Wheeled structure and carrier

Abstract

To provide a wheeled structure and a carrier that can perform a smooth go-over operation with little force from the beginning of going over a step to the end thereof.SOLUTION: According to this wheeled structure, a larger-diameter main wheel is placed at the back side in the travelling direction of a frame, and a smaller-diameter sub wheel is placed at the front side in the travelling direction. This wheeled structure is configured to cause the sub wheel to abut the upper surface of a step along with a touch of the main wheel to the step, and then to cause the main wheel to go over the upper surface of the step. The frame is provided with a frame support member. The frame support member is provided with a rotation mechanism provided with a turn shaft placed in parallel with the rotation shaft of the main wheel. Moreover, provided between the rotation shaft of the main wheel and the turn shaft are: a transmission mechanism that decelerates the counterclockwise rotation of the main wheel and transmits the decelerated rotation to the turn shaft; a transmission control mechanism that controls whether or not to transmit the rotation of the main wheel to the turn shaft; a clutch mechanism that changes the rotation of the turn shaft in accordance with the rotation of a clutch plate; and a return mechanism that returns the clutch mechanism to the initial position by force applied from an elastic body.SELECTED DRAWING: Figure 1

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 that can easily climb up steps. [Background technology]

[0002] In transport devices that use human power as a propulsion force, such as luggage transport carts, baby strollers, and wheelchairs, small wheel structures are often used as wheel structures in terms of size and weight. However, the environments in which these transport devices are used have many steps due to differences in road surface height and obstacles, and it is not easy to make the wheels smoothly ride up the step surface with little force without giving impact to the transported object.

[0003] Therefore, various techniques have been proposed in the past in which a small-diameter auxiliary wheel is provided in front of the original wheel (main wheel), and when approaching a step, the auxiliary wheel is first brought into contact with the top surface of the step, and then the main wheel is caused to ride up onto the top surface of the step (for example, Patent Document 1).

[0004] However, with conventional technology, the behavior of the main wheels when returning to their initial state differed depending on the amount of load applied to the main wheels, and the behavior before and after climbing over a step could not be said to be smooth, so further improvement is required.

[0005] For example, in technology using springs such as that in Patent Document 1, if the load on the main wheels is greater than the restoring force of the spring, the main wheels cannot be returned to their original position. Conversely, if the load on the main wheels is less than the restoring force of the spring, the main wheels return to their original position too suddenly, which may result in the transported goods being subjected to impact and the operation before and after climbing over a step cannot be said to be smooth. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2006-7855 A Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the problems with the conventional technology described above, an object of the present invention is to provide a wheel structure and a transport device that can smoothly carry out the step climbing operation with little force from the start to the end. [Means for solving the problem]

[0008] As a result of intensive research into solving the above problems, the present inventors have found that the above problems can be solved by the invention described below, and have completed the present invention.

[0009] The invention described in claim 1 is A wheel structure in which a large-diameter main wheel is disposed at the rear of a frame on which a transported object placement platform mounting portion is provided, and a small-diameter auxiliary wheel is disposed at the front of the frame, and the auxiliary wheel comes into contact with an upper surface of the step as the main wheel comes into contact with the 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 rotation mechanism having a rotation shaft that is arranged parallel to a rotation shaft of the main wheel, This wheel structure is characterized in that, between the rotation axis of the main wheel and the pivot shaft, there are provided a transmission mechanism that decelerates the counterclockwise (CCW: Counter Clock Wise) rotation of the main wheel and transmits it to the pivot shaft, a transmission control mechanism that controls whether or not to transmit the rotation of the main wheel to the pivot shaft, a clutch mechanism that switches the counterclockwise (CCW) rotation of the main wheel by rotating a clutch plate so that the pivot shaft rotates counterclockwise (CCW) or clockwise (CW: Clock Wise) and, further, a return mechanism that returns the clutch mechanism to its initial position by the biasing force of an elastic body. Note that clockwise (CW) and counterclockwise (CCW) refer to the rotational directions when the wheel structure moving leftward is viewed from the left side.

[0010] The invention described in claim 2 is During normal driving, the counterclockwise (CCW) rotation of the main wheel is not transmitted to the pivot shaft, and the main wheel moves forward while the auxiliary wheel is lifted off the ground. When the main wheel contacts the step, the frame support member rotates counterclockwise (CCW) by the rotating shaft to which the counterclockwise (CCW) rotation of the main wheel is transmitted as is, and the auxiliary wheel descends and abuts on the upper surface of the step, and then the main wheel rotating counterclockwise (CCW) rises and rides onto the upper surface of the step, The wheel structure according to claim 1, characterized in that after the main wheel rides up onto the top surface of the step, the counterclockwise (CCW) rotation of the main wheel is replaced by the clockwise (CW) rotation of the main wheel, and the frame support member rotates clockwise (CW) by the pivot shaft to which the auxiliary wheel rises and returns to its initial position, while the main wheel rotates counterclockwise (CCW) to move forward on the top surface of the step.

[0011] The invention described in claim 3 is The wheel structure described in claim 1 or 2, characterized in that the frame support member is provided with a first subframe having a hole portion through which the rotation shaft of the main wheel is inserted, and a second subframe having a hole portion through which a rotation shaft for rotating the frame support member is inserted, and the rotation mechanism is arranged between the first subframe and the second subframe.

[0012] The invention described in claim 4 is The wheel structure described in claim 3, characterized in that the first subframe is box-shaped and the second subframe is lid-shaped, and the rotation mechanism, the transmission mechanism, the transmission control mechanism, the clutch mechanism, and the return mechanism are housed within a housing formed by the first subframe and the second subframe.

[0013] The invention described in claim 5 is The wheel structure according to claim 1 or 2, characterized in that the elastic body is a spring or a spiral spring.

[0014] The invention described in claim 6 is A transport device comprising the wheel structure according to claim 1 or 2.

[0015] The invention described in claim 7 is The rotation mechanism includes: A first gear inserted and supported on a rotation shaft of the main wheel; A second gear that meshes with the first gear; a third gear integrated with the clutch mechanism; a fourth gear having a toothless portion and a toothed portion and arranged to mesh with the third gear at the toothed portion; an intermediate shaft that is disposed parallel to a rotation axis of the main wheel, and has one end that is in upright contact with the second subframe so as to rotatably support each of the second gear, the third gear, the fourth gear, and the clutch plate; The wheel structure described in claim 1 or claim 2, characterized in that it is configured to include a rotating shaft through which the fourth gear fixed to the frame is inserted, the rotating shaft being inserted through a hole portion of the second subframe.

[0016] The invention described in claim 8 is The elastic body is When the frame support member is located at the initial position, in a state where it is contracted relative to a free state, one end is engaged with the second gear and the other end is engaged with the clutch plate, 8. The wheel structure of claim 7, wherein the second gear is biased to engage the clutch plate in a counterclockwise (CCW) direction.

[0017] The invention described in claim 9 is 8. The wheel structure according to claim 7, wherein the radius of the first gear is smaller than the radius of the second gear.

[0018] The invention described in claim 10 is the second gear has a diameter larger than that of the clutch plate, and includes an engagement pawl on a side surface of the clutch plate that is radially outward from an outer edge of the clutch plate, The clutch plate is disc-shaped and has a protrusion on an outer circumferential surface thereof that protrudes radially outward. 8. The wheel structure according to claim 7, wherein the second gear and the clutch plate are engaged with each other by the engaging claw and the protrusion.

[0019] The invention described in claim 11 is A recess or a protrusion is formed on a surface of the clutch plate facing the third gear, A protrusion that can be fitted into a recess of the clutch plate or a recess that can be fitted into the protrusion of the clutch plate is formed on a surface of the third gear that faces the clutch plate, The wheel structure as described in claim 7, characterized in that the clutch plate and the third gear are integrated by fitting a concave or convex portion of the clutch plate into a convex or concave portion of the third gear.

[0020] The invention described in claim 12 is 8. The wheel structure according to claim 7, wherein the radius of the third gear is smaller than the radius of the toothed portion of the fourth gear.

[0021] The invention described in claim 13 is The second subframe has a circular hole at an end portion supported by the rotating shaft, the fourth gear includes a cylindrical protrusion having the same diameter as an inner diameter of the circular hole on a surface facing the second subframe, The protrusion is rotatably fitted into the circular hole, 8. The wheel structure according to claim 7, wherein the second sub-frame is configured to be rotatably supported on the rotation shaft.

[0022] The invention described in claim 14 is When the wheel structure to which the transported object carrier is attached is viewed from the side, The wheel structure described in claim 7, characterized in that the positions of the rotation shaft and the pivot shaft are set so that when the frame support member rotates clockwise (CW) and the toothed portions of the third gear and the fourth gear are released from their meshed state, the center of the rotation shaft is located forward in the direction of travel of a vertical line passing through the center of the rotation shaft.

[0023] The invention described in claim 15 is The wheel structure described in claim 7, characterized in that the frame support member is provided with a stopper protruding toward the frame on the side of the second subframe facing the frame, and is configured to stop at the fixed position when rotated clockwise (CW) by the stopper abutting the end face of the frame.

[0024] The invention described in claim 16 is The rotation mechanism includes: A first gear inserted and supported on a rotation shaft of the main wheel; A second gear that meshes with the first gear; a third gear and a fourth gear arranged to mesh with each other; an intermediate shaft having one end in contact with the second subframe and perpendicular to the second subframe; The clutch mechanism includes two clutch plates, a first clutch plate and a second clutch plate. the second gear and the third gear are each rotatably supported by the intermediate shaft, The first clutch plate and the second clutch plate are journalled on the same side of either the intermediate shaft or the rotating shaft, The rotation shaft is fixed to the frame, When the first clutch plate and the second clutch plate are rotatably supported on the intermediate shaft, and the fourth gear is journaled and fixed to the rotating shaft, one surface of the second clutch plate faces the second gear and the other surface faces one surface of the first clutch plate, the first clutch plate is integrated with the third gear at a surface other than a surface facing the second clutch plate, When the first clutch plate is journaled and fixed to the rotating shaft, and the second clutch plate and the fourth gear are journaled and rotatably supported on the rotating shaft, the third gear is integral with the second gear, one surface of the second clutch plate faces the fourth gear and the other surface faces one surface of the first clutch plate, The transmission mechanism includes: a plurality of pawls that can mesh with each other are provided on the outer periphery of the facing surfaces of the second gear or the fourth gear and the second clutch plate, and an engagement portion that enables the second clutch plate and the first clutch plate to engage with each other, and when the pawls are meshed with each other and the engagement portion is engaged, the rotation of the main wheel is transmitted to the rotating shaft; The wheel structure described in claim 1 or claim 2, characterized in that the clutch mechanism transmits the counterclockwise (CCW) rotation of the main wheel so that the rotating shaft rotates clockwise (CW) by rotation of the second clutch plate, and allows counterclockwise (CCW) rotation of the rotating shaft when the counterclockwise (CCW) rotation of the main wheel stops.

[0025] The invention described in claim 17 is as follows: the elastic body has one end engaged with the second clutch plate and the other end engaged with the first clutch plate in a state in which the elastic body is contracted relative to a free state when the frame support member is located at an initial position, The wheel structure of claim 16, characterized in that when the first clutch plate and the second clutch plate are rotatably supported on the intermediate shaft and the fourth gear is rotatably fixed to the rotating shaft, the second clutch plate is biased to engage with the first clutch plate in a counterclockwise (CCW) direction, and when the first clutch plate is rotatably fixed to the rotating shaft and the second clutch plate and the fourth gear are rotatably supported, the second clutch plate is biased to engage with the first clutch plate in a clockwise (CW) direction.

[0026] The invention described in claim 18 is When the wheel structure to which the transported object carrier is attached is viewed from the side, The wheel structure described in claim 16, characterized in that the positions of the rotating shaft and the pivoting shaft are set so that when the frame support member rotates clockwise (CW) and the second gear and the second clutch plate are released from their meshed state, the center of the rotating shaft is located forward in the direction of travel of a vertical line passing through the center of the rotating shaft.

[0027] The invention described in claim 19 is The wheel structure according to claim 16, characterized in that the third gear and the fourth gear are non-circular gears that are constantly in mesh with each other.

[0028] The invention described in claim 20 is The transmission control mechanism includes: a moving mechanism that moves the second clutch plate in an axial direction of the intermediate shaft, The wheel structure described in claim 16, characterized in that the moving mechanism moves the second clutch plate toward the second gear when the rotating shaft rotates counterclockwise (CCW) to engage the claws of the second gear and the second clutch plate, and moves the second clutch plate in the opposite direction to the second gear when the rotating shaft rotates clockwise (CW) from a state in which the second gear and the second clutch plate are engaged, to release the engagement.

