Motor unit and electric bicycle

Abstract

To further increase a heat radiation amount from a switching element included in a motor unit to improve reliability of the motor unit.SOLUTION: A motor unit 2 for an electric bicycle includes a motor 4, a switching element 62 for driving the motor 4, a substrate 61 having a surface including a mounting surface 613 for mounting the switching element 62 and an opposite surface facing opposite to the surface including the mounting surface, and a case 3 accommodating the substrate 61. The substrate 61 further has a through hole 614 passing through between the mounting surface 613 and the opposite surface and metal foil 64 covering at least a part of an inner peripheral surface of the through hole 614. The switching element 62 is thermally connected to the metal foil 64. A portion of the case 3 opposite to the switching element 62 while interposing the substrate 61 therebetween is thermally connected to the metal foil 64 .SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a motor unit and an electric bicycle. [Background technology]

[0002] Electric bicycles equipped with a motor unit are known. The motor unit includes a motor, a circuit board on which various electronic components for controlling the motor are mounted, and a case that houses the motor and the circuit board.

[0003] In this type of electric bicycle, it has been proposed to thermally connect electronic components such as switching elements, which generate particularly large amounts of heat, to the case (see, for example, Patent Document 1, etc.), which increases the amount of heat dissipated by the electronic components. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-176354 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure aims to further increase the amount of heat dissipated from the switching elements included in the motor unit, thereby improving the reliability of the motor unit. [Means for solving the problem]

[0006] A motor unit according to one aspect of the present disclosure is a motor unit for use in an electric bicycle, comprising: a motor; a switching element for driving the motor; a substrate having a surface including a mounting surface for mounting the switching element and an opposite surface facing away from the mounting surface; and a case for accommodating the substrate. The substrate further has a through hole extending between the mounting surface and the opposite surface, and a metal foil covering at least a portion of an inner circumferential surface of the through hole. The switching element is thermally connected to the metal foil, and a portion of the case opposite the switching element across the substrate is thermally connected to the metal foil.

[0007] An electric bicycle according to one aspect of the present disclosure includes the motor unit, a wheel to which the rotational force of the motor is transmitted, and a frame that supports the motor unit and the wheel. [Effects of the Invention]

[0008] The present disclosure has the effect of further increasing the amount of heat dissipated from the switching elements included in the motor unit, thereby improving the reliability of the motor unit. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of an electric bicycle according to one embodiment. [Figure 2] FIG. 2 is a side view of the main part of the electric bicycle. [Figure 3] FIG. 3 is a schematic cross-sectional view of a motor unit provided in the electric bicycle. [Figure 4] FIG. 4 is a cross-sectional view showing the P portion of FIG. 3 in detail. [Figure 5] FIG. 5 is a side view of a substrate provided in the motor unit. [Figure 6] FIG. 6 is another side view of the substrate. [Figure 7] FIG. 7 is a side view of the same with a part of the motor unit removed. [Figure 8]FIG. 8 is a side view of a second divided body of the case provided in the motor unit. [Figure 9] FIG. 9 is a cross-sectional view of a main part of a first modified example of the motor unit of the same. [Figure 10] FIG. 10 is a cross-sectional view of a main part of a second modified example of the motor unit. [Figure 11] FIG. 11 is a side view of a main part of a third modified example of the motor unit. [Figure 12] FIG. 12 is a schematic cross-sectional view of a fourth modified example of the motor unit of the same. [Figure 13] FIG. 13 is a cross-sectional view showing the Q portion of FIG. 12 in detail. DETAILED DESCRIPTION OF THE INVENTION

[0010] (1) One embodiment An electric bicycle 1 in one embodiment is an electrically assisted bicycle. As shown in Figure 1, the electric bicycle 1 includes a frame 10, a motor unit 2 supported and fixed to the frame 10, and two wheels 11 rotatably supported on the frame 10. The two wheels 11 are a front wheel 111 and a rear wheel 112. Of these, the rear wheel 112 is rotated by the driving force output from the motor unit 2 (i.e., by the transmission of the rotational force of the motor 4 included in the motor unit 2).

[0011] The directions of front / rear, left / right, and up / down used in this document are defined relative to the rider of the electric bicycle 1. The direction in which the rider rides the electric bicycle 1 is forward, the opposite side is rearward, the direction to the left from the rider's perspective is leftward, and the direction to the right from the rider's perspective is rightward. Each configuration will be explained in detail below.

[0012] (1.1) Frame The frame 10 has a head pipe 101, a down tube 103, a seat tube 104, seat stays 105, chain stays 106, and a bracket 108.

[0013] The frame 10 (i.e., the above-mentioned components constituting the frame 10) is made of a metal such as aluminum or stainless steel, but may contain a non-metallic material in part. The entire frame 10 may be made of a non-metallic material, and the material of the frame 10 is not particularly limited.

[0014] A handle post 12 is rotatably inserted through the head pipe 101. A front fork 121 is formed at the lower end of the handle post 12. A front wheel 111 is rotatably attached to the front fork 121. A handle bar 122 is fixed to the upper end of the handle post 12.

[0015] A pipe 132 extending downward from the saddle 13 is inserted into the opening at the upper end of the seat tube 104. The saddle 13 is fixed in place by fixing this pipe 132 to the seat tube 104. The lower end of the seat tube 104 is fixed to a bracket 108.

[0016] The front end of a down tube 103 is fixed to the head pipe 101. The rear end of the down tube 103 is fixed to a bracket .

[0017] The motor unit 2 is fixed to the bracket 108. The front end of the chain stay 106 is fixed to the rear of the bracket 108.

