JP2011144789A - Variable compression ratio mechanism of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve ease of assembly of a seal member disposed between a cylinder block and a crank case and to improve durability of the seal member, in a variable compression ratio mechanism changing a compression ratio of the internal combustion engine by making the cylinder block and the crank case relatively slide. <P>SOLUTION: The variable compression ratio mechanism of an internal combustion engine changes the compression ratio of the internal combustion engine, by making the cylinder block and the crank case relatively slide in a cylinder axial direction. In the variable compression ratio mechanism, the annular seal member is suspended between the cylinder block and the crank case so as to cover a clearance between the cylinder block and the crank case in a whole circumference of the internal combustion engine, and the seal member is formed in a shape of bellows having one crest. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a variable compression ratio mechanism that changes the compression ratio of an internal combustion engine.

  As a mechanism for changing the compression ratio of an internal combustion engine, a variable compression ratio mechanism for changing a combustion chamber volume by relatively sliding a cylinder block and a crankcase in the cylinder axial direction is known.

  In the variable compression ratio mechanism, the gasket cannot be disposed at the connecting portion between the crankcase and the cylinder block as in the prior art. On the other hand, in order to maintain airtightness in the crankcase and prevent leakage of lubricating oil supplied to the sliding portion between the cylinder block and the crankcase, the gap between the crankcase and the cylinder block can be freely deformed or Techniques have been proposed in which a rollable seal material is arranged (see, for example, Patent Document 1).

JP 2006-316770 A

  By the way, in the conventional techniques as described above, it is necessary to press-fit the sealing material into the gap between the cylinder block and the crankcase when the sealing material is assembled. Therefore, a dedicated jig may be required. Further, since the sealing material described above is arranged over the entire circumference of the internal combustion engine, it is necessary to make the state of the sealing material (position, distortion, twist, etc. in the cylinder axial direction) uniform when the sealing material is press-fitted.

  In the variable compression ratio mechanism that changes the compression ratio of the internal combustion engine by sliding the cylinder block and the crankcase relative to each other, it is easy to assemble the seal material disposed between the cylinder block and the crankcase. The purpose is to improve the durability of the sealing material.

The present invention employs the following means in order to solve the above-described problems. That is, the present invention provides a variable compression ratio mechanism for an internal combustion engine that changes the compression ratio of the internal combustion engine by relatively sliding the cylinder block and the crankcase in the cylinder axial direction.
A seal member provided between the cylinder block and the crankcase to cover a gap between the cylinder block and the crankcase over the entire circumference of the internal combustion engine;
The sealing material is formed in a bellows shape having one peak portion, and is formed so that the rigidity of the top portion in the peak portion is higher than the rigidity of the skirt portion and the ridge portion.

  Since the seal material needs to expand and contract in the cylinder axial direction as the cylinder block and the crankcase slide relative to each other, the peak portion is formed to extend in a direction perpendicular to the cylinder axial direction. Shall be.

According to the present invention, since it is not necessary to press-fit a sealing material between the cylinder block and the crankcase, the ease of assembly of the sealing material is improved. Furthermore, since the sealing material of the present invention is formed in a bellows shape with only one peak, the curvature of the bent portion is larger than when a plurality of peaks are formed. When the curvature of the bent portion increases, it becomes possible to disperse the stress acting on the sealing material over a wide range when the sealing material expands and contracts due to the change of the compression ratio. As a result, the durability of the sealing material is improved.

  By the way, since the cylinder block and the crankcase have substantially rectangular outlines, the sealing material also has a substantially rectangular outline. When such a sealing material contracts (bends), the contour of the sealing material changes. For example, when the bellows-shaped peak portion is formed so as to protrude outward from the rectangular outline, the outer diameter of the sealing material increases. On the other hand, when the bellows-shaped peak is formed so as to protrude inward of the rectangular outline, the inner diameter of the sealing material is reduced.

  As described above, when the outline of the sealing material changes, a force for extending the sealing material or a force for compressing the sealing material acts on the sealing material positioned at the corners of the rectangle. As a result, wrinkles may occur in the sealing material around the corners. When wrinkles occur in the sealing material, stress tends to concentrate on the wrinkle generation site. As a result, the durability of the sealing material may be reduced.

