JP2013100806A - Variable compression ratio internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a seal member from being, for example, deteriorated and damaged.SOLUTION: The invention relates to a variable compression ratio internal combustion engine in which a cylinder block 3 and a crank case 4 are relatively movable in an axial cylindrical direction. An annular seal member 40 which is extended between the cylinder block 3 and the crank case 4 is provided to cover a gap between the cylinder block 3 and the crank case 4 at an entire circumference of the internal combustion engine. A protrusion 47 is formed at one end 41 of the seal member, and a groove 49 to fit the protrusion is formed at the crank case. A guard wall 57 for suppressing blowby gas and oil mist in the crank case 4 from entering the groove 49 is provided in either the seal member 40 or the crank case 4.

Description

  The present invention relates to a variable compression ratio internal combustion engine, and more particularly to a variable compression ratio internal combustion engine in which a cylinder block and a crankcase can move relative to each other.

  2. Description of the Related Art In recent years, techniques for changing the compression ratio of an internal combustion engine have been proposed for the purpose of improving the fuel efficiency performance and output performance of the internal combustion engine. As this type of technology, by providing a compression ratio variable mechanism that connects the cylinder block and the crankcase relatively close to and away from each other in the vertical direction or the cylinder axis direction, and operating or controlling the compression ratio variable mechanism, Techniques for changing the compression ratio have been proposed.

  In order to maintain airtightness in the crankcase or prevent fluid leakage from the fitting portion between the cylinder block and the crankcase, it is proposed to provide a seal member that covers the gap between the crankcase and the cylinder block. (For example, refer to Patent Document 1).

JP 2011-117366 A

  The seal member is generally formed in an annular shape that extends over the entire circumference of the internal combustion engine, and is provided between the cylinder block and the crankcase to cover these gaps. One opening edge of the sealing member is fixed to the crankcase, and the other opening edge of the sealing member is fixed to the cylinder head. In the fixed portion of the crankcase and the seal member, a protrusion that extends along the opening end edge of the seal member is provided. The protruding portion is fitted into a groove provided in the crankcase. In this fitted state, one open end edge of the seal member is sandwiched and fixed between the retainer and the crankcase.

  According to this structure, the groove portion located on the inner side of the crankcase with respect to the protruding portion is in a state of being directly opened in the crankcase. Then, blow-by gas and oil mist in the crankcase enter the portion, and condensed water caused by blow-by gas and oil caused by oil mist enter and accumulate. These condensed water and oil may eventually deteriorate the seal member and cause damage to the seal member.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a variable compression ratio internal combustion engine that can prevent deterioration or breakage of a seal member.

According to one aspect of the invention,
A variable compression ratio internal combustion engine in which the cylinder block and the crankcase are relatively movable in the cylinder axial direction;
An annular seal member provided between the cylinder block and the crankcase is provided to cover a gap between the cylinder block and the crankcase over the entire circumference of the internal combustion engine, and one end edge of the seal member Protruding portions are provided, grooves are formed in the crankcase for fitting the protruding portions, and a guard wall for suppressing blow-by gas and oil mist in the crankcase from entering the grooves is provided in the seal. Provided is a variable compression ratio internal combustion engine provided on a member or the crankcase.

  Preferably, the guard wall is provided on the seal member.

  Preferably, the guard wall covers an inner side surface portion of the crankcase located on the inner side of the crankcase with respect to the groove.

  Preferably, the guard wall forms a hanging wall that hangs down from the inner surface of the seal member.

  Preferably, the guard wall has one or more protrusions protruding toward the inner side surface of the crankcase.

  Preferably, the guard wall contacts an inner side surface portion of the crankcase.

  Alternatively, the guard wall may be provided on the crankcase. In this case, it is preferable that the guard wall contacts the seal member.

  Preferably, the guard wall is provided along the entire circumference of the annular seal member.

  Preferably, a retainer is provided that sandwiches one end edge of the seal member with the crankcase in a state where the convex portion is fitted in the groove.

  According to the present invention, it is possible to exhibit an excellent effect that the sealing member can be prevented from being deteriorated or damaged.

