Wheel structure and vehicle

Abstract

A wheel structure 1 includes: a drive wheel 20 which is attached to a main body portion 10 in a rotatable manner about a rotation axis Axr; a vehicle body attachment portion 30 which is capable of moving relative to the main body portion 10 along a first axis Ax1 perpendicular to the rotation axis Axr; and a link mechanism portion 40. The link mechanism portion 40 includes: a first link member 41 having a first connecting portion 41a which is connected to the main body portion 10 in a rotatable manner about a second axis Ax2 perpendicular to the first axis Ax1 and a second connecting portion 41b to which a driven wheel 50 is rotatably attached; and a second link member 42 having a fourth connecting portion 42a which is connected to a third connecting portion 41c located between the first connecting portion 41a and the second connecting portion 41b of the first link member 41 in a rotatable manner about a fourth axis Ax4 parallel to the second axis Ax2, and a fifth connecting portion 42b which is connected to the vehicle body attachment portion 30 in a rotatable manner about a fifth axis Ax5 parallel to the second axis Ax2.

Description

Wheel structure and vehicle

[0001] The present disclosure relates to a wheel structure and a vehicle.

[0002] Patent Document 1 discloses a wheel structure that improves traversal performance on uneven terrain having steps or the like. The wheel structure of Patent Document 1 is configured such that when a drive wheel moves relative to a base member extending in a first direction in a second direction perpendicular to the first direction, a first driven wheel and a second driven wheel move relative to each other in the second direction in an interlocking manner via a first lever member and a second lever member. As a result, the wheel structure of Patent Document 1 allows the drive wheel, the first driven wheel, and the second driven wheel to come into contact with each other even on uneven terrain, improving traversal performance on uneven terrain.

[0003] Japanese Patent Application Laid-Open No. 2018-94998

[0004] However, the wheel structure of Patent Document 1 has a relatively large number of parts and a relatively complex structure. On the other hand, there is a demand for a simpler wheel structure.

[0005] The present disclosure has been made in view of the above, and aims to provide a wheel structure and a vehicle that can simplify the structure.

[0006] A wheel structure according to one aspect of the present disclosure includes a main body portion, a drive wheel attached to the main body portion so as to be rotatable about a rotation axis relative to the main body portion, a vehicle body attachment portion movable relative to the main body portion along a first axis perpendicular to the rotation axis and attachable to a vehicle body, a link mechanism portion connecting the main body portion and the vehicle body attachment portion, and a driven wheel attached to the link mechanism portion, wherein the link mechanism portion is connected to the main body portion so as to be rotatable about a second axis parallel to the rotation axis and perpendicular to the first axis. a first link member having a first connection portion and a second connection portion to which the driven wheel is rotatably attached about a third axis parallel to the second axis; a fourth connection portion rotatably connected to the third connection portion between the first connection portion and the second connection portion of the first link member about a fourth axis parallel to the second axis, and a fifth connection portion connected to the vehicle body mounting portion about a fifth axis parallel to the second axis and perpendicular to the first axis.

[0007] According to this, the wheel structure 1 connects one driving wheel and one driven wheel via two links, the first link member and the second link member, thereby simplifying the structure of the wheel structure.

[0008] In a wheel structure according to one aspect of the present disclosure, when the first link member is viewed along the rotation axis, the angle between a first line segment connecting the second axis and the fourth axis and a second line segment connecting the second axis and the fifth axis is an acute angle, and the first link member has a bent portion between the third connection portion and the second connection portion, in which the second connection portion bends in a direction away from the fifth connection portion.

[0009] According to this, since the first link member has a bent portion, the reaction force acting on the driven wheel when the driven wheel hits a step makes it easier for the first link member to rotate, allowing the driven wheel to easily climb up the step. Therefore, the wheel structure can improve its ability to traverse steps.

[0010] In one aspect of the wheel structure of the present disclosure, a first spring member is further provided that is attached between the main body portion and the vehicle body mounting portion and biases the main body portion and the vehicle body mounting portion in a direction away from each other.

[0011] This makes it possible to adjust the force with which the drive wheels are pressed against the ground by the biasing force of the first spring member.

[0012] In a wheel structure according to one aspect of the present disclosure, a second spring member is further provided that is attached between the vehicle body mounting portion and the bent portion and biases the vehicle body mounting portion and the bent portion in directions in which the vehicle body mounting portion and the bent portion move away from each other.

[0013] According to this, the rotation speed of the first link member about the second axis can be adjusted by the biasing force of the second spring member, and the second spring member can also suppress the impact when the driven wheel hits a step.

[0014] In a wheel structure 1 according to one aspect of the present disclosure, the wheel structure 1 further includes a second driven wheel attached to the link mechanism, and the link mechanism further includes a second first link member and a second second link member that are symmetrical to the first link member and the second link member with the first axis as an axis of symmetry when viewed along the rotation axis, and the second first link member has a second first connection portion connected to the main body portion so as to be rotatable relative to the main body portion about the second axis, and a second second connection portion to which the second driven wheel is attached so as to be rotatable about a second third axis parallel to the second axis, and the second second link member has a second fourth connection portion connected to a second third connection portion between the second first connection portion and the second second connection portion of the second first link member so as to be rotatable relative to the second first link member about a second fourth axis parallel to the second axis, and a second fifth connection portion connected to the vehicle body mounting portion so as to be rotatable relative to the vehicle body mounting portion about the fifth axis.

[0015] According to this, the wheel structure connects one drive wheel and two driven wheels via four links, namely, the first link member, the second link member, the second first link member, and the second second link member, thereby simplifying the structure of the wheel structure.

[0016] A vehicle according to one aspect of the present disclosure comprises the above-described wheel structure and a vehicle body, wherein there are two wheel structures, and the two wheel structures are arranged on opposite sides of the vehicle body.

[0017] According to this, the vehicle can be constructed simply by attaching the wheel structure to the vehicle body.

[0018] An object of the present disclosure is to provide a wheel structure and a vehicle that can simplify the structure.

