JP2014193510A - Tightening method of screw and tightening device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tightening method, along with a tightening device used therefor, of a screw such as a bolt with a tightening force being uniform and of high precision.SOLUTION: In order to reduce an effect of frictional force at tightening of a screw, a friction force reduction effect under vibration is utilized, resonance of vibration is utilized for enhancing effect of vibration, conversion and synthesizing are performed in vibration direction, with a cross section being cross-shaped while dimensions in longitudinal direction and lateral direction being integer multiple of half-wavelength of the wavelength of target frequency, meanwhile, a vibration body in longitudinal direction and vibration body in lateral direction are made to cross each other at a node 13 of vibration, and a bolt or a nut is put at a position 12 at which vibrational amplitude due to resonance becomes maximum for excitation, thus, friction reduction effect due to vibration is enhanced for tightening. Vibration that is applied to the bolt or nut is basically a mode which utilizes vibration in screw axis direction, however, a mode is possible in which, by causing staggering to the axial line of the vibrator, torsional vibration around screw axis is applied to it.

Description

  The present invention relates to a method for fastening screws and a fastening device therefor. In particular, the present invention relates to a method capable of tightening a screw structure with high accuracy, and an apparatus used therefor.

  Conventionally, screws such as bolts have been used over a wide range such as assembly of mechanical devices, electrical devices, chemical devices, buildings, bridges, and the like.

  The tightening force of a screw is generally managed by the “torque method” defined in “Screw tightening rules” of JIS B 1083, that is, tightening torque. However, even if the tightening torque is kept constant, the variation in the tightening force increases, and the reliability of the tightening force management cannot be said to be sufficient. The reason is that the contact pressure on the sliding surface becomes uneven due to unevenness of the surface roughness between the screw and the object to be fastened, due to surface deposits, alterations such as oxidation, or when tightening. The frictional surface between the screw head and the seating surface and the coefficient of friction between the male screw and the female screw are different one by one because the sliding surfaces bite into each other or cause adhesion in the locally high contact pressure part of the surface. By becoming a value.

  If the tightening force of the screw is not appropriate, the screw may become loose, or the screw may be broken or the thread may be crushed due to metal fatigue. In the transportation sector and structures, screw breakage is an important issue that affects human life. Therefore, if high-precision tightening is realized, the safety of machines and structures is improved. In addition, if a high-precision tightening force is realized, the safety factor can be lowered in the design, and the weight can be reduced and the production cost can be reduced. In view of this, a tightening method for screws has been proposed in which the tightening force is made uniform by tightening while applying vibration to the screw, and the tightening is performed with high accuracy (see Patent Document 1).

  As means for reducing the influence of the frictional force, a frictional force reduction effect by vibration (Non-Patent Document 1) is known. As means for enhancing various effects due to vibration, a method using resonance of vibration (Non-Patent Document 1) and a method of changing the cross-sectional area of a vibrating body that transmits vibration (Non-Patent Document 1) are known.

  As a method of obtaining a large amplitude in vibration, a method using vibration resonance (Non-Patent Document 2) and a vibration body that transmits vibration by making the cross-sectional area of the output end smaller than the cross-sectional area of the input end of vibration There is known a method (Non-Patent Document 2) that utilizes the effect of increasing the amplitude of the signal.

JP 2004-330342 A

Japan Society for Technology of Plasticity "Ultrasonic Applied Machining" Morikita Publishing, P. 41-43, issued May 20, 2004 Japan Electronics and Information Technology Industries Association "Ultrasonic Engineering" Corona, P.A. 72-77, issued January 30, 1993

  In the method described in Patent Document 1, the vibrator 8 is interposed between the drive shaft 10 and the wrench rotary shaft 12 of the apparatus (see FIG. 1), or the drive shaft 58 is interposed via transmission gears 52 and 54. The vibrator 50 is attached to the end of the wrench rotating shaft that is driven to rotate (see FIG. 2), or vibration is applied to the fastened member 124 from the outer vibration housings 116 and 130 to which the vibrator 118 is attached (FIG. 3). The vibration is given to the screw structure.

  However, in the apparatus shown in FIG. 1 and FIG. 2 of Patent Document 1, since the vibrator is arranged coaxially with respect to the wrench rotation axis to give vibration, there is a great restriction on the tightening structure, and the tightening force is also low. There is a problem that the influence on the vibrator cannot be ignored.

