JP7787210B2 - Variable compression ratio device - Google Patents

Description

The present invention relates to a variable compression ratio device.

A shaft equipped with gears (hereafter referred to as a gear shaft) is known as a power transmission member used to transmit rotational force. For example, a gear shaft is used when the input power source and the output power transmission element are rotating bodies and are separated from each other. Patent Document 1 discloses a compression ratio variable device that varies the compression ratio of an internal combustion engine, which includes an eccentric cam that can support the central axis of the big end of the connecting rod in an eccentric position relative to the central axis of the crankpin of the internal combustion engine, and which rotates this eccentric cam with a gear shaft via an intermediate gear.

Special table 2017-503971 publication

However, in the case of a variable compression ratio device such as that described in Patent Document 1, it is desirable to make the assembly process easier. Furthermore, in the case of a variable compression ratio device such as that described in Patent Document 1, if the crank portion of the internal combustion engine is elastically deformed due to forces generated during the combustion stroke of the internal combustion engine, the intermediate gear may tilt relative to the gear shaft, resulting in uneven contact between the gear shaft and the intermediate gear. This uneven contact not only reduces load transmission efficiency but also has disadvantages such as reduced lifespan, abnormal noise, and vibration. Meanwhile, increasing the strength of the crank portion to prevent deformation requires changing its shape, such as by thickening the crank portion, or changing to a stronger material, which is not easy.
It is also desirable to increase the rigidity of the gear shaft so that it does not lack rigidity when the internal combustion engine rotates at high speeds.

The present invention was made in consideration of the above-mentioned circumstances, and aims to facilitate assembly work. Furthermore, although not an essential objective, the present invention aims to prevent uneven contact between the gears even when tilt occurs between the gear shaft and the gear meshing with the gear shaft, thereby increasing the rigidity of the shaft.

a variable compression ratio device including: an eccentric cam that is disposed between a crankpin and a big end of a connecting rod of an internal combustion engine and that gradually changes a cam thickness in a circumferential direction; a power source that rotates the eccentric cam; and a power transmission member between the power source and the eccentric cam, wherein the power transmission member has a shaft equipped with a gear that rotates the eccentric cam, the shaft and the gear being separate bodies, the shaft having at one end a splined shaft that fits into a splined hole formed in the gear, and the shaft having at the other end a connection portion with the power source, the diameter of the connection portion being equal to or greater than the diameter of the splined shaft, an oil supply passage formed in a space between the shaft and a crankshaft of the internal combustion engine, and oil being supplied to the oil supply passage via a plurality of oil delivery holes and an oil supply groove that are formed on the outer periphery of a positioning member that is provided at the end of the crankshaft .

By making the shaft and gear separate, it becomes easier to insert the shaft from the opposite side of the gear that meshes with the shaft, making assembly easier.

1 is a diagram showing the internal structure of a power unit equipped with a compression ratio variable device according to a first embodiment; FIG. 2 is a diagram showing a crank pin and an eccentric cam together with the surrounding configuration. FIG. 3 is an enlarged view of a part of FIG. 2. FIG. 2 is a diagram showing the configuration of a gear shaft. FIG. 2 is an enlarged view of a spline tooth. FIG. 10 is a diagram showing a state in which pressure generated in a combustion chamber acts on a crank pin. FIG. 7 is a diagram showing a cross-sectional structure in the state shown in FIG. 6. FIG. 10 is a diagram illustrating a comparative example. FIG. 10 is a diagram illustrating a modified example. 10 is a diagram showing the internal structure of a power unit equipped with a compression ratio variable device according to a second embodiment. FIG. FIG. 12 is a view taken along the line XII-XII in FIG. 11. FIG. 10 is an enlarged view of the vicinity of the bearing holder. FIG. FIG.

Embodiments of the present invention will now be described with reference to the drawings. Note that throughout the description, directions such as front, back, left, right, and up and down are the same as directions relative to the vehicle body unless otherwise specified. Also, the symbol FR in each drawing indicates the front of the vehicle body, and the symbol LH indicates the left side of the vehicle body.

[First Embodiment]
1 is a diagram showing the internal structure of a power unit 10 equipped with a compression ratio variable device 10a according to a first embodiment of the present invention. This power unit 10 is a power unit that is mounted on a motorcycle, and includes an internal combustion engine 11. This power unit is not limited to motorcycles, and may be a power unit that is mounted on various saddle-ride type vehicles, including three-wheeled and four-wheeled types.

