JP2014084032A - Stairway elevator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stairway elevator capable of making smaller an angle of inclination to a step of a stairway caused by turning of a body part in the stairway elevation.SOLUTION: First and second rotary actuators are disposed in a body part 10 so that the center of gravity G of the whole stairway elevator 1 is located above the respective centers of gravity Gr, Gh of the first and second rotary actuators 40, 50. Since an angle θ of inclination to a step Sd of a stairway S when the body part of the stairway elevator is rotated can be held down to a desired small angle, the stairway elevation by the stairway elevator can be stably operated so that the elevating speed can be increased. Further, interference between the body part or the like and the stairway in the stairway elevation can be prevented.

Description

  The present invention relates to a stair lift that mounts an object such as an object or a person and can move up and down a stair.

  For example, Patent Documents 1 and 2 describe a stair lift that includes a main body that can travel with four wheels and a mounting portion on which a person can ride. The front and rear axles are rotatably supported at both ends of the arm, the center of the arm is rotatably supported at the lower part of the main body, and the mounting part is rotatably supported at the upper part of the main body. Yes. In such a configuration, when the stair lift goes up the stairs, the main body rotates to the stairs side to move the center of gravity, the arm rotates around the axle of the rear wheel, for example, the rear wheel, and the front wheels are at the top of the stairs. Immediately before touching the step, a series of operations in which the main body rotates to the opposite side of the staircase and moves in the center of gravity is repeated.

Japanese Patent No. 4574016 Japanese Patent No. 4709390

  In the stair lift described in Patent Documents 1 and 2 described above, when the height of the center of gravity of the entire stair lift is lowered, the inclination angle with respect to the step of the staircase due to the rotation of the main body portion is increased, so that the stair lift is likely to be unstable during the stair lift There is a possibility that the ascending / descending speed may be restricted and the main body may interfere with the stairs.

  This invention is made | formed in view of such a situation, and it aims at providing the stair lift which can restrain the inclination angle with respect to the step of the stairway by rotation of a main-body part at the time of stair climbing small.

  (Claim 1) A stair lift according to the present invention includes a main body part, a support part that is disposed at a lower part of the main body part and rotatably supports the main body part, and the same rotation direction of the main body part in the support part. A front wheel and a rear wheel that are supported so as to be able to rotate in a rotational direction of the first wheel, a first rotary actuator that is provided in the main body and relatively rotates the front wheel, the rear wheel, and the support, and the main body A second rotary actuator that rotates the main body with respect to the support, a mounting portion that is provided on an upper portion of the main body and is capable of mounting an object, and is provided on the main body. A control device that drives the first and second rotary actuators and alternately grounds the front wheels and the rear wheels to the steps of the stairs to raise and lower the stairs, the stairs elevator as a whole Center of gravity, so as to be positioned above the respective centroids of the first and second rotary actuator, said first and second rotary actuator is disposed in the main body portion.

  (Claim 2) The stair lift is provided in the main body, and includes a drive battery for the first and second rotary actuators, and the center of gravity of the drive battery is the first and second rotary actuators. The drive battery may be arranged in the main body so as to be positioned above the center of gravity.

  (Claim 3) The second rotary actuator includes: a motor; and a belt mechanism for power transmission that connects a shaft of the motor and a shaft provided at a center of the support portion; However, the motor may be arranged in the main body so as to be positioned above the center of gravity of the support.

(Claim 4) The control device includes the first and second rotary actuators such that the center of gravity of the entire stair lift is located on a vertical line passing through an axle of a ground-side wheel when the stair is raised and lowered. May be driven.
(Claim 5) The stair lift may be configured such that the front and rear weight distribution with respect to a vertical line passing through the center of the support portion is symmetrical.

(Claim 6) The mounting portion is supported by the main body portion so as to be rotatable in the same rotation direction as the rotation direction of the main body portion, and the main body portion rotates the mounting portion under the control of the control device. A third rotary actuator may be provided.
(Claim 7) The mounting portion may be provided with a horizontal detection sensor for detecting a horizontal state of the mounting portion.

