FR3049998A1 - COMPRESSION RATE SYSTEM OF AN INTERNAL COMBUSTION ENGINE WITH A DAMPING DEVICE - Google Patents

Abstract

The invention relates primarily to a crankshaft of an internal combustion engine comprising: - a plurality of cranks and pins (14), - eccentric parts (18) each rotatably mounted on a bearing of a crankpin, - a control system adapted to control an angular position of a first eccentric part (18) cooperating with a pinion of said control system, - a through bore (41) axially right through said pins (14) to allow the mounting of transfer shafts movement, - each motion transfer shaft being provided with a pinion at each of its ends meshing with two eccentric pieces (18) consecutive to transmit the rotational movement imposed on said first eccentric part (18) by said control system stepwise on all the other eccentric pieces (18) from the first eccentric piece (18) to a last eccentric piece (18), characterized in that said crankshaft further comprises a damping device (42) located on the side of said last eccentric part (18).

Description

SYSTEM FOR VARYING THE COMPRESSION RATE OF AN INTERNAL COMBUSTION ENGINE EQUIPPED WITH A DEVICE

AMORTIZATION

The present invention relates to a system for varying the compression ratio of an internal combustion engine provided with a damping device. The invention finds a particularly advantageous, but not exclusive, application in the field of motor vehicles.

[0002] Variation of the compression ratio is known as a function of the operating conditions of the engine. These compression ratio variation systems comprise a set of eccentric parts mounted on the crankshaft crank pins so as to cooperate each with a connecting rod end. A control system of the angular position of the eccentric parts comprises an actuating shaft and a cascade of gears mounted between the actuating shaft and the eccentric part located on the side of the actuating shaft. In addition, through the crankshaft journals, shafts and transfer gears transmit the same kinematics of the eccentric piece step by step on all other eccentric pieces.

However, the transfer shafts between each eccentric piece are slightly flexible to the extent that they are not perfect. Consequently, excitation of an extreme eccentric by combustion of the motor will generate significant twists along the entire length of the system. Such constraints are likely to bring the system into resonance and thus cause its deterioration.

The invention aims to overcome this disadvantage by proposing a crankshaft of an internal combustion engine comprising: - a plurality of crank pins and trunnions, - eccentric parts rotatably mounted each on a bearing of a crankpin, - a system control device adapted to control an angular position of a first eccentric part cooperating with a pinion of the control system, - a bore passing axially right through the journals to allow the assembly of motion transfer shafts, - each shaft of transfer of motion being provided with a pinion at each of its ends meshing with two consecutive eccentric pieces to transmit the rotational movement imposed on the first eccentric piece by the control system step by step on all the other eccentric pieces since the first eccentric piece to a last eccentric piece, characterized in that the crankshaft comprises e n addition a damping device located on the side of the last eccentric part.

The invention thus makes it possible, by integrating the damping device in the crankshaft, to reduce the torque applied to the transfer shafts during combustion of the internal combustion engine. The invention thus makes it possible to improve the mechanical strength of the system while minimizing the risks of bringing it into resonance.

According to one embodiment, the damping device comprises: a pinion meshing with the last eccentric part, the pinion being mounted on a holding shaft positioned inside a section of the through bore, and a friction device mounted at the outer periphery of the holding shaft for rubbing with the inside of the section of the through bore.

In one embodiment, the friction device is constituted by an O-ring made of an elastomeric material.

In one embodiment, the damping device comprises a bearing mounted on the holding shaft.

In one embodiment, the bearing is disposed between the pinion and the O-ring.

According to one embodiment, the damping device comprises an axial stop means of the pinion.

The invention also relates to an internal combustion engine comprising a crankshaft as previously defined.

The invention also relates to a motor vehicle comprising an internal combustion engine as previously defined.

The invention will be better understood by reading the following description and examining the figures that accompany it. These figures are given for illustrative but not limiting of the invention.

Figure 1 is a perspective view illustrating the integration of the compression ratio variation system according to the present invention in a crankshaft; Figure 2 is a perspective view of the compression ratio variation system according to the present invention without the crankshaft; Figure 3 is an exploded perspective view of an eccentric part used with the compression ratio variation system according to the present invention; Figure 4 is a detailed sectional view of the damping device according to the present invention.

Identical elements, similar, or the like retain the same reference from one figure to another.

Figure 1 shows a perspective view of a compression ratio variation system 11 for operating an internal combustion engine at a high compression ratio under low load conditions to improve its performance. Under high load operating conditions, the compression ratio can be decreased to avoid jolts.

More specifically, the crankshaft 12 of the X-axis motor is intended to be rotatably mounted on a motor housing by means of bearings. The crankshaft 12 comprises a plurality of crank pins 13, and journals 14, separated by flanges 15 extending substantially perpendicular to the axis X. The crankshaft 12 further has a front end intended to be rotatably connected with a pulley (not shown). An flywheel (not shown) is rotatably connected to the rear end of the crankshaft 12.

Eccentric parts 18 are rotatably mounted on bearings of the crank pins 13. As can be seen more clearly in FIGS. 2 and 3, each eccentric part 18 comprises a body having an eccentric external face 30 intended to cooperate with a large diameter. end of a rod, which has its small end is connected in rotation with a piston of the engine. The eccentric part 18 also comprises two toothed rings 32 positioned on either side of the eccentric outer face 30.

