Motor unit and electric assist bicycle

Abstract

To provide a motor unit capable of suppressing noise generated in a signal line of a control substrate by reducing the influence of flux leakage in a motor.SOLUTION: A motor unit as an example of an embodiment comprises: a motor having a motor shaft, a rotor fixed to the motor shaft, and a stator; and a control substrate disposed so as to at least partially overlap the motor when viewed in a motor shaft direction. A sensor for detecting a magnetic field of the motor shaft, the rotor or a rotating body that rotates with the motor shaft, and a control element that controls the motor by using detection information from the sensor are mounted on the control substrate. The control substrate also includes a signal line connecting the sensor and the control element. The signal line includes an arc-shaped wiring portion that is curved so as to be convex to a radially outer side of a circle which is centered at an axis center of the motor shaft.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to a motor unit and an electrically assisted bicycle equipped with the motor unit. [Background technology]

[0002] Electrically assisted bicycles have been widely known in the past, equipped with a motor unit including a motor and a control board, which assists the force exerted by the user on the pedals with the power of the motor (see, for example, Patent Document 1). The control board of the motor unit generally has mounted thereon a sensor such as a Hall element that detects the magnetic field of a rotor that rotates together with the motor shaft, and a microcomputer that performs arithmetic processing using information detected by the sensor and controls the motor. The control board also has a signal line that connects the sensor and the microcomputer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-168180 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the Hall elements mounted on the control board are located close to the motor, and therefore leakage flux from the motor can cause noise in the signal lines connecting the Hall elements and the microcomputer, which can reduce the controllability of the motor.

[0005] An object of the present disclosure is to provide a motor unit that can reduce the effects of leakage magnetic flux from the motor and suppress noise generated in signal lines of a control board. [Means for solving the problem]

[0006] The motor unit of the present disclosure comprises a motor having a motor shaft, a rotor fixed to the motor shaft, and a stator, and a control board on which a sensor for detecting the magnetic field of the motor shaft, the rotor, or a rotating body rotating together with the motor shaft, and a control element for controlling the motor using information detected by the sensor are mounted, and at least a portion of the control board is arranged to overlap with the motor when viewed in the motor axial direction, the control board having a signal line connecting the sensor and the control element, and the signal line including an arc-shaped wiring portion bent so as to be convex radially outward of a circle centered on the axis of the motor shaft.

[0007] The electrically assisted bicycle according to the present disclosure is characterized by including the above-described motor unit. Effect of the Invention

[0008] The motor unit according to the present disclosure can reduce the effects of leakage magnetic flux from the motor and suppress noise generated in the signal lines of the control board. An electrically assisted bicycle equipped with a motor unit according to the present disclosure has, for example, excellent motor controllability and a good assist function. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing the appearance of an electrically assisted bicycle according to an embodiment; [Diagram 2] FIG. [Diagram 3] FIG. 4 is a right side view of the motor unit with the second divided body of the case removed. [Figure 4] FIG. 2 is a diagram showing a first surface of the control board. [Diagram 5] FIG. 4 is a diagram showing a second surface of the control board. [Figure 6] 5 is a diagram for explaining the configuration of a Hall element signal line of a control board. FIG. [Figure 7] 5 is a diagram for explaining the configuration of a Hall element signal line of a control board. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of a motor unit and an electrically assisted bicycle according to the present disclosure will be described in detail with reference to the drawings. The embodiments described below are merely examples, and the present disclosure is not limited to the following embodiments. Furthermore, the present disclosure includes forms that are formed by selectively combining multiple embodiments and modified examples described below.

[0011] The motor unit according to the present disclosure is suitable for electric assist bicycles, and in this embodiment, an electric assist bicycle 1 is shown as an example of an application target, but it can also be applied to electric vehicles such as electric cars and electric motorcycles, and electric equipment other than vehicles.

[0012] Fig. 1 is a diagram showing the appearance of an electrically power-assisted bicycle 1, which is an example of an embodiment. Note that the electrically power-assisted bicycle of the present disclosure is not limited to a city bicycle as exemplified in Fig. 1, and may be, for example, a sports bicycle, a folding bicycle, etc. In the following, for the sake of convenience of explanation, terms indicating directions such as front, back, up, down, left and right are used, but the front, back, up, down, left and right of the electrically power-assisted bicycle 1 and each component refer to the front, back, up, down, left and right when the bicycle is in a normal state of use.

[0013] As shown in Fig. 1, the power-assisted bicycle 1 includes a motor unit 10 and a battery 11 that supplies power to the motor unit 10. Similarly to a typical bicycle, the power-assisted bicycle 1 includes a frame 2, a front wheel 3a, a rear wheel 3b, a handlebar 4, a saddle 5, a crank arm 6, pedals 7, a chain 8, and a headlight 9. The crank arm 6 and the pedal 7 attached to one end thereof are provided on each of the left and right sides of the power-assisted bicycle 1, and the other ends of the left and right crank arms 6 are fixed to a crank shaft 12 (see Fig. 2, etc., described below).

[0014] The electrically assisted bicycle 1 is a bicycle that assists the force exerted by the user on the pedals 7 with the power of a motor 20 (see FIG. 2, etc., described later). In this embodiment, the force exerted on the pedals 7 and the output of the motor 20 are transmitted to the rear wheel 3b via a chain 8. The electrically assisted bicycle 1 is equipped with a sprocket 13 (see FIG. 2, described later) that rotates with the rotation of the pedals 7, and a rear wheel sprocket (not shown) provided on the rear wheel 3b, and the sprocket 13 and the rear wheel sprocket are connected via the chain 8.

