vehicle speed, and performs control to suppress slippage of the rear wheel 7 (rear wheel slip control).

[0034] The first control unit 53 includes a vehicle information storage means (memory) 53a that stores a program for rear wheel slip control and judgment thresholds L1, L2, etc.; a vehicle speed detection means 53b that calculates the vehicle speed based on information such as the tire circumference of the rear wheel 7 and the reduction ratio of the chain-type transmission mechanism 34, as well as the detection results of the cadence sensor 55 and the acceleration sensor 57; a slip judgment means 53c that detects slippage of the rear wheel 7 based on the calculation results of the vehicle speed; and a motor output command unit 53d that outputs a control signal to an electric control unit (PDU) 51a of the assist motor 15 in accordance with the judgment result of the slip judgment means 53c, and controls the drive of the assist motor 15 to suppress slippage of the rear wheel 7.

[0035] The cadence sensor 55 includes, for example, a cadence rotation speed sensor 55a that detects a magnet that rotates integrally with the pedal crankshaft 3 and its magnetic force at a fixed position to calculate the pedal rotation speed, and an A / D input circuit 55b that converts the detection result of the cadence rotation speed sensor 55a from analog to digital. The acceleration sensor 57 is, for example, an IMU (Inertial Measurement Unit) and includes an inertial measurement unit 57a. The inertial measurement unit 57a detects acceleration in the vehicle's traveling direction (front-rear direction), left-right direction, and elevation direction (up-down direction).

[0036] FIG. 3(A) is a side view of the power-assisted bicycle 1 during grip riding, and FIG. 3(B) is a graph showing the time variation of cadence, vehicle speed, and vehicle acceleration during grip riding. FIG. 4(A) is a side view of the electrically assisted bicycle 1 when slipping occurs during acceleration, and FIG. 3(B) is a graph showing the time changes in cadence, vehicle speed, and vehicle acceleration when slipping. FIG. 5 shows the main processing performed by the control unit 53 when rear wheel traction control is performed to suppress slip of the rear wheels 7 in the longitudinal direction.

[0037] As shown in FIG. 5, first, when the power supply of the assist drive system is turned on, the control unit 53 performs control (normal operation) to generate an assist torque by the assist motor 15 according to the torque input to the pedal crankshaft 3 and the rotation speed of the pedal crankshaft 3 (step Q11).

[0038] When normal operation begins, the control unit 53 determines whether the cadence has increased (whether the rate of increase per unit time has increased) and whether the vehicle acceleration has changed (whether the acceleration toward the front of the vehicle has increased). If the answer is NO in step Q12 (the cadence has not increased) or NO in step Q13 (the acceleration has not changed), the process returns to step Q11, for example. If the answers are both YES in steps Q12 and Q13 (the cadence has increased and the acceleration has changed), the process proceeds to step Q14.

[0039] In step Q14, it is determined whether the vehicle speed has changed (whether the rate of increase per unit time has decreased). NO If the rate of increase per unit time is not decreasing, it is determined that the vehicle has accelerated due to grip driving without rear wheel slip, and the slip control is not performed, and the process returns to step Q11, for example. YES If the rate of increase per unit time is decreased or close to a constant, it is determined that rear wheel slip is occurring, and the process proceeds to slip control from step Q15 onwards.

[0040] Referring to the graph in Figure 3(B), when the assist drive system is turned on and activated, and the rider accelerates the electric assist bicycle 1 from a stopped state to the desired speed, if the rider is gripping the bicycle (riding without the rear wheel 7, which is the drive wheel, slipping), the vehicle speed, vehicle acceleration, and cadence will each increase over time, tracing a line of "y = ax."

[0041] Referring to the graph in Figure 4(B), when the rear wheel 7 goes from a grip state to a slip state (between time t1 and t2) due to a low road surface friction coefficient μ or other reasons, the vehicle speed and vehicle acceleration decrease over time. Alternatively, the vehicle speed and vehicle acceleration decrease the rate of ascent per unit time (the slope of the graph), slowing the ascent speed. Conversely, the cadence (pedal rotation rate) increases the rate of ascent per unit time, speeding up the ascent speed.

