Electric casters

Abstract

To provide an electric caster which can be miniaturized with a simple structure and can enhance a degree of freedom in component arrangement on a mounting body.SOLUTION: An electric caster 1 includes: a main case 3 which is fixed to a base section 2; a brushless motor 31 which is fixed to the main case 3; a hollow shaft 12 which is rotatably supported by the main case 3; a brake mechanism 21 which is fixed to the main case 3; a drive shaft 13 which is inserted into the hollow shaft 12 and is rotated by receiving driving force of the brushless motor 31; a gear case 36 which is fixed to the hollow shaft 12; an axle 45 which is rotatably supported by the gear case 36; bevel gears 37, 38 which are stored in the gear case 36 and transmit rotation of the drive shaft 13 to the axle 45; a driving wheel 46 which is fixed to a first end 45a of the axle 45; and a driven wheel 47 which is relatively rotatably supported by a second end 45b of the axle 45.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electric caster. [Background technology]

[0002] Conventionally, there has been known a technology for making wheelchairs, transport carts, etc., self-propelled by using electric casters on wheelchairs or transport carts for transporting parts stored in a warehouse, etc. An electric caster comprises a support pole rotatably attached to a mounting body (car body), an axle that is attached below the support pole and extends horizontally, and a pair of wheels attached to both ends of the axle. The electric caster is driven by power supplied from a power source such as a battery attached to the mounting body.

[0003] Various electric caster technologies have been proposed to improve the running performance of wheelchairs, transport vehicles, and the like. For example, in Patent Document 1, one of a pair of wheels is provided with a drive unit such as a motor, making the wheel a drive wheel. The other wheel of the pair is a driven wheel. Furthermore, an electromagnetic brake is provided on the support post and the driven wheel, respectively. The electromagnetic brake, etc., provided on the support post is provided on a mounting body.

[0004] With this configuration, the corresponding electromagnetic brake restricts the rotation of the driven wheel while allowing the support column to rotate. The difference in rotation between the drive wheel and the driven wheel then causes the support column to rotate. This allows the wheelchair, transport cart, etc. to turn. At this time, the electromagnetic brakes on the driven wheels and the drive units on the drive wheels also rotate around the center axis of the support column. Meanwhile, the corresponding electromagnetic brake restricts the rotation of the support column while allowing the rotation of the driven wheel, allowing the wheelchair or transport cart to move in a straight line.

[0005] Furthermore, in Patent Document 2, two actuators are provided: one for running the wheelchair, transport cart, etc., and the other for turning the wheelchair, transport cart, etc. Each actuator is provided on a mounting body. In this configuration, the support pillar serves as the drive shaft, and the support pillar and axle are connected via gears. The driving force of the actuator for travel is then transmitted to the upper end of the support pillar. This causes the axle to rotate, allowing the wheelchair or transport cart to travel.

[0006] A hollow pivot shaft is provided through which the support pillar is inserted. An axle is rotatably supported on this pivot shaft via a housing. The driving force of a rotation actuator is transmitted to the upper end of the pivot shaft, causing the pivot shaft to rotate relative to the pillar. The orientation of the housing and axle changes around the central axis of the pivot shaft, becoming one with the pivot shaft. This allows a wheelchair, transport cart, or the like to rotate. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2020 / 059189 [Patent Document 2] International Publication No. 2020 / 110334 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the above-mentioned Patent Document 1, two electromagnetic brakes are required to satisfy both straight-line and turning operations, which poses a problem of increasing the size of the electric caster. In addition, the electromagnetic brakes on the driven wheels and the drive units on the drive wheels rotate around the central axis of the support column. Therefore, in order to supply power to each electromagnetic brake and drive unit from the power source on the mounting body, it is necessary to use a slip ring or wireless power supply system. This makes the electric caster's structure complex, which in turn leads to an increase in size. Furthermore, in Patent Document 1, many parts such as the electromagnetic brake protrude from the mounting body, which limits the space available for arranging the power supply and other components on the mounting body.

[0009] In the above-mentioned Patent Document 2, two actuators are required to satisfy both the straight movement and the turning movement, which poses a problem of increasing the size of the electric caster. Furthermore, each actuator is mounted on the mounting body. As a result, the support (drive shaft) and pivot shaft to which power from each actuator is transmitted also need to protrude from the mounting body. This increases the number of components mounted on the mounting body, which creates the problem of restricting the space available for arranging the power supply and other components on the mounting body.

