Wheel structure and transport tool

Abstract

Provided are a wheel structure and a transport tool that make it possible to smoothly perform mounting movement with minimal force from the start to the completion of mounting a step. In the wheel structure, a frame is provided with a frame support member, the frame support member is provided with a rotation mechanism including a rotating shaft fixed to the frame, the rotation mechanism is configured to enable the frame support member and the rotating shaft to rotate around the rotary shaft of a main wheel, and to enable the frame support member and the rotary shaft of the main wheel to rotate around the rotating shaft, and the rotation mechanism is configured from: a planetary gear mechanism that reduces the rotation speed due to rotation of the main wheel transmitted on the rotary shaft of the main wheel; a force transmission mechanism that transmits rotational force due to the rotation of the main wheel from the rotary shaft side of the main wheel to the rotating shaft side; a clutch mechanism that switches between transmission and non-transmission to the force transmission mechanism of the rotational force due to the rotation of the main wheel; and a transmission control mechanism that controls the switching between transmission and non-transmission in the clutch mechanism.

Description

Wheel Structure and Transport Apparatus

[0001] The present invention relates to a wheel structure and a transport apparatus, and more particularly to a wheel structure and a transport apparatus that can easily climb onto steps.

[0002] In transport apparatuses that use human power as propulsion, such as luggage carts, strollers, and wheelchairs, small-sized wheel structures are often used from the perspective of size and weight. On the other hand, in environments where these transport apparatuses are used, there are many steps caused by level differences on road surfaces and obstacles, and it is not easy to smoothly move wheels onto the upper surface of a step with a small force without imparting impact to the transported object.

[0003] Accordingly, various techniques have conventionally been proposed in which a small-diameter auxiliary wheel is provided in front of an original main wheel, such that when encountering a step, the auxiliary wheel is first brought into contact with the upper surface of the step, and then the main wheel is caused to climb onto the upper surface of the step (for example, Patent Document 1).

[0004] However, in the case of conventional techniques, the operation of the main wheel when returning to its initial state varies depending on the magnitude of the load applied to the main wheel, and the operation before and after climbing a step cannot be said to be smooth, so further improvement is required.

[0005] For example, in the technique using a spring as in Patent Document 1, when the load applied to the main wheel is larger than the restoring force of the spring, the main wheel cannot be returned to its original position. Conversely, when the load applied to the main wheel is smaller than the restoring force of the spring, the main wheel rapidly returns to its original position, which may impart impact to the transported object, and thus the operation before and after climbing a step cannot be said to be smooth.

[0006] Japanese Patent Application Laid-Open No. 2006-7855

[0007] In view of the above-mentioned problems in the conventional art, an object of the present invention is to provide a wheel structure and a transport apparatus that can smoothly perform a climbing operation with a small force from the start to the completion of climbing a step.

[0008] The inventors of this invention conducted diligent research to solve the above problems and, as a result, found that the above problems can be solved by the invention described below, and thus completed the present invention.

[0009] The invention described in claim 1 is a wheel structure wherein a large-diameter main wheel is arranged on the rear side in the direction of travel of a frame on which a transportable material mounting platform mounting portion is provided, and a small-diameter auxiliary wheel is arranged on the front side in the direction of travel of the frame, and the auxiliary wheel is configured to descend and abut against the upper surface of the step when the main wheel comes into contact with a step, and thereafter the main wheel rides up onto the upper surface of the step, and the auxiliary wheel rises as the main wheel moves along the upper surface of the step, the frame is provided with a frame support member that supports the frame, and the frame support member is provided with a pivot shaft that is arranged parallel to the rotation axis of the main wheel and fixed to the frame, the pivot mechanism is configured to make the frame support member and the pivot shaft rotatable around the rotation axis of the main wheel, and to make the frame support member and the rotation axis of the main wheel rotatable around the pivot shaft, The rotation mechanism comprises a planetary gear mechanism that reduces the rotational speed due to the rotation of the main wheel transmitted on the rotation axis of the main wheel, a force transmission mechanism that transmits the rotational force due to the rotation of the main wheel transmitted on the rotation axis of the main wheel from the rotation axis side of the main wheel to the rotation axis side, a clutch mechanism that switches whether or not to transmit the rotational force due to the rotation of the main wheel to the force transmission mechanism, and a transmission control mechanism that controls the switching of the clutch mechanism on or off. The clutch mechanism comprises a first rotating member that is immovable in the axial direction and has a plurality of rotational force transmission teeth to which the rotational force due to the rotation of the main wheel is transmitted, and a second rotating member that is movable in the axial direction and has a plurality of rotational force transmission teeth that are opposite to the first rotating member and can mesh with the plurality of rotational force transmission teeth of the first rotating member. The second rotating member and the first rotating member switch whether or not to transmit the rotational force due to the rotation of the main wheel to the rotation axis via the force transmission mechanism by contacting / separating from each other in the axial direction. The wheel structure is characterized in that the transmission control mechanism is composed of a moving mechanism that moves the second rotating member of the clutch mechanism in the axial direction.

[0010] The invention described in claim 2 is characterized in that the frame support member comprises a first subframe located on the main wheel side in the axial direction, and a second subframe located on the opposite side from the main wheel side in the axial direction and overlapping the first subframe in the axial direction to form the casing of the frame support member, the moving mechanism comprises an annular portion, a first projection projecting from the annular portion toward the first subframe side, and a second projection projecting from the annular portion toward the second subframe side, and is formed in an annular shape when viewed in the axial direction, is fixed in the circumferential direction and configured to be movable in the axial direction, and rotatably holds the second rotating member inside the annular portion, and a first rotating member is formed in a substantially annular shape when viewed in the axial direction, is fixed in the axial direction and configured to rotate in conjunction with the rotation of the frame support member around the rotation axis of the main wheel, and has a first contact projection that can contact the first projection of the moving member when the frame support member is rotated to a first angle, The wheel structure is as described in claim 1, wherein the second rotating member is formed in a substantially annular shape when viewed in the axial direction, is fixed in the axial direction while being positioned to sandwich the moving member in the axial direction between it and the first rotating member, and is configured to rotate in conjunction with the rotation of the frame support member around the rotation axis of the main wheel, and has a second contact projection on the second projection of the moving member that can contact the frame support member when it rotates to a second angle, and when the second projection of the moving member and the second contact projection of the second rotating member come into contact with each other, the moving member moves toward the first subframe and the second rotating member comes into contact with the first rotating member, and when the first projection of the moving member and the first contact projection of the first rotating member come into contact with each other, the moving member moves toward the second subframe and the second rotating member moves away from the first rotating member.

[0011] The invention described in claim 3 is a wheel structure according to claim 2, characterized in that the first projection of the moving member has a first projection inclined surface that slopes from the apex of the first projection in the axial direction away from the first subframe and in the counterclockwise (CCW) direction; the second projection of the moving member has a second projection inclined surface that slopes from the apex of the second projection in the axial direction away from the second subframe and in the clockwise (CW) direction; the first contact projection of the first rotating member has a first contact projection inclined surface that slopes from the apex of the first contact projection in the axial direction away from the second subframe and in the clockwise (CW) direction; and the second contact projection of the second rotating member has a second contact projection inclined surface that slopes from the apex of the second contact projection in the axial direction away from the first subframe and in the counterclockwise (CCW) direction. Note that clockwise (CW) and counterclockwise (CCW) directions refer to the direction of rotation when viewing a wheel structure moving to the left from its left side.

[0012] The invention described in claim 4 is a wheel structure according to claim 2, characterized in that the first angle is the rotation angle of the frame support member when the auxiliary wheel rises and is in the highest position relative to the height position of the main wheel, and the second angle is a specific angle in the range of an angle less than or equal to the rotation angle of the frame support member when the auxiliary wheel lowers and is in the lowest position relative to the height position of the main wheel, and at least 15 degrees smaller than said rotation angle.

[0013] The invention described in claim 5 is a wheel structure according to claim 2, characterized in that the force transmission mechanism comprises a main wheel shaft side member disposed on the rotation axis of the main wheel, a rotation axis side member disposed on the rotation axis, and a transmission member that transmits rotational force around the rotation axis of the main wheel from the main wheel shaft side member to the rotation axis side member, the main wheel shaft side member is configured not to rotate around the rotation axis of the main wheel even when the support frame rotates around the rotation axis of the main wheel, and the movable member is supported by the main wheel shaft side member so as to be movable along the rotation axis of the main wheel, and not to rotate around the rotation axis of the main wheel even when the support frame rotates around the rotation axis of the main wheel.

[0014] The invention described in claim 6 is a wheel structure according to claim 2, characterized in that a plurality of sets of the first projection, the second projection, the first contact projection, and the second contact projection are provided, each of the first projection and the second projection is arranged rotationally symmetrically with respect to each other with respect to the axis of rotation of the main wheel in the moving member, each of the first contact projections is arranged rotationally symmetrically with respect to the axis of rotation of the main wheel in the first rotating member, and each of the second contact projections is arranged rotationally symmetrically with respect to the axis of rotation of the main wheel in the first rotating member.

[0015] The invention described in claim 7 is a wheel structure wherein a large-diameter main wheel is arranged on the rear side in the direction of travel of a frame on which a transportable material mounting platform mounting portion is provided, and a small-diameter auxiliary wheel is arranged on the front side in the direction of travel of the frame, and the auxiliary wheel is configured to descend and abut against the upper surface of the step when the main wheel comes into contact with a step, and thereafter the main wheel rides up onto the upper surface of the step, and the auxiliary wheel rises as the main wheel moves along the upper surface of the step, the frame is provided with a frame support member that supports the frame, and the frame support member is provided with a pivot shaft that is arranged parallel to the rotation axis of the main wheel and fixed to the frame, the pivot mechanism is configured to make the frame support member and the pivot shaft rotatable around the rotation axis of the main wheel, and to make the frame support member and the rotation axis of the main wheel rotatable around the pivot shaft, The rotation mechanism comprises a planetary gear mechanism that reduces the rotational speed due to the rotation of the main wheel transmitted on the rotation axis of the main wheel; a power transmission mechanism that transmits the rotational force due to the rotation of the main wheel transmitted on the rotation axis of the main wheel from the rotation axis side of the main wheel to the rotation axis side; a clutch mechanism that switches whether or not to transmit the rotational force due to the rotation of the main wheel to the power transmission mechanism, or whether or not to transmit the rotational force output from the power transmission mechanism that has transmitted the rotational force due to the rotation of the main wheel to the rotation axis fixed to the frame; and a transmission control mechanism that controls the switching of the clutch mechanism on or off. The clutch mechanism comprises a first rotating member that is movable in the axial direction and has a plurality of rotational force transmission teeth to which the rotational force due to the rotation of the main wheel is transmitted, and a second rotating member that is not movable in the axial direction and has a plurality of rotational force transmission teeth that are opposite to the first rotating member and can mesh with the plurality of rotational force transmission teeth of the first rotating member, and the second rotating member and the first rotating member make contact with each other in the axial direction to switch whether or not to transmit the rotational force due to the rotation of the main wheel transmitted via the force transmission mechanism to the pivot shaft, and the transmission control mechanism comprises a moving mechanism that moves the first rotating member of the clutch mechanism in the axial direction, characterized in that the wheel structure comprises these components.