The engine 11 includes a crankcase 15 that rotatably supports a crankshaft 12 via a plurality of bearings 13 and 14, and a cylinder section 20 that slidably houses a piston (not shown) that is connected to the crankshaft 12 via a crank web 16, a crank pin 17, and a connecting rod (hereinafter referred to as a connecting rod) 18. A primary gear 21 is supported on the crankshaft 12. The primary gear 21 meshes with a driven gear (not shown).
1 shows a horizontal engine 11 in which a cylinder section 20 protrudes horizontally forward from a crankcase 15. In FIG. 1, reference character C1 indicates a crank axis passing through the axis of a crankshaft 12 supported by the crankcase 15. Reference character C2 indicates a crankpin axis passing through the axis of a crankpin 17. The crank axis C1 and the crankpin axis C2 are parallel to each other.

The compression ratio varying device 10a varies the compression ratio by eccentrically positioning the central axis of the big end 18a of the connecting rod 18 relative to the crank pin axis C2 so as to change the position of the piston's top dead center. The compression ratio varying device 10a includes an eccentric cam 31 that rotates to change the position of the central axis of the big end 18a of the connecting rod 18, a motor 32 that serves as a power source, and a power transmission mechanism 33 between the motor 32 and the eccentric cam 31. The rotation angle of the motor 32 is controlled by a control unit 41 installed on the motorcycle. The control unit 41 acquires the rotational position of a portion of the power transmission mechanism 33 (in this configuration, the rotational position of the gear shaft 52) via a potentiometer 42 and controls the rotation of the motor 32 to a target position based on the acquired rotational position. The control unit 41 is, for example, an ECU (Electronic Control Unit) installed on the motorcycle.

Next, the eccentric cam 31, the power transmission mechanism 33, and the surrounding structure will be described.
FIG. 2 is a view taken along the line II-II in FIG. 1 , showing the crank pin 17 and the eccentric cam 31 together with the surrounding configuration. The eccentric cam 31 is a component disposed between the big end 18a of the connecting rod 18 and the crank pin 17, and its cam thickness gradually changes along the circumferential direction. When the eccentric cam 31 is in its reference position (top dead center), the central axis of the big end 18a of the connecting rod 18 coincides with the crank pin axis C2. When power from the motor 32 is transmitted to the power transmission mechanism 33 and the eccentric cam 31 rotates in the circumferential direction, the cam thickness of the eccentric cam 31 gradually changes along the circumferential direction, and the central axis of the big end 18a of the connecting rod 18 gradually shifts (for example, to an eccentric position C3) and no longer coincides with the crank pin axis C2. Therefore, when the eccentric cam 31 is rotated to the eccentric position C3, the distance between the center axis of the big end 18a of the connecting rod 18 and the crank axis C1 changes, the piston stroke amount changes, and the compression ratio changes.

A gear portion 31 a is integrally provided on the outer periphery of the eccentric cam 31 .
The power transmission mechanism 33 includes an intermediate gear 50 that meshes with the gear portion 31a of the eccentric cam 31, a shaft 52 (hereinafter referred to as the gear shaft 52) having a gear 51 at its tip that meshes with the intermediate gear 50, and a drive side gear portion 53 provided at the base end of the gear shaft 52.

FIG. 3 is an enlarged view of a part of FIG.
2 and 3, the intermediate gear 50 is rotatably supported by the crank web 16. This intermediate gear 50 is configured as a two-stage gear including a large-diameter gear 50a that meshes with the gear portion 31a of the eccentric cam 31 and a small-diameter gear 50b that meshes with the gear 51 of the gear shaft 52. In the figures, reference numeral 54 denotes a component that is fastened to the crank web 16 by a fastening member 54t, with the intermediate gear 50 sandwiched between the crank web 16 and the large-diameter gear 50a. This component 54 functions as a detachment prevention component that prevents the intermediate gear 50 from falling off.

The gear shaft 52 passes through the crankshaft 12 and is arranged coaxially with the crankshaft 12, and is rotatably supported via a pair of bearings 56, 57. The gear shaft 52 passes through a cover 58 arranged on the right side of the crankshaft 12 and extends to the vicinity of the motor 32.
Oil (indicated by the symbol J in FIG. 2) from an oil pump (not shown) provided in the power unit 10 is supplied into the cover 58, and this oil lubricates the bearings 56, 57. The gear shaft 52 will be described in detail later.

The drive-side gear section 53 has a worm gear 53a that is keyed to the base end of the gear shaft 52, and this worm gear 53a reduces the rotation of the worm wheel provided on the motor 32 and transmits it to the gear shaft 52. Note that the configuration of the drive-side gear section 53 is not limited to a configuration that uses a worm gear 53a, and any known reduction mechanism can be used as appropriate. Also, while the example shows a case where the motor 32 is the power source, the power source may be something other than the motor 32.

