JP7738815B2 - Liftable wheelchair - Google Patents

Description

The present invention relates to a wheelchair that can be raised and lowered using a link mechanism.

A conventional wheelchair with a lifting function, in which the seat can be raised and lowered from a normal height, is disclosed in Patent Document 1. This wheelchair with a lifting function has a backward-tilting rod whose lower end is rotatably connected to the front wheel and a forward-tilting rod whose lower end is rotatably connected to the rear wheel, pivoted so that they cross each other at an intermediate position, a seating section pivoted to the upper end of the forward-tilting rod, and a link rod whose upper end is pivotally connected to the backrest section is pivotally connected to the upper end of the backward-tilting rod, and the pivoting position and length of the link rod are set so that the seating section can be raised and lowered while being kept horizontal in response to changes in the leg spread angle of the backward-tilting rod and the forward-tilting rod.
In addition, a backward-tilting rod whose lower end is rotatably connected to the front wheel and a forward-tilting rod whose lower end is rotatably connected to the rear wheel are pivotally connected to cross each other at an intermediate position, and the seating section is pivotally connected to the upper end of the forward-tilting rod, and a slide pin protruding from the upper end of the forward-tilting rod is slidably guided in a guide groove in the front-to-rear direction formed in an area forward of this pivoting position, and the shape of the guide groove is set so that the seating section can be raised and lowered while being maintained in a horizontal position in conjunction with changes in the leg opening angle of the backward-tilting rod and forward-tilting rod.

Wheelchairs with such a lifting function can keep the seat level on a horizontal surface, but the seat will tilt when moving up an inclined surface such as a slope.

Japanese Patent Application Laid-Open No. 2002-153515

The present invention aims to provide a wheelchair that can ascend and descend and that can maintain the seat level even on inclined surfaces such as slopes.

In order to solve the above problem, the wheelchair that can be raised and lowered according to claim 1 is characterized in that it has a first fulcrum on the front side of a horizontally arranged seat frame, an upper end of a first link arm rotatably connected to the first fulcrum, a front wheel rotatably connected to a second fulcrum at the lower end of the first link arm, a third fulcrum on the rear side of the seat frame, an upper end of a second link arm rotatably connected to the third fulcrum, a rear wheel rotatably connected to a fourth fulcrum at the lower end of the second link arm, a fifth fulcrum above or below the first fulcrum on the front side of the seat frame, a sixth fulcrum at the middle of the first link arm, a first actuator connected between the fifth and sixth fulcrums, a seventh fulcrum above or below the third fulcrum on the rear side of the seat frame, and an eighth fulcrum at the middle of the second link arm, and a second actuator connected between the seventh and eighth fulcrums.
The invention of claim 2 is such that, instead of rotatably connecting the upper end of the first link arm to the first fulcrum of the seat frame and the upper end of the second link arm to the third fulcrum, the upper end of the second link arm is rotatably connected to the first fulcrum of the seat frame and the upper end of the first link arm is rotatably connected to the third fulcrum.
The invention according to claim 3 is the same as claim 1 or 2, in which the front wheels are casters.
The invention of claim 4 is the same as claim 1 or 2, in which a ninth fulcrum is provided below the first fulcrum of the seat frame, and a tenth fulcrum is provided on the third link arm on the front wheel side extending downward from the second fulcrum, the ninth and tenth fulcrums are rotatably connected by a fourth link arm, and a parallel link mechanism is formed by the first fulcrum, the second fulcrum, the tenth fulcrum, and the ninth fulcrum.
According to a fifth aspect of the present invention, in the fourth aspect, a foot rest is provided on the link base that forms the third link arm on the front wheel side.
According to a sixth aspect of the present invention, in the fifth aspect, the link base on the front wheel side and the foot rest are integrated into one body.
According to a seventh aspect of the present invention, in the fourth aspect, the fulcrum on the front wheel side forming the parallel link mechanism is offset from the axle of the front wheel.
The invention of claim 8 is the same as claim 4 , in which an eleventh fulcrum is provided on the fifth link arm on the rear wheel side extending downward from the fourth fulcrum, the ninth fulcrum and the eleventh fulcrum are rotatably connected by a sixth link arm, and a parallel link mechanism is formed by the third fulcrum, the fourth fulcrum, the eleventh fulcrum, and the ninth fulcrum.
The invention according to claim 9 is the same as claim 8, wherein the fulcrum on the front wheel side forming the parallel link mechanism is offset from the axle of the front wheel, and the fulcrum on the rear wheel side forming the parallel link mechanism is offset from the axle of the rear wheel.
The invention of claim 10 is the same as claim 9, in which the first actuator is connected between the first fulcrum and the tenth fulcrum or between the first fulcrum and the sixth fulcrum at the middle of the fourth link arm, and the second actuator is connected between the third fulcrum and the eleventh fulcrum or between the third fulcrum and the eighth fulcrum at the middle of the sixth link arm, and the ninth fulcrum is divided into a front and a rear fulcrum, 9a and 9b.
The inventions according to claims 11 to 18 are those according to claims 1 to 5 and 7 to 10 , in which the center of gravity of the load of the wheelchair is lowered before the tilt of the wheelchair reaches the balance limit angle.

