JP6413655B2 - Variable compression ratio mechanism - Google Patents

Description

  The present invention relates to a variable compression ratio mechanism for changing the compression ratio of an engine.

  Conventionally, it is composed of a cylindrical piston outer that is provided on the combustion chamber side and whose upper surface is sealed, and a piston inner that is slidably provided inside the piston outer and is connected to a connecting rod via a piston pin. In a four-cycle engine including a piston, a configuration in which a compression ratio variable mechanism is provided between a piston outer and a piston inner is disclosed (for example, Patent Documents 1 and 2).

  The conventional compression ratio variable mechanism disclosed in Patent Documents 1 and 2 is provided on the upper surface of the piston inner, and includes a first rotating cam plate including a first convex portion and a first concave portion, and a piston outer. A second rotating cam plate provided on an opposing surface of the first rotating cam plate and configured to include a second concave portion and a second convex portion that mesh with the first convex portion and the first concave portion; And an actuator that rotates the actuator. The actuator includes a hydraulic mechanism that rotates the first rotating cam plate in one rotation direction and a return spring that biases the first rotating cam plate in the other rotation direction, and the plunger and the return spring of the hydraulic mechanism are pistons. Embedded in the inner.

  In the conventional compression ratio variable mechanism, the hydraulic mechanism of the actuator rotates the first rotating cam plate against the urging force of the return spring to bring the first convex portion and the second convex portion into contact with each other, and the piston The relative distance between the inner and the piston outer is increased to increase the compression ratio, the first convex portion and the first concave portion are meshed with the second concave portion and the second convex portion, and the gap between the piston inner and the piston outer is increased. The compression ratio is lowered by reducing the relative distance.

JP 2005-54619 A Japanese Patent No. 4657162

  As described above, in the conventional variable compression ratio mechanism, the actuator for rotating the first rotating cam plate is embedded in the piston inner, which complicates the shape of the piston and increases the manufacturing cost of the piston. There is a problem of end.

  Further, since the first rotating cam plate is always biased in the other rotation direction by the return spring, a shearing force is always applied to the first convex portion, the first concave portion, the second convex portion, and the second concave portion. It becomes. Therefore, it is necessary to increase the rigidity of the members constituting the variable compression ratio mechanism, and there is a problem that the material cost increases.

  In view of the above problems, an object of the present invention is to provide a variable compression ratio mechanism that can change the compression ratio at a low cost with a simple structure.

  In order to solve the above problems, the variable compression ratio mechanism of the present invention is provided in an engine in which a piston slides in a cylinder by an explosion pressure generated in a combustion chamber, and the compression ratio is changed by changing the stroke position of the piston. This is a variable compression ratio mechanism, and a plurality of teeth with teeth facing the combustion chamber are provided on the circumference with the central axis of the piston as the axis, and reciprocates in the stroke direction of the piston integrally with the piston. A first member that engages with the tooth part of the first member, and a meshing position where the meshing part meshes with the tooth part, and a position closer to the combustion chamber than the meshing position. Thus, it is movable between non-meshing positions where the meshing relationship between the meshing part and the tooth part is released, and at the non-meshing position, it is rotatable around the central axis of the piston, and at the meshing position, the first member The tooth and the chewing portion according to the relative rotation position A second member having different meshing depths, a contact portion provided on the second member and facing the first member, and a contacted portion provided on the first member side with respect to the contact portion and arranged to face the contact portion The contact portion and the contacted portion are brought close to each other in the stroke direction, the two are brought into contact with each other, and a pressing force is applied to the second member in the stroke direction via the contact portion, and then the contact portion and the contacted portion are stroked. And at least one of the contact portion and the contacted portion is configured by an inclined surface having an inclination angle in the rotation direction of the second member, and the second member is in the meshing position. When the contact portion and the contacted portion come into contact with each other by the driving portion, the pressing force provided by the driving portion is distributed to the stroke direction and the rotation direction by the inclined surface and transmitted to the second member, and from the meshing position by the pressing force in the stroke direction. Non-meshing position As the second member moves, the second member rotates due to the component force acting in the rotation direction, and the relative rotation position with the first member changes, and the contact portion and the contacted portion are separated after the second member rotates. Then, the second member moves to the meshing position.

  Further, the contacted portion is provided with a plurality of tooth bodies facing the tooth surface on the combustion chamber side on the circumference around the central axis of the piston. There may be a plurality of bites arranged on the same circumference, the bites may be engaged with the teeth, and the inclined surface may be provided on the teeth and the bites.

  Further, the drive unit moves the contacted part in a direction close to the combustion chamber, thereby bringing the contacted part into contact with the contact part, and moving the contacted part in a direction away from the combustion chamber. The part may be separated from the contact part.

  The contact portion may be provided along the circumferential direction of the second member, and the contacted portion may be provided along the circumferential direction of the first member.

