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 a mounting bracket (11) that is supported by a hand rim (5), a drive unit (12) that is supported above the bracket (11), and a battery unit (13) that is supported below the bracket (11). A drive unit housing (31) has, as a part of a grip portion (31a) gripped by a hand of a user, a palm placement surface (61) on which a palm is placed. The palm placement surface (61) forms an inclined surface that is higher on the inner side, and has, at an inner edge, a wall part (62) with which an outer edge of a base portion of the thumb comes into contact. When an operating force (F) applied by the hand of the user is directed obliquely downward, the operating force (F) thereby balances the moment caused by the weight of the device, and the weight of the device contributes to an improvement in contact pressure.

Description

Electric assist device for manual wheelchairs

[0001] This invention relates to an electric assist device for manual wheelchairs that enables simple electrification by being attached to a standard manual wheelchair.

[0002] Attempts to simply electrify a standard manual wheelchair have been made in the past. For example, Patent Document 1 discloses an electric assist device that propels a manual wheelchair by rotating friction rollers that contact the wheels of the manual wheelchair with an electric motor.

[0003] In the electric assist device described in Patent Document 1, a friction roller supported by the frame of a manual wheelchair is located above the wheelchair wheel, and the outer surface of this friction roller is in contact with the outer surface of the wheelchair wheel, thereby transmitting driving torque from the friction roller to the wheel.

[0004] In the electric assist device described above, if the transmission of driving torque through friction between the friction roller and the wheel is not performed properly, the friction roller will slip, resulting in poor operability. Patent Document 1 describes a spring-type unit connected to the friction roller, but such a configuration that uses a spring member to obtain contact pressure between the friction roller and the wheel tends to result in a complex mechanical structure.

[0005] Special 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 that is detachably attached to the handrim, having a hollow passage curved in an arc shape through which the handrim can pass, and the handrim is slidably fitted into the hollow passage; a drive unit that includes a drive roller that contacts the outer surface of the wheel and an electric motor that drives the drive roller, having a housing supported by the mounting bracket; and a grip portion provided at the front end of the housing for the user to grasp with their hand, wherein the grip portion has a palm rest surface on which the user rests their palm, and this palm rest surface is an inclined surface that is relatively higher on the inside in the width direction of the manual wheelchair.

[0007] In this configuration, the drive unit and mounting bracket of 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 travel, the handrim, which rotates together with the wheel, passes through the hollow passage of the mounting bracket.

[0008] Here, because the palm rest surface is tilted, the operating force from the user's hand naturally acts inward in the width direction of the manual wheelchair. As a result, the moment around the contact point between the drive roller and the wheel increases, approaching a state of equilibrium with the moment exerted by the device's own weight. Therefore, both the operating force and the device's own weight contribute to the contact pressure between the drive roller and the wheel.

[0009] According to this invention, both the force applied by the user to the electric assist device and the weight of the device itself are 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 force generated by the user's hand. A cross-sectional view showing a second embodiment in which the hand rest surface extends inside the frame of the manual wheelchair. An explanatory diagram showing a third embodiment in which the operation switch part is a separate component.

[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, although this will be described in detail later. Also, as shown in Figures 6 and 7, a part of the front end of the drive unit housing 31 protrudes forward of the drive roller 36, forming a grip portion 31a that is easy for the user to hold. 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 placed on the grip portion 31a. In addition, as will be described later, the drive unit 12 is equipped with a gravity sensor (not shown) at an appropriate position for switching between forward and reverse movement.

[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 housing 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 on the bottom surface, as shown in Figure 7.

[0025] In the illustrated example, the outer cover 41 includes a setting switch 51 for making various settings and a liquid crystal display unit 52, as shown in Figure 7.

[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. Batteries 39a and 39b are loaded into the first and second battery housings 53a and 53b, respectively, with their rear end caps 56 removed.

[0027] The control board housing space 40 is separated from the first and second battery housing chambers 53a and 53b by partition walls 58a and 58b, which are molded as part of the battery unit housing 32. Furthermore, as shown in Figures 8 and 9, 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. These two air vents 59a and 59b allow outside air to flow along the longitudinal direction within the control board housing space 40, thereby cooling 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, and the amount of protrusion of the plug 67 is reduced.

