FR3109418A1 - AUTOMATIC CLUTCH SYSTEM FOR AN AIRCRAFT PROPULSION SYSTEM - Google Patents

Abstract

This clutch system comprises: a shaft (108); first and second pinions (116, 118) mounted loose on the shaft (108); at least a first, respectively second, clutch element (122, 124) integral in rotation with the shaft (108) and designed to be selectively engaged and disengaged from the first, respectively second, pinion (116, 118); at least one movable part (122) relative to the shaft (108) and cooperating with the first clutch elements (122), so as to move between a first extreme position in which the first clutch element (s) (122) are disengaged and a second extreme position in which the first clutch element (s) (122) are engaged; and an interconnection system (810) of the clutch elements (122, 124) designed so that the clutch, respectively the disengagement, of the first clutch element (s) (122) causes the disengagement, respectively the clutch, of the second clutch element (s) (124). It further comprises a return device (808) designed to return each moving part (122) to a predefined of its two extreme positions regardless of the position of the moving part (122) Figure for the summary: Fig. 10

Description

AUTOMATIC CLUTCH SYSTEM FOR AN AIRCRAFT PROPULSION SYSTEM

The present invention relates to an automatic clutch system for an aircraft propulsion system.

• un arbre ;
• des premier et deuxième pignons montés fous sur l’arbre ;
• au moins un premier, respectivement deuxième, élément d’embrayage solidaire en rotation de l’arbre et conçu pour être sélectivement embrayé au premier, respectivement deuxième, pignon et débrayé du premier, respectivement deuxième, pignon ;
• au moins une pièce mobile par rapport à l’arbre et coopérant avec les premiers éléments d’embrayage, de manière à se déplacer entre une première position extrême dans laquelle le ou les premiers éléments d’embrayage sont débrayés et une deuxième position extrême dans laquelle le ou les premiers éléments d’embrayage sont embrayés, la pièce mobile étant conçue pour passer d’une position extrême à l’autre en prenant une succession continue de positions intermédiaires, en fonction d’une vitesse de rotation de l’arbre ; et
• un système d’interconnexion des éléments d’embrayage conçu pour que l’embrayage, respectivement le débrayage, du ou des premiers éléments d’embrayage entraîne le débrayage, respectivement l’embrayage, du ou des deuxièmes éléments d’embrayage.

French patent application published under number FR 2 952 677 A1 describes an automatic clutch system for an aircraft propulsion system, of the type comprising:

• a tree ;
• first and second sprockets mounted loose on the shaft;
• at least one first, respectively second, clutch element integral in rotation with the shaft and designed to be selectively engaged with the first, respectively second, pinion and disengaged from the first, respectively second, pinion;
• at least one part movable relative to the shaft and cooperating with the first clutch elements, so as to move between a first extreme position in which the first clutch element or elements are disengaged and a second extreme position in which the first clutch element or elements are engaged, the moving part being designed to pass from one extreme position to the other by taking a continuous succession of intermediate positions, as a function of a speed of rotation of the shaft; And
• a system for interconnecting the clutch elements designed so that the engagement, respectively the disengagement, of the first clutch element(s) causes the disengagement, respectively the engagement, of the second clutch element(s).

In this document, the movable part and the interconnection system are made together by a switching sleeve interposed between the two pinions and mounted so as to be able to move in axial translation on the shaft between an extreme clutch position on the first pinion and a position extreme clutch on the second gear. To this end, the switching sleeve has two side faces respectively facing the two pinions and respectively carrying the two sets of clutch elements, the latter being in the form of claws intended to engage respectively with the two pinions.

To make the sleeve pass from one of the extreme positions to the other, each pinion has ejection faces on which the claws coupled to this pinion are designed to slide, when this pinion rotates at a higher speed than that of the sleeve. (and therefore the shaft), to move the sleeve axially towards the other pinion.

Furthermore, to stabilize the sleeve in its two extreme positions, the clutch system comprises an indexing system in the form of a ball pushed transversely by a spring and cooperating with a peripheral cam provided on the sleeve. Thus, this indexing system constitutes a return device designed to return the sleeve to each extreme position when it is on the half stroke on the side of this extreme position.

