JP2008111387A - Double link type variable compression ratio engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double link type variable compression ratio engine capable of preventing flow of lubricating oil to a scavenging port, and reducing the size of an engine. <P>SOLUTION: The two-cycle double link type variable compression ratio engine is provided with a compression ratio variable mechanism 30 for connecting a piston rod 22 formed on a piston 21, and a crankshaft 36 by a plurality of links, a partition wall 12 where a partition piston rod 22 slidably passes through an inside of a cylinder 11 on a lower side of the piston 21 from a crank chamber 24, a pressure chamber 13 formed of a lower surface of the piston 21, a cylinder wall 11a, and the partition wall 12 which is enlarged and reduced in accordance with a reciprocation of the piston 21, valve mechanisms 12c, 12d for opening and closing a suction pipe 14 of new air connected to the pressure chamber 13, and the scavenging port 15 for connecting the pressure chamber 13 and a combustion chamber 2 when the piston 21 is in a periphery of a bottom dead center. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  Conventionally, a uniflow type two-cycle engine (hereinafter referred to as a “uniflow type engine”) in which a scavenging port is provided in a cylinder wall of a cylinder block and an exhaust port is provided in a cylinder head is widely known. In this uniflow type engine, there is a problem that the lubricating oil flows out to the scavenging port due to the reciprocating motion of the piston, and the amount of consumption of the lubricating oil increases.

In the invention described in Patent Document 1, an intake chamber that communicates with the scavenging port is provided, the lubricating oil that has flowed out to the scavenging port is stored in the air supply chamber, and the lubricating oil is recirculated into the crank chamber to consume the lubricating oil. Reduce the amount.
JP-A-5-280320

  However, in the engine described in Patent Document 1, it is possible to reduce the outflow of lubricating oil to the scavenging port, but it cannot be completely eliminated. Further, the engine described in Patent Document 1 is provided with an intake chamber, so that the engine becomes large, and is difficult to apply to a vehicle engine in which downsizing is prioritized.

  Accordingly, an object of the present invention is to provide a multi-link variable compression ratio engine that can prevent the lubricating oil from flowing out to the scavenging port and can be made compact.

  The present invention is a two-cycle engine, and includes a piston rod formed on a piston, a compression ratio variable mechanism that varies the mechanical compression ratio by connecting the piston rod and the crankshaft by a plurality of links, A pressure chamber that is formed by a partition through which the piston rod slides freely, a lower surface of the piston, a cylinder wall, and a partition, and that expands and contracts as the piston reciprocates; A valve mechanism for opening and closing a fresh air intake pipe connected to the chamber, and a scavenging port for communicating the pressure chamber and the combustion chamber when the piston is in the vicinity of the bottom dead center. Then, fresh air is introduced from the scavenging port into the combustion chamber, and combustion gas is scavenged from the combustion chamber to the exhaust port.

  According to the present invention, it is possible to form a pressure chamber by arranging the partition wall below the piston, and to supply fresh air to the engine using the pressure generated by the expansion and contraction of the pressure chamber. Thereby, it is not necessary to provide a piston pump etc. outside, and it becomes possible to achieve a compact engine. Further, since the piston rod formed on the piston slides through the partition wall, the side thrust load generated on the piston is reduced. Therefore, the piston skirt can be shortened, and the piston can reciprocate in the cylinder without lubricating oil. As a result, an increase in the amount of consumption of lubricating oil is prevented, and a two-cycle operation with internal air supply becomes possible.

(First embodiment)
Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1A is a schematic diagram showing a two-cycle multi-link variable compression ratio engine according to the first embodiment. FIG. 1B is a top view of the thrust support.

  The multi-link variable compression ratio engine 1 includes a crosshead mechanism 20 that reduces the side thrust load of the piston and a multi-link mechanism 30 that makes the compression ratio variable in 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 a crown surface 21a of the piston 21, a cylinder wall 11a, and an 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.

  The piston rod 22 is connected to the upper link 31 of the multi-link mechanism 30 by a piston pin 23 at the lower end thereof. Below the piston 21, a thrust support 12 is provided 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. The thrust support 12 is configured to be rotatable along the inner periphery of the cylinder 11 as will be described later. The piston rod 22 penetrates the thrust support 12 and is slidably supported by the hole 12a of the thrust support 12. The piston rod 22 and the hole 12a are sealed by an oil seal 12b having high lubricity.

