EP4055256A1

EP4055256A1 - Variable-length connecting rod for an engine with a controlled compression ratio

Info

Publication number: EP4055256A1
Application number: EP20817454.0A
Authority: EP
Inventors: René-Pierre BERTHEAU
Original assignee: MCE5 Development SA
Current assignee: MCE5 Development SA
Priority date: 2019-11-04
Filing date: 2020-11-04
Publication date: 2022-09-14
Also published as: WO2021089940A1; FR3102814A1; FR3102814B1; US20230042411A1; FR3102813A1; CN115298426A; KR20220090575A; JP2023500949A

Abstract

The invention relates to a variable-length connecting rod (10) comprising: - A connecting rod head (102), designed to establish a pivot connection with a crankpin of a crankshaft, - A hydraulic circuit (104) for controlling the length of the connecting rod (10), - A system for controlling (110) the hydraulic circuit. The control system (110) comprising: - At least one linear hydraulic slide (111) arranged within a housing of the connecting rod head (102), - At least a first shoe (113) arranged on a sidewall of the connecting rod head (102), suitable for undergoing a bearing force exerted by a controlling member, the bearing force allowing the slide (111) to be moved, - A return means for bringing the slide (111) back to its resting position in the absence of the bearing force, - At least a second shoe (115) arranged on the sidewall of the connecting rod head (102) and suitable for undergoing the bearing force.

Description

ROD WITH VARIABLE LENGTH FOR MOTOR WITH PILOT VOLUMETRIC RATIO

FIELD OF THE INVENTION

The present invention relates to an engine variable compression ratio, implementing a connecting rod whose variable length is controlled.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

Among the solutions making it possible to make the volumetric ratio of an engine variable, those using a connecting rod whose center distance (that is to say the length of the connecting rod) can be controlled. For example, when the connecting rod has a first length, the engine is configured to have a first compression ratio, and when the connecting rod has a second length, the engine is configured to have a second compression ratio.

The connecting rod may be of the telescopic type, as is for example known from US2016237889 or of the eccentric type. In general, the connecting rod is provided with a device, often of a hydromechanical nature, allowing its length to be adjusted.

Whatever shape is chosen, the connecting rod can be configured to allow continuous adjustment of its length, between its first length and its second length, so as to continuously adjust the volumetric ratio of the engine (so-called “continuous rate” connecting rod). Alternatively, the connecting rod can be said to be “bistable” or “bi-rate”: then only its first and its second length form stable positions making it possible to define two engine operating modes, each mode corresponding to a determined compression ratio. The connecting rod can also be “tri-rate”, three defined lengths in this case forming stable positions associated with defined volumetric ratios of the engine.

The control of the connecting rod consists in controlling the hydromechanical device for adjusting its length to a target length, so as to give the engine a set volumetric ratio.

According to a first approach known for example from document US2017089257, the transmission of the instruction is carried out mechanically. For example, the control is obtained by clashing, while the connecting rod is driven by the crankshaft, between an actuator of the adjustment device (for example the spool of a hydraulic distributor) and a control part fixed to the engine crankcase. Collision occurs at very high velocity, and this impact control requires extremely precise positioning of the control part in the engine block, which makes its manufacture particularly complex and expensive. Moreover, this control mode leads to a significant acoustic emission and to rapid wear of the parts which come into contact.

According to another known approach, the transmission of the setpoint is carried out by hydraulic means. Thus, the aforementioned document US2016237889 provides for using the connecting rod bearings lubrication circuit to act on an actuator of the connecting rod length adjustment device. The drawback of this type of hydraulic control is a high inertia to the control and a high sensitivity to the engine speed. OBJECT OF THE INVENTION

The present invention aims to overcome all or part of the aforementioned drawbacks. It relates in particular to a variable-length connecting rod controlled by mechanical transmission, capable of cooperating with an external control member, without shock.

BRIEF DESCRIPTION OF THE INVENTION

The invention relates to a variable-length connecting rod, the body of which extends along a longitudinal axis and comprising:

• A big end, intended to establish a pivot connection, along a transverse axis perpendicular to the longitudinal axis, with a crankpin of a crankshaft,

• A hydraulic circuit for controlling the length of the connecting rod,

• A hydraulic circuit control system.

The piloting system comprises:

• At least one linear hydraulic spool, arranged in a housing of the connecting rod head, and capable of occupying a first rest position and at least a second position, each position making it possible to open or close fluid communication with the circuit. hydraulic,

• At least a first pad disposed on a side of the connecting rod head and integral with one end of the slide, capable of undergoing a bearing force exerted by an annular piloting member, coaxial with the crank pin and external to the connecting rod, said support force allowing the drawer to be moved into the second position,

• A return means, to return the drawer to the first rest position, in the absence of the support force,

• At least one second shoe arranged on the side of the big end and able to withstand the support force. According to other advantageous and non-limiting characteristics of the invention, taken alone or in any technically feasible combination:

- The first and second shoe are arranged so that the barycenter of the forces undergone by the shoes when the bearing force is applied to them is located substantially at the center of the big end;

- at least one of the pads comprises end-of-travel stops, to limit its possible displacement along the transverse axis;

the hydraulic circuit comprises at least two hydraulic chambers, each being connected to the spool by at least one conduit, the chambers being associated with at least one hydraulic piston, the movement of which is capable of modifying the length of the connecting rod along the longitudinal axis; in particular, the chambers being associated with a central piston in the case of a telescopic connecting rod, and the chambers being associated respectively with a first piston and with a second piston in the case of an eccentric connecting rod;

- the (at least one) slide makes it possible, depending on the position it occupies, to establish an oil circulation between a hydraulic chamber and an oil supply, or to establish an oil circulation between a hydraulic chamber and an oil evacuation, or to establish an oil circulation between the two hydraulic chambers, or to block all oil circulation with the two hydraulic chambers;

- The oil supply is configured so as to recover the lubricating oil from the bearings of the big end;

- the (at least one) slide comprises at least one valve making it possible to define the direction of oil circulation;

- the hydraulic circuit comprises a conduit connecting the two hydraulic chambers and provided with a valve making it possible to define the direction of oil circulation;

- The connecting rod comprises a return or push element connected to at least one hydraulic piston; - At least one conduit, connecting a hydraulic chamber and the spool, comprises a shutter device configured to allow the circulation of oil between said hydraulic chamber and the spool when the hydraulic piston reaches a determined position.

