JP2006183480A - Uniflow two-stroke internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-stroke internal combustion engine for eliminating trade-off of fuel consumption and output. <P>SOLUTION: This uniflow two-stroke internal combustion engine has a scavenging port 7 arranged in a cylinder block 1 and opening in the vicinity of a piston bottom dead center position, and an exhaust valve 5 arranged on a cylinder head 2 so that opening-closing operation can be performed; and has a phase variable mechanism for advancing and delaying a phase of a central angle of a lift of the exhaust valve 5, and an intake control valve lift/operating angle variable mechanism for expanding and reducing a lift/operating angle of the exhaust valve 5. Thus, scavenging efficiency and expansion work can be effectively taken out in response to an operation condition of a wide range by variably controlling a valve opening characteristic of the exhaust valve 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a uniflow two-stroke internal combustion engine.

The aim of improving the scavenging efficiency by changing the lift and operating angle of the exhaust valve in a two-stroke engine (two-cycle engine) has already been proposed by the same applicant and is known (see Patent Document 1).
JP-A-11-93710

  However, as in Patent Document 1, when the lift / working angle of the exhaust valve is changed without changing the phase of the center angle of the lift of the exhaust valve (the center angle is constant), the lift / working angle of the exhaust valve is variable. Restrictions appear in fully exerting the effect obtained by making it. That is, for example, even when it is desired to reduce the lift / operating angle of the exhaust valve, the exhaust valve opens before the exhaust valve opens when the lift / operating angle of the exhaust valve falls below a predetermined value in consideration of the opening period of the scavenging port. As a result, the scavenging port opens, and the exhaust gas flows backward to the scavenging port. For this reason, the lift / operating angle of the exhaust valve cannot be set to be equal to or smaller than the predetermined size, and as a result, there is a problem in that there is a restriction in varying the lift / operating angle of the exhaust valve.

  Further, as in Patent Document 1, when the opening characteristic of the scavenging port is fixed, the actual compression ratio is determined by the timing when the scavenging port is closed. Therefore, in a setting that does not reduce the scavenging efficiency at low speed and low load, There is a problem that the fuel consumption / output trade-off mainly remains such that the opening period becomes relatively short and an opening area (period) for sufficient supercharging cannot be obtained at high speed and high load.

  Therefore, the present invention provides a uniflow two-stroke internal combustion engine having a scavenging port provided in a cylinder block and opened near a piston bottom dead center position, and an exhaust valve provided in the cylinder head so as to be opened and closed. It is characterized by having phase variable means for delaying the phase of the center angle of the lift and intake control valve lift / operating angle variable means for enlarging / reducing the lift / operating angle of the exhaust valve.

  According to the present invention, scavenging efficiency and expansion work can be effectively taken out in a wide range of operating conditions by variably controlling the valve opening characteristics of the exhaust valve.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 schematically shows a schematic configuration of a uniflow type two-stroke internal combustion engine according to the present invention. A plurality of cylinders 3 are formed in series in an engine body roughly constituted by the cylinder block 1 and the cylinder head 2. In these cylinders 3, pistons 4 are slidably arranged.

  An exhaust port 6 that is opened and closed by an exhaust valve 5 is formed in the cylinder head 2 for each cylinder 3. A scavenging port 7 that is opened and closed by the piston 4 is formed in the cylinder block 1 for each cylinder 3. An intake collector 9 is interposed in an intake passage 8 serving as an intake system connected to the scavenging port 7, and a supercharger 10 is disposed upstream of the intake collector 9.

  The scavenging port 7 is provided at a position on the anti-thrust side near the bottom dead center of the piston 4. Here, on the inner peripheral surface of the cylinder 3, when the piston 4 reciprocates in the cylinder 3, the piston reciprocates according to the inclination of the upper link 66 (described later) of the multi-link type piston-crank mechanism 61 described later. A thrust load in the direction perpendicular to the axis acts. That is, the scavenging port 7 faces the inner peripheral surface of the cylinder 3 where the thrust load does not act near the bottom dead center, in other words, the inner peripheral surface of the cylinder 3 where the thrust load acts near the bottom dead center. It is provided at the position.

