wheel structure

Abstract

To provide a wheel structure capable of smoothly performing a running-on action with small force from the start of running onto a step to its completion.SOLUTION: A wheel structure includes a frame provided with a main wheel of a large diameter, an auxiliary wheel of a small diameter and an object placing table installation part. The wheel structure is configured such that after the main wheel makes contact with a step, the auxiliary wheel abuts against an upper surface of the step and the main wheel runs onto the upper surface of the step. The frame supports the auxiliary wheel in a front lower end part thereof, and the frame has a hole portion of a shape that connects a short length hole extending backward and downward and a long length hole extending backward and upward via a curved hole part such that a main wheel shaft can be inserted into the hole portion. By movement of the main wheel shaft inserted into the hole portion through the hole portion, the main wheel runs onto the upper surface of the step while forming a predetermined path, and by movement of the main wheel shaft through the hole portion in an opposite direction to that in running on, the wheel structure returns to a state before contact with the step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wheel structure, and more particularly to a wheel structure that can easily climb up steps. [Background technology]

[0002] In transport devices that use human power as a propulsion force, such as luggage carts, 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 are often filled with many steps due to differences in road surface elevation and obstacles, and it is not easy to make the wheels smoothly climb up the steps with little force without impacting 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 first contacts the top surface of the step, and then the main wheel climbs 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 magnitude of the 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 the technology using springs as 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 quickly, which may cause the transported goods to be impacted, 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] Japanese Patent Application Laid-Open No. 2006-7855 Summary of the Invention [Problem to be solved by the invention]

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

[0008] As a result of extensive 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 having a frame provided with large-diameter main wheels, small-diameter auxiliary wheels, and transported object platform mounting portions, wherein after the main wheels come into contact with a step, the auxiliary wheels abut on an upper surface of the step, causing the main wheels to ride up onto the upper surface of the step, The frame supports the auxiliary wheels at a front lower end thereof, the frame is formed with a hole portion having a shape in which a short hole portion extending rearward and downward and a long hole portion extending rearward and upward are connected by a curved hole portion, so that the main wheel axle can be inserted therethrough; a pinion gear is provided on the main wheel shaft via a switching means that can switch between transmitting and not transmitting rotation of the main wheel; a rack gear capable of meshing with the pinion gear is provided along the hole portion on the rear side of the hole portion from the curved hole portion to the elongated hole portion of the hole portion, When the main wheel shaft inserted into the hole moves through the hole, the main wheel rides on the upper surface of the step while forming a predetermined trajectory, The wheel structure is characterized in that the main wheel axle is configured to return to the state before contacting the step by moving through the hole in the opposite direction to that when climbing over the step.

[0011] Claim 2 The invention described in As a means for transmitting rotation of the main wheel, the main wheel and the pinion gear are each provided with a concave-convex portion that can engage with each other, The switching means is configured by an engaging claw for engaging the concave and convex portions, and a disengaging claw for disengaging the engagement of the concave and convex portions. 1 2. The wheel structure according to claim 1 .

[0012] Claim 3 The invention described in The switching means is a free-type bidirectional clutch provided between the main wheel shaft and the pinion gear. 1 2. The wheel structure according to claim 1 .

[0013] Claim 4 The invention described in The switching means is configured by an elastic body having one end fixed to each of the main wheel and the pinion gear, and a rotation transmission locking portion provided on each of the main wheel and the pinion gear. 1 2. The wheel structure according to claim 1 .

[0014] Claim 5 The invention described in The present invention is characterized in that one or more intermediate rotating bodies provided with locking portions for transmitting rotation are disposed between the main wheel and the pinion gear. 4 2. The wheel structure according to claim 1 .

[0015] Claim 6 The invention described in The pinion gear and the rack gear are provided in pairs, one pair each, symmetrically on either side of the main wheel, so as to operate synchronously. 1 or claims 5 The wheel structure according to any one of the above items.

[0016] Claim 7The invention described in A wheel structure having a frame provided with large-diameter main wheels, small-diameter auxiliary wheels, and transported object platform mounting portions, wherein after the main wheels come into contact with a step, the auxiliary wheels abut on an upper surface of the step, causing the main wheels to ride up onto the upper surface of the step, The frame supports the auxiliary wheels at a front lower end thereof, the frame is formed with a hole portion having a shape in which a short hole portion extending rearward and downward and a long hole portion extending rearward and upward are connected by a curved hole portion, so that the main wheel axle can be inserted therethrough; A pinion gear that rotates together with the main wheel is provided on the main wheel shaft, A rack gear is provided along the hole on the front side of the hole, and a clutch gear is provided to mesh with the rack gear and move from the curved hole portion to the elongated hole portion of the hole portion; An elastic body connected between the clutch gear and the pinion gear is configured to switch between transmission and non-transmission of rotation of the main wheel to the pinion gear. 、 When the main wheel shaft inserted into the hole moves through the hole, the main wheel rides on the upper surface of the step while forming a predetermined trajectory, The main wheel shaft moves through the hole in the opposite direction to when climbing over the step, thereby returning to the state before contacting the step. It is characterized by Car It is a ring structure.