  The biting portion of the second member is on the other side of the second member in the rotation direction with the top, the first bottom located on one side in the rotation direction of the second member with the top as a boundary, and the top of the second member. And a second bottom portion having a depth greater from the top portion than the first bottom portion, and the distance between the top portions of the teeth of the contact portion and the distance between the top portions of the tooth bodies of the contacted portion are the second The distance may be greater than the distance in the rotational direction between the top of the biting portion of the member and the second bottom adjacent to the top and less than the distance in the rotational direction between the first bottom and the second bottom.

  Further, when the piston reaches the bottom dead center, the drive unit brings the contact portion and the contacted portion close to each other in the stroke direction so as to contact them, and applies a pressing force to the second member via the contact portion in the stroke direction. After that, the contact portion and the contacted portion may be separated in the stroke direction.

  The engine also includes a piston rod having one end fixed to the piston, and a crosshead connected to the other end of the piston rod and reciprocating integrally with the piston. The first member and the second member are pistons. , A piston rod, and a cross head may be provided.

  According to the compression ratio variable mechanism of the present invention, the compression ratio can be changed with a simple structure and at a low cost.

It is a figure which shows the whole structure of a uniflow scavenging type 2 cycle engine. It is a figure for demonstrating a compression ratio variable mechanism. It is a perspective view of a compression ratio variable mechanism. It is a figure for demonstrating a compression ratio variable mechanism. It is a figure explaining the dimensional relationship of the tooth part of a 1st member, the tooth body of a to-be-contacted part, the biting part of a 2nd member, and the biting body of a contact part. It is a 1st figure for demonstrating the change of the compression ratio by a compression ratio variable mechanism. It is a 2nd figure for demonstrating the change of the compression ratio by a compression ratio variable mechanism. It is a figure explaining the positional relationship of the 1st member and the 2nd member by the difference in a meshing position. It is a figure explaining the 2nd member of the compression ratio variable mechanism concerning a modification.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  In the following embodiments, first, an engine provided with a variable compression ratio mechanism will be described, and then the compression ratio variable mechanism will be described in detail. In the present embodiment, as an engine provided with a variable compression ratio mechanism, an engine that is a uniflow scavenging type in which one cycle is two cycles (strokes) and gas flows in one direction inside the cylinder will be described as an example. To do. However, if the engine provided with the variable compression ratio mechanism is an engine in which the piston slides in the cylinder by the explosion pressure generated in the combustion chamber, the number of cycles and the gas flow direction are not limited.

(Uniflow scavenging two-cycle engine 100)
FIG. 1 is a diagram showing an overall configuration of a uniflow scavenging two-cycle engine 100. The uniflow scavenging two-cycle engine 100 of the present embodiment is used for, for example, ships. In addition, the uniflow scavenging two-cycle engine 100 of the present embodiment has one of an operation mode of a gas operation mode in which fuel gas that is gaseous fuel is mainly combusted and a diesel operation mode in which fuel oil that is liquid fuel is combusted. This is a so-called dual fuel type engine that can be selectively executed. More specifically, the uniflow scavenging two-cycle engine 100 includes a cylinder 110, a piston 112, a crosshead 114, a connecting rod 116, a crankshaft 118, an exhaust port 120, an exhaust valve 122, and a scavenging port. 124, a scavenging reservoir 126, a cooler 128, a scavenging chamber 130, and a combustion chamber 132.

  In the uniflow scavenging two-cycle engine 100, exhaust, intake, compression, combustion, and expansion are performed during the two strokes of the upward stroke and the downward stroke of the piston 112, and the piston 112 reciprocates in the cylinder 110. One end of a piston rod 112 a is fixed to the piston 112. The other end of the piston rod 112 a is connected to a cross head pin 114 a in the cross head 114, and the cross head 114 reciprocates together with the piston 112. The cross head 114 is restricted from moving in the direction perpendicular to the stroke direction of the piston 112 (left and right direction in FIG. 1) by the cross head shoe 114b.

  The cross head pin 114 a is inserted into a hole provided at one end of the connecting rod 116 and supports one end of the connecting rod 116. The other end of the connecting rod 116 is connected to the crankshaft 118 so that the crankshaft 118 rotates with respect to the connecting rod 116. As a result, when the cross head 114 reciprocates as the piston 112 reciprocates, the crankshaft 118 rotates in conjunction with the reciprocation.

  The exhaust port 120 is an opening provided in the cylinder head 110 a above the top dead center of the piston 112, and is opened and closed to exhaust the exhaust gas after combustion generated in the cylinder 110. The exhaust valve 122 is slid up and down at a predetermined timing by an unillustrated exhaust valve driving device to open and close the exhaust port 120. The exhaust gas exhausted through the exhaust port 120 in this way is supplied to the turbine side of the supercharger C through the exhaust pipe 120a and then exhausted to the outside.