[0018] The front ends of seat stays 105 are fixed to the upper end of the seat tube 104. The rear ends of the seat stays 105 are connected to the rear ends of the chain stays 106, and a rear wheel 112 is rotatably attached to this connected part. A battery 15 for supplying power to the motor unit 2 is detachably attached to the seat tube 104.

[0019] (1.2) Motor unit As shown in Figures 2, 3, etc., most of the outer shell of the motor unit 2 is made up of a case 3. A motor 4, which is a drive source for driving and rotating wheels 11, is attached to the case 3. The case 3 houses a reduction mechanism 5 connected to the motor 4 so as to be able to transmit power, a control board 6 that controls the rotation of the motor 4, as well as various components such as an input shaft 71, an input body 72, and output bodies 81 and 82.

[0020] The case 3 includes a first divided body 31 that constitutes a first half of the case 3, and a second divided body 32 that constitutes a second half of the case 3. The first side is the right side in one embodiment of the electric bicycle 1. The second side is the side opposite the first side, which is the left side in one embodiment of the electric bicycle 1. The hollow case 3 is formed by combining the first divided body 31 on the right side and the second divided body 32 on the left side.

[0021] The first divided body 31 has a space that is open on the left side. This space constitutes the right half of the storage space of the case 3. The second divided body 32 has a space that is open on the right side. This space constitutes the left half of the storage space of the case 3. A recess 322 for disposing the motor 4 is formed in the second divided body 32. The first divided body 31 and the second divided body 32 are fixed to each other so that their respective spaces are connected to each other.

[0022] The motor 4 has a cylindrical rotating shaft 41, a rotor 42 coupled to the rotating shaft 41 so as to rotate integrally with the rotating shaft 41, and a cylindrical stator 43 positioned to surround the rotor 42.

[0023] A bearing 45 is disposed on the inner bottom surface of the recess 322. The bearing 45 rotatably supports one axial end of the rotating shaft 41. The other axial end of the rotating shaft 41 is rotatably supported by a bearing 46 disposed on the inner surface of the first divided body 31. Teeth 415 for meshing with the reduction gear mechanism 5 are formed on the outer peripheral surface of the portion of the rotating shaft 41 that protrudes from the rotor 42.

[0024] An input shaft 71 is housed in the case 3 so as to be rotatable about its axis 710. The first divided body 31 and the second divided body 32 are formed with through holes 311, 321 through which the input shaft 71 is inserted.

[0025] Crank arms 18 are fixed to both ends of the input shaft 71 (see FIG. 2, etc.). Pedals 181 are rotatably attached to the tips of the crank arms 18. The rider can apply manual rotational force to the input shaft 71 by pedaling the pedals 181.

[0026] In the case 3, the input body 72 is disposed along the outer circumferential surface of the input shaft 71. The input body 72 is a cylindrical member, and rotates together with the input shaft 71.

[0027] The input body 72 is divided into a first input body 721 and a second input body 722. The first input body 721 is connected to the input shaft 71. The second input body 722 is connected to the first input body 721, and is configured to transmit a rotational force to the output body 81.

[0028] The output body 81 is a cylindrical member, and is rotatably disposed along the outer circumferential surface of the input shaft 71. One end of the output body 81 passes through the through-hole 311 of the first divided body 31 and protrudes outside the case 3. A front sprocket 191 is fixed to the portion of the output body 81 that protrudes from the case 3 (see FIG. 2). The sprocket 191 rotates integrally with the output body 81.

[0029] In one embodiment of the electric bicycle 1, the motor unit 2 includes an output body 82 separate from the output body 81. The output body 82 is a member that is rotationally driven by the rotational force of the motor 4. In the following, for the sake of distinction, the output body 81 that is rotationally driven by human power will be referred to as the first output body 81, and the output body 82 that is rotationally driven by the rotational force of the motor 4 will be referred to as the second output body 82.

[0030] A first end of the second output body 82 is located inside the case 3. The second output body 82 is rotatably supported by a bearing 85 arranged in the second divided body 32 and a bearing 86 arranged in the retainer 75.

[0031] The retainer 75 is a metal member housed within the case 3. The retainer 75 is preferably made of aluminum or an aluminum alloy, but may also be made of a magnesium alloy, an iron-based metal, or a resin. The retainer 75 is disposed so that at least a portion of the retainer 75 overlaps with the motor 4 when viewed along the axis 410 of the rotating shaft 41 of the motor 4.

[0032] A second end of the second output body 82 protrudes outside the case 3. Another sprocket 192 is fixed to the front of the second end of the second output body 82. The sprocket 192 rotates integrally with the second output body 82. For the sake of distinction, hereinafter, the sprocket 191 will be referred to as the first sprocket 191, and the sprocket 192 will be referred to as the second sprocket 192.

[0033] A reduction mechanism 5 is disposed between the second output body 82 and the rotating shaft 41 of the motor 4, which reduces the rotation of the motor 4 and transmits it to the second output body 82. The reduction mechanism 5 is a so-called one-stage reduction mechanism, and more specifically, a transmission gear 51 is attached to the outer circumferential surface of the second output body 82 via a one-way clutch 58. The transmission gear 51 meshes with the teeth 415 of the rotating shaft 41 of the motor 4.

[0034] The chain 195 is wound around the first and second sprockets 191, 192 on the front side and the rear sprocket 193. The rotational force of the second output body 82 is finally transmitted to the rear wheel 112 via the second sprocket 192, the chain 195, and the rear sprocket 193.

[0035] In one embodiment of the electric bicycle 1, when the rider is pedaling 181 to move forward, the rotating shaft 41 of the motor 4 rotates, causing the transmission gear 51 to rotate in conjunction with this, and this rotational force is transmitted to the second output body 82 via the one-way clutch 58, and then to the chain 195.

[0036] (1.3) Control board The control board 6 housed in the case 3 of the motor unit 2 will now be described in more detail.