According to the invention of claim 1, a first fulcrum is provided on the front side of a horizontally arranged seat frame, an upper end of a first link arm is rotatably connected to the first fulcrum, a front wheel is rotatably connected to a second fulcrum at a lower end of the first link arm, a third fulcrum is provided on the rear side of the seat frame, an upper end of a second link arm is rotatably connected to the third fulcrum, a rear wheel is rotatably connected to a fourth fulcrum at a lower end of the second link arm, a fifth fulcrum is provided above or below the first fulcrum on the front side of the seat frame, and a fifth fulcrum is provided on the rear side of the first link arm. A sixth fulcrum is provided in the middle of the link arm, a first actuator is connected between the fifth and sixth fulcrums, a seventh fulcrum is provided above or below the third fulcrum on the rear side of the seat frame, an eighth fulcrum is provided in the middle of the second link arm, and a second actuator is connected between the seventh and eighth fulcrums.By controlling the first and second actuators, the seat frame can be raised and lowered while maintaining its horizontal position, and the seat frame can also be maintained horizontal on an inclined surface.
According to the invention of claim 2, instead of rotatably connecting the upper end of the first link arm to the first fulcrum of the seat frame and the upper end of the second link arm to the third fulcrum, the upper end of the second link arm is rotatably connected to the first fulcrum of the seat frame and the upper end of the first link arm is rotatably connected to the third fulcrum, so that the seat can be made higher if the distance between the axles of the front and rear wheels is the same.
According to the invention of claim 3, in claim 1 or 2, the front wheels are casters, which makes steering easier and also makes it easier to follow uneven or sloped road surfaces.
According to the invention of claim 4, in claim 1 or 2, a ninth fulcrum is provided below the first fulcrum of the seat frame, and a tenth fulcrum is provided on the third link arm on the front wheel side extending downward from the second fulcrum, and the ninth and tenth fulcrums are rotatably connected by a fourth link arm, and a parallel link mechanism is formed by the first fulcrum, the second fulcrum, the tenth fulcrum, and the ninth fulcrum, so that the link base forming the third link arm on the front wheel side is maintained parallel to the seat frame, and by providing a platform on the link base, various accessories can be placed on the platform.
According to the invention of claim 5, in claim 4, a foot rest is provided on the link base that forms the third link arm on the front wheel side, so that the seat frame and the foot rest are maintained parallel to each other.
According to the sixth aspect of the present invention, the link base on the front wheel side and the foot rest are integrated into one body, which reduces the number of parts, simplifies the structure, and contributes to cost reduction.
According to the invention of claim 7, in claim 4 , the fulcrum on the front wheel side that forms the parallel link mechanism is offset from the front wheel axle, so if the axle length between the front and rear wheels is the same, the seat surface can be made higher or lower, increasing the degree of freedom in design.
According to the invention of claim 8, in claim 4 , an 11th fulcrum is provided on the fifth link arm on the rear wheel side extending downward from the fourth fulcrum, and the 9th fulcrum and the 11th fulcrum are rotatably connected by a sixth link arm, and a parallel link mechanism is formed by the third fulcrum, the fourth fulcrum, the 11th fulcrum, and the 9th fulcrum.Therefore, by providing a platform on the parallel link mechanism on the rear wheel side, the parallelism between the platform and the seat frame is maintained, and space can be secured on the platform to place various accessories.
According to the invention of claim 9, in claim 8, the fulcrum on the front wheel side that forms the parallel link mechanism is offset from the axle of the front wheel, and the fulcrum on the rear wheel side that forms the parallel link mechanism is offset from the axle of the rear wheel.Therefore, if the axle length between the front and rear wheels is the same, the seat surface can be made higher or lower, increasing the degree of freedom in design.
According to the invention of claim 10, in claim 9, the first actuator is connected between the first fulcrum and the tenth fulcrum or between the first fulcrum and the sixth fulcrum at the middle of the fourth link arm, and the second actuator is connected between the third fulcrum and the eleventh fulcrum or between the third fulcrum and the eighth fulcrum at the middle of the sixth link arm, and the ninth fulcrum is divided into fulcrum 9a and fulcrum 9b in front and behind, which increases the freedom of manufacture compared to when the ninth fulcrum is common to the front wheel side and the rear wheel side.
According to the inventions of claims 11 to 18 , the center of gravity of the wheelchair is lowered before the tilt of the wheelchair reaches the balance limit angle, thereby preventing the wheelchair from tipping over and increasing safety.

