Electrically assisted bicycles

Abstract

To facilitate a change of postures of a bicycle which is made in response to a rider's manipulation in a case where the bicycle runs on an uneven ground.SOLUTION: A bicycle 10 includes a bottom bracket 51 that supports a crank shaft 52, a motor unit 20, and a battery 13 attached to a down frame part 33 of a frame 30. The motor unit 20 is located behind the battery 13 above the bottom bracket 51. A lower end 13a of the battery 13 is located below a rotation center Cm of an electric motor 21.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] Electrically assisted bicycles are used for traveling on uneven terrain such as mountain roads and rough roads. In the electrically assisted bicycle of Patent Document 1, the frame has a down member that extends diagonally downward from the head pipe toward the crankshaft. The motor unit is supported between the lower end of the down member and the crankshaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2022 / 0289335 Summary of the Invention [Problem to be solved by the invention]

[0004] On rough terrain, it may be necessary to change the bicycle's position while riding. Reducing the bicycle's moment of inertia around the crankshaft makes it easier for the rider to change the bicycle's position. To reduce the moment of inertia, it is desirable to position the battery, a heavy component, close to the crankshaft. However, with electrically assisted bicycles, the layout of various components, such as the motor unit, rear suspension, and reduction mechanism, makes it difficult to position the battery close to the crankshaft. For example, in the bicycle disclosed in Patent Document 1, the motor unit is located between the down frame and the crankshaft, so even if the battery were attached to the down frame, it would be difficult to reduce the distance between the battery and the crankshaft. [Means for solving the problem]

[0005] (1) The electric assist bicycle proposed in this disclosure is: a bottom bracket supporting the crankshaft; a motor unit having an electric motor, a housing that accommodates the electric motor, and an output shaft that protrudes from the housing and outputs torque of the electric motor, the motor unit being disposed away from the bottom bracket; a frame having a head tube for supporting a steering shaft, a frame bottom portion supporting the bottom bracket, and a down frame portion extending obliquely downward from the head tube toward the frame bottom portion; and a battery attached to the down frame portion. The motor unit is located above the bottom bracket and behind the battery, and the lower end of the battery is located below the center of rotation of the electric motor.

[0006] This electrically assisted bicycle allows the distance between the crankshaft and the battery to be reduced, reducing the moment of inertia of the bicycle around the crankshaft, making it easier for the rider to change the bicycle's position.

[0007] (2) In the electrically assisted bicycle of (1), the entire lower surface of the battery may be located below the lower end of the electric motor. With this structure, the distance between the crankshaft and the battery can be further reduced.

[0008] (3) In the electrically assisted bicycle of (1) or (2), the distance from the crankshaft to the end of the battery is smaller than at least one of the distance from the crankshaft to the center of rotation of the electric motor and the distance from the crankshaft to the center of rotation of the output shaft.

[0009] (4) Any of the electric assist bicycles (1) to (3) may have a rear arm connected to the frame via a pivot shaft, and a rear suspension supporting the rear arm so that the rear arm can move up and down.

[0010] (5) In the electrically assisted bicycle of (4), the pivot shaft may be positioned higher than the center of rotation of the electric motor. By positioning the pivot shaft higher in this way, for example, when the rear wheel runs over a bump in the road, the direction of movement of the rear wheel will be tilted rearward relative to the vertical. As a result, the impact when the rear wheel hits the bump can be mitigated, and the rear wheel can smoothly run over the bump.

[0011] (6) The electrically assisted bicycle of (4) or (5) may have a first sprocket mounted on the crankshaft, a second sprocket mounted on the output shaft, and a chain wound around the first sprocket and the second sprocket. The pivot shaft and the output shaft may both be positioned higher than the center of rotation of the electric motor. This structure allows the distance between the pivot shaft and the output shaft to be reduced, and as a result, the distance between the center of swing of the rear wheel and the output shaft to be reduced. This prevents excessive tension on the chain when the rear wheel moves up and down.

[0012] (7) In any of the electrically assisted bicycles (4) to (6), the output shaft may be located in front of the pivot shaft. This structure reduces the distance between the pivot shaft and the output shaft, and as a result, the distance between the swing center of the rear wheel and the output shaft. This prevents excessive tension on the chain when the rear wheel moves up and down.

[0013] (8) In the electrically assisted bicycle of any one of (4) to (7), the distance from the output shaft to the pivot shaft may be shorter than the distance from the output shaft to the crankshaft.

[0014] (9) The electrically assisted bicycle of any one of (1) to (8) has a first sprocket mounted on the crankshaft, a second sprocket mounted on the output shaft and having a number of teeth fewer than that of the first sprocket, and a chain wound around the first sprocket and the second sprocket to transmit their rotation to the rear wheel. This structure allows the structure around the crankshaft to be smaller than, for example, a structure in which the rotation of the output shaft is transmitted to the crankshaft via a gear. As a result, the distance between the rear wheel axle and the crankshaft can be reduced, making it easier to change the position of the bicycle (for example, to perform a wheelie).

[0015] (10) In any one of the electrically assisted bicycles (1) to (9), the battery may be housed in the down frame portion. This allows the distance between the crankshaft and the battery to be smaller than, for example, a structure in which the battery is attached to the front side of the down frame portion.

[0016] (11) In any of the electrically assisted bicycles (1) to (10), the output shaft may be located above the electric motor. This allows the heavy electric motor to be positioned closer to the crankshaft, further reducing the moment of inertia of the bicycle.

[0017] (12) In any one of the electrically assisted bicycles (1) to (11), the frame may have a main frame portion extending rearward from the head tube and positioned above the down frame portion. At least a rear portion of the main frame portion may have a right extension portion and a left extension portion that are separated in the left-right direction, and a portion of the motor unit may overlap at least one of the right extension portion and the left extension portion in a side view. In this way, by shifting the position of the motor unit rearward to the position of the extension portion, it is easy to reduce the distance between the crankshaft and the battery located in front of the motor unit. [Brief explanation of the drawings]

[0018] [Figure 1]1 is a side view of a bicycle proposed in the present disclosure. [Figure 2] FIG. 1 is a perspective view showing the rear of a bicycle. [Figure 3] 1 is a perspective view illustrating a support structure for a motor unit, a bottom bracket, etc. In this figure, the right extension portion of the main frame is omitted. [Figure 4] FIG. 1 is a side view showing the rear of the bicycle. [Figure 5] FIG. 2 is a schematic side view showing the positional relationship of the motor unit, bottom bracket, battery, etc. [Figure 6] FIG. [Figure 7] FIG. 10 is a side view showing the movement of the seat support structure. DETAILED DESCRIPTION OF THE INVENTION

[0019] The bicycle proposed in this disclosure will be described below. As an example of the bicycle proposed in this disclosure, an electrically assisted bicycle 10 shown in FIG. 1 etc. will be described below. In the following description, the F direction and B direction shown in FIG. 1 etc. will be referred to as the front and rear, respectively. The U direction and D direction shown in FIG. 1 etc. will be referred to as the up and down, respectively. The L direction and R direction shown in FIG. 3 will be referred to as the left and right, respectively.