  On the other hand, the sealing material of the present invention is configured such that the rigidity of the top of the bellows-shaped peak is higher than the rigidity of the skirt or ridge. Therefore, when the sealing material is contracted (bent), the skirt and the ridge are deformed with almost no deformation of the top. That is, the top portion has a substantially constant shape regardless of the expansion / contraction state of the sealing material, and the skirt portion and the ridge portion are deformed (bent). As a result, in the direction perpendicular to the cylinder axis direction, the position of the top is substantially constant regardless of the expansion / contraction state of the sealing material.

  Thus, when the top is hardly deformed and the position of the top is hardly changed, the contour (outer diameter or inner diameter) of the sealing material becomes substantially constant regardless of the expansion / contraction state of the sealing material. Therefore, the force for extending the sealing material at the corner and the force for pressing and shrinking hardly occur. As a result, wrinkles are less likely to occur in the sealing material around the corners, and the durability of the sealing material is improved.

  Here, as a method for making the rigidity of the top part higher than the rigidity of the skirt part or the ridge part, a method of forming the top part in a plane parallel to the cylinder axial direction, A method of forming a thicker thickness than the thickness of the ridge or a method of casting a reinforcing material for maintaining the shape on the top can be used.

  In addition, as a method of preventing the occurrence of wrinkles at the corners of the substantially rectangular when the seal material contracts (bends), in addition to the method of making the rigidity of the top part higher than the rigidity of the skirt part and the ridge part, A method of providing a bellows portion in the vertical direction (cylinder axis direction) at the corner portion can also be used. According to this method, when the substantially rectangular sealing material contracts, the longitudinal bellows portion provided at the corner portion contracts or expands, whereby the force for extending the corner sealing material is reduced. The force to be compressed is absorbed. As a result, wrinkles are unlikely to occur at the corners of the sealing material.

  In the sealing material of the present invention, the opening end (hereinafter referred to as “upper opening end”) located on the top dead center side in the cylinder axial direction is fixed to the cylinder block, and the opening located on the bottom dead center side in the cylinder axial direction. The end (hereinafter referred to as “lower opening end”) is fixed to the crankcase.

  As a method for fixing the lower opening end of the sealing material to the crankcase, a method of sandwiching the lower opening end between the crankcase and the retainer can be exemplified. According to such a fixing method, the sealing material and the crankcase can be easily fixed.

  By the way, when a sealing material expand | extends, the edge part of the clamping surface (surface which clamps a sealing material) in a retainer may contact a sealing material. At this time, if the end portion is formed as a square surface, stress may concentrate on a part of the sealing material (a portion that contacts the corner of the end portion).

  Therefore, the end portion of the holding surface of the retainer may be formed as a curved surface curved toward the top dead center side in the cylinder axial direction. According to such a structure, when the edge part of the clamping surface in a retainer contacts with a sealing material, the situation where stress concentrates on a part of sealing material can be avoided.

  Moreover, as a method of fixing the upper opening end of the sealing material to the cylinder block, a method of sandwiching the lower opening end between the cylinder block and the cylinder head can be exemplified. According to such a fixing method, the sealing material and the cylinder block can be easily fixed.

  By the way, when a sealing material expand | extends, the edge part of the clamping surface (surface which clamps a sealing material) in a cylinder block may contact a sealing material. At that time, if the end of the clamping surface of the cylinder block is formed as a square surface, stress may concentrate on a part of the sealing material.

  Therefore, the end portion of the clamping surface in the cylinder block may be formed as a curved surface curved toward the bottom dead center side in the cylinder axial direction. According to such a structure, when the edge part of the clamping surface in a cylinder block contacts with a sealing material, the situation where stress concentrates on a part of sealing material can be avoided.

  According to the present invention, in the variable compression ratio mechanism that changes the compression ratio of the internal combustion engine by relatively displacing the cylinder block and the crankcase, it is easy to assemble the seal member disposed between the cylinder block and the crankcase. And the durability of the sealing material can be improved.

It is sectional drawing of the internal combustion engine to which this invention is applied. It is a perspective view of the sealing material concerning this invention. It is 1st sectional drawing which shows the structure of the sealing material in a 1st Example. It is 2nd sectional drawing which shows the structure of the sealing material in a 1st Example. It is sectional drawing which shows the structure of the sealing material as a comparative example. It is a top view which shows the structure of the sealing material as a comparative example. It is a figure which shows the expansion-contraction state of the sealing material in a 1st Example. It is sectional drawing which shows the structure of the sealing material in a 2nd Example. It is a figure which shows the structure of the sealing material in a 3rd Example. It is a figure which shows the shape of the retainer in a 4th Example. It is a figure which shows the other structural example of the retainer in a 4th Example. It is a figure which shows the structure of the part which clamps a sealing material in a cylinder block.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

  <Example 1>

  First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. An internal combustion engine 1 shown in FIG. 1 is a spark ignition type internal combustion engine (gasoline engine) in which a mechanical compression ratio (combustion chamber volume) is changed by relative sliding of a cylinder block 2 and a crankcase 3 in the cylinder axial direction. It is. The internal combustion engine 1 may be a compression ignition type internal combustion engine (diesel engine).

