JP2005172032A - Crankshaft structure for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crankshaft structure for an internal combustion engine capable of reducing mechanical loss caused by oil droplets floating in a crankcase. <P>SOLUTION: The crankshaft structure for an internal combustion engine has a counterweight 11 equipped with a balance weight section 11a which is formed on the opposite side of a crankpin 12. The counterweight 11 has a counterweight complement section 14 which approximately makes the counterweight 11 round around a crankshaft rotary shaft O as well as the balance weight section 11a and is lightweight in unit mass rather than the balance weight section 11a. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to the structure of a crankshaft of an internal combustion engine.

The crankshaft has a balance weight part to balance the combustion pressure and the inertial force generated by reciprocating parts such as pistons and connecting rods for each cylinder and reduce the stress and vibration of the crankshaft during rotation. A counterweight is formed. However, since the crankshaft rotates at a high speed, the air resistance received by the counterweight is large. Therefore, conventionally, an attempt has been made to reduce the air resistance during rotation of the crankshaft by making the cross-sectional shape along the rotation direction of the counterweight streamlined (see Patent Document 1).
Japanese Utility Model Publication No. 5-27330

  However, if the shape of the counterweight is such a shape, the calculation of the weight balance becomes very complicated, and the design of the shape of the counterweight becomes difficult, which is not realistic.

  Further, in order to achieve streamline, the outer edge portion of the counterweight must be thinned, so the moment is greatly reduced. In order to cover it, other parts must be thickened, resulting in an increase in the overall weight, leading to a reduction in output and fuel consumption.

  Furthermore, although oil droplets float and fill in the crankcase, mechanical loss occurs when the oil droplets collide with the rotating counterweight.

  The present invention has been made paying attention to such conventional problems, and provides a crankshaft structure of an internal combustion engine that can reduce mechanical loss due to oil droplets floating in the crankcase. The purpose is that.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention is a crankshaft structure of an internal combustion engine having a counterweight (11) having a balance weight portion (11a) formed on the opposite side of the crankpin (12) across the crankshaft rotating shaft O, The counterweight (11) has a counterweight (11) having a substantially circular shape together with the balance weight portion (11a) with the crankshaft rotation axis O as the center, and the counterweight is lighter in unit mass than the balance weight portion (11a). It has a complement part (14), It is characterized by the above-mentioned.

  According to the present invention, the crankshaft has a counterweight complementary portion that is formed in a side portion of the crankpin and the crankshaft rotation shaft in the direction of the crankshaft rotation axis and makes the counterweight substantially circular together with the balance weight portion. Even if it rotates, the position of the entire counterweight including the counterweight complementary member in the crankcase does not change. Therefore, the air resistance received as a whole of the counterweight is extremely small, and at the same time, oil droplets floating in the crankcase can be prevented from colliding with the counterweight, and mechanical loss due to collision of oil droplets is reduced. It can be done.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.
(First embodiment)
FIG. 1 is a view showing a first embodiment of a crankshaft structure of an internal combustion engine according to the present invention, FIG. 1 (A) is an enlarged side view of a part of the crankshaft, and FIG. 1 (B) is FIG. FIG. 1C is a cross-sectional view taken along the line CC in FIG. 1B, and FIG. 1D is a cross-sectional view taken along the line D-O-D in FIG. 1B. Point O is the rotation center (rotation axis) of the crankshaft.

  The crankshaft 10 includes a counterweight 11, a crankpin 12, a crank journal 13, and a counterweight complement member 14.

  As shown in FIG. 1B, the counterweight 11 has a balance weight portion 11a formed on the opposite side of the crankpin 12 with the crankshaft rotating shaft O interposed therebetween. The counterweight 11 is formed with a screw hole 11c in the outer edge portion 11b. In the present embodiment, two screw holes 11c are formed on each of the left and right side surfaces. The counterweight 11 has a constant thickness as shown in FIG.

