JP2009036128A - Multi-link variable compression ratio engine - Google Patents

Abstract

Provided is a multi-link variable compression ratio engine capable of preventing lubricating oil from flowing into a combustion chamber and suppressing oil deterioration due to blow-by gas.
In an engine 1 having a piston 21 that reciprocates in a cylinder, a piston rod 22 formed on the piston 21, a piston rod 22 and a crankshaft 36 are connected by a plurality of links to bring the vehicle into an operating state. Correspondingly, the compression ratio variable mechanism 30 that changes the compression ratio by changing the posture of the link, and a partition that partitions the cylinder from the crank chamber 24 below the piston 21 and through which the piston rod 22 penetrates freely. 50, the lower surface of the piston 21, the cylinder wall, and the partition wall 50. The expansion / contraction chamber 60 expands / contracts as the piston 21 reciprocates, and the expansion / contraction chamber 60 communicates with the intake system and leaks into the expansion / contraction chamber 60. And a return passage 13 for returning the blowby gas to the intake system.
[Selection] Figure 1

Description

  The present invention relates to a multi-link variable compression ratio engine.

  Conventionally, in a vehicle engine, there has been a problem that lubricating oil flows out into the combustion chamber from the gap between the piston and the cylinder due to the reciprocating movement of the piston, and the consumption amount of the lubricating oil increases.

The invention described in Patent Document 1 includes an expander spring in the oil ring groove, and adjusts the tension of the oil ring according to the load, thereby preventing seizure between the piston ring and the cylinder liner and consumption of lubricating oil. Reduce.
JP-A-6-123357

  However, in the invention described in Patent Document 1, if a response delay occurs in the control of the expander spring, the outflow of the lubricating oil into the combustion chamber cannot be reliably reduced. In addition, blow-by gas containing unburned fuel or the like flows from the combustion chamber into the crank chamber through the gap between the piston and the cylinder, and there is a problem that oil deterioration of the lubricating oil occurs.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a multi-link variable compression ratio engine that can prevent lubricating oil from flowing out into a combustion chamber and suppress oil deterioration due to blow-by gas.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention provides an engine (1) having a piston (21) that reciprocates in a cylinder, a piston rod (22) formed on the piston (21), the piston rod (22), and a crankshaft (36). Are connected by a plurality of links, and the compression ratio variable mechanism (30) for changing the compression ratio by changing the posture of the link according to the driving state of the vehicle, and the cylinder in the lower side of the piston (21) Is formed by a partition wall (50) through which the piston rod (22) freely slides, a lower surface of the piston (21), a cylinder wall, and the partition wall (50). The expansion / contraction chamber (60) that expands / contracts with the reciprocating motion of the piston (21), and the expansion / contraction chamber (60) communicates with an intake system so as to leak into the expansion / contraction chamber (60). It includes a recirculation passage for recirculating to the intake system (13) to Baigasu, the.

  According to the present invention, the partition wall is arranged below the piston, and the piston rod slides through the partition wall, so that the side thrust load generated in the piston is reduced. Therefore, the piston skirt can be shortened, and the piston can reciprocate in the cylinder without lubricating oil. Therefore, the consumption amount of lubricating oil can be reliably reduced, and the exhaust performance can be improved.

  In addition, since the expansion / contraction chamber communicated with the intake system is provided below the piston, the blow-by gas can be recirculated to the intake system using the pressure generated in the expansion / contraction chamber by the reciprocating motion of the piston. Deterioration can be suppressed.

  Furthermore, since the compression ratio is optimally controlled according to the driving state of the vehicle, the thermal efficiency can be improved and the fuel efficiency can be improved.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic view showing a multi-link variable compression ratio engine of the present embodiment.

  The multi-link variable compression ratio engine 1 includes a cross head mechanism 20 that reduces the side thrust load of the piston 21 and a multi-link mechanism 30 that makes the compression ratio variable inside the cylinder block 10. In addition, illustration of the cylinder head attached to the upper part of the cylinder block 10 is abbreviate | omitted.