  The upper link 31 is connected to the piston rod 22 via the piston pin 23 at the upper end thereof. 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 substantially 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 disposed 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, this multi-link variable compression ratio engine 1 has a pressure chamber 13 for introducing fresh air into the combustion chamber 2 by the reciprocating motion of the piston 21. The pressure chamber 13 is formed by the upper surface of the thrust support 12, the wall surface of the cylinder 11, and the lower surface of the piston 21, and the volume repeatedly expands and contracts as the piston 21 reciprocates.

  A suction port 14 a is provided on one side of the cylinder block 10, and the suction pipe 14 is connected so as to communicate with the pressure chamber 13. The suction pipe 14 constitutes all or part of the intake passage. A fuel injection valve (not shown) installed in the intake passage injects fuel to fresh air sucked from the outside to form an air-fuel mixture in the intake passage. A scavenging port 15 having a lower scavenging port 15 a and an upper scavenging port 15 b is formed on the other side of the cylinder block 10. The suction port 14a and the lower scavenging port 15a described above are formed so as to be opened and closed depending on the rotational position of the thrust support 12 as will be described later, and the upper scavenging port 15b burns when the piston 21 is in the vicinity of the bottom dead center. The chamber 2 and the pressure chamber 13 are formed to communicate with each other.

  The thrust support 12 described above is formed as a disk-shaped partition wall that partitions the inside of the cylinder 11, and is installed below the bottom dead center position of the piston 21. As shown in FIG. 1B, the thrust support 12 includes a communication portion 12c and a blocking portion 12d. The communication portion 12c is formed as a concave portion extending substantially halfway on the upper surface of the thrust support 12, and opens when the communication portion 12c faces the suction port 14a or the lower scavenging port 15a. On the other hand, the blocking part 12d is formed as a flat end part extending over almost the entire circumference of the upper surface of the thrust support 12, and is closed when the blocking part 12d faces the suction port 14a or the lower scavenging port 15a.

  As shown in FIG. 1A, the thrust support 12 is supported in the cylinder 11 so as to be rotatable around the axis of the piston rod 22 but not vertically movable. The thrust support 12 has a gear 12e formed at the lower part of the outer periphery. The gear 12e is provided on the side of the cylinder block 10 and meshes with the worm gear 51 that faces the cylinder 11 through the opening. The worm gear 51 is controlled by an actuator (not shown) and controls the rotational position of the thrust support 12 in synchronization with the rotation of the crankshaft 36. By the rotation of the thrust support 12, the communication portion 12c and the blocking portion 12d are controlled to open and close the suction port 14a and the lower scavenging port 15a.

  The controller 60 includes a CPU, a ROM, a RAM, and an I / O interface. The controller 60 receives outputs from various sensors that detect a vehicle driving state such as a knock sensor and a crank angle sensor (not shown). Based on these outputs, the controller 60 controls the actuator 44 to rotate the control shaft 41 to change the mechanical compression ratio, and controls the actuator to rotate the worm gear 51 to control the rotation of the thrust support 12.

  First, the operation of the first embodiment of the multi-link variable compression ratio engine 1 will be described.

  2 and 3 are schematic views showing the operation of the two-cycle multi-link variable compression ratio engine 1. FIG. 2A shows the flow of the air-fuel mixture when the piston 21 moves from the bottom dead center to the top dead center, and FIG. 2B shows the operation of the thrust support 12. FIG. 3A shows the flow of the air-fuel mixture when the piston 21 moves from the top dead center to the bottom dead center, and FIG. 3B shows the operation of the thrust support 12.

