JP7514656B2 - Drive unit for human-powered vehicles - Google Patents

Description

The present invention relates to a drive unit for a human-powered vehicle.

For example, Patent Document 1 discloses that in a motor drive device for a human-powered vehicle, a protection circuit shorts the coil of an electric motor.

Japanese Patent Application Laid-Open No. 10-323079

The motor drive device disclosed in Patent Document 1 requires a special protection circuit to short-circuit the coils of the electric motor, which makes the configuration complicated.

One of the objects of the present invention is to provide a drive unit for a human-powered vehicle that can short-circuit the coils of an electric motor as needed with a simple configuration.

A drive unit according to a first aspect of the present disclosure is a drive unit for a human-powered vehicle, comprising: an electric motor having a coil and configured to provide propulsive force to the human-powered vehicle; a plurality of switching elements electrically connected to the coil; and a control unit configured to drive the electric motor by controlling the plurality of switching elements so that current flows through the coil, wherein when a predetermined condition is satisfied, the control unit controls at least one of the plurality of switching elements to short-circuit the coil.
According to the drive unit of the first aspect, when a predetermined condition is satisfied, at least one of a plurality of switching elements for driving the electric motor is controlled to short-circuit the coil, so that the coil of the electric motor can be short-circuited as necessary with a simple configuration. By shorting the coil of the electric motor, the electric motor can be braked and the regenerative current from the electric motor to the power source can be suppressed.

In the drive unit of a second aspect according to the first aspect of the present disclosure, the predetermined condition includes a vehicle speed of the human-powered vehicle being equal to or greater than a first speed while the electric motor is being driven.
According to the drive unit of the second aspect, when the electric motor is driven, the coil can be short-circuited when the vehicle speed of the human-powered vehicle is equal to or higher than the first speed.

A drive unit according to a third aspect of the second aspect of the present disclosure further comprises a first storage section that variably stores information about the first speed.
According to the drive unit of the third aspect, the information about the first speed can be changed depending on, for example, the usage environment of the drive unit for a human-powered vehicle.

In a fourth aspect of the drive unit according to the second or third aspect of the present disclosure, the first speed is a value in the range of 20 km/h or more and 50 km/h or less.
According to the drive unit of the fourth aspect, the coil can be short-circuited when the vehicle speed of the human-powered vehicle is equal to or greater than a value in the range of 20 km/h or more and 50 km/h or less.

In a drive unit of a fifth aspect according to any one of the first to fourth aspects of the present disclosure, the predetermined condition includes that when the electric motor is driven, the human-powered driving force input to the crank of the human-powered vehicle is less than or equal to a first value.
According to the drive unit of the fifth aspect, when the electric motor is driven, the coil can be short-circuited if the human driving force input to the crank of the human-powered vehicle is equal to or smaller than a first value.

In a drive unit of a sixth aspect according to any one of the first to fifth aspects of the present disclosure, the predetermined condition includes a state in which, when the electric motor is driven, the human-powered driving force input to a crank of the human-powered vehicle is equal to or less than a second value, the state in which the crank rotates through a first rotation angle.
According to the drive unit of the sixth aspect, when the electric motor is driven, the coil can be short-circuited when the state in which the human-powered driving force input to the crank of the human-powered vehicle is less than or equal to a second value continues for the crank to rotate through a first angle.

In a drive unit of a seventh aspect according to any one of the first to sixth aspects of the present disclosure, the predetermined condition includes a state in which, while the electric motor is being driven, the human-powered driving force input to the crank of the human-powered vehicle continues to be equal to or less than a second value for a predetermined period of time.
According to the drive unit of the seventh aspect, when the electric motor is driven, the coil can be short-circuited when the state in which the human-powered driving force input to the crank of the human-powered vehicle is equal to or less than a second value continues for a predetermined period of time.

In a drive unit of an eighth aspect according to any one of the first to seventh aspects of the present disclosure, the predetermined condition includes the occurrence of an error in at least one sensor used to control the electric motor while the electric motor is being driven.
According to the drive unit of the eighth aspect, when an error occurs in at least one sensor used to control the electric motor while the electric motor is being driven, the coil can be short-circuited.

In a drive unit of a ninth aspect according to any one of the first to eighth aspects of the present disclosure, the predetermined condition includes that, when the electric motor is driven, the rotational speed of a crank of the human-powered vehicle is equal to or less than a first rotational speed.
According to the drive unit of the ninth aspect, when the electric motor is driven, the coil can be short-circuited if the rotation speed of the crank of the human-powered vehicle is equal to or lower than the first rotation speed.

In the drive unit of a tenth aspect according to any one of the first to ninth aspects of the present disclosure, the predetermined condition includes that a rotation speed of the electric motor is equal to or greater than a second rotation speed.
According to the drive unit of the tenth aspect, the coil can be short-circuited when the rotational speed of the electric motor is equal to or higher than the second rotational speed.

In the drive unit of an eleventh aspect according to the tenth aspect of the present disclosure, the second rotational speed is set so that when the electric motor rotates at the second rotational speed and the electric motor provides propulsive force to the human-powered vehicle, the vehicle speed of the human-powered vehicle is equal to or greater than 3 km/h and equal to or less than 7 km/h.
According to the drive unit of the eleventh aspect, when the electric motor is providing propulsive force to the human-powered vehicle, the rotational speed of the electric motor becomes equal to or greater than the second rotational speed, thereby short-circuiting the coil when the vehicle speed of the human-powered vehicle becomes greater than the range of 3 km/h or more and 7 km/h or less.

In the drive unit of aspect 12 according to the tenth or eleventh aspects of the present disclosure, the second rotational speed is set so that a voltage generated when the electric motor rotates at the second rotational speed is smaller than a voltage supplied to the electric motor from a power source.
According to the drive unit of the twelfth aspect, when the rotational speed of the electric motor becomes equal to or greater than the second rotational speed, the coil can be short-circuited when the voltage generated in the electric motor becomes equal to or greater than the voltage supplied to the electric motor from the power source.

A drive unit according to a thirteenth aspect according to any one of the tenth to twelfth aspects of the present disclosure further comprises a second storage unit that variably stores information relating to the second rotation speed.
According to the drive unit of the thirteenth aspect, the information relating to the second rotational speed can be changed to information suitable for a drive unit for a human-powered vehicle.

In a drive unit of a fourteenth aspect according to any one of the first to thirteenth aspects of the present disclosure, the electric motor rotates in a first rotational direction when providing propulsive force to the human-powered vehicle, and the predetermined condition includes the electric motor rotating in a second rotational direction opposite to the first rotational direction.
According to the drive unit of the fourteenth aspect, the coil can be short-circuited when the electric motor rotates in the second rotational direction.

In a drive unit of a fifteenth aspect according to any one of the first to thirteenth aspects of the present disclosure, the electric motor rotates in a first rotational direction when providing propulsive force to the human-powered vehicle, and the predetermined condition includes the electric motor rotating in a second rotational direction opposite to the first rotational direction when the electric motor is driven.
According to the drive unit of the fifteenth aspect, in a state in which the electric motor is driven, the coil can be short-circuited when the electric motor rotates in the second rotation direction.

A drive unit of a sixteenth aspect according to any one of the first to fifteenth aspects of the present disclosure, further comprising: a first terminal configured to be electrically connected to a positive electrode of a DC power supply; and a second terminal configured to be electrically connected to a negative electrode of the DC power supply, wherein the coil comprises a first coil, a second coil, and a third coil, the plurality of switching elements comprises a first switching element, a second switching element, a third switching element, a fourth switching element, a fifth switching element, and a sixth switching element, the first coil is electrically connected to the first terminal via the first switching element and to the second terminal via the second switching element, and the second coil the third coil is electrically connected to the first terminal via the third switching element and to the second terminal via the fourth switching element, the third coil is electrically connected to the first terminal via the fifth switching element and to the second terminal via the sixth switching element, and when the predetermined condition is satisfied, the control unit brings one of a first group including the first switching element, the third switching element, and the fifth switching element, and a second group including the second switching element, the fourth switching element, and the sixth switching element into a conductive state, and brings the other of the first group and the second group into a non-conductive state.
According to the drive unit of the sixteenth aspect, when a predetermined condition is satisfied, a short-circuit brake can be activated by making one of the first group and the second group conductive and making the other of the first group and the second group non-conductive.

In the drive unit of a seventeenth aspect according to any one of the first to sixteenth aspects of the present disclosure, the control unit, after short-circuiting the coil, releases the short circuit of the coil depending on time.
According to the drive unit of the seventeenth aspect, the short circuit of the coil can be controlled by time.

