JP2009281297A - Fastening structure and internal combustion engine - Google Patents

Abstract

By disposing a pressing force transmission member between a first fastening member such as a cylinder block and a second fastening member such as a cylinder head, deformation of a hole such as a cylinder bore opened on a fastening surface can be reduced. A fastening structure and an internal combustion engine that can reduce the frictional force and oil consumption of a piston using the fastening structure are provided.
In an internal combustion engine (1) in which a cylinder head (3) is fastened to a cylinder block (2) by a head bolt (5), a bolt insertion hole (2b) having a female thread portion (2ba) on the bottom side is formed in a fastening surface of the cylinder block (2). A spacer insertion groove 2c having a predetermined depth D2 is provided on the fastening surface of the cylinder block 2, a pressing force transmitting spacer 10 having a thickness T protruding from the fastening surface is disposed in the spacer insertion groove 2c, and the head bolt 5 Are screwed into the female screw portion 2ba to fasten the cylinder head 3 to the cylinder block 2.
[Selection] Figure 1

Description

  The present invention relates to a fastening structure using a bolt that can reduce deformation of a hole opening in a fastening surface such as a cylinder bore, and an internal combustion engine that can reduce cylinder bore deformation using the fastening structure.

  As shown in FIG. 9, a reciprocating engine 1X used as an automotive internal combustion engine or the like has a head bolt with a cylinder head 2 sandwiched between a cylinder block 2X having a cylinder bore 2a and a cylinder head gasket 4. 5 is firmly tightened. The cylinder head 3 covers the upper part of the cylinder bore 2a in which the piston (not shown) moves up and down, forms a combustion chamber between the piston upper part and the cylinder head 3, and excites the pressure increase due to the gas explosion in the combustion chamber up and down. It is converted into force.

  In the reciprocating engine 1X, the head bolt 5 for fastening the cylinder head 3 is fastened with a strong axial force in order to prevent gas leakage of combustion gas due to gas explosion in the cylinder bore 2a. Due to this strong bolt fastening force, the surface pressure between the joint surfaces of the cylinder head 3 and the cylinder block 2X rises, and the female screw portion 2ba on the bottom side of the bolt insertion hole 2b that engages with the male screw portion 5a of the head bolt 5 Since the cylinder bore 2a is pulled upward, the cylinder bore 2a is deformed into a barrel shape as shown by the thick line in FIG. When this deformation occurs, there arises a problem that the friction of the piston moving up and down increases, and a problem that the degree of adhesion between the piston ring and the cylinder bore 2a decreases and the amount of consumption of the lubricating oil increases.

  In order to reduce bore deformation when tightening the cylinder head bolts, especially bore deformation at the front end and rear end of an internal combustion engine that is severely deformed, all cylinder bolt holes in the upper deck of the cylinder block in which the cylinder bores are arranged in a row are arranged. The deck part in the vicinity of the connecting part that connects the cylinder bore and the outer wall of the cylinder bore adjacent to each cylinder head bolt hole is thicker than the other deck part, and the thickest part on the foremost side of the cylinder block is the rearmost part. A structure of a cylinder block of an internal combustion engine in which the rigidity is made larger than that of the thick part on the side has been proposed (for example, see Patent Document 1).

  In order to improve the roundness of deformation of the cylinder bore when assembling the cylinder head, adjacent head bolt hole bosses are connected with ribs in the closed deck type cylinder block, and the head bolt hole is There has also been proposed a cylinder block structure in which a bolt axial force applied to a boss portion is transmitted to an adjacent head bolt hole boss portion intermediate portion via a rib so that the cylinder bore is uniformly deformed (see, for example, Patent Document 2). .

However, in the structure of these cylinder blocks, it is a countermeasure for partially increasing the rigidity around the cylinder bolt hole, and the rigidity only in the vicinity of the fastening surface is increased, so that it becomes a barrel shape. There is a problem that it is insufficient to reduce deformation in the depth direction of the cylinder bore.
Japanese Patent Laid-Open No. 06-213064 Japanese Patent Laid-Open No. 06-213065

  The present invention has been made in view of the above situation, and an object thereof is to dispose a pressing force transmission member between a first fastening member such as a cylinder block and a second fastening member such as a cylinder head. Accordingly, an object of the present invention is to provide a fastening structure that can reduce deformation of a hole such as a cylinder bore that opens in a fastening surface, and an internal combustion engine that can reduce the frictional force and oil consumption of a piston by using this fastening structure.