[0019] FIG. 1 is a front view of a wheel structure according to an embodiment of the present disclosure. FIG. 2 is a rear view of the wheel structure. FIG. 3 is a side view of the wheel structure. FIG. 4 is a perspective view of the wheel structure as viewed from the rear side. FIG. 5 is a schematic diagram of a link mechanism. FIG. 6 is a diagram illustrating the relationship between a first Y-direction length, a second Y-direction length, and an X-direction length and a link angle. FIG. 7 is a schematic diagram illustrating a state in which a driven wheel has climbed over a step. FIG. 8 is a schematic diagram illustrating a state in which the wheel structure is positioned on the ground. FIG. 9 is a diagram illustrating the relationship between a link angle and a reduction ratio. FIG. 10 is a schematic diagram illustrating a state in which a driven wheel has hit a step while in contact with the ground. FIG. 11 is a partially enlarged perspective view of the wheel structure as viewed from the front side of the wheel structure. FIG. 12 is a front view of a vehicle. FIG. 13 is a side view of a vehicle. FIG. 14 is a schematic diagram of a link mechanism of a wheel structure according to a modified embodiment of the present disclosure.

[0020] Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings, but the present disclosure is not limited thereto. The components of each embodiment and each modified example described below can be combined as appropriate. In addition, some components may not be used. In this specification, rotation around an axis includes both clockwise and counterclockwise rotation around the axis.

[0021] <Wheel structure> Fig. 1 is a front view of a wheel structure 1 according to an embodiment of the present disclosure. Fig. 2 is a rear view of the wheel structure 1. Figs. 1 and 2 show a state in which the wheel structure 1 is positioned on flat ground G, and a drive wheel 20, a driven wheel 50, and a second driven wheel 60 (described later) are in contact with the ground G.

[0022] Fig. 3 is a side view of the wheel structure 1. The driven wheel 50 and the second driven wheel 60 are not shown in Fig. 3. Fig. 4 is a perspective view of the wheel structure 1 as seen from the rear side. In this specification, "plan view" refers to viewing the wheel structure 1 along the rotation axis Axr, which will be described later.

[0023] The wheel structure 1 includes a main body 10, a driving wheel 20, a vehicle body mounting portion 30, a link mechanism 40, a driven wheel 50, and a second driven wheel 60. In Figures 1, 2, 3, and 4, the driven wheel 50 and the second driven wheel 60 have the same outer diameter and are smaller than the outer diameter of the driving wheel 20.

[0024] The main body 10 is cylindrical and extends along a rotation axis Axr. The rotation axis Axr is the center of rotation of the drive wheels 20. A first rod member 11 is fixed to the outer circumferential surface of the main body 10 and extends along a first axis Ax1 that is perpendicular to the rotation axis Axr (see FIGS. 1, 2, and 3). A first shaft member 12 is fixed to the end face on the rear side of the main body 10 (see FIGS. 2 and 3). The first shaft member 12 is cylindrical and has a central axis that is a second axis Ax2 that is parallel to the rotation axis Axr and perpendicular to the first axis Ax1.

[0025] The drive wheel 20 is attached to the main body 10 so as to be rotatable about a rotation axis Axr relative to the main body 10. The drive wheel 20 includes a wheel portion 21 and a tire portion 22. The wheel portion 21 is rotatable about the rotation axis Axr relative to the main body 10.

[0026] The wheel unit 21 is rotated by a motor M (e.g., an in-wheel motor: see FIG. 3 ) housed in the main body unit 10. The wheel unit 21 and the motor M may be connected via a circular belt and a reducer including multiple gears. Furthermore, when the wheel structure 1 is applied to a vehicle (e.g., a wheelchair) in which a user rides, the main body unit 10 does not need to have a drive source such as the motor M. In this case, the wheel unit 21 is rotated manually.

[0027] The tire portion 22 is an annular elastic body and is attached to the outer periphery of the wheel portion 21. The tire portion 22 may be, for example, a so-called normal tire, a knobby tire, a studless tire, or the like. The tire portion 22 is detachable from the wheel portion 21. The type of tire portion 22 is selected depending on, for example, the condition of the ground G. It goes without saying that the tire portion 22 is not limited to an annular elastic body.

[0028] As the drive wheel 20 rotates, the wheel structure 1 moves along the ground G in a direction perpendicular to the rotation axis Axr.

[0029] The vehicle body mounting portion 30 is attached to a vehicle body 90, which will be described later. The vehicle body mounting portion 30 is a plate-like member that is T-shaped in a plan view. A fitting portion 31 that fits with the first rod member 11 and is movable along the first axis Ax1 is attached to the vehicle body mounting portion 30 (see FIG. 1 ). This allows the vehicle body mounting portion 30 to move relative to the main body portion 10 along the first axis Ax1.

[0030] The link mechanism 40 connects the main body 10 and the vehicle body mounting portion 30. The link mechanism 40 includes a first link member 41, a second link member 42, a second first link member 43, and a second second link member 44.

[0031] The first link member 41 is composed of a pair of first plate members S1 facing each other in the direction along the rotation axis Axr (see FIGS. 3 and 4). The pair of first plate members S1 each have the same L-shape in a plan view. As shown in FIG. 2, the first link member 41 has a first connecting portion 41a at a first end, a second connecting portion 41b at a second end, a third connecting portion 41c between the first connecting portion 41a and the second connecting portion 41b, and a bent portion 41d between the second connecting portion 41b and the third connecting portion 41c.

[0032] The first connection portion 41a is connected to the main body portion 10 so as to be rotatable about the second axis Ax2 relative to the main body portion 10. Specifically, the first connection portion 41a is connected to the main body portion 10 via the first shaft member 12. In other words, the second axis Ax2 is the center of rotation when the first link member 41 rotates relative to the main body portion 10.

[0033] The driven wheel 50 is attached to the second connection portion 41b so as to be rotatable about a third axis Ax3 that is parallel to the second axis Ax2. In other words, the third axis Ax3 is the center of rotation of the driven wheel 50. Specifically, the driven wheel 50 is attached to the second connection portion 41b via a cylindrical second shaft member 41e whose central axis coincides with the third axis Ax3.

[0034] A cylindrical third shaft member 41f having a central axis that coincides with a fourth axis Ax4 that is parallel to the second axis Ax2 is attached to the third connection portion 41c.

[0035] When the first link member 41 is viewed along the rotation axis Axr, the bent portion 41d is a portion of the first link member 41 where the second connection portion 41b bends in a direction away from a fifth connection portion 42b (described later) of the second link member 42. The bent portion 41d bends around a bending axis Axb that is parallel to the second axis Ax2.

[0036] In addition, the second axis Ax2, the fourth axis Ax4, and the bending axis Axb are located on the same straight line in a plan view. A fourth shaft member 41g having the bending axis Axb as its central axis is disposed in the bending portion 41d.