1A and 1B show a wheelchair according to a first embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1 is a side view illustrating the operation of the wheelchair according to the first embodiment. FIG. FIG. 2 is a side view illustrating the operation of the wheelchair according to the first embodiment 2. FIG. 10 is a side view illustrating the operation of the wheelchair according to the second embodiment. 10A and 10B are side views illustrating the operation of the wheelchair according to the third embodiment. FIG. 10 is a side view illustrating the operation of the wheelchair according to the third embodiment 2. 10A and 10B are side views illustrating the operation of the wheelchair according to the fourth embodiment. FIG. 10 is a side view showing the wheelchair according to the fourth embodiment on an inclined surface. FIG. 10 is a side view illustrating the operation of the wheelchair according to the fourth embodiment 2. FIG. 10 is a side view illustrating the operation of the wheelchair according to the fourth embodiment. FIG. 10 is a side view illustrating the operation of the wheelchair according to the fourth embodiment. 13A and 13B are side views illustrating the operation of the wheelchair according to the fifth embodiment. 13A and 13B are side views illustrating the operation of the wheelchair according to the sixth embodiment. 10 is a side view illustrating the operation of the wheelchair according to the seventh embodiment. FIG. FIG. 10 is a side view illustrating the operation of the wheelchair according to the seventh embodiment 2. 13 is a side view illustrating the operation of the wheelchair according to the eighth embodiment. FIG. FIG. 13 is a side view showing the wheelchair according to the eighth embodiment on an inclined surface. FIG. 13 is a side view illustrating the operation of the wheelchair according to the eighth embodiment 2. FIG. 10 is an explanatory diagram showing the wheelchair in a tilted state. FIG. 10 is an explanatory diagram showing a state in which the inclination of the wheelchair is at the balance limit angle θ.

The following is a detailed description of an embodiment of the present invention with reference to the drawings. A wheelchair 1a capable of ascending and descending according to a first embodiment (first embodiment 1, first embodiment 2) of the present invention shown in Figures 1 to 3 has as its main components a seat frame 2, front wheels 3, rear wheels 4, first and second link arms L1, L2 connecting these together, and first and second actuators A1, A2.
Specifically, a first fulcrum P1 is provided on the front side (left side in the drawing) of the horizontally disposed inverted trapezoidal seat frame 2, the upper end of a first link arm L1 is rotatably connected to the first fulcrum P1, and the front wheel 3 is rotatably connected to a second fulcrum P2 at the lower end of the first link arm L1. A third fulcrum P3 is provided on the rear side of the seat frame 2, the upper end of a second link arm L2 is rotatably connected to the third fulcrum P3, and the rear wheel 4 is rotatably connected to a fourth fulcrum P4 at the lower end of the second link arm L2.
1 and 2, a fifth fulcrum P5 is provided above (diagonally upward front) the first fulcrum P1 on the front side of the seat frame 2, a sixth fulcrum P6 is provided at the middle of the first link arm L1, and a first actuator A1 is connected between the fifth fulcrum P5 and the sixth fulcrum P6. Also, a seventh fulcrum P7 is provided above (diagonally upward rear) the third fulcrum P3 on the rear side of the seat frame 2, and an eighth fulcrum P8 is provided at the middle of the second link arm L2, and a second actuator A2 is connected between the seventh fulcrum P7 and the eighth fulcrum P8. Reference numeral 5 denotes a seat portion provided on the seat frame.