[0037] The control board 6 is configured by mounting various electronic components on a flat board 61. The various electronic components include a plurality of switching elements 62, an electrolytic capacitor 68, a microcontroller 69, etc. (See FIGS. 5 and 6, etc.). The plurality of switching elements 62 are controlled by the microcontroller 69.

[0038] The substrate 61 has a first surface 611 facing to the right (i.e., the first side) and a second surface 612 facing to the left (i.e., the second side). The first surface 611 and the second surface 612 are a pair of surfaces facing opposite each other, in other words, a pair of surfaces positioned at the front and back of the substrate 61. The first surface 611 and the second surface 612 are a pair of flat surfaces parallel to each other.

[0039] As shown in FIG. 4, the substrate 61 includes an outermost resist layer 6191 that forms the first surface 611, a metal layer 6181 that is covered thereby, an outermost resist layer 6192 that forms the second surface 612, and a metal layer 6182 that is covered thereby.

[0040] The second surface 612 includes a mounting surface 613 for mounting the switching element 62. That is, in the motor unit 2 of the first embodiment, the second surface 612 is a surface that includes the mounting surface 613 for mounting the switching element 62, and the first surface 611 is an opposite surface that faces away from the surface that includes the mounting surface 613.

[0041] The mounting surface 613 is located in an end region of the second surface 612. The switching element 62 is fixed to the mounting surface 613 via thermally conductive solder 63 (see FIG. 4). When the switching element 62 is mounted on the substrate 61 (hereinafter simply referred to as the mounted state), the solder 63 is in contact with the entire surface of the switching element 62 and is thermally connected to the switching element 62.

[0042] Note that two members being thermally connected means that the two members are in a state in which heat can be transferred between them. Two members being thermally connected also includes cases in which another member is interposed between the two members (for example, cases in which a film-like insulating member is interposed between the two members, cases in which a resist layer is interposed between the two members, or cases in which a film-like insulating member and a resist layer are interposed between the two members).

[0043] The switching element 62 includes a field effect transistor 621 and a package 625 that covers the field effect transistor 621. The package 625 is made of a resin mold that seals the field effect transistor 621, but is not limited to this, and the package 625 can also be made of a metal case.

[0044] Furthermore, the substrate 61 has a plurality of through holes 614 that enhance the heat dissipation of the switching elements 62, and a metal foil 64 that covers the inner circumferential surface of each through hole 614.

[0045] The through hole 614 is provided to penetrate between the first surface 611 and the second surface 612 of the substrate 61, and more specifically, is provided to penetrate in the shortest distance between the mounting surface 613 in the edge region of the second surface 612 and the edge region of the first surface 611. The through hole 614 is a circular through hole, and has a circular opening formed in the mounting surface 613 and a circular opening formed in the first surface 611.

[0046] The diameter of through-hole 614 is preferably in the range of 0.2 mm to 0.4 mm, and more preferably in the range of 0.2 mm to 0.35 mm. That is, the opening of through-hole 614 on mounting surface 613 preferably has a diameter in the range of 0.2 mm to 0.4 mm, and more preferably in the range of 0.2 mm to 0.35 mm. Furthermore, the opening of through-hole 614 on first surface 611 preferably has a diameter in the range of 0.2 mm to 0.4 mm, and more preferably in the range of 0.2 mm to 0.35 mm.

[0047] The metal foil 64 is made of, for example, copper foil and has high thermal conductivity. The thickness of the metal foil 64 is preferably within a range of 10 μm to 30 μm. The metal foil 64 covers at least a portion of the inner circumferential surface of the through-hole 614. The metal foil 64 preferably covers the entire inner circumferential surface of the through-hole 614, but it may also cover only a portion of the inner circumferential surface of the through-hole 614. In the mounted state, the switching element 62 faces the opening on the mounting surface 613 of the through-hole 614. Also, in the mounted state, the switching element 62 is thermally connected to the metal foil 64 via solder 63. In the mounted state, the solder 63 preferably contacts the metal foil 64.

[0048] In the motor unit 2 included in the electric bicycle 1 of one embodiment, the first divided body 31 and the second divided body 32 of the case 3 each have integral portions 315, 325 for promoting heat dissipation from the switching element 62. Both portions 315, 325 are in contact with the outside air and are capable of dissipating heat. Hereinafter, both portions 315, 325 will be referred to as heat dissipation portions 315, 325, respectively.

[0049] The heat dissipation portion 315 of the first divided body 31 is configured as the bottom of a portion of the first divided body 31 that is recessed inward (that is, toward the left side).

[0050] A thermally conductive sheet 76 is housed within the case 3 so as to be interposed between the heat dissipation portion 315 and the substrate 61. The thermally conductive sheet 76 preferably contacts the heat dissipation portion 315 from its left side, and preferably contacts a portion of the first surface 611 of the substrate 61 that is behind the mounting surface 613 from its right side. The metal foil 64 of each through-hole 614 provided in the substrate 61 is thermally connected to the heat dissipation portion 315 via the thermally conductive sheet 76. The metal foil 64 preferably contacts the thermally conductive sheet 76. In the motor unit 2 of the first embodiment, the heat dissipation portion 315 is located on the opposite side of the substrate 61 from the switching element 62 and is thermally connected to the metal foil 64.

[0051] The heat dissipation portion 325 of the second divided body 32 is configured as the bottom of a portion of the second divided body 32 that is recessed inward (that is, toward the right).

