Wheel structures and transport equipment

Abstract

To provide a wheel structure and transport device that can smoothly perform the act of riding over obstacles with minimal force, from the start to the completion of the ride over obstacle. [Solution] The frame is provided with a frame support member, and the frame support member is provided with a rotation mechanism equipped with a pivot shaft fixed to the frame, and the rotation mechanism is configured to allow the frame support member and the pivot shaft to rotate around the rotation axis of the main wheel, and to allow the frame support member and the rotation axis of the main wheel to rotate around the pivot shaft, and the rotation mechanism is configured to allow the rotation mechanism to rotate around the pivot shaft, and the wheel structure is composed of 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 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 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.

Description

Technical Field

[0001] The present invention relates to a wheel structure and a transport device, and more particularly to a wheel structure and a transport device capable of easily climbing a step.

Background Art

[0002] In transport devices that use human power as a driving force, such as carts for carrying luggage, baby strollers, and wheelchairs, small wheel structures are often used from the perspective of their size and weight. On the other hand, in the environments where these transport devices are used, there are many steps associated with height differences and obstacles on the road surface, and it is not easy to smoothly lift the wheels onto the step surface with a small force without imparting an impact to the transported object.

[0003] Therefore, conventionally, various techniques have been proposed in which an auxiliary wheel with a small diameter is provided in front of the original wheel (main wheel), and when facing a step, first, the auxiliary wheel is brought into contact with the step surface, and then the main wheel is lifted onto the step surface (for example, Patent Document 1, etc.).

[0004] However, in the case of the conventional technique, the operation when the main wheel returns to the initial state differs depending on the magnitude of the load applied to the main wheel, and the operation before and after climbing the step could not be said to be smooth, so further improvement has been demanded.

[0005] For example, in the technique using a spring as in Patent Document 1, when the load applied to the main wheel is greater 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, so there is a risk that the transported object will be impacted, and the operation before and after climbing the step could not be said to be smooth.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] In view of the problems of the prior art described above, the present invention aims 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. [Means for solving the problem]

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

[0009] The invention described in claim 1 is, 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 mounting platform 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 comes into contact with 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, 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 aforementioned rotation mechanism is a wheel structure characterized by comprising: 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.

[0010] The invention described in claim 2 is, The clutch mechanism comprises a ring gear-shaped rotating plate having a plurality of rotational force transmission teeth, a second clutch plate having a plurality of rotational force transmission teeth facing the rotating plate on one side and capable of meshing with the plurality of rotational force transmission teeth of the rotating plate, a first clutch plate facing the other side of the second clutch plate, and a return mechanism that returns the second clutch plate to its initial position relative to the first clutch plate by the biasing force of an elastic body. The first clutch plate has a projection that protrudes radially outward, The wheel structure according to claim 1 is characterized in that the second clutch plate has an engaging claw on the other side that can engage with a projection of the first clutch plate.

[0011] The invention described in claim 3 is, The clutch mechanism comprises a ring gear-shaped rotating plate having a plurality of rotational force transmission teeth, a second clutch plate having a plurality of rotational force transmission teeth facing the rotating plate on one side and capable of meshing with the plurality of rotational force transmission teeth of the rotating plate, a first clutch plate facing the other side of the second clutch plate, and a return mechanism that returns the second clutch plate to its initial position relative to the first clutch plate by the biasing force of an elastic body. The second clutch plate has a projection that protrudes radially outward, The wheel structure according to claim 1 is characterized in that the first clutch plate has an engaging claw on the other side that can engage with a projection of the second clutch plate.

[0012] The invention described in claim 4 is, The clutch mechanism comprises a ring gear-shaped rotating plate having a plurality of rotational force transmission teeth, a second clutch plate having a plurality of rotational force transmission teeth facing the rotating plate on one side and capable of meshing with the plurality of rotational force transmission teeth of the rotating plate, a first clutch plate facing the other side of the second clutch plate, and a return mechanism that returns the second clutch plate to its initial position relative to the first clutch plate by the biasing force of an elastic body. The first clutch plate has an engaging claw extending in the axial direction of the rotation shaft on the side facing the other side of the second clutch plate, The wheel structure according to claim 1 is characterized in that the second clutch plate has an engaging claw on the other side that can engage with the engaging claw of the first clutch plate.

[0013] The invention described in claim 5 is, Each of the rotational force transmission teeth of the rotating plate has a vertical surface perpendicular to the counterclockwise (CCW) direction and an inclined surface that slopes axially away from the second clutch plate and clockwise (CW) from the apex of the vertical surface. The wheel structure according to claim 2 is characterized in that each of the plurality of rotational force transmission teeth of the second clutch plate has a vertical surface perpendicular to the clockwise (CW) direction and an inclined surface that is inclined from the apex of the vertical surface in the axial direction away from the rotating plate 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.

[0014] The invention described in claim 6 is, The return mechanism of the clutch mechanism is a torsion spring connected to the first clutch plate and the second clutch plate respectively, and the second clutch plate is urged in the clockwise (CW) direction so that the engaging claw of the second clutch plate abuts against the protrusion of the first clutch plate. The engaging claw of the second clutch plate has a first contact surface capable of contacting the protrusion of the first clutch plate, a second contact surface capable of contacting the protrusion of the first clutch plate and formed at a position away from the first contact surface in the counterclockwise (CCW) direction and in the axial direction and toward the first clutch plate side, and an inclined surface connected to the first contact surface and the second contact surface respectively. The wheel structure according to claim 5 is characterized by this.

[0015] The invention according to claim 7 is The clutch mechanism is disposed between the main wheel and the planetary gear mechanism. The wheel structure according to claim 1 is characterized by this.

[0016] The invention according to claim 8 is The clutch mechanism is disposed between the planetary gear mechanism and a component provided on the rotation axis of the main wheel among the components of the power transmission mechanism. The wheel structure according to claim 1 is characterized by this.

[0017] The invention according to claim 9 is The clutch mechanism is disposed on the rotation axis. The wheel structure according to claim 1 is characterized by this.

[0018] The invention according to claim 10 is The power transmission mechanism includes a first sprocket rotatably supported on the rotation axis of the main wheel, a second sprocket fixedly supported on the rotation axis, and a chain meshing with the first sprocket and the second sprocket respectively and winding around the first sprocket and the second sprocket. The wheel structure according to claim 1 is characterized by this.

[0019] The invention according to claim 11 is The force transmission mechanism is composed of a first pulley rotatably supported on the rotation axis of the main wheel, a second pulley supported and fixed on the rotation axis, and a wire wound around the first pulley and the second pulley. The wheel structure according to claim 1, wherein the first pulley and the second pulley each have a fixing portion for fixing the wire.

[0020] The invention according to claim 12 is The force transmission mechanism is composed of a first gear rotatably supported on the rotation axis of the main wheel, a second gear supported and fixed on the rotation axis, and a third gear rotatably supported on an auxiliary shaft disposed between the rotation axis of the main wheel and the rotation axis and meshing with the first gear and the second gear respectively. The wheel structure according to claim 1, characterized in that.

[0021] The invention according to claim 13 is A transport device characterized by comprising the wheel structure according to any one of claims 1 to 12.

Effect of the Invention

[0022] According to the present invention, it is possible to provide a wheel structure and a transport device that can smoothly perform a mounting operation with a small force from the start to the completion of the step mounting.

Brief Description of the Drawings

[0023] [Figure 1] It is a perspective view schematically showing the structure of a wheel structure according to an embodiment of the present invention. [Figure 2] It is an exploded perspective view of the wheel structure shown in FIG. 1. [Figure 3] It is an exploded perspective view of a frame support member in a wheel structure according to a first embodiment of the present invention. [Figure 4]This is a side perspective view illustrating the state of a wheel structure according to the first embodiment of the present invention during normal driving. For clarity, the chain is omitted from the illustration. Similarly, the chain is omitted from the illustration in Figures 5 to 18. [Figure 5] (a) is a side perspective view illustrating the state at the moment when the main wheel of the wheel structure according to the first embodiment of the present invention comes into contact with a step (a state later than that shown in Figure 4). (b) is a perspective view of the inside of the frame support member, seen from the rear left diagonally above, when the transmission of rotational force from the main wheel by the rotational force transmission teeth is released in the state shown in (a). [Figure 6] (a) is a side perspective view illustrating the state of the wheel structure according to the first embodiment of the present invention at the start of riding over a step (rotation angle of the frame support member is 30°) (a state later than that shown in Figure 5). (b) is a perspective view of the inside of the frame support member, viewed from the rear left diagonally above, when the transmission of rotational force of the main wheel by the rotational force transmission teeth is released in the state shown in (a). [Figure 7] (a) is a side perspective view illustrating the state of the frame support member of the wheel structure according to the first embodiment of the present invention at a rotation angle of 37° (a state later than that shown in Figure 6). (b) is a perspective view of the inside of the frame support member as seen from the rear left and slightly above when the rotational force transmission teeth begin to mesh in the state shown in (a). [Figure 8] (a) is a side perspective view illustrating the state of the frame support member of the wheel structure according to the first embodiment of the present invention at a rotation angle of 42° (a state later than that shown in Figure 7). (b) is a perspective view of the inside of the frame support member as seen from the rear left diagonally above when the rotational force transmission teeth have fully meshed (measuring state) in the state shown in (a). [Figure 9] (a) is a side perspective view illustrating the state of the frame support member of the wheel structure according to the first embodiment of the present invention at a rotation angle of 60° (a state later than that shown in Figure 8). (b) is a perspective view of the inside of the frame support member when the rotational force transmission teeth are meshed together, as seen from the rear left and slightly above, in the state shown in (a). [Figure 10](a) is a side perspective view illustrating the state of the frame support member at a rotation angle of 80° (a state later than that shown in Figure 9) when the main wheel of the wheel structure according to the first embodiment of the present invention begins to ride up onto a step. (b) is a perspective view of the inside of the frame support member, as seen from the rear left diagonally above, when the rotational force transmission teeth are meshed together in the state shown in (a). [Figure 11] (a) is a side perspective view illustrating the state of the frame support member at a rotation angle of 140° (a state later than that shown in Figure 10) immediately after the main wheel of the wheel structure according to the first embodiment of the present invention has completed riding over a step. (b) is a perspective view of the inside of the frame support member, as seen from the rear left diagonally above, when the rotational force transmission teeth are meshed together in the state shown in (a). [Figure 12] (a) is a side perspective view illustrating the state of the wheel structure according to the first embodiment of the present invention at a rotation angle of 140° of the frame support member (a state later than that shown in Figure 11), after the main wheel has driven onto a step and moved slightly forward on the top surface of the step. (b) is a perspective view of the inside of the frame support member, viewed from the rear left diagonally above, in the state shown in (a), when the rotational force transmission teeth are meshed and the engaging claw of the second clutch plate is in contact with the projection of the first clutch plate. [Figure 13] (a) is a side perspective view illustrating the state of the frame support member at a rotation angle of 110° (a state later than that shown in Figure 12) after the main wheel of the wheel structure according to the first embodiment of the present invention has advanced further over the stepped surface. (b) is a perspective view of the inside of the frame support member, viewed from the rear left diagonally above, in the state shown in (a), when the rotational force transmission teeth are meshed and the engaging claw of the second clutch plate is in contact with the projection of the first clutch plate. [Figure 14] (a) is a side perspective view illustrating the state of the frame support member at a rotation angle of 30° (a state later than that shown in Figure 13) after the main wheel of the wheel structure according to the first embodiment of the present invention has advanced further over the stepped surface. (b) is a perspective view of the inside of the frame support member, viewed from the rear left diagonally above, in the state shown in (a), when the rotational force transmission teeth are meshed and the engaging claw of the second clutch plate is in contact with the projection of the first clutch plate. [Figure 15] (a) is a side perspective view illustrating the state of the frame support member at a rotation angle of 25° (a state later than that shown in Figure 14) after the main wheel of the wheel structure according to the first embodiment of the present invention has advanced further over the stepped surface. (b) is a perspective view of the inside of the frame support member, viewed from the rear left diagonally above, at the state shown in (a), when the engagement between the rotational force transmission teeth has begun to disengage and the engaging claw of the second clutch plate is in contact with the projection of the first clutch plate. [Figure 16] (a) is a side perspective view illustrating the state of the frame support member at a rotation angle of 18° (a state later than that shown in Figure 15) after the main wheel of the wheel structure according to the first embodiment of the present invention has advanced further over the stepped surface. (b) is a perspective view of the inside of the frame support member, viewed from the rear left diagonally above, in the state shown in (a), when the meshing of the rotational force transmission teeth is completely disengaged (non-meshing state) and the engaging claw of the second clutch plate is in contact with the projection of the first clutch plate. [Figure 17] (a) is a side perspective view illustrating the state of the frame support member at a rotation angle of 18°, immediately following Figure 16. (b) is a perspective view of the inside of the frame support member, viewed from the rear left and slightly above, when the engagement of the rotational force transmission teeth is completely disengaged (non-engaged state) in the state of (a), and the engagement claw of the second clutch plate returns from the state in which it was in contact with the projection of the first clutch plate to the initial non-contact state. [Figure 18] This is a side perspective view illustrating the state of the wheel structure according to the first embodiment of the present invention at a rotation angle of 0° of the frame support member, after the main wheel has advanced further over the step surface (a state later than that shown in Figure 17). [Figure 19] This is an exploded perspective view of a frame support member in a wheel structure according to a second embodiment of the present invention. [Figure 20] Figure 19 is a perspective view of the inside of the frame support member, seen from the front left and slightly above. [Figure 21] Figure 20 is a perspective view in which the chain, sprocket, planetary carrier, and planetary gears have been removed for clarity. [Figure 22]Figure 21 is a diagram in which the pivot axis and fork have been removed for better visibility (note that the elastic body, which is the return mechanism, is omitted from the illustration). [Figure 23] Figure 22 shows the process by which the rotational force transmission teeth of the second clutch plate and the rotational force transmission teeth of the first clutch plate gradually engage, as well as the process of contact between the engaging claw and the projection, from (a) to (d). [Figure 24] This is a partially illustrated perspective view focusing on the force transmission mechanism inside the frame support member of a wheel structure according to a third embodiment of the present invention. [Figure 25] This is an exploded perspective view of a frame support member in a wheel structure according to a fourth embodiment of the present invention. [Figure 26] (a) is a perspective view of the inside of the frame support member in Figure 25, seen from the rear left and slightly above, and (b) is a perspective view of the inside of the frame support member in Figure 25, seen from the rear right and slightly above. [Modes for carrying out the invention]