[0020] 1, the bicycle 10 has a motor unit 20, a battery 13, and a frame 30. The bicycle 10 also has a seat 19 and a seat support device 60.

[0021] [Frame and crankshaft support structure] As shown in Figure 1, the frame 30 has, at its front end, a head tube 31 that supports the steering shaft 16. A steering handlebar 15 is fixed to the upper part of the steering shaft 16. The steering handlebar 15 has grips 15a on both the right and left sides. A front fork 14 is fixed to the lower part of the steering shaft 16. The front wheel 11 is supported at the lower end of the front fork 14.

[0022] As shown in Figure 1, the bicycle 10 has a bottom bracket 51 (see Figure 2) that rotatably holds a crankshaft 52. The bottom bracket 51 is generally cylindrical, with the crankshaft 52 inserted inside. The crankshaft 52 has crank arms 52d at its right and left ends. Pedals 53 are fixed to the ends of the crank arms 52d.

[0023] As shown in FIG. 2, the frame 30 has a frame bottom 32 to which a bottom bracket 51 is attached. The frame bottom 32 is located at the lower end of the frame 30. The bottom bracket 51 is disposed, for example, below the rearmost part of the frame bottom 32. A recess 32a is formed in the rearmost part of the frame bottom 32. The bottom bracket 51 may be disposed in this recess 32a. The bottom bracket 51 is fixed to the lower part of the frame bottom 32 by fastening members 71a and 71b (see FIG. 3), such as bolts or screws. The bottom bracket 51 may be welded to the frame bottom 32.

[0024] As shown in Figure 1, the frame 30 has a down frame section 33 that extends obliquely rearward and downward from the head tube 31 toward the frame bottom section 32. The upper end (front end) of the down frame section 33 is welded to the head tube 31. The lower end (rear end) of the down frame section 33 is welded to the frame bottom section 32. The down frame section 33 and the frame bottom section 32 (the section that supports the bottom bracket 51) may be formed integrally.

[0025] As shown in FIG. 1, the frame 30 has a main frame portion 34 extending rearward from the head tube 31. A front portion 34a of the main frame portion 34 is located above the down frame portion 33. In the example shown in FIG. 1, the front portion 34a of the main frame portion 34 extends obliquely rearward and downward from the head tube 31. The main frame portion 34 is bent at the rear end of the front portion 34a, and a rear portion 34b of the main frame portion 34 extends downward toward the frame bottom 32. A bottom bracket 51 is located below the lower end of the main frame portion 34 (extension portions 34R and 34L, described below).

[0026] The shape of the main frame portion 34 is not limited to the example shown in the drawings. For example, the main frame portion 34 may extend from the head tube 31 toward the frame bottom portion 32 while gently curving.

[0027] 2 and 3, the lower end of the main frame portion 34 is connected to the upper end 32b (see FIG. 3) of the rear part of the frame bottom portion 32. The lower end of the down frame portion 33 is connected to the upper end 32c (see FIG. 3) of the front part of the frame bottom portion 32. A bottom bracket 51 is fixed to the underside of the rearmost part of the frame bottom portion 32.

[0028] The structure of the frame 30 is not limited to the example shown in FIG. 1 etc. For example, the frame bottom 32 may be formed with a through-hole that penetrates it in the left-right direction. The bottom bracket 51 may be fitted into this through-hole and supported by the frame bottom 32. In this case, the frame bottom 32 may be a cylindrical portion. The lower end of the main frame portion 34 or the lower end (rear end) of the down frame portion 33 may be connected to the outer peripheral surface of this frame bottom 32. Furthermore, instead of the rear arm 48 described below, a stay that supports the axle 12a of the rear wheel 12 may be provided on the frame 30. This stay may also be connected to the cylindrical frame bottom 32.

[0029] The main frame portion 34 may also be composed of a tube extending rearward from the head tube 31 and a tube extending downward from the rear end of this tube. That is, the main frame portion 34 may be composed of two tubes connected to each other. In the example shown in FIG. 2 etc., the down frame portion 33 extends straight from the head tube 31, but it may also have a bent portion somewhere along the way. For example, the down frame portion 33 may extend diagonally rearward and downward from the head tube 31, and then bend rearward at the lowest part of the down frame portion 33 to connect to the frame bottom portion 32.

[0030] [Rear wheel support structure] As shown in Figure 2, the bicycle 10 has a rear arm 48. The front end of the rear arm 48 is connected to the main frame portion 34 via a pivot shaft 39. The front end of the rear arm 48 is located between a right extension portion 34R and a left extension portion 34L (described later) of the main frame portion 34. The axle 12a of the rear wheel 12 is supported at the rearmost portion of the rear arm 48. The rear arm 48 is movable up and down around the pivot shaft 39.

[0031] As shown in Figure 2, the bicycle 10 has a rear suspension 47 and a link mechanism 40 that connects the rear suspension 47 to a rear arm 48. The rear suspension 47 is disposed, for example, between the rear portion 34b of the main frame portion 34 and the down frame portion 33. The lower end of the rear suspension 47 is attached to the down frame portion 33 via a bracket 35. The link mechanism 40 is connected to the upper end of the rear suspension 47.

[0032] 2, the link mechanism 40 includes, for example, a first link member 41 and a second link member 42. When the bicycle 10 travels over an uneven road, the shock acting on the rear wheel 12 is transmitted to the rear suspension 47 via the link members 42 and 41.

[0033] 3, a front portion 41a of the first link member 41 is connected to the upper end of the rear suspension 47 via a connecting shaft 43b. A rearmost portion 41b of the first link member 41 is connected to a frontmost portion 42b of the second link member 42 via the connecting shaft 43a. The first link member 41 can swing back and forth around a support shaft 36 supported by the main frame portion 34. The first link member 41 has a right link portion 41R and a left link portion 41L, each of which has a rearmost portion 41b and a frontmost portion 41a.

[0034] As shown in Figure 2, the rearmost portion 42a of the second link member 42 supports the axle 12a of the rear wheel 12. The rear end of the rear arm 48 is connected to the rearmost portion 42a of the second link member 42 via a connecting shaft 43c. The second link member 42 extends diagonally upward and forward from the rearmost portion 42a. The second link member 42 has a right link portion 42R and a left link portion 42L, each of which has a rearmost portion 42a and a foremost portion 42b.

[0035] [Motor unit] As shown in FIG. 3, the motor unit 20 has an electric motor 21 (see FIG. 4), a housing 22 that houses the electric motor 21, and an output shaft 23 for outputting the torque of the electric motor 21. The output shaft 23 protrudes rightward from the housing 22. A sprocket 23a is attached to the output shaft 23. The motor unit 20 may house a reduction mechanism in addition to the electric motor 21. The rotation of the electric motor 21 may be transmitted to the output shaft 23 via the reduction mechanism.

