Rotation mechanism
A simplified rotation mechanism with non-metallic drive units and multiple degrees of freedom addresses complexity and reliability issues, enabling use in MRI and CT environments.
Patent Information
- Application Number
- JP2024027735
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-02-27
- Publication Date
- 2025-09-08
AI Technical Summary
Existing rotation mechanisms with multiple degrees of freedom have complex configurations, leading to increased costs and reduced reliability.
A rotation mechanism with a sphere having first and second teeth on its outer surface, driven by non-metallic drive units that rotate the sphere around two intersecting axes, utilizing pneumatic cylinders for translational movement to engage with the teeth, allowing for multiple degrees of freedom without electromagnetic motors.
The mechanism achieves simpler configuration and multiple degrees of freedom, suitable for use in MRI and CT environments due to its non-metallic components, reducing complexity and enhancing reliability.
Smart Images
Figure 2025130514000001_ABST
Abstract
Description
[Technical Field]
[0001] The present disclosure relates to a rotation mechanism. [Background technology]
[0002] Patent Document 1 discloses a rotation mechanism that achieves two degrees of freedom of rotation. This rotation mechanism has motors placed in both the inner sphere and the outer spherical shell, and by transmitting power to the other using gears, rotates the inner sphere around two perpendicular axes. In other words, because power is transmitted by the meshing of gear teeth, it is possible to reliably transmit large amounts of power. [Prior art documents] [Non-patent literature]
[0003] [Non-Patent Document 1] Kenjiro Tadakuma, Hiroto Saito, Kazuki Abe, Shinnosuke Hao, Riichiro Tadakuma, "Study on a spherical omnidirectional drive gear mechanism with two degrees of freedom", Journal of the Robotics Society of Japan, Vol. 36, No. 9, pp. 627-638, 2018 Summary of the Invention [Problem to be solved by the invention]
[0004] The rotation mechanism of Patent Document 1 has a relatively complex configuration, which increases costs and also affects performance, such as reducing reliability.
[0005] The present disclosure has been made in this situation, and an exemplary purpose of an embodiment thereof is to provide a rotation mechanism with a simpler configuration that achieves rotation with multiple degrees of freedom. [Means for solving the problem]
[0006] In order to solve the above problems, one aspect of the present invention provides a rotation mechanism that includes a sphere, a first drive unit that rotates the sphere about a first axis passing through the sphere, and a second drive unit that rotates the sphere about a second axis that passes through the sphere and rotates together with the sphere about the first axis. The sphere has first teeth and second teeth on its outer surface. The first teeth include a plurality of teeth aligned along the outer surface in an imaginary plane that includes the second axis, and the plurality of teeth are shaped like a body of revolution rotated about the second axis. The second teeth include a plurality of teeth aligned along the outer surface in an imaginary plane that includes the first axis. The first drive unit contacts the first teeth of the sphere to rotate the sphere about the first axis, and the second drive unit is rotatable together with the sphere about the first axis and contacts the second teeth of the sphere to rotate the sphere about the second axis. [Effects of the Invention]
[0007] According to the present disclosure, it is possible to provide a rotation mechanism with a simpler configuration that realizes rotation with multiple degrees of freedom. [Brief explanation of the drawings]
[0008] [Figure 1] FIG. 2 is a perspective view of a rotation mechanism according to the embodiment. [Figure 2] FIG. 2 is a plan view of the rotation mechanism of FIG. [Figure 3] FIG. 2 is a cross-sectional view of the rotation mechanism of FIG. [Figure 4] FIG. 2 is a cross-sectional view of the rotation mechanism of FIG. [Figure 5] 5(a) to 5(c) are diagrams illustrating the operating principle of the rotation mechanism of FIG. DETAILED DESCRIPTION OF THE INVENTION
[0009] Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing will be given the same reference numerals, and redundant explanations will be omitted as appropriate. Furthermore, the embodiments are examples rather than limitations on the disclosure, and all features and combinations thereof described in the embodiments are not necessarily essential to the disclosure.
[0010] 1 to 4 are diagrams showing a rotation mechanism 1 according to an embodiment. Fig. 1 is a perspective view of the rotation mechanism 1, Fig. 2 is a top view of the rotation mechanism 1, Fig. 3 is a cross-sectional view of the rotation mechanism 1 of Fig. 2 taken along line AA, and Fig. 4 is a cross-sectional view of the rotation mechanism 1 of Fig. 3 taken along line BB.
