Wheel structure and vehicle

Abstract

The wheel structure 1 includes a drive wheel 20 that rotates relative to a main body 10 about a rotation axis Axr, a vehicle body attachment unit 30 that is movable relative to the main body 10 along a first axis Ax1, and a link mechanism unit 40. The link mechanism unit 40 includes a first link member 41 having a first connection portion 41a that is connected to the main body 10 so as to be rotatable about a second axis Ax2 and a second connection portion 41b to which a first driven wheel 50 is attached, a second link member 42 that has a fourth connection portion 42a that is connected between the first connection portion 41a and the second connection portion 41b so as to be rotatable about a fourth axis Ax4 and a fifth connection portion 42b that is connected to the vehicle body attachment unit 30 so as to be rotatable about a fifth axis Ax5, and a third link member 43 and a fourth link member 44 that are shaped symmetrically to the first link member 41 and the second link member 42 with respect to the first axis Ax1.

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a wheel structure that improves traversal of uneven terrain with steps and 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, first driven wheel, and second driven wheel to come into contact even on uneven terrain, improving traversal of uneven terrain. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-94998 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the wheel structure of Patent Document 1 has a relatively large number of parts and a relatively complicated structure. On the other hand, there is a demand for a simplified 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. [Means for solving the problem]

[0006] a link mechanism that connects the main body portion and the vehicle body mounting portion; and a first driven wheel and a second driven wheel that are mounted on the link mechanism, the link mechanism including: a first connection portion that is connected to the main body portion rotatably about a second axis that is parallel to the rotation axis and perpendicular to the first axis; a second connection portion to which the first driven wheel is mounted rotatably about a third axis that is parallel to the second axis; a fourth connection portion that is connected to a third connection portion between the first connection portion and the second connection portion of the first link member rotatably about a fourth axis that is parallel to the second axis; the rotation axis; and a third link member and a fourth link member which are symmetrical to the first link member and the second link member with the first axis as the axis of symmetry when viewed along the rotation axis, wherein the third link member has a sixth connection portion which is rotatably connected to the main body portion about the second axis, and a seventh connection portion to which the second driven wheel is rotatably attached about the sixth axis parallel to the second axis, and the fourth link member has a ninth connection portion which is rotatably connected to the third link member about the seventh axis parallel to the fourth axis at an eighth connection portion between the sixth connection portion and the seventh connection portion of the third link member, and a tenth connection portion which is rotatably connected to the vehicle body mounting portion about the eighth axis parallel to the fifth axis.

[0007] According to this, the wheel structure connects one drive wheel to the first driven wheel and the second driven wheel via four links, namely the first link member, the second link member, the third link member, and the fourth link member, thereby simplifying the structure of the wheel structure.

[0008] In a wheel structure according to one embodiment of the present disclosure, when the first link member is viewed along the rotation axis, the angle between the first axis and a first line segment connecting the second axis and the fourth 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, when the first driven wheel hits a step, the reaction force acting on the first driven wheel makes it easier for the first link member to rotate, allowing the first driven wheel to easily climb up the step. Therefore, the wheel structure can improve its ability to traverse steps.

[0010] The wheel structure according to one aspect of the present disclosure further includes a first spring member attached between the main body portion and the vehicle body mounting portion, and biasing the main body portion and the vehicle body mounting portion in a direction separating them.

[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 one embodiment of the wheel structure 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 a direction in which the vehicle body mounting portion and the bent portion move away from each other.

[0013] This allows the rotational speed of the first link member about the second axis to be adjusted by the biasing force of the second spring member. The second spring member also reduces the impact when the first driven wheel hits a step. The biasing force of the second spring member also allows the force with which the first driven wheel is pressed against the ground to be adjusted.

[0014] A vehicle according to one embodiment of the present disclosure comprises the above-mentioned 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.

[0015] According to this, the vehicle can be constructed simply by attaching the wheel structure to the vehicle body. [Effects of the Invention]

[0016] According to the present disclosure, the wheel structure and the vehicle can be simplified in structure. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a front view of a wheel structure according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a rear view of the wheel structure. [Figure 3] FIG. 3 is a side view of the wheel structure. [Figure 4] FIG. 4 is a perspective view of the wheel structure as seen from the front side. [Figure 5] FIG. 5 is a perspective view of the wheel structure as seen from the rear side. [Figure 6] FIG. 6 is a partially enlarged view of the wheel structure shown in FIG. [Figure 7] FIG. 7 is a schematic diagram of the link mechanism when viewed along the second axis. [Figure 8] FIG. 8 is a diagram showing the relationship between the first Y-direction length, the second Y-direction length, the X-direction length and the link angle. [Figure 9] FIG. 9 is a schematic diagram showing a state in which the first driven wheel runs over a step. [Figure 10] FIG. 10 is a schematic diagram showing a state in which the wheel assembly is positioned on the ground. [Figure 11] FIG. 11 is a diagram showing the relationship between the link angle and the reduction ratio. [Figure 12] FIG. 12 is a schematic diagram showing a state in which the first driven wheel, in contact with the ground, hits a step. [Figure 13] FIG. 13 is a front view of a vehicle according to an embodiment of the present disclosure. [Figure 14] FIG. 14 is a side view of the vehicle. [Figure 15]FIG. 15 is a rear view of a wheel structure of a comparative example in comparison with the wheel structure according to the embodiment of the present disclosure. [Figure 16] FIG. 16 is a partial side view of a wheel structure of a comparative example. [Figure 17] FIG. 17 is a schematic diagram of a link mechanism of a wheel structure according to a modified example of an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0018] 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.