In the drive unit of the 18th aspect according to the 16th aspect of the present disclosure, the control unit sets one of the first group and the second group to the conductive state, and then sets one of the first group and the second group to the non-conductive state depending on time.
According to the drive unit of the eighteenth aspect, the short circuit of the coil can be controlled by time.

A drive unit according to a nineteenth aspect of the present disclosure, further comprising a current detection unit, wherein the electric motor is a three-phase electric motor and includes a first connection portion electrically connected to a first switching element, a second switching element, and a first coil, a second connection portion electrically connected to a third switching element, a fourth switching element, and a second coil, and a third connection portion electrically connected to a fifth switching element, a sixth switching element, and a third coil, wherein the current detection unit is configured to detect currents in the first connection portion, the second connection portion, and the third connection portion, and the control unit is configured to control one of the first group and the second group. is turned on, and then when the current detection unit detects a zero crossing of the value of the current flowing through the first connection part, one of the first switching element and the second switching element that is in the conductive state is turned on, and when the current detection unit detects a zero crossing of the value of the current flowing through the second connection part, one of the third switching element and the fourth switching element that is in the conductive state is turned on, and when the current detection unit detects a zero crossing of the value of the current flowing through the third connection part, one of the fifth switching element and the sixth switching element that is in the conductive state is turned on, and
According to the drive unit of the nineteenth aspect, an increase in voltage between the first terminal and the second terminal can be suppressed.

In the drive unit of the twentieth aspect according to any one of the sixteenth, eighteenth, and nineteenth aspects of the present disclosure, the first coil, the second coil, and the third coil are star-connected or delta-connected.
According to the drive unit of the twentieth aspect, the coils of the electric motor that are star-connected (Y-connected) or delta-connected (Δ-connected) can be short-circuited as necessary with a simple configuration.

The drive unit for a human-powered vehicle disclosed herein has a simple configuration that allows the coils of the electric motor to be short-circuited as needed.

1 is a side view of a human-powered vehicle including a drive unit for a human-powered vehicle according to an embodiment. 1 is a block diagram showing an electrical configuration of a human-powered vehicle including a drive unit for a human-powered vehicle according to an embodiment; 3 is a circuit diagram showing an electrical configuration of an electric motor, a drive circuit, and a power supply included in the drive unit for the human-powered vehicle of FIG. 2 . 3 is a first part of a flowchart of a process executed by the control unit of FIG. 2 to control a plurality of switching elements. 3 is a second part of the flowchart of the process executed by the control unit of FIG. 2 to control a plurality of switching elements. FIG. 4 is a circuit diagram showing the electrical configuration of an electric motor and a drive circuit included in a drive unit for a human-powered vehicle according to a first modified example. FIG. 11 is a circuit diagram showing the electrical configuration of an electric motor, a drive circuit, and a power supply included in a drive unit for a human-powered vehicle according to a second modified example. 13 is a flowchart of a process executed by a control unit of a drive unit for a human-powered vehicle according to a third modified example, for controlling a plurality of switching elements.

<Embodiment>
A drive unit 40 for a human-powered vehicle according to an embodiment will be described with reference to Figs. 1 to 5. The human-powered vehicle 10 is a vehicle that has at least one wheel and can be driven by at least a human-powered driving force H. The human-powered vehicle 10 includes various types of bicycles, such as mountain bikes, road bikes, city bikes, cargo bikes, hand bikes, and recumbents. The number of wheels that the human-powered vehicle 10 has is not limited. The human-powered vehicle 10 also includes, for example, one-wheeled vehicles and vehicles with three or more wheels. The human-powered vehicle 10 is not limited to vehicles that can be driven only by the human-powered driving force H. The human-powered vehicle 10 includes an E-bike that uses not only the human-powered driving force H but also the driving force of an electric motor for propulsion. The E-bike includes an electrically assisted bicycle whose propulsion is assisted by an electric motor. In the following embodiment, the human-powered vehicle 10 will be described as an electrically assisted bicycle.

The human-powered vehicle 10 includes a crank 12 to which a human-powered driving force H is input. The human-powered vehicle 10 further includes wheels 14 and a vehicle body 16. The wheels 14 include a rear wheel 14A and a front wheel 14B. The vehicle body 16 includes a frame 18. The crank 12 includes an input rotating shaft 12A that can rotate relative to the frame 18, and a pair of crank arms 12B that are respectively provided at the axial ends of the input rotating shaft 12A. In this embodiment, the input rotating shaft 12A is a crank shaft. A pair of pedals 20 are respectively connected to each crank arm 12B. The rear wheel 14A is driven by the rotation of the crank 12. The rear wheel 14A is supported by the frame 18. The crank 12 and the rear wheel 14A are connected by a drive mechanism 22. The drive mechanism 22 includes a first rotating body 24 that is connected to the input rotating shaft 12A. The input rotating shaft 12A and the first rotating body 24 may be connected to rotate together, or may be connected via a first one-way clutch. The first one-way clutch is configured to rotate the first rotating body 24 forward when the crank 12 rotates forward, and to allow relative rotation between the crank 12 and the first rotating body 24 when the crank 12 rotates backward. The first rotating body 24 includes a sprocket, a pulley, or a bevel gear. The drive mechanism 22 further includes a second rotating body 26 and a connecting member 28. The connecting member 28 transmits the rotational force of the first rotating body 24 to the second rotating body 26. The connecting member 28 includes, for example, a chain, a belt, or a shaft.

The second rotating body 26 is connected to the rear wheel 14A. The second rotating body 26 includes a sprocket, a pulley, or a bevel gear. A second one-way clutch is preferably provided between the second rotating body 26 and the rear wheel 14A. The second one-way clutch is configured to rotate the rear wheel 14A forward when the second rotating body 26 rotates forward, and to allow relative rotation between the second rotating body 26 and the rear wheel 14A when the second rotating body 26 rotates backward.

A front wheel 14B is attached to the frame 18 via a front fork 30. A handlebar 34 is connected to the front fork 30 via a stem 32. In this embodiment, the rear wheel 14A is connected to the crank 12 by the drive mechanism 22, but at least one of the rear wheel 14A and the front wheel 14B may be connected to the crank 12 by the drive mechanism 22.

Preferably, the human-powered vehicle 10 further includes a power source 36. The power source 36 is a DC power source. The power source 36 includes a battery. The battery includes one or more battery elements. The battery element includes a rechargeable battery. The power source 36 is configured to supply power to the drive unit 40. The power source 36 is preferably connected to a control unit 46 of the drive unit 40 so as to be able to communicate with the control unit 46 by wired or wireless communication. The power source 36 can communicate with the control unit 46 by, for example, power line communication (PLC), a controller area network (CAN), or a universal asynchronous receiver/transmitter (UART).

Preferably, the human-powered vehicle 10 includes a sensor 38. The sensor 38 is used to control the electric motor 42 of the drive unit 40. For example, the sensor 38 includes at least one of a vehicle speed sensor 38A, a crank rotation sensor 38B, and a human-powered driving force detection unit 38C.

The vehicle speed sensor 38A is configured to detect information corresponding to the rotation speed NW of the wheel 14 of the human-powered vehicle 10. The vehicle speed sensor 38A is configured to detect, for example, a magnet provided on the wheel 14 of the human-powered vehicle 10. The vehicle speed sensor 38A is configured to output a predetermined number of detection signals during one rotation of the wheel 14. The predetermined number is, for example, 1. The vehicle speed sensor 38A outputs a signal corresponding to the rotation speed NW of the wheel 14. The control unit 46 can calculate the vehicle speed V of the human-powered vehicle 10 based on the rotation speed NW of the wheel 14 and information related to the circumference of the wheel 14. Information related to the circumference of the wheel 14 is stored in the memory unit 50. The vehicle speed sensor 38A includes, for example, a magnetic reed constituting a reed switch, or a Hall element. The vehicle speed sensor 38A may be attached to a chain stay of the frame 18 of the human-powered vehicle 10 and configured to detect a magnet attached to the rear wheel 14A, or may be attached to the front fork 30 and configured to detect a magnet attached to the front wheel 14B. In this embodiment, the vehicle speed sensor 38A is configured such that a reed switch detects the magnet once when the wheel 14 rotates once. The vehicle speed sensor 38A is not limited to a configuration that detects a magnet attached to the wheel 14, and may be configured to include, for example, an optical sensor or a GPS (Global Positioning System) receiver, and may be configured in any manner as long as it is capable of detecting information related to the vehicle speed V. The vehicle speed sensor 38A is connected to the control unit 46 via a wireless communication device or an electric cable.