FIG. 4 is a diagram showing the configuration of the gear shaft 52.
The gear shaft 52 is formed by a gear 51 and a shaft 55, which are separate bodies, and the gear 51 is attached to the tip of the shaft 55 so that it can swing freely. For ease of explanation, the axial direction of the gear shaft 52 is indicated by the symbol X. This axial direction X coincides with the axial directions of the shaft 55, the gear 51, and the crankshaft 12. The gear 51 swings in directions that include a direction tilting toward the tip end of the shaft 55 and a direction tilting toward the rear end of the shaft 55, and includes the direction indicated by the symbol R in FIG. 4 .

The shaft 55 has a splined shaft 55a that fits into a splined hole 51a provided in the gear 51. The splined hole 51a is a hole with grooves 51b (hereinafter referred to as spline grooves 51b) that are continuous in the axial direction X on the inner periphery of the hole 51a and spaced apart circumferentially. The splined shaft 55a also has teeth 55b (hereinafter referred to as spline teeth 55b) that are continuous in the axial direction X and spaced apart circumferentially on the outer periphery of the shaft 55a. The splined grooves 51b and spline teeth 55b engage with each other to allow the shaft 55 and gear 51 to rotate together.

The spline hole 51a and the spline teeth 55b are provided with locking grooves 51c, 55c at positions corresponding to the centers of the spline hole 51a and the spline teeth 55b in the axial direction X, respectively, that can lock a common clip 60. A C-shaped ring is used for the clip 60, allowing for easy attachment. This clip 60 functions as a fall-prevention member that prevents the gear 51 from falling off the shaft 55. Furthermore, because the position of the clip 60 restricts movement of the gear 51 relative to the shaft 55, the gear 51 can easily swing relative to the shaft 55 using the position of the clip 60 as a reference. In other words, the clip 60 also functions as a swing-assisting member that sets a reference position for swing. The clip 60 is not limited to a C-shaped ring, and a wide range of fall-prevention members can be used.

As shown in Figure 4, each spline tooth 55b is shaped in the axial direction X so that the central portion of each spline tooth 55b is higher than both ends. This allows the gap between the spline tooth 55b and the spline groove 51b to widen the further away from the central portion of the spline tooth 55b. This makes it easier to oscillate the gear 51 based on the central portion of the spline tooth 55b, and also makes it easier to widen the oscillating angle of the gear 51.

In addition, in this configuration, each spline tooth 55b is formed in a mountain shape in the axial direction X, becoming higher from both ends of each spline tooth 55b toward the center. As a result, the spline shaft 55a is formed into a barrel shape that protrudes radially outward as it approaches the center in the axial direction X. This configuration makes it easier to smoothly oscillate the gear 51 based on a point near the center, and also makes it easier to widen the oscillating angle of the gear 51.

FIG. 5 shows an enlarged view of the spline teeth 55b.
As shown in FIG. 5, the width of each spline tooth 55b narrows in the axial direction X from the center of each spline tooth 55b toward both ends (width Wa > Wb, Wc in FIG. 5). This shape is formed by crowning, which adds a rounded (bulging) shape to the spline teeth 55b in the tooth width direction. This also makes it possible to increase the gap between the spline tooth 55b and the spline groove 51b as the distance from the center of the spline tooth 55b increases. This makes it easier to oscillate the gear 51 based on the center of the spline tooth 55b, and also makes it easier to increase the oscillating angle of the gear 51.

The width of each spline groove 51b may be constant in the axial direction X. In other words, the width of the portion between the spline grooves 51b (which may also be referred to as the spline teeth 55b on the spline hole 51a side) may be constant in the axial direction X.
Furthermore, the width of the spline teeth 55b on the spline hole 51a side may be narrowed from the center to both ends in the axial direction X, similar to the spline teeth 55b on the spline shaft 55a side. Alternatively, the width of the spline teeth 55b on the spline shaft 55a side may be constant in the axial direction X, and the spline teeth 55b on the spline hole 51a side may be narrowed from the center in the axial direction X toward the distance in the axial direction X. In this case as well, it becomes easier to oscillate the gear 51 based on the central point of the spline teeth 55b, and it also becomes easier to widen the oscillating angle of the gear 51.