[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 configured above, the electric assist device 1 is attached to each of the left and right wheels 2 of the manual wheelchair. Then, it is operated in a form where the user seated on the seat part places both hands on the left and right electric assist devices 1. For example, with the uppermost part of the wheel 2 as the reference position, when the user tilts the electric assist device 1 forward while pressing the operation switch 38, the drive roller 36 of the drive unit 12 drives the wheel 2 in the forward direction. If the left and right electric assist devices 1 are operated in the same way, the manual wheelchair travels forward. The fact that the electric assist device 1 has been tilted forward by the user is detected by a gravity sensor (e.g., a 6-axis gravity sensor) built into the drive unit 12. Conversely, when the user tilts the electric assist device 1 backward while pressing the operation switch 38, the wheel 2 is driven in the reverse direction. Therefore, when the left and right electric assist devices 1 are tilted backward simultaneously, the manual wheelchair travels backward. Also, by operating one of the left and right electric assist devices 1 in the forward direction and the other in the reverse direction respectively, the manual wheelchair can be turned.

[0035] Here, in the above description, the uppermost part of the wheel 2 was described as the reference position of the electric assist device 1, but it is also possible to set an angular position other than the uppermost part (an angular position tilted at an appropriate angle forward or backward) as the reference position. Even if the reference position is set to an appropriate angular position, whether the electric assist device 1 is tilted forward or backward from this reference position can be detected by the gravity sensor. Also, the displacement amount of the electric assist device 1 due to the user's operation (how much it is tilted) can also be detected by the gravity sensor. In one embodiment, the larger this displacement amount, the greater the torque with which the wheel 被動詞2 is driven. Thus, since the user can move the left and right electric assist devices 1 back and forth to obtain the corresponding driving force, it is possible to easily realize traveling along with the user's intention.

[0036] Next, the configuration of the upper surface of the drive unit housing 31, which is the main part of the present invention, will be described in detail with reference to FIGS. 7 to 13. As described above, a part of the front end portion of the drive unit housing 31 protrudes forward of the drive roller 36, forming a grip portion 31a that is easy for the user to hold. The foremost end portion of the grip portion 31a has a shape rounded into a substantially semi-circular cross-section so as to be gripped by the four fingers other than the thumb of the user's hand. The user's thumb is basically positioned so as to face the operation switch 38. The grip portion 31a further has a palm placement surface 61 on the front side as viewed from the user, on which the user places the palm (especially the part near the thumb). This palm placement surface 61 has a shape that partially rises from the flat surface on the front end side of the grip portion 31a on which the index finger and the ring finger rest. And this palm placement surface 61 forms an inclined surface that is relatively higher on the inner side in the width direction (left-right direction) of the manual wheelchair. Further, the palm placement surface 61 is provided with a wall portion 62 rising from the palm placement surface 61 at the edge on the inner side of the palm placement surface 61 in the width direction. This wall portion 62 is formed so that the outer edge of the base of the thumb contacts it when the user places the hand on the grip portion 31a.

[0037] More specifically, as shown in the cross-sectional view of FIG. The palm placement surface 61 is configured as a separate part having a substantially T-shaped cross-section formed separately from the main body portion of the drive unit housing 31, together with the wall portion 62 at its side edge, and is fixed to the main body portion of the drive unit housing 31 by appropriate means such as adhesion or screwing. The boundary line S between the two is shown in FIG. 11. By configuring the portion of the palm placement surface 61 as a separate part in this way, it becomes possible to combine it with different parts according to the specifications of the manual wheelchair and the physique of the user.

[0038] In one embodiment, as shown in FIG. 5, the palm placement surface 61 extends inward in the width direction (left-right direction) beyond the drive roller 36, and the wall portion 62 is located inside the wheel 2 in the above width direction. In addition, in order to avoid interference with the protection plate 4, the drive unit housing 31 is located in a range outside the protection plate 4.

[0039] FIG. 15 is an explanatory diagram showing the force relationship when the user's hand 64 shown schematically grasps the grip portion 31a and operates the drive unit 12, for example, forward. When the user operates the drive unit 12 forward with, for example, the right hand, at the same time, the drive unit 12 is pressed downward, and an operating force F acting downward is generated. In the above embodiment, since the palm placement surface 61 is inclined and has the wall portion 62 at the inner edge as described above, as shown in FIG. 15, the user's operating force F acts obliquely downward and naturally inclined inward. This force F can be decomposed into a vertical component F ax , bg , ug , b , bg , ug , a , u , th , ug , ug , bg , bg , t , , ax ,

[0041] , a , th and a horizontal component F th and can be decomposed into.

