JP4784049B2 - Bolt fastening structure - Google Patents

Description

The present invention relates to a bolt fastening structure useful for reducing noise in a cylinder block having a ladder frame structure for an engine.

The main body of the engine is composed of a cylinder head, a cylinder block, an oil pan, and the like, and a cylinder block having a ladder frame structure is often used mainly for diesel engines with the aim of improving rigidity. As shown in FIG. 10, the cylinder block of the ladder frame structure has a configuration in which the bearing cap portion 20 is connected in a ladder shape.
With this configuration, the rigidity of the engine block and the support rigidity of the crankshaft are improved.

And in an engine, a cylinder head and a cylinder block are fastened by bolting, and various devices are made | formed in this fastening structure.

For example, in order to reduce thermal deformation based on the difference in coefficient of thermal expansion between the cylinder block and cylinder head, a cylindrical positioning pin is installed concentrically with the bolt hole, and this positioning pin is used for thermal expansion. An engine cylinder head positioning device provided on a small intake side has been proposed (see, for example, Patent Document 1).

Also, when the bolts of the cylinder and cylinder head are inserted into the stud bolts installed in the crankcase and the nuts are fastened to the upper ends of the stud bolts, the stud bolts are tilted by vibration during engine operation. In order to prevent vibration noise from coming into contact with the bolt holes of the cylinder, etc., elastic cylinders are inserted around both ends of the cylinder bolt holes and around the cylinder head bolt holes. An engine cylinder and cylinder head mounting device has been proposed in which stud bolts are applied to the cylinder (for example, Patent Document 2).
reference. ).

  On the other hand, the inventors have obtained the following knowledge through experiments and the like.

In other words, it has been found that the influence of the joint between the joint members such as the cylinder head, cylinder block, and oil pan on the vibration characteristics and noise of the engine is large, and the pressure distribution on the joint surface is more uniform. As the true contact area, which is the area actually receiving pressure, is wider, the damping action at the joint surface becomes larger. In other words, the wider the contact area and the wider the contact pressure, the greater the frictional damping of the joint, which is thought to be due to the frictional damping effect due to the micro-slip between the joint surfaces, and the vibration suppression effect and noise reduction effect increase. I understood.

From this point of view, when the bolt tightening state is observed in detail, as shown in FIG.
When the joining members 10X and 20X are overlapped, the bolt 30 is screwed into the female screw portion 11 of the first joining member 10X through the bolt hole 21 of the second joining member 20X, and the bolt 30 is tightened.
Gradually, the periphery of the female thread portion 11 screwed into the bolt 30 is deformed and rises on the joint surface. Then, as indicated by a dotted line B in FIG. 7, the contact surface pressure around the female screw portion 11 is increased, and the contact surface pressure is remarkably decreased at a portion away from the female screw portion 11 in the radial direction. In this state, since the joint surface pressure is supported only by the peripheral portion of the female screw portion 11, the contact force between the joining members 10X and 20X is weakened, and the structure damping action generated at the joint portion is reduced.
Japanese Utility Model Publication No. 58-75936 JP 2002-285822 A

An object of the present invention is to join a plurality of joint members by screwing a bolt into a female thread portion of one joining member, and a joining surface in the vicinity of the female screw portion hole of one joining member having the female thread portion. An object of the present invention is to provide a bolt fastening structure capable of reducing noise by making the pressure distribution uniform and increasing the structure damping action on the joint surface.

To achieve the above object, a bolt fastening structure according to the present invention is used in an engine structural component or engine structure, and is bolted to the bolt in a bolt fastening structure in which a plurality of joining members are fastened using bolts. A concave portion is formed in a portion through which the bolt is inserted in at least one of the joint surfaces of the first joint member having the female screw portion and the second joint member in contact with the first joint member, and the length under the neck of the bolt is determined. When L (mm), the thread pitch is p (mm), and the Young's modulus is E (kgf / mm ² ), the depth of the recess is the lower limit of 0.18 × L / E (mm) or more. The upper limit value is 4.0 × p (mm) or less, and the lower limit value is decreased as the Young's modulus is increased, and the upper limit value is increased as the pitch is increased.