  An object of the present invention is to provide a method for tightening screws such as bolts and the like, and a tightening device for screws used in the tightening force, which can obtain a highly accurate tightening state with a uniform tightening force. In particular, it is an object of the present invention to realize a method and an apparatus that can reduce structural restrictions of the apparatus by a structure that can give a sufficient vibration to the screw structure from the outside of the tightening axis.

  The present invention uses a frictional force reduction effect due to vibration to reduce the influence of frictional force in screw tightening, a bifurcated (for example, cross-shaped) vibrating body, and an orthogonal direction of vibration by the vibrating body. It is characterized by using transformation, preferably by using vibrational resonance to enhance the effect of vibration. Here, a first branch portion provided with a tip for inputting longitudinal vibration generated by a vibrator or the like and extending along the first axis, and a tip connected to a fastening screw member or a member to be fastened are provided. A vibration having a branch shape (for example, a cross shape) having a second branch portion that extends along the second axis and an intersection portion where the first branch portion and the second branch portion intersect with each other. Use the body. The longitudinal vibration in the direction of the first axis input to the first branch portion is converted into the longitudinal vibration in the direction of the second axis by orthogonal transformation and propagates through the second branch portion, so that It is given to a fastening member. Here, it is preferable that the tip of the second branch portion is connected to the fastening screw member or the fastened member in a posture in which the second axis is disposed along the axis of the screw structure. Moreover, typically, it is preferable that the vibrating body is configured such that the first axis is orthogonal to the second axis. Furthermore, it is preferable that the second axis coincides with the axis of the screw structure when the fastening screw member is tightened. In particular, a plurality of first branch portions are provided in the vibrating body, and longitudinal vibrations having the same phase are input to each other, thereby synthesizing the longitudinal vibrations of the plurality of vibrators, and fastening screw members or members to be fastened. It becomes possible to vibrate strongly.

  In this case, in the vibrating body, the dimension of the first branch portion extending in the direction of the first axis (for example, the horizontal direction) and the second dimension extending in the direction of the second axis (for example, the vertical direction). The dimensions of the two branch portions are substantially set to a quarter wavelength of the longitudinal vibration or an odd multiple thereof, respectively, and the length along the first axis of the vibrator and the second axis It is preferable that the length along the length is substantially set to a half wavelength of longitudinal vibration or an integral multiple thereof. As a result, the longitudinal vibration input from the vibrator can resonate the vibrating body in the direction of the first axis, and also resonate the vibrating body in the second direction by orthogonal transformation through the intersection. Therefore, the screw structure can be vibrated efficiently. That is, the vibration generated by the vibrator causes the vibrating body to resonate in the direction of the first axis, which is in the direction of the second axis at the second branch due to the Poisson's ratio effect at the intersection of the vibrating bodies. Converted to longitudinal vibration. Then, the converted longitudinal vibration causes the second branch portion of the vibrating body to resonate also in the direction of the second axis. Since the change of the vibration direction is due to the effect of the Poisson's ratio, the vibration in the direction of the first axis and the vibration in the direction of the second axis are accompanied by a phase difference of a half period of the vibration period. Then, the fastening screw member (for example, a bolt or nut) or the member to be fastened is vibrated by placing it at a position where the vibration amplitude in the direction of the second axis due to resonance is maximized, thereby reducing the frictional effect due to longitudinal vibration. Can be tightened.