[0037] The second link member 42 is formed by a single second plate member S2 (see FIGS. 3 and 4). The second plate member S2 is linear in plan view. The second link member 42 is sandwiched between a pair of first plate members S1. The second link member 42 has a fourth connecting portion 42a at a first end and a fifth connecting portion 42b at a second end.

[0038] The fourth connection portion 42a is connected to the third connection portion 41c of the first link member 41 so as to be rotatable about the fourth axis Ax4 with respect to the first link member 41. Specifically, the fourth connection portion 42a is connected to the third connection portion 41c of the first link member 41 via the third shaft member 41f. In other words, the fourth axis Ax4 is the center of rotation when the first link member 41 and the second link member 42 rotate relative to each other.

[0039] The fifth connection portion 42b is connected to the vehicle body mounting portion 30 so as to be rotatable relative to the vehicle body mounting portion 30 about a fifth axis Ax5 that is parallel to the second axis Ax2 and perpendicular to the first axis Ax1. Specifically, a cylindrical fifth shaft member 32 having the fifth axis Ax5 as its central axis is fixed to the vehicle body mounting portion 30, and the fifth connection portion 42b is connected to the vehicle body mounting portion 30 via the fifth shaft member 32. Therefore, the fifth connection portion 42b is movable together with the vehicle body mounting portion 30 along the first axis Ax1. In other words, the fifth axis Ax5 is the center of rotation about which the second link member 42 rotates relative to the vehicle body mounting portion 30. Furthermore, the second link member 42 is movable together with the vehicle body mounting portion 30 along the first axis Ax1.

[0040] In this embodiment, the intersection of the first axis Ax1 with the rotation axis Axr is between the intersection with the second axis Ax2 and the intersection with the fifth axis Ax5. When the first link member 41 is viewed along the rotation axis Axr, the angle between a first line segment Ln1 connecting the second axis Ax2 and the fourth axis Ax4 and a second line segment Ln2 connecting the second axis Ax2 and the fifth axis Ax5 (corresponding to the link angle θ, described below) is an acute angle. The first axis Ax1 is indicated by a thin dashed line, and the second line segment Ln2 is indicated by a thick dashed line. The portion where the first axis Ax1 and the second line segment Ln2 overlap is indicated by the second line segment Ln2.

[0041] The second first link member 43 has a shape that is line-symmetrical to the first link member 41 with the first axis Ax1 as the axis of symmetry when viewed along the rotation axis Axr. The second first link member 43 is formed of a pair of second first plate members S1a that face each other in the direction in which the rotation axis Axr extends (see FIGS. 3 and 4). The pair of second first plate members S1a each has a shape that is line-symmetrical to the pair of first plate members S1 with the first axis Ax1 as the axis of symmetry when viewed along the rotation axis Axr. The pair of second first plate members S1a sandwich the pair of first plate members S1.

[0042] The second first link member 43 has a second first connection portion 43a at the first end, a second second connection portion 43b at the second end, a second third connection portion 43c between the second first connection portion 43a and the second second connection portion 43b, and a second bent portion 43d between the second second connection portion 43b and the second third connection portion 43c.

[0043] The second first connection portion 43a corresponds to the first connection portion 41a of the first link member 41. The second first connection portion 43a is connected to the main body portion 10 so as to be rotatable relative to the main body portion 10 about the second axis Ax2. Specifically, the second first connection portion 43a is connected to the main body portion 10 via the first shaft member 12. In other words, the second axis Ax2 is the center of rotation when the second first link member 43 rotates relative to the main body portion 10.

[0044] The second second connection portion 43b corresponds to the second connection portion 41b of the first link member 41. The second driven wheel 60 is rotatably attached to the second second connection portion 43b about a second third axis Ax3a that is parallel to the second axis Ax2. In other words, the second third axis Ax3a is the center of rotation of the second driven wheel 60. Specifically, the second driven wheel 60 is attached to the second second connection portion 43b via a cylindrical second second shaft member 43e whose central axis is the second third axis Ax3a.

[0045] The second third connection portion 43c corresponds to the third connection portion 41c of the first link member 41. A cylindrical second third shaft member 43f having a central axis coincident with a second fourth axis Ax4a that is parallel to the second axis Ax2 is attached to the second third connection portion 43c.

[0046] The second bent portion 43d corresponds to the bent portion 41d of the first link member 41. When the second first link member 43 is viewed along the rotation axis Axr, the second bent portion 43d is a portion of the second first link member 43 where the second second connecting portion 43b bends in a direction away from a second fifth connecting portion 44b (described later) of the second second link member 44. The second bent portion 43d bends around a second bending axis Axba. The second bending axis Axba corresponds to the bending axis Axb of the first link member 41 and is parallel to the second axis Ax2.

[0047] In addition, in a plan view, the second axis Ax2, the second fourth axis Ax4a, and the second bending axis Axba are located on the same straight line. A second fourth shaft member 43g having the second bending axis Axba as its central axis is disposed in the second bending portion 43d.

[0048] The second second link member 44 has a shape that is line-symmetrical to the second link member 42 with the first axis Ax1 as the axis of symmetry when viewed along the rotation axis Axr. The second second link member 44 is formed of a pair of second second plate members S2a that face each other in the direction in which the rotation axis Axr extends (see FIGS. 3 and 4). The pair of second second plate members S2a has a shape that is line-symmetrical to the second plate member S2 with the first axis Ax1 as the axis of symmetry when viewed along the rotation axis Axr. The pair of second second plate members S2a sandwich the second plate member S2 and are also sandwiched between the pair of second first plate members S1a.

[0049] The second second link member 44 has a second fourth connecting portion 44a at a first end and a second fifth connecting portion 44b at a second end.

[0050] The second fourth connection portion 44a corresponds to the fourth connection portion 42a of the second link member 42. The second fourth connection portion 44a is connected to the second third connection portion 43c of the second first link member 43 so as to be rotatable about the second fourth axis Ax4a with respect to the second first link member 43. Specifically, the second fourth connection portion 44a is connected to the second third connection portion 43c of the second first link member 43 via a second third shaft member 43f. In other words, the second fourth axis Ax4a is the center of rotation when the second first link member 43 and the second second link member 44 rotate relative to each other.

[0051] The second fifth connection portion 44b corresponds to the fifth connection portion 42b of the second link member 42. The second fifth connection portion 44b is connected to the vehicle body mounting portion 30 so as to be rotatable relative to the vehicle body mounting portion 30 about the fifth axis Ax5. Specifically, the second fifth connection portion 44b is connected to the vehicle body mounting portion 30 via the fifth shaft member 32. Therefore, the second fifth connection portion 44b is movable together with the vehicle body mounting portion 30 along the first axis Ax1. In other words, the fifth axis Ax5 is the center of rotation about which the second second link member 44 rotates relative to the vehicle body mounting portion 30. Furthermore, the second second link member 44 is movable together with the vehicle body mounting portion 30 along the first axis Ax1.

