FR3050234A1 - ASSEMBLY FOR THERMAL ENGINE COMPRESSION RATE VARIATION SYSTEM - Google Patents

Abstract

The invention relates primarily to an assembly for a system for varying the compression ratio of an internal combustion engine comprising: - an eccentric part (18) having a body (19) made from two assembled half-shells (22) between them, said body (19) comprising an inner face (27), an eccentric outer face (23) with respect to said inner face (27) of said body (19), two toothed rings (24) positioned on the one side and another of said outer face (23), and an eccentricity plane (P2) passing through an axis (X1) of said inner face (27) and an axis (X2) of said outer face (23), and - two bearings (40) intended to be pressed against said inner face (27) of said body (19), said two pads (40) having a joining zone (Z) at their free ends, characterized in that said joining zone ( Z) pads (40) extend in a plane (P3) forming an angle (A1) with respect to the eccentricity plane (P2) ) between 0 ° and -23.7 °.

Description

ASSEMBLY FOR THERMAL ENGINE COMPRESSION RATE VARIATION SYSTEM

The present invention relates to a set for thermal engine compression ratio system. 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.

[0003] A control device makes it possible to adjust the position of the eccentric pieces. For this purpose, the control device comprises an actuating shaft and a cascade of sprockets constituted by an actuating pinion integral with the actuating shaft, and intermediate pinions meshing on the one hand with the actuating pinion. and on the other hand with a toothed ring integral with the eccentric piece.

As shown in Figure 1, the eccentric parts 1 are split into 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 by fitting locking elements 3 inside housings 4 formed in the half-shells 2. The body 8 of each part 1 comprises an inner face 5, an eccentric outer face 6 with respect to the inner face 5, and two toothed rings 7 positioned on either side of said eccentric face 6. Generally, the cutting plane PI of the eccentric pieces is made at an angle of 90 degrees by relative to an eccentricity plane P2 passing through the axis XI of the inner face 5 and the axis X2 of the outer face 6 (see Figure 2a). In addition, pads 10 mounted between the inner face 5 of each eccentric part 1 and the corresponding pin have a junction zone Z located in the extension of the cutting plane PI.

In operation, the system varies the eccentric adjustment at different angles, for example an angle of 90 degrees, 45 degrees, 0 degrees, and 45 degrees. The observable pressure peak M for each of these configurations is represented respectively in FIGS. 2a, 2b, 2c and 2d. It is recalled that the eccentric adjustment angle corresponds to the angle between the eccentricity plane P2 and the crank arm at the moment of the top dead center.

Note that for an eccentric adjustment of 90 degrees or -45 degrees, the pressure peaks M are distant from the junction zone Z between the bearings 10 and do not pose a problem of mechanical strength of the system ( see Figures 2a and 2d). However, the junction zone Z between the two pads 10 is subjected to a peak pressure M for eccentric adjustments of between 0 and 45 degrees (see Figures 2b and 2c). These settings corresponding to a high load operation of the engine, such a peak pressure is likely to deteriorate the assembly between the pads 10 and eccentric part 1.

The invention aims to overcome this disadvantage by proposing an assembly for a variation of the compression ratio of an internal combustion engine system comprising: an eccentric piece having a body made from two half-shells assembled between they, the body comprising an inner face, an external eccentric face relative to the inner face of the body, two toothed crowns positioned on either side of the outer face, and an eccentricity plane passing through an axis of the face internal and an axis of the outer face, and - two pads intended to be pressed against the inner face of the body, the two pads having a junction zone at their free ends, such that the junction area of the pads extends in a plane forming an angle with respect to the eccentricity plane between 0 ° and -45 °, in particular between 0 and -40 °.

Preferably, the angle (Al) is between 0 and -30 °, especially between 0 and -23.7 °, preferably between -2 and -10 ° or between -3 and -6 °.

The invention thus minimizes junction constraints between the bushings for adjustments of the eccentric corresponding to operations under heavy load of the engine and to improve the mechanical strength of the bushings.

In one embodiment, the two half-shells are positioned relative to each other along a cutting plane located in an extension of the junction area of the pads. This facilitates assembly of the assembly to the extent that it will be possible to previously assembled a bearing with a corresponding half-shell before positioning the assembly around a crankpin crankshaft.

According to one embodiment, the two half-shells are positioned relative to each other in a cutting plane offset from the plane of the junction area of the pads.