[0011] The rotation mechanism 1 comprises a sphere 10, an output member 12 fixed to the sphere 10, a first drive unit 14 that rotates the sphere 10 around a first axis Ax1, a second drive unit 16 that rotates the sphere 10 around a second axis Ax2, two pillars 18 that support the sphere 10, and a stage 20 that supports these members.
[0012] All of the components of the sphere 10, the output member 12, the first drive unit 14, the second drive unit 16, the support column 18 and the stage 20 may be made of a non-metallic material, for example, a resin.
[0013] The first axis Ax1 is an axis that passes through the center C of the sphere 10 and is fixed relative to the stage 20.
[0014] The second axis Ax2 is an axis that passes through the center C of the sphere 10, is perpendicular to the first axis Ax1, and rotates around the first axis Ax1 together with the sphere 10. However, the first axis Ax1 and the second axis Ax2 need not be perpendicular to each other as long as they at least intersect.
[0015] The stage 20 fixedly supports the first drive unit 14. The stage 20 supports the second drive unit 16 rotatably about a first axis Ax1.
[0016] The two support columns 18 are disposed opposite each other across the first axis Ax1. The two support columns 18 support the sphere 10 rotatably about the second axis Ax2. The two support columns 18 rotatably support the sphere, for example, by sliding contact. As a variant, the sphere 10 may have a shaft, and the two support columns 18 may rotatably support the shaft.
[0017] On the other hand, the two support pillars 18 restrict the rotation of the sphere 10 about the first axis Ax1 relative to the two support pillars 18. In other words, the sphere 10 rotates about the second axis Ax2 relative to the two support pillars 18, but does not rotate about the first axis Ax1 relative to the two support pillars 18.
[0018] The two support columns 18 are supported by the base 46 of the second drive unit 16. As described above, the second drive unit 16 is rotatable about the first axis Ax1, and therefore the two support columns 18 supported by the second drive unit 16 are also rotatable about the first axis Ax1.
[0019] Therefore, when the sphere 10 is driven by the first drive unit 14 to rotate about the first axis Ax1, the two support columns 18, and therefore the second drive unit 16, rotate together with the sphere 10 about the first axis Ax1.
[0020] The output member 12 is fixed to the sphere 10 and rotates around the first axis Ax1 and / or the second axis Ax2 together with the sphere 10. In this embodiment, the output member 12 is a shaft-shaped member that passes through the center C of the sphere 10.
[0021] In this embodiment, the sphere 10 has a spherical shape, but may have an oval spherical shape. In this embodiment, the sphere 10 is solid, but may be hollow. The sphere 10 has a first tooth portion 10b and a second tooth portion 10c on an outer surface 10a.
[0022] The first toothed portion 10b includes a plurality of teeth 10d. The plurality of teeth 10d are arranged in the circumferential direction along the outer surface 10a in any imaginary plane (for example, the plane in FIG. 4) including the second axis Ax2. Each of the plurality of teeth 10d has a shape of a solid of revolution obtained by rotating the outline in the imaginary plane about the second axis Ax2. The plurality of teeth 10d are formed so that the intervals between adjacent teeth 10d are equal along the outer surface 10a. The plurality of teeth 10d have the same cross-sectional shape in any plane including the second axis Ax2.
[0023] The second toothed portion 10c includes a plurality of teeth 10e. The plurality of teeth 10e are arranged in the circumferential direction along the outer surface 10a so as to surround the second axis Ax2. In this embodiment, the plurality of teeth 10e are arranged in two circumferential rows along the equator EL (see FIG. 1) when the sphere 10 is likened to the Earth with the second axis Ax2 as its axis. The number of rows of the plurality of teeth 10e is not particularly limited, and may be, for example, one row. The plurality of teeth 10e are formed so that the intervals between adjacent teeth 10e in each row are equal along the outer surface 10a. The plurality of teeth 10e have the same cross-sectional shape as one another when viewed from a plane perpendicular to the second axis Ax2 that passes through each row.
[0024] In this embodiment, the second teeth portion 10c overlaps with the first teeth portion 10b. That is, the plurality of teeth 10e of the second teeth portion 10c also function as the teeth 10d of the first teeth portion 10b. In other words, the plurality of teeth 10e of the second teeth portion 10c also function as the teeth 10d of the first teeth portion 10b. Specifically, the plurality of teeth 10e of the second teeth portion 10c and the teeth 10d of the first teeth portion 10b have the same cross-sectional shape in a plane perpendicular to the second axis Ax2.