[0052] The driven wheel 50 and the second driven wheel 60 are attached to the link mechanism 40 as described above.

[0053] Next, a description will be given of the operation of the link mechanism 40. When the drive wheel 20 is driven and the wheel structure 1 is moving on the ground G, and one of the driven wheel 50 and the second driven wheel 60 runs over a step, the link mechanism 40 operates as described below.

[0054] Fig. 5 is a schematic diagram of the link mechanism 40 as viewed along the second axis Ax2. For ease of explanation, Fig. 5 shows a case in which the rotation axis Axr and the second axis Ax2 are coaxial, but as described above, the operation of the link mechanism 40 is the same even when the rotation axis Axr and the second axis Ax2 are at different positions on the first axis Ax1.

[0055] In Fig. 5, the fifth axis Ax5 is fixed, and the rotation axis Axr and the second axis Ax2 move along the first axis Ax1. Fig. 5 also shows the fifth axis Ax5 as the origin O, a Y axis that overlaps with the first axis Ax1, and an X axis that is perpendicular to the Y axis. Hereinafter, the direction in which the Y axis extends may be referred to as the Y direction, and the direction in which the X axis extends may be referred to as the X direction.

[0056] As described above, the second first link member 43 and the second second link member 44 are symmetrical with the first link member 41 and the second link member 42 about the first axis Ax1, and the link mechanism 40 is also symmetrical with the first axis Ax1. In other words, the movement of the link mechanism 40 is symmetrical about the first axis Ax1. For ease of explanation, the following description will mainly focus on the movement of the first link member 41 and the second link member 42.

[0057] In FIG. １ is the length between the second axis Ax2 and the bending axis Axb in the first link member 41, and L ２ is the length between the second axis Ax2 and the fourth axis Ax4 in the first link member 41, and L ３ is the length between the fourth axis Ax4 and the fifth axis Ax5 in the second link member 42, and L ４ is the length between the bending axis Axb and the third axis Ax3 in the first link member 41, and L ５ is the length of the third line segment Ln3 connecting the second axis Ax2 and the third axis Ax3 in the first link member 41, and L ６ is the length in the Y direction between the second axis Ax2 and the third axis Ax3.

[0058] Furthermore, θ is the angle between the first line segment Ln1 and the second line segment Ln2 (hereinafter referred to as the link angle θ), α is the angle at which the first link member 41 bends around the bending axis Axb at the bending portion 41d (hereinafter referred to as the caster angle α), and β is the angle between the first line segment Ln1 and the third line segment Ln3. １ is the Y-direction length between the fifth axis Ax5 and the third axis Ax3 (hereinafter referred to as the first Y-direction length Y1), and y ２is the length in the Y direction between the fifth axis Ax5 and the second axis Ax2 (hereinafter referred to as the second Y direction length Y2), and x １ is the length in the X direction between the second axis Ax2 and the third axis Ax3 (hereinafter referred to as the X direction length X1).

[0059] From the structure of the link mechanism 40, the following equations (1), (2), (3), (4), and (5) can be derived.

[0060]

[0061]

[0062]

[0063]

[0064]

[0065] Furthermore, due to the structure of the link mechanism 40, the X-direction length X1 can be expressed by equation (6). Furthermore, the second Y-direction length Y2 can be expressed by equation (7) by modifying equation (5). Furthermore, the first Y-direction length Y1 can be expressed by equation (8) from equations (3), (4), and (7). As shown in equations (6), (7), and (8), the equations for the X-direction length X1, the first Y-direction length Y1, and the second Y-direction length Y2 are expressed using the link angle θ as a variable.

[0066]

[0067]

[0068]

[0069] 6 is a diagram showing the relationship between the first Y-direction length Y1, the second Y-direction length Y2, the X-direction length X1, and the link angle θ. FIG. 7 is a schematic diagram showing a state in which the driven wheel 50 runs over a step D.

[0070] When the driven wheel 50 rides over the step D, the first link member 41 rotates around the second axis Ax2 relative to the main body 10 in a direction that decreases the link angle θ. At this time, the second link member 42 rotates around the fourth axis Ax4 relative to the first link member 41 and also rotates around the fifth axis Ax5 relative to the vehicle body mounting portion 30. At this time, the main body 10, which has the rotation axis Axr and the second axis Ax2, and the vehicle body mounting portion 30, which has the fifth axis Ax5, move away from each other along the first axis Ax1 (in FIG. 5 , the main body 10, which has the rotation axis Axr and the second axis Ax2, moves toward the +Y side along the Y axis).

[0071] In FIG. 6, the first Y-direction length Y1 (y １ ) and the second Y-direction length Y2 (y ２ ) have opposite inclinations. For example, as the link angle θ decreases, the first Y-direction length Y1 decreases and the second Y-direction length Y2 increases. This means that when the driven wheel 50 climbs over the step D, as shown in FIG. 6 , the first link member 41 rotates and the link angle θ decreases, causing the link mechanism 40 to push the main body 10 and the driving wheel 20 down along the first axis Ax1. In other words, when the driven wheel 50 climbs over the step D (see FIG. 7 ) from a state in which the driving wheel 20 and the driven wheel 50 are in contact with the ground G, the link mechanism 40 presses the driving wheel 20 against the ground G. Therefore, even when the driven wheel 50 climbs over the step D, the link mechanism 40 can efficiently transmit the driving force of the driving wheel 20 to the ground G.

[0072] 6, the first Y-direction length Y1 and the second Y-direction length Y2 corresponding to the intersection P1 are equal to each other. When the first Y-direction length Y1 and the second Y-direction length Y2 are equal to each other, the outer diameters of the drive wheel 20 and the driven wheel 50 are equal to each other, and the driven wheel 50 is not riding over a step D, the drive wheel 20 and the driven wheel 50 each come into contact with the ground G.

[0073] In addition, when the first Y-direction length Y1 and the second Y-direction length Y2 are equal to each other and the drive wheel 20 and the driven wheel 50 are each in contact with the ground G, if the outer diameter of the drive wheel 20 is made larger than the outer diameter of the driven wheel 50, as shown in Figure 1, it is advisable to move the rotation axis Axr along the first axis Ax1 relative to the second axis Ax2 by the difference between the outer diameter of the driven wheel 50 and the outer diameter of the drive wheel 20.