[0010] Therefore, the present invention provides an electric caster that has a simple structure, can be made compact, and allows for greater freedom in the arrangement of parts on the mounting body. [Means for solving the problem]

[0011] In order to solve the above problems, a first aspect of the present invention includes a main case fixed to a mounting body, a drive unit fixed to the main case, a hollow shaft rotatably supported by the main case, a brake mechanism fixed to the main case and allowing and restricting rotation of the hollow shaft relative to the main case, a drive shaft inserted into the hollow shaft and supported rotatably relative to the hollow shaft and rotated by the driving force of the drive unit, a gear case fixed to the hollow shaft, an axle rotatably supported by the gear case, a gear housed in the gear case and transmitting the rotation of the drive shaft to the axle, a drive wheel fixed to a first axial end of the axle and rotating integrally with the axle, and a driven wheel fixed to a second axial end opposite the first end of the axle and supported rotatably relative to the axle.

[0012] This configuration allows the electric caster to move straight and turn with a single drive unit, which simplifies the configuration of the electric caster and makes it smaller. Furthermore, there is no need to use a configuration in which components are placed above the mounting body, which reduces the space required for the components that make up the electric caster on the mounting body, thereby increasing the degree of freedom in component placement on the mounting body.

[0013] In a second aspect of the present invention, in the electric caster of the first aspect, the hollow shaft and the drive shaft are arranged above the axle, and the axial directions of the hollow shaft and the drive shaft are arranged so that they intersect with the axial direction of the axle, and further comprises a rotational position detection sensor for detecting the rotational position of the hollow shaft, and a reduction unit that is attached to the drive unit and to which the drive shaft is attached, and that reduces the drive of the drive unit and transmits it to the drive shaft, and only the drive unit protrudes above the mounting body.

[0014] In this way, only the drive section protrudes above the mounting body, and all other components are arranged below the mounting body, which reliably increases the degree of freedom in component placement on the mounting body.

[0015] In a third aspect of the present invention, in the electric caster of the second aspect, the rotational position detection sensor comprises a sensor magnet attached to the hollow shaft and a sensor board housed in the main case that detects changes in magnetism caused by the rotation of the sensor magnet, and the brake mechanism is arranged around the hollow shaft.

[0016] This configuration allows the rotational position detection sensor and the brake mechanism to be efficiently arranged in a space-saving manner, thereby further reducing the size of the electric caster.

[0017] In a fourth aspect of the present invention, in the electric caster of the third aspect, the brake mechanism, the rotational position detection sensor, and the deceleration unit are arranged in the main case in that order from bottom to top, and a sensor holder is provided between the rotational position detection sensor and the deceleration unit, and the sensor board is attached to the sensor holder.

[0018] Here, dust and water are likely to enter the main case through gaps between the main case and the hollow shaft at the bottom of the main case. The rotational position detection sensor is easily damaged by dust and water. Therefore, according to the fourth aspect, by providing a brake mechanism below the rotational position detection sensor, this brake mechanism acts as a barrier to reduce the effects of dust and water on the rotational position detection sensor. This stabilizes the operation of the electric caster. [Effects of the Invention]

[0019] According to the present invention, the electric caster can be made smaller with a simple structure, and the degree of freedom in arranging parts on the mounting body can be increased. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 is a cross-sectional view of the electric caster in the axial direction according to the embodiment of the present invention. [Figure 2] FIG. 2 is a plan view of the electric caster according to the embodiment of the present invention, viewed from below. DETAILED DESCRIPTION OF THE INVENTION

[0021] Next, an embodiment of the present invention will be described with reference to the drawings.

[0022] <Electric casters> FIG. 1 is a cross-sectional view of the electric caster 1 taken along the axial direction. As shown in Fig. 1, an electric caster 1 is used in a wheelchair, a transport cart, etc. that transports parts stored in a warehouse, etc. The electric caster 1 comprises a main case 3 attached to a base part (an example of a mounting body in the claims) 2 of the wheelchair or transport cart, a main mechanism part 4 housed in the main case 3, an axle unit 5 rotatably supported by the main case 3, a gear part 6 connected to the axle unit 5, and a wheel unit 7 rotatably supported by the gear part 6.

