JP7228399B2 - Countersunk fastener joint structure and elastic body for countersunk fasteners - Google Patents

Description

The present invention relates to a countersunk head fastener such as a bolt or rivet having a countersunk head, a countersunk fastener joint structure including a member to be fastened, and an elastic body used in the countersunk fastener joint structure.

A countersunk head bolt having an inverted frustoconical countersunk head is used to fasten various members. For example, countersunk bolts are used in the fuselage skin to reduce air resistance on the fuselage surface of an aircraft. The tapered seat surface of the countersunk head of the countersunk bolt is accommodated inside the receiving surface formed in a tapered shape by countersinking the member to be fastened.

Patent Literature 1 discloses a tapered washer for countersunk bolts for fastening cast exterior members. In Patent Document 1, in order to cope with the misalignment of the hole center of the member to be fastened, the countersunk head of the countersunk bolt is arranged in a hole having a larger diameter than the hole into which the shaft portion of the countersunk bolt is inserted, and the countersunk head has a flange. It is fitted with a conical tapered washer with a ridge.
In Patent Document 1, the entire countersunk head is placed in the cylindrical hole of the member to be fastened, so the countersunk head is in a free state. The flange of the tapered washer is arranged with a margin in the concave portion of the member to be fastened that is larger than the flange. A fastening force acts on a member to be fastened by the collar portion that engages the member to be fastened and the shank portion of the bolt that engages another member to be fastened.

According to the description of Patent Document 1, even if the member to be fastened thermally expands, the countersunk bolt is provided with enough margin to change its relative position within the through hole of the member to be fastened. is tilted along with the sliding of the taper washer in the direction in which the stress is applied without being forced to force the stress to be concentrated.

JP-A-9-170617

Aluminum alloys and fiber-reinforced resins containing reinforcing fibers such as carbon fibers, which are used for members of various devices including transport aircraft such as aircraft, generally have lower strength than iron, steel, and the like.
Therefore, when fastening members made of aluminum alloy or fiber-reinforced resin with countersunk bolts, the fastening force is the same as when fastening members made of iron, steel, etc. with countersunk bolts. is difficult to apply to the member to be fastened.
Then, due to the load in the direction orthogonal to the fastening force in the axial direction of the countersunk bolt, the workpiece is fastened by the amount of the clearance set between the shaft of the countersunk bolt and the inner peripheral part of the insertion hole of the member to be fastened. The members slide over each other. A clearance should be provided between the shaft of the countersunk bolt and the inner circumference of the insertion hole in order to accommodate the tolerance of the hole center position and to facilitate the insertion and removal of the countersunk bolt. can.
As the member to be fastened slides, the countersunk bolt inclines with respect to the insertion hole, and transmits the load to the member to be fastened while generating shear stress in the shaft portion. Furthermore, bending stress is generated in the countersunk head by the reaction force from the receiving surface of the member to be fastened against which the bearing surface of the bolt countersunk head abuts.

The strength of the countersunk head of the countersunk bolt may be lower than the strength of the member to be fastened. Even in this case, it is difficult to apply a sufficient fastening force to the members to be fastened, as in the case where the members to be fastened are made of aluminum alloy or fiber-reinforced resin. Therefore, the members to be fastened slide against each other due to the load in the direction orthogonal to the shaft portion, the countersunk bolt is inclined with respect to the insertion hole, and bending stress is generated in the countersunk head of the bolt due to the reaction force from the receiving surface.

Unlike the countersunk bolt joint structure of Patent Document 1, FIG. The deformation of is exaggerated. FIG. 9 is a schematic diagram based on an example of stress analysis.
As shown in FIG. 9 , bending stress is generated in the countersunk head 81 due to the reaction force from the receiving surface 91A due to the sliding of the fastened members 91 and 92 and the inclination of the countersunk bolt 8 . A curved arrow shown in FIG. 9 indicates a bending moment M related to a bending stress caused by the bending deformation of the countersunk head 81 from the shape shown by the two-dot chain line to the shape shown by the solid line due to the inclination of the countersunk bolt 8 . In the example shown in FIG. 9, the bending stress of the neck portion 81A of the countersunk head 81 is particularly large.
According to the configuration of Patent Document 1, when the countersunk bolt is tilted due to the slippage of the member to be fastened, the countersunk head is not restrained, so an increase in the bending stress of the countersunk head can be avoided. It is inferior in bonding strength to

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to prevent damage to a countersunk fastener joint structure by reducing the stress generated by the slip even if a fastening member fastened by a countersunk head fastener is slipped. .

The countersunk fastener joint structure of the present invention comprises a countersunk fastener including a shaft portion and a countersunk head in the shape of an inverted truncated cone whose diameter increases from the shaft portion toward the top surface, and a plurality of fastened members fastened by the countersunk fastener. , a seat surface of the countersunk head, and an elastic body disposed between a receiving surface formed on one member to be fastened and receiving the seat surface.
In the present invention, the elastic body includes a radially inner first region and a radially outer second region, and both the first region and the second region are formed with the countersunk fastener and the receiving surface. The rigidity in the thickness direction of the elastic body is lower than that of the member to be fastened, and compared to the maximum elastic deformation amount in the thickness direction set in the first region, in the thickness direction set in the second region characterized by a large maximum elastic deformation amount.

"Fastener" includes members such as bolts and rivets that are used to fasten together a plurality of members. "Countersunk fastener" shall mean a fastener that includes an inverted frustoconical countersunk head.

In the joint structure of the disk fastener of the present invention, the disk fastener is preferably a bolt that can be attached to and detached from the member to be fastened.

In the joint structure of the disk fastener of the present invention, if the angle formed by the bearing surface with respect to the axis of the insertion hole of the member to be fastened into which the disk fastener is inserted is θ1, and the angle formed by the receiving surface with respect to the axis is θ2, then: It is preferable that θ1<θ2.

In the joint structure of the disk fastener of the present invention, it is preferable that t1<t2, where t1 is the thickness of the first region in an unloaded state, and t2 is the thickness of the second region in an unloaded state.

In the disk fastener joint structure of the present invention, it is preferable that k1>k2, where k1 is the stiffness of the first region and k2 is the stiffness of the second region.

