JP6318978B2 - Variable compression ratio internal combustion engine - Google Patents

Description

  The present invention relates to a variable compression ratio internal combustion engine.

  A variable compression ratio mechanism for changing the relative position of the crankcase and the cylinder block in the cylinder axial direction is disposed at the connecting portion between the crankcase and the cylinder block. The variable compression ratio mechanism is supported by the crankcase so as to be rotatable. And a drive shaft extending in the longitudinal direction of the engine body, the drive shaft having an eccentric shaft portion that is eccentric with respect to the axis of the drive shaft, and a free rotation shaft is rotatably attached to each eccentric shaft portion. A variable compression ratio internal combustion engine in which a cylinder block is supported by each free rotating shaft via a cylinder block bearing is known (see, for example, Patent Document 1).

JP 2009-299778 A

  In this variable compression ratio internal combustion engine, the clearance between the free rotation shaft and the eccentric shaft portion and the clearance between the free rotation shaft and the cylinder block bearing are gradually increased outward from the center portion, thereby Fine particles entering between the eccentric shaft portions and between the free rotating shaft and the cylinder block side bearing are easily discharged to the outside. By the way, in such a variable compression ratio mechanism, the drive shaft of the variable compression ratio mechanism vibrates during engine operation to generate vibration noise, and the cylinder block supported by the free rotation shaft vibrates to generate vibration noise. There is a problem. In this case, if the bearing clearance of the bearing supporting the drive shaft is reduced, the vibration noise of the drive shaft can be suppressed, and if the bearing clearance of the cylinder block bearing is reduced, the vibration noise of the cylinder block is reduced. Occurrence can be suppressed. However, simply reducing the bearing clearance increases the friction loss in the bearing and causes a problem that a large amount of energy is required to drive the drive shaft.

As described above, when the variable compression ratio mechanism is used, how to suppress the vibration noise of the drive shaft and the cylinder block and the increase of the drive energy of the drive shaft is a big problem. In this known variable compression ratio internal combustion engine, no consideration is given to this.
An object of the present invention is to provide a variable compression ratio internal combustion engine that can suppress generation of vibration noise of a drive shaft and a cylinder block and increase in drive energy of the drive shaft.

  That is, according to the present invention, the variable compression ratio mechanism for changing the relative position of the crankcase and the cylinder block in the cylinder axial direction is arranged at the connecting portion between the crankcase and the cylinder block. A drive shaft that is rotatably supported by the crankcase via a drive shaft support bearing and extends in the longitudinal direction of the engine body. The drive shaft is at least at both ends of the drive shaft with respect to the axis of the drive shaft. Each of the eccentric shaft portions has an eccentric shaft portion that is eccentric, and a free rotation shaft is rotatably attached to each eccentric shaft portion, and the cylinder block is supported by the free rotation shaft via a cylinder block support bearing. In a specific internal combustion engine, the cylinder block bearings arranged on each free rotating shaft are composed of a pair of bearings, and the cylinder block bearing The bearing consists of a small clearance bearing with the smallest bearing clearance among all cylinder block bearings and a large clearance bearing with a larger clearance than the small clearance bearing. The drive shaft bearing is an eccentric shaft for each eccentric shaft. The drive shaft bearing bearing is composed of a small clearance bearing with the smallest bearing clearance among all the bearings for the drive shaft bearing and a large clearance bearing with a larger clearance than the small clearance bearing. The cylinder block bearing bearing located at least on the outermost side at both ends of the shaft is a small clearance bearing, and the bearing located outside of the drive shaft bearings disposed on both sides of the eccentric shaft portion at both ends of the drive shaft Is a large clearance bearing and the inner bearing is a small clearance shaft. And the variable compression ratio internal combustion engine is provided.

  The cylinder block bearing bearing positioned at least on the outermost side at both ends of the drive shaft is a small clearance bearing, and is positioned outside of the drive shaft bearing bearings disposed on both sides of the eccentric shaft portion at both ends of the drive shaft. The drive energy of the drive shaft can be reduced while suppressing the generation of vibration noise of the cylinder block and the drive shaft by making the bearing a large clearance bearing and the bearing located inside the small clearance bearing.

