WO2007138205A1

WO2007138205A1 - Track rod for the crank drive of a motive power group and crank drive including such track rod

Info

Publication number: WO2007138205A1
Application number: PCT/FR2007/051216
Authority: WO
Inventors: Guillaume Rymer; Olivier Sauvage
Original assignee: Peugeot Citroën Automobiles SA
Priority date: 2006-05-29
Filing date: 2007-05-04
Publication date: 2007-12-06
Also published as: FR2901585B1; FR2901585A1; EP2021600A1

Abstract

The invention concerns a track rod for the crank drive of a motive power group and a crank drive including such track rod. The invention involves a track rod, articulated between an initial linking pin connected to a piston and a second linking pin connected to a crank pin of a crankshaft, includes an interior chamber, featuring stops boarding the sides of the chamber, perpendicular to the longitudinal axis of the track rod, in which a pit houses said linking pins and designed to move in relation to the body of the track rod.

Description

Connecting rod for a mobile coupling of a powertrain and mobile coupling comprising such a connecting rod.

The present invention claims the priority of the French application 0651929 filed on May 29, 2006 whose content (description, claims and drawings) is incorporated herein by reference.

The invention relates to powertrains, including those fitted to motor vehicles. More specifically, the invention relates to the movable coupling constituted by all the pistons, connecting rods and crankshafts set in motion during operation of an internal combustion engine.

[0003] The control of radiating noise both inside and outside the vehicle is a problem whose importance has increased in recent years. However, among the sources of vibration, and therefore of noise, include the noise resulting from combustion, perceived as a "slam", most often with an unpleasant connotation.

In practice, the so-called combustion noise has as its main source the violent explosions of the gases contained in the cylinders. These explosions generate impulsive forces, transmitted to the various casings of the motor base via the mobile coupling, and are particularly noticeable on the engines with self - controlled ignition, hence the "coloration" very specific to the noise of a vehicle said Diesel.

To minimize this clacking noise, the strategies employed are most often aimed at reducing the violence of the combustion process, in particular by developing appropriate injection strategies, typically developed on engine benches. However, a compromise must be established between acoustic approval and engine performance, both from the point of view of fuel consumption and that of pollutant emissions.

It would therefore be desirable to have means to control this click noise without having to change the combustion process.

The invention therefore relates to a means for limiting the transmission, by the movable coupling, of the pulses generated by the combustion explosions.

This object is achieved according to the invention by the use of a rod articulated on the axis of a piston and on the axis of a crankpin, this connecting rod having an inner chamber in which is disposed a core that can move relative to the body of the connecting rod, the core having a housing for one of the connecting axes. The inner chamber is also provided with axial stops which limit the movements of the core along the axis of the body of the connecting rod and above all are capable of damping at least part of the energy released by the impacts caused by the engine explosions. while maintaining the transmission function of the connecting rod.

With such a connecting rod, the mobile coupling can participate in the control of engine vibration, and thus the reduction of "slam".

[001 0] The invention is particularly applicable to diesel engines but can in fact be applied to any type of engine equipped with a movable coupling comprising a connecting rod.

[001 1] Other details and advantageous features of the invention emerge more particularly from the description of an embodiment of the invention given below with reference to the figures which represent:

• Figure 1: a skinned showing the main components of a mobile equipment associated with an internal combustion engine; • Figure 2: a sectional view of a connecting rod according to the principle of the invention.

• Figure 3: a sectional view of a connecting rod according to a first embodiment of the invention;

• Figure 4: a sectional view of a connecting rod according to a second embodiment of the invention; • Figure 5: a sectional view of a connecting rod according to a third embodiment of the invention.

A conventional moving assembly, as illustrated in FIG. 1, allows the transmission of the reciprocating rectilinear motion of the piston to the motor shaft. This crew consists mainly of a rod 1. The small end 2 is articulated on the axis 3 of a piston 4. Optionally, a connecting rod 5 is interposed between the axis 3 and the small end 2. The central portion of the connecting rod, typically thinned relative to the small end 2 and especially to the connecting rod head 6, is the connecting rod body, substantially oblong and admitting a longitudinal axis of symmetry also called connecting rod.

The connecting rod head 6 is articulated around a crank pin 7 of the crankshaft 8. A crankshaft bearing 9 is interposed between the connecting rod head 6 and the crank pin 7.

In this Figure 1, there is also shown for the record a few balancing masses 10. At the end of the shaft 11 is disposed a flywheel, in this figure simply evoked by the fastener 12.

[001 5] Returning to the rod 1, it may be noted that the head is in fact made of two parts, including a reported portion 13, said head cap, attached to the rest of the connecting rod by head screws.

[001 6] The connecting rod is well articulated on two axes of connection, in this case, the axis of the piston and the axis of the crankpin. In general, the connecting rod, or more precisely all the mobile coupling, is designed as a mechanically rigid assembly, this to meet its primary function of transmitting the forces of the piston to the motor shaft, and this throughout the cycle of engine life. Under these conditions, it is clear that this set will also transmit all the vibrations considered as parasites like those generated by the explosions at each combustion cycle.

[001 7] Such is no longer the case with a connecting rod according to the invention which allows to dissipate the very first solidian transfers caused by the shocks due to explosions which determine the impulsiveness of the snapping noise, while now a sufficient rigidity to ensure the primary function of the movable coupling, namely the transmission to the crankshaft of the forces created by the combustion on the piston.

[001 8] Figure 2 schematically illustrates the principle of a connecting rod according to the invention. This connecting rod is essentially constituted by an oblong body admitting a longitudinal axis of symmetry 21. The connecting rod head 22 is provided with a housing 23 for the axis of a piston and is therefore very similar to the conventional rod head illustrated in FIG. 1.