  The internal combustion engine 1 includes a cylinder block 2, a crankcase 3, and a cylinder head 4. The cylinder block 2 and the crankcase 3 are slidably fitted in the cylinder axis direction. In the example shown in FIG. 1, the lower part of the cylinder block 2 (the part on the bottom dead center side in the cylinder axis direction) is surrounded by the upper part of the crankcase 3 (the part on the top dead center side in the cylinder axis direction). The outer wall surface 2 and the inner wall surface of the crankcase 3 slide. Further, the cylinder block 2 and the cylinder head 4 are integrally connected.

  A cylinder (cylinder) 5 is formed in the cylinder block 2. A piston 6 is loaded in the cylinder 5 so as to be slidable in the cylinder axial direction. A crankshaft 7 is rotatably supported on the crankcase 3. The piston 6 and the crankshaft 7 are connected via a connecting rod 8.

  The cylinder head 4 is provided with an intake port 9 and an exhaust port 10 communicating with the inside of the cylinder 5. The cylinder head 4 is provided with an intake valve 11 for opening and closing the opening end of the intake port 9 and an exhaust valve 12 for opening and closing the opening end of the exhaust port 10. The intake valve 11 is driven to open and close by an intake camshaft 13 that is rotatably supported by the cylinder head 4. The exhaust valve 12 is driven to open and close by an exhaust camshaft 14 that is rotatably supported by the cylinder head 4. In addition, a fuel injection valve 15 that injects fuel into the intake port 9 and a spark plug 16 that generates a spark in the cylinder 5 are attached to the cylinder head 4.

  Next, a variable compression ratio mechanism 100 for displacing the cylinder block 2 in the cylinder axial direction with respect to the crankcase 3 is provided at a portion where the cylinder block 2 and the crankcase 3 overlap each other. Examples of the variable compression ratio mechanism 100 include a mechanism for displacing the cylinder block 2 in the cylinder axial direction by an actuator such as an electric motor rotating an eccentric cam.

  According to the variable compression ratio mechanism 100, the combustion chamber volume can be increased by moving the cylinder block 2 away from the crankcase 3 in the cylinder axis direction (displace the cylinder block 2 toward the top dead center side in the cylinder axis direction). it can. As a result, the mechanical compression ratio (a value obtained by dividing the sum of the stroke volume and the combustion chamber volume by the combustion chamber volume) becomes low.

  Further, according to the variable compression ratio mechanism 100 described above, the cylinder block 2 is moved closer to the crankcase 3 in the cylinder axial direction (the cylinder block 2 is displaced toward the bottom dead center side in the cylinder axial direction), thereby reducing the combustion chamber volume. Can be small. As a result, the mechanical compression ratio of the internal combustion engine 1 is increased.

The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 17 for electrically controlling various devices such as the fuel injection valve 15, the spark plug 16, and the variable compression ratio mechanism 100. . The ECU 17 is a unit composed of a CPU, ROM, RAM, backup RAM, and the like.

  Electric signals from various sensors such as a crank position sensor 18 and an accelerator position sensor 19 are input to the ECU 17. The crank position sensor 18 is a sensor that is disposed in the vicinity of the crankshaft 7 and outputs a pulse signal correlated with the rotational position of the crankshaft 7. The accelerator position sensor 19 is a sensor that outputs a signal correlated with the amount of operation of the accelerator pedal (accelerator opening).

  ECU17 discriminate | determines the driving | running state (engine driving | running state) of the internal combustion engine 1 according to the electric signal of above-mentioned various sensors, and controls the above-mentioned various apparatuses according to the discrimination | determination result. For example, the ECU 17 controls the variable compression ratio mechanism 100 based on the engine speed and the engine load determined from the output signals of the crank position sensor 18 and the accelerator position sensor 19.