The crank rotation sensor 38B is configured to detect information corresponding to the rotation state of the input rotating shaft 12A. The rotation state of the input rotating shaft 12A includes at least one of the rotation speed C of the input rotating shaft 12A and the rotation angle D of the input rotating shaft 12A. The crank rotation sensor 38B is provided, for example, on the frame 18 or the drive unit 40 of the human-powered vehicle 10. The crank rotation sensor 38B is configured, for example, to include a magnetic sensor that outputs a signal corresponding to the strength of a magnetic field. An annular magnet whose magnetic field strength changes in the circumferential direction is provided on the input rotating shaft 12A, a member that rotates in conjunction with the input rotating shaft 12A, or a power transmission path between the input rotating shaft 12A and the first rotating body 24. The member that rotates in conjunction with the input rotating shaft 12A may include the output shaft of the electric motor 42. In this embodiment, the crank rotation sensor 38B outputs a signal corresponding to the rotation speed C of the input rotating shaft 12A and a signal corresponding to the rotation angle D of the input rotating shaft 12A. The magnet may be provided on a member that rotates integrally with the input rotating shaft 12A in the power transmission path of the human-powered driving force H from the input rotating shaft 12A to the first rotating body 24. For example, the magnet may be provided on the first rotating body 24 when a first one-way clutch is not provided between the input rotating shaft 12A and the first rotating body 24. The crank rotation sensor 38B may include an optical sensor, an acceleration sensor, a gyro sensor, or a torque sensor instead of a magnetic sensor, and may have any configuration as long as it can detect at least one of the rotation speed C of the input rotating shaft 12A and the rotation angle D of the input rotating shaft 12A. The crank rotation sensor 38B is connected to the control unit 46 via a wireless communication device or an electric cable.

The human-powered driving force detection unit 38C includes, for example, a torque sensor. The torque sensor is configured to output a signal corresponding to the torque applied to the crank 12 by the human-powered driving force H. When, for example, a first one-way clutch is provided in the power transmission path, the torque sensor is preferably provided upstream of the first one-way clutch in the power transmission path. The torque sensor includes a strain sensor, a magnetostrictive sensor, or a pressure sensor. The strain sensor includes a strain gauge. The torque sensor is provided in the power transmission path or in a member included in the power transmission path or in the vicinity of a member included in the power transmission path. The member included in the power transmission path is, for example, the input rotating shaft 12A, a member that transmits the human-powered driving force H between the input rotating shaft 12A and the first rotating body 24, the crank arm 12B, or the pedal 20. The torque sensor is connected to the control unit 46 via a wireless communication device or an electric cable. The manual driving force detection unit 38C may have any configuration as long as it can acquire information about the manual driving force H, and may include, for example, a sensor that detects the pressure applied to the pedal 20 or a sensor that detects the tension of the chain.

The drive unit 40 includes an electric motor 42, a plurality of switching elements 44, and a control unit 46. The electric motor 42 is configured to provide a propulsive force to the human-powered vehicle 10. Preferably, the drive unit 40 includes a housing 40A. The electric motor 42 is provided in the housing 40A. Preferably, the housing 40A is attached to the body 16 of the human-powered vehicle 10. The drive unit 40 includes one or more electric motors 42. The electric motor 42 is configured to transmit rotation to a power transmission path of the human-powered driving force H from the pedal 20 to the rear wheel 14A and at least one of the front wheels 14B. The power transmission path of the human-powered driving force H from the pedal 20 to the rear wheel 14A also includes the rear wheel 14A. Preferably, the drive unit 40 includes a reduction gear, and the electric motor 42 is configured to transmit rotation to at least one of the power transmission path of the human-powered driving force H from the pedal 20 to the rear wheel 14A and the front wheel 14B via the reduction gear. In this embodiment, the drive unit 40 is provided on the frame 18 of the human-powered vehicle 10 and configured to transmit rotation to the first rotating body 24. The housing 40A is provided on the frame 18. The housing 40A is detachably attached to the frame 18, for example. A third one-way clutch is preferably provided on the power transmission path between the electric motor 42 and the input rotating shaft 12A so that the rotational force of the crank 12 is not transmitted to the electric motor 42 when the input rotating shaft 12A is rotated in the forward direction of the human-powered vehicle 10. When the electric motor 42 is provided on at least one of the rear wheel 14A and the front wheel 14B, the electric motor 42 may include a hub motor.

Preferably, the control unit 46 is configured to control the electric motor 42. Preferably, the control unit 46 is configured to control the electric motor 42 according to the human-powered driving force H input to the human-powered vehicle 10. The human-powered driving force H may be expressed by the torque HT or may be expressed by the power HW. When the human-powered driving force H is expressed by the power HW, the human-powered driving force H is obtained by multiplying the torque detected by the human-powered driving force detection unit 38C by the rotation speed NC of the input rotating shaft 12A detected by the crank rotation sensor 38B.

The control unit 46 is configured to control the electric motor 42 so that the assist force M by the electric motor 42 is a predetermined ratio A relative to the human-powered driving force H. The predetermined ratio A is not constant, but may change, for example, according to the human-powered driving force H, the vehicle speed V, or both the human-powered driving force H and the vehicle speed V. The human-powered driving force H and the assist force M may be expressed by torque or by power. When the human-powered driving force H and the assist force M are expressed by torque, the human-powered driving force H is written as the human-powered torque HT, and the assist force M is written as the assist torque TM. When the human-powered driving force H and the assist force M are expressed by power, the human-powered driving force H is written as the human-powered power WH, and the assist force M is written as the assist power WM. The torque ratio of the output torque MT to the human-powered torque HT of the human-powered vehicle 10 may be written as the assist ratio AT. The ratio of the assist power WM by the electric motor 42 to the manual power WH may be referred to as the assist ratio AW.

Preferably, the drive unit 40 includes an interface 86 electrically connected to the control unit 46. The interface 86 includes at least one of a connector for an electric cable and a wireless communication device. Preferably, the control unit 46 is configured to control the electric motor 42 in accordance with a plurality of operation modes. Preferably, the plurality of operation modes include a plurality of operation modes in which the characteristics of the predetermined ratio A are different from each other. Preferably, the human-powered vehicle 10 further includes an operation unit 37. The operation unit 37 includes, for example, a switch that can be operated by the user of the human-powered vehicle 10 with the fingers. The operation unit 37 may be, for example, a smartphone. The operation unit 37 is configured to connect to the interface 86 via at least one of the wireless communication device and the electric cable. The control unit 46 is configured to switch between a plurality of operation modes in accordance with the operation of the operation unit 37. Preferably, the plurality of operation modes includes an off mode in which the electric motor 42 is not driven. Preferably, the plurality of operation modes includes a push-walk mode in which the electric motor 42 is driven in accordance with the operation of the operation unit 37. In the push-walk mode, for example, while the operating unit 37 is being operated, the control unit 46 is configured to drive the electric motor 42 so that the human-powered vehicle 10 moves at a speed within a predetermined range. The predetermined range is, for example, from 3 km/h to 6 km/h.

The control unit 46 is configured to control the electric motor 42 so that the assist force M is equal to or less than the upper limit value MX. When the assist force M is expressed by torque, the control unit 46 is configured to control the electric motor 42 so that the output torque MT is equal to or less than the upper limit value MTX. Preferably, the upper limit value MTX is a value in the range of 30 Nm to 90 Nm. The upper limit value MTX is, for example, 80 Nm. The upper limit value MTX is determined, for example, by the output characteristics of the electric motor 42. When the assist force M is expressed by power, the control unit 46 is configured to control the electric motor 42 so that the assist power WM is equal to or less than the upper limit value WMX.

Preferably, the control unit 46 is configured to control the electric motor 42 in response to at least one of the human-powered driving force H input to the human-powered vehicle 10, the vehicle speed V of the human-powered vehicle 10, the rotation speed C of the input rotating shaft 12A, and the rotation angle D of the input rotating shaft 12A.

Preferably, the drive unit 40 includes a motor rotation sensor 84. The motor rotation sensor 84 may be included in the electric motor 42. The motor rotation sensor 84 is configured to detect the rotation state of the electric motor 42. The motor rotation sensor 84 is provided, for example, on at least one of the rotor and the output shaft of the electric motor 42. The motor rotation sensor 84 outputs information regarding at least one of the rotation speed and the rotation angle of the rotor and the output shaft. The motor rotation sensor 84 includes, for example, a magnetic sensor or an optical sensor. The magnetic sensor includes, for example, a Hall element. The motor rotation sensor 84 may include a resolver. The motor rotation sensor 84 is electrically connected to the control unit 46. The control unit 46 controls the drive circuit 44X according to the information output from the motor rotation sensor 84 to drive the electric motor 42.