[0016] The invention described in claim 8 is a moving mechanism having an annular portion, a first projection projecting from the annular portion toward the first subframe, and a second projection projecting from the annular portion toward the second subframe, and being formed in an annular shape when viewed in the axial direction, fixed in the circumferential direction, and configured to be movable in the axial direction, and rotatably holding the first rotating member inside the annular portion, and a first rotating member having a substantially annular shape when viewed in the axial direction, fixed in the axial direction, and configured to rotate in conjunction with the rotation of the frame support member around the rotation axis of the main wheel, and having a first contact projection that can contact the first projection of the moving member when the frame support member is rotated to a first angle, The wheel structure according to claim 7, wherein the second rotating member is formed in a substantially annular shape when viewed in the axial direction, is fixed in the axial direction while being positioned to sandwich the moving member in the axial direction between it and the first rotating member, and is configured to rotate in conjunction with the rotation of the frame support member around the rotation axis of the main wheel, and has a second contact projection on the second projection of the moving member that can contact the frame support member when it rotates to a second angle, and when the second projection of the moving member and the second contact projection of the second rotating member come into contact with each other, the moving member moves toward the first subframe and the second rotating member comes into contact with the first rotating member, and when the first projection of the moving member and the first contact projection of the first rotating member come into contact with each other, the moving member moves toward the second subframe and the second rotating member moves away from the first rotating member.

[0017] The invention described in claim 9 is a wheel structure according to claim 8, characterized in that the force transmission mechanism comprises a main wheel shaft side member disposed on the rotation axis of the main wheel, a rotation axis side member disposed on the rotation axis, and a transmission member that transmits the rotational force of the main wheel shaft side member around the rotation axis of the main wheel to the rotation axis side member, the support frame is configured so that the rotation axis side member does not rotate around the rotation axis even when the support frame rotates around the rotation axis of the main wheel, and the movable member is supported by the rotation axis side member so as to be movable along the rotation axis and so as not to rotate around the rotation axis even when the support frame rotates around the rotation axis of the main wheel.

[0018] The invention described in claim 10 is a wheel structure according to claim 8, characterized in that a plurality of sets of the first projection, the second projection, the first contact projection, and the second contact projection are provided, each of the first projection and the second projection is arranged rotationally symmetrically with respect to each other with respect to the axis of rotation of the main wheel in the moving member, each of the first contact projections is arranged rotationally symmetrically with respect to the axis of rotation of the main wheel in the first rotating member, and each of the second contact projections is arranged rotationally symmetrically with respect to the axis of rotation of the main wheel in the first rotating member.

[0019] The invention described in claim 11 is a transport device characterized by comprising a wheel structure as described in any one of claims 1 to 10.

[0020] According to the present invention, it is possible to provide a wheel structure and a transport device that can perform a smooth step-climbing operation with minimal force, from the start to the completion of step-climbing.

[0021] Figure 5(b) is a schematic perspective view showing the structure of a wheel structure according to an embodiment of the present invention. Figure 1 is an exploded perspective view of the wheel structure shown in Figure 1. Figure 5(b) is an exploded perspective view of the frame support member in a wheel structure according to an embodiment of the present invention. Figure 5(b) is a schematic perspective view showing the relationship between the circumferential fixing member and the reinforcing member of the frame support member in a wheel structure according to an embodiment of the present invention. Note that in Figure 4, the movable member and the second rotating member located between the annular portion of the circumferential fixing member and the reinforcing member are omitted from the illustration. (a) is a side view illustrating the state of the wheel structure according to an embodiment of the present invention during normal running or immediately after the main wheel contacts a step. (b) is a perspective view of the inside of the frame support member viewed from the front right diagonally above in the state of (a). Note that in Figure 5(b), the chain of the force transmission mechanism is partially omitted from the illustration. (a) is a side view illustrating the state of the wheel structure according to an embodiment of the present invention during the process of riding over a step (rotation angle of the frame support member is 60 degrees) (a state later than that in Figure 5), showing the moment when the auxiliary wheel descends and contacts the top surface of the step. (b) is a perspective view of the inside of the frame support member as seen from the front right diagonally above in the state of (a). Note that in Figure 6(b), the chain of the force transmission mechanism is omitted from the illustration. (a) is a side view illustrating the state of the frame support member at a rotation angle of 140 degrees (a state later than that in Figure 6) immediately after the main wheel of the wheel structure according to the embodiment of the present invention has completed riding over the step. (b) is a diagram showing the inside of the frame support member as seen in the state of (a), illustrating the relationship between the second contact projection of the second rotating member and the second projection of the moving member, and is a perspective view seen from the front right diagonally above. Note that in Figure 7(b), the chain of the force transmission mechanism is omitted from the illustration. (a) is a side view illustrating the state of the frame support member at a rotation angle of 30 degrees (a state later than that in Figure 7) after the main wheel of the wheel structure according to the embodiment of the present invention has advanced over the top surface of the step. (b) is a diagram showing the inside of the frame support member in the state of (a), and shows the relationship between the first contact projection of the first rotating member and the first projection of the moving member, and is a perspective view taken from the front right upper side. Note that in Figure 8(b), the chain of the force transmission mechanism is omitted from the illustration.(a) is a schematic front view showing the relationship between the first rotating member, the moving member and the second rotating member at a rotation angle of 125 degrees (second angle) of the frame support member; (b) is a schematic front view showing the relationship between the first rotating member and the second rotating member in the state of (a); (c) is a schematic front view showing the relationship between the first rotating member, the moving member and the second rotating member at a rotation angle of 30 degrees (first angle) of the frame support member; (b) is a schematic front view showing the relationship between the first rotating member and the second rotating member in the state of (a). This is an exploded perspective view of the frame support member in a wheel structure according to a first modified example of an embodiment of the present invention.

[0022] [A] Features of the present invention First, the features of the present invention will be described.

[0023] [1] Basic configuration of the wheel structure according to the present invention The wheel structure according to the present invention has a large-diameter main wheel on the rear side in the direction of travel of the frame on which the transported material mounting platform attachment part is provided, and a small-diameter auxiliary wheel on the front side in the direction of travel of the frame. The auxiliary wheel is configured to descend and come into contact with the upper surface of the step as the main wheel comes into contact with a step, and then the main wheel rides up onto the upper surface of the step, and the auxiliary wheel rises as the main wheel moves along the upper surface of the step.

[0024] Furthermore, the frame is provided with frame support members that support the frame, and the frame support members are provided with a rotation mechanism that has a pivot shaft fixed to the frame and arranged parallel to the rotation axis of the main wheel. The rotation mechanism is configured to allow the frame support members and the pivot shaft to rotate around the rotation axis of the main wheel, and to allow the frame support members and the rotation axis of the main wheel to rotate around the pivot shaft. In addition, the rotation mechanism is composed of a planetary gear mechanism that reduces the rotational speed caused by the rotation of the main wheel transmitted to the rotation axis of the main wheel, a power transmission mechanism that transmits the rotational force caused by the rotation of the main wheel transmitted on the rotation axis of the main wheel from the rotation axis side of the main wheel to the pivot shaft side, a clutch mechanism that switches whether or not to transmit the rotational force caused by the rotation of the main wheel to the power transmission mechanism, or whether or not to transmit the rotational force output from the power transmission mechanism that has transmitted the rotational force caused by the rotation of the main wheel to the pivot shaft fixed to the frame, and a transmission control mechanism that controls the switching of the clutch mechanism's transmission.

[0025] The clutch mechanism comprises a first rotating member which has a plurality of rotational force transmission teeth to which the rotational force due to the rotation of the main wheel is transmitted and is either immovable or movable in the axial direction, and a second rotating member which faces the first rotating member and has a plurality of rotational force transmission teeth that can mesh with the plurality of rotational force transmission teeth of the first rotating member and is either movable or immovable in the axial direction. The second rotating member and the first rotating member make contact with each other in the axial direction / separate from each other to switch whether or not the rotational force due to the rotation of the main wheel is transmitted to the pivot shaft via the force transmission mechanism, or whether or not the rotational force due to the rotation of the main wheel transmitted via the force transmission mechanism is transmitted to the pivot shaft.

[0026] The transmission control mechanism consists of a moving mechanism that moves the first or second rotating member of the clutch mechanism in the axial direction.

[0027] By providing such a rotating mechanism and appropriately controlling the movement of the main and auxiliary wheels, the vehicle can smoothly climb over obstacles with minimal force, from the start to the completion of the climb.

[0028] Furthermore, the wheel structure according to the present invention is configured to perform the following actions during normal driving, when contacting a step, and when riding over a step.

[0029] First, during normal operation, the counterclockwise (CCW) rotation of the main wheels caused by the propulsive force in the direction of travel is not transmitted to the pivot point, and the main wheels move forward while the auxiliary wheels remain lifted off the ground.

[0030] Then, when the main wheel of the wheel structure approaches the step and makes contact with the step, the rotation of the main wheel stops, but the propulsive force in the direction of travel causes the frame support member to rotate counterclockwise (CCW) around the rotation axis of the main wheel, causing the auxiliary wheel to descend and come into contact with the top surface of the step.

[0031] Subsequently, the main wheel, which is in contact with the corner of the step, rotates counterclockwise (CCW) in conjunction with the rotation of the frame support member, using the corner of the step as a pivot point, and with little force, the main wheel smoothly rides up onto the top surface of the step.

[0032] Then, after the main wheel has driven onto the step, the thrust in the direction of travel causes the main wheel to rotate counterclockwise (CCW) and move forward on the step. At the same time, the rotational force of the main wheel is transmitted to the pivot shaft, which rotates clockwise (CW) around the main wheel's axis of rotation. This causes the frame support member to rotate clockwise (CW) around the main wheel's axis of rotation, causing the auxiliary wheel to rise and return to its initial position.

[0033] Note that clockwise (CW, forward rotation) and counterclockwise (CCW, reverse rotation) refer to the direction of rotation when viewing a wheel structure moving to the left from its left side.

[0034] [2] Effects of the present invention According to the present invention, when riding over a step, the main wheels can be rotated with less force to ride over the step. Furthermore, after the main wheels have ridden over the step, the frame can be raised back to its initial position with less force. In addition, the wheel structure can be ridden over the step with a single action of moving the wheel structure forward. For this reason, the entire process of riding over a step does not require a large amount of force and can be done smoothly.

[0035] Furthermore, according to the present invention, by using a planetary gear mechanism as a reduction mechanism, a large reduction ratio can be obtained with fewer stages compared to a reduction mechanism that combines, for example, spur gears. The mechanism can be made more compact because the input shaft and output shaft can be arranged coaxially. In addition, a large rotational force can be obtained by increasing the reduction ratio. Obtaining a large rotational force is advantageous for lifting a frame that is subjected to a large load via the transportable object mounting part, via the frame support member.

[0036] [B] Preferred embodiment of the wheel structure according to the present invention The wheel structure according to the present invention preferably takes the following embodiment.

[0037] [1] Frame support member In the present invention, the frame support member is provided with a first subframe located on the main wheel side in the axial direction and having a hole through which the rotation shaft of the main wheel is inserted, and a second subframe located on the opposite side from the main wheel side in the axial direction and having a hole through which a pivot shaft for rotating the frame support member is inserted, and it is preferable that a rotation mechanism is arranged between the first subframe and the second subframe.

