Control agency

Abstract

To provide a gripping mechanism that can stably grip an article, regardless of a size and a shape of the article which is gripped.SOLUTION: A gripping mechanism 1 comprises a plurality of finger parts 2 for gripping an article M. At least one finger part 2 has: a base part 5; a holding part 6 extending from the base part 5; and a contact part 7 that is held in an elastically extended state by being hung across a base end part 11 and a tip part 12 of the holding part 6, which constitutes an inner portion of the finger part 2 that contacts the article M.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a gripping mechanism. [Background technology]

[0002] Patent Document 1 discloses a gripping mechanism (robot hand) having multiple fingers for gripping an object. In the gripping mechanism of Patent Document 1, each finger is configured by adhering a highly rigid outer skin member to the outside of an elastic elastic finger body member such as silicone rubber. In the gripping mechanism of Patent Document 1, when gripping an object with the multiple fingers, the elastic finger body member of each finger is pressed against the object, and the object is gripped by residual stress in the elastic finger body member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6815631 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the gripping mechanism of Patent Document 1, when an article is gripped with the multiple fingers, the elastic finger body member is elastically compressed and deformed between the article and the outer cover member. Therefore, if the size or shape of the article being gripped by the gripping mechanism changes, the area of ​​contact between the fingers and the article becomes smaller, which causes a problem in that the article cannot be gripped stably. Although it may be possible to stably grasp an object by increasing the force with which the fingers press against the object, this would not allow for stable grasping of soft objects such as strawberries.

[0005] The present invention has been made in consideration of the above circumstances, and aims to provide a gripping mechanism that can stably grip an item even if the size or shape of the item to be gripped changes. [Means for solving the problem]

[0006] The gripping mechanism according to the present invention includes a plurality of fingers for gripping an article, and at least one finger includes a base portion, a holding portion extending from the base portion, and a contact portion that is held in an elastically stretched state by being stretched between a base end and a tip end of the holding portion and that constitutes an inner portion of the finger that comes into contact with the article. The holding portion has an outer elastic portion that is arranged outside the contact portion with a gap therebetween, excluding the tip and base ends of the holding portion, so as to constitute an outer portion of the finger portion, and is elastically deformable by bending, and the bending stiffness of the outer elastic portion in the arrangement direction of the contact portion and the outer elastic portion is higher than the bending stiffness of the contact portion in the arrangement direction, and the outer elastic portion constitutes the entire holding portion from the base end to the tip end. . [Effects of the Invention]

[0007] According to the present invention, an article can be stably gripped even if the size or shape of the article to be gripped changes. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective view showing a state in which a gripping mechanism according to an embodiment of the present invention is attached to a robot arm. FIG. [Figure 2] FIG. 2 is a perspective view showing a gripping mechanism according to an embodiment of the present invention. [Figure 3] 3 is a perspective view showing a holding portion and a contact portion of a finger portion provided in the gripping mechanism of FIG. 2. FIG. [Figure 4] 4 is a perspective view of the holding portion and the contact portion of FIG. 3 as viewed from a different angle. [Figure 5] FIG. 5 is a perspective view showing a state in which the contact portion in FIGS. 3 and 4 has been removed from the holding portion. [Figure 6] 10 is a graph showing elastic characteristics of a plurality of types of contact portions having different flexural rigidities. [Figure 7] 10 is a graph showing the elasticity characteristics of the contact portion alone and the elasticity characteristics when the contact portion and the outer elastic portion are combined. [Figure 8] 3 is a top view schematically showing a state before an article is gripped by the gripping mechanism of FIG. 2.

[0023] FIG. [Figure 9] 3 is a top view schematically showing a state in which an article is gripped by the gripping mechanism of FIG. 2.