  The exhaust valve 5 according to the first embodiment of the present invention can be changed in its lift and operating angle by a lift / operating angle variable mechanism 30 (details will be described later), and by a phase variable mechanism 31 (details will be described later). The phase of the center angle of the lift (phase with respect to the crankshaft) can be advanced or retarded.

  First, the above-described lift / operating angle variable mechanism 30 will be described with reference to FIG. The lift / operating angle variable mechanism 30 is known from Japanese Patent Laid-Open No. 2002-89303 and Japanese Patent Laid-Open No. 2002-89341 previously proposed by the present applicant, and only the outline thereof will be described. .

  A lift / working angle variable mechanism 30 for enlarging / reducing the lift / working angle of the exhaust valve 5 includes a hollow drive shaft 13 rotatably supported by a cam bracket (not shown) above the cylinder head 1, and the drive shaft. 13, an eccentric cam 15 fixed by press-fitting or the like, a control shaft 16 rotatably supported by the same cam bracket at a position above the drive shaft 13, and disposed parallel to the drive shaft 13, and the control shaft 16 The rocker arm 18 is swingably supported by the eccentric cam portion 17, and the swing cam 20 is in contact with the tappet 19 disposed at the upper end portion of each exhaust valve 5. The eccentric cam 15 and the rocker arm 18 are linked by a link arm 25, and the rocker arm 18 and the swing cam 20 are linked by a link member 26.

  The drive shaft 13 is driven by an engine crankshaft via a timing chain or a timing belt.

  The eccentric cam 15 has a circular outer peripheral surface, the center of the outer peripheral surface is offset by a predetermined amount from the axis of the drive shaft 13, and the annular portion 25a of the link arm 25 is rotatable on the outer peripheral surface. It is mated.

  The rocker arm 18 is supported substantially at the center by the eccentric cam portion 17, and the extension portion 25 b of the link arm 25 is linked to one end portion thereof, and the upper end portion of the link member 26 is linked to the other end portion thereof. is doing. The eccentric cam portion 17 is eccentric from the axis of the control shaft 16, and accordingly, the rocking center of the rocker arm 18 changes according to the angular position of the control shaft 16.

  The swing cam 20 is rotatably supported by being fitted to the outer periphery of the drive shaft 13, and the lower end portion of the link member 26 is linked to the end portion 20 a extending sideways. On the lower surface of the swing cam 20, a base circle surface 24a that forms a concentric arc with the drive shaft 13, a cam surface 24b extending in a predetermined curve from the base circle surface 24a to the end portion 20a, Are formed continuously, and the base circle surface 24 a and the cam surface 24 b come into contact with the upper surface of the tappet 19 according to the swing position of the swing cam 20.

  That is, the base circle surface 24a is a section where the lift amount becomes 0 as a base circle section. When the swing cam 20 swings and the cam surface 24b contacts the tappet 19, the base circle surface 24a gradually lifts. . A slight ramp section is provided between the base circle section and the lift section.

  The control shaft 16 is configured to rotate within a predetermined angle range by a lift / operating angle control hydraulic actuator (not shown) provided at one end. The hydraulic pressure supply to the lift / operating angle control hydraulic actuator is controlled based on a control signal from an engine control unit (not shown).

  The operation of the variable lift / operating angle mechanism 30 will be described. When the drive shaft 13 rotates, the link arm 25 moves up and down by the cam action of the eccentric cam 15, and the rocker arm 18 swings accordingly. The swing of the rocker arm 18 is transmitted to the swing cam 20 via the link member 26, and the swing cam 20 swings. The tappet 19 is pressed by the cam action of the swing cam 20, and the exhaust valve 5 is lifted.

  Here, when the angle of the control shaft 16 changes via the lift / operating angle control hydraulic actuator, the initial position of the rocker arm 18 changes, and consequently, the initial swing position of the swing cam 20 changes.