1 is a diagram showing a schematic configuration of an internal combustion engine according to an embodiment of the present invention. It is a disassembled perspective view which shows the attachment structure of an internal combustion engine roughly. It is sectional drawing which shows the detail of the attachment part of a sealing member. It is sectional drawing of the 1st modification of this embodiment. It is sectional drawing of the 2nd modification of this embodiment. It is sectional drawing of the 3rd modification of this embodiment. It is sectional drawing of a comparative example. It is sectional drawing of the 4th modification of this embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of a variable compression ratio multi-cylinder internal combustion engine according to the present embodiment. The internal combustion engine (engine) 1 changes the compression ratio by moving the cylinder block 3 formed with the cylinder 2 relative to the crankcase 4 to which the crankshaft 20 is assembled in the cylinder axial direction. The crankcase 4 and the cylinder block 3 are connected by a variable compression ratio mechanism 21 so as to be able to move close to and away from each other in the vertical direction or the cylinder axis direction. The internal combustion engine 1 of the present embodiment is a gasoline engine (spark ignition internal combustion engine), but the present invention is also applicable to a diesel engine (compression ignition internal combustion engine).

  Although not shown, the compression ratio variable mechanism 21 includes a mechanism that displaces the cylinder block 3 in the cylinder axial direction with respect to the crankcase 4 by rotating an eccentric cam by an actuator such as an electric motor.

  According to the compression ratio variable mechanism 21, the cylinder block 3 is moved away from the crankcase 4 in the cylinder axial direction (the cylinder block 3 is displaced upward or to the top dead center side), whereby the combustion chamber volume is increased and the internal combustion engine 1 is expanded. The compression ratio can be reduced.

  Further, by bringing the cylinder block 3 closer to the crankcase 4 in the cylinder axial direction (displace the cylinder block 3 downward or to the bottom dead center side), the combustion chamber volume can be reduced and the compression ratio of the internal combustion engine 1 can be increased. it can.

  In the present embodiment, the internal combustion engine 1 is mounted on a vehicle, and the crankcase 4 is fixed to the vehicle via an engine mount. Therefore, the cylinder block 3 moves up and down with respect to the fixed crankcase 4. However, the mounting method may be reversed to fix the cylinder block 3 to the vehicle. The internal combustion engine 1 may not be mounted on the vehicle.

  The internal combustion engine 1 includes a piston 24 that can be moved up and down in the cylinder 2, a cylinder head 25 that is attached to the top of the cylinder block 3, and a head cover 26 that is attached to the top of the cylinder head 25 and covers it from above. The oil pan 27 is attached to the bottom of the crankcase 4 and covers it from below. The piston 24 is connected to the crankshaft 20 via a connecting rod 19.

  A valve operating chamber 28 is defined inside the head cover 26 and the cylinder head 25. The valve chamber 28 includes an intake valve Vi and an exhaust valve Ve that open and close the intake port Pi and the exhaust port Pe, a valve spring that urges the intake valve Vi and the exhaust valve Ve, respectively, in a valve closing direction, and an intake valve Vi. And an intake camshaft Ci and an exhaust camshaft Ce for driving the exhaust valve Ve in the valve opening direction, respectively. The valve operating chamber 28 is supplied with oil for valve operating lubrication from an oil supply port (not shown). An injector 29 for injecting fuel and a spark plug 30 for igniting the air-fuel mixture are attached to the cylinder head 25.

  A combustion chamber 31 is defined above the piston 24, and a crank chamber 32 is defined below the piston 24. A crankshaft 20 is provided in the crank chamber 32, and oil (not shown) is stored at the bottom thereof.

  A surge tank 34 is connected to the intake port Pi via an intake manifold 33 for each cylinder, and intake air is distributed from the surge tank 34 to the intake port Pi of each cylinder via the intake manifold 33. An intake pipe 35 is connected to the upstream side of the surge tank 34, and an electronically controlled throttle valve 36 and an air filter 37 are provided in the intake pipe 35. An intake passage is defined by the intake port Pi, the intake manifold 33, the surge tank 34, and the intake pipe 35.

  An exhaust pipe (not shown) is connected to the exhaust port Pe of each cylinder via an exhaust manifold 38, and an exhaust passage is defined by the exhaust port Pe, the exhaust manifold 38 and the exhaust pipe.

  As shown in the drawing, the lower side of the cylinder block 3 is fitted inside the upper side of the crankcase 4 so as to be movable and slidable in the cylinder axial direction. A water jacket W is defined in the cylinder block 3 so as to surround the cylinder 2.