[0015] The frame 2 is a framework that connects the front wheel 3a, the rear wheel 3b, the handlebars 4, the saddle 5, etc. The motor unit 10 and the battery 11 are supported by the frame 2. The frame 2 is composed of a plurality of pipes. In this embodiment, the plurality of pipes include a head pipe 2a, a front fork 2b, a down pipe 2c, a seat pipe 2d, a chain stay 2e, a seat stay 2f, and a bottom bracket (not shown). The bottom bracket is a pipe that connects the down pipe 2c, the seat pipe 2d, and the chain stay 2e.

[0016] The head pipe 2a supports the front fork 2b and the handlebars 4 in a rotatable state around the central axis of the pipe. The front fork 2b has a pair of legs that rotatably support the front wheel 3a, and a steering column that extends upward from the upper ends of the legs and is inserted into the cylinder of the head pipe 2a. The handlebars 4 are attached to the upper end of the steering column.

[0017] The down pipe 2c is a pipe that connects the head pipe 2a and the bottom bracket. The down pipe 2c is inclined so that the closer it is to the front of the electric assisted bicycle 1, the higher it is located. The seat pipe 2d is a pipe that holds the saddle 5, and is inclined in the vertical direction so that its upper end is located further rearward of the electric assisted bicycle 1 than its lower end. In this embodiment, the battery 11 is attached to the seat pipe 2d, and the motor unit 10 is attached to the bottom bracket.

[0018] The chain stays 2e are pipes that connect the seat stays 2f and the bottom bracket, and extend from the rear end of the bottom bracket toward the rear of the bicycle, with one on each side sandwiching the rear wheel 3b. Similarly to the chain stays 2e, the seat stays 2f are also provided on each side sandwiching the rear wheel 3b. The left and right seat stays 2f extend from the upper part of the seat pipe 2d to the radial center of the rear wheel 3b, and are connected one-to-one to the left and right chain stays 2e at the center. The rear wheel 3b is rotatably fixed to the rear end of the chain stay 2e.

[0019] Hereinafter, the configuration of the motor unit 10 as an example of an embodiment will be described in detail with reference to FIGS.

[0020] As shown in Figs. 2 and 3, the motor unit 10 includes a motor 20, a crankshaft unit 30 including a crankshaft 12, and a case 40 that houses the motor 20 and the crankshaft unit 30. The motor unit 10 is a drive unit that assists the pedaling force of the pedal 7. The output of the motor 20 is controlled based on, for example, the torque (pedaling force) acting on the crankshaft 12 that connects a pair of crank arms 6 (see Fig. 1) and the vehicle speed. The output of the motor 20 may also be controlled using the rotation speed of the crankshaft 12. Both axial ends of the crankshaft 12 extend left and right from within the case 40, and a sprocket 13 is fixed to the axial right portion of the crankshaft 12 via an output body 33.

[0021] In the motor unit 10, a second sprocket 14 is provided attached to an output shaft 16, and the sprockets 13, 14 are connected to the rear wheel sprocket via a chain 8. The output shaft 16 is a rotating shaft for outputting the power of the motor 20, and is connected to a motor shaft 21 of the motor 20 via a reduction mechanism 15. The output shaft 16 is a rotating shaft for a gear of the reduction mechanism 15. A gear of the reduction mechanism 15 is attached to the output shaft 16 via a one-way clutch 17. The motor unit 10 is a two-shaft motor unit in which the power of the motor 20 is output from an output shaft 16 separate from the crankshaft 12, but the configuration of the present disclosure is similarly applicable to a single-shaft motor unit.

[0022] The motor unit 10 further includes a control board 50 for controlling the output of the motor 20 to realize an appropriate electric assist function. The control board 50 includes a board 51 and various electronic components mounted on the board 51. The control board 50 is disposed so that at least a portion of it overlaps with the motor 20 when viewed in the motor axial direction, and is housed in the case 40 together with the motor 20. As will be described in detail later, the control board 50 is mounted with a sensor that detects the magnetic field of the motor shaft 21, the rotor 22, or a rotating body that rotates together with the motor shaft 21, and a microcomputer 53 that controls the motor 20 using information detected by the sensor. One example of a suitable sensor is a Hall element 52.

[0023] The motor 20 has a motor shaft 21, a rotor 22 fixed to the motor shaft 21, and a stator 23. The motor 20 is an inner rotor type in which an annular stator 23 is arranged to surround the rotor 22, but the motor may be an outer rotor type in which the rotor is arranged outside the stator. The motor 20 is arranged in the case 40 with the motor shaft 21 aligned in the left-right direction. In this specification, the term "motor axial direction" refers to the direction along the motor shaft 21.

[0024] The motor shaft 21 is rotatably supported by bearings 19a and 19b. A rotor 22 is fixed to one axial end of the motor shaft 21, and an engagement groove that meshes with a gear of the reduction gear mechanism 15 is formed on the other axial end. In this embodiment, a rotating body 24 is fixed between the rotor 22 of the motor shaft 21 and the engagement groove. The rotating body 24 includes a permanent magnet and serves as a part to be detected by the Hall element 52. Since the rotating body 24 rotates together with the motor shaft 21 and the rotor 22, the Hall element 52 can detect the magnetic field of the rotating body 24 to detect the position of the rotor 22.