  The thrust support 12 rotates in synchronization with the crankshaft 36, and rotates once when the crankshaft 36 rotates once. When the piston 21 is at the bottom dead center, as shown in FIG. 2B, the thrust support 12 closes the suction port 14a and the lower scavenging port 15a. Then, in the process in which the piston 21 rises from the bottom dead center to the top dead center, as shown in FIGS. 2 (A) and 2 (B), the suction port 14a is opened by the communication portion 12c of the thrust support 12, The pressure chamber 13 and the suction pipe 14 communicate with each other. At this time, the communication between the pressure chamber 13 and the lower scavenging port 15a is blocked in the blocking unit 12d. When the piston 21 moves up in the cylinder 11 and the pressure chamber 13 expands, a negative pressure is generated inside the pressure chamber 13 and the air-fuel mixture is sucked into the pressure chamber 13 from the suction pipe 14 (intake stroke). When the pressure chamber 13 expands, the combustion chamber 2 contracts at the same time, so the air-fuel mixture in the combustion chamber 2 is compressed (compression stroke). When the piston 21 reaches top dead center, as shown in FIG. 2B, the thrust support 12 closes the suction port 14a and the lower scavenging port 15a by the blocking portion 12d.

  The air-fuel mixture compressed in the compression stroke is ignited by an ignition plug (not shown) in the vicinity of the top dead center to explode and burn, and pushes down the piston 21 from the top dead center toward the bottom dead center (expansion stroke). In the process of lowering the piston 21, as shown in FIGS. 3A and 3B, the suction port 14a is closed by the blocking portion 12d, and the lower scavenging port 15a is opened by the communication portion 12c. Until the piston 21 descends from the top dead center and passes through the upper scavenging port 15b, the pressure chamber 13 contracts to pressurize the air-fuel mixture. When the piston 21 passes through the upper scavenging port 15 b, the combustion chamber 2 and the pressure chamber 13 communicate with each other through the scavenging port 15. Thereby, the pressurized air-fuel mixture is introduced into the combustion chamber 2 expanded from the contracted pressure chamber 13. Since the upper scavenging port 15b is provided on the upper side in the vicinity of the bottom dead center of the piston 21, when an air-fuel mixture is introduced from the lower side of the combustion chamber 2, an exhaust valve provided in a cylinder head (not shown) is opened. The combustion gas is scavenged from the exhaust port (scavenging stroke).

  Thereafter, as shown in FIG. 2, the piston 21 reverses from the bottom dead center and moves toward the top dead center, the exhaust valve (not shown) is closed, and the process proceeds to the compression stroke.

  As described above, in the first embodiment, the air-fuel mixture is supplied into the combustion chamber 2 by expansion and contraction of the pressure chamber 13 (hereinafter referred to as “internal air supply”) without providing an external air supply device such as a piston pump. Two-cycle operation can be performed.

  Here, a conventional uniflow engine will be described for comparison. FIG. 10 is a schematic view showing a conventional uniflow engine.

  As shown in FIG. 10, the uniflow engine 60 is provided with a scavenging port 63 in a cylinder block 62 near the bottom dead center of a piston 61, and an exhaust port 67 is connected to a cylinder head 65 above the combustion chamber 64 via an exhaust valve 66. Provide. In this uniflow type engine 60, since the scavenging port 63 is opened and closed by the piston 61, the lubricating oil flows into the scavenging port 63 when the lubricating oil is lifted up when the piston 61 rises from the bottom dead center. For this reason, there is a problem that the consumption amount of the lubricating oil increases or the lubricating oil flows into the combustion chamber 64 to deteriorate the cleanliness inside the combustion chamber 67.

  However, in the first embodiment, the problem is solved by combining the multi-link mechanism 30 and the thrust support 12 as shown in FIG. In the multi-link variable compression ratio engine 1, the upper link 31 connected to the piston rod 22 is placed in an upright posture (piston rod) in the vicinity where the pressure in the combustion chamber 2 reaches the maximum value by selecting the alignment of the multi-link mechanism 30. The tilt angle of the shaft center of the upper link 31 with respect to the shaft center 22 can be maintained in a state close to 0 °. Therefore, the side thrust load generated in the piston according to the inclination of the upper link 31 can be reduced. Further, since the piston rod 22 of the piston 21 passes through the hole 12a of the thrust support 12 and slides along the cylinder 11, the thrust support 12 receives most of the side thrust load generated in the piston 21. As described above, in the first embodiment, 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 within the cylinder 11 even without lubricating oil, and problems such as an increase in the amount of consumption of lubricating oil due to the reciprocating motion of the piston 21 can be solved.

