FR3009337A1 - MECHANICAL TRANSMISSION DEVICE WITH SWITCHABLE EPICYCLOIDAL TRAIN - Google Patents

Abstract

Mechanical transmission device comprising an epicyclic gear train comprising a ring coupled in rotation to an input shaft, a sun gear mounted on an output shaft, a planet carrier integral in rotation with the output shaft, and at least one mounted satellite. in rotation on the planet carrier and meshing with the sun gear and the ring gear, characterized in that it comprises: a coupling stop, integral with the planet carrier; an uncoupling abutment, integral with a fixed frame, and a switching system capable of adopting a coupling position and an uncoupling position.

Description

The invention relates to the field of mechanical transmission, and more specifically to distribution in internal combustion engines. In internal combustion engines, the main function of the distribution is to transmit a rotational movement of the crankshaft, driven by the reciprocating movement of the pistons via the connecting rods, to the camshafts which control the opening and closing of the valves. The distribution is conventionally provided by a belt or a chain, which meshes with a first toothed wheel integral with the crankshaft, and a second toothed wheel integral with each cam shaft, possibly by means of a phase shifter making it possible to adjust the wedging of the camshaft, this technique being known as the variable distribution. In four-stroke engines, the gear ratio of the crankshaft to the camshafts is usually 1: 2. This report is referred to as the transmission report. In other words, the rotational speed of the camshafts is half that of the crankshaft, each valve to be raised and lowered once for two turns of crankshafts. This transmission ratio is achieved in a very simple manner by mounting at the ends of the camshafts 25 toothed wheels having a diameter (or a number of teeth) equal to twice the diameter (respectively the number of teeth) of the toothed wheel integral with crankshaft. However, there is a need to modify the transmission ratio, in particular for the purpose of limiting fuel consumption at low engine speeds, at a steady speed, or in the event of engine braking. In this case, it is typically a transmission ratio of 1: 4, that is to say that each camshaft is driven by a rotational speed equal to one quarter of that of the crankshaft. In other words, each valve is raised and lowered once for four turns of crankshaft. One solution could be to provide a distribution system with two wheel diameters for each camshaft. But this system must include a mechanism to disengage the belt (or the chain) of the first wheel and engage the second, and reciprocally, smoothly in the distribution, and without displacement of the camshaft. Such a system would be cumbersome and complex.

Document EP 1 301 692 (MA INNOVATION) describes an epicyclic gear system making it possible to perform the function of dividing the transmission ratio. A first objective is to propose a solution making it possible to modify the transmission ratio in a mechanical transmission system. A second objective is to propose a concrete solution for switching between a first rotational speed of an output shaft (typically a camshaft) and a second rotational speed of the output shaft. A third objective is to provide such a compact solution. A fourth objective is to propose such a solution that is reliable. For this purpose, it is proposed, in the first place, a mechanical transmission device comprising an epicyclic gear train comprising a ring gear rotatably connected to an input shaft, a sun gear mounted on an output shaft, an integral carrier rotation of the output shaft, and at least one satellite mounted in rotation on the planet carrier and meshing with the sun gear and the ring gear, this device comprising: a coupling stop, integral with the planet carrier, a disengagement stop secured to a fixed frame, a switching system including a jack having a liner secured to the sun gear and a rod integral with a piston slidably mounted in the liner, the shank having a first end facing the planet carrier, and a second end opposite to a fixed frame, the rod being able to adopt: o a coupling position in which a first end of the rod cooperates with the abutment stop while a second end of the rod is spaced from the uncoupling abutment, the sun gear thus secured to the carrier, and o a disengagement position in which the second end of the rod cooperates with the uncoupling abutment while the first end is spaced apart from the mating abutment, the sun gear being thus disengaged from the carrier and secured to the frame. This system makes it possible to modify the transmission ratio between the input shaft and the output shaft in a compact and reliable manner, thanks to the switching system partially integrated in the epicyclic gear train. According to various additional features, considered alone or in combination: the jacket is integrated with the sun gear; The liner is formed by a bore made in the sun gear; the piston dividing the jacket into a first chamber and a second chamber, the switching system comprises a circuit, for example hydraulic, fluid supply of the first chamber; The jack is of the single-acting type, a compression spring being mounted in the second chamber; the spring urges the piston towards the coupling position; the coupling abutment is formed at one end of a helical ramp dug in a wall integral with the carrier; The uncoupling abutment is formed at one end of a helical ramp dug in a wall integral with the frame. Secondly, there is provided a motor vehicle engine, which includes a camshaft, a crankshaft and a belt or chain for transmitting a rotational movement of the crankshaft to the camshaft, and a mechanical transmission device as presented above, whose ring gear is in gear with the belt or the chain, and whose sun gear is mounted on the camshaft. Thirdly, a motor vehicle equipped with such an engine is proposed.