FIG. 1 is an overall view of a variable compression ratio internal combustion engine. FIG. 2 is an exploded perspective view of the variable compression ratio mechanism. FIG. 3 is a side sectional view of the drive shaft. 4A and 4B are side sectional views of the internal combustion engine schematically shown. FIG. 5 is a diagram for explaining the vibration of the cylinder block. 6A and 6B are diagrams for explaining the vibration of the drive shaft. 7A, 7B and 7C are diagrams schematically showing a preferred example of the arrangement of the small clearance bearing and the large clearance bearing of the cylinder block bearing. 8A, 8B and 8C are diagrams schematically showing a preferred example of the arrangement of the small clearance bearing and the large clearance bearing of the drive shaft bearing. FIG. 9 is a view schematically showing a preferable example of the arrangement of the small clearance bearing and the large clearance bearing of the drive shaft bearing. FIG. 10 is a diagram schematically showing an unfavorable example of the arrangement of the small clearance bearing and the large clearance bearing of the drive shaft bearing. FIG. 11 is a diagram schematically showing a preferable example of the arrangement of the small clearance bearing and the large clearance bearing of the drive shaft bearing. FIG. 12 is a view schematically showing an unfavorable example of the arrangement of the small clearance bearing and the large clearance bearing of the drive shaft bearing.

FIG. 1 shows a side view of a variable compression ratio internal combustion engine.
Referring to FIG. 1, 1 is a crankcase, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is a spark plug disposed at the center of the top surface of the combustion chamber 5, and 7 is intake air. 8 is an intake port, 9 is an exhaust valve, and 10 is an exhaust port. The intake port 8 is connected to a surge tank 12 via an intake branch pipe 11, and a fuel injection valve 13 for injecting fuel into the corresponding intake port 8 is arranged in each intake branch pipe 11. The surge tank 12 is connected to an air cleaner 15 via an intake duct 14, and a throttle valve 16 is disposed in the intake duct 14. On the other hand, the exhaust port 10 is connected to a catalytic converter 18 via an exhaust manifold 17.

  On the other hand, in the embodiment shown in FIG. 1, the piston 4 is positioned at the compression top dead center by changing the relative position of the crankcase 1 and the cylinder block 2 in the cylinder axial direction at the connecting portion between the crankcase 1 and the cylinder block 2. A variable compression ratio mechanism A is provided that can change the volume of the combustion chamber 5 when the intake valve 7 is closed, and the valve closing timing of the intake valve 7 is set in order to control the amount of intake air actually supplied into the combustion chamber 5. A controllable variable valve timing mechanism B is provided. FIG. 2 is an exploded perspective view of the variable compression ratio mechanism A. Referring to FIG. 2, bearing housings 20 are formed on the upper wall surface of the crankcase 1 so as to be arranged in two rows at intervals from each other. A bearing insertion hole 21 is formed in each bearing housing 20. ing. On the other hand, bearing housings 22 that are aligned and spaced apart from each other are also formed below both side walls of the cylinder block 2, and bearing insertion holes 23 are formed in the bearing housings 22.

  As shown in FIG. 2, the variable compression ratio mechanism A includes a pair of drive shafts 24 and 25. The drive shafts 24 and 25 have the same shape, and a side sectional view of the drive shafts 24 and 25 is shown in FIG. The drive shafts 24, 25 have eccentric shaft portions 26 that are eccentric with respect to the axis of the drive shafts 24, 25 at both ends of the drive shafts 24, 25, and each eccentric shaft portion 26 has a free rotation shaft 27. Is rotatably mounted. Drive shaft support bearings 28 are inserted into the bearing insertion holes 21 of the respective bearing housings 20, and the drive shaft support bearings corresponding to the bearing portions 29 of the drive shafts 24 and 25 on both sides of the eccentric shaft portion 26. 28 is supported. On the other hand, a pair of cylinder block bearings 30 juxtaposed in the bearing insertion holes 23 of the respective bearing housings 22 are inserted, and the cylinder block 2 can be freely connected via the cylinder block bearings 30. It is supported by a rotating shaft 27.