[0023] FIG. [Figure 10] 3 is a perspective view schematically showing a state in which an article is gripped by the gripping mechanism of FIG. 2. FIG. [Figure 11]3 is a perspective view showing an example of how an article gripped by the gripping mechanism of FIG. 2 is placed near another article. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1, the gripping mechanism 1 of this embodiment is provided, for example, at the tip of a robot arm 100, and grips an article M (see FIGS. 8 to 11). In order to move the article M from a predetermined position to another position, the robot arm 100 moves the gripping mechanism 1 so that the position of the gripping mechanism 1 gripping the article M changes.

[0010] As shown in FIG. 2, the gripping mechanism 1 has a plurality of fingers 2 for gripping an article M. The gripping mechanism 1 also has a gripping main body 3 to which the plurality of fingers 2 are attached. The plurality of fingers 2 are attached movably relative to the gripping main body 3 so that they can grip and release the article M. In this embodiment, there are two fingers 2. The two fingers 2 are movable relative to the gripping main body 3 so as to move toward and away from each other. In this embodiment, each finger 2 moves rotationally relative to the gripping main body 3 as illustrated in FIGS. 8 and 9, but may also move parallel to the gripping main body 3, for example. Also, for example, only one of the two fingers 2 may be movable relative to the gripping main body 3.

[0011] 2, each finger 2 has a base portion 5, a holding portion 6, and a contact portion 7. The base portion 5 is a portion of the finger 2 that is movably attached to the grip body 3.

[0012] The holding portion 6 extends from the base portion 5. For example, the holding portion 6 may extend linearly from the base portion 5. In this embodiment, the holding portion 6 is formed in an arch shape. Specifically, the holding portion 6 is formed in an arch shape that curves in a direction that intersects with the direction away from the base portion 5 as it moves away from the base portion 5. Furthermore, the holding portion 6 is curved so that the tips of the two finger portions approach each other.

[0013] As shown in FIGS. 2 to 4, the contact portion 7 is bridged between the base end 11 and the tip end 12 of the holding portion 6 in the extension direction of the holding portion 6, and is thereby held in an elastically stretched state between the base end 11 and the tip end 12 of the holding portion 6. The contact portion 7 constitutes the inner portion of the finger portions 2 that comes into contact with the article M when the article M is gripped by the multiple fingers 2 (see FIGS. 9 and 10). The contact portion 7 is positioned at a distance from the holding portion 6, except for the base end 11 and the tip end 12 of the holding portion 6. In this embodiment, the contact portion 7 is positioned inside the arch of the holding portion 6. With the contact portion 7 configured as described above, when the finger portion 2 is pressed against the article M to grip the article M using the gripping mechanism 1, the contact portion 7 elastically flexes and deforms (see FIGS. 9 and 10).

[0014] The finger portion 2 of this embodiment will be described in more detail below. In this embodiment, the holding portion 6 is disposed outside the contact portion 7 at a distance. That is, the holding portion 6 constitutes the outer portion of the finger portion 2. The holding portion 6 is also located outside the contact portion 7 at a distance, excluding the tip end 12 and the base end 11 thereof.

[0015] The holding part 6 in this embodiment has an outer elastic part 13 that is elastically flexible. The outer elastic part 13 is elastically flexible in the direction in which the contact part 7 and the outer elastic part 13 are aligned (the arrangement direction of the contact part 7 and the outer elastic part 13). The outer elastic part 13 is formed in a strip-like shape and is elastically flexible in the thickness direction. The strip-like outer elastic part 13 is curved in the thickness direction and formed into an arch shape. The width direction of the outer elastic part 13 made of a strip-like plate material corresponds to the up-and-down direction in FIGS. 2 to 4. The outer elastic portion 13 constituting the holding portion 6 may be made of, for example, a metal plate material.