The electric motor 42 has a coil 48. The electric motor 42 includes a stator and a rotor. One of the stator and the rotor includes the coil 48, and the other of the stator and the rotor includes a permanent magnet. The electric motor 42 may be any of an inner rotor type, an outer rotor type, and an axial gap type motor. In this embodiment, the coil 48 is included in the stator. The multiple switching elements 44 are electrically connected to the coil 48. Each of the multiple switching elements 44 is configured to selectively switch between a conductive state and a non-conductive state. Each of the multiple switching elements 44 is controlled by the control unit 46 to selectively switch between a conductive state and a non-conductive state. Preferably, each of the multiple switching elements 44 includes a MOSFET or an IGBT (Insulated Gate Bipolar Transistor). Preferably, a diode 45 is connected in parallel to each of the multiple switching elements 44. The cathode of the diode 45 is electrically connected to the positive electrode of the power source 36, and the anode of the diode 45 is electrically connected to the negative electrode of the power source 36. The electric motor 42 rotates in a first rotation direction R1 when providing a propulsive force to the human-powered vehicle 10. The control unit 46 is configured to drive the electric motor 42 by controlling the multiple switching elements 44 so that a current flows through the coil 48. When the electric motor 42 provides a propulsive force to the human-powered vehicle 10, the control unit 46 controls the multiple switching elements 44 so that a current flows through the coil 48, thereby rotating the rotor of the electric motor 42 in the first rotation direction R1. The control unit 46 controls the current flowing through the multiple switching elements 44, for example, by PWM (Pulse Width Modulation) control. The control unit 46 may include a driver circuit and control the switching elements 44 via the driver circuit.

The control unit 46 includes an arithmetic processing unit that executes a predetermined control program. The arithmetic processing unit includes, for example, a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The arithmetic processing unit may be provided in a plurality of locations that are separate from each other. The control unit 46 may include one or a plurality of microcomputers. Preferably, the drive unit 40 further includes a storage unit 50. The storage unit 50 stores various control programs and information used in various control processes. The storage unit 50 includes, for example, a non-volatile memory and a volatile memory. The non-volatile memory includes, for example, at least one of a ROM (Read-Only Memory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), and a flash memory. The volatile memory includes, for example, a RAM (Random access memory). Preferably, the control unit 46 has a function of measuring time. The control unit 46 may measure time using, for example, a CPU or an MPU, and may have a clock.

Preferably, the drive unit 40 includes a drive circuit 44X. The drive circuit 44X includes a plurality of switching elements 44. The drive circuit 44X may further include a diode 45. The drive circuit 44X and the control unit 46 are preferably provided in the housing 40A of the drive unit 40. The drive circuit 44X and the control unit 46 may be provided, for example, on the same circuit board. The drive circuit 44X includes an inverter circuit. The drive circuit 44X controls the power supplied from the power source 36 to the electric motor 42. The drive circuit 44X is connected to the control unit 46 by wire or wirelessly so as to be able to communicate with each other. The drive circuit 44X drives the electric motor 42 in response to a control signal from the control unit 46.

When a predetermined condition is satisfied, the control unit 46 controls at least one of the multiple switching elements 44 to short-circuit the coil 48. The control unit 46 shorts the coil 48 by setting the state of at least one of the multiple switching elements 44 to either a conductive state or a non-conductive state.

Preferably, the drive unit 40 further includes a first terminal 52 configured to be electrically connected to the positive pole of the DC power supply, and a second terminal 54 configured to be electrically connected to the negative pole of the DC power supply. The coil 48 includes a first coil 56, a second coil 58, and a third coil 60. For example, the first coil 56 constitutes a U phase, the second coil 58 constitutes a V phase, and the third coil 60 constitutes a W phase. In FIG. 3, the first coil 56, the second coil 58, and the third coil 60 are each shown by one coil 48, but the first coil 56 may include multiple coils 48 connected in parallel, the second coil 58 may include multiple coils 48 connected in parallel, and the third coil 60 may include multiple coils 48 connected in parallel. When the first coil 56, the second coil 58, and the third coil 60 each include a plurality of coils 48 connected in parallel, the number of coils 48 included in the first coil 56 is preferably equal to the number of coils 48 included in the second coil 58 and the number of coils 48 included in the third coil 60. The number of coils 48 included in the first coil 56, the second coil 58, and the third coil 60 is determined according to the number of slots in the stator of the electric motor 42. In the present invention, the number of slots in the stator is not particularly limited.

The multiple switching elements 44 include a first switching element 62, a second switching element 64, a third switching element 66, a fourth switching element 68, a fifth switching element 70, and a sixth switching element 72. The first switching element 62, the third switching element 66, and the fifth switching element 70 form a first group 44A. The second switching element 64, the fourth switching element 68, and the sixth switching element 72 form a second group 44B. The first switching element 62, the third switching element 66, and the fifth switching element 70 are, for example, P-channel MOSFETs. The second switching element 64, the fourth switching element 68, and the sixth switching element 72 are N-channel MOSFETs. The first coil 56 is electrically connected to the first terminal 52 via the first switching element 62, and is connected to the second terminal 54 via the second switching element 64. The second coil 58 is electrically connected to the first terminal 52 via a third switching element 66, and is connected to the second terminal 54 via a fourth switching element 68. The third coil 60 is electrically connected to the first terminal 52 via a fifth switching element 70, and is connected to the second terminal 54 via a sixth switching element 72.

Preferably, the electric motor 42 is a three-phase electric motor 42. The number of poles of the electric motor 42 is not particularly limited. Preferably, the first coil 56, the second coil 58, and the third coil 60 are star-connected or delta-connected. In this embodiment, the first coil 56, the second coil 58, and the third coil 60 are star-connected. In this embodiment, the electric motor 42 is a brushless DC motor. Preferably, the drive unit 40 includes a first connection portion 73, a second connection portion 74, and a third connection portion 75. The first connection portion 73 is electrically connected to the first switching element 62, the second switching element 64, and the first coil 56. The second connection portion 74 is electrically connected to the third switching element 66, the fourth switching element 68, and the second coil 58. The third connection portion 75 is electrically connected to the fifth switching element 70, the sixth switching element 72, and the third coil 60. Preferably, the drive circuit 44X is electrically connected to the first terminal 52 and the second terminal 54, and is connected in parallel to the power source 36. The drive circuit 44X preferably includes a capacitor 76. The capacitor 76 is provided between the positive and negative poles of the DC power source at a position closer to the power source 36 than the multiple switching elements 44. Preferably, the capacitor 76 is provided between the positive and negative poles of the DC power source, between the first terminal 52 and the second terminal 54, and the multiple switching elements 44. The capacitor 76 allows a stable supply of DC voltage to the multiple switching elements 44.

The predetermined conditions include an assist stop condition for the electric motor 42. The assist stop condition includes at least one condition. In this embodiment, the assist stop condition includes at least one of the first assist stop condition, the second assist stop condition, the third assist stop condition, the fourth assist stop condition, the fifth assist stop condition, the sixth assist stop condition, the seventh assist stop condition, and the eighth assist stop condition. The assist stop condition may include any two or more of the first assist stop condition, the second assist stop condition, the third assist stop condition, the fourth assist stop condition, the fifth assist stop condition, the sixth assist stop condition, the seventh assist stop condition, and the eighth assist stop condition.