  The crosshead mechanism 20 includes a piston 21, a piston rod 22, and an upper link 31.

  The piston 21 has no piston skirt or very little, and is accommodated in the cylinder 11 of the cylinder block 10. The combustion chamber 2 is partitioned by the crown surface of the piston 21, the wall surface of the cylinder 11, and the inner wall of a cylinder head (not shown).

  A piston rod 22 is integrally formed coaxially with the piston 21 at the lower part of the piston 21. The piston rod 22 may be provided so as to be separable from the piston 21. A thrust support 50 is provided on the lower side of the piston 21 as a partition wall that partitions the inside of the cylinder 11 between the lower side of the piston 21 and the crank chamber 24. Therefore, the piston rod 22 penetrates the thrust support 50 and is supported slidably by the hole 51 of the thrust support 50. Here, the piston rod 22 and the hole 51 of the thrust support 50 are sealed by an oil seal 52 having high lubricity.

  The lower end of the piston rod 22 of the piston 21 is connected to the upper end of the upper link 31 of the multi-link mechanism 30 via the piston pin 23. The lower end of the upper link 31 is connected to one end of the lower link 32 via a connecting pin 34. The other end of the lower link 32 is connected to the control link 33 via a connecting pin 35. The lower link 32 is configured to be divided from two members on the left and right in the figure, and has a connecting hole 32a at the center. The crank pin 36a of the crankshaft 36 is inserted into the connecting hole 32a.

  The crankshaft 36 includes a crankpin 36a, a journal 36b, and a counterweight 36c. The center of the crank pin 36a is eccentric by a predetermined amount from the center of the journal 36b, and the lower link 32 is rotatably connected to the crank pin 36a. The journal 36 b is rotatably supported by the cylinder block 10 and the ladder frame 37. The axis of the journal 36b is coincident with the axis of the crankshaft 36. The counterweight 36c is integrally formed with the crank arm and reduces the rotational primary vibration component of the piston motion.

  The upper end of the control link 33 is rotatably connected to the lower link 32 via a connecting pin 35. Further, the lower end of the control link 33 is connected to a control shaft 41 arranged in parallel with the crankshaft 36 via a connecting pin 38. The connecting pin 38 is eccentric from the axis of the control shaft 41 by a predetermined amount, and the control link 33 swings around the eccentric connecting pin 38 as an axis. The control shaft 41 forms a gear 42 on the outer periphery thereof. This gear 42 meshes with the pinion 43. The pinion 43 is provided on the rotating shaft 45 of the actuator 44 attached to the side of the cylinder block 10.

  In the multi-link variable compression ratio engine 1 configured as described above, the reciprocating motion of the piston 21 is transmitted to the upper link 31 by the piston rod 22 and further changed to the rotational motion of the crankshaft 36 via the lower link 32. . In this case, the lower link 32 rotates counterclockwise in the figure with respect to the center of the crankshaft 36 while swinging about the crankpin 36a as the center axis. The control link 33 connected to the lower link 32 swings around the connecting pin 38 of the control shaft 41 connected to the lower end thereof. Since the control shaft 41 and the connecting pin 38 are eccentric, when the control shaft 41 is rotated by the actuator 44, the connecting pin 38 moves. Since the swing center of the control link 33 is changed by the movement of the connecting pin 38, the inclination of the upper link 31 and the lower link 32 can be changed, and the top dead center position of the piston 21 can be arbitrarily set within a predetermined range. Can be adjusted. Thus, in the multi-link variable compression ratio engine 1, the mechanical compression ratio is variable by adjusting the top dead center position of the piston 21.

  On the other hand, in this multi-link variable compression ratio engine 1, blow-by gas that has flowed from the combustion chamber to the crank chamber side through the sliding gap between the piston 21 and the cylinder 11 flows into an intake passage (not shown) by reciprocation of the piston 21. The expansion / contraction chamber 60 is refluxed.