The clutch system of the patent application FR 2 952 677 A1 has the drawback that, despite the indexing system, the sleeve can remain in neutral because it takes a lot of energy to force the sleeve to reach and fully engage the face-to-face gable. In addition, the profile of the cam can dull over time and flatten, or even generate a hollow at the top of it, defining an intermediate stable position, in which the sleeve is not engaged with either of the two sprockets.

It may thus be desired to provide a clutch system for an aircraft engine which makes it possible to overcome at least some of the aforementioned problems and constraints.

To this end, an automatic clutch system is proposed for an aircraft propulsion system, of the specified type, characterized in that it further comprises a return device designed to return the moving part to a predefined one of its two extreme positions regardless of the position of the moving part.

Thus, thanks to the invention, the moving part is always returned to one of the predefined extreme positions when it is in an intermediate position. The risk of an intermediate equilibrium position in which the moving part could remain is therefore greatly reduced.

Optionally, each moving part comprises a counterweight integral in rotation with the shaft and movable radially with respect to the shaft, the extreme positions are a position close to and a position away from the shaft, and the counterweight is designed to pass from its close position to its remote position by undergoing a centrifugal force resulting from the speed of rotation of the shaft.

Also optionally, each flyweight comprises one of the clutch elements .

Also optionally, the interconnection system comprises, for each clutch element, a finger secured to this clutch element, and a cam movable relative to the shaft and having grooves in which the fingers are respectively engaged. .

Also optionally, the interconnection system comprises at least one articulated arm, a first end of which is pivotally mounted on one of the first clutch element(s) and a second end of which is pivotally mounted on one of the second clutch elements.

Also optionally, the clutch system further comprises a sleeve integral with the shaft, on which each clutch element is pivotally mounted.

Also optionally, the flyweights are separate from the first clutch elements.

Also optionally, the interconnection system comprises a sleeve mounted axially movable on the shaft and carrying the clutch elements, and the clutch system comprises a mechanism designed to convert a radial displacement of each flyweight into an axial displacement of the sleeve.

Also optionally, the mechanism comprises, for each counterweight, at least one articulated arm, a first end of which is pivotally mounted on the sleeve and a second end of which is pivotally mounted on the counterweight.

Also optionally, the moving part includes a sleeve mounted to move at least axially on the shaft and carrying the clutch elements, the interconnection system includes the sleeve, and the second pinion has ejection faces on which the sleeve is designed to slip when this sleeve rotates at a lower speed than the second gear, in order to be ejected towards the first gear.

Also optionally, the sleeve is mounted on the shaft by means of a helical connection.

Also optionally, the return system comprises, for each moving part, a return spring.

• un démarreur/ générateur présentant un arbre de démarreur/générateur ;
• un ensemble moteur présentant un arbre moteur ;
• des premier et deuxième pignons fixes portés par l’un parmi l’arbre moteur et l’arbre de démarreur/générateur ; et
• un système d’embrayage selon l’invention, dans lequel l’arbre est l’autre parmi l’arbre moteur et l’arbre de démarreur/générateur et dans lequel les premier et deuxième pignons fous sont respectivement engrenés avec les premier et deuxième pignons fixes.

An aircraft propulsion system is also proposed, comprising:

• a starter/generator having a starter/generator shaft;
• a motor assembly having a motor shaft;
• first and second fixed gears carried by one of the motor shaft and the starter/generator shaft; And
• a clutch system according to the invention, in which the shaft is the other of the motor shaft and the starter/generator shaft and in which the first and second idler gears are respectively meshed with the first and second gears fixed.

The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the appended drawings in which:

FIG. 1 schematically represents an aircraft propulsion system comprising a clutch system, according to a first embodiment of the invention, designed to engage a shaft with selectively first and second idler gears, and

figure 2 schematically represents the clutch system of figure 1 engaging the shaft with the second pinion, when the shaft is not rotating,

figure 3 schematically represents the clutch system of figure 1, engaging the shaft with the second pinion, when the shaft begins to rotate,

FIG. 4 schematically represents the clutch system of FIG. 1, at the start of switching from the clutch to the first pinion,

FIG. 5 schematically represents the clutch system of FIG. 1, at the end of switching from the clutch to the first pinion,

figure 6 schematically represents the clutch system of figure 1, engaging the shaft with the first pinion,

