JP7420456B2 - internal combustion engine crankshaft - Google Patents

Description

The present invention relates to a crankshaft used in a reciprocating internal combustion engine such as a gasoline engine or a diesel engine.

External bending and torsion forces act on the crankshaft used in reciprocating internal combustion engines as the engine operates, but the force received from the piston changes periodically, causing vibrations in the crankshaft. When this vibration matches the natural frequency of the crankshaft, resonance occurs, resulting in worsening noise vibration. In particular, since the crankshaft is subjected to strong torsional action as a result of its structure, noise vibrations caused by the torsion are likely to be noticeable.

Therefore, as a vibration damping means for the crankshaft, an annular recess is formed in the crank pulley, and a damper mass is relatively rotatably disposed in the annular recess via an elastic ring. That is, the crank pulley is configured as a damper pulley with a damper function. However, since the damper pulley adds an extra mass of damper mass that exceeds its function, there is a problem that the mass of the crank pulley becomes larger than necessary, which worsens fuel efficiency.

On the other hand, Patent Document 1 filed by the applicant of the present application discloses that a counterweight constituting a crankshaft is formed separately from a crank arm, and this separate counterweight is arranged perpendicularly to the axis of the crankshaft. Mounting on the crank arm for radial relative movement is disclosed.

Specifically, the separate counterweight is connected to the crank arm by two left and right bolts that are long in the direction perpendicular to the rotation axis, and there is a gap between the inner circumference of the counterweight and the outer circumference of the crank arm. By sandwiching an elastic sheet between the two, the counterweight is allowed to move relative to each other in a direction perpendicular to the rotation axis .

JP 2019-116919 Publication

Patent Document 1 uses a counterweight as a vibration damping member, so it has the advantage of being able to suppress an increase in weight, but it is aimed at suppressing vibrations caused by bending, and the counterweight moves relative to each other in the radial direction. Therefore, there was a problem in that it hardly contributed to suppressing vibrations caused by torsion.

Also, the counterweight is connected to the crank arm with two bolts, but since the entire counterweight is separate from the crank arm, the centrifugal force acting on the counterweight can only be supported by the bolts. Therefore, there was also the problem that it was difficult to maintain the counterweight stably over a long period of time.

The present invention was made in response to this current situation, and while following the idea of the previous application in providing the counterweight with a vibration damping function, it provides an improved configuration as a countermeasure against vibrations caused by torsion. This is what I am trying to do.

As claimed in claim 1, the crankshaft of the present invention has the following features:
"In a configuration in which a crank journal and a crank pin are connected via a crank arm, and a counterweight is integrally formed with the crank arm,
A recess is formed in the counterweight that opens in the centrifugal direction on the opposite side of the crank pin when viewed from the rotational axis direction, and the width in the circumferential direction gradually decreases toward the opening, and the recess A damping member that moves relative to the counterweight in the circumferential direction is fitted to prevent it from coming off.
The vibration damping member is supported in the recess through an elastic body so as to allow relative movement in the circumferential direction with the counterweight, and the vibration damping member passes through the recess to the rotation axis and the crank pin. The crank arm is fastened to the crank arm by a bolt extending in a direction perpendicular to the axis of the crank arm.
It has the following characteristics.

The present invention also includes expanded examples of claims 2 and 3. Among these, the invention of claim 2 is, in claim 1,
"There is a clearance between the inner surface of the recess located on the crank arm side and the vibration damping member, and between the head of the bolt and the vibration damping member."
The structure is as follows.
On the other hand, the invention of claim 3, in claim 1 or 2,
"The inner diameter of the bolt mounting hole formed in the vibration damping member is larger than the outer diameter of the bolt."
The structure is as follows.
Although the crankshaft includes a plurality of counterweights, in the present invention, it is sufficient to provide the vibration damping member on either one of the counterweights located at both ends of the crankshaft.

In the present invention, since the damping member moves relative to the counterweight in the circumferential direction via the elastic body, vibrations caused by torsion of the crankshaft can be prevented or significantly suppressed by the movement of the damping member. That is, the vibration damping member incorporated in the counterweight functions as a damper that absorbs vibrations around the axis of the crankshaft.

The damping member may be made of a material with a higher specific gravity than the counterweight in order to enhance its damping function, but even in this case, the counterweight only exists in a portion around the axis of the crankshaft. Therefore, the weight can be reduced compared to the case where a ring-shaped damper mass is used like a damper pulley. Therefore, engine noise and vibration can be suppressed while improving fuel efficiency.

Moreover, since the damping member is fitted into the recess of the counterweight, the damping member can be stably held. In particular, in the present invention, the recess is formed in a wedge shape that opens in the centrifugal direction facing away from the crank pin when viewed in the direction of the rotation axis, and the groove width decreases toward the opening. Since the vibration member can be reliably prevented from moving due to centrifugal force, the stability of the vibration damping member can be improved more reliably.