  One or more vibrators are attached. In the case of a single vibrator, the longitudinal vibration in the first direction generated from the vibrator is only orthogonally transformed at the crossing portion (for example, the orthogonal portion), but when a plurality of vibrators are attached, By driving so as to be in phase with each other, vibrations in the direction intersecting with the first axes (for example, a right angle direction) are synthesized at the intersecting portion, and strong vibrations in the direction of the second axis are obtained. Is converted. In order to realize the orthogonal transformation through the intersecting portion in the vibrating body, the configuration is such that a node of longitudinal vibration is formed at the intersecting portion of the vibrator. Here, in the vibrator, in order to realize resonance along the first axis, the length along the first axis of the vibrating body is set to ½ wavelength or an integral multiple thereof. In this case, a pair of first branch portions extending on both sides of the intersecting portion along the first axis line are provided, and the length of each first branch portion is set to ¼ wavelength of longitudinal vibration or its length, respectively. It is preferable to set to an odd multiple. In this case, the total length of the pair of first branch portions on both sides is set to ½ wavelength or an integral multiple thereof, and a standing wave is formed over the length. Further, in order to realize resonance along the second axis, the length along the second axis of the vibrating body is set to ½ wavelength or an integral multiple thereof. In this case, a pair of second branch portions extending on both sides of the intersecting portion along the second axis are provided, and the length of each second branch portion is set to 1/4 wavelength of longitudinal vibration or its It is preferable to set to an odd multiple. As a result, the length along the second axis of the vibrating body, that is, the total length of the pair of second branch portions on both sides is set to ½ wavelength or an integral multiple thereof, and the length is constant over the length. A wave is formed.

  By displacing the first axis that is the vibration input axis of the vibrator so as to be different from the second axis that is the vibration output axis, the longitudinal vibration in the direction of the second axis is caused on the fastening screw member or the member to be fastened. In addition, torsional vibration about the second axis can be provided. At this time, in terms of mathematical terms, the first axis and the second axis are in a positional relationship of torsion. In this case, when vibration is applied to the screw structure along the second axis, the vibration includes a component in the axial direction of the screw structure and a component in the torsional direction around the axis of the screw structure. The ratio of both components varies depending on the amount of deviation around the second axis (the axis of the screw structure) with respect to the first axis. When a plurality of vibrators are used, the plurality of vibrators are operated in the same phase, and each first axis is shifted in the same direction around the second axis, so that The component of torsional vibration can be increased.

  As a transmission mode of the vibration to the screw structure, the second rotation is the same from the rotation engagement portion (for example, the wrench-like engagement portion) provided on the second axis that is the vibration output axis of the tightening device including the vibrating body. The screw may be transmitted to the screw sliding portion through a fastening screw member having a screw structure disposed on the axis of the screw, or may be passed from a vibrating body through a member to be fastened (for example, a plate or other structure). It may be transmitted to the sliding portion. In particular, as a method of tightening screws, the fastening screw member is rotationally driven by using a tool other than the vibrator while applying longitudinal vibration to the fastening screw member or the fastening member using the vibrator. Then, it may be tightened.

The tightening device of the present invention has the following configuration.
(1) A vibrator as means for applying vibration and a vibrator connected to the vibrator. The vibrating body includes a first branch portion that extends along a first axis, a second branch portion that extends along a second axis different from the first axis, and a first branch. And an intersecting portion where the second branch portion intersects. A vibrator is connected to the tip of the first branch portion, and a fastening screw member or a member to be fastened is connected to the tip of the second branch portion. Further, the longitudinal vibration in the direction of the first axis is orthogonally transformed from the first branching portion to the longitudinal vibration in the direction of the second axis via the intersection, and propagates through the second branching portion.
(2) A rotational drive unit for rotationally driving the fastening screw member around the axis of the screw structure. This rotational drive part can be comprised by rotational drive sources, such as a handle | steering-wheel for giving rotational force around the axis line of a screw structure, a motor, etc., for example.
(3) A rotational engagement portion that engages with the fastening screw member in the rotational direction around the axis of the screw structure. This rotation engagement part can be comprised by a wrench-like engagement part, a spanner-like engagement part, a driver-like engagement part, etc., for example. In particular, by providing or connecting the rotation drive unit and the rotation engagement unit to the vibration body, the driving force applied by the rotation drive unit is applied to the fastening screw member via the vibration body and the rotation engagement unit. Therefore, the tightening device can be configured easily. Further, by providing the rotational drive portion and the rotational engagement portion at both ends along the second axis of the vibrating body, tightening by rotational drive while applying longitudinal vibration to the fastening screw member at the tip of the second branch portion It can be performed. The rotation engagement portion is preferably provided so that it can also be used as a vibration transmission portion for the fastening screw member at the tip of the second branch portion of the vibrating body. It may be provided separately. The vertical vibration propagating along the second axis can be applied to the member to be fastened from a place provided in the second branch portion separately from the rotation engaging portion that engages with the fastening screw member.

