Abstract
A front wheel unit includes a front wheel support portion, which rotationally supports a front wheel, and a front wheel seat, which supports the front wheel support portion such that the front wheel support portion is rotatable at least about the front axis. A rear wheel unit includes a rear wheel support portion, which rotationally supports a rear wheel, and a rear wheel seat, which supports the rear wheel support portion such that the rear wheel support portion is rotatable at least about the rear axis. The front wheel unit and the rear wheel unit are configured such that, when the board portion is tilted in a width direction, the amount of rotation of the rear wheel support portion about the rear axle is greater than the amount of rotation of the front wheel support portion about the front axis.
Claims
1. A skateboard, comprising: a board portion including a surface configured for a user to ride and a back surface that is opposite the surface; a front wheel unit including a front wheel located at a front portion of the back surface of the board portion; and a rear wheel unit including a rear wheel located at a rear portion of the back surface of the board portion, wherein the front wheel unit includes: a front wheel support portion that rotationally supports the front wheel; and a front wheel seat having a front axis extending in a direction intersecting the board portion, the front wheel seat supporting the front wheel support portion such that the front wheel support portion is rotatable at least about the front axis, the rear wheel unit includes: a rear wheel support portion that rotationally supports the rear wheel; and a rear wheel seat having a rear axis extending in a direction intersecting the board portion, the rear wheel seat supporting the rear wheel support portion such that the rear wheel support portion is rotatable at least about the rear axis, each of the front axis and the rear axis is inclined upward from front to rear in the board portion, and the front wheel unit and the rear wheel unit are configured such that, when the board portion is tilted in a width direction, an amount of rotation of the rear wheel support portion about the rear axis is greater than an amount of rotation of the front wheel support portion about the front axis.
2. The skateboard according to claim 1, further comprising a steering device configured to steer the front wheel unit and the rear wheel unit, wherein the steering device includes an linkage mechanism including a connection shaft, the linkage mechanism is configured to link rotation of the front wheel support portion and rotation of the rear wheel support portion by connecting the front wheel support portion and the rear wheel support portion to each other with the connection shaft, the connection shaft includes a first end connected to the front wheel support portion so as to be rotatable at least about the front axis, and the connection shaft includes a second end connected to the rear wheel support portion so as to be rotatable at least about the rear axis.
3. The skateboard according to claim 2, wherein a point at which the first end of the connection shaft is connected to the front wheel support portion is a front connection point, a point at which the second end of the connection shaft is connected to the rear wheel support portion is a rear connection point, and a distance between the front axis and the front connection point differs from a distance between the rear axis and the rear connection point, so that the connection shaft is placed at an angle with respect to a reference line extending in a front-rear direction in which the front wheel unit and the rear wheel unit are aligned.
4. The skateboard according to claim 3, wherein the connection shaft is placed on one side of the reference line in a direction intersecting the reference line.
5. The skateboard according to claim 2, wherein the first end of the connection shaft is connected to the front wheel support portion through a first elastic body used as a universal joint, and the second end of the connection shaft is connected to the rear wheel support portion through a second elastic body used as a universal joint.
6. The skateboard according to claim 2, wherein the connection shaft includes a display portion capable of displaying a design.
7. The skateboard according to claim 1, wherein the rear wheel is placed rearward of the rear axis in a direction intersecting the rear axis.
8. The skateboard according to claim 1, wherein the front wheel unit includes two front wheels arranged on opposite sides of the front axis, and the rear wheel unit includes one rear wheel.
9. A steering device, comprising a front wheel unit, a rear wheel unit, and an linkage mechanism including a connection shaft, wherein the front wheel unit includes: a front wheel support portion configured to rotationally support a front wheel of a mobile body; and a front wheel seat having a front axis extending in a direction intersecting an axle of the front wheel, the front wheel seat supporting the front wheel support portion such that the front wheel support portion is rotatable at least about the front axis, the rear wheel unit includes: a rear wheel support portion configured to rotationally support a rear wheel of the mobile body; and a rear wheel seat having a rear axis extending in a direction intersecting an axle of the rear wheel, the rear wheel seat supporting the rear wheel support portion such that the rear wheel support portion is rotatable at least about the rear axis, the linkage mechanism is configured to link rotation of the front wheel support portion and rotation of the rear wheel support portion by connecting the front wheel support portion and the rear wheel support portion to each other with the connection shaft, the connection shaft includes a first end connected to the front wheel support portion so as to be rotatable at least about the front axis, the connection shaft includes a second end connected to the rear wheel support portion so as to be rotatable at least about the rear axis, a point at which the first end of the connection shaft is connected to the front wheel support portion is a front connection point, a point at which the second end of the connection shaft is connected to the rear wheel support portion is a rear connection point, and a distance between the front connection point and the front axis differs from a distance between the rear connection point and the rear axis, so that the connection shaft is placed at an angle with respect to a reference line extending in a front-rear direction in which the front wheel unit and the rear wheel unit are aligned.
10. The steering device according to claim 9, wherein the connection shaft is placed on one side of the reference line in a direction intersecting the reference line.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a perspective view of a skateboard having a steering device according to one embodiment.
[0010] FIG. 2 is a top view of the skateboard of FIG. 1.
[0011] FIG. 3 is an exploded perspective view of the skateboard of FIG. 1.
[0012] FIG. 4 is a perspective view showing the configuration of the steering device of FIG. 1.
[0013] FIG. 5 is a side view of the skateboard of FIG. 1.
[0014] FIG. 6 is a side view of the skateboard of FIG. 1 during curving motion.
[0015] FIG. 7 is a top view of the skateboard of FIG. 1 during curving motion.
[0016] FIG. 8A is a rear view of the skateboard of FIG. 1 during straight motion.
[0017] FIG. 8B is a rear view of the skateboard of FIG. 1 during curving motion.