[0018] Claim 8 The invention described in A wheel structure having a frame provided with large-diameter main wheels, small-diameter auxiliary wheels, and transported object platform mounting portions, wherein after the main wheels come into contact with a step, the auxiliary wheels abut on an upper surface of the step, causing the main wheels to ride up onto the upper surface of the step, The inner circumferential surface of the main wheel is formed with a smooth area where a bearing rotatably inserted into each of three or more support pillars provided on the main wheel comes into contact, and an area where an internal gear that meshes with a gear attached to the tip of one of the bearings on the support pillars is provided, and the main wheel is supported by the rotation of each of the bearings on the support pillars, The frame supports the auxiliary wheels at a front lower end thereof, The frame is formed with two or more parallel rows of holes, each having a shape in which a short hole extending downward and rearward and a long hole extending upward and rearward are connected by a curved hole, The support pillars inserted into the respective hole portions move through the holes, causing the main wheels to ride on the upper surface of the step while forming a predetermined trajectory, The wheel structure is characterized in that the main wheel axle is configured to return to the state before contacting the step by moving through the hole in the opposite direction to that when climbing over the step. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a wheel structure that can smoothly perform a step climbing operation with a small force from the start to the end. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic side view of a wheel structure according to a first embodiment of the present invention; [Figure 2] 1 is a schematic front view of a wheel structure according to a first embodiment of the present invention; [Figure 3] FIG. 2 is a schematic perspective view illustrating a transmission means for transmitting rotation of a main wheel to a pinion gear in the first embodiment of the present invention. [Figure 4] FIG. 3 is a schematic side view showing a state when a main wheel comes into contact with a step end face in the first embodiment of the present invention. [Figure 5] FIG. 3 is a schematic side view illustrating a state in which a pinion gear moves along an elongated hole portion in the first embodiment of the present invention. [Figure 6] FIG. 3 is a schematic side view illustrating a state in which a main wheel has climbed onto an upper surface of a step in the first embodiment of the present invention. [Figure 7] FIG. 3 is a schematic perspective view illustrating engagement between a recess and a protrusion in the first embodiment of the present invention. [Figure 8] FIG. 4 is a schematic side view illustrating a state when a pinion gear reaches a curved hole portion in the first embodiment of the present invention. [Figure 9] 4 is a schematic perspective view illustrating disengagement between a recess and a protrusion by a disengagement claw in the first embodiment of the present invention. FIG. [Figure 10]FIG. 10 is a schematic side view showing an example of a wheel structure in which a free-type bidirectional clutch is used as a switching means in a first modified example of the first embodiment of the present invention. [Figure 11] FIG. 10 is a schematic perspective view illustrating a combination of an elastic body with a locking portion of a main wheel and a locking portion of a pinion gear in a second modified example of the first embodiment of the present invention. [Figure 12] FIG. 10 is a schematic perspective view illustrating the state of the main wheels and pinion gears during normal running in the second modified example of the first embodiment of the present invention. [Figure 13] FIG. 10 is a schematic perspective view showing a state of a main wheel and a pinion gear when the main wheel rides over the upper surface of a step in a second modified example of the first embodiment of the present invention. [Figure 14] FIG. 10 is a schematic perspective view showing a case where one intermediate rotor is disposed between a main wheel and a pinion gear in a second modified example of the first embodiment of the present invention. [Figure 15] FIG. 10 is a front view of a wheel structure according to a third modification of the first embodiment of the present invention, which is a modification 1 of the first embodiment. [Figure 16] FIG. 16 is a schematic perspective view illustrating a gear coupling portion in FIG. 15. [Figure 17] FIG. 10 is a schematic side view of a wheel structure according to a second embodiment of the present invention. [Figure 18] FIG. 10 is a schematic front view of a wheel structure according to a second embodiment of the present invention. [Figure 19] FIG. 10 is a schematic side view illustrating a state in which the clutch gear meshes with the rack gear and moves along the elongated hole portion in the second embodiment of the present invention. [Figure 20] FIG. 10 is a schematic side view illustrating a state in which a main wheel has climbed onto the upper surface of a step in the second embodiment of the present invention. [Figure 21] 10 is a diagram illustrating a state in which the clutch gear reaches the vicinity of the curved hole portion, which is the initial position, in the second embodiment of the present invention. FIG. [Figure 22] FIG. 10 is a schematic side view of a wheel structure according to a third embodiment of the present invention. [Figure 23]FIG. 10 is a schematic front view of a wheel structure according to a third embodiment of the present invention. [Figure 24] FIG. 11 is a schematic side view showing a state when a main wheel comes into contact with a step end face in the third embodiment of the present invention. [Figure 25] FIG. 11 is a schematic side view showing a state in which an auxiliary wheel comes into contact with an upper surface of a step in the third embodiment of the present invention. [Figure 26] FIG. 11 is a schematic side view showing a state in which the main wheels have completely climbed onto the upper surface of a step in the third embodiment of the present invention. [Figure 27] FIG. 11 is a schematic side view illustrating movement of a frame in the third embodiment of the present invention. [Figure 28] FIG. 11 is a schematic side view illustrating a state immediately before the frame and the training wheels return to their initial positions in the third embodiment of the present invention. [Figure 29] FIG. 10 is a schematic side view of a wheel structure according to a fourth embodiment of the present invention. [Figure 30] FIG. 10 is a schematic front view of a wheel structure according to a fourth embodiment of the present invention. [Figure 31] FIG. 13 is a schematic perspective view illustrating the rotation of a main wheel in a fourth embodiment of the present invention. [Figure 32] FIG. 13 is a schematic exploded perspective view illustrating the attachment of a main wheel in a fourth embodiment of the present invention. [Figure 33] FIG. 13 is a schematic side view showing a state when a main wheel comes into contact with a step end face in the fourth embodiment of the present invention. [Figure 34] FIG. 13 is a schematic side view showing a state in which the main wheels have completely climbed onto the upper surface of a step in the fourth embodiment of the present invention. [Figure 35] FIG. 13 is a schematic cross-sectional view showing a state in which each of the two support columns reaches the upper end of each hole in the fourth embodiment of the present invention. [Figure 36] FIG. 13 is a schematic side view illustrating movement of a frame in the fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be specifically described below using four embodiments (first to fourth embodiments) as examples.

[0022] 1. First embodiment (1) Wheel structure configuration Fig. 1 is a schematic side view of the wheel structure according to this embodiment, Fig. 2 is a schematic front view of the wheel structure, and Fig. 3 is a schematic perspective view illustrating a transmission means for transmitting the rotation of the main wheel 2 to the pinion gear 5 in this embodiment.

[0023] In Figs. 1 to 3, 1 is a frame, 2 is a main wheel, 3 is an auxiliary wheel, and 4 is a mounting portion for the transported object placing platform.

[0024] 1 and 2, the wheel structure according to this embodiment has a frame 1 provided with a large-diameter main wheel 2, a small-diameter auxiliary wheel 3, and a transported object platform mounting portion 4. The frame 1 supports the auxiliary wheel 3 at its front lower end, and is also formed with a hole 6 formed in the frame 1, the hole 6 having a shape in which a short hole 6a extending downward and rearward and a long hole 6b extending upward and rearward are connected by a curved hole 6c, and a main wheel axle (axle of the main wheel) 2a is inserted into the hole 6.

[0025] A pinion gear 5 is provided on the main wheel axle 2a, and a rack gear 9 is provided on the frame 1 from the curved hole portion 6c along the elongated hole portion 6b of the hole portion 6 so as to be able to mesh with the pinion gear 5. A taper 5a is formed on the surface of the pinion gear 5 facing the frame 1. 9a of the rack gear 9 is a long portion that follows the elongated hole portion 6b of the hole portion 6, and 9b is a curved portion that follows the curved hole portion 6c of the hole portion 6.

[0026] 2 and 3, recessed portion 2b is provided on a surface formed to protrude outward from main wheel 2, and as a result of this engaging with protruding portion 5b provided on pinion gear 5, the rotation of main wheel 2, which rotates forward (counterclockwise on the page), is transmitted to pinion gear 5. On the other hand, by disengaging recessed portion 2b from protruding portion 5b, the rotation of main wheel 2 can be prevented from being transmitted to pinion gear 5.

[0027] Reference numeral 7 denotes an engagement claw provided for engaging the recessed portion 2b with the protruding portion 5b, and 8 denotes an engagement release claw provided for releasing the engagement between the recessed portion 2b and the protruding portion 5b. By providing these claws 7 and 8, the recessed portion 2b and the protruding portion 5b can be engaged or released, thereby appropriately switching between transmitting and not transmitting the rotation of the main wheel 2 to the pinion gear 5.

[0028] (2) Operation Next, the operation of the wheel structure according to this embodiment from before contacting a step to after climbing over the step will be described.

[0029] 1, when the vehicle is traveling on a flat surface before coming into contact with a step, the wheel structure rotates counterclockwise and moves forward to the left on the page, with the auxiliary wheels 3 off the ground (not shown) and the main wheels 2 supporting the load applied via the transported object platform mounting parts 4. At this time, the recessed parts 2b and the protruding parts 5b are disengaged by the disengagement claws 8, and the rotation of the main wheels 2 is not transmitted to the pinion gear 5.