[0042] The assisted drive system of this embodiment includes an inertial measurement unit 57a as an acceleration sensor 57 that detects acceleration acting on the vehicle body, a cadence sensor 55 that detects cadence, and a first control unit 53 that calculates vehicle speed based on information such as previously given tire circumference and the reduction ratio of the chain-type power transmission mechanism 34, as well as the detection results of the cadence sensor 55 and the acceleration sensor 57. The first control unit 53 detects rear wheel slippage using the following relational expression.

[0043] That is, when the change in vehicle acceleration per control cycle (Δt=t2-t1) is ΔAC=AC2-AC1, the change in cadence per control cycle is ΔNc=Nc2-Nc1, and the change in vehicle speed per control cycle is ΔS=S2-S1, it is determined that the rear wheel 7 is slipping if the relationship in the following equation 1 is satisfied.

[0044] ΔAC=0, ΔS<L1、ΔNc> L2 (L1 and L2 are the decision thresholds L1 and L2) Equation 1

[0045] Equation 1 is pre-programmed in vehicle information storage means (memory) 53a of first control unit 53. Vehicle speed is calculated by vehicle speed detection means 53b of first control unit 53. A slip determination unit of first control unit 53 determines whether or not the rear wheels 7 are slipping based on determination thresholds L1 and L2 shown in Equation 1.

[0046] If it is determined that the rear wheels 7 are slipping based on the determination threshold values ​​L1 and L2 programmed in the first control unit 53, the torque of the assist motor 15 (hereinafter referred to as assist torque) is reduced by reducing the motor duty, thereby suppressing slippage of the rear wheels 7. Then, it is determined whether the slippage of the rear wheels 7 has stopped or significantly decreased (whether ΔS≧L1 and ΔNc≦L2). If the determination in step Q16 is NO, the process returns to step Q15, and the motor duty and therefore the assist torque are further reduced. If the determination in step Q16 is YES, the process proceeds to step Q17, where the motor duty and therefore the assist torque are maintained and the situation is monitored.

[0047] After that, it is determined again whether ΔS≧L1 and ΔNc≦L2, and whether the slip of the rear wheel 7 has completely subsided. If the determination in step Q18 is NO, the process returns to step Q17, where the assist torque is maintained and the situation is monitored. If the determination in step Q18 is YES, it is considered safe to restore the assist torque, so the process proceeds to step Q19, where the motor duty and therefore the assist torque are increased (restored) to return the assist torque to the value before slip suppression control. This causes current to flow to the assist motor 15 as in normal operation, increasing the assist torque and enabling bicycle acceleration assistance, allowing the rider to ride (accelerate) the bicycle stably.

[0048] In this embodiment, the inertial measurement unit 57a is used, so it is possible to detect acceleration not only in the vehicle's forward direction but also in the left-right and up-down directions. Therefore, not only is it possible to suppress slippage by combining the acceleration in the forward-backward and left-right directions of the vehicle, but also, by using the acceleration in the up-down direction of the vehicle, motor control similar to that described above is performed based on the programmed determination thresholds L1 and L2 even during the period from when the vehicle jumps until it lands (during the jump), to suppress spinning of the rear wheels 7 during the jump.

[0049] The cadence sensor 55 is mounted near the pedal crankshaft 3. The inertial measurement unit 57a is preferably located near the center of the vehicle body, and in this embodiment, is disposed near the pedal crankshaft 3, close to the cadence sensor 55. The first control unit 53 is also disposed near the pedal crankshaft 3. Arranging the first control unit 53, cadence sensor 55, and inertial measurement unit 57a together is preferable because it makes the entire system more compact and reduces the harness length. The operating system of the system is disposed away from the unit, such as near the handlebars. This operating system may be configured to be connected to the unit by wire, or may be connected using short-range wireless communication such as Bluetooth (registered trademark). In addition to the operating system, the unit may be configured to be wirelessly connected to the rider's mobile device, etc.