In the figures, the seat frame 2 is shown as being shaped like an inverted trapezoid or an inverted triangle when viewed from the side, but this is not limited to this and it may also be shaped like a rectangle, for example. In the inverted trapezoid seat frame 2, the fifth fulcrum P5 is located diagonally above and in front of the first fulcrum P1, but in a rectangular seat frame, it may be located above the first fulcrum. In the present invention, "above the fulcrum" is a concept that includes not only directly above but also diagonally above the front or diagonally above the rear, as long as it is above the fulcrum. Furthermore, "below the fulcrum" is a concept that includes not only directly below but also diagonally below the front or diagonally below the rear, as long as it is below the fulcrum.

The link arms L1, L2, front wheels 3, and rear wheels 4 are arranged in pairs on the left and right, and are connected to each other via shafts S1 to S8 at fulcrums P1 to P8 so that they can rotate or pivot freely (Figure 1(a)). Note that the seat 5 has been omitted from Figure 1(a) for clarity.

By controlling the first actuator A1 and the second actuator A2, the seat frame 2 (seat portion 5) can be moved up and down while maintaining the horizontality of the seat frame 2, and the seat frame 2 (seat portion 5) can be maintained horizontal even on an inclined surface.
The actuator in the present invention may be any means capable of varying the distance (dimension) between two fulcrums, and is not limited to devices that perform mechanical work using electricity, hydraulics, pneumatics, etc.

By controlling the first and second actuators A1 and A2 to expand and contract the distance between the fifth fulcrum P5 and the sixth fulcrum P6, and the distance between the seventh fulcrum P7 and the eighth fulcrum P8 while maintaining the same size, the seat frame 2 can be moved up and down while maintaining its horizontal state. Figure 2(a) shows the normal state, and Figure 2(b) shows the state in which the seat frame 2 has been lowered all the way down and has been lowered to near the center of rotation of the front wheels 3 and the rear wheels 4.
Furthermore, by controlling the distances (dimensions) between the fifth fulcrum P5 and the sixth fulcrum P6 and between the seventh fulcrum P7 and the eighth fulcrum P8 according to the inclination, the seat frame 2 can be held horizontally even on the inclined surface 13 (FIGS. 8 and 17). This also applies to each of the embodiments described below.
When raising or lowering the seat (seat portion 5), it is preferable to lock (brake) either the front wheels 3 or the rear wheels 4. However, this does not apply while the vehicle is moving.

The wheelchair 1a capable of ascending and descending according to the first embodiment 2 shown in Figure 3 is the same as the first embodiment 1 except that the fifth fulcrum P5 is located lower than the first fulcrum P1 (diagonally downward rear) and the seventh fulcrum P7 is located lower than the third fulcrum P3 (diagonally downward front). In the first embodiment 1, the positions of the first fulcrum P1 and the fifth fulcrum P5, and the third fulcrum P3 and the seventh fulcrum P7 are reversed. Compared to the first embodiment 1, the mounting positions of the first and second actuators A1 and A2 are set lower.
As a result, if the distance between the axles 6, 7 of the front wheels 3 and the rear wheels 4 is the same, the seat frame 2 can be set lower than in the first embodiment 1, thereby improving stability.

The wheelchair 1b capable of ascending and descending according to the second embodiment shown in Figure 4 is the same as the first embodiment (first embodiment 1) except that the upper end of the second link arm L2 is rotatably connected to the first fulcrum P1 on the front side of the seat frame 2 and the upper end of the first link arm L1 is rotatably connected to the third fulcrum P3 on the rear side. In side view, the first link arm L1 and the second link arm L2 are set to intersect.
If the distance between the axles 6, 7 of the front and rear wheels 3, 4 is the same, the first link arm L1 and the second link arm L2 become longer, so the seat 5 (seat frame 2) can be set higher.

The third embodiment of the wheelchair 1c shown in Figures 5 and 6 is similar to the first and second embodiments, except that the front wheels 3 are replaced with casters 8 (Figures 5 and 6). By replacing the front wheels 3 with casters 8 in this way, maneuverability is improved. It also makes it easier to follow uneven or sloped road surfaces. Foot rests 9 can also be installed on these casters 8. Each caster is a swivel caster. While the front wheels 3 in the second embodiment are not shown as casters, this is of course possible.