The recess only needs to be able to form a space that can absorb the rising deformation of the first joining member, that is, a range in which the rising deformation can be escaped. As shown in FIGS. A simple cross section may be a triangle, a circular arc, an elliptical arc, or the like). This recess can be processed by spot facing. The planar shape is usually formed in a circular shape because it is easy to process, but may be a polygon such as a quadrangle or a hexagon, or other shapes if restricted by the joining site. .

According to this configuration, when the presser bolt and the stud bolt are joined by the bolt, the bulge deformation around the female screw portion hole provided with the female screw portion and the female screw portion of the first joint member on the joint surface in the concave portion is absorbed. The distribution of the joint surface pressure in the periphery can be made uniform, and the structure damping effect on the joint surface can be increased.

And if this recessed part is a magnitude | size which can absorb the bulging deformation | transformation of the circumference | surroundings of the internal thread part (including the hole for internal thread parts provided with the internal thread part) in the joint surface of a 1st joining member which arises by the clamping force of a volt | bolt. It is good, but when the length under the neck of the bolt is L (mm), the pitch of the thread is p (mm), and the Young's modulus is E (kgf / mm ² ), the depth of the recess is the bolt In the case where the concave portion is formed in a circular shape, the length of the thread in the bolt is determined based on the length L (mm) below the neck , the pitch p (mm) of the thread, and the Young's modulus E (kgf / mm ² ). When the pitch is p (mm) and the bolt diameter is D (mm), the radius of the recess is 0.5 × D + 1.5 × p (mm) or more, 0.5 × D + 4.0 × p ( as mm) or less, the radius of the concave portion, the threads of the pitch By being determined on the basis of p (mm) and the bolt diameter D (mm), it is possible to obtain a more suitable bonding surface pressure distribution, a large effect of increasing the structural damping. The bolt diameter D refers to the male screw outer diameter.

When the depth of the recess is smaller than 0.18 × L / E (mm), the swell of the first joining member cannot be sufficiently absorbed, and when the depth is larger than 4.0 × p (mm). Since the second joint member and the thread engagement portion are too far apart, the rigidity of the joint portion is reduced, and the effect cannot be obtained. This range was obtained as a simple expression convenient for practical use by analyzing the phenomenon of swell deformation. In addition, when providing a recessed part in both the 1st joining member and the 2nd joining member, the sum of the depth of both recessed parts will respond | correspond to the depth of this recessed part.

Moreover, the range where the radius of the concave portion is 0.5 × D + 1.5 × p (mm) or more and 0.5 × D + 4.0 × p (mm) or less is the range where the contact surface pressure is the highest, and the deformation is increased. This is a simple expression that is useful for practical use. In this range, the surface pressure can be made uniform by escaping the swell deformation. Note that this range hardly changes if the material is used for engine structural parts .

And this bolt fastening structure is a holding bolt used for an engine structure, for example,
It can be applied to the bolt fastening part that connects the engine and the transmission, and the holding bolt that attaches the engine accessory to the cylinder block. When the member to be formed is a cylinder block having an engine ladder frame structure, the effect is particularly great, and the structural damping against vibration and noise can be increased without lowering the rigidity of the cylinder block structure. This increase in structural damping can greatly reduce the noise emitted from the engine. This effect is conspicuous in the frequency range where the noise radiated from the engine block is the largest, and can contribute to a significant reduction in engine noise.

According to the bolt fastening structure of the present invention, when a plurality of joining members are joined by screwing a bolt to the female thread portion of the first joining member, the female thread portion and the female screw portion of the first joining member at the joining surface at the concave portion. It is possible to absorb the bulging deformation around the female screw hole provided with the same, to uniformize the distribution of the joint surface pressure in the periphery, and to increase the structure damping action on the joint surface against vibration and noise.

And, when the bolt fastening structure of the present invention is applied to a cylinder block having a ladder frame structure, it is possible to increase structural damping against vibration and noise without lowering the rigidity of the cylinder block structure, and to reduce engine noise. Can do.

