JP2010255834A - Crankshaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crankshaft capable of distributing stress based on an explosion load applied to a crank pin constituting an engine. <P>SOLUTION: A virtual line A is assumed which passes an axis line B of a crank journal between a peripheral edge 40a of a thrust receiving portion of a first crank pin 20 and a peripheral edge 42a of a thrust receiving portion of the crank journal. A thin portion 50 is formed in a first crank arm 12 between the axis line B and the virtual line A. This thin portion 50 extends over an entire width of the first crank arm 12 in the direction perpendicular to an axis line C of the first crank pin 20 of the first crank arm 12. The stress applied to the first crank pin 20 causes the first crank arm to be bent 12 due to the presence of thin portion 50, so that the stress is distributed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a crankshaft, and more particularly, to a crankshaft that can distribute the stress without locally concentrating a load applied by a reciprocating motion of a piston constituting an internal combustion engine.

  A crankshaft constituting an internal combustion engine converts a reciprocating motion of a piston into a rotational motion via a connecting rod. The crankshaft includes a crankpin, crank arms provided at both ends of the crankpin, and a crank journal provided eccentrically with respect to the axis of the crankpin and provided outside the crank arm. In this case, the crank arm is provided with a counterweight, but some may not have it.

  As a prior art showing this type of crankshaft, Patent Document 1 is listed here. Japanese Patent Publication No. 60-564 discloses a “structure of an engine crankshaft”. In the engine crankshaft of this Patent Document 1, two pairs of crank arms 2 and 2 are connected to a journal 1 concentric with the crankshaft core, and the pair of crank arms 2 and 2 are connected to each other by a crankpin 3. The balance arms 4 are connected to each of the crank arms 2 and 2 and are integrally formed by casting. In particular, in the invention of Patent Document 1, a recessed portion 7 is formed at a connecting portion between the crank pin 3 and the crank arm 2, and the concentration of tensile stress on the crank arm 2 near the connecting portion is reduced by the recessed portion 7. (Patent Document 1, second column, line 14 to third column, eighth line).

  However, in the structure of the engine crankshaft described in Patent Document 1, when the reciprocating motion of the piston is transmitted to the crankpin 3 via the connecting rod and the engine explosion load is applied to the crankpin 3, the crankpin 3 is bent. The problem that stress concentrates in the recessed portions 7 and 7 provided at the base of the crank pin 3 is exposed.

Japanese Patent Publication No. 60-564

  The present invention has been made in order to overcome the above-described disadvantages. A thin portion is formed in a crank arm provided at both ends of the crank pin, and an explosion load of a piston is applied to the crank pin by the thin portion. Even in such a case, due to the presence of the thin-walled portion, the crank arm bends to disperse the stress, which causes stress concentration of both bending stress and torsional stress at the connecting portion of the crank pin and the crank arm. An object of the present invention is to provide a crankshaft capable of avoiding the above.

  In order to achieve the above object, the invention specified in claim 1 of the present application is a crankshaft having a crankpin that pivotally supports a connecting rod, a crank journal, and a crank arm that connects between the crankpin and the crank journal. The crank arm is provided with a thrust receiving portion concentric with the crank pin along the outer periphery of the crank pin at a connecting portion with the crank pin, and the crank arm side surface of the crank arm includes the crank pin. A thin-walled portion recessed toward the crank journal is formed, and the thin-walled portion is recessed on the crank arm side in a straight line connecting at least the outer periphery of the thrust receiving portion of the crank pin and the outer periphery of the thrust receiving portion of the crank journal. It is characterized by that.

  According to the invention specified in claim 1, when a load is applied to the crankpin by the reciprocating motion of the piston, the crank arm itself is bent by the thin portion provided in the crank arm to disperse the stress. This makes it possible to avoid concentration of two stresses, bending stress and torsional stress, generated between the crankpin and the crank arm. As a result, the life of the crankpin can be extended and a highly reliable crankshaft can be obtained.

  The invention specified in claim 2 is characterized in that, in the crankshaft according to claim 1, the thin portion is provided over the entire width of the crank arm in a direction orthogonal to the crankpin axis.