  For example, if the eccentric cam portion 17 is positioned upward as shown in FIG. 2A, the rocker arm 18 is positioned upward as a whole, and the end portion 20a of the swing cam 20 is relatively lifted upward. It becomes a state. That is, the initial position of the swing cam 20 is inclined in the direction in which the cam surface 24 b is separated from the tappet 19. Therefore, when the swing cam 20 swings with the rotation of the drive shaft 13, the base circle surface 24a continues to contact the tappet 19 for a long time, and the period during which the cam surface 24b contacts the tappet 19 is short. Therefore, the lift amount is reduced as a whole, and the angle range from the opening timing to the closing timing, that is, the operating angle is also reduced.

  Conversely, if the eccentric cam portion 17 is positioned downward as shown in FIG. 2B, the rocker arm 18 is positioned downward as a whole, and the end portion 20a of the swing cam 20 is pushed downward relatively. It will be in the state. That is, the initial position of the swing cam 20 is inclined in the direction in which the cam surface 24 b approaches the tappet 19. Accordingly, when the swing cam 20 swings with the rotation of the drive shaft 13, the portion that contacts the tappet 19 immediately shifts from the base circle surface 24a to the cam surface 24b. Therefore, the lift amount is increased as a whole, and the operating angle is increased.

  Since the initial position of the eccentric cam portion 17 can be continuously changed, the valve lift characteristic changes continuously as shown in FIG. That is, the lift and the operating angle can be continuously expanded and contracted simultaneously. In this embodiment, the opening timing and closing timing of the exhaust valve 5 change substantially symmetrically with changes in the lift and operating angle.

  The phase variable mechanism 31 that advances or retards the phase of the lift central angle of the exhaust valve 5 (phase with respect to the crankshaft) will be described with reference to FIG.

  The phase variable mechanism 31 is provided on one end side of the drive shaft 13 of the lift / operating angle variable mechanism 30 described above.

  A cam pulley (or cam sprocket) 43 is coaxially disposed on the outer periphery of the drive shaft 13 that is rotatably supported on the cylinder head side via the cam bracket 42. The cam pulley 43 receives rotational power from the crankshaft via a chain or a timing belt, and rotates in synchronization with the crankshaft.

  The phase variable mechanism 31 is provided in a rotation transmission path between the cam pulley 43 and the drive shaft 13 and continuously changes the rotation phase of both of them in multiple stages. Specifically, the phase variable mechanism 31 is fastened and fixed to the outer cylindrical portion 44 integrally formed on the inner peripheral side of the cam pulley 43 and the drive shaft 13 via a bolt 45, and is integrated with the drive shaft 13. A rotating inner cylinder part 46, a ring-shaped plunger 47 interposed between the outer cylinder part 44 and the inner cylinder part 46, and a return that constantly urges the plunger 47 in one direction (left direction in FIG. 4). And a spring 48. A sleeve 49 is fixed to the inner peripheral side of the outer cylindrical portion 44, and this sleeve 49 is rotatably supported by the bearing bracket 42 via a bearing 50.

  Here, the meshing portion 51 of the plunger 47, the outer peripheral surface, the outer peripheral surface of the inner cylindrical portion 46, and the inner peripheral surface of the outer cylindrical portion 44 is a helical spline. Accordingly, when the plunger 47 moves in the axial direction of the inner cylinder portions 46 and 44 (the left-right direction in FIG. 4), the movement in the axial direction becomes a relative rotational movement between the inner cylinder portion 46 and the outer cylinder portion 44. The relative rotational phase between the outer cylinder portion 44 and the inner cylinder portion 46 is continuously changed. As a result, as shown in FIG. 5, the operating angle of the exhaust valve 5 remains constant, and the central angle of the lift of the exhaust valve 5 continuously changes from the advance side (a) to the retard side (b). To do. For example, in the state where the plunger 47 is arranged in the leftmost direction of FIG. 4 (state of FIG. 4), as shown by the waveform (b) in FIG. Set to the retard side. On the other hand, in the state where the plunger 47 is disposed on the rightmost side in FIG. 4, as shown by the waveform (a) in FIG. 5, the lift center angle and the opening / closing timing of the exhaust valve 5 are set to the most advanced side. .