  When the drive shafts 24 and 25 are rotated in opposite directions as indicated by arrows from the state shown in FIG. 4A, the eccentric shaft portion 26 moves toward the upper center. In the inside, it first rotates in the same direction as the drive shafts 24 and 25, and in the middle, rotates in the opposite direction to the drive shafts 24 and 25. When the eccentric shaft portion 26 moves to the upper center as shown in FIG. The center of the shaft 27 moves upward.

  4A and 4B, the relative position of the crankcase 1 and the cylinder block 2 is determined by the distance between the center of the drive shafts 24 and 25 and the center of the free rotation shaft 27. As the distance between the center and the center of the free rotation shaft 27 increases, the cylinder block 2 moves away from the crankcase 1. When the cylinder block 2 moves away from the crankcase 1, the volume of the combustion chamber 5 when the piston 4 is located at the compression top dead center is increased. Therefore, by rotating the drive shafts 24 and 25, the piston 4 is compressed at the top dead center. The volume of the combustion chamber 5 when it is located at can be changed.

  As shown in FIG. 2, in order to rotate the drive shafts 24 and 25 in opposite directions, a pair of worm gears 42 and 43 having opposite screwing directions are attached to the rotation shaft 41 of the drive motor 40, respectively. Gears 44 and 45 meshing with the worm gears 42 and 43 are fixed to the end portions of the drive shafts 24 and 25, respectively. In this embodiment, by driving the drive motor 40, the volume of the combustion chamber 5 when the piston 4 is located at the compression top dead center is changed.

  Thus, in the embodiment according to the present invention, the variable compression ratio mechanism A for changing the relative position of the crankcase 1 and the cylinder block 2 in the cylinder axial direction is arranged at the connecting portion between the crankcase 1 and the cylinder block 2. The variable compression ratio mechanism A includes drive shafts 24 and 25 that are rotatably supported by the crankcase 1 via a drive shaft support bearing 28 and extend in the longitudinal direction of the engine body. 24 and 25 have an eccentric shaft portion 26 that is eccentric with respect to the axis of the drive shafts 24 and 25 at at least both ends of the drive shafts 24 and 25, and each of the eccentric shaft portions 26 can have a free rotating shaft 27 rotatable. The cylinder block 2 is supported by a free rotating shaft 27 via a cylinder block bearing 30.

  When such a variable compression ratio mechanism A is used, the cylinder block 2 supported by the cylinder block support bearing 30 vibrates to generate vibration noise, and the drive shaft support bearing 28 supports the vibration. There is a problem in that the drive shafts 24 and 25 are vibrated to generate vibration noise. In this case, if the bearing clearance of the cylinder block bearing 30 that supports the cylinder block 2 is reduced, the generation of vibration noise in the cylinder block 2 can be suppressed, and the drive shafts 24 and 25 are supported. If the bearing clearance of the shaft bearing 28 is reduced, generation of vibration noise of the drive shafts 24 and 25 can be suppressed. However, if the bearing clearance is simply reduced, the friction loss in the cylinder block bearing 30 and the drive shaft bearing 28 increases, which causes a problem that a large amount of energy is required to drive the drive shafts 24 and 25. Therefore, the bearing clearance cannot simply be reduced in order to suppress the generation of vibration noise.

  Accordingly, the present inventor has pursued the relationship between the generation of vibration noise in the cylinder block 2 and the drive shafts 24, 25, the friction loss in the cylinder block bearing 30 and the drive shaft bearing 28, and the bearing clearance, As the bearings for the block bearing 30 and the drive shaft bearing 28, either a small clearance bearing having a small bearing clearance or a large clearance bearing having a larger clearance than the small clearance bearing is used, and the small clearance bearing and the large clearance bearing are used. It is found that the increase in the drive energy of the drive shafts 24 and 25 can be suppressed while the generation of vibration noise of the cylinder block 2 and the drive shafts 24 and 25 is suppressed.

  Therefore, in describing the present invention, first, the small clearance bearing and the large clearance bearing will be described. In the embodiment according to the present invention, a bearing having a bearing clearance of 10 to 20 μm is used as the small clearance bearing, and a bearing having a bearing clearance of 30 to 40 μm is used as the large clearance bearing. That is, the bearing clearance of the large clearance bearing used in the embodiment according to the present invention is almost twice the bearing clearance of the small clearance bearing.