[0019] <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 first driven wheel 50, and a second driven wheel 60, which will be described later, are in contact with the ground G.

[0020] Fig. 3 is a side view of the wheel structure 1. The first 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 front side. Fig. 5 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.

[0021] The wheel structure 1 includes a main body 10, a driving wheel 20, a vehicle body mounting portion 30, a link mechanism 40, a first driven wheel 50, and a second driven wheel 60. As shown in Figures 1, 2, 3, 4, and 5, the outer diameters of the first driven wheel 50 and the second driven wheel 60 are equal to each other and smaller than the outer diameter of the driving wheel 20.

[0022] 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 wheel 20. The first axis Ax1 is perpendicular to the rotation axis Axr. A first shaft member 12 is fixed to the end face on the rear side of the main body 10 (see Figures 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.

[0023] 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.

[0024] The wheel unit 21 is rotated by a motor M (for example, 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 (for example, 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.

[0025] 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.

[0026] As the drive wheel 20 rotates, the wheel structure 1 moves along the ground surface G in a direction perpendicular to the rotation axis Axr.

[0027] Fig. 6 is a partially enlarged view of the wheel structure 1 shown in Fig. 1. In Fig. 6, the main body 10 and a first connecting member 32 (described later) are indicated by dashed lines, a first spring member 71 (described later) is indicated by a two-dot chain line, and the drive wheel 20 is omitted. The vehicle body mounting portion 30 is mounted to a vehicle body 90 (described later). The vehicle body mounting portion 30 is plate-shaped.

[0028] 4 and 6, the vehicle body mounting portion 30 is attached to the main body 10 via a linear guide 31 and a first connecting member 32. The linear guide 31 includes a guide rail 31a that is disposed on the vehicle body mounting portion 30 and extends along the first axis Ax1, and a slider 31b that is movable along the guide rail 31a.

[0029] The first connecting member 32 has an L-shaped cross section and is fixed to the slider 31b. The main body 10 is also fixed to the first connecting member 32. As a result, the vehicle body mounting portion 30 is connected to the main body 10 via the linear guide 31 and the first connecting member 32 and is movable relative to the main body 10 along the first axis Ax1. A plate-shaped second connecting member 33 is fixed to a portion of the vehicle body mounting portion 30 on the opposite side from the main body 10 across the guide rail 31a.

[0030] The link mechanism 40 connects the main body 10 and the vehicle body mounting portion 30. As shown in Figures 1, 2, 3, 4, and 5, the link mechanism 40 includes a first link member 41, a second link member 42, a third link member 43, and a fourth 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 in which the rotation axis Axr extends (see FIGS. 3, 4, and 5). Each of the pair of first plate members S1 has an L-shape in 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 first bent portion 41d (corresponding to a "bent portion") 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 relative to the main body portion 10 about the second axis Ax2. 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 first 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 first driven wheel 50. Specifically, the first 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 parallel to 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 first bent portion 41d is a portion of the first link member 41 where the second connecting portion 41b bends in a direction away from a fifth connecting portion 42b (described later) of the second link member 42. The first bent portion 41d bends around a first bending axis Axb1 that is parallel to the second axis Ax2.

[0036] In addition, in a plan view, the second axis Ax2, the fourth axis Ax4, and the first bending axis Axb1 are positioned on the same straight line. A fourth shaft member 41g having the first bending axis Axb1 as its central axis is disposed in the first bending portion 41d.

[0037] The second link member 42 is composed of a single second plate member S2 (see FIGS. 3 and 5). 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. The fifth axis Ax5 is located closer to the first driven wheel 50 than the first axis Ax1. A cylindrical fifth shaft member 34 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 34. 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 first axis Ax1 intersects with the rotation axis Axr at a position different from the position at which it intersects with the second axis Ax2. When the first link member 41 is viewed along the rotation axis Axr, the angle between the first axis Ax1 and a first line segment Ln1 connecting the second axis Ax2 and the fourth axis Ax4 (corresponding to the link angle θ described below) is an acute angle.

[0041] The third link member 43 has an axisymmetric shape with the first link member 41, with the first axis Ax1 as the axis of symmetry, when viewed along the rotation axis Axr. The third link member 43 is composed of a pair of third plate members S3 facing each other in the direction in which the rotation axis Axr extends (see FIG. 5). The pair of third plate members S3 each has an axisymmetric shape with the pair of first plate members S1, with the first axis Ax1 as the axis of symmetry, when viewed along the rotation axis Axr.

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

[0043] The sixth connection portion 43a corresponds to the first connection portion 41a of the first link member 41. The sixth 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 sixth 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 third link member 43 rotates relative to the main body portion 10.