[0024] [A] Characteristics of the information First, the features of the present invention will be described.

[0025] [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 positioned on the rear side in the direction of travel of a frame on which a transport platform mounting section is provided, and a small-diameter auxiliary wheel positioned on the front side in the direction of travel of the frame. The structure is configured such that when the main wheel comes into contact with a step, the auxiliary wheel comes into contact with the upper surface of the step, and then the main wheel rides up onto the upper surface of the step.

[0026] 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.

[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), 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 onto the top surface of the step.

[0032] Then, after the main wheel has driven onto the top of the step, the thrust in the direction of travel causes the main wheel to rotate counterclockwise (CCW) and move forward on the top of 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 pivot shaft of the main wheel. This causes the frame support member to rotate clockwise (CW), raising the auxiliary wheel back 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 surface. 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 surface with a single movement of moving the wheel structure forward. Therefore, the entire process of riding over a step can be done smoothly without requiring a large amount of force.

[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 form.

[0037] [1] Frame support member In the present invention, the frame support member is preferably provided with a first subframe having a hole through which the rotation shaft of the main wheel is inserted, and a second subframe having a hole through which a pivot shaft for rotating the frame support member is inserted, and a rotation mechanism is disposed 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 housing formed by a box-shaped first subframe and a lid-shaped second subframe. This makes it easy to miniaturize the wheel structure and also gives it a clean appearance.

[0039] [2] Elastic body Furthermore, the elastic body is preferably a spring, a coil spring, or a torsion spring, from the viewpoint that it can easily stretch and contract to control the operation of the clutch mechanism.

[0040] [3] Transport equipment By attaching the wheel structure according to the present invention to the lower part (bottom surface, lower end) of various transportable

[0041] 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.

[0042] [C]Specific Embodiments The present invention will be described in detail below with reference to the drawings, citing the first to fourth embodiments. However, these embodiments are illustrative and the present invention is not limited to them.

[0043] [1] First embodiment 1. Wheel structure configuration In this embodiment, the wheel structure is configured as follows in order to specifically realize the features and effects of the present invention described above. 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.

[0044] (wheel structure) As shown in Figure 1, the wheel structure 1 according to this embodiment comprises a frame 4 on which a transportable object mounting platform 5 is provided on the upper surface, a large-diameter main wheel 2 positioned below the frame 4 and on the rear side in the direction of travel of the frame 4, a small-diameter auxiliary wheel 3 positioned on the front side in the direction of travel of the frame 4, and a frame support member 6 interposed between the main wheel 2 and the frame 4 to support the frame 4 above the main wheel 2. The auxiliary wheel 3 is in a state where it is lifted off the ground by a predetermined distance during normal travel.

[0045] As shown in Figure 2, the main wheel 2 comprises a rotating shaft 21, a wheel 2b, and a tire 2a that covers the wheel 2b radially and circumferentially. The left side of the wheel 2b is cup-shaped and open. The rotating shaft 21 is erected at the center of the right side of the wheel 2b, thereby pivotally supporting and fixing the wheel 2b to the rotating shaft 21. The rotating shaft 21 extends to the vicinity of the second subframe 62 of the frame support member 6, which will be described later. Hereinafter, the rotating shaft of the main wheel may be referred to as the "main wheel shaft".

[0046] The auxiliary wheel 3 has a smaller diameter than the main wheel 2 and includes a wheel 3b and a tire 3a that covers the wheel 3b in the radial and circumferential directions.

[0047] As shown in Figures 1 and 2, the frame 4 comprises a canopy portion 4a, side wall portions 4b, and auxiliary wheel support portions 4c, and is positioned above the main wheel 2 to cover the main wheel 2. It supports the main wheel 2 via frame support members 6 and a rotating shaft 21, and also supports the auxiliary wheel 3 via a rotating shaft 31 of the auxiliary wheel 3 provided at the tip of the auxiliary wheel support portion 4c. A transportable material loading platform mounting portion 5 is attached to the upper surface of the canopy portion 4a so as to be integrated with the frame 4.

[0048] (Frame support member) As shown in Figure 3, the frame support member 6 comprises a box-shaped first subframe 61 and a lid-shaped second subframe 62, as described above. The planetary gear mechanism, power transmission mechanism, clutch mechanism, and transmission control mechanism that constitute the rotation mechanism are housed within the housing formed by the first subframe 61 and the second subframe 62.

[0049] The first subframe 61 has a roughly circular hole 61a formed in it, through which the rotating shaft 21 of the main wheel 2 is inserted and which opens around the rotating shaft 21. Multiple teeth are formed on the periphery of the hole 61a, and these multiple teeth function as the internal gear of the planetary gear mechanism. Therefore, in the following, the hole 61a will be referred to as the internal gear 61a.

[0050] The second subframe 62 has a circular hole 62a formed therein for inserting the left portion 70f of the pivot shaft 70, which will be described later. The diameter of the circular hole 62a is set to be larger than the diameter of the pivot shaft 70. The second subframe 62 is also equipped with a stopper 62b (shown in Figures 1 and 2) on its outer surface (the left side, which is the side facing the side wall portion 4b of the frame 4), and when the frame support member 6 rotates CW and the stopper 62b comes into contact with the lower end of the side wall portion 4b of the frame 4, the frame support member 6 stops rotating.

[0051] As shown in Figure 3, the frame support member 6 includes, in addition to the first subframe 61 and the second subframe 62, a sun gear 63, a planetary gear 64, a planetary carrier 65, a second clutch plate 66, a torsion spring 67, a first clutch plate 68, a first sprocket 69, a pivot shaft 70, a second sprocket 71, a chain 72, and a fork 73.

[0052] The sun gear 63, although not shown in the diagram, is pivotally fixed to the rotation axis 21 of the main wheel 2.

[0053] In this embodiment, there are three planetary gears 64, each positioned to surround the sun gear 63 and mesh with it. At the same time, the planetary gears 64 are positioned inside the internal gear 61a (hole 61a of the first subframe 61) and mesh with the internal gear 61a.

[0054] The planetary carrier 65 is rotatably supported on the rotation axis 21 of the main wheel 2. The planetary carrier 65 has three support shafts 65a. Each of the three support shafts 65a rotatably supports each of the three planetary gears 64.

[0055] The planetary carrier 65 has a plurality of rotational force transmission teeth 65b on its left side (opposite the planetary gear 64 side). Each of the plurality of rotational force transmission teeth 65b of the planetary carrier 65 has a vertical surface 65bs perpendicular to the counterclockwise (CCW) direction, and an inclined surface 65bk that slopes from the apex of the vertical surface 65bs toward the axial direction of the rotation axis 21 and toward the direction away from the second clutch plate 66 (described later) (i.e. toward the right) and toward the clockwise (CW) direction. In other words, the planetary carrier 65 constitutes a ring gear-shaped rotating plate.

[0056] The second clutch plate 66 is a substantially disc-shaped member. The second clutch plate 66 is rotatably supported on the rotation axis 21 of the main wheel 2 and is also rotatably supported so as to be movable in the axial direction (left-right direction) on the rotation axis 21 of the main wheel 2. The second clutch plate 66 faces the planetary carrier 65 on its right side and has a plurality of rotational force transmission teeth 66a that can mesh with a plurality of rotational force transmission teeth 65b of the planetary carrier 65. Each of the plurality of rotational force transmission teeth 66a of the second clutch plate 66 has a vertical surface 66as perpendicular to the clockwise (CW) direction and an inclined surface 66ak that slopes from the apex of the vertical surface 66as in the axial direction away from the planetary carrier 65 (i.e., to the left) and in the counterclockwise (CCW) direction.

[0057] Hereinafter, in this specification, the state in which the multiple rotational force transmission teeth 66a of the second clutch plate 66 and the multiple rotational force transmission teeth 65b of the planetary carrier 65 are meshed with each other will be referred to as the "mesh state," and the state in which they are not meshed with each other will be referred to as the "non-mesh state."

[0058] In this embodiment, the second clutch plate 66 has two engaging claws 66b on its left side (the side of the first clutch plate 68, which will be described later). The engaging claws 66b are projections that extend from near the outer edge of the left side of the second clutch plate 66 toward the first clutch plate 68 in the axial direction (i.e., toward the left). The engaging claws 66b transmit the rotational force caused by the rotation of the main wheel 2 from the second clutch plate 66 to the first clutch plate 68 by engaging with the projection 68a of the first clutch plate 68, which will be described later. The two engaging claws 66b are each positioned 180 degrees apart from each other in the circumferential direction of the second clutch plate 66.

[0059] The torsion spring 67 has two ends, each connected to one of the two engaging claws 66b of the second clutch plate 66 (the hole in the engaging claw 66b with a small hole as shown in Figure 3) and one of the two protrusions 68a of the first clutch plate 68 (the hole in the protrusion 68a with a small hole as shown in Figure 3), respectively. This ensures that an appropriate gap is formed between the engaging claw 66b of the second clutch plate 66 and the protrusion 68a of the first clutch plate 68 adjacent to the engaging claw 66b during normal driving of the wheel structure 1. The torsion spring 67 also functions as a return mechanism that returns the second clutch plate 66 to its initial position relative to the first clutch plate 68 by the biasing force of the torsion spring 67 (elastic body).

[0060] The first clutch plate 68 is a roughly disc-shaped member with a smaller diameter than the second clutch plate 66. The first clutch plate 68 is rotatably supported on the rotation axis 21 of the main wheel 2. The right side of the first clutch plate 68 faces the left side of the second clutch plate 66.

[0061] In this embodiment, the first clutch plate 68 has two projections 68a. The projections 68a are projections that protrude radially outward from the outer peripheral surface of the first clutch plate 68. The two projections 68a are each positioned 180 degrees apart from each other in the circumferential direction of the first clutch plate 68. The projections 68a are circumferentially engageable with the engaging claws 66b of the second clutch plate 66.

[0062] Since the two protrusions 68a of the first clutch plate 68 are spaced 180 degrees apart from each other in the circumferential direction, and the two engaging claws 66b of the second clutch plate 66 are spaced 180 degrees apart from each other in the circumferential direction, the counterclockwise (CCW) rotation of the second clutch plate 66 will not be transmitted to the first clutch plate 68 until the CCW-side surface of the engaging claws 66b of the second clutch plate 66 contacts the CW-side surface of the protrusions 68a of the first clutch plate 68. This is because, depending on the height of the step 11, when the main wheel 2 rides onto the upper surface 11b of the step, the second clutch plate 66 will rotate approximately 70° to 80° in the counterclockwise (CCW) direction, and a clearance of at least 80° is required between the adjacent engaging claws 66b and protrusions 68a.