Note that the present invention does not exclude the use of a damper pulley, and it is also possible to use the crankshaft and damper pulley of the present invention in combination as a means to further improve the quality of the internal combustion engine. Thereby, the vibration prevention effect and quietness of the engine can be further improved.

1 is a diagram showing an embodiment , in which (A) is a side view of a crankshaft, (B) is a cross-sectional view taken along line BB of (A), and (C) is an enlarged view of a main part of (B). (A) is a sectional view taken along line II-II in FIG. 1(B), and (B) is a diagram showing another example. FIG. 3 is a partially cutaway front view of a reference example .

Next, embodiments of the present invention will be described based on the drawings. In the following, we will use the words front and back to specify the direction, but the side where the crank pulley and timing chain are located is the front, and the side where the transmission case is located is the back.

The crankshaft of this embodiment is for a three-cylinder internal combustion engine, and therefore has a front journal 1 located at the front end, an end journal 2 located at the rear end, and two intermediate journals 3 located between the two. have.

The front journal 1 and one intermediate journal 3, the adjacent intermediate journal 3, and the other intermediate journal 3 and end journal 2 are connected by a crank pin 5 via a pair of crank arms (crank webs) 4, respectively. A counterweight (balance weight) 6 is provided integrally with each crank arm 4.

Therefore, in this embodiment, there are two counterweights 6 corresponding to each of the crank journals 1 to 3, but the one counterweight 6 located furthest is attached in the crank axis direction (front-rear direction). ) and a recess 7 opened in the centrifugal direction facing away from the crank pin 5 , and a damper 8 is fitted into this recess 7. It is preferable that all or a portion of the vibration damping member 8 be made of a material having a higher specific gravity than the crank arm 4.

The recess 7 has an upper surface 7a close to the crank axis (rotation axis) that is a flat surface perpendicular to the longitudinal centerline of the crank arm 4, and left and right inner surfaces 7b that are grooved in the centrifugal direction away from the crank pin 5. It is curved so that the width becomes small, and opens on the outer peripheral surface of the counterweight 6. Therefore, the recess 7 has a semicircular wedge shape as a whole.

On the other hand, the vibration damping member 8 has a semicircular shape similar to the recess 7, and a rubber elastic material such as elastomer is disposed between the left and right side surfaces 8a of the vibration damping member 8 and the left and right side surfaces 7b of the recess 7. A body 9 is interposed. The elastic body 9 is irremovably fixed to at least one of the recess 7 and the vibration damping member 8 by means of adhesive or the like. Further, there is a slight gap ( clearance) between the upper surface 8b of the damping member 8 and the upper surface 7a of the recess 7.

The damping member 8 is connected to the crank arm 4 by a single bolt 10 arranged concentrically with the longitudinal centerline of the crank arm 4 (a line perpendicular to the axis of rotation and the axis of the crank pin 5) . Therefore, the damping member 8 is formed with a counterbore hole 11 in which the head of the bolt 10 is hidden. A clearance is provided so that when the bolt 10 is completely screwed into the crank arm 4, the damping member 8 can move in the axial direction of the bolt 10, although it has a small dimension (as shown in FIG. 1(C)). , there is a gap between the head of the bolt 10 and the bottom of the counterbore hole 11). Furthermore, by setting the bolt mounting hole 12 of the vibration damping member 8 to have a slightly larger diameter than the outer diameter of the bolt 10, the vibration damping member 8 resists the elasticity of the elastic body 9 and moves around the counterweight 6. Relative movement in the direction is allowed.

As a holding means for the damping member 8, as shown in FIG. By adhering both the outer surface 8a of the vibration damping member 8 with adhesive, it is possible to prevent the vibration damping member 8 from touching and moving in the direction of the crank axis and from touching and moving around the axis of the bolt 10. This is preferable because it can be prevented.

Furthermore, as shown as a modification in FIG. 2(B), by press-fitting the pair of left and right guide pins 13 inserted into the counterweight 6 into the damping member 8, the damping member 8 can be touched and moved in the crank axis direction. Also, it is possible to prevent the damping member 8 from touching and moving around the axis of the bolt 10. Since the guide pin 13 is perpendicular to the bolt 10, the vibration damping member 8 can move relative to the direction perpendicular to the bolt 10 (also in this case, in a pseudo sense, the vibration damping member 8 can move relatively in the circumferential direction of the crankshaft). ).

(2). Effect As described above, in this embodiment, the vibration damping member 8 can move relative to the counterweight 6, the crank arm 4, and each of the crank journals 1 to 3 in the circumferential direction. Therefore, the vibration damping member 8 moves with a delay in response to vibrations caused by torsion of the crankshaft, thereby suppressing the vibrations. That is, the vibration around the axis can be suppressed by the damper effect of the vibration damping member 8. As a result, resonance of the crankshaft can be prevented and noise vibration of the internal combustion engine can be significantly suppressed.