  At this time, when the engine speed and the engine load are in a predetermined low load / low rotation operation region, the ECU 17 controls the variable compression ratio mechanism 100 so that the compression ratio of the internal combustion engine 1 becomes high. Specifically, the ECU 17 controls the variable compression ratio mechanism 100 so that the cylinder block 2 approaches the crankcase 3 (displaces toward the bottom dead center side in the cylinder axis direction).

  Further, when the engine speed and the engine load deviate from the low load / low rotation operation region described above, the ECU 17 causes the cylinder block 2 to move away from the crankshaft 7 (displaces toward the top dead center side in the cylinder axis direction). In addition, the compression ratio of the internal combustion engine 1 is reduced by controlling the variable compression ratio mechanism 100.

  It should be noted that the compression ratio of the internal combustion engine 1 may be switched in two steps as described above, or may be switched in a stepless manner according to the engine speed and the engine load.

  Thus, when the compression ratio of the internal combustion engine 1 is changed, it is possible to achieve both improvement in combustion efficiency in the low load / low rotation operation region and suppression of knocking in the high load / high rotation operation region.

  By the way, in order to maintain the airtightness in the crankcase 3, the gap (the gap between the outer wall surface of the cylinder block 2 and the inner wall surface of the crankcase 3) in the portion where the cylinder block 2 and the crankcase 3 overlap each other is sealed. There is a need to. On the other hand, the variable compression ratio mechanism of the internal combustion engine of the present embodiment is provided with a sealing material 200 as shown in FIG. 2 so as to cover the gap over the entire circumference of the internal combustion engine 1.

  Hereinafter, the structure of the sealing material 200 in the present embodiment will be described with reference to FIGS. FIG. 3 is a cross-sectional view showing a state of the sealing material 200 when the cylinder block 2 is positioned closest to the top dead center side with respect to the crankcase 3. FIG. 4 is a cross-sectional view showing a state of the sealing material 200 when the cylinder block 2 is positioned closest to the bottom dead center side with respect to the crankcase 3. In the following, “upper part” indicates a part on the top dead center side in the cylinder axis direction, and “lower part” indicates a part on the bottom dead center side in the cylinder axis direction.

  The sealing material 200 in the present embodiment is formed in a bellows shape having only one peak portion protruding inward. The sealing material 200 is formed by molding rubber, resin, or an intermediate composition of rubber and resin.

  The upper opening end 201 of the sealing material 200 is sandwiched between the cylinder block 2 and the cylinder head 4. A lower opening end 202 of the sealing material 200 is sandwiched between the crankcase 3 and the retainer 30.

  The top portion 203 of the bellows-shaped peak portion in the sealing material 200 is configured by a plane parallel to the cylinder axial direction. When the top portion 203 is formed in this way, the rigidity of the top portion 203 becomes higher than the rigidity of the skirt portion 204 and the ridge portion 205 of the mountain portion. Therefore, as shown in FIG. 4, when the sealing material 200 contracts (bends), the top 203 is hardly deformed, and the skirt 204 and the ridge 205 are deformed (bent).

  Here, as a comparative example of the present embodiment, a sealing material 400 in which the top portion of the bellows-shaped peak portion is configured by a curved surface is shown in FIG. 5A shows a state in which the sealing material 400 is extended, and FIG. 5B shows a state in which the sealing material 400 is contracted (bent).

  When the top 401 of the sealing material 400 is formed of a curved surface, the top 401 is bent when the sealing material 400 contracts (bends). Therefore, the position of the top portion 401 in the horizontal direction (direction perpendicular to the cylinder axis direction) changes between when the sealing material 400 is expanded and when the sealing material 400 is contracted (bent).

  When the position of the top portion 401 changes as described above, the inner diameter of the sealing material 400 is reduced as shown in FIG. In addition, the broken line in FIG. 6 has shown the internal diameter when the sealing material 400 expand | extends.

  Since the outline of the sealing material 400 is substantially rectangular, the force for compressing the sealing material 400 at both corners of the rectangular portion against the sealing material 400 at the corner (see arrows X and Y in FIG. 6). Work. As a result, wrinkles may occur in the sealing material 400 around the corner. When wrinkles occur in the sealing material 400, stress may concentrate on the wrinkle generation site and the durability of the sealing material 400 may be reduced.

  On the other hand, according to the sealing material 200 of this embodiment, when the sealing material 200 contracts (bends), the top portion 203 hardly deforms (bends), and the skirt portion 204 and the ridge portion 205 deform ( Bend). Therefore, the horizontal position of the top portion 203 is maintained at a substantially constant position regardless of the stretched state of the sealing material 200, as shown in FIG. 7A shows a state where the sealing material 200 is extended, and FIG. 7B shows a state where the sealing material 200 is contracted (bent).