[0036] As shown in Figure 3, the bottom bracket 51 and the motor unit 20 are positioned apart. In other words, the bottom bracket 51 is not a component housed in the housing 22. This allows for greater freedom in the layout of the motor unit 20 compared to a structure in which the bottom bracket 51 and motor unit 20 are unitized, i.e., a structure in which the electric motor 21, output shaft 23, and bottom bracket 51 are housed in a single housing. In the example shown in Figure 3 and other figures, the motor unit 20 is positioned above and apart from the bottom bracket 51.

[0037] [Torque transmission structure] 1, the bicycle 10 has a chain 18. The chain 18 is wound around a sprocket 23a provided on the output shaft 23, a sprocket 52a provided on the crankshaft 52, and a sprocket 12b provided on the axle of the rear wheel 12. The torque of the crankshaft 52 and the torque of the output shaft 23 are transmitted to the rear wheel 12 via the chain 18.

[0038] The number of teeth of sprocket 23a provided on output shaft 23 is smaller than the number of teeth of sprocket 12b of rear wheel 12. The number of teeth of sprocket 23a is also smaller than the number of teeth of sprocket 52a of crankshaft 52. As a result, the rotation of output shaft 23 is transmitted to rear wheel 12 and crankshaft 52 at a reduced speed.

[0039] In a structure in which the motor unit and bottom bracket are integrated, the rotation of the electric motor is transmitted to the crankshaft via multiple gears. To ensure a sufficient reduction ratio in this structure, a gear with a large number of teeth (a gear with a large diameter) must be attached to the crankshaft. This increases the size of the structure around the crankshaft, which in turn increases the size of the housing that houses the motor unit and other components, making it necessary to increase the distance between the rear wheel axle and the crankshaft.

[0040] In contrast, in bicycle 10, the rotation of output shaft 23 is slowed down by sprockets 23a, 12a, and 52a and chain 18, so there is no need to attach the large-diameter gear described above to crankshaft 52. As a result, the distance between axle 12a of rear wheel 12 and crankshaft 52 can be reduced. This reduces the moment of inertia around the axle of rear wheel 12, making it easier to change the position of bicycle 10 (for example, to perform a wheelie). In the example shown in FIG. 1, rear wheel 12 is close to rear portion 34b of main frame portion 34, and the frontmost portion of rear wheel 12 overlaps with sprocket 52a of crankshaft 52 in a side view.

[0041] The bicycle may have gears. In this case, multiple sprockets 12b with different numbers of teeth may be provided on the axle 12a of the rear wheel 12. The bicycle 10 may also have a derailleur mechanism that moves the chain 18 to the sprocket 12b that corresponds to the selected gear.

[0042] [Electric motor control] The battery 13 is electrically connected to the electric motor 21, and the electric motor 21 is driven by the current from the battery 13. The bicycle 10 has a control device for controlling the electric motor 21 and a drive device for supplying power from the battery 13 to the electric motor 21 (neither device is shown in the figure). The bicycle 10 also has a torque sensor for detecting the torque acting on the crankshaft 52 (the force acting on the pedals 53), and a vehicle speed sensor for detecting the vehicle speed (neither sensor is shown in the figure). The torque sensor is provided on the crankshaft 52, for example. The vehicle speed sensor is provided on the front wheel 11 or the rear wheel 12.

[0043] The control device calculates an assist ratio based on the output of the vehicle speed sensor, and calculates a current command value based on this assist ratio and the output of the torque sensor. The drive device supplies a current corresponding to the command value to the electric motor 21. The control device and drive device are housed, for example, in an electrical component case 17 (see FIG. 1) attached to the lower end of the down frame portion 33. The arrangement of the control device and drive device is not limited to the example described here.

[0044] [Motor unit and battery layout] The battery 13 is attached to the down frame portion 33. The battery 13 may be housed in the down frame portion 33, as shown in Fig. 4. More specifically, the down frame portion 33 has a box shape that is elongated in its extension direction (diagonally rearward and downward), and the battery 13 may be disposed inside the down frame portion 33.

[0045] To allow for such a layout of the battery 13, the frame 30 may have an opening for inserting the battery 13. For example, the down frame portion 33 and the frame bottom portion 32 may have openings on their lower sides. The battery 13 may then be insertable into the down frame portion 33 through the openings. The openings may be closed by the electrical component case 17.

[0046] The placement of the battery 13 is not limited to the example shown in Fig. 4. For example, the battery 13 may be attached to the front surface 33a of the down frame portion 33. Conversely, the battery 13 may be attached to the rear surface 33b of the down frame portion 33. Furthermore, an opening for inserting the battery 13 into the down frame portion 33 may be attached to the rear surface 33b of the down frame portion 33.

[0047] As another alternative structure, a recess that opens toward the front may be formed in the down frame portion 33. The battery 13 may be disposed in this recess. Conversely, a recess that opens toward the rear may be formed in the down frame portion 33. The battery 13 may be housed in this recess.

[0048] The electrical equipment case 17 (see FIG. 1) is located below the motor unit 20 and the battery 13. This reduces the distance between the circuit board (control device and / or drive device) housed in the electrical equipment case 17 and the electric motor 21, and the distance between the circuit board and the battery 13. The control device and drive device may be located higher than the sprocket 52a of the crankshaft 52.

[0049] As shown in Fig. 2, the motor unit 20 is located above the bottom bracket 51 and behind the battery 13. As shown in Fig. 4, at least the lower end 13a of the battery 13 is located below the center of rotation Cm of the electric motor 21. In other words, at least the lower end 13a of the battery 13 is located below a horizontal line H1 (see Fig. 5) that passes through the center of rotation Cm. In Fig. 4, the lower end 13a of the battery 13 is the lower end (corner) of the front surface of the battery 13.

[0050] With this layout of the motor unit 20, battery 13, and bottom bracket 51, the space formed diagonally below and in front of the motor unit 20 can be used to position the battery 13. This reduces the distance between the crankshaft 52, which is located below the motor unit 20, and the battery 13, reducing the moment of inertia of the bicycle 10 around the crankshaft 52. As a result, it is easier for the rider to change the position of the bicycle 10 when riding on rough terrain.

[0051] As shown in Figure 5, in bicycle 10, not only the lower end 13a of battery 13 but the entire lower surface 13b is located below the center of rotation Cm of electric motor 21. In other words, the entire lower surface 13b is located below horizontal line H1 (see Figure 5) that passes through center of rotation Cm. By lowering the position of battery 13 in this way, the distance between battery 13 and crankshaft 52 can be further reduced.

[0052] 5, in bicycle 10, the entire lower surface 13b of battery 13 is lower than the lower end 21a of electric motor 21. In other words, the entire lower surface 13b of battery 13 is lower than horizontal line H2 that passes through the lower end 21a of electric motor 21. This further reduces the distance between battery 13 and crankshaft 52.