[0025] The rotor 22 is a rotor that rotates together with the motor shaft 21, and is disposed in the radial center of the motor 20 surrounded by the stator 23. The rotor 22 includes, for example, a rotor core fixed to the motor shaft 21, and a plurality of permanent magnets embedded in the rotor core to form rotor poles. The rotor core is a laminated body in which a plurality of annular magnetic thin plates are stacked in the axial direction of the motor. A predetermined gap 27 is formed between the outer peripheral surface of the rotor 22 and the inner peripheral surface of the stator 23.

[0026] The stator 23 is a stator fixed to the case 40, and is composed of a stator core and a coil. The stator core includes, for example, an annular back yoke and a plurality of teeth 25 (see FIG. 7 described later) extending radially inward from the yoke. The gaps between adjacent teeth 25 in the circumferential direction of the motor are called slots 26. The coils are composed of a winding wound around the teeth 25. The winding may be concentrated winding, in which the winding is wound around one tooth 25, or distributed winding, in which the winding is wound across multiple teeth 25.

[0027] The motor 20 may be any motor capable of assisting the traveling of the power-assisted bicycle 1, and a suitable example is a three-phase motor having three-phase coils of U-phase, V-phase, and W-phase. A suitable three-phase motor is a three-phase brushless DC motor. In the motor 20, a rotational torque is generated by synchronizing a rotational magnetic flux component generated by the stator 23 with a magnetic flux component generated by the rotor 22. Between the rotor 22 and the stator 23, magnetic flux is generated from the rotor 22 toward the teeth 25 and from the teeth 25 toward the rotor 22, but the direction of the magnetic flux is opposite between the teeth 25 adjacent to each other in the circumferential direction of the motor, for example. In the case of a three-phase motor, strictly speaking, the direction of the magnetic flux vector is opposite between the three teeth 25 adjacent to each other in the circumferential direction of the motor.

[0028] Note that leakage flux that does not contribute to rotational torque is generated from the motor 20. The magnetic flux leaking from between the rotor 22 and the stator 23 reaches the control board 50, which is arranged so as to overlap the rotor 22 in the axial direction of the motor, and generates magnetic field noise in the electronic components and wiring of the control system. As will be described in detail later, the control board 50 is configured to reduce the effects of leakage flux and sufficiently suppress such magnetic field noise. Note that leakage flux is particularly likely to occur in the gap 27 formed between the rotor 22 and the stator 23.

[0029] In this embodiment, the maximum drive current of motor 20 is 15 A or more, and preferably 25 A or more. The upper limit of the drive current is, for example, 50 A. The maximum output torque of motor 20 is 75 N·m or more, and preferably 80 N·m or more. The upper limit of the output torque is, for example, 150 N·m. By adopting the configuration of control board 50, particularly a wiring structure including arc-shaped wiring portion 71 described below, it is possible to increase the current and output of motor 20.

[0030] The crankshaft unit 30 has the crankshaft 12 and cylindrical input bodies 31, 32 attached to the crankshaft 12. The input body 31 is fixed to the crankshaft 12 by, for example, spline connection. The input body 32 is attached to the crankshaft 12 via the input body 31. The crankshaft 12 is disposed along the left-right direction and is rotatably supported by bearings 36a, 36b. The crankshaft 12 is disposed in front of the motor 20 on the case 40 and parallel to the motor shaft 21.

[0031] The crankshaft unit 30 further has a cylindrical output body 33 to which the sprocket 13 is fixed. A one-way clutch 34 is provided between the input body 32 and the output body 33, and the rotational force of the crankshaft 12 is transmitted to the sprocket 13 via the input bodies 31, 32 and the output body 33. An inner member of the one-way clutch 34 is provided with a pawl that is biased toward the outer side to contact the inner circumferential surface of the outer member and that catches on teeth of the outer member when the crankshaft 12 rotates in the forward direction. In this embodiment, a part of the input body 32 may form the inner member of the one-way clutch 34, and a part of the output body 33 may form the outer member.

[0032] A torque sensor 35 is provided around the input body 31. The torque sensor 35 is, for example, a magnetostrictive sensor. The input body 31 fixed to the crankshaft 12 is twisted by the pedaling force of the pedal 7, and the degree of the twisting changes depending on the pedaling force, so that the pedaling force torque can be measured using the magnetostrictive torque sensor 35. Detection information from the torque sensor 35 is transmitted to the microcomputer 53 of the control board 50 and used for output control of the motor 20.

[0033] In this embodiment, the rotation speed of the crankshaft 12 is measured using a Hall element 62 mounted on the control board 50. The crankshaft unit 30 has a rotor 37a attached to the input body 32, a rotor shaft 38 arranged parallel to the crankshaft 12, a rotor 37b fixed to one axial end of the rotor shaft 38 and engaged with the rotor 37a, and a rotor 39 fixed to the other axial end of the rotor shaft 38. The rotors 37a and 37b include gears that mesh with each other. The rotor 39 includes a permanent magnet, like the rotor 24, and serves as a detection target for the Hall element 62. The rotor 39 rotates together with the crankshaft 12, so that the Hall element 62 detects the magnetic field of the rotor 39, thereby allowing the rotation speed of the crankshaft 12 to be measured.

[0034] The case 40 is a housing that houses the motor 20, the crankshaft unit 30, the reduction gear mechanism 15, etc., and holds these. Bearings 18a, 18b that support the output shaft 16, bearings 19a, 19b that support the motor shaft 21, and bearings 36a, 36b that support the crankshaft 12 are attached to the case 40. The case 40 includes, for example, a first divided body 41 and a second divided body 42, and is configured so that the second divided body 42 can be removed from the first divided body 41 to open the internal space. The first divided body 41 forms the left portion of the case 40 and houses the motor 20.