  In the embodiment shown in FIGS. 2 and 3, in order to support the load of the cylinder block 2, the cylinder block 2 has a pair of juxtaposed cylinder block bearings 30 at one end of the drive shafts 24 and 25. And the other ends of the drive shafts 24 and 25 are supported by a pair of juxtaposed cylinder block bearings 30. Further, in order to support the load of the cylinder block 2 and the drive shafts 24 and 25, the drive shafts 24 and 25 are a pair of drive shafts disposed on both sides of the eccentric shaft portion 26 at one end of the drive shafts 24 and 25. The bearings 28 are supported by a bearing 28, and the other ends of the drive shafts 24 and 25 are also supported by a pair of drive shaft support bearings 28 arranged on both sides of the eccentric shaft portion 26.

  When the load is supported by a pair of adjacently arranged bearings as described above, if a small clearance bearing is used as one bearing and a large clearance bearing is used as the other bearing, the load is small clearance bearing and large clearance bearing. Supported by both roller bearings. On the other hand, when the cylinder block 2 and the drive shafts 24 and 25 vibrate, this vibration motion is restrained by the small clearance bearing having the smaller bearing clearance, so that the vibration of the cylinder block 2 and the drive shafts 24 and 25 is not affected. A small clearance bearing with a small bearing clearance acts as a fulcrum. In the present invention, this is used to suppress vibrations of the cylinder block 2 and the drive shafts 24 and 25. A method for suppressing vibrations of the cylinder block 2 and the drive shafts 24 and 25 will be described below.

  First, the vibration of the cylinder block 2, that is, the pitching swing of the cylinder block 2 will be described with reference to FIG. As described above, the cylinder block 2 is supported by the cylinder block bearing 30 at both ends of the drive shafts 24 and 25. FIG. 5 schematically illustrates this. As described above, the small clearance bearing acts as a fulcrum for the vibration of the cylinder block 2, and this fulcrum is indicated by 40 in FIG.

  Now, since the cylinder block 2 is a rigid body, when the cylinder block 2 causes pitching swing, the entire cylinder block 2 swings. The broken line in FIG. 5 indicates a case where the cylinder block 2 swings upward by D with respect to one fulcrum 40 due to pitching swing, and the swing angle of the cylinder block 2 at this time is indicated by θ. . Here, reducing the pitching swing means reducing the swing angle θ, and the cylinder block 2 swings upward by D with respect to one fulcrum 40 as shown in FIG. In order to reduce the swing angle θ, the distance S between the fulcrums 40, that is, the distance between the small clearance bearings should be increased. That is, if the interval S between the fulcrums 40, that is, the interval between the small clearance bearings is increased, the vibration of the cylinder block 2, that is, the pitching oscillation of the cylinder block 2 can be reduced.

  Next, vibrations of the drive shafts 24 and 25 will be described with reference to FIGS. 6A and 6B. As described above, the drive shafts 24 and 25 are supported by the drive shaft bearings 28, and FIG. 6A schematically shows this. As described above, the small clearance bearing acts as a fulcrum for the vibration of the drive shafts 24 and 25, and this fulcrum is indicated by 41 in FIG. 6A. By the way, since the drive shafts 24 and 25 are elastic bodies, when the drive shafts 24 and 25 vibrate, vibration is generated with each fulcrum 41 as a node as shown by a broken line in FIG. 6A. In addition, the broken line in FIG. 6A represents the primary vibration with the highest vibration intensity.

