Wheel device for a moving body

Abstract

To provide a wheel device for a moving body in which a step difference part can be climbed over easily.SOLUTION: A double-lever mechanism of a four-section link mechanism is constituted by a main frame serving as a fixed link 11, a driven link 12, an intermediate link 13 and a motor link 14. A main wheel 21 is mounted in an intermediate part of the motor link 14, and a secondary wheel 22 is mounted in the proper position of the driven link 12, and thereby the wheel device 1 for the moving body is constituted. When getting over the step difference part 50, a bottom end of the motor link 14 is pushed backward by an effect of the double-lever mechanism of the four-section link mechanism. Thereby, a front part of the driven link 12 is rotated downward through the intermediate link 13, and the secondary wheel 22 mounted in this is moved downward and is brought into abutment with the upper surface 52 of the step difference part. The wheel device 1 is lifted centering on a pressure contact point of the secondary wheel 22 and the upper surface 52 of the step difference part. Thereby, the main wheel 21 is made to easily rise from the ground and it is structured to get over the step difference part 50.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wheel device for a moving body that can overcome steps with little force. [Background technology]

[0002] Generally, self-propelled wheelchairs and electric wheelchairs as moving bodies have large diameter drive wheels attached to the left and right of the frame behind the seat, and caster devices are attached to the left and right leg frames on the front side of the seat. These front left and right caster devices support the weight of the user sitting on the seat from the front while gently turning in the direction of travel to guide the wheelchair forward.

[0003] Generally, the caster device of a wheelchair is simply attached to the left and right legs at the front of the frame using mounting bolts, and when freed, it can easily rotate around a vertical axis in a horizontal plane. The wheels of the caster device are on the left and right, one on each side, and are smaller in diameter than the rear drive wheels. When moving the wheelchair, the user rotates the drive wheels by hand to drive it. When turning left or right, the drive wheel on the opposite side to the direction of the turn is turned more than the drive wheel on the side of the turn. Whether turning left or right, the caster device faces in the tangent direction of the turning circle while turning, and when the turn is completed and the user tries to move forward, it returns to an angle parallel to the direction of travel and moves forward while rotating straight.

[0004] In the case of such wheelchairs, the caster device is located at the front in the direction of travel, but since the wheels of the caster device are generally smaller in diameter than the drive wheels, they are sensitive to vibrations when passing over small uneven surfaces or steps, making the ride uncomfortable and requiring a lot of force to overcome them. For example, even if the step is only about 3 cm, it is not easy for an adult user sitting on the seat to turn the drive wheels and overcome the step. This is even more difficult when the user is a physically disabled person with weak strength.

[0005] In addition, the caster device has the property that when a force is applied, it rotates to the angle of the force and moves parallel to the direction of the force. Therefore, for example, when trying to ride up a step at an angle rather than perpendicular to the step, the wheels of the caster device receive a reaction force from the end face of the step and rotate to an angle parallel to the reaction force from the end face of the step, which is a problem that it is difficult to ride up the step. To overcome this, the user needs to correct their position just before the end face of the step so that the direction of travel of the wheelchair is perpendicular to the end face of the step, and then vigorously rotate the drive wheels, or have an assistant push the wheelchair.

[0006] Therefore, in the past, Patent Document 1 (Patent Publication No. 2019-09 9 A step-compatible caster device such as that disclosed in Japanese Patent Application Publication No. 2006-0666 is known. In this conventional step-compatible caster device, the main wheel and the auxiliary wheel are arranged at the front and rear, the two wheels are connected by a link mechanism, and a fixed link is attached to the frame of the wheelchair so that it can rotate horizontally freely. The reaction force that the main wheel receives from the end face of the step is converted into the movement of the auxiliary wheel via the two links and the guide groove, and the auxiliary wheel is pressed against the upper face of the step, thereby enabling the step to be overcome. The step-compatible caster device of this Patent Document 1 is a so-called four-joint link mechanism that applies a slider crank mechanism, but the force to counteract the self-weight and all the pedaling force required to overcome the step must be generated by the reaction force received by the main wheel, and a large driving force is required to obtain a large reaction force and therefore a large pedaling force, and further improvements were required to allow even physically disabled people with weak strength to easily overcome steps.