[0038] Furthermore, it is preferable that the frame support member houses the planetary gear mechanism, power transmission mechanism, clutch mechanism, and transmission control mechanism that constitute the aforementioned rotation mechanism within a casing formed by a box-shaped first subframe and a box-shaped second subframe. This makes it easy to miniaturize the wheel structure and gives it a clean appearance. The power transmission mechanism includes, for example, a main wheel shaft side member arranged on the rotation axis of the main wheel shaft, a rotation axis side member arranged on the rotation axis, and a transmission member that transmits the rotational force around the rotation axis of the main wheel from the main wheel shaft side member to the rotation axis side member. The main wheel shaft side member and the rotation axis side member can be, for example, sprockets, pulleys, gears, etc. Also, as the transmission member, a chain that transmits rotational force between sprockets, a wire that transmits rotational force between pulleys, an intermediate gear that transmits rotational force between gears, etc. can be used.

[0039] [2] Transport Equipment By attaching the wheel structure according to the present invention to the lower part (bottom surface, lower end) of various transport equipment via the transport equipment mounting part, a transport equipment suitable for transporting transport items corresponding to the transport equipment to which it is attached can be made.

[0040] Examples of specific items to be transported include various types of luggage, animals, and people, while examples of transport equipment include carts for transporting luggage, strollers, and wheelchairs.

[0041] [C] Specific Embodiments The present invention will be described in detail below with reference to the drawings, but these embodiments are illustrative and the present invention is not limited thereto.

[0042] [1] Configuration of wheel structure In the present embodiment, the wheel structure is configured as follows in order to specifically express the above-described features and effects of the present invention. In the present specification, when viewing from the rear side to the front side in the traveling direction of the wheel structure, the left side is defined as the left side, and the right side is defined as the right side. Further, the direction in which the rotation shaft of the main wheel and the pivot shaft arranged parallel to the rotation shaft of the main wheel extend is defined as "axial direction", the direction orthogonal to the axial direction is defined as "radial direction", and the direction around the axial direction is defined as "circumferential direction".

[0043] (Wheel structure) As shown in FIG. 1, the wheel structure 1 according to the present embodiment includes: a frame 4 provided with a conveyed object mounting table attachment portion 5 on an upper surface thereof; a large-diameter main wheel 2 arranged below the frame 4 and on the rear side in the traveling direction of the frame 4; a small-diameter auxiliary wheel 3 arranged on the front side in the traveling direction of the frame 4; and a frame support member 6 interposed between the main wheel 2 and the frame 4 and supporting the frame 4 above the main wheel 2. The auxiliary wheel 3 is in a state of floating from the ground by a predetermined distance during normal traveling. The wheel structure 1 is configured such that, as the main wheel 2 contacts the step 11, the auxiliary wheel 3 descends and abuts against the step upper surface 11b (illustrated in FIG. 6), then the main wheel 2 rides onto the step upper surface 11b (illustrated in FIG. 7), and as the main wheel 2 travels on the step upper surface 11b, the auxiliary wheel 3 ascends (illustrated in FIG. 8).

[0044] As shown in FIG. 2, the main wheel 2 includes a rotation shaft 21, a wheel 2b, and a tire 2a covering the wheel 2b in the radial direction and the circumferential direction. The wheel 2b has a cup shape with an opening on the left side surface. The wheel 2b has the rotation shaft 21 erected at the center of the right side surface, and is thereby pivotally fixed to the rotation shaft 21. The rotation shaft 21 extends to a second sub-frame 62 of the frame support member 6, which will be described later. Hereinafter, the rotation shaft of the main wheel may be referred to as "main wheel shaft".

[0045] The auxiliary wheel 3 has a smaller diameter than the main wheel 2, and includes a wheel 3b and a tire 3a covering the wheel 3b in the radial direction and the circumferential direction.

[0046] As shown in FIGS. 1 and 2, the frame 4 includes a canopy portion 4a, a side wall portion 4b, and an auxiliary wheel support portion 4c, is arranged above the main wheel 2 so as to cover the main wheel 2, supports the main wheel 2 via the frame support member 6 and the rotating shaft 21, and supports the auxiliary wheel 3 via the rotating shaft 31 of the auxiliary wheel 3 provided at the distal end portion of the auxiliary wheel support portion 4c. A transported article mounting base attachment portion 5 is attached to the upper surface of the canopy portion 4a so as to be integrated with the frame 4. The auxiliary wheel 3 and the frame 4 ascend or descend in accordance with rotation about the rotating shaft 21 (main wheel shaft 21) of a frame support member 6 described later.

[0047] (Frame Support Member) As shown in FIG. 3, the frame support member 6 includes a box-shaped first sub-frame 61 located on the main wheel 2 side in the axial direction, and a box-shaped second sub-frame 62 located on the side opposite to the main wheel 2 side in the axial direction. A planetary gear mechanism that constitutes the above-described rotating mechanism, a force transmission mechanism, a clutch mechanism, and a transmission control mechanism are housed in a housing (the casing of the frame support member 6) formed by the first sub-frame 61 and the second sub-frame 62 overlapping each other in the axial direction.

[0048] The first sub-frame 61 is formed with a circular circular hole 61h that is open around the rotating shaft 21 with the rotating shaft 21 of the main wheel 2 inserted therethrough. Inside the first sub-frame 61, a first rotating member 66, which is described later, is fixed, and the first rotating member 66 is disposed so as to surround the circular hole 61h with the circular hole 61h as the center.

[0049] The second sub-frame 62 is formed with a circular hole 62h for inserting a left side portion of a rotating shaft 74 described later. The diameter of the circular hole 62h is set to be slightly larger than the diameter of the rotating shaft 74.

[0050] Furthermore, the second sub-frame 62 is provided with a stopper 62b (illustrated in FIGS. 1, 2 and 3) on the outer surface (the left side surface, which is the side surface on the side wall portion 4b side of the frame 4), and when the frame support member 6 rotates clockwise and the stopper 62b abuts against the lower end of the side wall portion 4b of the frame 4, the frame support member 6 stops rotating.

[0051] Furthermore, as shown in Figure 6(b), an internal gear 62a, which will become an internal gear of the planetary gear mechanism described later, is formed on the inner surface (right side) of the second subframe 62, and a hole 62ah is formed at the center of the internal gear 62a for rotatably supporting the rotation shaft 21 (main wheel shaft 21) of the main wheel 2. In this embodiment, the hole 62ah is a non-through hole, but it may also be a through hole.

[0052] As shown in Figure 3, the frame support member 6 includes, in addition to the first subframe 61 and the second subframe 62, a first rotating member 63, a second rotating member 64, a moving member 65, a first rotating member 66, a second rotating member 67, a rotational force transmission member 68, a planetary gear 69, a planetary carrier 70, a first sprocket 71, a circumferential fixing member 72, a reinforcing member 73, a pivot shaft 74, a second sprocket 75, and a chain 76.

[0053] Then, through the action of the second rotating member 67 and the moving member 65, the first rotating member 63 and the second rotating member 64 engage, and the clockwise (CW) rotation of the main axle 21 is transmitted in the following order: first rotating member 63, second rotating member 64, rotational force transmission member 68, planetary gear 69, planetary carrier 70, first sprocket 71, chain 76, second sprocket 75, and rotating shaft 74, causing the frame support member 6 to rotate clockwise (CW) around the main axle 21. On the other hand, the first rotating member 63 has the function of separating the first rotating member 63 and the second rotating member 64.

[0054] The first rotating member 63, although not shown in the figure, is pivotally fixed to the rotation shaft 21 (main wheel shaft 21) of the main wheel 2. The first rotating member 63 is a ring gear-shaped member and has a plurality of rotational force transmission teeth 63a. The first rotating member 63 is configured to transmit rotational force from the rotation of the main wheel 2 and to be immovable in the axial direction. For example, the first rotating member 63 may be fixed to the main wheel shaft 21 through a hole formed in the center of the first rotating member 63.

[0055] Each of the multiple rotational force transmission teeth 63a has a vertical surface 63as perpendicular to the counterclockwise (CCW) direction, and an inclined surface 63ak that slopes from the apex of the vertical surface 63as toward the axial direction of the rotation axis 21 and toward the second subframe 62 (i.e. toward the right) and toward the clockwise (CW) direction.

[0056] The second rotating member 64 is a substantially annular member when viewed in the axial direction. The second rotating member 64 is pivotally supported so as to be integrally rotatable with the right end of the rotational force transmission member 68, which will be described later. The second rotating member 64 is positioned to the left of the first rotating member 63 and faces the first rotating member 63 in the axial direction. The second rotating member 64 has a plurality of rotational force transmission teeth 64a that can mesh with the plurality of rotational force transmission teeth 63a of the first rotating member 63. The substantially annular second rotating member 64 has a hole 64h on its inner diameter side. The hole 64h is formed in a gear shape with irregularities. The fitted gear 68a formed at the right end of the rotational force transmission member 68, which will be described later, is fitted into the hole 64h. The second rotating member 64 is configured to be movable in the axial direction on the fitted gear 68a when the fitted gear 68a is fitted into the hole 64h.

[0057] Each of the multiple rotational force transmission teeth 64a has a vertical surface 64as perpendicular to the clockwise (CW) direction, and an inclined surface 64ak that slopes from the apex of the vertical surface 64as in the axial direction away from the first subframe 61 (i.e., to the left) and in the counterclockwise (CCW) direction.

[0058] The second rotating member 64 is rotatably held inside the annular portion 65r of the movable member 65, which will be described later. As the movable member 65 moves in the axial direction, the second rotating member 64 also moves in the axial direction. As a result, the second rotating member 64 comes into contact with and separates from the first rotating member 63. When the second rotating member 64 comes into contact with the first rotating member 63, the rotational force transmission teeth 64a of the second rotating member 64 mesh with the rotational force transmission teeth 63a of the first rotating member 63. When the rotational force transmission teeth 64a mesh with the rotational force transmission teeth 63a, the rotational force transmitted to the first rotating member 63 by the rotation of the main wheel 2 is transmitted to the second rotating member 64.

[0059] The movable member 65 is formed in an annular shape when viewed in the axial direction and is configured to be fixed in the circumferential direction to the sprocket 71 and planetary carrier 70, which will be described later, and to be movable in the axial direction. The movable member 65 has an annular portion 65r, a first projection 65a projecting from the annular portion 65r toward the first subframe 61 (to the right), and a second projection 65b projecting from the annular portion 65r toward the second subframe 62 (to the left). In this embodiment, the first projection 65a and the second projection 65b are provided in pairs of two sets. Each first projection 65a is positioned 180 degrees apart from each other in the circumferential direction on the right surface (the surface toward the first subframe 61) of the annular portion 65r. On the other hand, each second projection 65a is positioned 180 degrees apart from each other in the circumferential direction on the left surface (the surface toward the second subframe 62) of the annular portion 65r. As described above, multiple sets of the first projection 65a and the second projection 65b may be provided. In this case, it is preferable that each of the first projection 65a and the second projection 65b is positioned at a rotationally symmetrical position around the axis of rotation of the main wheel on the annular portion 65r of the movable member 65 (for example, 180 degrees in the case of two projections, and 120 degrees in the case of three projections).

[0060] The annular portion 65r is a part formed in an annular shape. The annular portion 65r rotatably holds the second rotating member 64 from within. Specifically, a circumferentially extending ridge is formed on the radially outer circumferential surface of the second rotating member 64, and a circumferentially extending groove is formed on the radially inner circumferential surface of the annular portion 65r, and the ridge of the second rotating member 64 and the groove of the annular portion 65r are fitted together so as to be able to move relative to each other.