[0053] As described above, in bicycle 10, as shown in Figure 4, battery 13 is housed in down frame portion 33. This structure makes it possible to reduce the distance between battery 13 and crankshaft 52 compared to, for example, a structure in which battery 13 is attached to the front surface 33a of down frame portion 33.

[0054] The positional relationship between the battery 13 and the motor unit 20 is not limited to the example shown in Fig. 3. For example, a portion of the lower surface 13b of the battery 13 may be located higher than a horizontal line H2 passing through the lower end 21a of the electric motor 21.

[0055] Furthermore, the battery 13 may be attached to the rear surface 33b of the down frame portion 33, and the lower end 13a thereof may be located below the rotation center Cm of the electric motor 21. In this case, the down frame portion 33 may be formed to allow such an arrangement of the battery 13.

[0056] 5, the distance W1 from the center of the crankshaft 52 to the end 13c of the battery 13 is shorter than the distance W2 from the crankshaft 52 to the rotation center Cm of the electric motor 21. (In this description, the end 13c of the battery 13 refers to the rear end of the lower part of the battery 13.)

[0057] 5, the motor unit 20 is disposed so that the position of the output shaft 23 is higher than that of the electric motor 21. Therefore, the distance W1 is shorter than the distance from the crankshaft 52 to the output shaft 23.

[0058] Depending on the posture of the motor unit 20 (the positional relationship between the electric motor 21 and the output shaft 23), the distance W1 may be smaller than only one of the distance W2 from the crankshaft 52 to the center of rotation Cm of the electric motor 21 and the distance W2 from the crankshaft 52 to the output shaft 23.

[0059] The layout of the battery 13 and the electrical component case 17 utilizes the space formed below the motor unit 20. Therefore, as shown in Figure 4, a vertical line V1 passing through the front end of the motor unit 20 may intersect with the rear of the battery 13. The vertical line V1 may also intersect with the electrical component case 17.

[0060] In this way, the battery 13 is positioned close to the motor unit 20. More specifically, as shown in Figure 5, the distance W3 between the outer circumferential surface of the electric motor 21 and the battery 13 may be smaller than the radius of the electric motor 21.

[0061] [Motor unit and rear suspension placement] As shown in Figure 4, the bracket 35 that supports the lower end of the rear suspension 47 is located between the motor unit 20 and the lower part of the battery 13. In detail, a horizontal line H1 (see Figure 5) that passes through the rotation center Cm of the electric motor 21 intersects with the bracket 35 and the lower part of the battery 13. In this way, the bracket 35 is arranged using the space between the motor unit 20 and the battery 13 (in other words, the space between the motor unit 20 and the down frame portion 33).

[0062] 4, a lower end 47a of the rear suspension 47 is located in front of the motor unit 20. An upper end 47b (see FIG. 2) of the rear suspension 47 is located above the motor unit 20.

[0063] As shown in Figure 4, the motor unit 20 is positioned so that the output shaft 23 is located above the electric motor 21. This allows the heavy electric motor 21 to be positioned lower, reducing the moment of inertia around the crankshaft 52. As a result, it is easier for the rider to change the position of the bicycle 10 when riding on rough terrain.

[0064] [Relative position of motor unit and frame] As shown in FIG. 2, the main frame portion 34 is bifurcated midway. That is, the main frame portion 34 has a right extension portion 34R and a left extension portion 34L that are separated in the left-right direction. The main frame portion 34 has a first extension portion 34A connected to the head tube 31. The left and right extension portions 34L, 34R extend obliquely rearward and downward from the first extension portion 34A. Then, each extension portion 34L, 34R bends and extends downward. The extension portions 34L, 34R constitute a part of the front portion 34a (see FIG. 1) and a rear portion 34b (see FIG. 1) of the main frame portion 34. The lower end of each extension portion 34R, 34L is connected to the upper end 32b (see FIG. 3) of the rear of the frame bottom portion 32.

[0065] The motor unit 20 may be positioned so as to overlap a portion of one or both of the extension portions 34R and 34L in a side view of the bicycle 10. In the bicycle 10, as shown in Figure 4, the motor unit 20 is positioned so that the rearmost portion of the electric motor 21 overlaps with the right extension portion 34R.

[0066] This arrangement of the motor unit 20 allows the position of the motor unit 20 to be shifted rearward to the position of the extensions 34R and 34L, which makes it easy to reduce the distance between the battery 13, which is located in front of the motor unit 20, and the crankshaft 52.

[0067] The positional relationship between the motor unit 20 and the extensions 34R, 34L is not limited to the example described above. For example, a recess may be formed in the front surface 34c (see FIG. 4) of one or both of the extensions 34R, 34L, and a portion of the motor unit 20 may be disposed in this recess. For example, a recess may be formed in the left extension 34L, and a portion of the motor unit 20 may be disposed in this recess. This structure also allows the position of the motor unit 20 to be shifted rearward. Even in this case, no such recess may be formed in the right extension 34R, and the rearmost portion of the right extension 34R may overlap with the electric motor 21.

[0068] Alternatively, the rearmost portion of the motor unit 20 may be disposed between the left and right extension portions 34L and 34R. That is, the rearmost portion of the motor unit 20 may overlap both the left and right extension portions 34L and 34R in a side view of the vehicle. Alternatively, recesses may be formed in both the left and right extension portions 34L and 34R.

[0069] As a result of the motor unit 20 being positioned rearward in this manner, a vertical line V2 (see FIG. 5) passing through the rear end of the electric motor 21 intersects with the bottom bracket 51. This makes it easy to reduce the distance between the battery 13 and the crankshaft 52. As shown in FIG. 1, the entire motor unit 20 may be positioned forward of the rear end of the sprocket 52a of the crankshaft 52. Alternatively, the entire motor unit 20 may be positioned forward of the rear surfaces of the extensions 34R and 34L.

[0070] [Motor unit support structure using a frame] The motor unit 20 is supported by a frame 30. As shown in FIG. 3, the housing 22 of the motor unit 20 has an attachment portion 22b at its uppermost portion. The attachment portion 22b is fixed to the left and right extension portions 34R and 34L by fastening portions (e.g., screws) via a bracket 37. The housing 22 also has an attachment portion 22c at its lowermost portion. The attachment portion 22c is fixed to the frame bottom portion 32 by fastening portions (e.g., screws). The attachment portion 22c of the housing 22 may be fixed to the down frame portion 33.

[0071] [Rear arm placement] As described above, the bicycle 10 has a rear arm 48 (see FIG. 2). The rear arm 48 is connected to the main frame 34 via the pivot shaft 39. Therefore, the rear arm 48 is capable of moving up and down around the pivot shaft 39. As shown in FIG. 5, the position of the pivot shaft 39 is higher than the rotation center Cm of the electric motor 21. By positioning the pivot shaft 39 higher in this way, when the rear wheel 12 runs over a bump on the road, the direction of movement of the rear wheel 12 is tilted rearward relative to the vertical, as shown by arrow D1 in FIGS. 1 and 4. As a result, the impact when the rear wheel 12 collides with a bump can be mitigated, allowing the rear wheel 12 to smoothly run over the bump.