[0007] Furthermore, a battery-powered caster device is also known, as described in Patent Document 2. However, because it is battery-powered, it requires maintenance of the battery, which makes handling complicated.

[0008] Caster devices are not only used in wheelchairs, but are also widely used in products such as luggage carts, movable beds, and other products that move heavy objects, and the following technical issues are equally problematic for all types of mobile products. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2019-099066 A [Patent Document 2] JP 2019-137211 A DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0010] The present invention has been made in consideration of the above-mentioned problems with the conventional technology, and has as its object to provide a wheel device for a moving body which can reduce the force required to overcome a step, and which, by replacing wheel devices such as caster devices for wheelchairs, carts, and other moving bodies which have been conventionally used, can reduce the force required to overcome a step even for the moving body which has been used up to that point. [Means for solving the problem]

[0011] The present invention provides a wheel device for a moving body having a four-bar link mechanism composed of a main frame which is a fixed link, a driven link, an intermediate link, and a driving link, the main frame having a moving body mounting part for mounting and fixing the wheel device for a moving body to a moving body, the driven link, the intermediate link, and the driving link are movable to form a lever mechanism, The link length of the driving link is made longer than the link length of the driven link, A main wheel is attached to the driving link, and a secondary wheel is attached to the driven link.

[0013] above In the wheel device for a moving body of the present invention, the main wheel is On the ground When a reaction force directed backward is generated by contacting an end surface of the step portion, a force directed backward is generated on a connecting shaft portion between the driving link and the intermediate link, and the auxiliary wheel attached to the driven link is moved in the direction of the In front of the step endThe wheel device for a moving body can be supported simultaneously at two points: the contact point between the end face of the step portion and the main wheel, and the contact point between the top surface of the step portion and the secondary wheel, by abutting the step portion on the upper surface of the step portion to apply a downward force.

[0014] In the wheel device for a moving body of the above invention, a height difference can be provided so that the position of the lower end of the secondary wheel is higher than the position of the lower end of the main wheel when the moving body is running horizontally.

[0015] Furthermore, in the wheel device for a moving body of the above invention, a bottom dead center exceeding prevention means may be provided to prevent the driven link from rotating beyond the bottom dead center. Effect of the Invention

[0016] According to the present invention, the main frame is a fixed link, and the main frame, the driven link, the intermediate link, and the driving link constitute the two lever mechanisms of the four-bar link mechanism, and when the rear main wheel abuts against the end face of the step at the step and receives a rearward reaction force, the axle connection part at the intermediate part of the driving link receives the rearward reaction force, which generates a rearward rotation moment in the driving link, and a rearward force is generated at the connection part between the driving link and the intermediate link due to the moment. This rearward force pulls the intermediate link rearward, and the driven link connected to this intermediate link rotates downward. This downward rotation force of the driven link moves the auxiliary wheel attached to the driven link downward, abutting against the upper surface of the step and applying a downward pedaling force. In this state, when the wheel device for a moving body is pushed further forward, the driving link moves further backward due to the action of both lever mechanisms of the four-bar link mechanism, causing the driven link to rotate further downward via the intermediate link, the device is lifted around the pressure contact point between the secondary wheel and the upper surface of the step, and the main wheel rises from the ground and climbs over the end face of the step. This series of actions of both lever mechanisms of the four-bar link mechanism allows the wheel device for a moving body to easily climb over the step. [Brief description of the drawings]