  (Claim 1) Since the inclination angle with respect to the step of the staircase when the main body rotates can be suppressed to a desired small angle, the stair lift by the stair lift can be stably operated, and the lift speed is increased. Can do. Further, it is possible to prevent interference between the main body or the like and the stairs when the stairs are raised and lowered.

  (Claim 2) Since the driving battery having a relatively large specific gravity is disposed at the upper portion of the main body, the position of the center of gravity of the entire stair elevator can be further increased, and the inclination angle of the main body can be suppressed to a smaller angle.

  (Claim 3) Since the motor can be disposed away from the shaft of the support portion by the belt mechanism, the position of the center of gravity of the entire stair elevator is further increased by positioning the motor's center of gravity above the center of gravity of the support portion. The inclination angle of the main body can be suppressed to a smaller angle.

(Claim 4) Since the center of gravity of the entire stair lift does not move extremely forward or backward, the stair lift by the stair lift can be stably operated.
(Claim 5) Since the inclination angle with respect to the step of the staircase when the main body rotates can be made the same in the front and rear, the stair lift by the stair lift can be stably operated.

(Claim 6) Since the mounting portion can be maintained in a horizontal state even when the main body portion is inclined, the object can be transported stably.
(Claim 7) Since the horizontal state of the mounting portion can be maintained with high accuracy, the object can be transported more stably.

Embodiment of this invention: It is the figure which looked at the stair lift from back. It is the figure which looked at the stair lift from the right side. It is the figure which looked at the stair lift from the upper part. It is a schematic diagram which shows the 1st, 2nd rotary actuator of a stair lift. It is a schematic diagram which shows the 3rd rotation actuator of a stair lift. It is a figure which shows the state before stair raising / lowering of a stair lift. It is a figure which shows the state which the front wheel of the stair lift came in contact with the wall surface of a staircase. It is a figure which shows the state in which the rear wheel of the stair lift was revolved and reached the top dead center. It is a figure which shows the state in which the rear wheel of the stair lift was grounded to the upper surface step. It is a figure which shows the state in which the front wheel of the stair lift was revolved and reached the same height as the upper surface step. It is a figure for demonstrating the derivation | leading-out method of the inclination-angle of the main-body part in a stair lift. Another example of the embodiment of the present invention: FIG.

(1. Structure of stair lift)
A stair lift according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. The stair lift 1 of the present embodiment will be described as applied to a device that carries and transports an object (corresponding to the “object” of the present invention), but a person (corresponding to the “object” of the present invention) is used. It is also possible to apply to a wheelchair that can be boarded. In the following description, “front direction” and “rear direction” refer to the travel direction of the stair lift 1, and “left direction” and “right direction” refer to travel when the stair lift 1 is viewed from the rear. The direction perpendicular to the direction on the horizontal plane.

  As shown in FIG. 1 to FIG. 3, the stair lift 1 is configured to include a main body portion 10, a traveling portion 20, a mounting portion 30, and the like. The main body part 10 is formed in a rectangular parallelepiped shape by a frame member or the like, the traveling part 20 is disposed at the lower part of the main body part 10, and the mounting part 30 is disposed at the upper part. The traveling unit 20 is supported by a pair of hollow, substantially rectangular parallelepiped-shaped support units 21 that rotatably support the main body unit 10, and can rotate in the same rotation direction as the rotation direction of the main body unit 10 at both ends of each support unit 21. A pair of front wheels 22 and a pair of rear wheels 23 are provided. Support portions 21 including a pair of front wheels 22 and rear wheels 23 are respectively disposed on the left and right sides of the main body portion 10.

  The mounting portion 30 is formed in a basket shape by a frame member or the like, and is a bracket 31 that is rotatably supported by the main body portion 10, and a substantially spherical cover that is formed to cover the periphery of the bracket 31 and is fixed to the bracket 31. 32 and a rectangular tray 33 or the like fixed to the upper part of the cover 32 so that an object can be mounted.

