JPH04341638A - Flywheel setter for internal combustion engine - Google Patents

Abstract

PURPOSE:To get rid of any fretting erosion and cracking being produced in a gap between a crankshaft and a flywheel and shorten an overall length of this crankshaft as well as to facilitate a job for assembly. CONSTITUTION:A timing belt pulley 12 and a bush part 2 of a flywheel 1-separated from each other in the past-are unitized in one which is fitted and supported merely by a taper hole surface 2a of this bush part 2 and a taper part 3a of a crankshaft 3. In addition a keyway 2b of a key 4 being interposed between the taper hole surface 2a and the taper part 3a is installed in a small end alone.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for attaching a flywheel and a timing belt pulley to a crankshaft in an internal combustion engine.

0002

2. Description of the Related Art Conventionally, as a technique for attaching a flywheel and a timing belt pulley in an internal combustion engine, the technique described in Japanese Patent Application Laid-Open No. 1988-192164 has been known. The technology applied to the shaft internal combustion engine is Utility Model Application No. 60-95142.
The technique described in the above publication is known to the public. That is, in the conventional technology, the configuration was as shown in FIGS. 8, 9, and 10. FIG. 8 is a cross-sectional view taken perpendicular to the axial direction and showing a long keyway 1b opened in a tapered hole surface 1a, which is a boss portion of a conventional flywheel 1. As shown in FIG. FIG. 9 is an enlarged sectional view showing a support mechanism for the conventional timing belt pulley 15 and crankshaft 3, and FIG.
1 is a side cross-sectional view of a portion where a timing belt pulley 15 and a flywheel 1 are fixed to a conventional crankshaft 3. FIG. As shown in FIGS. 9 and 10, conventionally, a timing belt pulley 15 is first locked to the crankshaft 3 protruding from the engine block 20 via a key 5, and a timing belt pulley 15 is attached to the outer periphery of the timing belt pulley 15. The protrusion of the timing belt 11 was engaged with the belt protrusion locking groove 13. Further, with the timing belt pulley 15 fitted to the fitting portion of the crankshaft 3, a locking nut 16 for preventing the timing belt pulley 15 from coming off is attached to the threaded portion 3f provided on the crankshaft 3. It was screwed on. Then, a tapered portion 3 is provided on the outside of the threaded portion 3f.
A is provided, a key 9 is interposed in the tapered portion 3a, the tapered surface 2a provided on the boss portion of the flywheel 1 is fitted, and the end nut 10 is used to lock the key 9. Furthermore, conventionally, as shown in FIG. 8, a key 9 is fitted at approximately the center of the tapered hole surface 1a on the inner diameter of the flywheel 1, and the keyway 1b for the key 9 also extends along the entire length of the tapered hole surface 1a. A crossing had been built. Therefore, since the key groove 1b is bored to the full width of the tapered hole surface 1a, the taper hole surface 1
Not only is the strength of the portion a weakened, but also the corner of the large diameter portion of the taper hole surface 1a of the keyway 1b, which is unnecessarily drilled, hits or scrapes the surface of the taper portion 3a. , fretting erosion occurred.

0003

[Problems to be Solved by the Invention] In the conventional technology, the following problems have occurred. That is, in an outboard motor or the like, it is advantageous to arrange the flywheel and timing belt above the internal combustion engine from the viewpoint of structure and inspection service. Also, since a thin drive shaft for driving the propeller is fitted to the lower end of the crankshaft, the maximum mass of the shaft diameter is the part of the flywheel fixed at the top end. Therefore, the maximum stress due to torsional vibration and torque fluctuation occurs at this flywheel mounting portion. Also, in the case of diesel engines, the compression ratio is large,
This requires a flywheel with a large mass. For the above reasons, the corner of the keyway 1b hits or scrapes the outer periphery of the tapered part 3a in the large diameter part of the tapered part 3a, which is the part where the maximum stress is generated at the connection part between the crankshaft and the flywheel. There were problems with fretting erosion and fretting erosion occurring on the inner diameter of the timing belt pulley. In addition, the timing belt pulley 15 is fitted onto the protrusion of the crankshaft 3, and the locking nut 16 is inserted from the outside.
It is necessary to press and fix the timing belt pulley 15 against the stepped portion of the crankshaft 3 by screwing the timing belt pulley 15 onto the stepped portion of the crankshaft 3. As a result, the crankshaft 3 becomes smaller in diameter, resulting in a reduction in strength. The present invention is configured so that the diameter of the crankshaft 3 does not become small, and the rigidity of the part where the maximum stress occurs between the flywheel and the crankshaft is significantly increased, thereby reducing the stress in this part. This structure is designed to be effective in reducing the number of rotations and avoiding resonance. Furthermore, by configuring the inner diameter portion of the timing belt pulley so that there is no tapered fitting portion between it and the crankshaft, blistering of the timing belt pulley does not occur when the tapered fitting portion is tightened. First, it is designed to have the same dimensions and shape as machined, and to avoid problems such as timing belt failure.

