Power assist device for manual wheelchair

Abstract

A power assist device (1) is attached to a wheel (2) of a manual wheelchair. The device (1) comprises: an attachment bracket (11) supported by a hand rim (5); a drive unit (12) supported above the bracket (11); and a battery unit (13) supported below the bracket (11). The center of gravity (G) of the battery unit (13) is positioned between a support point (P0) of the bracket (11) with respect to the hand rim (5) and a contact point (P1) of a drive roller (36) with respect to the wheel (2) in the width direction of the manual wheelchair. Due to a moment about the support point (P0), the weight of the battery unit (13) contributes to an increase in contact pressure between the wheel (2) and the drive roller (36).

Description

Electric Assist Device for Manual Wheelchairs

[0001] The present invention relates to an electric assist device for manual wheelchairs that realizes simple electrification by being attached to a general manual wheelchair.

[0002] Attempts have been made to simply electrify general manual wheelchairs. For example, Patent Document 1 discloses an electric assist device that drives a manual wheelchair by rotating a friction roller that contacts the wheels of the manual wheelchair with an electric motor.

[0003] In the electric assist device of Patent Document 1, a friction roller supported by the frame of the manual wheelchair is located above the wheels of the wheelchair, and the outer peripheral surface of this friction roller contacts the outer peripheral surface of the wheels of the wheelchair, so that driving torque is transmitted from the friction roller to the wheels. Also, the battery is attached to the frame of the manual wheelchair at a position separate from the friction roller.

[0004] In the electric assist device as described above, if the transmission of driving torque due to friction between the friction roller and the wheels is not performed well, slipping of the friction roller occurs and the operability deteriorates. Although Patent Document 1 describes a spring-type unit connected to the friction roller, in a configuration that obtains the contact pressure between the friction roller and the wheels using such a spring member, the mechanical structure tends to become complex.

[0005] Japanese Patent Publication No. 2021-514799

[0006] This invention relates to an electric assist device to be attached to the wheel of a manual wheelchair, comprising: a mounting bracket attached to the handrim having a hollow passage curved in an arc shape through which the handrim can pass, and the handrim being slidably fitted into the hollow passage; a drive unit having a first housing supported by the mounting bracket, and including a drive roller that contacts the outer surface of the wheel and an electric motor that drives the drive roller; and a battery unit having a second housing supported by the mounting bracket and located on the inner circumference side of the handrim, and housing a battery, wherein the center of gravity of the battery unit is located in the width direction of the manual wheelchair between the support point of the mounting bracket on the handrim and the contact point of the drive roller on the wheel.

[0007] In this configuration, the drive unit, battery unit, and mounting bracket that constitute the electric assist device are integrated, and the entire unit is supported by the manual wheelchair by attaching the mounting bracket to the handrim of the manual wheelchair. The drive roller of the drive unit rotates due to the electric motor, transmitting rotational torque to the wheel. The reaction force acting on the electric assist device at this time is supported by the user sitting in the wheelchair holding the electric assist device with their hands. During movement, the handrim, which rotates together with the wheel, passes through the hollow passage of the mounting bracket.

[0008] Here, the center of gravity of the battery unit is located between the support point and the contact point in the width direction of the manual wheelchair. As a result, the weight of the heavy battery unit generates a moment around the support point, increasing the contact pressure between the drive roller and the wheel at the contact point.

[0009] According to this invention, the weight of the battery unit is effectively utilized to increase the contact pressure between the drive roller and the wheel, thereby suppressing slippage of the drive roller.

[0010] A side view of the main part of a manual wheelchair equipped with an electric assist device according to one embodiment. A top view of the same. A rear view of the manual wheelchair as seen from the rear. A perspective view of the same. A cross-sectional view of the main part along line A-A in Figure 1. A perspective view of the electric assist device. A side view of the electric assist device. A front view of the electric assist device. A rear view of the electric assist device. A top view of the electric assist device. A cross-sectional view along line B-B in Figure 7. A cross-sectional view along line C-C in Figure 11. A cross-sectional view along line D-D in Figure 7. An explanatory diagram of the electric motor and drive roller. An explanatory diagram of the moment generated in the electric assist device. A cross-sectional view of the main part showing the fixing structure of the outer cover of the battery unit housing.