As shown in FIG. 6, if a relatively strong force F1 acts on the crank pin 17 due to pressure (finger pressure) generated in the combustion chamber during the combustion stroke, the crank webs 16 on the left and right sides of the crank pin 17 may elastically deform and spread out to the left and right at points away from the crank pin 17.
The cross-sectional structure in this case is shown in Fig. 7. As shown in Figs. 6 and 7, the crank web 16 is inclined relative to the crankshaft 12, so the intermediate gear 50 is inclined relative to the gear shaft 52. In Fig. 7, reference symbol C4 indicates the axis of the intermediate gear 50.

In this configuration, the gear 51 of the gear shaft 52 is configured to be able to swing freely relative to the shaft 55, so when the intermediate gear 50 tilts relative to the gear shaft 52, the gear 51 can tilt in accordance with the tilt of the intermediate gear 50 (see the area indicated by the symbol AR in FIG. 7 ). Therefore, it is possible to prevent the gear 51 and the intermediate gear 50 from engaging with each other in a one-sided manner.
In particular, in this configuration, the spline teeth 55b provided on the spline shaft 55a are shaped so that the central part of the spline teeth 55b is higher in the axial direction X than both ends of the spline teeth 55b, which makes it easier for the gear 51 to oscillate so as to prevent one-sided contact between the gear 51 and the intermediate gear 50, thereby effectively preventing one-sided contact.

Figure 8 shows a comparative example in which the gear 51 and shaft 55 of the gear shaft 52 are integrally configured. In this comparative example, if the intermediate gear 50 is tilted relative to the gear shaft 52, the gear 51 and intermediate gear 50 are likely to mesh unevenly (see the area indicated by the symbol AR in Figure 8). This uneven contact not only reduces load transmission efficiency, but is also detrimental to the lifespan, abnormal noise, vibration, and high-precision control of the compression ratio.

As described above, this configuration has a shaft 55 equipped with a gear 51 that rotates the eccentric cam 31, the shaft 55 and the gear 51 being separate bodies, and the shaft 55 has at one end a splined shaft 55a that fits into a splined hole 51a provided in the gear 51. This makes it easier to insert the shaft 55 from the opposite side to the gear 51 (corresponding to the outside of the crankcase 15), which has the effect of facilitating the assembly work and improving the degree of freedom in assembly.
Furthermore, by configuring the spline teeth 55b on the spline shaft 55a of the gear shaft 52 constituting the power transmission mechanism so that the central portion of the spline teeth 55b is higher than both ends in the axial direction X of the spline shaft 55a, it is possible to prevent the gears 51, 50 from coming into contact with each other on one side, even if the intermediate gear 50 is tilted with respect to the gear shaft 52. This prevents a decrease in load transmission efficiency and is advantageous for highly accurate control of lifespan, abnormal noise, vibration, and compression ratio. The intermediate gear 50 is an example of the "predetermined object with which the gear 51 of the gear shaft 52 meshes" in the present invention.

The width of the spline teeth 55b narrows in the axial direction X from the center to both ends. This configuration further reduces the risk of one-sided contact when the intermediate gear 50 is tilted relative to the gear shaft 52. The spline teeth 55b also have a mountain-like shape that becomes taller from both ends to the center in the axial direction. This makes it easier to smoothly oscillate the gear 51 based on the central point, and also makes it easier to widen the oscillating angle of the gear 51.

The spline teeth 55b do not have to be configured to have a mountain-like shape that becomes higher from both ends toward the center. Even if the intermediate gear 50 is tilted relative to the gear shaft 52, the shape of the spline teeth 55b may be changed as appropriate, as long as the gear 51 can be tilted to match the tilt of the intermediate gear 50.

Furthermore, as is clear from Figures 1 and 2, in this configuration, the shaft 55 and gear 51 only rotate on their axes and do not revolve. Meanwhile, the intermediate gear 50 and eccentric cam 31 revolve around the gear 51 as the piston slides. Because the gear 51 does not revolve relative to the shaft 55, the load on the mating portion between the shaft 55 and gear 51 can be reduced compared to when the gear 51 revolves relative to the shaft 55. In addition, the shaft 55 is less susceptible to outward distortion caused by the centrifugal force of the revolving counterparts (intermediate gear 50, eccentric cam 31). These factors make it easier to ensure the durability of the gear shaft 52.

Furthermore, spline teeth 55b and spline holes 51a are provided with locking grooves 51c, 55c (Figure 4) at positions corresponding to the centers of the spline teeth 55b and spline holes 51a in the axial direction X, respectively, that can lock a common clip 60, and the gear 51 swings relative to the shaft 55 based on the position of the clip 60. With this configuration, the clip 60 can prevent the gear 51 from coming loose. Also, because the gear 51 swings based on the position of the clip 60, the gear 51 tends to tilt in accordance with the inclination of the intermediate gear 50. Note that the position of the clip 60 may be adjusted so that the gear 51 tends to tilt in accordance with the inclination of the intermediate gear 50; in other words, the position of the swing reference may be adjusted as appropriate.