[0063] The first clutch plate 68 is integrally connected to the left side of the first sprocket 69 so as to be rotatable. That is, the first sprocket 69 is rotatably supported on the rotation axis 21 of the main wheel 2.

[0064] The pivot shaft 70 is fixed to the frame 4 by passing through the circular hole 62a of the second subframe 62. As a result, the pivot shaft 70 moves in conjunction with the vertical movement of the frame 4. At the same time, the pivot shaft 70 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.

[0065] The pivot shaft 70 is equipped with a pair of pivot shaft guides: a first pivot shaft guide 70a on the right side in the direction of travel and a second pivot shaft guide 70b on the left side. Each of these pair of pivot shaft guides consists of circumferential protrusions that partially project radially from the outer surface of the pivot shaft 70.

[0066] The left portion 70f of the pivot shaft 70, relative to the second pivot shaft guide 70b, is formed in a shape resembling a rectangular prism with a rectangular cross-section.

[0067] The second sprocket 71 is pivotally fixed to the left portion 70f of the pivot shaft 70. The second sprocket 71 has an annular projection 71a on its left side. The left portion 70f of the pivot shaft 70 is inserted inside the annular projection 71a, thereby pivotally fixing the second sprocket 71 to the left portion 70f of the pivot shaft 70. The annular projection 71a is fitted from the inside into the circular hole 62a of the second subframe 62. The annular projection 71a and the circular hole 62a are rotatable relative to each other.

[0068] The first sprocket 69 and the second sprocket 71 are each formed such that their outer circumferences (the tooth-forming areas) are circular (excluding the tooth irregularities). Furthermore, the outer circumferences of the first sprocket 69 and the second sprocket 71 have the same radius. In other words, in the power transmission mechanism of this embodiment, neither acceleration nor deceleration occurs.

[0069] Chain 72 engages with the first sprocket 69 and the second sprocket 71, respectively, and wraps around them.

[0070] The fork 73 has a holding portion 73c at one end that opens in a semi-circular shape and rotatably holds the outer peripheral surface of the second clutch plate 66, and a hole 73d at the other end through which the pivot shaft 70 is rotatably inserted. Furthermore, the fork 73 has a first fork guide 73a to the right of the hole 73d and a second fork guide 73b to the left of the hole 73d. The first fork guide 73a and the second fork guide 73b are composed of protrusions that partially protrude axially (left-right) from the periphery of the hole 73d.

[0071] The retaining portion 73c has two claws, which grip the outer peripheral surface of the second clutch plate 66, thereby rotatably holding the second clutch plate 66. Specifically, the outer peripheral surface of the second clutch plate 66 is provided with a circumferential groove, while the inner surfaces of the two claws of the retaining portion 73c are provided with protrusions, and the protrusions and grooves are fitted together so as to be able to move relative to each other.

[0072] The hole 73d of the fork 73 is rotatably supported between the first pivot shaft guide 70a and the second pivot shaft guide 70b of the pivot shaft 70 (collectively referred to as the "pair of pivot shaft guides"), and is movable in the axial direction of the pivot shaft 70 between the pair of pivot shaft guides. The axial movement of the fork 73 controls whether or not the rotational force due to the rotation of the main wheel 2 is transmitted from the planetary carrier 65 to the second clutch plate 66. Specifically, the first fork guide 73a and the second fork guide 73b of the fork 73, and the first pivot shaft guide 70a and the second pivot shaft guide 70b of the pivot shaft 70 are formed such that when the end face of the second fork guide 73b and the end face of the second pivot shaft guide 70b come into contact, and the fork 73 rotates counterclockwise (CCW) around the pivot shaft 70, causing both end faces to push against each other, the fork 73 moves to the right in the axial direction. When the end face of the first fork guide 73a and the end face of the first pivot shaft guide 70a come into contact, and the fork 73 rotates clockwise (CW) around the pivot shaft 70, causing both end faces to push against each other, the fork 73 moves to the left in the axial direction.

[0073] As the fork 73 moves axially (left-right), the second clutch plate 66 held by the holding portion 73c of the fork 73 also moves axially (left-right). This allows the multiple rotational force transmission teeth 66a of the second clutch plate 66 and the multiple rotational force transmission teeth 65b of the planetary carrier 65 to engage or disengage.

[0074] In this embodiment, the internal gear 61a, sun gear 63, planetary gear 64, and planetary carrier 65 constitute a planetary gear mechanism. That is, the internal gear 61a, sun gear 63, planetary gear 64, and planetary carrier 65 can reduce the rotational speed caused by the rotation of the main wheel 2 transmitted on the rotation axis 21 of the main wheel 2.

[0075] The clutch mechanism consists of a planetary carrier 65 with multiple rotational force transmission teeth 65b, a second clutch plate 66 with multiple rotational force transmission teeth 66a on its right side and an engaging claw 66b on its left side, a first clutch plate 68 with a projection 68a projecting radially outward, and a return mechanism formed by a torsion spring 67 connected to the engaging claw 66b of the second clutch plate 66 and the projection 68a of the first clutch plate 68. In other words, the planetary carrier 65, the second clutch plate 66, the first clutch plate 68, and the torsion spring 67 can switch whether or not to transmit the rotational force caused by the rotation of the main wheel 2 to the force transmission mechanism.

[0076] The first sprocket 69, the second sprocket 71, and the chain 72 constitute a power transmission mechanism. In other words, the first sprocket 69, the second sprocket 71, and the chain 72 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 70 side of the main wheel 2.

[0077] The transmission control mechanism consists of a pivot shaft 70 on which a first pivot shaft guide 70a and a second pivot shaft guide 70b are formed, and a fork 73 on which a first fork guide 73a and a second fork guide 73b are formed, which rotatably holds the second clutch plate 66. In other words, the pivot shaft 70 and the fork 73 can control the switching of the clutch mechanism's transmission on or off.

[0078] In this embodiment, the clutch mechanism is disposed between the planetary gear mechanism and the components of the power transmission mechanism that are located on the rotation axis 21 of the main wheel 2. Specifically, the clutch mechanism is disposed between the planetary carrier 65 that constitutes the planetary gear mechanism and the first sprocket 69 located on the rotation axis 21 of the main wheel 2 that are located on the power transmission mechanism.

[0079] 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 70 to rotate around the rotation axis 21 of the main wheel 2, and also enable the frame support member 6 and the rotation axis 21 of the main wheel 2 to rotate around the pivot shaft 70.

[0080] 2. Operation of the wheel structure Next, the operation of the wheel structure 1 in this embodiment will be described.

[0081] (Normal driving) Figure 4 is a side perspective view illustrating the state of the wheel structure according to this embodiment during normal driving. In Figure 4, 10 is a flat surface. Note that in Figure 4, the elastic body (torsion spring 67) and chain 72 are omitted from the illustration for clarity. Similarly, in Figures 5 to 18, the elastic body (torsion spring 67) and chain 72 are omitted from the illustration. Also, in Figures 4 to 18, hatching is applied to the fork 73, the engaging claw 66b of the second clutch plate 66, and the projection 68a of the first clutch plate 68 for clarity.

[0082] As shown in Figure 4, during normal driving, the stopper 62b (shown in Figures 1 and 2) 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 frame support member 6, and the rotation axis 21 of the main wheel 2 is positioned forward of the rotation axis 70 in the direction of travel. At this time, as described above, the auxiliary wheel 3 is floating at a predetermined height above the contact surface (flat surface 10) of the main wheel 2.

[0083] When the wheel structure 1 is pushed forward, the main wheel 2 rotates in a counter-clockwise direction (CCW) and moves forward. As the main wheel 2 rotates, its rotation axis 21 and sun gear 63 also rotate in a CCW direction. Meanwhile, the planetary gear 64 that meshes with the sun gear 63 rotates in a clockwise direction (CW) while revolving in a CCW direction within the internal gear 61a of the first subframe 61. The planetary carrier 65 that supports the CCW-revolving planetary gear 64 also rotates in a CCW direction. At this time, the rotational force transmission teeth 65b of the planetary carrier 65 and the rotational force transmission teeth 66a of the second clutch plate 66 are not meshed (they are in a non-meshing state), so the rotational force of the main wheel 2 is not transmitted to the first sprocket 69 of the power transmission mechanism, nor is it transmitted to the pivot shaft 70 via the power transmission mechanism. As a result, the frame support member 6 does not rotate and maintains its initial position, allowing the wheel structure 1 to move forward.

[0084] (Driving over a step) Figure 5 is a side perspective view illustrating the state of the wheel structure according to this embodiment at the moment the main wheel contacts a step. In Figure 5, 11 is the step, 11a is the end face of the step, and 11b is the top surface of the step. In Figure 5, 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 happen to coincide, and the present invention is not limited to this case.

[0085] When the wheel structure 1 is pushed forward and the main wheel 2 comes into contact with the step 11, the main wheel 2 stops rotating and the wheel structure 1 stops moving forward.

[0086] 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 70 fixed to the frame 4, rotates in a counter-clockwise direction (CCW) around the pivot axis 70. Below, the rotation mechanism of the frame support member 6 will be explained, focusing on the rotation angle of the frame support member 6 around the pivot axis 70. Note that the rotation angle of the frame support member 6 during normal driving in Figure 4 is set to 0°.

[0087] (a) Rotation angle 30° As shown in Figure 6, when the frame 4 moves forward with the main wheel 2 in contact with the step 11, the frame support member 6 rotates in a counter-clockwise direction (CCW) around the pivot axis 70. Now, let's consider the movement within the frame support member 6. The main wheel 2, the main wheel axle 21, and the sun gear 63 are stationary (not rotating). The internal gear 61a is mounted on the first subframe 61 and rotates due to the rotation of the first subframe 61 (frame support member 6). In other words, the internal gear 61a rotates in a counter-clockwise direction (CCW) around the main wheel axle 21 by the same angle as its rotation angle. The planetary gear 64 rotates on its axis and revolves around the main wheel axle 21 in a CCW direction while meshing with the sun gear 63 and the internal gear 61a (typical operation of planetary gears). Therefore, the planetary carrier 65 rotates in a CCW direction around the main wheel axle 21. The rotational force transmission teeth 65b on the planetary carrier 65 also rotate in a CCW direction. Here, the rotation angle of the planetary carrier 65 (rotational force transmission teeth 65b) is smaller than the rotation angle of the frame support member 6 (first subframe 61).

[0088] The fork 73 is rotatably mounted on the pivot shaft 70 at one end and movable in the axial direction, while its other end (holding portion 73c) is fitted into the outer groove of the second clutch plate 66. The second clutch plate 66 is rotatably mounted on the main wheel axle 21 and movable in the axial direction. Therefore, the fork 73 rotates in sync with the rotation of the first subframe 61 around the pivot shaft 70. In addition, the second clutch plate 66 moves axially on the main wheel axle 21 in conjunction with the axial movement of the fork 73 on the pivot shaft 70. When the rotation angle is in the range of 0° to 30°, the fork 73 rotates on the pivot axis 70, but no axial movement occurs. Therefore, at this point, the rotational force transmission teeth 65b and 66a are separated (non-meshing).

[0089] (b) Rotation angle 37° As shown in Figure 7, when the frame 4 moves forward with the main wheel 2 in contact with the step 11, the frame support member 6 rotates in a counter-clockwise direction (CCW) around the pivot axis 70. Let's consider the movement within the frame support member 6. The main wheel 2, the main wheel shaft 21, and the sun gear 63 are stationary (not rotating). The internal gear 61a is mounted on the first subframe 61 and rotates due to the rotation of the first subframe 61 (frame support member 6). In other words, the internal gear 61a rotates in a counter-clockwise direction (CCW) around the main wheel shaft 21 by the same angle as the rotation angle. The planetary gear 64 rotates on its axis and revolves around the main wheel shaft 21 in a CCW direction while meshing with the sun gear 63 and the internal gear 61a (typical operation of planetary gears). Therefore, the planetary carrier 65 rotates in a CCW direction around the main wheel shaft 21. The rotational force transmission teeth 65b on the planetary carrier 65 also rotate in a CCW direction.