[0016] The holding part 6 of this embodiment has a main body part formed in an arch shape and constituting the outer elastic part 13, as well as an attachment part 14. The attachment part 14 is integrally formed at the base end part 11 of the main body part of the holding part 6. The attachment part 14 is a part for attaching the holding part 6 to the base part 5. In the illustrated example, the attachment part 14 is formed in a flat plate shape that is approximately perpendicular to the extension direction of the main body part of the holding part 6 (particularly the outer elastic part 13), but this is not limited to this. The attachment part 14 is detachably attached to the base part 5. In FIG. 2, the attachment part 14 is fixed to the base part 5 using screws 9, but this is not limited to this.

[0017] The contact portion 7 of this embodiment is detachable from the holding portion 6. Specifically, as shown in FIGS. 3 to 5, the contact portion 7 is configured by an annular elastic member 21. The annular elastic member 21 is formed in a cylindrical shape with its width dimension (the axial dimension of the annular elastic member 21) greater than its thickness dimension. The width direction of the elastic member 21 corresponds to the up-and-down direction in FIGS. 3 to 5. The width dimension of the elastic member 21 (contact portion 7) may be changed depending on, for example, the article M. For example, if the dimension of the article M in the width direction of the elastic member 21 is large, the width dimension of the elastic member 21 may be increased. The elastic member 21 that constitutes the contact portion 7 may be made of, for example, rubber.

[0018] As shown in FIGS. 3 and 4, the annular elastic member 21 of the contact portion 7 is wound around the holding portion 6 so as to elastically stretch at least between the base end 11 and the tip end 12 of the holding portion 6. In this embodiment, a portion of the elastic member 21 wound around the holding portion 6 is arranged along the outer side of the arch of the outer elastic portion 13. In addition, another portion of the elastic member 21 is arranged on the surface 14a of the mounting portion 14 of the holding portion 6 that faces the base portion 5. Therefore, as shown in FIG. 2 , when the holding portion 6 with the elastic member 21 attached is fixed to the base portion 5, a portion of the elastic member 21 is sandwiched between the mounting portion 14 and the base portion 5. In this state, the elastic member 21 cannot be removed from the holding portion 6. In other words, when the holding portion 6 is fixed to the base portion 5, the elastic member 21 is stably held in a state attached to the holding portion 6. To attach or detach the elastic member 21 to or from the holding portion 6, the holding portion 6 is simply removed from the base portion 5.

[0019] The flexural rigidity of the outer elastic portion 13 in the arrangement direction of the contact portion 7 and the outer elastic portion 13 is higher than the flexural rigidity of the contact portion 7 in the arrangement direction. Here, the flexural rigidity is a numerical value expressed in the same units as the modulus of elasticity. However, the flexural rigidity is a numerical value that can change depending on dimensions such as the thickness of the outer elastic portion 13, even if the modulus of elasticity is the same. For example, even if the material constituting the outer elastic portion 13 is the same (i.e., the modulus of elasticity is the same), the flexural rigidity of the outer elastic portion 13 increases as the thickness of the outer elastic portion 13 increases. The flexural rigidity of the outer elastic portion 13 being higher than the flexural rigidity of the contact portion 7 means that the outer elastic portion 13 is less likely to elastically flex than the contact portion 7.

[0020] The contact portion 7 has elastic properties as shown in FIG. 6. The horizontal axis in the graph of FIG. 6 represents the amount of displacement of the finger portion 2 including the contact portion 7 pressed against the article M. The amount of displacement of the finger portion 2 is the length indicated by the symbol ΔL in FIG. 9, and corresponds to the stroke amount of the finger portion 2 when gripping the article M. The vertical axis in the graph of FIG. 6 represents the force with which the multiple fingers 2 grip the article M (hereinafter referred to as gripping force). The gripping force corresponds to the force with which the finger portion 2 is pressed against the article M. As shown in FIG. 6, the contact portion 7 has elastic properties such that the gripping force increases as the amount of displacement of the finger portion 2 increases.