By cons, at the small end of the rod, the rod according to the invention comprises an inner chamber 24. This chamber 24 is lined on the one hand by a core 25 - provided with a housing 26 for articulation on a crankpin, and secondly abutments 27 which limit the movement of the core

25 in the direction of the longitudinal axis 21. In the embodiment shown here, guide means in translation of the core are provided, consisting of grooves dug in the body of the rod in which are slid members of the core forming behind the scenes 28.

In the following figures, references identical to those of Figure 2 were used for the unmodified elements whose description will not be repeated for the sake of clarity.

Figure 3 illustrates another means for ensuring the guiding in translation, consisting in providing studs 29 integral with the body of the connecting rod and associated with drums 30 formed in the core. The maximum displacement amplitude of the core in the inner chamber of the connecting rod can be adjusted by adjusting the length of the drums, the studs coming to a stop in the bottom of the drums when the core has reached its maximum amplitude of translation. Advantageously, the ends of the studs penetrating the barrels have the shape of a pointed cone, thus making it possible to create a stiffness of progressive contacting when the bolt comes into contact with the bottom of the barrel, thus contributing to a function of shock absorption.

The environment of the connecting rod must of course be taken into account for the realization of stops and the core. First, these elements must be even to withstand the temperatures at which the rods are subjected, which assumes materials capable of withstanding a temperature of the order of 150 ⁰ C, which in practice excludes elastomeric type materials without excluding all plastics. Furthermore, it should be emphasized that the stresses on a connecting rod are considerable, the pressure in the rolls being able to reach, for example, values of the order of 180 bars.

A material such as aluminum may be suitable, especially for producing the core. For the realization of stops, it is possible to use so-called rigid plastics having a Young's modulus of about 10 GPa which advantageously have a higher elastic limit than aluminum. It is still possible, according to another embodiment of the invention, to make abutments made of aluminum-based composites or metal braids.

The stops may also be constituted by an assembly of springs, Belleville washers, hydroelastic wedges according to the principle of those used for example for the suspension of an engine to a motor vehicle body.

In one embodiment illustrated in Figure 4, the stops are constituted by a series of fins s' straddling into each other, one 31 associated with the core and the other 32 to the body of the rod, as for a splice assembly. The faces of the fins are interconnected by a material of the "glue" type 33 which will shear when the core moves in translation relative to the connecting rod body, thus allowing the shock absorption and vibrations due to engine explosions. The "glue" is for example constituted by a material with elastic behavior, or preferably viscoelastic, such as an elastomer, a polymer or a polyamide, whose properties will be adapted to the engine temperature.

This embodiment also makes it possible to introduce a strong overall stiffness between the core and the connecting rod body when the mobile frame is at the end of the stroke and the viscoelastic layers have a shear. maximum. Indeed, when this case occurs, the ends of the fins associated with the core come into contact with the connecting rod body (and conversely, the fins of the connecting rod body abut on the core) and it is therefore the rigidity of the fins which characterizes the overall stiffness of the connecting rod. To make this stiffness more progressive depending on the position in abutment of the core fins may have slightly different lengths which allows better shock absorption.

Another embodiment is illustrated in Figure 5, wherein the stops consist essentially of friction dampers.

In this case, the stops consist essentially of plates 34, integral with the core and moving inside the chamber 35, to abut on buffer elements 36. The chamber is also filled with a viscous fluid which circulates around the plate 33 and through holes 36. The buffer elements 36 allow to maintain a significant but progressive stiffness between the core and the body of the connecting rod, stiffness necessary for the transmission of the piston force .

The viscous fluid used is for example oil or other viscous fluid compatible with this environment. It can be emphasized that the size and the number of bores 36 make it possible to optimize the viscous damping capacity of the abutments, as well as the viscosity of the fluid.

In all the description above, the core is disposed around the housing provided for the crankpin. However, the invention is not limited to this embodiment and it is also possible to have the damping means according to the invention arranged around the housing provided for the axis of a piston. Finally, it is also possible to have these means at the top and bottom of the connecting rod, even if, obviously, the realization is then more complex.

Claims

1. Connecting rod for movable coupling of a powertrain, said rod being articulated between a first connecting pin associated with a piston and a second connecting pin associated with a crank pin, and having an inner chamber lined with abutments the faces of the chamber perpendicular to the longitudinal axis of the connecting rod, in which is disposed a core provided with a housing for one of said connecting pins, and capable of relative movement relative to the body of the connecting rod.

2. Connecting rod according to claim 1, characterized in that the core is disposed at the connecting rod head, the housing being for the articulation on a crankpin crankshaft.

3. movable rod according to claim 1, characterized in that the core is disposed at the small end of the rod, the housing being for the articulation of a piston pin.

4. Connecting rod according to any one of the preceding claims, characterized by guide means in translation of the core.

5. Rod according to claim 4, characterized in that said guide means are constituted by a system of grooves dug in the body of the connecting rod.

6. Rod according to claim 4, characterized in that said guide means are constituted by studs.

7. Rod according to one of the preceding claims, characterized in that the stops are constituted by springs.

8. Rod according to one of the preceding claims, characterized in that the stops are constituted by friction dampers.

9. Rod according to one of the preceding claims, characterized in that the stops are constituted by damping shock absorbers fluid.

10. Rod according to any one of the preceding claims, characterized in that the abutments comprise by hydroelastic wedges.

11. Rod according to any one of the preceding claims, characterized in that the stops comprise viscoelastic means.

12. Movable coupling of a combustion engine of a motor vehicle comprising at least one connecting rod according to any one of the preceding claims.