  An annular seal member (or seal boot) 40 is provided between the cylinder block 3 and the crankcase 4 so as to cover the gap between the cylinder block 3 and the crankcase 4 over the entire circumference of the internal combustion engine 1. . The seal member 40 extends generally in the height direction of the internal combustion engine 1 as shown in the figure, and seals the gap in the fitting portion between the cylinder block 3 and the crankcase 4 from the outside.

  The seal member 40 is formed of a deformable elastic body having a cross section formed in a bellows shape as illustrated. The seal member 40 has a single peak protruding inward. One end edge of the seal member 40 is fixed to the crankcase 4, and the other end edge of the seal member 40 is sandwiched between the cylinder block 3 and the cylinder head 25. Fixed.

  When the cylinder block 3 descends and approaches the crankcase 4, the seal member 40 is deformed in the contraction direction. When the cylinder block 3 rises and moves away from the crankcase 4, the seal member 40 is deformed in the extending direction. Thus, even if the relative position between the cylinder block 3 and the crankcase 4 changes, the airtightness of the fitting portion can be maintained by the expansion / contraction operation of the seal member 40.

  The internal combustion engine 1 is provided with an electronic control unit (ECU) 100 as a control means for electrically controlling various devices such as an injector 29, a spark plug 30, a throttle valve 36, and a motor of the compression ratio variable mechanism 21. ing. The ECU 100 is a unit that includes a CPU, a ROM, a RAM, a backup RAM, and the like.

  The ECU 100 receives electrical signals from various sensors such as the crank position sensor 61, the accelerator position sensor 52, and the air flow meter 53. The crank position sensor 61 outputs a pulse signal correlated with the rotational position of the crankshaft 20. The accelerator position sensor 52 outputs a signal correlated with the operation amount (accelerator opening) of the accelerator pedal. The air flow meter 53 outputs a signal correlated with the intake air amount per unit time.

  The ECU 100 detects the operating state (engine operating state) of the internal combustion engine 1 according to the electrical signals of the various sensors described above, and controls the various devices described above according to the detection results. For example, ECU 100 is based on the rotational speed of the internal combustion engine (engine speed) detected from the output signal of crank position sensor 61 and the load of the internal combustion engine (engine load) detected from the output signal of accelerator position sensor 52. Thus, the compression ratio variable mechanism 21 is controlled.

  At this time, when the engine speed and the engine load are in a predetermined low rotation / low load operation region, the ECU 100 causes the compression ratio of the internal combustion engine 1 to increase, in other words, the cylinder block 3 approaches the crankcase 4. Thus, the variable compression ratio mechanism 21 is controlled.

  Further, when the engine speed and the engine load deviate from the low rotation / low load operation region, the ECU 100 compresses the internal combustion engine 1 so that the compression ratio is lowered, in other words, the cylinder block 3 is moved away from the crankcase 4. The ratio variable mechanism 21 is controlled.

  The compression ratio may be switched in two steps as described above, but 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 rotation / low load operation region and suppression of knocking in the high rotation or high load operation region outside the region. it can.

  FIG. 2 schematically shows a mounting structure for the cylinder block 3, the crankcase 4, the seal member 40, and the like in the present embodiment. As shown in the figure, the cylinder block 3 is fitted inside the crankcase 4 so as to be slidable up and down. The seal member 40 is formed in an annular shape so as to make a round around the outer surface of the internal combustion engine 1 or the cylinder block 3, its lower end edge 41 is fixed to the crankcase 4, and its upper end edge 42 is the cylinder block 3. Between the cylinder head 25 and the cylinder head 25. The illustrated retainer 43 is used when the seal member 40 is fixed to the crankcase 4.

  A head gasket 44 that seals a gap between the cylinder block 3 and the cylinder head 25 is interposed between the cylinder block 3 and the cylinder head 25, and an upper end edge 42 of the seal member 40 is attached to the head gasket 44. They are connected together. In other words, the seal member 40 has the head gasket 44 integrally. The head gasket 44 is sandwiched and fixed between the cylinder block 3 and the cylinder head 25, so that the seal member 40 is fixed to the cylinder block 3. Between the cylinder head 25 and the cylinder head 25.

  The seal member 40 may be a separate part separated from the head gasket 44, and the upper end edge 42 of the seal member 40 is sandwiched and fixed between the cylinder block 3 and the cylinder head 25. Also good. The upper end edge portion 42 of the seal member 40 may not be sandwiched and fixed between the cylinder block 3 and the cylinder head 25. For example, the seal member 40 may be fixed to the outer surface portion of the cylinder block 3 with a fixing tool such as a bolt. Also good. The fixing method of the upper edge 42 is arbitrary. In the drawing, well-known structures (mounting holes and the like) necessary for connecting and linking the components are schematically shown.