BRIEF DESCRIPTION OF THE FIGURES

Other characteristics and advantages of the invention will emerge from the detailed description of the invention which will follow with reference to the appended figures in which:

• Figure la shows a telescopic connecting rod according to the invention;

• Figures 1b and 1c show an eccentric connecting rod according to the invention;

• Figures 2a (exploded view), 2b and 2c show all or part of a control system of a connecting rod according to the invention;

• Figures 3a and 3b show the hydraulic diagram for a "two-rate" operation, without transfer between the chambers of the hydraulic circuit for controlling the length of the connecting rod, respectively of an eccentric connecting rod and of a telescopic connecting rod conforming. to invention;

• Figures 3c and 3d show the hydraulic diagram for a “two-rate” operation, with transfer between the chambers of the hydraulic circuit for controlling the length of the connecting rod, respectively of a connecting rod. telescopic and an eccentric connecting rod according to the invention;

• Figures 4a and 4b show the control system of an eccentric connecting rod according to the invention, and the associated hydraulic diagram for a “two-rate” operation, without transfer between the hydraulic chambers;

• Figures 5a and 5b show the control system of a telescopic connecting rod according to the invention, and the associated hydraulic diagram for "three-rate" operation, with transfer between the hydraulic chambers;

• Figures 5c and 5d show a variant of the control system of a telescopic connecting rod according to the invention, and the associated hydraulic diagram for a “three-rate” operation, with transfer between the hydraulic chambers;

• Figures 6a, 6b and 6c show the control system of an eccentric connecting rod according to the invention, and the associated hydraulic diagram for operation in “continuous rate”, without transfer between the hydraulic chambers;

• Figures 7a, 7b, 7c and 7d show the control system of a telescopic connecting rod according to the invention, and the associated hydraulic diagram for operation in "continuous rate", with transfer between the hydraulic chambers; • Figures 8a, 8b and 8c show control members carried by the crankshaft and configured to cooperate with a connecting rod according to the invention;

• Figure 8d shows the control system of a connecting rod according to the invention cooperating with a control member carried by the crankshaft.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a variable length connecting rod 10 for a piloted compression ratio engine.

Note that the same references in the figures can be used for elements of the same type or performing the same function.

The connecting rod 10 comprises a body 101 extending along a longitudinal axis z. The connecting rod 10 according to the invention can be of the telescopic type (figure la) or of eccentric type (figure lb, lc): a central cylinder mechanism or an eccentric mechanism is then fitted in the body 101 of the connecting rod 10. These mechanisms form part of a hydraulic control circuit 104, included in the connecting rod 10. In the two connecting rod configurations, the hydraulic circuit 104 preferably comprises at least two hydraulic chambers 1041, 1042 associated with at least one hydraulic piston. In particular, the hydraulic chambers 1041,1042 are associated with a central piston 1045 in the case of a telescopic connecting rod (figure la), and the chambers 1041,1042 are respectively associated with a first piston and with a second piston in the case of a telescopic rod. of an eccentric connecting rod (figure le). The modification of the supply, evacuation or circulation of oil in or between these two hydraulic chambers 1041,1042 will induce the displacement of the piston (s) hydraulic (s), which displacement allows the rod length to be modified along the longitudinal axis z.

Advantageously, in the case of the telescopic connecting rod (figure la), preference will be given to a long guide, between the part secured to the small end (body 101) and the part secured to the big end 102, which can be produced from a on the one hand at the level of the piston 1045 and on the other hand at the level of the sliding pivot connection 1048, in order to ensure the absorption of external forces when the connecting rod 10 is inclined and to limit friction or even jamming thereof. As illustrated in FIG. La, the central piston 1045 is held by a nut with a stud extending down to under the bore of the connecting rod small end thus achieving the sliding pivot connection 1048. Furthermore, a double spring with opposite pitch 1049 will be preferred. in order to avoid the creation of an antagonistic couple in the mechanism.

The connecting rod 10 also comprises a connecting rod end 102, intended to establish a pivot connection, along a transverse axis y perpendicular to the longitudinal axis z, with a crankpin 2 of the crankshaft 200 of the piloted volumetric ratio engine. As on a conventional engine, bearings 103 are provided to limit the friction between the big end 102 and crankpin 2.

The connecting rod 10 further comprises a control system 110, intended to control the hydraulic circuit 104; said control system 110 will make it possible to manage the fluidic communication with the hydraulic circuit 104, that is to say to open or close said communication to adjust the circulation of oil between the hydraulic circuit 104 and the outside and / or the circulation of oil in the hydraulic circuit 104. Note that the oil intended to circulate in this hydraulic circuit 104 is that of the engine.

The control system 110 comprises at least one linear hydraulic spool 111, arranged in a housing 112 of the head 102 of the connecting rod 10 (Figure 2a). The piloting system 110 is in fluid connection with the hydraulic circuit 104 by means of at least one duct 104a arranged in the big end 102 and communicating with the housing 112.

The housing 112 is preferably parallel to the transverse axis y. The drawer 111 is cylindrical in shape and has an outside diameter typically between 4 and 6 mm.

Advantageously, the housing 112 has a central section in which the spool 111 is housed, an anterior section 112a in communication with the oil supply 11 and a posterior section 112b, opposite the anterior section 112a (FIGS. 2b, 2c ). In some embodiments described later, the posterior section 112b communicates with the oil drain 12.

The small size of the slide 111 has the advantage of limiting the deformation of its housing 112 when forces are transmitted to the connecting rod 10; it also has the advantage of greater ease of placement of the drawer 111 in the head 102.

There is no provision for sealing between the spool 111 and the housing 112: the leak generated allows a progressive renewal of the oil in the hydraulic circuit 104. The small diameter of the spool 111 makes it possible to better control this leak.

In the embodiments for which the rear section 112b of the housing 112 communicates with the oil outlet 12, the oil resulting from this leak is discharged at said outlet 12, thus avoiding hydraulic compression in the section 112b.

Advantageously, the drawer 111 comprises a filter 1111 through which the oil arriving from the supply 11 will pass, and at least a first valve 1112 allowing the circulation of the oil from the filter 1111 towards the interior of the drawer 111. He also comprises at least one orifice 1113 for establishing fluid communication between the interior of the spool 111 and at least one duct of the hydraulic circuit 104 (FIGS. 2b, 2c).

The drawer 111 is said to be linear because it is able to move along the transverse axis y, in the housing 112. Thus, it is capable of occupying a first rest position PI and at least a second position P2. A position of drawer 111 will allow:

• either to establish fluid communication, through the spool 111, between the hydraulic circuit 104 and the oil supply 11,

• either to establish fluid communication, through the spool 111, between the hydraulic circuit 104 and the oil outlet 12,

• either to establish fluid communication, through the slide 111, between two hydraulic chambers of the circuit 104,

• or to block the fluid communication with the hydraulic circuit 104, isolating the latter in a closed circuit.

These different configurations will be detailed later in the particular embodiments.

The control system 110 also comprises a first pad 113 disposed on a side of the connecting rod end 102 and integral with one end of the spool 111. The first pad 113 is capable of undergoing at least one support force exerted by a member. pilot 50 to the connecting rod, said member 50 being for example carried by the crankshaft 200. This support force, transmitted to the spool 111 by the first pad 113 will cause the linear displacement of said spool 111, to make it occupy its ( at least one) second position P2. In the context of the invention, the outer pilot member 50 has an annular surface, coaxial with the crankpin 2, positioned opposite the side of the big end 102.

The outer pilot member 50 is configured to move along the transverse axis y and can thus come into contact with the first pad 113 and exert a bearing force thereon. Examples of embodiments of the control member 50 external to the connecting rod 10 and cooperating with the latter will be described below.

