JP7414401B2 - Rotational force transmission mechanism - Google Patents

Description

The present invention relates to a rotational force transmission mechanism.

A rotational force transmission mechanism that transmits rotational force to an annular transmission member or to which rotational force is transmitted from an annular transmission member includes a shaft and a rotating body that rotates integrally with the shaft. An annular transmission member is wound around the rotating body. In the rotational force transmission mechanism, noise may be generated due to contact between the rotating body and the annular transmission member. The rotational force transmission mechanism of Patent Document 1 includes a sprocket as a rotating body. A chain serving as an annular transmission member is wound around the sprocket. In Patent Document 1, a rubber cushioning member is provided on the sprocket to reduce the meshing noise of the chain. The buffer member projects radially outward from the tooth bottom of the sprocket. Direct contact between the chain and the tooth bottoms is less likely, reducing meshing noise.

Japanese Patent Application Publication No. 2008-128316

Since the cushioning member is made of rubber, it has the property of hardening over time. Therefore, when reducing meshing noise by providing a buffer member, a problem arises in the durability of the rotational force transmission mechanism.
An object of the present invention is to provide a rotational force transmission mechanism that can reduce noise while suppressing deterioration in durability.

A rotational force transmission mechanism that solves the above problems is a rotational force transmission mechanism that includes a shaft and a rotating body around which an annular transmission member is wound and rotates together with the shaft, wherein the shaft has an axial portion and a rotating body that rotates together with the shaft. a protrusion projecting from an outer circumferential surface of the shaft in the radial direction of the shaft; the rotating body includes an insertion hole forming surface forming an insertion hole into which the shaft is inserted; The insertion hole forming surface has a first forming surface facing the outer circumferential surface of the shaft portion, and the insertion hole forming surface is located on the outer side in the radial direction of the rotary body than the first forming surface, and the insertion hole forming surface a second forming surface forming a recess into which the part is inserted, and a gap is provided between the insertion hole forming surface and the shaft to allow movement of the shaft in a radial direction of the shaft part. It is sectioned.

If axial runout occurs in the shaft during rotation, the shaft moves in the radial direction of the shaft. At this time, when a force is transmitted from the shaft to the rotating body in the radial direction of the shaft, the rotating body moves together with the shaft in the radial direction of the shaft, causing the annular transmission member to flap. By defining a gap between the insertion hole forming surface and the shaft to allow movement of the shaft in the radial direction of the shaft, when axial runout occurs in the shaft, the force in the radial direction of the shaft is prevented from rotating. Difficult to transmit to the body. Further, the rotating body is provided with a recess into which the protrusion of the shaft is inserted, and the rotational force of the shaft is transmitted from the protrusion to the second forming surface forming the recess. Therefore, in the rotational force transmission mechanism, while the force in the radial direction of the shaft portion is difficult to be transmitted to the rotating body, the rotational force from the shaft is transmitted to the rotating body. Noise is reduced because the annular transmission member is less likely to fluctuate when axial runout occurs in the shaft. Since the noise is reduced by the gap provided between the insertion hole forming surface and the shaft, there is no need to provide a member such as a buffer member that cushions the impact generated on the annular transmission member and the rotating body. Therefore, it is possible to suppress a decrease in durability of the rotational force transmission mechanism due to deterioration of the buffer member.

In the rotational force transmission mechanism, the gap includes a first gap that is a gap in the radial direction of the shaft portion, and a second gap that is a gap in the rotational direction of the shaft portion, A dimension of the shaft portion in the radial direction may be larger than a dimension of the second gap in the rotational direction.

The dimension of the first gap in the radial direction of the shaft portion determines the range in which the shaft can move in the radial direction of the shaft portion when axial runout occurs in the shaft. By making the dimension of the first gap in the radial direction of the shaft section larger than the dimension of the second gap in the rotational direction of the shaft section, when axial runout occurs in the shaft, the force in the radial direction of the shaft section is reduced. Transmission to the rotating body is further suppressed.