[0030] The wheel structure then moves forward until it reaches just before the step, and the main wheel comes into contact with the edge of the step. Figure 4 is a schematic side view showing the state when the main wheel comes into contact with the edge of the step. In Figure 4, 10 is a flat surface (during normal driving), 11 is the step, 11a is the edge of the step 11, and 11b is the top surface of the step 11.

[0031] As shown in Figure 4, when the wheel structure advances on the flat surface 10 to just before the step 11 and the main wheel 2 comes into contact with the step end face 11a, the main wheel 2 stops rotating. At this time, the main wheel 2 receives a reaction force from contact with the step end face 11a, while the frame 1 moves forward due to the impact of the main wheel 2 hitting the step end face 11a. As a result, the main wheel axle 2a moves rearward and downward within the short hole portion 6a.

[0032] When the main wheel axle 2a, which has moved through the short hole 6a, reaches the curved hole 6c, the pinion gear 5, which has moved with the main wheel axle 2a, begins to mesh with the curved portion 9b of the rack gear 9 and rotates clockwise. As the pinion gear 5 rotates, the main wheel axle 2a moves from the curved hole 6c to the long hole 6b, and then, due to the load applied via the transported object platform mounting portion 4, the pinion gear 5 rotates and moves upward and rearward along the long hole 6b.

[0033] 5 is a schematic side view illustrating the state in which the pinion gear 5 moves along the elongated hole portion 6b. At this time, the main wheel axle 2a also moves rearward and upward along the elongated hole portion 6b in accordance with the movement of the pinion gear 5, which rotates while meshing with the elongated portion 9a of the rack gear 9. However, because the main wheel 2 is in contact with the flat surface 10, the frame 1 moves downward, and the front auxiliary wheel 3 comes into contact with the step upper surface 11b. At this time, because the recessed portion 2b and the protruding portion 5b are not engaged as described above, the main wheel 2 does not rotate even though the pinion gear 5 is rotating, and remains in the state in which it was in contact with the step end surface 11a.

[0034] When the auxiliary wheels 3 come into contact with the step upper surface 11b, most of the load on the wheel structure is applied to the auxiliary wheels 3, while the force applied to the main wheels 2 remains at about the weight of the main wheels 2. Then, as the main wheel axles 2a move further rearward and upward, the main wheels 2 tend to lift off the flat surface 10, and the force that moves the vehicle structure forward causes the main wheels 2 to resume rotation and try to climb up onto the step upper surface 11b. At this time, the forces acting on the main wheels 2 are the force that lifts the main wheels 2 off the flat surface 10 and the force that moves the vehicle structure forward, making it easy to lift light wheels.

[0035] Figure 6 is a schematic side view illustrating the state in which the main wheel 2 rides up on the step upper surface 11b. As shown in Figure 6, when the main wheel 2 rides up on the step upper surface 11b, the pinion gear 5 reaches the rear end of the elongated hole portion 6b. At this time, the engaging pawl 7 presses the tapered portion 5a of the pinion gear 5 toward the main wheel 2, engaging the recessed portion 2b and the protruding portion 5b, changing the state so that the rotation of the main wheel 2 is transmitted to the pinion gear 5.

[0036] Figure 7 is a schematic perspective view illustrating the engagement between the recessed portion 2b and the protruding portion 5b, but when the pinion gear 5 reaches the rear end of the elongated hole portion 6b, the positions of the recessed portion 2b and the protruding portion 5b are not necessarily in the same position (the phase is indefinite). Therefore, as shown in Figure 7, the pinion gear 5 is rotated while pressed against the main wheel 2, moving the protruding portion 5b to the position of the recessed portion 2b, and when the recessed portion 2b and the protruding portion 5b are in the same position, they are engaged. This allows the rotation of the main wheel 2 to be transmitted to the pinion gear 5, allowing the main wheel 2 and pinion gear 5 to rotate in the same counterclockwise direction.

[0037] 3 and 7, two recessed portions 2b and two protruding portions 5b are arranged at rotationally symmetrical positions so that the pinion gear 5 can engage with the main wheel 2 during 1 / 2 of a rotation, but one recessed portion may be used. Also, three or more n recessed portions may be arranged at equal angles, in which case the pinion gear 5 can engage with the main wheel 2 during 1 / n of a rotation. Also, either the recessed portion 2b or the protruding portion 5b may be the recessed portion or the protruding portion, as long as they are capable of engaging with each other.

[0038] As described above, engagement of the recessed portion 2b and the protruding portion 5b changes the state so that the rotation of the main wheel 2 is transmitted to the pinion gear 5. Then, as the pinion gear 5 rotates counterclockwise, the same as the main wheel 2, it moves forward and downward through the hole 6 from the rear end of the elongated hole 6b while engaging with the elongated portion 9a of the rack gear 9, and reaches the curved hole 6c.

[0039] FIG. 8 is a schematic side view illustrating the state when the pinion gear 5 reaches the curved hole portion 6c. As shown in FIG. 8, as the pinion gear 5 moves into the curved hole portion 6c, the frame 1 and the training wheels 3 rise to their initial positions. In this case, the pinion gear 5 rotates approximately two times before it reaches the curved hole portion 6c. That is, the main wheel 2 rotates approximately two times while rising to its initial position close to the radius of the main wheel, resulting in a gradual rise. When the pinion gear 5 reaches the curved hole portion 6c, it disengages from the rack gear 9. Then, due to the load applied to the wheel structure, the main wheel axle 2a moves forward and upward within the short hole portion 6a to its initial position. At the same time, the disengagement claw 8 disengages the recessed portion 2b from the protruding portion 5b. This prevents the rotation of the main wheel 2 from being transmitted to the pinion gear 5, and the pinion gear 5 returns to its initial state.

[0040] 9 is a schematic perspective view illustrating the disengagement between the recessed portion 2b and the protruding portion 5b by the disengagement claw 8. The tip of the disengagement claw 8 enters the tapered gap at the engagement between the main wheel 2 and the pinion gear 5, which moves forward and upward within the short hole 6a, thereby disengaging the recessed portion 2b and the protruding portion 5b.

[0041] In this way, the wheel structure is able to climb up the step. In this embodiment, when the main wheel moves back and forth in the hole of the main wheel axle, the rotation of the main wheel is switched between being transmitted and not transmitted to the pinion gear as appropriate, so that two forces are applied to the main wheel 2: a force that lifts the main wheel 2 off the flat surface 10, and a force that moves the vehicle structure forward, making it easy to lift light wheels.

[0042] (3) Modified Example of Switching Means In the above, the transmission and non-transmission of the rotation of the main wheel to the pinion gear is switched using the uneven portion provided between the main wheel and the pinion gear and the engaging and disengaging pawls, but the following modified examples can also be used as the switching means. Note that in each modified example, the configuration and operation other than the switching means are basically the same as those described above, so only the explanation related to the switching means will be given below.

[0043] (a) Free-type bidirectional clutch (first variant) The first modification is an example in which a free-type bidirectional clutch provided between the main wheel shaft and the pinion gear serves as the switching means.