DESCRIPTION OF EMBODIMENTS Hereinafter, a bolt fastening structure according to an embodiment of the present invention will be described with reference to the drawings, taking as an example an engine bolt fastening structure including a cylinder block having an engine ladder frame structure.

As shown in FIG. 1 , a cylinder block having a ladder frame structure has a first joint member 10 constituting an upper cylinder block portion and a second joint member 20 constituting a lower ladder frame portion joined by bolts 30. It is formed. The bolt 30 is inserted through the bolt hole 21 of the second joining member 20 from the lower side and is screwed into the female screw portion 11 of the first joining member 10.

In the bolt fastening structure 1A of the first embodiment shown in FIGS. 1 and 2, in the first joining member 10 having the female screw portion 11 into which the fastening bolt 30 is screwed, a recess is formed around the female screw portion 11 of the joining surface 12. 13 is provided. The recess 13 has a neck length L (mm) in the fastening bolt 30, a thread pitch p (mm), a Young's modulus (longitudinal elastic modulus) E (kgf / mm ² ), a bolt diameter (external thread external) When the diameter is D (mm), the depth h (mm) of the recess 13 is the thread pitch p (mm), the length L (mm) under the fastening bolt 30 and the Young's modulus E (kgf). / Mm ² ), it is determined to satisfy (0.18 × L / E) ≦ h ≦ (4.0 × p), and when the recess 13 is formed in a circle, the recess 13 Is based on the thread pitch p (mm) and the bolt diameter D (mm) of the fastening bolt 30 (0.5 × D + 1.5 × p) ≦ r ≦ (0.5 × D + 4.0 × p) .

When the depth h of the recess is smaller than this range, the swell of the first joining member 10 cannot be sufficiently absorbed, and when it is larger, the second joining member 20 and the thread engagement portion are too far apart. As a result, the rigidity of the joint is lowered, and the effect cannot be obtained .

The radius r of the concave portion is obtained by analyzing the phenomenon of swell deformation and obtaining a range where the contact surface pressure increases as a simple formula that is practically convenient. In this range, the surface pressure is uniformed by escaping the swell deformation. Can be achieved. Note that this range hardly changes if the material is used for engine structural parts .

In the bolt fastening structure 1B of the second embodiment shown in FIGS. 3 and 4, the fastening bolt 30 is inserted through the joint surface 22 of the second joint member 20 that joins the first joint member 10 having the male screw portion 11. A recess 23 is provided around the bolt 21. Similarly to the concave portion 13 of the first embodiment, the concave portion 23 has a depth h (mm) of the concave portion 23, a thread pitch p (mm), and a neck length L (mm) of the fastening bolt 30. And the Young's modulus E (kgf / mm ² ), it is determined to satisfy (0.18 × L / E) ≦ h ≦ (4.0 × p), and the radius r (mm) of the recess 23 is Based on the thread pitch p (mm) and the bolt diameter D (mm) of the fastening bolt 30 , a range of (0.5 × D + 1.5 × p) ≦ r ≦ (0.5 × D + 4.0 × p) It has been decided to be inside .

In the bolt fastening structure 1C of the third embodiment shown in FIGS. 5 and 6, in the first joining member 10 having the female screw portion 11 into which the fastening bolt 30 is screwed, a recess is formed around the female screw portion 11 of the joining surface 12. 13, and also in the second joint member 20 joined to the first joint member 10, a recess 23 is provided around the bolt hole 21 through which the fastening bolt 30 is inserted.

In the recesses 13 and 23, the sum h (mm) of both depths is the thread pitch p (mm), the neck length L (mm) of the fastening bolt 30, and the Young's modulus E (kgf / mm ² ). (0.18 × L / E) ≦ h ≦ (4.0 × p), and the radius r (mm) of both recesses 13 and 23 is the thread pitch p ( mm) and the bolt diameter D (mm) of the fastening bolt 30 are determined so as to be within the range of (0.5 × D + 1.5 × p) ≦ r ≦ (0.5 × D + 4.0 × p). Has been. In addition, although it is preferable on the process that this radius r is the same in both, it does not need to be the same.