In the rotational force transmission mechanism, the rotating body may be a sprocket around which a chain is wound as the annular transmission member.
When a sprocket around which a chain is wound is used as a rotating body, noise is more likely to be generated than when a pulley around which a belt is wound is used. By configuring the rotational force transmission mechanism that tends to generate noise so that the noise is reduced, the noise can be appropriately reduced.

Regarding the rotational force transmission mechanism, the sprocket may be a sprocket around which a timing chain is wound as the chain.
A timing chain is a chain that rotates due to the rotation of a crankshaft. The crankshaft can rotate at high speed and has large torque fluctuations. For this reason, noise is likely to be generated when the timing chain and sprocket engage with each other. In this way, by configuring the rotational force transmission mechanism that tends to generate noise so that the noise is reduced, the noise can be appropriately reduced.

Regarding the rotational force transmission mechanism, the shaft may be a crankshaft.
The rotational force of the crankshaft is transmitted to the timing chain via the sprocket, and from the timing chain to other sprockets. By suppressing the transmission of the axial runout of the crankshaft to the sprocket, noise can be appropriately suppressed.

According to the present invention, noise can be reduced while suppressing a decrease in durability.

Schematic diagram of the engine. FIG. 3 is a cross-sectional view of the drive-side rotational force transmission mechanism. FIG. 3 is a cross-sectional view of the drive-side rotational force transmission mechanism. FIG. 3 is a cross-sectional view of the drive-side rotational force transmission mechanism showing an enlarged view of the gap between the crankshaft and the insertion hole forming surface.

An embodiment of the rotational force transmission mechanism will be described below.
As shown in FIG. 1, the engine 10 includes a cylinder block 11, a cylinder head 12, a crankcase 13, an oil pan 14, and a chain cover 80. A cylinder head 12 is fixed to the upper part of the cylinder block 11. A crankcase 13 is fixed to the lower part of the cylinder block 11. An oil pan 14 is fixed to the lower part of the crankcase 13. The chain cover 80 is provided on the outer surface of the cylinder block 11 on the one end surface 15 side. One end surface 15 is, for example, a surface facing forward of the vehicle when the engine 10 is mounted on the vehicle.

The engine 10 includes a metal timing chain 21, a drive-side rotational force transmission mechanism 30, two driven-side rotational force transmission mechanisms 60 and 70, a damper 22, a slipper 23, and a tensioner 24. The drive-side rotational force transmission mechanism 30 is a mechanism that transmits rotational force to the driven-side rotational force transmission mechanisms 60 and 70 via the timing chain 21. The driven-side rotational force transmission mechanisms 60 and 70 are mechanisms to which the rotational force of the drive-side rotational force transmission mechanism 30 is transmitted via the timing chain 21.

The drive-side rotational force transmission mechanism 30 includes a crankshaft 31 that is connected via a connecting rod to the lower part of a piston that moves up and down in the cylinder and converts the up and down movement of the piston into rotational movement, and a rotating body that rotates together with the crankshaft 31. A crank sprocket 41 is provided. The crankshaft 31 is housed in the cylinder block 11 and crankcase 13.

The driven side rotational force transmission mechanism 60 includes an intake camshaft 61 and an intake sprocket 62 that rotates integrally with the intake camshaft 61. The driven side rotational force transmission mechanism 70 includes an exhaust camshaft 71 and an exhaust sprocket 72 that rotates integrally with the exhaust camshaft 71. The intake camshaft 61 opens and closes the intake valves by rotating. The exhaust camshaft 71 opens and closes the exhaust valves by rotating. To explain in detail, the cylinder head 12 blocks the upper part of the cylinder in the cylinder block 11 to partition the combustion chamber, and the cylinder head 12 has an intake port that communicates the combustion chamber with the intake pipe, and a combustion chamber. An exhaust port communicating with the exhaust pipe. The intake port is provided with an intake valve, and the intake valve is opened and closed by rotation of the intake camshaft 61. The exhaust port is provided with an exhaust valve, and the exhaust valve is opened and closed by rotation of the exhaust camshaft 71.