  The expansion / contraction chamber 60 is formed by the wall surface of the cylinder 11, the lower surface of the piston 21, and the upper surface of the thrust support 50. The thrust support 50 is fixed below the bottom dead center position of the piston 21, and a recess 53 is formed on the upper surface of the thrust support 50. A through hole 12 is provided on one side of the cylinder block 10, and a communication pipe 13 is connected to the through hole 12. The communication pipe 13 communicates the expansion / contraction chamber 60 and an intake passage (not shown) via the recess 53 of the thrust support 50 and the through hole 12. The expansion / contraction chamber 60 of the multi-link variable compression ratio engine 1 repeatedly expands and contracts as the piston 21 reciprocates, and the blow-by gas flowing from the combustion chamber 2 into the expansion / contraction chamber 60 is returned to the intake system. .

  The multi-link variable compression ratio engine 1 as described above includes a controller 70 for controlling the fuel injection amount, the ignition timing, the throttle valve opening, and the mechanical compression ratio in accordance with the driving state of the vehicle. The controller 70 includes a CPU, a ROM, a RAM, and an I / O interface.

  The controller 70 receives outputs from various sensors that detect vehicle operating conditions such as a knock sensor and a crank angle sensor (not shown). The controller 70 controls a throttle valve, a fuel injection valve, and a spark plug (not shown) based on these outputs. In addition, the controller 70 refers to a preset mechanical compression ratio map, optimally controls the mechanical compression ratio in accordance with the driving state of the vehicle, improves the thermal efficiency, and improves the fuel efficiency performance. For example, at low rotational speed and small torque, the mechanical compression ratio is increased to improve thermal efficiency, and on the high rotational speed and large torque side, the mechanical compression ratio is decreased to prevent knocking.

  By the way, in a conventional vehicle engine, the lubricating oil flows into the combustion chamber 2 through the gap between the piston 21 and the cylinder 11 due to the reciprocating motion of the piston 21, and the consumption amount of the lubricating oil increases. There is a problem that the oil flows into the chamber 24 and causes deterioration of the lubricating oil.

  However, in the multi-link variable compression ratio engine 1, the above problem is solved by combining the multi-link mechanism 30 and the thrust support 50 as shown in FIG.

  FIG. 2 is a diagram for explaining a reduction in the amount of consumption of lubricating oil in the multi-link variable compression ratio engine 1.

  In the multi-link variable compression ratio engine 1, by selecting the alignment of the multi-link mechanism 30, as shown in FIG. 2, in the first half of the expansion stroke in which the internal pressure of the combustion chamber 2 reaches the maximum value Pmax, The connected upper link 31 can be maintained in an upright posture (a state in which the inclination angle θ of the axis L2 of the upper link 31 with respect to the axis L1 of the piston rod 22 is close to 0 °). Therefore, the side thrust load generated in the piston 21 according to the inclination angle θ of the upper link 31 can be greatly reduced. Further, since the piston rod 22 of the multi-link variable compression ratio engine 1 slides with respect to the hole 51 of the thrust support 50, the thrust support 50 receives most of the side thrust load generated in the piston 21.

  As described above, in the multi-link variable compression ratio engine 1, the side thrust load generated in the piston 21 is significantly reduced, so that the piston skirt length of the piston 21 can be shortened. Therefore, the piston 21 can reciprocate inside the cylinder 11 even without lubricating oil. Therefore, it is possible to prevent the lubricating oil from flowing out into the combustion chamber due to the reciprocating motion of the piston 21, and it is possible to reliably reduce the consumption amount of the lubricating oil and improve the exhaust performance.

  In the multi-link variable compression ratio engine 1, the piston ring may be subjected to a surface treatment so that the piston ring 25 of the piston 21 can be easily lubricated with respect to the cylinder wall.

  Next, suppression of oil deterioration of the lubricating oil in the multi-link variable compression ratio engine 1 will be described with reference to FIG.

  FIG. 3 is a view showing the operation of the expansion / contraction chamber 60 of the multi-link variable compression ratio engine 1. FIG. 3A shows the flow of blow-by gas when the piston 21 moves from the bottom dead center to the top dead center in the compression stroke. FIG. 3B shows the flow of blow-by gas when the piston 21 moves from the top dead center to the bottom dead center in the expansion stroke.