[0018] FIG. 9A is a schematic view of the steering device of FIG. 1 during straight motion.
[0019] FIG. 9B is a schematic view of the steering device of FIG. 1 during left curving motion.
[0020] FIG. 9C is a schematic view of the steering device of FIG. 1 during right curving motion.
[0021] FIG. 10A is a schematic view of a trajectory of the skateboard of FIG. 1 during curving motion.
[0022] FIG. 10B is a schematic view of a trajectory of a typical skateboard during curving motion.
[0023] FIG. 11A is a schematic view of an linkage mechanism of a first comparative example in a neutral state in which the steering device is not steered.
[0024] FIG. 11B is a schematic view of the linkage mechanism of the first comparative example in an asynchronous state in which the steering device is steered.
[0025] FIG. 12A is a schematic view of an linkage mechanism of a second comparative example in a neutral state in which the steering device is not steered.
[0026] FIG. 12B is a schematic view of the linkage mechanism of the second comparative example in an asynchronous state in which the steering device is steered.
[0027] FIG. 12C is a schematic view of the linkage mechanism of the second comparative example in an asynchronous state in which the steering device is steered.
[0028] FIG. 13A is a schematic view of an linkage mechanism of a third comparative example in a neutral state in which the steering device is not steered.
[0029] FIG. 13B is a schematic view of the linkage mechanism of the third comparative example in an asynchronous state in which the steering device is steered.
[0030] FIG. 14A is a schematic view of an linkage mechanism of a fourth comparative example during straight motion.
[0031] FIG. 14B is a schematic view of the linkage mechanism of the fourth comparative example during curving motion.
[0032] FIG. 15A is a schematic view of an linkage mechanism of a fifth comparative example during straight motion.
[0033] FIG. 15B is a schematic view of the linkage mechanism of the fifth comparative example during curving motion.
[0034] FIG. 16A is an explanatory diagram illustrating changes in the traveling feeling of the skateboard of FIG. 1.
[0035] FIG. 16B is an explanatory diagram illustrating changes in the traveling feeling of the skateboard of FIG. 1.
[0036] FIG. 16C is an explanatory diagram illustrating changes in the traveling feeling of the skateboard of FIG. 1.
[0037] FIG. 17 is a perspective view of a skateboard including a display portion.
[0038] FIG. 18 is a cross-sectional view of the structure of an linkage mechanism according to another embodiment.
[0039] FIG. 19 is a perspective view of a skateboard according to another embodiment.
[0040] FIG. 20 is a plan view of a skateboard according to yet another embodiment.
[0041] FIG. 21 is a side view of the skateboard shown in FIG. 20.
[0042] Throughout the drawings and the detailed description, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and depiction of elements in the drawings may be exaggerated for clarity, illustration, and convenience.
DETAILED DESCRIPTION
[0043] This description provides a comprehensive understanding of the methods, apparatuses, and/or systems described. Modifications and equivalents of the methods, apparatuses, and/or systems described are apparent to one of ordinary skill in the art. Sequences of operations are exemplary, and may be changed as apparent to one of ordinary skill in the art, with the exception of operations necessarily occurring in a certain order. Descriptions of functions and constructions that are well known to one of ordinary skill in the art may be omitted.
[0044] Exemplary embodiments may have different forms, and are not limited to the examples described. However, the examples described are thorough and complete, and convey the full scope of the disclosure to one of ordinary skill in the art.
[0045] In this specification, at least one of A and B should be understood to mean only A, only B, or both A and B.
[0046] One embodiment of the present disclosure is now described.
Mobile Body 1
[0047] As shown in FIG. 1, a mobile body 1 is a skateboard 1a including a board portion 2 on which a user rides to travel. The board portion 2 has the shape of a rectangular plate, for example. The board portion 2 has a surface on which a user rides and a back surface opposite the surface. The skateboard 1a travels straight when the board portion 2 is in a neutral position. When the board portion 2 of the skateboard 1a is tilted to one side in the width direction (to one side in the direction of arrow A in FIG. 1), the skateboard 1a curves in the tilted direction. In the following description, directions expressed by terms such as front, back, up, down, left, and right are defined based on the skateboard 1a in straight motion. The width direction agrees with the left-right direction. The operation of tilting the board portion 2 in the width direction may also be referred to as a tilting operation.
Steering Device 7
[0048] As shown in FIG. 1, the mobile body 1 includes a steering device 7 for steering a front wheel unit 4, to which front wheels 3 are attached, and a rear wheel unit 6, to which a rear wheel 5 is attached. The front wheel unit 4 and the rear wheel unit 6 are aligned in the front-rear direction. The steering device 7 changes the traveling direction of the mobile body 1. When the mobile body 1 is a skateboard 1a and receives a tilting operation, the steering device 7 directs the front wheels 3 and the rear wheel 5 in a direction corresponding to the tilted direction of the board portion 2, causing the skateboard 1a to curve.
Front Wheel Unit 4
[0049] As shown in FIGS. 2 and 3, the front wheel unit 4 includes a front wheel support portion 8, which rotationally supports the front wheels 3, and a front wheel seat 9, which rotationally supports the front wheel support portion 8. As shown in FIG. 3, the front wheel seat 9 includes a seat body 10 fixed to the back surface of the board portion 2, and a fitting protrusion 11, which is formed on the seat body 10 and rotationally fitted to the front wheel support portion 8. The seat body 10 is preferably fixed at a position near the front portion of the back surface of the board portion 2 by a fastening portion such as a screw. The seat body 10 has a circular end surface. The fitting protrusion 11 may be annular and have a smaller diameter than the end surface of the seat body 10. The fitting protrusion 11 is provided on the end surface of the seat body 10.