[0035] The case 40 is generally made of metal, but may be made of resin. The motor 20, the reduction mechanism 15, the output shaft 16, a retainer 43, etc. are housed in the rear of the case 40, and the crankshaft unit 30, etc. are housed in the front of the case 40. The retainer 43 holds the bearings 18a, 18b. The retainer 43 also functions as a partition wall separating the space in which the reduction mechanism 15 is disposed from the space in which the control board 50 is disposed, and prevents grease or lubricating oil from the reduction mechanism 15 from scattering and adhering to the control board 50.

[0036] As described above, the control board 50 is disposed so that at least a portion thereof overlaps with the motor 20 when viewed in the motor axial direction. The Hall element 52 is mounted at a position where the control board 50 overlaps with the rotor 22 in the motor axial direction. For example, ⅓ or more of the board area of ​​the control board 50 overlaps with the motor 20 in the motor axial direction. The control board 50 is disposed in the center of the case 40 in the left-right direction, and is screwed to the first divided body 41. The control board 50 is disposed so as to straddle the motor 20 and the crankshaft unit 30 when viewed from the right side of the motor unit 10 with the second divided body 42 removed (FIG. 3).

[0037] The control board 50 has, as electronic components mounted on the board 51, a switching element 58 (see FIG. 4 described later) for driving the motor 20, a filter element 54, an electrolytic capacitor 56, etc., in addition to the Hall elements 52, 62 and the microcomputer 53. The board 51 is a substantially rectangular board, and is arranged such that its longitudinal direction is along the up-down direction. A curved recess is formed in the edge of the board 51 close to the motor shaft 21 so as to surround the motor shaft 21. As will be described in detail later, the microcomputer 53 is mounted on the upper end side of the board 51, and the switching element 58 is mounted on the lower end side of the board 51 away from the microcomputer 53.

[0038] The control board 50 is disposed, for example, such that the shortest distance from the gap 27 formed between the rotor 22 and the stator 23 to the control board 50 is 5 mm to 20 mm, or 10 mm to 20 mm. In other words, the distance along the motor axial direction from the gap 27 to the control board 50 is set to 5 mm to 20 mm, or 10 mm to 20 mm. In this case, the motor unit 10 can be made smaller while reducing the effect of leakage magnetic flux on the control board 50.

[0039] The configuration of control board 50 will be described in detail below with further reference to Figures 4 and 5. Figure 4 is a diagram showing first surface 51a of control board 50, and Figure 5 is a diagram showing second surface 51b of control board 50. Of the surfaces of control board 50 (substrate 51), the surface facing rotor 22 is referred to as "first surface 51a," and the surface opposite first surface 51a is referred to as "second surface 51b."

[0040] As shown in Figs. 3 to 5, the control board 50 is configured by mounting electronic components such as a Hall element 52 and a microcomputer 53 on a board 51. The board 51 is, for example, a printed wiring board in which wiring for electrically connecting the electronic components to each other is formed on the surface of an insulating resin board. The board 51 may have a multi-layer structure, and some of the wiring may be formed in an inner layer of the board 51. The board 51 has, as one of the wirings, a signal line 70 that connects the Hall element 52 and the microcomputer 53.

[0041] Hall elements 52 and 62, a filter element 55, a switching element 58, an inertial sensor 59, and the like are mounted on the first surface 51a of the substrate 51. An example of the switching element 58 is a field effect transistor (FET). The switching element 58 is driven based on a control signal output from the microcomputer 53, thereby controlling the output of the motor 20. An example of the inertial sensor 59 is an acceleration sensor, a six-axis acceleration sensor, an inclination sensor, and a gyro sensor. At least one of these sensors is provided on the control substrate 50 as the inertial sensor 59. Detection information of the inertial sensor 59 is transmitted to the microcomputer 53 and used for controlling the output of the motor 20.

[0042] A microcomputer 53, a filter element 54, an electrolytic capacitor 56, a power connector 57, and the like are mounted on the second surface 51b of the substrate 51. The electrolytic capacitor 56 has a function of smoothing the input voltage. In order to fully utilize the smoothing effect of the electrolytic capacitor 56, it is preferable to arrange the electrolytic capacitor 56 close to a power supply system such as a switching element 58, and to shorten the wiring connecting the electrolytic capacitor 56 and the switching element 58. A cable leading to the battery 11 is connected to the power connector 57.

[0043] Since the Hall element 52 is a sensor that detects the magnetic field of the rotor 24 that rotates together with the motor shaft 21, it is preferably mounted on the first surface 51a closer to the rotor 24. Similarly, the Hall element 62 is preferably mounted on the first surface 51a closer to the rotor 39. Meanwhile, the microcomputer 53 is preferably mounted on the second surface 51b. By disposing the microcomputer 53 on the second surface 51b farther from the rotor 22, stator 23, and rotor 24, which are sources of magnetic field noise, it is possible to suppress the generation of magnetic field noise in the microcomputer 53. Similarly, the signal line 70 that connects the Hall element 52 and the microcomputer 53 is preferably formed on the second surface 51b.