  In FIG. 3, the detail of the attachment part of the sealing member 40 is shown. As shown in the drawing, the seal member 40 has a reinforcing member 45 embedded in the upper end edge portion 42 thereof. The reinforcing member 45 is made of a material harder than the seal member main body 46 made of an elastic body, for example, a metal plate. The reinforcing member 45 protrudes from the seal member main body 46, and the protruding portion is embedded in the head gasket 44. As a result, the seal member 40 and the head gasket 44 are integrally connected.

  The seal member body 46 is formed of a material having flexibility and pressure resistance. Examples of such materials include rubber and thermoplastic elastomer (TPEE) which is an intermediate composition of rubber and resin. At that time, the chemical resistance of the seal member main body 46 may be improved by forming a film such as a fluororesin on the inner surface 40A of the seal member main body 46.

  For the fixing portion A where the lower end edge 41 of the seal member 40 is fixed to the crankcase 4, a downward convex portion 47 is provided on the lower end edge 41 of the seal member 40. Further, the upward fixed surface 48 of the crankcase 4 is provided with a groove 49 into which the convex portion 47 is fitted. By fitting the convex portion 47 into the groove 49, the lower end edge portion 41 of the seal member 40 is accurately positioned on the fixed surface 48 of the crankcase 4. Then, the retainer 43 holds the lower end edge 41 of the seal member 40 between the fixed surface 48 of the crankcase 4 with the convex portion 47 fitted in the groove 49. The retainer 43 is fixed on the fixing surface 48 by a bolt 50 as a fixing tool.

  Referring also to FIG. 2, the convex portion 47, the fixing surface 48, the groove 49, and the retainer 43 are formed in a continuous annular shape so as to make a round around the outer surface portion 62 of the cylinder block 3. However, since at least the convex portion 47 and the groove 49 are mainly for positioning, they are not necessarily continuous or annular. It may be discontinuous, intermittent or partial. The fixed surface 48 forms the upper end surface of the crankcase 4. The bolts 50 and the mounting holes 53 and 54 for the bolts 50 are arranged at predetermined intervals along the lower end edge 41 of the seal member 40. The retainer 43 has a pressing portion 51 that protrudes in a cantilevered manner on the inside, and the pressing portion 51 presses down the upper surface of the lower end edge portion 41 of the seal member 40 and presses the convex portion 47 into the groove 49. Of the retainer 43, a fixing portion 52 outside the pressing portion 51 is seated on the fixing surface 48 and is fixed by being sandwiched between the bolt 50 and the fixing surface 48.

  In the seal member main body 46, the upper edge portion 42 and the lower edge portion 41 are connected by a deformable portion 60 having one or more (one in the illustrated example) curved portion or bent portion. The deformation portion 60 is a main deformation portion when the seal member 40 expands and contracts in accordance with the compression ratio change, and has a structure that is more easily deformed than the upper end edge portion 42 and the lower end edge portion 41.

  Specifically, the deformable portion 60 is thinner than the lower end edge portion 41 and is easily deformable. In other words, the lower end edge portion 41 forming the fixed portion A has a structure that is more rigid than the deformable portion 60. Further, since the deformable portion 60 is thinner than the upper end edge portion 42 and there is no reinforcing member 45, the deformable portion 60 is easily deformable. In other words, the upper end edge portion 42 that forms a fixed portion with respect to the cylinder block 3 has a higher rigidity than the deformable portion 60.

  The cross-sectional shape of the seal member main body 46 may be other than the illustrated example, and may be, for example, a bellows shape having two or more curved portions or bent portions.

  An inner side wall 55 that defines the inner side surface of the groove 49 is formed in the crankcase 4. The inner side surface of the inner side wall 55 forms a part of the inner side surface portion 56 of the crankcase 4.

  Here, the “inner side” refers to a direction toward the center of the crankcase 4 in the width direction when viewed in a cross section in the width direction of the crankcase 4 (cross section perpendicular to the crankshaft axis). When viewed in a cross section in a direction (cross section parallel to the crankshaft axis), it refers to a direction toward the center of the longitudinal direction of the crankcase 4.