The timing chain 21, crank sprocket 41, intake sprocket 62, exhaust sprocket 72, damper 22, slipper 23, and tensioner 24 are provided inside the chain cover 80. Furthermore, a portion of the crankshaft 31, a portion of the intake camshaft 61, and a portion of the exhaust camshaft 71 are also provided within the chain cover 80.

Timing chain 21 is annular. The timing chain 21 is wound around a crank sprocket 41, an intake sprocket 62, and an exhaust sprocket 72. As the crank sprocket 41 rotates, the intake sprocket 62 and the exhaust sprocket 72 are driven to rotate. The rotation of the intake sprocket 62 causes the intake camshaft 61 to rotate, and the rotation of the exhaust sprocket 72 causes the exhaust camshaft 71 to rotate. The timing chain 21 is an annular transmission member that transmits the rotational force of the crank sprocket 41 to the intake sprocket 62 and the exhaust sprocket 72.

The damper 22 is provided on the tight side of the timing chain 21, that is, between the exhaust sprocket 72 and the crank sprocket 41 in the rotational direction of the timing chain 21. The damper 22 is a member that guides the movement of the timing chain 21 from the outside.

The slipper 23 and the tensioner 24 are provided on the slack side of the timing chain 21, that is, between the intake sprocket 62 and the crank sprocket 41 in the rotational direction of the timing chain 21. The slipper 23 is a member that guides the movement of the timing chain 21 from the outside. Tensioner 24 presses slipper 23 toward timing chain 21. As the tensioner 24, for example, a hydraulic actuator can be used.

Next, the drive-side rotational force transmission mechanism 30 as a rotational force transmission mechanism will be explained in detail.
As shown in FIGS. 2 and 3, the crankshaft 31 as a shaft includes a shaft portion 32 and a protruding portion 34 that projects from an outer circumferential surface 33 of the shaft portion 32 in the radial direction of the shaft portion 32. Eight protrusions 34 are provided. The protruding parts 34 are arranged at regular intervals in the circumferential direction of the shaft part 32, that is, in the rotational direction of the shaft part 32. Each protrusion 34 has the same shape. Note that the same shape allows for some errors within the tolerance range.

The protruding portion 34 is a rectangular, plate-like member. The protruding portion 34 is provided at the end on the one end surface 15 side of both ends of the shaft portion 32 . This end portion is a portion to be inserted into the crank sprocket 41, and it can be said that the protrusion portion 34 is provided at a position on the shaft portion 32 to be inserted into the crank sprocket 41. The protruding portion 34 includes two transmission surfaces 35 that intersect with the outer circumferential surface 33 of the shaft portion 32, and a tip surface 36 that intersects with the two transmission surfaces 35. The transmission surfaces 35 are surfaces that form a pair with respect to the rotational direction of the shaft portion 32. The transmission surfaces 35 can be said to be both end surfaces of the protruding portion 34 in the rotational direction of the shaft portion 32 . The distal end surface 36 is an end surface in the direction in which the protruding portion 34 projects from the shaft portion 32, that is, in the radial direction of the shaft portion 32.

The crank sprocket 41 as a sprocket includes a cylindrical journal 42 and a tooth portion 43 around which the timing chain 21 as a chain is wound. Since the journal 42 is supported by the bearing 19, the crank sprocket 41 is rotatably supported. Specifically, the cylinder block 11 includes a first support portion 17 protruding from one end surface 15 . The crankcase 13 includes a second support portion 18 protruding from one end surface 16. One end surface 16 of the crankcase 13 is an end surface in the same direction as the one end surface 15 of the cylinder block 11. The bearing 19 is supported by a first support part 17 and a second support part 18. The crank sprocket 41 is supported by a bearing 19 supported by a first support part 17 and a second support part 18 . In this embodiment, a sliding bearing is used as the bearing 19.