  According to the present invention, the first axis that is the vibration input axis of the vibrator and the second axis that is the vibration output axis toward the screw structure are set in different directions, and longitudinal vibration along the first axis. By orthogonally transforming to the vibration along the second axis, the vibrator can be placed at a position and direction deviating from the second axis, thereby reducing structural constraints on the position and orientation of the vibrator can do.

  In particular, by resonating the vibrating body or synthesizing the vibrations of a plurality of vibrators with the vibrating body, the friction reducing effect of longitudinal vibration can be further enhanced and used for tightening the screw structure. Thereby, the influence of friction on the tightening of the screw structure can be greatly reduced. By greatly reducing the influence of friction on the tightening of the screw structure, the influence of variation in the friction coefficient in the tightened screw structure can be greatly reduced. By greatly reducing the effect of variation in the friction coefficient of the tightened screw structure, it is possible to greatly reduce the variation in the axial force in torque method tightening, where the variation in the axial force is likely to occur due to the effect of the variation in the friction coefficient. it can.

  And as mentioned above, by greatly reducing the variation in the axial force of the screw, it is possible to prevent the object to be fastened from being distorted due to the uneven axial force in the direction of the axial line (bolt shaft) of the screw structure. In addition, the axial force can be made uniform at a high value, and the looseness of the screw can be prevented to increase the reliability. In addition, it is possible to perform tightening with a smaller number of bolts, which can realize weight reduction and production cost reduction.

1 is an external view of an apparatus for tightening while synthesizing vibrations of two vibrators and applying vibration in the direction of a bolt shaft, which is an embodiment of a screw structure tightening apparatus according to the present invention. FIG. It is sectional drawing of the apparatus shown in FIG. It is a detailed block diagram of the apparatus shown in FIG. FIG. 3 is an external view of a vibrating body that synthesizes vibrations of four vibrators, which is an embodiment of the vibrating body according to the present invention. FIG. 3 is an external view of a hexagonal vibrating body that synthesizes vibrations of three vibrators, which is an embodiment of the vibrating body according to the present invention. It is explanatory drawing which shows the amplitude distribution of a vibration when the vibrating body shown in FIGS. 1-4 becomes a resonance state. It is explanatory drawing which shows the example of the vibrating body which has the length from which the branch part of both sides differs. 1 is an external view of an apparatus for tightening while applying vibration in the direction of a bolt axis and torsional vibration by a vibrating body having a discrepancy in the axis of a vibrator, which is an embodiment of a screw operating device according to the present invention. It is sectional drawing of the horizontal surface of the apparatus shown in FIG. It is sectional drawing of the vertical surface of the apparatus shown in FIG.

Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIGS. 1 to 3 are configuration diagrams of an apparatus according to an embodiment of the present invention, which combines the longitudinal vibrations of two vibrators and tightens them while applying vibrations in the direction of the bolt shaft. As will be described later, the longitudinal vibration is preferably ultrasonic vibration.

  The vibrator 1 generates various kinds of vibrators such as a bolted Langevin vibrator (BLT) to be described later, which can generate longitudinal vibrations, preferably ultrasonic vibrations, and can input the longitudinal vibrations to the vibrating body. be able to. The vibrating body 2 connected to the vibrator 1 has a first branch portion extending along the first axis, and a second axis that intersects the first axis and is preferably orthogonal. It has a branching shape that includes a second branching portion that extends, and an intersecting portion where the first branching portion and the second branching portion intersect. The vibrating body 2 shown in FIG. 1 includes a pair of first branch portions projecting along a common horizontal first axis on both sides in the illustrated horizontal direction from the central intersection, and the illustrated vertical direction from the intersection. A plane including a first axis and a second axis, the second branch part projecting along a common vertical second axis on each side, and a total of four branch parts extending. The cross section along the cross has a cross shape. A vibrator mounting portion 5 is provided at the tip of each of the pair of left and right first branch portions, and the vibrator 1 is connected and fixed to each of the vibrator mounting portions 5. In addition, a handle attachment portion 4 is provided at the tip of the second branch portion on the upper side of the vibrating body 2, and a base end portion extending vertically of a handle 11 extending horizontally is connected and fixed to the handle attachment portion 4. Yes. Furthermore, a wrench attachment portion 6 is provided at the tip of the second branch portion on the lower side of the vibrating body 2, and for example, a wrench-like engagement portion 8 having a wrench structure such as a hexagonal hole is attached. Both the first branch portion and the second branch portion of the vibrating body 2 are formed in a prismatic shape (specifically, a regular quadrangular prism shape).