[0021] The flexural rigidity of the contact portion 7 in a direction perpendicular to the extension direction of the contact portion 7 is expressed as the magnitude of change in gripping force relative to the magnitude of change in displacement of the finger portion 2, i.e., corresponds to the slope of the graph in Fig. 6. The "direction perpendicular to the extension direction of the contact portion 7" mentioned above means the direction in which an external force acts on the contact portion 7 so that the contact portion 7 elastically flexes and deforms, and specifically corresponds to the arrangement direction of the contact portion 7 and the outer elastic portion 13. The flexural rigidity of the contact portion 7 may be, for example, 0.05 N / mm or more, or, for example, 0.4 N / mm or less.

[0022] The upper and lower limits of the bending rigidity of the contact portion 7 described above take into consideration the displacement amount (stroke amount) of the finger portion 2 for gripping the object M and the ability to grip a relatively soft object M (e.g., a strawberry). This point will be explained below.

[0023] In the gripping mechanism 1 of this embodiment, the displacement amount (stroke amount) of the finger portions 2 when gripping the article M is set to 5 mm or less so that the displacement amount (stroke amount) of the finger portions 2 does not become excessively large. Furthermore, it is preferable that the force for gripping the soft object M (gripping force) be, for example, 0.5 N or more and 2.0 N or less. This is because if the gripping force is greater than 2.0 N, there is a high possibility that the soft object M will be damaged when gripped. Also, if the gripping force is less than 0.5 N, there is a high possibility that the object M will accidentally fall from the gripping mechanism 1. If the soft object M is a strawberry, the target value of the gripping force for the smallest size strawberry (e.g., 2S size) may be, for example, about 0.5 N. Also, the gripping force for the largest size strawberry (e.g., 3L size) may be, for example, about 1.7 N.

[0024] Considering the above, it is preferable that the flexural rigidity of the contact portion 7 is 0.05 N / mm or more so that the gripping force is 0.5 N or more when the displacement is 5 mm or less. It is also preferable that the flexural rigidity of the contact portion 7 is 0.4 N / mm or less so that the gripping force is 2.0 N or less when the displacement is 5 mm or less. Note that the higher the flexural rigidity of the contact portion 7 (the closer it is to 0.4 N / mm), the more likely it is that the article M will be gripped with a smaller displacement.

[0025] Furthermore, in this embodiment, the friction coefficient of the contact portion 7 that comes into contact with the article M is defined as follows. The maximum force (maximum gripping force) with which the multiple fingers 2 grip the object M is F MAX In addition, the maximum weight of the item M is W MAX is defined as G. The maximum acceleration acting on the fingers 2 when moving the object M gripped by the fingers 2 is defined as G. MAX In this case, the friction coefficient μ of the contact portion 7 is defined by the following formula. μ>W MAX ×G MAX / F MAX By setting the friction coefficient μ of the contact portion 7 using the above formula, the article M gripped by the multiple fingers 2 can be effectively suppressed or prevented from falling from the multiple fingers 2.

[0026] An example of the friction coefficient μ of the contact portion 7 when the object M gripped by the plurality of fingers 2 is a relatively soft strawberry will be described below. For example, the maximum weight W of the largest strawberry (e.g., a 3L strawberry) MAX is 0.05 kg (50 g), and the maximum gripping force F MAX is 1.7N, and the maximum acceleration G when holding the strawberry is MAX 23 m / s 2 In this case, the friction coefficient μ of the contact portion 7 should be greater than 0.7. For example, if the actual friction coefficient μ (measured value) of the contact portion 7 is 1.3, a safety factor of 1.86 is obtained for a design value μ > 0.7. Therefore, even if there is some variation in the actual gripping force and friction coefficient, a sufficient safety factor can be ensured.