[0025] However, the second teeth 10c do not have to overlap with the first teeth 10b. In other words, the sphere 10 may have a portion where only the first teeth 10b are provided and a portion where only the second teeth 10c are provided.
[0026] In addition, in this embodiment, the teeth are provided on the entire outer surface 10a of the sphere 10, but there may be portions where the teeth are not provided. In this case, the range in which the sphere 10 can rotate may be limited.
[0027] In addition, in the present embodiment, the second teeth 10c are provided along the entire circumference along the equator EL, but the second teeth 10c may be provided only on a portion of the circumference along the equator EL, in which case the range in which the spherical body 10 can rotate around the second axis Ax2 may be limited.
[0028] The first drive unit 14 includes a plurality of N1 drive units 30. Here, N1=3. The plurality of N1 drive units 30 are arranged so as to be aligned along the circumferential direction D1 of a circle whose center is the first axis Ax1 and which surrounds the center C. In other words, the plurality of N1 drive units 30 are arranged so as to be aligned along the outer surface 10a of the sphere 10 on an imaginary plane (for example, the plane in FIG. 4) that passes through the center C of the sphere 10 and is perpendicular to the first axis Ax1.
[0029] Each of the multiple N1 drive units 30 includes a drive member 32 and a translation mechanism 34. The drive member 32 has a toothed portion 32a that faces the first toothed portion 10b of the sphere 10. The toothed portion 32a has a plurality of teeth 32b arranged along the circumferential direction D1.
[0030] The translation mechanism 34 translates the drive member 32 in the radial direction of a circle that is centered on the first axis Ax1 and surrounds the center C, thereby bringing the drive member 32 into contact with the first teeth portion 10b of the sphere 10 and moving the drive member 32 away from the first teeth portion 10b. In this embodiment, the translation mechanism 34 is a pneumatic cylinder. The translation mechanism 34 may have a reciprocating spring 36 (see FIG. 3). In this case, only one port is required for the cylinder tube.
[0031] The second drive unit 16 includes a plurality of N2 drive units 40 and a base 46 that supports them. Here, N2=3. The plurality of N2 drive units 40 are arranged so as to be aligned along the circumferential direction D2 of a circle that is centered on the second axis Ax2 and that surrounds the center C. In other words, the plurality of N2 drive units 40 are arranged so as to be aligned along the outer surface 10a of the sphere 10 on an imaginary plane (e.g., the plane in FIG. 3) that passes through the center C of the sphere 10 and is perpendicular to the second axis Ax2.
[0032] Each of the multiple N2 drive units 40 includes a drive member 42 and a translation mechanism 44. The drive member 42 has a toothed portion 42a that faces the second toothed portion 10c of the sphere 10. The toothed portion 42a has a plurality of teeth 42b arranged along the circumferential direction D2.
[0033] The translation mechanism 44 translates the drive member 42 in the radial direction of a circle that is centered on the second axis Ax2 and surrounds the center C, and brings the drive member 42 into contact with the second teeth portion 10c of the sphere 10 or moves the drive member 42 away from the second teeth portion 10c. Like the translation mechanism 34, the translation mechanism 44 is a pneumatic cylinder in this embodiment.
[0034] 5(a) to 5(c) are diagrams illustrating the principle by which the first drive unit 14 rotates the sphere 10 around the first axis Ax1.
[0035] The dotted line relating to the driving member 32 of the driving unit 30_2 in Figure 5(a) indicates the position of the driving member 32 of the driving unit 30_2 in Figure 5(b), i.e., the position of the driving member 32 of the driving unit 30_2 when the tooth portion 32a of the driving member 32 of the driving unit 30_2 is fully engaged with the first tooth portion 10b of the sphere 10, as described below.
[0036] Furthermore, the dotted line relating to the driving member 32 of the driving unit 30_3 in Figure 5(a) indicates the position of the driving member 32 of the driving unit 30_3 in Figure 5(c), that is, the position of the driving member 32 of the driving unit 30_3 when the tooth portion 32a of the driving member 32 of the driving unit 30_3 is fully engaged with the first tooth portion 10b of the sphere 10, as described below.
[0037] Each of the teeth 10d of the first toothed portion 10b of the sphere 10 has a first slide surface 10f facing one side in the circumferential direction D1 and a second slide surface 10g facing the other side in the circumferential direction D1.