[0029] The invention described in claim 21 is The rotation mechanism includes: A first gear inserted and supported on a rotation shaft of the main wheel; A second gear that meshes with the first gear; a third gear integral with the second gear; a fourth gear arranged to mesh with the third gear; an intermediate shaft having one end in contact with the second subframe and perpendicular to the second subframe; The clutch mechanism includes two clutch plates, a first clutch plate and a second clutch plate. the second gear and the third gear are rotatably supported by the intermediate shaft, the rotating shaft is fixed to the frame, the fourth gear and the second clutch plate are rotatably supported by the rotating shaft and face each other, and the first clutch plate is supported and fixed to the rotating shaft and faces the second clutch plate, the transmission mechanism includes a plurality of mutually meshable pawls on outer peripheral edges of opposing surfaces of the fourth gear and the second clutch plate, and an engagement portion that enables the second clutch plate and the first clutch plate to engage with each other, and transmits rotation of the main wheel to the rotating shaft when the pawls mesh with each other and the engagement portions are engaged; The wheel structure described in claim 16, characterized in that the clutch mechanism transmits the counterclockwise (CCW) rotation of the main wheel so that the rotating shaft rotates clockwise (CW) by rotation of the second clutch plate, and allows the rotating shaft to rotate counterclockwise (CCW) when the counterclockwise (CCW) rotation of the main wheel stops.

[0030] The invention described in claim 22 is The transmission control mechanism includes: a moving mechanism for moving the second clutch plate in an axial direction of the rotating shaft, The vehicle structure described in claim 21, characterized in that the moving mechanism moves the second clutch plate toward the fourth gear when the rotating shaft rotates counterclockwise (CCW) to engage the pawls of the fourth gear and the second clutch plate, and moves the second clutch plate in the opposite direction to the fourth gear when the rotating shaft rotates clockwise (CW) from a state in which the fourth gear and the second clutch plate are engaged, to disengage the engagement. Effect of the Invention

[0031] According to the present invention, a wheel structure and a transport device can be provided that can perform a smooth climbing operation with little force from the start to the end of climbing over a step. [Brief description of the drawings]

[0032] [Figure 1] 1 is a perspective view showing a schematic configuration of a wheel structure according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an exploded view of the wheel structure shown in FIG. [Diagram 3] FIG. 2 is a front perspective view of the assembly of the wheel structure shown in FIG. 1. [Figure 4] FIG. 2 is a perspective side view of the assembly of the wheel structure shown in FIG. 1. [Diagram 5] 2 is an exploded view of a frame support member in the wheel structure shown in FIG. 1. [Figure 6] 1 is a side perspective view illustrating a state during normal driving of a wheel structure according to an embodiment of the present invention; [Figure 7] FIG. 7 is a side perspective view illustrating a state (a state after FIG. 6) immediately before the wheel structure according to the embodiment of the present invention runs over a step. [Figure 8] FIG. 8 is a side perspective view illustrating a state when the wheel structure according to the embodiment of the present invention starts to climb over a step (a state after FIG. 7). [Figure 9]9 is a side perspective view illustrating a state (a state after FIG. 8) immediately after the wheel structure according to the embodiment of the present invention runs over a step. FIG. [Figure 10] 10 is a side perspective view illustrating a state (a state after FIG. 9) of the wheel structure according to the embodiment of the present invention when the wheel structure moves forward a little after climbing over a step. FIG. [Figure 11] 11 is a side perspective view illustrating a state (a state after FIG. 10) of the wheel structure according to the embodiment of the present invention when the wheel structure has further advanced forward after climbing over a step. FIG. [Figure 12] 12 is a side perspective view illustrating a state (a state after FIG. 11) immediately before the wheel structure according to the embodiment of the present invention completes climbing over a step. FIG. [Figure 13] FIG. 11 is a simplified exploded view of a wheel structure according to another embodiment of the present invention. [Figure 14] FIG. 11 is an overall component diagram of a wheel structure according to another embodiment of the present invention. [Figure 15] FIG. 11 is an exploded view of a frame support member according to another embodiment of the present invention. [Figure 16] 1A is a perspective view of the inside of the frame support member when the transmission is released, seen from diagonally above the front right; FIG. 1B is a front view of the inside of the frame support member when the transmission is released; and FIG. 1C is a perspective view of the inside of the frame support member when the transmission is released, seen from diagonally above the rear left. [Figure 17] 1A is a perspective view of the inside of the frame support member with the transmission released and the fourth frame removed, viewed from diagonally above the rear left, and FIG. 1B is a partially enlarged view of FIG. [Figure 18] 11 is a perspective view of the inside of the frame support member when in a transmission state, as viewed diagonally from above and rear left. FIG. [Figure 19] 1A is a side perspective view of the wheel structure during normal driving, FIG. 1B is a perspective view of the inside of the frame support member during normal driving, seen from diagonally above the rear left, and FIG. 1C is a front view of the inside of the frame support member during normal driving, seen from the front. [Figure 20]1A is a side perspective view of the wheel structure immediately after contact with a step, and FIG. 1B is a perspective view of the inside of the frame support member as viewed diagonally from above and rear left immediately after contact with the step. [Figure 21] 1A is a side perspective view of the wheel structure at a rotation angle of 30°, and FIG. 1B is a perspective view of the inside of the frame support member at a rotation angle of 30°, seen diagonally from above and rear left. [Figure 22] 1A is a side perspective view of the wheel structure at a rotation angle of 37°, FIG. 1B is a perspective view of the inside of the frame support member at a rotation angle of 37°, seen from diagonally above and to the rear left, and FIG. 1C is a front view of the inside of the frame support member at a rotation angle of 37°, seen from the front. [Figure 23] 1A is a side perspective view of the wheel structure at a rotation angle of 42°, FIG. 1B is a perspective view of the inside of the frame support member at a rotation angle of 42°, seen from diagonally above and to the rear left, and FIG. 1C is a front view of the inside of the frame support member at a rotation angle of 42°, seen from the front. [Figure 24] 1A is a side perspective view of the wheel structure at a rotation angle of 80°, and FIG. 1B is a perspective view of the inside of the frame support member at a rotation angle of 80° as viewed from diagonally above and rear left. [Diagram 25] 1A is a side perspective view of the wheel structure when it has moved forward a little from a rotation angle of 80°, and FIG. 1B is an oblique view of the inside of the frame support member when it has moved forward a little from a rotation angle of 80°, as seen from diagonally above and behind the vehicle. [Figure 26] 1A is a side perspective view of the wheel structure at a rotation angle of 110°, and FIG. 1B is a perspective view of the inside of the frame support member at a rotation angle of 110° as viewed from diagonally above and rear left. [Figure 27] 1A is a side perspective view of the wheel structure when the rotation angle is reduced to 30°, FIG. 1B is a perspective view of the inside of the frame support member when the rotation angle is reduced to 30°, seen from diagonally above the rear left, and FIG. 1C is a front view of the inside of the frame support member when the rotation angle is reduced to 30°. [Figure 28]1A is a side perspective view of the wheel structure when the rotation angle is reduced to 25°, FIG. 1B is a perspective view of the inside of the frame support member when the rotation angle is reduced to 25°, seen from diagonally above the rear left, and FIG. 1C is a front view of the inside of the frame support member when the rotation angle is reduced to 25°. [Figure 29] 1A is a side perspective view of the wheel structure when the rotation angle is reduced to 18°, FIG. 1B is a perspective view of the inside of the frame support member when the rotation angle is reduced to 18°, seen from diagonally above the rear left, and FIG. 1C is a front view of the inside of the frame support member when the rotation angle is reduced to 18°. [Diagram 30] 13 is a perspective view of the inside of the frame support member when it has returned to the initial position (rotation angle 0°), as viewed from diagonally above and rear left. FIG. [Diagram 31] FIG. 13 is a side perspective view of the wheel structure when it has returned to its initial state. [Diagram 32] FIG. 11 is an exploded view of a frame support member in still another embodiment of the present invention. [Diagram 33] 1A is a perspective view of the inside of the frame support member during normal driving, (b) is a perspective view of the inside of the frame support member at a rotation angle of 30°, (c) is a perspective view of the inside of the frame support member at a rotation angle of 37°, (d) is a perspective view of the inside of the frame support member at a rotation angle of 42°, (e) is a perspective view of the inside of the frame support member at a rotation angle of 80°, (f) is a perspective view of the inside of the frame support member at a rotation angle of 140°, and (g) is a perspective view of the inside of the frame support member when viewed from diagonally above rear left and right when the pawl of the second clutch plate contacts the pawl of the fourth gear. [Diagram 34]1A is a perspective view of the inside of the frame support member when the rotation angle has been reduced to 110°, as viewed from the upper rear left; FIG. 1B is a perspective view of the inside of the frame support member when the rotation angle has been reduced to 30°, as viewed from the upper rear left; FIG. 1C is a perspective view of the inside of the frame support member when the rotation angle has been reduced to 25°, as viewed from the upper rear left; FIG. 1D is a perspective view of the inside of the frame support member when the rotation angle has been reduced to 18°; and FIG. 1E is a perspective view of the inside of the frame support member when the second clutch plate has been initialized, as viewed from the upper rear left. [Diagram 35] FIG. 1(a) is an exploded view of a frame support member in which non-circular gears are used for the third and fourth gears, and FIG. 1(b) is a perspective view of the frame support member in which non-circular gears are used for the third and fourth gears, as viewed from diagonally above the front left. [Diagram 36] FIG. 13 is a diagram showing the relationship between frame height and travel distance when circular gears are used for the third gear and the fourth gear. [Figure 37] FIG. 13 is a diagram showing the relationship between frame height and travel distance when non-circular gears are used for the third gear and the fourth gear. [Figure 38] FIG. 13 is a diagram illustrating the height of a frame. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] [A] Features of the present invention First, the features of the present invention will be described.

[0034] [1] Basic configuration of the wheel structure according to the present invention The wheel structure of the present invention has a large diameter main wheel arranged at the rear of the frame on which the transported object platform mounting portion is provided, and a small diameter auxiliary wheel arranged at the front of the frame, and is configured so that when the main wheel comes into contact with the step, the auxiliary wheel abuts on the upper surface of the step, and then the main wheel rides up onto the upper surface of the step.

[0035] The frame is provided with a frame support member that supports the frame, and the frame support member is provided with a rotation mechanism equipped with a rotation shaft arranged parallel to the rotation shaft of the main wheels. Between the rotation shaft of the main wheels and the rotation shaft, there are provided a transmission mechanism that reduces the speed of the counterclockwise (CCW) rotation of the main wheels and transmits it to the rotation shaft, a transmission control mechanism that controls whether or not to transmit the rotation of the main wheels to the rotation shaft, a clutch mechanism that switches the counterclockwise (CCW) rotation of the main wheels so that the rotation shaft rotates counterclockwise (CCW) or clockwise (CW) by rotation of a clutch plate, and a return mechanism that returns the clutch mechanism to its initial position by the biasing force of an elastic body.

[0036] By providing such a rotation mechanism, transmission mechanism, transmission control mechanism, clutch mechanism and its return mechanism and appropriately controlling the movement of the main wheels and auxiliary wheels, the step-climbing operation can be performed smoothly with little force from the start to the end.

[0037] The wheel structure according to the present invention is configured to perform the following operations during normal running, when contacting a step, and when climbing over a step.

[0038] First, during normal driving, the counterclockwise (CCW) rotation of the main wheels caused by the propulsive force in the direction of travel is not transmitted to the pivot shaft, and the main wheels move forward while the auxiliary wheels remain lifted off the ground.

[0039] When the main wheel of the wheel structure approaches a step and comes into 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), and the auxiliary wheel descends and comes into contact with the top surface of the step.

[0040] After that, the main wheel that comes into contact with the corner of the step rotates counterclockwise (CCW) with the corner of the step as a fulcrum in accordance with the rotation of the frame support member, and the main wheel rides up onto the top of the step smoothly and with little force.

[0041] After the main wheels reach the top of the step, the propulsive force in the direction of travel causes the main wheels to rotate counterclockwise (CCW) and move forward along the top of the step, while the counterclockwise (CCW) rotation of the main wheels is transmitted to a rotating shaft which causes the frame support member to rotate clockwise (CW), causing the auxiliary wheels to rise and return to their initial position.

[0042] Note that clockwise (CW, forward rotation) and counterclockwise (CCW, reverse rotation) refer to the direction of rotation when the wheel structure moving leftward is viewed from the left side.

[0043] [2] Effects of the present invention According to the present invention, when climbing over a step, the main wheels can be rotated with a smaller force to cause the wheels to climb over the upper surface of the step. In addition, after the main wheels have climbed over the step, the frame can be raised to the initial position with a smaller force. In addition, the wheel structure can be caused to climb over the upper surface of the step by a single action of moving the wheel structure forward. Therefore, a large force is not required throughout the entire process of climbing over the step, and the step can be climbed over smoothly.