Furthermore, by using the above-mentioned gear shaft 52 in the compression ratio variable device 10a, even if the intermediate gear 50 tilts due to strong pressure F1 generated in the combustion chamber during the combustion stroke, a decrease in the load transmission efficiency between the gear shaft 52 and the intermediate gear 50 can be suppressed. This makes it easier to provide a compression ratio variable device 10a that is highly durable and capable of highly accurate control of the compression ratio.

Furthermore, the gear shaft 52 is rotatably disposed within the crankshaft 12, and the intermediate gear 50 is supported by the crank web 16 of the engine 11. This configuration ensures that space for the gear shaft 52 is secured within the crankshaft 12, which is also advantageous for reducing the weight of the crankshaft 12. This is therefore advantageous for reducing the size and weight of the variable compression ratio device 10a.

In the above embodiment, the spline teeth 55b are configured in a shape such that the central portion of the spline teeth 55b is higher than both ends in the axial direction X of the spline shaft 55a, thereby preventing one-sided contact between the gears 51 and 50 even if the intermediate gear 50 is tilted with respect to the gear shaft 52. However, the above configuration is not necessarily provided.
The gear 51 and shaft 55 of the gear shaft 52 may be separate bodies, and the shaft 55 may have a splined shaft 55a that fits into a splined hole 51a provided in the gear 51. The splined teeth 55b provided on the splined shaft 55a and the splined hole 51a may have locking grooves at their axial centers that can lock a common clip 60. The gear 51 may be configured to have a predetermined amount of play relative to the shaft 55 based on the position of the clip 60. This configuration also provides a power transmission member that can prevent one-sided contact between the gears 51 and 50 even if the intermediate gear 50 is tilted relative to the gear shaft 52. This configuration prevents a decrease in load transmission efficiency and is advantageous for lifespan, noise, vibration, and highly accurate control of the compression ratio.

[Embodiment 2]
10 is a diagram showing the internal structure of a power unit 10 equipped with a compression ratio variable device 10a according to Embodiment 2. The compression ratio variable device 10a according to Embodiment 2 is a compression ratio variable device that includes an eccentric cam 31 that is disposed between the crank pin 17 of the internal combustion engine 11 and the big end 18a of the connecting rod 18 and that gradually changes the cam thickness in the circumferential direction, a motor 32 that rotates the eccentric cam 31, and a gear shaft 52 between the motor (power source) 32 and the eccentric cam 31, the gear shaft 52 having a shaft 55 with a gear 51 that rotates the eccentric cam 31, the shaft 55 and the gear 51 being separate bodies, and the shaft 55 having at one end a splined shaft 55a that fits into a splined hole 51a formed in the gear 51 (see FIG. 4).

The shaft 55 has a connecting portion 70 at the other end for connecting with the motor 32, and the diameter L2 of the connecting portion 70 is equal to or greater than the diameter L1 of the spline shaft 55a.
In addition, an oil supply passage 94 is formed in the space between the shaft 55 and the crankshaft 12, and oil is supplied to the oil supply passage 94 via a positioning member 72 provided at the end of the crankshaft 12 (see Figure 13 described later).
The rest of the configuration of the variable compression ratio device 10a is the same as that of the variable compression ratio device according to the previously described embodiment (referred to as embodiment 1), and therefore description thereof will be omitted.

Figure 11 is an enlarged view of the vicinity of the positioning member 72. The shaft 55 has a flange 73, which is a radial bulge. The shaft 55 passes through the crankshaft 12 and is arranged coaxially with the crankshaft 12. A positioning member 72 is provided at the end of the crankshaft 12. The positioning member 72 includes a control shaft bearing 77, a crankshaft bearing 79, a spacer 81, shims 83 and 85, and a bearing holder 87 that holds these. The crankshaft bearing 79 includes a sealing portion on the spacer 81 side. The shims 83 and 85 can also be considered spacers that adjust the position of the control shaft bearing 77 in the axial direction of the shaft 55. The crankshaft bearing 79 is a bearing for the crankshaft 12, and the control shaft bearing 77 is a bearing for the shaft 55. The control shaft bearing 77 and the crankshaft bearing 79 are held in a bearing holder 87, which is supported by a support portion 93. The shaft 55 is also positioned axially between the flange 73 of the shaft 55 and the lock nut 84 via a control shaft bearing 77.