The crank sprocket 41 includes an insertion hole forming surface 47 that forms an insertion hole 44 into which the crankshaft 31 is inserted. The insertion hole 44 passes through the crank sprocket 41 in the axial direction. The central axis of the crank sprocket 41 and the central axis C1 of the insertion hole 44 coincide. The insertion hole 44 includes a shaft insertion portion 45 into which the shaft portion 32 is inserted, and a recess 46 into which the protrusion 34 is inserted. The shaft insertion portion 45 and the recess 46 are in communication.

As shown in FIGS. 3 and 4, the insertion hole forming surface 47 includes a first forming surface 48 and a second forming surface 50. As shown in FIGS. A plurality of first forming surfaces 48 are provided and divided in the rotational direction of the crank sprocket 41 . The curvature of each first forming surface 48 is the same, and a virtual surface C connecting the first forming surfaces 48 with a curved surface having the same curvature as the curvature of the first forming surface 48 has a circular shape. The region surrounded by this circular surface C is the shaft insertion portion 45. The dimension from the central axis C1 of the insertion hole 44 to the first forming surface 48, that is, the radius L1 of the shaft insertion portion 45 is longer than the radius L2 of the shaft portion 32.

The second forming surface 50 is located between the first forming surfaces 48. The second forming surface 50 forms a recessed portion 46 that is recessed from the shaft insertion portion 45 to the outside in the radial direction of the crank sprocket 41 . The second forming surface 50 includes a transmitted surface 51 that is two surfaces that intersect with the first formed surface 48 , and a bottom surface 52 that is a surface that intersects with the two transmitted surfaces 51 . The two transmitted surfaces 51 are pairs of surfaces in the rotational direction of the crank sprocket 41. The bottom surface 52 is a surface that becomes the bottom of the crank sprocket 41 in the radial direction in the recess 46 .

A dimension L3 of the transmitted surface 51 with respect to the radial direction of the crank sprocket 41 and a dimension L4 of the transmission surface 35 with respect to the radial direction of the shaft portion 32 are the same. In other words, the amount of depression of the concave portion 46 in the radial direction of the crank sprocket 41 from the first forming surface 48 is the same as the amount of protrusion of the protruding portion 34 in the radial direction of the shaft portion 32 from the outer peripheral surface 33 of the shaft portion 32. . The distance L5 between the transmission surfaces 51 is longer than the distance L6 between the transmission surfaces 35.

Let us assume that the dimensional difference between the radius L1 of the shaft insertion portion 45 and the radius L2 of the shaft portion 32 is the first dimensional difference, and the difference between the distance L5 between the transmitted surfaces 51 and the distance L6 between the transmission surfaces 35 is the second dimensional difference. , the first dimensional difference is larger than the second dimensional difference.

The crankshaft 31 is inserted into the insertion hole 44 with the axial direction of the shaft portion 32 and the axial direction of the crank sprocket 41 matching. Therefore, the axial direction of the shaft portion 32 and the axial direction of the sprocket, the radial direction of the shaft portion 32 and the radial direction of the crank sprocket 41, and the rotation direction of the shaft portion 32 and the rotation direction of the crank sprocket 41 can be said to be the same direction. The first forming surface 48 faces the outer circumferential surface 33 of the shaft portion 32 . Crankshaft 31 is supported by bearings within cylinder block 11 and crankcase 13, and crank sprocket 41 is supported by bearing 19, but crankshaft 31 and crank sprocket 41 are not fixed to each other. That is, the crankshaft 31 is allowed to move within the insertion hole 44 of the crank sprocket 41.

With the shaft portion 32 and the protruding portion 34 of the crankshaft 31 inserted into the insertion hole 44, gaps CA1, CA2, and CA3 are defined between the outer surface of the crankshaft 31 and the insertion hole forming surface 47.