  On the other hand, FIG. 6B shows the relationship between the vibration intensity and the vibration frequency when the drive shafts 24 and 25 vibrate. When the drive shafts 24 and 25 vibrate, the frequency changes according to the interval S between the fulcrums 41, and the frequency of the drive shafts 24 and 25 increases as the interval S between the fulcrums 41 decreases. In FIG. 6B, the solid line indicates when the distance S between the fulcrums 41 is large, and the broken line indicates when the distance S between the fulcrums 41 is small. As indicated by the solid line, when the distance S between the fulcrums 41 is large, a resonance point appears at a relatively low frequency, and when the distance S between the fulcrums 41 is reduced, the resonance frequency increases as indicated by the broken line. . In this case, the vibration frequency generated in the drive shafts 24 and 25 is a relatively low frequency region as indicated by an arrow. Therefore, if the distance S between the fulcrums 41 is reduced, the drive shafts 24 and 25 do not resonate, and therefore vibrations generated by the drive shafts 24 and 25 can be reduced. That is, if the distance S between the fulcrums 41, that is, the distance between the small clearance bearings is reduced, the vibration generated by the drive shafts 24 and 25 can be reduced.

  Thus, if the interval S between the fulcrums 40, that is, the interval between the small clearance bearings is increased, the vibration of the cylinder block 2, that is, the pitching oscillation can be reduced, and the interval S between the fulcrums 41, that is, If the space between the small clearance bearings is reduced, the vibration generated by the drive shafts 24 and 25 can be reduced. Therefore, it can be seen that the distance S between the small clearance bearings for reducing the vibration is opposite between the case where the vibration of the cylinder block 2 is reduced and the case where the vibrations of the drive shafts 24 and 25 are reduced.

  Next, an embodiment according to the present invention will be specifically described with reference to the arrangement of the small clearance bearing and the large clearance bearing schematically shown in FIGS. FIG. 7A schematically shows the cylinder block bearing 30 shown in FIG. 3, and reference numerals C1, C2, C3, and C4 are sequentially attached to the bearings of the cylinder block bearing 30 from the left. Yes. In FIG. 7A, the bearing clearance is drawn small for the small clearance bearing, and the bearing clearance is drawn large for the large clearance bearing. It should be noted that the method of assigning symbols for each bearing and the method of drawing the small clearance bearing and the large clearance bearing are the same in the embodiments shown in FIG. 7B and thereafter.

  First, the first embodiment of the cylinder block bearing 30 shown in FIG. 7A will be described. In this embodiment, the outermost bearing C1 and the bearing C4 are small clearance bearings, The two bearings C2 and C3 located at 1 are composed of large clearance bearings. That is, as described above, with respect to the cylinder block bearing 30, it is possible to reduce the pitching oscillation of the cylinder block 2 by increasing the distance S between the fulcrums 40, that is, the distance between the small clearance bearings. Therefore, in the first embodiment, in order to reduce the pitching swing of the cylinder block 2, the outermost bearing C1 and the bearing C4 are constituted by small clearance bearings.

  In the first embodiment, the two bearings C2 and C3 located inside each cylinder block bearing 30 are composed of large clearance bearings with small friction loss, and therefore each cylinder block bearing. The friction loss at 30 is smaller than when all the bearings C1, C2, C3, and C4 are constituted by small clearance bearings. Therefore, in the first embodiment, the pitching oscillation of the cylinder block 2 can be reduced while reducing the friction loss of the entire bearing.

  FIG. 7B shows a second embodiment of the cylinder block bearing 30. In the second embodiment, the same number of free rotation shafts 27 as the cylinders, that is, four free rotation shafts 27 are attached to the drive shafts 24 and 25. A bearing 30, that is, eight cylinder block bearings 30 are provided. In the second embodiment, the outermost bearing C1 and the bearing C8 are small clearance bearings, and the remaining six bearings C2 located on the inner side are all bearings C7. In the second embodiment, as in the first embodiment, the pitching oscillation of the cylinder block 2 can be reduced while reducing the friction loss of the entire bearing.

  FIG. 7C shows a third embodiment of the cylinder block bearing 30. In this third embodiment, twice as many cylinder block bearings 30 as the free rotation shaft 27, that is, eight cylinder block bearings 30 are provided. A pair of bearings C1 and C2 of the cylinder block bearing 30 positioned on the outermost side on one side of the shafts 24, 25 and a pair of cylinder block bearing 30 positioned on the outermost side on the other side of the drive shafts 24, 25. The bearings C7 and C8 are small clearance bearings, and the remaining four bearings C3 located inside are bearings C6. In this third embodiment, the distance between the small clearance bearings is slightly shorter than that in the second embodiment, but the distance between the small clearance bearings is still large, thus reducing the friction loss of the entire bearing. Meanwhile, the pitching swing of the cylinder block 2 can be reduced.