[0011] Hereinafter, an embodiment of this invention will be described in detail with reference to the drawings. Figures 1 to 4 show the electric assist device 1 of one embodiment mounted on the wheel 2 of a manual wheelchair. The entire manual wheelchair is not shown, and only one wheel 2 (for example, the right side) which is the so-called rear wheel and a part of the frame 3 are shown in Figures 1 to 4. The manual wheelchair has a general configuration, with a seat section where the user sits between a pair of wheels 2, and a pair of small-diameter front wheels (not shown) at the front of the frame 3 that supports the seat section and the wheels 2.

[0012] The wheel 2 is rotatably supported by the frame 3, and a handrim 5 is provided on the outside of the wheel 2 for the user to rotate the wheel 2 with their own hands. The handrim 5 is constructed by connecting metal tubes or metal rods with a circular cross-section in a ring shape, and is positioned slightly outside the wheel 2 and parallel to the wheel 2, and has a diameter slightly smaller than the outer diameter of the wheel 2. It is fixed to the wheel 2 via a plurality of connecting pieces 6 provided at equal angular intervals. On the inside of the wheel 2 (inside in the width direction of the manual wheelchair), a protective plate 4 is provided as part of the frame 3 to prevent contact between the user's body and the wheel 2.

[0013] In one embodiment, the electric assist device 1 is attached to the handrim 5 and drives the adjacent wheels 2, and is provided for each of the left and right wheels 2. The figure illustrates the electric assist device 1 for the right wheel 2, and the electric assist device for the left wheel has a symmetrical shape. Here, the electric assist devices 1 provided on both the left and right sides are not fixed in the circumferential direction when attached to the handrim 5, and the user seated on the seat supports the electric assist device 1 in the circumferential direction with both hands. In other words, the user bears the reaction force that acts on the electric assist device 1 when it drives the wheels 2. Figures 1 to 4 show the electric assist device 1 at the top of the wheel 2, assuming that the user is supporting it with their hands.

[0014] In the following description of the electric assist device 1, following the concepts of front-to-back, left-to-right, and up-and-down of a manual wheelchair, the X direction shown in Figures 1 and 2 will be referred to as the "front-to-back" direction, the Y direction as the "left-to-right" direction or "width" direction, and the Z direction as the "up-and-down" direction. Furthermore, it will be assumed that the electric assist device 1 is located at the top of the wheels 2 as shown in Figure 1.

[0015] Figures 6 to 13 show the electric assist device 1 as a standalone unit. As shown in Figures 6 and 7, the electric assist device 1 of one embodiment comprises a mounting bracket 11 for attaching the entire electric assist device 1 to the handrim 5, a drive unit 12 for driving the wheel 2, and a battery unit 13 that serves as a power source, with these three components integrated into a single unit. The drive unit 12 has a drive unit housing 31 made of rigid synthetic resin as its first housing. The drive unit housing 31 is a rectangular box shape with relatively similar dimensions in the front-rear direction and left-right direction, and is located on the outer circumference side of the handrim 5. The battery unit 13 has a battery unit housing 32, also made of rigid synthetic resin, as its second housing. The battery unit housing 32 is an elongated box shape in the front-rear direction, and is located on the inner circumference side of the handrim 5.