[0023] In the following description, the up-down direction refers to the up-down direction when the electric caster 1 is in use. The electric caster 1 is attached so that the main case 3 is fixed to the lower surface 2a of the base portion 2. At this time, the first rotation axis C1 of the axle unit 5 is parallel to the vertical direction. In the following description, the direction of the first rotation axis C1 may be referred to as the axial direction instead of the up-down direction. Also, the direction around the first rotation axis C1 may be referred to as the circumferential direction, and the radial direction of the shaft unit 5 perpendicular to the axial and circumferential directions may be simply referred to as the radial direction. Furthermore, the direction perpendicular to the up-down direction may be referred to as the horizontal direction instead of the circumferential direction and the radial direction.

[0024] An opening 2b is formed in the base 2 at a location where the electric caster 1 is attached. The main case 3 is fixed to the underside 2a of the base 2 so that part of the electric caster 1 is inserted into this opening 2b. A plurality of bolt insertion holes 2c, through which bolts 10 are inserted, are formed at equal intervals in the circumferential direction around the opening 2b in the base 2.

[0025] <Main case> The main case 3 is formed in a cylindrical shape with a bottom and an opening 3a at the top. An outer flange 8 is formed at the opening 3a of the main case 3, projecting radially outward. The outer flange 8 is used to fix the main case 3 to the base 2. The outer flange 8 has a plurality of female threads 8a formed coaxially with the bolt insertion holes 2c of the base 2. The main case 3 is fastened and fixed to the base 2 by threading bolts 10 inserted into the bolt insertion holes 2c from above the base 2 into the female threads 8a.

[0026] A cylindrical bearing boss 9 is formed on the bottom wall 3b of the main case 3, protruding downward from most of the radial center. Two bearings 11 are provided axially side by side in the axial center on the inner peripheral surface of the bearing boss 9. The shaft unit 5 is rotatably supported by these bearings 11. In addition, a seal portion 18 that seals between the main case 3 and the shaft unit 5 is provided on the inner peripheral surface of the bearing boss 9, below the bearings 11.

[0027] <Axis unit> The shaft unit 5 includes a hollow shaft 12 rotatably supported by a bearing 11 , and a drive shaft 13 inserted into the hollow shaft 12 and supported by the hollow shaft 12 so as to be rotatable relative to the hollow shaft 12 . The hollow shaft 12 is formed to a length that protrudes from the lower end 9a of the bearing boss 9 into the main case 3 via the bearing boss 9. A lower reduced diameter portion 12a, whose diameter is reduced via a step, is formed on the hollow shaft 12 between a position corresponding to the bearing 11 and the lower end of the hollow shaft 12. A cylindrical gear holder 14 is fitted and fixed to the outer circumferential surface of the lower reduced diameter portion 12a.

[0028] The upper end of the gear holder 14 abuts against the step of the lower reduced diameter portion 12a, thereby positioning the gear holder 14 in the axial direction relative to the hollow shaft 12. An outer flange portion 15 that protrudes radially is integrally formed at the lower end of the gear holder 14. The upper end of the outer flange portion 15 abuts against the inner ring of the bearing 11, thereby positioning the hollow shaft 12 in the axial direction relative to the main case 3.

[0029] The gear portion 6 is fastened to the outer flange portion 15 by bolts (not shown). A plurality of female screw portions 15a into which the bolts (not shown) are screwed are formed at equal intervals in the circumferential direction on the lower end surface of the outer flange portion 15. An upper reduced diameter portion 12b, the diameter of which is reduced via a step, is formed at the upper portion of the hollow shaft 12. The upper reduced diameter portion 12b is used to attach part of the main mechanism portion 4.

[0030] The drive shaft 13 inserted into the hollow shaft 12 has both axial ends protruding from both axial ends of the hollow shaft 12. The lower end of the drive shaft 13 is connected to the gear unit 6. An outer flange portion 16 that protrudes radially outward is integrally formed at the upper end of the drive shaft 13. A plurality of bolt insertion holes 16a that penetrate the outer flange portion 16 in the axial direction are formed at equal intervals around the circumference. Bolts 17 are inserted into the bolt insertion holes 16a. The bolts 17 are used to fasten and fix the drive shaft 13 to an actuator 23 (described later) of the main mechanism unit 4.