  Similarly, the “outside” means a direction away from the center of the crankcase 4 in the width direction when viewed in the cross-section in the width direction of the crankcase 4. The direction away from the center of the case 4 in the longitudinal direction.

  The seal member 40 is brought into contact with the upper end surface portion of the inner side wall 55. In the case of the present embodiment, the retainer 43 is not provided at a position directly above the inner side wall 55.

  Although FIG. 3 shows a cross section in the width direction, the same configuration can be applied to the cross section in the longitudinal direction.

  Now, in the seal member 40 of the present embodiment, a guard wall 57 is provided to prevent the blow-by gas and oil mist in the crankcase 4 or the crank chamber 32 from entering the groove 49.

  The guard wall 57 forms a cover wall that covers the inner side surface portion 56 of the crankcase 4 located on the inner side or the inner side of the crankcase 4 with respect to the groove 49. The guard wall 57 is a flat hanging wall hanging from the sealing member 40 or the inner surface 40A of the sealing member main body 46, and is formed integrally with the sealing member main body 46 in the present embodiment, but is formed separately. It may be fixed. The guard wall 57 is preferably formed of the same material as the seal member body 46. The shape of the guard wall 57 can be changed.

  The guard wall 57 of the present embodiment is formed in an annular shape along the entire circumference of the lower end edge portion 41 of the seal member 40 corresponding to the groove 49 being formed in an annular shape. However, the guard wall 57 only needs to cover at least the crankcase inner side surface 56 inside the groove 49. Therefore, when the groove 49 is intermittent, the guard wall 57 may also be intermittent, and the guard wall 57 may be provided only for a part of the plurality of grooves 49.

  In the case of the illustrated example, a gap is formed between the guard wall 57 and the crankcase inner side surface portion 56. However, this gap may not be present, and it is preferable that there is no gap. In other words, the guard wall 57 is preferably in surface contact or in close contact with the crankcase inner side surface portion 56.

  According to this embodiment, the following effects are exhibited. If it is assumed that there is no guard wall 57, the inner portion 49 </ b> A of the groove 49 located on the inner side or the inner side of the crankcase with respect to the convex portion 47 is directly open into the crankcase 4. The blow-by gas and the oil mist in the crankcase 4 enter the inner portion 49A, and the condensed water resulting from the blow-by gas and the oil resulting from the oil mist enter and accumulate. The infiltrated and accumulated condensed water is dried when the engine is stopped, etc., and generates an acidic substance. The oil that has entered and accumulated gradually deteriorates. These acidic substances and deteriorated oil may deteriorate and damage the seal member 40, in particular, the projection 47 of the seal member main body 46 adjacent to the portion 49A and the surrounding material. Moreover, since these infiltration deposits are accumulated in the narrow inner portion 49A in the groove 49, it is very difficult to discharge them once they enter.

  On the other hand, according to the present embodiment having the guard wall 57, the inner portion 49 </ b> A can be further closed with respect to the inside of the crankcase 4 by the guard wall 57, in other words, from the inside of the crankcase 4. The passage leading to the inner portion 49A can be narrowed. Therefore, it is possible to suppress the penetration of blowby gas and oil mist into the inner portion 49A, and the penetration and accumulation of condensed water and oil, thereby preventing the seal member 40 from being deteriorated or damaged.

  FIG. 4 shows a first modification of the present embodiment. As shown in the figure, the guard wall 57 is provided with one protrusion 58 that protrudes toward the inner side surface 56 of the crankcase 4. The tip of the projection 58 is in contact with the inner side surface 56.

  In the case of the present embodiment, the protrusion 58 is formed in a triangular or mountain shape in cross section that tapers toward the inner side surface portion 56, and increases the seal surface pressure at the contact portion with the inner side surface portion 56. Further, like the guard wall 57, the protrusion 58 is formed in an annular shape along the entire circumference of the lower end edge 41 of the seal member 40. However, when the guard wall 57 is intermittent, the protrusion 58 can also be provided intermittently. The protrusions 58 may be provided only on some of the plurality of guard walls 57. The protrusion 58 is formed integrally with the guard wall 57, but may be formed separately from the guard wall 57 and fixed. The cross-sectional shape of the protrusion 58 is arbitrary, and may be a rectangle, a semicircle, or the like.

  According to the first modification, the protrusion 58 narrows the gap between the guard wall 57 and the inner side surface 56, seals the gap, and the inner portion 49 </ b> A of the groove 49 is more than the inside of the crankcase 4. It can be in a closed state. Therefore, infiltration of blow-by gas and oil mist into the inner portion 49A, and further infiltration and accumulation of condensed water and oil can be further suppressed, and deterioration or breakage of the seal member 40 can be prevented in advance.