By way of example, as illustrated in FIGS. 2a, 2b and 2c, the first pad 113 is held integral with the end of the drawer 111 by means of cylindrical pins 113a. The first pad 113 also includes end-of-travel stops 113b, to limit its possible displacement along the transverse axis y. These stops can be achieved by means of two cylindrical pins 113b, integral with the head 102, plugged into windows 113c arranged in the first pad 113, thus limiting the movement of the first pad 113 in translation along the transverse axis y, at the waist from the window. The use of such stops 113b also allows the prior assembly of the spools 111 of the connecting rod 10 before mounting on the crankshaft 200.

Advantageously, the front section 112a of the housing 112 is configured to partially accommodate the first pad 113. In the example of Figures 2b, 2c, the front section 112a has an enlarged housing allowing the first pad 113 to establish a sliding connection according to the transverse axis y, with the big end 102.

The control system 110 also comprises a return means 114 (FIG. 2a), for example springs, for returning the spool 111 to the first rest position PI, in the absence of the support force exerted on the first pad. 113. The piloting system 110 also includes a second shoe 115 disposed on the same side of the big end 102 as the first shoe 113 (Figures la and lb). The second pad 115 is also able to withstand the support force exerted by the external pilot member 50. It is advantageously configured to balance the support force exerted by the external pilot member 50 and prevent the appearance of parasitic torque between the first pad 113 and the control member 50. For this, the first 113 and second 115 pads are arranged so that the barycenter of the forces undergone by said pads when the support force is applied to them is located substantially in the center of the big end 102. According to one possible embodiment, the second shoe 115 is symmetrical to the first shoe 113 with respect to the center of the big end 102 and has a contact surface equivalent to the first shoe 113. As illustrated in figures la and lb, the first 113 and second 115 pads may be aligned along the longitudinal axis z, the first as close as possible to the body 101 of the connecting rod 10 and the second at the level of the cap of the bie head 102. Alternatively, several second pads 115 could be arranged on the blank of the big end 102, and arranged so as to balance the forces.

Like the first shoe 113, the second shoe 115 establishes a sliding connection along the transverse axis y with the big end 102: its displacement amplitude is equivalent to that of the first shoe 113. Return means 114 and end stops can be used, as stated above for the first pad 113.

It should be noted that the oil supply 11 could be produced from a borehole through a bearing 103 opening into the front section 112a of the housing 112, as illustrated in FIG. 2b. Alternatively, the first pad 113 could be provided with a cavity 113d configured to collect the oil from lubrication of the bearings 103 at the level of the side of the big end 102, the cavity 113d also communicating with the front section 112a of the housing 112 (FIG. 2c).

Piloting system for telescopic or eccentric connecting rod

A so-called eccentric variable-length connecting rod and a telescopic variable-length connecting rod have in common the similarity between their hydraulic circuits 104. In fact, in each case, the objective is to be able to control the volume of oil at at least two hydraulic chambers 1041,1042 (Figures 3a, 3b). The difference in operation is found in the mechanics of extending the connecting rod and not in the piloting. Thus, the same control system 110 can be used as desired for an eccentric connecting rod or a telescopic connecting rod.

FIG. 3a illustrates a piloting system comprising two spools 111a, 111b, suitable for an eccentric connecting rod, and FIG. 3b illustrates the same piloting system for a telescopic connecting rod. The piloting system 111 remains identical in both cases and thus consists of a first pad 113 (and a second pad 115 - not shown), on which an external pilot member 50 exerts a support force, allowing The actuation of a first spool 111a and a second spool 111b, which control the supply and discharge of oil respectively from the first hydraulic chamber 1041 and from the second hydraulic chamber 1042. Note that in the examples of the figures 3a and 3b, the control system 111 does not allow oil to be transferred between the two chambers 1041, 1042 of the hydraulic circuit 104.

The operating mode of the piloting system 111 illustrated in FIGS. 3a and 3b is detailed below, with reference to a connecting rod of variable length with eccentric operating at “two-rate”. Another important aspect of the variable-length connecting rod according to the present invention relates to the desire or not to transfer part of the oil from one chamber 1041,1042 of the hydraulic circuit 104 into the other, when the length of the cylinder is changed. connecting rod. In the event that the transfer of oil between the hydraulic chambers 1041,1042 is desired, it is necessary to adapt the hydraulic circuit 104 accordingly by adding a fluid connection between the two chambers 1041,1042. Note that this fluidic connection may be independent or dependent on the position of the drawer (s) 111a, 111b. As for example illustrated in Figures 3c and 3d, the fluid connection can be provided by a transfer pipe 104c. The transfer pipe 104c advantageously comprises a device for orienting the oil flow 1046 such as for example a non-return valve.

This transfer capacity between the chambers 1041, 1042 of the hydraulic circuit 104 is more commonly considered in the case of telescopic rods but could be applied to eccentric rods. Figures 3c and 3d illustrate a control system 110 respectively for a telescopic connecting rod and an eccentric connecting rod, with transfer between the two hydraulic chambers 1041,1042. The piloting system 110 comprises a single slide 111 actuated by the first pad 113 on which the external pilot member 50 exerts the support force. The control system 110 remains identical in the two cases of connecting rods.

The length of the connecting rod 10 is maximum in the absence of a bearing force applied to the first pad 113, the spool 111 then being in its rest position PI and allowing the circulation of oil from the first hydraulic chamber 1041 to the second hydraulic chamber 1042; the transfer of oil between the second chamber 1042 to the first chamber 1041 is also possible via the transfer line 104c. A return or repel element 1042a (illustrated by a spring 1042a arranged in the hydraulic chamber 1042 in FIGS. 3c, 3d) makes it possible to guarantee the elongation of the connecting rod 10 thanks to a force, independent of the external forces applied to the connecting rod, during an engine cycle. Thus the second chamber 1042, by the action of the spring 1042a, will extend by pushing back the piston 1045. Note that the return or pushing element 1042a may be located outside the chamber 1042 (in particular in the case of the eccentric connecting rod) and perform the same function as described above.

The connecting rod length is minimum when the external control member 50 applies a bearing force on the first pad 113, which moves the spool 111 into a second position P2 which will block the flow of oil and isolate the hydraulic circuit 104 in a closed circuit. The oil can then only transfer from the hydraulic chamber 1042 to the hydraulic chamber 1041 due to the valve 1046 on the transfer pipe 104c. The transfer takes place gradually when the connecting rod is subjected to external compressive forces (in particular during the compression and combustion phases of the engine cycle), causing the connecting rod length to change by ratchet effect, until the minimum length is reached.

Bi-rate connecting rod

According to a first embodiment, the connecting rod 10 of variable length operates in two-rate mode, without transfer between the chambers 1041, 1042 of the hydraulic circuit 104 (FIGS. 3a, 3b, 4a, 4b). It should be remembered that a connecting rod 10 is said to be “two-rate”, when it can operate with two defined lengths: a maximum length corresponding to a maximum compression ratio of the engine, and a minimum length corresponding to a minimum compression ratio.

The first embodiment is described below with an eccentric connecting rod (FIG. 3a, 4a, 4b). Note, however, that the control system 110 according to this first embodiment could equally well be applied to a telescopic connecting rod (figure 3b).

The hydraulic control circuit 104 of the connecting rod 10 therefore comprises an eccentric mechanism. This mechanism is provided with two links fixed respectively to a first and to a second hydraulic piston sliding respectively in a first 1041 and a second chamber 1042 (FIG. 1c).