  In the multi-link variable compression ratio engine 1, the mechanical compression ratio can be adjusted by changing the top dead center position of the piston 21 by controlling the posture of the lower link 32 by the control link 33 and changing the mechanical compression ratio. Then, the bottom dead center position also changes according to the top dead center position of the piston 21. In the conventional uniflow engine 61, the scavenging port 63 is opened and closed only by the reciprocating motion of the piston 62. Therefore, when the piston bottom dead center position changes, the opening and closing of the scavenging port 63 cannot be controlled. Accordingly, when the piston bottom dead center position is below the scavenging port 63, the air-fuel mixture flowing into the combustion chamber 64 enters the scavenging port 63 until the piston 61 passes through the scavenging port 63 from the bottom dead center. Backflow.

  However, in the multi-link variable compression ratio engine 1 according to the first embodiment, the timing of scavenging can be adjusted by opening and closing the lower scavenging port 15a by the thrust support 12.

  FIG. 4 shows the operation of the thrust support 12 when the mechanical compression ratio is changed. 4A shows a case where the mechanical compression ratio is high, and FIG. 4B shows a case where the mechanical compression ratio is low.

  As shown in FIG. 4A, when the mechanical compression ratio is high, when the piston 21 descends near the bottom dead center, the blocking portion 12d of the thrust support 12 gradually closes the lower scavenging port 15a. Then, the lower scavenging port 15b is completely closed at the bottom dead center position. Therefore, most of the air-fuel mixture in the pressure chamber 13 flows into the combustion chamber 2 when the piston 21 reaches bottom dead center. Further, since the lower scavenging port 15a is also closed, the air-fuel mixture does not flow backward from the combustion chamber 2 to the pressure chamber 13 even before the piston 21 passes through the upper scavenging port 15b. Further, when the mechanical compression ratio is low, the bottom dead center position of the piston 21 is lower than in the case of the high compression ratio, as shown in FIG. Also in this case, since the thrust support 12 rotates in synchronization with the crankshaft, when the piston 21 descends from the top dead center to the vicinity of the bottom dead center as in the case of the high compression ratio, the blocking portion 12d. Gradually closes the lower scavenging port 15a, and when the piston 21 reaches the bottom dead center, completely closes the lower scavenging port 15b. Therefore, even when the compression ratio is low, the air-fuel mixture in the pressure chamber 13 almost flows into the combustion chamber 2 when the piston 21 reaches bottom dead center. Further, since the lower scavenging port 15a is also closed, the air-fuel mixture does not flow backward from the combustion chamber 2 to the pressure chamber 13 even before the piston 21 passes through the upper scavenging port 15b. As described above, in the multi-link variable compression ratio engine 1, even when the mechanical compression ratio changes and the bottom dead center position of the piston 21 changes, the scavenging port 15 is opened and closed by the thrust support 12, so that the scavenging timing is optimized. Can be adjusted.

  By the way, if the crosshead mechanism 20 is provided in order to perform internal air supply as described above, the multi-link variable compression ratio engine 1 will be enlarged. The 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 rod.

  FIG. 11 shows an increase in the engine height of the conventional engine due to the provision of the crosshead mechanism.

  The conventional engine 70 includes a piston 71 and a connecting rod 72 as shown in FIG. The piston 71 is connected to the upper end of the connecting rod 72 via a piston pin 73. The lower end of the connecting rod 72 is connected to a crankpin 75 that is eccentric by a predetermined amount from the journal 74 a of the crankshaft 74. In this conventional engine 70, when internal air supply by a crosshead mechanism is performed, as shown in FIG. 11B, a piston rod 76 is formed on the piston 71, and the piston rod 76 and the connecting rod 72 are connected to the piston pin 73. Because of the connection through the engine, the engine height increases. In order to suppress the engine height, it is conceivable to shorten the connecting rod 72 to reduce the linkage ratio. Here, the linkage ratio is expressed by the following formula.

  However, in the conventional engine 70, if the length of the connecting rod 73 is shortened to reduce the linkage ratio, the piston stroke characteristics are greatly deviated from simple vibrations, and vibrations caused by the reciprocating motion of the piston 71 and the rotational motion of the crankpin 75 ( Hereinafter referred to as “inertial secondary vibration”). Therefore, in the conventional engine 70, since the inertial secondary vibration is deteriorated, the linkage ratio cannot be reduced. When the crosshead mechanism is provided, an increase in the engine height is unavoidable.