[0044] [3] Preferred embodiment of the wheel structure according to the present invention The wheel structure according to the present invention preferably has the following features.

[0045] 1. Frame support member In the present invention, it is preferable that the frame support member is provided with a first subframe having a hole portion through which the rotation shaft of the main wheel is inserted, and a second subframe having a hole portion through which a rotation shaft for rotating the frame support member is inserted, and that a rotation mechanism is arranged between the first subframe and the second subframe.

[0046] In addition, it is preferable that the frame support member has a housing formed by a box-shaped first subframe and a lid-shaped second subframe, and the above-mentioned rotation mechanism, transmission mechanism, transmission control mechanism, clutch mechanism, and return mechanism are housed and integrated in the housing, which makes it possible to easily reduce the size of the wheel structure and to achieve a neater appearance.

[0047] In addition, each mechanism may be integrated without being stored. In this case, the rotating shaft can be supported on both sides of the frame, making it possible to use larger gears and support a larger load.

[0048] 2. Elastic body From the viewpoint of being able to easily expand and contract and control the operation of each mechanism, it is preferable that the elastic body be a spring or a spiral spring.

[0049] [4] Transportation equipment By attaching the wheel structure of the present invention to the lower part (underside, lower end) of various transport item loading platforms via the transport item loading platform mounting part, it can be made into a transport device suitable for transporting items corresponding to the attached transport item loading platform.

[0050] Specific examples of transported objects include various types of luggage, animals, people, etc., and examples of transport equipment include luggage carts, strollers, wheelchairs, etc.

[0051] [B] Specific embodiment The present invention will be specifically described below with reference to the drawings using first to third embodiments, however, these embodiments are merely examples and the present invention is not limited to these.

[0052] [1] First embodiment 1. Wheel structure configuration In this embodiment, in order to specifically realize the above-mentioned features and effects of the present invention, the wheel structure is configured as follows.

[0053] Rotation mechanism (1) The first gear is inserted and supported on the rotating shaft of the main wheel. (2) A second gear that meshes with the first gear (3) The third gear integrated with the clutch mechanism (4) A fourth gear having a toothless portion and a toothed portion and arranged to mesh with the third gear at the toothed portion. (5) An intermediate shaft that is arranged parallel to the rotation axis of the main wheels and has one end that is in upright contact with the second subframe so as to rotatably support the second gear, the third gear, the fourth gear, and the clutch plate. (6) A rotating shaft through which a fourth gear fixed to the frame is inserted and which is inserted through a hole in the second subframe. The present invention is configured with the following features.

[0054] The elastic body is contracted relative to its free state when the frame support member is located in the initial position, and has one end engaged with the second gear and the other end engaged with the clutch plate, and is biased so that the second gear engages with the clutch plate in a counterclockwise (CCW) direction.

[0055] In this case, it is preferable that the radius of the first gear is smaller than the radius of the second gear.

[0056] It is also preferable that the second gear has a larger diameter than the clutch plate and has an engaging claw radially outward from the outer edge of the clutch plate on its side facing the clutch plate, and that the clutch plate is disc-shaped and has a protrusion on its outer circumferential side that protrudes radially outward, so that the second gear and clutch plate engage with each other via the engaging claw and protrusion.

[0057] It is also preferable that a recess or a protrusion is formed on the surface of the clutch plate facing the third gear, and a protrusion that can fit into the recess of the clutch plate or a recess that can fit into the protrusion of the clutch plate is formed on the surface of the third gear facing the clutch plate, and that the clutch plate and the third gear are integrated by fitting the recess or protrusion of the clutch plate with the protrusion or recess of the third gear.

[0058] It is preferable that the radius of the third gear is smaller than the radius of the toothed portion of the fourth gear.

[0059] Furthermore, it is also preferable that the second subframe has a circular hole at the end supported by the rotating shaft, and the fourth gear has a cylindrical protrusion on the surface facing the second subframe, the protrusion having the same diameter as the inner diameter of the circular hole, and the second subframe is rotatably supported on the rotating shaft by being rotatably fitted into the circular hole.

[0060] It is also preferable that, when the wheel structure to which the transported item loading platform is attached is viewed from the side, the rotation axis and the position of the pivot axis are set so that when the frame support member rotates clockwise (CW) and the toothed portions of the third gear and the fourth gear are released from their meshed state, the center of the rotation axis is located forward in the direction of travel of a vertical line passing through the center of the rotation axis.

[0061] It is also preferable that the frame support member is provided with a stopper that protrudes toward the frame on the side of the second subframe facing the frame, and is configured so that when rotated clockwise (CW), the stopper abuts against the end face of the frame, thereby stopping it in a fixed position.

[0062] The toothed portions of the third gear and the fourth gear may be non-circular so as to be constantly in mesh with each other while the toothed portion of the fourth gear faces the third gear.

[0063] 2. Specific embodiment The present embodiment will now be described in more detail.

[0064] (1) Wheel structure FIG. 1 is a perspective view showing a typical structure of the wheel structure according to the present embodiment, showing a state during normal driving. In FIG. 1, 1 is a wheel structure, 2 is a main wheel, 3 is an auxiliary wheel, 4 is a frame, 5 is a transported object placement platform mounting portion, and 6 is a frame support member. 2a is a tire of the main wheel 2, 2b is a wheel of the main wheel 2, 3a is a tire of the auxiliary wheel 3, and 3b is a wheel of the auxiliary wheel 3. 4a is a canopy portion of the frame 4, 4b is a side wall portion of the frame 4, and 4c is an auxiliary wheel support portion of the frame 4. In FIG. 1, the lower left side of the paper is the traveling direction of the wheel structure 1, the wheel structure 1 is erected with the main wheel 2 on the lower side, and the auxiliary wheel 3 is located in front of the main wheel 2 in the traveling direction.

[0065] Fig. 2 is an exploded view of the wheel structure 1 shown in Fig. 1, Fig. 3 is a front perspective view of the assembly of the wheel structure 1 shown in Fig. 1, and Fig. 4 is a side perspective view of the assembly of the wheel structure 1 shown in Fig. 1. Fig. 5 is an exploded view of a frame support member 6 in the wheel structure 1 shown in Fig. 1.

[0066] 3 to 5, parts that are covered by the frame 4 and parts that cannot be seen from the outside, such as the internal structure of the frame support member 6, are drawn with solid lines for convenience, since drawing them with dashed lines makes it difficult to distinguish their shapes. The same applies to Figures 6 to 12 described later (as well as the second and third embodiments described later).

[0067] 1 to 4, a wheel structure 1 according to this embodiment includes a large-diameter main wheel 2, a small-diameter auxiliary wheel 3, a frame 4, an object-placing platform mounting portion 5, and a frame support member 6. As shown in Fig. 1, during normal driving, the auxiliary wheel 3 is suspended a predetermined distance above the ground.

[0068] The frame 4 includes a canopy portion 4a, a side wall portion 4b, and an auxiliary wheel support portion 4c, and is disposed above the main wheels 2 so as to cover the main wheels 2, supporting the main wheels 2 via their rotation shafts 21, and supporting the auxiliary wheels 3 via their rotation shafts 31 provided at the tip of the auxiliary wheel support portion 4c. An object placement platform attachment portion 5 is attached to the upper surface of the canopy portion 4a so as to be integrated with the frame 4.

[0069] As described above, the frame support member 6 comprises a box-shaped first sub-frame 61 and a lid-shaped second sub-frame 62, and the above-mentioned rotation mechanism, transmission mechanism, transmission control mechanism, clutch mechanism and return mechanism are housed and integrated within the housing formed by the first sub-frame 61 and the second sub-frame 62.

[0070] The rotation mechanism includes a rotation shaft 70, the clutch mechanism includes a clutch plate 65, the transmission mechanism includes a third gear 67 and a fourth gear 69, and the return mechanism includes an elastic body 66. Each mechanism is configured by appropriately combining these with the second gear 64 and the intermediate shaft 68. The first gear 63 is journaled and fixed to the rotation shaft 21. One end of the rotation shaft 21 is fixed to the wheel 2b, and the other end is rotatably engaged with the second sub-frame 62. Note that if the rotation of the wheel and the rotation around the rotation shaft can be reversed, some of the above-mentioned gears may be substituted with a chain, a belt, or the like.

[0071] The intermediate shaft 68 is located approximately midway between the rotation shaft 21 and the turning shaft 70, and is disposed parallel to the rotation shaft 21 of the main wheel, with one end being in upright contact with the second sub-frame 62 so as to rotatably support each of the second gear 64, the third gear 67, the fourth gear 69, and the clutch plate 65. The elastic body 66 is located between the clutch plate 65 and the third gear 67, with the intermediate shaft 68 inserted through its center. As mentioned above, the elastic body 66 can suitably be a "spring spring" or a "spiral spring", etc.

[0072] The rotating shaft 70 is disposed on the side wall portion 4b of the frame 4 in parallel to the rotating shaft 21, and is inserted through a circular hole 62a provided in the second sub-frame 62, protruding into the inside of the frame support member 6. The fourth gear 69 is journaled and fixed to the rotating shaft 70. The fourth gear 69 is a missing-tooth gear that has a portion without teeth and a portion with teeth.

[0073] The first gear 63 and the second gear 64 mesh with each other. The second gear 64 and the clutch plate 65 are overlapped. The second gear 64 has a larger diameter than the clutch plate 65, and is provided with an engagement claw 64b radially outward from the outer edge of the clutch plate 65 on its side facing the clutch plate 65. The clutch plate 65 is disc-shaped (circular) and is provided with a protrusion 65c that protrudes radially outward from its outer circumferential side surface.

[0074] One end (outer edge end) of the elastic body 66 passes radially outside the outer edge of the protrusion 65c and is engaged with the outer edge side end of the second gear 64, and the other end (inner edge end) is engaged with the side surface of the clutch plate 65. At this time, the elastic body 66 is in a contracted state with respect to the free state. Therefore, an expanding force is applied to the elastic body 66, and a counterclockwise (CCW) force acts on the second gear 64, while a clockwise (CW) force acts on the clutch plate 65. As a result, the engagement claw 64b provided on the second gear 64 rotates counterclockwise (CCW) and comes into contact with the protrusion 65c provided on the clutch plate 65.

[0075] The clutch plate 65 and the third gear 67 are integrated by engaging their side surfaces with each other. Specifically, a recess 65b is formed on the surface of the clutch plate 65 facing the third gear 67, and a protrusion 67b is formed on the surface of the third gear 67 facing the clutch plate 65. The recess 65b and the protrusion 67b are fitted together to integrate the clutch plate 65 and the third gear 67. Note that the recess and protrusion described above may be formed in reverse, that is, a protrusion may be formed on the surface of the clutch plate 65 facing the third gear 67, and a recess may be formed on the surface of the third gear 67 facing the clutch plate 65.

[0076] The third gear 67 and the fourth gear 69 are arranged so that their outer circumferential surfaces face each other and mesh with each other when the outer circumferential surface of the third gear 67 faces the toothed portion of the fourth gear 69. The fourth gear 69 has a cylindrical protrusion 69b having the same diameter as the inner diameter of the circular hole 62a on the surface facing the second sub-frame 62, and the protrusion 69b is rotatably fitted into the circular hole 62a. As a result, the third gear 67 and the fourth gear 69 mesh with each other, and the third gear 67 rotates (turns) and revolves around the fourth gear 69, so that the second sub-frame 62, and further the entire frame support member 6 and the main wheel 2 can rotate in both clockwise (CW) and counterclockwise (CCW) directions about the rotation shaft 70.

[0077] In addition, the second sub-frame 62 has a stopper 62b on its outer surface (the side surface facing the side wall portion 4b), and when the frame support member 6 rotates CW and the stopper 62b abuts against the lower end of the side wall portion 4b of the frame 4, the frame support member 6 stops rotating.

[0078] When the radius of the first gear 63 is smaller than the radius of the second gear 64, the main wheel 2 can be rotated with a smaller force to rotate the frame support member 6 about the rotation shaft 70. Also, when the radius of the third gear 67 is smaller than the radius of the toothed portion of the fourth gear 69, the main wheel 2 can be rotated with a smaller force to rotate the frame support member 6 about the rotation shaft 70. When these are combined, the main wheel 2 can be rotated with an even smaller force to rotate the frame support member 6.

[0079] As described above, the turning shaft 70, the intermediate shaft 68, and the rotating shaft 21 of the main wheel are located at the upper end, the center, and the lower end of the frame support member 6, respectively. The positions of the toothless portion and the toothed portion of the fourth gear 69 are set so that, in a state in which the wheel structure 1 is erected, they do not mesh when the center of the first gear 67, i.e., the center of the rotating shaft 21 of the main wheel, is located forward of the vertical line VL passing through the center of the turning shaft 70 in the traveling direction (at least when the frame support member 6 is located at the initial position), but mesh when located behind the vertical line VL. The boundary between the meshing position and the non-meshing position is preferably when the center of the rotating shaft 21 of the main wheel is located on the vertical line VL or forward of the vertical line VL.