[0040] Here, considering the moment of the electric assist device 1 about the contact point P1 between the drive roller 36 and the wheel 2, the weight M ug of the drive unit 12 and the weight M bg of the battery unit 13 generate a clockwise moment (M ug ·L u + M bg ·L b ), and the operating force F generates a counterclockwise moment (F ax ·L a + F th ·L t ). Ideally, when both are in balance, in addition to the component force F ax of the operating force F, the weight M ug of the drive unit 12 and the weight M bg of the battery unit 13 can all be utilized as the contact pressure between the drive roller 36 and the wheel 2.

[0041] In the configuration of the above embodiment, as the distance L a to the acting point contributing to the counterclockwise moment increases, and since the operating force F acts obliquely downward to obtain the horizontal component F th , even with the same operating force of the user, the counterclockwise moment increases. That is, even with a relatively small operating force F by the user, the above balance state can be approached. As a result, the weight M ug of the drive unit 12 and the weight M bgBy utilizing this mechanism, the contact pressure between the drive roller 36 and the wheel 2 increases, which helps to suppress slippage of the drive roller 36.

[0042] In particular, in the above embodiment, because the rotation axis of the drive roller 36 is inclined, the drive roller 36 contacts the outer peripheral surface of the wheel 2 at an oblique angle, and the operating force F acts along this contact direction, so that the slippage of the drive roller 36 can be suppressed more effectively.

[0043] Next, Figure 16 shows the electric assist device 1 of the second embodiment. In this second embodiment, the hand rest surface 61 extends to the inside of the protective plate 4, passing over the protective plate 4. In this second embodiment as well, the hand rest surface 61 portion is configured as a separate part molded separately from the main body portion of the drive unit housing 31, and the line S in the figure is the boundary line. Therefore, it is possible to replace and apply the part for the hand rest surface 61 shown in Figure 11 of the above-mentioned embodiment. With this configuration, the aforementioned counterclockwise moment can be obtained with a smaller operating force F. In the example of Figure 16, the side edge wall portion 62 is not provided, but a wall portion 62 may be added to the side edge as in Figure 11.

[0044] Next, Figure 17 shows a third embodiment in which the operating switch 38 portion is included in a separate component that constitutes the palm rest surface 61. The line S in the figure indicates the boundary line. That is, as also shown in the second embodiment in Figure 16, if the size of the palm rest surface 61 is different, the appropriate position of the operating switch 38 operated by the thumb may also change. Therefore, if the palm rest surface 61 and the operating switch 38 are combined into a single separate component, handling such as replacement becomes easier.

[0045] 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.

[0046] 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.

[0047] Furthermore, although the battery unit 13 is supported by the mounting bracket 11 in the above embodiment, the present invention can be similarly applied to configurations in which the battery unit 13 is arranged separately from the drive unit 12 and the mounting bracket 11 (for example, in which it is arranged in the seat or seat back of a manual wheelchair).

Claims

1. An electric assist device for a manual wheelchair, which is attached to the wheel of a manual wheelchair, comprising: a mounting bracket that is detachably 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 that includes a drive roller that contacts the outer surface of the wheel and an electric motor that drives the drive roller, having a housing supported by the mounting bracket; and a grip portion provided at the front end of the housing for the user to grasp with their hand, wherein the grip portion has a palm rest surface on which the user rests their palm, and this palm rest surface is an inclined surface in which the inward side in the width direction of the manual wheelchair is relatively higher.

2. The electric assist device for a manual wheelchair according to claim 1, wherein the drive roller is inclined such that the axis of rotation is inclined so that the side that is inward in the width direction is relatively upward.

3. The drive unit is equipped with a gravity sensor that detects whether the handrim is tilted forward or backward based on its orientation at a reference position in the circumferential direction, and switches the drive direction to the forward direction when it is tilted forward, and to the reverse direction when it is tilted backward, as described in claim 1.

4. The electric assist device for a manual wheelchair according to claim 1, wherein the inner edge of the hand rest surface in the width direction is provided with a wall portion rising from the hand rest surface.

5. The electric assist device for a manual wheelchair according to claim 1, wherein the hand rest surface extends inward in the width direction, and the wall portion is located inward from the wheel in the width direction.

6. The electric assist device for a manual wheelchair according to claim 1, wherein a part of the housing extends inward in the width direction beyond the frame of the manual wheelchair, and the hand rest surface is located inward from the frame in the width direction.

7. The electric assist device for a manual wheelchair according to claim 1, wherein the portion constituting the hand rest surface is configured as a separate component from the main body portion of the housing and is fixed to the main body portion.

8. The electric assist device for a manual wheelchair according to claim 7, wherein the drive unit has an operating switch, and the operating switch is located on another component.

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