FIG. 7 is a three-dimensional view of a clutch system according to a second embodiment of the invention, which can be used in the aircraft propulsion system of FIG. 1,

FIG. 8 is a truncated three-dimensional view of the first pinion and of elements of the clutch system of FIG. 7 cooperating with this first pinion,

FIG. 9 is a truncated three-dimensional view of the second pinion and of elements of the clutch system of FIG. 7 cooperating with this second pinion,

Figure 10 is a view from each side of the clutch system of Figure 7, engaging the shaft with the second pinion,

Figure 11 is a view from each side of the clutch system of Figure 7, engaging the shaft with the first pinion,

FIG. 12 schematically represents a clutch system according to a third embodiment of the invention, which can be used in the aircraft propulsion system of FIG. 1 and coupling the shaft with the second pinion,

Figure 13 is a three-dimensional view of the clutch system of Figure 12,

figure 14 schematically represents the clutch system of figure 12, engaging the shaft with the first pinion,

FIG. 15 schematically represents a clutch system according to a fourth embodiment of the invention, which can be used in the aircraft propulsion system of FIG. 1 and coupling the shaft with the second pinion,

figure 16 schematically represents the clutch system of figure 15, engaging the shaft with the first pinion, and

FIG. 17 schematically represents a clutch system according to a fifth embodiment of the invention, which can be used in the aircraft propulsion system of FIG. 1.

In the following description, similar elements between the different embodiments described will be designated by the same references.

Referring to Figure 1, an aircraft propulsion system 100 implementing the invention will now be described.

The propulsion system 100, also called a turbomachine, first of all comprises an engine assembly 102 having an engine shaft 104. The engine assembly 102 comprises for example a gas generator 101 having an HP body (for "high pressure"), as well as one or more transmission boxes (from the English "Gear Box") 103, through which the HP body is designed to drive the motor shaft 104. For example, the motor assembly 102 can comprise a gearbox accessory transmission designated by the acronym AGB (from the English “Accessory Gear Box”) and the motor shaft 104 can then correspond to the output shaft of the AGB.

The propulsion system 100 further comprises, on the one hand, a starter / generator 106 (from the English "Starter Generator"), hereinafter simply called "SG", having an SG shaft 108 and, on the other hand , a clutch system 110, according to a first embodiment of the invention, connecting the SG shaft 108 to the motor shaft 104.

The clutch system 110 comprises two motor pinions 112, 114 fixedly mounted on the motor shaft 104, as well as two SG pinions 116, 118 loosely mounted on the SG shaft 108 and respectively meshed with the motor pinions 112, 114.

The clutch system 110 further comprises a sleeve 120 mounted axially movable on the shaft SG 108 between the two pinions SG 116, 118.

The sleeve 120 is thus designed to move between a first extreme position in which it is clutched to the first pinion SG 116 and a second extreme position in which it is clutched to the second pinion SG 118.

To engage with the SG pinions 116, 118, the sleeve 120 has two side faces respectively facing the two SG pinions 116, 118. The side face facing the first SG pinion 116 carries at least a first clutch element 122 designed to engage with this first pinion SG 116, in particular with complementary clutch elements 123 carried by the first pinion SG 116. Similarly, the side face facing the second pinion SG 118 carries at least one second element of clutch 124 designed to engage with this second pinion SG 118, in particular with complementary clutch elements 125 of this second pinion SG 118. In the example described the clutch elements 122, 123, 124, 125 are dogs.

Still in the example described, the clutch system 110 comprises a helical connection 130 by which the sleeve 120 is mounted on the shaft SG 108. For example, the shaft SG 108 is provided with an external thread (not shown ), while the sleeve 120 is provided with an internal thread (not shown) cooperating with the external thread of the SG shaft 108.

It will be appreciated that the sleeve 120 forms a system for interconnecting the clutch elements 122, 124. Indeed, the sleeve 120 carrying the clutch elements 122, 124 during its movement, the clutch, respectively the disengagement, of the first clutch element or elements 122 causes the disengagement, respectively the clutch, of the second clutch element or elements 124, and vice versa.