[0016] As shown in Figures 8 and 9, the mounting bracket 11 is mainly composed of a tubular portion 16 with a circular cross-section that forms a hollow passage 15 curved in an arc shape through which the handrim 5 can pass. The tubular portion 16 is made of a hard synthetic resin with appropriate elasticity and, as shown in Figures 6 and 7, extends forward and backward while curving in an arc shape with a curvature corresponding to the curvature of the handrim 5, and has a roughly C-shaped cross-section with an open side portion facing the wheel 2. Because the tubular portion 16 has a roughly C-shaped cross-section, it is possible to press-fit the tubular portion 16 into the handrim 5 by utilizing the elasticity of the resin material. In the press-fitted state, the opening width of the side portion is smaller than the diameter of the handrim 5, so the mounting bracket 11 will not naturally fall off the handrim 5. The inner diameter of the tubular section 16, which has a roughly C-shaped cross-section, that is, the diameter of the hollow passage section 15, is set to be slightly larger than the diameter of the handrim 5, allowing the handrim 5 to pass through the hollow passage section 15 in the circumferential direction. In other words, the mounting bracket 11 is configured to move freely in the circumferential direction relative to the handrim 5.

[0017] As shown in Figure 6, a notch 17 is provided in the center of the tubular portion 16 in the longitudinal direction (front-to-back direction) over a relatively large length range to avoid interference with the drive unit housing 31. Within the range of this notch 17, the tubular portion 16 has a shape in which the upper part is cut off, leaving only the lower part (inner circumference) of the C-shaped cross-section. The range in which this notch 17 is formed roughly corresponds to the front-to-back dimension of the drive unit housing 31.

[0018] A pair of drive unit mounting portions 18 for supporting the drive unit 12 are provided at positions adjacent to the front and rear ends of the notch 17 of the tubular portion 16. As shown in Figures 8 and 9, each drive unit mounting portion 18 is equipped with a circular shaft support hole 20, and each of the pair of front and rear cylindrical boss portions 33 formed on the drive unit housing 31 is configured to fit into the shaft support hole 20 of the pair of drive unit mounting portions 18. Specifically, each drive unit mounting portion 18 consists of a fixing piece 18a molded integrally with the tubular portion 16 and a cap 18b fixed to the fixing piece 18a by a screw 19 (see Figure 7). The boss portion 33 is fixed by adjusting the angle of the drive unit 12 with respect to the mounting bracket 11 and then tightening the screw 19. In other words, the inner diameter of the shaft support hole 20 is slightly smaller than the outer diameter of the boss portion 33. The pair of boss portions 33 and the corresponding pair of shaft support holes 20 are configured around a single common center line along the tangential direction of the handrim 5. Therefore, when the screw 19 is loosened, the angle of the drive unit 12 can be adjusted with the above center line as the center of rotation.

[0019] As shown in Figures 5 and 11, the drive unit 12 has a configuration in which a pair of electric motors 35, a drive roller 36, and a reduction gear 37 between them are housed in a drive unit housing 31. As shown in Figure 14, the pair of electric motors 35 are arranged in a front-to-back arrangement, and one drive roller 36 rotates via a reduction gear 37 consisting of the pinion 37a of each electric motor 35 and a relatively large-diameter gear 37b on the drive roller 36 side. As shown in Figure 5, the drive roller 36 is in contact with the outer circumferential surface of the wheel 2, thereby transmitting rotational torque from the drive roller 36 to the wheel 2. As mentioned above, the drive unit 12 is supported with respect to the mounting bracket 11 so that its angle can be adjusted, and by adjusting the angle in accordance with the actual position of the outer circumferential surface of the wheel 2 relative to the handrim 5, it is possible to reliably ensure that the drive roller 36 is in contact with the outer circumferential surface of the wheel 2.

[0020] The drive roller 36 is made of hard synthetic resin or metal, and its outer surface is treated with an appropriate anti-slip finish. The drive roller 36 is rotatably supported at both ends of its rotating shaft by the drive unit housing 31 via bearing members.

[0021] In the drive unit 12, the rotation axis of the drive roller 36 is inclined such that the side facing inward in the width direction of the manual wheelchair is relatively upward. For example, it is inclined at an angle of about 30 to 60° with respect to the horizontal plane. This inclination of the rotation axis of the drive roller 36 makes it possible to relatively minimize both the upward and lateral protrusion of the drive unit 12 from the wheels 2 of the manual wheelchair.