  A pair of first rotary actuators 40 that relatively rotate the front wheel 22 and the rear wheel 23 of the traveling unit 20 and the support unit 21 are disposed on both the left and right sides in the main body unit 10. The first rotary actuator 40 includes a first motor 41, a first speed reducer 42, a gear train 43 (see FIG. 4), and the like.

  As shown in FIG. 4, the gear train 43 has five spur gears 43 a meshed side by side and is rotatably supported in the support portion 21. The motor shaft 41a of the first motor 41 fixedly arranged on the main body 10 is connected to the first speed reducer 42 fixedly arranged on the main body 10, and the output shaft 42a of the first speed reducer 42 is supported. A hollow shaft 21 a is provided so as to project integrally with the central portion of the portion 21. A spur gear 43 a disposed at the center of the gear train 43 is fitted to the output shaft 42 a of the first reduction gear 42.

  Spur gears 43 a arranged on both sides of the gear train 43 are respectively fitted to the axle 22 a of the front wheel 22 and the axle 23 a of the rear wheel 23. The hollow shaft 21a of the support portion 21 is inserted through the lower portion of the main body portion 10 via a bearing (not shown) so that the main body portion 10 and the support portion 21 can be relatively rotated.

  A pair of second rotary actuators 50 that rotate the main body 10 itself are arranged on both the left and right sides in the main body 10. The second rotary actuator 50 includes a second motor 51, a second speed reducer 52, a belt mechanism 53, and the like. As shown in FIGS. 1 and 4, the belt mechanism 53 includes a belt 53a and two pulleys 53b and 53c.

  The motor shaft 51a of the second motor 51 fixedly disposed on the main body 10 is connected to a second speed reducer 52 fixedly disposed on the main body 10, and the output shaft 52a of the second speed reducer 52 includes A pulley 53b is fitted. Further, a pulley 53 c is fitted to the hollow shaft 21 a of the support portion 21. A belt 53a is bridged between the pulley 53b and the pulley 53c.

  A third rotary actuator 60 that rotates the mounting portion 30 is disposed in the main body portion 10. The third rotary actuator 60 includes a third motor 61, a third speed reducer 62, a brake 63, etc., and the third motor 61 and the third speed reducer 62 are arranged in the left and right sides of the main body 10. The brake 63 is disposed on the other left and right sides in the main body 10.

  As shown in FIGS. 1 and 5, the motor shaft 61 a of the third motor 61 fixedly arranged on the main body 10 is connected to a third speed reducer 62 fixedly arranged on the main body 10. The output shaft 62 a of the speed reducer 62 is fitted to a bearing 64 a mounted on one of the left and right sides of the bracket 31. The brake shaft 63 a of the brake 63 is fitted into a bearing 64 b that is mounted on the left and right other side of the bracket 31. The brake 63 is provided to maintain the horizontal state of the tray 33 even after the third motor 61 is turned off.

  Further, in the main body 10, a control device 70 that controls the operation of the first, second, and third rotary actuators 40, 50, 60, and the first, second, and third rotary actuators 40, 50, A drive battery 80 for supplying power to 60 and the like, an inclination detection sensor 71 for detecting an inclination angle of the main body 10, and electric components such as a servo amplifier and a relay (not shown) are arranged and fixed.

  In addition, an inclination detection sensor 72 (see FIG. 4) that detects the inclination angle of the support portion 21 is disposed and fixed on the traveling unit 20. Further, between the cover 32 of the mounting unit 30 and the tray 33, there are a horizontal detection sensor 91 that detects the horizontal state of the tray 33 and four weight detection sensors 92 that detect the weight of an object placed on the tray 33. Arranged at the four corners of the rectangular tray 33. Between the cover 32 and the bracket 31, an unillustrated damper made of a cushion material or the like is disposed in order to suppress the vibration of the tray 33 and prevent the object from falling.