  According to the invention specified in claim 2, since forging is possible, there is an effect that the manufacturing cost can be further reduced.

  According to a third aspect of the present invention, in the crankshaft according to the first or second aspect, a counterweight is provided integrally with the crank arm, and the counterweight crosses the counterweight. It is characterized by providing a lightening part.

  According to the invention specified in claim 3, when a load is applied to the crankpin by the reciprocating motion of the piston, the stress is dispersed by the thin portion provided in the crank arm, and the counterweight also contributes to the dispersion of the stress. In addition, the weight is reduced.

  Even when a stress such as an engine explosion load is applied to the crank pin, the stress can be dispersed by the bending of the thin portion provided in the crank arm. That is, it is possible to avoid stress concentration without applying bending stress and torsional stress to the connecting portion between the crankpin and the crank arm.

FIG. 1 is a front view of a crankshaft according to the present embodiment. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a partially omitted front view of a state in which a thin portion is formed between the crank pin and the thrust receiving portion of the crank arm. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a partially omitted front view showing a state where a thin wall portion is formed on a crank arm without a counterweight. FIG. 6 is a partially omitted front view illustrating the height and depth of the thin portion provided in the crank arm. FIG. 7 is a graph showing a stress ratio based on the height of the thin portion. FIG. 8 is a graph showing a stress ratio based on the depth in the thin-walled portion. FIG. 9 is a graph showing the stress ratio based on the width of the thin portion.

  Next, preferred embodiments of the crankshaft according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a front view of a crankshaft according to the present embodiment, and FIG. 2 is a sectional view taken along line II-II in FIG.

  The crankshaft 10 according to the present embodiment includes a first crank arm 12 and a second crank arm 14 that is disposed opposite to the first crank arm 12 with a predetermined distance therebetween. The first counterweight 16 is integrally formed, and the second counterweight 18 is integrally formed on the second crank arm 14. A first crank pin 20 is provided between the first crank arm 12 and the second crank arm 14. A crank journal 22 is provided by displacing the shaft center of the first crankpin 20, and a third crank arm 24 is connected to the crank journal 22, and a second crank arm 26 is connected to the second crank arm 26. A crankpin 28 is provided. In the same manner, the crankshaft 10 is configured by extending from the front side to the transmission side in the order of the crank journal, the crank arm, and the crankpin in accordance with the number of cylinders of the engine.

  By the way, in the configuration as described above, the first thrust receiving portion 40 is formed between the first crank arm 12 and the first crank pin 20 and between the first crank pin 20 and the second crank arm 14. The As can be easily understood from FIG. 1, the first thrust receiving portion 40 is formed in a planar shape perpendicular to the axis of the first crankpin 20. The first thrust receiving portion 40 receives a displacement in the thrust direction of a large diameter portion of a connecting rod (not shown), and is substantially concentric with the axial center of the first crankpin 20 as shown in FIG. It is a perfect circle.

  On the other hand, a second thrust receiving portion 42 is formed on the outer surface of the first crank arm 12 so as to be concentric with the crank journal 22. This is for receiving a journal bearing (not shown). The second thrust receiving portion 42 is formed in a planar shape orthogonal to the axis of the crank journal 22. The second thrust receiving portion 42 has a substantially perfect circle shape concentric with the crank journal 22.

  In the above configuration, an imaginary line A is drawn between the outer peripheral edge 40a of the first thrust receiving part 40 and the outer peripheral edge 42a of the second thrust receiving part 42 (see FIG. 3). A thin portion 50 is provided on the first crank arm 12 side in the imaginary line A and the axis B of the crank journal 22. The thin-walled portion 50 is curved from the end of the flat surface 40b that is perpendicular to the axis B after the outer peripheral edge 40a terminates, and is recessed toward the first crank arm 12, and is continuous with the flat surface 12b that is parallel to the flat surface 40b. As can be easily understood from FIG. 2, the thin-walled portion 50 has its linear upper end 50 a as close as possible to the outer peripheral edge 40 a of the first thrust receiving portion 40, and in some cases, the first thrust receiving portion It may be a tangent line of 40 outer peripheral edges 40a. If comprised from the above structure, the shape of the cross-sectional step shape for stress distribution will be formed by the said plane 40b, the thin part 50, and the plane 12b so that it may mention later.