[0022] The uppermost part of the drive unit housing 31 that covers the drive roller 36 has a generally flat shape that follows the horizontal plane. Also, as shown in Figures 6 and 7, a part of the front end of the drive unit housing 31 protrudes forward from the drive roller 36, forming a grip portion 31a that is easy for the user to hold. A part of the upper surface of the drive unit housing 31, more specifically the part where the user's palm rests, is slightly raised as a palm rest surface 61, and a wall portion 62 is provided on the inner side edge of this surface to support the outer surface of the base of the thumb. As shown in the cross-sectional view of Figure 11, the palm rest surface 61 and the wall portion 62 are molded as separate parts from the main body of the drive unit housing 31 (the line S is the boundary line) and are fixed to the main body by adhesive or screws. Furthermore, as shown in Figures 6 and 10, an operation switch 38 is provided on the side of the grip portion 31a. In one embodiment, the operation switch 38 is of the push-button type and is positioned so that it can be pressed by the thumb of the hand resting on the grip portion 31a. Furthermore, the drive unit 12 is equipped with a gravity sensor (not shown) at an appropriate location for switching between forward and reverse movement, as will be described later.

[0023] As shown in Figure 7, the battery unit 13, which has a battery unit housing 32, is supported by being suspended from a mounting bracket 11 mainly consisting of an arc-shaped tubular portion 16. The battery unit housing 32 has a rectangular parallelepiped shape that is long in the front-to-back direction, with a front-to-back length dimension corresponding to the chord of the arc of the tubular portion 16. Inside it, as shown in Figures 11 and 12, are housed two rod-shaped batteries 39 (first battery 39a and second battery 39b) arranged along the longitudinal direction of the battery unit housing 32. Each of the batteries 39a and 39b is a rod-shaped package with an oval cross-section formed by bundling multiple cylindrical batteries together. In a preferred embodiment, the batteries 39a and 39b are rechargeable secondary batteries.

[0024] As shown in Figure 11, the first battery 39a is positioned along the top of the battery unit housing 32 with its oval cross-section oriented horizontally, and the second battery 39b is positioned below the first battery 39a and inside the battery unit housing 32 (inside in the width direction) with its oval cross-section oriented vertically. Because the second battery 39b is positioned off-center inside the battery unit housing 32, a control board housing space 40 for accommodating a control board (not shown) is provided inside the battery unit housing 32 in a relatively outer (outer in the width direction) area. This control board housing space 40 is covered by an outer cover 41 which has a substantially L-shaped cross-section and is part of the battery unit housing 32. The outer cover 41 is detachably fixed to the main body of the battery unit housing 32 by screws 42 on the outer surface and similar screws 42 on the bottom surface, as shown in Figure 7.

[0025] In the illustrated example, the outer cover 41, as shown in Figure 7, includes setting switches 51 for making various settings and a liquid crystal display unit 52. These setting switches 51 and liquid crystal display unit 52 are positioned to face outwards in the left-right direction when the electric assist device 1 is mounted on a manual wheelchair.

[0026] As shown in Figure 11, the battery unit housing 32, which is molded from synthetic resin, has first and second battery housing chambers 53a and 53b, which have an oval cross-section and house the first battery 39a and the second battery 39b, respectively. Also, as shown in Figure 12, the battery unit housing 32 has a front end cap portion 55 and a rear end cap portion 56 at both ends in the longitudinal direction, which form part of the battery unit housing 32. As shown in Figure 12, the front end of the first and second battery housing chambers 53a and 53b is closed, and the rear end is covered by the rear end cap portion 56, forming a battery insertion opening. As shown in Figure 6, the front end cap portion 55 and the rear end cap portion 56 are detachably fixed to the main body portion of the battery unit housing 32 by screws 57. As described above, the front end of the battery housing chambers 53a and 53b is closed, which prevents the batteries 39a and 39b from falling out when the electric assist device 1 is tilted forward. In other words, when the manual wheelchair is moved forward, the electric assist device 1 tilts forward as will be described later, so if the front ends of the battery housings 53a and 53b are insertion openings, the batteries 39a and 39b are likely to fall out. The batteries 39a and 39b are loaded into the first and second battery housings 53a and 53b, respectively, with the rear end caps 56 removed.