In the joint structure of the disk fastener of the present invention, the elastic body includes the first elastic portion and the second elastic portion having different rigidity in the thickness direction, and the rigidity of the second elastic portion is equal to the rigidity ka of the first elastic portion. It is preferable that kb is small and k1>k2 based on the volume ratio of the first elastic portion and the second elastic portion.

The disk fastener joint structure of the present invention is arranged between the shaft and the inner peripheral portion of the insertion hole of the member to be fastened into which the shaft is inserted, and has rigidity in the thickness direction compared to the shaft and the member to be fastened. It is preferable to provide a second elastic body with a low .

In the joint structure of the disk fastener of the present invention, the elastic body preferably includes a cover region covering the top surface.

In the joint structure of the disk fastener of the present invention, it is preferable that the member to be fastened is a member that constitutes the fuselage of an aircraft.

Further, the present invention provides an elastic body disposed between the bearing surface of the countersunk head of the countersunk fastener and a receiving surface formed on one of a plurality of fastened members to be fastened by the countersunk fastener and receiving the bearing surface. a radially inner first region and a radially outer second region, both the first region and the second region relative to the fastened member on which the countersunk fastener and the receiving surface are formed; The rigidity in the thickness direction is low, and the maximum elastic deformation amount in the thickness direction set in the second area is larger than the maximum elastic deformation amount in the thickness direction set in the first area. do.

According to the disk fastener joint structure and the elastic body for a disk fastener of the present invention, even if the member to be fastened slips, the inclination displacement of the countersunk head due to the slip is absorbed by the elastic deformation of the elastic body. Since the bending deformation of the head is relaxed, the stress generated in the neck of the countersunk head can be reduced. Therefore, damage such as fatigue fracture of the disc fastener joint structure can be prevented.

1(a) and 1(b) are cross-sectional views showing a disc fastener joint structure according to a first embodiment of the present invention; FIG. (b) is a partially enlarged schematic diagram of (a). (a) is a cross-sectional view showing a state before fastening of a disk fastener and an elastic body. (b) is a cross-sectional view showing a state before fastening of a member to be fastened and an elastic body. FIG. 10 is a diagram schematically showing a state in which the disc fastener is tilted as the member to be fastened slides; FIG. 5 is a cross-sectional view showing a modification of the elastic body; It is a schematic diagram which shows the disk fastener joint structure which concerns on 2nd Embodiment. It is a schematic diagram which shows the disk fastener joint structure which concerns on 3rd Embodiment. FIG. 10 is a schematic diagram showing a disc fastener joint structure of a fourth embodiment obtained by combining the first embodiment and the second embodiment; 8(a) and 8(b) both show a fifth embodiment with a second elastic body arranged around the shank of the Belleville fastener; FIG. It is a schematic diagram which shows the conventional dish fastener joint structure.

An embodiment of the present invention will be described below with reference to the accompanying drawings.
In any of the disk fastener joint structures 1 to 4 described below, as will be described later, the elastic body disposed between the bearing surface 12B of the countersunk bolt 10 and the receiving surface 21A of the member to be fastened 21 is mainly configured. characteristics.

[Common component]
First, taking the disk fastener joint structure 1 of the first embodiment shown in FIGS.
As shown in FIGS. 1(a) and 1(b), the countersunk fastener joint structure 1 includes a countersunk bolt 10 as a countersunk fastener having a shaft portion 11 and an inverted frustoconical countersunk head 12, and a a plurality of fastened members 21 and 22 fastened by the countersunk bolt 10 and the nut 18; and an elastic body 30.

The Belleville fastener joint structure 1 of this embodiment can be applied to a member that constitutes the body of an aircraft.
In that case, the members 21 and 22 to be fastened are members such as the fuselage and main wings of an aircraft. These fastened members 21 and 22 are fastened at a plurality of locations using a plurality of countersunk bolts 10 .
For example, the fastened member 21 is the main wing skin, and the fastened member 22 is a stringer or rib that supports the skin from the back side. Alternatively, the member to be fastened 21 may be the skin of the body, and the member to be fastened 22 may be a frame that supports the skin from the back side.
The number of members to be fastened (21, 22) fastened by the same countersunk bolt 10 is not limited to two, and may be three or more.

(Member to be fastened)
The members 21 and 22 to be fastened are preferably made of a material having a higher specific strength than iron, steel, or the like, such as an aluminum alloy or fiber-reinforced resin. The fiber-reinforced resin includes a fiber base material made of reinforcing fibers such as carbon fiber, glass fiber, and aramid fiber, and a matrix resin impregnated in the fiber base material.

Of the members to be fastened 21 and 22, one member to be fastened 21 arranged on the outer surface of the airframe is formed with a receiving surface 21A for receiving the bearing surface 12B of the countersunk head 12 of the countersunk bolt 10. As shown in FIG. The diameter of the inner opening of the receiving surface 21</b>A is gradually reduced toward the bolt insertion hole 20 by countersinking (countersinking) with a depth corresponding to the height of the countersunk head 12 .
The seat surface 12B is pressed against the receiving surface 21A via the elastic body 30 .

When the shaft portion 11 of the countersunk bolt 10 is inserted into the bolt insertion hole 20 extending through the members to be fastened 21 and 22, the countersunk head 12 of the countersunk bolt 10 forms a receiving surface 21A recessed from the surface 21B of the member to be fastened 21. can be accommodated inside the At this time, the countersunk head 12 does not protrude from the surface 21B of the member 21 to be fastened. Therefore, the air resistance of the airframe can be reduced by using the countersunk bolt 10 for fastening the members exposed on the outer surface of the airframe.

The bolt insertion hole 20 consists of an insertion hole 201 formed in the member to be fastened 21 and an insertion hole 202 formed in the member to be fastened 22 . An axis line passing through the cross-sectional center of the bolt insertion hole 20 is called A.
A clearance C having a predetermined dimension is set between the inner peripheral portion of the bolt insertion hole 20 and the outer peripheral portion of the shaft portion 11 . The dimension of the clearance C is determined by the ease of inserting the countersunk bolt 10 into the bolt insertion hole 20 and removing the countersunk bolt 10 from the bolt insertion hole 20, and the cross-sectional center of the insertion holes 201 and 202 due to tolerances in dimensions and assembly. It is set in consideration of the tolerance of the position of

Since the clearance C is set, a gap 24 exists between the inner peripheral portion of the bolt insertion hole 20 and the outer peripheral portion of the shaft portion 11 . The fastened members 21 and 22 resist the frictional force between the fastened members 21 and 22 by the load F1 (FIG. 3), which is a component acting in a direction orthogonal to the axis A of the external force, and the gap 24 is formed. It is relatively displaced while sliding by the amount.
The slip-causing load F1 is, for example, the tension acting on the fuselage skin due to the pressure difference between the exterior and interior of the fuselage. Alternatively, the load F1 is, for example, the tension acting on the main wing skin when the main wing bends due to an aerodynamic load occurring in the main wing.
Between the inner peripheral portion of the bolt insertion hole 20 and the outer peripheral portion of the shaft portion 11 is a gap 24, in which a member such as a cylinder made of steel is arranged to resist the slippage of the members 21 and 22 to be fastened. It has not been.