[0017] [Figure 1] FIG. 4 is a diagram illustrating the principle of both lever mechanisms of the four-bar link mechanism used in the wheel device for a moving body of the present invention. [Diagram 2] FIG. 4 is an explanatory diagram for numerical analysis of both lever mechanisms of the wheel device for a moving body. [Diagram 3] 1 is a perspective view of a wheel device for a moving body according to one embodiment of the present invention; [Figure 4] FIG. 2 is a front view of the wheel device for a moving body according to the embodiment. [Figure 5A] 13 is a front view showing a state in which the main wheel collides with a corner of a step during a series of step climbing operations of the wheel device for a moving body of the embodiment described above. FIG. [Figure 5B] This is a front view showing a state in which, during a series of step-over-step operations of the wheel device for a moving body of the above embodiment, after the main wheel collides with the corner of the step, the wheel device for a moving body moves further forward and the secondary wheel comes into contact with the top surface of the step due to the action of the four-bar link mechanism. [Figure 6A] 1 is a front view showing a state in which the main wheel begins to lift off the ground to overcome a step, during a series of step-over-step operations of the wheel device for a moving body of the embodiment described above. FIG. [Figure 6B] 13 is a front view showing a state in which the main wheel is midway through climbing over a step during a series of step-climbing operations of the wheel device for a moving body of the embodiment described above. FIG. [Figure 7A] 13 is a front view showing a state in which the main wheel has almost overcome the step during the series of step-over-step operations of the wheel device for a moving body of the embodiment described above. FIG. [Figure 7B] 13 is a front view showing a state in which the main wheel has completely climbed over the step during a series of step climbing operations of the wheel device for a moving body of the embodiment described above. FIG. [Figure 8] 11 is a front view showing the reaction force and the stepping force acting state when the wheel device for a moving body of the embodiment performs a series of steps climbing over the steps. FIG. [Figure 9] FIG. 4 is an explanatory diagram of a four-bar link mechanism used in the wheel device for a moving body according to the embodiment. [Figure 10] 5 is an explanatory diagram of forces and moments of both lever mechanisms of the four-bar link mechanism used in the wheel device for a moving body of the embodiment. FIG. [Figure 11]An explanation will be given of the stability of the wheel device for a moving body according to the above embodiment when going over a step. [Figure 12] FIG. [Figure 13] FIG. 1 is an explanatory diagram of a mechanical analysis of a link mechanism according to a conventional technique. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0019] The mechanical principle of the wheel device 1 for a moving body of the present invention will be described. Generally, a lever mechanism among four-bar link mechanisms in mechanics is as shown in Fig. 1, in which a short driven link 12 and a long driving link 14 are rotatably connected to both ends of a fixed link 11 at connecting parts 112, 114. The other ends of the driven link 12 and the driving link 14 are rotatably connected to both ends of an intermediate link 13 at connecting parts 123, 134.

[0020] With the fixed link 11 fixed by this connection, when the driving link 14 at one end of the fixed link 11 rotates downward and rearward in the figure around the connecting part 114, the connecting part 123 side of the driven link 12 is pulled rearward via the intermediate link 13, and the driven link 12 also rotates downward and rearward around the connecting part 112 with the fixed link 11. In other words, it operates as a double-lever mechanism. At this time, a force multiplier effect is generated between the long driving link 14 and the short driven link 12, and the driven link 12 can be rotated downward at a large angle simply by rotating the long driving link 14 rearward by a small angle, and the secondary wheel 22 attached to the driven link 12 can be moved downward by a large amount.

[0021] The driving force that rotates the driving link 14 by a small angle is the force that makes the main wheel 21 attached to the driving link 14 abut against the end face of the step, and the reaction force F of this abutment force rotates the driving link 14 backward by a small angle. However, the driving link 14 is long. Therefore, the rearward movement distance of the lower end of the driving link 14 is relatively long, and the intermediate link 13 connected to it also moves rearward by a large distance, and as a result, the driven link 12 connected to the tip side of the intermediate link 13 rotates downward and rearward by a relatively large angle around the connecting part 112 on its upper end side. This allows the secondary wheel 22 attached to the driven link 12 to rotate downward by a large angle. However, when a pedaling force P is applied from above to the upper surface of the step, P When the wheel 21 comes into contact with the step, it cannot descend any further, and instead the wheel device 1 is lifted up. In other words, the wheel device 1 is lifted up in the vertical direction by the horizontal force F that tries to lift the main wheel 21 up onto the step end face. P Moreover, the wheel device 1 can be lifted lightly by moving it a short distance in the horizontal direction using the power boosting mechanism.

[0022] FIG. 2 is an explanatory diagram for the numerical analysis of FIG. 1. The reaction force F and the pedaling force P P The relationship is as follows in equation 1:

[0023]

number

[0024] The angles in Equation 1 are expressed by the following Equation 2. The positional relationship between these angles and the links is shown in Figure 2. Additionally, in the equation, A represents the link length of the fixed link 11, B represents the link length of the driving link 14, C represents the link length of the intermediate link 13, and D represents the link length of the driven link 12.