[0038] Each of the multiple teeth 32b of the tooth portion 32a of the drive member 32 of the first drive unit 14 has a first slidable surface 32c facing the other side in the circumferential direction D1 and a second slidable surface 32d facing one side in the circumferential direction D1.
[0039] The first sliding surface 10f and the first sliding surface 32c are inclined in the same direction, the second sliding surface 10g and the second sliding surface 32d are inclined in the same direction, and the teeth 32a of the driving member 32 and the first teeth 10b of the sphere 10 mesh with each other.
[0040] When the pitch of the teeth 32b of the toothed portion 32a is θ1, the driving members 32 of the three driving units 30 are each arranged with a shift of (an integer equal to or greater than 0+1 / N1)×θ1 from the toothed portion 32a of the adjacent driving member 32.
[0041] In FIG. 5(a), the teeth 32a of the driving member 32 of the driving unit 30_1 and the first teeth 10b of the sphere 10 are fully engaged with each other. From this state, the driving member 32 of the driving unit 30_1 is returned to the separated position. Also, the driving member 32 of the driving unit 30_2 is translated toward the sphere 10. As a result, the first slidable surface 32c of the driving member 32 of the driving unit 30_2 comes into contact with the first sliding surface 10f of the first teeth 10b of the sphere 10.
[0042] When the teeth 32a of the driving member 32 are further pressed into the first teeth 10b of the sphere 10, the first sliding surface 10f of the first teeth 10b of the sphere 10 is pressed against the first slidable surface 32c of the teeth 32a of the driving member 32, and the sphere 10 rotates around the first axis Ax1 until the teeth 32a of the driving member 32 of the driving unit 30_2 and the first teeth 10b of the sphere 10 completely mesh with each other, as shown in Fig. 5(b). Specifically, the sphere 10 rotates by θ1 / N1 around the first axis Ax1.
[0043] Subsequently, the driving member 32 of the driving unit 30_2 is returned to the separated position. Also, the driving member 32 of the driving unit 30_3 is translated toward the sphere 10. As a result, the first slidable surface 32c of the driving member 32 of the driving unit 30_3 comes into contact with the first sliding surface 10f of the first tooth portion 10b of the sphere 10.
[0044] When the driving member 32 is further pressed in, the sphere 10 rotates around the first axis Ax1 until the teeth 32a of the driving member 32 of the driving unit 30_3 and the first teeth 10b of the sphere 10 completely mesh with each other, as shown in Fig. 5(c). Specifically, the sphere 10 rotates 1 / N1 pitch around the first axis Ax1.
[0045] Subsequently, the driving member 32 of the driving unit 30_3 is returned to the retracted position. Also, the tooth portion 32a of the driving member 32 of the driving unit 30_1 is translated toward the first tooth portion 10b of the sphere 10. As a result, the sphere 10 rotates by θ1 / N1 around the first axis Ax1.
[0046] As described above, by repeatedly moving the driving member 32 of driving unit 30_1, the driving member 32 of driving unit 30_2, and the driving member 32 of driving unit 30_3 in this order in a translational motion toward the first tooth portion 10b of the sphere 10, the sphere 10 can be rotated around the second axis Ax2.
[0047] Furthermore, by repeatedly moving the driving member 32 of driving unit 30_3, the driving member 32 of driving unit 30_2, and the driving member 32 of driving unit 30_1 in this order in a translational motion toward the first tooth portion 10b of the sphere 10, the sphere 10 can be rotated in the opposite direction around the second axis Ax2.
[0048] The principle by which the second drive unit 16 rotates the sphere 10 about the second axis Ax2 is the same as the principle by which the first drive unit 14 rotates the sphere 10 about the first axis Ax1. That is, when the pitch of the teeth 42b of the toothed portion 42a is θ2, the drive members 42 of the three drive sections 40 of the second drive unit 16 are each arranged with a shift of (an integer equal to or greater than 0+1 / N2)×θ2 from the toothed portion 42a of the adjacent drive member 42. Then, by repeatedly translating the drive members 42 of the drive units 40_1, 40_2, and 40_3 of the second drive unit in this order toward the second tooth portion 10c, the sphere 10 can be rotated around the second axis Ax2, and by repeatedly translating the drive members 42 of the drive units 40_1, 40_2, and 40_3 in this order toward the second tooth portion 10c, the sphere 10 can be rotated in the opposite direction around the second axis Ax2.