(flask bolt)
The countersunk bolt 10 has a shank 11 formed with a male thread 11A and a countersunk head 12 (flush) in the shape of an inverted truncated cone whose diameter gradually increases with respect to the diameter of the shank 11 toward the top surface 12A. head).
The axis of the countersunk bolt 10 basically coincides with the axis A of the bolt insertion hole 20 when the members to be fastened 21 and 22 are fastened by the countersunk bolt 10 .
The male thread 11A of this embodiment is formed over a predetermined range on the tip portion 11B side of the shaft portion 11, but the male thread 11A may be formed over the entire length of the shaft portion 11. FIG.

The countersunk head 12 has a top surface 12A located on the outer surface of the body and a seat surface 12B tapered from the top surface 12A to the shaft portion 11. As shown in FIG. 12 A of top surfaces of this embodiment are formed flat along the surface orthogonal to the axis line A. As shown in FIG. Preferably, top surface 12A is flush with surrounding surface 21B.
The countersunk head 12 is formed with a groove 12D (recess) recessed from the top surface 12A into which a tool is inserted during fastening.
Illustration of the groove 12D is omitted in FIG. 1B, FIG. 2, FIG.

When the countersunk bolt 10 is inserted into the bolt insertion holes 20 of the members 21 and 22 to be fastened, the bearing surface 12B of the countersunk head 12 is arranged on the receiving surface 21A, and the male thread 11A of the shaft portion 11 is pulled out from the member 22 to be fastened. protrude inside the machine. When the female thread (not shown) of the nut 18 is engaged with the male thread 11A of the shaft portion 11, a fastening force F0 acts in the direction of the axis A of the countersunk bolt 10, as indicated by the white arrow in FIG. 1(a). The member to be fastened 21 and the member to be fastened 22 are fastened by the fastening force F0.

A washer (not shown) can be sandwiched between the end surface 18A of the nut 18 and the inner side surface 22A of the member 22 to be fastened. This washer can be made of a metal material, a resin material, a rubber material, or the like.
Further, a cap (not shown) that covers the nut 18 and the tip portion 11B of the shaft portion 11 can be provided inside the member 22 to be fastened.

The countersunk bolt 10 can be made of an appropriate material having corrosion resistance, heat resistance, weather resistance, etc., as required, in addition to the rigidity required for fastening the members 21 and 22 to be fastened. Typically, the countersunk bolt 10 can be constructed using metal materials such as iron, nickel, titanium, and alloys thereof. The rigidity of the countersunk bolt 10 is generally higher than that of the fastened members 21 and 22 made of aluminum alloy or fiber-reinforced resin, but the invention is not limited to this. It is also permissible to use a resin material for the countersunk bolt 10 .
The nut 18 can also be constructed using the same material as the countersunk bolt 10 .

A predetermined tightening torque is applied to the countersunk bolt 10 in consideration of the rigidity of the members to be fastened 21 and 22 and the rigidity of the countersunk bolt 10 and the nut 18 . By applying a torque that enables reliable joining as a joint, the bearing surface 12B is pressed against the receiving surface 21A, and the nut 18 is pressed against the surface 22A inside the machine of the member 22 to be joined, thereby joining by fastening. Strength is ensured. Appropriate tightening torque can be applied to the countersunk bolt 10 within the limit of the torque that allows deformation of the members 21 and 22 to be fastened due to pressure from the countersunk head 12 and the nut 18 to be kept within the elastic range.

Since the strength (surface pressure strength) of the members to be fastened 21 and 22 made of aluminum alloy or fiber-reinforced resin is lower than that of iron or the like, iron or the like is placed between the members to be fastened 21 and 22 fastened by the countersunk bolt 10 . Only a lower fastening force F0 can be given compared to the case of using . Therefore, the frictional force between the members to be fastened 21 and 22 made of aluminum alloy or fiber-reinforced resin is lower than when the members to be fastened are made of iron or the like. Moreover, a gap 24 corresponding to the clearance C exists between the outer peripheral portion of the shaft portion 11 and the inner peripheral portion of the bolt insertion hole 20 . Therefore, for example, the members to be fastened 21 and 22 are likely to slip on each other due to an external load F1 such as vibration or aerodynamic load.

(elastic body)
Next, the elastic body 30 will be explained. The elastic body 30 is a member formed annularly from an elastic material such as rubber and arranged between the seat surface 12B and the receiving surface 21A. Both the outer diameter and the inner diameter of the elastic body 30 gradually increase from the shaft portion 11 toward the top surface 12A.
A substantially unloaded condition of the elastic body 30 is shown in FIGS. 2(a) and 2(b).

The elastic body 30 absorbs the bending displacement of the countersunk head 12 to reduce stress as will be described later. It is preferably arranged over the entire area. However, this is not essential, and it is permissible that the elastic body 30 is not arranged near the neck portion 12C of the countersunk head 12 and/or near the top surface 12A.

The elastic body 30 has low rigidity at least in the thickness direction with respect to both the countersunk bolt 10 and the member 21 to be fastened.
The elastic body 30 is elastically deformed by being pressed between the seat surface 12B and the receiving surface 21A during fastening. In addition, the elastic body 30 is elastically deformed by being pressed between the seat surface 12B and the receiving surface 21A when the countersunk bolt 10 is tilted by the members 21 and 22 to be fastened slipping on each other.

The elastic body 30 seals between the seat surface 12B and the receiving surface 21A. By sealing the space between the seat surface 12B and the receiving surface 21A, it is possible to reduce the air resistance due to the existence of the gap on the surface of the aircraft body.