[0025]

number

[0026] From equation 1, the following equation 3 expresses the multiplication factor from reaction force F to pedal force Pp.

[0027]

number

[0028] The maximum value of this formula 3 is determined by the lengths A, B, C, and D of the links, and the maximum value changes according to the value of θ, and is in the range of approximately 0.3 to 4. This value is preferably 1 or more, and more preferably in the range of 1.3 to 2. In the wheel device 1 for a moving body of the embodiment shown in Figs. 3 and 4 described later, the condition for making the maximum value of the value of formula 3 1 or more is that the value of the fractional part containing the trigonometric function in formula 3 is 1 or more. When the relationship between the link length B of the driving link 14 and the link length D of the driven link 12 that satisfies this condition is numerically calculated as B>D, and it is necessary to make the driving link 14 long and the driven link 12 short. In addition, in the wheel device 1 for a moving body of the embodiment shown in Figs. 3 and 4, the maximum value of the value of formula 3 is approximately 1.8. Therefore, formula 1 can be expressed as formula 4 below, and formula 4 expresses the reaction force F and the pedaling force P due to the link structure of this embodiment. P Represents the relationship between.

[0029]

number

[0030] The vehicle wheel device 1 of the embodiment shown in Figures 3 and 4 rotates horizontally to freely change direction, but in the following description, the left side in the illustrated position is the front and the right side is the rear. In addition, in the fore-and-aft direction of the vehicle wheel device 1 of the embodiment, the secondary wheel 22 is defined as the front and the main wheel 21 as the rear, and the left side of the fore-and-aft center line connecting the secondary wheel 22 and the main wheel 21 when facing forward is defined as the left and the right side as the right.

[0031] In the embodiment of the wheel device 1 for a moving body shown in Figs. 3 and 4, the rear ends of two left and right driven links 12 are connected to the left and right sides of the front end of a main frame 11 with a U-shaped cross section that opens downwards, so that they can rotate freely by a connecting shaft 112 as a first connecting part. The front ends of two left and right intermediate links 13 are connected to the left and right sides of the front end of the driven link 12, so that they can rotate freely by a connecting shaft 123 as a third connecting part. The lower ends of two left and right driving links 14 are connected to the rear ends of the left and right intermediate links 13, so that they can rotate freely by a connecting shaft 134 as a fourth connecting part. The upper end of the left and right driving links 14 is connected to the upper ends of the left and right driving links 14, so that the upper rear end of the gate-shaped frame 11 can rotate freely by a connecting shaft 114 as a second connecting part. By connecting these four links, the main frame 11, the driven links 12, the intermediate links 13, and the driving links 14 constitute two lever mechanisms of a four-bar link mechanism in which the main frame 11 is a fixed link.

[0032] A main wheel shaft 211 is passed horizontally through an appropriate position in the vertical middle of the left and right driving links 14, and the main wheels 21 are journaled by this main wheel shaft 211. In addition, a secondary wheel 22 is journaled on a connecting shaft 123 that connects the front end of the front left and right driven links 12 and the front end of the intermediate link 13. Therefore, this connecting shaft 123 also serves as a rotating shaft 221 of the secondary wheel 22. In the embodiment, the connecting shaft 123 is configured to be used in common with the rotating shaft 221 to simplify the mechanism, but the mounting position of the secondary wheel 22 is not limited to this. Since it is sufficient for the secondary wheel 22 to move together with the driven link 12, it may be mounted by the rotating shaft 221 at another appropriate position between the left and right driven links 12.

[0033] A spring support bar 31 is stretched across the left and right sides at the front upper part of the main frame 11. A spring stopper hole 32 is provided at the front-rear center position of the left and right intermediate links 13. The upper ends of two tension springs 33 on the left and right sides are hooked on the spring support bar 31, and the lower ends of each are hooked on the left and right spring stopper holes 32. The tension springs 33 apply a spring force to the intermediate link 13 to pull up its front end side. The spring force of the tension springs 33 keeps the driven link 12 in a substantially horizontal state in an unloaded state. The tension springs 33 are one of the means for maintaining and returning the mechanism to its initial state, and other structures that perform the same function can be used. For example, a structure can be adopted in which a torsion spring is installed around the connecting part 114 and a spring force acts on the driving link 14 in a counterclockwise direction.