Other objects and advantages of the invention will become apparent in the light of the description of an embodiment, given below with reference to the accompanying drawings in which: FIG. 1 is a perspective view from above of a vehicle comprising an engine equipped with a mechanical transmission device with epicyclic gear train; Figure 2 is a perspective view from above of an engine equipped with a mechanical transmission device epicyclic train; FIG. 3 is an exploded perspective view of the epicyclic gear transmission device in the coupling position; Figure 4 is a detail sectional view of the epicyclic gear transmission device in the coupling position; FIG. 5 is an exploded perspective view of the epicyclic gear transmission device of FIG. 3, from another angle of view and in the uncoupling position; Figure 6 is a view similar to the view of Figure 4 in an uncoupling position. FIG. 1 shows a vehicle 1 equipped with a four-stroke internal combustion engine 2. The engine 2 comprises, in a conventional manner, a frame 3 fixed (relative to the chassis of the vehicle 1) comprising a housing in which are formed a series of cylinders (typically four) closed by a yoke secured to the housing.

In the cylinders slide pistons which rotate, via rods, a crankshaft 4 which constitutes the output shaft of the engine 2, driving the wheels and, in a subsidiary manner, all the functional members of the engine 2 itself. even. The air intake (for a direct injection engine 2) or air + fuel mixture (for an indirect injection engine 2), and the evacuation of the combustion gases, are realized via valves driven in a linear movement. alternatively by camshafts (in this case two in number: one controlling the intake valves, the other the exhaust valves, this number could be greater, for example a two-cylinder engine 2 V-shaped includes four camshafts).

The camshafts, which each constitute an output shaft in the sense of the present description, are rotated by the crankshaft 4 via a distribution which is partially shown in FIGS. 1 and 2.

This distribution comprises a wheel 6 (or a pulley) integral with the crankshaft 4, a transmission device 7 (described below) for each camshaft, and a chain 8 (or a belt) of gearing distribution. with the wheel 6 and each transmission device 7 to couple them in rotation.

It will be noted that the chain 8 or the timing belt drives other members (especially a water pump), which are not shown in the figures for the purpose of simplifying the presentation. As can be seen in the figures, each transmission device 7 comprising an epicyclic gear train 9, which comprises a ring 10 in gear engagement with the chain 8 or the belt and thus rotatably coupled to the crankshaft 4, this ring 10 having a diameter equal to twice the diameter of the crankshaft wheel 4; a sun gear 11 mounted for free rotation on the camshaft, for example (as illustrated in FIGS. 4 and 6) at one end thereof; as seen in the figures, the sun gear 11 is however fixed in translation relative to the camshaft 5, being for example blocked on both sides by circlips 12; a satellite carrier 13 integral in rotation with the camshaft 5, and at least one satellite 14 (in this case two in number) mounted in rotation on the planet carrier 13 and meshing with both the sun gear 11 and the ring gear 10. The transmission device 7 is designed to adopt two configurations respectively corresponding to two different operating modes, namely: a full speed at which the speed of rotation of the camshafts is equal to half the speed of the rotation of the crankshaft 4; a mid-speed at which the rotational speed of the camshafts is equal to a quarter of the speed of rotation of the crankshaft 4.