[0061] The annular portion 65r has through-holes 65rh through which the two phase transmission rods 72a of the circumferential fixing member 72, which will be described later, are inserted. In this embodiment, two through-holes 65rh are formed, and each is formed 180 degrees apart from the other in the circumferential direction on the annular portion 65r, corresponding to the circumferential positions of the two phase transmission rods 72a. As will be described later, by inserting each of the two phase transmission rods 72a of the circumferential fixing member 72 into each of the two through-holes 65rh, the movable member 65 is configured to be fixed in the circumferential direction and movable in the axial direction relative to the sprocket 71 and planetary carrier 70, which will be described later.

[0062] The first projection 65a has a vertex surface 65at and a first projection inclined surface 65ak that is inclined axially from the vertex surface 65at toward the left (i.e., toward the left) and in a counterclockwise (CCW) direction. In this embodiment, two first projections 65a are formed, and each is positioned 180 degrees apart from the other in the circumferential direction on the right surface (the surface on the first subframe 61 side) of the annular portion 65r.

[0063] The second projection 65b has a vertex surface 65bt and a second projection inclined surface 65bk that is inclined axially from the vertex surface 65bt toward the direction away from the second subframe 62 (i.e., toward the right) and in a clockwise (CW) direction. In this embodiment, two second projections 65b are formed, and each is positioned 180 degrees apart from the other in the circumferential direction on the left surface of the annular portion 65r (the surface on the second subframe 62 side).

[0064] The first rotating member 66 is a member that is formed in a substantially annular shape when viewed in the axial direction. The first rotating member 66 is positioned inside the box-shaped first subframe 61, surrounding the circular hole 61h of the first subframe 61, and is fixed to the first subframe 61. As a result, the first rotating member 66 is configured to rotate in conjunction with the rotation of the frame support member 6 around the rotation axis 21 (main wheel shaft 21) of the main wheel 2.

[0065] The first rotating member 66 includes an annular portion 66r formed in an annular shape, a first contact projection 66a projecting to the left on the left surface of the annular portion 66r (the surface on the second subframe 62 side), a radial projection 66b projecting radially outward from the radial outer surface of the annular portion 66r, and a connecting member 66c fixed to the radial projection 66b and extending axially to the left from the radial projection 66b.

[0066] The inner diameter of the annular portion 66r is set to be larger than the outer diameter of the first rotating member 63 and also larger than the outer diameter of the reinforcing member 73. That is, the reinforcing member 73 is contained within the inner diameter of the annular portion 66r, and the first rotating member is contained inside the reinforcing member 73.

[0067] The first contact projection 66a is a projection that can come into contact with the first projection 65a of the movable member 65 when the frame support member 6 is rotated to a first angle. The first angle will be defined in the description of the operation of the wheel structure 1.

[0068] The first abutment projection 66a has a vertex surface 66at and a first abutment projection inclined surface 66ak that is inclined axially from the vertex surface 66at toward the direction away from the second subframe 62 (i.e., toward the right) and in a clockwise (CW) direction. As shown in Figure 9(c), the first abutment projection inclined surface 66ak can abut (surface contact) with the first projection inclined surface 65ak of the first projection 65a of the movable member 65. In this embodiment, two first abutment projections 66a are formed, and each is positioned 180 degrees apart from the other in the circumferential direction on the left surface of the annular portion 66r (the surface on the second subframe 62 side). Thus, there may be multiple first contact protrusions 66a, in which case it is preferable that each first contact protrusion 66a is positioned so as to be rotationally symmetric with respect to the rotation axis of the main wheel in the first rotating member 66 (for example, 180 degrees in the case of two, and 120 degrees in the case of three). This allows the movable member 65 and the second rotating member 64 held by the movable member 65 to move smoothly.

[0069] As shown in Figure 3, the radial projection 66b is the portion for connecting the connecting member 66c to the radial projection 67b of the second rotating member 67, which will be described later. Specifically, the radial projection 66b is the portion that protrudes radially outward from the radial outer surface of the annular portion 66r in order to extend the connecting member 66c radially outward from the members (first rotating member 63, reinforcing member 73, second rotating member 64, and moving member 65) that are positioned between the first rotating member 66 and the second rotating member 67. In this embodiment, two radial projections 66b are formed, each formed 180 degrees apart in the circumferential direction from the radial outer surface of the annular portion 66r.

[0070] As described above, the connecting member 66c is a rod-shaped member that connects the radial projection 66b of the first rotating member 66 to the radial projection 67b of the second rotating member 67. That is, the right end of the connecting member 66c is connected and fixed to the radial projection 66b of the first rotating member 66, and the left end of the connecting member 66c is connected and fixed to the radial projection 67b of the second rotating member 67. In this way, the second rotating member 67 is fixed to the first rotating member 66. The connecting member 66c extends in the axial direction. In this embodiment, two connecting members 66c are provided because there are two radial projections 66b of the first rotating member 66 and two radial projections 67b of the second rotating member 67.

[0071] The second rotating member 67 is a member formed in the same shape as the first rotating member 66 when viewed in the axial direction. That is, the second rotating member 67 is a member formed in a substantially annular shape when viewed in the axial direction. As described above, the second rotating member 67 is fixed to the first rotating member 66 by the connecting member 66c of the first rotating member 66. As a result, the second rotating member 67 is fixed in the axial direction and is configured to rotate in conjunction with the rotation of the frame support member 6 around the rotation axis 21 (main wheel axis 21) of the main wheel 2. Also, as described above, the second rotating member 67 is positioned to sandwich the first rotating member 63, the reinforcing member 73, the second rotating member 64, and the moving member 65 in the axial direction between it and the first rotating member 66.

[0072] The second rotating member 67 has an annular portion 67r formed in an annular shape, a second contact projection 67a projecting to the right on the right surface of the annular portion 67r (the surface on the first subframe 61 side), and a radial projection 67b projecting radially outward from the radial outer surface of the annular portion 67r.

[0073] The inner diameter of the annular portion 67r is the same as the inner diameter of the annular portion 66r of the first rotating member 66, but the length of the annular portion 67r is set to allow the two phase transmission rods 72a of the circumferential fixing member 72, which will be described later, to pass through it.

[0074] The second contact projection 67a is a projection that can come into contact with the second projection 65b of the movable member 65 when the frame support member 6 is rotated to a second angle. The second angle will be defined in the description of the operation of the wheel structure 1.

[0075] The second abutment projection 67a has a vertex surface 67at and a second abutment projection inclined surface 67ak that is inclined axially from the vertex surface 67at toward the left (i.e., toward the left) and in a counterclockwise (CCW) direction. As shown in Figure 9(a), the second abutment projection inclined surface 67ak can abut (surface contact) with the second projection inclined surface 65bk of the second projection 65b of the movable member 65. In this embodiment, two second abutment projections 67a are formed, and each is arranged 180 degrees apart from the other in the circumferential direction on the right surface (the surface on the first subframe 61 side) of the annular portion 67r. Thus, there may be multiple second contact protrusions 67a, in which case it is preferable that each second contact protrusion 67a is positioned at a rotationally symmetrical position with respect to the rotation axis of the main wheel in the second rotating member 67 (for example, 180 degrees apart in the case of two, and 120 degrees apart in the case of three). This allows the movable member 65 and the second rotating member 64 held by the movable member 65 to move smoothly.

[0076] As shown in Figure 3, the radial projection 67b is a portion that protrudes radially outward from the radial outer surface of the annular portion 67r in order to connect to the left end of the connecting member 66c of the first rotating member 66. In this embodiment, two radial projections 67b are formed, each formed 180 degrees apart in the circumferential direction on the radial outer surface of the annular portion 67r relative to each other.

[0077] The rotational force transmission member 68 is a member that transmits the rotational force caused by the rotation of the main wheel 2, which is transmitted from the first rotating member 63 to the second rotating member 64, to the planetary gears 69 that constitute the planetary gear mechanism described later. The rotational force transmission member 68 is formed in a substantially annular shape and has a fitted gear 68a formed on the right end side, a sun gear 68b formed on the left end side, and a main body portion 68m formed between the fitted gear 68a and the sun gear 68b. A hole 68h is formed at the radial center of the rotational force transmission member 68, through which the rotation shaft 21 (main wheel shaft 21) of the main wheel 2 is rotatably inserted. That is, by the rotation shaft 21 (main wheel shaft 21) of the main wheel 2 being rotatably inserted into the hole 68h, the rotational force transmission member 68 is rotatably supported on the rotation shaft 21 (main wheel shaft 21) of the main wheel 2. Furthermore, it is preferable that the rotational force transmission member 68 does not move in the axial direction in order to maintain the magnitude of the force that can be transmitted by maintaining the meshing width between the sun gear 68b and the planetary gear 69.

[0078] The embedded gear 68a is formed in a gear shape with protrusions and indentations that correspond to the shape of the groove 64h formed in the second rotating member 64, which has a gear shape with protrusions and indentations. As a result, the embedded gear 68a is embedded in the groove 64h of the second rotating member 67. Since the second rotating member 64 moves in conjunction with the axial movement of the moving member 65 by a moving mechanism described later, the embedded gear 68a has an axial length corresponding to the axial movement distance of the second rotating member 64, so that the second rotating member 64 does not fall out of the embedded gear 68a.

[0079] The sun gear 68b is positioned between the three planetary gears 69 so as to mesh with each of the three planetary gears 69 that constitute the planetary gear mechanism described later.

[0080] The main body portion 68m has the length necessary to pass through the holes drilled in the centers of the circumferential fixing member 72, the first sprocket 71, and the planetary carrier 70, which will be described later, so that the sun gear 68b is positioned between the three planetary gears 69.

[0081] In this embodiment, there are three planetary gears 69, each arranged to surround the sun gear 68b and mesh with it. At the same time, the planetary gears 69 are positioned inside the internal gear 62a (formed inside the second subframe 62, shown in Figure 6(b)) and mesh with the internal gear 62a.

[0082] The planetary carrier 70 is rotatably supported on the main body 68m of the rotational force transmission member 68. A hole 70h is formed in the center of the planetary carrier 70 through which the main body 68m of the rotational force transmission member 68 is rotatably inserted. In this embodiment, the planetary carrier 70 has three support shafts 70a. Each of the three support shafts 70a rotatably supports each of the three planetary gears 69.

[0083] On the right side of the planetary carrier 70 (the side of the first subframe 61), a first sprocket 71, which constitutes a power transmission mechanism described later, is connected so as to be rotatable as a whole. However, as will be described later, the first sprocket 71 is configured to be non-rotatable except when the first rotating member 63 and the second rotating member 64 are in contact and the rotational force of the main wheel 2 is transmitted, so the planetary carrier 70 is also non-rotatable.

[0084] A circumferential fixing member 72 is connected to the right side (first subframe 61 side) of the first sprocket 71. The circumferential fixing member 72 is also immobile because the first sprocket 71 is configured to be immobile except when the first rotating member 63 and the second rotating member 64 are in contact and the rotational force of the main wheel 2 is transmitted.

[0085] The circumferential fixing member 72 is a member that fixes the movable member 65 so that it does not rotate in the circumferential direction. The circumferential fixing member 72 has an annular portion 72r which is formed in an annular shape when viewed in the axial direction, and a phase transmission rod 72a which extends from the right side surface of the annular portion 72r to the right in the axial direction (in the axial direction and toward the first subframe 61).