The wheelchair 1d according to the fourth embodiment (Fourth Embodiment 1 and Fourth Embodiment 2) is a variation of the first and second embodiments, except that a ninth fulcrum P9 is provided below (diagonally downward and rearward from) the first fulcrum P1 of the seat frame 2, a front-wheel-side third link arm L3 extending downward (diagonally downward and rearward from) the second fulcrum P2 of the first link arm L1 is rotatably connected to the second fulcrum P2 of the first link arm L1, a tenth fulcrum P10 is provided at the lower end of the third link arm L3, and a fourth link arm L4 rotatably connects the ninth fulcrum P9 and the tenth fulcrum P10, forming a parallel link mechanism (see FIGS. 7 and 8 for the first embodiment, and FIG. 9 for the second embodiment). It is also possible to form a parallel link mechanism between the seat frame 2 and the front wheel 3 in the second embodiment (not shown).
By forming a parallel link mechanism on the front wheel 3 side in this way, the link base 10 that forms the third link arm L3 on the front wheel side is also maintained parallel to the horizontally disposed seat frame 2. If a stand is installed on the link base 10, various accessories can be placed on the stand.

In addition, a foot rest 11 can be provided on the link base 10 that forms the front-wheel-side third link arm L3 (Figures 7 to 9). This allows the seat frame 2 and the foot rest 11 to be kept parallel.

Furthermore, the link base 10 and foot rest 11 can be integrated (see Figure 10 for an example of fourth embodiment 3 and Figure 11 for an example of fourth embodiment 4). Integrating them in this way reduces the number of parts, simplifies the structure, and contributes to cost reduction.

The ascendable wheelchair 1e according to the fifth embodiment is the same as the fourth embodiment (fourth embodiment 1, fourth embodiment 2), except that the fulcrums on the front wheel side (second fulcrum P2, tenth fulcrum P10) that form the parallel link mechanism are offset from the front wheel axle 6. In the example shown in Figure 12, the fulcrums are offset rearward from the front wheel axle 6. Although not shown, the fulcrums may be offset forward, or may be offset forward and rearward across the axle 6.
As a result, if the distance between the axles 6 and 7 of the front and rear wheels 3 and 4 is the same, the seat surface 5 can be made higher or lower, increasing the degree of freedom in design.

The wheelchair if of the sixth embodiment is a wheelchair with liftability similar to that of the fourth embodiment (fourth embodiment 1, fourth embodiment 2), except that a fifth link arm L5 on the rear wheel side, which extends downward (diagonally downward and forward) from the fourth fulcrum P4 of the second link arm L2, is rotatably connected to the fourth fulcrum P4 of the second link arm L2, an eleventh fulcrum P11 is provided on the fifth link arm L5, and the ninth fulcrum P9 and the eleventh fulcrum P11 are rotatably connected by a sixth link arm L6, and a parallel link mechanism is formed by the third fulcrum P3, the fourth fulcrum P4, the eleventh fulcrum P11, and the ninth fulcrum P9. In addition to the front wheel 3, a parallel link mechanism is also formed on the rear wheel 4. In the horizontal position, the parallel link mechanisms are formed symmetrically in the front and rear directions with respect to the midline between the front and rear wheels 3, 4.
As a result, a parallel link mechanism is also formed on the rear wheel 4 side, and by providing a platform on the parallel link base 12 on the rear wheel 4 side, the parallelism between the horizontally arranged seat frame 2 and the platform can be maintained, and space can be secured on the platform to place various accessories.
In Fig. 13, a parallel link mechanism is also formed on the rear wheel 4 side in the fourth embodiment 1, but a parallel link mechanism can also be formed on the rear wheel 4 side in the fourth embodiment 2 (not shown). Note that the base is not shown in Fig. 13.