  In the vibrating body mounting portion 5 of the vibrating body 2, the vibrator 1 and the vibrating body 2 are coupled by a vibrator mounting screw 10 shown in FIG. Here, both are firmly coupled in the direction of the first axis to such an extent that the vibrator 1 and the vibrator 2 can be regarded as one body with respect to the longitudinal vibration. This first axis corresponds to a vibration input axis along the propagation direction of the longitudinal vibration input from the vibrator 1 to the vibrating body 2. Moreover, it is preferable that the said handle | steering-wheel attachment part 4 of the vibrating body 2 is connected with the base end part of the handle | steering-wheel 11 so that attachment or detachment is possible by the connection aspect engaged in rotation directions, such as fitting of a square hole and a prism.

  A wrench mounting portion 6 at the tip of the second branch portion on the lower side of the vibrating body 2 is connected to a fastening screw member such as a nut 3 or a bolt 7 via a wrench-like engagement portion 8. Here, the wrench-like engaging portion 8 is a fitting structure that engages with a fastening screw member such as the nut 3 or the bolt 7 in the rotational direction, for example, a wrench-like engaging portion, a spanner-like engaging portion, a driver. It is an example of the fitting member provided with the shape engaging part. It is preferable that the wrench mounting portion 6 of the vibrating body 2 is also detachably connected to the wrench-like engagement portion 8 by a connection mode that engages in a rotational direction such as fitting of a square hole and a prism. The nut 3 and the bolt 7 which are fastening screw members are screwed together to fasten the fastened object 9 which is a fastened member. In this case, by rotating the handle 11, the wrench-like engaging portion 8 holds the nut 3 via the vibrating body 2 and rotates around the axis of the bolt 7 (axis of the screw structure). Is done. Thereby, the article 9 is fastened and fixed.

  At this time, alternating current voltages having the same frequency and the same phase are applied to the two vibrators 1, and the vibration generated thereby vibrates the vibrating body 2. Here, the lengths of the left and right first branch portions of the vibrating body 2 are adjusted in advance to a quarter wavelength of the vibration (may be an odd multiple of a quarter wavelength). As a result, the total length of the pair of first branch portions along the first axis becomes ½ wavelength (an integral multiple of ½ wavelength), and therefore the standing wave along the first axis. Is formed to resonate the vibrator 2. In this example, the vibration generated by the two vibrators 1 connected to both sides is synthesized. When the object 9 is tightened by rotating the handle 11, friction is generated between the contact surface of the male screw and the female screw in the screw structure and between the seat surface of the bolt 7 or the nut 3 and the object 9 to be fastened. Therefore, even if the vibration is applied to any of the bolt 7, the nut 3, and the fastened object 9, a friction reducing effect can be obtained. The tightening torque is transmitted from the handle 11 to the vibrating body 2 via the handle mounting portion (supporting portion) 4 of the vibrating body 2 and further transmitted from the wrench-like engaging portion 8 attached to the vibrating body 2 to the nut 3. The nut 3 and the bolt 7 are fastened.

  FIG. 4 is a vibration that can be used in the embodiment of the present invention and can be tightened while synthesizing the vibrations of the four vibrators 1 and applying vibrations in the axial direction of the bolt 7 (axial line of the screw structure). 3 is a perspective view showing a shape of a body 2. FIG. The vibrating body 2 protrudes sideways so as to intersect (in the illustrated example, orthogonal) with the second axis of the two upper and lower second branch portions having the handle attachment portion 4 and the wrench attachment portion 6. The four first branch portions are provided, and the vibrator mounting portion 5 is provided at the tip of each first branch portion. Here, each of the four first branch portions includes a first axis that is set to be 90 degrees apart on a horizontal plane. Even when this vibrator 2 is used, the number of vibrators 1 attached to the vibrator 2 can be arbitrarily selected from 1 to 4 at the time of manufacture. However, if any one of the four first branch portions to which the vibrator 1 is not attached is provided, the number of the vibrators 1 is reduced correspondingly, so that the synthesized second axis The energy of longitudinal vibration along the axis is also reduced. Further, the vibration energy leaks from the intersecting portion to the first branch portion to which the vibrator 1 is not connected, but the vibration from the second branch portion along the second axis toward the screw structure is slightly reduced. Energy is reduced. Therefore, in the vibrating body 2, it is most preferable to attach the vibrator 1 to all of the first branch portions extending from the intersecting portions. This also applies to other embodiments.