  As shown in FIG. 3A, when the piston 21 rises from the bottom dead center to the top dead center, the expansion / contraction chamber 60 expands and the combustion chamber 2 contracts, so the air-fuel mixture in the combustion chamber is compressed. When this compressed air-fuel mixture explodes and burns near the top dead center of the piston by the spark plug, the piston 21 is pushed down from the top dead center to the bottom dead center, and blow-by gas containing unburned fuel and the like is separated from the piston 21. It flows into the expansion / contraction chamber 60 from the combustion chamber 2 through the gap with the cylinder 11. As shown in FIG. 3B, when the piston 21 descends from the top dead center to the bottom dead center, the combustion chamber 2 expands and the expansion / contraction chamber 60 contracts. Thus, when the expansion / contraction chamber 60 contracts, the blow-by gas in the expansion / contraction chamber is pressurized, and the blow-by gas flows into the communication pipe 13 and returns to the intake passage (not shown) through the communication pipe 13.

  Thus, the multi-link variable compression ratio engine 1 recirculates the blow-by gas from the combustion chamber 2 to the intake system (hereinafter referred to as “internal recirculation of blow-by gas”) by the expansion / contraction operation of the expansion / contraction chamber 60 (internal recirculation). means). Further, since the piston rod 22 of the piston 21 is slidably sealed by the oil seal 52 of the thrust support 50, the above-described blow-by gas is also suppressed from flowing into the crank chamber 24 from the expansion / contraction chamber 60. Therefore, in the multi-link variable compression ratio engine 1, oil deterioration of the lubricating oil in the crank chamber due to blow-by gas is suppressed.

  When the blow-by gas is internally recirculated by the expansion / contraction of the expansion / contraction chamber 60 as described above, pressure fluctuation occurs in the expansion / contraction chamber 60 and the pumping of the piston 21 increases. The passages formed in the block may communicate with each other to suppress the pressure fluctuation and reduce the pumping loss.

  By the way, if the crosshead mechanism 20 is provided in order to reduce the consumption amount of lubricating oil or suppress the oil deterioration, the multi-link variable compression ratio engine 1 is increased in size.

  Therefore, an increase in engine height due to the provision of the crosshead mechanism will be described with reference to an engine (hereinafter referred to as “conventional engine”) in which a piston and a crankshaft are connected by a single connecting rod.

  FIG. 4 is a diagram showing a configuration of a conventional engine.

  The conventional engine 100 includes a piston 121 and a connecting rod 131 as shown in FIG. The piston 121 is connected to the upper end of the connecting rod 131 through a piston pin 123. The lower end of the connecting rod 131 is connected to a crankpin 136a that is eccentric from the journal 136b of the crankshaft 136 by a predetermined amount.

  In such a conventional engine 100, when the blow-by gas is internally recirculated by the crosshead mechanism 120, as shown in FIG. 4B, a piston rod 122 is formed on the piston 121, and the piston rod 122 and the connecting rod 131 are formed. Are connected via a piston pin 123. In the conventional engine 100 including the crosshead mechanism 120, the piston pin 123 is set at the same position as that in FIG. 4A, so that the engine height is increased by the piston rod 122 formed on the piston 121.

  In order to suppress the engine height, it is conceivable to shorten the connecting rod 131 to reduce the linkage ratio. Here, the linkage ratio is expressed by the following formula.

  However, in the conventional engine 100, when the length of the connecting rod 131 is shortened and the linkage ratio is reduced, the piston stroke characteristics are greatly deviated from simple vibrations, and vibrations caused by the reciprocating motion of the piston 121 and the rotational motion of the crank pin 136a ( Hereinafter referred to as “inertial secondary vibration”). As described above, in the conventional engine 100, since the inertial secondary vibration is deteriorated, the linkage ratio cannot be reduced. When the crosshead mechanism 120 is provided, an increase in the engine height is inevitable.