[0080] It is preferable to use rolling bearings for the insertion portion of the rotating shaft 21 through the first sub-frame 61, the engaging portion of the second sub-frame 62, and the support portions of the second gear 64 and the third gear 67, as this reduces rotational resistance.

[0081] (2) Operation of the wheel structure Next, the operation of the wheel structure 1 in this embodiment will be described.

[0082] (a) Normal driving Fig. 6 is a side perspective view for explaining the state of the wheel structure according to the present embodiment during normal running. In Fig. 6, 10 is a flat surface. In Fig. 6, the elastic body is omitted in order to make the drawing easier to see.

[0083] 6, during normal driving, the stopper 62b provided on the second sub-frame 62 of the frame support member 6 abuts against the lower end of the side wall portion 4b, so that the rotation of the frame support member 6 is stopped and the rotation axis 21 of the main wheels is located forward in the direction of travel of the rotation axis 70. At this time, as described above, the auxiliary wheels 3 are in a state of being suspended at a predetermined height above the ground contact surface (flat surface 10) of the main wheels 2.

[0084] When the wheel structure 1 is pushed forward, the main wheel 2 rotates in the CCW direction and moves forward. As the main wheel 2 rotates, the rotation shaft 21 of the main wheel and the first gear 63 rotate in the CCW direction. Meanwhile, the second gear 64 meshing with the first gear 63 rotates in the CW direction, and the engagement claw 64b provided on the second gear 64 also rotates in the CW direction. At this time, the toothless portion of the fourth gear 69 faces the third gear 67, and the third gear 67 and the fourth gear 69 are not meshed with each other. Therefore, the rotation of the main wheel 2 is not transmitted to the rotating shaft 70 through which the fourth gear 69 is inserted, and the rotating shaft 70 does not rotate. As a result, the frame support member does not rotate, and the wheel structure 1 moves forward while maintaining the initial position.

[0085] (b) Climbing a step (part 1) 7 is a side perspective view illustrating the state of the wheel structure according to the present embodiment immediately before it runs over a step, in which 11 is the step, 11a is the step end face, and 11b is the step top face.

[0086] When the wheel structure 1 is pushed forward and the main wheel 2 abuts against the step 11, the main wheel 2 stops rotating, and the wheel structure 1 stops moving forward. At this time, when the wheel structure 1 is pushed further forward, the frame 4 is also pushed forward. Accordingly, the frame support member 6 located below the rotation shaft 70 fixed to the frame 4 rotates in the CCW direction around the rotation shaft 70. With the rotation of the frame support member 6, the third gear 67 revolves around the fourth gear 69 in the CCW direction and comes to mesh with the toothed portion of the fourth gear 69. Then, the protrusion 65c starts to rotate in the CCW direction relative to the engagement claw 64b. At this time, the main wheel 2 rotates in the CCW direction, so that the frame 4 descends, and the auxiliary wheel 3 supported by the auxiliary wheel support portion 4c descends toward the step upper surface 11b.

[0087] (c) Climbing a step (part 2) FIG. 8 is a side perspective view for explaining the state of the wheel structure according to the present embodiment at the start of climbing up a step. As shown in FIG. 8, the forward movement of the main wheel 2 is stopped by the step, so even if the wheel structure 1 is pushed further forward, the rotation shaft 21 of the main wheel 2, the first gear 63, and the second gear 64 meshing with the first gear 63 do not rotate. On the other hand, as the frame 4 is pushed further forward, the frame support member 6 rotates further in the CCW direction. As a result, the frame 4 and the auxiliary wheel 3 further descend, and finally, as shown in FIG. 8, the auxiliary wheel 3 touches the step upper surface 11b. The load applied to the frame 4 is dispersed by the main wheel 2 and the auxiliary wheel 3 touching the step upper surface 11b. At this time, the CCW rotation of the protrusion 65c relative to the engagement claw 64b continues.

[0088] At this time, in accordance with the rotation of the frame support member 6, the third gear 67 meshing with the fourth gear 69 and the clutch plate 65 integral with the third gear 67 also rotate in the CCW direction about the intermediate shaft 68. As a result, the engagement between the engagement claw 64b and the protrusion 65c is released, and the elastic body 66 is further contracted.

[0089] (d) Climbing a step (part 3) 9 is a side perspective view illustrating the state of the wheel structure according to this embodiment immediately after it climbs over a step. By pushing the wheel structure 1 further forward, the climbing operation progresses further, and the main wheel 2 rotates about 60 degrees CCW around the corner of the step when climbing over it. In response to this, the first gear 63 also rotates about 60 degrees CCW, and the second gear 64 meshing with the first gear 63 rotates CW. Meanwhile, the third gear 67 meshing with the fourth gear 69 rotates CCW around the intermediate shaft 68 while revolving around the fourth gear 69 CCW around the pivot shaft 70.

[0090] (e) Climbing a step (part 4) 10 is a side perspective view illustrating the state when the wheel structure according to the present embodiment moves forward a little after climbing over a step. At this time, the engaging claw 64b of the second gear 64 rotates clockwise (CW) as shown in FIG. 10, and comes into contact with and engages with the protrusion 65c of the clutch plate 65 from the upstream side.

[0091] That is, when the main wheel 2 rotates CCW and moves forward, the wheel 2b of the main wheel 2 and the first gear 63 inserted in the rotating shaft 21 also rotate CCW. On the other hand, the second gear 64 meshing with the first gear 63 rotates CW, and the engaging claw 64b of the second gear 64 also rotates CW. At this time, the fourth gear 69 is fixed to the side wall 4b of the frame 4, and the third gear 67 cannot rotate because it is meshed with the fourth gear 69 as described above, and the clutch plate 65 integrated with the third gear 68 cannot rotate either. As a result, the second gear 64 rotates CW relative to the clutch plate 65, and the engaging claw 64b of the second gear 64 also rotates CW, so that it comes into contact with the protrusion 65c of the clutch plate 65 from the upstream side of the CW rotation.

[0092] (f) Climbing a step (part 5) FIG. 11 is a side perspective view for explaining a state when the wheel structure according to the present embodiment moves forward after climbing over a step. As the wheel structure 1 moves forward, the main wheel 2 and the first gear 63 rotate in the CCW direction, and the second gear 64 rotates in the CW direction. At this time, as described above, the engagement claw 64b of the second gear 64 also rotates in the CW direction, contacts the protrusion 65c of the clutch plate 65 from the upstream side of the CW rotation, and presses the protrusion 65c. As a result, the clutch plate 65 and the third gear 67 integrated with the clutch plate 65 rotate in the CW direction. At this time, the third gear 67 is engaged with the fourth gear 69 fixed to the side wall portion 4b of the frame 4, so in order to rotate the third gear 67 in the CW direction, it is necessary for the third gear 67 to revolve around the fourth gear 69 while engaging with the fourth gear 69.

[0093] In accordance with the CW revolution of the fourth gear 69, the frame support member 6 rotates CW to raise the frame 4, so that the auxiliary wheels 3 lift off the step upper surface 11b and attempt to return to their initial position.

[0094] (g) Climbing a step (part 6) FIG. 12 is a side perspective view for explaining the state immediately before the wheel structure according to the present embodiment completes climbing over a step. As shown in FIG. 12, when the wheel structure 1 advances with the third gear 67 meshed with the fourth gear 69, the frame support member 6 further rotates CW around the rotation shaft 70. As the frame support member 6 continues to rotate CW, the center of the rotation shaft 21 of the main wheel 2 moves forward from the vertical line VL passing through the center of the rotation shaft 70, and the meshing between the third gear 67 and the fourth gear 69 is released, but the rotation of the frame support member 6 continues due to the weight of the entire wheel structure 1. When the stopper 62b, which rotates in accordance with the rotation of the frame support member 6, abuts against the lower end of the side wall portion 4b, the rotation of the frame support member 6 is stopped and returns to the initial position. At the same time that the meshing between the third gear 67 and the fourth gear 69 is released, the elastic body 66 is deformed and returns to the original state.

[0095] This completes a series of steps climbing operations of the wheel structure 1.

[0096] As described above, in this embodiment, the frame 4 rises as the wheel structure moves forward due to a rotational motion; however, since the forward distance is sufficiently large compared to the upward distance and the apparent slope is gentle, even a small force of several hundred g can smoothly cause the main wheel 2 to ride up onto the step upper surface 11b.

[0097] [2] Second embodiment 1. Wheel structure configuration In this embodiment, in order to specifically realize the above-mentioned features and effects of the present invention, the wheel structure is configured as follows.

[0098] The rotation mechanism is (1) The first gear is inserted and supported on the rotating shaft of the main wheel. (2) A second gear that meshes with the first gear (3) A third gear and a fourth gear arranged to mesh with each other (4) An intermediate shaft, one end of which is in upright contact with the second subframe It is equipped with:

[0099] The clutch mechanism includes two clutch plates: a first clutch plate and a second clutch plate.

[0100] The second gear, the third gear, the first clutch plate, and the second clutch plate are each rotatably supported by an intermediate shaft.

[0101] The rotating shaft is fixed to the frame, and the fourth gear is journalled and fixed to the rotating shaft.

[0102] The second clutch plate has one surface facing the second gear and the other surface facing one surface of the first clutch plate, and the first clutch plate is configured so that it is integrated with the third gear on the other surface of the first clutch plate other than the surface facing the second clutch plate.

[0103] The transmission mechanism is provided with a plurality of intermeshable pawls on the outer peripheral edges of the opposing surfaces of the second gear and the second clutch plate, and an engagement portion that enables the second clutch plate and the first clutch plate to engage with each other, and is configured to transmit the rotation of the main wheel to the rotating shaft when the pawls are intermeshed with each other and the engagement portion is engaged.

[0104] The clutch mechanism is configured so that the counterclockwise (CCW) rotation of the main wheel can be transmitted so that the rotation of the second clutch plate causes the rotating shaft to rotate counterclockwise (CCW) and then clockwise (CW).

[0105] At this time, it is preferable that when the frame support member is located in the initial position, the elastic body is contracted relative to its free state, one end is engaged with the second clutch plate and the other end is engaged with the first clutch plate, and the second clutch plate is biased so as to engage with the first clutch plate in a counterclockwise (CCW) direction.

[0106] The second clutch plate has a larger diameter than the first clutch plate and is provided with an engagement claw radially outward from the outer edge of the first clutch plate on the side facing the first clutch plate as an engagement portion, while the first clutch plate is disc-shaped and is provided with a protrusion protruding radially outward from its outer peripheral side as an engagement portion, and it is preferable that the second clutch plate and the first clutch plate are configured to engage with each other via the engagement claw and protrusion.

[0107] In addition, when the wheel structure to which the transported item loading platform is attached is viewed from the side, it is preferable that the rotation axis and the position of the rotation axis are set so that when the frame support member rotates clockwise (CW) and the second gear and the second clutch plate are released from their meshed state, the center of the rotation axis is located forward in the direction of travel of a vertical line passing through the center of the rotation axis.

[0108] In addition, it is preferable that the frame support member is provided with a stopper protruding toward the frame on the side of the second subframe facing the frame, and is configured so that when rotated clockwise (CW), the stopper abuts against the end face of the frame, thereby stopping it in a fixed position.

[0109] It is preferable that the radius of the first gear is smaller than the radius of the second gear, so that the counterclockwise (CCW) rotation of the main wheel can be transmitted to the rotating shaft at a reduced speed.

[0110] It is also preferable that the third gear and the fourth gear are non-circular gears that are constantly in mesh with each other.

[0111] The above also applies to a third embodiment described later.

[0112] In this embodiment, the transmission control mechanism further includes a moving mechanism that moves the second clutch plate in the axial direction of the intermediate shaft, and this moving mechanism is configured to move the second clutch plate toward the second gear when the rotating shaft rotates counterclockwise (CCW) to engage the pawls of the second gear and the second clutch plate, and to move the second clutch plate in the opposite direction to the second gear when the rotating shaft rotates clockwise (CW) from a state in which the second gear and the second clutch plate are engaged, to disengage the engagement.

[0113] In addition, a recess or a protrusion is formed on the surface of the first clutch plate facing the third gear, and a protrusion that can be fitted into the recess of the first clutch plate or a recess that can be fitted into the protrusion of the first clutch plate is formed on the surface of the third gear facing the first clutch plate, and the first clutch plate and the third gear are configured to be integrated by fitting the recess or protrusion of the first clutch plate with the protrusion or recess of the third gear.