The first assist stop condition includes that the vehicle speed V of the human-powered vehicle is equal to or greater than the first speed VX. The first assist stop condition is satisfied when the vehicle speed V of the human-powered vehicle is equal to or greater than the first speed VX. The second assist stop condition includes that the human-powered driving force H input to the crank 12 of the human-powered vehicle 10 is equal to or less than the first value HX. The second assist stop condition is satisfied when the human-powered driving force H input to the crank 12 of the human-powered vehicle 10 is equal to or less than the first value HX. The third assist stop condition includes that the state in which the human-powered driving force H input to the crank 12 of the human-powered vehicle 10 is equal to or less than the second value HY continues throughout the first rotation angle AX of the crank 12. The third assist stop condition is satisfied when the state in which the human-powered driving force H input to the crank 12 of the human-powered vehicle 10 is equal to or less than the second value HY continues throughout the first rotation angle AX of the crank 12. The fourth assist stop condition includes a state in which the human-powered driving force H input to the crank 12 of the human-powered vehicle 10 is equal to or less than the second value HY for a predetermined time TA. The fourth assist stop condition is satisfied when the human-powered driving force H input to the crank 12 of the human-powered vehicle 10 is equal to or less than the second value HY for a predetermined time TA. The fifth assist stop condition includes a rotation speed C of the crank 12 of the human-powered vehicle 10 is equal to or less than the first rotation speed CX. The fifth assist stop condition is satisfied when the rotation speed C of the crank 12 of the human-powered vehicle 10 is equal to or less than the first rotation speed CX. The sixth assist stop condition includes a temperature of a predetermined portion of the drive unit 40 being equal to or greater than a predetermined temperature. The sixth assist stop condition is satisfied when the temperature of a predetermined portion of the drive unit 40 is equal to or greater than a predetermined temperature. The seventh assist stop condition includes a change of the operation mode to the off mode. The seventh assist stop condition is satisfied when the operation mode is changed to the off mode. The eighth assist stop condition includes unstable communication with the manual driving force detection unit 38C. The eighth assist stop condition is satisfied when unstable communication with the manual driving force detection unit 38C.

The predetermined condition may include that the vehicle speed V of the human-powered vehicle is equal to or greater than the first speed VX when the electric motor 42 is being driven. The first condition is that the vehicle speed V of the human-powered vehicle is equal to or greater than the first speed VX when the electric motor 42 is being driven. The state in which the electric motor 42 is being driven includes a state in which the rotor is rotating. The control unit 46 may determine whether the electric motor 42 is being driven in response to a signal output from the motor rotation sensor 84, or may determine whether the electric motor 42 is being driven depending on whether the control unit 46 is driving the drive circuit 44X. The first condition includes a first assist stop condition. Preferably, the first speed VX is a value in a range of 20 km/h or more and 50 km/h or less. For example, the first speed VX is 24 km/h or 45 km/h.

The drive unit 40 preferably includes a first storage unit 78 that stores information about the first speed VX in a changeable manner. The first storage unit 78 includes, for example, a non-volatile memory. The first storage unit 78 is preferably included in the storage unit 50, but may be formed separately from the storage unit 50. The control unit 46 is preferably configured to be able to update the first speed VX stored in the first storage unit 78 in response to a signal from an external device of the drive unit 40. The external device includes, for example, an information processing device such as a personal computer, a tablet computer, or a smartphone. The first speed VX is stored in the first storage unit 78, for example, when the drive unit 40 is manufactured, when the drive unit 40 is shipped from the manufacturer, or when the human-powered vehicle 10 is assembled. The first speed VX is set to a suitable value corresponding to, for example, the region to which the drive unit 40 is shipped or the region to which the human-powered vehicle 10 is shipped.

The predetermined condition may include the human-powered driving force H input to the crank 12 of the human-powered vehicle 10 being equal to or less than a first value HX when the electric motor 42 is being driven. The second condition is that the human-powered driving force H input to the crank 12 of the human-powered vehicle 10 being equal to or less than a first value HX when the electric motor 42 is being driven. The second condition includes a second assist stop condition.

The predetermined condition may include a state in which the human-powered driving force H input to the crank 12 of the human-powered vehicle 10 is equal to or less than the second value HY while the electric motor 42 is being driven, and the state in which the crank 12 is equal to or less than the second value HY continues throughout the first rotation angle AX of the crank 12. A third condition is that the human-powered driving force H input to the crank 12 of the human-powered vehicle 10 is equal to or less than the second value HY while the electric motor 42 is being driven, and the state in which the crank 12 is equal to or less than the first rotation angle AX continues throughout the first rotation angle AX of the crank 12. The first rotation angle AX is, for example, an angle in the range from 90 degrees to 720 degrees. The first rotation angle AX is, for example, 180 degrees. The third condition includes a third assist stop condition.

The predetermined condition may include a state in which the human-powered driving force H input to the crank 12 of the human-powered vehicle 10 is equal to or less than the second value HY for a predetermined time TA while the electric motor 42 is being driven. A fourth condition is that the human-powered driving force H input to the crank 12 of the human-powered vehicle 10 is equal to or less than the second value HY for a predetermined time TA while the electric motor 42 is being driven. The fourth condition includes a fourth assist stop condition.

The predetermined conditions may include the rotation speed C of the crank 12 of the human-powered vehicle 10 being equal to or less than the first rotation speed CX when the electric motor 42 is being driven. The fifth condition is that the rotation speed C of the crank 12 of the human-powered vehicle 10 being equal to or less than the first rotation speed CX when the electric motor 42 is being driven. The first rotation speed CX is, for example, a value in the range of 3 rpm to 7 rpm. The first rotation speed CX is, for example, 5 rpm. The fifth condition includes a fifth assist stop condition.

The predetermined condition may include that the temperature of the predetermined part of the drive unit 40 is equal to or higher than a predetermined temperature when the electric motor 42 is driven. The sixth condition is that the temperature of the predetermined part of the drive unit 40 is equal to or higher than a predetermined temperature when the electric motor 42 is driven. The sixth condition includes a sixth assist stop condition. When the predetermined condition includes the sixth condition, the drive unit 40 includes a temperature sensor 83. The temperature of the predetermined part of the drive unit 40 may be the temperature of the electric motor 42, the temperature of a part of the electric motor 42, the temperature of the control unit 46, the temperature of the drive circuit 44X, or the temperature of the reducer. The temperature of the control unit 46 is , for example, the temperature of a circuit board on which at least one of the CPU and MPU of the control unit 46 is provided. The temperature of the drive circuit 44X is, for example, the temperature of a circuit board on which the drive circuit 44X is provided, or the temperature of a circuit board constituting a part of the drive circuit 44X. The temperature of a part of the reducer is, for example, the temperature of a gear included in the reducer.

The predetermined condition may include changing the operation mode to the off mode while the electric motor 42 is being driven. Changing the operation mode to the off mode while the electric motor 42 is being driven is a seventh condition. The seventh condition includes a seventh assist stop condition.

The predetermined condition may include a state in which communication with the manual driving force detection unit 38C is unstable when the electric motor 42 is being driven. An eighth condition is that communication with the manual driving force detection unit 38C is unstable when the electric motor 42 is being driven. The eighth condition includes an eighth assist stop condition. For example, the control unit 46 is configured to periodically acquire a signal from the manual driving force detection unit 38C. For example, the control unit 46 determines that communication is unstable when the period of the signal acquired from the manual driving force detection unit 38C deviates from a predetermined period.

The predetermined conditions may include that the electric motor 42 rotates in a second rotation direction R2 opposite to the first rotation direction R1 when the electric motor 42 is driven. The ninth condition is that the electric motor 42 rotates in the second rotation direction R2 when the electric motor 42 is driven. The control unit 46 determines the rotation direction of the electric motor 42 according to the information output from the motor rotation sensor 84.

The predetermined condition may include an error occurring in at least one sensor 38 used to control the electric motor 42 when the electric motor 42 is being driven. The tenth condition is that an error occurs in at least one sensor 38 used to control the electric motor 42 when the electric motor 42 is being driven. The error in the at least one sensor 38 includes, for example, at least one of an abnormality in the output of the at least one sensor 38 and an abnormality in the communication state between the at least one sensor 38 and the control unit 46. When the at least one sensor 38 is in an abnormal state, the at least one sensor 38 may transmit information about its own abnormality to the control unit 46. When an abnormal signal is included in the signal input from the at least one sensor 38, the control unit 46 may determine that an error occurs in the at least one sensor 38. The at least one sensor 38 includes at least one of the vehicle speed sensor 38A, the crank rotation sensor 38B, the current detection unit 82, the temperature sensor 83, and the motor rotation sensor 84. At least one sensor 38 may include a manual driving force detection unit 38C.

The predetermined condition may include that the control unit 46 detects an overcurrent of the electric motor 42 when the electric motor 42 is driven. The eleventh condition is that the control unit 46 detects an overcurrent of the electric motor 42 when the electric motor 42 is driven. Preferably, the drive unit 40 further includes a current detection unit 82. The current detection unit 82 is configured to detect the current of the first connection unit 73, the second connection unit 74, and the third connection unit 75. The first connection unit 73, the second connection unit 74, and the third connection unit 75 each include a resistor. The current detection unit 82 detects the current of the first connection unit 73, the second connection unit 74, and the third connection unit 75 by detecting the voltage between both ends of the resistor. The control unit 46 determines that an overcurrent exists when the current of at least one of the first connection unit 73, the second connection unit 74, and the third connection unit 75 exceeds a predetermined value. The predetermined value is appropriately set according to the electric motor 42. Information regarding the predetermined values is stored in the memory unit 50.