  On the other hand, the lower end portion 50b of the thin portion 50 is linear and slightly shifted from the axis B of the crank journal 22 to the first crank pin 20 side. That is, it will be easily understood that the thin portion 50 extending from the upper end portion 50a to the lower end portion 50b crosses the first crank arm 12 in a direction orthogonal to the axis of the first crankpin 20. In the first crank arm 12, notches 52 a and 52 b are provided on both sides of the upper end 50 a constituting the thin portion 50. This is for weight reduction.

  In this case, a first counterweight 16 is formed integrally with the first crank arm 12. Therefore, in the present embodiment, the thinned portion 60 extending downward in FIG. 2 is formed from the lower end portion 50b forming the thin portion 50 of the first crank arm 12. Actually, the lightening portion 60 has a shape that passes through the axis B of the crank journal 22 from a part of the first crank arm 12 and is further bent toward the upper side of the first counterweight 16. Similarly to the first crank arm 12, a thin portion 50 is formed on the second crank arm 14, and a thinned portion 60 is formed continuously with the thin portion 50. A lower end portion 60 b of the thinned portion 60 is parallel to the lower end portion 50 b of the thin portion 50. Note that the upper end portion 60 a of the thinned portion 60 overlaps with the lower end portion 50 b of the thin portion 50.

  Here, as shown in FIG. 1, the first counterweight 16 and the second counterweight 18 as described above are not provided in the third crank arm 24 and the fourth crank arm 26. Therefore, these are not provided with the thinned portion 60. That is, only the thin portion 50 is provided. This is shown in FIG.

  4, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, detailed description thereof is omitted, and the same applies to other drawings. Reference symbol C indicates the axis of the first crankpin 20.

  The crankshaft 10 according to the present embodiment is basically configured as described above. Next, the operation and effects thereof will be described.

  In the crankshaft 10 incorporated in an engine (not shown), when the engine performs a combustion process, a reciprocating motion of a piston (not shown) is transmitted to the first crankpin 20 via a connecting rod (not shown). Since the crank journal 22 and the first crankpin 20 are eccentric to each other, the reciprocating motion of the piston is converted into rotational motion by the first crankpin 20, which is the front side of the crankshaft 10, The rotary motion is transmitted to the mission side, and is used for various purposes, for example, for use in traveling or cooling water for cooling.

  By the way, according to the present inventor, in the peripheral corner portion of the first crankpin 20 as described above, the place where the stress concentration is most likely to occur due to the operation caused by the explosion load of the engine is the first crankpin. 20 is within the region of the phantom line A connecting the outer peripheral edge 40a of the first thrust receiving portion 40 and the outer peripheral edge 42a of the second thrust receiving portion 42 of the crank journal 22, and stress concentration occurs over a predetermined range within that region. To do. Therefore, by thinning the portion where the stress is concentrated, when an engine explosion load is applied to the first crank pin 20 via the connecting rod, the thin portion is bent, and as a result, the stress is distributed. It was found that this is possible.

  On the other hand, according to the prior art described in Patent Document 1, the balance weight 4 in the vicinity of the axial center of the journal 1 where the stress concentration occurs most is formed with a considerably large thickness. The stress concentration on the part cannot be reduced.

  According to the present invention, since the crankshaft 10 is a rotating body, the explosion load transmitted to the first crankpin 20 is first bent toward the first crankpin 20 as bending stress and torsional stress due to the reciprocating motion of the piston. In this case, since the flat surface 12b extends to the vicinity of the axis B of the crank journal 22 together with the thin wall portion 50 provided across the first crank arm 12, the stress distribution is sufficiently achieved. That is, as the thin portion 50 is bent, the stress is dispersed and does not concentrate in one place. Therefore, the presence of the thin-walled portion 50 has solved the problem of stress dispersion, which is a disadvantage of the prior art.

  In addition, the thickness reduction part 60 of the 1st counterweight 16 provided in a row by the said 1st crank arm 12 contributes to weight reduction, and the effect which can further diffuse the stress transmitted from the thin part 50 is acquired. .