  As shown in FIG. 7, when the position of the top portion 203 of the sealing material 200 is maintained at a fixed position, the inner diameter of the sealing material 200 is hardly reduced. Therefore, when the substantially rectangular sealing material 200 contracts (bends), almost no force is generated to push and compress the corner sealing material 200. As a result, wrinkles are less likely to occur around the corners of the sealing material 200, and the durability of the sealing material 200 is improved.

  Further, since the sealing material 200 of the present embodiment is formed in a bellows shape having only one peak portion, a portion that is bent when the sealing material 200 contracts (bends) (for example, a skirt portion 204 or a ridge portion 205). ) Is larger than the bellows shape having a plurality of peaks. Therefore, the stress acting on the bent portion can be dispersed over a wide range. As a result, the durability of the sealing material 200 is improved.

  Furthermore, since the sealing material 200 of the present embodiment is configured to cover the gap between the cylinder block 2 and the crankcase 3, no special jig is required when the sealing material 200 is assembled to the internal combustion engine 1. . Therefore, the ease of assembly of the sealing material 200 is increased.

According to the embodiment described above, in the variable compression ratio mechanism that changes the compression ratio of the internal combustion engine 1 by relatively sliding the cylinder block 2 and the crankcase 3, while improving the ease of assembly of the sealing material 200, The durability of the sealing material 200 can also be improved.

  In the present embodiment, the sealing material 200 in which the bellows-shaped peak portion protrudes inward is taken as an example, but it is needless to say that the bellows-shaped peak portion may protrude outward.

<Example 2>
Next, a second embodiment of the variable compression ratio mechanism for an internal combustion engine according to the present invention will be described with reference to FIG. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  The difference between the first embodiment described above and this embodiment is the shape of the top portion 203 of the sealing material 200. That is, in the first embodiment described above, the top portion 203 of the sealing material 200 is formed as a flat surface, whereas in this embodiment, the top portion 203 of the sealing material 200 is formed thicker than the skirt portion 204 and the ridge portion 205. Is done.

  FIG. 8 is a cross-sectional view showing the configuration of the sealing material 200 in the present embodiment. 8A shows a state where the sealing material 200 is extended, and FIG. 8B shows a state where the sealing material 200 is contracted (bent).

  As shown in FIG. 8, the shape of the top 203 of the sealing material 200 is a curved surface. However, the thickness of the sealing material 200 at the top portion 203 is formed to be thicker than the thickness of the sealing material 200 at the skirt portion 204 and the ridge portion 205. Therefore, the rigidity of the top portion 203 is higher than that of the skirt portion 204 and the ridge portion 205.

  Therefore, as shown in FIG. 8B, when the sealing material 200 contracts (bends), the top part 203 hardly deforms (bends), and the skirt part 204 and the ridge part 205 deform (bend). It will be. Thus, when the top part 203 hardly deforms, the position of the top part 203 in the horizontal direction becomes a substantially constant position regardless of the stretched state of the sealing material 200. As a result, an effect equivalent to that of the first embodiment can be obtained.

<Example 3>
Next, a third embodiment of the variable compression ratio mechanism for an internal combustion engine according to the present invention will be described with reference to FIG. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  The difference between the first embodiment and the present embodiment is in the shape of the sealing material 200 located at the corner of the substantially rectangular outline. That is, in the first embodiment described above, the shape of the corner is formed to be equal to the shape of the straight portion, whereas in this embodiment, the shape of the corner is different from the shape of the straight portion.

  FIG. 9 is a diagram illustrating a configuration of a corner portion of the sealing material 200 having a substantially rectangular outline. 9A is a perspective view of a corner portion, FIG. 9B is a diagram showing a cross section A shown in FIG. 9A, and FIG. 9C is a diagram in FIG. It is a figure which shows the B cross section shown to).

  As shown in FIG. 9, a bellows portion 206 extending in the cylinder axial direction is provided at a corner portion of the sealing material 200 having a substantially rectangular outline. Therefore, when the sealing material 200 contracts, the bellows portion 206 contracts (bends) when a force is generated that the sealing material 200 positioned on both sides of the corner compresses the sealing material 200 at the corner. become. As a result, wrinkles do not occur in the sealing material 200 located around the corner.