[0044] A free-type bidirectional clutch has the characteristic that it transmits force applied to the input shaft to the output shaft but does not transmit force applied to the output shaft to the input shaft, so even if a free-type bidirectional clutch is used as the switching means instead of the engaging pawl and disengaging pawl, it is possible to switch between transmitting and not transmitting the rotation of the main wheel to the pinion gear. When a free-type bidirectional clutch is used as the switching means, the configuration of the wheel structure can be simplified and reliability is improved.

[0045] Fig. 10 is a schematic side view showing an example of a wheel structure using a free-type bidirectional clutch as a switching means. In Fig. 10, 13 is a free-type bidirectional clutch, which is arranged between the main wheel shaft 2a and the pinion gear 5 so that the main wheel shaft 2a side serves as the input shaft.

[0046] During normal running, the main wheel 2, which is the input shaft, rotates to move the wheel structure forward, and at the same time, the pinion gear 5, which is the output shaft, also rotates. However, at this time, the pinion gear 5 is in the initial position of the short hole portion 6a and is not yet engaged with the rack gear 9, so it is in an idling state relative to the rack gear 9.

[0047] Then, from the time the main wheel 2 comes into contact with the end face of the step until the auxiliary wheel 3 abuts on the top face of the step, the main wheel 2 stops rotating and maintains the state it was in when it came into contact with the end face of the step, just as described above (see Figures 4 and 5). However, after moving into the curved hole 6c, the main wheel shaft 2a also moves rearward and upward along the elongated hole 6b in accordance with the movement of the pinion gear 5, which rotates while meshing with the elongated portion 9a of the rack gear 9, within the hole 6. At this time, the pinion gear 5 rotates clockwise, opposite to the rotation of the main wheel 2, due to its meshing relationship with the rack gear 9. However, the force applied to the output shaft (pinion gear 5) is not transmitted to the input shaft (main wheel 2) by the free-type bidirectional clutch 13, so the main wheel 2 remains stopped from rotating.

[0048] After that, the main wheel 2 resumes rotation as it climbs over the step upper surface 11b, but the pinion gear 5 (output shaft) continues to rotate in the opposite direction to the main wheel 2 (input shaft). At this time, since the rotation angle of the main wheel 2 is less than the rotation angle of the pinion gear 5, the output shaft (pinion gear 5) is rotating relatively to the input shaft (main wheel 2), and no force is transmitted from the output shaft to the input shaft.

[0049] After the main wheel 2 rides up onto the step upper surface 11b, the rotation of the input shaft (main wheel 2) is transmitted to the output shaft (pinion gear 5) via the bidirectional clutch 13, causing the pinion gear 5 to rotate counterclockwise, the same as the main wheel 2. Then, the pinion gear 5, which rotates counterclockwise, the same as the main wheel 2, moves through the hole 6 while meshing with the rack gear 9, and returns to the initial position as described above (see Figures 6 and 8).

[0050] (b) Combination of elastic body and locking portion (second modified example) The second modification is an example in which an elastic body is combined with a locking portion of the main wheel and a locking portion of the pinion gear to provide the same function as the free-type bidirectional clutch described above, thereby serving as a switching means.

[0051] Fig. 11 is a schematic perspective view illustrating the combination of this elastic body with the locking portion of the main wheel and the locking portion of the pinion gear. Fig. 12 is a schematic perspective view illustrating the state of the main wheel and pinion gear during normal driving in this modified example, and Fig. 13 is a schematic perspective view showing the state of the main wheel and pinion gear when the main wheel rides over the top of a step.

[0052] 11 to 13, reference numeral 14 denotes an elastic body such as a torsion spring, and as shown in Fig. 11, one end 14a of elastic body 14 is fixed to a fixed portion 5d provided on pinion gear 5, and the other end 14b is fixed to a fixed portion 2d provided on main wheel 2, and is disposed in a free state in which no external force is applied, or in a state in which it is biased counterclockwise. A locking portion 5e provided on pinion gear 5 and a locking portion 2e provided on main wheel 2 are configured to be able to lock with each other.

[0053] As shown in FIG. 12, during normal running, the main wheel 2 and the pinion gear 5 are in surface contact with each other.

[0054] After the main wheel contacts the end face of the step, the rotation of the main wheel 2 is stopped until the auxiliary wheel abuts on the upper surface of the step, as described above (see Figures 4 and 5). Meanwhile, the pinion gear 5 rotates clockwise while meshing with the rack gear 9. As the pinion gear 5 rotates, the elastic body 14 is gradually compressed.

[0055] After that, until the main wheel resumes rotation and rides over the top of the step, as in Figure 10, the main wheel 2 rotates counterclockwise, while the pinion gear 5 rotates clockwise because it is meshed with the rack gear 9. At this time, because (rotation angle of the main wheel) < (rotation angle of the pinion gear), the rotation of the main wheel 2 is not transmitted to the pinion gear 5, and the pinion gear 5 rotates clockwise, causing the locking portion 5e of the pinion gear 5 to move from a position behind the locking portion 2e of the main wheel 2 to a position in front of the locking portion 2e of the main wheel 2. Accordingly, the elastic body 14 is further compressed.

[0056] Thereafter, when the rotationally moved locking portion 5e comes into contact with locking portion 2e, the two locking portions 5e, 2e enter a locked state, and the rotation of the main wheel 2 is transmitted to the pinion gear 5 via the two locking portions 5e, 2e, causing the main wheel 2 and pinion gear 5 to rotate in the same counterclockwise direction. Then, as in Figure 10, the pinion gear 5 moves through the hole portion 6 toward the initial position while meshing with the rack gear 9, completing the climb-up.

[0057] In this way, this modified example has a simple configuration using inexpensive, common components, namely an elastic body and two locking parts, but it can switch between transmitting and not transmitting the rotation of the main wheel to the pinion gear as appropriate, thereby providing the same functionality as a free-type bidirectional clutch with high reliability and at a lower cost.

[0058] In the above-mentioned Figures 11 to 13, the pinion gear 5 rotates a maximum of just under one rotation relative to the main wheel 2, causing the two locking portions 5e, 2e to come into contact and lock, but if a rotation range of more than one rotation is required, this can be accommodated by placing an intermediate rotating body between the main wheel and the pinion gear.

[0059] FIG. 14 is a schematic perspective view showing a case where one intermediate rotor 15 is arranged between the main wheel 2 and pinion gear 5 shown in FIGS. 11 to 13. In FIG. 14, reference numeral 15 denotes the intermediate rotor, which is provided with an elastic body 16. The main wheel 2 side of intermediate rotor 15 is provided with a locking portion 15a that comes into contact with locking portion 2e, and the pinion gear 5 side is provided with a locking portion 15b that comes into contact with locking portion 5e. Although not shown, intermediate rotor 15 is provided with a fixing portion to which one end 14a of elastic body 14 provided on the main wheel 2 is fixed, and a fixing portion to which one end of elastic body 16 is fixed. The other end of elastic body 16 is fixed to fixing portion 5d.