[0114] In this case, it is preferable that the second subframe has a circular hole at the end that is supported by the rotating shaft, and the fourth gear has a cylindrical protrusion on the surface facing the second subframe, the protrusion having the same diameter as the inner diameter of the circular hole, and the second subframe is rotatably supported on the rotating shaft by being rotatably fitted into the circular hole.

[0115] 2. Specific embodiment The present embodiment will now be described in more detail.

[0116] (1) Wheel structure Fig. 13 is a simplified exploded view of the wheel structure according to this embodiment, Fig. 14 is an overall parts view, and Fig. 15 is an exploded view of the frame support member 6 in the wheel structure 1 shown in Fig. 13. The wheel structure 1 includes main wheels 2, a rotating shaft 21 of the main wheels, auxiliary wheels 3, a frame 4, a transported object platform mounting portion 5, and a frame support member 6, and has the same configuration as the wheel structure 1 according to the first embodiment, except that the transmission mechanism, transmission control mechanism, and clutch mechanism in the frame support member 6 are different from those in the first embodiment.

[0117] The transmission mechanism includes a second clutch plate 71 rotatably supported by an intermediate shaft 68 at a position opposite to the second gear 64. The second gear 64 and the second clutch plate 71 are provided with a plurality of engagement pawls (hereinafter also referred to as "cap teeth") 64c, 71a arranged in a bevel tooth shape in the circumferential direction on the outer circumferential edges of their opposing faces, and the rotation of the second gear 64 is transmitted to the second clutch plate 71 by the bevel teeth 64c engaging with the bevel teeth 71a.

[0118] The second clutch plate 71 faces the first clutch plate 65 with the elastic body 66 sandwiched therebetween, has a diameter larger than that of the first clutch plate 65, and is provided with engagement pawls 71b on its outer edge that protrude toward the clutch plate 65.

[0119] On the other hand, the first clutch plate 65 has a protrusion 65c protruding radially outward from the outer edge, and when the engagement pawl 71b engages with the protrusion 65c, the rotation of the second clutch plate 71 is transmitted to the first clutch plate 65 and a third gear 67 integrated with the first clutch plate 65. For the fourth gear 69, a normal spur gear is used instead of the missing-tooth gear in the first embodiment, and the third gear 67 and the fourth gear 69 are constantly meshed with each other, so that the rotation of the third gear 67 is transmitted to the fourth gear 69 and the rotating shaft 70.

[0120] The transmission control mechanism includes a fork 72. The fork 72 has two claws that open in a fan shape, with a rotating shaft 70 inserted through a key portion of the fan and rotatably supported by the rotating shaft 70. The two claws also sandwich the outer peripheral edge end face of a second clutch plate 71, rotatably supporting the second clutch plate 71. Specifically, a circumferential protrusion is provided on the outer peripheral edge end face of the second clutch plate 71, while a groove is provided on the inner surface of the claws of the fork 72, and the protrusion and the groove are fitted together.

[0121] Fork 72 has a first fork guide 72a on the right side of the axial direction of the fork's shaft and a second fork guide 72b on the left side of the axial direction of the fork's shaft. First fork guide 72a and second fork guide 72b each have a protrusion that protrudes partially from the fork's shaft in the axial direction.

[0122] Meanwhile, the rotating shaft 70 is provided with a pair of rotating shaft guides, a first rotating shaft guide 70a on the right side in the traveling direction and a second rotating shaft guide 70b on the left side. Each of the pair of rotating shaft guides is formed of a circumferential protrusion that partially protrudes in the radial direction from the outer circumferential surface of the rotating shaft 70. The fork 72 is journaled between the pair of rotating shaft guides and is movable in the axial direction of the rotating shaft 70 between the pair of rotating shaft guides, and the axial movement of the fork 72 controls whether or not transmission is possible. In other words, these guides are configured so that when the end face of the second fork guide 72b comes into contact with the end face of the second pivot guide 70b, the fork 72 rotates counterclockwise (CCW) around the pivot shaft 70, and both end faces push against each other, the fork 72 moves to the right in the direction of travel, and when the end face of the first fork guide 72a comes into contact with the end face of the first pivot guide 70a, the fork 72 rotates clockwise (CW) around the pivot shaft 70, and both end faces push against each other, the fork 72 moves to the left in the direction of travel.

[0123] 16, 17, and 18 are diagrams for explaining the operation of the transmission control mechanism in this embodiment. Fig. 16(a) is a perspective view of the inside of the frame support member 6 as seen from the front left diagonally upward, Fig. 16(b) is a front view as seen from the front, and Fig. 16(c) is a perspective view as seen from the rear left diagonally upward. These diagrams show the initial state, that is, the state when the rotating shaft 70 is not rotating in the traveling direction (transmission is released), and since the bevel teeth 64c of the second gear 64 and the bevel teeth 71a of the second clutch plate 71 are separated from each other in the axial direction as shown in Fig. 16(b), the rotation of the first gear 63 and the second gear 64 interlocked with the main wheel 2 is not transmitted to the second clutch plate 71.

[0124] Fig. 17(a) is a view in which the fourth gear 69 in Fig. 16(c) has been removed to show the axial position of the fork 72 and the engagement state between the pivot shaft guide and the fork guide, and Fig. 17(b) is a partially enlarged view of Fig. 17(a). The first pivot shaft guide 70a and the second pivot shaft guide 70b each have an end face 70ae of the first pivot shaft guide and an end face 70be of the second pivot shaft guide, while the first fork guide 72a and the second fork guide 72b each have an end face 72ae of the first fork guide and an end face 72be of the second fork guide. The end faces of these guides are all flat, and when the pivot shaft 70 and the core of the fork 72 are viewed in the direction of travel with the end faces of the guides facing forward, they are inclined upward to the right at the same angle with respect to the axial direction.

[0125] 18, when the rotating shaft 70 rotates CCW from the initial state and the fork 72 rotates counterclockwise (CCW) with respect to the rotating shaft 70 (for example, when the main wheel 2 comes into contact with a step 11 and stops, and the frame support member 6 rotates counterclockwise (CCW) from the initial state), the end face 72be of the second fork guide slides on the end face 70be of the second rotating shaft guide toward the right in the traveling direction. Then, correspondingly, the fork 72 moves to the right in the traveling direction along the rotating shaft, so that the second clutch plate 71 moves to the right in the traveling direction along the intermediate shaft 68 and comes into contact with the second gear 64, and the bevel teeth 64c and the bevel teeth 71a mesh with each other.

[0126] On the other hand, as shown in FIG. 18, when the rotating shaft 70 rotates clockwise (CW) from a state in which it has rotated counterclockwise (CCW) (for example, when the main wheel 2 comes into contact with the step 11 and stops, the frame support member 6 rotates counterclockwise (CCW) from the initial state, and the auxiliary wheel 3 comes into contact with the step upper surface 11b, and then the counterclockwise (CCW) rotation of the main wheel 2 resumes and the frame support member 6 rotates clockwise (CW)), the fork 72 rotates clockwise (CW) relative to the rotating shaft 70, and the end face 72ae of the first fork guide comes into contact with the end face 70ae of the first rotating shaft guide and slides on the end face 70ae of the first rotating shaft guide toward the left in the traveling direction. In response to this, the fork 72 moves to the left in the direction of travel along the pivot shaft 70, causing the second clutch plate 71 to move to the left in the direction of travel along the intermediate shaft 68 and away from the second gear 64, thereby releasing the engagement between the bevel teeth 64c and the bevel teeth 71a.

[0127] The clutch mechanism includes a first clutch plate 65 and a second clutch plate 71, and the return mechanism includes an elastic body 66. One end (outer edge) of the elastic body 66 is engaged with the outer peripheral edge of the second clutch plate 71, and the other end (inner edge) is engaged with the side surface of the first clutch plate 65, and the elastic body 66 is in a state contracted with respect to a free state when the frame support member 6 is in the initial position. Therefore, a force is applied to the second clutch plate 71 in the CCW direction, and the engaging claw 71b engages with the protrusion 65c in the CCW direction, as shown in Fig. 17(a).

[0128] In a natural state, when the wheel structure 1 moves forward, the main wheel 2 and the first gear 63 rotate counterclockwise (CCW) and the second gear 64 rotates clockwise (CW). At this time, the meshing between the bevel teeth 64c of the second gear 64 and the bevel teeth 71a of the second clutch plate 71 is released, so the second clutch plate 71 does not rotate. When the main wheel 2 rotates counterclockwise (CCW) with the bevel teeth 64c of the second gear 64 meshing with the bevel teeth 71a of the second clutch plate 71, the clutch mechanism transmits the counterclockwise (CCW) rotation of the main wheel 2 to the clockwise (CW) rotation of the rotating shaft 70 by the clockwise (CW) rotation of the first clutch plate 65 and the second clutch plate 71. When the counterclockwise (CCW) rotation of the main wheel 2 stops, the counterclockwise (CCW) rotation of the frame support member 6 is permitted.

[0129] Specifically, for example, when the main wheel 2 comes into contact with the step 11 and stops, the frame support member 6 rotates counterclockwise (CCW) from the initial state, and the transmission mechanism is in the transmission state, i.e., the bevel teeth 64c and the bevel teeth 71a are engaged, the second clutch plate 71 does not rotate because the main wheel 2 is stopped. However, due to the counterclockwise (CCW) rotation of the frame support member 6, the first clutch plate 65 together with the third gear contracts the elastic body 66, and rotates counterclockwise (CCW) within a range where the protrusion 65c of the first clutch plate 65 does not engage with the engagement claw 71b of the second clutch plate 71.

[0130] In this state, when the auxiliary wheel 3 touches the step upper surface 11b, the main wheel 2 resumes counterclockwise (CCW) rotation, and the second gear 64 rotates clockwise (CW), the second clutch plate 71 rotates clockwise (CW) while compressing the elastic body 66, the engagement claw 71b of the second clutch plate 71 engages with the protrusion 65c of the first clutch plate 65 in the CW direction, and the first clutch plate 65 and the third gear 67 rotate CW, transmitting a force in the CCW direction to the fourth gear, and the frame support member 6 begins to rotate clockwise (CW).

[0131] On the other hand, when the clockwise (CW) rotation of the frame support member 6 progresses and the meshing between the bevel teeth 64c and the bevel teeth 71a is released, and the clockwise (CW) rotation of the second gear 64 due to the counterclockwise (CCW) rotation of the main wheel 2 is no longer transmitted to the second clutch plate 71, the contracted elastic body 66 expands, causing the second clutch plate to rotate counterclockwise (CCW) and the engagement claw 71b momentarily engages with the protrusion 65c of the first clutch plate 65 in the CCW direction, returning to the initial state.

[0132] (2) Operation of the wheel structure Next, there will be described an operation of the wheel structure 1. Except for the inside of the frame support member 6, the basic operation of the wheel structure 1 is the same as that of the first embodiment.

[0133] (a) Normal driving Fig. 19(a) is a side perspective view explaining the state of the wheel structure 1 according to this embodiment during normal driving, and Fig. 19(b) and Fig. 19(c) are a perspective view of the inside of the frame support member 6 as seen from diagonally above the left rear in the traveling direction, and a front view as seen from the front, respectively. Note that in Fig. 19(a), the elastic body is omitted in order to make the drawing easier to see.

[0134] As shown in Fig. 19(c), during normal driving, the engagement pawl (cap tooth) 64c of the second gear 64 and the engagement pawl (cap tooth) 71a of the second clutch plate 71 are not engaged, so the transmission mechanism is in a disengaged state. Therefore, the rotating shaft 70 does not rotate, and the frame support member 6 does not rotate either, so the vehicle can drive while maintaining the state shown in Fig. 19(a), i.e., the initial state.

[0135] (b) Climbing a step (part 1) Fig. 20(a) is a side perspective view explaining the state of the wheel structure 1 according to this embodiment just before it runs over a step, i.e., just after the main wheel 2 comes into contact with the step, and Fig. 20(b) is a perspective view of the inside of the frame support member 6 at this time, as seen from diagonally above and to the left rear in the direction of travel. At this time, the wheel structure 1 remains in its initial state. Note that 10 is a flat surface, 11 is the step, 11a is the step end face, and 11b is the step top face.

[0136] When the wheel structure 1 is pushed forward and the main wheel 2 abuts against the step 11, the main wheel 2 stops rotating and the wheel structure 1 stops moving forward. At this time, the engaging claw 71b of the second clutch plate 71 is engaged with the protrusion 65c of the first clutch plate 65 in the CCW direction due to the biasing force of the elastic body, and the third gear 67 is engaged with the fourth gear 69.