  On the other hand, in the multi-link variable compression ratio engine 1, by selecting the alignment of the multi-link mechanism 30, the crank when the piston 21 rises from the stroke center, passes through the top dead center, and falls to the stroke center again. The angle and the crank angle when descending from the center of the stroke and rising to the center of the stroke again through the bottom dead center can be made substantially the same. Thus, the inertial secondary vibration based on the piston stroke characteristic can be reduced by making the stroke characteristic with respect to the crank angle of the piston 21 close to a simple vibration. For details of the configuration in which the stroke characteristics are substantially simple vibrations, refer to JP-A-2005-180302.

  Further, in the multi-link variable compression ratio engine 1, the Y-direction component of the inertial secondary vibration can be reduced by selecting the alignment of the multi-link mechanism 30.

  FIG. 5A is a diagram schematically showing 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. 5B shows the Y direction component of the inertial secondary vibration generated in the piston pin 23, and FIG. 5C shows the Y direction component of the inertial secondary vibration generated in the connecting pin. The horizontal axis indicates the position of the piston 21 in the cylinder 11, 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. 5B, 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 that maximizes the inertial secondary vibration is selected. Further, as shown in FIG. 5C, 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. Select alignment. 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, the multi-link variable compression ratio engine 1 can perform the secondary inertia vibration, so that the distance between the crank pin 23 and the connecting pin 34 can be set short to suppress the engine height. Further, in the multi-link variable compression ratio engine 1, as shown in FIG. 1A, the center line S (hereinafter referred to as “cylinder axis”) in the axial direction of the cylinder and the rotational axis C (hereinafter “ By increasing the piston 21 to a longer stroke, the increase in engine height can be further suppressed. This will be described with reference to FIG.

  FIG. 6 is a schematic diagram showing a multi-link variable compression ratio engine (hereinafter, referred to as “long stroke engine”) 80 that achieves a long stroke of the piston 81. A locus W of the outermost diameter of the counterweight formed on the crankshaft 82 is indicated by a broken line. FIG. 6 is for explaining the concept of a long stroke, and the configuration of the internal air supply mechanism of FIG. 1 is omitted.

  In order to suppress the engine height while maintaining the piston stroke amount, it is necessary to lower the top dead center position of the piston 81 and lower the bottom dead center position. As indicated by the dotted line in FIG. 6, even if the cylinder 83 is simply extended downward to extend the distance that the piston 81 can reciprocate, the outermost diameter locus W of the counterweight and the cylinder 83 interfere with each other. Therefore, in the long stroke engine 80, when the rotation direction of the crankshaft 82 is counterclockwise, the cylinder axis S is offset to the left from the crankshaft center C as shown in FIG. When offset is performed in this manner, the side thrust load generated in the piston 81 acts on the cylinder 83 on the side farther from the crankshaft 82 (left side in the figure) regardless of the position of the piston 81 in the cylinder 83. Therefore, it is only necessary to have a cylinder wall 11a on which the piston 81 can slide below the cylinder 83 on the left side in the figure. The right cylinder wall 11a on which the side thrust load does not act is shown in FIG. It can be sharpened so as not to interfere with W. Thereby, the cylinder 83 on the side on which the side thrust load acts can be extended downward, and the distance that the piston 81 can reciprocate becomes longer. As a result, the piston 81 can be made to have a long stroke, the top dead center position and the bottom dead center position of the piston 81 can be lowered while maintaining the piston stroke amount, and the height of the engine can be reduced.

  Also in the first embodiment, the cylinder axis S is offset from the crank rotation axis C as shown in FIG. Further, in the first embodiment, since the piston skirt of the piston 21 is also shortened, the bottom dead center position can be lowered, and an increase in engine height can be suppressed while maintaining the piston stroke amount. .

  As described above, the operation of the piston 21 of the multilink variable compression ratio engine 1 that reduces the inertial secondary vibration and suppresses the engine height is shown in FIG. Note that the air supply mechanism is not shown.

  FIG. 7 is a diagram schematically showing the reciprocation of the piston 21 of the first embodiment. FIG. 7A shows a case where the piston 21 is at the top dead center, and 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.