(2. Stair elevator operation)
Next, the raising / lowering operation | movement of the stairs by the stair elevator 1 is demonstrated with reference to FIG. Here, the operation until the stair lift 1 positioned on the horizontal lower surface step Sd of the staircase S rises on the horizontal upper surface step Su higher by the height of the wall surface Sw under the control of the control device 70 will be described. 6A to 6E, the main body portion 10, the traveling portion 20, and the mounting portion 30 of the stair lift 1 are shown by simplified skeletons. The right wheel in the drawing is the front wheel 22, and the left wheel in the drawing is the rear wheel 23. And

  First, as shown in FIG. 6A, the stair lift 1 is in a normal posture in which the support portion 21 of the traveling unit 20 is in a horizontal state and the main body unit 10 and the mounting unit 30 are in a vertical state, That is, when traveling forward, the front wheel 22 comes into contact with the wall surface Sw of the stairs S as shown in FIG. 6B.

  Here, for example, the fact that the stair lift 1 has come into contact with the wall surface Sw by a pressure sensor provided on the axle 22a of the front wheel 22 or a step detection sensor using infrared rays provided on the front surface (rear surface) of the main body 10. When detected, the first, second, and third motors 41, 51, 61 are driven to change the relative phases of the main body portion 10, the support portion 21, and the mounting portion 30. While rotating around the hollow shaft 21a as a center, the mounting portion 30 is rotated backward around the bearings 64a and 64b of the bracket 31.

  Then, the inclination detection sensors 71, 72 indicate that the inclination angle of the main body 10 is θ degrees forward with respect to the vertical line Lv passing through the hollow shaft 21 a of the support portion 21, and the horizontal detection sensor 91 determines that the mounting portion When it is detected that the inclination angle of the 30 trays 33 is 90 degrees (horizontal state), the first, second, and third motors 41, 51, and 61 are stopped. Details of the inclination angle θ will be described later.

  Next, as shown in FIG. 6C, the first, second, and third motors 41, 51, 61 are driven to change the relative phases of the main body portion 10, the support portion 21, and the mounting portion 30. While rotating forward about the axle 22a of the front wheel 22, the main body 10 is rotated backward about the hollow shaft 21a of the support portion 21, and the mounting portion 30 is moved forward around the bearings 64a and 64b of the bracket 31. Rotate. Accordingly, the rear wheel 23 revolves clockwise around the front wheel 22 and is lifted upward from the lower surface step Sd.

  The inclination detection sensors 71 and 72 allow the inclination angle of the main body 10 and the support 21 to be 0 with respect to the vertical line Lv passing through the hollow shaft 21a of the support 21, that is, the main body 10 and the support 21 are in the vertical direction. When it is detected that the inclination angle of the tray 33 of the mounting portion 30 has reached 90 degrees (horizontal state), the first, second, and third motors 41 and 51 are detected. , 61 is stopped. As a result, the rear wheel 23 is positioned vertically above the front wheel 22.

  Next, as shown in FIG. 6D, the first, second, and third motors 41, 51, 61 are driven to change the relative phases of the main body portion 10, the support portion 21, and the mounting portion 30. While rotating forward about the axle 22a of the front wheel 22, the main body 10 is rotated backward about the hollow shaft 21a of the support portion 21, and the mounting portion 30 is moved forward around the bearings 64a and 64b of the bracket 31. Rotate. As a result, the rear wheel 23 revolves clockwise around the front wheel 22 and exceeds the front wheel 22.

  Then, the inclination detection sensors 71 and 72 indicate that the inclination angle of the main body part 10 and the support part 21 has become θ degrees backward with respect to the vertical line Lv passing through the hollow shaft 21a of the support part 21, and the horizontal detection sensor 91. Thus, when it is detected that the inclination angle of the tray 33 of the mounting unit 30 is 90 degrees (horizontal state), the first, second, and third motors 41, 51, and 61 are stopped. Thereby, the rear wheel 23 is grounded to the upper surface step Su.