  The fastening structure of the present invention for achieving the above object is a fastening structure in which a second fastening member is fastened to a first fastening member having a hole opening in the fastening surface with a bolt, and the fastening surface of the first fastening member A bolt insertion hole having a female screw portion on the bottom side is formed in the first fastening member, and a pressing force transmission member insertion groove is provided on the fastening surface of the first fastening member, and the thickness protruding from the fastening surface to the pressing force transmission member insertion groove is provided. And a part of the pressing force generated by fastening when the bolt is screwed into the female screw portion and the second fastening member is fastened to the first fastening member. The pressing force transmitting member is configured to transmit the portion of the first fastening member to a predetermined depth.

  According to this configuration, in the first fastening member, a part of the pressing force generated by the fastening is applied to the tensile force generated by the screwing of the bolt and the female thread portion of the bolt insertion hole by the pressing force transmitting member. Since the bottom of the pressing force transmitting member insertion groove can be transmitted to a certain depth, the tensile force of the threaded portion that deforms the hole opening in the fastening surface and the pressing force acting on the fastening surface, It is possible to reduce the deformation of the hole by applying a pressing force of an appropriate size to a predetermined depth. The magnitude of the pressing force acting on the portion of the predetermined depth depends on the protruding amount from the fastening surface and the shape of the pressing force transmitting member, particularly the area of the protruding portion and the area contacting the bottom of the pressing force transmitting member insertion groove. It can be adjusted relatively easily.

  In order to achieve the above object, an internal combustion engine of the present invention is an internal combustion engine in which a cylinder head is fastened to a cylinder block having a cylinder bore by a head bolt, and a bolt having a female thread portion on the bottom side of the fastening surface of the cylinder block. The head bolt is formed by forming an insertion hole, providing a spacer insertion groove on the fastening surface of the cylinder block, and arranging a pressing force transmission spacer having a thickness protruding from the fastening surface in the spacer insertion groove. When a cylinder head is fastened to the cylinder block by being screwed into the female thread portion, a part of the pressing force generated by the fastening is transmitted to a portion of a predetermined depth of the cylinder block by the pressing force transmission spacer. To be configured.

  According to this configuration, in the cylinder block, a part of the pressing force generated by this fastening is applied to the tensile force generated by the screwing of the bolt and the female screw portion of the bolt insertion hole by the pressing force transmitting spacer. Since it can be transmitted to a predetermined depth at the bottom of the spacer insertion groove, it is suitable for a portion of a predetermined depth against the tensile force of the threaded portion that deforms the cylinder bore and the pressing force acting on the fastening surface. The deformation of the cylinder bore can be reduced by applying a large pressing force. The magnitude of the pressing force acting on the portion of the predetermined depth is relatively large depending on the protruding amount from the fastening surface and the shape of the pressing force transmitting spacer, particularly the area of the protruding portion and the area contacting the bottom of the spacer insertion hole. Can be adjusted easily.

  This configuration not only maintains the roundness of the cylinder bore, but also reduces the degree of barrel deformation, which is the deformation in the stroke direction of the piston. Improvements can be made. In addition, since the degree of adhesion between the piston ring and the cylinder bore can be improved, oil consumption can also be reduced.

  In the internal combustion engine, the pressing force transmission spacer is provided with a through hole through which the head bolt passes, and the pressing force transmission spacer is arranged around the head bolt inserted into the bolt insertion hole. To do.

  According to this configuration, a part of the pressing force can be transmitted to the peripheral part of the bolt insertion hole against the tensile force generated by the screwing of the bolt and the female thread part of the bolt insertion hole, and the spacer insertion It also becomes easy to take the space for arranging the grooves. Also, if the pressing force transmission spacer is arranged around the cylinder bore, deformation from the periphery of the cylinder bore is prevented, but if the pressing force transmission spacer is arranged only around the bolt insertion hole, the bolt and bolt insertion hole Since the pressing force transmitted by the pressing force transmitting spacer can be applied to the tensile force generated by the screwing, it becomes easy to determine the magnitude of the pressing force with respect to the tensile force.

  In the internal combustion engine described above, the start position of the internal thread portion on the bottom side of the bolt insertion hole is set near the position where the amount of deformation of the cylinder bore is maximized or at the center position between the top dead center and the bottom dead center of the piston. Configure as neighborhood.

  That is, in order to reduce the friction when the piston slides, it is necessary to increase the clearance. On the other hand, if it is assumed that fluid lubrication is provided between the piston and the cylinder bore, the friction coefficient increases as the piston speed increases, depending on the piston speed. Since this piston speed is maximum at half the piston stroke L (L / 2), the inner diameter of the cylinder bore is the largest at a position where the depth from the top surface of the cylinder block where the piston speed is maximum is L / 2. It is preferable to be greatly deformed. Therefore, the depth of the starting position of the female screw portion is set to half of the stroke L (L / 2), and a tensile force by screwing is applied to the periphery thereof to increase the piston clearance in this peripheral portion.