  On the other hand, in the multi-link variable compression ratio engine 1, the alignment of the multi-link mechanism 30 is selected, and the piston stroke characteristic (solid line A) is changed to the piston stroke characteristic (dashed line B) of the conventional engine 100 as shown in FIG. ), The inertial secondary vibration based on the piston stroke characteristics is reduced. In this way, the crank angle when the piston rises from the center of the stroke and descends to the center of the stroke again through the top dead center, and the crank angle when the piston descends from the center of the stroke and rises again to the center of the stroke through the bottom dead center Are substantially the same, and for details of a configuration in which the piston stroke characteristics are substantially simple vibrations, refer to JP-A-2005-180302.

  The reduction of the Y direction component of the inertial secondary vibration in the multi-link variable compression ratio engine 1 will be described with reference to FIG.

  FIG. 6A schematically shows a multi-link mechanism 30 that reduces the Y-direction component of the inertial secondary vibration. Here, the direction in which the piston 21 reciprocates is the Y direction, and the direction orthogonal thereto is the X direction. FIG. 6B shows the Y direction component of the secondary inertia vibration generated in the piston pin 23. FIG. 6C shows the Y direction component of the inertial secondary vibration generated in the connecting pin 34. 6B and 6C, the horizontal axis indicates the position of the piston 21 in the cylinder, and the vertical axis indicates the Y direction component of the inertial secondary vibration.

  In the multi-link variable compression ratio engine 1, as shown in FIG. 6B, when the piston 21 is at the top dead center or the bottom dead center, the Y-direction generated in the piston pin 23 by the swing of the upper link 31 The alignment of the multi-link mechanism 30 that maximizes the inertial secondary vibration is selected. Further, as shown in FIG. 6C, when the piston 21 is at the top dead center and the bottom dead center, the inertial secondary vibration in the Y direction generated in the connecting pin 34 due to the swing of the control link 33 is minimized. The alignment of the multi-link mechanism 30 is selected. By selecting the alignment of the multi-link mechanism 30 in this way, the Y-direction component of the inertial secondary vibration generated in the piston pin 23 can be canceled by the Y-direction component of the inertial secondary vibration generated in the connecting pin 34. Secondary vibration can be reduced.

  As described above, in the multi-link variable compression ratio engine 1, the secondary inertia vibration can be reduced. Therefore, even if the crosshead mechanism 20 is provided, the distance between the piston pin 23 and the connecting pin 34 is set short (the linkage ratio is reduced). By setting), the engine height can be suppressed.

  FIG. 7 is a diagram schematically showing reciprocation of the piston 21 of the multi-link variable compression ratio engine 1. FIG. 7A shows a case where the piston 21 is at the top dead center. FIG. 7B shows a case where the piston 21 is at the bottom dead center. The center of coordinates indicates the rotation center of the crankshaft 36. 7A and 7B, the detailed configuration of the internal recirculation of blow-by gas is omitted for convenience of explanation.

  The cylinder 11 shown in FIGS. 7A and 7B has substantially the same height as the cylinder 11 used in the multi-link variable compression ratio engine 1 that does not include the crosshead mechanism 20. In the multi-link variable compression ratio engine 1, since the alignment of the multi-link mechanism 30 is selected so that the secondary inertia vibration can be reduced, the linkage ratio is small. Specifically, the piston pin 23 and the connecting pin 34 The distance can be set short. Therefore, as shown in FIG. 7B, the piston pin 23 can be lowered to a position substantially the same as the rotation center of the crankshaft 36 at the bottom dead center position of the piston 21. Therefore, even if the cylinder 11 has substantially the same height as the cylinder 11 used in the multi-link variable compression ratio engine 1 that does not include the crosshead mechanism 20, FIG. 7 (A) and FIG. 7 (B) As shown, the piston 21 can reciprocate with the conventional piston stroke.

  As described above, the multi-link variable compression ratio engine 1 of the present embodiment can obtain the following effects.

  According to the present invention, since the thrust support 50 is disposed below the piston 21 and the piston rod 22 slides through the thrust support 50, the side thrust load generated in the piston 21 is reduced. Therefore, the piston skirt can be shortened, and the piston 21 can reciprocate in the cylinder even without lubricating oil. Therefore, the consumption amount of lubricating oil can be reliably reduced, and the exhaust performance can be improved.