0004

[Means for Solving the Problems] The problems to be solved by the present invention are as described above, and next, the means for solving the problems will be explained. In other words, in a configuration in which a timing belt pulley and a flywheel are arranged in series on a crankshaft part that protrudes from the engine block, with the flywheel located on the outside, the crankshaft 3 has a shaft diameter of the part that protrudes from the engine block. is formed to be smaller than the shaft diameter of the oil seal mounting portion 3c, and the shaft end side is formed into a tapered shape, and a timing belt pulley is integrally attached to the tapered portion on the shaft end side of the crankshaft. The bush portion of the constructed flywheel is fitted into the bush portion, and a gap is formed between the inner periphery of the timing belt pulley portion and the outer periphery of the crankshaft. Further, the timing belt pulley and the bushing portion are molded separately and then integrated. Further, in a configuration in which a flywheel mounting boss or a flywheel boss is fitted into a tapered portion formed at the shaft end of the crankshaft, a keyway on the boss side is provided only on the small end side. Further, the machined surface of the boss-side keyway is parallel to the angle of the opposing tapered surface 2a at a position rotated 180 degrees with respect to the tapered hole position where the keyway is drilled, or an inclined machined surface larger than this angle. , or a keyway machined surface parallel to the axis of the crankshaft.

[0005]

[Operation] Next, the operation of the present invention will be explained. The reciprocating motion of the piston 24 in the engine block 20 is transmitted as rotation to the crankshaft 3 by the connecting rod 25, and the rotation of the crankshaft 3 is taken out to the outside of the engine block 20, transmitted to the propeller shaft, etc., and then transferred to the opposite side. A timing belt pulley and a flywheel 1 are fixedly installed. The flywheel 1 eliminates uneven rotation and provides inertial rotational force. Therefore, the joint between the crankshaft 3 and the flywheel 1 is a part where large torsional stress acts, and fretting erosion occurs at the part of the crankshaft 3 where the stress is most concentrated, and this becomes the starting point for cracks to occur. be. The present invention eliminates the conventional technique of fixing the timing belt pulley 15 and the flywheel 1 separately on the crankshaft 3, and instead integrates the timing belt pulley 12 and the bushing part 2. The flywheel 1 can be attached to this using the dowel pin 6 and the fixing bolt 7. Further, the inner diameter of the timing belt pulley 12 is provided with gap fitting holes 2d and 2e so that it is not fixed to the crankshaft 3, and is in a floating state.

[0006]

[Example] Next, an example of the present invention will be described. FIG. 1 is a side cross-sectional view showing the mounting configuration of the crankshaft 3, bushing portion 2, and flywheel 1 of the present invention, and FIG. 2 shows the bushing portion 2 and timing belt pulley 12 being constructed separately and later integrated. 3 is an enlarged sectional view showing the positional relationship between the bushing part 2, the crankshaft 3, and the key 4; FIG. 4 is an enlarged sectional view of another processing example of the bushing part 2; FIG. 5 is a drawing showing another embodiment of the key groove into which the key 4 is inserted, FIG. 6 is a drawing showing an embodiment of the key 4 on an arc,
FIG. 7 is a sectional view taken in a direction perpendicular to the axis.