[0090] The second fork guide 73b of the fork 73 contacts the second pivot shaft guide 70b of the pivot shaft 70, and the CCW rotation of the fork 73 causes the fork 73 to move to the right in the direction of travel along the pivot shaft 70. The second clutch plate 66 moves to the right in the direction of travel along the main axle 21 due to the movement of the fork 73. As a result, the rotational force transmission teeth 65b of the planetary carrier 65 and the rotational force transmission teeth 66a of the second clutch plate 66 begin to overlap, and in some cases interfere. If interference occurs, the second clutch plate 66 rotates CW so that the rotational force transmission teeth 65b and 66a slide against each other. This operation is performed while stretching the elastic body (torsion spring 67). In Figure 7, a gap is provided between the engagement claw 66b of the second clutch plate 66 and the projection 68a of the first clutch plate 68 in the CW direction to avoid the above interference, but this gap can be eliminated. If you try to eliminate the problem, you will need to make the rotational force transmission teeth 65b and 66a smaller, so it is better to leave a gap if possible. By making the rotational force transmission teeth 65b and 66a larger, the force that can be transmitted will increase.

[0091] (c) Rotation angle 42° Up to a rotation angle of 42°, the operation is the same as described for a rotation angle of 37°, but as shown in Figure 8, at a rotation angle of 42°, the lateral movement of the fork 73 on the pivot axis 70 is completed. That is, the rotational force transmission teeth 65b and 66a are fully engaged (engaged state). Let's consider the movement within the frame support member 6. Even at rotation angles of 37° to 42°, the main wheel 2, main wheel shaft 21, and sun gear 63 remain stationary (not rotating). Therefore, as explained above in (a) (at a rotation angle of 30°), the rotational force transmission teeth 65b on the planetary carrier 65 rotate in a counter-clockwise direction (CCW). Because the rotational force transmission teeth 65b and 66a are meshed together, the second clutch plate 66 rotates in a CCW direction on the main wheel shaft 21. The first clutch plate 68 remains stationary in terms of rotation due to the second sprocket 71 fixed to the pivot shaft 70 via the chain 72. Since one end of the elastic body (torsion spring 67) is fixed to the first clutch plate 68 and the other end is fixed to the second clutch plate 66, the second clutch plate 66 first rotates clockwise due to the meshing of the rotational force transmission teeth 65b and 66a, and then rotates counterclockwise while compressing the elastic body (torsion spring 67).

[0092] (d) Rotation angle 60° As shown in Figure 9(a), the auxiliary wheel 3 contacts the upper surface 11b of the step. The operation described so far is the same as that explained for a 42° rotation angle. As shown in Figure 9(b), the second clutch plate 66 rotates in a cross-clockwise direction on the main axle 21 while compressing the elastic body (torsion spring 67). Although not apparent from Figure 9(a) alone, from the point where the rotation angle is 60°, the main wheel 2 begins to ride up onto the upper surface 11b of the step 11, centered on the corner of the step 11.

[0093] (e) Rotation angle 80° As shown in Figure 10(a), the main wheel 2 rotates around the corner of the step 11 so as to ride up onto the upper surface 11b of the step. As shown in Figure 10(b), the second clutch plate 66 further rotates in a counter-clockwise direction on the main wheel shaft 21.

[0094] (f) Rotation angle 140° As shown in Figure 11, after the auxiliary wheel 3 makes contact with the upper surface 11b of the step, as the vehicle moves forward further, the main wheel 2 rotates around the corner of the step 11 and rides onto the upper surface 11b of the step. At the same time, the main wheel 2 also rotates in a counter-clockwise direction (CCW) relative to the pivot axis 70. At this time, two movements occur inside the frame support member 6: the rotation of the sun gear 63 and the rotation of the internal gear 61a. These need to be considered separately.

[0095] (i) Regarding the rotation of the sun gear 63 First, the main wheel 2 rotates around the corner of the step 11. At the same time, the main wheel 2 is also rotating. Therefore, due to this planetary motion, the second clutch plate 66 rotates in a counter-clockwise direction (CCW). For example, if the sun gear 63 has 12 teeth, the planetary gear 64 has 24 teeth, and the internal gear 61a has 60 teeth, and the rotation angle of the main wheel 2 around the corner of the step 11 when riding over the step 11 is 60°, then the rotation angle of the second clutch plate 66 is 10°.

[0096] (ii) Rotation of the internal gear 61a Since the rotation angle ranges from 60° to 140°, the rotation angle of the frame support member 6 is 80°. Here, the rotation angle of 80° is derived from the difference between the rotation angle of 140° and the rotation angle of 60°. Assuming that the sun gear 63 is stationary, this results in a solar-type operation, and the rotation angle of the second clutch plate 66 is approximately 67°. Since the rotations of both are added together, the rotation angle of the second clutch plate 66 is approximately 77°. In other words, the second clutch plate 66 rotates 77° CCW around the main axle 21, and the engaging claw 66b in Figure 11 reflects this.

[0097] (g) With a rotation angle of 140°, the main wheel 2 moves forward on the upper surface 11b of the step. As the wheel structure 1 moves forward over the step surface 11b, the main load is applied to the auxiliary wheel 3 via the frame 4. The main wheel 2 moves forward while rotating counterclockwise (CCW) due to friction from contact with the step surface 11b. Consequently, the sun gear 63 rotates CCW. As described above, the second clutch plate 66 rotates CCW, and the engaging claw 66b of the second clutch plate 66 rotates CCW. If this state continues for a while, as shown in Figure 12, the engaging claw 66b comes into contact with the projection 68a of the first clutch plate 68 from upstream.

[0098] When the engaging claw 66b is in contact with the projection 68a, and the entire wheel structure 1 moves forward, the rotation of the main wheel 2 acts to rotate the projection 68a. On the other hand, the projection 68a, i.e., the first clutch plate 68, is provided with a first sprocket 69, and a chain 72 is meshed with the first sprocket 69, which is also meshed with a second sprocket 71 provided on the pivot shaft 70. Therefore, the force that rotates the projection 68a of the first clutch plate 68 tries to rotate the second sprocket 71 provided on the pivot shaft 70 in a counter-clockwise direction (CCW). However, the second sprocket 71 provided on the pivot shaft 70 is fixed to the pivot shaft 70, and the pivot shaft 70 is fixed to the frame 4, so the second sprocket 71 cannot rotate. Therefore, the force acts to rotate the frame support member 6 in a clockwise direction (CW) around the pivot shaft 70. As a result, the frame 4 is gradually lifted.

[0099] (h) Rotation angle 110° As shown in Figure 13, the rotational force from the rotation of the main wheel 2 is transmitted from the first sprocket 69, which constitutes the power transmission mechanism, to the second sprocket 71 via the chain 72. As a result, the frame support member 6 rotates in the CW direction around the pivot axis 70. Consequently, the rotation angle of the frame support member 6 gradually decreases as the main wheel 2 moves forward. And as the rotation angle of the frame support member 6 decreases, the frame 4 and auxiliary wheels 3 gradually rise.

[0100] (i) Rotation angle 30° Figure 14(a) shows the state in which the frame support member 6 rotates clockwise around the pivot axis 70 due to the rotation of the main wheel 2, and the pivot axis 70 reaches the VL line. The VL line is the vertical line passing through the main wheel axle 21. Up to this point, the rotation of the main wheel 2 has caused the frame support member 6 to rotate CW around the pivot axis 70, thereby raising the frame 4. When the pivot axis 70 reaches the VL line, as shown in Figure 14(b), the first fork guide 73a on the right side in the direction of travel of the fork 73 comes into contact with the first pivot axis guide 70a on the right side in the direction of travel of the pivot axis 70. As the wheel structure 1 moves further forward, the fork 73 moves to the left in the axial direction due to the first fork guide 73a and the first pivot axis guide 70a. As a result, the second clutch plate 66 moves to the left, and the engagement (meshing state) between the rotational force transmission teeth 65b and rotational force transmission teeth 66a begins to disengage.

[0101] (j) Rotation angle 25° As shown in Figure 15(b), the fork 73 moves to the left by the first fork guide 73a and the first pivot shaft guide 70a, and the meshing (engaged state) between the rotational force transmission teeth 65b and 66a is being resolved.

[0102] (k) Rotation angle 18° (torsion spring 67 before extension) As shown in Figure 16(b), the fork 73 completes its lateral movement to the left. Before reaching this state, the rotational force transmission teeth 65b and 66a are no longer meshed (non-meshing state) (because there is clearance between the rotational force transmission teeth).

[0103] (l) Rotation angle 18° (after torsion spring 67 is extended) As shown in Figure 17, when the engagement between the rotational force transmission teeth 65b and 66a is released, the return mechanism (torsion spring 67) quickly returns the rotational phase of the second clutch plate 66 to its initial state (the phase during normal driving). At this time, the compressed elastic body (torsion spring 67) extends and returns to its original state.

[0104] (m) Rotation angle 0° Due to the load on frame 4, the frame support member 6 continues to rotate in the CW direction. However, as shown in Figure 18, when the rotation angle becomes 0°, the stopper 62b (shown in Figures 1 and 2) contacts the lower end of the side wall portion 4b of frame 4, stopping the rotation of the frame support member 6. The wheel structure 1 then returns to its normal running state on the stepped upper surface 11b.

[0105] With the above steps completed, the series of actions for the wheel structure 1 to climb over the step is finished.

[0106] 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.

[0107] 3. Other effects and benefits of the wheel structure configuration Next, other effects and advantages of the configuration of the wheel structure 1 in this embodiment will be described.

[0108] According to the wheel structure 1, the clutch mechanism is composed of a ring gear-shaped planetary carrier 65 having a plurality of rotational force transmission teeth 65b, a second clutch plate 66 having a plurality of rotational force transmission teeth 66a that face the planetary carrier 65 on one side (right side) and can mesh with the plurality of rotational force transmission teeth 65b of the planetary carrier 65, a first clutch plate 68 facing the other side (left side) of the second clutch plate 66, and a return mechanism that returns the second clutch plate 66 to the first clutch plate 68 to its initial position by the biasing force of a torsion spring 67. The first clutch plate 68 has a projection 68a that protrudes radially outward, and the second clutch plate 66 has an engaging claw 66b on the other side (left side) that can engage with the projection 68a of the first clutch plate 68. As a result, when the rotational force transmission teeth 65b and 66a, which can mesh with each other, mesh, the rotational force caused by the rotation of the main wheel 2 is transmitted to the second clutch plate 66. Furthermore, when the engaging claw 66b and the projection 68a, which can mesh with each other, engage with each other, the rotational force can be transmitted from the second clutch plate 66 to the first clutch plate 68. In addition, if the rotational force transmission teeth 65b and 66a become disengaged, or if the engaging claw 66b and the projection 68a cease to engage with each other, the rotational force will no longer be transmitted to the first clutch plate 68. Thus, according to the wheel structure 1, since it is equipped with the clutch mechanism, it is possible to switch between transmitting and not transmitting the rotational force caused by the rotation of the main wheel 2 to the power transmission mechanism.

[0109] Furthermore, according to the wheel structure 1, each of the multiple rotational force transmission teeth 65b of the planetary carrier 65 has a vertical surface 65bs perpendicular to the counterclockwise (CCW) direction and an inclined surface 65bk that slopes from the apex of the vertical surface 65bs axially away from the second clutch plate 66 (to the right) and clockwise (CW) direction. Each of the multiple rotational force transmission teeth 66a of the second clutch plate 66 has a vertical surface 66as perpendicular to the clockwise (CW) direction and an inclined surface 66ak that slopes from the apex of the vertical surface 66as axially away from the planetary carrier 65 (to the left) and counterclockwise (CCW) direction. Therefore, when the rotational force transmission teeth 65b and 66a are meshed, the rotational force in the counterclockwise (CCW) direction caused by the rotation of the main wheel 2 can be transmitted from the planetary carrier 65 to the second clutch plate 66.

[0110] Furthermore, according to the wheel structure 1, the power transmission mechanism is composed of a first sprocket 69 rotatably supported on the rotation axis 21 of the main wheel 2, a second sprocket 71 fixedly supported on the pivot axis 70, and a chain 72 that meshes with the first sprocket 69 and the second sprocket 71 respectively and winds around the first sprocket 69 and the second sprocket 71. 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 to the pivot axis 70. In addition, the number of axes can be reduced compared to, for example, the case in the third embodiment described later, where the power transmission mechanism is composed of three gears.