According to these configurations, when the fastening bolt 30 is screwed into the female screw portion 11 and tightened, as shown schematically in FIGS. 2, 4, and 6, the fastening bolt 30 is fastened to the female screw portion 11 of the first joining member 10. Bolt 3
A force in the direction of the bolt axis due to tightening of 0 acts and a bulge is generated in the vicinity of the female screw portion 11. However, since at least one of the concave portion 13 or the concave portion 23 is provided, the bulged portion is absorbed by the concave portion 13 or the concave portion 23. Since this is possible, the first outside the recess 13 and the recess 23
The joint surface pressure between the joining member 10 and the second joining member 20 can be made uniform.

As can be seen from a comparison of the joint surface pressure (solid line A) of the bolt fastening structure 1A, 1B, 1C, etc. of the present invention shown in FIG. , 23 can suppress the joint surface pressure from significantly increasing around the female screw portion 11 and the bolt hole 21.

Therefore, this uniform joint surface pressure increases the structural damping against engine vibration,
Noise emitted from the engine can be greatly reduced. Since this effect appears remarkably in the frequency range where the noise emitted from the engine block is the largest, the generation of engine noise can be greatly reduced.

The bolt fastening structure of the present invention is particularly effective when applied to a cylinder block having a ladder frame structure as shown in FIG. 10, but the present invention is not limited to this, and the presser bolt used for the engine structure is not limited to this. All can be applied. For example, it can be applied to a bolt fastening portion that connects the engine and the transmission, a presser bolt that attaches the engine accessory to the cylinder block, and the like.

It is a fragmentary sectional view showing the bolt conclusion structure of a 1st embodiment concerning the present invention. It is a fragmentary sectional view which shows typically the bolt fastening state in the bolt fastening structure of FIG. It is a fragmentary sectional view which shows the bolt fastening structure of 2nd Embodiment which concerns on this invention. It is a fragmentary sectional view which shows typically the bolt fastening state in the bolt fastening structure of FIG. It is a fragmentary sectional view which shows the bolt fastening structure of 3rd Embodiment which concerns on this invention. It is a fragmentary sectional view which shows typically the bolt fastening state in the bolt fastening structure of FIG. It is a figure which shows typically the joint surface pressure of the radial direction around an internal thread part and a bolt hole. It is a fragmentary sectional view which shows the bolt fastening structure of another embodiment which concerns on this invention. It is a fragmentary sectional view which shows the bolt fastening structure of another embodiment which concerns on this invention. It is a perspective view which shows an example of the cylinder block which has a ladder frame structure. It is a fragmentary sectional view showing typically the bolt tightening state in the bolt fastening structure of the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder block 10 1st joining member 11 Female thread part 12 Joining surface 13 Recessed part 20 2nd joining member 21 Bolt hole 22 Joining surface 23 Recessed part 30 Bolt D Bolt diameter (mm)
E Young's modulus of bolt (kgf / mm ² )
L Neck length of fastening bolt (mm)
h Depth of recess (mm)
p Bolt thread pitch (mm)
r Radius of recess (mm)

Claims (3)

In a bolt structure used for an engine structural component or an engine structure, in which a plurality of joining members are fastened using bolts, a first joining member having a female thread portion screwed into the bolts is in contact with the first joining member. A recess is formed in a portion through which the bolt is inserted in at least one joining surface with the second joining member, a length under the neck of the bolt is L (mm), a thread pitch is p (mm), and a Young's modulus. Is E (kgf / mm ² ), the depth of the recess is not less than the lower limit of 0.18 × L / E (mm) and not more than the upper limit of 4.0 × p (mm), The bolt fastening structure, wherein the lower limit value is decreased as the Young's modulus is increased, and the upper limit value is increased as the pitch is increased . In the case where the concave portion is formed in a circular shape, when the pitch of the screw thread in the bolt is p (mm) and the diameter of the bolt is D (mm), the radius of the concave portion is 0.5 × D + 1.5 ×. 2. The bolt fastening structure according to claim 1, wherein the bolt fastening structure is not less than p (mm) and not more than 0.5 × D + 4.0 × p (mm) . The bolt fastening structure according to claim 1 or 2, wherein a member obtained by joining the joining members is a cylinder block having a ladder frame structure of an engine .

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