[0007] In the conventional technology, FIGS. 8, 9, and 1
0, first fix the timing belt pulley 15 on the crankshaft 3 with the locking nut 16, then attach the tapered hole part of the flywheel 1 to the tapered part 3a located further outward. 9 and fixed with an end nut 10. On the other hand, in the present invention, the timing belt pulley 15 and the bushing portion 2 of the flywheel 1 are mounted on the crankshaft 3.
It is designed to be fixed in a unified manner. In FIG. 1, within an engine block 20 of an internal combustion engine, the rotation of a piston 24 is transmitted to a crankshaft 3 via a connecting rod 25. The crankshaft 3 has a metal bearing 22
A bearing metal 22 is interposed in the oil seal mounting portion 3c of the crankshaft 3, and an oil seal 2 is mounted on the outside of the bearing metal 22.
1 is interposed. The crankshaft 3 on the outside from the oil seal 21 is provided to protrude to the outside of the engine block 20, and a straight portion 3b forming a gap between the oil seal 21 and the timing belt pulley is formed in this portion. The outer portion of the straight portion 3b constitutes a tapered portion 3a into which the tapered hole surface 2a of the bush portion 2 of the flywheel 1 is fitted. In an embodiment of the invention,
Although the flywheel 1 is integrated with the bushing part 2 by the dowel pin 6 and the fixing bolt 7, the bushing part 2 and the flywheel 1 may be integrally molded from the beginning. A large-diameter gear 8 is fixed to the outer periphery of the flywheel 1 and is engaged with a gear of a starting motor.

In the embodiment shown in FIG. 1, a belt protrusion locking groove 13 is formed on the inner side of the bushing portion 2 so that the timing belt 11 can be wound thereon. A specific configuration of the bush portion 2 shown in FIG. 1 is disclosed in FIG. 4. That is, the timing belt pulley 12 does not fit on the outer periphery of the straight portion 3b of the crankshaft 3, but rather forms the gap fitting holes 2d and 2e, and the crankshaft 3 It is configured so that it does not contact the straight portion 3b of the tapered hole surface 2a, and
It is fitted with part a. Also, crankshaft 3
and the tapered hole surface 2 of the bushing portion 2.
The part a fits with the tapered surface, but power is not transmitted between the tapered hole surface 2a and all parts of the tapered part 3a, and the outside of the tapered part 3a The crankshaft 3 and the bush portion 2 are engaged by the key 4 only at the small diameter portion. As a result, the keyway 2b is not formed at the large diameter position of the tapered portion 3a, where fretting erosion is likely to occur in the past.

Furthermore, conventionally, as shown in FIG.
In the present invention, the keyway 1b, which was long drilled in the part of the taper hole surface 1a that fits into the keyway 1a, caused fretting erosion in the large diameter part of the taper part 3a. A key groove 2b formed in a portion of the tapered hole surface 2a is made short enough to insert a key 4. Referring to FIG. 3, the length relationship of the keyway 2b will be explained. The keyway 2b on the boss side of the bushing portion 2 is provided only on the small end side of the tapered portion 3a. As shown in FIG. 3, when the key 4 is a feather key, a gap c is provided between the tip of the key 4 and the tip of the keyway 2b, and a gap a larger than the gap c is provided between the key 4 and the tip of the key groove 2b. and the keyway 3g on the crankshaft 3 side, and the gap a is formed between the end of the tapered portion 3a and the washer 28.
It is configured to be larger than the gap b between it and the inner surface.

With the configuration as shown in FIG. 3, it is possible to eliminate the fretting erosion that occurs due to the unnecessary corners of the large diameter portion of the long keyway 1b, as in the conventional case. It was also possible to eliminate cracks that would otherwise occur as a starting point. In addition, in the past, since the keyway 1b was present, the taper part 3a was not held around the entire circumference of the taper hole surface 1a, resulting in a significant decrease in rigidity, but in the present invention, the crankshaft 3, it is possible to solve this problem, and it is also possible to solve the problem that when the end nut 10 is tightened, the boss part of the flywheel 1 expands and gradually fits into the tapered part 3a. It was possible. Furthermore, by maintaining the dimensional relationship shown in Fig. 3, even when the boss expands and the flywheel 1 is fitted in the axial direction of the crankshaft 3, the key 4 will not come into contact with the keyway 2b or the keyway 3g. As a result, no unexpected stress is applied to the keyway of the shaft or boss, and no local surface pressure is applied to the washer. Additionally, the adoption of a feather key increased the shear strength, making it possible to transmit power through the key even if the taper loosened.

In FIG. 2, the bush portion 2 and the timing belt pulley 12 are integrally constructed, but in the machining process, they are processed as separate parts, and after the machining is completed, they are integrated to form the bush portion. is disclosed. With this configuration, the timing belt 11
Among the steady rests 17, the steady rest on the flywheel 1 side is connected to the timing belt pulley 12 of the bushing part 2.
This made it possible to construct a large-diameter stepped portion on the side and use it for both purposes. In this case as well, the steady rest 17 of the timing belt pulley 12 on the engine block 20 side is necessary. As shown in FIGS. 4, 5, and 6, when the bush portion 2 and the timing belt pulley 12 are integrated, the belt protrusion locking groove 13 of the timing belt pulley 12 can be machined using a hobbing machine. In order to do this, a circular arc is required for relief at the cut-up part of the hobbing machine, and the step part that also serves as the steady rest 17 mentioned above is used as the bushing part 2.
Therefore, it cannot be provided on the outer periphery of the For this purpose, a locking groove 2h for fitting the steady rest 17 is provided. In the present invention, if the flywheel 1 and the timing belt pulley 12 are processed separately, there is no need for a cut-up portion in hobbing the outer periphery of the timing belt pulley 12.