Figure 12 is a view taken along the arrows XII-XII in Figure 11. Oil is supplied through the oil supply passage 96. Oil from the oil supply passage 96 is supplied to the shaft 55 via the oil transfer hole 90 (Figure 14) provided in the bearing holder 87 and the oil transfer hole 95 (Figure 15) provided in the spacer 81. Oil is also supplied to the crankshaft bearing 79 and the control shaft bearing 77.

13 is an enlarged view of the vicinity of the bearing holder 87. The bearing holder 87 has the control shaft bearing 77, the spacer 81, and the crankshaft bearing 79 provided on the inner periphery thereof.
As shown in FIG. 11, shims 83 and 85 are provided at both ends of the control shaft bearing 77 to adjust the position of the control shaft bearing 77 in the axial direction of the shaft 55 .
The shim 83 is disposed on the crankshaft bearing 79 side of the control shaft bearing 77, and a spacer 81 is disposed between the shim 83 and the crankshaft bearing 79. The shim 85 is disposed on the opposite side of the control shaft bearing 77 from the crankshaft bearing 79. The control shaft bearing 77 abuts against the crankshaft bearing 79 via the spacer 81 and shim 83, and therefore does not move toward the crankshaft bearing 79. The thickness of the shim 83 is adjusted so as to fill the space between the spacer 81 and the control shaft bearing 77 abutting against the flange portion 73.

14 is a perspective view of the bearing holder 87. The bearing holder 87 is provided with oil transfer holes 90 spaced apart in the circumferential direction. The bearing holder 87 also has a shim thickness adjustment window 92 that opens into part of the circumferential surface.
The shim thickness adjustment window 92 is provided in a position where at least the arrangement area of the shims 83, 85 can be viewed from the outside. For example, an assembler can use the shim thickness adjustment window 92 to easily measure the size of the gap at both ends of the control shaft bearing 77 and select and arrange shims 83, 85 with a thickness that will fill that gap. This makes it possible to suppress rattling of the control shaft bearing 77 in the thrust direction and to appropriately adjust the clearance of the control gear 51 in the thrust direction.

The oil transfer holes 90 are provided at intervals in the circumferential direction of the bearing holder 87 , so that oil from the oil supply passage 96 easily flows into one of the oil transfer holes 90 .
FIG. 15 is a perspective view of the spacer 81. As shown in FIG.
The spacer 81 is provided with oil transfer holes 95 spaced apart in the circumferential direction, so that oil that flows into the oil transfer hole 90 flows into one of the oil transfer holes 95 and is supplied to the shaft 55 side. In this way, oil is guided from the outside of the bearing holder 87 to the inside of the spacer 81.
The oil is then sent toward one end of the shaft 55 through the space between the shaft 55 and the crankshaft 12 as an oil supply passage 94 (FIG. 10).
One end of the bearing holder 87 is provided with an oil supply groove 97 to facilitate oil dripping into the crankshaft bearing 79. Specifically, multiple oil supply grooves 97 are provided so that oil can drip no matter where the bearing holder 87 is assembled in the rotational direction. Alternatively, active oil supply may be achieved by positioning the seal portion of the crankshaft bearing 79 on the side opposite the spacer side. By providing multiple oil transfer holes 90 and oil supply grooves 97 at equal intervals around the outer periphery in this way, it is not necessary to determine the rotational phase of the bearing holder 87 and spacer 81, making assembly easier.

As explained above, this configuration also has a shaft 55 equipped with a gear 51 that rotates the eccentric cam 31, the shaft 55 and the gear 51 are separate bodies, and the shaft 55 has a splined shaft 55a at one end that fits into a splined hole 51a provided in the gear 51, similar to the configuration in embodiment 1, and therefore provides various effects similar to those in embodiment 1.

Furthermore, the shaft 55 constituting the compression ratio variable device 10a has a connection portion 70 at the other end for connecting to the power source 32, and the diameter L2 of the connection portion 70 is configured to be equal to or greater than the diameter L1 of the spline shaft, thereby increasing the strength of the shaft 55 and the joint. The diameter of the connection portion 70 can be made thicker by separating the shaft 55 and the gear 51, thereby enabling the shaft 55 to be inserted from the opposite side of the gear.

The positioning member 72 constituting the compression ratio variable device 10 a positions the shaft 55 in the axial direction of the crankshaft 12 , and is supported in the radial direction by a support portion 93 of the power source 32 .
This configuration improves the coaxiality of the crankshaft 12 and the shaft 55, thereby increasing reliability.