A sealant made of polysulfide-based synthetic rubber or the like can be used so that the space between the seat surface 12B and the receiving surface 21A is more sufficiently sealed. The sealant is applied to the seat surface 12B and the receiving surface 21A in a fluid state, or is filled between the seat surface 12B and the receiving surface 21A and solidified to fill the space between the seat surface 12B and the receiving surface 21A. Seal.

The elastic body 30 includes a first region 31 on the radially inner side (shaft portion 11 side) and a second region 32 on the radially outer side (top surface 12A side).
Both the rigidity of the first region 31 and the rigidity of the second region 32 are low with respect to both the countersunk bolt 10 and the member to be fastened 21 . Here, the stiffness in the thickness direction of the elastic body 30 is compared.
The first region 31 and the second region 32 are within the elastic region even if the assumed maximum fastening force F0 and the assumed maximum load that presses the elastic body 30 due to the slippage of the fastened members 21 and 22 act. It elastically deforms and recovers from the elastically deformed state by unloading. Thickness and rigidity for realizing this are ensured in each of the first region 31 and the second region 32 .

An appropriate amount of elastic deformation in the thickness direction of the elastic body 30 is set for each of the first region 31 and the second region 32 based on the thickness and rigidity.
Here, the "maximum elastic deformation amount" is defined as the elastic deformation amount from the time when no load is applied to the maximum elastic deformation in the thickness direction up to the elastic limit.
The maximum elastic deformation amount δ1 of the first region 31 and the maximum elastic deformation amount δ2 of the second region 32 are different.

When the fastened members 21 and 22 slip due to the input of the load F1, the elastic deformation of the first region 31 and the second region 32 of the elastic body 30 reduces the bending stress of the countersunk head 12 .

The elastic body 30 can be made of an appropriate material such as a rubber material depending on the conditions of use corresponding to the machine or device provided with the disc fastener joint structure 1 .
For example, rubber materials such as styrene-butadiene rubber, isoprene rubber, butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, isobutene-isoprene rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, urethane rubber, silicone rubber, fluororubber, etc. The material used for 30 can be selected.

The elastic body 30 is not necessarily limited to a rubber material. A resin material such as polytetrafluoroethylene or polyamide can also be used for the elastic body 30 .

A metal material can also be used for the elastic body 30 as long as a rigidity lower than that of the fastened members 21 and 22 and the countersunk bolt 10 can be obtained. For example, when the countersunk bolt 10 is made of a titanium alloy and the member to be fastened 21 is made of an aluminum alloy, a metallic material having a smaller elastic modulus such as a longitudinal elastic modulus than the aluminum alloy, such as magnesium, phosphorus, The elastic body 30 can be made of tin, an alloy thereof, or the like.
Alternatively, even if a metal material having a higher elastic modulus than the aluminum alloy of the member to be fastened 21 is used in terms of a solid structure, the shape of the elastic body 30 can be changed by using a wire net-like or mesh-like material made of the metal material. The elastic body 30 may be given a lower rigidity than both the countersunk bolt 10 and the members 21 and 22 to be fastened.

When the application target is an aircraft, it is preferable to use a rubber material having necessary properties such as weather resistance and rigidity for the elastic body 30 . For example, silicone rubber, ethylene propylene diene rubber and the like are suitable.

As will be described below, each embodiment of the present invention differs in a method of realizing an appropriate maximum elastic deformation amount in each of the first and second regions 31 and 32 of the elastic body 30 .

[First embodiment]
In the first embodiment shown in FIGS. 1 to 3, unlike the second and third embodiments to be described later, the taper angle of the bearing surface 12B of the countersunk bolt 10 and the receiving surface 21A of the member to be fastened 21 are different. The taper angle is different.
Both the seat surface 12B and the receiving surface 21A are inclined such that the diameter increases from the shaft portion 11 side toward the top surface 12A, but the angles of inclination (θ1, θ2) are different.
That is, as shown in FIG. 1B, if the angle formed by the seat surface 12B with respect to the axis A is θ1, and the angle formed by the receiving surface 21A with respect to the axis A is θ2, then θ1<θ2.

Accordingly, the dimension of the gap between the bearing surface 12B and the receiving surface 21A is different between the radially inner side (the shaft portion 11 side) and the radially outer side (the top surface 12A side).
Therefore, in the first embodiment, the radially inner first region 31 and the radially outer second region 32 have different thicknesses in a no-load state where no load is applied to the elastic body 30 . . The thickness of the elastic body 30 arranged between the seat surface 12B and the receiving surface 21A gradually increases from the inner side to the outer side in the radial direction. Therefore, the maximum amount of elastic deformation of the elastic body 30 increases from the inner side toward the outer side in the radial direction.

From the above, as shown in FIG. 1B, when the thickness of the first region 31 is t1 and the thickness of the second region 32 is t2, t1<t2. The wall thicknesses t1 and t2 under no load are also t1<t2. The state of the elastic body 30 under no load is substantially the same as the state shown in FIGS. 2(a) and 2(b).

According to the elastic body 30 of the first embodiment, even if the rigidity of the first region 31 and the rigidity of the second region 32 in the thickness direction are the same, the difference in the thicknesses t1 and t2 causes the second region 32 to 2 is larger than the maximum elastic deformation .delta.1 obtained in the first region 31. As shown in FIG.
In the first embodiment, the entire elastic body 30 including the first region 31 and the second region 32 can be made of a single material.

In a no-load state (see FIGS. 2A and 2B), the outer peripheral portion 30A of the elastic body 30 forms an angle with respect to the axis A that is substantially the same as the angle θ2 of the receiving surface 21A (FIG. 1B). None. The inner peripheral portion 30B of the elastic body 30 forms an angle with respect to the axis A that is substantially the same as the angle θ1 (FIG. 1(b)) of the seat surface 12B.
An inclination angle different from the angle θ2 can be given to the outer peripheral portion 30A, and an inclination angle different from the angle θ1 can be given to the inner peripheral portion 30B. The inclination angle of the inner peripheral portion 30B can be appropriately determined according to the desired thickness of the second region 32 among the first and second regions 31 and 32 .