[0052] A thermally conductive sheet 77 is housed within the case 3 so as to be interposed between the heat dissipation portion 325 and the switching element 62. The thermally conductive sheet 77 preferably contacts the heat dissipation portion 325 from its right side, and preferably contacts the package 625 of the switching element 62 from its left side. The switching element 62 is thermally connected to the heat dissipation portion 325 via the thermally conductive sheet 77. In the motor unit 2 of the first embodiment, the heat dissipation portion 325 is located on the same side of the case 3 as the switching element 62 with respect to the substrate 61, and is thermally connected to the switching element 62. The switching element 62 is sandwiched between the substrate 61 and the heat dissipation portion 325 via the thermally conductive sheet 77.

[0053] Therefore, in the motor unit 2 provided in the electric bicycle 1 of one embodiment, the switching element 62 is thermally connected from the left side (i.e., the second side) to the metal foil 64 provided in each through-hole 614 of the substrate 61, and the heat dissipation portion 315 that constitutes part of the case 3 is thermally connected from the right side (i.e., the first side). Therefore, the heat generated from the switching element 62 is efficiently conducted to the heat dissipation portion 315 via the thermally conductive metal foil 64 provided in multiple locations, and is dissipated to the outside air through the heat dissipation portion 315.

[0054] Additionally, in the motor unit 2 included in the electric bicycle 1 of one embodiment, a heat dissipation part 325 that constitutes another part of the case 3 is thermally connected to the left side (i.e., the second side) of the switching element 62. Therefore, the heat generated from the switching element 62 is also conducted to the heat dissipation part 325, and is dissipated to the outside air through the heat dissipation part 325.

[0055] In addition, in the motor unit 2 provided in the electric bicycle 1 of one embodiment, the switching element 62 and the microcontroller 69 are mounted on the substrate 61 so that they are positioned at a sufficient distance from each other. This prevents electrical noise generated on the switching element 62 side from affecting the microcontroller 69.

[0056] Specifically, the mounting surface 613 on which the switching element 62 is mounted is provided on a first half 615 that is the lower half of the substrate 61 (see FIG. 6). The switching element 62 is mounted on the first half 615 of the substrate 61. In contrast, the microcontroller 69 is mounted on a second half 616 that is the upper half of the substrate 61 (see FIG. 5). Here, up and down are defined based on the state in which the electric bicycle 1 equipped with the motor unit 2 is being driven. It is preferable that the distance between the microcontroller 69 and the switching element 62 in the up and down direction be equal to or greater than half the vertical dimension of the substrate 61.

[0057] Furthermore, in order to prevent electrical noise generated by the motor 4 from affecting the microcontroller 69, it is preferable that the entire microcontroller 69 or at least its central chip is positioned so as not to overlap with the motor 4 when viewed along the central axis of rotation of the motor 4 (i.e., the axis 410 of the rotation shaft 41).

[0058] In addition, in the motor unit 2 provided in the electric bicycle 1 of one embodiment, the switching element 62 is mounted in an end region of the substrate 61. This makes it easy to thermally connect the switching element 62 to a part of the case 3 (i.e., the heat dissipation portions 315, 325), and to easily ensure a heat dissipation path from the switching element 62 to the case 3.

[0059] 2 and other figures, in one embodiment of the electric bicycle 1, the portion of the case 3 that is thermally connected to the switching element 21 (i.e., the heat dissipation portions 315, 325) is located below the line connecting the central axis of rotation of the input shaft 71 and the central axis of rotation of the motor 4 (see the chain line L in FIG. 2) in a side view. Therefore, heat from the switching element 21 is efficiently dissipated through the heat dissipation portions 315, 325. The side view here is taken along the central axis of rotation of the motor 4, or in other words, along the central axis of rotation of the input shaft 71.

[0060] (1.4) Variations The following describes various modified examples of the electric bicycle 1 of one embodiment. Note that the same components as those already described in the first embodiment are given the same reference numerals and detailed descriptions thereof will be omitted.

[0061] 9 shows a cross section of a main part of a first modified example of the motor unit 2. The main part corresponds to the part shown in FIG. 4 in the embodiment. The first modified example of the motor unit 2 further includes an insulating member 65 provided on the first surface 611 of the substrate 61.

[0062] In the first modification, the thermally conductive sheet 76 and the metal layer 6181 are thermally connected to each other via the insulating member 65 and the resist layer 6191 located between them.

[0063] The insulating member 65 covers a portion of each through-hole 614 provided in the substrate 61, and has the function of preventing a portion of the solder 63 applied to the second surface 612 from leaking out to the first surface 611 through each through-hole 614. If a portion of the solder 63 leaks out to the first surface 611, it may cause a short circuit or the like.

[0064] The insulating member 65 can be formed, for example, by printing a colored insulating resin on the first surface 611 by a so-called screen printing method. The printing method is not limited to this, and other methods such as so-called inkjet printing, UV printing using a UV-curable insulating resin, and printing using a thermosetting insulating resin can also be used. When forming the insulating member 65 by printing, it is preferable to perform the printing on the resist layers 6191 and 6192 that form the outermost layers of the substrate 61. It is also possible to perform the insulating resin printing operation multiple times in the same location.

[0065] In the first modified example, the insulating member 65 has a plurality of holes 653 that communicate one-to-one with the plurality of through holes 614. The holes 653 are circular holes that penetrate the insulating member 65. The outer diameter of the holes 653 is smaller than the outer diameter of the corresponding through holes 614. The outer diameter of the holes 653 is smaller than the outer diameter of the openings that the corresponding through holes 614 have on the first surface 611. The opening area of ​​the holes 653 is smaller than the opening area of ​​the corresponding through holes 614, and when viewed along the direction in which the through holes 614 penetrate, the opening edge of the holes 653 is located inside the opening edge of the through holes 614.