[0031] <Main mechanism> The main mechanism 4 mainly comprises a brake mechanism 21 arranged on the bottom wall 3b of the main case 3, a rotational position detection sensor 22 arranged above the brake mechanism 21, and an actuator 23 arranged above the rotational position detection sensor 22.

[0032] <Brake mechanism> The brake mechanism 21 restricts the rotation of the hollow shaft 12 relative to the main case 3. The brake mechanism 21 is, for example, an electromagnetic brake. The brake mechanism 21 is provided so as to surround the periphery of the hollow shaft 12. An armature hub 21a of the brake mechanism 21 is fitted and fixed to the upper reduced diameter portion 12b of the hollow shaft 12. The armature hub 21a abuts against a step in the upper reduced diameter portion 12b, thereby positioning the armature hub 21a in the axial direction relative to the hollow shaft 12. With the brake mechanism 21 positioned in this manner, it is disposed on the bottom wall 3b of the main case 3.

[0033] With this configuration, the brake armature 21b is pressed against the armature hub 21a or the brake armature 21b is separated from the armature hub 21a by turning on or off the current to the brake mechanism 21. When the brake armature 21b is pressed against the armature hub 21a, the sliding resistance acting between them restricts the rotation of the hollow shaft 12 relative to the main case 3 (brake on).

[0034] When the brake armature 21b is separated from the armature hub 21a, no resistance is generated between them, and therefore the hollow shaft 12 is allowed to rotate relative to the main case 3 (brake off). In other words, the hollow shaft 12 can rotate smoothly relative to the main case 3.

[0035] <Rotational position detection sensor> The rotational position detection sensor 22 is a so-called magnetic encoder that detects the rotational position of the hollow shaft 12. The rotational position detection sensor 22 includes a magnet unit 24 provided on the hollow shaft 12, a sensor board 25 that detects the magnet unit 24, and a sensor holder 26 that supports the sensor board 25 inside the main case 3. The magnet unit 24 includes a magnet holder 27 that is fitted and fixed to the upper reduced diameter portion 12b of the hollow shaft 12 from above the armature hub 21a, and a sensor magnet 28 that is held by the magnet holder 27. The upper end surface of the sensor magnet 28 and the upper end surface of the hollow shaft 12 are located on the same plane.

[0036] Sensor holder 26 is formed in a cylindrical shape with a bottom and an opening 26a at the top. The outer diameter of peripheral wall 26b of sensor holder 26 is slightly smaller than the inner diameter of peripheral wall 3c of main case 3. As a result, peripheral wall 26b of sensor holder 26 is accommodated within main case 3. An outer flange portion 29 that protrudes radially outward is formed at opening 26a of sensor holder 26. The outer diameter of outer flange portion 29 is the same as the outer diameter of outer flange portion 8 of main case 3. When sensor holder 26 is housed in main case 3, outer flange portions 8, 29 overlap with each other, thereby positioning sensor holder 26 in the axial direction relative to main case 3.

[0037] A bolt insertion hole 29a is formed in the outer flange portion 29 of the sensor holder 26, coaxially with the female thread portion 8a formed in the outer flange portion 8 of the main case 3. A bolt 10 is inserted into the bolt insertion hole 2c from above the base portion 2 and threadedly engages with the female thread portion 8a of the main case 3 via the bolt insertion hole 29a of the sensor holder 26. This causes the sensor holder 26 and the main case 3 to be fastened together to the base portion 2.

[0038] A bottom opening 26d is formed in the bottom wall 26c of the sensor holder 26 over most of the radial center. The outer flange portion 16 of the drive shaft 13 is disposed in the bottom opening 26d. A sensor board 25 is attached to the bottom wall 26c of the sensor holder 26. The sensor board 25 is disposed below the bottom wall 26c of the sensor holder 26 via a stud bolt 30 disposed at a position that avoids the bottom opening 26d. An element (not shown) that detects changes in the magnetism of the sensor magnet 28 is mounted on the sensor board 25. The element faces the sensor magnet 28 in the axial direction. For example, a Hall IC is used as the element.

[0039] <Actuator> Actuator 23 includes a flat brushless motor (an example of a drive unit in the claims) 31 and a speed reducer 32 arranged coaxially with brushless motor 31 below brushless motor 31. Brushless motor 31 is driven by power supplied from a power source such as a battery (not shown) provided on base 2.