[0050] As described above, the electrically assisted bicycle 1 in the above embodiment is an electrically assisted bicycle 1 equipped with an assist drive unit 10 that applies assist torque from the assist motor 15 to the rear wheel 7 via the pedal crankshaft 3, and is equipped with an acceleration sensor 57 that detects the acceleration acting on the vehicle body, a cadence sensor 55 that detects the pedal rotation speed, and a control unit 53 that controls the drive of the assist motor 15.The control unit 53 calculates the vehicle speed from the detection results of the cadence sensor 55 and the acceleration sensor 57, detects slippage of the rear wheel 7 based on the calculated vehicle speed, and performs control to suppress slippage of the rear wheel 7. With this configuration, slippage of the rear wheel 7 is detected based on changes in pedal rotation speed and changes in vehicle speed and acceleration, and control is performed to suppress this slippage, thereby achieving traction control of the rear wheel 7 of the power-assisted bicycle 1. Because the vehicle speed is calculated from the detection results of the cadence sensor 55 and the acceleration sensor 57, there is no need to use the vehicle speed (wheel speed) detection device provided in conventional power-assisted bicycles 1, and the manufacturing costs of the power-assisted bicycle 1 can be reduced.

[0051] In the above-described power-assisted bicycle 1, the control unit 53 determines that the rear wheel 7 is slipping when the vehicle speed and acceleration decrease while the pedal rotation speed increases. According to this configuration, if both the vehicle speed and acceleration decrease while the pedal rotation speed is increasing, it is determined that the rear wheel 7 is slipping, and the slip determination of the rear wheel 7 can be made with high accuracy based on multiple parameters.

[0052] In the above-described electrically assisted bicycle 1, the acceleration sensor 57 includes an inertial measurement unit 57a that detects acceleration in the front-rear direction, the left-right direction, and the up-down direction of the vehicle. According to this configuration, by providing an inertial measurement unit 57a that detects acceleration in multiple directions, various motor controls can be realized, such as control related to vehicle acceleration / deceleration, control related to wheel skidding, and control related to the vertical direction of the vehicle.

[0053] In the above-described power-assisted bicycle 1, the inertial measurement unit 57a is provided integrally with the assist drive unit . According to this configuration, by providing the inertial measurement unit 57a integrally with the assist drive unit 10, it is possible to easily position the inertial measurement unit 57a and simply configure the power-assisted bicycle 1. In the embodiment, the inertial measurement unit 57a is housed inside the unit case 11, but it may also be configured to be attached externally to the outside of the case.

[0054] In the above-described electrically assisted bicycle 1, the control unit 53 determines that the vehicle is jumping when the change in acceleration measured by the inertial measurement unit 57a is in the vertical direction of the vehicle. According to this configuration, it is possible to determine whether the vehicle is jumping, thereby suppressing unnecessary assistance to the rear wheel 7 that is floating in the air.

[0055] In the above-described electrically assisted bicycle 1, the control unit 53 determines that the rear wheel 7 is skidding when the change in acceleration measured by the inertial measurement unit 57a is in the left-right direction of the vehicle. According to this configuration, it is possible to determine whether the rear wheels 7 are skidding, and therefore it is possible to provide appropriate drive assist that suppresses skidding of the rear wheels 7.

[0056] <Front wheel electric drive unit 60> Here, the electrically power-assisted bicycle 1 of the embodiment may be provided with a front wheel electric drive unit 60 that is integrally provided on the hub portion of the front wheel 6. For example, when accelerating by pedaling force, the front wheel electric drive unit 60 functions as an electric motor that applies torque to the front wheel 6 in the accelerating direction, and when decelerating by braking, it functions as a generator that applies torque to the front wheel 6 in the decelerating direction.

[0057] <Front wheel anti-lock regenerative braking system S2> FIG. 10 is a diagram showing the configuration of the front wheel antilock regenerative braking system S2. As shown in Figure 10, the front wheel antilock regenerative braking system S2 includes a front wheel electric drive unit 60, a second ECU (second control unit) 63 that controls the drive of the front wheel electric drive unit 60, and an acceleration sensor 67 (inertial measurement unit 67a) that detects the acceleration acting on the vehicle body.