In this first embodiment, the control system 110 comprises two drawers 111a, 111b (FIGS. 4a, 4b). And the hydraulic circuit 104 comprises a conduit 104a to connect one of the two drawers 111a to the first chamber 1041 and a conduit 104b to connect the other drawer 111b to the second chamber 1042.

Each drawer comprises a filter 1111, at its end integral with the first pad 113, through which passes the oil coming from the oil supply 11. Each drawer 111a, 111b also comprises a first inlet valve 1112, which allows the circulation of oil from the filter 1111 towards the interior of the drawer and not the reverse circulation. Each slide 111a, 111b finally comprises two orifices 1113,1114 making it possible to establish fluid communication with the hydraulic circuit 104 when one and / or the other orifice 1113,1114 is opposite a duct 104a , 104b of said circuit 104.

Fluid communication can consist of supplying the hydraulic circuit 104, the oil circulation is then established from the supply 11 to the conduit 104a, 104b, passing through the slide 111a, 111b; alternatively, the fluidic communication can consist in evacuating the oil from the hydraulic control circuit 104, the oil circulation is then established from the conduit 104a, 104b towards the evacuation 12, passing through the slide 111a, 111b.

FIG. 4b illustrates the operation of the connecting rod 10 according to this first embodiment. The first rest position PI of the drawers 111a, 111b is obtained when no support force is exerted on the first pad 113 by the external control member 50.

In this first rest position PI, one of the drawers 111a is configured to supply the first chamber 1041 with oil to which it is connected by the conduit 104a. In practice, the oil coming from the supply 11 and having passed through the filter 1111 of said slide passes through the first valve 1112 to reach the orifice 1113 of the slide 111a, placed opposite the conduit 104a, when the slide 111a is in the first PI rest position. The external forces of combustion and inertia undergone by the combustion piston of the engine and acting on the eccentric mechanism of the connecting rod will promote the circulation of oil towards the first chamber 1041, the return of oil from the first chamber 1041 in the opposite direction being prohibited by the first valve 1112.

Still in the first rest position PI, the other slide 111b is configured to evacuate the oil from the second chamber 1042 to which it is connected by the conduit 104b. In practice, the orifice 1114 of the drawer 111b, which communicates with the rear section 112b of the housing 112 and therefore with the outlet 12, is placed opposite the duct 104b. The combustion and inertia forces here again promote the circulation of oil from the second chamber 1042 to the discharge 12.

In the first rest position PI of the drawers 111a, 111b, the first chamber 1041 is supplied with oil and the second chamber 1042 is emptied, which makes it possible to adjust the connecting rod to a maximum length, corresponding to a maximum rate of the engine.

The second position P2 of the drawers 111a, 111b is obtained following a translation of the drawers 111a, 111b along the transverse axis y, when a force F is applied to the first pad 113, by the external control member 50. In this second position P2, one of the drawers 111a is configured to evacuate the oil from the first chamber 1041 via the conduit 104a. In practice, the orifice 1114 of the drawer 111a, which communicates with the rear section 112b of the housing 112 and therefore with the outlet 12, is placed opposite the duct 104a. The efforts of combustion and inertia will here again promote the circulation of the oil.

Still in this second position P2, the other slide 111b is configured to supply the second chamber 1042 with oil via the duct 104b. In practice, the oil coming from the supply 11 and having passed through the filter 1111 of said slide passes through the first valve 1112 to reach the orifice 1113 of the slide 111b, placed opposite the conduit 104b. The circulation of oil to the second chamber 1042 is favored by the combustion and inertia forces undergone by the connecting rod 10.

In the second position P2 of the drawers 111a, 111b, the second chamber 1042 is supplied with oil and the first chamber 1041 is emptied, which makes it possible to adjust the connecting rod 10 to a minimum length, corresponding to a minimum rate of the engine.

The change of center-to-center distance of the connecting rod 10 according to the invention takes place thanks to the combustion and inertia forces undergone by the connecting rod 10, which cause the oil to circulate in the hydraulic circuit 104 and through the one or more. drawers 111, 111a, 111b of the control system 110, gradually inducing the change in length of the connecting rod. This is true for the first embodiment which has just been described and also for the other embodiments to be followed in the description.

According to a second embodiment, the connecting rod 10 of variable length operates in two-rate mode, with transfer between the chambers 1041, 1042 of the hydraulic circuit 104 (FIGS. 3c, 3d). The second embodiment is described below with a telescopic rod (figure 3c). Note, however, that the control system 110 according to this second embodiment could equally well be applied to an eccentric connecting rod (FIG. 3d).

The hydraulic circuit 104 for controlling the connecting rod 10 comprises a telescopic mechanism. The telescopic mechanism is arranged in the body 101 of the connecting rod 10 and provided with a central cylinder defining an upper chamber 1042 (or second chamber) and a lower chamber 1041 (or first chamber) on either side of a piston hydraulic 1045 called central piston 1045, the lower chamber 1041 located on the side of the big end 102 (Figure 3c). Advantageously, the upper chamber 1042 and the lower chamber 1041 have equivalent sections.

In this second embodiment, the control system 110 comprises a single spool 111. The hydraulic circuit 104 comprises a duct 104a to connect the spool 111 to the upper chamber 1042 and a duct 104b to connect the spool 111 to the lower chamber 1041 The jack piston 1045 comprises a transfer duct 104c connecting the two chambers 1041, 1042; a valve 1046 (called the third valve hereinafter) arranged on said conduit 104c allows the circulation of oil only from the upper chamber 1042 to the lower chamber 1041.

As described above, the spool 111 comprises a filter 1111, at its end integral with the first pad 113, through which passes the oil coming from the oil supply 11. It also comprises a first inlet valve 1112. , which allows the circulation of the oil from the filter 1111 towards the interior of the drawer and not the reverse circulation. It further comprises a second valve 1115, in series with the first valve 1112 (Figures 2b, 2c). The drawer 111 comprises at least two orifices 1113,1114, each downstream of a valve 1112,1115, making it possible to establish fluid communication with the circuit. hydraulic 104 when one and / or the other of the orifices 1113,1114 is opposite a conduit 104a, 104b of said circuit 104. Fluid communication may consist of supplying the hydraulic circuit 104 and of circulating the oil from the lower chamber 1041 to the upper chamber 1042, via the conduits 104a, 104b, passing through the spool 111. Alternatively, the fluid communication can be blocked, putting the hydraulic circuit 104 in a closed circuit, a transfer via the transfer duct 104c being only possible from the upper chamber 1042 to the lower chamber 1041.