  FIG. 5 is a perspective view showing a vibrating body 2 having a hexagonal planar shape, which can be used in the embodiment of the vibrating body according to the present invention and can synthesize vibrations of three vibrators. The vibrator 2 is provided with a plate-like portion having a hexagonal planar shape as a first branch portion, and a pair of second branch portions protruding vertically from the central intersection of the plate-like portion. Yes. The vibrator attachment portions 5 are provided on the other side surfaces of the six outer surfaces of the first branch portion. Therefore, 1 to 3 vibrators 1 can be attached to the vibrator 2. When the vibrators 1 are attached to all the vibrator attachment portions 5, the vibrators 1 are connected around the second axis at intervals of 120 degrees, and the first axis also corresponds to each vibrator 1. Arranged at intervals of 120 degrees. The vibrating body 2 extends along three horizontal first axes, and has a first branch portion having a vibrator mounting portion 5 at the tip, and an intersection with respect to the first branch portion. The handle attachment portion 4 and the wrench attachment portion 6 are connected to each other at the tip, and two upper and lower second branch portions extending along a vertical second axis. Also in this example, the longitudinal section along the first axis and the second axis is a cross shape, and the dimension along the first axis is used to resonate the vibrations emitted from the plurality of vibrators 1. (The sum of the lengths along any two of the three first axes) and the dimension along the second axis (dimension in the vertical direction in the figure) is an integral multiple of a half wavelength of vibration. If the requirement that all the vibrators 1 are driven in the same phase is satisfied, the same effect as described above can be obtained. As shown in this example, it can be seen that the number of vibrators 1 may be an odd number. Further, in the case of the vibrating body 2 having a hexagonal planar shape in the illustrated example, the vibrator mounting portions 5 may be provided on all outer faces (six faces), and the vibrator may be provided on an arbitrarily selected outer face. 1 may be attached.

  FIG. 6 is a distribution diagram of vibration amplitudes in the resonance state of the various vibrating bodies 2 shown so far. A vertical cross section along a plane (paper surface in FIG. 6) including both the first axis of the first branch portion extending on both sides in the horizontal direction and the second axis lines of the upper and lower second branch portions. As a mold, the horizontal dimension along the first axis and the vertical dimension along the second axis are set to integer multiples of a half wavelength of the wavelength of the target frequency, and the first axis in the horizontal direction The structural portion (a plurality of first branching portions) along the crossing and the structural portion (a pair of upper and lower second branching portions) along the second axis in the vertical direction intersect at the vibration node 13. As a result, resonance occurs in the vertical direction and the horizontal direction, and the tip of each branch portion becomes a vibration antinode 12 and the intersection portion becomes a vibration node 13. In order to form the vibration nodes 13 at the intersections with respect to the vibration in the direction of the first axis, the length of the first branch portions on both sides of the branch portions (the intersections from the tips of the branch portions). The length to the portion) may be set to 1/4 wavelength of the vibration or an odd multiple thereof. Similarly, in order to form a vibration node 13 at the intersection with respect to the vibration in the direction of the second axis, the length of the second branch on both sides of the branch (from the tip of each branch) What is necessary is just to make the length to an intersection part) into 1/4 wavelength of vibration, or its odd number multiple. In FIG. 6, the length of each branching portion is set to ¼ wavelength. There is a half-cycle phase difference between the direction of the first axis, i.e., the lateral vibration, and the direction of the second axis, i.e., the longitudinal vibration. The vibration is converted and synthesized into a vertical vibration (orthogonal transformation).

  In addition, as shown in FIG. 7, when the 1st branch part is each provided in the both sides of an intersection part along a common 1st axis line, these 1st branch parts may have different length. . FIG. 7 shows a case where one first branch portion (left side in the figure) has a length corresponding to ¼ wavelength, and the other first branch portion (right side in the figure) has a length corresponding to 3/4 wavelength. Similarly to the above, when the second branch portions are provided on both sides of the intersection along the common second axis, the second branch portions may have different lengths. FIG. 7 shows a case where one second branch portion (upper side in the drawing) has a length corresponding to ¼ wavelength, and the other second branch portion (lower side in the drawing) has a length corresponding to 3/4 wavelength. .

