Gripping method and component

A gripping method is for gripping an object using a gripping mechanism including a roller and a frame that houses the roller. The gripping method includes a first stage and a second stage. In the first stage, the gripping mechanism moves relative to the object such that a first portion of the object is gripped between an outer surface of the roller and an inner surface of the frame. In the second stage, the gripping mechanism further moves relative to the object such that the roller is lifted by a second portion of the object before gripping of the object is released.

INCORPORATION BY REFERENCE

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2019-102594, filed on May 31, 2019. The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND

The present disclosure relates to a gripping method and a component.

A known assembly apparatus includes a chuck mechanism which grips a member to be conveyed. The chuck mechanism is an electric gripping mechanism. Other gripping mechanisms are known which use air suction or electric suction.

SUMMARY

A gripping method according to an aspect of the present disclosure is for gripping an object using a gripping mechanism including a roller and a frame that houses the roller. The gripping method includes a first stage and a second stage. In the first stage, the gripping mechanism moves relative to the object such that a first portion of the object is gripped between an outer surface of the roller and an inner surface of the frame. In the second stage, the gripping mechanism further moves relative to the object such that the roller is lifted by a second portion of the object before the gripping of the object is released.

A component according to an aspect of the present disclosure includes a component main body and a gripped section protruding from the component main body. The gripped section has a first portion and a second portion joined to the first portion. The first portion includes a part of a main surface of a plate with a constant thickness. The second portion has a thickness which increases along with distance from a point where the second portion is joined to the first portion.

DETAILED DESCRIPTION

The following describes an embodiment of the present disclosure with reference toFIGS. 1 to 7. InFIGS. 1 and 2, as a matter of convenience, a direction from the left to the right is referred to as a positive X axial direction, a direction from the back to the front is referred to as a positive Y axial direction, and a direction from up to down is referred to as a positive Z axial direction. Elements which are the same or equivalent are labeled with the same reference signs in the drawings and description thereof is not repeated.

First, an assembly apparatus100in which a gripping method is applied according to the embodiment is described with reference toFIG. 1.FIG. 1is a diagram illustrating an example of the assembly apparatus100.

As illustrated inFIG. 1, the assembly apparatus100is an apparatus which assembles by fitting a first component4to a second component5. The assembly apparatus100includes a robot1, a position correcting device2, and a gripping mechanism3.

The gripping mechanism3grips the first component4. The position of the second component5is determined on a position determining mechanism10. The first component4is equivalent to an example of a “component”.

The position correcting device2corrects, relative to the second component5, positional shift of the first component4gripped by the gripping mechanism3. Specifically, the position correcting device2detects the direction of force exerted on the first component4during fitting of the first component4to the second component5and corrects a positional shift of the first component4according to the direction of the force.

The robot1moves the gripping mechanism3relative to the first component4and also moves the gripping mechanism3relative to the second component5. Specifically, the robot1moves the gripping mechanism3to a storage location of the first component4, grips the first component4with the gripping mechanism3, and then moves the gripping mechanism3and the first component4to a point directly above the second component5. Thereafter, the robot1fits the first component4to the second component5by moving the gripping mechanism3and the first component4in the positive Z axial direction. After fitting has been achieved, the robot1releases the first component4from the gripping of the gripping mechanism3and moves the gripping mechanism3in the negative Z axial direction.

Next, the gripping mechanism3is described with reference toFIGS. 2 and 3.FIG. 2is a front view of an example of the gripping mechanism3.FIG. 3is a cross-sectional view taken along a line III-III inFIG. 2.

As illustrated inFIG. 2, the gripping mechanism3includes a holder31and a gripping roller32. The longitudinal directions of the holder31and the gripping roller32are both parallel to the X axial direction. The holder31is equivalent to an example of a “frame”. The gripping roller32is equivalent to an example of a “roller”.

As illustrated inFIG. 3, the gripping roller32includes a cylindrical core321and a covering section322which covers the peripheral surface of the core321. For example, the core321is made from a metal such as iron, and the covering section322is made from an elastic object such as polyacetal resin. The density of the core321is greater than the density of the covering section322. The covering section322can be compressed and deformed. The friction coefficient of the peripheral surface of the covering section322is greater than the friction coefficient of the peripheral surface of the core321.

As illustrated inFIG. 3, the holder31is a frame housing the gripping roller32and includes a back plate311, a top plate312, an upper front plate313, a lower front plate314, and left and right side plates316. The holder31is made of a light metal such as aluminum, for example.