  Therefore, according to this embodiment, it is possible to obtain the same effects as those of the first and second embodiments described above. The shape of the top portion 203 of the sealing material 200 may be the same as that of either the first embodiment or the second embodiment described above, or may be a shape that allows the top portion 203 to be bent. Good. At that time, when the shape of the top portion 203 of the sealing material 200 is formed in the same manner as in the first or second embodiment described above, a force to slightly compress the corner sealing material 200 is generated. Even if it exists, it becomes possible to suppress generation | occurrence | production of soot more reliably.

<Example 4>
Next, a fourth embodiment of the variable compression ratio mechanism for an internal combustion engine according to the present invention will be described with reference to FIG. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  The difference between the first embodiment and the present embodiment is the shape of the retainer 30. That is, in the first embodiment described above, the end portion of the holding surface (the surface holding the sealing material 200) in the retainer 30 is formed as a square surface, whereas in this embodiment, the end portion of the holding surface in the retainer 30 is formed. Is formed with a curved surface.

  FIG. 10 is a cross-sectional view showing the configuration of the retainer 30 in the present embodiment. As shown in FIG. 10, the end portion of the clamping surface of the retainer 30 (in other words, the inner peripheral surface of the retainer 30) 30 a is formed by a curved surface curved toward the top dead center side in the cylinder axis direction.

  According to such a configuration, even when the sealing material 200 is in contact with the end portion 30a when the sealing material 200 is extended, a situation in which stress is concentrated on a part of the sealing material 200 is avoided. In other words, the stress is dispersed throughout the portion of the sealing material 200 that contacts the end 30a. As a result, the durability of the sealing material 200 can be further improved.

  In addition, as a method of forming the end portion 30a with a curved surface, as shown in FIG. 11, in addition to the method of chamfering the corners of the lower surface and the side surface of the retainer 30 into round surfaces as shown in FIG. A method of bending the end 30a of the retainer 30 can be exemplified.

  As shown in FIG. 12, the end 2a of the clamping surface of the cylinder block 2 may also be formed as a curved surface curved toward the bottom dead center side in the cylinder axial direction.

  The configuration of this embodiment may be combined with the configuration described in the second or third embodiment described above, instead of the configuration of the first embodiment described above.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder block 2a End part 3 Crankcase 4 Cylinder head 5 Cylinder 6 Piston 7 Crankshaft 8 Connecting rod 9 Intake port 10 Exhaust port 11 Intake valve 12 Exhaust valve 13 Intake camshaft 14 Exhaust camshaft 15 Fuel injection valve 16 Spark plug 30 Retainer 30a End portion 100 Variable compression ratio mechanism 200 Seal material 201 Upper opening end 202 Lower opening end 203 Top portion 204 Bottom portion 205 Ridge portion 206 Bellows portion

Claims (5)

In a variable compression ratio mechanism of an internal combustion engine that changes the compression ratio of the internal combustion engine by relatively sliding the cylinder block and the crankcase in the cylinder axial direction,
In order to cover the gap between the cylinder block and the crankcase over the entire circumference of the internal combustion engine, a sealing material provided between the cylinder block and the crankcase is provided,
The internal combustion engine characterized in that the sealing material is formed in a bellows shape having one peak portion, and the rigidity of the top portion of the peak portion is higher than the rigidity of the skirt portion and the ridge portion. Variable compression ratio mechanism.   2. The variable compression ratio mechanism for an internal combustion engine according to claim 1, wherein a top portion of the peak portion is formed by a plane parallel to the cylinder axial direction.   2. The variable compression ratio mechanism for an internal combustion engine according to claim 1, wherein a thickness of a top portion of the mountain portion is formed to be thicker than thicknesses of a skirt portion and a ridge portion. 4. The retainer according to claim 1, further comprising a retainer that clamps an opening end of the seal material that is located on a bottom dead center side in a cylinder axial direction with the crankcase.
The variable compression ratio mechanism for an internal combustion engine, wherein an end of a surface of the retainer that contacts the sealing material is formed as a curved surface that is curved toward the top dead center in the cylinder axis direction. In any one of Claims 1 thru | or 4, the opening end located in the cylinder shaft direction top dead center side in the said sealing material is clamped between the said cylinder block and a cylinder head,
The variable compression ratio mechanism for an internal combustion engine, wherein an end of a surface of the cylinder block that comes into contact with the sealing material is formed as a curved surface that is curved toward the bottom dead center side in the cylinder axial direction.

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