The above-described embodiment shows one aspect of the present invention, and the present invention is not limited to the above-described embodiment.
For example, in the above embodiment, the clip 60 is used to prevent the gear 51 from falling off, but this configuration is not limiting. For example, as shown in Fig. 9, a retaining member 61 may be provided at the end of the gear shaft 52, which abuts against at least a portion of the gear 51 to prevent the gear 51 from falling off toward the end. This retaining member 61 is formed of a plate member whose diameter is larger in the radial direction than the shaft 55, and is attached to the end of the shaft 55 using a fastening member 62. This simple configuration can prevent the gear 51 from falling off.

In addition, in the above embodiment, the present invention is described as being applied to a compression ratio variable device 10a employed in a saddle-ride vehicle such as a motorcycle, and to a gear shaft 52 used in this compression ratio variable device 10a, but this is not a limitation. The present invention is widely applicable to power transmission components that have a shaft 52 equipped with a gear 51 that meshes with a predetermined gear and are used to transmit rotational force.

[Configuration supported by the above embodiment]
The above embodiment supports the following configurations.

(Configuration 1) A power transmission component used to transmit rotational force, having a shaft equipped with a gear that meshes with a predetermined gear, characterized in that the shaft and the gear are separate bodies, the shaft has a spline shaft that fits into a spline hole provided in the gear, and the spline teeth provided on the spline shaft are shaped so that the central part of the spline teeth is higher in the axial direction of the spline shaft than both ends.
With this configuration, when a gear that meshes with a gear is tilted relative to a shaft equipped with the gear, the gear can be tilted to match the tilt of the gear, preventing the gears from contacting one side. Also, it becomes easier to insert the shaft from the opposite side of the gear, which has the effect of facilitating assembly work.

(Configuration 2) A power transmission member according to configuration 1, characterized in that the width of the spline teeth narrows from the center of the spline teeth to both ends in the axial direction of the spline shaft.
This configuration can further prevent a situation in which a predetermined gear meshing with the gear is inclined and makes one-sided contact.

(Configuration 3) A power transmission member according to configuration 1 or 2, characterized in that the spline teeth are formed in a mountain shape that becomes higher from both ends of the spline teeth toward the center in the axial direction of the spline shaft.
This configuration makes it easier to smoothly swing the gear around the central portion, and also makes it easier to widen the swing angle of the gear.

(Configuration 4) A power transmission member described in any one of configurations 1 to 3, characterized in that the shaft and the gear are configured to only rotate on their axes and not revolve, and the specified gear is configured to revolve around the gear.
With this configuration, the gear does not revolve around the shaft, so the load on the mating portion between the shaft and gear can be reduced compared to when the gear revolves around the shaft. Also, the gear is less susceptible to outward distortion caused by the centrifugal force of the revolving gear.

(Configuration 5) A power transmission member described in any one of configurations 1 to 4, characterized in that the spline teeth and the spline holes are provided with locking grooves at positions corresponding to the centers of their respective axial directions, capable of locking a common clip, and the gear oscillates relative to the shaft based on the position of the clip.
According to this configuration, the clip can prevent the gear from coming off, and the gear can be easily tilted in accordance with the predetermined gear tilt.

(Configuration 6) A power transmission member described in any one of configurations 1 to 5, characterized in that a retaining member is provided at the end of the shaft, which abuts against at least a portion of the gear to prevent the gear from coming off toward the end.
This configuration makes it possible to prevent the gear from coming off with a simple configuration.

(Configuration 7) A power transmission member used to transmit rotational force, having a shaft equipped with a gear that meshes with a predetermined gear, wherein the shaft and the gear are separate bodies, the shaft has a splined shaft that fits into a splined hole provided in the gear, the spline teeth provided on the splined shaft and the splined hole are provided with engagement grooves at positions corresponding to the centers of their respective axial directions, capable of engaging a common clip, and the gear oscillates relative to the shaft based on the position of the clip.
According to this configuration, by adopting this power transmission member, when a specific gear that meshes with the gear is tilted relative to a shaft equipped with the gear, the gear can tilt in accordance with the tilt of the specific gear, thereby preventing uneven contact between the gears.

(Configuration 8) A compression ratio variable device comprising: an eccentric cam that is arranged between a crank pin and a big end of a connecting rod of an internal combustion engine and that gradually changes the cam thickness along the circumferential direction; a power source that rotates the eccentric cam; and a power transmission member between the power source and the eccentric cam, wherein the power transmission member has a shaft equipped with a gear that rotates the eccentric cam, the shaft and the gear are separate bodies, and the shaft has at one end a splined shaft that fits into a splined hole provided in the gear.
This configuration allows the shaft to be inserted from the outside of the crankcase, which makes it possible to assemble the gear and shaft after insertion, which has the effect of facilitating assembly work.