[0060] By providing such an intermediate rotor 15, it is possible to achieve a maximum rotation of just under one full rotation. That is, first, as the pinion gear 5 rotates in mesh with the rack gear, the locking portion 5e rotates and contacts and engages with the locking portion 15b. Then, as the pinion gear 5 rotates further, the locking portion 15b, which has locked the locking portion 5e, causes the intermediate rotor 15 to rotate together with the pinion gear 5, and the locking portion 15a rotates and contacts and engages with the locking portion 2e. In this way, in this modified example, by providing an intermediate rotor, it is possible to achieve a maximum rotation of just under two full rotations of the pinion gear. Based on this concept, if n intermediate rotors are provided, it is possible to achieve a maximum rotation of just under n full rotations.

[0061] (c) Symmetrical arrangement of pinion gear and rack gear (third variant) The third modified example is an example in which the pinion gear and the rack gear, together with the above-mentioned switching means, are symmetrically arranged on both sides of the main wheels.

[0062] In the first embodiment and each of the modifications described above, the pinion gear, rack gear, and switching device are all arranged on one side of the main wheel, but they may also be arranged symmetrically on both sides of the main wheel. In this case, it is preferable to provide a gear coupling section that connects the pinion gears on both sides. This allows the pinion gears on both sides to rotate synchronously and in phase, thereby maintaining an appropriate balance of forces, stabilizing the climbing operation, and enabling smoother step climbing.

[0063] An example is shown in Figures 15 and 16. Note that Figure 15 is a schematic cross-sectional view of the wheel structure configured as shown in Figures 1 and 2, in which a pinion gear, a rack gear, etc. are arranged on both sides of the main wheel. Figure 16 is a schematic perspective view illustrating the gear coupling portion in Figure 15. In Figures 15 and 16, 12 is the gear coupling portion. By engaging the convex portion 12a provided on the gear coupling portion 12 with the concave portion 5c provided on the pinion gear 5, the left and right pinion gears can be fixed and operated synchronously, and the main wheel 2 can be prevented from moving in the axial direction.

[0064] 2. Second embodiment (1) Wheel structure configuration The wheel structure according to this embodiment, like the wheel structure according to the first embodiment, has a frame provided with large-diameter main wheels, small-diameter auxiliary wheels, and transported object platform mounting portions, and is configured so that after the main wheels contact a step, the auxiliary wheels abut on the upper surface of the step and the main wheels climb up onto the upper surface of the step. The frame supports the auxiliary wheels at its front lower end, and is formed with a hole formed in the frame, into which the main wheel axle can be inserted, the hole being formed by a short hole extending rearward and downward and a long hole extending rearward and upward, connected by a curved hole. The main wheel axle inserted into the hole moves through the hole, causing the main wheels to climb up onto the upper surface of the step while forming a predetermined trajectory, and then the main wheel axle moves through the hole in the opposite direction from when it climbed up, returning to the state it was in before contacting the step. This is also similar to the first embodiment.

[0065] However, this embodiment differs from the first embodiment in that the rack gear is positioned in front of the hole, a clutch gear is provided that can mesh with both the pinion gear and the rack gear, and the rotation of the clutch gear is switched between being transmitted and not transmitted to the pinion gear using an elastic body that connects the clutch gear and the pinion gear.

[0066] Figure 17 is a schematic side view of the wheel structure according to this embodiment, and Figure 18 is a schematic front view of the wheel structure. In Figures 17 and 18, 17 is a clutch gear, and 18 is an elastic body. As shown in Figures 17 and 18, the pinion gear 5 and the clutch gear 17 are connected by the elastic body 18, and the clutch gear 17 is meshed with the rack gear 9. The pinion gear 5 is engaged with the main wheel shaft 2a and rotates together with the main wheel 2. The diameter of the pinion gear 5 is smaller than the diameter of the clutch gear 17 to avoid contact with the rack gear 9.

[0067] (2) Operation 17, when the vehicle is traveling normally on a flat surface before coming into contact with a step, the auxiliary wheels 3 are off the ground and the main wheels 2 rotate counterclockwise to move forward while supporting the load applied via the transported object platform mounting parts 4. At this time, the clutch gear 17 is not engaged with the pinion gear 5, so the rotation of the main wheel shaft 2a and pinion gear 5 is not transmitted to the clutch gear 17.

[0068] The wheel structure then moves forward until it reaches just before the step, and the main wheel 2 comes into contact with the step end face. At this time, as in the first embodiment, the main wheel 2 stops rotating and receives a reaction force from contact with the step end face 11a, while the frame 1 moves forward due to the impact of the main wheel 2 hitting the step end face 11a. As a result, the main wheel axle 2a moves rearward and downward within the short hole portion 6a.

[0069] When the main wheel axle 2a, having moved through the short hole 6a, reaches the curved hole 6c, the pinion gear 5, which has moved with the main wheel axle 2a, is pushed upward by the elastic body 18, via the load applied through the transported article platform mounting portion 4, and the clutch gear 17, which is meshed with the rack gear 9, begins to rotate counterclockwise while meshing with the rack gear 9. As the clutch gear 17 rotates, the main wheel axle 2a moves from the curved hole 6c to the elongated hole 6b, and then moves rearward and upward along the elongated hole 6b. However, because the clutch gear 17 is still not engaged with the pinion gear 5, the rotation of the clutch gear 17 is not transmitted to the main wheel axle 2a.

[0070] 19 is a schematic side view illustrating the state in which the clutch gear 17 is engaged with the rack gear 9 and moving along the elongated hole 6b. At this time, the main wheel shaft 2a also moves rearward and upward along the elongated hole 6b in accordance with the movement of the pinion gear 5, which is pushing the clutch gear 17 via the elastic body 18. However, because the main wheel 2 is in contact with the flat surface 10, the frame 1 moves downward, and the front auxiliary wheel 3 comes into contact with the step upper surface 11b. Note that because the clutch gear 17 is still not engaged with the pinion gear 5, the main wheel shaft 2a and pinion gear 5 do not rotate even though the clutch gear 17 is rotating, and remain stopped in the state in which they were in contact with the step end surface 11a.

[0071] When the auxiliary wheels 3 come into contact with the step upper surface 11b, most of the load on the wheel structure is applied to the auxiliary wheels 3, while the force applied to the main wheels 2 remains at about the weight of the main wheels 2. Then, as the main wheel axles 2a move further rearward and upward, the main wheels 2 tend to lift off the flat surface 10, and the force that moves the vehicle structure forward causes the main wheels 2 to resume rotation and try to climb up onto the step upper surface 11b. At this time, the forces acting on the main wheels 2 are a force that lifts the main wheels 2 off the flat surface 10 and a force that moves the vehicle structure forward, so the main wheels 2 can smoothly climb up onto the step upper surface 11b, as if climbing a gentle slope.

[0072] Figure 20 is a schematic side view illustrating a state in which the main wheel 2 rides up on the step upper surface 11b. As shown in Figure 20, when the main wheel 2 rides up on the step upper surface 11b, the clutch gear 17 reaches the rear end of the elongated hole portion 6b, and therefore, when further load is applied to the main wheel 2 thereafter, the elastic body 18 is pressed and compressed by the pinion gear 5. Finally, the pinion gear 5 and the clutch gear 17 mesh and engage with each other.