[0072] As shown in FIG. 5, both the pivot shaft 39 and the output shaft 23 of the motor unit 20 are positioned higher than the rotation center Cm of the electric motor 21. The output shaft 23 is located forward of the pivot shaft 39. More specifically, the pivot shaft 39 and the output shaft 23 may be arranged so that a straight line extending in the front-to-rear direction intersects both of these two axes. For example, the pivot shaft 39 and the output shaft 23 may be positioned at substantially the same height. This layout allows the distance between the pivot shaft 39 and the output shaft 23 to be reduced. In the example shown in FIG. 5, the distance W3 from the output shaft 23 of the motor unit 20 to the pivot shaft 39 is shorter than the distance W4 from the output shaft 23 to the crankshaft 52. By reducing the distance between the pivot shaft 39 and the output shaft 23 in this way, the movement of the rear wheel 12 can be made smoother. This will be explained below.

[0073] As shown in Figure 4, the axle 12a of the rear wheel 12 is supported by the rearmost portion 42a of the second link member 42, which is located further rearward than the rear end of the rear arm 48. The rearmost portion 42a is connected to the rear end of the rear arm 48 via a connecting shaft 43c. Therefore, when the bicycle 10 travels over an uneven road, the rear wheel 12 moves up and down around a swing center Cs (see Figure 4), which is located slightly forward of the pivot shaft 39. By reducing the distance between the pivot shaft 39 and the output shaft 23, the distance between the swing center Cs and the output shaft 23 can also be reduced.

[0074] As described above, since the pivot shaft 39 is positioned higher than the axle 12a of the rear wheel 12, when the rear wheel 12 rides over a bump on the road, the rear wheel 12 tends to move diagonally rearward and upward (in the direction D1 shown in FIG. 4). If the distance between the swing center Cs (see FIG. 4) of the rear wheel 12 and the output shaft 23 is large, the higher the position of the rear wheel 12, the greater the distance between the axle 12a of the rear wheel 12 and the output shaft 23. This increases the tension acting on the chain 18, hindering the movement of the rear wheel 12. By placing both the pivot shaft 39 and the output shaft 23 higher than the rotation center Cm of the electric motor 21 and reducing the distance between the swing center Cs and the output shaft 23, it is possible to prevent the tension acting on the chain 18 from becoming excessive. The swing center Cs may be positioned at the same position as the output shaft 23.

[0075] [Seat support device] The bicycle 10 has a seat support device 60. The seat support device 60 has a seat post 61 and a connecting arm 62, as shown in FIG.

[0076] As shown in FIG. 6, the seat post 61 has a lower post 61A and an upper post 61B. The lower post 61A is movable forward and backward around a support shaft 64a having an axis along the left-right direction. The support shaft 64a is located at the lower part of the lower post 61A. As shown in FIG. 3, a clamp member 64 is fixed to the lower part of the lower post 61A. The clamp member 64 is annular. The lower post 61A is fitted inside and held in place by the clamp member 64. The clamp member 64 is supported by the main frame portion 34 via the support shaft 64a. Therefore, the lower post 61A is movable forward and backward relative to the main frame portion 34 around the support shaft 64a. The mounting position of the clamp member 64 is not limited to the example shown in FIG. 6. The clamp member 64 may be located at or near the center of the lower post 61A in the up-down direction.

[0077] As shown in FIG. 6, the upper post 61B extends upward from the lower post 61A. The upper side of the upper post 61B supports the seat 19 (see FIG. 1). The upper end of the upper post 61B is attached to a seat stay 65, and the seat 19 is attached to this seat stay 65. The upper post 61B is movable up and down relative to the lower post 61A. In other words, the upper post 61B can move relative to the lower post 61A in the extension direction of the seat post 61. The lower post 61A is cylindrical, and the upper post 61B is inserted inside it. Conversely, the lower post 61A may be inserted inside the upper post 61B.

[0078] [Seat position adjustment mechanism] The seat post 61 has a seat position adjustment mechanism M inside it. As shown in Fig. 6, the seat position adjustment mechanism M switches between a locked state in which the relative position of the upper post 61B and the lower post 61A is locked, and an unlocked state in which the relative position of the upper post 61B and the lower post 61A is allowed to change. The user adjusts the position (height) of the seat 19 with the seat position adjustment mechanism M in the unlocked state, and then sets the seat position adjustment mechanism M to the locked state.

[0079] The seat position adjustment mechanism M has a biasing means that biases the upper post 61B upward relative to the lower post 61A in the unlocked state. The biasing means is realized, for example, by a gas chamber 61e filled with high-pressure gas, which will be described later, and an oil chamber 61f filled with hydraulic oil. The seat position adjustment mechanism M also has an operating unit 66 that can be operated by a user. The seat position adjustment mechanism M can be switched between a locked state and an unlocked state by operating the operating unit 66.

[0080] The seat post 61 is called a dropper seat post, and the seat position adjustment mechanism M operates, for example, as follows. When the seat post 61 is set to the unlocked state by operating the operating unit 66, the upper post 61B automatically moves upward due to the action of the biasing means, and as a result, the position of the seat 19 becomes higher. In this unlocked state, when the user presses down on the seat 19 against this biasing force, the position of the upper post 61B (the position of the seat 19) drops. When the seat post 61 is set to the locked state by operating the operating unit 66, the height of the upper post 61B is fixed.

[0081] As shown in FIG. 6, the seat position adjustment mechanism M has a gas chamber 61e, a first oil chamber 61f, and a second oil chamber 61g within the seat post 61. The gas chamber 61e and the oil chambers 61f and 61g are separated by a free piston 61h. The first oil chamber 61f and the second oil chamber 61g are separated by a piston 61i. An oil flow path is formed in the piston 61i. Oil can move between the first oil chamber 61f and the second oil chamber 61g through this oil flow path. A valve 61m that opens and closes the oil flow path is attached to the piston 61i. The piston 61i is fixed to the tip of a piston rod 61j. The piston rod 61j passes upward through the second oil chamber 61g. The piston rod 61j is cylindrical, and a push rod 61k is disposed inside the piston rod 61j. A valve 61m provided in an oil flow path of the piston 61i can be operated by moving the push rod 61k in the axial direction of the seat post 61. The push rod 61k and an operating unit 66 are connected via, for example, a cable 67, and the user can operate the push rod 61k through the operating unit 66. The operating unit 66 may be, for example, a button or lever attached to the steering handlebars 15.

[0082] The seat position adjustment mechanism M operates as follows. When the push rod 61k is pushed via the operating unit 66 to open the valve 61m, the seat post 61 enters an unlocked state. At this time, the first oil chamber 61f and the second oil chamber 61g communicate with each other via an oil passage formed in the piston 61i. The pressure in the gas chamber 61e causes oil to move from the second oil chamber 61g to the first oil chamber 61f via the oil passage, and the upper post 61B moves upward. Conversely, when the user presses down on the seat 19 against the pressure of the gas chamber 61e, oil moves from the first oil chamber 61f to the second oil chamber 61g via the oil passage, and the upper post 61B moves downward.