In one embodiment, the cutting plane passes through diametrically opposite spaces between two successive teeth of the toothed crowns.

In one embodiment, the angle depends on a number of teeth belonging to the ring gear and a combustion wedge on points of full load.

Preferably, the angle is between -3 ° and -6 °, in particular about -4.2 ° for a number of teeth of 42.

According to one embodiment, the body of each eccentric piece comprises at least one lubrication liquid passage hole. This ensures a lubrication of a hydrodynamic bearing formed by the bearings.

The invention also relates to an internal combustion engine comprising: - a crankshaft, and - a variation system of a compression ratio of the engine comprising at least one assembly as defined above mounted on a crankpin crankpin .

The invention will be better understood from 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, already described, is an exploded perspective view of an eccentric piece according to the state of the art; Figures 2a to 2d, already described, are sectional views of an eccentric piece illustrating the pressure peaks observable for eccentric settings respectively worth 90 degrees, 45 degrees, 0 degrees, and -45 degrees; Figure 3 is a perspective view illustrating the integration of the compression ratio variation system of a heat engine according to the present invention along the entire length of the crankshaft; Figure 4 is a perspective view of the compression rate variation system of a heat engine according to the present invention without the crankshaft; Figures 5a and 5b are sectional views of an eccentric piece with improved configuration according to the present invention.

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

FIG. 3 shows a perspective view of a system 11 for varying the compression ratio integrated in a crankshaft 12. The system 11 makes it possible to operate an internal combustion engine at a high compression ratio under conditions of low load to improve its performance. Under high load operating conditions, the compression ratio may be decreased to reduce the risk of self-ignition of the mixture.

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 X axis.

The crankshaft 12 further has a front end intended to be rotatably connected with a pulley. An flywheel (not shown) is rotatably connected to the rear end of the crankshaft 12.

Eccentric parts 18 are mounted rotatably on the crank pins 13. As is best seen in Figures 3 and 4, each eccentric member 18 comprises a body 19 made from two half-shells 22 assembled together. The body 19 comprises an external eccentric face 23 and two toothed rings 24 positioned on either side of the eccentric face 23 and concentric with an inner face 27. The external eccentric face 23 is intended to cooperate with a large end of a connecting rod, which further has a small end rotatably connected with a piston of the engine.

Pads 40 are intended to be mounted between the inner face 27 of the body 19 and an outer periphery of the crankpin 13 to form a hydrodynamic bearing. The inner face 27 and the faces of the pads 40 have an axis substantially coincident with the axis of the crankpin 13, while the outer face 23 is eccentric with respect to the inner face 27 and thus with respect to the crankpin 13.

As can be seen in FIGS. 5a and 5b, the pads 40 have a junction zone Z at their free ends extending in a plane P3 forming an angle Al with respect to the eccentricity plane P2 of the eccentric part 18. This eccentricity plane P2 is defined by the plane passing through an axis XI of the inner face 27 and an axis X2 of the outer face 23. Thus, the eccentricity plane P2 corresponds to the plane passing through the extra thickness the largest between the inner periphery 27 and the outer periphery 23 of the eccentric part 18.

The angle Al is between 0 ° and -23.7 degés. It is noted that the positive values of the angle A1 are measured in a clockwise direction from the eccentricity plane P2 while the negative values of the angle Al are measured in a counter-clockwise direction, indicated by an arrow, in starting from the eccentricity plane P2. Such an angular range makes it possible to minimize junction stresses between the bearings 40 for eccentric adjustments corresponding to operations under heavy load of the heat engine. Indeed, the junction zone Z is then subjected to a pressure peak M when the adjustment of the eccentric corresponds to the high compression rates of the engine used on points of low loads, so with low cylinder pressure levels.

In the embodiment of FIG. 5a, the two half-shells 22 are positioned relative to each other along a cutting plane P 1 located in an extension of the junction zone Z of the pads 40. The junction zone Z of the pads 40 is then aligned with the cutting plane PI. This makes it easier to assemble the assembly in so far as it is possible to assemble beforehand a bearing 40 with a corresponding half-shell 22 before positioning the assembly around the crankpin 13 of the crankshaft 12. In this case, each pad 40 is mounted constrained against the inner face 27 of a corresponding half-shell 22.

The cutting of the eccentric part 18 is carried out along the plane PI passing between diametrically opposite spaces extending between two successive teeth of the rings 24. The angle A1 therefore depends on a number of teeth of the toothed crowns 24 and ignition timing on full load points. In an exemplary embodiment, the rings 24 each comprise 42 teeth so that there are 21 possible fracturing positions.