Before fastening, the elastic body 30 can be attached to the countersunk head 12 of the countersunk bolt 10 as shown in FIG. 2(a). By setting the diameter of the inner peripheral portion of the elastic body 30 smaller than the diameter of the shaft portion 11 and the diameter of the countersunk head 12 of the countersunk bolt 10, the elastic force of the elastic body 30 causes the elastic body 30 to be attached to the countersunk bolt 10. can hold. Then, the countersunk bolt 10 and the elastic body 30 can be handled integrally, so that the fastening work is easy.

The elastic body 30 does not necessarily have to be attached to the countersunk bolt 10 . As shown in FIG. 2(b), the elastic body 30 may be arranged on the receiving surface 21A at the time of fastening, and the shaft portion 11 of the countersunk bolt 10 may be passed through the hole inside the inner end 30C of the elastic body 30. As shown in FIG.

In the example shown in FIG. 2(a) or (b), the top portion 30D of the elastic body 30 is set lower than the top surface 12A of the countersunk head 12 and the surface 21B of the member to be fastened 21 in an unloaded state. . In this example, when the top portion 30D is pushed up from between the seat surface 12B and the receiving surface 21A during fastening, the top portion 30D of the elastic body 30, like the top surface 12A of the countersunk head 12, is pushed up from the surface of the member 21 to be fastened. 21B and flush with each other.
However, the top portion 30D of the elastic body 30 does not necessarily need to be arranged flush with the surface 21B. Even if the top portion 30D is located below the surface 21B, it is possible to smooth the fuselage surface by applying a sealant to the top portion 30D, for example.

2(a) and 2(b), the countersunk bolt 10 is inserted into the bolt insertion hole 20, and one of the countersunk bolt 10 and the nut 18 is rotated about the axis with respect to the other. , the male thread 11A and the female thread of the nut 18 are engaged to fasten the fastened members 21 and 22 as shown in FIGS. 1(a) and 1(b).
At the time of fastening, the countersunk bolt 10 is displaced in the axial direction of the shaft portion 11 with respect to the fastened members 21 and 22, so that the elastic body 30 is pressed between the receiving surface 21A and the seat surface 12B and is elastically deformed. At this time, the elastic body 30 can be regarded as being elastically deformed by a constant amount of deformation in the thickness direction over the entire area from the radially inner side to the outer side. The elastic body 30 is maintained in an elastically deformed state by the fastening force F0 of the countersunk bolt 10 .

Even if elastically deformed by fastening, the amount of elastic deformation of each of the first regions 31 and 32 does not reach the maximum amount of elastic deformation. That is, the first region 31 and the second region 32 can be elastically deformed in the thickness direction by further applying a load.
If it is not necessary for the elastic body 30 to seal between the seat surface 12B and the receiving surface 21A, the elastic body 30 may be in a no-load state when the fastening is completed.

Main actions of the elastic body 30 will be described with reference to FIGS. 3 and 9. FIG. The actions described below also apply to the elastic bodies of the second and subsequent embodiments.
As shown in FIG. 3, due to an external load F1 such as an aerodynamic load, the members to be fastened 21 and 22 are separated from each other by a gap 24 between the outer peripheral portion of the shaft portion 11 and the inner peripheral portion of the bolt insertion hole 20. slide. Accordingly, the countersunk bolt 10 is inclined with respect to the axis A of the bolt insertion hole 20 .
Then, the load F1 is transmitted from the shaft portion 11 to the fastened members 21 and 22 while generating shear stress in the shaft portion 11, and the reaction force from the receiving surface 21A against which the seat surface 12B of the countersunk head 12 abuts is generated. occur. At this time, the bending deformation of the countersunk head 12 due to the reaction force from the receiving surface 21A is relieved by the elastic deformation of the elastic body 30 in the thickness direction.

As shown in FIG. 9, when the elastic body 30 does not exist, the countersunk head 81 is bent and deformed by the countersunk head 81 due to the reaction force from the receiving surface 91A as the countersunk bolt 8 tilts as the members to be fastened 91 and 92 slide. However, according to the present embodiment, the bending deformation of the countersunk head 12 can be alleviated by the elastic body 30 as shown in FIG. 3 to reduce the stress. In other words, the bending stress of the countersunk head 12 is reduced by the elastic deformation of the elastic body 30 instead of the deformation of the countersunk head 12 .

In the example shown in FIG. 3, the countersunk head 10 is inclined as a whole so that the countersunk head 12 is shifted to the right side in FIG. is pressed against the receiving surface 21A. Therefore, from the state shown in FIG. 1B, the elastic body 30 is compressed on the right side of FIG. 3 and expanded on the left side of FIG.

As can be understood from the shape shown by the two-dot chain line and the shape shown by the solid line of the countersunk head 81 that is not bent and deformed in FIG. displacement increases from the neck portion 12</b>C toward the radially outer side of the countersunk head 12 . The maximum elastic deformation amount of each of the first region 31 and the second region 32 of the elastic body 30 corresponds to the distribution of the bending displacement amount of the countersunk head 12 . That is, the maximum elastic deformation amount δ2 in the radially outer second region 32 where the amount of bending displacement of the countersunk head 12 is relatively large is larger than the maximum elastic deformation amount δ1 in the radially inner first region 31 .

Therefore, the relatively large radially outward bending displacement of the countersunk head 12 is absorbed by the elastic deformation of the second region 32 that has left a larger amount of deformation in the elastic region than the first region 31 . . Then, the bending deformation of the countersunk head 12 can be relieved by the elastic body 30 over the entire area from the first region 31 to the second region 32 . As a result, it is possible to reduce the bending stress of the countersunk head 12 and avoid stress concentration on the neck portion 12C in particular.

Depending on the rigidity of each of the member to be fastened 21 and the countersunk bolt 10, the countersunk head 12 may be bent when the countersunk bolt 10 is tilted due to the sliding of the members to be fastened 21 and 22 when the elastic body 30 is not used. Without deformation, it may be pressed against the member to be fastened 21 with a force exceeding the reaction force from the receiving surface 21A. Even in such a case, the elastic body 30 is interposed between the receiving surface 21A and the seat surface 12B. By doing so, when the countersunk bolt 10 is tilted, the radially outer displacement of the countersunk head 12, which is relatively large with respect to the receiving surface 21A, is absorbed by the elastic deformation of the second region 32 of the elastic body 30. Therefore, it is possible to reduce the stress of the member to be fastened 21 and prevent the receiving surface 21A from compressively breaking.