  The counterweight complement member 14 is formed separately from the balance weight portion 11a by a material (for example, resin) that is lighter than the balance weight portion 11a, and is screwed to the balance weight portion 11a. As shown in FIG. 1 (B), the counterweight complement member 14 is attached to the outer edge portion 11b of the side portion of the crankpin 12 and the crankshaft rotating shaft O, and the counterweight 11 is attached to the crankshaft together with the balance weight portion 11a. A substantially circular shape around the rotation axis O is used. For this reason, even if the crankshaft 10 rotates, the position of the entire counterweight including the counterweight complementary member 14 in the crankcase does not change. It is possible to prevent oil droplets floating on the counterweight 11 from colliding with the counterweight 11. The counterweight complement member 14 is made of a material (for example, resin) that is lighter than the balance weight portion 11a, so that the weight balance by the counterweight 11 is not lost. The counterweight complementary member 14 is screwed into the screw hole 11 c of the counterweight 11 by a male screw 15. The counterweight complementary member 14 is a solid plate-like member having substantially the same thickness as the counterweight 11 as shown in FIG. 1 (D), and a hole portion 14a for inserting the male screw 15 is formed in a part thereof. (See FIG. 1D). Thus, the counterweight 11 (balance weight portion 11a) has a substantially constant thickness, and the counterweight complement member 14 has substantially the same thickness as the counterweight 11 (balance weight portion 11a). The required performance (namely, weight balance performance) is not lowered.

  Next, the effect of this embodiment will be described.

  For comparison, a conventional crankshaft structure of an internal combustion engine will be described with reference to FIG. 4A is an enlarged side view of a part of the crankshaft, FIG. 4B is a cross-sectional view taken along the line BB in FIG. 4A, and FIG. 4C is a cross-sectional view taken along the line CC in FIG. FIG. In the following description, the same reference numerals are given to portions that perform the same functions as those in the first embodiment, and a duplicate description is omitted.

  As shown in FIG. 4B, the balance weight portion 11a of the counterweight 11 has a fan shape or a similar shape thereto. When the crankshaft 10 rotates around the point O, the outer edge portion 11b (shown by a thick line in the figure) of the counterweight 11 receives air resistance. As a countermeasure, in the invention described in the above-mentioned Japanese Utility Model Laid-Open No. 5-27330, the cross-sectional shape along the rotation direction of the counterweight is made streamlined. However, although oil droplets float and fill in the crankcase, the oil droplets collide with the rotating counterweight, resulting in mechanical loss.

  Therefore, in the present embodiment, the counterweight complementing member 14 that makes the counterweight 11 substantially circular together with the balance weight portion 11a is screwed to the outer edge portion 11b of the side portion of the crankpin 12 and the crankshaft rotation axis O. By doing so, the air resistance received by the counterweight 11 during rotation of the crankshaft 10 is reduced, and oil droplets floating in the crankcase are prevented from colliding with the counterweight 11. Can do. Therefore, mechanical loss due to collision of oil droplets can be reduced.

  The inventors of the present invention have demonstrated the above effect by experiments. The experimental results are shown in FIG. FIG. 2 shows the experimental results using a V-type 6-cylinder gasoline engine, and is a diagram showing the mechanical loss (vertical axis) when the engine speed (horizontal axis) is changed. In the figure, the solid line indicates the case where the counterweight complementary member is screwed (that is, the product of the present invention), and the broken line indicates the case where the counterweight complementary member is removed (that is, the conventional product).

  As can be seen from FIG. 2, the effect of reducing the mechanical loss is particularly remarkable in the high rotation range, and the product of the present invention can reduce the mechanical loss by 2 to 7% compared to the conventional product. did it.