The gaps CA1, CA2, and CA3 include first gaps CA1 and CA2, which are gaps CA1 and CA2 in the radial direction of the shaft portion 32, and a second gap CA3, which is a gap CA3 in the rotational direction of the shaft portion 32. The first gaps CA1 and CA2 are a gap CA1 between the outer circumferential surface 33 of the shaft portion 32 and the first forming surface 48 and a gap CA2 between the tip surface 36 of the protrusion 34 and the bottom surface 52 of the second forming surface 50. including. The second gap CA3 is a gap CA3 between the transmission surface 35 and the transmitted surface 51. When the center axis of the shaft portion 32 and the center axis of the sprocket are aligned, the dimensions d1 and d2 of the first gaps CA1 and CA2 with respect to the radial direction of the shaft portion 32 are the same as the dimensions d1 and d2 of the second gap CA3 with respect to the rotation direction of the shaft portion 32. It is larger than the dimension d3.

The dimension d1 of the first gap CA1 increases as the first dimension difference increases. The dimension d2 of the first gap CA2 increases as the first dimension difference increases, and the dimension L3 of the transmitted surface 51 in the radial direction of the crank sprocket 41 is larger than the dimension L4 of the transmission surface 35 in the radial direction of the shaft portion 32. The longer it gets, the bigger it gets. In this embodiment, since the dimension L3 of the transmitted surface 51 in the radial direction of the crank sprocket 41 and the dimension L4 of the transmission surface 35 in the radial direction of the shaft portion 32 are the same, the dimension d1 of the first gap CA1 and the The dimension d2 of one gap CA2 is the same dimension. The dimension d1 of the first gap CA1 and the dimension d2 of the first gap CA2 may be different, but even in this case, the dimensions d1 and d2 of both the first gaps CA1 and CA2 are different from each other. It is preferable that the dimension d3 of CA3 is larger. The dimension d3 of the second gap CA3 increases as the second dimension difference increases.

The operation of this embodiment will be explained.
If axial runout occurs in the crankshaft 31 during rotation of the crankshaft 31, the crankshaft 31 moves in the radial direction of the shaft portion 32. At this time, when force is transmitted from the crankshaft 31 to the crank sprocket 41 in the radial direction of the shaft portion 32, the crank sprocket 41 moves in the radial direction of the shaft portion 32 together with the crankshaft 31, and the timing chain 21 It causes flapping. For example, when the shaft portion 32 is press-fitted into the crank sprocket 41, when force is easily transmitted from the crankshaft 31 to the crank sprocket 41 in the radial direction of the shaft portion 32, the timing chain 21 is likely to flap. When the timing chain 21 flaps, not only does it cause noise, but also the tension in the timing chain 21 may become excessively large, making the timing chain 21 more likely to reach its fatigue limit.

In this embodiment, gaps CA1, CA2, and CA3 are defined between the insertion hole forming surface 47 and the crankshaft 31. By providing the first gaps CA1, CA2 and the second gap CA3, the crankshaft 31 can move inside the insertion hole 44 within the range where the gaps CA1, CA2, CA3 exist. The gaps CA1, CA2, and CA3 allow movement of the shaft portion 32 of the crankshaft 31 in the radial direction. The dimensions d1 and d2 of the first gaps CA1 and CA2 can be said to be the range within which the crankshaft 31 can move in the radial direction of the shaft portion 32. Note that when the dimension d1 of the first gap CA1 and the dimension d2 of the first gap CA2 are different, the crankshaft 31 is moved closer to the shaft portion 32 depending on the dimensions d1 and d2 of the first gaps CA1 and CA2, whichever is smaller. The movable range in the radial direction is determined.