As described above, according to the disc fastener joint structure 1 having the elastic body 30, the second region 32 on the radially outer side of the elastic body 30 has a larger elastic deformation amount δ1 than the maximum elastic deformation amount δ1 of the first region 31 on the radially inner side. Since the maximum elastic deformation amount δ2 is set, the stress generated in the countersunk fastener joint structure 1 can be reduced even if the members to be fastened 21 and 22 slip and the countersunk bolt 10 tilts accordingly.
Contrary to the present embodiment, if the radially inner first region 31 where the bending displacement of the countersunk head 12 is small is set to a maximum elastic deformation amount larger than the maximum elastic deformation amount of the second region 32, In other words, the stress reduction effect is smaller than that of the present embodiment.

As described above, according to the disk fastener joint structure 1 of the present embodiment, the action of the elastic body 30 can reduce the stress generated in the disk fastener joint structure 1 . Therefore, damage to the countersunk bolt 10 due to bending stress and compression failure of the member to be fastened 21 against which the countersunk head 12 abuts can be prevented, and the countersunk fastener joint structure 1 can be maintained in a sound state.
The slippage of the members 21 and 22 to be fastened can be caused by vibrations of the device including the Belleville fastener joint structure 1 or, in the case of an aircraft, a repeated load F1 accompanying pressure fluctuations during flight. Due to the action of the elastic body 30, fatigue failure of the disc fastener joint structure 1 can be prevented.

The thicknesses t1 and t2 of the first region 31 and the second region 32 of the elastic body 30 do not necessarily have a relationship of t1<t2.
However, as in the case of t1<t2, the maximum elastic deformation amount δ2 set in the second region 32 is larger than the maximum elastic deformation amount δ1 set in the first region 31, and after fastening, the first, A requirement is that further elastic deformation is possible in the second regions 31 , 32 .

[Modified example of elastic body]
The elastic body 35 shown in FIG. 4 has a cover region 33 that covers the top surface 12A of the countersunk head 12 in addition to the first region 31 and the second region 32 . The cover area 33 covers the entire top surface 12A. The elastic body 35 is mounted around the countersunk head 12 by inserting the countersunk head 12 inside the inner end 30C of the elastic body 35 . By rotating the nut 18 with respect to the countersunk bolt 10 to which the elastic body 35 is attached, the members 21 and 22 to be fastened can be fastened. A sealant S is filled around the cover region 33 .
If a groove 12D for inserting a tool is formed in the countersunk head 12 as shown in FIG. 35 is attached to the countersunk head 12, fastening work can be performed by inserting a tool into the groove 12D. When the defective portion corresponding to the groove 12D is filled with a sealant or the like, the top surface 12A is entirely covered.

The elastic body 35 is typically made of an insulating rubber material or resin material. By covering the countersunk head 12 with the insulating elastic body 35, the conductive countersunk head 12 is prevented from being exposed on the surface of the member to be fastened 21, thereby preventing excessive current from flowing through the countersunk bolt 10 when struck by lightning. can be prevented. In particular, when the member to be fastened 21 is made of a fiber-reinforced resin having a low conductivity compared to a metal material, and lightning current tends to concentrate on the countersunk bolt 10, if the elastic body 35 is used, a sealant or the like is used. Compared to the case, the countersunk bolt 10 can be stably provided with insulation.

As with the elastic body 30 of the first embodiment, the elastic body 35 is configured such that the second region 32 is thicker than the first region 31, but the present invention is not limited to this.
It is also possible to provide the cover region 33 to the elastic body in the second and subsequent embodiments.

[Second embodiment]
Next, a disk fastener joint structure 2 according to a second embodiment will be described with reference to FIG.
The following description focuses on matters that are different from the first embodiment. The same symbols are given to the same components as in the first embodiment.
The Belleville fastener joint structure 2 includes an elastic body 40 arranged between the receiving surface 21A and the bearing surface 12B. In the second embodiment, the angle θ1 of the seat surface 12B with respect to the axis A and the angle θ2 of the receiving surface 21A with respect to the axis A are the same. The angle θ1 and the angle θ2 may be slightly different depending on the size and shape of the seat surface 12B and the receiving surface 21A and the tolerance of assembly.

Since the angles θ1 and θ2 are the same, the thickness of the elastic body 40 sandwiched between the receiving surface 21A and the bearing surface 12B is constant when the members 21 and 22 are fastened by the countersunk bolt 10. is. Therefore, the thickness t1 of the first radially inner region 41 and the thickness t2 of the radially outer second region 42 of the elastic body 40 shown in FIG. 5 are the same. The respective thicknesses t1 and t2 of the first region 41 and the second region 42 under no load may also be constant over the first region 41 and the second region 42 . Note that the thickness t1 of the first region 41 and the thickness t2 of the second region 42 may be slightly different due to the dimensional tolerance of the elastic body 40 .

The Belleville fastener joint structure 2 of the second embodiment is characterized in that k1>k2, where k1 is the stiffness of the first region 41 and k2 is the stiffness of the second region 42 in the thickness direction of the elastic body 40. . Rigidities k1 and k2 are lower than both the rigidity of countersunk bolt 10 and the rigidity of fastened member 21 in the thickness direction of elastic body 40 .

In the second embodiment, even if the thickness of the elastic body 40 is constant, the stiffness k2 of the second region 42 is lower than the stiffness k1 of the first region 41. 1. Similarly to the second regions 31 and 32, the maximum elastic deformation amount δ2 of the second region 42 is larger than the maximum elastic deformation amount δ1 of the first region 41 .

Each of the first region 41 and the second region 42 can be molded using a material appropriately selected from the above-described rubber materials, resin materials, and the like. Among the materials having different elastic moduli, one material having a relatively large elastic modulus can be used for the first region 41 and the other material having a relatively small elastic modulus can be used for the second region 42 .
Alternatively, while using the same material for the first region 41 and the second region 42, for example, by forming the first region 41 solid and forming the second region 42 hollow or mesh-like, k1>k2 can satisfy the requirements of

The first region 41 and the second region 42 may be integrated by being separately molded and joined, or may be integrally formed by two-color molding, which is injection molding using two materials, or lamination molding. It may be molded. According to layered manufacturing, it is possible to easily form structures having different rigidity (solid, mesh, etc.) as the first and second regions 41 and 42 .
Note that the first region 41 and the second region 42 do not necessarily have to be integrated. The elastic body 40 may consist of separate first and second regions 41 and 42 .