[0074] In addition, at the link angle θ corresponding to the intersection point P1 shown in FIG. 6, the X-direction length X1 (x １ ) is maximized, and the amount of change in the X-direction length X1 with respect to the link angle θ is smaller than that at other link angles θ. In other words, when the link mechanism 40 operates near the link angle θ corresponding to the intersection point P1, the length between the drive wheel 20 and the driven wheel 50 corresponding to the X-direction length X1 can be stabilized, and the length between the drive wheel 20 and the driven wheel 50 can be made longer than when the link mechanism 40 operates near other link angles θ, thereby stabilizing the operation of the wheel structure 1.

[0075] Fig. 7 shows a fourth line segment Ln4 connecting the third axis Ax3 and the second third axis Ax3a. Also, the symbol "a" in Fig. 7 indicates the height of the step D. In Fig. 7, the rotation axis Axr and the second axis Ax2 are coaxial, and the outer diameters of the drive wheel 20 and the driven wheel 50 are equal to each other.

[0076] When the driven wheel 50 is on the step D, the length (b) of the perpendicular line Lv drawn from the second axis Ax2 to the fourth line segment Ln4 is ６ (i.e., b = L ６ ). The length (H) between the second axis Ax2 and the intersection P2 of the vertical line Lg passing through the second axis Ax2 and the fourth line segment Ln4 corresponds to half the height (a) of the step D (i.e., H = a / 2). As is clear from FIG. 7, b is smaller than H (b < H). Therefore, in order for the driven wheel 50 to climb over a step D of a desired height, it is desirable that the length (b) of the perpendicular line Lv when the driven wheel 50 climbs over the step D be equal to or greater than half of the desired height (i.e., b ≥ (desired height) / 2).

[0077] Furthermore, it is generally known that in order for the driven wheel 50 to climb over a step D of a desired height, the outer diameter of the driven wheel 50 must be three times or more the desired height (i.e., (outer diameter of the driven wheel 50) ≥ 3 × (desired height)). Therefore, the length of the perpendicular line Lv when the driven wheel 50 climbs over the step D of the desired height (b(=L ６ ) is preferably equal to or greater than 1 / 6 of the outer diameter of the driven wheel 50 (i.e., b≧(outer diameter of the driven wheel 50) / 6).

[0078] FIG. 8 is a schematic diagram showing a state in which the wheel structure 1 is positioned on the ground G. In FIG. １ is a first normal force (hereinafter referred to as the first normal force N1) acting on the driven wheel 50 and the second driven wheel 60 from the ground G, and N ２ is a second normal force acting on the drive wheel 20 from the ground G (hereinafter referred to as the second normal force N2). ２ is the length in the X direction between the third axis Ax3 and the fourth axis Ax4, and x ３ is the length in the X direction between the second axis Ax2 and the fourth axis Ax4. From the balance of the moment around the fourth axis Ax4, the ratio of the second normal force N2 to the first normal force N1 (N ２ / N １ ) can be expressed by the following equations (9), (10), and (11) and the above equation (6) as equation (12) using the link angle θ as a variable.

[0079]

[0080]

[0081]

[0082]

[0083] By making the second normal force N2 of the driving wheel 20 larger than the first normal force N1 of the driven wheel 50, the driving force of the driving wheel 20 is efficiently transmitted to the ground G, and the running of the wheel structure 1 can be stabilized. In other words, the ratio of the second normal force N2 to the first normal force N1 (N ２ / N １) is preferably greater than 1. In addition, it is preferable that the ratio is determined depending on the condition of the ground G on which the wheel structure 1 is used. The ratio is determined by the L ２ , L ５ , β (see FIG. 5). For example, when the wheel structure 1 is used in a state where the ground G is slippery due to rain or the like, the ratio is set to about 3.6.

[0084] Furthermore, the smaller the link angle θ, the larger the second normal force N2 of the drive wheel 20 according to equation (12). This means that when the driven wheel 50 runs over a step D, the force with which the link mechanism 40 presses the drive wheel 20 against the ground G increases. In other words, the larger the step D, the smaller the link angle θ, and the larger the force with which the link mechanism 40 presses the drive wheel 20 against the ground G. In other words, even when the driven wheel 50 runs over a step D, the link mechanism 40 can efficiently transmit the drive force of the drive wheel 20 to the ground G.

[0085] 9 is a diagram showing the relationship between the link angle θ and the reduction ratio R. In this specification, the reduction ratio R is calculated by multiplying the second Y-direction length Y2 (y ２ ) with respect to the velocity (i.e., the moving velocity along the Y direction of the rotation axis Axr (second axis Ax2) relative to the origin O) １ ) with respect to time (i.e., the moving speed along the Y direction of the third axis Ax3 relative to the origin O). Furthermore, equation (14) is the ratio of the velocity obtained by differentiating the first Y-direction length Y1 with respect to time, the velocity obtained by differentiating the second Y-direction length Y2 with respect to time, and the X-direction length X1(x １ ) with respect to time (i.e., the moving speed along the X direction of the third axis line Ax3 relative to the origin O). The reduction ratio R can be calculated from equations (13) and (14). In equation (14), ω is the angular velocity of the link angle θ when the first link member 41 rotates in a direction that reduces the link angle θ (hereinafter referred to as angular velocity ω).

[0086]

[0087]

[0088] 9 shows the relationship between the link angle θ and the reduction ratio R for each of three angular velocities ω. １ , ω ２ , ω ３ and the angular velocity ω １ , ω ２ , ω ３ The magnitude of the angular velocity ω increases in this order.

[0089] As shown in Figure 9, the smaller the link angle θ, the larger the reduction ratio R. An increase in the reduction ratio R means that the speed at which the drive wheel 20 descends relative to the speed at which the driven wheel 50 ascends becomes smaller. Furthermore, the higher the height of the step D (see Figure 8) that the driven wheel 50 climbs over, the smaller the link angle θ. In other words, when the driven wheel 50 climbs over the step D, the higher the height of the step D (the smaller the link angle θ), the smaller the speed at which the drive wheel 20 is pushed down relative to the speed at which the driven wheel 50 ascends. Therefore, when the driven wheel 50 climbs over the step D, it is possible to prevent the drive wheel 20 from leaving the ground G.