[0050] As shown in FIG. 4, the front wheel support portion 8 includes a support body 12, which is connected to the front wheel seat 9 and supports the front wheels 3. The support body 12 has an end surface, which faces the end surface of the seat body 10, at a position near the board portion 2. The end surface of the support body 12 has a fitting recess 13, into which the fitting protrusion 11 is fitted in a slidable manner. The fitting between the fitting recess 13 and the fitting protrusion 11 allows the support body 12 to rotate about the axis of the fitting protrusion 11. The support body 12 includes an axle support portion 15, which rotationally supports an axle 14 of the front wheels 3. The axle support portion 15 is provided at a position of the support body 12 that is away from the board portion 2.
[0051] As shown in FIG. 5, the front wheel support portion 8 is supported by the front wheel seat 9 so as to be rotatable at least about a front axis L1. The front axis L1 extends in a direction intersecting the axle 14 of the front wheels 3, and is inclined upward (in the +Z-axis direction in FIG. 5) from the front to the rear in the mobile body 1 (board portion 2). In this embodiment, the front axis L1 is a rotation axis of the rotation of the fitting recess 13 relative to the fitting protrusion 11. The front wheel seat 9 may have any configuration that supports the front wheel support portion 8 such that the front wheel support portion 8 is rotatable at least about the front axis L1. The angle 1 that the front axis L1 forms with the back surface of the board portion 2 may have any value less than 90 degrees. In other words, the front axis L1 extends in a direction intersecting the board portion 2.
Rear Wheel Unit 6
[0052] As shown in FIGS. 2 to 4, the rear wheel unit 6 includes a rear wheel support portion 17, which rotationally supports the rear wheel 5, and a rear wheel seat 18, which rotationally supports the rear wheel support portion 17. As shown in FIG. 3, the rear wheel seat 18 has a similar configuration to the front wheel seat 9. That is, the rear wheel seat 18 includes a seat body 19 and a fitting protrusion 20. The seat body 19 is preferably fixed at a position near the rear portion of the back surface of the board portion 2 by a fastening portion such as a screw. The rear wheel seat 18 preferably has the same shape as the front wheel seat 9.
[0053] The rear wheel support portion 17 has a structure in which a first component 21 and a second component 22 are combined. In this embodiment, the first component 21 is connected to the rear wheel seat 18 and rotationally supports one end of an axle 23 of the rear wheel 5. The second component 22 is connected to the first component 21 and rotationally supports the other end of the axle 23 of the rear wheel 5. As shown in FIG. 4, the first component 21 has an end surface, which faces the end surface of the seat body 19, at a position near the board portion 2. The end surface of the first component 21 includes a fitting recess 24, into which the fitting protrusion 20 is fitted in a slidable manner. The fitting between the fitting recess 24 and the fitting protrusion 20 allows the first and second components 21 and 22 to rotate about the axis of the fitting protrusion 20.
[0054] As shown in FIG. 5, the rear wheel support portion 17 is supported by the rear wheel seat 18 so as to be rotatable at least about a rear axis L2. The rear axis L2 extends in a direction intersecting the axle 23 of the rear wheel 5, and is inclined upward (in the +Z-axis direction in FIG. 5) from the front to the rear in the mobile body 1 (board portion 2). The rear axis L2 is a rotation axis of the rotation of the fitting recess 24 relative to the fitting protrusion 20. The rear wheel seat 18 may have any configuration that supports the rear wheel support portion 17 such that the rear wheel support portion 17 is rotatable at least about the rear axis L2. The angle 2 that the rear axis L2 forms with the back surface of the board portion 2 may have any value less than 90 degrees. In other words, the rear axis L2 extends in a direction intersecting the board portion 2. In this embodiment, the angles 1 and 2 may be set to the same value, for example.
Arrangement of the Front Wheels 3 and the Rear Wheel 5
[0055] As shown in FIG. 5, the front wheels 3 are placed such that their rotation axis (the axis of the axle 14) is located on an extension of the front axis L1. The front wheels 3 do not necessarily need to be placed such that their rotation axis is on an extension of the front axis L1, and may be placed frontward or rearward of an extension of the front axis L1. The rear wheel 5 is placed rearward of the rear axis L2 in a direction intersecting a direction along the rear axis L2 and the width direction (the direction of arrow B in FIG. 5). In other words, the rear wheel 5 is placed on the opposite side of the rear wheel support portion 17 from the front wheels 3.
Number of Wheels of the Mobile Body 1
[0056] As shown in FIGS. 1 to 4, the front wheels 3 are placed on the opposite sides of the front axis L1. As such, the present embodiment includes two front wheels 3 in total placed on the opposite sides of the axle 14. In contrast, only one rear wheel 5 is provided. As such, the mobile body 1 of the present embodiment is of a three-wheel type having two front wheels 3 and one rear wheel 5.
Linkage Mechanism 27
[0057] As shown, for example, in FIGS. 1 to 3, the steering device 7 includes an linkage mechanism 27 including a connection shaft 28. The linkage mechanism 27 connects the front wheel support portion 8 and the rear wheel support portion 17 to each other with the connection shaft 28, thereby linking the rotation of the front wheel support portion 8 and the rotation of the rear wheel support portion 17. The connection shaft 28 may be a columnar rod, for example. As shown in FIG. 2, the connection shaft 28 is placed at an angle with respect to a reference line La extending in the front-rear direction. Specifically, the connection shaft 28 is placed in an inclined state such that a first end (front end) of the connection shaft 28 is positioned farther from the reference line La than a second end (rear end) of the connection shaft 28 is. Also, the connection shaft 28 is placed on only one side of the reference line La in a direction intersecting the reference line La. In other words, the connection shaft 28 is placed on one side of the reference line La in the width direction.