[0044] Since the Hall element 52 is disposed on the first surface 51a of the substrate 51, and the microcomputer 53 and the signal line 70 are disposed on the second surface 51b, a conductive path is formed in the control substrate 50, penetrating the substrate 51 in the thickness direction and connecting the Hall element 52 and the signal line 70. The signal line 70 may be formed on both surfaces of the substrate 51, in which case a conductive path may be formed that penetrates the substrate 51 in the thickness direction and connects the signal lines 70 on each surface.

[0045] As described above, the microcomputer 53 is a control element that controls the motor 20 using detection information from the torque sensor 35, the Hall element 52, the inertial sensor 59, etc. The microcomputer 53 includes, for example, a processor, a memory, and an input / output interface. The processor is composed of, for example, a CPU, and reads and executes a control program for the power-assisted bicycle 1 to control the output of the motor 20 and achieve an appropriate assist function. The memory includes non-volatile memory such as a ROM, HDD, SSD, etc. that stores the control program, etc., and volatile memory such as a RAM.

[0046] The microcomputer 53 is preferably mounted on the second surface 51b of the substrate 51 radially outward of the inner peripheral edge (gap 27) of the stator 23, and more preferably mounted at a position not overlapping with the motor 20 in the motor axial direction. Similarly, the inertial sensor 59 is preferably mounted on the first surface 51a of the substrate 51 at a position not overlapping with the motor 20 in the motor axial direction. In this case, generation of magnetic field noise caused by the motor 20 in the control signal system such as the microcomputer 53 and the inertial sensor 59 can be suppressed, and for example, inexpensive microcomputers, sensors, etc. with low magnetic field noise resistance can be used.

[0047] Furthermore, the microcomputer 53 and the inertial sensor 59 are mounted on one longitudinal end (upper end) of the substrate 51, and the switching element 58 is mounted on the other longitudinal end (lower end) of the substrate 51. That is, the control signal system, such as the microcomputer 53 and the inertial sensor 59, and the power supply system, such as the switching element 58, are disposed as far apart as possible on the substrate 51. In this case, the generation of magnetic field noise in the control signal system due to the power supply system can be suppressed.

[0048] The control board 50 has cables 60 (see FIG. 3) for supplying power to the coils of the stator 23. In this embodiment, three cables 60 are provided corresponding to the three-phase coils of the U-phase, V-phase, and W-phase.

[0049] As described above, the control board 50 is screwed to the first divided body 41 of the case 40. A conductive layer is formed around the periphery of the screw hole 61 formed in the board 51, and a ground is formed by the conductive layer and the conductive screw. A ground line including a capacitor is connected to the conductive layer around the periphery of the screw hole 61. It is preferable to arrange the ground close to the power supply line, and in this embodiment, the ground is provided at the front of the lower end of the control board 50.

[0050] The Hall element 52, the filter elements 54 and 55, and the signal line 70 will be described in detail below with further reference to Fig. 6 and Fig. 7. Fig. 6 and Fig. 7 are diagrams for explaining the configuration of the signal line 70 in relation to the motor 20. Fig. 6 illustrates the gap 27 of the motor 20. Fig. 7(b) illustrates the signal line 70 crossing over the gap 27 in Fig. 7(a).

[0051] As shown in FIGS. 4 to 7, the control board 50 has a plurality of Hall elements 52A, 52B, and 52C, and a plurality of signal lines 70 connecting each Hall element to the microcomputer 53. The control board 50 has signal lines 70A, 70B, and 70C formed thereon corresponding to the Hall elements 52A, 52B, and 52C. In addition, as described above, the control board 50 has the filter elements 54 and 55 mounted thereon. The filter elements 54 and 55 are connected to the signal line 70 and process the detection signal of the Hall element 52. The filter elements 54 and 55 are connected to the signal lines 70A, 70B, and 70C, one each.

[0052] The Hall element 52 is an element that detects a magnetic field by utilizing the Hall effect, and is mounted on the first surface 51a of the substrate 51 at a position overlapping with the rotor 24 in the motor axial direction so as to be able to detect the magnetic field of the rotor 24. When the motor 20 is a three-phase brushless DC motor, the Hall element 52 detects the magnetic field of the rotor 24 that rotates together with the rotor 22, thereby being able to detect the magnetic pole position of the rotor 22. The microcomputer 53 performs feedback control of the switching element 58 based on the magnetic pole position of the rotor 22, for example, to execute output control of the motor 20.

[0053] The same type of element can be used for the Hall elements 52A, 52B, and 52C. The Hall elements 52A, 52B, and 52C are arranged along the motor circumferential direction, and are preferably arranged on an arc centered on the axis 21x of the motor shaft 21. In this case, the magnetic field of the rotor 24 can be detected with high accuracy. The Hall elements 52A, 52B, and 52C are arranged, for example, at equal intervals on an arc centered on the axis 21x of the motor shaft 21. Note that a plurality of Hall elements 62 for measuring the rotation speed of the crankshaft 12 are also arranged on an arc centered on the rotating shaft 38. In this embodiment, two Hall elements 62A and 62B are arranged.

[0054] An example of the filter elements 54, 55 is an RC low-pass filter composed of a resistor and a capacitor, which performs signal processing to cut high-frequency components of the detection signal of the Hall element 52. The filter element 54 is disposed on the second surface 51b of the substrate 51, radially outward of the motor 20 from the gap 27 of the motor 20. The filter element 55 is disposed on the first surface 51a of the substrate 51, radially outward of the motor 20 from the filter element 54. That is, the filter elements 54, 55 may be mounted at a position overlapping the stator 23 in the motor axial direction, but are preferably mounted at a position not overlapping the rotor 22 and the gap 27 in the motor axial direction. In this case, the effect of leakage magnetic flux of the motor 20 on the filter elements 54, 55 can be reduced.