  The scavenging port 124 is a hole penetrating from the inner peripheral surface on the lower end side of the cylinder 110 (the inner peripheral surface of the cylinder liner 110 b) to the outer peripheral surface, and a plurality of scavenging ports 124 are provided over the entire periphery of the cylinder 110. The scavenging port 124 sucks the active gas into the cylinder 110 according to the sliding motion of the piston 112. Such an active gas includes an oxidizing agent such as oxygen and ozone, or a mixture thereof (for example, air).

  The scavenging reservoir 126 is filled with active gas (for example, air) pressurized by the compressor of the supercharger C, and the active gas is cooled by the cooler 128. The cooled active gas is pressed into a scavenging chamber 130 formed in the cylinder jacket 110c. Then, the active gas is sucked into the cylinder 110 from the scavenging port 124 with a differential pressure in the scavenging chamber 130 and the cylinder 110.

  The cylinder head 110a is provided with a pilot injection valve (not shown). In the gas operation mode, an appropriate amount of fuel oil is injected from the pilot injection valve at a desired point in the engine cycle. Such fuel oil is vaporized by the heat of the combustion chamber 132 surrounded by the cylinder head 110a, the cylinder liner 110b, and the piston 112 to become a fuel gas, and is spontaneously ignited and burns in a short time. The temperature of 132 is made extremely high. As a result, the fuel gas flowing into the cylinder 110 can be reliably burned at a desired timing. The piston 112 reciprocates mainly by the expansion pressure due to the combustion of fuel gas.

  Here, fuel gas shall be produced | generated by gasifying LNG (liquefied natural gas), for example. Further, the fuel gas is not limited to LNG, and for example, gasified LPG (liquefied petroleum gas), light oil, heavy oil, or the like can be applied.

  On the other hand, in the diesel operation mode, a larger amount of fuel oil is injected from the pilot injection valve than the fuel oil injection amount in the gas operation mode. The piston 112 reciprocates by an expansion pressure caused by combustion of fuel oil, not fuel gas.

  Further, the uniflow scavenging two-cycle engine 100 of the present embodiment is provided with a variable compression ratio mechanism that changes the compression ratio by changing the stroke position of the piston 112. Hereinafter, the variable compression ratio mechanism will be described in detail.

(Compression ratio variable mechanism 200)
FIG. 2 is a view for explaining the compression ratio variable mechanism 200, and shows a cross-sectional view of the piston 112 and the vicinity of the piston 112. As shown in FIG. 2, the piston 112 of the present embodiment includes a first member 210 connected to the piston rod 112a by a bolt 112b, and a second member 240 disposed on the combustion chamber 132 side from the first member 210. Consists of including.

  The compression ratio variable mechanism 200 includes a first member 210, a pressing member 220, a driving unit 230, a second member 240, and a pressed member 250.

  The first member 210 has a cylindrical shape, and a tooth portion 212 is provided on the surface on the combustion chamber 132 side. An annular groove 210a is formed radially outward from the tooth portion 212 of the first member 210, and a pressing member 220 is accommodated in the annular groove 210a so as to be movable in the stroke direction. The pressing member 220 is provided with a contacted portion 222 on the surface on the combustion chamber 132 side.

  The drive unit 230 communicates with the annular groove 210a and is inserted into insertion holes 210b formed at equal intervals in the circumferential direction of the annular groove 210a, and a rod 232 connected to the back surface of the contacted part 222 of the pressing member 220. And a spring 234 that urges the rod 232 toward the second member 240 and an actuator (not shown) (for example, a hydraulic mechanism or a motor) that presses the rod 232 toward the combustion chamber 132. Move in the stroke direction. Note that a plurality of rods 232 are connected to the pressing member 220 and restrict movement of the pressing member 220 in the rotational direction.

  The second member 240 has a cylindrical shape, and a biting portion 242 is provided on the surface facing the first member 210. Further, an annular groove 240a is formed radially outward from the biting portion 242 of the second member 240, and a pressed member 250 is fitted into the annular groove 240a. The pressed member 250 is fixed to the second member 240 by a pin 240b. Therefore, the pressed member 250 moves together with the second member 240. The pressed member 250 is provided with a contact portion 252 on the surface on the first member 210 side.

  In addition, although mentioned later in detail, in this embodiment, the 1st member 210 and the to-be-contacted part 222 (pressing member 220) move only to a stroke direction, and the 2nd member 240 and the contacting part 252 (to-be-pressed member 250) Moves in the stroke direction and rotates around the central axis P of the piston 112.

  3 and 4 are diagrams for explaining the first member 210, the pressing member 220, the second member 240, and the pressed member 250, and FIGS. 3A and 3B are surrounded by broken lines in FIG. 4 (a) is a plan view of the second member 240 and the contact portion 252 surrounded by a broken line in FIG. 2, and FIG. 4 (b) is a circumferential direction of the contact portion 252. 4 (c) is a development view of the second member 240 in the circumferential direction, and FIG. 4 (d) is a portion surrounded by a broken line in FIG. 4E is a development view of the first member 210 in the circumferential direction, and FIG. 4F is a development view of the contacted portion 222 in the circumferential direction.