[0034] A fixing bolt 41 is attached to the front upper surface of the main frame 11 as a mobile body mounting part for mounting the mobile body wheel device 1 to a wheelchair frame, the bottom surface of a dolly, etc. Furthermore, this fixing bolt 41 and the frame 11 are connected by a bearing member 42 so as to be freely rotatable. Instead of the combination of this fixing bolt 41 and the bearing member 42, other structures can be used as the mobile body mounting part as long as they have a similar function. For example, the mobile body wheel device 1 can be mounted to the bottom surface of a dolly, etc., by using a plate-shaped mounting seat instead of the fixing bolt 41 and allowing free rotation by a bearing member between this mounting seat and the main frame 11.

[0035] Next, the operation of wheel device 1 for a moving body of this embodiment overcoming step section 50 will be described with reference to Figures 5 to 7. For ease of explanation, wheel device 1 for a moving body of this embodiment is attached to the left and right sides of the front lower part of the wheelchair frame using fixing bolts 41, and the operation will be described when the user rotates the drive wheels of the wheelchair forward or when a caregiver manually pushes the wheelchair over step section 50.

[0036] As shown in Fig. 5A, in normal forward movement of the wheelchair, the front end side of the intermediate link 13 is pulled up by the pulling force of the tension spring 33, and as a result, the secondary wheels 22 attached to both the front ends of the driven link 12 and the intermediate link 13 are raised to a certain height h and move forward due to the rotation of the main wheels 21. Then, when the wheelchair reaches a step 50, the secondary wheels 22 pass through an upper surface 52 of the step 50 without colliding with the upper surface 52 of the step 50. Then, the main wheels 21 collide with a step end surface 51 of the step 50.

[0037] As shown in FIG. 5B, when the main wheel 21 collides with the step end surface 51, the main wheel 21 receives a rearward reaction force F1 from the step end surface 51. This reaction force F1 generates a counterclockwise moment τ F This acts as a tensile force F2 that pulls the intermediate link 13 backward via the connecting shaft 134 at the lower end of the driving link 14. When the rearward tensile force F2 acts on the lower end of the driving link 14 together with the rotating shaft 211, the rotating shaft 221 (connecting shaft 123) at the front end of the intermediate link 13 is also pulled backward, and a tensile force F3 also acts on the front connecting shaft 123. This tensile force F3 also generates a moment τ P And this moment τ P As a result, a downward pedaling force P P As a result, a stepping force P P Conversely, the main wheel 21 side is lifted up by the reaction force N.

[0038] As shown in Figures 6A and 6B, when the wheelchair is further advanced, the lower end of the driving link 14 moves backward together with the main wheel 21 due to the reaction force F1 from the step end surface 51, and the rear end of the intermediate link 13 is also pulled backward due to the characteristics of the four-bar link mechanism, and the front end of the intermediate link 13 rotates the front end of the driven link 12 downward. With this rotation, the auxiliary wheel 22 attached to the driven link 12 is further pressed downward with a pedaling force P Pand the reaction force N causes the main wheel 21 to rise even higher above the ground.

[0039] As shown in Fig. 7A, when the wheelchair is further advanced, the lower end of the driving link 14 is pulled backward to its maximum extent. At this time, the driven link 12 is rotated to the left in the figure to a nearly vertical state. In this rearmost position, the upper rear surface of the driving link 14 abuts against the stopper pin 15, and the driving link 14 is prevented from rotating any further backward. The stopper pin 15 is attached to a position where the driven link 12 does not exceed its bottom dead center even if it rotates downward following the backward movement of the lower end of the driving link 14. This stopper pin 15 constitutes a bottom dead center exceeding prevention means, and the link of both lever mechanisms and the position where it is installed can be appropriately set according to the actual structure.

[0040] When the driving link 14 is rotated to the rearmost position, the intermediate link 13 is in a nearly horizontal state. Then, the main wheel 21 is raised together with the driving link 14, and the difference in height between the bottom end position of the secondary wheel 22 and the bottom end position of the main wheel 21 becomes minimum. Then, by applying the forward force required to push up by this minimum difference in height, the step 50 can be easily overcome.