[0044] The seventh 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 seventh connection portion 43b around a sixth axis Ax6 that is parallel to the second axis Ax2. In other words, the sixth axis Ax6 is the rotation center of the second driven wheel 60. Specifically, the second driven wheel 60 is attached to the seventh connection portion 43b via a cylindrical sixth shaft member 43e whose central axis is the sixth axis Ax6.

[0045] The eighth connection portion 43c corresponds to the third connection portion 41c of the first link member 41. A cylindrical seventh shaft member 43f having a central axis parallel to the seventh axis Ax7 that is parallel to the second axis Ax2 is attached to the eighth connection portion 43c.

[0046] The second bent portion 43d corresponds to the first bent portion 41d of the first link member 41. When the third link member 43 is viewed along the rotation axis Axr, the second bent portion 43d is a portion of the third link member 43 where the seventh connecting portion 43b bends in a direction away from a tenth connecting portion 44b (described later) of the fourth link member 44. The second bent portion 43d bends around a second bending axis Axb2. The second bending axis Axb2 corresponds to the first bending axis Axb1 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 seventh axis Ax7, and the second bending axis Axb2 are positioned on the same straight line. An eighth shaft member 43g having the second bending axis Axb2 as its central axis is disposed in the second bending portion 43d.

[0048] The fourth 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 fourth link member 44 is composed of a single fourth plate member S4 (see FIG. 5). The fourth plate member S4 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 fourth plate member S4 is sandwiched between a pair of third plate members S3.

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

[0050] The ninth connection portion 44a corresponds to the fourth connection portion 42a of the second link member 42. The ninth connection portion 44a is connected to the eighth connection portion 43c of the third link member 43 so as to be rotatable with respect to the third link member 43 about the seventh axis Ax7. Specifically, the ninth connection portion 44a is connected to the eighth connection portion 43c of the third link member 43 via the seventh axis member 43f. In other words, the seventh axis Ax7 is the center of rotation when the third link member 43 and the fourth link member 44 rotate relative to each other.

[0051] The tenth connection portion 44b corresponds to the fifth connection portion 42b of the second link member 42. The tenth 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 an eighth axis Ax8 that is parallel to the second axis Ax2. The eighth axis Ax8 is located closer to the second driven wheel 60 than the first axis Ax1. A cylindrical ninth shaft member 34a having the eighth axis Ax8 as its central axis is fixed to the vehicle body mounting portion 30, and the tenth connection portion 44b is connected to the vehicle body mounting portion 30 via the ninth shaft member 34a. Therefore, the tenth connection portion 44b is movable together with the vehicle body mounting portion 30 along the first axis Ax1. In other words, the eighth axis Ax8 is the center of rotation when the fourth link member 44 rotates relative to the vehicle body mounting portion 30. Additionally, the fourth link member 44 is movable together with the vehicle body attachment portion 30 along the first axis Ax1.

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

[0053] Next, we will explain 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 first driven wheel 50 and the second driven wheel 60 runs over a step, the link mechanism 40 operates as described below.

[0054] Fig. 7 is a schematic diagram of the link mechanism 40 as viewed along the second axis Ax2. For ease of explanation, Fig. 7 shows a case where 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. 7, the fifth axis Ax5 and the eighth axis Ax8 are fixed, and the rotation axis Axr and the second axis Ax2 move along the first axis Ax1. Also, Fig. 7 shows the origin O, which is the intersection of the first axis Ax1 and a second line segment Ln2 connecting the fifth axis Ax5 and the eighth axis Ax8, and the Y axis overlapping the first axis Ax1 and the X axis overlapping the second line segment Ln2 and 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 third link member 43 and the fourth link member 44 have a shape symmetrical to the first link member 41 and the second link member 42 with the first axis Ax1 as the axis of symmetry, and the link mechanism 40 also has a shape symmetrical to the first axis Ax1 as the axis of symmetry. In other words, the movement of the link mechanism 40 is symmetrical with the first axis Ax1 as the axis of symmetry. For convenience 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. 7, L1 is the length between the second axis Ax2 and the first bending axis Axb1 in the first link member 41, L2 is the length between the second axis Ax2 and the fourth axis Ax4 in the first link member 41, L3 is the length between the fourth axis Ax4 and the fifth axis Ax5 in the second link member 42, L4 is the length between the first bending axis Axb1 and the third axis Ax3 in the first link member 41, L5 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 L6 is the length in the Y direction between the second axis Ax2 and the third axis Ax3.

[0058] Furthermore, L7 is the length in the X direction between the first axis Ax1 and the fifth axis Ax5, L8 is the length in the Y direction between the second axis Ax2 and the fourth axis Ax4, and L9 is the length in the X direction between the fourth axis Ax4 and the fifth axis Ax5.

[0059] Furthermore, θ is the angle between the first line segment Ln1 and the first axis Ax1 (hereinafter referred to as the link angle θ), α is the angle by which the first link member 41 is bent around the first bending axis Axb1 at the first 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. Furthermore, y1 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), y2 is the Y-direction length between the fifth axis Ax5 and the second axis Ax2 (hereinafter referred to as the second Y-direction length Y2), and x1 is the X-direction length between the second axis Ax2 and the third axis Ax3 (hereinafter referred to as the X-direction length X1).