  As shown in FIG. 3A, the first member 210 has a tooth portion 212 having a tooth surface facing the combustion chamber 132 (see FIG. 2), and the central axis P of the piston 112 (see FIG. 2). A plurality of shafts are provided on the circumference, and reciprocate in the stroke direction.

  Further, as shown in FIGS. 4D and 4E, the tooth portions 212 of the first member 210 are arranged such that the top portions 212a and the bottom portions 212b are alternately spaced at equal intervals in the rotation direction. In addition, the tooth portion 212 of the first member 210 has a circumferential direction around the central axis P from the top portion 212a to the bottom portion 212b (the rotation direction of the second member 240, hereinafter simply referred to as “rotation direction”). ) Are provided with an inclined surface 212c having an inclination angle and an inclined surface 212d having an inclination angle in the rotational direction from the bottom portion 212b toward the top portion 212a. The heights of the tooth portions 212 of the first member 210 are all equal.

  As shown in FIG. 3B, the second member 240 has a plurality of biting portions 242 arranged on the same circumference as the tooth portions 212 of the first member 210. Further, as shown in FIGS. 4A and 4C, the biting portion 242 has a top portion 242a and bottom portions 242b and 242c having different depths from the top portion 242a in the stroke direction. More specifically, the depth in the stroke direction from the top 242a to the bottom 242b (second bottom) is larger by the width D than from the top 242a to the bottom 242c (first bottom).

  Further, the biting portion 242 of the second member 240 is arranged such that the bottom portion 242b and the bottom portion 242c are alternately arranged with the top portion 242a interposed therebetween. Further, the biting portion 242 of the second member 240 has an inclined surface 242d having an inclination angle in the rotation direction from the top portion 242a to the bottom portion 242b, and an inclination surface having an inclination angle in the rotation direction from the bottom portion 242b to the top portion 242a. 242e, an inclined surface 242f having an inclination angle in the rotation direction from the top portion 242a toward the bottom portion 242c, and an inclination surface 242g having an inclination angle in the rotation direction from the bottom portion 242c to the top portion 242a are provided.

  In addition, as will be described in detail later, the second member 240 has a meshing position where the meshing part 242 meshes with the tooth part 212, and meshing between the meshing part 242 and the tooth part 212 on the combustion chamber 132 side from the meshing position. It can move between non-meshing positions where the relationship is released, and can rotate about the central axis P of the piston 112 at the non-meshing positions. At the meshing position, the top 212a of the tooth 212 and the bottom 242b of the mesh 242 mesh with each other, or the top 212a of the tooth 212 and the mesh 242 according to the relative rotation position with the first member 210. Or the bottom portion 242c of the mesh. That is, the second member 240 makes the meshing depths of the tooth part 212 and the meshing part 242 different according to the relative rotation position with the first member 210.

  As shown in FIG. 3A, the contacted portion 222 includes a plurality of tooth bodies 224 provided along the circumferential direction of the first member 210. The tooth body 224 includes the combustion chamber 132 (see FIG. 2). ) The tooth surface is facing the side. The contacted part 222 is provided in the pressing member 220 so as to be relatively movable with respect to the first member 210, and is moved in the stroke direction as the pressing member 220 is moved by the driving unit 230.

  Further, as shown in FIGS. 4D and 4F, the tooth bodies 224 of the contacted portion 222 are arranged so that the top portions 224a are equally spaced in the rotational direction, that is, the bottom portions 224b are equally spaced in the rotational direction. It is arranged to become. In addition, the tooth body 224 of the contacted portion 222 includes an inclined surface 224c having an inclination angle in the rotation direction from the top portion 224a to the bottom portion 224b, and a vertical surface 224d erected vertically from the bottom portion 224b to the top portion 224a. Is provided.

  As shown in FIG. 3B, the contact portion 252 is provided on the second member 240 along the circumferential direction of the second member 240, and is arranged on the same circumference as the tooth bodies 224 of the contacted portion 222. It comprises a plurality of chewing bodies 254, and the chewing bodies 254 mesh with the tooth bodies 224. As described above, in the present embodiment, the contact portion 252 is provided on the pressed member 250, and the pressed member 250 is fixed to the second member 240 by the pin 240b. It rotates integrally or reciprocates in the stroke direction integrally with the second member 240.

  Further, as shown in FIGS. 4 (a) and 4 (b), the body 254 of the contact portion 252 has the top portion 254a equally spaced in the rotational direction, that is, the bottom portion 254b is equally spaced in the rotational direction. Is arranged. Further, the body 254 of the contact portion 252 is provided with an inclined surface 254c having an inclination angle in the rotation direction from the top 254a toward the bottom 254b, and a vertical surface 254d standing upright from the bottom 254b toward the top 254a. It has been.