  In addition, an expansion / contraction chamber 60 communicating with the intake passage is provided below the piston 21, and blow-by gas is recirculated to the intake system using the pressure generated in the expansion / contraction chamber 60 by the reciprocation of the piston 21. Therefore, inflow of blow-by gas into the crank chamber 24 is suppressed, and oil deterioration of the lubricating oil due to blow-by gas can be suppressed.

  Further, in the multi-link variable compression ratio engine 1, the secondary inertia vibration can be reduced by selecting the alignment of the multi-link mechanism 30, and the linkage ratio can be set small. Therefore, at the bottom dead center position of the piston 21, the piston pin 23 can be lowered to a position substantially the same as the rotation center of the crankshaft 36, and even if the crosshead mechanism 20 is provided, an increase in engine height is suppressed. Can do.

  It is obvious that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the technical idea.

  For example, you may make it improve the sealing performance with respect to the cylinder 11 of the piston 21 by making the joint part 25a of the piston ring 25 of the piston 21 into a double angle structure.

  FIG. 8 is a view showing a piston ring 25 attached to the piston 21.

  As shown to FIG. 8 (A), the piston ring 25 has the abutment part 25a in a part of circumferential direction. Assuming that the end face of the joint portion 25a of the piston ring 25 is a flat surface, when the piston 21 with the piston ring 25 rises from the bottom dead center toward the top dead center in the cylinder 11, combustion occurs as shown by the arrow. Since the air-fuel mixture in the chamber 2 flows out through the joint portion 25a, the sealing performance of the piston 21 with respect to the cylinder 11 is low.

  Therefore, as shown in FIG. 8B, a convex portion 25b having a triangular cross section is formed at the corner of one end surface of the joint portion 25a of the piston ring 25, and the other end surface corresponding to the convex portion 25b. A recess 25c having the same cross-sectional shape is also formed at the corner of the piston ring 25, and the piston ring 25 is configured so that the protrusion 25b and the recess 25c are combined when the piston ring 25 is attached to the piston 21 (double angle structure). ). In FIG. 8B, the cross sections of the convex portions 25b and the concave portions 25c are right-angled triangle shapes, but are not limited to this, and may be rectangular shapes or the like.

  Sealing performance is improved by attaching (in order) the piston ring 25 of this double angle structure to the piston 21 so that the convex portion 25b is located on the opposite side of the piston crown surface as shown in FIG. 8C. To do. That is, even if the piston 21 moves up from the bottom dead center toward the top dead center inside the cylinder 11 and the air-fuel mixture or the like flows into the joint portion 25a, as shown by the arrow in FIG. The flow of the air-fuel mixture can be cut off, and the sealing performance in the combustion chamber can be improved.

  However, in a conventional engine that requires lubricating oil for the piston 21 to slide on the cylinder 11, as described above, when the piston ring 25 is assembled to the piston 21 in order to improve the sealing performance in the combustion chamber, Although it is possible to suppress the outflow of the air-fuel mixture in the combustion chamber, there is a problem that the lubricating oil that has flowed into the combustion chamber 2 is less likely to return to the crank chamber side, and the amount of lubricating oil consumption increases. . Therefore, in such a conventional engine, the piston ring 25 having the double angle structure is mounted on the piston 21 so that the convex portion 25b is positioned on the piston crown side as shown in FIG. ) Then, when the piston 21 rises, the lubricating oil that has flowed into the combustion chamber easily returns to the crank chamber side through the joint portion 25a as indicated by the arrow in FIG. Therefore, in a conventional engine that requires lubricating oil for the piston 21 to slide on the cylinder 11, the seal performance is slightly reduced by using the piston ring 25 in the reverse assembly instead of the forward assembly. The increase in lubricating oil consumption is suppressed.