[0137] In the following description, the position of the pivot shaft 70 relative to the pivot shaft 21 of the main wheel 2 when the wheel structure 1 is in the initial state is defined as the initial position, the straight line connecting the centers of the pivot shaft 70 and the pivot shaft 21 of the main wheel 2 when the pivot shaft 70 is in the initial position is defined as the reference line, and the inclination angle of the straight line connecting the centers of the pivot shaft 21 and the pivot shaft 70 of the main wheel 2 when the pivot shaft 70 rotates relative to the reference line is defined as the rotation angle. The rotation angle can be freely set according to the design. The rotation angles at each stage of climbing up the step described below are merely examples, and the present invention is not limited to these. The rotation angle of the pivot shaft 70 relative to the pivot shaft 21 corresponds to the rotation angle of the frame support member 6 from the initial state.

[0138] (c) Rotation angle 30° Figure 21(a) is a side perspective view explaining the state of the wheel structure 1 when the rotating shaft 70 rotates 30° CCW around the rotating shaft 21 of the main wheel 2, and Figure 21(b) is an oblique view of the inside of the frame support member 6 at this time, viewed diagonally from above and rearward on the left side in the direction of travel.

[0139] When the main wheel 2 is pushed further forward from the state where it abuts against the step, the frame 4 is also pushed forward. Accordingly, the rotating shaft 70 fixed to the frame 4 rotates CCW around the rotating shaft 21 of the main wheel 2, and when rotated 30°, the rotating shaft 70 is aligned with the vertical line VL passing through the rotating shaft 21 of the main wheel 2, as shown in FIG. 21(a).

[0140] The third gear 67 rotates counterclockwise (CCW) around the fourth gear 69 while meshing with the fourth gear 69, and at the same time rotates counterclockwise (CCW) around the intermediate shaft 68. As a result, the protrusion 65c of the first clutch plate 65 integral with the third gear 67 and the engagement claw 71b of the second clutch plate receiving a counterclockwise (CCW) force from the protrusion 65 of the first clutch plate via the elastic body 66 move to the positions shown in Fig. 21(b). Furthermore, the fork 72 rotates CCW around the rotating shaft 70, and the end face 72be of the second fork guide comes into contact with the end face 70be of the second rotating shaft guide.

[0141] (d) Rotation angle 37° Figure 22(a) is a side perspective view explaining the state of the wheel structure 1 when it has rotated further and the rotation angle has reached 37°, Figure 22(b) is an oblique view of the inside of the frame support member 6 at this time, seen diagonally from above and rearward in the direction of travel, and Figure 22(c) is a front view of the inside of the frame support member 6, seen from the front.

[0142] When the rotation angle reaches 37°, the fork 72 moves to the right in the traveling direction, and the bevel teeth 64c of the second gear 64 and the bevel teeth 71a of the second clutch plate 71 begin to mesh with each other.

[0143] (e) Rotation angle 42° Figure 23(a) is a side perspective view explaining the state of the wheel structure 1 when the rotation angle becomes 42°, Figure 23(b) is an oblique view of the inside of the frame support member 6 at this time, seen from diagonally above and behind on the left side in the direction of travel, and Figure 23(c) is a front view of the inside of the frame support member 6, seen from the front.

[0144] When the rotation angle reaches 42°, the fork 72 moves further to the right in the direction of travel, completing the meshing between the bevel teeth 64c of the second gear 64 and the bevel teeth 71a of the second clutch plate 71. As a result, the second clutch plate 71 is fixed to the second gear 64 which is meshed with the first gear 63 which is linked to the main wheel 2, and therefore cannot rotate when the main wheel 2 is stopped.

[0145] On the other hand, the third gear 67 rotates counterclockwise (CCW) around the fourth gear 69 in accordance with the rotation of the frame support member 6 in accordance with the rotation of the rotating shaft 70, and also rotates counterclockwise (CCW) around the intermediate shaft 68. At this time, the second clutch plate 71 cannot rotate, but the first clutch plate 65 integrated with the third gear 67 rotates CCW while compressing the elastic body 66.

[0146] (f) Rotation angle 80° The main wheel 2 is fixed until the rotation angle reaches 80°, and the first gear 63 does not rotate, but the second gear 64 and the second clutch plate 71 rotate in the CCW direction around the rotation shaft 21 while rotating in the CCW direction around the intermediate shaft 68 in conjunction with the rotation of the frame support member 6. Meanwhile, the third gear 67 continues to rotate and turn in the counterclockwise (CCW) direction, and the first clutch plate 65 continues to rotate in the counterclockwise (CCW) direction while compressing the elastic body 66 relative to the second clutch plate 71.

[0147] Fig. 24(a) is a side perspective view explaining the state of the wheel structure 1 when the rotation angle becomes 80°, and Fig. 24(b) is a perspective view of the inside of the frame support member 6 at this time, as seen from diagonally above the left rear in the traveling direction. As the frame support member 6 continues to rotate counterclockwise (CCW), the frame 4 descends. Accordingly, the training wheel 3 descends and comes into contact with the step upper surface 11b. After the training wheel 3 comes into contact with the step upper surface 11b, the counterclockwise (CCW) rotation of the rotating shaft 70 and the frame support member 6 stops.

[0148] (g) Climbing a step When the wheel structure 1 is moved further forward with the auxiliary wheel 3 in contact with the step upper surface 11b, the rotation shaft 21 of the main wheel 2 rotates counterclockwise (CCW) around the edge of the step 11, and the main wheel 2 resumes counterclockwise (CCW) rotation and rides up onto the step upper surface 11b.

[0149] Figure 25(a) is a side perspective view explaining the state of the wheel structure 1 when the main wheel 2 moves forward a little after riding over the step upper surface 11b, and Figure 25(b) is an oblique view of the inside of the frame support member 6 at this time, as seen from diagonally above and to the left rear in the direction of travel.

[0150] When the wheel structure 1 moves forward after climbing over the step, the main wheel 2 and the first gear 63 rotate counterclockwise (CCW), and the second gear 64 rotates clockwise (CW). Meanwhile, the rotating shaft 70 and the frame support member 6 stop rotating counterclockwise (CCW), and the third gear 67 meshing with the fourth gear 69 stops rotating counterclockwise (CCW). As a result, the engaging claw 71b of the second clutch plate engages with the protrusion 65c of the first clutch plate 65 in the clockwise (CW) direction. The rotation angle at this time exceeds 120° and is about 140°.

[0151] (h) Rotation angle 110° Figure 26(a) is a side perspective view explaining the state of the wheel structure 1 when the wheel structure moves further forward, the third gear rotates clockwise (CW) together with the first clutch plate 65 with the second clutch plate 71 engaged clockwise (CW), the rotating shaft 70 starts to rotate clockwise (CW), and the rotation angle returns to 110°, and Figure 26(b) is an oblique view of the inside of the frame support member 6 at this time, viewed diagonally from above and rearward on the left side in the direction of travel.

[0152] When the wheel structure 1 is moved forward after the main wheel 2 rides up onto the step upper surface 11b, the third gear 67 rotates CW around the intermediate shaft 68 while rotating CW around the fourth gear. As a result, the rotating shaft 70 rotates CW and the rotation angle starts to decrease, and the frame 4 rises. In addition, the auxiliary wheel 3 rises and is lifted off the step upper surface 11b.

[0153] (i) Rotation angle 30° Figure 27(a) is a side perspective view explaining the state of the wheel structure 1 when the wheel structure 1 moves further forward and the pivot axis 70 rotates CW so that the pivot angle decreases to 30°, Figure 27(b) is an oblique view of the inside of the frame support member 6 at this time, seen from diagonally above and behind on the left side in the direction of travel, and Figure 27(c) is a front view of the inside of the frame support member 6, seen from the front.

[0154] The rotating shaft 70 is located on a vertical line VL that passes through the rotation axis 21 of the main wheel 2, and at least until the rotating shaft 70 moves rearward of the vertical line VL, the bevel teeth 64c of the second gear 64 mesh with the bevel teeth 71a of the second clutch plate 71. In addition, as the rotating shaft 70 rotates clockwise (CW), the fork 72 rotates clockwise (CW) and an end face 72ae of the first fork guide comes into contact with an end face 70ae of the first rotating shaft guide.

[0155] (j) Rotation angle 25° Figure 28(a) is a side perspective view explaining the state of the wheel structure 1 when the wheel structure 1 moves further forward and the rotation angle decreases to 25°, Figure 28(b) is an oblique view of the inside of the frame support member 6 at this time, seen from diagonally above and behind the left side in the direction of travel, and Figure 28(c) is a front view of the inside of the frame support member 6, seen from the front.

[0156] As the rotating shaft 70 rotates clockwise (CW), the fork 72 rotates CW, causing the end face 72ae of the first fork guide to slide leftward in the traveling direction on the end face 70ae of the first rotating shaft guide. In response to this, the second clutch plate 71 moves away from the second gear 64, so that the meshing between the bevel teeth 64c of the second gear 64 and the bevel teeth 71a of the second clutch plate 71 begins to be released.

[0157] (k) Rotation angle 18° Figure 29(a) is a side perspective view explaining the state of the wheel structure 1 when the wheel structure 1 moves further forward and the rotation angle decreases to 18°, Figure 29(b) is an oblique view of the inside of the frame support member 6 at this time, seen from diagonally above and behind on the left side in the direction of travel, and Figure 29(c) is a front view of the inside of the frame support member 6, seen from the front.

[0158] When the rotation angle decreases to 18°, the meshing between the bevel teeth 64c of the second gear 64 and the bevel teeth 71a of the second clutch plate 71 is released. At this time, until the meshing between the bevel teeth 64c and the bevel teeth 71a is released, the wheel structure 1 moves forward, causing the main wheel 2 and the first gear 63 to rotate counterclockwise (CCW), the second gear and the third gear to rotate clockwise (CW), and the clockwise (CW) rotation of the rotating shaft 70 progresses, or, since the rotating shaft 70 is located behind the vertical line VL, a CW rotation force is applied to the rotating shaft 70 due to the weight of the wheel structure 1. As a result, the rotation of the rotating shaft 70 in the CW direction progresses, so the fork 72 rotates CW, the meshing between the bevel teeth 64c of the second gear 64 and the bevel teeth 71a of the second clutch plate 71 is released, and the second clutch plate 71 is separated from the second gear 64.

[0159] (l) Return to the initial state FIG. 30 is a perspective view of the inside of the frame support member when it has returned to the initial position (rotation angle 0°) as seen from the upper left rear, and shows a state in which the meshing between the cap teeth 64c and the cap teeth 71a is released from the state in which the elastic body 66 was contracted in FIG. 29 (rotation angle 18°) and the elastic body 66 is stretched to return to the initial state. The movement of the elastic body 66 returning to the initial state occurs instantly due to the bias of the elastic body 66 after the meshing between the cap teeth 64c and the cap teeth 71a is released. Therefore, the rotation angle after the elastic body 66 returns to the initial state remains at 18°. Then, when the elastic body 66 stretches to return to the initial state, the second clutch plate 71 rotates counterclockwise (CCW) by an angle of just under one rotation, and the state of FIG. 30 is reached, which is the initial state in which the engagement claw 71b contacts the protrusion 65c counterclockwise (CCW). 29 and 30, the relative positional relationship between the engagement pawls 71b of the second clutch plate 71 and the projections 65c of the first clutch plate 65 is reversed.

[0160] That is, when the bevel teeth 64c and bevel teeth 71a are released from meshing and the second clutch plate 71 is separated from the second gear 64 and becomes rotatable, it rotates counterclockwise (CCW) due to the bias of the elastic body 66, and the positions of the protrusion 65c of the first clutch plate 65 and the engagement claw 71b of the second clutch plate try to return to their initial states, as shown in Fig. 30. Furthermore, the frame support member 6 returns to its initial position due to gravity, as shown in Fig. 31, so that the entire wheel structure is initialized and returns to its initial state. Note that Fig. 31 is a side perspective view of the wheel structure when it has returned to its initial state.

[0161] This completes a series of steps climbing operations of the wheel structure 1.

[0162] In this manner, in this embodiment as well, as in the first embodiment, the frame 4 rises as the wheel structure moves forward due to a rotational motion in accordance with the forward movement of the wheel structure; however, since the forward movement distance is sufficiently greater than the upward movement distance and the apparent slope is gentle, even a small force of, for example, several hundred g can smoothly cause the main wheel 2 to ride up onto the step upper surface 11b.

[0163] [3] Third embodiment In this embodiment, in addition to the configuration described in the second embodiment as being similar to that of the first embodiment, the wheel structure is configured as follows.

[0164] 1. Wheel structure configuration Referring to Figure 32, the rotation mechanism includes a first gear 63 inserted and supported on the rotating shaft 21 of the main wheel 2, a second gear 64 meshing with the first gear 63, a third gear 67 integrated with the second gear 64, a fourth gear 69 arranged to mesh with the third gear 67, and an intermediate shaft 68 one end of which is in upright contact with the second subframe 62.