  As can be seen from the embodiments shown in FIGS. 7A to 7C, in the present invention, the cylinder block bearing 30 disposed on each free rotating shaft 27 is composed of a pair of bearings, and the cylinder block bearing 30 is The cylinder block is composed of a small clearance bearing having the smallest bearing clearance among all cylinder block bearings and a large clearance bearing having a larger clearance than the small clearance bearing, and is positioned at least on the outermost side at both ends of the drive shafts 24 and 25. The bearings for support C1, C4, C8 are constituted by small clearance bearings.

  In this case, in the first embodiment shown in FIG. 7A and the second embodiment shown in FIG. 7B, the cylinder block support bearings C1, C4, C8 located on the outermost sides at both ends of the drive shafts 24, 25. Is composed of a small clearance bearing, and all the remaining cylinder block bearings are composed of large clearance bearings. On the other hand, in the third embodiment shown in FIG. 7C, a pair of cylinder block bearings C1, C2, C7, C8 disposed at both ends of the drive shafts 24, 25 are constituted by small clearance bearings, All the remaining cylinder block bearings are composed of large clearance bearings.

  Next, the drive shaft bearing 28 will be described with reference to FIGS. 8A to 12. FIG. 8A schematically shows the drive shaft support bearing 28 shown in FIG. 3, and reference numerals D1, D2, D3, and D4 are attached to the respective bearings of the drive shaft support bearing 28 from the left. Yes. First, the first embodiment of the drive shaft bearing 28 shown in FIG. 8A will be described. In this embodiment, the outermost bearing D1 and the bearing D4 are large clearance bearings, and are located on the inner side. The two bearings D2 and D3 are small clearance bearings. That is, as described above, with respect to the drive shaft bearing 28, the vibration of the drive shafts 24 and 25 can be reduced by reducing the distance S between the fulcrums 41, that is, the distance between the small clearance bearings. Therefore, in the first embodiment, in order to reduce the vibration of the drive shaft bearing 28, the bearing D2 and the bearing D3 located on the inner side are composed of small clearance bearings.

  FIG. 8B shows a second embodiment of the drive shaft bearing 28. In the second embodiment, the drive shafts 24 and 25 are formed with the same number of eccentric shaft portions 26 as the cylinders, that is, four eccentric shaft portions 26, and drive shaft bearings are provided on both sides of the eccentric shaft portions 26. 28 is provided. In the second embodiment, the outermost bearing D1 and the bearing D8 are large clearance bearings, and the bearing D2 and the bearing D7 located just inside the large clearance bearing are small clearance bearings. The arrangement of the large clearance bearings D1, D8 and the small clearance bearings D2, D7 is the same after FIG. 8C.

On the other hand, if one of the drive shaft bearings 28 disposed on both sides of the two eccentric shaft portions 26 located at the center of the drive shafts 24 and 25 is a small clearance bearing, the other is a large clearance bearing. For example, paying attention to the drive shaft bearings 28 on both sides of the second eccentric shaft portion 26 from the left,
In the second embodiment shown in FIG. 8B, the bearing D3 is a large clearance bearing and the bearing D4 is a small clearance bearing. In the third embodiment shown in FIG. 8C, the bearing D3 is a large clearance bearing. The bearing D4 is a small clearance bearing. In the fourth embodiment shown in FIG. 9, the bearing D3 is a small clearance bearing and the bearing D4 is a large clearance bearing. In the example shown in FIG. 10, the bearing D3 is a small clearance bearing and the bearing. D4 is a large clearance bearing.

  On the other hand, paying attention to the drive shaft bearings 28 on both sides of the third eccentric shaft portion 26 from the left, in the second embodiment shown in FIG. 8B, the bearing D5 is a small clearance bearing and the bearing D6 is a large clearance bearing. In the third embodiment shown in FIG. 8C, the bearing D5 is a large clearance bearing and the bearing D6 is a small clearance bearing. In the fourth embodiment shown in FIG. 9, the bearing D5 is a small clearance bearing and the bearing D6 is a large clearance bearing. In the example shown in FIG. 10, the bearing D5 is a large clearance bearing and the bearing. D6 consists of a small clearance bearing.