[0066] It is not essential that the insulating member 65 has the holes 653, and the insulating member 65 may not have the holes 653. In this case, the plurality of through holes 614 formed in the substrate 61 are blocked by the insulating member 65. It is also possible that only some of the plurality of through holes 614 formed in the substrate 61 are blocked by the insulating member 65.

[0067] 10 shows a cross section of a main part of a second modified example of the motor unit 2. This main part corresponds to the part shown in FIG. 4 in the embodiment. In the second modified example of the motor unit 2, the case 3 does not have a heat dissipation portion 325, and the thermally conductive sheet 77 is not disposed inside the case 3. The switching element 62 does not have a direct heat dissipation path to the second divided body 32 of the case 3, but has a direct heat dissipation path to the first divided body 31 of the case 3 via the metal foil 64 in the multiple through holes 614, etc.

[0068] Additionally, in the second modified example of the motor unit 2, the switching element 62 has a plurality of field-effect transistors 621 and a package 625 that covers the plurality of field-effect transistors 621. This type of switching element 62 has superior heat dissipation properties compared to the type having a single field-effect transistor 621 as shown in FIG.

[0069] 11 shows a substrate 61 included in a third modified example of the motor unit 2. The substrate 61 includes a resist layer 6191 that forms the outermost layer on the first surface 611 side, and a metal layer 6181 that is covered by the resist layer 6191, and the metal layer 6181 is thermally connected to the metal foil 64 in the multiple through holes 614. The resist layer 6191 is patterned to expose a portion of the metal layer 6181, and a solder portion 67 for heat dissipation is fixed to this exposed portion.

[0070] The solder portions 67 are thermally connected to the metal foil 64 in the plurality of through-holes 614 via the metal layer 6181, and are therefore thermally connected to the switching element 62. In the third modification, the plurality of solder portions 67 are arranged in a matrix around the back side of the mounting surface 613 of the first surface 611 of the substrate 61, thereby further improving heat dissipation. The plurality of solder portions 67 are preferably thermally connected to the heat dissipation portion 315 of the case 3 via the thermally conductive sheet 76, but may also be in direct contact with the heat dissipation portion 315.

[0071] 12 shows a fourth modified example of the motor unit 2. In the fourth modified example, a metal retainer 75 that holds bearings 86 and the like has a heat-conducting portion 751 that is integral with the retainer 75 and is interposed between the second divided body 32 of the case 3 and the heat-conducting sheet 76. In other words, the heat-conducting portion 751, which is part of the retainer 75 housed in the case 3, is interposed between the second divided body 32 and the heat-conducting sheet 76, and thermally connects the second divided body 32 and the heat-conducting sheet 76.

[0072] In the fourth modification, the portion of the second divided body 32 surrounding the portion 323 to which heat is transferred from the retainer 75 constitutes a heat dissipation portion 325 that can come into contact with the outside air.

[0073] In the fourth modified example, the switching element 62 is mounted on the first surface 611 side of the substrate 61. That is, in the fourth modified example, the first surface 611 is a surface that includes a mounting surface 613 for mounting the switching element 62, and the second surface 612 is an opposite surface that faces away from the surface that includes the mounting surface 613.

[0074] In the fourth modification, the heat dissipation portion 325 is located on the opposite side of the substrate 61 from the switching element 62 and is thermally connected to the metal foil 64 via a retainer 75 or the like. The heat dissipation portion 315 is located on the same side of the case 3 as the switching element 62 with respect to the substrate 61 and is thermally connected to the switching element 62. The switching element 62 is sandwiched between the substrate 61 and the heat dissipation portion 315.

[0075] In addition to the various modifications described above, the motor unit 2 provided in the electric bicycle 1 of one embodiment can also be provided with the following configurations.

[0076] For example, it is also preferable that the motor unit 2 in one embodiment includes two or more electrolytic capacitors 68 mounted on the substrate 61. The two or more electrolytic capacitors 68 may be mounted on only one of the first surface 611 and the second surface 612 of the substrate 61, or may be distributed over both surfaces. Having two or more electrolytic capacitors 68 increases the degree of freedom in arranging the electrolytic capacitors 68 on the substrate 61, and enables effective use of the space within the case 3.

[0077] It is also preferable that the motor unit 2 of one embodiment further includes an inertial sensor (not shown) mounted on the substrate 61. The inertial sensor is, for example, an acceleration sensor, an inclination sensor, or a gyro sensor, and the microcontroller 69 can control the motor 4 based on the output from the inertial sensor. The inertial sensor is preferably mounted on the second half 616 of the substrate 61. As described above, the second half 616 is the upper half of the substrate 61, and the mounting surface 613 is provided on the lower half of the substrate 61 (i.e., the first half 615).

[0078] In addition, in the motor unit 2 of one embodiment, the motor 4 is located to the left of the substrate 61 (i.e., the second side), but the motor 4 may also be located to the right of the substrate 61 (i.e., the first side).

[0079] In one embodiment of the motor unit 2, the base material of the substrate 61 that is covered with the resist layers 6191, 6192 is preferably formed from a thermally conductive material. The thermally conductive material is, for example, a metal such as aluminum or copper, or ceramic. In this case, the heat dissipation of the switching elements 62 is further improved through the base material of the substrate 61.

[0080] Furthermore, in the motor unit 2 of the embodiment, the speed reducing mechanism 5 is a one-stage speed reducing mechanism, but the speed reducing mechanism 5 may be a two-stage or three-stage speed reducing mechanism.

[0081] Furthermore, the motor unit 2 in one embodiment is a so-called two-shaft motor unit, and is provided with a rotatable output body 81 to which the first sprocket 191 is connected and a rotatable output body 82 to which the second sprocket 192 is connected separately, but the motor unit 2 can also be configured as a so-called single-shaft motor unit. When the motor unit 2 is configured as a single-shaft motor unit, the reduction mechanism 5 can be configured to transmit the rotational force of the motor 4 to the output body 81 side. As a result, both the rotational force of the input shaft 71 and the rotational force of the motor 4 are transmitted to the output body 81. In this case as well, the reduction mechanism 5 can be configured as a one-stage reduction, two-stage reduction, or three-stage reduction.