Next, a description will be given with reference to FIG. As shown in FIG. 4, a configuration is disclosed in which the tapered hole surface 2a of the bushing portion 2 is longer than the tapered portion 3a of the crankshaft 3. Then, a timing belt pulley 12 is formed from the position where the tapered hole surface 2a ends, and gap fitting holes 2d and 2e are formed in the inner diameter portion of the timing belt pulley 12 so as not to contact the straight portion 3b. It is composed of Therefore, at the part of the crankshaft 3 that changes from the straight part 3b to the straight part 3b, a protrusion of a bent part is formed, and this is in contact with the inside of the surface of the tapered hole surface 2a.
In this portion, fretting erosion tends to occur on the side of the tapered hole surface 2a, and there is a high possibility that cracks will occur in the bushing portion 2 from the fretting erosion. On the other hand, if the tapered hole surface 2a ends in the middle of the tapered part 3a and the gap fitting hole 2e starts, a bending protrusion will be formed on the side of the bushing part 2, and fretting erosion will occur in the crankshaft 3. This could be the starting point for cracks. In the present invention, the projecting corner portion of the crankshaft 3 is brought into contact with the bushing portion 2, so that fretting erosion is caused in the bushing portion 2. This is because replacing the crankshaft 3 is more troublesome to repair than replacing the bushing portion 2, and the replacement parts are more expensive.

Further, in FIG. 4, a slotter is used to drill the keyway 2b, but a space is required for the cutting edge of the slotter to escape, and the drilled hole 2c is drilled from the outside of the bushing portion 2. A hole is made through which the slotter's cutting edge can escape. In the case of a feather key, the drill hole 2c has a rounded tip, so there is no problem even if the end of the hole is rounded. In the embodiment shown in FIG. 5, in a slotter in which the cutting blade reciprocates in a straight line, the keyway 2b is configured to allow the cutting blade to be inserted obliquely in order to obtain a clearance space for the tip of the cutting blade. The keyway 2b is 180
The direction is approximately parallel to the surface of the tapered portion 3a on the opposite side of the rotation, thereby increasing the margin for reciprocating movement of the cutting blade of the slotter. In the case of the embodiment of FIG. 5, key 4
is a trapezoid. FIG. 6 discloses an embodiment in which the keyway 2b is bored by a slotter whose cutting blade rotates in an arc, rather than by a slotter whose cutting blade moves in a straight line. In this case, the key 4 must also be an arc-shaped key, and the washer 28 and the inner end portion of the flywheel 1 are fixed by abutting on the key 4. In this case, as shown in FIG. 7, it is not necessary to fit all of the tall keys 4 into the keyway 2b, and the shearing force is applied to the keys in the fitting portion between the crankshaft 3 and the bushing portion 2. 4, the thickness of the other parts is made thinner as shown in Fig. 7, and the arc-shaped key groove 2b is
The structure is such that it does not come into contact with the groove.

[0014]

[Effects of the Invention] Since the present invention is constructed as described above, the following effects can be achieved. In other words, since the configuration as claimed in claim 1 eliminates the need for the stepped portion for bringing the timing belt pulley into contact with the crankshaft 3 and the threaded portion 3f for the locking nut 16, This allows the shaft diameter of the tapered portion 3a to be increased. Furthermore, since the threaded portion 3f and the locking nut 16 that were necessary in the conventional technology are no longer necessary, the overall length of the crankshaft 3 can be shortened. By removing the end nut 10, it became possible to remove the flywheel 1 and the timing belt pulley at the same time. In addition, in the conventional mechanism, the fretting erosion that occurs inside the timing belt pulley can be removed using the gap fitting holes 2d and 2e.
This problem could be solved by providing . Furthermore, the flywheel 1 can now be easily removed by simply removing the small-diameter fixing bolt 7.