The clutch system 110 further comprises a return device 132 designed to return the sleeve 120 to one of the two predefined extreme positions, the extreme clutch position with the second pinion SG 118 in the example described, whatever or the position of the sleeve 120. In the example described, the return device 132 comprises at least one spring fixed, at one end, to the first pinion SG 116 and, at another end, to the sleeve 120, so as to be compressed when sleeve 120 approaches first SG pinion 116 to provide sleeve 120 with a biasing force toward second SG pinion 118.

With reference to FIG. 2, the complementary clutch elements 123, 125 of the SG pinions 116, 118 have oblique faces 202, 204 for ejecting the sleeve 120. Furthermore, the clutch elements 122, 124 of the sleeve 120 have hooks 206, 208 intended to cooperate with complementary hooks 210, 212 presented by the complementary clutch elements 123, 125 of the SG pinions 116, 118.

Figures 2 to 6 illustrate different positions of the sleeve 120 during its movement between its position engaged in the second pinion SG 118 and its position engaged in the first pinion SG 116.

The operation of the clutch system 110 will now be described.

Initially, engine assembly 102 and SG 106 are stationary. Due to the return system 132, the sleeve 120 is clutched to the second pinion SG 118. This initial configuration is illustrated in Figure 2.

To start the motor assembly 102, the SG 106 is turned on in starter mode so as to rotate the SG shaft 108. Due to the helical link 130, the rotation of the SG shaft 108 causes the rotation of the sleeve 120 which in turn drives the second pinion 118 in rotation. In addition, still due to the helical connection 130, the rotation of the shaft SG 108 causes the translation of the sleeve 120 in the direction of the first pinion SG 116. This translation is stopped by the cooperation of the hooks 208, 212 (FIG. 3), so that the shaft SG 108 and the sleeve 120 are at this time integral in rotation and rotate at the same speed. Thus, SG 106 in starter mode provides torque to motor assembly 102 through SG shaft 108, sleeve 120, second SG pinion 118, second motor pinion 114, and motor shaft 104. of this starting phase of the motor assembly 102, the speed of rotation is initially zero, then low, which leads to the need for a high torque. Thus, it is possible to size the second pinions 114, 118 so that they have a high reduction ratio making it possible to limit the torque in the meshes between them by increasing the relative speed of the SG 106 in starter mode with respect to the whole engine 102.

Starting the motor assembly 102 has the consequence that the latter drives the SG pinions 116, 118 through the motor shaft 104 and respectively the motor pinions 112, 114. In particular, the motor assembly 102 drives the pinion SG 118 at a higher speed than the sleeve 120 and the SG shaft 108. The second clutch elements 124 then uncouple from the complementary clutch elements 125 and come into contact with the ejection faces 204 on which they slide (Figure 4), thereby ejecting the sleeve 120 towards the first SG pinion 116 overcoming the restoring force of the restoring device 132.

The presence of the helical connection 130 facilitates the ejection of the sleeve 120. Indeed, the SG 106 detects the start of the motor assembly 102 and, in response, suddenly accelerates the rotation of the shaft SG 108 for a time, by example of predefined duration. Due to the inertia of the sleeve 120, this acceleration is converted by the helical connection 130 mainly into a translation of the sleeve 120 towards the first pinion SG 116, adding to the translation due to the ejection by the faces of ejection 204 of the second pinion SG 118. After this acceleration time, the SG 106 goes into generator mode.

The sleeve 120 then comes to its clutch position with the first SG pinion 116 (Figure 5), where the clutch elements 122, 123 mate (Figure 6). At this time, the motor assembly 102 provides torque to the SG 106 in generator mode through the motor shaft 104, the first motor pinion 112, the first SG pinion 116 and the sleeve 120. However, in generator mode, the SG 106 needs the lowest possible rotational speed variation range, associated with a maximum rotational speed that is not too high. Indeed, a high speed would lead to equally high stresses on the generator rotor, as well as dynamic forces related to the kinetic energy. To avoid this, it is possible to size the first pinions 112, 116 differently from the second pinions 114, 118 so that they have a low reduction ratio (lower than the reduction ratio of the second pinions 114, 118) making it possible to limit the speed of the SG 108 shaft.

With reference to Figures 7 to 11, a clutch system 700 according to a second embodiment of the invention will now be described.