  The cylinder 11 shown in FIGS. 7A and 7B has substantially the same height as a cylinder used in a multi-link variable compression ratio engine that does not include the crosshead mechanism 20. In the first embodiment, since the alignment of the multi-link mechanism 30 that can reduce the inertial secondary vibration is selected, the distance between the crank pin 23 and the connecting pin 34 can be set short. Therefore, as shown in FIG. 7B, the crank 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. In addition, by shortening the piston skirt and increasing the stroke of the piston 21 as described above, the top dead center and bottom dead center positions can be lowered below the cylinder 11 while maintaining the conventional piston stroke. Therefore, even if the cylinder 11 has substantially the same height as a cylinder used in a multi-link variable compression ratio engine that does not include the crosshead mechanism 20, the cylinder 11 is shown in FIGS. 7A and 7B. As described above, the piston 21 can reciprocate with the conventional piston stroke.

  As described above, the first embodiment can obtain the following effects.

  According to the present invention, the thrust support 12 is disposed below the piston 21 to form the pressure chamber 13, and the air-fuel mixture is supplied into the combustion chamber 2 using the pressure generated in the pressure chamber 13 by the reciprocating motion of the piston 21. be able to. Further, since the piston rod 22 formed on the piston 21 slides through the thrust support 12, the side thrust load generated on the piston 21 is reduced. Therefore, the piston skirt can be shortened, and the piston 21 can reciprocate in the cylinder 11 without lubricating oil. As a result, the multi-link variable compression ratio engine 1 can prevent the increase in the consumption amount of the lubricating oil and the like, and can perform a two-cycle operation with internal air supply.

  Further, since the suction port 14a and the lower scavenging port 15a are opened and closed by the thrust support 12, even if the mechanical compression ratio changes and the bottom dead center position of the piston 21 changes, the scavenging timing can be optimally controlled. it can.

  Furthermore, since the internal air supply in the combustion chamber 2 is performed by the reciprocating motion of the piston 21, it is not necessary to provide a piston pump or the like outside. Further, in the first embodiment, by selecting the alignment of the multi-link mechanism 30, the inertial secondary vibration can be reduced even if the linkage ratio is reduced, and the piston stroke amount is maintained by shortening the piston skirt or increasing the stroke. The bottom dead center position of the piston 21 can be lowered while keeping it. As a result, even if the crosshead mechanism 20 is provided, an increase in engine height can be suppressed, and the multi-link variable compression ratio engine 1 can have a compact structure.

(Second Embodiment)
FIG. 8A is a schematic diagram showing a second embodiment of a two-cycle multi-link variable compression ratio engine 1. FIG. 8B is a top view of the thrust support 80 according to the second embodiment.

  The configuration of the second embodiment of the multi-link variable compression ratio engine 1 is substantially the same as the basic configuration of the first embodiment, but is partially different in the configuration of the scavenging port. That is, two scavenging ports 90 and 91 are provided in the cylinder row direction, respectively, and the differences will be mainly described below.

  In the second embodiment, as shown in FIG. 8A, scavenging ports 90 and 91 are provided to face the side of the cylinder block 10 in the cylinder row direction. A scavenging port 90 formed on one side is an upper scavenging port 90a that is opened and closed by a thrust support 92 and an upper side that connects the combustion chamber 2 and the pressure chamber 13 when the piston 21 is in the vicinity of the bottom dead center. A scavenging port 90b is provided. The scavenging port 91 formed on the other side has the same shape as the scavenging port 90, and includes a lower scavenging port 91a and an upper scavenging port 91b. The scavenging ports 90 and 91 are opened and closed by a thrust support 92 that is rotatably supported in the cylinder 11 around the axis of the piston rod 22. The lower scavenging ports 90a and 91a and the upper scavenging ports 90b and 91b of the scavenging ports 90 and 91 are smaller than the lower and upper scavenging ports 15a and 15b of the first embodiment, but are scavenged into the combustion chamber 2. The scavenging amount of the air-fuel mixture is set to be approximately the same as in the first embodiment. In addition, the scavenging port formed in the side part of the cylinder block 10 is not restricted to two, You may make it provide multiple.