[0015] Since the structure is configured as in claim 2, it is possible to form a stepped portion that also serves as a steady rest 17 in the portion where the bush portion 2 is in close contact with the timing belt pulley 12, thereby reducing the run-out on the side of the flywheel 1. This made it possible to eliminate the stop 17. Furthermore, since there is no need for an arcuate relief groove for machining with a hobbing machine, the length of the bushing portion 2 can be shortened. This made it possible to further shorten the overall length of the crankshaft 3.

[0016] Since the structure is as set forth in claim 3, the keyway 2b
The part is not provided over the entire length of the tapered hole surface 2a, but is provided only in the small diameter part, so that the corner of the unnecessary keyway in the large diameter part is fretted in the large diameter part of the tapered part 3a. Erosion occurred and this part no longer became the starting point for cracks. Furthermore, since the keyway 2b is not provided on the large diameter side, the rigidity of this portion is increased, and the axial displacement when the end nut 10 is tightened can be reduced.

With the construction as set forth in claim 4, when machining the key groove 2b up to the middle of the tapered hole surface 2a with the slotter, the clearance space of the cutting edge of the slotter is used as the bushing part 2.
Since the hole in the boss part can be formed, it is no longer necessary to open the through hole 2c with a drill. Furthermore, when inserting the bushing part 2 into the crankshaft 3,
Since the assembly can be performed while fitting the key 4 at the same time, after fitting the bushing part 2 to the crankshaft 3, the keyway 3g
The key 4 can be inserted more easily than when the key 4 is inserted by matching the key groove 2b with the key groove 2b.

[Brief explanation of the drawing]

FIG. 1 is a side cross-sectional view showing a mounting structure of a crankshaft 3, a bushing portion 2, and a flywheel 1 according to the present invention.

[Figure 2] Bush part 2 and timing belt pulley 1
FIG. 2 is a side cross-sectional view of an embodiment in which the parts 2 and 2 are constructed separately and later integrated.

FIG. 3 is an enlarged cross-sectional view showing the positional relationship among the bush portion 2, crankshaft 3, and key 4. FIG.

FIG. 4 is an enlarged sectional view of another processed example of the bush portion 2. FIG.

FIG. 5 is a drawing showing another embodiment of a keyway into which a key 4 is inserted.

FIG. 6 is a drawing showing an embodiment of the key 4 on an arc.

FIG. 7 is a cross-sectional view taken in a direction perpendicular to the axis.

FIG. 8 is a cross-sectional view taken perpendicular to the axial direction and showing a long keyway 1b opened in a tapered hole surface 1a, which is a boss portion of a conventional flywheel 1.

FIG. 9 is an enlarged sectional view showing a conventional support mechanism for a timing belt pulley 15 and a crankshaft 3. FIG.

FIG. 10 is a side sectional view of a portion where a timing belt pulley 15 and flywheel 1 are fixed to a conventional crankshaft 3.

[Explanation of symbols]

1 Flywheel 2 Bush part 2a Tapered hole surface 2b Keyway 2d, 2e Gap fitting hole 3a Taper part 3g Keyway 4 Key 11 Timing belt 12 Pulley for timing belt

Claims (4)

[Claims] Claim 1: In a configuration in which a timing belt pulley and a flywheel are arranged in series on a crankshaft part that protrudes from the engine block, with the flywheel located on the outside, the crankshaft is attached to the part of the crankshaft that protrudes from the engine block. The crankshaft is formed so that its shaft diameter is smaller than the shaft diameter of the oil seal mounting part, and the shaft end side is formed into a tapered shape, and the timing belt pulley is integrated with the tapered part on the shaft end side of the crankshaft. 1. A flywheel mounting device for an internal combustion engine, characterized in that a bushing portion of a flywheel configured as shown in FIG. 2. The flywheel mounting device for an internal combustion engine according to claim 1, wherein the timing belt pulley and the bushing portion are formed separately and then integrated. 3. In a configuration in which a flywheel mounting boss or a flywheel boss is fitted into a tapered portion formed at the shaft end of the crankshaft, a keyway on the boss side is provided only on the small end side. Flywheel mounting device for internal combustion engines. 4. The machined surface of the boss-side keyway is parallel to or larger than the angle of the opposing tapered hole surface at a position rotated 180 degrees with respect to the tapered hole position where the keyway is drilled. 4. The flywheel mounting device for an internal combustion engine according to claim 3, wherein the flywheel mounting device for an internal combustion engine has an inclined machined surface or a keyway machined surface parallel to the axis of the crankshaft.