JP2011117366A - Variable compression ratio mechanism for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the ease of assembly of a sealing member disposed between a cylinder block and a crankcase, and to improve the durability of the sealing member, in a variable compression ratio mechanism changing the compression ratio of an internal combustion engine by relatively sliding the cylinder block and the crankcase. <P>SOLUTION: The variable compression ratio mechanism for an internal combustion engine changes the compression ratio of the internal combustion engine by relatively sliding the cylinder block and the crank case in a cylinder axis direction. In the variable compression ratio mechanism for an internal combustion engine, an annular sealing member installed between the cylinder block and the crankcase is provided to cover the clearance between the cylinder block and the crankcase over a whole circumference of the internal combustion engine, and the sealing member is formed into a shape of bellows having only one crest part. <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 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 above-described mechanism, a gasket cannot be disposed at a connecting portion between the crankcase and the cylinder block as in the conventional case. On the other hand, in order to maintain airtightness in the crankcase or prevent leakage of lubricating oil supplied to the sliding part 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. It aims at improving and durability of a 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.
An annular seal member provided between the cylinder block and the crankcase so as to cover a gap between the cylinder block and the crankcase over the entire circumference of the internal combustion engine;
The sealing material was formed in a bellows shape having one peak.

  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 having only one peak, the curvature of the bent portion is larger than that of a bellows having a plurality of peaks. When the curvature of the bent portion increases, it is 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 in the compression ratio. Therefore, the durability of the sealing material can be improved.

In the present invention, as a method of joining the sealing material and the cylinder block, a method of sandwiching one open end of the sealing material between the cylinder block and the cylinder head can be used. According to this joining method, when the cylinder head is assembled to the cylinder block, it is only necessary to sandwich one opening end of the sealing material, so that the joining work between the sealing material and the cylinder block becomes easy.

  Note that a reinforcing member such as an iron plate may be cast into a portion of the sealing material sandwiched between the cylinder block and the cylinder head. According to such a configuration, when the cylinder head is assembled to the cylinder block, it is possible to avoid a situation where the sealing material is excessively deformed or broken. As a result, the joining operation between the sealing material and the cylinder block can be facilitated and the durability of the sealing material can be improved.

  In the present invention, as a method for joining the sealing material and the crankcase, a method of sandwiching the other open end of the sealing material between the crankcase and the retainer can be used. According to this joining method, the other opening end of the sealing material may be sandwiched between the crankcase and the retainer, so that the joining work between the sealing material and the crankcase becomes easy.

  In addition, an annular ridge is provided at the other opening end of the seal material, an annular groove is provided on the outer periphery of the crankcase, and the seal material and the crankcase are joined with the ridge fitted into the groove. You may make it do. According to such a configuration, the sealing performance at the joint between the sealing material and the crankcase can be improved.

  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. 1 is an exploded perspective view of an internal combustion engine to which the present invention is applied. It is sectional drawing which shows the structure of a sealing material. It is sectional drawing which shows the junction part of a sealing material and a cylinder block. It is a top view of a cylinder block. It is sectional drawing which shows the junction part of a sealing material and a crankcase. It is a top view of a crankcase.

  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.

  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 airtightness in the crankcase 3, it is necessary to seal a gap at a portion where the cylinder block 2 and the crankcase 3 overlap each other. On the other hand, in the variable compression ratio mechanism of the internal combustion engine of this embodiment, as shown in FIG.

  Here, the structure of the sealing material 200 is demonstrated based on FIG. 3 thru | or FIG. FIG. 3 is a cross-sectional view of the sealing material 200. FIG. 4 is a cross-sectional view showing a joint portion between the sealing material 200 and the cylinder block 2. FIG. 5 is a plan view of the cylinder block 2. FIG. 6 is a cross-sectional view showing a joint portion between the sealing material 200 and the crankcase 3. FIG. 7 is a plan view of 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.

  As shown in FIG. 3, the seal material 200 according to the present embodiment is provided with a bellows-like seal body 201 having only one peak protruding inward, and an upper opening end of the seal body 201. And a first support part 202 sandwiched between the cylinder block 2 and a second support part 203 provided at the lower opening end of the seal body 201 and sandwiched between the crankcase 3 and the retainer 30. I have.

  The seal body 201 is made of a material having flexibility and pressure resistance. An example of the material having flexibility and pressure resistance is thermoplastic elastomer (TPEE) which is an intermediate composition of rubber and resin. At that time, the chemical resistance of the seal body 201 may be improved by forming a film such as a fluororesin on the inner surface of the seal body 201.

  The first support portion 202 is an annular body having a lower surface parallel to the upper surface of the cylinder block 2 and is integrally formed with the seal body 201. As shown in FIG. 4, a metal reinforcing member 220 is cast into the first support portion 202. The reinforcing member 220 is cast into the first supporting portion 202 such that the upper surface of the reinforcing member 220 is exposed from the first supporting portion 202 and the lower surface of the reinforcing member 220 is covered by the first supporting portion 202. ing.

Two annular ribs 221 are provided on a portion of the lower surface of the first support portion 202 that contacts the upper surface of the cylinder block 2. Correspondingly, as shown in FIG. 5, two annular grooves 20 are formed in a portion of the upper surface of the cylinder block 2 facing the rib 221.