[0060] From the structure of the link mechanism 40, the following equations (1), (2), (3), (4), (5), (6), and (7) can be derived.

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[0065]

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[0068] Furthermore, due to the structure of the link mechanism 40, the X-direction length X1 can be expressed by equation (8). Furthermore, the second Y-direction length Y2 can be expressed by equation (9) by modifying equations (5), (6), and (7). Furthermore, the first Y-direction length Y1 can be expressed by equation (10) from equations (3), (4), and (9). As shown in equations (8), (9), and (10), 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.

[0069]

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[0070]

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[0071]

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[0072] Fig. 8 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. 9 is a schematic diagram showing a state in which the first driven wheel 50 runs over a step D.

[0073] When the first driven wheel 50 rides over the step D, the first link member 41 rotates about 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 about the fourth axis Ax4 relative to the first link member 41 and also rotates about the fifth axis Ax5 relative to the vehicle body mounting part 30. At this time, the main body 10, which has the rotation axis Axr and the second axis Ax2, and the vehicle body mounting part 30, which has the fifth axis Ax5 and the eighth axis Ax8, move away from each other along the first axis Ax1 (in FIG. 7, the main body 10, which has the rotation axis Axr and the second axis Ax2, moves toward the +Y side along the Y axis).

[0074] In FIG. 8, the first Y-direction length Y1 (y1) and the second Y-direction length Y2 (y2) have opposite slopes. 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 first driven wheel 50 climbs over a step D as shown in FIG. 8, 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 first driven wheel 50 climbs over the step D (see FIG. 9) from a state in which the driving wheel 20 and the first 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 first 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.

[0075] 8, 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 diameter of the driving wheel 20 and the outer diameter of the first driven wheel 50 are equal to each other, and the first driven wheel 50 is not riding over a step D, the driving wheel 20 and the first driven wheel 50 each come into contact with the ground G.

[0076] 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 first 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 first 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 amount equal to the difference between the outer diameter of the first driven wheel 50 and the outer diameter of the drive wheel 20.

[0077] Also, at the link angle θ corresponding to the intersection point P1 shown in FIG. 8, the X-direction length X1(x1) is maximized, and the change amount of the X-direction length X1 with respect to the link angle θ is smaller than that of other link angles θ. That is, when the link mechanism portion 40 operates in the vicinity of the link angle θ corresponding to the intersection point P1, the length between the drive wheel 20 corresponding to the X-direction length X1 and the first driven wheel 50 can be stabilized, and the length between the drive wheel 20 and the first driven wheel 50 can be made longer compared to the case where the link mechanism portion 40 operates in the vicinity of other link angles θ, and the operation of the wheel structure 1 can be stabilized.

[0078] In FIG. 9, a fourth line segment Ln4 connecting the third axis line Ax3 and the sixth axis line Ax6 is shown. Also, a shown in FIG. 9 indicates the height of the step D. In FIG. 9, the rotation axis line Axr and the second axis line Ax2 are coaxial, and the outer diameters of the drive wheel 20 and the first driven wheel 50 are equal to each other.

[0079] In a state where the first driven wheel 50 rides on the step D, the length (b) of the perpendicular line Lv drawn from the second axis line Ax2 to the fourth line segment Ln4 is equal to L6 (that is, b = L6). Also, the length (H) between the intersection point P2 of the vertical line Lg passing through the second axis line Ax2 and the fourth line segment Ln4 and the second axis line Ax2 can be approximated to half of the height (a) of the step D when the height (a) of the step D is sufficiently small with respect to the X-direction length X1 (that is, H = a / 2). Also, as is clear from FIG. 9, b is smaller than H (b < H). Therefore, in order for the first driven wheel 50 to ride on the step D of a desired height, it is desirable that the length (b) of the perpendicular line Lv when the first driven wheel 50 rides on the step D is at least 1 / 2 of the desired height (that is, b ≧ (desired height) / 2).

[0080] Furthermore, it is generally known that in order for the first driven wheel 50 to ride on the step D of a desired height, the outer diameter of the first driven wheel 50 needs to be at least 3 times the desired height (that is, (outer diameter of the first driven wheel 50) ≧ 3 × (desired height)). Therefore, it is desirable that the length (b(=L6)) of the perpendicular line Lv when the first driven wheel 50 rides on the step D of a desired height is at least 1 / 6 of the outer diameter of the first driven wheel 50 (that is, b ≧ (outer diameter of the first driven wheel 50) / 6).

[0081] FIG. 10 is a schematic diagram showing a state in which the wheel structure 1 is positioned on the ground G. In FIG. 10, N1 is a first normal force (hereinafter referred to as the first normal force N1) acting from the ground G to the first driven wheel 50 and the second driven wheel 60, and N2 is a second normal force (hereinafter referred to as the second normal force N2) acting from the ground G to the drive wheel 20. Furthermore, x2 is the length in the X direction between the third axis Ax3 and the fourth axis Ax4, and x3 is the length in the X direction between the second axis Ax2 and the fourth axis Ax4. From the balance of the moment about the fourth axis Ax4, the ratio (N2 / N1) of the second normal force N2 to the first normal force N1 can be expressed by the following equations (11), (12), and (13) and the above equation (8), as equation (14) in which the link angle θ is a variable.