  Subsequently, a dimensional relationship among the tooth portion 212 of the first member 210, the tooth body 224 of the contacted portion 222, the biting portion 242 of the second member 240, and the biting body 254 of the contact portion 252 will be described.

  FIG. 5 is a diagram for explaining a dimensional relationship among the tooth portion 212 of the first member 210, the tooth body 224 of the contacted portion 222, the biting portion 242 of the second member 240, and the biting body 254 of the contact portion 252. As shown in FIG. 5, the distance (rotation angle) in the rotation direction between the top portions 254a of the contact portion 252, that is, the distance in the rotation direction (rotation angle) between the top portions 224a of the contacted portion 222 is defined as a distance L1. The distance (rotation angle) in the rotation direction between the top portion 242a of the member 240 and the bottom portion 242b adjacent to the top portion 242a is the distance L2, and the distance (rotation angle) in the rotation direction between the bottom portion 242b of the second member 240 and the bottom portion 242c. Is a distance L3, a distance (rotation angle) in the rotation direction between the bottom portions 242b, and a distance (rotation angle) in the rotation direction between the bottom portions 242c is a distance L4.

  In this case, the contacted part 222, the second member 240, and the contact part 252 are designed so that the distance L1 is greater than the distance L2 and less than the distance L3. Further, the first member 210 is designed so that the distance between the top portions 212a is the distance L4.

  Next, the change of the compression ratio by the variable compression ratio mechanism 200 will be described. 6 and 7 are diagrams for explaining the change of the compression ratio by the compression ratio variable mechanism 200. FIG. In order to facilitate understanding, the first member 210, the contacted portion 222, the second member 240, and the contact portion 252 are simplified in FIGS. Further, the first member 210 and the second member 240 are indicated by hatching, the contacted part 222 is indicated by black, and the contact part 252 is indicated by white. 6 and 7, the movement in the stroke direction is indicated by a white arrow, and the movement in the rotation direction is indicated by a black solid arrow.

  At the meshing position where the tooth portion 212 of the first member 210 and the meshing portion 242 of the second member 240 mesh with each other, as shown in FIG. Separated in the stroke direction. 6A, the top 212a of the first member 210 and the bottom 242b of the second member 240 are engaged. Further, in the meshing position, the top portion 254a of the contact portion 252 and the bottom portion 224b of the contacted portion 222 are different in the circumferential position. That is, the top portion 224 a of the contacted portion 222 has a positional relationship facing the inclined surface 254 c of the contact portion 252.

  And when changing a compression ratio, the to-be-contacted part 222 (pressing member 220) is moved to the contact part 252 (to-be-pressed member 250) side (direction close to the combustion chamber 132) by the drive part 230 in the stroke direction, As shown in FIG. 6B, the contacted part 222 is brought into contact with the contact part 252, and a pressing force is applied to the second member 240 via the contact part 252 in the stroke direction. As described above, since the top portion 224a of the contacted portion 222 has a positional relationship facing the inclined surface 254c of the contact portion 252, the pressing force provided by the driving unit 230 is applied to the stroke direction and the rotational direction by the inclined surface 254c. And is transmitted to the second member 240.

  Thereby, as shown in FIG.6 (c), while the contact part 252 and the 2nd member 240 rotate, the 2nd member 240 will move from a meshing position to a non-meshing position with the pressing force of a stroke direction. And if the top part 224a of the to-be-contacted part 222 and the bottom part 254b of the to-be-pressed member 250 mesh, the relative rotation position (position of the circumferential direction) with respect to the 1st member 210 will change the 2nd member 240, The top 212a of the first member 210 has a positional relationship facing the inclined surface 242e or the inclined surface 242g (here, the inclined surface 242g) of the second member 240. That is, in the meshing position shown in FIG. 6A, the top 212a of the first member 210 and the bottom 242b of the second member 240 are meshed, but in the non-meshing position shown in FIG. The top 212a of the first member 210 has a positional relationship facing the inclined surface 242e or the inclined surface 242g (here, the inclined surface 242g) of the second member 240.

  Subsequently, as illustrated in FIG. 7A, the drive unit 230 moves the contacted part 222 (pressing member 220) in a direction away from the combustion chamber 132, and strokes the contact part 252 and the contacted part 222. Separate in the direction. In the uniflow scavenging two-cycle engine 100, the force directed from the combustion chamber 132 toward the crankshaft 118 is constantly acting on the second member 240. Therefore, the contacted portion 222 is moved away from the combustion chamber 132. The second member 240 and the contact portion 252 move to the first member 210 side.