[0083] The structure of the seat position adjustment mechanism M is not limited to the example shown in Fig. 6. The seat position adjustment mechanism M may have other structures as long as it is capable of switching the seat post 61 between an unlocked state and a locked state and has the function of urging the upper post 61B upward at least in the unlocked state.

[0084] [Connecting arm] As shown in FIG. 6, the rear of the connecting arm 62 is connected to the upper post 61B. More specifically, a clamp member 68 (see FIG. 2) is attached to the upper post 61B. The upper post 61B is fitted inside the clamp member 68 and held therein. The clamp member 68 is connected to the rear end of the connecting arm 62 via a connecting shaft 62a. The connecting shaft 62a has an axis that runs along the left-right direction. This connecting structure allows the angle between the upper post 61B and the connecting arm 62 to change depending on the position (height) of the upper post 61B.

[0085] 6, a support shaft 62b is disposed in front of the seat post 61. The support shaft 62b also has an axis that runs in the left-right direction. The front portion of the connecting arm 62 is supported by the support shaft 62b so that the connecting arm 62 can move up and down around the support shaft 62b. The support shaft 62b is supported by the main frame portion 34. In other words, the front portion of the connecting arm 62 is connected to the main frame portion 34 via the support shaft 62b.

[0086] [Movement of the seat support device] The seat post 61 can move between a high post state and a low post state. The high post state is a state in which the upper post 61B and the seat 19 are positioned at a relatively high position, and is, for example, the state (position and length) of the seat post 61 shown by the two-dot chain line in FIG. 7. The low post state is a state in which the upper post 61B and the seat 19 are positioned at a relatively low position, and is, for example, the state (position and length) of the seat post 61 shown by the solid line in FIG. 7. The seat post 61 can also be positioned in an intermediate state.

[0087] As described above, the lower post 61A is supported by the support shaft 64a, and the frontmost portion of the connecting arm 62 is supported by the support shaft 62b. Therefore, when the seat post 61 moves between the high-post state and the low-post state, the position of the upper post 61B in the fore-and-aft direction (the position of the seat 19 in the fore-and-aft direction) also changes. As shown in Figure 7, the position of the upper post 61B in the low-post state is further rearward than the position of the upper post 61B in the high-post state.

[0088] With this seat support device 60, when going up a slope, for example, the rider can position the seat post 61 in the high-post state to comfortably pedal the pedals 53. Also, when going down an uneven slope, for example, the rider can position the seat post 61 in the low-post state to easily move his / her body along the unevenness.

[0089] As described above, the lower post 61A is held by the clamp member 64 and supported by the support shaft 64a. The clamp member 64 may be fixed to the lower post 61A with, for example, a screw. The position of the clamp member 64 on the lower post 61A may be adjustable in the up and down direction by loosening the screw. By adjusting the position of the clamp member 64, the position of the seat post 61 in both the high-post state and the low-post state can be raised or lowered.

[0090] A clamp member 68 is fixed to the upper post 61B. As shown by the solid line in FIG. 7, when the seat post 61 is in the low post state, the clamp member 68 may be in contact with the upper end of the lower post 61A. In other words, the movable range of the upper post 61B may be restricted by the clamp member 68. The clamp member 68 may be fixed to the upper part of the upper post 61B, for example. This ensures a sufficient movable range for the seat 19.

[0091] The clamp member 68 may also be fixed to the upper post 61B with, for example, a screw. The position of the clamp member 68 on the upper post 61B may be adjustable in the vertical direction by loosening the screw. By adjusting the position of the clamp member 68, the position of the upper post 61B in the low post state, in other words, the lowest position of the upper post 61B, can be raised or lowered.

[0092] As shown in Figure 6, when the seat post 61 is in the high post state, the position of the support shaft 62b that supports the connecting arm 62 is lower than the height of the upper end of the upper post 61B. Due to this positional relationship, when the seat post 61 moves from the high post state to the low post state, the position of the upper end of the upper post 61B and the seat 19 moves rearward, as shown in Figure 7.

[0093] [Shape of connecting arm] 6, the connecting arm 62 is curved so as to bulge downward from a straight line L1 connecting the connecting shaft 62a located at the rear of the connecting arm 62 and the support shaft 62b located at the front of the connecting arm 62. This shape of the connecting arm 62 makes it easy for the rider to dismount onto the front side of the seat 19, for example, when the seat post 61 is in the high-post state.

[0094] As shown in Figure 6, the connecting arm 62 has a rear extending portion 62c and a front extending portion 62d extending from the rear extending portion 62c. When the seat post 61 is in the high post state, the rear extending portion 62c extends diagonally forward and downward from the portion (connecting shaft 62a) connected to the clamp member 68. The front extending portion 62d is bent from the rear extending portion 62c. The front extending portion 62d extends generally forward. The front extending portion 62d may also extend diagonally upward.

[0095] [Support structure for connecting arms] As described above, the main frame portion 34 has a right extension portion 34R and a left extension portion 34L. As shown in FIG. 2, the front portion of the connecting arm 62 is disposed between the right extension portion 34R and the left extension portion 34L, and the support shaft 62b is supported by the extension portions 34R and 34L. In a plan view of the bicycle 10, the connecting arm 62 is located between the right extension portion 34R and the left extension portion 34L. This structure allows for greater flexibility in the position and shape of the connecting arm 62. For example, it is possible to position the connecting arm 62 so that it partially overlaps the extension portions 34R and 34L in a side view.

[0096] 7, when the seat post 61 is in the low-post position, the connecting arm 62 can be positioned so that the front extension 62d of the connecting arm 62 overlaps with the extensions 34R and 34L. By positioning the front extension 62d so that it overlaps with the extensions 34R and 34L, the effect of the connecting arm 62 on the rider's getting on and off the bicycle can be reduced.

[0097] The positional relationship between the connecting arm 62 and the main frame portion 34 is not limited to the examples shown in Figures 6 and 7. For example, depending on the shape of the connecting arm 62 and the position (height) of the main frame portion 34, the rear extension portion 62c of the connecting arm 62 may partially overlap the extension portions 34R and 34L.

[0098] [Seatpost support structure] 2 and 3, the support shaft 64a of the clamp member 64 that holds the seat post 61 is disposed between the left extension 34L and the right extension 34R of the main frame portion 34, and is supported by these extensions 34L and 34R. The lower part of the seat post 61 is disposed between the right extension 34L and the left extension 34L.