When axial runout occurs in the crankshaft 31, some of the plurality of protrusions 34 move toward the bottom surface 52, and the first gaps CA1 and CA2 become narrower. Until the tip surface 36 of the protrusion 34 comes into contact with the bottom surface 52, no force in the radial direction of the shaft portion 32 is transmitted from the tip surface 36 of the protrusion 34 to the bottom surface 52. Therefore, by providing the gaps CA1, CA2, and CA3, the force in the radial direction of the shaft portion 32 is difficult to be transmitted to the crank sprocket 41. The dimensions d1 and d2 of the first gaps CA1 and CA2 are set to be longer than the amount of movement, for example, after deriving the amount of movement of the crankshaft 31 in the radial direction of the shaft portion 32 due to the axial runout of the crankshaft 31. Ru. This can prevent the tip end surface 36 of the protrusion 34 from hitting the bottom surface 52. Furthermore, even if the tip end surface 36 of the protruding portion 34 hits the bottom surface 52, by providing the first gaps CA1 and CA2, the force in the radial direction of the shaft portion 32 that is transmitted from the crankshaft 31 to the crank sprocket 41 is reduced.

The crank sprocket 41 is provided with a recess 46 into which the protrusion 34 of the crankshaft 31 is inserted. It is transmitted to the transmitted surface 51 of the surface 50. Thereby, the crankshaft 31 and the crank sprocket 41 rotate together. Therefore, in the drive side rotational force transmission mechanism 30, while the force in the radial direction of the shaft portion 32 is difficult to be transmitted to the crank sprocket 41, the rotational force from the crankshaft 31 is transmitted to the crank sprocket 41.

The effects of this embodiment will be explained.
(1) Gaps CA1, CA2, and CA3 are defined between the insertion hole forming surface 47 and the crankshaft 31. The gaps CA1, CA2, and CA3 allow movement of the crankshaft 31 in the radial direction of the shaft portion 32, so that when the crankshaft 31 undergoes axial runout, the timing chain 21 is less likely to flap. Therefore, noise caused by flapping of the timing chain 21 is reduced. Since noise is reduced by the gaps CA1, CA2, and CA3 provided between the insertion hole forming surface 47 and the crankshaft 31, the impact generated on the timing chain 21 and the crank sprocket 41 is reduced like a buffer member. There is no need to provide any members. Therefore, it is possible to suppress a decrease in durability of the drive-side rotational force transmission mechanism 30 due to deterioration of the buffer member.

(2) By suppressing the flapping of the timing chain 21, it is possible to suppress the timing chain 21 from being bent or the tension of the timing chain 21 from becoming excessive. Therefore, the reliability of the chain system including the slipper 23, damper 22, tensioner 24, crank sprocket 41, intake sprocket 62, exhaust sprocket 72, and timing chain 21 is improved. Further, since the tension of the timing chain 21 can be suppressed from becoming excessive, stress is less likely to be generated in each member constituting the chain system, and the life of the chain system can be extended.

(3) The dimensions d1 and d2 of the first gaps CA1 and CA2 are larger than the dimension d3 of the second gap CA3. The dimensions d1 and d2 of the first gaps CA1 and CA2 determine the range in which the crankshaft 31 can move in the radial direction of the shaft portion 32 when axial runout occurs in the crankshaft 31. On the other hand, the dimension d3 of the second gap CA3 may be a size that does not inhibit the movement of the crankshaft 31, and is preferably small. By making the dimensions d1 and d2 of the first gaps CA1 and CA2 larger than the dimension d3 of the second gap CA3, when axial runout occurs in the crankshaft 31, the tip surface 36 and the bottom surface 52 of the protrusion 34 are Since contact is difficult, transmission of force in the radial direction of the shaft portion 32 to the crank sprocket 41 is further suppressed.

(4) The drive-side rotational force transmission mechanism 30 uses a sprocket as a rotating body. A chain is wrapped around the sprocket. When a chain is used as the annular transmission member, noise is more likely to be generated when flapping occurs than when a belt is used. By configuring the drive-side rotational force transmission mechanism 30, which tends to generate noise, to reduce noise, it is possible to appropriately reduce noise.