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[0085]

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[0086] By making the second normal force N2 of the driving wheel 20 larger than the first normal force N1 of the first driven wheel 50, the driving force of the driving wheel 20 is efficiently transmitted to the ground surface G, and the running of the wheel structure 1 can be stabilized. In other words, it is desirable to make the ratio (N2 / N1) of the second normal force N2 to the first normal force N1 larger than 1. It is also desirable to determine this ratio according to the condition of the ground surface G on which the wheel structure 1 is used. This ratio can be adjusted by changing L2, L5, and β (see FIG. 7) shown in equation (14). For example, when the wheel structure 1 is used in a condition where the ground surface G is slippery due to rain or the like, this ratio is set to approximately 3.6.

[0087] Furthermore, the smaller the link angle θ, the larger the second normal force N2 of the drive wheel 20 according to equation (14). This means that when the first 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 first 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.

[0088] FIG. 11 is a diagram illustrating the relationship between the link angle θ and the reduction ratio R. In this specification, the reduction ratio R is the ratio of the velocity obtained by differentiating the first Y-direction length Y1(y1) with respect to time (i.e., the moving velocity of the third axis Ax3 along the Y direction relative to the origin O) to the velocity obtained by differentiating the second Y-direction length Y2(y2) with respect to time (i.e., the moving velocity of the rotation axis Axr (second axis Ax2) along the Y direction relative to the origin O), as shown in equation (15). Furthermore, equation (16) indicates 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 velocity obtained by differentiating the X-direction length X1(x1) with respect to time (i.e., the moving velocity of the third axis Ax3 along the X direction relative to the origin O), which are derived using the above equations (8), (9), and (10). The reduction ratio R can be calculated from equations (15) and (16). In equation (16), ω is the angular velocity of the link angle θ when the first link member 41 rotates in a direction in which the link angle θ decreases (hereinafter referred to as angular velocity ω).

[0089]

number

[0090]

number

[0091] Fig. 11 shows the relationship between the link angle θ and the reduction ratio R for each of three angular velocities ω. In Fig. 11, the three angular velocities ω are ω1, ω2, and ω3, with the magnitude of the angular velocity ω increasing in the order of ω1, ω2, and ω3.

[0092] As shown in FIG. 11, 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 first driven wheel 50 ascends becomes smaller. Furthermore, the higher the step D (see FIG. 8) that the first driven wheel 50 climbs over, the smaller the link angle θ. In other words, when the first 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 first driven wheel 50 ascends. Therefore, when the first driven wheel 50 climbs over the step D, it is possible to prevent the drive wheel 20 from separating from the ground G.

[0093] On the other hand, when the first 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 first driven wheel 50 descends increases relative to 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 first driven wheel 50 is pushed down by the link mechanism 40. Therefore, when the first driven wheel 50 descends from the step D, the first driven wheel 50 can come into contact with the ground G earlier.

[0094] 11, 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 first driven wheel 50 climbs up the step D, the slower the speed at which the drive wheel 20 is pushed down by the link mechanism 40. Therefore, when the first driven wheel 50 climbs up the step D, the link mechanism 40 quickly pushes down the drive wheel 20, preventing the drive wheel 20 from separating from the ground G.

[0095] Furthermore, as the magnitude of the angular velocity ω increases, the greater the reduction ratio R, and 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 first 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.

[0096] FIG. 12 is a schematic diagram showing a state in which the first driven wheel 50, in contact with the ground G, hits a step D.

[0097] When the first 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 first driven wheel 50. The direction of the reaction force F is from the contact point Pd between the first driven wheel 50 and the step D toward the third axis Ax3. As described above, the first link member 41 has a first bent portion 41d that bends around the first bending axis Axb1. 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 first bent portion 41d.

[0098] 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 first bent portion 41d. Therefore, when the first link member 41 has the first bent portion 41d, the reaction force F makes it easier for the first link member 41 to rotate, and the first driven wheel 50 to climb up the step D. Therefore, the wheel structure 1 can improve its ability to traverse the step D.

[0099] 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 first driven wheel 50 climbs over, the ability of the wheel structure 1 to traverse the step D can be reliably improved.

[0100] As shown in FIGS. 3, 4 and 6, the wheel structure 1 further includes a first spring member 71, a second spring member 72 and a third spring member 73.

[0101] 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 sandwiched between the first connecting member 32 and the second connecting member 33 and disposed in a state that extends along the first axis Ax1. 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.

[0102] Furthermore, the position of the second connecting member 33 relative to the vehicle body mounting portion 30 is adjustable along the first axis Ax1. By adjusting the position of the second connecting member 33, the biasing force of the first spring member 71 can be adjusted.