[0082] Furthermore, although the electric bicycle 1 in one embodiment is a so-called power-assisted bicycle, it is not limited to this and may be an electric bicycle in which the wheels 11 can be rotated without human power. Furthermore, although the electric bicycle in one embodiment has two wheels 11, the number of wheels 11 is not particularly limited and may have, for example, three wheels 11.

[0083] While the present disclosure has been described above based on one embodiment and various modified examples shown in the accompanying drawings, the present disclosure is not limited to the above-described embodiment and modified examples. As long as it is within the intended scope of the present disclosure, it is possible to make appropriate design changes to the one embodiment and various modified examples, and to apply appropriate combinations of the configurations of the modified examples.

[0084] (2) Mode As is clear from the above-described embodiment and various modified examples, a motor unit (2) according to a first aspect is a motor unit (2) for use in an electric bicycle, and includes a motor (4), a switching element (62) for driving the motor (4), a substrate (61) having a surface including a mounting surface (613) for mounting the switching element (62) and an opposite surface facing away from the mounting surface (613), and a case (3) for accommodating the substrate (61). The substrate (61) further includes a through-hole (614) extending between the mounting surface (613) and the opposite surface, and a metal foil (64) covering at least a portion of the inner circumferential surface of the through-hole (614). The switching element (62) is thermally connected to the metal foil (64), and a portion of the case (3) opposite the switching element (62) across the substrate (61) is thermally connected to the metal foil (64).

[0085] According to the motor unit (2) of the first aspect, the amount of heat dissipated from the switching element (62) included in the motor unit (2) can be further increased, thereby improving the reliability of the motor unit (2).

[0086] The second aspect can be realized by combining the first aspect. The motor unit (2) of the second aspect further includes solder (63) that fixes the switching element (62) to the mounting surface (613). The switching element (62) is thermally connected to the metal foil (64) via the solder (63).

[0087] According to the motor unit (2) of the second aspect, the heat generated by the switching element (62) can be efficiently transferred via the thermally conductive solder (63).

[0088] The third aspect can be realized in combination with the second aspect. The motor unit (2) of the third aspect further includes an insulating member (65) provided on the opposite surface of the through-hole (614) so ​​as to cover at least a portion of the through-hole (614).

[0089] According to the motor unit (2) of the third aspect, the solder (63) can be prevented from flowing out through the through-hole (614).

[0090] The fourth aspect can be realized in combination with any one of the first to third aspects. In the motor unit (2) of the fourth aspect, the diameter of the through-hole (614) is within the range of 0.2 mm to 0.4 mm.

[0091] According to the motor unit (2) of the fourth aspect, the heat generated by the switching element (62) can be efficiently transferred through the metal foil (64) in the through-hole (614).

[0092] The fifth aspect can be realized in combination with any one of the first to third aspects. In the motor unit (2) of the fifth aspect, the diameter of the through-hole (614) is within the range of 0.2 mm to 0.35 mm.

[0093] According to the motor unit (2) of the fifth aspect, the heat generated by the switching element (62) can be efficiently transferred through the metal foil (64) in the through-hole (614).

[0094] The sixth aspect can be realized by combining it with any one of the first to fifth aspects. In the motor unit (2) of the sixth aspect, the motor (4) is located on the same side of the substrate (61) as the switching element (62).

[0095] According to the motor unit (2) of the sixth aspect, the heat generated by the switching element (62) can be dissipated to the side of the board (61) opposite to the side on which the motor (4) is located.

[0096] The seventh aspect can be realized by combining with any one of the first to sixth aspects. In the motor unit (2) of the seventh aspect, the switching element (62) includes a single field-effect transistor (621) and a package (625) that covers the single field-effect transistor (621).

[0097] According to the motor unit (2) of the seventh aspect, a switching element (62) with excellent heat dissipation properties can be obtained.

[0098] The eighth aspect can be realized by combining with any one of the first to sixth aspects. In the motor unit (2) of the eighth aspect, the switching element (62) includes a plurality of field-effect transistors (621) and a package (625) that covers the plurality of field-effect transistors (621).

[0099] According to the motor unit (2) of the eighth aspect, the switching element (62) can be configured compactly.

[0100] The ninth aspect can be realized in combination with any one of the first to eighth aspects. In the motor unit (2) of the ninth aspect, the thickness of the metal foil (64) is within a range of 10 μm to 30 μm.

[0101] According to the motor unit (2) of the ninth aspect, the heat generated by the switching element (62) can be efficiently transferred through the metal foil (64).

[0102] The tenth aspect can be realized in combination with any one of the first to ninth aspects. In the motor unit (2) of the tenth aspect, the mounting surface (613) is located in an end region of the substrate (61).

[0103] According to the motor unit (2) of the tenth aspect, it is easy to thermally connect the switching element (62) to a part of the case (3), and it is easy to ensure a heat dissipation path from the switching element (62) to the case (3).

[0104] The eleventh aspect can be realized in combination with any one of the first to tenth aspects. In the motor unit (2) of the eleventh aspect, the substrate (61) includes a base material formed of a thermally conductive material.

[0105] According to the motor unit (2) of the eleventh aspect, the heat generated by the switching element (62) can be efficiently transferred through the base material.

[0106] The twelfth aspect can be realized by combining with any one of the first to eleventh aspects. In the motor unit (2) of the twelfth aspect, a portion of the case (3) on the same side as the switching element (62) with respect to the substrate (61) is thermally connected to the switching element (62).