[0099] This arrangement of the seat post 61 and the main frame portion 34 facilitates an increase in the degree of freedom in the position of the seat post 61. For example, the seat post 61 can be arranged so that it overlaps the left and right extension portions 34L and 34R in a side view. As a result, the degree of freedom in the position of the seat 19 in the fore-and-aft direction can be increased. In the example shown in FIGS. 6 and 7, the lowest part of the lower post 61A overlaps the bent portion between the front portion 34a and the rear portion 34b of the main frame portion 34.

[0100] 7, the rear portion 34b of the main frame portion 34 (rear portions of the extension portions 34R and 34L) extends generally downward toward the frame bottom portion 32. When the seat post 61 is in the low-post state, the seat post 61 is inclined rearward relative to the extension direction of the rear portion 34b of the main frame portion 34. This allows the seat 19 to be moved rearward relative to the main frame portion 34 when the seat post 61 is in the low-post state.

[0101] As shown in FIG. 2, the second link member 42 has a right link portion 42R and a left link portion 42L. The right link portion 42R and the left link portion 42L each have the rearmost portion 42a and the frontmost portion 42b (see FIG. 3) described above. As shown in FIG. 3, a cross portion 42c is suspended between the frontmost portion 42b of the right link portion 42R and the frontmost portion 42b of the left link portion 42L. The first link member 41 also has a right link portion 41R and a left link portion 41L. The rearmost portion 41b of the right link portion 41R and the rearmost portion 41b of the left link portion 41L of the first link member 41 are connected to the frontmost portion 42b of the right link portion 42R and the frontmost portion 42b of the left link portion 42L of the second link member 42 via a connecting shaft 43a, respectively. The foremost portion 41a of the right link portion 41R and the foremost portion 41a of the left link portion 41L of the first link member 41 are connected to an upper end 47b of a rear suspension 47 via a connecting shaft 43b.

[0102] The seat post 61 is disposed between the right link portion 41R and the left link portion 41L of the first link member 41. The seat post 61 is also located between the upper end 47b of the rear suspension 47 and the cross portion 42c of the second link member 42, and is movable in the front-to-rear direction between the upper end 47b and the cross portion 42c.

[0103] [summary] (1) The electrically assisted bicycle 10 comprises a bottom bracket 51 supporting a crankshaft 52, an electric motor 21, a housing 22 accommodating the electric motor 21, a motor unit 20 positioned away from the bottom bracket 51 and having an output shaft 23 protruding from the housing 22 for outputting the torque of the electric motor 21, a head tube 31 supporting the steering shaft 16, a frame 30 having a frame bottom 32 supporting the bottom bracket 51 and a down frame portion 33 extending diagonally downward from the head tube 31 toward the frame bottom 32, and a battery 13 attached to the down frame portion 33. The motor unit 20 is located above the bottom bracket 51 and behind the battery 13, and the lower end 13a of the battery 13 is located below the center of rotation Cm of the electric motor 21.

[0104] With this electrically assisted bicycle 10, the distance between the crankshaft 52 and the battery 13 can be reduced, and the moment of inertia of the bicycle 10 around the crankshaft 52 can be reduced. As a result, when riding on rough terrain, the rider can easily change the position of the bicycle 10 through operation.

[0105] (2) In the power-assisted bicycle 10 of (1), the entire lower surface 13b of the battery 13 may be located lower than the lower end 21a of the electric motor 21. With this structure, the distance between the crankshaft 52 and the battery 13 can be further reduced.

[0106] (3) In the electrically assisted bicycle 10 of (1) or (2), the distance W1 from the crankshaft 52 to the end 13c of the battery 13 is smaller than at least one of the distance W2 from the crankshaft 52 to the center of rotation Cm of the electric motor 21 and the distance from the crankshaft 52 to the center of rotation of the output shaft 23.

[0107] (4) Any of the electric assist bicycles 10 described in (1) to (3) may have a rear arm 48 connected to the frame 30 via a pivot shaft 39, and a rear suspension that supports the rear arm 48 so that the rear arm 48 can move up and down.

[0108] (5) In the electrically assisted bicycle 10 of (4), the position of the pivot shaft 39 may be higher than the center of rotation Cm of the electric motor 21. By positioning the pivot shaft 39 higher in this way, for example, when the rear wheel 12 rides over a bump on the road, the direction of movement of the rear wheel 12 is tilted rearward relative to the vertical. As a result, the rear wheel 12 can ride over the bump smoothly, and the impact when the rear wheel 12 hits the bump can be mitigated.

[0109] (6) The electrically assisted bicycle 10 of (4) or (5) may have a sprocket 52a mounted on the crankshaft 52, a sprocket 23a mounted on the output shaft 23, and a chain 18 wound around the sprocket 52a and the sprocket 23a. The positions of both the pivot shaft 39 and the output shaft 23 may be higher than the center of rotation Cm of the electric motor 21. With this structure, the distance W3 between the pivot shaft 39 and the output shaft 23 can be reduced, and as a result, the distance between the swing center Cs of the rear wheel 12 and the output shaft 23 can also be reduced. This prevents excessive tension from acting on the chain 18 when the rear wheel 12 moves up and down.

[0110] (7) In any of the electrically assisted bicycles 10 described in (4) through (6), the output shaft 23 may be located in front of the pivot shaft 39. This structure allows the distance W3 between the pivot shaft 39 and the output shaft 23 to be reduced, and as a result, the distance between the swing center Cs of the rear wheel 12 and the output shaft 23 can also be reduced. This prevents excessive tension acting on the chain 18 when the rear wheel 12 moves up and down.

[0111] (8) In the power-assisted bicycle 10 of any one of (4) to (7), the distance W3 from the output shaft 23 to the pivot shaft 39 may be smaller than the distance W4 from the output shaft 23 to the crankshaft 52.

[0112] (9) The electrically assisted bicycle 10 of any one of (1) to (8) has a sprocket 52a mounted on the crankshaft 52, a sprocket 23a mounted on the output shaft 23 and having fewer teeth than the sprocket 52a, and a chain 18 wound around the sprockets 52a and 23a to transmit their rotation to the rear wheel 12. This structure allows the structure around the crankshaft 52 to be smaller than, for example, a structure in which the rotation of the output shaft 23 is transmitted to the crankshaft 52 via a gear. As a result, the distance between the axle 12a of the rear wheel 12 and the crankshaft 52 can be reduced, making it easier to change the position of the bicycle 10 (for example, to perform a wheelie).

[0113] (10) In any of the electrically assisted bicycles 10 described in (1) through (9), the battery 13 may be housed in the down frame portion 33. This allows the distance between the crankshaft 52 and the battery 13 to be smaller than, for example, a structure in which the battery 13 is attached to the front side of the down frame portion 33.

[0114] (11) In any of the electrically assisted bicycles 10 described in (1) through (10), the output shaft 23 may be positioned above the electric motor 21. This allows the heavy electric motor 21 to be positioned closer to the crankshaft 52, thereby further reducing the moment of inertia of the bicycle 10.