[0027] As described above, the flexural rigidity of the outer elastic portion 13 is higher than that of the contact portion 7. Therefore, when an article M is grasped with a plurality of fingers 2, the elastic properties of the finger portions 2 can be changed according to the amount of displacement by which the finger portions 2 including the contact portion 7 are pressed against the article M. This point will be described with reference to FIG. 7. The graph in Fig. 7 shows the elastic characteristics when only the contact portion 7 of the finger portion 2 elastically flexes (contact portion alone), and when both the contact portion 7 and the outer elastic portion 13 of the finger portion 2 elastically flex (contact portion + outer elastic portion). In the graph in Fig. 7, the horizontal axis represents the displacement (stroke amount) of the finger portion 2 when gripping the article M, and the vertical axis represents the gripping force when gripping the article M with multiple fingers 2.

[0028] 7, when the amount of displacement of the finger 2 pressed against the article M is small (for example, a range of 1 to 3 mm), only the contact portion 7 elastically flexes and deforms. In this case, the elasticity of the finger 2 is such that the change in the elastic force of the finger 2 (the elastic force that contributes to gripping the article M) relative to the change in the amount of displacement of the finger 2 is small. On the other hand, when the amount of displacement of the finger 2 pressed against the article M becomes large (for example, a displacement of 3 mm or more) and the elastic bending deformation of the contact portion 7 reaches a limit, the outer elastic portion 13 also elastically bends. As a result, in a range where the amount of displacement is large (for example, a range where the amount of displacement is 3 mm or more), the elastic characteristic of the finger 2 becomes an elastic characteristic where the change in the elastic force of the finger 2 in response to a change in the amount of displacement of the finger 2 is large.

[0029] 2 to 4, the finger portion 2 of this embodiment is formed in a shape that tapers from the base portion 5 toward the tip end in the extension direction of the holding portion 6. In this embodiment, the tapered shape of the finger portion 2 is formed by the holding portion 6 (particularly the outer elastic portion 13) and the contact portion 7 (the portion of the elastic member 21 that spans between the base end portion 11 and the tip end portion 12 of the holding portion 6).

[0030] An example of a method for gripping the object M by the gripping mechanism 1 configured as above will be described with reference to Figures 8 to 10. The object M illustrated in Figures 8 to 10 is a strawberry, but is not limited to this. When gripping the article M, first, as shown in Fig. 8, the two fingers 2 are positioned apart from each other and the article M is placed between the two fingers 2. At this time, it is more preferable that the article M is placed between the tip portions of the two fingers 2.

[0031] 9 and 10, the two fingers 2 are moved toward each other and pressed against the article M, thereby gripping the article M with the two fingers 2. At this time, the contact portion 7 of each finger 2 is pressed by the article M in a direction intersecting the extension direction of the contact portion 7 (generally the vertical direction in FIG. 9), causing it to elastically bend and deform in the intersecting direction. Then, the article M can be gripped by the elastic force of the fingers 2 generated in association with the elastic bending and deformation of the contact portion 7. Furthermore, in this embodiment, if the displacement of each finger portion 2 is large (for example, 3 mm or more) when gripping the article M, the outer elastic portion 13 also elastically flexes and deforms in addition to the contact portion 7. This allows the article M to be gripped with a larger elastic force. This completes the method for gripping the article M by the gripping mechanism 1.

[0032] As described above, in the gripping mechanism 1 of this embodiment, the finger portions 2 for gripping the article M are held in an elastically extended state by being stretched between the base end 11 and the tip end 12 of the holding portion 6, and have contact portions 7 that form the inner portions of the finger portions 2. Therefore, when the article M is gripped by the multiple fingers 2, the contact portions 7 elastically flex and deform. As the elastic flex deformation of the contact portions 7 increases, the contact area of ​​the contact portions 7 with the article M increases. Therefore, even if the size or shape of the article M gripped by the gripping mechanism 1 changes, it is possible to ensure a sufficient contact area between the finger portions 2 and the article M. This allows the article M to be gripped stably.

[0033] Furthermore, since the area where the finger portions 2 come into contact with the object M can be sufficiently secured, the object M can be stably gripped even if the force (gripping force) pressing the finger portions 2 against the object M is reduced. Therefore, even a soft object M (such as a strawberry) can be stably gripped.