In the second embodiment, similarly to the first embodiment, the member 21 to be fastened is engaged with the countersunk bolt 10 and the nut 18 while the elastic body 40 is interposed between the receiving surface 21A and the seat surface 12B. , 22.
The elastic body 40 functions in the same manner as the elastic body 30 of the first embodiment when the fastened members 21 and 22 are fastened, so that the stress generated in the disc fastener joint structure 2 can be reduced.

The elastic body 40 may have a first region 41, a second region 42, and an intermediate region between the first and second regions 41 and 42. In this case, if the stiffness in the thickness direction of the intermediate region is k3, k1>k3>k2, that is, the stiffness of each region may be set so as to decrease stepwise from the inner side to the outer side in the radial direction.

[Third embodiment]
Next, referring to FIG. 6, a disc fastener joint structure 3 according to a third embodiment will be described.
The following description focuses on matters that differ from the second embodiment. The same reference numerals are given to the same configurations as in the second embodiment.
The elastic body 50 provided in the disc fastener joint structure 3 includes a first elastic portion 50A and a second elastic portion 50B. The first elastic portion 50A is shown in gray, and the second elastic portion 50B is shown in a grid pattern.
The rigidity ka of the first elastic portion 50A and the rigidity kb of the second elastic portion 50B are smaller than both the countersunk bolt 10 and the member 21 to be fastened.
The rigidity kb of the second elastic portion 50B in the thickness direction of the elastic body 50 is smaller than the rigidity ka of the first elastic portion 50A (ka>kb).

In the third embodiment, based on the volume ratio between the first elastic portion 50A and the second elastic portion 50B, the first region 51 on the radially inner side of the elastic body 50 and the second region on the radially outer side of the elastic body 50 52 are different in stiffness k1 and k2.
The first elastic portion 50A and the second elastic portion 50B are separated by a boundary B that crosses the thickness direction of the elastic body 50, and the second elastic portion increases from the inner side to the outer side in the radial direction of the elastic body 50. The volume ratio occupied by 50B is increasing.

Therefore, compared to the stiffness k1 of the first region 51, which is occupied by the first elastic portion 50A, which has a relatively high stiffness ka, the second elastic portion 50B, which has a relatively low stiffness kb, occupies a large ratio. The stiffness k2 of the region 52 is small (k1>k2). In this respect, the third embodiment is similar to the above-described second embodiment.
However, in the third embodiment, the rigidity of the elastic body 50 gradually decreases from k1 to k2 as it goes radially from the inner side to the outer side. Accordingly, the maximum elastic deformation amount of the elastic body 50 increases from the inner side to the outer side in the radial direction, so in this respect the third embodiment is the same as the first embodiment.

The elastic body 50 of the third embodiment also functions in the same manner as the elastic body 30 of the first embodiment in a state where the members to be fastened 21 and 22 are fastened, thereby reducing the stress generated in the disc fastener joint structure 3. can be done.
Further, compared to the boundary between the first and second regions set along the thickness direction of the elastic body 40 as in the second embodiment, the boundary B in the third embodiment extends over the entire radial direction of the elastic body 50. Since it extends widely, when the first elastic portion 50A and the second elastic portion 50B are joined, a large joint area can be ensured and a sufficient joint strength can be ensured.

The boundary B between the first elastic portion 50A and the second elastic portion 50B is not limited to the example shown in FIG.
Based on the volume ratio of the first elastic portion 50A and the second elastic portion 50B, as long as the stiffness of the first region 51 and the second region 52 satisfies k1>k2, the first elastic portion 50A and the second elastic portion 50B can be determined as appropriate.

[Fourth embodiment]
The Belleville fastener joint structure 4 shown in FIG. 7 is constructed by combining features of the first embodiment (FIG. 1) and the second embodiment (FIG. 5).
That is, with respect to the angles θ1 and θ2 of the seat surface 12B and the receiving surface 21A, θ1<θ2, and the thickness direction stiffness k1, As for k2, k1>k2.
By combining the features of the first and second embodiments, the difference between the maximum elastic deformation amounts δ1 and δ2 of the first region 61 and the second region 62 can be increased. It is possible to set a maximum elastic deformation amount that is larger than the maximum elastic deformation amount obtained in the second regions 32 and 42 described above.

Although illustration is omitted, the same effects as those of the fourth embodiment can be obtained by combining the first embodiment (FIG. 1) and the third embodiment (FIG. 6).

By combining the features of multiple embodiments, the degree of freedom in designing the stress of the joint structure is increased, so that the optimal configuration can be realized for various countersunk bolts, loads, and other conditions.

[Fifth embodiment]
A countersunk fastener joint structure 5A shown in FIG. It has a second elastic body 70 arranged between the peripheral part.
The first elastic body 30 is the same as the elastic body 30 of the first embodiment.

A countersunk fastener joint structure 5B shown in FIG. It has a second elastic body 70 arranged between the peripheral part.

The configuration and effects of the second elastic body 70 common to FIGS. 8(a) and 8(b) will be described below.
The second elastic body 70 can be configured using a rubber material, a resin material, or a metal material, like the elastic body 30 of the first embodiment. The rigidity of the second elastic body 70 in the thickness direction (the radial direction of the shaft portion 11) is lower than the rigidity of the shaft portion 11 and the rigidity of the fastened members 21 and 22 in the same direction.

The second elastic body 70 can be molded in a cylindrical shape. In this case, the second elastic body 70, which is a molded body, can be mounted around the shaft portion 11 by elastic force. The second elastic body 70 of the molded body is preferably arranged over a wide range of the outer peripheral portion of the shaft portion 11 while avoiding the area of the male thread 11A. By inserting the shaft portion 11 to which the second elastic body 70 is attached into the bolt insertion hole 20 and engaging the nut 18 with the external thread 11A (FIG. 1(a)) of the shaft portion 11, the countersunk bolt 10 is fastened. The members 21, 22 can be fastened.
In addition, since the clearance C is set between the shaft portion 11 and the inner peripheral portion of the bolt insertion hole 20, the clearance C is not set while the second elastic body 70 is elastically deformed in the radial direction. The shaft portion 11 can be easily inserted into the bolt insertion hole 20 as compared with .