[0086] The phase transmission rod 72a is a rod-shaped member extending parallel to the rotation axis of the main wheel, and is directly or indirectly fixed to the first sprocket 71 (the main wheel shaft side member of the power transmission mechanism), and transmits the phase of the first sprocket 71. In this embodiment, two phase transmission rods 72a are provided, each positioned 180 degrees apart from the other in the circumferential direction on the right side of the annular portion 72r. The two phase transmission rods 72a each pass through the inner hole of the annular portion 67r of the second rotating member 67, through each of the two through holes 65rh formed in the annular portion 65r of the movable member 65, and are fitted into each of the two holes 73h, described later, of the reinforcing member 73 located to the right of the movable member 65 (towards the first subframe 61). As a result, the movable member 65 is fixed in the circumferential direction and movable in the axial direction by the phase transmission rods 72a of the circumferential fixing member 72.

[0087] The reinforcing member 73 is a member that reinforces the phase transmission rods 72a of the circumferential fixing member 72 to prevent them from breaking or bending. As shown in Figures 3 and 4, the reinforcing member 73 has two holes 73h formed in it, corresponding to the circumferential positions of the two phase transmission rods 72a. The holes 73h are configured so that the tips of the phase transmission rods 72a can be fitted into them and not pulled out. In this way, the reinforcing member 73 supports the two phase transmission rods 72a from their respective tip sides.

[0088] The pivot shaft 74 is fixed to the frame 4 by passing through the circular hole 62h of the second subframe 62. As a result, the pivot shaft 74 moves in conjunction with the vertical movement of the frame 4. At the same time, the pivot shaft 74 is able to rotate around the rotation axis 21 of the main wheel 2 in conjunction with the rotation of the first subframe 61 and the second subframe 62 (i.e., the frame support member 6) around the rotation axis 21 of the main wheel 2.

[0089] The second sprocket 75 is fixed to the pivot shaft 74 in a way that prevents it from rotating.

[0090] The first sprocket 71 and the second sprocket 75 are each formed such that their outer circumference (the tooth-forming portion) is circular (excluding the tooth irregularities). Furthermore, the outer circumferences of the first sprocket 71 and the second sprocket 75 have the same radius. The number of teeth on the second sprocket 75 is set to be equal to the number of teeth on the first sprocket 71. In other words, in the power transmission mechanism of this embodiment, neither acceleration nor deceleration occurs. Also, even if the frame support member 6 rotates around the rotation axis 21 of the main wheel 2, rotational force is not transmitted to the first sprocket 71 via the chain 76.

[0091] The chain 76 meshes with the first sprocket 71 and the second sprocket 75, respectively, and wraps around them. The pivot shaft 74 is fixed to the frame 4 in a way that prevents rotation, and the second sprocket 75 is pivotally fixed to the pivot shaft 74 in a way that prevents rotation, so the chain 76 also prevents the first sprocket 71 from rotating. On the other hand, as will be described later, the first sprocket 71 receives rotational force from the rotation of the main wheel 2 when the frame support member 6 is located within a range of rotation angles between the second angle (125 degrees in this embodiment) and the first angle (30 degrees in this embodiment) (when the first rotating member and the second rotating member are in contact), and so transmits this rotational force to the second sprocket 75 and the pivot shaft 74 via the meshing chain 76.

[0092] In this embodiment, the internal gear 62a (shown in Figure 6(b)), the sun gear 68b, the planetary gear 69, and the planetary carrier 70 constitute a planetary gear mechanism. That is, the internal gear 62a, the sun gear 68b, the planetary gear 69, and the planetary carrier 70 can transmit the rotational force caused by the rotation of the main wheel 2, which is transmitted on the rotation axis 21 of the main wheel 2, to the first sprocket 71 at a reduced rotational speed.

[0093] The first rotating member 63 and the second rotating member 64 constitute a clutch mechanism. That is, the first rotating member 63 and the second rotating member 64 can switch whether or not to transmit the rotational force caused by the rotation of the main wheel 2 to the power transmission mechanism. The clutch mechanism switches whether or not to transmit the rotational force caused by the rotation of the main wheel 2 by the second rotating member 64 contacting / separating from the first rotating member 63.

[0094] The first sprocket 71, the second sprocket 75, and the chain 76 constitute a power transmission mechanism. In other words, the first sprocket 71, the second sprocket 75, and the chain 76 can transmit the rotational force caused by the rotation of the main wheel 2, which is transmitted onto the rotation axis 21 of the main wheel 2, from the rotation axis 21 side to the pivot axis 74 side of the main wheel 2.

[0095] The movable member 65, the first rotating member 66, and the second rotating member 67 constitute a movable mechanism. That is, the movable member 65, the first rotating member 66, and the second rotating member 67 can move the second rotating member 64 of the clutch mechanism in the axial direction. Furthermore, in this embodiment, the movable mechanism constitutes a transmission control mechanism. That is, the movable member 65, the first rotating member 66, and the second rotating member 67 can control the switching of transmission in the clutch mechanism.

[0096] In this embodiment, the clutch mechanism is arranged on the rotation axis 21 (main wheel shaft 21) of the main wheel 2.

[0097] The planetary gear mechanism, clutch mechanism, power transmission mechanism, and transmission control mechanism described above constitute the rotation mechanism of the frame support member 6. Specifically, the planetary gear mechanism, clutch mechanism, power transmission mechanism, and transmission control mechanism enable the frame support member 6 and the pivot shaft 74 to rotate around the rotation axis 21 (main wheel shaft 21) of the main wheel 2, and enable the frame support member 6 and the rotation axis 21 (main wheel shaft 21) of the main wheel 2 to rotate around the pivot shaft 74.

[0098] [2] Operation of the wheel structure Next, the operation of the wheel structure 1 in this embodiment will be described.

[0099] (During normal driving or immediately after contact with a step) Figure 5(a) is a side view illustrating the state of the wheel structure 1 according to this embodiment during normal driving or immediately after contact with a step. In Figure 5(a), 10 is a flat surface, 11 is a step, 11a is the end face of the step, and 11b is the top surface of the step. In Figure 5(a), the auxiliary wheel 3 is in contact with the top surface 11b of the step, but this is an illustration of the case where the initial height position of the auxiliary wheel 3 and the height position of the top surface 11b of the step happen to coincide, and the present invention is not limited to this case. In Figure 5(a), the rotation angle of the frame support member 6 during normal driving is set to 0 degrees.

[0100] As shown in Figure 5(a), during normal driving, the stopper 62b provided on the second subframe 62 of the frame support member 6 abuts against the lower end of the side wall portion 4b, thereby stopping the rotation of the CW of the frame support member 6, and the rotation axis 21 of the main wheel 2 is located in front of the rotation axis 74 in the direction of travel. At this time, as described above, the auxiliary wheel 3 is floating at a predetermined height above the ground contact surface (flat surface 10) of the main wheel 2.

[0101] During normal operation, when the wheel structure 1 is pushed forward, the main wheel 2 rotates CCW and moves forward. As the main wheel 2 rotates, the rotation axis 21 and the first rotating member 63 of the main wheel 2 also rotate CCW. At this time, as shown in Figure 5(b), the rotational force transmission teeth 63a of the first rotating member 63 and the rotational force transmission teeth 64a of the second rotating member 64 do not mesh, so the rotational force of the main wheel 2 is not transmitted to the first sprocket 71 of the force transmission mechanism, nor is it transmitted to the pivot shaft 74 via the force transmission mechanism. As a result, the frame support member 6 does not rotate and maintains its initial position (rotation angle 0 degrees) while the wheel structure 1 moves forward. In Figure 5(b), the second projection 65b of the movable member 65 and the second contact projection 67a of the second rotating member 67 appear to be in contact with each other. However, as described above, the frame support member 6 will not rotate any further in the CW direction, and therefore the second rotating member 67 will not rotate any further in the CW direction (when viewed from the left). For this reason, the second projection 65b of the movable member 65 and the second contact projection 67a of the second rotating member 67 do not interfere with each other.

[0102] (Overcoming a step) As shown in Figure 5(a), when the wheel structure 1 is pushed forward and the main wheel 2 comes into contact with the step 11 (immediately after contact with the step), the main wheel 2 stops rotating and the wheel structure 1 stops moving forward.

[0103] At this time, if the wheel structure 1 is pushed further forward, the frame 4 is also pushed forward. Consequently, the frame support member 6, which is located below the pivot axis 74 fixed to the frame 4, rotates CCW around the rotation axis 21 (main wheel axle 21) of the main wheel 2. The following description will focus on the rotation angle of the frame support member 6 around the main wheel axle 21 and explain the rotation mechanism of the frame support member 6.

[0104] (a) Rotation angle 60 degrees Figure 6(a) is a side view showing the state of the wheel structure 1 when the frame support member 6 has rotated until the auxiliary wheel 3 contacts the upper surface 11b of the step. As shown in Figure 6(a), when the frame 4 moves forward with the main wheel 2 in contact with the step 11, the frame support member 6 rotates CCW around the main wheel shaft 21. Now let's consider the movement inside the frame support member 6. The main wheel 2, the main wheel shaft 21, and the first rotating member 63 are stationary (not rotating). The internal gear 62a is provided on the second subframe 62 and rotates due to the rotation of the second subframe 62 (frame support member 6). In other words, the internal gear 62a rotates CCW around the main wheel shaft 21 at the same angle as the rotation angle. The planetary gear 69 rotates CW in conjunction with the CCW rotation of the internal gear 62a, while meshing with the sun gear 68b and the internal gear 62a. Here, the planetary carrier 70 is connected to the non-rotatable first sprocket 71 and is therefore immobile, so the planetary gear 69 does not revolve around the sun gear 68b. Consequently, the sun gear 68b, which meshes with the planetary gear 69 that rotates in CW, rotates CCW at a speed several times that of the rotational speed of the frame support member 6. However, although the CCW rotation of the sun gear 68b is transmitted to the second rotating member 64 through the rotational force transmission member 68, the second rotating member 64 does not come into contact with the first rotating member 63 and therefore does not interfere with the stationary first rotating member 63.

[0105] Furthermore, at this stage (rotation angle of 60 degrees), the second contact projection 67a of the second rotating member 67, which rotates around the main axle 21 in conjunction with the rotation of the frame support member 6, does not contact the second projection 65b of the movable member 65, as shown in Figure 6(b). Therefore, the movable member 65 does not move to the right (towards the first subframe 61). Consequently, the second rotating member 64, which is rotatably held inside the movable member 65, remains axially separated from the first rotating member 63.

[0106] Although not apparent from Figure 6(a) alone, from the point where the rotation angle is 60 degrees, the main wheel 2 begins to ride up onto the upper surface 11b of the step 11, centering on the corner of the step 11.

[0107] (b) When the frame 4 moves forward with the main wheel 2 in contact with the step 11 at an angle greater than 60 degrees and less than 140 degrees, the main wheel 2 rides up onto the upper surface 11b of the step, and the frame support member 6 rotates CCW around the main wheel axle 21.

[0108] (c) Rotation angle of 140 degrees As shown in Figure 7, when the auxiliary wheel 3 is in contact with the upper surface 11b of the step, and the frame 4 and auxiliary wheel 3 move forward further, the main wheel 2 rotates around the corner of the step 11 and rides up completely onto the upper surface 11b of the step. At the same time, the frame support member 6 rotates CCW around the main wheel axle 21. At this time, the rotation angle of the frame support member 6 is 140 degrees. Note that at a rotation angle of 140 degrees of the frame support member 6, the auxiliary wheel 3 is in the lowest position relative to the height of the main wheel 2.