(Second Embodiment)
FIG. 3 is a view showing a second embodiment of the crankshaft structure of the internal combustion engine according to the present invention, FIG. 3 (A) is an enlarged side view of a part of the crankshaft, and FIG. 3 (B) is FIG. 3 (A). 3C is a cross-sectional view taken along the line CC in FIG. 3B, and FIG. 3D is a cross-sectional view taken along the line D-O-D in FIG. 3B. Point O is the rotation center (rotation axis) of the crankshaft.

  As shown in FIG. 3B, the counterweight 11 of the present embodiment is formed so that its outer shape is a circle centered on the rotation center O of the crankshaft. The counterweight 11 is a solid balance weight portion 11a in order to balance the weight on the opposite side of the crankpin 12 across the crankshaft rotation axis (rotation center) O (see FIG. 3C). 3) As shown in FIG. 3B, both side portions of the crankpin 12 are thinned to form hollow portions 11e. The hollow portion 11e is closed by a lid plate 11f. The cover plate 11 f is screwed into the screw hole 11 c of the counterweight 11 with a male screw 15. The counterweight 11 is recessed in accordance with the lid plate 11f, and the lid plate 11f is fitted in the recess, and there is no substantial step between the lid plate 11f and the counterweight 11. The top of the male screw 15 is also screwed in so that there is no substantial difference from the counterweight 11. A portion including the hollow portion 11e and the cover plate 11f is a counterweight complement portion.

  Thus, since the counterweight 11 is circular and the hollow portion 11e is formed, the counterweight 11 not only has the performance inherently required for the counterweight 11 (ie, weight balance performance), but also oil during crankshaft rotation. Mechanical loss due to droplet collision can be reduced.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea, and it is obvious that these are equivalent to the present invention.

  For example, in each of the above embodiments, the counterweight complement member 14 and the cover plate 11f are screwed, but the fixing method is not limited to such screwing. An adhesive may be used, or may be fixed by welding. In each of the above embodiments, the thickness of the entire counterweight is substantially constant. However, the shape of the counterweight is not limited to this, and the position of the entire counterweight in the crankcase is determined by the rotation of the crankshaft. Any shape that does not change, that is, a rotating body shape having the crankshaft rotation axis as the central axis may be used.

1 is a diagram showing a first embodiment of a crankshaft structure of an internal combustion engine according to the present invention. It is a figure which shows the experimental result explaining an effect. It is a figure which shows 2nd Embodiment of the crankshaft structure of the internal combustion engine by this invention. It is a figure which shows the crankshaft structure of the conventional internal combustion engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Crankshaft 11 Counterweight 11a Balance weight part 11b Outer edge part 11c Screw hole 11d Contour line 11e Hollow part 11f Cover plate 12 Crankpin 13 Crank journal 14 Counterweight complementary member

Claims (5)

A crankshaft structure of an internal combustion engine having a counterweight provided with a balance weight portion formed on the opposite side of the crankpin across the crankshaft rotating shaft,
The counterweight has a counterweight complement that is substantially circular with the balance weight part around the crankshaft rotation axis, and has a unit mass that is lighter than the balance weight part.
A crankshaft structure for an internal combustion engine. The counterweight complement portion is formed separately from the balance weight portion by a material that is lighter than the balance weight portion, and is fixed to the balance weight portion.
The crankshaft structure for an internal combustion engine according to claim 1. The counterweight complement portion is a portion including a hollow portion formed in a part of the counterweight.
The crankshaft structure for an internal combustion engine according to claim 1. The balance weight part has a substantially constant thickness,
The counterweight complement is approximately the same thickness as the balance weight.
The crankshaft structure for an internal combustion engine according to any one of claims 1 to 3, wherein the structure is a crankshaft structure. Crankshaft structure of an internal combustion engine having a counterweight composed of a balance weight portion formed on the opposite side of the crankpin across the crankshaft rotating shaft and a counterweight complement portion whose unit mass is lighter than the balance weight portion Because
The counterweight has an external shape that is axisymmetric with respect to the rotation axis of the crankshaft.
A crankshaft structure for an internal combustion engine.

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