[0055] The signal wire 70 includes an arc-shaped wiring portion 71 that is bent so as to be convex radially outward of a circle centered on the axis of the motor shaft 21. The signal wires 70 are formed in the same number as the Hall elements 52, and each of the signal wires 70A, 70B, and 70C has an arc-shaped wiring portion 71. A ground wiring 72 for the Hall elements 52 is formed on the control board 50, and a wiring loop is formed by the signal wires 70 and the ground wiring 72. It is assumed that leakage magnetic flux of the motor 20 passes through the wiring loop, which generates an electromotive voltage between the signal wires and causes noise to be carried on the detection signal of the Hall elements 52 propagating through the signal wire 70, but the provision of the arc-shaped wiring portion 71 can significantly reduce the effect of the leakage magnetic flux.

[0056] As described above, the direction of the magnetic flux between the teeth 25 of the rotor 22 and the stator 23 is opposite between adjacent teeth 25 in the circumferential direction of the motor, for example. Therefore, by providing the arc-shaped wiring portion 71 so that a plurality of magnetic fluxes pass through the wiring loop, an offset effect of adjacent magnetic fluxes is obtained, and magnetic field noise generated in the signal line 70 is suppressed. In other words, the arc-shaped wiring portion 71 has the function of canceling out magnetic field noise that affects the detection signal of the Hall element 52.

[0057] The arc-shaped wiring portions 71 of the signal lines are arranged side by side in the radial direction of the motor 20. The interval between adjacent arc-shaped wiring portions 71 in the motor radial direction is preferably small to the extent that they do not come into electrical contact. Specifically, it is preferably 0.30 mm or less, and more preferably 0.25 mm or less. As a result of the inventors' studies, it was found that the generation of magnetic field noise can be more effectively suppressed by setting the interval between the arc-shaped wiring portions 71 to 0.30 mm or less. In addition, the edge of the substrate 51 close to the motor shaft 21 is curved so as to follow the motor circumferential direction, and each arc-shaped wiring portion 71 is formed so as to follow the curved edge of the substrate 51.

[0058] The arc-shaped wiring portion 71 is formed in a region that overlaps with the rotor 22 and the rotating body 24 in the motor axial direction. In this embodiment, the diameter of the rotating body 24 is smaller than the diameter of the rotor 22, and the rotating body 24 is disposed closer to the control board 50 than the rotor 22. The arc-shaped wiring portion 71 may be formed only in a region that overlaps with the rotating body 24 in the motor axial direction. The signal line 70 may be formed linearly in a region that overlaps with the rotor 22 but does not overlap with the rotating body 24.

[0059] The signal line 70 is formed on the second surface 51b of the substrate 51 facing away from the rotor 22, at least in a region that overlaps with the gap 27 of the motor 20 in the motor axial direction. If the substrate 51 has a multi-layer structure, the signal line 70 may be formed in an inner layer of the substrate 51. That is, the signal line 70 is preferably formed on a surface other than the first surface 51a close to the rotor 22, at least in a region that overlaps with the signal line 70 in the motor axial direction. Since leakage magnetic flux of the motor 20 is particularly likely to occur from the gap 27, by arranging the signal line 70 on the second surface 51b, the effect of suppressing magnetic field noise is enhanced.

[0060] The signal line 70 is further connected to the microcomputer 53 on the second surface 51b of the substrate 51. The arc-shaped wiring portion 71 of the signal line 70 is also formed on the second surface 51b. When the substrate 51 has a multi-layer structure, the arc-shaped wiring portion 71 may be formed in an inner layer of the substrate 51. In this embodiment, the entire signal line 70 including the arc-shaped wiring portion 71 is formed on the second surface 51b. By arranging the signal line 70 on the second surface 51b farther from the rotor 22, the stator 23, the rotating body 24, and the gap 27, which are sources of magnetic field noise, the generation of magnetic field noise in the signal line 70 can be more effectively suppressed.

[0061] As shown in Fig. 6 and Fig. 7, the arc-shaped wiring portions 71 of the signal lines 70A, 70B, and 70C extend along the circumferential direction of the motor. Each arc-shaped wiring portion 71 is arranged in an arc shape centered on the axis 21x of the motor shaft 21. In this case, magnetic field noise generated in the signal line 70 is more effectively suppressed. The Hall elements 52A, 52B, and 52C are located in the order of increasing distance from the microcomputer 53, with the arc-shaped wiring portion 71 of the signal line 70A being the longest and the arc-shaped wiring portion 71 of the signal line 70C being the shortest. In the portion where the arc-shaped wiring portions 71 are lined up in the radial direction of the motor, the arc-shaped wiring portions 71 are arranged in parallel to each other at the above-mentioned interval (for example, 0.3 mm or less).

[0062] At least one of the arc-shaped wiring portions 71 preferably has a length that faces three teeth 25 adjacent to each other in the motor circumferential direction when the control board 50 is viewed in the motor axial direction. That is, at least one arc-shaped wiring portion 71 is formed so as to pass through a position facing three adjacent teeth 25 when the control board 50 is viewed in the motor axial direction. In other words, one arc-shaped wiring portion 71 extending in the motor circumferential direction is present on the inner side of the three adjacent teeth 25 in the motor radial direction. In the example shown in FIG. 7(a), the arc-shaped wiring portion 71 of the signal line 70A is formed so as to pass through a position facing three adjacent teeth 25. Note that all of the arc-shaped wiring portions 71 may have a length that faces three adjacent teeth 25.