[0027] The control board housing space 40 is separated from the first and second battery housing compartments 53a and 53b by partition walls 58a and 58b, which are molded as part of the battery unit housing 32. Although not shown in Figure 11, the aforementioned screws 42 for fixing the outer cover 41 are screwed into the thickened portions of the partition walls 58a and 58b, as shown in Figure 16. Furthermore, the front end cap portion 55 and the rear end cap portion 56 are provided with air vents 59a and 59b at positions corresponding to the respective control board housing spaces 40, as shown in Figures 8 and 9. These two air vents 59a and 59b allow outside air to flow along the longitudinal direction within the control board housing space 40, enabling effective cooling of the control board inside.

[0028] Furthermore, as shown in Figure 13, the ceiling wall of the rear end cap portion 56 is formed with a roughly L-shaped recess, creating a recess 65 on the upper surface of the rear end cap portion 56, and a connector 66 for the connecting cable is positioned in this recess 65. Figure 13 shows a plug 67 at one end of the connecting cable connected to the connector 66. The plug 68 at the other end of the connecting cable is provided on the drive unit 12 side, as shown in Figures 7 and 8. By providing the recess 65 as described above, the connector 66 is positioned recessed, protecting the connector 66 from collisions and the like, and reducing the amount of protrusion of the plug 67.

[0029] As shown in Figures 6 and 7, the mounting bracket 11 and the battery unit housing 32 are connected to each other via a pair of rail sections 44 extending in the width direction (left-right direction) of the manual wheelchair. The rail section 44 consists of a convex rail section 44a molded as part of a synthetic resin molded product on the battery unit housing 32 side so as to have a substantially T-shaped cross-section, and a concave rail section 44b having a substantially T-shaped groove that slidably engages with the convex rail section 44a. The concave rail section 44b is molded integrally with the tubular section 16 as part of the mounting bracket 11.

[0030] In the electric assist device 1 of the embodiment configured as described above, the drive unit 12, mounting bracket 11, and battery unit 13 are integrated into one unit. Installation of the entire device is completed simply by attaching the mounting bracket 11 to the handrim 5 of a manual wheelchair while the unit remains integrated. Conversely, removal is completed by pulling the tubular portion 16 of the mounting bracket 11 off the handrim 5. Therefore, a simple electrification of a manual wheelchair can be easily achieved. The integrated electric assist device 1 contains all the elements necessary for operation, and there is no need to attach other parts to other parts of the manual wheelchair.

[0031] Furthermore, since the drive unit 12 is located on the outer circumference, or upper part, of the handrim 5, while the battery unit 13 is located on the inner circumference, the overall design can be made compact. In other words, the battery unit 13 can be placed using the empty space on the inner circumference of the handrim 5.

[0032] Furthermore, while the drive unit 12 rests on top of the mounting bracket 11, the battery unit 13 is suspended downward from the mounting bracket 11. Since the weight of the battery unit 13, including batteries 39a and 39b, is relatively large, when the electric assist device 1 is attached to the handrim 5, the center of gravity of the electric assist device 1 is located on the inner circumference side of the handrim 5 (i.e., below the handrim 5 at the notch 17) due to the weight of the battery unit 13. As a result, the posture of the electric assist device 1 around the handrim 5 is stable, making it easy for the user to handle. In other words, the battery unit 13 also functions as a counterweight to stabilize the posture of the electric assist device 1 on the handrim 5.