At full speed, the sun gear 11 is secured to the planet carrier 13. The sun gear 11, the planet carrier 13 and the ring gear 10 are then integral in rotation and the camshaft 5 is thus in direct contact with the ring gear 10 ( and therefore the pulley 6). In this case, the epicyclic gear train 8 transmits the rotational movement of the ring gear 10 to the camshaft with a transmission ratio of 1: 1. Given the ratio of diameters between the ring 10 and the wheel 6 of the crankshaft 4, the general transmission ratio of the distribution is then 1: 2. At half-speed, on the other hand, the sun gear 11 is secured to the fixed frame 3 (that is to say the casing or the yoke) while being free to rotate with respect to the planet carrier 13. The rotation of the ring gear 10 is transmitted to the planet carrier 13 (and thus to the camshaft) by gearing of the satellites 14. In this case, the epicyclic gear train 9 transmits the rotational movement of the ring gear 10 to the camshaft with a transmission ratio of 1: 2. Given the ratio of diameters between the ring 10 and the wheel 6 of the crankshaft 4, the general transmission ratio of the distribution is then 1: 4. To allow the passage from the full speed configuration to the mid-speed configuration and vice versa, the transmission device 7 is equipped with a switching system as well as two stops 16, 17, namely a stop 16 of FIG. integral coupling of the planet carrier 13, and an abutment stop 17 integral with the frame 3. According to a preferred embodiment illustrated in Figures 3 and 4, the abutment 16 of coupling is formed at the end of a ramp 18 helicoidal hollowed in a wall 19 integral with the planet carrier 13. Likewise, according to an embodiment illustrated in FIGS. 5 and 6, the uncoupling abutment 17 is formed at the end of a helical ramp 20 hollowed in a wall 21 is connected to the frame 3. By a spiral ramp 18, 20 is meant a circular path flush at one of its ends to a wall 19, 21 and, at a second end, to the bottom of the abutment 16, 17 associated at the wall 19, 21, as is particularly visible in the detail of Figure 5. The switching system 15 comprises a jack 22 having a liner 23 secured to the sun gear 11 and a rod 24 secured to a piston 25 slidably mounted in the liner 23 .

The rod 24 has a first end 26 facing the planet carrier 13, and a second end 27, opposite, facing the fixed frame 3. In the coupling position, the first end 26 of the rod 24 cooperates with the abutment 16 coupling while the second end 27 of the rod 24 is spaced from the stop 17 of uncoupling, the sun gear 11 thus being secured to the In the uncoupling position, the second end 27 of the rod 24 cooperates with the uncoupling abutment 17 while the first end 26 is spaced apart from the mating abutment 16, the sun gear 11 thus being disengaged from the satellite carrier 13 and secured to the frame 3. According to a preferred embodiment illustrated in Figures 3 to 6, the liner 23 of the transmission device 7 is integrated with the sun gear 11. More specifically, the liner 23 is formed by a bore made in the sun gear 11. The piston 25, housed in the jacket 23, then divides the jacket 23 into two chambers 28, 29, namely a first chamber 28 facing the abutment 16 coupling and a second chamber 29 facing the stop 17 of uncoupling. According to an embodiment shown in the figures, the transmission system 7 further comprises a hydraulic fluid supply circuit 30 of the first chamber 28. The hydraulic circuit 30 comprises, in the first place, a feed duct 31 formed by a bore made axially in the camshaft and in communication with a source of pressurized fluid (typically compressed air) via a solenoid valve (not shown). The hydraulic circuit comprises, secondly, a cylindrical distribution chamber 32 formed internally in the sun gear 11, and a conduit 33 which puts the distribution chamber 32 in communication with the first chamber 28 of the jacket 23. A radial duct 34 is drilled in the cam shaft 5 to communicate the supply conduit 31 with the distribution chamber 32. In this way, the first chamber 28 of the jacket 23 is in permanent fluid communication with the source of fluid under pressure via the solenoid valve.