(Configuration 9) The compression ratio variable device according to Configuration 8, wherein the spline teeth provided on the spline shaft are shaped such that a central portion of the spline teeth is higher than both ends in the axial direction of the spline shaft.
According to this configuration, by adopting this compression ratio variable device, when a specific gear that meshes with a gear is tilted relative to a shaft equipped with the gear, the gear can be tilted to match the tilt of the specific gear, thereby preventing uneven contact between the gears.

(Configuration 10) A compression ratio variable device according to Configuration 9, characterized in that an intermediate gear is disposed between the eccentric cam and the gear, a shaft provided with the gear is rotatably disposed within a crankshaft of the internal combustion engine, and the intermediate gear is supported by a crank web of the internal combustion engine.
This configuration makes it easier to ensure space within the crankshaft for arranging the shaft equipped with the gear, and is also advantageous in terms of reducing the weight of the crankshaft.

(Configuration 11) The compression ratio variable device according to Configuration 8, wherein the shaft has a connecting portion at the other end for connecting to a power source, and the diameter of the connecting portion is equal to or larger than the diameter of the spline shaft.
This configuration can increase the rigidity of the shaft.

(Configuration 12) A variable compression ratio device according to Configuration 11, characterized in that an oil supply passage is formed in the space between the shaft and the crankshaft, and oil is supplied to the oil supply passage through a plurality of oil supply holes and oil supply grooves provided on the outer periphery of a positioning member provided at the end of the crankshaft.
According to this configuration, it is not necessary to determine the phase of the positioning member in the rotational direction, and assembly is easy.

(Configuration 13) The compression ratio variable device according to configuration 12, wherein the positioning member positions the shaft in the axial direction of the crankshaft and is supported in the radial direction by a support portion of the power source.
This configuration improves the coaxiality of the crankshaft and the shaft, increasing reliability.

10 Power unit 10a Compression ratio variable device 11 Engine (internal combustion engine)
12 crankshaft 15 crankcase 16 crank web 17 crankpin 18 connecting rod
18a: Big end 20: Cylinder portion 31: Eccentric cam 32: Motor (power source)
50 Intermediate gear (specified gear)
51 Gear 51a Spline hole 51b Spline groove 52 Gear shaft (power transmission member)
55 Shaft 55a Spline shaft 55b Spline teeth 60 Clip (retaining member)
61, 62 Anti-slip member 70 Connection portion 72 Positioning member 90 Oil transfer hole 93 Support portion 94 Oil supply passage 97 Oil supply groove C1 Crank axis C2 Crank pin axis C3 Eccentric position C4 Axis of intermediate gear X Axial direction

Claims (4)

an eccentric cam (31) disposed between a crank pin (17) of an internal combustion engine (11) and a big end (18a) of a connecting rod (18), the eccentric cam (31) gradually changing a cam thickness along a circumferential direction;
a power source (32) for rotating the eccentric cam (31);
a power transmission member (52) between the power source (32) and the eccentric cam (31),
The power transmission member (52) has a shaft (55) equipped with a gear (51) that rotates the eccentric cam (31),
The shaft (55) and the gear (51) are separate bodies,
The shaft (55) has a splined shaft (55a) at one end that fits into a splined hole (51a) provided in the gear (51),
The shaft (55) has a connecting portion (70) at the other end for connecting with the power source (32), and the diameter (L2) of the connecting portion (70) is equal to or greater than the diameter (L1) of the spline shaft (55a);
an oil supply passage (94) is formed in a space between the shaft (55) and a crankshaft (12) of the internal combustion engine (11), and oil is supplied to the oil supply passage (94) through a plurality of oil transfer holes (90) and an oil supply groove (97) provided on the outer periphery of a positioning member (72) provided at the end of the crankshaft (12) . The variable compression ratio device described in claim 1, characterized in that the spline teeth (55b) provided on the spline shaft (55a) are shaped so that the central portion of the spline teeth (55b) is higher than both ends in the axial direction of the spline shaft (55a). An intermediate gear (50) is disposed between the eccentric cam (31) and the gear (51),
The shaft (55) having the gear (51) is rotatably disposed within the crankshaft (12) of the internal combustion engine (11);
3. The compression ratio variable device according to claim 2, wherein the intermediate gear (50) is supported on a crank web (16) of the internal combustion engine (11). 4. The compression ratio variable device according to claim 1, wherein the positioning member (72) positions the shaft (55) in the axial direction of the crankshaft ( 12) and is supported in the radial direction by a support portion (93) of the power source (32).