The predetermined condition may include that the rotation speed S of the electric motor 42 is equal to or greater than the second rotation speed SX. The rotation speed S of the electric motor 42 being equal to or greater than the second rotation speed SX is the twelfth condition. Preferably, the predetermined condition includes that the rotation speed S of the electric motor 42 is equal to or greater than the second rotation speed SX, and the second rotation speed SX is set so that the vehicle speed V of the human-powered vehicle 10 is equal to or greater than 3 km/h and equal to or less than 7 km/h when the electric motor 42 rotates at the second rotation speed SX and the electric motor 42 provides a propulsive force to the human-powered vehicle 10. Preferably, the second rotation speed SX is set so that the voltage generated when the electric motor 42 rotates at the second rotation speed SX is smaller than the voltage supplied from the power source 36 to the electric motor 42.

When the predetermined condition includes the twelfth condition, the drive unit 40 preferably includes a second storage unit 80 that stores information about the second rotation speed SX in a changeable manner. The second storage unit 80 includes, for example, a non-volatile memory. Preferably, the second storage unit 80 is included in the storage unit 50, but may be formed separately from the storage unit 50. Preferably, the control unit 46 is configured to be able to update the second rotation speed SX stored in the second storage unit 80 in response to a signal from an external device of the drive unit 40. For example, the second rotation speed SX is stored in the second storage unit 80, for example, when the drive unit 40 is manufactured, when the drive unit 40 is shipped from the manufacturer, or when the human-powered vehicle 10 is assembled. The second rotation speed SX may be set, for example, in response to the DC voltage of the connected power source 36.

Preferably, the control unit 46 releases the short circuit of the coil 48 depending on the time after shorting the coil 48. Preferably, the control unit 46 releases the short circuit of the coil 48 depending on the time after a predetermined time TX has elapsed after shorting the coil 48 and activating the short circuit brake, and releases the short circuit brake. The predetermined time TX is, for example, 0.5 milliseconds or more and 100 milliseconds or less. Preferably, the predetermined time TX is set depending on the time until the rotational energy of the electric motor 42 is sufficiently reduced after the short circuit brake is activated. The predetermined time TX may be set to a different value for each of the first condition to the twelfth condition, or may be the same for at least some of the first condition to the twelfth condition. For example, the predetermined time TX1 when the ninth condition is satisfied and the coil 48 is short circuited is longer than the predetermined time TX2 when a condition other than the ninth condition is satisfied and the coil 48 is short circuited. For example, the predetermined time TX1 is three times or more and ten times or less than the predetermined time TX2.

The predetermined conditions include at least one of the first condition, the second condition, the third condition, the fourth condition, the fifth condition, the sixth condition, the seventh condition, the eighth condition, the ninth condition, the tenth condition, and the eleventh condition. The predetermined conditions may include any two or more of the first condition, the second condition, the third condition, the fourth condition, the fifth condition, the sixth condition, the seventh condition, the eighth condition, the ninth condition, the tenth condition, and the eleventh condition. When the predetermined conditions include at least one of the first condition, the second condition, the third condition, the fourth condition, the fifth condition, the sixth condition, the seventh condition, the eighth condition, and the tenth condition, preferably, the predetermined conditions also include the twelfth condition. In this embodiment, the predetermined conditions include all of the first condition, second condition, third condition, fourth condition, fifth condition, sixth condition, seventh condition, eighth condition, ninth condition, tenth condition, eleventh condition, and twelfth condition.

If the predetermined conditions include only one of the first condition, second condition, third condition, fourth condition, fifth condition, sixth condition, seventh condition, eighth condition, ninth condition, tenth condition, and eleventh condition, and do not include the twelfth condition, the predetermined condition is satisfied when one of the conditions included in the predetermined conditions is satisfied.

If the predetermined conditions include two or more of the first condition, second condition, third condition, fourth condition, fifth condition, sixth condition, seventh condition, eighth condition, ninth condition, tenth condition, and eleventh condition, but do not include the twelfth condition, the predetermined conditions are satisfied when at least one of the two or more conditions included in the predetermined conditions is satisfied.

If the predetermined conditions include one of the first condition, second condition, third condition, fourth condition, fifth condition, sixth condition, seventh condition, eighth condition, and tenth condition, and the twelfth condition, the predetermined conditions are satisfied when the twelfth condition is satisfied after one of the predetermined conditions other than the twelfth condition is satisfied.

If the predetermined conditions include two or more of the first condition, second condition, third condition, fourth condition, fifth condition, sixth condition, seventh condition, eighth condition, and tenth condition, and the twelfth condition, the predetermined conditions are satisfied when the twelfth condition is satisfied after at least one of the two or more conditions other than the twelfth condition included in the predetermined conditions is satisfied. If the predetermined conditions include the ninth condition, the predetermined conditions are satisfied when the ninth condition is satisfied. If the predetermined conditions include the eleventh condition, the predetermined conditions are satisfied when the eleventh condition is satisfied.

When a predetermined condition is satisfied, the control unit 46 sets one of the first group 44A including the first switching element 62, the third switching element 66, and the fifth switching element 70, and the second group 44B including the second switching element 64, the fourth switching element 68, and the sixth switching element 72 to a conductive state, and sets the other of the first group 44A and the second group 44B to a non-conductive state.

The control unit 46 sets one of the first group 44A and the second group 44B in a conductive state, and then sets one of the first group 44A and the second group 44B in a non-conductive state. For example, the control unit 46 sets one of the first group 44A and the second group 44B in a conductive state, and then sets one of the first group 44A and the second group 44B in a non-conductive state depending on time. For example, the control unit 46 sets one of the first group 44A and the second group 44B in a conductive state, and then sets one of the first group 44A and the second group 44B in a non-conductive state after a predetermined time TX has elapsed. The control unit 46 gradually stops the electric motor 42 by setting one of the first group 44A and the second group 44B in a conductive state, and then sets one of the first group 44A and the second group 44B in a non-conductive state depending on time. The control unit 46 stops the drive circuit 44X by putting both the first group 44A and the second group 44B into a non-conductive state.

For example, the control unit 46 may set one of the first group 44A and the second group 44B to a conductive state, and then set one of the first switching element 62 and the second switching element 64 that is in a conductive state to a non-conductive state when the current detection unit 82 detects a zero cross of the current value flowing through the first terminal 52; set one of the third switching element 66 and the fourth switching element 68 that is in a conductive state to a non-conductive state when the current detection unit 82 detects a zero cross of the current value flowing through the second terminal 54; and set one of the fifth switching element 70 and the sixth switching element 72 that is in a conductive state to a non-conductive state when the current detection unit 82 detects a zero cross of the current value flowing through the third connection unit 75.

The process of controlling the switching element 44 will be described with reference to Figures 4 and 5. When power is supplied to the control unit 46, the control unit 46 starts the process and proceeds to step S11 of the flowchart shown in Figure 4. When the flowchart in Figure 4 ends, the control unit 46 repeats the process from step S11 after a predetermined period until the supply of power is stopped.

In step S11, the control unit 46 determines whether the electric motor 42 is driving. If the electric motor 42 is not driving, the control unit 46 ends the process. If the electric motor 42 is driving, the control unit 46 proceeds to step S12.

In step S12, the control unit 46 determines whether the short circuit brake is operating. If the short circuit brake is operating, the control unit 46 proceeds to step S13. In step S13, the control unit 46 determines whether a predetermined time TX has elapsed. For example, if the predetermined time TX has elapsed since the start of operation of the short circuit brake, the control unit 46 determines that the predetermined time TX has elapsed. If the predetermined time TX has not elapsed, the control unit 46 ends the process. If the predetermined time TX has elapsed, the control unit 46 proceeds to step S14. In step S14, the control unit 46 releases the short circuit brake and ends the process.

If the short circuit brake is not activated in step S12, the control unit 46 proceeds to step S15. In step S15, the control unit 46 determines whether the electric motor 42 is rotating in the second rotation direction R2 . If the electric motor 42 is rotating in the second rotation direction R2, the control unit 46 proceeds to step S16. In step S16, the control unit 46 activates the short circuit brake and ends the process.