  Here, as described above, since the top portion 212a of the first member 210 is in a positional relationship facing the inclined surface 242g of the biting portion 242 of the second member 240, the second member 240 is in contact with the first member 210. Upon contact, the force from the combustion chamber 132 toward the crankshaft 118 acts in the rotational direction by the inclined surface 212c of the first member 210 and the inclined surface 242e of the second member 240. Accordingly, as shown in FIG. 7B, the second member 240 further rotates in the meshing process with the first member 210, and the top portion 212a of the first member 210 meshes with the bottom portion 242c of the second member 240. Will move to the meshing position. Further, as the second member 240 rotates at this time, the contact portion 252 rotates, so that the top portion 224a of the tooth body 224 of the contacted portion 222 faces the inclined surface 254c of the biting body 254 of the contact portion 252. It returns to the positional relationship, that is, the positional relationship substantially equal to that in FIG.

  FIG. 8 is a view for explaining the positional relationship between the first member 210 and the second member 240 depending on the difference in meshing position. FIG. 8A shows the first member 210 in the meshing position shown in FIG. FIG. 8B is a perspective view of the first member 210 and the second member 240 in the meshing position shown in FIG. 7B.

  As described above, the drive unit 230 moves the contacted part 222 (pressing member 220) in the direction approaching the combustion chamber 132 to contact the contact part 252, and the second member 240 is contacted with the second member 240 via the contact part 252 in the stroke direction. Then, the top 212a of the first member 210 is moved by moving the contact portion 252 away from the combustion chamber 132 and separating the contact portion 252 and the contacted portion 222 in the stroke direction. From the meshing position (see FIGS. 6A and 8A) that meshes with the bottom 242b of the second member 240, the meshing position (FIGS. 7B and 8) that meshes with the bottom 242c of the second member 240. (See (b)). Then, the height H of the first member 210 and the second member 240 is increased by a width D that is a difference in depth from the top portion 242a with respect to the bottom portion 242c. That is, the first member 210 protrudes from the second member 240 toward the combustion chamber 132 by the width D, which is the difference in depth between the bottom 242b and the bottom 242c from the top 242a. Thereby, the stroke position of the piston 112 changes, and the compression ratio can be changed from the low compression ratio to the high compression ratio.

  As described above, according to the compression ratio variable mechanism 200 according to the present embodiment, the second member 240 can be rotated simply by pressing the contacted portion 222 in the stroke direction. Therefore, the second member 240 is rotated. It is not necessary to embed an actuator for making the piston 112 inside, and the shape of the piston 112 can be simplified. Thereby, an increase in manufacturing cost of the piston 112 can be reduced.

  Further, since the second member 240 rotates only during the period in which the contacted portion 222 presses the contact portion 252, that is, while the first member 210 and the second member 240 are separated from each other, the first member A shearing force in the rotational direction does not act while the tooth portion 212 of 210 and the meshing portion 242 of the second member 240 are meshed. Therefore, it is not necessary to increase the rigidity of the first member 210 and the biting portion 242 unnecessarily, and it is possible to suppress an increase in material cost.

  Furthermore, the variable compression ratio mechanism 200 of the present embodiment has a simple configuration in which the contacted portion 222 is pressed and the pressing is released, and the first member 210 and the second member 240 are separated from each other, and the second Since the rotation of the member 240 can be performed, not only the uniflow scavenging two-cycle engine 100 but also the compression ratio of the four-cycle engine can be changed. In the four-cycle engine, there is a period in which a force from the crankshaft 118 to the combustion chamber 132 acts as well as a period in which the force from the combustion chamber 132 to the crankshaft 118 acts. Therefore, when the compression ratio variable mechanism 200 of this embodiment is applied to a four-cycle engine, the first member 210 and the second member 240 may be structured so as not to be separated from each other. For example, the first member 210 may be urged toward the second member 240 by an elastic member such as a spring.

  Further, the compression ratio can be changed at any time regardless of the stroke while the engine is being driven, whether the engine is being driven or the engine is being stopped.

  Although the compression ratio can be changed at any time, it is performed when the piston 112 reaches the bottom dead center. That is, when the piston 112 reaches the bottom dead center, the drive unit 230 touches the contact portion 252. The contact portion 252 may be moved away from the contacted portion 222 in the stroke direction after the two portions 240 are brought into contact with each other and a pressing force is applied to the second member 240 via the contact portion 252 in the stroke direction.

  Since the force from the combustion chamber 132 acting on the second member 240 toward the crankshaft 118 is the smallest when the piston 112 reaches the bottom dead center, the force with which the drive unit 230 presses the contacted portion 222 is minimized. Can be. Therefore, by changing the compression ratio when the piston 112 reaches the bottom dead center, the driving force of the driving unit 230 can be reduced, and the cost of the driving unit 230 can be reduced.

  Moreover, the compression ratio variable mechanism 200 may change a compression ratio according to an operation mode, and may change a compression ratio according to an engine load.