[0058] The first end of the connection shaft 28 is connected to the front wheel support portion 8 so as to be rotatable at least about the front axis L1. Specifically, the first end of the connection shaft 28 is connected to the front wheel support portion 8 through a first elastic body 29 used as a universal joint. In this embodiment, the first end of the connection shaft 28 is slidably connected to a connection portion 30 of the front wheel support portion 8 through the first elastic body 29. The connection portion 30 includes a proximal end portion 30a, which forms the body of the connection portion 30, and a projection portion 30b, which projects from a part of the proximal end portion 30a. The connection portion 30 is preferably configured to be detachable from the support body 12, for example. The projection portion 30b is preferably formed in a plate shape, for example.
[0059] The second end of the connection shaft 28 is connected to the rear wheel support portion 17 so as to be rotatable at least about the rear axis L2. Specifically, the second end of the connection shaft 28 is connected to the rear wheel support portion 17 through a second elastic body 31 used as a universal joint. In this embodiment, the second end of the connection shaft 28 is slidably connected to the second component 22 of the rear wheel support portion 17 through the second elastic body 31. In this embodiment, the second component 22 includes an axle support portion 32a, which forms the body of the second component 22, and a projection portion 32b, which projects from a part of the axle support portion 32a. The second component 22 is preferably configured to be detachable from the first component 21, for example. The projection portion 32b is preferably formed in a plate shape, for example.
[0060] As shown in FIG. 3, the first end of the connection shaft 28 is slidably inserted in a hole 34 extending through the projection portion 30b of the front wheel support portion 8. The first elastic body 29 includes two annular elastic pieces 35 and 36, which are fixed to the first end of the connection shaft 28 inserted in the hole 34. The elastic pieces 35 and 36 sandwich the projection portion 30b. The second end of the connection shaft 28 is slidably inserted in a hole 38 extending through the projection portion 32b of the rear wheel support portion 17. The second elastic body 31 includes two annular elastic pieces 39 and 40 similar to those of the first elastic body 29. The annular elastic pieces 35, 36, 39, and 40 are used as bushings (e.g., bearings) that support the connection shaft 28. The first and second elastic bodies 29 and 31 may be made of plastic or rubber, for example.
[0061] A washer 41 and a nut 42 for fixing the position of the first elastic body 29 attached to the connection shaft 28 are placed on each side of the first elastic body 29. For example, each nut 42 is engaged with a thread groove (not shown) formed at a predetermined position of the connection shaft 28. Washers 41 and nuts 42 are also placed on the opposite sides of the second elastic body 31.
[0062] The point at which the first end of the connection shaft 28 is connected to the front wheel support portion 8 is referred to as a front connection point P1 (see FIG. 2, for example). The point at which the second end of the connection shaft 28 is connected to the rear wheel support portion 17 is referred to as a rear connection point P2 (see FIG. 2, for example).
[0063] With the above configuration, the first end of the connection shaft 28 rotates in all directions about the front connection point P1. The second end of the connection shaft 28 rotates in all directions about the rear connection point P2. In this manner, the rotation of the first end of the connection shaft 28 in all directions about the front connection point P1 and the rotation of the second end of the connection shaft 28 in all directions about the rear connection point P2 allow the linkage mechanism 27 to link the rotation of the front wheel support portion 8 and the rotation of the rear wheel support portion 17.
Wheel Rotation During Curving Motion
[0064] As shown in FIGS. 6 and 7, to bring the mobile body 1 in curving motion, the user riding on the board portion 2 performs a tilting operation to tilt the board portion 2 toward one side in the width direction (the direction of arrow A1 in FIG. 6). At this time, due to the load applied to the board portion 2 by the tilting operation, the front wheel support portion 8 rotates about the front axis L1 (in the direction of arrow C1 in FIG. 6) and the rear wheel support portion 17 rotates about the rear axis L2 (in the direction of arrow C2 in FIG. 6). That is, the load applied to the board portion 2 acts as a load for rotating the front wheel support portion 8 and the rear wheel support portion 17. As a result, the front wheel support portion 8 and the rear wheel support portion 17 each rotate by an amount according to the load.
[0065] As shown in FIG. 7, the amount of rotation of the front wheel support portion 8 about the front axis L1 is referred to as a rotation amount R1, and the amount of rotation of the rear wheel support portion 17 about the rear axis L2 is referred to as a rotation amount R2. In the present embodiment, the rotation amount R1 of the front wheel support portion 8 is an angle that the front wheel support portion 8 forms with the reference line La extending in the front-rear direction, while the rotation amount R2 of the rear wheel support portion 17 is an angle that the rear wheel support portion 17 forms with the reference line La. The front and rear wheel units 4 and 6 are configured such that the rotation amount R2 of the rear wheel support portion 17 is greater than the rotation amount R1 of the front wheel support portion 8 when the board portion 2 is tilted in a width direction during curving motion.
Operation of Embodiment
[0066] Operation of the mobile body 1 of the present embodiment is now described.
During Straight Motion
[0067] As shown in FIGS. 2, 5, and 8A, when the mobile body 1 travels during straight motion, the board portion 2 is kept horizontal without being tilted. At this time, the rotation amount R1 of the front wheel support portion 8 and the rotation amount R2 of the rear wheel support portion 17 are both 0. In other words, neither the front wheel support portion 8 nor the rear wheel support portion 17 is rotated. This state of the steering device 7 is referred to as a neutral state. This state causes the mobile body 1 to travel in the straight direction (direction of the white arrow in FIG. 2).
During Curving Motion
[0068] As shown in FIGS. 6, 7, and 8B, to bring the mobile body 1 into a curving motion, a tilting operation is performed to tilt the board portion 2 toward one side in the width direction. In this embodiment, the front axis L1 and the rear axis L2 are both inclined upward (in the +Z-axis direction in FIG. 6) from the front to the rear in the board portion 2. As such, when a tilting operation is performed, the front wheel support portion 8 and the rear wheel support portion 17 rotate about the front axis L1 and the rear axis L2 in the direction (direction of arrows C1 and C2 in FIG. 6) that is opposite to the direction in which the mobile body 1 is to curve, in other word, opposite to the direction of the tilting operation. As a result, as shown in FIG. 7, when the mobile body 1 curves to the left, the front wheel support portion 8 and the rear wheel support portion 17 are oriented diagonally rightward (in the directions of arrow D1 and arrow D2 in FIG. 7) with respect to the traveling direction.