The wheelchair 1g capable of ascending and descending according to the seventh embodiment is the same as that according to the sixth embodiment, except that the fulcrums (second fulcrum P2, tenth fulcrum P10) on the front wheel 3 side that form the parallel link mechanism are offset from the front wheel axle 6, and the fulcrums (fourth fulcrum P4, eleventh fulcrum P11) on the rear wheel 4 side that form the parallel link mechanism are offset from the rear wheel axle 7. In the horizontal position, the fulcrums are offset symmetrically front to back with respect to the midline between the front and rear wheels 3, 4.
The direction of the bias is arbitrary, and in the seventh embodiment 1 shown in Figure 14, the second fulcrum P2 and the tenth fulcrum P10 are biased rearward from the front wheel axle 6, and the fourth fulcrum P4 and the eleventh fulcrum P11 are biased forward from the rear wheel axle 7. Although not shown, it is also possible to bias the second fulcrum P2 and the tenth fulcrum P10 forward from the front wheel axle 6, and to bias the fourth fulcrum P4 and the eleventh fulcrum P11 rearward from the rear wheel axle 7. In the seventh embodiment 2 shown in Figure 15, the second fulcrum P2 and the tenth fulcrum P10 are biased so as to straddle the front wheel axle 6, and the fourth fulcrum P4 and the eleventh fulcrum P11 are biased so as to straddle the rear wheel axle 7. In Figure 15, the first actuator A1 is shown connected between the first fulcrum P1 and the sixth fulcrum P6 at the middle of the fourth link arm L4, and the second actuator A2 is shown connected between the third fulcrum P3 and the eighth fulcrum P8 at the middle of the sixth link arm L6.
As a result, similar to the fifth embodiment, if the distance between the axles 6 and 7 of the front and rear wheels 3 and 4 is the same, the seat surface 5 can be made higher or lower, increasing the degree of freedom in design.

The wheelchair 1h of the eighth embodiment is similar to that of the seventh embodiment, except that the first actuator A1 is connected between the first fulcrum P1 and the tenth fulcrum P10 or between the first fulcrum P1 and the sixth fulcrum P6 at the middle of the fourth link arm L4, the second actuator A2 is connected between the third fulcrum P3 and the eleventh fulcrum P11 or between the third fulcrum P3 and the eighth fulcrum P8 at the middle of the sixth link arm L6, and the ninth fulcrum P9 is divided into a front and a rear fulcrum 9a P9a and a 9b P9b. The fourth link arm L4 is rotatably connected between the 9a fulcrum P9a and the tenth fulcrum P10, and the sixth link arm L6 is rotatably connected between the 9b fulcrum P9b and the eleventh fulcrum P11 (FIGS. 16 and 18). The front wheel side forms a parallel link mechanism with the first fulcrum P1, the second fulcrum P2, the tenth fulcrum P10, and the 9ath fulcrum P9a, while the rear wheel side forms a parallel link mechanism with the third fulcrum P3, the fourth fulcrum P4, the 11th fulcrum P11, and the 9bth fulcrum P9b. In the horizontal position, the parallel link mechanisms are formed symmetrically in the front and rear directions with respect to the midline between the front and rear wheels 3, 4.
If the ninth fulcrum were common to the front and rear wheels (FIGS. 13, 14, and 15), the upper end of the front-wheel-side fourth link arm L4 and the upper end of the rear-wheel-side sixth link arm L6 would be rotatably connected to the coaxial ninth shaft S9 that forms the ninth fulcrum, which would impose design restrictions. In contrast, in the eighth embodiment, the ninth fulcrum is divided into a fulcrum 9a P9a on the front wheel side and a fulcrum 9b P9b on the rear wheel side, which eliminates such restrictions and increases design freedom.
In the eighth embodiment 1 shown in Figure 16, the second fulcrum P2 and the tenth fulcrum P10 are biased rearward from the front wheel axle 6, the fourth fulcrum P4 and the eleventh fulcrum P11 are biased forward from the rear wheel axle 7, the first actuator A1 is connected between the first fulcrum P1 and the tenth fulcrum P10, and the second actuator A2 is connected between the third fulcrum P3 and the eleventh fulcrum P11. Figure 17 shows the wheelchair shown in Figure 16 in use on an upwardly inclined surface 13, and it can be seen that the seat 5 and footrest 11 are maintained horizontally.
In the eighth embodiment 2 shown in Figure 18, the second fulcrum P2 and the tenth fulcrum P10 are biased forward from the front wheel axle 6, and the fourth fulcrum P4 and the eleventh fulcrum P11 are biased rearward from the rear wheel axle 7, the first actuator A1 is connected between the first fulcrum P1 and the sixth fulcrum P6 at the middle of the fourth link arm L4, and the second actuator A2 is connected between the third fulcrum P3 and the eighth fulcrum P8 at the middle of the sixth link arm L6.
The actuators A1 and A2 may be attached at any position, and may be set at any appropriate position depending on the design.