  Furthermore, by designing the dimensional relationship of the tooth portion 212 of the first member 210, the tooth body 224 of the contacted portion 222, the biting portion 242 of the second member 240, and the biting body 254 of the contact portion 252 as described above, FIG. In addition to the rotation of the contact portion 252 (second member 240) due to the pressing force of the contacted portion 222 shown in FIG. 6C, the second member 240 (contact portion 252) is further rotated as shown in FIG. Can be made. By this further rotation, the relative positional relationship between the first member 210 and the second member 240 can always be kept constant. Therefore, each time the contacted part 222 presses the contact part 252, the meshing position of the tooth part 212 of the first member 210 and the meshing part 242 of the second member 240 can be shifted by one tooth. As described above, in the second member 240 of the present embodiment, the bottom portions 242b and 242c are alternately arranged, that is, the meshing depth of the first member 210 and the second member 240 is alternately one tooth at a meshing position. Since it is different, the meshing position can be changed by a single press by the contacted portion 222.

(Modification)
In the above embodiment, the compression ratio variable mechanism 200 that can change the compression ratio in two stages has been described. However, the compression ratio variable mechanism can change the compression ratio to three or more stages by devising the tooth portion of the first member and the meshing portion of the second member.

  FIG. 9 is a diagram illustrating the second member 340 of the compression ratio variable mechanism 200 according to the modification. As shown in FIG. 9, the biting portion 342 of the second member 340 includes four top portions 342b, 342d, 342f, and 342h and four bottom portions having different depths from the top portion 342b that is disposed closest to the first member 210 side. 342a, 342c, 342e, and 342g. By designing the biting portion 342 in this way, the compression ratio can be changed in four stages.

  In this case, the rotation direction distance L1 between the top portions 254a of the contact portion 252 is the distance L5 in the rotation direction between the bottom portion 342g and the top portion 342h, that is, the rotation between the bottom portion and the top portion of the engaging portion 342 of the second member 340. It is good to design based on the longest distance among the distances in the direction.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

  For example, in the above-described embodiment, the driving unit 230 has been described by taking as an example a configuration for moving the contacted part 222. However, the drive unit 230 brings the contact part 252 and the contacted part 222 into contact with each other in the stroke direction, contacts the both, and applies a pressing force to the second member 240 in the stroke direction via the contact part 252 before making contact. It is only necessary that the part 252 and the contacted part 222 can be separated in the stroke direction. For example, the drive unit 230 may move the contact part 252 or may move the contact part 252 and the contacted part 222.

  Moreover, in the said embodiment, the case where the to-be-contacted part 222 was provided in the radial direction outer side rather than the tooth | gear part 212 of the 1st member 210 was mentioned as an example, and was demonstrated. However, the contacted part 222 may be provided along the circumferential direction of the first member 210. For example, the contacted part 222 may be provided radially inward from the tooth part 212 of the first member 210.

  Moreover, in the said embodiment, the case where the contact part 252 was provided in radial direction outer side rather than the meshing part 242 of the 2nd member 240 was mentioned as an example, and was demonstrated. However, the contact portion 252 only needs to be provided along the circumferential direction of the second member 240. For example, the contact portion 252 may be provided radially inward from the biting portion 242 of the second member 240.

  Moreover, in the said embodiment, the height of the top part 212a of the 1st member 210 is made constant, and the depth (distance from the top part 212a of the 1st member 210) of the bottom parts 242b and 242c of the 2nd member 240 is varied. The configuration in which the engagement depths of the tooth portion 212 and the engagement portion 242 are different has been described as an example. However, the configuration is not limited as long as the meshing depths of the tooth portion 212 and the chewing portion 242 can be made different. For example, the height of the top portion 242a of the second member 240 may be constant, and the depth of the bottom portion 212b of the first member 210 may be varied to change the meshing depth between the tooth portion 212 and the meshing portion 242. .

  Moreover, in the said embodiment, the tooth | gear part 212 and the biting part 242 demonstrated and demonstrated the structure which has the inclined surfaces 212c and 242d-242g as an example. However, the tooth part 212 and the biting part 242 may not have an inclined surface. In this case, when the contact portion 252 and the contacted portion 222 come into contact with each other while the second member 240 is in the meshing position, the second member 240 is moved from the meshing position to the non-meshing position by the pressing force in the stroke direction. In addition, when the meshing relationship between the tooth portion 212 and the meshing portion 242 is released, the second member 240 is rotated by the component force acting in the rotation direction, and the relative rotational position with respect to the first member 210 is changed. Become.

  Further, in the above-described embodiment, the configuration in which the inclined surfaces 224c and 254c are provided on the biting body 254 of the contact portion 252 and the tooth body 224 of the contacted portion 222 has been described as an example. However, the inclined surface having an inclination angle in the rotation direction of the second member 240 may be provided in at least one of the contact portion 252 and the contacted portion 222.