  The phase variable mechanism 31 has a hydraulic pressure to the hydraulic chamber 54 that is liquid-tightly defined between one end of the plunger 47 and an end cap 53 that is fixed to the outer cylinder portion 44 via a pin 52. By controlling this, the plunger 47 is moved and held at a predetermined axial position, and the phase of the lift center angle of the exhaust valve 5 is made variable. The hydraulic chamber 54 is supplied with hydraulic pressure from a hydraulic supply source (not shown) through end caps 53, bolts 45, and oil passages 55a, 55b, 55c, 55d formed in the drive shaft 13. The supply of hydraulic pressure to the hydraulic chamber 54 is controlled based on a control signal from an engine control unit (not shown).

  In the first embodiment of the present invention, the exhaust valve according to the engine operating conditions with the opening characteristic of the scavenging port 7 (the opening period and opening height of the scavenging port 7) fixed to a predetermined opening characteristic. Both the lift / operating angle 5 and the phase of the lift center angle are optimally variably controlled.

  FIG. 6 shows the opening characteristic of the scavenging port 7 and the valve lift characteristic of the exhaust valve 5 in the first embodiment of the present invention. The lift / small operating angle is advanced, the phase of the lift central angle of the exhaust valve 5 is advanced, and the lift / operating angle of the exhaust valve 5 is increased to a large lift / large operating angle at high speeds. The phase of the central angle is retarded.

  On the other hand, FIG. 7 shows the opening characteristic of the scavenging port 7 and the valve of the exhaust valve 5 in the comparative example in which only the lift and operating angle of the exhaust valve 5 are varied according to the engine operating conditions in the configuration of the first embodiment described above. The lift characteristics are shown. In this comparative example, since the phase of the lift center angle of the exhaust valve 5 is fixed regardless of the engine operating conditions, the lift / operating angle of the exhaust valve 5 is not necessarily optimized according to the engine operating conditions. .

  That is, in the first embodiment of the present invention shown in FIG. 6, the phase of the lift center angle of the exhaust valve 5 can be advanced with respect to the above comparative example. Can be set smaller, and the overlap period in which the scavenging port 7 and the exhaust valve 5 are open can be further reduced. Thereby, in 1st Embodiment of this invention, since the blow-through of a fresh air can be prevented more, it can be set to the high supercharging pressure by that much. Further, in the first embodiment of the present invention, by increasing the lift / operating angle of the exhaust valve 5 to a large lift / large operating angle at a high speed and retarding the phase of the exhaust valve 5 lift center angle, The overlap period in which both the scavenging port 7 and the exhaust valve 5 are open can be made longer than that in the above comparative example, and the scavenging efficiency is further improved.

  Next, a second embodiment of the present invention will be described. In the second embodiment, the drive mechanism of the piston 4 is composed of a multi-link piston-crank mechanism 61 (described later) in the configuration of the first embodiment described above.

  FIG. 8 shows a multi-link type piston-crank mechanism 61 that is a drive mechanism of the piston 4. This multi-link type piston-crank mechanism 61 is capable of variably controlling the top dead center position and the bottom dead center position of the piston 4 by moving a part of the rotation center of the link structure. It is equivalent to.

  The multi-link type piston-crank mechanism 61 can change the engine compression ratio, that is, the nominal compression ratio by changing the piston top dead center position, and exhibits a function as a so-called variable compression ratio mechanism. is there. The multi-link piston-crank mechanism 61 is known from Japanese Patent Application Laid-Open No. 2001-227367 previously proposed by the applicant of the present application, and only the outline thereof will be described.