In the second chamber 29 of the jacket 23 is mounted a return spring 35 operating in compression, exerting on the piston 25 a force which urges it towards the coupling position. It is thus understood that the jack 22 of the switching system 5 is of the single-acting type. The passage in the coupled position is controlled by the connection, via the solenoid valve, of the first chamber 28 to the source of pressurized fluid, which puts the first chamber 28 under pressure against the return spring 35 which is located compressed (Figure 6), while the passage in the uncoupled position 10 is controlled via the solenoid valve by the interruption of the communication of the first chamber 28 with the source of pressurized fluid and the communication of the first chamber 28 with a discharge volume (eg free air), accompanied by the deployment of the return spring. According to a preferred embodiment illustrated in FIGS. 4 and 6, the rod 24 is provided at each of its ends with a cavity 36 in which a ball 37 is housed. The ball 37 is urged towards the outside of the rod. 24 by a compression spring (not shown). Each ball 37 is retained in its cavity 36 by a restriction 38 of diameter 20 at the end of the rod 24. These balls 37 have the function of damping the shocks between the rod 24 and the bottom of the ramps 18, 20 helical, and to limit the frictional wear of the rod 24 against the bottom of the ramps 18, 20. These balls 37 also make it possible to maintain a coupling position or in a disengagement position when the device 7 is in position. transition phase from one position to another. The operation of the transmission device 7 is now described, starting from the full-speed configuration, in which the sun gear 11 is secured to the planet carrier 13. In this configuration, the first chamber 28 of the jacket 23 is in communication with the discharge volume, and, by the return force of the spring 35, the first end 26 of the rod 24 cooperates with the abutment 16 of coupling while the second end 27 of the rod 24 is spaced from the stop 17 uncoupling. In this way, the sun gear 11 is secured to the planet carrier 13 and disengaged from the frame 3.

No rotation of the sun gear 11 relative to the planet carrier 13 being possible, the satellites 14 are secured to both the ring gear 10 and the sun gear 11, so that the rotation of the ring gear 10 causes, via the satellites 14 , the integral rotation of the sun gear 11 and thus that of the camshaft, with a transmission ratio of 1: 1 of the ring gear 10 to the camshaft 5 (and therefore a transmission ratio of 1: 2 of the crankshaft wheel 4 to the camshaft 5). The transition from the full-speed configuration to the mid-speed configuration is done by pressurizing the first chamber 28 of the liner 23 against the return spring. The first end 26 of the rod 24 leaves the abutment 16 of coupling while the second end 27 of the rod 24 slips into the helical ramp 20 until it cooperates with the abutment 17 of uncoupling, the sun gear 11 being then secured to rotation to the frame 3. The fastening of the sun gear 11 to the frame and its separation from the planet carrier 13 makes the satellites 14 independent of the sun gear 11. The rotation of the ring gear 10 causes, by simultaneously meshing of the satellites in the ring gear 10 and on the sun gear 11, the rotation of the planet carrier 13 and thus the rotation of the camshaft, with a transmission ratio of 1: 2 of the ring gear 10 to the camshaft (and therefore a transmission ratio of 1: 4 crankshaft 4 to the camshaft 5). The transition from full speed to mid-speed (or vice versa) can be controlled automatically by order of a computer connected to the solenoid valve. When the on-board computer orders the change of gear, the pressure generator pressurizes the first chamber 28 of the sheath 23 of the switching system 15 then pushing the piston 25 towards the disengagement stop 17 and compressing the compression spring 35 . When moving the rod 24 from the uncoupling position to the coupling position, the ball 37 housed in the cavity 36 of the first end 26 of the rod 24 comes into contact with the bottom of the spiral ramp 18 and rolls on the this, which limits the frictional wear of the first end 26 of the rod 24. Similarly, during the displacement of the rod 24 from the coupling position to the uncoupling position, the ball 37 housed in the cavity 36 of the second end 27 comes into contact with the bottom of the helical ramp and rolls on it, which limits the frictional wear of the second end 27 of the rod 24. According to an embodiment not shown in FIGS. Figures, the abutment 17 of uncoupling could be carried by a movable part relative to the frame 3, this part then being set in motion via a hydraulic, pneumatic or electrical. The mechanical transmission device 7 with epicyclic gear 9 makes it possible to switch from full speed to mid-speed, and conversely, in a compact and reliable manner. The compactness is in particular provided by the epicyclic gear and the integration of the switching system with the existing parts. Reliability is provided first by the intrinsic reliability of the proven epicyclic trains, then by the simplicity and robustness of the switching system. The presence of the helical ramps 18, 20 makes it possible to soften the shocks due to the change of regime.