  FIG. 5 shows a second modification of the present embodiment. As shown in the figure, the guard wall 57 is provided with a plurality of projections 58 similar to those of the first modification. Blow-by gas or the like in the crankcase 4 flows through the gap between the guard wall 57 and the inner side surface portion 56 from the lower side to the upper side and travels toward the inner portion 49 </ b> A of the groove 49. A plurality of protrusions 58 are provided in the flow direction of this blow-by gas or the like. Although there are three protrusions 58 in the illustrated example, the number of protrusions 58 is arbitrary.

  According to the second modified example, in addition to the operational effects of the first modified example, the labyrinth effect by the plurality of protrusions 58 allows the blow-by gas and oil mist to enter the inner portion 49A of the groove 49, and further the condensed water and Oil penetration and accumulation can be further suppressed, and deterioration or breakage of the seal member 40 can be prevented in advance.

  FIG. 6 shows a third modification of the present embodiment. In the third modified example, a guard wall 57A is provided in the crankcase 4 to prevent the blow-by gas and oil mist in the crankcase 4 from entering the inner portion 49A of the groove 49.

  In the third modification, the distance L between the inner side surface portion 56 of the crankcase 4 and the outer side surface portion 62 of the cylinder block 3 is larger than in the above-described embodiment. Accordingly, the lower end edge portion 41 of the seal member main body 46 and the pressing portion 51 of the retainer 43 are also extended inward. In other words, the third modified example can be suitably applied to a place where the distance L is increased and the lower edge 41 and the holding portion 51 are extended.

  The guard wall 57A protrudes inward from the inner side surface portion 56 of the crankcase 4 and comes into surface contact with the lower surface of the lower end edge portion 41 for a predetermined length so that blow-by gas and oil mist enter the inner portion 49A of the groove 49. While suppressing, the lower end edge part 41 is supported from the downward direction. In the illustrated example, the guard wall 57A is formed integrally with the crankcase 4 and has a triangular cross section. However, the guard wall 57A may be formed separately from the crankcase 4 and attached to the inner side surface portion 56 of the crankcase 4, and the cross-sectional shape thereof may be another shape such as a square.

  It can be said that the guard wall 57A has the above-mentioned inner side wall 55 protruding inward. The guard wall 57A extends inward by substantially the same length as the pressing portion 51 of the retainer 43.

  According to this third modified example, the inner portion 49A of the groove 49 can be further closed with respect to the inside of the crankcase 4 by the guard wall 57A as in the above embodiment. Then, infiltration of blow-by gas and oil mist into the inner portion 49A, and further infiltration and accumulation of condensed water and oil can be suppressed, and deterioration or breakage of the seal member 40 can be prevented in advance.

  In addition to this, the guard wall 57A of the present embodiment also has an effect as a reinforcing rib for preventing undesirable deformation of the seal member 40.

  That is, as in the comparative example shown in FIG. 7, if there is no guard wall 57A, there is no support for the lower end edge portion 41 (particularly, the extended portion) of the seal member 40 from below. Then, when the cylinder block 3 is lowered with respect to the crankcase 4 as indicated by an arrow in the drawing, or when the seal member 40 is sucked from the inside by the negative pressure in the crankcase 4, the seal member 40 is normal as shown in the figure. There is a risk that it will not deform.

  That is, only the expansion / contraction deformation of the deformation portion 60 of the seal member 40 is scheduled. However, when the lower end edge portion 41 is extended inward as described above and the guard wall 57A is eliminated, the deformed portion does not stop at the deformed portion 60, and the protruding portion from the inner side wall 55 of the lower end edge portion 41 as shown in the figure. P1 may also be reached. The lower end edge 41 bends downward at the protruding portion P1. There is a possibility that the amount of deformation of the deforming portion 60 is reduced due to the deformation of other portions. As described above, the seal member 40 may be deformed in a mode different from the original deformation mode, which may cause early deterioration of the seal member 40.

  In addition, since the holding portion 51 of the retainer 43 is extended, bending deformation upward of the lower end edge portion 41 is prevented, but there is nothing to support below the extended portion of the lower end edge portion 41. Downward bending deformation becomes a problem.