[0058] The front wheel electric drive device 60 includes a front wheel assist motor 60a configured coaxially with the front wheel 6, a front wheel rotation detection sensor 61b (including a Hall element for motor rotation) that detects the rotation speed of the front wheel assist motor 60a and, in turn, the front wheel 6, and an A / D input circuit 61c that converts the detection result of the front wheel rotation detection sensor 61b from analog to digital.

[0059] The second control unit 63 drives the assist motor 15 in conjunction with the pedal force of the occupant and the rotation speed of the pedal crankshaft 3, for example, to apply an assist torque to the front wheels 6. The second control unit 63 calculates the vehicle speed from the detection result of the front wheel rotation detection sensor 61b, detects slippage of the front wheels 6 based on the calculation result of the vehicle speed and the detection result of the acceleration sensor 67, and performs control to suppress slippage of the front wheels 6 (front wheel slip control).

[0060] The second control unit 63 includes a vehicle information holding means (memory) 63a that stores a program for front wheel slip control and judgment thresholds L3, L4, etc., a vehicle speed detection means 63b that calculates the vehicle speed based on information such as the tire circumference of the front wheels 6 and the detection results of the front wheel rotation detection sensor 61b, a slip judgment means 63c that detects slippage of the front wheels 6 based on the calculation results of the vehicle speed and the detection results of the inertial measurement unit 67a, and a motor output command unit 63d that outputs a control signal to the electric control unit (PDU) 61a of the front wheel assist motor 60a in accordance with the judgment result of the slip judgment means 63c, and controls the drive (regenerative operation) of the front wheel assist motor 60a to suppress slippage of the front wheels 6.

[0061] The second control unit 63 may be configured, for example, to be formed on the control board 36 together with the first control unit 53 so that they share hardware, or may be configured to be formed separately from the first control unit 53 and the control board 36 so that freedom of placement is increased. The acceleration sensor 67 is, for example, an IMU and includes an inertial measurement unit 67a. The inertial measurement unit 67a detects acceleration in the vehicle's forward (front-rear) direction, left-right direction, and elevation (up-down) direction. The inertial measurement unit 67a of the front wheel antilock regenerative braking system S2 may utilize the inertial measurement unit 57a of the rear wheel traction control system S1.

[0062] In the electrically power-assisted bicycle 1 equipped with the front wheel electric drive device 60, the operation of the front wheel electric drive device 60 is controlled by a second control unit 63. The second control unit 63 calculates the vehicle speed from the detection result of the front wheel rotation detection sensor 61b, and detects slippage of the front wheel 6 based on the calculation result of the vehicle speed and the detection result of the acceleration sensor 67, and performs control to suppress slippage of the front wheel 6. With this configuration, slippage of the front wheel 6 is detected based on changes in the front wheel rotation speed and changes in vehicle speed and acceleration, and control is performed to suppress this slippage, thereby achieving anti-lock control of the regenerative brake of the front wheel 6 of the power-assisted bicycle 1. Because the vehicle speed is calculated from the detection results of the front wheel rotation detection sensor 61b in the front wheel electric drive device 60, there is no need to use the vehicle speed (wheel speed) detection device provided in conventional power-assisted bicycles 1, and the manufacturing costs of the power-assisted bicycle 1 can be reduced.

[0063] For example, even when the front wheel electric drive unit 60 is used as a regenerative brake on a downhill slope, the inertial measurement unit 67a detects the acceleration of the vehicle in the forward, left, right, and vertical directions, and the rotation detection sensor 61b (a Hall element for motor rotation) of the front wheel electric drive unit 60 detects the front wheel rotation speed. The second control unit 63 calculates the vehicle speed based on the tire circumference input in advance and the detection result of the front wheel rotation detection sensor 61b. Based on the calculated vehicle speed and the detection result of the inertial measurement unit 67a, slippage of the front wheels 6 is detected and control to suppress slippage of the front wheels 6 (front wheel slip control) is performed.