[0040] The speed reducer 32 reduces the rotation speed of the brushless motor 31 and outputs the reduced speed. For example, a so-called hypocycloid reduction mechanism is used as the speed reducer 32. The speed reducer 32 includes a housing 33 that reduces in diameter in a stepped manner downward, a gear group 34 housed in the housing 33, and an output plate 35 fixed to the lower end of the gear group 34. The rotation of the brushless motor 31 is reduced in speed by the gear group 34 and output from the output plate 35.

[0041] The uppermost portion 33a of the housing 33 is fitted onto the inner peripheral surface of the peripheral wall 26b of the sensor holder 26 and is positioned on the peripheral edge of the opening 26a of the sensor holder 26 (on the outer flange portion 29 of the sensor holder 26). This positions the actuator 23 in the radial and axial directions relative to the sensor holder 26. Because the base portion 2 is also positioned on the outer flange portion 29 of the sensor holder 26, the uppermost portion 33a of the housing 33 is positioned radially inside the opening 2b of the base portion 2. Therefore, in the electric caster 1, only the brushless motor 31 protrudes above the base portion 2.

[0042] The output plate 35 has a female thread 35a formed coaxially with the bolt insertion hole 16a formed in the outer flange 16 of the drive shaft 13. A bolt 17 inserted from below into the bolt insertion hole 16a of the outer flange 16 is screwed into the female thread 35a. This fastens the drive shaft 13 to the output plate 35, and the output plate 35 and the drive shaft 13 rotate integrally.

[0043] <Gear section> The gear section 6 provided at the bottom of the drive shaft 13 comprises a gear case 36 fastened to the gear holder 14 of the hollow shaft 12 by bolts not shown, and two bevel gears 37, 38 (first bevel gear 37 and second bevel gear 38) housed within the gear case 36. The gear case 36 includes a box-shaped case body 41 having an opening 41a at the top, and a lid 42 that closes the opening 41a of the case body 41.

[0044] The cover 42 has a bolt insertion hole 42a formed therethrough in the axial direction and coaxial with the female thread portion 15a of the gear holder 14. A bolt (not shown) is inserted into the bolt insertion hole 42a from below and threadedly engages with the female thread portion 15a of the gear holder 14. This fastens and fixes the cover 42 to the gear holder 14. The cover 42 has a gear insertion hole 42b formed radially inward of the female thread portion 15a. A first bevel gear 37 of the two bevel gears 37, 38 is inserted into the gear insertion hole 42b. The first bevel gear 37 is fitted and fixed to the lower end of the drive shaft 13. The first bevel gear 37 rotates integrally with the drive shaft 13.

[0045] The case body 41 has through holes 41c formed in both horizontal side walls 41b, each penetrating in the thickness direction. The two through holes 41c are arranged coaxially in the horizontal direction. The both side walls 41b of the case body 41 are provided with disk-shaped bearing holders 43 that fit into the through holes 41c. Each bearing holder 43 is provided with a bearing 44. An axle 45 that constitutes the wheel unit 7 is rotatably supported on the case body 41 via these bearings 44 (bearing holders 43).

[0046] In other words, the axle 45 extends below the drive shaft 13 in a direction perpendicular to the drive shaft 13. The axle 45 protrudes outward from both side walls 41b of the case body 41 via bearings 44 (bearing holders 43). The second bevel gear 38 of the two bevel gears 37, 38 is fitted and fixed to such an axle 45.

[0047] The second bevel gear 38 rotates integrally with the axle 45. The second bevel gear 38 is meshed with the first bevel gear 37. As a result, the rotation of the drive shaft 13 is transmitted to the axle 45 via the two bevel gears 37, 38, causing the axle 45 to rotate. In other words, the gear unit 6 has the role of converting the rotation of the drive shaft 13, which rotates about the rotation axis C, into rotation of the axle 45 about the second rotation axis C2, which is aligned in the horizontal direction.

[0048] <Wheel unit> In addition to the axle 45, the wheel unit 7 includes a driving wheel 46 and a driven wheel 47 attached to both ends of the axle 45, respectively. The drive wheel 46 includes a disk-shaped wheel 51 fitted and fixed to a first end 45a (the left end in FIG. 1) of the axle 45, and a tire 52 attached to the outer periphery of the wheel 51. An axle insertion hole 51a, through which the axle 45 is inserted, is formed in the radial center of the wheel 51.