[0111] In this embodiment, as shown in Figure 3 and other figures, the first clutch plate 68 has a smaller diameter than the second clutch plate 66 and has a projection 68a that protrudes radially outward from its outer peripheral surface. The second clutch plate 66 has an engaging claw 66b that extends axially from near the outer edge of the side surface on the first clutch plate 68 side and is capable of engaging with the projection 68a of the first clutch plate 68. However, the embodiment is not necessarily limited to this configuration. For example, the first clutch plate 68 may have the same diameter as the second clutch plate 66, and instead of a projection 68b that protrudes radially outward, it may have an engaging claw that extends axially from the side surface on the second clutch plate 66 side and is capable of engaging with the engaging claw 66b of the second clutch plate 66. Furthermore, for example, the second clutch plate 66 may have a smaller diameter than the first clutch plate 68 and have a projection that protrudes radially outward from its outer peripheral surface, and the first clutch plate 68 may have an engaging claw that extends axially from near the outer edge of the side surface on the second clutch plate 66 side and can engage with the projection of the second clutch plate 66. These are also the same in the embodiments described later.

[0112] 4. Modified Examples of This Embodiment Next, a modified example of the wheel structure 1 in this embodiment will be described.

[0113] In the above description, the first sprocket 69 and the second sprocket 71 were described assuming that their outer circumferences (tooth-forming portions) are circular. However, both the first sprocket 69 and the second sprocket 71, or only the first sprocket 69, may be non-circular, for example, elliptical. If the first sprocket 69 is non-circular, the movement of the main wheel 2 over the step 11 becomes smoother.

[0114] Although not shown in the figures, one of the engaging claws 66b of the second clutch plate 66 and the projection 68a of the first clutch plate 68 may have a convex portion that protrudes in the circumferential direction, and the other may have a recess that is concave in the circumferential direction. In this case, the convex / concave portion of the engaging claw 66b of the second clutch plate 66, which is movable in the axial direction (left-right direction), and the recess / convex portion of the projection 68a will fit together, making the engagement between the engaging claw 66b and the projection 68a more secure and preventing the engaging claw 66b and the projection 68a from shifting in the axial direction (left-right direction) when engaged.

[0115] In the above, the power transmission mechanism is composed of a first sprocket 69, a second sprocket 71, and a chain 72. However, it may also be composed of a first pulley pivotally supported on the rotation axis 21 of the main wheel 2, a second pulley pivotally fixed to the pivot shaft 70, 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 securing the wire.

[0116] [2] Second embodiment 1. Wheel structure configuration Figure 19 is an exploded perspective view of the frame support member 6A in the wheel structure 1A according to this embodiment, Figure 20 is a perspective view of the assembled internal components of the frame support member 6A, and Figure 21 is a perspective view of Figure 20 with the chain 72, sprockets 69, 71, planetary carrier 65A, and planetary gear 64 removed. Figure 22 is a view of Figure 21 with the pivot shaft 70A and fork 73 removed (the elastic body, which is the return mechanism, is not shown). The wheel structure 1A (not shown) comprises a main wheel 2, a pivot shaft 21 of the main wheel 2, auxiliary wheels 3, a frame 4, a transportable load platform mounting part 5, and a frame support member 6A. Except for the arrangement of the clutch mechanism in the frame support member 6A, which differs from that of the first embodiment, it has the same configuration as the wheel structure 1 according to the first embodiment. Therefore, the same reference numerals are used for components identical to those in the first embodiment, and the description of the second embodiment will mainly focus on components that differ from those in the first embodiment.

[0117] (Frame support member) As shown in Figure 19, the subframe constituting the casing of the frame support member 6A consists of a box-shaped auxiliary subframe 60, a first subframe 61A having a hole (not shown) through which a pivot shaft 70A is rotatably inserted and an internal gear 61Aa, and a second subframe 62 having a circular hole 62a.

[0118] The planetary gear mechanism and the transmission control mechanism are housed between the auxiliary subframe 60 and the first subframe 61A. The planetary gear mechanism and the power transmission mechanism are housed between the first subframe 61A and the second subframe 62.

[0119] The auxiliary subframe 60 has a hole 60a through which the rotation shaft 21 (main wheel shaft 21) of the main wheel 2 passes. The diameter of the hole 60a is set to be larger than the diameter of the main wheel shaft 21.

[0120] In this embodiment, the clutch mechanism is located between the main wheel 2 and the planetary gear mechanism.

[0121] Specifically, the clutch mechanism is configured as follows: The clutch mechanism consists of a rotating plate 80, a second clutch plate 66A, a spring 67A, and a first clutch plate 68A.

[0122] The rotating plate 80 is pivotally fixed to the main axle 21, which passes through a hole 60a in the auxiliary subframe 60. The rotating plate 80 has an annular projection 80a on its right side. The main axle 21 is inserted inside the annular projection 80a. The annular projection 80a is fitted into the hole 60a of the auxiliary subframe 60 from the inside. The annular projection 80a and the hole 60a are rotatable relative to each other.

[0123] The rotating plate 80 faces the second clutch plate 66A in the axial direction (left-right direction) on the main wheel shaft 21. Multiple rotational force transmission teeth 80b are formed on the side (left side) of the second clutch plate 66A on the rotating plate 80. The multiple rotational force transmission teeth 80b can mesh with the multiple rotational force transmission teeth 66Aa of the second clutch plate 66A.

[0124] The second clutch plate 66A has two engaging claws 66Ab on its left side (the side facing the first clutch plate 68A). The engaging claws 66Ab will be described later.

[0125] The spring 67A has two ends, each connected to one of the two engaging claws 66Ab of the second clutch plate 66A and one of the two projections 68Aa of the first clutch plate 68A (described later), respectively. It biases the engaging claw 66Ab (second clutch plate 66A) in a clockwise (CW) direction, causing the engaging claw 66Ab to contact the projection 68Aa during normal operation of the wheel structure 1. The spring 67A also functions as a return mechanism that returns the second clutch plate 66A to its initial position relative to the first clutch plate 68A due to the biasing force of the spring 67A (elastic body). In other words, the clutch mechanism's return mechanism consists of springs 67A connected to the first clutch plate 68A and the second clutch plate 66A, respectively, which bias the second clutch plate 66A in a clockwise (CW) direction so that the engaging claws 66Ab of the second clutch plate 66A contact the protrusions 68Aa of the first clutch plate 68A.

[0126] In this embodiment, the first clutch plate 68A has two protrusions 68Aa. The protrusions 68Aa are circumferentially engageable with the engaging claws 66Ab of the second clutch plate 66A.

[0127] The first clutch plate 68A is integrally connected to the sun gear 63A on its left side so as to be rotatable. The sun gear 63A is rotatably supported on the main wheel shaft 21.

[0128] In this embodiment, the sun gear 63A, the internal gear 61Aa, the planetary gear 64, and the planetary carrier 65A constitute a planetary gear mechanism.

[0129] The rotating plate 80, the second clutch plate 66A, the first clutch plate 68A, and the spring 67A constitute the clutch mechanism. In other words, in this embodiment, the clutch mechanism can switch whether or not to transmit the rotational force caused by the rotation of the main wheel 2 to the power transmission mechanism via the planetary gear mechanism.

[0130] Based on the above, in this embodiment, the clutch mechanism is arranged between the main wheel 2 and the planetary gear mechanism.

[0131] Other configurations in this embodiment will now be described.

[0132] In this embodiment, the left portion of the pivot shaft 70A is not formed in the shape of a rectangular prism with a rectangular cross-section, but rather in the shape of a cylinder. However, the second sprocket 71, through which the left portion of the pivot shaft 70A is inserted, is fixed to the pivot shaft 70A in the same way as in the first embodiment.

[0133] Here, the relationship between the engaging claw 66Ab of the second clutch plate 66A and the projection 68Aa of the first clutch plate 68A will be explained using Figures 22 and 23(a) to (d). Note that the spring 67A is omitted from the illustrations in Figures 22 and 23(a) to (d). The partial hatching in Figures 23(a) to (d) is to highlight the engaging claw 66Ab of the second clutch plate 66A and the projection 68Aa of the first clutch plate 68A for easier viewing. The engaging claw 66Ab is biased by the spring 67A to contact the projection 68Aa from the upstream side in a clockwise (CW) direction.

[0134] In this case, when the multiple rotational force transmission teeth 80b of the rotating plate 80 and the multiple rotational force transmission teeth 66Aa of the second clutch plate 66A engage, if the vertices of the rotational force transmission teeth 80b and the vertices of the rotational force transmission teeth 66Aa interfere with each other, the second clutch plate 66A will attempt to rotate clockwise (CW) so that the inclined surface 80bk of the rotational force transmission teeth 80b and the inclined surface 66Aak of the rotational force transmission teeth 66Aa slide against each other.

[0135] However, due to the function of the spring 67A, the engaging claw 66Ab of the second clutch plate 66A is already in contact with the projection 68Aa of the first clutch plate 68A from the upstream side in the clockwise (CW) direction, so it appears that the second clutch plate 66A cannot rotate further in the clockwise (CW) direction (its rotation in the clockwise (CW) direction is obstructed by the projection 68Aa).

[0136] However, the engaging claw 66Ab of the second clutch plate 66A has a first contact surface 66Ab1 that can contact the projection 68Aa of the first clutch plate 68A, a second contact surface 66Ab2 that can contact the projection 68Aa of the first clutch plate 68A and is formed in a counterclockwise (CCW) direction and axially toward the first clutch plate side (left direction) away from the first contact surface 66Ab1, and an inclined surface 66Abk that is connected to the first contact surface 66Ab1 and the second contact surface 66Ab2, respectively.

[0137] As a result, as shown in Figures 23(a) to (d), the second clutch plate 66A rotates clockwise (CW) while the multiple rotational force transmission teeth 80b of the rotating plate 80 and the multiple rotational force transmission teeth 66Aa of the second clutch plate 66A engage.

[0138] To explain the process shown in Figures 23(a) to (d) in detail, at the point shown in Figure 23(a), that is, before the rotational force transmission tooth 80b and the rotational force transmission tooth 66Aa begin to engage, the engaging claw 66Ab is in contact with the projection 68Aa at its first contact surface 66Ab1. At this point, there is still a small clearance between the rotational force transmission tooth 80b and the rotational force transmission tooth 66Aa.

[0139] At the point shown in Figure 23(b), that is, when the second clutch plate 66 moves slightly toward the rotating plate 80 (to the right) by the transmission control mechanism, and the rotational force transmission teeth 80b and rotational force transmission teeth 66Aa begin to engage slightly, the contact position of the engaging claw 66Ab with the projection 68Aa begins to shift from the first contact surface 66Ab1 to the inclined surface 66Abk.

[0140] At the point shown in Figure 23(c), that is, while the rotational force transmission tooth 80b and the rotational force transmission tooth 66Aa are engaged, the second clutch plate 66A rotates clockwise (CW) while moving toward the rotating plate 80 (to the right). However, since the contact position between the engaging claw 66Ab and the projection 68Aa has shifted to the inclined surface 66Abk, the clockwise (CW) rotation of the second clutch plate 66A is released by the inclined surface 66Abk, and contact between the engaging claw 66Ab and the projection 68Aa continues.

[0141] At the point shown in Figure 23(d), that is, when the rotational force transmission tooth 80b and the rotational force transmission tooth 66Aa have finished engaging (engaged state), the movement of the second clutch plate 66A toward the rotating plate 80 (to the right) while rotating in a clockwise (CW) direction also ends. However, the contact position of the engaging claw 66Ab with the projection 68Aa has shifted to the second contact surface 66Ab2, and further clockwise (CW) rotation of the second clutch plate 66A is no longer possible.

[0142] The shape of the inclined surface 66Abk of the engaging claw 66Ab is such that it does not hinder the engagement of the rotational force transmission tooth 80b and the rotational force transmission tooth 66Aa. For example, the inclination angle of the inclined surface 66Abk is equal to the inclination angle of the inclined surface 80bk (inclined surface 66Aak) of the rotational force transmission tooth 80b (rotational force transmission tooth 66Aa) (shown in Figure 22).

[0143] 2. Other effects and benefits of the wheel structure configuration Next, other effects and advantages of the configuration of the wheel structure 1A in this embodiment will be described.

[0144] According to the wheel structure 1A, the clutch mechanism is disposed between the main wheel 2 and the planetary gear mechanism, and transmits the rotation of the main wheel 2 to the power transmission mechanism (first sprocket 69) via the planetary gear mechanism, which is a reduction mechanism. As a result, the torque loaded on the clutch mechanism can be reduced, and the components constituting the clutch mechanism can be made lighter and smaller.