[0109] Let's consider the movement within the frame support member 6. The first rotating member 66, which is fixed to the first subframe 61, and the second rotating member 67, which is fixed to the first rotating member 66 via a connecting member 66c, also rotate in conjunction with the rotation of the frame support member 6. A little before the frame support member 6 rotates to a rotation angle of 140 degrees, specifically when the rotation angle of the frame support member 6 is 125 degrees, the second contact projection 67a of the second rotating member 67 comes into contact with the second projection 65b of the movable member 65. Specifically, as shown in Figure 9(a), the inclined surface 67ak of the second contact projection 67a of the second rotating member 67 and the inclined surface 65bk of the second projection 65b of the movable member 65 come into surface contact with each other. As a result, a normal force is generated on the inclined surface 65bk of the second projection, and the axial component of this normal force moves the movable member 65 to the right (towards the first subframe 61). Then, as shown in Figure 9(b), the second rotating member 64, which is rotatably held inside the annular portion 65r of the movable member 65, approaches the first rotating member 63. When the rotation angle of the frame support member 6 reaches 140 degrees, the first rotating member 63 comes into contact with the second rotating member 64, and the rotational force transmission teeth 63a of the first rotating member 63 and the rotational force transmission teeth 64a of the second rotating member 64 mesh with each other. Note that in Figure 7(b), the first rotating member 63 and the second rotating member 64 are shown separated, but this is a schematic illustration to make them easier to see, and in reality, the first rotating member 63 and the second rotating member 64 are in contact with each other. Furthermore, Figure 7(b) shows the state in which the movement of the movable member 65 to the right has been completed.

[0110] Here, the rotation angle of the frame support member 6, which is 125 degrees, is defined as the "second angle." The "second angle" is the same as the "second angle" described in claims 2 and 4 of the present invention. That is, the second angle is the angle at which the second contact projection 67a of the second rotating member 67 and the second projection 65b of the moving member 65 come into contact with each other, and is 15 degrees smaller than the rotation angle of the frame support member 6 (140 degrees) when the auxiliary wheel 3 is lowered to its lowest position relative to the height of the main wheel 2.

[0111] The rotational force transmitted by the rotation of the main wheel 2 is transmitted from the first rotating member 63, which is pivotally fixed to the main wheel shaft 21, to the second rotating member 64 by the meshing of the rotational force transmitted teeth 63a of the first rotating member 63 and the rotational force transmitted teeth 64a of the second rotating member 64. This rotational force is then transmitted to the embedded gear 68a that meshes with the inside of the second rotating member 64, and then transmitted to the sun gear 68b via the main body 68m of the rotational force transmitted member 68. The rotational force transmitted to the sun gear 68b is amplified (speed reduced) by the planetary gear 69, internal gear 62a, and planetary carrier 70 that constitute the planetary gear mechanism, and then transmitted to the first sprocket 71 connected to the planetary carrier 70.

[0112] The chain 76 meshes with the first sprocket 71, and the chain 76 also meshes with the second sprocket 75, which is mounted on the pivot shaft 74. Therefore, the rotational force transmitted to the first sprocket 71 attempts to rotate the second sprocket 75, which is mounted on the pivot shaft 74, in a clockwise direction (CCW). However, the second sprocket 75, mounted on the pivot shaft 74, is fixed to the pivot shaft 74, and the pivot shaft 74 is fixed to the frame 4, so the second sprocket 75 cannot rotate. Therefore, this force (rotational force in the CCW direction) acts to rotate the frame support member 6 clockwise around the main wheel axle 21. As a result, the frame 4 gradually lifts up.

[0113] (d) An angle of rotation less than 140 degrees and greater than 30 degrees Although not shown in the diagram, the first rotating member 63 and the second rotating member 64 are in contact with each other, so as the main wheel 2 moves along the stepped upper surface 11b, the frame support member 6 rotates in the CW direction around the main wheel axle 21. As a result, the angle of rotation of the frame support member 6 gradually decreases as the main wheel 2 moves forward. And as the angle of rotation of the frame support member 6 decreases, the frame 4 and auxiliary wheels 3 gradually rise.

[0114] (e) Rotation angle of 30 degrees Figure 8(a) shows the state in which the frame support member 6 rotates CW around the main wheel axle 21 due to the rotation of the main wheel 2, and the pivot axis 74 has reached the VL line. The VL line is a vertical line passing through the main wheel axle 21. At a rotation angle of 30 degrees of the frame support member 6, the auxiliary wheel 3 is at the highest position relative to the height position of the main wheel 2. Up to this point, the frame support member 6 has been rotated CW around the main wheel axle 21 by the rotation of the main wheel 2, and the frame 4 has been raised. When the pivot axis 74 reaches the VL line, as shown in Figure 8(b), the first contact projection 66a of the first rotating member 66 comes into contact with the first projection 65a of the moving member 65. Specifically, as shown in Figure 9(c), the inclined surface 66ak of the first contact projection 66a of the first rotating member 66 and the inclined surface 65ak of the first projection 65a of the movable member 65 come into surface contact with each other. As a result, a normal force is generated on the inclined surface 65ak of the first projection, and the axial component of this normal force moves the movable member 65 to the left (towards the second subframe 62). When the movable member 65 moves to the left (towards the second subframe 62), as shown in Figure 9(d), the second rotating member 64, which is rotatably held inside the annular portion 65r of the movable member 65, separates from the first rotating member 63, and the engagement between the rotational force transmission teeth 63a of the first rotating member 63 and the rotational force transmission teeth 64a of the second rotating member 64 is released.

[0115] Here, the rotation angle of the frame support member 6 of 30 degrees is defined as the "first angle." The "first angle" is the same as the "first angle" described in claims 2 and 4 of the present invention. That is, the first angle is the angle at which the first contact projection 66a of the first rotating member 66 and the first projection 65a of the moving member 65 come into contact with each other, and is the rotation angle of the frame support member 6 when the auxiliary wheel 3 rises to the highest position relative to the height position of the main wheel 2.

[0116] Furthermore, when the wheel structure 1 rides over a step 11, the frame support member 6 rotates in the CCW direction around the main axle 21 from a rotation angle of 0 degrees to a rotation angle of 140 degrees, passing through a first angle of rotation of 30 degrees. At this time, the movable member 65 is positioned in its initial position, that is, a position where the movable member 65 is separated from the first rotating member 66 (a position close to the second rotating member 67). Therefore, the first contact projection 66a of the first rotating member 66 does not come into contact with the first projection 65a of the movable member 65.

[0117] (f) Rotation angle less than 30 degrees to 0 degrees (not shown in the diagram) Due to the load on the frame 4, the frame support member 6 continues to rotate CW, and when the rotation angle becomes 0 degrees, the stopper 62b comes into contact with the lower end of the side wall portion 4b of the frame 4, stopping the rotation of the frame support member 6. Then the wheel structure 1 returns to the normal running state on the stepped upper surface 11b.

[0118] With the above steps completed, the series of actions for the wheel structure 1 to climb over the step is finished.

[0119] Thus, in this embodiment, the frame 4 rises as the wheel structure 1 moves forward due to the rotational movement of the frame support member 6. However, since the forward distance is sufficiently large compared to the upward distance and the apparent incline is gentle, the main wheel 2 can be smoothly driven onto the step surface 11b even with a small force of, for example, a few hundred grams.

[0120] [3] Other effects and advantages of the wheel structure configuration Next, other effects and advantages of the wheel structure 1 in this embodiment will be described.

[0121] According to the wheel structure 1, the moving mechanism constituting the transmission control mechanism is composed of a moving member 65, a first rotating member 66, and a second rotating member 67. When the frame support member 6 rotates to a second angle and the second projection 65b of the moving member 65 and the second contact projection 67a of the second rotating member 67 come into contact with each other, the moving member 65 moves toward the first subframe 61, the second rotating member 64 comes into contact with the first rotating member 63, and the rotational force transmission teeth 64a of the second rotating member 64 and the rotational force transmission teeth 63a of the first rotating member 63 mesh with each other, thereby transmitting the rotational force caused by the rotation of the main wheel 2 from the first rotating member 63 to the second rotating member 64.

[0122] In other words, according to the wheel structure 1, the second projection 65b of the movable member 65 has a second projection inclined surface 65bk that is inclined axially in the direction away from the second subframe 62 (to the right) and clockwise (CW) from the apex surface 65bt of the second projection 65b, and the second contact projection 67a of the second rotating member 67 has a second contact projection inclined surface 67ak that is inclined axially in the direction away from the first subframe 61 (to the left) and counterclockwise (CCW) from the apex surface 67at of the second contact projection 67a. Therefore, when the frame support member 6, i.e., the second rotating member 67, is rotated CCW while the second projection inclined surface 65bk of the movable member 65 and the second contact projection inclined surface 67ak of the second rotating member 67 are in surface contact with each other, the movable member 65 can move toward the first subframe 61 (to the right).

[0123] Similarly, according to the wheel structure 1, since the moving mechanism constituting the transmission control mechanism is composed of a moving member 65, a first rotating member 66, and a second rotating member 67, when the frame support member 6 rotates to a first angle and the first projection 65a of the moving member 65 and the first contact projection 66a of the first rotating member 66 come into contact with each other, the moving member 65 moves toward the second subframe 62, the second rotating member 64 moves away from the first rotating member 63, the engagement between the rotational force transmission teeth 64a of the second rotating member 64 and the rotational force transmission teeth 63a of the first rotating member 63 is released, and rotational force due to the rotation of the main wheel 2 is not transmitted from the first rotating member 63 to the second rotating member 64.

[0124] In other words, according to the wheel structure 1, the first projection 65a of the movable member 65 has a first projection inclined surface 65ak that is inclined axially away from the first subframe 61 (to the left) and counterclockwise (CCW) from the apex surface 65at of the first projection 65a, and the first contact projection 66a of the first rotating member 66 has a first contact projection inclined surface 66ak that is inclined axially away from the second subframe 62 (to the right) and clockwise (CW) from the apex surface 66at of the first contact projection 66a. Therefore, when the frame support member 6, i.e., the first rotating member 66, is rotated CW while the first projection inclined surface 65ak of the movable member 65 and the first contact projection inclined surface 66ak of the first rotating member 66 are in surface contact with each other, the movable member 65 can move toward the second subframe 62 (to the left).

[0125] Furthermore, according to the wheel structure 1, each of the multiple rotational force transmission teeth 63a of the first rotating member 63 has a vertical surface 63as perpendicular to the counterclockwise (CCW) direction and an inclined surface 63ak that slopes from the apex of the vertical surface 63as axially away from the second subframe 62 (to the right) and clockwise (CW) direction. Similarly, each of the multiple rotational force transmission teeth 64a of the second rotating member 64 has a vertical surface 64as perpendicular to the clockwise (CW) direction and an inclined surface 64ak that slopes from the apex of the vertical surface 64as axially away from the first subframe 61 (to the left) and counterclockwise (CCW) direction. Therefore, when the rotational force transmission teeth 63a and 64a are meshed, the counterclockwise (CCW) rotational force caused by the rotation of the main wheel 2 can be transmitted from the first rotating member 63 to the second rotating member 64.

[0126] Furthermore, according to the wheel structure 1, the power transmission mechanism is composed of a first sprocket 71 rotatably supported on the rotation axis 21 of the main wheel 2, a second sprocket 75 fixed to the pivot axis 74, and a chain 76 that meshes with the first sprocket 71 and the second sprocket 75 respectively and winds around the first sprocket 71 and the second sprocket 75. Therefore, it is easy to give strength and durability to the components constituting the power transmission mechanism, and power can be transmitted more reliably from the main wheel axis 21 side to the pivot axis 74 side.