[0063] As long as the signal line 70 has the arc-shaped wiring portion 71, the signal line 70 can obtain the effect of suppressing magnetic field noise by canceling out adjacent magnetic fluxes even if the signal line 70 is short in length, but the noise suppression effect becomes more pronounced when the arc-shaped wiring portion 71 has a length that faces three adjacent teeth 25. In this embodiment, since a three-phase motor is applied to the motor 20, strictly speaking, the directions of the magnetic flux vectors are opposite in three teeth 25 that are adjacent in the circumferential direction of the motor. Therefore, the cancellation of adjacent magnetic fluxes appears more effectively, and the noise suppression effect becomes more pronounced.

[0064] It is preferable that the signal line 70 crosses the gap 27 of the motor 20 in a short length in the area where it overlaps with the gap 27 in the motor axial direction. Specifically, as shown in FIG. 7(b), when the control board 50 is viewed in the motor axial direction, it is preferable that the signal line 70 crosses the gap 27 so that an imaginary line connecting a point X where the signal line 70 overlaps with the inner periphery of the stator 23 and a point Y where the signal line 70 overlaps with the outer periphery of the rotor 22 forms an angle of 45° or less with an imaginary line Z passing through the point Y and the axis 21x of the motor shaft 21. The angle θ shown in FIG. 7(b) is more preferably 30° or less or 20° or less, and may be substantially 0°. By shortening the length of the signal line 70 crossing the gap 27 where leakage flux is likely to occur as much as possible, the influence of leakage flux can be reduced more effectively. When the angle θ is 45° or less, the noise suppression effect is particularly remarkable.

[0065] In the example shown in Fig. 7(b), the portion of the signal wire 70 that crosses the gap 27 is formed straight and not bent. That is, when the control board 50 is viewed in the motor shaft direction, the signal wire 70 crosses the gap 27 at an angle θ with respect to the imaginary line Z. Note that the signal wire 70 may be slightly bent on the gap 27 as long as the angle of the imaginary line passing through points X and Y with respect to the imaginary line Z is 45° or less. Furthermore, in each of the signal wires 70A, 70B, and 70C, the portions that cross the gap 27 are arranged parallel to each other with an interval of, for example, 0.3 mm or less.

[0066] The signal line 70 is preferably arranged so as to overlap with the slot 26, which is a gap between adjacent teeth 25, in the motor axial direction. The signal line 70 passes through an area overlapping with the stator 23 in the motor axial direction and is connected to the microcomputer 53 mounted on the outside of the motor 20, but is formed so as to pass through an area overlapping with the slot 26 as much as possible in the area overlapping with the stator 23 in the motor axial direction. In this case, the effect of leakage magnetic flux can be more effectively reduced. It is preferable that the length of the signal line 70 that is formed in the area overlapping with the stator 23 in the motor axial direction is longer than the length of the signal line that crosses the slot 26.

[0067] As described above, the motor unit 10 having the above configuration can reduce the effects of leakage magnetic flux from the motor 20 and suppress noise generated in the signal line 70 of the control board 50. Furthermore, the configuration of the control board 50 can effectively suppress magnetic field noise in other control signal systems such as the microcomputer 53, filter elements 54 and 55, and inertial sensor 59. Therefore, the electrically assisted bicycle 1 having the motor unit 10 has, for example, excellent controllability of the motor 20 and a good assist function.

[0068] The above-described embodiment may be modified as appropriate without departing from the scope of the present disclosure. For example, the above-described embodiment illustrates a configuration in which the Hall element 52 detects the magnetic field of the rotor 24 that rotates together with the motor shaft 21. However, the Hall element 52 may be configured to detect the magnetic field of the motor shaft 21 or the rotor 22. In this case, the motor 20 may not have the rotor 24.

[0069] Furthermore, as a sensor for detecting the magnetic field of the motor shaft, the rotor, or a rotating body rotating together with the motor shaft, for example, a magnetoresistance effect element (MR sensor) may be used instead of the Hall element 52. At least one MR sensor is mounted, for example, on the first surface facing the rotor side of the control board, at a position overlapping the rotor in the motor axial direction. [Explanation of symbols]

[0070] 1 Electrically assisted bicycle, 2 Frame, 2a Head pipe, 2b Front fork, 2c Down pipe, 2d Seat pipe, 2e Chain stay, 2f Seat stay, 3a Front wheel, 3b Rear wheel, 4 Handle, 5 Saddle, 6 Crank arm, 7 Pedal, 8 Chain, 9 Headlight, 10 Motor unit, 11 Battery, 12 Crankshaft, 13, 14 Sprocket, 15 Reduction mechanism, 16 Output shaft, 17, 34 One-way clutch, 18a, 18b, 19a, 19b, 36a, 36b Bearing, 20 Motor, 21 Motor shaft, 21x Shaft core, 22 Rotor, 23 Stator, 24, 37a, 37b, 39 Rotating body, 25 Teeth, 26 Slot, 27 Gap, 30 Crankshaft unit, 31, 32 Input body, 33 Output body, 35 Torque sensor, 38 rotating shaft, 40 case, 41 first division, 42 second division, 43 retainer, 50 control board, 51 board, 51a first surface, 51b second surface, 52, 52A, 52B, 52C, 62, 62A, 62B Hall element, 53 microcomputer, 54, 55 filter element, 56 electrolytic capacitor, 57 power connector, 58 switching element, 59 inertia sensor, 60 wiring, 61 screw hole, 70, 70A, 70B, 70C signal line, 71 arc-shaped wiring portion, 72 ground wiring