If the control unit 46 determines in step S15 that the electric motor 42 is not rotating in the second rotation direction R2, the process proceeds to step S17. In step S17, the control unit 46 determines whether or not an overcurrent in the electric motor 42 is detected. If the control unit 46 detects an overcurrent in the electric motor 42, the process proceeds to step S16. In step S16, the control unit 46 activates the short circuit brake and ends the process.

If the control unit 46 does not detect an overcurrent in the electric motor 42 in step S17, the control unit 46 proceeds to step S18. In step S18, the control unit 46 determines whether an error has occurred in the sensor 38. If an error has occurred in the sensor 38, the control unit 46 proceeds to step S19.

If no error has occurred in the sensor 38 in step S18, the control unit 46 proceeds to step S20. In step S20, the control unit 46 determines whether the assist stop condition is satisfied. If the assist stop condition is not satisfied, the control unit 46 ends the process. If the assist stop condition is satisfied, the control unit 46 proceeds to step S21. In step S20, the control unit 46 determines that the assist stop condition is satisfied when, for example, any one of the first assist stop condition, the second assist stop condition, the third assist stop condition, the fourth assist stop condition, the fifth assist stop condition, the sixth assist stop condition, the seventh assist stop condition, and the eighth assist stop condition included in the assist stop condition is satisfied. In step S21, the control unit 46 executes a stop process for the drive circuit 44X and proceeds to step S22. In step S21, the control unit 46 controls the drive circuit 44X so that, for example, the current value supplied to the electric motor 42 decreases as time passes.

In step S22, the control unit 46 determines whether or not the first time T1 has elapsed. For example, if the first time T1 has elapsed since the stop process of the drive circuit 44X was executed in step S21, the control unit 46 determines that the first time T1 has elapsed. If the first time T1 has not elapsed, the control unit 46 executes the determination process of step S22 again. If the first time T1 has elapsed, the control unit 46 proceeds to step S19. The control unit 46 reduces the current value supplied to the electric motor 42 as time elapses until the first time T1 has elapsed.

In step S19, the control unit 46 determines whether the rotation speed S of the electric motor 42 is equal to or lower than the second rotation speed SX. If the rotation speed S of the electric motor 42 is not equal to or lower than the second rotation speed SX, the control unit 46 proceeds to step S16. In step S16, the control unit 46 activates the short circuit brake and ends the process. If the rotation speed S of the electric motor 42 is equal to or lower than the second rotation speed SX in step S19, the control unit 46 proceeds to step S23. In step S23, the control unit 46 executes a stop process of the drive circuit 44X and ends the process. The stop process of the drive circuit 44X in step S23 is the same as the stop process of the drive circuit 44X in step S21. The stop process of the drive circuit 44X in step S23 may be different from the stop process of the drive circuit 44X in step S21. For example, in step S23, the control unit 46 sets the current value supplied to the electric motor 42 to 0 mA.

When a predetermined condition is satisfied, the control unit 46 uses the short-circuit brake to stop the drive of the electric motor 42. Therefore, by short-circuiting the coil 48 of the electric motor 42, the electric motor 42 can be braked, and the regenerative current accompanying the stopping of the electric motor 42 can be prevented from flowing into the power source 36. The short-circuit brake can be configured by the switching element 44 used to drive the electric motor 42, so that an increase in the number of parts can be suppressed. In the process shown in the flowcharts of Figures 4 and 5, even if the assist stop condition is satisfied, the control unit 46 does not immediately activate the short-circuit brake, but executes the stop process of the drive circuit 44X and activates the short-circuit brake only when the twelfth condition is satisfied. Therefore, the short-circuit brake is selectively activated only when it is necessary to suddenly stop the electric motor 42, and the ride comfort of the human-powered vehicle 10 can be improved compared to the case where the short-circuit brake is activated immediately when the assist stop condition is satisfied.

<Modification>
The description of the embodiments is merely an example of possible forms of a drive unit for a human-powered vehicle according to the present disclosure, and is not intended to limit the forms. A drive unit for a human-powered vehicle according to the present disclosure may take the form of, for example, a modified version of the embodiment shown below, or a combination of at least two mutually compatible modified versions. In the following modified versions, parts common to the embodiment will be given the same reference numerals as in the embodiment, and descriptions thereof will be omitted.

6, the electric motor 42 may be a brushed DC motor 42A. The brushed DC motor 42A includes a plurality of switching elements 44. The plurality of switching elements 44 includes a first switching element 62A, a second switching element 64A, a third switching element 66A, and a fourth switching element 68A. The first switching element 62A, the second switching element 64A, the third switching element 66A, and the fourth switching element 68A constitute a drive circuit 44Y. The first group 44A includes the first switching element 62A and the third switching element 66A. The second group 44B includes the second switching element 64A and the fourth switching element 68A. The electric motor 42A rotates in the first rotation direction R1 by setting the first switching element 62A and the fourth switching element 68A to a conductive state and setting the second switching element 64A and the third switching element 66A to a non-conductive state. By making one of the first group 44A and the second group 44B conductive and the other non-conductive, the coil 48 is short-circuited.

- The first coil 56, the second coil 58, and the third coil 60 may be delta connected as shown in FIG. 7.

The control unit 46 may execute the process of Fig. 8 instead of the processes of Fig. 4 and Fig. 5. A modified example of the process for controlling the switching element 44 will be described with reference to Fig. 8. When power is supplied to the control unit 46, the control unit 46 starts the process and proceeds to step S31 of the flowchart shown in Fig. 8. When the flowchart of Fig. 8 ends, the control unit 46 repeats the process from step S31 after a predetermined period until the supply of power is stopped.
In step S31, the control unit 46 determines whether or not a predetermined condition is satisfied. If the predetermined condition is not satisfied, the control unit 46 ends the process. If the predetermined condition is satisfied, the control unit 46 proceeds to step S32. In step S32, the control unit 46 controls the switching element 44 to short-circuit the coil 48, and proceeds to step S33. In step S33, the control unit 46 determines whether or not a predetermined time TX has elapsed. If the predetermined time TX has not elapsed, the control unit 46 executes the process of step S33 again. If the predetermined time TX has elapsed, the control unit 46 proceeds to step S34. In step S34, the control unit 46 controls the switching element 44 to release the short circuit of the coil 48, and ends the process.

- In the modified example shown in FIG. 8, the predetermined conditions may include that the electric motor 42 rotates in a second rotation direction R2 opposite to the first rotation direction R1. When the electric motor 42 rotates in the second rotation direction R2 opposite to the first rotation direction R1, the control unit 46 controls the switching element 44 to short-circuit the coil 48. In this modified example, for example, when the crank 12 is rotated backward, the short-circuit brake can be activated. In the modified example shown in FIG. 8, the predetermined conditions may include at least one of the first condition, the second condition, the third condition, the fourth condition, the fifth condition, the sixth condition, the seventh condition, the eighth condition, the ninth condition, the tenth condition, and the eleventh condition, in addition to the electric motor 42 rotating in the second rotation direction R2 opposite to the first rotation direction R1. In the modified example shown in FIG. 8, if the predetermined conditions include at least one of the first condition, the second condition, the third condition, the fourth condition, the fifth condition, the sixth condition, the seventh condition, the eighth condition, and the tenth condition, the predetermined conditions preferably also include the twelfth condition.

When the control unit 46 controls the electric motor 42 in the push-walking mode, the predetermined conditions include at least one of the sixth, seventh, eighth, ninth, tenth, and eleventh conditions. When the control unit 46 controls the electric motor 42 in the push-walking mode, the predetermined conditions may include a thirteenth condition in addition to the sixth, seventh, eighth, ninth, tenth, and eleventh conditions, or instead of at least one of the sixth, seventh, eighth, ninth, tenth, and eleventh conditions. The thirteenth condition includes that the vehicle speed V of the human-powered vehicle is greater than a predetermined speed VA when the electric motor 42 is driven. The predetermined speed VA is, for example, a value in the range of 6 km/h to 10 km/h. In this case, the vehicle speed V of the human-powered vehicle 10 can be suppressed, for example, on a downhill slope.