[0165] The clutch mechanism includes two clutch plates, a first clutch plate 65 and a second clutch plate 71. The second gear 64 and the third gear 67 are rotatably supported by an intermediate shaft 68. The rotating shaft 70 is fixed to the frame 4, and the fourth gear 69 and the second clutch plate 71 are rotatably supported on the rotating shaft 70 and face each other, and the first clutch plate 65 is rotatably fixed to the rotating shaft 70 and faces the second clutch plate 71.

[0166] The transmission mechanism is provided with a plurality of mutually intermeshing engagement pawls 69c, 71a on the outer circumferential edges of the opposing surfaces of the fourth gear 69 and the second clutch plate 71, as well as engagement portions 71b, 65c that enable the second clutch plate 71 and the first clutch plate 65 to engage with each other, and is configured to transmit the rotation of the main wheel 2 to the pivot shaft 70 when the pawls are intermeshed with each other and the engagement portions are engaged.

[0167] The clutch mechanism is configured to transmit the counterclockwise (CCW) rotation of the main wheel 2 to the rotating shaft 70 so that the counterclockwise (CCW) rotation of the main wheel 2 is rotated by the rotation of the second clutch plate 71, and to allow the rotating shaft 70 to rotate counterclockwise (CCW) when the counterclockwise (CCW) rotation of the main wheel 2 stops.

[0168] In this case, the transmission control mechanism is preferably equipped with a moving mechanism that moves the second clutch plate 71 in the axial direction of the rotating shaft 70, and is configured such that when the rotating shaft 70 rotates counterclockwise (CCW), this moving mechanism moves the second clutch plate 71 in the direction of the fourth gear 69 to engage the claws of the fourth gear 69 and the second clutch plate 71, and when the rotating shaft 70 rotates clockwise (CW) from a state in which the fourth gear 69 and the second clutch plate 71 are engaged, the second clutch plate 71 moves in the direction opposite to the fourth gear 69 to release the engagement.

[0169] 2. Specific embodiment The present embodiment will now be described in more detail.

[0170] (1) Wheel structure The wheel structure 1 of this embodiment is the same as that of the second embodiment except for the configuration of the frame support member 6. The configuration of the frame support member 6 differs from that of the second embodiment in that the transmission control mechanism and the clutch mechanism are provided on the rotating shaft rather than on the intermediate shaft.

[0171] Fig. 32 is an exploded view of the frame support member 6 of the wheel structure 1 in this embodiment. The differences from the frame support member 6 of the second embodiment shown in Fig. 15 include the following points.

[0172] (a) The rotating shaft 70 is inserted through the first clutch plate 65, the elastic body 66, and the second clutch plate 71. (b) The fourth gear 69 and the second clutch plate 71 are rotatably supported, while the first clutch plate 65 is fixedly supported. (c) The fourth gear 69 and the second clutch plate 71 face each other, and the fourth gear 69 has a plurality of engagement pawls (cap teeth) 69c on the surface facing the second clutch plate 71, and the second clutch plate 71 has a plurality of engagement pawls (cap teeth) 71a on the surface facing the fourth gear 69. (d) The fork 72 has a support portion 72e. The pivot shaft 70 is inserted into one end of the support portion 72e, which is rotatably supported by the pivot shaft 70, and a first fork guide 72a and a second fork guide 72b are provided at the end. The other end of the support portion 72e supports a shaft portion 72c erected at the pivot portion of the fork 72, and the shaft portion 72c is rotatably supported by a pin 62c erected on the second subframe 62 by inserting the pin 62c into an insertion hole 72d. (e) The spiral direction of the elastic body 66 is reversed.

[0173] (2) Operation of frame support members The operation of the frame support member 6 is basically the same as that of the second embodiment. Figures 33(a)-(g) and 34(a)-(e) show the operation of the frame support member 6 from normal driving, climbing over a step, to returning to the initial state, i.e., the state during normal driving. The definition of the rotation angle is the same as in the second embodiment. Figures 33 and 34 are both views of the inside of the frame support member 6 as viewed diagonally from above and rear left with respect to the direction of travel.

[0174] 33(a) shows the state during normal running, that is, the state when the rotation angle is 0°. At this time, the bevel teeth 69c of the fourth gear 69 and the bevel teeth 71a of the second clutch plate 71 are not engaged with each other, so the state of the frame support member 6 does not change even if the main wheel 2 rotates during running. Note that, due to the bias of the elastic body 66, the engagement claw 71b of the second clutch plate 71 engages with the protrusion 65c of the first clutch plate 65 in the CW direction.

[0175] FIG. 33(b) shows the state when the rotation angle becomes 30°. When the main wheel 2 comes into contact with the step 11, it stops rotating. When the frame 4 is pushed forward in this state, the rotation shaft 70 and the frame support member 6 rotate counterclockwise (CCW) around the rotation shaft 21. At this time, the frame support member 6 rotates counterclockwise (CCW) around the rotation shaft 70. Meanwhile, since the fork 72 is supported by the pin 62c, it rotates CCW around the rotation shaft 70 in accordance with the rotation of the frame support member 6, i.e., the rotation of the second sub-frame 62. In addition, with the rotation of the rotation shaft 70, the frame 4 rises until the rotation shaft 70 reaches the vertical line VL, i.e., until the rotation angle becomes 30°, and then it descends.

[0176] 33(c) shows the state when the rotation angle becomes 37°. When the rotation angle becomes 37°, the end face 72be of the second fork guide 72b located on the left side of the support portion 72e of the fork 72 in the traveling direction comes into contact with the end face 70be of the second rotating shaft guide 70b located on the left side of the support portion 72e of the rotating shaft 70 in the traveling direction, and the fork 72 and the second clutch plate 71 supported by the fork 72 move toward the right side in the traveling direction. As a result, the bevel teeth 69c of the fourth gear 69 and the bevel teeth 71a of the second clutch plate 71 start to mesh with each other.

[0177] 33(d) shows the state when the rotation angle reaches 42°. When the rotation angle reaches 42°, the meshing between the bevel teeth 69c of the fourth gear 69 and the bevel teeth 71a of the second clutch plate 71 is completed. As a result, the second clutch plate 71 becomes one with the fourth gear 69 and revolves counterclockwise (CCW) around the third gear 67, and rotates counterclockwise (CCW) while contracting the elastic body 66.

[0178] Fig. 33(e) shows the state when the rotation angle becomes 80°. When the rotation angle becomes 80°, the rotation of the rotation shaft 70, i.e., the counterclockwise (CCW) rotation of the frame support member 6, progresses, and the auxiliary wheel 3 comes into contact with the step upper surface 11b. On the other hand, even when the rotation angle becomes 80°, the main wheel 2 and the first gear 63 do not rotate. Therefore, the second gear 64 and the third gear 67 rotate counterclockwise (CCW) while revolving around the first gear 63, and the second clutch plate 71 and the fourth gear 69 continue to revolve counterclockwise (CCW) and rotate counterclockwise (CCW) while contracting the elastic body 66.

[0179] Fig. 33(f) shows the state when the rotation angle has reached 140°. By further pushing the frame 4 forward, the frame support member 6 rotates counterclockwise (CCW) and the main wheel 2 rides up onto the upper surface of the step. When the frame 4 is moved forward further after riding up onto the upper surface 11b of the step, the rotation of the rotating shaft 70 in the counterclockwise (CCW) direction further progresses and the rotation angle becomes larger, so that the engaging claw 71b of the second clutch plate 71 engages with the protrusion 65c of the first clutch plate 65 in the counterclockwise (CCW) direction, as shown in Fig. 33(g).

[0180] FIG. 34(a) shows the state when the rotating shaft 70, i.e., the frame support member 6, starts to rotate in the clockwise (CW) direction in conjunction with the counterclockwise (CCW) rotation of the main wheel 2, and the rotation angle decreases to 110°.

[0181] When the second clutch plate 71 moves further forward with the engagement claws 71b of the second clutch plate 71 engaged with the protrusions 65c of the first clutch plate 65 in the CCW direction, the first gear 63 rotates counterclockwise (CCW), the second gear 64 and the third gear 67 rotate clockwise (CW), and the fourth gear 69 and the second clutch plate 71 rotate CCW together while revolving clockwise (CW) around the third gear 67.

[0182] As a result, the rotating shaft 70 rotates CW around the rotating shaft 21, the rotation angle decreases, the frame 4 rises, and the auxiliary wheels 3 move away from the step upper surface 11b. Even when the rotation angle reaches 110°, the engaging pawl 71b of the second clutch plate 71 maintains the state of being engaged with the protrusion 65c of the first clutch plate 65 in the CCW direction.

[0183] As the rotating shaft 70 continues to rotate in the CW direction, the end face 72ae of the first fork guide 72 comes into contact with the end face 70ae of the first rotating shaft guide, and the fork 72 and the second clutch plate 71 supported by the fork 72 start to move leftward in the traveling direction. Then, when the rotation angle decreases to less than 18°, the meshing between the bevel teeth 69c of the fourth gear and the bevel teeth 71a of the second clutch plate is released.

[0184] As the meshing is released, the second clutch plate 71 is rotated in the CW direction at once by the bias of the elastic body 66, and the engaging claw 71b of the second clutch plate 71 engages with the protrusion 65c of the first clutch plate in the CW direction as shown in Fig. 34(b). Note that Fig. 34(b) shows the state when the rotation angle has decreased to 30°.

[0185] By further advancing, the rotation angle decreases and the frame 4 rises. Figures 34(c) and 34(d) show the states when the rotation angle has decreased to 25° and 18°, respectively. When the rotation angle reaches 18°, the second clutch plate 71 is initialized as shown in Figure 34(e) by the same mechanism as in the second embodiment.

[0186] This completes a series of steps climbing operations of the wheel structure 1.

[0187] In this manner, in this embodiment as well, as in the first and second embodiments, the frame 4 rises as the wheel structure moves forward due to a rotational motion in accordance with the forward movement of the wheel structure; however, since the forward movement distance is sufficiently greater than the upward movement distance and the apparent slope is gentle, even a small force of several hundred g can smoothly cause the main wheel 2 to ride up onto the step upper surface 11b.

[0188] [4] Application of non-circular gears As described above, in the second and third embodiments, the third gear and the fourth gear may be non-circular gears that are constantly meshed with each other.

[0189] Examples of non-circular gears include a pair of trigonometric function gears and an elliptical gear.

[0190] Fig. 35(a) shows an exploded view of the frame support member 6 in the second embodiment in which elliptical gears are used for the third gear 67 and the fourth gear 69, and Fig. 35(b) shows a perspective view of the inside of the frame support member 6 as seen diagonally from above and ahead to the left in the direction of travel. Here, the major axis of the fourth gear 69 is positioned horizontally, and the major axis of the third gear 67 is positioned vertically.

[0191] 36 and 37 show the relationship between the height of the frame 4 and the travel distance of the wheel structure 1 when the pivot shaft 70 and the frame support member 6 are pivoted CW by moving the wheel structure 1 forward on the upper surface of the step. Fig. 36 shows the case where the third gear 67 and the fourth gear 69 are combined as a combination of circular gears, while Fig. 37 shows the case where they are combined as a combination of non-circular gears. The height of the frame 4 can be found, for example, as the height of the canopy part 4a at the transported object platform mounting part 5 from the upper surface 11b of the step, as shown in Fig. 38.

[0192] As shown in Figure 36, when the third gear 67 and the fourth gear 69 are combined with a circular gear combination, the height of the frame 4 and the travel distance have a sinusoidal relationship, and the climbing angle is not constant and the climbing distance is long, so that a step can be climbed with less force. On the other hand, when a non-circular gear combination is used and the gear ratio is variable, the climbing angle can be made uniform and the climbing distance can be shortened, as shown in Figure 37.

[0193] [5] Application of snow tires In each embodiment, it is preferable to use a snow tire that has excellent grip performance on snowy roads for at least the tire 2a of the main wheel 2 out of the tire 2a of the main wheel 2 and the tire 3a of the auxiliary wheel 3, because this allows the vehicle to more reliably climb over steps even on slippery surfaces such as snow.

[0194] That is, when the frame 4 is raised after the main wheel 2 has climbed up onto the step surface, the rotating shaft 70 is rotated CW. For this purpose, the main wheel 2 needs to rotate without skidding when the wheel structure 1 is moved forward. However, when attempting to climb up a slippery road surface such as a snowy surface with a heavy load loaded on it, the main wheel 2 may skid, which may be dangerous, so it is preferable to use tires for snowy roads to suppress skidding. Specific examples of tires for snowy roads include tires made of foam rubber, and tires made of rubber mixed with crushed granules such as walnut shells, rice husks, egg shells, and animal bones.