[0090] On the other hand, when the driven wheel 50 descends from the step D, the link angle θ increases and the reduction ratio R decreases. A smaller reduction ratio R means that the speed at which the driven wheel 50 descends is greater than the speed at which the drive wheel 20 ascends. In other words, the larger the link angle θ, the greater the speed at which the driven wheel 50 is pushed down by the link mechanism 40. Therefore, when the driven wheel 50 descends from the step D, the driven wheel 50 can come into contact with the ground G earlier.

[0091] 9, the greater the magnitude of the angular velocity ω, the greater the reduction ratio R. This means that, for example, the greater the speed at which the driven wheel 50 climbs over the step D, the slower the speed at which the drive wheel 20 is pushed down by the link mechanism 40. Therefore, when the driven wheel 50 climbs over the step D, the link mechanism 40 quickly pushes down the drive wheel 20, preventing the drive wheel 20 from leaving the ground G.

[0092] Furthermore, as the magnitude of the angular velocity ω increases, the greater the reduction ratio R, the greater the force with which the link mechanism 40 presses the drive wheel 20 against the ground surface G. In other words, when the driven wheel 50 climbs over a step D, the greater the magnitude of the angular velocity ω, the more quickly the link mechanism 40 can transmit the drive force of the drive wheel 20 to the ground surface G.

[0093] FIG. 10 is a schematic diagram showing a state in which the driven wheel 50, in contact with the ground G, hits a step D.

[0094] When the driven wheel 50 hits a step D while in contact with the ground G, a reaction force F from the step D acts on the driven wheel 50. The direction of the reaction force F is from the contact point Pd between the driven wheel 50 and the step D toward the third axis Ax3. Furthermore, as described above, the first link member 41 has a bent portion 41d that bends around the bending axis Axb. As a result, the angle between the first line segment Ln1 connecting the second axis Ax2 and the fourth axis Ax4 and the direction of the reaction force F is closer to a right angle than when the first link member 41 does not have the bent portion 41d.

[0095] Therefore, the magnitude of the component of the reaction force F that rotates the first link member 41 about the second axis Ax2 is larger than when the first link member 41 does not have the bent portion 41d. Therefore, when the first link member 41 has the bent portion 41d, the reaction force F makes it easier for the first link member 41 to rotate, and the driven wheel 50 to climb up the step D. Therefore, the ability of the wheel structure 1 to traverse the step D can be improved.

[0096] Furthermore, the angle between the direction of the reaction force F and the first line segment Ln1 can be adjusted by the caster angle α. In other words, by determining the caster angle α according to the height of the step D that the driven wheel 50 climbs over, the ability of the wheel structure 1 to traverse the step D can be reliably improved.

[0097] 11 is a partially enlarged perspective view of the wheel structure 1 as seen from the front side of the wheel structure 1. As shown in FIGS. 1, 2, 3, and 11, the wheel structure 1 further includes a first spring member 71, a second spring member 72, and a third spring member 73.

[0098] The first spring member 71 is attached between the main body 10 and the vehicle body mounting portion 30, and biases the main body 10 and the vehicle body mounting portion 30 in directions that move the main body 10 and the vehicle body mounting portion 30 away from each other. Specifically, the first spring member 71 is a coil spring that is disposed around the first rod member 11 between the main body 10 and the fitting portion 31. The biasing force of the first spring member 71 can adjust the force with which the drive wheel 20 is pressed against the ground G and the reduction ratio R.

[0099] Furthermore, the position of the fitting portion 31 relative to the vehicle body mounting portion 30 along the first axis Ax1 is adjustable. Specifically, the vehicle body mounting portion 30 has an elongated hole 30a extending along the first axis Ax1, and the fitting portion 31 is fixed to the vehicle body mounting portion 30 by a bolt passing through the elongated hole 30a and a nut fitted with the bolt. By adjusting the position of the fitting portion 31 along the first axis Ax1, the biasing force of the first spring member 71 can be adjusted.

[0100] The second spring member 72 is attached between the vehicle body mounting portion 30 and the bent portion 41 d and biases the vehicle body mounting portion 30 and the bent portion 41 d in directions in which the vehicle body mounting portion 30 and the bent portion 41 d move away from each other. Specifically, the second spring member 72 is a coil spring attached between the vehicle body mounting portion 30 and the bent portion 41 d by the spring mounting portion 80.

[0101] As shown in FIG. 11 , the spring mounting portion 80 includes a first mounting member 81 , a second mounting member 82 , and a mounting plate member 83 .

[0102] The first mounting member 81 is disposed at a position on the vehicle body mounting portion 30 closer to the driven wheel 50 than the fitting portion 31. The first mounting member 81 has a second rod member 81a and is rotatable relative to the vehicle body mounting portion 30 about a sixth axis Ax6 that is parallel to the rotation axis Axr. This prevents the first mounting member 81 from interfering with the operation of the link mechanism portion 40. The second rod member 81a also has a male thread portion.

[0103] The second mounting member 82 is fitted with the second rod member 81a so as to be relatively movable, and is disposed on the bending portion 41d so as to be rotatable about the bending axis Axb with respect to the bending portion 41d. As a result, the second mounting member 82 does not interfere with the operation of the link mechanism 40.

[0104] The mounting plate 83 is attached to the second rod 81 a. The mounting plate 83 has a female thread that fits into the male thread of the second rod 81 a. By rotating the mounting plate 83 relative to the second rod 81 a, the position of the mounting plate 83 relative to the second rod 81 a can be adjusted in the direction along the central axis of the second rod 81 a.

[0105] The second spring member 72 is disposed around the second rod member 81 a between the second mounting member 82 and the mounting plate member 83. The biasing force of the second spring member 72 can adjust the rotational speed of the first link member 41 about the second axis Ax2, i.e., the angular velocity ω of the link angle θ. The second spring member 72 can also suppress the impact when the driven wheel 50 hits a step D. The biasing force of the second spring member 72 can be adjusted by adjusting the position of the mounting plate member 83.

[0106] The third spring member 73 is attached between the vehicle body mounting portion 30 and the second bent portion 43d and biases the vehicle body mounting portion 30 and the second bent portion 43d in directions in which the vehicle body mounting portion 30 and the second bent portion 43d move away from each other. Specifically, the third spring member 73 is a coil spring that is attached between the vehicle body mounting portion 30 and the second bent portion 43d by a spring mounting portion 80, similar to the second spring member 72. Note that a first mounting member 81 of the spring mounting portion 80 to which the third spring member 73 is attached is attached to the vehicle body mounting portion 30 so as to be rotatable relative to the vehicle body mounting portion 30 about the second sixth axis Ax6a, which is located on the vehicle body mounting portion 30 closer to the second driven wheel 60 than the fitting portion 31.