[0127] [4] Modifications of this embodiment Next, a modification of the configuration of the wheel structure 1 in this embodiment will be described.

[0128] (a) Modified Frame Support Member (i) First Modified Frame Member Figure 10 shows an exploded perspective view of the modified frame support member shown in Figure 3 above. Hereinafter, the frame support member of Figure 10 will be explained focusing on the differences from the frame support member of Figure 3, but the same names and reference numerals will be used for members having similar or corresponding functions and structures.

[0129] In this specification, when viewing the wheel structure from the rear to the front in the direction of travel, the left side is referred to as the left side, and the right side as the right side. Furthermore, the direction in which the rotation axis of the main wheel and the pivot axis arranged parallel to the rotation axis of the main wheel extend is referred to as the "axial direction," the direction perpendicular to the axial direction is referred to as the "radial direction," and the direction around the axial direction is referred to as the "circumferential direction."

[0130] The frame support member in Figure 10 differs from the frame support member in Figure 3 in the arrangement of the planetary gear mechanism, power transmission mechanism, and clutch mechanism. Specifically, in the frame support member in Figure 3, the components were arranged from the right side of the wheel structure in the following order: (a) clutch mechanism (first rotating member 63, second rotating member 64), (b) power transmission mechanism (first sprocket 71, second sprocket 75, chain 76), and (c) planetary gear mechanism (sun gear 68b, planetary gear 69, planetary carrier 70). However, in the frame support member in Figure 10, the components are arranged in the following order: (a) planetary gear mechanism, (b) clutch mechanism, and (c) power transmission mechanism.

[0131] In the frame support member shown in Figure 10, the sun gear 68b of the planetary gear mechanism is fixed to the main axle 21, and the first rotating member 63 is fixed to the planetary carrier 70 located to the right of the sun gear 68b and planetary gear 69 (towards the second subframe). The internal gear 62a is provided on the first subframe 61.

[0132] The clutch mechanism and the transmission control mechanism that controls the clutch mechanism (movable member 65, first rotating member 66, second rotating member 67) are the same as the frame support member in Figure 3. However, a fitted gear 68a is fitted into the hole 64h of the second rotating member 64 that constitutes the clutch mechanism, and the fitted gear 68a is fixed to the right side (first subframe side) of the circumferential fixing member 72. On the other hand, the first sprocket 71 is fixed to the left side (second subframe side) of the circumferential fixing member 72. Therefore, when the first rotating member 63 and the second rotating member 64 are in contact, the rotational force due to the rotation of the main wheel is transmitted to the first sprocket 71 via the fitted gear 68a, and further transmitted to the pivot shaft 74 via the chain 76 and the second sprocket 75.

[0133] Furthermore, the first rotating member 66 and the second rotating member 67 are positioned on the left side (second subframe side) of the planetary carrier 70. A connecting member 66c, which is erected from the inner side surface of the first subframe 61 toward the second subframe 62, passes through a through hole formed in the radial projection 66b of the first rotating member 66, and the tip of the connecting member 66c abuts against the radial projection 67b of the second rotating member 67, fixing them in place. Therefore, when the frame support member 6 rotates around the main axle 21, the first rotating member 66 and the second rotating member 67 also rotate in the same direction.

[0134] With the above structure, the frame support member in Figure 10 can perform the same function as the frame support member in Figure 3 in the wheel structure. That is, when the first rotating member 63 and the second rotating member 64 come into contact due to the action of the second rotating member 67 and the moving member 65, the clockwise (CW) rotation of the main axle 21 is transmitted in the following order: sun gear 68b, planetary gear 69, planetary carrier 70, first rotating member 63, second rotating member 64, embedded gear 68a, circumferential fixing member 72, first sprocket 71, chain 76, second sprocket 75, and pivot shaft 74, causing the frame support member 6 to rotate clockwise (CW) around the main axle 21. In addition, the first rotating member 63 and the second rotating member 64 can be separated by the action of the first rotating member 63 and the moving member 65. This makes it possible to switch whether or not the rotational force generated by the rotation of the main wheel 2 is transmitted to the pivot shaft 74 via the power transmission mechanism.

[0135] (ii) Second Modification In the second modification, as a modification of the frame support member (first modification) shown in Figure 10, the clutch mechanism (first rotating member 63, second rotating member 64) and the transmission control mechanism (moving member 65, first rotating member 66, second rotating member 67) are arranged on the pivot shaft. The first sprocket 71 is fixed to the planetary carrier 70 of the planetary gear mechanism arranged on the main wheel axle, and the second sprocket 75 is rotatably supported on the pivot shaft 74.

[0136] In the second modified example, the first rotating member 66 and the second rotating member 67 are fixed by a connecting member 66c erected on the inner surface of the first subframe 61 or the second subframe 62. On the other hand, the moving member 65 is fixed by a rod-shaped member (specifically, the phase transmission rod 72a of the circumferential fixing member 72 fixed to the second sprocket, which is a rotating shaft side member (a member positioned on the rotating shaft) of the force transmission mechanism) and extends parallel to the rotating shaft.

[0137] As a result, even if the frame support member 6 rotates around the main wheel axle 21, the movable member 65 does not rotate, but the first rotating member 66 and the second rotating member 67 rotate around the pivot shaft 74. By utilizing the rotation of the first rotating member 66 and the second rotating member 67, in the second modified example, as with the frame support member shown in Figure 3 and the first modified example shown in Figure 10, the rotation of the frame support member 6 can cause contact / separation between the first rotating member 63 and the second rotating member 64, making it possible to switch whether or not the rotational force from the rotation of the main wheel 2 is transmitted to the pivot shaft 74.

[0138] (b) Other Modifications In the above description, the angle at which the second contact projection 67a of the second rotating member 67 and the second projection 65b of the movable member 65 come into contact with each other (the second angle) was described as being 125 degrees, the rotation angle of the frame support member 6. However, it may be a specific angle in the range of 125 degrees or more and 140 degrees or less. That is, the second angle may be a specific angle in the range of 125 degrees or more, which is 15 degrees less than the rotation angle of the frame support member 6 when the auxiliary wheel 3 descends to the lowest position relative to the height position of the main wheel 2 (140 degrees). To put it another way, it is preferable that the second contact projection 67a of the second rotating member 67 and the second projection 65b of the movable member 65 come into contact with each other slightly before the moment when the auxiliary wheel 3 descends to the lowest position relative to the height position of the main wheel 2, but it may also be at that moment.

[0139] In the above, a reinforcing member 73 was used as a member to reinforce the phase transmission rod 72a of the circumferential fixing member 72, but the reinforcing member 73 is not an essential member. That is, as long as the phase transmission rod 72a passes through the through hole 65rh of the movable member 65, the movable member 65 is fixed in the circumferential direction and can move in the axial direction, and the circumferential fixing and axial movement of the movable member 65 are not hindered, the reinforcing member 73 does not need to be used.

[0140] In the above description, the first sprocket 71 and the second sprocket 75 were described on the premise that their outer circumferences (tooth-forming portions) are circular. However, both the first sprocket 71 and the second sprocket 75 may be non-circular, for example, elliptical. When the first sprocket 71 and the second sprocket 75 are non-circular, the main wheel 2 rides over the step 11 more smoothly. However, in the wheel structure 1 of this embodiment, it is necessary that the first sprocket 71 does not rotate in the circumferential direction even when the frame support member 6 rotates. Therefore, both the first sprocket 71 and the second sprocket 75 must have the same shape and size, and be arranged in the same orientation.

[0141] In the above, the force transmission mechanism is composed of a first sprocket 71, a second sprocket 75, and a chain 76. However, it may also be composed of a first pulley pivotally supported on the main body 68m of the rotational force transmission member 68, a second pulley pivotally fixed to the pivot shaft 74, and a wire that winds at least partially around the first and second pulleys. The first and second pulleys may each have a fixing portion for fixing the wire.

[0142] In the above explanation, it was assumed that the planetary gear mechanism consists of three planetary gears 69. However, the number of planetary gears 69 is not limited to three; at least one is sufficient, and there may be four or more.

[0143] Furthermore, although not shown in the figures, the force transmission mechanism may consist of two pulleys and a belt. That is, the force transmission mechanism may consist of a first pulley pivotally supported on the main body 68m of the rotational force transmission member 68, a second pulley non-rotatably pivotally supported on the pivot shaft 74, and a belt winding around the first and second pulleys.

[0144] In the above, the frame 4 was supported only by a frame support member 6 located on one side (left side) of the axial direction (left-right direction) of the wheel 2b of the main wheel 2. However, although not shown, there may be a support member on the opposite side (right side) of the axial direction (left-right direction) of the wheel 2b to support the frame 4. In other words, from the perspective of the frame 4, the support of the main wheel 2 is not limited to the frame support member 6 rotatably held on a pivot shaft 74 fixed to the frame 4, but may also be supported by, for example, a crank-shaped member rotatably supported by the frame 4. To put it another way, the support of the main wheel 2 may come from both sides of the axial direction (left-right direction) of the main wheel 2.

[0145] (c) Application of snow tires In the wheel structure 1 of this embodiment, if at least the tire 2a of the main wheel 2 is a snow tire with excellent grip performance on snowy roads, it is preferable that the vehicle can more reliably drive onto steps even on slippery road surfaces such as snow.

[0146] In other words, when raising the frame 4 after the main wheel 2 has driven onto a stepped surface, it is necessary to rotate the pivot shaft 74 in a CW direction around the rotation axis 21 of the main wheel 2. To achieve this, the main wheel 2 must rotate without slipping when the wheel structure 1 is moved forward. However, when attempting to drive over a slippery surface such as snow with a heavy load, the main wheel 2 may slip, which can be dangerous. Therefore, it is preferable to use snow tires to suppress slipping. Specific examples of snow tires include tires made of foamed rubber, and rubber tires mixed with granular materials such as crushed walnut shells, rice husks, eggshells, or animal bones.

[0147] Although the present invention has been described above based on embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above embodiments within the same and equivalent scope as the present invention.