Furthermore, since the recess 7 and the damping member 8 are formed in a semicircular shape (wedge shape), even if centrifugal force acts on the damping member 8, the inertia of the damping member 8 due to the centrifugal force is firmly supported by the recess 7. Therefore, the damping member 8 can be stably held inside the recess 7. Therefore, it has excellent reliability.

In the embodiment, the damping member 8 is provided only on the counterweight 6 located at the frontmost position, but since the amount of torsional displacement of the crankshaft is greatest between the front end and the rear end, the damping member 8 is provided only at the counterweight 6 located at the frontmost position. Even if the damping member 8 is provided only on the weight 6, a sufficient damping effect can be achieved. Different from the embodiment, it is also possible to provide the damping member 8 on the counterweight 6 located at the rearmost position.

Alternatively, it is also possible to provide the damping members 8 on the two counterweights 6 at the front end and the rear end. However, in a 3-cylinder crankshaft, the phases of the counterweights 6 located at both the front and rear ends are shifted by 120° (or 240°) in the circumferential direction, so when damping members 8 are provided on the counterweights 6 at both ends. , it is also assumed that the damper effects cancel each other out.

In the embodiment, the inner surface 7b of the recess 7 and the outer surface 8a of the vibration damping member 8 are formed into curved shapes, but the inner surface 7b of the recess 7 and the outer surface 8a of the vibration damping member 8 are connected by bolts. It is also possible to form a flat surface inclined with respect to the axis of 10. That is, it is also possible to form the recess 7 and the damping member 8 into a substantially trapezoidal shape when viewed from the front. Also in this case, the damping member 8 on which centrifugal force is applied can be stably supported by the recess 7 due to the wedge effect.

Further, it is also possible to arrange an elastic body between the flat upper surface 7a of the recess 7 and the vibration damping member 8. Furthermore, it is also possible to connect the vibration damping member 8 to the crank arm 4 with two bolts 10 on the left and right sides. In this case, since the damping member 8 can be prevented from rotating around the axis of the bolt 10, reliability can be significantly improved.

(3) .Reference example
In the reference example shown in FIG. 3, the recess 7 is of a closed type that does not open outward in the radial direction, and has a substantially trapezoidal shape with curved inner surfaces 7c and 7d. Correspondingly, the damping member 8 also has a substantially trapezoidal shape with curved outer surfaces 8c and 8d. An elastic body 9 is interposed between the curved side surfaces 7c, 7d of the recess 7 and the curved outer surfaces 8c, 8d of the damping member 8. Note that the recess 7 and the damping member 8 may be formed into a simple trapezoid.

Two left and right guide pins 14 separated in the circumferential direction are used as holding means for the vibration damping member 8, and the guide pins 14 penetrate the counterweight 6 and the vibration damping member 8 and cannot be removed to the crank arm 4. is press-fitted into the There is some clearance between the guide pin 14 and the damping member 8. Therefore, the damping member 8 is allowed to move relative to the circumferential direction against the elasticity of the elastic body 9.

In this reference example , since the damping member 8 does not move around the axis of the guide pin 13, the support stability of the damping member 8 can be significantly improved. Furthermore, since the counterweight 6 does not have a free end, a decrease in rigidity of the counterweight 6 can be prevented. Therefore, it has excellent strength and stability as a whole.

Although the embodiments of the present invention have been described above, the present invention can be embodied in various other ways. For example, the elastic body may be made of metal such as a coil spring or a leaf spring.

Although the recess in the embodiment is opened in the front-rear direction (crank axis direction), it is also possible to adopt a form in which it is opened in only one of the front-rear directions.

The present invention can be embodied in a crankshaft. Therefore, it can be used industrially.

1 Front journal 2 End journal 3 Intermediate journal 4 Crank arm 5 Crank pin 6 Counterweight 7 Recess 8 Vibration damping member 9 Elastic body 10 Bolt

Claims (3)

A crank journal and a crank pin are connected via a crank arm, and a counterweight is integrally formed with the crank arm,
A recess is formed in the counterweight that opens in the centrifugal direction on the opposite side of the crank pin when viewed from the rotational axis direction, and the width in the circumferential direction gradually decreases toward the opening. A damping member that moves relative to the counterweight in the circumferential direction is fitted to prevent it from coming off.
The vibration damping member is supported in the recess via an elastic body so as to allow relative movement in the circumferential direction with the counterweight, and the vibration damping member passes through the recess to the rotation axis and the crank pin. fastened to the crank arm by a bolt extending in a direction perpendicular to the axis of the crank arm;
Crankshaft of an internal combustion engine. There is a clearance between the inner surface of the recess located on the crank arm side and the vibration damping member, and between the head of the bolt and the vibration damping member.
A crankshaft for an internal combustion engine according to claim 1. The inner diameter of the bolt mounting hole formed in the vibration damping member is larger than the outer diameter of the bolt.
A crankshaft for an internal combustion engine according to claim 1 or 2.

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