[0069] FIGS. 9A to 9C are explanatory diagrams illustrating the principle of the linkage mechanism 27 during curving motion. In these drawings, regarding the configuration of the linkage mechanism 27, the front axis L1, the rear axis L2, the front connection point P1, and the rear connection point P2 are simply indicated by circle and double circle symbols. In these drawings, the front axis L1, the rear axis L2, the front connection point P1, and the rear connection point P2 are illustrated on the same horizontal plane. The distance from the front axis L1 to the front connection point P1 is referred to as a first distance Ls, and the distance from the rear axis L2 to the rear connection point P2 is referred to as a second distance Lt.
[0070] As shown in FIG. 9A, the connection shaft 28 is placed at an angle with respect to the reference line La because the first distance Ls is different from the second distance Lt. This structure creates a rotation difference between the rotation amount R1 and the rotation amount R2 when a tilting operation is performed. Specifically, the rotation amount R1 of the front wheel support portion 8 is less than the rotation amount R2 of the rear wheel support portion 17. Accordingly, this rotation difference acts as a moment that brings the mobile body 1 into the curving motion. In the present embodiment, this rotation difference acts as a moment, causing the mobile body 1 to travel during curving motion in the direction in which the board portion 2 is tilted.
[0071] In this manner, when a tilting operation for the curving motion is performed, the front wheel support portion 8 and the rear wheel support portion 17 rotate in the direction opposite to the curve direction. That is, the front wheels 3 and the rear wheel 5 are directed in directions different from the direction in which the mobile body 1 travels during curving motion. Thus, when the board portion 2 is tilted to perform a curving motion, a moment can be generated in the direction opposite to the curve direction. Also, a rotation difference is created between the rotation amount R1 of the front wheel support portion 8 and the rotation amount R2 of the rear wheel support portion 17. The mobile body 1 therefore travels during curving motion with a turning amount corresponding to that rotation difference. This allows for the curving motion while causing sideslip according to the directions of the front wheels 3 and the rear wheel 5.
[0072] FIG. 10A is a conceptual diagram of the skateboard 1a of this embodiment during curving motion. FIG. 10B is a conceptual diagram of a typical skateboard 1b in curving motion. With the typical skateboard 1b, the entire skateboard 1b is always on the trajectory of the curving motion, failing to provide a sufficient feeling of sideslip. In contrast, the skateboard 1a of this embodiment can provide a sufficient feeling of sideslip because the rear portion of the skateboard 1a moves to project from the trajectory of the curving motion in the direction in which the centrifugal force acts.
[0073] Also, during curving motion, although the axle 14 of the two front wheels 3 is parallel to the road surface, the axle 23 of the rear wheel 5 is inclined relative to the road surface. Thus, as shown in FIG. 8B, in curving motion, the two front wheels 3 remain firmly gripped to the road surface, but one side of the rear wheel 5 becomes lifted. In this manner, the contact area of the rear wheel 5 with the road surface is smaller than that of the front wheels 3. This reduces the resistance acting on the wheels from the road surface during curving motion, thereby reducing deceleration during curving motion. As a result, the smoothness of the curving motion is further improved.
Principle of Operation of Linkage Mechanism During Curving Motion
[0074] As indicated by the progression from FIG. 9A to FIG. 9B, during curving motion to the left, the front wheel support portion 8 rotates clockwise as viewed in the drawings about the front axis L1, and the rear wheel support portion 17 also rotates in the same direction while being assisted by the connection shaft 28. The rotation amount of the rear wheel support portion 17 differs from that of the front wheel support portion 8. The mobile body 1 curves to the left in this manner.
[0075] As indicated by the progression from FIG. 9A to FIG. 9C, during curving motion to the right, the front wheel support portion 8 rotates counterclockwise as viewed in the drawings about the front axis L1, and the rear wheel support portion 17 also rotates in the same direction while being assisted by the connection shaft 28. The rotation amount of the rear wheel support portion 17 differs from that of the front wheel support portion 8. The mobile body 1 curves to the right in this manner.
Structural Features of Linkage Mechanism 27
[0076] FIG. 11A shows an linkage mechanism 27 of a first comparative example, in which the front axis L1, the rear axis L2, the front connection point P1, and the rear connection point P2 are located on the reference line La when the steering device 7 is in the neutral state. With the linkage mechanism 27 of the first comparative example, when the steering device 7 is in the neutral state, the rear axis L2 is located on the axis of the connection shaft 28, so that the connection shaft 28 readily rotates about the rear axis L2 both clockwise and counterclockwise as viewed in the drawings. Thus, as shown in FIG. 11B, the front wheel support portion 8 and the rear wheel support portion 17 may rotate in mutually opposite directions. For this reason, it is not preferable to employ the linkage mechanism 27 of the first comparative example.
[0077] FIG. 12A shows an linkage mechanism 27 of a second comparative example, in which the rear axis L2 is located on the axis of the connection shaft 28 that is inclined with respect to the reference line La when the steering device 7 is in the neutral state. With also the linkage mechanism 27 of the second comparative example, when the steering device 7 is in the neutral state, the rear axis L2 is located on the axis of the connection shaft 28, so that the connection shaft 28 readily rotates about the rear axis L2 both clockwise and counterclockwise as viewed in the drawings. Thus, as shown in FIG. 12B, the front wheel support portion 8 and the rear wheel support portion 17 may rotate in mutually opposite directions. Also, as shown in FIG. 12C, when the connection shaft 28 rotates clockwise as viewed in the drawing from the neutral state of the steering device 7, a force Fa may act radially outward on the rear wheel support portion 17. This locks the rotation of the rear wheel support portion 17, stopping the front wheel support portion 8 from rotating. For the above reasons, it is not preferable to employ the linkage mechanism 27 of the second comparative example.