  In the above embodiment, the configuration in which the first member 210 and the second member 240 of the variable compression ratio mechanism 200 are provided in the piston 112 has been described as an example. However, the first member 210 and the second member 240 may be provided on the piston rod 112 a or the cross head 114.

  The present invention can be used in a variable compression ratio mechanism that changes the compression ratio of an engine.

P Center shaft 100 Uniflow scavenging two-cycle engine (engine)
112 Piston 112a Piston rod 114 Crosshead 132 Combustion chamber 200 Compression ratio variable mechanism 210 First member 212 Tooth portion 212a Top portion 212b Bottom portion 220 Pressing member 222 Contacted portion 224 Tooth body 224c Inclined surface 230 Driving portion 240 Second member 242 Chewing portion 242a Top 242b Bottom (second bottom)
242c Bottom (first bottom)
250 Pressed member 252 Contact portion 254 Coupling body 254c Inclined surface 340 Second member 342 Coupling portion

Claims (7)

A compression ratio variable mechanism that is provided in an engine in which a piston slides in a cylinder by an explosion pressure generated in a combustion chamber and changes a compression ratio by changing a stroke position of the piston,
A plurality of teeth having teeth facing the combustion chamber side, the first member reciprocating in the stroke direction of the piston integrally with the piston; ,
A plurality of meshing portions arranged on the same circumference as the tooth portion of the first member, the meshing position where the meshing portion meshes with the tooth portion, and the combustion chamber side from the meshing position. It is possible to move between non-meshing positions where the meshing relationship between the meshing part and the tooth part is released, and at the non-meshing position, it is rotatable around the central axis of the piston, and at the meshing position, A second member having different meshing depths between the tooth portion and the chewing portion according to a relative rotational position with the first member;
A contact portion provided on the second member and facing the first member;
A contacted part that is provided closer to the first member than the contact part and is disposed to face the contact part;
The contact portion and the contacted portion are brought close to each other in the stroke direction, both are brought into contact with each other, and a pressing force is applied to the second member via the contact portion in the stroke direction. A drive unit for separating the contact part in the stroke direction;
With
At least one of the contact part and the contacted part is configured by an inclined surface having an inclination angle in the rotation direction of the second member,
When the contact portion and the contacted portion come into contact with each other in the state where the second member is in the meshing position, the pressing force provided by the drive portion is caused by the inclined surface to the stroke direction and the rotation direction. The second member is moved from the meshing position to the non-meshing position by the pressing force in the stroke direction, and the second force is applied by the component force acting in the rotational direction. When the member rotates and the relative rotation position with respect to the first member changes, and the contact portion and the contacted portion are separated after the rotation of the second member, the second member moves to the meshing position. Characteristic variable compression ratio mechanism. The contacted portion is provided with a plurality of tooth bodies facing the tooth surface on the combustion chamber side on a circumference around the central axis of the piston,
The contact portion has a plurality of teeth arranged on the same circumference as the tooth body of the contacted portion, and the teeth mesh with the tooth body,
The compression ratio variable mechanism according to claim 1, wherein the inclined surface is provided on the tooth body and the biting body.   The drive unit moves the contacted part in a direction close to the combustion chamber, thereby bringing the contacted part into contact with the contact part and moving the contacted part in a direction away from the combustion chamber. The compression ratio variable mechanism according to claim 1, wherein the contacted portion is separated from the contact portion. The contact portion is provided along a circumferential direction of the second member,
The compression ratio variable mechanism according to any one of claims 1 to 3, wherein the contacted portion is provided along a circumferential direction of the first member. The biting portion of the second member includes a top portion, a first bottom portion located on one side of the rotation direction of the second member with the top portion as a boundary, and a rotation direction of the second member with the top portion as a boundary. A second bottom located on the other side and having a greater depth from the top than the first bottom;
The distance between the tops of the teeth of the contact part, and the distance between the tops of the teeth of the contacted part,
It is larger than the distance in the rotation direction between the top of the biting portion of the second member and the second bottom adjacent to the top, and is less than the distance in the rotation between the first bottom and the second bottom. The variable compression ratio mechanism according to any one of claims 2 to 4.   When the piston reaches the bottom dead center, the drive unit brings the contact unit and the contacted part close to each other in the stroke direction so as to contact both, and the second member is contacted with the second member via the contact unit. The compression ratio variable mechanism according to any one of claims 1 to 5, wherein after the pressing force is applied to the contact portion, the contact portion and the contacted portion are separated from each other in the stroke direction. The engine is
A piston rod having one end fixed to the piston;
A crosshead connected to the other end of the piston rod and reciprocally moving integrally with the piston;
With
The variable compression ratio according to any one of claims 1 to 6, wherein the first member and the second member are provided in any one of the piston, the piston rod, and the crosshead. mechanism.

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