Referring to Figure 7, in the clutch system 700, the sleeve, now designated by the reference 702, is integral with the shaft SG 108 in particular axially and in rotation. It therefore remains in the same axial position relative to the SG pinions 116, 118.

As can be seen in Figure 8, each first clutch element 122 is in the form of a shoe designed to rub against the complementary clutch element 123 carried by the first pinion SG 116 and in the form of a track. In addition, each first clutch element 122 is pivotally mounted on the sleeve 702 along a respective axis 806 parallel to the shaft SG 108. Thus, each first clutch element 122 is movable in particular radially relative to the shaft. SG 108, so as to move between a first position close to the shaft SG 108 in which it is disengaged from the first pinion SG 116 and a second position far from the shaft SG 108 in which it is engaged by friction with the first pinion SG 116 (situation illustrated in Figure 8).

The clutch system 700 further comprises a return device 808 designed to return each first clutch element 122 to its first position (disengaged position close to the SG shaft 108). In the example described, the return device 808 comprises, for each first clutch element 122, a return spring 808 fixed at one end to the sleeve 702 and at another end to the first clutch element 122.

In the example described, each first clutch element 122 forms a flyweight undergoing a centrifugal force resulting from a rotational speed of the SG shaft 108. As will be explained below, the passage from the first position to the second position is done using this centrifugal force.

The clutch system 700 further comprises a system 810 for interconnecting the clutch elements 122, 124 designed so that the engagement, respectively the disengagement, of the first clutch elements 122 causes the disengagement, respectively the clutch, second clutch elements 124 which will be described in detail later with reference to Figure 9.

The interconnection system 810 comprises first of all, for each first clutch element 122, a lever 812 integral with this first clutch element 122 so as to rotate at the same time as it around the axis 806. This lever 812 is provided with a finger 814.

The interconnection system 810 further comprises a cam 816 movable relative to the shaft SG 108, in rotation around the latter in the example described. The cam 816 has radial grooves 818 in which the fingers 814 of the levers 812 are respectively engaged. Thus, the movement of the first clutch elements 122 between their close and remote positions causes a corresponding rotation of the cam 816.

Referring to Figure 9, as with the first clutch elements 122, each second clutch element 124 is in the form of a shoe designed to rub against a track forming the complementary clutch element 125 of the second pinion. SG 118. In addition, each second clutch element 124 is pivotally mounted on the sleeve 702 along a respective axis 906, for example parallel to the shaft SG 108. Thus, each second clutch element 124 is movable in particular radially relative to the shaft SG 108, so as to move between a first position close to the shaft SG 108 in which it is disengaged from the second pinion SG 118 (situation illustrated in FIG. 9) and a second position far from the shaft SG 108 in which it is clutched by friction to the second pinion SG 118.

The interconnection system 810 further comprises, for each second clutch element 124, a lever 912 integral with this second clutch element 124 so as to rotate at the same time as it around the axis 906. This lever 912 is provided with a finger 914. The cam 816 also has radial grooves 918 in which the fingers 914 of the levers 912 are respectively engaged. Thus, the rotation of the cam 816 causes the displacement of the second clutch elements 124 between their near and far positions.

Figures 10 and 11 illustrate an embodiment identical to that of Figures 7 to 9, except that it comprises three first clutch elements 122 and three second clutch elements 124 instead of four, and that the grooves 818, 918 are oblique and not radial.

The operation of the clutch system 700 will now be described in more detail.

Initially, engine assembly 102 and SG 106 are stationary. Due to the return system 808, the sleeve 702 is engaged to the second pinion SG 118. This initial configuration is illustrated in Figure 10.

To start the engine assembly 102, the SG 106 is turned on in starter mode so as to rotate the shaft SG 108. Due to this rotation, the first clutch elements 122 experience a centrifugal force. Second clutch elements 124 also experience centrifugal force, but to a lesser extent due to lower mass and being located closer to SG shaft 108 than first clutch elements 122 .

However, the return system 808 is dimensioned so as to compensate for this centrifugal force so that the first clutch elements 122 remain in the disengaged position and the second clutch elements 124 remain in the engaged position. Thus, SG 106 in starter mode provides torque to motor assembly 102 through SG shaft 108, sleeve 702, second SG pinion 118, second motor pinion 114, and motor shaft 104.