(5) Force is suppressed from being transmitted in the radial direction of the shaft portion 32 from the crankshaft 31 to the crank sprocket 41 around which the timing chain 21 of the engine 10 is wound. The timing chain 21 is a chain that rotates as the crankshaft 31 rotates. The crankshaft 31 can rotate at high speed and has large torque fluctuations. Therefore, noise is likely to be generated when the timing chain 21 and the crank sprocket 41 engage with each other. In this way, by configuring the drive-side rotational force transmission mechanism 30 that tends to generate noise so that the noise is reduced, the noise can be appropriately reduced.

(6) Out of the crank sprocket 41, the intake sprocket 62, and the exhaust sprocket 72 around which the timing chain 21 is wound, transmission of force in the radial direction of the shaft portion 32 to the crank sprocket 41 is suppressed. The rotational force of the crankshaft 31 is transmitted to the timing chain 21 via the crank sprocket 41, and from the timing chain 21 to the intake sprocket 62 and the exhaust sprocket 72. That is, the crank sprocket 41 is a driving member that drives the intake sprocket 62 and the exhaust sprocket 72. When the crank sprocket 41 causes the timing chain 21 to fluttering, this fluttering is also transmitted to the intake sprocket 62 and the exhaust sprocket 72, which tends to cause noise. By suppressing the flapping of the timing chain 21 due to the crank sprocket 41, noise can be appropriately suppressed.

(7) Of the drive-side rotational force transmission mechanism 30 and the driven-side rotational force transmission mechanisms 60 and 70, only the driving-side rotational force transmission mechanism 30 is provided with a protrusion 34 on the shaft, a recess 46 on the sprocket, and a gap CA1, CA2, and CA3 allow movement of the shaft in the radial direction of the shaft portion. When noise is reduced by providing a buffer member on the sprocket, it is necessary to provide a buffer member on the sprockets of all driven-side rotational force transmission mechanisms 60 and 70. As a result, the number of sprockets provided with buffer members increases, which causes an increase in manufacturing costs. By configuring only the drive-side rotational force transmission mechanism 30 as in the present embodiment, an increase in manufacturing costs can be suppressed.

(8) A sliding bearing is used as the bearing 19. Therefore, the deflection of the shaft portion 32 of the crank sprocket 41 in the radial direction can be greatly reduced.
The embodiment can be modified and implemented as follows. The embodiments and the following modified examples can be implemented in combination with each other within a technically consistent range.

○The driven-side rotational force transmission mechanisms 60 and 70 are provided with a protrusion 34 on the shaft and a recess 46 on the sprocket, and the rotation allows movement of the shaft in the radial direction of the shaft by gaps CA1, CA2, and CA3. It may also be used as a force transmission mechanism. That is, the driven side rotational force transmission mechanisms 60 and 70 may have the same configuration as the drive side rotational force transmission mechanism 30. The portion of the intake camshaft 61 as a shaft to which the intake sprocket 62 is attached has the same configuration as the shaft portion 32 and the protruding portion 34 of the embodiment, and the intake sprocket 62 as a sprocket has the same configuration as the crank sprocket 41 of the embodiment. Make it. The part of the exhaust camshaft 71 as a shaft to which the exhaust sprocket 72 is attached has the same configuration as the shaft part 32 and the protruding part 34 of the embodiment, and the exhaust sprocket 72 as a sprocket has the same configuration as the crank sprocket 41 of the embodiment. Make it. Note that the above-mentioned "similar configuration" means that the shaft includes the shaft portion 32 and the protruding portion 34, the sprocket includes the first forming surface 48 and the second forming surface 50, and the shaft and the insertion hole forming surface 47. This means a configuration in which gaps CA1, CA2, and CA3 are defined between them to allow movement of the shaft in the radial direction of the shaft portion 32. That is, the dimensions of the shaft portion 32, the number of protrusions 34, the dimensions of the sprocket, the number of teeth of the tooth portions, etc. may be different. Note that at least one of the drive-side rotational force transmission mechanism 30 and the driven-side rotational force transmission mechanisms 60 and 70 may have the same configuration as the shaft and sprocket of the embodiment.