  Next, as shown in FIG. 6E, the first, second, and third motors 41, 51, and 61 are driven to change the relative phases of the main body portion 10, the support portion 21, and the mounting portion 30, and the support portion 21 is moved. The rear wheel 23 rotates forward about the axle 23a, the main body 10 rotates forward about the hollow shaft 21a of the support portion 21, and the mounting portion 30 moves rearward about the bearings 64a and 64b of the bracket 31. Rotate to. Accordingly, the front wheel 22 revolves clockwise around the rear wheel 23 and is lifted upward from the lower surface step Sd.

  Then, when the inclination angle of the support part 21 becomes 90 degrees (horizontal state) with respect to the vertical line Lv passing through the hollow shaft 21a of the support part 21 by the inclination detection sensors 71 and 72, the inclination angle of the main body part 10 Is controlled to be 90 degrees (horizontal state) by the horizontal detection sensor 91 so that the inclination angle of the tray 33 of the mounting unit 30 is 90 degrees (horizontal state). As a result, the stair lift 1 is in the state shown in FIG. 6B in the upper surface step Su, and thereafter, the staircase S can be raised by repeating the above-described operation. The same applies when going down the stairs S.

(3. Arrangement of each part in the stair lift)
As described above, the stair lift 1 drives the first, second, and third rotary actuators 40, 50, 60 by the control device 70, and relatively moves the main body unit 10, the traveling unit 20, and the mounting unit 30. The stairs S are moved up and down by alternately grounding the front wheels 22 and the rear wheels 23 to the steps of the stairs S. In order to increase the efficiency and stability of the raising / lowering operation of the stair lift 1, it is effective to keep the rotation angle of the main body portion 10, that is, the inclination angle θ, small and balance the weight. For this purpose, the arrangement of each part in the stair lift 1 of the present embodiment is devised, and the stair lift 1 is configured so that the position of the center of gravity of the stair lift 1 as a whole is high.

  That is, as shown in FIG. 6A, the driving battery 80 is positioned so that the center of gravity Gb of the driving battery 80 is located above the centers of gravity Gr, Gh of the first and second rotary actuators 40, 50. It is arranged on the main body 10. The center of gravity G of the stair lift 1 alone (the stair lift 1 as a whole when no object is placed on the tray 33) is larger than the centers of gravity Gr, Gh of the first and second rotary actuators 40, 50. The first and second rotary actuators 40 and 50 are arranged in the main body 10 so as to be positioned above. The above-described relationship between the positions of the center of gravity is maintained in the state where the stair lift 1 is in the traveling state (the state shown in FIG. 6A) and the state when the stair lift 1 is raised and lowered (the state shown in FIGS. 6B to 6E). Thereby, inclination-angle (theta) of the main-body part 10 can be restrained small, and the efficiency of the raising / lowering operation | movement of the stair lift 1 can be improved.

  Moreover, the stair lift 1 is configured such that the weight distribution before and after the vertical line Lv passing through the hollow shaft 21a of the support portion 21 is symmetrical in the state shown in FIG. 6A. Thereby, the inclination | tilt angle (theta) of the main-body part 10 can be made the same before and behind, and stability of the raising / lowering operation | movement of the stair elevator 1 can be improved. Then, as shown in FIGS. 6B to 6E, the control device 70 is configured so that the center of gravity G of the entire stair lift 1 is located on a vertical line passing through the axle of the ground-side wheel when ascending and descending the stair S. The second and third rotary actuators 40, 50 and 60 are driven. Thereby, the weight balance of the stair lift 1 can be taken, and the stability of the lift operation of the stair lift 1 can be enhanced.