[0103] The second spring member 72 is attached between the vehicle body mounting portion 30 and the first bent portion 41d, and biases the vehicle body mounting portion 30 and the first bent portion 41d in directions in which the vehicle body mounting portion 30 and the first bent portion 41d 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 first bent portion 41d by a spring mounting portion 80.

[0104] As shown in FIG. 6, the spring mounting portion 80 includes a first mounting member 81, a second mounting member 82, and a mounting plate member 83.

[0105] The first mounting member 81 is disposed on the vehicle body mounting portion 30 at a position closer to the first bent portion 41d than the second connecting member 33. The first mounting member 81 has a rod member 81a, and is rotatable relative to the vehicle body mounting portion 30 about a ninth axis Ax9 that is parallel to the rotation axis Axr. This allows the first mounting member 81 to not interfere with the operation of the link mechanism portion 40. The rod member 81a also has a male thread portion.

[0106] The second mounting member 82 is disposed on the first bending portion 41d so as to be rotatable about the first bending axis Axb1 relative to the first bending portion 41d. The rod member 81a is fitted into the second mounting member 82 so as to be relatively movable. This allows the second mounting member 82 to not interfere with the operation of the link mechanism 40.

[0107] The mounting plate member 83 is attached to the rod member 81a. The mounting plate member 83 has a female thread that fits into the male thread of the rod member 81a. By rotating the mounting plate member 83 relative to the rod member 81a, the position of the mounting plate member 83 relative to the rod member 81a can be adjusted in the direction along the central axis of the rod member 81a.

[0108] The second spring member 72 is disposed around the rod member 81a 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 first driven wheel 50 hits a step D. The biasing force of the second spring member 72 can also adjust the force with which the first driven wheel 50 is pressed against the ground G. The biasing force of the second spring member 72 can be adjusted by adjusting the position of the mounting plate member 83.

[0109] 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 that move the vehicle body mounting portion 30 and the second bent portion 43d away from each other. Specifically, like the second spring member 72, 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. 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 a tenth axis Ax10 that is located closer to the second bent portion 43d than the second connecting member 33 on the vehicle body mounting portion 30.

[0110] The biasing force of the third spring member 73 can adjust the rotational speed of the third 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 a step D. The biasing force of the third spring member 73 can also adjust the force with which the second driven wheel 60 is pressed against the ground G. The biasing force of the third spring member 73 can be adjusted by adjusting the position of the mounting plate member 83.

[0111] 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 movable relative to the main body 10 along a first axis Ax1 perpendicular to the rotation axis Axr and attachable to the vehicle body 90, a link mechanism part 40 connecting the main body 10 and the vehicle body mounting part 30, and a first driven wheel 50 and a second driven wheel 60 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 first driven wheel 50 is attached so as to be rotatable about a third axis Ax3 that is parallel to the second axis Ax2; The second link member 42 has a fourth connection portion 42a rotatably connected to the first link member 41 about the axis Ax4 and a fifth connection portion 42b rotatably connected to the vehicle body mounting portion 30 about a fifth axis Ax5 parallel to the second axis Ax2, and a third link member 43 and a fourth link member 44 which are symmetrical to the first link member 41 and the second link member 42 with the first axis Ax1 as the axis of symmetry when viewed along the rotation axis Axr. The third link member 43 has a sixth connection portion 43a rotatably connected to the main body portion 10 about the second axis Ax2, and a seventh connection portion 43b to which the second driven wheel 60 is rotatably attached about a sixth axis Ax6 parallel to the second axis Ax2. The fourth link member 44 has a ninth connection portion 44a that is rotatably connected to the third link member 43 around a seventh axis Ax7 parallel to the fourth axis Ax4 at an eighth connection portion 43c between the sixth connection portion 43a and the seventh connection portion 43b in the third link member 43, and a tenth connection portion 44b that is rotatably connected to the vehicle body mounting portion 30 around an eighth axis Ax8 parallel to the fifth axis Ax5.

[0112] According to this, the wheel structure 1 connects one driving wheel 20 to the first driven wheel 50 and the second driven wheel 60 via four links, namely, the first link member 41, the second link member 42, the third link member 43 and the fourth link member 44. Therefore, the wheel structure 1 can be simplified in structure.

[0113] Moreover, as described above, when the first driven wheel 50 runs over the step D, the drive wheel 20 is pressed against the ground G by the two links (the first link member 41 and the second link member 42). Furthermore, when the first 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. Furthermore, when the first 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 first 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.

[0114] 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 first axis Ax1 is an acute angle, and the first link member 41 has a first 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.

[0115] According to this, by having the first bent portion 41d in the first link member 41, as described above, when the first 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 becomes larger than when the first link member 41 does not have the first bent portion 41d. Therefore, by having the first bent portion 41d in the first link member 41, the first link member 41 becomes more likely to rotate due to the reaction force F, and the first driven wheel 50 becomes more likely to climb up the step D. Therefore, the wheel structure 1 can improve its ability to traverse the step D.

[0116] The wheel structure 1 further includes a first spring member 71 attached between the main body portion 10 and the vehicle body attachment portion 30 to bias the main body portion 10 and the vehicle body attachment portion 30 in a direction separating them.