The inventors of the present application actually used a bolted Langevin vibrator (BLT) as the vibrator 1, and used a block body made of aluminum as the vibrator (Horn) 2 shown in FIGS. A tightening experiment was conducted. The frequency of the vibrator 1 is basically about 28 kHz, but the experiment was performed by finely adjusting the frequency so as to actually be in a resonance state. The acoustic characteristic of the vibrating body 2 is a longitudinal wave velocity v = 5000 m / s, and the wavelength of longitudinal vibration at a frequency of 28 kHz is λ = f / v = 178.6 × 10 ⁻³ m. The dimensions of each branch portion of the vibrating body 2 were all set to a length corresponding to the half wavelength of vibration as described above. Actually, the oscillating body 2 having a plurality of shapes is examined by using the finite element method analysis based on the above values, but the cross-shaped horn shape shown in FIGS. These conditions and methods are the same in the experiments performed on the embodiments shown in FIGS.

  Further, the article 9 to be fastened was actually fastened by the bolt 7 and the nut 3 by the fastening device shown in FIG. Molybdenum disulfide grease was applied to the seat surface between the bolt 7, the nut 3, and the article 9 to be fastened, and the threaded surfaces of the bolt 7 and the nut 3. The vibrator 1 was attached to each of the pair of vibrator attachment portions 5 facing the vibrator 2, and an electrical signal emitted from the transmitter was applied to the vibrator. Then, the frequency of the electric signal was adjusted so that the entire frequency would resonate. Thereafter, the tightening torque was increased every 5 N · m by the torque method, and tightening was performed on nine bolts and nuts until finally reaching 35 N · m. Actually, an experiment was conducted for the presence or absence of vibration by the vibrator 1. From this experiment, it was confirmed that ultrasonic vibration could be applied efficiently and sufficiently when the bolt 7 and the nut 3 were tightened.

  8 to 10 show that the first axis of the vibrator 1 that can be used in the embodiment of the present invention has a discrepancy with respect to the second axis (screw structure axis) (in the radial direction around the second axis). With the vibrating body 2 having a deviation, the screw structure is tightened while adding both the vibration component in the direction of the second axis coincident with the axis and the component of torsional vibration around the second axis. It is a block diagram of the apparatus to perform. In this embodiment, by shifting the first axis of the vibrator 1 around the axis without intersecting the second axis, the screw or screw structure of the bolt or nut is subjected to vibration in the direction of the second axis. In addition, tightening is performed while applying torsional vibration around the second axis. Here, in this vibrating body 2, the first axis and the second axis are in a torsional position (mathematical term), so these axes do not intersect each other, but are shown in FIG. Thus, the 1st branch part and 2nd branch part which were provided in the vibrating body 2 cross | intersect in the center crossing part. Thereby, also in this embodiment, the vibrating body 2 can be made to resonate because the sum of the lengths along the plurality of first axes is a half wavelength of the vibration or an integral multiple thereof. .

  By applying the torsional vibration, vibration is applied in the tightening direction along the screw structure, so that the frictional force of the screw structure is substantially reduced, and variation in axial force generated after tightening is reduced. As a result of actually conducting an experiment in the same manner as described above using the vibrator 2 according to this embodiment, the variation in axial force (standard deviation σ of load axial force) is 5% compared to the case where no torsional vibration is applied. It was found to improve to some extent.

  The screw tightening method and the tightening device according to the present invention are not limited to the illustrated examples described above, and various changes can be made without departing from the scope of the present invention. For example, in each of the above embodiments, the number of vibrators is 2 to 4, but the cross section along the first axis and the second axis is a branched shape (for example, a cross-shaped shape), and The length of each branching portion is a quarter wavelength or an odd multiple thereof, and the length along the first axis of the vibrating body and the length along the second axis are the half wavelengths of vibration. If a plurality of vibrators 1 are connected and all vibrators are driven in the same phase, the number of vibrators, vibration The shape of the body is not particularly limited. Moreover, although the said Example demonstrated the method and apparatus which fasten a screw, this invention is applicable also when loosening a screw.