[0049] The collar 53 and wheel 51 are inserted into the first end 45a of the axle 45 in this order, and a fixing nut 54 is fastened to the first end 45a. The end of the collar 53 abuts against the inner ring of the bearing 44. As a result, the wheel 51 is clamped between the collar 53 and the fixing nut 54 and fixed to the axle 45. Therefore, the drive wheel 46 rotates integrally with the axle 45.

[0050] The driven wheel 47 includes a disk-shaped wheel 55 inserted onto the second end 45b (the right end in FIG. 1) of the axle 45, and a tire 56 attached to the outer periphery of the wheel 55. An axle insertion hole 55a having a diameter slightly larger than the diameter of the axle 45 is formed in the radial center of the wheel 55. A bearing 57 is provided in the axle insertion hole 55a. The wheel 55 is rotatably supported on the axle 45 via the bearing 57. The wheel 55 is positioned relative to the axle 45 in the direction of the second rotation axis C2 by collars 58 provided on both sides of the bearing 57 in the direction of the second rotation axis C2.

[0051] In this way, in the wheel unit 7, the rotation of the axle 45 is transmitted to the drive wheel 46, and the drive wheel 46 rotates integrally with the axle 45. On the other hand, the rotation of the axle 45 is not transmitted to the driven wheel 47. The driven wheel 47 rotates relative to the axle 45.

[0052] <Electric caster operation> Next, the operation of the electric caster 1 will be described with reference to FIGS. FIG. 2 is a plan view of the electric caster 1 as seen from below. First, the case where the electric caster 1 is turned will be described. 1 and 2, in this case, the brake mechanism 21 is released, allowing the hollow shaft 12 to rotate relative to the main case 3. When the actuator 23 is driven in this state, the drive wheel 46 is rotated integrally with the axle 45 via the drive shaft 13 and the two bevel gears 37 and 38 (see, for example, arrow Y1 in FIG. 2).

[0053] At this time, the rotation of the axle 45 is not transmitted to the driven wheel 47, so a rotation difference occurs between the driven wheel 47 and the drive wheel 46. The axle 45 is rotatably supported by the gear case 36. Therefore, the rotation difference between the driven wheel 47 and the drive wheel 46 causes the gear case 36 and the hollow shaft 12 to which the gear case 36 is fixed to rotate around the first rotation axis C1 (see, for example, arrow Y2 in FIG. 2). This causes the electric caster 1 to turn. When it is desired to rotate the electric caster 1 in the opposite direction to the above (for example, see arrow Y3 in FIG. 2), the drive wheel 46 may be rotated in the opposite direction (for example, see arrow Y4 in FIG. 2).

[0054] Next, a case where the electric caster 1 is moved straight will be described. In this case, the brake mechanism 21 is braked on, restricting the rotation of the hollow shaft 12 relative to the main case 3. When the actuator 23 is driven in this state, the drive wheel 46 is rotated integrally with the axle 45 via the drive shaft 13 and the two bevel gears 37 and 38 (see, for example, arrows Y1 and Y4 in FIG. 2).

[0055] At this time, because the driving force is transmitted only to the driving wheel 46, a rotational force about the first rotation axis is applied to the hollow shaft 12. However, because the rotation of the hollow shaft 12 relative to the main case 3 is restricted, the electric caster 1 moves straight without turning. At this time, the driven wheel 47 rotates as if being dragged by the straight movement of the electric caster 1. The rotational position of the hollow shaft 12 is detected by a rotational position detection sensor 22. This detection result is output as a signal to a control unit (not shown). The control unit controls the drive of an actuator 23 based on the detection result of the rotational position detection sensor 22. This allows a wheelchair, a transport cart, or the like to travel in a desired direction.

[0056] Incidentally, when the electric caster 1 is moving, for example, dust from the road surface may be stirred up or water accumulated on the road surface may splash up, causing dust or water to enter the main case 3. However, the inner peripheral surface of the bearing boss 9 in the main case 3 is provided with a seal portion 18 that seals between the main case 3 and the hollow shaft 12, so it is possible to prevent dust or water from entering the main case 3.