[0117] 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.

[0118] The wheel structure 1 further includes a second spring member 72 that is attached between the vehicle body mounting portion 30 and the first bent portion 41d and biases the vehicle body mounting portion 30 and the first bent portion 41d in a direction that moves the vehicle body mounting portion 30 and the first bent portion 41d away from each other.

[0119] According to this, the rotation 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. Also, the second spring member 72 can suppress the impact when the first driven wheel 50 hits a step D. Furthermore, the biasing force of the second spring member 72 can adjust the force with which the first driven wheel 50 is pressed against the ground surface G.

[0120] <Vehicle 2> 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.

[0121] Fig. 13 is a front view of a vehicle 2 according to an embodiment of the present disclosure. Fig. 14 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.

[0122] The vehicle body 90 includes a top plate 91 and a rectangular parallelepiped storage section 92 .

[0123] The two wheel structures 1 are arranged on opposite sides of the vehicle body 90. Specifically, the vehicle body mounting parts 30 of the two wheel structures 1 are fixed to the side surfaces of the top plate 91. By arranging the vehicle body mounting parts 30 on the vehicle body 90 in this way, the configuration of the vehicle 2 can be simplified.

[0124] In addition, 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.

[0125] As described above, according to this embodiment, the vehicle 2 includes the wheel structure 1 of the above embodiment and a 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.

[0126] According to this, by attaching the wheel structure 1 to the vehicle body 90, the vehicle 2 can be easily constructed.

[0127] The vehicle 2 may be a rover, a tractor, or a vehicle that a user rides in (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, and a robot that investigates places with bad roads that people cannot enter (for example, disaster areas).

[0128] 15 is a rear view of a wheel structure 3 as a comparative example to the wheel structure 1 according to the embodiment of the present disclosure. The configuration of the link mechanism 140 provided in the wheel structure 3 of the comparative example is different from the configuration of the link mechanism 40 provided in the wheel structure 1 described above. In the wheel structure 3 of the comparative example, the configuration other than the link mechanism 140 is the same as that of the wheel structure 1 described above.

[0129] Similar to the link mechanism 40 of the wheel structure 1, the link mechanism 140 of the comparative example includes a first link member 41, a second link member 42, a third link member 43, and a fourth link member 44. Similarly to the link mechanism 40, the link mechanism 140 of the comparative example has a first axis Ax1, a second axis Ax2, a third axis Ax3, a fourth axis Ax4, a fifth axis Ax5, a sixth axis Ax6, and a seventh axis Ax7.

[0130] On the other hand, the link mechanism 140 of the comparative example differs from the above-described link mechanism 40 in that the fifth connection portion 42b of the second link member 42 and the tenth connection portion 44b of the fourth link member 44 rotate around a single axis.

[0131] Specifically, the link mechanism 140 of the comparative example does not include the ninth shaft member 34a having the eighth axis Ax8 as its central axis. In the link mechanism 140 of the comparative example, the fifth axis Ax5 is perpendicular to the first axis Ax1. In the link mechanism 140 of the comparative example, the fifth connection portion 42b of the second link member 42 and the tenth connection portion 44b of the fourth link member 44 are 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, which is the central axis of the fifth shaft member 34.

[0132] Below, the above vehicle 2 shown in Figures 13 and 14 will be compared with a comparative vehicle (not shown) to which the comparative wheel structure 3 shown in Figure 15 is applied. In the comparative vehicle, two comparative wheel structures 3 are arranged on the vehicle body 90 shown in Figures 13 and 14 in the same manner as the above vehicle 2.

[0133] In the above vehicle 2, when luggage B is positioned offset against the surface of the top panel 91 as shown in Figure 14, a moment M1 around the fifth axis Ax5 and a moment M2 around the eighth axis Ax8 act on the above wheel structure 1 due to the mass of luggage B.

[0134] On the other hand, in the vehicle of the comparative example, when luggage B is positioned offset on the surface of the top plate 91, a moment M3 around the fifth axis Ax5 acts on the wheel structure 3 of the comparative example due to the mass of luggage B, as shown in Figure 15.

[0135] 14 and 15, the moment generated by the mass of the luggage B is distributed more effectively in the wheel structure 1 than in the wheel structure 3 of the comparative example. Therefore, the magnitude of the moment generated in the wheel structure 1 can be reduced. The moments M1, M2, and M3 are generated around axes perpendicular to the traveling direction of the wheel structures 1 and 3. In other words, the wheel structure 1 can improve rigidity against moments around axes perpendicular to the traveling direction of the wheel structures 1 and 3 compared to the wheel structure 3 of the comparative example.

[0136] 16 is a partial side view of the wheel structure 3 of the comparative example. In the wheel structure 3 of the comparative example, the second link member 42 and the fourth link member 44 are both arranged on the vehicle body attachment part 30 so as to be rotatable about the fifth axis Ax5, and therefore overlap with each other in the direction along the fifth axis Ax5.