[0145] Furthermore, according to the wheel structure 1A, the engaging claw 66Ab of the second clutch plate 66A has a first contact surface 66Ab1 that can contact the projection 68Aa of the first clutch plate 68A, and a second contact surface 66Ab2 that can contact the projection 68Aa of the first clutch plate 68A and is formed in a counterclockwise (CCW) direction and axially, away from the first contact surface 66Ab1 toward the first clutch plate 68A, and the first contact surface 66Ab1 and the second contact surface 66Ab2 are connected to each other. Since it has an inclined surface 66Abk, as described above, even if the engaging claw 66Ab of the second clutch plate 66A is in contact with the projection 68Aa of the first clutch plate 68A due to the action of the spring 67A, it is possible to maintain the contact state of the engaging claw 66Ab with the projection 68Aa while releasing the clockwise (CW) rotation of the second clutch plate 66A that may occur when the multiple rotational force transmission teeth 80b of the rotating plate 80 and the multiple rotational force transmission teeth 66Aa of the second clutch plate 66A engage.

[0146] [3] Third embodiment 1. Wheel structure configuration Figure 24 is a perspective view partially illustrating the force transmission mechanism within the frame support member 6C of the wheel structure 1C according to this embodiment. The wheel structure 1C (not shown) comprises a main wheel 2, a rotation axis 21 of the main wheel 2, an auxiliary wheel 3, a frame 4, a transportable object mounting part 5, and a frame support member 6C (not shown). Except for the configuration of the force transmission mechanism in the frame support member 6C, which differs from that of the first embodiment, the configuration is the same as that of the wheel structure 1 according to the first embodiment. Therefore, the same reference numerals are used for components identical to those in the first embodiment, and the description of the third embodiment will mainly focus on components that differ from those in the first embodiment.

[0147] (Frame support member) As shown in Figure 24, in this embodiment, the power transmission mechanism consists of a first gear 69C rotatably supported on the rotation shaft 21 of the main wheel 2, a second gear 71C fixed to the pivot shaft 70, and a third gear 75 that meshes with the first gear 69C and the second gear 71C.

[0148] Specifically, the force transmission mechanism is configured as follows:

[0149] The first gear 69C is integrally rotatably connected to the left side of the first clutch plate 68. The first gear 69C is a so-called circular gear.

[0150] The second gear 71C is pivotally fixed to the left portion 70f of the pivot shaft 70. The second gear 71C has an annular projection 71Ca on its left side. The left portion 70f of the pivot shaft 70 is inserted inside the annular projection 71Ca. The annular projection 71Ca is fitted from the inside into a circular hole 62a of the second subframe 62 (shown in Figure 3). The annular projection 71Ca and the circular hole 62a are rotatable relative to each other. The second gear 71C is a so-called circular gear.

[0151] The third gear 75 is positioned between the first gear 69C and the second gear 71C, and meshes with both the first gear 69C and the second gear 71C, respectively. This allows the third gear 75 to transmit the rotational force generated by the rotation of the main wheel 2, transmitted from the clutch mechanism to the first gear 69C, to the second gear 71C. The third gear 75 is a so-called circular gear.

[0152] The third gear 75 is rotatably supported on the auxiliary shaft 41. The auxiliary shaft 41 is positioned between the rotation axis 21 and the pivot axis 70 of the main wheel 2, and although not shown in the figure, it is erected and fixed to the right side (first subframe 61 side) main surface of the second subframe 62.

[0153] 2. Other effects and benefits of the wheel structure configuration Next, other effects and advantages of the configuration of the wheel structure 1C in this embodiment will be described.

[0154] According to the wheel structure 1C, the power transmission mechanism is composed of a first gear 69C rotatably supported on the rotation shaft 21 of the main wheel 2, a second gear 71C fixed to the pivot shaft 70, and a third gear 75 that meshes with the first gear 69C and the second gear 71C. 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 shaft 21 to the pivot shaft 70.

[0155] 3. Modified Examples of This Embodiment Next, a modified example of the configuration of the wheel structure 1C in this embodiment will be described.

[0156] In the above explanation, the first gear 69C, the second gear 71C, and the third gear 75 were described assuming they were circular gears, but they may also be non-circular, for example, elliptical. If the first gear 69C, the second gear 71C, and the third gear 75 are non-circular, the movement of the main wheel 2 over the step 11 becomes smoother.

[0157] [4] Fourth embodiment 1. Wheel structure configuration Figure 25 is an exploded perspective view of the frame support member 6D in the wheel structure 1D according to this embodiment. The wheel structure 1D (not shown) comprises a main wheel 2, a rotation axis 21 of the main wheel 2, an auxiliary wheel 3, a frame 4, a transportable load platform mounting part 5, and a frame support member 6D. Except for the arrangement of the clutch mechanism in the frame support member 6D, which differs from that of the first embodiment, and the configuration of the transmission control mechanism which differs from that of the first embodiment due to the different arrangement of the clutch mechanism, it is basically the same configuration as the wheel structure 1 according to the first embodiment. However, in this embodiment, for ease of understanding the configuration, all the components of the wheel structure 1D will be described.

[0158] (wheel structure) The wheel structure 1D according to this embodiment, although not shown, comprises a frame 4 on which a transportable object mounting platform attachment portion 5 is provided on its upper surface; a large-diameter main wheel 2 positioned below the frame 4 and on the rear side in the direction of travel of the frame 4; a small-diameter auxiliary wheel 3 positioned on the front side in the direction of travel of the frame 4; and a frame support member 6D interposed between the main wheel 2 and the frame 4 to support the frame 4 above the main wheel 2. The auxiliary wheel 3 is in a state where it is lifted off the ground by a predetermined distance during normal travel.

[0159] The main wheel 2 comprises a rotating shaft 21, a wheel 2b, and a tire 2a that covers the wheel 2b radially and circumferentially. The left side of the wheel 2b is cup-shaped and open. The rotating shaft 21 is erected at the center of the right side of the wheel 2b, thereby pivotally supporting and fixing the wheel 2b to the rotating shaft 21. The rotating shaft 21 extends to the vicinity of the second subframe 62, which will be described later, of the frame support member 6D.

[0160] The auxiliary wheel 3 has a smaller diameter than the main wheel 2 and includes a wheel 3b and a tire 3a that covers the wheel 3b in the radial and circumferential directions.

[0161] The frame 4 comprises a canopy section 4a, side wall sections 4b, and auxiliary wheel support sections 4c, and is positioned above the main wheel 2 to cover the main wheel 2. It supports the main wheel 2 via frame support members 6D and a rotating shaft 21, and also supports the auxiliary wheel 3 via a rotating shaft 31 of the auxiliary wheel 3 provided at the tip of the auxiliary wheel support section 4c. A transportable material loading platform mounting section 5 is attached to the upper surface of the canopy section 4a so as to be integrated with the frame 4.

[0162] (Frame support member) As shown in Figure 25, the frame support member 6D comprises a box-shaped first subframe 61D and a lid-shaped second subframe 62. The planetary gear mechanism, power transmission mechanism, clutch mechanism, and transmission control mechanism that constitute the aforementioned rotation mechanism are housed within the housing formed by the first subframe 61D and the second subframe 62.

[0163] The first subframe 61D has a roughly circular hole 61Da (not shown) through which the rotation shaft 21 of the main wheel 2 is inserted, with the opening centered on the rotation shaft 21. Multiple teeth are formed on the periphery of the hole 61Da, and these multiple teeth function as the internal gear of the planetary gear mechanism. Therefore, in the following, the hole 61Da will be referred to as the internal gear 61Da.

[0164] Furthermore, on the left side (second subframe 62 side) main surface of the right side wall of the first subframe 61D, as partially shown in Figure 25, a support shaft 61De is erected and fixed, which serves as a support shaft that gives movement to the fork 73D, so that the fork 73D, which will be described later, rotates in conjunction with the rotation of the frame support member 6D around the pivot axis 70D.

[0165] The second subframe 62 has a circular hole 62a through which the left portion 70Df of the pivot shaft 70D, which will be described later, is inserted. The diameter of the circular hole 62a is set to be larger than the diameter of the pivot shaft 70D. The second subframe 62 is also equipped with a stopper 62b (shown in Figure 2) on its outer surface (the left side, which is the side facing the side wall portion 4b of the frame 4), and when the frame support member 6D rotates CW and the stopper 62b comes into contact with the lower end of the side wall portion 4b of the frame 4, the frame support member 6D stops rotating.

[0166] As shown in Figure 25, the frame support member 6D includes, in addition to the first subframe 61D and the second subframe 62, a sun gear 63, a planetary gear 64, a planetary carrier 65D, a first sprocket 69D, a second sprocket 71D, a chain 72, a rotating plate 80D, a second clutch plate 66D, a torsion spring 67, a first clutch plate 68D, a pivot shaft 70D, and a fork 73D.

[0167] The sun gear 63, although not shown in the diagram, is pivotally fixed to the rotation axis 21 of the main wheel 2.

[0168] In this embodiment, there are three planetary gears 64, each positioned to surround the sun gear 63 and mesh with it. At the same time, the planetary gears 64 are positioned inside the internal gear 61Da (hole 61Da in the first subframe 61D) and mesh with the internal gear 61Da.

[0169] The planetary carrier 65D is rotatably supported on the rotation axis 21 of the main wheel 2. The planetary carrier 65D has three support shafts 65Da. Each of the three support shafts 65Da rotatably supports each of the three planetary gears 64.

[0170] An annular cylindrical portion 65De is erected and fixed in the center of the left side of the planetary carrier 65D, extending to the left (towards the second subframe 62). The rotation shaft 21 of the main wheel 2 is rotatably inserted inside the annular cylindrical portion 65De.

[0171] The first sprocket 69D is connected to and fixed near the left end of the annular cylindrical portion 65De of the planetary carrier 65D. In other words, the first sprocket 69D is rotatably supported on the rotation axis 21 of the main wheel 2 and can rotate integrally with the planetary carrier 65D.

[0172] The pivot shaft 70D is fixed to the frame 4 by passing through the circular hole 62a of the second subframe 62. As a result, the pivot shaft 70D is linked to the vertical movement of the frame 4. At the same time, the pivot shaft 70D is able to rotate around the rotation axis 21 of the main wheel 2 in conjunction with the rotation of the first subframe 61D and the second subframe 62 (i.e., the frame support member 6D) around the rotation axis 21 of the main wheel 2.

[0173] The pivot shaft 70D is equipped with a pair of pivot shaft guides: a first pivot shaft guide 70Da on the right side in the direction of travel and a second pivot shaft guide 70Db on the left side. Each of these pair of pivot shaft guides consists of circumferential protrusions that partially project radially from the outer surface of the pivot shaft 70D.

[0174] To the left of the second pivot shaft guide 70Db of the pivot shaft 70D, a rectangular portion 70Dd with a rectangular cross-section is formed. The rectangular portion 70Dd fits into the rectangular hole 68Db of the first clutch plate 68D, which will be described later, and supports the first clutch plate 68D while fixing the first clutch plate 68D so that it cannot rotate around the pivot shaft 70D.

[0175] The left portion 70Df of the pivot shaft 70D, beyond the rectangular portion 70Dd, is formed in a cylindrical shape and rotatably supports the second clutch plate 66D, the rotating plate 80D, and the second sprocket 71D, which will be described later. The tip of the left portion 70Df is inserted through the circular hole 62a of the second subframe 62 and fixed to the frame 4.

[0176] The second sprocket 71D is rotatably supported on the left portion 70Df of the pivot shaft 70D. The second sprocket 71D has an annular projection 71Da on its left side. The left portion 70Df of the pivot shaft 70D is inserted inside the annular projection 71Da. The annular projection 71Da is fitted from the inside into the circular hole 62a of the second subframe 62. The annular projection 71Da and the circular hole 62a are rotatable relative to each other.

[0177] The second sprocket 71D has an annular cylindrical portion 71Db on its right side. The left portion 70Df of the pivot shaft 70D is inserted inside the annular cylindrical portion 71Db.

[0178] The first sprocket 69D and the second sprocket 71D are each formed such that their outer circumferences (the tooth-forming areas) are circular (excluding the tooth irregularities). Furthermore, the outer circumferences of the first sprocket 69D and the second sprocket 71D have the same radius. In other words, in the power transmission mechanism of this embodiment, neither acceleration nor deceleration occurs.