Claims (9)

REVENDICATIONS1. Device (7) for mechanical transmission with epicyclic gear (9) which comprises a ring gear (10) rotatably coupled to an input shaft, a sun gear (11) mounted on an output shaft, a carrier (13) secured to in rotation of the output shaft, and at least one satellite (14) rotatably mounted on the planet carrier (13) and meshing with the sun gear (11) and the ring gear (10), characterized in that it comprises: a coupling stop (16), integral with the planet carrier (13); a stop (17) uncoupling, integral with a frame (3) fixed; a switching system (15) including a jack (22) having a liner (23) integral with the sun gear (11) and a rod (24) integral with a piston (25) slidably mounted in the liner (23), the rod (24) having a first end (26) facing the planet carrier (13), and an opposite second end (27) facing the fixed frame (3), the rod (24) being able to adopt: o a position in which the first end (26) of the rod (24) cooperates with the abutment (16) of coupling while the second end (27) of the rod (24) is spaced from the stop (17) of uncoupling, the sun gear (11) thus being secured to the planet carrier (13), and o an uncoupling position in which the second end (27) of the rod (24) cooperates with the stop (17) of uncoupling; the first end (26) is spaced from the coupling stop (16), the sun gear (11) thus being desolated darisé the carrier-satellite (13) and secured to the frame (3). 2. Device (7) according to claim 1, characterized in that the sleeve (23) is integrated in the sun gear (11). 3. Device (7) according to claim 2, characterized in that the liner (23) is formed by a bore made in the sun gear (11). 4. Device (7) according to one of the preceding claims, characterized in that, the piston (25) dividing the jacket (23) into a first chamber (28) and a second chamber (29), the system (15) of switching comprises a fluid supply circuit (30) of the first chamber (28). 5. Device (7) according to claim 4, characterized in that the cylinder (22) is of the single-acting type, a compression spring (35) being mounted in the second chamber (29). 6. Device (7) according to claim 5, characterized in that the spring (35) biases the piston (25) to the coupling position. 7. Device (7) according to one of the preceding claims, characterized in that the abutment (16) coupling is formed at one end of a ramp (18) hollowed in a wall (19) integral with the holder satellite (13). 8. Device (7) according to one of the preceding claims, characterized in that the abutment (17) of uncoupling is formed at one end of a ramp (20) helical dug in a wall (21) integral with the frame (3). ). Motor (2) to a motor vehicle (1), which comprises a camshaft (5), a crankshaft (4) and a belt (8) or a chain for transmitting a rotational movement of the crankshaft ( 4) to the camshaft (5), characterized in that it comprises, a device (7) for mechanical transmission according to one of the preceding claims, the crown (10) is in gear engagement with the belt or chain (8), and whose sun gear (11) is mounted on the camshaft (5). 1 O. Vehicle (1) automobile equipped with a motor (2) according to claim 9.