[0033] Furthermore, as described above, the electric assist device 1, which consists of a drive unit 12, a mounting bracket 11, and a battery unit 13, allows for the attachment and detachment of the drive unit 12 and the battery unit 13 to the mounting bracket 11. Therefore, if the diameter (i.e., curvature) of the handrim 5 of a manual wheelchair varies, by preparing several mounting brackets 11 having tubular sections 16 with different curvatures, it is possible to accommodate various manual wheelchairs by simply changing the mounting bracket 11.

[0034] As described above, the electric assist device 1 is attached to each of the left and right wheels 2 of the manual wheelchair. The user, seated in the seat, operates the device with both hands resting on the left and right electric assist devices 1. For example, with the top of the wheel 2 as the reference position, if the user presses the operation switch 38 and tilts the electric assist device 1 forward, the drive roller 36 of the drive unit 12 drives the wheel 2 in the forward direction. If both the left and right electric assist devices 1 are operated similarly, the manual wheelchair will move forward. The fact that the electric assist device 1 has been tilted forward by the user is detected by a gravity sensor (for example, a 6-axis gravity sensor) built into the drive unit 12. Conversely, if the user presses the operation switch 38 and tilts the electric assist device 1 backward, the wheel 2 will be driven in the reverse direction. Therefore, if both the left and right electric assist devices 1 are tilted backward simultaneously, the manual wheelchair will move backward. Furthermore, by operating one of the left and right electric assist devices 1 in the forward direction and the other in the reverse direction, the manual wheelchair can be turned around.

[0035] In the above explanation, the top of the wheel 2 was described as the reference position of the electric assist device 1, but it is also possible to set a reference position at an angle other than the top (an angle tilted at an appropriate angle forward or backward). Even if the reference position is set at an appropriate angle, the gravity sensor can detect whether the electric assist device 1 has been tilted forward or backward from this reference position. Furthermore, the amount of displacement of the electric assist device 1 due to user operation (how much it has been tilted) can also be detected by the gravity sensor, and in one embodiment, the larger this displacement, the greater the torque with which the wheel 2 is driven. In this way, by moving the left and right electric assist devices 1 forward and backward, the corresponding driving force can be obtained, making it easy to achieve driving that conforms to the user's intentions.

[0036] Next, the center of gravity of the battery unit 13, which is the main part of the present invention, and the moment generated in the electric assist device 1 as a result will be described in detail with reference to Figure 15. In the cross-sectional view of Figure 15, point G1 is the center of gravity of the first battery 39a, and point G2 is the center of gravity of the second battery 39b. Since batteries 39a and 39b are heavy objects and account for most of the weight of the battery unit 13, the center of gravity G of the entire battery unit 13 is determined to be approximately midway between the centers of gravity G1 and G2 of these two batteries 39a and 39b.

[0037] When the electric assist device 1 is supported on the handrim 5 as shown in Figure 15, the support point P0 of the mounting bracket 11 on the handrim 5 and the contact point P1 of the drive roller 36 on the wheel 2 are determined as shown. The center of gravity G of the battery unit 13 is located between the support point P0 and the contact point P1 with respect to the width direction (left-right direction) of the manual wheelchair. Therefore, considering the moment around the support point P0, the weight of the battery unit 13 (center of gravity G) generates a clockwise moment as shown in Figure 11, and this clockwise moment increases the contact pressure between the drive roller 36 of the drive unit 12 and the wheel 2. In other words, the weight of the battery unit 13 can be effectively utilized to improve the contact pressure.

[0038] In the illustrated example, a favorable position of the center of gravity G is obtained mainly by the layout of the two batteries 39a and 39b shown in Figure 11. When housing the two batteries 39a and 39b in the battery unit housing 32, instead of simply placing them side by side, the first battery 39a is positioned along the top of the battery unit housing 32 with its oval cross-section facing sideways, and the second battery 39b is positioned below the first battery 39a and inside the battery unit housing 32 (inside in the width direction) with its oval cross-section facing vertically. The remaining space is used as the control board housing space 40, which results in a position where the center of gravity G is shifted inward.