In the second embodiment, provision is made for the drawer 111 to be able to occupy two different positions along the transverse axis y. The first rest position PI of the spool 111 is established in the absence of a support force exerted on the first pad 113 by the external control member 50. The spool 111 is then configured to supply the upper chamber 1042 with oil. and allowing oil to circulate between the lower chamber 1041 and the upper chamber 1042. In practice, the orifice 1113 between the first 1112 and the second 1115 valve is in fluid communication with the lower chamber 1041; and the orifice 1114 downstream of the second valve 1115 is in fluid communication with the upper chamber 1042. Due to the presence of the third valve 1046, preventing the flow of fluid from the lower chamber 1041 to the upper chamber 1042, the oil from the supply 11 and having passed the first inlet valve 1112 circulates through the second valve 1115 and supplies the upper chamber 1042. Similarly, the oil from the lower chamber 1041, blocked by the first valve 1112 d The inlet flows through the second valve 1115 and feeds the upper chamber 1042. The upper chamber 1042 fills, while the lower chamber 1041 empties, allowing the connecting rod to be adjusted to its maximum length. The second position P2 of the spool 111 corresponds to a maximum support force F exerted by the external control member 50 on the first pad 113. In its second position P2, the spool 111 is configured to block fluid communication with the circuit. hydraulic 104. Due to the presence of the third valve 1046, allowing only the circulation of oil from the upper chamber 1042 to the lower chamber 1041, the fluid will gradually fill the lower chamber 1041 and empty the upper chamber 1042, until adjusting the connecting rod to a minimum length.

As mentioned above, in this embodiment as well as in all the other embodiments which will be stated, the combustion and inertia forces undergone by the connecting rod 10 will promote the circulation of oil, until the length of the rod 10 is reached. connecting rod 10 sighted.

Tri-rate connecting rod

According to a third embodiment, the connecting rod 10 of variable length operates in tri-rate, with transfer between the chambers 1041, 1042 of the hydraulic circuit 104 (FIGS. 5a, 5b). Remember that a connecting rod 10 is said to be “three-rate”, when it can operate with three defined lengths: a maximum length corresponding to a maximum compression ratio of the engine, an intermediate length and a minimum length corresponding to a compression ratio. minimal.

The third embodiment is described below with a telescopic connecting rod, but the piloting system 110 according to this third embodiment could equally well be applied to an eccentric connecting rod.

In this third embodiment, the control system 110 comprises two drawers 111a, 111b. The hydraulic control circuit 104 comprises four independent conduits 104a, 104a ', 104b, 104b', two to connect the first spool 111a on the one hand to the upper chamber 1042 and on the other hand to the lower chamber 1041, and two to connect the second slide 111b on the one hand to the upper chamber 1042 and on the other hand to the lower chamber 1041. The central piston

1045 comprises a transfer duct 104c between the upper chamber 1042 and the lower chamber 1041, the valve of which

1046 (referred to as the third valve hereinafter) allows the circulation of oil only from the upper chamber 1042 to the lower chamber 1041. The central piston 1045 further comprises a shutter device 1047, for example in the form of a valve controlled by a needle (and called the fourth valve 1047 hereinafter), on the duct 104b connecting the second slide 111b and the upper chamber 1042.

Each slide 111a, 111b comprises a filter 1111, a first inlet valve 1112, a second valve 1115 and at least two orifices 1113,1114 making it possible to establish fluid communication with the hydraulic circuit 104 when the orifice 1113,1114 is facing a duct 104a, 104a ', 104b, 104b'. The fluidic communication can consist in supplying the hydraulic circuit 104 with oil and in circulating the oil from the lower chamber 1041 to the upper chamber 1042. Alternatively, the fluidic communication can be blocked, putting the hydraulic circuit 104 in a closed circuit.

The control system further comprises a spring 1116, disposed in the housing 112, against the end of each slide 111a, 111b, opposite the end integral with the first pad 113 (FIG. 5a).

FIG. 5b illustrates the operation of the connecting rod 10 in accordance with this fourth embodiment. Provision is made for the two drawers 111a, 111b to be able to occupy three different positions along the transverse axis y.

In the first position PI of rest of the drawers (without force applied to the first pad 113 by the external control member 50), the first drawer 111a is configured to supplying oil to the upper chamber 1042 and allowing oil to circulate from the lower chamber 1041 to the upper chamber 1042. The second slide 111b is for its part configured to block the fluid communication with the hydraulic circuit 104. The upper chamber 1042 is fills, while the lower chamber 1041 empties: the connecting rod 10 thus adjusts to its maximum length.

In the second position P2 of the drawers 111a, 111b, corresponding to a maximum support force F exerted by the external control member 50 on the first pad 113, the first drawer 111a and the second drawer 111b are configured to block communication. fluidic with the hydraulic circuit 104. Due to the presence of the third valve 1046, allowing only the circulation of oil from the upper chamber 1042 to the lower chamber 1041, the fluid will gradually fill the lower chamber 1041 and empty the upper chamber 1042, until the connecting rod is adjusted to a minimum length.

The third position P3 of the drawers 111a, 111b corresponds to a median support force F _med exerted by the external control member 50 on the first pad 113. The presence of the spring 1116 in the housing 112 behind each drawer prevents the latter. it does not move to the bottom of the housing 112 in the extreme position; the spring 1116 allows the implementation of a third position P3 between the first rest position PI and the second position P2 (extreme) of the drawers 111a, 111b.

In the third position P3, the first spool 111a is configured to block fluid communication with the hydraulic circuit 104. The second spool 111b is itself configured to supply the upper chamber 1042 with oil and allow circulation of oil between the lower chamber 1041. and the upper chamber 1042, when the fourth valve 1047 is opened by the needle: in practice, the needle will open said valve 1047 when the central piston 1045 reaches a determined position, typically an intermediate position in the jack. The upper chamber 1042 will then fill, and as soon as the jack piston 1045 is below the determined position, the fourth valve 1047 will close and block the flow of fluid between the two chambers. The oil will then tend to pass from the upper chamber 1042 to the lower chamber 1041 (due to the combustion and inertia forces undergone by the connecting rod) via the third valve 1046; the central piston 1045 will return to the determined position or beyond, which will have the consequence of reopening the fourth valve 1047 and restoring the circulation of fluid from the lower chamber 1041 to the upper chamber 1042, and so to after. In the third position P3, the spools 111a, 111b of the piloting system 110 will therefore make it possible to maintain the connecting rod 10 at an intermediate length, corresponding more or less to the determined (intermediate) position of the central piston 1045.

By way of example, starting from the first rest position PI of the drawers 111a, 111b, the third position P3 can be obtained by a translation of the drawers 111a, 111b of 1mm, and the second position P2 can be obtained by a translation of 2mm.

According to a variant of this third embodiment of the connecting rod 10 according to the invention, the piloting system 110 comprises at least a third pad 116 arranged on the other side of the connecting rod 10, opposite the side on which the first pad 113 and the second pad 115 (Figure 5c, 5d).

The piloting system 110 also includes a fourth shoe 117, advantageously symmetrical with the third shoe 116 relative to the center of the big end 102, playing the same role as the second shoe 115 but on the other blank, for balancing the forces. support likely to be exerted on the third pad 116. It will be understood that in this variant, two piloting members 50, 50 ′ will be necessary to exert support forces, on the one hand on the first 113 and second 115 pads arranged on a side of the big end 102, and d 'on the other hand on the third 116 and fourth 117 pads arranged on the other side of the big end 102.

In this variant of the third embodiment, the control system 110 comprises two drawers 111a, 111b. Each drawer can be moved in one direction along the transverse axis y due to a force applied to the first pad 113, and in the other direction always along the transverse axis y, due to a force applied to the third shoe 116.