As can be seen in Figure 3, each eccentric part 18 may be formed from two half-shells 2 to allow their assembly on a one-piece crankshaft. For this purpose, the half-shells 2 are assembled on the crankshaft 12 by fitting locking elements 3 inside correspondingly shaped housings 4 formed in the half-shells 2.

A control system 20 of the angular position of the eccentric parts 18 comprises an actuating shaft 21 and a cascade of sprockets constituted by an actuating pinion 22 mounted on the actuating shaft 21, and an intermediate gear 23, said satellite, to reverse the direction of rotation, meshing on the one hand with the actuating pinion 22 and on the other hand with a ring gear 32 of the eccentric piece 18.

In operation and when the actuating shaft 21 is fixed in rotation relative to the frame, the system 11 has a fixed compression ratio configuration. In transient rate, the angular position of the eccentric part 18 located on the side of the pulley is controlled by the angular position of the actuating shaft 21 and thus pass to a new compression ratio point. For this purpose, the actuating shaft 21 may be actuated for example by means of a wheel and worm gear, or any other means of displacement adapted to the application.

Furthermore, through the journals 14 of the crankshaft 12, shafts 26 and 27 so-called transfer gears transmit the same kinematics of the eccentric part 18 located on the side of the actuating shaft 21 from near to on all other eccentric parts 18 of the crankshaft 12.

The crankshaft 12 further comprises a through bore 41 axially from one side to the trunnions 14 to allow the mounting of the transfer shafts 26 of movement. Each movement transfer shaft 26 is provided with a pinion 27 at each of its ends meshing with two consecutive eccentric parts 18 to transmit the rotational movement imposed on a first eccentric part 18 by the control system 20 step by step on all the other eccentric parts 18 from the first eccentric part 18 closest to the control system 20 to the last eccentric part 18 furthest from the control system 20.

In order to avoid excessive torsions of the transfer shafts 26, the crankshaft 12 is equipped with a damping device 42. The damping device 42 is located on the side of the last eccentric part 18 to which is transmitted the rotational movement imposed by the control system 20.

As shown in Figures 2 and 4, the damping device 42 comprises a pinion 44 located on the opposite side of the control system 20 and meshing with the last eccentric part 18. The pinion 44 is mounted on a shaft 45 is positioned within a portion of the through bore 41 formed in the journal 14 of the crankshaft 12. In other words, compared to a conventional system, the bore 41 is extended so as to integrate the device 42 damping in a trunnion 14 end of the crankshaft 12.

In addition, the damping device 42 comprises a friction device 47 mounted at the outer periphery of the holding shaft 45. This friction device 47 is intended to rub against an inner periphery of a section of the housing. In the exemplary embodiment shown, the friction device 47 is constituted by an O-ring 48 made of an elastomeric material. Alternatively, the seal 48 may be replaced by any other friction element adapted to the application.

In addition, a bearing 50 may be mounted on the holding shaft 45 between the pinion 44 and the O-ring 48. This ensures a rotational mounting of the holding shaft 45 relative to the pin 14 The bearing 50 is preferably a needle-type bearing but may alternatively be constituted by a ball bearing.

It will also be possible to provide an axial stop means of the pinion 44 consisting for example of an elastic ring circlips type or other.

To ensure the assembly of the damping device 42, the O-ring 48 is positioned on the holding shaft 45, and the bearing 50 is positioned on the shaft 45. The pinion 44 is fitted on the 45, at the opposite end of the O-ring 48. The assembly is then fitted inside the section of the through bore 41 located on the opposite side to the control system 20.

Claims (8)

Crankshaft (12) of an internal combustion engine comprising: - a plurality of crankpins (13) and trunnions (14), - eccentric parts (18) each rotatably mounted on a bearing of a crankpin (13), - a control system (20) adapted to control an angular position of a first eccentric part (18) cooperating with a pinion (23) of said control system (20), - a through-bore (41) axially from one side to the other journals (14) for allowing the assembly of transfer shafts (26) for movement, - each transfer shaft (26) being provided with a pinion (27) at each of its ends meshing with two eccentric pieces (18). ) to transmit the rotational movement imposed on said first eccentric part (18) by said control system (20) step by step on all the other eccentric parts (18) from the first eccentric part (18) to a last eccentric piece (18), cara characterized in that said crankshaft (12) further comprises a damping device (42) located on the side of said last eccentric piece (18). 2. A crankshaft according to claim 1, characterized in that said damping device (42) comprises: - a pinion (44) meshing with said last eccentric part (18), said pinion (44) being mounted on a holding shaft (45) positioned within a section of said through bore (41), and - a friction device (47) mounted at the outer periphery of the holding shaft (45) for rubbing with the interior of said section of the through bore (41). 3. Crankshaft according to claim 2, characterized in that said friction device (47) is constituted by an O-ring (48) made of an elastomeric material. 4. Crankshaft according to claim 2 or 3, characterized in that said damping device (42) comprises a bearing (50) mounted on said holding shaft (45). Crankshaft according to claims 3 & 4, characterized in that said bearing (50) is disposed between said pinion (44) and said O-ring (48). 6. Crankshaft according to any one of claims 2 to 5, characterized in that said damping device (42) comprises an axial stop means of said pinion (44). 7. Internal combustion engine characterized in that said engine comprises a crankshaft (12) as defined in any one of claims 1 to 6. 8. Motor vehicle comprising an internal combustion engine as defined in any one of the preceding claims.