  The crankshaft 62 includes a plurality of journal portions 63 and a crankpin portion 64, and the journal portion 63 is rotatably supported by a main bearing (not shown) of the cylinder block 1. The crankpin portion 64 is eccentric from the journal portion 63 by a predetermined amount, and a lower link 65 serving as a second link is rotatably connected thereto.

  The lower link 65 is configured by attaching a cap 65b to the main body 65a so as to sandwich the crankpin portion 64, and is rotatably connected to the crankpin portion 65 at this sandwiching portion.

  The upper link 66 serving as the first link has a lower end side rotatably connected to one end of the lower link 65 by a first connecting pin 67, and an upper end side rotatably connected to the piston 4 by a piston pin 68. The piston 4 receives the combustion pressure and reciprocates in the cylinder 3 of the cylinder block 1.

  The control link 69 serving as the third link is pivotally connected to the other end of the lower link 65 by the second connecting pin 70 at the upper end side, and the cylinder block 1 whose lower end side is part of the engine body via the control shaft 71. It is connected with the lower part of this so that rotation is possible. Specifically, the control shaft 71 is rotatably supported by the engine body, and has an eccentric cam portion 71a that is eccentric from the rotation center, and the lower end portion of the control link 69 is rotatable on the eccentric cam portion 71a. It is mated. The rotation position of the control shaft 71 is controlled by a compression ratio control actuator (not shown) using an electric motor or the like.

  In the multi-link piston-crank mechanism 61 as described above, when the control shaft 71 is rotated by the compression ratio control actuator, the center position of the eccentric cam portion 71a, particularly, the relative position with respect to the engine body changes. Thereby, the rocking | fluctuation support position of the lower end of the control link 69 changes. The stroke of the piston 4 changes due to the change in the swing support position of the control link 69, and the engine compression ratio can be changed. That is, the top dead center position and the bottom dead center position of the piston 4 can be changed.

  FIG. 9 compares the piston stroke when the engine compression ratio is increased (high ε) and when the engine compression ratio is decreased (low ε) by the multi-link type piston-crank mechanism 61 described above. is there. As is apparent from FIG. 9, the piston lowest point position at the piston bottom dead center is changed by changing the engine compression ratio. Therefore, by changing the engine compression ratio, the opening height of the scavenging port 7 changes as shown in FIG. Further, from the piston stroke characteristic shown in FIG. 9, the opening period of the scavenging port 7 also changes as the engine compression ratio changes. That is, when the engine compression ratio is changed to the high compression ratio side by increasing the piston bottom dead center position by the multi-link type piston-crank mechanism 61, the opening height of the scavenging port 7 is shown in FIG. And the opening period of the scavenging port 7 is shortened. On the other hand, when the engine compression ratio is changed to the low compression ratio side by lowering the piston bottom dead center position, the opening height of the scavenging port 7 is increased as shown in FIG. The opening period becomes longer.

  Further, in the multi-link type piston-crank mechanism 61, it is set so that a piston stroke characteristic close to simple vibration can be obtained by appropriately selecting a link dimension. This stroke characteristic close to simple vibration is advantageous in terms of vibration noise, but in particular, the piston speed near the top dead center is about 20% slower than that of a general single link piston-crank mechanism. This is advantageous in the generation and growth of initial flame kernels, particularly under conditions where the combustion rate is low, such as when cold. Incidentally, in the multi-link type piston-crank mechanism 61, a technique for setting the piston stroke characteristics so as to be close to simple vibration is known from Japanese Patent Laid-Open No. 2001-227367 previously proposed by the present applicant. It is.

  In the second embodiment of the present invention, the lift / operating angle of the exhaust valve 5 and the phase of the lift center angle of the exhaust valve 5 are variably controlled according to engine operating conditions, and the bottom dead center of the piston 4 is controlled. Variable control of position.

  FIG. 11 is a scavenging port in the second embodiment that combines variable control of the lift / working angle of the exhaust valve 5 and the phase of the central angle of the lift and variable compression ratio technology by the multi-link piston-stroke mechanism 61. 7 shows the opening characteristic and the valve lift characteristic of the exhaust valve 5.