  Furthermore, in the above-described embodiment, the wrench-like engagement portion 8 is connected to the tip of the second branch portion of the vibrating body, and the wrench-like engagement portion 8 is engaged with the fastening screw member to simultaneously apply vibration. While tightening, a part of the tip of the second branching part is brought into contact with the member to be fastened, and at the same time, another part of the tip of the second branching part is engaged with the fastening screw member. You may make it tighten. For example, a rotation engagement portion formed on the center side at the tip of the second branch portion of the vibrating body, and a vibration transmission portion that contacts the fastened member on the outer peripheral side of the rotation engagement portion are coaxially annular. Alternatively, it may be provided in a non-annular shape. Of course, there is provided a rotation engagement portion that engages with the rotation drive portion and the fastening screw member, which is different from the vibration body, while applying vibration by bringing the tip of the second branching portion of the vibration body into contact with the fastened member. The fastening screw member may be rotationally driven and tightened by the provided fastening device or apparatus.

1: vibrator, 2: vibration body, 3: nut, 4: handle attachment portion of (vibration body), 5: vibrator attachment portion of (vibration body), 6: wrench attachment portion of (vibration body), 7: Bolt, 8: Wrench-like engaging part, 9: Fastened object, 10: Vibrator mounting screw, 11: Handle, 12: Antinode of vibration, 13: Node of vibration, 14: Excitation by vibrator, 15: Vibration Vibration after transformation in the body

Claims (8)

A screw tightening method for tightening a screw structure while applying longitudinal vibration to a fastening screw member or a member to be fastened,
A first branch extending along a first axis, a second branch extending in a direction of a second axis different from the first axis, the first branch, and the Using a branch-shaped vibrating body having a crossing portion where the second branching portion intersects, longitudinal vibration is input in the direction of the first axis from the tip of the first branching portion, and the longitudinal vibration is It is converted into longitudinal vibration in the direction of the second axis by orthogonal transformation through the intersecting portion and propagated to the second branch portion, and the tip of the second branch portion is connected to the fastening screw member or The screw structure is tightened by rotationally driving the fastening screw member while applying the longitudinal vibration in the direction of the second axis by connecting to the member to be fastened. Tightening method.   The screw tightening method according to claim 1, wherein the first axis and the second axis are in a torsional positional relationship. Both the length along the first axis and the length along the second axis of the vibrating body are substantially ½ wavelength of the longitudinal vibration or an integral multiple thereof.
Both the length along the first axis of the first branch and the length along the second axis of the second branch are substantially ¼ wavelength of the longitudinal vibration or 2. The screw tightening method according to claim 1, wherein the length corresponds to an odd multiple thereof.   4. The vibration body is provided with a plurality of the first branch portions, and the longitudinal vibration is input from tips of the plurality of first branch portions, respectively. The tightening method for screws according to one item. A screw tightening device for tightening a screw structure while applying longitudinal vibration to a fastening screw member or a member to be fastened,
A vibrator that generates longitudinal vibration;
A first branch portion provided with a tip to which the vibrator is connected and extending along a first axis, a tip connected to the fastening screw member or the fastened member, and the screw structure A vibrator having a second branch portion extending along a second axis disposed along the axis, and an intersection formed by intersecting the first branch portion and the second branch portion; ,
A rotation driving unit that applies a driving force for driving the fastening screw member to rotate about the axis of the screw structure;
A rotational engagement portion for engaging the fastening screw member in a rotational direction around an axis of the screw structure and transmitting the driving force;
A screw tightening device comprising:   The screw tightening device according to claim 5, wherein the first axis and the second axis are in a torsional positional relationship.   The rotational engagement portion is provided at the tip of the second branch portion, or is connected to the tip of the second branch portion, and the second axis is the fastening screw. It is configured to be able to engage with the fastening screw member when the posture is matched with the axis of the screw structure of the member, and the rotational drive unit is opposite to the tip of the second branching portion in the vibrating body. The screw tightening device according to claim 5 or 6, wherein the screw tightening device is provided in a portion on the second axis or connected to the portion.   The vibration body is provided with a plurality of the first branch portions, and the vibration body is connected to tips of the plurality of first branch portions, respectively. The screw fastening device according to one item.

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