  Here, the specific arrangement of each part in the stair lift 1 will be described with reference to FIG. 1. The drive battery 80 is arranged at the center in the horizontal plane at the upper part in the main body part 10 because there is no restriction on the arrangement position. Has been. Further, the first motor 41 and the first speed reducer 42 of the pair of first rotary actuators 40 need to rotate the pair of front wheels 22, the rear wheels 23, and the support portion 21 (gear train 43). In the lower part in the main body 10, the weight distribution in the front-rear direction with respect to the vertical line Lv (see FIG. 6A) is symmetrical, and is arranged so as to be symmetrical on both the left and right sides.

  The second motor 51 and the second speed reducer 52 of the pair of second rotary actuators 50 are separated from the hollow shaft 21a of the support portion 21 by the belt mechanism 53, that is, the center of gravity of the second motor 51 is supported by the support portion. 21 can be positioned above the center of gravity. Therefore, the pair of second rotary actuators 50 are vertically arranged at a substantially central portion in the vertical direction in the main body 10 above the first motor 41 and the first speed reducer 42 of the pair of first rotary actuators 40. The weight distribution before and after the line Lv (see FIG. 6A) is symmetrical, and is arranged so as to be symmetrical on both the left and right sides.

  The mounting unit 30 is disposed on the uppermost part of the main body unit 10 because an object needs to be placed on the tray 33. With the above arrangement, the center of gravity G of the entire stair lift 1 and the center of gravity Gb of the driving battery 80 are configured to be positioned above the centers of gravity Gr, Gh of the first and second rotary actuators 40, 50. Can do.

(4. Method for deriving the inclination angle of the main body of the stair lift)
Next, a method for deriving the inclination angle θ of the main body 10 with respect to the vertical line Lv passing through the hollow shaft 21a of the support portion 21 of the stair lift 1 will be described. As shown in FIG. 7, the inclination angle θ of the main body 10 means that the center of gravity G of the entire stair lift 1 is the axle of the front wheel 22 with respect to the traveling unit 20 in a state where the front wheels 22 and the rear wheels 23 are grounded. This is the rotation angle of the main body 10 until it is positioned on the vertical line Ltv passing through 22a.

  Here, with the axle 22a of the front wheel 22 of the traveling unit 20 as the origin O, the X axis is taken in the horizontal direction and the Y axis is taken in the vertical direction. Then, the distance in the X-axis direction from the origin O to the center of gravity Gr of the traveling unit 10 (including the first rotary actuator 40 and the like, excluding the front wheel 22 and the rear wheel 23) is xr, and the main body 20 (first The distance in the X-axis direction to the center of gravity Gh of the second rotary actuator 50, including electrical components, etc. (excluding the first rotary actuator 40, etc.) is xh, and the mounting portion 30 (third rotary actuator 60, etc.) from the origin O The distance in the X-axis direction from the origin O to the center of gravity Gb of the drive battery 80 is xb. The distance in the Y-axis direction from the origin O to the center of gravity Gh of the main body 20 is yh, the distance in the Y-axis direction from the origin O to the center of gravity Gc of the mounting portion 30 is yc, and the center of gravity Gb of the driving battery 80 from the origin O. The distance in the Y-axis direction until is yb. The weight of the support portion 21 is mr, the weight of the front wheel 22 and the rear wheel 23 is mt, the weight of the main body portion 10 is mh, the weight of the driving battery 80 is mb, and the weight of the mounting portion 30 is mc.

Then, the balance of moments around the origin O is expressed by the following equation (1). The relationship between the distance in the X-axis direction and the distance in the Y-axis direction is expressed by the following equations (2) to (4). Based on these formulas (1) to (4), the inclination angle θ of the main body 10 can be suppressed to a desired small angle. Thereby, the stair lift by the stair lift 1 can be stably operated, and the lift speed can be increased. Further, it is possible to prevent interference between the main body or the like and the stairs when the stairs are raised and lowered.