  In the internal combustion engine, the predetermined depth of the spacer insertion groove is configured to be 30% to 70% of the depth of the start position of the female thread portion on the bottom side of the bolt insertion hole. Even if the position where the cylinder block is pushed down by the pressing force transmission spacer is too close to the cylinder head or too close to the screwed portion of the head bolt, the effect of reducing bore deformation is reduced, so the range is from 30% to 70%. Is preferable.

  According to the fastening structure according to the present invention, a pressure increasing portion due to bolt fastening is obtained by additionally providing a pressing force transmission spacer between a first fastening member such as a cylinder block and a second fastening member such as a cylinder head. Can also be generated inside the first fastening member, so that deformation of a hole such as a cylinder bore can be reduced. Further, in the engine using this fastening structure, the deformation of the cylinder bore can be reduced, so that the frictional force and oil consumption of the piston can be reduced.

  Hereinafter, a fastening structure and an engine according to embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration of an engine (internal combustion engine) 1 using a fastening structure according to an embodiment of the present invention. The engine 1 is fastened by a head bolt (bolt) 5 with a cylinder head (second fastening member) 3 sandwiched between a cylinder block (first fastening member) 2 and a cylinder head gasket 4.

  As shown in FIGS. 2 and 3, the cylinder block 2 has cylinder bores 2a in which pistons (not shown) move up and down arranged in a row, and bolt insertion holes 2b are formed so as to surround the cylinder bores 2a. Deploy. A female screw portion 2ba is provided at the bottom of the bolt insertion hole 2b, and is screwed into the male screw portion 5a of the head bolt 5, and the cylinder head 3 is fastened to the cylinder block 2 by the head bolt 5.

  In the present invention, a pressing force transmitting spacer 10 as shown in FIGS. 4 to 6 is further used. Further, as shown in FIGS. 2 and 3, the cylinder block 2 is provided with a spacer insertion groove 2 c for inserting and arranging the pressing force transmission spacer 10. The pressing force transmission spacer 10 is sandwiched between the cylinder head gasket 4 and the cylinder block 2, and transmits a part of the fastening force while being sandwiched between the cylinder head 3 and the cylinder block 2. To play a role. Therefore, the thickness T of the pressing force transmitting spacer 10 is important. The thickness T is adjusted to be slightly longer than the depth D2 from the upper surface (fastening surface) of the cylinder block 2 to the bottom of the spacer insertion groove 2c. The thickness T depends on the type of the engine 1, the cylinder head gasket 4 and the like. However, if these are set, the thickness T can be set so that an appropriate pressing force is generated by experiments or numerical simulations. it can.

  With this structure, when the head bolt 5 is tightened, the cylinder head gasket 4 pressed by the cylinder head 2 first hits the pressing force transmission spacer 10, and when the head bolt 5 is further tightened, the pressing force transmission The spacer 10 is deformed by the compressive load, and the cylinder head 3 and the cylinder block 2 tighten the cylinder head gasket 4 with a predetermined fastening force.

  By disposing the pressing force transmission spacer 10, a part of the pressing force (seal surface pressure) is applied to the cylinder head 3 side of the pressing force transmission spacer 10, and the opposite lower surface is the bottom of the spacer insertion groove 2c. Press and push down. Since the spacer insertion groove 2c is in the middle of the cylinder block 2, the amount of deformation of the cylinder bore 2a can be reduced by pushing down this portion.

  Next, the depth D1 of the starting position of the female thread portion 2b of the bolt insertion hole 2b and the depth D2 of the bottom portion of the spacer insertion groove 2c will be described. As shown in FIGS. 3 and 7, the starting position of the female thread portion 2ba on the bottom side of the bolt insertion hole 2b is set near the position where the deformation amount of the cylinder bore 2a is maximum, or the top dead center and the bottom dead center of the piston. In the vicinity of the center position (L / 2) (preferably 0.4 to 0.6 times the stroke L of the piston). Thus, a portion where the inner diameter of the cylinder bore 2 is maximized by applying a tensile force due to screwing to the periphery thereof is half the piston stroke L (L) from the upper surface of the cylinder block 2 where the piston speed is maximum. / 2). By this deformation, the clearance between the piston and the cylinder bore can be increased at the portion where the piston speed becomes maximum, and the frictional force when the piston slides can be reduced.