[0115] (12) In any one of the electrically assisted bicycles 10 described in (1) to (11), the frame 30 may have a main frame portion 34 extending rearward from the head tube 31 and positioned above the down frame portion 33. At least the rear of the main frame portion 34 may have a right extension portion 34R and a left extension portion 34L that are separated in the left-right direction, and a portion of the motor unit 20 may overlap at least one of the right extension portion 34R and the left extension portion 34L in a side view. In this way, by shifting the position of the motor unit 20 rearward to the positions of the extension portions 34R and 34L, it is easy to reduce the distance between the battery 13 and the crankshaft 52.

[0116] [others] The power-assisted bicycle proposed in this disclosure is not limited to the power-assisted bicycle 10 described with reference to FIG. 1 and the like.

[0117] For example, the electrically assisted bicycle 10 does not have to have the above-described seat support device 60. In this case, the seat 19 may be supported by a seat post fixed to the main frame portion 34.

[0118] Furthermore, the position and posture of the rear suspension 47 are not limited to the example shown in Fig. 1 etc. For example, the rear suspension 47 may be disposed along the front-rear direction. [Explanation of symbols]

[0119] 10: Electrically assisted bicycle, 11: Front wheel, 12: Rear wheel, 12a: Axle, 12b: Sprocket, 13: Battery, 13a: Lower end, 13b: Lower surface, 13c: End, 14: Front fork, 15: Steering handle, 15a: Grip, 16: Steering shaft, 17: Electrical equipment case, 18: Chain, 19: Seat, 20: Motor unit, 21: Electric motor, 21a: Lower end, 22: Housing, 22b: Mounting portion, 22c: Mounting portion, 23: Output shaft, 23a: Sprocket, 30 : Frame, 31: Head tube, 32: Frame bottom, 32a: Recess, 32b: Upper end, 32c: Upper end, 33: Down frame portion, 33a: Front surface, 33b: Rear surface, 34: Main frame portion, 34A: First extension portion, 34L: Left extension portion, 34R: Right extension portion, 34a: Front portion, 34b: Rear portion, 34c: Front surface, 35: Bracket, 36: Support shaft, 37: Bracket, 39: Pivot shaft, 40: Link mechanism, 41: First link member, 41L: Left link portion, 41R: Right link portion, 41a: Frontmost portion, 4 1b: rearmost portion, 42: second link member, 42R: right link portion, 42a: rearmost portion, 42b: frontmost portion, 42c: cross portion, 43a to 43c: connecting shaft, 47: rear suspension, 47a: lower end, 47b: upper end, 48: rear arm, 51: bottom bracket, 52: crankshaft, 52a: sprocket, 52d: crank arm, 53: pedal, 60: seat support device, 61: seat post, 61A: lower post, 61B: upper post, 61e: gas chamber, 61f: first oil chamber, 61g: second oil chamber chamber, 61h: free piston, 61i: piston, 61j: piston rod, 61k: push rod, 61m: valve, 62: connecting arm, 62a: connecting shaft, 62b: support shaft, 62c: rear extension portion, 62d: front extension portion, 64: clamp member, 64a: support shaft, 65: seat stay, 66: operating portion, 67: cable, 68: clamp member, 71a and 71b: fastening members, Cm: center of rotation, Cs: center of oscillation, D1: direction of movement of rear wheel, H1: horizontal line, H2: horizontal line, M: seat position adjustment mechanism.

Claims

1. a bottom bracket supporting the crankshaft; a motor unit having an electric motor, a housing that accommodates the electric motor, and an output shaft that protrudes from the housing and outputs torque of the electric motor, the motor unit being disposed away from the bottom bracket; a frame having a head tube for supporting a steering shaft, a frame bottom portion supporting the bottom bracket, and a down frame portion extending obliquely downward from the head tube toward the frame bottom portion; a battery attached to the down frame portion; a rear arm connected to the frame via a pivot shaft; a rear suspension that supports the rear arm so that the rear arm can move up and down; and the motor unit is located above the bottom bracket and behind the battery, a lower end of the battery is located below the rotation center of the electric motor; The pivot shaft is positioned higher than the rotation center of the electric motor. Electric assist bicycle.

2. a bottom bracket supporting the crankshaft; a motor unit having an electric motor, a housing that accommodates the electric motor, and an output shaft that protrudes from the housing and outputs torque of the electric motor, the motor unit being disposed away from the bottom bracket; a frame having a head tube for supporting a steering shaft, a frame bottom supporting the bottom bracket, a down frame portion extending obliquely downward from the head tube toward the frame bottom, and a main frame portion extending rearward from the head tube and positioned above the down frame portion; a battery attached to the down frame portion; and the motor unit is located above the bottom bracket and behind the battery, a lower end of the battery is located below the rotation center of the electric motor; At least a rear portion of the main frame portion has a right extension portion and a left extension portion that are separated in the left-right direction, A portion of the motor unit overlaps with at least one of the right extension portion and the left extension portion in a side view. Electric assist bicycle.

3. The entire lower surface of the battery is located below the lower end of the electric motor.

3. An electrically assisted bicycle according to claim 1 or 2.

4. The distance from the crankshaft to the end of the battery is smaller than at least one of the distance from the crankshaft to the rotation center of the electric motor and the distance from the crankshaft to the rotation center of the output shaft.

3. An electrically assisted bicycle according to claim 1 or 2.

5. a rear arm connected to the frame via a pivot shaft; a rear suspension that supports the rear arm so that the rear arm can move up and down; 3. The electrically assisted bicycle according to claim 2, further comprising:

6. The pivot shaft is positioned higher than the rotation center of the electric motor.

6. An electrically assisted bicycle according to claim 5.

7. a first sprocket provided on the crankshaft; a second sprocket provided on the output shaft; a chain wound around the first sprocket and the second sprocket; and The pivot shaft and the output shaft are both positioned higher than the rotation center of the electric motor.

6. An electrically assisted bicycle according to claim 1 or 5.

8. The output shaft is located in front of the pivot shaft.

6. An electrically assisted bicycle according to claim 1 or 5.

9. The distance from the output shaft to the pivot shaft is shorter than the distance from the output shaft to the crankshaft.

6. An electrically assisted bicycle according to claim 1 or 5.

10. a first sprocket provided on the crankshaft; a second sprocket provided on the output shaft and having a number of teeth less than the number of teeth of the first sprocket; a chain wound around the first sprocket and the second sprocket to transmit their rotation to a rear wheel; 3. The electrically assisted bicycle according to claim 1 or 2, further comprising:

11. The battery is housed in the down frame portion.

3. An electrically assisted bicycle according to claim 1 or 2.

12. The output shaft is located above the electric motor.

3. An electrically assisted bicycle according to claim 1 or 2.

13. the frame has a main frame portion extending rearward from the head tube and positioned above the down frame portion, At least a rear portion of the main frame portion has a right extension portion and a left extension portion that are separated in the left-right direction, A portion of the motor unit overlaps with at least one of the right extension portion and the left extension portion in a side view.

2. The electrically assisted bicycle according to claim 1.

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