[0041] As shown in Figure 7B, when the wheel device 1 for a moving body gets over the step portion 50 and the main wheel 21 rides up on the upper surface 52 of the step portion, the force that the main wheel 21 receives from the end surface 51 of the step portion is eliminated, and the tip side of the intermediate link 13 is pulled up by the tensile spring force of the tension spring 33, returning all of the driven link 12, intermediate link 13 and driving link 14 to their original states, i.e., the postures shown in Figures 4 and 5A.

[0042] Next, a dynamic consideration of the step-climbing operation will be described. Fig. 8 is a diagram corresponding to Fig. 6A. Fig. 9 is a mechanism diagram. The wheel device 1 for a moving body of the embodiment utilizes both lever mechanisms of the four-bar link mechanism, and is therefore capable of converting the lateral reaction force F1 when colliding with the step end surface 51 of the step 50 into the vertical pedaling force P required for climbing over. PIt has the advantage of converting and multiplying the

[0043] In Fig. 8, the wheel device 1 for a vehicle is in a state where it is halfway up the step 50 due to the driving force K that moves the wheelchair forward. The contact point of the main wheel 21 receives a reaction force F1 from the step end surface 51 against the driving force K. This reaction force F1 generates a moment τ F This moment τ F As a result, a tensile force F2 acts on the connecting portion 134 between the driving link 14 and the intermediate link 13, and a tensile force F3 acts on the connecting shaft 123 at the front end of the intermediate link 13. This tensile force F3 generates a moment τ P This moment τ P As a result, the secondary wheel 22 is pressed against the upper surface 52 of the step portion 50 with a tread force P P This pedaling force P P Conversely, this acts as a reaction force N that pushes up the rear end of the driving link 14 through the intermediate link 13, and acts as a force that pulls up the main wheel 21, the caster device 1, and the front of the wheelchair, centered on the contact point with the step end surface 51 of the step 50. As a result, the main wheel 21 is pulled up from the ground G.

[0044] A more detailed mechanical explanation will be given using Figure 9. P The mechanism by which this reaction force F1 occurs is as follows: The main wheel 21 receives a reaction force F1 from the end face 51 of the step portion 50. This reaction force F1 generates a counterclockwise force moment τ F (torque) is generated. This torque τ F appears as a tensile force F2 in the rightward (rearward) direction in the figure at the connecting shaft 134 at the lower end of the driving link 14. This tensile force F2 pulls the intermediate link 13 to the right in the figure, and applies a tensile force F3 to the connecting shaft 123 (axle 221) with the driven link 12 in the rightward direction in the figure. This tensile force F3 generates a counterclockwise force moment (torque) τ P This torque τ Pis the tread force P applied to the outer periphery of the auxiliary wheel 22 attached to the axle 221 (connecting shaft 123) at the tip of the driven link 12, on the upper surface 52 of the step portion 50. P To demonstrate.

[0045] Next, the reason why wheel device for a moving body 1 of this embodiment, as a boosting mechanism, requires less force to overcome a step will be explained using Figure 10. Consider a moment when a step is overcome. A necessary condition for overcoming step 50 is that the direction of the sum of the force moment (torque) around connecting shaft 112 is counterclockwise as shown in the figure.

[0046] In the case of the wheel device 1 for a moving body of this embodiment, the weight W of the moving body (here, a wheelchair) to which it is attached is supported at two points, the connecting shaft 112 and the connecting shaft 114. Here, it is assumed that the weight is evenly applied to the connecting shaft 112 and the connecting shaft 114. If this weight is W [N], the magnitude of the force applied to each shaft is W / 2 [N]. Of the weights applied to these two points, only the weight W / 2 applied to the connecting shaft 114 is the force moment τ around the connecting shaft 112. W / 2 is converted to

[0047]

number

[0048] Here, d1 is the horizontal distance between the connecting shaft 114 and the connecting shaft 112, and d2 is the horizontal distance between the ground contact point of the secondary wheel 22 with the step upper surface 52 and the connecting shaft 112. In order to overcome the step 50, a counterclockwise force moment (torque) τ around the connecting shaft 112 due to the reaction force F (corresponding to F1 in FIG. 10) is P is τ W / 2 It must be greater than or equal to this.