[0107] According to the motor unit (2) of the twelfth aspect, the case (3) can be thermally connected to both sides of the switching element (62), thereby further increasing the amount of heat dissipated from the switching element (62).

[0108] The thirteenth aspect can be realized by combining it with any one of the first to twelfth aspects. In the motor unit (2) of the thirteenth aspect, the substrate (61) includes a metal layer (6181) and a resist layer (6191) covering the metal layer (6181). The metal layer (6181) is thermally connected to the metal foil (64), and the resist layer (6191) is formed so as to expose a portion of the metal layer (6181). A solder portion (67) for heat dissipation is fixed to a portion of the metal layer (6181).

[0109] According to the motor unit (2) of the thirteenth aspect, the amount of heat dissipated from the switching element (62) can be further increased.

[0110] The fourteenth aspect can be realized in combination with any one of the first to thirteenth aspects. In the motor unit (2) of the fourteenth aspect, the through-hole (614) has an opening, and the switching element (62) faces the opening.

[0111] According to the motor unit (2) of the fourteenth aspect, the heat generated by the switching element (62) can be efficiently transferred through the metal foil (64) in the through-hole (614).

[0112] The fifteenth aspect can be realized in combination with any one of the first to fourteenth aspects. The motor unit (2) of the fifteenth aspect further includes two or more electrolytic capacitors (68) mounted on the substrate (61).

[0113] According to the motor unit (2) of the fifteenth aspect, the presence of two or more electrolytic capacitors (68) increases the degree of freedom in arranging the electrolytic capacitors (68) on the substrate (61), and enables effective use of the space within the case (3).

[0114] The sixteenth aspect can be realized in combination with any one of the first to fifteenth aspects. The motor unit (2) of the sixteenth aspect further includes an inertial sensor mounted on the first half (615) of the substrate (61). The mounting surface (613) is located on the second half (616) of the substrate (61).

[0115] According to the motor unit (2) of the sixteenth aspect, it is possible to control the motor (4) based on the output from the inertial sensor.

[0116] The seventeenth aspect can be realized in combination with any one of the first to fifteenth aspects. The motor unit (2) of the seventeenth aspect further includes a microcontroller (69) mounted on the first half (615) of the substrate (61). The mounting surface (613) is located on the second half (616) of the substrate (61).

[0117] According to the motor unit (2) of the seventeenth aspect, the influence of electrical noise generated on the switching element (62) side on the microcontroller (69) is suppressed.

[0118] The eighteenth aspect can be realized in combination with any one of the first to sixteenth aspects. The motor unit (2) of the eighteenth aspect further includes a microcontroller (69) mounted on the substrate (61). The microcontroller (69) does not overlap with the motor (4) when viewed along the central axis of rotation of the motor (4).

[0119] According to the motor unit (2) of the eighteenth aspect, the influence of electrical noise generated from the motor (4) on the microcontroller (69) is suppressed.

[0120] The 19th aspect can be realized by combining with any one of the 1st to 18th aspects. The motor unit (2) of the 19th aspect further includes a one-stage reduction mechanism (5) connected to the motor (4).

[0121] According to the motor unit (2) of the nineteenth aspect, the rotational force of the motor (4) can be output after being reduced by one stage.

[0122] The twentieth aspect can be realized by combining with any one of the first to eighteenth aspects. The motor unit (2) of the twentieth aspect further includes a two-stage reduction mechanism (5) connected to the motor (4).

[0123] According to the motor unit (2) of the twentieth aspect, the rotational force of the motor (4) can be output after being reduced in two stages.

[0124] The 21st aspect can be realized by combining with any one of the 1st to 18th aspects. The motor unit (2) of the 21st aspect further includes a three-stage reduction mechanism (5) connected to the motor (4).

[0125] According to the motor unit (2) of the twenty-first aspect, the rotational force of the motor (4) can be output after being reduced in three stages.

[0126] The 22nd aspect can be realized by combining with any one of the 1st to 21st aspects. The motor unit (2) of the 22nd aspect includes a rotatable input shaft (71) to which a crank arm (18) is connected, a rotatable first output body (81) to which a first sprocket (191) is connected, and a rotatable second output body (82) to which a second sprocket (192) is connected. The first output body (81) is configured to transmit the rotational force of the input shaft (71). The second output body (82) is configured to transmit the rotational force of the motor (4).

[0127] According to the motor unit (2) of the twenty-second aspect, a so-called two-shaft motor unit (2) can be obtained.

[0128] The 23rd aspect can be realized by combining with any one of the 1st to 21st aspects. The motor unit (2) of the 23rd aspect includes a rotatable input shaft (71) to which a crank arm (18) is connected, and a rotatable output body (81) to which a sprocket (191) is connected. The output body (81) is configured to transmit the rotational force of the input shaft (71) and the rotational force of the motor (4).

[0129] According to the motor unit (2) of the 23rd aspect, a so-called single-shaft motor unit (2) can be obtained.

[0130] The electric bicycle (1) of the 24th aspect comprises a motor unit (2) of any one of the first to 23rd aspects, a wheel (11) to which the rotational force of the motor (4) is transmitted, and a frame (10) that supports the motor unit (2) and the wheel (11).

[0131] According to the electric bicycle (1) of the twenty-fourth aspect, the amount of heat dissipated from the switching element (62) included in the motor unit (2) can be further increased, thereby improving the reliability of the motor unit (2).

[0132] An electric bicycle (1) of a 25th aspect includes the motor unit (2) of the 22nd or 23rd aspect, a wheel (11) to which the rotational force of the motor (4) is transmitted, and a frame (10) that supports the motor unit (2) and the wheel (11). In a side view, a heat dissipation portion of the case (3) that is thermally connected to the switching element (62) is located below a line (L) that connects the central axis of rotation of the input shaft (71) and the central axis of rotation of the motor (4).