Starting the motor assembly 102 has the consequence that the latter drives the SG pinions 116, 118 through the motor shaft 104 and respectively the motor pinions 112, 114. In particular, the motor assembly 102 drives the pinion SG 118 and hence the sleeve 702 and the SG shaft 108, at a high speed so that the centrifugal force overcomes the restoring force of the return device 808, as well as the centrifugal force of the second clutch elements 124. Thus, the first clutch elements 122 pass from their disengaged position to their engaged position. Due to the interconnection system 810, this displacement of the first clutch elements 122 causes the passage of the second clutch elements 124 from their engaged position to their disengaged position.

In parallel, the start of the engine assembly 102 is detected by the SG 106. To facilitate the passage of the first clutch elements 122 to their engaged position, the SG 106 preferably accelerates the rotation of the shaft SG 108 during one time, for example of predefined duration, in response to the detection of the start of the motor assembly 102. Thus, if the drive by the motor assembly 102 does not generate sufficient centrifugal force, the accelerated rotation of the SG 106 provides a centrifugal force allowing the transition to the engaged position of the first clutch elements 122. The SG 106 then switches to generator mode. At this time, motor assembly 102 provides torque to SG 106 in generator mode through motor shaft 104, first motor pinion 112, first SG pinion 116, sleeve 702 and SG shaft 108.

The advantage of using centrifugal force is that the shift to a engaged position at the first pinion SG 116 depends only on the speed of the shaft SG 108, and not on the speed difference between the speed of the SG shaft 108 and the speed of the second pinion 118 as in the first embodiment of Figure 1. Thus, it suffices to ensure that the SG shaft 108 reaches sufficient speed without worrying about the operating speed of the motor assembly 102 driving the second pinion 118.

With reference to Figures 12 to 14, a clutch system 1200 according to a third embodiment of the invention will now be described.

Referring to Figure 12, in the clutch system 1200, the clutch elements 122, 124 are pivotally mounted on the sleeve 702 along a respective axis 1202, but which is this time perpendicular to the shaft SG 108 (perpendicular in the plane of figure 12). In the example described, the clutch system 1200 comprises, for each clutch element 122, 124, a lever 1204 carrying the clutch element 122, 124 and having one end mounted on the sleeve 702 pivoting around the axis 1202. Still in the example described, the clutch elements 122, 124 are grouped in pairs each comprising a first clutch element 122 and a second clutch element 124 sharing the same axis 1202 of pivoting.

Each first clutch element 122 is thus designed to assume a position close to the shaft SG 108 in which it is disengaged from the first complementary element 123 (position of FIG. 12) and a position far from the shaft SG 108 in which it is clutched to one of the first complementary elements 123. Conversely, each second clutch element 124 is designed to assume a position close to the SG shaft 108 in which it is clutched to one of the second complementary elements 125 ( position of figure 12) and a position away from the shaft SG 108 in which it is disengaged from the second complementary elements 125.

In the clutch system 1200, the system for interconnecting the clutch elements 122, 124 comprises, for each pair of clutch elements 122, 124, an articulated arm 1206 whose first end is pivotally mounted on the first clutch element 122 of the pair, while a second end is pivotally mounted on the second clutch element 124 of the pair. In the example described, the ends of the articulated arm 1206 are respectively pivotally mounted on the levers 1204.

The articulated arm 1206 comprises several rigid bars pivoting relative to each other, for example five bars in the example described. Still in the example described, the bars are pivotable along axes parallel to the pivot axis 1202 of the clutch elements 122, 124. One of the rigid bars, designated by the reference 1208, is preferably mounted on the sleeve 702 movable in radial translation relative to the shaft SG 108. For example, this bar 1208 has a through hole 1210 engaged in a radial rod 1212 of the sleeve 702, so as to slide thereon.

Each articulated arm 1206 interconnects the two clutch elements 122, 124 of the corresponding pair, so that a displacement of one of the clutch elements 122, 124 from one position to the other causes the same displacement of the other of the clutch elements 122, 124.