  At the time of low speed and low load, the bottom dead center position of the piston 4 is increased to increase the engine compression ratio (high ε) and to relatively reduce the opening period and the opening height of the scavenging port 7. The lift / operating angle of the exhaust valve 5 is relatively reduced, and the phase of the lift center angle of the exhaust valve 5 is relatively retarded. On the other hand, at the time of high speed and high load, lowering the bottom dead center position of the piston 4 lowers the engine compression ratio (low ε) and relatively expands the opening period and opening height of the scavenging port 7. Yes. The lift / operating angle of the exhaust valve 5 is relatively enlarged, and the lift / center angle phase of the exhaust valve 5 is relatively advanced.

  In such a second embodiment, the expansion work can be recovered to the maximum at low speed and low load, and the overlap between the opening period of the exhaust valve 5 and the opening period of the scavenging port 7 is also reduced. And this overlap is fully expanded at high speed and high load.

  In a two-cycle engine, combustion at a low engine load becomes a problem. In particular, in a gasoline engine, combustion of an air-fuel mixture containing a large amount of residual gas or lean burn combustion is required. In such a situation, being able to set the engine compression ratio high has a great combustion improvement effect under any of these conditions.

  Next, a third embodiment of the present invention will be described. In the third embodiment, only the phase of the lift center angle of the exhaust valve 5 is variably controlled in the configuration of the first embodiment described above.

  FIG. 12 shows the valve lift characteristic of the exhaust valve 5 and the opening characteristic of the scavenging port 7 in the third embodiment.

  At low speed, the opening timing of the exhaust valve 5 is advanced by advancing the phase of the lift / center angle of the exhaust valve 5, and the opening period of the exhaust valve 5 and the opening period of the scavenging port 7 are overlapped. Reduced. At high speed, the scavenging port 7 is sufficiently opened, scavenging starts from an early stage, and new air can be supercharged after the exhaust valve 5 is closed. However, in the third embodiment, since the exhaust valve 5 opens quickly at a low speed, there is a trade-off in which the expansion ratio decreases.

  Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, only the phase of the lift center angle of the exhaust valve 5 and the bottom dead center position of the piston 4 are variably controlled in the configuration of the second embodiment described above.

  FIG. 13 shows the valve lift characteristic of the exhaust valve 5 and the opening characteristic of the scavenging port 7 in the fourth embodiment.

  At the time of low speed and low load, the bottom dead center position of the piston 4 is increased to increase the engine compression ratio (high ε) and to relatively reduce the opening period and the opening height of the scavenging port 7. The phase of the lift center angle of the exhaust valve 5 is relatively advanced. As a result, the overlap period in which the scavenging port 7 and the exhaust valve 5 are open is reduced, so that fresh air from the scavenging port 7 can be prevented from being released to the exhaust port 6. Accordingly, the opening timing of the exhaust valve 5 can be delayed from the case of the third embodiment described above.

  On the other hand, at the time of high speed and high load, lowering the bottom dead center position of the piston 4 lowers the engine compression ratio (low ε) and relatively enlarges the opening period and opening height of the scavenging port 7. is doing. As a result, since both the opening period of the scavenging port 7 and the opening period of the exhaust valve 5 become long, it is possible to ensure a sufficient scavenging period and a supercharging period.

  The technical idea of the present invention that can be grasped from the above embodiment will be listed together with the effects thereof.

  (1) In a uniflow two-stroke internal combustion engine having a scavenging port provided in a cylinder block and opened near the piston bottom dead center position, and an exhaust valve provided to be openable and closable in a cylinder head, Phase varying means for delaying the phase of the central angle and intake control valve lift / operating angle varying means for enlarging / reducing the lift / operating angle of the exhaust valve. As a result, by variably controlling the valve opening characteristics of the exhaust valve, it is possible to effectively extract the scavenging efficiency and the expansion work corresponding to a wide range of operating conditions.