[0057] Let us assume that dust or water gets into the main case 3 between the main case 3 and the hollow shaft 12. Even in this case, the brake mechanism 21 is disposed below the rotational position detection sensor 22, which is susceptible to the effects of dust and water. This brake mechanism 21 acts as a barrier that prevents dust and water from getting into the main case 3, and prevents dust and water from getting on the rotational position detection sensor 22. This prevents the rotational position detection sensor 22 from being affected by dust and water.

[0058] Thus, in the above-described embodiment, the electric caster 1 comprises a main case 3 fixed to the base portion 2, a brushless motor 31 fixed to the main case 3, a hollow shaft 12 rotatably supported on the main case 3, a brake mechanism 21 fixed to the main case 3, a drive shaft 13 inserted into the hollow shaft 12, a gear case 36 fixed to the hollow shaft 12, an axle 45 rotatably supported on the gear case 36, bevel gears 37, 38 housed in the gear case 36, a drive wheel 46 fixed to the first end 45a of the axle 45, and a driven wheel 47 supported to be rotatable relative to the second end 45b of the axle 45.

[0059] With this configuration, the electric caster 1 can move straight and turn with one brushless motor 31. This allows the configuration of the electric caster 1 to be simplified and made smaller. Furthermore, there is no need to adopt a configuration in which components are arranged above the base portion 2. This makes it possible to reduce the area occupied by the components that make up the electric caster 1 on the base portion 2. This increases the degree of freedom in arranging components on the base portion 2.

[0060] Moreover, the hollow shaft 12 and the drive shaft 13 are disposed above the axle 45. In addition, the first rotation axis C1 of the hollow shaft 12 and the drive shaft 13 and the second rotation axis C2 of the axle 45 are perpendicular to each other. Only the brushless motor 31 protrudes above the base 2, and the speed reducer 32 attached to the brushless motor 31 and all other components are disposed below the base 2. This increases the degree of freedom in component placement on the base 2. The rotational position detection sensor 22 is composed of a sensor board 25 and a sensor magnet 28, and the brake mechanism 21 and the sensor magnet are arranged around the hollow shaft 12. This allows the shaft length of the electric caster 1 to be shortened accordingly.

[0061] In the main case 3, the brake mechanism 21, the rotational position detection sensor 22, and the speed reducer 32 are arranged in this order from bottom to top. In addition, a sensor holder 26 is provided between the rotational position detection sensor 22 and the speed reducer 32. A sensor board 25 is attached to the sensor holder 26. Therefore, the brake mechanism 21 acts as a barrier to prevent dust and water from entering the main case 3, and prevents dust and water from getting on the rotational position detection sensor 22. This prevents the rotational position detection sensor 22 from being affected by dust and water, and stabilizes the operation of the electric caster 1.

[0062] Because the configuration of the electric caster 1 can be simplified and made smaller, it will be possible to contribute to Goal 7 of the United Nations-led Sustainable Development Goals (SDGs), which is to "Ensure access to affordable, reliable, sustainable and modern energy for all," Goal 9, which is to "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation," and Goal 12, which is to "Ensure sustainable consumption and production patterns."

[0063] The present invention is not limited to the above-described embodiment, and includes various modifications to the above-described embodiment without departing from the spirit of the present invention. For example, in the above embodiment, the electric caster 1 is described as being used in a wheelchair, a transport cart for transporting parts stored in a warehouse, etc. However, the electric caster 1 is not limited to this, and can be applied to various devices.

[0064] In the above embodiment, a case has been described in which the brushless motor 31 is used as the drive unit of the electric caster 1. However, this is not limiting, and a brushed motor can be used instead of the brushless motor 31. Also, the brushless motor 31 and the drive shaft 13 can be directly connected without using the reduction unit 32. In the above embodiment, the rotational position detection sensor 22 is a so-called magnetic encoder equipped with a sensor magnet 28. However, the present invention is not limited to this, and any encoder capable of detecting the rotational position of the hollow shaft 12 may be used. For example, an optical encoder may be used instead of a magnetic encoder.