[0073] When the pinion gear 5 and the clutch gear 17 are engaged, the state changes to one in which the rotation of the main wheel 2 and pinion gear 5 is transmitted to the clutch gear 17. Then, the clutch gear 17 meshes with the pinion gear 5, and its rotation reverses from counterclockwise to clockwise. Thereafter, while meshing with the long portion 9a of the rack gear 9, the pinion gear 5 moves through the hole 6 from the rear end of the long hole 6b toward the front and downward, and the pinion gear 5, which is moving through the hole 6 at the same time, reaches the curved hole 6c and simultaneously reaches the vicinity of the curved hole 6c, which is its initial position.

[0074] Fig. 21 is a diagram illustrating the state when the clutch gear 17 reaches the vicinity of the curved hole portion 6c, which is the initial position. In Fig. 21, the elastic body 18 is omitted to clearly show that the pinion gear 5 and the clutch gear 17 are engaged with each other.

[0075] As shown in Figure 21, the main wheel 2 and pinion gear 5 move in accordance with the clutch gear 17, causing the frame 1 and auxiliary wheels 3 to rise to their initial positions. Meanwhile, the pinion gear 5, which has reached the curved hole 6c, is disengaged from the clutch gear 17 by the restoring force of the elastic body 18 that had been compressed, returning to the initial state in which the rotation of the main wheel axle 2a and pinion gear 5 is not transmitted to the clutch gear 17. Thereafter, the load applied to the wheel structure causes the main wheel axle 2a to move forward and upward within the short hole 6a to its initial position, returning to its initial state.

[0076] In this manner, the wheel structure is able to climb up the step. In this embodiment, when the wheel axle moves back and forth in the hole, the transmission and non-transmission of the rotation of the main wheel and pinion gear to the clutch gear is switched appropriately, and two forces are applied to the main wheel 2: a force that lifts the main wheel 2 off the flat surface 10, and a force that moves the vehicle structure forward. This allows the main wheel 2 to smoothly climb up onto the step upper surface 11b, just like climbing a gentle slope.

[0077] 3. Third Embodiment In the first and second embodiments described above, the main wheel set that moves back and forth through the hole portion is made to trace a predetermined trajectory, thereby enabling the vehicle structure to smoothly climb up onto the step surface with little force. However, in the third embodiment, no hole portion is provided, and the main wheel set is made to trace a predetermined trajectory, enabling the vehicle structure to smoothly climb up onto the step surface with little force.

[0078] (1) Wheel structure configuration Fig. 22 is a schematic side view of a wheel structure according to a third embodiment, and Fig. 23 is a schematic front view of the same wheel structure. In Fig. 22 and Fig. 23, 19 is a main wheel frame, and 21 is a clutch gear frame, each of which is journalled at one end to a shaft 19a provided with an elastic body 23. The shaft 19a is journalled to the frame 1 so as to be freely rotatable.

[0079] As shown in Figures 22 and 23, the wheel structure of this embodiment, like the wheel structures of the first and second embodiments, has a frame 1 on which a large-diameter main wheel 2, a small-diameter auxiliary wheel 3, and a transported object platform mounting portion 4 are provided, and is configured so that after the main wheel 2 contacts the step, the auxiliary wheel 3 abuts on the upper surface of the step, causing the main wheel 2 to ride up onto the upper surface of the step.

[0080] However, in this embodiment, the frame 1 is provided with an elastic body 23, a main wheel frame stopper 20, a clutch gear frame stopper 22, and a rack gear 9.

[0081] The elastic body 23 is attached to the shaft 19a and applies a biasing force to the main wheel frame 19 in the forward direction (to the left on the page), connecting the main wheel frame 19 with a clutch gear frame 21, which has the clutch gear 17 disposed at one end, and supporting the main wheel frame 19 and the clutch gear frame 21 so that they can rotate freely. The main wheel frame stopper 20 stops the main wheel frame 19 from rotating forward, and the clutch gear frame stopper 22 stops the clutch gear frame 21 from rotating forward.

[0082] In addition, a pinion gear 5 is provided at the other end of the main wheel frame 19 so as to rotate together with the main wheel 2 via the main wheel shaft 2a, and a clutch gear 17 is provided at the other end of the clutch gear frame 21 so as to mesh with the rack gear 9.

[0083] (2) Operation When the vehicle is in a normal running state on a flat surface before coming into contact with a step, as shown in Figure 22, the auxiliary wheels 3 are off the ground and the main wheels 2 move forward while supporting the load applied via the transported object platform mounting parts 4. At this time, the main wheel frame 19 is prevented from rotating forward by the main wheel frame stopper 20, and the clutch gear frame 21 is prevented from rotating forward by the clutch gear frame stopper 22, so the counterclockwise rotation of the main wheel 2 and pinion gear 5 is not transmitted to the clutch gear 17.

[0084] The wheel structure then moves forward until just before the step, and the main wheel 2 comes into contact with the step end face. Figure 24 is a schematic side view showing the state when the main wheel 2 comes into contact with the step end face 11a. As shown in Figure 24, the wheel structure moves forward on the flat surface 10 until just before the step 11, and when the main wheel 2 comes into contact with the step end face 11a, the main wheel 2 stops rotating. At this time, the main wheel 2 receives a reaction force from contact with the step end face 11a, while the frame 1 moves forward due to the impact of the main wheel 2 hitting the step end face 11a. As a result, the main wheel axle 2a moves slightly backward (to the right on the page), and in response, the main wheel frame 19 rotates in an arc-shaped orbit around the axle 19a.

[0085] After that, when further forward force is applied to the wheel structure, the frame 1 descends while moving forward, and the front auxiliary wheel 3 comes into contact with the step upper surface 11b. Figure 25 is a schematic side view showing the state when this auxiliary wheel 3 comes into contact with the step upper surface 11b. At this time, as the frame 1 moves forward, the main wheel frame stopper 20 arranged on the frame 1 also moves forward, but because the forward movement of the main wheel 2 is stopped by the step end surface 11a, the main wheel frame 19 moves away from the main wheel frame stopper 20 and rotates further rearward.

[0086] When the auxiliary wheels 3 come into contact with the step upper surface 11b, most of the load on the wheel structure is applied to the auxiliary wheels 3, while the force applied to the main wheels 2 remains at about the weight of the main wheels 2. Then, as the main wheel frame 19 continues to rotate, the main wheels 2 begin to lift off the flat surface 10, and the force that moves the vehicle structure forward causes the main wheels 2 to resume rotation and try to climb up onto the step upper surface 11b. At this time, the forces acting on the main wheels 2 are divided into two: a force that lifts the main wheels 2 off the flat surface 10, and a force that moves the vehicle structure forward, making it easy to lift up a light wheel. Then, the main wheels 2, which had been in contact with the step end surface 11a, resume rotating forward.

[0087] At this time, the clutch gear frame 21 is still engaged by the clutch gear frame stopper 22 to prevent the clutch gear 17 from moving from its initial position, so the angle between the main wheel frame 19 and the clutch gear frame 21 gradually decreases, and at the same time, the elastic body 23 is contracted.

[0088] After that, when further forward force is applied to the wheel structure, the main wheel 2 completely climbs onto the step upper surface 11b. Figure 26 is a schematic side view showing the state when the main wheel 2 completely climbs onto the step upper surface 11b.