  (2) In a uniflow two-stroke internal combustion engine having a scavenging port that is provided in the cylinder block and that opens near the piston bottom dead center position and an exhaust valve that can be opened and closed in the cylinder head, reciprocating in the cylinder Piston position varying means for variably controlling the bottom dead center position of the piston to be operated according to engine operating conditions, and phase varying means for delaying the phase of the central angle of the lift of the exhaust valve. As a result, the scavenging efficiency and the expansion work can be effectively extracted corresponding to a wide range of operating conditions by variably controlling the opening characteristic of the scavenging port and the valve opening characteristic of the exhaust valve.

  (3) In a uniflow two-stroke internal combustion engine having a scavenging port provided in a cylinder block and opened near the piston bottom dead center position, and an exhaust valve provided in the cylinder head so as to be openable and closable, Phase variable means for retarding the phase of the central angle, intake control valve lift / operating angle variable means for expanding / reducing the exhaust valve lift / operating angle, and the bottom dead center position of the piston reciprocating in the cylinder Piston position variable means for variably controlling according to operating conditions. As a result, the scavenging efficiency and the expansion work can be effectively extracted corresponding to a wide range of operating conditions by variably controlling the opening characteristic of the scavenging port and the valve opening characteristic of the exhaust valve.

  (4) In the uniflow two-stroke internal combustion engine described in the above (1) or (3), specifically, the lift / operating angle varying means is rotated by a camshaft that rotates in conjunction with a crankshaft. An eccentric cam to be driven, a link arm slidably mounted on the eccentric cam, a rotatable control shaft provided in parallel with the cam shaft and provided with an eccentric cam portion, and an eccentric cam portion of the control shaft A rocker arm that is rotatably mounted on the camshaft and is pivotally supported by the camshaft, is rotatably supported by the camshaft, is connected to the rocker arm via a link, and swings along with the rocker arm, thereby And a swing cam that presses the tappet, and the lift and operating angle of the exhaust valve can be increased or decreased simultaneously by changing the rotational position of the eccentric cam portion of the control shaft. It is configured to.

  (5) In the uniflow two-stroke internal combustion engine described in the above (2) or (3), the piston position varying means specifically includes a piston bottom dead center position and a piston top dead center position depending on engine operating conditions. Are variably controlled at the same time.

  (6) The uniflow 2-stroke internal combustion engine in any one of said (1)-(5) has a supercharger in an intake system.

  (7) In the uniflow two-stroke internal combustion engine according to any one of (1) to (6), specifically, the phase variable means includes a camshaft that rotates in conjunction with a crankshaft, and a chain or timing belt. And a sprocket that is driven by the crankshaft and is arranged so as to be rotatable concentrically with the camshaft, and a means that is mounted between the sprocket and the camshaft and changes the relative phase of the two.

  (8) In the uniflow two-stroke internal combustion engine according to any one of (1) to (7), the piston is swingable to the first link connected to the piston via a piston pin, and the first link. And a third link rotatably connected to the crankpin portion of the crankshaft, and a third link swingably connected to the second link and swingably supported by the engine body, Is driven from the crankshaft by a multi-link piston-crank mechanism with

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which showed typically schematic structure of the 2-stroke internal combustion engine which concerns on this invention. Operation | movement explanatory drawing of a lift and a working angle variable mechanism. The characteristic view which shows the characteristic change of the lift and working angle by a lift and working angle variable mechanism. Explanatory drawing which shows schematic structure of a phase variable mechanism. Explanatory drawing which shows the phase change of the valve lift characteristic of an exhaust valve by a phase variable mechanism. The characteristic view which shows the opening characteristic of the scavenging port in 1st Embodiment of this invention, and the lift characteristic of an exhaust valve. The characteristic view which shows the opening characteristic of the scavenging port in a comparative example, and the lift characteristic of an exhaust valve. Explanatory drawing which shows schematic structure of a multi-link type piston-crank mechanism. The characteristic view which shows the piston stroke characteristic of a multiple link type piston-crank mechanism. Explanatory drawing which showed typically the change of the opening height of the scavenging port by piston stroke characteristics. The characteristic view which shows the opening characteristic of the scavenging port in 2nd Embodiment of this invention, and the lift characteristic of an exhaust valve. The characteristic view which shows the opening characteristic of the scavenging port in 3rd Embodiment of this invention, and the lift characteristic of an exhaust valve. The characteristic view which shows the opening characteristic of the scavenging port in 4th Embodiment of this invention, and the lift characteristic of an exhaust valve.