[0049]

number

[0050] The conditions for this are Equation 5 and the pedaling force P of the secondary wheel 22. Pand moment (torque) τ in the counterclockwise direction around the connecting shaft 112 P The relationship between P =d2P P This results in the following equation 7.

[0051]

number

[0052] Reaction force F and pedaling force P due to the link structure of this embodiment P An example of the relationship is given by the above formula 4 as follows:

[0053]

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[0054] By substituting this into equation 7, we obtain the following equation 9.

[0055]

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[0056] Equation 9 is the condition for reaction force F (i.e., driving force K of the arm) required from step end surface 51 of main wheel 21 to overcome step 50. As a result, in the case of wheel device for a moving body 1 of this embodiment, due to the double lever mechanism of the four-bar link mechanism, less than half the driving force of a conventional example is sufficient for driving force K. A comparison of forces with the conventional example will be made later.

[0057] Moreover, in the case of this embodiment, one end of driven link 12 is connected and fixed to fixed link 11 by connecting shaft 112, so the direction of lateral reaction force F can be converted to a vertical direction, and the reaction force F and its own weight that main wheel 21 receives from step end face 51 can be structurally supported. Therefore, there is no need to press main wheel 21 against step end face 51 more than necessary, and movable body wheel device 1 of this embodiment can overcome steps with a small force.

[0058] 11, in the case of the wheel device 1 for a moving body of this embodiment, when going over a step end face 51, the load of the wheel device 1 for a moving body and the front part of the wheelchair above it are supported simultaneously at two points: a contact point 61 between the main wheel 21 and the step end face 51, and a contact point 62 between the sub wheel 22 and the step upper face 52. Therefore, when the wheel device 1 for a moving body and the wheelchair above it go over a step diagonally, the wheel device 1 for a moving body itself does not swivel (does not assume a right-angled posture) and can effectively exert the propulsive force of the moving body to go over the step 50, and even when going over the step 50 diagonally, the posture of the wheel device 1 for a moving body does not change (it maintains a state parallel to the traveling direction of the moving body), and the step 50 can be efficiently and lightly gone over.

[0059] The mechanical and mechanical advantages of the wheel device 1 for a moving body according to the present embodiment will be compared with the step-compatible caster device of Patent Document 1, which is one of the prior arts. The step-compatible caster device of the prior art of Patent Document 1 has a mechanism as shown in Figs. 12 and 13. The step-compatible caster device of the prior art can be said to be an application of a slider crank mechanism among the four-bar link mechanisms. The frame is a fixed link 11A, and the fixed link 11A is also provided with a guide groove 12A constituting a slider link and a guide roller 12B sliding therein. The link that supports the main wheel 21A at the lower end axle 211A is a driving link 14A, and the rear end of the intermediate link 13A is connected to the axle 211A at the lower end of the driving link 14A. The front part of the intermediate link 13A is provided with a guide roller 12B constituting a slider link, and the guide roller 12B is connected so as to slide within the guide groove 12A of the fixed link 11A. The sub-wheel 22A is attached to the intermediate link 13A by an axle 221A at a position further forward than the position of the guide roller 12B.

[0060] As shown in Figs. 12 and 13, in this conventional example, when going over a step, the main wheel 21A receives a reaction force F from the end face of the step, and a driving force K is applied to overcome this reaction force F (i.e., the wheelchair is pushed forward), thereby reducing the pedaling force P of the sub-wheel 22A. C This pedaling force P CAs a result, the main wheel 21A is lifted up from the end face of the step portion and overcomes the step portion.

[0061] Referring to the mechanism diagram in Figure 13, in the conventional technology, the weight of the moving body (wheelchair in this case) supported by the casters is supported only at one point, the connecting shaft 114 between the driving link 14A and the fixed link 11A. Therefore, if the weight is W [N], the connecting shaft 114A is directly subjected to the weight of W [N]. This weight W is a moment τ of a clockwise force around the guide roller 12B in the figure. W is converted to

[0062]

number

[0063] Here, d1 is the horizontal distance of the slider between the connecting shaft 114A and the guide roller 12B, and d2 is the horizontal distance between the guide roller 12B and the grounding point of the secondary wheel 22A on the step upper surface 52. In order to overcome the step 50, a moment (torque) τ of a counterclockwise force around the guide roller 12B due to the reaction force F is C is the moment due to its own weight (torque τ W ) or more. The condition is as follows:

[0064]

number

[0065] Formula 10 and the pedaling force P of the secondary wheel 22A C and the moment (torque) τ of the counterclockwise force around the guide roller 12B C The relationship between C =d2P C Therefore, the above equation (11) becomes the following equation (12).

