FR2779493A1 - Crankshaft for a three cylinder internal combustion engine - Google Patents

Abstract

The crankshaft consists of cranks (M) and at one end an inertia flywheel (V). This flywheel has a regular circular form and contains a zone in which is realized a removal of material to create a first out of balance force (BV). The crankshaft also contains a zone, axially distant from the flywheel, in which is realized a mass of material creating a second out of balance force (BC2, BC22, BP), the first and second out of balance forces being virtually equal.

Description

1 "Crankshaft especially for internal combustion engine" This

  The invention relates to a crankshaft intended

  especially internal combustion engines.

  The mobile coupling of an internal combustion engine having three cylinders and operating in four stages generates galloping and yawing couples which cause vibrations and untimely wear. To limit these torques, the engine crankshaft is generally associated with a balancing shaft provided with masses at its ends, which rotates at the same speed as the crankshaft but in the opposite direction. This arrangement has the disadvantages of increasing the size of the mobile coupling, increasing friction and

  have a high production cost.

  The object of the present invention is to reduce the drawbacks

  above by proposing a crankshaft of particular structure.

  The crankshaft according to the invention, in particular for an engine,

  includes cranks and, at one end, a flywheel.

  According to the invention, said flywheel, which has a regular circular shape, comprises an area in which material is removed creating a first unbalance. The crankshaft further comprises an area, axially distant from said flywheel, in which an addition of material is created creating a second unbalance, said

  first and second unbalances being substantially equal.

  According to the invention, the crankshaft comprises a pulley at its other end, which has a regular circular shape and which can advantageously include an area from which said said is made.

  addition of material constituting said second unbalance.

  According to the invention, said addition of material constituting said second unbalance can advantageously be carried out in the area of its cranks. According to the invention, said addition of material may advantageously comprise a first part made in the area of its cranks and a second part made in an area of a 1 pulley provided at its other end, the sum of the unbalances created by these first and second parts added with material being substantially

equal to said first imbalance.

  Insofar as the crankshaft comprises three cranks, said second unbalance can advantageously be produced at least partially in the area of its central crank and / or its crank (M3)

the farthest from said steering wheel.

  According to the invention, the crankshaft preferably comprises counterweights for balancing said cranks, these counterweights and said unbalances being in the same radial plane angularly offset by 30

  relative to the crank closest to said flywheel.

  The present invention will be better understood from the study of a crankshaft of an internal combustion engine with three cylinders, described by way of nonlimiting example and illustrated by the drawing in which: FIG. 1 represents, in perspective, a schematic view of a crankshaft according to the present invention; - Figure 2 shows a schematic end view of the crankshaft of Figure 1; - Figure 3 shows an end view of a flywheel of the aforementioned crankshaft; - Figure 4 shows a radial section of the steering wheel of Figure 3; - And Figure 5 shows a perspective view of a pulley

of the aforementioned crankshaft.

  Referring mainly to Figures 1 and 2, we see that the crankshaft 1 shown comprises, in the direction of its horizontal axis xx 'three cranks M1, M2 and M3, U-shaped, which are angularly offset to 120 and intended for receive connecting rods on their central branches parallel to the axis xx ', and which are formed between

  successively axial pins T1, T2, T3 and T4.

  At its ends, the crankshaft 1 has a flywheel V located at the end of the journal T1 and a pulley P located at the end

of T4 pin.

  1 In the extension of the radial branches of the cranks M1 and M3, the crankshaft has radial extensions which constitute balancing counterweights respectively identified by the references

(C1, C11) and (C3, C33).

  These counterweights are arranged in the same plane passing through the axis xx 'situated at 30 relative to the plane passing through the axis xx' of the crank Ml1, so that the counterweights (C1, CHl) are opposite of the crank M1 and that the counterweights (C3, C33) are diametrically opposite the counterweight (C1, C11), on the same side as the

MI crank.

  As seen more particularly in FIGS. 3 and 4, the flywheel V has a regular circular shape and has an area in which a peripheral recess E is produced by removal of material, which creates an imbalance BV in its part

diametrically opposite.

  Referring to Figure 5, we see that the pulley P has a regular circular shape and includes an area in which is made an addition A of material creating an unbalance BP in its part

diametrically opposite.

  Returning to Figures 1 and 2, we see that in the extension of the branches of the central crank M2, the crankshaft has extensions which are understood radially in the same direction as the extensions of the crank M3 carrying the counterweights (C3, C33 ) and which carry or constitute additions of material creating unbalances

(BC2, BC22).

  The unbalance BV of the flywheel V, which is much greater than the unbalance BP of the pulley P, should be equal to the sum of the unbalance BP of the pulley P and the resulting unbalance created by the unbalances (BC2,

  BC22) associated with the M2 central crank.

  Thus, the galloping torque likely to appear along the horizontal axis yy 'perpendicular to the axis xx' can be limited and the yaw torque likely to appear along the vertical axis zz 'can be eliminated, thanks to a suitable choice of the aforementioned BV, BP, BC2 and BC22 unbalances. 1i According to variant embodiments, the aforementioned unbalances BP, BC2 and BC22, which are distant from the unbalance BV provided on the flywheel V, could be associated with the crank M3, the crank M2 and the crank M3, and / or to pulley P.

Claims (6)

1 CLAIMS   1. Crankshaft, in particular for an engine, comprising cranks (M) and, at one end, a flywheel (V), characterized in that said flywheel, which has a regular circular shape, comprises an area in which is carried out a removal of material creating a first unbalance (BV), that it comprises a zone, axially distant from said flywheel, in which is carried out an addition of material creating a second unbalance (BC2, BC22, BP), said first and second unbalances being substantially equal.   2. Crankshaft according to claim 1, characterized in that it comprises a pulley (P) at its other end, which has a regular circular shape and which comprises an area of which is   carried out said addition of material (A) constituting said second unbalance (BP).   3. Crankshaft according to claim 1, characterized in that said addition of material constituting said second unbalance (BC2,   BC22) is made in the area of its cranks.   4. Crankshaft according to claim 1, characterized in that said addition of material comprises a first part made in the area of its cranks and a second part made in an area of a pulley provided at its other end, the sum of the unbalances (BC2, BC22, BP) created by these first and second parts added to   material being substantially equal to said first unbalance (BV).   5. Crankshaft according to claim 3 and 4, characterized in that it comprises three cranks, said second unbalance being produced at least partly in the region of its central crank (M2)   and / or its crank (M3) furthest from said flywheel (V).   6. Crankshaft according to one of the preceding claims,   characterized by the fact that it includes balancing counterweights (C) of said cranks, these counterweights and said unbalances being in the same radial plane angularly offset by 30 relative to the crank (M3) closest to said flywheel.