In the embodiment of Figure 5b, the two half-shells 22 are positioned relative to each other along a cutting plane PI offset from the plane P3 of the junction zone Z pads 40. The plane P1 can then be located in a plane perpendicular to the eccentricity plane P2, while the plane P3 of the junction zone Z forms an angle A1 with respect to the plane P2. In this configuration, the pads 40 are previously positioned on the crankpin 13 and the two corresponding half-shells 22 are positioned offset on the pads 40 around the crankpin 13 of the crankshaft 12.

The body 19 of each eccentric part 18 may comprise at least one radially oriented lubricating liquid passage hole 41 to allow lubrication of the hydrodynamic bearing formed by the bearings 40.

Furthermore, a device 30 for controlling the angular position of the eccentric parts 18 comprises an actuating shaft 31 and a cascade of sprockets constituted by an actuating pinion 32 mounted on the actuating shaft 31, and an intermediate gear 33, said satellite, to reverse the direction of rotation, meshing on the one hand with the actuating gear 32 and on the other hand with a ring gear 24 of the corresponding eccentric part 18 (see Figure 3).

In operation and when the actuating shaft 31 is fixed in rotation relative to the frame, the device 30 has a fixed compression ratio configuration. In transient rate, the angular position of the eccentric piece 18 located on the side of the pulley is controlled by the angular position of the actuating shaft 31 and thus pass to a new compression ratio point. For this purpose, the actuating shaft 31 can be actuated for example by means of a wheel and worm gear, or any other means of displacement adapted to the application.

In addition, through the journals 14 of the crankshaft 12, shafts 36 and pinions 37, said transfer, transmit the same kinematics of the eccentric part 18 located on the side of the actuating shaft 31 of close by. close to all the other eccentric parts 18 of the crankshaft 12. To this end, the pinions 37 mounted on the transfer shafts 36 meshing with a ring 24 of an eccentric piece 18 upstream and a ring 24 of a corresponding downstream eccentric piece 18 .

Claims (9)

1. Assembly for a system (11) for varying the compression ratio of an internal combustion engine comprising: - an eccentric part (18) having a body (19) made from two half-shells (22) assembled together , said body (19) comprising an inner face (27), an eccentric outer face (23) with respect to said inner face (27) of said body (19), two toothed rings (24) positioned on either side of said outer face (23), and an eccentricity plane (P2) passing through an axis (XI) of said inner face (27) and an axis (X2) of said outer face (23), and - two bearings (40). ) intended to be pressed against said inner face (27) of said body (19), said two pads (40) having a junction zone (Z) at their free ends, characterized in that said junction zone (Z) pads (40) extend in a plane (P3) forming an angle (A1) with respect to the eccentricity plane (P2) between 0 ° and -45 ° , especially between 0 and - 40 °. 2. The assembly of claim 1, characterized in that the angle (Al) is between 0 and - 30 °, in particular between 0 and - 23.7 °, preferably between -2 and -10 ° or between -3 and-6 °. 3. An assembly according to claim 1 or 2, characterized in that the two half-shells (22) are positioned relative to each other along a cutting plane (PI) located in an extension of the junction zone (Z) pads (40). 4. An assembly according to claim 1 or 2, characterized in that the two half-shells (22) are positioned relative to each other in a cutting plane (PI) offset from the plane (P3) of the junction zone (Z) of the pads (40). 5. The assembly of claim 3 or 4, characterized in that said cutting plane (PI) passes through diametrically opposite spaces between two successive teeth of said ring gear (24). 6. An assembly according to any one of the preceding claims, characterized in that said angle (Al) depends on a number of teeth belonging to said ring gear (24) and a combustion timing on points of full load. 7. Assembly according to the preceding claim, characterized in that the angle (A1) is between - 3 ° and - 6 °, in particular about - 4.2 ° for a number of teeth of 42. 8. An assembly according to any one of the preceding claims, characterized in that said body (19) of each eccentric part (18) comprises at least one hole (41) of lubricating liquid passage. 9. Internal combustion engine characterized in that it comprises; - a crankshaft (12), and - a system (11) for varying a compression ratio of said engine comprising at least one assembly as defined in any one of the preceding claims mounted on a crankpin (13) of said crankshaft ( 12).