[0066]

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[0067] The radius of the guide groove 12A has a function equivalent to that of the driven link in the four-bar link mechanism. Therefore, by substituting the radius of the guide groove 12A for the driven link length D in FIG. 12 and using formula 2, the reaction force F by the link mechanism of the conventional technology is reduced by the pedaling force P. C The maximum conversion factor is approximately 1.4. Therefore, the reaction force F in the conventional link structure is converted into the pedal force P C The relationship is as follows:

[0068]

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[0069] By substituting formula 13 into formula 12, the following formula 14 is obtained.

[0070]

number

[0071] This formula (14) is the condition for the reaction force F (= the driving force of the arm required to get over) from the step end surface 51 of the main wheel 21A required to get over the step 50.

[0072] The reaction force required for the wheel device 1 for a moving body of this embodiment to overcome the step 50 with the caster device of the prior art is compared as follows. Equation 9 is the condition for the reaction force F for overcoming the step 50 of this embodiment, and the minimum value F of this equation is P is expressed as follows:

[0073]

number

[0074] On the other hand, in the case of the conventional technology, the formula is expressed as formula 14, and the minimum value of this value F C is expressed as follows:

[0075]

number

[0076] Taking the ratio of the above two equations, we get:

[0077]

number

[0078] Therefore, in the case of wheel device 1 for a moving body of this embodiment, it is possible to overcome step 50 with 39% of the force required for the prior art. Therefore, it can be said that wheel device 1 for a moving body of this embodiment has about twice as much step-over capability as the prior art.

[0079] Furthermore, the wheel device for a moving body of the present invention can be widely used not only for wheelchairs as moving bodies, but also for luggage carts, movable beds, and other moving products that carry heavy objects and are moved manually or using power. [Industrial Applicability]

[0080] The wheel device for a mobile body of the present invention can be widely used as a caster device for wheelchairs, carts, and other mobile products that can carry heavy objects and move using human or motorized power, allowing them to easily overcome steps. [Explanation of symbols]

[0081] 1 Wheel device for mobile objects 11 Main Frame (permanent link) 12 Follower link 13 Intermediate Links 14. Driving Link 21 Main Wheel 22 Secondary wheel 33 Tension Spring 41 Fixing bolt 42 Bearing parts 50 Step 51 Step end face 52 Top surface of step part 112,114,123,134 Connecting shaft 211 Axle 221 Axle

Claims

1. A wheel device for a moving body having a four-link mechanism composed of a main frame serving as a fixed link, a driven link, an intermediate link, and a driving link, the main frame includes a movable body mounting portion for mounting and fixing the movable body wheel device to a movable body, the driven link, the intermediate link and the driving link are movable to constitute two lever mechanisms; The link length of the driving link is made longer than the link length of the driven link, A main wheel is attached to the driving link; A wheel device for a moving body, characterized in that a secondary wheel is attached to the driven link.

2. 2. The wheel device for a mobile body according to claim 1, characterized in that, when the main wheel comes into contact with an end face of a step in the ground and a rearward reaction force is generated, a rearward force is generated in a connecting shaft portion between the driving link and the intermediate link, and the secondary wheel attached to the driven link is abutted against an upper surface of the step in front of the end face of the step to apply a downward force, so that the wheel device for a mobile body is supported simultaneously at two points, that is, a contact point between the end face of the step and the main wheel and a contact point between the upper surface of the step and the secondary wheel.

3. 3. The wheel device for a moving body according to claim 1 or 2, characterized in that a difference in height is provided so that the position of the lower end of the secondary wheel is higher than the position of the lower end of the main wheel when the moving body is running horizontally.

4. 4. The wheel device for a moving body according to claim 1, further comprising a bottom dead center preventing means for preventing the driven link from rotating beyond the bottom dead center.

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