[0107] The biasing force of the third spring member 73 can adjust the rotational speed of the second first link member 43 about the second axis Ax2, i.e., the angular velocity ω of the link angle θ. The third spring member 73 can also suppress the impact when the second driven wheel 60 hits the step D. The biasing force of the third spring member 73 can be adjusted by adjusting the position of the mounting plate member 83.

[0108] As described above, according to this embodiment, the wheel structure 1 comprises a main body 10, a drive wheel 20 attached to the main body 10 so as to be rotatable around the rotation axis Axr relative to the main body 10, a vehicle body mounting part 30 which is movable relative to the main body 10 along a first axis Ax1 perpendicular to the rotation axis Axr and which can be attached to the vehicle body 90, a link mechanism part 40 which connects the main body 10 and the vehicle body mounting part 30, and a driven wheel 50 attached to the link mechanism part 40. The link mechanism 40 includes a first link member 41 having a first connection portion 41a connected to the main body 10 so as to be rotatable relative to the main body 10 about a second axis Ax2 that is parallel to the rotation axis Axr and perpendicular to the first axis Ax1, and a second connection portion 41b to which the driven wheel 50 is rotatably attached about a third axis Ax3 that is parallel to the second axis Ax2; and a second link member 42 having a fourth connection portion 42a connected to a third connection portion 41c between the first connection portion 41a and the second connection portion 41b of the first link member 41 so as to be rotatable relative to the first link member 41 about a fourth axis Ax4 that is parallel to the second axis Ax2, and a fifth connection portion 42b connected to the vehicle body mounting portion 30 so as to be rotatable relative to the vehicle body mounting portion 30 about a fifth axis Ax5 that is parallel to the second axis Ax2 and perpendicular to the first axis Ax1.

[0109] According to this, the wheel structure 1 connects one drive wheel 20 and one driven wheel 50 via two links, the first link member 41 and the second link member 42. Therefore, the wheel structure 1 can be simplified in structure. Also, as described above, when the driven wheel 50 runs over a step D, the drive wheel 20 is pressed against the ground G by the two links. Furthermore, when the driven wheel 50 runs over the step D, the force with which the drive wheel 20 is pressed against the ground G by the two links increases. Also, when the driven wheel 50 runs over the step D, the two links quickly press the drive wheel 20 down, preventing the drive wheel 20 from separating from the ground G. Therefore, even when the driven wheel 50 runs over the step D, the link mechanism 40 can efficiently transmit the drive force of the drive wheel 20 to the ground G.

[0110] Furthermore, when the first link member 41 is viewed along the rotation axis Axr, the angle between the first line segment Ln1 connecting the second axis Ax2 and the fourth axis Ax4 and the second line segment Ln2 connecting the second axis Ax2 and the fifth axis Ax5 is an acute angle, and the first link member 41 has a bent portion 41d between the third connection portion 41c and the second connection portion 41b, where the second connection portion 41b is bent in a direction away from the fifth connection portion 42b.

[0111] According to this, by having the bent portion 41d in the first link member 41, as described above, when the driven wheel 50 hits the step D, the magnitude of the component of the reaction force F that rotates the first link member 41 about the second axis Ax2 is larger than when the first link member 41 does not have the bent portion 41d. Therefore, by having the bent portion 41d in the first link member 41, the first link member 41 is more likely to rotate due to the reaction force F, and the driven wheel 50 is more likely to climb up the step D. Therefore, the ability of the wheel structure 1 to traverse the step D can be improved.

[0112] The wheel structure 1 further includes a first spring member 71 attached between the main body portion 10 and the vehicle body mounting portion 30 to bias the main body portion 10 and the vehicle body mounting portion 30 in a direction separating them.

[0113] This makes it possible to adjust the force with which the drive wheels 20 are pressed against the ground G and the reduction ratio R by the biasing force of the first spring members 71 .

[0114] In addition, the wheel structure 1 further includes a second spring member 72 that is attached between the vehicle body mounting portion 30 and the bending portion 41d and biases the vehicle body mounting portion 30 and the bending portion 41d in a direction that moves the vehicle body mounting portion 30 and the bending portion 41d away from each other.

[0115] According to this, the rotational speed of the first link member 41 about the second axis Ax2 can be adjusted by the biasing force of the second spring member 72. In addition, the second spring member 72 can suppress the impact when the driven wheel 50 hits the step D.

[0116] The wheel structure 1 also includes a second driven wheel 60 attached to the link mechanism 40. The link mechanism 40 also includes a second first link member 43 and a second second link member 44 that are symmetrical to the first link member 41 and the second link member 42 with respect to the first axis Ax1 as an axis of symmetry when viewed along the rotation axis Axr. The second first link member 43 has a second first connection portion 43a connected to the main body 10 so as to be rotatable relative to the main body 10 about the second axis Ax2, and a second second connection portion 43b to which the second driven wheel 60 is attached so as to be rotatable about a second third axis Ax3a parallel to the second axis Ax2. The second second link member 44 has a second fourth connection portion 44a rotatably connected to the second first link member 43 around a second fourth axis Ax4a parallel to the second axis Ax2 at a second third connection portion 43c between the second first connection portion 43a and the second second connection portion 43b of the second first link member 43, and a second fifth connection portion 44b rotatably connected to the vehicle body mounting portion 30 around a fifth axis Ax5.

[0117] According to this, the wheel structure 1 connects one driving wheel 20 and two driven wheels 50 via four links, namely, the first link member 41, the second link member 42, the second first link member 43, and the second second link member 44. Therefore, the wheel structure 1 can be simplified in structure.

[0118] Next, a vehicle 2 according to an embodiment of the present disclosure will be described. The vehicle 2 is a vehicle for transporting luggage, meals, and the like.

[0119] Fig. 12 is a front view of the vehicle 2. Fig. 13 is a side view of the vehicle 2. The vehicle 2 includes a vehicle body 90 and a wheel structure 1. The vehicle 2 includes two wheel structures 1.

[0120] The vehicle body 90 includes a top plate 91 and a rectangular parallelepiped storage section 92 .

[0121] The two wheel structures 1 are arranged on opposite sides of the vehicle body 90. Specifically, the vehicle body mounting portions 30 of the two wheel structures 1 are fixed to the side surfaces of the top plate 91. By arranging the vehicle body mounting portions 30 on the vehicle body 90 in this way, the configuration of the vehicle 2 can be simplified.