[0089] As shown in Figure 26, when the main wheel 2 rides up onto the step upper surface 11b, the pinion gear 5, which is located at the tip of the rotating main wheel frame 19, reaches the uppermost rear position, and the pinion gear 5 begins to mesh with the clutch gear 17, transmitting the rotation of the pinion gear 5 to the clutch gear 17. After that, in accordance with the counterclockwise rotation of the pinion gear 5, the clutch gear 17 rotates clockwise, which is the opposite direction to the main wheel 2 and pinion gear 5, and moves downward along the rack gear 9.

[0090] Then, as the clutch gear 17 moves downward, the frame 1 rises. Figure 27 is a schematic side view illustrating this movement of the frame 1. As shown in Figure 27, as the frame 1 rises, the training wheels 3 move away from the step upper surface 11b and move toward the initial position. At this time, as the clutch gear 17 moves downward, the clutch gear frame 21 moves away from the clutch gear frame stopper 22 that had stopped the movement of the clutch gear frame 21.

[0091] After that, when the main wheel 2 rotates further, it reaches the state shown in Figure 28. Figure 28 is a schematic side view illustrating the state just before the frame 1 and auxiliary wheel 3 return to their initial positions, with the main wheel frame 19 positioned vertically to the shaft 19a and the clutch gear 17 moving to the bottom end of the rack gear 9.

[0092] When a load is applied to the vehicle structure via the transported article platform mounting portion 4, the pinion gear 5 and clutch gear 17 disengage, and then the angle between the main wheel frame 19 and the clutch gear frame 21 returns to its original position due to the restoring force of the compressed elastic body 23, causing the main wheel frame 19 to move until it contacts the main wheel frame stopper 20 and the clutch gear frame 21 until it contacts the clutch gear frame stopper 22, returning to their initial positions. At the same time, the clutch gear 17, which has been released from engagement with the pinion gear 5 and is now free, rotates counterclockwise along the rack gear 9 in accordance with the movement of the clutch gear frame 21, and rises to its initial position.

[0093] In this manner, the wheel structure is able to climb up the step. In this embodiment, the relationship between the main wheel frame 19 and the main wheel frame stopper 20, and the relationship between the clutch gear frame 21 and the clutch gear frame stopper 22 are switched as appropriate to cause the main wheel 2 to form a trajectory similar to that in the first and second embodiments, and two forces are applied to the main wheel 2: a force that lifts the main wheel 2 off the flat surface 10, and a force that moves the vehicle structure forward, making it easy to lift light wheels.

[0094] Furthermore, by appropriately adjusting the position of the axis 19a in the frame 1, the sizes of the main wheel frame 19 and the clutch gear frame 21, etc., the vehicle structure can be made to smoothly climb over steps that are higher than the radius of the main wheel 2, which was difficult to climb over in the first and second embodiments.

[0095] 4. Fourth Embodiment In the first and second embodiments, the pinion gear is provided on the main wheel axle to climb over steps, so as mentioned above, it is difficult to make the vehicle structure smoothly climb over steps that are higher than the radius of the main wheels.

[0096] Therefore, in the fourth embodiment, the concept of the first and second embodiments is further developed by raising the mounting position of the pinion gear, so that the vehicle structure can smoothly climb over steps that are higher than the radius of the main wheels.

[0097] (1) Wheel structure configuration Fig. 29 is a schematic side view of the wheel structure according to this embodiment, and Fig. 30 is a schematic front view of the wheel structure. Fig. 31 is a schematic perspective view illustrating the rotation of the main wheel in this embodiment. Fig. 32 is a schematic exploded perspective view illustrating the attachment of the main wheel in this embodiment. In Figs. 29 to 32, 24 is a main wheel, 25 is a bearing, 26 is a gear, 27 is an internal gear, and 28 is a second hole. Note that the second hole 28 is formed in the same shape as hole 6.

[0098] As shown in Figures 29 to 32, the wheel structure of this embodiment, like the wheel structures shown in the first and second embodiments, has a frame 1 on which a large-diameter main wheel 2, a small-diameter auxiliary wheel 3, and a transported object platform mounting portion 4 are provided, and is configured so that after the main wheel 2 contacts the step, the auxiliary wheel 3 abuts on the upper surface of the step, causing the main wheel 2 to ride up onto the upper surface of the step.

[0099] However, in this embodiment, unlike the first to third embodiments in which the main wheels are supported by the main wheel axles, the main wheels 2 are supported by four struts 24a to 24d provided on the main wheel 24.

[0100] Specifically, the inner circumferential surface of the main wheel 2 is formed with a smooth area where the bearings 25 rotatably inserted through each of the pillars 24a to 24d come into contact, and an area where an internal gear 27 is provided that meshes with a gear 26 attached to the end of the bearing 25 of the pillar 24a (see Figure 31), and the rotation of each of the bearings 25 supports the rotation of the main wheel 2. The pillars 24a and 24b extend to the back side of the main wheel 24, with the pillar 24a inserted through the hole 6 and the pillar 24b inserted through the second hole 28. The tip of the pillar 24a is formed with a concave-convex portion that can engage with the concave-convex portion of the pinion gear 5.

[0101] (2) Operation The operation of the wheel structure according to this embodiment is basically the same as that of the first and second embodiments in that the pinion gear 5 moves within the hole portion 6 and climbs over steps.

[0102] 29, when the vehicle is traveling on a flat surface before coming into contact with a step, the wheel structure moves forward with the auxiliary wheels 3 supported by the frame 1 in a floating state, and the main wheels 2 supporting the load applied via the transported object platform mounting parts 4. At this time, the pinion gear 5 and the gear 26 are disengaged by the disengagement claws 8, and the rotation of the support 24a is not transmitted to the pinion gear 5.

[0103] The wheel structure then moves forward until just before the step, and the main wheel 2 comes into contact with the step end face 11a. Figure 33 is a schematic side view showing the state when the main wheel 2 comes into contact with the step end face 11a. As shown in Figure 33, when the wheel structure moves forward on the flat surface 10 until just before the step 11, and the main wheel 2 comes into contact with the step end face 11a, the main wheel 2 stops rotating and moves slightly rearward due to the reaction force caused by the contact with the step end face 11a. Then, in response to this, the support pillar 24a moves rearward and downward within the hole 6, and the support pillar 24b also moves rearward and downward within the second hole 28.

[0104] When the main wheel axle 2a, having moved through the short hole 6a, reaches the curved hole 6c, the pinion gear 5 begins to mesh with the curved portion 9b of the rack gear 9 and starts to rotate, and in response, the support column 24a moves from the curved hole 6c to the long hole 6b. Thereafter, due to the load applied through the transported object platform mounting portion 4, the pinion gear 5 rotates while meshing with the long portion 9c of the rack gear 9, and moves rearward and upward along the long hole 6b. Then, in response to the movement of the support column 24a, the support column 24b also moves within the second hole 28. At this time, the pinion gear 5 and the gear 26 are not engaged, so even if the pinion gear 5 is rotating, the main wheel 2 does not rotate.