[0148] 1 Wheel structure 2 Main wheel 2a Tire 2b Wheel 3 Auxiliary wheel 3a Tire 3b Wheel 4 Frame 4a Canopy 4b Side wall 4c Auxiliary wheel support 5 Cargo platform mounting part 6 Frame support member 10 Flat surface 11 Step 11a Step end surface 11b Step top surface 21 Rotation axis of main wheel (main wheel axle) 31 Rotation axis of auxiliary wheel 61 First subframe 61h Circular hole of first subframe 62 Second subframe 62h Circular hole of second subframe 62a Internal gear 62ah Hole of second subframe 62b Stopper 63 First rotating member 63a Rotation force transmission tooth of first rotating member 63as Vertical surface of rotation force transmission tooth 63ak Inclined surface of rotation force transmission tooth 64 Second rotating member 64a Rotational force transmission teeth of the second rotating member 64as Vertical surface of the rotational force transmission teeth 64ak Inclined surface of the rotational force transmission teeth 64h Hole of the second rotating member 65 Moving member 65r Annular portion of the moving member 65rh Through hole of the annular portion 65a First projection of the moving member 65at Apex surface of the first projection 65ak Inclined surface of the first projection 65b Second projection of the moving member 65bt Apex surface of the second projection65bk Inclined surface of the second projection 66 First rotating member 66r Annular portion of the first rotating member 66a First contact projection of the first rotating member 66at Apex surface of the first contact projection 66ak Inclined surface of the first contact projection 66b Radial projection of the first rotating member 66c Connecting member of the first rotating member 67 Second rotating member 67r Annular portion of the second rotating member 67a Second contact projection 67at Apex surface of the second contact projection 67ak Inclined surface of the second contact projection 67b Radial projection of the second rotating member 68 Rotational force transmission member 68a Fitted gear 68b Sun gear 68m Main body of the rotational force transmission member 68h Hole of the rotational force transmission member 69 Planetary gear 70 Planetary carrier 70a Support shaft of the planetary carrier 70h Planetary carrier hole 71 First sprocket 72 Circumferential fixing member 72r Annular portion of circumferential fixing member 72a Phase transmission rod of circumferential fixing member 73 Reinforcement member 73h Hole of reinforcement member 74 Rotating shaft 75 Second sprocket 76 Chain VL Vertical line

Claims

A wheel structure is provided in which a large-diameter main wheel is positioned on the rear side in the direction of travel of a frame on which a transportable material loading platform mounting section is provided, and a small-diameter auxiliary wheel is positioned on the front side in the direction of travel of the frame, and the auxiliary wheel is configured to descend and abut against the upper surface of the step when the main wheel comes into contact with a step, and then the main wheel rides up onto the upper surface of the step, and as the main wheel moves along the upper surface of the step, the auxiliary wheel rises, The frame is provided with a frame support member that supports the frame, and the frame support member is provided with a pivot mechanism that has a pivot shaft that is arranged parallel to the rotation axis of the main wheel and fixed to the frame. The rotation mechanism is configured to allow the frame support member and the rotation shaft to rotate around the rotation axis of the main wheel, and to allow the frame support member and the rotation shaft of the main wheel to rotate around the rotation axis. The rotation mechanism comprises a planetary gear mechanism that reduces the rotational speed due to the rotation of the main wheel transmitted on the rotation axis of the main wheel, a force transmission mechanism that transmits the rotational force due to the rotation of the main wheel transmitted on the rotation axis of the main wheel from the rotation axis side of the main wheel to the rotation axis side, a clutch mechanism that switches whether or not to transmit the rotational force due to the rotation of the main wheel to the force transmission mechanism, and a transmission control mechanism that controls the switching of the clutch mechanism on or off. The clutch mechanism comprises a first rotating member that is immovable in the axial direction and has a plurality of rotational force transmission teeth to which the rotational force due to the rotation of the main wheel is transmitted, and a second rotating member that is movable in the axial direction and has a plurality of rotational force transmission teeth that can mesh with the plurality of rotational force transmission teeth of the first rotating member, and the second rotating member and the first rotating member make contact with each other in the axial direction, thereby switching whether or not to transmit the rotational force due to the rotation of the main wheel to the pivot shaft via the force transmission mechanism. The transmission control mechanism is comprised of a moving mechanism that moves the second rotating member of the clutch mechanism in the axial direction. A wheel structure characterized by the following features. 　 The frame support member comprises a first subframe located on the main wheel side in the axial direction, and a second subframe located on the opposite side from the main wheel side in the axial direction, overlapping the first subframe in the axial direction to form the casing of the frame support member. The aforementioned moving mechanism is A movable member having an annular portion, a first projection projecting from the annular portion toward the first subframe, and a second projection projecting from the annular portion toward the second subframe, formed in an annular shape when viewed in the axial direction, fixed in the circumferential direction and configured to be movable in the axial direction, and rotatably holding the second rotating member inside the annular portion, A first rotating member is formed in a substantially annular shape when viewed in the axial direction, is fixed in the axial direction, and is configured to rotate in conjunction with the rotation of the frame support member around the rotation axis of the main wheel, and the first projection of the moving member has a first contact projection that can contact the frame support member when it is rotated to a first angle, The second rotating member is formed in a substantially annular shape when viewed in the axial direction, is fixed in the axial direction while being positioned to sandwich the moving member axially between itself and the first rotating member, and is configured to rotate in conjunction with the rotation of the frame support member around the rotation axis of the main wheel, and the second rotating member has a second contact projection on the second projection of the moving member that can contact the frame support member when it is rotated to a second angle, It is composed of, When the second projection of the moving member and the second contact projection of the second rotating member come into contact with each other, the moving member moves in the direction toward the first subframe, and the second rotating member comes into contact with the first rotating member. When the first projection of the moving member and the first contact projection of the first rotating member come into contact with each other, the moving member moves toward the second subframe, and the second rotating member moves away from the first rotating member. The wheel structure according to Feature 1. 　 The first projection of the moving member has a first projection inclined surface that slopes from the apex of the first projection in the axial direction away from the first subframe and in the counterclockwise (CCW) direction, The second projection of the moving member has a second projection inclined surface that slopes from the apex of the second projection in the axial direction away from the second subframe and in a clockwise (CW) direction, The first contact projection of the first rotating member has a first contact projection inclined surface that is inclined axially and clockwise (CW) in the direction away from the second subframe, from the apex of the first contact projection, The second contact projection of the second rotating member has a second contact projection inclined surface that is inclined in the axial direction away from the first subframe and in the counterclockwise (CCW) direction from the apex of the second contact projection. The wheel structure according to feature 2. Note that clockwise (CW) and counterclockwise (CCW) directions refer to the direction of rotation when viewing a wheel structure moving to the left from its left side. 　 The first angle is the rotation angle of the frame support member when the auxiliary wheel rises to the highest position relative to the height position of the main wheel. The second angle is a specific angle within a range of at least 15 degrees less than the rotation angle of the frame support member when the auxiliary wheel is lowered to its lowest position relative to the height position of the main wheel. The wheel structure according to feature 2. 　 The aforementioned force transmission mechanism, The system comprises a main wheel shaft side member positioned on the rotation axis of the main wheel, a pivot shaft side member positioned on the pivot shaft, and a transmission member that transmits the rotational force of the main wheel around the rotation axis from the main wheel shaft side member to the pivot shaft side member. The support frame is configured such that even if it rotates around the rotation axis of the main wheel, the main wheel shaft side member does not rotate around the rotation axis of the main wheel. The aforementioned movable member, The main wheel axle side member is movable along the rotation axis of the main wheel, and The support frame is supported so as not to rotate around the rotation axis of the main wheel, even when the main wheel rotates around its rotation axis. The wheel structure according to feature 2. 　 Multiple sets of the first projection, the second projection, the first contact projection, and the second contact projection are provided. Each of the first and second projections is arranged rotationally symmetrically with respect to the rotation axis of the main wheel in the moving member. Each of the first contact protrusions is arranged rotationally symmetrically with respect to the rotation axis of the main wheel in the first rotating member. Each of the second contact protrusions is arranged in a rotationally symmetric manner with respect to the rotation axis of the main wheel in the first rotating member. The wheel structure according to feature 2. 　 A wheel structure is provided in which a large-diameter main wheel is positioned on the rear side in the direction of travel of a frame on which a transportable material loading platform mounting section is provided, and a small-diameter auxiliary wheel is positioned on the front side in the direction of travel of the frame, and the auxiliary wheel is configured to descend and abut against the upper surface of the step when the main wheel comes into contact with a step, and then the main wheel rides up onto the upper surface of the step, and as the main wheel moves along the upper surface of the step, the auxiliary wheel rises, The frame is provided with a frame support member that supports the frame, and the frame support member is provided with a pivot mechanism that has a pivot shaft that is arranged parallel to the rotation axis of the main wheel and fixed to the frame. The rotation mechanism is configured to allow the frame support member and the rotation shaft to rotate around the rotation axis of the main wheel, and to allow the frame support member and the rotation shaft of the main wheel to rotate around the rotation axis. The rotation mechanism comprises a planetary gear mechanism that reduces the rotational speed due to the rotation of the main wheel transmitted on the rotation axis of the main wheel; a power transmission mechanism that transmits the rotational force due to the rotation of the main wheel transmitted on the rotation axis of the main wheel from the rotation axis side of the main wheel to the rotation axis side; a clutch mechanism that switches whether or not to transmit the rotational force due to the rotation of the main wheel to the power transmission mechanism, or whether or not to transmit the rotational force output from the power transmission mechanism that has transmitted the rotational force due to the rotation of the main wheel to the rotation axis fixed to the frame; and a transmission control mechanism that controls the switching of the clutch mechanism on or off. The clutch mechanism comprises a first rotating member having a plurality of rotational force transmission teeth that transmit rotational force due to the rotation of the main wheel and is movable in the axial direction, and a second rotating member facing the first rotating member and having a plurality of rotational force transmission teeth that can mesh with the plurality of rotational force transmission teeth of the first rotating member and is not movable in the axial direction, and the second rotating member and the first rotating member make contact with each other in the axial direction and separate from each other, thereby switching whether or not to transmit the rotational force due to the rotation of the main wheel transmitted via the force transmission mechanism to the pivot shaft. The transmission control mechanism is comprised of a moving mechanism that moves the first rotating member of the clutch mechanism in the axial direction. A wheel structure characterized by the following features. 　 The aforementioned moving mechanism A movable member having an annular portion, a first projection projecting from the annular portion toward the first subframe, and a second projection projecting from the annular portion toward the second subframe, formed in an annular shape when viewed in the axial direction, fixed in the circumferential direction and configured to be movable in the axial direction, and rotatably holding the first rotating member inside the annular portion, A first rotating member is formed in a substantially annular shape when viewed in the axial direction, is fixed in the axial direction, and is configured to rotate in conjunction with the rotation of the frame support member around the rotation axis of the main wheel, and the first projection of the moving member has a first contact projection that can contact the frame support member when it is rotated to a first angle, The second rotating member is formed in a substantially annular shape when viewed in the axial direction, is fixed in the axial direction while being positioned to sandwich the moving member axially between itself and the first rotating member, and is configured to rotate in conjunction with the rotation of the frame support member around the rotation axis of the main wheel, and the second rotating member has a second contact projection on the second projection of the moving member that can contact the frame support member when it is rotated to a second angle, It is composed of, When the second projection of the moving member and the second contact projection of the second rotating member come into contact with each other, the moving member moves in the direction toward the first subframe, and the second rotating member comes into contact with the first rotating member. When the first projection of the moving member and the first contact projection of the first rotating member come into contact with each other, the moving member moves toward the second subframe, and the second rotating member moves away from the first rotating member. The wheel structure according to feature 7. 　 The aforementioned force transmission mechanism, The system comprises a main wheel shaft side member positioned on the rotation axis of the main wheel, a pivot shaft side member positioned on the pivot shaft, and a transmission member that transmits the rotational force of the main wheel shaft side member around the rotation axis of the main wheel to the pivot shaft side member. The support frame is configured such that even when it rotates around the rotation axis of the main wheel, the rotation axis side member does not rotate around the rotation axis. The aforementioned movable member, The pivot shaft side member allows movement along the pivot shaft, and The support frame is supported so as not to rotate around the rotation axis even when the main wheel rotates around its rotation axis. The wheel structure described in Feature 8. 　 Multiple sets of the first projection, the second projection, the first contact projection, and the second contact projection are provided. Each of the first and second projections is arranged rotationally symmetrically with respect to the rotation axis of the main wheel in the moving member. Each of the first contact protrusions is arranged rotationally symmetrically with respect to the rotation axis of the main wheel in the first rotating member. Each of the second contact protrusions is arranged in a rotationally symmetric manner with respect to the rotation axis of the main wheel in the first rotating member. The wheel structure described in Feature 8. 　 A transport device characterized by comprising a wheel structure according to any one of claims 1 to 10.

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