(5. Other)
In the stair lift 1 of the above-described embodiment, the pair of first rotary actuators 40 and the pair of second rotary actuators 50 are provided, but each of the first and second rotary actuators 40 and 50 is provided. It is good also as a structure. Moreover, although it was set as the structure provided with a pair of front wheel 22 and a pair of rear wheel 23, it is good also as a structure provided with one front wheel 22 and one rear wheel 23 as a wide wheel. Further, the third rotary actuator 60 may not be mounted. By reducing the number of first and second rotary actuators and eliminating the third rotary actuator 60, the cost of the stair elevator 1 can be reduced.

  Moreover, although it was set as the structure provided with the inclination detection sensors 71 and 72 which detect the inclination angle of the main-body part 10 and the driving | running | working part 20 (support part 21), the resolver with which the 1st, 2nd motors 41 and 51 were equipped, It is good also as a structure which detects the inclination-angle of the main-body part 10 and the traveling part 20 (support part 21) using an encoder. By eliminating the tilt detection sensors 71 and 72, the cost of the stair lift 1 can be reduced. Further, as shown in FIG. 8 corresponding to FIG. 1, a robot arm 101 and a robot hand 102 are further provided on the left and right sides of the mounting unit 30, and the robot arm 101 and the robot hand 102 are moved forward by driving motors 103 and 104. It is also possible to balance the weight by moving backward and left and right.

  1: Stair elevator, 10: Main body, 20: Traveling part, 21: Supporting part, 21a: Hollow shaft, 22: Front wheel, 23: Rear wheel, 30: Mounting part, 31: Bracket, 32: Cover, 33: Tray 40: first rotary actuator, 41: first motor, 43: gear train, 50: second rotary actuator, 51: second motor, 53: belt mechanism, 60: third rotary actuator, 61 : Third motor, 63: brake, 70: control device, 80: drive battery, 91: horizontal detection sensor, 92: weight detection sensor, 101: robot arm, 102: robot hand, 103, 104: motor.

Claims (7)

The main body,
A support portion disposed at a lower portion of the main body portion and rotatably supporting the main body portion;
A front wheel and a rear wheel that are supported so as to be able to rotate in the same rotation direction as the rotation direction of the main body portion in the support portion;
A first rotary actuator provided in the main body and relatively rotating the front and rear wheels and the support;
A second rotary actuator provided on the main body and rotating the main body with respect to the support;
A mounting portion provided on an upper portion of the main body portion and capable of mounting an object;
A stair lift provided on the main body, and driving the first and second rotary actuators to alternately ground the front wheel and the rear wheel at the step of the stair to raise and lower the stair. There,
The stair lift, wherein the first and second rotary actuators are arranged in the main body so that the center of gravity of the entire stair lift is located above the center of gravity of the first and second rotary actuators. . The stair lift is provided in the main body, and includes a battery for driving the first and second rotary actuators,
2. The stair lift according to claim 1, wherein the driving battery is disposed in the main body so that the center of gravity of the driving battery is positioned above the center of gravity of each of the first and second rotary actuators.   The second rotary actuator includes a motor and a belt mechanism for power transmission that connects a shaft of the motor and a shaft provided in the center of the support portion, and the center of gravity of the motor has the support portion The stair lift according to claim 1 or 2, wherein the motor is disposed in the main body so as to be positioned above the center of gravity of the main body.   The control device drives the first and second rotary actuators so that the center of gravity of the entire stair lift is located on a vertical line passing through an axle of a ground-side wheel when the stair is raised and lowered. Item 5. The stair lift according to any one of items 1 to 3.   The stair lift according to any one of claims 1 to 4, wherein the stair lift is configured such that a weight distribution before and after a vertical line passing through a center of the support portion is symmetric. The mounting portion is supported in the main body portion so as to be rotatable in the same rotation direction as the rotation direction of the main body portion,
The stair lift according to any one of claims 1 to 5, wherein the main body portion is provided with a third rotary actuator that rotates the mounting portion under the control of the control device.   The stair lift according to claim 6, wherein the mounting portion is provided with a horizontal detection sensor that detects a horizontal state of the mounting portion.

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