[0105] Fig. 34 is a schematic side view showing the state when the main wheel completely climbs up onto the upper surface of the step in this embodiment, and Fig. 35 is a schematic cross-sectional view of the wheel structure at that time. When the support 24a reaches the upper rear end within the hole 6, the pinion gear 5 is pressed by the engaging pawl 7, as in the first embodiment, and the pinion gear 5 and gear 26 are engaged, and the state changes to one in which the rotation of the main wheel 2 is transmitted to the pinion gear 5.

[0106] Thereafter, as in the first embodiment, the pinion gear 5 rotates counterclockwise, the same as the main wheel 2, and moves downward within the hole 6 to the initial position while meshing with the rack gear 9. In response to this, the support column 24b also moves downward within the second hole 28 to the initial position, and at the same time, the frame 1 also rises.

[0107] FIG. 36 is a schematic side view illustrating this movement of the frame, and as the frame 1 rises, the training wheels 3 move away from the step upper surface 11b and towards the initial position.

[0108] Then, when the pinion gear 5 further descends within the hole 6, the engagement between the pinion gear 5 and the gear 26 is released by the disengagement claw 8, as in the first embodiment, so that the rotation of the main wheel 2 is no longer transmitted to the pinion gear 5, and the main wheel 2 returns to its initial state.

[0109] In this embodiment, instead of the main wheel axle, a support pillar that supports the main wheel at a position higher than the main wheel axle is inserted into each hole and moved to climb over the step, so even higher steps can be easily climbed with little force.

[0110] Although the above description has been given with two holes, three or more holes may be provided, and although the above description has been given with four pillars, three or more pillars may be provided as long as support can be provided by two or more holes.

[0111] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments. It should be noted that various modifications can be made to the above-described embodiments within the scope of the same or equivalent to the present invention. [Explanation of symbols]

[0112] 1 frame 2 main wheels 2a Main wheel axle 2b Recess 2d Fixation part 2e Locking part 3 Training wheels 4 Transported object loading platform mounting section 5 Pinion gear 5a tapered 5b Convex part 5c Recess 5d Fixation part 5e Locking part 6 Hole 6a Short hole 6b Long hole 6c Curved hole 7 Engagement claw 8 Disengagement claw 9 Rack gear 9a Long section 9b Curved part 10 flat surface 11 Steps 11a Step edge 11b Step top 12 Gear connection part 12a Convex part 13 (Free type) bidirectional clutch 14 Elastic Body 14a One end of elastic body 15 Intermediate Rotor 15a, 15b Locking part 16 Elastic Body 17 Clutch gear 18 Elastic Body 19 Main wheel frame 19a axis 20 Main wheel frame stopper 21 Clutch gear frame 22 Clutch gear frame stopper 23 Elastic Body 24 Main Wheel 24a~24d Post 25 bearings 26 Gears 27 Internal gear 28 Second hole

Claims

1. A wheel structure having a frame provided with large-diameter main wheels, small-diameter auxiliary wheels, and transported object platform mounting portions, wherein after the main wheels come into contact with a step, the auxiliary wheels abut on an upper surface of the step, causing the main wheels to ride up onto the upper surface of the step, The frame supports the auxiliary wheels at a front lower end thereof, the frame is formed with a hole portion having a shape in which a short hole portion extending rearward and downward and a long hole portion extending rearward and upward are connected by a curved hole portion, so that the main wheel axle can be inserted therethrough; a pinion gear is provided on the main wheel shaft via a switching means that can switch between transmitting and not transmitting rotation of the main wheel; a rack gear capable of meshing with the pinion gear is provided along the hole portion on the rear side of the hole portion from the curved hole portion to the elongated hole portion of the hole portion, When the main wheel shaft inserted into the hole moves through the hole, the main wheel rides on the upper surface of the step while forming a predetermined trajectory, The wheel structure is characterized in that the main wheel axle is configured to return to the state before contacting the step by moving through the hole in the opposite direction to that when climbing over the step.

2. As a means for transmitting rotation of the main wheel, the main wheel and the pinion gear are each provided with a concave-convex portion that can engage with each other, 2. The wheel structure according to claim 1, wherein the switching means is composed of an engaging claw for engaging the concave-convex portion and an engaging disengagement claw for disengaging the engagement of the concave-convex portion.

3. 2. The wheel structure according to claim 1, wherein the switching means is a free-type bidirectional clutch provided between the main wheel shaft and the pinion gear.

4. 2. The wheel structure according to claim 1, wherein the switching means is composed of an elastic body having one end fixed to each of the main wheel and the pinion gear, and a locking portion for transmitting rotation provided on each of the main wheel and the pinion gear.

5. 5. The wheel structure according to claim 4, wherein one or more intermediate rotating bodies provided with locking portions for transmitting rotation are disposed between the main wheel and the pinion gear.

6. 6. The wheel structure according to claim 1, wherein the pinion gear and the rack gear are provided in pairs, one pair each, symmetrically on either side of the main wheel, so as to operate synchronously.

7. A wheel structure having a frame with a large diameter main wheel, a small diameter auxiliary wheel, and a transported object loading platform mounting portion, wherein after the main wheel comes into contact with a step, the auxiliary wheel abuts on the upper surface of the step, causing the main wheel to ride up on the upper surface of the step, The frame supports the auxiliary wheels at a front lower end thereof, the frame is formed with a hole portion having a shape in which a short hole portion extending rearward and downward and a long hole portion extending rearward and upward are connected by a curved hole portion, so that the main wheel axle can be inserted therethrough; A pinion gear that rotates together with the main wheel is provided on the main wheel shaft, A rack gear is provided along the hole on the front side of the hole, and a clutch gear is provided to mesh with the rack gear and move from the curved hole portion to the elongated hole portion of the hole portion; an elastic body connected between the clutch gear and the pinion gear is configured to switch between transmission and non-transmission of rotation of the main wheel to the pinion gear, When the main wheel shaft inserted into the hole moves through the hole, the main wheel rides on the upper surface of the step while forming a predetermined trajectory, The wheel structure is characterized in that the main wheel axle is configured to return to the state before contacting the step by moving through the hole in the opposite direction to that when climbing over the step.

8. A wheel structure having a frame provided with large-diameter main wheels, small-diameter auxiliary wheels, and transported object platform mounting portions, wherein after the main wheels come into contact with a step, the auxiliary wheels abut on an upper surface of the step, causing the main wheels to ride up onto the upper surface of the step, The inner peripheral surface of the main wheel is formed with a smooth area where a bearing rotatably inserted into each of three or more support posts provided on the main wheel comes into contact, and an area where an internal gear that meshes with a gear attached to the tip of one of the bearings of the support posts is provided, and the main wheel is supported by the rotation of each of the bearings of the support posts, The frame supports the auxiliary wheels at a front lower end thereof, the frame is formed with two or more parallel rows of holes, each having a shape in which a short hole extending downward and rearward and a long hole extending upward and rearward are connected by a curved hole portion; The support pillars inserted into the respective hole portions move through the holes, causing the main wheels to ride on the upper surface of the step while forming a predetermined trajectory, The wheel structure is characterized in that the main wheel axle is configured to return to the state before contacting the step by moving through the hole in the opposite direction to that when climbing over the step.

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