[0179] Chain 72 engages with the first sprocket 69D and the second sprocket 71D, respectively, and wraps around them.

[0180] A rotating plate 80D is connected to the right end of the annular cylindrical portion 71Db of the second sprocket 71D. This allows the rotating plate 80D and the second sprocket 71D to rotate together as a single unit.

[0181] The rotating plate 80D has multiple rotational force transmission teeth 80Db formed on its right side. In other words, the rotating plate 80D constitutes a ring gear-shaped rotating plate.

[0182] A second clutch plate 66D is positioned to the right of the rotating plate 80D. The second clutch plate 66D is a substantially disc-shaped member. The second clutch plate 66D is rotatably supported on the left portion 70Df of the pivot shaft 70D, and is also rotatably supported so as to be movable in the axial direction (left-right direction) on the left portion 70Df of the pivot shaft 70D. The second clutch plate 66D faces the rotating plate 80D on its left side and has a plurality of rotational force transmission teeth 66Da that can mesh with a plurality of rotational force transmission teeth 80Db of the rotating plate 80D.

[0183] Hereinafter, in this specification, the state in which the multiple rotational force transmission teeth 66Da of the second clutch plate 66D and the multiple rotational force transmission teeth 80Db of the rotating plate 80D are meshed with each other will be referred to as the "mesh state," and the state in which they are not meshed with each other will be referred to as the "non-mesh state."

[0184] In this embodiment, the second clutch plate 66D has two engaging claws 66Db on its right side (the side facing the first clutch plate 68D). The engaging claws 66Db are projections extending from near the outer edge of the right side of the second clutch plate 66D toward the first clutch plate 68D in the axial direction (i.e., toward the right). By engaging with the projection 68Da of the first clutch plate 68D, which will be described later, the engaging claws 66Db transmit the rotational force caused by the rotation of the main wheel 2, which is transmitted to the pivot shaft 70D side via the force transmission mechanism, from the second clutch plate 66D to the first clutch plate 68D. The two engaging claws 66Db are each positioned 180 degrees apart from each other in the circumferential direction of the second clutch plate 66D.

[0185] The torsion spring 67 has two ends, each connected to one of the two engaging claws 66Db of the second clutch plate 66D (the hole in the engaging claw 66Db where a small hole is formed as shown in Figure 25) and one of the two projections 68Da of the first clutch plate 68D (the hole in the projection 68Da where a small hole is formed as shown in Figure 25), respectively. The torsion spring 67 functions to create an appropriate gap between the engaging claw 66Db of the second clutch plate 66D, which is in a disengaged state during normal driving of the wheel structure 1D, and the projection 68Da of the first clutch plate 68D adjacent to the engaging claw 66Db. The torsion spring 67 also functions as a return mechanism that returns the second clutch plate 66D to the first clutch plate 68D in its initial position due to the biasing force of the torsion spring 67 (elastic body).

[0186] The first clutch plate 68D is a roughly disc-shaped member with a smaller diameter than the second clutch plate 66D. The first clutch plate 68D is pivotally supported on the pivot shaft 70D in a way that prevents rotation, as will be described later. In other words, the first clutch plate 68D is fixed to the pivot shaft 70D. The left side of the first clutch plate 68D faces the right side of the second clutch plate 66D.

[0187] In this embodiment, the first clutch plate 68D has two projections 68Da. The projections 68Da are projections that protrude radially outward from the outer peripheral surface of the first clutch plate 68D. The two projections 68Da are each spaced 180 degrees apart from each other in the circumferential direction of the first clutch plate 68D. The projections 68Da are circumferentially engageable with the engaging claws 66Db of the second clutch plate 66D.

[0188] Since the two protrusions 68Da of the first clutch plate 68D are spaced 180 degrees apart from each other in the circumferential direction, and the two engaging claws 66Db of the second clutch plate 66D are spaced 180 degrees apart from each other in the circumferential direction, the counterclockwise (CCW) rotation of the second clutch plate 66D will not be transmitted to the first clutch plate 68D until the CCW-side surface of the engaging claws 66Db of the second clutch plate 66D contacts the CW-side surface of the protrusions 68Da of the first clutch plate 68D. This is because, depending on the height of the step 11, when the main wheel 2 rides onto the upper surface 11b of the step, the second clutch plate 66D will rotate approximately 70° to 80° in the counterclockwise (CCW) direction, and at least 80° of play (gap) is required between the adjacent engaging claws 66Db and protrusions 68Da.

[0189] A rectangular hole 68Db is formed in the center of the first clutch plate 68D. The rectangular portion 70Dd of the pivot shaft 70D can be fitted into the rectangular hole 68Db. As a result, the first clutch plate 68D cannot rotate around the pivot shaft 70D.

[0190] The fork 73D has a U-shape with an open upper side when viewed in the front-to-back direction (direction of travel) in a normal driving state, and includes a holding portion 73Dc, a rotating portion 73De, and a connecting portion 73Df.

[0191] The retaining portion 73Dc opens in an arc shape and rotatably holds the outer peripheral surface of the second clutch plate 66D. The retaining portion 73Dc is formed in a substantially fan shape, with the tip of the substantially fan shape (opposite the pivot of the fan) opening in an arc shape. Specifically, the retaining portion 73Dc has two claw portions that form an arc-shaped opening, and the outer peripheral surface of the second clutch plate 66D is sandwiched between the two claw portions, thereby rotatably holding the second clutch plate 66D. More specifically, a circumferential groove is provided on the outer peripheral surface of the second clutch plate 66D, while a projection is provided on the inner surface of the two claw portions of the retaining portion 73Dc, and the projection and the groove are fitted together so as to be able to move relative to each other.

[0192] The rotating part 73De is formed in a substantially rod shape and has a hole 73Dd at one end through which the pivot shaft 70D is rotatably inserted. Furthermore, the rotating part 73De has a first fork guide 73Da to the right of the hole 73Dd and a second fork guide 73Db to the left of the hole 73Dd. The first fork guide 73Da and the second fork guide 73Db are composed of protrusions that partially protrude axially from the periphery of the hole 73Dd.

[0193] The rotating part 73De is rotatably supported between the first rotating shaft guide 70Da and the second rotating shaft guide 70Db (collectively referred to as the "pair of rotating shaft guides") of the rotating shaft 70D, and is movable in the axial direction of the rotating shaft 70D between the pair of rotating shaft guides. The axial movement of the rotating part 73De controls whether or not the rotational force due to the rotation of the main wheel 2 is transmitted from the rotating plate 80D to the second clutch plate 66D. Specifically, the first fork guide 73Da and the second fork guide 73Db of the rotating part 73De, and the first pivot shaft guide 70Da and the second pivot shaft guide 70Db of the pivot shaft 70D are formed such that when the end face of the second fork guide 73Db and the end face of the second pivot shaft guide 70Db are in contact, and the rotating part 73De rotates counterclockwise (CCW) around the pivot shaft 70D, causing both end faces to push against each other, the rotating part 73De moves to the right in the axial direction. Conversely, when the end face of the first fork guide 73Da and the end face of the first pivot shaft guide 70Da are in contact, and the rotating part 73De rotates clockwise (CW) around the pivot shaft 70D, causing both end faces to push against each other, the rotating part 73De moves to the left in the axial direction.

[0194] The connecting portion 73Df transmits the rotation and axial (left-right) movement of the rotating portion 73De about its pivot axis 70D to the holding portion 73Dc, and also transmits the rotation of the frame support member 6D itself about its pivot axis 70D, which triggers the rotation of the rotating portion 73De about its pivot axis 70D, from the first subframe 61D via the support shaft 61De.

[0195] The connecting portion 73Df is a cylindrical portion extending in the axial direction (left-right direction), with a hole 73Dfa formed on its inside. The support shaft 61De, which extends from the first subframe 61D, is fitted into the hole 73Dfa. The hole 73Dfa (connecting portion 73Df) and the support shaft 61De are rotatable relative to each other.

[0196] The connecting portion 73Df connects the other end of the rotating portion 73De (opposite the hole 73Dd) to the roughly fan-shaped pivot of the holding portion 73Dc in the axial direction (left-right direction), and transmits the rotation and axial (left-right) movement of the rotating portion 73De around the rotation axis 70D to the holding portion 73Dc.

[0197] As shown in Figures 25 and 26(b), the connecting portion 73Df extends axially (left-right direction) to connect the rotating portion 73De, located to the right of the rectangular portion 70Dd of the rotating shaft 70D, and the holding portion 73Dc, which holds the second clutch plate 66D, located to the left of the first clutch plate 68D into which the rectangular portion 70Dd is fitted. Therefore, it is positioned to straddle the first clutch plate 68D. In Figures 26(a) and 26(b), the engaging claw 66Db, the projection 68Da, and the fork 73D are shown with hatching for clarity. Also, in Figures 26(a) and 26(b), the elastic body (torsion spring 67) is omitted from the illustration.

[0198] Because the fork 73D is configured in this way, the fork 73D rotates around the pivot axis 70D in conjunction with the rotation of the frame support member 6D around the pivot axis 70D. Furthermore, interference occurs between the first fork guide 73Da and the second fork guide 73Db formed on the left and right sides of the hole 73Dd of the rotating part 73De and the first and second rotating shaft guides 70Da and 70Db of the rotating shaft 70D as the fork 73D (rotating part 73De) rotates. This interference causes the rotating part 73De to move axially (left and right), and this axial (left and right) movement of the rotating part 73De is transmitted to the holding part 73Dc by the connecting part 73Df. This causes the second clutch plate 66D held by the holding part 73Dc to move axially (left and right), and the fork 73D and the rotating shaft 70D can be controlled so that the rotational force transmission teeth 66Da of the second clutch plate 66D engage or disengage with the rotational force transmission teeth 80Db of the rotating plate 80D.

[0199] In this embodiment, the internal gear 61Da (not shown), the sun gear 63, the planetary gear 64, and the planetary carrier 65D constitute a planetary gear mechanism. That is, the internal gear 61Da, the sun gear 63, the planetary gear 64, and the planetary carrier 65D can reduce the rotational speed caused by the rotation of the main wheel 2 transmitted on the rotation axis 21 of the main wheel 2.

[0200] The clutch mechanism consists of a rotating plate 80D on which multiple rotational force transmission teeth 80Db are formed, a second clutch plate 66D on which multiple rotational force transmission teeth 66Da are formed on the left side and an engaging claw 66Db is formed on the right side, a first clutch plate 68D on which a projection 68Da is formed that protrudes radially outward, and a return mechanism consisting of a torsion spring 67 connected to the engaging claw 66Db of the second clutch plate 66D and the projection 68Da of the first clutch plate 68D. In other words, the rotating plate 80D, the second clutch plate 66D, the first clutch plate 68D, and the torsion spring 67 make it possible to switch whether or not to transmit the rotational force output from the force transmission mechanism that transmits the rotational force caused by the rotation of the main wheel 2 to the pivot shaft 70D to the pivot shaft 70D fixed to the frame 4.

[0201] The first sprocket 69D, the second sprocket 71D, and the chain 72 constitute a power transmission mechanism. In other words, the first sprocket 69D, the second sprocket 71D, and the chain 72 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 70D side of the main wheel 2.

[0202] The transmission control mechanism consists of a pivot shaft 70D on which the first pivot shaft guide 70Da and the second pivot shaft guide 70Db are formed, and a fork 73D on which the first fork guide 73Da and the second fork guide 73Db are formed and which rotatably holds the second clutch plate 66D. In other words, the pivot shaft 70D and the fork 73D can control the switching of the clutch mechanism's transmission on or off.

[0203] In this embodiment, the clutch mechanism is arranged on the pivot shaft 70D. Specifically, the clutch mechanism is arranged between the second sprocket 71D, which is rotatably supported on the left portion 70Df of the pivot shaft 70D and constitutes a power transmission mechanism, and the rotating portion 73De of the fork 73D, which is part of the transmission control mechanism and whose one end is rotatably supported on the pivot shaft 70D.

[0204] The planetary gear mechanism, clutch mechanism, power transmission mechanism, and transmission control mechanism described above constitute the rotation mechanism of the frame support member 6D. In other words, the planetary gear mechanism, clutch mechanism, power transmission mechanism, and transmission control mechanism enable the frame support member 6D and the pivot shaft 70D to rotate around the rotation axis 21 of the main wheel 2, and also enable the frame support member 6D and the rotation axis 21 of the main wheel 2 to rotate around the pivot shaft 70D.