[0034] Furthermore, in the gripping mechanism 1 of this embodiment, the contact portion 7 is located inside the arch of the holding portion 6. Therefore, the contact portion 7 can be disposed at a distance from the holding portion 6. As a result, when the gripping mechanism 1 grips the article M, when the article M is pressed against the contact portion 7, the contact portion 7 can elastically bend and deform so as to approach the holding portion 6. Therefore, it is possible to suppress or prevent the holding portion 6 from hindering the elastic bending and deformation of the contact portion.

[0035] Furthermore, in the gripping mechanism 1 of this embodiment, the flexural rigidity of the outer elastic portion 13 is higher than the flexural rigidity of the contact portion 7 in the arrangement direction of the contact portion 7 and the outer elastic portion 13 of the holding portion 6. This makes it possible to change the elastic properties of the finger portion 2 according to the amount of displacement (the movement length of the finger portion 2) by which the finger portion 2 including the contact portion 7 is pressed against the article M. Specifically, the finger portion 2 has elastic properties such that the change in gripping force (elastic force) relative to the change in the amount of displacement is small in a range where the amount of displacement is small, and has elastic properties such that the change in gripping force (elastic force) relative to the change in the amount of displacement is large in a range where the amount of displacement is large.

[0036] In this way, the elasticity characteristics of the finger portion 2 are variable, so that the force with which the finger portion 2 grips the article M (gripping force) can be adjusted over a wider range. Therefore, it is possible to expand the range of weights of the article M that can be gripped by the gripping mechanism 1.

[0037] Furthermore, since the holding portion 6 has an outer elastic portion 13 that can be elastically flexibly deformed, even if there is a limit to the elastic flexural deformation of the contact portion 7, the holding portion 6 can be elastically flexibly deformed, making it possible to grasp the item M with the finger portion 2 without damaging the item M.

[0038] Furthermore, because the retaining portion 6 is made of the outer elastic portion 13 that can be elastically flexibly deformed, when the contact portion 7 elastically flexes, it is possible to prevent a load from being concentrated on the connection portion of the contact portion 7 that is connected to the base end portion 11 or the tip end portion 12 of the retaining portion 6. This makes it possible to prevent local deterioration (for example, wear or breakage) of the connection portion of the contact portion 7 and to extend the life of the contact portion 7.

[0039] Furthermore, in the gripping mechanism 1 of this embodiment, when the flexural rigidity of the contact portion 7 is 0.05 N / mm or more, the article M can be stably gripped by the multiple finger portions 2. For example, when the gripping mechanism 1 is moved while gripping the article M, it is possible to effectively suppress or prevent the posture of the gripped article M from changing. By suppressing or preventing the posture of the gripped article M from changing, it is possible to place the article M at the desired position in the desired posture.

[0040] Furthermore, by setting the flexural rigidity of the contact portion 7 to 0.05 N / mm or more, it is possible to prevent the amount of displacement (stroke amount of the finger portion 2) that presses the finger portion 2 against the article M to grip the article M from becoming excessively large. Therefore, it is possible to prevent the gripping mechanism 1 from becoming large.

[0041] Furthermore, by keeping the displacement of the finger 2 small as described above, it becomes possible to easily place the article M gripped by the gripping mechanism 1 in a narrow space. For example, as shown in Fig. 11, when placing the article M gripped by the gripping mechanism 1 in a location close to another article M2, it is possible to suppress or prevent the finger 2 from coming into contact with the other article M2 and damaging the other article M2.

[0042] Furthermore, in the gripping mechanism 1 of this embodiment, the contact portion 7 is detachable from the holding portion 6. This allows the contact portion 7 to be replaced even if it deteriorates due to frequency of use or the passage of time. This makes it easy to perform maintenance on the finger portion 2.