[0064] FIG. 8 shows the main processing performed by the second control unit 63 when performing front wheel antilock regenerative braking control to suppress locking or slipping of the front wheels 6 in the longitudinal direction during regenerative braking of the front wheels 6. As shown in FIG. 8, first, when the power supply of the assist drive system is on and the front wheel electric drive device 60 is capable of regenerative operation, the second control unit 63 performs control (normal operation) to cause the front wheel electric drive device 60 to operate regeneratively in response to a deceleration request, such as a rider's brake operation, to function as a generator and generate braking force on the front wheel 6 using the regenerative brake (step Q21).

[0065] When normal operation begins, the second control unit 63 determines whether the front wheel rotation speed has increased (whether the rate of decrease per unit time has decreased) and whether the vehicle speed has changed (whether the rate of decrease per unit time has decreased). If the answer to step Q22 is NO (the front wheel rotation speed has not increased) or if the answer to step Q23 is NO (the vehicle speed has not changed), the process returns to step Q21, for example. If the answer to both steps Q22 and Q23 is YES (the front wheel rotation speed has increased and the vehicle speed has changed), the process proceeds to step Q24.

[0066] In step Q24, it is determined whether the vehicle acceleration has changed (whether the rearward acceleration (deceleration) of the vehicle has increased). If the answer is YES in step Q24 (deceleration has increased), it is determined that the vehicle has decelerated due to regenerative braking in a grip state with no front wheel slip, and slip control is not performed, and the process returns to step Q21, for example. If the answer is NO in step Q24 (deceleration has not increased), it is determined that front wheel slip has occurred, and the process proceeds to slip control from step Q25 onwards.

[0067] Referring to the graph in Figure 6(B), when the assist drive system is powered on and the front wheel electric drive unit 60 is capable of regenerative operation, if the bicycle is traveling at vehicle speed b and the rider decelerates the electrically assisted bicycle 1 to the desired speed by applying regenerative braking to the front wheel electric drive unit 60, if the bicycle is in grip riding (riding without the front wheel 6 locking), the vehicle speed, vehicle acceleration, and front wheel rotation speed will each decrease over time, tracing the line "y = -ax + b."

[0068] Referring to the graph in Figure 7(B), when the front wheels 6 go from a grip state to a lock state or slip state (between time t1 and t2) due to a low road surface friction coefficient μ or other reasons, the vehicle speed and vehicle acceleration increase over time. Alternatively, the vehicle speed and vehicle acceleration decrease the rate of decline per unit time (the slope of the graph), slowing down the rate of decline. Also, the front wheel rotation speed decreases the rate of decline per unit time, slowing down the rate of decline.

[0069] The assist drive system of this embodiment includes an inertial measurement unit 67a as an acceleration sensor 67 that detects acceleration acting on the vehicle body, a rotation detection sensor 61b (such as a Hall element for motor rotation) in the front wheel electric drive unit 60 built into the front wheel 6, and a second control unit 63 that calculates vehicle speed from information such as tire circumference given in advance. The second control unit 63 detects front wheel slip using the following relational expression.

[0070] That is, when the change in vehicle acceleration per control cycle (Δt=t2-t1) is ΔAC=AC2-AC1, the change in front wheel rotation speed per control cycle is ΔNf=Nf2-Nf1, and the change in vehicle speed per control cycle is ΔS=S2-S1, it is determined that the front wheels 6 are locked or slipping if the relationship in the following equation 2 is satisfied.

[0071] ΔAC=0, ΔS<L3、ΔNf> L4 (L3 and L4 are the decision thresholds) Equation 2

[0072] Equation 2 is pre-programmed in vehicle information storage means (memory) 63a of the second control unit 63. The vehicle speed is calculated by vehicle speed detection means 63b of the second control unit 63. The slip determination unit of the second control unit 63 determines whether the front wheels 6 are locked or slipping based on determination thresholds L3 and L4 shown in Equation 2.

[0073] If the determination thresholds L3 and L4 programmed in the second control unit 63 indicate that the front wheels 6 are locked or slipping, the regenerative torque of the front wheel electric drive unit 60 (hereinafter referred to as motor regenerative torque) is reduced by reducing the motor duty, thereby suppressing slippage of the front wheels 6. It is then determined whether the locking or slipping of the front wheels 6 has stopped or significantly decreased (whether ΔS≧L3 and ΔNf≦L4). If the determination in step Q26 is NO, the process returns to step Q25, where the motor duty and therefore the motor regenerative torque are further reduced. If the determination in step Q26 is YES, the process proceeds to step Q27, where the motor duty and therefore the motor regenerative torque are maintained and the situation is monitored.