  The thrust support 92 is formed as a disk-shaped partition that partitions the inside of the cylinder 11, and has a hole 92 a that slidably supports the piston rod 22 of the piston 21. Further, the thrust support 92 includes a pair of communication portions 92a and blocking portions 92b formed in a sector shape alternately as shown in FIG. 8B. The communicating portions 92c and 92c are disposed so as to face each other, and are connected to each other by a passage 92e formed in the hole 92a and the blocking portion 92d. The blocking portions 92b and 92b are independently formed at opposing positions. The thrust support 92 is synchronized with the rotation of the crankshaft 36 and rotates half a turn when the crankshaft rotates once. Since the rotation of the thrust support 92 is half of the rotation of the crankshaft, the load of an actuator (not shown) for controlling the rotation of the thrust support can be reduced as compared with the first embodiment even if the engine speed increases. Thus, as the piston 21 reciprocates, the communicating portion 92a communicates with the suction port 14a or the lower scavenging ports 90a and 91a, and the blocking portion 92b blocks communication with the suction port 14a or the scavenging ports 90a and 91a. To do.

  The operation of the second embodiment of the multi-link variable compression ratio engine 1 will be described below.

  FIG. 9 is a schematic view showing the operation of the thrust support 92 accompanying the reciprocating motion of the piston 21.

  When the piston 21 is at the bottom dead center, as shown in FIG. 9A, the blocking portion 92d of the thrust support 92 closes the suction port 14a and the lower scavenging ports 90a, 91a. . When the piston 21 rises from the bottom dead center to the top dead center, as shown in FIG. 9 (B), the thrust support 92 rotates counterclockwise, and the communicating portion 92c opens the suction port 14a, thereby blocking the blocking portion. 92d closes the lower scavenging ports 90a and 91a. When the piston 21 rises in the cylinder 11 and the pressure chamber 13 expands, a negative pressure is generated inside the pressure chamber 13 and the air-fuel mixture is sucked into the pressure chamber 13 from the suction pipe 14. When the piston 21 reaches top dead center, as shown in FIG. 9C, the blocking portion 92d closes the suction port 14a and the lower scavenging ports 90a and 91a. At this time, the air-fuel mixture compressed in the combustion chamber 2 is ignited by a spark plug (not shown), explosively burns, and pushes down the piston 21.

  When the piston 21 is lowered from the top dead center by the explosion combustion, as shown in FIG. 9D, the blocking portion 92d closes the suction port 14a, and the communication portion 92c opens the lower scavenging ports 90a and 91a. . Until the piston 21 descends from the top dead center and passes through the upper scavenging ports 90b and 91b of the scavenging ports 90 and 91, the combustion chamber 2 and the pressure chamber 13 do not communicate with each other. Pressurize the mixture. When the piston 21 passes through the upper scavenging ports 90b and 91b, the combustion chamber 2 and the pressure chamber 13 communicate with each other, and the air-fuel mixture pressurized in the pressure chamber 13 flows into the combustion chamber 2. Thereby, the air-fuel mixture is introduced into the combustion chamber 2 and the combustion gas in the combustion chamber 2 is scavenged from an exhaust port provided in a cylinder head (not shown). When the piston 21 reaches bottom dead center, the thrust support 92 closes the suction port 14a and the lower scavenging ports 90a and 91a.

  As described above, also in the second embodiment, as in the first embodiment, the air-fuel mixture is supplied into the combustion chamber 2 using the pressure generated in the pressure chamber 13 by the reciprocating motion of the piston 21, and the internal air supply is performed. can do.

  As described above, the second embodiment can obtain the following effects.

  According to the present invention, since the two scavenging ports 90 and 91 are provided, even if the upper scavenging ports 90a and 91a and the lower scavenging ports 90b and 91b are smaller than in the first embodiment, the same degree as in the first embodiment. A scavenging amount can be obtained, and the same effect as that of the first embodiment can be obtained by rotating the thrust support 92 in synchronization with the crankshaft to perform internal air supply.

  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, in the present invention, the fuel injection valve is installed in the intake passage constituting the intake pipe 14, but the fuel injection valve is installed in the cylinder head to inject fuel directly into the combustion chamber 2. An air-fuel mixture may be formed.

  Moreover, in 1st Embodiment and 2nd Embodiment, only the inlet 14a is opened in the process in which the piston 21 raises from a bottom dead center to a top dead center, and the piston 21 falls from a top dead center to a bottom dead center. It is also possible to supply fresh air into the combustion chamber 2 by expanding and contracting the pressure chamber 13 by closing only the intake port 14 a in the process.