The back plate311is a rectangular plate extending along a ZX plane. The top plate312is a rectangular plate extending along a XY plane starting from an upper edge of the back plate311. The upper front plate313is a rectangular plate extending diagonally downward in a direction away from the back plate311starting from the front edge of the top plate312. The lower front plate314is a rectangular plate extending diagonally downward in a direction approaching the back plate311starting from the lower edge of the upper front plate313.

An opening315is formed between the back plate311and the lower front plate314. The width of the opening315in the Y axial direction is shorter than the diameter of the gripping roller32. Accordingly, the gripping roller32does not fall through the opening315. The back plate311and the lower front plate314support the weight of the gripping roller32. The opening315can receive insertion of an object to be gripped.

The back plate311, the top plate312, the upper front plate313, and the lower front plate314form substantially pentagonal openings on the left and right side surfaces of the holder31. The left and right side plates316are located so as to cover the openings. However, at least one side plate316has a cutout317which allows passage of the object to be gripped but does not allow passage of the gripping roller32when gripping is released. The cutout317is positioned near the back plate311.

By configuring a side plate316to be freely openable and closable for example, it is possible to insert and remove the gripping roller32.

Next, the first component4according to the embodiment is described with reference toFIGS. 4 and 5.FIG. 4is a perspective view of an example of the first component4.FIG. 5is a cross-sectional view taken along a line V-V inFIG. 4.

As illustrated inFIG. 4, the first component4includes a component main body41and a gripped section42. The component main body41has a substantially rectangular parallelepiped shape. The gripped section42protrudes from the component main body41so as to be easily gripped by the gripping mechanism3. The gripped section42is rectangular plate-shaped and an end surface of the gripped section42is connected to one of the main surfaces of the component main body41.

The gripped section42has a first main surface421and a second main surface422. The first main surface421and the second main surface422extend along the ZX plane. The first main surface421is on a negative side in the Y axial direction, and the second main surface422is on a positive side in the Y axial direction.

The gripped section42further includes two ribs423. The two ribs423are provided with a space therebetween in the X axial direction. Each rib423protrudes from the second main surface422in the positive Y axial direction. Each rib423has an end surface formed as an inclined surface424slanted toward the second main surface422.

The second component5is formed with a recess52in a substantially rectangular parallelepiped-shaped component main body51. The recess52receives insertion of the component main body41of the first component4.

As illustrated inFIG. 5, the gripped section42includes a first portion L1and a second portion L2. The first portion L1includes an end on a negative side of the gripped section42in the Z axial direction. The second portion L2is joined to the first portion L1. The first portion L1includes a part of a main surface of a plate with a constant thickness t1, that is to say a part of the second main surface422. The second portion L2has a thickness t2which increases along with distance from the point where the second portion L2is joined to the first portion L1. The second portion L2includes the inclined surfaces424formed on the ribs423.

Next, a gripping method according to the embodiment is described with reference toFIGS. 6 and 7.FIG. 6is a cross-sectional view of a first stage of the gripping method.FIG. 7is a cross-sectional view of a second stage of the gripping method.

In the first stage as illustrated inFIG. 6, the gripping mechanism3grips the first component4between the outer surface of the gripping roller32and an inner surface of the holder31using gravity acting on the gripping roller32. Specifically, the second main surface422including the first portion L1of the gripped section42is gripped with suitable frictional force between the outer surface of the covering section322and the inner surface of the back plate311. Through the covering section322compressively deforming, great gripping force is realized because the covering section322has a larger surface area of contact with the gripped section42than in a case where the covering section322is formed with an inelastic material.

As illustrated inFIG. 7, the gripping mechanism3moves in the positive Z axial direction relative to the first component4before the first component4is released from gripping. The gripping method transitions from the first stage to the second stage. In the second stage, the gripping roller32is lifted by the inclined surfaces424of the ribs423composing the second portions L2of the gripped section42. As a result, the great gripping force is mitigated by the compressive deformation of the covering section322.

The following describes operation of the assembly apparatus100with reference toFIGS. 1 to 7.