[0195] Although the present invention has been described above based on the embodiment, the present invention is not limited to the above embodiment. Note that various modifications can be made to the above embodiment within the same and equivalent scope of the present invention. [Explanation of symbols]

[0196] 1 Wheel structure 2 main wheels 2a Tire 2b Wheel 3 Training wheels 3a Tire 3b Wheel 4 Frames 4a Canopy 4b Side wall part 4c Training wheel support part 5 Transport load platform attachment section 6 Frame support member 10 flat surface 11 Steps 11a Step edge 11b Step top 21 Main wheel rotation axis 31 Axis of support wheels 61 1st subframe 62 Second subframe 62a Circular hole 62b Stopper 62c Pin 63 First Gear 63a Shaft hole 64 2nd Gear 64a Shaft hole 64b Engagement claw 64c Engagement claw (cap teeth) 65 Clutch plate (first clutch plate) 65a shaft hole 65b Recess 65c protrusion 66 Elastic body (spring) 67 3rd Gear 67a shaft hole 67b Convex 68 Intermediate shaft 69 4th Gear 69a Shaft hole 69b Cylindrical protrusion 69c Engagement claw (cap teeth) 70 Rotating Axis 70a 1st rotating shaft guide 70ae End face of the first rotating shaft guide 70b Second rotating shaft guide 70be End face of second rotating shaft guide 71 No. 2 clutch plate 71a Engagement claw (capsule) 71b Engagement claw 72 Fork 72a 1st fork guide 72ae End face of first fork guide 72b 2nd fork guide 72be End face of second fork guide 72c shaft 72d Insertion hole 72e Support part VL vertical line

Claims

1. A wheel structure in which a large-diameter main wheel is disposed at the rear of a frame on which a transported object placement platform mounting portion is provided, and a small-diameter auxiliary wheel is disposed at the front of the frame, and the auxiliary wheel comes into contact with an upper surface of the step as the main wheel comes into contact with the 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 rotation mechanism having a rotation shaft that is arranged parallel to a rotation shaft of the main wheel, The wheel structure is characterized in that a transmission mechanism is provided between the rotation axis of the main wheel and the pivot shaft, the transmission mechanism decelerating the counterclockwise (CCW: Counter Clock Wise) rotation of the main wheel and transmitting it to the pivot shaft, a transmission control mechanism controlling whether or not to transmit the rotation of the main wheel to the pivot shaft, a clutch mechanism switching the counterclockwise (CCW) rotation of the main wheel by rotation of a clutch plate so that the pivot shaft rotates counterclockwise (CCW) or clockwise (CW: Clock Wise), and a return mechanism returning the clutch mechanism to an initial position by the biasing force of an elastic body. Note that clockwise (CW) and counterclockwise (CCW) refer to the rotational directions when the wheel structure moving leftward is viewed from the left side.

2. During normal running, the counterclockwise (CCW) rotation of the main wheel is not transmitted to the pivot shaft, and the main wheel moves forward while the auxiliary wheel is lifted off the ground, When the main wheel contacts the step, the frame support member rotates counterclockwise (CCW) by the rotating shaft to which the counterclockwise (CCW) rotation of the main wheel is transmitted as is, and the auxiliary wheel descends and abuts on the upper surface of the step, and then the main wheel rotating counterclockwise (CCW) rises and rides onto the upper surface of the step, The wheel structure according to claim 1, characterized in that after the main wheel rides up onto the top surface of the step, the counterclockwise (CCW) rotation of the main wheel is replaced by the clockwise (CW) rotation of the main wheel, and the frame support member rotates clockwise (CW) by the pivot shaft to which the auxiliary wheel rises and returns to its initial position, while the main wheel rotates counterclockwise (CCW) to move forward on the top surface of the step.

3. 3. The wheel structure according to claim 1, characterized in that the frame support member is provided with a first subframe having a hole through which a rotation shaft of the main wheel is inserted, and a second subframe having a hole through which a rotation shaft that rotates the frame support member is inserted, and the rotation mechanism is disposed between the first subframe and the second subframe.

4. The wheel structure according to claim 3, characterized in that the first subframe is box-shaped and the second subframe is lid-shaped, and the pivot mechanism, the transmission mechanism, the transmission control mechanism, the clutch mechanism, and the return mechanism are housed within a housing formed by the first subframe and the second subframe.

5. 3. The wheel structure according to claim 1, wherein the elastic body is a spring or a spiral spring.

6. A transport device comprising the wheel structure according to claim 1 or 2.

7. The rotation mechanism includes: A first gear that is inserted and journaled on a rotation shaft of the main wheel; A second gear that meshes with the first gear; a third gear integrated with the clutch mechanism; a fourth gear including a toothless portion and a toothed portion, the fourth gear being disposed so as to mesh with the third gear at the toothed portion; an intermediate shaft that is disposed parallel to a rotation axis of the main wheel, and has one end that is in upright contact with the second subframe so as to rotatably support each of the second gear, the third gear, the fourth gear, and the clutch plate; 3. The wheel structure according to claim 1, further comprising a rotation shaft through which the fourth gear fixed to the frame is inserted and which is inserted through a hole in the second subframe.

8. The elastic body is When the frame support member is located at an initial position and in a contracted state relative to a free state, one end of the frame support member is engaged with the second gear and the other end of the frame support member is engaged with the clutch plate, 8. The wheel construction of claim 7, wherein said second gear is biased to engage said clutch plate in a counterclockwise (CCW) direction.

9. 8. The wheel structure according to claim 7, wherein the radius of said first gear is smaller than the radius of said second gear.

10. the second gear has a diameter larger than that of the clutch plate, and includes an engagement pawl on a side surface of the clutch plate that is radially outward from an outer edge of the clutch plate, The clutch plate is disc-shaped and has a protrusion on an outer circumferential surface thereof that protrudes radially outward.

8. The wheel structure according to claim 7, wherein the second gear and the clutch plate are engaged with each other by the engaging claw and the protrusion.

11. A recess or a protrusion is formed on a surface of the clutch plate facing the third gear, a protrusion that can be fitted into a recess of the clutch plate or a recess that can be fitted into a protrusion of the clutch plate is formed on a surface of the third gear that faces the clutch plate, 8. The wheel structure according to claim 7, wherein the clutch plate and the third gear are integrated by fitting a concave or convex portion of the clutch plate with a convex or concave portion of the third gear.

12. 8. The wheel structure according to claim 7, wherein the radius of said third gear is smaller than the radius of the toothed portion of said fourth gear.

13. The second subframe has a circular hole at an end portion thereof that is supported by the rotating shaft, the fourth gear includes a cylindrical protrusion having the same diameter as an inner diameter of the circular hole on a surface facing the second subframe, The protrusion is rotatably fitted into the circular hole, The wheel structure according to claim 7, characterized in that the second sub-frame is rotatably supported on the rotation shaft.

14. When the wheel structure to which the transported object carrier is attached is viewed from the side, The wheel structure according to claim 7, characterized in that the positions of the rotation shaft and the pivot shaft are set so that when the frame support member rotates clockwise (CW) and the toothed portions of the third gear and the fourth gear are released from their meshed state, the center of the rotation shaft is located forward in the direction of travel of a vertical line passing through the center of the rotation shaft.

15. The wheel structure described in claim 7, characterized in that the frame support member has a stopper protruding toward the frame on the side of the second subframe facing the frame, and is configured to stop at the fixed position when rotated clockwise (CW) by the stopper abutting the end face of the frame.

16. The rotation mechanism includes: A first gear that is inserted and journaled on a rotation shaft of the main wheel; A second gear that meshes with the first gear; a third gear and a fourth gear arranged to mesh with each other; an intermediate shaft having one end in contact with the second subframe and perpendicular to the second subframe; The clutch mechanism includes two clutch plates, a first clutch plate and a second clutch plate. the second gear and the third gear are each rotatably supported by the intermediate shaft, the first clutch plate and the second clutch plate are journalled on the same side of either the intermediate shaft or the rotating shaft, The rotation shaft is fixed to the frame, When the first clutch plate and the second clutch plate are rotatably supported by the intermediate shaft, and the fourth gear is journaled and fixed to the rotating shaft, one surface of the second clutch plate faces the second gear and the other surface faces one surface of the first clutch plate, the first clutch plate is integral with the third gear at a surface other than a surface facing the second clutch plate, When the first clutch plate is journaled and fixed to the rotating shaft, and the second clutch plate and the fourth gear are journaled and rotatably supported on the rotating shaft, the third gear is integral with the second gear, one surface of the second clutch plate faces the fourth gear and the other surface faces one surface of the first clutch plate, The transmission mechanism includes: a plurality of pawls that can mesh with each other and an engagement portion that enables the second clutch plate and the first clutch plate to be engaged with each other are provided on the outer circumferential edge portions of the facing surfaces of the second gear or the fourth gear and the second clutch plate, and when the pawls are engaged with each other and the engagement portions are engaged, the rotation of the main wheel is transmitted to the rotating shaft; The wheel structure according to claim 1 or 2, characterized in that the clutch mechanism transmits the counterclockwise (CCW) rotation of the main wheel so that the rotating shaft rotates clockwise (CW) by rotation of the second clutch plate, and allows the counterclockwise (CCW) rotation of the rotating shaft when the counterclockwise (CCW) rotation of the main wheel stops.

17. the elastic body has one end engaged with the second clutch plate and the other end engaged with the first clutch plate in a state in which the elastic body is contracted relative to a free state when the frame support member is located at an initial position, The wheel structure of claim 16, characterized in that when the first clutch plate and the second clutch plate are rotatably supported on the intermediate shaft and the fourth gear is journalled and fixed on the rotating shaft, the second clutch plate is biased to engage with the first clutch plate in a counterclockwise (CCW) direction, and when the first clutch plate is journalled and fixed on the rotating shaft and the second clutch plate and the fourth gear are rotatably supported on the rotating shaft, the second clutch plate is biased to engage with the first clutch plate in a clockwise (CW) direction.

18. When the wheel structure to which the transported object carrier is attached is viewed from the side, The wheel structure according to claim 16, characterized in that the positions of the rotation shaft and the pivot shaft are set so that when the frame support member rotates clockwise (CW) and the second gear and the second clutch plate are released from their meshed state, the center of the rotation shaft is located forward in the direction of travel of a vertical line passing through the center of the rotation shaft.

19. 17. The wheel structure according to claim 16, wherein the third gear and the fourth gear are non-circular gears that are constantly in mesh with each other.

20. The transmission control mechanism includes: a moving mechanism that moves the second clutch plate in an axial direction of the intermediate shaft, The wheel structure of claim 16, characterized in that the moving mechanism moves the second clutch plate toward the second gear when the rotating shaft rotates counterclockwise (CCW) to engage the pawls of the second gear and the second clutch plate, and moves the second clutch plate in the opposite direction to the second gear when the rotating shaft rotates clockwise (CW) from a state in which the second gear and the second clutch plate are engaged, to release the engagement.

21. The rotation mechanism includes: A first gear that is inserted and journaled on a rotation shaft of the main wheel; A second gear that meshes with the first gear; a third gear integrated with the second gear; a fourth gear arranged to mesh with the third gear; an intermediate shaft having one end in contact with the second subframe and perpendicular to the second subframe; The clutch mechanism includes two clutch plates, a first clutch plate and a second clutch plate. the second gear and the third gear are rotatably supported by the intermediate shaft, the rotating shaft is fixed to the frame, the fourth gear and the second clutch plate are rotatably supported by the rotating shaft and face each other, and the first clutch plate is supported and fixed to the rotating shaft and faces the second clutch plate, the transmission mechanism includes a plurality of mutually meshable pawls on outer peripheral edges of opposing surfaces of the fourth gear and the second clutch plate, and an engagement portion that enables the second clutch plate and the first clutch plate to engage with each other, and transmits rotation of the main wheel to the rotating shaft when the pawls are meshed with each other and the engagement portions are engaged; The wheel structure according to claim 16, characterized in that the clutch mechanism transmits the counterclockwise (CCW) rotation of the main wheel so that the rotating shaft rotates clockwise (CW) by rotation of the second clutch plate, and allows the rotating shaft to rotate counterclockwise (CCW) when the counterclockwise (CCW) rotation of the main wheel stops.

22. The transmission control mechanism includes: a moving mechanism for moving the second clutch plate in an axial direction of the rotating shaft, The vehicle structure of claim 21, characterized in that the moving mechanism moves the second clutch plate toward the fourth gear when the rotating shaft rotates counterclockwise (CCW) to engage the pawls of the fourth gear and the second clutch plate, and moves the second clutch plate in the opposite direction to the fourth gear when the rotating shaft rotates clockwise (CW) from a state in which the fourth gear and the second clutch plate are engaged, to release the engagement.

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