[0074] After that, it is determined again whether ΔS≧L3 and ΔNf≦L4, and whether the locking or slipping of the front wheel 6 has completely subsided. If the determination in step Q28 is NO, the process returns to step Q27, where the motor regenerative torque is maintained and the situation is monitored. If the determination in step Q28 is YES, it is considered safe to restore the motor regenerative torque, so the process proceeds to step Q29, where the motor duty and therefore the motor regenerative torque are increased (restored), returning the motor regenerative torque to the value it had before the slip suppression control. This generates motor regenerative torque as in normal operation, enabling deceleration assistance for the bicycle and allowing the rider to ride (decelerate) the bicycle stably.

[0075] Since the inertial measurement unit 67a can detect acceleration not only in the vehicle's forward direction but also in the left-right and up-down directions, it can detect slippage from a combination of the front-rear and left-right directions of the vehicle even when the front wheels 6 are in a so-called skidding state without braking. Therefore, by programming the determination thresholds L3, L4, etc. in the second control unit 63 in advance, it becomes possible to take measures such as reducing the assist force of the assist motor 15 on the rear wheels 7 when the front wheels 6 are slipping.

[0076] The present invention is not limited to the above embodiment, and for example, the electrically assisted bicycle may be a type of bicycle (including three-wheeled and four-wheeled) different from that shown in Fig. 1. The present invention may also be applied to an electrically assisted bicycle that does not have a front-wheel electrically driven unit. The configurations in the above-described embodiments are merely examples of the present invention, and various modifications are possible within the scope of the gist of the present invention, such as replacing the components of the embodiments with well-known components. [Explanation of symbols]

[0077] 1. Electrically assisted bicycle 3 pedal crankshaft 6 front wheels 7 rear wheels 10 Assist drive unit 15 Assist motor 53 First Control Section (Control Section) 55 Cadence sensor 57 Acceleration Sensor 57a Inertial Measurement Unit 60 Front wheel electric drive unit 60a front wheel assist motor 61b Front wheel rotation detection sensor 63 Second Control Section 67 Acceleration Sensor 67a Inertial Measurement Unit S1 rear wheel traction control system S2 front wheel anti-lock regenerative braking system

Claims

1. An electrically assisted bicycle (1) equipped with an assist drive unit (10) that applies assist torque from an assist motor (15) to a rear wheel (7), an acceleration sensor (57) for detecting acceleration acting on the vehicle body; a cadence sensor (55) for detecting the number of pedal revolutions; a control unit (53) that controls the driving of the assist motor (15), The control unit (53) calculates the vehicle speed from the detection results of the cadence sensor (55) and the acceleration sensor (57) while the rider is riding the vehicle, detects slippage of the rear wheel (7) based on the calculation result of the vehicle speed, and performs control to suppress the slippage. The control unit (53) determines that the rear wheel (7) is slipping when the vehicle speed and the acceleration decrease while the pedal rotation speed is increasing.

2. 2. The electrically assisted bicycle according to claim 1, wherein the acceleration sensor (57) includes an inertial measurement unit (57a) that detects the acceleration in the longitudinal direction of the vehicle, the lateral direction of the vehicle, and the vertical direction of the vehicle.

3. 3. The electrically assisted bicycle according to claim 2, wherein the inertial measurement unit (57a) is provided integrally with the assist drive unit (10).

4. 3. The electrically assisted bicycle according to claim 2, wherein the control unit (53) determines that the vehicle is jumping when the change in acceleration measured by the inertial measurement unit (57a) is in the vertical direction of the vehicle.

5. 3. The electrically assisted bicycle according to claim 2, wherein the control unit (53) determines that the wheel is skidding when the change in acceleration measured by the inertial measurement unit (57a) is in the left-right direction of the vehicle.

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