The clutch system 1200 further comprises a device 1214 for returning the clutch elements 122, 124 to their position close to the shaft SG 108 (corresponding to a disengaged position for the first clutch elements 122 and an engaged position for the second clutch elements 124). In the example described, the return device 1214 comprises a spring 1214 mounted on each rod 1212 of the sleeve 702 and intended to push back the bar 1208 mobile in radial translation.

Figure 13 more specifically illustrates the structure of the clutch system 1200 and Figure 14 illustrates the situation where the clutch elements 122 are engaged and the clutch elements 124 are disengaged.

The operation of the clutch system 1200 is substantially similar to that of the clutch system 700, except that the centrifugal force experienced by the first clutch elements 122 and the centrifugal force experienced by the second clutch elements 124 reinforce to switch the clutch system 1200.

With reference to Figures 15 and 16, a clutch system 1500 according to a fourth embodiment of the invention will now be described.

Referring to Figure 15, in the clutch system 1500, the weights, designated by the reference 1502, are separate from the clutch elements 122, 124. These weights 1502 are radially movable relative to the shaft SG 108. For example, they are mounted in translation on respective radial rods 1504 integral with the shaft SG 108. Thus, each flyweight 1502 is designed to move between a position close to the shaft SG 108 and a position far from the shaft. SG108.

Also, in the 1500 clutch system, the interconnect system has a 1506 sleeve movably mounted axially on the shaft SG 108 (but integral in rotation) and carrying, on the side of the first pinion SG 116, the first clutch element(s) 122 and, on the side of the second pinion SG 116, the second element(s) clutch 124.

The clutch system 1500 further comprises a mechanism designed to convert a radial displacement of each counterweight 1502 into an axial displacement of the sleeve 1506. In the example described, this mechanism comprises, for each counterweight 1502, at least one articulated arm 1508 whose first end is pivotally mounted on the sleeve 1506 and whose second end is pivotally mounted on the counterweight 1502. In the example described, the articulated arm 1508 further comprises a third end pivotally mounted on the radial rod 1504.

Thus, when the flyweights 1502 are in the position close to the shaft SG 108, the sleeve 1506 is on the side of the second pinion SG 118 so that the second clutch element(s) 124 are engaged with the second pinion SG 118. When the flyweights 1502 are in a position away from the shaft SG 108, the sleeve 1506 is on the side of the first pinion SG 116 so that the first clutch element(s) 116 are engaged with the first pinion SG 116.

The clutch system 1500 further includes a return device 1510 designed to return each flyweight 1502 to its position close to the SG shaft 108, regardless of its position. In the example described, the return device 1510 comprises, for each flyweight 1502, a spring fixed, at one end, to the radial rod 1504 and, at another end, to the flyweight 1502, so as to be compressed when the flyweight 1502 moves away from SG shaft 108 to provide flyweight 1502 with a restoring force toward its position close to SG shaft 108.

As shown in Figure 15, clutch system 1500 is engaged to second gear SG 118, while Figure 16 illustrates clutch system 1500 engaged to first gear SG 116.

The operation of the clutch system 1500 is essentially similar to that of the clutch systems 700, 1200 described previously.

FIG. 17 illustrates a clutch system 1700 according to a fifth embodiment of the invention identical to the clutch system 1500 except that the clutch elements 122, 124 are toothed, for example rectilinear, while the clutch elements 122, 124 of the clutch system 1500 are disc allowing a certain continuity of coupling.

It is clear that a clutch system such as those described above makes it possible to reduce the risk of remaining in an intermediate position in which none of the idler gears is engaged on the shaft.

It will also be noted that the invention is not limited to the embodiments described above. It will indeed appear to those skilled in the art that various modifications can be made to the embodiments described above, in the light of the teaching which has just been disclosed to them.

It is also understood that instead of a friction clutch between a track and a pad, a dog clutch may be preferred.