The tilt described above is for the front-rear direction, but the tilt in the left-right direction will be described below.
19 and 20 are explanatory diagrams showing a state in which a liftable wheelchair 1 is tilted left or right, and are explanatory diagrams showing the wheelchair 1 as viewed from the front or back. Note that the reference numerals attached to the components in these Figures 19 and 20 are the same as those attached to the components explained above, and explanations of the components will be omitted. In the figures, PG indicates the load center of gravity, PF indicates the reaction point, and PV indicates the equilibrium point. The gravity acting on the load center of gravity PG is indicated by vector G, and the reaction force acting on the reaction point PF is indicated by vector F. The gravity G and the reaction force F (total reaction forces) are in opposite directions and are in equilibrium.

19(a) shows a horizontal state, with the load center of gravity PG located inside the reaction point PF and in a stable state. The angle θ formed by the horizontal line and the perpendicular line passing through the reaction point PF to the line connecting the load center of gravity PG and the reaction point PF is the balance limit angle. If the load center of gravity PG rises, the balance limit angle θ becomes smaller, making it easier for the vehicle to tip over. Conversely, if it falls, the balance limit angle θ becomes larger, making it harder for the vehicle to tip over.
Figure 1(b) shows a state in which the balance limit angle θ has been exceeded and the wheelchair has tilted (tilt angle β), with the load center of gravity PG being outside the reaction point PF, and a force acting in the direction of the arrow (to the right) acts on the wheelchair 1, causing it to tip over. If the load center of gravity PG is lowered by a distance H, the balance point PV will be reached.
Figure 1(c) shows the state in which the load center of gravity PG is lowered below the equilibrium point PV, so that the load center of gravity PG is inside the reaction point PF, and a restoring force acts on the wheelchair 1 in the direction of the arrow (to the left), preventing it from tipping over.
Figure 20 shows the state where the tilt is at the balance limit angle θ, and the center of gravity PG of the load and the reaction point PF are on the same vertical plane. If the tilt is even slightly greater than this state, the vehicle will tip over to the right, but if the tilt is even slightly smaller than this state (tilt angle α), the vehicle will not tip over.

The angle sensor 15 detects the inclination of the wheelchair body, and when it detects a predetermined angle α (α<θ) (Fig. 20) before the balance limit angle θ is reached, the seat (body) is immediately lowered to lower the load center of gravity PG (Fig. 19(c)), stabilizing the wheelchair and preventing it from tipping over. The predetermined angle α is θ-X (α=θ-X), and can be set to an appropriate angle such as X=1°, 1.5°, 2°, or 3°.
The load center of gravity PG is controlled so that it is always below the balance point PV, in other words, so that it is always inside the vehicle body relative to the reaction force point PF. This prevents the wheelchair from tipping over and increases safety. This is possible in the present invention because the seat 5 can be raised and lowered (up and down) by controlling the first actuator A1 and the second actuator A2.

19(a), 19(b) and 20, the center of gravity PG of the load is shown at a relatively high position because a person (luggage, etc.) sits on the seat frame 2.
Although the above description has been given for the case where the vehicle is tilted in the left-right direction, the same applies to the case where the vehicle is tilted in the front-rear direction.

1. Wheelchair with lifting mechanism 1a to 1h. Wheelchair with lifting mechanism according to first to eighth embodiments 2. Seat frame 3. Front wheel 4. Rear wheel 5. Seat 6. Front wheel axle
7 Rear wheel axle 8 Caster 9 Foot rest 10 Link base (front wheel side)
11 Foot rest 12 Link base (rear wheel side)
13 Inclined surface 15 Angle sensor P1 to P11 First fulcrum to eleventh fulcrum L1 to L6 First link arm to sixth link arm S1 to S11 First shaft to eleventh shaft A1 First actuator A2 Second actuator PG Center of gravity of load PF Reaction point PV Equilibrium point θ Equilibrium limit angle α Predetermined angle smaller than the equilibrium limit angle β Angle larger than the equilibrium limit angle X θ-α
G Load vector F Reaction force vector H Drop amount

Claims (18)