The hydraulic circuit 104 comprises four independent conduits 104a, 104a ', 104b, 104b', a transfer conduit 104c provided with a valve 1046 and a shut-off device 1047, for example in the form of a valve controlled by a needle as described in the third embodiment.

The drawer 111a comprises a filter 1111, at its end secured to the first pad 113, and the drawer 111b comprises a filter 1111, at its end secured to the third pad 116, through which passes the oil coming from the. oil supply 11. Each slide 111a, 111b also comprises a first inlet valve 1112, a second valve 1115 and at least two orifices 1113,1114 making it possible to establish fluid communication with the hydraulic circuit 104 (FIG. 5c). The fluidic communication can consist in supplying the hydraulic circuit 104 with oil and in circulating the oil from the lower chamber 1041 to the upper chamber 1042. Alternatively, the fluidic communication can be blocked, putting the hydraulic circuit 104 in a closed circuit.

FIG. 5d illustrates the operation of the connecting rod 10 in accordance with this variant of the third embodiment. Provision is made for the two drawers 111a, 111b to be able to occupy three different positions along the transverse axis y.

In the first position PI of rest of the drawers (without support force applied to the first pad 113 or to the third pad 116 by an external control member 50, 50 '), the first drawer 111a is configured to supply the upper chamber with oil. 1042 and allow circulation of oil from the lower chamber 1041 to the upper chamber 1042. The second slide 111b is for its part configured to block fluid communication with the hydraulic circuit 104. The upper chamber 1042 fills up, while the chamber lower 1041 empties: the connecting rod 10 thus adjusts to its maximum length.

In the second position P2 of the drawers 111a, 111b, corresponding to a maximum support force F exerted by one of the external piloting members 50 'on the third shoe 116 (no force being exerted on the first shoe 113) , the first slide 111a and the second slide 111b are configured to block fluid communication with the hydraulic circuit 104. Due to the presence of the third valve 1046, only allowing the circulation of oil from the upper chamber 1042 to the lower chamber 1041, the fluid will gradually fill the lower chamber 1041 and empty the upper chamber 1042, until the connecting rod is adjusted to a minimum length.

The third position P3 of the drawers corresponds to a median support force F _med exerted by the other external control member 50 on the first pad 113 (no force being exerted on the third pad 116). It should be noted that a valve (illustrated in FIG. 5d) could be placed on the independent oil circuit (hereinafter called the fluidic pilot circuit) actuating the external pilot members 50, 50 'to allow the actuation of one. and the other organ of pilot 50.50 'respectively for two different oil pressures.

In the third position P3, the first spool 111a is configured to block fluid communication with the hydraulic circuit 104. The second spool 111b is itself configured to supply the upper chamber 1042 with oil and allow circulation of oil from the lower chamber 1041. towards the upper chamber 1042, when the fourth valve 1047 is opened by the needle, which corresponds to a determined (intermediate) position of the central piston 1045. The upper chamber 1042 will then fill, and as soon as the central piston 1045 is in below the determined position, the fourth valve 1047 will close and block the flow of fluid between the two chambers. In the third position P3, the drawers 111a, 111b of the piloting system 110 will therefore make it possible to maintain the connecting rod 10 at an intermediate length, corresponding to the determined (intermediate) position of the central piston 1045.

Conrod continuous rate

According to a fourth embodiment, the connecting rod 10 of variable length operates at a continuous rate, without transfer between the chambers 1041, 1042 of the hydraulic circuit 104 (FIGS. 6a, 6b, 6c). The connecting rod 10 can thus operate with a plurality of lengths.

The fourth embodiment is described below with an eccentric connecting rod, but the piloting system 110 according to this fourth embodiment could equally well be applied to a telescopic connecting rod.

The control system 110 comprises two drawers 111a, 111b. And the hydraulic control circuit 104 comprises two independent conduits 104a, 104a 'to connect one of the two drawers 111a to the first chamber 1041 and two conduits 104b, 104b' independent to connect the other drawer 111b to the second chamber 1042.

As illustrated in FIGS. 6a and 6b, each slide comprises a filter 1111, a first inlet valve 1112 and two orifices 1113,1114 making it possible to establish fluid communication with the hydraulic circuit 104 when one or the other of the orifices 1113,1114 is opposite a duct 104a, 104a ', 104b, 104b'. Fluid communication can consist of supplying the hydraulic circuit 104, the oil circulation is then established from the supply 11 to one of the conduits 104a, 104a ', 104b, 104b' passing through the slide 111a, 111b. The fluidic communication can alternatively consist in evacuating the oil from the hydraulic control circuit 104, the oil circulation is then established from the conduit 104a, 104a ', 104b, 104b' to the outlet 12, passing through one drawers 111a, 111b. Finally, the fluidic communication can be blocked, putting the hydraulic circuit 104 in a closed circuit.

The control system 110 comprises a spring 1116, disposed in the housing 112, against the end of each slide 111a, 111b, opposite the end integral with the first pad 113.

FIG. 6c illustrates the operation of the connecting rod 10 in accordance with this fourth embodiment. Provision is made for the two drawers 111a, 111b to be able to occupy three different positions along the transverse axis y, respectively called first position PI, second position P2 and third position P3. For the sake of clarity, we will talk about the first position PI of rest after having mentioned the other two positions.

The second position P2 of the drawers 111a, 111b corresponds to a maximum support force F exerted by the external control member 50 on the first pad 113. In this second position P2, one of the drawers 111a is configured to evacuate the 'oil from the first chamber 1041 to which it is connected by the conduit 104a ', the orifice 1114 of the spool 111a in fluid communication with the posterior section 112b of the housing 112 (and therefore with the oil outlet 12) located opposite said conduit 104a'. The other drawer 111b is configured to supply oil to the second chamber 1042 to which it is connected by the conduit 104b (via the orifice 1113 of the second drawer 111b, in fluid communication with the oil supply 11). In the second position P2 of the drawers 111a, 111b, the second chamber 1042 is supplied with oil and the first chamber 1041 is emptied, which makes it possible to adjust the connecting rod to a minimum length, corresponding to a minimum rate of the engine.

The third position P3 of the drawers 111a, 111b corresponds to a median support force F _me d exerted by the external control member 50 on the first pad 113. The presence of the spring 1116 in the housing 112 behind each drawer 111a, 111b prevents it from moving to the bottom of housing 112 in the extreme position; the spring 1116 allows the implementation of the third position P3 between the first rest position PI and the second position P2 (extreme) of the drawers 111a, 111b.

In this third position P3, one of the drawers 111a is configured to supply oil to the first chamber 1041 and the other drawer 111b is configured to discharge oil from the second chamber 1042. In the third position P3 of the drawers 111a, 111b, the first chamber 1041 is supplied with oil and the second chamber 1042 is emptied, which makes it possible to adjust the connecting rod to a maximum length, corresponding to a maximum rate of the engine.

The first rest position PI of the drawers 111a, 111b is obtained when no force is exerted on the first pad 113. The two drawers 111a, 111b are then configured to block the fluid communication with the hydraulic circuit 104. By putting the two drawers 111a, 111b. drawers 111a, 111b in the first rest position PI, the hydraulic circuit 104 is in a closed circuit: the connecting rod 10 can thus be kept at a length intermediate, between its maximum length and its minimum length, corresponding to an intermediate rate of the engine. It is possible to gradually modify this intermediate length by applying pulses to the first pad 113, at a maximum force F or at a median force F _med , depending on whether it is desired to limit or increase the intermediate length.