1 is a schematic diagram showing a first embodiment of a two-cycle multi-link variable compression ratio engine. FIG. It is the schematic which shows operation | movement of a thrust support when a piston moves from a bottom dead center to a top dead center. It is the schematic which shows operation | movement of a thrust support when a piston moves from a top dead center to a bottom dead center. It is the schematic which shows operation | movement of the thrust support when a mechanical compression ratio is changed. It is the schematic of the multilink mechanism which shows the principle of reduction of an inertia secondary vibration. It is the schematic which shows long stroke-ization of a multilink type variable compression ratio engine. It is the schematic which shows typically the reciprocation of the piston of 1st Embodiment. FIG. 3 is a schematic diagram showing a second embodiment of a two-cycle, multi-link variable compression ratio engine. It is the schematic which shows operation | movement of the thrust support accompanying the reciprocation of a piston. It is the schematic which shows the conventional uniflow type | mold 2 cycle engine. It is the schematic which shows the internal supercharging in a conventional engine.

Explanation of symbols

1 Multi-link variable compression ratio engine 2 Combustion chamber 11 Cylinder 12, 92 Thrust support (partition)
12a, 92a Holes 12b, 92b Oil seals 12c, 92c Communication part (valve mechanism)
12d, 92d Blocking part (valve mechanism)
13 Pressure chamber 14 Suction pipe 14a Suction ports 15, 90, 91 Scavenging ports 15a, 90a, 91a Lower scavenging ports 15b, 90b, 91b Upper scavenging port 20 Crosshead mechanism 21 Piston 22 Piston rod 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 60 Controller

Claims (10)

An exhaust port formed in the cylinder head, a piston that reciprocates in the cylinder, and a scavenging port that is opened and closed by the piston, introduces fresh air from the scavenging port into the combustion chamber, and introduces new air that has been introduced. In a two-cycle engine that scavenges combustion gas from the combustion chamber to the exhaust port by air
A piston rod formed on the piston;
A compression ratio variable mechanism that connects the piston rod and the crankshaft by a plurality of links to make the mechanical compression ratio variable;
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 freely slid,
A pressure chamber formed by a lower surface of the piston, a cylinder wall, and the partition, and expands and contracts with reciprocation of the piston;
A valve mechanism for opening and closing a fresh air suction pipe connected to the pressure chamber;
A scavenging port that communicates the pressure chamber and the combustion chamber when the piston is near bottom dead center;
An engine characterized by comprising The valve mechanism is
The fresh air suction pipe communicating with the pressure chamber and the scavenging port are opened and closed in synchronism with engine rotation, and when the piston rises when the pressure chamber expands, only the suction pipe communicates with the pressure chamber, and the pressure chamber When the piston descends, the chamber shrinks, so that only the scavenging port communicates with the pressure chamber.
The engine according to claim 1. The valve mechanism is
Provided in the partition, comprising a communication part that communicates the pressure chamber and the inflow pipe or the scavenging port, and a blocking part that blocks communication between the pressure chamber and the inflow pipe or the scavenging port,
In the cylinder, the partition is rotated around the axis of the piston rod in synchronization with engine rotation, the pressure chamber and the inflow pipe are communicated when the piston is raised, and the pressure chamber and the scavenging port are lowered when the piston is lowered. The engine according to claim 2, wherein the engine is communicated. The rotation of the partition wall is
When the crankshaft of the engine makes one turn, it makes one turn.
The engine according to claim 3. The scavenging port is
In the arrangement direction of the cylinders, each cylinder block facing each other,
The engine according to any one of claims 1 to 3, wherein The rotation of the partition wall is
When the crankshaft of the engine rotates once, it makes a half rotation.
The engine according to claim 5. 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 can swing with the eccentric shaft portion of the control shaft as a swing axis;
The control shaft is rotated based on 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 6, characterized in that: The compression ratio variable mechanism is
In the rotation plane in which the crankshaft of the engine rotates, the cylinder axis and the axis passing through the crankshaft rotation center in the piston sliding direction are offset in parallel.
The engine according to claim 7. 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 7 or 8, characterized in that. 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 any one of claims 7 to 9, wherein the engines have the same stroke characteristics with respect to a crank angle of the piston, and have characteristics close to simple vibration.