The second elastic body 70 does not necessarily have to be shaped before fastening. For example, the second elastic body 70 may be applied inside the bolt insertion hole 20 in a fluid state like a sealant and solidified inside the bolt insertion hole 20 . By inserting the shaft portion 11 into the bolt insertion hole 20 in a state where the fluid sealant adheres to the inner peripheral portion of the bolt insertion hole 20 and engaging the male screw 11A with the nut 18, the sealant is applied to the outer periphery of the shaft portion 11. and the inner peripheral portion of the bolt insertion hole 20 .

As shown in FIG. 3, when the members to be fastened 21 and 22 slide against each other due to the load F1, the second elastic body 70 is elastically deformed in the radial direction, so that the shaft portion 11 of the countersunk bolt 10 is elastically supported. The inclination displacement of the countersunk bolt 10 is alleviated. At this time, the second elastic body 70 indirectly suppresses the slippage of the members 21 and 22 to be fastened.
According to the fifth embodiment, even if the members 21 and 22 to be fastened slip, the elastic deformation of the second elastic body 70 mitigates the tilt displacement of the countersunk bolt 10 . Forced bending deformation of the countersunk head 12 caused by pressing between the seat surface 12B and the receiving surface 21A is alleviated. Therefore, the stress generated in the disc fastener joint structures 5A, 5B can be further reduced than in the first to fourth embodiments.

In addition to the above, it is possible to select the configurations described in the above embodiments or to change them to other configurations as appropriate without departing from the gist of the present invention.

The countersunk head 12 of the countersunk bolt 10 is not limited to having a flat top surface 12A as in each of the above embodiments, and may have a convexly curved top surface.
Also, the countersunk bolt 10 may be engaged with a female thread formed in a member to be fastened. In this case the nut 18 is not required.

The countersunk fastener in the present invention is not limited to the countersunk bolt 10 that can be attached to and removed from the members 21 and 22 to be fastened, and may be a columnar or cylindrical rivet having a countersunk head 12 .
Even if such a countersunk rivet is used and the members to be fastened 21 and 22 may slip due to the existence of a gap between the shaft portion of the countersunk rivet and the inner peripheral portion of the insertion hole, the bearing surface 12B of the countersunk head 12 does not. The stress generated in the joint structure can be reduced by the action of the elastic body (30 or the like) interposed between the bearing surface 21A and the receiving surface 21A.

1 to 4, 5A, 5B Countersunk fastener joint structure 8 Countersunk bolt 10 Countersunk bolt 11 Shaft part 11A Male screw 11B Tip part 12 Countersunk head 12A Top surface 12B Seat surface 12C Neck part 12D Groove 18 Nut 18A End surface 20 Bolt insertion hole (insertion hole)
21 member to be fastened 21A receiving surface 21B surface 22 member to be fastened 22A surface 24 gaps 30, 35, 40, 50, 60 elastic body 30A outer peripheral portion 30B inner peripheral portion 30C inner end 30D top portion 31, 41, 51, 61 first region 32, 42, 52, 62 Second region 33 Cover region 50A First elastic portion 50B Second elastic portion 70 Second elastic body 81 Countersunk head 81A Neck portion 81B Seat surfaces 91, 92 Fastened member 91A Receiving surfaces 201, 202 Insertion hole A Axis B Boundary C Clearance F0 Fastening force F1 Load M Moment k1, k2 Rigidity ka, kb Rigidity S Sealant t1, t2 Thickness δ1, δ2 Maximum elastic deformation θ1, θ2 Angle

Claims (10)

a countersunk head fastener including a shank and an inverted truncated conical countersunk head whose diameter increases from the shank toward the top surface;
a plurality of fastened members fastened by the countersunk fastener;
an annular elastic body arranged between the seat surface of the countersunk head and a receiving surface formed on the one member to be fastened and receiving the seat surface;
the elastic body has an inner diameter and an outer diameter that increase from the shaft toward the top surface, and includes a first region on the shaft portion side and a second region on the top surface side;
Both the first region and the second region have lower rigidity in the thickness direction of the elastic body than the member to be fastened on which the countersunk fastener and the receiving surface are formed,
Compared to the maximum elastic deformation amount in the thickness direction set in the first region,
A countersunk fastener joint structure, wherein the maximum amount of elastic deformation in the thickness direction set in the second region is large. The countersunk fastener is a bolt that can be attached to and detached from the member to be fastened,
2. A Belleville fastener joint structure according to claim 1. θ1 is the angle formed by the seat surface with respect to the axis of the insertion hole of the member to be fastened into which the disk fastener is inserted;
Assuming that the angle formed by the receiving surface with respect to the axis is θ2,
θ1<θ2,
The countersunk fastener joint structure according to claim 1 or 2. t1 is the thickness of the first region in an unloaded state,
Assuming that the thickness of the second region in the unloaded state is t2,
t1<t2,
A Belleville fastener joint structure according to claim 3. k1 for the stiffness of the first region;
Assuming that the stiffness of the second region is k2,
k1>k2,
Belleville fastener joint structure according to any one of claims 1 to 4. The elastic body includes a first elastic portion and a second elastic portion having different rigidity in the thickness direction,
The rigidity kb of the second elastic portion is smaller than the rigidity ka of the first elastic portion,
k1>k2 based on the volume ratio of the first elastic portion and the second elastic portion;
A Belleville fastener joint structure according to claim 5. A second connector which is disposed between the shaft portion and the inner peripheral portion of the insertion hole of the member to be fastened into which the shaft portion is inserted, and has lower rigidity in the thickness direction than the shaft portion and the member to be fastened. 7. A countersunk fastener joint structure according to any one of claims 1 to 6, comprising an elastic body of . The elastic body includes a cover region covering the top surface,
Belleville fastener joint structure according to any one of claims 1 to 7. The member to be fastened is a member that constitutes the fuselage of an aircraft,
A Belleville fastener joint structure according to any one of claims 1 to 8. An annular elastic body arranged between the bearing surface of the countersunk head of the countersunk fastener and a receiving surface that is formed on one of a plurality of fastened members fastened by the countersunk fastener and receives the bearing surface,
the elastic body has an inner diameter and an outer diameter that increase from one axial direction to the other;
including a first region on one side in the axial direction and a second region on the other side in the axial direction ;
Compared to the maximum elastic deformation amount in the thickness direction set in the first region,
An elastic body for a disc fastener, wherein the maximum elastic deformation amount in the thickness direction set in the second region is large.

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