  In contrast, in the piston 21 of the multi-link variable compression ratio engine 1, the thrust load is reduced by the multi-link mechanism 30 and the thrust support 50, so that the piston 21 reciprocates in the cylinder 11 without lubricating oil. can do. Therefore, there is no need to reduce the lubricating oil consumption by reversely assembling the piston ring 25 as in the conventional engine. Therefore, in the multi-link variable compression ratio engine 1, the piston ring 25 is assembled in order to improve the sealing performance, and the thermal efficiency can be further improved.

It is a figure which shows the multiple link type variable compression ratio engine of this embodiment. It is a figure shown about reduction of the consumption of lubricating oil. It is a figure which shows operation | movement of an expansion / contraction chamber. It is a figure which shows the structure of the conventional engine. It is a figure which shows a piston stroke characteristic. It is a figure shown about reduction of an inertia secondary vibration. It is a figure which shows typically the reciprocation of the piston of a multiple link type variable compression ratio engine. It is a figure which shows the piston ring with which a piston is mounted | worn.

Explanation of symbols

1 Multi-link variable compression ratio engine 2 Combustion chamber 11 Cylinder 12 Through-hole 13 Communication pipe (recirculation passage)
20 Crosshead mechanism 21 Piston 22 Piston rod 24 Crank chamber 25 Piston ring 25a Joint portion 25b Convex portion 25c Concavity 30 Double link mechanism (compression ratio variable mechanism)
31 Upper link (1st link)
32 Lower link (second link)
33 Control link (3rd link)
36 Crankshaft 41 Control shaft 44 Actuator 50 Thrust support (partition wall)
52 Oil seal 60 Expansion / contraction chamber 70 Controller

Claims (7)

In an engine having a piston that reciprocates in a cylinder,
A piston rod formed on the piston;
The piston rod and the crankshaft are connected by a plurality of links, and the compression ratio variable mechanism that makes the compression ratio variable by changing the posture of the link according to the driving state of the vehicle,
Partitioning the inside of the cylinder from the crank chamber on the lower side of the piston, and a partition wall through which the piston rod slides freely;
An expansion / contraction chamber formed by a lower surface of the piston, a cylinder wall, and a partition wall, which expands / contracts as the piston reciprocates;
A recirculation passage that communicates the expansion chamber with the intake system and recirculates the blow-by gas leaked into the expansion chamber to the intake system;
An engine comprising:   The engine according to claim 1, wherein expansion / contraction chambers of the cylinders of the engine communicate with each other.   The engine according to claim 1, wherein the partition wall includes a sealing member having lubricity at a portion where the piston rod slides. The compression ratio variable mechanism is
A first link that is pivotably coupled to the piston rod;
A second link rotatably connected to the first link and rotatably mounted on the crankshaft;
A control shaft having an eccentric shaft portion that is rotatably supported by the cylinder block in parallel with the crankshaft and is eccentric with respect to the rotation axis;
A third link that is rotatably connected to the second link via a connecting pin, and that is capable of swinging with the eccentric shaft portion of the control shaft as a swing axis;
The control shaft is rotated according to the driving state of the vehicle, the position of the eccentric shaft portion is changed, and the mechanical compression ratio of the engine is changed.
The engine according to any one of claims 1 to 3, wherein The compression ratio variable mechanism is
In the vicinity of the maximum pressure in the combustion chamber, the inclination of the axis of the piston rod and the first link connected to the piston rod is set to approximately 0 °.
The engine according to claim 4. The compression ratio variable mechanism is
The crank angle when the piston ascends from the center of the stroke and descends to the center of the stroke again through the top dead center, and the crank angle when the piston descends from the center of the stroke and rises again to the center of the stroke through the bottom dead center The engine according to claim 4 or 5, wherein the stroke characteristics with respect to a crank angle of the piston are substantially the same as those of a simple vibration.   The piston ring fitted to the piston includes a convex portion formed in the piston ring circumferential direction so as to include an end portion on the piston ring outer peripheral side and the combustion chamber side on one end surface of the piston ring, and the piston ring The engine according to any one of claims 1 to 6, wherein a double-angle structure having a concave portion combined with the convex portion at an end face of the other abutment portion of the ring.

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