[0078] FIG. 13A shows an linkage mechanism 27 of a third comparative example, in which the connection shaft 28 is inclined with respect to the reference line La and the rear connection point P2 is located on the reference line La when the steering device 7 is in the neutral state. With this linkage mechanism 27 of the third comparative example, when the front connection point P1 rotates slightly from the neutral state of the steering device 7, the rear axis L2 is located on the axis of the connection shaft 28 as shown in FIG. 13B. In this case, similarly to FIG. 12C described above, the rotation of the rear wheel support portion 17 is locked, stopping the front wheel support portion 8 from rotating. For this reason, it is not preferable to employ the linkage mechanism 27 of the third comparative example.
[0079] In contrast, as shown in FIGS. 9A to 9C, with the linkage mechanism 27 of the present embodiment, the rear axis L2 is not located on the axis of the connection shaft 28 within the rotation range of the front wheel support portion 8 about the front axis L1. In other words, within the rotation range about the front axis L1, the front connection point P1, the rear connection point P2, and the rear axis L2 are not located on the same straight line. As such, the front wheels 3 are unlikely to rotate about the front axis L1 in the direction opposite to the rotation of the rear wheel 5 about the rear axis L2. Also, when the front wheels 3 rotate about the front axis L1, the application of a radially outward force Fa to the rear axis L2 (see FIGS. 12C and 13B) is unlikely to occur.
[0080] Thus, it is easier to control the rotation of the rear wheel 5 when the front wheels 3 rotate about the front axis L1. This facilitates the linkage between the rotation of the front wheel support portion 8 and the rotation of the rear wheel support portion 17. Moreover, zero point holding for keeping the rear wheel 5 directed in the straight direction in straight motion can be readily achieved.
[0081] Considering another perspective, FIG. 14A shows an linkage mechanism 27 of a fourth comparative example, in which the connection shaft 28 is inclined with respect to the reference line La in the direction opposite to that of the present embodiment when the steering device 7 is in the neutral state. Specifically, in the linkage mechanism 27 of the fourth comparative example, the second end (rear end) of the connection shaft 28 is positioned farther from the reference line La than the first end (front end) of the connection shaft 28 is. With the linkage mechanism 27 of the fourth comparative example, when the front wheel support portion 8 rotates about the front axis L1, the rear wheel support portion 17 can also rotate in the same direction about the rear axis L2. However, as shown in FIG. 14B, the rotation amount R2 of the rear wheel support portion 17 is less than the rotation amount R1 of the front wheel support portion 8. As a result, the curve direction of the mobile body 1 is opposite to the direction of the tilting operation.
[0082] Considering yet another perspective, FIG. 15A shows an linkage mechanism 27 of a fifth comparative example, in which the connection shaft 28 is parallel to the reference line La when the steering device 7 is in the neutral state. With the linkage mechanism 27 of the fifth comparative example, the rotation amount R2 of the rear wheel support portion 17 is also less than the rotation amount R1 of the front wheel support portion 8 as shown in FIG. 15B. As a result, the curve direction of the mobile body 1 is opposite to the direction of the tilting operation.
[0083] As described above, the connection shaft 28 is preferably placed in an inclined state such that the first end (front end) of the connection shaft 28 is positioned farther from the reference line La than the second end (rear end) of the connection shaft 28 is. In other words, the rotation range of the front wheels 3 about the front axis L1 and the rotation range of the rear wheel 5 about the rear axis L2 are preferably set such that the connection shaft 28 does not move beyond the position at which the connection shaft 28 is parallel to the reference line La.
Advantages of the Linkage Mechanism 27 Using the First Elastic Body 29 and the Second Elastic Body 31
[0084] As shown in FIGS. 3 to 5, the linkage mechanism 27 of the present embodiment uses the first and second elastic bodies 29 and 31 to connect the opposite ends of the connection shaft 28 to the front wheel support portion 8 and the rear wheel support portion 17. Thus, the linkage mechanism 27 does not need a complex structure because the connection shaft 28 is simply connected to the front wheel support portion 8 and the rear wheel support portion 17 using elastic members such as rubber. This simplifies the structure of the linkage mechanism 27 and thus the mobile body 1.
[0085] Additionally, it suffices to form the front wheel support portion 8 and the front wheel seat 9 so that the front wheel support portion 8 can simply rotate about the front axis L1. Similarly, it suffices to form the rear wheel support portion 17 and the rear wheel seat 18 so that the rear wheel support portion 17 can simply rotate about the rear axis L2. As a result, the portion connecting the front wheel support portion 8 and the front wheel seat 9 and the portion connecting the rear wheel support portion 17 and the rear wheel seat 18 do not involve complicated structures. This further contributes to simplifying the structure of the mobile body 1.
Change in the Positions of the Front Connection Point P1 and the Rear Connection Point P2
[0086] As shown in FIGS. 16A to 16C, the position of at least one of the front connection point P1 and the rear connection point P2 may be changeable to change the feeling of sideslip or curving motion. For example, the position of the front connection point P1 can be accommodated by changing the shape of the connection portion 30 of the front wheel unit 4. For example, the shape of the connection portion 30 may be changed by preparing multiple connection portions 30 with different shapes and replacing the connection portion 30 attached to the mobile body 1. The position of the rear connection point P2 can be accommodated by changing the shape of the second component 22 of the rear wheel unit 6. For example, this may be achieved by preparing multiple second components 22 with different shapes and replacing the second component 22 attached to the mobile body 1.