[0137] 2 and 3, in the above-described wheel structure 1, the second link member 42 and the fourth link member 44 are arranged at different positions on the vehicle body mounting portion 30, and therefore do not overlap with each other in the direction along the fifth axis Ax5. Therefore, the above-described wheel structure 1 can suppress rattle that occurs between the vehicle body mounting portion 30, the second link member 42, and the fourth link member 44 more than the wheel structure 3 of the comparative example. Therefore, the above-described wheel structure 1 can improve rigidity against a moment M4 (see FIGS. 3 and 16) acting from the first driven wheel 50 to the second link member 42 about an axis along the traveling direction of the wheel structures 1 and 3, compared to the wheel structure 3 of the comparative example.

[0138] Furthermore, in the wheel structure 3 of the comparative example, the second link member 42 and the fourth link member 44 overlap each other in the direction along the fifth axis Ax5, so that the distance between the fifth axis Ax5 and the third axis Ax3, which is the center of rotation of the first driven wheel 50, is smaller in the wheel structure 1 than in the wheel structure 3 of the comparative example. Therefore, the moment M4 generated in the wheel structure 1 shown in FIG. 3 is smaller than the moment M4 generated in the wheel structure 3 of the comparative example shown in FIG. 16. Therefore, the wheel structure 1 can improve the rigidity against the moment M4 about the axis along the traveling direction of the wheel structures 1, 3 compared to the wheel structure 3 of the comparative example.

[0139] Next, a wheel structure 1 according to a modified example of the embodiment of the present disclosure will be described.

[0140] For example, 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.

[0141] FIG. 17 is a schematic diagram of a link mechanism 240 of a wheel structure 1 according to a modified example of the embodiment of the present disclosure. The first link member 241 and the third link member 243 of the link mechanism 240 are linear and do not have the first bent portion 41d and the second bent portion 43d described above. Furthermore, when the driving wheel 20 and the first 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 241 and the third link member 243 are linear and the link angle θ is a right angle or an obtuse angle, the link mechanism 240 is configured similarly to the link mechanism 40 of the above embodiment. The link mechanism 240 also operates similarly to the link mechanism 40 of the above embodiment. [Explanation of symbols]

[0142] 1 Wheel structure 2 vehicles 10 Main body 20 drive wheels 30 Body mounting part 40 Link mechanism 41 first link member 41a First connection part 41b Second connection part 41c Third connection part 41d 1st bending part (bending part) 42 second link member 42a 4th connection part 42b 5th connection 43 Third link member 43a 6th connection 43b 7th connection 43c 8th Junction 43d Second bend 44 Fourth link member 44a 9th Junction 44b 10th connection 50 First driven wheel 60 Second driven wheel 71 First spring member 72 Second spring member 73 Third spring member 90 Body Ax1 1st axis Ax2 2nd axis Ax3 3rd axis Ax4 4th axis Ax5 5th axis Ax6 6th axis Ax7 7th axis Ax8 8th axis Axr Rotation axis Ln1 First line segment

Claims

1. a main body; 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 mounting portion that is movable relative to the main body portion along a first axis perpendicular to the rotation axis and that is mountable to a vehicle body; a link mechanism that connects the main body and the vehicle body mounting portion; a first driven wheel and a second driven wheel attached to the link mechanism; The link mechanism includes: a first link member having a first connection portion connected to the main body portion so as to be rotatable relative to the main body portion about a second axis parallel to the rotation axis and perpendicular to the first axis, and a second connection portion to which the first driven wheel is attached so as to be rotatable about a third axis parallel to the second axis; a second link member having a fourth connection portion rotatably connected to a 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 rotatably connected to the vehicle body mounting portion about a fifth axis parallel to the second axis; a third link member and a fourth link member that are shaped symmetrically 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, the third link member has a sixth connection portion connected to the main body portion rotatably about the second axis line with respect to the main body portion, and a seventh connection portion to which the second driven wheel is attached rotatably about a sixth axis line parallel to the second axis line, the fourth link member has a ninth connection portion connected to an eighth connection portion between the sixth connection portion and the seventh connection portion of the third link member so as to be rotatable relative to the third link member about a seventh axis parallel to the fourth axis, and a tenth connection portion connected to the vehicle body mounting portion so as to be rotatable relative to the vehicle body mounting portion about an eighth axis parallel to the fifth axis, wheel structure.

2. When the first link member is viewed along the rotation axis, an angle between the first axis and a first line segment connecting the second axis and the fourth axis is an acute angle; the first link member has a bent portion between the third connection portion and the second connection portion, the bent portion being bent in a direction in which the second connection portion moves away from the fifth connection portion; The wheel structure of claim 1 .

3. a first spring member attached between the main body portion and the vehicle body mounting portion and biasing the main body portion and the vehicle body mounting portion in a direction away from each other; The wheel structure of claim 1 .

4. a second spring member attached between the vehicle body attachment portion and the bent portion, the second spring member biasing the vehicle body attachment portion and the bent portion in directions in which the vehicle body attachment portion and the bent portion move away from each other; The wheel structure of claim 2.

5. The wheel structure according to claim 1 ; a vehicle body; There are two of the wheel structures, The two wheel structures are arranged on opposite sides of the vehicle body. vehicle.

Images