[0122] In order to keep the surface of the top plate 91 horizontal, at least one of the two wheel structures 1 may be rotatably attached to the vehicle body 90. In this case, in order to keep the surface of the top plate 91 horizontal, a weight may be placed on the bottom of the vehicle body 90, or a spring member may be placed between the vehicle body 90 and the wheel structure 1 to bias the wheel structure 1 in the rotational direction relative to the vehicle body 90.

[0123] As described above, according to this embodiment, the vehicle 2 includes the wheel structure 1 of the above embodiment and the vehicle body 90. The vehicle 2 includes two wheel structures 1. The two wheel structures 1 are arranged on opposite sides of the vehicle body 90.

[0124] According to this, the vehicle 2 can be easily constructed by attaching the wheel structure 1 to the vehicle body 90.

[0125] The vehicle 2 may be a research vehicle, a tractor, or a vehicle in which a user rides (for example, a wheelchair or an electric wheelchair). The wheel structure 1 may also be applied to things other than vehicles. For example, the wheel structure 1 may be applied to an autonomous service robot that carries luggage and meals, a robotic agricultural machine that performs agricultural work such as rice planting, a rescue robot, or a robot that investigates places with rough roads that people cannot enter (for example, disaster areas).

[0126] Next, a wheel structure 1 according to a modified example of the embodiment of the present disclosure will be described.

[0127] For example, it goes without saying that the numbers of the first plate members S1 of the first link member 41, the second plate members S2 of the second link member 42, the second first plate members S1a of the second first link member 43, and the second second plate members S2a of the second second link member 44 are not limited to the above numbers. For example, the first link member 41 may be formed of one first plate member S1. In this case, the second link member 42 may be formed of a pair of second plate members S2, and the pair of second plate members S2 sandwich the first plate member S1.

[0128] Furthermore, the wheel structure 1 does not necessarily have to include the second first link member 43 , the second second link member 44 , and the second driven wheel 60 .

[0129] Furthermore, the wheel structure 1 does not necessarily have to include the first spring member 71 , the second spring member 72 , the third spring member 73 , and the spring mounting portion 80 .

[0130] FIG. 14 is a schematic diagram of a link mechanism 140 of a wheel structure 1 according to a modified example of the embodiment of the present disclosure. The first link member 141 and the second first link member 143 of the link mechanism 140 are linear and do not have the bent portion 41 d and the second bent portion 43 d of the above embodiment. Furthermore, when the driving wheel 20 and the driven wheel 50 are in contact with the ground G, the link angle θ is a right angle or an obtuse angle. Except for the fact that the first link member 141 and the second first link member 143 are linear and the link angle θ is a right angle or an obtuse angle, the link mechanism 140 is configured similarly to the link mechanism 40 of the above embodiment. The link mechanism 140 also operates similarly to the link mechanism 40 of the above embodiment.

[0131] REFERENCE SIGNS LIST 1 Wheel structure 2 Vehicle 10 Main body 20 Drive wheel 30 Vehicle body mounting portion 40 Link mechanism 41 First link member 41a First connection portion 41b Second connection portion 41c Third connection portion 41d Bent portion 42 Second link member 42a Fourth connection portion 42b Fifth connection portion 43 Second first link member 43a Second first connection portion 43b Second second connection portion 43c Second third connection portion 43d Second bent portion 44 Second second link member 44a Second fourth connection portion 44b Second fifth connection portion 50 Driven wheel 60 Second driven wheel 71 First spring member 72 Second spring member 90 Vehicle body Ax1 First axis Ax2 Second axis Ax3 Third axis Ax3a Second third axis Ax4 Fourth axis Ax4a Second fourth axis Ax5 Fifth axis Axr Rotation axis Ln1 First line segment Ln2 Second line segment

Claims

1. A vehicle having a main body, a drive wheel attached to the main body rotatably about a rotation axis relative to the main body, a vehicle body attachment part movable relative to the main body along a first axis perpendicular to the rotation axis and attachable to a vehicle body, a link mechanism part connecting the main body and the vehicle body attachment part, and a driven wheel attached to the link mechanism part, wherein the link mechanism part comprises a first link member having a first connection part connected to the main body rotatably about a second axis parallel to the rotation axis and perpendicular to the first axis, and a second connection part to which the driven wheel is attached rotatably about a third axis parallel to the second axis; a fourth connection portion rotatably connected to the first link member about a fourth axis parallel to the second axis at a third connection portion between the first connection portion and the second connection portion of the first link member, and a second link member having a fifth connection portion rotatably connected to the vehicle body mounting portion about a fifth axis parallel to the second axis and perpendicular to the first axis.

2. The wheel structure described in claim 1, wherein, when the first link member is viewed along the rotation axis, an angle between a first line segment connecting the second axis and the fourth axis and a second line segment connecting the second axis and the fifth axis is an acute angle, and the first link member has a bent portion between the third connection portion and the second connection portion, where the second connection portion is bent in a direction away from the fifth connection portion.

3. The wheel structure according to claim 1, further comprising a first spring member attached between the main body portion and the vehicle body mounting portion, for biasing the main body portion and the vehicle body mounting portion in a direction separating them.

4. The wheel structure according to claim 2, further comprising a second spring member attached between the vehicle body mounting portion and the bent portion, for biasing the vehicle body mounting portion and the bent portion in directions in which the vehicle body mounting portion and the bent portion move away from each other.

5. The wheel structure according to claim 1, further comprising a second driven wheel attached to the link mechanism, wherein the link mechanism further comprises a second first link member and a second second link member which have an axisymmetrical shape to the first link member and the second link member with the first axis as an axis of symmetry when viewed along the rotation axis, wherein the second first link member has a second first connection portion connected to the main body portion rotatably relative to the main body portion about the second axis, and a second second connection portion to which the second driven wheel is rotatably attached about a second third axis parallel to the second axis, and wherein the second second link member has a second fourth connection portion rotatably connected to the second first link member about a second fourth axis parallel to the second axis to a second third connection portion between the second first connection portion and the second second connection portion of the second first link member, and a second fifth connection portion connected to the vehicle body mounting portion rotatably relative to the vehicle body mounting portion about the fifth axis.

6. A vehicle comprising: a wheel structure according to any one of claims 1 to 5; and a vehicle body, wherein there are two wheel structures, and the two wheel structures are arranged on opposite sides of the vehicle body.

Images