[0043] Furthermore, in the gripping mechanism 1 of this embodiment, the annular elastic member 21 that constitutes the contact portion 7 is attached to the holding portion 6 by being wound around the holding portion 6. This allows the contact portion 7 to be easily attached to and detached from the holding portion 6.

[0044] Furthermore, in the gripping mechanism 1 of this embodiment, the fingers 2 are formed in a tapered shape. Therefore, by gripping the article M with the tip portions of the fingers 2, the article M gripped by the gripping mechanism 1 can be easily placed in a narrow space. For example, as shown in FIG. 12 , when placing the article M gripped by the gripping mechanism 1 in a location close to another article M2, it is possible to suppress or prevent the fingers 2 from coming into contact with the other article M2 and damaging the other article M2.

[0045] Although the present invention has been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0046] In the present invention, the contact portion 7 is not limited to being constituted by the annular elastic member 21, and may be, for example, a band- or string-shaped elastic member 21 having both ends. In this case, for example, both ends of the band- or string-shaped elastic member 21 may be fixed to the base end 11 and the tip end 12 of the holding portion 6 so that the band- or string-shaped elastic member 21 can stretch elastically.

[0047] In the present invention, the base end 11 of the holding portion 6 on which the contact portion 7 is hooked may be located at the boundary with the base portion 5 as in the above embodiment, but may also be located away from the base portion 5, for example.

[0048] In the present invention, the finger portion 2 having the base portion 5, the holding portion 6, and the contact portion 7 is not limited to being applied to all of the finger portions 2 constituting the gripping mechanism 1, but may be applied to at least one of the multiple finger portions 2 of the gripping mechanism 1. [Explanation of symbols]

[0049] 1...Gripping mechanism 2...Finger part 5...Base 6...Holding part 7...Contact part 11...Proximal end 12...Tip 13...Outer elastic part 21...Elastic member

Claims

1. a plurality of fingers for gripping an article; At least one finger is A base portion and a holding portion extending from the base portion; a contact portion that is stretched between the base end and the tip end of the holding portion and is held in an elastically stretched state, and that constitutes an inner portion of the finger portion that comes into contact with the article; the holding portion has an outer elastic portion that is elastically deformable and is disposed outside the contact portion at a distance from the contact portion, excluding a tip end and a base end of the holding portion, so as to constitute an outer portion of the finger portion; a flexural rigidity of the outer elastic portion in an arrangement direction of the contact portion and the outer elastic portion is higher than a flexural rigidity of the contact portion in the arrangement direction; The outer elastic portion is a gripping mechanism that constitutes the entire holding portion from the base end to the tip end.

2. The holding portion is formed in an arcuate shape, The gripping mechanism according to claim 1 , wherein the contact portion is located inside the arc of the holding portion.

3. 3. The gripping mechanism according to claim 1, wherein the contact portion has a flexural rigidity of 0.05 N / mm or more in a direction perpendicular to the extension direction of the contact portion.

4. The coefficient of friction of the contact portion that comes into contact with the article is μ, and the maximum force with which the plurality of fingers grip the article is F ＭＡＸ and the maximum weight of the item is W ＭＡＸ and the maximum acceleration acting on the plurality of fingers when moving the object gripped by the plurality of fingers is G ＭＡＸ As such, the following equation: μ>η ＭＡＸ ×G ＭＡＸ / F ＭＡＸ 4. The gripping mechanism of claim 1, wherein:

5. The gripping mechanism according to claim 1 , wherein the contact portion is detachable from the holding portion.

6. the contact portion is configured by an annular elastic member, The gripping mechanism according to claim 5, wherein the elastic member is wound around the holding portion so as to elastically stretch at least between the base end and the tip end of the holding portion.

7. The gripping mechanism according to claim 1 , wherein the finger portion is formed in a shape that tapers from the base portion toward a tip end of the holding portion in an extension direction.

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