According to a fifth embodiment, the connecting rod 10 of variable length operates at a continuous rate, with transfer between the chambers 1041, 1042 of the hydraulic circuit 104 (FIGS. 7a, 7b, 7c, 7d). The fifth embodiment is described below with a telescopic connecting rod, but the piloting system 110 according to this fifth embodiment could equally well be applied to an eccentric connecting rod.

The control system 110 comprises two drawers 111a, 111b (Figures 7a). The hydraulic circuit 104 comprises four independent conduits 104a, 104a ', 104b, 104b', to connect each drawer 111a, 111b to the two chambers 1041,1042.

Each slide comprises a filter 1111, a first inlet valve 1112, a second valve 1115,1115 ', and at least two orifices 1113,1114 making it possible to establish fluid communication with the hydraulic circuit 104 via the conduits 104a, 104a' , 104b, 104b '.

The fluidic communication can consist in supplying the hydraulic circuit 104, and in circulating the oil from the upper chamber 1042 to the lower chamber 1041, via the conduits 104a, 104a ', passing through the first spool 111a. Alternatively, the fluidic communication can consist in supplying the hydraulic circuit 104, and in circulating the oil from the lower chamber 1041 to the upper chamber 1042, via the conduits 104b, 104b ', passing through the second spool 111b. Finally, the fluidic communication can be blocked, putting the hydraulic circuit 104 in a closed circuit. The control system further comprises a spring 1116, disposed in the housing 112, against the end of each slide 111a, 111b, opposite the end integral with the first pad 113.

FIG. 7d illustrates the operation of the connecting rod 10 in accordance with this fifth embodiment. Provision is made for the two drawers 111a, 111b to be able to occupy three different positions along the transverse axis y.

In the first rest position PI, occupied by the drawers 111a, 111b in the absence of a support force exerted by the external control member 50, the first slide 111a and the second slide 111b are configured to block the fluid communication. with the hydraulic circuit 104 (FIG. 7a). The hydraulic circuit 104 is then in a closed circuit, the central piston 1045 is blocked in its position, for example an intermediate position. The connecting rod 10 thus has an intermediate length.

In the second position P2 of the drawers (FIG. 7c), corresponding to a maximum support force F exerted by the external control member 50 on the first pad 113, the first slide 111a is configured to supply the lower chamber 1041 with oil. and allowing an oil circulation from the upper chamber 1042 to the lower chamber 1041, through the second valve 1115 'of the first spool 111a; this position P2 of the drawer 111a therefore allows a transfer between the two chambers 1041,1042. The second spool 111b is configured to block fluid communication with the hydraulic circuit 104.

In this second position P2 of the drawers, the lower chamber 1041 fills up and the upper chamber 1042 empties: the length of the connecting rod decreases until it reaches a minimum length. By returning the drawers 111a, 111b to the first rest position PI (the hydraulic circuit 104 then returning to a closed circuit), the connecting rod can be maintained 10 at various lengths between the intermediate length and the minimum length.

In the third position P3 of the drawers 111a, 111b (FIG. 7b) corresponding to a median support force F _me d exerted by the external control member 50 on the first pad 113, the second slide 111b is configured to supply oil the upper chamber 1041 and allow circulation of oil from the lower chamber 1041 to the upper chamber 1042, via the second valve 1115 of the second spool 111b. This position P3 of the drawer 111a allows a transfer between the two chambers 1041,1042. The first spool 111a is configured to block fluid communication with the hydraulic circuit 104.

In this third position P3 of the drawers, the upper chamber 1043 fills up and the lower chamber 1044 empties: the length of the connecting rod increases until it reaches a maximum length. By returning the spools to the first rest position PI (the hydraulic circuit 104 then returning to a closed circuit), the connecting rod 10 can be maintained at various lengths between the intermediate length and the maximum length. The connecting rod 10 according to this fifth embodiment provides continuously variable values of lengths, to drive a volumetric ratio motor driven at a continuous rate.

Note that in all the embodiments stated in which it is not established specific fluid communication with the oil outlet 12, the fact that the spools 111, 111a, 111b are mounted in the housing 112 of the big end 102 without sealing allows a gradual renewal of the oil of the hydraulic circuit 104, which prevents a degradation of the quality of the oil (degradation which could take place in a sealed closed circuit). External steering body exerting the downforce

The following embodiments described with reference to FIGS. 8a, 8b, 8c and 8d are given by way of example and illustrate piloting members 50 external to the connecting rod 10, compatible with a connecting rod 10 in accordance with the present invention.

The crankshaft 200 supporting the connecting rod 10 comprises at least one crank pin 2 and at least one journal 3 connected by a link arm 4. It further comprises at least one pilot member 50. The pilot member 50 is able to move. in translation along the transverse axis y to cooperate with the first shoe 113 (and the second shoe 115) of the control system 110 of the length of connecting rod 10.

Preferably, the total stroke of the pilot member 50 varies from approximately 1 to 2 mm, depending on the configurations and embodiments. Of course, other races can be considered depending on the dimensions of the engine.

The pilot member 50 is disposed at the level of the link arm 4, at one end of the crankpin 2. It comprises an annular part 51, a flat surface 52 of which extends in a plane (x, z) normal to the axis. transverse y. The annular portion 51 is coaxial with the crankpin 2 and it is capable of establishing continuous contact, via its flat surface 52, with the first pad 113 (and the second pad 115) of the piloting system 110, regardless of the angular position. of the crankshaft 1. Such a configuration has the advantage of a mechanical transmission without shock, by application of a continuous support force on the first 113 and second 115 pads.

The crankshaft 100 also comprises a fluidic pilot circuit 60 configured to move the pilot member 50 along the transverse axis y. The fluidic circuit 60 comprises at least one orifice 61 intended to communicate a fluid with a rear surface (opposite to the flat surface 52) of the pilot member 50, in order to apply pressure thereto and cause its displacement. The fluid can be a gas or a liquid. A gaseous fluid has the advantage of being less influenced by the rotation of the crankshaft, compared to a liquid fluid, due to its very low density.

Advantageously, the fluid control circuit 60 is formed by ducts 62 drilled over the entire length of the crankshaft 100, from one of its ends to the last crankpin 2, opposite this end. The fluidic circuit 60 has at least one orifice 61 for the outlet of the fluid at the level of the link arm 4, as stated previously, to communicate with the rear surface of the pilot element 50. The bores 62 in the crankshaft 100 are independent of those of lubrication connecting crankpin 2 and journal 3. The fluidic control circuit 60 is sealed by a series of plugs 63 at the outlet of each bore 62 towards the outside of the crankshaft 1.

According to a particular embodiment of the pilot member 50, an annular cavity 40 is arranged in the connecting arm 4, at one end of the crankpin 2 (FIG. 8b). This cavity 40 is intended to form the cylinder body of an annular piston, itself formed by the pilot member 50. An outlet 61 for the fluid from the fluidic pilot circuit 60 opens into the cavity 40. The arm link 4 also comprises an external centering 41, coaxial with the crankpin 2 as well as two lug housings 42, the function of which we will detail later. The piloting element 50 comprises two half-frames 53, for example with an H-profile, intended to be assembled around the crankpin 2, then positioned in the annular cavity 40. Advantageously, the half-frames 53 are made of metal. Pins are provided to align and secure the two half-frames 53 after their assembly.