[0065] In the above embodiment, the case where two bevel gears 37, 38 are provided to transmit the rotation of the drive shaft 13 to the axle 45 has been described. However, this is not limited to this, and any gear that can transmit the rotation of the drive shaft 13 to the axle 45 may be used. For example, a worm gear may be used. In the above embodiment, the axle 45 extends below the hollow shaft 12 and the drive shaft 13 in a direction perpendicular to these shafts 12 and drive shaft 13. However, this is not limited to this, and the axle 45 does not have to be completely perpendicular to the hollow shaft 12 and drive shaft 13. It is sufficient that the axle 45 intersects with the hollow shaft 12 and drive shaft 13. [Explanation of symbols]

[0066] 1...electric caster, 2...base portion (mounting body), 2a...underside, 2b...opening, 2c...bolt insertion hole, 3...main case, 3a...opening, 3b...bottom wall, 3c...peripheral wall, 4...main mechanism portion, 5...axle unit, 6...gear portion, 7...wheel unit, 8...outer flange portion, 8a...female thread portion, 9...bearing boss, 9a...lower end, 10...bolt, 11...bearing, 12...hollow shaft, 12a...lower reduced diameter portion, 12b...upper reduced diameter portion, 13...drive shaft, 14...gear holder, 15 ...outer flange portion, 15a...female thread portion, 16...outer flange portion, 16a...bolt insertion hole, 17...bolt, 18...seal portion, 21...brake mechanism, 21a...armature hub, 21b...brake armature, 22...rotational position detection sensor, 23...actuator, 24...magnet unit, 25...sensor board, 26...sensor holder, 26a...opening, 26b...peripheral wall, 26c...bottom wall, 26d...bottom opening, 27...magnet holder, 2 8...sensor magnet, 29...outer flange portion, 29a...bolt insertion hole, 30...stud bolt, 31...brushless motor (drive portion), 32...reduction portion, 33...housing, 33a...top portion, 34...gear group, 35...output plate, 35a...female thread portion, 36...gear case, 37...first bevel gear, 37...bevel gear, 38...second bevel gear, 38...bevel gear, 41...case body, 41a...opening, 41b...both side walls, 41c...through hole Through hole, 42...lid body, 42a...bolt insertion hole, 42b...gear insertion hole, 43...bearing holder, 43...each bearing holder, 44...bearing, 45...axle, 45a...first end, 45b...second end, 46...driving wheel, 47...driven wheel, 51...wheel, 51a...axle insertion hole, 52...tire, 53...collar, 54...fixing nut, 55...wheel, 55a...axle insertion hole, 56...tire, 57...bearing, 58...collar, C1...first rotation axis, C2...second rotation axis

Claims

1. a main case fixed to the mounting body; a drive unit fixed to the main case; a hollow shaft rotatably supported by the main case; a brake mechanism fixed to the main case for allowing and restricting rotation of the hollow shaft relative to the main case; a drive shaft that is inserted through the hollow shaft, supported by the hollow shaft so as to be relatively rotatable, and that is rotated by receiving the driving force of the drive unit; a gear case fixed to the hollow shaft; an axle rotatably supported by the gear case; a gear housed in the gear case and transmitting rotation of the drive shaft to the axle; a drive wheel fixed to a first axial end of the axle and rotating integrally with the axle; a driven wheel fixed to a second end of the axle opposite to the first end in the axial direction and supported by the axle so as to be rotatable relative to the axle; Equipped with Characterized by Electric casters.

2. The electric caster according to claim 1, the hollow shaft and the drive shaft are disposed above the axle, and the axial directions of the hollow shaft and the drive shaft are arranged so as to intersect with the axial direction of the axle, a rotational position detection sensor for detecting a rotational position of the hollow shaft; a speed reducer attached to the drive unit and the drive shaft, the speed reducer transmitting the driving force of the drive unit to the drive shaft; Furthermore, Only the drive unit protrudes from the mounting body. An electric caster characterized by:

3. The rotational position detection sensor a sensor magnet attached to the hollow shaft; a sensor board housed in the main case and configured to detect a change in magnetism caused by the rotation of the sensor magnet; Equipped with The brake mechanism is disposed around the hollow shaft. The electric caster according to claim 2 .

4. the brake mechanism, the rotational position detection sensor, and the speed reducer are arranged in this order from bottom to top in the main case, and a sensor holder is provided between the rotational position detection sensor and the speed reducer, The sensor substrate is attached to the sensor holder. The electric caster according to claim 3 .

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