A wheelchair that can ascend and descend, comprising: a first fulcrum on the front side of a horizontally positioned seat frame; a first link arm rotatably connected to the first fulcrum at its upper end; a front wheel rotatably connected to a second fulcrum at the lower end of the first link arm; a third fulcrum on the rear side of the seat frame; a second link arm rotatably connected to the upper end of the second link arm; a rear wheel rotatably connected to a fourth fulcrum at the lower end of the second link arm; a fifth fulcrum above or below the first fulcrum on the front side of the seat frame; a sixth fulcrum at the middle of the first link arm; a first actuator connected between the fifth and sixth fulcrums; a seventh fulcrum above or below the third fulcrum on the rear side of the seat frame; an eighth fulcrum at the middle of the second link arm; and a second actuator connected between the seventh and eighth fulcrums. The wheelchair capable of ascending and descending described in claim 1, in which, instead of pivotally connecting the upper end of the first link arm to the first fulcrum of the seat frame and the upper end of the second link arm to the third fulcrum, the upper end of the second link arm is pivotally connected to the first fulcrum of the seat frame and the upper end of the first link arm is pivotally connected to the third fulcrum. A wheelchair that can ascend and descend as described in claim 1 or 2, in which the front wheels are casters. A wheelchair that can ascend and descend as described in claim 1 or 2, in which a ninth fulcrum is provided below the first fulcrum on the seat frame, a tenth fulcrum is provided on the third link arm on the front wheel side that extends downward from the second fulcrum, the ninth and tenth fulcrums are rotatably connected by a fourth link arm, and a parallel link mechanism is formed by the first fulcrum, the second fulcrum, the tenth fulcrum, and the ninth fulcrum. The wheelchair capable of ascending and descending as described in claim 4, wherein a foot rest is provided on the link base forming the third link arm on the front wheel side. The wheelchair capable of ascending and descending described in claim 5, in which the link base on the front wheel side and the foot rest are integrated. 5. The wheelchair according to claim 4 , wherein the fulcrum on the front wheel side forming the parallel link mechanism is offset from the axle of the front wheel. 5. A wheelchair that can climb up and down as described in claim 4, wherein an eleventh fulcrum is provided on the fifth link arm on the rear wheel side extending downward from the fourth fulcrum, the ninth fulcrum and the eleventh fulcrum are rotatably connected by a sixth link arm, and a parallel link mechanism is formed by the third fulcrum, the fourth fulcrum, the eleventh fulcrum and the ninth fulcrum. The wheelchair capable of ascending and descending described in claim 8, wherein the fulcrum on the front wheel side forming the parallel link mechanism is offset from the axle of the front wheel, and the fulcrum on the rear wheel side forming the parallel link mechanism is offset from the axle of the rear wheel. A wheelchair capable of ascending and descending as described in claim 9, wherein the first actuator is connected between the first fulcrum and the tenth fulcrum or between the first fulcrum and the sixth fulcrum at the middle of the fourth link arm, the second actuator is connected between the third fulcrum and the eleventh fulcrum or between the third fulcrum and the eighth fulcrum at the middle of the sixth link arm, and the ninth fulcrum is divided into a front and a rear fulcrum, fulcrum 9a and fulcrum 9b. 3. The wheelchair according to claim 1, wherein the center of gravity of the wheelchair is lowered before the tilt of the wheelchair reaches a balance limit angle. 4. The wheelchair according to claim 3 , wherein the center of gravity of the load of the wheelchair is lowered before the tilt of the wheelchair reaches a balance limit angle. 5. The wheelchair according to claim 4 , wherein the center of gravity of the load of the wheelchair is lowered before the tilt of the wheelchair reaches a balance limit angle. 6. The wheelchair according to claim 5 , wherein the center of gravity of the wheelchair is lowered before the tilt of the wheelchair reaches a balance limit angle. 8. The wheelchair according to claim 7 , wherein the center of gravity of the load of the wheelchair is lowered before the tilt of the wheelchair reaches a balance limit angle. 9. The wheelchair according to claim 8 , wherein the center of gravity of the load of the wheelchair is lowered before the tilt of the wheelchair reaches a balance limit angle. 10. The wheelchair according to claim 9 , wherein the center of gravity of the load of the wheelchair is lowered before the tilt of the wheelchair reaches a balance limit angle. 11. The wheelchair according to claim 10 , wherein the center of gravity of the load of the wheelchair is lowered before the tilt of the wheelchair reaches a balance limit angle.