Claims

1. a motor having a motor shaft, a rotor fixed to the motor shaft, and a stator; a control board on which a plurality of sensors for detecting a magnetic field of the motor shaft, the rotor, or a rotating body rotating together with the motor shaft, and a control element for controlling the motor using information detected by the sensors are mounted, the control board being disposed so as to overlap at least a portion of the motor when viewed in the motor axial direction; Equipped with the control board includes a signal line connecting the sensor and the control element, and a ground line connected to the plurality of sensors; a wiring loop is formed by the signal line and the ground wiring, a recess is formed in an edge of the control board adjacent to the motor shaft, the recess being curved so as to surround only a portion of the motor shaft; all of the signal lines include arc-shaped wiring portions that are bent so as to protrude radially outward from a circle centered on the axis of the motor shaft, all the arc-shaped wiring portions are arranged side by side in a radial direction of the motor and arranged in an arc shape centered on the axis of the motor shaft; A motor unit for electric vehicles.

2. The sensor is disposed so as to overlap the rotor when viewed in the motor axial direction, the control element is disposed radially outward of an inner circumferential edge of the stator surrounding the rotor, 2. The motor unit of claim 1, wherein, when the control board is viewed in the motor axial direction, the signal line crosses a gap formed between the rotor and the stator so that an imaginary line connecting a first point where the signal line overlaps with an outer circumferential edge of the rotor and a second point where the signal line overlaps with an inner circumferential edge of the stator forms an angle of 45° or less with an imaginary line passing through the first point and an axis of the motor shaft.

3. The motor unit according to claim 1 or 2, wherein the arc-shaped wiring portion extends along a circumferential direction of the motor.

4. 4. The motor unit according to claim 1, wherein the arc-shaped wiring portion is disposed in an arc shape centered on an axis of the motor shaft.

5. The stator includes a plurality of teeth arranged in a circumferential direction of the motor, The motor unit according to any one of claims 1 to 4, wherein the signal line is arranged so as to overlap with a gap between adjacent ones of the teeth in the motor axial direction.

6. the motor is a three-phase motor; The motor unit according to claim 5 , wherein the arc-shaped wiring portion has a length sufficient to face three of the teeth adjacent to each other in a circumferential direction of the motor when the control board is viewed in the motor axial direction.

7. 7. The motor unit according to claim 1, wherein the sensor is constituted by at least one magnetoresistance effect element.

8. The motor unit according to any one of claims 1 to 7, wherein the sensor is constituted by a plurality of Hall elements.

9. The plurality of Hall elements are arranged on an arc centered on the axis of the motor shaft. The motor unit according to claim 8.

10. the signal lines are formed in the same number as the plurality of Hall elements, each of the signal lines includes the arc-shaped wiring portion, The motor unit according to claim 8 or 9, wherein the plurality of arc-shaped wiring portions are arranged side by side in a radial direction of the motor.

11. The motor unit according to claim 10 , wherein the interval between the arc-shaped wiring portions adjacent to each other in the motor radial direction is 0.3 mm or less.

12. A filter element is mounted on the control board, The motor unit according to any one of claims 1 to 11, wherein the filter element is arranged radially outward of the motor relative to a gap formed between the rotor and the stator.

13. A motor unit as described in any one of claims 1 to 12, wherein the signal line is arranged on a second surface opposite to a first surface facing the rotor of the control board, or on an inner layer of the control board, at least in an area overlapping with a gap formed between the rotor and the stator in the motor axial direction.

14. A motor unit as described in any one of claims 1 to 13, wherein the arc-shaped wiring portion is arranged on a second surface opposite to a first surface facing the rotor side of the control board, or on an inner layer of the control board.

15. The signal line is connected to the control element on the second surface of the control board. A motor unit according to claim 13 or 14.

16. The motor unit according to any one of claims 1 to 15, wherein a shortest distance from a gap formed between the rotor and the stator to the control board is 5 mm or more and 20 mm or less.

17. The motor unit according to any one of claims 1 to 16, wherein the control board is arranged so that ⅓ or more of the board area overlaps with the motor in the motor axial direction.

18. The motor unit according to any one of claims 1 to 17, wherein the control element is mounted on the control board at a position not overlapping with the motor in the motor axial direction.

19. A switching element for driving the motor is mounted on the control board, The motor unit according to any one of claims 1 to 18, wherein the control element is arranged on one end side of the control board, and the switching element is arranged on the other end side of the control board.

20. An inertial sensor is mounted on the control board, The motor unit according to claim 19 , wherein the inertial sensor is mounted on one end side of the control board at a position not overlapping with the motor in the motor axial direction.

21. The motor unit according to any one of claims 1 to 20, wherein a maximum value of a drive current of the motor is 15 A or more.

22. The motor unit according to any one of claims 1 to 21, wherein a maximum value of output torque of the motor is 75 N·m or more.

23. An electrically assisted bicycle comprising the motor unit according to any one of claims 1 to 22.

24. A motor unit described in any one of claims 1 to 22, wherein the length of the arc-shaped wiring portion is longer for the signal line arranged on the inner side in the motor radial direction than for the signal line arranged on the outer side in the motor radial direction.

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