[0133] According to the electric bicycle (1) of the twenty-fifth aspect, the amount of heat dissipated from the switching element (62) included in the motor unit (2) can be further increased, thereby improving the reliability of the motor unit (2). [Explanation of symbols]

[0134] 1. Electric bicycle 10 frames 11 wheels 18 crank arm 191 First sprocket (sprocket) 192 2nd sprocket 2 motor units 3 cases 4 motors 5 Reduction mechanism 61 PCB 613 Mounting surface 614 Through hole 615 First half 616 Second half 6181 Metal layer 6191 Resist layer 62 Switching element 621 Field Effect Transistor 625 packages 63 Solder 64 Metal foil 65 Insulating material 653 holes 67 Handabe 68 Electrolytic Capacitor 69 Microcontrollers 71 Input shaft 81 First output body (output body) 82 Second output body (output body)

Claims

1. A motor unit used in an electric bicycle, a motor having a stator; a switching element for driving the motor; a substrate having a surface including a mounting surface for mounting the switching element and an opposite surface facing away from the surface; solder for fixing the switching element to the mounting surface; a case that houses the substrate, has a first divided body and a second divided body that houses the motor, and has an input shaft passing through it so as to be rotatable about an axis line; the substrate further includes a through hole penetrating between the mounting surface and the opposite surface, and a metal foil covering at least a portion of an inner circumferential surface of the through hole; the switching element is thermally connected to the metal foil via the solder; the first divided body includes a first heat dissipation portion protruding toward the substrate, the second divided body includes a second heat dissipation portion protruding toward the switching element, the first heat dissipation portion is connected to the substrate via a first thermally conductive sheet; the second heat dissipation portion is connected to the switching element via a second thermally conductive sheet, The second heat dissipation portion is disposed outside the stator and between the input shaft and the stator in a direction perpendicular to the axis. Motor unit.

2. an insulating member provided on the opposite surface so as to cover at least a portion of the through hole, The insulating member has a second through hole communicating with the first through hole, which is the through hole. The motor unit according to claim 1.

3. The opening area of ​​the second through hole is smaller than the opening area of ​​the first through hole. The motor unit according to claim 2.

4. The diameter of the through hole is in the range of 0.2 mm to 0.4 mm. The motor unit according to any one of claims 1 to 3.

5. The diameter of the through hole is in the range of 0.2 mm to 0.35 mm. The motor unit according to any one of claims 1 to 3.

6. the motor is located on the same side of the substrate as the switching element; The motor unit according to any one of claims 1 to 5.

7. the switching element includes a single field-effect transistor and a package covering the single field-effect transistor. The motor unit according to any one of claims 1 to 6.

8. The switching element includes a plurality of field effect transistors and a package that covers the plurality of field effect transistors. The motor unit according to any one of claims 1 to 6.

9. The thickness of the metal foil is in the range of 10 μm to 30 μm. The motor unit according to any one of claims 1 to 8.

10. The mounting surface is located in an edge region of the substrate. The motor unit according to any one of claims 1 to 9.

11. The substrate includes a base material formed of a thermally conductive material. The motor unit according to any one of claims 1 to 10.

12. the substrate includes a metal layer and a resist layer covering the metal layer; the metal layer is thermally connected to the metal foil; the resist layer is formed so as to expose a portion of the metal layer; a solder portion for heat dissipation is fixed to the portion of the metal layer; A motor unit according to any one of claims 1 to 11.

13. The through-hole has an opening, and the switching element faces the opening. A motor unit according to any one of claims 1 to 12.

14. Further comprising two or more electrolytic capacitors mounted on the substrate. A motor unit according to any one of claims 1 to 13.

15. an inertial sensor mounted to the first half of the substrate; the mounting surface is located on a second half of the substrate; A motor unit according to any one of claims 1 to 14.

16. a microcontroller mounted on the first half of the substrate; the mounting surface is located on a second half of the substrate; A motor unit according to any one of claims 1 to 14.

17. a microcontroller mounted on the substrate; the microcontroller does not overlap the motor when viewed along the central axis of rotation of the motor; 16. A motor unit according to any one of claims 1 to 15.

18. Further comprising a one-stage reduction mechanism connected to the motor.

18. A motor unit according to any one of claims 1 to 17.

19. Further comprising a two-stage reduction mechanism connected to the motor.

18. A motor unit according to any one of claims 1 to 17.

20. Further comprising a three-stage reduction mechanism connected to the motor.

18. A motor unit according to any one of claims 1 to 17.

21. a rotatable input shaft to which the crank arm is coupled; a rotatable first output body to which the first sprocket is coupled; a rotatable second output body to which the second sprocket is coupled; the first output body is configured to transmit a rotational force of the input shaft, The second output body is configured to transmit the rotational force of the motor.

21. The motor unit according to any one of claims 1 to 20.

22. a rotatable input shaft to which the crank arm is coupled; a rotatable output body to which the sprocket is coupled; The output body is configured to transmit the rotational force of the input shaft and the rotational force of the motor.

21. The motor unit according to any one of claims 1 to 20.

23. A motor unit according to any one of claims 1 to 22; a wheel to which the rotational force of the motor is transmitted; a frame supporting the motor unit and the wheels; Electric bicycle.

24. a motor unit according to claim 21 or 22; a wheel to which the rotational force of the motor is transmitted; a frame supporting the motor unit and the wheels, a heat dissipation portion of the case that is thermally connected to the switching element is located below a line that connects the rotational axis of the input shaft and the rotational axis of the motor in a side view; Electric bicycle.

Images