  8B to 10 show all the small clearances that can be taken for the drive shaft bearings 28 on both sides of the second eccentric shaft portion 26 from the left and the drive shaft bearings 28 on both sides of the third eccentric shaft portion 26 from the left. All possible arrangements of combinations of bearings and large clearance bearings, ie small clearance bearings and large clearance bearings, are shown. Incidentally, as described above, with respect to the drive shaft bearing 28, the vibration of the drive shafts 24 and 25 can be reduced by reducing the distance S between the fulcrums 41, that is, the distance between the small clearance bearings. In this case, the magnitude of the vibration of the drive shafts 24 and 25 is determined by the largest interval between the small clearance bearings among the small clearance bearings, and between the largest small clearance bearings among the small clearance bearings. As the distance increases, the vibration of the drive shafts 24 and 25 increases. Therefore, in order to reduce the vibration of the drive shafts 24 and 25, it is necessary to reduce the largest interval between the small clearance bearings among the intervals between the small clearance bearings.

  When all possible combinations of the small clearance bearing and the large clearance bearing are performed, the distance between adjacent small clearance bearings is S1, S2, S3 (S1 <S2 <S3) as shown in FIGS. ). In this case, in the example shown in FIGS. 8B, 8C, and 9, the largest interval between the small clearance bearings among the intervals between the small clearance bearings is S2, and in the example shown in FIG. The largest clearance between the small clearance bearings is S3. Accordingly, in the example shown in FIG. 10, the vibrations of the drive shafts 24 and 25 are larger than those in the examples shown in FIGS. 8B, 8C, and 9. Therefore, the arrangement of the small clearance bearing and the large clearance bearing shown in FIGS. 8B, 8C, and 9 is preferable, but the arrangement of the small clearance bearing and the large clearance bearing shown in FIG. 10 is not preferable. Therefore, the small clearance bearing and the large clearance bearing need to be arranged as shown in FIGS. 8B, 8C, and 9.

  FIG. 11 shows a fifth embodiment of the drive shaft bearing 28. In the fifth embodiment, a third eccentric shaft portion 26 is formed at the center of the drive shafts 24 and 25, and drive shaft bearings 28 are provided on both sides of the eccentric shaft portion 26, respectively. . Also in the fifth embodiment, the outermost bearing D1 and the bearing D6 are made of large clearance bearings, and the bearing D2 and the bearing D5 located just inside the large clearance bearing are made of small clearance bearings. On the other hand, if one of the drive shaft bearings 28 disposed on both sides of the eccentric shaft portion 26 formed at the center of the drive shafts 24 and 25 is a small clearance bearing, the other is a large clearance bearing. In the fifth embodiment shown in FIG. 11, the bearing D3 is a large clearance bearing and the bearing D4 is a small clearance bearing. In the example shown in FIG. 12, the bearing D3 is a small clearance bearing and the bearing D4 is a bearing. It consists of a large clearance bearing.

  In the example shown in FIGS. 11 and 12, there are four types of intervals between adjacent small clearance bearings: S1, S2, S3, and S4 (S1 <S2 <S3 <S4). In this case, the interval S4 between the small clearance bearings is the largest interval S4 between the small clearance bearings in the arrangement shown in FIG. In this example, the vibrations of the drive shafts 24 and 25 are larger than in the example shown in FIG. Therefore, the arrangement of the small clearance bearing and the large clearance bearing shown in FIG. 11 is preferable, but the arrangement of the small clearance bearing and the large clearance bearing shown in FIG. 12 is not preferable. Therefore, it is necessary to arrange the small clearance bearing and the large clearance bearing as shown in FIG.

  As can be seen from the embodiments shown in FIGS. 8A to 9 and 11, in the present invention, the drive shaft bearings 28 are disposed on both sides of the eccentric shaft portion 26 with respect to each eccentric shaft portion 26. The drive shaft bearing 28 is composed of a small clearance bearing having the smallest bearing clearance among all the drive shaft bearings 28 and a large clearance bearing having a larger clearance than the small clearance bearing, and both end portions of the drive shafts 24 and 25. Among the drive shaft bearings 28 arranged on both sides of the eccentric shaft portion 26, the outer bearing is composed of a large clearance bearing and the inner bearing is composed of a small clearance bearing.