[0087] Referring to the connection shaft 28 indicated by solid lines in FIGS. 16A to 16C, the rotation amount R1 of the front wheel support portion 8 and the rotation amount R2 of the rear wheel support portion 17 in counterclockwise rotation shown in FIG. 16B are substantially equal to the rotation amount R1 of the front wheel support portion 8 and the rotation amount R2 of the rear wheel support portion 17 in clockwise rotation shown in FIG. 16C, respectively. Referring to the connection shaft 28 indicated by broken lines in FIGS. 16A to 16C, the rotation amount R1 of the front wheel support portion 8 and the rotation amount R2 of the rear wheel support portion 17 in counterclockwise rotation shown in FIG. 16B are substantially equal to the rotation amount R1 of the front wheel support portion 8 and the rotation amount R2 of the rear wheel support portion 17 in clockwise rotation shown in FIG. 16C, respectively.
[0088] A straight line that extends through the front axis L1 and is perpendicular to the reference line La is referred to as a first width direction line Lb, while a straight line that extends through the rear axis L2 and is perpendicular to the reference line La is referred to as a second width direction line Lc. Positioning the front connection point P1 on the first width direction line Lb and the rear connection point P2 on the second width direction line Lc allows the user to experience a similar feeling during left curving motion and right curving motion.
Display Portion 44
[0089] As shown in FIG. 17, the connection shaft 28 may include a display portion 44 capable of displaying a design. The display portion 44 may include a display plate 44a, which serves as a design display section, and a fixing portion 44b, which fixes the display portion 44 to the connection shaft 28. The display portion 44 is a part irrelevant to the traveling of the mobile body 1 and rotates integrally with the connection shaft 28. The display portion 44 (specifically, the display plate 44a) displays designs such as pictures, letters, numbers, and the like. It is also possible to place advertisements and the like on the display portion 44.
Advantageous Effects of the Embodiment
[0090] The steering device 7 (skateboard 1a) of the above embodiment has the following advantageous effects.
[0091] (1) According to this configuration, the front axis L1 and the rear axis L2 are both inclined upward from the front to the rear in the mobile body 1. As such, when the board portion 2 is tilted to one side in the width direction to travel during curving motion, the front wheel support portion 8 and the rear wheel support portion 17 rotate in the direction opposite to the curve direction. Although the front wheel support portion 8 and the rear wheel support portion 17 rotate in the direction opposite to the curve direction in this manner, the rotation difference between the rotation amount R1 of the front wheel support portion 8 and the rotation amount R2 of the rear wheel support portion 17 brings the mobile body 1 into the curving motion in the direction in which the board portion 2 is tilted with a turning radius according to the rotation difference.
[0092] As described above, during curving motion, the front wheel support portion 8 and the rear wheel support portion 17 rotate in the direction opposite to the curve direction, causing the front wheels 3 and the rear wheel 5 to be directed in the direction opposite to the curve direction. This creates a feeling of sideslip of the mobile body 1. Also, while providing a feeling of sideslip of the mobile body 1 during curving motion, the rotation difference created between the front wheel support portion 8 and the rear wheel support portion 17 also allows the mobile body 1 to curve in a desired direction. Thus, the mobile body 1 can travel during curving motion more smoothly, while providing a sufficient feeling of sideslip.
[0093] (2) The skateboard 1a includes the steering device 7, which steers the front wheel unit 4 and the rear wheel unit 6. The steering device 7 includes the linkage mechanism 27 including the connection shaft 28. The linkage mechanism 27 connects the front wheel support portion 8 and the rear wheel support portion 17 to each other with the connection shaft 28, thereby linking the rotation of the front wheel support portion 8 and the rotation of the rear wheel support portion 17. The first end of the connection shaft 28 is connected to the front wheel support portion 8 so as to be rotatable at least about the front axis L1. The second end of the connection shaft 28 is connected to the rear wheel support portion 17 so as to be rotatable at least about the rear axis L2. According to this configuration, the linkage mechanism 27 linkages the rotation of the front wheel support portion 8 and the rotation of the rear wheel support portion 17, so that the front wheels 3 and the rear wheel 5 can be readily rotated in the same direction during curving motion. This allows for curving motion in the direction intended by the user.
[0094] (3) The steering device 7 has the front connection point P1, at which the first end of the connection shaft 28 is connected to the front wheel support portion 8, and the rear connection point P2, at which the second end of the connection shaft 28 is connected to the rear wheel support portion 17. The connection shaft 28 is placed at an angle with respect to the reference line La extending in front-rear direction because the first distance Ls between the front axis L1 and the front connection point P1 differs from the second distance Lt between the rear axis L2 and the rear connection point P2. According to this configuration, by optimizing the positional relationship among the front axis L1, the rear axis L2, the front connection point P1, and the rear connection point P2, the front wheel support portion 8 and the rear wheel support portion 17 can readily rotate in the desired direction. This further contributes to achieving curving motion in the direction intended by the user.
[0095] (4) The connection shaft 28 is placed on only one side of the reference line La in a direction intersecting the reference line La. According to this configuration, it is possible to arrange the linkage mechanism 27 collectively on one side of the reference line La, thereby optimizing the arrangement of components.
[0096] (5) The first end of the connection shaft 28 is connected to the front wheel support portion 8 through the first elastic body 29 used as a universal joint, and the second end of the connection shaft 28 is connected to the rear wheel support portion 17 through the second elastic body 31 used as a universal joint. According to this configuration, the linkage mechanism 27 has a simple structure using elastic members.
[0097] (6) The connection shaft 28 includes the display portion 44 capable of displaying a design. According to this configuration, the display portion 44 provided on the connection shaft 28 can display designs such as pictures, numbers, letters, and the like.