  Further, the depth D2 of the spacer insertion groove 2c is configured to be 30% to 70% (0.3D1 to 0.7D1) of the depth D1 of the starting position of the female screw portion 2ba on the bottom side of the bolt insertion hole 2b. preferable. This is because even if the position where the cylinder block 2 is pushed down by the pressing force transmission spacer 10 is too close to the cylinder head 3, it is too close to the threaded portion between the male threaded portion 5a of the head bolt 5 and the female threaded portion 2ba of the bolt insertion hole 2b. However, the effect of reducing the deformation of the cylinder bore 2a is reduced.

  By disposing the pressing force transmission spacer 10, a part of the surface pressure is transmitted to the bottom of the spacer insertion groove 2 c via the pressing force transmission spacer 10, so that the middle of the cylinder block 2 can be obtained. Can be pushed downward, and the deformation amount of the cylinder bore 2 can be greatly reduced as shown by the thick line in FIG.

  According to the engine 1 having the above configuration, the amount of deformation of the cylinder bore a2 can be reduced, so that the frictional force of the piston is reduced and the fuel efficiency of the engine is improved. Further, the decrease in bore deformation increases the degree of adhesion between the piston ring and the cylinder bore 2a, thereby reducing oil consumption. Thereby, the exhaust gas of the engine 1 is purified.

  Further, since the sealing surface of the cylinder head gasket 4 is disposed between the pressing force transmission spacer 10 and the cylinder head 3, the sealing performance against the combustion gas is not deteriorated, and the pressing force transmission spacer 10 is inserted into the spacer. Since only the number of steps for inserting into the groove 2c is increased and the procedure for assembling the engine 1 does not need to be significantly changed, the engine can be assembled by an engine assembling procedure similar to that for the prior art engine.

It is a figure which shows the structure of the fastening structure of the engine of embodiment of this invention. It is a top view of a cylinder block in an embodiment of the invention. It is AA sectional drawing of FIG. It is a top view of the spacer for pressing force transmission in embodiment of this invention. It is a front view of the spacer for pressure transmission in the embodiment of the present invention. It is a side view of the spacer for pressure transmission in embodiment of this invention. It is a fragmentary sectional view which shows the relationship between the spacer for pressing force transmission, and the internal thread part of a volt | bolt insertion hole. It is a fragmentary sectional view showing typically modification of a cylinder bore in an example of the present invention. It is a figure which shows the structure of the fastening structure of the engine of a prior art. It is a fragmentary sectional view showing typically modification of a conventional cylinder bore.

Explanation of symbols

1,1X Engine 2,2X Cylinder block 2a Cylinder bore 2b Bolt insertion hole (counter bore hole)
2ba Female thread 2c Spacer insertion hole (spacer groove)
3 Cylinder head 4 Cylinder head gasket 5 Head bolt 6 Oil pan 7 Bearing cap 8 Bearing cap bolt

Claims (5)

  In a fastening structure in which a second fastening member is fastened by a bolt to a first fastening member having a hole opening in a fastening surface, a bolt insertion hole having a female screw portion on the bottom side is formed in the fastening surface of the first fastening member. In addition, a pressing force transmission member insertion groove is provided on the fastening surface of the first fastening member, and a pressing force transmission member having a thickness protruding from the fastening surface is disposed in the pressing force transmission member insertion groove, and the bolt When the second fastening member is fastened to the first fastening member by screwing into the female screw portion, a part of the pressing force generated by the fastening is transferred to the predetermined depth of the first fastening member by the pressing force transmitting member. Fastening structure characterized by transmitting to the part.   In an internal combustion engine in which a cylinder head is fastened to a cylinder block having a cylinder bore by a head bolt, a bolt insertion hole having a female thread portion on the bottom side is formed in a fastening surface of the cylinder block, and a spacer is inserted in a fastening surface of the cylinder block A groove is provided, and a pressing force transmission spacer having a thickness protruding from the fastening surface is arranged in the spacer insertion groove, and the head bolt is screwed into the female screw portion to attach the cylinder head to the cylinder block. An internal combustion engine characterized in that a part of a pressing force generated by the fastening is transmitted to a portion of a predetermined depth of the cylinder block by the pressing force transmission spacer when fastening.   3. The pressing force transmission spacer is provided with a through hole through which the head bolt penetrates, and the pressing force transmission spacer is disposed around the head bolt inserted into the bolt insertion hole. The internal combustion engine described in 1.   The starting position of the female thread portion on the bottom side of the bolt insertion hole is set to be in the vicinity of the position where the deformation amount of the cylinder bore is maximum, or in the vicinity of the center position between the top dead center and the bottom dead center of the piston. The internal combustion engine according to claim 2 or 3, characterized in that   The predetermined depth of the spacer insertion groove is 30% to 70% of the depth of the starting position of the female thread portion on the bottom side of the bolt insertion hole. Internal combustion engine.

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