In the embodiment and the modified example of the embodiment, the predetermined condition may include that the rotation speed S of the electric motor 42 is equal to or greater than the third rotation speed SY. The rotation speed S of the electric motor 42 being equal to or greater than the third rotation speed SY is the fourteenth condition. The third rotation speed SY is set so that the vehicle speed V of the human-powered vehicle 10 becomes the first speed VX when the electric motor 42 rotates at the third rotation speed SY and the electric motor 42 applies a propulsive force to the human-powered vehicle 10. When the predetermined condition includes the fourteenth condition, preferably, the storage unit 50 stores information about the third rotation speed SY in a changeable manner. Preferably, the control unit 46 is configured to be able to update the third rotation speed SY stored in the storage unit 50 in response to a signal from an external device of the drive unit 40. The external device includes, for example, an information processing device such as a personal computer, a tablet computer, or a smartphone. The third rotation speed SY is stored in the storage unit 50, for example, when the drive unit 40 is manufactured, when the drive unit 40 is shipped from the manufacturer, or when the human-powered vehicle 10 is assembled. The third rotation speed SY is set to a suitable value corresponding to, for example, the region to which the drive unit 40 is shipped or the region to which the human-powered vehicle 10 is shipped. When the predetermined conditions include the fourteenth condition, the assist stop condition includes the ninth assist stop condition. The ninth assist stop condition includes that the rotation speed S of the electric motor 42 is equal to or greater than the third rotation speed SY.

In each embodiment and its modified example, the predetermined conditions may include at least one of the first condition, the second condition, the third condition, the fourth condition, the fifth condition, the sixth condition, the seventh condition, the eighth condition, the ninth condition, the tenth condition, the eleventh condition, and the fourteenth condition. The predetermined conditions may include any two or more of the first condition, the second condition, the third condition, the fourth condition, the fifth condition, the sixth condition, the seventh condition, the eighth condition, the ninth condition, the tenth condition, the eleventh condition, and the fourteenth condition. When the predetermined conditions include at least one of the first condition, the second condition, the third condition, the fourth condition, the fifth condition, the sixth condition, the seventh condition, the eighth condition, the tenth condition, and the fourteenth condition, preferably, the predetermined conditions also include the twelfth condition. If the predetermined conditions include one of the first, second, third, fourth, fifth, sixth, seventh, eighth, tenth, and fourteenth conditions, and the twelfth condition, the predetermined condition is satisfied when the twelfth condition is satisfied after one of the predetermined conditions other than the twelfth condition is satisfied. If the predetermined conditions include two or more of the first, second, third, fourth, fifth, sixth, seventh, eighth, tenth, and fourteenth conditions, and the twelfth condition, the predetermined condition is satisfied when the twelfth condition is satisfied after at least one of the two or more conditions other than the twelfth condition is satisfied.

The term "at least one" as used herein means "one or more" of the desired options. As an example, the term "at least one" as used herein means "only one option" or "both of two options" if the number of options is two. As another example, the term "at least one" as used herein means "only one option" or "any combination of two or more options" if the number of options is three or more.

10...human-powered vehicle, 12...crank, 36...power source, 38...sensor, 40...drive unit, 42...electric motor, 48...coil, 56...first coil, 58...second coil, 60...third coil, 44...switching element, 44A...first group, 44B...second group, 52...first terminal, 54...second terminal, 62...first switching element, 64...second switching element, 66...third switching element, 68...fourth switching element, 70...fifth switching element, 72...sixth switching element, 73...first connection portion, 74...second connection portion, 75...third connection portion, 46...control portion, 78...first memory portion, 80...second memory portion, 82...current detection portion.

Claims (20)

A drive unit for a human-powered vehicle,
an electric motor having a coil and configured to provide propulsive force to the human powered vehicle;
A plurality of switching elements electrically connected to the coil;
a control unit configured to control the plurality of switching elements so that a current flows through the coil to drive the electric motor;
the electric motor is configured so that rotational force is not transmitted from a wheel side of the human-powered vehicle;
The control unit controls at least one of the plurality of switching elements to short-circuit the coil when a predetermined condition is satisfied. The drive unit according to claim 1, wherein the predetermined condition includes that the speed of the human-powered vehicle is equal to or greater than a first speed when the electric motor is driven. The drive unit according to claim 2, further comprising a first storage unit that stores information about the first speed in a changeable manner. The drive unit according to claim 2 or 3, wherein the first speed is a value in the range of 20 km/h or more and 50 km/h or less. The drive unit according to any one of claims 1 to 4, wherein the predetermined condition includes that the human-powered driving force input to the crank of the human-powered vehicle when the electric motor is driven is equal to or less than a first value. 6. The drive unit according to claim 1, wherein the predetermined condition includes a state in which, while the electric motor is being driven, the human-powered driving force input to a crank of the human-powered vehicle is equal to or less than a second value, the state continuing for a first rotation angle of the crank of the human-powered vehicle . The drive unit according to any one of claims 1 to 6, wherein the predetermined condition includes a state in which the human-powered driving force input to the crank of the human-powered vehicle is equal to or less than a second value while the electric motor is being driven, continuing for a predetermined period of time. The drive unit according to any one of claims 1 to 7, wherein the predetermined condition includes an error occurring in at least one sensor used to control the electric motor while the electric motor is being driven. The drive unit according to any one of claims 1 to 8, wherein the predetermined condition includes that the rotational speed of the crank of the human-powered vehicle is equal to or less than a first rotational speed when the electric motor is driven. The drive unit according to any one of claims 1 to 9, wherein the predetermined condition includes that the rotational speed of the electric motor is equal to or greater than a second rotational speed. The drive unit according to claim 10, wherein the second rotational speed is set so that the speed of the human-powered vehicle is equal to or greater than 3 km/h and equal to or less than 7 km/h when the electric motor rotates at the second rotational speed and provides a propulsive force to the human-powered vehicle. The drive unit according to claim 10 or 11, wherein the second rotational speed is set so that the voltage generated when the electric motor rotates at the second rotational speed is smaller than the voltage supplied to the electric motor from a power source. The drive unit according to any one of claims 10 to 12, further comprising a second storage unit that stores information relating to the second rotational speed in a changeable manner. the electric motor rotates in a first rotational direction when providing a propulsive force to the human-powered vehicle;
14. The drive unit of claim 1, wherein the predetermined condition includes the electric motor rotating in a second rotational direction opposite to the first rotational direction. the electric motor rotates in a first rotational direction when providing a propulsive force to the human-powered vehicle;
14. The drive unit according to claim 1, wherein the predetermined condition includes that the electric motor rotates in a second rotation direction opposite to the first rotation direction when the electric motor is driven. A first terminal configured to be electrically connected to a positive electrode of a DC power source;
a second terminal configured to be electrically connected to a negative electrode of the DC power source;
the coils include a first coil, a second coil, and a third coil;
the plurality of switching elements include a first switching element, a second switching element, a third switching element, a fourth switching element, a fifth switching element, and a sixth switching element;
The first coil is
electrically connected to the first terminal via the first switching element; and
connected to the second terminal via the second switching element,
The second coil is
electrically connected to the first terminal via the third switching element; and
connected to the second terminal via the fourth switching element,
The third coil is
electrically connected to the first terminal via the fifth switching element; and
connected to the second terminal via the sixth switching element,
16. The drive unit of claim 1, wherein, when the predetermined condition is satisfied, the control unit brings one of a first group including the first switching element, the third switching element, and the fifth switching element, and a second group including the second switching element, the fourth switching element, and the sixth switching element, into a conductive state, and brings the other of the first group and the second group into a non-conductive state. The drive unit according to claim 1 , wherein the control unit releases the short circuit of the coil when a predetermined time has elapsed after the short circuit of the coil. The drive unit of claim 16, wherein the control unit sets one of the first group and the second group to the conductive state when a predetermined time has elapsed after the control unit sets one of the first group and the second group to the non-conductive state. A current detection unit is further provided,
the electric motor is a three-phase electric motor;
a first connection portion electrically connected to the first switching element, the second switching element, and the first coil;
a second connection portion electrically connected to the third switching element, the fourth switching element, and the second coil;
a third connection portion electrically connected to the fifth switching element, the sixth switching element, and the third coil;
the current detection unit is configured to detect currents in the first connection portion, the second connection portion, and the third connection portion;
The control unit, after putting one of the first group and the second group into the conductive state,
when the current detection unit detects a zero cross of a current value flowing through the first connection unit, one of the first switching element and the second switching element that is in the conductive state is brought into the non-conductive state;
when the current detection unit detects a zero cross of a current value flowing through the second connection portion, one of the third switching element and the fourth switching element that is in the conductive state is brought into the non-conductive state;
17. The drive unit according to claim 16, wherein when the current detection unit detects a zero crossing of the current value flowing through the third connection portion, one of the fifth switching element and the sixth switching element that is in the conductive state is brought into the non-conductive state. The drive unit according to any one of claims 16, 18, and 19, wherein the first coil, the second coil, and the third coil are star-connected or delta-connected.