[0098] (7) The rear wheel 5 is placed rearward of the rear axis L2 in a direction intersecting the rear axis L2. According to this configuration, because the rear wheel 5 is positioned away from the front wheels 3, a large elastic force to return the direction of the rear wheel 5 acts on the rear wheel 5 when the board portion 2 that is tilted in the width direction is returned to the neutral position while traveling. This elastic force can be used for acceleration.
[0099] (8) The front wheel unit 4 includes two front wheels 3 arranged on the opposite sides of the front axis L1. The rear wheel unit 6 includes one rear wheel 5. According to this configuration, it is possible to reduce the number of wheels, thereby reducing the number of components of the mobile body 1. The cost of components can also be reduced.
[0100] (9) During curving motion, the front wheels 3 remain firmly gripped to the road surface, but the one side of the rear wheel 5 becomes lifted, so that the contact area of the rear wheel 5 with the road surface is smaller than that of the front wheels 3. This reduces the resistance acting on the wheels from the road surface during curving motion, thereby reducing deceleration during curving motion. This improves the smoothness during curving motion.
OTHER EMBODIMENTS
[0101] The embodiment described above may be modified as follows. The above embodiment and the following modifications may be combined to an extent that does not cause technical contradiction.
[0102] As shown in FIG. 18, the connection shaft 28 may include, at its axial ends, bulging portions 45a and 45b having an outer diameter that is increased by a predetermined amount. The bulging portions 45a and 45b preferably have a spherical surface and are formed around the entire circumference of the connection shaft 28. In this configuration, the surface shape of the bulging portions 45a and 45b allows each end of the connection shaft 28 to move smoothly as a universal joint. This improves the functionality of the linkage mechanism 27.
[0103] As shown in FIG. 19, the board portion 2 may have a cutout section 49 for avoiding interference with the front wheel unit 4 when the board portion 2 is tilted in the width direction. In this case, even if the board portion 2 is configured to be tilted significantly during curving motion, the board portion 2 does not come into contact with the front wheel unit 4.
[0104] As shown in FIGS. 20 and 21, in the mobile body 1, the front wheel unit 4 and the rear wheel unit 6 do not necessarily need to be connected by the linkage mechanism 27. Specifically, as shown in FIG. 20, the front wheel unit 4 may include two front wheels 3, and the rear wheel unit 6 may include two rear wheels 5. The front wheel unit 4 is not connected to the rear wheel unit 6 by an linkage mechanism 27. The rotation of the front wheels 3 about the front axis L1 is therefore independent from the rotation of the rear wheels 5 about the rear axis L2. As shown in FIG. 21, the angle 2 of the rear axis L2 is set to be greater than the angle 1 of the front axis L1. This provides a rotation difference such that the rotation amount R2 of the rear wheel support portion 17 is greater than the rotation amount R1 of the front wheel support portion 8 (R2>R1) when the board portion 2 is tilted during curving motion. As a result, smooth curving motion is achieved while providing a sufficient feeling of sideslip.
[0105] The first elastic body 29 and the second elastic body 31 do not necessarily need to be formed by multiple elastic pieces and may be formed by a continuous single member without any gaps.
[0106] The connection shaft 28 may be inclined such that the first end is closer to the reference line La and the second end is farther from the reference line La when the steering device 7 is in the neutral state. Also, the connection shaft 28 may be placed parallel to the reference line La when the steering device 7 is in the neutral state.
[0107] In FIG. 9A for example, the connection shaft 28 may be configured such that the front connection point P1 is located on one side of the reference line La in the left-right direction as viewed in the drawing, and the rear connection point P2 is located on the other side of the reference line La in the left-right direction.
[0108] The linkage mechanism 27 may be configured to rotate the opposite ends of the connection shaft 28 about an axis perpendicular to the connection shaft 28, for example. Specifically, the first end of the connection shaft 28 may be connected to the front wheel support portion 8 so as to be rotatable about an axis perpendicular to the connection shaft 28, and the second end of the connection shaft 28 may be connected to the rear wheel support portion 17 so as to be rotatable about an axis perpendicular to the connection shaft 28. The linkage mechanism 27 is not limited to a rotation type in which the connection shaft 28 rotates at the opposite ends in response to a tilting operation of the board portion 2. For example, the linkage mechanism 27 may be of a slider type and include a slider member that can move linearly in the axial direction.
[0109] The rotation difference between the rotation of the front wheel support portion 8 and the rotation of the rear wheel support portion 17 may be provided by setting the number of the front wheels 3 and the number of the rear wheels 5 to be the same, and by varying the wheel width between the front wheels 3 and the rear wheels 5.
[0110] The front wheel unit 4 and the rear wheel unit 6 are not limited to a structure with elastic members (first elastic body 29 and second elastic body 31), and may be a structure with trucks, which are widely used general structures.
[0111] The mobile body 1 is not limited to a skateboard 1a, and may be a kickboard (registered trademark), for example.
[0112] Although the present disclosure has been described with reference to exemplary embodiments, it is understood that the present disclosure is not limited to those embodiments or configurations. The present disclosure also encompasses various modifications and variations within the scope of equivalents. Additionally, various combinations and configurations, as well as other combinations and configurations that include only one element, one element or more, or one element or less, are within the scope and spirit of the present disclosure.
[0113] Various changes in form and details may be made to the examples above without departing from the spirit and scope of the claims and their equivalents. The examples are for the sake of description only, and not for purposes of limitation. Descriptions of features in each example are to be considered as being applicable to similar features or aspects in other examples. Suitable results may be achieved if sequences are performed in a different order, and/or if components in a described system, architecture, device, or circuit are combined differently, and/or replaced or supplemented by other components or their equivalents. The scope of the disclosure is not defined by the detailed description, but by the claims and their equivalents. All variations within the scope of the claims and their equivalents are included in the disclosure.