  However, in the present embodiment, as shown in FIG. 6, the guard wall 57 </ b> A is provided, so that the lower end edge portion 41 (particularly, the extended portion) of the seal member 40 can be supported from below. Even when the cylinder block 3 is lowered with respect to the crankcase 4 or when the seal member 40 is sucked from the inside due to the negative pressure in the crankcase 4, the lower end edge portion 41 is prevented from being bent downward and sealed. Undesirable deformation of the member 40 can be prevented. Thereby, the normal deformation mode of the seal member 40 can be maintained, and early deterioration of the seal member 40 can be prevented.

  Here, a case where the distance L between the inner side surface portion 56 of the crankcase 4 and the outer side surface portion 62 of the cylinder block 3 is enlarged and the lower end edge portion 41 of the seal member main body 46 and the pressing portion 51 of the retainer 43 are extended inwardly. Although described, if this is not the case, for example, this example can also be applied to the structure as shown in FIG.

  FIG. 8 shows a fourth modification of the present embodiment. In the fourth modification, a guard wall 57B similar to that in the third modification is provided not on the crankcase 4 but on the seal member 40.

  The lower edge 41 extends from the inner side wall 55 so as to protrude inward by a predetermined length. The guard wall 57B protrudes downward from the extended portion of the lower end edge 41 and is integrally formed with the lower end edge 41, and has a triangular cross section. However, the guard wall 57B may be formed separately from the lower edge 41 and attached to the lower edge 41, and the cross-sectional shape thereof may be another shape such as a square.

  The guard wall 57 </ b> B is in surface contact with the inner side surface portion 56 of the inner side wall 55 of the crankcase 4. Thereby, it is possible to suppress the penetration of blow-by gas or the like into the inner portion 49A of the groove 49, and the penetration and accumulation of condensed water, and prevent the seal member 40 from being deteriorated or damaged. Further, the guard wall 57B also functions as a reinforcing rib that prevents the lower end edge portion 41 from being bent downward, thereby preventing an undesirable deformation of the seal member 40 and preventing its early deterioration.

  The preferred embodiment of the present invention has been described in detail above, but various other embodiments of the present invention are conceivable.

  The embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention. The above embodiments and components can be combined as much as possible.

DESCRIPTION OF SYMBOLS 1 Variable compression ratio internal combustion engine 2 Cylinder 3 Cylinder block 4 Crankcase 20 Crankshaft 21 Compression ratio variable mechanism 40 Seal member 40A Inner surface 41 Lower end edge 43 Retainer 47 Protrusion 49 Groove 56 Inner side surface 57, 57A, 57B Guard wall 58 Protrusion Part

Claims (10)

A variable compression ratio internal combustion engine in which the cylinder block and the crankcase are relatively movable in the cylinder axial direction;
An annular seal member provided between the cylinder block and the crankcase is provided to cover a gap between the cylinder block and the crankcase over the entire circumference of the internal combustion engine, and one end edge of the seal member Protruding portions are provided, grooves are formed in the crankcase for fitting the protruding portions, and a guard wall for suppressing blow-by gas and oil mist in the crankcase from entering the grooves is provided in the seal. A variable compression ratio internal combustion engine provided on a member or the crankcase. The variable compression ratio internal combustion engine according to claim 1, wherein the guard wall is provided on the seal member. The variable compression ratio internal combustion engine according to claim 2, wherein the guard wall covers an inner side surface portion of the crankcase located on an inner side of the crankcase with respect to the groove. 4. The variable compression ratio internal combustion engine according to claim 2, wherein the guard wall forms a hanging wall that hangs down from an inner surface of the seal member. 5. The variable compression ratio internal combustion engine according to any one of claims 2 to 4, wherein the guard wall has one or more protrusions protruding toward an inner side surface of the crankcase. The variable compression ratio internal combustion engine according to any one of claims 2 to 5, wherein the guard wall is in contact with an inner side surface portion of the crankcase. The variable compression ratio internal combustion engine according to claim 1, wherein the guard wall is provided in the crankcase. The variable compression ratio internal combustion engine according to claim 7, wherein the guard wall is in contact with the seal member. The variable compression ratio internal combustion engine according to any one of claims 1 to 8, wherein the guard wall is provided along the entire circumference of the annular seal member. The retainer which clamps one edge part of the said sealing member between the said crankcase in the state which inserted the said convex part in the said groove | channel is provided. A variable compression ratio internal combustion engine according to 1.

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