[0205] 2. Other effects and benefits of the wheel structure configuration Next, other effects and advantages of the configuration of the wheel structure 1D in this embodiment will be described.

[0206] According to the wheel structure 1D, the clutch mechanism is composed of a ring gear-shaped rotating plate 80D having a plurality of rotational force transmission teeth 80Db, a second clutch plate 66D having a plurality of rotational force transmission teeth 66Da that face the rotating plate 80D on one side (left side) and can mesh with the plurality of rotational force transmission teeth 80Db of the rotating plate 80D, a first clutch plate 68D facing the other side (right side) of the second clutch plate 66D, and a return mechanism that returns the second clutch plate 66D to the initial position relative to the first clutch plate 68D by the biasing force of a torsion spring 67, and the first clutch plate 68 D has a projection 68Da that protrudes radially outward, and the second clutch plate 66D has an engaging claw 66Db on the other side (right side) that can engage with the projection 68Da of the first clutch plate 68D. As a result, when the mutually meshable rotational force transmission teeth 80Db and rotational force transmission teeth 66Da mesh, the rotational force caused by the rotation of the main wheel 2 output from the transmission control mechanism is transmitted to the second clutch plate 66D. Furthermore, when the mutually meshable engaging claw 66Db and projection 68Da engage with each other, the rotational force can be transmitted from the second clutch plate 66D to the first clutch plate 68D. In addition, if the meshable rotational force transmission teeth 80Db and rotational force transmission teeth 66Da become dismeshed, or if the engaging claw 66Db and projection 68Da cease to engage with each other, the rotational force will no longer be transmitted to the first clutch plate 68D. Thus, according to the wheel structure 1, since it is equipped with the clutch mechanism, it is possible to switch between transmitting and not transmitting the rotational force generated by the rotation of the main wheel 2 output from the power transmission mechanism to the pivot shaft 70D.

[0207] 3. Modified Examples of This Embodiment Next, a modified example of the configuration of the wheel structure 1D in this embodiment will be described.

[0208] In the above description, it was assumed that the first sprocket 69D and the second sprocket 71D have circular outer circumferences (tooth-forming areas). However, both the first sprocket 69D and the second sprocket 71D, or only the first sprocket 69D, may be non-circular, for example, elliptical. If the first sprocket 69D is non-circular, the movement of the main wheel 2 over the step 11 becomes smoother.

[0209] Although not shown in the figures, one of the engaging claws 66Db of the second clutch plate 66D and the projection 68Da of the first clutch plate 68D may have a convex portion that protrudes in the circumferential direction, and the other may have a recess that is concave in the circumferential direction. In this case, the convex / concave portion of the engaging claw 66Db of the second clutch plate 66D, which is movable in the axial direction (left-right direction), and the recess / convex portion of the projection 68Da will fit together, making the engagement between the engaging claw 66Db and the projection 68Da more secure and preventing the engaging claw 66Db and the projection 68Da from shifting in the axial direction (left-right direction) when engaged.

[0210] [5] Modifications common to all embodiments In the first to fourth embodiments described above, the number of planetary gears constituting the planetary gear mechanism was explained as being three. However, the number of planetary gears is not limited to three; at least one is sufficient, and there may be four or more.

[0211] In the first, second, and fourth embodiments described above, the power transmission mechanism was described as consisting of two sprockets and a chain, and in the third embodiment, the power transmission mechanism was described as consisting of three gears. However, these power transmission mechanisms are interchangeable in each embodiment. In other words, there is no correlation between the arrangement of the clutch mechanism and the configuration of the power transmission mechanism.

[0212] Furthermore, although not shown in the figures, the power transmission mechanism may consist of two pulleys and a belt in each embodiment. That is, the power transmission mechanism may consist of a first pulley rotatably supported on the rotation axis of the main wheel, a second pulley rotatably supported on the pivot shaft (if the clutch mechanism is located on the pivot shaft side) or non-rotatably (if the clutch mechanism is located on the rotation axis side of the main wheel), and a belt winding around the first and second pulleys.

[0213] In the first to fourth embodiments described above, the frame 4 was supported only by frame support members 6, 6A, 6C, and 6D 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 frame support member on the opposite side (right side) of the axial direction (left-right direction) of the wheel 2b. In other words, from the perspective of the frame 4, the support of the main wheel 2 is not limited to the frame support members 6, 6A, 6C, and 6D rotatably held on pivot shafts 70, 70A, and 70D 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 in the axial direction (left-right direction) of the main wheel 2.

[0214] [6] Application of snow tires In each embodiment, it is preferable that at least the tire 2a of the main wheel 2, among the tires 2a of the main wheel 2 and the tires 3a of the auxiliary wheel 3, is a snow tire with excellent grip performance on snowy roads, because it allows the vehicle to more reliably drive over steps even on slippery surfaces such as snow.

[0215] 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 axes 70, 70A, and 70D 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 structures 1, 1A, 1B, 1C, and 1D are 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.

[0216] 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. [Explanation of Symbols]

[0217] 1, 1A, 1B, 1C, 1D Wheel structure 2 main wheels 2a Tire 2b Wheel 3. Training wheels 3a tires 3b Wheel 4 frames 4a Canopy 4b Side wall part 4c Training wheel support part 5. Mounting section for transported goods platform 6, 6A, 6C, 6D Frame support members 10 flat surface 11 steps 11a Stepped end face 11b Upper surface of step 21. Main wheel rotation axis (main wheel axle) 31. The axis of rotation of the training wheels 41 Auxiliary shaft 60 Auxiliary subframe 60a Hole in auxiliary subframe 61, 61A, 61D First subframe 61a, 61Aa, 61Da Internal gears (holes in the first subframe) 61De spindle 62 Second Subframe 62a Circular hole in the second subframe 62b Stopper 63, 63A Sun gear 64 Planetary gears 65, 65A, 65D Planetary Carrier 65a, 65Da spindle 65b Rotational force transmission teeth of planetary carrier 65 bs Vertical surface of rotational force transmission teeth 65bk Inclined surface of rotational force transmission tooth 65De Annular cylindrical part 66, 66A, 66D Second clutch plate 66a, 66Aa, 66Da Rotational force transmission teeth of the second clutch plate 66as, 66Aas Vertical surface of rotational force transmission teeth 66ak, 66Aak Inclined surface of rotational force transmission tooth 66b, 66Ab, 66Db Engaging claws of the second clutch plate 66Ab1 First contact surface of the engaging claw 66Ab2 Second contact surface of the engaging claw 66Abk Inclined surface of engaging claw 67 Torsion spring 67A Spring 68, 68A, 68D First clutch plate 68a, 68Aa, 68Da Protrusions of the first clutch plate 68Db Square hole in the first clutch plate 69, 69D First sprocket 69C First gear 70, 70A, 70D Rotary shaft 70a, 70Da First rotation axis guide for the rotation axis 70b, 70Db Second pivot shaft guide for the pivot shaft 70Dd Square part of the pivot axis 70f, 70Df Left side of the pivot axis 71, 71D Second sprocket 71a, 71Da Annular projection of the second sprocket 71Db Annular cylindrical part of the second sprocket 71C Second gear 71Ca Annular projection of the second gear 72 chain 73, 73D Fork 73a, 73Da Fork's First Fork Guide 73b, 73Db Fork's Second Fork Guide 73c, 73Dc Fork retaining section 73d Fork holes 73De Fork Rotating Part 73Dd Hole in the rotating part of the fork 73Df Fork coupling section 73Dfa Hole in the connecting part of the fork 75 Third gear 80, 80D Rotating Plate 80a Annular projection of the rotating plate 80b, 80Db Rotating plate rotation force transmission teeth 80 bs Vertical surface of rotational force transmission teeth 80bk Inclined surface of rotational force transmission tooth VL vertical line

Claims

1. 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 mounting platform 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 comes into contact with 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, 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 wheel structure is characterized by comprising: 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 pivot 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 pivot axis fixed to the frame; and a transmission control mechanism that controls the switching of the clutch mechanism on or off.

2. The clutch mechanism comprises a ring gear-shaped rotating plate having a plurality of rotational force transmission teeth, a second clutch plate having a plurality of rotational force transmission teeth facing the rotating plate on one side and capable of meshing with the plurality of rotational force transmission teeth of the rotating plate, a first clutch plate facing the other side of the second clutch plate, and a return mechanism that returns the second clutch plate to its initial position relative to the first clutch plate by the biasing force of an elastic body. The first clutch plate has a projection that protrudes radially outward, The wheel structure according to claim 1, characterized in that the second clutch plate has an engaging claw on the other side that can engage with a projection of the first clutch plate.

3. The clutch mechanism comprises a ring gear-shaped rotating plate having a plurality of rotational force transmission teeth, a second clutch plate having a plurality of rotational force transmission teeth facing the rotating plate on one side and capable of meshing with the plurality of rotational force transmission teeth of the rotating plate, a first clutch plate facing the other side of the second clutch plate, and a return mechanism that returns the second clutch plate to its initial position relative to the first clutch plate by the biasing force of an elastic body. The second clutch plate has a projection that protrudes radially outward, The wheel structure according to claim 1, characterized in that the first clutch plate has an engaging claw on the other side that can engage with a projection of the second clutch plate.

4. The clutch mechanism comprises a ring gear-shaped rotating plate having a plurality of rotational force transmission teeth, a second clutch plate having a plurality of rotational force transmission teeth facing the rotating plate on one side and capable of meshing with the plurality of rotational force transmission teeth of the rotating plate, a first clutch plate facing the other side of the second clutch plate, and a return mechanism that returns the second clutch plate to its initial position relative to the first clutch plate by the biasing force of an elastic body. The first clutch plate has an engaging claw extending in the axial direction of the rotation shaft on the side facing the other side of the second clutch plate, The wheel structure according to claim 1, characterized in that the second clutch plate has an engaging claw on the other side that can engage with the engaging claw of the first clutch plate.

5. Each of the multiple rotational force transmission teeth of the rotating plate has a vertical surface perpendicular to the counterclockwise (CCW) direction, and an inclined surface that slopes from the apex of the vertical surface in the axial direction away from the second clutch plate and in the clockwise (CW) direction. The wheel structure according to claim 2, characterized in that each of the plurality of rotational force transmission teeth of the second clutch plate has a vertical surface perpendicular to the clockwise (CW) direction and an inclined surface that is inclined from the apex of the vertical surface in the axial direction away from the rotating plate 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.

6. The return mechanism of the clutch mechanism is a spring connected to the first clutch plate and the second clutch plate, respectively, which biases the second clutch plate clockwise (CW) so that the engaging claw of the second clutch plate contacts the projection of the first clutch plate. The wheel structure according to claim 5, characterized in that the engaging claw of the second clutch plate has a first contact surface that can contact the projection of the first clutch plate, a second contact surface that can contact the projection of the first clutch plate and is formed at a position away from the first contact surface in the counterclockwise (CCW) direction and in the axial direction toward the first clutch plate, and inclined surfaces connected to the first contact surface and the second contact surface, respectively.

7. The wheel structure according to claim 1, characterized in that the clutch mechanism is disposed between the main wheel and the planetary gear mechanism.

8. The wheel structure according to claim 1, characterized in that the clutch mechanism is disposed between the planetary gear mechanism and the component of the power transmission mechanism that is provided on the rotation axis of the main wheel.

9. The wheel structure according to claim 1, characterized in that the clutch mechanism is disposed on the pivot shaft.

10. The wheel structure according to claim 1, characterized in that the power transmission mechanism comprises a first sprocket rotatably supported on the rotation axis of the main wheel, a second sprocket fixed to the rotation axis, and a chain that meshes with the first sprocket and the second sprocket, respectively, and winds around the first sprocket and the second sprocket.

11. The power transmission mechanism comprises a first pulley rotatably supported on the rotation axis of the main wheel, a second pulley fixed to the pivot shaft, and a wire winding around the first and second pulleys. The wheel structure according to claim 1, characterized in that the first pulley and the second pulley each have a fixing portion for fixing the wire.

12. The wheel structure according to claim 1, characterized in that the power transmission mechanism comprises a first gear rotatably supported on the rotation axis of the main wheel, a second gear fixed to the pivot shaft, and a third gear rotatably supported on an auxiliary shaft disposed between the rotation axis of the main wheel and the pivot shaft, and meshing with the first gear and the second gear, respectively.

13. A transport device characterized by comprising a wheel structure according to any one of claims 1 to 12.

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