In the detailed presentation of the invention which is made above, the terms used must not be interpreted as limiting the invention to the embodiments set out in the present description, but must be interpreted to include therein all the equivalents whose provision is within the reach of those skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims (13)

An automatic clutch system (110; 700; 1200; 1500; 1700) for an aircraft propulsion system (100), comprising:

• a shaft (108);
• first and second pinions (116, 118) idly mounted on the shaft (108);
• at least one first, respectively second, clutch element (122, 124) integral in rotation with the shaft (108) and designed to be selectively engaged with the first, respectively second, pinion (116, 118) and disengaged from the first, respectively second, pinion (116, 118);
• at least one moving part (120; 122; 1502) relative to the shaft (108) and cooperating with the first clutch elements (122), so as to move between a first extreme position in which the first clutch elements (122) are disengaged and a second extreme position in which the first clutch element or elements (122) are engaged, the moving part (120; 122; 1502) being designed to pass from an extreme position to the other by taking a continuous succession of intermediate positions, depending on a speed of rotation of the shaft (108); And
• an interconnection system (120; 810; 1206; 1506) of the clutch elements (122, 124) designed so that the engagement, respectively the disengagement, of the first clutch element(s) (122) causes the disengagement, respectively the clutch, of the second clutch element(s) (124);

characterized in that it further comprises:

• a return device (132; 808; 1214; 1510) designed to return the moving part (120; 122; 1510) to one predefined of its two extreme positions regardless of the position of the moving part (120; 122; 1502).

Clutch system (700; 1200; 1500; 1700) according to claim 1, in which each movable part (122; 1510) comprises a flyweight (122; 1510) integral in rotation with the shaft (108) and movable radially by relative to the shaft (108), in which the extreme positions are a close position and a position far from the shaft (108), and in which the flyweight (122; 1510) is adapted to move from its close position to its remote position by experiencing centrifugal force resulting from the rotational speed of the shaft (108). A clutch system (700; 1200) according to claim 2, wherein each flyweight includes one of the clutch elements (122, 124). Clutch system (700) according to Claim 3, in which the interconnection system (810) comprises, for each clutch element (122, 124), a finger (814, 914) integral with this clutch element (122, 124), and a cam (816) movable relative to the shaft (108) and having grooves (818, 918) in which the fingers (814, 914) are respectively engaged. Clutch system (1200) according to claim 3, in which the interconnecting system (1206) comprises at least one articulated arm whose first end is pivotally mounted on one or more of the first clutch elements (122) and a second end of which is pivotally mounted on one or more of the second clutch elements (124). Clutch system (700; 1200) according to any one of claims 1 to 5, further comprising a sleeve (702) integral with the shaft (108), on which each clutch element (122, 124) is swivel mounted. A clutch system (1500; 1700) according to claim 2, wherein the shoes (1502) are separate from the clutch elements (122, 124). Clutch system (1500; 1700) according to claim 2 or 7, in which the interconnecting system comprises a sleeve (1506) mounted axially movable on the shaft (108) and carrying the clutch elements (122, 124 ), and further comprising a mechanism adapted to convert radial displacement of each weight (1502) into axial displacement of the sleeve (1506). Clutch system (1500; 1700) according to claim 8, in which the mechanism comprises, for each flyweight (1502), at least one articulated arm (1508) whose first end is pivotally mounted on the sleeve (1506) and whose a second end is pivotally mounted on the flyweight (1502). Clutch system (110) according to claim 1, in which the movable part comprises a sleeve (120) mounted movable at least axially on the shaft (108) and carrying the clutch elements (122, 124), in which the interconnect system includes the sleeve (120), and wherein the second pinion (118) has knockout faces (204) on which the sleeve (120) is designed to slide as the sleeve (120) rotates at a speed lower than that of the second pinion (118), in order to be ejected towards the first pinion (116). A clutch system (110) according to claim 10, wherein the sleeve (120) is mounted on the shaft (108) by means of a helical connection (130). Clutch system (110; 700; 1200; 1500; 1700) according to any one of claims 1 to 11, in which the return system comprises, for each moving part (120; 122; 1502), a return spring (132; 808; 1214; 1510). Aircraft propulsion system (100), comprising:

• a starter/generator (106) having a starter/generator shaft (108);
• a motor assembly (102) having a motor shaft (104);
• first and second fixed gears (112, 114) carried by one of the motor shaft (104) and the starter/generator shaft (108); And
• a clutch system (110; 700; 1200; 1500; 1700) according to any one of claims 1 to 12, wherein the shaft is the other of the motor shaft (104) and the starter shaft /generator (108) and wherein the first and second idler gears (116, 118) are respectively meshed with the first and second fixed gears (112, 114).