On each of the half-frames 53, an elastomer 54 is overmolded intended to ensure the seal between the surface rear 55 and the flat surface 52 of the control member 50, when the latter is disposed in the annular cavity 40. Note that with this type of annular piston with seal, the friction torque generated by these same seals is greater than that of contact with the shoe 113 of the connecting rod 10. It therefore seems unnecessary to add an anti-rotation system at the level of the pilot member 50.

The crankshaft 200 comprises a caliper 45 which is centered at the level of the external centering 41 and snaps directly onto the link arm 4, at the level of the lug housings 42. The caliper 45 forms an end stop of the l 'piloting member 50, when the latter moves along the transverse axis y, in the first direction Y1. It preferably has an annular segment, making it possible to standardize the abutment points against the annular part 51 of the piloting member 50. Advantageously, the yoke 45 can also play the role of a lateral stop of the big end 10.

The annular part 51 of the pilot member 50 (forming the annular piston) has a flat surface 52 capable of establishing continuous contact against the first 113 and the second 115 pad. Contact with the pads 113, 115 can be established when the pilot element 50 is moved in the first direction Y1 (Figures 8a, 8c). This displacement is caused by the application of a fluid pressure on the rear surface 55 of the pilot member 50. The fluid is conveyed to the annular cavity 40 (at the rear of the pilot member 50 ) via a conduit 62 of the fluidic control circuit 60. The depressurization of the fluidic circuit 60 causes a displacement of the control element 50 in the second direction Y2, and thus interrupts contact with the pads 113,115. Alternatively, a return element can be arranged, so as to push back the control member 50 when the fluid pressure on its rear surface 55 falls below a threshold value. According to a variant, a control member 50, 50 ′ is disposed at the level of each link arm 4, on either side of each crank pin 2 of the crankshaft 200. Such a configuration can allow the control of a tri-connecting rod 10. rate comprising a first 113 and a second 115 pads on one side of the big end 102, and a third 116 and a fourth 117 pads on the other side, as detailed in the variant of the third embodiment of the connecting rod 10 (tri-rate connecting rod).

Note that this variant of the piloting member also allows the piloting of two connecting rods 10, when the crankpin 2 is precisely configured to receive two connecting rods 10.

Variable compression ratio motor

The invention also relates to a controlled variable volumetric ratio engine, which may have an in-line or V-shaped architecture. The engine comprises an engine block and a crankshaft 200 as described above, arranged in the engine block. The engine further comprises at least one variable-length connecting rod 10 as described above, associated with a crankpin 2 of the crankshaft 200.

The fluidic control circuit 60 of the crankshaft 200 is connected to the outside by the end of the crankshaft 200. Said end is arranged to receive a rotating seal allowing the connection between the rotating part (crankshaft) and the fixed part (engine block) and thus allowing the fluidic connection of the pilot circuit 60 with an external pilot assembly, arranged outside the engine block. The external control assembly is configured to convey the fluid in the control circuit 60. It comprises in particular a pressure source such as for example an air compressor, when the fluid is compressed air. To put the control circuit 60 in depression (and control the movement of the control element 50 in the second direction Y2), the external control assembly can also include a dedicated or shared vacuum pump. The external control unit is controlled by the engine control unit (computer), depending on the engine speed and load.

Of course, the invention is not limited to the various embodiments described and it is possible to provide implementation variants without departing from the scope of the invention as defined by the claims.

Claims

1.Bielle (10) of variable length, the body (101) of which extends along a longitudinal axis (z) and comprising:

- A big end (102), intended to establish a pivot connection, along a transverse axis (y) perpendicular to the longitudinal axis (z), with a crankpin of a crankshaft,

- A hydraulic circuit (104) for controlling the length of the connecting rod (10),

- A control system (110) of the hydraulic circuit (104), The connecting rod (10) being characterized in that the control system (110) comprises:

- At least one linear hydraulic spool (111,11la, 11lb), arranged in a housing (112) of the big end (102), and capable of occupying a first rest position (PI) and at least a second position (P2), each position making it possible to open or close a fluid communication with the hydraulic circuit (104),

- At least a first pad (113) disposed on a side of the connecting rod head (102) and integral with one end of the slide (111,11la, 11lb), capable of undergoing a bearing force exerted by a control member annular piloting (50,50 '), coaxial with the crank pin and outside the connecting rod (10), said support force making it possible to move the spool (111,11la, 11lb) in the second position (P2),

A return means (114), to return the drawer (111,11la, 11lb) to the first rest position (PI), in the absence of the support force,

- At least one second shoe (115) arranged on the side of the big end (102) and able to withstand the support force.

2.Biel (10) of variable length according to the preceding claim, wherein the first (113) and second (115) pad are arranged so that the barycenter of the forces undergone by the pads when the bearing force is applied to them is located substantially in the center of the big end (102).

3.Biel (10) of variable length according to one of the preceding claims, wherein at least one of the pads (113,115) comprises end-of-travel stops, to limit its possible displacement along the transverse axis (y) ·

4.Biel (10) of variable length according to one of the preceding claims, wherein the hydraulic circuit (104) comprises at least two hydraulic chambers (1041,1042), each being connected to the spool (111,11la, 11lb) by at least one conduit

(104a, 104a ', 104b, 104b'), the chambers (1041,1042) being associated with at least one hydraulic piston whose displacement is able to modify the length of the connecting rod (10) along the longitudinal axis (z) .

5.Biel (10) of variable length according to the preceding claim, wherein the at least one drawer

(111,11la, 11lb) allows, depending on the position it occupies, to establish an oil circulation between a hydraulic chamber (1041,1042) and an oil supply (11), or to establish a circulation oil between a hydraulic chamber (1041,1042) and an oil outlet (12), or to establish an oil circulation between the two hydraulic chambers (1041,1042), or to block all oil circulation with the two hydraulic chambers (1041,1042).

6.Changing rod (10) of variable length according to the preceding claim, wherein the oil supply (11) is configured to collect lubricating oil from bearings (103) of the big end (102).

7.Biel (10) of variable length according to one of the two preceding claims, wherein the at least one slide (111,11la, 11lb) comprises at least one valve (1112,1115,1115 ') for defining the direction oil circulation.

8.Biel (10) of variable length according to one of the four preceding claims, wherein the hydraulic circuit (104) comprises a conduit (104c) connecting the two hydraulic chambers (1041,1042) and provided with a valve (1046 ) used to define the direction of oil circulation.

9.Biel (10) of variable length according to one of the five preceding claims, comprising a return or push element (1042a) connected to at least one hydraulic piston.

10. Connecting rod (10) of variable length according to one of the six preceding claims, wherein at least one conduit (104b), connecting a hydraulic chamber (1042) and the spool (111b), comprises a shutter device (1047) configured. to allow the circulation of oil between said hydraulic chamber (1042) and the spool (111b) when the hydraulic piston (1045) reaches a determined position.