  In this case, as shown in FIGS. 8B to 9 and 11, the drive shafts 24, 25 are further provided with one or more separate shafts between the eccentric shaft portions 26 provided at both ends of the drive shafts 24, 25. One of the drive shaft bearings 28 disposed on both sides of the eccentric shaft portion 26 is a small clearance bearing and the other eccentric shaft portion 26 is also formed of a small clearance bearing. When the bearing is composed of a large clearance bearing and the arrangement of the small clearance bearing and the large clearance bearing for the different eccentric shaft portion 26 is replaced with all possible arrangements, the interval between the adjacent small clearance bearings is changed each time the arrangement is replaced. Among the arrangements, the arrangement in which the interval between the adjacent small clearance bearings, which is the largest at this time, becomes the smallest is the small clearance bearing and the large clearance for another eccentric shaft portion 26. It is arranged with receiving.

  Thus, by arranging the small clearance bearing and the large clearance bearing, it is possible to reduce the vibration of the drive shafts 24 and 25 while reducing the friction loss of the entire bearing.

DESCRIPTION OF SYMBOLS 1 Crankcase 2 Cylinder block 24,25 Drive shaft 26 Eccentric shaft part 27 Free-rotation shaft 28 Drive shaft support bearing 30 Cylinder block support bearing A Variable compression ratio mechanism

Claims (4)

  A variable compression ratio mechanism for changing the relative position of the crankcase and the cylinder block in the cylinder axis direction is disposed at the connecting portion between the crankcase and the cylinder block. The variable compression ratio mechanism includes a drive shaft bearing. Via the crankcase and a drive shaft extending in the longitudinal direction of the engine body, the drive shaft being eccentric with respect to the axis of the drive shaft at at least both ends of the drive shaft In each variable-compression-ratio internal combustion engine, a free rotation shaft is rotatably attached to each eccentric shaft portion, and the cylinder block is supported by the free rotation shaft via a cylinder block bearing. The cylinder block bearings arranged on each free rotating shaft consist of a pair of bearings, and the cylinder block bearings are all It is composed of a small clearance bearing with the smallest bearing clearance and a large clearance bearing with a larger clearance than the small clearance bearing, and the drive shaft bearing is located on both sides of the eccentric shaft with respect to each eccentric shaft. Each of the drive shaft bearings is composed of a small clearance bearing having the smallest bearing clearance among all the bearings for driving shaft bearings and a large clearance bearing having a larger clearance than the small clearance bearings. In this example, at least the outermost cylinder block support bearing is a small clearance bearing, and the drive shaft support bearings arranged on both sides of the eccentric shaft at both ends of the drive shaft are the large clearance bearings. And variable compression with a small clearance bearing located inside Internal combustion engine.   The variable compression ratio internal combustion engine according to claim 1, wherein the outermost cylinder block bearings at both ends of the drive shaft are small clearance bearings, and all the remaining cylinder block bearings are large clearance bearings. . The variable compression ratio internal combustion engine according to claim 1, wherein the pair of cylinder block bearings disposed at both ends of the drive shaft are small clearance bearings, and all the remaining cylinder block bearing bearings are large clearance bearings. .   The drive shaft further includes one or a plurality of other eccentric shaft portions between the eccentric shaft portions provided at both ends of the drive shaft, and the other eccentric shaft portions are also arranged on both sides of the eccentric shaft portion. One of the drive shaft bearings is composed of a small clearance bearing and the other bearing is composed of a large clearance bearing, and it is possible to arrange the small clearance bearing and the large clearance bearing on the other eccentric shaft portion. When all of the arrangements are replaced, the interval between the adjacent small clearance bearings changes each time the arrangement is replaced. Among the arrangements, the arrangement in which the interval between the adjacent adjacent small clearance bearings is the smallest is the The variable compression ratio internal combustion engine according to claim 1, wherein the eccentric shaft portion is an array of a small clearance bearing and a large clearance bearing.

Images