  On the other hand, the second support portion 203 is an annular body having a lower surface parallel to the upper surface of the crankcase 3 and is integrally formed with the seal body 201. As shown in FIG. 6, an annular protrusion 230 is formed on the lower surface of the second support portion 203 over the entire circumference of the second support portion 203. The ridge 230 is covered with a cover 231 that is more flexible than the ridge 230. As a material of the cover 231, TPEE having a higher flexibility than the seal main body 201 using a method such as copolymerization, a material in which an elastomer component is blended with TPEE, or rubber can be used.

  An annular groove 32 is formed in a portion of the upper surface of the crankcase 3 facing the cover 231 as shown in FIG. A retainer 30 can be fastened to the crankcase 3 by a bolt 31.

  Hereinafter, a method for assembling the sealing material 200 will be described. When attaching the sealing material 200 to the cylinder block 2, the rib 221 of the first support portion 202 is fitted into the groove 20 of the cylinder block 2 before the cylinder block 2 and the cylinder head 4 are assembled. Subsequently, the first support portion 202 is sandwiched between the cylinder block 2 and the cylinder head 4 by fastening the cylinder block 2 and the cylinder head 4.

  Next, when attaching the sealing material 200 to the crankcase 3, the cover 231 is fitted into the groove 32 of the crankcase 3 with the cover 231 attached to the second support portion 203 being attached. Subsequently, the retainer 30 is fastened to the crankcase 3 by the bolt 31, whereby the second support portion 203 is sandwiched between the retainer 30 and the crankcase 3.

  As described above, according to the sealing material 200 of the present embodiment, a dedicated jig or the like is not required when assembling the sealing material 200 to the internal combustion engine 1, so that the ease of assembly is high. Furthermore, since the seal body 201 is formed in a bellows shape with only one peak portion, the curvature of the bent portion can be increased as compared with a bellows shape in which a plurality of peak portions are formed. As a result, when the sealing material 200 expands and contracts due to the relative displacement between the cylinder block 2 and the crankcase 3, it is difficult for wrinkles to move toward the sealing material 200 and the stress acting on the sealing material 200 is dispersed over a wide range. Can do. Therefore, the durability of the sealing material 200 can be improved.

  Further, by providing the ribs 221 on the first support portion 202, the sealing performance between the cylinder block 2 and the sealing material 200 can be enhanced. Further, by casting the reinforcing member 220 into the first support portion 202, unnecessary deformation of the first support portion 202 is suppressed, and the first support portion 202 is caused by the fastening pressure between the cylinder block 2 and the cylinder head 4. Can be prevented from being twisted or broken. Note that a sealing material formed of a bullet body such as rubber may be added between the first support portion 202 and the cylinder block 2. In that case, the sealing performance between the cylinder block 2 and the sealing material 200 can be further enhanced.

  On the other hand, an annular projecting cover 231 is attached to the lower surface of the second support portion 203, and a groove 32 for fitting the cover 231 is provided on the upper surface of the crankcase 3, whereby the crankcase 3 and the sealing material 200 are provided. The sealing property can be improved.

  Therefore, according to this embodiment, in the internal combustion engine in which the compression ratio is changed by relatively sliding the cylinder block 2 and the crankcase 3 in the cylinder axial direction, the cylinder block 2 and the crankcase 3 are disposed between the cylinder block 2 and the crankcase 3. The ease of assembly of the sealing material 200 to be performed can be improved, and the durability of the sealing material 200 can be improved.

  In the present embodiment, the configuration in which the first support portion 202 of the sealing material 200 is sandwiched between the cylinder head 4 and the cylinder block 2 has been described as an example, but the first support portion 202 may be sandwiched between the wall surface of the cylinder block 2 and the retainer. Good. In short, as long as the seal body 201 of the sealing material 200 is formed in a bellows shape having one peak, the fixing method of the first support portion 202 and the second support portion 203 may be any form.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder block 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 20 Groove 30 Retainer 31 Bolt 32 Groove 100 Variable compression ratio mechanism 200 Seal material 201 Seal body 202 First support section 203 Second support section 220 Reinforcing member 221 Rib 230 Projection 231 Cover

Claims (3)

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,
An annular seal member provided between the cylinder block and the crankcase so as to cover a gap between the cylinder block and the crankcase over the entire circumference of the internal combustion engine;
The variable compression ratio mechanism for an internal combustion engine, wherein the sealing material is formed in a bellows shape having one peak portion.   2. The sealing member according to claim 1, wherein a reinforcing member is cast into one opening end of the sealing material, and a portion where the reinforcing member is cast is sandwiched between the cylinder block and the cylinder head. Variable compression ratio mechanism for internal combustion engines. In Claim 1 or 2, an annular groove is provided on the outer periphery of the crankcase, and an annular protrusion that fits into the groove is provided at the other opening end of the seal material.
The variable compression ratio mechanism for an internal combustion engine, wherein the other open end of the seal material is sandwiched between the crankcase and the retainer in a state where the protrusion is fitted in the groove.

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