[0049] According to this embodiment, both the first tooth portion 10b and the second tooth portion 10c are provided on the outer surface 10a of the sphere 10, and since the second drive unit 16 rotates around the first axis Ax1 together with the sphere 10, the range in which the second tooth portion 10c is provided can be relatively narrow, thereby realizing a rotation mechanism 1 with a relatively simple configuration.
[0050] Furthermore, according to this embodiment, the sphere 10 is rotated around the first axis Ax1 and / or the second axis Ax2 by the translational movement of the drive member of the drive unit. Therefore, the drive units 14 and 16 can be configured without electromagnetic motors. Therefore, the rotation mechanism 1 can be realized without electromagnetic motors or metal parts. Image-guided therapy, in which a surgeon performs cancer treatment or lesion extraction in the liver, kidney, lung, etc. by simply inserting a needle into a lesion while viewing MRI or CT images, is attracting attention. However, MRI and CT scanners are confined spaces, and the presence of metal on the imaging surface can cause artifacts, making image diagnosis difficult. To address this issue, non-metallic surgical support robots that can be remotely operated from outside the operating room have been developed. Currently, non-metallic pneumatic motors used as needle positioning mechanisms only have one degree of freedom. Conventional rotation mechanisms that achieve multiple degrees of freedom require multiple electromagnetic motors, making them unusable in MRI and CT environments. In contrast, according to this embodiment, the rotation mechanism 1 can be realized using only non-metallic parts, such as resin parts, making it usable in MRI and CT environments.
[0051] Furthermore, according to this embodiment, the drive units 14 and 16 can be configured without electromagnetic motors, so that the drive units 14 and 16, and in turn the rotation mechanism 1, can be made smaller and lighter.
[0052] The present disclosure has been described above based on the embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each treatment process, and that such modifications are also within the scope of the present disclosure.
[0053] The present invention has been described using specific terms based on the embodiments, but the embodiments merely illustrate one aspect of the principles and applications of the present invention, and many modifications and changes in arrangement are permitted to the embodiments as long as they do not deviate from the concept of the present invention as defined in the claims. [Explanation of symbols]
[0054] 1 Rotation mechanism, 10 sphere, 10a outer surface, 10b first tooth portion, 10c second tooth portion, 10d tooth, 10e tooth, 14 first drive unit, 16 second drive unit, Ax1 first axis, Ax2 second axis.
Claims
1. A sphere and a first drive unit that rotates the sphere around a first axis that passes through the sphere; a second drive unit that rotates the sphere about a second axis that passes through the sphere and rotates together with the sphere about the first axis; Equipped with The sphere has a first tooth portion and a second tooth portion on an outer surface thereof, the first tooth portion includes a plurality of teeth arranged along the outer surface in an imaginary plane including the second axis, the plurality of teeth having a shape of a solid of revolution rotated around the second axis, the second tooth portion has a plurality of teeth arranged along the outer surface so as to circumscribe the second axis, the first drive unit contacts the first tooth portion of the sphere to rotate the sphere around a first axis; The second drive unit is a rotation mechanism that is rotatable around the first axis together with the sphere and contacts the second tooth portion of the sphere to rotate the sphere around the second axis.
2. The rotation mechanism according to claim 1 , wherein the second toothed portion overlaps with the first toothed portion.
3. The first drive unit includes a plurality of N teeth each having a tooth portion that can mesh with the first tooth portion. １ (N １ is an integer of 2 or more), and １ Each of the driving members has a distance of (an integer greater than or equal to 0 + 1 / N) from the adjacent driving members. １ ) are arranged opposite to the first tooth portion with a pitch shift, and １ the driving members are sequentially translated toward the first toothed portion and brought into contact with the first toothed portion, thereby rotating the sphere around the first axis; The second drive unit has a plurality of N teeth that can mesh with the second teeth. ２ (N ２ is an integer of 2 or more), and ２ Each of the driving members has a distance of (an integer greater than or equal to 0 + 1 / N) from the adjacent driving members. ２ ) are arranged opposite to the second tooth portion with a pitch difference, and ２ The rotation mechanism according to claim 1 , wherein the sphere is rotated around the second axis by sequentially translating the drive members toward the second toothed portion and bringing them into contact with the second toothed portion.
4. The rotation mechanism according to claim 3 , wherein all components of the sphere, the first drive unit, and the second drive unit are made of non-metallic materials.