Explanation of symbols

4 ... Piston 5 ... Exhaust valve 6 ... Exhaust port 7 ... Scavenging port

Claims (8)

In a uniflow two-stroke internal combustion engine having a scavenging port provided in a cylinder block and opening near a piston bottom dead center position, and an exhaust valve provided in a cylinder head so as to be opened and closed,
Phase variable means for delaying the phase of the central angle of the lift of the exhaust valve;
A uniflow two-stroke internal combustion engine comprising: an intake control valve lift / working angle variable means for expanding / reducing an exhaust valve lift / working angle. In a uniflow two-stroke internal combustion engine having a scavenging port provided in a cylinder block and opening near a piston bottom dead center position, and an exhaust valve provided in a cylinder head so as to be opened and closed,
Piston position variable means for variably controlling the bottom dead center position of the piston reciprocating in the cylinder according to engine operating conditions;
A uniflow two-stroke internal combustion engine comprising: phase varying means for delaying the phase of the central angle of the lift of the exhaust valve. In a uniflow two-stroke internal combustion engine having a scavenging port provided in a cylinder block and opening near a piston bottom dead center position, and an exhaust valve provided in a cylinder head so as to be opened and closed,
Phase variable means for delaying the phase of the central angle of the lift of the exhaust valve;
Intake control valve lift / working angle variable means for expanding / reducing exhaust valve lift / working angle,
A uniflow two-stroke internal combustion engine comprising: piston position variable means for variably controlling a bottom dead center position of a piston that reciprocates in a cylinder according to engine operating conditions.   The lift / operating angle variable means includes a camshaft that rotates in conjunction with a crankshaft, an eccentric cam that is driven to rotate by the camshaft, a link arm that is slidably mounted on the eccentric cam, and a camshaft that is parallel to the camshaft. A pivotable control shaft provided with an eccentric cam portion, a rocker arm rotatably mounted on the eccentric cam portion of the control shaft and pivoted by a link arm, and rotatably supported by the camshaft. And a rocking cam that is coupled to the rocker arm via a link and rocks with the rocker arm to press the tappet of the exhaust valve, thereby changing the rotational position of the eccentric cam portion of the control shaft. The uniflow two-stroke internal combustion engine according to claim 1 or 3, wherein the lift and the operating angle of the exhaust valve are simultaneously increased or decreased by Seki.   4. The uniflow two-stroke internal combustion engine according to claim 2, wherein the piston position varying means variably controls the bottom dead center position and the piston top dead center position in accordance with engine operating conditions.   The uniflow two-stroke internal combustion engine according to any one of claims 1 to 5, further comprising a supercharger in the intake system.   The phase varying means includes a camshaft that rotates in conjunction with the crankshaft, a sprocket that is driven by the crankshaft via a chain or timing belt, and that is arranged to be rotatable concentrically with the camshaft, and between the sprocket and the camshaft. The uniflow two-stroke internal combustion engine according to any one of claims 1 to 6, further comprising means for changing the relative phase of the two.   The piston includes a first link coupled to the piston via a piston pin, a second link coupled to the first link in a swingable manner and rotatably coupled to a crankpin portion of the crankshaft, It is driven from a crankshaft by a multi-link type piston-crank mechanism provided with a third link that is swingably connected to the two links and supported swingably on the engine body. Item 8. The uniflow two-stroke internal combustion engine according to any one of items 1 to 7.

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