  Here, the thin-walled portion 50 is formed into an arc-shaped groove that crosses the first crank arm 12, so that it is suitable when a die is inserted and forged from both sides of the thin-walled portion 50. Therefore, from this point of view, in FIG. 2, if both sides of the upper end portion 50a of the thin-walled portion 50 are gently inclined upward, it is suitable for die cutting of a forging die. Similarly, both sides of the lower end portion 50b of the thin wall portion 50 may be gently inclined downward from each other, and the gently inclined shapes on both sides are provided on both the upper end portion 50a and the lower end portion 50b. , They may be separated from each other.

  FIG. 5 is different only in that the first crank arm 12 does not include a counterweight. In this case, similarly to the first embodiment, the stress due to the explosion of the piston is dispersed by the thin portion 50.

  On the other hand, although not shown in relation to the structure shown in FIGS. 2 and 4, the axis C of the first crankpin 20 and the crank journal 22 are replaced by the thin portion 50 crossing the first crank arm 12. A thin portion 50 for stress distribution may be partially provided on the first crank arm 12 on a straight line connecting the axis B. This is effective for stress distribution at locations where explosive stress is applied locally.

  FIG. 6 is a partially omitted front view illustrating the relationship between the height H and the depth D of the thin portion 50.

  FIG. 7 shows a height H from the axis B of the crank journal 22 to the upper end 50a of the thin portion 50. In FIG. 7, the right end of the graph indicates that the upper end portion 50 a of the thin portion 50 is in contact with the outer peripheral edge 40 a of the first thrust receiving portion 40. As the height H decreases, the bending stress increases after increasing once, while the torsional stress decreases rapidly after being stably dispersed. It is optimal that the upper end portion 50 a is in contact with the outer peripheral edge 40 a of the first thrust receiving portion 40.

  FIG. 8 is a result of measuring the distance of the plane 12b between the plane 40b of the outer peripheral edge 40a of the first thrust receiving portion 40 and the lower end 50b of the thin portion 50, that is, the distance between planes parallel to each other as the depth D. is there. Since the torsional stress increases as the depth D decreases, a value that reduces both stresses is preferable. For this reason, a depth of about 30% of the thickness of the first crank arm 12 and the second crank arm 14 is preferred. It is optimal that it is.

  FIG. 9 relates to the width W of the thin portion 50 (see FIG. 2). In FIG. 9, the left end of the graph shows the case where there is no thin portion 50, and the right end shows the case where the thin portion 50 is present over the entire width of the crank arm. It is optimal to form the thin portion 50 over the entire width of the crank arm.

  The present invention has been described with reference to the preferred embodiment, but the present invention is not limited to this embodiment, and it goes without saying that various modifications can be made without departing from the scope of the present invention. Yes.

DESCRIPTION OF SYMBOLS 10 ... Crankshaft 12 ... 1st crank arm 14 ... 2nd crank arm 16 ... 1st counterweight 18 ... 2nd counterweight 20 ... 1st crankpin 22 ... Crank journal 40 ... 1st thrust receiving part 42 ... 2nd thrust Receiving part 50 ... Thin part 60 ... Meat extraction part

Claims (3)

A crankshaft having a crankpin that supports a connecting rod, a crank journal, and a crank arm that connects between the crankpin and the crank journal;
The crank arm is provided with a thrust receiving portion concentric with the crank pin along the outer periphery of the crank pin at a connecting portion with the crank pin,
A thin portion recessed toward the crank journal side is formed on the side of the crank pin of the crank arm,
The crankshaft is characterized in that the thin-walled portion is provided so as to be recessed toward the crank arm side in a straight line connecting at least the outer peripheral edge of the thrust receiving portion of the crank pin and the outer peripheral edge of the thrust receiving portion of the crank journal. The crankshaft according to claim 1, wherein
The crankshaft characterized in that the thin-walled portion is provided over the entire width of the crank arm in a direction orthogonal to the crankpin axis. The crankshaft according to claim 1 or 2,
A crankshaft characterized in that a counterweight is provided integrally with the crank arm, and a thinning portion that crosses the counterweight is provided in the counterweight.

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