The rotational force transmission mechanism may include a sprocket around which a chain is wound, and a shaft that rotates integrally with the sprocket, and does not need to include a sprocket around which the timing chain 21 is wound.

The rotational force transmission mechanism may include a pulley as a rotating body. When a pulley is used as the rotating body, an insertion hole forming surface 47 is provided on the pulley so that gaps CA1, CA2, and CA3 are formed. In this case, an annular belt wrapped around a pulley is used as the annular transmission member. The belt is made of rubber, for example. The pulley transmits rotational force to the belt. Alternatively, the rotational force from the belt is transmitted to the pulley. An example of this type of rotational force transmission mechanism is one that includes a pulley around which a timing belt is wound. That is, a timing belt may be used instead of the timing chain 21 of the embodiment, and pulleys may be used instead of the crank sprocket 41, intake sprocket 62, and exhaust sprocket 72.

The dimensions d1 and d2 of the first gaps CA1 and CA2 may be smaller than the dimension d3 of the second gap CA3. Moreover, the dimensions d1 and d2 of the first gaps CA1 and CA2 may be the same as the dimension d3 of the second gap CA3.

○The number of journals 42 of the crank sprocket 41 may be increased. For example, the journals 42 may be provided on both sides of the tooth portion 43. That is, a journal may be added to the crank sprocket 41 of the embodiment that protrudes toward the chain cover 80 side from the tooth portion 43 in the axial direction of the crank sprocket 41. In this case, for example, a support part that supports a bearing is extended from the chain cover 80, and the added journal is supported by the bearing supported by this support part. By supporting both sides of the tooth portion 43 with bearings, the crank sprocket 41 can be stably supported.

○The number of protrusions 34 may be changed as appropriate. The number of protrusions 34 may be singular or plural. Further, the number of recesses 46 may be changed as appropriate depending on the number of protrusions 34.
○The bearing 19 may be a rolling bearing. In this case, it is not necessary to supply oil to the bearing 19.

Gap... CA1, CA2, CA3, 10... Engine, 21... Timing chain as an annular transmission member and chain, 30... Drive-side rotational force transmission mechanism as a rotational force transmission mechanism, 31... Crankshaft as a shaft, 32... Shaft Part, 33... Outer circumferential surface, 34... Protruding part, 41... Crank sprocket as a rotating body and sprocket, 42... Journal, 44... Insertion hole, 46... Recessed part, 47... Insertion hole forming surface, 48... First forming surface, 50…Second formation

Claims (4)

A rotational force transmission mechanism comprising a shaft and a rotating body around which an annular transmission member is wound and rotates together with the shaft,
The shaft is
A shaft portion;
a protrusion that protrudes from the outer circumferential surface of the shaft in the radial direction of the shaft;
The rotating body is
an insertion hole forming surface forming an insertion hole into which the shaft is inserted;
a journal supported by a bearing supported by a case in which the shaft is housed;
The insertion hole forming surface is
a first forming surface facing the outer circumferential surface of the shaft portion;
a second forming surface that is located radially outward of the rotating body from the first forming surface and forms a recess into which the protrusion is inserted;
A gap is defined between the insertion hole forming surface and the shaft to allow movement of the shaft in a radial direction of the shaft portion,
The gap is
a first gap that is a gap in the radial direction of the shaft portion;
a second gap that is a gap in the rotational direction of the shaft portion,
A dimension of the first gap in the radial direction of the shaft portion is larger than a dimension of the second gap in the rotation direction,
The protrusion extends to one end surface of the shaft,
The rotational force transmission mechanism is such that the dimension of the protruding portion in the axial direction of the shaft portion is longer than the dimension of the insertion hole in the axial direction of the shaft portion . The rotational force transmission mechanism according to claim 1, wherein the rotating body is a sprocket around which a chain is wound as the annular transmission member. The rotational force transmission mechanism according to claim 2, wherein the sprocket is a sprocket around which a timing chain is wound as the chain. The rotational force transmission mechanism according to claim 3, wherein the shaft is a crankshaft.