[0039] Furthermore, the layout of the two batteries 39a and 39b may be the same as the layout shown in Figure 11, but inverted vertically. That is, the first battery 39a is placed along the bottom of the battery unit housing 32 with its oval cross-section facing sideways, and the second battery 39b is placed above the first battery 39a and inside the battery unit housing 32 (inside in the width direction) with its oval cross-section facing vertically, and the space remaining on the upper outside is used as the control board housing space 40. Even with this configuration, the center of gravity G is still shifted inward.

[0040] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, the mounting bracket 11 is mainly composed of a tubular portion 16 with a substantially C-shaped cross-section, but the mounting bracket 11 is not limited to such a configuration, and any structure is acceptable as long as it has a hollow passage portion 15 that is curved in an arc shape through which the handrim 5 can pass. For example, the mounting bracket 11 may have a two-part structure that allows it to be detachably attached to the handrim 5.

[0041] Furthermore, the present invention can be applied in the same way even if the rotation axis of the drive roller 36 is horizontal, thereby improving the contact pressure between the drive roller 36 and the wheel 2.

[0042] Furthermore, although the battery unit 13 in the above embodiment is configured to include two packaged batteries 39a and 39b, the shape and number of batteries in the present invention are not limited to this embodiment, and for example, a configuration in which a large number of cylindrical batteries are housed in the battery unit housing 32 without being bundled together may also be used.

Claims

1. An electric assist device for a manual wheelchair, which is attached to the wheel of a manual wheelchair, comprising: a mounting bracket attached to the handrim in a state in which the handrim is slidably fitted into the hollow passage portion that is curved in an arc shape through which the handrim can pass; a drive unit having a first housing supported by the mounting bracket and including a drive roller that contacts the outer surface of the wheel and an electric motor that drives the drive roller; and a battery unit having a second housing supported by the mounting bracket and located on the inner circumference side of the handrim and housing a battery, wherein the center of gravity of the battery unit is located in the width direction of the manual wheelchair between the support point of the mounting bracket on the handrim and the contact point of the drive roller on the wheel.

2. The electric assist device for a manual wheelchair according to claim 1, wherein the second housing has an elongated shape in a direction parallel to the tangential direction of the wheel, and in a cross-section of the battery unit along the radius of the wheel, it comprises a first battery arranged along the upper part of the second housing and a second battery located below the first battery and on the inside of the second housing in the width direction, and a space for housing a control board is provided inside the second housing on the outside of the second battery in the width direction.

3. The electric assist device for a manual wheelchair according to claim 2, wherein a battery housing chamber for loading the second battery along the longitudinal direction of the second housing and a circuit board housing space for housing the control board are separated by a partition wall, and the second housing is provided with a removable cover that covers the outer surface of the circuit board housing space.

4. The electric assist device for a manual wheelchair according to claim 2, wherein the second housing is provided with air vents at both ends in the longitudinal direction of the substrate housing space.

5. The electric assist device for a manual wheelchair according to claim 2, wherein the second housing has a battery housing for loading the first battery and the second battery along the longitudinal direction of the second housing, and the battery housing is closed at the front end of the manual wheelchair and the rear end is configured as a battery insertion opening with a cap.

6. The electric assist device for a manual wheelchair according to claim 3, wherein a battery housing chamber for loading the first battery along the longitudinal direction of the second housing and a circuit board housing space for housing the control board are separated by a second partition wall, the cover is fixed to the main body portion of the second housing with screws, and the screws are screwed into the partition wall and the thickened portion of the second partition wall.

7. The electric assist device for a manual wheelchair according to claim 1, wherein a recess is provided on the upper surface of the second housing, and a connector for a connecting cable is arranged in this recess.

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