In a first process, the robot1moves the gripping mechanism3to the storage location of the first component4as illustrated inFIG. 1. Then, upon adjusting the posture of the gripping mechanism3such that the gripped section42is parallel to the back plate311, the robot1moves the gripping mechanism3in the positive Z axial direction relative to the first component4. The gripped section42is inserted into the holder31through the opening315and ascends within the holder31while pushing aside the gripping roller32. Thereafter, the movement of the gripping mechanism3is halted before the inclined surfaces424push the gripping roller32upward. As a result, the first stage illustrated inFIG. 6is realized.

In a second process, the robot1moves the gripping mechanism3in the negative Z axial direction. By further moving the gripping mechanism3, the robot1conveys the first component4to a point directly above the second component5as illustrated inFIG. 1. The gripped section42is left gripped between the outer surface of the covering section322and the inner surface of the back plate311.

In a third process, the robot1moves the gripping mechanism3in the positive Z axial direction. As a result, the first component4is fitted to the second component5. The first stage illustrated inFIG. 6is maintained at least until just before fitting.

In a fourth process, the robot1further moves the gripping mechanism3in the positive Z axial direction. Through the inclined surfaces424pushing the gripping roller32upward, the second stage illustrated inFIG. 7is realized. The second stage is a preparation stage for gripping release.

In a fifth process, the robot1moves the gripping mechanism3in the positive X axial direction. The gripped section42slides between the outer surface of the covering section322and the inner surface of the back plate311and further passes through the cutout317. As a result, the gripping of the first component4by the gripping mechanism3is released. The first component4is left fitted to the second component5.

In a sixth process, the robot1moves the gripping mechanism3in the negative Z axial direction while returning the gripping mechanism3to the original position thereof in preparation for the next operation.

Next, a variation of the gripping mechanism3is described with reference toFIG. 8.FIG. 8is a front view of the variation of the gripping mechanism3.

The gripping mechanism3inFIG. 8differs from the gripping mechanism3inFIG. 2in that the holder31houses a plurality of gripping rollers32a. In a case where the gripping rollers32ahave different weights, a plurality of gripping forces can be used. Furthermore, the peripheral surfaces of the gripping rollers32amay have different friction coefficients.

Next, weight adjustment of the gripping roller32is described with reference toFIG. 9.FIG. 9is a cross-sectional view of an example of the weight adjustment of the gripping roller32.

The gripping roller32inFIG. 9differs from the gripping roller32inFIG. 3in that the diameter of the core321is reduced. Assuming the materials of the core321and the covering section322and the overall diameter of the gripping roller32are the same, the weight of the gripping roller32decreases as the diameter of the metal core321decreases. Conversely, the weight of the gripping roller32increases as the diameter of the metal core321increases. The weight of the gripping roller32may also be adjusted by changing the material of either or both of the core321and the covering section322.

Next, a variation of the gripping roller32is described with reference toFIG. 10.FIG. 10is a cross-sectional view of a variation of the gripping roller32.

The gripping roller32inFIG. 10differs from the gripping rollers32inFIGS. 3 and 9by including an inner ring323, an outer ring324, and cushion ribs325. The inner ring323is a small-diameter cylinder and the outer ring324is a large-diameter cylinder. The cushion ribs325are located so as to connect the inner ring323and the outer ring324in three places. The three places at which the cushion ribs325are located are separated from each other by an approximately 120 degree angle. The inner ring323, the outer ring324, and the cushion ribs325are all made of an elastic material such as polyacetal resin. The gripping roller32inFIG. 10is entirely compressively deformable and capable of realizing a great gripping force.

According to the embodiment, the gripping mechanism3which requires no motive power includes only the holder31and the gripping roller32(or32a). As a result, the gripping mechanism3which is difficult to damage can be realized at low cost. Moreover, gripping is easily released because the ribs423with the inclined surfaces424are provided on the first component4which is an object to be gripped.

The description of the above embodiment is of an ideal embodiment of the present disclosure, and therefore includes various favorable technical limitations. However, the technical scope of the present disclosure is not limited to the embodiment unless specifically described as such. That is, elements of configuration in the above embodiment may be appropriately replaced with existing elements of configuration and the like, and a number of variations including other existing elements of configuration are possible. The description of the above embodiment does not limit the content of the disclosure described in the claims.

For example, in the embodiment as illustrated inFIG. 4, the number of the ribs423is two, but the present disclosure is not limited as such. The number of the ribs423may be one or three or more. In addition, the gripped section42may lack a rib structure and instead have a continuous inclined surface424across an entire side of the gripped section42in the X axial direction.